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M. Spira

Publications and source records attributed to M. Spira.

At least 37 records · Page 2Linked to original sources
arXiv2012

Handbook of LHC Higgs Cross Sections: 2. Differential Distributions

This Report summarises the results of the second year's activities of the LHC Higgs Cross Section Working Group. 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 working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) focuses on predictions (central values and errors) for total Higgs production cross sections and Higgs branching ratios in the Standard Model and its minimal supersymmetric extension, covering also related issues such as Monte Carlo generators, parton distribution functions, and pseudo-observables. This second Report represents the next natural step towards realistic predictions upon providing results on cross sections with benchmark cuts, differential distributions, details of specific decay channels, and further recent developments.

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arXiv2011

Neutral Higgs Boson Decays to Squark Pairs reanalyzed

We analyze neutral Higgs boson decays into squark pairs in the minimal supersymmetric extension of the Standard Model and improve previous analyses. In particular the treatment of potentially large higher-order corrections due to the soft SUSY breaking parameters A_b, the trilinear Higgs coupling to sbottoms, and mu, the Higgsino mass parameter, is investigated. The remaining theoretical uncertainties including the SUSY-QCD corrections are analyzed quantitatively.

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arXiv2011

Standard Model Higgs-Boson Branching Ratios with Uncertainties

We present an update of the branching ratios for Higgs-boson decays in the Standard Model. We list results for all relevant branching ratios together with corresponding uncertainties resulting from input parameters and missing higher-order corrections. As sources of parametric uncertainties we include the masses of the charm, bottom, and top quarks as well as the QCD coupling constant. We compare our results with other predictions in the literature.

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arXiv2011

Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables

This Report summarizes the results of the first 10 months' activities of the LHC Higgs Cross Sections Working Group. The main goal of the working group was to present the status-of-art on Higgs Physics at the LHC integrating all new results that have appeared in the last few years. The Report is more than a mere collection of the proceedings of the general meetings. The subgroups have been working in different directions. An attempt has been made to present the first Report from these subgroups in a complete and homogeneous form. The subgroups' contributions correspondingly comprise the main parts of the Report. A significant amount of work has been performed in providing higher-order corrections to the Higgs-boson cross sections and pinning down the theoretical uncertainty of the Standard Model predictions. This Report comprises explicit numerical results on total cross sections, leaving the issues of event selection cuts and differential distributions to future publications. The subjects for further study are identified.

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arXiv2010

SUSY-QCD corrections to MSSM Higgs boson production via gluon fusion

In the MSSM scalar h,H production is mediated by heavy quark and squark loops. The higher order QCD corrections have been obtained some time ago and turned out to be large. The full SUSY QCD corrections have been obained recently including the full mass dependence of the loop particles. We describe our calculation and present first numerical results. We also address the question of the proper treatment of the large gluino mass limit, i.e. the consistent decoupling of heavy gluino effects, and present the effective Lagrangian for decoupled gluinos.

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arXiv2010

The Hunt for New Physics at the Large Hadron Collider

The Large Hadron Collider presents an unprecedented opportunity to probe the realm of new physics in the TeV region and shed light on some of the core unresolved issues of particle physics. These include the nature of electroweak symmetry breaking, the origin of mass, the possible constituent of cold dark matter, new sources of CP violation needed to explain the baryon excess in the universe, the possible existence of extra gauge groups and extra matter, and importantly the path Nature chooses to resolve the hierarchy problem - is it supersymmetry or extra dimensions. Many models of new physics beyond the standard model contain a hidden sector which can be probed at the LHC. Additionally, the LHC will be a top factory and accurate measurements of the properties of the top and its rare decays will provide a window to new physics. Further, the LHC could shed light on the origin of neutralino masses if the new physics associated with their generation lies in the TeV region. Finally, the LHC is also a laboratory to test the hypothesis of TeV scale strings and D-brane models. An overview of these possibilities is presented in the spirit that it will serve as a companion to the Technical Design Reports (TDRs) by the particle detector groups ATLAS and CMS to facilitate the test of the new theoretical ideas at the LHC. Which of these ideas stands the test of the LHC data will govern the course of particle physics in the subsequent decades.

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arXiv2009

SUSY Les Houches Accord 2

The Supersymmetry Les Houches Accord (SLHA) provides a universal set of conventions for conveying spectral and decay information for supersymmetry analysis problems in high energy physics. Here, we propose extensions of the conventions of the first SLHA to include various generalisations: the minimal supersymmetric standard model with violation of CP, R-parity, and flavour, as well as the simplest next-to-minimal model.

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arXiv2009

SUSY Les Houches Accord: Interfacing SUSY Spectrum Calculators, Decay Packages, and Event Generators

An accord specifying a unique set of conventions for supersymmetric extensions of the Standard Model together with generic file structures for 1) supersymmetric model specifications and input parameters, 2) electroweak scale supersymmetric mass and coupling spectra, and 3) decay tables is defined, to provide a universal interface between spectrum calculation programs, decay packages, and high energy physics event generators.

