Updated on June 8th 2007


Heavy Ion Collisions at the LHC

Last Call for Predictions

Monday May 14th to Friday June 8th 2007

The aim of this workshop, organized within the framework of the CERN Theory Institute, is to review and document the status of expectations and predictions for the heavy ion program at the LHC before its start. Analogous efforts prior to the start-up of RHIC proved very useful. They provided a natural forum for the exchange of the most recent ideas and helped to identify open questions. They also helped to distinguish pre- from post-dictions. This workshop aims at playing this role for the LHC. Participants may stay at CERN during part or the whole length of the workshop to prepare and discuss the predictions. Predictions from groups who may be unable to attend the workshop will be accepted for the publication, if they are received in writing prior to the start of the workshop.
Application is through the normal CERN-TH visitor form. IMPORTANT: do not forget to specify that the purpose of your visit is "to participate in the CERN-TH institute on Predictions for HIC at the LHC".

In addition, please send us an email informing us about your application, with the dates you plan to attend. For submission of predictions for an oral presentation: please send an email to the convenor of the topical session indicating a title.
We plan to decide on the seminar structure of the workshop and on possible
financial support for participants by end of March 2007.
Written contributions to the workshop proceedings must be received before
the start of the workshop on Monday May 14th 2007.
Néstor Armesto (main, Universidade de Santiago de Compostela)
Nicolas Borghini (Universität Bielefeld)
Sangyong Jeon (McGill University)
Urs Achim Wiedemann (local, CERN PH-TH)
The proceedings will be published in Journal of Physics G. Each prediction should be summarized on at most two pages plus a few (< 5) references. Predictions should be presented, whenever possible, in  figures which display measurable quantities. Each participant can summarize separately his predictions for each of the topics of the workshop. The workshop organizers are editors of the proceedings. They may solicit referee reports to determine whether contributions submitted are valid predictions. Also, significant editing of the received contributions is foreseen to turn them into a consistent document. However, this editing will not affect the content of contributions, and each contribution will be related clearly to its authors. Full model descriptions will not be accepted - the authors should just indicate the relevant references for the interested reader. For the format of the proceedings, please go to and then click on the link "LaTeX guidelines and class file" which is in the yellow column on the left side of the web page. References must be included using the SPIRES key. Predictions neither orally presented during the focus week nor sent before its start will not be accepted.

Focus week
Depending on the availability of participants, we foresee to center part of the workshop activities in a focus week, with multiple oral presentations and discussions per day. We plan to hold this focus week in the week from Tuesday May 29th to Saturday June 2nd 2007.

The program will be organized into the following topical sessions:
  1. Multiplicities and multiplicity distributions (convenor: Néstor Armesto)
  2. Azimuthal asymmetries (convenor: Nicolas Borghini)
  3. Hadronic flavor observables (convenor: Nicolas Borghini)
  4. Correlations at low transverse momentum (convenor: Néstor Armesto)
  5. Fluctuations (convenor: Sangyong Jeon)
  6. High transverse momentum observables and jets (convenor: Sangyong Jeon)
  7. Quarkonium (convenor: Néstor Armesto)
  8. Leptonic probes and photons (convenor: Sangyong Jeon)
  9. Others (convenor: Nicolas Borghini)
The structure of the program will be decided depending on availability
of participants.

Financial support
On the basis of fund availability, participants will be supported by per diems from the budget of the CERN Theory Institute.

Setup for the predictions
In making predictions, participants are encouraged to focus on those systems tested first in heavy ion collisions at the LHC, namely Pb+Pb at 2.75+2.75 TeV per nucleon. Predictions for lighter systems, for p+A collisions and for the energy dependence of nucleus-nucleus collisions are also accepted, of course. For those, authors are encouraged to underline how such additional experiments can contribute to understand the physics of Pb+Pb collisions at full center of mass energy. For a common definition of centrality, we propose that central events are defined as the 10 percent  more central ones. Kinematical cuts for the different detectors in the three experiments, ALICE, ATLAS and CMS, are provided below. We encourage the authors  to use them in order to ease the comparison of their predictions with the forthcoming experimental data.

Experiment Observable [Detector] Cuts
ALICE See enclosed document


CMS Tracking (unidentified h+/-) [Tracker]

pi/K/p PID [Tracker]

Calorimetry (electrons, photons) [ECAL]

Calorimetry (jets) [ECAL-HCAL, HF]

Muons [Muon chambers]

Forward energy flow [T2, CASTOR]

Forward neutrons, photons [ZDC]
 pT ~ 0.3 - 1000 GeV/c, |eta| < 2.5, full phi

pT ~ 0.3 - 1.5 GeV/c, |eta| < 2.5, full phi

pT ~ 4 - 1000 GeV/c, |eta| < 3, full phi

ET = 50 - 1000 GeV, |eta| < 5, full phi

p_T ~ 3.5 - 1000 GeV/c, |eta| < 2.5, full phi

5.3<~|eta|<~6.6, full phi

|eta| >~8.1, full phi