Showing papers in "International Journal of Modern Physics E-nuclear Physics in 2014"

The challenge of the EMC effect: Existing data and future directions

Abstract: 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.

Exactly separable Bohr Hamiltonian with the Morse potential for triaxial nuclei

Abstract: In this paper, the Morse potential is used in the β-part of the collective Bohr Hamiltonian for triaxial nuclei. Energy eigenvalues and eigenfunctions are obtained in a closed form through exactly separating the Hamiltonian into its variables by using an appropriate form of the potential. The results are applied to generate the nuclear spectrum of 192Pt, 194Pt and 196Pt isotopes which are known to be the best candidate exhibiting triaxiality. Electric quadrupole transition ratios are calculated and then compared with the experimental data and the Z(5) model results.

Effective field theory calculations of NN → NNπ

Abstract: In this review, we present the recent advances for calculations of the reactions NN → NNπ using chiral effective field theory χEFT. Discussed are the next-to-next-to leading order (N2LO) loop contributions with nucleon and Delta-isobar for near threshold s-wave pion-production. Results of recent experimental pion-production data for energies close to the threshold are analyzed. Several particular applications are discussed: (i) it is shown how the measured charge symmetry (CS) violating pion-production reaction can be used to extract the strong interaction contribution to the proton–neutron mass difference; (ii) the role of NN → NNπ for the extraction of the pion–nucleon scattering lengths from pionic atoms data is illuminated.

Energy levels and electromagnetic transition of 190–196Pt nuclei

Abstract: A description of the even–even Pt isotopes for A = 190 to 196 in the framework of the Interacting Boson Model (IBM-1) is carried out. Energy levels, B(E2) and B(M1) values, branching ratios, E2/M1 mixing ratios and QJ values of the above nuclei have been calculated. The energy levels, B(E2) values and the electric quadrupole moment QJ results are reasonably consistent with the experimental data. The magnetic dipole is compared with the available experimental data. Furthermore, the calculated results are better than previous studies.

Causality Constraints on Hadron Production In High Energy Collisions

Abstract: For hadron production in high energy collisions, causality requirements lead to the counterpart of the cosmological horizon problem: the production occurs in a number of causally disconnected regions of finite space-time size. As a result, globally conserved quantum numbers (charge, strangeness, baryon number) must be conserved locally in spatially restricted correlation clusters. This provides a theoretical basis for the observed suppression of strangeness production in elementary interactions (pp, e + e − ). In contrast, the space-time superposition of many collisions in heavy ion interactions largely removes these causality constraints, resulting in an ideal hadronic resonance gas in full equilibrium.

Applications of a nonlinear evolution equation I: The parton distributions in the proton

Abstract: The nonlinear Dokshitzer–Gribov–Lipatov–Altarelli–Parisi (DGLAP) evolution equations with parton recombination corrections are used to dynamically evaluate the proton's parton distribution functions starting from a low scale μ2, where the nucleon consists of valence quarks. We find that the resulting negative nonlinear corrections can improve the perturbative stability of the QCD evolution equation at low Q2. Our resulting parton distributions, with four free parameters, are compatible with the existing databases. This approach provides a powerful tool to connect the quark models of the hadron and various nonperturbative effects at the scale μ2 with the measured structure functions at the high scale Q2 ≫ μ2.

Chirality in atomic nuclei: 2013

Abstract: Progresses of the chirality in atomic nuclei are reviewed, in particular, the recently proposed collective Hamiltonian based on tilted axis cranking approach to describe chiral vibration and rotation modes, and the experimental achievements for chirality and multiple chiral doublets, i.e., in 106Ag, 133Ce and 103Rh. The first experimental evidences of multiple chiral doublet bands with distinct and identical configuration found in 133Ce and 103Rh are discussed in detail.

Studies of chirality in the mass 80, 100 and 190 regions

Abstract: A brief survey of results of studies of nuclear chirality in the mass 80 and 190 region at iThemba LABS is given, before looking at the case of 106Ag in detail. Here, the crossing of a pair of candidate chiral bands is re-interpreted as the crossing of a prolate band by an aligned four-quasiparticle band.

