Can we distinguish among different models for n mass in the near future?

1
Can we distinguish among different models for n
mass in the near future?

• Carla Biggio
• Max-Planck-Institut für Physik, München, Germany

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
2
The problem of n masses in 6 lines
3
The problem of n masses in 6 lines
Explaining the smallness of n masses with new
physics at high energy
? the seesaw
mechanism
4
The problem of n masses in 6 lines
Explaining the smallness of n masses with new
physics at high energy
? the seesaw
mechanism
The bansigo mechanism
5
Effective field theory approach
the effects of high energy NP _at_ low energy
encoded in higher dimensional operators
6
Effective field theory approach
the effects of high energy NP _at_ low energy
encoded in higher dimensional operators
Many Odgt4 op.s with SM fields but Od5 is UNIQUE!
7
Effective field theory approach
the effects of high energy NP _at_ low energy
encoded in higher dimensional operators
Many Odgt4 op.s with SM fields but Od5 is UNIQUE!
lab O(1) , MMGUT , vvEW ? mn10-3
lab depends on the model
D5 operator violates lepton number ? n must be
Majorana
8
Effective field theory approach
the effects of high energy NP _at_ low energy
encoded in higher dimensional operators
Many Odgt4 op.s with SM fields but Od5 is UNIQUE!
lab O(1) , MMGUT , vvEW ? mn10-3
lab depends on the model
D5 operator violates lepton number ? n must be
Majorana
In how many ways can I obtain this Od5?
9
Tree-level realisations of seesaw mechanism
Type I See-Saw NR fermionic singlet
Minkowski, Gell-Mann, Ramond, Slansky, Yanagida,
Glashow, Mohapatra, Senjanovic,
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Tree-level realisations of seesaw mechanism
Type I See-Saw NR fermionic singlet
Type II See-Saw D scalar triplet
Minkowski, Gell-Mann, Ramond, Slansky, Yanagida,
Glashow, Mohapatra, Senjanovic,
Magg, Wetterich, Lazarides, Shafi, Mohapatra,
Senjanovic, Schecter, Valle,
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Tree-level realisations of seesaw mechanism
Type I See-Saw NR fermionic singlet
Type II See-Saw D scalar triplet
Type III See-Saw tR fermionic triplet
Minkowski, Gell-Mann, Ramond, Slansky, Yanagida,
Glashow, Mohapatra, Senjanovic,
Magg, Wetterich, Lazarides, Shafi, Mohapatra,
Senjanovic, Schecter, Valle,
Foot, Lew, He, Joshi, Ma, Roy, , Bajc,
Nemevsek, Senjanovic, Dorsner, Fileviez-Perez
12
Tree-level realisations of seesaw mechanism
Type I See-Saw NR fermionic singlet
Type II See-Saw D scalar triplet
Type III See-Saw tR fermionic triplet
Minkowski, Gell-Mann, Ramond, Slansky, Yanagida,
Glashow, Mohapatra, Senjanovic,
Magg, Wetterich, Lazarides, Shafi, Mohapatra,
Senjanovic, Schecter, Valle,
Foot, Lew, He, Joshi, Ma, Roy, , Bajc,
Nemevsek, Senjanovic, Dorsner, Fileviez-Perez
13
Tree-level realisations of seesaw mechanism
Type I See-Saw NR fermionic singlet
Type II See-Saw D scalar triplet
Type III See-Saw tR fermionic triplet
Linearly prop to YD suppressed by m/M2
Minkowski, Gell-Mann, Ramond, Slansky, Yanagida,
Glashow, Mohapatra, Senjanovic,
Magg, Wetterich, Lazarides, Shafi, Mohapatra,
Senjanovic, Schecter, Valle,
Foot, Lew, He, Joshi, Ma, Roy, , Bajc,
Nemevsek, Senjanovic, Dorsner, Fileviez-Perez
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How can we distinguish among them?
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How can we distinguish among them?

• not from the d5 operator its the same!
• either we are able to produce heavy states
• or
• from the d6 operator

? which are the d6 operators associated to these
seesaw models?
16
D6 operators
Type I
Broncano, Gavela, Jenkins 02
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D6 operators
Type I
Broncano, Gavela, Jenkins 02
Type III
Abada, CB, Bonnet, Gavela, Hambye 07
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D6 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
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D6 operators
Type I
Broncano, Gavela, Jenkins 02
Type III
Abada, CB, Bonnet, Gavela, Hambye 07
D6 operators do not violate Lepton Number
Type II
Abada, CB, Bonnet, Gavela, Hambye 07
It is not suppressed by m
20
Phenomenological effects

• non-unitary mixing in CC
• FCNC for n

Type I
Broncano, Gavela, Jenkins 02 Antusch, CB,
F.dez-M.nez, Gavela, López-Pavón 06
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(D6 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
Antusch, CB, F.dez-M.nez, Gavela, López-Pavón 06
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Phenomenological effects

• non-unitary mixing in CC
• FCNC for n

Type I
Broncano, Gavela, Jenkins 02 Antusch, CB,
F.dez-M.nez, Gavela, López-Pavón 06
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Phenomenological effects

• non-unitary mixing in CC
• FCNC for n

Type I
Broncano, Gavela, Jenkins 02 Antusch, CB,
F.dez-M.nez, Gavela, López-Pavón 06

• non-unitary mixing in CC
• FCNC for n
• FCNC for charged leptons

Type III
Abada, CB, Bonnet, Gavela, Hambye 07
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Phenomenological effects

• non-unitary mixing in CC
• FCNC for n

Type I
Broncano, Gavela, Jenkins 02 Antusch, CB,
F.dez-M.nez, Gavela, López-Pavón 06

• non-unitary mixing in CC
• FCNC for n
• FCNC for charged leptons

Type III
Abada, CB, Bonnet, Gavela, Hambye 07
Type II
Abada, CB, Bonnet, Gavela, Hambye 07

• LFV 4-fermions
• interactions

25
Can we really use d6 ops to distinguish?
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Can we really use d6 ops to distinguish?
Generically if YO(1) ? cd6 (cd5)2 ? very
suppressed
(fermionic)
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Can we really use d6 ops to distinguish?
Generically if YO(1) ? cd6 (cd5)2 ? very
suppressed
(fermionic)
Is it possible to have a LARGE effect coming
from cd6 still with SMALL cd5 (n mass) without
fine-tuning?
28
Can we really use d6 ops to distinguish?
Generically if YO(1) ? cd6 (cd5)2 ? very
suppressed
(fermionic)
Is it possible to have a LARGE effect coming
from cd6 still with SMALL cd5 (n mass) without
fine-tuning?
We need to decouple d5 op. from d6
- d5 operator violates lepton number - d6
operators conserve it ? natural from the
point of view of symmetries
29
Direct Lepton Number Violation Scheme
Abada, CB, Bonnet, Gavela, Hambye 07

• assume L-conserving setup with small M (M1TeV)
• 
  and large Y (YO(1))
• 
  large
• 
  L conserved

30
Direct Lepton Number Violation Scheme
Abada, CB, Bonnet, Gavela, Hambye 07

• assume L-conserving setup with small M (M1TeV)
• 
  and large Y (YO(1))
• 
  large
• 
  L conserved
• 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
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Direct Lepton Number Violation Scheme
Abada, CB, Bonnet, Gavela, Hambye 07

• assume L-conserving setup with small M (M1TeV)
• 
  and large Y (YO(1))
• 
  large
• 
  L conserved
• 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?
32
Seesaw at low scale

• Type II seesaw

33
Seesaw at low scale

• Type II seesaw

• Inverse/Double type I (III) seesaw
• Ex.) 2 generations (naL, nbL, Nc1R, Nc2R)

González-García, Valle 89 Kersten, Smirnov 07
Abada, CB, Bonnet, Gavela, Hambye 07
If YO(1) and M1TeV ? large cd6 L is conserved
? mn0
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Seesaw at low scale

• Type II seesaw

• Inverse/Double type I (III) seesaw
• Ex.) 2 generations (naL, nbL, Nc1R, Nc2R)

González-García, Valle 89 Kersten, Smirnov 07
Abada, CB, Bonnet, Gavela, Hambye 07
If YO(1) and M1TeV ? large cd6 L is broken by
m ?
35
Seesaw at low scale

• Type II seesaw

• Inverse/Double type I (III) seesaw
• Ex.) 2 generations (naL, nbL, Nc1R, Nc2R)

González-García, Valle 89 Kersten, Smirnov 07
Abada, CB, Bonnet, Gavela, Hambye 07
If YO(1) and M1TeV ? large cd6 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
36
Testing the seesaws
Scalar seesaw
m?eee, t?lll, m?eg, t?lg bounds on
various combinations of
Type II LFV 4-fermions interactions
37
Testing the seesaws
Scalar seesaw
m?eee, t?lll, m?eg, t?lg bounds on
various combinations of
Type II LFV 4-fermions interactions
Fermionic seesaws non-unitarity
3x3
non-unitary
unitary
38
Testing the seesaws
Scalar seesaw
m?eee, t?lll, m?eg, t?lg bounds on
various combinations of
Type II LFV 4-fermions interactions
Fermionic seesaws non-unitarity
3x3
non-unitary
unitary
39
Testing the seesaws
Scalar seesaw
m?eee, t?lll, m?eg, t?lg bounds on
various combinations of
Type II LFV 4-fermions interactions
Fermionic seesaws non-unitarity
analogous for NC

• non-unitary mixing in CC
• FCNC for n

Type I

• W, Z, (semi)leptonic decays ? (NN)aa
• unsuppressed m?eg, t?lg ? (NN)ab

40
Testing the seesaws
Scalar seesaw
m?eee, t?lll, m?eg, t?lg bounds on
various combinations of
Type II LFV 4-fermions interactions
Fermionic seesaws non-unitarity
analogous for NC

