Exploring the Dark Sector at LHC: Search for dark photons from Higgs boson decay with the ATLAS detector

Speaker: Federica Piazza

Date: Monday, May 20, 2024

Time: 4:00 – 5:00 pm

Location: 472 Willamette Hall

Abstract: The Dark Matter (DM) problem is one of the crucial open questions in physics and an important hint of the incompleteness of the Standard Model (SM) of elementary particles.

The ATLAS experiment at the Large Hadron Collider (LHC) has an extensive BSM physics program, with multiple dedicated analyses exploring possible extensions of the SM with a Dark Sector.

This talk will mostly focus on two dark photon searches, using the 139 fb^{-1} dataset collected during LHC Run-2.  The dark photon is predicted as the gauge boson of a new U(1) dark symmetry group, and an interesting production channel would consist in the decay of a (SM or BSM) Higgs boson into a photon and a dark photon through a loop interaction featuring an additional BSM messenger field, coupled both to the SM and the Dark Sector. The first search targets final states with one photon and missing transverse momentum. This analysis originally set exclusion limits on the pair production of WIMP-like DM particles via the decay of a BSM mediator, and has been reinterpreted in terms of BSM Higgs produced via gluon-gluon fusion and decaying into photon and dark photon. The same process for the SM Higgs boson is explored in the ZH production channel, in a final state with a photon, two leptons and missing transverse momentum. These results have been combined with a similar search in the VBF production channel and provide the first limits set on this decay process.

Host: Pouya Asadi