Energy-Injection Constraints from CMB and How to Evade Them Sam - PowerPoint PPT Presentation

Energy-Injection Constraints from CMB and How to Evade Them Sam McDermott New Directions in the Search for Light Dark Matter Particles

What’s the Issue? 10 -22 10 -23 < σ v> (cm 3 /s) 10 -24 10 -25 Slatyer, 1506.03811 & PRD 10 -26 10 -26 10 -27 10 -27 10 100 1000 10000 10 -28 DM mass (GeV) < σ v> (cm 3 /s) 10 -29 Annihilation channels: 10 -30 10 -31 10 -32 10 -33 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 DM mass (GeV)

What’s the Issue? 10 -22 10 -23 < σ v> (cm 3 /s) 10 -24 10 -25 Slatyer, 1506.03811 & PRD 10 -26 10 -26 10 -27 10 -27 10 100 1000 10000 10 -28 DM mass (GeV) < σ v> (cm 3 /s) 10 -29 Annihilation channels: 10 -30 10 -31 10 -32 10 -33 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 DM mass (GeV)

Outline • Energy Injection During CMB • P-wave annihilation • Hidden Sector • Asymmetric Dark Matter • Freeze-in

Outline Caveats: • Energy Injection During CMB Many other good ideas to avoid CMB constraints! • P-wave annihilation Coannihilation (annihilation with partner, for inelastic states Griest & Seckel 1991, D’Agnolo & Ruderman 2018 ), forbidden/ • Hidden Sector impeded dark matter ( Griest & Seckel 1991, D’Agnolo & Ruderman 2015, Kopp et al. 2016, ), coscattering/co-decaying/“elastic • Asymmetric Dark Matter decoupling”( D’Agnolo & Ruderman 2017, Dror et al. 2016, Kuflik et al. 2017 ), … (many more) • Freeze-in

Outline • Energy Injection During CMB • P-wave annihilation • Hidden Sector • Asymmetric Dark Matter • Freeze-in

Energy Injection During CMB (shamelessly stolen from a talk I remember seeing by Tracy) Why is it plausible that DM annihilation is strongly constrained by CMB?

Energy Injection During CMB (shamelessly stolen from a talk I remember seeing by Tracy) Why is it plausible that DM annihilation is strongly constrained by CMB? • binding energy of hydrogen = 13.6 eV

Energy Injection During CMB (shamelessly stolen from a talk I remember seeing by Tracy) Why is it plausible that DM annihilation is strongly constrained by CMB? • binding energy of hydrogen = 13.6 eV • single annihilation of m DM ~ O(MeV) can ionize 10 5 H atoms

Energy Injection During CMB (shamelessly stolen from a talk I remember seeing by Tracy) Why is it plausible that DM annihilation is strongly constrained by CMB? • binding energy of hydrogen = 13.6 eV • single annihilation of m DM ~ O(MeV) can ionize 10 5 H atoms Poulin, Serpico, Lesgourgues 1508.01370 & JCAP

Energy Injection During CMB (shamelessly stolen from a talk I remember seeing by Tracy) Why is it plausible that DM annihilation is strongly constrained by CMB? • binding energy of hydrogen = 13.6 eV • single annihilation of m DM ~ O(MeV) can ionize 10 5 H atoms Poulin, Serpico, Lesgourgues 1508.01370 & JCAP

Energy Injection Rate Energy injection rate ~ E × n DM2 × ⟨ σ v ⟩ ann • E = 2 m DM , n DM = ρ DM /m DM • define p ann , which scales out density and includes efficiency factor: p ann ≡ f eff ⟨ σ v ⟩ ann /m DM

Energy Injection Rate Energy injection rate ~ E × n DM2 × ⟨ σ v ⟩ ann • E = 2 m DM , n DM = ρ DM /m DM • define p ann , which scales out density and includes efficiency factor: p ann ≡ f eff ⟨ σ v ⟩ ann /m DM Green, Meerburg, Meyers 1804.01055 & JCAP

