Ref HAL: in2p3-00024179_v1
Ref Arxiv: hep-ph/0501046
DOI: 10.1103/PhysRevLett.94.131601
Ref. & Cit.: NASA ADS
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21 citations
Résumé:

We remark that the high energy gauge boson scattering processes involving two-body initial and final states, satisfy certain selection rules described as helicity conservation of the $\underline{gauge boson}$ amplitudes (GBHC). These rules are valid at Born level, as well as at the level of the leading and sub-leading 1-loop logarithmic corrections, in both the Standard Model (SM) and the Minimal Supersymmetric Standard Model (MSSM). A "fermionic equivalence" theorem is also proved, which suggests that GBHC is valid at all orders in MSSM at sufficiently high energies, where the mass suppressed contributions are neglected.

Commentaires: 7 pages, 2 figures

Ref HAL: in2p3-00024084_v1
Ref Arxiv: hep-ph/0410364
DOI: 10.1016/j.physrep.2005.12.003
Ref. & Cit.: NASA ADS
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293 citations
Résumé:

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.

Commentaires: LHC/ILC Working group

Ref HAL: hal-00266464_v1
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Résumé:

A review of the activity of the European Network ``Physics at Colliders'' in the area of SUSY particle physics is presented.

Commentaires: Meeting of the European Network "Physics at Colliders", Montpellier (France) Sept-26-27 , 2004.

Ref HAL: in2p3-00149112_v1
Ref Arxiv: hep-ph/0412257
DOI: 10.1103/PhysRevD.71.093008
Ref. & Cit.: NASA ADS
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6 citations
Résumé:

We consider a large number of pair production processes at future colliders (LHC, ILC) for values of the c.m. energy in the TeV range, where a logarithmic expansion of Sudakov kind would provide a reliable description of Split supersymmetric electroweak effects. We calculate all the leading and next to leading terms of the expansions, that would differ drastically in the considered domain from those of an extreme "light" scenario. We imagine then two possible competitive future situations, at LHC and at ILC, where the determination of the energy dependence of the cross sections of certain processes could reveal a "signal" of the correct supersymmetric scheme.

Commentaires: 15 pages, 10 figures

Ref HAL: hal-00266461_v1
Ref Arxiv: hep-ph/0412152
DOI: 10.1016/j.physletb.2005.08.007
Ref. & Cit.: NASA ADS
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77 citations
Résumé:

ALEPH/OPAL data on the V-A spectral functions from hadronic tau decays are used in connection with a set of Laplace transform sum rules (LSR) for fixing the size of the QCD vacuum condensates up to dimension 18. Our results favour the ones from large-N_c QCD within the Minimal Hadronic Approximation (MHA) and show a violation of about a factor 2-5 of the vacuum saturation estimate of the dimension-six to -ten condensates. We scrutinize the different determinations of the QCD vacuum condensates using tau-decays data. After revisiting some of the existing results, we present coherent values of the condensates from different methods.

Ref HAL: hal-00259263_v1
Ref Arxiv: hep-ph/0412249
DOI: 10.1103/PhysRevD.71.073003
Ref. & Cit.: NASA ADS
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15 citations
Résumé:

We consider the top-antitop invariant mass distributions for production of unpolarized and polarized top quark pairs at LHC, in the theoretical framework of the MSSM. Assuming a "moderately" light SUSY scenario, we derive the leading logarithmic electroweak contributions at one loop in a region of large invariant mass, $M_{t\bar t}\simeq1$ TeV, for the unpolarized differential cross section $d\sigma/dM_{t\bar t}$ and for the differential longitudinal top polarization asymmetry $A_t(M_{t\bar t})$. We perform a realistic evaluation of the expected uncertainties of the two quantities, both from a theoretical and from an experimental point of view, and discuss the possibility of obtaining, from accurate measurements of the two mass distributions, stringent consistency tests of the model, in particular identifications of large $\tan\beta$ effects.

Commentaires: 11 pages

Ref HAL: hal-00266382_v1
Ref Arxiv: hep-ph/0412063
DOI: 10.1016/j.nuclphysbps.2005.08.045
Ref. & Cit.: NASA ADS
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19 citations
Résumé:

We rewiew and scrutinize the existing mass determinations of the pentaquarks from the exponential Laplace Sum Rules (LSR). We do not find any sum rule window for extracting optimal and reliable results from the LSR, due to the unusual slow convergence of the OPE and to the exceptional important role of the QCD continuum into the spectral function in this channel. Instead, we use in this channel,for the first time, Finite Energy Sum Rules (FESR), which exhibit a nice stability in the QCD continuum threshold t_c, at which one can extract, with a good accuracy, the mass of the lowest resonance. Including the D=7, 9 condensate contributions in the OPE, we obtain M_Theta=(1513+- 114) MeV, and the corresponding residue lambda_Theta^2= -(0.14-- 0.49)x 10^{-9} GeV^{12}, which favours the I=0, J=1/2, and negative parity S-wave interpretation of the Theta (1540). However, our analysis indicates a degeneracy between the unmixed I=0 and I=1 S-wave states. In the I=0, J=1/2, P-wave channel, we obtain, for the P-resonance, M_P = (1.99+- 0.19) GeV and lambda_P= -(0.7--7.1)x 10^{-9} GeV^{14}, which we expect to be discovered experimentally. Our results also suggest that some intuitive choices of the continuum threshold used in the LSR literature are inconsistent with the FESR results. Finally, a study of the Theta-K-N coupling using a vertex sum rule shows that, for the I=0, S-wave channel, the leading OPE contributions only start to order alpha_s^2 in the chiral limit m_s=0, indicating that the Theta is very narrow.

Commentaires: Contribution to the QCD 04 International Conference (Montpellier-5-9th July 2004) and to HEP-MAD 04 International Conference (Antananarivo 27th Sept-2nd Oct. 2004).