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 on a $20fb^{-1}$ fully simulated MC sample.
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 talk,we present direct measurements of $a^{0}_{0}(980)-f_{0}(980)$ mixing in the processes $J/ψ\toϕf_{0}(980)\toϕa^{0}_{0}(980)\toϕηπ^{0}$ and $ψ^{\prime}\toγχ_{c1},χ_{c1}\toπ^{0} a^{0}_{0}(980)\toπ^{0} f_{0}(980)\toπ^{0}π^{+}π^{-}$ with $2.25 \times 10^{8}$ $J/ψ$ data and $1.06 \times 10^{8}$ $ψ^{\prime}$ data at BESIII.
Type-III seesaw is a simple extension of the Standard Model~(SM) with the SU$(2)_\text{L}$ triplet fermion with zero hypercharge. It can explain the origin of the tiny neutrino mass and flavor mixing. After the electroweak symmetry breaking the light neutrino mass is generated by the seesaw mechanism which further ensures the mixings between the light neutrino and heavy neutral lepton mass eigenstates. If the triplet fermions are around the electroweak scale having sizable mixings with the SM sector allowed by the correct gauge symmetry, they can be produced at the high energy colliders leavin…
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.
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 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…
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 …
We study LHC signatures of Type III seesaw in which SU(2)_L triplet leptons are introduced to supply the heavy seesaw masses. To detect the signals of these heavy triplet leptons, one needs to understand their decays to standard model particles which depend on how light and heavy leptons mix with each other. We concentrate on the usual solutions with small light and heavy lepton mixing of order the square root of the ratio of light and heavy masses, (m_ν/M_{ν_R})^{1/2}. This class of solutions can lead to a visible displaced vertex detectable at the LHC which can be used to distinguish small m…
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 analyse three different New Physics scenarios for Delta F=2 flavour-changing neutral currents in the quark sector in the light of recent data on neutral-meson mixing. We parametrise generic New Physics contributions to B_q-Bbar_q mixing (q=d,s), in terms of one complex quantity Delta_q, while three parameters Delta_K^tt, Delta_K^ct and Delta_K^cc are needed to describe K-Kbar mixing. In Scenario I, we consider uncorrelated New Physics contributions in the B_d, B_s, and K sectors. In this scenario, it is only possible to constrain the parameters Delta_d and Delta_s whereas there are no non-t…
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.
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 $BR(χ_{c1} \to ωω)$,…
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 …
We propose a two Higgs doublet Type III seesaw model with $μ$-$τ$ flavor symmetry. We add an additional SU(2) Higgs doublet and three SU(2) fermion triplets in our model. The presence of two Higgs doublets allows for natural explanation of small neutrino masses with triplet fermions in the 100 GeV mass range, without fine tuning of the Yukawa couplings to extremely small values. The triplet fermions couple to the gauge bosons and can be thus produced at the LHC. We study in detail the effective cross-sections for the production and subsequent decays of these heavy exotic fermions. We show for …
A new fanning topology is proposed to precisely fan out fast control signals in the Beijing Spectrometer (BES III) end-cap time-of-flight (ETOF) electronics. However, uncertainty in transfer latency is introduced by the new fanning channel, which will degrade the precision of fast control. In this paper, latency uncertainty elimination for the BESIII ETOF upgrade is introduced. The latency uncertainty is determined by a Time-Digital-Converter (TDC) embedded in a Field-Programmable Gate Array (FPGA) and is eliminated by re-capturing at synchronous and determinate time. Compared with the existin…
