arXiv subjects

C. Geng

Publications and source records attributed to C. Geng.

At least 181 records · Page 10Linked to original sources

arXiv2021

Measurements of $e^+e^-\rightarrow η_{\rm c}π^+ π^-π^0$, $η_{\rm c}π^+ π^-$ and $η_{\rm c}π^0γ$ at $\sqrt{s}$ from 4.18 to 4.60\,GeV, and search for a $Z_{\rm c}$ state close to the $D\bar{D}$ threshold decaying to $η_{\rm c}π$ at $\sqrt{s}$ = 4.23 GeV

We study $η_{\rm c}$ production at center-of-mass energies $\sqrt{s}$ from 4.18 to 4.60 GeV in $e^+e^-$ annihilation data collected with the BESIII detector operating at the BEPCII storage ring, corresponding to 7.3 fb$^{-1}$ of integrated luminosity. We measure the cross sections of the three different exclusive reactions $e^+e^-\rightarrow η_{\rm c}π^+ π^-π^0$, $e^+e^- \rightarrow η_{\rm c}π^+ π^-$, and $e^+e^- \rightarrow η_{\rm c}π^0γ$. We find significant $η_{\rm c}$ production in $e^+e^-\rightarrow η_{\rm c}π^+ π^-π^0$ at $\sqrt{s}$ of 4.23 GeV and 4.26 GeV and observe a significant energy-dependent Born cross section that we measure to be consistent with the production via the intermediate $Y(4260)$ resonance. In addition, we perform a search for a charmonium-like $Z_{\rm c}$ state close to the $D\bar{D}$ threshold that decays to $η_{\rm c}π$, involving ground state charmonium, and observe no signal. Corresponding upper limits on the cross section of $η_{\rm c}$ and $Z_{\rm c}$ production are provided, where the yields are not found to be significant.

hep-ex↗

arXiv2020

Search for New Hadronic Decays of $h_c$ and Observation of $h_c\rightarrow K^{+}K^{-}π^{+}π^{-}π^{0}$

Ten hadronic final states of the $h_c$ decays are investigated via the process $ψ(3686)\rightarrow π^0 h_c$, using a data sample of $(448.1 \pm 2.9) \times 10^6$ $ψ(3686)$ events collected with the BESIII detector. The decay channel $h_c\rightarrow K^{+}K^{-}π^{+}π^{-}π^{0}$ is observed for the first time with a significance of $6.0 σ$. The corresponding branching fraction is determined to be $\mathcal{B}(h_c\rightarrow K^{+}K^{-}π^{+}π^{-}π^{0}) =(3.3 \pm 0.6 \pm 0.6)\times 10^{-3}$ (the first uncertainty is statistical and the second systematical). Evidence for the decays $h_c\rightarrow π^{+} π^{-} π^{0} η$ and $h_c\rightarrow K^{0}_{S}K^{\pm}π^{\mp}π^{+}π^{-}$ is found with a significance of $3.6 σ$ and $3.8 σ$, respectively. The corresponding branching fractions (and upper limits) are obtained to be $\mathcal{B}(h_c\rightarrow π^{+} π^{-} π^{0} η) =(7.2 \pm 1.8 \pm 1.3)\times 10^{-3}$ $(< 1.8 \times 10^{-2})$ and $\mathcal{B}(h_c\rightarrow K^{0}_{S}K^{\pm}π^{\mp}π^{+}π^{-}) =(2.8 \pm 0.9 \pm 0.5)\times 10^{-3}$ $(<4.7\times 10^{-3})$. Upper limits on the branching fractions for the final states $h_c \rightarrow K^{+}K^{-}π^{0}$, $K^{+}K^{-}η$, $K^{+}K^{-}π^{+}π^{-}η$, $2(K^{+}K^{-})π^{0}$, $K^{+}K^{-}π^{0}η$, $K^{0}_{S}K^{\pm}π^{\mp}$, and $p\bar{p}π^{0}π^{0}$ are determined at a confidence level of 90\%.

