We present the xF and pT differential cross sections of J/ψ and ψ′, respectively, in the ranges −0.05<xF<0.25 and pT<3.5 GeV/c. The data samples are constituted by about 12 000 J/ψ and 200 ψ′ produced in proton-silicon interactions at 800 GeV/c and decaying into opposite sign muons. The xF and pT distributions are compared with recent results from experiments E789 at the same energy and to leading order QCD predictions using the MRS D0 parametrization for the parton structure function. The measured shapes of the differential cross sections, except for the dσ/dxF at small xF, agree very well with the prediction, even though their value is quite a bit larger than the prediction. We also present the cosθ differential cross section of the J/ψ which indicates unpolarized production in contrast with color octet models predictions.
Additional systematic error given above.
Additional systematic error given above.
Additional systematic error given above.
Hadroproduction of the Jψ and ψ′ states has been studied in 300-GeV/c proton, antiproton, and π±Li interactions. Both total and differential cross sections in xF and pT have been measured for the Jψ for the π±, proton, and antiproton interactions. The ratio of ψ′ to Jψ production has been determined for the four types of beam particles.
No description provided.
No description provided.
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We report preliminary results on the production of electron-positron pairs in the mass range 2.5 to 4 GeV in 400-GeV p-Be interactions. Production cross sections of the ψ(3100) near x=0 as a function of pt, x, and the decay angle are presented and implications of these new data for single direct leptons are discussed. A ψ′(3700) signal is observed at a level corresponding to σ(ψ′)σ(ψ)=(10±3)%.
No description provided.
Muon-pair production has been measured in pCu, pU, OCu, OU and SU collisions at 200 GeV per nucleon. The cross sections are compatible with the atomic number dependence ( A proj. A targ. ) α where α =0.91±0.04 for the J/ψ resonance and α =1.01±0.04 for muon pairs produced in the mass continuum between 1.7 and 2.7 GeV/ c 2 .
Cross sections fitted with SIG0*(A(P=1)*A(P=2))** ALPHA. ALPHA is coded here as POWER(N=A*A,YN=SIG).
Cross sections fitted with SIG0*(A(P=1)*A(P=2))** ALPHA. ALPHA is coded here as POWER(N=A*A,YN=SIG).
No description provided.
The production of ${\rm J}/\psi$ and
The J/PSI production cross sections, per target nucleon, times the di-muon branching ratio for the two data samples.
The PSI(3685) production cross sections, per target nucleon, times the di-muon branching ratio for the two data samples.
J/PSI production cross section times the di-muon branching ratio for the BEtarget as a function of the Feynman X bin.
We report on the production of J/psi mesons in 530 and 800 GeV/c proton - Be collisions in the Feynman-x range 0.0 < xf < 0.6. The J/psi mesons were detected via decays into opposite sign muon pairs. Differential distributions for J/psi production have been measured as functions of xf, pT^2, and cosine of the Gottfried-Jackson decay angle. These distributions are compared with results on J/psi production obtained in 515 GeV/c pion - Be collisions, measured by the same experiment, as well as with results from other experiments using incident protons.
Differential XL distribution for J/PSI production in 530 GeV pBe collisions. Errors are combined statistics and systematics.
Differential PT**2 distribution for J/PSI production in 530 GeV pBe collisions. Errors are combined statistics and systematics.
Differential COS(THETA) distribution for J/PSI production in 530 GeV pBe collisions. Errors are combined statistics and systematics.
The production of J/ψ by π ± , K ± , p and p¯ incident on tungsten at 39.5GeV/ c beam momentum has been studied. Production of ψ' (3700) by π ± was also observed. The J/ψ relative particle/a ntiparticle cross-sections for x F 0 are σ(σ + ) σ(σ − =( are σ(σ ± )/σ(σ − )=(1.01±0.06), σ(K + )/σ(K) − )=(0.29±0.07) and σ(p) /σ(p¯)= (0.1+-0.03). The small p/p¯ and K + /K − cross-section ratios indicate the importance of valence quarks in the production process.
No description provided.
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Data is extrapolated to full x range.
Data requested from authors.
Ratios of the Psi' over the J/psi production cross sections in the dilepton channel for C, Ti and W targets have been measured in 920 GeV proton-nucleus interactions with the HERA-B detector at the HERA storage ring. The Psi' and J/psi states were reconstructed in both the mu+mu- and the e+e- decay modes. The measurements covered the kinematic range -0.35 < x_F < 0.1 with transverse momentum p_T < 4.5 GeV/c. The Psi' to J/psi production ratio is almost constant in the covered x_F range and shows a slow increase with p_T. The angular dependence of the ratio has been used to measure the difference of the Psi' and J/psi polarization. All results for the muon and electron decay channels are in good agreement: their ratio, averaged over all events, is R_psi'(mu)/R_psi'(e)=1.00+-0.08+-0.04. This result constitutes a new, direct experimental constraint on the double ratio of branching fractions, (B'(mu)*B(e))/(B(mu)*B'(e)), of Psi' and J/psi in the two channels.
Ratio of PSI(3685) and J/PSI cross sections for both muon and electron channels combined, obtained for different cos theta in the s-channel helicity frame.
Ratio of PSI(3685) and J/PSI cross sections for both muon and electron channels combined, obtained for intervals inpT using the data from all targets.
Ratio of PSI(3685) and J/PSI production cross sections per nucleus.
A measurement of the ratio R_chic = (chic -> Jpsi + gam)/ Jpsi in pC, pTi and pW interactions at 920 GeV/c (sqrt{s}=41.6 GeV) in the Feynman-x range -0.35 < x_F(Jpsi) < 0.15 is presented. Both mu+mu- and e+e- Jpsi decay channels are observed with an overall statistics of about 15000 chic events, which is by far the largest available sample in pA collisions. The result is R_chic = 0.188+-0.013(st)(+0.024)(-0.022)(sys) averaged over the different materials, when no Jpsi and chic polarisations are considered. The chic_1 to chic_2 production ratio R_12 = R_chic1/R_chic2 is measured to be 1.02+-0.40, leading to a cross section ratio sigma(chic_1)/sigma(chic_2)=0.57+-0.23. The dependence of R_chic on the Feynman-x of the Jpsi, x_F(Jpsi), and its transverse momentum, p_T(Jpsi), is studied, as well as its dependence on the atomic number, A, of the target. For the first time, an extensive study of possible biases on R_chic and R_12 due to the dependence of acceptance on the polarization states of Jpsi and chic is performed. By varying the polarisation parameter, lambda(obs), of all produced Jpsi's by two sigma around the value measured by HERA-B, and considering the maximum variation due to the possible chic_1 and chic_2 polarisations, it is shown that R_chic could change by a factor between 1.02 and 1.21 and R_12 by a factor between 0.89 and 1.16.
Measurement of R_CHI/C in <E+ E->, <MU+ MU-> and combined channel.
Measurement of R_12 in <E+ E->, <MU+ MU-> and combined channel.
Measurement of SIG(C1)/SIG(C2) in <E+ E->, <MU+ MU-> and combined channel.