Neutrino mass and grand unification
1 / 41

Neutrino Mass and Grand Unification - PowerPoint PPT Presentation

  • Uploaded on

Neutrino Mass and Grand Unification. R. N. Mohapatra University of Maryland LAUNCH, 2007 Heidelberg. Hypothesis of Grand unification.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about ' Neutrino Mass and Grand Unification' - kiaria

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Neutrino mass and grand unification

Neutrino Mass and Grand Unification

R. N. Mohapatra

University of Maryland

LAUNCH, 2007


Theme Group 2

Hypothesis of grand unification
Hypothesis of Grand unification

  • Grand unification is an interesting hypothesis which says that all forces and all matter become one at high energies no matter how different they look at low energies.

  • Two examples of theories where simple renormalization group analysis of the low energy couplings do indeed lead to coupling unification at high energies:

    (A). MSSM at TeV scale-> GUC


Theme Group 2

Unification of couplings
Unification of Couplings:

Weak scale susy

Non SUSY SO(10) with seesaw

Theme Group 2

Other advantages of guts
Other advantages of GUTs

  • (i) Higher symmetry could give better understanding of fermion masses ;

    (ii) Explains charge quantization;

    (iii) High scale explains proton stability;

    (iv) High scale goes well with cosmological issues such as inflation and baryogenesis.

Theme Group 2

Lessons from su 5 learning from failure
Lessons from SU(5): Learning from failure

  • Does not mean the idea of GUTs is dead.

  • Key to predictivity is to keep the model renormalizable; e.g. the coupling in SU(5) has to have a coupling < 10^-7 – also indicating that non-ren. Couplings have tiny couplings for whatever reason.

  • Neutrino mass has again put new life into the GUT idea- perhaps best to use theories with ren. Yukawas (as we do here).

Theme Group 2

To guts via seesaw
to GUTs via seesaw

  • Simplest way to understand small neutrino masses : why ?

    Add right handed neutrinos to the SM with large Majorana mass:

    MR is the new physics scale.

    [Minkowski; Gell-Mann, Ramond, Slansky; Yanagida; RNM, Senjanovic;Glashow]

Theme Group 2

What is the seesaw scale mr
What is the seesaw scale, MR?

  • Using Atmospheric mass measured by Super-K and in the seesaw

    One gets


    (ii) If is suppressed (by symmetries), seesaw scale could be lower (even TeV).

    Case (i) seesaw another indication for SUSY GUT since the GUT scale is GeV ?

Theme Group 2

Minimal gut group for neutrinos
Minimal GUT group for neutrinos

  • Seesaw provides the answer:

  • The fact that is most easily understood if there is a new symmetry associated with RH neutrino mass generation.

  • The obvious symmetry is B-L, which is

    broken by which gives RH neutrino mass.

    GUT group must have B-L as the subgroup.

Theme Group 2

So 10 grand unified theory
SO(10) Grand unified theory

  • Natural GUT group is SO(10) since its spinor rep contains all 16 needed fermions (including RH neutrino) in a single rep.

  • Georgi; Fritzsch, Minkowski (74)

  • Contains B-L needed to understand why MR<< M_Planck .

  • B-L if properly broken also allows a naturally stable dark matter in MSSM. (RNM, 1986)

Theme Group 2

From so 10 down to the std model
From SO(10) down to the Std Model

  • SO(10) Nu mass

  • Left-right sym. theory

  • Standard Model-> seesaw

Theme Group 2

How is b l broken 16 vs 126
How is B-L Broken ?{16} vs {126}

  • B-L can either be broken by {16}- Higgs by


    In which case M_R arises from non-renormalizable terms;

    Leads to R-parity breaking and hence no

    stable dark matter without extra assumptions.

Theme Group 2

Alternatively break b l by 126 higgs
Alternatively Break B-L by 126-Higgs

  • SM singlet in 126 is which has B-L=2;

  • Leaves R parity unbroken in MSSM and gives stable dark matter.

  • Also 16 X 16 = 10 + 126 + 120

    Matter Higgs

    Minimal model: one each of 10+126+ 120.

    126 gives mass to charged fermions as well as RH neutrinos relating RH neutrino spectrum to charged fermion spectrum.

    Also uses only renormalizable couplings.

    (not true for 16- Higgs models.)

Theme Group 2

Large neutrino mixings in minimal so 10
Large neutrino mixings in minimal SO(10)

  • How large mixings arise naturally in the minimal models:

    Simple Example: Model with only one {10} and {126} Higgs:

  • Has only 12 parameters (for CP conserving case)- all determined by quark masses and mixings and charged leptons; all neutrino mixings are predicted.

  • Babu, RNM (92); Bajc, Senjanovic, Vissani (2003); Goh, Ng, RNM (2003).

Theme Group 2

Details of minimal so 10
Details of minimal SO(10)

  • Yukawa: h16.16 10+f 16 .16.126-bar

  • Leads to fermion mass formulae

Theme Group 2

Neutrino mass and seesaw in so 10
Neutrino mass and seesaw in SO(10)

  • SO(10) model (and all LRS) models modify seesaw as follows:

    Type II Type I with

    [Magg, Wetterich; Lazaridis, Shafi, Wetterich; RNM, Senjanovic; 80]

    For first term to be significant, triplet mass must be around 10^14 GeV.

