[Cuga] ep/eA programme at the LHC and/or FCC

[Lorelei Carlson]

Dear colleagues,

On October 23, I received a new mandate from the CERN Directorate to further the development of the scientific potential and possible technical realization of an ep/eA collider and the associated detectors at CERN. Following the publication of the updated CDR [1], CERN continues to support studies for the LHeC and the FCC-eh as potential options for the future and to provide input to the next Update of the European Strategy for Particle Physics, with emphasis on FCC.

The ep/eA programme finds itself at the crossroad between nuclear and particle physics, with synergies as well with astroparticle physics. This programme has the potential to empower the (HL-)LHC physics programme in a unique way and allows for a deeper exploration of the EW/Higgs/top/strong physics sectors of the Standard Model beyond what can be achieved with the proton-proton collisions at the (HL-)LHC. In many cases, adding the LHeC data to the HL-LHC data results in significant improvements in precision Higgs physics similar to those expected when moving from LHC to HL-LHC.

At the recent workshop at IJCLab [2], I was impressed and inspired by the sense of innovation in the ep/eA community, which is already bearing fruit with the upcoming EIC project at Brookhaven with the first-ever polarized electron-ion collisions expected in the 2030’ies [3]. When the ep/eA community moves from HERA and EIC to higher energies at LHeC and FCC-eh, the threshold is reached to open the window for EW/Higgs/top physics in deep inelastic scattering (DIS) processes for the first time. In addition, these programmes are unique in exploring the low Bjorken-x frontier by orders of magnitude beyond current DIS knowledge. At this stage, it is unclear what physics we will unlock if we break the proton and hadronic matter in even smaller pieces.

In recent years, we have learned that the ultimate precision for Higgs physics lies in the complementarity of ee, pp and ep collisions, as embedded in the FCC programme, for example. Exploiting this complementarity is key to achieving our overall goals of exploring new territories via the Higgs sector and exploring the dark sector, amongst others, as well as preparing to zoom in to potentially emerging features in our data, such as phenomena that violate lepton flavour conservation.

The advantage of a joint ep/pp/eA/AA/pA interaction experiment should be underlined. For example, reaching a precision of 2 MeV on the W boson mass (the topic of my PhD thesis at LEP) could be within reach. With the LHC and/or FCC proton and ion beams, at this stage independent of implementation strategies, the scientific added value of this opportunity needs to be further explored and documented.

Reducing the energy footprint is our responsibility when using powerful accelerators to explore the fundaments of nature. PERLE [4], an expanding international collaboration revolving around a multi-turn demonstrator facility at IJCLab in Orsay for Energy Recovery Linacs (ERL) at high beam currents [5], is ready to become the leading center in Europe in our field for developing and testing sustainable accelerating systems. Power consumption is a major concern in society and has been identified by the UN as one of the global sustainable development goals. Contributing to these developments is not only a must, but also a privilege with our expertise. A very strong team of experts is being formed in the PERLE collaboration to make this happen in this decade, and they welcome collaborators.

The ERL principle, experience with PERLE, optimization of parameters and forthcoming technical developments such as higher-order mode damping at higher temperatures may further reduce the power consumption of the LHeC (and FCC-eh). From the original limit of around 100 MW to values possibly as low as 50 MW could be within reach, as demonstrated in the workshop. These values are to be compared to the GW power consumption if there was no energy recovery and therefore provide a power-economic avenue to extend the Higgs precision frontier beyond the HL-LHC.

While we are driven by our curiosity about the fundaments of nature, progress in our field crucially depends on society’s appreciation for our innovations in technology to make the invisible visible. With ERL technologies and the developments of other sustainable accelerating systems, the ep/eA programme delivers on this front. With PERLE, it has the ambition to deliver a demonstration of ERL technology at high beam current towards a potential ERL-based Higgs factory; a Higgs factory being the highest priority collider beyond the HL-LHC programme in our European Strategy for Particle Physics (ESPP).

For sure, we all have aspirations, and we should have them, but we are not here to rediscuss the ESPP. The strategy will be verified and discussed in due time. We are engaged to further develop an ep/eA programme with the ability to significantly enrich this overall strategy with a view to finding cracks in the Standard Model and/or finding new phenomena leading our path to a profound understanding of nature at both the smallest and the largest scales.

On this occasion, it is my greatest pleasure to thank Max Klein for his more than decade-long leadership towards the CDR of the LHeC/FCC-eh programme, the foundation of PERLE and much more. I have no doubt that our particle physics community is proud of having such a splendid scientific and technological programme available for our future.

In addition, I am very grateful to the organizers of the workshop, in particular Nestor Armesto, Walid Kaabi and Achille Stocchi.

