0412harveymudd

Black Holes and Extra Dimensions: 

Black Holes and Extra Dimensions Jonathan Feng UC Irvine Harvey Mudd Colloquium 7 December 2004

The Standard Model: 

The Standard Model

Precise Confirmation: 

Precise Confirmation In terms of coupling strengths:

Force Unification: 

Force Unification Forces are similar in strength There is even a beautiful explanation of why the coupling constants have the values they do Unification at high energies and short distances (with supersymmetry) Dashed – Standard Model Solid – Supersymmetry Martin (1997)

What’s Wrong with this Picture?: 

What’s Wrong with this Picture? The dog that didn’t bark – where’s gravity? Many deep problems, but one obvious one: Gravity is extraordinarily weak. It is important in everyday life only because it is universally attractive.

Slide6: 

More quantitatively: Even for the heaviest elementary particles (e.g., W bosons, top quarks) Fgravity ~ 10-32 FEM Gravity is comparable for masses (or energies) ~ 1015 TeV, far beyond experiment (Mweak ~ 1 TeV). The Hierarchy Problem: Why is gravity so weak? Maybe it isn’t…

Extra Dimensions: 

Extra Dimensions Suppose photons are confined to D=4, but gravity propagates in n extra dims of size L. r << L, Fgravity ~ 1/r2+n r >> L, Fgravity ~ 1/r2

Slide8: 

Gravity in Extra Dimensions Conclusion: the weakness of gravity might not be intrinsic, but rather may result from dilution in extra dimensions

Strong Gravity at the Weak Scale: 

Strong Gravity at the Weak Scale Suppose mstrong is Mweak ~ 1 TeV Arkani-Hamed, Dimopoulos, Dvali, PLB (1998) The number of extra dims n then fixes L Feng, Science (2003)

Tests of Newtonian Gravity: 

Tests of Newtonian Gravity

Slide11: 

Astrophysical probes (supernova cooling) provide even more stringent constraints, eliminate n = 2,3,4, but are ineffective for n >4. Tests of Newtonian gravity eliminate n = 1,2, but are ineffective for n >2. A better strategy: probe small distances, high energies.

Black Holes: 

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

Black Hole Evaporation: 

Black Hole Evaporation Quantum mechanically, black holes are not stable – they emit Hawking radiation Temperature: TH ~ 1/MBH Lifetime: t ~ (MBH)3 For MBH ~ Msun, TH ~ 0.01 K. Astrophysical BHs emit only photons, live ~ forever Form by accretion

BHs from Particle Collisions: 

BH creation requires ECOM > mstrong In 4D, mstrong ~ 1015 TeV, far above accessible energies ~ TeV But with extra dimensions, mstrong ~ TeV is possible, can create micro black holes in particle collisions! BHs from Particle Collisions Penrose (1974) D’Eath, Payne, PRD (1992) Banks, Fischler (1999)

Micro Black Holes: 

Micro Black Holes Where can we find them? What is the production rate? How will we know if we’ve seen one?

Black Holes at Colliders: 

Black Holes at Colliders BH created when two particles of high enough energy pass within ~ rs . Eardley, Giddings, PRD (2002) Yoshino, Nambu, PRD (2003) ... Large Hadron Collider: ECOM = 14 TeV pp  BH + X LHC may produce 1000s of black holes, starting ~ 2008 Dimopoulos, Landsberg, PRL (2001)

Event Characteristics: 

Event Characteristics For microscopic BHs, t ~ (MBH)3 ~ 10-27 s, decays are essentially instantaneous TH ~ 1/MBH ~ 100 GeV, so not just photons: q,g : l : g : n,G = 75 : 15 : 2 : 8 Multiplicity ~ 10 Spherical events with leptons, many quark and gluon jets De Roeck (2002)

Black Holes from Cosmic Rays: 

Black Holes from Cosmic Rays Cosmic rays – Nature’s free collider Observed events with 1019 eV produces ECOM ~ 100 TeV But meager fluxes. Can we harness this energy? Kampert, Swordy (2001)

1st Attempt: 

1st Attempt Look for cosmic ray protons to create BHs in the atmosphere: pp  BH + X Feng, Shapere, PRL (2002) Unfortunately, protons interact through standard strong interactions long before they create a BH.

Solution: Use Cosmic Neutrinos: 

Solution: Use Cosmic Neutrinos Cosmic protons scatter off the cosmic microwave background to create ultra-high energy neutrinos: These neutrinos have very weak standard interactions Dominant interaction: np  BH + X

Atmospheric Showers: 

Atmospheric Showers Coutu, Bertou, Billior (1999) np  BH gives inclined showers starting deep in the atmosphere Atmosphere filters out background from proton-initiated showers Rate: a few per minute somewhere on Earth

Auger Observatory: 

Auger Observatory

Slide23: 

Currently no such events seen  most stringent bound on extra dims so far. Auger can detect ~100 black holes in 3 years. Insensitive to number of extra dimensions n. USA Today version: “Dozens of tiny ‘black holes’ may be forming right over our heads… A new observatory might start spotting signs of the tiny terrors, say physicists Feng and Shapere… They’re harmless and pose no threat to humans.” Number of events

BHs vs. SM: 

BHs vs. SM BH rates may be 100 times SM rate. But large BH s  large rate large flux  large rate However, consider Earth-skimming neutrinos: large flux  large rate large BH s  small rate Bertou et al., Astropart. Phys. (2002) Feng, Fisher, Wilczek, Yu, PRL (2002) Degeneracy is resolved by ratio of rates alone.

AMANDA/IceCube: 

AMANDA/IceCube Neutrino telescopes: promising BH detectors Similar rate: ~10 BH/year Complementary information BH branching ratios (jets vs. muons) Angular distributions Kowalski, Ringwald, Tu, PLB (2002) Alvarez-Muniz, Feng, Han, Hooper, Halzen, PRD (2002)

What You Could Do With A Black Hole If You Found One: 

What You Could Do With A Black Hole If You Found One Discover extra dimensions Test Hawking evaporation, BH properties Explore last stages of BH evaporation, quantum gravity, information loss problem …

Conclusions: 

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 microscopic black holes and extra dimensions in cosmic rays and colliders