Analyzing powers for πp elastic scattering were measured using the CHAOS spectrometer at energies spanning the Δ(1232) resonance. This work presents π+ data at the pion kinetic energies 117, 130, 139, 155, 169, 180, 193, 218, 241, and 267 MeV and π− data at 87, 117, 193, and 241 MeV, covering an angular range of 50°<~θc.m.<~180° at the higher energies and 90°<~θc.m.<~180° at the lower energies. Unique features of the spectrometer acceptance were employed to reduce systematic errors. Single-energy phase shift analyses indicate the resulting S11 and S31 phases favor the results of the SM95 phase shift analysis over that of the older KH80 analysis.
Measurement of the PI+ analysing power at 117 MeV.. The data were collected in the conventional mode and may be independently floated within the systematic error.
Measurement of the PI+ analysing power at 139 MeV.. The data were collected in the conventional mode and may be independently floated within the systematic error.
Measurement of the PI- analysing power at 87 MeV.. The data were collected in the conventional mode and may be independently floated within the systematic error.
The electromagnetic form factors of the neutron in the time-like region have been measured for the first time, from the threshold up to q 2 ⋟ 6 GeV 2 . The neutron magnetic form factor turns out to be larger than the proton one; the angular distribution suggests that for the neutron, at variance with the proton case, electric and magnetic form factors could be different. Further measurements are also reported, concerning the proton form factors and the Σ Σ production, together with the multihadronic cross section and the J / Γ branching ratio into n n .
The uncertainty on the evaluated cross section is given by the quadratic combination of the following terms: the statistical uncertainty on the number of events, the statistical and systematic uncertainty on the luminosity (about 6PCT), the systematic uncertainty on the efficiency evaluation, dominated by the scanning efficiency contribution (about 15PCT). The SQRT(S) values with (C=NOMIN) and (C=SHIFT) correspond to the nominal energy and shifted energy analysis (see text of paper for details).
The uncertainty on the evaluated cross section is given by the quadratic combination of the following terms: the statistical uncertainty on the number of events, the statistical and systematic uncertainty on the luminosity (about 6PCT), the systematic uncertainty on the efficiency evaluation, dominated by the scanning efficiency contribution (about 15PCT). The NEUTRON formfactor value are calculated in two hypotheses: GE = GM and GE = 0.
The uncertainty on the evaluated cross section is given by the quadratic combination of the statistical and systematic uncertainties.
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.
This paper presents a large solid angle measurement of the positive pion absorption cross section on 4He and its decomposition into partial channels. The total absorption cross sections at incident pion kinetic energies of Tπ+=70, 118, 162, and 239 MeV are 35±5, 52±4, 51±5, and 27±2 mb, respectively. These values are lower than those reported in some previous experiments. At all pion energies a large fraction of the absorption cross section is due to multinucleon channels.
Data with (C=PRC) are taken from PR C56, 1872.
The total cross section of the 4He(π+,π−) reaction was measured for π+ kinetic energies ranging from 70 to 130 MeV using the CHAOS spectrometer at TRIUMF and a liquid 4He target. Around Tπ=90MeV, total cross sections exceed conventional model predictions by a factor of 3, whereas at Tπ=70MeV and for Tπ>130MeV the data are consistent with these calculations. An attempt is made to understand this behavior by assuming the production of the hypothetical d′ dibaryon.
Double charge exchange reaction. section.
A systematic study of the spectra and yields of K+ and K− is reported by experiment E866 as a function of centrality in Au+Au collisions at 11.6A GeV/c. The invariant transverse spectra for both kaon species are well described by exponentials in mt, with inverse slope parameters that are largest at midrapidity and which increase with centrality. The inverse slopes of the K+ spectra are slightly larger than the inverse slopes of the K− spectra. The kaon rapidity density peaks at midrapidity with the K+ distribution wider in rapidity than K−. The integrated total yields of K+ and K− increase nonlinearly and steadily with the number of projectile participants. The yield per participant for kaons is two to three times larger than the yield from N−N collisions. This enhancement suggests that the majority of kaons in central Au+Au reactions are produced in secondary hadronic collisions. There is no evidence for an onset of additional kaon production from a possible small volume of baryon-rich quark-gluon plasma. The differences between K+ and K− rapidity distributions and transverse spectra are consistent with a lower phase space for K− production due to a higher energy threshold. These differences also exclude simple thermal models that assume emission from a common equilibrated system.
In this case FRAGB=NUCLEAR FRAG + PROTONS.
In this case FRAGB = NUCLEAR FRAG + PROTONS.
A nonzero difference of the analyzing powers due to charge symmetry breaking has been measured with high precision in np elastic scattering at a neutron beam energy of 347 MeV. The neutron beam and proton target were alternately polarized for the measurements of An and Ap. A mirror-symmetric detection system was used to cancel geometry-related systematic errors. From fits of the measured asymmetry angular distributions over the range of 53.4°<~θcm<~86.9°, the difference in the zero-crossing angles of the analyzing powers was determined to be 0.438°±0.054°(stat.)±0.051°(syst.) in the center-of-mass system. Using the experimentally determined slope of the analyzing power dA/dθ=(−1.35±0.05)×10−2 deg−1 (c.m.), this is equivalent to ΔA≡An−Ap=[59±7(stat.)±7(syst.)±2(syst.)]×10−4. The shape of ΔA(θ) in the vicinity of the zero-crossing angle has also been extracted. Predictions of nucleon-nucleon interaction models based on meson exchange agree well with the results.
(C=N) or (C=P) stands for polarized beam or target.
The pion induced pion production reactions π±p→π+π±n were studied at projectile incident energies of 223, 243, 264, 284, and 305 MeV, using a cryogenic liquid hydrogen target. The Canadian High Acceptance Orbit Spectrometer was used to detect the two outgoing pions in coincidence. The experimental results are presented in the form of single differential cross sections. Total cross sections obtained by integrating the differential quantities are also reported. In addition, the invariant mass distributions from the (π+π−) channel were fitted to determine the parameters for an extended model based on that of Oset and Vicente-Vacas. We find the model parameters obtained from fitting the (π+π−) data do not describe the invariant mass distributions in the (π+π+) channel.
Total cross sections were obtained by integrating the differential cross section over all three variables: M(pi,pi)**2, t, Cos(Theta(pi)).
Total cross sections were obtained by integrating the differential cross section over all three variables: M(pi,pi)**2, t, Cos(Theta(pi)).
The production of Λ hypernuclei was studied in proton reactions with Bi nuclei and the lifetime of the produced heavy hypernuclei was measured by the observation of delayed fission using the recoil shadow method. The measurements were performed at 1.9 GeV proton energy whereas the background was determined at 1.0 GeV. From the distribution of the fission fragments in the shadow region the lifetime τ=[161±7( statist. )±14( system. )] ps was obtained and from a comparison of counting rates of prompt and delayed fission fragments the production cross section of hot Λ hypernuclei was determined to be (350±140) μ b.
No description provided.
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.
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