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Supersymmetry. Hitoshi Murayama Taiwan Spring School March 29, 2002. In the MSSM, electroweak symmetry does not get broken Only after supersymmetry is broken, Higgs can obtain a VEV v ~ m SUSY Regard EWSB as a consequence of supersymmetry breaking

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Hitoshi Murayama

Taiwan Spring School

March 29, 2002

Electroweak symmetry breaking

In the MSSM, electroweak symmetry does not get broken

Only after supersymmetry is broken, Higgs can obtain a VEV v~mSUSY

Regard EWSB as a consequence of supersymmetry breaking

EW symmetry and hierarchy “protected” by supersymmetry

Electroweak Symmetry Breaking

Origin of hierarchy

Origin of Hierarchy

  • v<<MPl because v~mSUSY<<MPl

  • Why mSUSY<<MPl?

  • Idea: dimensional transmutation

  • SUSY broken by strong gauge dynamics with

  • “Dynamical supersymmetry breaking”

Dynamical supersymmetry breaking

Simplest example: SO(10) with one 16

No moduli space, can’t analyze with Seibergian techniques

“non-calculable” (Affleck-Dine-Seiberg)

Add one 10, make it massive and decouple

When M10=0, moduli space spanned by 161610, 102, generically SO(10)SO(7)

SO(7) gaugino condensation generates dynamical superpotential

Add W=M10102, lifts moduli space, breaks SUSY

Decouple 10 smoothly(HM)

Dynamical Supersymmetry Breaking

Izawa yanagida intriligator thomas model

Izawa-Yanagida-Intriligator-Thomas model

  • Sp(Nc) gauge theory with Nf=Nc+1

  • Quantum modified moduli space

    Pf M = L2Nffor mesons Mij=QiQj

  • Add superpotential with singlets Sij

    W=Sij QiQjforces Mij=0

  • Contradiction  no SUSY vacua

Issue of mediation

Issue of mediation

  • Many gauge theories that break SUSY dynamically known

  • The main issue: how do we communicate the SUSY breaking effects to the MSSM? “mediation”



  • Supersymmetry is broken either by an F-component of a chiral superfield


    or a D-component of a vector superfield


  • Once they are frozen at their expectation values, they can be viewed as spurions of supersymmetry breaking order parameters

Soft supersymmetry breaking

Soft supersymmetry breaking

  • Purpose of supersymmetry is to protect hierarchy

  • Arbitrary terms in Lagrangian that break supersymmetry reintroduce power divergences

  • “Soft supersymmetry breaking” classified:

    mll, m2ijfi*fj, Aijkfjfjfk, Bijfjfj, Cifj

  • Dark horse terms (not always allowed):

    fj*fjfk, lyj, yiyj

Spurion operators

Spurion operators

  • Spurion z =fi/M=q2Fi/M generates soft terms

  • M is the “mediation scale” where the effects of SUSY breaking are communicated

    m ll = d2q z c Wa Wa

    m2ijfi*fj = d4q z*z cijfi*fj

    Aijkfjfjfk = d2q z cijkfjfjfk

    Bijfjfj = d2q z cijfjfj

    Cifj = d2q z cifj

  • Coefficients c are random at this point

Supersymmetric flavor problem

Supersymmetric flavor problem

  • Random SUSY breaking excluded by FCNC constraints

  • Consider scalar down quarks

  • Take the off-diagonal terms to be perturbation:

Supersymmetric flavor problem1

Supersymmetric flavor problem

  • Random SUSY breaking excluded by FCNC constraints

  • Want a reason why off-diagonal terms are suppressed




Two possible directions

Two possible directions

  • Develop a theory of flavor that predicts not only the pattern of Yukawa matrices (masses, mixings), but also soft masses

  • Develop a theory of mediation mechanism of supersymmetry breaking that predicts (approximately) flavor-blind soft masses

Gravity mediation

Gravity Mediation



  • Specify Kähler potential K and superpotential W

  • Minimal supergravity


  • SUSY broken if Fz=zW*+Wz0, W0

    Universal scalar mass, trilinear couplings etc



  • Got universal scalar mass!

  • “Of course, because gravity doesn’t distinguish flavor”

  • Wrong!

  • “Minimal” is a choice to obtain canonical kinetic terms with no Planck-suppressed corrections

  • But in general there are such corrections in non-renormalizable theory and SUGRA not minimal

Problems with minimal sugra

Problems with Minimal SUGRA

  • There is no fundamental reason to believe that Kähler potential in effective theory of quantum gravity is strictly minimal

  • In many string compactifications, it isn’t

    • Direct coupling of observable fields with moduli in Käler potential that depend on their modular weights

  • Thought to be an ad hoc convenient choice, not a theory of mediation

  • But phenomenologically excellent start point, explaning EWSB, dark matter, absence of FCNC

Problems with general sugra

Problems with general SUGRA

  • There may be arbitrary coupling between hidden and observable fields in Kähler potential under no control

  • Generically, soft masses expected to be arbitrary, with flavor violation

    m2ijfi*fj = d4q z*z cijfi*fj

  • Phenomenogically disaster

Remedy by flavor symmetry

Remedy by flavor symmetry

  • We need theory of flavor anyway

  • The issue of flavor-violating soft masses is intimately tied to the origin of flavor, Yukawa couplings

  • Seek for a common theory that solves the problem

Flavor blind mediation mechanisms

Flavor-blind Mediation Mechanisms

Gauge Mediation

Gaugino Mediation

Anomaly Mediation

Gauge mediation

Gauge Mediation

Dine nelson shirman model

Dynamical supersymmetry breaking sector

Take SU(5) with 10+5*

(“non-calculable DSB model”

add massive 5+5* and can show DSB; HM)

break it to SU(4)U(1) with non-anomalous global U(1)m

(6+2+4-3+1-8)+1 +(4*-1+1+4)-3

W= 4*-1 4-3 1+4+ 1+4 1+4 1-8

breaks supersymmetry dynamically

gauge global U(1)m as “messenger U(1)”

Problem with FY D-term for messenger U(1)  solved by changing the DSB model to SU(6)U(1)

(Dine, Nelson, Nir, Shirman)

Dine-Nelson-Shirman model

Dine nelson shirman model1

Messenger sector

a pair f charged under messenger U(1)

NF pairs of F+F* (5+5*) under SU(5) SU(3)SU(2)U(1)


f acquire negative mass-squred from two-loops in messenger U(1) interaction

triggers S to acquire both A- and F-component VEVs

gives both mass and B-term to F+F*

M=l2<S>, MB=l2<FS>

Dine-Nelson-Shirman model

Dine nelson shirman model2

Because F+F* are charged under the standard model gauge groups, their one-loop diagrams generate gaugino masses, and two-loop diagrams generate scalar masses

Generated scalar masses flavor-blind, because gauge interactions do not distinguish flavor

Dine-Nelson-Shirman model

Dine nelson shirman model3

Dine-Nelson-Shirman model

  • Lightest Supersymmetry Particle: gravitino

  • In general, a cosmological problem (overclosure)

    (de Gouvêa, Moroi, HM)

  • Collider signatures may be unique:

    • Bino  gravitino + photon

    • Decay length may be microns to km

  • Should not have any new flavor physics below the mediation scale to screw-up flavor-blindness of soft masses

Direct gauge mediation

Too many sectors to worry about!

DSB sector: Sp(4) with 5 flavors charged under SU(5) (HM)

Direct Gauge Mediation

Gaugino mediation

(Kaplan, Kribs, Schmaltz)

(Chacko, Luty, Nelson, Ponton)

DSB in another brane

Gauge multiplet in the bulk

Gauge multiplet learns SUSY breaking first, obtains gaugino mass

MSSM at the compactification scale with gaugino mass only

Scalar masses generated by RGE

Gaugino Mediation

Gaugino mediation1

Gaugino Mediation

  • Phenomenology similar to minimal supergravity with zero universal scalar mass

  • Gravitino heavy: less harmful

  • Needs high (~GUT scale) compactification to jack up slepton mass high enough

  • Should not have any new flavor physics below the compactification scale to screw-up flavor-blindness of soft masses

Anomaly mediation

(Randall, Sundrum)

(Giudice, Luty, HM, Rattazzi)

Try not to mediate

Zen of SUSY breaking

If no coupling between DSB and MSSM, there is no supersymmetry breaking at tree-level

But divergence of supercurrent in the same multiplet as the trace of energy momentum tensor

Conformal anomaly induces supersymmetry breaking

Anomaly Mediation

Weyl compensator formalism

Weyl compensator formalism

  • Conformal Supergravity “fixed” by Weyl compensator F

  • The only communication of SUSY breaking is through the auxiliary component of F=q2F

    d4q F*Ff*f +d2q F3(M f2+l f3)

  • Scale ff/F

    d4q f*f +d2q (FM f2+l f3)

  • Only dimensionful parameters acquire SUSY breaking

  • Massless theory  no SUSY breaking

Conformal anomaly

Conformal Anomaly

  • Any (non-finite) theory needs a regulator with an explicit mass scale

    • Pauli-Villars with heavy regulator mass

    • DRED with renormalization scale m

      (Boyda, HM, Pierce)

  • Regulator receives SUSY breaking

  • SUSY breaking induced by regulator effect: anomaly

Anomaly mediation1

Anomaly mediation predicts SUSY breaking with theory given at the scale of interest

UV insensitivity

Can be checked explicitly by integrating out heavy fields that their loops exactly cancel the differences in b-functions & anomalous dimensions

(Giudice, Luty, HM, Rattazzi)

(Boyda, HM, Pierce)

SUSY breakings always stay on the RGE trajectory

Anomaly Mediation

Too predictive

Too predictive!

