A Layer Correlation Technique for Pion Energy Calibration at the 2004 ATLAS Combined Beam Test

A new method for calibrating the hadron response of a segmented calorimeter is developed. It is based on a principal component analysis of the calorimeter layer energy deposits, exploiting longitudinal shower development information to improve the measured energy resolution. Corrections for invisible hadronic energy and energy lost in dead material in front of and between the ATLAS calorimeters were calculated with simulated Geant4 Monte Carlo events and used to reconstruct the energy of pions impinging on the calorimeters during the 2004 Barrel Combined Beam Test at the CERN H8 area. For pion beams with energies between 20 and 180 GeV, the particle energy is reconstructed within 3% and the energy resolution is improved by about 20% compared to the electromagnetic scale.Comment: 7 pages, 12 figures. Submitted to the Conference Record of the 2009 IEEE Nuclear Science Symposium (Orlando, Florida, USA

PDE-Foam - a probability-density estimation method using self-adapting phase-space binning

Probability Density Estimation (PDE) is a multivariate discrimination technique based on sampling signal and background densities defined by event samples from data or Monte-Carlo (MC) simulations in a multi-dimensional phase space. In this paper, we present a modification of the PDE method that uses a self-adapting binning method to divide the multi-dimensional phase space in a finite number of hyper-rectangles (cells). The binning algorithm adjusts the size and position of a predefined number of cells inside the multi-dimensional phase space, minimising the variance of the signal and background densities inside the cells. The implementation of the binning algorithm PDE-Foam is based on the MC event-generation package Foam. We present performance results for representative examples (toy models) and discuss the dependence of the obtained results on the choice of parameters. The new PDE-Foam shows improved classification capability for small training samples and reduced classification time compared to the original PDE method based on range searching.Comment: 19 pages, 11 figures; replaced with revised version accepted for publication in NIM A and corrected typos in description of Fig. 7 and

ATLAS Calorimetry : Hadronic Calibration Studies

The ATLAS experiment -- situated at the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) in Geneva -- is on schedule to take its first collision data in 2009. Physics topics include finding the Higgs boson, heavy quark physics, and looking for extensions of the standard model such as supersymmetry. Upon acceptance of an event by the level 1 trigger, data is read out from the liquid argon calorimeters using multi-mode optical fibers. In total, 58 cables were installed, corresponding to 232 12-fiber ribbons or 2784 individual fibers. The cables, about one hundred meters in length, were installed between the main ATLAS cavern and the counting room in the USA15 cavern. Patch cables were spliced onto the ribbons and the fiber attenuation was measured. For 1296 fiber pairs in 54 cables, the average attenuation was 0.69 dB. Only five fibers were found to have losses exceeding 4 dB, resulting in a failure rate of less than 2 per mil. In the ATLAS liquid argon barrel presampler, short circuits consisting of small pieces of dust, metal, etc. can be burned away in situ by discharging a capacitor over the high voltage lines. In a burning campaign in November 2006, seventeen existing short circuits were successfully removed. An investigation on how to implement saturation effects in liquid argon due to high ionization densities resulted into the implementation of the effect in the ATLAS Monte Carlo code, improving agreement with beam test data. The timing structure of hadronic showers was investigated using a Geant4 Monte Carlo. The expected behavior as described in the literature was reproduced, with the exception that some sets of physics models gave unphysical gamma energies from nuclear neutron capture. An ATLAS Combined Beam Test was conducted in the summer/fall of 2004 in the CERN H8 area, containing a whole slice of the ATLAS detectors in the central barrel region. The controlled single-particle environment allows the validation of Monte Carlo code and calibration. A method for calibrating the response of a segmented calorimeter to hadrons was developed. The ansatz is that information on longitudinal shower fluctuations gained from a principal component analysis of the layer energy depositions can improve energy resolution by correcting for hadronic invisible energy and dead material losses: projections along the eigenvectors of the correlation matrix are used as input for the calibration. The technique was used to reconstruct the energy of pions impinging on the ATLAS calorimeters during the 2004 Combined Beam Test. Simulated Monte Carlo events were used to derive corrections for invisible energy lost in nuclear reactions and in dead material in front and in between the calorimeters.  For pion beams with energies between 20 and 180 GeV, the particle energy was reconstructed within 3% and the resolution was improved by about 20%. As a comparison, a simple iterative scheme with a single e/π factor and dead material corrections was devised, giving similar performance.QC 2010111

Measurement of jets in top-anti-top events with ATLAS

Properties of jets, including jet multiplicity, are measured with the ATLAS detectorinsemileptonicttbar events in protonprotoncollisions at a centerofmassenergy of 7 TeV. Afterbackground subtraction, corrections are made for detector efficiencies andresolution effects. The results are compared to Monte Carlo models, consisting offixedordermatrix element calculations matched to parton showers

Measurement of Multi-Jet Production in Proton-Proton Collisions at 7 TeV Center-of-Mass Energy and Hadronic Calibration Studies with the ATLAS Detector at CERN

