Alignment and Survey

1
Beyond the Standard Model
OR
Fmn SUSY like In SUSY

• Outline
• Standard Model Woes
• Allowed Symmetry
• SUSY Fixes all??
• Broken SUSY
• Are we really better off?

Todd Huffman University of Oxford
2
Introduction
6 quarks
6 leptons
SM Required
3 generations
3
Finishing off Higgs (production processes)
Associate Production
Direct Production
WW(ZZ)-fusion (gg?qqH0)
tt-fusion (gg?ttH0)
B)
D)
gg-fusion (gg?H0)
Higgs-Strahlung (qq?W(Z0)H0)
C)
A)
4
Higgs Production (production cross section, NLO)
Compare this to stot(pp)O(100 mb) or even
s(tt)O(1 nb) at LHC
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Higgs Decay (Branching Ratios)
Hint mW 80.2
?
160 GeV
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Still Hunting for Higgs
CDF 2006 results!
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Standard Model Woes

• Does not predict the masses of ANY particles.
• Only predicts masses of W and Z if we know what
  the Higgs vacuum expectation value is
• Running coupling constants to not unify
• Why do the quarks and leptons form generations?
• All Fermions Left-hand SU(2) doublets and Right
  hand singlets
• (e, ne)L (e)R (n)R??
• Why are there only 3 generations?
• What makes up all the matter in the Universe?
• There is no obvious method of including gravity
  in this picture.

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Show Grand Unification Failure transparency!!
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Standard Model Woes

• Hierachy Problem
• Suppose we have a fundamental scalar boson (like
  the higgs boson)
• Renormalization has to deal with ?

F
h
h

l
l
F
Quadradically Divergent!! AARRGGHH
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Standard Model Woes

• Hierachy Problem
• OK Lets assume a cut-off where we are sure there
  is other physics at the scale of mF.
• Renormalization ?

Higgs mass we actually measure 0.10 TeV
Result of the divergent integral - cutoff at
mF. 1016-0.10 TeV
Bare Higgs mass 1016 TeV
Would Nature tune the cut-off scale so precisely??
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Standard Model Woes

• Higgs
• Indirect from
• Top Mass and
• W mass
• Direct Searches
• qqbar ? Higgs
• H ? bbbar
• Current lower limit -
• about 100 GeV/c2
• Upper limit from global Electroweak fits to all
  existing measurements.

12
Colman - Mandula Theorem

• Q What kind of symmetries can you impose on a
  field theory and still have non-zero scattering?
• Coleman and Mandula say there are only 2 classes
  of conserved quantities
• External
• Poincare symmetry (Lorentz invariance)
• Energy-momentum conservation
• Angular momentum conservation
• Internal
• Gauge symmetries
• Electric charge conservation
• Color Charge conservation
• Paper Claimed No More Symmetries Left!

13
Colman - Mandula Theorem

• Loop hole!
• The Theorem does not forbid conserved charges
  that anti-commute.
• The one symmetry left open to us is
• Qfermiongt ? bosongt
• Qbosongt ? fermiongt
• If we assume that nature takes on this symmetry
  you generate the SuperSymmetric family of
  theories.
• (nature has taken every other available symmetry
  why not this one?)

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Super Symmetry
Every Particle now has a Supersymmetric
partner. All quantum numbers are the same
except the spin. Particle Spin SUSY
spin 1/2 ? 0 1 ? ½ Why not spin 1? Not
Minimal, too many DOF
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The MSSM
Note The Supersymmetry is at the field level,
NOT the particle level
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The MSSM

• Electroweak force at the field level actually
  only couples to SU(2)L ? a pair of left-handed
  doublets.
• This is NOT the W and Z bosons we see.
• Need to add-in the observed right-handed fermions
  from QCD in a sensible way.
• Add them in as SU(2) right-handed singlets.

• Why do we need all these left and right-handed
  SUSY states?
• Why not just copy direct from the observed
  particles?

