Physics of right-handed neutrinos -- tests of the seesaw mechanism - - PowerPoint PPT Presentation

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Physics of right-handed neutrinos -- tests of the seesaw mechanism - - PowerPoint PPT Presentation

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Physics of right-handed neutrinos -- tests of the seesaw mechanism -- () @YITP TA, Tsuyuki arXiv:1508.04937 TA, Tsuyuki arXiv:1509.02678 @YITP , Kyoto

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Physics of right-handed neutrinos

  • - tests of the seesaw mechanism --

@YITP , Kyoto (2015/09/16)

淺賀 岳彦 (新潟⼤学)

基研研究会 素粒⼦物理学の進展２０１５@YITP

TA, Tsuyuki arXiv:1508.04937 TA, Tsuyuki arXiv:1509.02678

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Plan of this talk

2015/09/16 Takehiko Asaka (Niigata Univ.) 2  Introduction  the seesaw mechanism for neutrino masses  Limits on heavy neutral leptons in the seesaw mechanism  neutrino masses, cosmology, direct/indirect searches  Lepton number violation in the seesaw mechanism  neutrinoless double beta decay  → (“inverse neutrinoless double beta decay”)  Perturbativity in the seesaw mechanism  Summary

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Introduction

2015/09/16

3

Takehiko Asaka (Niigata Univ.)

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Origin of neutrino masses

2015/05/16 Takehiko Asaka (Niigata Univ.) 4  Neutrino mass scales  Atmospheric:

  • ≃ 2.4 10eV

 Solar：

  • ≃ 7.5 10eV

⇒ Clear signal for new physics beyond the SM !

 Important questions:

 What is the origin of neutrino masses?  What are the implications to other physics?  How do we test it experimentally?

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RH Neutrinos and Seesaw Mechanism

 Seesaw mechanism ( Φ ≪ )  Light active neutrinos

→ explain neutrino oscillations

 Heavy neutral leptons

 Mass  Mixing Θ /

+ h.c. 2

c M R R R R R

M L i F L

 

           

1 1 ( , ) . ( , ) . . 2 2

c c D c L L R T D R c M M

M M L h c h c M N M N M

                                 

  • 1

T D D M

M M M M

   1 2 3

( , , )

T

U M U diag m m m

  • mixing in CC current

Minkowski ʼ77 Yanagida ʼ79 Gell-Mann, Ramond, Slansky ʻ79 Glashow ʻ79 2015/05/16 Takehiko Asaka (Niigata Univ.) 5

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Review of Particle Physics

2015/05/16 Takehiko Asaka (Niigata Univ.) 6

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Yukawa Coupling and Mass of HNL

2015/05/16 Takehiko Asaka (Niigata Univ.) 7

10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 10-10 10-5 100 105 1010 1015 1020 F MN [GeV]

  • Φ

5 10 GeV Seesaw does not work !

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Yukawa Coupling and Mass of HNL

2015/05/16 Takehiko Asaka (Niigata Univ.) 8

10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 10-10 10-5 100 105 1010 1015 1020 F MN [GeV]

  • Φ

5 10 GeV Seesaw does not work !

Leptogenesis (Fukugita, Yanagida ʻ86) Baryogenesis via neutrino oscillation (Akhmedov, Rubakov, Smirnov ʼ98, TA, Shaposhnikov ʼ05) Resonant Leptogenesis (Pilaftsis, Underwood ʻ04)

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Mixing and Mass of HNL

2015/05/16 Takehiko Asaka (Niigata Univ.) 9

10-30 10-25 10-20 10-15 10-10 10-5 100 10-10 10-5 100 105 1010 1015 1020 |Θ|2 MN [GeV] Θ

  • 5 10 GeV

Leptogenesis Baryogenesis via neutrino oscillation Resonant Leptogenesis

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  • Φ
  • Important parameters of HNL

2015/09/16 Takehiko Asaka (Niigata Univ.) 10  Interactions of HNL  Two key parameters of HNL  mass  mixing

  • ,

ℓ,

gauge interaction through mixing Yukawa interaction

Θ

  • Θ

 relevant for search experiments

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Limits on HNLs in the seesaw mechanism

2015/09/16

11

Takehiko Asaka (Niigata Univ.)

See, for example, the recent analysis Deppisch, DeV, Pilaftsis (arXiv:1502.06541) and references therein.

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Limits on mixing of HNL

2015/09/16 Takehiko Asaka (Niigata Univ.) 12  Limits on mixing Θ

Deppisch, Dev, Pilaftis ʻ15

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Limits on mixing of HNL

2015/09/16 Takehiko Asaka (Niigata Univ.) 13  Limits on mixing Θ

Deppisch, Dev, Pilaftis ʻ15

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Limits on mixing of HNL

2015/09/16 Takehiko Asaka (Niigata Univ.) 14  Limits on mixing Θ

Deppisch, Dev, Pilaftis ʻ15

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Limits on mixing of HNL

2015/09/16 Takehiko Asaka (Niigata Univ.) 15  Limits on mixing Θ

Deppisch, Dev, Pilaftis ʻ15

Seesaw Search

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Bound from seesaw mechanism

2015/09/16 Takehiko Asaka (Niigata Univ.) 16  Mixings of HNL must be sufficiently large

to explain masses of active neutrinos !

 Bound on the mixing of the lightest HNL

Θ

  • Θ ≡
  • Θ

,,

NOTE: Θ can be zero for 3 in the NH (IH) for 3RHN ( 3) in the NH (IH) for 2RHN ( 2)

TA, Tsuyuki ʻ15

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Limits on mixing of HNL

2015/09/16 Takehiko Asaka (Niigata Univ.) 17  Limits on mixing Θ

Deppisch, Dev, Pilaftis ʻ15

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Seesaw relation between mixings

2015/09/16 Takehiko Asaka (Niigata Univ.) 18  Neutrino mass matrix  When Θ ≫ /,  Cancellation between HNLs is required  fine tuning  Stability of this relation can be ensured by some symmetry  This relation is crucial in physics of right-handed neutrinos

in the seesaw mechanism

  • ,,
  • Θ Θ
  • Seesaw relation

Kersten, Sumirnov ʼ07, …

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Limits on mixing of HNL

2015/09/16 Takehiko Asaka (Niigata Univ.) 19  Limits on mixing Θ

Deppisch, Dev, Pilaftis ʻ15

Seesaw Search

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BBN constraint on lifetime

07 March, 2011 Takehiko Asaka (Niigata Univ.) 20  Long-lived HNLs 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 ⇒ Lower bound on mixing

⟷ , …

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Lifetime bound from BBN

2015/09/16 Takehiko Asaka (Niigata Univ.) 21

20 40 60 80 100 120 140 0.1 0.2 0.5 1.0 2.0 5.0 10.0 Mass M s MeV Lifetim e Τs sec Mixing with Νe EXCLUDED REGION Present result Dolgov et al. 20 40 60 80 100 120 140 0.1 0.2 0.5 1.0 2.0 5.0 10.0 Mass M s MeV Lifetim e Τs sec Mixing with ΝΜ EXCLUDED REGION Present result Dolgov et al.

(sec) (sec)

  • 128.7

1699 0.04179 0.0544

  • 1.828
  • 2.652

,

  • Dolgov, Hansen, Raffelt, Semikoz ʻ00

Ruchayski, Ivashkov ʻ12

0.1 sec

/MeV

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Limits on mixing of HNL

2015/09/16 Takehiko Asaka (Niigata Univ.) 22  Limits on mixing Θ

Deppisch, Dev, Pilaftis ʻ15

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Limits on mixing of HNL

2015/09/16 Takehiko Asaka (Niigata Univ.) 23  Limits on mixing Θ

Deppisch, Dev, Pilaftis ʻ15

Seesaw Search

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Indirect search (EWPD)

2015/09/16 Takehiko Asaka (Niigata Univ.) 24  PMNS mixing matrix of active neutrinos is not “UNITARY”

 Impact of non-unitarity on decay: → ̅

 Upper bound from EW precision data (EWPD)

(

, Γ → ̅ , Γ, Γ → ℓ , , lepton universality, CKM elements, )

Θ

  • ΘΘ 1

Γ Γ

  • 2/8
  • Θ 2.1 10 , Θ

4 10 , Θ 5.3 10

Antusch, Fischer ʻ14 @90% CL

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Direct searches

07 March, 2011 Takehiko Asaka (Niigata Univ.) 25  Peak search in meson decays ( → ℓ )  Measure in →  Beam dump experiments

⟶ ℓ ℓ . .

  • 2

events → → ν

[Shrock ʼ80]

→

  • CERN

PS191  SHiP , LBNE (now DUNE)

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Direct searches

2015/09/16 Takehiko Asaka (Niigata Univ.) 26  Search @LEP  →

(3.3 10 )  FCC-ee (10 )

 Search @LEPII  → ( → with → )

 ILC ( 500 GeV, 500 fb)

 Search @LHC  → ℓ → ℓ ℓ  Search @LHCb  → →  Search @Belle  → ℓ, → ∓ , ∓

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Limits on mixing of HNL

2015/09/16 Takehiko Asaka (Niigata Univ.) 27  Limits on mixing Θ

Deppisch, Dev, Pilaftis ʻ15

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Lepton number violation in the seesaw mechanism

2015/09/16

28

Takehiko Asaka (Niigata Univ.)

1) Neutrinoless double beta decay 2) Inverse neutrinoless double beta decay

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Neutrinoless double beta ( ) decay

2015/03/21 Takehiko Asaka (Niigata Univ.) 29  Neutrinoless double beta (0ν) decay  LNV (Δ 2 process mediated

by Majorana massive neutrinos

 Half-life of 0 decay

W.H. Furry 1939

  • ,,

… , → 2, 2

  • Faessler, Gonzalez, Kovalenko, Simkovic ʻ14
  • /
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decay

2015/03/21 Takehiko Asaka (Niigata Univ.) 30  Contribution from active neutrinos

  • ,,

Planck 2015 Σ 0.23 eV ≲ 0.185 0.276 eV 0.07 0.06 eV ≲ 0.213 0.308 eV

KamLAND-Zen 1211.3863

Xe

GERDA 1307.4720

Ge

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decay in the seesaw

 HNLs may give a significant

contribution to !

,,

  • Θ
  • active neutrinos

heavy neutral leptons

2015/05/16 Takehiko Asaka (Niigata Univ.) 31

  • Θ
  • Θ
  • Faessler, Gonzalez, Kovalenko, Simkovic ʻ14
  • =

Θ

  • Θ
  • (

≪ )

(

≫ )

~ 200 MeV

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decay in the seesaw

2015/09/16 Takehiko Asaka (Niigata Univ.) 32  Stringent constraint on the mixing:

Atre, Han, Pascoli, Zhang ʻ09 Deppisch, Dev, Pilaftsis ʻ15

This bound cannot be applied to some cases in the seesaw mechanism !

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decay in the seesaw

2015/09/16 Takehiko Asaka (Niigata Univ.) 33  Seesaw relation plays an important role !  When all HNLs are light ≪

~0.1 GeV (i.e.

1),

 This shows 0 decay does not occur even if neutrinos are

Majorana fermions.

 In this case, there is no bound on the mixing from 0

decay

  • Θ
  • Θ
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decay in the seesaw

2015/09/16 Takehiko Asaka (Niigata Univ.) 34  When all HNLs are degenerate ,  This shows 0 decay does not depend on the mixing of HNL  In this case, there is no bound on the mixing from 0 decay

  • Θ
  • m

1

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 IH

TA, Eijima, Ishida ʻ11

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Another example of LNV:

  • 2015/09/16

35

Takehiko Asaka (Niigata Univ.)

  • 0 decay

Inverse 0 decay

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Inverse neutrinoless double beta (i) decay

2015/09/16 Takehiko Asaka (Niigata Univ.) 36  → offers test for LNV  collision is option of ILC, CLIC  Advantages over 0 decay

 Signal is clean  Free from uncertainty in nuclear matrix elements  Can occur even if 0 decay is absent

 Inverse 0 decay and 0 decay are complementary tests for LNV in the seesaw mechanism

[T. G. Rizzo 1982]

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Inverse decay in the seesaw

2015/09/16 Takehiko Asaka (Niigata Univ.) 37  Maximal cross section of →

2 3

TA, Tsuyuki ʻ15

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Inverse decay in the seesaw

2015/09/16 Takehiko Asaka (Niigata Univ.) 38  How obtain large cross section ? --- idea

# of right-handed neutrinos 3

 Even with the seesaw relation and the 0 bound,

the mixing of can be large as

  • ~

large Θ Seesaw relation

0≃ Θ

Θ

  • 0≃ Θ
  • Θ
  • Θ Θ
  • 2.1 10

 Large →

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Inverse decay in the seesaw

2015/09/16 Takehiko Asaka (Niigata Univ.) 39  Sensitivity of mixing (@100 fb)

10-14 10-12 10-10 10-8 10-6 10-4 10-2 1 10-1 1 101 102 103 104 105 |Θ1|2 M1 [GeV]

FCC-ee DELPHI ILC EWPD i0νββ

S e e s a w , N H

SHiP LBNE

IH

B-factory CHARM BBN

TA, Tsuyuki ʻ15

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LNV in the seesaw

2015/09/16 Takehiko Asaka (Niigata Univ.) 40  Comments on inverse 0 decay  Polarized beams

 cross section becomes four times larger  turned on/off by flipping beam polarization

 To avoid the 0 bound,

HNL with and Θ

  • Θ is required

 good target for experimental searches

 Inverse 0 is severely restricted from perturbativity  Other LNV processes in the seesaw mechanism  → ℓ → ℓ ℓ

@LHC

 → ℓ → ℓ ℓ @SuperKEKB  → ℓ → ℓ ℓ @J-PARC  …

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Perturbativity in the seesaw mechanism

2015/09/16

41

Takehiko Asaka (Niigata Univ.)

TA, Tsuyuki arXiv:1509.02678

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Testability of HNL

2015/09/16 Takehiko Asaka (Niigata Univ.) 42  HNL can be observed if it has sufficiently small mass

and large mixing Θ ≫ /

10-14 10-12 10-10 10-8 10-6 10-4 10-2 1 10-1 1 101 102 103 104 105 |Θ1|2 M1 [GeV]

FCC-ee DELPHI ILC EWPD i ν β β

Seesaw, NH

SHiP LBNE

IH

B-factory CHARM BBN

What is implication of with large mixing?

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Implication of

with large mixing

2015/09/16 Takehiko Asaka (Niigata Univ.) 43  Seesaw relation:  There exists at least one HNL to cancel the contribution !  Mixings:  Yukawa couplings:  Perturbativity gives the upper bound on the mixing

Θ Θ

  • Θ

Θ

Θ

  • Θ
  • Φ Θ
  • : # of RHNs

Θ Θ

  • Φ
  • 4 1 Φ
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Perturbativity in the seesaw mechanism

2015/09/16 Takehiko Asaka (Niigata Univ.) 44  Upper bound on mixing

10-30 10-25 10-20 10-15 10-10 10-5 1 1 102 104 106 108 1010 1012 1014 1016 1018 |Θ1|2 M1 [GeV] S e e s a w M2=109 GeV M2=M1 no RGE

2

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Implication to high energy phenomena

2015/09/16 Takehiko Asaka (Niigata Univ.) 45

10-14 10-12 10-10 10-8 10-6 10-4 10-2 1 10-1 1 101 102 103 104 105 |Θ1|2 M1 [GeV]

FCC-ee DELPHI ILC EWPD i0νββ

M2=109 GeV 1013 GeV 105 GeV

Seesaw, NH

M2=M1

S H i P LBNE

I H

B-factory CHARM BBN

If HNL with ~10 GeV and Θ ~10 is discovered, perturbativity requires 10 GeV ! Leptogenesis is disfavored !

HNL searches at low energy can probe high energy phenomena such as leptognesis !

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Summary

2015/09/16

46

Takehiko Asaka (Niigata Univ.)

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Summary

2015/09/16 Takehiko Asaka (Niigata Univ.) 47  Right-handed neutrinos are well-motivated physics beyond the

Standard Model

 They can explain neutrino masses through the seesaw

mechanism and baryon asymmetry of the universe (BAU) (via leptogenesis, neutrino oscillation, …) at the same time.

 Experimental tests of such right-handed neutrinos are

important to understand the origin of neutrino masses and BAU