اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدDirect Photons from Relativistic Heavy-Ion Collisions
104
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Direct photons have been proposed as a promising signature for the quark-gluon plasma (QGP) formation in relativistic heavy-ion collisions. Recently WA98 presented the first data on direct photons in Pb+Pb-collisions at SPS. At the same time RHIC started with its experimental program. The discovery of the QGP in these experiments relies on a comparison of data with theoretical predictions for QGP signals. In the case of direct photons new results for the production rates of thermal photons from the QGP and a hot hadron gas as well as for prompt photons from initial hard parton scatterings have been proposed recently. Based on these rates a variety of different hydrodynamic models, describing the space-time evolution of the fireball, have been adopted for calculating the direct photon spectra. The results have been compared to the WA98 data and predictions for RHIC and LHC have been made. So far the conclusions of the various models are controversial. The aim of the present review is to provide a comprehensive and up-to-date survey and status report on the experimental and theoretical aspects of direct photons in relativistic heavy-ion collisions.
قيم البحث
اقرأ أيضاً
We examine the spectrum of bremsstrahlung photons that results from the stopping of the initial net charge distributions in ultra-relativistic nucleus-nucleus collisions at the LHC. This effect has escaped detection so far since it becomes sizeable o
nly at very low transverse momentum and at sufficiently forward rapidity. We argue that it may be within reach of the next-generation LHC heavy-ion detector ALICE-3 that is currently under study, and we comment on the physics motivation for measuring it.
We investigate the behavior of low energy photons radiated by the deceleration processes of two colliding nuclei in relativistic heavy ion collisions using the Wigner function approach for electromagnetic radiation fields. The angular distribution re
veals the information of the initial geometric configurations. Such a property is reflected in the anisotropic parameter $v_{2}$, showing an increasing $v_{2}$ as energy decreases, which is a behavior qualitatively different from $v_{2}$ from hadrons produced in the collisions.
We study the dynamics of open charm production and the dilepton radiation of the semi-leptonic decays of correlated $Dbar D$ pairs versus the quark-gluon plasma (QGP) radiation and hadronic sources in relativistic heavy-ion collisions. Our study is b
ased on the Parton-Hadron-String Dynamics (PHSD) transport approach employing a non-perturbative QCD description of the strongly interacting quark-gluon plasma (sQGP) in terms of dynamical quasiparticles and the EoS based on lattice QCD. We compare the PHSD results for charm observables with the calculations from BAMPS (Boltzmann Approach to Multi-Parton Scatterings) which is based on perturbative QCD with massless partons and interaction cross sections calculated in leading order of the QCD coupling. We compare the $p_T$ dependence of the ratio $R_{AA}$ of $D$-mesons in $A+A$ over $p+p$ collisions scaled by the number of binary collisions $N_{bin}$ as well as the elliptic flow $v_2$ of $D$-mesons calculated within the PHSD and BAMPS at LHC energies. In other study, based on the PHSD calculations we find that the dileptons from correlated $D-$meson semi-leptonic decays dominate the thermal radiation from the QGP in central Pb+Pb collisions at the intermediate masses ($1.2 < M < 3$ GeV) for higher invariant energies However, for invariant energies $sqrt{s_{NN}} < 40$ GeV the QGP radiation overshines the contribution from $D,{bar D}$ decays such that one should observe a rather clear signal from the partonic dilepton radiation. This finding provides promising perspectives to measure the QGP radiation in the dilepton experiments at RHIC BES and the future FAIR/NICA facilities.
We predict a new effect due to the presence of the global vorticity in non-central relativistic heavy-ion collisions, namely a splitting of the elliptic flow parameter $v_2$ at non-zero rapidity. The size of the splitting is proposed as a new observa
ble that can be used to constrain the initial vortical configuration of the produced QCD matter in experiments. The new findings are demonstrated by numerical calculations employing the parton cascade model, Boltzmann Approach of MultiParton Scatterings (BAMPS), for non-central Au + Au collisions at $sqrt{s_{NN}} = 200 GeV$.
We investigate the two-particle intensity correlation function of $Lambda$ in relativistic heavy-ion collisions. We find that the behavior of the $LambdaLambda$ correlation function at small relative momenta is fairly sensitive to the interaction pot
ential and collective flows. By comparing the results of different source functions and potentials, we explore the effect of intrinsic collective motions on the correlation function. We find that the recent STAR data gives a strong constraint on the scattering length and effective range of $LambdaLambda$ interaction as, $-1.8 mathrm{fm}^{-1} < 1/a_0 < -0.8 mathrm{fm}^{-1}$ and $3.5 mathrm{fm} < r_mathrm{eff} < 7 mathrm{fm}$, respectively,if $Lambda$ samples do not include feed-down contribution from long-lived particles. We find that feed-down correction for $Sigma^0$ decay reduces the sensitivity of the correlation function to the detail of the $LambdaLambda$ interaction. As a result, we obtain a weaker constraint $1/a_0 <-0.8$ fm$^{-1}$. Implication for the signal of existence of $H$-dibaryon is discussed. Comparison with the scattering parameters obtained from the double $Lambda$ hypernucleus may reveal in-medium effects in the $LambdaLambda$ interaction.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
