Nuclear Theory·nucl-th

Monday·March 4, 2024

12 papers—4 primary·8 cross-listed

05
Pole properties of a resonance: When to subtract partial-decay widths to obtain the pole widths
J. A. Oller
When a resonance lies near the threshold of a heavier channel, an interesting feature can occur. The paradigmatic example employed here is the scalar isoscalar $f_{0} (980)$ resonance that couples to the lighter $π π$ and heavier $K K ˉ$ channels. It is shown that the decay width is given by the sum or subtraction of the partial decay widths depending on whether the pole lies in the Riemann sheet that is contiguous with the physical one above or below the $K K ˉ$ threshold, respectively. Next, we show that the usually disregarded renormalization of bare parameters in Flatté or energy-dependent Breit-Wigner parameterizations is essential to extract physical information. The compositeness of the $f_{0} (980)$ by using a Flatté parameterization matched to reproduce the pole properties obtained from Roy equations and other analytic constraints is evaluated.
↳ hep-phnucl-thActa Phys.Polon.Supp.(2024)·0 citations
06
Neural Simulation-Based Inference of the Neutron Star Equation of State directly from Telescope Spectra
Len Brandes🇩🇪 · Chirag Modi🇺🇸 · Aishik Ghosh🇺🇸 · Delaney Farrell🇺🇸 · Lee Lindblom🇺🇸 · Lukas Heinrich🇩🇪 · Andrew W. Steiner🇺🇸 · Fridolin Weber🇺🇸 · Daniel Whiteson🇺🇸
Neutron stars provide a unique opportunity to study strongly interacting matter under extreme density conditions. The intricacies of matter inside neutron stars and their equation of state are not directly visible, but determine bulk properties, such as mass and radius, which affect the star's thermal X-ray emissions. However, the telescope spectra of these emissions are also affected by the stellar distance, hydrogen column, and effective surface temperature, which are not always well-constrained. Uncertainties on these nuisance parameters must be accounted for when making a robust estimation of the equation of state. In this study, we develop a novel methodology that, for the first time, can infer the full posterior distribution of both the equation of state and nuisance parameters directly from telescope observations. This method relies on the use of neural likelihood estimation, in which normalizing flows use samples of simulated telescope data to learn the likelihood of the neutron star spectra as a function of these parameters, coupled with Hamiltonian Monte Carlo methods to efficiently sample from the corresponding posterior distribution. Our approach surpasses the accuracy of previous methods, improves the interpretability of the results by providing access to the full posterior distribution, and naturally scales to a growing number of neutron star observations expected in the coming years.
↳ astro-ph.HEastro-ph.IMgr-qchep-ph+1JCAP(2024)·28 citations
07
Charge-conjugation asymmetry and molecular content: the $D_{s 0}^{*} (2317)^{\pm}$ in matter
Victor Montesinos🇪🇸 · Miguel Albaladejo🇪🇸 · Juan Nieves🇪🇸 · Laura Tolos🇪🇸
We analyze the modifications that a dense nuclear medium induces in the $D_{s 0}^{*} (2317)^{\pm}$ and $D_{s 1} (2460)^{\pm}$ . In the vacuum, we consider them as isoscalar $D^{(*)} K$ and $D^{(*)} K$ $S$ -wave bound states, which are dynamically generated from effective interactions that lead to different Weinberg compositeness scenarios. Matter effects are incorporated through the two-meson loop functions, taking into account the self energies that the $D^{(*)}$ , $D^{(*)}$ , $K$ , and $K$ develop when embedded in a nuclear medium. Although particle-antiparticle [ $D_{s 0, s 1}^{(*)} (2317, 2460)^{+}$ versus $D_{s 0, s 1}^{(*)} (2317, 2460)^{-}$ ] lineshapes are the same in vacuum, we find extremely different density patterns in matter. This charge-conjugation asymmetry mainly stems from the very different kaon and antikaon interaction with the nucleons of the dense medium. We show that the in-medium lineshapes found for these resonances strongly depend on their $D^{(*)} K$ / $D^{(*)} K$ molecular content, and discuss how this novel feature can be used to better determine/constrain the inner structure of these exotic states.
↳ hep-phnucl-thPLB(2024)·9 citations
08
A Light-Front Model for the Transition Distribution Amplitudes for Backward Timelike Compton Scattering
B. Pasquini🇮🇹 · A. Schiavi🇮🇹
To access information on the internal structure of the nucleon, data from a variety of scattering experiments can be analyzed, in regimes where the information factorizes from an otherwise known scattering amplitude. A recent development, promising new insight, is the study of exclusive reactions in the backward kinematical region, where the information can be encoded in Transition Distribution Amplitudes (TDAs). We model the photon-to-nucleon TDAs, entering the factorized description of backward Timelike Compton Scattering, using techniques of light-front dynamics to integrate information from a quark model for the photon and the nucleon. We include the results of numerical predictions that could inform further experiments at Jefferson Lab and the future Electron--Ion Collider.
↳ hep-phnucl-exnucl-thPRD(2024)·4 citations
09
Hadron momentum spectra from analytical solutions of relativistic hydrodynamics
Mahammad Sabir Ali🇮🇳 · Deeptak Biswas🇮🇳 · Amaresh Jaiswal🇮🇳 · Sushant K. Singh🇮🇹
We present analytical solution of relativistic hydrodynamics for a system having cylindrical symmetry with boost-invariant longitudinal expansion and Hubble-like transverse expansion. We also consider analytical solution for Hubble-like spherically expanding system. For these two cases, we calculate analytical expression for transverse momentum spectra of hadrons, at constant temperature freeze-out hypersurface using Cooper-Frye prescription. We compare our results for transverse momentum spectra with experimental results from Large Hadron Collider and CERN SPS where one expects cylindrical and spherical geometry of the fireball, respectively. In the case of low-energy collisions with spherical geometry, we calculate rapidity spectra and compare with the results from CERN SPS.
↳ hep-phnucl-thEPJC(2025)·3 citations
10
Pseudoscalar Mesons and Emergent Mass
K. Raya🇪🇸 · A. Bashir🇪🇸 · D. Binosi🇮🇹 · C. D. Roberts🇨🇳 · J. Rodríguez-Quintero🇪🇸
Despite its role in the continuing evolution of the Universe, only a small fraction of the mass of visible material can be attributed to the Higgs boson alone. The overwhelmingly dominant share may/should arise from the strong interactions that act in the heart of nuclear matter; namely, those described by quantum chromodynamics. This contribution describes how studying and explaining the attributes of pseudoscalar mesons can open an insightful window onto understanding the origin of mass in the Standard Model and how these insights inform our knowledge of hadron structure. The survey ranges over distribution amplitudes and functions, electromagnetic and gravitational form factors, light-front wave functions, and generalized parton distributions. Advances made using continuum Schwinger function methods and their relevance for experimental efforts are highlighted.
↳ hep-phhep-latnucl-thFew Body Syst.(2024)·53 citations
11
J/psi-pair production at NLL in TMD factorisation at the LHC
Alice Colpani Serri🇵🇱 · Jelle Bor🇳🇱 · Daniel Boer🇳🇱 · Jean-Philippe Lansberg🇫🇷
J/psi-pair production at the LHC is currently one of the few tools available to probe gluon transverse momentum distributions (TMDs). In this context, data from LHCb in the collider mode have the potential to probe the evolution of the unpolarised-gluon TMDs and to measure the distribution of the linearly-polarised gluon in unpolarised protons for the first time. In this proceedings contribution, improved predictions obtained for the LHC (at sqrt(s) = 13 TeV) up to next-to-leading logarithm (NLL) in TMD factorisation are presented. We show the obtained predictions of transverse-momentum distributions at different invariant masses and rapidities computed in the LHCb acceptance along with PDF uncertainty. We predict the azimuthal modulations of the cross section that arise from linearly-polarised gluons.
↳ hep-phhep-exnucl-exnucl-thPoS(2024)·2 citations
12
Nonperturbative Collins-Soper Kernel from Chiral Quarks with Physical Masses
Dennis Bollweg🇺🇸 · Xiang Gao🇺🇸 · Swagato Mukherjee🇺🇸 · Yong Zhao🇺🇸
We present a lattice QCD calculation of the rapidity anomalous dimension of quark transverse-momentum-dependent distributions, i.e., the Collins-Soper (CS) kernel, up to transverse separations of about 1 fm. This unitary lattice calculation is conducted, for the first time, employing the chiral-symmetry-preserving domain wall fermion discretization and physical values of light and strange quark masses. The CS kernel is extracted from the ratios of pion quasi-transverse-momentum-dependent wave functions (quasi-TMDWFs) at next-to-leading logarithmic perturbative accuracy. Also for the first time, we utilize the recently proposed Coulomb-gauge-fixed quasi-TMDWF correlator without a Wilson line. We observe significantly slower signal decay with increasing quark separations compared to the established gauge-invariant method with a staple-shaped Wilson line. This enables us to determine the CS kernel at large nonperturbative transverse separations and find its near-linear dependence on the latter. Our result is consistent with the recent lattice calculation using gauge-invariant quasi-TMDWFs, and agrees with various recent phenomenological parametrizations of experimental data.
↳ hep-lathep-exhep-phnucl-ex+1PLB(2024)·40 citations

Affiliations

first authorsco-authorsvia INSPIRE