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Register a new userTowards establishing an abundant $B$ and $B_s$ spectrum up to the second orbital excitations
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Stimulated by the exciting progress in experiments, we carry out a combined analysis of the masses, and strong and radiative decay properties of the $B$ and $B_s$-meson states up to the second orbital excitations. Based on our good descriptions of the mass and decay properties for the low-lying well-established states $B_1(5721)$, $B_2^*(5747)$, $B_{s1}(5830)$ and $B_{s2}^*(5840)$, we give a quark model classification for the high mass resonances observed in recent years. It is found that (i) the $B_{J}(5840)$ resonance may be explained as the low mass mixed state $B(|SDrangle_L)$ via $2^3S_1$-$1^3D_1$ mixing, or the pure $B(2^3S_1)$ state, or $B(2^1S_0)$. (ii) The $B_J(5970)$ resonance may be assigned as the $1^3D_3$ state in the $B$ meson family, although it as a pure $2^3S_1$ state cannot be excluded. (iii) The narrow structure around 6064 MeV observed in the $B^+K^-$ mass spectrum at LHCb may be mainly caused by the $B_{sJ}(6109)$ resonance decaying into $B^{*+}K^-$, and favors the assignment of the high mass $1D$-wave mixed state $B_s(1D_2)$ with $J^P=2^-$, although it as the $1^3D_3$ state cannot be excluded. (iv) The relatively broader $B_{sJ}(6114)$ structure observed at LHCb may be explained with the mixed state $B_s(|SDrangle_H)$ via $2^3S_1$-$1^3D_1$ mixing, or a pure $1^3D_1$ state. Most of the missing $1P$-, $1D$-, and $2S$-wave $B$- and $B_s$-meson states have a relatively narrow width, they are most likely to be observed in their dominant decay channels with a larger data sample at LHCb.
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Some fine differences between the twin $b$-flavored unitarity triangles are calculated by means of a generalized Wolfenstein parametrization of the CKM matrix, and a possibility of experimentally establishing the second triangle is briefly discussed. We find that the apexes of these two triangles, characterized respectively by $(overline{rho}, overline{eta})$ and $(widetilde{rho}, widetilde{eta})$, are located on the same circular arc in the complex plane. This observation provides us with a new way to test consistency of the CKM picture of CP violation in the quark sector and probe possible new physics. The differences between the apexes (i.e., $widetilde{rho} - overline{rho}$ and $widetilde{eta} - overline{eta}$) are found to be of ${cal O}(lambda^2)$ with $lambda simeq 0.22$ being the Wolfenstein expansion parameter, and the shapes of these two triangles are found to be insensitive to the two-loop renormalization-group-equation running effects up to the accuracy of ${cal O}left(lambda^4right)$.
Rare semileptonic $b to s ell^+ ell^-$ transitions provide some of the most promising frameworks to search for new physics effects. Recent analyses of these decays have indicated an anomalous behaviour in measurements of angular distributions of the decay $B^0to K^*mu^+mu^-$ and lepton-flavour-universality observables. Unambiguously establishing if these deviations have a common nature is of paramount importance in order to understand the observed pattern. We propose a novel approach to independently and complementary probe this hypothesis by performing a simultaneous amplitude analysis of $bar{B}^0 to bar{K}^{*0} mu^+mu^-$ and $bar{B}^0 to bar{K}^{*0} e^+e^-$ decays. This method enables the direct determination of observables that encode potential non-equal couplings of muons and electrons, and are found to be insensitive to nonperturbative QCD effects. If current hints of new physics are confirmed, our approach could allow an early discovery of physics beyond the standard model with LHCb run II data sets.
We consider two-loop QCD corrections to the element $Gamma_{12}^q$ of the decay matrix in $B_q-bar{B}_q$ mixing, $q=d,s$, in the leading power of the Heavy Quark Expansion. The calculated contributions involve one current-current and one penguin operator and constitute the next step towards a theory prediction for the width difference $DeltaGamma_s$ matching the precise experimental data. We present compact analytic results for all matching coefficients in an expansion in $m_c/m_b$ up to second order. Our new corrections are comparable in size to the current experimental error and slightly increase $DeltaGamma_s$.
We investigate the possibility of indirectly constraining the $B^{+}to K^{+}tau^+tau^-$ decay rate using precise data on the $B^{+}to K^{+}mu^+mu^-$ dimuon spectrum. To this end, we estimate the distortion of the spectrum induced by the $B^{+}to K^{+}tau^+tau^-to K^{+} mu^+mu^-$ re-scattering process, and propose a method to simultaneously constrain this (non-standard) contribution and the long-distance effects associated to hadronic intermediate states. The latter are constrained using the analytic properties of the amplitude combined with data and perturbative calculations. Finally, we estimate the sensitivity expected at the LHCb experiment with present and future datasets. We find that constraints on the branching fraction of $O(10^{-3})$, competitive with current direct bounds, can be achieved with the current dataset, while bounds of $O(10^{-4})$ could be obtained with the LHCb upgrade-II luminosity.
One of the fundamental predictions of the Standard Model is Lepton Flavour Universality. Any deviation from this prediction would indicate the existence of physics beyond the Standard Model. Recent LHCb measurements present a pattern of deviations from this prediction in rare B-meson decays. While not yet statistically significant (currently $2.2-2.6 sigma$), these measurements show an imbalance in the ratio of B-meson decays to a pair of muons in association with a Kaon and decays to a pair of electrons in association with a Kaon. If the measured deviations are indeed present in nature, new physics may mediate interactions involving a pair of same flavour leptons, a $b$- and an $s$-quark. We present the prospect for a search of new physics in this type of interactions at the LHC, in a process that involves an $s$-quark, and a final state with two leptons and a $b$-jet. The proposed search can improve the sensitivity to new physics in these processes by a factor of four compared to current searches with in the total dataset expected at the LHC.
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