arXiv subjects

Ivo Schulthess

Publications and source records attributed to Ivo Schulthess.

13 recordsLinked to original sources

arXiv2026

A dump leakage calorimeter to measure the flux of high-energy electrons and photons

We developed a novel apparatus based on a lead-glass calorimeter that can measure the flux of high-energy electrons or photons. Our detector uses the electromagnetic shower leakage from the beam dump, where the particles are disposed of at the beamline's end. A prototype of such a calorimeter was set up at the FLASHForward experiment at DESY. We show that it can measure the electron bunch charge with a typical precision on the order of 10% and an accuracy at the few-percent level. Additionally, it is capable of determining the beam's position with a precision on the order of tens of micrometers. Finally, we demonstrate applicability to high-energy photons.

hep-ex↗

arXiv2026

Feasibility of Low-Energy True Muonium Photoproduction

True muonium, the bound state of a muon and an antimuon, is a theoretically well-understood but experimentally unobserved exotic atom. Its purely leptonic nature makes it a sensitive probe for bound-state quantum electrodynamics and possible physics beyond the Standard Model. We present a feasibility study of low-energy true muonium production via near-threshold photoproduction on a fixed target. The study includes simulations of the signal and dominant background processes, estimates of the required photon fluxes, and an overview of possible gamma sources. We show that the proposed Gamma Factory at CERN could provide the necessary photon energies and rates for the production of true muonium. Furthermore, cut-based selections are shown to suppress the background below the expected signal level. Finally, we discuss possible physics opportunities beyond the first observation, including measurements of its lifetime, hyperfine splitting, and Lamb shift.

hep-ex↗

arXiv2026

Dressed-State Spectroscopy of Proton Spins in Water Beyond the Rotating-Wave Approximation

The quantum Rabi model provides the framework for describing a two-level system interacting with a strong oscillating field beyond the rotating-wave approximation. We report the first experimental observation of the resulting dressed states of proton spins in water, realized using a Rabi-type setup with a strong off-resonant magnetic dressing field. The measured resonance spectrum exhibits multiple spin-state transitions involving several dressing-field quanta, including higher-order resonances predicted by the quantum Rabi model. The dressed-state energies show excellent agreement with theoretical expectations, extending dressed-state spectroscopy to proton spins and opening new possibilities for precision spin manipulation in nuclear magnetic resonance and related precision measurements.

hep-ex↗

arXiv2026

Resonant Cancellation Effect in Ramsey-type Nuclear Magnetic Resonance Experiments

We investigate the response of a Ramsey-type experiment on an additional oscillating magnetic field. This superimposed field is oriented in the same direction as the static main magnetic field and causes a modulation of the original Larmor spin precession frequency. The observable magnitude of this modulation reduces at higher frequencies of the oscillating field. It disappears completely if the interaction time of the particles matches the oscillation period, which we call resonant cancellation. We present an analytical approach that describes the effect and compare it to a measurement using a monochromatic cold neutron beam.

hep-ex↗

arXiv2026

New Limit on Axion-Like Dark Matter using Cold Neutrons

We report on a search for dark matter axion-like particles (ALPs) using a Ramsey-type apparatus for cold neutrons. A hypothetical ALP-gluon-coupling would manifest in a neutron electric dipole moment signal oscillating in time. Twenty-four hours of data have been analyzed in a frequency range from 23 $μ$Hz to 1 kHz, and no significant oscillating signal has been found. The usage of present dark-matter models allows to constrain the coupling of ALPs to gluons in the mass range from $10^{-19}$ to $4 \times 10^{-12}$ eV. The best limit of $C_G$/$f_a m_a = 2.7 \times 10^{13}$ GeV$^{-2}$ (95\% C.L.) is reached in the mass range from $2 \times 10^{-17}$ to $2 \times 10^{-14}$ eV.

hep-ex↗

arXiv2026

Primer of Strong-Field Quantum Electrodynamics for Experimentalists

This document serves as a conceptual and practical introduction to Strong-Field Quantum Electrodynamics (SFQED), written from the standpoint of experimental physicists. Rather than providing a comprehensive theoretical review, the document focuses on the core ideas, terminology, and challenges in SFQED that are most relevant to experimental design and interpretation. Our goal is to offer a first point of contact with the subject, bridging the gap between foundational theory and hands-on experimental work, and complementing more formal literature in the field.

