ALICE Spokesperson Paolo Giubellino talks to ALICE Matters, summarising the 2011 run and plans for 2012.
How was 2011 for the ALICE experiment? What sort of challenges and successes were there?
2011 was a fantastic year for ALICE. We were able to cope with unprecedented challenges and difficult conditions while operating the experiment during the proton-proton run. At the same time we were preparing for the heavy-ion run. At some point it became clear we would not be able to operate the experiment the way we were used to. This is because the forecast of what luminosity we could be getting had been growing rapidly. We decided we would have to stop recording the full information and would pre-process it in the High Level Trigger (HLT). This was extremely critical: If we had done something wrong the data would have been gone forever. We went through a very extensive test period for this and the HLT team worked extremely hard. At the end of the exercise they were really worn out. This was an enormous responsibility hanging over them and was really a 24 hour effort for a long time.
Thanks to this, and many more, efforts the experiment worked very well. We had a fantastic heavy ion run. The accelerator gave us five times the luminosity they had promised and in the end the data this year are at least an order of magnitude more than the 2010 data. This is very exciting and the analysis of the 2011 data is going to be great fun because such an increase in statistics opens new observables which we could not attain with the old data, so we will not just do better, but do many more things. On the other hand we still have the analysis from the 2010 run to finish. We must bear in mind that we still have a lot in the drawers. We also have to boost our efficiency in publishing papers. To do this we have re-organised for 2012 our physics working groups (PWGs) to accommodate all this physics. We have two big conferences with which to target our 2011 data analysis, but we must try to bring the analyses to an end so that they can be published.
What are the plans for 2012? How will it be different to 2011?
2012 is going to be a very challenging year because we have to fight on many different fronts at the same time. Aside from the 2010 and 2011 analysis we have a very important run at the end of this year in which the LHC will deliver proton-lead collisions. This is the first time this will be done at the LHC and we have to prepare the experiment for data taking and prepare ourselves for the analysis.
We must also continue to run ALICE during the proton-proton run because we don’t yet have adequate statistics for the comparison running with respect our heavy-ion data.
How is the ALICE Collaboration preparing this year for the upgrade of the experiment in 2018?
We already have a very full plate, but we must plan for the upgrades during 2012. Although we will be installing our upgrades in 2018 this is not very far away considering we still have to approve and build the new detectors, and often to perform R&D. So we are really very tight for time. We have begun all the procedures with the many committees that must approve our plans and provide the funding. We felt a great deal of urgency and have accelerated the process. We have tried to give the Collaboration as much information as possible about specific additions that we want to make to the experiment and to the overall strategy, in order to enable a process of conscious decisions. We called a special Collaboration Board meeting for the 2nd week of 2012 that approved our strategy document, which defines what we want regarding the running of ALICE and outlines the base physics programme we aim for with the high-rate operation ALICE with Lead beams. At this point we know what we want to do with the experiment as it is, therefore what has to be changed or added in order for it to operate well at a much higher rate and to exploit the opportunities provided with the integration of 10x the luminosity which we will have accumulated until 2018. For some detectors this requires some modest alterations but others, such as the Inner Tracking System (ITS), require complete replacement. So there is a whole range of interventions required.
We feel that the physics programme which the upgrades open for ALICE is unique and of compelling interest, and therefore it can be the base for our future. In addition, we have defined the sequence of steps that we will be following for the approval of the additions that has to happen, or not happen, by September.
We have identified 3 promising new detectors to add, and the final decision will depend on the scientific value but also on the feasibility of building and funding them:
• A detector that would expand the particle identification capability at high momentum – the Very High Momentum Particle Identification Detector (VHMPID).
• A silicon tracker to be placed in front of the Muon Absorber, so that a measurement of the muons would happen not only after the Absorber but also before. This would increase enormously the precision with which they are measured.
• A Calorimeter or a set of Calorimeters, depending on what will be decided, in the forward region where there is now the photon multiplicity detector.
These are all interesting potential additions and would all expand the physics capabilities of ALICE. Decisions will be made in the coming months.