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24 featured work(s)

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preprint2012arXiv

Single Spin Asymmetry through QCD Instantons

We revisit the effects of QCD instantons in semi-inclusive deep inelastic scattering (SIDIS). We show that large single spin asymmetry (SSA) effects can be induced in longitudinally and transversely polarized proton targets. The results are in agreement with most of the reported data for pion and kaon production. The same effects are found to be important in polarized proton on proton scattering for both charged and chargeless pion productions. The results agree with the reported data in a wide range of \sqrt{s} = 19.4-200 GeV. We predict the SSA for π^\pm production in p_\uparrow p in the collider range of \sqrt{s} = 62.4-500 GeV. The backward π^{\pm} and π^0 productions for the SSA in p_\uparrow p collisions are predicted to coincide at large \sqrt{s}.

0 citations0 reviewsNo code linkedOpen access
preprint2015arXiv

NJL model approach to diquarks and baryons in quark matter

We describe baryons as quark-diquark bound states at finite temperature and density within the NJL model for chiral symmetry breaking and restoration in quark matter. Based on a generalized Beth-Uhlenbeck approach to mesons and diquarks we present in a first step the thermodynamics of quark-diquark matter which includes the Mott dissociation of diquarks at finite temperature. In a second step we solve the Bethe-Salpeter equation for the baryon as a quark-diquark bound state in quark-diquark matter. We obtain a stable, bound baryon even beyond the Mott temperature for diquark dissociation since the phase space occupation effect (Pauli blocking for quarks and Bose enhancement for diquarks) in the Bethe-Salpeter kernel for the nucleon approximately cancel so that the nucleon mass follows the in-medium behaviour of the quark and diquark masses towards chiral restoration. In this situation the baryon is obtained as a "borromean" three-quark state in medium because the two-particle state (diquark) is unbound while the three-particle state (baryon) is bound.

0 citations0 reviewsNo code linkedOpen access
preprint2014arXiv

P-Odd Pion Azimuthal Charge Correlations in Heavy Ion Collisions

We argue that the large instanton induced Pauli form factor in polarized proton-proton scattering may cause, through topological fluctuations, substantial charge-dependent azimuthal correlations for pi^+/pi^- production in peripheral heavy ion collisions both at RHIC and LHC, thanks to the large induced magnetic field. Our results compare favorably to the measured pion azimuthal correlations by the STAR and ALICE collaborations.

0 citations0 reviewsNo code linkedOpen access
preprint2015arXiv

Properties of light (anti)nuclei and (anti) hypertriton production in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV

We investigate the properties of light (anti)nuclei and (anti)hypertriton production in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}=2.76$ TeV, based on the parton and hadron cascade and dynamically constrained phase-space coalescence (PACIAE + DCPC) model. We found that the yields of light (anti)nuclei and (anti)hypertriton strongly depend on the centrality, i.e., their yields decrease rapidly with the increase of centrality bins, but their yield ratios are independent of centrality. The results of theoretical model are well consistent with ALICE data. Furthermore, we found that the integrated yields of (anti)nuclei per participant nucleon increase from peripheral to central collisions more rapidly with increasing mass number. The transverse momentum distributions of $\overline{_{\overlineΛ}^3 H}, {_Λ^3 H},{\overline{^3 He}}$ and $^3{He}$ are also discussed in the 0-10% most central Pb-Pb collisions.The coalescence parameters $B_A$ of light (anti)nuclei and (anti)hypernuclei are analyzed.

0 citations0 reviewsNo code linkedOpen access
preprint2018arXiv

Interaction and Identification of the Meson-Baryon molecules

The challenges with the molecular model of the multiquark systems are the identification of the hadronic molecules and the interaction between two color neutral hadrons. We study the di-hadronic molecular systems with proposed interaction potential as s-wave one boson exchange potential along with Screen Yukawa-like potential, and arrived with the proposal that within hadronic molecule the two color neutral hadrons experience the dipole-like interaction. The present study is the continuation of our previous study \cite{arxiv-Rathaud-penta}. With the proposed interaction potential, the mass spectra of $Σ_{s}K^{*}$, $Σ_{c}K^{*}$, $Σ_{b}K^{*}$, $Σ_{s}D^{*}$, $Σ_{c}D^{*}$, $Σ_{b}D^{*}$, $Σ_{s}B^{*}$, $Σ_{c}B^{*}$, $Σ_{b}B^{*}$, $Ξ_{s}K^{*}$, $Ξ_{c}K^{*}$, $Ξ_{b}K^{*}$, $Ξ_{s}D^{*}$, $Ξ_{c}D^{*}$, $Ξ_{b}D^{*}$, $Ξ_{s}B^{*}$, $Ξ_{c}B^{*}$, $Ξ_{b}B^{*}$ meson-baryon molecules are predicted. The Weinberg compositeness theorem which provides clue for the compositeness of the state is used for determination of the scattering length and effective range. The present study predict $P_{c}(4450)$ pentaquark sate as $Σ_{c}D^{*}$ molecule with $I(J^{P})=\frac{1}{2}(\frac{3}{2}^{-})$. The formalism also predicts some very interesting open as well as hidden flavour near threshold molecular pentaquark states.

