LHCb实验上粲重子寿命和质量的精确测量  

Advances in precision measurements of the lifetimes and masses of the charmed baryons at LHCb

作　　者：吕晓睿 傅金林 Xiao-Rui Lyu;Jin-Lin Fu(School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院大学物理科学学院,北京100049

出　　处：《科学通报》2024年第31期4570-4576,共7页Chinese Science Bulletin

基　　金：国家自然科学基金(12221005)资助。

摘　　要：粲重子是一类包含粲夸克的重子.单粲重子谱中,所有的粲重子最终将衰变为Λ_(c)^(+)、Ξ_(c)^(+)、Ξ_(c)^(0)和Ω_(c)^(0).因此,这4个基态粲重子是整个单粲重子谱学的基石.由于它们只能通过弱相互作用发生衰变,涉及的衰变模式繁多且相互作用机制复杂,因此它们成为探索粒子物理基本相互作用的重要研究对象.特别是这4个粲重子的质量和寿命的精确测量有助于理解强相互作用的非微扰性质和精确检验粒子物理标准模型.位于欧洲核子中心大型强子对撞机上的LHCb实验在2011~2012和2015~2018年期间积累了两批质子-质子碰撞数据,其中包含了高统计量的粲重子实验样本.LHCb实验探测器具有性能优异的位置和动量测量系统,以及高效率的粒子鉴别能力,有效保证了LHCb实验能够开展一系列国际上最好的粲重子质量和寿命测量.本文介绍了LH Cb实验在建成运行以来,对基态粲重子Λ_(c)^(+)、Ξ_(c)^(+)、Ξ_(c)^(0)和Ω_(c)^(0)的质量和寿命的精确测量的进展,以及未来的研究前景.The charmed baryon is a class of baryons,that consists of at least one charm quark within.In the spectroscopy of the singly charmed baryons,all these baryons eventually decay into one of the four charmed baryons:Λ_(c)^(+)、Ξ_(c)^(+)、Ξ_(c)^(0) andΩ_(c)^(0).Therefore,these four ground-state charmed baryons become the cornerstone of the whole charmed baryon spectroscopy.As they decay only via the weak interaction,in which numerous decay modes and different complex interactions are involved,studies of their properties become an important laboratory for exploring the mechanism of the fundamental interactions in particle physics.Precise measurement of their masses and lifetimes enhances our understanding of the non-perturbative property in strong interactions and stringent test of the Standard Model of particle physics.The LHCb experiment,located at the Large Hadron Collider at CERN,is equipped with the position and momentum measurement system and particle identification system of the state-of-art performance.LHCb has accumulated highstatistics proton-proton collision data during the years 2011-2012 and 2015-2018 with an integrated luminosity of 8.6 fb~(-1),where huge numbers of charmed baryons have been produced.The lifetime order was long believed to beτ_(Ξ_(c)^(+))>τ_(Λ_(c)^(+))>τ_(Ξ_(c)^(0))>τ_(Ω_(c)^(0)),according to the measurements from fixed target experiments more than 20 years ago,where theΩ_(c)^(0) lifetime was the shortest.However,the situation changed dramatically when LHCb embarked on a series of new measurements of their lifetimes,which have established a new lifetime hierarchy to be:τ_(Ξ_(c)^(+))>τ_(Ω_(c)^(0))>τ_(Λ_(c)^(+))>τ_(Ξ_(c)^(0)).This means theΩ_(c)^(0) lifetime is the second longest and theΞ_(c)^(0) lifetime becomes the shortest.In particular,the LHCb studies show that theΩ_(c)^(0) lifetime should be nearly four times of the previous measurement.The newly established lifetime hierarchy will help improve our knowledge of quantum chromodynamics in charm hadrons and prov

关 键 词：大型强子对撞机 LHCb实验 粲重子 质量 寿命 

分 类 号：O572.33[理学—粒子物理与原子核物理]