The reaction np → ppπ− between 1.0 and 8.0 GeV/c (original) (raw)

Study of the np→ppπ− reaction in the incident neutron momentum range 1.0–1.9 GeV/c

Nuclear Physics A, 1988

We have studied the np-, ppv-reaction in the incident-momentum range 1.0-1.9 CeV/c using the dp-) pppv reaction in terms of the impulse approximation. The reaction cross sections and the 1 = 0 cross sections were measured. The 1 == 0 cross sections were almost zero except at 1.89 GeVic which indicates the onset of a substantial contribution from the f =O amplitude. The inclusive x angular distribution showed asymmetry' also at 1.89 GeV/c which was interpreted as an interference between the I = 0 and 1 amplitudes. The-l-production fraction, A angular distributions and j-decay density matrices were measured. These measurements indicate that A-production is substantial in the np-+pprr-reaction in our momentum range and that it is induced by pion exchange. Comparison with data from the pp-' ppv" reaction also confirms the dominance of the nucleon-nucleon f = 1 state in the np-tppn. reaction.

Detailed comparison of the pp→π+pn and pp→π+d reactions at 951 MeV

Physics Letters B, 2005

The positively charged pions produced in proton-proton collisions at a beam momentum of 1640 MeV/c were measured in the forward direction with a high resolution magnetic spectrograph. The missing mass distribution shows the bound state (deuteron) clearly separated from the pn continuum. Despite the very good resolution, there

The reactions π±p→pπ±π+π− at 18.5 GeV/c

Nuclear Physics B, 1974

Studies have been made of the reactions n+p-+ pn+n+rr-and *r p-+ prr+rr rr , both at an incident pion momentum of 18.5 GeV/c. The two-body (primarily a++ and po) and three-body (low-mass A enhancement, A3, N* (1400), and N* (1700)) subsystems are discussed. Cross sections for all significant channels of the reactions are given.

Positive Pion Production in Proton-Nucleus Collision

Progress of Theoretical Physics, 1977

Positive pion production process on 12 C by 185 MeV proton is studied within the framework of DWBA by adopting the Kisslinger-type optical potential for the final state interaction. The qualitative features of this reaction are explained if the off-shell part of the optical potential is modified by introducing the vertex function. This modification scarcely affects elastic pion-nucleus scattering. § 1. Introduction Pion production process (p, n+) on nuclei is one of the interesting phenomena m pion-nucleus interactions.v~sl As a neutron is transferred into the target nucleus, this reaction is analogous to the ordinary nuclear reactions, such as (d, p) and (n, r). Since the measurements of the cross sections of 12 C (p, n+) 13 C by the U ppsala group by the use of the 185 MeV proton beams,7)~lol this reaction has been paid much attention theoretically.11)~,sl Most of the theoretical work was based upon the DWBA theory by adopting the Kisslinger-type optical potential for describing the emitted pion! 1 l, 25 l and the conventional static pion-nucleon interaction for the vertex of pion production. The calculated values of the cross section were shown to be larger than the experimental values by one or two orders of magnitude.m. 18 l In this connection, Miller found the parameter set of the Kisslinger-type optical potential which explains elastic scattering and the (P, n+) reaction on 12 C. 19 l His parameters are, however, quite different from those commonly used in elastic scattering on 12 C." 6 l~zsl Recently Miller and Phatak 20 l have calculated the 12 C (P, ni) 13 C reaction cross section, using the separable pion-nucleon potential proposed by Landau et al." 9 l~sJJ Although the results are in agreement with the experimental data, the range parameters adopted for the nuclear form factor are somewhat too large. Besides, the vertex of pion emission was also investigated by Lee and Pittel, 22 l and by Noble. 23 l From the kinematical consideration the above complicated situations can be ascribed to the off-shell behavior of pion-nucleon interaction, to which elastic pionnucleus scattering is rather insensitive: If we switch off the initial and final state interactions in the above reaction, the momentum of the transferred neutron is 460~660 MeV/ c, \vhich is far above the Fermi momentum. Therefore, the cross section for this reaction is expected to be very small. However, if we take into

Study of the quasi-freenp→npπ+π−reaction with a deuterium beam at 1.25 GeV/nucleon

Physics Letters B, 2015

The tagged quasi-free np → npπ + π − reaction has been studied experimentally with the High Acceptance Di-Electron Spectrometer (HADES) at GSI at a deuteron incident beam energy of 1.25 GeV/nucleon (√ s ∼ 2.42 GeV/c for the quasi-free collision). For the first time, differential distributions of solid statistics for π + π − production in np collisions have been collected in the region corresponding to the large transverse momenta of the secondary particles. The invariant mass and angular distributions for the np → npπ + π − reaction are compared with different models. This comparison confirms the dominance of the t-channel with ∆∆ contribution. It also validates the changes previously introduced in the Valencia model to describe two-pion production data in other isospin channels, although some deviations are observed, especially for the π + π − invariant mass spectrum. The extracted total cross section is also in much better agreement with this model. Our new measurement puts useful constraints for the existence of the conjectured dibaryon resonance at mass M∼ 2.38 GeV and with width Γ ∼ 70 MeV.

