The Search For Supersymmetry
description
Transcript of The Search For Supersymmetry
![Page 1: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/1.jpg)
The Search For Supersymmetry
Liam Malone and Matthew French
![Page 2: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/2.jpg)
SupersymmetryA Theoretical View
![Page 3: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/3.jpg)
Introduction
Why do we need a new theory? How does Supersymmetry work? Why is Supersymmetry so popular? What evidence has been found?
![Page 4: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/4.jpg)
The Standard Model
6 Quarks and 6 Leptons.
Associated Anti-Particles.
4 Forces – but only successfully describes three.
![Page 5: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/5.jpg)
Symmetries and Group Theory
Each force has an associated symmetry. This can be described by a group. The group SU(N) has N2-1 parameters. These parameters can be seen as the amount of
mass-less bosons required to mediate the force. Ideally the standard model is a
SU(3)×SU(2)×U(1) model.
![Page 6: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/6.jpg)
Weak Force
Weak force is very short range due to its massive bosons.
Have difficulty adding massive bosons and keeping the gauge invariance of the theory.
Yet scalar bosons are proposed. Some other process is taking place.
![Page 7: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/7.jpg)
The Higgs Mechanism
Higgs mechanism solves this problem. Uses SPONTANEOUS SYMMETRY
BREAKING. Mix the SU(2) and U(1) symmetry into one
theory. Creates three massive bosons for the weak
force, the Higgs and the mass-less photon.
![Page 8: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/8.jpg)
Renormalisation
Used to calculate physical quantities like the coupling constants of each force or the mass of a particle.
Sum over all interactions. Have to use momentum cut-off. Results in the quantity being dependant on
the energy scale it is measured on.
![Page 9: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/9.jpg)
The Hierarchy Problem
Renormalizing fermion masses gives contributions from:
Renormalising the Higgs mass gives contributions from:
2
2
ln4
3~
fff m
Lm
π
αdm
)4
(~ 22 Lπ
αOdm
H
![Page 10: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/10.jpg)
Other Problems with the Standard Model
No one knows why the electroweak symmetry is broken at this scale.
Why are the three forces strengths so different?
Why the 21 seemingly arbitrary parameters?
![Page 11: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/11.jpg)
History of Supersymmetry
First developed by two groups, one in USSR and one in USA.
Gol’fund and Likhtmann were investigating space-time symmetries in the USSR.
Pierre Ramond and John Schwarz were trying to add fermions to boson string theory in the USA.
![Page 12: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/12.jpg)
Supersymmetry
In renormalisation fermion terms and boson terms have different signs.
Therefore a fermion with the same charge and mass a boson will have equal and opposite contributions.
The basis of supersymmetry – every particle has a super partner of the opposite type.
![Page 13: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/13.jpg)
Supersymmetry
In Quantum Mechanics this could be written as:
The operator Q changes particle type. Q has to commute with the Hamiltonian because
of the symmetry involved:
| |
| |
Q fermion boson
Q boson fermion
[ , ] 0Q H
![Page 14: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/14.jpg)
Supersymmetry
The renormalised scalar mass now has the contributions from two particles:
2 2 2 2 2 2 2~ ( )( ) - ( )( ) ( )( - )4 4 4H B F B Fdm O L m O L m O m m
The only thing that this requires is the stability of the weak scale:
222 1- TeVmm FB
![Page 15: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/15.jpg)
Constraints on SUSY
124 parameters required for all SUSY models.
However some phenomenological constraints exist.
These mean some SUSY models are already ruled out.
![Page 16: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/16.jpg)
Minimal Supersymmetric Standard Model
In supersymmetry no restrictions are placed on the amount of new particles.
Normally restrict the amount of particles to least amount required.
This is the Minimal Supersymmetric Standard Model (MSSM).
![Page 17: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/17.jpg)
MSSM
All particles gain one partner.
Gauge bosons have Gauginos: E.g The Higgs has the Higgsinos.
Fermions have Sfermions: E.g Electron has Selectron and Up quark has the
Sup.
![Page 18: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/18.jpg)
Constrained MSSM
A subset of the MSSM parameter space.
Assumes mass unification at a GUT scale.
This gives only five parameters to consider.
![Page 19: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/19.jpg)
The Five Parameters
M1/2 the mass that the gauginos unify at.
M0 the mass at which the sfermions unify at. Tan β is the ratio of the vacuum values of the
two Higgs bosons. A0 is the scalar trilinear interaction strength. The sign of the Higgs doublet mixing
parameter.
![Page 20: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/20.jpg)
Figure showing the mass unification at grand scales. The five parameters m1/2=250 GeV, m0 = 100 GeV, tan β= 3, A0=0 and μ>0.
![Page 21: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/21.jpg)
Local or Global?
