TEST BEAM STUDIES OF BES BARREL SHOWER COUNTER PROTOTYPE

The BES barrel shower counter prototype was tested with electron and pion beam in the momentum range from 0.2 to 2.0GeV/c at 12GeV PS test beam line of KEK, the preliminary results were reported. Four types of gas mixtures which were used in prototype have been tested: 40% Ar/60% Isobutane, 44.5% Ar/44.5%CH₄/11% Methylel, 47%Ar/47%%CH₄/6% Methylel, 49.3%Ar/49.3%CH₄/1.4% Ethyl alcohol. The results show that using SQS tube as sampling means in BES shower is feasible way for BEPC region.     

Yields of Charmed and Beautiful Mesons in e+e－ Annihilation at s=10—178GeV 的e+e-

Based on the electroweak unified standard model,the probability P_i for the production of i-quark jet (i=u,d,c and b)in e⁺e^－ annihilation has been studied.The probability P_i is a function of energy s.The calculated component ratios of P_u:P_d:P_s:P_c:P_b are 4:1:1:4:1 for s<30GeV.7:9:9:7:9 for s=m_z=91.16GeV and 1:1:1:1:1 for s=78 and 117GeV,respectively.Using P_c and P_b,we whave calculated the yields of charmed and beautiful mesons in e⁺e^－ annihilation at s=10—178GeV.     

Scale for the Production of Jets in High Energy e+e－ Collisions

The scale for visible jets produced in e⁺e^－ Collisions is studied in some details using Monte Carlo method. It is demonstrated, based on the historical fact that the 3-jet events were firstly observed in e+ e- experiments at √S=17—30GeV,and the relative transverse momentum for visible jets is in the region k_t,～5—10GeV/c. It is further shown, using a concrete example, that the number of jets in an event could be correctly evaluated only when k_t is in this region. The dynamical fluctuations inside jets determined through different values of k_t are compared carefully. It turns out that only when k_t,～5—10GeV/c the dynamical fluctuations inside jets will possess the best anomalous scaling property. The relation between the scale 5-10GeV/c of visible jets and the scale 1-2GeV of perturbative QCD is discussed.     

Rare decays B0s,d→l+l－ in a top quark two-Higgs-doublet model

In the framework of T2HDM, we calculated the new physics contributions involving neutral Higgs bosons to the branching ratios of B⁰_s,d→l⁺l^－ (l=e, μ) decays. Comparing the theoretical predictions with the experimental upper-limits, we found that (a) The data of Br(B⁰_d→l⁺l^－) give the upper bound on tanβ: tanβ≤22, while Br(B⁰_s→l⁺l^－) give tanβ≤12 for fixed δ=0°, m_H+=350 GeV, m_H0=160 GeV, m_h0=115 GeV and m_A0=120 GeV; (b) A light neutral Higgs boson mass m_h0 (m_A0) less than 50 GeV (120 GeV) is excluded by the data of branching ratios for B⁰_s,d→l⁺l^－(l=μ) decays with tanβ=10; (c) The bounds on m_h0 and tanβ, or m_A0 and tanβ are strongly correlated: a smaller (larger) tanβ means a lighter (heavier) neutral Higgs boson.

     

Ds（0^±） Meson Spectroscopy in Gaussian Sum Rules

Masses of the Ds（0^±） mesons are investigated from a view-point of ordinary light-heavy system in the framework of the Gaussian sum rules, which are worked out by means of the Laplacian transformation to the usual Borel sum rules. Using the standard input of QCD non-perturbative parameters, the corresponding mass spectra and couplings of the currents to the Ds（0^±） mesons are obtained. Our results are mDs（0-） = 1.968±0.016±0.003 GeV and mDs（0＋） = 2.320 ±0.014 ± 0.003 GeV, which are in good accordance with the experimental data, 1.969 GeV and 2.317 GeV.     

Energy Resolution and Its Simulation for the ESC of BES

With data collected by the Beijing Spectmmeter (BES) in the J/ψ,ψ′, and D_s energy region, a lot of e⁺e^－ final state evenb are selected in the solid angle region covered by the endcap shower counters (ESC). Some characteristics of the ESC are analysed, such as the spectrnun of pulse height for, a single counter cell, the hit nwnbers in the ESC and in every reading layer of the ESC, the shower energies deposited in the ESC and in every layer of the BSC. The energy resoiudon of the ESC in obtained to be about 22%/E(GeV) Based on the odginal frame of SOBER, a Monte Carlo simulation program for the ESC is developed with a dual Gaussian pulse height spectrtun of the single counter cell. The electromagnetic cascades are calculated by the EGS4 package and a three-dimension magnetic field in the BES is included. The simulation results agree with experimented data well.     

