1999 Vol. 23, No. 1

Display Method:          |     

Study and Simulation of the Features of Hadronic Events in the BEPC Energy Region
Qi Xiangrong, Chen Jiangchuan, Hu Haiming, Hu Tao, Huang Guangshun, Ju Xin, Li Jin, Li Xinhua, Mao Zepu, Xue Shengtian, Zhao Zhengguo, Zheng Zhipeng, Zhou Li
1999, 23(1): 1-9.
Using hadronic events sample collected around 3.55 GeV with Beijing Spectrometer (BES) at Beijing Electron Positron Collider (BEPC) and the published data, we studied distributions characterizing the hadronic events produced from the e+e annihilation and the most sensitive parameters in the LUND model and found that the characterizing distributions of the hadronic events of the BEPC data agree well with that predicted by the LUND model with tuned parameters.
Measurement of Structure Function of τ→π±0v
Yao Xueyi, Chen Guoming, Chen Gang, Chen Hesheng, Tang Xiaowei
1999, 23(1): 10-16.
The structure function of τ→π±0v is measured by model independent method. The result is compared with Kuhn-Santamaria model, Isgur-Morningstar-Reader model and Feindt model. Good consistency between data and the three models is shown within the experimental error range. The comparison with the structure function of τ→3π±v measured by OPAL Collaboration also shows there is no obvious difference within 0.52.
Production of Ring-like Events in pp Collisions at 400GeV/c
Wang Shaoshun, Liu Ran, Wang Zhaomin
1999, 23(1): 17-21.
The production mechanism of ring-like events has been investigated by using the data of pseudorapidity distribution of charged particles produced in pp collisions at 400GeV/c. The results show that the model of coherent gluon emission within a finite region of space-time is a possible production mechanism of ring-like events, but certainly not dominant.
Search for 10TeV γ-Ray Emission from Supernova Remnants and Active Galactic Nuclei
Zhang Jilong, Ding Linkai, Mu Jun, Wang Hui, Lu Hong, Liu Shaomin, Feng Zhenyong, Ren Jingru, Yu Guangce, Xu Xianwu, Zhou Wende
1999, 23(1): 22-34.
A search for 10Tev γ-ray continuous emission from 58 Supernova Remnants which include Crab Nebula and 25 Active Galactic Nuclei which include Mrk421 and Mrk501 with the data of Tibet I air shower array from 1990 June to 1993 October is executed by the method of equi-zenith angle to estimate the bacdground events. The significance of DC excess is calculated according to the Li and Ma prescription. No significant DC excess is observed from these candidates. The integral distribution of significances is checked by the Kolmogorov-Smirnov test which examines the divergence from a standard normal distribution. No significant deviation is found. Flux upper limit is obtained for each source at 95% C.L.
Search for TeV Gamma Ray Bursts From Evaporating Primordial Black Holes
Xu Chunxian, He Huilin, Chen Yongzhong, He Huihai, Li Huidong, Zhang Yong, Jiang Yinlin
1999, 23(1): 35-38.
Data taken with ACT2 and ACT3 betWeen 1995 and 1997 are used to search for 0.1 second bursts of TeV gamma Rays from evaporating Primordial Black Holes (PBHs). There is no evidence for such bursts in the dataset. Using the result,the upper limit of 3 ×108pc-3yr-1 on the rate-density of evaporating PBHs is set in the vicinity of the solar system at a 99% confidence level.
Extraction of Reaction Time in the 27Al+27Al Dissipative Collision
Wang Qi, Tian Wendong, Li Songlin, Lu Jun, Jiang Zhonghe, Hu Pengyun
1999, 23(1): 39-43.
Interaction time ~4.3×10-21s of the dissipative products in the collision 27Al+27Al is extracted from the measurement of excitation functions by using the developed Ericson statistical theory.
Multipion Correlation Signal for OGP Formation in High Energy Heavy Ion Collisions
Zhang Weining, Huo Lei, Chen Xiangjun, Liu Yiming
1999, 23(1): 44-50.
The multiparticle Bose-Einstein correlations for formation of quark-gloun plasma (QGP) in high energy heavy ion collisions are analysed. Investigating the average correlation intensities of multipions as a function of pion multiplicity indicats that they have obvious enhancements in the high multiplicity region. This signature can be used to detect the existence of QGP in rare high-pion-multiplicity events sensitively in high energy heavy ion collisions.
Two Modes in Three-fold Fragmentation of hot Nuclei
Dai Guangxi, Wu Heyu, Fu Yanbiao, Duan Limin, He Zhiyong, Li Zuyu, Zhang Baoguo, Liu Guoxing
1999, 23(1): 51-58.
