论文标题
部分可观测时空混沌系统的无模型预测
Enhanced deuteron coalescence probability in jets
论文作者
论文摘要
Transverse-Momentum（$ p _ {\ rm t} $）光谱和聚合参数$ b_2 $（anti）deuterons在$ \ sqrt {s} = 13 $ tev中首次在pp碰撞中测量。在此测量中，事件中具有最高$ p _ {\ rm t} $的领先粒子的方向（$ p _ {\ rm t}^{\ rm {lides}}> 5 $ gev/$ c $）用作射流轴的近似值。因此，该事件被分为三个方位区域，并且将射流信号作为朝向区域之间的差异获得，除了基础事件（UE）（UE）（UE）和横向区域外，该区域都包含射流片段化产物，而横向区域则由UE支配。发现射流中的合并参数大约比基础事件大10倍。该实验观察结果与聚结的图像一致，并且可以归因于与基础事件相比，射流锥体内核之间的平均相距距离较小。将本信中介绍的结果与简单核子合并模型的预测进行了比较，其中使用Pythia 8与Monash 2013调整一起生成核子的相空间分布，以及基于普通核反应的杜特龙生产模型的预测，具有与参数化能量依赖性的交叉截面对数据调谐的参数化能量。后一个模型在毕达雅8.3中实现。两种模型都重现了观察到的射流和射流外聚参数之间的巨大差异，尽管$ b^{\ rm jet} _2 $的几乎平坦的趋势不是由模型复制的，而模型却产生了降低的趋势。
The transverse-momentum ($p_{\rm T}$) spectra and coalescence parameters $B_2$ of (anti)deuterons are measured in pp collisions at $\sqrt{s} = 13$ TeV for the first time in and out of jets. In this measurement, the direction of the leading particle with the highest $p_{\rm T}$ in the event ($p_{\rm T}^{\rm{ lead}} > 5$ GeV/$c$) is used as an approximation for the jet axis. The event is consequently divided into three azimuthal regions and the jet signal is obtained as the difference between the Toward region, that contains jet fragmentation products in addition to the underlying event (UE), and the Transverse region, which is dominated by the UE. The coalescence parameter in the jet is found to be approximately a factor of 10 larger than that in the underlying event. This experimental observation is consistent with the coalescence picture and can be attributed to the smaller average phase-space distance between nucleons inside the jet cone as compared to the underlying event. The results presented in this Letter are compared to predictions from a simple nucleon coalescence model, where the phase space distributions of nucleons are generated using PYTHIA 8 with the Monash 2013 tuning, and to predictions from a deuteron production model based on ordinary nuclear reactions with parametrized energy-dependent cross sections tuned on data. The latter model is implemented in PYTHIA 8.3. Both models reproduce the observed large difference between in-jet and out-of-jet coalescence parameters, although the almost flat trend of the $B^{\rm Jet}_2$ is not reproduced by the models, which instead give a decreasing trend.
