Nuclear Theory·nucl-th

Tuesday·May 19, 2020

14 papers—8 primary·6 cross-listed

01
Topology of nuclear reaction networks of interest for astrophysics
Carlos A. Bertulani
Our understanding of the observed elemental abundance in the universe, stemming from nuclear reactions during the big bang or from nucleosynthesis within stellar environments, requires theoretical analyses based on multidimensional nucleosynthesis calculations involving hundreds of nuclei connected via thousands of nuclear processes. Up to recently, full nucleosynthesis network calculations remained computationally expensive and prohibitive. A recent publication by a Chinese group led by YuGang Ma [1] has proved that advanced computational algorithms developed in the last decade for the purpose of studying complex networks are paving the way to finally accomplish this ultimate goal of nuclear astrophysics.
nucl-thSCPMA(2020)·5 citations
02
Generic algorithm for multi-particle cumulants of azimuthal correlations in high energy nucleus collisions
Zuzana Moravcova🇩🇰 · Kristjan Gulbrandsen🇩🇰 · You Zhou🇩🇰
Multi-particle cumulants of azimuthal angle correlations have been compelling tools to probe the properties of the Quark-Gluon Plasma (QGP) created in the ultra-relativistic heavy-ion collisions and the search for the QGP in small collision systems at RHIC and the LHC. However, only very few of them are available and have been studied in theoretical calculations and experimental measurements. In this paper, we present a generic recursive algorithm for multi-particle cumulants, which enables the calculation of arbitrary order multi-particle cumulants. Among them, the new 10-, 12-, 14-, and 16-particle cumulants of a single harmonic, named $c_{n} {10}$ , $c_{n} {12}$ , $c_{n} {14}$ , and $c_{n} {16}$ , and the corresponding $v_{n}$ coefficients, will be discussed for the first time. These new multi-particle cumulants can be readily used along with updates to the generic framework of multi-particle correlations to a very high order. Finally, we propose a particular series of mixed harmonic multi-particle cumulants, which measures the general correlations between any moments of different flow coefficients. The predictions of these new observables are shown based on an initial state model MC-Glauber, a toy Monte Carlo model, and the HIJING transport model for future comparisons between experimental data and theoretical model calculations. The study of these new multi-particle cumulants in heavy-ion collisions will significantly improve the understanding of the joint probability density function which involves both different harmonics of flow and also the symmetry planes. This will pave the way for more stringent constraints on the initial state and help to extract more precisely how the created hot and dense matter evolves. Meanwhile, the efforts applied to small systems could be very helpful in the understanding of the origin of the observed collectivity at RHIC and the LHC.
nucl-thnucl-exPRC(2021)·43 citations
03
Quadrupole properties of the eight $S U (3)$ algebras in $(s d g i)$ space
R. Sahu · V.K.B. Kota · P.C. Srivastava
With nucleons occupying an oscillator shell $η$ , there are $2^{η /2}$ number of $S U (3)$ algebras; $η /2$ is the integer part of $η /2$ . Analyzing the first non trivial situation with four $S U (3)$ algebras in $(s d g)$ space, demonstrated recently is that they generate quite different quadrupole properties though they all generate the same spectrum. More complex situation is with eight $S U (3)$ algebras in $(s d g i)$ space. In the present work, quadrupole properties generated by these eight algebras are analyzed first using the more analytically tractable interacting boson model. In addition, shell model and the closely related deformed shell model are used with three examples of nucleons in $s d g i$ space. It is found that in general six of the $S U (3)$ algebras generate prolate shape and two oblate shape. Out of all these, one of the $S U (3)$ algebra generates quite small quadrupole moments for the low-lying states.
nucl-thEur.Phys.J.ST(2020)·2 citations
04
Exact Relations for Two-Photon-Exchange Effect in Elastic $e p$ Scattering by Dispersion Relation and Hadronic Model
Hui-Yun Cao🇨🇳 · Hai-Qing Zhou🇨🇳
The two-photon-exchange (TPE) effect plays a key role to extract the form factors (FFs) of the proton. In this work, we present some exact properties on the TPE effect in the elastic $e p$ scattering based on four types of typical and general interactions. The possible kinematical singularities, the asymptotic behaviors and the branch cuts of the TPE amplitudes are analyzed. The analytic expressions clearly indicate some exact relations between the dispersion relation (DR) method and the hadronic model (HM) method. It suggests that the two methods should be modified to general forms, respectively. After the modifications the new forms give the same results. Furthermore, they automatically and correctly include the contributions due to the seagull interaction, the meson-exchange effect, the contact interactions and the off-shell effect. To analyze the elastic $e^{\pm} p$ scattering data sets, the new forms should be used.
