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

Physics of right-handed neutrinos -- tests of the seesaw mechanism -- 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 @YITP , Kyoto (2015/09/16)

Plan of this talk 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 Takehiko Asaka (Niigata Univ.) 2015/09/16

3 Introduction Takehiko Asaka (Niigata Univ.) 2015/09/16

Origin of neutrino masses 4  Neutrino mass scales  Atmospheric: �� ��� � ≃ 2.4 � 10 �� eV � �  Solar： �� ��� ≃ 7.5 � 10 �� eV � ⇒ 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? Takehiko Asaka (Niigata Univ.) 2015/05/16

5 RH Neutrinos and Seesaw Mechanism Minkowski ʼ77 M Yanagida ʼ79              c M + h.c. L i F L Gell-Mann, Ramond, Slansky ʻ79  R R R R R 2 Glashow ʻ79  Seesaw mechanism ( � � � � Φ ≪ � � )           c 0 0 c M M 1 1          D c L c     ( , )   . ( , )   . . L h c N h c L R  T    0  2 M M   2 M  N D M M R 1    T M M M D D M M  Light active neutrinos  T ( , , ) U M U diag m m m  1 2 3 → explain neutrino oscillations  Heavy neutral leptons �  Mass � �  Mixing Θ � � � /� � � mixing in CC current � Takehiko Asaka (Niigata Univ.) 2015/05/16

Review of Particle Physics 6 Takehiko Asaka (Niigata Univ.) 2015/05/16

Yukawa Coupling and Mass of HNL 7 � � � � � � Φ � � � 5 � 10 ��� GeV 10 2 10 1 10 0 Seesaw 10 -1 does 10 -2 not 10 -3 work ! 10 -4 10 -5 10 -6 F 10 -7 10 -8 10 -9 10 -10 10 -11 10 -12 10 -13 10 -14 10 -10 10 -5 10 0 10 5 10 10 10 15 10 20 M N [GeV] Takehiko Asaka (Niigata Univ.) 2015/05/16

Yukawa Coupling and Mass of HNL 8 � � � � � � Φ � � � 5 � 10 ��� GeV 10 2 10 1 10 0 Seesaw 10 -1 does 10 -2 not 10 -3 work ! 10 -4 Leptogenesis 10 -5 (Fukugita, Yanagida ʻ86) 10 -6 F 10 -7 Resonant Leptogenesis 10 -8 (Pilaftsis, Underwood ʻ04) 10 -9 10 -10 Baryogenesis via neutrino oscillation 10 -11 (Akhmedov, Rubakov, Smirnov ʼ98, 10 -12 TA, Shaposhnikov ʼ05) 10 -13 10 -14 10 -10 10 -5 10 0 10 5 10 10 10 15 10 20 M N [GeV] Takehiko Asaka (Niigata Univ.) 2015/05/16

Mixing and Mass of HNL 9 � Θ � � � � � � � � � � � 5 � 10 ��� GeV � � � � 10 0 Baryogenesis via neutrino oscillation 10 -5 10 -10 Resonant Leptogenesis | Θ | 2 10 -15 Leptogenesis 10 -20 10 -25 10 -30 10 -10 10 -5 10 0 10 5 10 10 10 15 10 20 M N [GeV] Takehiko Asaka (Niigata Univ.) 2015/05/16

Important parameters of HNL 10  Interactions of HNL gauge interaction through mixing Yukawa interaction �, � Φ � � � � ℓ � , � � � � � Θ �� � ��  relevant for search experiments  Two key parameters of HNL  mass � �  mixing Θ �� Takehiko Asaka (Niigata Univ.) 2015/09/16

11 Limits on HNLs in the seesaw mechanism See, for example, the recent analysis Deppisch, DeV, Pilaftsis (arXiv:1502.06541) and references therein. Takehiko Asaka (Niigata Univ.) 2015/09/16

Limits on mixing of HNL 12  Limits on mixing Θ �� Deppisch, Dev, Pilaftis ʻ15 Takehiko Asaka (Niigata Univ.) 2015/09/16

Limits on mixing of HNL 13  Limits on mixing Θ �� Deppisch, Dev, Pilaftis ʻ15 Takehiko Asaka (Niigata Univ.) 2015/09/16

Limits on mixing of HNL 14  Limits on mixing Θ �� Deppisch, Dev, Pilaftis ʻ15 Takehiko Asaka (Niigata Univ.) 2015/09/16

Limits on mixing of HNL 15  Limits on mixing Θ �� Deppisch, Dev, Pilaftis ʻ15 Search Seesaw Takehiko Asaka (Niigata Univ.) 2015/09/16

