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Register a new userMeasurement of angular and CP asymmetries in $D^0topi^+pi^-mu^+mu^-$ and $D^0to K^+K^-mu^+mu^-$ decays
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The first measurements of the forward-backward asymmetry of the dimuon pair ($A_{FB}$), the triple-product asymmetry ($A_{2phi}$), and the charge-parity-conjugation asymmetry ($A_{CP}$), in $D^0topi^+pi^-mu^+mu^-$ and $D^0to K^+K^-mu^+mu^-$ decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5 fb$^{-1}$. The asymmetries are measured to be begin{align*} A_{FB}(D^0topi^+pi^-mu^+mu^-) &= (phantom{-}3.3pm3.7pm0.6)%, A_{2phi}(D^0topi^+pi^-mu^+mu^-)&= (-0.6pm3.7pm0.6)%, A_{CP}(D^0topi^+pi^-mu^+mu^-) &= (phantom{-}4.9pm3.8pm0.7)%, A_{FB}(D^0to K^+K^-mu^+mu^-) &= (0pm11pm2)%, A_{2phi}(D^0to K^+K^-mu^+mu^-)&= (9pm11pm1)%, A_{CP}(D^0to K^+K^-mu^+mu^-) &= (0pm11pm2)%, end{align*} where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent with the Standard Model predictions.
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The first observation of the $D^0 to pi^+pi^-mu^+mu^-$ and $D^0 to K^+K^-mu^+mu^-$ decays is reported using a sample of proton-proton collisions collected by LHCb at a center-of-mass energy of 8$,$TeV, and corresponding to 2$,$fb$^{-1}$ of integrated luminosity. The corresponding branching fractions are measured using as normalization the decay $D^0 to K^- pi^+[mu^+mu^-]_{rho^0/omega}$, where the two muons are consistent with coming from the decay of a $rho^0$ or $omega$ meson. The results are $mathcal{B}(D^0 to pi^+pi^-mu^+mu^-)=(9.64pm0.48pm0.51pm0.97)times10^{-7}$ and $mathcal{B}(D^0 to K^+K^-mu^+mu^-)=( 1.54pm0.27pm0.09pm0.16)times10^{-7}$, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalization branching fraction. The dependence of the branching fraction on the dimuon mass is also investigated.
A study of indirect CP violation in $D^0$ mesons through the determination of the parameter $A_Gamma$ is presented using a data sample of $pp$ collisions, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected with the LHCb detector and recorded at the centre-of-mass energy of 7 TeV at the LHC. The parameter $A_Gamma$ is the asymmetry of the effective lifetimes measured in decays of $D^0$ and $bar{D}^0$ mesons to the CP eigenstates $K^-K^+$ and $pi^-pi^+$. Fits to the data sample yield $A_Gamma(KK)=(-0.35pm0.62pm0.12)times 10^{-3}$ and $A_Gamma(pipi)=(0.33pm1.06pm0.14)times 10^{-3}$, where the first uncertainties are statistical and the second systematic. The results represent the worlds best measurements of these quantities. They show no difference in $A_Gamma$ between the two final states and no indication of CP violation.
A search for non-resonant D+(s) to pi+mu+mu- and D+(s) to pi-mu+mu+ decays is performed using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb-1, at sqrt(s) = 7 TeV recorded by the LHCb experiment in 2011. No signals are observed and the 90% (95%) confidence level (CL) limits on the branching fractions are B(D+ to pi+mu+mu-) < 7.3 (8.3) x 10-8, B(Ds+ to pi+mu+mu-) < 4.1 (4.8) x 10-7, B(D+ to pi-mu+mu+) < 2.2 (2.5) x 10-8, B(Ds+ to pi-mu+mu+) < 1.2 (1.4) x 10-7. These limits are the most stringent to date.
The direct $C!P$ asymmetries of the decays $B^0 rightarrow K^{*0} mu^+ mu^-$ and $B^+ rightarrow K^{+} mu^+ mu^-$ are measured using $pp$ collision data corresponding to an integrated luminosity of 3.0$mbox{fb}^{-1}$ collected with the LHCb detector. The respective control modes $B^0 rightarrow J/psi K^{*0}$ and $B^+ rightarrow J/psi K^{+}$ are used to account for detection and production asymmetries. The measurements are made in several intervals of $mu^+ mu^-$ invariant mass squared, with the $phi(1020)$ and charmonium resonance regions excluded. Under the hypothesis of zero $C!P$ asymmetry in the control modes, the average values of the asymmetries are begin{align} {cal A}_{C!P}(B^0 rightarrow K^{*0} mu^+ mu^-) &= -0.035 pm 0.024 pm 0.003, cr {cal A}_{C!P}(B^+ rightarrow K^{+} mu^+ mu^-) &= phantom{-}0.012 pm 0.017 pm 0.001, end{align} where the first uncertainties are statistical and the second are due to systematic effects. Both measurements are consistent with the Standard Model prediction of small $C!P$ asymmetry in these decays.
First observations of the rare decays $B^+rightarrow K^+pi^+pi^-mu^+mu^-$ and $B^+rightarrow phi K^+mu^+mu^-$ are presented using data corresponding to an integrated luminosity of $3.0,{fb}^{-1}$, collected by the LHCb experiment at centre-of-mass energies of $7$ and $8mathrm{,TeV}$. The branching fractions of the decays are begin{eqnarray*} mathcal{B}(B^+rightarrow K^+pi^+pi^-mu^+mu^-) &=& (4.36,^{+0.29}_{-0.27},mathrm{(stat)}pm 0.21,mathrm{(syst)}pm0.18,mathrm{(norm)})times10^{-7}, mathcal{B}(B^+rightarrowphi K^+mu^+mu^-) &=& (0.82 ,^{+0.19}_{-0.17},mathrm{(stat)},^{+0.10}_{-0.04},mathrm{(syst)}pm0.27,mathrm{(norm)}) times10^{-7},end{eqnarray*} where the uncertainties are statistical, systematic, and due to the uncertainty on the branching fractions of the normalisation modes. A measurement of the differential branching fraction in bins of the invariant mass squared of the dimuon system is also presented for the decay $B^+rightarrow K^+pi^+pi^-mu^{+}mu^{-}$.
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