After the hectic EPS conference last week there are a number of followup workshops organised for people to discuss the new results concerning the Higgs boson and possible new physics. The first is the three day meeting “Higgs Hunting 2011″ in Orsay which ended yesterday. For such a workshop the words of the presenters and discussions after are what count, but these are not webcast so all we have to go on as outsiders are the slides (Update 5-Aug-2011: video recordings of the talks have now also been made available at the same link). Nevertheless there are some interesting points in the slides and it is worth picking out some highlights. The workshop started with a talk by Massimiliano Grazzini with this slide showing the main new Higgs results and how it makes the theorists feel These exclusion plots only tell part of the story and it is easy to be misled by excesses that look convincing because they have lots of substructure that makes them appear to show complex signals. In truth the excess comes from a small number of events often seen in just one channel, with the detailed noise coming from the background. A slide from James Olsen for CMS shows the event data from the diphoton channel. On the lefthand plot you can see some excesses at 120 GeV and 140 GeV that make bumps in the exclusion plots but on their own they don’t count for very much. If you look at enough plots you are bound to see excesses of this size somewhere. A slide shown by Elisabetta Pianori shows some signals at around 120 GeV in the same diphoton channels. These are still weak and they are not seen elsewhere. It’s easy to get carried away if you are selective about what you show Here is an more extreme example from Aurelio Juste (see also Paul Thompson). This slide shows events recorded by ATLAS in the H-> ZZ->4l channels. As you can see there are not a lot of events there. This leads to the exclusion limits on the right. As you can see there are bumps giving nearly two sigma excesses, but they correspond to single events. These are not signals on their own. When we combine all the channels and all the experiments we do get some slightly better signals, but still the signal is quite weak. Ben Kilminster has conveniently lined up the plots to show us where they agree, Draw your own conclusions. Here is the update from Matthias Schott on behalf of the gfitter group As you can see they wont include the ATLAS and CMS data anymore claiming that it is “not trivial anymore”. This did not stop John Ellis using the “bloggers combination” to draw some tentative conclusions about the standard model Higgs

The discussion was not just about Higgs but I just have the energy to show one slide summarising the mass limits on various possible new particles according to Paris Sphicas on behalf of ATLAS

Today at the EPS conference in Grenoble the worlds largest hadron colliders will be revealing the results of their latest searches for the Higgs boson, using data collected up until the last few weeks. We will be posting the plots here as they appear.

The individual experiments Dzero, CDF, ATLAS and CMS will each show their all channel combined plots. There will also be separated plots for individual channels and some separate searches for a charged Higgs as predicted in some models such as MSSM.

Our expectation is that the Tevatron plots (Dzero and CDF) will show some good exclusion limits but we will have to wait for the plenary talks next week to see the full Tevatron combined plot. From a press release last night we already know that they will claim to limit the Higgs to a region of 114 geV to 137 GeV, but that is not the end of the story. Above 185 GeV they only use indirect measurements to exclude the Higgs and these assume that no new particles beyond the standard model exist. That could be a weak assumption.

Later today the CMS and ATLAS plots will tell us about those heavier mass regions with direct searches. They should be able to exclude a heavy Higgs or provide a plausible signal above 190 GeV, so what will it be?

We wont get a full combined LHC plot at this confernece but the individual  plots for ATLAS and CMS will already have strong results.

Click on big titles below to bring up the full slide presentation.

Dzero

First up is Dzero with this combined plot that we first saw a couple of days ago

It shows a good exclusion from 162GeV to 170 GeV, not a new result but good to see that the limits imposed by the individual experiments at Fermilab are already strong.

CDF

The CDF combined plot is not very different.

CMS ττ

In the Higgs to tau lepton pair decay channel CMS produce this plot. Remember that the observed limit has to drop below the horizontal line at 1.0 to provide a 95% confidence level exclusion. There is not enough data to do that here, but this data will go into the combined plot later too. It is good to see that 1.1/fb is being used. The same presentation also provides good SUSY exclusion results.

CMS γγ

The Higgs decay into two photons is a crucial channel for finding the Higgs. The LHC do not yet have enough data in this region but with this new plot we see just how close they are getting. A full combination of Tevatron and LHC data at this time might almost have something to say about low mass Higgs if this is anything to go by.

ATLAS γγ

Much the same from ATLAS

ATLAS bb

ATLAS have looked at the decays of a Higgs to decay into a bottom quark pair in conjunction with a W or Z boson. They see no excess at twenty times the standard model Higgs signal.

CMS ZZ

Tow Z bosons from a Higgs can decay into pairs of leptons, quarks or neutrinos giving different channels to search in. First the 2 leptons plus two quarks plot. This is an exciting result that comes close to exclusion at some points, but why has it been cut-off below 220 GeV?

The decay into two leptons and two neutrinos gets even closer

Finally the golden channel of four leptons crosses the line with a tiny exclusion around 185 GeV

ATLAS ZZ

The story from ATLAS is pretty much the same

The 2lepton+2 neutrino channel even has a good exclusion on its own

The golden channel is close to expectation levels for no Higgs

ATLAS WW

This splits into two main channels, first each W decays to a lepton and a neutrino. Here we get an impressive exclusion.

The lepton neutrino 2 quark channel is not so strong

CMS WW

For CMS just one combined plot for the WW channel is all we need

ATLAS

Combined result. WOW!

CMS

Finally the CMS combined plot. The exclusions are from CMS are 149-206 and 300-340 GeV with some large exclusions in the space between.

Conclusion

We still have to see the combined CMS plot and the combined Tevatron plot but already we have some strong results. Much of the Higgs mass range has now been excluded leaving just a window from about 114 GeV to 137 GeV and 205 GeV to 295 GeV. the higher range is excluded by precision tests for a standard Higgs, but a combination of massive particles is not ruled out.

There are excess in the 140 GeV to 150 GeV and a curious deficit at 350 GeV, seen consistently across the data. These results are compatible with a number of options including a light Higgs and a multiplet of Higges. More data will be required to finish and we should get enough this year but already we see that a standard model Higgs on its own only just fits the data if around 130 GeV. This is an outstanding result.

See also TRF for more discussion especially about the deficit.