Abstract:  

Long-Lived Particles (LLPs) are proposed in many extensions of the Standard Model. Massive, charged, long-lived particles have been searched for by ATLAS and CMS at the LHC, using more than 100 fb−1 of integrated luminosity collected during Run 2. If their mass exceeds 100 GeV, these LLPs are expected to move significantly slower than the speed of light and thus exhibit large ionization energy loss. Specific ionization in silicon detectors is the primary observable used in these measurements, sometimes supplemented by Time-of-Flight information. The results of these searches are used to set constraints on the Supersymmetric pair production of long-lived R-hadrons, top squarks, charginos, and staus. Since large specific ionization can also indicate the presence of doubly charged particles, CMS has investigated this scenario and set limits on certain proposed models. In this collider cross-talk seminar, the methods and results from ATLAS and CMS will be compared, and plans for measurements using the Run 3 data set will be discussed. 

Bios:

Leonardo Rossi is currently a research associate at Harvard University. Leonardo is an experimental physicist with a long career in particle physics and detector technology spent between INFN Genoa and CERN. He started working at CERN in 1974, where he led experiments using silicon detectors at the Omega facility at the CERN SPS. Since the 1990s, he has been a member of the ATLAS experiment. He contributed and led the design, build, and commissioning of the ATLAS tracker detector. He served also as Project Leader of the Pixel Detector from 1997 to 2005, and of the whole Inner Detector from 2005 to 2009. In recent years, his work has focused on the upgrade of the ATLAS detector for the High-Luminosity LHC, in particular with significant contributions to the ITk project. Leonardo is also actively involved in searching for charged long-lived particles, and he is currently coordinating the search for LLP’s using pixel dE/dx and calorimeter Time of Flight measurements.

Tamas Almos Vami is an experimental particle physicist working on CMS at CERN and LDMX at SLAC. He is currently a postdoctoral scholar at the University of California, Santa Barbara. He earned his PhD in Physics from Johns Hopkins University in 2023, where he led the CMS analysis for the search for heavy stable charged particles. Tamas has a strong background in pixel detector development and calibration. He has been working on the CMS Pixel detector since 2012, also serving as convener of the CMS Pixel Detector Performance Group and as a convener for the Alignment, Calibration, and Database Group from 2018 to 2023. He has also contributed to multiple exotics and SUSY searches, and he is now coordinating the Exotic Physics Monte Carlo and Interpretation group in CMS.