本文综述了Bu轻子衰变的研究和测量现状,重点介绍了在B工厂获得的最新结果。我们将描述B+ -> ell+ nu和B+ -> ell+ nu γ衰变的研究。
英文摘要:
This paper reviews the status of searches and measurements of Bu leptonic decays, concentrating on the most recent results obtained at B-factories. We will describe studies of decays of the type B+ -> ell+ nu and B+ -> ell+ nu gamma.
We present recent BESIII results about the study of mesons which contain at least one charm quark. We determined the D(s)+ decay constants, the form factors of D semi-leptonic decays, the CKM matrix elements |Vcs(d)|.
The recent experimental results on leptonic $D^+_{(s)}$ decays, semileptonic $D$ decays, determinations of decay constants and form factors, as well as extractions of $|V_{cd}|$ and $|V_{cs}|$ are briefly reviewed. Global analysis of all existing measurements of leptonic $D^+_{(s)}$ decays and semileptonic $D$ decays yields $|V_{cd}|=0.2157\pm 0.0045$ and $|V_{cs}|=0.983\pm 0.011$, which are the most precision determinations of these two CKM matrix elements up to date.
A review of the experimental status of purely leptonic ${B^0_{[s]}\to\ell^+\ell^-}$ decays is given and the new analysis of ${B^0_{[s]}\toμ^+μ^-}$ observables with the LHCb experiment is presented. The new results are the most precise single experiment measurements of the quantities to date and are consistent with the Standard Model. However, they also match the recent anomalies found in $b\to s\ell\ell$ transitions excellently.
本文研究了1991 ~ 1995年在LEP e ~+e-对撞机上用ALEPH探测器收集的400万个强子Z衰变样品中的纯轻子衰变Ds ~-> τ nu和Ds ~-> μ nu。从两个分析的组合中提取分支级分,一个优化以选择Ds -> tau nu衰变与tau -> e nu nubar或mu nu nubar,另一个优化Ds-> mu nu衰变。结果用于评估Ds衰变常数,在标准模型内:fDs = [285 +- 19(stat)+- 40(syst)] MeV
Based on 2.92 fb$^{-1}$ data taken at the center-of-mass energy $\sqrt s=3.773$ GeV with the BESIII detector, we report recent results on the decay constant $f_{D^+}$, the hadronic form factors, as well as the quark mixing matrix elements $|V_{cs(d)}|$, which are extracted from analyses of the leptonic decay $D^+ \to μ^+ν_μ$ and the semileptonic decays $D^0\to K(π)^-e^+ν_e$, $D^+\to K^0_L e^+ν_e$, $D^+\to K^-π^+e^+ν_e$ and $D^+\to ω(ϕ)e^+ν_e$ at BESIII.
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.
I review the theoretical and phenomenological status of two- and three-body charmless non-leptonic B decays, with an emphasis on factorization approaches. Most of the material presented here is based on talks given by the participants of the workshop "Future Challenges in Non-Leptonic B Decays: Theory and Experiment", held at Bad Honnef in February 2016.
We review measurements of semileptonic and leptonic charm meson decays performed by the Belle experiment, and we use these results to estimate the sensitivity of the follow-on Belle II experiment to these decays.
CP violation offers a powerful probe for testing the Standard Model. In this endeavour, non-leptonic decays of B mesons play a key role. I will discuss benchmark decays and puzzling patterns emerging from theoretical analyses of the current data.
A summary of WG II of the CKM 2018 conference on semileptonic and leptonic $b$-hadron decays is presented. This includes discussions on the CKM matrix element magitudes $|V_{ub}|$ and $|V_{cb}|$, lepton universality tests such as $R(D^{*})$ and leptonic decays. As is usual for semileptonic and leptonic decays, much discussion is devoted towards the interplay between theoretical QCD calculations and the experimental measurements.
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.
The recent experimental developments require a more precise theoretical study of weak decays of heavy baryon $Λ_b^0$. In this work, we provide an updated and systematic analysis of both the semi-leptonic and nonleptonic decays of $Λ^0_b$ into baryons $Λ^+_c$, $Λ$, $p$, and $n$. The diquark approximation is adopted so that the methods developed in the $B$ meson system can be extended into the baryon system. The baryon-to-baryon transition form factors are calculated in the framework of a covariant light-front quark model. The form factors $f_3, ~g_3$ can be extracted and are found to be non-neg…
Exclusive non-leptonic two-body decays of $B$ mesons have been studied extensively in the past two decades within the framework of factorization. However, the exploration of the corresponding three-body case has only started recently, in part motivated by new data. We consider here the simplest non-leptonic three-body $B$ decays from the point of view of factorization, namely heavy-to-heavy transitions. We provide a careful derivation of the SCET/QCDF factorized amplitudes to NNLO in $α_s$, and discuss the numerical impact of NLO and NNLO corrections. We then study the narrow-width limit, show…
We summarize the current status of the determination of the CKM matrix elements |V_ud| and |V_us|, which is at the precision frontier of CKM phenomenology. We also review recent progress on the study of charm (semi)leptonic decays, and the determination of |V_cd| and |V_cs|.
We investigate purely leptonic decays of leptons $ł^{\prime-}\to l^-\barν_lν_{l^{\prime}}$ to distinguish Dirac or Majorana neutrinos. We derive the differences of the decay width (and associated quantities) between the two neutrino hypotheses by the effect of identical particles. Evidence from experimental data makes the hypothesis of Majorana neutrinos very unlikely and our results strongly favor the hypothesis of Dirac neutrinos (in the standard three-neutrino theory). Moreover, our exploration for decay widths can be extended to the polarization angles of leptons, which will inspire new in…