Search

Abstract: Jet cross sections have been measured in proton-proton collisions at a centre-of-mass energy of 7 TeV using the ATLAS detector. The measurement uses an integrated luminosity of 17 nb−1 recorded at the Large Hadron Collider. The anti- algorithm is used to identify jets with a jet resolution parameter . The dominant uncertainty comes from the jet energy scale, which is determined to within 7% for central jets above 60 GeV transverse momentum. Inclusive single-jet differential cross sections are presented as functions of jet transverse momentum and rapidity. The results are compared to expectations based on next-to-leading-order QCD, which agree with the data, providing a validation of the theory in a new kinematic regime. [Copyright &y& Elsevier]

We present an Optimal Filtering (OF) algorithm to reconstruct the energy, time and pedestal of a photomultiplier signal from its digital samples. The OF algorithm was first developed for liquid ionization calorimeters, its implementation in scintillator calorimeters, specifically in the ATLAS hadronic Tile calorimeter (TileCal), is the aim of this study. The objective is to implement the algorithm on the DSPs of the Read Out Driver cards in order to reconstruct online the energy of the calorimeter and provide it to the second level trigger. The algorithm is tested and compared with a plain filtering algorithm using both calibration and real data from the TileCal detector. The results are promising specially in the regions where the electronic noise contributes significantly to the resolution. [ABSTRACT FROM AUTHOR]

In this letter, we evaluate the potential of linear e + e − colliders to measure the top quark mass in radiative events and in a suitable short-distance scheme. We present a calculation of the differential cross section for production of a top quark pair in association with an energetic photon from initial state radiation, as a function of the invariant mass of the t t ¯ system. This matched calculation includes the QCD enhancement of the cross section around the t t ¯ production threshold and remains valid in the continuum well above the threshold. The uncertainty in the top mass determination is evaluated in realistic operating scenarios for the Compact Linear Collider (CLIC) and the International Linear Collider (ILC), including the statistical uncertainty and the theoretical and experimental systematic uncertainties. With this method, the top quark mass can be determined with a precision of 110 MeV in the initial stage of CLIC, with 1 ab−1 at s = 380 GeV, and with a precision of approximately 150 MeV at the ILC, with L = 4 ab−1 at s = 500 GeV. Radiative events allow measurements of the top quark mass at different renormalization scales, and we demonstrate that such a measurement can yield a statistically significant test of the evolution of the MSR mass m t MSR (R) for scales R < m t. [ABSTRACT FROM AUTHOR]

This paper describes the concepts behind the TileCal design, as well as the requirements and the constraints that have finally produced the ATLAS central hadronic calorimeter. [ABSTRACT FROM AUTHOR]

TileCal is the hadronic tile calorimeter of the ATLAS experiment at LHC/CERN. The central element of the back-end system of the TileCal detector is the Read-Out Driver (ROD).The main components of the TileCal ROD are the Digital Signal Processors (DSPs) placed on the Processing Unit (PU) daughterboards. This paper presents a detailed description of the code developed for the DSPs. The code is divided into two different parts: the first part contains the core functionalities and the second part the reconstruction algorithms. The core acts as an operating system and controls configuration, data reception and transmission and synchronization between front-end data and the Timing, Trigger and Control (TTC) information. The reconstruction algorithms implemented on the DSP are the Optimal Filtering (OF), Muon Tagging (MTag) and Missing ET calculation. The OF algorithm reconstructs the deposited energy and the phase of the signal for every calorimeter channel within a front-end module. This reconstructed energy is used by the MTag algorithm to tag low transverse momentum muons that may escape the ATLAS muon spectrometer Level 1 trigger whereas the Missing ET algorithm computes the total transverse energy and the projection on X and Y axis for the entire module that will be used by the Level 2 trigger system. [ABSTRACT FROM AUTHOR]

The ATLAS Hadronic Tile Calorimeter detector (TileCal) is an iron-scintillating tiles sampling calorimeter de- signed to operate at the Large Hadron Collider accelerator at CERN. The central element of the back-end system of the TileCal detector is a 9U VME Read-Out Driver (ROD) board. The operation of the TileCal calorimeter requires a total of 32 ROD boards. This paper summarizes the tests performed during the ROD production and the results obtained. Data processing is performed in the ROD by digital signal processors, whose operation is based on the use of online algorithms such as the optimal filtering algorithm for the signal amplitude, pedestal and time reconstruction and the online Muon tagging algorithm which identifies low transverse momentum muons. The initial performance of both algorithms run during commissioning is also presented in this paper. [ABSTRACT FROM AUTHOR]

This paper describes the development of the optical multiplexer board (OMB), also known as PreROD board, for the TileCal readout system in the ATLAS experiment. The aim of this board is to overcome the problems that may arise in the integrity of data due to radiation effects. The solution adopted has been to add redundancy to data transmission and so two optical fibers with the same data come out from the detector front end boards. The OMB has to decide in real time which fiber, eventually, carries data with no errors switching it to the output link connected to the read out driver (ROD) motherboard where data processing takes place. Besides, the board may be also used as a data injector for testing purposes of the ROD motherboard. The paper describes the design and tests of the first prototype, implemented as a 6U VME64x slave module, including both hardware aspects, focusing on signal integrity problems, and firmware aspects, dealing with the cyclic redundancy code algorithms used to check data consistency used to make the decision. [ABSTRACT FROM AUTHOR]