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S. Fegan

Publications and source records attributed to S. Fegan.

At least 145 records · Page 8Linked to original sources

The 2014 TeV Gamma-ray Flare of Mrk 501 Seen with H.E.S.S.: Temporal and Spectral Constraints on Lorentz Invariance Violation

The blazar Mrk 501 (z=0.034) was observed at very-high-energy (VHE, $E\gtrsim 100$~GeV) gamma-ray wavelengths during a bright flare on the night of 2014 June 23-24 (MJD 56832) with the H.E.S.S. phase-II array of Cherenkov telescopes. Data taken that night by H.E.S.S. at large zenith angle reveal an exceptional number of gamma-ray photons at multi-TeV energies, with rapid flux variability and an energy coverage extending significantly up to 20 TeV. This data set is used to constrain Lorentz invariance violation (LIV) using two independent channels: a temporal approach considers the possibility of an energy dependence in the arrival time of gamma rays, whereas a spectral approach considers the possibility of modifications to the interaction of VHE gamma rays with extragalactic background light (EBL) photons. The non-detection of energy-dependent time delays and the non-observation of deviations between the measured spectrum and that of a supposed power-law intrinsic spectrum with standard EBL attenuation are used independently to derive strong constraints on the energy scale of LIV ($E_{\rm{QG}}$) in the subluminal scenario for linear and quadratic perturbations in the dispersion relation of photons. For the case of linear perturbations, the 95% confidence level limits obtained are $E_{\rm{QG},1} > 3.6 \times 10^{17} \ \rm{GeV} $ using the temporal approach and $E_{\rm{QG},1} > 2.6 \times 10^{19} \ \rm{GeV}$ using the spectral approach. For the case of quadratic perturbations, the limits obtained are $E_{\rm{QG},2} > 8.5 \times 10^{10} \ \rm{GeV} $ using the temporal approach and $E_{\rm{QG},2} > 7.8 \times 10^{11} \rm{ GeV}$ using the spectral approach.

astro-ph.HE↗

Observation of $D^+_s\rightarrow p\bar{n}$ and confirmation of its large branching fraction

The baryonic decay $D^+_s\rightarrow p\bar{n}$ is observed, and the corresponding branching fraction is measured to be $(1.21\pm0.10\pm0.05)\times10^{-3}$, where the first uncertainty is statistical and second systematic. The data sample used in this analysis was collected with the BESIII detector operating at the BEPCII $e^+e^-$ double-ring collider with a center-of-mass energy of 4.178~GeV and an integrated luminosity of 3.19~fb$^{-1}$. The result confirms the previous measurement by the CLEO Collaboration and is of greatly improved precision, which may deepen our understanding of the dynamical enhancement of the W-annihilation topology in the charmed meson decays.

hep-ex↗

Study of the $D^0\to K^-μ^+ν_μ$ dynamics and test of lepton flavor universality with $D^0\to K^-\ell^+ν_\ell$ decays

Using $e^+e^-$ annihilation data of $2.93~\mathrm{fb}^{-1}$ collected at center-of-mass energy $\sqrt{s}=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction of $D^{0}\to K^{-}μ^{+}ν_μ$ with significantly improved precision: ${\mathcal B}_{D^{0}\to K^{-}μ^{+}ν_μ}=(3.413\pm0.019_{\rm stat.}\pm0.035_{\rm syst.})\%$. Combining with our previous measurement of ${\mathcal B}_{D^0\to K^-e^+ν_e}$, the ratio of the two branching fractions is determined to be ${\mathcal B}_{D^0\to K^-μ^+ν_μ}/{\mathcal B}_{D^0\to K^-e^+ν_e}=0.974\pm0.007_{\rm stat.}\pm0.012_{\rm syst.}$, which agrees with the theoretical expectation of lepton flavor universality within the uncertainty. A study of the ratio of the two branching fractions in different four-momentum transfer regions is also performed, and no evidence for lepton flavor universality violation is found with current statistics. Taking inputs from global fit in the standard model and lattice quantum chromodynamics separately, we determine $f_{+}^{K}(0)=0.7327\pm0.0039_{\rm stat.}\pm0.0030_{\rm syst.}$ and $|V_{cs}| = 0.955\pm0.005_{\rm stat.}\pm0.004_{\rm syst.}\pm0.024_{\rm LQCD}$.

