The effect of a temperature dependent bulk viscosity to entropy density ratio (ζ/s) along with a ... more The effect of a temperature dependent bulk viscosity to entropy density ratio (ζ/s) along with a constant shear viscosity to entropy density ratio (η/s) on the space time evolution of the fluid produced in high energy heavy ion collisions have been studied in a relativistic viscous hydrodynamics model. The boost invariant Israel-Stewart theory of causal relativistic viscous hydrodynamics is used to simulate the evolution of the fluid in 2 spatial and 1 temporal dimension. The dissipative correction to the freezeout distribution for bulk viscosity is calculated using Grad's fourteen moment method. From our simulation we show that the method is applicable only for ζ/s < 0.004.
We show that if the hadronic resonance gas (HRG), with viscosity to entropy ratio η/s ≈0.24, is p... more We show that if the hadronic resonance gas (HRG), with viscosity to entropy ratio η/s ≈0.24, is physical at temperature T ≈220 MeV, charged particles pT spectra and elliptic flow in Au+Au collisions at RHIC, over a wide range of collision centrality do not distinguish between initial QGP fluid and initial hadronic resonance gas. Unambiguous identification of bulk of the matter produced in Au+Au collisions require clear demonstration that HRG is unphysical at temperature T >200 MeV. It calls for precise lattice simulations with realistic boundary conditions.
Assuming that in Au+Au collisions, a baryon free fluid is produced, transverse momentum spectra o... more Assuming that in Au+Au collisions, a baryon free fluid is produced, transverse momentum spectra of identified particles (π, K, p and φ), in evolution of ideal and viscous fluid is studied. Hydrodynamic evolution is governed by a lattice based equation of state (EOS), where the confinementdeconfinement transition is a cross-over at Tco=196 MeV. Ideal or viscous fluid was initialised to reproduce φ meson multiplicity in 0-5% Au+Au collisions. Ideal or minimally viscous (η/s=0.08) fluid evolution reasonably well explain the transverse momentum spectra of pion's, kaon's, and φ meson's in central and mid-central Au+Au collisions. Description to the data is much poorer in viscous fluid evolution with η/s ≥0.12. The model however under estimate proton production by a factor ∼ 2.
Abstract: The effect of a temperature dependent bulk viscosity to entropy density ratio (ζ/s) alo... more Abstract: The effect of a temperature dependent bulk viscosity to entropy density ratio (ζ/s) along with a constant shear viscosity to entropy density ratio (η/s) on the space time evolution of the fluid produced in high energy heavy ion collisions have been studied in a relativistic viscous hydrodynamics model. The boost invariant Israel-Stewart theory of causal relativistic viscous hydrodynamics is used to simulate the evolution of the fluid in 2 spatial and 1 temporal dimension. The dissipative correction to the freezeout distribution for bulk viscosity is calculated using Grad’s fourteen moment method. From our simulation we show that the method is applicable only for ζ/s < 0.004. PACS (2008): 12.38.Mh,47.75.+f, 25.75.Ld
Finding the existence and the location of the QCD critical point is one of the main goals of the ... more Finding the existence and the location of the QCD critical point is one of the main goals of the RHIC beam energy scan program. To make theoretical predictions and corroborate with the experimental data requires modeling the space-time evolution of the matter created in heavy-ion collisions by dynamical models such as the relativistic hydrodynamics with an appropriate Equation of State (EoS). In the present exploratory study, we use a viscous 2+1 dimensional event-by-event (e-by-e) hydrodynamic code at finite baryon densities with two different EoSs (i) Lattice QCD + HRG with a crossover transition and (ii) EoS with a first-order phase transition to studying the normalized symmetric cumulants of charged pions $v_n$ $(n=2-4)$. We show that the normalized symmetric cumulants can differentiate the two EoSs while all other conditions remain the same. The conclusion does not change for various initial conditions and shear viscosity. This indicates that these observables can be used to ga...
