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Effects of Radiative Corrections on Starobinsky Inflation
No full textWe analyze radiative corrections to the predictions of Starobinsky-like models of inflation arising from self-interactions of the inflaton, and from its Yukawa couplings, y, to matter fermions, and dimensionful trilinear couplings, κ, to scalar fields, which could be responsible for reheating the Universe after inflation. The inflaton self-interactions are found to be of higher order in the Hubble expansion rate during inflation, and hence unimportant for CMB observations. In contrast, Einstein-frame matter couplings to an inflaton generating Starobinsky-like inflation can have significant effects on the spectral index of scalar CMB perturbations, ns, and on the tensor-to-scalar ratio, r. Using a renormalization-group improved analysis of the effective inflationary potential, we find that the Planck measurement of ns constrains the inflaton coupling to light fermions in the Einstein frame; y<4.5×10-4, corresponding to an upper limit on the reheating temperature TRH<2×1011 GeV, whereas the ACT DR6 measurement of ns corresponds to 3.8×10-4<y<5.6×10-4 and 1.7×1011 GeV<TRH<2.8×1011 GeV, while the upper limits on r provide weaker constraints. Planck data also imply a constraint on a trilinear inflaton coupling to light scalars in the Einstein frame: κ≤4×1012 GeV, corresponding to TRH≤4.2×1013 GeV. We further present constraints on inflaton couplings to massive fermions and scalars, and analyze constraints on couplings in the Jordan frame.We analyze radiative corrections to the Starobinsky model of inflation arising from self-interactions of the inflaton, and from its Yukawa couplings, , to matter fermions, and dimensionful trilinear couplings, , to scalar fields, which could be responsible for reheating the Universe after inflation. The inflaton self-interactions are found to be of higher order in the Hubble expansion rate during inflation, and hence unimportant for CMB observations. In contrast, matter couplings to the Starobinsky inflaton can have significant effects on the spectral index of scalar CMB perturbations, , and on the tensor-to-scalar ratio, . Using a renormalization-group improved analysis of the effective inflationary potential, we find that the Planck measurement of constrains the inflaton coupling to light fermions in the Einstein frame: , corresponding to an upper limit on the reheating temperature , whereas the ACT DR6 measurement of corresponds to and , while the upper limits on provide weaker constraints. Planck data also imply a constraint on a trilinear inflaton coupling to light scalars in the Einstein frame: , corresponding to . We further present constraints on inflaton couplings to massive fermions and scalars, and analyze constraints on couplings in the Jordan frame
Accelerating CMS Matrix-Element Event Generation for Drell-Yan and Top Pair Production with Madgraph4GPU
No full textIn this note, we present the first analysis of the computational speedup achieved using the GPU version of Madgraph, known as Madgraph4GPU (MG4GPU), in the CMS workflow. Madgraph is one of the most widely used event generators in CMS. This work represents the initial step toward benchmarking the improvements offered by both the GPU and vectorized CPU implementations. We demonstrate timing improvements across a broad range of physics processes relevant to CMS. Speedups are quantified for both gridpack production and event generation. A gridpack is a pre-defined package that encapsulates all the necessary components for effectively executing Monte Carlo event simulations, eliminating redundant computations of common elements for each event. Preliminary results indicate a speedup of approximately a factor of three with vectorized CPUs and an order-of-magnitude improvement with GPUs in gridpack production for the Drell-Yan and top quark pair production processes. For event generation, we observe a speedup of 1.5 times with vectorized CPUs and 7 times with GPUs when generating 105 events. These workflows were tested using a variety of computational resources, including CUDA-enabled NVIDIA GPUs and modern vectorized CPUs from Intel and AMD, accessible via CERN resources and HPCs
Status and testing of the MDT Trigger Processor for the ATLAS Level-0 Muon Trigger at HL-LHC
No full textThe Monitored Drift Tube Trigger Processor (MDT-TP) will improve the rate capabilities of the first-level muon (L0 Muon) trigger of the ATLAS Experiment during the operation of the HL-LHC. The information of the trigger candidate, obtained by other muon trigger subsystems, will be combined with the precision of the MDT chambers in order to improve the resolution on the muon momentum measurement, while limiting the trigger rate to an acceptable level in the high pile-up environment of HL-LHC. The MDT-TP trigger logic is implemented on a AMD VU13P FPGA, where MDT hits are extracted around the region-of-interest identified by the trigger candidate and are used to perform muon reconstruction and transverse momentum estimate. For accepted events, MDT hits are transmitted by the MDT-TP to the ATLAS data acquisition system via FELIX. Monitoring, configuration and interfaces with other ATLAS subsystems are implemented via services running on a ZYNQ SoC. Several tests of the MDT-TP are being conducted, including the configuration and monitoring of the MDT-TP and the on-detector electronics, communication with other L0 Muon trigger boards and readout via FELIX
The Phase-1 Upgrade of the ATLAS Level-1 Calorimeter Trigger
No full textDuring the Long Shutdown 2 of the LHC the ATLAS detector received its Phase-1 Upgrade in order to better handle the increased luminosity during LHC Run 3 and beyond. As a significnat part of this upgrade comprises new custom hardware for the first-level calorimeter-trigger path using state-of-the-art FPGAs. An overview of the different subsystems, their capabilities and roles in the overall ATLAS trigger and data aquisition architecture, and their relevance for the ATLAS physics program are presented. Finally, exemplary preliminary performance estimates are discussed
ATLAS Tile Calorimeter Phase-II Upgrade: Electronics Certification with the Portable Readout Module "PROMETEO"
No full textThe High Luminosity Large Hadron Collider has motivated a complete upgrade of the ATLAS Tile Calorimeter system. The Phase-II upgrade will include a complete replacement of the on- and off-detector electronics, as well as the most affected 10% of photomultiplier tubes (PMTs). This large-scale replacement presents a considerable challenge in terms of testing and certification of the new electronics. To meet the challenge, the Portable ReadOut ModulE for Tile Electronics (PROMETEO) system has been developed as a portable tool for testing and certifying both the on- and off-detector electronics. It operates in conjunction with the PMT-Block test stand, which is specifically designed to certify the fully assembled PMT-Blocks. While PROMETEO was originally designed primarily for electronics certification, research and development efforts have revealed a clear need for fast and precise optical testing of both legacy and new PMT-Blocks. As a result, future developments of PROMETEO will incorporate optical measurement capabilities, including the ability to measure relative quantum efficiency and dark current for all 9,852 PMT-Blocks. These PMT-Blocks will be dismounted, refurbished with modern electronics, and reinstalled in TileCal. In this article, we present the upgraded TileCal readout chain, demonstrate how PROMETEO is being used for testing and certification, and discuss the plans for future enhancements of the system
Clearing up the Strong problem
No full textThe absence of a neutron electric dipole moment (EDM) constrains the quantum chromodynamics (QCD) theta angle to be less than one part in ten billion, posing the Strong problem. We revisit two classes of proposed solutions. First, we show that when or is realized as a gauged discrete symmetry - as can arise in quantum gravity - the vacuum necessarily preserves , contrary to recent claims that discrete-symmetry solutions fail. Gauged discrete models face model-building challenges, such as avoiding contributions to the neutron EDM after spontaneous or breaking, but in principle have no fundamental obstructions. Second, we critically examine recent arguments that the Strong problem is illusory, demonstrating that a nonzero neutron EDM at finite follows directly from well-understood QCD dynamics. Taken together, our results reinforce the reality of the Strong problem and highlight gauged discrete-symmetry realizations of or as plausible solutions
EWK Multiboson Production in ATLAS
No full textSlides for talk "EWK Multiboson Production in ATLAS" at Multi-boson Interatcions 2025 at Brandeis Universit
Federation of Agents: A Semantics-Aware Communication Fabric for Large-Scale Agentic AI
No full textWe present Federation of Agents (FoA), a distributed orchestration framework that transforms static multi-agent coordination into dynamic, capability-driven collaboration. FoA introduces Versioned Capability Vectors (VCVs): machine-readable profiles that make agent capabilities searchable through semantic embeddings, enabling agents to advertise their capabilities, cost, and limitations. Our aarchitecturecombines three key innovations: (1) semantic routing that matches tasks to agents over sharded HNSW indices while enforcing operational constraints through cost-biased optimization, (2) dynamic task decomposition where compatible agents collaboratively break down complex tasks into DAGs of subtasks through consensus-based merging, and (3) smart clustering that groups agents working on similar subtasks into collaborative channels for k-round refinement before synthesis. Built on top of MQTT,s publish-subscribe semantics for scalable message passing, FoA achieves sub-linear complexity through hierarchical capability matching and efficient index maintenance. Evaluation on HealthBench shows 13x improvements over single-model baselines, with clustering-enhanced laboration particularly effective for complex reasoning tasks requiring multiple perspectives. The system scales horizontally while maintaining consistent performance, demonstrating that semantic orchestration with structured collaboration can unlock the collective intelligence of heterogeneous federations of AI agents