arXiv subjects

Hao-Lin Wang

Publications and source records attributed to Hao-Lin Wang.

At least 19 recordsLinked to original sources

arXiv2026

Backward Compton scattering with three vortex particles

We investigate backward Compton scattering in which an incident vortex (vx) photon collides head-on with a plane-wave (pw) electron and both final-state particles are projected onto vortex states, $\gamma_{\rm vx}+e^-_{\rm pw}\to\gamma_{\rm vx}+e^-_{\rm vx}$. We derive analytically the scattering amplitude and differential cross sections in the energy and cone angle of either final particle. Rotational symmetry implies a selection rule associated with the conservation of the total angular momentum along the collision axis. A Bessel-Gaussian wave packet is adopted for the incident photon to provide a physical normalization and regularize the boundary singularities of ideal Bessel states. We present numerical results for a $10~{\rm MeV}$ electron colliding with a vortex photon of central energy $1~{\rm MeV}$ or $10~{\rm keV}$. The final-photon distributions exhibit strong energy--angle correlations, topological-charge-dependent interference fringes, and systematic shifts of their dominant peaks, allowing different topological charge sectors to be enhanced through angular or energy post-selection. For a longitudinally polarized incident electron, the dominant channels favor final photons of matching helicity. For the $1~{\rm MeV}$ photon benchmark, the final electron can likewise be produced as a MeV-scale vortex state with a sizable cone angle and a large angular-momentum projection. These results demonstrate that triple-vortex backward Compton scattering offers a potential means of generating and controlling high-energy vortex photons and electrons.

hep-ph↗

arXiv2026

Light fermionic dark matter window in the scotogenic inverse seesaw model

The origin of neutrino mass and the nature of dark matter (DM) remain unresolved puzzles in particle physics, and an appealing possibility is to address both in a unified picture. This paper explores a light fermionic DM candidate within the scotogenic inverse seesaw model, which can simultaneously provide a mechanism for neutrino mass generation. By incorporating constraints from neutrino oscillation data, charged lepton flavor violating processes, invisible decays of the Higgs and $Z$ bosons, DM relic density, and direct detection of DM, we uncover a light fermionic DM window in the mass range $58\,{\rm GeV} \lesssim m_{\tt DM} \lesssim 63\,{\rm GeV}$ that can satisfy all of the aforementioned constraints. We find that this window can be jointly tested by next-generation ton-scale DM direct detection experiments including PandaX-xT and XENONnT, Higgs invisible decays, and future lepton colliders such as ILC.

hep-ph↗

arXiv2025

Nucleon decays into three leptons: Noncontact contributions

We investigate baryon number violating (BNV) nucleon decays into three leptons from noncontact contributions that are induced by dimension-6 (dim-6) BNV operators in low-energy effective field theory (LEFT) with an exchange of a baryon, meson, lepton, or photon field. We systematically classify all these processes that change lepton flavor by one unit and formulate their decay widths in terms of the dim-6 LEFT Wilson coefficients. By applying constraints on these Wilson coefficients derived from current experimental limits on BNV two-body nucleon decays, we obtain stringent bounds on the rates of these triple-lepton modes. These bounds vary significantly from one dim-6 operator to another under consideration. Our results for the $\Delta(B-L)=0$ modes differ by several orders of magnitude from previous phase-space estimates in the literature, thereby providing a more reliable assessment of their potential occurrence. In addition, we provide improved bounds on $\Delta(B+L)=0$ modes compared to the existing experimental limits.

hep-ph↗

arXiv2025

Three-dimensional trapping of circular Rydberg atoms by a superimposed vortex light beam

We propose to trap circular Rydberg atoms (CRAs) by a ponderomotive potential well formed with a superimposed vortex light beam. We calculate analytically the ponderomotive potential energy for a Bessel vortex light beam. We work out a corrected version of the classical circular orbit approximation for a CRA which fits the exact result much better than the usual approximation. We reveal the three-dimensional characteristics of the potential well for some benchmark values of the CRA principal quantum number and beam parameters such as the frequency, the opening angle and topological charge of the vortex. We investigate how we can achieve similar trapping effects for different principal quantum numbers by varying beam parameters. The potential provides a lattice structure in the beam axis where one CRA could be trapped at each lattice site.

physics.atom-ph↗

arXiv2025

Nucleon Energy Correlators as a Probe of Light-Quark Dipole Operators at the Electron-Ion Collider

We propose nucleon energy correlators (NECs) as a novel framework to probe electroweak light-quark dipole operators in deep inelastic scattering with an unpolarized nucleon. These operators encode chirality-flipping interactions, whose effects are usually quadratically suppressed in unpolarized cross sections. We construct a chiral-odd quark NEC that accesses quark transverse spin via azimuthal angle asymmetries in the energy flow of the target fragmentation region. These asymmetries serve as clean and powerful observables, enabling linear constraints on the quark dipole couplings. Unlike existing methods, our approach requires neither polarized nucleon beams nor final-state hadron identification, relying instead on fully inclusive calorimetric measurements. This work establishes one of the first applications of energy correlator observables to new physics searches and opens a promising direction for precision studies of chirality-flipping effects at electron-ion colliders.

hep-ph↗

arXiv2025

Comprehensive investigation on baryon number violating nucleon decays involving an axion-like particle

In this study, we systematically investigate baryon number violating (BNV) nucleon decays into an axion-like particle (ALP), within a low energy effective field theory extended with an ALP, which is referred to as aLEFT. Unlike previous studies in the literature, we consider contributions to nucleon decays from a complete set of dimension-eight BNV aLEFT operators involving light $u,\,d,$ and $s$ quarks. We perform the chiral irreducible representation (irrep) decomposition of these interactions under the QCD chiral group $\rm SU(3)_{\tt L}\times SU(3)_{\tt R}$, and match them onto the recently developed chiral framework to obtain nucleon-level effective interactions among the ALP, octet baryons, and octet pseudoscalar mesons. Within this framework, we derive general expressions for the decay widths of nucleon two- and three-body decays involving an ALP. Subsequently, we analyze momentum distributions for three-body modes and find that operators belonging to the newly identified chiral irreps $\pmb{6}_{\tt L(R)}\times \pmb{3}_{\tt R(L)}$ exhibit markedly different behavior compared to that in the usual irreps $\pmb{8}_{\tt L(R)}\times \pmb{1}_{\tt R(L)}$ and $\pmb{3}_{\tt L(R)}\times \bar{\pmb{3}}_{\tt R(L)}$. In addition, we reanalyze experimental data collected by Super-Kamiokande and establish bounds on the inverse decay widths of these new modes by properly accounting for experimental efficiencies and Cherenkov threshold effects because of the lack of direct constraints on those exotic decay modes. Our recasting constraints are several orders of magnitude more stringent than inclusive bounds used in the literature. Based on these improved bounds, we set conservative limits on associated effective scales across a broad range of ALP mass and predict stringent bounds on certain neutron and hyperon decays involving an ALP.

hep-ph↗

arXiv2025

Chiral perturbation theory for baryon-number-violating nucleon decay into a vector meson

In a recent work [New chiral structures for baryon number violating nucleon decays, arXiv:2504.14855], we identified generic baryon-number-violating (BNV) structures containing triple light quarks and achieved their leading-order chiral realizations involving octet pseudoscalars and baryons. Although many two-body nucleon decays into a vector meson have been experimentally searched for and stringently constrained, a consistent theoretical framework for their calculation is still lacking. In this Letter, we fill the gap by implementing chiral matching of all these triple-quark interactions onto hadronic interactions involving octet vector mesons, baryons, and pseudoscalars. This paves the way for a consistent and comprehensive study of all relevant BNV processes. As an illustration of application, we show how degeneracy in the parameter space of Wilson coefficients can be broken by synthesizing experimental constraints on nucleon decays into a vector or pseudoscalar meson when relevant hadronic low-energy constants can be reasonably determined.

