Search

Experimental data are presented on differential cross sections of the formation of 11Be, 12Be, and 12B isotopes. The isotopes form upon the fragmentation of a carbon beam at 300 MeV/nucleon in the FRAGM experiment performed at the multipurpose ITEP−TWAC accelerating complex. The experimental data are compared to predictions made with the binary cascade and quantum molecular dynamic models of ion–ion interaction. [ABSTRACT FROM AUTHOR]

The FRAGM experiment is carried out on the basis of the ITEP–TWAC multipurpose accelerator complex, which generated proton and ion beams for various studies in the field of nuclear physics. A technique for identifying fragments in secondary ion beams based on the analysis of correlation distributions over the time of flight and signal amplitude from scintillation detectors is presented. The experimental data are obtained by fragmentation of a carbon beam with energy of 300 MeV per nucleon by scanning the rigidity of the magneto-optical channel with a step of 50 MeV/c. Differential cross sections for ion production are obtained using beryllium isotopes as an example. The results are compared with the predictions of the binary cascade model. [ABSTRACT FROM AUTHOR]

The results of searches for nucleon charge-exchange processes in the fragmentation of carbon ions are presented. The respective experimental data were obtained by means of the FRAGM facility at the TWAC-ITEP multipurpose accelerator complex with a 300-MeV/nucleon beam incident to a thin beryllium target. The experimental setup used, which was oriented at an angle of 3.5 with respect to the ion beam, possessed a hodoscope system, which ensured an accuracy of 0.4 in momentum measurements. The differential cross sections for the yields of isotopes Be and B produced upon single nucleon charge exchange were measured as a function of the fragment momentum. These experimental data were compared with theoretical predictions of two models of ion–ion interactions: the binary cascade (BC) model and the intranuclear cascade (INCL) model. In the above energy range, processes of nucleon charge exchange were measured for the first time. [ABSTRACT FROM AUTHOR]

In the FRAGM experiment at the heavy-ion accelerator accumulator complex ITEP TWA, yields of cumulative charged mesons have been measured in a fragmentation of carbon ions with the energy of 3.2 GeV/nucleon on a beryllium target. The momentum spectra of mesons cover four orders of the invariant cross section magnitude. They demonstrate the exponential fall with increasing energy. The measured inverse slope parameter is compared with similar measurements in nucleon–nucleus interactions and ion–ion collisions at lower energies. The energy dependence of the ratio of the yields of negative to positive mesons is presented. This dependence is discussed in a connection with Coulomb and isotopic effects. The obtained data are compared with predictions of several ion–ion interaction models. [ABSTRACT FROM AUTHOR]

Differential cross sections for the production of nuclear fragments at an angle of 3.5° in the fragmentation of 2-GeV/nucleon carbon ions on a beryllium target were measured in the FRAGM experiment performed at the ITEP-TWA heavy-ion accelerator-accumulator complex. The predictions of four Monte Carlo models of ion-ion interactions (BC, INCL, LAQGSM, and QMD) were tested on the basis of a comparison with the momentum spectra of fragments. Successes and drawbacks of these models are discussed. The energy spectra of protons and 3He nuclei in the cumulative region in the projectile rest frame are well described by an exponential dependence, which make it possible to estimate temperature parameters of their emission source. [ABSTRACT FROM AUTHOR]

The differential cross sections for the yields of nuclear fragments at an angle of 3.5◦ in the fragmentation of carbon nuclei with energy 0.95 GeV per nucleon on a beryllium target were measured in the FRAGM experiment at the ITEP TWA heavy-ion accelerator. The momentum spectra of fragments were used to test the following four models of ion-ion interactions: BC, INCL++, LAQGSM03.03, and QMD. For light fragments, the slope parameters of the kinetic-energy spectra were obtained in the cumulative region. [ABSTRACT FROM AUTHOR]

Momentum distributions of nuclear fragments at an angle of 3.5° in the interaction of 0.6-GeV/nucleon carbon ions with a beryllium target are measured in the FRAGM experiment on the ITEP-TWAC facility. The measured spectra are used for testing predictions of four ion-ion interaction models: BC, QMD, INCL, and LAQGSM03.03, and for comparison with the analytical parameterization within the thermodynamic concept of fragmentation. [ABSTRACT FROM AUTHOR]

The yields of long-lived nuclear fragments at an angle of 3.5° that originate fromthe fragmentation of carbon ions with an energy of T = 0.6 GeV per nucleon on a berylliumtarget were measured in the FRAGMexperiment at the ITEP TWA heavy-ion accelerator. The momentum spectra of these fragments cover both the fragmentation-maximum region and the cumulative region. The respective differential cross sections change by about five orders of magnitude. The momentum distributions of fragments in the laboratory frame and their kinetic-energy distributions in the rest frame of the fragmenting nucleus are used to test the predictions of four models of ion-ion interactions: BC, INCL++, LAQGSM03.03, and QMD. [ABSTRACT FROM AUTHOR]

Yields of protons at 3.5° from carbon ion fragmentation at energies of T = 0.3, 0.6, 0.95, and 2.0 GeV/nucleon on a Be target were measured in the FRAGM experiment at TWA-ITEP heavy-ion facility. Proton momentum spectra cover both the region of the fragmentation maximum and the cumulative region. The differential cross sections span six orders of its magnitude. The spectra are compared with the predictions of four models of ion-ion interactions: LAQGSM03.03, SHIELD-HIT, QMD, and BC. [ABSTRACT FROM AUTHOR]

