On the Origin of Neutrino Mass and Lepton Number Violating Searches - PowerPoint PPT Presentation

On the Origin of Neutrino Mass and Lepton Number Violating Searches Manimala Mitra IPPP, Durham University —————————————— December 23, 2013 IOP, Bhubaneswar Manimala Mitra Neutrinos and Lepton Number Violating Searches

Outline: ◮ Experimental observations ◮ Seesaw and massive neutrinos ◮ Lepton number violating searches ◮ Neutrinoless double beta decay ◮ Underlying mechanisms ◮ canonical and beyond standard model interpretations ◮ Complementarity with collider searches ◮ Seesaw and astroparticle probe ◮ Summary Manimala Mitra Neutrinos and Lepton Number Violating Searches

Experimental Observation: Non-zero eV neutrino masses m i and mixing U from oscillation and non-oscillation experiments 21 = (7 . 0 − 8 . 09) × 10 − 5 eV 2 ∆ m 2 ∆ m 2 31 = (2 . 27 − 2 . 69) × 10 − 3 eV 2 ◮ Cosmological bound sin 2 θ 12 = 0 . 27 − 0 . 34 on the sum of light neutrino masses sin 2 θ 23 = 0 . 34 − 0 . 67 sin 2 θ 13 = 0 . 016 − 0 . 030 � i m i < 0 . 23 − 1 . 08 eV Schwetz et al., 2012 Also Fogli., et al., 2012 Planck collaboration, 2013 Super Kamiokande, Long Baseline ∼ T2K, MINOS, K2K Reactor ∼ DAYA BAY, RENO, Double CHOOZ,... Solar ∼ SNO, Borexino, SAGE, GALLEX... ——————————————————————– Manimala Mitra Neutrinos and Lepton Number Violating Searches

List of Don’t Knows Neutrino Mass ⇓ Dirac or Majorana? ◮ Dirac mass, m D ¯ ν L N R → lepton number is conserved ◮ Majorana mass, mν T C − 1 ν → lepton number is violated by two units ————————————– Lepton number is a Global U (1) symmetry of the standard model Manimala Mitra Neutrinos and Lepton Number Violating Searches

Contd Normal or Inverted? 12 ∼ 10 − 5 eV 2 and ∆ m 2 ∆ m 2 13 ∼ 10 − 3 eV 2 Lightest neutrino state ν 1 or ν 3 ?? Oscillation Experiments Manimala Mitra Neutrinos and Lepton Number Violating Searches

Contd α , β ? ◮ Majorana phases → Neutrinoless double beta decay phase δ ? ◮ CP violation in leptonic sector → Oscillation experiments? m 0 ? ◮ Lightest mass scale → Low energy observable, like beta decay, neutrinoless double beta decay with cosmology θ 23 , θ 12 and θ 13 ? ◮ Precision in the mixing angles → Oscillation experiments Manimala Mitra Neutrinos and Lepton Number Violating Searches

Behind neutrino mass: Neutrinos ∼ eV mass?? Top to neutrino mass ratio 10 12 Seesaw Gell-mann, Raymond, Slansky, Minkowski ◮ Heavy modes integrated out ⇒ ˆ O = LLφφ M ⇒ Weinberg d=5 operator y 2 LL � φ �� φ � ⇒ m ν ⇒ Neutrino Mass ◮ M ◮ For M = 10 15 GeV, neutrino mass of eV is generated with y ∼ O (1) Manimala Mitra Neutrinos and Lepton Number Violating Searches

Contd Tree Level Mass Generation Type-II ← Seesaw → Type-I or Type-III ◮ ◮ Intermediate state bosonic/fermionic ◮ Type-I seesaw: Intermediate state fermionic gauge singlet ◮ Type-III seesaw: SU (2) triplet fermion with Y = 0 ◮ Type-II seesaw: SU (2) triplet scalar with Y = − 2 Manimala Mitra Neutrinos and Lepton Number Violating Searches

Contd: Type-I Type-II φ φ Type-III φ φ φ φ µ ∆ N R Y † Y N Σ R N Y † Y Σ ∆ Σ Y ∆ ℓ ℓ ℓ ℓ ℓ ℓ φ φ ⇓ ℓ ℓ Manimala Mitra Neutrinos and Lepton Number Violating Searches

Type-I/III Seesaw Add gauge singlet fermionic field N R or SU (2) triplet fermion Σ Lagrangian: −L ν = Y ν L ˜ HN R + 1 2 N c R MN R + h . c Lagrangian: � � � Σ R i Σ C ′ � Y lij l R i H † L j + Y Σ ij ˜ 1 H † Σ R i L j + h.c. −L Y = + 2 M Σ ij Tr R j + h.c. √ � Σ 0 / � Σ + 2 √ SU (2) triplet, Y = 0 fermion field, Σ = Σ − − Σ 0 / 2 M , M Σ ◮ Lepton Number Violation → ◮ m ν ∼ m T D M − 1 m D where m D = Y ν v ◮ For M ∼ 10 15 GeV, m ν ≃ 1 eV is generated without any fine tuning of yukawa. For M ∼ 1 TeV , we need Y ν ∼ 10 − 6 ◮ Fits within SO (10) , SU (5) Grand Unified Theory Manimala Mitra Neutrinos and Lepton Number Violating Searches

Type-II Seesaw � δ + / √ � δ ++ 2 √ ◮ Higgs triplet, ∆ (3,2), ∆ = δ 0 − δ + / 2 ◮ Lagrangian, Lagrangian: L C iτ 2 ∆ l L + µ ∆ φ T iτ 2 ∆ † φ + M ∆ Tr (∆ † ∆) + h . c + ... −L Y = y ∆ l T Lα � φ ∗ )( � C αβ ( l c φ † l Lβ ) ◮ Integrating out heavy Higgs triplet → µ ∆ ◮ C ∝ y ∆ M 2 ∆ ◮ M ν ∝ y ∆ v 2 µ ∆ M 2 ∆ ◮ Light neutrino mass is proportional to µ Manimala Mitra Neutrinos and Lepton Number Violating Searches

