Nuclear Theory·nucl-th

Tuesday·February 6, 2024

16 papers—6 primary·10 cross-listed

01
[Submitted on 3 Feb 2024]
Ab initio description of monopole resonances in light- and medium-mass nuclei: I. Technical aspects and uncertainties of ab initio PGCM calculations
Andrea Porro🇩🇪 · Thomas Duguet🇫🇷 · Jean-Paul Ebran🇫🇷 · Mikael Frosini🇫🇷 · Robert Roth🇩🇪 · Vittorio Somá🇫🇷
Giant resonances (GRs) are a striking manifestation of collective motions in mesoscopic systems such as atomic nuclei. Until recently, theoretical investigations have essentially relied on the (quasiparticle) random phase approximation ((Q)RPA), and extensions of it, based on phenomenological energy density functionals (EDFs). As part of a current effort to describe GRs within an ab initio theoretical scheme, the present work promotes the use of the projected generator coordinate method (PGCM). This method, which can handle anharmonic effects while satisfying symmetries of the nuclear Hamiltonian, displays a favorable (i.e. mean-field-like) scaling with system's size. Presently focusing on the isoscalar giant monopole resonance (GMR) of light- and medium-mass nuclei, PGCM's potential to deliver wide-range ab initio studies of GRs in closed- and open-shell nuclei encompassing pairing, deformation, and shape coexistence effects is demonstrated. The comparison with consistent QRPA calculations highlights PGCM's unique attributes and sheds light on the intricate interplay of nuclear collective excitations. The present paper is the first in a series of four and focuses on technical aspects and uncertainty quantification of ab initio PGCM calculations of GMR using the doubly open-shell $^{46}$ Ti as an illustrative example. The second paper displays results for a set of nuclei of physical interest and proceeds to the comparison with consistent (deformed) ab initio QRPA calculations. While the third paper analyzes useful moments of the monopolar strength function and different ways to access them within PGCM calculations, the fourth paper focuses on the effect of the symmetry restoration on the monopole strength function.
Comments:
23 pages, 26 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2402.02228 [pdf]
EPJA(2024)·17 citations
02
[Submitted on 4 Feb 2024]
System size and shape dependences of collective flow fluctuations in relativistic nuclear collisions
Xinrong Chen🇨🇳 · Xiang-Yu Wu🇨🇦 · Shanshan Cao🇨🇳 · Guang-You Qin🇨🇳
Quantum fluctuations plays an essential role in forming the collective flow of hadrons observed in relativistic heavy-ion collisions. Event-by-event fluctuations of the collective flow can arise from various sources, such as the fluctuations in the initial geometry, hydrodynamic expansion, hadronization, and hadronic evolution of the nuclear matter, while the exact contribution from each source is still an open question. Using a (3+1)-dimensional relativistic hydrodynamic model coupled to a Monte-Carlo Glauber initial condition, Cooper-Frye particlization and a hadronic transport model, we explore the system size and shape dependences of the collective flow fluctuations in Au+Au, Cu+Au, and O+O collisions at $s_{NN} = 200$ ~GeV. The particle yields, mean transverse momenta, 2-particle and 4-particle cumulant elliptic flows ( $v_{2} {2}$ and $v_{2} {4}$ ) from our calculation agree with the currently existing data from RHIC. Different centrality dependences of the flow fluctuations, quantified by the $v_{2} {4} / v_{2} {2}$ ratio, are found for different collision systems due to their different sizes and shapes. By comparing $v_{2} {4} / v_{2} {2}$ between different hadron species, and comparing $v_{2} {4} / v_{2} {2}$ to the initial state geometric fluctuations quantified by the cumulant eccentricity ratio $ε_{2} {4} / ε_{2} {2}$ , we find that while the initial state fluctuations are the main source of the $v_{2}$ fluctuations in large collision systems, other sources like nonlinear hydrodynamic response, hadronization, and hadronic afterburner can significantly affect the $v_{2}$ fluctuations in small systems.
