arXiv subjects

T. Schlüter

Publications and source records attributed to T. Schlüter.

7 recordsLinked to original sources

arXiv2015

Demonstrator of the Belle II Online Tracking and Pixel Data Reduction on the High Level Trigger System

The future Belle II experiment will employ a computer-farm based data reduction system for the readout of its innermost detector, a DEPFET-technology based silicon detector with pixel readout. A large fraction of the background hits can be rejected by defining a set of Regions Of Interest (ROI) on the pixel detector sensors and then recording just the data from the pixels inside the ROI. The ROIs are defined on an event by event basis by extrapolating back onto the PXD the charged tracks detected in the outer trackers (a 4 layer double-sided silicon strip detector surrounded by a wire chamber). The tracks are reconstructed in real time on the High Level Trigger (HLT). The pixel detector is then read out based on the ROI information. A demonstrator of this architecture was under beam test earlier this year in DESY (Hamburg, Germany). The demonstrator was operated in an electron beam whose momentum was in the 2-6 GeV/c range with a typical trigger rate of a few kHz in a magnetic field of strength up to 1 T. The demonstrator consists of one pixel sensor and 4 silicon strip sensors arranged in a 5 layers configuration mimicking the Belle II vertex detector. The detector readout was a scaled down version of the full Belle II DAQ + HLT chain. The demonstrator was used to detect the particles, reconstruct in real time the trajectories, identify the ROIs on the PXD plane and record the PXD data within. We describe the requirements and the architecture of the final system together with the results obtained with the demonstrator.

physics.ins-det↗

arXiv2015

Analysis Tools for Next-Generation Hadron Spectroscopy Experiments

The series of workshops on New Partial-Wave Analysis Tools for Next-Generation Hadron Spectroscopy Experiments was initiated with the ATHOS 2012 meeting, which took place in Camogli, Italy, June 20-22, 2012. It was followed by ATHOS 2013 in Kloster Seeon near Munich, Germany, May 21-24, 2013. The third, ATHOS3, meeting is planned for April 13-17, 2015 at The George Washington University Virginia Science and Technology Campus, USA. The workshops focus on the development of amplitude analysis tools for meson and baryon spectroscopy, and complement other programs in hadron spectroscopy organized in the recent past including the INT-JLab Workshop on Hadron Spectroscopy in Seattle in 2009, the International Workshop on Amplitude Analysis in Hadron Spectroscopy at the ECT*-Trento in 2011, the School on Amplitude Analysis in Modern Physics in Bad Honnef in 2011, the Jefferson Lab Advanced Study Institute Summer School in 2012, and the School on Concepts of Modern Amplitude Analysis Techniques in Flecken-Zechlin near Berlin in September 2013. The aim of this document is to summarize the discussions that took place at the ATHOS 2012 and ATHOS 2013 meetings. We do not attempt a comprehensive review of the field of amplitude analysis, but offer a collection of thoughts that we hope may lay the ground for such a document.

hep-ph↗

arXiv2014

Odd and Even Partial Waves of ηπ^- and η'π^- in 191 GeV/c π^-p

In the year 2008 COMPASS recorded diffractive events of the signature π^-(191 GeV) p --> X_fast p. We present results of the analysis of the subsystems X = η(')π^-. Besides the known resonances a_2(1320), a_4(2040), we study the properties of the spin-exotic P+ wave, and all other natural-exchange partial waves up to spin J = 6. We find a striking difference between the two final states: whereas the even partial waves J = 2, 4, 6 in the two systems are related by phase-space factors, the odd partial waves are relatively suppressed in the ηπ^- system. The relative phases between the even waves appear identical whereas the phase between the D and P waves behave quite differently, suggesting different resonant and non-resonant contributions in the two odd-angular-momentum systems. Branching ratios and parameters of the well-known resonances a_2 and a_4 are measured.

hep-ex↗

arXiv2012

Resonances of the systems π-ηand π-η' in the reactions π-p --> π-ηp and π-p --> π-η' p at COMPASS

We describe partial-wave analyses of the systems π-ηand π-η' produced in interactions of a π- beam (190 GeV/c) with a liquid hydrogen target. The data were recorded during the 2008 COMPASS run, where a slow recoiling proton (|t|>0.1 GeV^2) was required by the trigger. We compare analyses of the π-ηand π-η' data. Significant contributions can be attributed to the resonances a_2(1320), observed in the D_+-wave, and a_4(2040), observed in the G_+-wave. Between the two systems, we find similar compositions of the even partial waves D_+ and G_+ after taking phase-space factors into account, but a much enhanced P_+-wave in π-η'. Relative phase-differences indicate a large incoherent contribution of in the P_+-wave of the η'π- system, but other interpretations are not excluded. The known resonances a_2(1320), a_4(2040) and their parameters could be extracted from the data; their branchings are found to roughly agree with predictions from ηη' mixing.

hep-ex↗

arXiv2012

Comment on "Material Evidence of a 38 MeV Boson"

In the recent preprint 1202.1739 it was claimed that preliminary data presented by COMPASS at recent conferences confirm the existence of a resonant state of mass 38 MeV decaying to two photons. This claim was made based on structures observed in two-photon mass distributions which however were shown only to demonstrate the purity and mass resolution of the π0 and η signals. The additional structures are understood as remnants of secondary interactions inside the COMPASS spectrometer. Therefore, the COMPASS data do not confirm the existence of this state.

hep-ex↗

arXiv2012

The exotic eta'pi- Wave in 190 GeV pi-p --> pi-eta'p at COMPASS

A sample of 35,000 events of the type pi-p --> eta'pi-p_slow (eta' --> eta pi-pi+, eta --> gamma gamma) with -t>0.1 GeV^2/c^2 was selected from COMPASS 2008 data for a partial-wave analysis. We study the broad P_+ structure known from previous experiments at lower energies, in particular its phase motion relative to the D_+-wave near the a_2(1320) mass and relative to a broad D_+-wave structure at higher mass. We also find the a_4(2040). We compare kinematic plots for the eta'pi^- and eta pi- final states.

hep-ex↗

arXiv2011

Large-Area Sandwich Veto Detector with WLS Fibre Readout for Hadron Spectroscopy at COMPASS

A sandwich detector composed of scintillator and steel-covered lead layers was introduced in the fixed-target COMPASS experiment at CERN for vetoing events not completely covered by the two-stage magnetic spectrometer. Wavelength shifting fibres glued into grooves in the scintillator tiles serve for fast read-out. Minimum ionizing particles impinging on the $2 \textrm{m} \times 2 \textrm{m}$ detector outside of a central hole, sparing the spectrometer's entry, are detected with a probability of 98%. The response to charged particles and photons is modeled in detail in Monte Carlo calculations. Figures of merit of the veto trigger in $190 \textrm{GeV}/c$ $π^- + p$ (or nucleus) experiments are an enrichment of exclusive events in the recorded data by a factor of 3.5 and a false-veto probability of 1%.

physics.ins-det↗