1,721,034 research outputs found
Study of Correlations between Nuclear Flow and Stopping in Heavy-Ion Collisions
No full textThe present work deals with the study of collective flow and nuclear stopping for mass symmetric and asymmetric colliding nuclei in heavy-ion collisions. The simulations are carried out by using Isospin-dependent Quantum Molecular Dynamics (IQMD) model. The role of mass asymmetry on collective flow and nuclear stopping is studied in detail. The nuclear stopping associated with various fragments is also studied. The correlation of nuclear stopping with directed and elliptical flow is also established.
The present thesis is divided into following five chapters.
Chapter 1 presents the general introduction of heavy-ion collisions in mass symmetric and asymmetric reactions. The various observables and their correlation with nuclear equation of state have been discussed. It also presents the status of the available theoretical and experimental attempts made to understand the collective flow, nuclear stopping and correlations between them.
Chapter 2 gives the details of various theoretical models used in literature to study the heavy-ion collisions. This chapter include detailed explanation of the isospin dependent Quantum Molecular Dynamics model used to study the heavy-ion collisions. Primary model produce the phase space of the nucleons. The secondary model namely minimum spanning tree (MST) method used to analyze the phase space of nucleons generated by the primary models is also discussed.
In Chapter 3, the role of isospin degree of freedom in heavy-ion collisions through the transverse momentum (pt), isospin content ratio and system mass dependence of pt-differential transverse flow is discussed. The results are discussed for the symmetric systems. The pt-differential transverse flow is highly sensitive towards the symmetry energy and its density dependence. The pt-differential transverse flow dependence is found to be more sensitive towards the symmetry energy and its density dependence compared to the energy of vanishing flow. The effect of density dependent symmetry energy under different rapidity bins are discussed and compared the theoretical calculations with the experimental data of FOPI collaboration.
Chapter 4, author has studied the effect of mass asymmetry on nuclear stopping ⟨R⟩ by keeping the total mass fixed. A reasonable significance has found in fragments stopping over the nucleons stopping by comparing the theoretical results with experimental data of INDRA collaboration for nearly symmetric reactions. Correlations between directed transverse flow ⟨Pdirx⟩ and nuclear stopping ⟨R⟩ for mass asymmetric reactions have been studied. The study reveals that at high incident energy, correlation between the directed transverse flow and nuclear stopping follows a linear behavior, while at low incident energy, it follows a parabolic behavior. The positive value of elliptical flow signifies the in-plane particles emission, whereas negative value signifies the out-of-plane particles emission. Author has also studied the behavior of nuclear stopping for different fragments in out-of-plane and in-plane emitted particles by studying the nuclear stopping at and around the transition energy.
Finally, the results along with an outlook is summarized in Chapter 5
Role of Momentum Dependent Interactions in Nuclear Stopping
No full textM.Sc. (Physics)The relative role of momentum dependent interactions in nuclear stopping at intermediate energy heavy ion collisions is studied using isospin-dependent quantum dynamics model. The calculations have been done for colliding systems in the energy range between 50 and 1000 MeV/nucleon in the presence of symmetry energy. It is observed that nuclear stopping is sensitive to impact parameter, incident energies and the mass of the colliding system; however it is insensitive to N/Z ratio of the colliding system. The degree of stopping is suppressed by the inclusion of momentum dependent interactions, whereas the particle production is not affected by the MDI.SPM
Study of Anisotropic Flow and Rotational Dynamics at Intermediate Energies
No full textThe present study provides a deep insight on the different aspects of anisotropic flow
and rotational dynamics of heavy ion reactions.
Initially, the general introduction of the nuclear physics has been discussed. In this
thesis, the importance of isospin and rapidity in collective flow, scaling of flow of
fragments and rotational features of heavy ion reactions at the intermediate energies
region have been described extensively. The theoretical and experimental attempts on
the anisotropic flow, scaling of different component of flow and rotational dynamics
have also been discussed.
A brief survey of various primary models based on isospin degree of freedom explicitly in
the literature has also been summarised to study the different aspects of heavy-ion collisions. The model which is used to carry out the present study i.e., Isospin-dependent
Quantum Molecular Dynamics model (IQMD) model has been explained in detail.
Also, the secondary models such as Minimum Spanning Tree (MST) and its updated
versions MSTP have also been discussed.
Furthermore, the yield of nucleons participating in elliptic flow has been studied for the
reactions of 197
79 Au +197
79 Au,
150
60 N d +150
60 N d,
124
50 Sn +124
50 Sn,
96
44Ru +96
44 Ru,
78
36Kr +78
36 Kr,
48
20Ca +48
20 Ca and 40
20Ca +40
20 Ca for various impact parameter ranges over the intermediate energy region. It has been found that the peak of yield of nucleons/protons as
a function of rapidity decreases with decrease in the mass of colliding nuclei. First
and second both transition energies depend on the mass of the fragment. Rotational
phenomenon of nucleons can be observed for nucleons participating in elliptic flow.
The rotational dynamics has been studied for different mass asymmetric systems
122
49 In +126
50 Sn,
114
48 Cs +134
54 In,
100
40 Mo +148
64 Gd,
86
36Kr +162
67 Ho,
71
31Ga +177
71 Lu,
60
28N i +188
76 Os
and 50
24Cr +198
78 P t for incident energies ranging between 40 MeV/nucleon and 400
MeV/nucleon for impact parameter range 0.25 < ˆb < 0.45. Our calculations reveal
that the time evolutions of rotational quantities for participant and spectator nuclear
matter are different in mass asymmetric heavy ion reactions. Theoretical data of BUUmodel’s azimuthal distributions for free protons have been compared successfully with
IQMD model calculations. The rotational flow of free protons with increasing incident
energies has been observed. Elliptic flow (calculated from the fits of azimuthal distributions of free protons) dependence with energy has also been investigated.
