Probing origins of neutrino masses and baryon asymmetry
@KIAS (2013/11/15)
In collaboration withShintaro Eijima (EPFL, Switzerland) Atsushi Watanabe (MPIK, Germany)
References: JHEP1303 (2013) 125arXiv:1308.3550 (to appear in PTEP)
Takehiko Asaka (Niigata Univ.)
Introduction Neutrino mass scales
Atmospheric: ≃ 2.4 10 eV Solar: ≃ 7.5 10 eV⇒ Need for physics beyond the SM !
Important questions: “What is the origin of neutrino masses?”
“How do we test it experimentally?”
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Extension by RH neutrinos
Seesaw mechanism ( Φ ≪ )
Light, active neutrinos→ explain neutrino oscillations
Heavy neutrinos Mass Mixing Θ /
+ h.c.2
cMR R R R R
ML i F Lμμδ ν γ ν ν ν ν= ∂ − Φ −
0 01 1( , ) . ( , ) . .02 2
c cDc L
L R TD R
c
M M
M ML h c h c
M NMN
Mννν ν
ννν
− = + = +
1T
D DM
M M MMν = −
1 2 3( , , )TU M U diag m m mν =
≃ mixing in CC current
Where is the scale of mass?
Minkowski ’77Yanagida ’79Gell-Mann, Ramond, Slansky ‘79Glashow ‘79
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Scale of Majorana mass The simplest case: one pair of and
221 /TD D M
M
M M M F M MMν ν= − = Φ
2atmM mν = Δ
Majorana Mass
Neut
rino
Yuka
wa
Coup
ling
-12
-10
-8
-6
-4
-2
0
2
-10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16
log 1
0(F)
log10(MM/GeV)
tF F=
eF F=
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Scale of Majorana mass The simplest case: one pair of and
221 /TD D M
M
M M M F M MMν ν= − = Φ
Majorana Mass
Neut
rino
Yuka
wa
Coup
ling
-12
-10
-8
-6
-4
-2
0
2
-10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16
log 1
0(F)
log10(MM/GeV)
tF F=
eF F=
Baryogenesis via leptogenesisFukugita, Yanagida ‘86
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Scale of Majorana mass The simplest case: one pair of and
221 /TD D M
M
M M M F M MMν ν= − = Φ
Majorana Mass
Neut
rino
Yuka
wa
Coup
ling
-12
-10
-8
-6
-4
-2
0
2
-10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16
log 1
0(F)
log10(MM/GeV)
tF F=
eF F=
Baryogenesis via leptogenesisFukugita, Yanagida ‘86
Baryogenesis via neutrino osc.
Akhmedov, Rubakov, Smirnov ‘98
TA, Shaposhnikov ‘05
Takehiko Asaka (Niigata Univ.) 15/11/2013
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In this talk
15/11/2013Takehiko Asaka (Niigata Univ.)
Consider the minimal case with two RH neutrinos Lighter than charged kaon ,⟶ Test by Kaon decays ( → ℓ ) is possible
Current status of (RH) heavy neutrinos Region of successful baryogenesis Constraints from direct search and cosmology
Implication to 0 2 decay Search for (RH) heavy neutrinos at T2K
When adding one more DM RH neutrino , the results can be applied to the MSM !!
7
TA, Blanchet, Shappshnikov (‘05),TA, Shaposhnikov (‘05)
Current status of heavy neutrinos
§
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Baryogenesis via neutrino osc.Oscillation of heavy neutrinos can be a source of BAU
CPV in oscillation and production generates asymmetries Asymmetries are separated into LH and RH leptons Asymmetry in LH leptons is converted into BAU
Akhmedov, Rubakov, Smirnov (’98) / TA, Shaposhnikov (‘05)
Yield of BAU depends on Yukawa couplings and masses
Shaposhnikov (’08), Canetti, Shaposhnikov (‘10)TA, Ishida (‘10), Canetti, Drewes, Shaposhnikov (’12), TA, Eijima, Ishida (‘12)Canetti, Drewes, Shaposhnikov (‘12), Canetti, Drewes, Frossard, Shaposhnikov (‘12)
Especially, CP violating parametersand mass difference~ /
15/11/2013Takehiko Asaka (Niigata Univ.)
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Baryogenesis via neutrino osc.Region accounting for
Canetti, Shaposhnikov ‘10
IH
NH
Takehiko Asaka (Niigata Univ.) 15/11/2013
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8.55-9.00) 10
Baryogenesis via neutrino osc.Region accounting for
(1) quasi-degenerate(2) masses are
TA, Eijima ‘13
10-410-310-210-1100101102103104105106107
10-4 10-3 10-2 10-1 100
ΔΜ [e
V]
MN[GeV]
Two RH neutrino case
NHIH2.1 MeV (NH)0.7 MeV (IH)
Takehiko Asaka (Niigata Univ.) 15/11/2013
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8.55-9.00) 10
Baryogenesis via neutrino osc.Region accounting for
(1) quasi-degenerate(2) masses are
TA, Eijima ‘13
10-410-310-210-1100101102103104105106107
10-4 10-3 10-2 10-1 100
ΔΜ [e
V]
MN[GeV]
Two RH neutrino case
NHIH2.1 MeV (NH)0.7 MeV (IH)
Takehiko Asaka (Niigata Univ.) 15/11/2013
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8.55-9.00) 10
Such light RH neutrinos can be directly tested by experiments!
Direct search experiment PS191
Beam dump experimentperformed at CERN in 1984
Production Detection
Upper bounds mixing elements → Lower bound on lifetime of
[Bernardi et al ‘86, ’88]
, → ⟶ ℓ ℓ , ℓ
Takehiko Asaka (Niigata Univ.) 15/11/2013
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BBN constraint on lifetime Long-lived , may spoil the success of BBN
Speed up the expansion of the universe , ⇒ p-n conv. decouples earlier ⟹ overproduction of He
Distortion of spectrum of active neutrinos , → ̅ , , … Additional neutrinos may not be thermalized⇒ Upper bound on lifetime
Dolgov, Hansen, Rafflet, Semikoz (’00) One family case:
⟷ , …
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0.1 secfor
Constraints on light RH neutrinos
10-3
10-2
10-1
100
200 300 400τ N
[sec
]MN[MeV]
10-3
10-2
10-1
100
200 300 400
τ N [s
ec]
MN [MeV]
Cosmology
Direct search
Normal hierarchy Inverted hierarchy
MeV MeVMeV
TA, Eijima ‘13
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Implication to 0 2decay
§
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Constraints on light RH neutrinos
10-3
10-2
10-1
100
200 300 400τ N
[sec
]MN[MeV]
10-3
10-2
10-1
100
200 300 400
τ N [s
ec]
MN [MeV]
Cosmology
Direct search
Normal hierarchy Inverted hierarchy
MeV MeVMeV
TA, Eijima ‘13
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Mixing elements in IH caseMixing elements of heavy neutrinos Θ
Mixing elements strongly depend on “ ”
We find allowed range of Majorana phase !
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Θ ΦΘ ℓ
Majorana phase in IH case
η/π
MN [MeV]
0
0.5
1
200 250 300 350 400
sin ~1 sin ~0.3 all is allowed
→→ +cc→→ +cc
Majorana phase is restricted for MeV!
Excluded by BBN +PS191
Excluded by BBN +PS191
Takehiko Asaka (Niigata Univ.) 15/11/2013
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decays in IHEffective neutrino mass from light and heavy neutrinos
mef
f [10
-2eV
]
MN [MeV]
1
2
3
4
5
200 250 300 350 400
Θ 1 TA, Eijima, Ishida (‘11)
0~
cos cos sin 2 cos sin / Heavy neutrinos give
negative contribution to
Constraint on restricts the predicted range of
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Search for heavy neutrinos at T2K
§
TA, Eijima, Watanabe[JHEP1303 (2013) 125]
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Constraints on light RH neutrinos
10-3
10-2
10-1
100
200 300 400τ N
[sec
]MN[MeV]
10-3
10-2
10-1
100
200 300 400
τ N [s
ec]
MN [MeV]
Cosmology
Direct search
Normal hierarchy Inverted hierarchy
MeV MeVMeV
TA, Eijima ‘13
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Search for heavy neutrinos at T2K
SK
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Search for heavy neutrinos at T2K
Production of Detection of
Estimate flux of at ND280 Count # of signal decay inside ND280 Derive upper bounds on mixing angles
SK
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Sensitivity: PS191 vs T2K
T2K at 10 POT has a better sensitivity than PS191 (0.86 10 POT) !
PS191
T2K
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Signal vs Background Signal events:
BG events:
To reduce BG, Use the invariant mass distribution of ℓ and
since it has a peak at for signal decay Use the low density part of detector filled with argon gas
(9m^3) out of 61.25m^3
See also the recent proposal to search for heavy neutrinos at the CERN SPS. (Shaposhnikov’s talk)
→ℓ→ (CC- )O → O (CC-coherent )
Takehiko Asaka (Niigata Univ.) 15/11/2013
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arXiv:1310.1762
Summary We have considered the model with two right-handed neutrinos
which are lighter than charged Kaon.
We have found the possible region for neutrino oscillations and BAU, allowed from search and cosmological constraints.
We have discussed search for such right-handed neutrinos at near detector ND280 of T2K experiment
Neutrino masses by seesaw mechanism Baryogenesis via neutrino oscillations Search in Kaon decays
Signal: → , inside ND280 T2K at 10 POT has a better sensitivity than PS191
Majorana phase is restricted in IH→ Distinctive feature in 0 2 decay
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Backup
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Comparison
T2K2013/4/12: 6.39x10^20 POT2013/5/8: 6.63x10^20 POT
GOAL: 7.8x10^21 POT
Takehiko Asaka (Niigata Univ.) 15/11/2013
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Neutrino Yukawa couplings for ,1/2 1/2
PMNS /NF U D Dν= Ω Φ
2 31/2 diag( , )ND M M=
1 2 31/2 diag( , , )0D m m mν = =
0 0
cos sin
sin cos
ω ωω ωξ ξ
Ω = −
12 13 12 13 13
PMNS 23 12 23 12 13 23 12 23 12 13 23 13
23 12 23 12 13 23 12 23 12 13 23 13
1
1
i
i i i
i i
c c s c s e
U c s s c s e c c s s s e s c e
s s c c s e s c c s s e c c
δ
δ δ η
δ δ
−
= − − −
− − −
[Casas, Ibarra ’01]
Parameters of active neutrinos
Parameters of sterile neutrinos
: active ν masses
: sterile ν masses
1ξ = ±
Dirac phase δ
Imω
(in NH)
Majorana phase η
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:complex number
Effective neutrino mass , , , , Θ
active neutrinos sterile neutrinos
[Blennow, Frenandez-Martinez,Pavon, Mnendez ’10]
/ 0
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in the MSM
in the νMSM is smaller than active ’s one
No significant constraint on Θ in the νMSM !
10-5
10-4
10-3
10-2
10-1
10-2 10-1 100 101
|meff|[eV
]
MN[GeV]
10-5
10-4
10-3
10-2
10-1
10-2 10-1 100 101
|meff|[eV
]
MN[GeV]
NH case IH case
[TA, Eijima, Ishida ’11]
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