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Influence of Nucleon-Nucleon Collisions on Multi-Fragmentation and Nuclear Flow
No full textPh.D.The present work deals with the theoretical study of multi-fragmentation and its related
phenomena like rapidity distribution, collective
ow and nuclear stopping for asymmetric
colliding nuclei at intermediate energy heavy-ion collisions. The theoretical investigations
are carried out using microscopic isospin-dependent quantum molecular (IQMD) model. We
aim to discuss the role of Coulomb interactions, nuclear equations of state (NEOS) and various
rapidity bins by taking mass asymmetry into account. An attempt will also be made
to understand the disappearance of directed transverse
ow and elliptical
ow and hence
balance energy and transition energy, respectively. We shall also present the comparison of
theoretical simulations with data produced by various experimental collaborations.
The present thesis is divided into following seven chapters.
Chapter 1 outlines the general introduction and background of the present work. The
di erent phenomena, observables at intermediate energies i.e. NEOS, isospin physics, multifragmentation,
collective Flow, as well as nuclear stopping are introduced. It also presents
the status of the available experimental and theoretical attempts made to understand the
above mentioned phenomena.
Chapter 2 gives the detail of primary and secondary models. The primary models
include various theoretical models used in literature to study the phase space of nucleons
in heavy-ion reactions and secondary models include the di erent clusterization algorithms.
In the rst part, the di erent theoretical models like Boltzman Uehling-Uhlenbeck (BUU)
model, Classical Molecular Dynamics (CMD) model, Quantum Molecular Dynamics (QMD)
model, Relativistic QMD (RQMD) model and Isospin-dependent QMD (IQMD) model are
discussed to study heavy-ion reactions. The second part presents the di erent secondary
models used to analyze the phase space of nucleons generated by the primary models. These
secondary models include Minimum Spanning Tree (MST) method, MST with momentum
cut (MSTP), MST with binding energy cut (MSTB), and Simulated Annealing Clusteriza-
1
tion Algorithm (SACA). Since our theoretical basis is the QMD and IQMD model, we shall
discuss these two models in detail, while the detail of MST method is given where ever it is
used.
In Chapter 3, we present a complete systematic theoretical study of multi-fragmentation
for free nucleons and various fragments by simulating di erent asymmetric reactions at incident
beam energies between 50 and 600 MeV/nucl. at semi-central impact parameter using
soft and hard NEOS. While the total mass of the system stays constant, mass asymmetry
varies between 0.2 and 0.7. We nd that in the case of nearly symmetric reaction, spectator
parts will come from both projectile and target, whereas in the case of highly asymmetric
reaction, no spectator part will come from projectile i.e. only target will contribute to the
spectators. Although nearly symmetric nuclei depict a well-known trend of rising and falling
for intermediate mass fragment (IMF's) production with peak around E= 100 MeV/nucl.,
this trend, however, is completely missing for large asymmetric colliding nuclei. The measured
distributions are also given as a function of the total charge of all projectile fragments,
Zbound. The highly asymmetric system produces largest Zbound, while, maximum number of
intermediate mass fragments (IMF's) are produced at Zbound = 20. This observation may
throw light on the formation mechanisms behind multi-fragmentation. Moreover, the brief
study of the directed transverse
ow shows that balance energy is a ected by the Coulomb
interactions as well as di erent NEOS. This balance energy is further parametrized in terms
of mass power law.
In Chapter 4, within the semi-classical transport simulations of energetic semi-central
collisions of the 79Au197+79Au197 reaction, we present a new investigation of the interplay between
the participant and spectator regions in terms of rapidity distributions. The maxima
and minima in the incident energy dependence of elliptical
ow are produced by di erent
contributions of the passing time of the spectator and the expansion time of the participant.
The shadowing of the spectator matter plays an important role up to later times due to the
comparable magnitude of the passing and expansion times up to energies of 400 MeV/nucl.
However, at high energies the shadowing e ect is dominant only at earlier times due to the
2
fact that the passing time is shorter than the expansion time. The transition from in-plane
to out-of-plane emission is observed only when the mid-rapidity region is included into the
rapidity bin. Otherwise, no transition is observed. The transition energy is found to be
strongly dependent on the size of the rapidity bin, while only depends weakly on the type
of the rapidity distributions. The transition energy is parameterized by a straight-line interpolation.
A comparison with experimental bins reveals that a competition is observed
between the rapidity bins of jY redj 0:1 and jY redj 0:3.