hep-ex↗

Observation of $e^+e^- \rightarrow D_s^+ \overline{D}{}^{(*)0} K^-$ and study of the $P$-wave $D_s$ mesons

Studies of $e^+e^- \to D_s^+ \overline{D}{}^{(*)0}K^-$ and the $P$-wave charmed-strange mesons are performed based on an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567 pb$^{-1}$ collected with the BESIII detector at $\sqrt{s}= 4.600$ GeV. The processes of $e^+e^-\to D_s^+ \overline{D}{*}^{0} K^-$ and $D_s^+ \overline{D}{}^{0} K^-$ are observed for the first time and are found to be dominated by the modes $D_s^+ D_{s1}(2536)^-$ and $D_s^+ D^*_{s2}(2573)^-$, respectively. The Born cross sections are measured to be $σ^{B}(e^+e^-\to D_s^+ \overline{D}{*}^{0} K^-) = (10.1\pm2.3\pm0.8) pb$ and $σ^{B}(e^+e^-\to D_s^+ \overline{D}{}^{0} K^-) = (19.4\pm2.3\pm1.6) pb$, and the products of Born cross section and the decay branching fraction are measured to be $σ^{B}(e^+e^-\to D_s^+D_{s1}(2536)^- + c.c.)\cdot\mathcal{B}(D_{s1}(2536)^- \to \overline{D}{*}^{0} K^-) = (7.5 \pm 1.8 \pm 0.7) pb$ and $σ^{B}(e^+e^-\to D_s^+ D^*_{s2}(2573)^- + c.c.)\cdot\mathcal{B}(D^*_{s2}(2573)^- \to \overline{D}{}^{0} K^-) = (19.7 \pm 2.9 \pm 2.0) pb$. For the $D_{s1}(2536)^-$ and $D^*_{s2}(2573)^-$ mesons, the masses and widths are measured to be $M(D_{s1}(2536)^-) = (2537.7 \pm 0.5 \pm 3.1)~MeV/c^2,$ $ Γ(D_{s1}(2536)^-)) = (1.7\pm 1.2 \pm 0.6)~\rm MeV,$ and $M(D^*_{s2}(2573)^-) = (2570.7\pm 2.0 \pm 1.7)~MeV/c^2,$ $Γ(D^*_{s2}(2573)^-) = (17.2 \pm 3.6 \pm 1.1)~\rm MeV.$ The spin-parity of the $D^*_{s2}(2573)^-$ meson is determined to be $J^P=2^{+}$. In addition, the process $e^+e^-\to D_s^+ \overline{D}{}^{(*)0} K^-$ are searched for using the data samples taken at four (two) center-of-mass energies between 4.416 (4.527) and 4.575 GeV, and upper limits at the $90\%$ confidence level on the cross sections are determined.

hep-ex↗

Observation of $ψ(3686) \to p \bar{p} η^{\prime}$ and improved measurement of $J/ψ\to p \bar{p} η^{\prime}$

We observe the process $ψ(3686) \to p \bar{p} η^{\prime}$ for the first time, with a statistical significance higher than 10$σ$, and measure the branching fraction of $J/ψ\to p \bar{p} η^{\prime}$ with an improved accuracy compared to earlier studies. The measurements are based on $4.48 \times 10^8$ $ψ(3686)$ and $1.31 \times 10^{9}$ $J/ψ$ events collected by the BESIII detector operating at the BEPCII. The branching fractions are determined to be $B(ψ(3686) \to p \bar{p} η^{\prime}) = (1.10\pm0.10\pm0.08)\times10^{-5}$ and $B(J/ψ\to p \bar{p} η^{\prime})=(1.26\pm0.02\pm 0.07)\times10^{-4}$, where the first uncertainties are statistical and the second ones systematic. Additionally, the $η-η^{\prime}$ mixing angle is determined to be $-24^{\circ} \pm 11^{\circ}$ based on $ψ(3686) \to p \bar{p} η^{\prime}$, and $-24^{\circ} \pm 9^{\circ}$ based on $J/ψ\to p \bar{p} η^{\prime}$, respectively.

hep-ex↗

Measurements of the absolute branching fractions and $CP$ asymmetries for $D^+\rightarrow K_{S,L}^0 K^+(π^0)$

