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G. Belanger

Publications and source records attributed to G. Belanger.

At least 91 records · Page 5Linked to original sources
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

The INTEGRAL View of the Galactic Nucleus

We present the preliminary results of the observational campaign performed in 2003 to study the Galactic Nucleus with INTEGRAL. The mosaicked images obtained with the IBIS/ISGRI coded aperture instrument in the energy range above 20 keV, give a yet unseen view of the high-energy sources of this region in hard X and gamma-rays, with an angular resolution of 12'. We report on the discovery of a source, IGR J17456-2901, compatible with the instrument's point spread function and coincident with the Galactic Nucleus Sgr A* to within 0.9'. The source is visible up to 60-80 keV with a 20-100 keV luminosity at 8 kpc of 3 x 10E35 erg/s. Although we cannot unequivocally associate the new INTEGRAL source to the Galactic Nucleus, this is the first report of significant hard X-ray emission from within the inner 10' of the Galaxy and a contribution from the galactic center supermassive black hole itself cannot be excluded. Here we discuss the results obtained and the perspectives for future observations of the Galactic Nucleus with INTEGRAL and other observatories

astro-ph↗
arXiv2004

Detection of hard X-ray emission from the Galactic nuclear region with INTEGRAL

This letter presents the first results of an observational campaign to study the Galactic Centre with INTEGRAL. The mosaicked images obtained with the IBIS/ISGRI coded aperture instrument in the energy ranges 20-40 and 40-100 keV, give a yet unseen view of the high-energy sources of this region in hard X- and gamma-rays with an angular resolution of 12 arcmin (FWHM). We report on the discovery of a source, IGR J17456-2901, coincident with the Galactic Nucleus SgrA* to within 0.9 arcmin. Located at R.A.(J2000.0) = 17h45m38.5s, Dec.(J2000.0) = -29:01:15, the source is visible up to about 100 keV with a 20-100 keV luminosity at 8 kpc of (2.89 +/- 0.41) x 10^35 ergs/s. Although the new INTEGRAL source cannot unequivocally be associated to the Galactic Nucleus, this is the first report of significant hard X-ray emission from within the inner 10 arcmin of the Galaxy and a contribution from the galactic supermassive black hole itself cannot be excluded.

astro-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

In flight calibration of the ISGRI camera

ISGRI, the IBIS low energy camera (15 keV - 1 MeV) on board INTEGRAL, is the first large CdTe gamma-ray imager in orbit. We present here an overview of the ISGRI in-flight calibrations performed during the first months after launch. We discuss the stability of the camera as well as the CdTe pixels response under cosmic radiation. The energy calibra tions were done using lead and tungsten fluorescence lines and the $\mathrm{^{22}Na}$ calibration unit. Thermal effects and charge correction algorithm are discussed, and the resulting energy resolution is presented. The ISGRI background spatial and spectral non-uniformity is also described, and some image correction results are presented.

astro-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.

hep-ph↗
arXiv2003

First Results from the IBIS/ISGRI Data Obtained During the Galactic Plane Scan. II. The Vela Region

We report on INTEGRAL/IBIS observations of the Vela region during a Galactic Plane Scan (hereafter GPS) presenting the IBIS in-flight performances during these operations. Among all the known sources in the field of view we clearly detect 4U 0836-429, Vela X-1, Cen X-3, GX 301-2, 1E 1145.1-6141, and H0918-549 in the 20-40 keV energy range. Only Vela X-1 and GX 301-2 are detected in the 40-80 keV energy range, and no sources are visible above. We present the results of each individual observation (~2200 s exposure), as well as those from the mosaic of these scans.

astro-ph↗
arXiv2003

Full order_alpha electroweak and order alpha_s corrections to e^+e^- --> t t H

We present the full ${\cal O}(α)$ electroweak radiative corrections to associated Higgs top pair production in $e^+e^-$ collisions. We combine these results with a new calculation of the full one-loop QCD corrections. The computation is performed with the help of {\tt GRACE-loop}. We find that the ${\cal O}(α)$ correction can be larger than the ${\cal O}(α_s)$ corrections around the peak of the cross section especially for a light Higgs mass. At threshold these corrections are swamped by the QCD corrections which are enhanced by the gluon Coulomb contribution. We have also subtracted the complete QED corrections and expressed the genuine weak correction both in the $α$-scheme and the $G_μ$-scheme. This reveals that the genuine weak corrections are not negligible and should be taken into account for a precision measurement of this cross section and the extraction of the Yukawa $t \bar t H$ coupling.

hep-ph↗
arXiv2002

Full one-loop electroweak radiative corrections to single Higgs production in e+ e-

We present the full ${\cal O}(α)$ electroweak radiative corrections to single Higgs production in \epemt. This takes into account the full one-loop corrections as well as the effects of hard photon radiation. We include both the fusion and Higgs-strahlung processes. The computation is performed with the help of {\tt GRACE-loop} where we have implemented a generalised non-linear gauge fixing condition. The latter includes 5 gauge parameters that can be used for checks on our results. Besides the UV, IR finiteness and gauge parameter independence checks it proves also powerful to test our implementation of the 5-point function. We find that for a 500GeV machine and a light Higgs of mass 150GeV, the total ${\cal O}(α)$ correction is small when the results are expressed in terms of $α_{\rm QED}$. The total correction decreases slightly for higher energies. For moderate centre of mass energies the total ${\cal O}(α)$ decreases as the Higgs mass increases, reaching -10% for $M_H=350$GeV and $\sqrt{s}=500$GeV. In order to quantify the genuine weak corrections we have subtracted the universal virtual and bremsstrahlung correction from the full ${\cal O}(α)$. We find, for $M_H=150$GeV, a weak correction slowly decreasing from -2% to -4% as the energy increases from $\sqrt{s}=300$GeV to $\sqrt{s}=1$TeV after expressing the tree-level results in terms of $G_μ$

hep-ph↗
arXiv2002

micrOMEGAs: recent developments

The program micrOMEGAs that calculates the relic density of the lightest supersymmetric particle (LSP) in the MSSM is presented. The impact of coannihilation channels and of higher order corrections to Higgs widths is stressed. The dependence on the RGE code used to calculate the soft parameters is also discussed.

hep-ph↗
arXiv2002

Full O(alpha) corrections to e+e- --> nu nu-bar H by GRACE

We present the full O(alpha) corrections to single Higgs production in e+e- collision. The computation is performed with the help of GRACE-LOOP where a generalized non-linear gauge fixing condition is implemented. The numerical results are checked by testing their UV and IR finiteness as well as their independence on all five non-linear gauge parameters. We find that for a 500 GeV collider and a light Higgs boson of mass 150GeV, the total correction is small when the results are expressed in terms of alpha rather than G_mu. For a higher Higgs boson mass of 350GeV, the correction is of order -10%.

hep-ph↗
arXiv2002

micrOMEGAs and the relic density in the MSSM

micrOMEGAs is a program 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. The cross-sections extracted from CompHEP are calculated exactly. Relativistic formulae for the thermal average are used and care is taken to handle poles and thresholds by adopting specific integration routines. The Higgs masses are calculated with FeynHiggsFast and the QCD corrected Higgs widths with HDECAY.

hep-ph↗