This article describes the design, construction and use of a calibration and monitoring system, based on movable 137Cs gamma-ray sources, for the ATLAS Tile Calorimeter (TileCal). The sources, propelled by a water-based liquid through tubes that traverse all the calorimeter's cells, produce signals that precisely characterise the response of each tile, thereby providing very granular and accurate data on the response of TileCal to particles. The system has been used to guide and control the quality of the optical instrumentation of all TileCal modules, to set and equalise the dynamic range of the response to physics data, and to set the energy scale of the readout system. In the ATLAS cavern, periodic measurements of the whole detector's response to 137Cs sources allow monitoring the uniformity and stability of all the calorimeter's cells as well as maintaining precise knowledge of its energy calibration. The design of the source hydraulic drive system's hardware and software, the data acquisition system and the data processing algorithms are described. Finally, the results of this two-decade program are shown.

The production cross-sections for W +/- and Z bosons are measured using ATLAS data corresponding to an integrated luminosity of 4.0 pb-1 collected at a centre-ofmass energy v s = 2.76 TeV. The deca ...

Measurements of dijet p T correlations in Pb + Pb and pp collisions at a nucleon–nucleon centre-of- mass energy of √ s NN = 2 . 76 TeV are presented. The measurements are performed with the ATLAS detector at the Large Hadron Collider using Pb + Pb and pp data samples corresponding to integrated luminosities of 0 . 14 nb − 1 and 4 . 0 pb − 1 , respectively. Jets are reconstructed using the anti- k t algorithm with radius parameter values R = 0 . 3 and R = 0 . 4. A background subtraction procedure is applied to correct the jets for the large underlying event present in Pb + Pb collisions. The leading and sub-leading jet transverse momenta are denoted p T 1 and p T 2 . An unfolding procedure is applied to the two-dimensional ( p T 1 , p T 2 ) distributions to account for experimental effects in the measurement of both jets. Distributions of ( 1 / N ) d N / d x J , where x J = p T 2 / p T 1 , are presented as a function of p T 1 and collision centrality. The distributions are found to be similar in peripheral Pb + Pb collisions and pp collisions, but highly modified in central Pb + Pb collisions. Similar features are present in both the R = 0 . 3 and R = 0 . 4 results, indicating that the effects of the underlying event are properly accounted for in the measurement. The results are qualitatively consistent with expectations from partonic energy loss models.

The Tile Calorimeter (TileCal) is the hadronic calorimeter covering the central region of the ATLAS detector at the LHC. It is a sampling calorimeter consisting of alternating thin steel plates and scintillating tiles. Wavelength shifting fibers coupled to the tiles collect the produced light and are read out by photomultiplier tubes. Currently, an analog sum of the processed signal of several photomultipliers serves as input to the first level of trigger. Photomultiplier signals are then digitized and stored on detector and are only transferred off detector once the first trigger acceptance has been confirmed. The Large Hadron Collider (LHC) has envisaged a series of upgrades towards a High Luminosity LHC (HL-LHC) delivering five times the LHC nominal instantaneous luminosity. The ATLAS Phase II upgrade, in 2024, will accommodate the detector and data acquisition system for the HL-LHC. In particular, TileCal will undergo a major replacement of its on- and off-detector electronics. All signals will be digitized and then transferred directly to the off-detector electronics, where the signals will be reconstructed, stored, and sent to the first level of trigger at a rate of 40 MHz. This will provide better precision of the calorimeter signals used by the trigger system and will allow the development of more complex trigger algorithms. Changes to the electronics will also contribute to the reliability and redundancy of the system. Three different front-end options are presently being investigated for the upgrade. Results of extensive laboratory tests and with beams of the three options will be presented, as well as the latest results on the development of the power distribution and the off-detector electronics.

