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Michael Schmitt | USLHC | USA

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How should we check the CDF Anomaly?

There has been lots of buzz about the CDF anomaly, and many blog entries and discussion.   For example, there is Flip’s excellent discussion here, as well as entries at many other physics blogs.

Everyone understands, of course, that the next step is for CMS and ATLAS to check their data and see whether they might also observe a hint of a signal.   While the LHC luminosity is about 100 times smaller than what CDF used, the detectors are better and the cross sections are larger, so maybe they can see something.  It’s worth looking, right?

So, if you are are physicist with LHC data on your hard drive, how do you begin?  Instinct says: just implement the CDF cuts and run on the data.  If those cuts produce a signal at CDF, they should produce one at CMS or ATLAS, too, right?

Well, maybe.  But that attitude might be too simplistic.   If you look at the CDF plot below, you’ll see two peaks.   The point is not:  CDF looked at the di-jet mass (MJJ) spectrum and saw a bump.  The point is:  CDF established a signal for a predictable standard model (SM) process, namely, ppbar→W+V, where  V is W and Z together, and next to this SM signal, saw an extra bump.  The fact that they see W+V at the expected rate provides some strong proof that their analysis is valid. If they could not manage to see W+V, then I would be reluctant to take their analysis seriously.  And although they did not couch their discussion this way, for me an important fact is that the anomalous bump is roughly half the size of the SM W+V one.

So, in my opinion, any experiment that wants to check whether the CDF anomaly is present in their data must show that they at least see the W+V signal, first.  This is more important than blindly implementing the CDF cuts.   Show the benchmark, and then we will see whether there is an additional peak, roughly half the size, about 60 GeV higher in mass.

CDF anomaly

CDF MJJ distribution

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