Supersymmetry could be local or global symmetry.
Local symmetries are like the current standard model.
If SUSY is global has implications on symmetry breaking mechanisms.
![Page 22: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/22.jpg)
SUSY Breaking
SUSY has to be broken between current experiment scales and Planck scale.
Natural to try and add in Higgs mechanism but this reintroduces Hierarchy problem.
Two possible ways: Gravity Interactions of the current gauge fields and the
superpartners
![Page 23: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/23.jpg)
Gravity mediated breaking
In super gravity get graviton and gravitino.
Gravitino acquires mass when SUSY is broken.
If gravity mediates the breaking, LSP is the neutalino or sneutrino.
![Page 24: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/24.jpg)
Gauge Mediated Breaking
If SM gauge fields mediate the SUSY breaking then SUSY is broken a lower scale.
Gravitino therefore has a very small mass and is the LSP.
Other Models do exist.
![Page 25: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/25.jpg)
R-Parity Conservation
R-parity is a new quantity defined by:
All SM particles have R-parity 1 but all super partners have -1.
It is this that makes the LSP stable.
SLBR 2)-(31-
![Page 26: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/26.jpg)
Dark Matter
Cosmologists believe most matter is dark matter.
Inferred this from observing motions of galaxys.
No one’s sure what it is.
![Page 27: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/27.jpg)
Dark Matter
If R-parity is conserved then the Lightest Super Partner (LSP) will be stable.
Could explain the Dark Matter in the universe.
Depends on SUSY parameters whether the LSP is a gaugino or a sfermion.
![Page 28: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/28.jpg)
Which LSP?
Graph showing regions of different LSP’s.Tan β =2
![Page 29: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/29.jpg)
Proton Decay
The best GUT prediction is 1028 years.
Current best guess is greater than 5.5×1032
years.
SUSY can be used to fix this problem.
![Page 30: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/30.jpg)
Other Advantages of SUSY
Grand Unified Theories (GUTs). Current understanding is just a low energy
approximation to some grand theory. On a large energy scale all forces and
particles should essentially be the same. Coupling constants should equate at high
energy.
![Page 31: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/31.jpg)
Figure (a): Coupling constants in the standard model
Figure (b): Coupling constants a GUT based on SUSY
![Page 32: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/32.jpg)
Possible GUTs
The main competitor is a theory based on SU(5) symmetry.
Has 24 gauge bosons mediating a single force.
Others as well like one on SO(10) with 45 bosons!
![Page 33: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/33.jpg)
Conclusions
The Standard Model has problems when considered above the electroweak scale.
Supersymmetry solves some of these problems.
Supersymmetry can also be used to explain cosmological phenomena.
![Page 34: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/34.jpg)
SupersymmetryExperimental Issues and
Developments
![Page 35: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/35.jpg)
Outline
Motivation for SUSY (continued) Detecting SUSY Current and future searches Results & constraints so far
![Page 36: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/36.jpg)
Motivation for SUSY
Convergence of coupling constants Proton lifetime Dark matter (LSP) Anomalous muon magnetic moment Mass hierarchy problem
![Page 37: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/37.jpg)
Convergence of Coupling Constants 1
In a GUT coupling constants meet at high energy
GUT gauge group must be able to contain SU(3)xSU(2)xU(1)
SU(5) best candidate Three constants:
21 5 /(3cos )W
22 / sin W
23 /(4 )sg
![Page 38: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/38.jpg)
Convergence of Coupling Constants 2
Sou
rce:
Kaz
akov
, D I
; arx
iv.o
rg/h
ep-p
h/00
1228
8
![Page 39: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/39.jpg)
Dark Matter
A leading candidate is the LSP SM has R=1 & SUSY has R=-1 Conservation of R-parity R-parity conservation ensures SUSY
particles only decay to other SUSY particles so LSP is stable
3( ) 2( 1) B L SR
![Page 40: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/40.jpg)
WMAP 1
Sou
rce:
http
://m
ap.g
sfc.
nasa
.gov
![Page 41: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/41.jpg)
WMAP 2
Sou
rce:
http
://m
ap.g
sfc.
nasa
.gov
![Page 42: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/42.jpg)
WMAP 3
73% dark matter in universe Total matter density Improves prospect of discovery at LHC Within reach of 1TeV linear collider
2 0.01610.01810.1126CDMh
400 500m GeV
2
1
tan
![Page 43: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/43.jpg)
WMAP 4
Adapted from: J. Ellis et al, Phys, Lett B 565, 176-182
![Page 44: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/44.jpg)
Anomalous Muon Magnetic Moment
Experiment
Dirac theory:
QED corrections: virtual particles Deviation from SM of
1.00116592032muon
e
m
h
1.6 2.6
12muon
e
m
h
![Page 45: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/45.jpg)
Anomalous Muon Magnetic Moment 2
![Page 46: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/46.jpg)
Anomalous Muon Magnetic Moment 3
Sou
rce:
http
://ar
xiv.
org/
hep-
ex/0
4010
08
![Page 47: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/47.jpg)
Who is looking for SUSY particles?
