Measurement of B+ -> K+ tau- tau+, B -> K* l+ l- and B -> K pi+ pi- gamma decays at BABAR

TL;DR

This paper reports measurements of rare B meson decays, including searches for B+ -> K+ tau- tau+ and studies of B -> K* l+ l- and B0 -> KS0 pi- pi+ gamma decays, providing limits and asymmetry measurements to test the Standard Model.

Contribution

First measurement of B+ -> K+ tau- tau+ branching fraction and upper limit; detailed analysis of B -> K* l+ l- asymmetries; time-dependent CP asymmetry in B0 decays at BABAR.

Findings

No evidence for B+ -> K+ tau- tau+ signal; upper limit set.

Measured AFB and FL in B -> K* l+ l- decays across dilepton mass bins.

CP asymmetry parameter S in B0 -> KS rho gamma measured as -0.18 ± 0.32 (stat) +0.06 -0.05 (syst).

Abstract

We present some recent measurements of rare flavor-changing neutral current B decays, using data collected with the BABAR detector at the PEP-II e+e- collider at SLAC. First, we search for the rare process B+ -> K+ tau- tau+ and we do not find evidence for signal. The measured branching fraction is (1.31+0.66-0.61(stat.)+0.35-0.25(sys.)) x 10-3 with an upper limit, at the 90% confidence level, of B(B+ -> K+ tau+ tau-) < 2.25 x 10-3. We then study the lepton forward-backward asymmetry AFB and the longitudinal K* polarization FL in the rare decays B -> K* l+ l-, where l+ l- is either e+ e- or mu+ mu-. We report results for both the K*(892)0l+l- and K*(892)+l+l- final states, as well as their combination K*l+l-, in five disjoint dilepton mass-squared bins. Finally, we measure the time-dependent CP asymmetry in the radiative-penguin decay B0 -> KS0 pi- pi+ gamma. The Kpipi resonant structure is extracted by an amplitude analysis of the m_Kpipi and m_Kpi spectra in B+ -> K+ pi- pi+ gamma decays. We use these results to extract the mixing-induced CP parameters of the process B0 -> KS rho gamma from the time-dependent analysis of B0 -> KS0 pi+ pi- gamma decays and obtain S = -0.18 pm 0.32(stat.) +0.06 -0.05(syst.).