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Neutrino Mass and Flavor Physics
R. N. Mohapatra
Neutrino Mass- What do we know ?
Masses: ; Mixings: ; Overall mass scale: < .1- 1 eV (roughly) To be determined (expts in progress or
planning) (i) Majorana or Dirac ? (ii) Mass ordering: NH or IH (iii) Value of (iv) Any possible CP violation ? (v) Leptonic unitarity
252 1067.7 eVmsol 232 1039.2 eVmAtm
;312.sin 122 466.sin 23
2 04.sin 132
13
Many experiments on the way
(i) Majorana or Dirac
(ii) Absolute mass scale: (iii) Mass ordering: (iv) Value of (v) CP phase
13
0
Plan of the talk Neutrino mass New physics beyond SM:
Raises two new issues: New mass scale to explain why
Is it accessible at the LHC ?
New approach to flavor : Can we have a unified understanding quark- lepton mixings ?
lqmm ,
Why ?
Seesaw Paradigm: Add heavy right handed neutrinos to SM
and play seesaw:
Seesaw scale is the new physics scale !! Two different seesaws depending on whether N
Majorana or Dirac
RN
lqmm ,
Type I seesaw Majorana
Breaks B-L : New scale and new symmetry beyond SM. After EWSB -Neutrino majorana
key parameter to test seesaw type I
NNMHNLhL RRY
RM
R
wk
M
vhm
22
Minkowski,Gell-Mann, Ramond Slansky,Yanagida, Mohapatra,Senjanovic,Glashow
Inverse Seesaw Mostly Dirac i.e. add another
singlet
Seesaw parameter testing or larger (RNM’86;
RNM, Valle’86)
M
Mhv
hv
wk
wk
0
0
00D
TD mMMmm 11
),,( SRL
S
RNS SS M
310~
M
mD
New physics signal for simplest seesaw
Strength given by or mixing:
e.g. collider production:
Leptonic non-unitarity: Both negligible for type I seesaw but
observable for inverse seesaw MN ~ TeV Situation different with gauge forces !!
N
1. Seesaw (B-L) scale Neutrino masses do not determine seesaw scale ; MU~ GeV
Both and high seesaw scale indication for
SUSYGUTs; No collider signals ! (Common Lore) B-L scale at TeV LHC signals with only gauge forces; No GUTs with type I.
B-L at TeV and GUTs can co-exist: since possible
(Dev,
RNM’09)
tD mm GeVM R1410 1610
eD mm
Inverse seesaw
tD mm
tD mm
A concrete realization: Low scale B-L in Left-Right
NR Gauge group: New W’ and Z’ Fermion assignment
Two Avatars of LR: type I Inverse seesaw +
LBRL USUSU )1()2()2(
L
L
d
u
R
R
d
u
L
L
e
R
R
e
P
P
)0,2,2( )2,1,3()2,3,1(; LR
LW
RW ,',ZZ
)0,2,2( )1,2,1()1,1,2( RL
Bound on SUSYLR scale from Low energy data
M_WR > 2 TeV from a combination of KL-KS, epsilon, d_n together.(uncertainty from long distance contribution);
(An,Ji,Zhang’07)
Bounds from Nu-less double beta decay
New contributions from WR-N exchange (only for Case I) (RNM, 86; Hirsch, Klapdor, Panella 96)
Diagram:
From Ge76:
Seesaw signal from Nu contribution:
Inverse hierarchy Normal hierarchy
Punch line: Suppose long baseline
and nonzero signal for (+ RP if susy )
TeV WR and type I
0
0231 m
0
Constraints on Seesaw scale from coupling unification:
TeV type I does not grand unify: Landau Pole
(Kopp, Lindner, Niro, Underwood’09) (Parida, Sarkar, Majee, Raichaudhuri’09)
Discovery of type I signal at LHC will rule out GUTs.
TeV Inverse Seesaw (LR) Inverse seesaw does unify and give realstic
model: with both WR and Z’ in TeV range; MSSM GUT SUSYLR GUT
Look for not only susy but also WR, Z’, N at LHC:(Dev, RNM, 09; PRD);
SO(10) as the GUT theory
{16 }- spinor for all matter
Type I: only unification route:
Inverse seesaw:
TeVMGeVM RU ;1016
GeVM BLU16
, 102
Radiative Breaking of B-L and SM
Positive spartner mass square at GUT scale-
RGE turns them negaitve much like SM with large t-mass
(Dev, RNM’10)
LHC Signals for seesaw LHC production of WR: ; N-decay: type I Inv. Seesaw:
Type I case: (Keung, Senjanovic;
Han, Perez,Huang,Li, Wang; Del Aguila,
Aguilar-Saavedra; Azuelos,..)
