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Register a new userInclusive charged and neutral particle multiplicity distributions in $chi_{cJ}$ and $J/psi$ decays
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Using a sample of 106 million $psi(3686)$ decays, $psi(3686) to gamma chi_{cJ} (J = 0, 1, 2)$ and $psi(3686) to gamma chi_{cJ}, chi_{cJ} to gamma J/psi$ $(J = 1, 2)$ events are utilized to study inclusive $chi_{cJ} to$ anything, $chi_{cJ} to$ hadrons, and $J/psi to$ anything distributions, including distributions of the number of charged tracks, electromagnetic calorimeter showers, and $pi^0$s, and to compare them with distributions obtained from the BESIII Monte Carlo simulation. Information from each Monte Carlo simulated decay event is used to construct matrices connecting the detected distributions to the input predetection produced distributions. Assuming these matrices also apply to data, they are used to predict the analogous produced distributions of the decay events. Using these, the charged particle multiplicities are compared with results from MARK I. Further, comparison of the distributions of the number of photons in data with those in Monte Carlo simulation indicates that G-parity conservation should be taken into consideration in the simulation.
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Using $4.479 times 10^{8}$ $psi(3686)$ events collected with the BESIII detector, we search for the decays $psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2}$ and $chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi$. The decays $psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2}$ and $chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi$ are observed for the first time. The measured branching fractions are $mathcal{B}(psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2}) = (11.7 pm 2.5 pm 1.0)times10^{-4}$, $(8.6 pm 0.3 pm 0.6)times10^{-4}$, $(6.9 pm 0.5 pm 0.6)times10^{-4}$, and $mathcal{B}(chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi) = (1.51 pm 0.30 pm 0.13)times10^{-4}$, $(3.73 pm 0.09 pm 0.25)times10^{-3}$, $(2.48 pm 0.08 pm 0.16)times10^{-3}$. The ratios of the branching fractions $frac{mathcal{B}(psi(3686) rightarrow e^{+}e^{-}chi_{c0,1,2})}{mathcal{B}(psi(3686) rightarrow gammachi_{c0,1,2})}$ and $frac{mathcal{B}(chi_{c0,1,2} rightarrow e^{+}e^{-}J/psi)}{mathcal{B}(chi_{c0,1,2} rightarrow gamma J/psi)}$ are also reported.
Using $4.48 times 10^{8}$ $psi(3686)$ events collected with the BESIII detector, we search for the decays $chi_{cJ} rightarrow mu^{+}mu^{-}J/psi$ through the radiative decays $psi(3686) rightarrow gammachi_{cJ}$, where $J=0,1,2$. The decays $chi_{c1,2} rightarrow mu^{+}mu^{-}J/psi$ are observed, and the corresponding branching fractions are measured to be $mathcal{B}(chi_{c1} rightarrow mu^{+}mu^{-}J/psi) = (2.51 pm 0.18 pm 0.20)times10^{-4}$ and $mathcal{B}(chi_{c2} rightarrow mu^{+}mu^{-}J/psi) = (2.33 pm 0.18 pm 0.29)times10^{-4}$, where the first uncertainty is statistical and the second one systematic. No significant $chi_{c0} rightarrow mu^{+}mu^{-}J/psi$ decay is observed, and the upper limit on the branching fraction is determined to be $2.0times10^{-5}$ at 90% confidence level. Also, we present a study of di-muon invariant mass dependent transition form factor for the decays $chi_{c1,2} rightarrow mu^{+}mu^{-}J/psi$.
We compute fragmentation corrections to hadroproduction of the quarkonium states $J/psi$, $chi_{cJ}$, and $psi(2S)$ at leading power in $m_c^2/p_T^2$, where $m_c$ is the charm-quark mass and $p_T$ is the quarkonium transverse momentum. The computation is carried out in the framework of nonrelativistic QCD. We include corrections to the parton-production cross sections through next-to-leading order in the strong coupling $alpha_s$ and corrections to the fragmentation functions through second order in $alpha_s$. We also sum leading logarithms of $p_T^2/m_c^2$ to all orders in perturbation theory. We find that, when we combine these leading-power fragmentation corrections with fixed-order calculations through next-to-leading order in $alpha_s$, we are able to obtain good fits for $p_Tgeq 10$ GeV to hadroproduction cross sections that were measured at the Tevatron and the LHC. Using values for the nonperturbative long-distance matrix elements that we extract from the cross-section fits, we make predictions for the polarizations of the quarkonium states. We obtain good agreement with measurements of the polarizations, with the exception of the CDF Run II measurement of the prompt $J/psi$ polarization, for which the agreement is only fair. In the predictions for the prompt-$J/psi$ cross sections and polarizations, we take into account feeddown from the $chi_{cJ}$ and $psi(2S)$ states.
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.
At LHC energies, the charged-particle multiplicity dependence of particle production is a topic of considerable interest in $pp$ collisions. It has been argued that multiple partonic interactions play an important role in particle production mechanisms, not only affecting the soft processes but also the hard processes. Recently, ALICE has measured $J/psi$ production as a function of charged-particle multiplicity to study the correlation between soft and hard processes. In this contribution, we present the $J/psi$ production versus multiplicity for $pp$ and $p-Pb$ collisions measured by ALICE. We compare the results with different theoretical models.
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