Inverse Seesaw Add singlet fermionic fields N, S . . Small lepton number violating scale µ   m T 0 0 D   M T M ν = m D 0 0 M µ Mohapatra, PRL, 86 D M T − 1 µM − 1 m D m ν ∼ m T ◮ For µ ≪ m D < M → µ → Lepton number violation. µ → 0 = ⇒ M ν → 0 and enhanced lepton number symmetry. Inverse seesaw ———————————————————————— Loop generated mass? Radiative inverse seesaw ( Dev, Pilaftsis, 2012 ) Supersymmetry (R-parity violation) and neutrino mass Manimala Mitra Neutrinos and Lepton Number Violating Searches

Phenomenologies Astroparticle Physics → leptogenesis, dark matter, ... Collider Phenomenologies → lepton number and flavor violation Low Energy Experiments → lepton number and flavor violation Lepton Number Violating Searches Manimala Mitra Neutrinos and Lepton Number Violating Searches

Neutrinoless double beta decay The process is ( A, Z ) → ( A, Z + 2) + 2 e − Probing lepton number violation Manimala Mitra Neutrinos and Lepton Number Violating Searches

Why important? u L d L W e − L ν W W d d e − u u L W u L ν e d L ν e e − e − Schechter-Valle, PRD, 82 Information about the effective mass m ν ee Majorana Nature of Light Neutrinos ————————— L and B numbers are accidental symmetries of the standard model Manimala Mitra Neutrinos and Lepton Number Violating Searches

contd ◮ Chiral anomalies ∂ µ j µ B,L � = 0 ◮ The low energy effective Lagrangian O 5 O 6 L eff = L SM + ξ 1 M + ξ 2 M 2 + ... ◮ O 5 → LNV, O 6 → LFV, BNV ◮ Lepton and Baryon number violation might originate from high scale theory Not only mass measurement! 0 ν 2 β is a probe of lepton number violation Manimala Mitra Neutrinos and Lepton Number Violating Searches

Experimental Results Experimental Results for 76 Ge ◮ Heidelberg-Moscow, T 0 ν 1 / 2 > 1 . 9 × 10 25 yr , 90% C.L H. V. Klapdor-Kleingrothaus et al. , 2001 ◮ GERDA, T 0 ν 1 / 2 > 2 . 1 × 10 25 yr , 90% C.L ◮ GERDA combined (IGEX+Heidelberg-Moscow) T 0 ν 1 / 2 > 3 . 0 × 10 25 yr , 90% C.L GERDA collaboration, 2013 ———————————— Experimental Results for 136 Xe ◮ EXO-200, T 0 ν 1 / 2 > 1 . 6 × 10 25 yr at 90% C.L EXO collaboration, 2012 ◮ KamLAND-Zen, T 0 ν 1 / 2 > 1 . 9 × 10 25 yr at 90% C.L ◮ KamLAND-Zen combined, T 0 ν 1 / 2 > 3 . 4 × 10 25 yr at 90% C.L KamLAND-Zen collaboration, 2012 Manimala Mitra Neutrinos and Lepton Number Violating Searches

Contd Positive Claim − 0 . 23 × 10 25 yr, 68 % CL. 1 / 2 = 1 . 19 +037 ◮ The half-life for 76 Ge , T 0 ν H. V. Klapdor-Kleingrothaus et al. , 2004 − 0 . 31 × 10 25 yr, 68 % CL. 1 / 2 = 2 . 23 +0 . 44 ◮ The half-life for 76 Ge , T 0 ν H. V. Klapdor-Kleingrothaus et al. , 2006 slide courtesy: W. Rodejohann Manimala Mitra Neutrinos and Lepton Number Violating Searches

Future Experiments Slide courtesy: W. Rodejohann 1 / 2 ∼ 10 26 / 10 27 yrs Future experiments → expected sensitivity T 0 ν Manimala Mitra Neutrinos and Lepton Number Violating Searches

Contd 1 / 2 = G 0 ν |M ( A, Z ) η | 2 1 T 0 ν ◮ G 0 ν → Phase space factor ◮ M ( A, Z ) → Nuclear matrix element ◮ η → Particle physics parameter 1 / 2 ∝ η 2 → Quadratic in particle physics parameter 1 T 0 ν Improvement of η by O (0 . 1) requires improvement of half life T 0 ν 1 / 2 by O (10 2 ) Manimala Mitra Neutrinos and Lepton Number Violating Searches

The light neutrino contribution 1 / 2 = G 0 ν |M ν | 2 � � 2 � � � m ν 1 The half-life → ee � T 0 ν m e 1 ◮ G 0 ν → phase-space Positive claim 90 � GERDA 90 � GERDA � HDM � IGEX 90 � 0.1 IH QD ◮ M ν → nuclear matrix Ν � � eV � element 0.01 NH � m ee ◮ m ν ee = Σ m i U 2 Planck1 KATRIN Planck2 ei 0.001 effective mass of 0 ν 2 β 10 � 4 10 � 5 10 � 4 0.001 0.01 0.1 1 m lightest � eV � e 2 e 2 iα + m 3 U 2 | m ν ee | = | m 1 U 2 e 1 + m 2 U 2 e 3 e 2 iβ | ◮ α , β → Majorana phase, m i → light neutrino masses ◮ Unknown → neutrino mass spectra, absolute mass scale, CP phases Manimala Mitra Neutrinos and Lepton Number Violating Searches