Small-angle fragmentation of carbon ions at 0.6 GeV/n: a comparison with models of ion-ion interactions

Momentum distributions of hydrogen and helium isotopes from 12C fragmentation at 3.5° were measured at 0.6 GeV/nucleon in the FRAGM experiment at ITEP TWA heavy ion accelerator. The fragments were selected by correlated time of flight and dE/dx measurements with a magnetic spectrometer with scintillation counters. The main attention was drawn to the high momentum region where the fragment velocity exceeds the velocity of the projectile nucleus. The momentum spectra of fragments span the region of the fragmentation peak as well as the cumulative region. The differential cross sections cover six orders of magnitude. The distributions measured are compared to the predictions of three ion-ion interaction models: BC, QMD and LAQGSM03.03. The kinetic energy spectra of fragments in the projectile rest frame have an exponential shape with two temperatures, being defined by their slope parameters

Inclusive pion double charge exchange on Oxygen(16) at 0.6-1.1 GeV

The inclusive pion double charge exchange (DCX) on oxygen nuclei has been measured in the region where additional pion production is kinematically forbidden. The experiment was performed at ITEP PS at incident pi- kinetic energies T_0= 0.59, 0.75 and 1.1 GeV. The integrated forward differential cross section was found to decrease with energy slowly. At 1.1 GeV it exceeds the theoretical prediction within the conventional sequential single charge exchange mechanism with a neutral pion in the intermediate state (Glauber elastic rescattering) by about half an order of magnitude. The sequential mechanism with two pions in the intermediate state (Glauber inelastic rescatterings), which was proposed recently, seems to be able to explain the observed slow energy dependence and allows to predict the DCX cross section for higher energies.Comment: 27 pages, 13 figures. Minor corrections, one figure added. Accepted in NP

Splitting of fragmentation peaks of light ions in

The FRAGM experiment at the ITEP-TWA heavy ion facility has a unique opportunity of measuring the momentum distributions of nuclear fragments. We present the results of 56Fe fragmentation into light ions on 9Be target at 0.23 GeV/nucleon. The momentum spectra of projectile like fragments were measured with a high resolution beam line spectrometer. In contrast to the carbon fragmentation, where the momentum spectra have Gaussian-like shapes, in the emission of the light fragments the shapes have a double-humped structure. This splitting is most pronounced in proton spectra. The possibility of describing this effect by asymmetric fission and multifragmentation is discussed. A comparison is made with the results of the FRS measurements at GSI. The obtained experimental data are in a reasonable agreement with the predictions of several transport codes such as BC, INCL and LAQGSM

Splitting of fragmentation peaks of light ions in 56Fe + 9Be collisions at 0.23 GeV/nucleon

The FRAGM experiment at the ITEP-TWA heavy ion facility has a unique opportunity of measuring the momentum distributions of nuclear fragments. We present the results of 56Fe fragmentation into light ions on 9Be target at 0.23 GeV/nucleon. The momentum spectra of projectile like fragments were measured with a high resolution beam line spectrometer. In contrast to the carbon fragmentation, where the momentum spectra have Gaussian-like shapes, in the emission of the light fragments the shapes have a double-humped structure. This splitting is most pronounced in proton spectra. The possibility of describing this effect by asymmetric fission and multifragmentation is discussed. A comparison is made with the results of the FRS measurements at GSI. The obtained experimental data are in a reasonable agreement with the predictions of several transport codes such as BC, INCL and LAQGSM

Cumulative protons in

In the FRAGM experiment at heavy ion accelerator complex TWAC-ITEP, the proton yields at an angle 3.5° have been measured in fragmentation of carbon ions at T0 = 0.3, 0.6, 0.95 and 2.0 GeV/nucleon on beryllium target. The data are presented as invariant proton yields on cumulative variable x in the range 0.9 < x < 2.4. Proton spectra cover six orders of invariant cross section magnitude. They have been analyzed in the framework of quark cluster fragmentation model. Fragmentation functions of quarkgluon string model are used. The probabilities of the existence of multi-quark clusters in carbon nuclei are estimated to be 8–12% for six-quark clusters and 0.2–0.6% for ninequark clusters

Search for d' in pion inclusive spectra from pp-interactions

We report on our measurement of the inclusive spectrum of positive pions from the reaction $pp\rightarrow \pi^+ + X$ on a $CH_2$ internal target of the ITEP proton synchrotron at $1.5\ GeV/c$ with a missing mass resolution of about $1\ MeV/c^2$. The goal of our experiment was the search for the hypothetical narrow $\pi NN$ resonance ($0.5\ MeV/c^2$ width and a mass of $2.06\ GeV/c^2$) with $I(J^P)=even(0^-)$, called $d'$. We do not see any statistically significant $d'$-signal. The upper limit for $d'$ production cross-section in $pp$-interactions is near $2\ \mu b$ at $84\%\ C.L.

Small-angle fragmentation of carbon ions at 0.6 GeV/n: a comparison with models of ion-ion interactions

Momentum distributions of hydrogen and helium isotopes from 12C fragmentation at 3.5° were measured at 0.6 GeV/nucleon in the FRAGM experiment at ITEP TWA heavy ion accelerator. The fragments were selected by correlated time of flight and dE/dx measurements with a magnetic spectrometer with scintillation counters. The main attention was drawn to the high momentum region where the fragment velocity exceeds the velocity of the projectile nucleus. The momentum spectra of fragments span the region of the fragmentation peak as well as the cumulative region. The differential cross sections cover six orders of magnitude. The distributions measured are compared to the predictions of three ion-ion interaction models: BC, QMD and LAQGSM03.03. The kinetic energy spectra of fragments in the projectile rest frame have an exponential shape with two temperatures, being defined by their slope parameters

Light fragments from (C + Be) interactions at 0.6 GeV/nucleon

Nuclear fragments emitted at 3.5° in 12C fragmentation at 0.6 GeV/nucleon have been measured. The spectra obtained are used for testing the predictions of four ion-ion interaction models: INCL++, BC, LAQGSM03.03 and QMD as well as for the comparison with the analytical parametrization in the framework of thermodynamical picture of fragmentation

Carbon fragmentation at 300 MeV/nucleon vs transport codes

Momentum spectra of all long-lived fragments from 12C fragmentation at 3.5° have been measured. Differential cross sections span up to five orders of its magnitude. The preliminary results are compared with predictions of two transport codes: INCL++ and LAQGSM03.03. Both models give a good description of the data except few items which are discussed

Carbon fragmentation at 300 MeV/nucleon vs transport codes

Momentum spectra of all long-lived fragments from 12C fragmentation at 3.5° have been measured. Differential cross sections span up to five orders of its magnitude. The preliminary results are compared with predictions of two transport codes: INCL++ and LAQGSM03.03. Both models give a good description of the data except few items which are discussed