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Tensor Decomposition for Energy-Momentum Correlation Functions
Authors:
Guy D. Moore,
Jonas Winter
Abstract:
We establish the general functional form of the energy-momentum-tensor two-point function in Euclidean coordinate space at zero and finite temperature. The full correlation function is first decomposed into its fundamental tensorial structures based on the remaining rotational symmetry. We use energy-momentum conservation to derive differential relations between the resulting component functions.…
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We establish the general functional form of the energy-momentum-tensor two-point function in Euclidean coordinate space at zero and finite temperature. The full correlation function is first decomposed into its fundamental tensorial structures based on the remaining rotational symmetry. We use energy-momentum conservation to derive differential relations between the resulting component functions. Using these constraints, the full set of component functions of the correlator can finally be represented in the form of a smaller set of spectral functions. Finally, we show how to use these techniques for more efficient future lattice investigations.
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Submitted 9 June, 2026;
originally announced June 2026.
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Theory uncertainties of the irreducible background to VBF Higgs production
Authors:
Xuan Chen,
Silvia Ferrario Ravasio,
Yacine Haddad,
Stefan Höche,
Joey Huston,
Tomas Jezo,
Jia-Sheng Liu,
Christian T. Preuss,
Ahmed Tarek,
Jan Winter
Abstract:
Higgs boson production through gluon fusion in association with two jets is an irreducible background to Higgs boson production through vector boson fusion, one of the most important channels for analyzing and understanding the Higgs boson properties at the Large Hadron Collider. Despite a range of available simulation tools, precise predictions for the corresponding final states are notoriously h…
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Higgs boson production through gluon fusion in association with two jets is an irreducible background to Higgs boson production through vector boson fusion, one of the most important channels for analyzing and understanding the Higgs boson properties at the Large Hadron Collider. Despite a range of available simulation tools, precise predictions for the corresponding final states are notoriously hard to achieve. Using state-of-the-art fixed-order calculations as the baseline for a comparison, we perform a detailed study of similarities and differences in existing event generators. We provide consistent setups for the simulations that can be used to obtain identical parametric precision in various programs used by experiments. We find that NLO calculations for the two-jet final state are essential to achieve reliable predictions.
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Submitted 16 February, 2026; v1 submitted 12 September, 2025;
originally announced September 2025.
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Sensitivity to $\mathcal{CP}$-violating effective couplings in the top-Higgs sector
Authors:
Víctor Miralles,
Yvonne Peters,
Eleni Vryonidou,
Joshua K. Winter
Abstract:
The observed baryon asymmetry of the Universe requires new sources of charge-parity ($\mathcal{CP}$) violation beyond those in the Standard Model. In this work, we investigate $\mathcal{CP}$-violating effects in the top-Higgs sector using the Standard Model Effective Field Theory (SMEFT) framework. Focusing on top-pair production in association with a Higgs boson and single top-Higgs associated pr…
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The observed baryon asymmetry of the Universe requires new sources of charge-parity ($\mathcal{CP}$) violation beyond those in the Standard Model. In this work, we investigate $\mathcal{CP}$-violating effects in the top-Higgs sector using the Standard Model Effective Field Theory (SMEFT) framework. Focusing on top-pair production in association with a Higgs boson and single top-Higgs associated production at the LHC, we study $\mathcal{CP}$ violation in the top-Higgs Yukawa coupling and other Higgs and top interactions entering these processes. By analysing $\mathcal{CP}$-sensitive differential observables and asymmetries, we provide direct constraints on $\mathcal{CP}$-violating interactions in the top-Higgs sector. Our analysis demonstrates how combining $t\bar{t}h$ and $thj$ production can disentangle the real and imaginary components of the top-Yukawa coupling, offering valuable insights into potential sources of $\mathcal{CP}$ violation. The sensitivity of these observables to SMEFT operators provides model-independent constraints on the parameter space, advancing the search for new physics in the top-Higgs sector.
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Submitted 9 June, 2025; v1 submitted 13 December, 2024;
originally announced December 2024.
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Les Houches 2023: Physics at TeV Colliders: Standard Model Working Group Report
Authors:
J. Andersen,
B. Assi,
K. Asteriadis,
P. Azzurri,
G. Barone,
A. Behring,
A. Benecke,
S. Bhattacharya,
E. Bothmann,
S. Caletti,
X. Chen,
M. Chiesa,
A. Cooper-Sarkar,
T. Cridge,
A. Cueto Gomez,
S. Datta,
P. K. Dhani,
M. Donega,
T. Engel,
S. Ferrario Ravasio,
S. Forte,
P. Francavilla,
M. V. Garzelli,
A. Ghira,
A. Ghosh
, et al. (59 additional authors not shown)
Abstract:
This report presents a short summary of the activities of the "Standard Model" working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 12-30 June, 2023).
This report presents a short summary of the activities of the "Standard Model" working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 12-30 June, 2023).
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Submitted 2 June, 2024;
originally announced June 2024.
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CTEQ-TEA parton distribution functions with intrinsic charm
Authors:
Marco Guzzi,
Tie-Jiun Hou,
Sayipjamal Dulat,
Jun Gao,
Joey Huston,
Pavel Nadolsky,
Carl Schmidt,
Jan Winter,
Keping Xie,
C. -P. Yuan
Abstract:
The possibility of a (sizable) nonperturbative contribution to the charm parton distribution function (PDF) in a nucleon is investigated together with theoretical issues arising in its interpretation. Results from the global PDF analysis are presented. The separation of the universal component of the nonperturbative charm from the rest of the radiative contributions is discussed and the potential…
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The possibility of a (sizable) nonperturbative contribution to the charm parton distribution function (PDF) in a nucleon is investigated together with theoretical issues arising in its interpretation. Results from the global PDF analysis are presented. The separation of the universal component of the nonperturbative charm from the rest of the radiative contributions is discussed and the potential impact of a nonperturbative charm PDF on LHC scattering processes is illustrated. An estimate of nonperturbative charm magnitude in the CT14 and CT14HERA2 global QCD analyses at the next-to-next-to leading order (NNLO) in the QCD coupling strength is given by including the latest experimental data from HERA and the Large Hadron Collider (LHC). A comparison between different models of intrinsic charm is shown and prospects for standard candle observables at the LHC are illustrated.
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Submitted 29 September, 2018;
originally announced October 2018.
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NLO and off-shell effects in top quark mass determinations
Authors:
G. Heinrich,
A. Maier,
R. Nisius,
J. Schlenk,
M. Schulze,
L. Scyboz,
J. Winter
Abstract:
We study the impact of different theoretical descriptions of top quark pair production on top quark mass measurements in the di-lepton channel. To this aim, the full NLO corrections to $pp\rightarrow W^+W^-b\bar b\rightarrow (e^+ ν_e)\,(μ^- \barν_μ)\,b\bar b$ production are compared to calculations in the narrow width approximation, where the production of a top quark pair is calculated at NLO and…
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We study the impact of different theoretical descriptions of top quark pair production on top quark mass measurements in the di-lepton channel. To this aim, the full NLO corrections to $pp\rightarrow W^+W^-b\bar b\rightarrow (e^+ ν_e)\,(μ^- \barν_μ)\,b\bar b$ production are compared to calculations in the narrow width approximation, where the production of a top quark pair is calculated at NLO and combined with three different descriptions of the top quark decay: leading order, next-to-leading order and via a parton shower. The different theory predictions then enter the calibration of template fit functions, which are used for a fit to pseudo-data. The offsets in the top quark mass resulting from the fits based on the various theoretical descriptions are determined.
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Submitted 7 August, 2018; v1 submitted 25 September, 2017;
originally announced September 2017.
