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Chemical equilibration and thermal dilepton production from the quark gluon plasma at finite baryon density

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 Added by Dipanwita Dutta
 Publication date 1999
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and research's language is English




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The chemical equilibration of a highly unsaturated quark-gluon plasma has been studied at finite baryon density. It is found that in the presence of small amount of baryon density, the chemical equilibration for gluon becomes slower and the temperature decreases less steeply as compared to the baryon free plasma. As a result, the space time integrated yield of dilepton is enhanced if the initial temperature of the plasma is held fixed. Even at a fixed initial energy density, the suppression of the dilepton yields at higher baryo-chemical potential is compensated, to a large extent, by the slow cooling of the plasma.

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152 - N. N. Guan , Z. J. He , J. L. Long 2009
By considering the effect of shear viscosity we have investigated the evolution of a chemically equilibrating quark-gluon plasma at finite baryon density. Based on the evolution of the system we have performed a complete calculation for the dilepton production from the following processes: $qbar{q}{to}lbar{l}$, $qbar{q}{to}glbar{l}$, Compton-like scattering ($qg{to}qlbar{l}$, $bar{q}g{to}{bar{q}}lbar{l}$), gluon fusion $gbar{g}{to}cbar{c}$, annihilation $qbar{q}{to}cbar{c}$ as well as the multiple scattering of quarks. We have found that quark-antiquark annihilation, Compton-like scatterring, gluon fusion, and multiple scattering of quarks give important contributions. Moreover, we have also found that the dilepton yield is an increasing function of the initial quark chemical potential, and the increase of the quark phase lifetime because of the viscosity also obviously raises the dilepton yield.
We present a computation, within weakly-coupled thermal QCD, of the production rate of low invariant mass ($M^2 sim g^2 T^2$) dileptons, at next-to-leading order (NLO) in the coupling (which is $O(g^3 e^2 T^2)$). This involves extending the NLO calculation of the photon rate which we recently presented to the case of small nonzero photon invariant mass. Numerical results are discussed and tabulated forms and code are provided for inclusion in hydrodynamical models. We find that NLO corrections can increase the dilepton rate by up to 30-40% relative to leading order. We find that the electromagnetic response of the plasma for real photons and for small invariant mass but high energy dilepton pairs (e.g., $M^2 < (300:mathrm{MeV})^2$ but $p_T > 1 : mathrm{GeV}$) are close enough that dilepton pair measurements really can serve as Ersatz photon measurements. We also present a matching a la Ghisoiu and Laine between our results and results at larger invariant masses.
81 - S.S. Singh , Agam K. Jha 2006
A model of cut-off momentum distribution functions in a Quark Gluon Plasma with finite baryon chemical potential is discussed. This produces a quark gluon plasma signature in Ultra Relativistic Nuclear Collisions with a specific structure of the dilepton spectrum in the transverse momentum region of $(1-4)~GeV$ and the dilepton production rate is found to be a strong decreasing function of the chemical potential.
A model of statistical quark-gluon plasma formation is considered.We look the dilepton production at critical temperature $T_{c}sim170 Mev $ and completely free out temperature $T=150 MeV$ with the initial temperature as $T_{0}=570,400 (250) MeV$. Now we consider that quark mass is depending on the coupling value through parameterisation factor of the fireball formation and temperature. The rate of production is shown for invariant mass $M$ at the particular value of $ E=2.0,3.0 GeV$.It shows the significant production of leptons in this process for small value of invariant mass. However, the quark-hadron phase transition is a very weakly changed in the entropy of the system during this process of hadronisation.
A fireball of QGP is evoluted at temperature dependent chemical potential by a statistical model in the pionic medium. We study the dilepton emission rate at temperature dependent chemical potential (TDCP) from such a fireball of QGP. In this model, we take the dynamical quark mass as a finite value dependence on temparature and parametrization factor of the QGP evolution. The temperature and factor in quark mass enhance in the growth of the droplets as well as in the dilepton emission rates. The emission rate from the plasma shows dilepton spectrum in the intermediate mass region (IMR) of (1.0-4.0) GeV and its rate is observed to be a strong increasing function of the temperature dependent chemical potential for quark and antiquark annihilation.
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