AAAS 2001 San Francisco1 Supersymmetry The Coming Revolutions in Particle Physics Hitoshi Murayama (UC Berkeley)

AAAS 2001 San Francisco2 Introduction

AAAS 2001 San Francisco3 20th Century Physics Two great discoveries of 20th cent. physics: –Quantum Mechanics –Einstein’s Special Relativity (Electromagnetism) Marriage between the two  Existence of Anti-matter doubled #particles –Positron (anti-particle of electron) 1932 –Anti-proton 1955 (Bevatron, Berkeley)

AAAS 2001 San Francisco4 21st Century Physics Marriage of Quantum Mechanics and Gravity (Einstein’s General Relativity)  Existence of Super-matter Double #particles again Photino (superpartner of photon) 2004? Selectron (superpartner of electron) 2010?  Supersymmetry

AAAS 2001 San Francisco5 Outline Introduction Anti-Matter Weak Force and God Particle God Particle’s Problem Supersymmetry Conclusion

AAAS 2001 San Francisco6 Anti-Matter

AAAS 2001 San Francisco7 Matter & Anti-Matter Annihilate!

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9 Why was Anti-Matter Needed? At the end of 19th century: a “crisis” about electron –Like charges repel: hard to keep electric charge in a small pack –Electron is point-like –At least smaller than cm Need a lot of energy to keep it small!

AAAS 2001 San Francisco10 E=mc 2 Need more than 10 9 eV of energy to pack electric charge tightly inside the electron But the observed energy of the electron is only eV Electron cannot be smaller than 10 –13 cm?? Breakdown of theory of electromagnetism

AAAS 2001 San Francisco11 Uncertainty Principle Energy-Time Uncertainty Principle: You can violate energy conservation if it is only for a short time Vacuum is full of quantum bubbles! Werner Heisenberg

AAAS 2001 San Francisco12 Anti-Matter Helps Electron creates a force to repel itself Vacuum bubble of matter anti-matter creation/annihilation Electron annihilates the positron in the bubble  only 10% of mass

AAAS 2001 San Francisco13 Anti-Matter Helps “Anti-matter attraction” cancels “Like- charge repulsion” It does not cost too much energy to tightly pack the electric charge inside the electron Needed anti-matter: double #particles Theory of electromagnetism now works at very short distances (12 digits accuracy!)

AAAS 2001 San Francisco14 Weak Force and God Particle

AAAS 2001 San Francisco15 Mystery of the “weak force” Gravity pulls two massive bodies (long-ranged) Electric force repels two like charges (long-ranged) “Weak force” pulls protons and electrons (short-ranged) acts only over 10 –16 cm [need it for the Sun to burn!]

AAAS 2001 San Francisco16 Something is in the Universe There is something filling our Universe It doesn’t disturb gravity or electric force It does disturb weak force and make it short- ranged What is it??

AAAS 2001 San Francisco17 The God Particle “Higgs Boson” fills our Universe It disturbs the weak force so that it cannot act very far We are sure it exists. But nobody has seen it yet Mother of all masses

AAAS 2001 San Francisco18 But soon?

AAAS 2001 San Francisco19 Fermi’s dream era Fermi formulated the first theory of weak force (1933) Knew the required energy to study the problem: eV We are finally getting there!

AAAS 2001 San Francisco20 God Particle’s Problem

AAAS 2001 San Francisco21 Higgs repels itself, too Just like electron repeling itself because of its charge, Higgs boson also repels itself Requires a lot of energy to contain itself in its point-like size! Breakdown of theory of weak force

AAAS 2001 San Francisco22 But there is gravity Gravity and quantum mechanics unify at an extremely short distance 10 –33 cm Higgs boson must be this small, too, to have a sensible unified theory of gravity and quantum mechanics But current theory of weak force breaks down already at 10 –17 cm

AAAS 2001 San Francisco23 Supersymmetry

AAAS 2001 San Francisco24 History repeats itself? Double #particles again  superpartners “Vacuum bubbles” of superpartners cancels the energy required to contain Higgs boson in itself Theory of weak force made consistent with unification of gravity and quantum mechanics

AAAS 2001 San Francisco25 Einstein’s dream Forces with very different strengths: electromagnetism, strong, weak forces Strengths change at different distance scales They become equal: share the same origin  “Grand Unification”

AAAS 2001 San Francisco26 Where are the superpartners? They need to cancel self-repelling energy of the Higgs boson Cannot be too heavy to do this job Have to be below eV or “Fermi energy” We are getting there this decade –Tevatron (Fermilab, Illinois) 2001– –LHC (CERN, Switzerland) 2006–

AAAS 2001 San Francisco27 Superpartners everywhere? There are unknown “Dark Matter” in our galaxy and outside It amounts for about 30% of the Universe Lightest superpartner one of the best candidates

AAAS 2001 San Francisco28 Superpartners as probe Most exciting thing about superpartners beyond existence: They carry information of small- distance physics to something we can measure e.g., “Is Grand Unification true?”

AAAS 2001 San Francisco29 Conclusions –We are finally reaching “Fermi’s dream era” –We will know what is disturbing the weak force, and generating all masses soon –To make Higgs boson contain itself without needing too much energy, we need supersymmetry –Superpartners are within the reach this decade –They bring more information about ultimate short-distance physics

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