The new look pMSSM with neutralino and gravitino LSPs Cahill-Rowley, Matthew W.; Hewett, JoAnne L.; Hoeche, Stefan ...
European physical journal. C, Particles and fields,
09/2012, Letnik:
72, Številka:
9
Journal Article
Recenzirano
Odprti dostop
The pMSSM provides a broad perspective on SUSY phenomenology. In this paper we generate two new, very large, sets of pMSSM models with sparticle masses extending up to 4 TeV, where the lightest ...supersymmetric particle (LSP) is either a neutralino or gravitino. The existence of a gravitino LSP necessitates a detailed study of its cosmological effects and we find that Big Bang Nucleosynthesis places strong constraints on this scenario. Both sets are subjected to a global set of theoretical, observational and experimental constraints resulting in a sample of ∼225k viable models for each LSP type. The characteristics of these two model sets are briefly compared. We confront the neutralino LSP model set with searches for SUSY at the 7 TeV LHC using both the missing (MET) and non-missing
E
T
ATLAS analyses. In the MET case, we employ Monte Carlo estimates of the ratios of the SM backgrounds at 7 and 8 TeV to rescale the 7 TeV data-driven ATLAS backgrounds to 8 TeV. This allows us to determine the pMSSM parameter space coverage for this collision energy. We find that an integrated luminosity of ∼5–20 fb
−1
at 8 TeV would yield a substantial increase in this coverage compared to that at 7 TeV and can probe roughly half of the model set. If the pMSSM is not discovered during the 8 TeV run, then our model set will be essentially void of gluinos and lightest first and second generation squarks that are ≲700–800 GeV, which is much less than the analogous mSUGRA bound. Finally, we demonstrate that non-MET SUSY searches continue to play an important role in exploring the pMSSM parameter space. These two pMSSM model sets can be used as the basis for investigations for years to come.
A
bstract
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.
We present a simple yet efficient algorithm for phase-space integration at hadron colliders. Individual mappings consist of a single t-channel combined with any number of s-channel decays, and are ...constructed using diagrammatic information. The factorial growth in the number of channels is tamed by providing an option to limit the number of s-channel topologies. We provide a publicly available, parallelized code in C++ and test its performance in typical LHC scenarios.
Streams of event weights in particle-level Monte Carlo event
generators are a convenient and immensely CPU-efficient approach to
express systematic uncertainties in phenomenology calculations,
...providing systematic variations on the nominal prediction within a
single event sample. But the lack of a common standard for labelling
these variation streams across different tools has proven to be a major
limitation for event-processing tools and analysers alike. Here we
propose a well-defined, extensible community standard for the naming,
ordering, and interpretation of weight streams that will serve as the
basis for semantically correct parsing and combination of such
variations in both theoretical and experimental studies.
Even though jet substructure was not an original design consideration for the Large Hadron Collider (LHC) experiments, it has emerged as an essential tool for the current physics program. We examine ...the role of jet substructure on the motivation for and design of future energy Frontier colliders. In particular, we discuss the need for a vibrant theory and experimental research and development program to extend jet substructure physics into the new regimes probed by future colliders. Jet substructure has organically evolved with a close connection between theorists and experimentalists and has catalyzed exciting innovations in both communities. We expect such developments will play an important role in the future energy Frontier physics program.
We present a Monte Carlo approach to soft-gluon resummation at subleading color which can be used to improve existing parton shower algorithms. At the single-emission level, soft-collinear ...enhancements of the splitting functions are explicitly linked to quadratic Casimir operators, while wide angle single-soft enhancements are connected to nontrivial color correlators. We focus on a numerically stable implementation of color matrix element corrections to all orders and approximate the virtual corrections by requiring unitarity at the single-emission level. We provide a proof-of-concept implementation to compute nonglobal event shapes at lepton colliders.
Resolved Photons in Sherpa Hoeche, Stefan; Krauss, Frank; Meinzinger, Peter
arXiv.org,
10/2023
Paper, Journal Article
Odprti dostop
We present the first complete simulation framework, in the Sherpa event generator, for resolved photon interactions at next-to leading order accuracy. It includes photon spectra obtained through the ...equivalent-photon approximation, parton distribution functions to parametrize the hadronic structure of quasi-real photons, the matching of the parton shower to next-to leading order QCD calculations for resolved photon cross sections, and the modelling of multiple-parton interactions. We validate our framework against a wide range of photo-production data from LEP and HERA experiments, observing good overall agreement. We identify important future steps relevant for high-quality simulations at the planned Electron-Ion Collider.
Searching for Nambu-Goldstone bosons at the LHC Dedes, Athanasios; Figy, Terrance; Höche, Stefan ...
The journal of high energy physics,
11/2008, Letnik:
2008, Številka:
11
Journal Article
The compute efficiency of Monte-Carlo event generators for the Large Hadron Collider is expected to become a major bottleneck for simulations in the high-luminosity phase. Aiming at the development ...of a full-fledged generator for modern GPUs, we study the performance of various recursive strategies to compute multi-gluon tree-level amplitudes. We investigate the scaling of the algorithms on both CPU and GPU hardware. Finally, we provide practical recommendations as well as baseline implementations for the development of future simulation programs. The GPU implementations can be found at: https://www.gitlab.com/ebothmann/blockgen-archive.
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