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Register a new userDetermination of the number of $J/psi$ events with inclusive $J/psi$ decays
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A measurement of the number of $J/psi$ events collected with the BESIII detector in 2009 and 2012 is performed using inclusive decays of the $J/psi$ . The number of $J/psi$ events taken in 2009 is recalculated to be $(223.7pm1.4)times 10^6$, which is in good agreement with the previous measurement, but with significantly improved precision due to improvements in the BESIII software. The number of $J/psi$ events taken in 2012 is determined to be $(1086.9pm 6.0)times 10^6$. In total, the number of $J/psi$ events collected with the BESIII detector is measured to be $(1310.6pm 7.0)times 10^6$, where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.
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The products of the electron width of the J/psi meson and the branching fraction of its decays to the lepton pairs were measured using data from the KEDR experiment at the VEPP-4M electron-positron collider. The results are Gamma_{ee}(J/psi)*Br(J/psi->e^+e^-)=(0.3323pm0.0064pm0.0048) keV, Gamma_{ee}(J/psi)*Br(J/psi->mu^+mu^-)=(0.3318pm0.0052pm0.0063) keV. Their combinations Gamma_{ee}times(Gamma_{ee}+Gamma_{mumu})/Gamma=(0.6641pm0.0082pm0.0100) keV, Gamma_{ee}/Gamma_{mumu}=1.002pm0.021pm0.013 can be used to improve theaccuracy of the leptonic and full widths and test leptonic universality. Assuming emu universality and using the world average value of the lepton branching fraction, we also determine the leptonic Gamma_{ll}=5.59pm0.12 keV and total Gamma=94.1pm2.7 keV widths of the J/psi meson.
Observations of exotic structures in the $J/psi p$ channel, that we refer to as pentaquark-charmonium states, in $Lambda_b^0to J/psi K^- p$ decays are presented. The data sample corresponds to an integrated luminosity of 3/fb acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude analysis is performed on the three-body final-state that reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the $J/psi p$ mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of $4380pm 8pm 29$ MeV and a width of $205pm 18pm 86$ MeV, while the second is narrower, with a mass of $4449.8pm 1.7pm 2.5$ MeV and a width of $39pm 5pm 19$ MeV. The preferred $J^P$ assignments are of opposite parity, with one state having spin 3/2 and the other 5/2.
We report a measurement of the branching fraction of the decay $B^0_sto J/psi,phi(1020)$, evidence and a branching fraction measurement for $B^0_sto J/psi,f_2(1525)$, and the determination of the total $B^0_sto J/psi,K^+K^-$ branching fraction, including the resonant and non-resonant contributions to the $K^+K^-$ channel. We also determine the $S$-wave contribution within the $phi(1020)$ mass region. The absolute branching fractions are $mathcal{B}[B^0_sto J/psi,phi(1020)]=(1.25 pm 0.07left(mathrm{stat}right)pm 0.08left(mathrm{syst}right)pm 0.22left(f_sright))times 10^{-3}$, $mathcal{B}[B^0_sto J/psi,f_2(1525)]=(0.26pm 0.06left(mathrm{stat}right)pm 0.02left(mathrm{syst}right) pm 0.05left(f_sright))times 10^{-3}$ and $mathcal{B}[B^0_sto J/psi,K^+K^-] = (1.01pm 0.09left(mathrm{stat}right) pm 0.10left(mathrm{syst}right)pm 0.18left(f_sright))times 10^{-3}$, where the last systematic error is due to the branching fraction of $bbar{b}to B^{(*)}_s B^{(*)}_s$. The branching fraction ratio is found to be $mathcal{B}[B^0_sto J/psi,f_2(1525)]/mathcal{B}[B^0_sto J/psi,phi(1020)]=(21.5pm 4.9left(mathrm{stat}right) pm2.6left(mathrm{syst}right))%$. All results are based on a 121.4 fb$^{-1}$ data sample collected at the $Upsilon(5S)$ resonance by the Belle experiment at the KEKB asymmetric-energy $e^+e^-$ collider.
The data sample of $Lambda_b^0to J/psi p K^-$ decays acquired with the LHCb detector from 7 and 8~TeV $pp$ collisions, corresponding to an integrated luminosity of 3 fb$^{-1}$, is inspected for the presence of $J/psi p$ or $J/psi K^-$ contributions with minimal assumptions about $K^- p$ contributions. It is demonstrated at more than 9 standard deviations that $Lambda_b^0to J/psi p K^-$ decays cannot be described with $K^- p$ contributions alone, and that $J/psi p$ contributions play a dominant role in this incompatibility. These model-independent results support the previously obtained model-dependent evidence for $P_c^+to J/psi p$ charmonium-pentaquark states in the same data sample.
The numbers of $psi(3686)$ events accumulated by the BESIII detector for the two rounds of data taking during 2009 and 2012 are determined to be $(107.0pm0.8)times 10^6$ and $(341.1pm 2.1)times 10^6$, respectively, by counting inclusive hadronic events, where the uncertainty is dominated by systematics and the statistical uncertainty is negligible. The number of events for the sample taken in 2009 is consistent with that of the previous measurement. The total number of $psi(3686)$ events for the two data-taking periods is $(448.1pm2.9)times10^6$.
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