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Register a new userMeasurement of CP Violation in $mathrm{B}^{0}_{mathrm{s}} ! to mathrm{J} / psi,phi$ decays with the CMS detector
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Jacopo Pazzini
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The CP-violating weak phase $phi_mathrm{s}$ and the decay width difference $DeltaGamma_{mathrm{s}}$ of $mathrm{B}^{0}_{mathrm{s}}$ mesons are measured by the CMS experiment at the LHC using a data sample of $mathrm{B}^{0}_{mathrm{s}} ! to mathrm{J} / psi,phi$ decays. The analysed dataset corresponds to an integrated luminosity of about $20~mathrm{fb}^{-1}$ collected in $pp$ collisions at a centre-of-mass energy $sqrt{s} = 8~mathrm{TeV}$. A total of $49,000$ reconstructed $mathrm{B}^{0}_{mathrm{s}}$ decays are used to extract the values $phi_mathrm{s}$ and $DeltaGamma_mathrm{s}$ by performing a time-dependent and flavour-tagged angular analysis of the $mu^+mu^-mathrm{K}^+mathrm{K}^-$ final state.The weak phase is measured to be $phi_mathrm{s} = -0.03 pm 0.11~mathrm{(stat.)} pm 0.03~mathrm{(syst.)}~mathrm{rad}$, and the decay width difference between the $mathrm{B}^{0}_{mathrm{s}}$ mass eigenstates is $DeltaGamma_mathrm{s} = 0.096 pm 0.014~mathrm{(stat.)} pm 0.007~mathrm{(syst.)}~mathrm{ps}^{-1}$.
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Measurements are presented of the $CP$ violation observables $S$ and $C$ in the decays of $B^0$ and $overline{B}{}^0$ mesons to the $J/psi K^0_S$ final state. The data sample corresponds to an integrated luminosity of $3.0,text{fb}^{-1}$ collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of $7$ and $8,text{TeV}$. The analysis of the time evolution of $41500$ $B^0$ and $overline{B}{}^0$ decays yields $S = 0.731 pm 0.035 , text{(stat)} pm 0.020 ,text{(syst)}$ and $C = -0.038 pm 0.032 , text{(stat)} pm 0.005,text{(syst)}$. In the Standard Model, $S$ equals $sin(2beta)$ to a good level of precision. The values are consistent with the current world averages and with the Standard Model expectations.
The time-dependent $CP$ asymmetries of $B^0to pi^+pi^-$ and $B^0_mathrm{s}!to K^+K^-$ decays are measured using a data sample of $pp$ collisions corresponding to an integrated luminosity of 1.9 fb$^{-1}$, collected with the LHCb detector at a centre-of-mass energy of 13 TeV. The results are begin{eqnarray*} C_{pipi} & = & -0.311 pm 0.045 pm 0.015, S_{pipi} & = & -0.706 pm 0.042 pm 0.013, C_{KK} & = & phantom{-}0.164 pm 0.034 pm 0.014, S_{KK} & = & phantom{-}0.123 pm 0.034 pm 0.015, cal {A}^{mathrm{DeltaGamma}}_{mathit{KK}} & = & -0.83phantom{0} pm 0.05phantom{0} pm 0.09, end{eqnarray*} where the first uncertainties are statistical and the second systematic. The same data sample is used to measure the time-integrated $CP$ asymmetries of $B^0to K^+pi^-$ and $B^0_mathrm{s}to K^-pi^+$ decays and the results are begin{eqnarray*} A_{CP}^{B^0} & = & -0.0824 pm 0.0033 pm 0.0033, A_{CP}^{B^0_mathrm{s}} & = & phantom{-}0.236phantom{0} pm 0.013phantom{0} pm 0.011. end{eqnarray*} All results are consistent with earlier measurements. A combination of LHCb measurements provides the first observation of time-dependent $CP$ violation in $B^0_mathrm{s}$ decays.
A search for previously unobserved decays of beauty baryons to the final states $K^0_{mathrm{S}}ppi^-$ and $K^0_{mathrm{S}}pK^-$ is reported. The analysis is based on a data sample corresponding to an integrated luminosity of $1.0,mathrm{fb}^{-1}$ of $pp$ collisions. The $Lambda^0_b rightarrow K^0_{mathrm{S}}ppi^-$ decay is observed for the first time with a significance of $8.6,sigma$, and a measurement is made of the $CP$ asymmetry, which is consistent with zero. No significant signals are seen for $Lambda^0_b rightarrow K^0_{mathrm{S}}pK^-$ decays, $Xi^0_b$ decays to both $K^0_{mathrm{S}}ppi^-$ and $K^0_{mathrm{S}}pK^-$ final states, and the $Lambda^0_b rightarrow D^-_s (K^0_{mathrm{S}}K^-)p$ decay, and upper limits on their branching fractions are reported.
A measurement of the decay time dependent CP-violating asymmetry in $B_s^0 to phiphi$ decays is presented, along with measurements of the $T$-odd triple-product asymmetries. In this decay channel, the CP-violating weak phase arises from the interference between $B_s^0$-$bar{B}_s^0$ mixing and the loop-induced decay amplitude. Using a sample of proton-proton collision data corresponding to an integrated luminosity of $3.0, fb^{-1}$ collected with the LHCb detector, a signal yield of approximately 4000 $B_s^0 to phiphi$ decays is obtained. The CP-violating phase is measured to be ${phi_s =-0.17pm0.15mathrm{,(stat)}pm0.03mathrm{,(syst)}}$ rad. The triple-product asymmetries are measured to be ${A_U=-0.003pm0.017mathrm{,(stat)}pm0.006mathrm{,(syst)}}$ and ${A_V=-0.017pm0.017mathrm{,(stat)}pm0.006mathrm{,(syst)}}$. Results are consistent with the hypothesis of CP conservation.
The time-dependent $CP$ asymmetry in $B_s^0 to J/psi K^+K^-$ decays is measured using $pp$ collision data, corresponding to an integrated luminosity of $3.0$fb$^{-1}$, collected with the LHCb detector at centre-of-mass energies of $7$ and $8$TeV. In a sample of 96 000 $B_s^0 to J/psi K^+K^-$ decays, the $CP$-violating phase $phi_s$ is measured, as well as the decay widths $Gamma_{L}$ and $Gamma_{H}$ of the light and heavy mass eigenstates of the $B_s^0-bar{B}_s^0$ system. The values obtained are $phi_s = -0.058 pm 0.049 pm 0.006$ rad, $Gamma_s equiv (Gamma_{L}+Gamma_{H})/2 = 0.6603 pm 0.0027 pm 0.0015$ps$^{-1}$, and$DeltaGamma_s equiv Gamma_{L} - Gamma_{H} = 0.0805 pm 0.0091 pm 0.0032$ps$^{-1}$, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of those quantities to date. A combined analysis with $B_s^{0} to J/psi pi^+pi^-$ decays gives $phi_s = -0.010 pm 0.039 $rad. All measurements are in agreement with the Standard Model predictions. For the first time the phase $phi_s$ is measured independently for each polarisation state of the $K^+K^- $ system and shows no evidence for polarisation dependence.
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