6 results found
Aaij R, Beteta CA, Adeva B, et al., 2019, Search for Lepton-universality violation in B+ -> K(+)l(+)l(-) decays, Physical Review Letters, Vol: 122, Pages: 191801-1-191801-13, ISSN: 0031-9007
A measurement of the ratio of branching fractions of the decays B+→K+μ+μ− and B+→K+e+e− is presented. The proton-proton collision data used correspond to an integrated luminosity of 5.0 fb−1 recorded with the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. For the dilepton mass-squared range 1.1<q2<6.0 GeV2/c4 the ratio of branching fractions is measured to be RK=0.846+0.060−0.054+0.016−0.014, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of RK to date and is compatible with the standard model at the level of 2.5 standard deviations.
Aaij R, Adeva B, Adinolfi M, et al., 2018, Measurement of the ratio of the B-0 -> D*(-)iota(+)v(iota) and B-0 -> D*(-) mu(+)v(mu) branching fractions using three-prong tau-Lepton decays, Physical Review Letters, Vol: 120, ISSN: 0031-9007
The ratio of branching fractions R(D*−)≡B(B0→D*−τ+ντ)/B(B0→D*−μ+νμ) is measured using a data sample of proton-proton collisions collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. For the first time, R(D*−) is determined using the τ-lepton decays with three charged pions in the final state. The B0→D*−τ+ντ yield is normalized to that of the B0→D*−π+π−π+ mode, providing a measurement of B(B0→D*−τ+ντ)/B(B0→D*−π+π−π+)=1.97±0.13±0.18, where the first uncertainty is statistical and the second systematic. The value of B(B0→D*−τ+ντ)=(1.42±0.094±0.129±0.054)% is obtained, where the third uncertainty is due to the limited knowledge of the branching fraction of the normalization mode. Using the well-measured branching fraction of the B0→D*−μ+νμ decay, a value of R(D*−)=0.291±0.019±0.026±0.013 is established, where the third uncertainty is due to the limited knowledge of the branching fractions of the normalization and B0→D*−μ+νμ modes. This measurement is in agreement with the standard model prediction and with previous results.
Aaij R, Adeva B, Adinolfi M, et al., 2018, Measurement of the Ratio of Branching Fractions B(B-c(+) -> J/psi tau(+)nu(tau))/B(B-c(+) -> J/psi mu(+)nu(mu)), PHYSICAL REVIEW LETTERS, Vol: 120, ISSN: 0031-9007
A measurement is reported of the ratio of branching fractions R(J/ψ)=B(B+c→J/ψτ+ντ)/B(B+c→J/ψμ+νμ), where the τ+ lepton is identified in the decay mode τ+→μ+νμ¯ντ. This analysis uses a sample of proton-proton collision data corresponding to 3.0 fb−1 of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay B+c→J/ψτ+ντ at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be R(J/ψ)=0.71±0.17(stat)±0.18(syst). This result lies within 2 standard deviations above the range of central values currently predicted by the standard model.
Aaij R, Adeva B, Adinolfi M, et al., 2016, Measurements of the S-wave fraction in B-0 -> K+ pi(-) mu(+) mu(-) decays and the B-0 -> K*(892)(0) mu(+) mu(-) differential branching fraction, The Journal of High Energy Physics, Vol: 2016, ISSN: 1029-8479
A measurement of the differential branching fraction of the decay B0 → K∗(892)0μ+μ− is presented together with a determination of the S-wave fraction of the K+π− system in the decay B0 → K+π−μ+μ−. The analysis is based on pp-collision data corresponding to an integrated luminosity of 3 fb−1 collected with the LHCb experiment. The measurements are made in bins of the invariant mass squared of the dimuon system, q2. Precise theoretical predictions for the differential branching fraction of B0 → K∗(892)0μ+μ− decays are available for the q2 region 1.1 < q2< 6.0 GeV2/c4. In this q2 region, for the K+π− invariant mass range 796 < mKπ< 996 MeV/c2, the S-wave fraction of the K+π− system in B0 → K+π−μ+μ− decays is found to beFS=0.101±0.017(stat)±0.009(syst),FS=0.101±0.017(stat)±0.009(syst),and the differential branching fraction of B0 → K∗(892)0μ+μ− decays is determined to bedB/dq2=(0.392+0.020−0.019(stat)±0.010(syst)±0.027(norm))×10−7c4/GeV2.dB/dq2=(0.392−0.019+0.020(stat)±0.010(syst)±0.027(norm))×10−7c4/GeV2.The differential branching fraction measurements presented are the most precise to date and are found to be in agreement with Standard Model predictions.
Aaij R, Beteta CA, Adeva B, et al., 2016, Angular analysis of the B 0 → K *0 μ + μ − decay using 3 fb−1 of integrated luminosity, Journal of High Energy Physics, Vol: 2016, ISSN: 1126-6708
An angular analysis of the B 0 → K *0(→ K + π −)μ + μ − decay is presented. The dataset corresponds to an integrated luminosity of 3.0 fb−1 of pp collision data collected at the LHCb experiment. The complete angular information from the decay is used to determine CP-averaged observables and CP asymmetries, taking account of possible contamination from decays with the K + π − system in an S-wave configuration. The angular observables and their correlations are reported in bins of q 2, the invariant mass squared of the dimuon system. The observables are determined both from an unbinned maximum likelihood fit and by using the principal moments of the angular distribution. In addition, by fitting for q 2-dependent decay amplitudes in the region 1.1 < q 2 < 6.0 GeV2/c 4, the zero-crossing points of several angular observables are computed. A global fit is performed to the complete set of CP-averaged observables obtained from the maximum likelihood fit. This fit indicates differences with predictions based on the Standard Model at the level of 3.4 standard deviations. These differences could be explained by contributions from physics beyond the Standard Model, or by an unexpectedly large hadronic effect that is not accounted for in the Standard Model predictions.
Aaij R, Adeva B, Adinolfi M, et al., 2015, First measurement of the differential branching fraction and CP asymmetry of the B ± → π ± μ + μ − decay, Journal of High Energy Physics, Vol: 2015, ISSN: 1126-6708
The differential branching fraction with respect to the dimuon invariant mass squared, and the CP asymmetry of the B ± → π ± μ + μ − decay are measured for the first time. The CKM matrix elements |V td | and |V ts |, and the ratio |V td /V ts | are determined. The analysis is performed using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb−1, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The total branching fraction and CP asymmetry of B ± → π ± μ + μ − decays are measured to beB(B±→π±μ+μ−)=(1.83±0.24±0.05)×10−8andACP(B±→π±μ+μ−)=−0.11±0.12±0.01,B(B±→π±μ+μ−)=(1.83±0.24±0.05)×10−8andACP(B±→π±μ+μ−)=−0.11±0.12±0.01,where the first uncertainties are statistical and the second are systematic. These are the most precise measurements of these observables to date, and they are compatible with the predictions of the Standard Model.
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