Showing 1–50 of 99 results for author: Ke, W

Tracing Vacuum Hadronization with Conserved Currents

Authors: Weiyao Ke, Hai Tao Li, Wanchen Li, Xiaohui Liu, Ding Yu Shao

Abstract: We show that color triality constrains the nonperturbative states that screen a Wilson-line endpoint, allowing the joint flows of net electric charge, baryon number, and strangeness to probe QCD vacuum hadronization. Whether evaluated from resolved hadrons in a jet initiated by a quark of flavor $f$ or from the corresponding charge correlators, these flows satisfy the Gell-Mann--Nishijima relation… ▽ More We show that color triality constrains the nonperturbative states that screen a Wilson-line endpoint, allowing the joint flows of net electric charge, baryon number, and strangeness to probe QCD vacuum hadronization. Whether evaluated from resolved hadrons in a jet initiated by a quark of flavor $f$ or from the corresponding charge correlators, these flows satisfy the Gell-Mann--Nishijima relation $\langle Q_{\rm flow}\rangle_f \simeq I_{3,f} +\frac{1}{2}\left( \langle S_{\rm flow}\rangle_f +\langle B_{\rm flow}\rangle_f \right)$, where $I_{3,f}$ is the third component of the initiating-quark isospin. The net jet baryon number, $\langle B_{\rm flow}\rangle_f\simeq \frac{r_{qq}}{1+r_{qq}}$, directly probes the relative probability of a diquark--antidiquark vacuum excitation, with $r_{qq}$ the diquark-to-quark production ratio. Thus, for $r_{qq}\ll1$, the baryon number carried by the jet is substantially suppressed relative to the initiating-quark value $B_f=1/3$. Likewise, the strange-to-light pair-production ratio, defined by $u\bar u:d\bar d:s\bar s=1:1:r_s$, is encoded in the measured jet strangeness $\langle S_{\rm flow}\rangle_f \simeq S_f+\frac{3r_s}{2+r_s} \left(\frac{1}{3}- \langle B_{\rm flow}\rangle_f\right)$, predicting a nonzero mean net strangeness even in $u$- and $d$-initiated jets. The conserved-current moments appearing in these relations are independent of the renormalization scale. Their simultaneous measurement therefore provides a direct, flavor-resolved probe of vacuum pair production and quantum-number transport during hadronization. △ Less

Submitted 20 August, 2026; originally announced August 2026.

Comments: 25 pages, 8 figures, 3 tables, including 4 pages of appendices

Study the Longitudinal Entropy Deposition using d+Au Collision

Authors: Zhu Meng, Weiyao Ke, Long-Gang Pang

Abstract: Relativistic hydrodynamics successfully describes bulk observables in symmetric heavy-ion collisions, but struggles to reproduce charged-particle rapidity distributions in asymmetric systems such as d+Au collisions. To address this challenge, we introduce two key improvements to the initial-state modeling: sampling deuteron configurations from an ab initio wavefunction, and developing a new longit… ▽ More Relativistic hydrodynamics successfully describes bulk observables in symmetric heavy-ion collisions, but struggles to reproduce charged-particle rapidity distributions in asymmetric systems such as d+Au collisions. To address this challenge, we introduce two key improvements to the initial-state modeling: sampling deuteron configurations from an ab initio wavefunction, and developing a new longitudinal entropy deposition model that incorporates a transverse entropy deposition coefficient $β$ and a rapidity loss term scaling with the number of binary collisions $n_{\rm BC}$. Using the (3+1)-dimensional viscous hydrodynamic model CLVisc coupled with the SMASH afterburner, we simulate d+Au collisions at $\sqrt{s_{\rm NN}} = 200$ GeV and successfully reproduce the experimental charged-particle pseudorapidity distributions across five centrality classes with $β= 0.35$, as well as the transverse momentum spectra and anisotropic flow $v_n$. The entropy deposition coefficient $β$ and the $n_{\rm BC}$-dependent rapidity loss are found to play crucial roles in achieving this agreement. Furthermore, this longitudinal entropy deposition framework demonstrates excellent universality, as validated in p+Au, $^3$He+Au, and Au+Au collisions. Our entropy deposition mechanism could be widely applied to recent light-nucleus collisions such as O+O, Ne+Ne, and asymmetric systems like Pb+Ne at LHC energies, thereby better constraining the nuclear structure of light nuclei through an improved longitudinal description. △ Less

Submitted 27 July, 2026; originally announced July 2026.

Comments: 20 pages, 16 figures, 1 table

Leptogenesis and Low Reheating Temperatures

Authors: Marcos A. G. Garcia, Stephen E. Henrich, Wenqi Ke, Keith A. Olive

Abstract: We study leptogenesis during non-instantaneous reheating in the canonical type-I seesaw framework, with the dominant source of right-handed neutrino (RHN) production being non-thermal from inflaton decays ($φ\rightarrow NN$). While matter-like reheating ($w_φ=0$) fails to be compatible with standard leptogenesis for very low reheating temperatures, the situation is strikingly different for general… ▽ More We study leptogenesis during non-instantaneous reheating in the canonical type-I seesaw framework, with the dominant source of right-handed neutrino (RHN) production being non-thermal from inflaton decays ($φ\rightarrow NN$). While matter-like reheating ($w_φ=0$) fails to be compatible with standard leptogenesis for very low reheating temperatures, the situation is strikingly different for generalized Starobinsky potentials approximated by $V(φ)\proptoφ^k$ with $k\geq4$ about the minimum. In the latter cases, the observed baryon asymmetry can readily be obtained for arbitrarily low reheating temperatures above the BBN bound of $\sim4$ MeV. We study radiation-like reheating ($w_φ=1/3$, $k=4$) in detail, showing that the evolving effective mass of the inflaton condensate leads to kinematic shutoff of the $φ\rightarrow NN$ channel, which qualitatively changes the leptogenesis dynamics. We include a detailed treatment of the effects of fragmentation of the inflaton condensate. The final baryon asymmetry depends primarily on only two parameters: the inflaton-RHN coupling, $y_{φNN}$, and the CP-violating parameter $|ε|$. Interestingly, the final asymmetry is largely insensitive to the RHN mass, the reheating temperature, and the RHN decay rate. While we focus on fermionic reheating, we show that the general features of these results also hold for bosonic reheating to scalars. △ Less

Submitted 9 July, 2026; originally announced July 2026.

Comments: 39 pages, 11 figures

Report number: UMN--TH--4534/26, FTPI--MINN--26/14

Uncover the correlation between jet energy correlators and multiplicity fluctuations

Authors: Pi Duan, Weiyao Ke, Guang-You Qin, Lei Wang

Abstract: The energy-energy correlator (EEC) and multiplicity are two fundamental observables probing complementary aspects of QCD jets: the former characterizes the angular structure of energy flows in a scale-dependent manner, while the latter is sensitive to the entire history of particle production. In this \emph{Letter}, we uncover a nontrivial correlation between them by studying the EEC as a function… ▽ More The energy-energy correlator (EEC) and multiplicity are two fundamental observables probing complementary aspects of QCD jets: the former characterizes the angular structure of energy flows in a scale-dependent manner, while the latter is sensitive to the entire history of particle production. In this \emph{Letter}, we uncover a nontrivial correlation between them by studying the EEC as a function of jet internal multiplicity. We introduce the multiplicity-conditioned EEC jet function (MCJF) and perform a factorization calculation to next-to-leading order accuracy. It is found that, for jet samples selected at a given normalized multiplicity $ν= N_{\rm ch}/\langle N_{\rm ch} \rangle$, the EEC in the angular region $Λ_{\rm QCD}/p_{T,\rm jet}\llχ\ll R$ acquires a $ν$-dependent anomalous dimension. Thus the $ν$-conditioned EEC provides a direct and robust probe to the multiplicity generating function in the perturbative regime. In addition, understanding $ν$ dependence of the EEC is also crucial for isolating possible multiplicity-dependent bias effects in the EEC measurements in nuclear environment. △ Less

Submitted 1 April, 2026; originally announced April 2026.

Comments: 6 pages, 4 figures

Radiative Corrections in Supergravity Models of Inflation

Authors: John Ellis, Tony Gherghetta, Kunio Kaneta, Wenqi Ke, Keith A. Olive

Abstract: Supergravity provides the natural supersymmetric framework for early universe cosmology. A broad class of inflationary models in no-scale supergravity yields tree-level predictions for cosmic microwave background (CMB) observables that closely resemble those of the Starobinsky $R + R^2$ model. Using results from global supersymmetry and supergravity, we analyze radiative corrections in models with… ▽ More Supergravity provides the natural supersymmetric framework for early universe cosmology. A broad class of inflationary models in no-scale supergravity yields tree-level predictions for cosmic microwave background (CMB) observables that closely resemble those of the Starobinsky $R + R^2$ model. Using results from global supersymmetry and supergravity, we analyze radiative corrections in models with canonical and non-canonical kinetic terms, focusing particularly on Starobinsky-like no-scale supergravity models. We derive conditions on the superpotential that keep the gravitino mass finite during inflation and ensure that loop-induced corrections to the Kähler potential remain either finite or subdominant relative to the tree-level potential. We show that in some models, most notably the original no-scale supergravity model with a Wess-Zumino superpotential, radiative corrections grow at large inflaton field values and can dominate the inflationary dynamics, rendering unreliable the model predictions for CMB data. However, we identify a class of no-scale Starobinsky-like models, including the Cecotti model, in which radiative corrections remain very small for inflaton field values $\lesssim 8$ (in Planck units), preserving the agreement of the tree-level predictions with Planck CMB data. △ Less

Submitted 2 March, 2026; originally announced March 2026.

Comments: 30 pages, 11 figures

Report number: UMN-TH-4521/26, FTPI-MINN-26/05, KCL-PH-TH/2026-05, CERN-TH-2026-022

$S-P-D$ Mixing in Vector Quarkonia from the Salpeter Equation with Optimized Wave Function Representations

Authors: Wen-Yuan Ke, Qiang Li, Tianhong Wang, Tai-Fu Feng, Guo-Li Wang

Abstract: This paper proposes a novel mechanism based on the instantaneous Bethe-Salpeter (Salpeter) equation for investigating wave function mixing in vector mesons such as $ψ(3770)$. Conventional theories typically treat $ψ(3770)$ as a $2S-1D$ mixed state; however, considering only tensor forces or relativistic corrections alone often leads to mixing angles that are too small and inconsistent with experim… ▽ More This paper proposes a novel mechanism based on the instantaneous Bethe-Salpeter (Salpeter) equation for investigating wave function mixing in vector mesons such as $ψ(3770)$. Conventional theories typically treat $ψ(3770)$ as a $2S-1D$ mixed state; however, considering only tensor forces or relativistic corrections alone often leads to mixing angles that are too small and inconsistent with experimental data. Phenomenological $2S-1D$ mixing requires experimental data as input to determine the mixing angles, resulting in limited theoretical studies on states like $Υ(1D, 2D)$ in the absence of experimental data. To more accurately describe $S-D$ mixing and its relativistic effects, this paper systematically compares four relativistic wave function representations ($\varphi_1$, $\varphi_2$, $\varphi_3$, and $\varphi_4$) by solving the Salpeter equation and calculates the mass spectra and dileptonic decay widths of charmonium and bottomonium. The study finds that the wave function representation $\varphi_2$ can simultaneously reproduce the experimental data of both charmonium and bottomonium well. Further analysis reveals that, in addition to $S-D$ mixing, the wave functions of vector mesons contain a non-negligible $P$-wave component, meaning they are $S-P-D$ mixed states. We predict the mixing angles for bottomonium $Υ(1D)$ and $Υ(2D)$ to be $(1.78^{+0.32}_{-0.25})^\circ$ and $(5.44^{+1.10}_{-0.76})^\circ$, with dileptonic decay widths of $2.29^{+0.86}_{-0.69}$ eV and $10.5^{+4.2}_{-3.1}$ eV, respectively. △ Less

Submitted 29 July, 2026; v1 submitted 10 February, 2026; originally announced February 2026.

Comments: 17 pages, 1 figure

Renormalization Group Evolution for In-medium Energy Correlators

Authors: Weiyao Ke, Bianka Mecaj, Ivan Vitev

Abstract: We present a first-principles analysis of the renormalization group (RG) evolution of the two-point energy-energy correlator (EEC) in light-quark and gluon jets propagating through nuclear matter. Our work focuses on the analytic structure of the RG equations in the thin-medium regime, highlighting how collinear emissions in the presence of a dense QCD medium reshape the EEC observables. We work i… ▽ More We present a first-principles analysis of the renormalization group (RG) evolution of the two-point energy-energy correlator (EEC) in light-quark and gluon jets propagating through nuclear matter. Our work focuses on the analytic structure of the RG equations in the thin-medium regime, highlighting how collinear emissions in the presence of a dense QCD medium reshape the EEC observables. We work in the opacity expansion of the SCET$_{\rm G}$ formalism, where the propagating quarks and gluons interact with the medium via Glauber gluon exchanges. We compute the corresponding one-loop jet functions using the medium-induced splitting kernels at first order in opacity and perform resummation at leading logarithmic (LL) order. In particular, we identify an experimentally accessible regime of jet energies and EEC angles where one can directly investigate the medium-induced scale evolution and extract the corresponding opacity-one correction to the anomalous dimensions. Furthermore, we demonstrate analytically, using the method of regions, the Coulomb-logarithmic enhancement regulated by plasma screening for EEC. We compare our theoretical predictions with experimental data in $p$-Pb collisions and make projections for O-O collisions to test whether energy correlators could serve as sensitive probe of the quark-gluon plasma (QGP) dynamics in small collision systems, offering a robust and model-independent avenue for constraining jet evolution in QCD matter. △ Less

Submitted 26 February, 2026; v1 submitted 12 December, 2025; originally announced December 2025.

Comments: 57 Pages, 11 figures. Version to appear in JHEP: typos corrected, references added

Report number: LA-UR-25-24936

Fermi-liquid view of viscosity in cold and dense nucleon matter

Authors: Jianing Li, Weiyao Ke, Jin Hu

Abstract: We develop a framework to calculate transport properties in cold, dense relativistic quasiparticle system within the Fermi-liquid theory at the mean-field level. Building on our previous study J. Li \emph{et al.} [Phys. Rev. C \textbf{111}, 044904 (2025)], we start from the linearized relativistic Boltzmann equation tailored to quasiparticles with medium-dependent dispersion relation and implement… ▽ More We develop a framework to calculate transport properties in cold, dense relativistic quasiparticle system within the Fermi-liquid theory at the mean-field level. Building on our previous study J. Li \emph{et al.} [Phys. Rev. C \textbf{111}, 044904 (2025)], we start from the linearized relativistic Boltzmann equation tailored to quasiparticles with medium-dependent dispersion relation and implement Landau matching conditions, proving that the bulk viscosity is manifestly nonnegative. A low-temperature expansion then yields leading-order ($T/μ^*$) expressions for the shear ($η$) and bulk ($ζ$) viscosities, where the behavior $ζ/η\propto (T/μ^*)^4$ in the degenerate regime is found to be robust against quasiparticle mass correction. We couple the kinetic framework to a Walecka-type mean-field equation of state and compute $η$ and $ζ$ for cold, dense nucleon matter. The transport properties of nucleonic matter in the degenerate regime can be relevant for intermediate beam-energy nuclear experiments. △ Less

Submitted 14 June, 2026; v1 submitted 1 December, 2025; originally announced December 2025.

Comments: 8 pages, 3 figures. Fig. 3 legend corrected. Results and conclusions unchanged

Journal ref: Phys. Rev. C 113, 064901 (2026)

Effects of Radiative Corrections on Starobinsky Inflation

Authors: John Ellis, Tony Gherghetta, Kunio Kaneta, Wenqi Ke, Keith A. Olive

Abstract: We analyze radiative corrections to the Starobinsky model of inflation arising from self-interactions of the inflaton, and from its Yukawa couplings, $y$, to matter fermions, and dimensionful trilinear couplings, $κ$, to scalar fields, which could be responsible for reheating the Universe after inflation. The inflaton self-interactions are found to be of higher order in the Hubble expansion rate d… ▽ More We analyze radiative corrections to the Starobinsky model of inflation arising from self-interactions of the inflaton, and from its Yukawa couplings, $y$, to matter fermions, and dimensionful trilinear couplings, $κ$, to scalar fields, which could be responsible for reheating the Universe after inflation. The inflaton self-interactions are found to be of higher order in the Hubble expansion rate during inflation, and hence unimportant for CMB observations. In contrast, matter couplings to the Starobinsky inflaton can have significant effects on the spectral index of scalar CMB perturbations, $n_s$, and on the tensor-to-scalar ratio, $r$. Using a renormalization-group improved analysis of the effective inflationary potential, we find that the Planck measurement of $n_s$ constrains the inflaton coupling to light fermions in the Einstein frame: $y < 4.5 \times 10^{-4}$, corresponding to an upper limit on the reheating temperature $T_{\rm RH} < 2 \times 10^{11}~{\rm GeV}$, whereas the ACT DR6 measurement of $n_s$ corresponds to $3.8 \times 10^{-4} < y < 5.6 \times 10^{-4}$ and $1.7 \times 10^{11} ~{\rm GeV} < T_{\rm RH} < 2.8 \times 10^{11}~{\rm GeV}$, while the upper limits on $r$ provide weaker constraints. Planck data also imply a constraint on a trilinear inflaton coupling to light scalars in the Einstein frame: $κ\leq 4 \times 10^{12}~{\rm GeV}$, corresponding to $T_{\rm RH} \leq 4.2 \times 10^{13}~{\rm GeV}$. We further present constraints on inflaton couplings to massive fermions and scalars, and analyze constraints on couplings in the Jordan frame. △ Less

Submitted 16 October, 2025; originally announced October 2025.

Comments: 15 pages, 14 figures

Report number: UMN-TH-4511/25, FTPI-MINN-25/13, KCL-PH-TH/2025-39, CERN-TH-2025-198

Open heavy-flavor transport and hadronization in heavy-ion collisions

Authors: Yu Fu, Tharun Krishna, Weiyao Ke, Steffen A. Bass, Ralf Rapp

Abstract: We develop a comprehensive model for heavy-quark evolution in a realistic QGP, from their production in the initial collision to hadronic freeze-out. Heavy-quark transport is described by a Langevin approach including medium-induced radiation, coupled to a 2+1D viscous hydrodynamic bulk evolution. Transport coefficients are obtained from non-perturbative $T$-matrix calculations with resonant corre… ▽ More We develop a comprehensive model for heavy-quark evolution in a realistic QGP, from their production in the initial collision to hadronic freeze-out. Heavy-quark transport is described by a Langevin approach including medium-induced radiation, coupled to a 2+1D viscous hydrodynamic bulk evolution. Transport coefficients are obtained from non-perturbative $T$-matrix calculations with resonant correlations near the transition temperature. Hadronization is implemented via two fragmentation+recombination schemes: an improved sudden coalescence model and a resonance recombination model. We present results for key open heavy-flavor observables, i.e., the nuclear modification factor and elliptic flow, and compare to LHC Pb-Pb data at $\sqrt{s_{\NN}}$=5.02\,TeV.} △ Less

Submitted 9 October, 2025; originally announced October 2025.

Comments: Quark Matter 2025 proceeding

Internal multiplicity distributions of jets from nonlinear evolution within the jet function framework

Authors: Pi Duan, Weiyao Ke, Guang-You Qin, Lei Wang

Abstract: Jets selected with high internal charged-particle multiplicity exhibit markedly different substructure patterns compared to inclusive jet samples. Such correlations motivate a systematic study of jet observables as a function of the normalized multiplicity, $ν= N_{\rm ch}/\langle N_{\rm ch}\rangle$. In this work, we develop a theoretical framework for the full charged-particle multiplicity distrib… ▽ More Jets selected with high internal charged-particle multiplicity exhibit markedly different substructure patterns compared to inclusive jet samples. Such correlations motivate a systematic study of jet observables as a function of the normalized multiplicity, $ν= N_{\rm ch}/\langle N_{\rm ch}\rangle$. In this work, we develop a theoretical framework for the full charged-particle multiplicity distribution of exclusive and inclusive jets, formulated within the jet-function approach. The hard production and jet function are evaluated at NLO+LL$_R$ accuracy. The internal parton dynamics governing the multiplicity distribution are described by coupled nonlinear branching equations with angular ordering, supplemented by a nonperturbative modeling term that accounts for hadron-level effects. The resulting predictions are validated against \textsc{Pythia8} simulations and compared with CMS data. We examine the effects of both nonperturbative and perturbative components in shaping the multiplicity distribution, and show that Koba--Nielsen--Olesen (KNO) scaling is notably violated in the region $ν> 2$ in the full solution, with a trend consistent with Monte Carlo results. This framework that numerically solves the nonlinear multiplicity evolution goes beyond DLA-like approximations and reproduces key features seen in event generators, providing a solid foundation for future investigations of multiplicity -- conditioned jet substructure within the jet function formalism. △ Less

Submitted 6 October, 2025; originally announced October 2025.

Comments: 40 pages, 13 figures

Supergravity from the Bottom Up

Authors: Tony Gherghetta, Wenqi Ke

Abstract: We employ on-shell methods to construct scattering amplitudes and derive effective theories involving massive spin-3/2 fermions interacting with spin 0, 1 and 2 bosons. The four-point massive amplitudes are constructed using an all-line-transverse momentum shift, assuming that in the massless limit, three-point interactions are smooth and the Ward identity is satisfied. For a Majorana spin-3/2 fer… ▽ More We employ on-shell methods to construct scattering amplitudes and derive effective theories involving massive spin-3/2 fermions interacting with spin 0, 1 and 2 bosons. The four-point massive amplitudes are constructed using an all-line-transverse momentum shift, assuming that in the massless limit, three-point interactions are smooth and the Ward identity is satisfied. For a Majorana spin-3/2 fermion with mass $m_{3/2}$, we show that interactions with only spin 0 and massive spin-1 bosons do not lead to an effective theory valid up to a cutoff $Λ\gg m_{3/2}$ that is independent of particle masses. Instead, adding an interaction with a spin-2 graviton gives rise to four-point amplitudes with a Planck scale unitarity cutoff that reproduces well-known results from $N=1$ supergravity, such as $F$-term breaking with a complex scalar and $D$-term breaking with an additional massive photon. These bottom-up results are then extended to two Majorana spin-3/2 fermions where an interacting effective theory valid up to $Λ\gg m_{3/2}$ again requires the introduction of the spin-2 graviton. Unitarity up to the Planck scale is then achieved when the two Majorana spin-3/2 fermions have unequal masses, and necessarily couple to two massive spin-1 states corresponding to the spontaneous breaking of $N=2$ supergravity to $N=0$. Our results, obtained from the bottom-up and without any Lagrangian, imply that broken supergravity is the unique, effective theory involving interactions of massive spin-3/2 fermions valid up to a cutoff $Λ\gg m_{3/2}$ that does not depend on particle masses. △ Less

Submitted 16 July, 2025; originally announced July 2025.