Study of the neutron and proton capture reactions 10,11B(n, γ), 11B(p, γ), 14C(p, γ), and 15N(p, γ) at thermal and astrophysical energies

Abstract: 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

Transverse energy and charged particle production in heavy-ion collisions: From RHIC to LHC

Abstract: We study the charged particle and transverse energy production mechanism from AGS, SPS, Relativistic Heavy-Ion Collider (RHIC) to Large Hadron Collider (LHC) energies in the framework of nucleon and quark participants. At RHIC and LHC energies, the number of nucleons-normalized charged particle and transverse energy density in pseudorapidity, which shows a monotonic rise with centrality, turns out to be an almost centrality independent scaling behavior when normalized to the number of participant quarks. A universal function which is a combination of logarithmic and power-law, describes well the charged particle and transverse energy production both at nucleon and quark participant level for the whole range of collision energies. Energy dependent production mechanisms are discussed both for nucleonic and partonic level. Predictions are made for the pseudorapidity densities of transverse energy, charged particle multiplicity and their ratio (the barometric observable, dET /dη dNch /dη ≡ ET Nch ) at mid-rapidity for Pb + Pb collisions at √ sNN =5 .5TeV. A comparison with models based on gluon saturation and statistical hadron gas is made for the energy dependence of ET Nch .

Electromagnetic fields in high energy heavy-ion collisions

Abstract: I review properties of electromagnetic fields generated by colliding relativistic heavy ions and argue that they have a profound impact on the heavy-ion phenomenology. I discuss magnetic field effects on the quark gluon plasma flow, J/ψ dissociation, photon and dilepton production and quark energy loss.

κ state solutions for the fermionic massive spin-½ particles interacting with double ring-shaped Kratzer and oscillator potentials

Abstract: In recent years, an extensive survey on various wave equations of relativistic quantum mechanics with different types of potential interactions has been a line of great interest. In this regime, special attention has been given to the Dirac equation because the spin-½ fermions represent the most frequent building blocks of the molecules and atoms. Motivated by the considerable interest in this equation and its relativistic symmetries (spin and pseudospin), in the presence of solvable potential model, we attempt to obtain the relativistic bound states solution of the Dirac equation with double ring-shaped Kratzer and oscillator potentials under the condition of spin and pseudospin symmetries. The solutions are reported for arbitrary quantum number in a compact form. The analytic bound state energy eigenvalues and the associated upper- and lower-spinor components of two Dirac particles have been found. Several typical numerical results of the relativistic eigenenergies have also been presented. We found that the existence or absence of the ring shaped potential has strong effects on the eigenstates of the Kratzer and oscillator particles, with a wide band spectrum except for the pseudospin-oscillator particles, where there exist a narrow band gap.

Weighing the neutrino

Abstract: We investigate the potential of short-baseline experiments in order to measure the dispersion relation of the (muon) neutrino, with a prospect of eventually measuring the neutrino mass. As a byproduct, the experiment would help to constrain parameters of Lorentz-violating effects in the neutrino sector. The potential of a high-flux laser-accelerated proton beam (e.g., at the upcoming ELI facility), incident on a thick target composed of a light element to produce pions, with a subsequent decay to muons and muon-neutrinos, is discussed. We find a possibility for a muon neutrino mass measurement of unprecedented accuracy.

2013 update of the discoveries of nuclides

Abstract: The 2013 update of the discovery of nuclide project is presented. Details of the 12 new nuclides observed for the first time in 2013 are described. In addition, the discovery of 266Db has been included and the previous assignments of six other nuclides were changed. Overview tables of where and how nuclides were discovered have also been updated and are discussed.

Kinetic evolution of the glasma and thermalization in heavy ion collisions

Abstract: In relativistic heavy-ion collisions, a highly occupied gluonic matter is created shortly after initial impact, which is in a nonthermal state and often referred to as the Glasma. Successful phenomenology suggests that the glasma evolves rather quickly toward the thermal quark–gluon plasma (QGP) and a hydrodynamic behavior emerges at a very early time ~o(1) fm/c. Exactly how such "apparent thermalization" occurs and connects the initial conditions to the hydrodynamic onset, remains a significant challenge for theory as well as phenomenology. We briefly review various ideas and recent progress in understanding the approach of the glasma to the thermalized QGP, with an emphasis on the kinetic theory description for the evolution of such far-from-equilibrium and highly overpopulated, thus weakly-coupled yet strongly interacting glasma.

