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The CP-violating asymmetry a_{sl}^s is studied using semileptonic decays of Bs and anti-Bs mesons produced in pp collisions at a centre-of-mass energy of 7 TeV at the LHC, exploiting a data sample corresponding to an integrated luminosity of 1.0/fb. The reconstructed final states are Ds^(+/-)mu ^(-/+), with the Ds^(+/-) particle decaying in the phipi^(+/-) mode. The Ds^(+/-)mu ^{-/+) yields are summed over Bs and anti-Bs initial states, and integrated with respect to decay time. Data-driven methods are used to measure efficiency ratios. We obtain $a_{sl}^s$ = (-0.06 +/- 0.50 +/- 0.36)%, where the first uncertainty is statistical and the second systematic.
Measurements of $b$ hadron production ratios in proton-proton collisions at a centre-of-mass energy of 7 TeV with an integrated luminosity of 3 pb$^{-1}$ are presented. We study the ratios of strange $B$ meson to light $B$ meson production $f_s/(f_u+ f_d)$ and $Lambda_b^0$ baryon to light $B$ meson production $f_{Lambda_b}/(f_u+f_d)$ as a function of the charmed hadron-muon pair transverse momentum $p_T$ and the $b$ hadron pseudorapidity $eta$, for $p_T$ between 0 and 14 GeV and $eta$ between 2 and 5. We find that $f_s/(f_u+f_d)$ is consistent with being independent of $p_{rm T}$ and $eta$, and we determine $f_s/(f_u+f_d)$ = 0.134$pm$ 0.004 $^{+0.011}_{-0.010}$, where the first error is statistical and the second systematic. The corresponding ratio $f_{Lambda_b}/(f_u+f_d)$ is found to be dependent upon the transverse momentum of the charmed hadron-muon pair, $f_{Lambda_b}/(f_u+f_d)=(0.404pm 0.017 (stat) pm 0.027 (syst) pm 0.105 (Br))times[1 -(0.031 pm 0.004 (stat) pm 0.003 (syst))times p_T(GeV)]$, where Br reflects an absolute scale uncertainty due to the poorly known branching fraction Br(Lambda_c^+ to pK^-pi^+)$. We extract the ratio of strange $B$ meson to light neutral $B$ meson production $f_s/f_d$ by averaging the result reported here with two previous measurements derived from the relative abundances of $bar{B}_s to D_S^+ pi ^-$ to $bar{B}^0 to D^+K^-$ and $bar{B}^0 to D^+pi^-$. We obtain $f_s/f_d=0.267^{+0.021}_{-0.020}$.
93 - Marina Artuso 2009
LHC will offer the opportunity of probing the mass scale of the electro-weak symmetry breaking. Thus we expect to uncover direct manifestations of physics beyond the Standard Model, which will raise new questions that may be elucidated by precision m easurements of beauty and charm decays. The LHCb experiment is poised to pursue this ambitious program as soon as LHC turns on. An upgrade to enhance its physics sensitivity by at least one order of magnitude is critical to the completion of this study, as new physics effects may be subtle. A new vertex detector is a crucial element of this project. Important requirements are a radiation resistance up to a fluence of about 10$^{16} n_{eq} {rm cm}^{-2}$, and a front end electronics capable of delivering its event information to the back end receiver boards synchronously with the beam interactions, at 40 MHz.
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