Electron-ID and EM scale status Jan Stark LPSC Grenoble D0 France meeting, May 25th, 2004

Outline I will be very brief. This is presentation is just a quick reminder of problems you know. It is intended as an introduction to the talks and discussion that follows. Cosmetics: H-Matrix 7 (Some of) the real problems: - EM resolution - EM scale - Something new: electron -horns Jan Stark D0 France meeting, May 25th, 2004

H-Matrix 7 HMx8 CC HMx8 EC HMx7 CC HMx7 EC Michel Jaffré has implemented the new HMx7. HMx8 CC HMx8 EC Blue: Monte Carlo Red: data HMx8: data/MC agreement lets something to be desired, especially in CC. One of the worst offenders: shower shape in z. Removed one of the corresponding input variables from the H-matrix  HMx7. HMx7 CC HMx7 EC Rejection power of HMx7 and HMx8 in the CC for different cuts. HMx7 does not only have better data/MC agreement, it also gives better rejection. HMx7 is the new D0 standard. The upcoming version of d0correct (talk Frédéric) includes an electron-likelihood based on HMx7. Jan Stark D0 France meeting, May 25th, 2004

EM energy resolution Z  e+ e- Z  e+ e- At the winter conferences our Blue: Monte Carlo Red: data Z  e+ e- At the winter conferences our Z  e+ e- peak looked like this. Di-EM mass (GeV) Z  e+ e- But we to keep in mind that, before energy smearing it looks like this. Di-EM mass (GeV) Jan Stark D0 France meeting, May 25th, 2004

EM energy resolution Emeasured =  * Etrue +  Measurement of the constant term from Junjie Zhu (CALGO meeting, Dec 16th, 2003; D0 note 4323): Emeasured =  * Etrue +  CC = 1.0060  0.0017 EC = 0.9991  0.0036 CC = (0.0953  0.0793) GeV EC = (0.7953  0.2943) GeV CCC = (3.73  0.28) % CEC = (2.03  0.59) % Assumes Run I values for N,S.  includes any contributions from underlying event. Reminder: goal (from the electronics TDR) is to keep C below 2 %. Comments: - This measurement uses only the Z resonance  no sensitivity to S or N. We need to measure S and N using lower-mass resonances. We have the data in hand !!! - The above result is stable under variations of the assumed values of S and N. - We need to improve calibration to reduce the constant term. Lots of work on pulser-based calibration: Ursula B., Jean-Roch V., Robert Z., et al. New efforts: E/p calibration, phi-intercalibration using CEM(1,6.) data. Special session at Fresno chaired by Pétroff/Stark. Ample rooms for contributions ! Jan Stark D0 France meeting, May 25th, 2004

EM scale phi eta Comprehensive discussion of EM scale issues: J. Stark et al., “On the EM energy scale”, W mass workshop, March 30th, 2004. Among other things, we apply EM scale corrections derived from Z  e e data, separately for each readout crate. Aurélien and Smaïn will present the details in the next talk. crate 9 crate 8 The blue lines represent crate boundaries. Inside each crate, one coloured area represents one ADC card. phi crate 2 crate 3 eta crate 9 crate 8 Question: is this splitting of the calorimeter fine enough ? Let’s look at a finer splitting … Jan Stark D0 France meeting, May 25th, 2004

E/p – finer splitting of detector Diff (E/p adc-E/p mean crate) Studies of E/p with finer splittings (arbitrarily based on ADC cards) have been shown in these presentations: J. Stark, CALGO meeting, April 13th, 2004. P. Pétroff, Calop meeting, May 6th, 2004. The plots on the right are from P. Pétroff. We see large response variations inside a given crate. The calibration of the calorimeter is not that great – most likely related to our huge constant term. Crate 2 Crate 3 adc # adc # Crate 8 Crate 9 Jan Stark D0 France meeting, May 25th, 2004

Electron -horns Originally discovered in the context of my ttbar  l+jets/SLT analysis. Present in essentially all analyses involving W  e . Also seen in Z  e e + many jets. Muons look much better. Here are a few plots from the topological ttbar analysis: And from the W  e  cross section measurement: Current best hypothesis: QCD background not identified by the standard matrix method. Detailed discussion of our current understanding: J. Stark, Top Group meeting, May 18th, 2004. J. Stark, Top Group meeting, May 25th, 2004. Jan Stark D0 France meeting, May 25th, 2004