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F. Boudjema

Publications and source records attributed to F. Boudjema.

At least 55 records · Page 3Linked to original sources
arXiv2006

Les Houches "Physics at TeV Colliders 2005'' Beyond the Standard Model working group: summary report

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.

hep-ph↗
arXiv2005

Electroweak Corrections for the Study of the Higgs Potential at the LC

The full electroweak radiative correction is calculated for the process ee--> nunubarHH which is a window for the study of the Higgs potential at the future linear collider. The calculation is done by using GRACE, the automated system for the calculation of Feynman diagrams. The magnitude of the weak correction in the G-mu scheme is small in the high energy region where this process dominates over the ZHH production.

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arXiv2005

Self-annihilation of the neutralino dark matter into two photons or a Z and a photon in the MSSM

We revisit the one-loop calculation of the annihilation of a pair of the lightest neutralinos into a pair of photons, a pair of gluons and also a Z photon final state. For the latter we have identified a new contribution that may not always be negligible. For all three processes we have conducted a tuned comparison with previous calculations for some characteristic scenarios. The approach to the very heavy higgsino and wino is studied and we argue how the full one-loop calculation should be matched into a more complete treatment that was presented recently for these extreme regimes. We also give a short description of the code that we exploited for the automatic calculation of one-loop cross sections in the MSSM that could apply both for observables at the colliders and for astrophysics or relic density calculations. In particular the automatic treatment of zero Gram determinants which appear in the latter applications is outlined. We also point out how generalised non-linear gauge fixing constraints can be exploited.

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arXiv2005

Relic density of dark matter in the NMSSM

We present a code to compute the relic density of dark matter in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). Dominant corrections to the Higgs masses are calculated with NMHDECAY as well as theoretical and collider constraints. All neutralino annihilation and coannihilation processes are then computed with an extended version of micrOMEGAs, taking into acount higher order corrections to Higgs vertices. We explore the parameter space of the NMSSM and consider in particular the case of a bino LSP, of a mixed bino-higgsino LSP and of a singlino LSP. As compared to the MSSM, neutralino annihilation is often more efficient as it can take place via (additional) Higgs resonances as well as annihilation into light Higgs states. Models with a large singlino component can be compatible with WMAP constraints.

hep-ph↗
arXiv2004

Relic density of dark matter in mSUGRA and non-universal SUGRA

The measurements of WMAP on the relic density of dark matter strongly constrain supersymmetric models. In mSUGRA where the neutralino LSP is mostly a bino only rather fine-tuned models survive. On the other hand the relic density upper limit can be easily satisfied in models with a Higgsino or wino LSP.

hep-ph↗
arXiv2004

Physics at the CLIC Multi-TeV Linear Collider

This report summarizes a study of the physics potential of the CLIC e+e- linear collider operating at centre-of-mass energies from 1 TeV to 5 TeV with luminosity of the order of 10^35 cm^-2 s^-1. First, the CLIC collider complex is surveyed, with emphasis on aspects related to its physics capabilities, particularly the luminosity and energy, and also possible polarization, γγand e-e- collisions. The next CLIC Test facility, CTF3, and its R&D programme are also reviewed. We then discuss aspects of experimentation at CLIC, including backgrounds and experimental conditions, and present a conceptual detector design used in the physics analyses, most of which use the nominal CLIC centre-of-mass energy of 3 TeV. CLIC contributions to Higgs physics could include completing the profile of a light Higgs boson by measuring rare decays and reconstructing the Higgs potential, or discovering one or more heavy Higgs bosons, or probing CP violation in the Higgs sector. Turning to physics beyond the Standard Model, CLIC might be able to complete the supersymmetric spectrum and make more precise measurements of sparticles detected previously at the LHC or a lower-energy linear e+e- collider: γγcollisions and polarization would be particularly useful for these tasks. CLIC would also have unique capabilities for probing other possible extensions of the Standard Model, such as theories with extra dimensions or new vector resonances, new contact interactions and models with strong WW scattering at high energies. In all the scenarios we have studied, CLIC would provide significant fundamental physics information beyond that available from the LHC and a lower-energy linear e+e- collider, as a result of its unique combination of high energy and experimental precision.

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arXiv2004

Requirements on collider data to match the precision of WMAP on supersymmetric dark matter

If future colliders discover supersymmetric particles and probe their properties, one could predict the dark matter density of the Universe and would constrain cosmology with the help of precision data provided by WMAP and PLANCK. We investigate how well the relic density can be predicted in minimal supergravity (mSUGRA), with and without the assumption of mSUGRA when analysing data. We determine the parameters to which the relic density is most sensitive, and quantify the collider accuracy needed. Theoretical errors in the prediction are investigated in some detail.

hep-ph↗
arXiv2004

Physics Interplay of the LHC and the ILC

Physics at the Large Hadron Collider (LHC) and the International e+e- Linear Collider (ILC) will be complementary in many respects, as has been demonstrated at previous generations of hadron and lepton colliders. This report addresses the possible interplay between the LHC and ILC in testing the Standard Model and in discovering and determining the origin of new physics. Mutual benefits for the physics programme at both machines can occur both at the level of a combined interpretation of Hadron Collider and Linear Collider data and at the level of combined analyses of the data, where results obtained at one machine can directly influence the way analyses are carried out at the other machine. Topics under study comprise the physics of weak and strong electroweak symmetry breaking, supersymmetric models, new gauge theories, models with extra dimensions, and electroweak and QCD precision physics. The status of the work that has been carried out within the LHC / LC Study Group so far is summarised in this report. Possible topics for future studies are outlined.

hep-ph↗
arXiv2004

WMAP constraints on SUGRA models with non-universal gaugino masses and prospects for direct detection

We discuss constraints on supersymmetric models arising from the relic density measurements of WMAP as well as from direct and precision measurements, LEP, b-sgamma, g-2, Bs-mumu. We consider mSUGRA models and their extensions with non-universal gaugino masses. We find, as commonly known, that the relic density pinpoints towards very specific regions of the mSUGRA models: coannihilation, focus and Heavy Higgs annihilation. The allowed regions widen significantly when varying the top quark mass. Introducing some non-universality in the gaugino masses significantly changes this conclusion as in specific non-universal models the relic density upper limit can be easily satisfied. This occurs with models where M1>M2 at the GUT scale when the LSP has a high wino component. Models where M3<M2 favours the Higgs annihilation channel in large regions of parameter space and at large $\tanβ$ also favours the annihilation of neutralinos in gauge bosons pairs.We discuss also the potential of direct detection experiments to probe supersymmetric models and point out at the main consequences for colliders based on the mass spectrum. Our calculation of the relic density of neutralinos is based on micrOMEGAs and the SUSY spectrum is generated with SoftSUSY

hep-ph↗
arXiv2004

Multi-leg calculations with the GRACE/1-LOOP system. --Toward Radiative Corrections to e+e- -> mu nu-bar u d-bar --

We performed the calculation of the full O(alpha) corrections to e+e- -> mu- nu-bar u d-bar with the help of the GRACE/1-LOOP system. We discuss how a finite decay width introduces a serious gauge invariance breaking, particularly for infrared 5-point functions. This is related to the way the reduction of those functions is performed and to the treatment of the width in the reduction.

hep-ph↗
arXiv2004

Electroweak corrections to Higgs production through ZZ fusion at the linear collider

We present the full order alpha electroweak radiative corrections to e+e- -> e+e-H. The computation is performed with the help of GRACE-loop. The extraction of the full QED corrections is performed, these are quite large at threshold. The genuine weak corrections, for the linear collider energies, when expressed in the G_mu scheme are of order -2 to -4 for Higgs masses preferred by the latest precision data. We also extract the m_t^2 type corrections and make a comparison with the weak corrections for the process e+e- ->nu nu H.

