A first hint of Higgs !!? April 1, 2008Posted by dorigo in news, physics, science.
A plot blessed last Friday at the CDF Higgs meeting made me jump on my chair today. It is the combined result of ZH search channels with Higgs boson decay to b-quark pairs. What you see in the graph below is the distribution of the reconstructed dijet invariant mass for the two jets accompanying the Z-boson signal (either a pair of opposite-signed leptons, or a significant amount of missing Et). The data (2.7/fb collected by CDF in Run 2) are the black points with error bars, and the various contributing physics processes are represented by stacked histograms.
This analysis does much better than the previous ones in selecting b-jets, and an optimized Neural Network was used to improve the dijet mass resolution, for the first time reaching the 10% point; also, the inclusion of multijet data with a signal improves the acceptance by about 20%. There is a clear excess of events at about 120 GeV, where the expected Higgs signal (purple histogram) provides a better fit to the data than the rest of backgrounds. Pseudoexperiments indicate that the excess represents only a 1.9-sigma significance, but I believe the estimate has been conservative.
I will have more to say about this later today.
UPDATE: since I am already getting in my mailbox messages from reporters and interested outsiders asking for more details, I have better clarify directly here that the above is, indeed, an April’s Fool. The plot comes from the report of the Tevatron Higgs Sensitivity Working Group, and it refers to a pseudo-experiment generated with an equivalent luminosity of 10/fb. The black points are not data! They are randomly fished events from the Monte Carlo generations.