arXiv subjects

M. Groll

Publications and source records attributed to M. Groll.

4 recordsLinked to original sources

arXiv2026

Surface-exciton enhanced SHG response in few-layer 2H-TMDC

We explore the nonlinear optical properties of few-layer MoS2 by means of polarization and laser-power-dependent measurements as well as ab initio techniques. While for even layer samples a weak second-harmonic (SH) signal can be attributed to the presence of surface defects or interface effects, our measurements resolve a layer-number dependent signal for odd-layer samples. For the excitation energy of 780 nm, we find that the SH intensity decreases steadily with the layer number. Our simulations demonstrate that this effect cannot be purely attributed to modifications of the band structure, but requires the inclusion of excitonic effects and can be explained by the increasing delocalization of excitons with increasing sample thickness.

physics.optics↗

arXiv2010

Study of the interactions of pions in the CALICE silicon-tungsten calorimeter prototype

A prototype silicon-tungsten electromagnetic calorimeter for an ILC detector was tested in 2007 at the CERN SPS test beam. Data were collected with electron and hadron beams in the energy range 8 to 80 GeV. The analysis described here focuses on the interactions of pions in the calorimeter. One of the main objectives of the CALICE program is to validate the Monte Carlo tools available for the design of a full-sized detector. The interactions of pions in the Si-W calorimeter are therefore confronted with the predictions of various physical models implemented in the GEANT4 simulation framework.

physics.ins-det↗

arXiv2010

Construction and Commissioning of the CALICE Analog Hadron Calorimeter Prototype

An analog hadron calorimeter (AHCAL) prototype of 5.3 nuclear interaction lengths thickness has been constructed by members of the CALICE Collaboration. The AHCAL prototype consists of a 38-layer sandwich structure of steel plates and highly-segmented scintillator tiles that are read out by wavelength-shifting fibers coupled to SiPMs. The signal is amplified and shaped with a custom-designed ASIC. A calibration/monitoring system based on LED light was developed to monitor the SiPM gain and to measure the full SiPM response curve in order to correct for non-linearity. Ultimately, the physics goals are the study of hadron shower shapes and testing the concept of particle flow. The technical goal consists of measuring the performance and reliability of 7608 SiPMs. The AHCAL was commissioned in test beams at DESY and CERN. The entire prototype was completed in 2007 and recorded hadron showers, electron showers and muons at different energies and incident angles in test beams at CERN and Fermilab.

physics.ins-det↗

arXiv2008

Design and Electronics Commissioning of the Physics Prototype of a Si-W Electromagnetic Calorimeter for the International Linear Collider

The CALICE collaboration is studying the design of high performance electromagnetic and hadronic calorimeters for future International Linear Collider detectors. For the electromagnetic calorimeter, the current baseline choice is a high granularity sampling calorimeter with tungsten as absorber and silicon detectors as sensitive material. A ``physics prototype'' has been constructed, consisting of thirty sensitive layers. Each layer has an active area of 18x18 cm2 and a pad size of 1x1 cm2. The absorber thickness totals 24 radiation lengths. It has been exposed in 2006 and 2007 to electron and hadron beams at the DESY and CERN beam test facilities, using a wide range of beam energies and incidence angles. In this paper, the prototype and the data acquisition chain are described and a summary of the data taken in the 2006 beam tests is presented. The methods used to subtract the pedestals and calibrate the detector are detailed. The signal-over-noise ratio has been measured at 7.63 +/- 0.01. Some electronics features have been observed; these lead to coherent noise and crosstalk between pads, and also crosstalk between sensitive and passive areas. The performance achieved in terms of uniformity and stability is presented.

physics.ins-det↗