hep-ph↗

arXiv2025

RGE solver for the complete dim-7 SMEFT interactions and its application to $0\nu\beta\beta$ decay

We present an automatic renormalization group equations (RGEs) solver, D7RGESolver, designed for the precise numerical solution of one-loop RGEs of dimension-7 (dim-7) operators within the standard model effective field theory (SMEFT). This tool is capable of calculating the RGE effects of dim-5 and dim-7 SMEFT operators between any two scales above the electroweak scale. We take the nuclear neutrinoless double beta ($0\nu\beta\beta$) decay process as an example to appreciate the importance of the running effects in phenomenological studies. Our analysis demonstrates that $0\nu\beta\beta$ decay can constrain nearly all dim-7 SMEFT operators involving first-generation leptons that violate lepton number by two units, after accounting for RGE effects. Specifically, we have placed meaningful constraints on 55 dim-7 Wilson coefficients, compared to only 10 from a simple tree-level analysis. Certain operators exhibit much stricter constraints when RGE effects are included, especially for the operators that mix with neutrino mass operators. We provide a complete code documentation for D7RGESolver, along with examples of its usage and interfacing with external automated codes for calculating $0\nu\beta\beta$ decay. The D7RGESolver code is available at: \href{https://github.com/ZhaoXiang210/D7RGESolver}{Github: D7RGESolver}

hep-ph↗

arXiv2025

New chiral structures for baryon number violating nucleon decays

We examine the most general nucleon decay interactions that involve three light quarks without being acted upon by a derivative. We identify four generic operator structures that correspond to the irreducible representations in the chiral group ${\rm SU(3)}_{\tt L}\otimes {\rm SU(3)}_{\tt R}$ of QCD, \{$\pmb{8}_{\tt L}\otimes \pmb{1}_{\tt R}$, $\bar{\pmb{3}}_{\tt L}\otimes \pmb{3}_{\tt R}$, $\pmb{6}_{\tt L}\otimes \pmb{3}_{\tt R}$, $\pmb{10}_{\tt L}\otimes \pmb{1}_{\tt R}$\}, plus their chirality partners under the interchange of chiralities ${\tt L}\leftrightarrow {\tt R}$. While half of them have been extensively discussed in the literature, the other half, $\pmb{6}_{\tt L(R)}\otimes \pmb{3}_{\tt R(L)}$ and $\bar{\pmb{10}}_{\tt L(R)}\otimes \pmb{1}_{\tt R(L)}$, are identified for the first time. We perform chiral matching for these interactions at the leading chiral order and find that each has a unique chiral realization in terms of the octet baryons and pseudoscalars. Notably, the chiral interaction in the $\pmb{6}_{\tt L(R)}\otimes \pmb{3}_{\tt R(L)}$ representation appears at the same chiral order as those of the known ones, while the one in the $\pmb{10}_{\tt L(R)}\otimes \pmb{1}_{\tt R(L)}$ representation appears at a higher chiral order. These new structures are prevalent in effective field theories and ultraviolet models, and they offer novel experimental avenues to search for baryon number violating nucleon decays.

hep-ph↗

arXiv2025

A systematic investigation on vector dark matter-nucleus scattering in effective field theories

In this paper, we systematically investigate the general spin-one dark matter-nucleus interactions within the framework of effective field theories (EFT). We consider both the nonrelativistic (NR) and the relativistic EFT descriptions of the DM interactions with nucleons and quarks. In the NREFT framework, we present a complete list of NR operators for spin-one DM coupling to nucleons and compute their contributions to the DM response functions. Next, we consider all possible leading-order relativistic EFT operators between DM and light quarks and the photon, and perform NR reductions to match them onto the NREFT. We then derive the nuclear scattering rate from these interactions, and employ recent DM direct detection data (from both the nuclear recoil and the Migdal effect) to constrain all these EFT operators and DM electromagnetic properties. We find the elastic nuclear recoil data (from PandaX-4T, XENONnT, LZ, and DarkSide-50) set stringent bounds on the EFT coefficients for a DM mass above a few GeV while the Migdal effect datasets (from PandaX-4T, XENONnT, and DarkSide-50) can probe the DM mass region as small as 20 MeV. Lastly, we construct a UV complete model that can provide a complex spin-one DM candidate, and at the same time generate DM-quark/photon operators discussed in this work.