hep-ex↗

arXiv2020

Observation of the decays $χ_{cJ}\toΣ^{0}\bar{p}K^{+}+{\rm c.c.}~(J=0, 1, 2)$

The decays $χ_{cJ}\toΣ^{0}\bar{p}K^{+}+{\rm c.c.}~(J = 0, 1, 2)$ are studied via the radiative transition $ψ(3686)\toγχ_{cJ}$ based on a data sample of $(448.1 \pm 2.9)\times10^{6}$ $ψ(3686)$ events collected with the BESIII detector. The branching fractions of $χ_{cJ}\toΣ^{0}\bar{p}K^{+}+{\rm c.c.}~(J = 0, 1, 2)$ are measured to be $(3.03 \pm 0.12\pm 0.15)\times10^{-4}$, $(1.46 \pm 0.07\pm 0.07)\times10^{-4}$, and $(0.91 \pm 0.06\pm 0.05)\times10^{-4}$, respectively, where the first uncertainties are statistical and the second are systematic. In addition, no evident structure is found for excited baryon resonances on the two-body subsystems with the limited statistics.

hep-ex↗

arXiv2020

The physics of a small-scale tearing mode in collisionless slab plasmas

Microtearing modes have been widely reported as a tearing parity electron temperature gradient driven plasma instability, which leads to fine scale tearing of the magnetic flux surfaces thereby resulting in reconnection of magnetic field lines and formation of magnetic islands. In slab geometry it has previously been shown that the drive mechanism requires a finite collision frequency. However, we find in linear gyrokinetic simulations that a collisionless fine-scale tearing parity instability exists even at low and zero collision frequency. Detailed studies reveal that these slab modes are also driven by electron temperature gradient but are sensitive to electron finite Larmor radius effects, and have a radial wavenumber much smaller than the binormal wavenumber, which is comparable to the ion Larmor radius. Furthermore, they exist even in the electrostatic limit and electromagnetic effects actually have a stabilising influence on this collisionless tearing mode. An analytic model shows that this collisionless small scale tearing mode is consistent with a tearing parity slab electron temperature gradient (ETG) mode, which can be more unstable than the twisting parity ETG mode that is often studied. This small-scale tearing parity mode can lead to magnetic islands, which, in turn, can influence turbulent transport in magnetised plasmas.

physics.plasm-ph↗

arXiv2017

Dark Photon Search in the Mass Range Between 1.5 and 3.4 GeV/$c^2$

Using a data set of 2.93 fb$^{-1}$ taken at a center-of-mass energy $\sqrt{s}$ = 3.773 GeV with the BESIII detector at the BEPCII collider, we perform a search for an extra U(1) gauge boson, also denoted as a dark photon. We examine the initial state radiation reactions $e^+e^-\rightarrow e^+e^-γ_{\rm ISR}$ and $e^+e^-\rightarrow μ^+μ^-γ_{\rm ISR}$ for this search, where the dark photon would appear as an enhancement in the invariant mass distribution of the leptonic pairs. We observe no obvious enhancement in the mass range between 1.5 and 3.4 GeV/$c^{2}$ and set a 90% confidence level upper limit on the mixing strength of the dark photon and the Standard Model photon. We obtain a competitive limit in the tested mass range.

hep-ex↗

arXiv2016

Measurement of the leptonic decay width of $J/ψ$ using initial state radiation

Using a data set of 2.93 fb$^{-1}$ taken at a center-of-mass energy of $\sqrt{s}$ = 3.773 GeV with the BESIII detector at the BEPCII collider, we measure the process $e^+e^-\rightarrow J/ψγ\rightarrow μ^+μ^-γ$ and determine the product of the branching fraction and the electronic width $\mathcal B_{μμ}\cdot Γ_{ee} = (333.4 \pm 2.5_{\rm stat} \pm 4.4_{\rm sys})$~eV. Using the earlier-published BESIII result for $\mathcal B_{μμ}$ = (5.973 $\pm$ 0.007$_{\rm stat}$ $\pm$ 0.037$_{\rm sys}$)\%, we derive the $J/ψ$ electronic width $Γ_{ee}$~= (5.58 $\pm$ 0.05$_{\rm stat}$ $\pm$ 0.08$_{\rm sys}$) keV.

hep-ex↗

arXiv2016

Search for the weak decay $η^{\prime}\to K^{\pm}π^{\mp}$ and precise measurement of the branching fraction ${\cal B}(J/ψ\toϕη^{\prime})$

We present the first search for the rare decay of $η^\prime$ into $K^{\pm}π^{\mp}$ in $J/ψ\toϕη^{\prime}$, using a sample of $1.3\times10^{9}$ $J/ψ$ events collected with the BESIII detector. No significant signal is observed, and the upper limit at the 90\% confidence level for the ratio $\frac{{\cal B}(η^{\prime}\to K^{\pm}π^{\mp})}{{\cal B}(η^{\prime}\toγπ^{+}π^{-})}$ is determined to be $1.3\times10^{-4}$. In addition, we report the measurement of the branching fraction of $J/ψ\toϕη^{\prime}$ to be $(5.10\pm0.03(\text{stat.})\pm0.32(\text{syst.}))\times10^{-4}$, which agrees with previous results from BESII.

hep-ex↗

arXiv2015

Search for the isospin violating decay $Y(4260)\rightarrow J/ψηπ^{0}$

Using data samples collected at center of mass energies of $\sqrt{s}$ = 4.009, 4.226, 4.257, 4.358, 4.416 and 4.599 GeV with the BESIII detector operating at the BEPCII storage ring, we search for the isospin violating decay $Y(4260)\rightarrow J/ψηπ^{0}$. No signal is observed, and upper limits on the cross section $σ(e^{+}e^{-}\rightarrow J/ψηπ^{0})$ at the 90\% confidence level are determined to be 3.6, 1.7, 2.4, 1.4, 0.9 and 1.9 pb, respectively.

hep-ex↗

arXiv2015

Measurement of the branching fractions of $D_{s}^{+}\rightarrow η'X$ and $D_{s}^{+}\rightarrow η'ρ^{+}$ in $e^+e^-\to D^+_{s}D^-_{s}$

We study $D_{s}^{+}$ decays to final states involving the $η'$ with a 482$\,$pb$^{-1}$ data sample collected at $\sqrt{s}$ = 4.009$\,$GeV with the \mbox{BESIII} detector at the BEPCII collider. We measure the branching fractions $\mathcal{B}(D^+_{s}\rightarrow η'X)$ = (8.8$\pm$1.8$\pm$0.5)$\%$ and $\mathcal{B}(D_{s}^{+}\rightarrow η'ρ^{+})$ = ($5.8\pm1.4\pm0.4$)$\%$ where the first uncertainty is statistical and the second is systematic. In addition, we estimate an upper limit on the non-resonant branching ratio $\mathcal{B}(D_{s}^{+}\rightarrow η'π^+π^0)<5.1\%$ at the 90$\%$ confidence level. Our results are consistent with CLEO's recent measurements and help to resolve the disagreement between the theoretical prediction and CLEO's previous measurement of $\mathcal{B}(D_{s}^{+}\rightarrow η'ρ^{+})$.

hep-ex↗

arXiv2015

Observation of a neutral charmoniumlike state $Z_c(4025)^0$ in $e^{+} e^{-} \to (D^{} \bar{D}^{})^{0} π^0$

