Nuclear Theory·nucl-th

Thursday·March 28, 2024

11 papers—4 primary·7 cross-listed

05
Pressure and speed of sound in two-flavor color-superconducting quark matter at next-to-leading order
Andreas Geißel🇩🇪 · Tyler Gorda🇩🇪 · Jens Braun🇩🇪
Deconfined quark matter at asymptotically high densities is weakly coupled, due to the asymptotic freedom of Quantum Chromodynamics. In this weak-coupling regime, bulk thermodynamic properties of quark matter, assuming a trivial ground state, are currently known to partial next-to-next-to-next-to-leading order. However, the ground state at high densities is expected to be a color superconductor, in which the excitation spectrum of (at least some) quarks exhibit a gap with a non-perturbative dependence on the strong coupling. In this work, we calculate the thermodynamic properties of color-superconducting quark matter at high densities and zero temperature at next-to-leading order (NLO) in the coupling in the presence of a finite gap. We work in the limit of two massless quark flavors, which corresponds to deconfined symmetric nuclear matter, and further assume that the gap is small compared to the quark chemical potential. In these limits, we find that the NLO corrections to the pressure and speed of sound are comparable in size to the leading-order effects of the gap, and further increase both quantities above their values for non-superconducting quark matter. We also provide a parameterization of the NLO speed of sound to guide phenomenology in the high-density region, and we furthermore comment on whether our findings should be expected to extend to the case of three-flavor quark matter of relevance to neutron stars.
↳ hep-phnucl-thPRD(2024)·32 citations
06
Parity doublet model for baryon octets: ground states saturated by good diquarks and the role of bad diquarks for excited states
Bikai Gao🇯🇵 · Toru Kojo🇯🇵 · Masayasu Harada🇯🇵
Parity doublet model is an effective chiral model that includes the chiral variant and invariant masses of baryons. The chiral invariant mass has large impacts on the density dependence of models which can be constrained by neutron star observations. In the previous work, models of two-flavors have been considered up to a few times nuclear saturation density, but in such dense region it is also necessary to consider hyperons. With the chiral invariant masses baryons can stay massive in extreme environments (e.g., neutron stars) where the chiral symmetry restoration takes place. In this work, we generalize the previous $\mbox S U (2)_{L} \times \mbox S U (2)_{R}$ parity models of nucleons to $\mbox S U (3)_{L} \times \mbox S U (3)_{R}$ models of the baryon octet, within the linear realization of the chiral symmetry. The major problem in constructing such models has been too many candidates for the chiral representations of baryons. Motivated by the concepts of diquarks and the mended symmetry, we choose the $(3_{L}, 3 ˉ_{R}) + (3 ˉ_{L}, 3_{R})$ , $(3_{L}, 6_{R}) + (6_{L}, 3_{R})$ and $(1_{L}, 8_{R}) + (8_{L}, 1_{R})$ representations and use quark diagrams to constrain the possible types of Yukawa interactions. The masses of the baryon octets for positive and negative baryons up to the first excitations are successfully reproduced. As expected from the diquark considerations, the ground state baryons are well dominated by $(3_{L}, 3 ˉ_{R}) + (3 ˉ_{L}, 3_{R})$ and $(1_{L}, 8_{R}) + (8_{L}, 1_{R})$ representations, while the excited states require $(3_{L}, 6_{R}) + (6_{L}, 3_{R})$ representations. Important applications of our model are the chiral restoration for strange quarks at large density and the continuity of diquarks from hadronic to quark matter. We also address the problem of large Yukawa couplings which are enhanced in three-flavor construction.
↳ hep-phnucl-thPRD(2024)·17 citations
07
A Deep Learning Framework for Disentangling Triangle Singularity and Pole-Based Enhancements
Darwin Alexander O. Co🇵🇭 · Vince Angelo A. Chavez🇵🇭 · Denny Lane B. Sombillo🇵🇭
Enhancements in the invariant mass distribution or scattering cross-section are usually associated with resonances. However, the nature of exotic signals found near hadron-hadron thresholds remain a puzzle today due to the presence of experimental uncertainties. In fact, a purely kinematical triangle diagram is also capable of producing similar structures, but do not correspond to any unstable quantum state. In this paper, we report for the first time, that a deep neural network can be trained to distinguish triangle singularity from pole-based enhancements with a reasonably high accuracy of discrimination between the two seemingly identical line shapes. We also identify the type of triangle enhancement that can be misidentified as a dynamic pole structure. We apply our method to confirm that the $P_{ψ}^{N} (4312)^{+}$ state is not due to a triangle singularity, but is more consistent with a pole-based interpretation, as determined solely through pure line-shape analysis. Lastly, we explain how our method can be used as a model-selection framework useful in studying other exotic hadron candidates.
↳ hep-phhep-exnucl-thPRD(2024)·15 citations
08
Role of hidden-color components in the tetraquark mixing model
Hungchong Kim🇰🇷 · K.S.Kim🇰🇷
