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C. Chen

Publications and source records attributed to C. Chen.

At least 343 records · Page 19Linked to original sources
arXiv2023

Improved measurement of the absolute branching fraction of inclusive semileptonic $Λ_c^+$ decay

Using $4.5 \mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data samples collected at center-of-mass energies ranging from 4.600 to 4.698 GeV with the BESIII detector at the BEPCII collider, we measured the absolute branching fraction for the inclusive semileptonic decay $Λ_c^+\rightarrow Xe^+ν_e$, where $X$ refers to any possible particle system. The branching fraction of the decay is determined to be $\mathcal{B}({\it Λ}^+_c\rightarrow Xe^+ν_e)=(4.06\pm0.10_{\rm stat.}\pm0.09_{\rm syst.})\%$. Our result improves the precision of previous measurement of $\mathcal{B}({\it Λ}^+_c\rightarrow Xe^+ν_e)$ by more than threefold. Using the known $Λ_c^+$ lifetime and the charge-averaged semileptonic decay width of nonstrange charmed mesons, we measure the ratio of inclusive semileptonic decay widths $Γ(Λ_c^+\rightarrow X e^+ν_e)/\barΓ(D\rightarrow Xe^+ν_e)=1.28\pm0.05$, where statistical and systematic uncertainties are combined.

hep-ex↗
arXiv2023

Study of the $e^+e^- \to π^{+}π^{-}ω$ process at center-of-mass energies between 4.0 and 4.6 GeV

Using $15.6$ $\rm fb^{-1}$ of $e^+e^-$ collision data collected at twenty-four center-of-mass energies from $4.0$ to $4.6$ GeV with the BESIII detector, the helicity amplitudes of the process $e^+e^-\to π^{+}π^{-}ω$ are analyzed for the first time. Born cross section measurements of two-body intermediate resonance states with statistical significance greater than 5$σ$ are presented, such as $f_{0}(500)$, $f_{0}(980)$, $f_{2}(1270)$, $f_{0}(1370)$, $b_{1}(1235)^{\pm}$, and $ρ(1450)^{\pm}$. In addition, evidence of a resonance state in $e^+e^-\to π^+π^-ω$ production is found. The mass of this state obtained by line shape fitting is about 4.2 GeV/$c^2$, which is consistent with the production of $ψ(4160)$ or $Y(4220)$.

hep-ex↗
arXiv2023

Measurement of the Branching Fraction for the Decay $ψ(3686) \rightarrow ϕK_{S}^{0} K_{S}^{0}$

Based on $(448.1 \pm 2.9 )\times 10^6$ $ψ(3686)$ events collected with the BESIII detector operating at the BEPCII collider, the decay $ψ(3686)\rightarrow ϕK_{S}^{0} K_{S}^{0}$ is observed for the first time. Taking the interference between $ψ(3686)$ decay and continuum production into account, the branching fraction of this decay is measured to be $\mathcal{B}(ψ(3686)\rightarrowϕK_S^0 K_S^0 )$ = $(3.53 $ $\pm$ $0.20$ $\pm$ $0.21$)$\times 10^{-5}$, where the first uncertainty is statistical and the second is systematic. Combining with the world average value for ${\mathcal B}(J/ψ\to ϕK^0_SK^0_S)$, the ratio $\mathcal{B}(ψ(3686)\rightarrow ϕK_{S}^{0} K_{S}^{0})/\mathcal{B}(J/ψ\rightarrow ϕK_{S}^{0} K_{S}^{0}) $ is determined to be $(6.0\pm 1.6)$%, which is suppressed relative to the 12% rule.

hep-ex↗
arXiv2023

Measurement of the $e^{+}e^{-}\rightarrowΛ\barΛ$ cross section from threshold to 3.00 GeV using events with initial-state radiation

Using initial-state radiation events from a total integrated luminosity of 11.957 fb$^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at BEPCII, the cross section for the process $e^{+}e^{-}\rightarrowΛ\barΛ$ is measured in 16 $Λ\barΛ$ invariant mass intervals from the production threshold up to 3.00 GeV$/c^{2}$. The results are consistent with previous results from BaBar and BESIII, but with better precision and with narrower $Λ\barΛ$ invariant mass intervals than BaBar.

hep-ex↗
arXiv2023

Helicity amplitude analysis of $χ_{cJ} \rightarrow ϕϕ$

Using (447.9 $\pm$ 2.3) million $ψ$(3686) events collected with the BESIII detector, the decays of $χ_{cJ} \rightarrow ϕϕ$ ($J$=0, 1, 2) have been studied via the decay $ψ(3686)\rightarrowγχ_{cJ}$. The branching fractions of the decays $χ_{cJ} \rightarrow ϕϕ$ ($J$=0, 1, 2) are determined to be $(8.48\pm0.26\pm0.27)\times10^{-4}$, $(4.36\pm0.13\pm0.18)\times10^{-4}$, and $(13.36\pm0.29\pm0.49)\times10^{-4}$, respectively, which are the most precise measurements to date. From a helicity amplitude analysis of the process $ψ(3686) \rightarrow γχ_{cJ}, χ_{cJ}\rightarrow ϕϕ, ϕ\rightarrow K^{+}K^{-}$, the polarization parameters of the $χ_{cJ} \rightarrow ϕϕ$ decays are determined for the first time.

hep-ex↗
arXiv2023

Study of $e^+e^-\rightarrowΩ^{-}\barΩ^{+}$ at center-of-mass energies from 3.49 to 3.67 GeV

Using data samples of $e^+e^-$ collisions collected with the BESIII detector at eight center-of-mass energy points between 3.49 and 3.67 GeV, corresponding to an integrated luminosity of 670 pb$^{-1}$, we present the upper limits of Born cross sections and the effective form factor for the process $e^+e^-\rightarrowΩ^{-}\barΩ^{+}$. A fit to the cross sections using a pQCD-derived energy dependent function shows no significant threshold effect. The upper limit on the measured effective form factor is consistent with a theoretical prediction within the uncertainty of 1$σ$. These results provide new experimental information on the production mechanism of $Ω$.

hep-ex↗
arXiv2023

Partial wave analysis of $J/ψ\rightarrowγηη'$

Based on a sample of (10.09$\pm$0.04)$\times$10$^{9}$ $J/ψ$ events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay $J/ψ\rightarrow γηη'$ is performed. An isoscalar state with exotic quantum numbers $J^{PC}=1^{-+}$, denoted as $η_1(1855)$, has been observed for the first time with statistical significance larger than 19$σ$. Its mass and width are measured to be (1855$\pm$9$_{-1}^{+6}$)~MeV/$c^{2}$ and (188$\pm$18$_{-8}^{+3}$)~MeV, respectively. The product branching fraction ${\cal B}(J/ψ$$\rightarrow$$ γη_1(1855)$$\rightarrow$$γηη')$ is measured to be (2.70$\pm 0.41 _{-0.35}^{+0.16}) \times$10$^{-6}$. The first uncertainties are statistical and the second are systematic. In addition, an upper limit on the branching ratio ${\cal B}(f_0(1710)$$\rightarrow$$ηη')$/${\cal B}(f_0(1710)$$\rightarrow$$ππ)$ is determined to be $1.61 \times 10^{-3}$ at 90\% confidence level, which lends support to the hypothesis that the $f_0(1710)$ has a large glueball component.

hep-ex↗
arXiv2023

Observation of an isoscalar resonance with exotic $J^{PC}=1^{-+}$ quantum numbers in $J/ψ\rightarrowγηη'$

Using a sample of (10.09$\pm$0.04)$\times$10$^{9}$ $J/ψ$ events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay $J/ψ\rightarrow γηη'$ is performed. The first observation of an isoscalar state with exotic quantum numbers $J^{PC}=1^{-+}$, denoted as $η_1(1855)$, is reported in the process $J/ψ\rightarrow γη_1(1855)$ with $η_1(1855)\rightarrowηη'$. Its mass and width are measured to be (1855$\pm$9$_{-1}^{+6}$)MeV/$c^{2}$ and (188$\pm$18$_{-8}^{+3}$)MeV, respectively, where the first uncertainties are statistical and the second are systematic, and its statistical significance is estimated to be larger than 19$σ$.

hep-ex↗
arXiv2023

Study of $η(1405)/η(1475)$ in $J/ψ\toγK^{0}_{S} K^{0}_{S}π^{0}$ decay

Using a sample of $(10.09\pm0.04)\times10^{9}$ $J/ψ$ decays collected with the BESIII detector, partial wave analyses of the decay $J/ψ\toγK^{0}_{S} K^{0}_{S}π^{0}$ are performed within the $K^{0}_{S}K^{0}_{S}π^{0}$ invariant mass region below $1.6\mathrm{\ Ge\kern -0.1em V}/c^2$. The covariant tensor amplitude method is used in both mass independent and mass dependent approaches. Both analysis approaches exhibit dominant pseudoscalar and axial vector components, and show good consistency for the other individual components. Furthermore, the mass dependent analysis reveals that the $K^{0}_{S}K^{0}_{S}π^{0}$ invariant mass spectrum for the pseudoscalar component can be well described with two isoscalar resonant states using relativistic Breit-Wigner model, ${\it i.e.}$, the $η(1405)$ with a mass of $1391.7\pm0.7_{-0.3}^{+11.3}\mathrm{\ Me\kern -0.1em V}/c^2$ and a width of $60.8\pm1.2_{-12.0}^{+5.5}\mathrm{\ Me\kern -0.1em V}$, and the $η(1475)$ with a mass of $1507.6\pm1.6_{-32.2}^{+15.5}\mathrm{\ Me\kern -0.1em V}/c^2$ and a width of $115.8\pm2.4_{-10.9}^{+14.8}\mathrm{\ Me\kern -0.1em V}$. The first and second uncertainties are statistical and systematic, respectively. Alternate models for the pseudoscalar component are also tested, but the description of the $K^{0}_{S}K^{0}_{S}π^{0}$ invariant mass spectrum deteriorates significantly.

hep-ex↗
arXiv2023

Thermal hysteretic behavior and negative magnetoresistance in an unusual charge-density-wave material EuTe4

EuTe4 is a newly-discovered van der Waals material exhibiting a novel charge-density wave (CDW) with a large thermal hysteresis in the resistivity and CDW gap. In this work, we systematically study the electronic structure and transport properties of EuTe4 using high-resolution angle-resolved photoemission spectroscopy (ARPES), magnetoresistance measurements, and scanning tunneling microscopy (STM). We observe a CDW gap of about 200 meV at low temperatures that persists up to 400 K, suggesting that the CDW transition occurs at a much higher temperature. We observe a large thermal hysteretic behavior of the ARPES intensity near the Fermi level, consistent with the resistivity measurement. The hysteresis in the resistivity measurement does not change under a magnetic field up to 7 T, excluding the thermal magnetic hysteresis mechanism. Instead, the surface topography measured with STM shows surface domains with different CDW trimerization directions, which may be important for the thermal hysteretic behavior of EuTe4. Interestingly, we observe a large negative magnetoresistance at low temperatures that can be associated with the canting of magnetically ordered Eu spins. Our work shed light on the understanding of magnetic, transport, and electronic properties of EuTe4.

cond-mat.str-el↗
arXiv2023

Constraining High-Energy Neutrino Emission from Supernovae with IceCube

Core-collapse supernovae are a promising potential high-energy neutrino source class. We test for correlation between seven years of IceCube neutrino data and a catalog containing more than 1000 core-collapse supernovae of types IIn and IIP and a sample of stripped-envelope supernovae. We search both for neutrino emission from individual supernovae, and for combined emission from the whole supernova sample through a stacking analysis. No significant spatial or temporal correlation of neutrinos with the cataloged supernovae was found. The overall deviation of all tested scenarios from the background expectation yields a p-value of 93% which is fully compatible with background. The derived upper limits on the total energy emitted in neutrinos are $1.7\times 10^{48}$ erg for stripped-envelope supernovae, $2.8\times 10^{48}$ erg for type IIP, and $1.3\times 10^{49}$ erg for type IIn SNe, the latter disfavouring models with optimistic assumptions for neutrino production in interacting supernovae. We conclude that strippe-envelope supernovae and supernovae of type IIn do not contribute more than $14.6\%$ and $33.9\%$ respectively to the diffuse neutrino flux in the energy range of about $10^3-10^5$ GeV, assuming that the neutrino energy spectrum follows a power-law with an index of $-2.5$. Under the same assumption, we can only constrain the contribution of type IIP SNe to no more than $59.9\%$. Thus core-collapse supernovae of types IIn and stripped-envelope supernovae can both be ruled out as the dominant source of the diffuse neutrino flux under the given assumptions.

astro-ph.HE↗
arXiv2023

Determination of Spin-parity Quantum Numbers for the Narrow Structure Near the $p\barΛ$ Threshold in $e^+e^-\to pK^-\barΛ+c.c.$

A narrow structure in the $p\barΛ$ system near the mass threshold, named as $X(2085)$, is observed in the process $e^+e^- \to p K^-\barΛ$ with a statistical significance greater than $20σ$. Its spin and parity are determined for the first time to be $J^P=1^+$ in an amplitude analysis, with statistical significance greater than $5σ$ over other quantum numbers. The pole positions of $X(2085)$ are measured to be $M_{\rm pole}=(2086\pm4\pm6)$~MeV and $Γ_{\rm pole}=(56\pm5\pm16)$ MeV, where the first uncertainties are statistical and the second ones are systematic. The analysis is based on the study of the process $e^+e^-\to pK^-\barΛ$ and uses the data samples collected with the BESIII detector at the center-of-mass energies $\sqrt{s}=4.008$, $4.178$, $4.226$, $4.258$, $4.416$, and $4.682$ GeV with a total integrated luminosity of $8.35~\text{fb}^{-1}$.

hep-ex↗
arXiv2023

Search for invisible decays of a dark photon using $e^+e^-$ annihilation data at BESIII

We report a search for a dark photon using $14.9$~fb$^{-1}$ of $e^+e^-$ annihilation data taken at center-of-mass energies from 4.13 to 4.60~GeV with the BESIII detector operated at the BEPCII storage ring. The dark photon is assumed to be produced in the radiative annihilation process of $e^+e^-$ and to predominantly decay into light dark matter particles, which escape from the detector undetected. The mass range from 1.5 to 2.9~GeV is scanned for the dark photon candidate, and no significant signal is observed. The mass dependent upper limits at the 90$\%$ confidence level on the coupling strength parameter $ε$ for a dark photon coupling with an ordinary photon vary between $1.6\times 10^{-3}$ and $5.7\times10^{-3}$.

hep-ex↗
arXiv2023

Improved measurement of the branching fractions of the inclusive decays $D^+ \to K_S^0X $ and $D^0 \to K_S^0X $

By analyzing 2.93 fb$^{-1}$ of $e^+e^-$ collision data taken at the center-of-mass energy of 3.773 GeV with the BESIII detector, the branching fractions of the inclusive decays $D^+\to K^0_S X$ and $D^0\to K^0_S X$ are measured to be $(32.78\pm 0.13\pm 0.27)\%$ and $(20.54\pm 0.12\pm 0.18)\%$, respectively, where the first uncertainties are statistical and the second are systematic. These results are consistent with the world averages of previous measurements, but with improved precision.

hep-ex↗
arXiv2023

Measurement of the $B^+/B^0$ production ratio in $e^+e^-$ collisions at the $Υ(4S)$ resonance using $B \rightarrow J/ψ(\ell\ell) K$ decays at Belle

We measure the ratio of branching fractions for the $Υ(4S)$ decays to $B^+B^-$ and $B^0\bar{B}{}^0$ using $B^+ \rightarrow J/ψ(\ell\ell) K^+$ and $B^0 \rightarrow J/ψ(\ell\ell) K^0$ samples, where $J/ψ(\ell\ell)$ stands for $J/ψ\to \ell^+\ell^-$ ($\ell = e$ or $μ$), with $711$ fb$^{-1}$ of data collected at the $Υ(4S)$ resonance with the Belle detector. We find the decay rate ratio of $Υ(4S) \rightarrow B^+B^-$ over $Υ(4S) \rightarrow B^0\bar{B}{}^0$ to be $1.065\pm0.012\pm 0.019 \pm 0.047$, which is the most precise measurement to date. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainty is systematic due to the assumption of isospin symmetry in $B \to J/ψ(\ell\ell) K$.

hep-ex↗
arXiv2023

Measurement of the $B^0$ lifetime and flavor-oscillation frequency using hadronic decays reconstructed in 2019-2021 Belle II data

We measure the $B^0$ lifetime and flavor-oscillation frequency using $B^0\to D^{(*)-}π^+$ decays collected by the Belle II experiment in asymmetric-energy $e^+e^-$ collisions produced by the SuperKEKB collider operating at the $Υ(4S)$ resonance. We fit the decay-time distribution of signal decays, where the initial flavor is determined by identifying the flavor of the other $B$ meson in the event. The results, based on $33000$ signal decays reconstructed in a data sample corresponding to ${190}\text{fb}^{-1}$, are $τ_{B^0} = {1.499}\pm{0.013}\pm{0.008}\;\text{ps}$, $Δm_d = {0.516}\pm{0.008}\pm{0.005}\;\text{ps}^{-1}$, where the first uncertainties are statistical and the second are systematic. These results are consistent with the world-average values.

hep-ex↗
arXiv2023

Evidence for the Cusp Effect in $η'$ Decays into $ηπ^0π^0$

Using a sample of $4.3\times 10^5$ $η'\toηπ^0π^0$ events selected from the ten billion $J/ψ$ event dataset collected with the BESIII detector, we study the decay $η'\toηπ^0π^0$ within the framework of nonrelativistic effective field theory. Evidence for a structure at $π^+π^-$ mass threshold is observed in the invariant mass spectrum of $π^0π^0$ with a statistical significance of around $3.5σ$, which is consistent with the cusp effect as predicted by the nonrelativistic effective field theory. After introducing the amplitude for describing the cusp effect, the $ππ$ scattering length combination $a_0-a_2$ is determined to be $\rm 0.226\pm0.060_{stat}\pm0.013_{syst}$, which is in good agreement with theoretical calculation of $0.2644\pm0.0051$.

hep-ex↗
arXiv2023

Observation of $e^+e^-\toπ^0π^0ψ_2(3823)$

Using a data sample corresponding to an integrated luminosity of 11.3 $\rm fb^{-1}$ collected at center-of-mass energies from $4.23$ to $4.70$~GeV with the BESIII detector, we observe the process $e^+e^-\toπ^0π^0ψ_2(3823)$ for the first time with a statistical significance of $6.0σ$. The ratio of average cross sections for $e^+e^-\toπ^0π^0ψ_2(3823)$ over $π^+π^-ψ_2(3823)$ is determined to be $\mathcal{R}=\frac{σ[e^+e^-\toπ^0π^0ψ_2(3823)]}{σ[e^+e^-\toπ^+π^-ψ_2(3823)]}=0.57\pm 0.14\pm0.05$, which is consistent with expectations from isospin symmetry. Here and below, the first uncertainties are statistical and the second are systematic. The mass of the $ψ_2(3823)$ is measured to be $M[ψ_2(3823)]=3824.5\pm 2.4\pm 1.0$~MeV/$c^2$. Due to the limited statistics, the intrinsic width of the $ψ_2(3823)$ is measured as an upper limit of $18.8$~MeV at $90\%$ confidence level.

hep-ex↗