Carla Biggio MaxPlanckInstitut fr Physik Mnchen Germany Can

Carla Biggio Max-Planck-Institut für Physik, München, Germany Can we distinguish among different models for n mass in the near future? Based on collaborations with: A. Abada, S. Antusch, F. Bonnet, E. Fernández-Martínez, B. Gavela, T. Hambye, J. López-Pavón Convegno informale di fisica teorica – Sestri Levante 2008

The “problem” of n masses in 6 lines… • n are exactly massless in the Standard Model (SM) • Experimentally: they oscillate → they are massive there is leptonic flavour mixing • mn « ml : mn < O(e. V) → we need new physics (NP) beyond the SM to describe their masses → we’d like this new physics to explain their smallness Carla Biggio, MPI, Germany Sestri Levante 08

The “problem” of n masses in 6 lines… • n are exactly massless in the Standard Model (SM) • Experimentally: they oscillate → they are massive there is leptonic flavour mixing • mn « ml : mn < O(e. V) → we need new physics (NP) beyond the SM to describe their masses → we’d like this new physics to explain their smallness Explaining the smallness of n masses with new physics at high energy: → the seesaw mechanism Carla Biggio, MPI, Germany Sestri Levante 08

The “problem” of n masses in 6 lines… • n are exactly massless in the Standard Model (SM) • Experimentally: they oscillate → they are massive there is leptonic flavour mixing • mn « ml : mn < O(e. V) → we need new physics (NP) beyond the SM to describe their masses → we’d like this new physics to explain their smallness Explaining the smallness of n masses with new physics at high energy: → the seesaw mechanism The “bansigo” mechanism… Carla Biggio, MPI, Germany Sestri Levante 08

Effective field theory approach the effects of high energy NP @ low energy encoded in higher dimensional operators Carla Biggio, MPI, Germany Sestri Levante 08

Effective field theory approach the effects of high energy NP @ low energy encoded in higher dimensional operators Many Od>4 op. s with SM fields but Od=5 is UNIQUE! Carla Biggio, MPI, Germany Sestri Levante 08

Effective field theory approach the effects of high energy NP @ low energy encoded in higher dimensional operators Many Od>4 op. s with SM fields but Od=5 is UNIQUE! → lab depends on the model v v na nb lab ~O(1) , M~MGUT , v=v. EW → mn~10 -3 D=5 operator violates lepton number → n must be Majorana Carla Biggio, MPI, Germany Sestri Levante 08

Effective field theory approach the effects of high energy NP @ low energy encoded in higher dimensional operators Many Od>4 op. s with SM fields but Od=5 is UNIQUE! → lab depends on the model v v na nb lab ~O(1) , M~MGUT , v=v. EW → mn~10 -3 D=5 operator violates lepton number → n must be Majorana In how many ways can I obtain this Od=5? Carla Biggio, MPI, Germany Sestri Levante 08

Tree-level realisations of seesaw mechanism Type I See-Saw NR fermionic singlet Minkowski, Gell-Mann, Ramond, Slansky, Yanagida, Glashow, Mohapatra, Senjanovic, … Carla Biggio, MPI, Germany Sestri Levante 08

Tree-level realisations of seesaw mechanism Type I See-Saw NR fermionic singlet Minkowski, Gell-Mann, Ramond, Slansky, Yanagida, Glashow, Mohapatra, Senjanovic, … Carla Biggio, MPI, Germany Type II See-Saw D scalar triplet Magg, Wetterich, Lazarides, Shafi, Mohapatra, Senjanovic, Schecter, Valle, … Sestri Levante 08

Tree-level realisations of seesaw mechanism Type I See-Saw NR fermionic singlet Minkowski, Gell-Mann, Ramond, Slansky, Yanagida, Glashow, Mohapatra, Senjanovic, … Carla Biggio, MPI, Germany Type II See-Saw D scalar triplet Magg, Wetterich, Lazarides, Shafi, Mohapatra, Senjanovic, Schecter, Valle, … Type III See-Saw t. R fermionic triplet Foot, Lew, He, Joshi, Ma, Roy, …, Bajc, Nemevsek, Senjanovic, Dorsner, Fileviez-Perez Sestri Levante 08

Tree-level realisations of seesaw mechanism Type I See-Saw NR fermionic singlet Type II See-Saw D scalar triplet Type III See-Saw t. R fermionic triplet Linearly prop to YD suppressed by m/M 2 Minkowski, Gell-Mann, Ramond, Slansky, Yanagida, Glashow, Mohapatra, Senjanovic, … Carla Biggio, MPI, Germany Magg, Wetterich, Lazarides, Shafi, Mohapatra, Senjanovic, Schecter, Valle, … Foot, Lew, He, Joshi, Ma, Roy, …, Bajc, Nemevsek, Senjanovic, Dorsner, Fileviez-Perez Sestri Levante 08

