probing origins ofneutrino masses and baryon...

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

2

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


3

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=


4


221 /TD D M

M


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


5


221 /TD D M

M


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


6

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

§


8

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~ /


9

Baryogenesis via neutrino osc.Region accounting for

Canetti, Shaposhnikov ‘10

IH

NH


10

8.55-9.00) 10


(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)


11

8.55-9.00) 10


(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)


12

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


13

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:

⟷ , …


14

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


15

Implication to 0 2decay

§


16


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


MeV MeVMeV

TA, Eijima ‘13


17

Mixing elements in IH caseMixing elements of heavy neutrinos Θ

Mixing elements strongly depend on “ ”

We find allowed range of Majorana phase !


18

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


19

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


20

Search for heavy neutrinos at T2K

§

TA, Eijima, Watanabe[JHEP1303 (2013) 125]


21


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


MeV MeVMeV

TA, Eijima ‘13


22


SK


23


Production of Detection of

Estimate flux of at ND280 Count # of signal decay inside ND280 Derive upper bounds on mixing angles

SK


24

Sensitivity: PS191 vs T2K

T2K at 10 POT has a better sensitivity than PS191 (0.86 10 POT) !

PS191

T2K


25

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 )


26

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


27

Backup


28

Comparison

T2K2013/4/12: 6.39x10^20 POT2013/5/8: 6.63x10^20 POT

GOAL: 7.8x10^21 POT


29

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


30

: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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probing origins ofneutrino masses and baryon...

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