International Journal of Modern Physics E

The relativistic heavy-ion collider (RHIC) was constructed to achieve an asymptotic state of nuclear matter in heavy-ion collisions, a near-ideal gas of deconfined quarks and gluons denoted quark–gluon plasma or QGP. RHIC collisions are indeed very different from the hadronic processes observed at the Bevalac and AGS, but high-energy elementary-collision mechanisms are also non-hadronic. The two-component model (TCM) combines measured properties of elementary collisions with the Glauber eikonal model to provide an alternative asymptotic limit for A–A collisions. RHIC data have been interpreted to indicate formation of a strongly-coupled QGP (sQGP) or "perfect liquid". In this review, I consider the experimental evidence that seems to support such conclusions and alternative evidence that may conflict with those conclusions and suggest different interpretations.

Since the discovery that the ratio of inclusive charged lepton (per-nucleon) cross-sections from a nucleus A to the deuteron is not unity — even in deep inelastic scattering kinematics — a great deal of experimental and theoretical effort has gone into understanding the phenomenon. The EMC effect, as it is now known, shows that even in the most extreme kinematic conditions the effects of the nucleon being bound in a nucleus cannot be ignored. In this paper, we collect the most precise data available for various nuclear to deuteron ratios, as well as provide a commentary on the current status of the theoretical understanding of this thirty year old effect.

The successful precision measurement of the rate of muon capture on a proton by the MuCap Collaboration allows for a stringent test of the current theoretical understanding of this process. Chiral perturbation theory (χPT), which is a low-energy effective field theory (EFT) that preserves the symmetries and the pattern of symmetry breaking in the underlying theory of QCD, offers a systematic framework for describing μp capture and provides a basic test of QCD at the hadronic level. We describe how this effective theory with no free parameters reproduces the measured capture rate. A recent study has addressed new sources of uncertainties that were not considered in the previous works, and we review to what extent these uncertainties are now under control. Finally, the rationale for studying muon capture on the deuteron and some recent theoretical developments regarding this process are discussed.

We have studied the neutron-capture reactions ^10,11B(n, γ) and the role of the ¹¹B(n, γ) reaction in seeding r-process nucleosynthesis. The possibility of the description of the available experimental data for cross-sections of the neutron capture reaction on ¹⁰B at thermal and astrophysical energies, taking into account the resonance at 475 keV, was considered within the framework of the modified potential cluster model (MPCM) with forbidden states (FS) and accounting for the resonance behavior of the scattering phase shifts. In the framework of the same model, the possibility of describing the available experimental data for the total cross-sections of the neutron radiative capture on ¹¹B at thermal and astrophysical energies were considered with taking into account the 21 and 430 keV resonances. Description of the available experimental data on the total cross-sections and astrophysical S-factor of the radiative proton capture on ¹¹B to the GS of ¹²C was treated at astrophysical energies. The possibility of description of the experimental data for the astrophysical S-factor of the radiative proton capture on ¹⁴C to the GS of ¹⁵N at astrophysical energies, and the radiative proton capture on ¹⁵N at the energies from 50 to 1500 keV was considered in the framework of the MPCM with the classification of the orbital states according to Young tableaux. It was shown that, on the basis of the M1 and the E1 transitions from different states of the p¹⁵N scattering to the GS of ¹⁶O in the p¹⁵N channel, it is quite succeed to explain general behavior of the S-factor in the considered energy range in the presence of two resonances.

A plasma boundary reconstruction code has been designed by using current filament method to calculate the magnetic flux and consequently plasma boundary in Damavand tokamak. Hence, a computer-based code "The Plasma Boundary Reconstruction Code in Tokamak (PBRCT)" was developed to make a graphical user interface and to speed up the plasma boundary estimation algorithm. All required tools as the plasma boundary and magnetic surface display (MSD), error display, primary conditions and modeling panel as well as a search motor to determine a good position and number of the current filaments to find a precise model have been considered. The core is a 3000 lines Matlab code and the graphical user interface is 10,000 lines in C# language.

Experiment and lattice simulation show that the quark–gluon plasma (QGP) system displays strong interaction between constituents at temperature a few times the critical temperature T_c. This QGP picture can be explained by assuming that the QGP matter above T_c is rich in different kinds of bound states, namely resonance-like QGP (RQGP). The chemical composition of the QGP system produced in ultra-relativistic heavy-ion collisions can be investigated through a general charge balance function which describes two-wave quark production during expansion afterward. In this paper, we investigate the signals of this RQGP through general charge balance functions. We find that the quasiparticles in QGP contribute a little to the balance functions because of their heavy masses. The balance functions reduce to the situation discussed before where only one-wave charge production is involved if only the quasiparticles in QGP are considered. However, the baryonic bound states in QGP have a significant effect on the balance function , causing a dip in the balance function at small Δy. The existence of the binary and baryonic bound states amplify the negative dip of the balance function B_pK^-(Δy) at Δy ∽ 1.