Two positively charged heavy nuclei produce ultra-intense magnetic fields in collider experiments... more Two positively charged heavy nuclei produce ultra-intense magnetic fields in collider experiments at the Relativistic Heavy Ion Collider (RHIC) and at the Large Hadron Collider (LHC), e.g. B ∼ 10 − 10 G for √ sNN = 200 GeV Au+Au collisions. The intensity of the magnetic field in the transverse plane grows approximately linearly with the center-of-mass energy ( √ sNN) [1]. The corresponding electric field in the transverse plane also becomes very large since it is enhanced by a Lorentz factor. Such intense electric and magnetic fields are believed to have a strong impact on the dynamics of high-energy heavyion collisions. For example, in the case of an imbalance in the number of leftvs. righthanded fermions, a charge current is induced in the Quark-Gluon Plasma (QGP), leading to the separation of electrical charges, which is known as the “chiral magnetic effect” (CME) [2].
We derive the relativistic non-resistive, viscous second-order magnetohydrodynamic equations for ... more We derive the relativistic non-resistive, viscous second-order magnetohydrodynamic equations for the dissipative quantities using the relaxation time approximation. The Boltzmann equation is solved for a system of particles and antiparticles using Chapman-Enskog like gradient expansion of the single-particle distribution function truncated at second order. In the first order, the transport coefficients are independent of the magnetic field. In the second-order, new transport coefficients that couple magnetic field and the dissipative quantities appear which are different from those obtained in the 14-moment approximation [1] in the presence of a magnetic field. However, in the limit of the weak magnetic field, the form of these equations are identical to the 14-moment approximation albeit with different values of these coefficients. We also derive the anisotropic transport coefficients in the Navier-Stokes limit.
An intense transient magnetic field is produced in high energy heavy-ion collisions mostly due to... more An intense transient magnetic field is produced in high energy heavy-ion collisions mostly due to the spectator protons inside the two colliding nucleus. The magnetic field introduces anisotropy in the medium and hence the isotropic scalar transport coefficients become anisotropic and split into multiple components. Here we calculate the anisotropic transport coefficients shear, bulk viscosity, electrical conductivity, and the thermal diffusion coefficients for a multicomponent Hadron-Resonance-Gas (HRG) model for a non-zero magnetic field by using the Boltzmann transport equation in a relaxation time approximation (RTA). The anisotropic transport coefficient component along the magnetic field remains unaffected by the magnetic field, while perpendicular dissipation is governed by the interplay of the collisional relaxation time and the magnetic time scale, which is inverse of the cyclotron frequency. We calculate the anisotropic transport coefficients as a function of temperature and magnetic field using the HRG model. The neutral hadrons are unaffected by the Lorentz force and do not contribute to the anisotropic transports, we estimate within the HRG model the relative contribution of isotropic and anisotropic transports as a function of magnetic field and temperature. We also give an estimation of these anisotropic transport coefficients for the hadronic gas at finite baryon chemical potential (µB).
Here we derive the relativistic resistive dissipative second-order magnetohydrodynamic evolution ... more Here we derive the relativistic resistive dissipative second-order magnetohydrodynamic evolution equations using the Boltzmann equation, thus extending our work from the previous paper JHEP 03 (2021) 216 where we considered the non-resistive limit. We solve the Boltzmann equation for a system of particles and antiparticles using the relaxation time approximation and the Chapman-Enskog like gradient expansion for the off-equilibrium distribution function, truncating beyond second-order. In the first order, the bulk and shear stress are independent of the electromagnetic field, however, the diffusion current, shows a dependence on the electric field. In the second-order, the new transport coefficients that couple electromagnetic field with the dissipative quantities appear, which are different from those obtained in the 14-moment approximation [1] in the presence of the electromagnetic field. Also we found out the various components of conductivity in this case.
In this article, there are 18 sections discussing various current topics in the field of relativi... more In this article, there are 18 sections discussing various current topics in the field of relativistic heavy-ion collisions and related phenomena, which will serve as a snapshot of the current state of the art. Section 1 reviews experimental results of some recent light-flavored particle production data from ALICE collaboration. Other sections are mostly theoretical in nature. Very strong but transient magnetic field created in relativistic heavy-ion collisions could have important observational consequences. This has generated a lot of theoretical activity in the last decade. Sections 2, 7, 9, 10 and 11 deal with the effects of the magnetic field on the properties of the QCD matter. More specifically, Sec. 2 discusses mass of [Formula: see text] in the linear sigma model coupled to quarks at zero temperature. In Sec. 7, one-loop calculation of the anisotropic pressure are discussed in the presence of strong magnetic field. In Sec. 9, chiral transition and chiral susceptibility in th...