How can we distinguish among them? Carla Biggio, MPI, Germany Sestri Levante 08

How can we distinguish among them? • not from the d=5 operator: it’s the same! • either we are able to produce heavy states or from the d=6 operator → which are the d=6 operators associated to these seesaw models? Carla Biggio, MPI, Germany Sestri Levante 08

D=6 operators Type I: Broncano, Gavela, Jenkins 02 Carla Biggio, MPI, Germany Sestri Levante 08

D=6 operators Type I: Broncano, Gavela, Jenkins 02 Type III: Abada, CB, Bonnet, Gavela, Hambye 07 Carla Biggio, MPI, Germany Sestri Levante 08

D=6 operators Type I: Broncano, Gavela, Jenkins 02 Type III: Abada, CB, Bonnet, Gavela, Hambye 07 Type II: Abada, CB, Bonnet, Gavela, Hambye 07 It is not suppressed by m Carla Biggio, MPI, Germany Sestri Levante 08

D=6 operators Type I: Broncano, Gavela, Jenkins 02 Type III: Abada, CB, Bonnet, Gavela, Hambye 07 Type II: Abada, CB, Bonnet, Gavela, Hambye 07 D=6 operators do not violate Lepton Number It is not suppressed by m Carla Biggio, MPI, Germany Sestri Levante 08

Phenomenological effects Type I: Broncano, Gavela, Jenkins 02 Antusch, CB, F. dez-M. nez, Gavela, López-Pavón 06 Carla Biggio, MPI, Germany • non-unitary mixing in CC • FCNC for n Sestri Levante 08

(D=6 op and non-unitarity in type I seesaw) Kinetic terms → diagonalized and normalized → unitary transf. + rescaling mab → diagonalized → unitary transformation Un N is not unitary (O(e)) Antusch, CB, F. dez-M. nez, Gavela, López-Pavón 06 Carla Biggio, MPI, Germany Sestri Levante 08

Phenomenological effects Type I: Broncano, Gavela, Jenkins 02 Antusch, CB, F. dez-M. nez, Gavela, López-Pavón 06 Carla Biggio, MPI, Germany • non-unitary mixing in CC • FCNC for n Sestri Levante 08

Phenomenological effects Type I: Broncano, Gavela, Jenkins 02 Antusch, CB, F. dez-M. nez, Gavela, López-Pavón 06 Type III: Abada, CB, Bonnet, Gavela, Hambye 07 Carla Biggio, MPI, Germany • non-unitary mixing in CC • FCNC for n • FCNC for charged leptons Sestri Levante 08

Phenomenological effects Type I: Broncano, Gavela, Jenkins 02 Antusch, CB, F. dez-M. nez, Gavela, López-Pavón 06 Type III: Abada, CB, Bonnet, Gavela, Hambye 07 • non-unitary mixing in CC • FCNC for n • FCNC for charged leptons Type II: Abada, CB, Bonnet, Gavela, Hambye 07 • LFV 4 -fermions interactions Carla Biggio, MPI, Germany Sestri Levante 08

Can we really use d=6 ops to distinguish? Carla Biggio, MPI, Germany Sestri Levante 08

Can we really use d=6 ops to distinguish? Generically if Y≈O(1) → cd=6 ≈ (cd=5)2 → very suppressed (fermionic) Carla Biggio, MPI, Germany Sestri Levante 08

Can we really use d=6 ops to distinguish? Generically if Y≈O(1) → cd=6 ≈ (cd=5)2 → very suppressed (fermionic) Is it possible to have a LARGE effect coming from cd=6 still with SMALL cd=5 (n mass) without fine-tuning? Carla Biggio, MPI, Germany Sestri Levante 08

Can we really use d=6 ops to distinguish? Generically if Y≈O(1) → cd=6 ≈ (cd=5)2 → very suppressed (fermionic) Is it possible to have a LARGE effect coming from cd=6 still with SMALL cd=5 (n mass) without fine-tuning? We need to decouple d=5 op. from d=6 - d=5 operator violates lepton number - d=6 operators conserve it → natural from the point of view of symmetries… Carla Biggio, MPI, Germany Sestri Levante 08

Direct Lepton Number Violation Scheme Ø assume L-conserving setup with small M (M~1 Te. V) and large Y (Y~O(1)): Abada, CB, Bonnet, Gavela, Hambye 07 large L conserved Carla Biggio, MPI, Germany Sestri Levante 08

