arXiv subjects

K. Deiters

Publications and source records attributed to K. Deiters.

9 recordsLinked to original sources

arXiv2026

The MUSE Target Chamber Post Veto

The Muon Scattering Experiment (MUSE) was developed to address the proton radius puzzle through simultaneous electron-proton and muon-proton scattering using the Paul Scherrer Institute's PiM1 secondary beamline. MUSE uses a large-solid-angle, non-magnetic spectrometer to detect beam particles scattering from a liquid hydrogen cell contained within a vacuum chamber. Due to the large scattering windows, the structural integrity of the chamber is supported by posts located at small scattering angles. While out of the acceptance, particles in the tails of the beam distribution can strike these posts, causing a significant trigger background. We describe the design and performance of the Target Chamber Post Veto (TCPV) detector installed inside the vacuum chamber to remove these background events at the trigger level.

physics.ins-det↗

arXiv2024

The MUSE Beamline Calorimeter

The MUon Scattering Experiment (MUSE) was motivated by the proton radius puzzle arising from the discrepancy between muonic hydrogen spectroscopy and electron-proton measurements. The MUSE physics goals also include testing lepton universality, precisely measuring two-photon exchange contribution, and testing radiative corrections. MUSE addresses these physics goals through simultaneous measurement of high precision cross sections for electron-proton and muon-proton scattering using a mixed-species beam. The experiment will run at both positive and negative beam polarities. Measuring precise cross sections requires understanding both the incident beam energy and the radiative corrections. For this purpose, a lead-glass calorimeter was installed at the end of the beam line in the MUSE detector system. In this article we discuss the detector specifications, calibration and performance. We demonstrate that the detector performance is well reproduced by simulation, and meets experimental requirements.

physics.ins-det↗

arXiv2024

Instrumental uncertainties in radiative corrections for the MUSE experiment

The MUSE experiment at the Paul Scherrer Institute is measuring elastic lepton-proton scattering cross sections in a four-momentum transfer range from $Q^2$ of approximately 0.002 to 0.08 GeV$^2$ using positively and negatively charged electrons and muons. The extraction of the Born cross sections from the experimental data requires radiative corrections. Estimates of the instrumental uncertainties in those corrections have been made using the ESEPP event generator. The results depend in particular on the minimum lepton momentum that contributes to the experimental cross section and the fraction of events with hard initial-state radiation that is detected in the MUSE calorimeter and is excluded from the data. These results show that the angular-dependent instrumental uncertainties in radiative corrections to the electron cross section are better than 0.4 % and are negligible for the muon cross section.

hep-ex↗

arXiv2021

Characterization of Muon and Electron Beams in the Paul Scherrer Institute PiM1 Channel for the MUSE Experiment

The MUon Scattering Experiment, MUSE, at the Paul Scherrer Institute, Switzerland, investigates the proton charge radius puzzle, lepton universality, and two-photon exchange, via simultaneous measurements of elastic muon-proton and electron-proton scattering. The experiment uses the PiM1 secondary beam channel, which was designed for high precision pion scattering measurements. We review the properties of the beam line established for pions. We discuss the production processes that generate the electron and muon beams, and the simulations of these processes. Simulations of the $π$/$μ$/$e$ beams through the channel using TURTLE and G4beamline are compared. The G4beamline simulation is then compared to several experimental measurements of the channel, including the momentum dispersion at the IFP and target, the shape of the beam spot at the target, and timing measurements that allow the beam momenta to be determined. We conclude that the PiM1 channel can be used for high precision $π$, $μ$, and $e$ scattering.

