Particle Physics Seminar: Probing the Higgs landscape: From Higgs exotic decays with boosted ditau topologies at ATLAS to precision H→WW* feasibility studies at the FCC-ee

Abstract:

The Higgs sector provides a powerful window to physics beyond the Standard Model through direct searches for exotic decays and precision measurements. This seminar will address these two complementary approaches. The first part presents an ATLAS search [1] for the exotic Higgs boson decay to pseudoscalar resonances, H→aa, in the γγττ final state. To overcome the reconstruction challenges posed by highly collimated hadronic tau pairs in this low-mass topology, a dedicated low-pT boosted ditau tagger [2] was developed and its efficiency was measured in data. Implementing this novel tagger allowed us to exploit the excellent diphoton mass resolution and set upper limits on this exotic decay mode branching ratio, extending the sensitivity of ATLAS to highly collimated signatures.

Shifting to the precision frontier, the second part of the seminar explores the proposed Future Circular Collider (FCC-ee) through a feasibility study of the fully leptonic H→WW* decay via the Higgs-strahlung process at center-of-mass-energy of 240 and 365 GeV. By leveraging the FCC-ee's exceptionally clean environment and the recoil mass method, this channel provides a direct probe of the HWW coupling and a complementary measurement of the total Higgs width.

References:

[1] JHEP 03 (2025) 190 (arXiv: 2412.14046)

[2] EPJC 85 (2025) 561 (arXiv: 2411.09357)
 

Seminar Organizer: Dr. Igor Korover