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Fmn SUSY like In SUSY
Outline

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

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Standard Model Woes
Allowed Symmetry
SUSY Fixes all??
Broken SUSY
Are we really better off?
Todd Huffman
University of Oxford
Introduction
SM Required:
Higgs
7/20/2015
H0
0
110<mH<250
Finishing off Higgs (production processes)
Associate Production
Direct Production
tt-fusion (ggttH0)
WW(ZZ)-fusion (ggqqH0)
q’
q
W,Z
H0
B)
W,Z
q’’
t
g
H0
D)
g
t
Higgs-Strahlung (qqW(Z0)H0)
0
H
q’
W,Z0
C)
q
W,Z0
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q’’’
gg-fusion (ggH0)
g
A)
g
x
H0
Higgs Production (production cross section, NLO)
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Compare this to stot(pp)=O(100 mb)
or even s(tt)=O(1 nb) at LHC
Higgs Decay
(Branching Ratios)
?
160 GeV
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Hint:
mW = 80.2
Still Hunting for Higgs
Peter Higgs
Edinburgh U.
CDF 2006 results!
7/20/2015
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
~
c

2
16
2
F
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
4
d k
0 k 2  mF2  
Quadradically Divergent!! AARRGGHH
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 
physical
h
m
Higgs mass we
actually measure
~ 0.10 TeV
Bare Higgs mass
~ 1016 TeV
 mh  O(mF )
Result of the
divergent integral cutoff at mF.
~ 1016-0.10 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
• q+qbar  Higgs
• H  b+bbar
Current lower limit about 100 GeV/c2
Upper limit from global
Electroweak fits to all
existing measurements.
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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!
7/20/2015
Colman - Mandula Theorem
– Loop hole!
– The Theorem does not forbid conserved charges that
anti-commute.
– The one symmetry left open to us is:
• Q|fermion>  |boson>
• Q|boson>  |fermion>
– 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
SM particle
Superpartner
LH quark QL
RH (u,c,t) uR
RH down dR
LH lepton LL
RH lepton eR
Higgs H1
Higgs H2
Gluon g
W bosons W
Y boson B
Squark QL
Squark uR
Squark uR
Slepton LL
Slepton eR
Higgsino H1
Higgsino H2
Gluino g
Winos W
Bino B
SU(3),SU(2),Y
(3,2,1/6)
(3,1,2/3)
(3,1,2/3)
(1,2,1/2)
(1,1,-1)
(1,2,1/2)
(1,2,-1/2)
(8,1,0)
(1,3,0)
(1,1,-1)
Note: The Supersymmetry is at the field level, NOT the particle level
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The MSSM
 Why do we need
all these left and
right-handed
SUSY states?
 Why not just copy
direct from the
observed
particles?
 Electroweak force at
the field level actually
only couples to
SU(2)L  a pair of lefthanded 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.
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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
F
h
FL,R
+
h
2
h


F
h
=0
OK…So where are all the selectrons?
A: SUSY must be a broken symmetry like SU(2) (Electro-weak).
7/20/2015
SUSY Solution
Soft Breaking
– Make the scalar partners heavier than
the fermions:
m
2
~
f L ,R
 m 
2
F
2
– Then we get a correction to Mh of

m
2
2
4
m ~
(4  2 ln
)  o( )
2
16
m
2
h
2
F
2
If  < O(1 TeV), There’s no fine tuning needed in mh!
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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
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.
q~
g
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~
q
Decay
chain
~10
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 interact
via the weak force. Even the
chargino (EM force) is suppressed
compared to QCD at Tevatron.
7/20/2015
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.
• It’s essentially a
gluon collider
anyway.
 Note sbottom in
final state!
7/20/2015
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!
60
Electromagnetic
IF:
There is SUSY. 1/a
AND:
Forces do unify
Then:
SUSY threshold lies
at 103 ±1 GeV
50
40
Weak
30
20
Strong
10
100
105
1010
1015
1020
SUSY Model Success?
– We solve the Hierarchy problem
– We get a motivation for the Higgs sector
• But it’s 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 one…in 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!!!
7/20/2015
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!!!
7/20/2015
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!!!
7/20/2015