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H. Gao

Publications and source records attributed to H. Gao.

At least 55 records · Page 3Linked to original sources
arXiv2025

Decadal evolution of a repeating fast radio burst source

The origin of fast radio bursts (FRBs), the brightest cosmic radio explosions, is still unknown. Bearing critical clues to FRBs' origin, the long-term evolution of FRBs has yet to be confirmed, since the field is still young and most FRBs were seen only once. Here we report clear evidence of decadal evolution of FRB~20121102A, the first precisely localized repeater. In conjunction with archival data, our FAST and GBT monitoring campaign since 2020 reveals a significant 7% decline of local dispersion measure (DM). The rotation measure (RM) of 30,755$\pm$16 $\mathrm{rad\,m^{-2}}$ detected in the last epoch represents a 70% decrease compared to that from December 2016. The $σ_{RM}$ parameter, which describes the complexity of the magneto-ionic environment surrounding the source, was shown to have decreased by 13%. These general trends reveal an evolving FRB environment, which could originate from an early-phase supernova associated with an enhanced pair wind from the FRB central engine.

astro-ph.HE↗
arXiv2025

First Measurement of the Decay Dynamics in the Semileptonic Transition of the $D^{+(0)}$ into the Axial-vector Meson $\bar K_1(1270)$

Using $e^+e^-$ data taken at the center-of-mass energy of 3.773 GeV with the BESIII detector, corresponding to an integrated luminosity of 20.3 fb$^{-1}$, we report the first measurement of the decay dynamics of the semileptonic decays $D^{+(0)}\to K^-π^+π^{0(-)} e^+ν_e$. The amplitude analysis gives the hadronic form factors of the semileptonic $D$ transitions into the axial-vector meson $\bar{K}_1(1270)$ to be $r_A=(-11.2\pm1.0_{\rm stat}\pm0.9_{\rm syst})\times10^{-2}$ and $r_V = (-4.3\pm 1.0_{\rm stat}\pm2.5_{\rm syst})\times 10^{-2}$. This is the first in the semileptonic decays of heavy mesons into axial-vector mesons. The angular analysis yields an up-down asymmetry $\mathcal{A}^\prime_{ud} = 0.01\pm0.11$, which is consistent with the Standard Model prediction. In addition, the branching fractions of $D^+\to \bar K_1(1270)^0 e^+ν_e$ and $D^0\to K_1(1270)^- e^+ν_e$ are determined with improved precision to be $(2.27\pm0.11_{\rm stat}\pm0.07_{\rm syst}\pm0.07_{\rm input})\times10^{-3}$ and $(1.02\pm0.06_{\rm stat}\pm0.06_{\rm syst}\pm0.03_{\rm input})\times10^{-3}$, respectively. No significant signals of $D^+\to \bar K_1(1400)^0 e^+ν_e$ and $D^0\to K_1(1400)^- e^+ν_e$ are observed and their branching fraction upper limits are set as $1.4\times10^{-4}$ and $0.7\times10^{-4}$ at 90\% confidence level, respectively.

hep-ex↗
arXiv2025

A fast X-ray transient from a weak relativistic jet associated with a type Ic-BL supernova

Massive stars end their lives as core-collapse supernovae, amongst which some extremes are broad-lined type Ic supernovae from Wolf-Rayet stars associated with long-duration gamma-ray bursts (LGRBs) having powerful relativistic jets. Their less-extreme brethren make unsuccessful jets that are choked inside the stars, appearing as X-ray flashes or low-luminosity GRBs. On the other hand, there exists a population of extragalactic fast X-ray transients (EFXTs) with timescales ranging from seconds to thousands of seconds, whose origins remain obscure. Here, we report the discovery of the bright X-ray transient EP240414a detected by the Einstein Probe (EP), which is associated with the type Ic supernova SN 2024gsa at a redshift of 0.401. The X-ray emission evolution is characterised by a very soft energy spectrum peaking at $< 1.3$ keV, which makes it different from known LGRBs, X-ray flashes, or low-luminosity GRBs. Follow-up observations at optical and radio bands revealed the existence of a weak relativistic jet that interacts with an extended shell surrounding the progenitor star. Located on the outskirts of a massive galaxy, this event reveals a new population of explosions of Wolf-Rayet stars characterised by a less powerful engine that drives a successful but weak jet, possibly owing to a progenitor star with a smaller core angular momentum than in traditional LGRB progenitors.