Energy Injection Rate Energy injection rate ~ E × n DM2 × ⟨ σ v ⟩ ann • E = 2 m DM , n DM = ρ DM /m DM • define p ann , which scales out density and includes efficiency factor: p ann ≡ f eff ⟨ σ v ⟩ ann /m DM Green, Meerburg, Meyers 1804.01055 & JCAP

Energy Injection Rate Energy injection rate ~ E × n DM2 × ⟨ σ v ⟩ ann • E = 2 m DM , n DM = ρ DM /m DM • define p ann , which scales out density and includes efficiency factor: p ann ≡ f eff ⟨ σ v ⟩ ann /m DM Green, Meerburg, Meyers 1804.01055 & JCAP Note: similar lines of evidence from 21cm signal (Liu & Slatyer 1803.09739 & PRD;…), from behavior of star forming halos (Schön, et al. 1411.3783 & MNRAS), and other probes

Constraints Planck 2015: p ann < 4.1 × 10 -28 cm 3 /s/GeV Planck 2018: p ann < 3.2 × 10 -28 cm 3 /s/GeV Madhavacheril, Sehgal, Slatyer 1310.3815 & PRD

Constraints Planck 2015: p ann < 4.1 × 10 -28 cm 3 /s/GeV Planck 2018: p ann < 3.2 × 10 -28 cm 3 /s/GeV Madhavacheril, Sehgal, Slatyer 1310.3815 & PRD

Constraints 10 -22 10 -23 < σ v> (cm 3 /s) 10 -24 10 -25 Slatyer, 1506.03811 & PRD 10 -26 10 -26 10 -27 10 -27 10 100 1000 10000 10 -28 DM mass (GeV) < σ v> (cm 3 /s) 10 -29 Annihilation channels: 10 -30 10 -31 10 -32 10 -33 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 DM mass (GeV)

Outline • Energy Injection During CMB • P-wave annihilation • Hidden Sector • Asymmetric Dark Matter • Freeze-in

What is p-wave annihilation? • In generality ⟨ σ v ⟩ ann = ∑ l c l × ( σ v) ann, l × v DM 2 l

What is p-wave annihilation? • In generality ⟨ σ v ⟩ ann = ∑ l c l × ( σ v) ann, l × v DM 2 l • If there is a nonzero l = 0 term (e.g., c 0 ≠ 0), the annihilation is called s-wave

What is p-wave annihilation? • In generality ⟨ σ v ⟩ ann = ∑ l c l × ( σ v) ann, l × v DM 2 l • If there is a nonzero l = 0 term (e.g., c 0 ≠ 0), the annihilation is called s-wave • If the first nonzero term is l =1 (e.g., c 0 =0 & c 1 ≠ 0), the annihilation is called p-wave

What is p-wave annihilation? • In generality ⟨ σ v ⟩ ann = ∑ l c l × ( σ v) ann, l × v DM 2 l • If there is a nonzero l = 0 term (e.g., c 0 ≠ 0), the annihilation is called s-wave • If the first nonzero term is l =1 (e.g., c 0 =0 & c 1 ≠ 0), the annihilation is called p-wave ( σ v) ann,p (v b )/( σ v) ann,p (v a ) = (v b /v a ) 2

Why is this of interest? • v CMB ~ (T CMB /m DM ) 1/2 ~ 10 -3 (m DM /MeV) -1/2 is much smaller than v fo ~ 1/5

Why is this of interest? • v CMB ~ (T CMB /m DM ) 1/2 ~ 10 -3 (m DM /MeV) -1/2 is much smaller than v fo ~ 1/5 • thus, annihilations during (and after) CMB are suppressed by (v CMB /v fo ) 2 ~ 10 -5 /(m DM /MeV)

Why is this of interest? • v CMB ~ (T CMB /m DM ) 1/2 ~ 10 -3 (m DM /MeV) -1/2 is much smaller than v fo ~ 1/5 • thus, annihilations during (and after) CMB are suppressed by (v CMB /v fo ) 2 ~ 10 -5 /(m DM /MeV) ⟹ CMB bounds potentially lifted

How unusual is p-wave annihilation?