Combining the new spectroscopy results of ¹⁴⁴Tb and previous spectroscopy studies of neighboring nuclei, a systematic investigation on the low-lying spectra in N = 78 ~ 80 isotones is performed. Good systematics have been found for the coupling patterns which couple the odd nucleon(s), such as πh_11/2, , to the 2⁺, 4⁺, 6⁺ and 3^- core excitations. It is found that the relative excitation energies of the states formed by coupling h_11/2 proton(s) to the 2⁺, 4⁺ core excitations are pushed up, in contrast with those formed by coupling h_11/2 neutron hole(s) to the 2⁺, 4⁺ core excitations, which are pulled down. According to the systematics, the interpretation that the 17/2⁺ states observed in ¹⁴¹Sm and ¹⁴³Gd are the fully aligned member of coupling the odd h_11/2 neutron hole to the octupole 3^- core excitation, is explored to the isotones ¹⁴⁵Dy, ¹⁴²Eu, and ¹⁴⁴Tb.

The random phase approximation (RPA) equations based on the generalized density matrix (GDM), the so-called GDRPA are reformulated in a more compact matrix form, which renders the method especially suitable for realistic nuclear structure calculations. The GDRPA Hamiltonian is expressed in terms of the one-body particle–particle (pp) and hole–hole (hh) density matrices, and the nuclear force contributes not only in the particle–hole (ph) channel, as in normal ph-RPA, but also in the pp and hh channels. The Hamiltonian is diagonalized iteratively starting from initial guess values and the iterating process is carried out until self-consistency is achieved. The calculation in the model space 1p, 1d and 2s using Warburton and Brown interaction WBP is performed for ¹⁶O. The GDRPA in the ph shell model calculations is tested, by comparing the energy eigenvalues and the electron scattering form factors with the results of the normal RPA and with the available experimental data.

By exploiting supersymmetry inspired factorization method nucleon–nucleon (n–n) potentials, both energy dependent and independent, in the partial waves ¹P₁ and ³P₁ are generated by judicious use of appropriate ground state wave functions and interactions. The energy independent Hulthen and energy dependent equivalent local Yamaguchi potentials and their corresponding S-wave functions are used as the starting point of our calculation. The scattering phase shifts are computed for the constructed potentials through Phase Function Method (PFM) and compared with the standard results to examine the merit of our approach to the problem.

A detailed study on the multiplicity characteristics of the slow target fragments emitted in relativistic heavy-ion collisions has been carried out at E_Lab = 3.7A and 200A GeV using ³²S projectile. The beam energy dependence of the black particles produced in the full phase space of ³²S-emulsion (³²S-Em) interactions on the target size in terms of their moments (mean, variance, skewness and kurtosis) is investigated. The various order moments of target fragments emitted in the interactions of ³²S beams with the heavy (AgBr) target nuclei are estimated in the forward (FHS) and backward (BHS) hemispheres. The investigated values of ratio of variance to mean at both energies show that the multiplicity distributions (MDs) are not Poissonian and the strongly correlated emission of target fragments are in the forward directions. The degree of anisotropic fragment emission and nature of correlation among the emitted fragments are investigated. The energy dependence of entropy is examined in both hemispheres. The entropy values normalized to average multiplicity are found to be energy independent. Scaling of MD of black particles produced in these interactions has been studied to verify the validity of scaling hypothesis via two scaling (Koba–Nielsen–Olesen (KNO)-scaling and Hegyi-scaling) functions. A simplified universal function has been used in each scaling to display the experimental data.

The elastic scattering of deuterons, ³He and ⁴He on ⁶Li at different incident energies have been analyzed in the framework of the optical model (OM) using ECIS88 as well as SPI GENOA codes. The optical potential parameters were extracted in the phenomenological treatment. A good agreement between theoretical and experimental differential cross-sections was obtained in whole angular range. Parameters for real part of potential have been also calculated microscopically with double-folding model for the d, ³He and ⁴He scattering, respectively, using DFPOT code. The elastic transfer mechanism has been studied by coupled reaction channel (CRC) method using FRESCO code. Spectroscopic amplitudes of ⁶Li ≡ t + ³He and ⁶Li ≡ α + d configurations have been extracted from d, ³He and ⁴He scattering on ⁶Li at wide energy range. A comparison between spectroscopic amplitudes obtained from deuteron and α elastically scattering from ⁶Li has been made. The extracted spectroscopic amplitudes of ⁶Li ≡ ⁴He + d(SF = SA²) from ⁶Li(d, ⁶Li)d and ⁶Li(α, ⁶Li)α are not the same as expected theoretically.

Formation of multibaryon clusters in ⁴He + ¹²C and ¹²C + ¹²C collisions at 4.2A GeV/c, and in π^- + ¹²C and p + ²⁰Ne collisions at 40 and 300 GeV/c, respectively, is studied using universal binary B algorithm of separation of clusters in 4-velocity space. The masses and widths of multibaryon clusters increase linearly with an increase in the number of protons (n_p) in a cluster. The dependences of width of clusters on n_p in π^- + ¹²C and p + ²⁰Ne collisions differ noticeably from the corresponding dependences in ⁴He + ¹²C and ¹²C + ¹²C collisions. In nucleus–nucleus collisions, the widths of clusters are significantly larger and grow more rapidly, as the number of protons in a cluster increases, as compared to hadron–nucleus collisions. This result is in line with the fact that, in case of identical target nuclei, the degree of "destruction" of a target nucleus is greater in case of nucleus–nucleus collisions as compared to hadron–nucleus collisions. The lifetimes of multibaryon clusters are of the same order of magnitude with those of strongly decaying baryon resonances. The lifetime of clusters decreases with an increase in n_p.