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The CDF Higgs Discovery group October 28, 2006

Posted by dorigo in news, physics, science.

The CDF experiment distributes physics analyses in a small number of working groups, called “Physics groups”, which meet regularly every two weeks to discuss the advancement of all the studies relevant to a particular branch of hadron collider physics. At the meetings of the working groups, each run by two conveners, new physics results are discussed, scrutinized, and approved (we say “blessed”) for public consumption.

Right now, we have five main physics groups: the top, bottom, exotics, QCD, and electroweak group. Each of these spawns their own subgroups, so for instance the top group has a “top properties” subgroup and a “top mass” subgroup, the exotics group has a “Higgs” subgroup, the electroweak group has the “W/Z cross section” subgroup, etcetera. The subgroup leaders report periodically to the main group meetings.

The number and division of these physics groups has not been constant during the history of CDF. Following the varying needs of the many physics analyses, the amount of work being carried out in different studies, and the importance of selected topics, groups have merged, split, branched. For instance, I remember that in 1992, when I joined CDF as a summer student, I used to follow the meetings of the “Heavy flavor group”: it was a place where B analyses and charm physics analyses (yes we did some of that as well even back then) were discussed together with top quark searches – the top was not born yet!

The CDF heavy flavor group split into the B physics group and the Top group soon thereafter, a division that lives through to our days. Interestingly, the opposite trend happened in 2000, when the leftovers of Run I physics analyses were dealt with in little-attended meetings, and a merging was decided between the top group and the electroweak group. It made sense, since W and Z boson signatures (whose study had always happened in the electroweak group) were the basis of top physics searches too. 

Now, let’s come to the subject of this post… The Higgs boson has been searched in CDF for a long time, since Run I, and the analyses have always been discussed in the Exotics physics group, together with fancy SUSY searches, extra dimensions, technicolor and what not, but specific technical details were presented at the Higgs subgroup.

Now things are going to change. At the last executive board meeting, the CDF collaboration has decided to create a new “Higgs Discovery Group”. This group will draw a lot of resources from everybody, and is designed to catch attention, manpower, trigger bandwidth, and to produce a coherent effort from the whole collaboration, in order to do our utmost to discover the Higgs boson, if Nature (the bitch) gives us a chance to do so.

It does make a lot of sense. Indeed, CDF has already bagged the two most important results it was after in Run II: the measurement of Bs mixing, and a 1% precision in the top quark mass. Well, the latter is not in the bag yet, but there seems no possibility other than a major incident to the accelerator to take that result away from us before the end of Run II.

Instead, finding the Higgs boson in CDF (and D0: on that endeavour the two experiments have long known they have to work together, to double the statistical power of their data) would be the crowning of a really illustrious career, from 1985, when the experiment was first put together. A quarter of a century of successes, O(1000) physics papers and technical articles, the discovery of a fundamental SM particle, plus countless other composite hadrons. The measurement of SM properties with unmatched precision, the discovery of Bs mixing… What would be better to top it off with the discovery of the Higgs boson ?

The demonstration that the experiment is going to start acting coherently and speak with a common voice will come soon, when the trigger menu will be revised to allow Higgs boson collection to be unhindered by bandwidth problems – at the cost of a significant reduction of other, now less urgent, datasets. Until now, in fact, the trigger was a common resource that was split among the different endeavours by trying to make everybody happy with their own little dataset… I have always thought of our 600+ people collaboration as more like two or three different sub-collaboration, a large one being the CDF-B physics collaboration, and another large one being the CDF-top physics collaboration. Now I hope CDF will be all CDF-Higgs!

As my involvement in CDF is ramping down, I will not be able to help out much, most of my attention being driven by CMS. But I still hope to see a final success of this great experiment, despite the fact that it goes a bit against my own interests, since CMS would then be left with the mission of discover the non-existent SUSY and improve by a riduculous amount the top mass precision. It would be quite interesting to see how long the LHC would then keep running…

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