Run 3 of the Large Hadron Collider (LHC) collides protons at an unprecedented energy of 13.6 TeV every 25 ns. The high luminosity conditions result in a high pile-up background which is challenging for the ATLAS trigger to contend with. The L1 trigger system operates at fixed latency, receiving inputs at a rate of 40 MHz and an output rate limited to 100 kHz. To maintain Run 2 acceptance rate and improve sensitivity to interesting physics processes, the trigger systems underwent major Phase-I upgrades. The L1 calorimeter trigger upgrades included the addition of three FPGA-based feature extractors that utilise the increased granularity of the Run3 liquid argon calorimeter to efficiently trigger electromagnetic and hadronic objects. The Global Feature Extractor (gFEX) receives the complete calorimeter data at a granularity (0.2 η x 0.2 ɸ towers) and implements novel algorithms to study physics objects - large radius jets, missing transverse energy (MET) and total transverse energy. Global trigger objects (TOBs) are computed by gFEX with an algorithm called Jets-Without-Jets (JwoJ) while the large R jets are computed by a seedless cone clustering algorithm. This is effective in triggering physics processes with highly energetic boosted objects in the hadronic decays of high momentum Higgs, bosons, top quarks, and exotic particles. In addition, gFEX implements event-by-event pileup suppression for these jets using baseline subtraction techniques developed for offline analyses. The pileup suppression coupled with novel algorithms allows for efficient triggering of large R jets and global trigger objects with good background rejection.

Relativistic outflows enriched with electron-positron pair plasma can be found in various highly energetic astrophysical environments, e.g. around active galactic nuclei, black holes or in the jets of gamma ray bursts. Plasma instabilities associated with such pair-dominated outflows play an important role in explaining their energy dissipation and the radiative signatures we observe from these objects on Earth. In our last experiment, HRMT62 [1], inaugurating a newly developed experimental platform for such studies at the HiRadMat facility of CERN [2,3], high intensity, high density, ultra-relativistic, quasi-neutral electron- positron pair beam production was achieved, opening up the possibility to study the microphysics of such pair plasmas via experimental means. In the follow-up experiment, HRMT64, modifications including a secondary target and a magnetic collimating setup will be introduced in order to study the emergence of magnetic fields associated with the growth of filamentation instabilities as collimated relativistic pair-plasma beams propagate through ambient plasma; an analogue for the propagation of astrophysical pair jets through intergalactic medium.

Particle correlations are powerful tools for studying quantum chromodynamics in hadron collisions. In heavy-ion collisions, azimuthal angular correlations probe collective phenomena in hot, dense, nuclear media, such as QGP. Angular correlations in small collision systems could point to QGP production or potential initial-state correlations. The LHCb experiment has the unique ability to study particle correlations in high-energy hadron collisions at forward rapidity, complementing the results from other experiments. In this contribution, recent results on collective flow from the LHCb experiment will be discussed

Understanding the nonperturbative process of hadronization is a persistent goal in experimental studies of QCD. Since heavy quark production is suppressed at the hadronization scale, heavy-flavor hadrons offer a high-precision probe of the connection between theoretical calculations and experimental final states. Jets containing different flavors of these heavy hadrons, reconstructed across a broad range of jet transverse momentum, explore the dependence of local hadronic formation at different partonic mass scales with distinct final states. Furthermore, quarkonia production in jets explores the intersection between the parton shower, where gluons split into heavy quark-antiquark pairs, and the production of closed heavy-flavor hadrons. Jet substructure can also be used to probe the formation of exotic hadrons, whose structure is still not well understood. This talk presents recent studies of hadronization using heavy-flavor jets detected with the LHCb detector. These studies include inclusive hadron production in heavy-flavor jets, as well as quarkonia and tetraquark production in jets. Results are compared to various models of hadronization, providing strong new constraints on theoretical predictions of confinement in jets.

In this contribution, recent results for helium identification and production at LHCb will be discussed. From √sNN = 13 TeV pp collisions, a nearly background-free sample of more than 105 helium candidates is identified by their ionisation losses in the silicon detectors, combined with information from the calorimeter, the muon chambers and the RICH detector. Combined with the excellent LHCb vertexing capabilities, (anti)helium production from (anti)hypertriton or (anti)Lambda-b decays is studied. In both cases, a rich programme of QCD and astrophysics interest, exemplifying LHCb flexibility in exploring new research fields, is foreseen.

Open charm production is a sensitive probe of both hot and cold nuclear matter effects. Charm meson production provides strong constraints on nuclear parton distributions, while charm baryon and strange charm hadron production can be used to probe strangeness- and baryon-enhancing hot QCD effects, respectively. The LHCb detector is designed to study heavy flavor hadrons at the LHC, providing unique opportunities to study open charm production in heavy ion collisions. In this contribution, recent LHCb results on open charm production will be discussed, as well as their comparisons with recent theoretical models.

Strange hadron production provides information about the hadronization process in high-energy hadron collisions. Strangeness enhancement has been interpreted as a signature of quark-gluon plasma formation in heavy-ion collisions, and recent observations of strangeness enhancement in small collisions systems have challenged conventional hadronization models. With its forward geometry and excellent particle identification capabilities, the LHCb detector is well-suited to study strangeness production in a unique kinematic region. Recent studies of strangeness production with the LHCb detector will be presented, including measurements of strangeness enhancement in the charm- and beauty-hadron systems

In preparation to the LHC Run3, the LHCb gaseous fixed-target, SMOG, was upgraded to offer higher instantaneous luminosity by up to two orders of magnitude with respect to Run2, new gases, including non-noble ones such as hydrogen, and an increased experimental accuracy. Since 2022, LHCb is working with two independent collision points and as a collider and a fixed-target experiment simultaneously, a unique opportunity in the scientific panorama. In this contribution, the performance of the system from the 2024 acquired data, the first obtained results and the physics prospects for the incoming years will be presented.

The LHCb detector’s forward geometry provides unprecedented access to the very low regions of Bjorken x inside the nucleon. LHCb is able to study charged and neutral light hadron production, as well as relatively rare probes such as heavy quark. These data provide unique constraints on nuclear parton distributions. This contribution will discuss recent LHCb measurements sensitive to the low-x structure of nucleons, and discuss the impact of recent LHCb measurements on global analyses of nuclear parton distributions

Series of exhibition banners on the history of the ATLAS Experiment. Covers milestones from 1992 to today. Translated into Italian by the ATLAS Italia Outreach team.