Comments: 40 pages

Report number: UMN-TH-4425/25, FTPI-MINN-25-06

Large Relativistic Corrections to Nonrelativistic $M1$ Transitions in Heavy Quarkonium

Authors: Su-Yan Pe, Wei Li, Wen-Yuan Ke, Yi-Yi Rui, Qiang Li, Guo-Li Wang

Abstract: As double heavy quarkonia, charmonium and bottomonium are generally considered to have small relativistic corrections and can be treated using nonrelativistic models. However, this is not always the case. In this paper, we employ the relativistic Bethe-Salpeter (BS) equation method to calculate the electromagnetic (EM) radiative decays of heavy quarkonium where the $M1$ transition provides the lea… ▽ More As double heavy quarkonia, charmonium and bottomonium are generally considered to have small relativistic corrections and can be treated using nonrelativistic models. However, this is not always the case. In this paper, we employ the relativistic Bethe-Salpeter (BS) equation method to calculate the electromagnetic (EM) radiative decays of heavy quarkonium where the $M1$ transition provides the leading-order contribution. Compared to nonrelativistic method which only computes $M1$ transition, our calculations include $M1+E2+M3+E4$ transitions, where the higher-order multipoles, $E2$, $M3$, and $E4$, account for relativistic corrections. The study finds that relativistic effects are large in such transitions even for bottomonium. For instance: the relativistic corrections in the decays $ψ(nS)\rightarrowγη_c(mS)$ ($n\geq m$) range from $68.1\%$ to $83.2\%$, while those for $Υ(nS)\rightarrowγη_b(mS)$ range between $65.9\%$ and $75.2\%$. △ Less

Submitted 28 February, 2026; v1 submitted 10 July, 2025; originally announced July 2025.

Comments: 22 pages, 1 figure

Identification of $D^*_2(3000)$ as the $D_2^*(2^3P_2)$ and exploring potential of undiscovered $2^+$ mesons via $B$ decays

Authors: Shi-Hang Zhang, Wen-Yuan Ke, Su-Yan Pei, Wei Li, Xiao-Ze Tan, Lili Zhu, Guo-Li Wang

Abstract: Following the discovery of the $D^*_2(3000)$, its mass and full width have been extensively studied. Yet its nature remains undetermined to date. Since it was discovered through nonleptonic decay of $B$ meson and the corresponding cascade process, we therefore in this paper investigate the nonleptonic and semileptonic decays of $B$ meson to $J^P = 2^+$ charmed mesons using the Bethe-Salpeter equat… ▽ More Following the discovery of the $D^*_2(3000)$, its mass and full width have been extensively studied. Yet its nature remains undetermined to date. Since it was discovered through nonleptonic decay of $B$ meson and the corresponding cascade process, we therefore in this paper investigate the nonleptonic and semileptonic decays of $B$ meson to $J^P = 2^+$ charmed mesons using the Bethe-Salpeter equation approach. Our calculations on nonleptonic $B$ decays reveal that the unconfirmed resonance $D^*_2(3000)$ aligns well with $D^*_2(2^3P_2)$ predictions. Other candidates, including $D^*_2(1^3F_2)$, $D^*_2(3^3P_2)$, and $D^*_2(2^3F_2)$, are excluded due to their very small branching ratios in $B$ decays. Considering that the $D^*_2(1F)$, $D^*_2(3P)$, and $D^*_2(2F)$ have not yet been experimentally observed, we investigate the feasibility of their detection in $B$-meson decays. △ Less

Submitted 11 December, 2025; v1 submitted 16 June, 2025; originally announced June 2025.

Comments: 28 pages, 7 figures

Journal ref: Phys.Rev.D 112 (2025), 113001

On-shell recursion relations for higher-spin Compton amplitudes

Authors: Yohei Ema, Ting Gao, Wenqi Ke, Zhen Liu, Ishmam Mahbub

Abstract: We recursively construct tree-level electromagnetic and gravitational Compton amplitudes of higher-spin massive particles by the all-line transverse momentum shift. With three-point amplitude as input, we demonstrate that higher-point electromagnetic and gravitational Compton amplitudes are on-shell constructible up to spin $s = 3/2$ and $s = 5/2$, respectively, under the all-line transverse shift… ▽ More We recursively construct tree-level electromagnetic and gravitational Compton amplitudes of higher-spin massive particles by the all-line transverse momentum shift. With three-point amplitude as input, we demonstrate that higher-point electromagnetic and gravitational Compton amplitudes are on-shell constructible up to spin $s = 3/2$ and $s = 5/2$, respectively, under the all-line transverse shift after imposing the current constraint condition. We unambiguously derive the four-point electromagnetic and gravitational Compton amplitudes for $s \leq 3/2$ and $s \leq 5/2$, which are uniquely determined by the on-shell recursion relation and are free from unphysical spurious poles. In addition, we explore amplitudes of spin-$3/2$ particles with non-minimal three-point interactions with photon, as well as $s > 3/2$ particles, and comment on their notable features. Our work furthers the understanding of on-shell methods for massive amplitudes, with hopes to shed light on physical observables in particle physics and higher-spin amplitudes relevant for Kerr black-hole scattering. △ Less

Submitted 2 June, 2025; originally announced June 2025.

Comments: 32 pages, 2 tables

Report number: CERN-TH-2025-090, UMN-TH-4423/25, FTPI-MINN-25-05

Bayesian inference of the magnetic field and chemical potential on holographic jet quenching in heavy-ion collisions

Authors: Liqiang Zhu, Zhan Gao, Weiyao Ke, Hanzhong Zhang

Abstract: Jet quenching is studied in a background magnetic field and a finite baryon chemical potential. The production of energetic partons is calculated using the next-to-leading order (NLO) perturbative Quantum Chromodynamics (pQCD) parton model, while the parton energy loss formula is obtained from the AdS/CFT correspondence incorporating the magnetic field and baryon chemical potential effects. Using… ▽ More Jet quenching is studied in a background magnetic field and a finite baryon chemical potential. The production of energetic partons is calculated using the next-to-leading order (NLO) perturbative Quantum Chromodynamics (pQCD) parton model, while the parton energy loss formula is obtained from the AdS/CFT correspondence incorporating the magnetic field and baryon chemical potential effects. Using Bayesian inference, we systemically compare the theoretical calculations with experimental data for the nuclear modification factor $R_{AA}$ of the large transverse momentum hadrons in different-centrality nucleus-nucleus collisions at 0.2, 2.76 and 5.02 TeV, respectively. The form of the holographic energy loss leads to a strong negative correlation between the magnetic field and the chemical potential after the calibration, from which we discussed the sensitivity of jet quenching phenomena to magnetic field and baryon chemical potential. △ Less

Submitted 29 September, 2025; v1 submitted 30 May, 2025; originally announced June 2025.

How Accidental was Inflation?

Authors: Ignatios Antoniadis, John Ellis, Wenqi Ke, Dimitri V. Nanopoulos, Keith A. Olive

Abstract: Data on the cosmic microwave background (CMB) are discriminating between different models of inflation, disfavoring simple monomial potentials whilst being consistent with models whose predictions resemble those of the Starobinsky $R + R^2$ cosmological model. However, this model may suffer from theoretical problems, since it requires a large initial field value, threatening the validity of the ef… ▽ More Data on the cosmic microwave background (CMB) are discriminating between different models of inflation, disfavoring simple monomial potentials whilst being consistent with models whose predictions resemble those of the Starobinsky $R + R^2$ cosmological model. However, this model may suffer from theoretical problems, since it requires a large initial field value, threatening the validity of the effective field theory. This is quantified by the Swampland Distance Conjecture, which predicts the appearance of a tower of light states associated with an effective ultra-violet cutoff. This could be lower than the inflation scale for cases with an extended period of inflation, leading to an additional problem of initial conditions. No-scale supergravity models can reproduce the predictions of the Starobinsky model and accommodate the CMB data at the expense of fine-tuning of parameters at the level of $10^{-5}$. Here, we propose a solution to this problem based on an explicit realisation of the Starobinsky model in string theory, where this `deformation' parameter is calculable and takes a value of order of the one corresponding to the Starobinsky inflaton potential. Within this range, there are parameter values that accommodate more easily the combination of Planck, ACT and DESI BAO data, while also restricting the range of possible inflaton field values, thereby avoiding the swampland problem and predicting that the initial conditions for inflation compatible with the CMB data are generic. △ Less

Submitted 16 April, 2025; originally announced April 2025.

Comments: 27 pages, 17 figures

Report number: UMN-TH-4418/25, FTPI-MINN-25/03, KCL-PH-TH/2025-09, CERN-TH-2025-076

Scalar Field Fluctuations and the Production of Dark Matter

Authors: Marcos A. G. Garcia, Wenqi Ke, Yann Mambrini, Keith A. Olive, Sarunas Verner

Abstract: One of the simplest possible candidates for dark matter is a stable scalar singlet beyond the Standard Model. If its mass is below the Hubble scale during inflation, long-wavelength modes of this scalar will be excited during inflation, and their subsequent evolution may lead to the correct relic density of dark matter. In this work, we provide a comprehensive analysis of the evolution of a specta… ▽ More One of the simplest possible candidates for dark matter is a stable scalar singlet beyond the Standard Model. If its mass is below the Hubble scale during inflation, long-wavelength modes of this scalar will be excited during inflation, and their subsequent evolution may lead to the correct relic density of dark matter. In this work, we provide a comprehensive analysis of the evolution of a spectator scalar. We examine three cases: (1) a non-interacting massive scalar, (2) a massive scalar with self-interactions of the form $λ_χχ^p$, and (3) a massive scalar coupled to the inflaton $φ$ through an interaction term of the form $σ_{n,m} φ^n χ^m$. In all cases, we assume minimal coupling to gravity and compare these results with the production of short-wavelength modes arising from single graviton exchange. The evolution is tracked during the reheating phase. Our findings are summarized using $(m_χ, T_{\rm RH})$ parameter planes, where $m_χ$ is the mass of the scalar field and $T_{\rm RH}$ is the reheating temperature after inflation. The non-interacting scalar is highly constrained, requiring $m_χ> 3 \times 10^{12}~\rm {GeV}$ and $ T_{\rm RH} \lesssim 7~\text{TeV}$ for an inflationary potential with a quadratic minimum. However, when self-interactions or couplings to the inflaton are included, the viable parameter space expands considerably. In these cases, sub-GeV and even sub-eV scalar masses can yield the correct relic abundance, opening new possibilities for light dark matter candidates. In all cases, we also impose additional constraints arising from the production of isocurvature fluctuations, the prevention of a secondary inflationary phase triggered by the spectator field, and the fragmentation of scalar condensates. △ Less

Submitted 27 February, 2025; originally announced February 2025.