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CT14 Intrinsic Charm Parton Distribution Functions from CTEQ-TEA Global Analysis
Authors:
Tie-Jiun Hou,
Sayipjamal Dulat,
Jun Gao,
Marco Guzzi,
Joey Huston,
Pavel Nadolsky,
Carl Schmidt,
Jan Winter,
Keping Xie,
C. -P. Yuan
Abstract:
We investigate the possibility of a (sizable) nonperturbative contribution to the charm parton distribution function (PDF) in a nucleon, theoretical issues arising in its interpretation, and its potential impact on LHC scattering processes. The "fitted charm" PDF obtained in various QCD analyses contains a process-dependent component that is partly traced to power-suppressed radiative contribution…
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We investigate the possibility of a (sizable) nonperturbative contribution to the charm parton distribution function (PDF) in a nucleon, theoretical issues arising in its interpretation, and its potential impact on LHC scattering processes. The "fitted charm" PDF obtained in various QCD analyses contains a process-dependent component that is partly traced to power-suppressed radiative contributions in DIS and is generally different at the LHC. We discuss separation of the universal component of the nonperturbative charm from the rest of the radiative contributions and estimate its magnitude in the CT14 global QCD analysis at the next-to-next-to leading order in the QCD coupling strength, including the latest experimental data from HERA and the Large Hadron Collider. Models for the nonperturbative charm PDF are examined as a function of the charm quark mass and other parameters. The prospects for testing these models in the associated production of a Z boson and a charm jet at the LHC are studied under realistic assumptions, including effects of the final-state parton showering.
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Submitted 25 January, 2018; v1 submitted 3 July, 2017;
originally announced July 2017.
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Handbook of LHC Higgs Cross Sections: 4. Deciphering the Nature of the Higgs Sector
Authors:
D. de Florian,
C. Grojean,
F. Maltoni,
C. Mariotti,
A. Nikitenko,
M. Pieri,
P. Savard,
M. Schumacher,
R. Tanaka,
R. Aggleton,
M. Ahmad,
B. Allanach,
C. Anastasiou,
W. Astill,
S. Badger,
M. Badziak,
J. Baglio,
E. Bagnaschi,
A. Ballestrero,
A. Banfi,
D. Barducci,
M. Beckingham,
C. Becot,
G. Bélanger,
J. Bellm
, et al. (351 additional authors not shown)
Abstract:
This Report summarizes the results of the activities of the LHC Higgs Cross Section Working Group in the period 2014-2016. The main goal of the working group was to present the state-of-the-art of Higgs physics at the LHC, integrating all new results that have appeared in the last few years. The first part compiles the most up-to-date predictions of Higgs boson production cross sections and decay…
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This Report summarizes the results of the activities of the LHC Higgs Cross Section Working Group in the period 2014-2016. The main goal of the working group was to present the state-of-the-art of Higgs physics at the LHC, integrating all new results that have appeared in the last few years. The first part compiles the most up-to-date predictions of Higgs boson production cross sections and decay branching ratios, parton distribution functions, and off-shell Higgs boson production and interference effects. The second part discusses the recent progress in Higgs effective field theory predictions, followed by the third part on pseudo-observables, simplified template cross section and fiducial cross section measurements, which give the baseline framework for Higgs boson property measurements. The fourth part deals with the beyond the Standard Model predictions of various benchmark scenarios of Minimal Supersymmetric Standard Model, extended scalar sector, Next-to-Minimal Supersymmetric Standard Model and exotic Higgs boson decays. This report follows three previous working-group reports: Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002), Handbook of LHC Higgs Cross Sections: 2. Differential Distributions (CERN-2012-002), and Handbook of LHC Higgs Cross Sections: 3. Higgs properties (CERN-2013-004). The current report serves as the baseline reference for Higgs physics in LHC Run 2 and beyond.
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Submitted 15 May, 2017; v1 submitted 25 October, 2016;
originally announced October 2016.
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Full mass dependence in Higgs boson production in association with jets at the LHC and FCC
Authors:
Nicolas Greiner,
Stefan Hoeche,
Gionata Luisoni,
Marek Schonherr,
Jan-Christopher Winter
Abstract:
The first computation of Higgs production in association with three jets at NLO in QCD has recently been performed using the effective theory, where the top quark is treated as an infinitely heavy particle and integrated out. This approach is restricted to the regions in phase space where the typical scales are not larger than the top quark mass. Here we investigate this statement at a quantitativ…
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The first computation of Higgs production in association with three jets at NLO in QCD has recently been performed using the effective theory, where the top quark is treated as an infinitely heavy particle and integrated out. This approach is restricted to the regions in phase space where the typical scales are not larger than the top quark mass. Here we investigate this statement at a quantitative level by calculating the leading-order contributions to the production of a Standard Model Higgs boson in association with up to three jets taking full top-quark and bottom-quark mass dependence into account. We find that the transverse momentum of the hardest particle or jet plays a key role in the breakdown of the effective theory predictions, and that discrepancies can easily reach an order of magnitude for transverse momenta of about 1 TeV. The impact of bottom-quark loops are found to be visible in the small transverse momentum region, leading to corrections of up to 5 percent. We further study the impact of mass corrections when VBF selection cuts are applied and when the center-of-mass energy is increased to 100 TeV.
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Submitted 3 August, 2016;
originally announced August 2016.
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Physics at a 100 TeV pp collider: Higgs and EW symmetry breaking studies
Authors:
R. Contino,
D. Curtin,
A. Katz,
M. L. Mangano,
G. Panico,
M. J. Ramsey-Musolf,
G. Zanderighi,
C. Anastasiou,
W. Astill,
G. Bambhaniya,
J. K. Behr,
W. Bizon,
P. S. Bhupal Dev,
D. Bortoletto,
D. Buttazzo,
Q. -H. Cao,
F. Caola,
J. Chakrabortty,
C. -Y. Chen,
S. -L. Chen,
D. de Florian,
F. Dulat,
C. Englert,
J. A. Frost,
B. Fuks
, et al. (50 additional authors not shown)
Abstract:
This report summarises the physics opportunities for the study of Higgs bosons and the dynamics of electroweak symmetry breaking at the 100 TeV pp collider.
This report summarises the physics opportunities for the study of Higgs bosons and the dynamics of electroweak symmetry breaking at the 100 TeV pp collider.
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Submitted 30 June, 2016;
originally announced June 2016.
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The Main Results of the Borexino Experiment
Authors:
A. Derbin,
V. Muratova,
M. Agostini,
K. Altenmuller,
S. Appel,
G. Bellini,
J. Benziger,
D. Bick,
G. Bonfini,
D. Bravo,
B. Caccianiga,
F. Calaprice,
A. Caminata,
M. Carlini,
P. Cavalcante,
A. Chepurnov,
D. D'Angelo,
S. Davini,
L. Di Noto,
I. Drachnev,
A. Etenko,
K. Fomenko,
A. Formozov,
D. Franco,
F. Gabriele
, et al. (74 additional authors not shown)
Abstract:
The main physical results on the registration of solar neutrinos and the search for rare processes obtained by the Borexino collaboration to date are presented.
The main physical results on the registration of solar neutrinos and the search for rare processes obtained by the Borexino collaboration to date are presented.
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Submitted 22 May, 2016;
originally announced May 2016.
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Les Houches 2015: Physics at TeV Colliders Standard Model Working Group Report
Authors:
S. Badger,
J. Bendavid,
V. Ciulli,
A. Denner,
R. Frederix,
M. Grazzini,
J. Huston,
M. Schönherr,
K. Tackmann,
J. Thaler,
C. Williams,
J. R. Andersen,
K. Becker,
M. Bell,
J. Bellm,
E. Bothmann,
R. Boughezal,
J. Butterworth,
S. Carrazza,
M. Chiesa,
L. Cieri,
M. Duehrssen-Debling,
G. Falmagne,
S. Forte,
P. Francavilla
, et al. (70 additional authors not shown)
Abstract:
This Report summarizes the proceedings of the 2015 Les Houches workshop on Physics at TeV Colliders. Session 1 dealt with (I) new developments relevant for high precision Standard Model calculations, (II) the new PDF4LHC parton distributions, (III) issues in the theoretical description of the production of Standard Model Higgs bosons and how to relate experimental measurements, (IV) a host of phen…
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This Report summarizes the proceedings of the 2015 Les Houches workshop on Physics at TeV Colliders. Session 1 dealt with (I) new developments relevant for high precision Standard Model calculations, (II) the new PDF4LHC parton distributions, (III) issues in the theoretical description of the production of Standard Model Higgs bosons and how to relate experimental measurements, (IV) a host of phenomenological studies essential for comparing LHC data from Run I with theoretical predictions and projections for future measurements in Run II, and (V) new developments in Monte Carlo event generators.
