A. V. Blinov

Cross sections of 4He interaction with protons and 4He-p elastic scattering at 2.7 GeV/c

Abstract The 2m hydrogen bubble chamber was exposed to a separated beam of α-particles from the ITEP synchrotron. The momentum of the 4 He-nuclei beam averaged over the bubble-chamber fiducial volume was equal to 2.7 GeV/ c (the kinetic energy of the initial protons in the nuclear rest frame was T p = 220 MeV). The total and topological cross sections were measured as well as the cross section of separate 4 He-p interaction channels and the differential cross sections d σ d t of the elastic 4 He-p scattering. The experimental results have been compared with the data of the previous experiments and with the theoretical predictions based on the Glauber-Sitenko multiple-scattering theory.

Study of the mechanism of the 3He + p → p + p + d reaction at a 3He momentum of 5 GeV/c

Abstract The mechanism of the reaction 3 He + p → p + p + d is studied by making use of the ITEP 80 cm liquid-hydrogen bubble chamber exposed to a beam of 5 GeV/ c 3 He nuclei. The reaction cross section is equal to 20.6 ± 0.3 mb. The phase-space regions associated with quasifree scattering (QFS) and final-state interactions (FSI) are selected. Angular, mass and momentum distributions of the reaction products are obtained in the entire kinematically allowed range. The experimental data in the QFS region are compared with theoretical calculations based on the simplest pole-diagram approximation. The 3 He and deuteron wave functions (WF) correspond to the realistic RSC potential. The D-wave components of these WF are taken into account. The absolute value of the cross section and shape of the distributions are described as a whole reasonably well within the frame of the model considered in the kinematical region where FSI may be neglected. But at large spectator momenta there is an essential disagreement. The possible reasons for this are discussed.

Determination of the nuclear vertex function of 3He to pd disintegration and the vertex constant 3He dp from 3He p to ppd reaction data at 2.5 and 5 GeV/c 3He momenta

Nuclear vertex functions and nuclear vertex constants have been obtained from analysis of the reaction 3He+p to p+p+d at 3He momenta of 2.5 and 5 GeV/c. The experimental data have been obtained by means of an 80 cm liquid hydrogen bubble chamber, exposed to 3He separated beams of 2.5 and 5 GeV/c momenta. The method of calculation of vertex functions and vertex constants is well founded. The effect of off-shell elastic scattering on the vertex functions and vertex constants has been investigated. The following values for the squares of the vertex constants have been obtained (Coulomb corrections were taken into account): 0.95+or-0.07+or-0.05 fm at 2.5 GeV/c and 0.99+or-0.07+or-0.05 fm at 5 GeV/c. The authors compare their vertex constants with available phenomenological results as well as with theoretical predictions calculated for different NN potentials.

Cross sections for 4He interaction with protons at 5 GeV/c

The total and topological 4Hep cross sections, as well as the cross sections for individual αpinteraction channels and the differential cross sections dσ/dt for elastic αp scattering, were measured by using a 2-m hydrogen bubble chamber exposed to a separated beam of 5-GeV/cα particles from the ITEP synchrotron (the kinetic energy of initial protons in the nuclear rest frame was Tp=620 MeV). The data obtained are compared with the results of previous experiments and with theoretical predictions based on Glauber-Sitenko multiple-scattering theory.

Determination of the nuclear vertex function 3He → ppn from the 3He p → pppn reaction data at the 3He momenta of 2.5 and 5 GeV/c

Abstract The nuclear vertex function of 3 He → ppn disintegration has been determined from analysis of the reaction 3 He p → pppn . The experimental data have been obtained in the 4π geometry by means of the 80 cm ITEP liquid-hydrogen bubble chamber, exposed to 3 He separated beams at momenta of 2.5 and 5 GeV/ c . The method used for extraction of the nuclear vertex function is well founded. For the first time, the 3 He → ppn vertex function has been investigated simultaneously as a function of two Jacobi momenta. The singlet part of the vertex function has been extracted separately. The momentum distributions of protons, neutrons, pp and pn pairs in 3 He have been obtained also. These results are compared with the available data and with theoretical calculations performed with the wave functions for the Reid and Yamaguchi potentials.

