Study of Neutral Track Measurement at BESⅡ

The measurement errors of the deposited energy and position of neutral tracks in Barrel Shower Counter (BSC) of BESⅡ are investigated. The errors of energy and position of real data are determined by radiative Bhabha events, while the errors of Monte Carlo Data are determined by e⁺e^－→γγ events. Then the corrections are tested by the selected ρπ sample, which shows better pull and Confidence Level distribution after the correction. The results are already applied to the kinematic fitting, which can improve the physics results at BESⅡ.     

Muon Identification Using the Efficiencies Ratio Method at BESⅡ

The momentum and polar angle depended position resolution and hit efficiency in each layer of BES(Ⅱ) muon detector are calibrated by using cosmic ray and hadron samples. Based on the calibration results, the efficiencies ratio function is constructed to separate μ/π effectively and applied in physics analysis.     

Study of Kso Reconstruction and Lifetime Measurement at BESⅡ

The beam collision center of the BEPC has slightly shifted from geometrical origin of the BES detector and the beam bunch of the BEPC also has certain size. For these reasons, to measure K_s^o lifetime, primary vertex reconstruction must be carried out. After the investigation of di-muon, bhabha and hadron events, the beam collision center for each run is determined by bhabha and di-muon events. For the large branching ratio of and the existence of the resonance of KⅡ0 , this channel is chosen to provide much pure K_s^o signal. With the aid of M. C. tools at BES Ⅱ , existing software for secondary vertex reconstruction is adjusted and improved. A new method of secondary vertex determination is used and a better position resolution of secondary vertex is obtained. The lifetime of Ks0 is measured with channel and the inclusive K_s^o mass is investigated with BES Ⅱ 's 50M J/ψ data sample, which give consistent Ks0 lifetime and mass with PDG' s value within error. 1C fit on K⁰_s mass is also studied with M. C. events. The resolution of momentum and energy of 7π+ , π- and K, is improved too.     

Study of the efficiency of event start time determination at BESⅢ

A method to estimate the efficiency of event start time determination at BESⅢ is developed. This method estimates the efficiency at the event level by combining the efficiencies of various tracks (e, μ, π, K, p, γ) in a Bayesian way. Efficiencies results and the difference between data and MC at the track level are presented in this paper. For a given physics channel, event start time efficiency and systematic error can be estimated following this method.     

Study of the efficiency of event start time determination at BESⅢ

A method to estimate the efficiency of event start time determination at BESIII is developed.This method estimates the efficiency at the event level by combining the efficiencies of various tracks(e,μ,π,K,p,γ)in a Bayesian way.Efficiencies results and the difference between data and MC at the track level are presented in this paper.For a given physics channel,event start time efficiency and systematic error can be estimated following this method.     

Determination of the number of ψ' events at BESⅢ

The number of ψ’ events accumulated by the BESⅢ experiment from March 3 through April 14, 2009, is determined by counting inclusive hadronic events. The result is 106.41×(1.00±0.81%)×106 . The error is systematic dominant; the statistical error is negligible.     

Determination of the number of ψ' events at BES Ⅲ

The number of ψ' events accumulated by the BESⅢ experiment from March 3 through April 14, 2009, is determined by counting inclusive hadronic events. The result is 106.41×(1.00±0.81%)×106 . The error is systematic dominant; the statistical error is negligible.     

Study of the online event filtering algorithm for BESⅢ

The results of a study of event tagging strategies for elementary physics processes in the τ-charm region are presented. The algorithm for online event filtering is optimized by adopting the information provided by different sub-detectors according to their strengths and capacities. The algorithm is tested with various generated physics and background events. The results indicate that the algorithm satisfies the requirements of BESⅢ physics analysis and its     

A Monte Carlo Study on the Identification of Quark and Gluon Jets

Three-jet events in e^ e^- collisions at 91.2 GeV are investigated using both HERWIG and JETSET Monte Carlo generators.The angles among the three jets are used to identify the quark and gluon jets.An analysis at the parton level is carried out to ensure the reasonableness of this method and an angular cut is utilized to improve the purity of this identification.The multiplicity inside the identified quark or gluon jets agrees with the quantum chromodynamic predictions qualitatively.     

Simulation Study of the Electromagnetic Calorimeter Triggers in BESⅢ

Based on the detector and trigger simulation of beijing spectrometer Ⅲ (besⅢ), schemes of besⅢ emc triggers are studied. neutral triggers, bhabha triggers and charged event triggers are designed to fulfill the requirements of the physics goals. the trigger parameters are optimized and the ability of backgrounds rejection are carefully studied. trigger simulation for some typical physics channels are studied and the expected backgrounds event rates are obtained     

Measurements of the center-of-mass energies at BESⅢ via the di-muon process

From 2011 to 2014,the BESIII experiment collected about 5 fb~(-1) data at center-of-mass energies around 4 GeV for the studies of the charmonium-like and higher excited charmonium states.By analyzing the di-muon process e~+e~- → Yisr/fsr μ~+μ~-,the center-of-mass energies of the data samples are measured with a precision of 0.8 MeV.The center-of-mass energy is found to be stable for most of the time during data taking.     

