arXiv subjects

M. Ehlert

Publications and source records attributed to M. Ehlert.

4 recordsLinked to original sources

arXiv2021

Sensitivity of the SHiP experiment to dark photons decaying to a pair of charged particles

Dark photons are hypothetical massive vector particles that could mix with ordinary photons. The simplest theoretical model is fully characterised by only two parameters: the mass of the dark photon m$_{γ^{\mathrm{D}}}$ and its mixing parameter with the photon, $\varepsilon$. The sensitivity of the SHiP detector is reviewed for dark photons in the mass range between 0.002 and 10 GeV. Different production mechanisms are simulated, with the dark photons decaying to pairs of visible fermions, including both leptons and quarks. Exclusion contours are presented and compared with those of past experiments. The SHiP detector is expected to have a unique sensitivity for m$_{γ^{\mathrm{D}}}$ ranging between 0.8 and 3.3$^{+0.2}_{-0.5}$ GeV, and $\varepsilon^2$ ranging between $10^{-11}$ and $10^{-17}$.

hep-ex↗

arXiv2020

SND@LHC

We propose to build and operate a detector that, for the first time, will measure the process $pp\toνX$ at the LHC and search for feebly interacting particles (FIPs) in an unexplored domain. The TI18 tunnel has been identified as a suitable site to perform these measurements due to very low machine-induced background. The detector will be off-axis with respect to the ATLAS interaction point (IP1) and, given the pseudo-rapidity range accessible, the corresponding neutrinos will mostly come from charm decays: the proposed experiment will thus make the first test of the heavy flavour production in a pseudo-rapidity range that is not accessible by the current LHC detectors. In order to efficiently reconstruct neutrino interactions and identify their flavour, the detector will combine in the target region nuclear emulsion technology with scintillating fibre tracking layers and it will adopt a muon identification system based on scintillating bars that will also play the role of a hadronic calorimeter. The time of flight measurement will be achieved thanks to a dedicated timing detector. The detector will be a small-scale prototype of the scattering and neutrino detector (SND) of the SHiP experiment: the operation of this detector will provide an important test of the neutrino reconstruction in a high occupancy environment.

physics.ins-det↗

arXiv2018

Proof-of-principle measurements with a liquid-scintillator detector using wavelength-shifting optical modules

Based on test-beam measurements, we study the response of a liquid-scintillator detector equipped with wavelength-shifting optical modules, that are proposed e.g. for the IceCube experiment and the SHiP experiment, and adiabatic light guides that are viewed either by a photomultiplier tube or by an array of silicon photomultipliers. We report on the efficiency, the time resolution and the detector response to different particle types and point out potential ways to improve the detector performance.

physics.ins-det↗

arXiv2018

Engineering and improving the magnetic properties of thin Fe layers through exchange coupling with hard magnetic Dysprosium layers

We report on a comprehensive study of the magnetic coupling between soft magnetic Fe layers and hard magnetic Dysprosium (Dy) layers at low temperatures (4.2 - 120K). For our experiments we prepared thin films of Fe and Dy and multilayers of Fe/Dy by ultra-high vacuum sputtering. The magnetic properties of each material were determined with a superconducting quantum interference device. Furthermore, we performed magnetoresistance measurements with similarly grown, microstructured devices, where the anisotropic magnetoresistance (AMR) effect was used to identify the magnetization state of the samples. By analyzing and comparing the corresponding data of Fe and Dy, we show that the presence of a Dy layer on top of the Fe layer significantly influences its magnetic properties and makes it magnetically harder. We perform a systematic evaluation of this effect and its dependence on temperature and on the thickness of the soft magnetic layer. All experimental results can consistently be explained with exchange coupling at the interface between the Fe and the Dy layer. Our experiments also yield a negative sign of the AMR effect of thin Dy films, and an increase of the Dy films' Curie temperature, which is due to growth conditions.

cond-mat.mtrl-sci↗