Low-energy neutrino physics

1. Low-energy neutrino physics Belén Gavela Universidad Autónoma de Madrid and IFT

2. Low-energy neutrino physics and leptogenesis Belén Gavela Universidad Autónoma de Madrid and IFT

3. What are the main physics goals in  physics? • To determine the absolute scale of masses • To determine whether they are Dirac or Majorana • * To discover Leptonic CP-violation in neutrino oscillations

4. What are the main physics goals in  physics? • To determine the absolute scale of masses • To determine whether they are Dirac or Majorana • * To discover Leptonic CP-violation in neutrino oscillations What is the relation of those putative discoveries to the matter-antimatter asymmetry of the universe? Can leptogenesis be “proved”?

5. The short, and rather accurate answer, is NO Nevertheless, a positive discovery of both 2 last points, that is: • To establish the Majorana character (neutrinoless decay) • Leptonic CP-violation in neutrino oscillations plus (at -e oscillations at superbeams, betabeams…. neutrino factory) would constitute a very compelling argument in favour of leptogenesis

6. The short, and rather accurate answer, is NO Nevertheless, a positive discovery of both 2 last points, that is: • To establish the Majorana character (neutrinoless decay) • Leptonic CP-violation in neutrino oscillations plus (at -e oscillations at superbeams, betabeams…. neutrino factory) would constitute a very compelling argument in favour of leptogenesis Go for those discoveries!

7. …..This talk deals much with the Majorana character masses ----> Beyond SM scale • * What is the prize for ~TeVwithout unnatural fine-tunings? • * What observable observable effects could we then expect?

8. No masses in the SM because the SM accidentally preserves B-L ……only left-handed neutrinos and ……only scalar doublets (Higgs)

9. No masses in the SM because the SM accidentally preserves B-L i.e. Adding singlet neutrino fields NR - • right-handed nR→ NR Y L NR + NR + Would require Y~10-12 !!! Why ns are so light??? Why nR does not acquire large Majorana mass? Y NR OK with gauge invariance L~M (RR

10. No masses in the SM because the SM accidentally preserves B-L i.e. Adding singlet neutrino fields NR - • right-handed nR→ NR Y L NR + NR + Would require Y~10-12 !!! Why ns are so light??? Why nR does not acquire large Majorana mass? NR OK with gauge invariance L~M (RR

11. No masses in the SM because the SM accidentally preserves B-L i.e. Adding singlet neutrino fields NR - • right-handed nR→ NR Y L NR + NR + Would require Y~10-12 !!! Why ns are so light??? Why nR does not acquire large Majorana mass? NR OK with gauge invariance L~M (RR Seesaw model Which allows YN~1 --> M~MGut

12. No masses in the SM because the SM accidentally preserves B-L i.e. Adding singlet neutrino fields NR - • right-handed nR→ NR Y L NR + NR + Would require Y~10-12 !!! Why ns are so light??? Why nR does not acquire large Majorana mass? NR OK with gauge invariance L~M (RR Seesaw model Which allows YN~1 --> M~MGut YN~10-6 --> M~TeV

13. masses beyond the SM Favorite options: new physics at higher scale M Heavy fields manifest in the low energy effective theory (SM) via higher dimensional operators O i L= c i Dimension 5 operator: 2 /M (L L H H) v/M ( → O d=5 It’s unique → very special role of n masses: lowest-order effect of higher energy physics c

14. masses beyond the SM Favorite options: new physics at higher scale M Heavy fields manifest in the low energy effective theory (SM) via higher dimensional operators O i L= c i Dimension 5 operator: 2 /M (L L H H) v/M ( → O d=5 It’s unique → very special role of n masses: lowest-order effect of higher energy physics This mass term violates lepton number (B-L) →Majorana neutrinos

