Elastic backward scattering of negative pions on protons at 25 and 38 GeV/c

The backward elastic scattering reaction π^?p → pπ^? at momenta 25 and 38 GeV/c have been measured using a magnetic spectrometer with hybrid chambers. The experimental data on the dependence of the cross section dσ/du on the momentum transfer u as well as the energy dependence dσ/du at u = 0 are given.     

Elastic scattering of polarized deuterons by protons at intermediate energies

The tensor analyzing power T₂₀(θ) in dp backward scattering has been measured at or near center-of-mass angle θ = 180° in the energy range 0.3–2.3 GeV. A pronounced structure is observed around T_d = 0.5 GeV which is explained by a predominant one-neutron-exchange mechanism. Other structures appear around 1 GeV and higher. They are not explained by calculations which include Δ-excitations in intermediate states. In addition, full angular distributions of vector A_y and tensor A_yy analyzing powers and differential cross sections have been obtained at 1.2 GeV and limited angular ranges explored at 0.5 GeV (back angles) and 1.6 GeV (forward angles).     

The pion-nucleon scattering amplitudes at 40 GeV/c

The helicity amplitudes for isospin-0 exchange are determined at 40 GeV/c. For isospin-1 exchange only partial information is obtained. The model-independent analysis is extended to the four-momentum transfer interval from t = 0 to t = ?0.6 (GeV/c)². One of the two solutions presented has a behaviour similar to the previous results at lower energy.     

Semicoherent elastic pion-carbon scattering at 25 and 40 GeV/c

In the frame of a systematic study of hadron-nucleus interactions performed at the Serpukhov accelerator (CERN-IHEP 5th experiment), semicoherent elastic scattering on carbon $\text{π}{}^{\mathrm{?12}}\text{C}\text{a}\text{?}\text{π}{}^{\mathrm{?12}}\text{C}{}^1\text{(4.44}\text{MeV}\text{)}$ was investigated with 25 and 40 GeV/c incident pions.The experimental data were obtained with a counter technique, looking at the coincidence between the scattered pion and the 4.44 MeV photon from the J^P = 2⁺ carbon excited state detected by a NaI counter.The value obtained for the integrated cross section at 40 GeV/c in the 0.0032 ? |t| ? 0.27 (GeV/c)² four-momentum transfer range isσ = 1.16 ± 0.11 mb.According to the theoretical models, this t-range at 40 GeV/c covers more than 99% of the angular distribution, so the above value almost corresponds to the total semicoherent elastic cross section.     

Compton scattering of 3.5 GeV polarized photons on protons

Elastic scattering of linearly polarized photons on protons has been measured between 3.2 and 3.7 GeV for four-momentum transfers ranging from −0.1 to −0.7 (GeV/c)². The observed cross section asymmetry in this range is consistent with zero within ±0.05.     

K+P elastic scattering at 32 GeV/c

Elastic scattering of 32.1 GeV/c K⁺ on protons has been measured in a bubble chamber experiment. Results are presented in the momentum transfer interval 0.06–1.40 GeV² and compared with data at different energies. An effective Regge trajectory is calculated using K⁺p elastic data from 10 to 175 GeV/c.     

K−p elastic scattering at 14.3 GeV/c

Results are presented of a bubble chamber experiment on K^?p elastic scattering at 14.3 GeV/c, in four-momentum transfer range 0.04 < |t| < 2.74 GeV² using an initial set of 40 000 events. The total elastic cross section is (2.96 ± 0.10) mb. The results are compared with K⁺p elastic scattering data at 13.8 GeV/c, and the effective Regge trajectory is calculated using K^?p data from 5 to 100 GeV/c.     

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.     

Measurement of diffractive 3π production on a polarized target at 17 GeV/c

The reaction π^?p↑→π^?π⁺π^?p has been measured at 17 GeV/c using a polarized target. The data sample contains about 60 000 interactions on polarized protons. The nucleon polarization as a function of momentum transfer is very similar to elastic π^?p scattering and is nearly independent of the π mass, except for a possible structure around 1.2 GeV.Using the isobar model, we have performed a partial-wave analysis and extracted the 3π amplitudes. The generalized 3π density matrix elements agree with earlier determinations. Relative phases obtained from density matrix elements agree well with the ones obtained from transversity amplitudes. This proves the validity of the coherence assumption made in the interpretation of unpolarized target results. Our results confirm the existence of an A₁ resonance in the region 1.2–1.3 GeV.     

