Neutrinos and the Baryon Asymmetry of the Universe

Valerie Domcke DESY Hamburg Neutrino Platform 2018 @ CERN based partly on 1507.06215, 1709.00414 in collaboration with A. Abada, G. Arcadi, and M. Lucente

bla The observed baryon asymmetry of the Universe

tiny matter-antimatter asymmetry in the early universe as particles and anti-particles annihilate, tiny asymmetry results in matter dominated Universe Sakharov conditions for dynamical generation [Sakharov ’67] • violation of B (or L) • violation of C and CP • departure from thermal equilibrium [Particle Data Group]

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 2 Baryogenesis meets particle physics

electroweak baryogenesis thermal leptogenesis

(1st order phase EW PT) (NR decay) ARS leptogenesis

GUT baryogenesis (NR oscillations) (X decay) Baryogenesis / Leptogenesis SM sphalerons, violate B+L

gravitational (SM gravitiational anomaly, RR˜) non-thermal leptogenesis

(NR decay) Affleck-Dine through magnetogenesis (B L charged scalar) − (helical magnetic fields) and more ...

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 3 Baryogenesis meets particle physics

electroweak baryogenesis thermal leptogenesis

(1st order phase EW PT) (NR decay) ARS leptogenesis

GUT baryogenesis (NR oscillations) (X decay) Baryogenesis / Leptogenesis SM sphalerons, violate B+L

gravitational (SM gravitiational anomaly, RR˜) non-thermal leptogenesis

(NR decay) Affleck-Dine through magnetogenesis (B L charged scalar) − (helical magnetic fields) and more ...

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 3 Outline

(Standard) thermal leptogenesis • overview • implications for the neutrino sector

Leptogenesis through neutrino oscillations (ARS) • overview • neutrino mass models

Neutrino observables from ARS • active-sterile mixing • tests at colliders • neutrinoless double beta decay

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 4 (Standard) thermal leptogenesis

[Fukugita,Yanagida ’86] right-handed Majorana neutrinos with ∆L = 2 process

h h LH ν N N¯ ν H¯ L¯ → → → thermal initial conditions eq ( nN,N¯ 1 for T > MN = 2 3/2 n π mN
MN /T γ ζ(3) 2πT e− for T < MN

if ΓN . H T =MN , abundance cannot track rapidly falling thermal abundance| departure from thermal equilibrium: → 2 Γ H (h† h )M M /M N . |T =MN → ν ν N . N P

CP violation  in N-decays n /s  TRH/M → ∆L ∼ N conversion to baryon asymmetry through sphaleron processes

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 5 (Standard) thermal leptogenesis

The two key parameters of thermal leptogenesis are closely tied to neutrino physics:

CP 2 ¨ ΓN LH ΓN L¯H¯ (hν† hν )v ¨CP :  = → − → wash-out : m CP e 1 M ΓN LH + ΓN L¯H¯ ∼ N → → Type - I seesaw mechanism:

1 T 1 2 mν MN m = (h M − h )v m ,  0.1 ν 2 ν N ν ∼ e 1 . v2

8 lower bound: TRH > MN > 10 GeV [Davidson,Ibarra ’02] A→ typical example ( GUT scale leptogenesis): ∼ 13 3 M 10 GeV , m˜ 0.01 eV , h 0.1 ,  10− N ∼ 1 ∼ ν ∼ ∼ Neutrino mass generation + cosmic history viable high-scale leptogenesis mechanism →

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 6 (Standard) thermal leptogenesis

[Buchm¨uller,Di Bari, Pl¨umacher ’04]

thermal initial conditions

vanishing initial conditions

Beautiful - but very hard to test!

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 7 Outline

(Standard) thermal leptogenesis • (overview • (implications for the neutrino sector

Leptogenesis through neutrino oscillations (ARS) • overview • neutrino mass models

Neutrino observables from ARS • active-sterile mixing • tests at colliders • neutrinoless double beta decay