Comments:
12 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2402.02348 [pdf]
PRC(2024)·4 citations
03
[Submitted on 5 Feb 2024]
Tunable-fidelity wave functions for the \textit{ab initio} description of scattering and reactions
Konstantinos Kravvaris · Sofia Quaglioni · Petr Navratil
The no-core shell model (NCSM) is an \textit{ab initio} method that solves the nuclear many-body problem by expanding the many-particle wave function into a (typically) harmonic oscillator basis and minimizing the energy to obtain the expansion coefficients. Extensions of the NCSM, such as its coupling with microscopic-cluster basis states, further allow for an \textit{ab initio} treatment of light-ion nuclear reactions of interest for both astrophysics and nuclear technology applications. A downside of the method is the exponential scaling of the basis size with increasing number of nucleons and excitation quanta, which limits its applicability to mass $A ≲ 16$ nuclei, except for variants where the basis is further down-selected via some truncation scheme. We consider a basis selection method for the NCSM that captures the essential degrees of freedom of the nuclear wave function leading to a favorable complexity scaling for calculations and enabling \textit{ab initio} reaction calculations in $s d$ -shell nuclei. The particle configurations within the NCSM basis are ordered based on their contribution to the first moment of the Hamiltonian matrix that results from the projection onto the many-body basis. The truncation scheme then consists in retaining only the lowest-first-moment configurations, which typically contain only few many-body basis states (Slater determinants). We present calculations for $^{7}$ Li and $n +^{12}$ C scattering using nucleon-nucleon interactions derived from chiral effective field theory and softened using the similarity renormalization group method. The obtained energy levels invariably demonstrate exponential convergence with the size of the basis, and we find improved convergence in scattering calculations. To demonstrate the possibilities enabled by the approach, we also present a first calculation for the scattering of neutrons from $^{24}$ Mg.
Comments:
13 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2402.02677 [pdf]
PRC(2024)·5 citations
04
[Submitted on 5 Feb 2024]
Nuclear mass table in deformed relativistic Hartree-Bogoliubov theory in continuum, II: Even- $Z$ nuclei
DRHBc Mass Table Collaboration: Peng Guo · Xiaojie Cao · Kangmin Chen · Zhihui Chen · Myung-Ki Cheoun · Yong-Beom Choi · Pak Chung Lam · Wenmin Deng · Jianmin Dong · Pengxiang Du · Xiaokai Du · Kangda Duan and 70 other authors
The mass table in the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) with the PC-PK1 density functional has been established for even- $Z$ nuclei with $8 \leq Z \leq 120$ , extended from the previous work for even-even nuclei [Zhang $et. al.$ (DRHBc Mass Table Collaboration), At. Data Nucl. Data Tables 144, 101488 (2022)]. The calculated binding energies, two-nucleon and one-neutron separation energies, root-mean-square (rms) radii of neutron, proton, matter, and charge distributions, quadrupole deformations, and neutron and proton Fermi surfaces are tabulated and compared with available experimental data. A total of 4829 even- $Z$ nuclei are predicted to be bound, with an rms deviation of 1.477 MeV from the 1244 mass data. Good agreement with the available experimental odd-even mass differences, $α$ decay energies, and charge radii is also achieved. The description accuracy for nuclear masses and nucleon separation energies as well as the prediction for drip lines is compared with the results obtained from other relativistic and nonrelativistic density functional. The comparison shows that the DRHBc theory with PC-PK1 provides an excellent microscopic description for the masses of even- $Z$ nuclei. The systematics of the nucleon separation energies, odd-even mass differences, pairing energies, two-nucleon gaps, $α$ decay energies, rms radii, quadrupole deformations, potential energy curves, neutron density distributions, and neutron mean-field potentials are discussed.
Comments:
394 pages, 17 figures, 2 tables, published in Atomic Data and Nuclear Data Tables, data file in the TXT form is available for download under "Ancillary files"
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
2402.02935 [pdf]
Atom.Data Nucl.Data Tabl.(2024)·94 citations
05
[Submitted on 5 Feb 2024]
The footprint of nuclear saturation properties on the neutron star $f$ mode oscillation frequencies: a machine learning approach
Deepak Kumar🇮🇳 · Tuhin Malik🇵🇹 · Hiranmaya Mishra🇮🇳
We investigate the intricate relationships between the non-radial $f$ mode oscillation frequencies of neutron stars (NS)s and the corresponding nuclear matter equation of state (EOS) using a machine learning (ML) approach within the ambit of the relativistic mean field (RMF) framework for nuclear matter. With two distinct parameterizations of the Walecka model, namely, (1) with non-linear self interactions of the scalar field (NL) and, (2) a density dependent Bayesian model (DDB), we perform a thorough examination of the $f$ mode frequency in relation to various nuclear saturation properties. The correlations between the $f$ mode frequencies and nuclear saturation properties reveal, through various analytical and ML methods, the complex nature of NSs and their potential as the cosmic laboratory for studying extreme states of matter. A principal component analysis (PCA) has been performed using mixed datasets from DDB and NL models to discriminate the relative importance of the different components of the EOS on the $f$ mode frequencies. Additionally, a {\it Random forest feature importance} analysis also elucidates the distinct roles of these properties in determining the $f$ mode frequency across a spectrum of NS masses. Our findings are further supported by symbolic regression searches, yielding high-accuracy relations with strong Pearson coefficients and minimal errors. These relations suggest new methodologies for probing NS core characteristics, such as energy density, pressure, and speed of sound from observations of non-radial $f$ mode oscillations of NSs.
Comments:
23 pages, 15 figures (accepted in JCAP)
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2402.03054 [pdf]
JCAP(2025)·3 citations
06
[Submitted on 5 Feb 2024]
Intertwined quantum phase transitions in the zirconium and niobium isotopes
N. Gavrielov🇫🇷
Nuclei in the $A \approx 100$ region exhibit intricate shape-evolution and configuration crossing signatures. Exploring both even-even and their adjacent odd-mass nuclei gives further insight on the emergence of deformation and shape-phase transitions. We employ the algebraic frameworks of the interacting boson model with configuration mixing and the new interacting boson-fermion model with configuration mixing in order to investigate the even-even zirconium with neutron number 52-70 ( $^{40}$ Zr) and odd-mass niobium ( $_{41}$ Nb) isotopes with 52-62. We compare between the evolution in energy levels, configuration and symmetry content of the wave functions, two neutron separation energies and $E 2$ transition rates. The comparisons between the two chains of isotopes denote the occurrence of intertwined quantum phase transitions (IQPTs) in both chains. Such a situation occurs when two configurations, normal and intruder, cross through the critical point of a Type II quantum phase transition (QPT), and the intruder configuration undergoes on its own a Type I shape-evolution QPT from a spherical shape (weak coupling scenario) to axially deformed rotor (strong coupling scenario) in the Zr (Nb) isotopes.
Comments:
13 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2402.03200 [pdf]
Phys.Scripta(2024)·3 citations
07
[Submitted on 2 Feb 2024] (cross-list from hep-ph)
Baryon Spin and Emergent Hadron Mass
Peng Cheng🇨🇳
This thesis describes the use of Dyson-Schwinger equations (DSEs) to study baryon bound states in QCD. In this work, octet baryon axial form factors are calculated using a symmetry-preserving treatment of a vector $\times$ vector contact interaction (SCI). The baryons are considered as quark-plus-interacting-diquark bound states, whose structure (wave function) is obtained by solving a Poincaré-covariant Faddeev equation. Since it preserves symmetries, all consequences of partial conservation of the axial current are manifest. For instance, one finds that octet baryon axial properties are consistent with only minor violations of SU(3)-flavour symmetry, being interpreted as a dynamical consequence of emergent hadron mass (EHM). Considering neutral axial currents, the SCI delivers predictions for the flavour separation of octet baryon axial charges and, consequently, produces values for the associated SU(3) singlet, triplet, and octet axial charges. The results indicate that, at the hadron scale $ζ_{H}$ , valence degrees of freedom carry approximately $50%$ of an octet baryon's total spin. Proton structure is one of the principal topics in hadron physics. Its study is expected to reveal key features of both the origin of mass and strong interaction dynamics. This work therefore extended the above analyses to an examination of in-proton parton helicity (spin) distribution functions (DFs). Using Ansätze for hadron-scale proton polarised valence quark DFs, predictions are delivered for all proton polarised DFs at the measurement scale $ζ_{C}^{2} = 3$ GeV $^{2}$ . The pointwise behaviour of the predicted DFs and, consequently, their moments, shows good agreement with results inferred from data. Based on these results, one finds that experimental measurements of the proton flavour-singlet axial charge should return a value $a_{0}^{E} (ζ_{C}) = 0.35 (2)$ .
Comments:
146 pages, 18 figures, PhD Thesis
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2402.01814 [pdf]
0 citations
08
[Submitted on 2 Feb 2024] (cross-list from hep-ph)
Transverse momentum moments
Oscar del Rio🇪🇸 · Alexei Prokudin🇺🇸 · Ignazio Scimemi🇪🇸 · Alexey Vladimirov🇪🇸
We establish robust relations between Transverse Momentum Dependent distributions (TMDs) and collinear distributions. We define weighted integrals of TMDs that we call Transverse Momentum Moments (TMMs) and prove that TMMs are equal to collinear distributions evaluated in some minimal subtraction scheme. The conversion to the modified minimal subtraction ( $M S ˉ$ ) scheme, can be done by a calculable factor, which we derive up to three loops for some cases. We discuss in detail the zeroth, the first, and the second TMMs and provide phenomenological results for them based on the current extractions of TMDs. The results of this paper open new avenues for theoretical and phenomenological investigation of the three-dimensional and collinear hadron structures.
Comments:
This version matches the published version in Phys.Rev.D 110 (2024) 1, 016003 on July 1, 2024
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2402.01836 [pdf]
PRD(2024)·29 citations
09
[Submitted on 2 Feb 2024] (cross-list from gr-qc)
Primordial black hole capture, gravitational wave beats, and the nuclear equation of state
Thomas W. Baumgarte · Stuart L. Shapiro
Primordial black holes (PBHs), if captured by neutron stars (NSs), would emit a characteristic gravitational wave (GW) signal as they orbit inside the host star. We identify a specific and qualitatively new feature of these signals, namely quasi-periodic beats caused by the precession of noncircular PBH orbits. We demonstrate numerically and analytically that the beat frequency depends rather sensitively on the NS structure, so that hypothetical future observations with next-generation GW detectors would provide valuable constraints on the nuclear equation of state.
Comments:
13 pages (including 6 pages of supplemental material), 1 figure
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2402.01838 [pdf]
PRD(2024)·11 citations
10
[Submitted on 3 Feb 2024] (cross-list from hep-ph)
The relativistic three-body scattering and the $D^{0} D^{*+} - D^{+} D^{* 0}$ system
Xu Zhang🇨🇳
Scattering amplitudes involving three-particle scattering processes are investigated within the isobar approximation which respects constraints from two- and three-body unitarity. The particular system considered is the $D^{0} D^{*+} - D^{+} D^{* 0}$ , where the $D^{*+}$ $(D^{* 0})$ enters as a $p$ -wave $D^{+} π^{0}$ or $D^{0} π^{+}$ ( $D^{0} π^{0}$ or $D^{+} π^{-}$ ) resonance. The interaction potentials in the coupled-channel $D^{0} D^{*+} - D^{+} D^{* 0}$ system contain the $σ$ , $ρ$ , $ω$ and $π$ -exchange. The analytic continuation of the amplitudes across the three-body unitary cuts is investigated to search for poles on the unphysical Riemann sheets. Associated with an unstable particle $D^{*+}$ $(D^{* 0})$ is a complex two-body unitarity cut, through which one can further analytically continue into another unphysical Riemann sheet. Dynamical singularities emerged from the $π$ -exchange potential are stressed. The pole generated from the $D^{0} D^{*+} - D^{+} D^{* 0}$ interaction and its line shape in $D^{0} D^{0} π^{+}$ break-up production are in agreement with double-charmed tetraquark $T_{cc}^{+}$ observed by the LHCb Collaboration.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2402.02151 [pdf]
PRD(2024)·21 citations
11
[Submitted on 3 Feb 2024] (cross-list from cond-mat.quant-gas)
Three-body scattering area for particles with infinite or zero scattering length in two dimensions
Junjie Liang · Shina Tan
We derive the asymptotic expansions of the wave function of three particles having equal mass with finite-range interactions and infinite or zero two-dimensional scattering length colliding at zero energy and zero orbital angular momentum, from which a three-body parameter $D$ is defined. The dimension of $D$ is length squared, and we call $D$ three-body scattering area. We find that the ground state energy per particle of a zero-temperature dilute Bose gas with these interactions is approximately $\frac{ℏ ^{2} D}{6 m} ρ^{2}$ , where $ρ$ is the number density of the bosons, $m$ is the mass of each boson, and $ℏ$ is Planck's constant over $2 π$ . Such a Bose gas is stable at $D \geq 0$ in the thermodynamic limit, and metastable at $D < 0$ in the harmonic trap if the number of bosons is less than $N_{cr} \approx 3.6413 \frac{ℏ}{mω ∣ D ∣}$ , where $ω$ is the angular frequency of the harmonic trap. If the two-body interaction supports bound states, $D$ typically acquires a negative imaginary part, and we find the relation between this imaginary part and the amplitudes of the pair-boson production processes. We derive a formula for the three-body recombination rate constant of the many-boson system in terms of the imaginary part of $D$ .
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
arXiv:
2402.02202 [pdf]
PRA(2024)·3 citations
12
[Submitted on 5 Feb 2024] (cross-list from hep-ph)
Charmonium states in a coupled-channel model
Zi-Long Man🇨🇳 · Cheng-Rui Shu🇨🇳 · Yan-Rui Liu🇨🇳 · Hong Chen🇨🇳
We systematically investigate the mass spectrum and two-body open-charm strong decays of charmonium states in a coupled-channel model where the $^{3} P_{0}$ quark-antiquark pair creation mechanism is employed. The results of masses, mass shifts, proportions of the $c c ˉ$ component, and open-charm decay widths are provided. The $S$ - $D$ wave mixing angles and di-electric decay widths for vector mesons are also presented. Based on our results, we find that the $ψ (3770)$ , $ψ (4040)$ , $ψ (4160)$ , $ψ (4360)$ , and $ψ (4415)$ can be assigned as the $1^{3} D_{1}$ -, $3^{3} S_{1}$ -, $2^{3} D_{1}$ -, $4^{3} S_{1}$ -, and $3^{3} D_{1}$ -dominated charmonium states, respectively. The $ψ_{3} (3842)$ is a good candidate of the $ψ_{3} (1 D)$ charmonium state. The calculated mass and strong decay width of $χ_{c 1} (2 P)$ with significant continuum contribution ( $\sim$ 57\%) favor the charmonium interpretation for the mysterious $χ_{c 1} (3872)$ . When considering the large uncertainty in the observed decay width, the possibility to assign the $χ_{c 0} (3860)$ as the $χ_{c 0} (2 P)$ charmonium state cannot be ruled out. One may describe well the properties of $χ_{c 2} (3930)$ with the $χ_{c 2} (2 P)$ charmonium. The predictions on properties of other $c c ˉ$ states can be tested by future experiments.
Comments:
19 pages,1 figure, 12 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2402.02765 [pdf]
EPJC(2024)·19 citations
13
[Submitted on 5 Feb 2024] (cross-list from astro-ph.HE)
Thermal x-ray studies of neutron stars and the equation of state
Zhiqiang Miao🇨🇳 · Liqiang Qi🇨🇳 · Juan Zhang🇨🇳 · Ang Li🇨🇳 · Mingyu Ge🇨🇳
The understanding of neutron star equation of state hinges on a comprehensive analysis of multi-messenger, multi-wavelength data. The recent scrutiny of PSR J0030+0451 data by NICER introduces complexities, unveiling a tension with another X-ray observation of the central compact object in HESS J1731-347, specifically concerning the mass-radius constraint of low-mass neutron stars. This tension persists when integrating NICER's updated data with LIGO/Virgo's gravitational-wave data from the GW170817 binary neutron star merger. Despite attempts to reconcile these disparate observations, the current combined data still can not distinguish different types of neutron stars -- whether they are pure neutron stars or hybrid stars. Bayesian inference indicates only modest changes in the posterior ranges of parameters related to the nuclear matter and deconfinement phase transition. This ongoing exploration underscores the intricate challenges in precisely characterizing neutron stars. It also points out that it is possible to probe the equation of state at different density regimes from future more accurate radii of neutron stars with various masses.
Comments:
12 pages, 6 figures, 3 tables, To appear in Phys. Rev. D (2024)
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2402.02799 [pdf]
PRD(2024)·11 citations
14
[Submitted on 5 Feb 2024] (cross-list from hep-ph)
Constraining kaon PDFs from Drell-Yan and $J / ψ$ production
Wen-Chen Chang🇹🇼 · Jen-Chieh Peng🇺🇸 · Stephane Platchkov🇫🇷 · Takahiro Sawada🇯🇵
The kaon parton distribution functions (PDFs) are poorly known due to paucity of kaon-induced Drell-Yan data. Nevertheless, these Drell-Yan data suggest a softer valence $u$ quark distribution of kaon than that of pion. We discuss the opportunity to constrain kaon PDFs utilizing existing kaon-induced $J / ψ$ production data. We compare the $K^{-} / π^{-}$ and $K^{+} / π^{+}$ cross-section ratio data with calculations based on two global-fit parametrizations and two recent theoretical predictions for the kaon and pion PDFs, and test the results with two quarkonium production models. The $K^{-} / π^{-}$ cross-section ratio for $J / ψ$ production provides independent evidence of different valence quark distributions in pion and kaon. The $K^{+} / π^{+}$ $J / ψ$ data are found to be sensitive to the gluon distribution in kaon. We show that these $J / ψ$ production data provide valuable constraints for evaluating the adequacy of currently available sets of kaon PDFs.
Comments:
7 pages, 5 figures; published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2402.02860 [pdf]
PLB(2024)·10 citations
15
[Submitted on 5 Feb 2024] (cross-list from hep-lat)
Improved analysis of isovector nucleon matrix elements with $N_{f} = 2 + 1$ flavors of $O (a)$ improved Wilson fermions
Dalibor Djukanovic🇩🇪 · Georg von Hippel🇩🇪 · Harvey B. Meyer🇩🇪 · Konstantin Ottnad🇩🇪 · Hartmut Wittig🇩🇪
We present an update of our determination of the isovector charges $g_{A}^{u - d}$ , $g_{S}^{u - d}$ and $g_{T}^{u - d}$ , and the isovector twist-2 forward matrix elements $⟨ x ⟩_{u - d}$ , $⟨ x ⟩_{Δ u - Δ d}$ and $⟨ x ⟩_{δ u - δ d}$ on the $N_{f} = 2 + 1$ gauge ensembles generated by the Coordinated Lattice Simulations (CLS) effort. We have significantly extended our coverage of the parameter space by adding ensembles at the physical pion mass and fine lattice spacing, at nearly-physical pion masses and very fine lattice spacings, and at very large physical lattice volumes, enabling a well-controlled extrapolation to the physical point. Another major improvement is achieved owing to the extended range of source-sink separations, which allows us to perform two-state fits to summed correlator ratios, leading to a much higher level of control over excited-state effects. Systematic uncertainties from the chiral, continuum and infinite-volume extrapolations are incorporated via model averages based on the Akaike Information Criterion. Our final results at the physical point are $g_{A}^{u - d} = 1.254 (19)_{stat} (15)_{sys} [24]_{total}$ , $g_{S}^{u - d} = 1.203 (77)_{stat} (81)_{sys} [112]_{total}$ , $g_{T}^{u - d} = 0.993 (15)_{stat} (05)_{sys} [16]_{total}$ , $⟨ x ⟩_{u - d} = 0.153 (15)_{stat} (10)_{sys} [17]_{total}$ , $⟨ x ⟩_{Δ u - Δ d} = 0.207 (15)_{stat} (06)_{sys} [16]_{total}$ , and $⟨ x ⟩_{δ u - δ d} = 0.195 (17)_{stat} (15)_{sys} [23]_{total}$ . While our results for the isovector charges are in excellent agreement with the FLAG\,21 averages, we note that our error for the tensor charge $g_{T}^{u - d}$ is considerably smaller.
Comments:
20 pages, 11 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2402.03024 [pdf]
PRD(2024)·29 citations
16
[Submitted on 5 Feb 2024] (cross-list from nucl-ex)
The nonflow issue in connecting anisotropy measurements to hydrodynamics in relativistic heavy-ion collisions
Fuqiang Wang🇺🇸
Hydrodynamics can describe majority of the measured azimuthal anisotropies in relativistic heavy-ion collisions. Many of the anisotropy measurements are contaminated by nonflow correlations (i.e., those unrelated to global event-wise correlations). Those nonflow contamination can cause incorrectness or compromise the accuracy of the physics extracted from data-hydrodynamics comparison, particularly when one relies on subtle difference in the measurements. In the recent preprint by STAR (arXiv:2401.06625) extracting the Uranium nucleus deformation parameter, nonflow contamination is assessed by subevents in the limited STAR acceptance. In this note, we demonstrate that such assessment is inadequate and illustrate how large an effect nonflow can cause by using the HIJING model, in which all correlations are nonflow and non-hydrodynamic. We thereby conclude that the extracted Uranium deformation parameter is premature and emphasize the importance of an earnest assessment of or correction for nonflow contamination, not only for this STAR analysis but more generally for studies relying on comparing anisotropy measurements to hydrodynamic calculations.
Comments:
9 pages, 4 figs. This note points out a severe underestimation of nonflow in the recent STAR preprint (arXiv:2401.06625) and deems the extracted uranium deformation parameter premature. The note emphasizes, in general terms, the importance of rigorous nonflow estimation before comparing experimental anisotropy measurements to theoretical hydrodynamic calculations to extract quantitative physics
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2402.03222 [pdf]
3 citations

Affiliations

first authorsco-authorsvia INSPIRE