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Nuclear Theory·nucl-th

Friday·May 19, 2023

11 papers—4 primary·7 cross-listed

All11Primary4Cross-lists7
  1. 05

    The Photon Content of the Neutron

    Keping Xie🇺🇸 · Bei Zhou🇺🇸 · T.J. Hobbs🇺🇸

    In this work, we complete our CT18qed study with the neutron's photon parton distribution function (PDF), which is essential for the nucleus scattering phenomenology. Two methods, CT18lux and CT18qed, based on the LUXqed formalism and the DGLAP evolution, respectively, to determine the neutron's photon PDF have been presented. Various low- non-perturbative variations have been carefully examined, which are treated as additional uncertainties on top of those induced by quark and gluon PDFs. The impacts of the momentum sum rule as well as isospin symmetry violation have been explored, and turn out to be negligible. A detailed comparison with other neutron's photon PDF sets has been performed, which shows a great improvement in the precision and a reasonable uncertainty estimation in our results. Finally, two phenomenological implications are demonstrated with photon-initiated processes: neutrino-nucleus -boson production, which is important for the near-future TeV--PeV neutrino observations, and the axion-like particle production at a high-energy muon beam-dump experiment.

    ↳ hep-phastro-ph.HEnucl-thJHEP(2024)·32 citations
  2. 06

    Hadron-hadron potentials coupled to quark degrees of freedom for exotic hadrons

    Ibuki Terashima🇯🇵 · Tetsuo Hyodo🇯🇵

    We study the properties of the hadron-hadron potentials and quark-antiquark potentials from the viewpoint of the channel coupling. We demonstrate that, for finite quark masses, the coupling to the two-hadron continuum induces the imaginary part of the quark-antiquark potential, in contrast to the string-breaking phenomena in the static limit. It is also shown that the elimination of the different degrees of freedom induces the nonlocality and energy dependence of the effective potentials. For the obtained nonlocal potentials, we apply two methods of the local approximation proposed previously, the formal derivative expansion and the derivative expansion in the HAL QCD method, by carefully examining the energy dependence of the potential. As an application, we construct a coupled-channel model of and to describe , and discuss the property of the effective potentials. We confirm that the local approximation by the HAL QCD method works better than the formal derivative expansion also for the energy-dependent potential. At the same time, we show that, in the HAL QCD method, the resulting phase shift is sensitive to the choice of the wavefunction to construct the local potential when the system has a shallow bound state such as .

    ↳ hep-phnucl-thPRC(2023)·11 citations
  3. 07

    Analysis of resonance and scattering length with chiral unitary approach

    Takuma Nishibuchi🇯🇵 · Tetsuo Hyodo🇯🇵

    We study the resonance near the threshold in the light of the recent experimental constraints. The Belle collaboration have found a resonance peak of slightly below the threshold in the invariant mass spectrum, and the ALICE collaboration have determined the scattering length from the measurement of the momentum correlation functions in the heavy ion collisions. Using the effective range expansion, we classify the nature of the pole of the near-threshold eigenstate in terms of the scattering length, in the presence of the decay channel. It is shown that the quasibound state below the threshold can be described by only the scattering length, while the description of the resonance above the threshold requires the contribution from the effective range. Based on the chiral unitary approach, we construct a theoretical model which generates the pole of below the threshold with relatively narrow width, as reported by the Belle collaboration. It is quantitatively demonstrated that the spectrum of the quasibound state is distorted by the effect of the nearby threshold. We then construct another model which reproduces the scattering length by the ALICE collaboration. In this case, the eigenstate pole does not appear in the physically relevant Riemann sheets, and the spectrum shows a cusp structure at the threshold. We finally examine the compatibility of the value of the scattering length and the subthreshold pole of including the experimental uncertainties.

    ↳ hep-phnucl-thPRC(2024)·21 citations
  4. 08

    Microscopic Encoding of Macroscopic Universality: Scaling Properties of Dirac Eigenspectra near QCD Chiral Phase Transition

    Heng-Tong Ding🇨🇳 · Wei-Ping Huang🇨🇳 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸

    Macroscopic properties of the strong interaction near its chiral phase transition exhibit scaling behaviors, which are the same as those observed close to the magnetic transition in a 3-dimensional classical spin system with symmetry. We show that the universal scaling properties of the chiral phase transition in Quantum Chromodynamics (QCD) at the macroscale are, in fact, encoded within the microscopic energy levels of its fundamental constituents, the quarks. We establish a connection between the cumulants of the chiral order parameter, i.e., the chiral condensate, and the correlations among the energy levels of quarks, i.e., the eigenspectra of the massless QCD Dirac operator. This relation elucidates how the fluctuations of the chiral condensate arise from the correlations within the infrared part of the energy spectra of quarks, and naturally leads to a generalization of the Banks-Casher relation for the cumulants of the chiral condensate. Then, through (2+1)-flavor lattice QCD calculations with varying light quark masses near the QCD chiral transition, we demonstrate that the correlations among the infrared part of the Dirac eigenvalue spectra exhibit same universal scaling behaviors as expected of the cumulants of the chiral condensate. We find that these universal scaling behaviors extend up to the physical values of the up and down quark masses. Our study reveals how the hidden scaling features at the microscale give rise to the macroscopic universal properties of QCD.

    ↳ hep-lathep-phhep-thnucl-thPRL(2023)·16 citations
  5. 09

    Production of -nuclei from -process seeds: the -process

    Zewei Xiong · Gabriel Martínez-Pinedo · Oliver Just · Andre Sieverding

    We present a new nucleosynthesis process that may take place on neutron-rich ejecta experiencing an intensive neutrino flux. The nucleosynthesis proceeds similarly to the standard -process, a sequence of neutron-captures and beta-decays, however with charged-current neutrino absorption reactions on nuclei operating much faster than beta-decays. Once neutron capture reactions freeze-out the produced -process neutron-rich nuclei undergo a fast conversion of neutrons into protons and are pushed even beyond the -stability line producing the neutron-deficient -nuclei. This scenario, which we denote as the -process, provides an alternative channel for the production of -nuclei and the short-lived nucleus Nb. We discuss the necessary conditions posed on the astrophysical site for the -process to be realized in nature. While these conditions are not fulfilled by current neutrino-hydrodynamic models of -process sites, future models, including more complex physics and a larger variety of outflow conditions, may achieve the necessary conditions in some regions of the ejecta.

    ↳ astro-ph.HEnucl-exnucl-thPRL(2024)·14 citations
  6. 10

    Renormalization of the gluon distribution function in the background field formalism

    Tolga Altinoluk🇵🇱 · Guillaume Beuf🇵🇱 · Jamal Jalilian-Marian🇺🇸

    We derive the Leading Order DGLAP evolution of gluon distribution function in the target light cone gauge starting from its standard operator definition. The derivation is performed using the background field formalism also employed in the Color Glass Condensate effective theory of small QCD. We adopt Mandelstam-Leibbrandt prescription to regulate in an unambiguous way the spurious singularity appearing in the light-cone gauge Feynman propagator. UV divergences are regulated via dimensional regularization. The methods introduced in this paper represent the first steps in the construction of a unified framework for QCD evolution, which could address collinear physics as well as small physics and gluon saturation.

    ↳ hep-phnucl-thPRD(2025)·19 citations
  7. 11

    Moments of proton GPDs from the OPE of nonlocal quark bilinears up to NNLO

    Shohini Bhattacharya🇺🇸 · Krzysztof Cichy🇵🇱 · Martha Constantinou🇺🇸 · Xiang Gao🇺🇸 · Andreas Metz🇺🇸 · Joshua Miller🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Fernanda Steffens🇩🇪 · Yong Zhao🇺🇸

    For the first time, we present a lattice QCD determination of Mellin moments of unpolarized generalized parton distributions (GPDs) of the proton from an analysis of the quasi-GPD matrix elements within the short-distance factorization framework. We perform our calculation on an =2+1+1 twisted mass fermions ensemble with a clover improvement at lattice spacing fm and a pion mass of MeV. Focusing on the zero-skewness case, the iso-vector and iso-scalar quasi-GPDs are calculated from the definition, as well as a recently proposed Lorentz-invariant definition. We utilize data on both symmetric and asymmetric kinematic frames, which allows us to obtain the Mellin moments for several values of the momentum transfer, , in the range 0.17 to . We use the ratio scheme for GPDs, i.e. renormalization group invariant ratios with leading-twist factorization formula and perturbatively calculated matching coefficients up to the next-next-to-leading order (NNLO) to extract Mellin moments of GPDs, which are consistent with renormalization-group improved results. We compare our determination from quasi-GPDs with the results extracted using standard calculations of Mellin moments of local operators, specifically those related to the electromagnetic and gravitational form factors. We estimated the moments of GPDs up to the fifth ones for the first time. By extrapolating the Mellin moments to , we obtained the quark charges, momentum fraction, as well as the angular momentum contributions to the proton spin. The impact parameter space interpretation of the GPD moments is discussed, which provides insights into the spatial distribution of unpolarized quarks and their correlations in the transverse plane of an unpolarized or transversely polarized proton.

    ↳ hep-lathep-phnucl-thPRD(2023)·55 citations

Affiliations

first authorsco-authorsvia INSPIRE