The spin correlation parameter A00NN for 497.5 MeV proton + proton elastic scattering was determined over the center-of-momentum scattering angle region 23.1°–64.9 °. The new A00NN extend to more forward angles than existing A00NN and have significantly smaller statistical errors (±0.01–0.04). The A00NN are qualitatively described by recent phase shift analyses, but a quantitative shape and normalization discrepancy remains in the forward angle region. These new data provide important constraints for nucleon-nucleon spin-dependent amplitudes at forward angles which are used in theoretical models of nucleon-nucleus scattering.
Errors include statistical and systematic uncertainties.
The total cross sections σT of p, p¯, π±, and K± on hydrogen and deuterium have been measured between 6 and 22 GeVc at intervals of 2GeVc to an accuracy greater than previously reported. The method utilized was a conventional good-geometry transmission experiment with scintillation counters subtending various solid angles at targets of liquid H2 and D2. With the increase in statistical accuracy of the data, it was found that a previously adopted procedure of linearly extrapolating to zero solid angle the partial cross sections measured at finite solid angles was not a sufficiently accurate procedure from which to deduce σT. The particle-neutron cross sections are derived by applying the Glauber screening correction to the difference between the particle-deuteron and particle-proton cross sections. The cross sections σT(π+d) and σT(π−d) are equal at all measured momenta, which confirms the validity of charge symmetry up to 20GeVc. Results are presented showing the variation of cross sections with momentum; evidence is presented for a small but significant decrease in σT(pp) [and σT(pn)] in the momentum region above 12GeVc.
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The absolute differential cross section for proton-proton elastic scattering has been measured at 90° c.m. for 300, 350, 400, 450 and 500 MeV. The statistical uncertainty of the measurements is 0.5% with an additional systematic normalization uncertainty of 1.8%. The results are compared to phase-shift analyses.
The statistical and systematic errors are added in quadrature.
Excitation functions AN(pp,Θc.m.) of the analyzing power in pp→ elastic scattering have been measured with a polarized atomic hydrogen target for projectile momenta pp between 1000 and 3300 MeV/ c. The experiment was performed for scattering angles 30°≤Θc.m.≤90° using the recirculating beam of the proton storage ring COSY during acceleration. The resulting excitation functions and angular distributions of high internal consistency have significant impact on the recent phase shift solution SAID SP99, in particular, on the spin triplet phase shifts between 1000 and 1800 MeV, and demonstrate the limited predictive power of single-energy phase shift solutions at these energies.
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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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We have measured the spin-correlation parameters A00kk, A00ks, and A00ss in p−p scattering between 400 and 600 MeV using a longitudinally polarized beam and a butanol target polarized in the horizontal plane. Owing to the restrictive geometrical acceptance of the target, the polarization axis of the target was oriented at an angle α with respect to beam direction. The parameters A00kk and A00ks were therefore measured as a linear combination at 577, 536, 514, 494, and 445 MeV. These experiments were extended to the measurement of A00ks and A00ss by using a transversely polarized beam. We present the results, which are compared with phase-shift predictions.
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At the Cooler Synchrotron COSY/J\ulich spin correlation parameters in elastic proton-proton (pp) scattering have been measured with a 2.11 GeV polarized proton beam and a polarized hydrogen atomic beam target. We report results for A$_{NN}$, A$_{SS}$, and A_${SL}$ for c.m. scattering angles between 30$^o$ and 90$^o$. Our data on A$_{SS}$ -- the first measurement of this observable above 800 MeV -- clearly disagrees with predictions of available of pp scattering phase shift solutions while A$_{NN}$ and A_${SL}$ are reproduced reasonably well. We show that in the direct reconstruction of the scattering amplitudes from the body of available pp elastic scattering data at 2.1 GeV the number of possible solutions is considerably reduced.
Spin correlation parameters.
Recent data are presented on spin-spin correlation parameters CLL=(L,L;0,0) and CSL=(S,L;0,0) at forward angles from 1.18 to 2.47 GeV/c incident momenta in proton-proton elastic scattering. Values for ΔσL (inelastic) are derived and are shown to disagree with predictions of theoretical models attempting to describe p−p scattering without dibaryon resonances. Finally, the CLL and CSL data discriminate among various phase-shift solutions, and will lead to a clarification of the p−p phase shifts.
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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.
Total cross section measurements.. Errors are mainly systematic.
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.
The measured pion angular distribution in the CM system in the reaction P P --> DEUT PI+.
The differential elastic p−p scattering cross section was measured at 6 GeV/c at the Argonne Zero Gradient Synchrotron in the range P⊥2=0.60−1.0 (GeV/c)2 using a 65% polarized target and a 75% polarized proton beam of intensity 3 × 109 protons/pulse. The polarization of the recoil proton was simultaneously measured with a well calibrated carbon-target polarimeter. All three polarizations were measured perpendicular to the horizontal scattering plane. Our results indicate that P and T invariance are both obeyed to good precision even at our largest P⊥2. Parity invariance implies that the eight single-flip transversity cross sections are zero, so our data gives the magnitudes of the eight remaining pure spin cross sections where all spins are measured. We find that the four double-flip transversity cross sections are nonzero.
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THE FIVE INDEPENDENT PURE FOUR-SPIN CROSS SECTIONS AS DERIVED FROM THE EIGHT MEASURED THREE-SPIN CROSS SECTIONS ASSUMING P AND T INVARIANCE. THE ABSOLUTE DIFFERENTIAL CROSS SECTION VALUES ASSUME THAT THE SPIN-AVERAGED D(SIG)/DT IS 2.25, 1.17, 0.365 AND 0.167 MB/GEV**2 FOR EACH VALUE OF PT**2 RESPECTIVELY.
WOLFENSTEIN PARAMETERS. POL(NAME=A) IS (N000) OR (0N00), THE ANALYZING POWER AVERAGED OVER TARGET OR BEAM POLARIZATION. POL(NAME=P) IS (00N0), THE POLARIZATION PARAMETER. TIME-REVERSAL INVARIANCE REQUIRES THAT P = A. POL.POL(NAME=CNN) IS (NN00) USING T-INVARIANCE. POL.POL(NAME=DNN) IS (0N0N). POL.POL(NAME=KNN) IS (N00N). POL.POL(NAME=C3N) IS A COMPONENT OF THE TRIPLE SPIN CORRELATION TENSOR. PARITY INVARIANCE REQUIRES THAT C3N = P.
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