ALICE on the move

A new management, new modules for its sub-detectors and an increased capacity to probe the properties of the quark-gluon plasma. The new year bodes well for ALICE and ion physics as quarks and gluons prepare to unveil their most profound mysteries.


Installation of one of the new EMCal modules in the detector.

Paolo Giubellino, the new ALICE spokesperson, talks with enthusiasm about what has already been done by the ALICE collaboration and what is yet to come. He has recently taken over from Jurgen Schukraft, who led the collaboration from its earliest beginnings. “We had a very exciting first year of operation, with many interesting results coming up in a very short space of time,” says Giubellino, a heavy-ion-physics expert from the Italian National Institute for Nuclear Physics (see box for details). “The Christmas technical stop wasn’t a break for us as we upgraded the detector, completing the installation of the electromagnetic calorimeter (EMCal), which will extend ALICE's capability to study the properties of the quark gluon plasma through its interaction with particle jets. In addition, we added three modules to the Transition Radiation Detector (TRD), thereby increasing its acceptance by 50%.” The TRD installation will be completed during the next shutdown, while the latest addition to the ALICE detector, the DCAL, will have to wait for the long LHC shut down.

In parallel with the hardware upgrade, the ALICE collaboration – more than 1000 scientists from 116 institutes in 33 countries – is working on the analysis of data taken during the one-month ion run in November last year. “In the field of ion physics the results from the experiments drive the research and often come before the theory. Before operating the LHC, nobody could really say what characteristics strongly interacting matter would have at such high energies. Already with the first measurements we have established that it still exhibits behaviour close to that of an ideal liquid and that the energy loss of fast partons, the “jet quenching”, is surprisingly large. We have also measured the energy density reached in the collisions, which is about three times higher than at RHIC, while the interaction volume is twice as large. Our data analysis went very fast because the LHC is a very powerful instrument: even with the data taken at low luminosity in 2010, the reach in many variables already exceeds that of RHIC. Another big advantage of ALICE with respect to previous heavy ion experiments is its very high accuracy in the identification of the particles produced by the collisions,” explains Giubellino.

So, while busy analyzing last year’s data, ALICE is also getting ready for an exciting new year. The internal organisation of the collaboration very naturally moved from ‘primacy’ of the technology to ‘primacy’ of the physics. As of 1st January 2011, not only does ALICE have a new spokesperson and new deputy spokespersons but it also has new chairs of its Collaboration Board, the Conference Committee and the Editorial Board, new coordinators for its detectors (Muon Detector, Time Projection Chamber and Inner Tracking System), a new Upgrade Coordinator and new conveners for some of its physics groups. “Thanks to the great job done by the past management, ALICE is in very good shape. The data analysis phase will automatically increase the need for closer collaboration among all the members and the fact that I come from an external institute will hopefully be of help in meeting this requirement. ALICE is ready to enter a new, very dynamic phase of its history,” concludes Giubellino.

Since completing his studies at Torino University and the University of California, Santa Cruz, Paolo Giubellino has dedicated most of his scientific career to the physics of high-energy heavy-ion collisions, first in HELIOS, then in NA50 and finally in ALICE. He was involved in ALICE right from the very first feasibility studies, and later took on a number of responsibilities within the experiment, including as project leader for the inner tracking system, chair of the Conference Committee, Upgrade Coordinator and, for the past six years, deputy spokesperson. He has been active in the development of silicon detectors and is a member of the ICFA Instrumentation Panel. He has served in many scientific committees and panels and is currently chair of the G-PAC at GSI and a member of the scientific committee of IN2P3. He also chaired the working group entrusted with writing the "Phase Transitions" chapter of the NUPECC long-term plan.

by CERN Bulletin