hep-ph↗

arXiv2026

From LUXE to Future Colliders: Probing Strong-Field QED and Beyond

Strong-field quantum electrodynamics offers a unique window into non-perturbative phenomena such as vacuum pair production, in which electron--positron pairs are created from the vacuum in the presence of intense electromagnetic fields. The LUXE experiment at DESY is designed to probe this regime using collisions between a high-intensity laser and the 16.5 GeV electron beam of the European XFEL. Future accelerator infrastructures, such as linear colliders, could extend these studies to even higher intensity and energy scales. Additionally, high-energy photons produced in such interactions can be used in beam-dump experiments to search for new physics.

hep-ph↗

arXiv2025

A High-Flux Electron Detector System to Measure Non-linear Compton Scattering at LUXE

Recently, advancements in high-intensity laser technology have enabled the exploration of non-perturbative Quantum Electrodynamics (QED) in strong-field regimes. Notable aspects include non-linear Compton scattering and Breit-Wheeler pair production, observable when colliding high-intensity laser pulses and relativistic electron beams. The LUXE experiment at DESY and the E-320 experiment at SLAC aim to study these phenomena by measuring the created high-flux Compton electrons and photons. We propose a novel detector system featuring a segmented gas-filled Cherenkov detector with a scintillator screen and camera setup, designed to efficiently detect high-flux Compton electrons. Preliminary results from E-320 measurement campaigns demonstrate methods for reconstructing electron energy spectra, aiming to reveal crucial features of non-perturbative QED.

physics.ins-det↗

arXiv2025

New Physics Search with the Optical Dump Concept at Future Colliders

Beam-dump experiments offer an opportunity to search for new physics beyond the Standard Model of particle physics. In this work, we explore the use of a high-energy photon beam on a fixed target. Such photons can be produced via Compton backscattering when colliding high-energy electrons with a high-intensity laser pulse, such as in setups of strong-field quantum electrodynamics experiments. We present various options for implementing such photon sources at future facilities and discuss how the photons can be used to search for axion-like particles. We compare the projected sensitivities of the proposed options with existing constraints, projections from current experiments, and direct searches at future colliders.

hep-ph↗

arXiv2024

Frequency-offset separated oscillatory fields technique applied to neutrons

The novel technique of frequency-offset separated oscillatory fields (FOSOF) has been originally proposed as a modification to Ramsey's method of separated oscillatory fields. It has recently been employed in precision measurements with atomic beams since it allows for an alternative approach to determine absolute resonance frequencies. We present results from a systematic investigation of the FOSOF technique adapted to a beam of cold neutrons.

physics.ins-det↗

arXiv2023

A Ramsey apparatus for proton spins in flowing water

We present an apparatus that applies Ramsey's method of separated oscillatory fields to proton spins in water molecules. The setup consists of a water circuit, a spin polarizer, a magnetically shielded interaction region with various radio frequency elements, and a nuclear magnetic resonance system to measure the spin polarization. We show that this apparatus can be used for Rabi resonance measurements and to investigate magnetic and pseudomagnetic field effects in Ramsey-type precision measurements with a sensitivity below 100 pT.

physics.ins-det↗

arXiv2019

Passive alignment stability and auto-alignment of multipass amplifiers based on Fourier transforms

The stability properties of Fourier-based multipass amplifier to misalignments (tilts) of its optical components has been investigated. For this purpose, a method to quantify the sensitivity to tilts based on the amplifier small signal gain has been elaborated and compared with measurements. To improve on the tilt stability by more than an order of magnitude a simple auto-alignment system has been proposed and tested. This study, combined with other investigations devoted to the stability of the output beam to variations of aperture and thermal lens effects of the active medium, qualifies the Fourier-based amplifier for the high-energy and the high-power sector.

physics.optics↗

arXiv2018

Multi-pass amplifiers with self-compensation of the thermal lens

We present a novel architecture for a multi-pass amplifier based on a succession of optical Fourier transforms and short propagations that shows a superior stability for variations of the thermal lens compared to state-of-the-art 4f-based amplifiers. We found that the proposed multi-pass amplifier is robust to variations of the active medium dioptric power. The superiority of the proposed architecture is demonstrated by analyzing the variations of the size and divergence of the output beam in form of a Taylor expansion around the design value for variations of the thermal lens in the active medium. The dependence of the output beam divergence and size is investigated also for variations of the number of passes, for aperture effects in the active medium and as a function of the size of the beam on the active medium. This architecture makes efficient use of the transverse beam filtering inherent in the active medium to deliver a beam with excellent quality (TEM00) without additional losses.

physics.optics↗