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Mini-Proceedings of the "Fourth International Workshop on the Extension Project for the J-PARC Hadron Experimental Facility (HEF-ex 2024)"
Authors:
P. Achenbach,
K. Aoki,
S. Aoki,
C. Curceanu,
S. Diehl,
T. Doi,
M. Endo,
M. Fujita,
T. Fukuda,
H. Garcia-Tecocoatzi,
L. S. Geng,
T. Gunji,
C. Hanhart,
M. Harada,
T. Harada,
S. Hayakawa,
B. R. He,
E. Hiyama,
R. Honda,
Y. Ichikawa,
M. Isaka,
D. Jido,
A. Jinno,
K. Kamada,
Y. Kamiya
, et al. (36 additional authors not shown)
Abstract:
The mini proceedings of the "Fourth International Workshop on the Extension Project for the J-PARC Hadron Experimental Facility (HEF-ex 2024) [https://kds.kek.jp/event/46965]" held at J-PARC, February 19-21, 2024, are presented. The workshop was devoted to discussing the physics case that connects both the present and the future Hadron Experimental Facility at J-PARC, covering a wide range of topi…
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The mini proceedings of the "Fourth International Workshop on the Extension Project for the J-PARC Hadron Experimental Facility (HEF-ex 2024) [https://kds.kek.jp/event/46965]" held at J-PARC, February 19-21, 2024, are presented. The workshop was devoted to discussing the physics case that connects both the present and the future Hadron Experimental Facility at J-PARC, covering a wide range of topics in flavor, hadron, and nuclear physics related to both experimental and theoretical activities being conducted at the facility.
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Submitted 31 August, 2024;
originally announced September 2024.
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Measurement of the mesonic decay branch of the $\bar{K}\!N\!N$ quasi-bound state
Authors:
T. Yamaga,
S. Ajimura,
H. Asano,
G. Beer,
H. Bhang,
M. Bragadireanu,
P. Buehler,
L. Busso,
M. Cargnelli,
S. Choi,
C. Curceanu,
S. Enomoto,
H. Fujioka,
Y. Fujiwara,
T. Fukuda,
C. Guaraldo,
T. Hashimoto,
R. S. Hayano,
T. Hiraiwa,
M. Iio,
M. Iliescu,
K. Inoue,
Y. Ishiguro,
T. Ishikawa,
S. Ishimoto
, et al. (45 additional authors not shown)
Abstract:
We conducted measurements of $K^- + {^3{\rm He}} \to π\!Y \!N + N'$ reactions using a $1~{\rm GeV}/c$ $K^-$-beam, with the objective of understanding the broad decay width of $\bar{K} \!N \!N$ (approximately twice as broad as that of $Λ(1405)$ considered to be the $\bar{K} \!N$ quasi-bound state). We successfully reproduced distributions of the $π\! Y \! N$ invariant mass and momentum transfer for…
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We conducted measurements of $K^- + {^3{\rm He}} \to π\!Y \!N + N'$ reactions using a $1~{\rm GeV}/c$ $K^-$-beam, with the objective of understanding the broad decay width of $\bar{K} \!N \!N$ (approximately twice as broad as that of $Λ(1405)$ considered to be the $\bar{K} \!N$ quasi-bound state). We successfully reproduced distributions of the $π\! Y \! N$ invariant mass and momentum transfer for $π\! Y \! N$ using model fitting functions for $\bar{K} \!N \!N$ formation and quasi-free $\bar{K}$ absorption (${\rm QF}_{\bar{K}-{\rm abs}}$) processes. The model can describe the experimental data quite well, and four $\bar{K} \! N \! N \to π\! Y \! N $ cross-sections were obtained. The results indicate that mesonic decay is the dominant decay branch of $\bar{K} \! N \! N$. The results also suggest that $Γ_{πΛN} \sim Γ_{πΣN}$, which indicates that the $I_{\bar{K} \! N}=1$ absorption channel, in addition to the $I_{\bar{K} \! N}=0$ absorption channel, substantially contribute to the $\bar{K} \! N \! N$ decay, making the $\bar{K} \! N \! N$ state approximately twice as unstable as $Λ$(1405).
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Submitted 2 June, 2024; v1 submitted 2 April, 2024;
originally announced April 2024.
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Particle Physics at the European Spallation Source
Authors:
H. Abele,
A. Alekou,
A. Algora,
K. Andersen,
S. Baessler,
L. Barron-Palos,
J. Barrow,
E. Baussan,
P. Bentley,
Z. Berezhiani,
Y. Bessler,
A. K. Bhattacharyya,
A. Bianchi,
J. Bijnens,
C. Blanco,
N. Blaskovic Kraljevic,
M. Blennow,
K. Bodek,
M. Bogomilov,
C. Bohm,
B. Bolling,
E. Bouquerel,
G. Brooijmans,
L. J. Broussard,
O. Buchan
, et al. (154 additional authors not shown)
Abstract:
Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world's brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons…
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Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world's brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).
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Submitted 30 January, 2024; v1 submitted 18 November, 2022;
originally announced November 2022.
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Pole position of $Λ(1405)$ measured in $d(K^-,n)πΣ$ reactions
Authors:
J-PARC E31 Collaboration,
:,
S. Aikawa,
S. Ajimura,
T. Akaishi,
H. Asano,
G. Beer,
C. Berucci,
M. Bragadireanu,
P. Buehler,
L. Busso,
M. Cargnelli,
S. Choi,
C. Curceanu,
S. Enomoto,
H. Fujioka,
Y. Fujiwara,
T. Fukuda,
C. Guaraldo,
T. Hashimoto,
R. S. Hayano,
T. Hiraiwa,
M. Iio,
M. Iliescu,
K. Inoue
, et al. (53 additional authors not shown)
Abstract:
We measured a set of $π^\pmΣ^\mp$, $π^0Σ^0$, and $π^-Σ^0$ invariant mass spectra below and above the $\bar{K}N$ mass threshold in $K^-$-induced reactions on deuteron. We deduced the $S$-wave $\bar{K}N\rightarrowπΣ$ and $\bar{K}N\rightarrow\bar{K}N$ scattering amplitudes in the isospin 0 channel in the framework of a $\bar{K}N$ and $πΣ$ coupled channel. We find that a resonance pole corresponding t…
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We measured a set of $π^\pmΣ^\mp$, $π^0Σ^0$, and $π^-Σ^0$ invariant mass spectra below and above the $\bar{K}N$ mass threshold in $K^-$-induced reactions on deuteron. We deduced the $S$-wave $\bar{K}N\rightarrowπΣ$ and $\bar{K}N\rightarrow\bar{K}N$ scattering amplitudes in the isospin 0 channel in the framework of a $\bar{K}N$ and $πΣ$ coupled channel. We find that a resonance pole corresponding to $Λ(1405)$ is located at 1417.7$^{+6.0}_{-7.4}$(fitting errors)$^{+1.1}_{-1.0}$(systematic errors) + $[-26.1^{+6.0}_{-7.9}$(fitting errors)$^{+1.7}_{-2.0}$(systematic errors)]$i$ MeV/$c^2$, closer to the $\bar{K}N$ mass threshold than the value determined by the Particle Data Group.
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Submitted 17 September, 2022;
originally announced September 2022.
