78,081 research outputs found

    QCD CORRECTIONS TO THE H+ -->t anti-b decay within the minimal supersymmetric standard model

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    I present the results of the QCD corrections to the H+ --> t anti-b decay within the minimal supersymmetric standard model, if gluinos and scalar quarks are taken within the relevant loop diagram. I include the mixing of the scalar partners of the left- and right-handed top quark, which is proportional to the top quark mass. The standard corrections via gluons and quarks are about +8% for a charged Higgs mass of 300 GeV and about -11% for a Higgs mass of 800 GeV. I show that the standard corrections are diminished or enhanced by a non-negligible amount for certain values of the supersymmetric parameter space. I also obtain sign changes.Comment: UQAM-PHE-94/03, 5 pages, plain tex, 5 figures not included, available under request via mail or fa

    Primordial hadrosynthesis in the Little Bang

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    The present status of soft hadron production in high energy heavy-ion collisions is summarized. In spite of strong evidence for extensive dynamical evolution and collective expansion of the fireball before freeze-out I argue that its chemical composition is hardly changed by hadronic final state interactions. The measured hadron yields thus reflect the primordial conditions at hadronization. The observed production pattern is consistent with statistical hadronization at the Hagedorn temperature from a state of uncorrelated, color deconfined quarks and antiquarks, but requires non-trivial chemical evolution of the fireball in a prehadronic (presumably QGP) stage before hadron formation.Comment: 10 pages LaTeX, including 5 figures. Invited overview talk given at Quark Matter '99, Torino, Italy, May 10-15, 1999. To appear in Nucl. Phys.

    Inhomogeneous condensates in the parity doublet model

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    Within the parity doublet model coupled to the linear sigma model including vector mesons it is possible to describe vacuum properties of the low energy mesons and to achieve nuclear saturation at nonzero density. Motivated by recent studies we investigate the emergence of inhomogeneous condensation in the parity doublet model. As a first step the chiral density wave (CDW) is con- sidered, which allows for a straightforward investigation of inhomogeneous condensation. As a result it is still possible to have a homogeneous ground state of nuclear matter, but at larger baryon chemical potential the CDW is favored with respect to the homogeneous phase.Comment: 7 pages, 4 figure

    Strange and Multi-Strange Particle Production in P+P Collisions at s\sqrt{s}=200 Gev in Star

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    We present measurements of the transverse momentum spectra for K0s, Lambda, Xi and their antiparticles in p+p collisions at s=200\sqrt{s}=200 GeV. The extracted mid-rapidity yields and are in agreement with previous p+pˉp+\bar{p} experiments while they have smaller statistical errors. We compare the measured particle spectra and values to predictions from the PYTHIA leading order pQCD model (v6.221) and see significant disagreements with the default settings. Finally we compare the spectra to the latest calculations from NLO pQCD and see a good agreement for the K0s, but large discrepancies Lambda.Comment: 4 pages, Proceedings for the 40th Rencontres de Moriond (QCD), La Thuile, March 200

    Phenomenological improvement of the linear-σ\sigma model in the large-N_c limit

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    The linear-σ\sigma model has been widely used to describe the chiral phase transition. Numerically, the critical temperature TcT_{c} of the chiral phase transition is in agreement with other effective theories of QCD. However, in the large-NcN_{c} limit TcT_{c} scales as Nc\sqrt{N_{c}} which is not in line with the NJL model and with basic expectations of QCD, according to which TcT_{c} is --just as the deconfinement phase transition- NcN_{c}-independent. This mismatch can be corrected by a phenomenologically motivated temperature dependent parameter
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