Quantal effects on growth of spinodal instabilities in charge asymmetric nuclear matter are investigated in the framework of a stochastic mean field approach. Due to quantal effects, in both symmetric and asymmetric matter, dominant unstable modes shift towards longer wavelengths and modes with wave numbers larger than the Fermi momentum are strongly suppressed. As a result of quantum statistical effects, in particular at lower temperatures, magnitude of density fluctuations grows larger than those calculated in semi-classical approximation. (c) 2008 Elsevier B.V. All rights reserved.
Highlights of the results obtained by the CMS experiment at the LHC on collective flow and dihadron correlations in PbPb collisions are presented. At lower transverse momenta of the outgoing particles and for a wide range of collision centralities, the 2nd-through 6th-order Fourier components of the azimuthal distribution have been found using different analysis techniques with different sensitivities to non-flow and flow fluctuation effects. An ultra-central collision trigger allows the Fourier components to be extended to a region of centrality where initial-state effects are expected to be small. A high-p(T) single-track trigger has allowed the elliptic anisotropy (v(2)) and higher-order harmonics to be explored up to approximate to 60 GeV/c, as a function of pseudorapidity and collision centrality. The CMS results provide new information on both the hydrodynamic properties of the medium at low p(T) and the path-length dependence of in-medium parton energy loss at high P-T. By subtracting the long-range in pseudorapidity anisotropy components arising from hydrodynamic flow from dihadron correlation results, it is possible to gain further insight into the medium effect on dijets. This is done with a study of the "near-side" and "away-side" yields of dijets measured in PbPb collisions compared to those found in pp collisions.
DOI : 10.1016/j.nuclphysa.2013.01.050
Sayi :904 Sayfa :98C-105C
In this study, we investigate the role of the nuclear deformation on the calculated electron capture cross section (ECC) of even-even chromium (Cr) isotopes. We first determined the nuclear structure properties of these nuclei within the interacting boson model-1 (IBM-1). The energy spectra and E2 transition probabilities were calculated by fitting the parameters in the model formalism. The analysis of the potential energy surface were also performed to predict the geometric shape of the Cr nuclei by plotting their contour plot in the plane of (beta, gamma ) deformation parameters. Later, we calculated the ECC within the proton-neutron quasiparticle random phase approximation (pn-QRPA) model. In particular we studied how the calculated ECC changed with different values of nuclear deformation parameter. The calculated Gamow-Teller (GT) strength distributions were widely spread among the daughter states. The total GT strength decreased with increasing value of the beta parameter. The computed ECC values, however, increased with increase in the beta value of the Cr isotopes. (c) 2020 Elsevier B.V. All rights reserved.
We study the strong interactions among the heavy bottom spin-1/2 Sigma(b) baryon, nucleon and B meson as well as the heavy charmed spin-1/2 Sigma(c) baryon, nucleon and D meson in the context of QCD sum rules. We calculate the corresponding strong coupling form factors defining these vertices by using a three point correlation function. We obtain the numerical values of the corresponding strong coupling constants via the most prominent structure entering the calculations. (C) 2015 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2015.09.005
Sayi :943 Sayfa :159-167
The low-lying dipole strength of the deformed nucleus Gd-156 was investigated in the energy region from 3.1 MeV to 6.2 MeV using the method of nuclear resonance fluorescence (NRF). The NRF experiments were performed at the Darmstadt High Intensity Photon Setup (DHIPS) at Technische Universitat Darmstadt using unpolarized continuous-energy bremsstrahlung and at the High-Intensity gamma-ray Source (HI gamma S) at Duke University using quasi-monoenergetic and linearly-polarized photon beams. The combination of both experiments allows to separate electric and magnetic contributions and to determine absolute transition strengths for individual excited states as well as averaged quantities over narrow excitation energy regions. The investigated energy regions cover the region of the scissors mode as well as the low-energy part of the Pygmy Dipole Resonance. This is the first experiment where both of these excitation modes as well as the region in between has been successfully studied in a deformed heavy nucleus using the NRF method. (C) 2019 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2019.03.014
Sayı :987 Sayfa :79-89
Collective effects in the level density are not well understood, and including these effects as enhancement factors to the level density does not produce sufficiently consistent predictions of observables. Therefore, collective effects are investigated in the level density parameter instead of treating them as a final factor in the level density. A new Laplace-like formula is proposed for the energy dependence of the level density parameter, including collective effects. A significant improvement has been achieved in agreement between observed and predicted energy levels. This new model can also be used in both structure and reaction calculations of the nuclei far from stability, especially near the drip lines. (C) 2014 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2014.05.020
Sayi :929 Sayfa :54-70
The Collective model with the Kratzer potential has been used to study the properties of the gamma-unstable odd nuclei. An uncoupled nucleon in the odd nucleus has been assumed to move freely in the j = 1/2, 3/2, 5/2 orbits. The energy eigenvalues and eigenfunctions have been obtained in closed form from the analytical solution of the Hamiltonian for the odd-system. Excitation energy spectra of some selected W, Os, Pt and Hf isotopes have been predicted within this model. Due to lack of experimental B(E2) data, some intra-band and inter-band electric quadrupole transition rates were presented only for Os-179 isotope. Acceptable results have been obtained for these isotopes. (C) 2020 Elsevier B.V. All rights reserved.