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Snowmass Neutrino Frontier: Neutrino Interaction Cross Sections (NF06) Topical Group Report
Authors:
A. B. Balantekin,
S. Gardiner,
K. Mahn,
T. Mohayai,
J. Newby,
V. Pandey,
J. Zettlemoyer,
J. Asaadi,
M. Betancourt,
D. A. Harris,
A. Norrick,
F. Kling,
B. Ramson,
M. C. Sanchez,
T. Fukuda,
M. Wallbank,
M. Wurm
Abstract:
A thorough understanding of neutrino cross sections in a wide range of energies is crucial for the successful execution of the entire neutrino physics program. In order to extract neutrino properties, long-baseline experiments need an accurate determination of neutrino cross sections within their detector(s). Since very few of the needed neutrino cross sections across the energy spectrum are direc…
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A thorough understanding of neutrino cross sections in a wide range of energies is crucial for the successful execution of the entire neutrino physics program. In order to extract neutrino properties, long-baseline experiments need an accurate determination of neutrino cross sections within their detector(s). Since very few of the needed neutrino cross sections across the energy spectrum are directly measured, we emphasize the need for theoretical input and indirect measurements such as electron scattering, which would complement direct measurements. In this report we briefly summarize the current status of our knowledge of the neutrino cross sections and articulate needs of the experiments, ongoing and planned, at energies ranging from CEvNS and supernova neutrino energies to the DUNE and atmospheric neutrino energies.
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Submitted 26 October, 2022; v1 submitted 14 September, 2022;
originally announced September 2022.
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Bubble Chamber Detectors with Light Nuclear Targets: A Snowmass 2021 White Paper
Authors:
Luis Alvarez-Ruso,
Joshua L. Barrow,
Leo Bellantoni,
Minerba Betancourt,
Alan Bross,
Linda Cremonesi,
Eric Dahl,
Kirsty Duffy,
Steven Dytman,
Laura Fields,
Tsutomu Fukuda,
Mikhail Gorchtein,
Richard J. Hill,
Alex Himmel,
Thomas Junk,
Dustin Keller,
Huey-Wen Lin,
Xianguo Lu,
Kendall Mahn,
Aaron S. Meyer,
Jorge G. Morfin,
Jonathan Paley,
Vishvas Pandey,
Gil Paz,
Roberto Petti
, et al. (7 additional authors not shown)
Abstract:
Neutrino cross sections are a critical ingredient in experiments that depend on neutrino scattering to reconstruct event kinematics and infer neutrino characteristics, like NOvA and T2K. An opportunity exists to reduce the 5-10% broad uncertainty on neutrino cross sections by producing more measurements of neutrino scattering from light nuclear targets at the relevant energies. Bubble chambers wit…
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Neutrino cross sections are a critical ingredient in experiments that depend on neutrino scattering to reconstruct event kinematics and infer neutrino characteristics, like NOvA and T2K. An opportunity exists to reduce the 5-10% broad uncertainty on neutrino cross sections by producing more measurements of neutrino scattering from light nuclear targets at the relevant energies. Bubble chambers with light nuclear targets would be ideal for these measurements but the most recent device designed for use with an accelerator neutrino source is at least fifty years old. A new bubble chamber with light nuclear targets could be designed by observing how the technology has progressed for use in dark matter experiments and producing smaller modular devices that use more efficient cooling systems. A smaller modular device could also be designed for deployment to all functioning neutrino beams, but an investigation of the proper operating characteristics is necessary to adapt newer detectors to the structure of contemporary neutrino beams.
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Submitted 21 March, 2022;
originally announced March 2022.
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Recent results and future prospects of kaonic nuclei at J-PARC
Authors:
F. Sakuma,
S. Ajimura,
T. Akaishi,
H. Asano,
M. Bazzi,
G. Beer,
H. Bhang,
M. Bragadireanu,
P. Buehler,
L. Busso,
M. Cargnelli,
S. Choi,
A. Clozza,
C. Curceanu,
S. Enomoto,
H. Fujioka,
Y. Fujiwara,
T. Fukuda,
C. Guaraldo,
T. Hashimoto,
R. S. Hayano,
T. Hiraiwa,
M. Iio,
M. Iliescu,
K. Inoue
, et al. (51 additional authors not shown)
Abstract:
$\bar K$-nuclear bound systems, kaonic nuclei, have been widely discussed as products of the strongly attractive $\bar K N$ interaction in $I = 0$ channels. Recently, we demonstrated that kaonic nuclei can be produced via in-flight $(K^-,N)$ reactions using the low-momentum DC kaon beam at the J-PARC E15 experiment. We observed the simplest kaonic nuclei, $K^-pp…
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$\bar K$-nuclear bound systems, kaonic nuclei, have been widely discussed as products of the strongly attractive $\bar K N$ interaction in $I = 0$ channels. Recently, we demonstrated that kaonic nuclei can be produced via in-flight $(K^-,N)$ reactions using the low-momentum DC kaon beam at the J-PARC E15 experiment. We observed the simplest kaonic nuclei, $K^-pp$, having a much deeper binding energy than normal nuclei. For further studies, we have proposed a series of experimental programs for the systematic investigation of light kaonic nuclei, from $\bar K N$ ($Λ(1405)$) to $\bar K NNNN$. In the new experiment approved as J-PARC E80, we will measure the $\bar K NNN$ ($A=3$) system as a first step toward a comprehensive study.
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Submitted 6 October, 2021;
originally announced October 2021.
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Observation of a $\bar{K}NN$ bound state in the $^3{\rm He} (K^-, Λp)n$ reaction
Authors:
T. Yamaga,
S. Ajimura,
H. Asano,
G. Beer,
H. Bhang,
M. Bragadireanu,
P. Buehler,
L. Busso,
M. Cargnelli,
S. Choi,
C. Curceanu,
S. Enomoto,
H. Fujioka,
Y. Fujiwara,
T. Fukuda,
C. Guaraldo,
T. Hashimoto,
R. S. Hayano,
T. Hiraiwa,
M. Iio,
M. Iliescu,
K. Inoue,
Y. Ishiguro,
T. Ishikawa,
S. Ishimoto
, et al. (44 additional authors not shown)
Abstract:
We have performed an exclusive measurement of the $K^{-}+\! ~^{3}{\rm He} \to Λpn$ reaction at an incident kaon momentum of $1\ {\rm GeV}/c$.In the $Λp$ invariant mass spectrum, a clear peak was observed below the mass threshold of $\bar{K}\!+\!N\!+\!N$, as a signal of the kaonic nuclear bound state, $\bar{K}NN$.The binding energy, decay width, and $S$-wave Gaussian reaction form-factor of this st…
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We have performed an exclusive measurement of the $K^{-}+\! ~^{3}{\rm He} \to Λpn$ reaction at an incident kaon momentum of $1\ {\rm GeV}/c$.In the $Λp$ invariant mass spectrum, a clear peak was observed below the mass threshold of $\bar{K}\!+\!N\!+\!N$, as a signal of the kaonic nuclear bound state, $\bar{K}NN$.The binding energy, decay width, and $S$-wave Gaussian reaction form-factor of this state were observed to be $B_{K} = 42\pm3({\rm stat.})^{+3}_{-4}({\rm syst.})\ {\rm MeV}$, $Γ_{K} = 100\pm7({\rm stat.})^{+19}_{-9}({\rm syst.})\ {\rm MeV}$, and $Q_{K} = 383\pm11({\rm stat.})^{+4}_{-1}({\rm syst.})\ {\rm MeV}/c$, respectively. The total production cross-section of $\bar{K}NN$, determined by its $Λp$ decay mode, was $σ^{tot}_{K} \cdot BR_{Λp} = 9.3\pm0.8({\rm stat.})^{+1.4}_{-1.0}({\rm syst.})\ μ{\rm b}$.We estimated the branching ratio of the $\bar{K}NN$ state to the $Λp$ and $Σ^{0}p$ decay modes as $BR_{Λp}/BR_{Σ^{0}p} \sim 1.7$, by assuming that the physical processes leading to the $ΣN\!N$ final states are analogous to those of $Λpn$.