Direct Lepton Number Violation Scheme Ø assume L-conserving setup with small M (M~1 Te. V) and large Y (Y~O(1)): Abada, CB, Bonnet, Gavela, Hambye 07 large L conserved Ø assume L broken by small perturbation m: Neutrino mass directly proportional to a small source of L violation rather than inversely proportional to a large one Carla Biggio, MPI, Germany Sestri Levante 08

Direct Lepton Number Violation Scheme Ø assume L-conserving setup with small M (M~1 Te. V) and large Y (Y~O(1)): Abada, CB, Bonnet, Gavela, Hambye 07 large L conserved Ø assume L broken by small perturbation m: Neutrino mass directly proportional to a small source of L violation rather than inversely proportional to a large one Is this possible? Carla Biggio, MPI, Germany Sestri Levante 08

Seesaw at low scale • Type II seesaw: Carla Biggio, MPI, Germany cd=5 ≈ Ym 2 M cd=6 †Y Y ≈ M 2 Sestri Levante 08

Seesaw at low scale • Type II seesaw: cd=5 ≈ Ym 2 M cd=6 • Inverse/Double type I (III) seesaw: Ex. ) 2 generations (na. L, nb. L, Nc 1 R, Nc 2 R): †Y Y ≈ M 2 González-García, Valle 89 … Kersten, Smirnov 07 Abada, CB, Bonnet, Gavela, Hambye 07 If Y~O(1) and M~1 Te. V → large cd=6 L is conserved → mn=0 Carla Biggio, MPI, Germany Sestri Levante 08

Seesaw at low scale • Type II seesaw: cd=5 ≈ Ym 2 M cd=6 • Inverse/Double type I (III) seesaw: Ex. ) 2 generations (na. L, nb. L, Nc 1 R, Nc 2 R): †Y Y ≈ M 2 González-García, Valle 89 … Kersten, Smirnov 07 Abada, CB, Bonnet, Gavela, Hambye 07 If Y~O(1) and M~1 Te. V → large cd=6 L is broken by m → Carla Biggio, MPI, Germany Sestri Levante 08

Seesaw at low scale • Type II seesaw: cd=5 ≈ Ym 2 M cd=6 • Inverse/Double type I (III) seesaw: Ex. ) 2 generations (na. L, nb. L, Nc 1 R, Nc 2 R): †Y Y ≈ M 2 González-García, Valle 89 … Kersten, Smirnov 07 Abada, CB, Bonnet, Gavela, Hambye 07 If Y~O(1) and M~1 Te. V → large cd=6 L is broken by m → Direct Lepton Number Violation can be realised in any seesaw model → low scale seesaw is possible and its effects can be observed in the near future Carla Biggio, MPI, Germany Sestri Levante 08

Testing the seesaws… Scalar seesaw: Type II: LFV 4 -fermions interactions Carla Biggio, MPI, Germany m→eee, t→lll, m→eg, t→lg bounds on various combinations of Sestri Levante 08

Testing the seesaws… Scalar seesaw: Type II: m→eee, t→lll, m→eg, t→lg LFV 4 -fermions interactions bounds on various combinations of Fermionic seesaws: non-unitarity 3 x 3 non-unitary Carla Biggio, MPI, Germany Sestri Levante 08

Testing the seesaws… Scalar seesaw: Type II: m→eee, t→lll, m→eg, t→lg LFV 4 -fermions interactions bounds on various combinations of Fermionic seesaws: non-unitarity analogous for NC • non-unitary mixing in CC Type I: • FCNC for n • W, Z, (semi)leptonic decays → (NN†)aa • unsuppressed m→eg, t→lg → (NN†)ab Carla Biggio, MPI, Germany Sestri Levante 08

Testing the seesaws… Scalar seesaw: Type II: m→eee, t→lll, m→eg, t→lg LFV 4 -fermions interactions bounds on various combinations of Fermionic seesaws: non-unitarity analogous for NC • non-unitary mixing in CC Type I: • FCNC for n • W, Z, (semi)leptonic decays → (NN†)aa • unsuppressed m→eg, t→lg → (NN†)ab Type III: • non-unitary mixing in CC • FCNC for n • FCNC for charged leptons Carla Biggio, MPI, Germany Similar to type I but m→eee, t→lll at tree-level → stronger bounds Sestri Levante 08

Bounds on (Y†Y/M 2) in type II • Upper bounds from LFV 4 -fermions processes: indep. of m or stronger Abada, CB, Bonnet, Gavela, Hambye 07 Partly from: Barger et al. 82, Pal 83, Bernabeu et al. 84, 86, Bilenky, Petcov 87, Gunion et al. 89, 06, Mohapatra 92 Carla Biggio, MPI, Germany Sestri Levante 08

