The resonance parameters of the excited psi-family resonances, namely the psi(4040), psi(4160), and psi(4415), were determined by fitting the R-values measured by experiments. It is found that the previously reported leptonic partial widths of these states were merely one possible solutions among a four-fold ambiguity. By fitting the most precise experimental data on the R-values measured by the BES collaboration, this work presents all four sets of solutions. These results may affect the interpretation of the charmonium and charmonium-like states above 4GeV/c^2.
A comparison of the rates for psi(2S) -> pi^+ pi^- J/psi, J/psi -> l^+l^- and J/psi -> anything is used to determine the J/psi leptonic branching fractions. The results are B(J/psi -> e^+e^-) = (5.90 +/- 0.05 +/- 0.10)% and B(J/psi -> mu^+ mu^-) = (5.84 +/- 0.06 +/- 0.10)%, where the first error is statistical and the second is systematic. Assuming lepton universality, the leptonic branching fraction of the J/psi is B(J/psi -> l^+ l^-) = (5.87 +/- 0.04 +/- 0.09)% per species. This result is used to estimate the QCD scale factor Lambda_MSbar and the strong coupling constant alpha_s.
Taking advantage of large top production rates at the LHC, the leptonic final states with J/psi are explored for a precise determination of the top quark mass. The top is partially reconstructed by combining the isolated lepton from the W with the J/psi from the decays of the corresponding b-quark. The method relies, to a large extent, on the proper Monte-Carlo description of top production and decay. The main emphasis is put on the expected systematics uncertainties. Mass measurement accuracy is dominated by the current understanding of theoretical uncertainties which result in a systematic e…
In this note we present a study of the radiative tails in the invariant mass spectra of muon or electron pairs from J/psi, psi(2S) and Upsilon(1S) decays which is due to an additional emission of a photon. An analytic formula for dilepton mass spectra in radiative decays is derived and a Monte Carlo simulation for realistic detector conditions is used to study effects on the spectra. A rather simple parameterisation is given, suitable for the treatment of real data.
The latest data for J/psi and psi' leptonic decays, and the latest measurement of the R-parameter are used to show that the present summary values of the branching ratios of the virtual photon mediated hadronic decays of both J/psi and psi' are overestimated. The current best results are B(J/psi -> gamma^{*} -> h) = (13.3 +- 0.3)%, and B(psi' -> gamma^{*} -> h) = (1.65 +- 0.10)%.
We report a new precise determination of the leptonic widths of the J/psi meson performed with the KEDR detector at the VEPP-4M $e^{+}e^{-}$ collider. The measured values of the J/psi parameters are: Γ_{ee}\timesΓ_{ee}/Γ= 0.3323 \pm 0.0064 (stat.) \pm 0.0048 (syst.) keV Γ_{ee}\timesΓ_{μμ}/Γ=0.3318 \pm 0.0052 (stat.) \pm 0.0063 (syst.) keV. Assuming $eμ$ universality and using the table value of the branching ratios the leptonic Γ_{ll}= 5.59 \pm 0.12 keV width and the total Γ=94.1 \pm 2.7 keV widths were obtained. We also discuss in detail a method to calculate radiative corrections at a narrow…
Based on 14 million psi(2S) and 58 million J/psi events collected by the BESII detector, the leptonic decay of psi(2S) into $τ^+τ^-$, psi(2S) multi-body decays, chi_cJ decays, and J/psi hadronic decays are studied, and the branching fractions of these decays are reported. These results may shed light on the understanding of QCD.
We measure the branching fractions of the psi(2S) meson to the leptonic final states e+e- and mu+mu- relative to that for psi(2S)-->J/psi pi+pi-. The method uses psi(2S) mesons produced in the decay of B mesons at the Upsilon(4S) resonance in a data sample collected with the BABAR detector at the Stanford Linear Accelerator Center. Using previous measurements for the psi(2S)-->J/psi pi+pi- branching fraction, we determine the e+e- and mu+mu- branching fractions to be 0.0078+/-0.0009+/-0.0008 and 0.0067+/-0.0008+/-0.0007 respectively.
In this talk, we present the recent results on charmonium decays from the BES experiment at the BEPC collider. The analyses are based on a 14 million psi(2S) events data sample. We report results on leptonic decays, hadronic decays, and radiative decays of psi(2S), as well as hadronic decays of chi_cJ states and rare or forbidden decays of J/psi.
The branching fraction of the psi(2S) decay into tau pair has been measured for the first time using the BES detector at the Beijing Electron-Positron Collider. The result is $B_{ττ}=(2.71\pm 0.43 \pm 0.55) \times 10^{-3}$, where the first error is statistical and the second is systematic. This value, along with those for the branching fractions into e+e- and mu+mu of this resonance, satisfy well the relation predicted by the sequential lepton hypothesis. Combining all these values with the leptonic width of the resonance the total width of the psi(2S) is determined to be $(252 \pm 37)$ keV.
