The spin-rotation parameters A and R and the related spin-rotation angle β have been measured for π+p and π−p elastic scattering using protons polarized in the scattering plane. The pion-beam momenta are 427, 471, 547, 625, and 657 MeV/c and the angular range is −0.9≤cosΘc.m.≤0.3. The scattered pion and recoil proton were detected in coincidence, using a scintillator hodoscope for the pions, and the Large Acceptance Spectrometer combined with the JANUS polarimeter for the recoil protons. The results are compared with the four recent πN partial wave analyses (PWA's). Our data show that the major features of these PWA's are correct. The A and R measurements complete our program of pion-nucleon experiments, providing full data sets at three of the above beam momenta. Such sets can be used to test the constraints in the PWA's or to obtain a model-independent set of πN scattering amplitudes.
BETA is the spin-rotation angle.
BETA is the spin-rotation angle.
BETA is the spin-rotation angle.
It is shown that the energy dependence of charge-exchange a2+ photoproduction (γp→na2+) agrees with a one-pion exchange mechanism. No evidence for the photoproduction of the a1+(1260) is observed. If the dynamics of a1 and a2 photoproduction are assumed to be the same, the absence of evidence for the a1 is shown to be consistent with either an extremely large a1 hadronic width or with an a1 of mass somewhat less than 1260 MeV.
No description provided.
The yields and average transverse momenta of pions, kaons, and antiprotons produced at the Fermilab p¯p collider at s=300, 540, 1000, and 1800 GeV are presented and compared with data from the energies reached at the CERN collider. We also present data on the dependence of average transverse momentum 〈pt〉 and particle ratios as a function of charged particle density dNcdη; data for particle densities as high as six times the average value, corresponding to a Bjorken energy density 6 GeV/fm3, are reported. These data are relevant to the search for quark-gluon phase of QCD.
PT RANGE FROM 0 TO INFINITY.
PT RANGE FROM 0 TO INFINITY.
No description provided.
The reaction γ+d → π++π−+p + n has been measured in a kinematically complete way at incident photon energies from 570 to 850 MeV in steps of 40 MeV. From detailed comparison of measured data with results of event simulations, it is concluded that three different mechanisms, the quasi-free, double-delta and phase space productions, contribute to the reaction. Each of the cross sections corresponding to these mechanisms is determined separately.
SYSTEMATIC ERRORS ARE NOT INCLUDED.
SYSTEMATIC ERRORS ARE NOT INCLUDED.
Polycarbonate track detector Makrofol, sensitive to fragments withA≧16 was used to register products of interactions of 6.3 GeV deuterons with Th, Bi, Au, and Ag. Cross sections for the production of events with one, two and three fragments have been determined and their variation as a function of theZ2/A of the target analyzed. Possible mechanisms were proposed and discussed. Geometric characteristics of binary events were used in order to identify those binary events which resulted from the process of fission. The results were compared with corresponding proton data.
Cross sections for the production of events with one, two and three fragments have been determined.
The subthreshold production of neutral pions was studied in the reactions 24 Mg(α,π 0 )X at 43 MeV·. A and 24 Mg( 16 O,π 0 )X at 24 and 33 MeV·. A . The energies and emission angles of the two coincident photons from the π 0 -decay were measured with a lead glass shower detector. The cross sections of 3.5 and 6.6 nb from the 16 O-induced reactions are compatible with other experiments in this energy region. For the α-induced reaction a production cross section of 1.3 nb was found. Here, only 22 MeV above the absolute threshold, the pion emission from an excited Δ -nucleon hole state is strongly suppressed. The differential cross sections at very backward angles are by an order of magnitude bigger than the yields at 90° pointing to a strong absorption of the produced pions by the larger target nucleus.
No description provided.
Antinucleon-nucleus annihilations into two-body final states containing only one or no meson are unusual annihilations (Pontecorvo reactions), practically unexplored experimentally, with the exception of the channel p d → π − p , for which only two low-statistics measurements exist. Their physical interest lies in the possibility of exploring small-distance nuclear dynamics, in which an important role can be played by non-nucleonic degrees of freedom. A new measurement of the p d → π − p reaction rate at rest, performed with the OBELIX spectrometer at LEAR, with the best statistics up to now and a careful evaluation of systematic effects is reported, together with a critical analysis of the existing theoretical models. The measured branching ratio, which confirms the previous results, can represent a reference point for the studies in the field.
No description provided.
The differential cross section for n-p elastic scattering at 459 MeV in the c.m. angular region 50°<θ*<180° has been measured with high statistical precision and good relative accuracy. The uncertainty in the absolute normalization (based on the simultaneously measured yield of deuterons from the np→dπ0 reaction) was initially estimated to be ∼7%. The results agree well with back-angle data obtained independently at LAMPF but less well with results from Saclay and the Princeton-Pennsylvania Accelerator and, except for a normalization difference of 10%, are fairly well represented by a phase-shift fit. The pole-extrapolation method of Chew was used to extract the pion-nucleon coupling constant f2 from the back-angle portion of the data. The value obtained, f2=0.069, is somewhat smaller than the values 0.0735–0.0790 obtained from analyses of pion-nucleon scattering, tending to confirm the need for an upward renormalization of the angular distribution by ∼10%.
No description provided.
It is shown that in interactions of protons at 200, 300, and 400 GeV, and negative pions at 300 GeV with emulsion nuclei, the scaling of the multiplicity of relativistic charged secondaries is valid and described by a linear function of the scaling variable, z.
No description provided.
No description provided.
Absolute pp-elastic-differential cross sections were measured at incident energies 492, 576, 642, 728, and 793 MeV from about 30° to 90° c.m. The total uncertainty was determined to be less than 1%, made possible by particle counting for beam normalization and extensive cross-checks of systematic effects. These new data are consistent with previous data above 600 MeV but have uncertainties about a factor of 10 smaller. Near 500 MeV these data are consistent with 90° data from TRIUMF, but differ significantly from similar data from PSI; the cause of this discrepancy is discussed.
No description provided.
No description provided.
No description provided.
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