We investigate the causality and the stability of the relativistic viscous non-resistive magneto-... more We investigate the causality and the stability of the relativistic viscous non-resistive magneto-hydrodynamics in the framework of the Israel-Stewart (IS) second-order theory, and also within a modified IS theory which incorporates the effect of magnetic fields in the relaxation equations of the viscous stress. We compute the dispersion relation by perturbing the fluid variables around their equilibrium values. In the ideal magnetohydrodynamics limit, the linear dispersion relation yields the well-known propagating modes: the Alfvén and the magneto-sonic modes. In the presence of bulk viscous pressure, the causality bound is found to be independent of the magnitude of the magnetic field. The same bound also remains true, when we take the full non-linear form of the equation using the method of characteristics. In the presence of shear viscous pressure, the causality bound is independent of the magnitude of the magnetic field for the two magneto-sonic modes. The causality bound for t...
We calculate the δf correction to the one particle distribution function in presence of magnetic ... more We calculate the δf correction to the one particle distribution function in presence of magnetic field and non-zero shear viscosity within the relaxation time approximation. The δf correction is found to be electric charge dependent. Subsequently, we also calculate one longitudinal and four transverse shear viscous coefficients as a function of dimensionless Hall parameter χH in presence of the magnetic field. We find that a proper linear combination of the shear viscous coefficients calculated in this work scales with the result obtained from Grad's moment method in [42]. Calculation of invariant yield of π − in a simple Bjorken expansion with cylindrical symmetry shows no noticeable change in spectra due to the δf correction for realistic values of the magnetic field and relaxation time. However, when transverse expansion is taken into account using a blast wave type flow field we found noticeable change in spectra and elliptic flow coefficients due to the δf correction. The δf is also found to be very sensitive on the magnitude of magnetic field. Hence we think it is important to take into account the δf correction in more realistic numerical magnetohydrodynamics simulations.
We investigate the effect of intense magnetic fields on the (2 + 1)-dimensional reducedmagnetohyd... more We investigate the effect of intense magnetic fields on the (2 + 1)-dimensional reducedmagnetohydrodynamical (MHD) expansion of hot and dense quark-gluon plasma (QGP) produced in √ s NN = 200 GeV Au+Au collisions. For the sake of simplicity, we consider the case in which the magnetic field points in the direction perpendicular to the reaction plane. We also consider this field to be external, with energy density parametrized as a two-dimensional Gaussian. The width of the Gaussian along the directions orthogonal to the beam axis varies with the centrality of the collision. The dependence of the magnetic field on proper time (τ) is parametrized for the case of zero and finite electrical conductivity of the QGP. We solve the equations of motion of ideal hydrodynamics for such an external magnetic field. For collisions with a non-zero impact parameter we observe a considerable increase in the elliptic-flow coefficient v 2 of π − in the presence of an external magnetic field, and the increment in v 2 is found to depend on the evolution and the initial magnitude of the magnetic field.
Journal of Physics G: Nuclear and Particle Physics, 2018
The interplay of magnetic field and thermal vorticity in a relativistic ideal fluid might generat... more The interplay of magnetic field and thermal vorticity in a relativistic ideal fluid might generate fluid vorticity during the fluid evolution provided the flow fields and the entropy density of the fluid is inhomogeneous [1]. Exploiting this fact and assuming large magnetic Reynolds number we study the evolution of generalised magnetic field (B) which is defined as a combination of the usual magnetic field (B) and relativistic thermal vorticity (ω µν), in a 2(space)+1(time) dimensional isentropic evolution of Quark Gluon Plasma (QGP) with longitudinal boost invariance. The temporal evolution ofB is found to be different than B , and theB evolution also depends on the position of the fluid along the beam direction (taken along the z axis) with respect to the mid-plane z = 0. Further it is observed that the transverse components (Bx,By) evolve differently around the mid-plane.