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Submitted 23 June, 2020;
originally announced June 2020.
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"$\mathbf{{\textit K^-}{\textit p}{\textit p}}$", a ${\overline{K}}$-Meson Nuclear Bound State, Observed in $^{3}{\rm He}({K^-}, Λ p)n$ Reactions
Authors:
J-PARC E15 collaboration,
S. Ajimura,
H. Asano,
G. Beer,
C. Berucci,
H. Bhang,
M. Bragadireanu,
P. Buehler,
L. Busso,
M. Cargnelli,
S. Choi,
C. Curceanu,
S. Enomoto,
H. Fujioka,
Y. Fujiwara,
T. Fukuda,
C. Guaraldo,
T. Hashimoto,
R. S. Hayano,
T. Hiraiwa,
M. Iio,
M. Iliescu,
K. Inoue,
Y. Ishiguro,
T. Ishikawa
, et al. (45 additional authors not shown)
Abstract:
We observed a distinct peak in the $Λp$ invariant mass spectrum of $^{3}{\rm He}(K^-, \, Λp)n$, well below the mass threshold of $m_K + 2 m_p$. By selecting a relatively large momentum-transfer region $q = 350 \sim 650$ MeV/$c$, one can clearly separate the peak from the quasi-free process, $\overline{K}N \rightarrow \overline{K}N$ followed by the non-resonant absorption by the two spectator-nucle…
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We observed a distinct peak in the $Λp$ invariant mass spectrum of $^{3}{\rm He}(K^-, \, Λp)n$, well below the mass threshold of $m_K + 2 m_p$. By selecting a relatively large momentum-transfer region $q = 350 \sim 650$ MeV/$c$, one can clearly separate the peak from the quasi-free process, $\overline{K}N \rightarrow \overline{K}N$ followed by the non-resonant absorption by the two spectator-nucleons $\overline{K}NN \rightarrow ΛN $. We found that the simplest fit to the observed peak gives us a Breit-Wigner pole position at $B_{\rm {\it Kpp}} = 47 \pm 3 \, (stat.) \,^{+3}_{-6} \,(sys.)$ MeV having a width $Γ_{\rm {\it Kpp}} = 115 \pm 7 \, (stat.) \,^{+10}_{-9} \,(sys.)$ MeV, and the $S$-wave Gaussian reaction form-factor parameter $Q_{\rm {\it Kpp}} = 381 \pm 14 \, (stat.)\,^{+57}_{-0} \,(sys.)$ MeV/$c$, as a new form of the nuclear bound system with strangeness -- "$K^-pp$".
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Submitted 25 October, 2018; v1 submitted 30 May, 2018;
originally announced May 2018.
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Missing-mass spectroscopy with the ${}^{6}$Li($π^{-}, K^{+}$)X reaction to search for ${}^{6}_Λ$H
Authors:
R. Honda,
M. Agnello,
J. K. Ahn,
S. Ajimura,
Y. Akazawa,
N. Amano,
K. Aoki,
H. C. Bhang,
N. Chiga,
M. Endo,
P. Evtoukhovitch,
A. Feliciello,
H. Fujioka,
T. Fukuda,
S. Hasegawa,
S. H. Hayakawa,
K. Hosomi,
S. H. Hwang,
Y. Ichikawa,
Y. Igarashi,
K. Imai,
N. Ishibashi,
R. Iwasaki,
C. W. Joo,
R. Kiuchi
, et al. (41 additional authors not shown)
Abstract:
We searched for the bound state of the neutron-rich $Λ$-hypernucleus ${}^{6}_Λ$H, using the ${}^{6}$Li($π^{-}, K^{+}$)X double charge-exchange reaction at a $π^{-}$ beam momentum of 1.2 GeV/c at J-PARC. A total of $1.4 \times 10^{12}$ $π^{-}$ was driven onto a ${}^{6}$Li target of 3.5-g/$\rm cm^2$ thickness. No event was observed below the bound threshold, i.e., the mass of ${}^{4}_Λ$H + 2n, in th…
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We searched for the bound state of the neutron-rich $Λ$-hypernucleus ${}^{6}_Λ$H, using the ${}^{6}$Li($π^{-}, K^{+}$)X double charge-exchange reaction at a $π^{-}$ beam momentum of 1.2 GeV/c at J-PARC. A total of $1.4 \times 10^{12}$ $π^{-}$ was driven onto a ${}^{6}$Li target of 3.5-g/$\rm cm^2$ thickness. No event was observed below the bound threshold, i.e., the mass of ${}^{4}_Λ$H + 2n, in the missing-mass spectrum of the ${}^{6}$Li($π^{-}, K^{+}$)X reaction in the $2^{\circ}$ < $θ_{πK}$ < $20^{\circ}$ angular range. Furthermore, no event was found up to 2.8 MeV/$c^2$ above the bound threshold. We obtained the the double-differential cross section spectra of the ${}^{6}$Li($π^{-}, K^{+}$)X reaction in the angular range of $2^{\circ}$ < $θ_{πK}$ < $14^{\circ}$. An upper limit of 0.56 nb/sr (90% C.L.) was obtained for the production cross section of the ${}^{6}_Λ$H hypernucleus bound state. In addition, not only the bound state region, but also the $Λ$ continuum region and part of the $Σ^{-}$ quasi-free production region of the ${}^{6}$Li($π^{-}, K^{+}$)X reaction, were obtained with high statistics. The present missing-mass spectrum will facilitate the investigation of the $Σ^{-}$-nucleus optical potential for $Σ^{-}$-${}^{5}$He through spectrum shape analysis.
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Submitted 3 March, 2017; v1 submitted 2 March, 2017;
originally announced March 2017.
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Search for Tetraneutron by Pion Double Charge Exchange Reaction at J-PARC
Authors:
Hiroyuki Fujioka,
Tomokazu Fukuda,
Toru Harada,
Emiko Hiyama,
Kenta Itahashi,
Shunsuke Kanatsuki,
Tomofumi Nagae,
Takuya Nanamura,
Takahiro Nishi
Abstract:
Tetraneutron ($^4n$) has come back in the limelight, because of recent observation of a candidate resonant state at RIBF. We propose to investigate the pion double charge exchange (DCX) reaction, i.e. $^4\mathrm{He}(π^- , π^+)$, as an alternative way to populate tetraneutron. An intense $π^-$ beam with the kinetic energy of ~850 MeV, much higher than that in past experiments at LAMPF and TRIUMF, w…
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Tetraneutron ($^4n$) has come back in the limelight, because of recent observation of a candidate resonant state at RIBF. We propose to investigate the pion double charge exchange (DCX) reaction, i.e. $^4\mathrm{He}(π^- , π^+)$, as an alternative way to populate tetraneutron. An intense $π^-$ beam with the kinetic energy of ~850 MeV, much higher than that in past experiments at LAMPF and TRIUMF, will open up a possibility to improve the experimental sensitivity of the formation cross section, which will be much smaller than hitherto known DCX cross sections such as $^9\mathrm{Be}(π^-, π^+)^9\mathrm{He}\ (g.s.)$.