We systematically investigate the influence of nuclear deformations of the cluster and daughter nuclei on the half-lives of He-4, Be-8,Be-10, C-12,C-14,C-16 and O-16,O-18,O-20,O-22 cluster decays from Ra210-226. The Wentzel-Kramers-Brillouin (WKB) method and Bohr-Sommerfeld quantization condition with the deformed squared Woods-Saxon and Cosh potentials are used phenomenologically in order to compute the half-lives. The calculations are performed for the spherical cluster and deformed daughter, deformed cluster and spherical daughter and deformed cluster and daughter cases. The half-lives for different orientation angles as well as over all angles are calculated, in order to show the deformation effects on the systems. In cases where the deformation of both cluster and daughter effect the result, it is found that the deformation of the cluster is more important than the deformation of the daughter. Furthermore, it is also found that taking into account the orientation angles of the daughter and cluster also improves the results when compared to experiment. However, the results for a Cosh potential with certain parameters without any deformation are found to be more compatible with both the results obtained by the Coulomb and proximity potential model (CPPM) and the universal formula for cluster decay (UNIV), as well as the experimental values for He-4 and C-14 decays. The results provide a useful method for estimating the unknown experimental half-lives of possible exotic decays from Ra isotopes. (C) 2015 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2015.01.008
Sayi :936 Sayfa :59-73
We present a detailed analysis of the 6He elastic scattering on different target nuclei over a wide energy range within the framework of the double folding model using a phenomenological imaginary potential. We show the microscopic real potential generated by No-core Shell model density distributions provides good agreement in explaining the elastic scattering angular distributions. In this study we also present a new formulation depending on the incident energy and atomic charge of the target nucleus for the phenomenological imaginary potential and investigate the threshold anomaly in halo nuclei by analyzing the 6He 208Pb system. 2014 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2014.04.020
Sayi :927 Sayfa :195-208
The elastic scattering angular distributions of He-6 projectile on different medium and heavy mass target nuclei including C-12, Al-27, Ni-58, Zn-64, (65)Cn, (197)An, (208)pb and (209) Bi have been examined by using the few-body and Gaussian-shaped density distributions at various energies. The microscopic real parts of the complex nuclear optical potential have been obtained by using the double-folding model for each of the density distributions and the phenomenological imaginary potentials have been taken as the Woods-Saxon type. Comparative results of the few-body and Gaussian-shaped density distributions together with the experimental data are presented within the framework of the optical model. (C) 2010 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2010.09.005
Sayi :848 issue :3-4 Sayfa :245-259
Weak rates in nickel isotopes play an integral role in the dynamics of supernovae. Electron capture and beta-decay of nickel isotopes, dictated by Gamow-Teller transitions, significantly alter the lepton fraction of the stellar matter. In this paper we calculate Gamow-Teller (GT) transitions for isotopes of nickel, Ni56-64, using QRPA methods. The GT strength distributions were calculated using four different QRPA models. Our results are also compared with previous theoretical calculations and measured strength distributions wherever available. Our investigation concluded that amongst all RPA models, the pn-QRPA(C) model best described the measured GT distributions (including total GT strength and centroid placement). It is hoped that the current investigation of GT properties would prove handy and may lead to a better understanding of the presupernova evolution of massive stars. (C) 2017 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2017.11.006
Sayi :970 Sayfa :86-106
The production of electroweak bosons (photons, W and Z particles) in PbPb collisions at a centre-of-mass energy per nucleon pair of 2.76 TeV has been measured with the CMS detector at the LHC. Direct photons are selected by applying isolation criteria, while W and Z bosons are reconstructed through their muonic decay. The production rates in PbPb data are studied as a function of the collision centrality and compared to that in pp interactions (or next-to-leading-order calculations), once normalised by the number of binary nucleon-nucleon interactions. Apart from an expected asymmetry between W+ and W- due to the different quark content of protons and Pb nuclei, no deviation from binary-scaled production is observed. The isolated-photon energy is further used as a reference for away-side jets, which are found to be less energetic in PbPb than in pp collisions.