Study of radiation background at the north crossing point of the BEPCⅡ in collision mode

Understanding the radiation background at the north crossing point (NCP) in the tunnel of BEPCII is crucial for the performance safety of the High Purity Germanium (HPGe) detector, and in turn of great significance for long-term stable running of the energy measurement system. Therefore, as the first step, a NaI(Tl) detector is constructed to continuously measure the radiation level of photons as background for future experiments. Furthermore, gamma and neutron dosimeters are utilized to explore the radiation distribution in the vicinity of the NCP where the HPGe detector will be located. Synthesizing all obtained information, the shielding for neutron irradiation is studied based on model-dependent theoretical analysis.     

The Study of BES Reconstruction Codes at PC LX ＆ HP—UX

This note describes the modifications of the BES offline data reconstruction codes from the HP-UNIX to PC LINUX platform.The main changes of the codes and the results compairson with that of before modifications are presented.     

Monte Carlo Study of the Neutron Detection Wall at RIBLLⅡ in HIRFL-CSR

With the construction of the new Radioactive Ion Beam Line in Lanzhou (RIBLLⅡ) which connects the CSRm and the CSRe, an experimental setup for physics research is highly required. A large area neutron detection wall is the main part of the setup. This paper introduced the detection principle of the neutron detection wall and the Monte-Carlo simulation of its design under the environment of the Geant4 toolkit. We presented the final design with the optimized parameters and the performance of the wall.     

Determination of the number of ψ(3686)events at BESⅢ

The numbers of ψ(3686) events accumulated by the BESⅢ detector for the data taken during 2009 and2012 are determined to be(107.0±0.8)×10~6 and(341.1±2.1)×10~6, respectively, by counting inclusive hadronic events,where the uncertainties are systematic and the statistical uncertainties are negligible. The number of events for the sample taken in 2009 is consistent with that of the previous measurement. The total number of ψ(3686) events for the two data taking periods is(448.1±2.9)×10~6.     

Measurement of the integrated luminosities of the data taken by BESⅢ at √s=3.650 and 3.773 GeV

Data sets were collected with the BESⅢ detector at the BEPCⅡ collider at the center-of-mass energy of √s=3.650 GeV during May 2009 and at √s=3.773 GeV from January 2010 to May 2011. By analyzing the large angle Bhabha scattering events, the integrated luminosities of the two data sets are measured to be （44.49±0.02±0.44） pb-1 and （2916.94±0.18±29.17） pb-1, respectively, where the first error is statistical and the second error is systematic.     

Study of the mechanism of the 3He + p → p + p + d reaction at a 3He momentum of 5 GeV/c

The mechanism of the reaction ³He + p → p + p + d is studied by making use of the ITEP 80 cm liquid-hydrogen bubble chamber exposed to a beam of 5 GeV/c ³He nuclei. The reaction cross section is equal to 20.6 ± 0.3 mb. The phase-space regions associated with quasifree scattering (QFS) and final-state interactions (FSI) are selected. Angular, mass and momentum distributions of the reaction products are obtained in the entire kinematically allowed range. The experimental data in the QFS region are compared with theoretical calculations based on the simplest pole-diagram approximation. The ³He and deuteron wave functions (WF) correspond to the realistic RSC potential. The D-wave components of these WF are taken into account. The absolute value of the cross section and shape of the distributions are described as a whole reasonably well within the frame of the model considered in the kinematical region where FSI may be neglected. But at large spectator momenta there is an essential disagreement. The possible reasons for this are discussed.     

Study of inclusive production of π± and protons in\bar p p interactions at 32 GeV/c

Results are presented on the inclusive production of π^± mesons and protons in \(\bar p\) p interactions at an incident antiproton momentum of 32 GeV/c in the MIRABELLE bubble chamber, based on a sample of 55,000 inelastic events. The spectra of π⁺(π^?) andp( \(\bar p\) ) are separated in the whole kinematically admitted region of phase space by a statistical method. The semi-inclusive and inclusive cross sections and the main average characteristics of π andp production are calculated. The invariant differential cross sections are studied as functions of the Fevnman scaling variablex, the rapidity and the transverse momentum. Thex distribution of π^± mesons in the proton fragmentation region does not show any significant contribution from quark exchange or annihilation processes. A possible contribution of hard quark scattering on mesons or baryons is observed for large transverse momenta.     

Thepp —p \bar p difference and the behaviour of phases at high energies

Predictions based on axiomatic field theory are obtained from the assumption that the difference between thepp and thep \(\bar p\) elastic scattering observed at the CERN ISR is caused by an “odderon-like” term in the scattering amplitude. A wide class of amplitudes violating the Pomeranchuk relation is considered. Contrary to common opinion, severe restrictions on the high-energy behaviour of the phase of the crossing-odd amplitude are shown to follow for the whole class. Less pronounced but still visible consequences follow for the phases of thepp andp \(\bar p\) amplitudes separately. We derive the corresponding high-energy bounds and correlations using the general frame of analyticity, crossing symmetry and unitarity. As a special case, the maximal odderon amplitude is discussed.