Nuclear Theory·nucl-th

Thursday·April 2, 2026

22 papers—13 primary·9 cross-listed

14
[Submitted on 31 Mar 2026] (cross-list from hep-ph)
Light-by-light scattering: asymptotic expansions, Coulomb resummation and NLO corrections
Ajjath A H🇬🇧 · Ekta Chaubey🇩🇪 · Hua-Sheng Shao🇫🇷
Light-by-light (LbL) scattering is one of the earliest predictions of quantum electrodynamics (QED). Interest in this process has been renewed following its experimental observation at the LHC and the prospects of future measurements at free-electron laser facilities. In this paper, we refine theoretical predictions for LbL scattering by improving the full fermion-mass-dependent two-loop QCD and QED helicity amplitudes using high- and low-energy asymptotic expansions, and by performing Coulomb resummation in the threshold region. We present state-of-the-art predictions for LbL cross sections in the Standard Model and provide a new event generator, LbLatNLO, for Monte Carlo simulations of LbL scattering.
Comments:
69 pages, 12 figures, 6 tables. The LbLatNLO code is available at https://github.com/huashengshao/LbLatNLO. Ancillary files for amplitudes and integrals
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Theory (hep-th); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2604.00099 [pdf]
1 citation
15
[Submitted on 31 Mar 2026] (cross-list from quant-ph)
Scattering phase shift in quantum mechanics on quantum computers: non-Hermitian systems and imaginary-time simulations
Peng Guo🇺🇸 · Paul LeVan🇺🇸 · Frank X. Lee🇺🇸 · Yong Zhao🇺🇸
To overcome the fast oscillatory behavior of correlation functions for extracting scattering phase shift in real-time quantum simulations encountered in Ref.\cite{Guo:2026qkx}, we propose and test two solutions in the present work. One is to simulate Hermitian systems in imaginary time, the other is to simulate non-Hermitian systems in real time. We demonstrate that both approaches lead to the problem of non-unitary quantum evolution which can be solved by combining two quantum algorithms: block encoding and Hadamard test. The combined quantum algorithm does not require mid-circuit measurements or adjustment of the input parameters of the Hamiltonian, and can be easily implemented on quantum computers. Numerical tests on quantum simulators show that both approaches agree with exact solutions for a sufficiently long time before the signal is lost in statistical fluctuations. The results bode well for using non-Hermitian and imaginary-time simulations to circumvent oscillations inherent in real-time simulation of other quantum systems. In particular, the non-Hermitian approach shows a decisive advantage over the imaginary-time one on the number of required ancillary qubits, and hence is more practical to scale up.
Comments:
11 pages, 11 figures, match to accepted version at APS open science
Subjects:
Quantum Physics (quant-ph); cond-mat.other (cond-mat.other); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.00127 [pdf]
APS Open Sci.(2026)·2 citations
16
[Submitted on 1 Apr 2026] (cross-list from hep-lat)
QCD in strong magnetic fields: fluctuations of conserved charges and equation of state
Heng-Tong Ding🇨🇳 · Jin-Biao Gu🇨🇳 · Arpith Kumar🇨🇳 · Sheng-Tai Li🇨🇳
We present continuum-estimated (2+1)-flavor lattice QCD results for second-order fluctuations of conserved charges and the leading-order equation of state in the presence of strong magnetic fields at nonzero baryon chemical potential, using the HISQ action at the physical pion mass. The baryon-electric charge correlation $χ_{11}^{BQ}$ exhibits striking sensitivity to the magnetic field: $R_{c p}$ -like double ratios $χ_{11}^{BQ} / χ_{2}^{Q}$ and $χ_{11}^{BQ} / χ_{11}^{QS}$ reach enhancements of $\sim 2$ and $\sim 2.25$ at $e B ≃ 8 M_{π}^{2}$ along the transition line, establishing $χ_{11}^{BQ}$ as a magnetometer of QCD. To bridge theoretical predictions and experimental observations, we construct HRG-based proxy observables and apply systematic kinematic cuts emulating STAR and ALICE detector acceptances, which retain $\sim 80%$ of the lattice QCD magnetic sensitivity. Extending to the QCD equation of state under strangeness neutrality and isospin asymmetry, we determine the chemical potential ratio $q_{1} \equiv (μ_{Q} / μ_{B})_{LO}$ and the pressure coefficient $P_{2}$ for magnetic field strengths up to $e B ≃ 0.8 GeV^{2} \sim 45 M_{π}^{2}$ . The results reveal temperature-band crossings, hierarchy reversals, and non-monotonic structures driven by the nontrivial interplay between thermal and magnetic effects.
Comments:
10 pages, 3 figures, contribution to the 42nd International Symposium on Lattice Field Theory (LATTICE2025), 2-8 November 2025, Tata Institute of Fundamental Research, Mumbai, India
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2604.00370 [pdf]
0 citations
17
[Submitted on 1 Apr 2026] (cross-list from cond-mat.quant-gas)
Emergent Weyl Nodes and Berry Curvature in Bose Polarons via $p$ -Wave Feshbach Coupling
Hiroyuki Tajima🇯🇵 · Eiji Nakano🇯🇵 · Kei Iida🇯🇵
We show that an impurity quasiparticle immersed in a Bose-Einstein condensate, known as a Bose polaron, exhibits topological properties characterized by a nonzero Berry curvature, which is induced by Weyl nodes that emerge via interspecies $p$ -wave Feshbach resonance. Such nodes occur even in the absence of spin degrees of freedom and spin-orbit coupling. For charged impurities, the corresponding $p$ -wave polarons are shown to be accompanied by chiral anomaly. The above predictions can be tested in a cold atomic environment by observing the Hall transport of the atomic or ionic impurity cloud.
Comments:
6 pages, 2 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2604.00797 [pdf]
0 citations
18
[Submitted on 1 Apr 2026] (cross-list from quant-ph)
Graph-Structured Number-Conserving Variational Quantum Eigensolver for Fermionic Pairing Hamiltonians
Abhishek🇮🇳 · Nabeel Salim🇮🇳 · P. Arumugam🇮🇳
Simulating strongly correlated fermionic pairing in the presence of rotational and pair-breaking fields requires deep quantum circuits. We present a graph-structured variational quantum eigensolver whose pair-transfer and single-excitation rotations follow the nonzero pairing and one-body mixing edges of the Hamiltonian. The circuit conserves particle number exactly and uses one parameter per retained edge. We benchmark one layer against exact fixed-number diagonalization for 1500, $M = 8$ Hamiltonians represented by 16 qubits. Its mean energy error rises from 0.86 keV without one-body driving to 691 keV at the strongest drive; the one-layer circuit loses accuracy as pair breaking strengthens. In a matched eight-qubit comparison, the graph circuit reaches the 0.42 keV high-drive error of a pair-plus-all-singles circuit with 8 instead of 34 parameters. Fixed-number Adaptive Derivative-Assembled Pseudo-Trotter VQE reaches 0.056 keV with 304 decomposed controlled-NOT gates and iterative pool screening, while a 52-parameter, single-repetition unitary coupled-cluster singles-and-doubles circuit gives 17.6 keV with 2752 such gates. At a separate twelve-qubit point, a second graph layer reduces the high-drive error from 378 to 35 keV. Across the exact grid, an off-diagonal pair-coherence scale tracks the leading pair-density eigenvalue, condensate fraction, and interaction energy. Cranked zirconium Hamiltonians provide the benchmark instances and tune the strength of one-body pair breaking.
Comments:
12 pages, 8 figures
Subjects:
Quantum Physics (quant-ph); Nuclear Theory (nucl-th)
arXiv:
2604.00844 [pdf]
0 citations
19
[Submitted on 1 Apr 2026] (cross-list from hep-ph)
