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SUMMARY:Exploring baryon semileptonic decays through polarization and enta
 nglement
DTSTART:20260918T040000Z
DTEND:20260918T053000Z
DTSTAMP:20260926T035300Z
UID:indico-event-5288@indico-tdli.sjtu.edu.cn
DESCRIPTION:Speakers: Tao Luo（罗涛） (复旦大学)\n\nAbstract:\nThi
 s report will present our latest research results on the β decay of the 
 Λ hyperon through polarization and quantum entanglement\, based on 10 bil
 lion J/ψ events collected by the BESIII experiment.The CKM matrix element
  |𝑉_𝑢𝑠 | is a key parameter for testing the three-generation quar
 k mixing mechanism and the unitarity of the CKM matrix. However\, current 
 measurements of |𝑉_𝑢𝑠 |  from different decay channels show sign
 ificant discrepancies\, and exhibit some tension with theoretical predicti
 ons\, urgently calling for independent cross-check methods. The β decay o
 f the Λ hyperon is one of the ideal places to study |𝑉_𝑢𝑠 |\, bu
 t the final-state antineutrino cannot be directly detected\, leading to th
 e loss of key kinematic information\; this field has thus failed to achiev
 e high-precision breakthroughs for over thirty years.To address these diff
 iculties\, based on ten billion J/ψ events collected by the BESIII experi
 ment\, we exploit the quantum entanglement inherent in the production of h
 yperon–antihyperon pairs\, and infer unknown physical information from o
 bservable particle signals\, effectively compensating for the observationa
 l blind spots. We have developed a joint angular distribution multivariate
  fitting method that analyzes the production\, polarization\, quantum enta
 nglement\, and decay of Λ and anti-Λ as a complete unified process\, and
  reconstructs the kinematic information of the antineutrino using energy
 –momentum conservation. By combining the "visible" and "invisible" infor
 mation\, we successfully extracted |𝑉_𝑢𝑠 |\, and for the first ti
 me measured the absolute branching fraction of Λ hyperon β decay\, the w
 eak-electric coupling parameters\, and multiple decay parameters of the an
 ti-Λ\, filling several experimental gaps. The related paper was published
  in Nature.\nBiography:\nLuo Tao is a professor and doctoral supervisor at
  Fudan University. He received his Ph.D. from the Institute of High Energy
  Physics\, Chinese Academy of Sciences\, in 2011\, and joined Fudan Univer
 sity in 2017. He has been selected for the Shanghai Pujiang Talent Program
  and the Young Scholars of the National Major Talent Project. Over the pas
 t five years\, he has published more than twenty JCR Q1 SCI papers based o
 n the BESIII experiment\, including one in Nature and nine in Physical Rev
 iew Letters. His current research focuses on experimental studies at BESII
 I\, including hyperon semileptonic decays\, hyperon excited states\, charm
 ed meson physics\, and charmonium transitions. In 2025\, one of his doctor
 al students was selected for the 16th "Academic Star" of Fudan University 
 (only 10 students across all science and engineering disciplines universit
 y-wide each year).\nHost: Prof. Wei Wang\nAlternative online link: https:/
 /meeting.tencent.com/dm/0pI4Vl2fKdiO\nID: 990734030   Password: 123456\n\
 nhttps://indico-tdli.sjtu.edu.cn/event/5288/
LOCATION:5#/6th-603 - Meeting Room 603 (Science Building)
URL:https://indico-tdli.sjtu.edu.cn/event/5288/
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