Nuclear Theory·nucl-th

Tuesday·June 9, 2020

17 papers—7 primary·10 cross-listed

01
Level density within a micro-macroscopic approach
A.G. Magner · A.I. Sanzhur · S.N. Fedotkin · A.I. Levon · S. Shlomo
Statistical level density $ρ (E, A)$ is derived for nucleonic system with a given energy $E$ , particle number $A$ and other integrals of motion in the micro-macroscopic approximation beyond the standard saddle-point method of the Fermi gas model. This level density reaches the two limits; the well-known Fermi gas grand-canonical ensemble limit for a large entropy $S$ related to large excitation energies, and the finite micro-canonical limit for a small combinatorical entropy $S$ at low excitation energies. The inverse level density parameter $K$ as function of the particle number $A$ in the semiclassical periodic orbit theory, taking into account the extended Thomas-Fermi and Strutinsky shell corrections, is calculated and compared with experimental data.
nucl-thnucl-exNPA(2022)·8 citations
02
Successful prediction of total $α$ -induced reaction cross sections at astrophysically relevant sub-Coulomb energies using a novel approach
P. Mohr · Zs. Fülöp · Gy. Gyürky · G. G. Kiss · T. Szücs
The prediction of stellar ( $γ$ , $α$ ) reaction rates for heavy nuclei is based on the calculation of ( $α$ , $γ$ ) cross sections at sub-Coulomb energies. These rates are essential for modeling the nucleosynthesis of so-called $p$ -nuclei. The standard calculations in the statistical model show a dramatic sensitivity to the chosen $α$ -nucleus potential. The present study explains the reason for this dramatic sensitivity which results from the tail of the imaginary $α$ -nucleus potential in the underlying optical model calculation of the total reaction cross section. As an alternative to the optical model, a simple barrier transmission model is suggested. It is shown that this simple model in combination with a well-chosen $α$ -nucleus potential is able to predict total $α$ -induced reaction cross sections for a wide range of heavy target nuclei above $A ≳ 150$ with uncertainties below a factor of two. The new predictions from the simple model do not require any adjustment of parameters to experimental reaction cross sections whereas in previous statistical model calculations all predictions remained very uncertain because the parameters of the $α$ -nucleus potential had to be adjusted to experimental data. The new model allows to predict the reaction rate of the astrophysically important $^{176}$ W( $α$ , $γ$ ) $^{180}$ Os reaction with reduced uncertainties, leading to a significantly lower reaction rate at low temperatures. The new approach could also be validated for a broad range of target nuclei from $A \approx 60$ up to $A ≳ 200$ .
nucl-thastro-ph.IMPRL(2020)·39 citations
03
Pairing, quasi-spin and seniority
Bijay Kumar Agrawal · Bhoomika Maheshwari
We present our concise notes for the lectures and tutorials on pairing, quasi-spin and seniority delivered at SERB school on Role of Symmetries in Nuclear Physics, AMITY University, $2019$ . Starting with some generic features of residual nucleon-nucleon interactions, we provide detailed derivation of the matrix elements for the $δ$ -interaction which is the basis for the standard pairing Hamiltonian. The eigen values for standard pairing Hamiltonian are then obtained within the quasi-spin formalism. The algebra involving quasi-spin operators is performed explicitly using the annihilation and creation operators for single nucleon together with the application of Wicks theorem. These techniques are expected to be helpful in deriving the mean-field equations for the $H a r t r ee - F oc k$ , $B a r d ee n - C oo p er - S c h r i e f f er$ and $H a r t r ee - F oc k$ Bogoliubov theories.
nucl-thEur.Phys.J.ST(2020)·1 citation
04
Radiative pion photoproduction in covariant chiral perturbation theory
J. Rijneveen🇩🇪 · N. Rijneveen🇩🇪 · H. Krebs🇩🇪 · A. M. Gasparyan🇩🇪 · E. Epelbaum🇩🇪
We present a calculation of radiative pion photoproduction in the framework of covariant chiral perturbation theory with explicit $Δ (1232)$ degrees of freedom. The analysis is performed employing the small scale expansion scheme adjusted for the $Δ$ region. Depending on the channel, we include contributions up to next-to-next-to-leading order. We fit the available experimental data for the reaction $γ p \to γ p π^{0}$ and extract the value of the $Δ^{+}$ magnetic moment. Errors from the truncation of the small scale expansion are estimated using the Bayesian approach. We compare our results both with the previous studies within the $δ$ -expansion scheme and with the $Δ$ -less theory. We also give predictions for radiative charged-pion photoproduction.