0 citations0 reviewsNo code linkedOpen access
preprint2018arXiv

A reciprocal formulation of non-exponential radiative transfer. 1: Sketch and motivation

Previous proposals to permit non-exponential free-path statistics in radiative transfer have not included support for volume and boundary sources that are spatially uncorrelated from the scattering events in the medium. Birth-collision free paths are treated identically to collision-collision free paths and application of this to general, bounded scenes with inclusions leads to non-reciprocal transport. Beginning with reciprocity as a desired property, we propose a new way to integrate non-exponential transport theory into general scenes. We distinguish between the free-path-length statistics between correlated medium particles and the free-path-length statistics beginning at locations not correlated to medium particles, such as boundary surfaces, inclusions and uncorrelated sources. Reciprocity requires that the uncorrelated free-path distributions are simply the normalized transmittance of the correlated free-path distributions. The combination leads to an equilibrium imbedding of a previously derived generalized transport equation into bounded domains. We compare predictions of this approach to Monte Carlo simulation of multiple scattering from negatively-correlated suspensions of monodispersive hard spheres in bounded two-dimensional domains and demonstrate improved performance relative to previous work. We also derive new, exact, reciprocal, single-scattering solutions for plane-parallel half-spaces over a variety of non-exponential media types.

0 citations0 reviewsNo code linkedOpen access
preprint2018arXiv

The symmetry energy $γ$ parameter of relativistic mean-field models

The relativistic mean-field models tested in previous works against nuclear matter experimental values, critical parameters and macroscopic stellar properties are revisited and used in the evaluation of the symmetry energy $γ$ parameter obtained in three different ways. We have checked that independent of the choice made to calculate the $γ$ values, a trend of linear correlation is observed between $γ$ and the symmetry energy ($\mathcal{S}_0$) and a more clear linear relationship is established between $γ$ and the slope of the symmetry energy ($L_0$). These results directly contribute to the arising of other linear correlations between $γ$ and the neutron star radii of $R_{1.0}$ and $R_{1.4}$, in agreement with recent findings. Finally, we have found that short-range correlations induce two specific parametrizations, namely, IU-FSU and DD-ME$δ$, simultaneouslycompatible with the neutron star mass constraint of $1.93 < M_{max}/M_\odot < 2.05$ and with the overlap band for the $L_0\times\mathcal{S}_0$ region, to present $γ$ in the range of $γ=0.25\pm0.05$.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Light (anti)nuclei production in Cu+Cu collisions at $\sqrt{s_{\rm{NN}}}=200$GeV

The production of light (anti)nuclei have been investigated using the dynamically constrained phase-space coalescence model based on the final-state hadrons generated by the PACIAE model in Cu+Cu collisions at $\sqrt{s_{\rm{NN}}}=200$GeV with $|η|<0.5$ and $0<p_T<8$GeV/c. The results show that there is a strong centrality dependence of yields of $\rm d$, $\rm\overline d$, $\rm ^3He$, $\rm^3\overline {He}$, $\rm ^4He$, and $\rm^4\overline {He}$, i.e., their yields decrease rapidly with the increase of centrality, and the greater the mass is, the greater the dependence shows; whereas their ratio of antinucleus to nucleus and coalescence parameter $B_A$ remain constant as the centrality increases. In addition, the yields of (anti)nuclei are strongly dependent on the mass of the (anti)nuclei, indicating that the (anti)nuclei produced have mass scaling properties in high-energy heavy-ion collisions. Our results are consistent with the STAR experimental data.

0 citations0 reviewsNo code linkedOpen access
preprint2018arXiv

Individual low-energy E1 toroidal and compression states in light nuclei: deformation effect, spectroscopy and interpretation

The existence of individual low-energy E1 toroidal and compression states (TS and CS) in $^{24}$Mg was predicted recently in the framework of quasiparticle random-phase-approximation (QRPA) model with Skyrme forces. It was shown that the strong axial deformation of $^{24}$Mg is crucial to downshift the toroidal strength to the low-energy region and thus make the TS the lowest E1(K=1) dipole state. In this study, we explain this result by simple mean-field arguments. Comparing TS in two strongly axial nuclei, $^{24}$Mg and $^{20}$Ne, we show that the lowest TS is not not a universal phenomenon but rather a peculiarity of $^{24}$Mg. The spectroscopy of TS and CS is analyzed and some additional interpretation of these states is suggested.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Combining nuclear reactions and structure with the dispersive optical model

