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Register a new userInfluence of charge asymmetry and isospin dependent cross-section on elliptical flow
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Using the isospin dependent quantum molecular dynamics model, we study the effect of charge asymmetry and isospin dependent cross-section on different aspects of elliptical flow. Simulations have been carried out for the reactions of $^{124}X_{m}+^{124}X_{m}$, where m = (47, 50, 53, 57 and 59) and $^{40}X_{n}+^{40}X_{n}$, where n= (14, 16, 18, 21 and 23). Our study shows that elliptical flow depend strongly on the isospin of cross-section. The transition energy remains almost constant with increase in N/Z of the system. A good agreement is obtained with experimental measurements.
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Using the isospin dependent quantum molecular dynamics model, we study the effect of charge asymmetry and isospin dependent cross-section on nuclear stopping and multiplicity of free nucleons and LMFs. Simulations were carried out for the reactions $^{124}X_{m}+^{124}X_{m}$, where m varies from 47 to 59 and for $^{40}Y_{n}+^{40}Y_{n}$, where n varies from 14 to 23. Our study shows that nuclear stopping as well as the production of LMFs depend strongly on the isospin of the cross-section.
We aim to explore the effect of isospin dependence of cross section on symmetric and neutron rich system. We also aim to explore whether the analysis is affacted if one discusses in terms of $E_{bal}$ as a function of N/Z or N/A of the system.
The charge asymmetry ($A_{rm ch}$) dependence of the $pi^{-}$ and $pi^{+}$ elliptic flow difference, $Delta v_{2}(A_{rm ch})$, has been regarded as a sensitive observable for the possible chiral magnetic wave (CMW) in relativistic heavy ion collisions. In this work, we first demonstrate that, due to non-flow backgrounds, the flow measurements by the Q-cumulant method using all charged particles as reference introduce a trivial linear term to $Delta v_{2}(A_{rm ch})$. The trivial slope can be negative in the triangle flow difference $Delta v_{3}(A_{rm ch})$ if the non-flow is dominated by back-to-back pairs. After eliminating the trivial term, we find that the non-flow between like-sign pairs gives rise to an additional positive slope to $Delta v_{2}(A_{rm ch})$ because of the larger dilution effect to $pi^{+}$ ($pi^{-}$) at positive (negative) $A_{rm ch}$. We further find that the competition between different $pi$ sources can introduce another non-trivial linear-$A_{rm ch}$ term due to their different multiplicity fluctuations and anisotropic flows. We then study the effect of neutral cluster (resonance) decays as a mechanism for local charge conservation on the slope parameter of $Delta v_{2}(A_{rm ch})$. We find that the slope parameter is sensitive to the kinematics of those neutral clusters. Light resonances give positive slopes while heavy resonances give negative slopes. Local charge conservation from continuum cluster mass distribution can give a positive slope parameter comparable to experimental data. Our studies indicate that many non-CMW physics mechanisms can give rise to a $A_{rm ch}$-dependent $Delta v_{2}(A_{rm ch})$ and the interpretation of $Delta v_{2}(A_{rm ch})$ in terms of the CMW is delicate.
We explore the influence of in-medium nucleon-nucleon cross section, symmetry potential and impact parameter on isospin sensitive observables in intermediate-energy heavy-ion collisions with the ImQMD05 code, a modified version of Quantum Molecular Dynamics model. At incident velocities above the Fermi velocity, we find that the density dependence of symmetry potential plays a more important role on the double neutron to proton ratio $DR(n/p)$ and the isospin transport ratio $R_i$ than the in-medium nucleon-nucleon cross sections, provided that the latter are constrained to a fixed total NN collision rate. We also explore both $DR(n/p)$ and $R_i$ as a function of the impact parameter. Since the copious production of intermediate mass fragments is a distinguishing feature of intermediate-energy heavy-ion collisions, we examine the isospin transport ratios constructed from different groups of fragments. We find that the values of the isospin transport ratios for projectile rapidity fragments with $Zge20$ are greater than those constructed from the entire projectile rapidity source. We believe experimental investigations of this phenomenon can be performed. These may provide significant tests of fragmentation time scales predicted by ImQMD calculations.
The isospin splitting of the in-medium $NNrightarrow NDelta$ cross sections in asymmetric nuclear medium are investigated in the framework of the one-boson exchange model by including $delta$ and $rho$ mesons. Our results show that the that the correction factors $R=sigma_{ NNrightarrow NDelta}^*/sigma_{NNrightarrow NDelta}^{text{free}}$ have $R_{pp to nDelta ^{++}} < R_{nn to pDelta ^{-}}$ and $R_{NN to NDelta ^{+}} <R_{NN to NDelta ^{0}}$ by using the without-$delta$ sets. By including the $delta$ meson, it appears the totally opposite results in the $R$ for different channels, i.e., $R_{pp to nDelta ^{++}} > R_{nn to pDelta ^{-}}$ and $R_{NN to NDelta ^{+}} >R_{NN to NDelta ^{0}}$.
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