Calculation ofB0→K*0μ+μ

Abstract

We calculate the differential branching fractions and angular distributions of the rare decays B 0 → K Ã0 μ þ μ − and B 0 s → ϕμ þ μ − , using for the first time form factors from unquenched lattice QCD. We focus on the kinematic region where the K Ã or ϕ recoils softly; there, the newly available form factors are most precise and the nonlocal matrix elements can be included via an operator product expansion. Our results for the differential branching fractions calculated in the standard model are higher than the experimental data. We consider the possibility that the deviations are caused by new physics and perform a fit of the Wilson coefficients C 9 and C 0 9 to the experimental data for multipleIn agreement with recent results from complementary studies, we obtain C 9 − C SM 9 ¼ −1.0 AE 0.6 and C Decays involving the transition of a bottom quark to a strange quark are highly suppressed in the standard model. Contributions from nonstandard interactions could therefore be significant, causing observable changes in the decay rates and angular distributions. The search for such discrepancies is one of the most important routes to discovering what might lie beyond our current model of fundamental particle physics, and complements efforts to directly produce nonstandard particles. Because of quark confinement, the b → s transitions are being observed with hadronic initial and final states. Among the cases that have been measured experimentally [1], the decaywhere l is an electron or muon) is proving to be particularly powerful in looking for physics beyond the standard model [2][3][4][5][6][7][8][9][10][11][12][13].The LHCb Collaboration recently published new precision measurements of the decay B → K Ã μ þ μ − , and one of the observables shows a significant deviation from the standard model predictions [14]. There is currently an intense effort to understand this discrepancy, which could be a manifestation of new physics [15][16][17][18][19][20][21][22]. Previous calculations of the matrix elements that relate the underlying b → s interactions and the hadronic observables are reliable only in the kinematic region of high recoil (large K Ã momentum in the B rest frame), and consequently it was in this region that a discrepancy was found. In the low-recoil region, numerical lattice QCD computations must be performed. We recently completed the first unquenched lattice QCD calculation of the form factors that parametrize the hadronic matrix elements relevant forIn this Letter, we investigate the consequences of using these results in combination with experimental data. We find that hints of deviations from the standard model are present also in the lowrecoil region, and a better fit of the data is obtained by allowing nonstandard interactions consistent with those suggested to explain the aforementioned anomaly at high recoil.At hadronic energy scales, b → sγ and b → sl þ l − transitions can be described using an effective Hamiltonian of the form [24-31]where O 9 ¼ e 2 =ð16π 2 Þsγ μ P LðRÞ blγ μ l;10 ¼ e 2 =ð16π 2 Þ...

Nonperturbative comparison of clover and highly improved staggered quarks in lattice QCD and the properties of the ϕ meson

“…The accuracy of our φ meson correlators led to the first flavour-separated determination of the valence s quark hadronic vacuum polarisation contribution to the anomalous magnetic moment of the muon [28]; an uncertainty of 1% was reached in that calculation. These uncertainties are also promising for improvements to lattice QCD calculations of form factors for decay processes that include φ mesons [18,20].…”

“…For example, V cs can be determined from D s → φ ν given lattice QCD results and experimental rates [17][18][19]. B s → φ + − is potentially an important rare decay mode for searches for new physics [20].…”

New Physics inBdecays

“…Concerning b → sμ + μ − transitions, already in 2013 LHCb reported deviations from the SM predictions [1] (mainly in an angular observable called P 5 [2]) in B → K * μ + μ − [3] with a significance of 2-3 σ depending on the assumptions of hadronic uncertainties [4][5][6] being confirmed in 2015 [7]. Also in the decay B s → φμ + μ − [8] LHCb uncovered differences compared to the SM prediction from lattice QCD [9,10] …”

Round table: Flavour anomalies inb→sl+l−processes

“…The data are compared to SM predictions based on Refs. [9,10] and [11]. The rise in the branching fraction at low q 2 arises from virtual photon contributions to the decay.…”

“…The resulting distribution is then fitted to a z-series expansion with flat priors on the coefficients [10]. The lattice FFs themselves are fitted to the same expansion including a full error correlation matrix [11]. In addition, a fit interpolating between the LCSR and lattice results is provided [10].…”