nucl-thhep-exhep-phnucl-exCPC(2021)·5 citations
05
Heavy flavors under extreme conditions in high energy nuclear collisions
Jiaxing Zhao🇨🇳 · Kai Zhou🇩🇪 · Shile Chen🇨🇳 · Pengfei Zhuang🇨🇳
Heavy flavor hadrons have long been considered as a probe of the quark gluon plasma created in high energy nuclear collisions. In this paper we review the heavy flavor properties under extreme conditions and the realization in heavy ion experiments. After a short introduction on heavy flavor properties in vacuum, we emphasize the cold and hot nuclear matter effects on heavy flavors, including shadowing effect, Cronin effect and nuclear absorption for the former and Debye screening and regeneration for the latter. Then we discuss, in the frame of transport and coalescence models, these medium induced changes in open and closed heavy flavors in nuclear collisions and the comparison with nucleon-nucleon collisions. Considering the extremely strong electromagnetic and rotational fields generated in non-central nuclear collisions, which are widely studied in recent years, we finally investigate their effects on heavy flavor production and evolution in high energy nuclear collisions.
nucl-thhep-phPPNP(2020)·138 citations
06
Warm dense matter and cooling of supernovae remnants
Ankit Kumar · H. C. Das · S. K. Biswal · Bharat Kumar · S. K. Patra
We study the thermal effects on the nuclear matter (NM) properties such as binding energy, incompressibility, free symmetry energy and its coefficients using NL3, G3 and IU-FSU parameter sets of relativistic mean-field models. These models being consistent with the properties of cold NM, have also been used to study the effect of temperature by incorporating the Fermi function. The critical temperature for the liquid-gas phase transition in the symmetric NM is found to be 14.60, 15.37 and 14.50 MeV for NL3, G3 and IU-FSU parameter sets respectively, which is in excellent agreement with previous theoretical and experimental studies. We inspect that the properties related to second differential coefficient of the binding energy and free symmetry energy at saturation density ( i.e. K 0 (n, T ) and Q sym,0) exhibit the contrary effects for NL3 and G3 parameters as the temperature increases. We find that the prediction of saturated curvature parameter ( K sym,0 ) for G3 equation of state at finite temperature favour the combined analysis of K sym,0 for the existence of massive pulsars, gravitational waves from GW170817 and NICER observations of PSR J0030+0451. Further, we investigate the cooling mechanism of newly born stars through neutrino emissivity controlled by direct Urca process and instate some interesting remarks about neutrino emissivity. We also deliberate the effect of temperature on the M-R profile of Proto-Neutron star.
nucl-thastro-ph.HEEPJC(2020)·34 citations
07
Charmonium transition in electromagnetic and rotational fields
Shile Chen🇨🇳 · Jiaxing Zhao🇨🇳 · Pengfei Zhuang🇨🇳
We study charmonia in electromagnetic and rotational fields in the frame of a potential model. Different from the temperature field which is isotropic and leads to the well-known charmonium dissociation, the electromagnetic and rotational fields break down the radial symmetry, and the competition between strong interaction and electromagnetic and rotational interaction in the direction of Lorentz force makes the charmonia transit from an isotropic bound state of strong interaction with positive binding energy to an anisotropic bound state of electromagnetic and rotational interaction with negative binding energy. The transition seems possible to be realized in high energy nuclear collisions.
nucl-thhep-phPRC(2021)·21 citations
08
Level-density parameters in superheavy nuclei
A. Rahmatinejad · A. N. Bezbakh · T. M. Shneidman · G. Adamian · N. V. Antonenko · P. Jachimowicz · M. Kowal
We systematically study the nuclear level densities of superheavy nuclei, including odd systems, using the single-particle energies obtained with the Woods-Saxon potential diagonalization. Minimization over many deformation parameters for the global minima - ground states and the "imaginary water flow" technique on many deformation energy grids for the saddle points, including nonaxial shapes has been applied. The level density parameters are calculated by fitting the obtained results with the standard Fermi gas expression. The total potential energy and shell correction dependencies of the level-density parameter are analyzed and compared at the ground state and saddle point. These parameters are compared with the results of the phenomenological expression. As shown, this expression should be modified for the saddle points, especially for small excitation energy. The ratio of the level-density parameter at the saddle point to that at the ground state is shown to be crucial for the survival probability of the heavy nucleus.
nucl-thcond-mat.str-elPRC(2021)·24 citations
09
Role of chiral two-body currents in $^{6}$ Li magnetic properties in light of a new precision measurement with the relative self-absorption technique
U. Friman-Gayer · C. Romig · T. Hüther · K. Albe · S. Bacca · T. Beck · M. Berger · J. Birkhan · K. Hebeler · O. J. Hernandez · J. Isaak · S. König and 9 other authors
A direct measurement of the decay width of the excited $0_{1}^{+}$ state of $^{6}$ Li using the relative self-absorption technique is reported. Our value of $Γ_{γ, 0_{1}^{+} \to 1_{1}^{+}} = 8.17 (14)_{stat.} (11)_{syst.} eV$ provides sufficiently low experimental uncertainties to test modern theories of nuclear forces. The corresponding transition rate is compared to the results of ab initio calculations based on chiral effective field theory that take into account contributions to the magnetic dipole operator beyond leading order. This enables a precision test of the impact of two-body currents that enter at next-to-leading order.
