共查询到17条相似文献,搜索用时 156 毫秒
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《中国科学院高能物理研究所年报》1998,(1):1-13
利用BES在τ质量测量期间获取的√S=3.55GeV的约5pb^-1的数据开展R值测量的预先实验研究。详细研究了与R值测量有关的各种因素.如强子事例挑选、本底扣除、亮度测量、辐射修正、效率确定等。特别是利用挑选出的强子事例的各种形态特征分布与现有的LUND模型的强子事例产生子Jetset 74相比较,调整其有关参数,首次得到适合于低能区的强子事例产生子,从而比较可靠地确定了效率。以上研究为下一步的R值扫描测量打下了良好基础。 相似文献
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在羊八井测量初级宇宙线直达质子研究质子和空气核非弹性作用截面 总被引:1,自引:0,他引:1
提出了一种在高海拔通过测量直达质子来确定质子和空气核(p-air)的非弹性作用截面的方法, 并通过Monte Carlo模拟, 研究了其可行性. 假定将一台类似于KASCADE的强子量能器设置在西藏羊八井ARGO探测器的中央,选择大气簇射(AS)轴心落在强子量能器内的事例, 用全覆盖ARGO阵列作AS的反符合,用强子量能器测量非伴随的高能强子,即能以已知的效率得到一个直达质子事例样本. 利用这个样本,本工作以1%—2%的精确度还原了Monte Carlo模拟中所使用的p-air非弹性作用截面, 从而证明了这一方法的可行性. 相似文献
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The fraction of events in hadronic decays has been measured by the OPAL experiment using the data collected at LEP between 1992 and 1995. The decays were tagged using displaced secondary vertices, and high momentum electrons and muons. Systematic uncertainties were
reduced by measuring the b-tagging efficiency using a double tagging technique. Efficiency correlations between opposite hemispheres
of an event are small, and are well understood through comparisons between real and simulated data samples. A value of was obtained, where the first error is statistical and the second systematic. The uncertainty on , the fraction of events in hadronic decays, is not included in the errors. The dependence on is where $\Delta R_{\rm c}$ is the deviation of from the value 0.172 predicted by the Standard Model. The result for agrees with the value of predicted by the Standard Model.
Received: 28 August 1998 / Published online: 7 April 1999 相似文献
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About ScienceDirect 《Physics letters. [Part B]》1977,70(4):487-490
The anomalous eμ and 2-prong μx events produced in e+e− annihilation are used to determine the properties of the proposed τ charged lepton. We find the τ mass is 1.90 ± 0.10 GeV/c2; the mass of the associated neutrino, ντ, is less than 0.6 GeV/c2 with 95% confidence; V - A coupling is favored over V + A coupling for the τ − ντ current; and the leptonic branching ratios are 0.186 ± 0.010 ± 0.028 from the eμ events and 0.175 ± 0.027 ± 0.030 from the μx events where the first error is statistical and the second is systematic. 相似文献
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T. Aziz S. Ahmad H. Ahrar S. B. Beri V. S. Bhatia S. N. Ganguli S. K. Gupta V. K. Gupta A. Gurtu M. Irfan R. R. Joseph G. L. Kaul Manjit Kaur S. Kumar P. K. Malhotra L. K. Mangotra I. S. Mittra Y. Prakash N. K. Rao M. Shafi M. Shyam S. K. Tuli 《Zeitschrift fur Physik C Particles and Fields》1984,26(1):13-18
A search has been carried out for neutral charm production in 5,108 proton-emulsion interactions at 400 GeV/c. Nine charm candidates have been observed in our fiducial volume which extends from 100 μm-1,000 μm in the forward cone. One of these is a 4-prong and the others are 2-prong events with opening angle>10 mrad and momenta of both decay tracks>150 MeV/c. Search for associated charm decays was made in an extended fiducial volume around the primary stars of these nine candidates. This yielded two neutral 2-prong events, one associated with the 4-prong and the other with a 2-prong candidate. All unassociated candidates are consistent with being backgrounds due toK s , Λ decays, neutral interactions and γ conversions whereas the background to associated events is negligible. Based on the two associated decays the inclusive cross section forD 0, ?0 production is determined as 27±20 μb/nucleon. Detailed measurements on the 4-prong candidate lead to the identification of one decay track as an electron and another as a kaon. This is interpreted as a semi-leptonic, Cabbibo favouredD 0/D ?0 decay. 相似文献
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M. Ablikim et al. 《中国物理C(英文版)》2013,37(6):063001-063001
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. 相似文献
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D.P. Barber U. Becker H. Benda A. Boehm J.G. Branson J. Bron D. Buikman J. Burger C.C. Chang H.S. Chen M. Chen C.P. Cheng Y.S. Chu R. Clare P. Duinker G.Y. Fang H. Fesefeldt D. Fong R.Y. Zhu 《Physics letters. [Part B]》1979,89(1):139-144
We report the measurement of the reaction e+ + e? → hadronic jets at a center-of-mass energy √s=30 GeV using the MARK-J detector at PETRA. By measuring the energy and angular distribution of both neutrals and charged particles we were able to isolate unambiguously the three-jet events in a kinematic region where the backgrounds from q and phase space contributions and other processes are small. Various comparisons of the data with quantum chromodynamics were made. The relative yield of three-jet events and the shape distribution of the events enable us to determine αs = 0.23 ± 0.02 (statistical error) with a systematic error of ± 0.04. 相似文献
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Introduction of the Trigger System and the Measurement for Trigger Efficiency at L3+Cosmics Experiment 下载免费PDF全文
The trigger process of L3+Cosmics experiment at CERN is introduced briefly. Also we checked whether the settings of L3+Cosmics trigger system by simulation are correct or not and introduced a method on trigger efficiency calculation. To get trigger efficiency for μ spectrum measurement, an experimental data sample, which includes events passing the trigger set to measure the μ spectrum and not passing, is needed. Then L?3+C trigger process is simulated with these events in this sample to know how many events should pass the trigger. By checking a trigger bit recorded in the experimental data, one can know how many events passed the trigger in hardware in these simulated events. The ratio then determines the trigger efficiency for μ spectrum measurement. And the systematic error is analyzed. The results on trigger efficiency have been used to the measurement of μ spectrum. 相似文献