Nuclear Theory·nucl-th

Wednesday·December 17, 2025

14 papers—5 primary·9 cross-listed

06
Asymptotic-freedom and massive glueballs in a qubit-regularized SU(2) gauge theory
Rui Xian Siew🇺🇸 · Shailesh Chandrasekharan🇺🇸 · Tanmoy Bhattacharya🇺🇸
We argue that a simple qubit-regularized $SU (2)$ lattice gauge theory (LGT) on a plaquette chain serves as a pseudo-one-dimensional toy model for Yang-Mills (YM) theory in three spatial dimensions. We map the chain Hamiltonian to the Transverse Field Ising Model (TFIM) in a uniform magnetic field and demonstrate that it can be tuned to a continuum limit in which the short-distance physics is governed by the asymptotically free Ising conformal field theory (CFT) describing free Majorana fermions, while the long-distance regime contains massive excitations of the $E_{8}$ quantum field theory (QFT) that can be interpreted as one-dimensional analogues of glueballs. Furthermore, we find $σ / m_{1} = 0.249 (1)$ where $σ$ is the string tension between two static quarks and $m_{1}$ is the mass of the lightest glueball.
↳ hep-latcond-mat.str-elhep-thnucl-th+1PRD(2026)·6 citations
07
Resonances: Universality and Factorization on Higher Sheets
Miguel Correia🇨🇦 · Celina Pasiecznik🇨🇦
Most particles in nature are unstable, manifesting as resonances in scattering processes. Using analyticity and unitarity, we show nonperturbatively that resonances, defined as poles on higher Riemann sheets of scattering amplitudes, share basic properties with stable particles: (i) Universality, that a resonance generically appears in every S-matrix element; and (ii) Factorization, that amplitudes factorize on resonance poles. Our framework applies in any spacetime dimension and across arbitrarily many two-particle cuts, including cases where the kinematic Riemann surface becomes infinitely sheeted. Importantly, we find that resonance data (mass, width, couplings, and sheet index) are fully encoded on the physical sheet, where causality can impose additional constraints. These results are relevant for extending S-matrix bootstrap studies beyond elastic scattering.
↳ hep-thhep-phnucl-th4 citations
08
Improved Standard-Model predictions for $η^{(')} \to ℓ^{+} ℓ^{-}$
Noah Messerli🇨🇭 · Martin Hoferichter🇨🇭 · Bai-Long Hoid🇩🇪 · Simon Holz🇨🇭 · Bastian Kubis🇩🇪
The rare decays $η^{(')} \to ℓ^{+} ℓ^{-}$ , $ℓ \in {e, μ}$ , are highly suppressed in the Standard Model, both by their chirality structure and the required loop attaching the lepton line to the $η^{(')} \to γ^{*} γ^{*}$ matrix element. The latter is described by a single scalar function, the transition form factor, which has recently been studied in great detail for $η^{(')}$ in the context of the pseudoscalar-pole contributions to hadronic light-by-light scattering in the anomalous magnetic moment of the muon. Based on these results, we evaluate the corresponding prediction for the $η^{(')}$ dilepton decays, supplemented by an improved evaluation of the asymptotic contributions including pseudoscalar mass effects. In particular, the dispersive representation for the $η^{(')}$ transition form factors allows us, for the first time, to perform a robust evaluation of the imaginary parts due to subleading channels besides the dominant two-photon cut. Our final results are $Br [η \to e^{+} e^{-}] = 5.37 (4) (2) [4] \times 1 0^{- 9}$ , $Br [η \to μ^{+} μ^{-}] = 4.54 (4) (2) [4] \times 1 0^{- 6}$ , $Br [η^{'} \to e^{+} e^{-}] = 1.80 (2) (3) [3] \times 1 0^{- 10}$ , and $Br [η^{'} \to μ^{+} μ^{-}] = 1.22 (2) (2) [3] \times 1 0^{- 7}$ , where the errors refer to the uncertainty in the normalized branching fraction, the one propagated from $Br [η^{(')} \to γ γ]$ , and the total uncertainty, respectively. The branching fraction for $η \to μ^{+} μ^{-}$ exhibits a mild $1.6 σ$ tension with experiment, and we explore the bounds that can be derived on physics beyond the Standard Model.
