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Beyond%20the%20Standard%20Model

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Title: Beyond%20the%20Standard%20Model


1
Beyond the Standard Model
  • Commissioning update
  • Status of the Standard Model
  • Search for the Higgs boson
  • Look for supersymmetry/extra dimensions,
  • Find something the theorists did not expect
  • LHC Startup Forum
  • Coseners House, April 12th, 2007
  • John Ellis, TH Division, PH Department, CERN

2
LHC Installation Complete
3
LHC Cryogenic Operating Conditions
  • SC magnets _at_ 1.9 K, 1.3 bar
  • Superfluid He II below ? point
  • Low viscosity permeates magnets
  • High thermal conductivity, large specific heat
    stability

4
Cooldown of Sector 78
5
Magnet Temperatures in Sector 78
6
Inner-Triplet Saga I
  • Failure of heat exchanger at 9 bar
  • Thin copper accordion weakened by brazing
  • Engineering solution found
  • Remove and replace in situ

7
Inner-Triplet Saga II
  • Failure of cold-mass support at 20 bar
  • Broke apart damage to feed box?
  • Due to asymmetric force on quadrupole
  • Damaged assembly must be replaced
  • Others may be reinforced in situ
  • Insert tie rods in cryostat
  • Cock-up
  • dixit UK
  • ambassador

8
Remaining LHC Milestones
Last magnet delivered October 2006
Last magnet tested December 2006
Last magnet installed March 2007
Machine closed August 2007
First collisions November 2007 ?
9
Status of the Standard Model
  • Perfect agreement with all confirmed accelerator
    data
  • Consistency with precision electroweak data (LEP
    et al) only if there is a Higgs boson
  • Agreement seems to require a relatively light
    Higgs boson weighing lt 150 GeV
  • Raises many unanswered questions
  • mass? flavour? unification?

10
Indications on the Higgs Mass
March 2007
Combined information on Higgs mass
Sample observable W mass _at_ LEP Tevatron
mW, mt both reduced by ½ s
11
The LHC Physics Haystack(s)
  • Cross sections for heavy particles
  • 1 /(1 TeV)2
  • Most have small couplings a2
  • Compare with total cross section
  • 1/(100 MeV)2
  • Fraction 1/1,000,000,000,000
  • Need 1,000 events for signal
  • Compare needle
  • 1/100,000,000 m3
  • Haystack 100 m3
  • Must look in 100,000 haystacks

Interesting cross sections
Susy
Higgs
12
Huge Statistics thanks to High Energy and
Luminosity
Event rates in ATLAS or CMS at L 1033 cm-2 s-1

LHC is a factory for anything top, W/Z, Higgs,
SUSY, etc. mass reach for discovery of new
particles up to m 5 TeV
13
Start-up Physics
  • Measure and understand minimum bias
  • Measure jets, start energy calibration
  • Measure W/Z, calibrate lepton energies
  • Measure top, calibrate jet energies missing ET
  • First searches for Higgs
  • Combine many signatures
  • need to understand detector very well
  • First searches for SUSY, etc.

14
Looking for New Physics _at_ LHC
  • Need to understand SM first
  • calibration, alignment, systematics
  • Searches for specific scenarios, e.g., SUSY, vs
    signature-based searches, e.g., monojets?
  • False dichotomy!
  • How to discriminate between models?
  • different Z models?
  • missing energy SUSY vs UED?
  • higher excitations, spin correlations, spectra,

15
Some Sample Higgs Signals
A la recherche du Higgs perdu
??
??
tt
ZZ -gt 4 leptons
16
Potential of Initial LHC running
  • A Standard Model Higgs boson could be discovered
    with 5-s significance with 5fb-1, 1fb-1 would be
    sufficient to exclude a Standard Model Higgs
    boson at the 95 confidence level
  • Signal would include tt, ??, bb, WW and ZZ
  • Will need to understand detectors very well

17
Subsequent LHC Running
  • Will be possible to determine spin of Higgs
    decaying to ?? or ZZ
  • Can measure invisible Higgs decays at 15-30
    level
  • Will be possible to determine many Higgs-particle
    couplings at the 10-20 level

18
The Big Open Questions
  • The origin of particle masses?
  • Higgs boson? extra physics?
  • solution at energy lt 1 TeV (1000 GeV)
  • Why so many types of particles?
  • and the small matter-antimatter difference?
  • Unification of the fundamental forces?
  • at very high energy?
  • explore indirectly via particle masses,
    couplings
  • Quantum theory of gravity?
  • string theory extra dimension?

