Thesis defense - Yongyu Pan

jeudi 25 juin 2026, 14:00 → 16:30 Europe/Paris

Amphi Charpak (LPNHE)

Yongyu PAN

The PhD Defense will be held at Amphithéâtre Georges Charpak at Sorbonne Université at Jussieu:
Tower 22, RDC level, 4 Pl. Jussieu, 75005 Paris

Jury composition:

TONAZZO Alessandra, APC, reviewer
SCORZA Silvia, LPSC, reviewer
ARAUJO Henrique, Imperial College, jury member
CIRELLI Marco, LPTHE, jury member
DIGLIO Sara, SUBATECH, jury member
GAO Fei, Tsinghua University, co-supervisor
SCOTTO LAVINA Luca, LPNHE, supervisor

Videoconference (zoom link): 
https://cern.zoom.us/j/2412832984?pwd=AVaspk3qB6nUapmP6b8wD7vTdAoWes.1

14:00 → 14:50 Presentation

Abstract:

Cosmological evidence confirms dark matter's (DM) existence, yet its microscopic nature remains a major mystery. This thesis searches for light dark matter (LDM) using the XENONnT detector. Standard searches require both scintillation (S1) and ionization (S2) signals, but low-mass DM often falls below the S1 threshold. Consequently, this work develops a dedicated ionization-only (S2-only) analysis.

A detailed S2 pulse shape model is constructed to characterize electron drift and electric-field distortions, improving the understanding of ionization signals. The thesis's core achievement is the S2-only analysis framework. Since dropping S1 introduces instrumental backgrounds, this thesis designs robust event-selection strategies using machine learning and waveform analysis to build and validate the first complete background model for S2-only searches. Analyzing a 7.8 tonne-year exposure, this framework is applied to various LDM candidates. It successfully sets new constraints on few-GeV WIMPs, sub-GeV DM, axion-like particles, and dark photons.

Orateur: Yongyu PAN

14:50 → 15:50 Questions

15:50 → 16:30 Jury closed session and deliberation