Peking University, Apr. 11, 2011: PKU Professor Li Chongsheng’s team made progress in the study of quark, a type of subatomic particle.

Professor Li’s team presents the exact next-to-leading order (NLO) QCD corrections to the dijet production induced by the quark contact interactions at the CERN Large Hadron Collider (LHC). The study shows that as compared to the exact calculation, the scaled NLO QCD prediction adopted by the ATLAS Collaboration has overestimated the new physics effect on some direct observables by more than 30% and renders a higher limit on the quark compositeness scale. The destructive contribution from the exact NLO correction will also lower the compositeness scale limit set by the CMS Collaboration.

The progress contributes to the scientists’ search for compound quark structures at the LHC. Until now, people’s knowledge of substances’ basic structure is on the level of quark and lepton, but they never stopped their step studying the deeper layers. Since the establishment of quark’s model in the 1960s, physicists started exploring the entire possibilities of compound models. The operations of the LHC enable people to further explore the internal structure of quark.

The team’s work, “Next-to-Leading QCD Effect on the Quark Compositeness Search at the LHC,” was published on the April 4 issue of Physical Review Letters. The achievement raised attention from scientists at the LHC and the Tevatron, who requested the team’s relevant data and procedure. In this study, Gao Jun, a doctoral candidate with Professor Li, made significant contributions.

Written by: Liu Yineng

Edited by: Jacques

Source: PKU News (Chinese)