Decays of both $η$ and $η^\prime$ provide very useful information in our understanding of low-energy QCD, and experimental signatures for these decays would be extremely helpful at BES-III. The rare decays of the $η$ and $η^\prime$ mesons could serve as a low-energy test of the Standard Model and its beyond. The sensitivities of the measurements of $η$ and $η^\prime$ decays are discussed at BES-III, in which the $η$ and $η^\prime$ mesons are produced in the $ψ$ decays.
The light unflavoured meson $η/η^{\prime}$ decays are valuable for testing non-perturbative quantum chromodynamics and exploring new physics beyond the Standard Model. This paper describes a series of event generators, including $η/η^{\prime}\toγl^{+}l^{-}$, $η/η^{\prime}\toγπ^{+}π^{-}$, $η^{\prime}\toωe^{+}e^{-}$, $η\toπ^{+}π^{-}π^{0}$, $η/η^{\prime}\toπ^{0}π^{0}π^{0}$, $η^{\prime}\toηππ$ and $η^{\prime}\toπ^{+}π^{-}π^{+}π^{-}/π^{+}π^{-}π^{0}π^{0}$, which have been developed for investigating $η/η^\prime$ decay dynamics. For most of these generators, their usability has been validated in BESI…
The results of an analysis are presented of some recent data on the reactions $e^+e^-\toπ^+π^-π^+π^-$, $e^+e^-\toπ^+π^-π^0π^0$ with the subtracted $ωπ^0$ events, $e^+e^-\toωπ^0$, $e^+e^-\toηπ^+π^-$, $e^+e^-\toπ^+π^-$, $K^-p\toπ^+π^-Λ$, the decays $J/ψ\toπ^+π^-π^0$, $tau^-\toν_tauπ^+π^-π^-π^0$ $tau^-\toν_τωπ^-$, upon taking into account both the strong energy dependence of the partial widths on energy and the previously neglected mixing of the $ρ$ type resonances. The above effects are shown to exert an essential influence on the specific values of masses and coupling constants of heavy resonan…
Most recently, both BaBar and Belle experiments found evidences of neutral $D$ mixing. In this paper, we discuss the constraints on the strong phase difference in $D^0 \to Kπ$ decay from the measurements of the mixing parameters, $y^\prime$, $y_{CP}$ and $x$ at the $B$ factories. The sensitivity of the measurement of the mixing parameter $y$ is estimated in BES-III experiment at $ψ(3770)$ peak. We also make an estimate on the measurements of the mixing rate $R_M$. Finally, the sensitivity of the strong phase difference at BES-III are obtained by using data near the $D\bar{D}$ threshold with CP…
We study an experimental search of a GeV scale vector boson at BES-III/BEPCII. It is responsible for mediating a new U(1)$_d$ interaction, as recently exploited in the context of weakly interacting massive particle dark matter. At low energy $e^+ e^-$ colliders this dark state can be efficiently probed. We discuss the direct productions of this light vector $U$ boson and the decay of this state with BES-III data and its foreseen larger data. In particular, we show that Higgs' strahlung in the dark sector can lead to multilepton signatures, which probe the physics range for kinetic mixing param…
Using about $226\times 10^6$ $\jpsi$ events and $106\times 10^6$ $ψ^{\prime}$ events collected with the BESIII detector at the BEPCII $e^+e^-$ collider, the Dalitz plot of $\etap \to ηπ^+ π^-$ decay is studied, the direct measurement of $a^{0}_{0}(980)-f_{0}(980)$ mixing is performed, $X(2120)$ and $X(2370)$ are observed in the $π^+π^-η^\prime$ invariant mass spectrum, $ψ^{\prime}\toγπ^0$ and $ψ^{\prime}\toγη$ are observed for the first time, and the decays $χ_{cJ}\toγV$ ($V=ϕ$, $ρ^0$, $ω$) are studied.
We discuss the possible searching for the oscillation by coherent $Λ\barΛ$ production in $J/ψ\rightarrow Λ\barΛ$ decay process. The sensitivity of measurement of $Λ- \barΛ$ oscillation in the external field at BES-III experiment is considered. These considerations indicate an alternative way to probe the $ΔB =2$ amplitude in addition to neutron oscillation experiments. Both coherent and time-dependent information can be used to extract $Λ-\barΛ$ oscillation parameter. With one year's luminosity at BES-III, we can set an upper limit of $δm < 10^{-15}$ MeV at 90% confidence level, corresponding …
The world's largest sample of $J/ψ$ events accumulated at the BESIII dector offers a unique opportunity to investigate $η$ and $η^\prime$ physics via two body $J/ψ$ radiative or hadronic decays. In recent years the BESIII experiment has made significant progresses in $η/η^\prime$ decays. A selection of recent highlights in light meson spectroscopy at BESIII are reviewed in this report, including the observation of $η^\prime\rightarrowπ^+π^-μ^+μ^-$, the study of $η^\prime\rightarrowπ^+π^-e^+e^-$, and search for $CP$-violation in this decay, search for the rare decays of $η^\prime\rightarrow4π^0…
Interesting results from BES-II and other experiments raised actually many new questions which shall be answered by its upgrade program, BEPCII and BES-III. The design and current status of BEPCII and BES-III are reported.
