arXiv subjects

Y. Fang

Publications and source records attributed to Y. Fang.

At least 37 records · Page 2Linked to original sources

arXiv2025

Measurement of branching fractions of $Λ_{c}^{+}$ decays to $Σ^{+} η$ and $Σ^{+} η'$

By analyzing $e^+e^-$ collision data taken at center-of-mass energies $\sqrt{s}$ between 4.600 and 4.699 GeV with the BESIII detector at the BEPCII collider, corresponding to an integrated luminosity of $\rm 4.5~fb^{-1}$, we study the hadronic decays $Λ_{c}^{+} \rightarrow Σ^{+} η$ and $Λ_{c}^{+} \rightarrow Σ^{+} η^{\prime}$ using the single-tag method. The branching fraction ratio of $Λ_{c}^+ \rightarrow Σ^+ η$ relative to $Λ_{c}^+ \rightarrow Σ^+ π^0$ is determined to be $0.305 \pm 0.046_{\rm stat.} \pm 0.007_{\rm syst.}$, and that of $Λ_{c}^+ \rightarrow Σ^+ η'$ relative to $Λ_{c}^+ \rightarrow Σ^+ ω$ is $0.336 \pm 0.094_{\rm stat.} \pm 0.037_{\rm syst.}$. The ratio of $\frac{\mathcal{B}\left(Λ_{c}^{+} \rightarrow Σ^{+} η'\right)}{\mathcal{B}\left(Λ_{c}^{+} \rightarrow Σ^{+} η\right)} $ is determined to be $1.73 \pm 0.22_{\rm stat.} \pm 0.16_{\rm syst.}$. These results enrich our knowledge of charmed baryon decays.

hep-ex↗

arXiv2025

Discovery and Analysis of Afterglows from Poorly Localised GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey

Gamma-ray bursts (GRBs), particularly those detected by wide-field instruments such as the Fermi/GBM, pose a challenge for optical follow-up due to their large initial localisation regions, leaving many GRBs without identified afterglows. The Gravitational-wave Optical Transient Observer (GOTO), with its wide field of view, dual-site coverage, and robotic rapid-response capability, bridges this gap by rapidly identifying and localising afterglows from alerts issued by space-based facilities, including Fermi, SVOM, Swift, and EP, providing early optical positions for coordinated multiwavelength follow-up. In this paper, we present optical afterglow localisation and multiband follow-up of five Fermi/GBM (240619A, 240910A, 240916A, 241002B, and 241228B) and two MAXI/GSC (240122A and 240225B) triggered long GRBs (LGRBs) discovered by GOTO in 2024. Spectroscopy for six GRBs (no spectroscopic data for GRB 241002B) with VLT/X-shooter and GTC/OSIRIS yields precise redshifts spanning $z\approx0.40-$3.16 and absorption-line diagnostics of host and intervening systems. Radio detections for four events confirm the presence of long-lived synchrotron emission. Prompt-emission analysis with Fermi and MAXI data reveals a spectrally hard population, with two bursts lying $>3σ$ above the Amati relation. Although their optical afterglows resemble those of typical LGRBs, the prompt spectra are consistently harder than the LGRBs' average. Consistent modelling of six GOTO-discovered GRB afterglows yields jet half-opening angles of a few degrees and beaming-corrected kinetic energies ($E_{jet}\sim10^{51-52}$)erg, consistent with the canonical LGRB population. These findings suggest that optical discovery of poorly localised GRBs may be subject to observational biases favouring luminous events with high spectral peak energy, while also providing insight into jet microphysics and central engine diversity.

astro-ph.HE↗

arXiv2025

Partial Wave Analysis of $e^{+}e^{-} \rightarrow π^{+}π^{-}J/ψ$ and Cross Section Measurement of $e^{+}e^{-} \rightarrow π^{\pm}Z_{c}(3900)^{\mp}$ from 4.1271 to 4.3583 GeV