DOI : 10.1016/j.nuclphysa.2013.01.065
Sayi :904 Sayfa :241C-247C
The low-lying magnetic dipole (M1) strength in deformed odd-mass Ho155-169 nuclei is investigated using rotational invariant (RI-) Quasiparticle Phonon Nuclear Model (QPNM). The gross features and fragmentation of the scissors mode in Ho-165 is well reproduced by RI-QPNM calculations. The systematics of the low-energy M1 excitation in Ho isotopic chain is discussed with respect to summed strength. Besides, the results for M1 excitations in odd-mass Ho isotopes are compared with the systematics of the scissors mode in the neighbouring even-even nuclei. The obtained results generally match the systematic and trends typical for the scissors motion. In addition to the low-lying M1 excitations, a M1 giant resonance in the 7-15 MeV energy region is predicted for Ho155-169 nuclei in the present study. (C) 2017 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2017.04.039
Sayi :964 Sayfa :1-17
Measurements of the nuclear modification factor of mesons with open heavy flavor content in PbPb collisions at root s(NN) = 2.76 TeV from the CMS experiment will be presented. These modification factors provide stringent constraints on the theoretical models of heavy quark energy loss. Until recently only indirect measurements of this effect existed, through single electrons from semileptonic open heavy-flavor decays. The importance of an unambiguous measurement of open bottom flavor is driven by the lack of knowledge regarding key features of the dynamics of parton energy loss in the QGP, such as its color-charge and parton-mass dependencies and the relative role of radiative and collisional energy loss. CMS measures the nuclear modification factor of b hadrons, identified via their decays into J/psi displaced from the primary collision vertex. First results have shown that b hadrons are strongly suppressed in PbPb collisions at a level comparable to open charm. New results on the centrality dependence of non-prompt J/psi R-AA are presented, based on the full 2011 PbPb data sample corresponding to an integrated luminosity of 150 mu b(-1).
DOI : 10.1016/j.nuclphysa.2013.02.101
Sayi :904 Sayfa :657C-660C
An odd-mass nucleus has been thought as coupling of a single nucleon in the j = 3/2 single-particle orbit with the gamma-unstable even-core. To get the properties of such a system, the Collective model Hamiltonian with the Morse potential has been used. Two cases, in which the interaction strength between the nucleon and the core are fixed or deformation dependent, are examined. The excitation energy spectrum and the electric quadrupole transition ratios have been obtained. Then the results have been used to predict the experimental data of the some selected odd-mass nuclei. (C) 2019 Elsevier B.V. All rights reserved.
In order to provide data for the simulation of the astrophysical gamma-process, the cross section measurement of the (124)xe(p,gamma)Cs-125 reaction is in progress at MTA Atomki using the activation technique. Precise information on the decay characteristics of the reaction products is of crucial importance for measurements carried out using this method. The half-lives of the produced Cs-125 and its daughter Xe-125 are published in previous works, but with large uncertainties and ambiguous values. To make these nuclear parameters more precise, the half-lives have been re-measured with high precision using gamma-spectroscopy. The obtained new half-life values are t(1/2) = 44.35 +/- 0.29 minutes for Cs-125 and t(1/2) = 16.87 +/- 0.08 hours for Xe-125. (C) 2019 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2019.04.002
Sayi :986 Sayfa :213-222
The non-prompt J/psi from B-meson decays, the prompt J/psi, the inclusive psi' and the three Y states were measured separately using the Compact Muon Solenoid (CMS) experimental apparatus in both pp and heavy-ion collisions at root s(NN) = 2.76 TeV. The results are based on data collected in 2011 which correspond to an integrated luminosity of 150 pb-1 of PbPb and 231 nb(-1) of pp collisions. The yields measured in heavy-collisions are compared to those in pp scaled by the number of binary collisions via the nuclear modification factor, R-AA. The high-p(T) prompt J/psi show a suppression that does not vary with rapidity or p(T). The R-AA versus centrality calculated separately for Y(1S) and Y(2S), shows less suppression for the ground state. An upper limit for Y(3S) was also calculated. Combining all the quarkonia states RAA measured by CMS, and considering the binding energy of each state, an ordering of the suppression is observed, which establishes, experimentally, the validity of the sequential melting scenario in heavy-ion collisions. The non-prompt J/psi R-AA dependence with p(T) and rapidity was measured in fine bins of centrality. These represent the first detailed measurements, in heavy-ion collision, of the b-quark energy loss kinematic dependence.
