Inelastic intermediate states in proton-deuteron and deuteron-deuteron elastic collisions at the ISR

We present experimental results on proton-deuteron and deuteron-deuteron elastic scattering measured at the two highest ISR energies, √s = 53 GeV and √s = 63 GeV. The data cover the single- and multiple-scattering regions over a wide interval of four-momentum transfer t. In both reactions we find clear evidence for a substantial t-dependent contribution of inelastic intermediate states in the multiple-scattering region, as well as in single scattering. In the analysis we use the Glauber multiple-scattering theory extended to include inelastic shadow effects. This extension of the basic theory contains as input a triple-Regge parametrization describing the high-mass inclusive spectrum. The analysis of inelastic corrections to multiple scattering on deuterons at high energies is shown to provide a sensitive test of different parametrization of inclusive production in proton-proton collisions.     

Differential cross sections of proton compton scattering at photon laboratory energies between 700 and 1000 MeV

Differential cross sections of proton Compton scattering have been measured at the Bonn 2.5 GeV synchrotron. 78 data points are presented as angular distributions at photon lab energies of 700, 750, 800, 850, 900, and 950MeV. The c.m. scattering angle ranges from 40°–130°, corresponding to a variation of the four momentum transfer squared betweent=?0.10 tot=?0.96 GeV² at 700 and 950 MeV, respectively. Two additional differential cross sections have been measured at 1000MeV, 35.6° and 47.4°. The angular distributions show forward peaks whose extrapolations to 0° are consistent with calculated forward cross sections taken from literature. The small angle data (|t| ?0.2 GeV²) together with the calculated cross sections at 0° are also consistent with the assumption of a slope parameterB of 5 GeV^?2. For the first time a rerise of the angular distributions towards backward angles has been observed. It becomes less steep with increasing energy. The most interesting feature of the angular distributions is a sharp structure which appears betweent=?0.55 GeV² at 700MeV andt=?0.72 GeV² at 950 MeV. Such a rapid varation of the differential cross section witht has never been ovserved in elastic hadron-hadron scattering or photoproduction processes. It indicates the existence of a dynamical mechanism which could be a peculiarity of Compton scattering.     

Elastic scattering and coherent single pion production in proton-helium interactions at 18.6 GeV/c

Proton-helium elastic scattering and coherent single-pion production have been studied at 18.6 GeV/c in the four-momentum transfer region (?0.06, ?0.17) GeV/c². The elastic t-distribution has a somewhat steeper slope than is predicted by the Glauber approximation. The invariant-mass distribution of the Nπ system agrees with the double Regge-pole model except at about 1.65 GeV/c² where an enhancement presumably due to N¹ resonances is seen. The model also predicts the correct magnitude of the slope for nπ⁺α events. By using our cross sections at t′ = ?0.06 (GeV/c)² where the impulse approximation should be valid, the isospin-zero exchange elementary cross section for the nπ⁺ production is evaluated. The inelastic angular distributions are consistent with several spinparity states contributing at all Nπ masses.     

p-4He elastic scattering at 2.68 GeV

The p-⁴He elastic differential cross section has been measured at a kinetic energy of 2.68 GeV. The momentum transfer region studied is t = 0.15–0.66 (GeV/c)². The cross section displays a shallow first minimum and shape very similar to recent data at 1 GeV.     

Photoproduction of eta mesons from hydrogen

The differential cross section for eta photoproductions has been measured for incident photon energies of 4 and 8 GeV and momentum tranfers −t = 0.3 to 0.8 (GeV/c)².     

Measurement of the polarization parameter in pp elastic scattering at 150 GeV/c

The polarization parameter in pp elastic scattering at 150 GeV/c, and in the momentum transfer interval 0.4 ? ?t ? 3.0 GeV², has been measured in an MWPC and scintillation counter experiment at the CERN SPS using a polarized proton target. The polarization is decreasing steadily from zero to ≈ ? 10% in the range 0.4 < ?t < 1.3 GeV²; for higher |t| the data suggests a change of sign. Results are also given for the differential cross section, which exhibits a small dip at ?t = (1.46 ± 0.01) GeV.     

Evidence for a change of slope in large-t elastic proton-proton scattering at s=53 GeV

New experimental results are presented on proton-proton elastic scattering in the range of momentum transfer 4 GeV² < ?t < 10 GeV² at the centre-of-mass energy of √s = 53 GeV. The data have been obtained using the Split-Field Magnet detector at the CERN Intersecting Storage Rings. We observe another change of slope of the differential cross section near ?t=6.5 GeV².     

Compton-effect on π−-meson

The reaction π^? A→Aπ^? γ at 40 GeV/c was studied on “Sigma” spectrometer on six different nuclear targets in the region of four-momentum transfer |t|<0.05 (GeV/c)². A phenomenon of elastic scattering of pions on the nuclear Coulomb field photons was observed, its total and differential cross sections were measured. The cross section of Compton effect on π^?-meson was measured.     

Taking into Account the Centre-of-Mass Correlations in the Cross Sections for Elastic Scattering of Intermediate Energy Protons on the Exotic Nuclei <Superscript>6</Superscript>He and <Superscript>8</Superscript>He

We calculate the differential cross sections for proton elastic scattering on the exotic halo nuclei ⁶He and ⁸He at energies around ~0.7 GeV at the momentum transfers squared up to 0.30 (GeV/c)² and investigate the influence of the nucleon centre-of-mass correlations on the calculated cross sections. In particular, we show that the approximate account of the centre-of-mass correlations used previously considerably overestimates the cross sections at high values of the momentum transfer.     

Large t elastic proton-proton scattering at √s = 53 GeV

New experimental results are presented on proton-proton elastic scattering in the range of momentum transfer 0.8GeV² < ?t < 9 GeV² at a centre-of-mass energy of √s = 53 GeV. The data are obtained sing the Split-Field- Magnet Detector at the CERN Intersecting Storage Rings. The cross section has well-known minimum at ?t = (1.34±0.02) GeV² but no further minimum or change of slope is observed between 2 and 6.5 GeV².     

Neutron-proton elastic scattering from 10 to 70 GeV/c

The neutron-proton elastic differential cross section has been measured for incident momenta between 10 and 70 GeV/c and for values of the momentum transfer squared between 0.1 and 2.8 (GeV/c)². The forward peak and the break at about ∣t∣ = 1 (GeV/c)² are very similar to corresponding pp data.     

Diffractive one-pion production in the αp → αX process at Pα = 7.0 GeV/c

Inclusive coherent proton dissociation on helium has been measured for a missing mass near the threshold of one-pion production, in the |t| range 0.05–1.6 (GeV/c)² and at an alpha incident momentum of 7.0 GeV/c. A strong t-slope dependence of the cross section at |t| ? 0.2 (GeV/c)² is followed at larger |t| by a less structured distribution. Data were analyzed using the Glauber-Margolis formula and by assuming a peripheral elementary diffraction amplitude for the production process.     

High Energy Proton-Proton Elastic Scattering in the Pomeron Exchange Model

We study high energy proton-proton elastic scattering in the framework of Pomeron exchange model. The cross section of the process are calculated without any free parameters. Our finding is that Pomeron exchange theory gives perfect fits to total cross section at the energy of√s higher than 10 GeV and to differential cross section at the momentum transfer [t] less than 1.5 GeV2. For total cross section at lower energy √s ＜ 10 GeV and differential cross section at larger momentum transfer region of |t| ＞ 1.5 GeV2, the Pomeron exchange theory needs to be improved.     

Soft π−p and pp elastic scattering in the energy range 30 to 345 GeV

Differential cross sections for π^?p and pp elastic scattering have been measured at incident momenta ranging from 30 to 345 GeV and in the t range 0.002 (GeV/c)² ? |t| ? 0.04 (GeV/c)². From the analysis of the data, the ratio ? (t = 0) of the real to the imaginary parts of the forward scattering amplitude was determined together with the logarithmic slope b of the diffraction cone.The results on the real parts confirm the validity of the forward dispersion relations at high energies. Using the dispersion relations, it was shown that the experimental data on ?_{π?p(t = 0)} require a continuous rise of the total πp cross sections, at least up to the energy of 2000 GeV, thus revealing a close similarity in high-energy behaviour of πp and pp interactions.The results on the slope parameters from this experiment together with the analysis of the available world data demonstrate that the existing experimental data are consistent with the hypothesis of a universal shrinkage of the hadronic diffraction cone at high energies. The value of the asymptotic shrinkage parameter α_p^′ was found to be independent of the kind of the incident hadron and of the momentum transfer in the t range |t| ? 0.2 (GeV/c)² : 2α_{p^′ = ± 3 (GeV/c)^?2}.     

