We study some phenomenological effects of kinetic mixing between the hypercharge field and a new $U(1)$ gauge field in specific $Z^\prime$ models that ameliorate the tensions between measurements and Standard Model predictions in $b \rightarrow s\ell^+ \ell^-$ decays. To this end, we rederive the dimension-6 SMEFT coefficients resulting from integrating out the kinetically-mixed (`malaphoric') $Z^\prime$ field. The kinetic mixing provides a family-universal component to the couplings of the $Z^\prime$ field, which can improve fits to lepton flavour universality observables. We show how kinetic mixing improves the best fit of the $B_3-L_2$ model to $b\rightarrow s$ data by 7.0 units of $χ^2$ while remaining compatible with other relevant data sets such as electroweak precision observables and measurements of $e^+ e^- \rightarrow \ell^+ \ell^-$ at LEP2.
In this work we study possible connections between $B$-meson anomalies and Kaon physics observables in the context of combined solutions with the singlet and triplet scalar leptoquarks $S_1$ and $S_3$. By assuming a flavor structure for the leptoquark couplings dictated by a minimally broken $U(2)^5$ flavor symmetry we can make a sharp connection between these two classes of observables. We find that the bound on $\mathcal{B}(K^+ \rightarrow π^+ νν)$ from NA62 puts already some tension in the model, while the present limits on $\mathcal{B}(K_L \rightarrow μ^+ μ^-)$ and $μ\to e$ conversion in n…
Inspired by the recent experimental results which show deviations from the standard model (SM) predictions of $b\rightarrow s \ell^+\ell^-$ transitions, we study the $R$-parity violating minimal supersymmetric standard model (RPV-MSSM) extended by the inverse seesaw mechanism. The trilinear $R$-parity violating terms, together with the chiral mixing of sneutrinos, induce the loop contributions to the $b\rightarrow s \ell^+\ell^-$ anomaly. We study the parameter space of the single-parameter scenario $C^{\rm NP}_{9,μ}=-C^{\rm NP}_{10,μ}=C_{\rm V}$ and the double-parameter scenario $(C_{\rm V},C…
We present a likelihood analysis of the general two Higgs doublet model, using the most important currently measured flavour observables, in view of the anomalies in charged current tree-level and neutral current one-loop rare decays of $B$ mesons in $b\to c l \overlineν$ and $b\to sμ^{+}μ^{-}$ transitions, respectively. We corroborate that the model explains the latter and it is able to simultaneously fit the experimental values of the $R(D)$ ratio at $1σ$, but it can not accommodate the $R(D^{*})$ and $F_{L}(D^{*})$ observables. We find that the fitted values for the angular observables in $…
Anomalies in (semi)-leptonic $B$ decays $B^{\pm} \to τ^{\pm} ν$, $B^{\pm} \to D τ^{\pm} ν$ and $B^{\pm} \to D^* τ^{\pm} ν$, and possible resolution with sterile neutrino
$B^*_s\rightarrow l^+l^-$ decays in light of recent $B$ anomalies
中性电流扇区$b\rightarrow s l^+l^-$($l=e$或$μ$)以及带电电流扇区$b \rightarrow c τ\barν$中的一些最近测量结果显示出与标准模型预测的显著偏差。结果表明,两种不同的新物理解,即矢量解和(或)轴矢量解,可以解释$b\rightarrow s l^+l^-$扇区的所有异常。我们表明,μ子的纵向极化不对称性在$B^*_s\rightarrow μ^+\,μ^-$衰变是一个很好的判别两个解决方案之间,如果它可以测量到$\sim 10\%$的精度,提供新的物理威尔逊系数是真实的。我们还研究了$b \rightarrow c τ\barν$异常对$B_s^* \rightarrow τ^+ τ^-$衰变的潜在影响。我们考虑一个模型,其中新的物理贡献,这两个过渡是强相关的。我们发现,两个数量级的增强$B^*_s\rightarrow τ^+\,τ^-$的分支比是允许由本$b \rightarrow c τ\barν$数据。
New physics effects in purely leptonic $B^*_s$ decays
最近,中性电流扇区$b\rightarrow s l^+l^-$($l=e$或$μ$)以及充电电流扇区$b \rightarrow c τ\barν$中的几个测量结果显示出与标准模型预测的显著偏差。结果表明,两种不同的新物理解可以解释$b\rightarrow s l^+l^-$扇区的所有异常。这两个解都是两个算子$(\bar{s}γ^αP_Lb)(\barμγ_αμ)$和$(\bar{s}γ^αP_Lb)(\barμγ_αγ_5μ)$的线性组合的形式。我们证明了在$B^*_s\rightarrow μ^+\,μ^-$衰变中μ子的纵向极化不对称性是两个解之间的一个很好的判别式,如果它可以测量到$10\%$的精度,提供新的物理威尔逊系数是真实的。如果它们是复杂的,这种不对称性的理论不确定性太大,无法提供有效的区分。我们还研究了$b \rightarrow c τ\barν$异常对$b \rightarrow s τ^+ τ^-$跃迁的潜在影响。我们考虑一个模型,其中新的物理贡献,这两个转变是强相关的。我们发现,$B^*_s\rightarrow τ^+\,τ^-$的分支比可以提高三个数量级。
As shown in Ref. \cite{Allanach:2021kzj}, the Third Family Hypercharge ($Y_3$) Model changes the Standard Model prediction for $M_W$ whilst simultaneously explaining anomalies in $b\to s\ell\ell$ transitions via a heavy $Z^\prime$ gauge boson which is spawned by a spontaneously broken gauged $U(1)_{Y_3}$ symmetry. The 2022 CDF II measurement of $M_W$, which is far from the Standard Model prediction, somewhat disfavours the $Y_3$ model. Here, we generalise the gauge charge assignments to the anomaly-free combination $s Y_3 + t (B_3-L_3)$ and show that incorporating the 2022 CDF II measurement o…