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Submitted 16 February, 2017; v1 submitted 31 August, 2016;
originally announced September 2016.
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Structure near $K^-$+$p$+$p$ threshold in the in-flight $^3$He$(K^-,Λp)n$ reaction
Authors:
J-PARC E15 Collaboration,
:,
Y. Sada,
S. Ajimura,
M. Bazzi,
G. Beer,
H. Bhang,
M. Bragadireanu,
P. Buehler,
L. Busso,
M. Cargnelli,
S. Choi,
C. Curceanu,
S. Enomoto,
D. Faso,
H. Fujioka,
Y. Fujiwara,
T. Fukuda,
C. Guaraldo,
T. Hashimoto,
R. S. Hayano,
T. Hiraiwa,
M. Iio,
M. Iliescu,
K. Inoue
, et al. (48 additional authors not shown)
Abstract:
To search for an S= -1 di-baryonic state which decays to $Λp$, the $ {\rm{}^3He}(K^-,Λp)n_{missing}$ reaction was studied at 1.0 GeV/$c$. Unobserved neutrons were kinematically identified from the missing mass $M_X$ of the $ {\rm{}^3He}(K^-,Λp)X$ reaction in order to have a large acceptance for the $Λpn$ final state. The observed $Λp n$ events, distributed widely over the kinematically allowed reg…
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To search for an S= -1 di-baryonic state which decays to $Λp$, the $ {\rm{}^3He}(K^-,Λp)n_{missing}$ reaction was studied at 1.0 GeV/$c$. Unobserved neutrons were kinematically identified from the missing mass $M_X$ of the $ {\rm{}^3He}(K^-,Λp)X$ reaction in order to have a large acceptance for the $Λpn$ final state. The observed $Λp n$ events, distributed widely over the kinematically allowed region of the Dalitz plot, establish that the major component comes from a three nucleon absorption process. A concentration of events at a specific neutron kinetic energy was observed in a region of low momentum transfer to the $Λp$. To account for the observed peak structure, the simplest S-wave pole was assumed to exist in the reaction channel, having Breit-Wigner form in energy and with a Gaussian form-factor. A minimum $χ^2$ method was applied to deduce its mass $M_X\ =$ 2355 $ ^{+ 6}_{ - 8}$ (stat.) $ \pm 12$ (syst.) MeV/c$^2$, and decay-width $Γ_X\ = $ 110 $ ^{+ 19}_{ - 17}$ (stat.) $ \pm 27$ (syst.) MeV/c$^2$, respectively. The form factor parameter $Q_X \sim$ 400 MeV/$c$ implies that the range of interaction is about 0.5
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Submitted 17 March, 2016; v1 submitted 25 January, 2016;
originally announced January 2016.
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Search for the deeply bound $K^-pp$ state from the semi-inclusive forward-neutron spectrum in the in-flight $K^-$ reaction on helium-3
Authors:
Tadashi Hashimoto,
Shuhei Ajimura,
George Beer,
Hyoungchan Bhang,
Mario Bragadireanu,
Luigi Busso,
Michael Cargnelli,
Seonho Choi,
Catalina Curceanu,
Shun Enomoto,
Diego Faso,
Hiroyuki Fujioka,
Yuya Fujiwara,
Tomokazu Fukuda,
Carlo Guaraldo,
Ryugo S. Hayano,
Toshihiko Hiraiwa,
Masami Iio,
Mihai Iliescu,
Kentaro Inoue,
Yosuke Ishiguro,
Takashi Ishikawa,
Shigeru Ishimoto,
Kenta Itahashi,
Masaaki Iwai
, et al. (42 additional authors not shown)
Abstract:
An experiment to search for the $K^-pp$ bound state was performed via the in-flight $^3$He($K^-,n)$ reaction using 5.3 $\times$ $10^9$ kaons at 1 GeV/$c$ at the J-PARC hadron experimental facility. In the semi-inclusive neutron missing-mass spectrum at $θ_{n}^{lab}=0^\circ$, no significant peak was observed in the region corresponding to $K^-pp$ binding energy larger than 80 MeV, where a bump stru…
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An experiment to search for the $K^-pp$ bound state was performed via the in-flight $^3$He($K^-,n)$ reaction using 5.3 $\times$ $10^9$ kaons at 1 GeV/$c$ at the J-PARC hadron experimental facility. In the semi-inclusive neutron missing-mass spectrum at $θ_{n}^{lab}=0^\circ$, no significant peak was observed in the region corresponding to $K^-pp$ binding energy larger than 80 MeV, where a bump structure has been reported in the $Λp$ final state in different reactions. Assuming the state to be isotropically decaying into $Λp$, mass-dependent upper limits on the production cross section were determined to be 30--180, 70--250, and 100--270 $μ$b/sr, for the natural widths of 20, 60, and 100 MeV, respectively, at 95\% confidence level.
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Submitted 1 May, 2015; v1 submitted 24 August, 2014;
originally announced August 2014.
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Search for $^6_Λ$H hypernucleus by the $^6$Li$(π^-,K^+)$ reaction at $p_{π^-}$ = 1.2 GeV/$c$
Authors:
H. Sugimura,
M. Agnello,
J. K. Ahn,
S. Ajimura,
Y. Akazawa,
N. Amano,
K. Aoki,
H. C. Bhang,
N. Chiga,
M. Endo,
P. Evtoukhovitch,
A. Feliciello,
H. Fujioka,
T. Fukuda,
S. Hasegawa,
S. Hayakawa,
R. Honda,
K. Hosomi,
S. H. Hwang,
Y. Ichikawa,
Y. Igarashi,
K. Imai,
N. Ishibashi,
R. Iwasaki,
C. W. Joo
, et al. (41 additional authors not shown)
Abstract:
We have carried out an experiment to search for a neutron-rich hypernucleus, $^6_Λ$H, by the $^6$Li($π^-,K^+$) reaction at $p_{π^-}$ =1.2 GeV/$c$. The obtained missing mass spectrum with an estimated energy resolution of 3.2 MeV (FWHM) showed no peak structure corresponding to the $^6_Λ$H hypernucleus neither below nor above the $^4_Λ$H$+2n$ particle decay threshold. An upper limit of the producti…
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We have carried out an experiment to search for a neutron-rich hypernucleus, $^6_Λ$H, by the $^6$Li($π^-,K^+$) reaction at $p_{π^-}$ =1.2 GeV/$c$. The obtained missing mass spectrum with an estimated energy resolution of 3.2 MeV (FWHM) showed no peak structure corresponding to the $^6_Λ$H hypernucleus neither below nor above the $^4_Λ$H$+2n$ particle decay threshold. An upper limit of the production cross section for the bound $^6_Λ$H hypernucleus was estimated to be 1.2 nb/sr at 90% confidence level.
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Submitted 5 February, 2014; v1 submitted 22 October, 2013;
originally announced October 2013.
