We have investigated the reactions p p π + π − a ̊ and p p a ̊ p p 2π + 2π − at 100 GeV /c . The p p π + π − final state is dominated by diffractive production of a p π + π − ( or p π + π − ) system which shows a strong tendency to form Δ ++ π − ( or Δ ++ π + ) . The process p p a ̊ Δ ++ Δ ++ is also observed in this reaction, indicating an energy dependence of s −1.5±0.1 . The p p 2π + 2π − channel shows less single diffraction, and has a doubly diffractive component consistent with pomeron factorization. Strong Δ ++ ( Δ ++ ) production is agoain seen, but in contrast to the p p π + π − channel we also observe considerable ϱ 0 production.
No description provided.
Results are presented on the topological cross sections obtained for antiproton-proton interactions from an exposure of the Fermilab 30-inch bubble chamber to a 100 GeV/ c negative beam enriched in p 's. The p p inelastic cross section is found to be σ inel = 34.6 ± 0.4 mb, and the average inelastic charged particle multiplicity to be 〈 n 〉 = 6.74 ± 0.05.
ERRORS ARE STATISTICAL ONLY EXCEPT FOR 2-PRONG CROSS-SECTIONS.
EXPONENTIAL FIT TO ELASTIC T DISTRIBUTION TO CORRECT FOR AN APPARENT LOSS OF EVENTS AT SMALL -T.
We derive cross-sections for the inclusive productiion in p̄p interactions at 100 GeV /c of π 0 , K S 0 and Λ 0 Λ 0 of 91.5±5.7 mb, 5.2±0.4 mb and 4.8±0.4 mb respectively, which are all higher than pp cross-sections at energy. We find indications that these differences can be attributed to “annihilation” processes.
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Single- and double-pion inclusive spectra are presented for 100-GeV/c p¯p interactions and compared with related pp data. Double-fragmentation distributions are shown to be understood within a Mueller-Regge framework as a product of single-fragmentation distributions. Consideration of pp and p¯p−pp distributions shows factorization to hold in Pomeron and in Reggeon exchanges independently.
No description provided.
Inclusive spectra are presented for π± production in 100-GeV/cp¯p interactions. The rapidity distribution for the difference (p¯p−pp) approximately scales as the difference in total cross sections in the fragmentation region between 12 and 100 GeV/c and exhibits an approximate s−12dependence in the central region.
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Inclusive and semi-inclusive $ρ^0$ production in 100-GeV/c $\bar{p}p$ interactions has been studied as a function of c.m. rapidity and transverse momentum. Cross sections are compared with those for $\bar{p}p$ interactions at other energies, as well as pp and π±p interactions, over the range ∼2 < $p_{lab} < 200$ GeV/c. A measurement of the $f^0$ production cross section has been made. Calculations of the contribution from $\rho^0$ decay to prompt lepton production are presented.
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We have investigated the inclusive production of γ, KS0, Λ0, and Λ¯0 in 100-GeV/c p¯p interactions in the 30-in. hydrogen bubble chamber at Fermilab. We present various inclusive distributions and compare them with corresponding distributions in 100-GeV/c pp interactions and lower-energy p¯p interactions. We find some evidence for Σ(1385) production but none for K*(890) production. We find evidence for a nonzero Λ0 polarization of -0.45 ± 0.21.
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We present results on inclusive Δ ++ (1236) production in 100 GeV/ c p p interactions. In the region | t | < 1 GeV 2 we find a cross section of 1.29 ± 0.15 mb. Comparisons with pp interactions at high energies show Δ ++ production in pp and p p interactions to be very similar. The decay angular distributions of the Δ ++ are consistent with production predominantly through pion-exchange and the properties of the system recoiling from the Δ ++ are similar to those of real π + p interactions. However, the p π + background is found to show qualitatively similar behaviour. In contrast to the indications of Δ ++ production through pion exchange we also find evidence that events proceeding through diffraction dissociation are more likely to contain Δ ++ than other events. We present results on the forward production of Δ ++ in association with Δ ++ and protons.
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Measurements of the midrapidity transverse energy distribution, $d\Et/d\eta$, are presented for $p$$+$$p$, $d$$+$Au, and Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV and additionally for Au$+$Au collisions at $\sqrt{s_{_{NN}}}=62.4$ and 130 GeV. The $d\Et/d\eta$ distributions are first compared with the number of nucleon participants $N_{\rm part}$, number of binary collisions $N_{\rm coll}$, and number of constituent-quark participants $N_{qp}$ calculated from a Glauber model based on the nuclear geometry. For Au$+$Au, $\mean{d\Et/d\eta}/N_{\rm part}$ increases with $N_{\rm part}$, while $\mean{d\Et/d\eta}/N_{qp}$ is approximately constant for all three energies. This indicates that the two component ansatz, $dE_{T}/d\eta \propto (1-x) N_{\rm part}/2 + x N_{\rm coll}$, which has been used to represent $E_T$ distributions, is simply a proxy for $N_{qp}$, and that the $N_{\rm coll}$ term does not represent a hard-scattering component in $E_T$ distributions. The $dE_{T}/d\eta$ distributions of Au$+$Au and $d$$+$Au are then calculated from the measured $p$$+$$p$ $E_T$ distribution using two models that both reproduce the Au$+$Au data. However, while the number-of-constituent-quark-participant model agrees well with the $d$$+$Au data, the additive-quark model does not.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, $A_{LL}$, for $\pi^0$ and $\eta$ production in $\sqrt{s} = 200$ GeV polarized $p$$+$$p$ collisions. Comparison of the $\pi^0$ results with different theory expectations based on fits of other published data showed a preference for small positive values of gluon polarization, $\Delta G$, in the proton in the probed Bjorken $x$ range. The effect of adding the new 2009 \pz data to a recent global analysis of polarized scattering data is also shown, resulting in a best fit value $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}} = 0.06^{+0.11}_{-0.15}$ in the range $0.05<x<0.2$, with the uncertainty at $\Delta \chi^2 = 9$ when considering only statistical experimental uncertainties. Shifting the PHENIX data points by their systematic uncertainty leads to a variation of the best-fit value of $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}}$ between $0.02$ and $0.12$, demonstrating the need for full treatment of the experimental systematic uncertainties in future global analyses.
PI0 ASYM(LL) measurements from 2005.
PI0 ASYM(LL) measurements from 2006.
PI0 ASYM(LL) measurements from 2009.
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