LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Amplitude analysis of the B0 (s)! K0K0 decays and measurement of the branching fraction of the B0! K0K0 decay. J. High Energy Phys., 07(7), 032–31pp.
Abstract: The B0 K0K0 and B0 s K0K0 decays are studied using proton-proton collision data corresponding to an integrated luminosity of 3 fb. An untagged and timeintegrated amplitude analysis of B0 (s) (K+)(K) decays in two-body invariant mass regions of 150MeV/c2 around the K0 mass is performed. A stronger longitudinal polarisation fraction in the B0 K0K0 decay, fL = 0 : 724 0 : 051 (stat) 0 : 016 (syst), is observed as compared to fL = 0 : 240 0 : 031 (stat) 0 : 025 (syst) in the B0 s K0K0 decay. The ratio of branching fractions of the two decays is measured and used to determine B (B0 K0K0) = (8 : 0 0 : 9 (stat) 0 : 4 (syst)) x 10(-7).
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2020). Search for Rare or Forbidden Decays of the D-0 Meson. Phys. Rev. Lett., 124(7), 071802–8pp.
Abstract: We present a search for nine lepton-number-violating and three lepton-flavor-violating neutral charm decays of the type D-0 -> h'(-) h(-) l'(+) l(+) and D-0 -> h'(-) h(+) l'(+/-) l(-/+), where h and h' represent a K or pi meson and l and l' an electron or muon. The analysis is based on 468 fb(-1) of e(+) e(-) annihilation data collected at or close to the Upsilon(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. No significant signal is observed for any of the twelve modes, and we establish 90% confidence level upper limits on the branching fractions in the range (1.0-30.6) x 10(-7). The limits are between 1 and 3 orders of magnitude more stringent than previous measurements.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Measurement of |V-cb| with B-s(0) -> D-s(()*()-) mu(+)nu(mu) decays. Phys. Rev. D, 101(7), 072004–25pp.
Abstract: The element vertical bar V-cb vertical bar of the Cabibbo-Kobayashi-Maskawa matrix is measured using semileptonic B-s(0) decays produced in proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1). Rates of B-s0 -> D-s(-) mu(+)nu(mu) and B-s0 -> D-s*(-) mu(+)nu(mu) decays are analyzed using hadronic form-factor parametrizations derived either by Caprini, Lellouch and Neubert (CLN) or by Boyd, Grinstein and Lebed (BGL). The measured values of vertical bar V-cb vertical bar are (41.4 +/- 0.6 +/- 0.9 +/- 1.2) x 10(-3) and (42.3 +/- 0.8 +/- 0.9 +/- 1.2) x 10(-3) in the CLN and BGL parametrization, respectively. The first uncertainty is statistical, the second systematic, and the third is due to the external inputs used in the measurement. These results are in agreement with those obtained from decays of B+ and B-0 mesons. They are the first determinations of vertical bar V-cb vertical bar at a hadron-collider experiment and the first using B-s(0) meson decays.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Precision measurement of the B-c(+) meson mass. J. High Energy Phys., 07(7), 123–21pp.
Abstract: A precision measurement of the B-c(+) meson mass is performed using proton- proton collision data collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to a total integrated luminosity of 9.0 fb(-1). The B-c(+) mesons are reconstructed via the decays B-c(+)-> J/psi pi(+), B-c(+)-> J/psi pi(+)pi(-)pi(+), B-c(+)-> J/psi pp<overbar>pi(+), B-c(+)-> J/psi D-s(+), B-c(+)-> J/psi (DK+)-K-0 and B-c(+)-> B-s(0)pi(+). Combining the results of the individual decay channels, the B-c(+) mass is measured to be 6274.47 +/- 0.27 (stat) +/- 0.17 (syst) MeV/c(2). This is the most precise measurement of the B-c(+) mass to date. The difference between the B-c(+) and B-s(0) meson masses is measured to be 907.75 +/- 0.37 (stat) +/- 0.27 (syst) MeV/c(2).
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). First branching fraction measurement of the suppressed decay Xi(0)(c) -> pi(-) Lambda(+)(c). Phys. Rev. D, 102(7), 071101–11pp.
Abstract: The Xi(0)(c) baryon is unstable and usually decays into charmless final states by the c -> sud transition. It can, however, also disintegrate into a pi(-) meson and a Lambda(+)(c) baryon via s quark decay or via cs -> dc weak scattering. The interplay between the latter two processes governs the size of the branching fraction B(Xi(0)(c) -> pi(-) Lambda(+)(c)), first measured here to be (0.55 +/- 0.02 +/- 0.18)%, where the first uncertainty is statistical and second systematic. This result is compatible with the larger of the theoretical predictions that connect models of hyperon decays using partially conserved axial currents and SU(3) symmetry with those involving the heavy-quark expansion and heavy-quark symmetry. In addition, the branching fraction of the normalization channel, B(Xi(+)(c) -> pK(-) pi(+)) = (1.135 +/- 0.002 +/- 0.387)% is measured.
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