↳ hep-phhep-exhep-latnucl-thJHEP(2026)·7 citations
09
Magnetoviscosity of relativistic plasma
Ritesh Ghosh🇺🇸 · Igor A. Shovkovy🇺🇸
Using first-principles quantum field-theoretical methods, we investigate the shear and bulk viscosities of strongly magnetized relativistic plasmas. The analysis is performed within the weak-coupling approximation and utilizes known results for the fermion damping rates in the Landau-level representation, $Γ_{n} (p_{z})$ , which are dominated by one-to-two and two-to-one processes in the presence of a strong magnetic field. The transverse and longitudinal components of the viscosities are derived using Kubo's linear response theory. Our results reveal a pronounced anisotropy in both shear and bulk viscosities induced by the magnetic field. In the case of an electron-positron plasma, where the weak-coupling approximation is well justified, the dimensionless longitudinal shear viscosity $η_{∥} / T^{3}$ increases rapidly with the magnetic field strength, while the transverse component $η_{⊥} / T^{3}$ decreases and can even drop below the KSS bound at sufficiently large fields. In contrast, both the dimensionless longitudinal and transverse bulk viscosities, $ζ_{⊥} / T^{3}$ and $ζ_{∥} / T^{3}$ , initially rise from small values, reach a maximum, and then gradually decrease toward zero. We find that the bulk viscosity is highly sensitive to the longitudinal and transverse components of the sound velocity, particularly at high magnetic fields, indicating that its quantitative values should be interpreted with caution. We also calculate an additional cross viscosity, which is negative and whose magnitude increases with the magnetic field strength. Finally, we discuss the physical implications of these magnetoviscosity results in the contexts of magnetar physics and the strongly magnetized quark-gluon plasma produced in heavy-ion collisions.
↳ hep-phnucl-th0 citations
10
Generalized relativistic second order magnetohydrodynamics: A correlation function approach using Zubarev's nonequilibrium statistical operator
Abhishek Tiwari🇮🇳 · Binoy Krishna Patra🇮🇳
We use total energy-momentum conservation and the Bianchi identity (magnetic-flux conservation) to construct second-order relativistic magnetohydrodynamics in a Zubarev's non-equilibrium statistical operator (NESO) framework. We obtain all dissipative tensors in the medium by focusing on a relativistic magnetized plasma that preserves parity and is symmetric to charge-conjugation. We also provide Kubo formulas for all transport coefficients that arise at second order. Moreover, we extend the NESO formalism to systematically take into account for nonlocal contributions.
↳ physics.flu-dynhep-phhep-thnucl-th+1PRD(2026)·1 citation
11
Symmetry-preserving calculation of pion light-front wave functions
Zhao-Qian Yao🇩🇪 · Zhen-Ni Xu🇪🇸 · Yu-Yang Xiao🇨🇳 · Craig D. Roberts🇨🇳 · Jose Rodriguez-Quintero🇪🇸
Poincaré-covariant Bethe-Salpeter wave functions are used to calculate light-front wave functions (LFWFs) of the pion, $π$ , and an analogue state, $π_{s s ˉ}$ . The current masses of the degenerate valence constituents in the $π_{s s ˉ}$ are around $25$ -times larger than those of the pion's valence constituents. Both valence spin-antialigned ( $L = 0$ ) and valence spin-aligned ( $L = 1$ ) components are obtained and combined to produce the complete LFWF for each system. Comparing predictions delivered by two distinct Bethe-Salpeter kernels, the impact of nonperturbative dynamical effects contained in the more sophisticated (bRL) kernel are seen to be significant; and contrasts between $π$ , $π_{s s ˉ}$ results reveal the interplay between emergent hadron mass and mass effects owing to Higgs-boson couplings. Amongst the results, one finds that for $π$ , $π_{s s ˉ}$ , the LFWFs can be approximated by a separable form, with that representation being pointwise reliable in the bRL cases. Moreover, the $L = 1$ component is important; so a LFWF obtained after omission of this piece is typically a poor representation of the system. These features are naturally expressed in $π$ , $π_{s s ˉ}$ transverse momentum dependent parton distribution functions (TMDs). In this connection, it is found that a Gaussian \textit{Ansatz} can only provide a rough guide to TMD pointwise behaviour: magnitude deviations between \textit{Ansatz} and prediction exceed a factor of two on $k_{⊥}^{2} ≳ 0.55$ GeV $^{2}$ . One should therefore be cautious in interpreting conclusions drawn from phenomenological analyses based upon Gaussian \textit{Ansätze}.
