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Elimination of Dispersion Ripples in a Waveguide Cavity Using Two Slightly Dispersion-Shifted Bragg Gratings
No full textChip-integrated chirped or apodized Bragg gratings (CBGs) are key components for on-chip dispersion compensation. They are increasingly sought after for applications such as dispersion compensation for telecommunications, integrated chirped pulse amplifiers [1], mode-locked lasers [2], and ultrashort pulse soliton generation [3] on a silicon chip. However, maintaining flat group-delay dispersion (GDD) over a large bandwidth without strong ripples is challenging. These ripples typically arise from imperfect apodization profiles, and reflections at the grating boundaries, which can introduce phase inconsistencies and disrupt the desired dispersion profile
Electroweak, QCD and flavour physics studies with ATLAS data from Run 2 of the LHC
No full textA summary of precision measurements sensitive to electroweak, QCD and quark-flavour effects performed by the ATLAS Collaboration at the Large Hadron Collider is reported. The measurements are predominantly performed on proton–proton (pp) collision data recorded at a centre-of-mass energy of 13 TeV taken from 2015 to 2018, with an integrated luminosity of up to 140 fb−1, with some results based on pp and Pb+Pb data recorded at lower nucleon centre-of-mass energies. The results cover a wide range of topics, from strong production of particles at low energies and the spectroscopy of hadrons to perturbative QCD with hadronic jets and electroweak and strong production of single and multiple vector bosons. They provide precise measurements of fundamental constants and stringent tests of the Standard Model with unprecedented precision and in energy ranges never explored before. They are also used to explore the proton structure and to perform model-independent searches for new physics
Status of the International Linear Collider
No full textThis paper is not a proposal for a CERN future project but provides information on the International Linear Collider (ILC) considered for Japan in order to facilitate the European Strategy discussion in a global context. It describes progress to date, ongoing engineering studies, updated cost estimate for the machine at and the situation in Japan. The physics of the ILC is not presented here, but jointly for all Linear Collider projects in a separate document ``A Linear Collider Vision for the Future of Particle Physics'' submitted for the forthcoming European Strategy deliberations
HALHF: a hybrid, asymmetric, linear Higgs factory using plasma- and RF-based acceleration. Backup Document
No full textThis document expands on the Comprehensive Summary submitted to the EPPSU 2026. It contains details on aspects of the HALHF project that could not be fitted into the Summary. Some sections contain work that is still preliminary and/or status reports on current progress
Flow-based Sampling for Entanglement Entropy and the Machine Learning of Defects
No full textWe introduce a novel technique to numerically calculate Rényi entanglement entropies in lattice quantum field theory using generative models. We describe how flow-based approaches can be combined with the replica trick using a custom neural-network architecture around a lattice defect connecting two replicas. Numerical tests for the scalar field theory in two and three dimensions demonstrate that our technique outperforms state-of-the-art Monte Carlo calculations, and exhibit a promising scaling with the defect size
Diffuse continuum emission and large extended sources at MeV energies
No full textFuture gamma-ray survey instruments, such as newASTROGAM and AMEGO-X, willsignificantly improve previous and current all-sky surveys at MeV energies. Inthis paper we discuss the continuum emission from the Milky Way, two prominentlarge extended sources, the Fermi bubbles and Loop I, and the extragalacticgamma-ray background. We highlight the importance of measurements in the MeV toGeV energy range for understanding CR production and propagation in the Galaxy,for the determination of the nature of the Fermi bubbles and Loop I, and forexploring the origin of the extragalactic gamma-ray background
Top-quark spin correlations as a tool to distinguish pseudoscalar and scalar signatures in final states at the LHC
No full textBoth ATLAS and CMS have recentlyperformed the first searches for a heavy newspin-0 resonance decayinginto a lighter new spin-0 resonance and a boson, wherethe lighter spin-0 resonance subsequently decaysinto pairs.These searches are of particularinterest to probe Two Higgs doublet model~(2HDM)parameter space regions that predict a strongfirst-order electroweak phase transition.In the absence of CP violation, the investigated decay ispossible if the lighterand the heavier spin-0 particles have oppositeCP parities. The analysis techniques employedby ATLAS and CMS do not distinguishbetween the two possible signatures and ,where and denote CP-odd and CP-even Higgs bosons,respectively, if both signals are predicted to have the same totalcross sections.We demonstratethe capability of angular variables{that are}sensitive to spin correlations of the top quarksto differentiate between and decays,even in scenarios where both signalspossess identical totalcross sections. Focusing on masses of 600~GeV and 800~GeVas a representative 2HDM benchmark, we find that a distinction betweenthe two possible channels is possible with highsignificance with the anticipated data from the high-luminosity LHC,if the invariant mass distribution of the system is further binned inangular variables defined by the direction of flightof the leptons produced in the top-quark decays.Moreover, we find a moderategain in experimental sensitivity due tothe improved background rejection for both signals
Beam dynamics optimization in high-brightness Photo Injector with various photocathode laser pulse shapes
No full textAt PITZ, a comprehensive study is conducted to analyze the factors influencing emittance growth in the Eu-ropean XFEL (EuXFEL) continuous wave (CW) setup. Emittance growth due to space charge effects can be mitigated using advanced photocathode laser pulse shapes. To optimize beam quality, multi-objective optimization studies using ASTRA are performed, focusing not only on minimizing emittance but also on maximizing beam brightness for various laser temporal profiles and durations. The opti-mization is initially carried out for the CW injector section planned for EuXFEL. The optimized cases are then further tracked through start-to-end (S2E) simulations to evaluate their behavior in the compression stages of EuXFEL. A comparative analysis of gaussian, flattop, ellipsoidal, and inverted parabolic laser profiles is presented, assessing their efficiency not only in terms of emittance but also in 4D and 6D bright-ness. Finally, the results of the optimized photoinjector setup and the beam properties after the final bunch com-pression are presente
A LOFAR-style reconstruction of cosmic-ray air showers with SKA-Low
No full textCosmic-ray air shower detection with the low-frequency part of the Square Kilometre Array (SKA) radio telescope is envisioned to yield very high precision measurements of the particle composition of cosmic rays between 1016 and 1018 eV. This is made possible by the extreme antenna density of the core of SKA-Low, surpassing the current most dense radio air shower observatory LOFAR by over an order of magnitude. In order to make these measurements, the technical implementation of this observation mode and the development of reconstruction methods have to happen hand in hand. As a first lower limit of what is obtainable, we apply the current most precise reconstruction methods as used at LOFAR to a first complete simulation of air shower signals for the SKA-Low array. We describe this simulation setup and discuss the obtainable accuracy and resolution. A special focus is put on effects of the dynamic range of the system, beam-forming methods to lower the energy threshold, as well as the limits to the mass composition accuracy given by statistical and systematic uncertainties