The feast is set January 16, 2007Posted by dorigo in news, personal, physics, science.
…May’st hear the merry din.
No, not Coleridge – although for some reason today’s news made me recall the verses of “The Rime of the Ancient Mariner“. The news are that after more than four years of work we have set the dates for the preblessing and blessing (the way CDF calls its publication approval) of the Z->bb analysis.
Four and a half years, or actually five. Or maybe 11 ?
It was 4.5 years ago -on September 3rd, 2002- when the first meeting of the “Z to bbbar working group” was held around a table in the Fermilab cafeteria, with myself and Giorgio Cortiana representing Padova, Mel Shochet and Matt Baumgart for the University of Chicago, and Sal Rappoccio, Joao Guimaraes and Ayana Holloway for Harvard University. That was the start of a long collaboration and endless meetings with a varying mixture of researchers and students from the mentioned institutions, plus Berkeley and Geneva.
But by then I had already worked at a preliminary study with Giorgio about the extractability of the Z signal with Run II data earlier that year, so it would be more correct to say that five years have passed.
And then again, my first studies of the Z->bb decay and its extractability in CDF date back to the winter of 1996, when I was scavenging around for a suitable PhD thesis. Suitable to my style of autarchic seeker, who would not accept the established belief that a Z boson could not be extracted from such a huge pile of background in the Tevatron proton-antiproton collisions… But I did bless a result in Run I, so that is really pre-history.
Anyway. Hopefully, by February 23rd we will have a new, precise, innovative measurement of the b-jet energy scale, with a total uncertainty of less than 2 percent, obtained from the signal of about five thousand Z->bb decays. That measurement will reduce the error bar on the top quark mass measurements in CDF significantly. It will make me proud, and it will win me a beer with Jean-Francois Arguin (formerly from University of Toronto).
Yes, another bet… That one was cast at a meeting when the cross-calibration of the jet energy scale in top quark mass fits with the W boson mass was discussed in some detail, three years ago. Back then I bet we would have obtained a more precise measurement of the jet energy scale from the Z peak than from W events in top pair decays. The bar chart here has been partly amended of the private information, and the Z point (the bottom one, in magenta) has been shifted randomly from its true location, but it shows we will be indeed doing better than previous estimates of the b-jet energy scale – and with quite a bit less data (about half an inverse femtobarn).
That success will make me proud. It will have been made possible by the construction and maintenance of the Silicon Vertex Tracker, a daring hardware enterprise dreamed almost 20 years ago by Luciano Ristori, as much as by years of trigger studies by Mel Shochet, Ray Culbertson, Sandra Leone and Ciro Bigongiari. But of course, more than anything else, it will be the merit of Julien Donini, my colleague in Padova who took it over his own shoulders to bring the analysis to completion, with me as little more than a by-stander during the last two years.