DOI : 10.1016/j.nuclphysa.2013.01.066
Sayi :904 Sayfa :194C-201C
The method of Pyatov, proposed for the exclusion of the spurious states associated with the spontaneous symmetry breaking due to the mean field approximation, is applied to restore broken translation and Galilean invariance of the Quasiparticle Phonon Nuclear Model (QPNM) Hamiltonian of deformed odd-mass nuclei for the first time. The point of the formulated translation and Galilean invariant (TGI-) QPNM is to study electric dipole (E1) response of odd-mass deformed nuclei. The proposed TGI-QPNM is tested by the calculations for fine and gross features of E1 resonance in Ho-165, Tm-169 and U-235 in a wide range of excitation energy from 2 to 20 MeV. Predictions of the TGI-QPNM are shown to be in good agreement with the corresponding experimental data. (C) 2020 Elsevier B.V. All rights reserved.
A restoration method of a broken symmetry which allows self-consistent determination of the separable effective restoration forces is now adapted to odd-mass nuclei in order to restore violated rotational invariance (RI-) of the Quasiparticle Phonon Nuclear Model (QPNM) Hamiltonian. Because of the self consistency of the method, these effective forces contain no arbitrary parameters. Within RI-QPNM, the properties of the low-lying magnetic dipole excitations in odd-mass deformed Th229-233 and U233-239 nuclei have been investigated for the first time. It has been shown that computed fragmentation of the M1 strengths below 4 MeV in these nuclei is much stronger than that in neighboring doubly even Th228-232 and U232-238 nuclei. For U-235 the summed M1 strength in the energy range 1.5-2.8 MeV is in agreement with the relevant experimental data where the missing strength was extracted by means of a fluctuation analysis. (C) 2016 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2016.07.004
Sayi :957 Sayfa :33-50
The spinodal instabilities for symmetric nuclear matter at finite temperature are studied within different relativistic mean-field models in the semi-classical approximation and the relativistic results are compared with Skyrme type non-relativistic calculations. Qualitatively similar results appear in the unstable response of the system in both non-relativistic and relativistic descriptions. Furthermore, the early growth of baryon, scalar and current density correlation functions are calculated for hot symmetric nuclear matter. (C) 2011 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2011.04.004
Sayi :859 issue :1 Sayfa :73-86
The magnetic dipole (M1) response of the Tm-169 nucleus is investigated from a theoretical point of view. The theoretical tool used in this study is the Rotational Invariant Quasiparticle Phonon Nuclear Model (RI-QPNM) which gives a possibility to eliminate spurious contributions in the M1 spectrum. In the frame-work of this model, both the low-lying and high-lying parts of the M1 excitation spectrum of Tm-169 are calculated. The result shows that the low-lying excitations have almost pure orbital character and can be interpreted as scissors mode, whereas the high-lying transitions can be read as spin-flip mode because of its spin nature. The reduced transition probability summed up in the energy range 2-4 MeV is found to be B(M1 up arrow) = 3.040 mu(2)(N) which agrees with the available experimental data. The fragmentation of the low-energy M1 strength is also well reproduced. This is also the first study in which both the low-lying and high-lying M1 spectrum of the Tm-169 nucleus is theoretically investigated. (C) 2018 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2018.07.001
Sayi :981 Sayfa :130-146
The CMS collaboration has used a data set of 1 billion PbPb collisions at the LHC to study the behavior of strongly interacting matter at high temperature. In this Paper, we present selected recent highlights from this effort, with a particular emphasis on results related to the hydrodynamic expansion of the produced matter, the energy loss of partons and the dissociation of quarkonia.
DOI : 10.1016/j.nuclphysa.2013.01.043
Sayi :904 Sayfa :43C-50C
Measurements of dihadron correlations triggered by very high-p(T) particles in 2.76 TeV PbPb collisions are presented. The analysis explores the full 2011 PbPb data set corresponding to an integrated luminosity of 150 mu b(-1) collected by CMS. Long-range correlations driven by single-particle azimuthal anisotropies (characterized by the Fourier harmonics, nu(n)) are measured up to p(T) similar to 50 GeV/c. After subtracting the nu(2)-nu(4) harmonic components, the associated particle yields on the near and away side of the residual jet-like dihadron correlations are studied over a wide kinematic range in trigger and associated particle p(T), as a function of collision centrality. By comparing to pp data at the same energy, a suppression of about 50% in the away-side associated yield is observed for p(T)(assoc) > 3GeV/c. The yield is found to be significantly enhanced up to a factor of 3-4 on the away side at p(T)(assoc) similar to 0.5GeV/c. A moderate enhancement is suggested on the near side.
