Right-handed currents in rare exclusive decays

Abstract

The effects of possible right-handed weak hadronic currents in rare exclusive semileptonic decays B → (K, K * )νν are investigated using a lattice-constrained dispersion quark model for the calculation of the relevant mesonic form factors. The results obtained for the branching ratios and the missing energy spectra are presented and the sensitivity of various observables to long-distance physics is investigated. It is shown that the asymmetry of transversely polarized K * T mesons as well as the K/K * T production ratio are only slightly sensitive to long-distance contributions and mostly governed by the relative strength and phase of right-handed currents. In particular, within the Standard Model the production of right-handed K * T mesons turns out to be largely suppressed with respect to left-handed ones, thanks to the smallness of the final to initial meson mass ratio. Therefore, the measurement of produced right-handed K * T mesons in rare B → K * νν decays offers a very interesting tool to investigate right-handed weak hadronic currents.

Probing right-handed currents in transitions

“…2 shows the distributions of the righthanded (a) and the left-handed (b) K * . One can see that the yield of the right-handed K * in the region of small q 2 might be remarkably increased in the LR models (see also [6]). Such an increase of the right-handed K * mesons in comparison with the predictions of models having suppressed RH quark currents, like the SM or the MSSM, can provide a very specific behavior of the transverse asymmetry (12), as it is shown clearly in Fig.…”

“…the MSSM extention of the SM can be probed by the analysis of the forward-backward (A F B ) and lepton polarization (P L ) asymmetries: namely, there are regions in the MSSM parameter space which yield qualitatively different behaviors of A F B and P L compared with the SM predictions. Moreover, a possibilty to probe the RH currents in B → K * νν decays has been recently pointed out in [6]. In this letter we discuss a possibility to discriminate between the MSSM and LR models by a study of the q 2 -distributions of the transversely polarized K * mesons produced in the B → K * ℓ + ℓ − decays.…”

Dispersion approach to quark-binding effects in weak decays of heavy mesons

“…The asymptotic relations (103) and (105) are the zero-order terms of the 1/m Q -expansion which is calculable within the Heavy quark effective theory (HQET) [3]. A particular form of the IW function depends on the heavy meson wave function.…”

“…In next Sections we discuss in detail the structure of this expansion for the transition of a heavy pseudoscalr meson into pseudoscalar and vector mesons. The expressions (103) and (105) mean that the HQ symmetry restricts the possible behavior of the meson wave function at large m Q . In the HQ limit, for a finite binding energy of the meson the heavy meson and the heavy quark masses coincide, M Q /m Q = 1.…”

“…So, the value of √ m Q f P should be independent of the heavy quark mass. Clearly, the asymptotic relations (103) and (105) However, there is an attractive possibility to specify α D,B more precisely. Namely, it seems reasonable to assume α to be approximately constant in the region m Q ≥ 1 ÷ 2 GeV .…”