The FACET Project: Forward Aperture CMS ExTension to search for new Long-Lived Particles

TL;DR

The FACET project proposes a new CMS subsystem to detect long-lived particles like dark photons and axion-like particles in the forward direction at the High Luminosity LHC, enhancing the search for new physics beyond the Standard Model.

Contribution

It introduces a novel forward aperture extension to CMS designed specifically for detecting long-lived particles decaying inside a large vacuum pipe.

Findings

Design of the FACET subsystem for CMS

Capability to detect particles penetrating 50 m of iron

Potential to discover new long-lived particles

Abstract

FACET is a proposed new subsysem for CMS to search for portals such as dark photons, dark higgs, heavy neutral leptons and axion-like particles in the very forward direction at the High Luminosity LHC. Such particles can penetrate up to 50 m of iron and then decay inside a 14 m$^3$ vacuum pipe made by enlarging an 18 m long section of the LHC pipe to a radius of 50 cm.