hep-ph↗

arXiv2024

Baryon number violating hydrogen decay

Most studies on baryon number violating (BNV) processes in the literature focus on free or bound nucleons in nuclei, with limited attention given to the decay of bound atoms. Given that hydrogen is the most abundant atom in the universe, it is particularly intriguing to investigate the decay of hydrogen atom as a means to probe BNV interactions. In this study, for the first time, we employ a robust effective field theory (EFT) approach to estimate the decay widths of two-body decays of hydrogen atom into standard model particles, by utilizing the constraints on the EFT cutoff scale derived from conventional nucleon decay processes. We integrate low energy effective field theory (LEFT), chiral perturbation theory (ChPT), and standard model effective field theory (SMEFT) to formulate the decay widths in terms of the LEFT and SMEFT Wilson coefficients (WCs), respectively. By applying the bounds on the WCs from conventional nucleon decays, we provide a conservative estimate on hydrogen BNV decays. Our findings indicate that the bounds on the inverse partial widths of all dominant two-body decays exceed $10^{44}$ years. Among these modes, the least constrained diphoton decay $\Hy\to \gamma\gamma$ might be astrophysically interesting, although the monochromatic photon signal from our Sun is difficult to detect with current near-Earth telescopes.

hep-ph↗

arXiv2024

Probing dimension-8 SMEFT operators through neutral meson mixing

We investigate the impact of effective interactions of dimension-8 (dim-8) operators in the standard model effective field theory (SMEFT) on neutral meson mixing, focusing on the $K^0-\bar K^0$, $B_{d,s}-\bar B_{d,s}$, and $D^0-\bar D^0$ systems. Within the framework of the low energy effective field theory (LEFT), each system is governed by eight dim-6 operators, with four originating at tree level from dim-6 SMEFT operators and the other four from dim-8 SMEFT operators. Notably, in certain UV complete models those dim-8 operators instead of the dim-6 ones are generated at the leading order. Our analysis focuses on those dim-8 operators and includes their one-loop QCD renormalization group running effects. By leveraging the LEFT master formula we impose stringent constraints on the effective scales associated with these dim-8 operators. We find that neutral meson mixing can probe an effective scale up to 80 TeV for some operators, surpassing the constraints imposed on other dim-8 operators by other observables. Lastly, we present a UV complete model capable of generating dim-8 operators at the leading order, thus offering a unique perspective on the interplay between different operator dimensions in probing new physics phenomena.

hep-ph↗

arXiv2024

Comprehensive constraints on fermionic dark matter-quark tensor interactions in direct detection experiments

Effective field theory (EFT) provides a model-independent framework for interpreting the results of dark matter (DM) direct detection experiments. In this study, we demonstrate that the two fermionic DM-quark tensor operators, $(\barχ iσ^{μν} γ^5 χ) (\bar{q} σ_{μν}q)$ and $(\barχ σ^{μν} χ) (\bar{q} σ_{μν} q)$, can contribute to the DM electric and magnetic dipole moments via nonperturbative QCD effects, in addition to the well-studied contact DM-nucleon operators. We then investigate the constraints on these two operators by considering both the contact and the dipole contributions using the XENON1T nuclear recoil and Migdal effect data. We also recast other existing bounds on the DM dipole operators, derived from electron and nuclear recoil measurements in various direct detection experiments, as constraints on the two tensor operators. For $m_χ\lesssim 1\,\rm GeV$, our results significantly extend the reach of constraints on the DM-quark tensor operators to masses as low as $5\,\rm MeV$, with the bound exceeding that obtained by the Migdal effect with only contact interactions by an order of magnitude or so. In particular, for the operator $(\barχ σ^{μν}iγ_5 χ) (\bar{q} σ_{μν}q)$ with DM mass $m_χ\gtrsim 10\,\rm GeV$, the latest PandaX constraint on the DM electric dipole moment puts more stringent bounds than the previous direct detection limit.

