Spin-dependent observables and the D_2 parameter in breakup of deuteron and 3He

We analyze the momentum distributions of constituents in 3He, as well as the spin-dependent observables for (3He,d), (3He,p), and (d,p) breakup reactions. Special attention is paid to the region of small relative momenta of the helium-3 and the deuteron constituents, where a single parameter, D_2, has determining role for the spin-dependent observables. We extract also this parameter for the deuteron, basing on existing data for the tensor analyzing power of this reaction.Comment: 10 pages, 6 figures. Talk given at the Conference SYMMETRIES AND SPIN (SPIN-Praha-2012), Prague, July 1 - 8, 2012 (Tribute to memory of Frantishek Lehar). Some misprints are correcte

Isoscalar Roper Excitation in p(α,α′)p(\alpha, \alpha') Reactions in the 10−1510 - 15 GeVGeV Region

Recent experiments at Saturne at $4$ $GeV$ showed that the $(\alpha,\alpha')$ reaction on the proton shows two distinctive peaks, which were associated to $\Delta$ projectile excitation and Roper target excitation. A subsequent theoretical analysis has shown that this picture is qualitatively correct but there are important interference effects between the two mechanisms. Futhermore, at this energy the ratio of strengths for the Roper and $\Delta$ peak is about $1/4$. In the present paper we show that by going to the $10 - 15$ $GeV$ region the interference effects become negligible, the signal for the Roper excitation is increased by more than an order of magnitude and the ratio of cross sections at the peaks for Roper and $\Delta$ excitation becomes of the order of unity, thus making this range of energies ideal for studies of isoscalar Roper excitation.Comment: Latex 10 pages; figures available by request; Phys. Lett. B submitte

SPIN-DEPENDENT OBSERVABLES AND THE D 2 PARAMETER IN BREAKUP OF DEUTERON AND 3 He

We analyze the momentum distributions of constituents in 3 He, as well as the spin-dependent observables for ( 3 He, d), ( 3 He, p), and (d, p) breakup reactions. Special attention is paid to the region of small relative momenta of the helium-3 and deuteron constituents, where a single parameter, D 2 , has determining role for the spin-dependent observables. We extract also this parameter for the deuteron, basing on the existing data for the tensor analyzing power of this (d, p) breakup. The investigation has been performed at the Veksler and Baldin Laboratory of High Energy Physics, JINR

Isoscalar short-range current in the deuteron induced by an intermediate dibaryon

A new model for short-range isoscalar currents in the deuteron and in the NN system is developed; it is based on the generation of an intermediate dibaryon which is the basic ingredient for the medium- and short-range NN interaction which was proposed recently by the present authors.This new current model can very well describe the experimental data for the three basic deuteron observables of isoscalar magnetic type, viz. the magnetic moment, the circular polarization of the photon in the $np\to d\gamma$ process at thermal neutron energies and the structure function B up to Q$^2$=60 fm$^{-2}$.Comment: LaTex, 22 pages with 8 figure

Formation of 24Mg* in the Splitting of 28Si Nuclei by 1-GeV Protons

The 28Si(p, p' gamma)24Mg reaction has been studied at the ITEP accelerator by the hadron-gamma coincidence method for a proton energy of 1 GeV. Two reaction products are detected: a 1368.6-keV gamma-ray photon accompanying the transition of the 24Mg* nucleus from the first excited state to the ground state and a proton p' whose momentum is measured in a magnetic spectrometer. The measured distribution in the energy lost by the proton in interaction is attributed to five processes: the direct knockout of a nuclear alpha cluster, the knockout of four nucleons with a total charge number of 2, the formation of the DeltaSi isobaric nucleus, the formation of the Delta isobar in the interaction of the incident proton with a nuclear nucleon, and the production of a pi meson, which is at rest in the nuclear reference frame. The last process likely corresponds to the reaction of the formation of a deeply bound pion state in the 28P nucleus. Such states were previously observed only on heavy nuclei. The cross sections for the listed processes have been estimated.Comment: 14 pages, 3 figures submitted to JETP Letter

Projectile Δ\Delta and target-Roper excitation in the p (d, d')X reaction

In this paper we compare a model that contains the mechanisms of $\Delta$ excitation in the projectile and Roper excitation in the target with experimental data from two (d, d') experiments on a proton target. The agreement of the theory with the experiment is fair for the data taken at T_d = 2.3 GeV. The $\Delta$ excitation in the projectile is predicted close to the observed energy with the correct width. The theory, however, underpredicts by about 40% the cross sections measured at T_d = 1.6 GeV at angles where the cross section has fallen by about two orders of magnitude. The analysis done here allows to extract an approximate strength for the excitation of the Roper [N^*(1440)] excitation and a qualitative agreement with the theoretical predictions is also found.Comment: 8 ps figure

Mechanism of Pion Production in alphaalphap Scattering at 1 GeV/nucleon

The one-pion and two-pion production in the p(alpha, alpha prime)X reaction at an energy of E{alpha} = 4.2 GeV has been studied by simultaneous registration of the scattered alpha particles and the secondary pion or proton. The obtained results demonstrate that the inelastic alpha-particle scattering on the proton at the energy of the experiment proceeds either through excitation and decay of Delta resonance in the projectile or through excitation in the target proton of the Roper resonance, which decays mainly on a nucleon and a pion or a nucleon and a sigma meson - system of two pions in the isospin I = 0, S-wave.Comment: 16 pages, 10 figures. Submitted to Proceedings of the XX International Baldin Seminar on High - Energy Physics Problems, Dubna, October 4 - 9, 201