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SUMMARY:From light quark ratio to nucleon/nuclear structure
DTSTART;VALUE=DATE-TIME:20260519T040000Z
DTEND;VALUE=DATE-TIME:20260519T053000Z
DTSTAMP;VALUE=DATE-TIME:20260528T122600Z
UID:indico-event-5010@indico-tdli.sjtu.edu.cn
DESCRIPTION:Speakers: Siqi Yang（杨思奇） (University of Science and 
 Technology of China)\n\nAbstract:Over the years\, a classic picture has be
 en established from comprehensive experiments: nucleons such as the proton
  and neutron are composed of quarks tightly bound together\, while atomic 
 nuclei are further formed from those nucleons\, held together by relativel
 y weak interactions. Since 1990s\, a series of experiments found that the 
 deuteron\, which is formed by a proton and a neutron\, exhibits an anomalo
 usly large cross section in GeV-scale high-energy interactions. This pheno
 menon has been interpreted as the presence of the SU(2) flavour asymmetry\
 , meaning that there are more anti-down quarks than anti-up quarks in the 
 proton. This finding suggests that sea quarks are generated via  flavour-
 asymmetric mechanisms. In this talk\, I report an analysis of a series of 
 new measurements recently obtained from pure proton interactions which are
  free from those nuclear assumptions. The analysis of the new proton data 
 unexpectedly shows that the anti-down quark component is rather consistent
  with the anti-up quark inside the proton. This result provides evidence n
 ot only that quarks are generated via a symmetric mechanism\, but also tha
 t the nuclear assumptions underlying the classic picture may break down at
  high energy scale\, meaning that both the structure of the proton and the
  structure of high energy nuclei could differ fundamentally from our estab
 lished understanding.Biography:Siqi Yang is an experimental particle physi
 cist from University of Science and Technology of China. He has been focus
 ing on the electroweak interactions at TeV-hardron colliders. Before 2020\
 , his physical interest was the precise measurement on the electroweak sym
 metry breaking\, which is essential both to the global test of the standar
 d model and to the indirect constraint on the potential new physics. Howev
 er\, in the past years he realized that the precision of the measurements 
 were severely limited by the uncertainty induced from the PDF of the quark
 s in the initial state. Then\, his research focus gradually shifted to the
  fields of proton structure and nuclear structure. Although the experiment
 al measurements still rely on the electroweak production\, the physics goa
 l is no longer electroweak itself. Instead\, he aims to exploit the unique
  properties of electroweak symmetry breaking to launch new studies of prot
 on structure and nuclear structure at hadron colliders. Host: Prof. Wei W
 angAlternative online link：https://meeting.tencent.com/dm/k8RFBvrBtXO4ID
 :120117708   Password: 123456\n\nhttps://indico-tdli.sjtu.edu.cn/event/50
 10/
LOCATION:5#/6th-603 - Meeting Room 603 (Science Building)
URL:https://indico-tdli.sjtu.edu.cn/event/5010/
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