Monday 26 July 2010

Higgs still at large

Finally, the picture we were dying to see:
Tevatron now excludes the standard model Higgs for masses between 156 and 175 GeV. The exclusion window widened considerably since the last combination. Together with the input from direct Higgs searches at LEP and from electroweak precision observables it means that Higgs is most likely hiding somewhere between 115 and 155 GeV (assuming Higgs exists and has standard model properties). We'll get you bastard, sooner or later.

One interesting detail: Tevatron can now exclude a very light standard model Higgs, below 110 GeV. Just in case LEP screwed ;-) Hopefully, Tevatron will soon start tightening the window from the low mass side.

Another potentially interesting detail: there is some excess of events in the $b \bar b$ channel where a light Higgs could possibly show up. The distribution of the signal-to-background likelihood variable (which is some inexplicably complicated function that mortals cannot interpret) has 5 events in one of the higher s/b bins, whereas only 0.8 are expected. This cannot be readily interpreted as the standard model Higgs signal, as this should also produce events with higher s/b where there is none. Most likely the excess is a fluke, or maybe some problem with background modeling. But it could also be an indication that something weird is going on that does not quite fit the standard model Higgs paradigm. Maybe the upcoming Tevatron publications will provide us with more information.

More details in the slides of the ICHEP'10 talk by Ben Kilminster.


Anonymous said...

I hope we find the "bastard", becuase if the window closes completely, we Europeans will have a really bad time explaining why we built such an expensive machine for nothing ...

Jester said...

Even if the window closes completely there remains the region with mh>200 GeV which Tevatron cannot reach. So the LHC will not be dismantled so quickly ;-)

tulpoeid said...

(About the anonymoys reader above:) Isn't it high time to do something for the notion that excluding the higgs is a failure instead of major news and a major feat? I'm just saying...

Bill K said...

History of the Tevatron's exclusion window:

170 GeV - Aug 2008
160-170 GeV - Mar 2009
163-166 GeV - Nov 2009
158-175 GeV - Jul 2010

On the average it has been widening at a majestic grass-growing paint-drying rate of about 5 GeV per year.