physics.ins-det↗

arXiv2019

A Liquid Hydrogen Target for the MUSE Experiment at PSI

A 280 ml liquid hydrogen target has been constructed and tested for the MUSE experiment at PSI to investigate the proton charge radius via simultaneous measurement of elastic muon-proton and elastic electron-proton scattering. To control systematic uncertainties at a sub-percent level, strong constraints were put on the amount of material surrounding the target and on its temperature stability. The target cell wall is made of $120\,μ$m-thick Kapton, while the beam entrance and exit windows are made of $125\,μ$m-thick aluminized Kapton. The side exit windows are made of Mylar laminated on aramid fabric with an areal density of $368\,$g/m$^2$. The target system was successfully operated during a commissioning run at PSI at the end of 2018. The target temperature was stable at the 0.01 K level. This suggests a density stability at the $0.02\,$% level, which is about a factor of ten better than required.

physics.ins-det↗

arXiv2017

Technical Design Report for the Paul Scherrer Institute Experiment R-12-01.1: Studying the Proton "Radius" Puzzle with μp Elastic Scattering

The difference in proton radii measured with $μp$ atoms and with $ep$ atoms and scattering remains an unexplained puzzle. The PSI MUSE proposal is to measure $μp$ and $e p$ scattering in the same experiment at the same time. The experiment will determine cross sections, two-photon effects, form factors, and radii independently for the two reactions, and will allow $μp$ and $ep$ results to be compared with reduced systematic uncertainties. These data should provide the best test of lepton universality in a scattering experiment to date, about an order of magnitude improvement over previous tests. Measuring scattering with both particle polarities will allow a test of two-photon exchange at the sub-percent level, about a factor of four improvement on uncertainties and over an order of magnitude more data points than previous low momentum transfer determinations, and similar to the current generation of higher momentum transfer electron experiments. The experiment has the potential to demonstrate whether the $μp$ and $ep$ interactions are consistent or different, and whether any difference results from novel physics or two-photon exchange. The uncertainties are such that if the discrepancy is real it should be confirmed with $\approx$5$σ$ significance, similar to that already established between the regular and muonic hydrogen Lamb shift.

physics.ins-det↗

arXiv2013

Studying the Proton "Radius" Puzzle with μp Elastic Scattering

The Proton Radius Puzzle is the inconsistency between the proton radius determined from muonic hydrogen and the proton radius determined from atomic hydrogen level transitions and ep elastic scattering. No generally accepted resolution to the Puzzle has been found. Possible solutions generally fall into one of three categories: the two radii are different due to novel beyond-standard-model physics, the two radii are different due to novel aspects of nucleon structure, and the two radii are the same, but there are underestimated uncertainties or other issues in the ep experiments. The MUon proton Scattering Experiment (MUSE) at the Paul Scherrer Institut is a simultaneous measurement of μ^+ p and e^+ p elastic scattering, as well as μ^- p and e^- p elastic scattering, which will allow a determination of the consistency of the μp and the ep interactions. The differences between + and - charge scattering are sensitive to two-photon exchange effects, higher-order corrections to the scattering process. The slopes of the cross sections as Q^2 -> 0 determine the proton "radius". We plan to measure relative cross sections at a typical level of a few tenths of a percent, which should allow the proton radius to be determined at the level of ~0.01 fm, similar to previous ep measurements. The measurements will test several possible explanations of the proton radius puzzle, including some models of beyond-standard-model physics, some models of novel hadronic physics, and some issues in the radius extraction from scattering data.

nucl-ex↗

arXiv2009

Radiation hardness qualification of PbWO4 scintillation crystals for the CMS Electromagnetic Calorimeter

Ensuring the radiation hardness of PbWO4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered.

physics.ins-det↗

arXiv2007

Measurement of the Fermi Constant by FAST

An initial measurement of the lifetime of the positive muon to a precision of 16 parts per million (ppm) has been performed with the FAST detector at the Paul Scherrer Institute. The result is tau_mu = 2.197083 (32) (15) microsec, where the first error is statistical and the second is systematic. The muon lifetime determines the Fermi constant, G_F = 1.166353 (9) x 10^-5 GeV^-2 (8 ppm).

hep-ex↗