A review of recent applications of the nonlocal dispersive optical model (DOM) is presented that allows a simultaneous description of nuclear structure and nuclear reactions. An assessment of the quality of the resulting potentials for $^{40}$Ca and $^{48}$Ca is discussed for the description of the $(e,e&#39;p)$ reaction to valence hole states and the possibility of interpreting the data in terms of absolute spectroscopic factors. The relevance of these results in the context of conflicting interpretations between transfer and knockout reactions is pointed out as well as the importance of proton reaction cross sections for isotopes with neutron excess. Application of the nonlocal DOM to $^{48}$Ca incorporates the effect of the 8 additional neutrons and allows for an excellent description of elastic scattering data of both protons and neutrons. The corresponding neutron distribution constrained by all available data generates a prediction for the neutron skin that is larger than most mean-field and available \textit{ab initio} results. Results are presented for the most recent nonlocal DOM analysis of $^{208}$Pb.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Short-range correlations for neutrinoless double-beta decay and low-momentum NN potentials

We approach the calculation of the nuclear matrix element of the neutrinoless double-beta decay process, considering the light-neutrino-exchange channel, by way of the realistic shell-model. In particular the focus of our work is spotted on the role of the short-range correlations, which should be taken into account because of the short-range repulsion of the realistic potentials. Our shell-model wave functions are calculated using an effective Hamiltonian derived from the high-precision CD-Bonn nucleon-nucleon potential, the latter renormalized by way of the so-called V-low-k approach. The renormalization procedure decouples the repulsive high-momentum component of the potential from the low-momentum ones by the introduction of a cutoff Lambda, and is employed to renormalize consistently the two-body neutrino potentials to calculate the nuclear matrix elements of candidates to this decay process in mass interval ranging from A=76 up to A=136. We study the dependence of the decay operator on the choice of the cutoff, and compare our results with other approaches that can be found in present literature.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Collectivity of the electromagnetic transitions in near-threshold resonances

Mixing of the shell model (SM) eigenstates due to the coupling via the common decay channel leads in many cases to the formation of a collective eigenstate which carries many features of the nearby decay channel. This generic mechanism in open quantum systems explains the phenomenological Ikeda diagram and generalizes it for various clusters/correlations in the vicinity of the respective cluster decay thresholds. The near-threshold collectivization of the SM states may also influence their electromagnetic decays. We discuss this phenomenon on the example of B(EL) decays of near-threshold 2+ states in 14C.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Triangular symmetry in cluster nuclei

In this contribution, we present evidence for the occurrence of triangular symmetry in cluster nuclei. We discuss the structure of rotational bands for 3-alpha and 3-alpha+1 configurations with triangular D(3h) symmetry by exploiting the double group D&#39;(3h), and study the application to 12C and 13C. The structure of rotational bands can be used as a fingerprint of the underlying geometric configuration of alpha-particles.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Recent advances in the description of reactions involving exotic nuclei

In this contribution to the proceedings of the International Nuclear Physics Conference 2019, I review recent developments made in reaction models used to analyse data measured at radioactive-ion beam facilities to study exotic nuclear structures. I focus in particular on reactions like elastic scattering and breakup, which are used to study halo nuclei. Although these peculiar nuclei challenge usual nuclear-structure models, some can now be computed ab initio. This brief review illustrates the progresses made in nuclear-reaction theory in the last few years to improve the description of the projectile within reaction models. I dedicate this contribution to the memory of Mahir Hussein, who has significantly contributed to this field and who passed away in May this year.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Nuclear incompressibility from spherical and deformed nuclei

We present an analysis based on the deformed Quasi Particle Random Phase Approximation, on top of a deformed Hartree-Fock-Bogoliubov description of the ground state, aimed at studying the isoscalar monopole and quadrupole response in a deformed nucleus. This analysis is motivated by the need of understanding the coupling between the two modes and how it might affect the extraction of the nuclear incompressibility from the monopole distribution. After discussing this motivation, we present the main ingredients of our theoretical framework, and we show some results obtained with the SLy4 and SkM$^{*}$ interactions for the nucleus ${}^{24}$Mg.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Glitching pulsars: unraveling the interactions of general relativity with quantum fields in the strong field regimes

