## Thursday, May 24, 2012

### A Picture from Work

I have the greatest job in the world! (While, apart from being the chair of the Math Department, but that's just for another year.) Having tenure at a great up-and-coming liberal arts university, and conducting nuclear physics research at the world's premier medium energy electron accelerator-- which is only a 10 minute drive from our campus! It is darn near a perfect situation.

The accelerator has gone quiet. Data taking has stopped for the next 18 months, after which will turn back on with twice the energy (12 GeV).

Everyone is getting ready. New detectors have to be built and new software written. One of my tasks is to write the event display software for Hall B, one of the four experimental halls: Hall A, Hall B, Hall C and Hall Tim. (Just kidding, Hall D.)

Here is a screen shot from version 0.1:

This shows one set of detectors for our experiment: drift chambers. This is a 2D slice (we also have 3D views) in which you can imagine the tilted 2D rectangles are actually tilted 3D boxes perpendicular to the page. Each box contains six layers of wires, with 112 wires per layer. The wires are also (roughly) perpendicular to the page. The wires are maintained at high voltage (to produce an Electric field) and embedded in a gas. After a collision at the target (roughly the lower left corner) the outgoing reaction particles go flying toward the detectors. Going through the gas they cause ionization, and the ions collect on the wire which then produces an electronic signal. That results in a rough set of locations of the track which, together with the magnetic field (shown as a "thermal" plot in the picture) allows us to determine the momentum (but not, by itself, the identify) of the particles.

What is show is a simulation (from GEANT4) which is why it is so clean (this simulation did not, in this instance, simulate background) and why we know "truth". That is, the particles are colored based on what type they are. In real data, prior to analysis, we wouldn't know one track was a pion, one a muon, etc.

Another:

And another:

## Wednesday, May 23, 2012

### Randall Munroe comes home

Randy Munroe of xkcd fame came back to his alma mater (CNU) in April, giving a fantastic talk. I am in the picture--but not up front.