The impact of the experimental acceptance, i.e. transverse-momentum ($p_T$) cut-off and limited rapidity region, on the earlier predicted irregularity in the excitation function of the baryon stopping is studied. This irregularity is a consequence of the onset of deconfinement occurring in the compression stage of a nuclear collision and manifests itself as a wiggle in the excitation function of the reduced curvature ($C_y$) of the net-proton rapidity distribution at midrapidity. It is demonstrated that the wiggle is a very robust signal of a first-order phase transition that survives even under conditions of a very limited acceptance. At the same time the $C_y$ for pure hadronic and crossover transition scenarios become hardly distinguishable, if the acceptance cuts off too much of the low-$p_T$ proton spectrum and/or puts too narrow rapidity window around midrapidity. It is found that the shape of the net-proton rapidity distribution near midrapidity depends on the $p_T$ cut-off. This implies that the measurements should be taken at the same acceptance for all collision energies in order to reliably conclude on the presence or absence of the irregularity.
Baryon fluctuation signatures of the onset of deconfinement
Jan Kochanowski University（扬·科哈诺夫斯基大学）；Bogolyubov Institute for Theoretical Physics（博戈柳博夫理论物理研究所）；GSI Helmholtzzentrum für Schwerionenforschung（德国重离子研究中心）
Baryon Stopping as a Probe of Deconfinement Onset in Relativistic Heavy-Ion Collisions
有人认为，在重子停止的不规则性是一个自然的后果发生在核碰撞的压缩阶段的相变。这是一个综合的影响，固有的最软点的状态方程（EoS）与相变和变化的非平衡动力学从强子到部分子输运。因此，这种不规则性是来自核碰撞的高温和高密度阶段的信号。为了说明这一命题，在三流体模型中进行计算与三个不同的EoS：一个纯强子EoS，一个EoS与一阶相变和一个平滑的交叉过渡。结果发现，在一阶跃迁的情况下的预测确实揭示了一个强烈的不规则性的入射能量依赖的形式的净质子快度分布在中心碰撞。这种行为与强子情形相反，在强子情形中，分布形式逐渐演变，没有显示出不规则性。交叉EoS的情况是中间的。只有微弱的不规则性发生。实验数据也表现出类似的不规则性的趋势，然而，这是基于能量为20 A GeV和30 A GeV的初步数据。
The paper briefly presents history, status, and plans of the search for the critical structures - the onset of fireball, the onset of deconfinement, and the deconfinement critical point - in high energy nucleus-nucleus collisions. First, the basic ideas are introduced, the history of the observation of strongly interacting matter in heavy ion collisions is reviewed, and the path towards the quark-gluon plasma discovery is sketched. Then the status of the search for critical structures is discussed - the discovery of the onset of deconfinement, indications for the onset of fireball, and still i…
With the first multi-messenger observation of a binary neutron star merger (GW170817) new constraints became available for masses and radii of neutron stars. We introduce a class of hybrid EoS that fulfils all these constraints and predicts a region in the mass-radius diagram that could be populated only by hybrid neutron stars with quark matter cores. A confirmation of this conjecture would be provided when the NICER radius measurement for the high-mass pulsar PSR J0740+6620 yields a radius less than 11 km. Would this radius measurement yield a result in excess of 12 km, this would allow for …
NA61/SHINE is a fixed target experiment at the CERN Super-Proton- Synchrotron. The main goals of the experiment are to discover the critical point of strongly interacting matter and to study the properties of the onset of deconfinement. In order to reach these goals, a study of hadron production properties is performed in nucleus-nucleus, proton-proton and proton-nucleus interactions as a function of collision energy and size of the colliding nuclei. In this paper, I will review recent results on strangeness production in p+p, Be+Be and Ar+Sc collisions in the SPS energy range. Kinematic spect…