Using $e^+e^-$ collision data corresponding to an integrated luminosity of 2.93 fb$^{-1}$ taken at a center-of-mass energy of 3.773 GeV with the BESIII detector, we determine the absolute branching fractions $\mathcal{B}(D^+\rightarrow K_S^0 K^+)$ = $(3.02 \pm 0.09 \pm 0.08)\times10^{-3}$, $\mathcal{B}(D^+\rightarrow K_S^0 K^+ π^0)$ = $(5.07 \pm 0.19 \pm 0.23)\times10^{-3}$, $\mathcal{B}(D^+\rightarrow K_L^0 K^+)$ = $(3.21 \pm 0.11 \pm 0.11)\times10^{-3}$, and $\mathcal{B}(D^+\rightarrow K_L^0 K^+ π^0)$ = $(5.24 \pm 0.22 \pm 0.22)\times10^{-3}$, where the first and second uncertainties are statistical and systematic, respectively. The branching fraction \wbrksk is consistent with the world average value and the other three branching fractions are measured for the first time. We also measure the $CP$ asymmetries for the four decays and do not find a significant deviation from zero.

hep-ex↗

Particle Transport within the Pulsar Wind Nebula HESS J1825-137

Aims: We present a detailed view of the pulsar wind nebula (PWN) HESS J1825-137. We aim to constrain the mechanisms dominating the particle transport within the nebula, accounting for its anomalously large size and spectral characteristics. Methods: The nebula is studied using a deep exposure from over 12 years of H.E.S.S. I operation, together with data from H.E.S.S. II improving the low energy sensitivity. Enhanced energy-dependent morphological and spatially-resolved spectral analyses probe the Very High Energy (VHE, E > 0.1 TeV) gamma-ray properties of the nebula. Results: The nebula emission is revealed to extend out to 1.5 degrees from the pulsar, ~1.5 times further than previously seen, making HESS J1825--137, with an intrinsic diameter of ~100 pc, potentially the largest gamma-ray PWN currently known. Characterisation of the nebula's strongly energy-dependent morphology enables the particle transport mechanisms to be constrained. A dependence of the nebula extent with energy of R $\propto$ E^αwith α= -0.29 +/- 0.04 (stat) +/- 0.05 (sys) disfavours a pure diffusion scenario for particle transport within the nebula. The total gamma-ray flux of the nebula above 1~TeV is found to be (1.12 +/- 0.03 (stat) +/- 0.25 (sys)) $\times 10^{-11}$ cm$^{-2}$ s$^{-1}$, corresponding to ~64% of the flux of the Crab Nebula. Conclusions: HESS J1825-137 is a PWN with clear energy-dependent morphology at VHE gamma-ray energies. This source is used as a laboratory to investigate particle transport within middle-aged PWNe. Deep observations of this highly spatially-extended PWN enable a spectral map of the region to be produced, providing insights into the spectral variation within the nebula.

astro-ph.HE↗

Measurement of $e^{+} e^{-} \rightarrow K^{+} K^{-}$ cross section at $\sqrt{s} = 2.00 - 3.08$ GeV

The cross section of the process $e^{+} e^{-} \rightarrow K^{+} K^{-}$ is measured at a number of center-of-mass energies $\sqrt{s}$ from 2.00 to 3.08 GeV with the BESIII detector at the Beijing Electron Positron Collider (BEPCII). The results provide the best precision achieved so far. A resonant structure around 2.2 GeV is observed in the cross section line shape. A Breit-Wigner fit yields a mass of $M=2239.2 \pm 7.1 \pm 11.3$~and a width of $Γ=139.8\pm12.3\pm20.6$ MeV, where the first uncertainties are statistical and the second ones are systematic. In addition, the time-like electromagnetic form factor of the kaon is determined at the individual center-of-mass energy points.

hep-ex↗

Observation of the $W$-Annihilation Decay $D^{+}_{s} \rightarrow ωπ^{+}$ and Evidence for $D^{+}_{s} \rightarrow ωK^{+}$

We report on the observation of the $W$-annihilation decay $D^{+}_{s} \rightarrow ωπ^{+}$ and the evidence for $D_{s}^{+} \rightarrow ωK^{+}$ with a data sample corresponding to an integrated luminosity of 3.19 fb$^{-1}$ collected with the BESIII detector at the center-of-mass energy $\sqrt{s} = 4.178$ GeV. We obtain the branching fractions $\mathcal{B}(D^{+}_{s} \rightarrow ωπ^{+}) = (1.77\pm0.32_{\rm stat.}\pm0.11_{\rm sys.}) \times 10^{-3}$ and $\mathcal{B}(D^{+}_{s} \rightarrow ωK^{+}) = (0.87\pm0.24_{\rm stat.}\pm0.07_{\rm sys.}) \times 10^{-3}$, respectively.

hep-ex↗

Measurement of the Branching Fraction For the Semi-Leptonic Decays $D^{0(+)}\to π^{-(0)}μ^+ν_μ$ and Test of Lepton Flavor Universality

Using a data sample corresponding to an integrated luminosity of $2.93\,\rm fb^{-1}$ taken at a center-of-mass energy of 3.773\,GeV with the BESIII detector operated at the BEPCII collider, we perform an analysis of the semi-leptonic decays $D^{0(+)}\to π^{-(0)}μ^+ν_μ$. The branching fractions of $D^0\to π^-μ^+ν_μ$ and $D^+\to π^0μ^+ν_μ$ are measured to be $(0.272 \pm 0.008_{\rm stat.} \pm 0.006_{\rm syst.})\%$ and $(0.350 \pm 0.011_{\rm stat.} \pm 0.010_{\rm syst.})\%$, respectively, where the former is of much improved precision compared to previous results and the latter is determined for the first time. Using these results along with previous BESIII measurements of $D^{0(+)}\to π^{-(0)}e^+ν_e$, we calculate the branching fraction ratios to be ${\mathcal R}^0\equiv {\mathcal B}_{D^{0}\to π^{-}μ^+ν_μ}/{\mathcal B}_{D^{0}\to π^{-}e^+ν_e}=0.922\pm 0.030_{\rm stat.}\pm0.022_{\rm syst.}$ and ${\mathcal R}^+\equiv {\mathcal B}_{D^{+}\to π^{0}μ^+ν_μ}/{\mathcal B}_{D^{+}\to π^{0}e^+ν_e}=0.964\pm 0.037_{\rm stat.}\pm0.026_{\rm syst.}$, which are compatible with the theoretical expectation of lepton flavor universality within $1.7σ$ and $0.5σ$, respectively. We also examine the branching fraction ratios in different four-momentum transfer square regions, and find no significant deviations from the standard model predictions.

hep-ex↗

Observation of $h_1(1380)$ in the $J/ψ\to η^{\prime} K\bar K π$ Decay

Using $1.31 \times 10^9$ $J/ψ$ events collected by the BESIII detector at the BEPCII $e^+e^-$ collider, we report the first observation of the $h_1(1380)$ in $J/ψ\to η^{\prime} h_1(1380)$ with a significance of more than ten standard deviations. The mass and width of the possible axial-vector strangeonium candidate $h_1(1380)$ are measured to be $M = (1423.2 \pm 2.1 \pm 7.3)\mevcc$ and $Γ= (90.3 \pm 9.8 \pm 17.5)\mev$. The product branching fractions, assuming no interference, are determined to be $\mathcal{B}(J/ψ\to η^{\prime}h_1(1380)) \times \mathcal{B}(h_1(1380) \to K^{*}(892)^{+} K^{-} +c.c.) = (1.51 \pm 0.09 \pm 0.21) \times 10^{-4}$ in $η^{\prime}K^+K^-π^0$ mode and $\mathcal{B}(J/ψ\to η^{\prime}h_1(1380)) \times \mathcal{B}(h_1(1380) \to K^{*}(892)\bar K +c.c.) = (2.16 \pm 0.12 \pm 0.29) \times 10^{-4}$ in $η^{\prime}K_S^0K^{\pm}π^{\mp}$ mode. The first uncertainties are statistical and the second are systematic. Isospin symmetry violation is observed in the decays $h_1(1380) \to K^{*}(892)^{+} K^{-} +c.c.$ and $h_1(1380) \to K^{*}(892)^{0}\bar K^{0} +c.c.$. Based on the measured $h_1(1380)$ mass, the mixing angle between the states $h_1(1170)$ and $h_1(1380)$ is determined to be $(35.9\pm2.6)^{\circ}$, consistent with theoretical expectations.

hep-ex↗

Measurements of $e^+e^- \to K_{S}^{0}K^{\pm}π^{\mp}π^0$ and $K_{S}^{0}K^{\pm}π^{\mp}η$ at center-of-mass energies from $3.90$ to $4.60~\mathrm{GeV}$

Using $5.2 \ \mathrm{fb}^{-1}$ $e^+ e^-$ annihilation data samples collected with the BESIII detector, we measure the cross sections of $e^+e^- \to K_S^0 K^\pm π^\mp π^0$ and $K_{S}^{0}K^{\pm}π^{\mp}η$ at center-of-mass energies from $3.90$ to $4.60$ GeV. In addition, we search for the charmonium-like resonance $Y(4260)$ decays into $K_{S}^{0}K^{\pm}π^{\mp}π^0$ and $K_{S}^{0}K^{\pm}π^{\mp}η$, and $Z_c^{0,\pm}(3900)$ decays into $K_{S}^{0}K^{\pm}π^{\mp,0}$ and $K_{S}^{0}K^{\pm}η$. Corresponding upper limits are provided since no clear signal is observed.

hep-ex↗

Beam-Target Helicity Asymmetry $E$ in $K^{0}Λ$ and $K^{0}Σ^0$ Photoproduction on the Neutron

We report the first measurements of the $E$ beam-target helicity asymmetry for the $\vecγ \vec{n} \to K^{0}Λ$, and $K^{0}Σ^{0}$ channels in the energy range 1.70$\leq W\leq$2.34 GeV. The CLAS system at Jefferson Lab uses a circularly polarized photon beam and a target consisting of longitudinally polarized solid molecular hydrogen deuteride with low background contamination for the measurements. The multivariate analysis method boosted decision trees was used to isolate the reactions of interest. Comparisons with predictions from the KaonMAID, SAID, and Bonn-Gatchina models are presented. These results will help separate the isospin $I=0$ and $I=1$ photo-coupling transition amplitudes in pseudoscalar meson photoproduction.

nucl-ex↗

VHE $γ$-ray discovery and multi-wavelength study of the blazar 1ES 2322-409

A hotspot at a position compatible with the BL Lac object 1ES 2322-409 was serendipitously detected with H.E.S.S. during observations performed in 2004 and 2006 on the blazar PKS 2316-423. Additional data on 1ES 2322-409 were taken in 2011 and 2012, leading to a total live-time of 22.3h. Point-like very-high-energy (VHE; E>100GeV) $γ$-ray emission is detected from a source centred on the 1ES 2322-409 position, with an excess of 116.7 events at a significance of 6.0$σ$. The average VHE $γ$-ray spectrum is well described with a power law with a photon index $Γ=3.40\pm0.66_{\text{stat}}\pm0.20_{\text{sys}}$ and an integral flux $Φ(E>200GeV) = (3.11\pm0.71_{\rm stat}\pm0.62_{\rm sys})\times10^{-12} cm^{-2} s^{-1}$, which corresponds to 1.1$\%$ of the Crab nebula flux above 200 GeV. Multi-wavelength data obtained with Fermi LAT, Swift XRT and UVOT, RXTE PCA, ATOM, and additional data from WISE, GROND and Catalina, are also used to characterise the broad-band non-thermal emission of 1ES 2322-409. The multi-wavelength behaviour indicates day-scale variability. Swift UVOT and XRT data show strong variability at longer scales. A spectral energy distribution (SED) is built from contemporaneous observations obtained around a high state identified in Swift data. A modelling of the SED is performed with a stationary homogeneous one-zone synchrotron-self-Compton (SSC) leptonic model. The redshift of the source being unknown, two plausible values were tested for the modelling. A systematic scan of the model parameters space is performed, resulting in a well-constrained combination of values providing a good description of the broad-band behaviour of 1ES 2322-409.

astro-ph.HE↗

Searches for gamma-ray lines and `pure WIMP' spectra from Dark Matter annihilations in dwarf galaxies with H.E.S.S

Dwarf spheroidal galaxies are among the most promising targets for detecting signals of Dark Matter (DM) annihilations. The H.E.S.S. experiment has observed five of these systems for a total of about 130 hours. The data are re-analyzed here, and, in the absence of any detected signals, are interpreted in terms of limits on the DM annihilation cross section. Two scenarios are considered: i) DM annihilation into mono-energetic gamma-rays and ii) DM in the form of pure WIMP multiplets that, annihilating into all electroweak bosons, produce a distinctive gamma-ray spectral shape with a high-energy peak at the DM mass and a lower-energy continuum. For case i), upper limits at 95\% confidence level of about $\langle σv \rangle \lesssim 3 \times 10^{-25}$ cm$^3$ s$^{-1}$ are obtained in the mass range of 400 GeV to 1 TeV. For case ii), the full spectral shape of the models is used and several excluded regions are identified, but the thermal masses of the candidates are not robustly ruled out.

