Measurement of Form-Factor-Independent Observables in the DecayB0→K*0μ+μ−

Abstract

We present a measurement of form-factor-independent angular observables in the decay B(0)→K*(892)(0)μ(+)μ(-). The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb(-1), collected by the LHCb experiment in pp collisions at a center-of-mass energy of 7 TeV. Four observables are measured in six bins of the dimuon invariant mass squared q² in the range 0.1<q²<19.0 GeV²/c(4). Agreement with recent theoretical predictions of the standard model is found for 23 of the 24 measurements. A local discrepancy, corresponding to 3.7 Gaussian standard deviations is observed in one q² bin for one of the observables. Considering the 24 measurements as independent, the probability to observe such a discrepancy, or larger, in one is 0.5%.

Anomaly-free models for flavour anomalies

“…The LHCb Collaboration and other experiments have reported a number of anomalies in semileptonic B decays, including apparent violations of μ-e universality in B → K ( * ) + − decays [1][2][3][4], and apparent deviations from the Standard Model (SM) predictions for the P 5 angular variable in B → K * + − decay [5][6][7][8][9] and the m μ + μ − distribution in B s → φμ + μ − decay [10,11]. These anomalies have reached a high level of statistical significance.…”

Rare B decays as tests of the Standard Model

“…In order to measure these observables with a modest number of events, Belle exploits the folding technique introduced in Ref. [253]. This reduces the amount of information that is extracted from the angular distribution in a single fit to the data.…”

A new generation of Lepton Flavour Universality observables from $B\rightarrow$$K^∗$$\mu^+$$\mu^−$

“…In particular, processes driven by the flavour-changing neutral current (FCNC) transition b → s + − have been providing hints of several deviations from the Standard Model (SM) in various observables. In 2015, the LHCb analysis [1] of the 3 fb −1 data on B → K * µ + µ − confirmed a ∼ 3σ anomaly in two large K * -recoil bins of the angular observable P 5 [2,3] that was already present in the 2013 results with 1 fb −1 [4]. The same experiment measured the observable R K = B(B → Kµ + µ − )/B(B → Ke + e − ) [5] in the dilepton mass range from 1 to 6 GeV 2 and found a 2.6σ tension with its SM value, predicted to be equal one (to a one per cent accuracy).…”

“…Belle has been the first experiment to measure the observable Q 5 [25], finding a 1.2σ tension w.r.t. the SM prediction in the relevant bin [4,8] GeV 2 (this tension is reduced to 0.6σ in the presence of a NP contribution C NP 9µ = −1.1). The low statistical significance of this result makes impossible to draw any conclusion, although it is interesting to notice its connection with the deviation in R K .…”

“…Finally, in Sec. 4 we present a set of new observables able to test lepton-flavour universality violations (LFUV) [9] and briefly review its properties.…”