Physics beyond the standard model

2006

The work contained herein constitutes a report of the "Beyond the Standard Model" working group for the Workshop "Physics at TeV Colliders", Les Houches, France, 2-20 May, 2005. We present reviews of current topics as well as original research carried out for the workshop. Supersymmetric and non-supersymmetric models are studied, as well as computational tools designed in order to facilitate their phenomenology.

Proceedings of Corfu Summer Institute 2017 "Schools and Workshops on Elementary Particle Physics and Gravity" — PoS(CORFU2017), 2018

Physical Review D, 2002

We investigate the prospects for heavy charged Higgs boson production through the mechanisms pp (pp) →H Ϯ tbϩX at the upgraded Fermilab Tevatron and at the upcoming LHC at CERN, respectively. We focus on the minimal supersymmetric standard model case and include the leading quantum corrections at high tan ␤. A detailed study is performed for all important production modes and basic background processes for the t tbb signature. At the upgraded Tevatron a charged Higgs signal is potentially viable in the 220-250 GeV range or excluded at 95% C.L. up to 300 GeV. At the LHC, a H Ϯ of mass up to 800 GeV can be discovered at 5 or else be excluded up to a mass of ϳ1.5 TeV. The presence of SUSY quantum effects may highly influence the discovery potential in both machines and can typically shift these limits by 200 GeV at the LHC.

2006

2 Contents 1. Foreword 4 I STANDARD MODEL BENCHMARKS AND BACKGROUNDS 5 2. Model predictions for σ tot at the LHC 5 3. Tuning models for minimum bias and the underlying event 11 4. Small x 17 5. Parton-parton luminosity functions for the LHC 34 6. A simple model for large-x resummed parton distributions 40 7. Bottom-quark fragmentation: from e + e − data to top and Higgs decays 43 8. Study of jet clustering algorithms at the LHC 48 9. Colour annealing -a toy model of colour reconnections 55 10. Tuned comparison of electroweak corrections to Drell-Yan-like W -and Z-boson production -a status report 61 11. Electroweak corrections to large transverse momentum production of Z bosons and photons at the LHC 67 12. Impact of weak corrections on LHC jet cross sections 72 13. Search for anomalous couplings in top decay at hadron colliders 74 14. Effective NLO approach in the model of single top quark production 82

Journal of Physics: Conference Series, 2010

Discovering the Higgs boson is one of the primary goals of both the Tevatron and the Large Hadron Collider (LHC). The present status of the Higgs search is reviewed and future prospects for discovery at the Tevatron and LHC are considered. This talk focuses primarily on the Higgs boson of the Standard Model and its minimal supersymmetric extension. Theoretical expectations for the Higgs boson and its phenomenological consequences are examined.

Journal of High Energy Physics, 2013

We perform the fit of electroweak precision observables within the Standard Model with a 126 GeV Higgs boson, compare the results with the theoretical predictions and discuss the impact of recent experimental and theoretical improvements. We introduce New Physics contributions in a model-independent way and fit for the S, T and U parameters, for the 1,2,3,b ones, for modified Zbb couplings and for a modified Higgs coupling to vector bosons. We point out that composite Higgs models are very strongly constrained. Finally, we compute the bounds on dimension-six operators relevant for the electroweak fit.

arXiv (Cornell University), 1995

Physics Letters B, 1998

Recently, the LEP collaborations have reported a lower bound on a Standard Model-like Higgs boson of order 89 GeV. We discuss the implications of this bound for the minimal supersymmetric extension of the Standard Model (MSSM). In particular, we show that the lower bound on tan β, which can be obtained from the presently allowed Higgs boson mass value, becomes stronger than the one set by the requirement of perturbative consistency of the theory up to scales of order M GU T (associated with the infrared fixed-point solution of the top quark Yukawa coupling) in a large fraction of the allowed parameter space. The potentiality of future LEP2 searches to further probe the MSSM parameter space is also discussed.

Nuclear Physics B - Proceedings Supplements, 2010

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. In addition to the standard Higgs decay scenarios, nonstandard Higgs decay scenarios can be envisaged. In the nonstandard scenarios the Higgs dominantly decays into new light states, ultimately resulting in a cascade decay into multiple Standard Model particles.

2005

This working group has investigated Higgs boson searches at the Tevatron and the LHC. Once Higgs bosons are found their properties have to be determined. The prospects of Higgs coupling measurements at the LHC and a high-energy linear e+e-collider are discussed in detail within the Standard Model and its minimal supersymmetric extension (MSSM). Recent improvements in the theoretical knowledge of the signal and background processes are presented and taken into account. The residual uncertainties are analyzed in detail. Theoretical progress is discussed in particular for the gluon-fusion processes gg-+ H(+j), Higgsbremsstrahlung off bottom quarks and the weak vector-boson-fusion (VBF) processes. Following the list of open questions of the last Les Houches workshop in 2001 several background processes have been. calculated at next-to-leading order, resulting in a significant reduction of the theoretical uncertainties. Further improvements have been achieved for the Higgs sectors of the MSSM and NMSSM. This report summarizes our work performed before and after the workshop in Les Houches. Part A describes the theoretical developments for signal and background processes. Part B presents recent progress in Higgs boson searches at the Tevatron collider. Part C addresses the determination of Higgs boson couplings, part D the measurement of tan ,O and part E Higgs boson searches in the VBF processes at the LHC. Part F summarizes Higgs searches in supersymmetric Higgs decays, part G photonic Higgs decays in Higgs-strahlung processes at the LHC, while part H concentrates on MSSM Higgs bosons in the intense-coupling regime at the LHC. Part I presents progress in charged Higgs studies and part J the Higgs discovery potential in the NMSSM at the LHC. The last part K describes Higgs coupling measurements at a 1 TeV linear e+e-collider.