hep-ph↗

arXiv2024

A systematic investigation on dark matter-electron scattering in effective field theories

In this paper, we systematically investigate the general dark matter-electron interactions within the framework of effective field theories (EFT). We consider both the non-relativistic (NR) EFT and the relativistic EFT descriptions of the interactions with the spin of dark matter (DM) up to one, i.e., the scalar ($ϕ$), fermion ($χ$), and vector $(X)$ DM scenarios. We first collect the leading-order NR EFT operators describing the DM-electron interactions, and construct especially the NR operators for the vector DM case. Next, we consider all possible leading-order relativistic EFT operators including those with a photon field and perform the NR reduction to match them onto the NR EFT. Then we rederive the DM-bound-electron scattering rate within the NR EFT framework and find that the matrix element squared, which is the key input that encodes the DM and atomic information, can be compactly decomposed into three terms. Each term is a product of a DM response function $(a_{0,1,2})$, which is essentially a factor of Wilson coefficients squared, and its corresponding generalized atomic response function ($\widetilde W_{0,1,2}$). Lastly, we employ the electron recoil data from the DM direct detection experiments (including XENON10, XENON1T, and PandaX-4T) to constrain all the non-relativistic and relativistic operators in all three DM scenarios. We set strong bounds on the DM-electron interactions in the sub-GeV region. Particularly, we find that the latest PandaX-4T S2-only data provide stringent constraints on dark matter with a mass greater than approximately 20 MeV, surpassing those from the previous XENON10 and XENON1T experiments.

hep-ph↗

arXiv2024

Revisiting general dark matter-bound-electron interactions

In this Letter we revisit general dark matter (DM)-bound-electron interactions studied previously in the influential work [R. Catena {\it et al.,} Atomic responses to general dark matter-electron interactions, Phys. Rev. Res. 2, 033195 (2020)] For the most general DM-electron nonrelativistic or relativistic interactions for DM with spin up to 1, we find the average ionization matrix element squared can be organized into three terms, each of which is a product of a DM response function ($a_{0,1,2}$) and a linear combination ($\widetilde W_{0,1,2}$) of the four atomic response functions ($W_{1,2,3,4}$) given in that work, $ \widetilde W_0 = W_1, \, \widetilde W_1 = |\pmb{v}_0^\perp|^2 W_1 - 2 {m_e\, \pmb{q}\cdot \pmb{v}_0^\perp \over \pmb{q}^2} W_2 + W_3,\, \widetilde W_2 = { (\pmb{q}\cdot \pmb{v}_0^\perp)^2 \over \pmb{q}^2} W_1 - 2 {m_e\, \pmb{q}\cdot \pmb{v}_0^\perp \over \pmb{q}^2} W_2 + {m_e^2 \over \pmb{q}^2}W_4$. Furthermore, we find a crucial minus sign was missed for the calculation of $W_2$ in that work, which has significant phenomenological consequences when explaining experimental bounds on specific DM scenarios. Due to the corrected sign, there can be significant cancellations between the $W_2$ and $W_{3,4}$ terms, so that $\widetilde W_{1,2}$ are dominated by the usual response function $W_1$ in some cases. Many DM scenarios involving DM or electron axial-vector current can yield $W_2$ and thus are potentially affected by the sign. As an example, we show that the recent XENON1T constraint on the fermionic DM anapole moment is weakened by a factor of 2 or so. We also present a complete list of NR operators for spin-1 DM and compute their contributions to the DM response functions.

hep-ph↗

arXiv2024

Probing the four-fermion operators via the transverse double spin asymmetry at the Electron-Ion Collider