Measurement of polarization in K−p elastic scattering between 0.955 GeV/c and 1.272 GeV/c

The polarization parameter has been measured for K^?p elastic scattering at nine incident beam momenta between 0.955 and 1.272 GeV/c covering the c.m. angular range $\text{?0.9 < cos θ}{}^1\text{< + 0.9}$. Experimental results and coefficients of Legendre polynomial fits to the data are presented and compared with other measurements and a partial-wave analysis.     

Neutrino scattering on polarized deuterons

The possible presence of anI=0 axial vector piece in the hadronic neutral current may be detected by looking for an asymmetry in the emission of the recoil deuterons in elastic scattering of neutrinos or antineutrinos on polarized deuterons. It is estimated that this asymmetry could be about 40% with the incident neutrinos in the energy range of tens of MeV.     

Elastic scattering of 0.8 GeV polarized protons from 46,48Ti

Differential cross sections and analyzing powers for elastic scattering of 800 MeV polarized protons from ^46,48Ti have been measured at laboratory angles ranging between 4° and 21°. The data are analyzed within the spin-dependent KMT formalism. Neutron density distributions are extracted and compared with the results of other experiments and with theoretical predictions. Disagreements between empirical results and DME calculations are found.     

Angular distributions of channeled pions and protons up to 250 GeV/c

Channeling phenomena are observed for positive particles of momentum up to 250 GeV/c in a germanium crystal. The polar angular distributions of the channeled particles are compared with theoretical predictions based on a diffusion model. The results indicate that at high particle energy there may be additional mechanisms besides those operative at low energy leading to dechanneling of the particles. In spite of this, channeling effects are observed for particles incident at up to several times the critical angle, in contrast with the results from low energy channeling. Statistical equilibrium in the azimuthal angular distribution has also been observed at all measured beam momenta to about twice the calculated channeling critical angle. The breakdown of statistical equilibrium for the 2 cm crystal used occurs at an incident angle 2–3 times smaller than predicted theoretically.     

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.     

Observation of parametric X-rays produced by 400 GeV/c protons in bent crystals

Spectral maxima of parametric X-ray radiation (PXR) produced by 400 GeV/c protons in bent silicon crystals aligned with the beam have been observed in an experiment at the H8 external beam of the CERN SPS. The total yield of PXR photons was about 10⁻⁶ per proton. Agreement between calculations and the experimental data shows that the PXR kinematic theory is valid for bent crystals with sufficiently small curvature as used in the experiment. The intensity of PXR emitted from halo protons in a bent crystal used as a primary collimator in a circular accelerator may be considered as a possible tool to control its crystal structure, which is slowly damaged because of irradiation. The intensity distribution of PXR peaks depends on the crystal thickness intersected by the beam, which changes for different orientations of a crystal collimator. This dependence may be used to control crystal collimator alignment by analyzing PXR spectra produced by halo protons.     

Measurement of neutron-proton charge exchange scattering at 8, 19 and 24 GeV/c

The t-dependence of the differential cross-section for elastic neutron-proton charge exchange scattering has been measured at 8, 19.2 and 24 GeV/c. The extremely narrow peak in the forward direction, previously observed for momenta up to 8 GeV/c, presists at the higher momenta, and the t-dependence shows practically no change with energy. Approximate values of the absolute cross-section were also determined for these momenta.     

Multiparticle production in pTa interactions at 8 GeV/c

pTa interactions have been studied. The total inelastic cross section, multiplicities, net charge distributions and inclusive momentum and rapidity spectra for produced particles are reported. The correlations between fast and slow particles are presented and the reaction mechanisms for multiparticle production in pTa interactions are discussed.     

Measurement of the polarization parameter in π−p elastic scattering at 40 GeV/c

We report our first measurements of the polarization in the elastic scattering of negative pions from polarized protons at an incident pion momentum of 40 GeV/c. The momentum-transfer region covered was 0.08 < |t| < 1.3 (GeV/c)². The angular distribution of the polarization exhibits a first minimum of ～ ? 5% and the well-known zero around t ≈ ? 0.6 (GeV/c)². The energy variation of the first minimum (at around t = ? 0.2) may be expressed in a simple form, $\text{P}{}_{\mathrm{<mtext>avr</mtext>}}\text{= ?(0.48±0.06) s}{}^{\mathrm{?0.52\pm 0.05}}$.