论文标题
$ψ（2s）$在LHC的PB-PB碰撞中抑制
$ψ(2S)$ suppression in Pb-Pb collisions at the LHC
论文作者
论文摘要
$ψ（2s）$ charmone状态的生产是用爱丽丝（Alice）在$ \ sqrt {s _ {\ rm nn}} = 5.02 $ tev中的pb-pb碰撞中测量的。在LHC能量下，第一次观察到一个明显的信号，以降低到零横向动量，以前的速度（2.5美元<y <4 $）。据报道，$ψ（2s）$和j/$ψ$共振的包含生产交叉部分的比率是碰撞中心和横向动量的函数，在该区域$ p _ {\ rm t} <12 $ gev/$ c $。将结果与PP碰撞中的相应测量结果进行比较，形成双比$ [σ^{ψ（2S）}/σ^{J/ψ}] _ {\ rm {\ rm {pb-pb}}}/[σ^{ψ^{ψ（2S）}/σ^^^{j/f}发现在PB-PB碰撞中，相对于J/$ψ$，$ψ（2s）$被抑制了$ \ sim 2 $。 $ψ（2s）$核修饰因子$ r _ {\ rm aa} $也是中心性和$ p _ {\ rm t} $的函数。结果表明，$ψ（2s）$共振的产量在PB-PB碰撞中强烈抑制，相对于pp。相对于pp。比较横截面比的比较与Na50实验的先前SPS的比较相对于$ r _ {\ rm aa} $与较高的$ p _ comportiment的比较相对于先前的SPS结果，也是$ r _ {\ rm aa} $ ats formial-p _ c rm t c and c and c rm t.这些结果以及与运输和统计模型的计算的相应比较涉及有关LHC核碰撞中形成的Quark-Gluon血浆中炭状态的存在和特性的问题。
The production of the $ψ(2S)$ charmonium state was measured with ALICE in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity ($2.5<y<4$). The measurement of the ratio of the inclusive production cross sections of the $ψ(2S)$ and J/$ψ$ resonances is reported as a function of the centrality of the collisions and of transverse momentum, in the region $p_{\rm T}<12$ GeV/$c$. The results are compared with the corresponding measurements in pp collisions, by forming the double ratio $[σ^{ψ(2S)}/σ^{J/ψ}]_{\rm{Pb-Pb}}/[σ^{ψ(2S)}/σ^{J/ψ}]_{\rm{pp}}$. It is found that in Pb-Pb collisions the $ψ(2S)$ is suppressed by a factor of $\sim 2$ with respect to the J/$ψ$. The $ψ(2S)$ nuclear modification factor $R_{\rm AA}$ was also obtained as a function of both centrality and $p_{\rm T}$. The results show that the $ψ(2S)$ resonance yield is strongly suppressed in Pb-Pb collisions, by a factor up to $\sim 3$ with respect to pp. Comparisons of cross section ratios with previous SPS findings by the NA50 experiment and of $R_{\rm AA}$ with higher-$p_{\rm T}$ results at LHC energy are also reported. These results and the corresponding comparisons with calculations of transport and statistical models address questions on the presence and properties of charmonium states in the quark-gluon plasma formed in nuclear collisions at the LHC.
