Magnetic Monopoles in the Cosmos and at the LHC
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Magnetic Monopoles in the Cosmos and at the LHC Arttu Rajantie MoEDAL Physics Workshop CERN, 20 June 2012
description
Magnetic Monopoles in the Cosmos and at the LHC. Arttu Rajantie MoEDAL Physics Workshop CERN, 20 June 2012. Maxwell Equations. Duality. Dirac Monopole (1931). Vector potential Dirac string: Singularity along QM: Unobservable if . Dirac Monopole (1931). - PowerPoint PPT Presentation
Transcript of Magnetic Monopoles in the Cosmos and at the LHC
Magnetic Monopolesin the Cosmos and at the LHC
Arttu RajantieMoEDAL Physics WorkshopCERN, 20 June 2012
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 220 June 2012
Maxwell Equations
Duality
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 3
Vector potential
Dirac string: Singularity along QM: Unobservable if
20 June 2012
Dirac Monopole (1931)
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 4
Dirac quantisation condition:All electric and magnetic charges must satisfy
Existence of monopoles would explain observed quantisation of electric charge
“…one would be surprised if Nature had made no use of it”
20 June 2012
Dirac Monopole (1931)
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 5
Magnetic Coulomb field:
Magnetic charge localised at a point
Divergent energy:
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Dirac Monopole (1931)
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 6
Full quantum calculation: Monopole loops Difficult to formulate:
Two vector potentials (Schwinger 1975) Strong coupling
20 June 2012
QFT of Monopoles
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 7
Smooth “hedgehog” solution in SU(2)+adjoint Higgs Magnetic charge Finite mass
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‘t Hooft-Polyakov Monopole (1974)
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 8
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20 June 2012
‘t Hooft-Polyakov Monopole (1974)
Consistent quantum field theory setup Large : Still non-perturbative Lattice simulations:
Mass, scattering (AR&Weir 2011)
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 9
‘t Hooft-Polyakov Monopole (1974)
20 June 2012
Exist whenever a simple Lie group is broken to something with a U(1) factor: Grand Unification
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 10
Standard Model:EM & weak forces unified above 100 GeV
Grand Unified Theory (GUT): Electroweak & strong forces unified above 1016 GeV◦ e.g.
20 June 2012
Grand Unification
Electro- weak
Theory
Grand Unified Theory
Theory of Everything
grav
ity
stro
ng
wea
k
elec
trom
agne
tic
ener
gy
102 GeV
1019 GeV
1016 GeV
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 11
Generic prediction of GUTs
Mass typically at GUT scale
Also dyons with both electric and magnetic charge
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GUT Monopoles
Electro- weak
Theory
Grand Unified Theory
Theory of Everything
grav
ity
stro
ng
wea
k
elec
trom
agne
tic
ener
gy
102 GeV
1019 GeV
1016 GeV
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 12
More complex GUTs,e.g.
Monopoles with different charges
Can be lightere.g. in an family unification model (Kephart et al)
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GUT Monopoles
Electro- weak
Theory
Grand Unified Theory
Theory of Everything
grav
ity
stro
ng
wea
k
elec
trom
agne
tic
ener
gy
102 GeV
1019 GeV
1016 GeV
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 13
S-duality:Any superstring theory has magnetic monopoles
Typical mass Can be reduced by large extra dimensions or warped
compactification, perhaps even to (Witten 2002)
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String Theory Monopoles
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 14
Massive range of energies between EW and GUT:Plenty of room for new physics
Cho-Maison monopole (1996):Dirac solution generalised to electroweak theory
Monopoles do not have to arise from unification
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Other Light Monopoles
Electro- weak
Theory
Grand Unified Theory
Theory of Everything
grav
ity
stro
ng
wea
k
elec
trom
agne
tic
ener
gy
102 GeV
1019 GeV
1016 GeV
?
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 15
Hot Big Bang:GUT symmetry breaksin a phase transition
The Higgs field chooses a direction randomly
Kibble (1976):Monopoles form, at least one per horizon→
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Monopoles in Cosmology
x
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 16
Monopoles annihilate until they cannot find partners:Density decreases to
(Zel’dovich & Khlopov 1979, Preskill 1979) Total energy density in the universe: Monopoles exceed this unless Guth (1981):
Period of inflation (accelerating expansion) dilutes monopoles away
20 June 2012
Monopole Problem
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 17
Density constraint interms of flux :Monopoles hitting unit area per unit time
Uniform distribution:
20 June 2012
Monopole Problem
(Turner et al 1982)
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 18
Galactic magnetic fields
If , thiscreates a magnetic current, which dissipates the field
Sets an upper bound on flux
Bound gets weaker at higher
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Parker Bound (1970)
(Turner et al 1982)
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 19
If , monopoles remain bound to galaxies
Constraint from the totalmass of the Milky Way:
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Parker Bound (1970)
(Turner et al 1982)
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 20
Early detections:◦ Berkeley 1975, Stanford 1982, Imperial 1986◦ All turned out to be false
20 June 2012
Cosmic Rays
(Cabrera 1982)
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 21
MACRO (Gran Sasso, Italy):◦ Upper bound over wide mass range
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Cosmic Rays
(Giacomelli et al 2011)
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 22
RICE (South Pole):◦ Intermediate mass monopoles
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Cosmic Rays
(Hogan et al 2008)
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 23
Preskill (1979): Monopole density today
Light monopoles are relativistic, so
Compatible with RICE bound only if Therefore we do need inflation to wipe out the
monopoles!
20 June 2012
Monopole Problem?
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 24
Direct searches: ◦ Tevatron, LEP, HERA→ Lower bound ◦MoEDAL: Up to
Indirect searches:◦ Virtual monopoles
◦ Large theoretical uncertainties
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Accelerator Searches
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 25
Possible, but not really predicted by any theory◦ Perhaps large extra dimensions,
or simply unrelated to unified theories Mass relation means there would be lots of new
exciting physics at accessible energies Monopoles would be a fantastic probe:◦ Absolutely stable◦ Strong EM interaction◦ Easy to handle
20 June 2012
-scale monopoles
A. Rajantie, Magnetic Monopoles in the Cosmos and at the LHC, 26
Monopoles are perhaps the best motivated new particles:◦ Explain charge quantisation◦ Exist in GUTs, string theory
Produced copiously in the early universe,wiped away by inflation:◦ Stringent bounds from astrophysics, cosmic rays
-scale monopoles possible◦ Detectable in MoEDAL◦Would open up a window to exciting new physics
(For more: See AR, Contemporary Physics 2012)
20 June 2012
Summary