Based on 12.0 $\mathrm{fb^{-1}}$ of $e^{+}e^{-}$ collision data samples collected by the BESIII detector at center-of-mass energies from 4.1271 to 4.3583 GeV, a partial wave analysis is performed for the process $e^{+}e^{-} \rightarrow π^{+}π^{-}J/ψ$. The cross sections for the sub processes ${e^{+}e^{-}\rightarrowπ^{+}Z_{c}(3900)^{-}+c.c.\rightarrowπ^{+}π^{-}J/ψ}$, $f_{0}(980)(\rightarrowπ^{+}π^{-})J/ψ$, and $(π^{+}π^{-})_{\rm{S\mbox{-}wave}} J/ψ$ are measured for the first time. The mass and width of the $Z_{c}(3900)^{\pm}$ are determined to be $3884.6\pm0.7\pm3.3$ MeV/$c^{2}$ and $37.2\pm1.3\pm6.6$ MeV, respectively. The first errors are statistical and the second systematic. The final state $(π^{+}π^{-})_{\rm{S\mbox{-}wave}} J/ψ$ dominates the process $e^{+}e^{-} \rightarrow π^{+}π^{-}J/ψ$. By analyzing the cross sections of $π^{\pm}Z_{c}(3900)^{\mp}$ and $f_{0}(980)J/ψ$, $Y(4220)$ has been observed. Its mass and width are determined to be $4225.7\pm4.1\pm3.4$ MeV/$c^{2}$ and $57.5\pm9.4\pm12.1$ MeV, respectively.

hep-ex↗

arXiv2025

Measurement of Born Cross Sections and Effective Form Factors of $e^+e^-\to Ω^{-}\barΩ^{+}$ from$\sqrt{s}$ = 3.7 to 4.7 GeV

Using $e^+e^-$ collision data corresponding to an integrated luminosity of 22.7 fb$^{-1}$, collected at center-of-mass energies between 3.7 and 4.7 GeV with the BESIII detector at the BEPCII storage ring, we measure the energy-dependent Born cross sections of $e^+e^-\to Ω^{-}\barΩ^+$ and the effective form factors of the $Ω^-$ baryon. The analysis employs a single baryon tagging method, and the results are consistent with theoretical predictions, providing critical constraints on the electromagnetic structure of the $Ω^-$ hyperon. No significant signal of charmonium or charmonium-like states decaying to $Ω^{-}\barΩ^+$ is observed in the investigated energy range.

hep-ex↗

arXiv2025

First observation of $Λ_{c}(2595)^{+} \to Λ^{+}_{c}π^0π^0$ and $Λ_{c}(2625)^{+}\to Λ^{+}_{c}π^0π^0$

By analysing $e^+e^-$ annihilation data corresponding to an integrated luminosity of 368.48~pb$^{-1}$ collected at the centre-of-mass energies of $\sqrt{s} = 4.918$ and $4.951$~GeV with the BESIII detector, we report the first observation of $Λ_{c}(2595)^{+}$ and $Λ_{c}(2625)^{+}\to Λ^{+}_{c}π^0π^0$ with statistical significances of 7.9$σ$ and 11.8$σ$, respectively. The branching fractions of $Λ_{c}(2595)^{+}$ and $Λ_{c}(2625)^{+}\to Λ^{+}_{c}π^0π^0$ are measured to be $(59.5 \pm 11.1_{\rm stat.} \pm 7.9_{\rm syst.}) \%$ and $(41.0 \pm 5.2_{\rm stat.} \pm 3.3_{\rm syst.}) \%$, respectively. The absolute branching fraction of $Λ_{c}(2595)^{+}$ is consistent with the expectation of the mechanism referred to as the threshold effect, proposed for the strong decays of $Λ_{c}(2595)^{+}$ within uncertainty.

hep-ex↗

arXiv2025

Precision Measurement of the Branching Fraction of $D^{+}\to μ^{+}ν_μ$

Using $20.3~\mathrm{fb}^{-1}$ of $e^+e^-$ collision data collected at a center-of-mass energy of $E_{\rm c.m.}=3.773$ GeV with the BESIII detector operating at the BEPCII collider, we determine the branching fraction of the leptonic decay $D^+\toμ^+ν_μ$ to be $(4.034\pm0.080_{\rm stat}\pm0.040_{\rm syst})\times10^{-4}$. Interpreting our measurement with knowledge of the Fermi coupling constant $G_F$, the masses of the $D^+$ and $μ^+$ as well as the lifetime of the $D^+$, we determine $f_{D^+}|V_{cd}|=(48.02\pm0.48_{\rm stat}\pm0.24_{\rm syst}\pm0.12_{\rm input}\pm0.15_{\rm EM})~\mathrm{MeV}$ after taking into account necessary radiative corrections. This result is a factor of 2.3 more precise than the previous best measurement. Using the value of the magnitude of the $c\to d$ Cabibbo-Kobayashi-Maskawa matrix element $|V_{cd}|$ given by the global standard model fit, we obtain the $D^+$ decay constant $f_{D^+}=(213.5\pm2.1_{\rm stat}\pm1.1_{\rm syst}\pm0.8_{\rm input}\pm0.7_{\rm EM})$\,MeV. Alternatively, using the value of $f_{D^+}$ from a precise lattice quantum chromodynamics calculation, we extract $|V_{cd}|=0.2265\pm0.0023_{\rm stat}\pm0.0011_{\rm syst}\pm0.0009_{\rm input}\pm0.0007_{\rm EM}$.