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Submitted 16 May, 2016;
originally announced May 2016.
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Higgs + Multi-jets in Gluon Fusion
Authors:
Nicolas Greiner,
Stefan Hoeche,
Gionata Luisoni,
Marek Schonherr,
Jan-Christopher Winter,
Valery Yundin
Abstract:
We present a detailed phenomenological analysis of the production of a Standard Model Higgs boson in association with up to three jets. The Higgs is produced via gluon fusion, which is an irreducible background to the vector boson fusion mechanism. We calculate the next-to-leading order corrections in QCD in the limit of an infinitely heavy top quark. Numerical results are presented for a large va…
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We present a detailed phenomenological analysis of the production of a Standard Model Higgs boson in association with up to three jets. The Higgs is produced via gluon fusion, which is an irreducible background to the vector boson fusion mechanism. We calculate the next-to-leading order corrections in QCD in the limit of an infinitely heavy top quark. Numerical results are presented for a large variety of observables, for different selection cuts, and for different choices of the jet tagging scheme.
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Submitted 14 January, 2016;
originally announced January 2016.
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Phenomenological analysis of Higgs boson production through gluon fusion in association with jets
Authors:
Nicolas Greiner,
Stefan Hoeche,
Gionata Luisoni,
Marek Schonherr,
Jan-Christopher Winter,
Valery Yundin
Abstract:
We present a detailed phenomenological analysis of the production of a Standard Model Higgs boson in association with up to three jets. We consider the gluon fusion channel using an effective theory in the large top-quark mass limit. Higgs boson production in gluon fusion constitutes an irreducible background to the vector boson fusion (VBF) process; hence the precise knowledge of its characterist…
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We present a detailed phenomenological analysis of the production of a Standard Model Higgs boson in association with up to three jets. We consider the gluon fusion channel using an effective theory in the large top-quark mass limit. Higgs boson production in gluon fusion constitutes an irreducible background to the vector boson fusion (VBF) process; hence the precise knowledge of its characteristics is a prerequisite for any measurement in the VBF channel. The calculation is carried out at next-to-leading order (NLO) in QCD in a fully automated way by combining the two programs GoSam and Sherpa. We present numerical results for a large variety of observables for both standard cuts and VBF selection cuts. We find that for all jet multiplicities the NLO corrections are sizeable. This is particularly true in the presence of kinematic selections enhancing the VBF topology, which are based on vetoing additional jet activity. In this case, precise predictions for the background can be made using our calculation by taking the difference between the inclusive H+2 jets and the inclusive H+3 jets result.
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Submitted 2 June, 2015;
originally announced June 2015.
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NLO QCD corrections to W+b W-antib production at hadron colliders: new developments and new issues
Authors:
Jan Winter
Abstract:
This short summary reviews the recent progress in the computation of higher-order corrections to W+b W-antib production. In addition, new phenomenological studies reveal potential problems that may affect precision measurements at the LHC.
This short summary reviews the recent progress in the computation of higher-order corrections to W+b W-antib production. In addition, new phenomenological studies reveal potential problems that may affect precision measurements at the LHC.
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Submitted 13 December, 2014;
originally announced December 2014.
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Model-Independent Production of a Top-Philic Resonance at the LHC
Authors:
Nicolas Greiner,
Kyoungchul Kong,
Jong-Chul Park,
Seong Chan Park,
Jan-Christopher Winter
Abstract:
We investigate the collider phenomenology of a color-singlet vector resonance, which couples to the heaviest quarks, the top quarks, but very weakly to the rest of the fermions in the Standard Model. We find that the dominant production of such a resonance does not appear at the tree level -- it rather occurs at the one-loop level in association with an extra jet. Signatures like t anti-t plus jet…
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We investigate the collider phenomenology of a color-singlet vector resonance, which couples to the heaviest quarks, the top quarks, but very weakly to the rest of the fermions in the Standard Model. We find that the dominant production of such a resonance does not appear at the tree level -- it rather occurs at the one-loop level in association with an extra jet. Signatures like t anti-t plus jets readily emerge as a result of the subsequent decay of the resonance into a pair of top quarks. Without the additional jet, the resonance can still be produced off-shell, which gives a sizeable contribution at low masses. The lower top quark multiplicity of the loop induced resonance production facilitates its reconstruction as compared to the tree level production that gives rise to more exotic signatures involving three or even four top quarks in the final state. For all these cases, we discuss the constraints on the resonance production stemming from recent experimental measurements in the top quark sector. We find that the top-philic vector resonance remains largely unconstrained for the majority of the parameter space, although this will be scrutinized closely in the Run 2 phase of the LHC.
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Submitted 22 October, 2014;
originally announced October 2014.
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Les Houches 2013: Physics at TeV Colliders: Standard Model Working Group Report
Authors:
J. Butterworth,
G. Dissertori,
S. Dittmaier,
D. de Florian,
N. Glover,
K. Hamilton,
J. Huston,
M. Kado,
A. Korytov,
F. Krauss,
G. Soyez,
J. R. Andersen,
S. Badger,
L. Barzè,
J. Bellm,
F. U. Bernlochner,
A. Buckley,
J. Butterworth,
N. Chanon,
M. Chiesa,
A. Cooper-Sarkar,
L. Cieri,
G. Cullen,
H. van Deurzen,
G. Dissertori
, et al. (63 additional authors not shown)
Abstract:
This Report summarizes the proceedings of the 2013 Les Houches workshop on Physics at TeV Colliders. Session 1 dealt primarily with (1) the techniques for calculating standard model multi-leg NLO and NNLO QCD and NLO EW cross sections and (2) the comparison of those cross sections with LHC data from Run 1, and projections for future measurements in Run 2.
This Report summarizes the proceedings of the 2013 Les Houches workshop on Physics at TeV Colliders. Session 1 dealt primarily with (1) the techniques for calculating standard model multi-leg NLO and NNLO QCD and NLO EW cross sections and (2) the comparison of those cross sections with LHC data from Run 1, and projections for future measurements in Run 2.
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Submitted 5 May, 2014;
originally announced May 2014.
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NLO QCD corrections to W+ W- b anti-b production with leptonic decays in the light of top quark mass and asymmetry measurements
Authors:
Gudrun Heinrich,
Andreas Maier,
Richard Nisius,
Johannes Schlenk,
Jan Winter
Abstract:
We present the NLO QCD corrections to the processes p p and p anti-p to W+ W- b anti-b including leptonic decays of the W bosons. Non-resonant contributions as well as diagrams with doubly resonant and singly resonant top quark propagators are fully taken into account. We employ the narrow width approximation to perform the decays of the W bosons; spin correlations are however preserved. We also c…
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We present the NLO QCD corrections to the processes p p and p anti-p to W+ W- b anti-b including leptonic decays of the W bosons. Non-resonant contributions as well as diagrams with doubly resonant and singly resonant top quark propagators are fully taken into account. We employ the narrow width approximation to perform the decays of the W bosons; spin correlations are however preserved. We also calculate observables relevant for top quark mass measurements, and study the impact of kinematical requirements and different scale choices on t anti-t asymmetries.
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Submitted 17 June, 2014; v1 submitted 23 December, 2013;
originally announced December 2013.
