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The single-pion production reactions $pp\to d\pi^+$, $pp\to np\pi^+$ and $pp\to pp\pi^0$ were measured at a beam momentum of 0.95 GeV/c ($T_p \approx$ 400 MeV) using the short version of the COSY-TOF spectrometer. The implementation of a central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements. Thus all pion production channels were recorded with 1-4 overconstraints. The total and differential cross sections obtained are compared to previous data and theoretical calculations. Main emphasis is put on the discussion of the $pp\pi^0$ channel, where we obtain angular distributions different from previous experimental results, however, partly in good agreement with recent phenomenological and theoretical predictions. In particular we observe very large anisotropies for the $\pi^0$ angular distributions in the kinematical region of small relative proton momenta revealing there a dominance of proton spinflip transitions associated with $\pi^0$ $s$- and $d$-partial waves and emphasizing the important role of $\pi^0$ d-waves.
Measured angular distribution for elastic P P scattering in the CM system normalised to the data in the SAID database (Arndt et al. PR C62,034005(2000). This measurement is made to determine the luminosity.
Cross sections or upper limits are reported for 12 meson-baryon and two baryon-baryon reactions for an incident momentum of 9.9 GeV/c, near 90° c.m.: π±p→pπ±,pp±,π+°±,K+Σ±, (Λ0/Σ0)K0; K±p→pK±; p±p→pp. By studying the flavor dependence of the different reactions, we have been able to isolate the quark-interchange mechanism as dominant over gluon exchange and quark-antiquark annihilation.
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We present preliminary results on the measurement of a variety of exclusive hadron interactions at center of mass scattering angles of 90°. Data are also presented which show the relative transparency of nuclei to πp and pp elastic scattering in this kinematic range.
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The polarization parameter in elastic proton-proton scattering has been measured at 0.75, 1.03, 1.32, 1.63, 2.24, and 2.84 GeV by employing a double-scattering technique. An external proton beam from the Brookhaven Cosmotron was focused on a 3 in.-long liquid-hydrogen target and the elastic recoil and scattered protons were detected in coincidence by scintillation counters. The polarization of the recoil beam was determined from the azimuthal asymmetry exhibited in its scattering from a carbon target. This asymmetry was measured by a pair of scintillation-counter telescopes which symmetrically viewed the carbon target. The analyzing power of this system was previously determined in an independent calibration experiment employing a 40%-polarized proton beam at the Carnegie Institute of Technology synchrocyclotron. False asymmetries were cancelled to a high order by periodically rotating the analyzer 180° about the recoil beam line. Spark chambers were utilized to obtain the spatial distribution of the beam as it entered the analyzer; this information allowed an accurate determination of the corrections necessary to compensate for any misalignment of the axis of the analyzer relative to the incident-beam centroid. Values of the polarization parameter as a function of the center-of-mass scattering angle are given for each incident beam energy. The predictions of the Regge theory for polarization in elastic proton-proton scattering and recently published phase-shift solutions are compared with the experimental results. Surprisingly good agreement with the Regge predictions is found despite the low energies involved.
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Excitation functions of proton-proton elastic scattering cross sections have been measured in narrow steps for projectile momenta pp (energies Tp) from 1100 to 3300MeV/c (500 to 2500 MeV) in the angular range 35°≤Θc.m.≤90° with a detector providing ΔΘc.m.≈1.4° resolution. Measurements have been performed continuously during projectile acceleration in the cooler synchrotron COSY with an internal CH2 fiber target, taking particular care to monitor luminosity as a function of Tp. The advantages of this experimental technique are demonstrated, and the excitation functions obtained are compared to existing cross section data. No evidence for narrow structures was found.
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Differential cross sections for elastic π±−p scattering have been measured at lab momenta of 8 and 12 GeV/c in a momentum-transfer region corresponding to 1.2≤−t≤6 (GeV/c)2. Also, differential cross sections near 180° were measured for 4 and 8 GeV/c pions. At momentum transfers greater than −t=2 (GeV/c)2, the π−p cross sections drop much faster with increasing angle than the corresponding p−p cross sections. Also, in the region −t≃1.3 (GeV/c)2, there is structure in the π−p angular distribution but not in the p−p angular distribution. At −t≃3 (GeV/c)2, the drop in cross section appears to stop and from then on the angular distribution is consistent with isotropy. But in the angular region 170° to 180°, the cross sections have become much larger, and sharp backward peaks are observed. Information is given on the energy and charge dependences and widths of these backward peaks.
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The polarization P in proton-proton elastic scattering has been measured at 3.83 GeV/ c for 0.35 ⩽ | t | ⩽ 3.0 (GeV/ c ) 2 , i.e. 29° ⩽ θ c.m. ⩽ 93°. The polarization shows a minimum at − ⋍ 1.0 ( GeV /c) 2 followed by a maximum at −⋍1.5 ( GeV /c) 2 . At the same energy the spin rotation parameter R has been measured in the interval 0.18 ⩽ | t | ⩽ 0.57 (GeV/ c ) 2 . Comparison with the results at 6.0 and 15.75 GeV/ c shows a similar t -dependence and the same average value at all three energies.
POLARIZED TARGET ASYMMETRY EQUALS RECOIL PROTON POLARIZATION BY TIME REVERSAL INVARIANCE.
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The parameters D, R, R' and P for pp elastic scattering have been measured in the centre-of-mass angular range 13 degrees to 58 degrees with an accuracy of about +or-0.02 at 209, 324, 379, 425 and 515 MeV. These results are incorporated with earlier data into a phase-shift analysis. Phase-shifts are generally in agreement with the theoretical predictions of the Paris group, although the F-wave spin-orbit combination is rather stronger than predicted. The fitted value for the pi 0pp coupling constant in g02=14.06+or-0.65.
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The spin rotation parameter R in elastic proton-proton scattering has been determined at incident momenta 6 and 16 GeV/ c in the interval from t = −0.18 (GeV/ c ) 2 to −0.54 (GeV/ c ) 2 . R pp at 16 GeV/ c is close to the val obtained for R in π − p elastic scattering at the same incident momentum. Equality of R pp ( s , t ) and R π p ( s , t ) is expected if Pomeron exchange dominates and if factorization holds. The t -dependence of R at 16 GeV/ c is consistent with weak helicity flip.
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