We analyse the results recently presented on the $B^{+} \to K^{*+} μ^+ μ^-$ angular observables by the LHCb Collaboration which show indications for New Physics beyond the Standard Model. Within a model-independent analysis, we compare the fit results with the corresponding results for the angular observables in $B^{0} \to K^{*0} μ^+ μ^-$.
We apply the formalism of amplitude symmetries to the angular distribution of the decays $B \to D^* \ell ν$ for $\ell=e,μ,τ$. We show that the angular observables used to describe the distribution of this class of decays are not independent in absence of New Physics contributing to tensor operators. We derive sets of relations among the angular coefficients of the decay distribution for the massless and massive lepton cases which can be used to probe in a very general way the consistency among the angular observables and the underlying New Physics at work. We use these relations to access the …
We probe the effective field theory extending the Standard Model with a sterile neutrino in B meson decays at B factories and lepton colliders, using angular and polarization observables. We put bounds on different effective operators characterized by their distinct Dirac-Lorentz structure, and probe the $N$-mediated B decays sensitivity to these interactions. We define a Forward-Backward asymmetry $A_{FB}^{\ell γ}$ between the muon and photon directions for the $B \to μνγ$ decay, which allows us to separate the SM contribution from the effective lepton number conserving and violating processe…
Lepton polarization dependent angular observables and the polarization asymmetries in the four-fold $Λ_b \rightarrow Λ(\rightarrow N π) \ell^+\ell^-$ decay
National University of Sciences and Technology (NUST)(国立科学技术大学);National Centre for Physics(国家物理中心);Quaid-i-Azam University(奎德-e-阿扎姆大学)
We consider the time-dependent analysis of $B_d\to K_S\ell\ell$ taking into account the time-evolution of the $B_d$ meson and its mixing into $\bar{B}_d$. We discuss the angular conventions required to define the angular observables in a transparent way with respect to CP conjugation. The inclusion of time evolution allows us to identify six new observables, out of which three could be accessed from a time-dependent tagged analysis. We also show that these observables could be obtained by time-integrated measurements in a hadronic environment if flavour tagging is available. We provide simple …
In $Λ_b^0 \to Λ_c^+ (\to Λ^0 π^+) τ^- \barν_τ$ decay, the solid angle of the final-state particle $τ^-$ cannot be determined precisely since the decay products of the $τ^-$ include an undetected $ν_τ$. Therefore, the angular distribution of this decay cannot be measured. In this work, we construct a {\it measurable} angular distribution by considering the subsequent decay $τ^- \to π^- ν_τ$. The full cascade decay is $Λ_b^0 \to Λ_c^+ (\to Λ^0 π^+)τ^- (\to π^- ν_τ)\barν_τ$. The three-momenta of the final-state particles $Λ^0$, $π^+$, and $π^-$ can be measured. Considering all Lorentz structures …
Angular observables and branching ratio for $B_s\to ϕ\ell^+ \ell^-$ decay
The Institute of Nuclear Physics, Agency of the Republic of Kazakhstan for Atomic Energy(哈萨克斯坦原子能机构核物理研究所);Joint Institute for Nuclear Research(俄罗斯杜布纳联合核研究所)
Angular and invariant-mass observables in the four-body Higgs decay $h\to\ell\barν_\ell\bar{\ell}^\primeν_{\ell^\prime}$
Zhengzhou University(郑州大学);Chongqing University of Posts & Telecommunications(重庆邮电大学);Chongqing University(重庆大学);Chongqing University of Science and Technology(重庆科技大学)
This paper describes the angular distribution of $Λ_b^0\to Λ(\to pK^-)\ell^+\ell^-$ decays. A full expression is given for the case of multiple interfering spin-states with spin $\leq \tfrac{5}{2}$. This distribution is relevant for future measurements of $Λ_b^0\to pK^-\ell^+\ell^-$ decays, where different states cannot easily be separated based on their mass alone. New observables arise when considering spin-$\tfrac{5}{2}$ states as well as interference between states. An exploration of their behaviour for a variety of beyond the Standard Model scenarios shows that some of these observables e…
In two meson photoproduction off a nucleon, for the case in which two of the three final state hadrons are products of the decay of an intermediate resonance, general expressions for its decay distribution and for polarization observables are derived in a model independent way. These are functions of either the spin density matrix elements (SDME's) or statistical tensors of the resonance, and the angles of its decay products. The expressions are general enough that it also describes cases where more than one resonance of arbitrary quantum numbers contributes, including interference effects. Th…
Decays based on the $b\to sγ$ transition are expected to yield left-handed photons in the Standard Model, but could be particularly sensitive to New Physics contributions modifying the short-distance Wilson coefficients $\mathcal{C}_7$ and $\mathcal{C}_{7'}$ defined in the low-energy Effective Field Theory. These coefficients can be determined by combining observables of several modes, among which $B_s\toϕee$ at low $q^2$, in a kinematic range where the photon-pole is dominant. We investigate the impact of $B_s-\bar{B}_s$ mixing on the angular observables available for this mode, which induces…
The flavor anomalies reported in $R_K$, $R_{K^*}$, $P_{5}^{\prime}$ and $\mathcal{B}(B_s\, \to\, ϕ\, μ^+\, μ^-)$ indicate lepton flavor universality violation in $b \to s\,l^+\,l^-$ quark level transition decays. The deviation from the SM prediction reported in the underlying flavor observables currently stand at the level of $2.5σ$, $2.4σ$, $3.3σ$ and $3.7σ$, respectively. In this context, we perform an angular analysis of the four-body differential decay of $B_s\, \to\, f_{2}^{\prime}\,(1525)\,(\to K^+\,K^-)\,μ^+ \,μ^-$ in a model independent effective field theory framework. The decay mode …
We analyze in detail the angular distributions in $\bar{B}\to D^*\ell \barν$ decays, with a focus on lepton-flavour non-universality. We investigate the minimal number of angular observables that fully describes current and upcoming datasets, and explore their sensitivity to physics beyond the Standard Model (BSM) in the most general weak effective theory. We apply our findings to the current datasets, extract the non-redundant set of angular observables from the data, and compare to precise SM predictions that include lepton-flavour universality violating mass effects. Our analysis shows that…
$b \to c$ semileptonic sum rule: Extension to angular observables
KEK Theory Center, IPNS, KEK(高能加速器研究机构理论中心);Graduate Institute for Advanced Studies, SOKENDAI(日本综合研究大学院大学高等研究院);Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University(名古屋大学小林-益川粒子与宇宙起源研究所);Institute for Advanced Research, Nagoya University(名古屋大学先进研究院);Institute for Theoretical Particle Physics (TTP), Karlsruhe Institute of Technology (KIT)(卡尔斯鲁厄理工学院理论粒子物理研究所);Department of Liberal Arts, Saitama Medical University(埼玉医科大学人文学部);Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University(华中师范大学粒子物理与夸克轻子物理教育部重点实验室)