LHC
LHC
LHC
LHC
19
What is Supersymmetry (Susy)?
  • The last undiscovered symmetry?
  • Could unify matter and force particles
  • Links fermions and bosons
  • Relates particles of different spins
  • 0 - ½ - 1 - 3/2 - 2
  • Higgs - Electron - Photon - Gravitino -
    Graviton
  • Helps fix masses, unify fundamental forces

20
Loop Corrections to Higgs Mass2
  • Consider generic fermion and boson loops
  • Each is quadratically divergent ??d4k/k2
  • Leading divergence cancelled if
  • Supersymmetry!

2
2
21
Other Reasons to like Susy
It enables the gauge couplings to unify
It predicts mH lt 150 GeV
As suggested by EW data
Erler 2007
JE, Nanopoulos, Olive Santoso hep-ph/0509331
22
Astronomers say that most of the matter in
the Universe is invisible Dark Matter
Supersymmetric particles ?
We shall look for them with the LHC
23
Lightest Supersymmetric Particle
  • Stable in many models because of conservation of
    R parity
  • R (-1) 2S L 3B
  • where S spin, L lepton , B baryon
  • Particles have R 1, sparticles R -1
  • Sparticles produced in pairs
  • Heavier sparticles ? lighter sparticles
  • Lightest supersymmetric particle (LSP) stable

Fayet
24
Possible Nature of LSP
  • No strong or electromagnetic interactions
  • Otherwise would bind to matter
  • Detectable as anomalous heavy nucleus
  • Possible weakly-interacting scandidates
  • Sneutrino
  • (Excluded by LEP, direct searches)
  • Lightest neutralino ?
  • Gravitino
  • (nightmare for astrophysical detection)

25
Constraints on Supersymmetry
  • Absence of sparticles at LEP, Tevatron
  • selectron, chargino gt 100 GeV
  • squarks, gluino gt 250 GeV
  • Indirect constraints
  • Higgs gt 114 GeV, b ? s ?
  • Density of dark matter
  • lightest sparticle ?
  • WMAP 0.094 lt O?h2 lt 0.124

26
Current Constraints on CMSSM
Assuming the lightest sparticle is a neutralino
Excluded because stau LSP
Excluded by b ? s gamma
WMAP constraint on relic density
Excluded (?) by latest g - 2
JE Olive Santoso Spanos
27
Classic Supersymmetric Signature
Missing transverse energy carried away by dark
matter particles
28
Search for Supersymmetry
Light sparticles _at_ low luminosity
Heavy sparticles
29
Initial LHC Reach for Supersymmetry
How soon will we know?
30
Implications of LHC Search for ILC
In CMSSM
LHC gluino mass reach
Corresponding sparticle thresholds _at_ ILC
LHC already sees beyond ILC at turn-on
1 year _at_ 1033
month _at_ 1032
1 year _at_ 1034
month _at_ 1033
Blaising et al 2006
31
Precision Observables in Susy
Can one estimate the scale of supersymmetry?
Sensitivity to m1/2 in CMSSM along WMAP
lines for different A
mW
tan ß 50
tan ß 10
sin2?W
Present possible future errors
JE Heinemeyer Olive Weber Weiglein 2007
32
MoreObservables
tan ß 10
tan ß 50
b ? s?
gµ - 2
JE Heinemeyer Olive Weber Weiglein 2007
33
Global Fitto allObservables
tan ß 10
tan ß 50
Likelihood for m1/2
Likelihood for Mh
JE Heinemeyer Olive Weber Weiglein 2007
34
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35
Search for Squark ? W ? Hadron Decays
  • Use kT algorithm to define jets
  • Cut on W mass
  • W and QCD jets have different subjet splitting
    scales
  • Corresponding to y cut