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NLO QCD corrections to WWbb production and top quark observables
Authors:
Johannes Schlenk,
Gudrun Heinrich,
Jan Winter
Abstract:
We present the NLO QCD corrections to the production of a W+W- pair and two b-jets, including the leptonic decays of the W bosons. Contributions from singly resonant and non-resonant top quarks are fully taken into account. We also discuss observables relevant for top quark mass measurements and top quark asymmetries.
We present the NLO QCD corrections to the production of a W+W- pair and two b-jets, including the leptonic decays of the W bosons. Contributions from singly resonant and non-resonant top quarks are fully taken into account. We also discuss observables relevant for top quark mass measurements and top quark asymmetries.
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Submitted 24 December, 2013; v1 submitted 19 December, 2013;
originally announced December 2013.
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New limits on heavy sterile neutrino mixing in ${^{8}\rm{B}}$-decay obtained with the Borexino detector
Authors:
Borexino collaboration,
G. Bellini,
J. Benziger,
D. Bick,
G. Bonfini,
D. Bravo,
M. Buizza Avanzini,
B. Caccianiga,
L. Cadonati,
F. Calaprice,
P. Cavalcante,
A. Chavarria,
A. Chepurnov,
D. DAngelo,
S. Davini,
A. Derbin,
I. Drachnev,
A. Empl,
A. Etenko,
K. Fomenko,
D. Franco,
C. Galbiati,
S. Gazzana,
C. Ghiano,
M. Giammarchi
, et al. (65 additional authors not shown)
Abstract:
If heavy neutrinos with mass $m_{ν_{H}}\geq$2$ m_e $ are produced in the Sun via the decay ${^8\rm{B}} \rightarrow {^8\rm{Be}} + e^+ + ν_H$ in a side branch of pp-chain, they would undergo the observable decay into an electron, a positron and a light neutrino $ν_{H}\rightarrowν_{L}+e^++e^-$. In the present work Borexino data are used to set a bound on the existence of such decays. We constrain the…
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If heavy neutrinos with mass $m_{ν_{H}}\geq$2$ m_e $ are produced in the Sun via the decay ${^8\rm{B}} \rightarrow {^8\rm{Be}} + e^+ + ν_H$ in a side branch of pp-chain, they would undergo the observable decay into an electron, a positron and a light neutrino $ν_{H}\rightarrowν_{L}+e^++e^-$. In the present work Borexino data are used to set a bound on the existence of such decays. We constrain the mixing of a heavy neutrino with mass 1.5 MeV $\leq m_{ν_{H}} \le$ 14 MeV to be $|U_{eH}|^2\leq (10^{-3}-4\times10^{-6})$ respectively. These are tighter limits on the mixing parameters than obtained in previous experiments at nuclear reactors and accelerators.
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Submitted 21 November, 2013;
originally announced November 2013.
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NLO merging in tt+jets
Authors:
Marek Schonherr,
Stefan Hoeche,
Junwu Huang,
Gionata Luisoni,
Jan Winter
Abstract:
In this talk the application of the recently introduced methods to merge NLO calculations of successive jet multiplicities to the production of top pairs in association with jets will be discussed, in particular a fresh look is taken at the top quark forward-backward asymmetries. Emphasis will be put on the achieved theoretical accuracy and the associated perturbative and non-perturbative error es…
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In this talk the application of the recently introduced methods to merge NLO calculations of successive jet multiplicities to the production of top pairs in association with jets will be discussed, in particular a fresh look is taken at the top quark forward-backward asymmetries. Emphasis will be put on the achieved theoretical accuracy and the associated perturbative and non-perturbative error estimates.
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Submitted 14 November, 2013;
originally announced November 2013.
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Update of the Binoth Les Houches Accord for a standard interface between Monte Carlo tools and one-loop programs
Authors:
S. Alioli,
S. Badger,
J. Bellm,
B. Biedermann,
F. Boudjema,
G. Cullen,
A. Denner,
H. van Deurzen,
S. Dittmaier,
R. Frederix,
S. Frixione,
M. V. Garzelli,
S. Gieseke,
E. W. N. Glover,
N. Greiner,
G. Heinrich,
V. Hirschi,
S. Hoeche,
J. Huston,
H. Ita,
N. Kauer,
F. Krauss,
G. Luisoni,
D. Maitre,
F. Maltoni
, et al. (22 additional authors not shown)
Abstract:
We present an update of the Binoth Les Houches Accord (BLHA) to standardise the interface between Monte Carlo programs and codes providing one-loop matrix elements.
We present an update of the Binoth Les Houches Accord (BLHA) to standardise the interface between Monte Carlo programs and codes providing one-loop matrix elements.
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Submitted 15 August, 2013;
originally announced August 2013.
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Zero and one jet combined NLO analysis of the top quark forward-backward asymmetry
Authors:
Stefan Hoeche,
Junwu Huang,
Gionata Luisoni,
Marek Schoenherr,
Jan Winter
Abstract:
We present an analysis of the forward-backward asymmetry in the production of top quark pairs at the Tevatron collider. We use novel Monte Carlo methods for merging matrix elements and parton showers to combine NLO QCD predictions for tt and tt+jet production. Theoretical uncertainties are quantified in detail. We find agreement with experimental data on the transverse momentum dependence of the a…
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We present an analysis of the forward-backward asymmetry in the production of top quark pairs at the Tevatron collider. We use novel Monte Carlo methods for merging matrix elements and parton showers to combine NLO QCD predictions for tt and tt+jet production. Theoretical uncertainties are quantified in detail. We find agreement with experimental data on the transverse momentum dependence of the asymmetry.
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Submitted 17 July, 2013; v1 submitted 11 June, 2013;
originally announced June 2013.
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Monte Carlo event generators & the top quark forward--backward asymmetry
Authors:
Jan Winter,
Peter Z. Skands,
Bryan R. Webber
Abstract:
The leading-order accurate description of top quark pair production, as usually employed in standard Monte Carlo event generators, gives no rise to the generation of a forward--backward asymmetry. Yet, non-negligible -- differential as well as inclusive -- asymmetries may be produced if coherent parton showering is used in the hadroproduction of top quark pairs. In this contribution we summarize t…
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The leading-order accurate description of top quark pair production, as usually employed in standard Monte Carlo event generators, gives no rise to the generation of a forward--backward asymmetry. Yet, non-negligible -- differential as well as inclusive -- asymmetries may be produced if coherent parton showering is used in the hadroproduction of top quark pairs. In this contribution we summarize the outcome of our study of this effect. We present a short comparison of different parton shower implementations and briefly comment on the phenomenology of the colour coherence effect at the Tevatron.
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Submitted 13 February, 2013;
originally announced February 2013.
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Data driving the top quark forward--backward asymmetry with a lepton-based handle
Authors:
Adam Falkowski,
Michelangelo L. Mangano,
Adam Martin,
Gilad Perez,
Jan Winter
Abstract:
We propose that, within the standard model, the correlation between the $t\bar{t}$ forward--backward asymmetry $A_{t\bar t}$ and the corresponding lepton-based asymmetry $A_l$ -- at the differential level -- is strong and rather clean both theoretically and experimentally. Hence a combined measurement of the two distributions as a function of the lepton $p_T$, a direct and experimentally clean obs…
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We propose that, within the standard model, the correlation between the $t\bar{t}$ forward--backward asymmetry $A_{t\bar t}$ and the corresponding lepton-based asymmetry $A_l$ -- at the differential level -- is strong and rather clean both theoretically and experimentally. Hence a combined measurement of the two distributions as a function of the lepton $p_T$, a direct and experimentally clean observable, would lead to a potentially unbiased and normalization-free test of the standard model prediction. To check the robustness of our proposal we study how the correlation is affected by mis-measurement of the $t\bar t$ system transverse momenta, acceptance cuts, scale dependence and compare the results of MCFM, POWHEG (with & without PYTHIA showering), and SHERPA's CSSHOWER in first-emission mode. We find that the shape of the relative differential distribution $A_{l} (p^{l}_{T}) [A_{t\bar{t}} (p^l_T)]$ is only moderately distorted hence supporting the usefulness of our proposal. Beyond the first emission, we find that the correlation is not accurately captured by lowest-order treatment. We also briefly consider other differential variables such as the system transverse mass and the canonical $t\bar t$ invariant mass. Finally, we study new physics scenarios where the correlation is significantly distorted and therefore can be more readily constrained or discovered using our method.