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SUSY Solution

• Hierachy Problem
• Exact SUSY adds 2 scalars (one for left and one
  for right handed) for every massive Fermion

FL,R

l2
h
h
0
OKSo where are all the selectrons? A SUSY must
be a broken symmetry like SU(2) (Electro-weak).
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SUSY Solution

• Soft Breaking
• Make the scalar partners heavier than the
  fermions
• Then we get a correction to Mh of

If d lt O(1 TeV), Theres no fine tuning needed in
mh!
19
Broken SUSY

• Supersymmetric Theories describe the breaking
  through parameter sets all have
• 2 Higgs doublets ? 8 degrees of Freedom
• Need 3 of them to make the physical W and Z
  bosons.
• Left with 5 physical Higgs states
• h0, H0(CP), A0(CP-), H
• SUSY particles with identical quantum numbers
  will mix
• (uL,uR) ? u1,2 (analogous for d squarks and
  selectrons)
• (B,W3,H01,H02) ? ?01,2,3,4
• (W?,H?) ? ?1,2

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Broken SUSY

• Many Supersymmetric Theories Require a new
  quantum number called R - parity
• Multiplicative quantum number
• sparticles and (antisparticles) have R parity
  -1
• particles (antiparticles) have R parity 1
• If conserved then the lightest Supersymmetric
  sparticle would be stable.
• Cannot have Electric or Colour charge
• Would behave like a really massive neutrino in a
  detector.

g
Decay chain
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Show Long Decay Chain!
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CDF Detector
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Latest CDF Results(Neutralino)
Simple Search! Search for Two high energy
photons Large Missing Energy Harder to set limit
because neutralino is likely to interactvia the
weak force. Even the chargino (EM force) is
suppressedcompared to QCD at Tevatron.
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Latest CDF Results(Gluino QCD interactions)

• Much better!
• Gluino has the same quantum numbers as the gluon,
  but it is a fermion.
• Expect much higher rate of production at the
  Tevatron.
• Its essentially a gluon collider anyway.
• Note sbottom in final state!

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Latest CDF Results(Gluino QCD interactions)

• Combined Limit
• Sbottom and gluino
• Expect to gain factor of 3 by the end of data
  taking in 2009.
• ? 400-500 GeV/c2 for gluino and squark mass
  limits.

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ATLAS Unclothed!
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Show ATLAS SUSY projections!!!

• Not a real slide

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SUSY allows Unification

• Unification of Strong, Weak, and Electromagnetic
  forces.
• They now all come together!

Electromagnetic
IF There is SUSY. AND Forces do
unify Then SUSY threshold lies at 103 1 GeV
Weak
Strong
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SUSY Model Success?

• We solve the Hierarchy problem
• We get a motivation for the Higgs sector
• But its more complicated than SM Higgs.
• The Minimal Supersymmetric model allows the 3
  forces to Unify at the GUT scale.
• Requires a higgs mass less than 130 GeV/c2
  (falsifiable!)
• Possible candidates for Dark Matter.
• MSSM is a Superset of all reasonable models of
  Supersymmetry breaking.
• Nature will pick only onein which case we can
  gain
• Example SUGRA
• 5 parameters predicts masses of ALL the SUSY
  particles, including Vacuum Exp. Value of Higgs
  (and hence W and Z mass)
• Also requires that the Top quark mass be much
  larger than the masses of all the other
  quarks..one mystery explained.
• To Be Continued at a Large Hadron Collider near
  you!!!

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Problem with the Heirarchy problem?

• Higgs
• Indirect from
• Top Mass
• W mass
• Upper limit from global Electroweak fits to all
  existing measurements.
• Demands a light Higgs boson!!!

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SUSY The Small Heirarchy Problem?Or what
happens when theorists get nervous

• Tevatron data is showing no sign of gluino or
  squark.
• Soon the limits on their masses will make
  cancelation in the propogation of the Higgs so
  imperfect that it will be inconsistent with a
  low-mass Higgs.
• Thus inconsistent with indirect searches!
• Does this problem really exist???
• To Be Continued at a Large Hadron Collider near
  you!!!