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Hypernuclear spectroscopy of products from 6Li projectiles on a carbon target at 2 AGeV
Authors:
C. Rappold,
E. Kim,
D. Nakajima,
T. R. Saito,
O. Bertini,
S. Bianchin,
V. Bozkurt,
M. Kavatsyuk,
Y. Ma,
F. Maas,
S. Minami,
B. Özel-Tashenov,
K. Yoshida,
P. Achenbach,
S. Ajimura,
T. Aumann,
C. Ayerbe Gayoso,
H. C. Bhang,
C. Caesar,
S. Erturk,
T. Fukuda,
B. Göküzüm,
E. Guliev,
T. Hiraiwa,
J. Hoffmann
, et al. (28 additional authors not shown)
Abstract:
A novel experiment, aiming at demonstrating the feasibility of hypernuclear spectroscopy with heavy-ion beams, was conducted. Using the invariant mass method, the spectroscopy of hypernuclear products of 6Li projectiles on a carbon target at 2 AGeV was performed. Signals of the Λ-hyperon and 3ΛH and 4ΛH hypernuclei were observed for final states of p+π^-, 3He+π^- and 4He+π^-, respectively, with si…
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A novel experiment, aiming at demonstrating the feasibility of hypernuclear spectroscopy with heavy-ion beams, was conducted. Using the invariant mass method, the spectroscopy of hypernuclear products of 6Li projectiles on a carbon target at 2 AGeV was performed. Signals of the Λ-hyperon and 3ΛH and 4ΛH hypernuclei were observed for final states of p+π^-, 3He+π^- and 4He+π^-, respectively, with significance values of 6.7, 4.7 and 4.9σ. By analyzing the proper decay time from secondary vertex distribution with the unbinned maximum likelihood fitting method, their lifetime values were deduced to be $262 ^{+56}_{-43} \pm 45$ ps for Λ, $183 ^{+42}_{-32} \pm 37$ ps for 3ΛH, and $140 ^{+48}_{-33}\pm 35 $ ps for 4ΛH.
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Submitted 22 May, 2013; v1 submitted 21 May, 2013;
originally announced May 2013.
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Automatic scanning of nuclear emulsions with wide-angle acceptance for nuclear fragment detection
Authors:
T. Fukuda,
S. Fukunaga,
H. Ishida,
K. Kodama,
T. Matsuo,
S. Mikado,
S. Ogawa,
H. Shibuya,
J. Sudo
Abstract:
Nuclear emulsion, a tracking detector with sub-micron position resolution, has played a successful role in the field of particle physics and the analysis speed has been substantially improved by the development of automated scanning systems. This paper describes a newly developed automated scanning system and its application to the analysis of nuclear fragments emitted almost isotropically in nucl…
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Nuclear emulsion, a tracking detector with sub-micron position resolution, has played a successful role in the field of particle physics and the analysis speed has been substantially improved by the development of automated scanning systems. This paper describes a newly developed automated scanning system and its application to the analysis of nuclear fragments emitted almost isotropically in nuclear evaporation. This system is able to recognize tracks of nuclear fragments up to |tanθ|< 3.0 (where θ is the track angle with respect to the perpendicular to the emulsion film), while existing systems have an angular acceptance limited to |tanθ|< 0.6. The automatic scanning for such a large angle track in nuclear emulsion is the first trial. Furthermore the track recognition algorithm is performed by a powerful Graphics Processing Unit (GPU) for the first time. This GPU has a sufficient computing power to process large area scanning data with a wide angular acceptance and enough flexibility to allow the tuning of the recognition algorithm. This new system will in particular be applied in the framework of the OPERA experiment : the background in the sample of tau decay candidates due to hadronic interactions will be reduced by a better detection of the emitted nuclear fragments.
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Submitted 9 January, 2013;
originally announced January 2013.
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Search for a bound state of kaon and pion
Authors:
T. Kishimoto,
F. Khanam,
T. Hayakawa,
S. Ajimura,
T. Itabashi,
K. Matsuoka,
S. Minami,
Y. Mitoma,
A. Sakaguchi,
Y. Shimizu,
K. Terai,
T. Sato,
H. Noumi,
M. Sekimoto,
H. Takahashi,
T. Fukuda,
W. Imoto,
Y. Mizoi
Abstract:
We have searched for a bound state of kaon and pion denoted by $X$. The $X$ was conjectured to explain the so-called $Θ^+$ resonance as a bound state of kaon, pion and nucleon. This model explains almost all properties of the $Θ^+$, however, the model works only if the $K π$ interaction is strongly attractive. It is so strong that it could make a bound state $X$. Here we report a result of the sea…
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We have searched for a bound state of kaon and pion denoted by $X$. The $X$ was conjectured to explain the so-called $Θ^+$ resonance as a bound state of kaon, pion and nucleon. This model explains almost all properties of the $Θ^+$, however, the model works only if the $K π$ interaction is strongly attractive. It is so strong that it could make a bound state $X$. Here we report a result of the search for the $X$ by using the $K^+ + N \rightarrow X^+ + N$ reaction at P$_K\sim$ 1.2 GeV/c. The $X^+ \rightarrow K^+ γγ$ decay produces $K^+$ in momentum region where other processes cannot fill. We observed signature of the $X^+$ with statistical significance of 2 $σ$. Production cross section of $X$ with respect to that of $π^0$ is 1$\pm$0.5% if we take it as an evidence and 1.5% if we set an upper limit.
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Submitted 27 September, 2012;
originally announced September 2012.
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The K1.8BR spectrometer system at J-PARC
Authors:
Keizo Agari,
Shuhei Ajimura,
George Beer,
Hyoungchan Bhang,
Mario Bragadireanu,
Paul Buehler,
Luigi Busso,
Michael Cargnelli,
Seonho Choi,
Catalina Curceanu,
Shun Enomoto,
Diego Faso,
Hiroyuki Fujioka,
Yuya Fujiwara,
Tomokazu Fukuda,
Carlo Guaraldo,
Tadashi Hashimoto,
Ryugo S. Hayano,
Toshihiko Hiraiwa,
Erina Hirose,
Masaharu Ieiri,
Masami Iio,
Mihai Iliescu,
Kentaro Inoue,
Yosuke Ishiguro
, et al. (60 additional authors not shown)
Abstract:
A new spectrometer system was designed and constructed at the secondary beam line K1.8BR in the hadron hall of J-PARC to investigate $\bar K N$ interactions and $\bar K$-nuclear bound systems. The spectrometer consists of a high precision beam line spectrometer, a liquid $^3$He/$^4$He/D$_2$ target system, a Cylindrical Detector System that surrounds the target to detect the decay particles from th…
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A new spectrometer system was designed and constructed at the secondary beam line K1.8BR in the hadron hall of J-PARC to investigate $\bar K N$ interactions and $\bar K$-nuclear bound systems. The spectrometer consists of a high precision beam line spectrometer, a liquid $^3$He/$^4$He/D$_2$ target system, a Cylindrical Detector System that surrounds the target to detect the decay particles from the target region, and a neutron time-of-flight counter array located $\sim$15 m downstream from the target position. Details of the design, construction, and performance of the detector components are described.
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Submitted 21 November, 2012; v1 submitted 1 June, 2012;
originally announced June 2012.