Recent developments in the study of deconfinement in nucleus–nucleus collisions

Abstract: Deconfinement refers to the creation of a state of quasi-free quarks and gluons in strongly interacting matter. Model predictions and experimental evidence for the onset of deconfinement in nucleus–nucleus collisions were discussed in our first review on this subject. These results motivated further experimental and theoretical studies. This review addresses two subjects. First, a summary of the past, present and future experimental programmes related to discovery and study of properties of the onset of deconfinement are presented. Second, recent progress is reviewed on analysis methods and preliminary experimental results for new strongly intensive fluctuation measures are discussed, which are relevant for current and future studies of the onset of deconfinement and searches for the critical point of strongly interacting matter.

Estimations of fission barrier heights for Ra, Ac, Rf and Db nuclei by neural networks

Abstract: Accurate information about the fission barrier is important for studying of the fission process. Fission barrier is needed for discovering the island of stability in superheavy region and searching of the superheavy elements. Furthermore, the astrophysical r-process is closely related to the fission barrier of the neutron-rich nuclei. In this study, by using artificial neural network (ANN) method, we have estimated the fission barrier heights of the Rf, Db, Ra and Ac nuclei covering 230 isotopes. For inner barrier calculation, we have used Rf and Db nuclei and the barrier heights have been determined between nearly 1 MeV and 7 MeV. The related mean square error value has been obtained as 0.108 MeV. For outer barrier calculation, we have used Ra and Ac nuclei and the heights have been determined between nearly 8 MeV and 28 MeV. The related mean square error has been obtained as 0.407. The results of this study indicate that ANN is capable for the estimations of inner and outer fission barrier heights.

The origin of thermal component in the transverse momentum spectra in high energy hadronic processes

Abstract: The transverse momentum spectra of hadrons produced in high energy collisions can be decomposed into two components: the exponential ("thermal") and the power ("hard") ones. Recently, the H1 Collaboration has discovered that the relative strength of these two components in Deep Inelastic Scattering (DIS) depends drastically upon the global structure of the event — namely, the exponential component is absent in the diffractive events characterized by a rapidity gap. We discuss the possible origin of this effect and speculate that it is linked to confinement. Specifically, we argue that the thermal component is due to the effective event horizon introduced by the confining string, in analogy to the Hawking–Unruh effect. In diffractive events, the t-channel exchange is color-singlet and there is no fragmenting string — so the thermal component is absent. The slope of the soft component of the hadron spectrum in this picture is determined by the saturation momentum that drives the deceleration in the color field, and thus the Hawking–Unruh temperature. We analyze the data on nondiffractive pp collisions and find that the slope of the thermal component of the hadron spectrum is indeed proportional to the saturation momentum.

Bottom-strange mesons in hyperonic matter

Abstract: The in-medium behavior of bottom-strange pseudoscalar mesons in hot, isospin asymmetric and dense hadronic environment is studied using a chiral effective model. The same was recently generalized to the heavy quark sector and employed to study the behavior of open-charm and open-bottom mesons. The heavy quark (anti-quark) is treated as frozen and all medium modifications of these bottom-strange mesons are due to their strange anti-quark (quark) content. We observe a pronounced dependence of their medium mass on baryonic density and strangeness content of the medium. Certain aspects of these in-medium interactions are similar to those observed for the strange-charmed mesons in a preceding investigation, such as the lifting of mass-degeneracy of and mesons in hyperonic matter, while the same is respected in vacuum as well as in nuclear matter. In general, however, there is a remarkable distinction between the two species, even though the formalism predicts a completely analogous in-medium interaction Lagrangian density. We discuss in detail the reason for different in-medium behavior of these bottom-strange mesons as compared to charmed-strange mesons, despite the dynamics of the heavy quark being treated as frozen in both cases.