We estimate the event-by-event (e-by-e) distribution of the ratio (σ) of the magnetic field energ... more We estimate the event-by-event (e-by-e) distribution of the ratio (σ) of the magnetic field energy to the fluid energy density in the transverse plane of Au-Au collisions at √ sNN = 200 GeV. A Monte-Carlo (MC) Glauber model is used to calculate the σ in the transverse plane for impact parameter b=0, 12 fm at time τi ∼0.5 fm. The fluid energy density is obtained by using Gaussian smoothing with two different smoothing parameter σg=0.25 , 0.5 fm. For b = 0 fm collisions σ is found to be ≪ 1 in the central region of the fireball and σ > ∼ 1 at the periphery. For b=12 fm collisions σ > ∼ 1. The e-by-e correlation between σ and the fluid energy density (ε) is studied. We did not find strong correlation between σ and ε at the centre of the fireball, whereas they are mostly anti-correlated at the periphery of the fireball.
In the initial stage of relativistic heavy-ion collisions, strong magnetic fields appear due to t... more In the initial stage of relativistic heavy-ion collisions, strong magnetic fields appear due to the large velocity of the colliding charges. The evolution of these fields appears as a novel and intriguing feature in the fluid-dynamical description of heavy-ion collisions. In this work, we study analytically the one-dimensional, longitudinally boost-invariant motion of an ideal fluid in the presence of a transverse magnetic field. Interestingly, we find that, in the limit of ideal magnetohydrodynamics, i.e., for infinite conductivity, and irrespective of the strength of the initial magnetization, the decay of the fluid energy density e with proper time τ is the same as for the time-honored "Bjorken flow" without magnetic field. Furthermore, when the magnetic field is assumed to decay ∼ τ −a , where a is an arbitrary number, two classes of analytic solutions can be found depending on whether a is larger or smaller than one. In summary, the analytic solutions presented here highlight that the Bjorken flow is far more general than formerly thought. These solutions can serve both to gain insight on the dynamics of heavy-ion collisions in the presence of strong magnetic fields and as testbeds for numerical codes.
The effect of a temperature dependent bulk viscosity to entropy density ratio (ζ/s) along with a ... more The effect of a temperature dependent bulk viscosity to entropy density ratio (ζ/s) along with a constant shear viscosity to entropy density ratio (η/s) on the space time evolution of the fluid produced in high energy heavy ion collisions have been studied in a relativistic viscous hydrodynamics model. The boost invariant Israel-Stewart theory of causal relativistic viscous hydrodynamics is used to simulate the evolution of the fluid in 2 spatial and 1 temporal dimension. The dissipative correction to the freezeout distribution for bulk viscosity is calculated using Grad's fourteen moment method. From our simulation we show that the method is applicable only for ζ/s < 0.004.
We show that if the hadronic resonance gas (HRG), with viscosity to entropy ratio η/s ≈0.24, is p... more We show that if the hadronic resonance gas (HRG), with viscosity to entropy ratio η/s ≈0.24, is physical at temperature T ≈220 MeV, charged particles pT spectra and elliptic flow in Au+Au collisions at RHIC, over a wide range of collision centrality do not distinguish between initial QGP fluid and initial hadronic resonance gas. Unambiguous identification of bulk of the matter produced in Au+Au collisions require clear demonstration that HRG is unphysical at temperature T >200 MeV. It calls for precise lattice simulations with realistic boundary conditions.
Assuming that in Au+Au collisions, a baryon free fluid is produced, transverse momentum spectra o... more Assuming that in Au+Au collisions, a baryon free fluid is produced, transverse momentum spectra of identified particles (π, K, p and φ), in evolution of ideal and viscous fluid is studied. Hydrodynamic evolution is governed by a lattice based equation of state (EOS), where the confinementdeconfinement transition is a cross-over at Tco=196 MeV. Ideal or viscous fluid was initialised to reproduce φ meson multiplicity in 0-5% Au+Au collisions. Ideal or minimally viscous (η/s=0.08) fluid evolution reasonably well explain the transverse momentum spectra of pion's, kaon's, and φ meson's in central and mid-central Au+Au collisions. Description to the data is much poorer in viscous fluid evolution with η/s ≥0.12. The model however under estimate proton production by a factor ∼ 2.
