Abstract:

The decay $B_c^+ \to \psi(2S)\pi^+$ with $\psi(2S) \to \mu^+\mu^-$ is observed with a significance of $5.2\,\sigma$ using $pp$ collision data corresponding to an integrated luminosity of $1.0\,\invfb$ collected by the LHCb experiment. The branching fraction of $B_c^+ \to \psi(2S)\pi^+$ decays relative to that of the $B_c^+ \to J/\psi\pi^+$ mode is measured to be \begin{equation*} \frac{\mathcal{B}(B_c^+ \to \psi(2S)\pi^+)}{\mathcal{B}(B_c^+ \to J/\psi\pi^+)} = 0.250 \pm 0.068 \,\text{stat} \pm 0.014 \,\text{\syst} \pm 0.006 \,(\mathcal{B}). \end{equation*} The last term is the uncertainty on the ratio $\mathcal{B}(\psi(2S) \to \mu^+\mu^-)/\mathcal{B}(J/\psi \to \mu^+\mu^-)$.

Abstract:

We report a measurement of the time-dependent ratio of D0→K +π- to D0→K-π+ decay rates in D*+-tagged events using 1.0 fb-1 of integrated luminosity recorded by the LHCb experiment. We measure the mixing parameters x′2=(-0.9±1.3)×10-4, y′=(7.2±2.4)×10-3, and the ratio of doubly-Cabibbo-suppressed to Cabibbo-favored decay rates RD=(3. 52±0.15)×10-3, where the uncertainties include statistical and systematic sources. The result excludes the no-mixing hypothesis with a probability corresponding to 9.1 standard deviations and represents the first observation of D0-D̄0 oscillations from a single measurement. © 2013 CERN.

Abstract:

\noindent A search for the decays $B^0_{s}\rightarrow \mu^+ \mu^- \mu^+ \mu^-$ and $B^0 \rightarrow \mu^+ \mu^- \mu^+ \mu^-$ is performed using data, corresponding to an integrated luminosity of 1.0\ensuremath{\{\,fb}^{-1}}\xspace, collected with the LHCb detector in 2011. The number of candidates observed is consistent with the expected background and, assuming phase-space models of the decays, limits on the branching fractions are set: \{${\ensuremath{\cal B}\xspace}(B^0_{s}\rightarrow \mu^+ \mu^- \mu^+ \mu^-) < 1.6 \ (1.2) \times 10^{-8}$} and \{${\ensuremath{\cal B}\xspace}(B^0 \rightarrow \mu^+ \mu^- \mu^+ \mu^-)< 6.6 \ (5.3) \times 10^{-9}$} at 95\,% (90\,%) confidence level. In addition, limits are set in the context of a supersymmetric model which allows for the $B^0_{(s)}$ meson to decay into a scalar ($S$) and pseudoscalar particle ($P$), where $S$ and $P$ have masses of 2.5 GeV and 214.3 MeV, respectively, both resonances decay into $\mu^+\mu^-$. The branching fraction limits for these decays are \{${\ensuremath{\cal B}\xspace}(\ensuremath{B^0_{s}\rightarrow SP}\xspace) < 1.6 \ (1.2) \times 10^{-8}$} and \{${\ensuremath{\cal B}\xspace}(\ensuremath{B^0\rightarrow SP}\xspace)< 6.3 \ (5.1) \times 10^{-9}$} at 95% (90%) confidence level.

Abstract:

Interpretation of CP violation measurements using charmonium decays, in both the B̄0 and B̄s0 systems, can be subject to changes due to "penguin" type diagrams. These effects can be investigated using measurements of the Cabibbo-suppressed B̄0→J/ ψπ+π- decays. The final state composition of this channel is investigated using a 1.0 fb-1 sample of data produced in 7 TeV pp collisions at the LHC and collected by the LHCb experiment. A modified Dalitz-plot analysis is performed using both the invariant mass spectra and the decay angular distributions. An improved measurement of the B ̄0→J/ψπ+π- branching fraction of (3.97±0.09±0.11±0.16)×10-5 is reported where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty of the branching fraction of the decay B-→J/ψK- used as a normalization channel. Significant production of f0(500) and ρ(770) resonances is found in the substructure of the J/ψπ+π- final state, and this indicates that they are viable final states for CP violation studies. In contrast evidence for the f0(980) resonance is not found. This allows us to establish the first upper limit on the branching fraction product B(B̄0→J/ψf0(980))×B(f 0(980)→π+π-)<1.1×10 -6, leading to an upper limit on the absolute value of the mixing angle of the f0(980) with the f0(500) of less than 31, both at 90% confidence level. © 2013 CERN, for the LHCb Collaboration. Published by the American Physical Society under the terms of the http://creativecommons.org/licenses/by/3.0/ 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:

The B0-B̄0 oscillation frequency δmd is measured by the LHCb experiment using a dataset corresponding to an integrated luminosity of 1.0fb-1 of proton-proton collisions at √s=7TeV, and is found to be δmd=0.5156±0.0051(stat.)±0.0033(syst.)ps-1. The measurement is based on results from analyses of the decays B0→D-π+ (D-→K+π-π-) and B0→J/ψK*0 (J/ψ→μ+μ-, K*0→K+π-) and their charge conjugated modes. © 2013 CERN.