In addition to this, scaling of anisotropic flow of fragments has been studied in mass
asymmetric nuclear reactions 122
49 In+126
50 Sn,
114
48 Cs+134
54 In,
100
40 Mo+148
64 Gd,
86
36Kr+162
67 Ho,
71
31Ga+177
71 Lu,
60
28N i+188
76 Os,
50
24Cr+198
78 P t and 40
20Ca+208
82 P b for incident energies ranging
between 50 MeV/nucleon and 400 MeV/nucleon for the range of impact parameter
0.25 < ˆb < 0.45. Our findings have revealed that strength of flow depends on the fragment mass and mass asymmetry content of the reaction for a rapidity range. Rapidity
constraints play a dominant role in the calculation of scaling of flow of fragments.
Lastly, the results of the thesis have been summarised along with the prospect for the
extension of present work
Systematic Study of Multi Fragmentation by using IQMD Model
No full textM.Sc. (Physics)The present work deals with the theoretical study of multifragmentation and its associated phenomena in heavy ion collisions. This work is done with the framework of Isospin Quantum Molecular Dynamical Model (IQMD) and using Minimum Spanning Tree (MST) algorithm. Firstly we give the brief introduction about multifragmentation and the experimental setup of ALADIN Spectrometer at GSI (Germany), which gave the complete set of multifragmentation data. After that we discussed the Isospin Quantum Molecular Dynamics (IQMD). Finally we gives the various simulated results and we discussed some of them with experimental data obtained experimentally from ALADIN. Finally we will summaries our results with an outlook.SPM
Study the Effect of Density Dependence of Symmetry Energy on Fragmentation in Heavy-Ion Collisions at Intermediate Energies
No full textDoctor of PhilosophyIn the present study, we aim to investigate the effect of density dependence of symmetry
energy on multifragmentation, fragment’s flow (i.e. elliptical flow) as well as on nuclear
stopping. The present work is performed within the framework of microscopic dynamical
isospin-dependent quantum molecular dynamics (IQMD) model. We shall here attempt
a descriptive analysis of the fragment production, elliptical flow associated with nucle-
ons and fragments, nuclear dynamics (density & temperature) and nuclear stopping (or
thermalization) reached in heavy-ion collisions subjected to different forms of density
dependence of symmetry energy. Present study includes a detailed discussion of the con-
sequences of different forms of symmetry energy in heavy-ion collisions at intermediate
energies (i.e. between 10 MeV/nucleon and 1 GeV/nucleon).School of Physics and Material Science, Thapar University, Patial
Influence of Symmetry Energy on Fragment Production
No full textM.Sc. (SPMS)The present work deals with the theoretical study dealing with influence of density dependence of symmetry energy on multifragmentation and in heavy ion collision at intermediate energies. We present a complete systematic theoretical study of multifragmentation for mass symmetric colliding nuclei for heavy-ion reactions in the energy range between 50 MeV/nucleon and 1000 MeV/nucleon by using soft equations of state using isospin dependent quantum molecular dynamics (IQMD) model. We envision an interesting outcome for symmetric colliding nuclei small but clear signature influence of density dependence of symmetry energy on fragmentation can be seen. The effect of isospin dependent and constant cross section also has been studied
Nuclear Stopping in Heavy Ion Collisions
No full textM.Sc. (Physics)A semi-classical transport model, namely, Isospin quantum molecular dynamics (IQMD) model, is employed to investigate the emission of free, light charged particles and degree of equilibrium or stopping reached in heavy ion collisions. We study the dependence of nuclear stopping Qzz and R in intermediate energy heavy ion collisions on transverse momentum, rapidity, energy, N/Z and scaled impact parameter. For this study, simulations were carried out for the systems 52Cr24 + 54Ni28, 52Cr24 + 56Ni28, 52Cr24 + 58Ni28, 52Cr24 + 60Ni28, 52Cr24 + 62Ni28 at different beam energies from 50 to 200 MeV/nucleon at reduced impact parameters i.e. at = 0, 0.1, 0.2, 0.3 using soft equation of state (EOS) employed at symmetry energy E = 32 MeV/n. We find that the effect of N/Z on stopping is weak. It is shown that R and Qzz behave as a global stopping parameter. Moreover, maximum stopping is obtained for low beam energies in the presence of symmetry energy in central collisions
Elliptic Flow in Heavy Ion Nuclear Reactions
No full textM.Sc(Physics), SPMSElliptic flow develops because of almond shape of the overlapping region in a heavy ion collision. Elliptical or higher order azimuthal shapes can provide help (a) when the phase space coverage is limited to a narrow region around midrapidity, and (b) at beam energies close to the balance energy, where no net deflection of nucleons is observed. The elliptic flow is expected to be larger in more peripheral collisions because of the anisotropy in coordinate space which is the source of this flow. The study of elliptic flow provides valuable data on the nuclear equation of state and isospin dependent N-N cross section. Study of dependence of elliptic flow and different fragment flows on beam energies, mass number, isospin and impact parameter have revealed quite interesting physics about the properties and origin of collective flow.SPMS, Thapar Universit
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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