Test Beam Results on the ATLAS Electromagnetic Calorimeters Lucia Di Ciaccio – LAPP Annecy (on behalf of the ATLAS LAr Group) OUTLINE Description of the calorimeters Construction status Test beam results E.M. LAr Calorimeters : |η|< <|η|<3.2 BarrelBarrel End-capsEnd-caps ∼ 8 m

HEP 2003 – L.DiCiaccio - 2 BARREL CALORIMETER Lead-liquid argon with accordion geometry 2x16 modules 3.4 tons each gap thickness 2.1 mm absorbers mm HV 2kV MIDDLE STRIP 2 half barrels BACK γ/π° separation main energy deposition had/em separation PRESAMPLER |η|<1.8 for dead material φ η >22 X ₀ η R

HEP 2003 – L.DiCiaccio - 3 END-CAP CALORIMETER Structure similar to barrel but : 8 modules per wheel gap varying from 0.9 to 3.1 mm HV set in 9 η sectors high granularity( ∽ 2 · 10 ⁵ channels) CONSTRUCTION STATUS completed 32/32 modules 11/16 modules completed Barrel + End-cap calorimeters: Barrel: End cap: absorbers 2nd half barrel assembled 1st half barrel assembled, inserted in cryostat and tested 1st wheel assembled in final (vertical) position …on schedule in final (horizontal) position 2 wheels

HEP 2003 – L.DiCiaccio - 4 3m 3 layers 2  /16 CONSTRUCTION STATUS in cryostat (26/2/03) and connections (may 03) connections (may 03) Half barrel after insertion ( ∼ channels) End-cap wheel in vertical position (24/6/03) End-cap module construction: Barrel module construction:

HEP 2003 – L.DiCiaccio - 5 TEST BEAM SETUP located at CERN North Area(H6 & H8) located at CERN North Area(H6 & H8) electron beam GeV electron beam GeV read-out similar to Atlas but not radiation hard read-out similar to Atlas but not radiation hard : 4 barrel, 3 end-cap final modules : 4 barrel, 3 end-cap final modules BC1 BC2 BC3 BC4 S1 pion counter muon counter Fe S3 S4 Pb η=0 topics studied: energy resolution, linearity, topics studied: energy resolution, linearity, uniformity, position, angular & time resolution, MIP response, γ/π° separation, noise, X-talk, … : barrel, end-cap full size prototypes : barrel, end-cap full size prototypes η φ η=1.4 ATLAS int. point ∨ 3X ₀ 5 λ φ η 2002: combined electromagnetic-hadronic end-caps 2002: combined electromagnetic-hadronic end-caps

HEP 2003 – L.DiCiaccio - 6 ENERGY RECONSTRUCTION 1rst step: Signal reconstruction Signal after shaping is sampled every 25 ns E = Σ a i × S i O.F. method allows: noise reduction corrections for sampling To estimate the shape of the physics signal the calibration signals E in a cell: are used + procedure to take into account: different calibration/physicsdifferent calibration/physics injected waveforms different calibration/physics injection points a i are computed with from the signal shape and the noise autocorrelation matrix off the peak before after shaping samplings S i ( in GeV, ADC ⇒ GeV from Optimal Filtering Optimal Filtering Amplitude Time (ns) Time(ns) Amplitude Residues ⃟ physics — predicted used to estimate the energy electronic calibration+‘first principles’

HEP 2003 – L.DiCiaccio - 7 ENERGY RECONSTRUCTION E=α *E PS +E strip +E middle +β*E back corrects for longitudinal leakages compensates for dead material ( β ⇒ 0 for E < 40 GeV ) 2nd step: Cluster reconstruction 3rd step: Corrections along η and φ for accordion φ trigger-clock phase discrete HV setting in the end-cap sectors + corrections for: (α and β obtained by minimizing the energy resolution at each η) (asynchronous runs) for finite cluster size modulations E(GeV) Norm. E η φ Δη = impact point Δt = 25ns time barrel barrel end-cap Δφ =0.1 η=