With the new measurements of $J/ψ$ and $ψ^\prime\to γη_c \ (γη_c^\prime)$ from CLEO and BES-III Collaboration, we re-investigate the intermediate meson loop (IML) contributions to these radiative decays in association with the quark model M1 transitions in an effective Lagrangian approach. It shows that the "unquenched" effects due to the intermediate hadron loops can be better quantified by the new data for $J/ψ\to γη_c$. Although the IML contributions are relatively small in $J/ψ\to γη_c$, they play a crucial role in $ψ^\prime\to γη_c \ (γη_c^\prime)$. A prediction for the IML contributions …
The world's largest sample of 1.31 billion $J/ψ$ events accumulated at the BESIII detector, provides a unique opportunity to investigate $η$ and $η^\prime$ physics via two body $J/ψ$ radiative or hadronic decays. For many $η^\prime$ decay channels the low background data samples are up to three orders of magnitude larger than collected in any previous experiment. Here we review the most significant results on $η$ and $η^\prime$ obtained at BESIII so far. The analyses range from detailed studies of the common decays dynamics, observations of new radiative and Dalitz decays, and search for rare/…
Using the ~ 6 pb-1 of e+e- annihilation data taken at psi-prime(3686) with CLEO III and CLEO-c detectors with estimated ~ 3.0 million psi-prime events, we have searched for the h_c(1^1P_1) state of charmonium in the reaction psi-prime(3686) -> pi^{0} hc -> (gamma gamma) (gamma eta_c). The preliminary results are reported.
The recent observations of the purely leptonic decay $\Ds \to μ^+ ν_μ$ and $τ^+ν_τ$ at CLEO-c and $B$ factory may allow a possible contribution from a charged Higgs boson. One such measurement of the decay constant $f_{D_s}$ differs from the most precise unquenched lattice QCD calculation by 4 $σ$ level. Meanwhile, the measured ratio, ${\cal BR}(\Ds \to μ^+ ν_μ)$ / ${\cal BR}(\Dp \to μ^+ ν_μ)$, is larger than the standard model prediction at 2.0$σ$ level. We discuss that the precise measurement of the ratio ${\cal BR}(\Ds \to μ^+ ν_μ)$ / ${\cal BR}(\Dp \to μ^+ ν_μ)$ at BES-III will shed light …
Recent BES results on light scalars are reported in this talk, including the observation of a charged kappa decaying to K pi0 with 5.8 * 10^7 J/psi data at BES II and the direct measurements of a0(980)-f0(980) mixing in the processes J/psi --> phi f0(980) --> phi a0(980) --> phi eta pi0 and chi_c1 --> pi0 a0(980) --> pi0 f0(980) --> pi0 pi+ pi- with 2.26 * 10^8 J/psi data and 1.06 * 10^8 psi' data at BES III.
In this paper, the lepton flavor violating $τ\to \ell P(V)$ ($P,V= π^0, η, η^{\prime}, ρ^0, ω, ϕ$) and $τ\to 3\ell$ ($\ell = e, μ$) decays are studied in the framework of the type-III seesaw model, in which new triplet fermions with a zero hypercharge (Y=0) interact with ordinary lepton doublets via Yukawa couplings, and affect tree-level leptonic Z-boson couplings. We investigate the experimental bound from the leptonic Z decay to get contraint on the exsiting parameters space. We predict that the upper limits on the branching ratios of $τ\to \ell P(V)$ and $τ\to 3\ell$ can reach the experime…
Likelihood analysis of the newly observed $f_0(2020)$, $f_0(2330)$, and $f_0(2470)$ in $J/ψ\to γη^\primeη^\prime$ as high-lying unflavored scalar mesons
It is shown that the molecular model for the X{3872) state contradicts the new experimental data as well as the old ones. It is suggested to study the χ_{c1} and χ_{b1} states in the e+e-\toχ_{c1}/χ_{b1} reactions.