nucl-thhep-phPRC(2021)·5 citations
05
Far From Equilibrium Hydrodynamics and the Beam Energy Scan
Travis Dore🇺🇸 · Emma McLaughlin🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸
The existence of hydrodynamic attractors in rapidly expanding relativistic systems has shed light on the success of relativistic hydrodynamics in describing heavy-ion collisions at zero chemical potential. As the search for the QCD critical point continues, it is important to investigate how out of equilibrium effects influence the trajectories on the QCD phase diagram. In this proceedings, we study a Bjorken expanding hydrodynamic system based on DMNR equations of motion with initial out of equilibrium effects and finite chemical potential in a system with a critical point. We find that the initial conditions are not unique for a specific freeze-out point, but rather the system can evolve to the same final state freeze-out point with a wide range of initial baryon chemical potential, $μ_{B}$ . For the same initial energy density and baryon density, depending on how far out of equilibrium the system begins, the initial $μ_{B}$ can vary by $Δ μ_{B} \sim 350$ MeV. Our results indicate that knowledge of the out-of-equilibrium effects in the initial state provide vital information that influences the search for the QCD critical point.
nucl-thhep-phnucl-exJ.Phys.Conf.Ser.(2020)·9 citations
06
Markov Chain Monte Carlo Predictions of Neutron-rich Lanthanide Properties as a Probe of $r$ -process Dynamics
Nicole Vassh · Gail C. McLaughlin · Matthew R. Mumpower · Rebecca Surman
Lanthanide element signatures are key to understanding many astrophysical observables, from merger kilonova light curves to stellar and solar abundances. To learn about the lanthanide element synthesis that enriched our solar system, we apply the statistical method of Markov Chain Monte Carlo to examine the nuclear masses capable of forming the $r$ -process rare-earth abundance peak. We describe the physical constraints we implement with this statistical approach and demonstrate the use of the parallel chains method to explore the multidimensional parameter space. We apply our procedure to three moderately neutron-rich astrophysical outflows with distinct types of $r$ -process dynamics. We show that the mass solutions found are dependent on outflow conditions and are related to the $r$ -process path. We describe in detail the mechanism behind peak formation in each case. We then compare our mass predictions for neutron-rich neodymium and samarium isotopes to the latest experimental data from the CPT at CARIBU. We find our mass predictions given outflows that undergo an extended (n, $γ$ ) $⇄$ ( $γ$ ,n) equilibrium to be those most compatible with both observational solar abundances and neutron-rich mass measurements.
nucl-thastro-ph.HEApJ(2021)·26 citations
07
Resonance structure of $^{8}$ Be with the two-cluster resonating group method
V. O. Kurmangaliyeva · N. Kalzhigitov · N. Takibayev · V. S. Vasilevsky
A two-cluster microscopic model is applied to study elastic alpha-alpha scattering and resonance structure of $^{8}$ Be. The model is an algebraic version of the Resonating Group Method, which makes use complete set of oscillator functions to expand wave function of two-cluster system. Interaction between clusters is determined by well-known semi-realistic nucleon-nucleon potentials of Hasegawa-Nagata, Minnesota and Volkov. Detail analysis of resonance wave functions is carried out in oscillator, coordinate and momentum spaces. Effects of the Pauli principle on wave functions of the $^{8}$ Be continuous spectrum states are thoroughly studied.
