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Review of the Open Questions and the Potential for Discoveries

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Title: Prospects in Particle Physics Author: johne Last modified by: johne Created Date: 9/26/2005 3:52:44 PM Document presentation format: On-screen Show – PowerPoint PPT presentation

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Title: Review of the Open Questions and the Potential for Discoveries


1
Review of the Open Questions and thePotential
for Discoveries
  • ICFA Seminar
  • Taegu, September 2005
  • John Ellis, TH Division, PH Department, CERN

2
Open Questions beyond the Standard Model
  • What is the origin of particle masses?
  • due to a Higgs boson? other physics?
  • solution at energy lt 1 TeV (1000 GeV)
  • Why so many types of matter particles?
  • matter-antimatter difference?
  • Unification of the fundamental forces?
  • at very high energy 1016 GeV?
  • probe directly via neutrino physics, indirectly
    via masses, couplings
  • Quantum theory of gravity?
  • (super)string theory extra space-time
    dimensions?

3
At what Energy is the New Physics?
Origin of mass
Dark matter
4
The State of the Higgs Summer 2005
  • Direct search limit
  • mH gt 114 GeV
  • Electroweak fit sensitive to mt
  • Currently mt 172.7 2.9 GeV
  • (previously mt 178 ? 174.3)
  • Best-fit value
  • mH 914532 GeV
  • 95 confidence-level upper limit
  • mH lt 186 GeV, or 219 GeV including direct limit

5
Indications on the Higgs Mass
Summer 2005
Sample observable W mass _at_ LEP Tevatron
6
Theorists getting Cold Feet
  • Composite Higgs model?
  • conflicts with precision electroweak data
  • Interpretation of EW data?
  • consistency of measurements? Discard some?
  • Higgs higher-dimensional operators?
  • corridors to higher Higgs masses?
  • Little Higgs models?
  • extra Top, gauge bosons, Higgses
  • Higgsless models?
  • strong WW scattering, extra D?

7
Elementary Higgs or Composite?
  • Higgs field
  • lt0H0gt ? 0
  • Quantum loop problems
  • Fermion-antifermion condensate
  • Just like QCD, BCS superconductivity
  • Top-antitop condensate? needed mt gt 200 GeV

Cutoff ? 10 TeV
  • New technicolour force?
  • inconsistent with
  • precision electroweak data?
  • Cut-off ? 1 TeV with
  • Supersymmetry?

8
Heretical Interpretation of EW Data
Do all the data tell the same story? e.g., AL vs
AH
What most of us think
9
Higgs Higher-Order Operators
Corridor to heavy Higgs?
Precision EW data suggest they are small why?
Do not discard possibility of heavy Higgs
10
Little Higgs Models
How to cancel loops?
Loop cancellation mechanisms
Supersymmetry
Little Higgs
11
Higgsless Models?
  • Four-dimensional versions
  • Strong WW scattering _at_ TeV, incompatible with
    precision data?
  • Break EW symmetry by boundary conditions in extra
    dimension
  • delay strong WW scattering to 10 TeV?
  • Kaluza-Klein modes mKK gt 300 GeV?
  • compatibility with precision data?

Lightest KK mode _at_ 300 GeV, strong WW _at_ 6-7 TeV
12
Higgs Discovery _at_ Tevatron?
13
Higgs Detection at the LHC
The Higgs may be found quite quickly
Higgs detection easier if heavier!
14
Tasks for the TeV ILC
  • Measure mt to lt ? 100 MeV
  • If there is a light Higgs of any kind, pin it
    down
  • Does it have standard model couplings?
  • What is its precise mass?
  • If there are extra light particles
  • Measure mass and properties
  • If LHC sees nothing new below 500 GeV
  • Look for indirect signatures

15
Precision Higgs Physics _at_ ILC
Higgs peak recoiling against Z ?µµ
Accuracy in Higgs couplings vs Standard Model,
2-Higgs doublets
16
Advantages of Higher Energy LC
Larger cross section _at_ 3 TeV can measure rare
decay modes
H ? bb
?g/g 4
?g/g 2
mH 120 GeV
mH 180 GeV
17
Loop Corrections to Higgs Mass2
  • Consider generic fermion and boson loops
  • Each is quadratically divergent ??d4k/k2
  • Leading divergence cancelled if
  • Supersymmetry!

2
2
18
Other Reasons to like Susy
It enables the gauge couplings to unify
It predicts mH lt 150 GeV
Approved by Fabiola Gianotti
19
Astronomers say that most of the matter in
the Universe is invisible Dark Matter
Lightest Supersymmetric particles ?
We shall look for them with the LHC
20
Possible Nature of Supersymmetric Relic from Big
Bang
  • 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 ? (partner of Z, H, ?)
  • Gravitino
  • (nightmare for astrophysical detection)

