Origin of the dark matter mass scale for asymmetric dark matter. Ray Volkas School of Physics The University of Melbourne

Transcription

1 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

2 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.

3 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.

4 p ' n p n Sakharov s conditions: 1. Baryon number violation 2. C and CP violation 3. Out-of-equilibrium

5 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, 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.

6 Simultaneous creation of correlated asymmetries. Pangenesis Cogenesis p ' Dark VISIBLE SECTOR Stabilising conserve (baryon) DARK SECTOR number

7 Or: visible to dark reprocessing asymmetry created here VISIBLE SECTOR shared s.t. p ' Dark DARK SECTOR

8 Or: dark to visible reprocessing asymmetry created here VISIBLE SECTOR shared s.t. p ' Dark DARK SECTOR

9 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

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?

11 Image credit: universe-review.ca

12 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: : can t make symmetric mirror matter work

13 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.

14 Our work on spontaneously broken mirror models: Stephen J. Lonsdale, RV: PRD90 (2014) (E) PRD91 (2015) S.J. Lonsdale: PRD91 (2015) parameter space for Λ D Λ S.J. Lonsdale, M. Schroor, RV: PRD96 (2017) dark hadron spectra from hyperspherical constituent quark model S.J. Lonsdale, RV: in preparation example of complete theory

15 L H GeVL Non-susy Need at least one very light dark quark to form the DM baryon. 5 massive 1 light 100 target area massive 5 light m H GeVL dark quark mass Greater # of massive dark quarks => faster running of dark QCD coupling => higher dark confinement scale

16 Ξ Ξ 5 N MeV MeV P2 P1 PDG P P2 P1 PDG P J P 3 light dark quarks J P Examples of dark baryon spectra plots. ξ = Λ D /Λ MeV Ξ 5. m s 1000 MeV 2 light, 1 intermediate n p uds

17 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).