Nuclear Theory·nucl-th

Tuesday·August 13, 2024

16 papers—8 primary·8 cross-listed

01
Toward Reliable $0 ν β β$ -decay Nuclear Matrix Elements: Exploring the potential of measuring $γ γ$ -transitions
Beatriz Romeo Zaragozano🇪🇸
In this work, a physics process known since quite long ago, double-gamma decay ( $γ γ$ ), has been revisited from a new perspective: providing valuable insights into neutrinoless double-beta decay ( $0 ν β β$ ) nuclear matrix elements. At the same time that an eager experimental search of $0 ν β β$ decay is underway, the nuclear and particle physics communities have made huge progress during the last years. The main goal of this thesis has been to investigate one of those approaches which is the computation of nuclear observables related to $0 ν β β$ decay as a way to help in determining and reducing the theoretical uncertainties in $0 ν β β$ -decay NMEs. This way, we have proposed that the measurement of the double magnetic dipole $γ γ$ decay from the double isobaric analog state in the $β β$ -decay final nucleus could establish the value and reduce the uncertainty in $0 ν β β$ -decay NMEs, because the NMEs of the two processes are very well correlated. We have explored the validity of this approach to predict and quantify NMEs uncertainties in the case where data is available for the nuclear observable related to $0 ν β β$ decay, that is for the Standard Model allowed $2 ν β β$ decay. A further objective has been to start with the theoretical characterization of the first steps toward the measurement of the proposed $γ γ$ double magnetic dipole decay from the double isobaric analogue state. In particular, we have studied the main decaying modes that can compete with this process: single gamma decay and proton emission, vi and we have calculated the corresponding branching ratios. In addition, we have also given the first steps in the study of the relation between $γ γ$ and $0 ν β β$ -decay NMEs in the ab initio valence space in-medium similarity renormalization group.
nucl-th1 citation
02
Applications of the Modified Hulthén-Kohn Method for Bound and Scattering States
M. A. Sharaf · A. M. Shirokov · W. Du · J. P. Vary
We apply the Hulthèn-Kohn method suggested by V. D. Efros [Phys. Rev. C 99, 034620 (2019)] for calculating various observables in the continuum and discrete spectrum using two-body interactions in single- and coupled-channel systems. This method is promising for many-body applications and ab initio description of nuclear reactions. We explore the convergence of phase shifts and wave functions as well as the location of S-matrix poles which enables obtaining both resonance and bound state parameters. We find that adopting wave functions from approximate bound-state solutions for the short-range components of basis wave functions leads to good convergence.
nucl-thPRC(2025)·5 citations
03
Constraining the competition between the deconfinement and chiral phase transitions in light of the multimessenger era
Wen-Li Yuan🇨🇳 · Bikai Gao🇯🇵 · Yan Yan🇨🇳 · Bo-Lin Li🇨🇳 · Renxin Xu🇨🇳
We extend the parity doublet model for hadronic matter and study the possible presence of quark matter inside the cores of neutron stars with the Nambu-Jona-Lasinio (NJL) model. Considering the uncertainties of the QCD phase diagram and the location of the critical endpoint, we aim to explore the competition between the chiral phase transition and the deconfinement phase transition systematically, regulated by the vacuum pressure $- B$ in the NJL model. Employing a Maxwell construction, a sharp first-order deconfinement phase transition is implemented combining the parity doublet model for the hadronic phase and the NJL model for the high-energy quark phase. The position of the chiral phase transition is obtained from the NJL model self-consistently. We find stable neutron stars with a quark core within a specific parameter space that satisfies current astronomical observations. The observations suggest a relatively large chiral invariant mass $m_{0} = 600$ MeV in the parity doublet model and a larger split between the chiral and deconfinement phase transitions while assuming the first-order deconfinement phase transition. The maximum mass of the hybrid star that we obtain is $\sim 2.2 M_{⊙}$ .
nucl-thastro-ph.HEhep-phMod.Phys.Lett.A·6 citations
04
Modified Trento initial condition and its impact on collective flows and global polarization in Cu+Au collisions
Ze-Fang Jiang🇨🇳 · Shanshan Cao🇨🇳 · Ben-Wei Zhang🇨🇳
Collective flow coefficients and spin polarization are valuable probes of the geometry and flow velocity field of the quark-gluon plasma (QGP) produced in relativistic heavy-ion collisions. Using a modified TRENTo initial condition coupled to a (3+1)-dimensional (D) viscous hydrodynamic model CLVisc, we study the directed flow and elliptic flow coefficients of hadrons, together with the global polarization of $Λ$ and $Λ ˉ$ hyperons in asymmetric Cu+Au collisions. We extend the 2D TRENTo model to the 3D space, and find that the initial tilted geometry of the QGP fireball with respect to the longitudinal direction leads to a decrease of directed flow from positive to negative values with increasing pseudorapidity, an enhancement of elliptic flow at forward and backward pseudorapidities, and a non-monotonic dependence of global polarization on the transverse momentum of hyperons. The initial longitudinal flow velocity gradient further enhances the values of directed flow and global polarization. Our model calculation provides a satisfactory description of the rapidity, transverse momentum, and centrality dependences of the directed flow of charged hadrons in Cu+Au collisions for the first time, and proposes that such asymmetric heavy-ion collisions create a better environment for studying the initial tilted geometry and longitudinal flow field of the QGP than symmetric Au+Au collisions do.
