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Nuclear Theory·nucl-th

Monday·June 1, 2026

12 papers—7 primary·5 cross-listed

All12Primary7Cross-lists5
  1. 08

    Factorizing quarkonium production matrix elements using effective field theory

    Marston Copeland🇺🇸 · Ivan Vitev🇺🇸

    We use effective field theory to factorize production matrix elements that appear in quarkonium cross sections in NRQCD. By applying a Hubbard-Stratonovich transformation we show that the soft and ultrasoft sectors of NRQCD can be decoupled from the heavy quark and antiquark fields in a hybrid vNRQCD/pNRQCD Lagrangian at leading order in the velocity power counting. This enables us to separate quarkonium production matrix elements in terms of matrix elements of color-singlet composite fields, which we can write as the wavefunction at the origin, and state independent vacuum correlators of chromo-electric and chromo-magnetic gluon fields. This approach verifies powerful connections between the LDMEs of different S-wave vector quarkonium states, originally derived using pNRQCD. Additionally, we find new operator contributions for the color-octet P-wave mechanism, which satisfy a similar set of relationships. Finally, this approach allows us to factorize the production matrix elements that appear in the transverse momentum dependent factorization framework, known as TMD soft transition functions, in terms of state independent gluon correlators. This work restores some universality for TMD production operators and dramatically improves the predictive power of NRQCD in the TMD framework.

    ↳ hep-phhep-thnucl-th4 citations
  2. 09

    Functional renormalization group study of the jet quenching parameter near the QCD critical end point

    Yi-zhen Huang🇨🇳 · Shi Yin🇩🇪 · Sheng-nan Han🇨🇳 · Jing Wu🇨🇳 · Feng Li🇨🇳 · Wei-jie Fu🇨🇳

    We investigate the jet quenching parameter in the QCD phase diagram within a QCD-assisted low-energy effective theory using the functional renormalization group (fRG). Following the formalism that relates to the spectral functions of the chiral order-parameter field, we compute the and meson contributions to at finite temperature and baryon chemical potential from analytically continued mesonic two-point functions. We find that receives appreciable contributions mainly above the chiral phase boundary and exhibits a pronounced enhancement at large baryon chemical potential as the chiral crossover sharpens toward the critical end point (CEP), a behavior consistent with the picture of partonic critical opalescence (PCO), a pronounced enhancement of jet transverse momentum broadening induced by the critical field fluctuations.

    ↳ hep-phnucl-th1 citation
  3. 10

    Functional methods for quantum thermodynamics

    Sibo Wang · Samuel Degen · Haozhao Liang

    The functional renormalization group provides a nonperturbative and systematically improvable route to constructing density functionals for quantum many-body systems from microscopic Hamiltonians. Here we advance this program by benchmarking functional-renormalization-group density functional theory (FRG-DFT) against the exact thermodynamics of the single-site Bose-Hubbard model. This model provides an ideal testing ground because it is analytically solvable, yet remains subtle in the imaginary-time coherent-state path integral, where a naive continuum treatment generates a spurious self-interaction. We show that a careful Hubbard-Stratonovich derivation identifies the self-interaction correction term that must be included in the FRG-DFT flow to recover the exact thermodynamics. We then systematically compare several closures of the resulting hierarchy of flow equations for the free energy, chemical potential, and connected density correlators over broad ranges of density, temperature, and interaction strength. The benchmark shows that the free energy is comparatively robust, whereas the chemical potential and fluctuation observables provide much sharper diagnostics of the hierarchy closure. A maximum-entropy closure gives the most accurate overall description and reproduces even the low-temperature oscillatory structure of the connected two-density correlator. These results identify two general requirements for functional approaches to quantum thermodynamics: the renormalization group flow equation must retain the equal-time contact subtraction to avoid spurious self-interactions, and any closure of the hierarchy must preserve the statistical consistency of density correlators. This work provides a controlled foundation for deriving ab initio density functionals for quantum many-body systems across condensed-matter, ultracold-atom, and nuclear physics, as well as quantum chemistry.

    ↳ cond-mat.quant-gascond-mat.stat-mechnucl-th0 citations
  4. 11

    Radiative Corrections to Elastic Lepton-Proton Scattering with Focus on Two-Photon-Exchange Diagrams

    Daniel Crowe🇺🇸 · Syed Mehedi Hasan🇩🇪 · Doreen Wackeroth🇺🇸

    Lepton (electron and muon) scattering experiments are excellent tools to gain insight into the nucleon structure. Elastic electron-proton scattering probes the spatial distribution of charge and magnetization inside the proton, and comparing electron-proton and muon-proton scattering data tests lepton universality. The availability of a plethora of scattering data with increased precision and observed discrepancies such as the proton form factor puzzle and the proton radius puzzle motivated a renewed effort to improve the theoretical framework. Realizing that the one-photon-exchange approximation (OPE), i.e. the Born approximation, is not sufficient, radiative corrections in QED, especially the two-photon-exchange (TPE) diagrams, are under investigation. The TPE diagrams are of special interest among the radiative corrections, since they depend on the proton structure. In this work, we present a complete calculation of QED radiative corrections to elastic electron-proton and muon-proton scattering at next-to-leading order, taking into account loop-momentum-dependent form factors. In the discussion of their numerical impact on lepton-proton scattering cross sections, we pay special attention to the TPE diagrams and compare them with existing theoretical predictions and lepton-proton scattering data.

    ↳ hep-phnucl-th0 citations
  5. 12

    Deeply bound dibaryon from meson-exchange saturation effective field theory

    Prin Sawasdipol🇹🇭 · Chinadanai Bubpatate🇹🇭 · Daris Samart🇹🇭

    We propose an RG-improved effective-field-theory framework for the deeply bound dibaryon , a bound state in the channel. Its binding momentum MeV gives , indicating the need to re-organize the short-range dynamics beyond a formal pionless EFT. We match the large--constrained pionless contact potential to a meson-exchange-saturated contact interaction in which the dynamics are integrated out at the hadronic scale , yielding the controlled expansion parameter . Normalizing the contact coupling to the deuteron and substituting the phenomenological CD-Bonn couplings gives MeV. The discrepancy from MeV is of the natural size of corrections to the potential, confirming compatibility with a controlled EFT expansion organized around the finite-range hadronic scale. As a result, the observed pole emerges from the virtual state to bound state by using the EFT re-organization in this work.

    ↳ hep-phnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE