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

该项目将基于与LHCb检测器在魅力部门的CP违规（CPV）的搜索。在粲强子衰变中首次观察到CPV是在2019年，在D 0-> K K和D 0-> pi pi衰变中。该项目将使用D 0-> K π衰变在中性D 0介子混合中寻找CPV，其中D 0由B介子衰变产生。一个信号事件的时间轴开始于LHC pp碰撞，随后是在主顶点产生B介子。B介子在第二顶点衰变为D* 介子和μ介子之前，会传播一小段距离。D* 介子然后迅速衰变到D 0沿着软π介子。由于μ介子和软π介子的存在，事件通道被命名为“双标记次级D 0-> Kpi”。这两个伴随粒子上的电荷允许标记D 0介子的味道，这对于识别D 0衰变的类型很重要。对于D 0介子，末态K-π +表示为“正号”，K+ π-表示为“错号”。对前一个末态有贡献的过程是Cabibbo偏爱的衰变模式D 0-> K-pi+和一个可忽略的D 0介子振荡到它们的反物质粒子D 0-bar的分量，随后是一个双重Cabibbo抑制的衰变D 0-bar -> K-pi+。“错号”态可以通过两种衰变机制产生（双重抑制的D 0-> K+ pi衰变，或者D 0振荡成D 0-bar介子，然后是Cabibbo偏好的D 0-bar->K+ pi-衰变），其中可以引入CPV。研究正确的符号和错误的符号模式（分裂D 0介子味）的衰变率将提供一个测量的D 0介子混合参数和CPV在混合的魅力部门。除了双标记衰变，我们还将研究包括单标记半轻子B介子衰变的可能性。在这种情况下，B介子直接衰变为D 0介子。此外，我们将研究早期运行3数据中D 0-> K3 pi与D 0-> Kpi衰变的分支分数之比。这个标准烛光测量将为LHC运行3开始时的早期数据验证提供有用的输入。

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.