arXiv subjects

Dazhuang He

Publications and source records attributed to Dazhuang He.

8 recordsLinked to original sources

arXiv2026

The role of triangle singularity in the $B^0 \to D^- \pi^+ a_0(980)(\pi^0 \eta)$ decay

The triangle singularity interpretation of the \replyhe{$a_1(1420)$} observed by the COMPASS Collaboration has been widely accepted. In this work, we investigate the triangle mechanism in the decay $B^0 \to D^- \pi^+ a_0(980)(\pi^0 \eta)$, where the $a_0(980)$ is treated as a dynamically generated state. The $\bar{K}^{*0}$-$K^+$-$K^-$ triangle loop originates from the decay $B^0 \to D^- K^+ \bar{K}^{*0}$, which has been observed by the Belle Collaboration, followed by the subsequent decay $\bar{K}^{*0} \to K^- \pi^+$. The triangle amplitude develops a pronounced peak around 1420 MeV, which is reflected in the invariant mass spectrum of the $\pi a_0(980)$ system. The differential decay width is calculated and exhibits a narrow peak around $980~\mathrm{MeV}$ in the $\pi^0 \eta$ invariant mass distribution. Furthermore, the invariant mass distribution of the $\pi^+ \pi^0 \eta$ system shows a clear peak around $1420~\mathrm{MeV}$, which further \replyhe{confirms} the triangle singularity explanation of the \replyhe{$a_1(1420)$}. We expect that the proposed $B^0$ decay mode could provide a potential platform for further exploring the triangle-singularity nature of the \replyhe{$a_1(1420)$} and could be tested in future experiments such as LHCb, BESIII, and Belle~II.

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arXiv2026

Probing the dark axion portal via $J/\psi$ decays at BESIII and STCF

Large numbers of $J/\psi$ mesons can be resonantly produced at BESIII and STCF at the center-of-mass energy $\sqrt{s}=3.097$~GeV. Such $J/\psi$ mesons may undergo rare decays into an axionlike particle (ALP) $a$ and a dark photon $\gamma'$ through the dark axion portal. We investigate the exclusion reach of the existing BESIII dataset and the projected sensitivity of STCF, focusing on the mono-photon signature. We perform Monte Carlo simulations of the signal and estimate both the irreducible $J/\psi\to\gamma\nu\bar{\nu}$ background and the continuum and resonant three-photon reducible backgrounds. Detector-induced migration of three-photon events into the mono-photon signal region is parameterized by the event-level leakage probability $\epsilon_{3\gamma}^{\rm leak}=0,10^{-6},10^{-4},10^{-3}$. In the zero- and sufficiently small-leakage benchmarks, the existing BESIII dataset could probe previously unexplored parameter space, while STCF can further improve the coupling reach. Increasing leakage probabilities progressively weaken these projections, highlighting the importance of detector-level three-photon rejection in realizing the projected reach.

hep-ph↗

arXiv2026

The effects of a scalar singlet Leptoquark at the $Z$ factory

We evaluate the observability of the effects of a scalar singlet leptoquark (LQ) in $\mu$ and $\tau$-pair productions at the $Z$ factory. In the scenario addressing the charged-current anomalies, the LQ contributions to $\mu$-pair final state are negligible. In contrast, a sizable contribution arises in the $\tau$-pair production, which is identical in both $Z$ decay and $e^+e^-$ collider at $Z$ pole. These effects are mainly sensitive to left-handed interaction, showing a maximum deviation of about $-0.7\%$ for both 1\,TeV and 2\,TeV LQ. The suppression of new physics effects from the heavy LQ can be compensated by the enlarged couplings parameter space. For the $\tau$-pair production channel, we further specify the coupling constraints corresponding to the expected measurement precision at the future $Z$ factory. Moreover, we provide an analytic function in terms of the LQ mass and couplings to quantify the LQ effects. The differential distributions in the collision process indicate that the LQ effects remain stable throughout the kinematic region. Meanwhile, the measurement sensitivity of the $\tau$-pair final state at the future $Z$ factory is expected to impose further constraints on the LQ theory.

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arXiv2025

Higgs-strahlung at the LHC in the inert doublet model

$pp \to W^{\pm} h, Zh$ processes at the LHC are studied in the framework of the inert doublet model (IDM). To quantify the effects of the IDM and their observability in these processes we revisit the NLO (QCD and EW) predictions in the Standard Model (SM) and their uncertainty. Taking all available current constraints on the parameter space of the IDM, we consider both the case of the IDM providing a good Dark Matter (DM) candidate within the freeze-out mechanism as well as when the DM restrictions are relaxed. In the former, deviations from the SM of only a few per mil in these cross sections at the LHC are found and may not be measured. In the latter, the deviations can reach a few percents and should be observable. Smaller discrepancies in this case require that the theoretical uncertainties be improved, in particular those arising from the parton distribution functions (PDFs). We stress the importance of the photon-induced real corrections and the need for further improvement in the extraction of the photon PDF. The analysis also showcases the development and exploitation of our automated tool for the computation of one-loop electroweak and QCD corrections for a New Physics model with internal tests such as those concerning the soft and collinear parts provided through both dipole subtraction and phase space slicing besides tests for ultra-violet finiteness and gauge-parameter independence.

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arXiv2024

Exploring the molecular scenario of X(4160)

In this work, we investigate the decays of meson $X(4160)$ in the molecular frame. By using an effective lagrangian approach, we calculate the widths of $X(4160)\to J/ψϕ$, $D^*\bar{D}^*$, $D^*\bar{D}$ and $D\bar{D}$ through the triangle loop mechanism in the molecular scenario. Based on the compositeness condition, the coupling between $X(4160)$ and the $D_s^*\bar{D}_s^*$ molecular state is determined. The other coupling constants used are determined phenomenologically. The calculation of the decay widths shows that the $D^*\bar{D}^*$ decay mode has a larger branching ratio. These predictions can be seen as a test for the charmonium assignment of $X(4160)$.

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arXiv2023

The role of triangle singularity in the decay process $D^0 \to π^+ π^- f_0(980),\ f_0 \to π^+ π^-$

We study the process $D^0 \to π^+ π^- f_0(980),\ f_0 \to π^+ π^-$ by introducing the triangle mechanism, in which $f_0(980)$ is considered to be dynamically generated from the meson-meson interaction. For the total contribution of this process, the contribution of the triangular loop formed by $K^{*} \bar{K} K$ particles could generate a triangular singularity of about 1418 MeV. We calculate the differential decay width of this process and show a narrow peak of about 980 MeV in the $π^+ π^-$ invariant mass distribution, which comes from $f_0$ decay. For the $M_{inv}(πf_0)$ invariant mass distribution, we obtain a finite peak at 1418 MeV, which is consistent with the triangle singularity.

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arXiv2022

The strong coupling $g_{X J/ψϕ}$ of $X(4700) \to J/ψϕ$ in the light-cone sum rules

We assign the scalar tetraquark and the D-wave tetraquark state for $X(4700)$ and calculate the width of the decay $X(4700)$ $\to J/ψϕ$ within the framework of light-cone sum rules. The strong coupling $g_{X J/ψϕ}$ is obtained by considering the technique of soft-meson approximation. We also investigate the mass and the decay constant of $X(4700)$ in the framework of SVZ sum rules. Our prediction for the mass is in agreement with the experimental measurement, and that for the decay width of $X(4700)$ $\to J/ψϕ$ support the possibility that $X(4700)$ could be a scalar tetraquark state if $X(4700)$ $\to J/ψϕ$ is the predominant decay channel, or a D-wave tetraquark state if $X(4700)$ $\to J/ψϕ$ is not the predominant one and there exist other decays.

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arXiv2021

Triangle mechanism in the decay process $J/ψ\to K^- K^+ a_1(1260)$

The role of triangle mechanism in the decay process $J/ψ\to K^- K^+ a_1(1260)$ is probed. In this mechanism, a close-up resonance with mass $1823$ MeV and width $122$ MeV decays into $K^* ϕ, K^* \to K π$ and then $K^* \bar{K}$ fuses into the $a_1(1260)$ resonance. We find that this mechanism leads to a triangle singularity around $M_{\rm inv}(K^- a_1(1260))\approx 1920$ MeV, where the axial-vector meson $a_1(1260)$ is considered as a dynamically generated resonance. With the help of the triangle mechanism we find sizable branching ratios $\text{Br}(J/ψ\to K^- K^+ a_1(1260),a_1 \to πρ)=1.210 \times 10^{-5}$ and $\text{Br}(J/ψ\to K^- K^+ a_1(1260))=3.501 \times 10^{-5}$. Such a effect from triangle mechanism of the decay process could be investigated by such as BESIII, LHCb and Belle-II experiments. This potential investigation can help us obtain the information of the axial-vector meson $a_1(1260)$.

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