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Hessian-free force-gradient integrators and their application to lattice QCD simulations
No full textWe present initial results on Hessian-free force-gradient integrators for lattice field theories. Integrators of this framework promise to provide substantial performance enhancements, particularlyfor larger lattice volumes where higher-order integrators demonstrate greater efficiency. Numericalresults demonstrate the superior efficiency of the proposed integrators compared to commonlyemployed non-gradient schemes, particularly due to enhanced stability properties. It is anticipatedthat the advantages of the Hessian-free framework will become even more pronounced in nestedintegration approaches and for smaller fermion masses, where the numerical stability propertiesof the integrators become increasingly important.We present initial results on Hessian-free force-gradient integrators for lattice field theories. Integrators of this framework promise to provide substantial performance enhancements, particularly for larger lattice volumes where higher-order integrators demonstrate greater efficiency. Numerical results demonstrate the superior efficiency of the proposed integrators compared to commonly employed non-gradient schemes, particularly due to enhanced stability properties. It is anticipated that the advantages of the Hessian-free framework will become even more pronounced in nested integration approaches and for smaller fermion masses, where the numerical stability properties of the integrators become increasingly important
Performance of a new Beam halo tagger for the ECAL endcap
No full textBeam halo can be a huge background for analyses that search for the presence of a single photon accompanied by missing transverse energy in the detector. It can be rejected in the ECAL barrel (EB) by requiring the timing of the photon within a certain window. In addition, the requirement MIP GeV is applied to photons detected in the EB, where MIP is the maximum of the total calorimeter energy summed along all possible paths of beam halo particles passing through the cluster. The same strategy used in the EB to remove beam halo is ineffective in
the ECAL endcap (EE) due to its geometry. In this region, beam halo particles hit the detector nearly parallel to the beamline, making it challenging to distinguish them from genuine photons produced at the interaction point.
Due to the presence of various magnets (dipoles, quadrupoles, etc), the beam halo peaks around and of the photons
Numerical Optimization of 6D Cooling Solenoids for a Muon Collider
No full textIn the current most evolved design concept of a machine for accelerating and colliding muons, there exists two long
(∼1 km) channels for cooling newly created muons and antimuons. Termed the ‘6D cooling channels’, the beam is cooled in
momentum and position space using a series of alternating polarity
solenoids which create an oscillating field in the beam direction,
absorbers and radio-frequency cavities. In total there are around
3000 solenoids per channel, contributing to a significant portion
of the cost and engineering demands of the entire machine. The
integration of the requirements of the field profile with feasible
solenoid configurations is a difficult and unique problem, without
analytic descriptions to readily relate these. We have addressed
this problem in two ways: in the first we constrain the optimization
studies of the optics by setting limits on solenoid parameters; in
the second we have developed a numerical optimization routine to
find the best configuration given a desired field profile, in terms
of cost and engineering complexity. The following paper reviews
semi-analytic descriptions of solenoids, select operating limits considering HTS, followed by the numerical optimization approach
and subsequent results. This procedure is applicable to any solenoid
or set of solenoids and can be an extremely useful optimization tool,
running much quicker than current commercial softwares
Online track reconstruction with graph neural networks on FPGAs for the ATLAS experiment
No full textFor the HL-LHC upgrade of the ATLAS TDAQ system, a heterogeneous computing farm deploying GPUs and/or FPGAs is considered to be used for the Event Filter system, together with the use of modern machine learning algorithms such as Graph Neural Networks (GNNs) to solve computationally complex tasks within that system. In this study, the development of a GNN based track finding pipeline on FPGAs for the ATLAS Inner Tracker is presented as part of the Event Filter system. Each step in the GNN-based tracking pipeline is explored: graph construction, edge classification using an interaction network, and segmentation of the graph into track candidates. Optimizations of the GNN approach are investigated to minimize FPGA resource utilization and maximize throughput while maintaining high track reconstruction efficiency and low fake rates required for the ATLAS Event Filter tracking system. These optimizations include model hyperparameter tuning, model pruning, quantization-aware training, and sequential processing of sub-graphs across the detector
Proof of principle for a light dark matter search with low-energy positron beams at NA64
No full textThermal light dark matter (LDM) with particle masses in the 1 MeV - 1 GeV range could successfully explain the observed dark matter abundance as a relic from the primordial Universe. In this picture, a new feeble interaction acts as a “portal” between the Standard Model and LDM particles, allowing for the exploration of this paradigm at accelerator experiments. In the last years, the “missing energy” experiment NA64e at CERN SPS (Super Proton Synchrotron) has set world-leading constraints in the vector-mediated LDM parameter space, by exploiting a 100 GeV electron beam impinging on an electromagnetic calorimeter, acting as an active target. In this paper, we report a detailed description of the analysis of a preliminary measurement with a 70 GeV positron beam at NA64e, performed during summer 2023 with an accumulated statistic of 1.6 × 1010 positrons on target. This data set was analyzed with the primary aim of evaluating the performance of the NA64e detector with a lower energy positron beam, towards the realization of the post-LS3 program. The analysis results, other than additionally probing unexplored regions in the LDM parameter space, provide valuable information towards the future NA64e positron campaign
Performance of missing-energy triggers in 2022, 2023 and 2024
No full textThis note presents the performance of triggers based on missing-transverse energy using pp-collisions data collected by the CMS experiment in 2022, 2023 and 2024