    Does it affect unification ?

Theme Group 2

A new sumrule for neutrino mass
A New sumrule for neutrino mass:

  • Dominant Type II

Theme Group 2

Including cp violation
Including CP violation:

  • In the 10+126 model, CP violation can arise from complex Yukawas- (but works only for a narrow range of parameters)

  • In the full minimal 10+126+120 model, CP is more natural.

  • Grimus and Kuhbock, 2006

Theme Group 2

Some predictions of the 120 model
Some predictions of the 120 model:

  • Prediction for U_e3:

Theme Group 2

Predictions for the mnsp phase
Predictions for the MNSP Phase

Dirac phase can be predicted

= 0.5-0.7

Theme Group 2

Beyond flavor issues
Beyond Flavor Issues

  • Realization of type II seesaw dominance in the models:

    (i) Higher B-L scale

    (ii) together with lower triplet mass

  • Coupling Unification and avoiding early non-perturbativity;

  • Proton decay

Theme Group 2

What happens in the truly minimal model
What happens in the truly minimal model:

  • {10}+{126}+{210}: Implies

  • Needs modification: Two possibilities:

  • (i) Add extra {54} to lower Triplet mass by a mini-seesaw; also overcomes large thershold effect objection.

  • (ii) Use mini-warping- Physics above GUT scale strongly coupled.

Theme Group 2

Coupling unification with type ii seesaw
Coupling Unification with type II seesaw

Usual allegation of large threshold effects FALSE !! Could have higher unif. scale with SO(10)-> SU(5) and Triplet, {15 } of SU(5) at 10^13 GeV; Goh, RNM, Nasri,04

Theme Group 2

Another way to achieve type ii dominance
Another way to achieve Type II dominance

  • Use mini-warped 5-D model:

  • Idea: (Fukuyama, Kikuchi, Okada(2007);

    Okada, Yu, RNM-in prep.)

  • Consider warped 5-D model with warping from Planck to GUT:

  • Locate Higgs in the Bulk so that their effect on the 4-D brane depends on location and U(1) charge. That way one can ensure lighter {15} and also unification.

  • No large Threshold effect since theory non-perturbative after M_U.

Theme Group 2

True test of gut hypothesis
True test of GUT hypothesis

  • Coupling unification, often

    cited as evidence for GUTs are not really so.

    True test of GUTs is proton decay;

    In particular no proton decay to the level of 10^36-37 years will be evidence against GUTs.

Theme Group 2

Nucleon decay in susy guts
Nucleon Decay in SUSY GUTs

  • Gauge Boson exchange:

Theme Group 2

Predictions for proton decay in so 10 16
Predictions for proton decay in SO(10)-16

  • B-L could be broken either by {16}-H or {126}-H.

  • SU(5) type problem avoided due to cancellation between diagrams.

  • Proton decay in {16} models: model dependent: in one class of models

    (Babu, Pati and Wilczek (2000))

Theme Group 2

Proton decay in so 10 126
Proton decay in SO(10)-126

  • Minimal SO(10) model with 10+126 which predict neutrino mixings:

  • 4 parameter model: predicts

  • For large tan the model is incompatible with proton decay

    (Goh, R.N. M, Nasri, Ng (2004))

Theme Group 2

Are guts the only choice for seesaw
Are GUTs the only choice for seesaw ?

  • It could be that B-L scale is lower : How to test for that possibility ?

  • Searching for neutron-anti-neutron oscillation is one way.

  • Few questions: N-N-bar operator:

    Leads to Osc. Time

    Since seesaw scale is >10^11 GeV, any chance to see it ?

Theme Group 2

Yes since new operators can appear

  • New operators appear with SUSY as well as unexplored TeV scale spectrum!!

  • Examples:

    With SUSY:

    If there is SUSY + diquark fields:





Even weaker


Theme Group 2

224 models do lead to such operators
224 models do lead to such operators

  • New Feynman diagrams lead to observable N-N-bar transition time with high seesaw scale of 10^11 GeV:

Theme Group 2

Proposal to search for n n bar at dusel
Proposal to search for N-N-bar at DUSEL

  • Dedicated small-power TRIGA

  • research reactor with cold neutron

  • moderator  vn ~ 1000 m/s

  •  Vertical shaft ~1000 m deep with

  • diameter ~ 6 m at DUSEL

  •  Large vacuum tube, focusing

  • reflector, Earth magnetic field

  • compensation system

  •  Detector (similar to ILL N-Nbar

  • detector) at the bottom of the shaft

  • (no new technologies)

  • Kamyshkov et al. (2005)

Theme Group 2


  • Neutrino mass introduces B-L as a symmetry of Nature. What is its scale ?

  • Very interesting possibility is that B-L scale is GUT scale: Minimal SO(10) realizations with 10+120+126 Higgs are realistic and predictive. Can be tested by forthcoming neutrino experiments !

  • Lower B-L scales can be tested by neutron-anti-neutron oscillation using current reactor fluxes. Urge a renewed effort to search for this process.

Theme Group 2

Unification scenario with s 4 sym
Unification scenario with S_4 sym.






Theme Group 2