Abstract: The effect of a temperature dependent bulk viscosity to entropy density ratio (ζ/s) alo... more Abstract: The effect of a temperature dependent bulk viscosity to entropy density ratio (ζ/s) along with a constant shear viscosity to entropy density ratio (η/s) on the space time evolution of the fluid produced in high energy heavy ion collisions have been studied in a relativistic viscous hydrodynamics model. The boost invariant Israel-Stewart theory of causal relativistic viscous hydrodynamics is used to simulate the evolution of the fluid in 2 spatial and 1 temporal dimension. The dissipative correction to the freezeout distribution for bulk viscosity is calculated using Grad’s fourteen moment method. From our simulation we show that the method is applicable only for ζ/s < 0.004. PACS (2008): 12.38.Mh,47.75.+f, 25.75.Ld
Finding the existence and the location of the QCD critical point is one of the main goals of the ... more Finding the existence and the location of the QCD critical point is one of the main goals of the RHIC beam energy scan program. To make theoretical predictions and corroborate with the experimental data requires modeling the space-time evolution of the matter created in heavy-ion collisions by dynamical models such as the relativistic hydrodynamics with an appropriate Equation of State (EoS). In the present exploratory study, we use a viscous 2+1 dimensional event-by-event (e-by-e) hydrodynamic code at finite baryon densities with two different EoSs (i) Lattice QCD + HRG with a crossover transition and (ii) EoS with a first-order phase transition to studying the normalized symmetric cumulants of charged pions $v_n$ $(n=2-4)$. We show that the normalized symmetric cumulants can differentiate the two EoSs while all other conditions remain the same. The conclusion does not change for various initial conditions and shear viscosity. This indicates that these observables can be used to ga...
Two positively charged heavy nuclei produce ultra-intense magnetic fields in collider experiments... more Two positively charged heavy nuclei produce ultra-intense magnetic fields in collider experiments at the Relativistic Heavy Ion Collider (RHIC) and at the Large Hadron Collider (LHC), e.g. B ∼ 10 − 10 G for √ sNN = 200 GeV Au+Au collisions. The intensity of the magnetic field in the transverse plane grows approximately linearly with the center-of-mass energy ( √ sNN) [1]. The corresponding electric field in the transverse plane also becomes very large since it is enhanced by a Lorentz factor. Such intense electric and magnetic fields are believed to have a strong impact on the dynamics of high-energy heavyion collisions. For example, in the case of an imbalance in the number of leftvs. righthanded fermions, a charge current is induced in the Quark-Gluon Plasma (QGP), leading to the separation of electrical charges, which is known as the “chiral magnetic effect” (CME) [2].
We derive the relativistic non-resistive, viscous second-order magnetohydrodynamic equations for ... more We derive the relativistic non-resistive, viscous second-order magnetohydrodynamic equations for the dissipative quantities using the relaxation time approximation. The Boltzmann equation is solved for a system of particles and antiparticles using Chapman-Enskog like gradient expansion of the single-particle distribution function truncated at second order. In the first order, the transport coefficients are independent of the magnetic field. In the second-order, new transport coefficients that couple magnetic field and the dissipative quantities appear which are different from those obtained in the 14-moment approximation [1] in the presence of a magnetic field. However, in the limit of the weak magnetic field, the form of these equations are identical to the 14-moment approximation albeit with different values of these coefficients. We also derive the anisotropic transport coefficients in the Navier-Stokes limit.
