We analyze the suppression of particle production at large transverse momenta in ($0-5%$ most) central collisions of gold nuclei at $\sqrt{s_\textrm{NN}}=$ 200 GeV and lead nuclei at $\sqrt{s_{\textrm{NN}}}=$ 2.76 TeV. Full next-to-leading order radiative corrections at ${\cal{O}}(α_s^3)$, and nuclear effects like shadowing and parton energy loss are included. The parton energy loss is implemented in a simple multiple scattering model, where the partons lose an energy $ε=λ\times dE/dx$ per collision, where $λ$ is their mean free path. We take $ε=κE$ for a treatment which is suggestive of the Bethe Heitler (BH) mechanism of incoherent scatterings, $ε= \sqrt{αE}$ for LPM mechanism, and $ε=$ constant for a mechanism which suggests that the rate of energy loss ($dE/dx$) of the partons is proportional to total path length ($L$) of the parton in the plasma, as the formation time of the radiated gluon becomes much larger than $L$.
We find that while the BH mechanism describes the nuclear modification factor $R_{\textrm{AA}}$ for $p_T \leq$ 5 GeV/$c$ (especially at RHIC energy), the LPM and more so the constant $dE/dx$ mechanism provides a good description at larger $p_T$. This confirms the earlier expectation that the energy loss mechanism for partons changes from BH to LPM for $p_T \ge λ<k_T^2>$, where $λ\approx$ 1 fm and $<k_T^2> \approx$ 1 GeV$^2$ is the average transverse kick-squared received by the parton per collision. The energy loss per collision at the $\sqrt{s_\textrm{NN}}$ =2.76 TeV is found to be about twice of that at 0.2 TeV.
A Study of Parton Energy Loss in Au+Au Collisions at RHIC using Transport Theory
通过数值求解包含$2 \leftrightarrow 2$和$2 \to 2 + final state radiation$碰撞过程的相对论Boltzmann方程，研究了RHIC能区Au+Au碰撞中部分子的能量损失.最终的粒子谱得到使用两个强子化模型，隆德弦碎裂和独立的碎裂模型。最近，初步的$π^0$横向动量分布的中心金+金碰撞在RHIC的胶子-胶子散射截面的5-12 mb，取决于强子化模型再现。并与HIJING射流淬火算法进行了比较。
The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical background is extended to include transport of both light partons and heavy quarks through the quark-gluon plasma (QGP) in high-energy heavy-ion collisions. The LBT model includes both elastic and inelastic medium-interaction of both primary jet shower partons and thermal recoil partons within perturbative QCD (pQCD). It is shown to simultaneously describe the experimental data on heavy and light flavor hadron suppression in high-energy heavy-ion collisions for different centralities at RHIC and LHC energies. More detailed in…
We study the emission characteristics of thermal photons at RHIC and LHC as affected by both the space-time evolution of the bulk medium and the thermal emission rates. For the former we compare the results of two evolution models (expanding fireball and hydrodynamics). For the latter, we detail the influence of hadronic emission components and study a speculative scenario by upscaling the default QGP and hadronic rates around the pseudo-critical region.
STAR collaboration at RHIC has recently measured the polarization of $Λ$ hyperons in non-central heavy ion collisions in the RHIC Beam Energy Scan (BES) program. The magnitude of the polarization was found to decrease from few percents at the lowest BES energies to $\approx0.2$% at the top RHIC energy. The polarization signal has been reproduced in different hydrodynamic calculations assuming a thermodynamic spin-vorticity coupling mechanism at the Cooper-Frye hypersurface. In this work an extension of our existing calculations of the $Λ$ polarization in the RHIC BES program to the top RHIC an…
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.
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…
$J/ψ$ suppression/production is one of the main signature of quark-gluon plasma detection at RHIC and LHC. In order to study $j/ψ$ suppression/production in high energy heavy-ion collisions at RHIC and LHC, one needs to prove the factorization theorem of $j/ψ$ production in non-equilibrium QCD medium, otherwise one will predict infinite cross section of $j/ψ$. In this paper we prove factorization theorem of $j/ψ$ production in non-equilibrium QCD at RHIC and LHC at all order in coupling constant.
Recently we have proved the factorization of NRQCD S-wave heavy quarkonium production at all orders in coupling constant. In this paper we extend this to prove the factorization of infrared divergences in $χ_{cJ}$ production from color singlet $c{\bar c}$ pair in non-equilibrium QCD at RHIC and LHC at all orders in coupling constant. This can be relevant to study the quark-gluon plasma at RHIC and LHC.
Recently we have proved NRQCD color octet factorization of S-wave and P-wave heavy quarkonia production at all orders in coupling constant in QCD in vacuum at high energy colliders in Eur. Phys. J. C76 (2016) 448 and in arXiv:1807.04722 [hep-ph] respectively. In this paper we extend this to prove NRQCD color octet factorization of P-wave heavy quarkonium production in non-equilibrium QCD at RHIC and LHC at all orders in coupling constant. This proof is necessary to study the quark-gluon plasma at RHIC and LHC.
The features of magnetic field in relativistic heavy-ion collisions are systematically studied by using a modified magnetic field model in this paper. The features of magnetic field distributions in the central point are studied in the RHIC and LHC energy regions. We also predict the feature of magnetic fields at LHC $\sqrt{s_{NN}}$= 900, 2760 and 7000 GeV based on the detailed study at RHIC $\sqrt{s_{NN}}$ = 62.4, 130 and 200 GeV. The dependencies of the features of magnetic fields on the collision energies, centralities and collision time are systematically investigated, respectively.
The properties of strange pseudoscalar and vectors mesons as well as strange baryon resonances in dense matter are reviewed. Some open questions on the properties of strange hadrons in medium are addressed, such as the experimental signatures of in-medium effects coming from the hadronic phase on the final observables in heavy-ion collisions for the experimental conditions at SIS, RHIC and LHC energies.
