17177612
The optical instrumentation of the ATLAS Tile Calorimeter
The Tile Calorimeter, covering the central region of the ATLAS experiment up to pseudorapidities of +/-1.7, is a sampling device built with scintillating tiles that alternate with iron plates. The ...
96502755
Charged-particle multiplicities inppinteractions measured with the ATLAS detector at the LHC
New Journal of Physics The open–access journal for physics Charged-particle multiplicities in pp interactions measured with the ATLAS detector at the LHC The ATLAS Collaboration New Journal of Physics 13 (2011) 053033 (68pp) Received 22 December 2010 Published 19 May 2011 Online at http://www.njp.org/ doi:10.1088/1367-2630/13/5/053033 Measurements √ are presented from proton–proton collisions at centre-of-mass energies of s = 0.9, 2.36 and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum- bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. The results are compared to each other and to various Monte Carlo (MC) models, including a new AMBT1 pythia6 tune. In all the kinematic regions considered, the particle multiplicities are higher than predicted by the MC models. The central charged-particle multiplicity per event and unit of pseudorapidity, for tracks √ with p T > 100 MeV, is measured to be 3.483 ± 0.009 (stat) (syst) at s = 0.9 TeV and 5.630 ± 0.003 (stat) ± 0.169 (syst) at s = 7 TeV. Abstract. New Journal of Physics 13 (2011) 053033 © 2011 CERN for the benefit of the ATLAS Collaboration, published under licence by IOP Publishing Ltd for the Institute of Physics and Deutsche Physikalische Gesellschaft. Content may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation and DOI.
118662023
Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics
A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN.
120805024
Search for First Generation Scalar Leptoquarks in pp Collisions at $\sqrt{s}=7$ TeV with the ATLAS Detector
We report a search for first generation scalar leptoquarks using 1.03 fb−1 of proton–proton collisions data produced by the Large Hadron Collider at and recorded by the ATLAS experiment. Leptoquarks are sought via their decay into an electron or neutrino and a quark, producing events with two oppositely charged electrons and at least two jets, or events with an electron, missing transverse momentum and at least two jets. Control data samples are used to validate background predictions from Monte Carlo simulation. In the signal region, the observed event yields are consistent with the background expectations. We exclude at 95% confidence level the production of first generation scalar leptoquark with masses when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5).
66116773
A mobile data acquisition system
A mobile data aquisition (MobiDAQ) was developed for the ATLAS central hadronic calorimeter (TileCal). MobiDAQ has been designed in order to test the functionalities of the TileCal front-end electronics and to acquire calibration data before the final back-end electronics were built and tested. MobiDAQ was also used to record the first cosmic ray events acquired by an ATLAS subdetector in the underground experimental area.
202105722
Search for strong gravity signatures in same-sign dimuon final states using the ATLAS detector at the LHC
A search for microscopic black holes has been performed in a same-sign dimuon final state using 1.3 fb(-1) of proton-proton collision data collected with the ATLAS detector at a centre of mass energy of 7 TeV at the CERN Large Hadron Collider. The data are found to be consistent with the expectation from the Standard Model and the results are used to derive exclusion contours in the context of a low scale gravity model.
30333745
First beam operation of the CMS calorimeter trigger synchronization boards
The CMS experiment uses information from its electromagnetic and hadronic calorimeters and muon detectors to decide whether to readout the whole detector. For such a task to be successful, all trigger primitives pushed through the trigger decision tree must be flawlessly aligned in time for operation at 40 MHz. Both calorimeters in CMS use the Synchronization Link Board for this purpose. In this article we report on the results of tests of this board using realistic beam conditions, which demonstrate the soundness of the adopted architecture and synchronization principle.
119257623
An updated analysis on the rise of the hadronic total cross-section at the LHC energy region
pp elastic scattering above 5 GeV is presented. The dataset includes the recent high-precision TOTEM measurements of the pp total and elastic (integrated) cross-sections at 7 TeV and 8 TeV. Following previous works, the leading high-energy contribution for the total cross-section (�tot) is parametrized as ln(s/sh), where and sh are free real fit parameters. Singly-subtracted derivative dispersion relations are used to connecttot and the rho parameter (�) in an analytical way. Different fit procedures are considered, including individual fits totot data, global fits totot anddata, constrained and unconstrained data reductions. The results favor a rise of thetot faster than the log-squared bound by Froissart and Martin at the LHC energy region. The parametrization fortot is extended to fit the elastic cross-section (�el) data with satisfactory results. The analysis indicates an asymptotic ratioel/�tot consistent with 1/3 (as already obtained in a previous work). A critical discussion on the correlation, practical role and physical implications of the parameters and sh is presented. The discussion confronts the 2002 prediction oftot by the COMPETE Collaboration and the recent result by the Particle Data Group (2012 edition of the Review of Particle Physics). Some conjectures on possible implications of a fast rise of the proton-proton total cross-section at the highest energies are also presented.
26680612
Search for solar axions by the CERN axion solar telescope with 3He buffer gas: closing the hot dark matter gap.
The CERN Axion Solar Telescope has finished its search for solar axions with (3)He buffer gas, covering the search range 0.64 eV ≲ ma ≲ 1.17 eV. This closes the gap to the cosmological hot dark matter limit and actually overlaps with it. From the absence of excess x rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of gaγ ≲ 3.3 × 10(-10)  GeV(-1) at 95% C.L., with the exact value depending on the pressure setting. Future direct solar axion searches will focus on increasing the sensitivity to smaller values of gaγ, for example by the currently discussed next generation helioscope International AXion Observatory.
73558306
Precision measurements in the top quark sector with the CMS experiment at the LHC
A review of the measurements of the t production cross section (inclusive and differential) performed by the CMS experiment at the LHC is given. The results are used to constrain the magnitude of most of the relevant systematics affecting precision measurements in the top quark sector. In addition from the determination of the top quark pair production cross section it is possible to determine the strong coupling constant as ?S(mZ) = 0.1178+0.0046?0.0040 in agreement with the current world average. After the combination of several channels and techniques explored to measure the top quark mass in data, a precise determination of this quantity is made at CMS: mt = 173.4?0.4stat ? 0.9syst GeV. The measurement of the difference ?mt = mt ? m is also presented.
120562248
Test beam operation of the CMS calorimeter trigger synchronization boards
The CMS experiment uses information from its electromagnetic and hadronic calorimeters and muon detectors to decide whether to read out the whole detector. For such a task to be successful, all trigger primitives pushed through the trigger decision tree must be flawlessly aligned in time for operation at 40 MHz. Both calorimeters in CMS use the Synchronization Link Board for this purpose. In this article we report on the test results of this board using the bunched beams available in the H4 electron beam line at CERN.