Forward-backward and isospin asymmetry forB→K*ell⁺ell⁻decay in the standard model and in supersymmetry

Abstract

We discuss two dedicated observables in exclusive B → K * ℓ + ℓ − decay that can be used to study effects of physics beyond the standard model, namely the forwardbackward asymmetry in the lepton spectrum and the isospin-asymmetry between decays of charged and neutral B mesons. We consider the region of large recoilenergy (i.e. small invariant mass of the lepton pair), and employ the QCD factorization approach to exclusive B meson decays. Sub-leading effects in the heavy quark mass expansion have been taken into account for the calculation of the isospinasymmetry. We give predictions for decay asymmetries in the standard model, and its supersymmetric extension with minimal flavor violation, using parameter values allowed by current experimental constraints on B → X s γ decay.

DirectCP, Lepton Flavor, and Isospin Asymmetries in the DecaysB→K(*)l+Aubert1, Bóna2, Karyotakis3 et al. 2009Phys. Rev. Lett.802260View full textAdd to dashboardCite

“…where r = τ 0 /τ + = 1/(1.07 ± 0.01) is the ratio of the B 0 and B + lifetimes [8], has a SM expectation of +6−13% as q 2 → 0 GeV 2 /c 4 [9]. This is consistent with the measured asymmetry of 3±3% in B → K * γ [8].…”

Search for the rare decaysB→πℓ+ℓ−andB0→ηℓ+Lees1, Poireau2, Tisserand3 et al. 2013Phys. Rev. D11120View full textAdd to dashboardCite

“…þ ' À Þ < 6:4 Â 10 À8 ; (9) all at the 90% CL. A lepton-flavor and isospin averaged branching fraction upper limit of…”

“…s' þ ' À decays provide a promising avenue in which to search for new physics (NP). Amplitudes from these NP contributions can interfere with those from the SM, altering physical observables (e.g., decay rates, CP, isospin, and forward-backward asymmetries) from the SM predictions [3,4,[7][8][9][10]. Measurements in the ' þ ' À and ' þ ' À systems complement and provide independent searches of NP from those in the K ðÃÞ ' þ ' À channels [11][12][13][14][15][16][17], as physics beyond the SM may have nontrivial flavor couplings [18].…”

Review of recent Heavy Flavour Physics results from the ATLAS experiment

“…The angular distributions of the signal are given by Equations (3) and (4). To take into account angular detector efficiencies due to trigger, event reconstruction, detector effects and the selection cuts, the angular signal distributions are weighted by acceptance maps α K and α L , determined for cos θ K and cos θ L , respectively.…”

“…Angular distributions of the 4-particle final state, as well as the decay amplitudes, are sensitive to physics beyond the Standard Model, mainly as a result of the interference of new diagrams with the Standard Model diagrams [4]. In thee proceedings we summarise the measurement of the lepton forward-backward asymmetry A FB in bins of the di-muon invariant mass q 2 and compare the results to theoretical predictions [5] .…”