Comments: 57 pages, 11 figures

Report number: UMN--TH--4417/25, FTPI--MINN--25/02

Transport coefficients of dense nucleon matter at low temperature

Authors: Jianing Li, Weiyao Ke

Abstract: The transport property of cold and dense nucleon matter is important for nuclear physics but is relatively less studied than that at finite temperatures. In this paper, we present a primary study of bulk and shear viscosities in the limit $T/μ_B \ll 1$, where $T$ and $μ_B$ are the temperature and the baryon chemical potential. The analysis is performed for a generic system where nucleons are dress… ▽ More The transport property of cold and dense nucleon matter is important for nuclear physics but is relatively less studied than that at finite temperatures. In this paper, we present a primary study of bulk and shear viscosities in the limit $T/μ_B \ll 1$, where $T$ and $μ_B$ are the temperature and the baryon chemical potential. The analysis is performed for a generic system where nucleons are dressed by the condensation of both scalar and vector interactions. Under the relaxation time approximation of the Boltzmann equation, we compute the viscosities of the system to leading power in $T/μ_B$ expansion and establish a relation between the thermodynamic potential and transport coefficients, including bulk viscosity ($ζ$) and shear viscosity ($η$). It is found that hydrodynamic stability ($ζ>0$) imposes additional constraints on the thermodynamic potential. As an example, these relations are applied to the Walecka model. The fluid properties of the cold and dense nucleon matter are characterized by the dimensionless combination of viscosities times the quasi-Fermi momentum over the enthalpy. Furthermore, we discuss the implication of the stability condition on the range of applicability of the model. △ Less

Submitted 8 April, 2025; v1 submitted 29 December, 2024; originally announced December 2024.

Comments: 15 pages, 6 figures. Updated to match the published version, including revised content, results, and references

Journal ref: Phys. Rev. C 111, 044904 (2025)

Anisotropic jet broadening and jet shape

Authors: Weiyao Ke, John Terry, Ivan Vitev

Abstract: In this paper, we explore the use of jet substructure as a way of probing phenomena which break the isotropic behavior of jets, such as jet propagation through an anisotropically flowing quark-gluon plasma or spin correlations. We introduce two novel observables for this purpose: the azimuthal-dependent jet broadening and the azimuthal-dependent jet shape, which generalize the traditional isotropi… ▽ More In this paper, we explore the use of jet substructure as a way of probing phenomena which break the isotropic behavior of jets, such as jet propagation through an anisotropically flowing quark-gluon plasma or spin correlations. We introduce two novel observables for this purpose: the azimuthal-dependent jet broadening and the azimuthal-dependent jet shape, which generalize the traditional isotropic substructure studies. Using Soft-Collinear Effective Theory, we explicitly calculate the jet functions associated with these observables with a standard jet axis and with a Winner-Take-All jet axis in both the resummed and fixed order limits. While our analysis first and foremost establishes the formalism for the azimuthal-dependent jet substructure, it also brings to light new results for jet substructure in the azimuthally integrated case, such as the semi-inclusive jet function and the exclusive jet shape for the Winner-Take-All axis, and the jet broadening in the fixed order region. As an illustrative example for the new formalism we demonstrate that the azimuthal-dependent jet broadening can be used as a direct probe of the transversity parton distribution function in deep inelastic scattering. △ Less

Submitted 16 December, 2024; originally announced December 2024.

Comments: 59 pages, 9 figures

The Role of the Curvaton Post-Planck

Authors: Gongjun Choi, Wenqi Ke, Keith A. Olive

Abstract: The expected improvements in the precision of inflationary physics observables including the scalar spectral index $n_{s}$ and the tensor-to-scalar ratio $r$ will reveal more than just the viability of a particular model of inflation. In the presence of a curvaton field $χ$, supposedly dead models of inflation can be resurrected as these observables are affected by curvaton perturbations. For curr… ▽ More The expected improvements in the precision of inflationary physics observables including the scalar spectral index $n_{s}$ and the tensor-to-scalar ratio $r$ will reveal more than just the viability of a particular model of inflation. In the presence of a curvaton field $χ$, supposedly dead models of inflation can be resurrected as these observables are affected by curvaton perturbations. For currently successful models, improved constraints will enable us to constrain the properties of extra decaying scalar degrees of freedom produced during inflation. In this work, we demonstrate these diverse uses of a curvaton field with the most recent constraints on ($n_{s},r$) and two exemplary inflation models, the Starobinsky model, and a model of new inflation. Our analysis invokes three free parameters: the curvaton mass $m_χ$, its decay rate $Γ_χ$ the reheating temperature $T_{\rm RH}$ produced by inflaton decays. We systematically analyze possible post-inflationary era scenarios of a curvaton field. By projecting the most recent CMB data on ($n_{s},r$) into this parameter space, we can either set constraints on the curvaton parameters from successful models of inflation (so that the success is not spoiled) or determine the parameters which are able to save a model for which $n_{s}$ is predicted to be below the experimental data. We emphasize that the initial value of $\langle χ^2 \rangle \propto H^4/m_χ^2$ produced during inflation is determined from a stochastic approach and thus not a free parameter in our analysis. We also investigate the production of local non-Gaussianity $f_{NL}^{(\rm loc)}$ and apply current CMB constraints to the parameter space. Intriguingly, we find that a large value of $f_{NL}^{(\rm loc)}$ of $\mathcal{O}(1)$ can be produced for both of the two representative inflation models. △ Less

Submitted 12 September, 2024; originally announced September 2024.

Comments: 14 pages, 4 figures

Report number: UMN-TH-4401/24, FTPI-MINN-24/21

Effective interactions and on-shell recursion relation for massive spin 3/2

Authors: Tony Gherghetta, Wenqi Ke

Abstract: We use on-shell methods to compute all three-point interactions of massive spin-3/2 particles involving a graviton and particles of spin $\leq 1$. By employing the massive spinor-helicity formalism we identify the interactions which have a smooth massless limit as expected from the superHiggs mechanism. These interactions are then used to on-shell construct four-point massive spin-3/2 amplitudes u… ▽ More We use on-shell methods to compute all three-point interactions of massive spin-3/2 particles involving a graviton and particles of spin $\leq 1$. By employing the massive spinor-helicity formalism we identify the interactions which have a smooth massless limit as expected from the superHiggs mechanism. These interactions are then used to on-shell construct four-point massive spin-3/2 amplitudes using an all-line transverse shift for the external momenta, which correctly reproduces the contact gravitino interactions in the $N=1$ supergravity Lagrangian. The on-shell constructed four-point amplitudes are also used to derive well-known unitarity bounds in supergravity. In particular, by adding scalar and pseudoscalar interactions to construct the four-point massive spin-3/2 amplitudes that scale as $E^2$ in the high-energy limit, we recover the on-shell Polonyi model with a Planck scale unitarity bound. These effective three-point interactions and on-shell recursion relations provide an alternative and simpler way to study the interactions of massive spin-3/2 particles without a Lagrangian or the use of Feynman diagrams. △ Less

Submitted 28 August, 2024; originally announced August 2024.

Comments: 46 pages

Report number: UMN-TH-4332/24,FTPI-MINN-24-19

Toward a first-principles description of transverse momentum dependent Drell-Yan production in proton-nucleus collisions

Authors: Weiyao Ke, John Terry, Ivan Vitev

Abstract: In this paper, we study the parton dynamics in Drell-Yan collisions involving proton-nuclei interactions in the limit of small transverse momentum, emphasizing the role of the cold nuclear matter effects. The distribution of transverse momentum that enter into these collisions differs from that in Drell-Yan collisions with free nucleons in two distinct ways: the intrinsic parton structure of the T… ▽ More In this paper, we study the parton dynamics in Drell-Yan collisions involving proton-nuclei interactions in the limit of small transverse momentum, emphasizing the role of the cold nuclear matter effects. The distribution of transverse momentum that enter into these collisions differs from that in Drell-Yan collisions with free nucleons in two distinct ways: the intrinsic parton structure of the TMDs are altered, the perturbative dynamics undergo additional modification due to interactions with the nuclear medium. In this paper, we focus on the perturbative dynamics, which we demonstrate enter from forward scattering between the parton constituents of the proton and the nuclear medium. We then derive these partonic contributions to the TMD Drell-Yan cross section up to next-to-leading order in the strong coupling constant and to the first order in the medium opacity. We demonstrate that the collinear and rapidity divergences related to parton showers in matter lead to i) an in-medium renormalization group equation that encodes the transverse momentum dependence of parton energy loss, and ii) a Balitsky-Fadin-Kuraev-Lipatov evolution equation for the forward scattering cross section. We discuss the relation of our results to the phenomenological extraction of nuclear TMDs and apply the new formalism to Drell-Yan production at small transverse momenta in $p$+$A$ reactions. △ Less

Submitted 19 August, 2024; originally announced August 2024.

Comments: 79 pages, 26 figures

Report number: LA-UR-24-21409, INT-PUB-24-034

Momentum shift and on-shell recursion relation for electroweak theory

Authors: Yohei Ema, Ting Gao, Wenqi Ke, Zhen Liu, Kun-Feng Lyu, Ishmam Mahbub

Abstract: We study the All-Line Transverse (ALT) shift which we developed for on-shell recursion of amplitudes for particles of any mass. We discuss the validity of the shift for general theories of spin $\leq$ 1, and illustrate the connection between Ward identity and constructibility for massive spin-1 amplitude under the ALT shift. We apply the shift to the electroweak theory, and various four-point scat… ▽ More We study the All-Line Transverse (ALT) shift which we developed for on-shell recursion of amplitudes for particles of any mass. We discuss the validity of the shift for general theories of spin $\leq$ 1, and illustrate the connection between Ward identity and constructibility for massive spin-1 amplitude under the ALT shift. We apply the shift to the electroweak theory, and various four-point scattering amplitudes among electroweak gauge bosons and fermions are constructed. We show explicitly that the four-point gauge boson contact terms in massive electroweak theory automatically arise after recursive construction, independent of UV completion, and they automatically cancel the terms growing as (energy)$^4$ at high energy. We explore UV completion of the electroweak theory that cancels the remaining (energy)$^2$ terms and impose unitarity requirements to constrain additional couplings. The ALT shift framework allows consistent treatment in dealing with contact term ambiguities for renormalizable massive and massless theories, which we show can be useful in studying real-world amplitudes with massive spinors. △ Less

Submitted 12 November, 2024; v1 submitted 19 July, 2024; originally announced July 2024.

Comments: 39 pages, 2 figures

Report number: UMN-TH-4325/24, FTPI-MINN-24-16

Inflaton Production of Scalar Dark Matter through Fluctuations and Scattering

Authors: Gongjun Choi, Marcos A. G. Garcia, Wenqi Ke, Yann Mambrini, Keith A. Olive, Sarunas Verner

Abstract: We study the effects on particle production of a Planck-suppressed coupling between the inflaton and a scalar dark matter candidate, $χ$. In the absence of this coupling, the dominant source for the relic density of $χ$ is the long wavelength modes produced from the scalar field fluctuations during inflation. In this case, there are strong constraints on the mass of the scalar and the reheating te… ▽ More We study the effects on particle production of a Planck-suppressed coupling between the inflaton and a scalar dark matter candidate, $χ$. In the absence of this coupling, the dominant source for the relic density of $χ$ is the long wavelength modes produced from the scalar field fluctuations during inflation. In this case, there are strong constraints on the mass of the scalar and the reheating temperature after inflation from the present-day relic density of $χ$ (assuming $χ$ is stable). When a coupling $σφ^2 χ^2$ is introduced, with $σ= {\tilde σ} m_φ^2/ M_P^2 \sim 10^{-10} {\tilde σ}$, where $m_φ$ is the inflaton mass, the allowed parameter space begins to open up considerably even for ${\tilde σ}$ as small as $\gtrsim 10^{-7}$. For ${\tilde σ} \gtrsim \frac{9}{16}$, particle production is dominated by the scattering of the inflaton condensate, either through single graviton exchange or the contact interaction between $φ$ and $χ$. In this regime, the range of allowed masses and reheating temperatures is maximal. For $0.004 < {\tilde σ} < 50$, constraints from isocurvature fluctuations are satisfied, and the production from parametric resonance can be neglected. △ Less

Submitted 10 June, 2024; originally announced June 2024.

