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تسجيل مستخدم جديدPossible strategy of discriminating 1D new physics solutions in $bto sellell$ decays after Moriond 2021
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The recent measurements of $R_K$, $B_stomu^+mu^-$, a set of CP-averaged angular observables for the $B^0to K^{*0}mu^+mu^-$ decay, and its isospin partner $B^+to K^{*+}mu^+mu^-$ by the LHCb Collaboration, consistently hint at lepton universality violation in the $bto sellell$ transitions. The so-called $B$ anamolies can be best explained in five one-dimensional scenarios, i.e, $delta C_9^{mu}$, $delta C_{10}^{mu}$, $delta C_L^{mu}$, $delta C_9^{mu}=delta C_{10}^{muprime}$, and $delta C_9^{mu}=-delta C_9^{muprime}$, as demonstrated in recent model independent anlayses~cite{Alok:2019ufo,Alguero:2021anc,Geng:2021nhg,Altmannshofer:2021qrr}. In this work we explore how these scenarios can be distinguished from each other. We show that the combinations of four angular asymmetries $A_i$~$(i=3,4,5,9)$ together with the ratio $R_6$ first proposed in~cite{Jager:2014rwa} can discriminate the five new physics scenarios in proper intervals of $q^2$ and with future high-precision measurements.
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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 $1.2sigma$. After inclusion of these measurements, the global tension in $R_D
- R_{D^*}$ has reduced from $4.1sigma$ to $3.1sigma$ which is still significant. The measurements of these ratios indicate towards the violation of lepton flavor universality in $brightarrow c,l,bar{ u}$ decay. Assuming new physics in $brightarrow c,tau,bar{ u}$ 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 $brightarrow c,tau,bar{ u}$ transition. We show that a simultaneous measurement of the $tau$ polarization fraction and forward-backward asymmetry in $Brightarrow D,tau,bar{ u}$, the zero crossing point of forward backward asymmetry in $Brightarrow D^*taubar{ u}$ and the branching ratio of $B_crightarrow tau,bar{ u}$ decay can distinguish these seven new physics solutions if they can be measured with a required precision.
We investigate new-physics contributions to $bto s ellell$ transitions in the context of an effective field theory extension of the Standard Model, including operator mixing at one loop. We identify the few scenarios where a single Wilson coefficient
, $C/Lambda^2 sim 1/{rm TeV}^2$, induces a substantial shift in the lepton flavour universality ratios $R_K$ and $R_{K^*}$ at one loop, while evading $Z$-pole precision tests, collider bounds, and other flavour constraints. Good fits to the present data are achieved by a left-handed current operator with quark-flavour indices $(2,2)$ or $(3,3)$, hitherto overlooked. Interestingly, the running of the Standard Model Yukawa matrices gives the dominant effect for these scenarios. We match the favoured effective-theory scenarios to minimal, single-mediator models, which are subject to additional stringent constraints. Notably, we recognise three viable instances of a leptoquark with one coupling to fermions only. If the anomalies were confirmed, it appears that one-loop explanations have good prospects of being directly tested at the LHC.
We present results of global fits of all relevant experimental data on rare $b to s$ decays. We observe significant tensions between the Standard Model predictions and the data. After critically reviewing the possible sources of theoretical uncertain
ties, we find that within the Standard Model, the tensions could be explained if there are unaccounted hadronic effects much larger than our estimates. Assuming hadronic uncertainties are estimated in a sufficiently conservative way, we discuss the implications of the experimental results on new physics, both model independently as well as in the context of the minimal supersymmetric standard model and models with flavour-changing $Z$ bosons. We discuss in detail the violation of lepton flavour universality as hinted by the current data and make predictions for additional lepton flavour universality tests that can be performed in the future. We find that the ratio of the forward-backward asymmetries in $B to K^* mu^+mu^-$ and $B to K^* e^+e^-$ at low dilepton invariant mass is a particularly sensitive probe of lepton flavour universality and allows to distinguish between different new physics scenarios that give the best description of the current data.
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