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Register a new userMeasurement of Y(5S) decays to B^0 and B^+ mesons
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A. Drutskoy
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Decays of the Y(5S) resonance to channels with B^+ and B^0 mesons are studied using a 23.6 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy e^+ e^- collider. Fully reconstructed B^+ -> J/psi K^+, B^0 -> J/psi K^{*0}, B^+ -> bar{D}^0 pi^+ and B^0 -> D^- pi^+ decays are used to obtain the charged and neutral B production rates per bbar{b} event, f(B^+) = (72.1 ^{+3.9}_{-3.8} pm 5.0)% and f(B^0) = (77.0 ^{+5.8}_{-5.6} pm 6.1)%. Assuming equal rates to B^+ and B^0 mesons in all channels produced at the Y(5S) energy, we measure the fractions for transitions to two-body and three-body channels with B meson pairs, f(Bbar{B}) = (5.5 ^{+1.0}_{-0.9} pm 0.4)%, f(Bbar{B}^* + B^*bar{B}) = (13.7 pm 1.3 pm 1.1)%, f(B^*bar{B}^*) = (37.5 ^{+2.1}_{-1.9} pm 3.0)%, f(Bbar{B}pi) = (0.0 pm 1.2 pm 0.3)%, f(Bbar{B}^*pi + B^*bar{B}pi) = (7.3 ^{+2.3}_{-2.1} pm 0.8)%, and f(B^*bar{B}^*pi) = (1.0 ^{+1.4}_{-1.3} pm 0.4)%. The latter three fractions are obtained assuming isospin conservation.
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Decays of the Y(5S) resonance to channels with B^+ and B^0 mesons are studied using a 23.6 fb^-1 data sample collected on the Y(5S) resonance with the Belle detector at the KEKB asymmetric energy e^+ e^- collider. The fully reconstructed B^+ -> J/psi K^+, B^0 -> J/psi K^{*0}, B^+ -> bar_D^0 pi^+ and B^0 -> D^- pi^+ decays are used to obtain the B^+ and B^0 production rates per bb_bar event, f(B^+) = (67.5 pm 3.6 pm 4.8)% and f(B^0)=(70.4^{+5.2}_{-5.1} pm 6.2)%$. Assuming equal rates to B^+ and B^0 mesons in all channels produced at the Y(5S) energy, we measure the fractions for bb_bar event transitions to the two-body and multi-body channels with B^{+/0} meson pairs, f(Bbar{B}) = (5.1 pm 0.9 pm 0.4)%, f(Bbar{B}^*+B^*bar{B}) = (12.6^{+1.2}_{-1.1} pm 1.0)%, f(B^*bar{B}^*) = (34.5^{+1.9}_{-1.8} pm 2.7)%, f(B^{(*)}bar{B}^{(*)}pi(pi)) = (16.4^{+1.6}_{-1.5} pm 1.2)%, f(Bbar{B} pi) = (0.0 pm 1.1 pm 0.2)%, f(Bbar{B}^*pi+B^*bar{B}pi) = (6.8^{+2.1}_{-2.0} pm 0.7)%, and f(B^*bar{B}^*pi) = (1.0^{+1.3}_{-1.2} pm 0.3)%.
The $B^0$--$bar B^0$ oscillation frequency $Delta m_d$ is measured by the LHCb experiment using a dataset corresponding to an integrated luminosity of $1.0,$fb$^{-1}$ of proton-proton collisions at $sqrt{s} = 7,$TeV, and is found to be $Delta m_d = 0.5156 pm 0.0051,($stat.$) pm 0.0033,($syst.$),$ps$^{-1}$. The measurement is based on results from analyses of the decays $B^0 to D^- pi^+$ ($D^- to K^+ pi^- pi^-$) and $B^0 to J/ psi K^{*0}$ ($ J/ psi to mu^+ mu^-$, $K^{*0} to K^+ pi^-$) and their charge conjugated modes.
The $CP$ asymmetry in $B^-to D_s^-D^0$ and $B^-to D^-D^0$ decays is measured using LHCb data corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV. The results are $A^{CP}(B^-to D_s^-D^0)=(-0.4pm 0.5pm 0.5)%$ and $A^{CP}(B^-to D^-D^0)=( 2.3pm 2.7pm 0.4)%$, where the first uncertainties are statistical and the second systematic. This is the first measurement of $A^{CP}(B^-to D_s^-D^0)$ and the most precise determination of $A^{CP}(B^-to D^-D^0)$. Neither result shows evidence of $CP$ violation.
The decay of the narrow resonance $overline{B}{}_{s2}^{*0}!rightarrow B^- K^+$ can be used to determine the $B^-$ momentum in partially reconstructed decays without any assumptions on the decay products of the $B^-$ meson. This technique is employed for the first time to distinguish contributions from $D^0$, $D^{*0}$, and higher-mass charmed states ($D^{**0}$) in semileptonic $B^-$ decays by using the missing-mass distribution. The measurement is performed using a data sample corresponding to an integrated luminosity of 3.0 fb${}^{-1}$ collected with the LHCb detector in $pp$ collisions at center-of-mass energies of 7 and 8 TeV. The resulting branching fractions relative to the inclusive $B^- !rightarrow D^0 X mu^- overline{ u}_mu$ are $f_{D^0} = mathcal{B}( B^- rightarrow D^0mu^-overline{ u}_mu )/mathcal{B}( B^- rightarrow D^0 X mu^- overline{ u}_mu ) = 0.25 pm 0.06$, $f_{D^{**0}} = mathcal{B}( B^- rightarrow ( D^{**0} rightarrow D^0 X)mu^-overline{ u}_mu )/mathcal{B}( B^- rightarrow D^0 X mu^- overline{ u}_mu ) = 0.21 pm 0.07$, with $f_{D^{*0}} = 1 - f_{D^0} - f_{D^{**0}}$ making up the remainder.
We report measurements of CP violation parameters in $B^0 to K^0 pi^0$ decays based on a data sample of $657 times 10^6 Bbar{B}$ pairs collected with the Belle detector at the KEKB $e^+ e^-$ asymmetric-energy collider. We use $B^0 to K^0_S pi^0$ decays for both mixing-induced and direct $CP$ violating asymmetry measurements and $B^0 to K^0_L pi^0$ decays for the direct CP violation measurement. The CP violation parameters obtained are $sin 2 phi_1^{rm eff} = +0.67 pm 0.31{(stat)} pm 0.08 {(syst)}$ and $mathcal{A}_{K^0 pi^0} = +0.14 pm 0.13{(stat)} pm 0.06 {(syst)}$. The branching fraction of $B^0 to K^0 pi^0$ decay is measured to be $mathcal{B}(B^0 to K^0 pi^0) = (8.7pm0.5 (rm{stat.})pm0.6 (rm{syst.}))times 10^{-6}$. The observed $mathcal{A}_{K^0 pi^0}$ value differs by 1.9 standard deviations from the value expected from an isospin sum rule.
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