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The Gamma-Ray Luminosity Function of Flat-spectrum Radio Quasars
No full textWe have utilized the largest sample of gamma-ray-selected Fermi flat-spectrum radio quasars (FSRQs) ever used (519 sources) to construct the luminosity function and its evolution through cosmic history. In addition to spanning large redshift (0 < z ≲ 4) and luminosity ranges (2.9 × 10 erg s–7.3 × 10 erg s), this sample also has a robust calculation of the detection efficiency associated with its observation, making its selection effects and biases well understood. We confirm that the local luminosity function is best explained by a double power law. The evolution of the luminosity function of FSRQs follows a luminosity-dependent density evolution. FSRQs experience positive evolution, with their space density growing with increasing redshift up to a maximum redshift, after which the numbers decrease. This peak in redshift occurs at larger redshifts for higher-luminosity sources and at lower redshifts for lower-luminosity sources. We find an unexpected similarity between the luminosity function of FSRQs and that of BL Lacertae objects (BL Lacs) at intermediate luminosity. This could be a sign of a strong genetic link between the two blazar subclasses or of BL Lac samples being contaminated by large amounts of FSRQs with their jets nearly perfectly aligned with our line of sight
Twin-bunch modelling in linear accelerators for plasma wakefield acceleration
No full textTwin electron bunches accelerated by high-energy linacs are attracting increasing interest especially in twin free-electron laser (FEL) pulse generation andbeam-driven plasma wakefield acceleration (PWFA) studies. High-energy linacs may benefit from plasma accelerators, where a trailing bunch is accelerated inGV/m fields in a plasma wave driven by the leading bunch. This could facilitate high-energy physics, as well as greatly increase the available photon energyrange of existing FELs without increasing the footprint. Here, initial analytical studies of twin-bunch generation in FLASH accelerator are carried out. With theinitial beam longitudinal phase space properly tuned by temporally shaping the photocathode laser, together with optimizing linac settings, high-quality twinelectron bunches with tunable delay and simultaneous bunch shaping can be generated, which is essential for energy-efficient PWFA with low energy spread
Bandwidth and signal-to-noise ratio control for hard x-ray self-seeded free-electron lasers
No full textLong-duration ionisation effects in beam-driven plasma-wakefield accelerators
No full textHigh-repetition-rate operation of plasma-wakefield accelerators is essential for their suitability in the design of colliders and FELs. Energy remaining in the plasma after the wakefield acceleration event can limit the ultimate repetition rate of the plasma accelerator as the plasma takes time to relax to its initial state. This relaxation is limited by two ion-driven effects: their redistribution after the wakefield event and potential further collisional ionisation caused by this motion, as was observed at FACET [Nat. Commun 11, 1–11]. A tens-of-nanoseconds recovery of the original on-axis plasma density directly from ion motion was measured for standard FLASHForward operational settings [Nature 603, 58–62], prompting further investigations into possible ionisation effects. In this work, we investigated hydrogen and argon plasmas at a variety of working points with two different diagnostics: the pump-probe electron-beam-based technique and optical emission spectrometry. In some regimes, both diagnostics indicated additional ionisation happening on the nanoseconds-microseconds timescale, which elongated the recovery time. The dependency of the exact evolution rate of ion-motion-driven ionisation on the initial plasma conditions, namely plasma density and the degree of ionisation, was explored, which will inform the design of the highest repetition rate plasma sources for future colliders and FELs
Coulomb crystallization of xenon highly charged ions in a laser-cooled Ca matrix
No full textWe report on the sympathetic cooling and Coulomb crystallization of xenon highly charged ions (HCIs) with laser-cooled Ca ions. The HCIs are produced in a compact electron beam ion trap, then charge selected, decelerated, and finally injected into a cryogenic linear Paul trap. There, they are captured into Ca Coulomb crystals, and co-crystallized within them, causing dark voids in their fluorescence images. Fine control over the number of trapped ions and HCIs allows us to realize mixed-species crystals with arbitrary ordering patterns. By investigating Xe--Ca strings, we confirm the HCI charge states, measure their lifetime and characterize the mixed-species motional modes. Our system effectively combines the established quantum control toolbox for Ca with the rich set of atomic properties of Xe highly charged ions, providing a resourceful platform for optical frequency metrology, searches for signatures of new physics, and quantum information science
Preliminary luminosity calibration of the ATLAS 13.6 TeV data recorded in 2024 and combination with the 2022 and 2023 measurements
No full textThis note presents a preliminary calibration of the integrated luminosity recorded by the ATLAS experiment in pp collisions at √s=13.6 TeV in 2024. A detailed breakdown of the systematic uncertainties in 2024, as well as the uncertainties for the combined 2022-2024 dataset, is presented. The total luminosity usable for physics analyses in 2024 is 108 fb−1 with an uncertainty of 2.0% while the corresponding luminosity for the combined 2022-2024 dataset is 164 fb−1 with an uncertainty of 1.9%
An exceptional cluster algebra for Higgs plus jet production
No full textA recent evaluation of three-loop nonplanar Feynman integrals contributing to Higgs plus jet production has established their dependence on two novel symbol letters. We show that the resulting alphabet is described by a G cluster algebra, enlarging the C cluster algebra found to cover all previously known integrals relevant for this process. The cluster algebra connection we find reveals new adjacency relations, which significantly reduce the function space dimension of the non-planar triple ladder integral. These adjacencies may be understood in part by embedding G inside higher-rank cluster algebras
Physics Performance and Detector Requirements at an Asymmetric Higgs Factory
No full textThe Hybrid Asymmetric Linear Higgs Factory (HALHF) proposes a shorter and cheaper design for a future Higgs factory. It reaches a √s = 250 GeV using a 500 GeV electron beam accelerated by an electron-driven plasma wake-field, and a conventionally-accelerated 31 GeV positron beam.Assuming plasma acceleration R&D challenges are solved in a timely manner, the asymmetry of the collisions brings additional challenges regarding the detector and the physics analyses, from forward boosted topologies and beam backgrounds. This contribution will detail the impact of beam parameters on beam-induced backgrounds, and provide a first look at what modification compared to e.g. the ILD can improve the physics performance at such a facility. The studies will be benchmarked against some flagship Higgs Factory analyses for comparison
PETRA-IV FOFB System Integration Test Setup
No full textThe PETRA-IV Fast Orbit Feedback (FOFB) system will be a large-scale Multi-Input Multi-Output (MIMO) control system, utilizing 790 Beam Position Monitors (BPM) and 560 Fast Corrector Magnets (FCM) to maintain the desired orbit trajectory. Data acquisition and distribution will be managed across 16 supply areas and connected via an extended star network topology. This contribution focuses on system integration test setups while describing the Model-Based Design (MBD) methodologies that are being used for developing, verifying, and commissioning the complete system step by step. Integration of the components of such a large system must be systematic so that potential issues can be isolated and fixed efficiently. The setups will also be used for the characterization of sensors, actuators, and transmission lines. Subsystem identification is of utmost importance for a comprehensive understanding of the system dynamics, which will guide the design of appropriate filters and control strategies to ensure optimal orbit stabilization performance. The analysis will also precisely assess the overall system latency, which is critical for feedback bandwidth and stability