The Large Hadron Collider has now delivered over 10/fb at 8 TeV during 2012 in the middle of a long 11 week summer run between technical stops. The 10/fb is for ATLAS and CMS but LHCb has also passed 1/fb in 2012 to add to their 1/fb from last year.
About 3.5/fb have been added in the first 5 weeks after a slow start with time taken out from pp luminosity production for floating MDs, 90m physics (TOTEM and ALFA) and VDM scans. The collider has now settled into a straight stretch with about 1/fb added each week. Peak luminosities are a little down compared to before the last technical stop due to problems with beam instabilities but if they keep it steady the results will be good. There are six more weeks before the next stop with time scheduled for more floating MD and 500m physics. We can expect them to end on 16th September with about 15/fb recorded this year in addition to the 5/fb from last year.
While this run is in progress we can expect to see results from before the last technical stops at a series of specialised conferences SUSY 2012, TOP 2012 etc., see the viXra calendar for details. It seems most likely that the next Higgs update will come around early october with 20/fb of data available. This will be in keeping with past updates where the amount of data has doubled each time. With the Higgs discovery behind them the next update may be a little more low-key but I think there is a good prospect for reporting a significant excess beyond standard model in the diphoton channel. It may even pass three sigma in one of the experiments.
This list of LHC Higgs updates looks roughly like this
- Moriond, March 2011 – 0.04/fb
- EPS, July 2011 – 1.2/fb
- Lepton-Photon, August 2011 - 2.3/fb
- CERN council, December 2011 - 4.9/fb
- ICHEP, July 2012 – 10.4/fb
- October 2012 – about 20/fb ?
- Dec/Jan 2013 – ??
Assuming they update at around 20/fb in October, can they double the dataset one last time by the end of the year? The final 10 week proton run schedule looks like this,
If they run with the same parameters they will add another 10/fb to the total luminosity, but with the target for the year already achieved I think they will want to do something different for this run. The scheduled scrubbing run after the technical stop only makes sense if they are considering the option of running at 25ns spacing. Earlier MD tests at 25ns have worked but with reduced beam lifetimes. The scrubbing run will help clean the pipes to make the runs more successful. To run at 25ns they will have to reduce the bunch intensity. The PS will need to split the bunches in half one extra time before injection and also because the present high intensities at 25ns would result in too much heating. This means that luminosity will not increase at 25ns unless they can also improve the squeeze.
In fact the MD tests for tighter squeeze down to 0.2m went very well (as far as I know). Current beta* is 0.6m so they have plenty of scope to at least double the luminosity with the tighter squeeze. The 25ns spacing means less pileup making an increase in luminosity more manageable. I don’t know what the actual plans are but I think a 25ns final run with 0.3m would make complete sense if they can get it to work. As well as giving them a chance at doubling the integrated luminosity yet again it will be a valuable trial for runs after the technical stop which will certainly have to be at 25ns spacing. Running at 25ns this year is a risk but definitely one worth taking.