Guy Wilkinson

Abstract:

A search for time-integrated CP violation in D0 → h-h+ (h = K, π) decays is presented using 0.62 fb-1 of data collected by LHCb in 2011. The flavor of the charm meson is determined by the charge of the slow pion in the D∗+ → D0π+ and D∗- → D¯0π- decay chains. The difference in CP asymmetry between D0 → K-K+ and D0 → π-π+, ΔACP ≈ ACP(K-K+)-ACP(π-π+), is measured to be [-0.82 ± 0.21(stat) ± 0.11(syst)]%. This differs from the hypothesis of CP conservation by 3.5 standard deviations. © 2012 CERN, for the LHCb Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.

Abstract:

We present a measurement of the time-dependent CP-violating asymmetry in Bs0→J/ψ decays, using data collected with the LHCb detector at the LHC. The decay time distribution of Bs0→J/ψ is characterized by the decay widths Γ H and Γ L of the heavy and light mass eigenstates, respectively, of the Bs0-B̄s0 system and by a CP-violating phase s. In a sample of about 8500 Bs0→J/ψevents isolated from 0.37fb -1 of pp collisions at √s=7TeV, we measure s=0.15±0.18(stat)±0.06(syst)rad. We also find an average Bs0 decay width Γ s (Γ L+Γ H)/2=0.657±0.009(stat)±0.008(syst)ps -1 and a decay width difference ΔΓ s Γ L- Γ H=0.123±0.029(stat)±0.011(syst)ps -1. Our measurement is insensitive to the transformation ( s, ΔΓ s) (π- s,-ΔΓ s). © 2012 CERN. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Abstract:

A search is performed for the lepton number violating decay B +→h -μ +μ +, where h - represents a K - or a π -, using an integrated luminosity of 36pb -1 of data collected with the LHCb detector. The decay is forbidden in the standard model but allowed in models with a Majorana neutrino. No signal is observed in either channel and limits of B(B +→K -μ +μ +)<5. 4×10 -8 and B(B +→π -μ +μ +)<5.8×10 -8 are set at the 95% confidence level. These improve the previous best limits by factors of 40 and 30, respectively. © 2012 CERN, for the LHCb Collaboration. Published by the American Physical Society under the terms of the http://creativecommons.org/licenses/by/3.0/. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.