Differential cross sections as a function of momentum are presented for the production of K+ mesons in p−p collisions at incident proton energies of 2.54, 2.88, and 3.03 GeV. The measurements were made at 20°, 30°, and 40° relative to the direction of the internal proton beam of the Princeton-Pennsylvania accelerator. At 2.54 GeV, the results follow closely the predictions from phase space (with 60% K+ΣN and 40% K+Λp in the final state). At 2.88 and 3.03 GeV, however, there is a definite disagreement with phase space. The data are compared to the predictions of three models: (1) a model based on the assumption that K's are produced via p+p→K++X+, where X+ is a B=2, S=−1 resonance which decays into a nucleon+hyperon; (2) the isobar model; and (3) the one-pion-exchange model. Model (1) is found to be inconclusive, model (2) is inadequate, and model (3) is partly successful in predicting total cross sections, but not in interpreting the detailed experimental observations.
The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y|<0.9 and 2.5<y<4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L^e_int=1.1 nb^-1 and L^mu_int=19.9 nb^-1, and the corresponding signal statistics are N_J/psi^e+e-=59 +/- 14 and N_J/psi^mu+mu-=1364 +/- 53. We present dsigma_J/psi/dy for the two rapidity regions under study and, for the forward-y range, d^2sigma_J/psi/dydp_t in the transverse momentum domain 0<p_t<8 GeV/c. The results are compared with previously published results at sqrt(s)=7 TeV and with theoretical calculations.
The dielectron yield in p + d and p + p collisions at a beam kinetic energy of 4.9 GeV has been measured using the Dilepton Spectrometer (DLS) at the Bevalac. The measured ratio of the yield in p + d to that in p + p collisions, 1.92±0.06, is in disagreement with the assumptions of model calculations applied to our ealier p +Be data, where it was found that p + n bremsstrahlung dominated other sources. While the measured ratio is consistent with a hadron-like origin of the dielectrons, the contributions of known hadronic decays are smaller than the measured yield from p + p collissions.
Dielectron production in p+d and p+p collisions at the beam kinetic energy of 4.9 GeV has been measured with the Dilepton Spectrometer. Features of the dielectron cross section have been studied with cuts on the mass and transverse momentum of the pairs. The spectra for several regions of phase space are presented as a function of the pair mass and transverse momentum.
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