hep-ph↗
arXiv2004

micrOMEGAs: Version 1.3

We present the latest version of micromegas, a code that calculates the relic density of the lightest supersymmetric particle in the MSSM. All tree-level processes for the annihilation of the LSP are included as well as all possible coannihilation processes with neutralinos, charginos, sleptons, squarks and gluinos. The cross-sections extracted from CalcHEP are calculated exactly using loop-corrected masses and mixings as specified in the SUSY Les Houches Accord. Relativistic formulae for the thermal average are used and care is taken to handle poles and thresholds by adopting specific integration routines. The input parameters can be either the soft SUSY parameters in a general MSSM or the parameters of a SUGRA model specified at some high scale (GUT). In the latter case, a link with Suspect, Softsusy, Spheno and Isajet allows to calculate the supersymmetric spectrum, Higgs masses, as well as mixing matrices. Higher-order corrections to Higgs couplings to quark pairs including QCD as well as some SUSY corrections (deltaMb) are implemented. Routines calculating (g-2), bsgamma and bsmumu are also included. In particular the bsgamma routine includes an improved NLO for the SM and the charged Higgs while the SUSY large tan(beta) effects beyond leading-order are included. This new version also provides cross-sections for any 2->2 process as well as partial decay widths for two-body final states in the MSSM allowing for easy simulation at colliders.

hep-ph↗
arXiv2004

Les Houches "Physics at TeV Colliders 2003" Beyond the Standard Model Working Group: Summary Report

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, 26 May--6 June, 2003. The research presented is original, and was performed specifically for the workshop. Tools for calculations in the minimal supersymmetric standard model are presented, including a comparison of the dark matter relic density predicted by public codes. Reconstruction of supersymmetric particle masses at the LHC and a future linear collider facility is examined. Less orthodox supersymmetric signals such as non-pointing photons and R-parity violating signals are studied. Features of extra dimensional models are examined next, including measurement strategies for radions and Higgs', as well as the virtual effects of Kaluza Klein modes of gluons. An LHC search strategy for a heavy top found in many little Higgs model is presented and finally, there is an update on LHC $Z'$ studies.

hep-ph↗
arXiv2004

Uncertainties in Relic Density Calculations in mSUGRA

We compare the relic density of neutralino dark matter within the minimal supergravity model (mSUGRA) using four different public codes for supersymmetric spectra evaluation. While the predictions for the relic density of neutralinos are rather stable in most of the mSUGRA space, it is in the most physically interesting regions that large discrepancies can be observed, in particular the focus point, large tan beta and coannihilation regions.

hep-ph↗
arXiv2003

Lower limit on the neutralino mass in the general MSSM

We discuss constraints on SUSY models with non-unified gaugino masses and R_P conservation. We derive a lower bound on the neutralino mass combining the direct limits from LEP, the indirect limits from gmuon, bsgamma, Bsmumu and the relic density constraint from WMAP. The lightest neutralino (mneutralino=6GeV) is found in models with a light pseudoscalar with MA<200GeV and a large value for $tanβ$. Models with heavy pseudoscalars lead to mneutralino>18(29)GeV for $\tanβ=50(10)$. We show that even a very conservative bound from the muon anomalous magnetic moment can increase the lower bound on the neutralino mass in models with mu<0 and/or large values of $\tanβ$. We then examine the potential of the Tevatron and the direct detection experiments to probe the SUSY models with the lightest neutralinos allowed in the context of light pseudoscalars with high $\tanβ$. We also examine the potential of an e+e- collider of 500GeV to produce SUSY particles in all models with neutralinos lighter than the W. In contrast to the mSUGRA models, observation of at least one sparticle is not always guaranteed.

hep-ph↗
arXiv2003

Full order alpha electroweak corrections to double Higgs-strahlung at the linear collider

We present the full order alpha electroweak radiative corrections to the double Higgs-strahlung process e+e- --> ZHH. The computation is performed with the help of GRACE-loop. After subtraction of the initial state QED radiative corrections, we find that the genuine weak corrections in the $α$-scheme are small for Higgs masses and energies where this cross section is largest and is most likely to be studied. These corrections decrease with increasing energies attaining about $\sim -10%$ at $\sqrt{s}=1.5$TeV. The full order alpha correction on the other hand is quite large at threshold but small at energies around the peak. We also study changes in the shape of the invariant mass of the Higgs pair which has been shown to be a good discriminating variable for the measurement of the triple Higgs vertex in this reaction.

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