On centrality and rapidity dependences of transverse momentum spectra of negative pions in 12 C + 12 C collisions at 4.2 GeV/c per nucleon

Abstract: The dependences of the experimental transverse momentum spectra of the negative pions, produced in minimum bias 12C + 12C collisions at a momentum of 4.2A GeV/c, on the collision centrality and the pion rapidity range were studied. To analyze quantitatively the change in the pt spectra of π- mesons with the changes of collision centrality and pion rapidity range, the extracted pt spectra were fitted by Hagedorn, Boltzmann, Simple Exponential and Gaussian functions. The values of the extracted spectral temperatures T1 and T2 were consistently larger for the pt spectra of π- mesons coming from midrapidity range as compared to those of the negative pions generated in the target and projectile fragmentation regions. The spectral temperatures T1 and T2 extracted from fitting the pt spectra of π- mesons in range pt = 0.1–1.2 GeV/c practically coincided with each other in peripheral, semicentral and central 12C + 12C collision events, and thus did not show any collision centrality dependence. However, the values...

Oklo reactors and implications for nuclear science

Abstract: We summarize the nuclear physics interests in the Oklo natural nuclear reactors, focusing particularly on developments over the past two decades. Modeling of the reactors has become increasingly sophisticated, employing Monte Carlo simulations with realistic geometries and materials that can generate both the thermal and epithermal fractions. The water content and the temperatures of the reactors have been uncertain parameters. We discuss recent work pointing to lower temperatures than earlier assumed. Nuclear cross-sections are input to all Oklo modeling and we discuss a parameter, the 175Lu ground state cross-section for thermal neutron capture leading to the isomer 176mLu, that warrants further investigation. Studies of the time dependence of dimensionless fundamental constants have been a driver for much of the recent work on Oklo. We critically review neutron resonance energy shifts and their dependence on the fine structure constant α and the ratio Xq = mq/Λ (where mq is the average of the u and d current quark masses and Λ is the mass scale of quantum chromodynamics (QCD)). We suggest a formula for the combined sensitivity to α and Xq that exhibits the dependence on proton number Z and mass number A, potentially allowing quantum electrodynamic (QED) and QCD effects to be disentangled if a broader range of isotopic abundance data becomes available.

Search of double shell closure in the superheavy nuclei using a simple effective interaction

Abstract: This paper refers to another attempt to search for spherical double shell closure nuclei beyond Z = 82, N = 126. All calculations and results are based on a newly developed approach entitled as simple effective interaction (SEI). Our results predict that the combination of magic nucleus occurs at N = 182 (Z = 114, 120, 126). All possible evidences for the occurrence of magic nuclei are discussed systematically. And, the obtained results for all observables are compared with the relativistic mean field theory for NL3 parameter.

Triaxiality in excited states of lanthanide and actinide even–even nuclei

Abstract: The energy levels of excited states of ground state, β- and γ-bands of the lanthanide and actinide even–even nuclei have been studied within the Davydov–Chaban model (for three different types of the potential energy of the β-deformations) and approximations for a small and free triaxiality. It is shown that the approximation with a free triaxiality better describes the spectrum of the excited collective states for considered nuclei.

A critical review of RHIC experimental results

Abstract: 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.

A study of event-by-event fluctuations in relativistic heavy-ion collisions

Abstract: A method for selecting events with densely populated narrow regions or spikes in a given data sample is discussed. Applying this method to 200 A GeV/c 32S-AgBr and 32S-Gold collision data, a few events having "hot regions" are chosen for further analysis. The finding reveals that a systematic study of particle density fluctuations, if carried out in terms of scaled factorial moments, and the results are compared with those for the analysis of correlation free Monte Carlo events, would be useful in identifying events with large dynamical fluctuations. Formation of clusters or jet-like structure in multihadronic final states in the selected spiky events is also looked into and compared with the predictions of AMPT and independent emission hypothesis models by carrying out Monte Carlo simulation. The findings suggest that clustering or jet-like algorithm adopted in the present study may also serve as an important tool for triggering different classes of events.

