Aliaksei Hrynevich on behalf of the ATLAS Collaboration Performance of the INSTR17 Novosibirsk ATLAS Tile Calorimeter March 1 st , 2017
Introduction ATLAS detector Hadronic Tile Calorimeter 12 m 8.5m 2900 tons • ATLAS is the multipurpose detector • Tile Calorimeter is the hadronic at the LHC. sampling detector within ATLAS • Consists of internal tracker, • Located at the outer barrel of the electromagnetic and hadronic calorimeters, ATLAS calorimetry system and external muon spectrometer. • Intended for energy measurements • Allows a wide spectrum of high energy of jets, single hadrons, tau-particles physics studies both within the Standard and missing transverse energy 2 Model and Beyond.
� Tile Calorimeter structure Long barrel (LB) 𝜽 < 𝟐. 𝟏 Extended barrel (EB) 𝟏. 𝟗 < 𝜽 < 𝟐. 𝟖 D layer BC layer Crack / Gap A layer • Tile Calorimeter consists of one central Long Barrel cylinder and two Extended Barrels cylinders covering | η | < 1.7 and 0< 𝜒 < 2 𝜌 • Segmented into 64 modules in azimuth Has three radial layers ( 7.4 𝜇 ./0 ) and the longitudinal Gap/Crack layer • between barrels • The granularity is Δη x Δφ = 0.1 x 0.1 (0.2 x 0.1 in the last radial layer) • Consists of 5182 readout cells ⁄ ⁄ 3 Designed energy resolution 𝜏 𝐹 = 50% 𝐹 ⊕ 3% •
Tile Calorimeter Read-Out 3-in-1 Digitizer Interface Detector signals OTx PMT 64 ADC S M to ROD FORMAT E E 1 ADC L M Analog PIPELINE GLINK Σ trigger sums Low amplification gain High amplification gain Tile Calorimeter is the sampling detector made of plastic scintillator and steel as absorber (scintillator only in crack/gap cells) PMT • Signal from each cell is routed by WLS to two PMTs Photomultiplier Wavelength (giving 9852 readout channels) Shifting Fiber (WLS) Wave-length shifting fiber • Analog signal from each PMT is amplified by two Scintillator Steel Scintillator Steel gains (1:64), shaped and digitized by 3-in-1 card every 25 ns • The digitised samples are stored in pipeline awaiting for L1 trigger accept • Analog signals contribute to L1 trigger • The slower Integrator readout is routed before Source tubes amplifiers and used for Cs (or MinBias) calibration 4
Signal reconstruction �� �� �� • 7 sets of ADC counts (samples) spaced by 25 ns are used for signal reconstruction (150 ns window) • Amplitude ( 𝐵 ), time ( 𝑢 = ) and quality factors ( 𝑅𝐺 ) are obtained with Optimal Filter (OF) algorithm • OF uses weighted sum of samples ( 𝑇 . ) in order to minimise noise , 𝑢 = = C • 𝐵 = ∑ 𝑏 . 𝑇 . D ∑ 𝑐 . 𝑇 . , 𝑅𝐺 = ∑(𝑇 . − (𝐵 . + 𝐵𝑢 = . + 𝑄𝑓𝑒)) N • The time calibration is important for OF performance • Time measurements and calibration is performed using “splash” events (single beam events hitting closed collimator) • Tuned later with collisions, exploiting jet events The slope matches the time 5 the particles cross calorimeter across beam axis
Energy calibration Scint Electronics PMT . 𝐹 = 𝐵 [ 𝐷 QY [ 𝐷 WXYUZ [ 𝐷 DPQ→SQ [ 𝐷 SQ→TUV • The energy calibration allows to reconstruct the energy of jets in GeV. • Performed using various calibration systems (with precision of 1% of the cell response) • The injection of known charge to digitiser (CIS) allows to calibrate electronics ( 𝐷 DPQ→SQ ) • 𝐷 SQ→TUV conversion factor has been defined at testbeam via the response to electron beams of known momentum (setting the absolute energy scale) • Injected laser light with known intensity allows to equalise PMT response ( 𝐷 WXYUZ ) • Cs source moved through all the cells (except crack scintillators) allows to equalise scintillator response ( 𝐷 QY ) • Scintillator response equalisation can be improved using Minimum Bias events 6
Energy calibration: Cs 𝐹 = 𝐵 [ 𝐷 QY [ 𝐷 WXYUZ [ 𝐷 DPQ→SQ [ 𝐷 SQ→TUV • Calibration of the initial part of the Deviation from expected response in 2009-2015 signal readout path (scintillator response) with movable radioactive 137 Cs γ -sources ( 𝐹 \ = 0.662 𝑁𝑓𝑊 ) • The signal is read out through a special “slow” integrator • The correction applies to maintain global conversion factor and corrects for residual cell differences • The calibration is usually performed The deviation from expected response rises ~1th per month (was not available in due irradiation effects in scintillators, variations of PMT gain. 2016 due to water leak) 7