Study of spectator tagging in the reaction np → ppπwith a deuteron beam

European Physical Journal A, 2006

The reaction dp → pppπ − has been studied in a kinematically complete experiment at a single beam momentum p d = 1.85 GeV/c (T = 759 MeV). All four ejectiles have been detected in the largeacceptance time-of-flight spectrometer COSY-TOF. We analyzed the data along the lines of the spectator model as a means to isolate the quasi-free np → ppπ − reaction. The spectator proton was identified by its momentum and flight direction thus yielding access to the associated Fermi motion of the bound neutron. A comparison is carried out with Monte Carlo simulations based on two different parameterizations of the deuteron wave function. Up to a Fermi momentum of roughly 150 MeV/c no significant deviations between experimental and simulated data of various observables were found from which we conclude that the deuteron can indeed be taken as a valid substitute for the neutron.

The (π+,pd) and (π+,dd) reactions on light nuclei at 100 and 165 MeV incident pion energies

Nuclear Physics A, 2002

The (π + , pd), and (π + , dd) reactions were investigated with pions of 100 and 165 MeV kinetic energy on 6 Li and 12 C targets. In comparison with previously published (π + , pp) data on the same targets and at the same beam energies, kinematic regions were identified in which the neutron pickup process n+p → d dominated the observed deuteron yield. The importance of this mechanism increases with energy, contributing half of the observed cross section at 165 MeV. The contribution of direct quasi-triton absorption is significant only at 100 MeV.

Total cross section of the reaction π+d→pp at pion energies 26–40 MeV

Physics Letters B, 1993

Total cross sections for the reaction n +d-,pp have been measured for incident pion energies T~= 26.5, 28.5, 30.5, 32.5 and 39.5 MeV. The data are in good agreement with previous experiments. There is some indication of a peculiarity in the energy dependence of the total cross section near incident pion energy T~= 30 MeV. Numerous theoretical and experimental investigations are devoted to the reaction rc +d~pp and its inverse pp-, rc +d. The study of these reactions is interesting not only for their own sake. They are main processes for pion absorption and production at intermediate energies. Understanding them is the basis for understanding the NN interaction since pp~ 7z +d is the main inelastic process in this energy region. On the other hand, we can relate the rrNN system to teN properties because of extensive theoretical study of the two-baryon system [ 1 ]. The Faddeev approach has been successful in explaining n +d~pp, NN~NN, n +d-, rt +d, and ze +d~ nNN reactions in terms of iterated rtN and NN interactions, treating a set of two-baryon reactions as part of a coupled system. Also, the relative simplicity of these processes makes them attractive for the detailed examination of various dynamic microscopic models applied to nucleon-nucleus and pion-nucleus interactions as well.

Multinucleon contributions to the 12C(π+, pp) reaction at 100 and 165 MeV incident pion energies

Nuclear Physics A, 1997

Differential and total cross sections for ~-+ absorption on ~2C are presented at incident pion energies of 100 and 165 MeV. This is the first time that this reaction has been measured with a combination of good energy and angle information over an extensive region of phase space. Results are compared to extensive Monte Carlo simulations in order to investigate the role of two-and multinucleon absorption processes in this nucleus. Signatures of ISI and FSI in the pion absorption process are also investigated, in order to explain the complex reaction mechanism implied by the data. @ 1997 Elsevier Science B.V.

General properties of the pion production reaction in nuclear matter

Nuclear Physics A, 2004

The pion production reaction π + → π + π ± on 45 Sc was studied at incident pion energies of T π + = 240, 260, 280, 300, and 320 MeV. The experiment was performed using the M 11 pion-channel at TRIUMF, and multiparticle events, (π + , π + π ± ) and (π + , π + π ± p), were detected with the CHAOS spectrometer. Results are reported in the form of both differential and total cross sections, and are compared to theoretical predictions and the reaction phase space. The present investigation of the T-dependence of the π + A → π + π ± A ′ reaction complements earlier examinations of the Adependence of the reaction, which was measured using 2 H, 4 He, 12 C, 16 O, 40 Ca, and 208 P b targets at ∼280 MeV. Some general properties of the pion-induced pion production reaction in nuclear matter will be presented, based on the combined results of the two studies.