Jian-Ping Ma

The electric dipole moment (EDM) of baryons provides a sensitive probe of C P -violating interactions beyond the standard model. Motivated by the recent BESIII measurement on the Λ hyperon EDM [Ablikim , .], we present the first perturbative QCD analysis of the Λ EDM form factor to elucidate its origin in C P -violating quark dipole interactions. In particular, we derive a QCD factorization formula that relates the Λ EDM form factor to quark EDMs and chromoelectric dipole moments through convolutions with light-cone distribution amplitudes of Λ . These connections allow us to extract constraints on C P -violating dipole couplings from current and future hyperon EDM measurements. Our numerical analysis demonstrates that the Λ EDM exhibits unique sensitivity to the strange-quark chromoelectric dipole moment, providing complementary information to that obtained from the neutron EDM.

We present our new findings on how various fundamental interactions decisively shape quantum entanglement and the Bell measure within and beyond the quantum field theory (QFT). In QFT, parity symmetry plays a key role in determining entanglement. Parity-conserving interactions produce maximally entangled bipartite systems, while maximally parity-violating interactions result in disentangled bipartite systems, placing the Bell measure on the boundary between classical and quantum theories. By examining the relation between quantum entanglement and Bell measure, we find that clean signals for interactions beyond QFT may be obtained. We propose methods to test these potential signals. Furthermore, we highlight the previously overlooked influence of magnetic fields within detectors, which radically alters predictions for quantum entanglement and Bell nonlocality. This environmental effect induces spurious P and charge-parity (CP) violations, which has to be carefully accounted for to reveal the true P, CP, and Bell nonlocality effects.

A nonzero electric dipole moment of a tauon, d _τ , signals CP violation and provides an important probe for new physics. We study methods to measure d _τ at low energy e ⁺ e ⁻ colliders through the processes e ⁺ e ⁻ → γ ^*, ψ(2S) → τ ⁺ τ ⁻ with τ ^± decays into a charged hadron and a tau neutrino. We point out that, with measuring energies of the charged hadron, Im(d _τ ) can be measured. On the other hand, selecting events of τ decays after traveling more than the detector resolution distance, Re(d _τ ) can also be determined. We find that the precision at Super Tau-Charm Facility (STCF) running at the center energy of m _ψ(2S) for 10 year data accumulation, the precision of Im(d _τ ) and Re(d _τ ) are found to be 1.8 and 11 in unit of 10⁻¹⁸ e cm, respectively. The sensitivity for d _τ measurement precision at the STCF can be reached its optimum at a central energy of 6.3 GeV, achieving a precision of 0.7 for Im(d _τ ) and 2.8 for Re(d _τ ) in unit of 10 ⁻¹⁸ e cm.

We systematically investigate tests of the parity P and the combined parity and charge-conjugate C P symmetries from differential angular distributions of J / ψ decaying into the lowest-lying baryon pairs at BESIII and the next-generation super tau-charm facilities (STCFs). Large corrections from Z and W exchange induced parity-violating effects are found for J / ψ decays with large logarithms resummed up to O ( α s ) . The parity-violating asymmetries on the production and the decay sides of J / ψ are both estimated to be of O ( 10 − 4 ) , thus barely observable with the 10 billion J / ψ events currently collected at BESIII. Nevertheless, these asymmetries utilizing the current BESIII data already permit a measurement of the weak mixing angle with an absolute uncertainty δ s w 2 ≈ 0.09 , corresponding to the first determination of s w 2 at the J / ψ threshold. In the future, STCFs are estimated to improve this bound by a factor of ∼ 20 to δ s w 2 ≈ 0.005 within one year based on luminosity rescaling. We also obtain the 95% confidence level upper bounds on the electric dipole moments of the octet baryons, which are of O ( 10 − 18 ) e cm for BESIII and O ( 10 − 19 ) e cm for STCFs. These bounds are improved by 2 to 3 orders of magnitude in comparison with the only existing one on Λ from Fermilab. The method discussed in this work also paves a way for a first and direct measurement of the Ξ and Σ electric dipole moments. Published by the American Physical Society 2024

A bstract: We establish a sum rule that connects fracture functions to nucleon energy-energy correlators (NEECs) in a one-to-one correspondence. Using this sum rule, we study the energy pattern in the target fragmentation region of deep inelastic scatterings. Through investigations up to twist-3, we express all eighteen energy-pattern structure functions in terms of associated NEECs, elucidating various azimuthal and spin asymmetries critical for nucleon tomography. Additionally, we investigate the perturbative matching of the twist-2 quark NEECs. We demonstrate that the Sivers-type and worm-gear-type quark NEECs match onto twist-3 multi-parton distributions. Our work provides a framework for examining energy-weighted observables through hadron production processes in the target fragmentation region, offering new insights into nucleon tomography.

We study one-loop contributions to semi-inclusive deep inelastic scattering in the target fragmentation region for a polarized lepton beam and nucleon target. Complete one-loop results at leading twist are derived, with a particular focus on the gluonic channel. It shows that four structure functions are generated uniquely by the gluon fracture functions starting at one-loop. Additionally, we obtain two structure functions associated with the longitudinal polarization of the virtual photon, and they are contributed by both gluon and quark channels. By combining existing twist-3 results, all eighteen structure functions for the studied process are predicted in terms of fracture functions convoluted with perturbative coefficient functions.

We present the complete results up to twist-3 for hadron production in the target fragmentation region of semi-inclusive deep inelastic scattering with a polarized lepton beam and polarized nucleon target. The nonperturbative effects are factorized into fracture functions. The calculation up to twist-3 is nontrivial since one has to keep gauge invariance. By applying collinear expansion, we show that the hadronic tensor can be expressed by gauge-invariant fracture functions. We also present the results for the structure functions and azimuthal asymmetries.

We present the complete results up to twist-3 for hadron production in the target fragmentation region of semi-inclusive deep inelastic scattering with a polarized lepton beam and polarized nucleon target. The nonperturbative effects are factorized into fracture functions. The calculation up to twist-3 is nontrivial since one has to keep gauge invariance. By applying collinear expansion, we show that the hadronic tensor can be expressed by gauge-invariant fracture functions. We also present the results for the structure functions and azimuthal asymmetries.

We study the factorization relations between quasi gluon GPDs and twist-2 GPDs. The perturbative coefficient functions are obtained at one-loop level. They are free from any collinear- or I.R. divergences. Unlike the case of the factorization of quasi quark GPDs at one-loop, we have to add ghost contributions for the factorization of quasi gluon GPDs in order to obtain gauge-invariant results. In general, operators will be mixed beyond tree-level. Our work shows that the mixing pattern of the nonlocal operators in quasi gluon GPDs is the same as those of local operators, i.e., the nonlocal operators considered are mixed with gauge-invariant operators, BRST-variation operators and operators involving EOM operator. The factorization relations are obtained for all quasi gluon GPDs. Taking the forward limit, we also obtain the relations between quasi gluon PDFs and twist-2 PDFs.