# Tag Archives: higgs boson

## Particle Flow Calorimetry

I took a break today from thesis writing to attend the weekly computing seminar, since it had calorimetry in the title, which should supposedly be one of my skills. The slides aren’t posted yet, but whenever they are you can find them here. Mark Thomson was the speaker, who also has a few papers out on the same subject on the web, this one seems to have the most overlap with the talk.

The idea goes a bit like this: If you want to test new physics at a collider, you need to measure collision products very carefully. Specifically, testing electroweak sector models (all this higgs hubub) requires identifying and differentiating Z and W bosons real well. Single production Z and W’s both decay in to quark-antiquark pairs. We can’t see quarks in detectors directly, but we observe sprays of particles called jets which have basically the same energy and direction, etc. So they want to measure jets real well at the proposed and under-development International Linear Collider (ILC), and the main technique to do this that they are trying to develop is called Particle Flow Calorimetry (PFC).

## CDF/D0 Combined Top Mass Result

For those of you interested in HEP in general and Higgs searches in specific, you may have already heard of the Combined CDF/D0 top mass preliminary release. They’ve changed from $170.9^+_- 1.1(sta)^+_- 1.5(sys)$ last year to $172.6^+_- 0.8(sta)^+_- 1.1(sys)$ which is a total uncertainty of 0.8%. Tommaso Dorigo has a really nice post on the individual measurements and combined uncertainties that went in to the result. There’s also a bit of general discussion on how to combine measurements and an interesting point on how top mass measurements may-or-may-not be effected by jet multiplicities in the final state. He suggests that the full luminoisty this might improve to 0.5% .

For those of you who don’t get all giggly at slightly lower error bars for their own sake, the top quark is the heaviest of the six flavors of quarks, and was first measured with certainty around 1994-5. The mass of the top is an important parameter in estimating properties of the yet-to-be-seen Higgs Boson, as well as an important input to describing the plethora of other physics processes at the LHC. If you want to know where to look for the Higgs, and you want to know what backround stuff isn’t new physics, then you want to know the top mass really really well.