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Submitted 17 December, 2012;
originally announced December 2012.
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Lifetime measurements of 214Po and 212Po with the CTF liquid scintillator detector at LNGS
Authors:
Borexino Collaboration,
G. Bellini,
J. Benziger,
D. Bick,
G. Bonfini,
D. Bravo,
M. Buizza Avanzini,
B. Caccianiga,
L. Cadonati,
F. Calaprice,
C. Carraro,
P. Cavalcante,
A. Chavarria,
A. Chepurnov,
V. Chubakov,
D. D'Angelo,
S. Davini,
A. Derbin,
A. Etenko,
K. Fomenko,
D. Franco,
C. Galbiati,
S. Gazzana,
C. Ghiano,
M. Giammarchi
, et al. (70 additional authors not shown)
Abstract:
We have studied the alpha decays of 214Po into 210Pb and of 212Po into 208Pb tagged by the coincidence with the preceding beta decays from 214Bi and 212Bi, respectively. The employed 222Rn, 232Th, and 220Rn sources were sealed inside quartz vials and inserted in the Counting Test Facility at the underground Gran Sasso National Laboratory in Italy. We find that the mean lifetime of 214Po is (236.00…
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We have studied the alpha decays of 214Po into 210Pb and of 212Po into 208Pb tagged by the coincidence with the preceding beta decays from 214Bi and 212Bi, respectively. The employed 222Rn, 232Th, and 220Rn sources were sealed inside quartz vials and inserted in the Counting Test Facility at the underground Gran Sasso National Laboratory in Italy. We find that the mean lifetime of 214Po is (236.00 +- 0.42(stat) +- 0.15(syst)) μs and that of 212Po is (425.1 +- 0.9(stat) +- 1.2(syst)) ns. Our results, obtained from data with signal-to-background ratio larger than 1000, reduce the overall uncertainties and are compatible with previous measurements.
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Submitted 5 July, 2013; v1 submitted 6 December, 2012;
originally announced December 2012.
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QCD Coherence and the Top Quark Asymmetry
Authors:
Peter Z. Skands,
Bryan R. Webber,
Jan Winter
Abstract:
Coherent QCD radiation in the hadroproduction of top quark pairs leads to a forward--backward asymmetry that grows more negative with increasing transverse momentum of the pair. This feature is present in Monte Carlo event generators with coherent parton showering, even though the production process is treated at leading order and has no intrinsic asymmetry before showering. In addition, depending…
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Coherent QCD radiation in the hadroproduction of top quark pairs leads to a forward--backward asymmetry that grows more negative with increasing transverse momentum of the pair. This feature is present in Monte Carlo event generators with coherent parton showering, even though the production process is treated at leading order and has no intrinsic asymmetry before showering. In addition, depending on the treatment of recoils, showering can produce a positive contribution to the inclusive asymmetry. We explain the origin of these features, compare them in fixed-order calculations and the Herwig++, Pythia and Sherpa event generators, and discuss their implications.
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Submitted 20 September, 2012; v1 submitted 7 May, 2012;
originally announced May 2012.
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Systematic improvement of QCD parton showers
Authors:
Jan Winter,
Stefan Hoeche,
Hendrik Hoeth,
Frank Krauss,
Marek Schonherr,
Steffen Schumann,
Frank Siegert,
Korinna Zapp
Abstract:
In this contribution, we will give a brief overview of the progress that has been achieved in the field of combining matrix elements and parton showers. We exemplify this by focusing on the case of electron--positron collisions and by reporting on recent developments as accomplished within the Sherpa event generation framework.
In this contribution, we will give a brief overview of the progress that has been achieved in the field of combining matrix elements and parton showers. We exemplify this by focusing on the case of electron--positron collisions and by reporting on recent developments as accomplished within the Sherpa event generation framework.
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Submitted 25 April, 2012;
originally announced April 2012.
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The SM and NLO Multileg and SM MC Working Groups: Summary Report
Authors:
J. Alcaraz Maestre,
S. Alioli,
J. R. Andersen,
R. D. Ball,
A. Buckley,
M. Cacciari,
F. Campanario,
N. Chanon,
G. Chachamis,
V. Ciulli,
F. Cossutti,
G. Cullen,
A. Denner,
S. Dittmaier,
J. Fleischer,
R. Frederix,
S. Frixione,
J. Gao,
L. Garren,
S. Gascon-Shotkin,
N. Greiner,
J. P. Guillet,
T. Hapola,
N. P. Hartland,
G. Heinrich
, et al. (57 additional authors not shown)
Abstract:
The 2011 Les Houches workshop was the first to confront LHC data. In the two years since the previous workshop there have been significant advances in both soft and hard QCD, particularly in the areas of multi-leg NLO calculations, the inclusion of those NLO calculations into parton shower Monte Carlos, and the tuning of the non-perturbative parameters of those Monte Carlos. These proceedings desc…
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The 2011 Les Houches workshop was the first to confront LHC data. In the two years since the previous workshop there have been significant advances in both soft and hard QCD, particularly in the areas of multi-leg NLO calculations, the inclusion of those NLO calculations into parton shower Monte Carlos, and the tuning of the non-perturbative parameters of those Monte Carlos. These proceedings describe the theoretical advances that have taken place, the impact of the early LHC data, and the areas for future development.
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Submitted 9 May, 2012; v1 submitted 29 March, 2012;
originally announced March 2012.
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Semileptonic decays of the Higgs boson at the Tevatron
Authors:
Joseph D. Lykken,
Adam O. Martin,
Jan-Christopher Winter
Abstract:
We examine the prospects for extending the Tevatron reach for a Standard Model Higgs boson by including the semileptonic Higgs boson decays h --> WW --> l nu jj for M_h >~ 2 M_W, and h --> W jj --> l nu jj for M_h <~ 2 M_W, where j is a hadronic jet. We employ a realistic simulation of the signal and backgrounds using the Sherpa Monte Carlo event generator. We find kinematic selections that enhanc…
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We examine the prospects for extending the Tevatron reach for a Standard Model Higgs boson by including the semileptonic Higgs boson decays h --> WW --> l nu jj for M_h >~ 2 M_W, and h --> W jj --> l nu jj for M_h <~ 2 M_W, where j is a hadronic jet. We employ a realistic simulation of the signal and backgrounds using the Sherpa Monte Carlo event generator. We find kinematic selections that enhance the signal over the dominant W+jets background. The resulting sensitivity could be an important addition to ongoing searches, especially in the mass range 120 <~ M_h <~ 150 GeV. The techniques described can be extended to Higgs boson searches at the Large Hadron Collider.
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Submitted 11 November, 2011;
originally announced November 2011.
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A Forward Branching Phase-Space Generator
Authors:
Walter T. Giele,
Gerben C. Stavenga,
Jan-Christopher Winter
Abstract:
We develop a forward branching phase-space generator for use in next-to-leading order parton level event generators. By performing 2 -> 3 branchings from a fixed jet phase-space point, all bremsstrahlung events contributing to the given jet configuration are generated. The resulting phase-space integration is three-dimensional irrespective of the considered jet multiplicity. In this first study, w…
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We develop a forward branching phase-space generator for use in next-to-leading order parton level event generators. By performing 2 -> 3 branchings from a fixed jet phase-space point, all bremsstrahlung events contributing to the given jet configuration are generated. The resulting phase-space integration is three-dimensional irrespective of the considered jet multiplicity. In this first study, we use the forward branching phase-space generator to calculate in the leading-color approximation next-to-leading order corrections to fully differential gluonic jet configurations.