astro-ph.HE↗
arXiv2025

Study of the light scalar $a_{0}(980)$ through the decay $D^{0} \to a_{0}(980)^-e^{+} ν_{e}$ with $a_{0}(980)^- \to ηπ^-$

Using 7.93 ${\rm fb^{-1}}$ of $e^+e^-$ collision data collected at a center-of-mass energy of 3.773 ${\rm GeV}$ with the BESIII detector, we present an analysis of the decay $D^{0} \to ηπ^- e^+ ν_{e}$. The branching fraction of the decay $D^{0} \to a_{0}(980)^{-} e^+ ν_{e}$ with $a_{0}(980)^{-} \to ηπ^{-}$ is measured to be $(0.86\pm0.17_{\text{stat}}\pm0.05_{\text{syst}})\times 10^{-4}$. The decay dynamics of this process is studied with a single-pole parameterization of the hadronic form factor and the Flatté formula describing the $a_0(980)$ line shape in the differential decay rate. The product of the form factor $f^{ a_0}_{+}(0)$ and the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cd}|$ is determined for the first time with the result $f^{ a_0}_+(0)|V_{cd}|=0.126\pm0.013_{\rm stat}\pm0.003_{\rm syst}$.

hep-ex↗
arXiv2025

Study of the electromagnetic Dalitz decay $J/ψ\to e^+e^- π^0$

We report the first measurement of the di-electron invariant mass dependent transition form factor in the electromagnetic Dalitz decay $J/ψ\to e^+e^- π^0$ using $(10087 \pm 44) \times 10^6$ $J/ψ$ events collected by the BESIII detector. A clear $ρ-ω$ interference structure is observed, consistent with the pion form factor, which offers a novel approach to extract the hadronic vacuum polarization contribution to the anomalous muon magnetic moment ($a_μ$) and refine the predictions of the Vector Meson Dominance (VMD) model and hadronic light-by-light contribution to $a_μ$. By taking into account the contribution of this $ρ-ω$ interference structure, the branching fraction of $J/ψ\to e^+e^- π^0$ in the full $e^+e^-$ invariant mass range is also measured for the first time to be $(8.06 \pm 0.31 (\rm{stat}) \pm 0.38 (\rm{syst}))\times 10^{-7}$, approximately twice the non-resonant VMD prediction.

hep-ex↗
arXiv2025

Improved measurement of absolute branching fraction of the inclusive decay $Λ_{c}^{+} \to K_{S}^{0} X$

By analyzing $4.5$ fb$^{-1}$ of $e^{+}e^{-}$ collision data accumulated with the BESIII detector at center-of-mass energies ranging from $4599.53$ MeV to $4698.82$ MeV, we report the measurement of the absolute branching fraction (BF) of the inclusive decay $Λ_{c}^{+} \to K_{S}^{0} X$ using the double-tag technique. The result is $\mathcal{B}(Λ_{c}^{+} \to K_{S}^{0} X)=(10.9\pm0.2\pm0.1)\%$, where the first uncertainty is statistical and the second is systematic. This result indicates that there are still undiscovered decay channels containing $K_{S}^{0}$ in the final state with a combined BF of $(3.1\pm0.4)\%$. The BF of the inclusive decay $Λ_{c}^{+} \to \overline{K}^{0} / K^{0} X$ is calculated to be $\mathcal{B}(Λ_{c}^{+} \to \overline{K}^{0} / K^{0} X)=(21.8 \pm0.4 \pm0.2 \pm1.1)\%$, where the third uncertainty accounts for a possible difference between $\mathcal{B}(Λ_{c}^{+} \to K_{S}^{0} X)$ and $\mathcal{B}(Λ_{c}^{+} \to K_{L}^{0} X)$. The result is in agreement with the prediction of the statistical isospin model.

hep-ex↗
arXiv2025

Massive stars exploding in a He-rich circumstellar medium. XI. Diverse evolution of five Ibn SNe 2020nxt, 2020taz, 2021bbv, 2023utc and 2024aej

We present the photometric and spectroscopic analysis of five Type Ibn supernovae (SNe): SN 2020nxt, SN 2020taz, SN 2021bbv, SN 2023utc, and SN 2024aej. These events share key observational features and belong to a family of objects similar to the prototypical Type Ibn SN 2006jc. The SNe exhibit rise times of approximately 10 days and peak absolute magnitudes ranging from $-$16.5 to $-$19 mag. Notably, SN 2023utc is the faintest Type Ibn supernova discovered to date, with an exceptionally low r-band absolute magnitude of $-16.4$ mag. The pseudo-bolometric light curves peak at $(1-10) \times 10^{42}$ erg s$^{-1}$, with total radiated energies on the order of $(1-10) \times 10^{48}$ erg. Spectroscopically, these SNe display relatively slow spectral evolution; the early spectra are characterised by a hot blue continuum and prominent He I emission lines. Early spectra show blackbody temperatures exceeding $10000~\mathrm{K}$, with a subsequent decline in temperature during later phases. Narrow He I lines, indicative of unshocked circumstellar material (CSM), show velocities of approximately $1000~\mathrm{km~s^{-1}}$. The spectra suggest that the progenitors of these SNe underwent significant mass loss prior to the explosion, resulting in a He-rich CSM. Light curve modelling yields estimates for the ejecta mass ($M_{\rm ej}$) in the range $1-3~M_{\odot}$, with kinetic energies ($E_{\rm Kin}$) of $(0.1-1) \times 10^{50}$ erg. The inferred CSM mass ranges from $0.2$ to $1~M_{\odot}$. These findings are consistent with expectations for core-collapse events arising from relatively massive, envelope-stripped progenitors.

astro-ph.HE↗
arXiv2025

Search for $e^+e^-\to K_S^0 K_S^0 h_c$

Using $e^+e^-$ collision data at 13 center-of-mass energies ranging from 4.600 to 4.950 GeV collected with the BESIII detector, we search for the unmeasured $e^+e^-\to K_S^0 K_S^0 h_c$ process . No significant signal is observed, and the upper limits of the Born cross sections at each center-of-mass energy are presented.

hep-ex↗
arXiv2025

Observation of the $W$-annihilation process $D_s^+ \to ωρ^+$ and measurement of $D_s^+ \to ϕρ^+$ in $D^+_s\to π^+π^+π^-π^0π^0$ decays

We present the first amplitude analysis and branching fraction measurement of the decay $D^+_s\to π^+π^+π^-π^0π^0$, using $e^+e^-$ collision data collected with the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV corresponding to an integrated luminosity of 7.33 fb$^{-1}$, and report the first observation of the pure $W$-annihilation decay $D_s^+ \to ωρ^+$ with a branching fraction of $(0.99\pm0.08_{\rm stat}{\ ^{+0.05}_{-0.07}}_{\rm syst})\%$. %The absolute branching fraction is measured to be $(0.99\pm0.08_{\rm stat}\pm0.07_{\rm syst})\%$. In comparison to the low significance of the $\mathcal{D}$ wave in the decay $D_s^+ \to ϕρ^+$, the dominance of the $\mathcal{D}$ wave over the $\mathcal{S}$ and $\mathcal{P}$ waves, with a fraction of $(51.85\pm7.28_{\rm stat}{\ ^{+4.83}_{-7.90}}_{\rm syst})\%$ observed in the decay $D_s^+ \to ωρ^+$, provides crucial information for the``polarization puzzle", as well as for the understanding of charm meson decays. The branching fraction of $D^+_s\to π^+π^+π^-π^0π^0$ is measured to be ($4.41\pm0.15_{\rm stat}\pm0.13_{\rm syst}$)\%. Moreover, the branching fraction of $D_s^+ \to ϕρ^+$ is measured to be $(3.98\pm0.33_{\rm stat}{\ ^{+0.21}_{-0.19}}_{\rm syst})\%$, and the $R_ϕ= {\mathcal{B}(ϕ\toπ^+π^-π^0)}/{\mathcal{B}(ϕ\to K^+K^-)}$ is determined to be $(0.222\pm0.019_{\rm stat}{\ ^{+0.016}_{-0.016}}_{\rm syst}$), which is consistent with the previous measurement based on charm meson decays, but deviates from the results from $e^+e^-$ annihilation and $K$-$N$ scattering experiments by more than 3$σ$.

hep-ex↗
arXiv2025

Test of local realism via entangled $Λ\barΛ$ system

The non-locality of quantum correlations is a fundamental feature of quantum theory. The Bell inequality serves as a benchmark for distinguishing between predictions made by quantum theory and local hidden variable theory (LHVT). Recent advancements in photon-entanglement experiments have addressed potential loopholes and have observed significant violations of variants of Bell inequality. However, examples of Bell inequalities violation in high energy physics are scarce. In this study, we utilize $(10.087\pm0.044)\times10^{9}$ $J/ψ$ events collected with the BES-III detector at the BEPCII collider, performing non-local correlation tests using the entangled hyperon pairs. The massive-entangled $Λ\barΛ$ systems are formed and decay through strong and weak interactions, respectively. Through measurements of the angular distribution of $p\bar{p}$ in $J/ψ\to γη_c$ and subsequent $η_c\toΛ(pπ^-)\barΛ(\bar{p}π^{+})$ cascade decays, a significant violation of LHVT predictions is observed. The exclusion of LHVT is found to be statistically significant at a level exceeding $5.2σ$ in the testing of three Bell-like inequalities.

hep-ex↗
arXiv2025

Final Moments III: Explosion Properties and Progenitor Constraints of CSM-Interacting Type II Supernovae

We present analysis of the plateau and late-time phase properties of a sample of 39 Type II supernovae (SNe II) that show narrow, transient, high-ionization emission lines (i.e., "IIn-like") in their early-time spectra from interaction with confined, dense circumstellar material (CSM). Originally presented by Jacobson-Galán et al 2024a, this sample also includes multicolor light curves and spectra extending to late-time phases of 35 SNe with no evidence for IIn-like features at <2 days after first light. We measure photospheric phase light-curve properties for the distance-corrected sample and find that SNe II with IIn-like features have significantly higher luminosities and decline rates at +50 days than the comparison sample, which could be connected to inflated progenitor radii, lower ejecta mass, and/or persistent CSM interaction. However, we find no statistical evidence that the measured plateau durations and $^{56}$Ni masses of SNe II with and without IIn-like features arise from different distributions. We estimate progenitor zero-age main sequence (ZAMS) masses for all SNe with nebular spectroscopy through spectral model comparisons and find that most objects, both with and without IIn-like features, are consistent with progenitor masses <12.5 M$_{\odot}$. Combining progenitor ZAMS masses with CSM densities inferred from early-time spectra suggests multiple channels for enhanced mass loss in the final years before core collapse such as a convection-driven chromosphere or binary interaction. Finally, we find spectroscopic evidence for ongoing ejecta-CSM interaction at radii $>10^{16}$ cm, consistent with substantial progenitor mass-loss rates of $\sim 10^{-4}$--$10^{-5}$ M$_{\odot}$ yr$^{-1}$ ($v_w < 50$ km/s) in the final centuries to millennia before explosion.

astro-ph.HE↗
arXiv2025

Measurement of the branching fraction of the decay $J/ψ\to p \bar{p} η$

A high precision measurement of the branching fraction of the decay $J/ψ\to p \bar{p} η$ is performed using $(10 087 \pm 44) \times 10^6$ $J/ψ$ events recorded by the {BESIII} detector at the {BEPCII} storage ring. The branching fractions of the two decays $J/ψ\to p \bar{p} η(η\to γγ)$ and $J/ψ\to p \bar{p} η(η\to π^+ π^- π^0)$ are measured individually to be $\mathcal{B}(J/ψ\to p \bar{p} η(η\to γγ)) = (1.480 \pm 0.001 \pm 0.024)\times\,10^{-3}$ and $\mathcal{B}(J/ψ\to p \bar{p} η(η\to π^+ π^- π^0)) = (1.557 \pm 0.003 \pm 0.038)\times\,10^{-3}$, where the first uncertainties are statistical and the second systematic. Both results are compatible within their uncorrelated systematic uncertainties. The combined result is $\mathcal{B}(J/ψ\to p \bar{p} η)=(1.495 \pm 0.001 \pm 0.023)\times\,10^{-3}$ where the first uncertainty is the combined statistical uncertainty and the second one the combined systematic uncertainty of both analyses, incorporating correlations between them. In addition, the $p \bar{p}$ threshold region is investigated for a potential threshold enhancement, and no evidence for one is observed.

hep-ex↗
arXiv2025

SN 2024abfo: a partially stripped SN II from a yellow supergiant

We present photometric and spectroscopic data of the type IIb supernova (SN) 2024abfo in NGC 1493 (at 11 Mpc). The ATLAS survey discovered the object just a few hours after the explosion, and observed a fast rise on the first day. Signs of the sharp shock break-out peak and the subsequent cooling phase are observed in the ultraviolet and the bluest optical bands in the first couple of days, while no peak is visible in the reddest filters. Subsequently, in analogy with normal SNe IIb, the light curve of SN 2024abfo rises again in all bands to the broad peak, with the maximum light reached around one month after the explosion. Its absolute magnitude at peak is $M_r=-16.5\pm0.1$ mag, making it a faint SN IIb. The early spectra are dominated by Balmer lines with broad P-Cygni profiles indicating ejecta velocity of 22,500 km/s. One month after the explosion, the spectra display a transition towards being He-dominated, though the H lines do not completely disappear, supporting the classification of SN 2024abfo as a relatively H-rich SN IIb. We identify the progenitor of SN 2024abfo in archival images of the Hubble Space Telescope, the Dark Energy Survey, and the XMM-Newton space telescope, in multiple optical filters. From its spectral energy distribution, the progenitor is consistent with being a yellow supergiant, having an initial mass of 15 $M_{\odot}$. This detection supports an emerging trend of SN IIb progenitors being more luminous and hotter than SN II ones, and being primaries of massive binaries. Within the SN IIb class, fainter events such as SN 2024abfo tend to have cooler and more expanded progenitors than luminous SNe IIb.

astro-ph.HE↗
arXiv2025

Evidence for Two Excited $Ω^{-}$ Hyperons

Using $e^+e^-$ collision data corresponding to an integrated luminosity of 19,fb$^{-1}$ collected by the BESIII detector at center-of-mass energies ranging from 4.13 to 4.70,GeV, we report the first evidence for a new excited $Ω^{-}$ hyperon, the $Ω(2109)^{-}$, through the process $e^+ e^- \to Ω(2109)^{-} \barΩ^{+} +c.c.$ with a significance of 4.1 $σ$. The mass and width of $Ω(2109)^{-}$ are measured to be $2108.5 \pm 5.2_{\rm stat} \pm 0.9_{\rm syst}\,{\rm MeV}/c^{2}$ and $18.3 \pm 16.4_{\rm stat} \pm 5.7_{\rm syst}\,{\rm MeV}$, respectively. We also present evidence for a new production mechanism for the previously identified $Ω(2012)^-$ via the process $e^+ e^- \to Ω(2012)^{-} \barΩ^{+} +c.c.$ with a significance of 3.5 $σ$.

hep-ex↗
arXiv2025

Evidence of mini-jet emission in a large emission zone from a magnetically-dominated gamma-ray burst jet

The second brightest GRB in history, GRB230307A, provides an ideal laboratory to study the mechanism of GRB prompt emission thanks to its extraordinarily high photon statistics and its single episode activity. Here we demonstrate that the rapidly variable components of its prompt emission compose an overall broad single pulse-like profile. Although these individual rapid components are aligned in time across all energy bands, this overall profile conspires to show a well-defined energy-dependent behavior which is typically seen in single GRB pulses. Such a feature demonstrates that the prompt emission of this burst is from many individual emitting units that are casually linked in a emission site at a large distance from the central engine. Such a scenario is in natural consistency with the internal-collision-induced magnetic reconnection and turbulence framework, which invokes many mini-jets due to local magnetic reconnection that constantly appear and disappear in a global magnetically-dominated jet.

astro-ph.HE↗
arXiv2025

Observation of $D\to \bar{K}_{1}(1270)μ^+ν_μ$ and test of lepton flavor universality with $D\to \bar{K}_1(1270) \ell^{+} ν_{\ell}$

By analyzing 7.93 $\rm fb^{-1}$ of $e^+e^-$ collision data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector operated at the BEPCII collider, we report the observation of the semimuonic decays of $D^+\to \bar K_1(1270)^0μ^+ν_μ$ and $D^0\to K_1(1270)^-μ^+ν_μ$ with statistical significances of $12.5σ$ and $6.0σ$, respectively. Their decay branching fractions are determined to be ${\mathcal B}[D^{+}\to \bar{K}_1(1270)^0 μ^{+}ν_μ]=(2.36\pm0.20^{+0.18}_{-0.27}\pm 0.48)\times10^{-3}$ and ${\mathcal B}[D^{0}\to K_1(1270)^{-} μ^{+}ν_μ]=(0.78\pm0.11^{+0.05}_{-0.09}\pm 0.15)\times10^{-3}$, where the first and second uncertainties are statistical and systematic, respectively, and the third originates from the input branching fraction of $\bar K_{1}(1270)^0\to K^- π^+π^0$ or $K_1(1270)^-\to K^-π^+π^-$. Combining our branching fractions with the previous measurements of ${\mathcal B}[D^+\to \bar K_1(1270)^0e^+ν_{e}]$ and ${\mathcal B}[D^0\to K_1(1270)^-e^+ν_{e}]$, we determine the branching fraction ratios to be ${\mathcal B}[D^+\to \bar K_1(1270)^0μ^+ν_μ]/{\mathcal B}[D^+\to \bar K_1(1270)^0e^+ν_{e}]=1.03 \pm 0.14 \substack{+0.11\\-0.15}$ and ${\mathcal B}[D^0\to K_1(1270)^-μ^+ν_μ]/{\mathcal B}[D^0\to K_1(1270)^-e^+ν_{e}]=0.74\pm 0.13 \substack{+0.08\\-0.13}$. Using the branching fractions measured in this work and the world-average lifetimes of the $D^+$ and $D^0$ mesons, we determine the semimuonic partial decay width ratio to be $Γ[D^+\to \bar K_1(1270)^0 μ^+ν_μ]/Γ[D^0\to K_1(1270)^- μ^+ν_μ]=1.22\pm 0.10\substack{+0.06\\-0.09}$, which is consistent with unity as predicted by isospin conservation.

hep-ex↗
arXiv2025

Observation and branching fraction measurement of the decay $J\!/\!ψ\rightarrow \bar{p} Σ^{+} K_{S}^{0} + c.c.$

The first observation of the decays $J\!/\!ψ\rightarrow \bar{p} Σ^{+} K_{S}^{0}$ and $J\!/\!ψ\rightarrow p \barΣ^{-} K_{S}^{0}$ is reported using $(10087\pm44)\times10^{6}$ $J\!/\!ψ$ events recorded by the BESIII detector at the BEPCII storage ring. The branching fractions of each channel are determined to be $\mathcal{B}(J\!/\!ψ\rightarrow \bar{p} Σ^{+} K_{S}^{0})=(1.361 \pm 0.006 \pm 0.025) \times 10^{-4}$ and $\mathcal{B}(J\!/\!ψ\rightarrow p \barΣ^{-} K_{S}^{0})=(1.352 \pm 0.006 \pm 0.025) \times 10^{-4}$. The combined result is $\mathcal{B}(J\!/\!ψ\rightarrow \bar{p} Σ^{+} K_{S}^{0} +c.c.)=(2.725 \pm 0.009 \pm 0.050) \times 10^{-4}$, where the first uncertainty is statistical and the second systematic. The results presented are in good agreement with the branching fractions of the isospin partner decay $J\!/\!ψ\rightarrow p K^- \barΣ^0 + c.c.$.

hep-ex↗
arXiv2025

Search for the baryon and lepton number violating decay $J/ψ\to pe^-$ + c.c

Based on $(2712.4\pm 14.3) \times 10^{6} $ ${ψ(3686)}$ events collected by the BESIII detector operating at the BEPCII storage ring, we perform a search for the baryon- and lepton-number violating decay $J/ψ\to pe^{-}+c.c.$ via $ψ(3686) \to π^{+}π^{-}J/ψ$. No significant signal is found. An upper limit on the branching fraction of $\mathcal{B}(J/ψ\to p e^{-}+ c.c.) < 3.1 \times 10^{-8}$ at 90\% confidence level.

hep-ex↗