On the Nature of f0(400-1200)

We discuss about the nature of f₀(400-1200) which we decompose into three parts, i.e., t-channel ρ meson and f₂(1270) meson exchange plus an additional s-channel resonance f₀(X). Below 1.2GeV of ππ invariant mass, t-channel ρ meson exchange can explain the I=2 ππ S-wave scattering very well. However, the f₂(1270) meson exchange must be considered for the ππ invariant mass above 1.2GeV. With the t-channel ρ meson and f₂(1270) meson exchange fixed by the isotensor ππ→ππ S-wave scattering, we re-fit the CERN-Mülich(CM) data on ππ scattering to get parameters for the f₀(X). We find that it is necessary to introduce a broad 0⁺⁺ resonance with a pole about 1.6-1.7GeV.     

Experimental Determination of the Radiative Correction Factor Δr and Phenomenological Analyses

In this paper the experimental value of radiative correction Δr was derived from the new data of sin ²θ_w and W boson mass M_w given by LEP,CDF and other collaborations.A careful comparison of (Δr)_exp with the standard model expectation was carried out.We first calculated the Δr at full one-loop level,and then the main two-loop contributions were included.More stringent upper bounds on M_t were obtained from the analysis of probability distribution:M_t175GeV at 95%C.L. for a given M_H=100GeV.The effects on N_t from other experimental and theoretical errors were also computed.     

ANALYSIS OF HADRONIC EVENTS

In this paper I summarize some results obtained from analyses of hadronic final state events. The analyzed data sample comes from Mark-J collaboration and covers an energy range from √S=12GeV to √S =46.78GeV. The integrated luminosity is 128.06Pb^－1. We can search for production of open top quarks and toponium by measuring the total hadronic crossection R =3.85±0.02±0.12 was measured in the above mentioned energy range. It is consistent with R≈3.9 as expected from QCD for five different quark flavors. We search for the narrow bound states of the toponium from 39.79GeV to 46.78GeV. The most prominent resonance signal is at a c.m. energy √S=45.12±0.04GeV and results in an upper limit of B_h.Γ_ee≤3.00keV(95% C.L.).     

Main linac lattice design and optimization for Ecm=1 TeV CLIC

The Compact Linear Collider (CLIC) is a future e⁺e^- linear collider. The CLIC study concentrated on a design of center-of-mass energy of 3 TeV and demonstrated the feasibility of the technology. However, the physics also demands lower energy collision. To satisfy this, CLIC can be built in stages. The actual stages will depend on LHC results. Some specific scenarios of staged constructions have been shown in CLIC Concept Design Report (CDR). In this paper, we concentrate on the main linac lattice design for E_cm=1 TeV CLIC aiming to upgrade from E_cm=500 GeV CLIC and then to E_cm=3 TeV one. This main linac accelerates the electron or positron beam from 9 GeV to 500 GeV. A primary lattice design based on the 3 TeV CLIC main linac design and its optimization based on the beam dynamics study will be presented. As we use the same design principles as 3TeV CLIC main linac, this optimization is basically identical to the 3 TeV one. All the simulations results are obtained using the tracking code PLACET.     

The W-boson mass and precision tests of the Standard Model

We have examined the electroweak radiative corrections in the LEP precision data in view of the new measurements of M_W and m_t as well as the recent progress in the higher order radiative corrections. From the minimal L²-fit to the experimental Z-decay parameters (with the aid of a modified ZFITTER program), we predict that M_W=80.29(4)(2)rGeV where the first error is due to the uncertainty in the fitted m_t for a fixed m_H and the second error comes from the m_H in the range 60􊖸rGeV, which is to be compared with the current world average M_W=80.23(18)rGeV. The current world average value of M_W and the 1994 LEP data definitely favor nonvanishing electroweak radiative corrections and are consistent with a heavy m_t as measured by the recent CDF report but with a heavy Higgs scalar of about 400rGeV within the context of the minimal standard model. The sensitivity of and the errors in the best fit solutions due to the uncertainties in the gluonic coupling !_s(M_Z) and !(M_Z) are also studied carefully. In addition we discuss how the future precision measurements of M_W can provide a decisive test for the standard model with radiative corrections and give a profound implication for the measurement of t-quark and Higgs masses.     

