Approximately 1200 π−-proton interactions in a liquid hydrogen bubble chamber were studied to obtain the elastic differential cross section and inelastic partial cross sections at 950±20 Mev mean laboratory energy. Relative cross sections were converted to absolute values using the total cross section obtained by Cool and co-workers with counters. The differential cross section is inconsistent with a resonance of definite total angular momentum and parity and can be fitted by a superposition of partial waves of angular momenta up to 3ℏ without spin-flip scattering. In the center-of-mass system, 30% of the pions scatter beyond a broad minimum of the cross section at 75°.
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Phys. Rev. Lett. 14, 408 (1965)
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We have investigated the interactions of (650±15) MeV π— in a hydrogen bubble chamber. About 104 pictures were examined and 4561 events (1946 elastic, 1204 neutrals, 1315 single-pion production, 96 multi-pion production) were found along a 33.75·105 cm total track length. The values of the deduced cross-sections are σ(π--p, elastic) = = (17.82 ± 0.70) mb, σ(neutrals) = (11.35 ± 0.54) mb, σ(π-π0p) = (4.79 ± 0.26)mb, σ(π-π+n) = (7.05 ± 0.34)mb, σ(π-π+π0n) = (0.71 ± 0.08)mb, σ(π-π0π0p) = (0.05 ± 0.02)mb, σ(total) = (41.82 ± 0.15) mb For the elastic events, the differential cross-section was fitted by a fifth-order polynomial of cos ϑ and also expanded in a sum of Legendre polynomials: we deduce that the higher azimuthal states, up toF5/2, are present. For the single-pion production the effective mass distributions were compared with the Olsson-Yodh isobar model predictions. The agreement with the model is not very satisfactory for the enhancements in the mass effective spectra of the π+π-, π-π0, di-pion channels nor for the c.m.s. angular distributions.
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Differential and double differential cross sections of positive pion production by 240 MeV protons on carbon and copper nuclei are measured. The energy dependence of differential cross section for copper nucleus at 90 deg angle within the 240-500 MeV energy range of protons and angular dependence of the integrated differential cross section are obtained. It is shown that the differential cross section at 250 MeV is 80 times less than that at 585 MeV
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Photoproduction cross-section of the η-particle for incident photon energiesK from ∼800 to ∼1000 MeV has been measured at the 1.1 GeV Frascati electronsynchrotron. The differential cross-section for this process, at a c.m. angle of the η of ∼110°, turns out to be fairly constant for 830 MeV≤K≤900 MeV, and drops down by a factor 5 to 10 atK=950 MeV. These results are discussed in terms of a comparison with the data on the production of η's by pions, and with the data on pion-nucleon scattering and pion photoproduction. The conclusions are in agreement with the hypothesis that the η-N system is dominated at low energies by a resonance with orbital angular momentuml=0 (S 1/2,1/2 resonance).
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We present the analysis of ∼30,000 high mass dimuons (Mμμ>4.5 GeV/c2) produced in 400 GeV/c proton-platinum interactions. A determination of theK-factor is given for different values ofxF andMμμ, and its variations are compared to QCD predictions. The proton structure functions derived from these events are compared to the values obtained in deep inelastic lepton scattering.
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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).
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Results are presented on a measurement of the ttbar pair production cross section in ppbar collisions at sqrt{s} = 1.8 TeV from nine independent decay channels. The data were collected by the Dzero experiment during the 1992-1996 run of the Fermilab Tevatron Collider. A total of 80 candidate events are observed with an expected background of 38.8 +- 3.3 events. For a top quark mass of 172.1 GeV/c^2, the measured cross section is 5.69 +- 1.21 (stat) +- 1.04 (sys) pb.
Measured top quark pair production cross section in the different channels and the various averages, including the overall average.
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DD IVENTS SELECTED BY THE RAPIDITY GAP METHOD.
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Photoproduction reactions occur when the electromagnetic field of a relativistic heavy ion interacts with another heavy ion. The STAR collaboration presents a measurement of rho^0 and direct pi^+pi^- photoproduction in ultra-peripheral relativistic heavy ion collisions at sqrt(s_{NN})=200 GeV. We observe both exclusive photoproduction and photoproduction accompanied by mutual Coulomb excitation. We find a coherent cross-section of sigma(AuAu) -> Au^*Au^*rho^0 = 530 pm 19 (stat.) pm 57 (syst.) mb, in accord with theoretical calculations based on a Glauber approach, but considerably below the predictions of a color dipole model. The rho^0 transverse momentum spectrum (p_{T}^2) is fit by a double exponential curve including both coherent and incoherent coupling to the target nucleus/ we find sigma_{inc}/sigma_{coh} = 0.29 pm 0.03 (stat.) pm 0.08 (syst.). The ratio of direct pi^+pi^- to rho^0 production is comparable to that observed in gamma p collisions at HERA, and appears to be independent of photon energy. Finally, the measured rho^0 spin helicity matrix elements agree within errors with the expected s-channel helicity conservation.
ZDC spectra obtained with the minimum bias sample after the $\rho^{0}$ selection cuts are applied, and fit with three Gaussians. The east ZDC is shown on the left and the west ZDC is shown on the right. The ratio of numbers of candidates in the West ZDC of 1n:2n:3n is 1: 0.48 $\pm$ 0.03: 0.42 $\pm$ 0.03, while in the East ZDC, we find 1n:2n:3n is 1: 0.46 $\pm$ 0.03: 0.42 $\pm$ 0.03.
ZDC spectra obtained with the minimum bias sample after the $\rho^{0}$ selection cuts are applied, and fit with three Gaussians. The east ZDC is shown on the left and the west ZDC is shown on the right. The ratio of numbers of candidates in the West ZDC of 1n:2n:3n is 1: 0.48 $\pm$ 0.03: 0.42 $\pm$ 0.03, while in the East ZDC, we find 1n:2n:3n is 1: 0.46 $\pm$ 0.03: 0.42 $\pm$ 0.03.
The invariant mass distribution for the coherently produced $\rho^{0}$ candidates from the minimum bias sample with the cut on the $\rho^{0}$ transverse momentum $p_{T}$ < 150 MeV/c. The hatched area is the contribution from the combinatorial background. The solid line corresponds to Eq. 3 which encompasses the Breit-Wigner (dashed), the mass independent contribution from the direct $\pi^{+}\pi^{-}$ production (dash-dotted), and the interference term(dotted).
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