nucl-thUkr.J.Phys.(2023)·7 citations
08
Studying the parameters of the extended $σ$ - $ω$ model for neutron star matter
David Alvarez-Castillo🇵🇱 · Alexander Ayriyan🇷🇺 · Gergely Gábor Barnaföldi🇭🇺 · Hovik Grigorian🇷🇺 · Péter Pósfay🇭🇺
In this work we study the parameters of the extended $σ$ - $ω$ model for neutron star matter by a Bayesian analysis on state-of-the-art multi-messenger astronomy observations, namely mass, radius and tidal deformabilities. We have considered three parameters of the model, the Landau mass $m_{L}$ , the nuclear compressibility $K_{0}$ , and the value of the symmetry energy $S_{0}$ , all at saturation density $n_{0}$ . As a result, we are able to estimate the values of the Landau mass of f $m_{L} = 739 \pm 17$ MeV, whereas the values of $K_{0}$ and $S_{0}$ fall within already known empirical values. Furthermore, for neutron stars we find the most probable value of 13 km $< R_{1.4} <$ 13.5 km and the upper mass limit of $M_{ma x} \approx 2.2$ M $_{⊙}$ .
↳ astro-ph.HEhep-phnucl-thEur.Phys.J.ST(2020)·13 citations
09
Estimating Compressibility from Maximal-mass Compact Star Observations
Gergely Gábor Barnaföldi · Péter Pósfay · Balázs E. Szigeti · Antal Jakovác
We investigated recent observation data of pulsar masses of PSR J0740 $+$ 6620, PSR J0348 $+$ 0432, and PSR J1614 $-$ 2230 based on the extended $σ$ - $ω$ model. We assumed that these pulsars are maximal mass compact star, which suggest that the core approximation can be applied. Using the linear relations between the microscopic and macroscopic parameters of neutron stars suggested by this model, we estimated the values of the nucleon Landau mass and nuclear compressibility $m_{L} = 776. 0_{- 84.9}^{+ 38.5}$ ~MeV and $K = 242. 7_{- 28.0}^{+ 57.2}$ , respectively.
↳ astro-ph.HEnucl-thEur.Phys.J.ST(2020)·4 citations
10
Lambda(1405) as a K-bar N Feshbach resonance in the Skyrme model
Takashi Ezoe🇯🇵 · Atsushi Hosaka🇯🇵
We describe the Lambda(1405) hyperon as a Feshbach resonance of a bar-KN quasi-bound state coupled by a decaying channel of pi Sigma in the Skyrme model. A weakly bound bar-KN state is generated in the laboratory frame, while the Sigma hyperon as a strongly bound state of bar-KN in the intrinsic frame. We obtain a coupling of bar-KN and pi Sigma channels by computing a baryon matrix element of the axial current. This coupling enables the decay of the bar-KN bound state to pi-Sigma . It is shown that the Skyrme model supports the Lambda(1405) as a narrow Feshbach resonance.
↳ hep-phnucl-thPRD(2020)·9 citations
11
Constraining the onset density of the hadron-quark phase transition with gravitational-wave observations
Sebastian Blacker🇩🇪 · Niels-Uwe F. Bastian🇵🇱 · Andreas Bauswein🇩🇪 · David B. Blaschke🇵🇱 · Tobias Fischer🇵🇱 · Micaela Oertel🇫🇷 · Theodoros Soultanis🇩🇪 · Stefan Typel🇩🇪
We study the possible occurrence of the hadron-quark phase transition (PT) during the merging of neutron star binaries by hydrodynamical simulations employing a set of temperature dependent hybrid equations of state (EoSs). Following previous work we describe an unambiguous and measurable signature of deconfined quark matter in the gravitational-wave (GW) signal of neutron star binary mergers including equal-mass and unequal-mass systems of different total binary mass. The softening of the EoS by the PT at higher densities, i.e. after merging, leads to a characteristic increase of the dominant postmerger GW frequency f_peak relative to the tidal deformability Lambda inferred during the premerger inspiral phase. Hence, measuring such an increase of the postmerger frequency provides evidence for the presence of a strong PT. If the postmerger frequency and the tidal deformability are compatible with results from purely baryonic EoS models yielding very tight relations between f_peak and Lambda, a strong PT can be excluded up to a certain density. We find tight correlations