For the past 11 days the Large Hadron Collider has been running with a 1092 bunch filling scheme adding 325/pb to the total data delivered. Based on an average peak luminosity of 1.13/nb/s this gives a Hübner Factor of 0.3 which is very respectable for this early stage of the run.
During this time the beams have been dumped frequently by problems such as software errors that are being rapidly fixed. UFOs have been another major headache. These are thought to be dust particles that fall into the beam. There is so far no sign of their numbers dropping as the beam zaps them up, but the dump thresholds can be changed in the worst hit areas to reduce the number of UFOs that cause a run to be aborted. This means that overall the run efficiency should improve and the expectation should be for a somewhat better Hübner Factor once they settle into the longer run.
The first successful fill with 144 bunch injection ran last night. The longer train length means a few more bunches can be fitted into the ring. They just need two long fills with this filling scheme before they can step up to 1226 bunches in each beam, so higher luminosities should be with us soon.
The schedule for the rest of the year has been modified to replace the four planned maintenance breaks with just three breaks, but slightly longer in duration. The immediate effect is that the next stop moves back from 16th June to 29th June, allowing more data to be collected in time for the big HEP-EPS conference at the end of July.
This week it has been the Physics at LHC conference in Perugia that has been grabbing most attention. There have already been some new limits shown, such as seen on these plots from a talk today on ATLAS top physics by Marina Cobal.
The talks on the final day tomorrow are the ones most likely to declare any new observations rather than just exclusions using the 240/pb on offer. Indications from conference notes already released suggest that we should not expect too much. A lot of the talks have not explored beyond the 40/pb dataset from 2010.
A pessimist would say that they have concentrated on the best-hope channels for presentations at this conference so the absence of new observations beyond the standard model here means that nothing new is showing up yet. An optimist, however, might say that they have only been able to approve the less interesting searches in the time available. All the best results may be in the places where no new data was shown this week because they will want to wait a little longer for more data to get conclusive results. We wont have long to wait until the EPS-HEP conference where 1000/pb of data should be on the table.
Meanwhile the main buzz is about the CDF bump at 150 GeV. Tomorrow there should be a seminar at Fermilab from the D0 group to tell us whether or not they also see the bump. It will be webcast here. Another version of the talk will be seen at PLHC on Saturday. Woit has already passed on a rumour that says the answer will be negative. Even if he is right, this will leave open the question of how the bump seen by CDF can be explained. The results should be consistent so the two groups will need to compare their analysis methods to find out what went wrong.
Update 9-Jun-2011: I have checked all of the talks at PLHC 2011. There are 10 talks from ATLAS and one from CMS where new searches using 2011 data up to 236/pb are presented. They all correspond to notes already published last week so we know that only new exclusions limits are found. No new physics is forthcoming this week from the LHC, unless they slip in an extra last minute talk.