MAGNETIC MONOPOLES Andrey Shmakov Physics 129 Fall 2010 UC Berkeley

OVERVIE W Dirac Monopoles Appeal to symmetry Quantum Mechanical explanation GUT Monopoles Symmetry Breaking Gauge Theories Monopole Searches Methods Experiments Current Experimental Limits Nothing! Graphs!

DIRAC MONOPOLE The Dirac Relation: Angular Momentum of a test particle around a magnetic charge:

DIRAC MONOPOL E

GUT MONOPOLE Symmetry is lost during phase transitions Water: isotropic, full Rotational symmetry Ice: Crystal Lattice With preferred axis

GUT MONOPOL E

Phase transitions cause topological defects Causality forces distant regions to precipitate into different states

ASIDE: GAUGE INVARIANCE We intuitively understand position, time, rotational, and potential invariance These transformations are universal What if our transformation was a smooth function of space-time?

ASIDE: GAUGE INVARIANCE UGH! Let’s Try that again ✔

EXPERIMENTALISTS! MEET MR MONO POLE! Charge: Coupling constant: Mass Assume monopole classical radius ~ electron radius GUT Mass depends on symmetry breaking

EXPERIMENTAL SEARCHES: EXPLOITABLE PROPERTIES o Monopoles acquire energy in the galactic MF o Monopoles can get trapped in ferromagnetic materials, stopped in celestial bodies o Interactions: High Energy: Behave like electrons: synchrotron radiation, heavy energy loss, measurable with scintillation counters. Slow Monopoles: ionizing radiation, detectable Very Slow Monopoles: elastic collisions, infrared radiation Interaction with superconducting magnets: regardless of velocity

EXPERIMENTAL SEARCHES: SQUIDS A magnetic monopole passing through a superconducting loop will induce a very distinct signal Equally sensitive at all velocities and monopole masses Used to test materials for embedded monopoles

EXPERIMENTAL SEARCHES: TANTALIZING CANDIDATES On Valentines Day, 1982, a superconducting induction coil detector recorded this event Phys Rev. Lett (1982)

EXPERIMENTAL SEARCHES: COSMOLOGY Experiments are conducted to measure a flux of magnetic monopoles that hit the earth as cosmic rays There are theoretical limits on the flux of heavy MM from the galactic MF Monopole, Astrophysics and Cosmic Ray Observatory (MACRO) searched for superheavy MM in the beta < 1 range.

EXPERIMENTAL SEARCHES: COSMOLOGICAL LIMITS

EXPERIMENTAL SEARCHES: DIRECT TESTS Accelerators used to probe for possible light Dirac monopoles Tevatron collision exclude energies below 850GeV

EXPERIMENTAL SEARCHES: DIRECT TESTS

CONCLUSION Monopoles are hypothetical, but predicted by the most major theoretical models No confirmed repeatable monopole events have been recorded Strong lower limits on energy place Dirac monopoles out of reach of colliders Strong upper limits on cosmic ray flux Maybe finding reason they don’t exist is more interesting than finding them?