Jet quenching parameter of the quark-gluon plasma in a strong magnetic field: Perturbative QCD and AdS / CFT correspondence
Jet quenching parameter of the quark-gluon plasma in a strong magnetic field: Perturbative QCD and AdS / CFT correspondence
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DOI：
10.1103/physrevd.94.085016
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发表时间：
2016-05
影响因子：
5
通讯作者：
Shiyong Li;Kiminad A. Mamo;Ho-Ung Yee
中科院分区：
文献类型：
--
作者：
Shiyong Li;Kiminad A. Mamo;Ho-Ung Yee
在弱耦合区用微扰QCD(PQCD)计算了强磁场下夸克-胶子等离子体的喷注猝灭参数，在强耦合区用微扰QCD(PQCD)计算了强场下夸克-胶子等离子体的喷注猝灭参数.在弱耦合条件下，假定标度层次为${\ensuremath{\alpha}}_{s}eB\ensuremath{\ll}{T}^{2}\ensuremath{\ll}eB$.，在完全前序(即前导对数和对数下的常量)下，我们计算了pQCD中耦合常数${\Ensureath{\α}}_{S}$的值我们考虑了两种喷流方向相对于磁场的情况：1)喷流平行于磁场运动的情况；2)喷流垂直于磁场运动的情况。在前一种情况下，我们发现$\stackrel{^}{q}\ensuremath{\sim}{\ensuremath{\alpha}}_{s}^{2}(eB)T\mathrm{log}(1/{\ensuremath{\alpha}}_{s})$，而在后者，我们有$\stackrel{^}{q}\ensuremath{\sim}{\ensuremath{\alpha}}_{s}^{2}(eB)T\mathrm{log}({T}^{2}/{\ensuremath{\alpha}}_{s}eB)$.在这两种情况下，这个前序结果都是由热填充的最低朗道能级夸克的散射引起的。在由对应关系所描述的强耦合区域中，我们发现$\stackrel{^}{q}\ensuremath{\sim}\sqrt{\ensuremath{\lambda}}(eB)T$或$\stackrel{^}{q}\ensuremath{\sim}\sqrt{\ensuremath{\lambda}}\sqrt{eB}{T}^{2}$分别根据射流是平行还是垂直于磁场移动而处于相同的层次结构中。这表明在平行情况下，在两种情况下，Stackrel{q}都普遍依赖于$(Eb)T$，其起源应该是与$Eb成比例的最低Landau态的横向密度。最后，在喷流垂直于磁场运动的情况下，不对称的横向动量扩散可能给出Baier-Dokshitzer-Mueller-Peigne-Schiff和Zakharov(BDMPS-Z)形式的胶子韧致辐射光谱的有趣的方位不对称性。
We compute the jet quenching parameter $\stackrel{^}{q}$ of a quark-gluon plasma in the presence of a strong magnetic field using perturbative QCD (pQCD) in the weakly coupled regime, and $\mathrm{AdS}/\mathrm{CFT}$ correspondence in the strongly coupled regime of $\mathcal{N}=4$ super Yang-Mills. In the weakly coupled regime, we compute $\stackrel{^}{q}$ in pQCD at complete leading order (that is, leading log as well as the constant under the log) in the QCD coupling constant ${\ensuremath{\alpha}}_{s}$, assuming the hierarchy of scales ${\ensuremath{\alpha}}_{s}eB\ensuremath{\ll}{T}^{2}\ensuremath{\ll}eB$. We consider two cases of jet orientations with respect to the magnetic field: 1) the case of a jet moving parallel to the magnetic field; 2) the case of a jet moving perpendicular to the magnetic field. In the former case, we find $\stackrel{^}{q}\ensuremath{\sim}{\ensuremath{\alpha}}_{s}^{2}(eB)T\mathrm{log}(1/{\ensuremath{\alpha}}_{s})$, while in the latter we have $\stackrel{^}{q}\ensuremath{\sim}{\ensuremath{\alpha}}_{s}^{2}(eB)T\mathrm{log}({T}^{2}/{\ensuremath{\alpha}}_{s}eB)$. In both cases, this leading-order result arises from the scatterings with thermally populated lowest-Landau-level quarks. In the strongly coupled regime described by the $\mathrm{AdS}/\mathrm{CFT}$ correspondence, we find $\stackrel{^}{q}\ensuremath{\sim}\sqrt{\ensuremath{\lambda}}(eB)T$ or $\stackrel{^}{q}\ensuremath{\sim}\sqrt{\ensuremath{\lambda}}\sqrt{eB}{T}^{2}$ in the same hierarchy of ${T}^{2}\ensuremath{\ll}eB$ depending on whether the jet is moving parallel or perpendicular to the magnetic field, respectively, which indicates a universal dependence of $\stackrel{^}{q}$ on $(eB)T$ in both regimes for the parallel case, the origin of which should be the transverse density of lowest-Landau-level states proportional to $eB$. Finally, the asymmetric transverse momentum diffusion in the case of a jet moving perpendicular to the magnetic field may give an interesting azimuthal asymmetry of the gluon bremsstrahlung spectrum in the Baier-Dokshitzer-Mueller-Peigne-Schiff and Zakharov (BDMPS-Z) formalism.