An intense transient magnetic field is produced in high energy heavy-ion collisions mostly due to... more An intense transient magnetic field is produced in high energy heavy-ion collisions mostly due to the spectator protons inside the two colliding nucleus. The magnetic field introduces anisotropy in the medium and hence the isotropic scalar transport coefficients become anisotropic and split into multiple components. Here we calculate the anisotropic transport coefficients shear, bulk viscosity, electrical conductivity, and the thermal diffusion coefficients for a multicomponent Hadron-Resonance-Gas (HRG) model for a non-zero magnetic field by using the Boltzmann transport equation in a relaxation time approximation (RTA). The anisotropic transport coefficient component along the magnetic field remains unaffected by the magnetic field, while perpendicular dissipation is governed by the interplay of the collisional relaxation time and the magnetic time scale, which is inverse of the cyclotron frequency. We calculate the anisotropic transport coefficients as a function of temperature and magnetic field using the HRG model. The neutral hadrons are unaffected by the Lorentz force and do not contribute to the anisotropic transports, we estimate within the HRG model the relative contribution of isotropic and anisotropic transports as a function of magnetic field and temperature. We also give an estimation of these anisotropic transport coefficients for the hadronic gas at finite baryon chemical potential (µB).
Here we derive the relativistic resistive dissipative second-order magnetohydrodynamic evolution ... more Here we derive the relativistic resistive dissipative second-order magnetohydrodynamic evolution equations using the Boltzmann equation, thus extending our work from the previous paper JHEP 03 (2021) 216 where we considered the non-resistive limit. We solve the Boltzmann equation for a system of particles and antiparticles using the relaxation time approximation and the Chapman-Enskog like gradient expansion for the off-equilibrium distribution function, truncating beyond second-order. In the first order, the bulk and shear stress are independent of the electromagnetic field, however, the diffusion current, shows a dependence on the electric field. In the second-order, the new transport coefficients that couple electromagnetic field with the dissipative quantities appear, which are different from those obtained in the 14-moment approximation [1] in the presence of the electromagnetic field. Also we found out the various components of conductivity in this case.
In this article, there are 18 sections discussing various current topics in the field of relativi... more In this article, there are 18 sections discussing various current topics in the field of relativistic heavy-ion collisions and related phenomena, which will serve as a snapshot of the current state of the art. Section 1 reviews experimental results of some recent light-flavored particle production data from ALICE collaboration. Other sections are mostly theoretical in nature. Very strong but transient magnetic field created in relativistic heavy-ion collisions could have important observational consequences. This has generated a lot of theoretical activity in the last decade. Sections 2, 7, 9, 10 and 11 deal with the effects of the magnetic field on the properties of the QCD matter. More specifically, Sec. 2 discusses mass of [Formula: see text] in the linear sigma model coupled to quarks at zero temperature. In Sec. 7, one-loop calculation of the anisotropic pressure are discussed in the presence of strong magnetic field. In Sec. 9, chiral transition and chiral susceptibility in th...
We investigate the causality and the stability of the relativistic viscous non-resistive magneto-... more We investigate the causality and the stability of the relativistic viscous non-resistive magneto-hydrodynamics in the framework of the Israel-Stewart (IS) second-order theory, and also within a modified IS theory which incorporates the effect of magnetic fields in the relaxation equations of the viscous stress. We compute the dispersion relation by perturbing the fluid variables around their equilibrium values. In the ideal magnetohydrodynamics limit, the linear dispersion relation yields the well-known propagating modes: the Alfvén and the magneto-sonic modes. In the presence of bulk viscous pressure, the causality bound is found to be independent of the magnitude of the magnetic field. The same bound also remains true, when we take the full non-linear form of the equation using the method of characteristics. In the presence of shear viscous pressure, the causality bound is independent of the magnitude of the magnetic field for the two magneto-sonic modes. The causality bound for t...
We calculate the δf correction to the one particle distribution function in presence of magnetic ... more We calculate the δf correction to the one particle distribution function in presence of magnetic field and non-zero shear viscosity within the relaxation time approximation. The δf correction is found to be electric charge dependent. Subsequently, we also calculate one longitudinal and four transverse shear viscous coefficients as a function of dimensionless Hall parameter χH in presence of the magnetic field. We find that a proper linear combination of the shear viscous coefficients calculated in this work scales with the result obtained from Grad's moment method in [42]. Calculation of invariant yield of π − in a simple Bjorken expansion with cylindrical symmetry shows no noticeable change in spectra due to the δf correction for realistic values of the magnetic field and relaxation time. However, when transverse expansion is taken into account using a blast wave type flow field we found noticeable change in spectra and elliptic flow coefficients due to the δf correction. The δf is also found to be very sensitive on the magnitude of magnetic field. Hence we think it is important to take into account the δf correction in more realistic numerical magnetohydrodynamics simulations.
