New measurement of Lambda-c production in Pb-Pb collisions with the Alice experiment at the LHC

ALICE（大型离子对撞机实验）是大型强子对撞机（欧洲核子研究中心，日内瓦）的四个主要实验之一，其物理项目侧重于重离子碰撞测量。在极端的温度和/或密度条件下，强子物质“融化”成由“自由”夸克和胶子组成的等离子体，即所谓的夸克-胶子等离子体（QGP）。这是大爆炸后几微秒内早期宇宙的状态。为了在实验室中创造这些条件，重离子（铅核）被加速，并以前所未有的能量迎头相撞。开放重味产生是测量在大型强子对撞机重离子碰撞中形成的致密QCD介质性质的最有价值的探针之一。重夸克，一旦在碰撞的早期阶段产生，预计会在穿越周围物质时重新散射并失去能量，携带有关热介质特性的重要信息。最近，利用现有的ALICE探测器对pp、p-Pb和Pb-Pb碰撞中的D介子和Ac重子产生进行了初步测量，尽管统计数据和分辨率有限。该博士项目旨在开发一种分析策略，首次在LHC的5tev Pb-Pb碰撞的高多重环境中从衰变通道提取Ac重子信号到pKn。这将在开发最先进的机器学习分析工具的同时完成。然后，学生将估计必要的修正并测量粲重子的pt微分产生横截面，并确定与此新测量相关的系统误差。

ALICE (A Large Ion Collider Experiment) is one of the four main experiments at the LHC (CERN, Geneva), whose physics programme focuses on heavy-ion collision measurements. Under extreme conditions of temperature and/or density, hadronic matter 'melts' into a plasma of 'free' quarks and gluons - the so-called quark-gluon plasma (QGP). This was the state of the Early Universe a few microseconds after the Big Bang. To create these conditions in the laboratory, heavy ions (Pb nuclei) are accelerated and made to collide head on at unprecedented energies. Open heavy-flavour production is one of the most valuable probes to measure properties of the dense QCD medium formed in heavy-ion collisions at the LHC. Heavy quarks, once produced in the early stages of the collision, are expected to re-scatter and lose energy while traversing the surrounding matter, carrying important information on the properties of the hot medium. First preliminary measurements using the current ALICE detector have been made recently of D meson and Ac baryon production in pp, p-Pb and Pb-Pb collisions, though with limited statistics and resolution.The PhD project aims to develop an analysis strategy to extract for the first time the Ac baryon signal from the decay channel into pKn, in the high multiplicity environment of the 5 TeV Pb-Pb collisions at the LHC. This will be done while developing state-of-the-art machine learning analyses tools. The student will then estimate the necessary corrections and measure the pT-differential production cross-section of the charmed baryon and determine the systematic errors associated with this new measurement.