Baryonic form factors of light pseudoscalar mesons
A.S. Miramontes🇪🇸 · J.M. Morgado🇪🇸 · J. Papavassiliou🇪🇸
Employing the Bethe-Salpeter formalism, we present a computation of the space-like baryonic form factor for the pion and kaon. In the exact isospin-symmetric limit this observable is forbidden by $G$ -parity, so that any nonzero signal constitutes a direct probe of the quark mass difference $m_{d} - m_{u}$ . The form factors are evaluated in the impulse approximation using fully dressed quark propagators, meson Bethe-Salpeter amplitudes, and a dressed baryon-current vertex constrained by the vector Ward-Takahashi identity. The baryonic radius computed with this method for the pion is given by $⟨ r_{B}^{2} ⟩_{π^{+}}^{1/2} = 0.043 (2)$ fm, and is consistent with the available dispersive benchmarks. Our predictions for the kaons, namely $⟨ r_{B}^{2} ⟩_{K^{+}}^{1/2} = 0.265 (7)$ fm and $⟨ r_{B}^{2} ⟩_{K^{0}}^{1/2} = 0.262 (7)$ fm, indicate a larger spatial extent than in the pion case; these results have no dispersive counterparts, and are compatible with chiral QCD models.
Comments:
10 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.00959 [pdf]
PLB(2026)·2 citations
20
[Submitted on 1 Apr 2026] (cross-list from hep-ph)
Electromagnetic form factors of heavy-light pseudoscalar mesons
A.S. Miramontes🇪🇸 · J. Papavassiliou🇪🇸 · J.M. Pawlowski🇩🇪
We report calculations of space-like electromagnetic form factors and charge radii of pseudoscalar mesons, covering both light and heavy-light flavour sectors within a flavour-dependent Bethe-Salpeter framework.
Comments:
6 pages, 3 figures. Submitted to the proceedings of the Excited QCD Workshop 2026
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.00974 [pdf]
Acta Phys.Polon.Supp.(2026)·1 citation
21
[Submitted on 1 Apr 2026] (cross-list from hep-ph)
Pions reloaded
M.N. Ferreira🇧🇷 · A.S. Miramontes🇪🇸 · J.M. Morgado🇪🇸 · J. Papavassiliou🇪🇸 · J.M. Pawlowski🇩🇪
We present a novel version of the pion Bethe-Salpeter equation in the chiral limit, solved using as ingredients state-of-the-art QCD correlation functions. The constraints imposed by the axial Ward-Takahashi identities are exactly fulfilled, both formally and numerically.
Comments:
6 pages, 4 figures. Submitted to the proceedings of the Excited QCD Workshop 2026
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.00996 [pdf]
Acta Phys.Polon.Supp.(2026)·0 citations
22
[Submitted on 1 Apr 2026] (cross-list from hep-ph)
Uncover the correlation between jet energy correlators and multiplicity fluctuations
Pi Duan🇨🇳 · Weiyao Ke🇨🇳 · Guang-You Qin🇨🇳 · Lei Wang🇨🇳
The energy-energy correlator (EEC) and multiplicity are two fundamental observables probing complementary aspects of QCD jets: the former characterizes the angular structure of energy flows in a scale-dependent manner, while the latter is sensitive to the entire history of particle production. In this \emph{Letter}, we uncover a nontrivial correlation between them by studying the EEC as a function of jet internal multiplicity. We introduce the multiplicity-conditioned EEC jet function (MCJF) and perform a factorization calculation to next-to-leading order accuracy. It is found that, for jet samples selected at a given normalized multiplicity $ν = N_{ch} / ⟨ N_{ch} ⟩$ , the EEC in the angular region $Λ_{QCD} / p_{T, jet} ≪ χ ≪ R$ acquires a $ν$ -dependent anomalous dimension. Thus the $ν$ -conditioned EEC provides a direct and robust probe to the multiplicity generating function in the perturbative regime. In addition, understanding $ν$ dependence of the EEC is also crucial for isolating possible multiplicity-dependent bias effects in the EEC measurements in nuclear environment.
Comments:
6 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2604.01102 [pdf]
3 citations

Affiliations

first authorsco-authorsvia INSPIRE