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Jia-Jun Wu

Publications and source records attributed to Jia-Jun Wu.

At least 19 recordsLinked to original sources

Can a minimal radiative seesaw explain the LZ 248 keV event?

We interpret the recently reported 248~keV nuclear recoil event in the LUX-ZEPLIN (LZ) experiment via inelastic dark matter scattering within the minimal Scotogenic model. A sub-MeV mass splitting between neutral inert scalars suppresses low-energy scattering while permitting signals from the high-velocity halo tail. Crucially, co-annihilation with nearly degenerate right-handed fermions accommodates the thermal relic density for dark matter masses up to $\sim {\cal O} (1)$~TeV, extending the viable range significantly beyond the pure inert doublet model limit while evading direct detection bounds. However, to resolve the severe tension with IceCube neutrino limits on solar capture, we extend this minimal framework by introducing a hidden $U(1)_X$ gauge symmetry that naturally leads us to tiny $λ_5$ coupling at the one-loop level. This realizes an isospin-violating scenario that suppresses dark matter capture in the Sun while preserving the coherent scattering signal in the Xenon-based LZ detector. We numerically verify that this extended framework naturally generates neutrino masses and satisfies constraints from Big Bang Nucleosynthesis and indirect detection, providing a robust and testable solution to the LZ anomaly.

hep-ph

Charmed baryon semileptonic decays in a relativistic three-quark model

We study the spin-$1/2\to1/2$ semileptonic decays of singly charmed baryons ($Λ_c^+$, $Ξ_c^{0,+}$, and $Ω_c^0$) into the light baryon octet within a relativistic three-quark model. The constituent quark masses and spatial wave functions are determined by the baryon mass spectrum. For the physical $Ξ_c$ states, the light flavor $\mathrm{SU}(3)$ breaking ($m_s > m_{u,d}$) naturally induces a coherent mixing between the flavor antitriplet and flavor sextet configurations, which is completely fixed by the mass eigenstates. Consequently, no adjustable parameters are introduced in calculating the weak transition amplitudes. Using these wave functions, we calculate the $c\to s,d$ helicity amplitudes with the Bakamjian--Thomas boost, including the spatial Jacobian and the Wigner rotations of the constituent spins. The branching fractions, $q^2$ distributions, longitudinal polarizations, and form factors are then obtained from these amplitudes. For the $Λ_c^+\toΛ\ell^+ν_\ell$ and $Λ_c^+\to n\ell^+ν_\ell$ modes, our branching fractions and form factors are in good agreement with the experimental data and Lattice QCD results. For $Ξ_c^0\toΞ^-e^+ν_e$, we obtain branch ratio $\mathcal B_{\ell} \simeq 4.0~\%$, which is consistent with recent Lattice QCD calculations but lies well above the current experimental average. Clarifying the origin of this discrepancy calls for further dedicated efforts from both experimental and theoretical sides. For the $Ω_c^0\toΞ^-\ell^+ν_\ell$ decay, the spin-$1$ $ss$ spectator yields a positive longitudinal polarization of the final $Ξ^-$, in contrast to the negative polarizations in the predominantly antitriplet decay modes. Our predictions for the $q^2$ spectra, angular asymmetries, and final baryon polarizations may provide useful references for future measurements of singly charmed baryon semileptonic decays.

hep-ph

Unified study of hyperon semileptonic decays in a relativistic three-quark model

We present a unified theoretical study of semileptonic decays of ground state octet hyperons using the relativistic three-quark model (R3QM). A key innovation of our approach is that all baryon wave functions are determined by fitting the baryon mass spectrum with a semirelativistic potential model, leading to predictions for weak transition amplitudes without free parameters. Adopting these wave functions, we calculate the decay widths, branching fractions, lepton flavor universality ratios, as well as the angular correlation and spin asymmetry parameters for the octet channels. The calculated values agree with the available experimental data and give predictions for channels with limited experimental information. We further compute the complete set of octet transition form factors without any additional free parameters, so that the weak current can be examined beyond the rate observables. In the well measured $Λ\to p \ell^-\barν_\ell$ channel, the calculated leading vector and axial-vector form factors, $f_1(0)$ and $g_1(0)$, agree well with recent lattice QCD results, and the $g_1/f_1$ ratio is consistent with recent BESIII measurements. Beyond the leading vector and axial-vector terms, the complete form factor set separates the weak magnetism, second class, and the pole contribution associated with the partially conserved axial current (PCAC) relation. The weak magnetism term $f_2$ shows the clearest channel dependence compared with lattice QCD results, and its smaller values in some channels may point to transverse current strength not fully saturated by pure $qqq$ valence components. This work provides a framework for connecting octet hyperon weak form factors to the spin--flavor and spatial structure of baryons at the quark level, and gives testable weak current observables for future hyperon semileptonic decay measurements.

