19 research outputs found
Particle Yields and Ratios within Equilibrium and Non-Equilibrium Statistics
In characterizing the yields and ratios various of well identified particles
in the ALICE experiment, we utilize extensive {\it additive} thermal
approaches, to which various missing states of the hadron resonances are taken
into consideration, as well. Despite some non-equilibrium conditions that are
slightly driving this statistical approach away from equilibrium, the
approaches are and remain additive and extensive. Besides van der Waals
repulsive interactions (assuming that the gas constituents are no longer
point-like, i.e. finite-volume corrections taken into consideration), finite
pion chemical potentials as well as perturbations to the light and strange
quark occupation factors are taken into account. When confronting our
calculations to the ALICE measurements, we conclude that the proposed
conditions for various aspects deriving the system out of equilibrium notably
improve the reproduction of the experimental results, i.e. improving the
statistical fits, especially the finite pion chemical potential. This points
out to the great role that the non-equilibrium pion production would play, and
the contributions that the hadron resonance missing states come up with, even
when the principles of statistical extensivity and additivity aren't violated.
These results seem to propose revising the conclusions propagated by most of
the field, that the produced particles quickly reach a state of local
equilibrium leading to a collective expansion often described by fluid
dynamics. This situation seems not remaining restrictively valid, at very large
collision energies.Comment: 15 pages, 4 figures, submitted to EP
Extensive/nonextensive statistics for distributions of various charged particles produced in p+p and A+A collisions in a wide range of energies
We present a systematic study for the statistical fits of the transverse
momentum distributions of charged pions, Kaons and protons produced at energies
ranging between 7.7 and 2670 GeV to the extensive Boltzmann-Gibbs (BG) and the
nonextensive statistics (Tsallis as a special type and the generic axiomatic
nonextensive approach). We also present a comprehensive review on various
experimental parametrizations proposed to fit the transverse momentum
distributions of these produced particles. The inconsistency that the BG
approach is to be utilized in characterizing the chemical freezeout, while the
Tsallis approach in determining the kinetic freezeout is elaborated. The
resulting energy dependence of the different fit parameters largely varies with
the particle species and the degree of (non)extensivity. This manifests that
the Tsallis nonextensive approach seems to work well for p+p rather than for
A+A collisions. Drawing a complete picture of the utilization of Tsallis
statistics in modeling the transverse momentum distributions of several charged
particle produced at a wide range of energies and accordingly either disprove
or though confirm the relevant works are main advantages of this review. We
propose analytical expressions for the dependence of the fit parameters
obtained on the size of the colliding system, the energy, as well as the types
of the statistical approach applied. We conclude that the statistical
dependence of the various fit parameters, especially between Boltzmann and
Tsallis approaches could be understood that the statistical analysis ad hoc is
biased to the corresponding degree of extensivity (Boltzmann) or nonextensivity
(Tsallis). Alternatively, the empirical parameterizations, the other models,
and the generic (non)extensive approach seem to relax this biasness.Comment: 42 pages, 17 figures, IX tables, submitted to JSTA
Properties of signature partner superdeformed bands in mercury nuclei
The properties of superdeformed (SD) bands of five pairs signature partners in mercury nuclei have been systematically analyzed in framework of four parameters formula including higher order terms of Bohr-Mottelson collective rotational energies. The level spins and the model parameters are determined by fitting procedure using a computer simulated search program in order to obtain minimum root mean square deviations between the calculated and the experimental transition energies.The best fitted parameters have been used to calculate the transition energies Eγ, the rotational frequencies , the kinematic J(1) and dynamic J(2) moments of inertia. The calculated results agree excellently with the experimental data. J(2) is significantly larger than J(1) for all values of . Also J(2) show a smooth increase with increasing . The appearance of ΔI = 1 and ΔI = 2 staggering in γ-ray transition energies have been examined by using the five-points formula representing the finite difference approximation to the fourth derivative of the γ-ray transition energies at a given spin. The signature partners in Hg nuclei show large amplitude staggering. Also to appear the ΔI = 1 staggering, the transition energies relative to a rigid rotor with a moment of inertia J = 128.219 are plotted against spins for each signature partner pairs. The difference in transition energies between transitions in the two SD bands 191Hg(SD3)and 193Hg(SD3) are small, therefore, these two bands have been considered as identical bands
Phenomenology of strangeness production at high energies
The strange-quark occupation factor () is determined from the
statistical fit of the multiplicity ratio in a wide range
of nucleon-nucleon center-of-mass energies (). From this
single-strange-quark-subsystem, was parametrized as a
damped trigonometric functionality and successfully implemented to the hadron
resonance gas model, at chemical semi-equilibrium. Various particle ratios
including , , and
are well reproduced. The phenomenology of
suggests that, the hadrons ( raises) at
GeV seems to undergo a phase transition to a mixed
phase ( declines), which is then derived into partons (
remains unchanged with increasing ), at GeV.Comment: 6 pages, 2 figures, accepted for publication in EP
Energy staggering in superdeformed bands for isodiaphere nuclei in A ~ 40-60 mass region
The properties of superdeformed (SD) bands of isodiaphere nuclei ((_ ^40)Ca,(_ ^58)Cu,(_ ^60)Zn) have been studied in the scope of four and five parameters’ formulas of the Bohr-Mottelson collective model. The unknown parameters are obtained by fitting the experimental measurements of the gamma-ray transition energies using MATLAB software. The rotational frequency ℏω, the kinematic J^((1)), and dynamic J^((2)) moments of inertia are determined by using the best fitted parameters. The obtained -ray transition energies are in good agreement with the experimental measurements. Also, the theoretical results of the kinematic J^((1)), and dynamic J^((2)) moments of inertia using both formulas agree well with the experimental data. The staggering ΔI=2 phenomenon is represented by using various order derivatives of -ray transition energies E_γ with respect to spin angular momentum I. We conclude that the five parameters formula of Bohr-Mottelson collective model successes in interpreting the appeared pairing correlations in the experimental measurements for the studied nuclei