Publications (172) View all
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Article: Search for the rare decay $D^0 \to \mu^+ \mu^-$
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ABSTRACT: A search for the rare decay $D^0 \to \mu^+ \mu^-$is performed using a data sample, corresponding to an integrated luminosity of 0.9 fb$^{-1}$, of $pp$ collisions collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The observed number of events is consistent with the background expectations and corresponds to an upper limit of \mbox{${\cal B}(D^0 \to \mu^+ \mu^-) < 6.2(7.6) \times 10^{-9}$} at \mbox{90%} \mbox{(95%)} confidence level. This result represents an improvement of more than a factor twenty with respect to previous measurements.05/2013; -
Article: Differential branching fraction and angular analysis of the decay $B_s^0\to\phi\mu^{+}\mu^{-}$
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ABSTRACT: The determination of the differential branching fraction and the first angular analysis of the decay $B_s^0\to\phi\mu^{+}\mu^{-}$ are presented using data, corresponding to an integrated luminosity of $1.0\,{\rm fb}^{-1}$, collected by the LHCb experiment at $\sqrt{s}=7\,{\rm TeV}$. The differential branching fraction is determined in bins of $q^{2}$, the invariant dimuon mass squared. Integration over the full $q^{2}$ range yields a total branching fraction of ${\cal B}(B_s^0\to\phi\mu^{+}\mu^{-}) = (7.07\,^{+0.64}_{-0.59}\pm 0.17 \pm 0.71)\times 10^{-7}$, where the first uncertainty is statistical, the second systematic, and the third originates from the branching fraction of the normalisation channel. An angular analysis is performed to determine the angular observables $F_{\rm L}$, $S_3$, $A_6$, and $A_9$. The observables are consistent with Standard Model expectations.05/2013; -
Article: Measurement of the CKM angle \gamma\ from a combination of B->Dh analyses
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ABSTRACT: A combination of three LHCb measurements of the CKM angle \gamma\ is presented. The decays B->DK and B->D\pi\ are used, where D denotes an admixture of D0 and D0-bar mesons, decaying into KK, \pi\pi, K\pi, K\pi\pi\pi, KS\pi\pi, or KSKK final states. Combining results from B->DK decays alone a best-fit value of \gamma=70.5 deg is found, and confidence intervals are set \gamma\ in [54.9, 85.4] deg at 68% CL, \gamma\ in [41.8, 98.1] deg at 95% CL. The best-fit value of \gamma\ found from a combination of results from B->D\pi\ decays alone, is \gamma=97.1 deg, and the confidence intervals \gamma\ in [8.8, 43.8] deg or [79.3, 137.4] deg or [165.8, 177.1] deg at 68% CL are set, without constraint at 95% CL. The combination of results from B->DK and B->D\pi\ decays gives a best-fit value of \gamma=86.0 deg and the confidence intervals \gamma\ in [49.0, 72.5] deg or [79.1, 94.2] deg at 68% CL, \gamma\ in [35.2, 105.6] deg at 95% CL are set. All values are expressed modulo 180 deg.05/2013; -
Article: Precision measurement of D meson mass differences
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ABSTRACT: Using three- and four-body decays of $D$ mesons produced in semileptonic $b$-hadron decays, precision measurements of $D$ meson mass differences are made together with a measurement of the $D^{0}$ mass. The measurements are based on a dataset corresponding to an integrated luminosity of $1.0 fb^{-1}$ collected in $pp$ collisions at 7\,TeV. Using the decay $D^0 \rightarrow K^{+} K^{-} K^{-} \pi^{+}$, the $D^0$ mass is measured to be $M(D^0) &=& 1864.75 \pm 0.15 \,({\rm stat}) \pm 0.11 \,({\rm syst}) \, \textrm{MeV/c^2}$. The mass differences $M(D^{+}) - M(D^{0}) = 4.76 \pm 0.12 \,({\rm stat}) \pm 0.07 \,({\rm syst}) \, \textrm{MeV/c^2}$ and $M(D^{+}_s) - M(D^{+}) = 98.68 \pm 0.03 \,({\rm stat}) \pm 0.04 \,({\rm syst}) \, \textrm{MeV/c^2}$ are measured using the $D^0 \rightarrow K^{+} K^{-} \pi^{+} \pi^{-}$ and $D^{+}_{(s)} \rightarrow K^{+}K^{-} \pi^{+}$ modes.04/2013; -
Article: Production of J/psi and Upsilon mesons in pp collisions at sqrt(s) = 8 TeV
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ABSTRACT: The production of J/psi and Upsilon mesons in pp collisions at sqrt(s) = 8 TeV is studied with the LHCb detector. The J/psi and Upsilon mesons are reconstructed in the mu+mu- decay mode and the signal yields are determined with a fit to the mu+mu- invariant mass distributions. The analysis is performed in the rapidity range 2.0<y<4.5 and transverse momentum range 0<p_T<14(15) GeV/c of the J/psi(Upsilon) mesons. The J/psi and Upsilon production cross-sections and the fraction of J/psi mesons from b-hadron decays are measured as a function of the meson p_T and y.04/2013;
