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Register a new userMeasurement of the effective $B^0_srightarrow K^+K^-$ lifetime
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A measurement of the effective $B^0_srightarrow K^+K^-$ lifetime is presented using approximately $37 pb^{-1}$ of data collected by LHCb during 2010. This quantity can be used to put constraints on contributions from processes beyond the Standard Model in the $B^0_s$ meson system and is determined by two complementary approaches as $tau_{B^0_sto K^+K^-} = 1.440 pm 0.096 (stat) pm 0.008 (syst) pm 0.003 (model) ps$.
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A precise determination of the effective $B_s^0 rightarrow K^+ K^-$ lifetime can be used to constrain contributions from physics beyond the Standard Model in the $B_s^0$ meson system. Conventional approaches select $B$ meson decay products that are significantly displaced from the $B$ meson production vertex. As a consequence, $B$ mesons with low decay times are suppressed, introducing a bias to the decay time spectrum which must be corrected. This analysis uses a technique that explicitly avoids a lifetime bias by using a neural network based trigger and event selection. Using 1.0 fb$^{-1}$ of data recorded by the LHCb experiment, the effective $B_s^0 rightarrow K^+ K^-$ lifetime is measured as $1.455 pm 0.046 ; mathrm{(stat.)} pm 0.006 ; mathrm{(syst.)} , mathrm{ps}.$
A search for the decay $B^0_srightarrow J/psi K^{*0}$ with $K^{*0} rightarrow K^-pi^+$ is performed with 0.37 fb$^{-1}$ of $pp$ collisions at $sqrt{s}$ = 7 TeV collected by the LHCb experiment, finding a $Bs to Jpsi K^-pi^+$ peak of $114 pm 11$ signal events. The $K^-pi^+$ mass spectrum of the candidates in the $B^0_s$ peak is dominated by the $K^{*0}$ contribution. Subtracting the non-resonant $K^-pi^+$ component, the branching fraction of BsJpsiKst is $(4.4_{-0.4}^{+0.5} pm 0.8) times 10^{-5}$, where the first uncertainty is statistical and the second systematic. A fit to the angular distribution of the decay products yields the Kst polarization fractions $f_L = 0.50 pm 0.08 pm 0.02$ and $f_{||} = 0.19^{+0.10}_{-0.08} pm 0.02$.
Measurements of the effective lifetimes in the $B_{s}^{0} rightarrow K^{+}K^{-}$, $B^{0} rightarrow K^{+}pi^{-}$ and $B_{s}^{0} rightarrow pi^{+}K^{-}$ decays are presented using $1.0~mathrm{fb^{-1}}$ of $pp$ collision data collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The analysis uses a data-driven approach to correct for the decay time acceptance. The measured effective lifetimes are $tau_{B_{s}^{0} rightarrow K^{+}K^{-}}$ = $1.407~pm~0.016~pm~0.007~mathrm{ps}$, $tau_{B^{0} rightarrow K^{+}pi^{-}}$ = $1.524~pm~0.011~pm~0.004~mathrm{ps}$, $tau_{B_{s}^{0} rightarrow pi^{+}K^{-}}$ = $1.60~pm~0.06~pm~0.01~mathrm{ps}$. This is the most precise determination to date of the effective lifetime in the $B_{s}^{0} rightarrow K^{+}K^{-}$ decay and provides constraints on contributions from physics beyond the Standard Model to the $B_{s}^{0}$ mixing phase and the width difference $DeltaGamma_{s}$.
After having announced the statistically significant observation (5.6~$sigma$) of the new exotic $pi K$ atom, the DIRAC experiment at the CERN proton synchrotron presents the measurement of the corresponding atom lifetime, based on the full $pi K$ data sample: $tau = (5.5^{+5.0}_{-2.8}) cdot 10^{-15}s$. By means of a precise relation ($<1%$) between atom lifetime and scattering length, the following value for the S-wave isospin-odd $pi K$ scattering length $a_0^{-}~=~frac{1}{3}(a_{1/2}-a_{3/2})$ has been derived: $left|a_0^-right| = (0.072^{+0.031}_{-0.020}) M_{pi}^{-1}$.
We report a measurement of the $B^0$ and $B^+$ meson decays to the $D_s^-K^0_S pi^+$ and $D_s^- K^+K^+$ final states, respectively, using $657 times 10^{6} Boverline{B}$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. Using the $D_s^-to phipi^-$, $K^{*}(892)^0 K^-$ and $K^0_S K^-$ decay modes for the $D_s$ reconstruction, we measure the following branching fractions: ${cal B}(B^0to D_s^{-}K^0_Spi^+)=[0.47 pm 0.06 (mathrm {stat}) pm 0.05 (mathrm {syst})]times 10^{-4}$ and ${cal B}(B^+to D_s^-K^+K^+)= [0.93 pm 0.22 (mathrm {stat})pm 0.10 (mathrm {syst})]times 10^{-5}$. We find the ratio of the branching fraction of $B^+to D_s^-K^+K^+$ to that of the analogous Cabibbo favored $B^+to D_s^-K^+pi^+$ decay to be ${cal R}_{cal B} = 0.054 pm 0.013 ({rm stat}) pm 0.006 ({rm syst})$, which is consistent with the na{i}ve factorization model. We also observe a deviation from the three-body phase-space model for both studied decays.
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