Measurements of the kinematic distributions of $J/\psi$ mesons produced in $p-$C, $p-$Ti and $p-$W collisions at $\sqrt{s}=41.6 \mathrm{GeV}$ in the Feynman-$x$ region $-0.34 < x_{F} < 0.14$ and for transverse momentum up to $p_T = 5.4 \mathrm{GeV}/c$ are presented. The $x_F$ and $p_T$ dependencies of the nuclear suppression parameter, $\alpha$, are also given. The results are based on $2.4 \cdot 10^{5}$ $J/\psi$ mesons in both the $e^+ e^-$ and $\mu^{+}\mu^{-}$ decay channels. The data have been collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The measurement explores the negative region of $x_{F}$ for the first time. The average value of $\alpha$ in the measured $x_{F}$ region is $0.981 \pm 0.015$. The data suggest that the strong nuclear suppression of $J/\psi$ production previously observed at high $x_F$ turns into an enhancement at negative $x_F$.
J/PSI distributions (dN/dp_T, normalized to their integrals over the measured range) for three targets materials with statistical and systematics uncertainties.
J/PSI distributions (dN/dx_F, normalized to their integrals over the measured range) for three targets materials with statistical and systematics uncertainties.
The parameter Alpha as a function of p_T. Statistical and systematic uncertainties are indicated separately.
Absolute J/ ψ and ψ ′ production cross sections have been measured at the CERN SPS, with 450 GeV/ c protons incident on a set of C, Al, Cu and W targets. Complementing these values with the results obtained by experiment NA51, which used the same beam and detector with H and D targets, we establish a coherent picture of charmonia production in proton-induced reactions at SPS energies. In particular, we show that the scaling of the J/ ψ cross section with the mass number of the target, A, is well described as A α , with α ψ =0.919±0.015. The ratio between the J/ ψ and ψ ′ yields, in our kinematical window, is found to be independent of A, with α ψ ′ − α ψ =0.014±0.011.
The ratio of the production cross sections, in the di-muon channel. Note that there are wo set of CU and WT data with targets of different lengths. An average values is also given for these.
The J/PSI absolute cross sections, times the BR to di-muons.
The PSI(3685) absolute cross sections, times the BR to di-muons.
Results are presented from an experiment with a large acceptance spectrometer that measured the production cross section of high mass muon pairs from the collision of 225 GeV/c hadron beams with a nuclear target including, for the first time, measurements using positive and negative pion beams. Various features of the data, such as the helicity anqle of the muon pairs and the ratio of the cross sections for positive and negative pions provide conclusive evidence for the quark-antiquark annihilation model for the production of muon pairs. This model is then used to determine the momentum distribution for valence quarks in pion. our best fit to the distribution,$\bar{\mu} (x) = (.73 \pm .11) x^{-1/2} [1-x] ^{(1.28 \pm .15)}$ , shows that the pion's structure! is clearly different from the proton's structure.
DATA ON (E/2*PI*PMAX(RF=CM))*D2(SIG)/D(XL)/D(PT)/PT WHERE THE CENTER OF MASS DEFINITION OF THE XL ASSUMED THAT THE TARGET WAS A SINGLE NUCLEON OF MASS 0.938 GEV. Axis error includes +- 0.0/0.0 contribution (?////SYSTEMATIC ERRORS NOT GIVENFERMI//COULOMBRES-DEF(RES=J/PSI,BACK=UNCORRECTED,DEF=2.7 < M(MU+ MU-) IN GEV < 3.5)).
DATA ON (E/2*PI*PMAX(RF=CM))*D2(SIG)/D(XL)/D(PT)/PT WHERE THE CENTER OF MASS DEFINITION OF THE XL ASSUMED THAT THE TARGET WAS A SINGLE NUCLEON OF MASS 0.938 GEV. Axis error includes +- 0.0/0.0 contribution (?////SYSTEMATIC ERRORS NOT GIVENFERMI//COULOMBRES-DEF(RES=J/PSI,BACK=UNCORRECTED,DEF=2.7 < M(MU+ MU-) IN GEV < 3.5)).
DATA ON (E/2*PI*PMAX(RF=CM))*D2(SIG)/D(XL)/D(PT)/PT WHERE THE CENTER OF MASS DEFINITION OF THE XL ASSUMED THAT THE TARGET WAS A SINGLE NUCLEON OF MASS 0.938 GEV. Axis error includes +- 0.0/0.0 contribution (?////SYSTEMATIC ERRORS NOT GIVENFERMI//COULOMBRES-DEF(RES=J/PSI,BACK=UNCORRECTED,DEF=2.7 < M(MU+ MU-) IN GEV < 3.5)).
We present results of a large-acceptance experiment in which muon pairs were observed in the mass range 0.6 to 6.0 GeV/c2. Emphasis is given to features of the production of Jψ and ψ′(3.7) particles. We find [Bσ]ψ′(3.7)[Bσ]Jψ to be 0.007±0.004 for p-C and 0.018±0.007 for π+-C interactions. Comparison with results from e+e− storage rings indicates that both the Jψ and the ψ′(3.7) are produced strongly rather than electromagnetically in our experiment.
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