In Chapter 5, we present the systematic theoretical results on elliptical
ow by analyzing
nearly symmetric and asymmetric reactions at di erent incident energies. In the case of
nearly symmetric reactions, general features of the elliptical
ow are investigated with the
help of theoretical simulations, particularly, the transverse momentum, impact parameter,
system size and incident energy dependence. Special emphasis is put on the energy dependence
of the elliptical
ow. We also compare our theoretical calculations with 4 Array
data. This comparison, performed for the reaction of 18Ar40 +21 Sc45 shows that the hard
NEOS explains the data nicely. In general, a reasonable agreement is obtained between the
data and calculations. We also predict that elliptical
ow for di erent kind of fragments
follows power law dependence C(Atot) .
Moreover, in the case of asymmetric reactions, elliptical
ow is analyzed by varying the
mass asymmetry of colliding nuclei while total mass is kept xed. The mass asymmetry dependence
of elliptical
ow (in terms of transverse momentum dependence) for free nucleons
and LMF's shows a weaker squeeze-out
ow as compared to larger asymmetric reactions.
Moreover, the elliptical
ow is found to show a transition from in-plane to out-of-plane in
the mid rapidity region with incident energy, while no such transition is observed when integrated
over the entire rapidity region. The transition energy, at which elliptical
ow < V2 >
changes sign from positive to negative values, is di erent for di erent mass asymmetries,
and is found to increase with the mass asymmetry for lighter fragments. The comparison
with experimental data of INDRA@(GSI+GANIL) and MSU collaborations supports our
ndings.
3
In Chapter 6, we study the nuclear stopping in asymmetric colliding channels by keeping
total mass xed. The calculations are carried out by varying the mass asymmetry of the
colliding pairs with di erent neutron-proton ratios at incident beam energy 250 MeV/nucl.
The contribution of the neutrons and protons is checked in terms of anisotropy ratio < R >
and quadrupole moment < Qzz >. The maximum stopping is obtained for nearly symmetric
systems. Also a reasonable agreement is observed between theoretical results of anisotropy
ratio < R > and energy dependent anisotropy ratio < RE > with the experimental data of
INDRA collaboration.
Finally, we will summarize our results in Chapter 7
Dependence of Nuclear Flow on Different Parts of Nuclear Interaction Potential
No full textBackground: During a heavy ion reaction, the interaction between projectile and target nucleons takes place and the outcome of a reaction depends strongly on the nuclear interaction potential, which is the imperative factor in deciding the fate of reaction. Several efforts have been made in this direction to explore number of phenomena. One of the most sought after phenomena in this direction is the collective flow and its various forms.
Purpose: This study aims to investigate the dependence of collective nuclear flow on different parts of nucleon-nucleon interaction potential for different mass asymmetric reactions ^{129}Xe + ^{124}Sn (\eta = 0), ^{82}Kr + ^{158}Gd (\eta = 0.3), ^{56}Fe + ^{184}W (\eta = 0.5) and ^{35}Cl + ^{205}Tl (\eta = 0.7) by keeping Atotal=240Atotal=240 units. Two different signatures of collective flow have been studied: a) bounce-off of compressed matter in the reaction plane called directed flow and b) squeeze-out of the participant matter out of the reaction plane called elliptical flow.
Methods: The present work is carried out within the Isospin dependent Quantum Molecular Theoretical Framework in which total interaction potential is composed of Skyrme potential, Yukawa Potential, Coulomb Potential, Momentum dependent interaction potential and symmetry potential.
Results: The findings reveal that the directed flow increases with addition of momentum dependent interactions and symmetry potential while the elliptical flow tend to decrease with addition of these potentials.
Conclusions: Both the momentum dependent interaction potential and symmetry potential have sizable affect on the magnitude of collective nuclear flow. A comparison between our calculations and experimental data for the energy dependence of elliptical flow for ^{129}{50}Xe + ^{124}{50}Sn reaction reveals that all the components of nuclear potential are necessary to explain the reaction dynamics
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Effect of clusterization algorithm with isospin-dependent nuclear charge radii parameterization on azimuthal angle dependence of elliptical flow
Full text link638-642The momentum constraint (Pclus) in Minimum Spanning Tree (MST) clusterization algorithm has been modified from isospin - independent (RLDM) to isospin - dependent (RRR) nuclear charge radii parameterization. The influence of MST with modified momentum constraint has been examined on the azimuthal angle dependence of dN/d (Cos2ϕ) (a signature of elliptical flow) for the reaction of Ca + Ca and Au + Au at incident energies of 50 and 400 MeV/nucleon by using isospin-dependent quantum molecular dynamics (IQMD) model. The study reveals that the influence of modified momentum constraint is significant for lighter colliding nuclei at low incident energies. Furthermore, this effect diminishes as the incident energy and composite system mass increases
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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