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Neutrino Interaction Vertex Reconstruction in DUNE with Pandora Deep Learning
No full textThe Pandora Software Development Kit and algorithm libraries perform reconstruction of neutrino interactions in liquid argon time projection chamber detectors. Pandora is the primary event reconstruction software used at the Deep Underground Neutrino Experiment, which will operate four large-scale liquid argon time projection chambers at the far detector site in South Dakota, producing high-resolution images of charged particles emerging from neutrino interactions. While these high-resolution images provide excellent opportunities for physics, the complex topologies require sophisticated pattern recognition capabilities to interpret signals from the detectors as physically meaningful objects that form the inputs to physics analyses. A critical component is the identification of the neutrino interaction vertex. Subsequent reconstruction algorithms use this location to identify the individual primary particles and ensure they each result in a separate reconstructed particle. A new vertex-finding procedure described in this article integrates a U-ResNet neural network performing hit-level classification into the multi-algorithm approach used by Pandora to identify the neutrino interaction vertex. The machine learning solution is seamlessly integrated into a chain of pattern-recognition algorithms. The technique substantially outperforms the previous BDT-based solution, with a more than 20% increase in the efficiency of sub-1 cm vertex reconstruction across all neutrino flavours.The Pandora Software Development Kit and algorithm libraries perform reconstruction of neutrino interactions in liquid argon time projection chamber detectors. Pandora is the primary event reconstruction software used at the Deep Underground Neutrino Experiment, which will operate four large-scale liquid argon time projection chambers at the far detector site in South Dakota, producing high-resolution images of charged particles emerging from neutrino interactions. While these high-resolution images provide excellent opportunities for physics, the complex topologies require sophisticated pattern recognition capabilities to interpret signals from the detectors as physically meaningful objects that form the inputs to physics analyses. A critical component is the identification of the neutrino interaction vertex. Subsequent reconstruction algorithms use this location to identify the individual primary particles and ensure they each result in a separate reconstructed particle. A new vertex-finding procedure described in this article integrates a U-ResNet neural network performing hit-level classification into the multi-algorithm approach used by Pandora to identify the neutrino interaction vertex. The machine learning solution is seamlessly integrated into a chain of pattern-recognition algorithms. The technique substantially outperforms the previous BDT-based solution, with a more than 20% increase in the efficiency of sub-1 cm vertex reconstruction across all neutrino flavours
The hadronic contribution to the running of and the electroweak mixing angle
No full textWe report on our update to \cite{Ce:2022eix} on the hadronic running of electroweak couplings from -improved Wilson fermions with flavours. The inclusion of additional ensembles at very fine lattice spacings together with a number of techniques to split the different contributions for a better control of cutoff effects allows us to substantially improve the precision. We employ two different discretizations of the vector current to compute the subtracted Hadronic Vacuum Polarization (HVP) functions and for Euclidean time momenta up to . To reduce cutoff effects in the short distance region we apply a suitable subtraction to the TMR kernel function, which cancels the leading behaviour. The subtracted term is then computed in perturbative QCD using the Adler function and added back to compensate for the subtraction. Chiral-continuum extrapolations are performed with five values of the lattice spacing and several pion masses, including its physical value, and several fit ansätze are explored to estimate the systematics arising from model selection. Our results show excellent prospects for high-precision estimates of at the Z-pole.We report on our update to [1] on the hadronic running of electroweak couplings from -improved Wilson fermions with flavours. The inclusion of additional ensembles at very fine lattice spacings together with a number of techniques to split the different contributions for a better control of cutoff effects allows us to substantially improve the precision. We employ two different discretizations of the vector current to compute the subtracted Hadronic Vacuum Polarization (HVP) functions and for Euclidean time momenta up to . To reduce cutoff effects in the short distance region we apply a suitable subtraction to the TMR kernel function, which cancels the leading behaviour. The subtracted term is then computed in perturbative QCD using the Adler function and added back to compensate for the subtraction. Chiral-continuum extrapolations are performed with five values of the lattice spacing and several pion masses, including its physical value, and several fit ansätze are explored to estimate the systematics arising from model selection. Our results show excellent prospects for high-precision estimates of at the Z-pole
Transforming Concept into Reality: Overcoming Challenges in the HL-LHC IT String Test Stand Implementation
