The energy dependence of the photon-proton total cross section, sigma-tot, was determined from ep scattering data collected with the ZEUS detector at HERA at three values of the center-of-mass energy, W, of the gamma-p system in the range 194<W<296 GeV. This is the first determination of the W dependence of sigma-tot from a single experiment at high W. Parameterizing sigma-tot proportional to W^(2 epsilon), epsilon = 0.111 +/- 0.009 (stat.) +/- 0.036 (syst.) was obtained.
Ratios of the cross sections for 3 energy bins. The first DSYS error isthe uncorrelated uncertainty and the second is the correlated uncertainty.
Fitted power law energy dependence.
Exclusive rho^0 electroproduction at HERA has been studied with the ZEUS detector using 120 pb^{-1} of integrated luminosity collected during 1996-2000. The analysis was carried out in the kinematic range of photon virtuality 2 < Q^2 < 160 GeV$^2, and gamma^* p centre-of-mass energy 32 < W < 180 GeV. The results include the Q^2 and W dependence of the gamma^* p --> rho^0 p cross section and the distribution of the squared-four-momentum transfer to the proton. The helicity analysis of the decay-matrix elements of the rho^0 was used to study the ratio of the gamma^* p cross section for longitudinal and transverse photon as a function of Q^2 and W. Finally, an effective Pomeron trajectory was extracted. The results are compared to various theoretical predictions.
Measurement of the spin density matrix element r_04_00 as a function of Q**2.
Measurement of the spin density matrix element RE(r_04_10) as a function of Q**2.
Measurement of the spin density matrix element r_04_1-1 as a function of Q**2.
Exclusive electroproduction of $\phi$ mesons has been studied in $e^\pm p$ collisions at $\sqrt{s}=318 \gev$ with the ZEUS detector at HERA using an integrated luminosity of 65.1 pb$^{-1}$. The $\gamma^*p$ cross section is presented in the kinematic range $2<Q^2<70 \gev^2$, $35<W<145 \gev$ and ${|t|}<0.6 \gev^2$. The cross sections as functions of $Q^2$, $W$, $t$ and helicity angle $\theta_h$ are compared to cross sections for other vector mesons. The ratios $R$ of the cross sections for longitudinally and transversely polarized virtual photons are presented as functions of $Q^2$ and $W$. The data are also compared to predictions from theoretical models.
Exclusive GAMMA* P --> PHI P cross section in the Q**2 range 2 to 3 GeV**2.
Exclusive GAMMA* P --> PHI P cross section in the Q**2 range 3 to 5 GeV**2.
Exclusive GAMMA* P --> PHI P cross section in the Q**2 range 5 to 9 GeV**2.
The exclusive electroproduction of J/psi mesons, ep->epJ/psi, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15<Q^2<0.8 GeV^2 and 2<Q^2<100 GeV^2 using integrated luminosities of 69 pb^-1 and 83 pb^-1, respectively.The photon-proton centre-of-mass energy was in the range 30<W<220 GeV and the squared four-momentum transfer at the proton vertex |t|<1.The cross sections and decay angular distributions are presented as functions of Q^2, W and t. The effective parameters of the Pomeron trajectory are in agreement with those found in J/psi photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections, sigma_L/sigma_T, grows with Q^2, whilst no dependence on W or t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 0.15 to 0.18 GeV**2.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 2 to 5 GeV**2.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 5 to 10 GeV**2.
We report on a measurement of the inclusive cross sections of $\Lambda$ , $\overline\Lambda$ , K 0
Total inclusive hyperon production cross sections for the SIGMA- beam on the Copper target.
Total inclusive hyperon production cross sections for the SIGMA- beam on the Carbon target.
Total inclusive hyperon production cross sections per nucleon for the SIGMA- beam, and the exponent in the cross section parametrization of the form A**POWER.
