Nuclear Theory·nucl-th

Thursday·January 11, 2024

9 papers—3 primary·6 cross-listed

04
Understanding the nature of baryon resonances
Derek B. Leinweber🇦🇺 · Curtis D. Abell🇦🇺 · Liam C. Hockley🇦🇺 · Waseem Kamleh🇦🇺 · Zhan-Wei Liu🇨🇳 · Finn M. Stokes🇦🇺 · Anthony W. Thomas🇦🇺 · Jia-Jun Wu🇨🇳
This presentation opens with a brief review of lattice QCD calculations showing the $2 s$ radial excitation of the nucleon sits at approximately 2 GeV, well above the Roper resonance position. We then proceed to reconcile this observation with experimental scattering data. While the idea of dressing quark-model states in a coupled-channel analysis to describe scattering data has been around for decades, it's now possible to bring these descriptions to the finite-volume of lattice QCD for confrontation with lattice-QCD calculations. This combination of lattice QCD and experiment demands that we reconsider our preconceived notions about the quark-model and its excitation spectrum. We close with a discussion of an unanticipated resolution to the missing baryon resonances problem.
↳ hep-lathep-phnucl-thNuovo Cim.C(2024)·12 citations
05
Toward an estimate of the amplitude $X (3872) \to π^{0} χ_{c 1} (1 P)$
N. N. Achasov🇷🇺 · G. N. Shestakov🇷🇺
The well-known model of the triangle diagrams with $D^{*} D ˉ D^{*}$ and $D ˉ^{*} D D ˉ^{*}$ mesons in the loops is compared with the modern data on the amplitude of the $X (3872) \to π^{0} χ_{c 1} (1 P)$ decay. Considering the $X (3872)$ object as a $χ_{c 1} (2 P)$ charmonium state, we introduce a parameter $ξ$ characterizing the scale of the isotopic symmetry violation in this decay and find a lower limit of $ξ ≃ 0.0916$ . The model incorporates the only fitted parameter associated with the form factor. We analyze in detail the influence of the form factor on the amplitude $X (3872) \to π^{0} χ_{c 1} (1 P)$ and on the parameter $ξ$ . As the suppression of the amplitude by the form factor increases, $ξ$ increases. Due to the fact that the $X (3872)$ resonance is located practically at the threshold of the $D^{0} D ˉ^{* 0}$ channel, the amplitude of $X (3872) \to π^{0} χ_{c 1} (1 P)$ turns out to be proportional to $m_{d} - m_{u}$ . Using the estimating values for the coupling constants $g_{X D D ˉ^{*}}$ , $g_{χ_{c 1} D D ˉ^{*}}$ , and $g_{D^{* 0} D^{* 0} π^{0}}$ , we show that the model of the triangle loop diagrams is in reasonable agreement with the available data. Apart from the difference in the masses of neutral and charged charmed mesons, any additional exotic sources of isospin violation in $X (3872) \to π^{0} χ_{c 1} (1 P)$ (such as a significant difference between the coupling constants $g_{X D^{0} D ˉ^{* 0}}$ and $g_{X D^{+} D^{*-}}$ ) are not required to interpret the data. This indirectly confirms the isotopic neutrality of the $X (3872)$ , which is naturally realized for the $c c ˉ$ state $χ_{c 1} (2 P)$ .
↳ hep-phhep-exnucl-thPRD(2024)·10 citations
06
Lee-Yang edge singularities in QCD via the Dyson-Schwinger Equations
Zi-Yan Wan🇨🇳 · Yi Lu🇨🇳 · Fei Gao🇨🇳 · Yu-Xin Liu🇨🇳
We take the Dyson-Schwinger Equation approach of QCD for the quark propagator at complex chemical potential to study the QCD phase transition. The phase transition line of the $(2 + 1)$ -flavor QCD matter in the imaginary chemical potential region is computed via a simplified truncation scheme, whose curvature is found to be consistent with the one at real chemical potential. Moreover, the computation in the complex chemical potential plane allows us to determine the location of the Lee-Yang edge singularities. We show explicitly that the critical end point coincides with the Lee-Yang edge singularities on the real $μ_{B}$ axis. We also investigate the scaling behavior of the singularities and discuss the possibility of extrapolating the CEP from a certain range of chemical potential.
↳ hep-phhep-thnucl-thEPJC(2024)·10 citations
07
Importance of strange sea to the charge radii and quadrupole moment of $J^{P} = \frac{1}{2}^{+}, \frac{3}{2}^{+}$ baryons
Preeti Bhall🇮🇳 · A. Upadhyay🇮🇳
