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Physics Beyond Colliders at CERN: Beyond the Standard Model Working Group Report

J. Beacham, C. Burrage, D. Curtin, A. De Roeck, J. Evans, J. L. Feng, C. Gatto, S. Gninenko, A. Hartin, I. Irastorza, J. Jaeckel, K. Jungmann, K. Kirch, F. Kling, S. Knapen, M. Lamont, G. Lanfranchi, C. Lazzeroni, A. Lindner, F. Martinez-Vidal, M. Moulson, N. Neri, M. Papucci, I. Pedraza, K. Petridis, M. Pospelov, A. Rozanov, G. Ruoso, P. Schuster, Y. Semertzidis, T. Spadaro, C. Vallee, G. Wilkinson

TL;DR

The report maps a broad, intensity-frontier program at CERN aimed at discovering physics beyond the Standard Model across sub-eV to multi-TeV scales. It presents a portal-based framework (vector, scalar, neutrino, axion) to connect hidden sectors with the SM and catalogs ~15 proposals exploiting CERN’s beams and infrastructures to probe these regimes. It details the physics reach, benchmark models, experimental strategies (fixed-target, beam dumps, LHC IP detectors, helioscopes, storage-ring EDMs), and anticipated timelines, emphasizing complementarity with the LHC and other facilities. The study argues that, despite no NP signals yet, a diversified program could explore vast, poorly probed regions of parameter space over the next decade or two, with significant potential to reveal new particles, interactions, or CP-violating phenomena.

Abstract

The Physics Beyond Colliders initiative is an exploratory study aimed at exploiting the full scientific potential of the CERN's accelerator complex and scientific infrastructures through projects complementary to the LHC and other possible future colliders. These projects will target fundamental physics questions in modern particle physics. This document presents the status of the proposals presented in the framework of the Beyond the Standard Model physics working group, and explore their physics reach and the impact that CERN could have in the next 10-20 years on the international landscape.

Physics Beyond Colliders at CERN: Beyond the Standard Model Working Group Report

TL;DR

The report maps a broad, intensity-frontier program at CERN aimed at discovering physics beyond the Standard Model across sub-eV to multi-TeV scales. It presents a portal-based framework (vector, scalar, neutrino, axion) to connect hidden sectors with the SM and catalogs ~15 proposals exploiting CERN’s beams and infrastructures to probe these regimes. It details the physics reach, benchmark models, experimental strategies (fixed-target, beam dumps, LHC IP detectors, helioscopes, storage-ring EDMs), and anticipated timelines, emphasizing complementarity with the LHC and other facilities. The study argues that, despite no NP signals yet, a diversified program could explore vast, poorly probed regions of parameter space over the next decade or two, with significant potential to reveal new particles, interactions, or CP-violating phenomena.

Abstract

The Physics Beyond Colliders initiative is an exploratory study aimed at exploiting the full scientific potential of the CERN's accelerator complex and scientific infrastructures through projects complementary to the LHC and other possible future colliders. These projects will target fundamental physics questions in modern particle physics. This document presents the status of the proposals presented in the framework of the Beyond the Standard Model physics working group, and explore their physics reach and the impact that CERN could have in the next 10-20 years on the international landscape.

Paper Structure

This paper contains 54 sections, 31 equations, 41 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Physics Motivations
  3. Hidden Sector portals
  4. Vector portal models
  5. Scalar portal models
  6. Neutrino portal models
  7. Axion portal models
  8. Experiments proposed in the PBC context
  9. Proposals sensitive to New Physics in the sub-eV mass range
  10. Solar axions helioscopes: IAXO
  11. Laboratory experiments: JURA
  12. Proposals sensitive to New Physics in the MeV-GeV mass range
  13. Proposals at the PS beam lines
  14. REDTOP
  15. Proposals at the SPS beam lines
  16. ...and 39 more sections

Figures (41)

  • Figure 1: Schematic overview of the BSM landscape, based on a selection of specific models, with a rough outline of the areas targeted by the PBC experiments. The $x-$axis corresponds to the mass $m_X$ of the lightest BSM state, and the $y-$axis to the scale of the effective new interaction $f = M_{\rm Mediator}/g$, where $M_{\rm Mediator}$ is the mass of a heavy mediator and $g$ its (dimensionless) coupling constant to the Standard Model. The grey shaded area outlines the currently excluded regions for a class of models corresponding to the benchmarks BC9 and BC11 (see Refs Abel:2017rtmJaeckel:2010niIrastorza:2018dyq).
  • Figure 2: Tentative timescale for PBC projects exploring the MeV-GeV mass range compared to other similar initiatives in the world that could compete on the same physics cases.
  • Figure 3: Schematic layout of REDTOP detector.
  • Figure 4: Layout of the NA62 experiment.
  • Figure 5: The LDMX experiment layout.
  • ...and 36 more figures