We report a study of the process $e^{+} e^{-} \to (D^{*} \bar{D}^{*})^{0} π^0$ using $e^+e^-$ collision data samples with integrated luminosities of $1092 \rm{pb}^{-1}$ at $\sqrt{s}=4.23 \rm{GeV}$ and $826 \rm{pb}^{-1}$ at $\sqrt{s}=4.26 \rm{GeV}$ collected with the BESIII detector at the BEPCII storage ring. We observe a new neutral structure near the $(D^{*} \bar{D}^{*})^{0}$ mass threshold in the $π^0$ recoil mass spectrum, which we denote as $Z_{c}(4025)^{0}$. Assuming a Breit-Wigner line shape, its pole mass and pole width are determined to be $(4025.5^{+2.0}_{-4.7}\pm3.1) \rm{MeV}/c^2$ and $(23.0\pm 6.0\pm 1.0) \rm{MeV}$, respectively. The Born cross sections of $e^{+}e^{-}\to Z_{c}(4025)^{0} π^0\to (D^{*} \bar{D}^{*})^{0}π^0$ are measured to be $(61.6\pm8.2\pm9.0) \rm{pb}$ at $\sqrt{s}=4.23 \rm{GeV}$ and $(43.4\pm8.0\pm5.4) \rm{pb}$ at $\sqrt{s}=4.26 \rm{GeV}$. The first uncertainties are statistical and the second are systematic.

hep-ex↗

arXiv2015

Search for new phenomena in events with a photon and missing transverse momentum in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector

Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the LHC are reported. Data were collected in proton--proton collisions at a center-of-mass energy of 8 TeV and correspond to an integrated luminosity of 20.3 fb$^{-1}$. The observed data are well described by the expected Standard Model backgrounds. The expected (observed) upper limit on the fiducial cross section for the production of such events is 6.1 (5.3) fb at 95% confidence level. Exclusion limits are presented on models of new phenomena with large extra spatial dimensions, supersymmetric quarks, and direct pair production of dark-matter candidates.

hep-ex↗

arXiv2015

Observation and Spin-Parity Determination of the $X(1835)$ in $J/ψ\rightarrowγK^0_S K^0_Sη$

We report an observation of the process $J/ψ\rightarrowγX(1835)\rightarrowγK^0_S K^0_Sη$ at low $K^0_S K^0_S$ mass with a statistical significance larger than 12.9$σ$ using a data sample of $1.31 \times 10^{9}$ $J/ψ$ events collected with the BESIII detector. In this region of phase space the $K^0_S K^0_S$ system is dominantly produced through the $f_0(980)$. By performing a partial wave analysis, we determine the spin-parity of the $X(1835)$ to be $J^{PC}=0^{-+}$. The mass and width of the observed $X(1835)$ are $1844\pm9(\text{stat})^{+16}_{-25}(\text{syst})$~\MeV~and $192^{+20}_{-17}(\text{stat})^{+62}_{-43}(\text{syst})$~MeV, respectively, which are consistent with the results obtained by BESIII in the channel $J/ψ\rightarrowγπ^+π^-η^{\prime}$.

hep-ex↗

arXiv2015

An amplitude analysis of the $π^{0}π^{0}$ system produced in radiative $J/ψ$ decays

An amplitude analysis of the $π^{0}π^{0}$ system produced in radiative $J/ψ$ decays is presented. In particular, a piecewise function that describes the dynamics of the $π^{0}π^{0}$ system is determined as a function of $M_{π^{0}π^{0}}$ from an analysis of the $(1.311\pm0.011)\times10^{9}$ $J/ψ$ decays collected by the BESIII detector. The goal of this analysis is to provide a description of the scalar and tensor components of the $π^0π^0$ system while making minimal assumptions about the properties or number of poles in the amplitude. Such a model-independent description allows one to integrate these results with other related results from complementary reactions in the development of phenomenological models, which can then be used to directly fit experimental data to obtain parameters of interest. The branching fraction of $J/ψ\to γπ^{0}π^{0}$ is determined to be $(1.15\pm0.05)\times10^{-3}$, where the uncertainty is systematic only and the statistical uncertainty is negligible.