15. masses beyond the SM Favorite options: new physics at higher scale M Heavy fields manifest in the low energy effective theory (SM) via higher dimensional operators O i L= c i Dimension 5 operator: 2 /M (L L H H) v/M ( → O d=5 It’s unique → very special role of n masses: lowest-order effect of higher energy physics This mass term violates lepton number (B-L) →Majorana neutrinos O d=5 is common to all models of Majoranas

16. Dimension 6 operators, O discriminate among models. d=6 Which are the d=6 operators characteristic of Seesaw models? (A. Abada, C. Biggio, F.Bonnet, T. Hambye +MBG )

17. n masses beyond the SM : tree level Fermionic Singlet Seesaw ( or type I) 2 x 2 = 1 + 3 m~ v2cd=5= v2YN YN /MN T

18. n masses beyond the SM : tree level Fermionic Singlet Seesaw ( or type I) (Fukugita, Yanagida) 2 x 2 = 1 + 3 LEPTOGENESIS: L NR’ NR + + NR’ H (Flanz, Paschos, Sarkar,Covi, Roulet,Vissani, Pilaftsis) H L

19. n masses beyond the SM : tree level Fermionic Triplet Seesaw ( or type III) 2 x 2 = 1 + 3 m~ v2cd=5= v2YY/M T

20. n masses beyond the SM : tree level Fermionic Triplet Seesaw ( or type III) 2 x 2 = 1 + 3 LEPTOGENESIS: T L R R’ R R + + + R’ H (Hambye, Li, Papucci, Notari, Strumia)) 

21. n masses beyond the SM : tree level Scalar Triplet Seesaw ( or type II) 2 x 2 = 1 + 3 m~ v2cd=5= v2Y/M2

22. n masses beyond the SM : tree level Scalar Triplet Seesaw ( or type II) 2 x 2 = 1 + 3 LEPTOGENESIS: T L L   ’ + + (Ma, Sarkar, Hambye)

23. Or hybrid models, i.e Fermionic Singlet + Scalar Triplet L H  NR H L ( O'Donnell, Sarkar, Hambye, Senjanovic; Antusch, King )

24. n masses beyond the SM : tree level Heavy fermion singletNR (Type I See-Saw) Minkowski, Gell-Mann, Ramond, Slansky, Yanagida, Glashow, Mohapatra, Senjanovic  Heavyscalar tripletD Magg, Wetterich, Lazarides, Shafi, Mohapatra, Senjanovic, Schecter, Valle Heavy fermion tripletR Ma, Roy, Senjanovic, Hambye et al., …

25. Minimal see-saw (fermionic singlet) _ _ L = LSM+ i NRdNR - Y L H NR - M NR NR Integrate outNR 2 M M + T YN YN/M2 (L H) (H L) YN YN/M (LL H H) d=5 operator it gives mass ton d=6 operator it renormalises kinetic energy Broncano, Gavela, Jenkins 02

26. Minimal see-saw (fermionic singlet) _ _ L = LSM+ i NRdNR - Y L H NR - M NR NR Integrate outNR 2 M M + T YN YN/M2 (L H) (H L) YN YN/M (LL H H) d=5 operator it gives mass ton d=6 operator it renormalises kinetic energy Kaluza-Klein model: De Gouvea, Giudice, Strumia, Tobe

27. with m~ v2cd=5= v2YN YN /MN T while cd=6= YY/M2 + For Y´s ~ O(1), cd=6~ (cd=5)2 and the smallness of neutrino masses would preclude in practice observable effects fromcd=6 How to evade this without ad-hoc cancelations of Yukawas?