hep-ph

First Evidence for an Unambiguous Triangle Singularity from $ψ(2S) \to p\bar{p}η$

Triangle singularities, predicted by Landau in 1959, are purely kinematic enhancements arising from hadronic rescattering loops. Despite their proposed role in various anomalous decay processes and exotic hadron candidates, a direct experimental confirmation has remained elusive for more than six decades. We analyze the $pη/\bar{p}η$ invariant mass spectrum in $ψ(2S) \to p\bar{p}η$ measured by the BESIII Collaboration. The data exhibit a clear cusp-like structure around 1.564~GeV in the $N(1535)$ region, in precise agreement with the kinematic position predicted for the triangle singularity. Including the triangle singularity loop in the fit substantially improves the description of the data, with $χ^2/\mathrm{d.o.f.}$ decreasing from 1.22 to 0.90, corresponding to a significance of $\sim 3.8σ$ for the triangle singularity contribution. The precise alignment of the observed excess with the predicted kinematic position provides the first compelling evidence for the triangle singularity effect.

hep-ph

Two-nucleon systems at $m_π\approx292$ MeV from lattice QCD

Nucleon-nucleon systems in the $^3S_1$ and the $^1S_0$ channels are studied in lattice quantum chromodynamics at a pion mass of approximately $m_π\approx292$ MeV, employing three $N_f = 2+1$ ensembles with the same pion mass and lattice spacing $a=0.10530(18)$ fm but different spatial volumes. Finite-volume energies of the nucleon-nucleon systems are determined in both the rest frame and a moving frame. The distillation quark smearing method is applied to improve the precision and to ensure the symmetric correlators by using the same interpolating operators at sink and source. The scattering amplitudes are extracted from the finite-volume spectra using the Lüscher's finite-volume method. At the studied pion mass, both the $^3S_1$ (deuteron) and $^1S_0$(di-neutron) channels exhibit a virtual state pole, with binding energies of $6^{+5}_{-3}$ MeV and $11^{+6}_{-5}$ MeV, respectively. To investigate the effects of the left-hand cut, an alternative method -- the Non-Perturbative Hamiltonian framework (NPHF) -- is used for the scattering analysis and yields consistent results with those from the Lüscher method.

hep-lat

Low-energy $DD$ scattering in lattice QCD

We present the first lattice QCD calculation of single-channel $DD$ scattering with quantum numbers $I(J^P)=1(0^+)$ and $0(1^-)$. The calculation is performed on the $2+1$ flavor Wilson-Clover ensembles with a lattice spacing $a\simeq 0.077$ fm and two different pion masses, $m_π\simeq207$ and $305$ MeV. The scattering parameters are determined using the Lüscher's finite volume method. Our results indicate a weak repulsive interaction in the $1(0^+)$ channel and a slightly attractive interaction in the $0(1^-)$ channel. The $S$-wave isovector $DD$ scattering length and effective range, extrapolated to the physical pion mass, are $(-0.25\pm0.08\pm 0.12)$ fm and $(-5.7\pm4.5\pm 1.7)$ fm, respectively.

hep-lat

How to understand the $ρ$ resonance from the quark model and $ππ$ $P$-wave phase shift

As the lightest isovector vector meson, the $ρ$ meson is an important object for investigating the structure of resonant states in strong interactions. Owing to its strong coupling to the $ππ$ channel and its large decay width, the conventional constituent quark model treatment, in which it is simply regarded as a pure $q\bar q$ bound state while the hadronic-channel coupling effects are neglected, is insufficient to fully characterize its physical properties. To this end, in the present work we establish a unified framework for studying the structure and resonant properties of the $ρ$ meson by combining the quark-gluon and hadronic degrees of freedom. At the quark-gluon level, we first determine the parameters of the chiral quark model by refitting a set of narrow mesons for which open Okubo-Zweig-Iizuka-allowed strong-decay channels are absent or strongly suppressed. With these parameters fixed, the bare mass of the $ρ$ meson is obtained and used as the input for the subsequent hadronic-level analysis. At the hadronic level, based on inverse-scattering theory, we construct a model including the coupling between the bare state and the $ππ$ continuum, extract the $ρ_0-ππ$ interaction using the $P$-wave $ππ$ scattering phase-shift data, and further calculate the width of the $ρ$ meson as well as the bare-state component in the physical state. The present work also provides a generalizable analytical framework for further studies of other hadronic resonances with significant coupled-channel effects.