Bound from seesaw mechanism 16  Mixings of HNL must be sufficiently large to explain masses of active neutrinos !  Bound on the mixing of the lightest HNL � � TA, Tsuyuki ʻ15 Θ � � � � � Θ � � ≡ Θ �� � � � � ���,�,� � � � � in the NH (IH) for 3RHN ( � � 3 ) � � � � � � � in the NH (IH) for 2RHN ( � � 2 ) NOTE: Θ � � can be zero for � � 3 Takehiko Asaka (Niigata Univ.) 2015/09/16

Limits on mixing of HNL 17  Limits on mixing Θ �� Deppisch, Dev, Pilaftis ʻ15 Takehiko Asaka (Niigata Univ.) 2015/09/16

Seesaw relation between mixings 18  Neutrino mass matrix � � � � ���� � � �� � � � � � � � � � �� � � � � � � � � � �� Seesaw relation 0 � � � � � �� � �� � � � � Θ �� Θ �� ���,�,� �  When Θ � � ≫ � � /� � ,  Cancellation between HNLs is required  fine tuning  Stability of this relation can be ensured by some symmetry Kersten, Sumirnov ʼ07, …  This relation is crucial in physics of right-handed neutrinos in the seesaw mechanism Takehiko Asaka (Niigata Univ.) 2015/09/16

Limits on mixing of HNL 19  Limits on mixing Θ �� Deppisch, Dev, Pilaftis ʻ15 Search Seesaw Takehiko Asaka (Niigata Univ.) 2015/09/16

BBN constraint on lifetime 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 Takehiko Asaka (Niigata Univ.) 07 March, 2011

Lifetime bound from BBN 21 10.0 Dolgov, Hansen, Raffelt, Semikoz ʻ00 Ruchayski, Ivashkov ʻ12 Mixing with Ν e 5.0 � � � � � Lifetim e Τ s � sec � 2.0 Present result � � � � � � � /MeV � � � � 1.0 EXCLUDED REGION 0.5 Dolgov et al. 0.2 � � (sec) � � (sec) � 0.1 -1.828 128.7 0.04179 � -2.652 0.0544 �, � 1699 20 40 60 80 100 120 140 Mass M s � MeV � 10.0 Mixing with Ν Μ 5.0 � � � � � Lifetim e Τ s � sec � 2.0 Present result � � � 0.1 sec 1.0 EXCLUDED REGION 0.5 Dolgov et al. 0.2 0.1 20 40 60 80 100 120 140 Mass M s � MeV � Takehiko Asaka (Niigata Univ.) 2015/09/16

Limits on mixing of HNL 22  Limits on mixing Θ �� Deppisch, Dev, Pilaftis ʻ15 Takehiko Asaka (Niigata Univ.) 2015/09/16

Limits on mixing of HNL 23  Limits on mixing Θ �� Deppisch, Dev, Pilaftis ʻ15 Search Seesaw Takehiko Asaka (Niigata Univ.) 2015/09/16

Indirect search (EWPD) 24  PMNS mixing matrix � of active neutrinos is not “UNITARY” �� � � ΘΘ � � 1 � � �� � � �� � � � Θ �� � � � �  Impact of non-unitarity on � decay: � → � �̅ � � � � � � � Γ � Γ �� � �� � �� � �� � � �� �� � � � 2� � /�8� � � � � � �� � �� � �� � �� � � � � ��� � � � ��  Upper bound from EW precision data (EWPD) Antusch, Fischer ʻ14 � , Γ � → ��̅ , Γ ��� , Γ � → ℓ� , � � , lepton universality, CKM elements, ) ( � � � � 4 � 10 �� , Θ � � � 5.3 � 10 �� Θ � � � 2.1 � 10 �� , Θ � @90% CL Takehiko Asaka (Niigata Univ.) 2015/09/16

Direct searches 25  Peak search in meson decays ( � � → ℓ � � ) [Shrock ʼ80]  Measure � � in � � → � � � � � → � � ν events � � � � � � � � � � � � � � 2 � � � � → � � �  Beam dump experiments � � � � → � � � � ⟶ ℓ � ℓ � � � �. �. CERN PS191  SHiP , LBNE (now DUNE) Takehiko Asaka (Niigata Univ.) 07 March, 2011

Direct searches 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� , � → � � � ∓ , � � � ∓ Takehiko Asaka (Niigata Univ.) 2015/09/16

Limits on mixing of HNL 27  Limits on mixing Θ �� Deppisch, Dev, Pilaftis ʻ15 Takehiko Asaka (Niigata Univ.) 2015/09/16

28 Lepton number violation in the seesaw mechanism 1) Neutrinoless double beta decay 2) Inverse neutrinoless double beta decay Takehiko Asaka (Niigata Univ.) 2015/09/16