Feebly Interacting Particles Physics Centre


Small numbers are ubiquitous in Nature. Prominent examples of small numbers are:

1. Higgs mass:    m2(Higgs)/m2(Planck) = 10-33
2. theta(QCD):   thetaQCD < 10-10
3. cosmological constant:  rho ~ 10-120 m4 (Planck)
4. matter -antimatter asymmetry:  (nB - nantiB)/ngamma = 10-9
5. DM abundance: nDM/ngamma ~ 10-12 mDM/TeV
6. primordial density fluctuations: delta rho/rho ~ 10-5
7. flavor (all the Yukawa's couplings): eg: y(electron) /y(top) ~ 10-6.

New Physics may interact with the SM particles through small, very feeble, dimensionless or dimensional couplings.  These are Feebly-Interacting Particles or FIPs. The smallness of the couplings can be due either to an approximate symmetry slightly broken or to a large separation of scales (as data seem to suggest).


The FIP Physics Centre (FPC) has the main goal of developing and further boosting the potential of the PBC experiments for the physics of feebly-interacting particles, taking into account the worldwide context, recent theory progress and relevant results from neighboring fields (axion physics, dark matter direct detection, active neutrino physics, astroparticle, cosmology, etc.).


The FPC will act as a central forum for exchanges between the PBC experimental community and theorists for assessment of the FIP physics reach of the proposed projects in a global landscape.

Working Group Core Members


Maxim Pospelov (Minnesota University and Perimeter Institute), Felix Kahlhoefer (Karlsruhe Institute of Technology)

Core Active Members:

James Beacham (Duke U., US), Albert de Roeck (CERN), Marco Drewes (Louvain, BE), Torben Ferber (KIT, D), Maurizio Giannotti (Barry U., US), Stefania Gori (Santa Cruz U., US), Philip Harris (MIT, US),  Matheus Hostert (Minnesota U. & Perimeter Institute, US/CA), Igor Irastorza (Zaragoza U., ES), Joerg Jaeckel (Heidelberg U., D), Juraj Klaric (Louvain, BE), Jacobo Lopez Pavon (Valencia U., ES), Jocelyn Monroe (Royal Halloway U., UK), Silvia Pascoli (Bologna U, IT),   Mikhail Shaposhnikov (EPFL, CH), Jessie Shelton (Urbana U., US),  Yevgeni Stadnik (Tokio U, JP), Stefan Ulmer (Riken, JP)

Experiments' Representatives - One representative per experiment/proposal related to FIP physics:

NA64(mu) (Dmitrii Kirpichnikov, INR, RU), Muonium (Paolo Crivelli, ETH-Zurich), EDM with crystals (Fernando Martinez Vidal, University of Valencia, ES), MATHUSLA (David Curtin, University of Toronto, CA), FORMOSA (Albert De Roeck, CERN), CODEX-b (Michele Papucci, CALTECH, US), Forward Physics Facility and FASER2 (Jonathan Feng, University of California, US), FLArE  (Milind Diwan, BNL, US), ANUBIS (Oleg Brandt, DESY, D), Gamma Factory (Witek Krasny, Paris VI, FR), proton EDM (Paolo Lenisa, Ferrara University, IT), AION (Oliver Buchmuller, Imperial College London, UK),  AD experiments (Stefan Ulmer, RIKKEN, JP), ISOLDE (Gerda Neyens, CERN), ENUBET (Fabio Pupilli, INFN, IT), NuTAG (Juergen Brunner, CPPM, FR)

For any question related to the FPC please contact:

Maxim Pospelov (mpospelov@perimeterinstitute.ca), Felix.Kahlhoefer@kit.edu

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