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Photon emission in neutral current interactions at intermediate energies  [PDF]
E. Wang,L. Alvarez-Ruso,J. Nieves
Physics , 2013, DOI: 10.1103/PhysRevC.89.015503
Abstract: Neutral current photon emission reactions with nucleons and nuclei are studied. These processes are important backgrounds for nu_mu to nu_e (bar(nu)_mu to bar(nu)_e) appearance oscillation experiments where electromagnetic showers instigated by electrons (positrons) and photons are not distinguishable. At intermediate energies, these reactions are dominated by the weak excitation of the Delta(1232) resonance and its subsequent decay into Ngamma There are also non-resonant contributions that, close to threshold, are fully determined by the effective chiral Lagrangian of strong interactions. In addition, we have also included mechanisms mediated by nucleon excitations (N*) from the second resonance region above the Delta(1232). From these states, the contribution of the D13 N*(1520) turns out to be sizable for (anti)neutrino energies above 1.5 GeV. We have extended the model to nuclear targets taking, into account Pauli blocking, Fermi motion and the in-medium Delta resonance broadening. We present our predictions for both the incoherent and coherent channels, showing the relevance of the nuclear corrections. We also discuss the target mass dependence of the cross sections. This study is important in order to reduce systematic effects in neutrino oscillation experiments.
Particle and light fragment emission in peripheral heavy ion collisions at Fermi energies  [PDF]
S. Piantelli,P. R. Maurenzig,A. Olmi,L. Bardelli,A. Bartoli,M. Bini,G. Casini,C. Coppi,A. Mangiarotti,G. Pasquali,G. Poggi,A. A. Stefanini,N. Taccetti,E. Vanzi
Physics , 2006, DOI: 10.1103/PhysRevC.74.034609
Abstract: A systematic investigation of the average multiplicities of light charged particles and intermediate mass fragments emitted in peripheral and semiperipheral collisions is presented as a function of the beam energy, violence of the collision and mass of the system. The data have been collected with the "Fiasco" setup in the reactions 93Nb+93Nb at 17, 23, 30, 38AMeV and 116Sn+116Sn at 30, 38AMeV. The midvelocity emission has been separated from the emission of the projectile-like fragment. This last component appears to be compatible with an evaporation from an equilibrated source at normal density, as described by the statistical code Gemini at the appropriate excitation energy. On the contrary, the midvelocity emission presents remarkable differences for what concerns both the dependence of the multiplicities on the energy deposited in the midvelocity region and the isotopic composition of the emitted light charged particles.
Isospin dependence of projectile-like fragment production at intermediate energies  [PDF]
C. W. Ma,H. L. Wei,J. Y. Wang,G. J. Liu,Y. Fu,D. Q. Fang,W. D. Tian,X. Z. Cai,H. W. Wang,Y. G. Ma
Physics , 2009, DOI: 10.1103/PhysRevC.79.034606
Abstract: The cross sections of fragments produced in 140 $A$ MeV $^{40,48}$Ca + $^9$Be and $^{58,64}$Ni + $^9$Be reactions are calculated by the statistical abration-ablation(SAA) model and compared to the experimental results measured at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The fragment isotopic and isotonic cross section distributions of $^{40}$Ca and $^{48}$Ca, $^{58}$Ni and $^{64}$Ni, $^{40}$Ca and $^{58}$Ni, and $^{48}$Ca and $^{64}$Ni are compared and the isospin dependence of the projectile fragmentation is studied. It is found that the isospin dependence decreases and disappears in the central collisions. The shapes of the fragment isotopic and isotonic cross section distributions are found to be very similar for symmetric projectile nuclei. The shapes of the fragment isotopic and isotonic distributions of different asymmetric projectiles produced in peripheral reactions are found very similar. The similarity of the distributions are related to the similar proton and neutron density distributions inside the nucleus in framework of the SAA model.