of f_peak and Lambda with the maximum density during the early postmerger remnant evolution. These GW observables thus inform about the density regime which is probed by the remnant and its GW emission. Exploiting such relations we devise a directly applicable, concrete procedure to constrain the onset density of the QCD PT from future GW measurements. We point out two interesting scenarios: if no indications for a PT are inferred from a GW detection, our procedure yields a lower limit on the onset density of the hadron quark PT. On the contrary, if a merger event reveals evidence for the occurrence of deconfined quark matter, the inferred GW parameters set an upper limit on the PT onset density. (abridged)
↳ astro-ph.HEhep-phnucl-thPRD(2020)·119 citations
12
Search for CP-violating nuclear magnetic quadrupole moment using the LuOH $^{+}$ cation
D.E. Maison🇷🇺 · L.V. Skripnikov🇷🇺 · V.V. Flambaum🇦🇺 · M. Grau🇨🇭
The CP-violating interaction of the nuclear magnetic quadrupole moment (MQM) of the $^{175}$ Lu nucleus with electrons in the molecular cation LuOH $^{+}$ is studied. The resulting effect is expressed in terms of CP-odd parameters, such as quantum chromodynamics angle $θ ˉ$ , quark electric dipole moment (EDM) and chromo-EDM. For this we have performed a calculation of the nuclear MQM as well as the molecular constant that characterises the interaction of this MQM of $^{175}$ Lu with electrons. Additionally, we predict the hyperfine structure constants for the ground electronic state of LuOH $^{+}$ . We conclude that LuOH $^{+}$ is a promising system to measure the nuclear MQM.
↳ physics.atom-phhep-phnucl-thJ.Chem.Phys.(2020)·23 citations
13
Study of the ground state energies of some nuclei using hybrid model
R. Hussien🇪🇬 · Sh. M. Sewailem🇪🇬 · L. I. Abou-Salem🇪🇬
The quark-quark QQ interaction as a perturbed term to the nucleon-nucleon interaction NN without any coupling between them is studied in a hybrid model. This model is used to calculate the ground-state energies of 2H1 and 4He2 nuclei. In a semi-relativistic framework, this model is encouraged for light nuclei and the instanton induced interaction by using the QQ potential and the NN interaction for a small scale around the hadron boundaries. This hybrid model depends on two theories, the one-boson exchange potential OBEP and the Cornell-dressed potential CDP for QQ. A small effect of quark-quark interaction is obtained on the values of the ground state energies, around 6.7 for 2H1 and 1.2 for 4He2 by using the considered hybrid model.
↳ hep-phnucl-thAdv.High Energy Phys.(2021)·0 citations
14
Quantification of the Chiral Magnetic Effect in Au+Au collisions at $s_{NN} = 200$ GeV
Roy A. Lacey (1) · Niseem Magdy (2) ((1) Depts. of Chemistry and Physics, Stony Brook University, Stony Brook USA, (2) Department of Physics, University of Illinois at Chicago, Chicago, Illinois, USA)
The Multi-Phase Transport model, AMPT, and the Anomalous Viscous Fluid Dynamics model, AVFD, are used to assess a possible chiral-magnetically-driven charge separation ( $Δ S$ ) recently measured with the $R_{Ψ_{2}} (Δ S)$ correlator in Au+Au collisions at $s_{NN} = 200$ GeV. The Comparison of the experimental and simulated $R_{Ψ_{2}} (Δ S)$ distributions indicates that background-driven charge separation is insufficient to account for the measurements. The AVFD model calculations, which explicitly account for CME-driven anomalous transport in the presence of background, indicate a CME signal quantified by the $P$ -odd Fourier dipole coefficient $a_{1}^{'} \approx 0.5%$ in mid-central collisions. A similar evaluation for the $Δ γ$ correlator suggests that only a small fraction of this signal ( $f_{CME} = Δ γ_{CME} /Δ γ \approx 25%$ ) is measurable with this correlator in the same collisions. The related prediction for signal detection in isobaric collisions of Ru+Ru and Zr+Zr are also presented.
