BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:The Symposium of Ultra-High-Energy Gamma Rays from Supernova Remna nts and the Origin of Galactic Cosmic Rays DTSTART:20260226T040000Z DTEND:20260302T100000Z DTSTAMP:20261104T161300Z UID:indico-event-27978@indico.ihep.ac.cn CONTACT:liaosy@ihep.ac.cn DESCRIPTION:Speakers: Felix Aharonian (YSU/USTC/TCRRC/MPIK)\, Zhen Cao (In stitute of High Energy Physics\, CAS)\n\nSupernova remnants (SNRs) have lo ng been considered the dominant sources of Galactic cosmic rays (CRs)\, su pported by energetic arguments and the paradigm of the diffusive shock acc eleration (DSA) as a robust particle-acceleration mechanism. Over the past two decades\, observations of TeV gamma rays and nonthermal X-rays from many young SNRs have confirmed that these systems with significant magne tic amplification can accelerate particles to beyond 1 TeV. At the same t ime\, these measurements revealed unexpectedly steep spectra at multi-TeV energies. The lack of ultra-high-energy (UHE\; E>100 TeV) gamma-ray det ections by LHAASO for any young SNR has initiated debates over whether SNR s can truly act as PeVatrons capable of supplying CRs around and above the knee. \n\nHowever\, the observed spectral steepening does not necessaril y imply early cutoffs (below the "knee") in the parent particle distributi ons. Recently recognised new features of DSA\, along with current detector s' sensitivity limitations\, may still allow young SNRs to reach PeV energ ies. Moreover\, the detections of UHE gamma rays from dense environments a round several middle-aged SNRs - interpreted as "smoking-gun" signatures o f CR interactions with nearby gas complexes - provide indirect but relativ ely strong evidence that these SNRs may have operated as PeVatrons tens of thousands of years ago. Understanding the origin of UHE gamma-ray emis sion also benefits from coordinated multi-wavelength efforts that combine gamma-ray\, X-ray\, millimeter\, and radio observations to disentangle the roles of particle acceleration\, ambient conditions\, and the SNR propert ies.\n\nThis workshop aims to bring together experts in CR physics and SN R research to examine the implications of UHE gamma-ray observations of b oth young and middle-aged SNRs. Using multi-wavelength data from SNRs and their environments\, participants will explore competing interpretations\, assess the physical conditions required for PeVatron activity\, and discu ss the broader consequences for the origin of Galactic cosmic rays. \n\nW e invite interested researchers to join us for an in-depth\, collaborative discussion of this central question in cosmic-ray astrophysics.\n\n\n\nht tps://indico.ihep.ac.cn/event/27978/ LOCATION:Chengjiang\, Yuxi\, Yunnan Province\, China URL:https://indico.ihep.ac.cn/event/27978/ END:VEVENT END:VCALENDAR