hep-ph

A Paradigm for the Coupled-Channel Origin of Resonances: the Exotic $T_{c\bar{s}}$ in $D_{s1}(2460/2536)\to D_sππ$

The $T_{c\bar{s}}$ state observed in the decay $D_{s1}(2460)^+ \to D_s^+π^+π^-$ provides direct evidence for an isovector open-charm tetraquark state with strangeness--a discovery that demands a systematic framework connecting its origin to the nature of the parent $D_{s1}$. We successfully achieve this connection by two mechanisms, triangle loops and the coupled channel of $DK$-$D_sπ$ with pure off-diagonal potentials. We first point out the behavior of propagator of $D_sπ$ will influence the effective potential of $DK\to DK$, then we can successfully obtain the pole of $T_{c\bar{s}}$ on the second Reimann Sheet. By combing with the $ππ$-$KK$ rescattering, not only the two-peak structure in $D_{s1}(2460)$ decay is well reproduced, but also a single-peak structure is predicted in $D_{s1}(2536)$ decay. The marked difference, testable at LHCb and Belle II, is driven by the $S$-wave versus $D$-wave nature of their $D^*K$ couplings, revealing the underlying structural distinction between the two $D_{s1}$ states. By directly linking hadronic structure to decay patterns, this work provides a template for deciphering the nature of such exotic states. More broadly, by revealing how non-perturbative coupled-channel effects manifest in exotic hadrons, our analysis connects to a universal mechanism shared by systems ranging from halo nuclei to atomic Feshbach resonances, offering a unified perspective across these fields.

hep-ph

Subtraction of infrared divergences in light-quark QCD sum rules

In QCD sum rules for light-quark systems, infrared (IR) divergences can appear in the Wilson coefficients of certain condensates. These divergences manifest explicitly in the coordinate-space expressions of the light-quark propagators. We propose an improved method to eliminate these IR divergences at the propagator level and present a subtraction formula that implements this procedure. Compared to the existing methods that rely on the mixing between quark and gluon condensates of the same dimension to eliminate IR divergences, this method is more intuitive and easier to apply in practical QCD sum rule calculations.

hep-ph

Study of the $Ω_{ccc}Ω_{ccc}$ and $Ω_{bbb}Ω_{bbb}$ dibaryons in QCD Sum Rules

The recent observation of a family of fully-charm tetraquark states by the LHCb, ATLAS and CMS Collaborations suggests the possible existence of fully-heavy dibaryons. In this work, we investigate the $Ω_{ccc}Ω_{ccc}$ and $Ω_{bbb}Ω_{bbb}$ dibaryons in both the $^1S_0$ and $^5S_2$ channels using the method of QCD sum rules. We employ the iterative dispersion relation (IDR) method to efficiently compute the massive five-loop banana diagrams that appear in these systems, and properly address the tricky small-circle divergence problem in the nonperturbative terms. Our analyses reveal that for both charm and bottom systems, the scalar dibaryon lies lower than its tensor counterpart. In $\overline{\text{MS}}$ scheme, the mass of the scalar $Ω_{ccc}Ω_{ccc}$ dibaryon is found to be slightly above the $2Ω_{ccc}$ mass threshold, while the $Ω_{bbb}Ω_{bbb}$ systems may form bound states. However, they are predicted to be much heavier in the on-shell scheme.

hep-ph

Unveiling the elusive $Σ(1380)$ resonance through coupled-channel dynamics in $Λ_c^+\toηπ^+Λ$ reaction

We investigate the $Λ_c^+ \to ηπ^+ Λ$ decay measured by the Belle and BESIII Collaborations, focusing on the possible role of the $Σ(1380)$ state with spin-parity $J^P=1/2^-$. In our theoretical framework, the $Λ(1670)$ and $a_0(980)$ are dynamically generated from meson-baryon and meson-meson final-state interactions, respectively, and the corresponding line shapes of these two states used here are applicable to all relevant hadronic reactions. Furthermore, the contributions from the intermediate $Σ(1385)$ resonance and the possible $Σ(1380)$ state are included explicitly. By comparing the invariant mass and angular distributions obtained with and without the $Σ(1380)$ state, we demonstrate that this state plays an important role in improving the description of the experimental data. We also identify the kinematic regions most sensitive to the possible $Σ(1380)$ contribution. Future high-precision measurements of this process will be instrumental for testing the existence of the $Σ$ state with $J^P=1/2^-$.

