Mid-rapidity open charm spectra from direct reconstruction of $D^{0}$($\bar{D^0}$)$\to K^{\mp}\pi^{\pm}$ in d+Au collisions and indirect electron/positron measurements via charm semileptonic decays in p+p and d+Au collisions at \srt = 200 GeV are reported. The $D^{0}$($\bar{D^0}$) spectrum covers a transverse momentum ($p_T$) range of 0.1 $
Inclusive electrons yield versus transverse momentum in D+AU collisions Data points at PT = 2.2, 2.7 and 3.5 GeV/c was obtained using only the TPC (Time Projection Chamber) and cover a pseudo-rapidity range of -1<eta<1, while other points were obtained using both a prototypeTime-of-Flight System and the TPC and cover a pseudo-rapidity range of -1<eta<0.
Inclusive electrons yield versus transverse momentum in P+P collisions.
D0 yield versus transverse momentum in D+AU collisions.
J/psi production has been measured in proton-proton collisions at sqrt(s)= 200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at RHIC. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 3.99 +/- 0.61(stat) +/- 0.58(sys) +/- 0.40(abs) micro barns. The mean transverse momentum is 1.80 +/- 0.23(stat) +/- 0.16(sys) GeV/c.
Measured J/PSI distribution in PT for the e+e- channel. The value of B, the branching fraction to either electrons or muons is the average value from PDG : 5.9%.The rapidity range is -0.35<y<0.35. Incertainties are 1-sigma statistical errors on the (signal - background) net yield. There is a 10% overall absolute cross section normalization error in addition to the error given.
Measured J/PSI distribution in PT for the mu+mu- channel. The value of B, the branching fraction to either electrons or muons, is the average value from PDG: 5.9%.The rapidity range is -2.2<y<-1.2. Incertainties are 1-sigma statistical errors on the (signal - background) net yield.There is a 10% overall absolute cross section normalization error in addition to the error given.
J/PSI distribution in rapidity. The data at rapidity = 0 is from the electron arm, the data from the muon arm, corresponding to forward rapidity is divided in two bins.The value of B,the branching fraction to either electrons or muons, is 5.9%, the average value from PDG.Incertainties are 1-sigma statistical errors on the (signal - background) net yield.There is a 10% overall absolute cross section normalization error in addition to the error given.
We report on the first measurement of the rapidity distribution dsigma/dy over nearly the entire kinematic region of rapidity for e^+e^- pairs in the Z-boson region of 66
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The neutral π0 and η mesons are studied in 197Au−197Au collisions at an incident energy of 800AMeV, substantially below the threshold for η production in N−N collisions. While the gross π0 multiplicity increases almost linearly with the number of participant nucleons, the multiplicities of η and hard π0 mesons show a stronger than linear dependence. The nonlinearity is governed by the average transverse-mass excess 〈mt〉−(s−2mN) of the mesons and is insensitive to their final-state interaction in the nuclear medium.
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In a joint effort the CERES/NA45 and TAPS collaborations have measured low-mass electron pairs in p–Be and p–Au collisions at 450 GeV/c at the CERN SPS. In the range covered up to ≈ 1.5 GeV/c2 the mass spectra from p–Be and p–Au collisions are well explained by electron pairs from decays of neutral mesons. For p–Au our result is new. For p–Be, the simultaneously measured electron pair inclusive pair spectrum in which instrumental uncertainties are highly reduced. We confirm the earlier finding of HELIOS-1 with significantly reduced systematic uncertainties of 23% in the mass range below 450 MeV/c2, and of 28% in the mass range above 750 MeV/c2 at 90% confidence limit. Any unconventional source of electron pairs is limited by these error margins as the percentage fraction of the hadronic contribution.
Relative production cross sections.
With a data sample containing 1.1×105 J/ψ→μ+μ− decays reconstructed with 16 MeV/c2 rms mass resolution, we have measured the differential cross sections versus Feynman-x, rapidity, and pT for the production of J/ψ and ψ’ in 800 GeV/c p-Au collisions. Our results are compared with leading-order QCD predictions and with previous measurements. While the shapes of the cross sections are in qualitative agreement with QCD predictions, the magnitudes disagree by factors of 7 (J/ψ) and 25 (ψ’). Assuming an appropriate form for the differential cross sections in regions not measured we derive a total J/ψ production cross section σ(p+N→J/ψ+X)=442±2±88 nb/nucleon and a (model-dependent) total ψ’ cross secton σ(p+N→ψ’+X)=75±5±22 nb/nucleon. For J/ψ produced at central rapidity, dσ(p+N→J/ψ+X)/dy‖y=0=230±5±46 nb/nucleon.