Open heavy flavour and J/psi production are powerful tools to test pQCD calculations in proton-proton collisions in the new LHC energy regime. In addition, they provide the necessary reference for the ALICE heavy-ion program. The ALICE experiment at the LHC collected proton-proton collisions at sqrt{s} = 7 and 2.76 TeV in 2010 and 2011. We report here the latest results of open heavy flavour and J/psi production at both mid- and forward-rapidity via their various hadronic and leptonic decay channels. These include, among other topics, the first LHC result on J/psi polarization, multiplicity de…
Over sixty million J/psi events have been collected by the BES Collaboration at the Beijing Electron-Positron Collider (BEPC). J/psi decays provide an excellent place for studying excited nucleons and hyperons -- N*, $Λ^*$, $Σ^*$ and $Ξ^*$ resonances, as well as meson resonances, including possible glueballs and hybrids. Physics objectives, recent results and future prospects of light hadron spectroscopy at BEPC are presented.
In this work we investigate the photoproduction of radially excited vector mesons off nuclei in heavy ion relativistic collisions. In particular, we analyze the exclusive photoproduction of psi(2S) off nuclei, evaluating the coherent and the incoherent contributions to that process. The theoretical framework used in the present analysis is the light-cone dipole formalism and predictions are done for PbPb collisions at the CERN-LHC energy of 2.76 TeV. The theoretical uncertainties are analyzed and comparison is also done to the recent ALICE Collaboration data for the psi(1S) state photoproducti…
We revisit earlier calculations of leptonic decay constants of vector charmonia and present and illustrate our decomposition of the corresponding covariant Bethe-Salpeter amplitudes in terms of orbital angular momentum as interpreted in the meson's rest frame. Our results confirm our previous conclusions drawn from the magnitudes of vector-meson leptonic decay constants, identifying the Psi(3770) and Psi(4160) as D-wave states in our setup.
Using an improved "analytic K-matrix model", we reconsider the extraction of the sigma/f_0(600) and f_0(980) gamma-gamma widths from gamma-gamma to pi-pi scatterings data of Crystal Ball and Belle. Our main results are summarized in Tables 3 and 4. The averaged sigma "direct width" to gamma-gamma is 0.16(3) keV which confirms a previous result of [1] and which does neither favour a large four-quark (diquark-antidiquark) nor a molecule nor a pure \bar qq component. The "direct width" of the f_0(980) of 0.28(2) keV is much larger than the four-quark expectation but can be compatible with a \bar …
We report the initial results from CLEO-c based on the 55.8/pb data obtained at the psi(3770) resonance last year. We give a concise summary of the various CLEO-c analyses on leptonic and semileptonic decays of neutral and charged D mesons. The data used for this report is the first part of the psi(3770) data sets to be collected during next several years using the Cornell Electron Storage Ring. Most of the results shown here have already better or the same level of precision compared to the 2004 world averages compiled by the Particle Data Group.
We revisit the heavy quarkonium leptonic decays $ψ(nS) \to \ell^+\ell^-$ and $Υ(nS) \to \ell^+\ell^-$ using the Bethe-Salpeter method. The emphasis is on the relativistic correction. For the $ψ(1S-5S)$ decays, the relativistic effects are $22^{+3}_{-2}\%$, $34^{+5}_{-5}\%$, $41^{+6}_{-6}\%$, $52^{+11}_{-13}\%$ and $62^{+14}_{-12}\%$, respectively. For the $Υ(1S-5S)$ decays, the relativistic effects are $14^{+1}_{-2}\%$, $23^{+0}_{-3}\%$, $20^{+8}_{-2}\%$, $21^{+6}_{-7}\%$ and $28^{+2}_{-7}\%$, respectively. Thus, the relativistic corrections are large and important in heavy quarkonium leptonic…
Using a data sample of 17.7 $\rm pb^{-1}$ collected at 3.773 GeV with the BES-II detector at the BEPC, the cross sections for $D^0 \bar D^{0}$ and $D^+D^-$ productions at 3.773 GeV have been measured. From the data sample about 33 $\rm pb^{-1}$ taken around 3.773 GeV, 3 purely leptonic decay events of $D^+ \to μ^+ν$ are observed. The branching fraction and the decay constant are measured to be $BF(D^+ \to μ^+ν)=(0.120^{+0.092+0.010}_{-0.063-0.009}) %$ and $f_D=(365^{+121+32}_{-113-28})$ MeV. The semileptonic decay branching fractions for $D^0 \to K^-e^+ν$, $D^0 \to π^-e^+ν$ and $D^+ \to \bar K…
It is shown that two physical phenomena are important for high excitations: (i) the screening of the universal gluon-exchange potential and (ii) the flattening of the confining potential owing to creation of quark loops, and both effects are determined quantitatively. Taking the first effect into account, we predict the masses of the ground states with $l=0,1,2$ in agreement with experiment. The flattening effect ensures the observed linear behaviour of the radial Regge trajectories $M^2(n)=m_0^2 + n_r μ^2$ GeV$^2$, where the slope $μ^2$ is very sensitive to the parameter $γ$, which determines…
We report on charmonium measurements [J/psi(1S), psi'(2S), and chi_c(1P)] in p+p collisions at sqrt(s)=200 GeV. We find that the fraction of J/psi coming from the feed-down decay of psi' and chi_c in the midrapidity region ($|η|<0.35$) is 9.6+/-2.4% and 32+/-9%, respectively. We also report new, higher statistics p_T and rapidity dependencies of the J/psi yield via dielectron decay in the same midrapidity range and at forward rapidity (1.2<|eta|<2.4) via dimuon decay. These results are compared with measurements from other experiments and discussed in the context of current charmonium producti…