Butterworth JE Raklev 2007
36
Search for Hadronic W, Z Decays
  • Background-subtracted qW mass combinations in
    benchmark scenarios
  • Constrain sparticle mass spectra

Butterworth JE Raklev 2007
37
Possible Nature of SUSY Dark Matter
  • No strong or electromagnetic interactions
  • Otherwise would bind to matter
  • Detectable as anomalous heavy nucleus
  • Possible weakly-interacting scandidates
  • Sneutrino
  • (Excluded by LEP, direct searches)
  • Lightest neutralino ?
  • Gravitino
  • (nightmare for astrophysical detection)

GDM a bonanza for the LHC!
38
Possible Nature of NLSP if GDM
  • NLSP next-to-lightest sparticle
  • Very long lifetime due to gravitational decay,
    e.g.
  • Could be hours, days, weeks, months or years!
  • Generic possibilities
  • lightest neutralino ?
  • lightest slepton, probably lighter stau
  • Constrained by astrophysics/cosmology

39
Triggering on GDM Events
Will be selected by many separate triggers
via combinations of µ, E energy, jets, t
JE, Raklev, Øye 2007
40
Efficiency for Detecting Metastable Staus
Good efficiency for reconstructing stau tracks
JE Raklev Oye
41
ATLAS Momentum resolution
Good momentum resolution
JE Raklev Oye
42
Reconstructing GDM Events
Squark ? q ?
? ? stau t
JE, Raklev, Øye 2006
43
Stau Momentum Spectra
  • ß? typically peaked 2
  • Staus with ß? lt 1 leave central tracker
  • after next beam crossing
  • Staus with ß? lt ¼ trapped inside calorimeter
  • Staus with ß? lt ½ stopped within 10m
  • Can they be dug out of cavern wall?

De Roeck, JE, Gianotti, Moortgat, Olive Pape
hep-ph/0508198
44
Extract Cores from Surrounding Rock?
Very little room for water tank in LHC
caverns, only in forward directions where few
staus
  • Use muon system to locate impact point on cavern
    wall with uncertainty lt 1cm
  • Fix impact angle with accuracy 10-3
  • Bore into cavern wall and remove core of size 1cm
    1cm 10m 10-3m3 100 times/year
  • Can this be done before staus decay?
  • Caveat radioactivity induced by collisions!
  • 2-day technical stop 1/month
  • Not possible if lifetime 104s, possible if 106s?

De Roeck, JE, Gianotti, Moortgat, Olive Pape
hep-ph/0508198
45
String Theory
  • Candidate for reconciling gravity with quantum
    mechanics
  • Point-like particles ? extended objects
  • Simplest possibility lengths of string
  • Quantum consistency fixes dimensions
  • Bosonic string 26, superstring 10
  • Must compactify extra dimensions, scale 1/mP?
  • Or larger?

46
How large could extra Dimensions be?
  • 1/TeV?
  • could break supersymmetry, electroweak
  • micron?
  • can rewrite hierarchy problem
  • Infinite?
  • warped compactifications
  • Look for black holes, Kaluza-Klein excitations
    _at_ colliders?

47
Spin Effects in Decay Chains
Shape of dilepton spectrum
Chain DCBA Scalar/Fermion/Vector
Distinguish supersymmetry from extra-D scenarios
Angular asymmetry in q-lepton spectrum
Shape of q-lepton spectrum
AthanasiouLesterSmillieWebber
48
Black Hole Production at LHC?
And if gravity becomes strong at the TeV scale
Multiple jets, leptons from Hawking radiation
49
Black Hole Production _at_ LHC
Cambridge al et Webber
50
Black Hole Decay Spectrum
Cambridge al et Webber
51
Summary
  • The origin of mass is the most pressing in
    particle physics
  • Needs a solution at energy lt 1 TeV
  • Higgs? Supersymmetry?
  • LHC will tell!
  • Lots of speculative ideas for other physics
    beyond the Standard Model
  • Grand unification, strings, extra dimensions?
  • LHC may also probe these speculations

We do not know what the LHC will find its
discoveries will set agenda for future projects
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