Extrapolated measured total cross sections.
J/PSI cross section at central rapidity.
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The production of Λ 's and Ξ − 's in proton-antiproton collisions at 200 and 900 GeV c.m. energy has been studied using decays observed in the UA5 streamer chambers. The results are compared to previously published 546 GeV data, to results from other experiments, and to four theoretical models. The Λ yield per inelastic event is estimated to be 0.42±0.11 at 200 GeV and 0.66±0.14 at 900 GeV. We find a mean number of Ξ − 's per inelastic collision of 0.03 −0.02 +0.04 at 200 GeV and 0.06 −0.03 +0.05 at 900 GeV. The average transverse momentum of Λ's in the rapidity region | y |⩽2 is found to be 0.80 −0.14 +0.20 GeV/ c at 200 GeV and 0.74±0.09 GeV/ c at 900 GeV. The average transverse momentum of Ξ − 's in the rapidity region | y |⩽3 is estimated to be 0.8 −0.2 +0.4 GeV/ c at 200 GeV and 0.7 −0.1 +0.2 GeV/ c at 900 GeV which is lower than the unexpectedly high value of 1.1±0.2 GeV/ c measured at 546 GeV. The ratio of Ξ − production to Λ production in the region | y |⩽2, p t >1 GeV/ c is 0.07 −0.04 +0.08 at 900 GeV. This value is consistent with the ratio found in e + e − collisions and lower energy pp collisions but lower than the value obtained at 546 GeV. The average particle composition of events at 200 and 900 GeV, estimated using UA5 data, is presented.
Corrected lambda transverse momentum distributions. Numerical values supplied by F. Lotse. Data at 546 GeV are taken from an earlier publication - Phys. Rep. 154 (87) 247.
Data at 546 GeV are taken from an earlier publication - Phys. Rep. 154 (87) 247.
Corrected lambda transverse momentum distributions. Numerical values supplied by F. Lotse. Data at 546 GeV are taken from an earlier publication - Phys. Rep. 154 (87) 247.
Inclusive single-particle spectra for π± production are presented for data from π±p interactions at 100 GeV/c. The spectra for the four reactions π±p→π±+anything are compared as a function of laboratory longitudinal momentum, Feynman x, center-of-mass (c.m.) rapidity, and transverse momentum squared. Comparisons are also made between these data and analogous data from 16 and 18.5 GeV/c π±p interactions and the energy dependence is discussed. Average values of the transverse momentum are given as a function of the longitudinal momentum and charged-particle multiplicity. A comparison of the charge distributions is presented as a function of rapidity and c.m. energy.
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π+p, K+p, and pp interactions at 100 GeV are studied using the Fermilab hybrid 30-inch bubble chamber with associated downstream multiparticle spectrometer and an unseparated tagged positive beam. Topological cross sections and charged-particle-multiplicity moments are presented and good agreement is found with Koba-Nielsen-Olesen scaling. The charged-multiplicity second moment, f2cc, and the second moment of produced (+ -) pairs, f2−−, are presented both with and without the diffractive-dissociation events, and are discussed in terms of the two-component model invoked to explain pp multiplicity distributions above 100 GeV. Single-particle inclusive distributions are presented and studied in terms of the Regge-Mueller forms of approach to scaling at asymptotic energies. Pomeron factorization is found to hold in the target-proton-associated backward center-of-mass hemisphere for inclusive particle production by incident π+, K+, and protons.
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The single-particle inclusive pion spectrum from the reaction p + p → π ± + anything at 28.5 GeV is presented in both tabular and graphical form. The data are from exposures in the BNL 203 cm bubble chamber. The emphasis of this paper is on exhibiting the single-particle spectra in sufficient detail so that the data will be useful to those interested in testing models and developing new concepts.
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