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J. Cvach

Publications and source records attributed to J. Cvach.

27 records · Page 2Linked to original sources
arXiv2016

DHCAL with Minimal Absorber: Measurements with Positrons

In special tests, the active layers of the CALICE Digital Hadron Calorimeter prototype, the DHCAL, were exposed to low energy particle beams, without being interleaved by absorber plates. The thickness of each layer corresponded approximately to 0.29 radiation lengths or 0.034 nuclear interaction lengths, defined mostly by the copper and steel skins of the detector cassettes. This paper reports on measurements performed with this device in the Fermilab test beam with positrons in the energy range of 1 to 10 GeV. The measurements are compared to simulations based on GEANT4 and a standalone program to emulate the detailed response of the active elements.

physics.ins-det↗
arXiv2015

Opticle fibre calibration system and adaptive power supply

We summarize the recent activity of our group in the calibration, monitoring and gain stabilization of photodetectors, primarily silicon photomultipliers, in calorimeters using scintillator as active medium. The task originally solved for the CALICE analog hadron calorimeter founds application in other experiments.

physics.ins-det↗
arXiv2011

Calibration prototype for the EUDET HCAL

The electronics producing a few nanoseconds long LED pulses tuneable in the amplitude and the optical system distributing the LED light to scintillators by a single optical fibre are described. The properties of the LED pulses are controlled by a computer connected via a CANbus to the controller on the board. We produced a prototype with 6 LED pulse drivers placed on a 4-layer PCB with dimension 250 x 147 mm2. The pulse width is constant and 3 ns long. Its amplitude can be tuned from zero to 1.2 A. The pulse frequency can be set in the range up to 100 kHz. The LED light is distributed by a 1 mm diameter optical fibre. On the length of 2 m the fibre has every 30 mm a notch which flashes light with homogeneity of \pm20%. The system is foreseen for calibration of silicon photomultipliers embedded in scintillation tiles.

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↗
arXiv2005

QCD Analysis of Dijet Production at Low {\boldmath $Q^2$} at HERA

Recent H1 data on triple differential dijet cross sections in $e^\pm p$ interactions in the region of low photon virtualities are shown to be in reasonable agreement with the predictions of the NLO QCD calculations obtained using the program NLOJET++. The implications of this observation for the phenomenological relevance of the concept of resolved virtual photon are discussed.

hep-ph↗
arXiv1999

Real and virtual photon structure from dijet events

Jet production in $ep$ collisions is sensitive to the partonic structure of photon. The latest measurements of dijet production from the H1 experiment provide new results of the gluon density of real photons at low $x$ and, for the first time, on the partonic density of virtual photons. Properties of the photon remnant were measured as a function of the hard scale defined by the $p_T$ of the jets. The comparison of dijet cross sections with the NLO QCD calculation shows the non-triviality of the concept of virtual photon structure.

hep-ex↗