Inelasticity corrections in the elastic proton-deuteron back-angle scattering at intermediate energies

The elastic proton-deuteron scattering cross sections at back angles have been calculated in the light of Kerman-Kisslinger model, using a generalised baryon transfer mechanism on the assumption that theN ^*'s exist (with a probability～1 %) in the deuteron and that the backward peak is caused by their exchange. The effect of numerous competing open inelastic channels at intermediate energies on the elastic cross section is computed in a particularly simple model of Sopkovich. The resultant damping of the back scattering amplitude is expressed directly in terms of the forward angle elastic scattering data. The results are compared with the experimental cross sections in the energy range of 1.5–2.5 GeV.     

Elastic antiproton-deutron scattering below 1.0 GeV/c

We present differential cross sections for elastic $\text{p}$d scattering at beam momenta 0.735 and 0.940 GeV/c and momentum transfers in the range 0.04<|t|<0.5(GeV/c)². The $\text{p}$d elastic differential cross section is expressed in terms of a deutron form factor and the I=0 t-channel exchange $\text{N}$N amplitudes, enabling us to isolate the corresponding I=0 t-channel exchange cross sections.     

Physics (and technique) of gas jet experiments

Recently gas jet targets have been used for the study of small momentum transfer p-p and p-d elastic and inelastic scattering. In these experiments, which were performed at Serpukhov in the USSR and at the Fermilab in the USA, the gas jet is introduced in the main ring of the accelerator. We review the techniques associated with these measurements and summarize the published results which cover 4-momentum transfers 0.001< |t|< 0.12 (GeV/c)^?2 and incident energies 8<E< 400 GeV. Elastic scattering data have yielded precise values for the slope of the nuclear scattering amplitude and for the ratio of the real to imaginary part as a function of energy. The implications of these data on the understanding of high energy hadronic interactions are discussed in some detail. We also present and discuss information on the diffractive dissociation of the proton to low mass states, obtained from inelastic scattering using the gas jet target.     

Coulomb-nuclear interference in π±p and K±p elastic scattering below 3 GeV: Measurements,real parts and K±p dispersion relations

The differential cross sections for π⁺p elastic scattering at0.6, 1.0, 1.5, 2.0, GeV/c for π^-p at 1.0, 1.5, 2.0 GeV/c, for K^-p at 1.2, 1.8, 2.6 GeV/c and for K^-p at 0.9, 1.2, 1.4, 1.6, 1.8, 2.6 GeV/c have been measured with an overall accuracy ofthe order of 1 to 2% in an electronics experiment over the angular region corresponding to momentum transfer t between 0.0005 and 0.10 GeV². Making use of the interference effects between the Coulomb and the nuclear interaction, we have determined the magnitude and sign of the real part of the scattering amplitude near t = 0. The K^±p real parts have been used in a dispersion relation to derive the value of the KNΛ coupling constant.     

The four-momentum transfer distribution for the deuteron break up at 3.3 GeV/c incident deuteron momentum

The differential cross section (dσ/dt) for the dp → ppn charge retention reaction at 3.3 GeV/c deuteron momentum is studied and compared with the Glauber multiple scattering theory. Within the limits of the uncertainties of the existing elementary nucleon-nucleon data, the simple Glauber model calculations give, in general, a fair agreement with experiment, except for the low |t| region where possible spin effects may play a role.     

Event structure investigation of AuAu interactions from HIJING model using fractal dimensions

This work presents an implementation of fractal geometry methods in the study of event structure for AuAu interactions at collision energies √s _NN = 9.2, 62 and 200 GeV for different interaction dynamics. The events are generated by using the HIJING model. It is shown, that the fractal dimension of events in phase space projections rapidity-transverse momentum (y - p_t) and azimuthal angle-transverse momentum (φ - p_t) are sensitive to the interaction dynamics.