On June 5, 2026, as part of the "NangaoShi· Physics Salon" brand lecture series organized by the School of Physics and Technology of Nanjing Normal University, Professor Xiao Meng from Zhejiang University was invited to deliver a lecture entitled "Jet substructure measurement at the CMS experiment" in Room 437 of the Xingjian Building at Nanjing Normal University. The lecture was hosted by Wang Hui from the School of Physics and Technology, and was attended by faculty members, graduate students, and undergraduate students from relevant disciplines.

At the start of this salon, Professor Xiao gave a general introduction on CMS using the LHC as a precision laboratory for QCD, with jet substructure emerging as a central tool for probing how quarks and gluons turn into hadrons. Professor Xiao highlighted traditional observables such as soft-drop mass, then moved to more fundamental measurements based on Lund planes and energy-energy correlators, which can trace the jet-formation chain more directly.

Professor Xiao detailed CMS’s energy-energy correlator program, which shows clear scaling behavior across jet transverse-momentum bins and agrees well with high-order theory. In particular, the E3C/E2C observable was used to extract a value of αs with combined statistical, theoretical, and experimental uncertainties, offering one of the most precise jet-substructure-based determinations to date.

In the second half of the salon, Professor Xiao shifted to gluon spin effects inside jets. Using Run 3 CMS data and subjet tagging, the analysis found evidence for spin correlations in parton showers, with the data favoring the correlation-on model and showing a 6.8σ separation from the correlation-off hypothesis in one category. Professor Xiao concluded that these measurements are reshaping both generator development and future searches, while also helping calibrate jet substructure in CMS.

This lecture not only deepened the attendees’ understanding of jet and QCD, but also provided a valuable opportunity for academic exchange in related fields. Professor Xiao’s brilliant presentation and insightful analysis were highly praised and sparked enthusiastic discussions among the participants.

Biography of Professor Xiao Meng

Xiao Meng is a Hundred Talents Program Researcher at Zhejiang University. She received her Bachelor’s degree from Kuang Yaming School, Nanjing University, and her Ph.D. from the French Atomic Energy Commission (CEA). She later conducted postdoctoral research at Johns Hopkins University in the United States. She has worked on both the ATLAS and CMS experiments at the Large Hadron Collider. Her research interests include experimental measurements in Higgs physics and QCD physics. Within the CMS Collaboration, she has served as the convener of the Higgs Physics Group and has been honored with the CMS Young Researcher Award.