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Register a new userCollider signature of $V_2$ Leptoquark with $bto s$ flavour observables
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The Leptoquark model has been instrumental in explaining the observed lepton flavour universality violating charged ($bto c$) and neutral ($bto s$) current anomalies that have been the cause for substantial excitement in particle physics recently. In this article we have studied the role of one (designated as $V_2^{frac 43}$) of the components of {boldmath${V}_2$} Vector Leptoquark doublet with electromagnetic charge $frac 43$ in explaining the neutral current ($bto s$) anomalies $R_{K^{(*)}}$ and $B_stomu^+mu^-$. Moreover, we have performed a thorough collider search for this $V_2^{frac 43}$ Leptoquark using $bbar{b} ell^+ ell^-$ ($ellequiv e, mu$) final state at the Large Hadron Collider. From our collider analysis we maximally exclude the mass of the $V_2^{frac 43}$ Leptoquark up to 2340 GeV at 95% confidence level for the 13 TeV Large Hadron Collider for an integrated luminosity of 3000 ${rm fb}^{-1}$. Furthermore, a significant portion of the allowed parameter space that is consistent with the neutral current ($bto s$) observables is excluded by collider analysis.
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One of the most popular models that is known to be able to solve the lepton flavour universality violating charged ($bto c$) and neutral current ($bto s$) anomalies is the Leptoquark Model. In this work we examine the {it multijet} + $mET$ collider signature of a vector leptoquark ($U_1$) which has the potential to mediate both the charged and neutral current processes at tree level. From our collider analysis we derive the exclusion limits on mass for the $U_1$ leptoquark at 95% C.L. at the current and future experiment of the Large Hadron Collider. We also calculate the effect of such a leptoquark in $bto c$ observables.
In a couple of recent publications ( arXiv:1706.08437 and arXiv:1712.01593 ), the authors attempted to achieve simultaneous explanation of the persistent flavor anomalies in $bto s$ and $bto c$ semileptonic decays with a minimal scheme by using only three unknown new parameters. The analysis was obtained with a handful of precise observables. Motivated by their proposal, in this paper we reanalyze the models proposed in the aforementioned papers with a total of 170 observables from those channels including newly available measurements, correlated theoretical results, and constraints. We validate our results by searching for the most influential points and outliers. By analyzing the parameter spaces and their relationship with the constraints, we gain new insight and statistical significance in those models. We also provide a new and precise calculation of $R(J/Psi)$, obtained during the analysis.
We explore the decays of $Bto V_1V_2$ ($V_{1,2}= (rho, omega,K^*, phi)$ and $B= (B^0, B^+,B_s)$) with transverse polarizations. We explicitly evaluate the eigenstates of T-odd scalar operators involving spins for the first time, which offer physical insight among the T violating observables. Based on the helicity suppression of tree operators for transverse polarizations in the standard model (SM), we deduce that $Delta phi_p = phi_parallel - phi_perp=0$ with $phi_{perp,parallel}$ the complex phases of the transverse amplitudes. In contrast, the experiments show that $Delta phi _p (B^0 to K^{*0} omega)= -0.84pm 0.54$, which would be a signal of new physics. There is also a discrepancy between our result in the SM and the experimental data for the transverse polarized branching ratio in $B^0 to K^{*0} omega$. In addition, by counting the helicity flips, we obtain that $sin(phi_p ) approx 0$ in $Bto V_1T_2$ with $T_2$ an arbitrary spin-$n$ meson ($nge1$).
LHCb found hints for physics beyond the Standard Model (SM) in $Bto K^*mu^+mu^-$, $R(K)$ and $B_stophimu^+mu^-$. These intriguing hints for NP have recently been confirmed by the LHCb measurement of $R(K^*)$ giving a combined significance for NP above the $5,sigma$ level. In addition, the BABAR, BELLE and LHCb results for $Bto D^{(*)}tau u$ also point towards lepton flavour universality (LFU) violating new physics (NP). Furthermore, there is the long-standing discrepancy between the measurement and the theory prediction of the anomalous magnetic moment of the muon ($a_mu$) at the $3,sigma$ level. Concerning NP effects, $bto smu^+mu^-$ data can be naturally explained with a new neutral gauge bosons, i.e. a $Z^prime$ but also with heavy new scalars and fermions contributing via box diagrams. Another promising solution to $bto smu^+mu^-$, which can also explain $Bto D^{(*)}tau u$, are leptoquarks. Interestingly, leptoquarks provide also a viable explanation of $a_mu$ which can be tested via correlated effects in $Ztomu^+mu^-$ at future colliders. Considering leptoquark models, we show that an explanation of $Bto D^{(*)}tau u$ predicts an enhancement of $bto stau^+tau^-$ processes by around three orders of magnitude compared to the SM. In case of a simultaneous explanation of $Bto D^{(*)}tau u$ and $bto smu^+mu^-$ data, sizable effects in $bto staumu$ processes are predicted.
We show that the current bounds on the leptoquark couplings imply that if leptoquarks are produced in e p collisions, a significant fraction of them could form a leptoquark-quark bound state. The decay of the bound state has a distinct event shape with rapidity gap. A possible application of this observation in the leptoquark search at HERA is discussed.
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