↳ hep-phhep-exhep-latnucl-ex+14 citations
12
Substructure grooming of inclusive and photon-tagged jets in heavy-ion collisions
Sa Wang🇨🇳 · Shuang Li🇨🇳 · Jin-Wen Kang🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳
Jet substructure provides a powerful probe of partonic interactions within the quark-gluon plasma (QGP) in heavy-ion collisions. In this paper, we present a systematic theoretical study of the groomed substructures for both inclusive jets and photon-tagged jets ( $γ +$ jets) utilizing the Dynamical and Soft-Drop Grooming algorithms in PbPb collisions by employing the SHELL transport model. Our theoretical calculations exhibit a suppression at high $k_{T, g}$ , the relative transverse momentum between the two subjets in the groomed substructure, consistent with the recent ALICE measurements. We show that the suppression of high $k_{T, g}$ arises from the combined effects of the reduction of the subleading subjet transverse momentum due to partonic energy loss and the narrowing of the groomed jet radius $R_{g}$ induced by selection bias. Our findings demonstrate that no enhancement is observed at high $k_{T, g}$ , even in the complete absence of selection bias. Furthermore, we propose that the broadening of $R_{g}$ in photon-tagged jets, which are less susceptible to selection bias compared to inclusive jets, provides relatively direct evidence of the jet substructure broadening. Our analysis reveals that the $R_{g}$ broadening becomes more pronounced as the jet radius increases, where the medium-induced gluon radiation plays a dominant role in driving such broadening. In particular, we find that as the jet radius increases, the Soft Drop grooming algorithm exhibits a better resolving power for the contribution of the medium response to the jet substructure broadening.
↳ hep-phnucl-th0 citations
13
Signatures of local acceleration of quark-gluon plasma in the dilepton production
Aritra Bandyopadhyay🇷🇴 · Moulindu Kundu🇷🇴 · Victor E. Ambrus🇷🇴 · Maxim N. Chernodub🇷🇴
Dilepton production is one of the key probes of the Quark-Gluon Plasma (QGP) that encodes the imaginary part of the electromagnetic current-current correlator. We investigate the effect of local acceleration on the dilepton production by treating acceleration as a small perturbation. Using the thermal Dirac propagator in an accelerated frame within the imaginary-time formalism, we compute the photon polarization tensor and extract its imaginary part. Comparison with the zero-acceleration case isolates the distinct contributions of acceleration to dilepton yields.
↳ hep-phnucl-thJ.Subatomic Part.Cosmol.(2026)·1 citation
14
Drell-Yan at the Electron-Ion Collider
Henry T. Klest🇺🇸
The photon is arguably the most universally important particle across all fields of physics. Despite its status as a fundamental particle, at high energies the photon can be seen as a hadronic source of partons. The partonic content of the photon is very poorly constrained compared to that of the proton, with photon PDF uncertainties typically one or two orders of magnitude larger than their proton counterparts, despite the fact that its source, the $γ \to q q ˉ$ splitting, is perturbatively calculable. The high luminosity, excellent particle identification, and far-backward electron tagging capabilities of the Electron-Ion Collider make it an ideal environment for studying photon parton distribution functions. Similar to the $p + p$ or $π + p$ systems, photoproduction at the EIC can be thought of as two parton distributions colliding. One of the most powerful processes in such collisions is production of lepton pairs, i.e. $h + p \to l^{+} l^{-} + X$ , known as the Drell--Yan process. This process has the ability to access for the first time the transverse-momentum-dependent parton distributions of the photon. The transversely polarized proton beam of the EIC additionally provides a possible means of accessing the transversity distribution of the proton without relying on fragmentation functions.
↳ nucl-exhep-exhep-phnucl-thPRD(2026)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE