LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Search for decays of neutral beauty mesons into four muons. J. High Energy Phys., 03(3), 001–19pp.
Abstract: A search for the non-resonant decays B-s(0) -> mu(+) mu(-) mu(+)mu(-) and B-0 -> mu(+) mu(-) mu(+) mu(-) is presented. The measurement is performed using the full Run 1 data set collected in proton-proton collisions by the LHCb experiment at the LHC. The data correspond to integrated luminosities of 1 and 2 fb(-1) collected at centre-of-mass energies of 7 and 8 TeV, respectively. No signal is observed and upper limits on the branching fractions of the non-resonant decays at 95% confidence level are determined to be B(B-s(0) -> mu(+) mu(-) mu(+)mu(-)) < 2.5 x 10(-9) B(B-0 -> mu(+) mu(-) mu(+) mu(-)) < 6.9 x 10(-10)
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Search for the lepton-flavour violating decays B-0 -> K-*0 mu(+/-)e(-/+) and B-s(0)-> phi mu(+/-)e(-/+). J. High Energy Phys., 06(6), 073–25pp.
Abstract: A search for the lepton-flavour violating decays B-0 -> K-*0 μe(-/+) and B-s(0)-> mu(+/-)e(-/+) is presented, using proton-proton collision data collected by the LHCb detector at the LHC, corresponding to an integrated luminosity of 9 fb(-1). No significant signals are observed and upper limits of are set at 90% (95%) confidence level. These results constitute the world's most stringent limits to date, with the limit on the decay B-s(0) -> phi mu(+/-) e(-/+) the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2024). A search for rare B → D μ+ μ- decays. J. High Energy Phys., 02(2), 032–23pp.
Abstract: A search for rare B. D mu+ mu- decays is performed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb-1. No significant signals are observed in the non-resonant mu+ mu- modes, and upper limits of B -> B0. D0 mu+ mu- < 5.1 x 10-8, B B+. D+ s mu+ mu- -> < 3.2 x 10-8, B -> B0 s. D0 mu+ mu--> < 1.6 x 10-7 and fc/fu center dot B B+ c. D+ s mu+ mu--> < 9.6 x 10-8 are set at the 95% confidence level, where fc and fu are the fragmentation fractions of a B meson with a c and u quark respectively in proton-proton collisions. Each result is either the first such measurement or an improvement by three orders of magnitude on an existing limit. Separate upper limits are calculated when the muon pair originates from a J/.. mu+ mu- decay. The branching fraction of B+ c. D+ s J/. multiplied by the fragmentation-fraction ratio is measured to be fc fu center dot B -> B+ c. D+ s J/.-> = (1.63 +/- 0.15 +/- 0.13) x 10-5, where the first uncertainty is statistical and the second systematic.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., Oyanguren, A., et al. (2024). Amplitude analysis of the radiative decay Bs0 → K+K-γ. J. High Energy Phys., 08(8), 093–39pp.
Abstract: A search for radiative decay of B-s(0) mesons to orbitally excited K+K- states is performed using proton proton collisions recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb(-1). The dikaon spectrum in the mass range m(KK) < 2400 MeV/c(2) is dominated by the phi(1020) resonance that accounts for almost 70% of the decay rate. Considering the possible contributions of f(2)(1270), f(2)'(1525) and f(2)(2010) meson states, the overall tensor contribution to the amplitude is measured to be F-{f2} = 16.8 +/- 0.5 (stat.) +/- 0.7 (syst.)%, mostly dominated by the f2 '(1525) state. Several statistically equivalent solutions are obtained for the detailed resonant structure depending on whether the smaller amplitudes interfere destructively or constructively with the dominant amplitude. The preferred solution that corresponds to the lowest values of the fit fractions along with constructive interference leads to the relative branching ratio measurement B(B-s(0) -> f(2)'gamma)/B(B-s(0) -> phi gamma) = 19.4(-0.8)(+0.9)(stat.)(-0.5)(+1.4) (syst.) +/- 0.5(B)%, where the last uncertainty is due to the ratio of measured branching fractions to the K+K- final state. This result represents the first observation of the radiative B-s(0) -> f(2)'(1525)gamma decay, which is the second radiative transition observed in the B-s(0) sector.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., Oyanguren, A., et al. (2024). Search for the Bs0 → μ+ μ-γ decay. J. High Energy Phys., 07(7), 101–27pp.
Abstract: A search for the fully reconstructed B-s(0)-> mu(+)mu(-)gamma decay is performed at the LHCb experiment using proton-proton collisions at root s = 13 TeV corresponding to an integrated luminosity of 5.4 fb(-1). No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set B(B-s(0)-> mu(+)mu(-)gamma) < 4.2 x 10(-8), m(mu(+)mu(-)) is an element of[2m(mu),1.70] GeV/c(2), B(B-s(0) -> mu(+)mu(-)gamma) < 7.7 x 10(-8), m(mu(+)mu(-)) is an element of [1.70, 2.88] GeV/c(2), B(B-s(0) -> mu(+)mu(-)gamma) < 4.2 x 10(-8), m(mu(+)mu(-) ) is an element of[3.92, m(Bs0)]GeV/c(2), at 95% confidence level. Additionally, upper limits are set on the branching fraction in the [2m(mu), 1.70] GeV/c(2) dimuon mass region excluding the contribution from the intermediate phi(1020) meson, and in the region combining all dimuon-mass intervals.
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