Multiquarks can have two-hadron components and hidden-color components in their wave functions. The presence of two-hadron components in multiquarks introduces a potential source of confusion, particularly with respect to their resemblance to hadronic molecules. On the other hand, hidden-color components are essential for distinguishing between multiquarks and hadronic molecules. In this work, we study the hidden-color components in the wave functions of the tetraquark mixing model, a model that has been proposed as a suitable framework for describing the properties of two nonets in the $J^{P} = 0^{+}$ channel: the light nonet [ $a_{0} (980)$ , $K_{0}^{*} (700)$ , $f_{0} (500)$ , $f_{0} (980)$ ] and the heavy nonet [ $a_{0} (1450)$ , $K_{0}^{*} (1430)$ , $f_{0} (1370)$ , $f_{0} (1500)$ ]. Our analysis reveals a substantial presence of hidden-color components within the tetraquark wave functions. To elucidate the impact of hidden-color components on physical quantities, we conduct computations of the hyperfine masses, $⟨ V_{C S} ⟩$ , for the two nonets, considering scenarios involving only the two-meson components and those incorporating the hidden-color components. We demonstrate that the hidden-color components constitute an important part of the hyperfine masses, such that the mass difference formula, $Δ M \approx Δ ⟨ V_{C S} ⟩$ , which has been successful for the two nonets, cannot be achieved without the hidden-color contributions. This can provide another evidence supporting the tetraquark nature of the two nonets.
↳ hep-phhep-exnucl-exnucl-thEPJC(2024)·5 citations
09
The effect of cutoff dependence on heavy quark spin symmetry partners
Duygu Yıldırım🇹🇷
Hadron spectroscopy is revealed by observing heavy resonances. Among various explanations of the internal structure of these hadronic states, hadronic molecules play a unique role. For hadronic molecules, which are associated with meson-meson or meson-baryon interactions, the $Λ$ cutoff is a significant factor in determining the composite states' binding energies and overall properties. The cutoff becomes important when it comes to the location of hadronic molecules' masses because it influences the predictions. From this perspective, in the light of cutoff dependency, heavy quark spin partners of near-threshold the $χ_{c 0} (3915)$ , $χ_{c 1} (3872)$ , $P_{c} (4440)$ , and $P_{c} (4457)$ resonances, which are considered as hadronic molecules, are examined.
↳ hep-phnucl-thMod.Phys.Lett.A(2024)·0 citations
10
Effects of Dark Matter on $f$ -mode oscillations of Neutron Stars
Swarnim Shirke🇮🇳 · Bikram Keshari Pradhan🇮🇳 · Debarati Chatterjee🇮🇳 · Laura Sagunski🇩🇪 · Jürgen Schaffner-Bielich🇩🇪
The effect of dark matter (DM) on $f$ -mode oscillations in DM admixed neutron stars (NSs) is investigated in a comprehensive analysis with particular attention to the role of the nuclear equation of state. Hadronic matter is modeled by the relativistic mean field model and the DM model is based on the neutron decay anomaly. The non-radial $f$ -mode oscillations for such DM admixed NS are studied in a full general relativistic framework. We investigate the impact of DM, DM self-interaction, and DM fraction on the $f$ -mode characteristics. We derive relations encoding the effect of DM on $f$ -mode parameters. We then perform a systematic study by varying all the model parameters within their known uncertainty range and obtain a universal relation for the DM fraction based on the total mass of the star and DM self-interaction strength. We also perform a correlation study among model parameters, NS observables, in particular, $f$ -mode parameters. Finally, we check the $f$ -mode universal relations (URs) for the case of DM admixed NSs and demonstrate the existence of a degeneracy between purely hadronic NSs and DM admixed NSs.
↳ gr-qcastro-ph.HEhep-phnucl-thPRD(2024)·37 citations
11
Measuring the Lense-Thirring Orbital Precession and the Neutron Star Moment of Inertia with Pulsars
Huanchen Hu · Paulo C. C. Freire
Neutron stars (NSs) are compact objects that host the densest forms of matter in the observable universe, providing unique opportunities to study the behaviour of matter at extreme densities. While precision measurements of NS masses through pulsar timing have imposed effective constraints on the equation of state (EoS) of dense matter, accurately determining the radius or moment of inertia (MoI) of a NS remains a major challenge. This article presents a detailed review on measuring the Lense-Thirring (LT) precession effect in the orbit of binary pulsars, which would give access to the MoI of NSs and offer further constraints on the EoS. We discuss the suitability of certain classes of binary pulsars for measuring the LT precession from the perspective of binary star evolution, and highlight five pulsars that exhibit properties promising to realise these goals in the near future. Finally, discoveries of compact binaries with shorter orbital periods hold the potential to greatly enhance measurements of the MoI of NSs. The MoI measurements of binary pulsars are pivotal to advancing our understanding of matter at supranuclear densities as well as improving the precision of gravity tests, such as the orbital decay due to gravitational wave emission and of tests of alternative gravity theories.
↳ gr-qcastro-ph.HEnucl-thUniverse(2024)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE

Pressure and speed of sound in two-flavor color-superconducting quark matter at next-to-leading order

Parity doublet model for baryon octets: ground states saturated by good diquarks and the role of bad diquarks for excited states

A Deep Learning Framework for Disentangling Triangle Singularity and Pole-Based Enhancements

Role of hidden-color components in the tetraquark mixing model

The effect of cutoff dependence on heavy quark spin symmetry partners

Effects of Dark Matter on f-mode oscillations of Neutron Stars

Measuring the Lense-Thirring Orbital Precession and the Neutron Star Moment of Inertia with Pulsars

Affiliations

Effects of Dark Matter on $f$ -mode oscillations of Neutron Stars