  • Anomaly mediation highly predictive with only one parameter: overall scale

  • Slepton mass-squareds come out negative

  • Phenomenologically dead on start

  • Remedies:

    • Add uinversal scalar mass

    • Cause symmetry breaking via SUSY breaking

  • Destroys UV insensitivity

Viable uv insensitive anomaly mediation

Add U(1)B-L and U(1)YD-terms

Three SUSY-breaking parameters now

Can show that UV-insensitive

(Arkani-Hamed, Kaplan, HM, Nomura)

Viable UV-insensitiveAnomaly Mediation

Conformal sequestering

Conformal sequestering

  • Inspiration from AdS/CFT correspondence

  • Make hidden sector nearly superconformal

  • Dangerous coupling between hidden and observable fields suppressed because Kähler potential of hidden fields flow to IR fixed point (Luty, Sundrum)

  • Can be extended to include U(1) breaking sector to make the scenario phenomenologically viable (Harnik, HM, Pierce)

U 1 breaking sector

U(1) breaking sector

  • SO(5) theory with 6 spinors, no mass parameters

  • Gauge SU(4)SU(2)U(1) subgroup of global SU(6) symmetry

  • Quantum modified moduli space breaks U(1) (and also SU(4)Sp(2))

  • D-term “non-calculable” because compositeness scale L~v U(1)-breaking scale

  • Can be made calculable within the same universality class by (1) additional flavor L>>v or (2) additional color&flavor L<<v to show D0

  • Can be used to generate right-handed neutrino mass

    (Harnik, HM, Pierce)

Susy spectra

SUSY spectra

Models of flavor

Models of Flavor

Question of flavor

Question of Flavor

  • What distinguishes different generations?

    • Same gauge quantum numbers, yet different

  • Hierarchy with small mixings:

     Need some ordered structure

  • Probably a hidden flavor quantum number

     Need flavor symmetry

    • Flavor symmetry must allow top Yukawa

    • Other Yukawas forbidden

    • Small symmetry breaking generates small Yukawas

Broken flavor symmetry

Broken Flavor Symmetry

  • Flavor symmetry broken by a VEV ~0.02

  • SU(5)-like:

    • 10(Q, uR, eR) (+2, +1, 0)

    • 5*(L, dR) (+1, +1, +1)

    • mu:mc:mt~ md2:ms2:mb2~ me2:mm2:mt2 ~4: 2:1

Not bad

Not bad!

  • mb~ mt, ms ~ mm, md ~ me @MGUT

  • mu:mc:mt~ md2:ms2:mb2~ me2:mm2:mt2

New data from neutrinos

New Data from Neutrinos

  • Neutrinos are already providing significant new information about flavor symmetries

  • If LMA, all mixing except Ue3 large

    • Two mass splittings not very different

    • Atmospheric mixing maximal

    • Any new symmetry or structure behind it?

Is there a structure in neutrino masses mixings

Is There A StructureIn Neutrino Masses & Mixings?

  • Monte Carlo random complex 33 matrices with seesaw mechanism

    (Hall, HM, Weiner; Haba, HM)



  • No particular structure in neutrino mass matrix

    • All three angles large

    • CP violation O(1)

    • Ratio of two mass splittings just right for LMA

  • Three out of four distributions OK

    • Reasonable

       Underlying symmetries don’t distinguish 3 neutrinos.

Anarchy is peaceful

Anarchy is Peaceful

  • Anarchy (Miriam-Webster):

    “A utopian society of individuals who enjoy complete freedom without government”

  • Peaceful ideology that neutrinos work together based on their good will

  • Predicts large mixings, LMA, large CP violation

  • sin22q13 just below the bound

  • Ideal for VLBL experiments

  • Wants globalization!

More flavor parameters

More flavor parameters

  • Squarks, sleptons also come with mass matrices

  • Off-diagonal elements violate flavor: suppressed by flavor symmetries

  • Look for flavor violation due to SUSY loops

  • Then look for patterns to identify symmetries

     Repeat Gell-Mann–Okubo!

  • Need to know SUSY masses

To figure it out

To Figure It Out…

  • Models differ in flavor quantum number assignments

  • Need data on sin22q13, solar neutrinos, CP violation, B-physics, LFV, EWSB, proton decay

  • Archaeology

  • We will learn insight on origin of flavor by studying as many fossils as possible

    • cf. CMBR in cosmology

More fossils lepton flavor violation

More Fossils:Lepton Flavor Violation

  • Neutrino oscillation

     lepton family number is not conserved!

    • Any tests using charged leptons?

    • Top quark unified with leptons

    • Slepton masses split in up- or neutrino-basis

    • Causes lepton-flavor violation (Barbieri, Hall)

    • predict B(tmg), B(meg), me at interesting (or too-large) levels


Barbieri, Hall, Strumia

More fossils quark flavor violation

Now also large mixing between nt and nm

(nt, bR) and (nm , sR) unified in SU(5)

Doesn’t show up in CKM matrix

But can show up among squarks

CP violation in Bs mixing (BsJ/y f)

Addt’l CP violation in penguin bs (Bdf Ks)

(Chang, Masiero, HM)

More Fossils:Quark Flavor Violation



  • Dynamical supersymmetry breaking successfully produces hierarchy

  • Various mediation mechanisms

    • Gravity mediation + flavor symmetry

    • Gauge mediation

    • Anomaly mediation

    • Gaugino mediation

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