hep-ex↗

arXiv2025

Precise Measurement of the $χ_{c0}$ Resonance Parameters and Branching Fractions of $χ_{c0,c2}\toπ^+π^-/K^+K^-$

By analyzing a $ψ(3686)$ data sample containing $(107.7\pm0.6)\times10^{6}$ events taken with the BESIII detector at the BEPCII storage ring in 2009, the $χ_{c0}$ resonance parameters are precisely measured using $χ_{c0,c2} \to π^+π^-/K^+K^-$ events. The mass of $χ_{c0}$ is determined to be $M(χ_{c0})=(3415.63\pm0.07\pm0.07\pm0.07$)~MeV/$c^2$, and its full width is $Γ(χ_{c0})=(12.52\pm0.12\pm0.13)~{\rm MeV}$, where the first uncertainty is statistical, the second systematic, and the third for mass comes from $χ_{c2}$ mass uncertainty. These measurements improve the precision of $χ_{c0}$ mass by a factor of four and width by one order of magnitude over the previous individual measurements, and significantly boost our knowledge about the charmonium spectrum. Together with additional $(345.4\pm2.6)\times10^{6}$ $ψ(3686)$ data events taken in 2012, the decay branching fractions of $χ_{c0,c2}\toπ^+π^-/K^+K^-$ are measured as well, with precision improved by a factor of three compared to previous measurements. These $χ_{c0}$ decay branching fractions provide important inputs for the study of glueballs.

hep-ex↗

arXiv2025

Interplay between trimer structure and magnetic ground state in Ba5Ru3O12 probed by Neutron and muSR techniques

We report a detailed inelastic neutron scattering (INS) and muon spin relaxation (muSR) investigation of a trimer Ruthenate Ba5Ru3O12 system, which undergoes long-range antiferromagnetic ordering at TN = 60 K. The INS reveals two distinct spin wave excitations below TN: one at 5.6 meV and the other at 10-15 meV. By accompanying the INS spectra based on a linear spin wave theory using SpinW software and machine learning force fields (MLFFs), we show that Ba5Ru3O12 exhibits spin frustration due to competing exchange interactions between neighboring and next-neighboring Ru-moments, exchange anisotropy, and strong spin-orbit coupling, which yields a non-collinear spin structure, in contrast to other ruthenate trimers in this series. Interestingly, these magnetic excitations do not completely vanish even at high temperatures above TN, evidencing short-range magnetic correlations in this trimer system. This is further supported by muSR spectroscopy, which exhibits a gradual drop in the initial asymmetry around the magnetic phase transition and is further verified through maximum entropy analysis. The results of muSR spectroscopy indicate a dynamic nature of magnetic order, attributed to local magnetic anisotropy within the trimer as a result of local structural distortion and different hybridization, consistent with canted spin-structure. We predict the ground state of Ru3O12-isolated trimer through theoretical calculations, which agree with the experimentally observed spin excitation

cond-mat.str-el↗

arXiv2025

Observation of resonant contribution to the $e^+e^-\to Ω^{-}\barΩ^{+}$ around 4.2 GeV and evidence of $ψ(3770)\to Ω^{-}\barΩ^{+}$

Using $e^+e^-$ collision data corresponding to a total integrated luminosity of 22.7 fb$^{-1}$, collected at center-of-mass energies between 3.7 and 4.7 GeV with the BESIII detector, we present a measurement of energy-dependent cross sections and effective form factors for the process of $e^+e^-\to Ω^{-}\barΩ^+$. By conducting a fit to the cross sections of $e^+e^-\to Ω^{-}\barΩ^+$ considering the continuum and resonant contributions, a clear resonant structure in the spectrum around 4.2 GeV is observed for the first time with a statistical significance exceeding 10$σ$, and it can be well described with the line shape of the $Y(4230)$ and $Y(4320)$ observed in $e^+e^-\to π^{+}π^{-}J/ψ$. Evidence for the decay $ψ(3770) \to Ω^-\barΩ^{+}$ is observed with a statistical significance of 4.4$σ$ by analyzing the measured cross sections together with earlier BESIII results, and the branching fraction is firstly measured to be $(4.0\pm1.0\pm0.6)$ $\times$ $10^{-5}$, where the first uncertainty is statistical and the second is systematic.

hep-ex↗

arXiv2025

Measurement of the phase between strong and electromagnetic amplitudes in the decay $J/ψ\toϕη$

The first direct measurement of the relative phase between the strong and electromagnetic amplitudes for a $J/ψ$ decaying into a vector-pseudoscalar final state is performed using 26 energy points of $e^+e^-$ annihilation data between $3.00\ \text{GeV}$ and \mbox{3.12 GeV}. The data sets were collected by the BESIII detector with a total integrated luminosity of 452 pb$^{-1}$. By investigating the interference pattern in the cross section lineshape of $e^+e^-\toϕη$, the relative phase between the strong and electromagnetic amplitudes of $J/ψ$ decay is determined to be within $[133^\circ,228^\circ]$ at 68\% confidence level.

hep-ex↗

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

Euclid Quick Data Release (Q1): From images to multiwavelength catalogues: the Euclid MERge Processing Function

The Euclid satellite is an ESA mission that was launched in July 2023. \Euclid is working in its regular observing mode with the target of observing an area of $14\,000~\text{deg}^2$ with two instruments, the Visible Camera (VIS) and the Near IR Spectrometer and Photometer (NISP) down to $I_{\rm E} = 24.5~\text{mag}$ ($10\, σ$) in the Euclid Wide Survey. Ground-based imaging data in the \textit{ugriz} bands complement the \Euclid data to enable photo-$z$ determination and VIS PSF modeling for week lensing analysis. Euclid investigates the distance-redshift relation and the evolution of cosmic structures by measuring shapes and redshifts of galaxies and clusters of galaxies out to $z\sim 2$. Generating the multi-wavelength catalogues from \Euclid and ground-based data is an essential part of the \Euclid data processing system. In the framework of the \Euclid Science Ground Segment (SGS), the aim of the MER Processing Function (PF) pipeline is to detect objects in the \Euclid imaging data, measure their properties, and MERge them into a single multi-wavelength catalogue. The MER PF pipeline performs source detection on both visible (VIS) and near-infrared (NIR) images and offers four different photometric measurements: Kron total flux, aperture photometry on PSF-matched images, template fitting photometry, and Sérsic fitting photometry. Furthermore, the MER PF pipeline measures a set of ancillary quantities, spanning from morphology to quality flags, to better characterise all detected sources. In this paper, we show how the MER PF pipeline is designed, detailing its main steps, and we show that the pipeline products meet the tight requirements that Euclid aims to achieve on photometric accuracy. We also present the other measurements (e.g. morphology) that are included in the OU-MER output catalogues and we list all output products coming out of the MER PF pipeline.

astro-ph.IM↗

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

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

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

An extremely soft and weak fast X-ray transient associated with a luminous supernova

Long gamma-ray bursts (LGRBs), including their subclasses of low-luminosity GRBs (LL-GRBs) and X-ray flashes (XRFs) characterized by low spectral peak energies, are known to be associated with broad-lined Type Ic supernovae (SNe Ic-BL), which result from the core collapse of massive stars that lose their outer hydrogen and helium envelopes. However, the soft and weak end of the GRB/XRF population remains largely unexplored, due to the limited sensitivity to soft X-ray emission. Here we report the discovery of a fast X-ray transient, EP250108a, detected by the Einstein Probe (EP) in the soft X-ray band at redshift $z = 0.176$, which was followed up by extensive multiband observations. EP250108a shares similar X-ray luminosity as XRF\,060218, the prototype of XRFs, but it extends GRBs/XRFs down to the unprecedentedly soft and weak regimes, with its $E_{\rm peak} \lesssim 1.8\,\mathrm{keV}$ and $E_{\rm iso} \lesssim 10^{49}\, \mathrm{erg}$, respectively. Meanwhile, EP250108a is found to be associated with SN\,2025kg, one of the most luminous and possibly magnetar-powered SNe Ic-BL detected so far. Modeling of the well-sampled optical light curves favors a mildly relativistic outflow as the origin of this event. This discovery demonstrates that EP, with its unique capability, is opening a new observational window into the diverse outcomes of death of massive stars.

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↗