Tuesday, June 07, 2011

CMS at 191/pb: no SUSY seen in Z + jets + MET

The CMS Collaboration has joined ATLAS and it began to release new papers with a significant amount of new data from the 2011 LHC run. The first paper is
Search for Physics Beyond the Standard Model in Z + jets + E^miss_T events at the LHC (PDF)
To process events where a Z-boson, missing transverse energy, and at least three jets are produced (quite complicated, right?), they use a new Jet-Z Balance (JZB) method; the Czech readers shouldn't confuse it with JZD which was a Czech kolkhoz (a farm stolen from the farmers and collectively owned by peasants obedient to the communist party) during socialism. And in the 0.191/fb of the 2011 data, there's clearly nothing significant.

You see that this is a slightly more contrived channel - but it is complementary to some of the most straightforward searches for the squarks and gluinos that ATLAS has already released. Some benchmark points were excluded, others were not. In particular, the benchmark points LM4 and LM8 - forget about my initials - are resilient. ;-)

But you can see that the number of relevant events is very low in this particular kind of search which makes all values of JZB above 50 GeV very noisy. There are only 20 events with JZB above 50 GeV and 6 events above 100 GeV. Because of the absence of hints, it's clear that a 5-sigma SUSY discovery in the channels that have already posted their 2011 data can't occur before a few femtobarns of the data - which can be rather soon, however.

Each major detector has already recorded 0.8/fb of the data. Note that the plan for the whole 2011 was just one inverse femtobarn!

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