Inverse seesaw: Only
Trileptons; no same sign dileptons(30 fb^-1)(del Aguila,Aguilar-Saavedra, de Blas)
NlWdu R NNZuu '
jjlN ll,
lljjlN ,
Other TeV scale Type I Signals
TeV type I Seesaw requires B-L=2 Higgs:
Doubly charged Higgs can have sub-TeV mass. Decays to lepton pairs
Four lepton signals at LHC
2
12
1
0
,,ee ,, ee
LHC signals for type I seesaw will rule out simple GUTs
New Dark matter in TeV scale Inverse seesaw:
If super-partner of RH neutrino is the lightest, it will be stable due to R-parity- become DM.
Soft breaking:
Lightest linear combination is dark matter:
SSNSfvLHNhWW RMSSM
SNBNHLASSMNNMLL SMSSMsoft
~~~~~~~~ 22
Minimal Type I case: Usual Bino-Higgsino
Dark matter in type I GUT vs TeV scale Inverse seesaw:
Inverse seesaw case: (Fornengo, Arina, Bazzochi, Romao, Valle’08)
New DMNew DM : :Two contributions to relic density: Z’ exchange (Matchev, Lee, Nasri) No or small Z’
effect
c~
TeVM Z 5.2'
2. Understanding Flavor
(i) Mass hierarchies(ii) Strange mixing patterns: Leptons: Quarks:
UPMNS= UCKM =
(Harrison, Perkins, Scott; He, Zee,Wolfenstein; Xing,..)
1
1
1
23
2
3
Mass Texture Up-quark and charged lepton diagonal
basis:
= Cabibbo angle
123
223
335
bd mM
133
313
331
11
11
M
~i
Strategy for texture Key idea: SM has a large sym for zero fermion
masses : [SU(3)]^5;
Choose subgroup: Discrete subgroup with 3-d. rep.
Replace Yukawa’s by scalar fields (flavons);
Minima of the flavon theory determines Yukawas:
Application to Neutrinos
Successful Family symmetries for TBM:
Flavon fields are triplets: (Ma, Rajasekaran; Babu, Ma, Valle, King, Ross; Altarelli, Feruglio, Chen, Mahanthappa;
Everett, Ramond; Luhn, Nasri, Yu, RNM, Hagedorn, Morissi,…..)
Grand unified theories: SU(5)
)(2 S ),...3( 2n
How can we unify with quarks ?
High scale Ansatz for unifying quark-lepton flavor
(Dutta, Mimura, RNM’PRD-09)
f diagonal. Anarchic M0, quark mixings small while
lepton mixings large.
explains mass hierarchies +
dd rMM 0 Lfvm uu MM 0
0,, Mldu ll rMM 0
mmb Rank 1 M0
A
B
SUSY SO(10) realization Fermions in {16}:
16mx16m={10}H+{120}H+{126}H
Fermion masses from Yukawas as in SM:
(Babu, Mohapatra, 93)
HHHY hfhL ]10,120[1616'6211616101616
Neutrino mass formula in GUT scale B-L in SO(10):
Type II seesaw:
TD
BLD M
fvMfvm
1
Lazaridis, Shafi, Wetterich; R.N.M.,Senjanovic’81
SO(10) with GUT scale B-L unified approach to flavor
fermion mass formulae:
(Babu, Mohapatra’92) Bajc, Senjanovic, Vissani’03
For f, h’ << h, yields ansatz part A at MU; Rank from flavor symmetry: e.g.
fvm
),..27(,4 S
An S4 xSO(10)- example Solar mass Dutta, Mimura, RNM
arXiv:0911.2242
Bottom-tau: and
Leading order PMNS: U(Harrison, Perkins, Scott; He, Zee, Xing; Wolfenstein)
Corrections: Testable Bjorken, King, Pakvasa Ferrandis; Chen, Mahanthappa
Double beta mass 3 meV.
catm
solar
m
m
mmb smm 3
05.023
13 c
Prospects for measuring Reactor, Long base line e.g. T2K, NoVA: (Lindner, Huber,Schwetz,Winter’09)
Our prediction 01.02sin 132
Conclusion: TeV scale WR compatible with
SO(10) GUT; Can be tested at LHC; New dark matter candidate:
New unified approach to flavor based on typeII+ SO(10)- testable via theta_13.
WR, Z’ at LHC_14
Production : WR Z’
Signals for Type I case Two and three lepton signals in colliders
N-decay gives signal:
Like sign dilepton plus trilepton+ (Han, Perez, Li, Del Aguila, Aguilar Saavedra,…)
NlWdu R
jjlN ll,
E
NNZuu '
l
Inverse seesaw case N is mostly Dirac
Collider leptonic signal from WR production:
No like sign dilepton but only trileptons +
WlN
NlWdu R
E
Distinguishing between seesaws
Observation of relative abundance of like sign dileptons vs trileptons can distinguish between TeV scale Inverse seesaw vs type I seesaw
(Aguilar-Saavedra)
Type I
Inverse