Coupling of the quark-gluon plasma from the early stage of heavy-ion collisions is argued to be weaker at LHC than at RHIC. For this reason, the role of instabilities - the pre-equilibrium plasma is unstable with respect to chromomagnetic modes - will be enhanced. The instabilities isotropize the system and speed up the process of equilibration. A possibility to observe direct signals of the instabilities is considered.
We study the radiative correction to $p_\perp$-broadening of a fast quark in a quark-gluon plasma beyond the soft gluon approximation. We find that the radiative contribution to quark $\langle p_\perp^2\rangle$ for RHIC and LHC conditions is negative.
Gluon shadowing effects on J/psi and Upsilon production in p+Pb collisions at sqrt s_NN = 115 GeV and Pb+p collisions at sqrt s_NN = 72 GeV at AFTER@LHC
We calculate the Compton scattering for photon and gluon with the Klein-Nishina formula in fixed-target collisions by using the proton and lead beams at AFTER@LHC. In these collisions, we can investigate the particular case of Compton scattering at the partonic level, such as $γq\rightarrow qγ$, $γq\rightarrow qg$, $gq\rightarrow qγ$, and $gq\rightarrow qg$, that can help to check of the equivalent-photon approximation and understand the dynamics of hadron collisions at high energies, as well as probe the inner hadron structure.
Although Tevatron has discovered top quark and LHC (pp collisions) has discovered Higgs boson but the RHIC and LHC heavy-ion colliders have not discovered thermalized quark-gluon plasma (QGP). This is because the experimental data of top quark at Tevatron and the experimental data of Higgs boson at LHC are compared with the exact first principle calculation but the experimental data at RHIC and LHC are compared with simplistic models and assumptions which are not exact first principle calculation. In this paper we show that the exact first principle method to study quark-gluon plasma at RHIC a…
The presence of thermal gluons reduces the stimulated gluon emission off a heavy quark propagating in the quark-gluon plasma (QGP) while absorption causes reduction of the radiative energy loss. On the other hand, the chromo-electromagnetic field fluctuations present in the QGP lead to collisional energy gain of the heavy quark. The net effect of the thermal gluon absorption and field fluctuations is a reduction of the total energy loss of the heavy quark, prominent at the lower momenta. We consider both kind of the energy gains along with the usual losses, and compute the nuclear modification…
Determining the existence and nature of the quark-gluon plasma by Upsilon suppression at the LHC
在LHC的$\sqrt{s} = 5.5$ TeV Pb+Pb碰撞中，微型喷流的产生有望产生一个具有大初始温度和能量密度的胶子主导的等离子体。我们讨论了高初始温度对筛选质量和对$Υ$家族成员的相对抑制的影响。我们证明，$p_T$依赖的$Υ'/Υ$比预计只有当一个夸克-胶子等离子体具有显着的能量密度是存在的，这个比例的精确依赖性将强烈约束QGP模型。我们还提出，$Υ$共振本身的$p_T$光谱将提供有价值的信息，通过比较这些光谱的$Z$玻色子，这不应该受到等离子体的生产。
Gluon saturation and energy dependence of hadron multiplicity in pp and AA collisions at the LHC
ALICE合作组在大型强子对撞机（LHC）上进行的\sqrt{s} =2.76 TeV Pb+Pb碰撞的最新结果表明，Pb+Pb碰撞中带电强子多重数的能量依赖性与p+p碰撞中的有很大不同.我们表明，这种不同的能量依赖性可以解释列入一个强的角度排序的胶子衰变级联内的颜色玻璃凝聚（或胶子饱和）的方法。这种效应在饱和尺度大于1 GeV的核-核碰撞中更为重要。我们的公式很好地描述了p+p和Pb+Pb碰撞的LHC数据。
We study the relevance of experimental data on heavy-flavor [$D^0$, $J/ψ$, $B\rightarrow J/ψ$ and $Υ(1S)$ mesons] production in proton-lead collisions at the LHC to improve our knowledge of the gluon-momentum distribution inside heavy nuclei. We observe that the nuclear effects encoded in both most recent global fits of nuclear parton densities at next-to-leading order (nCTEQ15 and EPPS16) provide a good overall description of the LHC data. We interpret this as a hint that these are the dominant ones. In turn, we perform a Bayesian-reweighting analysis for each particle data sample which shows…
We show that the production of J/psi or Upsilon pairs in unpolarised pp collisions is currently the best process to measure the momentum-distribution of linearly-polarised gluons inside unpolarised protons through the study of azimuthal asymmetries. Not only the short-distance coefficients for such reactions induce the largest possible cos 4 phi modulations, but analysed data are already available. Among the various final states previously studied in unpolarised pp collisions within the TMD factorisation approach, di-J/psi production exhibits by far the largest asymmetries, up to 50% in the re…