I look forward to working with all of you to further our developments of an energy frontier ep/eA programme at CERN.


With kind regards,

Jorgen D’Hondt
incoming Spokesperson of the LHeC/FCC-eh study at CERN


Do not hesitate to distribute this message in your research network. Anyone with a CERN account or a light account can register to this “lhec-all" email list (as well as sign out). The LHeC/FCC-eh mailing list will be used to inform the wide particle physics community about general progress, organization, and opportunities in the domain of ep/eA studies at CERN. It will soon change name to reflect both LHeC and FCC-eh. In due time you will be informed about the possibilities to subscribe to additional mailing lists that will  be used, at higher frequencies, for concrete research actions in the realm of LHeC/FCC-eh and ERL. Subscribe/unsubscribe to the LHeC/FCC-eh list via: https://urldefense.proofpoint.com/v2/url?u=https-3A__e-2Dgroups.cern.ch_&d=DwIGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=h0ddwZahF7UudlBHJ5C8U0UdF0FQd7mWAANW-z6-AOM&m=Rhb00r3oQGVcTNxvRMtyE2I94RCdDyn_5byY3z_jFMJkAOgAQBtl-p9CqpnGKidl&s=vsmjHBFqHXAaDYQEqWJyJJP4ceAY_hQdsgqIx3oSNP0&e=  (use the search option, and search for “lhec-all” in all e-groups)

[1] LHeC updated CDR: https://urldefense.proofpoint.com/v2/url?u=https-3A__inspirehep.net_literature_1809802&d=DwIGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=h0ddwZahF7UudlBHJ5C8U0UdF0FQd7mWAANW-z6-AOM&m=Rhb00r3oQGVcTNxvRMtyE2I94RCdDyn_5byY3z_jFMJkAOgAQBtl-p9CqpnGKidl&s=5OQBH2JTE5OLKGi__GFMou5d8tnYV9RKIyStZjjGp3w&e=
[2] Oct 2022 workshop at IJCLab: https://urldefense.proofpoint.com/v2/url?u=https-3A__indico.ijclab.in2p3.fr_event_8623_&d=DwIGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=h0ddwZahF7UudlBHJ5C8U0UdF0FQd7mWAANW-z6-AOM&m=Rhb00r3oQGVcTNxvRMtyE2I94RCdDyn_5byY3z_jFMJkAOgAQBtl-p9CqpnGKidl&s=RQSfqYkl6m0kLxcZKYUnhh7ClCZiIu8Iakckmn4Taxk&e=
[3] EIC programme: https://urldefense.proofpoint.com/v2/url?u=https-3A__www.bnl.gov_eic_&d=DwIGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=h0ddwZahF7UudlBHJ5C8U0UdF0FQd7mWAANW-z6-AOM&m=Rhb00r3oQGVcTNxvRMtyE2I94RCdDyn_5byY3z_jFMJkAOgAQBtl-p9CqpnGKidl&s=TroPSpKRFKgkAZcw7dmLaHCSlP87z3rXY5J1783ThMc&e=
[4] PERLE: https://urldefense.proofpoint.com/v2/url?u=https-3A__inspirehep.net_literature_1601165&d=DwIGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=h0ddwZahF7UudlBHJ5C8U0UdF0FQd7mWAANW-z6-AOM&m=Rhb00r3oQGVcTNxvRMtyE2I94RCdDyn_5byY3z_jFMJkAOgAQBtl-p9CqpnGKidl&s=pRLDS_zR58ga6x932ehZiMG7ph6hjW7UqnG-4UHowaU&e=
[5] Accelerator R&D Roadmap: https://urldefense.proofpoint.com/v2/url?u=https-3A__inspirehep.net_literature_2014192&d=DwIGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=h0ddwZahF7UudlBHJ5C8U0UdF0FQd7mWAANW-z6-AOM&m=Rhb00r3oQGVcTNxvRMtyE2I94RCdDyn_5byY3z_jFMJkAOgAQBtl-p9CqpnGKidl&s=2PEXx5PjMHq8Tx_kKKvW5eQBow5VqOmz0AcTsCDTbBc&e=  ; and the extensive overview paper on ERL developments: https://urldefense.proofpoint.com/v2/url?u=https-3A__inspirehep.net_literature_2106268&d=DwIGaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=h0ddwZahF7UudlBHJ5C8U0UdF0FQd7mWAANW-z6-AOM&m=Rhb00r3oQGVcTNxvRMtyE2I94RCdDyn_5byY3z_jFMJkAOgAQBtl-p9CqpnGKidl&s=SPm6MG3_5ifYgBxlGyNi3lZfRa52Y5EFTnsAiH_clj8&e=




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