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Register a new userMeasurement of B_s mixing phase at CDF
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Michal Kreps
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We present improved bounds on the CP-violating phase beta_s^{Jpsiphi} and on the decay-width difference DeltaGamma of the neutral B_s^0 meson system obtained by the CDF experiment at the Tevatron collider . We use 6500 B_s^0 --> J/psi phi decays collected by the dimuon trigger and reconstructed in a sample corresponding to integrated luminosity of 5.2 fb-1. Besides exploiting a two-fold increase in statistics with respect to the previous measurement, several improvements have been introduced in the analysis including a fully data-driven flavour-tagging calibration and proper treatment of possible S-wave contributions.
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The latest results for the measurement of the CP violating phase beta_s in B0s -> J/psi phi decays, from 5.2 fb-1 integrated luminosity of CDF data are presented. For the first time, this measurement includes the contribution of B0s -> J/psi K+K- or B0s -> J/psi f0 events to the signal sample, where the f0 and non-resonant K+K- are S-wave states. Additional improvements to the analysis include more than doubling the signal sample, improved selection and particle ID, and fully calibrated flavour tagging for the full dataset. Additionally, the worlds most precise single measurements of the B0s lifetime, tau_s, and width difference, DeltaGamma_s are given.
The $CP$ asymmetry in the mixing of $B_s^0$ and $overline{B}{}_s^0$ mesons is measured in proton-proton collision data corresponding to an integrated luminosity of 3.0 fb$^{-1}$, recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Semileptonic $B_s^0$ and $overline{B}{}_s^0$ decays are studied in the inclusive mode $D_s^{mp} mu^{pm} u_{mu} X$ with the $D_s^{mp}$ mesons reconstructed in the $K^+ K^- pi^{mp}$ final state. Correcting the observed charge asymmetry for detection and background effects, the $CP$ asymmetry is found to be $a_{text{sl}}^s = (0.39 pm 0.26 pm 0.20) % $, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of $a_{text{sl}}^s$ to date. It is consistent with the prediction from the Standard Model and will constrain new models of particle physics.
We present preliminary results on inclusive direct photon production in $pbar{p}$ collisions at $sqrt{s}$=1.96 TeV, using data collected with the upgraded Collider Detector at Fermilab in Run II, corresponding to an integrated luminosity of 451 pb$^{-1}$. Measurements are performed as a function of the photon transverse momentum for photons with $p_{T}>$30 GeV and $|eta|<$1.0. Photons are required to be isolated in the calorimeter. The measurement is corrected to the hadron level and compared to NLO pQCD predictions.
A time-dependent analysis of the $B_s^0 to phigamma$ decay rate is performed to determine the $CP$-violating observables $S_{phigamma}$ and $C_{phigamma}$, and the mixing-induced observable $mathcal{A}^{Delta}_{phigamma}$. The measurement is based on a sample of $pp$ collision data recorded with the LHCb detector, corresponding to an integrated luminosity of 3 fb$^{-1}$ at center-of-mass energies of 7 and 8 TeV. The measured values are begin{align*} S_{phigamma} &= 0.43 pm 0.30 pm 0.11, C_{phigamma} &= 0.11 pm 0.29 pm 0.11, mathcal{A}^{Delta}_{phigamma} &= -0.67 , ^{+0.37}_{-0.41} pm 0.17, end{align*} where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables $S$ and $C$ in radiative $B_s^0$ decays. The results are consistent with the Standard Model predictions.
We report the first direct measurement of the inclusive branching fraction ${mathcal B}(B_s rightarrow D_s X)$ via $B_s$ tagging in $e^+e^-toUpsilon$(5S) events. Tagging is accomplished through a partial reconstruction of semileptonic decays $B_s rightarrow D_s X ell u$, where $X$ denotes unreconstructed additional hadrons or photons and $ell$ is an electron or muon. With 121.4 fb$^{-1}$ of data collected at the $Upsilon$(5S) resonance by the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider, we obtain ${mathcal B}(B_s rightarrow D_s X)$ = $(61.6 pm 5.3 pm 2.1)$%, where the first uncertainty is statistical and the second is systematic.
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