The ATLAS experiment at the CERN Large Hadron Collider has performed searches for new, heavy bosons decaying to W W , W Z and Z Z final states in multiple decay channels using 20 . 3 fb − 1 of pp collision data at √ s = 8 TeV. In the current study, the results of these searches are combined to provide a more stringent test of models predicting heavy resonances with couplings to vector bosons. Direct searches for a charged diboson resonance decaying to W Z in the (cid:3) ν (cid:3) (cid:3) (cid:3) (cid:3) ( (cid:3) = μ , e ), (cid:3)(cid:3) q ¯ q , (cid:3) ν q ¯ q and fully hadronic final states are combined and upper limits on the rate of production times branching ratio to the W Z bosons are compared with predictions of an extended gauge model with a heavy W (cid:3) boson. In addition, direct searches for a neutral diboson resonance decaying to W W and Z Z in the (cid:3)(cid:3) q ¯ q , (cid:3) ν q ¯ q , and fully hadronic final states are combined and upper limits on the rate of production times branching ratio to the W W and Z Z bosons are compared with predictions for a heavy, spin-2 graviton in an extended Randall–Sundrum model where the Standard Model fields are allowed to propagate in the bulk of the extra dimension. © 2016 CERN for the benefit of the ATLAS Collaboration. Published by Elsevier B.V. This is an open

The ATLAS Tile Calorimeter collaboration assesses the quality of calibration data in order to ensure its proper operation. A number of tasks is then performed by executing several tools and accessing web systems, which were independently developed to meet distinct collaboration's requirements and do not necessarily are connected with each other. Thus, to attend the collaboration needs, several programs are usually implemented without a global perspective of the detector, requiring basic software features. In addition, functionalities may overlap in their objectives and frequently replicate resources retrieval mechanisms.Tile-in-ONE is a designed and implemented platform that assembles various web systems used by the calorimeter community through a single framework and a standard technology. It provides an infrastructure to support the code implementation, avoiding duplication of work while integrating with an overall view of the detector status. Database connectors smooth the process of information access since developers do not need to be aware of where records are placed and how to extract them. Within the environment, a dashboard stands for a particular Tile operation aspect and gets together plug-ins, i.e. software components that add specific features to an existing application. A server contains the platform core, which represents the basic environment to deal with the configuration, manage user settings and load plug-ins at runtime. A web middleware assists users to develop their own plug-ins, perform tests and integrate them into the platform as a whole. Backends are employed to allow that any type of application is interpreted and displayed in a uniform way. This paper describes Tile-in-ONE web platform.

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead–lead collisions at √ s NN = 2 . 76 TeV corresponding to an integrated luminosity of approximately 7 μb − 1 , ATLAS has measured jets with a calorimeter system over the pseudorapidity interval | η | < 2 . 1 and over the transverse momentum range 38 < p T < 210 GeV. Jets were reconstructed using the anti- k t algorithm with values for the distance parameter that determines the nominal jet radius of R = 0 . 2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet “central-to-peripheral ratio,” R CP . Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. R CP varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.

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 light is collected in wave-length shifting (WLS) fibers and is read out with photomultipliers. In the characteristic geometry of this calorimeter the tiles lie in planes perpendicular to the beams, resulting in a very simple and modular mechanical and optical layout. This paper focuses on the procedures applied in the optical instrumentation of the calorimeter, which involved the assembly of about 460,000 scintillator tiles and 550,000 WLS fibers. The outcome is a hadronic calorimeter that meets the ATLAS performance requirements, as shown in this paper.

This paper summarises the mechanical construction and installation of the Tile Calorimeter for the ATLAS experiment at the Large Hadron Collider in CERN, Switzerland. The Tile Calorimeter is a sampling calorimeter using scintillator as the sensitive detector and steel as the absorber and covers the central region of the ATLAS experiment up to pseudorapidities +/- 1.7. The mechanical construction of the Tile Calorimeter occurred over a period of about 10 years beginning in 1995 with the completion of the Technical Design Report and ending in 2006 with the installation of the final module in the ATLAS cavern. During this period approximately 2600 metric tons of steel were transformed into a laminated structure to form the absorber of the sampling calorimeter. Following instrumentation and testing, which is described elsewhere, the modules were installed in the ATLAS cavern with a remarkable accuracy for a structure of this size and weight.

Citation Aad, G., B. Abbott, J. Abdallah, S. Abdel Khalek, A.A. Abdelalim, O. Abdinov, B. Abi, et al. “Measurement of W and Z Production Cross Sections in Pp Collisions at s = 7 TeV and Limits on Anomalous Triple Gauge Couplings with the ATLAS Detector.” Physics Letters B 717, no. 1–3 (October 2012): 49–69. © 2012 CERN As Published http://dx.doi.org/10.1016/j.physletb.2012.09.017 Publisher Elsevier

The isospin symmetry-breaking (ISB) decay f 1(1285) → π+π−π0 has been studied at the VES facility. The branching ratio is measured: \(\frac{{BR\left( {f_1 \to \pi ^ + \pi ^ - \pi ^0 } \right)}}{{BR\left( {f_1 \to \eta \pi ^ + \pi ^ - } \right)}} = 0.86 \pm 0.16_{ - 0.20}^{ + 0.70} \%\). An upper limit for the f 1 decay into ρ(770)π is obtained: BR(f 1(1285) → ρ +−π−+) < 0.31% at 95% CL.