We present a modification of our previous model for the mechanisms underlying the glitch phenomena in pulsars and young neutron stars. Accordingly, pulsars are born with embryonic cores comprising of purely incompressible superconducting gluon-quark superfluid (henceforth SuSu-cores). As the ambient medium cools and spins down due to emission of magnetic dipole radiation, the mass and size of SuSu-cores are set to grow discretely with time, in accordance with the Onsager-Feynmann analysis of superfluidity. Presently, we propose that the spacetime embedding glitching pulsars is dynamical and of bimetric nature: inside SuSu-cores the spacetime must be flat, whereas the surrounding region, where the matter is compressible and dissipative, the spacetime is Schwarzschild. It is further proposed that the topological change of spacetime is derived by the strong nuclear force, whose operating length scales is found to increase with time to reach O(1) cm at the end of the luminous lifetimes of pulsars. The model presented here model is in line with the recent radio and GW observations of pulsars and NSs.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Recent progress on hypernuclei

Some of last year&#39;s progress made in hypernuclear physics is reviewed as follows: (i) resolving the $_Λ^5$He overbinding problem in single-$Λ$ hypernuclei [1]; (ii) arguing that the onset of binding double-$Λ$ hypernuclei is most likely at $A$=5, with the neutral systems $_{ΛΛ}^{\,\,3}$n and $_{ΛΛ}^{\,\,4}$n unbound by a large margin [2]; and (iii) revising the calculated value of the loosely bound $_Λ^3$H lifetime to a level of $\sim$20% shorter than the free $Λ$ lifetime [3], given recent claims from relativistic heavy ion experiments that $τ(_Λ^3$H) is shorter than $τ_Λ$ by as much as $\approx$(30$\pm$8)%. Also discussed briefly in this context is the lifetime expected for the questionable $_Λ^3$n hypernucleus.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Signatures of octupole shape phase transitions in radioactive nuclei

We analyze the octupole deformations and the related collective excitations in medium-heavy and heavy nuclei based on the microscopic framework of the nuclear energy density functional theory. Constrained self-consistent mean-field calculation with a given energy density functional is performed to provide for each nucleus a potential energy surface with axial quadrupole and octupole shape degrees of freedom. Spectroscopic properties are computed by means of the interacting-boson Hamiltonian, which is determined by mapping the fermionic potential energy surface onto the bosonic counterpart. The overall systematics of the calculated spectroscopic observables exhibit phase transitional behaviors between stable octupole deformation and octupole vibration characteristic of the octupole-soft potential within the set of nuclei in light actinide and rare-earth regions, Th, Ra, Sm, Gd, and Ba isotopes, where octupole shapes are most likely to occur.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Regularized pseudopotential for mean-field calculations

We present preliminary results obtained with a finite-range two-body pseudopotential complemented with zero-range spin-orbit and density-dependent terms. After discussing the penalty function used to adjust parameters, we discuss predictions for binding energies of spherical nuclei calculated at the mean-field level, and we compare them with those obtained using the standard Gogny D1S finite-range effective interaction.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

A New Approach to Determine Radiative Capture Reaction Rates at Astrophysical Energies

Radiative capture reactions play a crucial role in stellar nucleosynthesis but have proved challenging to determine experimentally. In particular, the large uncertainty ($\sim$100%) in the measured rate of the $^{12}$C$(α,γ)^{16}$O reaction is the largest source of uncertainty in any stellar evolution model. With development of new high current energy-recovery linear accelerators (ERLs) and high density gas targets, measurement of the $^{16}$O$(e,e^\prime α)^{12}$C reaction close to threshold using detailed balance opens up a new approach to determine the $^{12}$C$(α,γ)^{16}$O reaction rate with significantly increased precision ($<$20%). We present the formalism to relate photo- and electro-disintegration reactions and consider the design of an optimal experiment to deliver increased precision. Once the new ERLs come online, an experiment to validate the new approach we propose should be carried out. This new approach has broad applicability to radiative capture reactions in astrophysics.

0 citations0 reviewsNo code linkedOpen access
preprint2019arXiv

Jet fragmentation functions for $Z$-tagged jets

Recently the LHCb collaboration has measured both longitudinal and transverse momentum distribution of hadrons produced inside $Z$-tagged jets in proton-proton collisions at the Large Hadron Collider. These distributions are commonly referred to as jet fragmentation functions and are characterized by the longitudinal momentum fraction $z_h$ of the jet carried by the hadron and the transverse momentum $j_\perp$ with respect to the jet direction. We derive a QCD formalism within Soft-Collinear Effective Theory to describe these distributions and find that the $z_h$-dependence provides information on standard collinear fragmentation functions, while $j_\perp$-dependence probes transverse momentum dependent (TMD) fragmentation functions. We perform theoretical calculations and compare our results with the LHCb data. We find good agreement for the intermediate $z_h$ region. For $j_\perp$-dependence, we suggest binning in both $z_h$ and $j_\perp$, which would lead to a more direct probing of TMD fragmentation functions.

0 citations0 reviewsNo code linkedOpen access

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