nucl-thhep-phnucl-exPRC(2025)·3 citations
05
Universal bound states and resonances with Coulomb plus short-range potentials
Shunta Mochizuki · Yusuke Nishida
We study charged particles in three dimensions interacting via a short-range potential in addition to the Coulomb potential. When the Bohr radius and the scattering length are much larger than the potential range, low-energy physics of the system becomes independent from details of the short-range potential. We develop the zero-range theory to describe such universal physics in terms of the Bohr radius and the scattering length by generalizing the Bethe-Peierls boundary condition, which is then applied to two charged particles to reveal their bound states and resonances. Infinite resonances are found for a repulsive Coulomb potential, one of which turns into a bound state with increasing inverse scattering length, whereas infinite bound states exist for an attractive Coulomb potential with no resonances at any scattering length. The zero-range theory is also applied to three equally charged particles at infinite scattering length under the variational Born-Oppenheimer approximation. We find that the effective potential between two heavy particles induced by a light particle is an inverse-square attraction at distances shorter than the Bohr radius, leading to infinite deep bound states, whereas shallow ones successively turn into resonances with increasing Coulomb repulsion.
nucl-thcond-mat.mes-hallphysics.atom-phphysics.chem-phPRC(2024)·7 citations
06
Isotropization by shock waves generation in anisotropic hydrodynamics
Aleksandr Kovalenko🇷🇺
Anisotropic hydrodynamics (aHydro) has proven successful in modeling the evolution of quark-gluon matter created in heavy-ion collisions. The hydrodynamic description of quark-gluon plasma has also been widely used to study sound phenomena, such as shock waves. It has recently been shown that initial fluctuations in energy density and supersonic partons can generate fairly strong shock waves. However, significant anisotropic properties of the system due to the rapid longitudinal expansion of matter have not been taken into account in such studies. Moreover, the process of isotropization and its characteristic time-scales were not considered along with the question of the shock waves formation. Previous studies on shock discontinuous solutions in anisotropic hydrodynamics assumed constant anisotropy, leading to flow refraction towards the anisotropy axis and flow acceleration, characteristics of rarefaction waves, indicating limitations in this approach. This paper investigates discontinuous solutions for normal shock waves without flow refraction, introducing two compression parameters for longitudinal and transverse pressures. The resulting analytical solutions, as well as numerical computations, provide an isotropization mechanism of the system.
nucl-thhep-phEPJC(2024)·0 citations
07
The Connection between the Stochastic Schrödinger Equation and Boltzmann Equation
Zichao Li · Xingbo Zhao
The heavy quarks present in the quark-gluon plasma (QGP) can act as a probe of relativistic heavy ion collisions as they retain the memory of their interaction history. In a previous study, a stochastic Schrödinger equation (SSE) has been applied to describe the transport process of heavy quarks, where an external field with random phases is used to simulate the thermal medium. In this work, we study the connection between the SSE and the Boltzmann equation (BE) approach in the Keldysh Green's function formalism. By comparing the Green's function of the heavy quark from the SSE and the Keldysh Green's functions leading to the Boltzmann equation, we demonstrate that the SSE is consistent with the Boltzmann equation in the weak coupling limit. We subsequently confirm their consistency through numerical calculations.
nucl-thhep-phNucl.Phys.Rev.(2025)·0 citations
08
On sensitivity of nucleus deformation on final-state flow harmonics
Henrique Mascalhusk🇨🇳 · Dener S. Lemos🇺🇸 · Otavio Socolowski Jr.🇧🇷 · Wei-Liang Qian🇨🇳 · Sandra S. Padula🇧🇷 · Rui-Hong Yue🇨🇳
In this work, we explore the effect of deformation of the nuclei on collective flow in relativistic heavy-ion collisions. The parameter associated with the geometrical deformation in the Glauber model is tuned to reproduce the empirical multiplicity probability distributions correctly. Subsequently, the particle spectra and collective flows for Au+Au and U+U collisions are evaluated using a hybrid hydrodynamic code CHESS. We analyze the effects of the degrees of freedom associated with the IC on the final-state flow harmonics by exploring the parameter space of the former. The connection between the deformation parameters, specifically $β_{2}$ and $β_{4}$ , and the flow anisotropies is scrutinized. In particular, deviations in elliptic flow at $p_{T} \sim 2$ GeV are observed at smaller values of $β_{2}$ in Au+Au collisions. On the other hand, for U+U collisions, the averaged overall flow harmonics are found to be less sensitive to the geometrical parameters. Despite the difference in the model's specifications, our findings largely confirm those obtained in the literature employing different approaches, which indicate that flow harmonics can be used as a sensible probe for the initial geometry fluctuations and to discriminate between different theoretical models.
nucl-thCPC(2025)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE