# Search for light long-lived neutral particles produced in pp collisions at \sqrts = 13 TeV and decaying into collimated leptons or light hadrons with the ATLAS detector

Franconi, Laura; Haug, Sigve; Weber, Michele; Anders, John Kenneth; Beck, Hans Peter; Ereditato, Antonio; Miucci, Antonio; Merlassino, Claudia; Weston, Thomas Daniel (2020). Search for light long-lived neutral particles produced in pp collisions at \sqrts = 13 TeV and decaying into collimated leptons or light hadrons with the ATLAS detector. European physical journal. C - particles and fields, 80(5) EDP Sciences 10.1140/epjc/s10052-020-7997-4

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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 s√=13 TeV 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.

#### Item Type:

Journal Article (Original Article)

#### Division/Institute:

10 Strategic Research Centers > Albert Einstein Center for Fundamental Physics (AEC)
08 Faculty of Science > Physics Institute > Laboratory for High Energy Physics (LHEP)

#### UniBE Contributor:

Franconi, Laura; Haug, Sigve; Weber, Michele; Anders, John Kenneth; Beck, Hans Peter; Ereditato, Antonio; Miucci, Antonio; Merlassino, Claudia and Weston, Thomas Daniel

#### Subjects:

500 Science > 530 Physics

1434-6044

EDP Sciences

English

#### Submitter:

BORIS Import LHEP

#### Date Deposited:

02 Jun 2021 13:31

06 Jun 2021 03:15

#### Publisher DOI:

10.1140/epjc/s10052-020-7997-4

Kollaboration - Es sind nur die Berner Autoren namentlich erwaehnt

10.48350/155609

#### URI:

https://boris.unibe.ch/id/eprint/155609