Investigation of pn correlations in 4Hep interactions at a momentum of 5 GeV/c

Proton-neutron correlations in 4Hep interactions are studied in an exclusive experiment by using a 2-m bubble chamber exposed to a 5-GeV/c beam of α particles (the kinetic energy of the protons in the nucleus rest frame is Tp = 620 MeV). Data on the production of pn pairs in 4π geometry for three channels, where it is possible to reconstruct the neutron momentum unambiguously, are used to determine the pn correlation function in 4Hep interactions. The experimental results are compared with the predictions of a modified Lednicky-Lyuboshitz model. The value obtained for the root-mean-square radius of the pn-emission region is Rpn = 2.1 ± 0.3 fm. The dependence of the correlation function on the modulus of the total momentum of the emitted nucleon pair and on the direction of the momentum transfer is studied. An indication that the emission of a pn pair proceeds predominantly through the production of a virtual deuteron is obtained.

Two-proton correlations in 4Hep interactions at a primary momentum of 5 GeV/c

Correlations of secondary protons in 4Hep interactions are investigated in an exclusive experiment with the aid of a 2-m liquid-hydrogen bubble chamber exposed to an alpha-particle beam of momentum 5 GeV/c the kinetic energy of primary protons in the rest frame of the nucleus is Tp=620 MeV). By using data obtained in 4π geometry for six basic channels of 4Hep interaction that lead to the production of two protons, the total correlation function for the pp system is determined, along with two-proton correlation functions for individual channels. Experimental results are compared with the predictions of the modified Lednicky-Lyuboshitz model. The value of R=1.6±0.3 fm is obtained for the root-meansquare spacetime radius of pp emission in 4Hep interactions. The dependence of the correlation function on the total momentum of two emitted protons and on the momentum-transfer direction is investigated.

Search for dibaryon production in 4Hep interactions at intermediate energies

With the aid of the 2-m liquid-hydrogen bubble chamber constructed at the Institute of Theoretical and Experimental Physics (ITEP, Moscow), 4Hep interactions are studied at primary alpha-particle momenta of 2.7 and 5 GeV/c (the respective kinetic energies of primary protons in the 4He rest frame are Tp=220 and 620 MeV). The effective-mass spectra of two nucleons from the reactions 4Hep → dppn and 4Hep → pppnn are analyzed. The effective-mass spectrum of the two-proton system produced in the quasielastic-charge-exchange reaction p4He → nF(pp)d at Tp=620 MeV (here, nF stands for the fast neutron in the 4He rest frame) shows a narrow peak, which is indicative of the existence of a dibaryon whose mass and width are M2p=2008±13 MeV and Γ2p=0±5 MeV, respectively. In the mass spectra of the two-proton system from the reactions p4He → nF(pp)d and p4He → pF(pp)(nn), narrow threshold peaks are also found at a mass of M2p⋍1878–1879 MeV.

Quasi-elastic 3H-p and 3He-p scattering at medium energies and Glauber sum rules

The differential cross sections and the mean energy losses of fast protons in the reactions p+3H to pF+X and p+3He to pF+X are investigated using the ITEP 80 cm liquid-hydrogen bubble chamber exposed to beams of 2.5 GeV/c tritons (the kinetic energy of initial protons in the nuclear rest frame is Tp=0.318 GeV) and 5 GeV/c 3He nuclei (Tp=0.978 GeV). The experimental results are compared with predictions based on the sum rules for the differential cross sections and the mean energy losses which are valid in the Glauber-Sitenko multiple scattering theory when the completeness condition for the wavefunctions of the excited nuclear states and the locality of the nuclear potential are used. The data at 2.5 GeV/c are found to be in good agreement with the theory. The discrepancies between the Glauber sum-rule predictions and the data on 3He-p scattering at 5 GeV/c are explained by the effects of intermediate Delta -isobar production. Possible six-quark bag admixture in 3H or 3He nuclei is found to be not more than 5%.

Investigation of the reactions 3H+p to 3He+n and 3H+p to 3H+p at a triton momentum of 2.5 GeV/c

The differential cross sections d sigma /dt of the reactions 3H+p to 3He+n and 3H+p to 3H+p at a triton momentum of 2.5 GeV/c (equivalent to a proton kinetic energy Tp=318 MeV) have been measured. The ITEP 80 cm hydrogen bubble chamber was exposed to a 2.5 GeV/c separated triton beam. 2350 events of the reaction 3H(p,n)3He and 2574 events of the reaction 3H(p,p)3H were selected and analysed. Calculations performed in the framework of the multiple scattering theory taking the spin-isospin structure of the NN amplitude into account fit the data very well and show the high sensitivity of the charge-exchange cross section to the double spin-flip NN amplitudes.