Energy calibration: Laser PMT gain variation in 2016 𝐹 = 𝐵 [ 𝐷 QY [ 𝐷 WXYUZ [ 𝐷 DPQ→SQ [ 𝐷 SQ→TUV Scintillator irradiation in 2016 Highest PMT gain variations are observed during 2016 pp collisions: 5% to 10% in cells closest to beam pipe • Laser light pulses are sent directly to PMT to measure PMT gain variation and correct for non-linearities of the readout electronics • Laser is also used for time calibration and The difference between Laser monitoring and MinBias (or Cesium) • Calibration is usually done 2 times per week response allows to estimate the effect of the scintillators (or even more often in case Cs is n/a) irradiation. 8
Energy calibration: CIS High gain 𝐹 = 𝐵 [ 𝐷 QY [ 𝐷 WXYUZ [ 𝐷 DPQ→SQ [ 𝐷 SQ→TUV • Calibration of the front-end electronic gains with a charge injection system (CIS) located in 3-in-1 card (allows to Low gain test each channel) • Fires both amplification gains • Corrects for non-linearities of electronics associated to the PMTs • Performed 2 times per week for monitoring CIS calibration was very stable during 2016 data taking 9
Detector status by the end of 2016 pp collisions Evolution of TileCal masked cells in 2010-2016 The 2016 was the best year for the Tile Calorimeter from the beginning of LHC data taking. • Good stability of electronics The eta-phi map of masked cells in 2016 Less than 1% cells were excluded from reconstruction at the end of 2016 pp collisions. • One module is excluded due to the water leak in cooling system • Another module had readout problems 10
Noise performance Electronics noise Pile-up noise Normalised entries 1 Noise [MeV] 900 ATLAS Preliminary ATLAS Preliminary Tile Calorimeter Tile Calorimeter 800 − s =13 TeV 1 s =13 TeV 10 700 EBA A12 Data MC EBA 600 − 2 10 A13 500 B13 D6 400 − 3 10 µ σ MC16 < >=20 =122.53 MeV E3 300 µ σ MC16 < >=30 =150.34 MeV µ σ Data 2016 < >=20 =131.61 MeV − 200 4 10 µ σ Data 2016 < >=30 =161.69 MeV − − − 100 600 400 200 0 200 µ 400 600 µ Data/MC Data < >=20 / MC < >=20 2 µ µ Data < >=30 / MC < >=30 1.5 0 10 20 30 40 50 1 µ < > 0.5 − − − 600 400 200 0 200 400 600 E [MeV] • Electronics noise is measured • Energy distribution in Tile Calorimeter cells and monitored in special runs gets wider and larger in presence of pile-up without collisions • Total noise (standard deviation of the energy • Defined as the width of distribution) is increasing as the function of Gaussian fit to the average number of interactions per bunch reconstructed cell energy crossing (driven by pile-up contribution) distributions • Cells closest to beam beam pipe are affected • Stays at the level of 15-20 MeV by higher noise for most of cells 11
Performance with jets and hadrons • The ratio of the calorimeter energy over the track momentum (E/p) of single hadrons is used to evaluate TileCal uniformity and linearity during data taking • The calorimeter calibration at the electromagnetic scale results in E/p<1, while jets are further calibrated in a more complicated way • Good linearity and uniformity is observed. The data/MC agreement is within 3%. • The jet energy resolution is below 10% for jets with p b > 100 GeV . • The constant term is at the level of 3%, compatible with the expectations 12
Performance with muons • Muons from cosmic rays, beam halo and collisions (e.g. 𝑋 → 𝜈𝜉 events) are exploited to study the electromagnetic energy scale in-situ • Energy deposited by muons in scintillator proportional to its path length (dE/dx) Cosmic muons • 1% response non-uniformity with 𝜃 in Long Barrel • 2-3% response non-uniformity with 𝜃 in Extended Barrel • The response is uniform across 𝜒 within 2% Collision muons (W-> 𝜈𝜉 ) 1.8 1.8 1.8 ATLAS Preliminary ATLAS Preliminary ATLAS Preliminary • A good energy response Tile Calorimeter Tile Calorimeter Tile Calorimeter A-layer BC-layer D-layer 1.7 1.7 1.7 2012 s = 8 TeV 2012 s = 8 TeV 2011 s = 7 TeV uniformity is found with Monte Carlo Monte Carlo Monte Carlo x [MeV/mm] x [MeV/mm] x [MeV/mm] 1.6 1.6 1.6 8 TeV collisions data in 1.5 1.5 1.5 ∆ ∆ ∆ all calorimeter layers E/ E/ E/ ∆ ∆ ∆ 1.4 1.4 1.4 • The data/MC agreement 1.3 1.3 1.3 1.06 1.06 1.06 〉 1.5 1 0.5 0 0.5 1 1.5 〉 1.5 1 0.5 0 0.5 1 1.5 〉 1.5 1 0.5 0 0.5 1 1.5 is within 3% MC MC MC 1.04 1.04 1.04 1.02 1.02 1.02 〈 〈 〈 / / / 〉 1 〉 1 〉 1 data data data 0.98 0.98 0.98 13 0.96 0.96 0.96 〈 〈 〈 1.5 1 0.5 0 0.5 1 1.5 1.5 1 0.5 0 0.5 1 1.5 1.5 1 0.5 0 0.5 1 1.5 − − − − − − − − − pseudorapidity pseudorapidity pseudorapidity η η η
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