实验核物理进展

本文回顾我所实验核物理科研人员在低能核反应机制、中子物理、核衰变性质及核结构研究中所做一系列工作,同时简单介绍了目前工作和设想． The paper reviews the research activities at SINR on experimental nuclear physics. The studies have been focused on mechanism of nuclear reactions, neutron physics,properties of nuclear decay and nuclear structure. Brief introductions are given to the ongoing research projects and future plans in the field of research.     

Trigger efficiencies at BESⅢ

Trigger efficiencies at BESⅢ were determined for both the J/ψ and ψ＇ 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 ψ＇→π＋π-J/ψ, J/ψ→ 1＋1- events.The efficiencies are found to lie well above 99% for all relevant physics cases, thus fulfilling the BESⅢ design specifications.     

Next-to-leading order QCD corrections to the decay of Higgs to vector meson and Z boson

The exclusive decay of the Higgs boson to a vector meson(J/ψ or Υ(1 S)) and Z boson is studied in this work. The decay amplitudes are separated into two parts in a gauge invariant manner. The first part comes from the direct coupling of the Higgs boson to the charm(bottom) quark and the other from the HZZ*or the loop-induced HZγ*vertexes in the standard model. While the branching ratios from the direct channel are much smaller than those of the indirect channel, their interference terms give nontrivial contributions. We further calculate the QCD radiative corrections to both channels, which reduce the total branching ratios by around 20% for both J/ψ and Υ(1S) production. Our results provide a possible chance to check the SM predictions of the Hcc(Hbb)coupling and to seek for hints of new physics at the High Luminosity LHC or future hadron colliders.     

An overview of η and η' decays at BESIII

The world's largest sample of J/ψ events, 1.31 billion events accumulated at the BESIII detector, provides a unique opportunity to investigate η and η physics via two-body J/ψ radiative or hadronic decays. For many η 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 obtained at BESIII so far. The analyses range from detailed studies of common decay dynamics, observations of new radiative and Dalitz decays, and searches for rare/forbidden decays with sensitivity up to B～10-5. Finally, prospects of forthcoming runs at the J/ψ peak forη and η physics are discussed.     

Charmonium results from BES

Using ～14×106ψ(2S) and ～58×106J/ψ data collected at BESⅡ/BEPC,the branching fraction of ψ(2S) →Ω+Ωˉ+ is measured with about 5σ statistical significance.The Λ electric dipole and Λ decay parameter are studied using the decay J/ψ→ΛΛ→ ppˉπ+π-.Using(106±3)×106 ψ(2S) decays collected at BESⅢ/BEPCⅡ,we have obtained some interesting physics results.The branching fractions of χcJ →π0π0,ηη are measured with precision improved.The mass and width of hc(11P1) state,together with the branching fractions of Br(ψ(2S) →π0hc) and Br(hc →γηc) are the first measurements.Surprisingly,the decays of χc1 →φφ,ωω,and ωφ are firstly observed in BESⅢ data.     

首次测定短寿命缺中子同位素153Er和157Yb的EC/β＋衰变纲图简介

本文简单介绍了首次成功地测定这两个衰变纲图的技术难点、实验过程、主要实验结果及物理意义。 EC/β+ decay schemes of 153Er and 157Yb are proposed for the first time. The related technical difficulty, experimental process, main results and their physics are representedbrigly.     

Searching for Electrical Dipole and Chromodipole Moments of a Charm Quark in J／ψ→γφφ Decay

We propose a scheme to search for the electrical dipole moments (EDMs) and chromodipole moments (CDMs) of a charm quark in the decay J/ψ→γφφ based on J/ψ data samples accumulated on the Beijing Electron Positron Collider (BEPC). The EDM and CDM interactions are introduced in this decay and then we relate them to some CP asymmetrical observables, which are predicted in the valence quark model. We propose a method to hunt for these values by measuring associated CP asymmetrical observables, and we also discuss the prospect of such measurement on the BEPC.     

J/ψ→μ^＋μ^- reconstruction in the CMS experiment

In this paper the J/ψ→μ^＋μ^- reconstruction performance in the CMS experiment at the LHC is studied in detail by using B8→J/ψφ→μμKK events. The reconstruction efficiencies of J/ψ mesons and their decay muons are obtained as a function of the transverse momentum PT and the pseudo-rapidity η. We also study the muon trigger efficiency for this channel with the planned Level-1 trigger and High Level Trigger selection criteria. It was observed that the muon reconstruction efficiency decreases when the two decay muons have a small or large 3D angular separation, which further affects the overall J/ψ reconstruction efficiency.     

