We would like to warmly thank all colleagues who contributed to the first call for community input on New Ion Collisions @ LHC Run 4 (https://indico.cern.ch/event/1655628/). The response was very positive and underscored broad community interest in the initiative.
We recall that the approved ion program for LHC Run 4 currently comprises $p$–Pb and Pb–Pb collisions (see e.g. CERN-2019-007). From the inputs received, we identified compelling physics cases for collisions with additional ion species that merit further development and that, should the opportunity arise, could be considered for inclusion in the Run 4 program. A summary of the outcome of the first phase is provided at the bottom of this page (see the document Summary_NewIons@LHC4.pdf).
There are essentially two lines of interest. (i) One concerns unique opportunities offered by high-statistics $^{16}$O+$^{16}$O collisions for hot QCD studies. (ii) In parallel, the cases propose a system-size scan for both hot QCD and inter-disciplinary studies, using selected high-impact ion species.
Following this, we hereby open the call for abstracts for the White Paper. The goal is to collect prospective studies that can quantify the physics potential, experimental requirements, and beam-time needs of the proposed run scenarios. These studies will form the basis for the White Paper.
When submitting an abstract, contributors are asked to select one of the following tracks.
To provide guidance and ensure that the prospective physics studies are as aligned as possible with actual accelerator capabilities, below we provide, for each of the considered ion species, realistic estimates of integrated luminosity.
This figure indicates the integrated luminosity of $^{16}$O+$^{16}$O collisions as a function of running time, both from the setup achieved in Run 3 [orange curve] and as expected in high-intensity mode [blue curve].
The following table provides estimates of integrated luminosity for one week of running time, for all nuclei considered above. [The values will become available in early September, 2026]
Here are more details about the call for abstracts and the next phases of this initiative:
- The deadline for abstract submission is October 31, 2026. We will take a first glance at the progress of the submissions in a dedicated discussion session at the EMMI Workshop on Light Ion Collisions 2026 (https://indico.gsi.de/event/25022/).
- After the deadline, we will open, on this Indico page, a call for contributions to the White Paper. These will be short publication-level contributions that will be part of the final manuscript.
- The planned deadline for these contributions will be October 31, 2028 --> We leave two years for the realization of the prospective physics studies. After that, we will gather the material and proceed to the write-up of the White Paper.
On behalf of the coordinators (Reyes Alemany Fernandez, Giuliano Giacalone) as well as of the conveners of the LPCC Heavy Ion Working Group (https://lpcc.web.cern.ch/content/lhc-hi-wg), we would like to thank you in advance for your contribution to the initiative.
We are looking forward to making progress with you toward the finalization of the White Paper.