The reconstruction of photons in the ATLAS detector is stud ied with data taken during the 2004 Combined Test Beam, where a full slice of the ATLAS de tector was exposed to beams of particles of known energy at the CERN SPS. The results pres ent d show significant differences in the longitudinal development of the electromagnetic sho wer between converted and unconverted photons as well as in the total measured energy. The potentia l to use the reconstructed converted photons as a means to precisely map the material of the tracke r in front of the electromagnetic calorimeter is also considered. All results obtained are co mpared with a detailed Monte-Carlo simulation of the test-beam setup which is based on the same s imulation and reconstruction tools as those used for the ATLAS detector itself.

The charge-exchange reaction π - p → ω(780)ɸ(1020)n is studied with the VES setup. The (ωΦ) system is observed at relatively low background. Its invariant mass distribution peaks near threshold. The two-particles partial wave analyses shows that the J PC = 0 ++ state dominates. Comparison with scalar wave in ωω system at the comparable mass gives evidence for violation of the OZI rule. Another subject is a search for possible transition f 0 (980) → a 0 (980), which violates the isospin symmetry.

In 2004 at the ATLAS (A Toroidal LHC ApparatuS) combined test beam, one slice of the ATLAS barrel detector (including an Inner Detector set-up and the Liquid Argon calorimeter) was exposed to particles from the H8 SPS beam line at CERN. It was the first occasion to test the combined electron performance of ATLAS. This paper presents results obtained for the momentum measurement p with the Inner Detector and for the performance of the electron measurement with the LAr calorimeter (energy E linearity and resolution) in the presence of a magnetic field in the Inner Detector for momenta ranging from 20 GeV/c to 100 GeV/c. Furthermore the particle identification capabilities of the Transition Radiation Tracker, Bremsstrahlungs-recovery algorithms relying on the LAr calorimeter and results obtained for the E/p ratio and a way how to extract scale parameters will be discussed.

A fully instrumented slice of the ATLAS detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the results of the measurements of the response of the barrel calorimeter to hadrons with energies in the range 20–350GeV and beam impact points and angles corresponding to pseudo-rapidity values in the range 0.2–0.65 are reported. The results are compared to the predictions of a simulation program using the Geant 4 toolkit.

The response of pions and protons in the energy range of 20–180GeV, produced at CERN's SPS H8 test-beam line in the ATLAS iron–scintillator Tile hadron calorimeter, has been measured. The test-beam configuration allowed the measurement of the longitudinal shower development for pions and protons up to 20 nuclear interaction lengths. It was found that pions penetrate deeper in the calorimeter than protons. However, protons induce showers that are wider laterally to the direction of the impinging particle. Including the measured total energy response, the pion-to-proton energy ratio and the resolution, all observations are consistent with a higher electromagnetic energy fraction in pion-induced showers. The data are compared with GEANT4 simulations using several hadronic physics lists. The measured longitudinal shower profiles are described by an analytical shower parametrization within an accuracy of 5–10%. The amount of energy leaking out behind the calorimeter is determined and parametrized as a function of the beam energy and the calorimeter depth. This allows for a leakage correction of test-beam results in the standard projective geometry.

The charge-exchange reaction it pi(-) p -> n omega(780)phi(1020) is studied with the YES setup. The (omega phi) system is observed at relatively low background. Its invariant mass distribution peaks near threshold. The two-particles partial wave analyses shows that the J(PC) = 0(++) state dominates. This wave is compared with 0(++) component in the (omega omega) system at the comparable mass, which was measured earlier.

A fully instrumented slice of the ATLAS central detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the response of the central calorimeters to pions with energies in the range between 3 and 9 GeV is presented. The linearity and the resolution of the combined calorimetry (electromagnetic and hadronic calorimeters) was measured and compared to the prediction of a detector simulation program using the toolkit Geant 4.