我讨论了第一个半轻子$B_s$衰变测量在LHCb，和精确的研究$B_s$半轻子衰变性质的前景。这里所涵盖的分析是基于收集的数据与LHCb探测器在质子-质子碰撞在一个中心的质量能量为7 TeV。特别研究了半轻子衰变$\Bs\to D_s^+ X \munu$和$\Bs\to D^0K^+ X \munu$。在$D^0K^+$质谱中观察到两种结构，其质量与已知的$D_{s1}(2536)^+$和$D^*_{s2}(2573)^{+}$介子一致。相对于总$\Bs$半轻子速率的测量的分支分数为${\cal{B}(\Bs\to D_{s2}^{*+} X \munu)}/{\cal{B}(\Bs\to X \munu)}= (3.3\pm 1.0\pm 0.4)%$和${\cal{B}(\Bs\to D_{s1}^+ X \munu)}/{\cal{B}(\Bs\to X \munu)}= (5.4\pm 1.2({\rm stat})\pm 0.5({\rm sys}))%$。这是在$\Bs$衰变中首次观察到$D_{s2}^{*+}$态。
英文摘要：
I discuss the first semileptonic $B_s$ decay measurements performed at LHCb, and the prospects for precise studies of $B_s$ semileptonic decay properties. The analyses covered here are based on data collected with the LHCb detector in proton-proton collisions at a centre-of-mass energy of 7 TeV. In particular the semileptonic decays $\Bs\to D_s^+ X \munu$ and $\Bs\to D^0K^+ X \munu$ are studied. Two structures are observed in the $D^0K^+$ mass spectrum at masses consistent with the known $D_{s1}(2536)^+$ and $D^*_{s2}(2573)^{+}$ mesons. The measured branching fractions relative to the total $\Bs$ semileptonic rate are ${\cal{B}(\Bs\to D_{s2}^{*+} X \munu)}/{\cal{B}(\Bs\to X \munu)}= (3.3\pm 1.0\pm 0.4)%$, and ${\cal{B}(\Bs\to D_{s1}^+ X \munu)}/{\cal{B}(\Bs\to X \munu)}= (5.4\pm 1.2({\rm stat})\pm 0.5({\rm sys}))%$. This is the first observation of the $D_{s2}^{*+}$ state in $\Bs$ decays.
Leptonic and semileptonic decays in the charm sector have been well studied in recent years. With the largest data sample near $D\bar D$ threshold, precision measurements of leptonic and semileptonic decays of charm meson and baryon are perfromed at BESIII. Test for letpon flavor universality is also performed. Sensitivity for rare leptonic and semileptonic charm decays is significantly improved taking advantage of the huge statistics in LHCb and the $B$ factories.
LHCb has productive studies of quarkonia and $b$-hadrons which provide essential inputs to study quantum chromodynamics (QCD). In this proceeding, seven recent results are reported: the observation of a new excited $Ξ_b^0$ resonance in $Ξ_b^- π^+$ final states, the new excited $B_s^0$ state is observed in $B^+ K^-$ mass spectrum, the first observation of suppressed semileptonic $B_s^0 \rightarrow K^- μ^+ ν_μ$ decay, the first observation of the decay $B^0 \rightarrow D^0 \bar{D}^0 K^+ π^-$, the first observation of the Cabibbo-suppressed decay $Λ_b^0 \rightarrow χ_{c1} p π^-$, the first observ…
We review the prospects of measurements of the CKM matrix elements corresponding to the first two generations of quarks, as well as measurements of leptonic and semileptonic charm meson decays at LHCb. We review the status of searches for Lepton Non-Universality in the charm sector, and provide motivation to continue such searches.
Two of the elements of the Cabibbo-Kobayashi-Maskawa quark mixing matrix, $|V_{ub}|$ and $|V_{cb}|$, are extracted from semileptonic B decays. The results of the B factories, analysed in the light of the most recent theoretical calculations, remain puzzling, because for both $|V_{ub}|$ and $|V_{cb}|$ the exclusive and inclusive determinations are in clear tension. Further, measurements in the $τ$ channels at Belle, Babar, and LHCb show discrepancies with the Standard Model predictions, pointing to a possible violation of lepton flavor universality. LHCb and Belle II have the potential to resol…