Bounds on (Y†Y/M 2) in type II • Upper bounds from LFV 4 -fermions processes: indep. of m or stronger Abada, CB, Bonnet, Gavela, Hambye 07 Partly from: Barger et al. 82, Pal 83, Bernabeu et al. 84, 86, Bilenky, Petcov 87, Gunion et al. 89, 06, Mohapatra 92 Best signature of this model at LHC: dileptons Kadastic, Raidal, Rebane 07, Garayoa, Schwetz 07, … Carla Biggio, MPI, Germany Sestri Levante 08

Bounds on (Y†Y/M 2) in type I and III • No deviations from unitarity measured so far → only upper bounds TYPE III Antusch, CB, F. dez-M. nez, Gavela, López-Pavón 06 Abada, CB, Bonnet, Gavela, Hambye 07 Bounds are a bit stronger for type III. In particular we have better bounds on off-diag elements due to tree-level m→eee and t→ 3 l due to FCNC for charged leptons Carla Biggio, MPI, Germany General trend: or smaller Sestri Levante 08

m→eg and t→lg in type III @ O(e) and MS>>MW Abada, CB, Bonnet, Gavela, Hambye 08 • worst bounds with respect to tree-level decays l→ 3 l; But: Observation of radiative decays and no tree level decays → the type III seesaw cannot be the only source of lepton flavour violating new physics Carla Biggio, MPI, Germany Sestri Levante 08

Conclusions Can we distinguish among different models for n mass in the near future? Carla Biggio, MPI, Germany Sestri Levante 08

Conclusions Can we distinguish among different models for n mass in the near future? YES, IF… Carla Biggio, MPI, Germany …if the new physics scale is low enough… Sestri Levante 08

Conclusions Can we distinguish among different models for n mass in the near future? YES, IF… …if the new physics scale is low enough • d=6 effective operators crucial to distinguish among different models Carla Biggio, MPI, Germany Sestri Levante 08

Conclusions Can we distinguish among different models for n mass in the near future? YES, IF… …if the new physics scale is low enough • d=6 effective operators crucial to distinguish among different models • d=6 ops are usually suppressed but not necessarily: Carla Biggio, MPI, Germany Sestri Levante 08

Conclusions Can we distinguish among different models for n mass in the near future? YES, IF… …if the new physics scale is low enough • d=6 effective operators crucial to distinguish among different models • d=6 ops are usually suppressed but not necessarily: Direct Lepton Violation pattern: d=5 op. suppressed by small scale d=6 ops. unsuppressed Carla Biggio, MPI, Germany Sestri Levante 08

Conclusions Can we distinguish among different models for n mass in the near future? YES, IF… …if the new physics scale is low enough • d=6 effective operators crucial to distinguish among different models • d=6 ops are usually suppressed but not necessarily: Direct Lepton Violation pattern: d=5 op. suppressed by small scale d=6 ops. unsuppressed this pattern is the same in all models: natural in the scalar case, inverse seesaw for fermionic seesaws Carla Biggio, MPI, Germany Sestri Levante 08

Conclusions Can we distinguish among different models for n mass in the near future? YES, IF… …if the new physics scale is low enough • d=6 effective operators crucial to distinguish among different models • d=6 ops are usually suppressed but not necessarily: Direct Lepton Violation pattern: d=5 op. suppressed by small scale d=6 ops. unsuppressed this pattern is the same in all models: natural in the scalar case, inverse seesaw for fermionic seesaws • rich phenomenology associated to low scale seesaws: Carla Biggio, MPI, Germany Sestri Levante 08

Conclusions Can we distinguish among different models for n mass in the near future? YES, IF… …if the new physics scale is low enough • d=6 effective operators crucial to distinguish among different models • d=6 ops are usually suppressed but not necessarily: Direct Lepton Violation pattern: d=5 op. suppressed by small scale d=6 ops. unsuppressed this pattern is the same in all models: natural in the scalar case, inverse seesaw for fermionic seesaws • rich phenomenology associated to low scale seesaws: - provides bounds on high energy theory parameters Carla Biggio, MPI, Germany Sestri Levante 08

Conclusions Can we distinguish among different models for n mass in the near future? YES, IF… …if the new physics scale is low enough • d=6 effective operators crucial to distinguish among different models • d=6 ops are usually suppressed but not necessarily: Direct Lepton Violation pattern: d=5 op. suppressed by small scale d=6 ops. unsuppressed this pattern is the same in all models: natural in the scalar case, inverse seesaw for fermionic seesaws • rich phenomenology associated to low scale seesaws: - provides bounds on high energy theory parameters - stay tuned!!! Maybe interesting results in the near future… Carla Biggio, MPI, Germany Sestri Levante 08