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). First observation of the B+ → Ds+ Ds- K+ decay. Phys. Rev. D, 108(3), 034012–14pp.
Abstract: B+ -> D-s(+) D-s(-) K+ decay is observed for the first time using proton-proton collision data collected by the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb-1. Its branching fraction relative to that of the B+ -> D-s(+) D-s(-) K+ decay is measured to be B(B+ -> D-s(+) D-s(-) K+)/(KB+ -> D-s(+) D-s(-) K+) = 0.525 +/- 0.0333 +/- 0.027 +/- 0.034; where the first uncertainty is statistical, the second s D-s Kthornthorn systematic, and the third is due to the uncertainties on the branching fractions of the D-s(+/-) -> (KK +/-)-K--/+pi(+/-) and D-+/- -> K--/+pi(+/-)pi(+/-) decays. This measurement fills an experimental gap in the knowledge of the family of Cabibbo-favored (b) over bar -> (b) over barc (c) over bar transitions and opens the path for unique studies of spectroscopy in future.
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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 Rare Decays of D0 Mesons into Two Muons. Phys. Rev. Lett., 131(4), 041804–13pp.
Abstract: A search for the very rare D-0 -> mu(+)mu(-) decay is performed using data collected by the LHCb experiment in proton-proton collisions at root s = 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb(-1). The search is optimized for D-0 mesons from D*(+) -> D-0 pi(+) decays but is also sensitive to D-0 mesons from other sources. No evidence for an excess of events over the expected background is observed. An upper limit on the branching fraction of this decay is set at B(D-0 -> mu(+)mu(-)) < 3.1 x 10(-9) at a 90% C.L. This represents the world's most stringent limit, constraining models of physics beyond the standard model.
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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). Test of lepton flavor universality using B0 → D*- τ+ ντ decays with hadronic τ channels. Phys. Rev. D, 108(1), 012018–18pp.
Abstract: The branching fraction B(B-0 -> D*(-)tau(+)nu(tau)) is measured relative to that of the normalization mode B-0 -> D*(-) pi(+)pi(-)pi(+) using hadronic tau(+) -> pi(+)pi(-)pi(+) (pi(0))(nu) over bar (tau) decays in proton-proton collision data at a center-of-mass energy of 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb(-1). The measured ratio is B(B-0 -> D*(-)tau(+)nu(tau))/B(B-0 -> D*(-) pi(+)pi(-)pi(+)) = 1.70 +/- 0.10(-0.10)(+0.11), where the first uncertainty is statistical and the second is related to systematic effects. Using established branching fractions for the B-0 -> D*(-) pi(+)pi(-)pi(+) and B-0 -> D*(-)mu(+)nu(mu) modes, the lepton universality test R(D*(-)) = B(B-0 -> D*(-)tau(+)nu(tau))/B(B-0 -> D*(-)mu(+)nu(mu)) is calculated, R(D*(-)) = 0.247 +/- 0.015 +/- 0.015 +/- 0.012, where the third uncertainty is due to the uncertainties on the external branching fractions. This result is consistent with the Standard Model prediction and with previous measurements.
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