Accelerator Prospects for Sub-GeV DM. June 07 2019, New Directions - PowerPoint PPT Presentation

Accelerator Prospects 
 for Sub-GeV DM. June 07 2019, New Directions in the Search for LDM Particles, Fermilab Torben Ferber (torben.ferber@desy.de) cluster of Excellence Quantum universe

� 2 Accelerator Prospects for Sub-GeV DM (Torben Ferber) Overview • Types of accelerator searches • Types of DM signatures at accelerators • Benchmark searches: Visible and Invisible Dark Photons • Beyond simple models: iDM, DM bound states, Z’

� 3 Accelerator Prospects for Sub-GeV DM (Torben Ferber) New mediators ✓ 1 ◆ c n Λ n O (SM) O (med) X L = = L portals + O k l Λ n = k + l � 4 ✓ 1 ◆ = − ✏ N ¯ µ ν − H † H ( AS + � S 2 ) − Y ij 2 B µ ν A 0 L i HN j + O Λ Vector Portal: Massive A’ mixes with SM γ via strength parameter ε Scalar Portal: Additional dark Higgs Neutrino Portal: Sterile neutrinos, heavy neutral leptons e.g. Axion Portal: Massive ALP couples to SM bosons

� 4 Accelerator Prospects for Sub-GeV DM (Torben Ferber) Accelerator landscape Specialized Collider Beam dumps Fixed target (e.g. g-2, EDM)


 5 � Accelerator Prospects for Sub-GeV DM (Torben Ferber) Accelerator landscape Specialized Collider Beam dumps Fixed target (e.g. g-2, EDM) e + e - (intensity frontier, e.g. Belle II) Electrons Electrons pp (energy frontier, LHC) Protons 
 future e + e - (energy frontier, e.g. ILC) Active target Passive target Multi-purpose detectors 
 (tracking, calorimeters, 
 particle identification, …)

� 6 Accelerator Prospects for Sub-GeV DM (Torben Ferber) Accelerator landscape Particle decays Direct (new) mediator production DM Resonances in meson decays, e.g. π 0 → A’ γ (Dark Photon) SM DM B → K (*) a (ALP) B → K χχ
 DM SM DM + clean, e ffj cient trigger, di fg erent couplings - kinematics limited by meson mass Missing energy or resonance searches, e.g. Precision measurements A → Invisible (Dark Photon) a →γγ (ALP) Precision observables modified by DM, e.g. + maximum mass reach, high rate Di fg erential cross section B → K μμ - high backgrounds, di ffj cult trigger

� 7 Accelerator Prospects for Sub-GeV DM (Torben Ferber) Accelerator landscape Particle decays Direct (new) mediator production DM Resonances in meson decays, e.g. π 0 → A’ γ (Dark Photon) SM DM B → K (*) a (ALP) B → K χχ
 DM SM DM + clean, e ffj cient trigger, di fg erent couplings - kinematics limited by meson mass Missing energy or resonance searches, e.g. Precision measurements A → Invisible (Dark Photon) a →γγ (ALP) Precision observables modified by DM, e.g. + maximum mass reach, high rate Di fg erential cross section B → K μμ - high backgrounds, di ffj cult trigger

8 � Accelerator Prospects for Sub-GeV DM (Torben Ferber) New mediator production and decay Mediator mass m A’ o fg -shell Invisible 
 m A’ = 2m DM (subleading visible) DM Visible e, μ , … DM e, μ , … 2m e γ long-lived γ γ DM mass m DM

� 9 Accelerator Prospects for Sub-GeV DM (Torben Ferber) Visible Dark Photon decays: e + e - collider photon positron electron A’ leptons or hadrons * *prompt or displaced

� 10 Accelerator Prospects for Sub-GeV DM (Torben Ferber) Visible Dark Photon decays: e + e - collider (e.g. BaBar, Belle II) • Bump hunts over smooth, large SM Entries / 0.1 GeV Entries / 0.1 GeV backgrounds Phys. Rev. Lett. 113, 201801 (2014) Data 6 6 10 10 + - + - MC e e → γ µ µ BaBar + - MC e e R → γ • Sensitivity scales only very slowly with integrated luminosity: ~ ℒ 1/4 5 5 10 10 • Hadronic final states are more challenging but possible Data/MC 0 0 2 2 4 4 6 6 8 8 10 10 1 0.9 • ττ channels have not been exploited 0 2 4 6 8 10 2 2 µ m = m - 4m (GeV) yet (missing energy from neutrinos) µ µ R

� 11 Accelerator Prospects for Sub-GeV DM (Torben Ferber) Visible Dark Photon decays: Fixed target electron electron A’ electrons thin target