Search for Physics beyond the Standard Model in Events with Overlapping Photons and Jets.

Area of Science:

• High Energy Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• The Standard Model of particle physics describes fundamental particles and forces.
• Searches for physics beyond the Standard Model (BSM) are crucial for understanding the universe.
• Supersymmetry (SUSY) theories predict partner particles for known particles, including gluinos.

Purpose of the Study:

• To search for new particles decaying into a photon and two gluons.
• To develop and apply novel jet substructure techniques for photon identification in hadronic environments.
• To set limits on new physics processes, specifically gluino pair production within a simplified stealth supersymmetry model.

Main Methods:

• Analysis of proton-proton collision data collected by the CMS experiment at the LHC.
• Utilized data from 2016 at a center-of-mass energy of 13 TeV with an integrated luminosity of 35.9 fb^{-1}.
• Employed novel jet substructure techniques for identifying photons amidst dense hadronic activity.

Main Results:

• No statistically significant excess of events beyond Standard Model predictions was observed.
• The first cross-section limits were established for new physics processes resulting in photon + two gluon final states.
• Upper limits were placed on the rate of gluino pair production.

Conclusions:

• The study sets stringent upper limits on gluino pair production, excluding gluino masses up to 1.7 TeV for a 200 GeV neutralino.
• These results extend previous mass constraints from analyses focusing on isolated photons.
• The developed jet substructure techniques demonstrate effectiveness in identifying photons in complex hadronic environments.