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Register a new userMeasurement of $B^0 to J/psi eta^{(}{}{}^{)}$ and Constraint on the $eta-eta$ Mixing Angle
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We measure the branching fractions of $B^{0} to J/psi eta^{(}{}{}^{)}$ decays with the complete Belle data sample of $772 times 10^{6}$ $Bbar{B}$ events collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The results for the branching fractions are: ${cal B}(B^{0} to J/psi eta)=(12.3 pm ^{1.8}_{1.7} pm 0.7) times 10^{-6}$ and ${cal B}(B^{0} to J/psieta) < 7.4 times 10^{-6}$ at 90% confidence level. The $eta-eta$ mixing angle is constrained to be less than $ 42.2^{circ}$ at 90% confidence level.
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A study of $B^0$~and $B^0_s$ meson decays into $J/psieta$~and $J/psieta^{prime}$ final states is performed using a data set of proton-proton collisions at centre-of-mass energies of 7 and 8TeV, collected by the LHCb experiment and corresponding to 3.0fb$^{-1}$ of integrated luminosity. The decay $B^0 rightarrow J/psi eta^{prime}$ is observed for thefirst time. The following ratios of branching fractions are measured: $$ frac{mathcal{B}(B^0 rightarrow J/psi eta^{prime})}{mathcal{B}(B^0_s rightarrow J/psi eta^{prime})} = (2.28pm0.65,(stat),pm0.10,(syst),pm0.13,(f_{s}/f_{d}))times10^{-2},$$ $$ frac{mathcal{B}(B^0 rightarrow J/psi eta)}{mathcal{B}(B^0_s rightarrow J/psi eta)} = (1.85pm0.61,(stat),pm0.09,(syst),pm0.11,(f_{s}/f_{d}))times10^{-2},$$ where the third uncertainty is related to the present knowledge of $f_{s}/f_{d}$, the ratio between the probabilities for a $b$ quark to form a $B^0_s$ or $B^0$ meson. The branching fraction ratios are used to determine the parameters of $eta-eta^{prime}$ meson mixing. In addition, the first evidence for the decay $B^0_s rightarrow psi(2S) eta^{prime}$ is reported, and the relative branching fraction is measured, $$frac{mathcal{B}(B^0_s rightarrow psi(2S) eta^{prime})}{mathcal{B}(B^0_s rightarrow J/psi eta^{prime})} = (38.7pm9.0,(stat),pm1.3,(syst),pm0.9(mathcal{B}))times10^{-2},$$ where the third uncertainty is due to the limited knowledge of the branching fractions of $J/psi$ and $psi(2S)$~mesons.
We measure the mass of the eta meson using psi(2S) --> eta J/psi events acquired with the CLEO-c detector operating at the CESR e+e- collider. Using the four decay modes eta --> gamma gamma, 3pi0, pi+pi-pi0, and pi+pi-gamma, we find M(eta)=547.785 +- 0.017 +- 0.057 MeV, in which the first uncertainty is statistical and the second systematic. This result has an uncertainty comparable to the two most precise previous measurements and is consistent with that of NA48, but is inconsistent at the level of 6.5sigma with the much smaller mass obtained by GEM.
Based on a sample of $2.25times 10^{8}$ $J/psi$ events collected with the BESIII detector at BEPCII, a full partial wave analysis on $J/psitogammaetaeta$ was performed using the relativistic covariant tensor amplitude method. The results show that the dominant $0^{++}$ and $2^{++}$ components are from the $f_0(1710)$, $f_0(2100)$, $f_0(1500)$, $f_2(1525)$, $f_2(1810)$ and $f_2(2340)$. The resonance parameters and branching fractions are also presented.
Using a data set corresponding to an integrated luminosity of $3 fb^{-1}$, collected by the LHCb experiment in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV, the effective lifetime in the $B^0_s rightarrow J/psi eta$ decay mode, $tau_{textrm{eff}}$, is measured to be $tau_{textrm{eff}} = 1.479 pm 0.034~textrm{(stat)} pm 0.011 ~textrm{(syst)}$ ps. Assuming $CP$ conservation, $tau_{textrm{eff}}$ corresponds to the lifetime of the light $B_s^0$ mass eigenstate. This is the first measurement of the effective lifetime in this decay mode.
We report a search for $B^{0}to eta eta $ with a data sample corresponding to an integrated luminosity of $698 ,{rm fb}^{-1}$ containing $753 times 10^{6}$ $Bbar{B}$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. The branching fraction is measured to be $mathcal{B}(B^{0} to eta eta ) = (7.6^{+2.7 +1.4}_{-2.3 -1.6}) times 10^{-7}$ at the level of 3.3 standard deviations above zero, which provides the first evidence for the decay $B^{0} to eta eta$.
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