We present results on J/ψ production in muon interactions with tin and carbon targets at incident muon energies of 200 and 280 GeV. The ratio of cross sections per nucleon for J/ψ production on tin and carbon, R (Sn/C), is studied as a function of p T 2 , z and x . We find an enhancement for coherent J/ψ production R coh (Sn/C) = 1.54 ± 0.07, a suppression for quasielastic production R qe (Sn/C) = 0.79 ± 0.06 and for inelastic production R in (Sn/C) = 1.13 ± 0.08. The inelastic cross section ratio can be interpreted within the Colour Singlet model as an enhancement of the gluon distribution in tin with respect to that in carbon. The dependence of the ratio on z and p T 2 can explain the discrepancy between the results obtained in previous experiments.
Data for coherent events.
Data for quasielastic events.
Data for inelastic events.
Polarization transfer observables in π + d elastic scattering have been measured for the first time. Four polarization transfer parameters were determined at pion energies T π =134 MeV and 180 MeV at scattering angles θ π ,C.M. between 100° and 140° using a deuteron target polarized perpendicular to the scattering plane and a deuteron tensor polarimeter. The data are compared to different predictions from the SAID phase shift analysis and Faddeev calculations.
Systematic and statistical errors are added in quadrature.
Systematic and statistical errors are added in quadrature.
Absolute π±p elastic scattering differential cross sections have been measured at five incident pion energies between 87 and 139 MeV. An active target of scintillator material (CH1.1) was used to detect recoil protons in coincidence with scattered pions. Pions were detected at forward angles between 27 and 98°c.m. where the low-energy recoil protons stop in the target. The cross sections, typically 5–10% lower than phase shift predictions for π+p and 10–20% lower for the π−p cross sections, are consistent with earlier measurements by this group.
No description provided.
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The structure function ratiosF2C/F2Li,F2Ca/F2Li andF2Ca/F2C were measured in deep inelastic muonnucleus scattering at an incident muon energy of 90 GeV, covering the kinematic range 0.0085
Overall normalization error of 0.7%, due to uncertainties in target thickness, not included in the table.
Overall normalization error of 0.8%, due to uncertainties in target thickness, not included in the table.
Overall normalization error of 0.5%, due to uncertainties in target thickness, not included in the table.
We present the structure function ratiosF2He/F2D,F2C/F2D andF2Ca/F2D measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. The kinematic range 0.0035
No description provided.
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The structure functions F p 2 and F d 2 measured by deep inelastic muon scattering at incident energies of 90 and 280 GeV are presented. These measurements cover a large kinematic range, 0.006⩽ x ⩽0.6 and 0.5⩽ Q 2 ⩽55GeV 2 , and include the first precise data at small x , where large scaling violations are observed. The data agree with earlier results from SLAC and BCDMS but exhibit differences with respect to those of EMC-NA2. Extrapolations to small x of recent phenomenological parton distributions are shown to disagree with the present results.
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Results are presented on the ratio of neutron and proton structure functions, F 2 n / F 2 p , deduced from deep inelastic scattering of muon from hydrogen and deuterium. The data, which were obtained at the CERN muon beam at 90 and 280 GeV incident energy, cover the kinematic range x = 0.002−0.80 and Q 2 = 0.1−190 GeV 2 . The measured structure function ratios have small statistical and systematic errors, particularly at small and intermediate x . The observed Q 2 dependence in the range x = 0.1−0.4 is stronger than predicted by perturbative QCD. From the present data together with results from other experiments it is suggested that the twist-four coefficient for the proton is smaller than that for the neutron for x larger than 0.2.
No description provided.
No description provided.
Merged 90 and 280 GeV data.
We have studied the two reactions 12C(π+,pp) and 12C(π+,ppp) in one experiment, using the CHAOS spectrometer at TRIUMF, at incident pion energies of 200, 240, and 280 MeV. In both cases, we are able to distinguish between reaction mechanisms involving only the detected protons, and those in which additional nucleons must have participated, on the basis of missing momentum. In the case of 12C(π+,ppp), we identify events due to the two step process of π+p quasielastic scattering followed by two-nucleon absorption. Estimates are made for the total cross sections for the various absorption mechanisms.
The total observed cross sections are not corrected for limited experimental acceptance. No errors are given. The comments (C=MNKO), (C=2NP), and (C=GT2NP) stand for multy nucleon knockout, 2 nucleons participated, and more than 2 nucleons participated, respectively.
Measurements of the vector analyzing power iT11 in πd elastic scattering at 49 MeV have been performed using a dynamically polarized target and a magnetic spectrometer. Data at seven π+ laboratory scattering angles between 50° and 130° were taken together with a complementary measurement at 60° for π−d elastic scattering. In general, we find agreement with models that include the πN P11 amplitude and disagreement with models that exclude or suppress it.
No description provided.
No description provided.
Differential cross sections for pi- p and pi+ p elastic scattering were measured at five energies between 19.9 and 43.3 MeV. The use of the CHAOS magnetic spectrometer at TRIUMF, supplemented by a range telescope for muon background suppression, provided simultaneous coverage of a large part of the full angular range, thus allowing very precise relative cross section measurements. The absolute normalisation was determined with a typical accuracy of 5 %. This was verified in a simultaneous measurement of muon proton elastic scattering. The measured cross sections show some deviations from phase shift analysis predictions, in particular at large angles and low energies. From the new data we determine the real part of the isospin forward scattering amplitude.
Elastic PI- P cross section for incident kinetic energy 43.3 MeV for the rotated target data. Errors shown are statistical only.
Elastic PI- P cross section for incident kinetic energy 43.3 MeV. Errors shown are statistical only.
Elastic PI- P cross section for incident kinetic energy 37.1 MeV. Errors shown are statistical only.
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