Intermediate Mass Fragment Emission in ${^{32}}$S +${^{51}}$V, ${^{109}}$Ag, and ${^{238}}$U Collisions at E~=~31.6~MeV~A  [PDF]
H. Machner,M. Nolte,M. Palarczyk,T. Kutsarova
Physics , 2015,
Abstract: Intermediate mass fragment emission for reactions of $^{32}\text{S} +\,^{51}\text{V},\,^{109}$Ag, and $^{238}\text{U}$ has been studied. Double differential cross sections were analysed in terms of the generalised moving source model yielding charge distributions. Isotope ratios show strong fragment mass dependencies. The data were successfully reproduced by the coalescence model as well as by statistical multifragmentation model calculations. Quantum molecular dynamics model calculations were not so successful.
Complex fragment emission in low energy light-ion reactions  [PDF]
S. Kundu,C. Bhattacharya,K. Banerjee,T. K. Rana,S. Bhattacharya,A. Dey,T. K. Ghosh,G. Mukherjee,J. K. Meena,P. Mali,S. Mukhopadhyay,D. Pandit,H. Pai,S. R. Banerjee,D. Gupta,P. Banerjee,Suresh Kumar,A. Shrivastava,A. Chatterjee,K. Ramachandran,K. Mahata,S. K. Pandit,S. Santra
Physics , 2013, DOI: 10.1103/PhysRevC.85.064607
Abstract: Inclusive energy spectra of the complex fragments (3 $\leq$ Z $\leq$ 5) emitted in the reactions $^{12}$C (77 MeV)+ $^{28}$Si, $^{11}$B (64 MeV)+ $^{28}$Si and $^{12}$C (73 MeV)+ $^{27}$Al (all having the same excitation energy of $ \sim$ 67 MeV), have been measured in the angular range of 10$^\circ$ $\lesssim \theta_{lab} \lesssim$ 60$^\circ$. The fully energy damped (fusion-fission) and the partially energy damped (deep inelastic) components of the fragment energy spectra have been extracted. It has been found that the yields of the fully energy damped fragments for all the above reactions are in conformity with the respective statistical model predictions. The time scales of various deep inelastic fragment emissions have been extracted from the angular distribution data. The angular momentum dissipation in deep inelastic collisions has been estimated from the data and it has been found to be close to the corresponding sticking limit value.
Model of the bremsstrahlung emission accompanying interactions between protons and nuclei from low up to intermediate energies: role of magnetic emission  [PDF]
Sergei P. Maydanyuk
Physics , 2012, DOI: 10.1103/PhysRevC.86.014618
Abstract: A new model of the bremsstrahlung emission which accompanies proton decay and collisions of protons off nuclei in the energy region from the lowest up to intermediate, has been developed. This model includes spin formalism, potential approach for description of interaction between protons and nuclei, and operator of emission includes component of the magnetic emission (defined on the basis of Pauli equation). In the problem of the bremsstrahlung during the proton decay in the first time a role of the magnetic emission is studied using such a model. For the studied $^{146}{\rm Tm}$ nucleus it has been studied the following: (1) How much does the magnetic emission change the full bremsstrahlung spectrum? (2) At which angle is the magnetic emission the most intensive relatively electric one? (3) Is there some space region where the magnetic emission increases strongly relatively electric one? (4) How intensive is the magnetic emission in the tunneling region? (5) Which values has the probability at its maximum and at zero energy limit of the emitted photons? It is demonstrated that the model is able to describe enough well experimental data of the bremsstrahlung emission which accompanies collisions of protons off the $^{9}{\rm Be}$, $^{12}{\rm C}$ and $^{208}{\rm Pb}$ nuclei at the incident energy $T_{\rm lab}=140$ MeV (at the photon energy up to 120 MeV).