↳ nucl-exnucl-thPRL(2021)·25 citations
10
Precision measurement of $^{210}$ Bi $β$ -spectrum
I.E. Alekseev🇷🇺 · S.V. Bakhlanov🇷🇺 · A.V. Derbin🇷🇺 · I.S. Drachnev🇷🇺 · I.M. Kotina🇷🇺 · I.S. Lomskaya🇷🇺 · V.N. Muratova🇷🇺 · N.V. Niyazova🇷🇺 · D.A. Semenov🇷🇺 · M.V. Trushin🇷🇺 · E.V. Unzhakov🇷🇺
The precision measurement of the $β -$ spectrum shape for $^{210}$ Bi (historically RaE) have been performed with a spectrometer based on semiconductor Si(Li) detector. This first forbidden non-unique transition has the transition form-factor strongly deviated from unity and knowledge of its spectrum would play an important role in low-background physics in presence of $^{210}$ Pb background. The measured transition form-factor could be approximated as $S (W) = 1 + (- 0.4363 \pm 0.0037) W + (0.0523 \pm 0.0010) W^{2}$ , that is in good agreement with previous studies and has significantly increased parameter precision.
↳ nucl-exhep-exhep-phnucl-th+1PRC(2021)·12 citations
11
Two-photon decays and transition form factors of $π^{0}$ , $η$ , and $η^{'}$ in large- $N_{c}$ chiral perturbation theory
Patricia Bickert🇩🇪 · Stefan Scherer🇩🇪
We present a calculation of $P \to γ^{(*)} γ^{(*)}$ processes, where $P = π^{0}, η, η^{'}$ , at the one-loop level up to and including next-to-next-to-leading order (NNLO) in large- $N_{c}$ chiral perturbation theory. The results are numerically evaluated successively at LO, NLO, and NNLO. The appearing low-energy constants are determined through fits to the available experimental data. We investigate the decay widths to real photons, the single-virtual transition form factors, and the widths of $P \to γ l^{+} l^{-}$ , where $l = e, μ$ . Furthermore, we provide results for the slopes and curvatures of the transition form factors.
↳ hep-phnucl-exnucl-thPRD(2020)·16 citations
12
Statistical Behavior of Lepton Pair Spectrum in Drell-Yan Process and Signal from Quark-Gluon Plasma in High Energy Collisions
Xu-Hong Zhang🇨🇳 · Fu-Hu Liu🇨🇳
We analyze the transverse momentum ( $p_{T}$ ) spectra of lepton pairs ( $ℓ ℓ ˉ$ ) generated in the Drell-Yan process, as detected in proton-nucleus (pion-nucleus) and proton-(anti)proton collisions by ten collaborations over a center-of-mass energy ( $s_{N N}$ or $s$ if in a simplified form) range from $\sim 20$ GeV to above 10 TeV. Three types of probability density functions (the convolution of two Lévy-Tsallis functions, the two-component Erlang distribution, and the convolution of two Hagedorn functions) are utilized to fit and analyze the $p_{T}$ spectra. The fit results are approximately in agreement with the collected experimental data. Consecutively, we obtained the variation law of related parameters as a function of $s$ and invariant mass ( $Q$ ). In the fit procedure, a given Lévy-Tsallis (or Hagedorn) function can be regarded as the probability density function of transverse momenta contributed by a single quark ( $q$ ) or anti-quark ( $q ˉ$ ). The Drell-Yan process is then described by the statistical method.
↳ hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2021)·1 citation
13
Solutions to Problems at Les Houches Summer School on EFT
Marcel Balsiger🇨🇭 · Marios Bounakis🇬🇧 · Mehdi Drissi🇫🇷 · John Gargalionis🇦🇺 · Erik Gustafson🇺🇸 · Greg Jackson🇨🇭 · Matthew Leak🇬🇧 · Christopher Lepenik🇦🇹 · Scott Melville🇬🇧 · Daniel Moreno🇪🇸 · Michele Tammaro🇺🇸 · Selim Touati🇫🇷 · Timothy Trott🇺🇸
This work details worked solutions to the various problems set by the lecturers during the course of the Les Houches summer school 2017 on effective field theories in particle physics and cosmology.
↳ hep-phgr-qcnucl-thLes Houches Lect.Notes(2020)·3 citations
14
Hadronization of heavy diquark and light quark within NJL-Model
Yu-Ji Shi🇩🇪
We present a path-integral hadronization for doubly heavy baryons. The two heavy quarks in the baryon are approximated as a scalar or axial-vector diquark described by a heavy diquark effective theory. The gluon dynamics are represented by a NJL-Model interaction for the heavy diquarks and light quarks, which leads to an effective action of the baryon fields after the quark and diquark fields are integrated out. This effective action for doubly heavy baryon includes the electromagnetic and electroweak interactions, as well as the interaction with light mesons. We also verify the Ward-Takahashi identity at the baryon level, obtain the Isgur-Wise function for weak transitions, and calculate the strong coupling constant of the doubly heavy baryon and pion. Numerical studies are also performed.
↳ hep-phnucl-th1 citation

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