共查询到18条相似文献,搜索用时 109 毫秒
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利用有非极化和极化的A和A超子产生的中微子和反中微子的深度非弹性散射,可以清晰地测量各种味的夸克变为A超子的各种非极化和极化的碎裂函数,也就是得到了碎裂函数的夸克味分离.这种方法不但适用于轻味夸克。反夸克,也适用于奇异夸克s和s.和产生A和A的极化电子的深度非弹性散射结合起来,人们就能够系统地测量或核实各种味和各种自旋的夸克的相关碎裂函数.这样的测量给有关强子的自旋结构和核子海的夸克一反夸克不对称性的各种预言提供判决性的实验. 相似文献
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NuTeV实验组报道了用中微子–核子深度非弹散射方法测量到的温伯格角(Weinbergangle)sin2θw的值,并且发现这个值与标准模型的预言值相差3个标准偏差.在这篇文章中,推导了考虑核子海中s夸克与反夸克不对称时Paschos-Wolfenstein关系,分别用两种不同类型的波函数计算了在光锥介子–重子波动模型(light-conemeson-baryonfluctuationmodel)下核子海中s夸克与反夸克分布的情况且得出相近的结果.并且发现,由核子海中奇异夸克反夸克不对称所引起的修正能够降低NuTeV的测量的温伯格角的值和标准模型的预言值之间偏差的30%—80%. 相似文献
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总结了利用核子内的奇异夸克反奇异夸克不对称性来解释NuTeV反常的工作,表明奇异夸克反奇异夸克不对称性可作为解释NuTeV反常的一种合理机制,也说明了NuTeV反常现象也可能是对奇异夸克反奇异夸克不对称性的一种支持。This talk summarized the results of using strange quark-antistrage quark asymmetry of the nucleon to explain the NuTeV anomaly. It is shown that asymmetric strange quark-antistrage quark distributions may be a reasonable explanation for the NuTeV defect. On the other side, the NuTeV anomaly could be the evidence for the existence of asymmetric strange-antistrange quark distributions. 相似文献
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强相互作用味道无关性的检验 总被引:2,自引:2,他引:0
通过比较不同味道初始夸克碎裂的带电粒子多重数可以对强相互作用味道无关性进行检验.计算了e+e–湮没成轻味夸克u,d,s碎裂的粒子多重数,发现不同味道夸克事例中,平均粒子产率,同位旋对称性,由奇异与非奇异粒子多重数比值确定的奇异抑制因子等都与初始夸克味道有关,而且这种依赖性在低能时更加明显.但3种轻味夸克事例的平均带电粒子多重数近似相等,这与QCD强相互作用与味道无关的预言一致. 相似文献
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分别基于组夸克质量模型和流夸克质量模型, 讨论了超新星核心区两味夸克物质到更稳定的三味夸克物质的相变过程. 结果表明, 两种质量模型下相变的特征时标都短于10-8s, 且质量越小的流夸克质量模型的相变速率越快;组分夸克质量模型下所得到的超新星核区的s夸克丰度, 中微子丰度及中微子总能量(除温度)相比前人的结果有轻微的增加, 而流夸克质量模型下所得到的这些参量的增加更为明显, 采用流夸克质量模型更有利于超新星的中微子延迟爆发机理的成功.
关键词:
夸克相变
组分夸克质量
流夸克质量
超新星 相似文献
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The asymmetry of D- and D+ meson production in π-N scattering observed by the E791 experiment is a phenomenon typical for what is known as the leading particle effect in charm
hadroproduction. We show that the phenomenon can be explained by the effect of light quark fragmentation into charmed hadrons
(LQF). Meanwhile, the size of the LQF effect is estimated from the data of the E791 experiment. A comparison is made with
the estimate of the LQF effect from the prompt like-sign dimuon rate in neutrino experiments. The influence of the LQF effect
on the measurement of the nucleon strange distribution asymmetry from charged current charm production processes is briefly
discussed.
