Light hadrons constitute the bulk of particle production in heavy-ion collisions. Its properties, such as the production cross-sections of different hadron species or their average transverse momentum, are sensitive to both collective phenomena and the initial state of heavy-ion collisions. Bulk physics measurements in small collision systems can reveal the interplay between initial- and final-state effects in heavy-ion collisions, and can provide new insights into the origins of collective phenomena. The LHCb detector, with its high-resolution tracking system and its hadron ID capabilities, is perfectly suited for these studies in the forward region. In this contribution, new results on bulk measurements in small systems will be presented.

The $\phi$ meson is a unique probe of strange quark dynamics in high-energy nuclear collisions. The $\phi$ meson's mass lies at the threshold between perturbative and nonperturbative QCD. Consequently, $\phi$ production provides sensitivity to both regimes. In heavy-ion collisions, $\phi$-meson production is senstive to strange-quark coalescence in quark-gluon plasma. The $\phi$ meson's net-zero strangeness means that $\phi$ production measurements can help disentangle the physical mechanisms behind strangeness enhancement in high-energy hadron and nucleaer collisions. The LHCb detector's hadron identification capabilities allow for precise studies of $\phi$ meson production in nuclear collisions. In addition, the SMOG system allows LHCb to study production in fixed-target collisions. New measurements of $\phi$ production in both collider and fixed-target configurations will be presented.

Ultra-peripheral collisions provide a unique environment to study pomeron- and photon-induced reactions with heavy nuclei. These interactions can produce a wide range of final state particles, from light vector mesons to heavy quarkonia, and probe potentially exotic phenomena. With a fast and flexible DAQ, full particle ID, and the ability to reconstruct very low pt particles, LHCb is uniquely well suited to study final states with leptons, hadrons or photons. Also, using the HeRSCheL detector, the far forward event activity can be detected and used to tag events with nuclear break-up. In this contribution, we will present recent LHCb results from ultra-peripheral heavy ion collisions and discuss how these impact our understanding new exotic phenomena, the partonic structure of nuclei and hadronization in small systems.

A detailed study exploiting novel trigger and reconstruction techniques developed to search for Beyond Standard Model (BSM) Long-Lived Particles (LLPs) with very displaced vertices is presented. Building on feasibility studies that have successfully reconstructed Standard Model decays occurring up to 8m forward of the interaction point in LHCb’s magnet region, the search for LLP particles into charged final states exploits LHCb’s unique forward geometry and segmented tracking system—comprising the Vertex Locator, Upstream Tracker, and SciFi stations—to extend sensitivity into previously inaccessible regions. The proceeding will cover innovative trigger strategies implemented in LHCb’s software trigger for inclusively selecting very displaced dimuon pairs, alongside advanced offline selection methods using multivariate analysis methods to robustly suppress background while maintaining high signal efficiency. Preliminary sensitivity estimates for Dark Higgs 𝐻′ → 𝜇+𝜇− search indicate that these approaches can achieve competitive performance compared to dedicated LLP experiments. Future prospects will also be discussed. This work aims to provide a comprehensive framework for enhancing LLP discovery potential at LHCb and offers insights that could be beneficial for the broader BSM LLP search community.

containing an anticharm quark in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=13.6 \ \text{TeV}$ using data recorded by the LHCb experiment. The asymmetries of $D^0$, $D^+$ and $D^+_s$ mesons are measured for two-dimensional intervals in transverse momentum and pseudorapidity, within the range $2.5 < p_T < 25.0 \ \text{GeV}/c$ and $2.0 < \eta < 4.5$. No significant production asymmetries are observed. Comparisons to the Pythia 8 and Herwig 7 event generators are also presented, and their agreement with the data is evaluated. These measurements constitute the first measurements of production asymmetries at this centre-of-mass energy of colliding beams, and the first measurements with the LHCb Run 3 detector.

Prospects to search for dilepton resonances below 100 MeV/$c^2$ with the upgraded LHCb detector are presented. These resonances could be mediators between the Standard Model and a hypothesised dark sector, and are investigated for the first time at a hadron collider in the energy region below the dimuon threshold. The search is based on radiative charmed-meson decays, by combining a displaced charmed meson to an electron-positron pair. Increased instantaneous luminosity and triggering efficiency on charmed hadrons since Run 3 are crucial to obtain results competitive with B factories. Ongoing efforts, based on 2024 data, aim to use this unique dataset to test dark-photons, and in particular protophobic models that could explain the X17 anomaly observed by the ATOMKI collaboration in collisions between protons and nuclei.

A measurement of CP asymmetry in D0→ K0 SK0 S decays is reported, based on a data sample of proton-proton collisions collected with the LHCb Upgrade I detector in 2024 at a centre-of-mass energy of 13.6 TeV, corresponding to an integrated luminosity of 6.2 fb−1 . The D0→ K0 S π +π − decay is used as calibration channel to cancel residual detection and production asymmetries. The time-integrated CP asymmetry for the D0→ K0 SK0 S mode is measured to be A CP (D0→ K0 SK0 S ) = (1.86 ± 1.04 ± 0.41)%, where the first uncertainty is statistical, and the second is systematic. This is the most precise determination of this quantity to date.

Heavy Neutral Leptons (HNLs) are hypothetical long-lived particles that extend the Standard Model (SM) and provide a natural explanation for the non-zero neutrino masses. In addition, they could play a key role in addressing some of the most profound open questions in particle physics and cosmology, including the origin of the matter–antimatter asymmetry via baryogenesis. In this poster, we present the status and state-of-the-art of HNL searches at the LHCb experiment. We report the latest and most stringent LHCb limits on muon-coupled HNLs in the 1.6–5 GeV mass range, obtained from a Run 2 (2016–2018) analysis targeting displaced vertices corresponding to HNL flight distances of 0.02–0.5 m. Looking ahead, for Run 3 we introduce a novel reconstruction technique that exploits track segments downstream of the LHCb magnet, thereby extending the accessible displacement window to 0.5–8.0 m. This approach enhances sensitivity dramatically, providing a 40-fold increase in the number of accessible HNL events and extending the lifetime reach by a factor of 16 compared to the Run 2 analysis. A dedicated sensitivity study shows how these improvements translate into a significantly extended reach in the HNL mass–coupling parameter space, positioning LHCb to set world-leading constraints on HNLs.

I hope I understood your question correctly, but tell me if you would like me to submit the abstract somewhere else. In any case, here is my abstract: During the Long Shutdown 2 (LS2) period, the LHCb experiment underwent an upgrade to its tracking system. Part of this is a new pixel detector close to the interaction point called the VErtex LOcator’s (VELO). An accurate simulation of its behaviour is crucial to exploit the detector in physics analysis. In this poster, a method for measuring cluster efficiencies in data and how it is used to optimize the LHCb VELO simulation, will be shown. The presented method has shown to be sensitive to minor variations due to local ASIC inefficiencies or evolution of the sensor behaviour with radiation and high voltage, and is applied in blocks of similar operation condition. These improved simulation conditions are applied centrally and will be used by all analyses.

The innovative fixed-target programme initiated by the LHCb exper- iment during the LHC Run 2 has been enhanced for Run 3 with the introduction of a dedicated gas injection system, SMOG2. This upgrade features a gas cell to boost fixed-target luminosity and that allows the injection of non-noble gases. SMOG2 enables the collection of large datasets from pA and PbA fixed-target collisions, including high-statistics samples of charm hadrons. Recent results on charm hadronization in fixed-target collisions with SMOG are reported and the latest open charm samples recorded with SMOG2 during Run 3 are also presented.