Measurement of differences between J/psi and psi(') suppression in p-A collisions

Measurements of the suppression of the yield per nucleon of J/psi and psi(') production for 800 GeV/ c protons incident on heavy nuclear targets, relative to light nuclear targets, have been made with very broad coverage in x(F) and p(T). The observed suppression is smallest at x(F) values of 0.25 and below, and increases at larger values of x(F). It is also strongest at small p(T). Substantial differences between psi(') and J/psi production are observed for the first time in p-A collisions. The suppression for psi(') production is stronger than that for J/psi for x(F) near zero, but becomes comparable to that for J/psi for x(F)>0.6.     

Measurement of J/psi and psi(2S) polarization in pp collisions at sqrt[s] = 1.8 TeV

We have measured the polarization of J/psi and psi(2S) mesons produced in pp collisions at sqrt[s] = 1.8 TeV, using data collected at the Collider Detector at Fermilab during 1992-1995. The polarization of promptly produced J/psi [psi(2S)] mesons is isolated from those produced in B-hadron decay, and measured over the kinematic range 4 [5.5]相似文献   

Production of prompt charmonia in e(+)e(-) annihilation at square root of s approximately equals 0.6 GeV

The production of prompt J/psi, psi(2S), chi(c1), and chi(c2) is studied using a 32.4 fb(-1) data sample collected with the Belle detector at Upsilon(4S) and at 60 MeV below the resonance. The yield of prompt J/psi mesons in the Upsilon(4S) sample is compatible with that of continuum production; we set an upper limit B(Upsilon(4S)-->J/psiX) < 1.9 x 10(-4) at the 95% confidence level, and find sigma(e(+)e(-)-->J/psiX) = 1.47 plus/minus 0.10 plus/minus 0.13 pb. The cross sections for prompt psi(2S) and direct J/psi are measured. The J/psi momentum spectrum, production angle distribution, and polarization are studied.     

Next-to-leading-order QCD corrections to J/psi polarization at Tevatron and Large-Hadron-Collider energies

We calculate the next-to-leading-order QCD corrections to J/psi polarization at the Fermilab Tevatron and CERN Large Hadron Collider. Our results show that the J/psi polarization status drastically changes from transverse-polarization dominant at leading order to longitudinal-polarization dominant at next-to-leading order. Although the theoretical evaluation predicts a larger longitudinal polarization than the value measured at the Tevatron, it may provide a solution towards the previous large discrepancy for J/psi polarization between theoretical predication and experimental measurement.     

Search for the invisible decay of J/psi in psi(2S) --> pi(+)pi(-) J/psi

Using psi(2S) --> pi(+)pi(-) J/psi events in a sample of 14.0 x 10(6) psi(2S) decays collected with the BES-II detector, a search for the decay of the J/psi to invisible final states is performed. No signal is found, and an upper limit at the 90% confidence level is determined to be 1.2 x 10(-2) for the ratio B(J/psi --> invisible)/B(J/psi-->mu(+)mu(-)). This is the first search for J/psi decays to invisible final states.     

Observation of polarization in bottomonium production at square root of s = 38.8 GeV

We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at square root of s = 38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state shows no polarization at small values of the fractional longitudinal momentum x(F) and transverse momentum p(T) but significant positive transverse production polarization for either p(T)>1.8 GeV/c or for x(F)>0.35. The Upsilon(2S+3S) (unresolved) states show a large transverse production polarization at all values of x(F) and p(T) measured. These observations challenge NRQCD calculations of the polarization expected in the hadronic production of bottomonium states.     

Phenomenological evidence for gluon depletion in pA collisions

The data of J/psi suppression at large x(F) in pA collisions are used to infer the existence of gluon depletion as the projectile proton traverses the nucleus. The modification of the gluon distribution is studied by use of a convolution equation whose nonperturbative splitting function is determined phenomenologically. The depletion factor at x(1) = 0.8 is found to be about 25% at A = 100.     

