December 20, 2011

Higg Non-News

I missed the brouhaha surrounding the LHC Joint Higgs Search Progress Report. But, luckily, there’s still something contentful to add to what’s already been said.

Both groups (ATLAS and CMS) found statistically-significant excesses in two channels, corresponding to

• $H\to \gamma \gamma$
• $H\to Z{Z}^{*}$

with an invariant mass centered around 125 GeV.

The latter decay mode yields a 4-lepton final state where one of the ${\ell }^{+}{\ell }^{-}$ pairs has an invariant mass of 91 Gev, corresponding to the decay of an on-shell $Z$ (the other $Z$ is, necessarily, off-shell). Since the relevant 4-lepton final states have relatively low backgrounds, the experimentalists could have (modestly) improved their results by relaxing their constraint that one of the $Z$s be on-shell. My colleague, Can Kiliç, and collaborators have a recent paper advocating exactly such an analysis.

According to Can, this wouldn’t quite have boosted CERN into $5\sigma$ discovery-territory, but it would have made the result more compelling (or, conversely, less-so, depending on the result).

In fact, Can and co. go a little further, and advocate looking in a number of multi-lepton channels:

• same-sign $2\ell$ (the standard $H\to W{W}^{*}$ search looks for opposite-sign di-leptons)
• $3\ell$
• $4\ell$

with varying amounts of MET. Of course, nothing substitutes for greater integrated luminosity, which is what 2012 is all about.

Posted by distler at 5:04 PM | Permalink | Followups (4)

December 19, 2011

Vivian Distler 1965-2011

More here, here and, yes, here.

Posted by distler at 4:55 PM | Permalink | Followups (7)