Hydrodynamical model for J / ψ suppression and elliptic flow

2015

Phys. Rev. C

The fragmentation of excited hypernuclear system formed in heavy ion collisions has been described by the canonical thermodynamical model extended to three component systems. The multiplicity distribution of the fragments has been analyzed in detail and it has been observed that the hyperons have the tendency to get attached to the heavier fragments. Another important observation is the phase coexistence of the hyperons, a phenomenon which is linked to liquid gas phase transition in strange matter. PACS numbers: 25.70.Mn, 25.70.Pq Introduction:-The physics of hypernuclei is an important area of study in the regime of high energy heavy ion collisions. It has been observed that baryons and mesons(strange hadrons) are produced abundantly in high energy heavy ion reactions. Hypernuclei are formed when the strange hyperons or baryons are captured by the nuclei. The Λ-nucleon interactions are well studied and the potential depth of Λ hyperons is such that bound Λ hypernuclear states exist. The only bound Σ hypernucleus known so far is which is bound by isospin forces [1]. Several Ξ hypernuclear states are reported in the literature and hence its interaction with nucleon seems to be attractive. On the other hand the hyperon-hyperon interaction is not really well known; a few double Λ hypernuclear states have been reported. The interaction between other pairs of hyperons as Λ Ξ or Ξ Ξ is not known experimentally [2]. The formation of multi-strange nuclei is especially important in order to study the properties of strange matter. Deep understanding of strange matter is extremely important for the formulation of models of strong interaction [3]. Another important application of this study is the core of neutron stars [4] where the hyperons are expected to be produced in abundance at high density nuclear matter. The stability of hypernuclei beyond the neutron and proton driplines(normal nuclear chart) is also a fascinating subject which is important in recent day activities [5][6][7]. The knowledge of structure of normal nuclei [8] as well as the extension of the nuclear chart into the strangeness sector [9-11] gets valuable input from the results of hypernuclei study. Another important area in the study of intermediate energy heavy ion collisions is the phenomenon of phase coexistence or liquid gas phase transition [12][13][14]. The appearance of 'liquid-like' as well as 'gas-like' fragments simultaneously over a temperature interval is linked to first order phase transition. Whether this phase-coexistence will still persist in the presence of hyper-fragments(strange fragments) is the object of investigation in this work. The canonical thermodynamical model has already been extended to three component systems [15] i.e, inclusion of hyperons(usually Λ in addition to the neutrons and the protons). Due to fragmentation of the PLF, normal (non-strange) components as well as hypernuclei will be

mentioning

confidence: 84%

“…fragments. This phenomenon has been well studied for non strange fragments in both statistical [14,23,29,30] and dynamical [31] models as well as in experimental observations [13,32] and hence we will not elaborate here. Our main motivation is to investigate the fragmentation of a nucleus with considerable amount of strangeness H = 8.…”

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confidence: 99%

Liquid-gas phase transition in hypernuclei

2015

Phys. Rev. C

“…In this section we describe briefly the canonical and the grand canonical models of nuclear multifragmentation. The basic output from canonical [3] or grand canonical model [16] is multiplicity of the fragments. After calculating the multiplicities, isoscaling and isobaric yield ratio parameters can be obtained.…”

Section: The Canonical and The Grand Canonical Modelmentioning

confidence: 99%

“…In the grand canonical model [16], if the neutron chemical potential is µ n and the proton chemical potential is µ p , then statistical equilibrium implies [17] that the chemical potential of a composite with N neutrons and Z protons is µ n N + µ p Z. The average number of composites with N neutrons and Z protons is given by [16] n N,Z gc = e βµnN +βµpZ ω N,Z…”

Section: The Canonical and The Grand Canonical Modelmentioning

confidence: 99%

Effect of particle fluctuation on isoscaling and isobaric yield ratio of nuclear multifragmentation

2013

Physics Letters B

Isoscaling and isobaric yield ratio parameters are compared from canonical and grand canonical ensembles when applied to multifragmentation of finite nuclei. Source dependence of isoscaling parameters & source and isospin dependence of isobaric yield ratio parameters are examined in the framework of the canonical and the grand canonical models. It is found that as the nucleus fragments more, results from both the ensembles converge and observables calculated from the canonical ensemble coincide more with those obtained from the formulae derived using the grand canonical ensemble.

“…Calculations by canonical or any other ensemble that are otherwise better suited for describing intermediate energy nuclear reactions might lead to values widely different from the input value of C sym used. Results from canonical [18] and grand canonical ensemble [24] differ in general for finite nuclei [25]. This work also presents a comparative analysis of the predictive power of the different existing formulas both at the primary stage and also after evaporation and their relative agreement with experimental data.…”

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confidence: 95%

Symmetry energy from nuclear multifragmentation

2013

Phys. Rev. C

The ratio of symmetry energy coefficient to temperature Csym/T is extracted from different prescriptions using the isotopic as well as the isobaric yield distributions obtained in different projectile fragmentation reactions. It is found that the values extracted from our theoretical calculation agree with those extracted from the experimental data but they differ very much from the input value of the symmetry energy used. The best possible way to deduce the value of the symmetry energy coefficient is to use the fragment yield at the breakup stage of the reaction and it is better to use the grand canonical model for the fragmentation analysis. This is because the formulas that are used for the deduction of the symmetry energy coefficient are all derived in the framework of the grand canonical ensemble which is valid only at the break-up (equilibrium) condition. The yield of "cold" fragments either from the theoretical models or from experiments when used for extraction of the symmetry energy coefficient using these prescriptions might lead to the wrong conclusion.PACS numbers: 25.70Mn, 25.70PqIntroduction:-Isospin-dependent phenomena in nuclear physics has been an active area of research [1,2] in recent years with the aim of enriching our knowledge about the symmetry term of the nuclear equation of state. The study of this quantity at different regimes of density and temperature is a hot topic [3][4][5] in the nuclear physics community. This term plays an important role in areas of astrophysical interest such as the study of supernova explosions and the properties of neutron stars [6]. This also has significant influence in deciding the structure of neutron-rich and neutron-deficient nuclei. The study of nuclear multifragmentation in heavyion reactions is an important tool for extracting information about the symmetry energy term, and this has created much interest in the nuclear physics community in recent years [7][8][9][10][11][12][13][14][15][16][17]. In nuclear multifragmentation reactions, the neutronproton composition of the break-up fragments is dictated by the asymmetry term of the equation of state and hence the study of the multifragmentation process allows one to obtain information about the symmetry term. Statistical models [18][19][20] that are simple and economic are very successful in predicting the outcome of nuclear multifragmentation reactions. Different formulas [14,[21][22][23] have been proposed in the literature that connect the measurable fragment isotopic and isobaric observables of multifragmentation reactions to the symmetry energy of excited nuclei and these have been applied to the analysis of heavy-ion collision data. These formulas have all been deduced using the grand canonical version of the nuclear multifragmentation model assuming an equilibrium scenario for the break-up stage of the disintegrating system. They have been used to analyze experimental data from different projectile fragmentation as well as central collision reactions and the extracted values for the symmetry ener...