Observation of a resonance in Chi(1835) in J/psi --> gammapi+ pi- eta-

The decay channel J/psi --> gamma(pi)(+)pi(-)eta is analyzed using a sample of 5.8 x 10(7) J/psi events collected with the BESII detector. A resonance, the Chi(1835), is observed in the pi(+)pi(-)eta invariant-mass spectrum with a statistical significance of 7.7 sigma. A fit with a Breit-Wigner function yields a mass M = 1833.7 +/- 6.1(stat) +/- 2.7(syst) MeV/c(2), a width Tau = 67.7 +/- 20.3(stat) +/- 7.7(syst) MeV/c(2), and a product branching fraction B(J/psi --> gammaChi) . B(Chi --> pi(+)pi(-)eta) = [2.2 +/- 0.4(stat) +/- 0.4(syst)] x 10(-4). The mass and width of the Chi(1835) are not compatible with any known meson resonance. Its properties are consistent with expectations for the state that produces the strong pp mass threshold enhancement observed in the J/psi --> gammapp process at BESII.     

Observation of a threshold enhancement in the plambda invariant-mass spectrum

An enhancement near the m(p)+M(Lambda) mass threshold is observed in the combined pLambda and pLambda invariant-mass spectrum from J/psi-->pK(-)Lambda;+c.c. decays. It can be fit with an S-wave Breit-Wigner resonance with a mass m=2075+/-12(stat)+/-5(syst) MeV and a width of Gamma=90+/-35(stat)+/-9(syst) MeV; it can also be fit with a P-wave Breit-Wigner resonance. Evidence for a similar enhancement is also observed in psi(')-->pK(-)Lambda;+c.c. decays. The analysis is based on samples of 5.8x10(7)J/psi and 1.4x10(7)psi(') decays accumulated in the BES II detector at the Beijing Electron-Positron Collider.     

Study of B+/ --> J/psi pi+/- and B+/ -->J/psi K+/- decays: measurement of the ratio of branching fractions and search for direct CP violation

We study B+/ --> J/psi pi(+/-) and B+/ --> J/psi K+/- decays in a sample of about 89 x 10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric B factory at SLAC. We observe a signal of 244+/-20 B+/ --> J/psi pi(+/-) events and determine the ratio B(B+/ --> J/psi pi(+/-))/B(B+/ --> J/psi K+/-) to be [5.37+/-0.45(stat)+/-0.11(syst)]%. The charge asymmetries for the B+/ --> J/psi pi(+/-) and B+/ --> J/psi K+/- decays are determined to be A(pi)=0.123+/-0.085(stat)+/-0.004(syst) and A(K)=0.030+/-0.015(stat)+/-0.006(syst), respectively.     

J/psi suppression in nucleus-nucleus collisions

We propose a model for calculating J/psi suppression in high-energy hadron-nucleus and nucleus-nucleus collisions. We factorized the process into a production of the cc- pairs convoluted with a transition probability into the observed J/psi mesons. As the produced cc- pairs exit the nuclear matter, multiple scattering increases the square of the relative momentum between the c and c- such that some pairs are transmuted into open charm states. With only one parameter, the energy gained by the produced cc- pair per unit length in the nuclear medium, our model can fit all observed J/psi suppression data in hadron-nucleus and nucleus-nucleus collisions.     

Observation of Y(2175) in J/psi --> etaphif0 (980)

The decays of J/psi --> etaphif(0)(980)[eta --> gammagamma, phi --> K(+) K(-), f(0)(980) --> pi(+)pi(-)] are analyzed using a sample of 5.8 x 10(7) J/psi events collected with the BESII detector at the Beijing Electron-Positron Collider. A structure at around 2.18 GeV/c(2) with about 5 sigma significance is observed in the phif(0)(980) invariant mass spectrum. A fit with a Breit-Wigner function gives the peak mass and width of m = 2.186+/-0.010(stat)+/-0.006(syst) GeV/c(2) and Gamma = 0.065+/-0.023(stat)+/-0.017(syst) GeV/c(2), respectively, which are consistent with those of Y(2175), observed by the BABAR Collaboration in the initial-state radiation process e(+)e(-) --> gamma(ISR) phif(0)(980). The production branching ratio is determined to be Br(J/psi --> etaY(2175))Br(Y(2175)- -> phif(0)(980))Br(f(0)(980) --> pi(+)pi(-)) = [3.23+/-0.75(stat)+/-0.73(syst)] x 10(-4), assuming that the Y(2175) is a 1(--) state.     

