Test of lepton universality with B0 → K*0ℓ+ℓ− decays

By R. Aaij, B. Adeva, M. Adinolfi, Z. Ajaltouni, S. Akar, J. Albrecht, Federico Alessio, M. Alexander, S. Ali, G. Alkhazov and 489 more. Journal of High Energy Physics, 2017

568 citations recorded by the source corpus.

A test of lepton universality, performed by measuring the ratio of the branching fractions of the B0 → K*0μ+μ− and B0 → K*0e+e− decays, RK*0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {R}_{K^{*0}} $$\end{document}, is presented. The K*0 meson is reconstructed in the final state K+π−, which is required to have an invariant mass within 100 MeV/c2 of the known K*(892)0 mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3 fb−1, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ratio is measured in two regions of the dilepton invariant mass squared, q2, to be RK*0=0.66−+0.070.11stat±0.03systfor0.045<q2<1.1GeV2/c4,0.69−+0.070.11stat±0.05systfor1.1<q2<6.0GeV2/c4.\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {R}_{K^{*0}}=\left\{\begin{array}{l}{0.66_{-}^{+}}_{0.07}^{0.11}\left(\mathrm{stat}\right)\pm 0.03\left(\mathrm{syst}\right)\kern1em \mathrm{f}\mathrm{o}\mathrm{r}\kern1em 0.045<{q}^2<1.1\kern0.5em {\mathrm{GeV}}^2/{c}^4,\hfill \\ {}{0.69_{-}^{+}}_{0.07}^{0.11}\left(\mathrm{stat}\right)\pm 0.05\left(\mathrm{syst}\right)\kern1em \mathrm{f}\mathrm{o}\mathrm{r}\kern1em 1.1<{q}^2<6.0\kern0.5em {\mathrm{GeV}}^2/{c}^4.\hfill \end{array}\right. $$\end{document} The corresponding 95.4% confidence level intervals are [0.52, 0.89] and [0.53, 0.94]. The results, which represent the most precise measurements of RK*0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {R}_{K^{*0}} $$\end{document} to date, are compatible with the Standard Model expectations at the level of 2.1–2.3 and 2.4–2.5 standard deviations in the two q2 regions, respectively.

Subfields: Nuclear and High Energy Physics

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Citations in the corpus

Detecting and studying high-energy collider neutrinos with FASER at the LHC (2019, result): “II, this possibility has been motivated by recent results from collider experiments, which provide tentative evidence of lepton universality violation in the decays B → D∗`ν [52–54], B → K∗`` [55], and B → K`` [56].”
Combined explanations of the b→sμ+μ− and b→cτ−ν¯ anomalies: A general model analysis (2018, unknown): “b → sμ+μ−: discrepancies with the SM can be found in several observables in B → K∗μ+μ− [1–5] and B0 s → φμ+μ− [6, 7] decays, as well as in the observation of lepton flavour universality (LFU) violation in RK ≡ B(B+ → K+μ+μ−)/B(B+ → K+e+e−) [8] and RK∗ ≡ B(B0 → K∗0μ+μ−)/B(B0 → K∗0e+e−) [9].”
New Physics in $${\varvec{b \rightarrow s \ell ^+ \ell ^-}}$$ confronts new data on lepton universality (2019, background): “Several hints in favour of LFUV have surfaced in the past few years in experimental searches at LHCb [41,42] and Belle [14].”
Baryon number and lepton universality violation in leptoquark and diquark models (2017, background): “Since many models for the recently discovered B meson decay anomalies [9, 10] rely on the existence of new scalar or vector leptoquarks, it is interesting to investigate which of the new particle explanations proposed in the literature do not trigger rapid proton decay.”
Maximal flavour violation: a Cabibbo mechanism for leptoquarks (2018, background): “The violations of LFU measured in the RK [5] and RK∗ [12] ratios (as well as Q4,5 = Pμ′ 4,5 − P e′ 4,5 [77]) fix the (non-universal) tree-level contribution.”
Patterns of New Physics in b → sℓ+ℓ− transitions in the light of recent data (2017, background): “On the other hand, the LHCb collaboration has recently updated the differential branching ratio for B → K∗μ+μ− [11], and it has presented striking new results concerning the LFUV ratio RK∗ = BB→K∗μ+μ− /BB→K∗e+e− at large K∗ recoil [24], exhibiting significant deviations from SM expectations.”
Physics beyond colliders at CERN: beyond the Standard Model working group report (2019, background): “A Zμ model gauging the Lμ−Lτ lepton number could also explain the hints of LFU violations in RK and RK∗ ratios observed by LHCb [61, 62].”
The leptoquark hunter’s guide: pair production (2017, background): “Recently, additional motivation for LQs arrived from a number of anomalies observed in B meson decays [2, 3] which could be explained in models with leptoquarks of TeV scale masses.”
Charged Lepton Flavour Violation: An Experimental and Theoretical Introduction (2017, background): “[211] R. Aaij et al. [LHCb Collaboration], “Angular analysis of the B0 → K∗0µ+µ− decay using 3 fb−1 of integrated luminosity,” JHEP 1602 (2016) 104 [arXiv:1512.04442 [hep-ex]].”