Nuclear Theory·nucl-th

Thursday·February 16, 2023

17 papers—10 primary·7 cross-listed

11
Generalized parton distributions through universal moment parameterization: non-zero skewness case
Yuxun Guo🇺🇸 · Xiangdong Ji🇺🇸 · M. Gabriel Santiago🇺🇸 · Kyle Shiells🇨🇦 · Jinghong Yang🇺🇸
We present the first global analysis of generalized parton distributions (GPDs) combing lattice quantum chromodynamics (QCD) calculations and experiment measurements including global parton distribution functions (PDFs), form factors (FFs) and deeply virtual Compton scattering (DVCS) measurements. Following the previous work where we parameterize GPDs in terms of their moments, we extend the framework to allow for the global analysis at non-zero skewness. Together with the constraints at zero skewness, we fit GPDs to global DVCS measurements from both the recent JLab and the earlier Hadron-Electron Ring Accelerator (HERA) experiments with two active quark flavors and leading order QCD evolution. With certain choices of empirical constraints, both sea and valence quark distributions are extracted with the combined inputs, and we present the quark distributions in the proton correspondingly. We also discuss how to extend the framework to accommodate more off-forward constraints beyond the small $ξ$ expansion, especially the lattice calculated GPDs.
↳ hep-phnucl-thJHEP(2023)·61 citations
12
Empirical Determination of the Pion Mass Distribution
Yin-Zhen Xu🇪🇸 · Khépani Raya🇪🇸 · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇨🇳 · J. Rodríguez-Quintero🇪🇸
Existing pion+nucleus Drell-Yan and electron+pion scattering data are used to develop ensembles of model-independent representations of the pion generalised parton distribution (GPD). Therewith, one arrives at a data-driven prediction for the pion mass distribution form factor, $θ_{2}$ . Compared with the pion elastic electromagnetic form factor, $θ_{2}$ is harder: the ratio of the radii derived from these two form factors is $r_{π}^{θ_{2}} / r_{π} = 0.79 (3)$ . Our data-driven predictions for the pion GPD, related form factors and distributions should serve as valuable constraints on theories of pion structure.
↳ hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2023)·24 citations
13
Prospects for ditauonium discovery at colliders
David d'Enterria🇨🇭 · Hua-Sheng Shao🇫🇷
The feasibility of observing ditauonium, the bound state of two tau leptons, at $e^{+} e^{-}$ colliders (BES III at $s = 3.78$ GeV, Belle II at $s = 10.6$ GeV, a future super tau-charm factory (STCF) at $s \approx 2 m_{τ}$ , and the FCC-ee at $s = 91.2$ GeV) as well as in hadronic and photon-photon collisions at the LHC, is studied. Cross sections and expected yields for spin-0 para- ( $T_{0}$ ) and spin-1 ortho- ( $T_{1}$ ) ditauonium are presented for nine different production and decay processes. Para-ditauonium can be observed at the FCC-ee via photon fusion in its diphoton decay ( $γ γ \to T_{0} \to γ γ$ ). Ortho-ditauonium can be observed at STCF via $e^{+} e^{-} \to T_{1} \to μ^{+} μ^{-}$ , where a threshold scan with monochromatized beams can also provide a very precise extraction of the tau lepton mass with a $O (25$ keV) uncertainty or less. Observing pp $\to T_{1} (μ^{+} μ^{-}) + X$ at the LHC is possible by identifying its displaced vertex with a good control of the combinatorial dimuon background. In addition, we compute the rare decay branching fractions of ditauonium into quarkonium plus a photon.
↳ hep-phhep-exnucl-exnucl-thPLB(2023)·32 citations
14
First Evidence of Axial Shape Asymmetry and Configuration Coexistence in $^{74}$ Zn: Suggestion for a Northern Extension of the $N = 40$ Island of Inversion
M. Rocchini🇨🇦 · P. E. Garrett🇨🇦 · M. Zielinska🇫🇷 · S. M. Lenzi🇮🇹 · D. D. Dao🇫🇷 · F. Nowacki🇫🇷 · V. Bildstein🇨🇦 · A. D. MacLean🇨🇦 · B. Olaizola🇨🇦 · Z. T. Ahmed🇨🇦 · C. Andreoiu🇨🇦 · A. Babu🇨🇦 and 32 other authors
The excited states of $N = 44$ $^{74}$ Zn were investigated via $γ$ -ray spectroscopy following $^{74}$ Cu $β$ decay. By exploiting $γ$ - $γ$ angular correlation analysis, the $2_{2}^{+}$ , $3_{1}^{+}$ , $0_{2}^{+}$ and $2_{3}^{+}$ states in $^{74}$ Zn were firmly established. The $γ$ -ray branching and $E 2/ M 1$ mixing ratios for transitions de-exciting the $2_{2}^{+}$ , $3_{1}^{+}$ and $2_{3}^{+}$ states were measured, allowing for the extraction of relative $B (E 2)$ values. In particular, the $2_{3}^{+} \to 0_{2}^{+}$ and $2_{3}^{+} \to 4_{1}^{+}$ transitions were observed for the first time. The results show excellent agreement with new microscopic large-scale shell-model calculations, and are discussed in terms of underlying shapes, as well as the role of neutron excitations across the $N = 40$ gap. Enhanced axial shape asymmetry (triaxiality) is suggested to characterize $^{74}$ Zn in its ground state. Furthermore, an excited $K = 0$ band with a significantly larger softness in its shape is identified. A shore of the $N = 40$ ``island of inversion'' appears to manifest above $Z = 26$ , previously thought as its northern limit in the chart of the nuclides.
