Happy 30th birthday, heavy-ion physics!

Virginia Greco

ALICE celebrated the 30-year anniversary of heavy-ion physics at CERN hosting a special event on 9 November 2016, including talks by distinguished speakers.

Poster of the 30 Years of Heavy Ion Beams celebration event at CERN

Heavy-ion physics was born at the beginning of the 1980's. Building on nuclear and particle physics, it became quickly an independent branch of this discipline. Thanks to the intuition and commitment of a group of physicists of GSI, LBL and CERN, the scene for a series of discoveries and spectacular measurements was set. Heavy-ion physics took off at the CERN's Super Proton Synchrotron (SPS), where the Quark-Gluon Plasma (QGP) was observed for the first time, continued at the Relativistic Heavy-Ion Collider (RHIC) at the Brookhaven National Laboratory, where its defining properties were discovered, and keeps being a fertile field of which the LHC experiments, mainly ALICE, are harvesting interesting results.

On the occasion of the 30-year anniversary of the first heavy-ion collisions at the SPS, on 9 November 2016 ALICE organized at CERN a celebration event, with an afternoon dedicated to seminars followed by a reception. Great speakers, involved at different levels and times in the history of heavy-ion physics, gave interesting talks on both the history and the physics of this field.

The commemoration kicked off with an introduction by CERN Director for Research and Computing Eckhard Elsen, who is a particle physicist from DESY.  Since he could not be present because of overlapping obligations, his speech was read by the chairman, Guy Paic, from UNAM, Mexico.

Guy Paic, chairman of the first session of talks.

In the first session the floor was taken in turn by four good orators who retraced the history of heavy-ion physics, focusing in particular on its beginnings and offering each his insight into the key events that signed the birth and evolution of the field.

Reinhard Stock, from IKG Frankfurt, Germany, discussed the start of heavy-ion physics at CERN, being himself one of those who wrote a proposal to the management of the centre to push for it. Then, Hans Specht, from the University of Heidelberg, Germany, gave an account of the same events from the point of view of an “insider”. He was a member of a German Government Committee 1979-1980 called to judge various proposals for new accelerators including SIS 100 at GSI. The alternative to the latter was to open the field of ultra-relativistic heavy-ion physics at CERN in a GSI/CERN collaboration. To push in that direction and to finally do himself experiments in this new field, he decided to join the high-energy physics community, entering for discussions already right towards the end of 1980. He also provided an overview of the most important physics results achieved by the experiments at the SPS.

Afterwards, Herwig Schopper came on stage. He was Director General of CERN when the LEP was built and the heavy-ion programme was started, so he could tell about the political and economical aspects of the story. Finally, the announcement of the observation at the SPS of a new state of matter, the anticipated Quark-Gluon Plasma (QGP) – as later confirmed -, was discussed by Luciano Maiani, who was CERN's DG at the time of the event.

The second session, chaired by Yves Schutz, from IPHC Strasburg, France, was richer in technical aspects and physics issues. It began with a presentation by William Zajc, from Columbia University, US, who reported on the history of heavy-ion physics at RHIC and its most remarkable results. Krishna Rajagopal, from MIT, US, followed with a talk about the study of the characteristics of QGP, which he defined not only as the “most liquid liquid that has ever existed”, but also as “the original liquid”.

Luciano Musa discussed the evolution of detector technology along the three generations of heavy-ion experiments at the SPS and then at LHC, from the streamer chambers of the beginnings, to the time projection chambers and then the silicon detectors of ALICE. The series of talks was concluded by the open questions and future challenges of heavy-ion physics, presented by Jan Fiete Grosse-Oetringhaus, from CERN.

Discussions and celebrations continued over the evening, during the special reception hosted at the main restaurant of CERN. Many members and collaborators of ALICE attended the event and ALICE's spokesperson Paolo Giubellino had also the pleasure to welcome CERN's DG Fabiola Gianotti to the evening party.

Reception at CERN. From the left: Paolo Giubellino, Luciano Maiani, Sergio Bertolucci. Reception at CERN. From the left: Urs Wiedemann, Hans Specht, Guy Paic, Reinhard Stock, Hans Gutbrod, Fabiola Gianotti.


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