No full textThe objective of the High-Luminosity Large Hadron Collider (HL-LHC) Inner Triplet (IT) String is to faithfully represent and validate, within a surface building at CERN, the installation and collective behavior of all major systems in the new HL-LHC IT zone. These systems encompass superconducting magnets, protection, cryogenics for the superconducting magnets and the superconducting link, powering, vacuum, alignment, interconnections between magnets, and the superconducting link itself. The construction of this test facility, intended to complete its validation program before the installation of equipment in the LHC tunnel, is currently in an advanced state. From the initial concept to the final design and implementation of the IT String, numerous challenges had to be addressed in both technical and management domains. This publication aims to outline and classify these challenges, providing detailed insights into the proposed solutions for the problems encountered. Following an introduction to the project and its structure, the publication will delve into challenges related to integration, scheduling, budget and resource estimates, installation aspects, responsibilities, collaborations between teams, safety, and communication. Finally, we will conclude summarizing the key challenges addressed and solutions implemented, and we will discuss the potential overall impact and benefits of the HL-LHC IT String test stand on the broader HL-LHC project
Conceptual Structural Design and Analysis of a 20 T Hybrid Cos Dipole for Future Particle Colliders
No full textTo reach high collision energy for future high-energy particle colliders, like the Future Circular Collider (FCC) or the Muon Collider, it is required to achieve high field strength of the bending dipoles. Currently, the practical limit for Nb Sn technology is around 16 T and, in order to further increase the magnetic field, the superconducting magnet community is considering High Temperature Superconductors (HTS), in particular Bi-2212 and REBCO conductors. However, their relevant higher cost has led the community to consider a hybrid approach where HTS materials are used in the high field region of the coils with so-called “insert coils”, and Low Temperature Superconductors are involved in the lower field part ( 16 T) with so-called “outsert coils”. This paper describes the conceptual mechanical design of a 20 T hybrid cos dipole configuration. The high stress levels that the structure is facing due to the high magnetic field are discussed. Moreover, it presents the results of the optimization analysis of the shell-based support structure based on the key-and-bladder technology that provides the azimuthal pre-stress during room temperature assembly and cooldown to cryogenic temperatures. The aim of this work is to present a feasible design that satisfies the stress requirements
Highlights on top quark properties, mass and cross-section measurements with the ATLAS detector
No full textThe top-quark mass is one of the key fundamental parameters of the Standard Model that must be determined experimentally. Its value has an important effect on many precision measurements and tests of the Standard Model. The Tevatron and LHC experiments have developed an extensive program to determine the top quark mass using a variety of methods. In this contribution, the top quark mass measurements by the ATLAS experiment are reviewed. These include measurements in two broad categories, the direct measurements, where the mass is determined from a comparison with Monte Carlo templates, and determinations that compare differential cross-section measurements to first-principle calculations. In addition, new results on top-quark properties are shown. This includes the first observation of quantum entanglement in top-quark pair events and a test of lepton-flavour universality in emu final states
Status and challenges of NbSn accelerator magnets at CERN: Lessons learned from ITER to HL-LHC
No full textThe High-Luminosity Large Hadron Collider (HL-LHC) project at CERN has offered the opportunity to promote and develop various types of enabling accelerator technologies, such as MgB superconducting links for cold powering and NbSn accelerator magnets for the interaction regions where the two high-luminosity experimental areas of the machine are located.A prototype superconducting link system has been successfully tested in the second quarter of 2024 and series production is now ongoing. The NbSn magnet development has encountered some difficulties characterized by performance limitation or degradation, which have now been overcome. We report on the status and challenges of HL-LHC NbSn accelerator magnets at CERN, with a primary focus on the root-cause analyses and recovery actions implemented for the 11 T dipole magnet program and for the final-focusing quadrupole magnet program. The symptoms have similarities with those encountered over a decade ago on the NbSnCable-in-Conduit conductors for the magnets of the International Thermonuclear Experimental Reactor (ITER) and the methodology to address them was inspired from that developed to resolve the ITER crisis. Thanks to the successful efforts of ITER and HL- LHC, NbSn has been demonstrated to be a viable technology for fusion and accelerator magnet applications and is now reaching maturity
Picture of Fourth MKI Cool installation in Pt8
No full textGiven the expected higher High-Luminosity LHC beam intensities, the LHC injector kickers are undergoing an upgrade to reduce the equivalent beam coupling impedance and the resulting induced heating (MKI Cool upgrade). The first MKI Cool was installed during EYETS 22/23, followed by the second during EYETS 23/24 at Point 8. The installation of the third and fourth MKI Cool magnets at Point 8 marks a significant milestone, completing the upgrade of an entire injection point
