EMMI Workshop: Light-ion collisions 2026

The sPHENIX detector at RHIC is designed for precision measurements of high-pT jets, providing strong constraints on the properties of the quark–gluon plasma. Having completed its data taking, sPHENIX has recorded full datasets of Au+Au and O+O collisions, along with the reference dataset of p+p collisions, at a center-of-mass energy of 200 GeV. This talk presents measurements of the nuclear...

The recent light-ion runs at the LHC allow us to study how the formation and properties of the QGP depend on the size of the system produced. We present results from the newly developed NuclearConfectionery hybrid model [1], which couples (3+1)D relativistic viscous hydrodynamics (CCAKE) with in-medium jet energy loss via the MELT (Module Energy Loss Treatment) module in a single...

Light-ion collisions provide a unique opportunity to investigate the transition between small and large collision systems and to explore the onset of jet quenching. Following the dedicated O+O and Ne+Ne runs at the LHC in 2025, recent measurements by ALICE and CMS have established evidence for parton energy loss in O+O collisions, motivating detailed theoretical studies. In this contribution,...

The oxygen-oxygen and neon-neon collisions provided by the LHC in the summer of 2025 have proved to be enormously scientifically fruitful. Clear signatures of energy loss have been observed in dijets. Hadron measurements also show signs of energy loss. It is of clear interest in Run 4 to further explore the transition between proton-lead collisions, where no energy loss signatures have been...

We present a new global analysis of nuclear parton distribution functions (nPDFs) within the nCTEQ framework.
The analysis includes neutral-current and charged-current deep-inelastic scattering data, fixed-target Drell–Yan measurements, and a substantial set of proton–lead collision data from the LHC.
In particular, W/Z-boson and heavy-flavor production measurements provide important...

The recent light-ion collision programme at RHIC and the LHC provides a unique opportunity to investigate the onset of quark-gluon plasma formation and parton energy loss in small systems. A quantitative interpretation of emerging jet-quenching measurements requires precise control over cold nuclear matter (CNM) effects, which modify hard-process cross sections independently of any hot-medium...

The first oxygen–oxygen and proton–oxygen collisions delivered by the LHC in 2025 provide a unique opportunity to study the onset of parton energy loss in collision systems significantly smaller than those traditionally used for heavy-ion physics. While recent measurements have revealed several signatures of collective behavior in oxygen collisions, establishing the presence of parton energy...

We present perturbative QCD predictions for high-momentum particle suppression in very light ion collisions — $^{10}$B $+$ $^{10}$B, $^{6}$Li $+$ $^{6}$Li, $^{4}$He $+$ $^{4}$He, and $^{3}$He $+$ $^{3}$He — comparing calculations with and without medium-induced parton energy loss. Our energy loss model predicts non-trivial suppression across the full range of system sizes at minimum bias, from...

Light-ion collisions at the LHC provide a unique opportunity to study parton energy loss in compact systems with controlled initial geometry and a direct $pp$ baseline at the same energy. In 2025, the ATLAS detector recorded integrated luminosities of $8~\mathrm{nb}^{-1}$ of O+O and $1~\mathrm{nb}^{-1}$ of Ne+Ne collisions, together with approximately $400~\mathrm{pb}^{-1}$ of $pp$ collisions,...

The apparent tension between the absence of jet quenching in small systems and the observation of azimuthal anisotropy in the distribution of high-$p_\perp$ particles pushes for the development of new observables capable of probing different aspects of the medium formed in such collisions. With that purpose we study the formation time of jets ($\tau_f$) as a probe for early medium effects in...

Jet modification in heavy-ion collisions is typically attributed to parton energy loss in the Quark-Gluon Plasma (QGP). Yet, the preceding pre-equilibrium Glasma phase features remarkably large gluon densities and transport coefficients, raising the question of how much jet modification occurs prior to QGP formation. Because early-time jets are highly virtual, their evolution is dominated by a...

Based on arXiv:2603.23596, we show that oxygen-oxygen (OO) collisions provide a unique arena for detecting rare, high momentum-transfer $2 \rightarrow 2$ Molière scatterings between energetic jet partons and quark- and gluon-like quasiparticles in quark-gluon plasma (QGP). In larger collision systems such as PbPb, jet substructure measurements are often dominated by a jet selection bias: jets...