Comments: 13 pages, 4 Figures

Report number: UMN--TH--4321/24, FTPI--MINN--24/13

Inflaton decay in No-Scale Supergravity and Starobinsky-like models

Authors: Yohei Ema, Marcos A. G. Garcia, Wenqi Ke, Keith A. Olive, Sarunas Verner

Abstract: We consider the decay of the inflaton in Starobinsky-like models arising from either an $R+R^2$ theory of gravity or $N=1$ no-scale supergravity models. If Standard Model matter is simply introduced to the $R + R^2$ theory, the inflaton (which appears when the theory is conformally transformed to the Einstein frame) couples to matter predominantly in Standard Model Higgs kinetic terms. This will t… ▽ More We consider the decay of the inflaton in Starobinsky-like models arising from either an $R+R^2$ theory of gravity or $N=1$ no-scale supergravity models. If Standard Model matter is simply introduced to the $R + R^2$ theory, the inflaton (which appears when the theory is conformally transformed to the Einstein frame) couples to matter predominantly in Standard Model Higgs kinetic terms. This will typically lead to a reheating temperature of $\sim 3 \times 10^9$~GeV. However, if the Standard Model Higgs is conformally coupled to curvature, the decay rate may be suppressed and vanishes for a conformal coupling $ξ= 1/6$. Nevertheless, inflaton decays through the conformal anomaly leading to a reheating temperature of order $10^8$~GeV. The Starobinsky potential may also arise in no-scale supergravity. In this case, the inflaton decays if there is a direct coupling of the inflaton to matter in the superpotential or to gauge fields through the gauge kinetic function. We also discuss the relation between the theories and demonstrate the correspondence between the no-scale models and the conformally coupled $R+R^2$ theory (with $ξ= 1/6$). △ Less

Submitted 22 April, 2024; originally announced April 2024.

Comments: 21 pages, 2 figures, Contribution to Universe Special Issue: Particle Physics and Cosmology: A Themed Issue in Honour of Professor Dimitri Nanopoulos

Report number: UMN-TH-4317/24, FTPI-MINN-24/08

Momentum shift and on-shell constructible massive amplitudes

Authors: Yohei Ema, Ting Gao, Wenqi Ke, Zhen Liu, Kun-Feng Lyu, Ishmam Mahbub

Abstract: We construct tree-level amplitude for massive particles using on-shell recursion relations based on two classes of momentum shifts: an all-line transverse shift that deforms momentum by its transverse polarization vector, and a massive BCFW-type shift. We illustrate that these shifts allow us to correctly calculate four-point and five-point amplitudes in massive QED, without an ambiguity associate… ▽ More We construct tree-level amplitude for massive particles using on-shell recursion relations based on two classes of momentum shifts: an all-line transverse shift that deforms momentum by its transverse polarization vector, and a massive BCFW-type shift. We illustrate that these shifts allow us to correctly calculate four-point and five-point amplitudes in massive QED, without an ambiguity associated with the contact terms that may arise from a simple ''gluing'' of lower-point on-shell amplitudes. We discuss various aspects and applicability of the two shifts, including the large-z behavior and complexity scaling. We show that there exists a ''good'' all-line transverse shift for all possible little group configurations of the external particles, which can be extended to a broader class of theories with massive particles such as massive QCD and theories with massive spin-1 particles. The massive BCFW-type shift enjoys more simplicity, but a ''good'' shift does not exist for all the spin states due to the specific choice of spin axis. △ Less

Submitted 12 November, 2024; v1 submitted 22 March, 2024; originally announced March 2024.

Comments: 26 pages, 1 figure and comments are welcome

Report number: UMN-TH-4316/24, FTPI-MINN-24-07

Minimal Production of Prompt Gravitational Waves during Reheating

Authors: Gongjun Choi, Wenqi Ke, Keith A. Olive

Abstract: The inflationary reheating phase begins when accelerated expansion ends. As all Standard Model particles are coupled to gravity, gravitational interactions will lead to particle production. This includes the thermal bath, dark matter and gravitational radiation. Here, we compute the spectrum of gravitational waves from the inflatoncondensate during the initial phase of reheating. As particular exa… ▽ More The inflationary reheating phase begins when accelerated expansion ends. As all Standard Model particles are coupled to gravity, gravitational interactions will lead to particle production. This includes the thermal bath, dark matter and gravitational radiation. Here, we compute the spectrum of gravitational waves from the inflatoncondensate during the initial phase of reheating. As particular examples of inflation, we consider the Starobinsky model and T-models, all of which are in good phenomenological agreement with CMB anisotropy measurements. The T-models are distinguished by the shape of the potential about its minimum and can be approximated by $V \sim φ^k$, where $φ$ is the inflaton. Interestingly, the shape of the gravitational wave spectrum (when observed) can be used to distinguish among the models considered. As we show, the Starobinsky model and T-models with $k=2$, provide very different spectra when compared to models with $k=4$ or $k>4$. Observation of multiple harmonics in the spectrum can be interpreted as a direct measurement of the inflaton mass. Furthermore, the cutoff in frequency can be used to determine the reheating temperature. △ Less

Submitted 6 February, 2024; originally announced February 2024.

Comments: 11 pages, 4 figures

Report number: UMN--TH--4311/24, FTPI--MINN--24/03

Initial-state and final-state effects on hadron production in small collision systems

Authors: Ivan Vitev, Weiyao Ke

Abstract: Heavy meson production in reactions with nuclei is an active new frontier to understand QCD dynamics and the process of hadronization in nuclear matter. Measurements in various colliding systems at RHIC and LHC, including Pb-Pb, Xe-Xe, O-O, p-Pb, and p-O, enable precision tests of the medium-size, temperature, and mass dependencies of the in-medium parton propagation and shower formation. We emplo… ▽ More Heavy meson production in reactions with nuclei is an active new frontier to understand QCD dynamics and the process of hadronization in nuclear matter. Measurements in various colliding systems at RHIC and LHC, including Pb-Pb, Xe-Xe, O-O, p-Pb, and p-O, enable precision tests of the medium-size, temperature, and mass dependencies of the in-medium parton propagation and shower formation. We employ a coupled DGLAP evolution framework that takes advantage of splitting functions recently obtained in soft-collinear effective theory with Glauber gluons (SCET$_{\rm G}$) and hard thermal loop (HTL) motivated collisional energy loss effects. With jet quenching effects constrained to the nuclear modification factor of charged hadrons in Pb-Pb collisions at 5.02 TeV, we present predictions for light and heavy-meson in Xe-Xe, O-O and p-Pb collisions at the LHC. We find that the nuclear modification scales non-trivially with the quark mass and medium properties. In particular, there can be sizeable collision-induced attenuation of heavy mesons in small systems such as oxygen-oxygen and high-multiplicity p-Pb events. Finally, we analyze the impact of different models of initial-state parton dynamics on the search for QGP signatures in small colliding systems. △ Less

Submitted 19 December, 2023; originally announced December 2023.

Comments: Quark Matter 2023 Proceedings; 4 pages, 3 figures

Non-hydrodynamic response in QCD-like plasma

Authors: Weiyao Ke, Yi Yin

Abstract: Quark-gluon plasma's (QGP) properties at non-hydrodynamic and non-perturbative regimes remain largely unexplored. Here, we examine the response functions describing how a QGP-like plasma responds to initial energy-momentum disturbance in both static and Bjorken-expanding plasma at non-hydrodynamic gradient using the Boltzmann equation in the relaxation-time approximation (RTA). We show that the re… ▽ More Quark-gluon plasma's (QGP) properties at non-hydrodynamic and non-perturbative regimes remain largely unexplored. Here, we examine the response functions describing how a QGP-like plasma responds to initial energy-momentum disturbance in both static and Bjorken-expanding plasma at non-hydrodynamic gradient using the Boltzmann equation in the relaxation-time approximation (RTA). We show that the resulting response functions are remarkably similar in both static and expanding backgrounds at non-hydrodynamic gradients. While non-hydrodynamic response can not be described by the conventional first-order and second-order theories, its behavior is reasonably captured by the extended version of hydrodynamics proposed by us (arXiv: 2208.01046). The potential sensitivity of the Euclidean correlator to non-hydrodynamic response is also illustrated. △ Less

Submitted 9 April, 2024; v1 submitted 13 December, 2023; originally announced December 2023.

Comments: 32 pages, 8 figures

Semirelativistic study on the semileptonic decays of $B_q$ mesons to orbital excited heavy Tensors

Authors: Wen-Yuan Ke, Su-Yan Pei, Tianhong Wang, Guo-Li Wang

Abstract: Based on the method of solving the complete Salpeter equation, we study the semileptonic decays of a $0^-$ heavy meson to $1P$, $2P$, or $3P$ heavy tensor mesons, $B_q \to (\bar c q)(nP) \ell^+ ν_\ell$ $(q=u,d,s,c;n=1,2,3)$. The obtained branching ratio of $\mathcal{B} (B \rightarrow D_2^{\star}(2460)\ell^{+} ν_{\ell})$ agrees with the experimental data. We predict… ▽ More Based on the method of solving the complete Salpeter equation, we study the semileptonic decays of a $0^-$ heavy meson to $1P$, $2P$, or $3P$ heavy tensor mesons, $B_q \to (\bar c q)(nP) \ell^+ ν_\ell$ $(q=u,d,s,c;n=1,2,3)$. The obtained branching ratio of $\mathcal{B} (B \rightarrow D_2^{\star}(2460)\ell^{+} ν_{\ell})$ agrees with the experimental data. We predict $\mathcal{B}\left(B_s^{0} \rightarrow D_{s2}^{\star-}(1P) \ell^{+} ν_{\ell}\right)$$=$$3.76\times 10^{-3}$ and $\mathcal{B}\left(B_c^+ \rightarrow χ_{c2}(1P)\ell^{+} ν_{\ell}\right)$$=$$1.82\times 10^{-3}$. The branching ratios of decays to $2P$ and $3P$ final states are found to be very small. The ratios $\mathcal{R}(\bar{D}_{2}^{\star 0})=0.045$, $\mathcal{R}({D}_{s2}^{\star})=0.048$ and $\mathcal{R}(χ_{c2})=0.059$ are also obtained. This study focuses on the contribution of relativistic corrections. The wave function of the pseudoscalar includes non-relativistic $S$-wave and relativistic $P$-wave. While for a tensor, it contains non-relativistic $P$-wave and relativistic $P$, $D$ and $F$ waves in its wave function. We find the individual contributions of relativistic partial waves are significant in the decay $B \to D_2^{\star }(2460)\ell^{+} ν_{\ell}$, but the overall contribution of the relativistic effect is $24.4\%$, which is small due to cancellation. Similarly, for the decay $B_s^{0} \rightarrow D_{s2}^{\star-}(1P) \ell^{+} ν_{\ell}$, the contribution of the relativistic effect is $28.8\%$. While for $B_c^+ \rightarrow χ_{c2}(1P)\ell^{+} ν_{\ell}$, the individual contributions of relativistic partial waves and the overall relativistic correction are both small, the later of which is $22.1\%$. △ Less

Submitted 16 March, 2024; v1 submitted 27 November, 2023; originally announced November 2023.

