New Physics solutions for $b\rightarrow c\,τ\,\barν$ anomalies after Moriond 2019
Suman Kumbhakar, Ashutosh Kumar Alok, Dinesh Kumar, S. Uma Sankar
备注：
6 pages, 1 figure, Contribution to proceedings of Workshop on Frontiers in High Energy Physics 2019 (FHEP 2019), 14-17 Oct 2019, Hyderabad, Telangana, India. arXiv admin note: text overlap with arXiv:1909.02840
At Moriond 2019, Belle collaboration has announced new measurements on the flavour ratios $R_D - R_{D^*}$ which are consistent with their Standard Model predictions within $1.2σ$. After inclusion of these measurements, the global tension in $R_D - R_{D^*}$ has reduced from $4.1σ$ to $3.1σ$ which is still significant. The measurements of these ratios indicate towards the violation of lepton flavor universality in $b\rightarrow c\,l\,\barν$ decay. Assuming new physics in $b\rightarrow c\,τ\,\barν$ transition, we have done a global fit to all available data in this sector to identify the allowed new physics solutions. We find that there are seven allowed new physics solutions which can account for all measurements in $b\rightarrow c\,τ\,\barν$ transition. We show that a simultaneous measurement of the $τ$ polarization fraction and forward-backward asymmetry in $B\rightarrow D\,τ\,\barν$, the zero crossing point of forward backward asymmetry in $B\rightarrow D^*τ\barν$ and the branching ratio of $B_c\rightarrow τ\,\barν$ decay can distinguish these seven new physics solutions if they can be measured with a required precision.
Explaining the Flavor Anomalies with a Vector Leptoquark (Moriond 2019 update)
几个实验揭示了半轻子$B$介子衰变中轻子味普适性（LFU）违反新物理（NP）的有趣线索，主要是在$3-5\,σ$水平上的$b \to c τν$和$b \to s \ell^+ \ell^-$跃迁。轻子夸克（LQ）是解决这些异常的主要候选者，因为它们有助于半轻子衰变已经在树水平，而在其他味观测量的影响，同意标准模型（SM），被环抑制。在这些程序中，我们审查矢量leptoquark $SU(2)_L$单线态，包含在著名的Pati-Salam模型，这是能够解决$b \to cτν$和$b \to s μ^+ μ^-$数据同时进行。由于需要考虑到$b \to c τν$数据的大耦合到tau轻子，出现了相当大的回路效应，我们包括在我们的唯象分析。更新我们以前的结果与最近的测量LHCb和BELLE，我们发现一个更好的拟合数据比以前。
The anomalies in rare $B$ decays endure. We present results of an updated global analysis that takes into account the latest experimental input -- in particular the recent results on $R_K$ and BR$(B_s \to μ^+μ^-)$ -- and that qualitatively improves the treatment of theory uncertainties. Fit results are presented for the Wilson coefficients of four-fermion contact interactions. We find that muon specific Wilson coefficients $C_9 \simeq -0.73$ or $C_9 = -C_{10} \simeq -0.39$ continue to give an excellent description of the data. If only theoretically clean observables are considered, muon specif…
In view of the emerging hints for the violation of lepton flavour universality in several $B$-meson decays, we conduct a model-independent study (effective field theory approach) of several well-motivated new physics scenarios. Taking into account the most recent LHCb data, we provide updates to Wilson coefficient fits for numerous popular new physics hypotheses. We also consider a promising model of vector leptoquarks, which in addition to explaining the $B$-meson decay anomalies ($R_{K^{(*)}}$ and $R_{D^{(*)}}$) would have an extensive impact for numerous flavour observables. We identify pro…
$B^*_s\rightarrow l^+l^-$ 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。
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 …
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
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$…
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。
The anomalies in the measurements of $R_D$ and $R_{D^*}$ continue to provide motivation for physics beyond the Standard Model. In this work, we assume the new physics Wilson coefficients to be complex and find their values by doing a global fit to the present $b\rightarrow cτ\barν$ data. We find that the number of allowed solutions depend on the choice of the upper limit on $Br(B_c\rightarrow τ\barν)$. We find that the forward-backward asymmetries in $B\rightarrow (D, D^*)τ\barν$ decays have the capability to distinguish between different solutions. Further we calculate the maximum values of C…
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…
Experimental measurements collected by the BABAR, Belle, and LHCb experiments on different observables associated with the semileptonic transition $b \to c τ\barν_τ$, indicate the existence of disagreement respect with the Standard Model predictions. We analyse the charged scalar boson contributions to these charged-current $B$ meson anomalies within the framework of two Higgs doublet model with the most general Yukawa couplings to quarks and leptons from the third generation, involving left-handed and right-handed (sterile) neutrinos. We perform a phenomenological study of the Yukawa coupling…
We present a model of radiative neutrino masses which also resolves anomalies reported in $B$-meson decays, $R_{D^{(\star)}}$ and $R_{K^{(\star)}}$, as well as in muon $g-2$ measurement, $Δa_μ$. Neutrino masses arise in the model through loop diagrams involving TeV-scale leptoquark (LQ) scalars $R_2$ and $S_3$. Fits to neutrino oscillation parameters are obtained satisfying all flavor constraints which also explain the anomalies in $R_{D^{(\star)}}$, $R_{K^{(\star)}}$ and $Δa_μ$ within $1\, σ$. An isospin-3/2 Higgs quadruplet plays a crucial role in generating neutrino masses; we point out tha…
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。
The anomalies in the measurements of observables involving $b \to s μμ$ decays, namely $R_K$, $R_{K^*}$, $P_5^{\prime}$, and $B_s^ϕ$, may be addressed by adding lepton-universality-violating new physics contributions to the effective operators ${\cal O}_9, {\cal O}_{10}, {\cal O}^\prime_9, {\cal O}^\prime_{10}$. We analyze all the scenarios where the new physics contributes to a pair of these operators at a time. We perform a global fit to all relevant data in the $b \to s$ sector to estimate the corresponding new Wilson coefficients, $C_9^{\rm NP}, C_{10}^{\rm NP}, C_9^\prime, C_{10}^\prime$.…
We propose a direct search for the X17 particle, which was conjectured to explain the ATOMKI $^8$Be and $^4$He anomalies, through the dilepton photoproduction process on a nucleon in the photon energy range below or around the pion production threshold. For the scenarios of either pseudoscalar, vector, or axial-vector quantum numbers of the conjectured X17, we use existing constraints to estimate the X17 signal process. For dilepton resolutions which have been achieved in previous experiments, a signal-to-background ratio of up to an order of magnitude is found for a neutron target, and in par…
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 physics and the mirror world: how exact parity symmetry explains the solar neutrino deficit, the atmospheric neutrino anomaly and the LSND experiment
We critically analyze the body of results that hints to the existence of New Physics from possible violations of lepton universality observed by the LHCb experiment in the $μ/e$ ratios $R_{K}$ and $R_{K^*}$ to the $g-2$ lepton anomalies. The analysis begins with a theoretical, in depth, study of the $μ/e$ ratios $R_{K}$ and $R_{K^*}$ as well as the process $B_s \rightarrow μ^+ μ^-$. Here we consider the impact of complex Wilson coefficients and derive constraints on their imaginary and real parts. We then move to a comprehensive comparison with experimental results. We show that, by fitting a …