28. _ Fermionic triplet seesaw _ _ L = LSM+ i RDR - Y L .H R - MR R Integrate outNR 2 M M T + YY/M (LL H H) YY/M2 (L H) D(H  L) d=5 operator it gives mass ton d=6 operator it renormalises kinetic energy+…

29. Scalar triplet see-saw L = LSM + DD - +M2 + YL . L + H . H + V(H,, i) Y/M2 (LL H H) d=5 _ _ + YY/M2 (L L) (L L)  /M4 (H+H)3 d=6 2 i /M4(HH)DD(HH) 2

31. Y Y M + 2

32. Y Y M + Notice that the combination 2 also is crucial to the LEPTOGENESIS CP-asymmetries i.e., in Type I: L NR’ NR + + + NR’ YN YNT H in addition to the mcombination ~YNT YN v2/M

33. Indeed, in Type I (fermionic seesaw) the individual CP asymmetries: degenerate cd=5 (that is, m ) eigenvalues vanish for or degenerate cd=6 eigenvalues (Broncano, Gavela, Jenkins)

34. Y Y M Can M be close to EW scale, say ~ TeV? + 2

35. M~1 TeV is suggested by electroweak hierarchy problem N H L (Vissani, Casas et al., Schmaltz)  H  H L

36. M~1 TeV actively searched for in colliders i.e. Scalar Triplet  l+  l+ Same sign dileptons….~ no SM background -> m> 136 GeV by CDF Atlas groups studying searches of Triplet Seesaws (scalar and fermionic) (Ma……….Bajc, Senjanovic)

37. Is it possible to have M ~ 1 TeV with large Yukawas (even O(1) ) ? It requires to decouple the coefficient cd=5of Od=5 from cd=6 of Od=6

38. Notice that all d=6operators preserve B-L, in contrast to the d=5operator. This suggests that, from the point of view of symmetries, it may be natural to have large cd=6, while having small cd=5.

39. Light Majorana m should vanish: - inversely proportional to a Majorana scale ( cd=5~1/M) - or directly proportional to it

40. Light Majorana m should vanish: - inversely proportional to a Majorana scale ( cd=5~1/M) - or directly proportional to it Ansatz: When the breaking of L is proportional to a small scale << M, while M ~ O(TeV), c d=5 is suppressed while c d=6 is large:     1 cd=5~ cd=6~

41. Light Majorana m should vanish: - inversely proportional to a Majorana scale ( cd=5~1/M) - or directly proportional to it Ansatz: When the breaking of L is proportional to a small scale << M, while M ~ O(TeV), c d=5 is suppressed while c d=6 is large: +   f(Y)   Y Y cd=5~ cd=6~

42. Y Y M + 2

43. Y Y M  M2 + Y 2

44. * The minimal scalar triplet model obeys that ansatz: H H +     Y Y cd=6 ~ cd=5~ Y L L In fact, any Scalar mediated Seesaw will give 1/(D2-M2) ~ -1/M2- D2/M4 + …… m~ v2cd=5 ~1/M2 * Singlet fermion seesaws with M~1 TeV also obey it !!! : i.e. INVERSE SEESAW

45. What about fermionic-mediated Seesaws? * Singlet fermion seesaws with M~1 TeV also obey it !!! : i.e. INVERSE SEESAW

46. INVERSE SEESAW texture * Toy: 1 light  L N1 N2 L N1 N2 Mohapatra, Valle, Glez- Garcia

47. INVERSE SEESAW texture * Toy: 1 light  L N1 N2 L N1 N2

48. INVERSE SEESAW texture * Toy: 1 light  L N1 N2 L N1 N2 e ,  ,  , N1, N2, N3 * 3 generation Inverse Seesaw: Abada et al., Kersten+Smirnov

49. Not easily Were M~ TeV and Y’s ~ 1, is LEPTOGENESIS possible? Yes, but not easy It would require resonant leptogenesis NR with rather degenerate heavy statesM-M’ <<M

50. Not easily Were M~ TeV and Y’s ~ 1, is LEPTOGENESIS possible? Yes, but not easy It would require resonant leptogenesis NR with rather degenerate heavy statesM-M’ <<M • Very interesting for FERMIONIC inverse seesaws, as they are • naturally resonant ( have 2 NR or 2 SR degenerate)