Origin of the dark matter mass scale for asymmetric dark matter Ray Volkas School of Physics The University of Melbourne 4 th Joint CAASTRO-CoEPP Workshop: Challenging Dark Matter, Barossa Valley, Nov. 2017
Observationally, it is now very well established that DM ' 5 VM This cosmological connection may be a clue to the particle nature of DM. In almost all DM theories, this relation has to be ascribed to a coincidence. There is an important exception: asymmetric DM.
The origin of VM has been identified, if not dynamically understood. It is the baryon asynmetry of the universe: VM p c p ' p c p = proton/neutron c = critical DM may similarly be the stable component of a dark sector whose relic density is determined by a dark matter-antimatter asymmetry.
p ' n p n 10 10 Sakharov s conditions: 1. Baryon number violation 2. C and CP violation 3. Out-of-equilibrium
Common general mechanisms: Out-of-equilibrium decays of heavy particles: (! x 1 x 2...) 6= (! x 1 x 2...) Affleck-Dine: production of charged scalar condensate through time-dep. phase. Supersymmetry, uses flat directions. First-order phase transition: nucleation of bubbles of true vacuum, sphalerons, CP-violating collisions with bubble walls. Out-of-equilibrium scattering: DM particles scatter/coannihilate with SM particles at a different rate from DM antiparticles. NEW! Baldes, Bell, Petraki, RV: PRL 113 (2014) 18, 181601 and Baldes, Bell, Millar, Petraki, RV: JCAP 1411 (2014) 11, 041 Asymmetric thermal production (asymmetric freeze-in): DM and anti-dm never in thermal equilibrium; slowly produced at different rates. Spontaneous genesis: Sakharov conditions presuppose CPT invariance. Expanding universe induces effective CPT violation. Asymmetry generation in eq. without C, CP violation.
Simultaneous creation of correlated asymmetries. Pangenesis Cogenesis p ' Dark VISIBLE SECTOR Stabilising conserve (baryon) DARK SECTOR number
Or: visible to dark reprocessing asymmetry created here VISIBLE SECTOR shared s.t. p ' Dark DARK SECTOR
Or: dark to visible reprocessing asymmetry created here VISIBLE SECTOR shared s.t. p ' Dark DARK SECTOR
Back to: DM ' 5 VM m D n D ' 5 m V n V proton mass: Λ QCD Baryon-antibaryon asymmetry p ' n p n 10 10
Obtaining number density relation, n D ~ n p, is a staple of the asymmetric DM literature. But why m D ~ m p? Could the DM particle be a dark neutron? The lightest, stable fermionic bound state of dark QCD?
Image credit: universe-review.ca
Origin of dark QCD? Probably some version of a (probably) broken mirror matter model: Gauge group: G VM x G DM with G VM G DM G = SU(3) x SU(2) x U(1), SU(5), SO(10), Pre-modern: Lee+Yang, Kobzarev+Okun+Pomeranchuk, Blinnikov+Khlopov, Modern: Foot+Lew+RV, Berezhiani+Mohapatra, H.-J. He et al,... R. Foot, arxiv:1707.02528: can t make symmetric mirror matter work
Ordinary hadron mass spectrum depends on: Confinement scale Λ 300 MeV. m q Λ (true for q = up, down) m q Λ (true for q = strange) m q Λ (true for q = charm, bottom, top) For dark QCD want: Λ D Λ. The dark quark mass spectrum is open question.
Our work on spontaneously broken mirror models: Stephen J. Lonsdale, RV: PRD90 (2014) 083501 (E) PRD91 (2015) 129906 S.J. Lonsdale: PRD91 (2015) 125019 parameter space for Λ D Λ S.J. Lonsdale, M. Schroor, RV: PRD96 (2017) 055027 dark hadron spectra from hyperspherical constituent quark model S.J. Lonsdale, RV: in preparation example of complete theory
L H GeVL 10 4 1000 Non-susy Need at least one very light dark quark to form the DM baryon. 5 massive 1 light 100 target area 10 1 1 massive 5 light 1000 10 6 10 9 10 12 10 15 m H GeVL dark quark mass Greater # of massive dark quarks => faster running of dark QCD coupling => higher dark confinement scale
12 000 Ξ 5 20 000 Ξ 5 N MeV 10 000 8000 6000 MeV 15 000 10 000 4000 2000 P2 P1 PDG P3 5000 P2 P1 PDG P3 1 1 2 2 3 3 2 2 J P 3 light dark quarks 1 1 2 2 3 3 2 2 J P Examples of dark baryon spectra plots. ξ = Λ D /Λ MeV 20 000 15 000 10 000 5000 Ξ 5. m s 1000 MeV 2 light, 1 intermediate 0 0 0 0 0 0 n p uds
Final remarks Is the DM mass density deeply related to baryon mass density? If so asymmetric DM with dark neutrons or dark nuclei. What would be evidence for this scenario? No WIMPs (sorry world!), axions (sorry Mike Tobar!), or kev sterile neutrinos (sorry Alex Kusenko, Mischa Shaposhnikov!) Few-GeV DM mass. Need for self-interactions (sub-galactic CDM issues). DM bound states. Compact DM objects (exist in some scenarios).