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Production of Neutron-Rich Lambda Hypernuclei at J-PARC
Authors:
A. Sakaguchi,
S. Ajimura,
H. Bhang,
L. Busso,
M. Endo,
D. Faso,
T. Fukuda,
T. Kishimoto,
K. Matsuda,
K. Matsuoka,
Y. Mizoi,
O. Morra,
H. Noumi,
P. K. Saha,
C. Samanta,
Y. Shimizu,
T. Takahashi,
T. N. Takahashi,
K. Yoshida
Abstract:
We discuss the usefulness of the double charge-exchange reactions (DCX) for the production of the neutron-rich Lambda-hypernuclei. We believe the (pi-,K+) reaction is one of the most promising DCX reactions, and propose to produce the neutron-rich Lambda-hypernuclei, 6(Lambda)H and 9(Lambda)He, at the J-PARC 50 GeV PS by the reaction (J-PARC E10 experiment). The design of the experiment is prese…
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We discuss the usefulness of the double charge-exchange reactions (DCX) for the production of the neutron-rich Lambda-hypernuclei. We believe the (pi-,K+) reaction is one of the most promising DCX reactions, and propose to produce the neutron-rich Lambda-hypernuclei, 6(Lambda)H and 9(Lambda)He, at the J-PARC 50 GeV PS by the reaction (J-PARC E10 experiment). The design of the experiment is presented.
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Submitted 1 April, 2009;
originally announced April 2009.
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The HypHI project: Hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and FAIR
Authors:
S. Bianchin,
P. Achenbach,
S. Ajimura,
O. Borodina,
T. Fukuda,
J. Hoffmann,
M. Kavatsyuk,
K. Koch,
T. Koike,
N. Kurz,
F. Maas,
S. Minami,
Y. Mizoi,
T. Nagae,
D. Nakajima,
A. Okamura,
W. Ott,
B. Özel,
J. Pochodzalla,
C. Rappold,
T. R. Saito,
A. Sakaguchi,
M. Sako,
M. Sekimoto,
H. Sugimura
, et al. (4 additional authors not shown)
Abstract:
The HypHI collaboration aims to perform a precise hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and fAIR in order to study hypernuclei at extreme isospin, especially neutron rich hypernuclei to look insight hyperon-nucleon interactions in the neutron rich medium, and hypernuclear magnetic moments to investigate baryon properties in the nuclei. We are current…
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The HypHI collaboration aims to perform a precise hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and fAIR in order to study hypernuclei at extreme isospin, especially neutron rich hypernuclei to look insight hyperon-nucleon interactions in the neutron rich medium, and hypernuclear magnetic moments to investigate baryon properties in the nuclei. We are currently preparing for the first experiment with $^6$Li and $^{12}$C beams at 2 AGeV to demonstrate the feasibility of a precise hypernuclear spectroscopy by identifying $^{3}_Λ$H, $^{4}_Λ$H and $^{5}_Λ$He. The first physics experiment on these hypernuclei is planned for 2009. In the present document, an overview of the HypHI project and the details of this first experiment will be discussed.
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Submitted 22 December, 2008;
originally announced December 2008.
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Measurements of total and partial charge-changing cross sections for 200-400 MeV/nucleon 12C in water and polycarbonate
Authors:
T. Toshito,
K. Kodama,
L. Sihver,
K. Yusa,
M. Ozaki,
K. Amako,
S. Kameoka,
K. Murakami,
T. Sasaki,
S. Aoki,
T. Ban,
T. Fukuda,
M. Komatsu,
H. Kubota,
N. Naganawa,
T. Nakamura,
T. Nakano,
M. Natsume,
K. Niwa,
S. Takahashi,
J. Yoshida,
H. Yoshida,
M. Kanazawa,
N. Kanematsu,
M. Komori
, et al. (7 additional authors not shown)
Abstract:
We have studied charged nuclear fragments produced by 200 - 400 MeV/nucleon carbon ions, interacting with water and polycarbonate, using a newly developed emulsion detector. Total and partial charge-changing cross sections for the production of B, Be, and Li fragments were measured and compared with both previously published measurements, and model predictions. This study is of importance for va…
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We have studied charged nuclear fragments produced by 200 - 400 MeV/nucleon carbon ions, interacting with water and polycarbonate, using a newly developed emulsion detector. Total and partial charge-changing cross sections for the production of B, Be, and Li fragments were measured and compared with both previously published measurements, and model predictions. This study is of importance for validating and improving carbon ion therapy treatment planning systems, and for estimating the radiological risks for personnel on space missions, since carbon is a significant component of the Galactic Cosmic Rays.
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Submitted 27 March, 2007;
originally announced March 2007.
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Coincidence Measurement of the Nonmesonic Weak Decay of ^{12}_{Lambda}C
Authors:
M. J. Kim,
S. Ajimura,
K. Aoki,
A. Banu,
H. Bhang,
T. Fukuda,
O. Hashimoto,
J. I. Hwang,
S. Kameoka,
B. H. Kang,
E. H. Kim,
J. H. Kim,
T. Maruta,
Y. Miura,
Y. Miyake,
T. Nagae,
M. Nakamura,
S. N. Nakamura,
H. Noumi,
S. Okada,
Y. Okayasu,
H. Outa,
H. Park,
P. K. Saha,
Y. Sato
, et al. (9 additional authors not shown)
Abstract:
We have measured the angular correlation of the pair nucleons np and nn emitted from the nonmesonic weak decay (NMWD) of ^{12}_{Lambda}C produced via the (pi^+,K^+) reaction in coincidence measurement. The Lambda p -> np and Lambda n -> nn modes were clearly identified by measuring the back-to-back correlation of the emitted nucleon pairs which is the characteristic of two-body kinematics. From…
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We have measured the angular correlation of the pair nucleons np and nn emitted from the nonmesonic weak decay (NMWD) of ^{12}_{Lambda}C produced via the (pi^+,K^+) reaction in coincidence measurement. The Lambda p -> np and Lambda n -> nn modes were clearly identified by measuring the back-to-back correlation of the emitted nucleon pairs which is the characteristic of two-body kinematics. From the measured nucleon pair numbers N_{nn} and N_{np}, the ratio Gamma_n/Gamma_p of the partial decay widths Gamma_n(Lambda n -> nn) and Gamma_p(Lambda p -> np) of ^{12}_{Lambda}C was extracted to be 0.51+-0.13(stat) +- 0.05(syst); this result is almost free from the ambiguity due to the nuclear final state interaction and 3-body decay process, which were inherent in the previous results. The obtained Gamma_n/Gamma_p ratio of ^{12}_{Lambda}C (p-shell) is close to that of ^5_{Lambda}He (s-shell). The results are consistent with those of recent theoretical calculations.
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Submitted 17 July, 2006; v1 submitted 21 January, 2006;
originally announced January 2006.
