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