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arXiv 2210.09192hep-phnucl-th
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磁化物质中重夸克偶素衰变宽度的狄拉克海效应——一种复合强子的场论模型

Dirac sea effects on Heavy Quarkonia decay widths in magnetized matter -- a field theoretic model of composite hadrons

Amruta Mishra, S. P. Misra

AI总结:

本研究采用复合强子场论模型,考虑狄拉克海效应与核子反常磁矩,计算磁化核物质中重夸克偶素的分衰变宽度,发现磁催化/反磁催化效应及PV混合,对重离子碰撞中的重味介子产生有观测意义。

摘要:

我们采用以夸克(及反夸克)为组分的复合强子场论模型,研究了磁化(核)物质中粲偶素(底偶素)态衰变为D反D(B反B)介子的分衰变宽度。这些衰变宽度是通过手征有效模型中衰变介子与产生介子的质量修正计算得到的,计算包含了核子狄拉克海效应。开粲(底)介子的质量修正由它们与核子及标量介子的相互作用计算得出,而重夸克偶素态的质量偏移则通过标量伸缩子场χ的介质改变得到,该场模拟了QCD的胶子凝聚。\n我们观察到,狄拉克海贡献会导致夸克凝聚随磁场增强而上升(下降),这一效应被称为(反)磁催化。这些效应十分显著,且核子的反常磁矩(AMMs)发挥着重要作用。当重子数密度ρ_B=0时,无论是否考虑AMMs,均存在磁催化(MC);而当ρ_B=ρ_0时,考虑AMMs时会出现反磁催化(IMC),这与忽略AMMs时的磁催化现象相反。在磁场存在的情况下,还会发生自旋0(赝标量)态与自旋1(矢量)态的混合(PV混合),这会改变这些介子的质量。\n磁场对重夸克偶素衰变宽度的影响,应当会对重味介子的产生产生可观测的后果——这些重味介子产生于RHIC和LHC的超相对论周边重离子碰撞的早期阶段,此时产生的磁场仍然可以极强。

英文摘要:

We study the partial decay widths of charmonium (bottomonium) states to ${\rm D\bar D \; (B\bar B)}$ mesons in magnetized (nuclear) matter using a field theoretical model of composite hadrons with quark (and antiquark) constituents. These are computed from the mass modifications of the decaying and produced mesons within a chiral effective model, including the nucleon Dirac sea effects. The mass modifications of the open charm (bottom) mesons are calculated from their interactions with the nucleons and the scalar mesons, whereas the mass shift of the heavy quarkonium state is obtained from the medium change of a scalar dilaton field, $χ$, which mimics the gluon condensates of QCD. The Dirac sea contributions are observed to lead to a rise (drop) in the quark condensates as the magnetic field is increased, an effect called the (inverse) magnetic catalysis. These effects are observed to be significant and the anomalous magnetic moments (AMMs) of the nucleons are observed to play an important role. For $ρ_B$=0, there is observed to be magnetic catalysis (MC) without and with AMMs, whereas, for $ρ_B=ρ_0$, the inverse magnetic catalysis (IMC) is observed when the AMMs are taken into account, contrary to MC, when the AMMs are ignored. In the presence of a magnetic field, there are also mixings of spin 0 (pseudoscalar) and spin 1 (vector) states (PV mixing) which modify the masses of these mesons. The magnetic field effects on the heavy quarkonium decay widths should have observable consequences on the production the heavy flavour mesons, which are created in the early stage of ultra-relativistic peripheral heavy ion collisions, at RHIC and LHC, when the produced magnetic fields can still be extremely large.

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