Theoretical Particle Physics Beyond the Standard Model Jonathan
Theoretical Particle Physics: Beyond the Standard Model Jonathan Feng UC Irvine UCI Pizza Talk 18 April 2003 UCI Pizza Talk
The Standard Model Carrier Force Mass g photon E&M 0 g gluon Strong 0 Weak 91 Ge. V 80 Ge. V Z W 18 April 2003 UCI Pizza Talk 2
Precise Confirmation Tevatron 18 April 2003 UCI Pizza Talk 3
Why is Mweak so small? • How big should it be? We know of only three constants: – Special relativity: speed of light c – General Relativity: Newton’s constant GN – Quantum mechanics: Planck’s constant h • From these we can form – Planck time: t. Pl ~ 10 -43 s – Planck distance: l. Pl ~ 10 -33 m – Planck mass: MPl ~ 1019 Ge. V • Why is MWeak so small compared to MPl ? 18 April 2003 UCI Pizza Talk 4
Solution 1: Symmetry • Photon is light, but this doesn’t bother us, because it is massless because of a symmetry • There is only one symmetry that can explain the weak scale: supersymmetry (SUSY) • Predicts a partner particle for every known particle 18 April 2003 Soap Bubble Standard Model Large parameter Length L Height H MPl Small parameter L-H Mweak Symmetry explanation Rotational invariance SUSY Prediction Particles traveling in different directions Particles with different spin Symmetry Breaking Gravity SUSY breaking UCI Pizza Talk 5
Prediction of Supersymmetry • Supersymmetry predicts new particles with masses ~ 1 Te. V • If SUSY is right, these will be discovered at the Large Hadron Collider (~2008) or in other experiments 18 April 2003 UCI Pizza Talk 6
Solution 2: Extra Dimensions • Maybe GN isn’t what we thought it was • MPl is very large because GN is very small, that is, gravity is very weak For protons, gravity is 10 -36 times weaker. 18 April 2003 UCI Pizza Talk 7
Extra Dimensions • But suppose gravity propagates in n extra dimensions of size L: For r >> L, Fgrav ~ 1/r 2 For r << L, Fgrav ~ 1/r 2+n Garden Hose 18 April 2003 UCI Pizza Talk 8
Gravity in Extra Dimensions Strength EM … gravity 1/mstrong 18 April 2003 r UCI Pizza Talk 9
Strong Gravity at the Weak Scale • Suppose mstrong is at the weak 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 18 April 2003 UCI Pizza Talk 10
Tests of Newtonian Gravity Strength of Deviation Relative to Newtonain Gravity Long, Chan, Price; Hoyle et al. 18 April 2003 UCI Pizza Talk 11
Prediction of Extra Dimensions • Black holes can be created if ECOM > mstrong • In 4 D, mstrong ~ 1018 Ge. V, far above accessible energies ~ Te. V • But with extra dimensions, mstrong ~ Te. V is possible, can create micro black holes in elementary particle collisions! 18 April 2003 UCI Pizza Talk 12
Micro Black Hole Events • Black holes decay through Hawking evaporation g g De Roeck (2002) 18 April 2003 UCI Pizza Talk 13
Auger Observatory 18 April 2003 UCI Pizza Talk 14
AMANDA/Ice. Cube • Neutrino telescopes may also detect BHs: contained jets through-going muons • Rates of ~10 BH/year Cosmic rays provide first chance to see black holes, discover extra dimensions 18 April 2003 UCI Pizza Talk 15
Conclusions • There must be new physics at the weak scale • We will find SUSY, extra dimensions, or something completely unexpected while you are getting your Ph. D (or during your first postdoc. . . ) • This will address some profound mysteries, such as force unification, dark matter, quantum gravity, … 18 April 2003 UCI Pizza Talk 16
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