J/psi production versus centrality, transverse momentum, and rapidity in Au+Au collisions at square root sNN=200 GeV

The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured J/psi production for rapidities -2.2相似文献   

Study of time-dependent CP asymmetry in neutral B decays to J/psi pi0

We present the first study of the time-dependent CP-violating asymmetry in B0-->J/psi pi(0) decays using e(+)e(-) annihilation data collected with the BABAR detector at the Upsilon(4S) resonance during the years 1999-2002 at the PEP-II asymmetric-energy B Factory at SLAC. Using approximately 88 x 10(6) BB; pairs, our results for the coefficients of the cosine and sine terms of the CP asymmetry are C(J/psi pi(0))=0.38+/-0.41(stat)+/-0.09(syst) and S(J/psi pi(0))=0.05+/-0.49(stat)+/-0.16(syst).     

Observation of the decay psi(2S)-->K0SK0L

The decay psi(2S)-->K(0)(S)K(0)(L) is observed using psi(2S) data collected with the Beijing Spectrometer at the Beijing Electron-Positron Collider; the branching fraction is determined to be B(psi(2S)-->K(0)(S)K(0)(L))=(5.24+/-0.47+/-0.48)x10(-5). Compared with J/psi-->K(0)(S)K(0)(L), the psi(2S) branching fraction is enhanced relative to the prediction of the perturbative QCD "12%" rule. The result, together with the branching fractions of psi(2S) decays to other pseudoscalar meson pairs (pi(+)pi(-) and K+K-), is used to investigate the relative phase between the three-gluon and the one-photon annihilation amplitudes of psi(2S) decays.     

Anti-de sitter/conformal-field-theory calculation of screening in a hot wind

One of the challenges in relating experimental measurements of the suppression in the number of J/psi mesons produced in heavy ion collisions to lattice QCD calculations is that whereas the lattice calculations treat J/psi mesons at rest, in a heavy ion collision a cc[over ] pair can have a significant velocity with respect to the hot fluid produced in the collision. The putative J/psi finds itself in a hot wind. We present the first rigorous nonperturbative calculation of the consequences of a wind velocity v on the screening length L(s) for a heavy quark-antiquark pair in hot N=4 supersymmetric QCD. We find L(s)(v,T)=f(v)[1-v(2)](1/4)/piT with f(v) only mildly dependent on v and the wind direction. This L(s)(v,T) approximately L(s)(0,T)/sqrt[gamma] velocity scaling, if realized in QCD, provides a significant additional source of J/psi suppression at transverse momenta which are high but within experimental reach.     

Bound on the ratio of decay amplitudes for -B0-->J/psiK*0 and B0-->J/psiK*0

We have measured the time-dependent decay rate for the process B-->J/psiK(*0) (892) in a sample of about 88x10(6) Upsilon(4S)-->B(-)B decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. In this sample we study flavor-tagged events in which one neutral B meson is reconstructed in the J/psiK(*0) or J/psi(-)K(*0) final state. We measure the coefficients of the cosine and sine terms in the time-dependent asymmetries for J/psiK(*0) and J/psi(-)K(*0), find them to be consistent with the standard model expectations, and set upper limits at 90% confidence level (C.L.) on the decay amplitude ratios |A((-)B(0)-->J/psiK(*0))|/|A(B0-->J/psiK(*0))|<0.26 and |A(B0-->J/psi(-)K(*0))|/|A((-)B(0)-->J/psi(-)K(*0))|<0.32. For a single ratio of wrong-flavor to favored amplitudes for B0 and (-)B(0) combined, we obtain an upper limit of 0.25 at 90% C.L.     

Observation of J/psi-->3gamma

We report the first observation of the decay J/psi-->3gamma. The signal has a statistical significance of 6sigma and corresponds to a branching fraction of B(J/psi-->3gamma)=(1.2+/-0.3+/-0.2)x10;{-5}, in which the errors are statistical and systematic, respectively. The measurement uses psi(2S)-->pi;{+}pi;{-}J/psi events acquired with the CLEO-c detector operating at the CESR e;{+}e;{-} collider.     

Search for invisible decays of eta and eta' in J/psi --> phi eta and phi eta'

Using a data sample of 58 x 10(6) J/psi decays collected with the Beijing Spectrometer II detector at the Beijing Electron Positron Collider, searches for invisible decays of eta and eta' in J/psi to phi eta and phi eta' are performed. The phi signals, which are reconstructed in K+K- final states, are used to tag the eta and eta' decays. No signals are found for the invisible decays of either eta or eta', and upper limits at the 90% confidence level are determined to be 1.65 x 10(-3) for the ratio B(eta-->invisible)/B(eta --> gamma gamma) and 6.69 x 10(-2) for B(eta' --> invisible)/B(eta' --> gammagamma). These are the first searches for eta and eta' decays into invisible final states.