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Submitted 24 June, 2011;
originally announced June 2011.
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Calculation of QCD loops using tree-level matrix elements
Authors:
Jan Winter
Abstract:
The possibility of treating colour in one-loop amplitude calculations alike the other quantum numbers is briefly discussed for semi-numerical algorithms based on generalized unitarity and parametric integration techniques. Numerical results are presented for the calculation of virtual corrections in multi-gluon scattering.
The possibility of treating colour in one-loop amplitude calculations alike the other quantum numbers is briefly discussed for semi-numerical algorithms based on generalized unitarity and parametric integration techniques. Numerical results are presented for the calculation of virtual corrections in multi-gluon scattering.
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Submitted 17 May, 2010;
originally announced May 2010.
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The Physics Potential of the LENA Detector
Authors:
Michael Wurm,
Franz von Feilitzsch,
Marianne Goeger-Neff,
Tobias Lachenmaier,
Timo Lewke,
Quirin Meindl,
Randolph Moellenberg,
Lothar Oberauer,
Juha Peltoniemi,
Walter Potzel,
Marc Tippmann,
Juergen Winter
Abstract:
The large-volume liquid-scintillator detector LENA (Low Energy Neutrino Astronomy) has been proposed as a next-generation experiment for low-energy neutrinos. High-precision spectroscopy of solar, Supernova and geo-neutrinos provides a new access to the otherwise unobservable interiors of Earth, Sun and heavy stars. Due to the potent background discrimination, the detection of the Diffuse Supernov…
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The large-volume liquid-scintillator detector LENA (Low Energy Neutrino Astronomy) has been proposed as a next-generation experiment for low-energy neutrinos. High-precision spectroscopy of solar, Supernova and geo-neutrinos provides a new access to the otherwise unobservable interiors of Earth, Sun and heavy stars. Due to the potent background discrimination, the detection of the Diffuse Supernova Neutrino Background is expected for the first time in LENA. The sensitivity of the proton lifetime for the decay into Kaon and antineutrino will be increased by an order of magnitude over existing experimental limits. Recent studies indicate that liquid-scintillator detectors are capable to reconstruct neutrino events even at GeV energies, providing the opportunity to use LENA as far detector in a long-baseline neutrino beam experiment.
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Submitted 20 April, 2010;
originally announced April 2010.
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Spectroscopy of Solar Neutrinos
Authors:
Michael Wurm,
Franz von Feilitzsch,
Marianne Goeger-Neff,
Tobias Lachenmaier,
Timo Lewke,
Quirin Meindl,
Randoplh Moellenberg,
Lothar Oberauer,
Walter Potzel,
Marc Tippmann,
Christoph Traunsteiner,
Juergen Winter
Abstract:
In the last years, liquid-scintillator detectors have opened a new window for the observation of low-energetic astrophysical neutrino sources. In 2007, the solar neutrino experiment Borexino began its data-taking in the Gran Sasso underground laboratory. High energy resolution and excellent radioactive background conditions in the detector allow the first-time spectroscopic measurement of solar ne…
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In the last years, liquid-scintillator detectors have opened a new window for the observation of low-energetic astrophysical neutrino sources. In 2007, the solar neutrino experiment Borexino began its data-taking in the Gran Sasso underground laboratory. High energy resolution and excellent radioactive background conditions in the detector allow the first-time spectroscopic measurement of solar neutrinos in the sub-MeV energy regime. The experimental results of the Beryllium-7 neutrino flux measurements as well as the prospects for the detection of solar Boron-8, pep and CNO neutrinos are presented in the context of the currently discussed ambiguities in solar metallicity. In addition, the potential of the future SNO+ and LENA experiments for high-precision solar neutrino spectroscopy will be outlined.
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Submitted 6 April, 2010;
originally announced April 2010.
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THE TOOLS AND MONTE CARLO WORKING GROUP Summary Report from the Les Houches 2009 Workshop on TeV Colliders
Authors:
J. M. Butterworth,
F. Maltoni,
F. Moortgat,
P. Richardson,
S. Schumann,
P. Skands,
J. Alwall,
A. Arbey,
L. Basso,
S. Belov,
A. Bharucha,
F. Braam,
A. Buckley,
M. Campanelli,
R. Chierici,
A. Djouadi,
L. Dudko,
C. Duhr,
F. Febres Cordero,
P. Francavilla,
B. Fuks,
L. Garren,
T. Goto,
M. Grazzini,
T. Hahn
, et al. (47 additional authors not shown)
Abstract:
This is the summary and introduction to the proceedings contributions for the Les Houches 2009 "Tools and Monte Carlo" working group.
This is the summary and introduction to the proceedings contributions for the Les Houches 2009 "Tools and Monte Carlo" working group.
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Submitted 8 March, 2010;
originally announced March 2010.
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The SM and NLO multileg working group: Summary report
Authors:
T. Binoth,
G. Dissertori,
J. Huston,
R. Pittau,
J. R. Andersen,
J. Archibald,
S. Badger,
R. D. Ball,
G. Bevilacqua,
I. Bierenbaum,
T. Binoth,
F. Boudjema,
R. Boughezal,
A. Bredenstein,
R. Britto,
M. Campanelli,
J. Campbell,
L. Carminati,
G. Chachamis,
V. Ciulli,
G. Cullen,
M. Czakon,
L. Del Debbio,
A. Denner,
G. Dissertori
, et al. (70 additional authors not shown)
Abstract:
This report summarizes the activities of the SM and NLO Multileg Working Group of the Workshop "Physics at TeV Colliders", Les Houches, France 8-26 June, 2009.
This report summarizes the activities of the SM and NLO Multileg Working Group of the Workshop "Physics at TeV Colliders", Les Houches, France 8-26 June, 2009.
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Submitted 5 March, 2010;
originally announced March 2010.
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Thread-Scalable Evaluation of Multi-Jet Observables
Authors:
Walter Giele,
Gerben Stavenga,
Jan-Christopher Winter
Abstract:
A leading-order, leading-color parton-level event generator is developed for use on a multi-threaded GPU. Speed-up factors between 150 and 300 are obtained compared to an unoptimized CPU-based implementation of the event generator. In this first paper we study the feasibility of a GPU-based event generator with an emphasis on the constraints imposed by the hardware. Some studies of Monte Carlo c…
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A leading-order, leading-color parton-level event generator is developed for use on a multi-threaded GPU. Speed-up factors between 150 and 300 are obtained compared to an unoptimized CPU-based implementation of the event generator. In this first paper we study the feasibility of a GPU-based event generator with an emphasis on the constraints imposed by the hardware. Some studies of Monte Carlo convergence and accuracy are presented for PP -> 2,...,10 jet observables using of the order of 1e11 events.
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Submitted 18 February, 2010;
originally announced February 2010.
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A proposal for a standard interface between Monte Carlo tools and one-loop programs
Authors:
T. Binoth,
F. Boudjema,
G. Dissertori,
A. Lazopoulos,
A. Denner,
S. Dittmaier,
R. Frederix,
N. Greiner,
S. Hoche,
W. Giele,
P. Skands,
J. Winter,
T. Gleisberg,
J. Archibald,
G. Heinrich,
F. Krauss,
D. Maitre,
M. Huber,
J. Huston,
N. Kauer,
F. Maltoni,
C. Oleari,
G. Passarino,
R. Pittau,
S. Pozzorini
, et al. (3 additional authors not shown)
Abstract:
Many highly developed Monte Carlo tools for the evaluation of cross sections based on tree matrix elements exist and are used by experimental collaborations in high energy physics. As the evaluation of one-loop matrix elements has recently been undergoing enormous progress, the combination of one-loop matrix elements with existing Monte Carlo tools is on the horizon. This would lead to phenomeno…
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Many highly developed Monte Carlo tools for the evaluation of cross sections based on tree matrix elements exist and are used by experimental collaborations in high energy physics. As the evaluation of one-loop matrix elements has recently been undergoing enormous progress, the combination of one-loop matrix elements with existing Monte Carlo tools is on the horizon. This would lead to phenomenological predictions at the next-to-leading order level. This note summarises the discussion of the next-to-leading order multi-leg (NLM) working group on this issue which has been taking place during the workshop on Physics at TeV colliders at Les Houches, France, in June 2009. The result is a proposal for a standard interface between Monte Carlo tools and one-loop matrix element programs.