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Exclusive proton asymmetry measurement in non-mesonic weak decay of polarized 5_Lambda_He
Authors:
T. Maruta,
S. Ajimura,
K. Aoki,
A. Banu,
H. Bhang,
T. Fukuda,
O. Hashimoto,
J. I. Hwang,
S. Kameoka,
B. H. Kang,
E. H. Kim,
J. H. Kim,
M. J. Kim,
Y. Miura,
Y. Miyake,
T. Nagae,
M. Nakamura,
S. N. Nakamura,
H. Noumi,
S. Okada,
Y. Okayasu,
H. Outa,
H. Park,
P. K. Saha,
Y. Sato
, et al. (8 additional authors not shown)
Abstract:
The asymmetry parameter alpha_p^NM for a proton exclusively emitted in the Lambda p -> np process was, for the first time, measured in the non-mesonic weak decay of a polarized 5_La,bda_He hypernucleus by selecting the proton-neutron pairs emitted in the back-to-back kinematics. The highly polarized 5_Lambda_He was abundantly produced with the (pi+,K+) reaction at 1.05GeV/c in the scattering ang…
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The asymmetry parameter alpha_p^NM for a proton exclusively emitted in the Lambda p -> np process was, for the first time, measured in the non-mesonic weak decay of a polarized 5_La,bda_He hypernucleus by selecting the proton-neutron pairs emitted in the back-to-back kinematics. The highly polarized 5_Lambda_He was abundantly produced with the (pi+,K+) reaction at 1.05GeV/c in the scattering angular range of +-15$ degrees. The obtained value alpha_p^NM=0.31+-0.22, as well as that for inclusive protons, alpha_p^NM=0.11+-0.08+-0.04, largely contradicts recent theoretical values of around -0.6, although these calculations well reproduce the branching ratios of non-mesonic weak decay.
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Submitted 12 September, 2005;
originally announced September 2005.
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Exclusive Measurement of the Nonmesonic Weak Decay of ^{5}_ΛHe Hypernucleus
Authors:
B. H. Kang,
S. Ajimura,
K. Aoki,
A. Banu,
H. Bhang,
T. Fukuda,
O. Hashimoto,
J. I. Hwang,
S. Kameoka,
E. H. Kim,
J. H. Kim,
M. J. Kim,
T. Maruta,
Y. Miura,
Y. Miyake,
T. Nagae,
M. Nakamura,
S. N. Nakamura,
H. Noumi,
S. Okada,
Y. Okayasu,
H. Outa,
H. Park,
P. K. Saha,
Y. Sato
, et al. (8 additional authors not shown)
Abstract:
We performed a coincidence measurement of two nucleons emitted from the nonmesonic weak decay (NMWD) of ^{5}_ΛHe formed via the ^{6}Li(π^+,K^+) reaction. The energies of two nucleons and the pair number distributions in the opening angle between them were measured. In both np and nn pairs, we observed a clean back-to-back correlation coming from the two-body decay of Λp --> n p and Λn --> n n, r…
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We performed a coincidence measurement of two nucleons emitted from the nonmesonic weak decay (NMWD) of ^{5}_ΛHe formed via the ^{6}Li(π^+,K^+) reaction. The energies of two nucleons and the pair number distributions in the opening angle between them were measured. In both np and nn pairs, we observed a clean back-to-back correlation coming from the two-body decay of Λp --> n p and Λn --> n n, respectively. The ratio of the nucleon pair numbers was N_{nn}/N_{np}=0.45 \pm 0.11(stat)\pm 0.03(syst) in the kinematic region of cos(theta_{NN}) < -0.8. Since each decay mode was exclusively detected, the measured ratio should be close to the ratio of Γ(Λp --> np)/Γ(Λn --> nn).
The ratio is consistent with recent theoretical calculations based on the heavy meson/direct quark exchange picture.
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Submitted 1 December, 2005; v1 submitted 11 September, 2005;
originally announced September 2005.
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Measurement of the Xi-p Scattering Cross Sections at Low Energy
Authors:
J. K. Ahn,
S. Aoki,
K. S. Chung,
M. S. Chung,
H. Enyo,
T. Fukuda,
H. Funahashi,
Y. Goto,
A. Higashi,
M. Ieiri,
T. Iijima,
M. Iinuma,
K. Imai,
Y. Itow,
J. M. Lee,
S. Makino,
A. Masaike,
Y. Matsuda,
Y. Matsuyama,
S. Mihara,
C. Nagoshi,
I. Nomura,
I. S. Park,
N. Saito,
M. Sekimoto
, et al. (12 additional authors not shown)
Abstract:
In this paper we report cross-section measurements for $Ξ^-p$ elastic and inelastic scatterings at low energy using a scintillating fiber active target. Upper limit on the total cross-section for the elastic scattering was found to be 24 mb at 90% confidence level, and the total cross section for the $Ξ^-p\toΛΛ$ reaction was found to be $4.3^{+6.3}_{-2.7}$ mb. We compare the results with current…
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In this paper we report cross-section measurements for $Ξ^-p$ elastic and inelastic scatterings at low energy using a scintillating fiber active target. Upper limit on the total cross-section for the elastic scattering was found to be 24 mb at 90% confidence level, and the total cross section for the $Ξ^-p\toΛΛ$ reaction was found to be $4.3^{+6.3}_{-2.7}$ mb. We compare the results with currently competing theoretical estimates.
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Submitted 8 February, 2005;
originally announced February 2005.
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Nucleon-nucleon coincidence measurement in the non-mesonic weak decay of 5_Lambda-He and 12_Lambda-C hypernuclei
Authors:
S. Okada,
S. Ajimura,
K. Aoki,
A. Banu,
H. C. Bhang,
T. Fukuda,
O. Hashimoto,
J. I. Hwang,
S. Kameoka,
B. H. Kang,
E. H. Kim,
J. H. Kim,
M. J. Kim,
T. Maruta,
Y. Miura,
Y. Miyake,
T. Nagae,
M. Nakamura,
S. N. Nakamura,
H. Noumi,
Y. Okayasu,
H. Outa,
H. Park,
P. K. Saha,
Y. Sato
, et al. (8 additional authors not shown)
Abstract:
We have measured both yields of neutron-proton and neutron-neutron pairs emitted from the non-mesonic weak decay process of 5_Lambda-He and 12_Lambda-C hypernuclei produced via the (pi^+,K^+) reaction for the first time. We observed clean back-to-back correlation of the np- and nn-pairs in the coincidence spectra for both hypernuclei. The ratio of those back-to-back pair yields, Nnn / Nnp, must…
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We have measured both yields of neutron-proton and neutron-neutron pairs emitted from the non-mesonic weak decay process of 5_Lambda-He and 12_Lambda-C hypernuclei produced via the (pi^+,K^+) reaction for the first time. We observed clean back-to-back correlation of the np- and nn-pairs in the coincidence spectra for both hypernuclei. The ratio of those back-to-back pair yields, Nnn / Nnp, must be close to the ratio of neutron- and proton-induced decay widths of the decay, Gn(Lambda n -> nn)/Gp(Lambda p -> np). The obtained ratios for each hypernuclei support recent calculations based on short-range interactions.
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Submitted 9 November, 2004;
originally announced November 2004.
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Neutron and proton energy spectra from the non-mesonic weak decays of 5_Lambda-He and 12_Lambda-C
Authors:
S. Okada,
S. Ajimura,
K. Aoki,
A. Banu,
H. C. Bhang,
T. Fukuda,
O. Hashimoto,
J. I. Hwang,
S. Kameoka,
B. H. Kang,
E. H. Kim,
J. H. Kim,
M. J. Kim,
T. Maruta,
Y. Miura,
Y. Miyake,
T. Nagae,
M. Nakamura,
S. N. Nakamura,
H. Noumi,
Y. Okayasu,
H. Outa,
H. Park,
P. K. Saha,
Y. Sato
, et al. (8 additional authors not shown)
Abstract:
We have simultaneously measured the energy spectra of neutrons and protons emitted in the non-mesonic weak decays of 5_Lambda-He and 12_Lambda-C hypernuclei produced via the (pi^+,k^+) reaction with much higher statistics over those of previous experiments. The neutron-to-proton yield ratios for both hypernuclei at a high energy threshold (60 MeV) were approximately equal to two, which suggests…
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We have simultaneously measured the energy spectra of neutrons and protons emitted in the non-mesonic weak decays of 5_Lambda-He and 12_Lambda-C hypernuclei produced via the (pi^+,k^+) reaction with much higher statistics over those of previous experiments. The neutron-to-proton yield ratios for both hypernuclei at a high energy threshold (60 MeV) were approximately equal to two, which suggests that the ratio of the neutron- and proton-induced decay channels, Gn(Lambda n -> nn)/Gp(Lambda p -> np), is about 0.5. In the neutron energy spectra, we found that the yield of the low-energy component is unexpectedly large, even for 5_Lambda-He.