Splitting of a hot nucleus into three comparable pieces in the 40Ar+159Tb reaction at 30MeV/u was measured. For the splitting there are two modes: one is a successive binary process, such as sequential fission or a cascade fission, another is a prompt threefold fragmentation (3F). The paper presents the identification between the two modes of the threefold fragmentation by the experimental results, such as the mass distribution of the fragments, the orientation of the fragmentation plane, etc.. In the two modes, the prompt one with collective deformation is emphasized.Furthermore fitting the mass distribution and finding a scaling law about the most-probable mass ratio in the 3F are given. In addition, the orientation of the fragmentation plane could also be used to measure the impact parameters, there for to distinguish 3F events associated with cental collision from the sequential fission after a quasi-elastic scattering or deep-inelastic collision.
Correction on the Energy Spectra of the O(6) Limit of IBM1 Containing af-Boson With Three-Body Potential
Liu Yingtai, Liao Jizhi
1999, 23(1): 59-64.
Within the O(6) limit of s-d IBM1, the effective three-body potential between the interactions of d-bosons is introduced with the consideration of octupole states, which are produced by a f-boson plus (N-1) s-d-bosons. Then the analytic expressions of positive and negative parity energy spectrum formula are obtained. Also the energy spectra of even-even nuclei 118Xe and 120Xe are calculated. Good fits with the experimental data are obtained, and Staggering phenomena is quantitatively analyzed with Staggering index formula.
Studies on the Behavior of High Intense Beam in the Periodic Filed
Ouyang Huafu, Yu Qingchang
1999, 23(1): 65-71.
In this paper, we study the behavior of high intense beams in the periodic filed by using thin lens approximation for the space-charge forces. The main chaotic behavior and halo formation can be shown through simple calculations. Meanwhile, it is very easy for us to study the behavior of high intense beams with more complicated realistic distributions than K-V distribution by this approximation, which is rather difficult by other ways.
Study of Long Range Beam-Beam Effects
Wang Lanfa, Zhang Chuang, Wang Shuhong, Guo Zhiyuan, Lin Yuzheng, Tong Dechun
1999, 23(1): 72-78.
The operation of colliders are often limited by the nonlinear effects of beam-beam interaction, especially for the strong current machines, such as BEPCⅡ (BEPC multibunch collision scheme). The beam-beam interaction in BEPCⅡ is very complicated. The bunch will collide with another bunch head on at the south interaction point and interact with another bunches due to the long distance beam-beam force at other eleven points along the ring. This paper has studied the tune shift and tune spread due to the long distance beam-beam interaction effects. The long distance beam-beam effects of BEPCⅡ injection mode have also been studied.
Mixing Effect on the Scalar Glueball Mass in QCD Sum Rules
Huang Tao, Jin Hongying, Zhang Ailin
1999, 23(1): 79-86.
We consider the mass dependence on the mixing between a pure glueball and a normal qq meson in QCD sum rules. In the normal correlation functions, the gluonic current and qq current are assumed to couple to both glueball and qq states. By using the low-energy theorem, we construct a sum rule for the mixing correlation function (the gluonic current and the qq current). Through these relationships and based on the assumption of two states (one glueball and one qq meson) dominance, we find the masses of the 0++ lowest-lying glueball and qq meson.
H Moment Oscillation and Three Fire Ball Model
Zhang Fan, Liu Lianshou
1999, 23(1): 87-92.
The oscillatory behavior of H moments obtained from the experimental data in pp and pp collisions is studied in the Three-Fireball Model (TFM). It is found that similar to that in the negtive binomial distribution (NBD), the H moment in the full TFM distribution is a monotonic function of q, but oscillates when the distribution is truncated by a not too large value of ncut. This shows that H moment oscillation is not a special property of pQCD or NBD, but is common for many truncated multiplicity distributions.
A New Heavy Neutron-rich Isotope 238Th
Xu Yanbing, Yuan Shuanggui, Yang Weifan, He Jianjun, Li Zongwei, Ma Taotao, Xiong Bing, Qin Zhi, Mou Wantong, Gan Zaiguo, Shi Lijun, Guo Tianrui, Chen Zhantu, Guo Junsheng
1999, 23(1): 93-95.
A new nuclide 238Th has been produced via multinucleon transfer reaction induced by 60MeV/u 18O ion irradiation of natural uranium. The thorium was radiochemically separated from the mixture of uranium and its reaction products. The activity of thorium was measured by using a HPGe detector and a planar HPGe detector. The 238Th has been identified for the first time by measuring the growth and decay of the γ-rays from its daughter 238Pa. The half-life of 238Th was determined to be (9.4±2.0)min. In addition,a new (89.0±0.3)keV γ-ray with T1/2=(8.9±1.5)min was observed and assigned to 238Th decay based on the measurement of transition energy and half life.