Early Run-3 data validation with the LHCb detector and the search for charm CP violation

使用 LHCb 探测器进行早期 Run-3 数据验证并寻找 charm CP 违规

• 批准号: 2487529
• 金额: --
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2487529
• 关键词: Early; Run; data; validation; LHCb

The project will be based on searches for CP violation (CPV) in the charm sector with the LHCb dectector. The first observation of CPV in decays of charm hadrons was as recent as 2019, in D0 -> K K and D0 -> pi pi decays. The project will search for CPV in neutral D0 meson mixing using D0 -> K pi decays, where the D0 is produced from B-meson decays. The timeline of a signal event begins with the LHC pp collisions, followed by the production of a B meson at the primary vertex. The B meson travels a short distance before decaying at the secondary vertex to a D* meson and a muon. The D* meson then promptly decays to the D0 along with a soft pion. The event channel is named "doubly-tagged secondary D0 -> Kpi" due to the presence of the muon and the soft pion. The charges on these two companion particles allow for tagging of the flavour of the D0 meson, which is important for the identification of the type of decay of the D0. For D0 mesons, the final state K- pi+ is denoted the "right sign" and the K+ pi - is referred to as the "wrong sign". The processes contributing to the former final state are a Cabibbo-favoured decay mode D0-> K- pi+ and a negligible component of D0 mesons oscillating into their antimatter particle D0-bar, followed by a doubly-Cabibbo suppressed decays D0-bar -> K- pi+. The "wrong-sign" state can be produced via two decay mechanisms (doubly-suppressed D0-> K+ pi decay, or D0 oscillating into a D0-bar meson followed by a Cabibbo-favoured decay D0-bar->K+ pi-) where CPV can be introduced. Studying the decay rates of the right sign and wrong sign modes (split by D0 meson flavour) will provide a measurement of the D0 meson mixing parameters and CPV in mixing in the charm sector. As well as the doubly-tagged decays, we will investigate the possibility of including singly-tagged semi-leptonic B-meson decays. In this case, the B meson decays directly to the D0 meson. Then, there is no soft pion present to help tag the D0 flavour.Additionally, we will study the ratio of the branching fractions of D0 -> K3pi to D0 -> Kpi decays with early Run 3 data. This standard candle measurement will provide useful input for the Early data validation at the start of the LHC Run 3.

该项目将基于使用LHCb探测器在粲扇区搜索CP违逆（CPV）。在粲强子衰变中首次观测到CPV是在2019年，在D0 -> K K和D0 -> π π衰变中。该项目将使用D0 -> K π衰变在中性D0介子混合中寻找CPV，其中D0是由b介子衰变产生的。信号事件的时间线从LHC的pp碰撞开始，随后在主顶点产生B介子。B介子在次级顶点衰变为D*介子和介子之前会移动一小段距离。然后，D*介子与软介子一起迅速衰变为D0。由于介子和软介子的存在，该事件通道被命名为“双标记次级D0 -> Kpi”。这两个伴生粒子上的电荷允许标记D0介子的味道，这对识别D0衰变的类型很重要。对于D0介子，最终态K- pi+表示为“正确符号”，K+ pi -表示为“错误符号”。导致前一种最终状态的过程是cabibbo有利的衰变模式D0-> K- pi+和一个可忽略不计的D0介子振荡到它们的反物质粒子D0-bar，然后是双cabibbo抑制的衰变D0-bar -> K- pi+。“错误符号”状态可以通过两种衰变机制产生（双抑制D0-> K+ pi衰变，或者D0振荡成D0-bar介子，然后是可引入CPV的cabibbo -有利衰变D0-bar->K+ pi-）。研究正确符号和错误符号模式（按D0介子风味划分）的衰变速率，将提供一个测量D0介子混合参数和混合CPV的方法。除了双标签衰变外，我们还将研究包括单标签半轻子b介子衰变的可能性。在这种情况下，B介子直接衰变成D0介子。然后，没有软介子存在，以帮助标记D0的味道。此外，我们将研究D0 -> K3pi与D0 -> Kpi衰减的分支分数与早期Run 3数据的比率。这个标准的烛光测量将为LHC运行3开始时的早期数据验证提供有用的输入。