Probing new physics via the transverse amplitudes of B 0 →K *0 (→K - π + )l + l - at large recoil

By F. Kruger, J. Matias. 2005

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We perform an analysis of the K* polarization states in the exclusive B meson decay B{sup 0}{yields}K*{sup 0} ({yields}K{sup -}{pi}{sup +})l{sup +}l{sup -} (l=e,{mu},{tau}) in the low dilepton mass region, where the final vector meson has a large energy. Working in the transversity basis, we study various observables that involve the K* spin amplitudes A{sub perpendicular}, A{sub parallel}, A{sub 0} by exploiting the heavy-to-light form-factor relations in the heavy quark and large-E{sub K*} limit. We find that at leading order in 1/m{sub b} and {alpha}{sub s} the form-factor dependence of the asymmetries that involve transversely polarized K* completely drops out. At next-to-leading logarithmic order, including factorizable and nonfactorizable corrections, the theoretical errors for the transverse asymmetries turn out to be small in the standard model (SM). Integrating over the lower part of the dimuon mass region, and varying the theoretical input parameters, the SM predicts A{sub T}{sup (1)}=0.9986{+-}0.0002 and A{sub T}{sup (2)}=-0.043{+-}0.003. In addition, the longitudinal and transverse polarization fractions are found to be (69{+-}3)% and (31{+-}3)%, respectively, so that {gamma}{sub L}/{gamma}{sub T}=2.23{+-}0.31. Beyond the SM, we focus on new physics that mainly gives sizable contributions to the coefficients C{sub 7}{sup eff(')} of the electromagnetic dipole operators. Taking into accountmore » experimental data on rare B decays, we find large effects of new physics in the transverse asymmetries. Furthermore, we show that a measurement of longitudinal and transverse polarization fractions will provide complementary information on physics beyond the SM.« less

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/b4c6f38b28ca079f4b6847cb701fe9da1f00328b

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Citations in the corpus

Physics case for an LHCb Upgrade II - Opportunities in flavour physics, and beyond, in the HL-LHC era (2018, result): “Measurements of angular observables in B0→ K∗0μ+μ− decays show a discrepancy with respect to SM predictions [290,291,318–335].”
New observables in the decay mode anti-B --> anti-K*0 l+ l- (2008, methodology): “The precise definitions of the form factors and of the effective operators are given in Appendix B. One obtains [ 19 ]”
B → K∗ℓ+ℓ− decays at large recoil in the Standard Model: a theoretical reappraisal (2015, background): “2 From these coefficients, exploiting the symmetries of the infinite mass limit, one can define “optimized” observables in which the soft form factors cancel out, drastically reducing the theoretical uncertainties [22–24].”