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arXiv2009

Gluino Polarization at the LHC

Gluinos are produced pairwise at the LHC in quark-antiquark and gluon-gluon collisions: $qqbar,gg \to \tilde{g} \tilde{g}$. While the individual polarization of gluinos vanishes in the limit in which the small mass difference between L and R squarks of the first two generations is neglected, non-zero spin-spin correlations are predicted within gluino pairs. If the squark/quark charges in Majorana gluino decays are tagged, the spin correlations have an impact on the energy and angular distributions in reconstructed final states. On the other hand, the gluino polarization in single gluino production in the supersymmetric Compton process $g q \to \tilde{g} \tilde{q}_{R,L}$ is predicted to be non-zero, and the polarization affects the final-state distributions in super-Compton events.

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arXiv2008

Examining the Identity of Yukawa with Gauge Couplings in Supersymmetric QCD at LHC

The identity of the quark-squark-gluino Yukawa coupling with the corresponding quark-quark-gluon QCD coupling in supersymmetric theories can be examined experimentally at the Large Hadron Collider (LHC). Extending earlier investigations of like-sign di-lepton final states, we include jets in the analysis of the minimal supersymmetric standard model, adding squark-gluino and gluino-pair production to squark-pair production. Moreover we expand the method towards model-independent analyses which cover more general scenarios. In all cases, squark decays to light charginos and neutralinos persist to play a dominant role.

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arXiv2008

Collider aspects of flavour physics at high Q

This review presents flavour related issues in the production and decays of heavy states at LHC, both from the experimental side and from the theoretical side. We review top quark physics and discuss flavour aspects of several extensions of the Standard Model, such as supersymmetry, little Higgs model or models with extra dimensions. This includes discovery aspects as well as measurement of several properties of these heavy states. We also present public available computational tools related to this topic.

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arXiv2007

Concepts of Electroweak Symmetry Breaking and Higgs Physics

We present an introduction to the basic concepts of electroweak symmetry breaking and Higgs physics within the Standard Model and its supersymmetric extensions. A brief overview will also be given on alternative mechanisms of electroweak symmetry breaking. In addition to the theoretical basis, the present experimental status of Higgs physics and prospects at the Tevatron, the LHC and e+e- linear colliders are discussed.

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arXiv2006

Heavy neutral MSSM Higgs Bosons at the PLC - a comparison of two analyses

Measurement of the heavy neutral MSSM Higgs bosons H and A production in the process gamma gamma --> A, H --> b anti-b at the Photon Linear Collider has been considered in two independent analyses for the parameter range corresponding to the so-called "LHC wedge". Significantly different conclusions were obtained; signal to background ratio 36 vs 2. Here assumptions and results of these two analyses are compared. We have found that differences in the final results are mainly due to different assumptions on gamma-gamma-luminosity spectra, jet definitions and selection cuts.

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arXiv2006

Decays of Supersymmetric Particles: the program SUSY-HIT (SUspect-SdecaY-Hdecay-InTerface)

We present the program package SUSY-HIT for the computation of supersymmetric particle decays within the framework of the Minimal Supersymmetric extension of the Standard Model. The code is based on two existing programs HDECAY and SDECAY for the calculation of the decay widths and branching ratios of, respectively, the MSSM Higgs bosons and the SUSY particles, and calls a program for the calculation of the SUSY particle spectrum such as SuSpect. Including all important higher order effects, the package allows the consistent calculation of the MSSM particle spectrum and decays with the presently highest level of precision.

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arXiv2006

SM and MSSM Higgs Boson Production: Spectra at large transverse Momentum

Strategies for Higgs boson searches require the knowledge of the total production cross section and the transverse momentum spectrum. The large transverse momentum spectrum of the Higgs boson produced in gluon fusion can be quite different in the Standard Model and the Minimal Supersymmetric Standard Model. In this paper we present a comparison of the Higgs transverse momentum spectrum obtained using the PYTHIA event generator and the HIGLU program as well as the program HQT, which includes NLO corrections and a soft gluon resummation for the region of small transverse momenta. While the shapes of the spectra are similar for the Standard Model, significant differences are observed in the spectra of Minimal Supersymmetric Standard Model benchmark scenarios with large tan(beta).

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arXiv2006

Toward High Precision Higgs-Boson Measurements at the International Linear e+e- Collider

This report reviews the properties of Higgs bosons in the Standard Model (SM) and its various extensions. We give an extensive overview about the potential of the ILC operated at centre-of-mass energies up to 1 TeV (including the gamma gamma option) for the determination of the Higgs boson properties. This comprises the measurement of the Higgs boson mass, its couplings to SM fermions and gauge bosons, and the determination of the spin and the CP quantum numbers of the Higgs. The extensions of the SM that are analyzed in more detail are heavy SM-like Higgs bosons, heavy Higgs bosons in the framework of Supersymmetry (SUSY) and further exotic scenarios. We review recent theoretical developments in the field of Higgs boson physics. The important question what the ILC can contribute to Higgs boson physics after the LHC, the LHC/ILC interplay and synergy is discussed. The impact of Higgs boson physics on cosmology in several SUSY frameworks is analyzed. The impact of the accelerator and dector performance on the precision of measurements are discussed in detail. We propose a strategy to optimize future analyses. Open questions arising for the various topics are listed, further topics of study and corresponding roadmaps are suggested.

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