DOI : 10.1016/j.nuclphysa.2013.02.046
Sayi :904 Sayfa :451C-454C
A microscopic model analysis of the magnetic dipole (M1) properties of Pu-239 nucleus, which is a fissile material not only used in nuclear weapons but also used in some nuclear reactors as a source of energy, has been performed. The microscopic formalism used in the study is based on the Quasiparticle Phonon Nuclear Model (QPNM) and includes an axially symmetric Woods-Saxon potential as a mean field, a spin-spin residual interaction as well as the symmetry-restoring forces for the rotational invariance of the Hamiltonian. The investigations have been carried out in two steps. Firstly, the theoretical value of the ground-state magnetic moment and quenching spin gyromagnetic factor have been determined and it has been found that the predicted magnetic moment show a good agreement with the experimental data. Secondly, the calculations of M1 transitions from ground- to excited-states have been carried out in the energy range 2-4 MeV. A satisfactorily good agreement is obtained from the comparison of the theoretical results with the experimental data for 2-2.5 MeV. (C) 2019 Elsevier B.V. All rights reserved.
DOI : 10.1016/j.nuclphysa.2019.04.004
Sayi :987 Sayfa :202-221
We try to give a detailed analysis of the 2 nu beta(-)beta(-) decay rates to the final ground states for decay emitters: (70)ZN, Se-80, Kr-86, (94)zr, Ru-104, (110)pd, Cd-114 and Sn-124. The nucleon nucleon residual interaction potential is defined according to Pyatov's restoration method. The nuclear matrix element for 2 nu beta(-)beta(-) decay is obtained by including the virtual contributions coming from the isobar analogue excitations within the framework of proton neutron quasi-particle random phase approximation (pnQRPA). The calculated decay rates are compared with mean field, schematic model and other calculations.
DOI : 10.1016/j.nuclphysa.2016.10.001
Sayi :957 Sayfa :491-512
This paper reviews recent experimental results on jet production and properties in heavy-ion collisions from the CMS Collaboration. These studies include various energy loss phenomena (di-jet and photon-jet energy imbalance, nuclear modification factors - R-AA - for inclusive and b-quark jets); observables related to jet properties like jet shapes and fragmentation functions; and measurements of high-p(T) charged hadrons (R-AA up to 100 GeV/c, azimuthal asymmetry up to 60 GeV/c and two-particle correlations triggered by a high-p(T) hadron). The presented results utilize the high statistics PbPb data, about 150 mu b(-1), collected in 2011 at the LHC.
DOI : 10.1016/j.nuclphysa.2013.01.056
Sayi :904 Sayfa :146C-153C
We discuss the angular dependence of the shape-elastic resonance wave function for a state so broad decay occurs before the ions orbit the interaction region. In the shadow of the interaction region the non-stationary angular dependence is described by a Legendre function for complex angular momentum, Pα (cos ϑ). In the lit region the same state has the angular dependence e−iπαPα(−cos ϑ). After presenting theoretical arguments which show the necessity of using these different analytic continuations in the shadow and lit regions to states of complex angular momentum we show, by way of illustration of the theoretical argument, results for a strong absorption model introduced several years ago by Austern.
The (p, γ) reactions on the 92Mo, 94Mo and 96Mo isotopes were studied in the energy range Ep = 2.4–3.0 MeV using a Ge(Li) detector incorporated into a three-crystal pair spectrometer and a Ge(Li) detector in coincidence with a NaI(Tl) detector. A three-crystal pair spectrometer was utilized to determine the average yield of γ-rays leading directly to the low-lying states in each of the three residual nuclei. These average yields were examined for a possible correlation between the intensity of high-energy γ-ray transitions and the Jπ of the final state. The data indicate that such a correlation exists. A two-dimensional coincidence experiment determined the decay scheme of the low-lying excited states in 93Tc 95Tc and 97Tc. The Jπ assignments inferred from these experiments are consistent with those for the states in 93Tc, 95Tc and 97Tc which have previously been obtained. For those states which were previously unassigned, the results of this experiment are as follows (all energies are in keV): 93Tc-680 (72+), 1193 (52+), 1406 (12−, 32−), 1555 (12−, 32−), 2429 (≦ 52); 95Tc-1278 (32+), 1619 (32+, 52−), 2556 (≧ 52); 97Tc-948 (12−, 32−), 1060 (52±, 72+), 1138 (52±), 1366 (32+), 1387 (32+, 52∼), 1517 (12−, 32−), 1573(32+, 52±), 1676 (32+, 52±). The state at 2429 keV in 93Tc has not been reported previously.