LEP Tevatron LHC – from 2007? ILC
Currently no experimental evidence found Can only constrain models
![Page 48: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/48.jpg)
LEP
Sou
rce:
http
://in
tran
et.c
ern.
ch/P
ress
/Pho
toD
atab
ase/
![Page 49: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/49.jpg)
LEP
Sou
rce:
http
://in
tran
et.c
ern.
ch/P
ress
/Pho
toD
atab
ase/
![Page 50: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/50.jpg)
s-fermion searches
Production
Decay
Events with missing energy ~ 0
1fM m m
![Page 51: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/51.jpg)
LEP Results 1
sleptons: selectron, smuon, stau Decay of sleptons Mass of s-lepton depends on mass of
neutralino
~
1R ll
![Page 52: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/52.jpg)
LEP Results 2
Sou
rce:
LE
P2
SU
SY
Wor
king
Gro
up
![Page 53: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/53.jpg)
LEP Results 3
s-lepton lower mass limit
neutralino mass
selectron 99.9 GeV 0 GeV
99.9 GeV 40 GeV
smuon 94.9 GeV 0 GeV
96.6 GeV 40 GeV
stau 86.6 GeV 0 GeV
92.6 GeV 40 Gev
Source: LEP2 SUSY Working Group
![Page 54: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/54.jpg)
LEP Results 4
Sou
rce:
LE
P2
SU
SY
Wor
king
Gro
up
![Page 55: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/55.jpg)
Tevatron
Sou
rce:
ww
w.f
nal.g
ov/p
ub/p
ress
pass
/vis
med
ia/in
dex.
htm
l
![Page 56: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/56.jpg)
Tevatron
Sou
rce:
ww
w.f
nal.g
ov/p
ub/p
ress
pass
/vis
med
ia/in
dex.
htm
l
![Page 57: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/57.jpg)
Tevatron Results 1
CDF & D0 Searches for bottom squarks
Photon + missing energy searches
Search for R-parity violation
NLSP LSP
01b b % %
![Page 58: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/58.jpg)
Tevatron Results 2
Sou
rce:
htt
p://
ww
w.d
pf99
.libr
ary.
ucla
.edu
/ses
sion
7/H
ED
IN07
09.P
DF
![Page 59: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/59.jpg)
LHC
Starting 2007 14TeV proton-proton collider ATLAS & CMS
![Page 60: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/60.jpg)
ATLAS
Sou
rce:
http
://at
las.
ch
![Page 61: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/61.jpg)
SUSY at ATLAS
Assuming MSSM & R-parity conservation SUSY production at LHC dominated by
gluino and squark production Decay signature is distinctive cf SM Large missing energy & multiple jets
![Page 62: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/62.jpg)
SUSY at ATLAS 2
Sou
rce:
SU
SY
at A
TL
AS
talk
, Fra
nk P
aige
![Page 63: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/63.jpg)
CMS
Source: http://cmsinfo.cern.ch
![Page 64: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/64.jpg)
ILC
International linear collider Election-positron
Large electron polarisation Clean beams Beam energy can be tuned
![Page 65: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/65.jpg)
Verifying SUSY at ILC
Pair production Precise study: mass, spin, coupling, mixing Look of SUSY breaking mechanism
Highly polarised source means background can be reduced to ~0
![Page 66: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/66.jpg)
Mass and Spin
SUSY: and
Electron :: spin ½ :: light Selectron :: spin 0 :: heavy
Higgs :: spin 0 :: heavy Higgsino :: spin ½ :: light
0 0 0, , , ,h H H H A 0 0 0, , , ,h H H H A % %% % %
![Page 67: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/67.jpg)
If SUSY is not Found
![Page 68: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/68.jpg)
Summary SUSY Particle Masses
46m GeV01%02%03%
62.4m GeV
99.9m GeV
1 % 94m GeV
Source: Particle Date Group: http://pdg.lbl.gov/2004/tables/sxxx.pdf
e%%%
73m GeV
94m GeV
81.9m GeV
q%b%
t%
250m GeV
89m GeV
95.7m GeV
![Page 69: The Search For Supersymmetry](https://reader035.fdocuments.in/reader035/viewer/2022062723/56813de4550346895da7b8e4/html5/thumbnails/69.jpg)
Summary
WMAP, LEP, Tevatron have placed limits If SUSY exists LHC expected to find it ILC – detailed examination of SUSY
particles