Study of $χ_{cJ}\to ηηη^\prime$ via intermediate charmed meson loop mechanisms and its implications for non-observation of $η_1(1855)$ in $χ_{cJ}$ decays
College of Physics and Engineering, Qufu Normal University（曲阜师范大学物理工程学院）；Institute of Particle and Nuclear Physics, Henan Normal University（河南师范大学粒子与核物理研究所）；State Key Laboratory of Heavy Ion Science and Technology, Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所重离子科学和技术重点实验室）；School of Nuclear Science and Technology, University of Chinese Academy of Sciences（中国科学院大学核科学与技术学院）；Southern Center for Nuclear-Science Theory (SCNT), Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所南方核科学理论中心）
This paper presents the results of searches for the flavor-changing neutral current, lepton-number-violating and lepton-flavor-violating processes in the charm mesons decays. Recent results from charged $D$ mesons decays to final states with dielectrons from CLEO-c are reported. The prospects of the searches for the rare charm decays at BES-III are also discussed.
Trigger efficiencies at BES III were determined for both the J/psi and psi' data taking of 2009. Both dedicated runs and physics datasets are used; efficiencies are presented for Bhabha-scattering events, generic hadronic decay events involving charged tracks, dimuon events and psi' -> pi+pi-J/psi, J/psi -> l+l- events (l an electron or muon). The efficiencies are found to lie well above 99% for all relevant physics cases, thus fulfilling the BES III design specifications.
We report on the charm physics potential at BES-III at BEPC-II which will make significant contribution to quark flavor physics this decade. The charm physics program will include studies of leptonic, semileptonic and hadronic charm decays, and tests for physics beyond the Standard Model. Event samples of the order of 30 million $\DD$ pairs, 2 million $\DspDsm$ pairs at threshold and $10\times 10^9$ $J/ψ$ decays will be produced with one year design luminosity. High precision charm data will enable us to validate forthcoming Lattice QCD calculations at the few percent level. These can then be …
The branching ratio of the electromagnetic rare decays $η\toπ^0γγ$ and $η^\prime\to (π^0,η)γγ$ are analysed in terms of scalar and vector meson exchange contributions using the frameworks of the Linear Sigma Model and Vector Meson Dominance, respectively. The measured $η\toπ^0γγ$ process serves as a test of our approach while the non yet measured $η^\prime\to (π^0,η)γγ$ reactions are predicted for the first time. Our prediction for the $η\toπ^0γγ$ decay agrees with recent experimental reported values, thus supporting the validity of our framework. Therefore, our predictions for the $η^\prime\t…
Semileptonic decays $D_{(s)} \to η^{(\prime)} \ell^+ ν_\ell$ from QCD Light-Cone Sum Rules
School of Physics and Electronics, Hunan University（湖南大学物理与电子学院）；School for Theoretical Physics, Hunan University（湖南大学理论物理学院）；Hunan Provincial Key Laboratory of High-Energy Scale Physics and Applications（湖南省高能标物理与应用重点实验室）
The Dalitz plot of $η^{\prime} \to ηπ^+ π^-$ decay is studied using $(225.2\pm2.8)\times 10^6$ $\jpsi$ events collected with the BESIII detector at the BEPCII $e^+e^-$ collider. With the largest sample of $η^{\prime}$ decays to date, the parameters of the Dalitz plot are determined in a generalized and a linear representation. Also the branching fraction of $\jpsi \to γη^{\prime}$ is determined to be $(4.84\pm0.03\pm0.24)\times 10^{-3}$, where the first error is statistical and the second systematic.
In this work, we discuss the contribution of the mesonic loops to the decay rates of $χ_{c1}\to ϕϕ,\,ωω$ which are suppressed by the helicity selection rules and $χ_{c1}\to ϕω$ which is a double-OZI forbidden process. We find that the mesonic loop effects naturally explain the clear signals of $χ_{c1}\to ϕϕ,\,ωω$ decay modes observed by the BES collaboration. Moreover, we investigate the effects of the $ω-ϕ$ mixing which may result in the order of magnitude of the branching ratio $BR(χ_{c1} \to ωϕ)$ being $10^{-7}$. Thus, we are waiting for the accurate measurements of the $BR(χ_{c1} \to ωω)$,…
Motivated by recent measurements of the radiative decay rates of the \emph{P}-wave spin singlet charmonium $h_c$ to the light meson $η$ or $η^\prime$ by the BESIII Collaboration, we investigate the decay rates of these channels at order $αα_s^4$. The photon is radiated mainly from charm quark pairs in the lowest order Feynman diagrams, since the diagrams where a photon radiated from light quarks are suppressed by $α_s$ or the relative charm quark velocity $v$, due to Charge parity conservation. The form factors of two gluons to $η$ or $η^\prime$ are employed, which are the major mechanism for …
We propose to search the monophoton events at the BESIII detector and future Super Tau Charm Factory to probe the sub-GeV dark photon decay into lighter dark matter. We compute the cross section due to the dark photon associated a standard model photon production, and study the corresponding standard model irreducible/reducible backgrounds. By using the data about 17 fb$^{-1}$ collected at the BESIII detector since 2011, we derive new leading limits of the mixing strength $\varepsilon$, $\varepsilon\lesssim(1.1-1.6)\times 10^{-4}$, in the mass range of 0.04 GeV $\lesssim m_{A^\prime} \lesssim$…
Partial wave analysis is a core tool in hadron spectroscopy. With the high statistics data available at facilities such as the Beijing Spectrometer III, this procedure becomes computationally very expensive. We have successfully implemented a framework for performing partial wave analysis on graphics processors. We discuss the implementation, the parallel computing frameworks employed and the performance achieved, with a focus on the recent transition to the OpenCL framework.
