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941.
The LEP Energy Working Group 《The European Physical Journal C - Particles and Fields》2005,39(3):253-292
The determination of the centre-of-mass energies for all LEP 2 running is presented. Accurate knowledge of these energies
is of primary importance to set the absolute energy scale for the measurement of the W boson mass. The beam energy between
80 and 104 GeV is derived from continuous measurements of the magnetic bending field by 16 NMR probes situated in a number
of the LEP dipoles. The relationship between the fields measured by the probes and the beam energy is defined in the NMR model,
which is calibrated against precise measurements of the average beam energy between 41 and 61 GeV made using the resonant
depolarisation technique. The validity of the NMR model is verified by three independent methods: the flux-loop, which is
sensitive to the bending field of all the dipoles of LEP; the spectrometer, which determines the energy through measurements
of the deflection of the beam in a magnet of known integrated field; and an analysis of the variation of the synchrotron tune
with the total RF voltage. To obtain the centre-of-mass energies, corrections are then applied to account for sources of bending
field external to the dipoles, and variations in the local beam energy at each interaction point. The relative error on the
centre-of-mass energy determination for the majority of LEP 2 running is 1.2 x 10-4, which is sufficiently precise so as not to introduce a dominant uncertainty on the W mass measurement.
Received: 4 August 2004, Revised: 15 December 2004, Published online: 21 January 2005 相似文献
942.
943.
944.
Charged particle pseudorapidity distributions have been measured in Au+ Au collisions using the BRAHMS detector at RHIC. The
results are presented as a function of the collision centrality and the center of mass energy. They are compared to the predictions
of different parton scattering models and the important role of hard scattering processes at RHIC energies is discussed. Keywords.
Relativistic heavy-ion collisions; charged hadron production; pseudorapidity distributions; centrality dependence; hard scattering
processes. 相似文献
945.
The OPAL Collaboration G. Abbiendi et al. 《The European Physical Journal C - Particles and Fields》2003,26(4):479-503
This paper summarises the search for the Standard Model Higgs boson in e
+
e
-
collisions at centre-of-mass energies up to 209 GeV performed by the OPAL Collaboration at LEP. The consistency of the data
with the background hypothesis and various Higgs boson mass hypotheses is examined. No indication of a signal is found in
the data and a lower bound of 112.7 Gev/c2 is obtained on the mass of the Standard Model Higgs boson at the 95% CL.
Received: 13 March 2002 / Revised version: 9 October 2002 / Published online: 13 December 2002 相似文献
946.
用分子动力学方法和MonteCarlo方法相结合,模拟了Paul阱中离子体系的阻尼冷却,系统地得到了3~20个离子的有序构形。结果表明:离子的晶相结构随着离子数目的增加呈现出有规律的变化;同时,晶相结构的有序构形与囚禁场的赝势阱形状具有几何相似性的关联。 相似文献
947.
讨论了引起统计蒸发模型计算结果与高温热核偶极巨共振实验结果之间存在差别的因素,对比了标准CASCADE程序计算结果与加入复杂粒子发射后的计算结果,计算显示复杂粒子发射对高温热核偶极巨共振的性质有影响. 相似文献
948.
949.
催化动力学光度法测定痕量硫氰酸根的研究 总被引:3,自引:0,他引:3
基于硫氰酸根对碘氧化叠氮化钠的催化作用,建立了催化动力学光度法测定硫氰酸根的新方法.于352nm处分别测定催化体系和非催化体系的吸光度A和A_V,以△A=A_c-A定量,线性范围为1.0~700μg·L~-1,检出限1.0μg·L~-1.用于生物样品中痕量硫氰酸根的测定,结果满意. 相似文献
950.
In total 1317 di-lepton events with significant missing transverse momentum were identified in a total data sample of 680 pb-1 collected at e + e- centre-of-mass energies ranging from 183 GeV to 209 GeV. The number of di-lepton events, the dependence on centre-of-mass energy, and the event properties are consistent with expectations from Standard Model processes, predominantly W + W- production with both W bosons decaying leptonically. This topology is also an experimental signature for the pair production of new particles that decay to a charged lepton accompanied by one or more invisible particles. No evidence for new phenomena is apparent. Upper limits are presented on the production cross-section multiplied by the relevant branching ratio squared for sleptons, leptonically decaying charginos and charged Higgs bosons. Mass limits are also given.Received: 14 July 2003, Published online: 9 January 2004 相似文献