Complex Particle and Light Fragment Emission in the Cascade-Exciton Model of Nuclear Reactions  [PDF]
Stepan G. Mashnik,Arnold J. Sierk,Konstantin K. Gudima
Physics , 2002,
Abstract: A brief description of our improvements and refinements that led from the CEM95 version of the Cascade-Exciton Model (CEM) code to CEM97 and to CEM2k is given. The increased accuracy and predictive power of the code CEM2k are shown by several examples. To describe fission and light-fragment (heavier than 4He) production, the CEM2k code has been merged with the GEM2 code of Furihata. We present some results on proton-induced fragmentation and fission reactions predicted by this extended version of CEM2k. We show that merging CEM2k with GEM2 allows us to describe many fission and fragmentation reactions in addition to the spallation reactions which are already relatively well described. We have initiated another approach to describe fission, complex particles and fragment emission by developing further our CEM2k code addressing specifically these problems. In this effort, we have developed our own universal approximation for inverse cross sections, new routines to calculate Coulomb barriers and widths of emitted particles and to simulate their kinetic energy using arbitrary approximations for the inverse cross sections. To describe fission-fragment production, we have incorporated into CEM2k a thermodynamical model of fission by Stepanov. This extended version of CEM2k allows us to describe much better complex particle emission and many fission fragments, but it is still incomplete and needs further work.
Characterization of fragment emission in ^{20}Ne (7 - 10 MeV/nucleon) + ^{12}C reactions  [PDF]
Aparajita Dey,C. Bhattacharya,S. Bhattacharya,S. Kundu,K. Banerjee,S. Mukhopadhyay,D. Gupta,T. Bhattacharjee,S. R. Banerjee,S. Bhattacharyya,T. K. Rana,S. K. Basu,R. Saha,K. Krishan,A. Mukherjee,D. Bandopadhyay,C. Beck
Physics , 2007, DOI: 10.1103/PhysRevC.76.034608
Abstract: The inclusive energy distributions of the complex fragments (3 $\leq$ Z $\leq$ 7) emitted from the bombardment of ^{12}C by ^{20}Ne beams with incident energies between 145 and 200 MeV have been measured in the angular range 10$^{o} \leq \theta_{lab} \leq$ 50^{o}. Damped fragment yields in all the cases have been found to be the characteristic of emission from fully energy equilibrated composites. The binary fragment yields are compared with the standard statistical model predictions. Enhanced yields of entrance channel fragments (5 $\leq$ Z $\leq$ 7) indicate the survival of orbiting-like process in ^{20}Ne + ^{12}C system at these energies.
Semiclassical Distorted Wave Model Analysis of Backward Proton Emission from $(p,p^{\prime}x)$ Reactions at Intermediate Energies  [PDF]
M. K. Gaidarov,Y. Watanabe,K. Ogata,M. Kohno,M. Kawai,A. N. Antonov
Physics , 2003,
Abstract: A semiclassical distorted wave (SCDW) model with Wigner transform of one-body density matrix is presented for multistep direct $(p,p^{\prime}x)$ reactions to the continuum. The model uses Wigner distribution functions obtained in methods which include nucleon-nucleon correlations to a different extent, as well as Woods-Saxon (WS) single-particle wave function. The higher momentum components of target nucleons that play a crucial role in reproducing the high-energy part of the backward proton spectra are properly taken into account. This SCDW model is applied to analyses of multistep direct processes in $^{12}$C$(p,p^{\prime}x)$, $^{40}$Ca$(p,p^{\prime}x)$ and $^{90}$Zr$(p,p^{\prime}x)$ in the incident energy range of 150--392 MeV. The double differential cross sections are calculated up to three-step processes. The calculated angular distributions are in good agreement with the experimental data, in particular at backward angles where the previous SCDW calculations with the WS single-particle wave function showed large underestimation. It is found that the result with the Wigner distribution function based on the coherent density fluctuation model provides overall better agreement with the experimental data over the whole emission energies.
Nucleon-nucleon resonances at intermediate energies using a complex energy formalism  [PDF]
G. Papadimitriou,J. P. Vary
Physics , 2015, DOI: 10.1016/j.physletb.2015.04.058
Abstract: We apply our method of complex scaling, valid for a general class of potentials, in a search for nucleon-nucleon S-matrix poles up to 2 GeV laboratory kinetic energy. We find that the realistic potentials JISP16, constructed from inverse scattering, and chiral field theory potentials N$^3$LO and N$^2$LO$_{opt}$ support resonances in energy regions well above their fit regions. In some cases these resonances have widths that are narrow when compared with the real part of the S-matrix pole.
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