The chirality-flipping operators of light fermions are currently poorly constrained by experimental analyses due to the lack of interference with Standard Model (SM) amplitudes in traditional observables. In this work, we propose to investigate the semi-leptonic scalar/tensor four-fermion operators of electron and quarks through the transverse double spin asymmetry (DSA) at Electron-Ion Collider, where both the electron and proton beams could be highly transversely polarized. Due to the chirality-flipping nature of these operators, we demonstrate that their interference with the SM results in an unsuppressed contribution to the DSA, and could lead to non-trivial azimuthal $\cos2ϕ$ and $\sin2ϕ$ distributions that are linearly dependent on their Wilson coefficients. This new method has the potential to significantly improve the current constraints on these scalar/tensor four-fermion operators without relying on theoretical assumptions about other types of new physics effects, particularly for the tensor type operator of the $u$-quark. Additionally, our findings indicate that both the real and imaginary parts of these operators can be simultaneously constrained and offer a new opportunity for probing potential $CP$-violation effects. However, it is important to note that these results would be sensitive to the quark transversity distributions, which are currently poorly constrained by the experimental data, but could be significantly improved at the upcoming Electron-Ion Collider. Therefore, our work opens up a new avenue to utilize this new spin asymmetry for exploring the new physics effects from the scalar/tensor four-fermion operators.

hep-ph↗

arXiv2023

Dark Sector Effective Field Theory

We introduce the effective field theory of two different light dark particles interacting with the standard model (SM) light states in a single vertex, termed dark sector effective field theory (DSEFT). We focus on the new light particles with spin up to 1 and being real in essence, namely, new real scalars $ϕ$ and $S$, Majorana fermions $χ$ and $ψ$, and real vectors $X_μ$ and $V_μ$. In the framework of low energy effective field theory with QED and QCD symmetry, the DSEFT can be classified into six categories, including the scalar-scalar-SM ($ϕS$-SM), fermion-fermion-SM ($χψ$-SM), vector-vector-SM ($X V$-SM), scalar-fermion-SM ($ϕχ$-SM), scalar-vector-SM ($ϕX$-SM), and fermion-vector-SM ($χX$-SM) cases. For each case, we construct the effective operator basis up to canonical dimension 7, which will cover most interesting phenomenology at low energy. As a phenomenological example, we investigate the longstanding neutron lifetime anomaly through the neutron dark decay modes $n \to χϕ\text{ or } χX$ from the effective interactions in the fermion-scalar-SM or fermion-vector-SM case. When treating the light fermion as a dark matter candidate, we also explore the constraints from DM-neutron annihilation signal at Super-Kamiokande. We find the neutron dark decay in each scenario can accommodate the anomaly, at the same time, without contradicting with the Super-Kamiokande limit.

hep-ph↗

arXiv2021

Effective field theory approach to lepton number violating $τ$ decays

We continue our endeavor to investigate lepton number violating (LNV) processes at low energy in the framework of effective field theory (EFT). In this work we study the LNV tau decays $τ^+\rightarrow \ell^-P_i^{+}P_j^{+}$, where $\ell=e,~μ$ and $P^+_{i,j}$ are the lowest-lying charged pseudoscalars $π^+,~K^+$. We analyze the dominant contributions in a series of EFTs from high to low energy scales, namely, the standard model effective field theory (SMEFT), the low-energy effective field theory (LEFT), and the chiral perturbation theory ($χ$PT). The decay branching ratios are expressed in terms of the Wilson coefficients of dimension-five and -seven operators in SMEFT and hadronic low energy constants. These Wilson coefficients involve the first and second generations of quarks and all generations of leptons and thus cannot be explored in low energy processes such as nuclear neutrinoless double decay or LNV kaon decays. Unfortunately, the current experimental upper limits on the branching ratios are too weak to set useful constraints on those coefficients. Or, if we assume the new physics scale is larger than 1 TeV, the branching ratios are well below the current experimental bounds. We also estimate hadronic uncertainties incurred in applying $χ$PT to $τ$ decays by computing one-loop chiral logarithms and attempt to improve convergence of chiral perturbation by employing dispersion relations in the short-distance part of the decay amplitudes.

hep-ph↗