hep-ex↗

arXiv2015

Observation of the isospin-violating decay $J/ψ\to ϕπ^{0}f_{0}(980)$

Using a sample of 1.31 billion $J/ψ$ events collected with the BESIII detector at the BEPCII collider, the decays $J/ψ\to ϕπ^{+}π^{-}π^{0}$ and $J/ψ\to ϕπ^{0}π^{0}π^{0}$ are investigated. The isospin violating decay $J/ψ\to ϕπ^{0} f_{0}(980)$ with $f_{0}(980) \to ππ$, is observed for the first time. The width of the $f_{0}(980)$ obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the $π^{0} f_{0}(980)$ mass spectrum, there is evidence of $f_1(1285)$ production. By studying the decay $J/ψ\to ϕη'$, the branching fractions of $η' \to π^{+}π^{-}π^{0}$ and $η' \to π^{0}π^{0}π^{0}$, as well as their ratio, are also measured.

hep-ex↗

arXiv2015

Search for $Z_c(3900)^\pm\toωπ^\pm$

The decay $Z_c(3900)^\pm\toωπ^\pm$ is searched for using data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies $\sqrt{s}=4.23$ and $4.26$~GeV. No significant signal for the $Z_c(3900)^\pm$ is found, and upper limits at the 90\% confidence level on the Born cross section for the process $e^+e^-\to Z_c(3900)^\pmπ^\mp\toωπ^+π^-$ are determined to be $0.26$ and $0.18$ pb at $\sqrt{s}=4.23$ and 4.26 GeV, respectively.

hep-ex↗

arXiv2015

Searches for isospin-violating transitions $χ_{c0,2} \rightarrow π^{0} η_{c}$

We present the first upper-limit measurement of the branching fractions of the isospin-violating transitions $χ_{c0,2} \rightarrow π^{0} η_{c}$. The measurements are performed using $106\times 10^{6}$ $ψ(3686)$ events accumulated with the BESIII detector at the BEPCII $e^{+}e^{-}$ collider at a center-of-mass energy corresponding to the $ψ(3686)$ mass. We obtained upper limits on the branching fractions at a 90\% confidence level of $B(χ_{c0} \rightarrow π^{0} η_{c}) < 1.6 \times 10^{-3}$ and $B(χ_{c2} \rightarrow π^{0} η_{c}) < 3.2 \times 10^{-3}$.

hep-ex↗

arXiv2015

Search for $D^0\toγγ$ and improved measurement of the branching fraction for $D^0 \to π^0π^0$

Using $2.92$ fb$^{-1}$ of electron-positron annihilation data collected at $\sqrt{s} = 3.773$~GeV with the BESIII detector, we report the results of a search for the flavor-changing neutral current process $D^0\toγγ$ using a double-tag technique. We find no signal and set an upper limit at $90\%$ confidence level for the branching fraction of $B(D^0\toγγ) < 3.8\times10^{-6}$. We also investigate $D^0$-meson decay into two neutral pions, obtaining a branching fraction of $B(D^0\toπ^0π^0) = (8.24\pm0.21(\text{stat.})\pm0.30(\text{syst.}))\times10^{-4}$, the most precise measurement to date and consistent with the current world average

hep-ex↗

arXiv2015

Measurement of the Matrix Elements for the Decays $η\rightarrow π^{+}π^{-}π^0$ and $η/η^{\prime}\rightarrowπ^0π^0π^0$

Based on a sample of $1.31 \times 10^9$ $J/ψ$ events collected with the BESIII detector at the BEPCII collider, Dalitz plot analyses of selected 79,625 $η\rightarrowπ^{+}π^{-}π^0$ events, 33,908 $η\rightarrowπ^0π^0π^0$ events and 1,888 $η^{\prime}\rightarrowπ^0π^0π^0$ events are performed. The measured matrix elements of $η\rightarrowπ^+π^-π^0$ are in reasonable agreement with previous measurements. The Dalitz plot slope parameters of $η\rightarrowπ^0π^0π^0$ and $η^{\prime}\rightarrowπ^0π^0π^0$ are determined to be $-0.055 \pm 0.014 \pm 0.004$ and $-0.640 \pm 0.046 \pm 0.047$, respectively, where the first uncertainties are statistical and the second systematic. Both values are consistent with previous measurements, while the precision of the latter one is improved by a factor of three. Final state interactions are found to have an important role in those decays.

hep-ex↗