Abstract
Several models of physics beyond the Standard Model predict the existence of dark photons, light neutral particles decaying into collimated leptons or light hadrons. This paper presents a search for long-lived dark photons produced from the decay of a Higgs boson or a heavy scalar boson and decaying into displaced collimated Standard Model fermions. The search uses data corresponding to an integrated luminosity of 36.1 fb^{-1} collected in proton–proton collisions at sqrt{s} = 13 text {Te}text {V} recorded in 2015–2016 with the ATLAS detector at the Large Hadron Collider. The observed number of events is consistent with the expected background, and limits on the production cross section times branching fraction as a function of the proper decay length of the dark photon are reported. A cross section times branching fraction above 4 pb is excluded for a Higgs boson decaying into two dark photons for dark-photon decay lengths between 1.5 mm and 307 mm.
Highlights
The search for displaced DPJs presented in this paper uses the dataset collected by the ATLAS detector during 2015–2en0e1r6gyin√psroto=n–pr1o3tonTe(Vp,p)cocrorellsipsioonndsinagt a centre-of-mass to an integrated luminosity of 36.1 fb−1
ATLAS [50] is a multipurpose detector at the Large Hadron Collider (LHC), consisting of an inner detector (ID) contained in a superconducting solenoid, which provides a 2 T magnetic field parallel to the beam direction, electromagnetic and hadronic calorimeters (ECAL and HCAL) and a muon spectrometer (MS) that has a system of three large air-core toroid magnets, each composed of eight coils
The background estimate includes both the multi-jet and cosmic-ray background, where the former is obtained as described in Sect. 7, and the latter is estimated from the cosmic dataset
Summary
2en0e1r6gyin√psroto=n–pr1o3tonTe(Vp,p)cocrorellsipsioonndsinagt a centre-of-mass to an integrated luminosity of 36.1 fb−1. The analysis exploits multivariate techniques for the suppression of the main multi-jet background, optimised for the different DPJ channels. This technique allows the exploitation of the fully hadronic signature for the first time in ATLAS DPJ searches, resulting in increased sensitivity compared with previous ATLAS results using the data collected in 2011 and 2012 at 7 and 8 TeV respectively [10,11]. The results are complementary to those from related ATLAS searches for prompt DPJs using 7 and. J. C (2020) 80:450 photon with a kinetic mixing term < 10−5 is allowed for γd masses greater than 100 MeV
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
