The mQ Experiment

SLAC 1 Jun 1994

The Millicharged Particle Search (mQ) is a new experiment to search for unconventional, millicharged elementary particles.

A millicharged elementary particle would have an electric charge three or more factors of ten smaller than the charge on the electron. We do not have a deep understanding of charge quantization; as far as we now know, theory does not exclude the existence of millicharged particles. Experimental bounds, which come from precise QED checks and high-energy beam-dump experiments, exclude q/e > 10**-2 over a wide range of masses. Very small charges (q/e < 10**-6) are disfavored by astrophysical arguments, but particles with 10**-6 < q/e < 10**-3 could exist in nature. Theorists have suggested that millicharged elementary particles may consitute the so-called dark matter or account for other experimental anomalies.

This experiment will run parasitically during routine SLC operation, which requires production of positron beams. Electroproduction is the mechanism for producing millicharged particles, and is fully calculable, allowing a definitive search over a wide range of charge and mass. Unlike other beam-dump experiments, this search will exploit a low-energy signature in the ionization and/or excitation in the atoms by using a scintilation detector to search for very small energy depositions. Understanding the scintillation mechanism at the single-photon level is an important component of the experiment.

This experiment presents an opportunity often missing from large-scale high-energy physics experiments: participation in all aspects of an experiment, from detector construction, to Feynman diagram evaluation, to experiment operation, to data analysis.(1)

The collaborators are:

For further information about the mQ experiment , contact John Jaros.


(1) This material was quoted from "Stanford University: SLAC: The Graduate Student Handbook " (September, 1993), pp. 19-20.

The page was compiled by Joan Winters with help on image scanning from Patrick Clancey.

Owner: Willy Langeveld