We investigate the effect of intense magnetic fields on the (2 + 1)-dimensional reducedmagnetohyd... more We investigate the effect of intense magnetic fields on the (2 + 1)-dimensional reducedmagnetohydrodynamical (MHD) expansion of hot and dense quark-gluon plasma (QGP) produced in √ s NN = 200 GeV Au+Au collisions. For the sake of simplicity, we consider the case in which the magnetic field points in the direction perpendicular to the reaction plane. We also consider this field to be external, with energy density parametrized as a two-dimensional Gaussian. The width of the Gaussian along the directions orthogonal to the beam axis varies with the centrality of the collision. The dependence of the magnetic field on proper time (τ) is parametrized for the case of zero and finite electrical conductivity of the QGP. We solve the equations of motion of ideal hydrodynamics for such an external magnetic field. For collisions with a non-zero impact parameter we observe a considerable increase in the elliptic-flow coefficient v 2 of π − in the presence of an external magnetic field, and the increment in v 2 is found to depend on the evolution and the initial magnitude of the magnetic field.
Journal of Physics G: Nuclear and Particle Physics, 2018
The interplay of magnetic field and thermal vorticity in a relativistic ideal fluid might generat... more The interplay of magnetic field and thermal vorticity in a relativistic ideal fluid might generate fluid vorticity during the fluid evolution provided the flow fields and the entropy density of the fluid is inhomogeneous [1]. Exploiting this fact and assuming large magnetic Reynolds number we study the evolution of generalised magnetic field (B) which is defined as a combination of the usual magnetic field (B) and relativistic thermal vorticity (ω µν), in a 2(space)+1(time) dimensional isentropic evolution of Quark Gluon Plasma (QGP) with longitudinal boost invariance. The temporal evolution ofB is found to be different than B , and theB evolution also depends on the position of the fluid along the beam direction (taken along the z axis) with respect to the mid-plane z = 0. Further it is observed that the transverse components (Bx,By) evolve differently around the mid-plane.
We estimate the event-by-event (e-by-e) distribution of the ratio (σ) of the magnetic field energ... more We estimate the event-by-event (e-by-e) distribution of the ratio (σ) of the magnetic field energy to the fluid energy density in the transverse plane of Au-Au collisions at √ sNN = 200 GeV. A Monte-Carlo (MC) Glauber model is used to calculate the σ in the transverse plane for impact parameter b=0, 12 fm at time τi ∼0.5 fm. The fluid energy density is obtained by using Gaussian smoothing with two different smoothing parameter σg=0.25 , 0.5 fm. For b = 0 fm collisions σ is found to be ≪ 1 in the central region of the fireball and σ > ∼ 1 at the periphery. For b=12 fm collisions σ > ∼ 1. The e-by-e correlation between σ and the fluid energy density (ε) is studied. We did not find strong correlation between σ and ε at the centre of the fireball, whereas they are mostly anti-correlated at the periphery of the fireball.
In the initial stage of relativistic heavy-ion collisions, strong magnetic fields appear due to t... more In the initial stage of relativistic heavy-ion collisions, strong magnetic fields appear due to the large velocity of the colliding charges. The evolution of these fields appears as a novel and intriguing feature in the fluid-dynamical description of heavy-ion collisions. In this work, we study analytically the one-dimensional, longitudinally boost-invariant motion of an ideal fluid in the presence of a transverse magnetic field. Interestingly, we find that, in the limit of ideal magnetohydrodynamics, i.e., for infinite conductivity, and irrespective of the strength of the initial magnetization, the decay of the fluid energy density e with proper time τ is the same as for the time-honored "Bjorken flow" without magnetic field. Furthermore, when the magnetic field is assumed to decay ∼ τ −a , where a is an arbitrary number, two classes of analytic solutions can be found depending on whether a is larger or smaller than one. In summary, the analytic solutions presented here highlight that the Bjorken flow is far more general than formerly thought. These solutions can serve both to gain insight on the dynamics of heavy-ion collisions in the presence of strong magnetic fields and as testbeds for numerical codes.
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