Comments: 26 pages, 4 figures, to be published in PRD

The Role of Vectors in Reheating

Authors: Marcos A. G. Garcia, Kunio Kaneta, Wenqi Ke, Yann Mambrini, Keith A. Olive, Sarunas Verner

Abstract: We explore various aspects concerning the role of vector bosons during the reheating process. Generally, reheating occurs during the period of oscillations of the inflaton condensate and the evolution of the radiation bath depends on the inflaton equation of state. For oscillations about a quadratic minimum, the equation of state parameter, $w = p/ρ=0$, and the evolution of the temperature,… ▽ More We explore various aspects concerning the role of vector bosons during the reheating process. Generally, reheating occurs during the period of oscillations of the inflaton condensate and the evolution of the radiation bath depends on the inflaton equation of state. For oscillations about a quadratic minimum, the equation of state parameter, $w = p/ρ=0$, and the evolution of the temperature, $T(a)$ with respect to the scale factor is independent of the spin of the inflaton decay products. However, for cases when $w>0$, there is a dependence on the spin, and here we consider the evolution when the inflaton decays or scatters to vector bosons. We also investigate the gravitational production of vector bosons as potential dark matter candidates. Gravitational production predominantly occurs through the longitudinal mode. We compare these results to the gravitational production of scalars. △ Less

Submitted 24 November, 2023; originally announced November 2023.

Comments: 37 pages, 9 Figures

Report number: UMN--TH--4303/23, FTPI--MINN--23/22, OU--HET--1209

Precision three-dimensional imaging of nuclei using recoil-free jets

Authors: Shen Fang, Weiyao Ke, Ding Yu Shao, John Terry

Abstract: In this study, we explore the azimuthal angle decorrelation of lepton-jet pairs in e-p and e-A collisions as a means for precision measurements of the three-dimensional structure of bound and free nucleons. Utilizing soft-collinear effective theory, we perform the first-ever resummation of this process in e-p collisions at NNLL accuracy using a recoil-free jet axis. Our results are validated again… ▽ More In this study, we explore the azimuthal angle decorrelation of lepton-jet pairs in e-p and e-A collisions as a means for precision measurements of the three-dimensional structure of bound and free nucleons. Utilizing soft-collinear effective theory, we perform the first-ever resummation of this process in e-p collisions at NNLL accuracy using a recoil-free jet axis. Our results are validated against Pythia simulations. In e-A collisions, we address the complex interplay between three characteristic length scales: the medium length $L$, the mean free path of the energetic parton in the medium $λ$, and the hadronization length $L_h$. We demonstrate that in the thin-dilute limit, where $L \ll L_h$ and $L \sim λ$, this process can serve as a robust probe of the three-dimensional structure for bound nucleons. We conclude by offering predictions for future experiments at the Electron-Ion Collider within this limit. △ Less

Submitted 15 May, 2024; v1 submitted 3 November, 2023; originally announced November 2023.

Comments: 23 pages, 4 figures; v2: fixed language typos and added journal reference

Report number: LA-UR-23-30764

Journal ref: JHEP05(2024)066

Gravitational Production of Spin-3/2 Particles During Reheating

Authors: Kunio Kaneta, Wenqi Ke, Yann Mambrini, Keith A. Olive, Sarunas Verner

Abstract: We compute the density of a spin-$\frac32$ particle, the raritron, produced at the end of inflation due to gravitational interactions. We consider a background inflaton condensate as the source of this production, mediated by the exchange of a graviton. This production greatly exceeds the gravitational production from the emergent thermal bath during reheating. The relic abundance limit sets an ab… ▽ More We compute the density of a spin-$\frac32$ particle, the raritron, produced at the end of inflation due to gravitational interactions. We consider a background inflaton condensate as the source of this production, mediated by the exchange of a graviton. This production greatly exceeds the gravitational production from the emergent thermal bath during reheating. The relic abundance limit sets an absolute minimum mass for a stable raritron, though there are also model dependent constraints imposed by unitarity. We also examine the case of gravitational production of a gravitino, taking into account the goldstino evolution during reheating. We compare these results with conventional gravitino production mechanisms. △ Less

Submitted 21 October, 2025; v1 submitted 26 September, 2023; originally announced September 2023.

Comments: 21 pages, 7 figures. v2: discusses the vanishing sound speed, matches published version

Report number: UMN--TH--4225/23, FTPI--MINN--23/17, OU--HET--1204

Journal ref: Phys.Rev.D 108 (2023) 11, 115027

Effects of multi-scale jet-medium interactions on jet substructures

Authors: JETSCAPE Collaboration, Y. Tachibana, A. Angerami, R. Arora, S. A. Bass, S. Cao, Y. Chen, T. Dai, L. Du, R. Ehlers, H. Elfner, W. Fan, R. J. Fries, C. Gale, Y. He, M. Heffernan, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, K. Kauder, L. Kasper, W. Ke, M. Kelsey , et al. (35 additional authors not shown)

Abstract: We utilize event-by-event Monte Carlo simulations within the JETSCAPE framework to examine scale-dependent jet-medium interactions in heavy-ion collisions. The reduction in jet-medium interaction during the early high-virtuality stage, where the medium is resolved at a short distance scale, is emphasized as a key element in explaining multiple jet observables, particularly substructures, simultane… ▽ More We utilize event-by-event Monte Carlo simulations within the JETSCAPE framework to examine scale-dependent jet-medium interactions in heavy-ion collisions. The reduction in jet-medium interaction during the early high-virtuality stage, where the medium is resolved at a short distance scale, is emphasized as a key element in explaining multiple jet observables, particularly substructures, simultaneously. By employing the MATTER+LBT setup, which incorporates this explicit reduction of medium effects at high virtuality, we investigate jet substructure observables, such as Soft Drop groomed observables. When contrasted with existing data, our findings spotlight the significant influence of the reduction at the early high-virtuality stages. Furthermore, we study the substructure of gamma-tagged jets, providing predictive insights for future experimental analyses. This broadens our understanding of the various contributing factors involved in modifying jet substructures. △ Less

Submitted 16 July, 2023; originally announced July 2023.

Comments: 6 pages, 4 figures, contribution to the Hard Probes 2023 proceedings

The case for an EIC Theory Alliance: Theoretical Challenges of the EIC

Authors: Raktim Abir, Igor Akushevich, Tolga Altinoluk, Daniele Paolo Anderle, Fatma P. Aslan, Alessandro Bacchetta, Baha Balantekin, Joao Barata, Marco Battaglieri, Carlos A. Bertulani, Guillaume Beuf, Chiara Bissolotti, Daniël Boer, M. Boglione, Radja Boughezal, Eric Braaten, Nora Brambilla, Vladimir Braun, Duane Byer, Francesco Giovanni Celiberto, Yang-Ting Chien, Ian C. Cloët, Martha Constantinou, Wim Cosyn, Aurore Courtoy , et al. (146 additional authors not shown)

Abstract: We outline the physics opportunities provided by the Electron Ion Collider (EIC). These include the study of the parton structure of the nucleon and nuclei, the onset of gluon saturation, the production of jets and heavy flavor, hadron spectroscopy and tests of fundamental symmetries. We review the present status and future challenges in EIC theory that have to be addressed in order to realize thi… ▽ More We outline the physics opportunities provided by the Electron Ion Collider (EIC). These include the study of the parton structure of the nucleon and nuclei, the onset of gluon saturation, the production of jets and heavy flavor, hadron spectroscopy and tests of fundamental symmetries. We review the present status and future challenges in EIC theory that have to be addressed in order to realize this ambitious and impactful physics program, including how to engage a diverse and inclusive workforce. In order to address these many-fold challenges, we propose a coordinated effort involving theory groups with differing expertise is needed. We discuss the scientific goals and scope of such an EIC Theory Alliance. △ Less

Submitted 23 May, 2023; originally announced May 2023.

Comments: 44 pages, ReVTeX, White Paper on EIC Theory Alliance

eHIJING: an Event Generator for Jet Tomography in Electron-Ion Collisions

Authors: Weiyao Ke, Yuan-Yuan Zhang, Hongxi Xing, Xin-Nian Wang

Abstract: We develop the first event generator, the electron-Heavy-Ion-Jet-INteraction-Generator (eHIJING), for the jet tomography study of electron-ion collisions. In this generator, energetic jet partons produced from the initial hard scattering undergo multiple collisions with the nuclear target. The collision rate is proportional to the transverse-momentum-dependent (TMD) gluon density in the nucleus, w… ▽ More We develop the first event generator, the electron-Heavy-Ion-Jet-INteraction-Generator (eHIJING), for the jet tomography study of electron-ion collisions. In this generator, energetic jet partons produced from the initial hard scattering undergo multiple collisions with the nuclear target. The collision rate is proportional to the transverse-momentum-dependent (TMD) gluon density in the nucleus, which is given by a simple model inspired by the physics of gluon saturation. Medium-modified QCD splitting functions within the higher-twist (HT) and generalized higher-twist (GHT) frameworks are utilized to simulate parton showering in the nuclear medium that takes into account the non-Abelian Landau-Pomeranchuck-Midgal interference effect. Employing eHIJING, we revisit hadron production in semi-inclusive deep inelastic scattering (SIDIS) as measured by EMC, HERMES, and recent CLAS experiments. eHIJING with both GT and GHT frameworks gives reasonably good descriptions of these experimental data. Predictions for experiments at the future electron-ion colliders are also provided. It is demonstrated that future measurements of the transverse momentum broadening of single hadron spectra can be used to map out the two-dimensional kinematic ($Q^2, x_B$) dependence of the jet transport coefficient $\hat{q}$ in cold nuclear matter. △ Less

Submitted 20 June, 2024; v1 submitted 21 April, 2023; originally announced April 2023.

Comments: 32 pages, 35 figures

Report number: LA-UR-23-24141

Bayesian inference of the path-length dependence of jet energy loss

Authors: Jordan Wu, Weiyao Ke, Xin-Nian Wang

Abstract: A simple model for medium modification of the jet function can be used to extract the jet energy loss distribution through a parameterized form. We carry out a comprehensive Bayesian analysis of the world data on single inclusive jet spectra in heavy-ion collisions at both RHIC and LHC energies. We extract the average jet energy loss $\langle ΔE\rangle$ as a function of jet transverse momentum… ▽ More A simple model for medium modification of the jet function can be used to extract the jet energy loss distribution through a parameterized form. We carry out a comprehensive Bayesian analysis of the world data on single inclusive jet spectra in heavy-ion collisions at both RHIC and LHC energies. We extract the average jet energy loss $\langle ΔE\rangle$ as a function of jet transverse momentum $p_T$ for each collision system and centrality independently. Assuming jet energy loss is proportional to the initial parton density $ρ\sim dN_{\rm ch}/dη/πR_{\rm eff}^2$ as estimated from the pseudorapidity density of charged hadron multiplicity $dN_{\rm ch}/dη$ and the effective system size $R_{\rm eff}\sim N_{\rm part}^{1/3}$ given by the number of participant nucleons $N_{\rm part}$, the scaled average jet energy loss $\langle ΔE\rangle/ρ\sim R_{\rm eff}^{0.59} p_T^{0.13}\ln p_T $ for jet cone-size $R=0.4$ is found to have a momentum dependence that is slightly stronger than a logarithmic form while the system size or length dependence is slower than a linear one. The fluctuation of jet energy loss is, however, independent of the initial parton density or the system size. △ Less

Submitted 4 October, 2023; v1 submitted 13 April, 2023; originally announced April 2023.