astro-ph.HE↗

First measurement of $e^+ e^- \to pK^{0}_{S}\bar{n}K^{-} + c.c.$ above open charm threshold

The process $e^+e^-\rightarrow pK^{0}_{S}\bar{n}K^{-} + c.c.$ and its intermediate processes are studied for the first time, using data samples collected with the BESIII detector at BEPCII at center-of-mass energies of 3.773, 4.008, 4.226, 4.258, 4.358, 4.416, and 4.600 GeV, with a total integrated luminosity of 7.4 fb$^{-1}$. The Born cross section of $e^+e^- \to p K^{0}_S\bar{n}K^- + c.c.$ is measured at each center-of-mass energy, but no significant resonant structure in the measured cross-section line shape between 3.773 and 4.600 GeV is observed. No evident structure is detected in the $pK^-$, $nK^{0}_S$, $pK^0_{S}$, $nK^+$, $p\bar{n}$, or $K^{0}_S K^-$ invariant mass distributions except for $Λ(1520)$. The Born cross sections of $e^+e^-\rightarrowΛ(1520)\bar{n}K^{0}_{S} + c.c.$ and $e^+e^-\rightarrow Λ(1520)\bar{p}K^{+} + c.c.$ are measured, and the 90\% confidence level upper limits on the Born cross sections of $e^+e^-\rightarrowΛ(1520)\barΛ(1520)$ are determined at the seven center-of-mass energies.

hep-ex↗

Polarization and Entanglement in Baryon-Antibaryon Pair Production in Electron-Positron Annihilation

Using a sample of $1.31\times 10^9$ $J/ψ$ events collected with the BESIII detector, we report the first observation of spin polarization of $Λ$ and $\barΛ$ hyperons from the coherent production in the $J/ψ\toΛ\barΛ$ decay. We measure the phase between the hadronic form factors to be $ΔΦ=(42.4\pm0.6\pm0.5)^\circ$. The decay parameters for $Λ\to pπ^-$ ($α_-$), $\barΛ\to\bar pπ^+$ ($α_+$) and $\barΛ\to\bar nπ^0$ ($\barα_0$) are measured to be $α_-=0.750\pm0.009\pm0.004$, $α_+=-0.758\pm0.010\pm0.007$ and $\barα_0=-0.692\pm0.016\pm0.006$, respectively. The obtained value of $α_-$ is higher by $(17\pm 3)\%$ than the current world average. In addition, the $CP$ asymmetry of $-0.006\pm0.012\pm0.007$ is extracted with substantially improved precision. The ratio $\barα_0/α_{+} = 0.913\pm 0.028 \pm 0.012$ is also measured.

hep-ex↗

Amplitude analysis of the $K_{S}K_{S}$ system produced in radiative $J/ψ$ decays

An amplitude analysis of the $K_{S}K_{S}$ system produced in radiative $J/ψ$ decays is performed using the $(1310.6\pm7.0)\times10^{6}$ $J/ψ$ decays collected by the BESIII detector. Two approaches are presented. A mass-dependent analysis is performed by parameterizing the $K_{S}K_{S}$ invariant mass spectrum as a sum of Breit-Wigner line shapes. Additionally, a mass-independent analysis is performed to extract a piecewise function that describes the dynamics of the $K_{S}K_{S}$ system while making minimal assumptions about the properties and number of poles in the amplitude. The dominant amplitudes in the mass-dependent analysis include the $f_{0}(1710)$, $f_{0}(2200)$, and $f_{2}^\prime(1525)$. The mass-independent results, which are made available as input for further studies, are consistent with those of the mass-dependent analysis and are useful for a systematic study of hadronic interactions. The branching fraction of radiative $J/ψ$ decays to $K_{S}K_{S}$ is measured to be $(8.1 \pm 0.4) \times 10^{-4}$, where the uncertainty is systematic and the statistical uncertainty is negligible.

hep-ex↗