Transcript Was Einstein right or are there extra space-time dimensions? Nigel Glover Institute for Particle Physics Phenomenology Durham University.

Was Einstein right or are there extra
space-time dimensions?
Nigel Glover
Institute for Particle Physics Phenomenology
Durham University
Standard Model of Particle Physics
1974
1937
1949
1995
1976
1977
Standard Model of Particle Physics
1979
1983
1983
Higgs, H?
Gravity not here!
Much too weak – 1040 times weaker than the strong force
Only becomes strong at the Planck scale 1019 GeV
String theory best candidate for quantum gravity
Extra Dimensions?
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What are they?
Why are we asking the question?
Why haven’t we found them yet?
What are their consequences?
How are we going to find evidence for
them?
Where are the extra dimensions?
From a distance, we see only the rope – one dimension
From close up, the ant sees two dimensions
So far, we only see three space dimensions because
we haven’t been able to resolve them
Extra Dimensions
• One possibility is that we
live in a subspace of the
extra dimensions
w, v,…
• All particles and most
forces might be confined
to our world: photons
(electromagnetism),
electrons, protons, …
gravity
E&M
x, y, z
But gravity, the weakest of the four forces,
might be able to propagate in the extra dimensions
Extra dimensions could explain
why gravity is so weak!
Gravitational flux lines travel into the normal dimensions
M
Potential falls off as
V ~ G3/r
and into the extra dimensions for r < L:
gravitational potential is increased in proportion
L
Potential falls off as
V ~ Gd/rd-2
This changes the force of gravity
Strength
EM
…
Gravity could become strong at small distances!
gravity
1/mstrong
r
Making Black Holes!
• Lots of
mass/energy in a
small volume 
black hole
• If two particles pass close enough with enough energy,
they will form a microscopic black hole
• For 3 spatial dimensions, gravity is too weak for this to
happen. But with extra dimensions, gravity becomes
stronger, micro black holes could be created in particle
collisions!
Micro Black Holes
• Where could they
be produced?
• How will we know
if we’ve seen one?
S. Harris
Black Holes
• Classically, light and other
particles do not escape;
black holes are black.
g
• But quantum mechanically,
black holes Hawking
radiate; black holes emit
light
g
Black Hole Evaporation
• “Normal” black holes:
Mass: MBH ~ Msun
Size: kilometer
Temperature: 0.01 K
Lifetime: ~ forever
• Micro black holes:
Mass: MBH ~ 1000 Mproton
Size: 10-18 m
Temperature: 1016 K
Lifetime: 10-27 s
They explode!
…
Extra Dimensional Matter
• A particle moving in an extra dimension
of size L appears to us as a set of
particles with masses
4/L
0, 1/L, 2/L, 3/L, 4/L, …
• We can search for these particles by
looking for their decay into lighter
particles
2/L
mass
• Each known particle has a heavy
partner at each mass level.
3/L
1/L
0
The Large Hadron Collider at CERN
World’s most
powerful particle
accelerator
CMS
Superconducting
magnets
– 8.3T at 1.9K
ALICE
ATLAS
LHCb
2 beams of protons
will collide 40
million times a
second
In construction since 1998
Due to start later this year
aside: LHC vs. circle line
LHC
Circle line
Length
27km
22.5km
Depth
100m
15m
Diameter 3.8m
3.4m
LHC Beam Stored Energy
2808 bunches, 1.1 x 1011 protons/bunch @ 7 TeV
350 MJ stored energy per proton beam
Same as colliding 2 x 120 elephants...
120 elephants with 40 km/h
The energy of a
single 7 TeV proton
is equivalent to a
flying mosquito (1 µJ)
120 elephants with 40 km/h
eye of a needle:
0.3 mm diameter
proton beams at interaction point are 10x smaller:
0.03 mm diameter
LHC Magnet Installation
Lowering through an elliptical shaft
Storage on car-parks all
over CERN
Interconnection welding
Transport with
optically guided
vehicle
Last connection made 7 November 2007
Quality Control
http://lhc.web.cern.ch/lhc/
Cooldown Status (as of 28
th
Apr 2008, 5pm)
sector 12: warm
sector 23: 50-150 K
sector 34: 180-280 K
sector 45: warm
sector 56: 1.9 K
sector 67: 30-90 K
sector 78: 1.9 K
sector 81: 1.9 K
total cold mass: 40,000 tons
10,000 tons of liquid nitrogen
120 tons of superfluid Helium (1.9 K) for cooling
vacuum: 10-10 Torr = 3 million molecules per cm3
ATLAS
(A Toroidal LHC ApparatuS)
Length = 55 m
Width = 32 m
Height = 35 m
Construction from Oct 2003 – Mar 2008
CMS (Compact Muon Spectrometer)
210 m2 silicon detectors
main assembly on surface,
then lowering into cavern in
5 big parts by ~2500 t crane
15 m
4T
22 m
~12,500 t
CMS Lowering of 2000 t Central Part (Feb 2007)
Black Hole event at ATLAS simulated by CHARYBDIS
Are micro black holes dangerous?
• On 21 March, Luis Sancho, from Spain, and Hawaii
resident Walter Wagner filed a lawsuit in Hawaii's US
District Court against CERN and US contributors to the
project demanding that they do not operate the LHC until
they prove it is safe.
• The lawsuit's claims are "complete nonsense", said
James Gillies, a spokesman for CERN. "The LHC will
start up this year, and it will produce all sorts of exciting
new physics and knowledge about the universe," he
said, adding: "A year from now, the world will still be
here."
Summary
• Extra dimensions are well-motivated theoretically (string
theory)
– May lead to micro black hole production or other phenomena at the
LHC
– May shed light on longstanding puzzles on the weakness of gravity
• LHC startup approaching – later this summer
– “discoveries are guaranteed…at least the Higgs boson…likely
observe new symmetries of nature, new particles and forces”
STFC delivery plan
– Biggest leap in energy since discovery of jets/W/Z/SUSY/top at
UA1/UA2 in 1983
Are micro black holes dangerous?
Q What if the micro black holes produced at the LHC do not decay as
rapidly as calculated, or might even not be prone to decay and, if
unable to rapidly evaporate, they could start interacting, grow larger
and potentially be disastrous to Earth itself?
A Collisions at these energies (and higher) have been happening in
nature for billions of years apparently without hazardous effects, as
ultra high energy cosmic rays impact Earth's atmosphere.
Q What if the micro black holes created at LHC have less than the
Earth's escape velocity (of 11.2 km/s), and therefore would be
captured by the Earth's gravitational field?
A If so, its very likely that cosmic rays would destroy dense objects
like neutron stars/pulsars
CERN Accelerator Complex
7 TeV
5
LHC
5
450 GeV
4
SPS
4
26 GeV
3
PS
1.4 GeV
2
2
BOOSTER
50 MeV
1
3
1
LINAC2
start here
PROTONS
I’ll try to keep it simple…but please ask