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Join the dots to measure antimatter

The crowdsourcing software records the particle tracks you trace and renders them as a 3D image. Image courtesy AEGIS, CERN.

Ever wondered what happens when you drop antimatter?

The AEGIS experiment at CERN needs your help to analyse experimental results to figure out how antimatter is affected by gravity. Just join the dots to reconstruct particle tracks and your contribution could be included in an upcoming scientific publication.

The aim of AEGIS is to measure the effect of the Earth's gravitational acceleration on antihydrogen. Seeing different behavior for antimatter than for matter would be a huge surprise, and would indicate that gravity is much more complicated than our present understanding indicates.

In the AEGIS experiment, antihydrogen atoms are made to fly horizontally, dropping by a tiny amount, before colliding with matter. On collision, the antihydrogen and matter annihilate, producing a burst of mostly pions and some other particles. These particles then travel through an emulsion containing silver bromide, developed by the University of Bern in Switzerland, that makes their tracks visible. Tracing these tracks to their point of origin tells the AEGIS team exactly where each annihilation occurred, which in turn allows them to calculate how far each particle travels, and how far the particle's path drops. From the distance the particles fly and fall, the AEGIS team hopes to calculate the effect of gravity on antimatter.

AEGIS needs your help to map the paths that particles take through the emulsion. As part of the CERN Summer Webfest, some of this year's summer students have created a web application to map particle tracks. All you have to do is join the dots!

"In principle, tracking could be digitized, but computers can miss tracks that are related, but far apart," says AEGIS spokesperson Michael Doser, who, inspired by astronomy websites such as Astrowatch and Galaxy Zoo, decided to crowdsource the analysis. "I'm using human pattern recognition - we're pretty good at seeing things that belong together."

The experiment requires about 1000 antihydrogen annihilations for a statistically significant observation, says Doser, but he hopes to have anywhere from 10,000 to 100,000 particle tracks analysed to check AEGIS's algorithms for even tiny biases.

"Algorithms are not curious," says Doser. "If we had something unexpected, a computer may not see it. But humans are open to new ways of looking at things. And besides, it's fun!"

The data you provide will be openly available and help physicists at CERN with their analysis of the experiment. The results from an initial prototype run, which Doser describes as having worked "amazingly well", are visualized on this page as a 3D model.

After the original set of data made available through the web application was analyzed in just a few hours, the AEGIS team now needs feedback from users and other programmers to improve the software for a beta release with even more data.

Visit the web application, here. Once more data has been made available, you too can take part in the analysis.

Epilepsy warning: The particle tracks contain rapidly flashing screens.

This article has been adapted from the CERN website.

- James Doherty

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