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Studies of deep inelastic scattering at ep collider HERA

EP 对撞机 HERA 的深层非弹性散射研究

基本信息

批准号：
11694103
负责人：
TOKUSHUKU Katsuo
金额：
$ 9.02万
依托单位：
Institute of Particle and Nuclear Studies(IPNS)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11694103/
关键词：
electron-proton collision HERA ZEUS deep inelastic scattering quark gluon the standard model leptoquark 回折反応中性流荷電流

项目摘要

We have studied deep inelastic electron-proton scatterings with the unique e-p collider HERA built at DESY in Germany. HERA provides high-energy collisions, whose maximum four momentum transfer squared(Q^2) reaches 10^5 GeV^2. The experiment was performed with a multi purpose detector (ZEUS) which was constructed and operated by an international collaboration of 12 countries. In this two year period, the data were collected with 27.5GeV electrons (or positrons) and 920GeV protons. Total integrated luminosity reached 67pb-1.Precise measurements of the neutral-current cross sections were performed in a wide Q^2 range from 0.04GeV^2 to 30000GeV^2 in order to determine the proton structure functions. Charged current cross sections were also measured in the Q^2 range above 200GeV^2. The results were fitted with models based on the perturbative quantum chromodynamics (QCD). It is found that the models describe the measured proton structure functions above 〜1GeV^2. Distributions of quarks and gluons inside the proton were extracted. It is found that the gluons increase rapidly as Bjorken-x decreases. The coupling coupling constant of the strong interaction(αs) is precisely determined and found to be consistent to the other results from completely different measurements such as jet-multiplicities in e+ e- and ep experiments. The fact demonstrates the universality of the strong interaction and the validity of the QCD.As Q^2 goes lower below 〜1GeV^2 measured structure functions lay below the QCD prediction. The extracted gluon distribution tends to become negative in the regions. These might indicates the limit in the perturbative approach although one needs to wait for the progress in the higher order calculations.The measured cross sections at high Q^2 were consistent with the extrapolation from low Q^2 measurements. There is no significant deviation from the expectation of the standard model. The constraint on new particles such as leptoquarks was set.

我们利用德国DESY的HERA对撞机研究了电子-质子的深度非弹性散射。HERA提供高能碰撞，其最大四次动量转移平方（Q^2）达到10^5 GeV^2。该实验是用一个多用途探测器（ZEUS）进行的，该探测器由12个国家的国际合作建造和操作。在这两年的时间里，收集了27.5GeV电子（或正电子）和920 GeV质子的数据。总积分光度达到67 pb-1。为了确定质子结构函数，在0.04GeV^2 - 30000GeV^2的宽Q^2范围内进行了中性流截面的精确测量。在200 GeV^2以上的Q^2范围内也测量了带电电流截面。结果与微扰量子色动力学（QCD）模型进行了拟合。结果表明，这些模型能较好地描述1GeV^2以上的质子结构函数。提取了质子内部夸克和胶子的分布。发现胶子数随Bjorken-x的减小而迅速增加。强相互作用的耦合常数（αs）被精确地确定，并与其它完全不同的测量结果（如e+ e-和ep实验中的喷注多重数）一致。这一事实证明了强相互作用的普遍性和QCD的有效性，当Q^2低于101GeV^2时，测得的结构函数低于QCD的预言。提取的胶子分布在区域内趋于负值。这可能表明了微扰方法的局限性，尽管我们需要等待高阶计算的进展，但在高Q^2下测得的截面与从低Q^2测量值外推得到的截面是一致的。与标准模型的预期没有显著偏差。对新粒子如细夸克的约束被设定。