hep-ph

Systematic Study of Coupled-Channel Dynamics in Doubly Heavy Hadronic Molecules

Heavy Quark Spin Symmetry (HQSS) is widely use to predict heavy molecules by extending the effective interactions fitted from low-lying states to heavier sectors. In this work, we systematically investigate the reliability of this approach for higher double heavy tetraquarks by comparing a single-channel effective interaction (Scheme I) with an explicit coupled-channel dynamics framework (Scheme II). The interactions are obtained within one-boson-exchange potential model and fixed by fitting the $T_{cc}^+$ lineshape. Utilizing the complex scaling method and $T$-matrix pole analysis, we extract the possible poles in the $S$-wave $D^{(*)}D^{(*)}$, $\bar{B}^{(*)}\bar{B}^{(*)}$ and $D^{(*)}\bar{B}^{(*)}$ systems with $J^{P}=1^+$. We find that both schemes provide consistent descriptions of the lowest-lying state. This confirms isoscalar-dominated $T_{cc}$ as a predominant $DD^*$ molecule (binding energy $\sim$ 381 keV), and predicts an isoscalar deeply bound $T_{bb}$ state ($40-60$ MeV) and an isovector $T^\prime_{bb}$ resonance in the bottom sector, together with a virtual $T_{bc}$ state. In contrast, significant differences emerge for higher-lying states. The inclusion of explicit coupled-channel dynamics modifies the effective interaction and reshapes the pole structure. The states predicted as bound or resonant in the single-channel framework can be shifted far from the physical region or disappear. These results indicate that while single-channel descriptions are adequate for near-threshold states, an explicit treatment of coupled-channel dynamics is required for reliable predictions of excited doubly heavy tetraquarks.

hep-ph

A possible $Σ^*$ or $Λ^*$ resonance with $J^P=3/2^-$ in $K^-p\to KΞ$ scattering

We analyze the $K^-p\to K^+Ξ^-$ and $K^-p\to K^0Ξ^0$ processes in the energy region $1.8<\sqrt{s}<2.8$ GeV within an effective Lagrangian approach. The $Λ(1800)$ and $Σ(2250)$ resonances, along with the ground states $Σ$ and $Λ$, are included. Additionally, a possible $J^P=3/2^-$ $Σ^*$ or $Λ^*$ resonance with a mass around 1.9 GeV and a width of approximately 200 MeV is introduced to describe the structure at 2.0 GeV in the total cross section and reproducing the threshold behavior. The two possible solutions corresponding to $Σ^*(3/2^-)$ and $Λ^*(3/2^-)$ cannot be distinguished by the existing data. Predictions for the polarization of the final-state $Ξ$ and the cross section of $K^-n \to K^0Ξ^-$ are compared with the experimental data, we find that the results of solution-II with $Λ^*(3/2^-)$ are much better. We also discuss the possible interpretations of the introduced $3/2^-$ hyperon as a pentaquark candidate, e.g. an $S$-wave $KΞ(1530)$ hadronic molecule. However, since the polarization data suffer from rather large uncertainties, more data inputs are needed in future experiments, for example, J-PARC, HIAF and JLab.

hep-ph

Higher excited charmed and charmed-strange mesons in an unquenched quark model

In this paper, as a continuation of our previous work, we systematically study the mass spectra and OZI-allowed strong decays of the higher $3S$-, $2P$-, $2D$-, and $1F$-wave charmed and charmed-strange mesons within a unified unquenched quark model. It is found that for most of the higher excitations, the masses are significantly shifted down by the coupled-channel effects. The newly observed $D_{s1}(2933)^+$ reported by the LHCb collaboration could be identified as the low-mass axial-vector state $D_s(2P_1)$ via the $2^1P_1-2^3P_1$ mixing. For the broad structure $D_{sJ}(3040)^+$ observed earlier by the \emph{BABAR} collaboration, the $D_s(3^1S_0)$ assignment seems to be favored over the high-mass mixed state $D_s(2P_1^\prime)$. Meanwhile, the $D(3000)^0$ signals observed at LHCb cannot be well understood with any $3S$, $2P$, $2D$, or $1F$ assignments in the $D$-meson family. Our predicted masses and decay properties of the missing higher $D$ and $D_s$ mesons may provide useful information for future experimental searches.