Comments: 9 pages with 10 figures final version published in Phys. Rev. C 108 (2023) 3, 034911

Probing cold nuclear matter with energy correlators

Authors: Kyle Devereaux, Wenqing Fan, Weiyao Ke, Kyle Lee, Ian Moult

Abstract: The future electron-ion collider (EIC) will produce the first-ever high energy collisions between electrons and a wide range of nuclei, opening a new era in the study of cold nuclear matter. Quarks and gluons produced in these collisions will propagate through the dense nuclear matter of nuclei, imprinting its structure into subtle correlations in the energy flux of final state hadrons. In this ar… ▽ More The future electron-ion collider (EIC) will produce the first-ever high energy collisions between electrons and a wide range of nuclei, opening a new era in the study of cold nuclear matter. Quarks and gluons produced in these collisions will propagate through the dense nuclear matter of nuclei, imprinting its structure into subtle correlations in the energy flux of final state hadrons. In this article, we apply recent developments from the field of jet substructure, namely the energy correlator observables, to decode these correlations and provide a new window into nuclear structure. The energy correlators provide a calibrated probe of the scale dependence of vacuum quantum chromodynamics (QCD), enabling medium modifications to be imaged and interpreted as a function of scale. Using the eHIJING parton shower to simulate electron-nucleus collisions, we demonstrate that the size of the nucleus is imprinted as an angular scale in the correlators, with a magnitude that is visible for realistic EIC kinematics. We can observe the size difference between the proposed EIC nuclear targets ${}^3$He, ${}^4$He, ${}^{12}$C, ${}^{40}$Ca, ${}^{64}$Cu, ${}^{197}$Au, and ${}^{238}$U, showing that the energy correlators can image femtometer length scales using asymptotic energy flux. Our approach offers a unified view of jet substructure across collider experiments, and provides numerous new theoretical tools to unravel the complex dynamics of QCD in extreme environments, both hot and cold. △ Less

Submitted 2 October, 2025; v1 submitted 14 March, 2023; originally announced March 2023.

Comments: 11 pages, 11 beautiful figures, and appendices

Report number: MIT-CTP 5513, LA-UR-23-22542

Journal ref: Phys. Rev. C 112, 035202 (2025)

Spin-3/2 and spin-2 charged massive states in a constant electromagnetic background

Authors: Karim Benakli, Cassiano A. Daniel, Wenqi Ke

Abstract: We develop in components the superspace action obtained in arXiv:2110.07623 describing the first massive level of the open charged superstring in a flat four-dimensional spacetime. In the absence of an electromagnetic background, we show how the Rarita-Schwinger and Fierz-Pauli Lagrangians are retrieved for spin-3/2 and 2, respectively. We then write different forms of the action in the presence o… ▽ More We develop in components the superspace action obtained in arXiv:2110.07623 describing the first massive level of the open charged superstring in a flat four-dimensional spacetime. In the absence of an electromagnetic background, we show how the Rarita-Schwinger and Fierz-Pauli Lagrangians are retrieved for spin-3/2 and 2, respectively. We then write different forms of the action in the presence of the electromagnetic background. The resulting equations of motion describe the propagation of fields of charged spin-3/2 and spin-1/2 on the one hand, and spin-2, 1 and 0 on the other. △ Less

Submitted 13 February, 2023; originally announced February 2023.

Comments: 70 pages, summary of the main results was presented in arXiv:2211.13689 and arXiv:2211.13691

Understanding parton evolution in matter from renormalization group analysis

Authors: Weiyao Ke, Ivan Vitev

Abstract: We perform a renormalization group (RG) analysis of collinear hadron production in deep inelastic scattering on nuclei. We consider the limit where the parent parton energy $E$ is large, while the medium opacity $L/λ_g$ remains small. We identify the fixed order and leading $\ln(E/ξ^2 L)$ enhanced medium contributions to the semi-inclusive cross sections and derive RG equations that resum multiple… ▽ More We perform a renormalization group (RG) analysis of collinear hadron production in deep inelastic scattering on nuclei. We consider the limit where the parent parton energy $E$ is large, while the medium opacity $L/λ_g$ remains small. We identify the fixed order and leading $\ln(E/ξ^2 L)$ enhanced medium contributions to the semi-inclusive cross sections and derive RG equations that resum multiple emissions near the endpoints of the splitting functions at first order in opacity. These evolution equations treat the same type of radiation enhancement in matter as the modified Dokshitzer-Gribov-Lipatov-Altarelli-Parisi approach, but differ in the way one regulates the collinear divergences. They provide a unique analytic insight into the problem of resummation and a faster and more efficient path to phenomenology. The new RG evolution framework is applied to study fragmentation in $e$A reactions. △ Less

Submitted 22 May, 2024; v1 submitted 27 January, 2023; originally announced January 2023.

Comments: Accepted by Phys. Lett. B., 7 pages, 2 figures

Report number: LA-UR-23-20730

Hard jet substructure in a multistage approach

Authors: Y. Tachibana, A. Kumar, A. Majumder, A. Angerami, R. Arora, S. A. Bass, S. Cao, Y. Chen, T. Dai, L. Du, R. Ehlers, H. Elfner, W. Fan, R. J. Fries, C. Gale, Y. He, M. Heffernan, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, K. Kauder, L. Kasper, W. Ke , et al. (34 additional authors not shown)

Abstract: We present predictions and postdictions for a wide variety of hard jet-substructure observables using a multistage model within the JETSCAPE framework. The details of the multistage model and the various parameter choices are described in [A. Kumar et al., arXiv:2204.01163]. A novel feature of this model is the presence of two stages of jet modification: a high virtuality phase [modeled using the… ▽ More We present predictions and postdictions for a wide variety of hard jet-substructure observables using a multistage model within the JETSCAPE framework. The details of the multistage model and the various parameter choices are described in [A. Kumar et al., arXiv:2204.01163]. A novel feature of this model is the presence of two stages of jet modification: a high virtuality phase [modeled using the modular all twist transverse-scattering elastic-drag and radiation model (MATTER)], where modified coherence effects diminish medium-induced radiation, and a lower virtuality phase [modeled using the linear Boltzmann transport model (LBT)], where parton splits are fully resolved by the medium as they endure multiple scattering induced energy loss. Energy-loss calculations are carried out on event-by-event viscous fluid dynamic backgrounds constrained by experimental data. The uniform and consistent descriptions of multiple experimental observables demonstrate the essential role of modified coherence effects and the multistage modeling of jet evolution. Using the best choice of parameters from [A. Kumar et al., arXiv:2204.01163], and with no further tuning, we present calculations for the medium modified jet fragmentation function, the groomed jet momentum fraction $z_g$ and angular separation $r_g$ distributions, as well as the nuclear modification factor of groomed jets. These calculations provide accurate descriptions of published data from experiments at the Large Hadron Collider. Furthermore, we provide predictions from the multistage model for future measurements at the BNL Relativistic Heavy Ion Collider. △ Less

Submitted 16 October, 2024; v1 submitted 6 January, 2023; originally announced January 2023.

Comments: 20 pages, 12 figures

Journal ref: Phys. Rev. C 110, 044907 (2024)

Comprehensive Study of Multi-scale Jet-medium Interaction

Authors: Y. Tachibana, A. Angerami, R. Arora, S. A. Bass, S. Cao, Y. Chen, T. Dai, L. Du, R. Ehlers, H. Elfner, W. Fan, R. J. Fries, C. Gale, Y. He, M. Heffernan, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, L. Kasper, W. Ke, M. Kelsey, M. Kordell II, A. Kumar , et al. (33 additional authors not shown)

Abstract: We explore jet-medium interactions at various scales in high-energy heavy-ion collisions using the JETSCAPE framework. The physics of the multi-stage modeling and the coherence effect at high virtuality is discussed through the results of multiple jet and high-$p_{\mathrm{T}}$ particle observables, compared with experimental data. Furthermore, we investigate the jet-medium interaction involved in… ▽ More We explore jet-medium interactions at various scales in high-energy heavy-ion collisions using the JETSCAPE framework. The physics of the multi-stage modeling and the coherence effect at high virtuality is discussed through the results of multiple jet and high-$p_{\mathrm{T}}$ particle observables, compared with experimental data. Furthermore, we investigate the jet-medium interaction involved in the hadronization process. △ Less

Submitted 23 December, 2022; originally announced December 2022.

Comments: 6 pages, 5 figures, contribution to the Quark Matter 2022 proceedings

Journal ref: Acta Phys. Pol. B Proc. Suppl. 16, 1-A50 (2023)

Open Superstring First Mass Level Effective Lagrangian: Massive Spin-3/2 Fields in an Electromagnetic Background

Authors: Karim Benakli, Cassiano A. Daniel, Wenqi Ke

Abstract: We derive fully explicit equations of motion, and the associated set of constraints, describing the propagation in a flat space-time of a charged spin-3/2 massive state in a constant electromagnetic background. For this purpose, we provide the Lagrangian for the physical fermionic fields in the first massive level of the open superstring. We first write a compact Lagrangian, allowing a simple deri… ▽ More We derive fully explicit equations of motion, and the associated set of constraints, describing the propagation in a flat space-time of a charged spin-3/2 massive state in a constant electromagnetic background. For this purpose, we provide the Lagrangian for the physical fermionic fields in the first massive level of the open superstring. We first write a compact Lagrangian, allowing a simple derivation of the equations of motion and constraints. Then another one is given that yields directly a decoupled system of equations, though the fields of different spins look coupled at the level of the Lagrangian. △ Less

Submitted 24 November, 2022; originally announced November 2022.

Comments: 4 pages

Open Superstring First Mass Level Effective Lagrangian: Massive Spin-2 in an Electromagnetic Background

Authors: Karim Benakli, Cassiano A. Daniel, Wenqi Ke

Abstract: Minimal coupling leads to problems such as loss of causality if one wants to describe charged particles of spin greater than one propagating in a constant electromagnetic background. Regge trajectories in string theory contain such states, so their study may allow us to investigate possible avenues to remedy the pathologies. We present here two explicit forms, related by field redefinitions, of th… ▽ More Minimal coupling leads to problems such as loss of causality if one wants to describe charged particles of spin greater than one propagating in a constant electromagnetic background. Regge trajectories in string theory contain such states, so their study may allow us to investigate possible avenues to remedy the pathologies. We present here two explicit forms, related by field redefinitions, of the Lagrangian describing the bosonic states in the first massive level of open superstrings in four dimensions. The first one reduces, when the electromagnetic field is set to zero, to the Fierz-Pauli Lagrangian for the spin-2 mode. The second one is a more compact form which simplifies the derivation of a Fierz-Pauli system of equations of motion and constraints. △ Less

Submitted 24 November, 2022; originally announced November 2022.