↳ nucl-exhep-exnucl-th2 citations
15
Thermodynamic and Transport Properties of Matter Formed in $pp$ , $p$ -Pb, Xe-Xe and Pb-Pb Collisions at the Large Hadron Collider using Color String Percolation Model
Dushmanta Sahu🇮🇳 · Raghunath Sahoo🇮🇳
To have a better understanding of the matter formed in ultra-relativistic collisions, using the Color String Percolation Model (CSPM), we have estimated initial energy density, mean free path, squared speed of sound, shear viscosity to entropy density ratio ( $η / s$ ), bulk viscosity to entropy density ratio and bulk modulus for $pp$ , $p$ -Pb, Xe-Xe and Pb-Pb collisions at the Large Hadron Collider (LHC). These observables are studied as a function of final state charged particle multiplicity density and initial state percolation temperature. The results from this work are compared with the results from well known QCD models and with the transport properties of matter found in day-to-day life. These observables allow us to conclude an array of important findings about the matter formed in high energy collisions at the LHC. This work gives a threshold of charged particle multiplicity $⟨ d N_{c h} / d η ⟩ ≃$ 20, after which there are indications of change in the dynamics of the systems. The critical initial energy density and temperature as estimated by lattice QCD, are observed to be achieved for events with final state multiplicity $⟨ d N_{c h} / d η ⟩ \geq$ 20. In addition, for these high-multiplicity events, the estimated $η / s$ are comparable with that is observed for heavy-ion collisions, which is an indication of a strongly coupled Quark Gluon Plasma. This makes LHC high-multiplicity $pp$ collision events as probable candidates for the search of QGP droplets.
↳ hep-phhep-exnucl-exnucl-thJ.Phys.G(2021)·23 citations
16
Charge separation measurements in $p$ ( $d$ )+Au and Au+Au collisions; implications for the chiral magnetic effect
STAR Collaboration
Charge separation ( $Δ S$ ) measurements, obtained relative to the $2^{nd}$ -order ( $Ψ_{2}$ ) and $3^{rd}$ -order ( $Ψ_{3}$ ) event planes with a new charge-sensitive correlator $R_{Ψ_{m}} (Δ S)$ , are presented for $p$ ( $d$ )+Au and Au+Au collisions at $s_{N N} = 200$ ~GeV. The correlator, which is sensitive to the hypothesized Chiral Magnetic Effect (CME), show the expected patterns of background-driven charge separation for the measurements relative to $Ψ_{3}$ and those relative to $Ψ_{2}$ for the $p$ ( $d$ )+Au systems. By contrast, the Au+Au measurements relative to $Ψ_{2}$ , show event-shape-independent $R_{Ψ_{2}} (Δ S)$ distributions consistent with a CME-driven charge separation, quantified by widths having an inverse relationship to the Fourier dipole coefficient $a ~_{1}$ , which evaluates the CME. The extracted values of these widths and their dependencies on centrality and event-shape give new constraints for possible CME-driven charge separation in relativistic heavy-ion collisions.
↳ nucl-exhep-exhep-phnucl-th14 citations
17
The remnant of GW170817: a trapped neutron star with a hypermassive incompressible superfluid core
A.A. Hujeirat · R. Samtaney
Our bimetric spacetime model of glitching pulsars is applied to the remnant of GW170817. Accordingly, pulsars are born with embryonic incompressible superconducting gluon-quark superfluid cores (SuSu-matter) that are embedded in Minkowski spacetime, whereas the ambient compressible and dissipative media (CDM) are imbedded in curved spacetime. As pulsars cool down, the equilibrium between both spacetime is altered, thereby triggering the well-observed glitch phenomena. Based thereon and assuming all neutron stars (NSs) to be born with the same initial mass of $M_{N S} (t = 0) \approx 1.25 M_{⊙},$ we argue that the remnant of GW170817 should be a relatively faint NS with a hypermassive central core made of SuSu-matter. The effective mass and radius of the remnant are predicted to be $[2.8 M_{⊙} < M_{r e m} \leq 3.351 M_{⊙}]$ and $R_{r e m} = 10.764$ km, whereas the mass of the enclosed SuSu-core is $M_{cor e} = 1.7 M_{⊙} .$ Here, about $1/2 M_{cor e}$ is an energy enhancement triggered by the phase transition of the gluon-quark-plasma from the microscopic into macroscopic scale. The current compactness of the remnant is $α_{c} = 0.918,$ but predicted to increase as the CDM and cools down, rendering the remnant an invisible dark energy object, and therefore to an excellent black hole candidate.
↳ astro-ph.HEgr-qcnucl-th2 citations

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