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Submitted 18 June, 2004;
originally announced June 2004.
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Study of the Sigma-nucleus potential by the (pi^-,K^+) reaction on medium-to-heavy nuclear targets
Authors:
P. K. Saha,
H. Noumi,
D. Abe,
S. Ajimura,
K. Aoki,
H. C. Bhang,
K. Dobashi,
T. Endo,
Y. Fujii,
T. Fukuda,
H. C. Guo,
O. Hashimoto,
H. Hotchi,
K. Imai,
E. H. Kim,
J. H. Kim,
T. Kishimoto,
A. Krutenkova,
K. Maeda,
T. Nagae,
M Nakamura,
H. Outa,
T. Saito,
A. Sakaguchi,
Y. Sato
, et al. (12 additional authors not shown)
Abstract:
In order to study the Sigma-nucleus optical potential, we measured inclusive (pi^-,K^+) spectra on medium-to-heavy nuclear targets: CH_2, Si, Ni, In and Bi. The CH_2 target was used to calibrate the excitation energy scale by using the elementary process p + pi^- -> K^+ + Sigma^-, where the C spectrum was also extracted. The calibration was done with +-0.1 MeV precision. The angular distribution…
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In order to study the Sigma-nucleus optical potential, we measured inclusive (pi^-,K^+) spectra on medium-to-heavy nuclear targets: CH_2, Si, Ni, In and Bi. The CH_2 target was used to calibrate the excitation energy scale by using the elementary process p + pi^- -> K^+ + Sigma^-, where the C spectrum was also extracted. The calibration was done with +-0.1 MeV precision. The angular distribution of the elementary cross section was measured, and agreed well with the previous bubble chamber data, but with better statistics, and the magnitudes of the cross sections of the measured inclusive (pi^-,K^+) spectra were also well calibrated. All of the inclusive spectra were found to be similar in shape at a region near to the Sigma^- binding energy threshold, showing a weak mass-number dependence on the magnitude of the cross section. The measured spectra were compared with a theoretical calculation performed within the framework of the Distorted Wave Impulse Approximation (DWIA). It has been demonstrated that a strongly repulsive \sig-nucleus potential with a non-zero size of the imaginary part is required to reproduce the shape of the measured spectra.
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Submitted 26 May, 2004;
originally announced May 2004.
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Measurement of the $π^-$ decay width of $^5_Λ$He
Authors:
S. Kameoka,
S. Ajimura,
K. Aoki,
A. Banu,
H. C. Bhang,
T. Fukuda,
O. Hashimoto,
J. I. Hwang,
B. H. Kang,
E. H. Kim,
J. H. Kim,
M. J. Kim,
T. Maruta,
Y. Miura,
Y. Miyake,
T. Nagae,
M. Nakamura,
S. N. Nakamura,
H. Noumi,
S. Okada,
Y. Okayasu,
H. Outa,
H. Park,
P. K. Saha,
Y. Sato
, et al. (8 additional authors not shown)
Abstract:
We have precisely measured $Λ\to pπ^-$ decay width of \5LHe and demonstrated significantly larger $α$ -$Λ$ overlap than expected from the central repulsion $α$-$Λ$ potential, which is derived from YNG Λ$-nucleon interaction.
We have precisely measured $Λ\to pπ^-$ decay width of \5LHe and demonstrated significantly larger $α$ -$Λ$ overlap than expected from the central repulsion $α$-$Λ$ potential, which is derived from YNG Λ$-nucleon interaction.
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Submitted 27 February, 2004;
originally announced February 2004.
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pi^0 decay branching ratios of 5_Lambda-He and 12_Lambda-C hypernuclei
Authors:
S. Okada,
S. Ajimura,
K. Aoki,
A. Banu,
H. C. Bhang,
T. Fukuda,
O. Hashimoto,
J. I. Hwang,
S. Kameoka,
B. H. Kang,
E. H. Kim,
J. H. Kim,
M. J. Kim,
T. Maruta,
Y. Miura,
Y. Miyake,
T. Nagae,
M. Nakamura,
S. N. Nakamura,
H. Noumi,
Y. Okayasu,
H. Outa,
H. Park,
P. K. Saha,
Y. Sato
, et al. (8 additional authors not shown)
Abstract:
We precisely measured pi^0 branching ratios of 5_Lambda-He and 12_Lambda-C hypernuclei produced via (pi^+,k^+) reaction. Using these pi^0 branching ratios with the pi^- branching ratios and the lifetimes, we obtained the pi^0 decay widths and the non-mesonic weak decay widths at high statistics with the accuracy of ~5 % (stat) for both hypernuclei.
We precisely measured pi^0 branching ratios of 5_Lambda-He and 12_Lambda-C hypernuclei produced via (pi^+,k^+) reaction. Using these pi^0 branching ratios with the pi^- branching ratios and the lifetimes, we obtained the pi^0 decay widths and the non-mesonic weak decay widths at high statistics with the accuracy of ~5 % (stat) for both hypernuclei.
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Submitted 26 February, 2004;
originally announced February 2004.
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Proton asymmetry in non-mesonic weak decay of light hypernuclei
Authors:
T. Maruta,
S. Ajimura,
K. Aoki,
A. Banu,
H. Bhang,
T. Fukuda,
O. Hashimoto,
J. I. Hwang,
S. Kameoka,
B. H. Kang,
E. H. Kim,
J. H. Kim,
M. J. Kim,
Y. Miura,
Y. Miyake,
T. Nagae,
M. Nakamura,
S. N. Nakamura,
H. Noumi,
S. Okada,
Y. Okayasu,
H. Outa,
H. Park,
P. K. Saha,
Y. Sato
, et al. (8 additional authors not shown)
Abstract:
We have obtained the decay asymmetry parameters in non-mesonic weak decay of polarized Lambda-hypernuclei by measuring the proton asymmetry. The polarized Lambda-hypernuclei, 5_Lambda-He, 12_Lambda-C, and 11_Lambda-B, were produced in high statistics via the (pi^+,k^+) reaction at 1.05 GeV/c in the forward angles. Preliminary analysis shows that the decay asymmetry parameters are very small for…
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We have obtained the decay asymmetry parameters in non-mesonic weak decay of polarized Lambda-hypernuclei by measuring the proton asymmetry. The polarized Lambda-hypernuclei, 5_Lambda-He, 12_Lambda-C, and 11_Lambda-B, were produced in high statistics via the (pi^+,k^+) reaction at 1.05 GeV/c in the forward angles. Preliminary analysis shows that the decay asymmetry parameters are very small for these s-shell and p-shell hypernuclei.
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Submitted 24 February, 2004;
originally announced February 2004.