Feebly coupled hidden sectors. Kimmo Tuominen University of Helsinki

Transcription

1 Feebly coupled hidden sectors Kimmo Tuominen University of Helsinki

2 Outline Background Scalar portal models Outlook Collaborators: N. Bernal, K. Enqvist, M. Heikinheimo, K. Kainulainen, S. Nurmi, T. Tenkanen, V. Vaskonen ArXiv: , , ,

3 1. Background

4 Dark matter: DM h 2 = ± The WIMP paradigm: Thermal relic, Weakly interacting, Massive Weakly coupled: should see systems like the bullet cluster

5 Thermal relic & direct detection S S sm sm 1. Abundance from ZOPLW-equ. Y. Zel dovich, L. Okun, S. Pikelner Sov. Phys. Uspekhi. 8 (1966) B.W. Lee and S. Weinberg PRL 39 (1977) Constraints from direct searches S S n n Note implicit assumptions in this plot!

6 b h 2 = ± is not simple. Why DM h 2 = ± should be? This to explain 4% of the universe Why not also some similar patterns to explain the rest? - Vector, scalar, fermion dofs. - Compositeness.

7 Hidden sectors - Elementary or composite - Very weakly coupled with SM - Motivated by Dark Matter - Gravitational waves, - (Strong) self-interactions

8 Self-interacting dark matter Problems* in CDM small scale structure: Missing satellites CDM prediction to the right of the blue line Core-cusp problem Solved if DM has self-interactions: m ( )cm2 g E. Papastergis et al *assuming that these are not numerical glitches, but real physical issues (that can be resolved by self-interacting DM).

9 Cosmic colliders Bullet cluster: m apple 1 cm2 g Abell 520 (and 3827): m 1 cm2 g

10 Feebly coupled singlet sectors To avoid direct search limits SM hss 2 H 2 Hidden hs S A a µ Other possibilities: - Neutrino portal - Vector portal

11 FIMP DM Abundance produced via freeze-in. S hs ' DM h /2 GeV m s 1/2 n (eq) h (T ) S -4-6 J. McDonald, PRL 88 (2002) A. Kusenko, PRL 97 (2008), L.J. Hall et al. JHEP 1003 (2010) log10 Y Γ S self-interactions can be large log 10 x

12 2. Feeble scalar portals Ramifications to the simple picture

13 Primordial fields Light scalar fields during inflation: h s H V (h, s) = h 4 h4 + hs 2 s2 h 2 + µ2 s 2 s2 + s 4 s4 µ 2 S > 0 sh Energetically subdominant fields. -To estimate average field values use the stochastic approach (Starobinsky, Yokoyama PRD50 (1994)) P (h, s) =N exp 8 2 V (h, s) 3H 4 h p hh 2 i s p hs 2 i

14 At the end of the inflationary epoch, the scalar fields are displaced from origin: hs p h s Fields approach their vacuum values: - Oscillate around the minumum, - Amplitude diluted by the expansion, - Decays, produces particles.

15 At the end of the inflationary epoch, the scalar fields are displaced from origin: h p hh 2 i = O(0.1) H 1/4 h s p hs 2 i = O(0.1) H 1/4 s,, hs p h s h =0.12 The coherent higgs field dissipates rapidly into the SM thermal bath. hs apple 10 7 (Enqvist et al ) - S remains out of equilibrium. - contributes to dark matter - primordial isocurvature fluctuatio

16 Applies to any scalar portal model. For simplicity, consider now only L = L SM V (s) = µ2 s 2 s2 + s 4 s4 hs 2 h2 s 2 V (s) i.e. Real singlet scalar DM Parameters: (Also, assume that the quartic terms dominate)

17 DM abundance from primordial field s0 +4H s0 = h s0!ssi s0 (s 0) DM h ' /4 s mdm GeV s GeV 3/2 (K. Kainulainen et al ) is isocurvature: PLANCK: ( )

18 DM abundance from primordial field h s0 + 4H s0 = (s0 ) 2 DM h 0.12 ' s 1/4 s0!ss i s0 m DM GeV s 1011 GeV is isocurvature: PLANCK: ( ) 3/2

19 Isocurvature constraint P.Ade et al, ArXiv: Stringent bound from PLANCK: (Planck 2015 Constraints on Inflation) (s 0) DM h apple s H Combine with the computed abundance: m DM GeV apple 6 3/8 s H GeV 3/2

20 Primordial abundance is small Isocurvature constraint: m DM GeV apple 6 3/8 s H GeV 3/2 0 A lower bound on self-coupling -2 log 10 Ωh log 10 λ s log 10 (m s /GeV)

21 Self interactions Generally: 1 DM apple 1 cm2 m DM g ss-scattering: log 10 λ s log 10 H * GeV s m s = 9 2 s 32 m 3 s log 10 (m s /GeV) An upper bound on self-coupling: 3/ /3 s apple m s GeV apple 6 3/8 s H GeV

22 Total abundance: ordinary freeze-in DM = (s 0) DM + (fi) DM

23 Dark sector thermo? Initial freeze-in abundance: Chemical equilibration: n DM h vi 2!4 ' H n ini DM ' 3 neq h T ' m s H h!ss T =mh Role of number changing processes? E.D. Carlson et al. Astrophys J. 398 (1992), X. Chu et al. JCAP 1205 N. Bearnal and X. Chu,JCAP 1601 (2016) m s =0.1 GeV f.i. OK log 10 hs f.o. OK log 10 s Dark freezeout: decoupling of 4->2 process

24 The abundance 1 hs = log 10 s log 10 (m s /GeV)

25 + Isocurvature (light grey) + Self interactions (orange) 1 hs = log 10 s log (H /GeV) = log 10 (m s /GeV)

26 Adding a fermion DM L = L SM hs 2 h2 s 2 V (s) +L V (s) = µ2 s 2 s2 + s 4 s4 L = (i µ m ) + igs 5 (K. Kainulainen et al ) Isocurvature constrains abundance to be small

27 Equilibration: f.i. vs dark f.o. 1 0 Assuming quick decay of scalars to fermions log 10 g -1-2 and equlibration of fermions log 10 (m /GeV) Different thermal histories of the hidden sector possible log 10 Y log 10 Y log 10 x

28 Outlook Study equilibration in more detail, taking two-to-four processes into account. (in progress)

29 3. Conclusions Feebly coupled, freezing-in DM: A paradigm to avoid direct searches. Primordial fields from inflation. Isocurvature fluctuations: Primordial DM abundance negligible. Nontrivial constraint on self-couplings. Strong self-interactions: Novel thermal history of dark sector