Evolutionary algorithms for Wakefields
No full textThis project addresses the challenge of computing beam-coupling impedance, a critical problem in high-intensity particle accelerators. Simulating and analyzing these impedances for complex devices, particularly those with high-conductivity materials, is computationally intensive due to the slowly decaying nature of the wakefields they generate. To tackle this, the project continues the work of S. Joly on the application of machine learning techniques for fitting narrow-band resonators to wakefields and impedances. Specifically, evolutionary algorithms are employed to analyze the frequency content of wake potentials, enabling the fitting of multiple resonators. The ultimate goal is to reconstruct fully decayed wakes in the time domain efficiently. By leveraging this extrapolation method, the need for simulating fully decayed wakes is eliminated, resulting in significant savings in computational time and resources. This work includes the theoretical foundations of wakefields and evolutionary algorithms to detail the proposed extrapolation approach. The method is evaluated using both analytical impedance models and simulated impedances of real devices, with the results analyzed and discussed throughout
Jet energy flow fluctuations with ALICE
No full textThis dissertation advances the understanding of the strong nuclear force under extreme conditions akin to those in the early universe by analyzing data from the ALICE detector at CERN's Large Hadron Collider (LHC). It leverages high-energy collisions of fundamental particles to study Quantum Chromo-Dynamics (QCD), the theory governing the strong force, where partons (quarks, antiquarks, and gluons) interact via color charge. A key feature of QCD is parton confinement into color-neutral hadrons, the particles observed in nature. In particle collisions, partons scatter, producing particle showers through QCD radiation, a process culminating in hadronization. Since detectors measure hadrons rather than partons directly, jet-finding algorithms are employed to reconstruct parton-level interactions from collimated sprays of particles. These algorithms are critical in both proton-proton (pp) and heavy-ion collisions. Heavy-ion collisions, involving large nuclei such as lead, create conditions of extreme temperature and density, leading to the formation of a Quark-Gluon Plasma (QGP). This state of deconfined quarks and gluons behaves like a near-perfect liquid and alters the structure of jets passing through it, a phenomenon known as jet quenching. This dissertation introduces and evaluates a novel jet observable, jet energy flow, defined as the difference in transverse momentum between small and large jets, to probe these interactions. By analyzing pp and Pb-Pb (heavy-ion) collisions, this study characterizes how jet energy flow is modified by the QGP. The results demonstrate a monotonic decrease in energy flow with increasing jet radius in pp collisions, confirming prior observations that most jet energy resides in a compact core near the jet axis. In Pb-Pb collisions, jets exhibit narrower energy profiles and enhanced energy loss, indicative of the QGP's effects. The sensitivity of the jet energy flow observable to QGP-induced modifications was evaluated using the JEWEL Monte Carlo model, which simulates jet-medium interactions. Notably, the recoil-inclusive and recoil-exclusive modes of JEWEL provide distinct predictions for energy flow behavior, highlighting the observable's potential for probing medium effects. The findings suggest a strong agreement between the JEWEL recoil-exclusive mode and experimental measurements, although discrepancies remain. These discrepancies underscore the need for further refinement of theoretical models and more extensive measurements, particularly at larger jet radii, to capture medium-induced radiation redistribution. In conclusion, the jet energy flow observable represents a significant advancement in the study of jet quenching. Its ability to capture event-by-event fluctuations offers unique insights into QGP dynamics, complementing existing jet substructure measurements. These results pave the way for future investigations into the strong nuclear force and the properties of the QGP, contributing to a deeper understanding of high-energy nuclear interactions and the early universe
Total Cost of Ownership and Evaluation of Google Cloud Resources for the ATLAS Experiment at the LHC
No full textThe ATLAS Google Project was established as part of an ongoing evaluation of the use of commercial clouds by the ATLAS Collaboration, in anticipation of the potential future adoption of such resources by WLCG grid sites to fulfil or complement their computing pledges. Seamless integration of Google cloud resources into the worldwide ATLAS distributed computing infrastructure was achieved at large scale and for an extended period of time, and hence cloud resources are shown to be an effective mechanism to provide additional, flexible computing capacity to ATLAS. For the first time a Total Cost of Ownership analysis has been performed, to identify the dominant cost drivers and explore effective mechanisms for cost control. Network usage significantly impacts the costs of certain ATLAS workflows, underscoring the importance of implementing such mechanisms. Resource bursting has been successfully demonstrated, whilst exposing the true cost of this type of activity. A follow-up to the project is underway to investigate methods for improving the integration of cloud resources in data-intensive distributed computing environments and reducing costs related to network connectivity, which represents the primary expense when extensively utilising cloud resources