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 8 defining a generalized lepton number under which also the Ns are charged, both the active and sterile sectorL develop a ∆ of equal magnitude but opposite sign (for M T ) L N  Sphaleron processes only pick up the ∆ = ∆L of the active sector, leading to a net baryon asymmetry L

low-scale leptogenesis mechanism experimentally accessible ! →

Leptogenesis through neutrino oscillations

[Akhmedov, Rubakov, Smirnov ’98]

nearly degenerate right-handed Majorana neutrinos N with MN 7 2 ∼ MeV - GeV and weak coupling to SM, h 10− ± ν ∼ starting from a vanishing initial abundance, Ns are thermally produced but do not reach full thermal equilibrium before the EW phase transition (= sphaleron freeze-out)

NR oscillations create a CP violating background for the active neutrinos

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 9 Leptogenesis through neutrino oscillations

[Akhmedov, Rubakov, Smirnov ’98]

nearly degenerate right-handed Majorana neutrinos N with MN 7 2 ∼ MeV - GeV and weak coupling to SM, h 10− ± ν ∼ starting from a vanishing initial abundance, Ns are thermally produced but do not reach full thermal equilibrium before the EW phase transition (= sphaleron freeze-out)

NR oscillations create a CP violating background for the active neutrinos defining a generalized lepton number under which also the Ns are charged, both the active and sterile sectorL develop a ∆ of equal magnitude but opposite sign (for M T ) L N  Sphaleron processes only pick up the ∆ = ∆L of the active sector, leading to a net baryon asymmetry L

low-scale leptogenesis mechanism experimentally accessible ! →

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 9 Boltzmann equations

Kinetic equations for neutrino density matrix ρ , A, B N, N,¯ ν, ν¯ AB ∈ { } dρ i i i = [H, ρ] Γ, ρ + Γp,I ρ [Sigl, Raffelt ’93] dt − 2 { } 2 { − }

Assuming MN mν : active-sterile oscillations suppressed,  eq kinetic equilibrium: ρNN (T, k) = RN (T )ρNN (T, k), thermal equilibrium for active ν: ρ ρeq(T, k) exp [ diag(µ )]: ν,ν¯ ∼ ± Lα

dRN 1 (0)  1 (1b)  = i [ H ,R ] γ F †F,R I γ F †µ F,R dt − h i N − 2h i N − − 2h i L N (1a) + γ F †µ F, h i L dµ∆α 9 ζ(3) n (0) T
(1a) = 2 γ FRN F † F ∗RN¯ F 2 γ µLFF †+ dt − 2ND π h i − − h i (1b) T
o + γ µL FRN F † + F ∗RN¯ F , [Asaka, Shaposhnikov ’05] h i αα w. F = Yukawa coupling in mass basis, H = eff. Hamiltonian, h·i = thermal average

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 10 Benchmark solutions

[Abada, Arcadi, VD, Lucente ’15, ’17] 7 weak washout regime, F 10− (analytical solutions available) | | .

6 intermediate/strong washout regime, F 10− (perturbative expansion) | | ∼

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 11 Neutrino mass models for ARS leptogenesis

Inverse Seesaw [Wyler, Wolfenstein ’83; Mohapatra, Valle ’86] (schematically for ‘active’, ‘RH’, ‘sterile’)

 0 1 h v 0   √2 ν 0 0 0 M = 1 h v 0 Λ + ξ 0 0 0 ν  √2 ν    0 Λ 0 0 0 Λ | {z } | {z } L conserving ∆L=2

ξ(h v)2 m ν , ∆m2 = M 2 M 2 2ξΛ2 ⇒ ν ' 2Λ N2 − N1 ' Linear Seesaw [Barr ’04; Malinsky, Romao, Valle ’05]

 0 1 h v 0  0 0 1 h v √2 ν √2 ν0 M = 1 h v 0 Λ +  0 0 0 ν  √2 ν    1 h v 0 0 0 Λ 0 √2 ν0 | {z } | {z } L conserving ∆L=2

(h v)2 m ν , ∆m2 = M 2 M 2 2(h v)2 ⇒ ν ' Λ N2 − N1 ' ν Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 12 Neutrino mass models for ARS leptogenesis

Inverse Seesaw [Wyler, Wolfenstein ’83; Mohapatra, Valle ’86] (schematically for ‘active’, ‘RH’, ‘sterile’)

 0 1 h v 0   √2 ν 0 0 0 M = 1 h v 0 Λ + ξ 0 0 0 ν  √2 ν    0 Λ 0 0 0 Λ | {z } | {z } L conserving ∆L=2

ξ(h v)2 m ν , ∆m2 = M 2 M 2 2ξΛ2 ⇒ ν ' 2Λ N2 − N1 ' Linear Seesaw [Barr ’04; Malinsky, Romao, Valle ’05] plus Inverse Seesaw

1  1   0 h v 0 0 0 h0 v √2 ν √2 ν M = 1 h v 0 Λ +   0 0 0  ν  √2 ν    1 h v 0 ξ Λ 0 Λ 0 √2 ν0  | {z } | {z } L conserving ∆L=2 (h v)2 m ν , ∆m2 = M 2 M 2 2(h v)2 ⇒ ν ' Λ N2 − N1 ' ν Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 12 Strategy

[Abada, Arcadi, VD, Lucente ’15,’17] Generate data points which respect all constraints on active neutrino masses/mixings as well as laboratory constraints on sterile neutrinos minimial models: LISS(1,1), ISS(2,2), ISS(2,3) [Abada, Lucente ’14] ⇒ Calculate baryon asymmetry by solving Boltzmann equations • analytically in the weak washout regime • perturbative numerical procedure otherwise

requirements for successful leptogenesis: constraints⇒ on masses, Yukawa couplings, mixing angles...

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 13 Neutrino mass models for ARS leptogenesis

weak washout regime, LISS model (2 additional NR’s):

intermediate/strong washout regime: LISS ISS(2,2)

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 14 Why consider specific mass models?

fewer parameters / more predictive

small parameters are symmetry protected directions for further model building → distinguish model independent from model-dependent features

but do not cover entire ARS parameter space

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 15 An example: dark matter in the ISS(2,3)

MPD decouple

mPD GeV leptogenesis ∆m keV ∼

keV mDM dark matter (Dodelson-Widrow)

eV mν ν oscillations

with

 5  1/2 1/2 mDM ∆m 3 10− mPD   mν  10− mPD ' mPD ' F GeV 0.05 eV | |

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 16 An example: dark matter in the ISS(2,3)

generic ISS points

DM compatible

DM - active mixing

ISS + ARS leptogenesis too constraining on mixing angles

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 17 Complementary approach: bayesian analysis

[Hern´andez,Kekic, L´opez-Pav´on,Racker, Salvado, ’16]

1 )

1 2 M / 2 1 3 M

log ∆M /M ∆ (

10 12 1 0 1 g

o 4 l log∆M prior logM prior 2.0 ) V

e 2.5 / β β m (

log m /eV 0 1 3.0

10 ββ g

o neutrino mass model: l

3.5 small mass splitting 8.85 ) 1 1

− 8.70 0 1 ×

−11 (

B 8.55 YB [10 ] Y low tuning / generic 8.40

6

) 8 2 | 4 e U |

( 10 0 1 g

2 o log10|Ue4| l 12

14

6

) 8 2 | 4 µ U |

( 10 0 1 g o

2 l log10|Uµ4| 12 14

6

) 8 2 | 4 τ U |

( 10 0 1 g o 2 l 12 log10|Uτ4| 14 1 0 1 2 4 3 2 1 3.5 3.0 2.5 2.0 8.40 8.55 8.70 8.85 14 12 10 8 6 14 12 10 8 6 14 12 10 8 6 11 2 2 2 log (M /GeV) log (∆M /M ) log (m /eV) Y ( 10− ) log ( U ) log ( U ) log ( U ) 10 1 10 12 1 10 ββ B × 10 | e4| 10 | µ4| 10 | τ4| M ∆M12 mββ 2 2 2 log 1 log log YB log|U | log|U | log|U | GeV M1 eV e4 µ4 τ4

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 18 Outline

(Standard) thermal leptogenesis • overview • implications for the neutrino sector

Leptogenesis through neutrino oscillations (ARS) • overview • neutrino mass models

Neutrino observables from ARS leptogenesis • active-sterile mixing • tests at colliders • neutrinoless double beta decay

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 19 [Hern´andez,Kekic, L´opez-Pav´on,Racker, Salvado, ’16]

[Abada, Arcadi, VD, Lucente ’17]

A significant part of the relevant parameter space can be probed!