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Submitted 17 February, 2010; v1 submitted 8 January, 2010;
originally announced January 2010.
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Efficient Color-Dressed Calculation of Virtual Corrections
Authors:
Walter Giele,
Zoltan Kunszt,
Jan Winter
Abstract:
With the advent of generalized unitarity and parametric integration techniques, the construction of a generic Next-to-Leading Order Monte Carlo becomes feasible. Such a generator will entail the treatment of QCD color in the amplitudes. We extend the concept of color dressing to one-loop amplitudes, resulting in the formulation of an explicit algorithmic solution for the calculation of arbitrary…
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With the advent of generalized unitarity and parametric integration techniques, the construction of a generic Next-to-Leading Order Monte Carlo becomes feasible. Such a generator will entail the treatment of QCD color in the amplitudes. We extend the concept of color dressing to one-loop amplitudes, resulting in the formulation of an explicit algorithmic solution for the calculation of arbitrary scattering processes at Next-to-Leading order. The resulting algorithm is of exponential complexity, that is the numerical evaluation time of the virtual corrections grows by a constant multiplicative factor as the number of external partons is increased. To study the properties of the method, we calculate the virtual corrections to $n$-gluon scattering.
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Submitted 10 November, 2009;
originally announced November 2009.
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Calculating gluon one-loop amplitudes numerically
Authors:
Jan-Christopher Winter,
Walter T. Giele
Abstract:
This note reports on an independent implementation of calculating one-loop amplitudes semi-numerically using generalized unitarity techniques. The algorithm implemented in form of a C++ code closely follows the method by Ellis, Giele, Kunszt and Melnikov. For the case of gluons, the algorithm is briefly reviewed. Double-precision results are presented documenting the accuracy and efficiency of t…
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This note reports on an independent implementation of calculating one-loop amplitudes semi-numerically using generalized unitarity techniques. The algorithm implemented in form of a C++ code closely follows the method by Ellis, Giele, Kunszt and Melnikov. For the case of gluons, the algorithm is briefly reviewed. Double-precision results are presented documenting the accuracy and efficiency of this computation.
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Submitted 31 January, 2009;
originally announced February 2009.
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Event generation with SHERPA 1.1
Authors:
T. Gleisberg,
S. Hoeche,
F. Krauss,
M. Schoenherr,
S. Schumann,
F. Siegert,
J. Winter
Abstract:
In this paper the current release of the Monte Carlo event generator Sherpa, version 1.1, is presented. Sherpa is a general-purpose tool for the simulation of particle collisions at high-energy colliders. It contains a very flexible tree-level matrix-element generator for the calculation of hard scattering processes within the Standard Model and various new physics models. The emission of additi…
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In this paper the current release of the Monte Carlo event generator Sherpa, version 1.1, is presented. Sherpa is a general-purpose tool for the simulation of particle collisions at high-energy colliders. It contains a very flexible tree-level matrix-element generator for the calculation of hard scattering processes within the Standard Model and various new physics models. The emission of additional QCD partons off the initial and final states is described through a parton-shower model. To consistently combine multi-parton matrix elements with the QCD parton cascades the approach of Catani, Krauss, Kuhn and Webber is employed. A simple model of multiple interactions is used to account for underlying events in hadron--hadron collisions. The fragmentation of partons into primary hadrons is described using a phenomenological cluster-hadronisation model. A comprehensive library for simulating tau-lepton and hadron decays is provided. Where available form-factor models and matrix elements are used, allowing for the inclusion of spin correlations; effects of virtual and real QED corrections are included using the approach of Yennie, Frautschi and Suura.
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Submitted 27 November, 2008;
originally announced November 2008.
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From multileg loops to trees (by-passing Feynman's Tree Theorem)
Authors:
German Rodrigo,
Stefano Catani,
Tanju Gleisberg,
Frank Krauss,
Jan-Christopher Winter
Abstract:
We illustrate a duality relation between one-loop integrals and single-cut phase-space integrals. The duality relation is realised by a modification of the customary +i0 prescription of the Feynman propagators. The new prescription regularizing the propagators, which we write in a Lorentz covariant form, compensates for the absence of multiple-cut contributions that appear in the Feynman Tree Th…
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We illustrate a duality relation between one-loop integrals and single-cut phase-space integrals. The duality relation is realised by a modification of the customary +i0 prescription of the Feynman propagators. The new prescription regularizing the propagators, which we write in a Lorentz covariant form, compensates for the absence of multiple-cut contributions that appear in the Feynman Tree Theorem. The duality relation can be extended to generic one-loop quantities, such as Green's functions, in any relativistic, local and unitary field theories.
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Submitted 3 July, 2008;
originally announced July 2008.
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From loops to trees by-passing Feynman's theorem
Authors:
Stefano Catani,
Tanju Gleisberg,
Frank Krauss,
German Rodrigo,
Jan-Christopher Winter
Abstract:
We derive a duality relation between one-loop integrals and phase-space integrals emerging from them through single cuts. The duality relation is realized by a modification of the customary +i0 prescription of the Feynman propagators. The new prescription regularizing the propagators, which we write in a Lorentz covariant form, compensates for the absence of multiple-cut contributions that appea…
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We derive a duality relation between one-loop integrals and phase-space integrals emerging from them through single cuts. The duality relation is realized by a modification of the customary +i0 prescription of the Feynman propagators. The new prescription regularizing the propagators, which we write in a Lorentz covariant form, compensates for the absence of multiple-cut contributions that appear in the Feynman Tree Theorem. The duality relation can be applied to generic one-loop quantities in any relativistic, local and unitary field theories. %It is suitable for applications to the analytical calculation of %one-loop scattering amplitudes, and to the numerical evaluation of %cross-sections at next-to-leading order. We discuss in detail the duality that relates one-loop and tree-level Green's functions. We comment on applications to the analytical calculation of one-loop scattering amplitudes, and to the numerical evaluation of cross-sections at next-to-leading order.
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Submitted 11 September, 2008; v1 submitted 20 April, 2008;
originally announced April 2008.
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Initial-state showering based on colour dipoles connected to incoming parton lines
Authors:
Jan-Christopher Winter,
Frank Krauss
Abstract:
A parton-shower model for hadronic collisions based on the emission properties of QCD dipoles is proposed. This proposal therefore extends the well-known radiation pattern of pure final-state colour dipoles to QCD initial-state radiation, both of which are treated perturbatively. Corresponding dipole splitting functions are derived and the kinematics of all dipole splittings is discussed. Applic…
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A parton-shower model for hadronic collisions based on the emission properties of QCD dipoles is proposed. This proposal therefore extends the well-known radiation pattern of pure final-state colour dipoles to QCD initial-state radiation, both of which are treated perturbatively. Corresponding dipole splitting functions are derived and the kinematics of all dipole splittings is discussed. Application to hadron production in electron-positron annihilation, to Drell-Yan lepton-pair and QCD jet production yields encouraging results.
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Submitted 23 December, 2007;
originally announced December 2007.
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Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions
Authors:
J. Alwall,
S. Hoeche,
F. Krauss,
N. Lavesson,
L. Lonnblad,
F. Maltoni,
M. L. Mangano,
M. Moretti,
C. G. Papadopoulos,
F. Piccinini,
S. Schumann,
M. Treccani,
J. Winter,
M. Worek
Abstract:
We compare different procedures for combining fixed-order tree-level matrix-element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW and MLM schemes using different matrix-element generators and different parton cascades. We find that although similar results are obtained in all cases, there are…
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We compare different procedures for combining fixed-order tree-level matrix-element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW and MLM schemes using different matrix-element generators and different parton cascades. We find that although similar results are obtained in all cases, there are important differences.
