Ref Arxiv: hep-ph/0402028
DOI: 10.1103/PhysRevD.69.113004
Ref. & Cit.: NASA ADS
14 citations
Résumé:

We consider the production of heavy (b,t) quark pairs at proton colliders in the theoretical framework of the MSSM. Under the assumption of a "moderately" light SUSY scenario, we first compute the leading logarithmic MSSM contributions at one loop for the elementary processes of production from a quark and from a gluon pair in the 1 TeV c.m. energy region. We show that in the initial gluon pair case (dominant in the chosen situation at energies reached at the CERN LHC) the electroweak and the strong SUSY contributions concur to produce an enhanced effect whose relative value in the cross sections could reach the twenty percent size for large tan beta values in the realistic proton-proton LHC process.

Ref HAL: hal-00328139_v1
Ref Arxiv: hep-ph/0208271
Ref. & Cit.: NASA ADS
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Résumé:

We quantitatively study the effects, beyond the SVZ-expansion, due to instanton and tachyonic gluon mass, to the scalar isoscalar two-point functions supporting the fact that the QCD spectral sum do not favour the $\bar uu+\bar dd$ interpretation of the broad and low mass ?(0.6). Then, we emphasize that a measurement of the Ds semileptonic decays into ?? can reveal in a model-independent way its eventual gluon component ?B. The analysis also implies that one expects an observation of the $K\bar K$ final states from the ?B which may compete (if phase space allowed) with the one from a low mass $\bar ss$ state assumed in the literature to be the SU(3) partner of the observed u(0.6) if the latter is a $\bar uu+\bar dd$ state.

Commentaires: DOI: 10.1016/S0920-5632(03)01824-3

Ref Arxiv: astro-ph/0410032
DOI: 10.1103/PhysRevD.70.123003
Ref. & Cit.: NASA ADS
191 citations
Résumé:

A detailed numerical and analytical examination of the evolution of stochastic magnetic fields between a putative magnetogenesis era at high cosmic temperatures T~100 MeV–100 GeV and the present epoch is presented. The analysis includes all relevant dissipation processes, such as neutrino- and photon-induced fluid viscosities as well as ambipolar and hydrogen diffusion. A simple and intuitive analytical model matching the results of the three-dimensional MHD simulations allows for the prediction of prerecombination and present day magnetic field correlation lengths and energy densities as a function of initial magnetic field energy density, helicity, and spectral index. Our conclusions are multifold. (a) Initial primordial fields with only a small amount of helicity are evolving into maximally helical fields at the present. Furthermore, the simulations show a self-similarity in the evolution of maximally helical fields implying a seemingly acausual amplification of magnetic fields on large scales is observed. (b) There exists a correlation between the strength of the magnetic field B at the peak of its spectrum and the location of the peak, given at the present epoch by B[approximate]5×10-12 G(L/kpc), where L is the magnetic field correlation length determined by the initial properties of the magnetic field. (c) Concerning studies of the generation of cosmic microwave background (CMBR) anisotropies due to primordial magnetic fields of B~10-9 G on >~10 Mpc scales, such fields are not only impossible to generate in early causal magnetogenesis scenarios but also seemingly ruled out by distortions of the CMBR spectrum due to magnetic field dissipation on smaller scales and the overproduction of cluster-magnetic fields. (d) The most promising detection possibility of CMBR distortions due to primordial magnetic fields may be on much smaller scales at higher multipoles l~106 where the signal is predicted to be the strongest. (e) It seems possible that magnetic fields in clusters of galaxies are entirely of primordial origin, without invoking dynamo amplification. Such fields would be of (precollapse) strength 10-12–10-11 G with correlation lengths in the kpc range and would also exist in voids of galaxies.

Ref Arxiv: hep-ph/0311076
DOI: 10.1140/epjc/s2003-01520-x
Ref. & Cit.: NASA ADS
7 citations
Résumé:

We present a complete one-loop study of the process $\gamma \gamma \to \tilde \chi^0_i \tilde \chi^0_j$ and the predicted cross section in a $\gamma \gamma $ Linear Collider. A suitable numerical code, PLATONlc, valid for any set of real MSSM parameters, is released. This study and code are complementary to those suitable for dark matter detection through the inverse process $\tilde \chi^0_i \tilde \chi^0_j \to \gamma\gamma$ describing neutralino-neutralino annihilation at rest, which were presented previously. If SUSY is realized in nature, both codes should be very helpful in future astrophysical and collider studies of the neutralino sector.