THE VERTICAL INTEGRATED MOMENTUM SPECTRUM OF THE MUON WITH MOMENTUM LARGER THAN 4 GeV/c AT 3220m ABOVE SEA-LEVEL

At an altitude of 3220 meters above sea level in Yunnan Province, we measured, by using a G-M counter-magnetic spectrometer, the vertical integratted momentum spectrum of the cosmic muon with momentum larger than 4 GeV/c. The spectrum obtained from this experiment is expressed by a power function in the form of I（>p）=Q （p+4）^-1.86±0.06(cm^-2·sr^-1·s^-1), where p is in GeV/c and Q is a constant. We also measured the charge ratio of muon in the 4—23 GeV/c momentum range. The result is N_μ/N_μ-=1.26±0.11. The error in the momentum measurement with spectrometer has been discussed and calculated.     

Angular Distributions of Projectile Fragments Produced in Collisions of 200A GeV 32S Beam with Cu

Angular distributions of projectile fragments P,Si,Al and Mg produced in collisions of 200A GeV ³²S beam with Cu are measured.The range of σ_pt deduced is within 130—270MeV/c.     

Possibility of a Symmetric Weak Mixing and its Implications

A general parametrization of the symmetric KM matrix is given.The unitarity triangle is discussed,which embodies the unitarity of the symmetric KM matrix and CP violation.It is shown that the symmetric KM matrix is consistent with the directly measured values of the KM matrix elements,CP violation parameter │ε│ of K-K system,and B0d-B0d mixing parameter χ_d,provided the t-quark mass is large,m_t≥160GeV.If │V₁₂│=│V₂₁│is confirmed by further experiments,KM matrix will turn out to be symmetric,so that a parameter is reduced in the standard model.     

HIGH ENERGY DEUTERON-DEUTERON SCATTERING

The differential cross section of deuteron-deuteron elastic scattering at P_d=5.76 GeV/c is calculated based on the Glauber multiple scattering theory in nucleus-nucleus collision. The theoretical result is compared with the experimental data and the agreement is satisfactory. In addition, the influence of the input amplitude is discussed.     

EMC EFFECT ON P-A HIGH ENERGY COLLISION

According to the perturbative QCD method,we have calculated the P_⊥ distributive cross sections,the Y distributive cross sections of the large P jets and the final state meson productivities in 800GeV/c Proton-Nucleus (Be,C,Al,Cu and Pb) collisions.The A dependence of the cross section at a given P_⊥ was discussed by the EMC effect. The dσ/dP_⊥ differential cross sections vs .P_⊥ for various PA collisions are consistent with the new data.     

Absolute Measurement of Important Branching Fractions of the Ds Meson

Absolute measurement of branching fractions of purely leptonic decay, semi-leptonic decay and φπ⁺ decay of the D_s meson at a c.m. energy of 4.03 GeV were completed from the BES experiment at the BEPC electron-positron collider. The method by using combined confidence level for pion and kaon separation, the D_s single and double tagging technology, and the maximum likelihood functions in the estimate of the D_s branching fractions are described in details. Discussion and comments on these physics results are made. Prospect for improved measurement of D_s physics in future is also given.     

Clockwise vs Counter-Clockwise I-V Hysteresis of Point-Contact Metal-Tip/Pr0.7 Ca0.3MnO3/Pt Devices

Metal-tip/Pr0.7Ca0.3MnO3/Pt devices possess two types of I-V hysteresis： clockwise vs counter clockwise depending on the tip materials. The criteria for categorization of these two types of devices can be simply based on whether the Gibbs free energy of oxidation for the metal tip is lower or higher than that of PCMO, respectively. While the clockwise hysteresis can be attributed to electric field induced oxidation/reduction, the counter clockwise hysteresis can be explained by oxygen vacancy migration in an electrical field. Alternating-current conductance spectra also reveal distinct hopping barriers between these two categories of devices at high resistive states.     

LONG RANGE CORRELATION SINGLE PARTICLE SPECTRUM AND PION CONDENSATION IN PROTON-NUCLEUS COLLISION

The combination of partition temperature with Bose-Einstein statistics is generalized to describe the proton nucleus collision. The rapidity distribution of pp, p-Ar and p-Xe at P_L=200GeV/c have been calculated and compared with experiment. The interesting possibility of observing pion condensation in p-A collision is investigated.

     

The Source of Anomalous Positrons in the Cosmic Rays Above 10GeV

We suggest that the heavy neutral lepton in a specific version of SU(3)_L×U(1) model can not only act as dark matter but also provide with a source of anomalous positrons in the cosmic rays above 10GeV.