An empirical relation for cluster decay preformation probability

Abstract: Empirical relations for the preformation probability of cluster decay process in terms of the Q-value, mass asymmetry (η), mass number of the emitted cluster A2 is analyzed based on the discrepancy between the calculated and experimental half-lives of the cluster emitters. For the different empirical expressions considered corresponding to different physical quantities the preformation probability for the complete binary breakup of 226Ra is calculated and the obtained results are compared with the preformed cluster model calculation (P0(PCM)) and another calculation in which the overlapping penetration probability is treated as the preformation probability (P0(μ)). Our empirical results for the use of Q-value compare well with P0(μ). Results due to the use of Q and its powers along with the combination of mass number A2 of the cluster emitted, and mass asymmetry η, reveal that preformation factor depends strongly on Q-value rather than A2 and η. Calculated half-lives of different cluster decays for the use of empirical P0 values are found to be in good agreement with the experimental values.

Solution to the proton radius puzzle

Abstract: The relationship between the static electric form factor for the proton in the rest frame and the Sachs electric form factor in the Breit momentum frame is used to provide a value for the difference in the mean squared charge radius of the proton evaluated in the two frames. Associating the muonic–hydrogen data analysis for the proton charge radius of 0.84087 fm with the rest frame and associating the electron scattering data with the Breit frame yields a prediction of 0.87944 fm for the proton radius in the relativistic frame. The most recent value deduced via electron scattering from the proton is 0.877(6) fm so that the frame dependence used here yields a plausible solution to the proton radius puzzle.

The zero-point field and the emergence of the quantum

Abstract: A new way of arriving at the quantum formalism is presented, based on the recognition of the reality of the random zero-point radiation field (ZPF). The quantization of both matter and radiation field is shown to emerge as a result of the permanent interaction of matter with the ZPF. Quantum mechanics (QM) is obtained both in its Schrodinger and its Heisenberg version, under certain well-defined conditions and approximations. The theory provides for an explanation of the origin of entanglement. Further, the same physical elements and hypotheses allow us to cross the doorway and go beyond QM, to the realm of (nonrelativistic) quantum electrodynamics (QED).

34Si accompanied ternary fission of 242Cm in equatorial and collinear configuration

Abstract: Taking the interacting potential as the sum of Coulomb and proximity potential, 34Si accompanied cold ternary fission of 242Cm has been studied with fragments in the equatorial and collinear configuration. The cold valley plots (plot of driving potential versus mass number of fragments) and the calculations on the yields for the charge minimized fragments have been used to obtain the favorable fragment combinations. Thus, our study on the 34Si accompanied ternary fission of 242Cm reveals the role of near doubly magic shell closures (of 130Sn, 132Te, 134Te, etc.) in cold ternary fission. The comparison of relative yield reveals that in 34Si accompanied ternary fission of 242Cm, collinear configuration is preferred than the equatorial configuration. The relative yield for binary exit channel is found to be higher than that of ternary fragmentation (both equatorial and collinear configuration). The predicted yield for the binary fragmentation of 4He and 34Si from 242Cm are in agreement with the experimental data.

Probable cluster decays from $^{270-318}$118 superheavy nuclei

Abstract: The cluster decay process in 270–318118 superheavy nuclei has been studied extensively within the Coulomb and proximity potential model (CPPM), thereby investigating the probable cluster decays from the various isotopes of Z = 118. On comparing the predicted decay half-lives with the values evaluated using the Universal formula for cluster decay (UNIV) of Poenaru et al., the Universal Decay Law (UDL) of Qi et al., and the Scaling Law of Horoi et al., it was seen that, our values matches well with these theoretical values. A comparison of the predicted alpha decay half-life of the experimentally synthesized superheavy isotope 294118 with its corresponding experimental value shows that, our theoretical value is in good agreement with the experimental value. The plots for log10(T1/2) against the neutron number of the daughter in the corresponding decay reveals the behavior of the cluster half-lives with the neutron number of the daughter nuclei and for most of the decays, the half-life was found to be the mi...