We established a method on measuring the $\dzdzb$ mixing parameter $y$ for BESIII experiment at the BEPCII $e^+e^-$ collider. In this method, the doubly tagged $ψ(3770) \to D^0 \overline{D^0}$ events, with one $D$ decays to CP-eigenstates and the other $D$ decays semileptonically, are used to reconstruct the signals. Since this analysis requires good $e/π$ separation, a likelihood approach, which combines the $dE/dx$, time of flight and the electromagnetic shower detectors information, is used for particle identification. We estimate the sensitivity of the measurement of $y$ to be 0.007 based …
Based on 5.8x10^7 J/psi events detected in BESII, the branching fractions of J/psi--> phi eta and phi eta^prime are measured for different eta and eta^prime decay modes. The results are significantly higher than previous measurements. An upper limit on B(J/psi--> phi pi^0) is also obtained.
The decay channel $ψ^\prime\toπ^+π^-J/ψ(J/ψ\toγp\bar{p})$ is studied using a sample of $1.06\times 10^8$ $ψ^\prime$ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the $p\bar{p}$ invariant mass spectrum. The enhancement can be fit with an $S$-wave Breit-Wigner resonance function with a resulting peak mass of $M=1861^{+6}_{-13} {\rm (stat)}^{+7}_{-26} {\rm (syst)} {\rm MeV/}c^2$ and a narrow width that is $Γ<38 {\rm MeV/}c^2$ at the 90% confidence level. These results are consistent with published BESII results. These mass and width values d…
Using a data sample of $58\times 10^6$ $J/ψ$ decays collected with the BES II detector at the BEPC, searches for invisible decays of $η$ and $η^\prime$ in $J/ψ$ to $ϕη$ and $ϕη^\prime$ are performed. The $ϕ$ signals, which are reconstructed in $K^+K^-$ final states, are used to tag the $η$ and $η^\prime$ decays. No signals are found for the invisible decays of either $η$ or $η^\prime$, and upper limits at the 90% confidence level are determined to be $1.65 \times 10^{-3}$ for the ratio $\frac{B(η\to \text{invisible})}{B(η\toγγ)}$ and $6.69\times 10^{-2}$ for $\frac{B(η^\prime\to \text{invisibl…
Rare weak decays of $η^\prime\to Kπ$ have been investigated in the framework of the $U(3)$ chiral perturbation theory at the leading order. Our study shows that the branching ratio ${\cal B}(η^\prime\to Kπ)$ is of the order of $10^{-11}$, which is far below the present experimental upper bound given by the BESIII Collaboration. By further analysis of $η^\prime\to K^+π^-$ and $η^\prime\to K^0π^0$, the ratio of isospin amplitudes is found that $|A_{1/2}/A_{3/2}|\simeq 35$, which supports that the $ΔI=1/2$ transition enhancement, namely, the $ΔI=1/2$ rule, could be functional in $η^\prime$ weak d…
The scalar and vector meson exchange contributions to the doubly radiative decays $η^{(\prime)}\toπ^0γγ$ and $η^\prime\toηγγ$ are analysed within the Linear Sigma Model and Vector Meson Dominance frameworks, respectively. Predictions for the diphoton invariant mass spectra and the associated integrated branching ratios are given and compared with current available experimental data. Whilst a satisfactory description of the shape of the $η\toπ^{0}γγ$ and $η^\prime\toπ^{0}γγ$ decay spectra is obtained, thus supporting the validity of the approach, the corresponding branching ratios cannot be rep…
An automatic clock synchronizing method implemented in field programmable gate array (FPGA) is proposed in this paper. It is developed for the clock system which will be applied in the end-cap time of flight (ETOF) upgrade of the Beijing Spectrometer (BESIII). In this design, an FPGA is used to automatically monitor the synchronization circuit and deal with signals coming from external clock synchronization circuit. By testing different delay time of the detection signal and analyzing state signals returned, the synchronization windows will be found automatically in FPGA. The new clock system …
