A Lightning Review of Dark Matter R.L. Cooper

Orbital Velocity: A Sample Calculation The radial velocity of a probe a distance r from the galactic center The mass contained within r is M(r)

Expected Form Star light is majority of Baryonic mass Expectation: radial velocity fall-off Similar to Solar System Keplerian motion

Measured Radial Velocity Radial velocity mostly flat There’s a massive halo dictating galactic dynamics

More Evidence for Dark Matter Cosmic Microwave BackgroundLarge Scale Structure

Dark Matter Properties Local galactic velocity Energy density Cross section controls number density

Dark Matter Candidates Sources Baryonic Matter (e.g. MACHOS – MAssive Compact Halo ObjectS) Neutrinos Other exotics (Axions) Weakly Interacting Massive Particles (WIMPs -  ) Consequences Brown dwarfs, neutron stars, black holes, cold gas clouds, etc. Gravitational lensing Not enough matter

Dark Matter Candidates Sources Baryonic Matter (e.g. MACHOS – MAssive Compact Halo ObjectS) Neutrinos Other exotics (Axions) Weakly Interacting Massive Particles (WIMPs -  ) Consequences Hot dark matter Low mass implies relativistic at formation Large-scale structure is smoothed Masses < 1 eV Steriles?

Dark Matter Candidates Sources Baryonic Matter (e.g. MACHOS – MAssive Compact Halo ObjectS) Neutrinos Other exotics (Axions) Weakly Interacting Massive Particles (WIMPs -  ) Consequences Introduced to address the strong CP problem of QCD Low mass – Nambu- Goldstone boson Mass << eV Deeper analysis is beyond the scope of this report

Dark Matter Candidates Sources Baryonic Matter (e.g. MACHOS – MAssive Compact Halo ObjectS) Neutrinos Other exotics (Axions) Weakly Interacting Massive Particles (WIMPs -  ) Consequences GeV, very non- relativistic at formation Tiny cross-section Froze-out in early universe expansion Lightest Superparticle in SUSY (LSP) a top candidate Kaluza-Klein, extra-dim.

Dark Matter Abundance Annhilation rate in early universe (in equilibrium) Hubble expansion freezes out

Dark Matter Collisions Non-relativistic c Elastic scattering Neutralino LSP can interact through Higgs, Z, squark with matter Interaction on nucleon Coherent on nuclei implies A 2 enhancement (A,Z) 

Recoil Energy Spectrum Recoil energy uniformly distributed from 0 to maximum energy deposit Incident WIMP energy Maxwellian A given energy deposit Exponential signal in energy deposit

Detection of Dark Matter Other neutral elastic collisions are backgrounds ( , n)  and n recoil on nuclei  recoil on electrons Recoils have very different Can imply different light output (e.g. quenching) Different excitation alter signal time-dependence Discrimination possible

Detection Methods Standard Techniques And combinations of these Other Methods (A,Z)  n Ionization Scintillation Phonons Bubble Chamber Gas / Directional Axion Cavities Direct / Indirect searches Yearly / sidereal variation

 decay ( , n) reaction fissions  n n  n n  -induced n spallation Multiplicity? Uncorrelated Neutron Backgrounds rock Coherent scattering

 n  -induced n spallation Correlated Neutron Backgrounds rock radio-impurities n

Reading Exclusion Plots Finite detection threshold Flux decrease ~ 1 / m  Excluded Available Phase Space