Ref HAL: hal-00182662_v1
Ref Arxiv: astro-ph/0306211
DOI: 10.1103/PhysRevLett.91.251301
Ref. & Cit.: NASA ADS
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54 citations
Résumé:

We present results of a detailed and fully non-linear numerical and analytical investigation of magnetic field evolution from the very earliest cosmic epochs to the present. We find that, under reasonable assumptions concerning the efficiency of a putative magnetogenesis era during cosmic phase transitions, surprisingly strong magnetic fields 10^{-13} - 10^{-11} Gauss, on comparatively small scales 100 pc - 10 kpc may survive to the present. Building on prior work on the evolution of magnetic fields during the course of gravitational collapse of a cluster, which indicates that pre-collapse fields of 4\times 10^{-12} Gauss extant on small scales may suffice to produce clusters with acceptable Faraday rotation measures, we question the widely hold view that cluster magnetic fields may not be entirely of primordial origin.

Commentaires: 4 pages, 3 figures, missing factor in Eq.4 added Erratum-ibid. 9317(2004) 179901, 1 page DOI: 10.1103/PhysRevLett.93.179901 PACS: 98.62.En, 98.65.Cw, 98.80.Cq, 99.10.Cd

Ref HAL: hal-00335193_v1
Ref Arxiv: hep-ph/0307391
DOI: 10.1016/j.physletb.2003.10.006
Ref. & Cit.: NASA ADS
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47 citations
Résumé:

We study the Higgs-boson decays h0 -> b \bar{b}, h0 -> \gamma \gamma and h0 -> \gamma Z within the framework of the Two Higgs Doublet Model (THDM) in the context of the decoupling regime, together with tree level unitarity constraints. We show that when the light CP-even Higgs boson of the THDM mimics the Standard-Model Higgs boson, not only the one-loop effects to h0 -> {\gamma \gamma ,\gamma Z} but also the one-loop contribution to h0 -> b \bar{b} can be used to distinguish between THDM and SM. The size of the quantum effects in h0 -> b \bar{b} are of the same order as in h0 -> {\gamma \gamma ,\gamma Z} and can reach 25% in both cases.

Commentaires: LaTeX, 13 pages, 5 figures. Improved text, added references, appendix removed. Version to appear in PLB

Ref HAL: hal-00266460_v1
Ref Arxiv: hep-ph/0307248
DOI: 10.1016/j.physletb.2004.11.002
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
90 citations
Résumé:

We study the dynamics of the the spin zero open charm and beauty mesons using QCD spectral sum rules (QSSR), where we observe the important r\^ole of the chiral condensate <\bar \psi\psi> in the mass-splittings between the scalar-pseudoscalar mesons. Fixing the sum rule parameters for reproducing the well-known D(0-) and Ds(0-) masses, we re-obtain the running charm quark mass: mc(mc)=1.13^{+0.08}_{-0.04} GeV, which confirms our recent estimate from this channel [1]. Therefore, using sum rules, with no-free parameters, we deduce M_{Ds(0+)}= (2297+- 113) MeV, which is consistent with the observed Ds(2317) meson, while a small SU(3) breaking of about 25 MeV for the Ds(0+)-D(0+) mass-difference has been obtained. We extend our analysis to the B-system and find M{B(0+)}- M{B(0-)}= (422+- 196) MeV confirming our old result from moment sum rules [2]. Assuming an approximate (heavy and light) flavour and spin symmetries of the mass-splittings as indicated by our results, we also deduce M_{D*s(1+)}= (2440+-113) MeV in agreement with the observed D{sJ}(2457). We also get: f{D(0+)}= (217+- 25) MeV much bigger than fpi=130.6 MeV, while the size of the SU(3) breaking ratio f{Ds(0+)}/f{D(0+)}= 0.93+- 0.02 is opposite to the one of the 0- channel of about 1.14.