A statistical framework in conjugation with the principle of detailed balance is employed to examine the low-energy properties i.e. charge radii and quadrupole moment of J $^{P}$ = $\frac{1}{2}^{+}$ octet and J $^{P}$ = $\frac{3}{2}^{+}$ decuplet baryon. The statistical approach assumes the expansion of baryonic system in terms of quark-gluon Fock states. We systematically apply operator formalism along with the statistical approach to study the charge radii and quadrupole moment of baryons. Based on the probabilities of all possible Fock states in spin, flavor and color space, the importance of sea with quarks and gluons is studied. The individual contribution of the constituent quarks and sea which contains terms of scalar, vector and tensor is explored. Due to large mass difference between strange and non-strange content, the SU(3) breaking effect are also investigated. The extent to which strange quark-antiquark pair is considered in sea is constrained by the mass of hadrons, the free energy of gluons in conformity with experimental indications. We focus on the individual contribution of strange and non-strange sea (g, $⟨ u u ˉ ⟩$ , $⟨ d d ˉ ⟩$ and $⟨ s s ˉ ⟩$ ) accomodability in the respective hadrons for their charge radii and quadrupole moment. The present work has been compared with various theoretical approaches and some known experimental observations. Our computed results may provide important information for upcoming experimental findings.
↳ hep-phnucl-thPTEP(2024)·3 citations
08
State-Specific Coupled-Cluster Methods for Excited States
Yann Damour · Anthony Scemama · Denis Jacquemin · Fábris Kossoski · Pierre-François Loos
We reexamine $Δ$ CCSD, a state-specific coupled-cluster (CC) with single and double excitations (CCSD) approach that targets excited states through the utilization of non-Aufbau determinants. This methodology is particularly efficient when dealing with doubly excited states, a domain where the standard equation-of-motion CCSD (EOM-CCSD) formalism falls short. Our goal here is to evaluate the effectiveness of $Δ$ CCSD when applied to other types of excited states, comparing its consistency and accuracy with EOM-CCSD. To this end, we report a benchmark on excitation energies computed with the $Δ$ CCSD and EOM-CCSD methods, for a set of molecular excited-state energies that encompasses not only doubly excited states but also doublet-doublet transitions and (singlet and triplet) singly-excited states of closed-shell systems. In the latter case, we rely on a minimalist version of multireference CC known as the two-determinant CCSD method to compute the excited states. Our dataset, consisting of 276 excited states stemming from the \textsc{quest} database [Véril \textit{et al.}, \textit{WIREs Comput. Mol. Sci.} \textbf{2021}, 11, e1517], provides a significant base to draw general conclusions concerning the accuracy of $Δ$ CCSD. Except for the doubly-excited states, we found that $Δ$ CCSD underperforms EOM-CCSD. For doublet-doublet transitions, the difference between the mean absolute errors (MAEs) of the two methodologies (of \SI{0.10}{\eV} and \SI{0.07}{\eV}) is less pronounced than that obtained for singly-excited states of closed-shell systems (MAEs of \SI{0.15}{\eV} and \SI{0.08}{\eV}). This discrepancy is largely attributed to a greater number of excited states in the latter set exhibiting multiconfigurational characters, which are more challenging for $Δ$ CCSD.
↳ physics.chem-phcond-mat.mtrl-scinucl-thJ.Chem.Theor.Comput.(2024)·5 citations
09
Exploring the QCD phase diagram with three flavors of Möbius domain wall fermions
Yu Zhang🇯🇵 · Yasumichi Aoki🇯🇵 · Shoji Hashimoto🇯🇵 · Issaku Kanamori · Takashi Kaneko🇯🇵 · Yoshifumi Nakamura🇯🇵
We present an update on the study of the QCD phase transition with 3 flavors of Möbius domain wall fermions at zero baryon density. We performed simulations on lattices of size $3 6^{3} \times 12 \times 16$ and $2 4^{3} \times 12 \times 32$ with a variety of quark masses at a fixed lattice spacing $a = 0.1361 (20)$ fm, which correspond to a temperature 121(2) MeV. By analyzing the chiral condensate, chiral susceptibilitities and Binder cumulant on $3 6^{3} \times 12 \times 16$ lattices together with the result obtained from our previous study on $2 4^{3} \times 12 \times 16$ lattices, we identified a crossover occurring at quark mass around $m_{q}^{MS} (2 GeV) \sim 3 - 4$ MeV for this temperature. Besides, we show the effects of residual chiral symmetry breaking on chiral condensate and chiral susceptibilities between $L_{s} = 16$ and 32.
↳ hep-lathep-phhep-thnucl-thPoS(2024)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE

Understanding the nature of baryon resonances

Toward an estimate of the amplitude X(3872)→π0χc1​(1P)

Lee-Yang edge singularities in QCD via the Dyson-Schwinger Equations

Importance of strange sea to the charge radii and quadrupole moment of JP=21​+,23​+ baryons

State-Specific Coupled-Cluster Methods for Excited States

Exploring the QCD phase diagram with three flavors of Möbius domain wall fermions

Affiliations

Toward an estimate of the amplitude $X (3872) \to π^{0} χ_{c 1} (1 P)$

Importance of strange sea to the charge radii and quadrupole moment of $J^{P} = \frac{1}{2}^{+}, \frac{3}{2}^{+}$ baryons