• Juliette Alimena
  • James Beacham
  • Martino Borsato
  • Yangyang Cheng
  • Xabier Cid Vidal
  • Giovanna Cottin
  • David Curtin
  • Albert De Roeck
  • Nishita Desai
  • Jared A Evans
  • Simon Knapen
  • Sabine Kraml
  • Andre Lessa
  • Sascha Mehlhase
  • Michael J Ramsey-Musolf
  • Heather Russell
  • Jessie Shelton
  • Brian Shuve
  • Monica Verducci
  • Jose Zurita
  • Todd Adams
  • Michael Adersberger
  • Cristiano Alpigiani
  • Artur Apresyan
  • Robert John Bainbridge
  • Varvara Batozskaya
  • Hugues Beauchesne
  • Lisa Benato
  • S Berlendis
  • Eshwen Bhal
  • Christina Borovilou
  • Jamie Boyd
  • Benjamin P Brau
  • Lene Bryngemark
  • Oliver Buchmueller
  • Malte Buschmann
  • William Buttinger
  • Mario Campanelli
  • Cari Cesarotti
  • Chunhui Chen
  • Hsin-Chia Cheng
  • Sanha Cheong
  • Matthew Citron
  • Andrea Coccaro
  • V Coco
  • Eric Conte
  • Félix Cormier
Particles beyond the Standard Model (SM) can generically have lifetimes that are long compared to SM particles at the weak scale. When produced at experiments such as the Large Hadron Collider (LHC) at CERN, these long-lived particles (LLPs) can decay far from the interaction vertex of the primary proton–proton collision. Such LLP signatures are distinct from those of promptly decaying particles that are targeted by the majority of searches for new physics at the LHC, often requiring customized techniques to identify, for example, significantly displaced decay vertices, tracks with atypical properties, and short track segments. Given their non-standard nature, a comprehensive overview of LLP signatures at the LHC is beneficial to ensure that possible avenues of the discovery of new physics are not overlooked. Here we report on the joint work of a community of theorists and experimentalists with the ATLAS, CMS, and LHCb experiments—as well as those working on dedicated experiments such as MoEDAL, milliQan, MATHUSLA, CODEX-b, and FASER—to survey the current state of LLP searches at the LHC, and to chart a path for the development of LLP searches into the future, both in the upcoming Run 3 and at the high-luminosity LHC. The work is organized around the current and future potential capabilities of LHC experiments to generally discover new LLPs, and takes a signature-based approach to surveying classes of models that give rise to LLPs rather than emphasizing any particular theory motivation. We develop a set of simplified models; assess the coverage of current searches; document known, often unexpected backgrounds; explore the capabilities of proposed detector upgrades; provide recommendations for the presentation of search results; and look towards the newest frontiers, namely high-multiplicity ‘dark showers’, highlighting opportunities for expanding the LHC reach for these signals.
Original languageEnglish
Article number090501
Number of pages226
JournalJournal of Physics G: Nuclear and Particle Physics
Volume47
Issue number9
DOIs
Publication statusPublished - 2 Sep 2020

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