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##### Low-energy neutrino physics

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**Low-energy neutrino physics**Belén Gavela Universidad Autónoma de Madrid and IFT**Low-energy neutrino physics**and leptogenesis Belén Gavela Universidad Autónoma de Madrid and IFT**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 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”?**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**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!**…..This talk deals much with the Majorana character**masses ----> Beyond SM scale • * What is the prize for ~TeVwithout unnatural fine-tunings? • * What observable observable effects could we then expect?**No masses in the SM because the SM accidentally**preserves B-L ……only left-handed neutrinos and ……only scalar doublets (Higgs)**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 (RR**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 (RR**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 (RR Seesaw model Which allows YN~1 --> M~MGut**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 (RR Seesaw model Which allows YN~1 --> M~MGut YN~10-6 --> M~TeV**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**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**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 Majoranas**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 )**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**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**n masses beyond the SM : tree level**Fermionic Triplet Seesaw ( or type III) 2 x 2 = 1 + 3 m~ v2cd=5= v2YY/M T**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)) **n masses beyond the SM : tree level**Scalar Triplet Seesaw ( or type II) 2 x 2 = 1 + 3 m~ v2cd=5= v2Y/M2**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)**Or hybrid models, i.e Fermionic Singlet + Scalar Triplet**L H NR H L ( O'Donnell, Sarkar, Hambye, Senjanovic; Antusch, King )**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 tripletR Ma, Roy, Senjanovic, Hambye et al., …**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**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**with**m~ v2cd=5= v2YN YN /MN T while cd=6= YY/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?**_**Fermionic triplet seesaw _ _ L = LSM+ i RDR - Y L .H R - MR R Integrate outNR 2 M M T + YY/M (LL H H) YY/M2 (L H) D(H L) d=5 operator it gives mass ton d=6 operator it renormalises kinetic energy+…**Scalar triplet see-saw**L = LSM + DD - +M2 + YL . L + H . H + V(H,, i) Y/M2 (LL H H) d=5 _ _ + YY/M2 (L L) (L L) /M4 (H+H)3 d=6 2 i /M4(HH)DD(HH) 2**Y Y**M + 2**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 mcombination ~YNT YN v2/M**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)**Y Y**M Can M be close to EW scale, say ~ TeV? + 2**M~1 TeV is suggested by electroweak hierarchy problem**N H L (Vissani, Casas et al., Schmaltz) H H L**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)**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**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.**Light Majorana m should vanish:**- inversely proportional to a Majorana scale ( cd=5~1/M) - or directly proportional to it**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~**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~**Y Y**M + 2**Y Y**M M2 + Y 2*** 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**What about fermionic-mediated Seesaws?*** Singlet fermion seesaws with M~1 TeV also obey it !!! : i.e. INVERSE SEESAW**INVERSE SEESAW texture*** Toy: 1 light L N1 N2 L N1 N2 Mohapatra, Valle, Glez- Garcia**INVERSE SEESAW texture*** Toy: 1 light L N1 N2 L N1 N2**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**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**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)