Active sterile mixing

Minimimal type-I seesaw [Drewes, Garbrecht, Gueter, Klaric ’16]

FCC-ee(B) Belle II 10-5 BAU( upper bound) FCC-ee(W)

LHC 10-7 NA62 2 μ

U 10-9 T2K SHiP

10-11

disfavoured by global constraints BAU( lower bound) 10-13

0.5 1 5 10 50 M [GeV]

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 20 A significant part of the relevant parameter space can be probed!

Active sterile mixing

Minimimal type-I seesaw [Drewes, Garbrecht, Gueter, Klaric ’16]

FCC-ee(B) Belle II 10-5 BAU( upper bound) FCC-ee(W)

LHC 10-7 NA62 2 μ

U 10-9 T2K [Hern´andez,Kekic, L´opez-Pav´on,Racker, Salvado, ’16] SHiP [Abada, Arcadi, VD, Lucente ’17]

10-11

disfavoured by global constraints BAU( lower bound) 10-13

0.5 1 5 10 50 M [GeV]

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 20 [Hern´andez,Kekic, L´opez-Pav´on,Racker, Salvado, ’16]

[Abada, Arcadi, VD, Lucente ’17]

Active sterile mixing

Minimimal type-I seesaw [Drewes, Garbrecht, Gueter, Klaric ’16]

BAU( upper bound) 10-5

-7 10 ILC

CEPC 2

U -9 10 FCC-ee(Z) SHiP LBNE BAU( lower bound) 10-11

disfavoured by global constraints 10-13

0.5 1 5 10 50 M [GeV] A significant part of the relevant parameter space can be probed!

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 20 Next step: Testing leptogenesis at future colliders

minimal type-I seesaw compare parameter space for neutrino mass generation, leptogenesis and collider searches viable leptogenesis How well can we hope to measure parameters?

[Antusch, Cazzato, Drewes, Fischer, Garbrecht, Gueter, Klaric ’17]

Valuable information contained in multidimensional parameter space

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 21 Neutrinoless double beta decay (IH)

[Hern´andez,Kekic, L´opez-Pav´on,Racker, Salvado, ’16] [Drewes, Eijima ’16]

enhancement possible, in particular for large mass splitting

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 22 Next step: from discovery to testability

[Hern´andez,Kekic, L´opez-Pavon, Racker, Salvado ’16]

0.1 11 Obs. Y = 8.6 10− B × IH active ν’s hypothetical

) measuriment of masses eV

( and mixings by SHIP | 0.01 ββ (and δCP by DUNE) for m | IH parameter point correlation in Y vs ∆ U 2 = 1% ,∆M = 0.1% B | | ∆ U 2 = 1% ,∆M = 0.1% ,∆δ = 17 rad m plane 0.001 | | ββ -20 -10 0 10 20 11 YB(10− )

proof of principle of predictivity

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 23 Things I did not discuss

violation of total lepton number [Hambye, Teresi ’16/’17; Eijima, Shaposhnikov ’17; Ghiglieri, Laine ’17]

More than two right-handed neutrinos [Drewes, Garbrecht ’12]; Hern´andez,Kekic, L´opez-Pav´on,Racker, Rius ’15]

testing CP violation

many technical improvements in the theoretical computations over the past few years

dark matter (νMSSM and ISS(2,3))

...

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 24 Thank you!

Conclusion

observed matter-antimatter asymmetry requires BSM physics leptogenesis through neutrino oscillations provides a testable mechanism • oscillations of GeV right-handed neutrinos before EW phase transition • nonzero lepton number in the active sector • transmitted to baryons through sphaleron processes

Generic predictions (mass range, sizeable active sterile mixing) but also sensitivity to underlying neutrino mass model • symmetry inspired vs minimal tuning • strong washout vs weak washout • minimal particle content vs minimal parameters • individual mixing elements experimentally accessible

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 25 Conclusion

observed matter-antimatter asymmetry requires BSM physics leptogenesis through neutrino oscillations provides a testable mechanism • oscillations of GeV right-handed neutrinos before EW phase transition • nonzero lepton number in the active sector • transmitted to baryons through sphaleron processes

Generic predictions (mass range, sizeable active sterile mixing) but also sensitivity to underlying neutrino mass model • symmetry inspired vs minimal tuning • strong washout vs weak washout • minimal particle content vs minimal parameters • individual mixing elements experimentally accessible

Thank you!

Neutrinos and the Baryon Asymmetry of the Universe— Valerie Domcke — DESY — 01.02.2018 — Page 25