Black Holes and Extra Dimensions

Jonathan Feng

UC Irvine

Penn State Physics Department Colloquium

30 January 2003

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The Standard Model

Carrier Force Group

photon

E&M U(1)

g gluon Strong SU(3)

Z

WWeak SU(2)

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Tevatron

Precise Confirmation

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Grand Unification

Unification “explains” SM charges

Requires c, massive neutrinos

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Coupling Unification

• Forces are similar in strength

• Forces become more similar at high energies and short distances

• Unification almost exact with supersymmetry Dashed – Standard Model

Solid – Supersymmetry

Martin (1997)

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What’s Missing

• The dog that didn’t bark – where’s gravity?

• Many deep problems, but one obvious one:

For protons, gravity is 10-36 times weaker.

• Equal for mstrong ~ 1018 GeV, where gravity becomes strong, far beyond expt. (~ TeV).

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Kaluza-Klein Unification• Kaluza (1921) and Klein (1926)

considered D=5, with 1 dimension rolled into a circle:

D=5 gravity D=4 gravity + EM + scalar

gAB g + g5 + g55

• Kaluza: “virtually unsurpassed formal unity...which could not amount to the mere alluring play of a capricious accident.”

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Extra Dimensions

• Suppose photons are confined to D=4, but gravity propagates in n extra dimensions of size L:

For r L, Fgrav ~ 1/r2

For r L, Fgrav ~ 1/r2+n

Garden Hose

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…

gravity

EM

Str

engt

h

r1/mstrong

Gravity in Extra Dimensions

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Strong Gravity at the Electroweak Scale

• Suppose mstrong is 1 TeV, the electroweak

unification scale

• The number of extra dims n then fixes L

• n=1 excluded by solar system, but n=2, 3,… are allowed by tests of Newtonian gravity

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Tests of Newtonian GravitySt

reng

th o

f D

evia

tion

R

elat

ive

to N

ewto

nain

Gra

vity

Long, C

han, Price; H

oyle et al.

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Kaluza-Klein States

• Extra dimensions of size L towers of Kaluza-Klein particles with masses ~1/L

• Large extra dims light states

• KK states may appear at colliders, in astrophysics (supernova cooling), …

f

f f ’

f ’graviton

_ _

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Black Holes

• Solutions to Einstein’s equations

• Schwarzschild radius rs ~ MBH – requires large mass/energy in small volume

• Light and other particles do not escape; classically, BHs are stable

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Black Hole Evaporation

• Quantum mechanically, black holes are not black – they emit Hawking radiation

• Temperature: TH ~ 1/MBH

Lifetime: ~ MBH3

• For MBH ~ Msun, TH ~ 0.01 K. Astrophysical BHs emit only photons, live ~ forever

• Form by accretion

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• BH creation requires

ECOM > mstrong

• In 4D, mstrong ~ 1018 GeV,

far above accessible energies ~ TeV

• But with extra dimensions, mstrong ~ TeV is possible, can create micro black holes in elementary particle collisions!

BHs from Particle Collisions

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Black Holes in the Laboratory

• What is the production rate?

• How will you know if you’ve created one?

S. Harris

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Black Holes at Colliders• BH created when two

particles of high enough energy pass within rs . Cross section ~ rs

2

Penrose (1974)D’Eath, Payne (1992)

Eardley, Giddings (2001) ...

• Large Hadron Collider (2007): ECOM = 14 TeV

pp BH + X

• Find as many as 1 BH produced per second

Dimopoulos, Landsberg (2001)

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Event Characteristics• For microscopic BHs,

~ 10-27 s, decays are essentially instantaneously

• TH ~ 100 GeV, so not just photons

j:l::,G = 75:15:2:8

• Multiplicity ~ 10

• Spherical events with leptons, many jets

De Roeck (2002)

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Black Holes from Cosmic Rays

• Cosmic rays – the high energy frontier

• Observed events with 1019 eV ECOM ~ 100 TeV

• But meager fluxes! Can we harness this energy?

Kampert, Swordy (2001)

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Use Cosmic Neutrinos• Cosmic rays create ultra-high

energy neutrinos:

BH gives inclined showers starting deep in the atmosphere

• Rate: as large as a few per minute somewhere on Earth

Feng, Shapere (2001)

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Auger Observatory

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Deep Inclined Showers

Coutu, Bertou, Billior (1999)

Capelle, Cronin, Parente, Zas (1998)Diaz, Shellard, Amaral (2001)

Anchordoqui, Feng, Goldberg, Shapere (2001)HiRes Collaboration (1994)

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Cosmic Ray Black Holes

• Auger can detect ~100 black holes in 3 years

mst

rong

(T

eV)

Feng, Shapere (2001)

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AMANDA/IceCube

• Neutrino telescopes may also detect BHs:

contained jets

through-going muons

• Similar rate: ~10 BH/year

Cosmic rays provide first chance to see black holes from extra dimensions

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What You Could Do With A Black Hole If You Made One

• Discover extra dimensions

• Test Hawking evaporation, BH properties

• Explore last stages of BH evaporation, quantum gravity, information loss problem

• ……

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Conclusions

• Gravity is either intrinsically weak or is strong but diluted by extra dimensions

• If gravity is strong at the TeV scale, we will find black holes in cosmic rays and colliders

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Conclusions

• Gravity is either intrinsically weak or is strong but diluted by extra dimensions

• If gravity is strong, we will find black holes in cosmic rays and colliders

Anchordoqui, Feng, Goldberg, Shapere (2001)

mst

rong

(T

eV)

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Gravity Is Weak

gravity

EM

Str

engt

h

r