arXiv subjects

L. Feng

Publications and source records attributed to L. Feng.

At least 109 records · Page 6Linked to original sources

arXiv2025

Search for CP violation in $e^{+}e^{-} \to ψ(3770) \to D^{0}\bar{D}^{0}$ via $D -> K^{0}_{S} π^{0}$

Utilizing data sample of electron-positron collisions recorded with the BESIII detector at the center of mass energy of 3.773 GeV, corresponding to an integrated luminosity of 20.28 fb$^{-1}$, we report the first search for the CP forbidden process $e^+e^- \to ψ(3773) \to D^0\bar{D}^0 \to (K^0_Sπ^0)(K^0_Sπ^0)$. No significant signal is observed. We set the upper limit on the observed cross section to be 7.37 fb, and the upper limit on the joint branching fraction of the C-odd correlated neutral $D$ pair $\mathcal{B}[(D^{0} \bar{D}^{0})_{\text{C-odd}} \to (K^{0}_{S} π^{0})(K^{0}_{S} π^{0})] < 2.04 \times 10^{-6}$ at the 90% confidence level.

hep-ex↗

arXiv2025

Measurement of the Born cross section for $e^+e^- \to p K^- K^- \barΞ^+$ at $\sqrt{s} =$ 3.5-4.9 GeV

Using $e^+ e^-$ collision data corresponding to a total integrated luminosity of 20 ${\rm fb}^{-1}$ collected with the BESIII detector at the BEPCII collider, we present a measurement of the Born cross section for the process $e^+e^- \to p K^-K^-\barΞ^{+}$ at 39 center-of-mass energies between 3.5 and 4.9 GeV with a partial reconstruction technique. By performing a fit to the dressed cross section of $e^{+}e^{-}\to p K^- K^-\barΞ^{+}$ with a power law function for continuum production and one resonance at a time for the $ψ(3770)$, $ψ(4040)$, $ψ(4160)$, $ψ(4230)$, $ψ(4360)$, $ψ(4415)$ or $ψ(4660)$, respectively, the upper limits for the product of partial electronic width and branching fraction into the final state $p K^- K^- \barΞ^+$ for these resonances are determined at the $90\%$ confidence level.

hep-ex↗

arXiv2025

Search for the lepton number violating process $Ξ^- \rightarrow Σ^+ e^- e^- +c.c.$

We present a search for the lepton number violating decay $Ξ^-\rightarrowΣ^+e^-e^- +c.c.$ with $(10087\pm44)\times10^6$ $J/ψ$ events collected by the BESIII detector at the BEPCII collider. Employing a blind analysis strategy, no significant signal is observed above the expected background yield. The upper limit on the branching fraction is determined to be ${\rm Br}(Ξ^-\rightarrowΣ^+e^-e^-+c.c.)< 2.0\times10^{-5}$ at the $90\%$ confidence level.

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arXiv2025

All-sky search for individual Primordial Black Hole bursts with LHAASO

Primordial Black Holes~(PBHs) are hypothetical black holes with a wide range of masses that formed in the early universe. As a result, they may play an important cosmological role and provide a unique probe of the early universe. A PBH with an initial mass of approximately $10^{15}$~g is expected to explode today in a final burst of Hawking radiation. In this work, we conduct an all-sky search for individual PBH burst events using the data collected from March 2021 to July 2024 by the Water Cherenkov Detector Array of the Large High Altitude Air Shower Observatory (LHAASO). Three PBH burst durations, 10~s, 20~s, and 100~s, are searched, with no significant PBH bursts observed. The upper limit on the local PBH burst rate density is set to be as low as 181~pc$^{-3}$~yr$^{-1}$ at 99$\%$ confidence level, representing the most stringent limit achieved to date.

astro-ph.HE↗

arXiv2025

Test of $CP$ Symmetry in the Neutral Decays of $Λ$ via $J/ψ\toΛ\barΛ$

Using $(10087\pm44)\times10^{6}$ $J/ψ$ events collected with the BESIII detector, a full angular distribution analysis is carried out on the process $J/ψ\rightarrowΛ\barΛ\rightarrow nπ^{0}\bar{p}π^{+}+c.c.$ The decay parameters $α_{0}$ for $Λ\rightarrow nπ^{0}$ and $\barα_{0}$ for $\barΛ\rightarrow \bar{n}π^{0}$ are measured to be $0.668\pm0.007\pm0.002$ and $-0.677\pm0.007\pm0.003$, respectively, yielding the most precise test for $CP$ symmetry of neutral decays of $Λ$, $A_{CP}^{0}=(α_{0}+\barα_{0})/(α_{0}-\barα_{0})$, to be $-0.006\pm0.007\pm0.002$. The ratios $α_{0}/α_{-}$ and $\barα_{0}/α_{+}$ are determined to be $0.884\pm0.013\pm0.006$ and $0.885\pm0.013\pm0.004$, where $α_{-}$ and $α_{+}$ are the decay parameters of $Λ\rightarrow pπ^{-}$ and $\barΛ\rightarrow\bar{p}π^{+}$, respectively. The ratios, found to be smaller than unity by more than $5σ$, confirm the presence of the $ΔI = 3/2$ transition in the $Λ$ and $\barΛ$ decays, which is expected to improve the theoretical calculations for strong and weak phases, and $A_{CP}$, in hyperon decays. In all results, the first and second uncertainties are statistical and systematic, respectively.

hep-ex↗

arXiv2025

Measurements of the absolute branching fractions of the doubly Cabibbo-suppressed decays $D^+\to K^+π^0$, $D^+\to K^+η$ and $D^+\to K^+η^{\prime}$

Using $20.3\,\rm fb^{-1}$ of $e^+e^-$ collision data collected at a center-of-mass energy of 3.773\,GeV with the BESIII detector, we present the measurements of the absolute branching fractions of the doubly Cabibbo-suppressed decays $D^+\to K^+π^0$, $D^+\to K^+η$ and $ D^+ \to K^+ η^{\prime}$ with the double-tag method, with significantly improved precision compared to the previous measurements. The statistical significance of each signal decay exceeds $10σ$. The branching fractions are determined to be ${\mathcal B}(D^+\to K^+ π^0) = (1.45 \pm 0.06 \pm 0.08)\times 10^{-4}$, ${\mathcal B}(D^+\to K^+ η) = (1.17 \pm 0.10 \pm 0.03)\times 10^{-4}$ and ${\mathcal B}(D^+\to K^+ η^{\prime}) = (1.88 \pm 0.15 \pm 0.11)\times 10^{-4}$, where the first uncertainties are statistical and the second systematic. The branching fractions of $D^+\to K^+η$ and $ D^+ \to K^+ η^{\prime}$ are consistent with the world average values. The reported branching fraction of $D^+\to K^+π^0$ deviates with the world average value by 3$σ$.

hep-ex↗

arXiv2025

Search for the charmonium weak decays $J/ψ\to D_{s}^{-}ρ^{+}+c.c.$ and $J/ψ\to D_{s}^{-}π^{+}+c.c.$

Based on $(10087\pm44)\times 10^6$ $J/ψ$ events recorded with the BESIII detector, we search for the rare charmonium weak decays $J/ψ\to D_{s}^{-}ρ^{+}+c.c.$ and $J/ψ\to D_{s}^{-}π^{+}+c.c.$ No signal is observed, and upper limits on the branching fractions at the $90\%$ confidence level are set as $\mathcal{B}(J/ψ\to D_{s}^{-}ρ^{+}+c.c.)<8.0\times10^{-7}$ and $\mathcal{B}(J/ψ\to D_{s}^{-}π^{+}+c.c.)<4.1\times10^{-7}$. Our results provide the most stringent experimental constraints on these decays.

hep-ex↗

arXiv2025

Measurements of absolute branching fractions of $D^{0(+)}\to KKKπ$ decays

Using an $e^+e^-$ sample of $20.3\,\rm fb^{-1}$ collected at the center-of-mass energy $\sqrt{s}=$ 3.773 GeV with the BESIII detector, we report measurements of several four-body hadronic decays of the $D$ mesons. The absolute branching fractions are determined to be ${\mathcal B}(D^0\to K^0_S K^+K^-π^0 )=( 18.4^{+2.6}_{-2.5}\pm 2.4)\times 10^{-5}$, ${\mathcal B}(D^0\to K^0_S K^0_S K^-π^+ )=( 12.9^{+1.7}_{-1.6}\pm 2.5)\times 10^{-5}$, ${\mathcal B}(D^0\to K^0_S K^0_S K^+π^-)=(5.7^{+1.2}_{-1.1}\pm 1.3)\times 10^{-5}$, ${\mathcal B}(D^0\to K^+K^-K^-π^+ )=(17.4^{+1.8}_{-1.7}\pm { 2.2})\times 10^{-5}$, and ${\mathcal B}(D^+\to K^0_S K^+K^-π^+)=(13.8^{+2.4}_{-2.2}\pm 2.5)\times 10^{-5}$. Furthermore, significant $ϕ$ signals are found in the decay channels involving $K^+K^-$ pair, and the corresponding branching fractions are measured as ${\mathcal B}(D^0\to ϕK^0_Sπ^0 )=( 22.7^{+5.4}_{-5.1}\pm 3.7)\times 10^{-5}$, ${\mathcal B}(D^0\to ϕK^-π^+ )=(25.2^{+3.5}_{-3.3}\pm 4.6)\times 10^{-5}$, ${\mathcal B}(D^+\to ϕK^0_Sπ^+)=(16.5 ^{+6.0}_{-5.3}\pm 2.6 )\times 10^{-5}$. The branching fractions of $D^0\to K^0_S K^+K^-π^0$, $D^0\to ϕK^0_Sπ^0$, and $D^+\to ϕK^0_S π^+$ are measured for the first time, and those of $D^0\to K^0_S K^0_SK^-π^+$, $D^0\to K^0_S K^0_SK^+π^-$, $D^0\to K^+K^-K^-π^+$, $D^0\to ϕK^-π^+$, and $D^+\to K^0_S K^+K^-π^+$ are measured with improved precision. The first uncertainties are statistical and the second are systematic.

hep-ex↗

arXiv2025

Search for the charged lepton flavor violating decay $ψ(3686)\to e^{\pm}μ^{\mp}$

By analyzing $(2367.0\pm11.1)\times10^6$ $ψ(3686)$ events collected in $e^+e^-$ collisions at $\sqrt{s}=3.686~\rm GeV$ with the BESIII detector at the BEPCII collider, we report the first search for the charged lepton flavor violating decay $ψ(3686)\to e^{\pm}μ^{\mp}$. No signal is found. An upper limit on the branching fraction $\mathcal{B}(ψ(3686)\to e^{\pm}μ^{\mp})$ is determined to be $1.4\times10^{-8}$ at the 90\% confidence level.

hep-ex↗

arXiv2025

Observation of $D^+\to K^0_Sπ^0μ^+ν_μ$, Test of Lepton Flavor Universality and First Angular Analysis of $D^+\to \bar{K}^\ast(892)^0\ell^+ν_\ell$

We report a study of the semileptonic decays $D^+\to K_S^0π^0\ell^+ν_\ell$ ($\ell = e, μ$) based on $20.3\,\mathrm{fb}^{-1}$ of $e^+e^-$ collision data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The $D^+\to K_S^0π^0μ^+ν_μ$ decay is observed for the first time, with a branching fraction of $(0.896\pm0.017_{\rm stat}\pm0.008_{\rm syst})\%$, and the branching fraction of $D^+\to K_S^0π^0e^+ν_e$ is determined with the improved precision as $(0.943\pm0.012_{\rm stat}\pm0.010_{\rm syst})\%$. From the analysis of the dynamics, we observe that the dominant $\bar{K}^\ast(892)^0$ component is accompanied by an $S$-wave contribution, which accounts for $(7.10 \pm 0.68_{\rm stat} \pm 0.41_{\rm syst})\%$ of the total decay rate of the $μ^+$ channel and $(6.39 \pm 0.17_{\rm stat} \pm 0.14_{\rm syst})\%$ of the $e^+$ channel. Assuming a single-pole dominance parameterization, the hadronic form factor ratios are extracted to be $r_V=V(0)/A_1(0)=1.42 \pm\, 0.03_{\rm stat} \pm\, 0.02_{\rm syst}$ and $r_2=A_2(0)/A_1(0)=0.75 \pm\, 0.03_{\rm stat} \pm\, 0.01_{\rm syst}$. Based on the first comprehensive angular and the decay-rate $CP$ asymmetry analysis, the full set of averaged angular and $CP$ asymmetry observables are measured as a function of the momentum-transfer squared; they are consistent with expectations from the Standard Model. No evidence for violation of $μ-e$ lepton-flavor universality is observed in either the full range or the five chosen bins of momentum-transfer squared.

hep-ex↗

arXiv2025

Study of $ϕ\to K\bar{K}$ and $K_{S}^{0}-K_{L}^{0}$ Asymmetry in the Amplitude Analysis of $D_{s}^{+} \to K_{S}^{0}K_{L}^{0}π^{+}$ Decays

Using $e^+e^-$ annihilation data corresponding to a total integrated luminosity of 7.33 $\rm fb^{-1}$ collected at center-of-mass energies between 4.128 and 4.226~GeV with the BESIII detector, we provide the first amplitude analysis and absolute branching fraction measurement of the hadronic decay $D_{s}^{+} \to K_{S}^{0}K_{L}^{0}π^{+}$. The branching fraction of $D_{s}^{+} \to K_{S}^{0}K_{L}^{0}π^{+}$ is determined to be $(1.86\pm0.06_{\rm stat}\pm0.03_{\rm syst})\%$. Combining the $\mathcal{B}[D_{s}^{+} \to ϕ(\to K_{S}^0K_{L}^0) π^+]$ obtained in this work and the world average of $\mathcal{B}[D_{s}^{+} \to ϕ(\to K^+K^-) π^+]$, we measure the relative branching fraction $\mathcal{B}(ϕ\to K_S^0K_L^0)/\mathcal{B}(ϕ\to K^+K^-)$=($0.593 \pm 0.023_{\rm stat} \pm 0.014_{\rm syst} \pm 0.016_{ϕπ}$), where the third error is due to the uncertainty of the $\mathcal{B}(D_s^+ \to ϕπ^+,ϕ\to K^+K^-)$. Our result deviates from the Particle Data Group value by more than 3$σ$. Furthermore, the asymmetry of the branching fractions of $D^+_s\to K_{S}^0K^{*}(892)^{+}$ and $D^+_s\to K_{L}^0K^{*}(892)^{+}$, $\frac{\mathcal{B}[D_{s}^{+} \to K_{S}^0K^{*}(892)^{+}]-\mathcal{B}[D_{s}^{+} \to K_{L}^0K^{*}(892)^{+}]}{\mathcal{B}[D_{s}^{+} \to K_{S}^0K^{*}(892)^{+}]+\mathcal{B}[D_{s}^{+} \to K_{L}^0K^{*}(892)^{+}]}$, is determined to be $(-14.5\pm 5.1_{\rm stat}\pm 1.8_{\rm syst})\%$.

hep-ex↗

arXiv2025

Single Inclusive $π^\pm$ and $K^\pm$ Production in $e^+e^-$ Annihilation at center-of-mass Energies from 2.000 to 3.671GeV

Using data samples with a total integrated luminosity of 253 $\rm pb^{-1}$ collected by the BESIII detector operating at the BEPCII collider, the differential cross-sections of inclusive $π^\pm$ and $K^\pm$ production, as a function of momentum and normalized by the total hadronic cross-section, are measured at center-of-mass energies from 2.000 to 3.671 GeV. The measured $π^{\pm}$ cross sections are consistent with the previously reported $π^{0}$ cross-sections by BESIII, while the $K^{\pm}$ cross sections are systematically higher than the $K^0_S$ cross sections by a factor of approximately 1.4. These new results are in agreement with state-of-the-art QCD analyses at next-to-next-to-leading order accuracy, particularly in the large hadron momentum region at energy scales down to 3 GeV. These findings support the validity of isospin symmetry in parton fragmentation processes.

hep-ex↗

arXiv2025

First measurement of the cross sections for $e^{+}e^{-}\to K^{0}K^{-}π^{+}J/ψ+c.c.$ at $\sqrt{s}$ from 4.396 to 4.951 GeV

Using $e^+e^-$ collision data at 19 center-of-mass energies ranging from $4.396$ to $4.951~\mathrm{GeV}$ corresponding to a total integrated luminosity of $8.86~{\rm fb}^{-1}$ collected by the BESIII detector, the process $e^+e^-\to K^{0}K^-π^+ J/ψ+c.c.$ is observed for the first time, with a statistical significance of $9.4σ$ summing up all the data samples. For this process, the cross section and the upper limit at the $90\%$ confidence level are reported at each of the 19 center-of-mass energies.~No statistically significant vector structures are observed in the cross section line shape, nor are any intermediate states of $Kπ$, $K\bar{K}$, $K\bar{K}π$, $KJ/ψ$, $πJ/ψ$, and $KπJ/ψ$ seen at individual energy points or in the combined data sample.

hep-ex↗

arXiv2025

First Measurement of the $D_s^+\rightarrow K^0μ^+ν_μ$ Decay

We report the first measurement of the semileptonic decay $D^+_s \rightarrow K^0μ^+ν_μ$, using a sample of $e^+e^-$ annihilation data corresponding to an integrated luminosity of $7.33~\mathrm{fb}^{-1}$ collected at center-of-mass energies between 4.128 to 4.226~GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be $\mathcal{B}(D^+_s\rightarrow K^0μ^+ν_μ) = (2.89 \pm 0.27_{\rm stat} \pm 0.12_{\rm syst})\times 10^{-3}$, where the first uncertainty is statistical and the second is systematic. Based on a simultaneous fit to the partial decay rates in $q^2$ intervals measured in $D^+_s \rightarrow K^0μ^+ν_μ$ and $D^+_s \rightarrow K^0e^+ν_{e}$ decays, the product value of the form factor $f^{K^0}_{+}(0)$ and the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cd}|$ is measured to be $f^{K^0}_{+}(0)|V_{cd}|=0.140\pm0.008_{\rm stat}\pm0.002_{\rm syst}$. Using $|V_{cd}|=0.22486\pm0.00068$ as an input, the hadronic form factor is determined to be $f^{K^0}_{+}(0)=0.623\pm0.036_{\rm stat} \pm 0.009_{\rm syst}$ at $q^2=0$. This is the most precise determination of $f^{K^0}_{+}(0)$ in the $D^+_s \rightarrow K^0$ transition to date. The measured branching fraction and form factor presented in this work provide the most stringent test on various non-perturbative theoretical calculations. Taking $f^{K^0}_{+}(0)=0.6307\pm0.0020$ from lattice calculations as an input, we obtain $|V_{cd}|=0.220\pm0.013_{\rm stat}\pm0.003_{\rm syst}\pm0.001_{\rm LQCD}$, which is the most precise determination of $|V_{cd}|$ using the $D_s^+\rightarrow K^0\ell^+ν_{\ell}$ decays. In addition, lepton flavor universality is tested for the first time with $D^+_s \rightarrow K^0\ell^+ν_{\ell}$ decays in full and separate $q^2$ intervals. No obvious violation is found.

hep-ex↗

arXiv2025

Search for the lepton number violating decay $η\to π^+π^+e^-e^- + c.c.$ via $J/ψ\toϕη$

Based on a sample of $ (10.087\pm 0.044)\times 10^{9} J/ψ$ events collected by the BESIII detector at the BEPCII collider, we perform the first search for the lepton number violating decay $η\to π^+π^+ e^-e^- + \text{c.c.}$ No signal is found, and an upper limit on the branching fraction of $η\to π^+π^+ e^-e^- + c.c.$ is set to be $4.6 \times 10^{-6}$ at the 90\% confidence level.

hep-ex↗

arXiv2025

Observation of Transverse Polarization and Determination of Psionic Form Factors of the $Λ$ Hyperon at $\sqrt{s}= 3.773$ GeV

Using a data sample of $e^{+}e^{-}$ collision data corresponding to an integrated luminosity of 20.3 fb$^{-1}$ collected by the BESIII detector at the BEPCII collider, we present an observation of transverse polarization and a complete determination of the psionic form factors of the $Λ$ hyperon in $e^{+}e^{-}\toΛ\barΛ$ decay with the entangled $Λ-\barΛ$ pair at $\sqrt{s}=3.773$ GeV. The relative phase between the psionic form factors is determined to be $ΔΦ=(1.53\pm0.36\pm0.03)$~rad with a significance of 5.5 $σ$ taking into account systematic uncertainty. This result indicates a non-zero phase between the transition amplitudes of the $Λ\barΛ$ helicity states. Additionally, we measure the angular distribution parameter and the modulus of the ratio between the psionic form factors to be $η=0.86\pm0.05\pm0.03$ and $R(s)=|G_{E}(s)/G_{M}(s)|=0.47\pm0.08\pm0.05$, where the first uncertainty is statistical and the second systematic.

hep-ex↗

arXiv2025

Investigation of hadronic cross sections of cosmic ray carbon and oxygen on BGO from 200 GeV to 10 TeV energy at the DAMPE experiment

The Dark Matter Particle Explorer (DAMPE) has made significant progress in measuring the fluxes of cosmic rays. These new measurements are pivotal in advancing our understanding of the origins and propagation mechanisms of cosmic rays. The bismuth germanium oxide (BGO) calorimeter plays a crucial role in these measurements, particularly in the precise determination of cosmic ray fluxes. However, for a calorimetric experiment like DAMPE, uncertainties in hadronic models persist as a major barrier in achieving more accurate measurements of fluxes of cosmic ray nuclei. This study centers on the measurement of the inelastic hadronic cross sections of carbon and oxygen nuclei interacting with BGO crystals target over an extensive energy range, spanning from 200 GeV to 10 TeV. For carbon nuclei interacting with the BGO target, the measurements of the cross sections have achieved a total relative uncertainty of less than 10% below 8 TeV for carbon, and below 3 TeV for oxygen. For oxygen nuclei, the same level of precision was attained below 3 TeV. Additionally, we compare the experimental results with Geant4 and FLUKA simulations to validate the accuracy and consistency of these simulation tools. Through comprehensive analysis of the inelastic hadronic interaction cross sections, this research provides validation for the hadronic interaction models used in DAMPE's cosmic-ray flux measurements.

hep-ex↗

arXiv2025

Search for sub-GeV invisible particles in inclusive decays of $J/ψ$ to $ϕ$

A search for an invisible particle, $X$, with a mass between 0 and 0.96 $\textrm{GeV}/\textit{c}^{2}$, is performed in the process $J/ψ\rightarrowϕ+ X$ using $(8774.0\pm39.4)\times10^{6}$ $J/ψ$ events collected with the BESIII detector from 2017 to 2019. The $ϕ$ meson is fully reconstructed and an efficient veto of photons, neutral and charged hadrons up to twice the $K_L^0$ mass is applied to the rest of the event and the recoil mass against the $ϕ$ is obtained precisely from the kinematic constraint in the event. No significant signal over the expected background is observed in the investigated region and the upper limit on the inclusive branching fraction of $J/ψ\rightarrowϕ+ X$ is determined to be $7.0\times10^{-8}$ at 90\% confidence level. Upper limits at a 90\% confidence level are also given for this branching fraction as a function of the invisible particle mass, varying from $4\times10^{-9}$ to $4\times10^{-8}$ over the investigated mass range. Additionally, a 90\% confidence level upper limit on the branching fraction of $η\rightarrow \rm{invisible}$ is determined to $2.4\times10^{-5}$, which improves the previous best results by more than four times. The analysis technique in this work offers a clean window to search for sub-GeV invisible particles, which can be adapted for other $J/ψ$ decays and direct $e^+e^-$ annihilation experiments in future studies, and improve the sensitivity by orders of magnitude.

hep-ex↗