Comments: 11 pages

Higher-Order Cumulants and Correlation Functions of Proton Multiplicity Distributions in $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV Au+Au Collisions at the RHIC STAR Experiment

Authors: STAR Collaboration, M. S. Abdallah, B. E. Aboona, J. Adam, L. Adamczyk, J. R. Adams, J. K. Adkins, I. Aggarwal, M. M. Aggarwal, Z. Ahammed, D. M. Anderson, E. C. Aschenauer, J. Atchison, V. Bairathi, W. Baker, J. G. Ball Cap, K. Barish, R. Bellwied, P. Bhagat, A. Bhasin, S. Bhatta, J. Bielcik, J. Bielcikova, J. D. Brandenburg, X. Z. Cai , et al. (349 additional authors not shown)

Abstract: We report a measurement of cumulants and correlation functions of event-by-event proton multiplicity distributions from fixed-target Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 3 GeV measured by the STAR experiment. Protons are identified within the rapidity ($y$) and transverse momentum ($p_{\rm T}$) region $-0.9 < y<0$ and $0.4 < p_{\rm T} <2.0 $ GeV/$c$ in the center-of-mass frame. A systematic a… ▽ More We report a measurement of cumulants and correlation functions of event-by-event proton multiplicity distributions from fixed-target Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 3 GeV measured by the STAR experiment. Protons are identified within the rapidity ($y$) and transverse momentum ($p_{\rm T}$) region $-0.9 < y<0$ and $0.4 < p_{\rm T} <2.0 $ GeV/$c$ in the center-of-mass frame. A systematic analysis of the proton cumulants and correlation functions up to sixth-order as well as the corresponding ratios as a function of the collision centrality, $p_{\rm T}$, and $y$ are presented. The effect of pileup and initial volume fluctuations on these observables and the respective corrections are discussed in detail. The results are compared to calculations from the hadronic transport UrQMD model as well as a hydrodynamic model. In the most central 5\% collisions, the value of proton cumulant ratio $C_4/C_2$ is negative, drastically different from the values observed in Au+Au collisions at higher energies. Compared to model calculations including Lattice QCD, a hadronic transport model, and a hydrodynamic model, the strong suppression in the ratio of $C_4/C_2$ at 3 GeV Au+Au collisions indicates an energy regime dominated by hadronic interactions. △ Less

Submitted 22 February, 2023; v1 submitted 24 September, 2022; originally announced September 2022.

Comments: 25 pages, 20 figures, 4 tables

Journal ref: Phys. Rev. C 107, 024908(2023)

Beam Energy Dependence of Triton Production and Yield Ratio ($\mathrm{N}_t \times \mathrm{N}_p/\mathrm{N}_d^2$) in Au+Au Collisions at RHIC

Authors: STAR Collaboration, M. I. Abdulhamid, B. E. Aboona, J. Adam, J. R. Adams, G. Agakishiev, I. Aggarwal, M. M. Aggarwal, Z. Ahammed, A. Aitbaev, I. Alekseev, D. M. Anderson, A. Aparin, S. Aslam, J. Atchison, G. S. Averichev, V. Bairathi, W. Baker, J. G. Ball Cap, K. Barish, P. Bhagat, A. Bhasin, S. Bhatta, I. G. Bordyuzhin, J. D. Brandenburg , et al. (333 additional authors not shown)

Abstract: We report the triton ($t$) production in mid-rapidity ($|y| <$ 0.5) Au+Au collisions at $\sqrt{s_\mathrm{NN}}$= 7.7--200 GeV measured by the STAR experiment from the first phase of the beam energy scan at the Relativistic Heavy Ion Collider (RHIC). The nuclear compound yield ratio ($\mathrm{N}_t \times \mathrm{N}_p/\mathrm{N}_d^2$), which is predicted to be sensitive to the fluctuation of local ne… ▽ More We report the triton ($t$) production in mid-rapidity ($|y| <$ 0.5) Au+Au collisions at $\sqrt{s_\mathrm{NN}}$= 7.7--200 GeV measured by the STAR experiment from the first phase of the beam energy scan at the Relativistic Heavy Ion Collider (RHIC). The nuclear compound yield ratio ($\mathrm{N}_t \times \mathrm{N}_p/\mathrm{N}_d^2$), which is predicted to be sensitive to the fluctuation of local neutron density, is observed to decrease monotonically with increasing charged-particle multiplicity ($dN_{ch}/dη$) and follows a scaling behavior. The $dN_{ch}/dη$ dependence of the yield ratio is compared to calculations from coalescence and thermal models. Enhancements in the yield ratios relative to the coalescence baseline are observed in the 0\%-10\% most central collisions at 19.6 and 27 GeV, with a significance of 2.3$σ$ and 3.4$σ$, respectively, giving a combined significance of 4.1$σ$. The enhancements are not observed in peripheral collisions or model calculations without critical fluctuation, and decreases with a smaller $p_{T}$ acceptance. The physics implications of these results on the QCD phase structure and the production mechanism of light nuclei in heavy-ion collisions are discussed. △ Less

Submitted 18 May, 2023; v1 submitted 16 September, 2022; originally announced September 2022.

Comments: 6 pages, 4 figures, Supplemental Material: http://link.aps.org/supplemental/10.1103/PhysRevLett.130.202301

Journal ref: Phys. Rev. Lett. 130, 202301 (2023)

Search for the Chiral Magnetic Effect in Au+Au collisions at $\sqrt{s_{_{\rm{NN}}}}=27$ GeV with the STAR forward Event Plane Detectors

Authors: STAR Collaboration, B. E. Aboona, J. Adam, L. Adamczyk, J. R. Adams, I. Aggarwal, M. M. Aggarwal, Z. Ahammed, D. M. Anderson, E. C. Aschenauer, J. Atchison, V. Bairathi, W. Baker, J. G. Ball Cap, K. Barish, R. Bellwied, P. Bhagat, A. Bhasin, S. Bhatta, J. Bielcik, J. Bielcikova, J. D. Brandenburg, X. Z. Cai, H. Caines, M. Calderón de la Barca Sánchez , et al. (347 additional authors not shown)

Abstract: A decisive experimental test of the Chiral Magnetic Effect (CME) is considered one of the major scientific goals at the Relativistic Heavy-Ion Collider (RHIC) towards understanding the nontrivial topological fluctuations of the Quantum Chromodynamics vacuum. In heavy-ion collisions, the CME is expected to result in a charge separation phenomenon across the reaction plane, whose strength could be s… ▽ More A decisive experimental test of the Chiral Magnetic Effect (CME) is considered one of the major scientific goals at the Relativistic Heavy-Ion Collider (RHIC) towards understanding the nontrivial topological fluctuations of the Quantum Chromodynamics vacuum. In heavy-ion collisions, the CME is expected to result in a charge separation phenomenon across the reaction plane, whose strength could be strongly energy dependent. The previous CME searches have been focused on top RHIC energy collisions. In this Letter, we present a low energy search for the CME in Au+Au collisions at $\sqrt{s_{_{\rm{NN}}}}=27$ GeV. We measure elliptic flow scaled charge-dependent correlators relative to the event planes that are defined at both mid-rapidity $|η|<1.0$ and at forward rapidity $2.1 < |η|<5.1$. We compare the results based on the directed flow plane ($Ψ_1$) at forward rapidity and the elliptic flow plane ($Ψ_2$) at both central and forward rapidity. The CME scenario is expected to result in a larger correlation relative to $Ψ_1$ than to $Ψ_2$, while a flow driven background scenario would lead to a consistent result for both event planes. In 10-50\% centrality, results using three different event planes are found to be consistent within experimental uncertainties, suggesting a flow driven background scenario dominating the measurement. We obtain an upper limit on the deviation from a flow driven background scenario at the 95\% confidence level. This work opens up a possible road map towards future CME search with the high statistics data from the RHIC Beam Energy Scan Phase-II. △ Less

Submitted 19 April, 2023; v1 submitted 7 September, 2022; originally announced September 2022.

Comments: main: 16 pages, 5 figures; supplementary material: 2 pages, 1 figure

Global constraint on the jet transport coefficient from single hadron, dihadron and $γ$-hadron spectra in high-energy heavy-ion collisions

Authors: Man Xie, Weiyao Ke, Hanzhong Zhang, Xin-Nian Wang

Abstract: Modifications of large transverse momentum single hadron, dihadron, and $γ$-hadron spectra in relativistic heavy-ion collisions are direct consequences of parton-medium interactions in the quark-gluon plasma (QGP). The interaction strength and underlying dynamics can be quantified by the jet transport coefficient $\hat{q}$. We carry out the first global constraint on $\hat{q}$ using a next-to-lead… ▽ More Modifications of large transverse momentum single hadron, dihadron, and $γ$-hadron spectra in relativistic heavy-ion collisions are direct consequences of parton-medium interactions in the quark-gluon plasma (QGP). The interaction strength and underlying dynamics can be quantified by the jet transport coefficient $\hat{q}$. We carry out the first global constraint on $\hat{q}$ using a next-to-leading order pQCD parton model with higher-twist parton energy loss and combining world experimental data on single hadron, dihadron, and $γ$-hadron suppression at both RHIC and LHC energies with a wide range of centralities. The global Bayesian analysis using the information field (IF) priors provides the most stringent constraint on $\hat q(T)$. We demonstrate in particular the progressive constraining power of the IF Bayesian analysis on the strong temperature dependence of $\hat{q}$ using data from different centralities and colliding energies. We also discuss the advantage of using both inclusive and correlation observables with different geometric biases. As a verification, the obtained $\hat{q}(T)$ is shown to describe data on single hadron anisotropy at high transverse momentum well. Predictions for future jet quenching measurements in oxygen-oxygen collisions are also provided. △ Less

Submitted 8 November, 2023; v1 submitted 30 August, 2022; originally announced August 2022.

Comments: 32 pages in ReVtex with 32 figures. Version submitted to PRC

Bayesian analysis of QGP jet transport using multi-scale modeling applied to inclusive hadron and reconstructed jet data

Authors: R. Ehlers, A. Angerami, R. Arora, S. A. Bass, S. Cao, Y. Chen, L. Du, T. Dai, H. Elfner, W. Fan, R. J. Fries, C. Gale, Y. He, M. Heffernan, U. Heinz, B. V. Jacak, P. M. Jacobs, S. Jeon, Y. Ji, L. Kasper, W. Ke, M. Kelsey, M. Kordell II, A. Kumar, J. Latessa , et al. (33 additional authors not shown)

Abstract: The JETSCAPE Collaboration reports a new determination of jet transport coefficients in the Quark-Gluon Plasma, using both reconstructed jet and hadron data measured at RHIC and the LHC. The JETSCAPE framework incorporates detailed modeling of the dynamical evolution of the QGP; a multi-stage theoretical approach to in-medium jet evolution and medium response; and Bayesian inference for quantitati… ▽ More The JETSCAPE Collaboration reports a new determination of jet transport coefficients in the Quark-Gluon Plasma, using both reconstructed jet and hadron data measured at RHIC and the LHC. The JETSCAPE framework incorporates detailed modeling of the dynamical evolution of the QGP; a multi-stage theoretical approach to in-medium jet evolution and medium response; and Bayesian inference for quantitative comparison of model calculations and data. The multi-stage framework incorporates multiple models to cover a broad range in scale of the in-medium parton shower evolution, with dynamical choice of model that depends on the current virtuality or energy of the parton. We will discuss the physics of the multi-stage modeling, and then present a new Bayesian analysis incorporating it. This analysis extends the recently published JETSCAPE determination of the jet transport parameter $\hat{q}$ that was based solely on inclusive hadron suppression data, by incorporating reconstructed jet measurements of quenching. We explore the functional dependence of jet transport coefficients on QGP temperature and jet energy and virtuality, and report the consistency and tensions found for current jet quenching modeling with hadron and reconstructed jet data over a wide range in kinematics and $\sqrt{s_{\text{NN}}}$. This analysis represents the next step in the program of comprehensive analysis of jet quenching phenomenology and its constraint of properties of the QGP. △ Less

Submitted 16 August, 2022; originally announced August 2022.

Comments: 6 pages, 2 figures, contribution to the Quark Matter 2022 proceedings