Investigations of mechanisms of particle production in proton-induced nuclear spallation
Supervisor: prof. Krzysztof Pysz
Auxilliary supervisor: dr Sushil Sharma
abstract
Defence year: 2021
Studies of the selected problems in understanding of nuclear spallation physics are undertaken. Among them are the description of the initial phase of proton - target nucleus collision and proceeding of the intranuclear cascade, isotropic emission of nuclear fragments of very broad mass spectrum, contribution of the nonequlibrium and equilibrium processes to the total production
cross-section and its dependence on the isotope isospin, variation of the total production cross-section related to the number and ratio of protons and neutrons of the emitted particle. New experimental distributions of the double differential production cross-sections (d^2sigma/dOmegadE) for p, d, t, pi+ and pi- in the p + Nb reaction at 3.5 GeV proton beam energy are provided. They have been measured by High Acceptance DiElectron Spectrometer (HADES) experiment. The measured energy range of hydrogen isotopes are significantly extended in comparison to the experimental data available in the literature. The new experimental spectra are confronted with the theoretical prediction of three models of intranuclear cascade - GiBUU, UrQMD, INCL++. Discrepancies of the experimental and theoretical distributions are noticed and discussed. Experimental data derived from the literature are
used for examination of nuclear mechanisms assigned to the nuclear deexcitation phenomena. The comparative analysis of the four model prediction (ABLA07, GEMINI++, GEM2, SMM) of the selected observables relevant to the isotropic nuclear fragment emission is performed. Disagreement of the model prediction and the experimental data is observed.
Directed, elliptic and higher order flow harmonics of protons, deuterons and tritons in Au+Au collisions at sqrt(s_NN) = 2.4 GeV
J. Adamczewski-Musch, ...., G. Korcyl, ...., R. Lalik, ..., A. Malige, ...K. Nowakowski,...., W. Przygoda,...K. Pysz, ..., N. Rathod, ...,P. Salabura, .., U. Singh, J. Smyrski, et al
abstract
Flow coefficients vn of the orders n = 1 - 6 are measured with the High-Acceptance DiElectron Spectrometer (HADES) at GSI for protons, deuterons and tritons as a function of centrality, transverse momentum and rapidity in Au+Au collisions at sqrt(s_NN) = 2.4 GeV. Combining the information from the flow coefficients of all orders allows to construct for the first time, at collision energies of a few GeV, a complete, multi-differential picture of the emission pattern of these particles. The ratio v4/v22 at mid-rapidity is found to be remarkably close to the value 0.5, as might be indicative for an ideal fluid scenario.
Experimental and theoretical L-shell ionization cross sections of heavy atoms by impact of Si ions
M. Oswal, S. Kumar, U. Singh, S. Singh, G. Singh, K.P. Singh, D. Mehta, A. M. P. Mendez, D. M. Mitnik, C. C. Montanari, D. Mitra, T. Nandi
abstract
We present a theoretical and experimental study of the subshell resolved L-shell ionization of relativistic targets such as 73Ta, 78Pt, 90Th, and 92U. The measurements of x-ray production cross sections by (84?140 MeV) Si+q ions (q = 8; 12), were held at the Inter-University Accelerator Centre of New Delhi. Multiple-hole fluorescence and Coster-Kronig yields were used to obtain the Li(i = 1?3) ionization cross sections from the measured x-ray production cross sections of L?, L?, and L?, L?, and L? lines. The experimental results are compared with ab initio theoretical calculations by means of the shell-wise local plasma approximation (SLPA). This model uses the quantum dielectric formalism to obtain the total ionization cross sections from an initial ground state. The wave functions and binding energies of the different targets were obtained by solving the fully relativistic Dirac equation using the HULLAC code package. These calculations are based on first order perturbation theory with a central field, including Breit interaction and quantum electrodynamics corrections. The present SLPA ionization cross sections of the L-shell are found to be independent of the charge state of the Si ions. The experimental observations display also quite similar character if the correct mean projectile charge state inside the target is used for including the multiple ionization effect during ion-solid collisions. A general good agreement between the experimental measurements and full theoretical calculations supports the reliability of present results. The comparison also includes the well-known ECPSSR and ECUSAR semi empirical approximations. We noted that the ECUSAR results agree well with the SLPA, while the ECPSSR cross sections are rather low
Odd-even staggering in the yields of intermediate mass fragments from p+Ag collisions at Ep = 480 MeV
U. Singh, B. Kamys , S. Sharma, K. Pysz
abstract
The experimental total production cross-sections of intermediate-mass fragments (isotopes of Li, Be, B, C, N, O, F, Ne, Na, and Mg) were extracted by integration of d2s/dOmegadE data measured at several angles for p+Ag collisions at proton beam energy of 480 MeV. The total cross sections show typical odd?even staggering (OES) when presented as a function of the atomic number Z of ejectiles. The effect is the strongest for products with N = Z and N = Z + 2. Similar behaviour is observed for theoretical cross sections evaluated in the two-step model in which the first stage of the reaction is described by intranuclear cascade INCL++ and the second stage by GEMINI++ model or by two other models, namely ABLA07 and SMM. The OES seems to be even more pronounced for theoretical than for the experimental cross sections.
The predictive power of spallation models for isotopic cross sections
U. Singh, D. Filges, F. Goldenbaum, Boguslaw Kamys, Z. Rudy, and S. Sharma
abstract
The experimental cross sections of isotopically identified products of spallation reactions induced
by 136Xe projectiles at 1 GeV/nucleon on hydrogen target were compared with predictions of a two-step
model. The first stage of the reaction was described by the INCL++ model (version 5.3) of an intranuclear
cascade of nucleon-nucleon and pion-nucleon collisions whereas the second stage was analyzed by means
of four different models; ABLA07, GEM2, GEMINI ++ and SMM. Due to the fact that the experimental
data cover a very broad range of elements; from Li (Z=3) to Ba(Z= 56), the analysis could impose severe
constraints on the applied reaction models. The quality of data reproduction by the theoretical models
is discussed. Some systematic deviations of the theoretical predictions from the experimental results are
observed.