A number of observables related to the $b \to s \ell^+ \ell^-$ transition show deviations from their standard model predictions. A global fit to the current $b\rightarrow s\ell^+\ell^-$ data suggests several new physics solutions. Considering only one operator at a time and new physics only in the muon sector, it has been shown that the new physics scenarios (I) $C_9^{\rm NP}<0$, (II) $C_{9}^{\rm NP} = -C_{10}^{\rm NP}$, (III) $C_9^{\rm NP} = -C_9^{\prime \rm NP}$ can account for all data. In this work, we develop a procedure to uniquely identify the correct new physics solution. The scenario …
The observation of anomalies in the charged current $b\rightarrow c\bar{\ell}ν_{\ell}$ transitions hints the possibility of the existence of new physics beyond the standard model. Inspired by the work done in the beauty quark sector, we explore new physics in the charm quark sector with $c \rightarrow (s,d)\bar{\ell}ν_{\ell}$ charged current transitions. We analyze the decay modes $D_{(s)}^+ \to η^{(')} \bar{\ell} ν_{\ell}$ within an effective Lagrangian framework which includes both standard model and new physics contributions. We use the available experimental measurements of the semileptoni…
New insights into the $b\rightarrow c \bar{u}q$ puzzle through Top-Bottom synergies
University College London(伦敦大学学院);City St. George’s, University of London(伦敦大学圣乔治城市学院);University of Manchester(曼彻斯特大学);Durham University(杜伦大学);Universität Siegen(锡根大学)
研究通过顶-底协同性探讨$b\ ightarrow c \bar{u}q$异常,分析强耦合新物理对碰撞实验的影响,发现即使增加$t\ar{t}$衰变分支比,弱双态标量的限制仍强,且QCD因子化可能因高次修正而破裂。
Flavour Anomalies: A comparative analysis using a machine learning algorithm
Universidad de Zaragoza(萨拉戈萨大学);Centro de Astropartículas y Física de Altas Energías (CAPA), Universidad de Zaragoza(高能物理与天体粒子中心(CAPA),萨拉戈萨大学);Università degli Studi di Padova(帕多瓦大学);Istituto Nazionale di Fisica Nucleare (INFN), Sezione Padova(意大利国家核物理研究所(INFN)帕多瓦分部)
Experimental data on $ R(D^{(*)}) $, $ R(K^{(*)}) $ and $ R(J/ψ) $, provided by different collaborations, show sizable deviations from the SM predictions. To describe these anomalies many new physics scenarios have been proposed. One of them is leptoquark model with introducing the vector and scalar leptoquarks coupling simultaneously to the quarks and leptons. To look for similar possible anomalies in baryonic sector, we investigate the effects of a vector leptoquark $U_3 (3,3, \frac{2}{3})$ on various physical quantities related to the tree-level $ Λ_b \rightarrow Λ_c \ell ~ \overlineν_\ell$…
In order to address this question, we consider a simple renormalisable and gauge invariant model in which the $Z'$ only has couplings to the electron and muon and their associated neutrinos, arising from mixing with a heavy vector-like fourth family of leptons. Within this model we discuss the contributions to the electron and muon anomalous magnetic moments from $Z'$ exchange, subject to the constraints from $μ\rightarrow e γ$ and neutrino trident production. Using analytic and numerical arguments, we find that such a $Z'$ model can account for either the electron or the muon $g-2$ anomalies,…
Neutrino physics and the mirror world: how exact parity symmetry explains the solar neutrino deficit, the atmospheric neutrino anomaly and the LSND experiment
We have witnessed some flavor anomalies appeared in the past years, and explanations based on extended gauge sectors are among the most popular solutions. These beyond the Standard Model (SM) theories often assume flavor changing interactions mediated by new vector bosons, but at the same time they could yield deviations from the SM in the $K^{0}-\bar{K}^{0}$, $D^{0}-\bar{D}^{0}$, $B^0_d-\bar{B^0}_d$ and $B^0_s-\bar{B^0}_s$ meson systems. Using up-to-date data on the mass difference of these meson systems, we derive lower mass bounds on vector mediators for two different parametrizations of th…
Neutrino telescopes provide strong sensitivity to sterile neutrino oscillations through matter-enhanced oscillation, occurring in the few TeV energy range for eV$^{2}$-scale neutrino mass-squared splittings. Prior searches have focused on $ν_μ$ disappearance, which has a particularly strong sensitivity to the mixing angle $θ_{24}$ via $ν_μ\rightarrowν_s$ transitions. Nowadays, the $ν_μ\rightarrowν_e$ and $ν_μ\rightarrowν_τ$ appearance channels have been considered less promising at neutrino telescopes, due in part to the much smaller target volume for cascades relative to tracks. This work exp…