ECAL intercalibrations EBEE ECAL startup insitu strategy and

ECAL intercalibrations (EB/EE) ECAL startup, in-situ strategy and interplay with the corrections scheme • Definitions and interplay with correction scheme • Intercalibration constants and cluster corrections • Intercalibrations at startup • In situ strategy and goal with first data • Use of “fast” intercalibration procedures • Validation, extraction of results, improvemeny on startup conditions • Summary Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008

ECAL Definitions • Estimate of electromagnetic particles’s energy in ECAL • E = F cluster G ci Ai • Calibrated Rec. Hit • G global scale factor • Ai uncalibrated Rec. Hit (ADC counts) • ci channel-to-channel intercalibrations • Include bare intercalibrations, transparency corrections, temperature, … • F are cluster corrections (see Y. Maravin’s talk) Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008 • f( ) energy leakage known from TB (valid for unconverted ’s) • f(brem) parameterised on brem measuring quantities

ECAL Interplay with cluster corrections • Definition of calibrated Rec. Hits related to correction scheme • Adopted definition tied to test beam “single crystal” calibration • Intercalibrate the relative response to energy deposit in single crystals • More info at: • http: //cmsdoc. cern. ch/cms/performance/ecal/calib-def. pdf • http: //cmsdoc. cern. ch/cms/performance/ecal/addendum. pdf • Derivation of ci and of f(ET, ) from in situ events need to be done properly and independently of one another Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008 • Need f(ET, ) to derive ci (inter-ring) from physics events • Need ci (inter-ring) to derive/test f(ET, )

ECAL Intercalibrations at startup • Initial relative response spread 15%/25% (EB/EE) • ECAL Barrel precalibrations: Intercalibratio ns from cosmic rays • 0. 3% on 9 SM (TB data) • 1. 5 -2. 5% on 27 SM (cosmic rays) • ECAL Endcaps precalibrations: • 10 15% (lab measurements) Intercalibratio ns from electron TB • Sufficient precision in EB for startup physics • Precise inter-ring calibration (in EB) • Handle for validation of in situ procedures in EB Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008 • Transportability of pre-calibrations to CMS requires transparency corrections (eta dependent radiation dose and transparency loss)

ECAL Z physics with first data CSA 07: P. Meridiani, A. Palma, R. Paramatti Ldt = 10/pb EB Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008 EE • No impact on Z ee mass resolution in EB • Sizeable effect in EE Use Z width to intercalibrations

ECAL Inter-ring calibration at startup • Relative average response of crystals Cosmic ray vs testbeam inter-ring in a ring precisely determined calibration by pre-calibrations • Key to test dependent effects • ECAL barrel < 0. 5% • High statistical accuracy (sinlge crystal precision/ Ncrystals) • Systematic difference between supermodules < 0. 5% RMS • ECAL Endcap 1 2% ? • Statistical accuracy • < 15%/ 80 2% (worst case at large ) • Systematic effects unknown Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008

ECAL In situ strategy with first data • Exploit “fast” intercalibration procedures • -invariance of minimum bias events • Use of Zee events • Invariant mass of 0 candidates • Goal with first data • Validate procedures against precalibrations (in EB) • Derive intercalibration contants and f(ET, ) corrections • Improve on the precision at the startup Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008

ECAL calibration triggers ECAL • Inter-calibration in “one day” require min-bias and 0 candidates be logged at about 1 k. Hz • Dedicated HLT Filters • Alca. Raw Ecal. Phy. Sim Select Xtals above “noise” in L 1 min-bias Still under study (possible bias due to trigger bits) • Alca. Raw Ecal. Pi 0 Strip 0 candidates around L 1 EM objects Being optimised • Standalone tests symmetry 0 filter Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008 • Single- 1 ms/evt (on top of 15 ms/evt for unpaking) 250 500 k. B/s 8 20 ms/evt depending on hardness of 1. 2 2. 4 and di-electron triggers for Zee (and. MB/s We ) QCD event

ECAL - symmetry (at startup) • Based on -invariance of energy flow to equalize counting statistics above noise level in xtals in the same ring • “Single crystal” intra-ring calibration with Min. Bias or Dijets samples • Expected “intra-ring” precision 1 -2% (EB), >3% (EE) • Systematic limit achieved after about 20 M Min. Bias events (assuming no knowledge of traker material) • About 1 day upon 1 k. Hz L 1 Min. Bias trigger at startup CSA 07: S. Argirò, • Robustness of assumptions tested on MC Validate Gozzellino with data Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008 Worse than expected from CSA 06

ECAL Use of precalibrations • Validation against precalibration in EB • Precision comparable (cosmic rays) or better (TB) than symmetry • Use precalibrations to set inter-ring scale (normalise coefficients in each ring/sub-ring to precalibrations): [Valid for laser corrected data or low instant lumi at startup] • Derive a complete set of “single crystal” intercalibrations • Largely independent of precalibrations (error on scale factor small) • Comparable precision Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008 Combination and improvement on precalibration possible Can bring EB to 1 -2% and EE to 3 -4%

ECAL Use of Z ee • Require f(ET, ) correction to get “single crystal intercalibrations” Tune/test cluster corrections on EB (i. e. make invariant mass of the electron pair independent of ) CSA 07: P. Meridiani, A. Palma, R. Paramatti Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008 • Test/improve the interring scale (relevant in EE) • Bring EE to 4% intercalibration precision with 10 pb-1 • Use Z width to monitor 3% @ 10/pb 1% @ 100/pb

0 calibration ECAL CSA 07: M. Gataullin, V. Litvine, Y • Intercalibrate xtals on 0 mass peak • 0 stripping based on local quantities implemented in HLT Filter • Kinematics, shower-shape, isolation • Efficiency ( 0’s/EM L 1 objects) from 1% (Min. Bias) to 6 -10% (QCD evts) p. That. EB = 15 -20 • Precision 0. 5% with 2000 0/Xstal (1 day at 2 k. Hz) Ge. V S/B = 3. 3 7. 02% Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008

ECAL Use of precalibrations at startup • Validate results against TB precalibrations (0. 3% precise) • Need cluster corrections (module boundaries and dependent) to get “single crystal intercalibrations” • Photon candidates reconstructed in 3 x 3 matrices • Use precalibrations in EB to test/derive them Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008

ECAL Corrections for Xtal transparency changes • Crystal transparency changes monitored by laser calibrations • Laser data collected in orbit gaps (Calibration trigger) • Laser farm (Data processing and DB filling) • Offline transparency correction, trhough DB access • Interplay of transprency corrections with intercalibrations not discussed in this talk • Transparency changes expected to be small at startup (<1032 cm-2 s-1) • Otherwise need to correct for transparency changes to intercalibrate (eta dependent and crystal dependent effects) • Exact interplay need to be studied and understood with data Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008 Fexibile scheme of laser correction in calibration worklows (Ecal. Recalib. Rec. Hit. Producer) to fold/unfold calibrations on

ECAL Summary • Pre-calibration data and in situ calibration procedures provide sufficient redundancy and flexibility to • Derive intercalibrations and test cluster corrections separately • Improve on precalibration precision (in EE) • Cross-check and combine independent procedures • … Tommaso Tabarelli de Fatis Università/INFN Milano Bicocca April 16 th, 2008 • … Upon the condition that procedures be validated