Discussion forum... to participate, click here

This forum is a place to share information on the public project, help steer where it goes, interact with the physicists involved, and help improve it.

We are asking for your help

At the heart of the AEgIS experiment lies the detection of annihilations of antiprotons with nuclei, which produce nuclear fragments, protons, and high energy pions. The process is poorly studied, but we need to understand it very well.

For this reason, we are taking data on antiproton annihilations either directly in photographic film or in very thin foils of different materials directly in front of it. Each annihilation produces a starburst-like pattern in the photographic film, formed by the particles produced by the annihilation or as a side product of the annihilation. For each annihilation, we are asking you to help us count the annihilation products as imaged in the film, identify each of them (are the produced tracks barely visible, well visible or really dark lines?), and give an estimate of where the annihilation took place (the annihilation point itself may not be visible if the annihilation takes place in a foil, rather than in the film). You'll be able to scan through the fim like with a microscope, changing the focus into deeper and deeper parts of the film.

We'll then tabulate the types of annihilation products, their numbers and perhaps even their energy (if they come to rest in the photographic film), and use that information to compare with (and improve!) simulations of the annihilation process.

Beta release of the AEgIS public science site

This new site is geared towards high school students and their (physics) teachers. It contains introductory material into the physics and gives a detailed explanation of what we hope to learn through your help. If you are interested in participating as a high school class, please get in touch with us.

Alpha release of the AEgIS public science site

This is our first attempt to ask for public help in analyzing photographic images of antiproton annihilations, which has received much attention. This site is now closed for further analysis, but still contains a good overview of what we are trying to achieve.

Crowd sourcing particle physics data analysis...

Hi everybody, and first of all, thank you for your interest! As an avid follower of galaxyzoo and related crowdcrafting and public science projects, I have been thinking about how to open high energy physics research to public involvement in a similar manner. With the AEgIS experiment, we may have a first possibility, but I am sure that we will find more.


AEgIS is built around the attempt to measure the gravitational interaction between matter and antimatter using antihydrogen atoms. Specifically, the AEgIS experiment will form a horizontal pulsed beam of antihydrogen atoms. These will follow a parabolic trajectory, dropping for a small amount of time (about 2ms), and will then hit a surface made of matter, where they annihilate. The tiny vertical shift caused by gravity (20 micrometers if antimatter behaves as matter does) needs to be detected to about 1 micrometer, and the dropping time to 10 microseconds. To measure the drop, or rather the impact point of each atom with the "wall" (actually a thin foil), we intend to place photographic emulsion plates behind it which will detect the fragments flying off in all directions that result from the annihilation of an antihydrogen nucleus with a nucleus of the wall. Only a handful of fragments are produced in each annihilation, and finding the few that fly through the emulsion is tricky: some may fly straight through, but some may fly off at a shallow angle, and not be detected in the immediate vicinity of the annihilation point, and in any case, we can't see the annihilation vertex itself, since that happens in the wall. We thus rely on finding and tagging individual tracks, and associating them to annihilation points. Once we have those points, we can associate flight times to each of them by matching them with other, external detectors and see how much a given atom has dropped in a given amount of time.

This project

In the future, each of the emulsion plates should have an area of about 10x10 cm^2, and we will change plates about once a week once the experiment is running. If we are lucky, we should see about 1000 annihilations in that period of time, which we want to tag unambiguously, but perhaps 100's of thousands of tracks that go straight through, produced by antiprotons annihilating far away from this detector, and we need to tag those as well. Some of those particles will also strike a nucleus in the wall and can lead to fragments that look like annihilations (but aren't). By characterizing annihilations (caused by antiprotons or antihydrogen atoms), as well as these background processes, we expect to be able to get a clean(er) data sample. However, annihilation-induced fragmentation depends on the material of the wall, and very little data are available to help us fine-tune our algorithms.

For this reason, we have taken (last days of 2012) and are continuing to take data on the annihilation of antiprotons with different foil materials. These are the data you are looking at right now. We are trying to determine our antiproton annihilation tagging efficiencies, our background rates, and the annihilation process itself, as well as trying to optimize our detection scheme. One important element is the presence of protons, or better yet, a heavy nuclear fragment, stemming from the break-up of the nucleus that the antiproton annihilated with. Because these are probably slow and heavy, these should generate dark (in the case of protons) or very dark (in the case of fragments) tracks in the emulsion, that are very different from the very light tracks (pions) stemming from the annihilation between an antiproton and a proton or a neutron of the nucleus. We hope to count the numbers of each type of annihilation product, possibly their energy, and furthermore try to find out whether they all come from the same annihilation (by tagging the intersection point they .


Our plans (status August 2014) are thus the following:

- in a first step, carry out tests of the track tagging (this means finding tracks, and determining their end points). We also want to measure of the identity of the particle leaving the track, by tagging it as weakly visible (pions or other "minimum ionizing particles", well visible (protons) or very pronounced (nuclear fragments), which provides us with richer possibilities to understand the annihilation process on different nuclei. Here, we will need help from you for suggestions what should be improved, and if you are a programmer, perhaps help in implementing the suggestions.

- a second step, in which tracks are tied together into "vertices", common origins of tracks, which may or may not be visible (in case the annihilation took place before the photographic film). That's new in the user interface, and will need some testing.

- once we have the vertices, and know the identity of the fragments coming from them, we can start writing papers on the annihilation and fragmentation processes of antiprotons on Al, Ti, Fe, Cu, Ag, Au, Pb (we tried to cover a large range of nuclei, from very light ones to very heavy ones). We can also use the vertices to see how parallel the foil was to the emulsion in order to better understand how well we can reconstruct vertices via this technique.

The longer term step, that of detecting antihydrogen annihilations with this method, and measuring their gravitational interaction, will happen once we understand how to make a beam of antihydrogen, something we are working on right now. In the mean time, however, we're also spending a small amount of our antiproton time on taking the data that you will be looking at.

Our goal in this beta release is to understand our systematic errors using the data we have, work on the user interface, and generally try to get the machinery working so that we'll be ready once more data come in. As involving the public in our analysis is something completely new for us, please bear with us as we stumble, make embarrassing mistakes, and slowly get to the point where you have as much fun as we do.