The ATLAS experiment – situated at the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) in Geneva – took its first collsion data in 2010. Physics topics include finding the Higgs boson, heavy quark physics, and looking for extensions of the Standard Model of Particle Physics such as supersymmetry. In this thesis, inclusive multi-jet production has been studied with the ATLAS detector in proton-proton collisions at a center-of-mass energy of 7 TeV, using an integrated luminosity of 17 nb−1. The anti-kt algorithm with distance parameter ℝ = 0.6 is used to identify jets. The inclusive multi-jet cross section is measured, as well as the ratio ofcross sections for inclusive production of n − 1 and n jets for n ≤ 6. The differential cross sections of the first, second, third and fourth leading jets as a function of transverse momentum, and the differential cross section as a function of the scalar sum of the pT of selected jets, HT, for different jet multiplicities are presented. The ratio of the differential cross section as a function of HT for 3-jet and 2-jet events is also measured. The results are compared to expectations based on leading order QCD, which agree with the data. In addition, a new method for calibrating the hadron response of a segmented calorim-ter is developed and successfully applied to 2004 ATLAS combined beam test data. It is based on a principal component analysis of the calorimeter layer energy deposits, exploiting longitudinal shower development information to improve the measured energyresolution. For pion beams with energies between 20 and 180 GeV, the particle energy is reconstructed within 3% and the energy resolution is improved by 11% to 25% comparedto the response at the electromagnetic scale. Multi-mode optical readout cables for the ATLAS liquid argon calorimeters, about one hundred meters in length, were installed between the main ATLAS cavern and the counting room in the USA15 cavern. Patch cables were spliced onto the ribbons and the fiber attenuation was measured. For 1296 fiber pairs in 54 cables, the average attenuation was 0.69 dB. Only five fibers were found to have losses exceeding 4 dB, resulting in a failure rate of less than 2 per mill. In the ATLAS liquid argon barrel presampler, short circuits consisting of small pieces of dust, metal, etc. can be burned away in situ by discharging a capacitor over the high voltage lines. In a burning campaign in November 2006, seventeen existing short circuits were successfully removed. An investigation on how to implement saturation effects in liquid argon due to high ionization densities resulted in the implementation of the effect in the ATLAS Monte Carlo code, improving agreement with beam test data. The timing structure of hadronic showers was investigated using a Geant4 Monte Carlo. The expected behavior as described in the literature was reproduced, with the exception that some sets of physics models gave unphysical gamma energies from nuclear neutron capture.QC 2011012

Top mass measurement

Top mass measurements at the Tevatron and the LHC are reviewed

Local and remote team cohesion effect on performance in the software industry

Background: The COVID-19 pandemic forced many companies to transition to remote work, which has created a social distance among team members that may affect team performance. Although previous studies have examined the relationship of team cohesion and team performance, few have investigated the question whether remote work affects team performance. Specifically, this study examines the correlation between team cohesion and team performance by comparing the same teams working locally versus remotely. Objectives: The objective is to investigate the correlation between team cohesion and team performance based on whether teams work locally or remotely. Method: The study was quantitative, using regression analysis. Data was gathered at a software company in Sweden. Team cohesion was evaluated based on verbal mimicry via the Language Style Matching (LSM) algorithm, applied on chat messages. Team performance was evaluated based on git contributions and tickets done. Team efficiency was analyzed via Data Envelopment Analysis (DEA). Team efficiencies were analyzed in the context of both time periods, before and during the COVID-19 pandemic, and both work settings. Association between team efficiency and team cohesion was investigated based on the work setting. Tools such as Excel, R, Python, LIWC, and MS Forms were used. Analysis results: When efficiency is correlated with LSM score (cohesion) for teams working remotely, there is a significantly strong positive correlation, suggesting cohesion plays an important role on team efficiency when working remotely. This observation is in line with previous research on cohesion influence on performance of local teams. The change of work setting did not affect the cohesion level of teams. Conclusions: Teams working remotely can be as effective as teams working locally. Teams working remotely can be as cohesive as teams working locally. Cohesion is especially relevant for team performance when teams work remotely. Recommendations for future research: One suggestion is to add Social Network Analysis (SNA) in the study to enhance internal validity of team cohesion measurement. Additional research could be done by conducting a qualitative study to compare against the perceived cohesion and performance

The Simulation of the ATLAS Liquid Argon Calorimetry

n ATLAS, all of the electromagnetic calorimetry and part of the hadronic calorimetry is performed by a calorimeter system using liquid argon as the active material, together with various types of absorbers. The liquid argon calorimeter consists of four subsystems: the electromagnetic barrel and endcap accordion calorimeters; the hadronic endcap calorimeters, and the forward calorimeters. A very accurate geometrical description of these calorimeters is used as input to the Geant 4-based ATLAS simulation, and a careful modelling of the signal development is applied in the generation of hits. Certain types of Monte Carlo truth information ("Calibration Hits") may, additionally, be recorded for calorimeter cells as well as for dead material. This note is a comprehensive reference describing the simulation of the four liquid argon calorimeteter components