Compton scattering from the proton was investigated at s=6.9 (GeV/c)**2 and \t=-4.0 (GeV/c)**2 via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in excellent agreement with a prediction based on a reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton and in disagreement with a prediction of pQCD based on a two-gluon exchange mechanism.
Polarization transfer parameters.
Diffractive dissociation of quasi-real photons at a photon-proton centre of mass energy of W 200 GeV is studied with the ZEUS detector at HERA. The process under consideration is gamma p -> X N, where X is the diffractively dissociated photon system of mass M_X and N is either a proton or a nucleonic system with mass M_N < 2GeV. The cross section for this process in the interval 3 < M_X < 24 GeV relative to the total photoproduction cross section was measured to be sigma~partial_D / sigma_tot = 6.2 +- 0.2(stat) +- 1.4(syst)%. After extrapolating this result to the mass interval of m_phi~2 < M_X~2 < 0.05 W~2 and correcting it for proton dissociation, the fraction of the total cross section attributed to single diffractive photon dissociation, gamma p -> X p, is found to be sigma_SD / sigma_tot = 13.3 +- 0.5(stat) +- 3.6(syst)%. The mass spectrum of the dissociated photon system in the interval 8 < M_X < 24 GeV can be described by the triple pomeron (PPP) diagram with an effective pomeron intercept of alpha_P(0) = 1.12 +- 0.04(stat) +- 0.08(syst). The cross section for photon dissociation in the range 3 < M_X < 8 GeV is significantly higher than that expected from the triple pomeron amplitude describing the region 8 < M_X < 24 GeV. Assuming that this discrepancy is due to a pomeron-pomeron-reggeon (PPR) term, its contribution to the diffractive cross section in the interval 3 < M_X < 24 GeV is estimated to be f_PPR = 26 +- 3(stat) +- 12(syst)%.
Fraction of the total photoproduction cross section attributed to the photon dissociation.
The fraction of the total photoproduction cross section due to single dif fractive photon dissociation, in the mass range M_phi**2 < M_DD < X >**2 < 0.05 *W**2.
Identification of the diffractive processes was performed on the basis of the shape of reconstructed hadronic mass spectrum. No rapidity-gap was required.
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DD IVENTS SELECTED BY THE RAPIDITY GAP METHOD.
/DD EVENTS SELECTED BY RAPIDITY GAP METHOD.
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Measurements are presented of two exclusive diffractive reactions, pp → (Λ 0 φ 0 K + ) p and pp → (Λ 0 Λ 0 p)p , at √ s = 63 GeV . Pronounced correlations with the beam direction are observed (in the rest frame of the forward-going bracketed system) for those outgoing particles which contain the beam valence quarks. In each case there is a forward-Λ 0 in correlation with a backward K + or p, respectively. No such behavior is seen for the particles which do not contain beam valence quarks (φ 0 and Λ 0 , respectively) . Interpreted as examples of pomeron-proton scattering, these results constitute evidence that, for these final states, the pomeron interacts with a single valence quark and apparently back-scatters it. The subsequent hadronization leads to a longitudinal event structure.
Cross sections for forward LAMBDA signal counting both arms of the p p interaction.
Cross sections for forward LAMBDA signal counting both arms of the p p interaction.
We report on experimental results on proton-deuteron elastic scattering at a centre-of-mass energy of √ s = 63 GeV . The data were obtained using the Split Field Magnet detector at the CERN Intersecting Storage Rings. The t -dependence of the elastic differential cross section, measured up to − t = 2.0 GeV 2 , is compared with the prediction of an extended Glauber theory including contributions from inelastic intermediate states. Discrepancies of up to 30% with the basic theory are observed in the interference region. The inelastic contributions are essential for the detailed description of the data both in the single- and double-scattering regions.
No description provided.
No description provided.
We report on experimental results on deuteron-deuteron elastic scattering at a centre-of-mass energy of √ s = 53 GeV . The data were obtained using the Split Field Magnet detector at the CERN intersecting Storage Rings. The t -dependence of the elastic cross section is measured up to − = 1.5 GeV 2 . We observed a narrow interference minimum in the differential cross section at − = 0.18 GeV 2 . The inclusion of inelastic intermeduate states in the multiple scattering Glauber theory is essential in the description of the data over the entire t -range where discrepancies of up to 25% are observed with the basic theory.
No description provided.
No description provided.
Σ + p elastic scattering has been studied using a scintillating fiber block (SCIFI) which served as a target for the production of Σ + hyperons as well as for subsequent Σ + scattering on hydrogen. A new technique for the analysis of the hyperon-nucleon scattering in the SCIFI has been developed and established. In this paper, Σ + p elastic scattering events have been identified in the Σ + momentum range of 300–600 MeV/ c , and differential cross sections have been obtained at two angles. The results are compared with various theoretical baryon-baryon interaction models.
No description provided.
Measurements of the differential cross section for proton-deuteron elastic scattering are reported for incident proton momenta ranging from 20 to 210 GeV and for invariant four-momentum transfers of 0.6 ≤ − t ≤ 3.0 GeV 2 . The results are in disagreement with a very simple Glauber double scattering model calculation.
Axis error includes +- 5/5 contribution (ERROR IN RECONSTRUCTION EFFICIENCY AND ACCEPTANCE CALCULATION).
The neutron-proton elastic differential cross section has been measured with high statistics for incident momenta between 10 and 24 GeV/ c using wire spark chambers for the neutron detection. The t -range covered by previous experiments could thus be extended to 0.06–3 (GeV/ c ) 2 . In this t -interval the np cross section is found to be very similar to the corresponding pp cross section.
No description provided.
No description provided.
No description provided.
Differential cross sections for p̄p elastic scattering have been measured in the full angular range for the p̄ momenta between 180 and 600 MeV/ c . It is found that s- and p-wave scattering is dominant below 300 MeV/ c . The s-wave component in the total cross section is 40–60% below 300 MeV/ c , in contrast to the NN scattering where it is about 90%. The s-, p- and d-wave scattering amplitudes are derived.
No description provided.
No description provided.
No description provided.
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