• non-unitary mixing in CC
• FCNC for n

Type I

• 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

Similar to type I but m?eee, t?lll at
tree-level ? stronger bounds
41
Bounds on (YY/M2) in type II

• Upper bounds from LFV 4-fermions processes
  indep. of m

42
Bounds on (YY/M2) in type II

• Upper bounds from LFV 4-fermions processes
  indep. of m

Best signature of this model at LHC dileptons
Kadastic, Raidal, Rebane 07, Garayoa, Schwetz 07,

43
Bounds on (YY/M2) in type I and III

• No deviations from unitarity measured so far ?
  only upper bounds

TYPE I
Antusch, CB, F.dez-M.nez, Gavela, López-Pavón 06
TYPE III
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?3l due to
FCNC for charged leptons
44
m?eg and t?lg in type III
_at_ O(e) and MSgtgtMW
Abada, CB, Bonnet, Gavela, Hambye 08

• worst bounds with respect to tree-level decays
  l?3l
• 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
45
Conclusions
Can we distinguish among different models for n
mass in the near future?
46
Conclusions
Can we distinguish among different models for n
mass in the near future?
YES, IF if the new physics
scale is low enough
47
Conclusions
Can we distinguish among different models for n
mass in the near future?
YES, IF if the new physics
scale is low enough

• d6 effective operators crucial to distinguish
  among different models

48
Conclusions
Can we distinguish among different models for n
mass in the near future?
YES, IF if the new physics
scale is low enough

• d6 effective operators crucial to distinguish
  among different models
• d6 ops are usually suppressed but not
  necessarily

49
Conclusions
Can we distinguish among different models for n
mass in the near future?
YES, IF if the new physics
scale is low enough

• d6 effective operators crucial to distinguish
  among different models
• d6 ops are usually suppressed but not
  necessarily
• Direct Lepton Violation pattern d5 op.
  suppressed by small scale
• 
  d6 ops. unsuppressed

50
Conclusions
Can we distinguish among different models for n
mass in the near future?
YES, IF if the new physics
scale is low enough

• d6 effective operators crucial to distinguish
  among different models
• d6 ops are usually suppressed but not
  necessarily
• Direct Lepton Violation pattern d5 op.
  suppressed by small scale
• 
  d6 ops. unsuppressed
• this pattern is the same in all
  models
• natural in the scalar case, inverse
  seesaw for fermionic seesaws

51
Conclusions
Can we distinguish among different models for n
mass in the near future?
YES, IF if the new physics
scale is low enough

• d6 effective operators crucial to distinguish
  among different models
• d6 ops are usually suppressed but not
  necessarily
• Direct Lepton Violation pattern d5 op.
  suppressed by small scale
• 
  d6 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

52
Conclusions
Can we distinguish among different models for n
mass in the near future?
YES, IF if the new physics
scale is low enough

• d6 effective operators crucial to distinguish
  among different models
• d6 ops are usually suppressed but not
  necessarily
• Direct Lepton Violation pattern d5 op.
  suppressed by small scale
• 
  d6 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

53
Conclusions
Can we distinguish among different models for n
mass in the near future?
YES, IF if the new physics
scale is low enough

• d6 effective operators crucial to distinguish
  among different models
• d6 ops are usually suppressed but not
  necessarily
• Direct Lepton Violation pattern d5 op.
  suppressed by small scale
• 
  d6 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

54
Back-up
55
D6 op and non-unitarity in type I seesaw
Kinetic terms ? diagonalized and normalized
? unitary transf.
rescaling mab ? diagonalized ? unitary
transformation
Un

• neutrino oscillations
• CC interactions
• unsuppressed la ?lbg
• neutrino oscillations in matter
• invisible Z decay

ABFGL 06
56
D6 op and non-unitarity in type III seesaw
N is not unitary new processes ex. m ? eee _at_
tree level ABBGH 07
57
Rare leptons decays in type I

• From rare leptons decays
• 
  Infos on (NN)ab

SM ? GIM suppression
Now ? no suppression ? constant term
leading

• m-e conversion in nuclei
• m ? ee-e (only _at_ 1 loop) suppressed by a
  factor a

58
n are massless in the Standard Model

• No Dirac mass
• because no fermionic singlet nR ?
• No Majorana mass
• because - no scalar triplet D
  ?
• - SM is renormalizable
  ?
• - global U(1)B-L not anomalous ?
  not radiatively generated

59
Present status of n parameters
Fogli et al. 06

• From oscillations experiments (2s)
• Solar
• Atmospheric
• Bounds on absolute mass scale (2s)
• Tritium b decay
• 0nbb decay
• Cosmology
• ? Open questions hierarchy, absolute mass
  scale, q13, d, (f1, f2)

Mainz, Troitsk
Heidelberg-Moscow
CMB CMB LSS CMB LSS Lyman-a
model dependent