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Submitted 16 January, 2008; v1 submitted 18 June, 2007;
originally announced June 2007.
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New trends in modern event generators
Authors:
Tanju Gleisberg,
Stefan Hoeche,
Frank Krauss,
Radoslaw Matyszkiewicz,
Marek Schoenherr,
Steffen Schumann,
Frank Siegert,
Jan Winter
Abstract:
Some features of modern simulation tools for high-energy physics are reviewed.
Some features of modern simulation tools for high-energy physics are reviewed.
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Submitted 31 May, 2007;
originally announced May 2007.
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Large underground, liquid based detectors for astro-particle physics in Europe: scientific case and prospects
Authors:
D. Autiero,
J. Aysto,
A. Badertscher,
L. Bezrukov,
J. Bouchez,
A. Bueno,
J. Busto,
J. -E. Campagne,
Ch. Cavata,
L. Chaussard,
A. de Bellefon,
Y. Declais,
J. Dumarchez,
J. Ebert,
T. Enqvist,
A. Ereditato,
F. von Feilitzsch,
P. Fileviez Perez,
M. Goger-Neff,
S. Gninenko,
W. Gruber,
C. Hagner,
M. Hess,
K. A. Hochmuth,
J. Kisiel
, et al. (46 additional authors not shown)
Abstract:
This document reports on a series of experimental and theoretical studies conducted to assess the astro-particle physics potential of three future large-scale particle detectors proposed in Europe as next generation underground observatories. The proposed apparatus employ three different and, to some extent, complementary detection techniques: GLACIER (liquid Argon TPC), LENA (liquid scintillato…
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This document reports on a series of experimental and theoretical studies conducted to assess the astro-particle physics potential of three future large-scale particle detectors proposed in Europe as next generation underground observatories. The proposed apparatus employ three different and, to some extent, complementary detection techniques: GLACIER (liquid Argon TPC), LENA (liquid scintillator) and MEMPHYS (\WC), based on the use of large mass of liquids as active detection media. The results of these studies are presented along with a critical discussion of the performance attainable by the three proposed approaches coupled to existing or planned underground laboratories, in relation to open and outstanding physics issues such as the search for matter instability, the detection of astrophysical- and geo-neutrinos and to the possible use of these detectors in future high-intensity neutrino beams.
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Submitted 29 May, 2007; v1 submitted 1 May, 2007;
originally announced May 2007.
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HERA and the LHC - A workshop on the implications of HERA for LHC physics: Proceedings - Part B
Authors:
S. Alekhin,
G. Altarelli,
N. Amapane,
J. Andersen,
V. Andreev,
M. Arneodo,
V. Avati,
J. Baines,
R. D. Ball,
A. Banfi,
S. P. Baranov,
J. Bartels,
O. Behnke,
R. Bellan,
J. Blumlein,
H. Bottcher,
S. Bolognesi,
M. Boonekamp,
D. Bourilkov,
J. Bracinik,
A. Bruni,
G. Bruni,
A. Buckley,
A. Bunyatyan,
C. M. Buttar
, et al. (169 additional authors not shown)
Abstract:
The HERA electron--proton collider has collected 100 pb$^{-1}$ of data since its start-up in 1992, and recently moved into a high-luminosity operation mode, with upgraded detectors, aiming to increase the total integrated luminosity per experiment to more than 500 pb$^{-1}$. HERA has been a machine of excellence for the study of QCD and the structure of the proton. The Large Hadron Collider (LHC…
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The HERA electron--proton collider has collected 100 pb$^{-1}$ of data since its start-up in 1992, and recently moved into a high-luminosity operation mode, with upgraded detectors, aiming to increase the total integrated luminosity per experiment to more than 500 pb$^{-1}$. HERA has been a machine of excellence for the study of QCD and the structure of the proton. The Large Hadron Collider (LHC), which will collide protons with a centre-of-mass energy of 14 TeV, will be completed at CERN in 2007. The main mission of the LHC is to discover and study the mechanisms of electroweak symmetry breaking, possibly via the discovery of the Higgs particle, and search for new physics in the TeV energy scale, such as supersymmetry or extra dimensions. Besides these goals, the LHC will also make a substantial number of precision measurements and will offer a new regime to study the strong force via perturbative QCD processes and diffraction. For the full LHC physics programme a good understanding of QCD phenomena and the structure function of the proton is essential. Therefore, in March 2004, a one-year-long workshop started to study the implications of HERA on LHC physics. This included proposing new measurements to be made at HERA, extracting the maximum information from the available data, and developing/improving the theoretical and experimental tools. This report summarizes the results achieved during this workshop.
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Submitted 19 March, 2007; v1 submitted 2 January, 2006;
originally announced January 2006.
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HERA and the LHC - A workshop on the implications of HERA for LHC physics: Proceedings - Part A
Authors:
S. Alekhin,
G. Altarelli,
N. Amapane,
J. Andersen,
V. Andreev,
M. Arneodo,
V. Avati,
J. Baines,
R. D. Ball,
A. Banfi,
S. P. Baranov,
J. Bartels,
O. Behnke,
R. Bellan,
J. Blumlein,
H. Bottcher,
S. Bolognesi,
M. Boonekamp,
D. Bourilkov,
J. Bracinik,
A. Bruni,
G. Bruni,
A. Buckley,
A. Bunyatyan,
C. M. Buttar
, et al. (169 additional authors not shown)
Abstract:
The HERA electron--proton collider has collected 100 pb$^{-1}$ of data since its start-up in 1992, and recently moved into a high-luminosity operation mode, with upgraded detectors, aiming to increase the total integrated luminosity per experiment to more than 500 pb$^{-1}$. HERA has been a machine of excellence for the study of QCD and the structure of the proton. The Large Hadron Collider (LHC…
▽ More
The HERA electron--proton collider has collected 100 pb$^{-1}$ of data since its start-up in 1992, and recently moved into a high-luminosity operation mode, with upgraded detectors, aiming to increase the total integrated luminosity per experiment to more than 500 pb$^{-1}$. HERA has been a machine of excellence for the study of QCD and the structure of the proton. The Large Hadron Collider (LHC), which will collide protons with a centre-of-mass energy of 14 TeV, will be completed at CERN in 2007. The main mission of the LHC is to discover and study the mechanisms of electroweak symmetry breaking, possibly via the discovery of the Higgs particle, and search for new physics in the TeV energy scale, such as supersymmetry or extra dimensions. Besides these goals, the LHC will also make a substantial number of precision measurements and will offer a new regime to study the strong force via perturbative QCD processes and diffraction. For the full LHC physics programme a good understanding of QCD phenomena and the structure function of the proton is essential. Therefore, in March 2004, a one-year-long workshop started to study the implications of HERA on LHC physics. This included proposing new measurements to be made at HERA, extracting the maximum information from the available data, and developing/improving the theoretical and experimental tools. This report summarizes the results achieved during this workshop.
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Submitted 31 January, 2006; v1 submitted 2 January, 2006;
originally announced January 2006.
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Event generator for the LHC
Authors:
T. Gleisberg,
S. Hoeche,
F. Krauss,
A. Schaelicke,
S. Schumann,
J. Winter
Abstract:
In this contribution the new event generation framework Sherpa will be presented. It aims at the full simulation of events at current and future high-energy experiments, in particular the LHC. Some results related to the production of jets at the Tevatron will be discussed.
In this contribution the new event generation framework Sherpa will be presented. It aims at the full simulation of events at current and future high-energy experiments, in particular the LHC. Some results related to the production of jets at the Tevatron will be discussed.
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Submitted 31 August, 2005;
originally announced August 2005.