hep-ph

Lattice QCD study of the $K^*(892)$ resonance at the physical point

We present a lattice QCD study of the $K^*(892)$ resonance using eight $N_f=2+1$ Wilson-Clover ensembles with three lattice spacings and six pion masses ranging from 135 to 320 MeV. For each ensemble, a large number of finite volume energy levels in the $P$-wave $Kπ$ channel are determined. The energy dependence of the scattering phase shift is then obtained from Lüscher's finite-volume method. To systematically assess parametrization dependence, the amplitude is described using three different models, which yield consistent results. The resulting phase shifts show a clear resonant behavior for all ensembles, and the corresponding $K^*(892)$ resonance pole is identified on the second Riemann sheet in the complex energy plane. The pole positions are extrapolated to the physical pion mass and the continuum limit, yielding a $K^*(892)$ resonance located at $\sqrt{s_0} = [883(22)-i20(13)]\mathrm{MeV}$, which is in excellent agreement with the experimental value. This study provides a first-principles QCD determination of the $K^*(892)$ mass and width with controlled systematic uncertainties.

hep-lat

Form factors of the $ρ$ meson from effective field theory and the lattice

The calculation of resonance form factors in effective field theory as well as on the lattice is a highly challenging task. In a recent paper, we proposed a novel method based on the introduction of a background field and the Feynman-Hellmann theorem to address the problem, and applied it to a toy model. In the present work we use this method for the electromagnetic form factors of the $ρ$-meson. By matching the results to Chiral Perturbation Theory, we provide a first, crude estimate of all three form factors of the $ρ$-meson within the effective field theory. Contact contributions to these form factors turn out to be substantial. A procedure for lattice calculations is outlined, paving the way for an ab initio approach to the problem.

hep-lat

Dynamical Determination of the Cut-off Scale in Loop-Induced Neutrino Mass Models with Non-Invertible Symmetry

We propose our framework as an effective field theory valid below the cut-off scale $Λ$, in which we explain the tiny scale of neutrino masses by integrating a non-invertible symmetry with the dynamical determination of the cut-off scale. In our model, we introduce three families of SU(2)$_L$ quintet fermions ($Σ_R$) and a quartet scalar ($ϕ_4$), both of which are charged under the Fibonacci fusion rule (FFR). A central feature of this construction is that the vacuum expectation value (VEV) $v_4$ of $ϕ_4$ is induced at the one-loop level via dynamical symmetry breaking. To resolve the inherent arbitrariness of the cut-off scale $Λ$ in loop-induced VEV models, we identify $Λ$ with the scale at which the SU(2)$_L$ gauge coupling $g_2$ encounters the renormalization group evolution (RGE) of $g_2$, naturally fixing the physical cut-off within the range of approximately $10^5$ to $10^7$ GeV. Quantitatively, this framework yields $v_4\sim 0.07-0.1$ GeV, which in turn leads to neutrino Yukawa couplings on the order of $10^{-3}$. This result provides a significantly more natural explanation for the neutrino mass hierarchy compared to standard seesaw models, which typically require couplings as small as $10^{-6}$ or less. Notably, our approach maintains a relatively simple particle content and does not necessitate additional (gauge) bosons for symmetry breaking.

hep-ph

General Hamiltonian Approach to the $\mathbf{N}$-Body Finite-Volume Formalism: Extracting the $\mathbfω$ Resonance Parameters from Lattice QCD

We present a nonperturbative Hamiltonian framework (NPHF) to address the general $N$-body problem. This framework rigorously connects finite-volume spectra from lattice QCD to scattering observables from experiment. To demonstrate its applicability, we extract the resonance parameters of the $ω$ meson by simultaneously analyzing the isoscalar $3π$ and isovector $2π$ systems. The Hamiltonian unifies single-particle $ω$, two-particle $ρπ$, and three-particle $πππ$ dynamics within a single unitary formalism. Using leading lattice QCD spectra from the Chinese Lattice QCD Collaboration at $m_π$ = 208 and 305 MeV, we perform a fit in the isovector and isoscalar channels, accurately describe the lattice spectra and obtain robust determinations of the $ρ$ and $ω$ pole positions. This work establishes a foundational approach for extracting resonance dynamics from finite-volume spectra. Given the ubiquity of three-body dynamics in exotic hadrons, halo nuclei, and neutron star matter, this general formalism holds broad relevance across particle, nuclear, and astrophysical physics.

hep-lat