HEP 2003 – L.DiCiaccio - 8 ENERGY RESOLUTION σ/ E =a/ √E ⊕ b σ E / E =a/ √E ⊕ b Design goals (SM Higgs mainly, E): Design goals (SM Higgs mainly, E Tmiss ): constant term b ∼ 0.5 % in Δη ⅹ Δφ=0.2 ⅹ 0.4 radconstant term b ∼ 0.5 % in Δη ⅹ Δφ=0.2 ⅹ 0.4 rad sampling term a ~ 10 % √GeVsampling term a ~ 10 % √GeV ( when noise and beam spread subtracted) good agreement with MC good agreement with MC within requirements within requirements a=(10.35 ± 0.05) % b=( 0.27± 0.02) % Data Data a=8.95% b=0.33% η =0.48±0.01 END-CAP ⃘ MC E_beam(GeV) σ E /E(%) σ/E(%) σ E /E(%) e ⁻ impact point: Δφ= 0.02 rad BARREL noise subtracted no noise subtracted: a=6.8% b=0.19% c=180 MeV σ E /E= a/√E ⊕ b ⊕ c/E η = noise and beam spread subtracted Data MC η=1.9±0.01 Δφ=±0.01 rad energy scale from ‘first principles’ corrected at 5%

HEP 2003 – L.DiCiaccio - 9 BARREL UNIFORMITY RESPONSE H→2γ requires a global constant term < 0.7% Energy(GeV) rms/E= 0.57% η # of events Energy (GeV) 10%/√E ⊕ 0.3% ⊕ 0.6% sampling term Module M10 σ E /E=0.98% 0.98% ∼ ‘cell’ constant term E233.6 GeV E peak = GeV Nev ∼ 9 10 ⁶ cell to cell non unif ⁵ 0 E peak =232.9 GeV max difference between 2 modules: 0.85% max Epeak difference between 2 modules: 0.85% all (4) barrel modules analysed: all (4) barrel modules analysed: rms/E= 0.67% for M10: ⇒ modules are ‘uniform’ /

HEP 2003 – L.DiCiaccio - 10 END CAP UNIFORMITY RESPONSE η Energy(GeV) φ (rad) η for the whole module σ/E = 0.5% σ Energy (GeV) Number of cells Module ECC5 (ΔηxΔφ ∼ 0.8x0.8) within specs

HEP 2003 – L.DiCiaccio - 11 POSITION & ANGULAR RESOLUTION η position resolution: η x10-4 END-CAP Strips and middle position measurements give vertex and angular resolution Middle Strip 245 GeV e ⁻ BARREL MC Data Data MC Δφ=±0.01 BARREL Energy(GeV) Energy (GeV) Δφ =±0.01 rad η= σ ( mm ) σ z ( mm ) σ θ ( mrad ) √E( GeV ) BARREL 1.5 η Ec=compartment energy Ei=cell energy ( important for non pointing γ) σ θ ( mrad )√E( GeV ) σ θ within specifications

HEP 2003 – L.DiCiaccio - 12 INTRINSIC TIME RESOLUTION tool to reject instrumental backgrounds GMSB searches (‘delayed’ γ) Cell energy(GeV) ⇒ σ t is estimated from cell to cell time differences σ t in physics ~ 70 ps at 70 GeV as expected Barrel Time resolution (ps) Time resolution : Time resolution : σ = time(cell pulse)-time(trigger) σ t = time(cell pulse)-time(trigger) dominated by the trigger time resolution ( ∼ 150 ps) all source to this σ are understood all source to this σ t are understood σ = time(cell 1) – time (cell 2) σ t = time(cell 1) – time (cell 2) (1)

HEP 2003 – L.DiCiaccio - 13 CONCLUSIONS & OUTLOOK construction and assembly on schedule. construction and assembly on schedule. Significant parts of the detector completed, Significant parts of the detector completed, Next steps: Next steps: insertion of second half barrel 08/2003 insertion of second half barrel 08/2003 barrel cryostat in the pit 07/2004 barrel cryostat in the pit 07/2004 insertion of end-cap wheels 09/2003 and 07/2004 insertion of end-cap wheels 09/2003 and 07/2004 end-cap cryostats in the pit 12/2004 and 06/2005 end-cap cryostats in the pit 12/2004 and 06/2005 Test beam results from final modules show that Test beam results from final modules show that the detector meets the physics requirements for the detector meets the physics requirements for the LHC physics. Work going on, main topics: the LHC physics. Work going on, main topics: ⇒ NIM paper on barrel and end-cap results ⇒ NIM paper on barrel and end-cap results barrel: trackers, em and barrel: trackers, em and end-cap: em, hadronic end-cap: em, hadronic Thinking is moving to commissioning andThinking is moving to commissioning and combined test beam in Next: Next: hadronic calorimeters, and forward calorimeters muons linearity linearity module response comparison module response comparison in situ calibration procedures 2004