The proton yields at an angle of 3.5° have been measured in the FRAGM experiment on the fragmentation of carbon ions with the energies T = 0.6, 0.95, and 2.0 GeV/nucleon on a beryllium target at the heavy-ion accelerator complex TWAC (terawatt accumulator, Institute for Theoretical and Experimental Physics). The data are represented in the form of the dependences of the invariant cross section for proton yield on the cumulative variable x in the range of 0.9 < x < 2.4. This invariant cross section varies within six orders of magnitude. The proton spectra have been analyzed within the theoretical approach of the fragmentation of quark clusters with the fragmentation functions obtained in the quark-gluon string model. The probabilities of the existence of six- and nine-quark clusters in the carbon nuclei are estimated as 8-12 and 0.2-0.6%, respectively. The results are compared to the estimated of quark effects obtained by other methods. [ABSTRACT FROM AUTHOR]

The spectra of protons were measured in fragmentation of C ions in the cumulative region at energies of 0.2-3.2 GeV/nucleon. The energy dependence of the slope parameters in the obtained spectra was traced. The probability of the existence of two- and three-nucleon clusters in the carbon nucleus was estimated within the model of quark-gluon strings. [ABSTRACT FROM AUTHOR]

Data on the yields of hydrogen isotopes (p, d, t) and helium isotopes (from 3He to 8He) at the angle of 3.5° in fragmentation of the carbon ions with the energy of 0.3 GeV/nucleon on the beryllium target are reported. The momentum spectra of the fragments in the rest frame of the fragmenting nucleus are measured in a considerably larger momentum range than in the previous experiments. [ABSTRACT FROM AUTHOR]

The A dependence of the forward cross section for inclusive pion double charge exchange on nine target nuclei from 6Li to 209Bi at T0 = 0.59 GeV, as well as the cross section for 6Li, 7Li, and 12C nuclei at T0 = 0.59, 0.75, and 1.1 GeV, was measured with the 3-m magnetic spectrometer of the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The resulting A dependence is well described within the model involving two sequential single charge exchanges and taking into account the renormalization of the amplitude for pion single charge exchange in a nucleus. A relatively weak energy dependence of the cross section for the 6Li, 7Li, and 12C nuclei agrees with the analogous dependence obtained previously for the 16O nucleus, but it contradicts the predicted sharp decrease in the cross section within the model involving two sequential single charge exchanges. This result provides an additional piece of evidence that the contribution from the mechanism of inelastic Glauber rescattering is significant at T0 >= 0.6 GeV.© 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Quasielastic deuteron and triton knockout from 6Li and 7Li nuclei that was induced by a π–-meson beam of momentum p0 = 0.72 and 0.88 GeV/c was studied under conditions of full kinematics. The experiment was performed at the Institute of Theoretical and Experimental Physics (ITEP, Moscow) by using a 3-m magnetic spectrometer equipped with spark chambers. The distributions with respect to the momenta of quasideuteron and quasitriton internal motion, the excitation-energy spectra of residual nuclei, and the effective numbers of quasideuterons in 6Li and 7Li nuclei were obtained.© 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Results of a kinematically complete experiment on backward π[sup –]d quasielastic scattering by [sup 6]Li are presented. The experiment was carried out at the ITEP 3-m magnetic spectrometer with pion beams of momenta 0.72, 0.88, and 1.28GeV/c. The Fermi-motion parameters of a quasideuteron cluster and the effective number of quasideuterons in [sup 6]Li are determined for the [sup 6]Li(π[sup –],π[sup –]d)[sup 4]He reaction. These values agree well with the proton- and electron-beam measurements. The possibility of observation of the effects of deuteron wave-function modification in nuclear matter is discussed for this reaction. © 2001 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The effective mass spectrum of two protons from the reaction p+ n→ pp+ π ( backward) was investigated. The work was carried out at ITEP using a 3-meter magnet spectrometer and a proton beam of 1.98 GeV/c momentum. Liquid deuterium was used as a target. The presented mass spectrum includes about 34000 events. No statistically significant signals from narrow dibaryons were found in the mass region 1.89-2.17 GeV/ c ; the upper limits on narrow dibaryon production cross-section are given. At a mass of 1.8775 GeV/ c a narrow enhancement was found. A more detailed investigation of the observed phenomenon is needed. [ABSTRACT FROM AUTHOR]

The plane-wave approximation was used to examine the proton Fermi-momentum distribution in experiments on quasielastic large-momentum-transfer pion–nucleon scattering in light nuclei [sup 6]Li,[sup 7]Li, and [sup 12]C. It was found that, unlike the (e,e′) reaction, the Fermi-gas model is in poor agreement with experiment, whereas the oscillator model adequately describes the spectrum shape. However, the parameters obtained for these distributions are sizably smaller than those derived from the (e,e′) experiments. This suggests that the plane-wave approach is inadequate and that more complicated theoretical approaches, supposedly allowing for pion–nucleon amplitude modification in nuclear matter, are necessary for the analysis of experimental data. © 2000 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]