PACS 14.60.Pq; 12.15.Ff 相似文献
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We propose a means to detect the nucleon strange quark-antiquark asymmetry, which is predicted as a non-perturbative effect, but still unchecked directly by available experiments. The difference for the
and
meson production cross sections in neutrino and antineutrino induced charged current deep inelastic scattering is illustrated to be sensitive to the nucleon strange asymmetry. A prospect is given and the effect due to the light quark fragmentation is also discussed for the extraction of the strange asymmetry in future experiments.Received: 23 April 2005, Published online: 27 July 2005PACS:
14.60.Pq, 12.15.Ff 相似文献
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P. Abreu et al. 《The European Physical Journal C - Particles and Fields》2000,14(4):613-631
A precise measurement of the strange quark forward-backward asymmetry used 3.2M multihadronic events around the Z peak collected by the DELPHI experiment from 1992 to 1995. The ring imaging Cherenkov detectors in the barrel and end-cap
regions identify high energy charged kaons which tag the s quark. The s quark asymmetry was measured at different centre-of-mass
energies; in particular at the Z pole
taking the expected d and u quark asymmetries from the Standard Model. The quark flavour fractions are assumed from the Standard
Model and the fragmentation process is modelled by JETSET. From the s quark pole asymmetry the electroweak mixing angle was
determined:
The parity violating coupling of the s quark to the Z was determined to be:
Received: 8 October 1999 / Revised version: 23 February 2000 / Published online: 18 May 2000 相似文献
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Experimentally, the production of oppositely charged dimuon events by neutrino and antineutrino deep inelastic scattering
(DIS) is used to determine the strangeness asymmetry inside a nucleon. Here we point out that the direct production of a D-meson in DIS may have a substantial influence on the measurement of nucleon strangeness distributions. Direct D-meson production is via heavy quark recombination (HQR) and via light-quark fragmentation from perturbative QCD (LQF-P).
To see the influence precisely, we compute the direct D-meson productions via HQR and LQF-P quantitatively and estimate their corrections to the analysis of the strangeness asymmetry.
The results show that HQR has a stronger effect than LQF-P does, and the former may influence the experimental determination
of the nucleon strangeness asymmetry. 相似文献
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Mason D Brau J Drucker RB Frey R Spentzouris P Conrad J Fleming BT Formaggio J Kim JH Koutsoliotas S McNulty C Romosan A Shaevitz MH Stern EG Vaitaitis A Zimmerman ED Johnson RA Suwonjandee N Vakili M Bernstein RH Bugel L Lamm MJ Marsh W Nienaber P Tobien N Yu J Adams T Alton A Bolton T Goldman J Goncharov M de Barbaro L Buchholz D Schellman H Zeller GP Boyd S McDonald J Naples D Radescu V Tzanov M Avvakumov S de Barbaro P Bodek A Budd H Harris DA McFarland KS Sakumoto WK Yang UK 《Physical review letters》2007,99(19):192001
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M. G. Sapozhnikov 《Few-Body Systems》2011,50(1-4):145-152
A review of experimental results for the measurement of the strange quark distributions in the nucleon, is given. Contributions of the strange quarks to the nucleon mass, electromagnetic form factors and spin, are discussed. 相似文献
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Though none of the experimental evidences for the strange quark contributions to nucleon properties is explained convincingly by an alternative, the recent experiments, even HAPPEX Collab. and A4 Collab., on a measurement of the parity-violating asymmetries show no strangeness in the proton. Despite this conclusion we demonstrate here no accidental compatibility of our theoretical predictions for nucleon strange form factors with some nonzero parity violation experimental results which strengthens our belief in the strangeness in the nucleon. 相似文献
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Guan-Qiu Feng Fu-Guang Cao Xin-Heng Guo A. I. Signal 《The European Physical Journal C - Particles and Fields》2012,72(12):1-6
There are two mechanisms for the generation of an asymmetry between the strange and anti-strange quark distributions in the nucleon: nonperturbative contributions originating from nucleons fluctuating into virtual baryon?Cmeson pairs such as ??K and ??K, and perturbative contributions arising from gluons splitting into strange and anti-strange quark pairs. While the nonperturbative contributions are dominant in the large-x region, the perturbative contributions are more significant in the small-x region. We calculate this asymmetry taking into account both nonperturbative and perturbative contributions, thus giving a more accurate evaluation of this asymmetry over the whole domain of x. We find that the perturbative contributions are generally a few times larger in magnitude than the nonperturbative contributions, which suggests that the best region to detect this asymmetry experimentally is in the region 0.02<x<0.03. We find that the asymmetry may have more than one node, which is an effect that should be taken into account, e.g. for parameterizations of the strange and anti-strange quark distributions used in global analysis of parton distributions. 相似文献