Positivity bounds on vector boson scattering

by Dr Cen Zhang (IHEP)

Thursday 11 Apr 2019, 10:30 → 11:30 Asia/Shanghai

B105 (CHEP)

Searching for deviations in quartic gauge boson couplings (QGCs) is one of the main goals of the electroweak program at the LHC. We consider positivity bounds adapted to the Standard Model EFT, and show that a set of positivity constraints on 18 anomalous QGC couplings can be derived, by requiring that the vector boson scattering amplitudes satisfy the fundamental principles of quantum field theory.  We solve the positivity inequalities and find that the allowed parameter space is carved out by the intersection of pyramids, prisms, and cones. Altogether, the allowed parameter space is reduced to ~2% of total. These bounds provide guidance to future BSM searches and could affect the limits on couplings by modifying the prior.

Cen Zhang obtained his PhD in University of Illinois at Urbana-Champaign.  He then spent time in Louvain-la-Neuve and in Brookhaven National Lab as a postdoctoral researcher, and now he is an associate professor in the theory division of Institute of High Energy Physics, Chinese Academy of Sciences.  His main research interests focus on the collider phenomenological aspects of the Standard Model Effective Field Theory (SMEFT), in particular in its top-quark sector.  He has been working on accurate predictions of collider observables via the development of Monte Carlo tools for SMEFT, understanding of signatures and indirect measurements, and global fits to collider data.  The talk will be related to his recent research on the application of positivity approach in SMEFT.