We present data from Fermilab experiment E781 (SELEX) on the hadroproduction asymmetry for anti-Lambda_c compared to Lambda_c+ as a function of xF and pt2 distributions for Lambda_c+. These data were measured in the same apparatus using incident pi-, sigma- beams at 600 GeV/c and proton beam at 540 GeV/c. The asymmetry is studied as a function of xF. In the forward hemisphere with xF >= 0.2 both baryon beams exhibit very strong preference for producing charm baryons rather than charm antibaryons, while the pion beam asymmetry is much smaller. In this energy regime the results show that beam fragments play a major role in the kinematics of Lambda_c formation, as suggested by the leading quark picture.
The number of events reconstructed in the signal mass region of LAMBDA/C+ production. Statistical errors only.
The number of events reconstructed in the signal mass region of LAMBDA/CBAR- production. Statistical errors only.
The number of events reconstructed in the signal mass region of LAMBDA/C+ production. Statistical errors only.
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Total inclusive production cross sections for the SIGMA- beam on the Coppertarget.
Total inclusive production cross sections for the SIGMA- beam on the Carbontarget.
Total inclusive production cross sections per nucleon for the SIGMA- beam, and the exponent in the cross section parametrization of the form A**POWER.
The production of the J/ ψ and ψ ′ charmonia states has been studied, through their dimuon decay, in proton, Oxygen and Sulphur induced reactions, by the NA38 experiment at the CERN SPS. The proton data was collected with beams of 200 and 450 GeV, while the ion beams had an energy of 200 GeV per incident nucleon. The J/ ψ production cross-section per nucleon-nucleon collision exhibits a remarkably continuous pattern, as a function of the product of the mass numbers of the interacting nuclei, from pp up to S-U reactions. The same pattern is observed within S-U collisions, as a function of the collision centrality. While in p-A interactions both charmonia states exhibit the same A-dependence, in S-U collisions the ψ ′ production is very strongly suppressed.
Results of fitting the 200 and 450 GeV J/PSI data separately with a power law parametrization SIG=SIG0*(A*B)**POWER, where A and B are the beam and targetmass numbers. The value obtained from a combined fit is also given, as well as the ratio between the values of SIG0 for the 200 and 450 GeV data sets.
The J/PSI cross sections per nucleon (times the BR to di-muons) rescaled to 200 GeV/nucleon, using the SIG0 ratio detemined in the previous table, and to the cm rapidity window 0 to 1. The errors are combined statistical and systematic.
The ratio between the PSI(3685) and the J/PSI production cross section, times their BR into di-muons, at an incident beam energy of 450 GeV per nucleon. The errors are combined statistical and systematic.
The production of charmed particles by Sigma- of 340 Gev/c momentum was studied in the hyperon beam experiment WA89 at the CERN-SPS, using the Omega-spectrometer. In two data-taking periods in 1993 and 1994 an integrated luminosity of 1600 microb^-1 on copper and carbon targets was recorded. From the reconstruction of 930 +- 90 charm particle decays in 10 decay channels production cross sections for D, antiD, Ds and Lambdac were determined in the region xF>0. Assuming an A^1 dependence of the cross section on the nucleon number, we calculate a total ccbar production cross section of sigma(x_F > 0) = 5.3+- 0.4(stat)+-1.0(syst)+1.0(Xi_c) microb per nucleon. The last term is an upper limit on the unknown contribution from charmed-strange baryon production.
Fits to the DSIG/DXL and DSIG/DPT**2 distributions in the range XL > 0. Theerrors shown are statistical only.. The fits are of the following form:. DSIG/DXL : Const*(1-X)**N. DSIG/DPT**2 : Const*EXP(-B*PT**2).
The production cross sections for anti-charmed and charmed hadrons in the range XL > 0. The Errors are statistical only.
The total CQUARK+CQUARKBAR cross section in the range XL > obtained as the weighted average of the sum of all the measured contributions to the charmed andanti-charmed hadron production in the previous table. second systematic (DSYS) error is due to the uncertainty in the contribution of XI/C production to the cross section.
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.
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