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Looking into the Crystal Ball

Whenever a B-factory researcher reconstructs a B meson and wants to model its energy-substituted mass, the go-to function is the so-called “Crystal Ball” function [1]. This function combined a Gaussian for the peak and a power-law for a non-Gaussian, low-side tail. Many younger physicists don’t know that this function takes its proper name from  the Crystal Ball collaboration, a group of physicists which originally operated the Crystal Ball multi-photon spectrometer at SLAC.

In the spirit of answering the question, “what happens to old particle detectors”, I wanted to note that a collaboration in Germany has recently reported results on eta -> 3pi0 using the Crystal Ball detector [2]. Makes you wonder: what will parts of our current detectors be doing in 20 years?

The top of the Crystal Ball detector

[1] http://en.wikipedia.org/wiki/Crystal_Ball_function

[2] http://arxiv.org/abs/0812.1999

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A Physicist in the Inner Circle

As I discussed in my personal blog [1], Dr. Steven Chu has been picked by President-elect Obama for Secretary of Energy. The Newshour [2] profiled Dr. Chu, repeating an older story on him. We have to manage our expectations about what this means for curiosity-driven research (CDR) and application-driven research (ADR) in the U.S. However, I think I speak for many of us when I say that a physicist is a welcome Secretary of Energy at a time when energy and research policy are more critical than ever.

[1] http://steve.cooleysekula.net/blog/2008/12/11/a-physicist-in-the-inner-circle/

[2] http://www.pbs.org/newshour/bb/environment/jan-june07/climatechange_05-02.html

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Confirming the eta_b

Just shy of 6 months after the presentation of the discovery of the bottomonium ground state, BaBar has presented confirmation of the discovery using Y(2S) decays to the ground state instead of Y(3S) decays. The results were presented by on of the core analysts, Peter Kim, at the QWG workshop in Nara, Japan. His slides are available online [1].

The compatibility of the results is excellent, with variations only at the level of a single statistical deviation. You can see a comparison of the (non-peaking) background-subtracted data and the overlays of the fitted peaking backgrounds (left two peaks) and the signal (right-hand peak). The previous result was a 10-sigma result; the current one is just over 3 sigma, enough for a clear confirmation but not, by itself, an independent discovery. That’s OK – we were going for confirmation, so this worked out as well as we could have hoped!

Every analysis on BaBar is led by a core team of researchers, but reflects the hard work of dozens of people in guiding and reviewing the result. As with the original bottomonium ground state work, I continue to find it remarkable what discoveries lay in this Upsilon data, and how the hard work of the BaBar collaboration continues to pay off.

A paper will soon follow.

[1] http://www-conf.kek.jp/qwg08/session1_1/kim.pdf