21
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
22
Supersymmetry Searches at LHC
LHC reach in supersymmetric parameter space
Typical supersymmetric Event at the LHC
Can cover most possibilities for astrophysical dar
k matter
23
Studies of Supersymmetric Parameter Space
Lines in susy space allowed by accelerators, WMAP
data
Specific benchmark Points along WMAP lines
Sparticle detectability Along one WMAP line
Calculation of relic density at a benchmark
point
Battaglia, De Roeck, Gianotti, JE, Olive, Pape
24
Sparticles at LC along WMAP Line
Complementary to LHC weakly-interacting
sparticles
Battaglia, De Roeck, Gianotti, JE, Olive, Pape
25
Examples of Sparticle Measurements
Threshold excitation _at_ LC
Spectrum edges _at_ LHC
Spectra _at_ LC
26
Added Value of LC Measurements
27
Tests of Unification Ideas
For gauge couplings
For sparticle masses
28
Sparticles may not be very light
Full Model samples
? Second lightest visible sparticle
Detectable _at_ LHC
Provide Dark Matter
Dark Matter Detectable Directly
Lightest visible sparticle ?
JE Olive Santoso Spanos
29
Sparticle Visibility at Higher E
CMSSM
3 TeV
5 TeV
See all sparticles measure heavier ones better
than LHC
30
What if Gravitino is Supersymmetric Relic?
  • NLSP next-to-lightest sparticle has
  • very long lifetime due to gravitational decay,
    e.g.
  • Could be hours, days, weeks, months or years!
  • Generic possibilities for NLSP
  • lightest neutralino ?
  • lightest slepton, probably lighter stau

31
Minimal Supergravity Model (mSUGRA)
More constrained than CMSSM m3/2 m0, B? A?
1
Excluded by b ? s ?
LEP constraints On mh, chargino
JE Olive Santoso Spanos
32
Slepton Trapping at the LHC?
If stau next-to-lightest sparticle (NLSP) may be
metastable may be stopped in detector/water tank
Trapping rate
Kinematics
Feng Smith
Hamaguchi Kuno Nakaya Nojiri
33
All Sparticles ? Stau NLSPs
  • Triggers include staus
  • Staus come with
  • many jets leptons
  • with pT hundreds of GeV,
  • produced centrally

De Roeck, JE, Gianotti, Moortgat, Olive Pape
34
Stau Mass Measurements by Time-of-Flight
  • Event-by-event
  • accuracy lt 10
  • lt 1 with full sample

De Roeck, JE, Gianotti, Moortgat, Olive Pape
35
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?

De Roeck, JE, Gianotti, Moortgat, Olive Pape
36
Extract Cores from Surrounding Rock?
Little room for water tanks in LHC
caverns, mainly 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
37
Open Questions beyond the Standard Model
  • What is the origin of particle masses?
  • due to a Higgs boson? other physics?
  • solution at energy lt 1 TeV (1000 GeV)
  • Why so many types of matter particles?
  • matter-antimatter difference?
  • Unification of the fundamental forces?
  • at very high energy 1016 GeV?
  • probe directly via neutrino physics, indirectly
    via masses, couplings
  • Quantum theory of gravity?
  • (super)string theory extra space-time
    dimensions?

38
Super B Factory Physics
Search for deviations from CKM CP violation
Search for rare decays that may deviate from the
Standard Model
39
Neutrino Mixing
  • Diagonalize neutrino mass matrix in flavour
    space
  • where
  • Two observable Majorana phases as well as
    Maki-Nakagawa-Sakata (MNS) mixing matrix
  • MNS matrix has 3 real angles and 1 phase
  • Even more parameters in minimal seesaw model!

40
Chasing the Third Mixing Angle
41
Chasing the CP-violating Phase
42
Open Questions beyond the Standard Model
  • What is the origin of particle masses?
  • due to a Higgs boson? other physics?
  • solution at energy lt 1 TeV (1000 GeV)
  • Why so many types of matter particles?
  • matter-antimatter difference?
  • Unification of the fundamental forces?
  • at very high energy 1016 GeV?
  • probe directly via neutrino physics, indirectly
    via masses, couplings
  • Quantum theory of gravity?
  • (super)string theory extra space-time
    dimensions?

43
String Theory
  • Candidate theory of quantum gravity
  • Point-like particles ? extended objects
  • Simplest possibility lengths of string
  • Open and/or closed
  • Quantum consistency fixes dimensions
  • Bosonic string 26, superstring 10
  • Requires extra dimensions
  • How large are they? scale 1/mP?

44
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?

45
Black Hole Production at LHC?
And if gravity becomes strong at the TeV scale
Multiple jets, leptons from Hawking radiation
46
Excitations in Models with Universal Extra
Dimensions
Can be distinguished via mass, angular
distributions
Spectra more degenerate than Susy - additional
higher-level states
47
Kaluza-Klein Gravitons in ee- Collisions
Spectrum of excitations in Randall-Sundrum model
Angular distribution in ee- ?µµ-
48
Summary
  • There are good prospects for new physics
    discoveries with upcoming colliders
  • Reasons to expect new physics _at_ TeV
  • Higgs, supersymmetry, extra dimensions (?)
  • Distinctive experimental signatures
  • The LHC _at_ CERN will open new energy range
  • Linear ee- colliders could explore in more
    detail
  • LHC will tell us the optimal energy

49
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