The rare decays B 0 → K Ã0 μ þ μ − and B s → ϕμ þ μ − are now being observed with enough precision to test Standard Model predictions. A full understanding of these decays requires accurate determinations of the corresponding hadronic form factors. Here we present results of lattice QCD calculations of the B → K Ã and B s → ϕ form factors. We also determine the form factors relevant for the decays B s → K Ã lν and B s →K Ã0 l þ l − . We use full-QCD configurations including 2 þ 1 flavors of sea quarks using an improved staggered action, and we employ lattice nonrelativistic QCD to describe the bottom quark.
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...
We propose a novel type of interpolating field operators, which manifests the hybrid-like configuration that the charm quark-antiquark pair recoils against gluonic degrees of freedom. A heavy vector charmonium-like state with a mass of 4.33(2) GeV is disentangled from the conventional charmonium states in the quenched approximation. This state has affinity for the hybrid-like operators but couples less to the relevant quark bilinear operator. We also try to extract its leptonic decay constant and give a tentative upper limit that it is less than one tenth of that of J/ψ, which corresponds to a leptonic decay width about dozens of eV. The connection of this state with X(4260) is also discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.