Readiness of the ATLAS Tile Calorimeter for LHC collisions

TL;DR

This study assesses the readiness of the ATLAS TileCal for LHC collisions by evaluating its energy and timing calibration, noise performance, and data-quality stability across calibration systems (Cs source, laser, CIS), plus validation with cosmic muons and single-beam data. It demonstrates that EM scale transfer from testbeam to the ATLAS cavern is achieved with a total systematic uncertainty around 0.7%–4% depending on the component and time, and confirms sub-percent intercalibration stability. The results show high detector availability (≈99% functional cells), stable HV and temperature, and a timing precision at the 1–2 ns level within modules and across partitions, with a strong S/N for muon signals. Collectively, these findings indicate TileCal is ready for physics data-taking, with well-understood calibration pathways and cross-validated performance against MC simulations. The work provides a detailed blueprint for ongoing monitoring and calibration during LHC operation.

Abstract

The Tile hadronic calorimeter of the ATLAS detector has undergone extensive testing in the experimental hall since its installation in late 2005. The readout, control and calibration systems have been fully operational since 2007 and the detector successfully collected data from the LHC single beams in 2008 and first collisions in 2009. This paper gives an overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data. The detector operation status, noise characteristics and performance of the calibration systems are presented, as well as the validation of the timing and energy calibration carried out with minimum ionising cosmic ray muons data. The calibration systems' precision is well below the design of 1%. The determination of the global energy scale was performed with an uncertainty of 4%.

Figures (35)

• Figure 1: A cut-away drawing of the ATLAS inner detector and calorimeters. The Tile Calorimeter consists of one barrel and two extended barrel sections and surrounds the Liquid Argon barrel electromagnetic and endcap hadronic calorimeters. In the innermost radii of ATLAS, the inner detector (shown in grey) is used for precision tracking of charged particles.
• Figure 2: Segmentation in depth and $\eta$ of the Tile Calorimeter modules in the barrel (left) and extended barrel (right). The bottom of the picture corresponds to the inner radius of the cylinder. The Tile Calorimeter is symmetric with respect to the interaction point. The cells between two consecutive dashed lines form the first level trigger calorimeter tower.
• Figure 3: Schematic showing the mechanical assembly and the optical readout of the Tile Calorimeter, corresponding to a $\phi$ wedge. The various components of the optical readout, namely the tiles, the fibres and the photomultipliers, are shown. The trapezoidal scintillating tiles are oriented radially and normal to the beam line and are read out by fibres coupled to their non-parallel sides.
• Figure 4: Position in $\eta$ and $\phi$ of the masked cells representing the status on November 9th, 2009. The colours corresponding to numbers 1,2,3 show the number of layers masked for this ($\eta,\phi$) region. The non-integer numbers indicate that one readout channel of the cell is masked.
• Figure 5: Stability of the PMT high voltage with respect to its set value, averaging over all PMTs for two periods of 3 and 6 months (left) separated by the maintenance period. The distribution of the differences of the measured and the set HV values for all PMTs over the period considered is also shown (right).