Asymmetric Dark Matter (and the Sun)

Transcription

1 Exploring the dark Universe, Quy Nhon, Vietnam, 27/07/2017 Asymmetric Dark Matter (and the Sun) Aaron Vincent Imperial College London 1

2 Overview Why asymmetric dark matter Superfast ADM overview Ultrafast solar abundance problem ADM in the sun and stars 2

3 Dark Matter in the Sun arxiv: / JCAP/04019 (ACV, P. Scott) Thermal conduction by dark matter with velocity and momentumdependent crosssections arxiv: / PRL (ACV, P. Scott, A. Serenelli) Possible Indication of MomentumDependent Asymmetric Dark Matter in the Sun arxiv: / JCAP 1508 (2015) 08, 040 (ACV, Scott, Serenelli) Generalised form factor dark matter in the Sun arxiv: /JCAP1611 (2016) 007 (ACV, Scott, Serenelli) Updated constraints on velocity and momentum dependent asymmetric dark matter arxiv: /jcap03(2017)029 (B. Geytenbeek, S. Roa, P. Scott, A. Serenelli, ACV, M. White, A. Williams) Effect of electromagnetic dipole dark matter on energy transport in the solar interior arxiv: (2017): G.Busoni, A. de Simone, P. Scott, ACV Generalised solar capture and evaporation of DM 3

4 The WIMP miracle and all that 1) Chemical equilibrium equipartition between species 3) Freezeout occurs when Hubble expansion stops annihilation 2) Falling temperature: heavy particles become 1 2 a 3 n / exp( m/t ) Boltzmann suppressed 3 n h vi ann ' H 4

5 WIMP miracle Let s try with SM 1 2 a 3 n / exp( m/t ) Similar approach with Neutrinos (keeping in mind m << T) n h vi ann ' H 3,F O =,obs (N,eff =3.046) Baryons? Weak scale cross section Annihilation of a symmetric baryon component: B,FO m DM & 100 GeV DM h baryon disaster (Sarkar) Require an initial asymmetry 5

6 Starting over: Require Note b = n B n Reviews Petraki & Volkas Zurek n B DM 5 b 10 9 So if we start with an initial (shared) asymmetry such that n b n DM ) m DM 5m b Observed abundance> prediction of a mass scale If asymmetry is generated before thermal freezeout Exponential Boltzmann suppression means h vi ann & few h vi WIMP Massasymmetry relation: m DM m p D /q B = 1 r 1 1r 1 DM b 6

7 Initial asymmetry: 3 conceptual options Zurek 1) SM asymmetry transferred to dark sector Need to be careful to avoid washout 2) Cogenesis Leptogenesis: Outofeq. decays to both sectors AffleckDine: Extend BLcarrying flat direction: Can conserve BLD, but break BL, D EW cogenesis: Spontaneous breaking of global D symmetry, simultaneous w/ SM Falkowski Cheung&Zurek ) Dark(o)genesis (~inverse of 1) Many models that mimic SM baryogenesis scenarios e.g. phase transition sphaleron processes > D, CP violation transfer to BL 7

8 Annihilation Once the initial asymmetry is there, the symmetric part must efficiently annihilate while: Avoiding washout of the asymmetry Avoiding overproduction of radiation e.g. if D is U(1).Residual U(1) charge > bound states: dark atoms, nuggets, (see also Kalliopi s talk) Avoiding other constraints (e.g. large cross section means strong collider bounds) h vi ann const. ) swave (heavy mediator) strongly constrained Dark forces/ v, qdependent models worth considering ( e.g. Baldes & Petraki ) ADM freezeout or freezein, or low cross section can lead to Coannihilation u! d d partial asymmetry Small majorana mass term 8

9 Detection: ADM vs WIMPs Indirect detection suppressed antidm: suppressed ID bound state: level transitions? Residual asymmetry: CMB becomes a lower limit? Collider production: depends how secluded your secluded sector is? Lin/Yu/Zurek Direct detection Yes! Keep the new mass scale in mind though! 9

10 m ADM 3 10 GeV = (s, t, u) E CM,q 2 v CM,q 2 tr 10

11 Direct detection DM? SM χ χ χ χ 11

12 Direct detection χ Ionisation Underground (low background) Heavy nuclei (more sensitive to heavy particles, A 2 enhancement) Nuclear recoil (phonon signal) Most sensitive to heavy, fast particles > larger recoil signal R = E T de R ρ 0 m N m χ v min vf(v) dσ WN de R (v, E R ) dv 12

13 The sun is a direct detection experiment M = 2 x kg 73% Hydrogen 25% Helium 2% Heavier elements (important since N / A 2 ) 13

14 The sun is a direct detection experiment χ χ χ Collision E kin E WIMP E escape Population: dn dt WIMP gravitationally bound = C(t) 2A(t) E(t) 14

15 Differences with earthbased DD Probing different parts of the halo velocity distribution solar lab f (v) 0.5 DD: above threshold Solar: low part (vesc) v (km/s) Probing different kinematic range (scattering with lighter elements: H, He) Spin sensitivity (sun mostly H) More sensitive to lighter DM Different couplings? 15

16 Population: dn dt = C(t) 2A(t) E(t) C(t) Capture rate A(t) Annihilation rate E(t) Evaporation rate (low m) 16

17 Capture rate C(t) =4 Z R? 0 r 2 Z 1 0 f(u) u w v (w)du dr, where is the local height in the star, is the in f(u) Halo DM velocity distribution (w) / w X i w(r) = p u 2 v 2 esc(r, t) n i Z F i (E R ) 2 d i de R de R Velocity at r, due to gravity Rate at which a WIMP of velocity w can scatter below vesc c.f. direct detection: R = E T de R ρ 0 m N m χ v min vf(v) dσ WN de R (v, E R ) dv 17

18 Maximum capture rate: geometric limit Once gravitation focusing is taken into account C,max / R 2 However, it should be a smooth transition, rather than a sharp cutoff n n baryon max geometric limit recovered (without imposing it by hand) effect of optical depth Busoni, de Simone, Scott, ACV ) 18

19 Asymmetric DM in stars If the population of antidm is suppressed enough (as in ADM) or if there s an asymmetry between the DM vs antidm capture rate (Blennow & Clementz ), then heat transport can be important: Core nucleus/photon mean free path nuc r core DM mean free path nuc This idea dates back to first solar crisis: the neutrino disappearance problem Neuenberg, Gould, Spergel, Press, 19

20 Probes of the sun Obvious Mass, age, radius, luminosity are extremely wellmeasured and are the first thing any solar model must satisfy. Neutrinos pp constrained by overall luminosity, but other byproducts of pp chain extremely sensitive to T. e.g, 8 B / T 25 c 20

21 Probes of the sun Obvious Mass, age, radius, luminosity are extremely wellmeasured and are the first thing any solar model must satisfy. Helioseismology Neutrinos pp constrained by overall luminosity, but other byproducts of pp chain extremely sensitive to T. e.g, 8 B / T 25 c NASA/SOHO Given a solar model, helioseismological observations (frequencies of different modes on the solar surface) can be inverted to obtain very precise determinations of observables including the sound speed, convective zone radius and structure of the core 21

22 Solar composition problem Bergemann & Serenelli 2014 R CZ, revised old abundances =0.713 ± R R CZ,SSM =0.722 ± R Mainly: smaller mean molecular weight, which shifts temperature, pressure, density gradients 22

23 Solar composition problem Small frequency separations: a probe of the core r r l(n) n,l n 1,l d l,l2 (n) n,l n 1,l2 l(n) ' (4l 6) 4 2 n,l Z R 0 dc s dr dr r 0.11 BiSON data Standard solar model BiSON data Standard solar model (rmod! robs)=<obs (7Hz) r 02 (n) = d 02(n) 1(n) (rmod! robs)=<obs (7Hz) r 13 (n) = d 13(n) 0(n 1) SSM describes the core very badly 23

24 Heat transport: two regimes Interactions too strong Efficient momentum transfer but DM is stuck" Interactions too weak DM goes far but cannot efficiently transfer momentum 24

25 Knudsen (nonlocal) K & 1 Calculable Transported energy [erg/s] Spindependent K l /r σ 0,SD (cm 2 ) LTE K<1 Somewhat calculable not calculable optimal heat transport 25

26 Putting it all together: Constant cross section Gould & Raffelt 1990 K l /r interpolating fcs 26 nonlocal Local

27 10 30 Spindependent Constant cross section 34 <SD (cm 2 ) log R ;j0(r; <)jdv [erg/s] Efficient energy conduction m 1 3 GeV m ADM <SI (cm 2 ) (GeV) Spinindependent (GeV) log R ;j0(r; <)jdv [erg/s] q cm 2 Requires large cross sections (disallowed by direct detection) but these are disfavoured by ADM anyways 27

28 Strange centre Sound speed /cs=cs #10 3 Constant cross section Modelling error Helioseismology error SSM SI, const., m = 5 GeV, < 0 = 10!35 cm 2 Ruled out by direct detection R=R Great improvement See also Taoso Cumberbatch Frandsen 28

29 Beyond the billiard ball 1) Very large cross sections Sun & direct detection probe the same process (elastic scattering), but in very different regimes Sun Sensitive to the lowvelocity end of the Milky Way DM distribution: easier to capture slowlymoving DM. Direct detection Large momentum transfers (recoil energies) much easier to detect: sensitive to high v, highq interactions 2) Crazy effects near the centre Can we smooth out the effect of transport to get an effect higher up, while reducing it near r = 0? 29

30 For concreteness, let s look at two forms: = 0 vrel n = 0 q v 0 q 0 n ACV Scott Serenelli where n = { 2, 2, 4} SI: Couples to everything SD: mostly hydrogen Need to recompute: Z Z 1 0 f(u) u w v (w)du! F (E R ) 2 de R = Capture rate Z Z 1 0 f(u) u e aq2 dq! 2n w w v (w)du Z v 0 e aq2 q q 0 2n dq gamma fcts. (µ), apple(µ) dark diffusion dark conduction 30

31 Change capture rate conduction rate 31

32 DarkStars (Scott, Edsjo, Fairbairn 2009) STARS DarkSUSY WIMP capture, annihilation and heat transport Generic stellar evolution GARSTEC (Weiss & Schlattl 2008) Highprecision (10 5 ) solar simulation code Standard Solar Model: Full evolution from protostar to current age (4.57 Gyr) Nuclear burning, heat transport, convection, accurate EOS, molecular diffusion. DarkStec Highprecision solar DM code including v and qdependence 32

33 900 simulations later. 33

34 Neutrino fluxes 8 B/ 8 Bobs Green: 2 sigma away from obs. 34

35 /cs=cs # Modelling error Helioseismology error No DM SI, const., m = 15 GeV, < 0 = 10!37 cm 2 SD, q 2, m = 3, < 0 = 10!39 cm 2 SD, v 2, m = 5, < 0 = 10!35 cm 2 SI, q 4, m = 3, < 0 = 10!32 cm 2 Sound speed R=R Core r BiSON data Standard solar model SD, q 2, m = 3, < 0 = 10!39 cm 2 SD, v 2, m = 5, < 0 = 10!35 cm SI, q 4, m = 3, < 0 = 10!32 cm 2 SI, const., m = 15 GeV, < 0 = 10!37 cm r BiSON data 0.12 Standard solar model SD, q 2, m = 3, < 0 = 10!39 cm SD, v 2, m = 5, < 0 = 10!35 cm 2 SI, q 4, m = 3, < 0 = 10!32 cm 2 SI, const., m = 15 GeV, < 0 = 10!37 cm (rmod! robs)=<obs wow! (7Hz) (rmod! robs)=<obs (7Hz) 35

36 CDMSlite (2015), CRESSTII ROI ~300 ev threshold: very sensitive to light DM!! Spindependent interactions? about 7% of Ge carries nonzero spin 36

37 CDMSlite (2015), CRESSTII ROI ROI Spindependent interactions? about 7% of Ge carries nonzero spin 37

38 Spindependent b.f. x CDMS x CDMS v 2 v 4 x CDMS q 2 x CDMS SSM Within 3 sigma of BF X Allowed 38

39 Longrange forces? Dipole Anapole, apple also speciesdependent See also Lopes 39

40 Dipole dark matter Geytenbeek Rao, Scott, Serenelli Vincent, White, Williams These are rather large values: disfavoured by DD experiments 40

41 Evaporation For a constant cross section, m < 4 GeV or so means the DM will evaporate (Gould, 1987, 1990) Again needs to be recomputed with! (q, v) Busoni, de Simone, Scott, Serenelli, ACV

42 Evaporation Gould: 1990 Anything below m = 4 GeV evaporates Optically thick: evaporation suppressed log Weak interactions: evaporation suppressed m Different approach, but looks a lot like the Knudsen transition! 42

43 evaporation o Could evaporation make overshoot regions better? o 43

44 Other stars for m ~ 1.1 solar mass, can suppress convective cores (Casanellas, Lopes) Large amounts of ADM (near gc?) can mess with stellar evolution prevent H ignition in lowmass stars ADM can accumulate in and destroy neutron stars, WDs (more efficient if boson) Goldman & Nussinov

45 Where to now? Next steps: Add evaporation to simulation, realistic particle models: full connection with ADM cosmology Better understanding of the Knudsen transition Apply this to other stars. What can we say about DM this way? 45