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

2. 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

3. 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

4. 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

5. EM energy resolution Emeasured =  * Etrue + 
Measurement of the constant term from Junjie Zhu (CALGO meeting, Dec 16th, 2003; D0 note 4323):
Emeasured =  * Etrue + 
CC =  EC = 
CC = (  ) GeV EC = (  ) 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

6. 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

7. 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

8. 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