Charmonium results from BES

Using ～ 14 × 10^6 ψ（2S） and ～ 58 × 10^ J/ ψ data collected at BES Ⅱ/BEPC, the branching fraction of ψ（2S）→Ω-Ω^＋ is measured with about 5a statistical significance. The A electric dipole and ∧ decay parameter are studied using the decay J/ψ →∧∧→ ppπ^＋π^-. Using （106±3）× 10^6 ψ（2S） decays collected at BESⅢ/BEPC Ⅱ, we have obtained some interesting physics results. The branching fractions of XcJ→π^0π^0, ηη are measured with precision improved. The mass and width of he（l^1P1） state, together with the branching fractions of Br（ψ（2S） →π^0hc） and Br（hc →γηc） are the first measurements. Surprisingly, the decays of Xc1→φφ, ωω, and ωφ are firstly observed in BESⅢ data.     

J/ψ→μ+μ- reconstruction in the CMS experiment

In this paper the J/ψ→μ+μ- reconstruction performance in the CMS experiment at the LHC is studied in detail by using B5→ J/ψψ →μμКК events. The reconstruction efficiencies of J/ψ mesons and their decay muons are obtained as a function of the transverse momentum PT and the pseudo-rapidity η. We also study the muon trigger efficiency for this channel with the planned Level-1 trigger and High Level Trigger selection criteria. It was observed that the muon reconstruction efficiency decreases when the two decay muons have a small or large 3D angular separation, which further affects the overall J/ψ reconstruction efficiency.     

Trigger efficiencies at BESⅢ

Trigger efficiencies at BESⅢ were determined for both the J/ψ and ψ' 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 ψ'→π+π-J/ψ, J/ψ→ 1+1- events.The efficiencies are found to lie well above 99% for all relevant physics cases, thus fulfilling the BESⅢ design specifications.     

ηc Physics at BESⅢ

An introduction for η_c physics research is presented in this paper, which shows that the meachnism of η_c decays can't be well described by current theoretical models and detailed experimental measurements need to be done with larger η_c sample. Based on the expected J/ψ and ψ′events taken with the planed BESⅢ detector in one year, the η_c physics researches are discussed extensively, including the measurements of branching fractions of different final states, the search for new decay modes, precision measurements of mass and width, and the search for rare decays. At last, the study of η′_c decays is also discussed briefly.     

Search for Exotic States in J／ψ→ρηπ

It is an ideal place to search for exotic states through J/ψ hadronic decays.In this paper,we discuss the way to use the partial wave analysis (PWA) based on covariant helicity amplitude analysis to study the invariant mass spectrum of ηπ and to find the evidence of the existence of exotic states in this channel.The formula for PWA is also given.It is the theoretical foundation of experimental physics analysis on exotic states searching in J/ψ hadronic decays.The theoretical formula can also be used in physics analysis of J/ψ decays into ωππ,φππ,ωKK,φKK and K^* (892)Kπ.     

First observation of η(1405) decays into f(0)(980)π0

The decays J/ψ → γ π+ π- π0 and J/ψ → γ π0 π0 π0 are analyzed using a sample of 225×10(6) J/ψ events collected with the BESIII detector. The decay of η(1405) → f(0)(980)π0 with a large isospin violation is observed for the first time. The width of the f(0)(980) observed in the dipion mass spectra is anomalously narrower than the world average. Decay rates for three-pion decays of the η' are also measured precisely.     

J/ψ polarization in pp collisions at √s=7 TeV

The ALICE Collaboration has studied J/ψ production in pp collisions at √s=7 TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J/ψ polarization parameters λ(θ) and λ(φ) were obtained. The study was performed in the kinematic region 2.5相似文献   

Comments on the Ratio of Hadronic Decay Rates of ψ(2S)to J/ψ

The perturbative QCD prediction of “15% rule” for the ratio of ψ(2S) to J/ψ hadronic decay rates suffers seveal apparent approximations. Calculations using existing experimental data are made in this paper; further corrections to this radio for a number of exclusive decay channels are also discussed.     

Overveiw of the BES physics

Recent physics results at Beijing Electron-Positron Collider (BEPC) are reviewed, especially on excited baryons. Substantial improvements are expected at the newly built BESⅢ experiment, which is operational since 2008. The detector performance is excellent and a total of 100 million ψ(2S) and 200 million J/ψ event are collected in 2009. Preliminary results shows that a new era of excited baryon physics will begin.     

Large SU（3） Symmetry Breaking in J／ψ→BB Decays

Large SU(3) symmetry breaking effects in J/ψ→BB decay processes are discussed using the Mark I,Mark II,DM2 and the recent data from BES Collaboration.