↳ nucl-exnucl-thPRL(2023)·17 citations
15
Parton Decomposition of Nucleon Spin and Momentum: Gluons from Dressed Quarks
Peter C. Tandy🇺🇸
The lowest two Mellin moments of hadronic Generalized Parton Distributions are explored within a model that allows investigation of the inter-related quark and gluon contributions. For light quarks their dynamical connection is strong due to quark dressing. Our principal focus is the angular momentum $J$ of the nucleon. This work employs and extends dynamical insights obtained from our recent model results for quark and gluon momentum fractions $⟨ x ⟩_{q/g}$ in both pion and nucleon. The employed model is based on the Rainbow-Ladder truncation of the Dyson-Schwinger equations of QCD. The special case of a 1-loop treatment of a single hadronic quark is used to motivate several insights and obtain initial estimates such as the Wilson line correction to the established Landau gauge model ( $- 7%$ for both $J_{q}$ and $⟨ x ⟩_{q}$ ), and the "binding gluon" contribution to $⟨ x ⟩_{g}$ ( $\leq 10%$ ). We obtain the proton $J$ within 1\% after inclusion of the pion cloud mechanism to produce the sea. The gluon second Mellin moments of the proton reflect similar dynamics; ( $⟨ x ⟩_{g}$ , $J_{g}$ ) are (26\% , 24\%) at model scale, and (40\%, 38\%) at $2$ GeV. We also find that $J_{tot}$ is shared almost equally between the total orbital and total intrinsic spin contributions.
↳ hep-phhep-latnucl-exnucl-thPLB(2023)·5 citations
16
Electric dipole polarizability of $^{40}$ Ca
R. W. Fearick (1) · P. von Neumann-Cosel (2) · S. Bacca (3,4) · J. Birkhan (2) · F. Bonaiti (3) · I. Brandherm (2) · G. Hagen (5,6) · H. Matsubara (7,8) · W. Nazarewicz (9) · N. Pietralla (2) · V. Yu. Ponomarev (2) · P. -G. Reinhard (10) and 5 other authors
The electric dipole strength distribution in $^{40}$ Ca between 5 and 25 MeV has been determined at RCNP, Osaka, from proton inelastic scattering experiments at very forward angles. Combined with total photoabsorption data at higher excitation energy, this enables an extraction of the electric dipole polarizability $α_{D}$ ( $^{40}$ Ca) = 1.92(17) fm $^{3}$ . Together with the measured $α_{D}$ in $^{48}$ Ca, it provides a stringent test of modern theoretical approaches, including coupled cluster calculations with chiral effective field theory interactions and state-of-the art energy density functionals. The emerging picture is that for this medium-mass region dipole polarizabilities are well described theoretically, with important constraints for the neutron skin in $^{48}$ Ca and related equation of state quantities.
↳ nucl-exnucl-thPRResearch(2023)·26 citations
17
Impact of vorticity and viscosity on the hydrodynamic evolution of hot QCD medium
Bhagyarathi Sahoo🇮🇳 · Captain R. Singh🇮🇳 · Dushmanta Sahu🇮🇳 · Raghunath Sahoo🇮🇳 · Jan-e Alam🇮🇳
The strongly interacting transient state of quark-gluon plasma (QGP) medium created in ultra-relativistic collisions survives for a duration of a few fm/c. The spacetime evolution of QGP crucially depends on the equation of state (EoS), vorticity, viscosity, and external magnetic field. In the present study, we obtain the lifetime of a vortical QGP fluid within the ambit of relativistic second-order viscous hydrodynamics. We observe that the coupling of vorticity and viscosity significantly increases the lifetime of vortical QGP. The inclusion of a static magnetic field, vorticity, and viscosity makes the evolution slower. However, the static magnetic field slightly decreases the QGP lifetime by accelerating the evolution process for a non-rotating medium. We also report the rate of change of vorticity in the QGP, which will be helpful in studying the behavior of the medium in detail.
↳ hep-phhep-exnucl-exnucl-thEPJC(2023)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE

Generalized parton distributions through universal moment parameterization: non-zero skewness case

Empirical Determination of the Pion Mass Distribution

Prospects for ditauonium discovery at colliders

First Evidence of Axial Shape Asymmetry and Configuration Coexistence in 74Zn: Suggestion for a Northern Extension of the N=40 Island of Inversion

Parton Decomposition of Nucleon Spin and Momentum: Gluons from Dressed Quarks

Electric dipole polarizability of 40Ca

Impact of vorticity and viscosity on the hydrodynamic evolution of hot QCD medium

Affiliations

First Evidence of Axial Shape Asymmetry and Configuration Coexistence in $^{74}$ Zn: Suggestion for a Northern Extension of the $N = 40$ Island of Inversion

Electric dipole polarizability of $^{40}$ Ca