1. Missing ET with the First Data: Wl (l=e,)
X.Chen, B.Mellado, S.Padhi and Sau Lan Wu
(University of Wisconsin)
Munich Workshop 03-05/05/06

2. Bruce Mellado, Munich Workshop
Introduction
Need control samples to evaluate and check the Missing ET performance with the very first data
Need to address needs of discovery physics during the early stages of data taking
Understanding of tails in missing ET will come form events with no (large) “real” missing energy: multi-jets, Z(ll)+jets
Can also address resolution issues
Use Wl as high statistics sample to check missing ET reconstruction with “real” missing energy
Same check can be made with more luminosity with Z (ll)+jets (turn electrons into “neutrino”)
Bruce Mellado, Munich Workshop

3. Bruce Mellado, Munich Workshop
One can use the sharp end of the transverse mass in different missing ET bins
Shape of transverse mass changes with Missing ET, due to acceptance
One can also use the fact that in the average the pt of the charged lepton and the pt of the neutrino are of the W decay are known function, which can be calculated with MC
Function can be calculated with MC (small uncertainties) and depends on experimental cuts
Bruce Mellado, Munich Workshop

4. Bruce Mellado, Munich Workshop
R calculated using truth
No cuts
PTL>20 GeV, |l|<2.5
Bruce Mellado, Munich Workshop

5. Bruce Mellado, Munich Workshop
PTL>20 GeV, |l|<2.5
Fullsim (We)
ATLFAST
R calculated using truth
Bruce Mellado, Munich Workshop

6. Bruce Mellado, Munich Workshop
PTL>20 GeV, |l|<2.5
ATLFAST
100pb-1
+3%
+2%
Nominal
Bruce Mellado, Munich Workshop

7. Bruce Mellado, Munich Workshop
Back-up Slides
Bruce Mellado, Munich Workshop

8. Bruce Mellado, Munich Workshop
Outlook and Plans
ppW(l, l=e, )+X is a copious source of events with missing energy.
Expect 0(10K) per 1pb-1
With 100 pb-1 of data can check missing ET in most of useful range for low mass Higgs physics
Allows to perform checks with different jet topologies
Method is very sensitive to shifts in missing ET
Less sensitive to missing ET resolution. This can be better constrained with di-jets
Need to address luminosity required to study missing ET with different jet topologies
Need to address contamination from top
Bruce Mellado, Munich Workshop

9. Bruce Mellado, Munich Workshop
PTL>20 GeV, |l|<2.5
Acceptance in W for PTL>20 GeV, |l|<2.5
Acceptance
Bruce Mellado, Munich Workshop

10. Bruce Mellado, Munich Workshop
PTL>20 GeV, |l|<2.5
Truth
Solid histogram |W|<
|W|<2
|W|>2
Bruce Mellado, Munich Workshop

11. Bruce Mellado, Munich Workshop
PT>90 GeV
Ratio
No cuts
PTL>20 GeV, |l|<2.5
Bruce Mellado, Munich Workshop

12. Bruce Mellado, Munich Workshop

13. Bruce Mellado, Munich Workshop
Events here were produced with Pythia
Will re-do analysis with ALPGEN
Expect harder PTW spectrum
Bruce Mellado, Munich Workshop

14. Bruce Mellado, Munich Workshop
Truth
W, l
Wl, l=e,
Bruce Mellado, Munich Workshop

15. Bruce Mellado, Munich Workshop
PTL>20 GeV, |l|<2.5
5 GeV
Smearing
4 GeV
3 GeV
100pb-1
Nominal
ATLFAST
Bruce Mellado, Munich Workshop

16. Bruce Mellado, Munich Workshop
PTL>20 GeV, |l|<2.5
ATLFAST
100pb-1
7 GeV smearing
+3% shift
Bruce Mellado, Munich Workshop

17. Bruce Mellado, Munich Workshop
After the application of PTL>20 GeV, |l|<2.5 cuts the contribution from W, l amounts to few % of signal and can be easily subtracted with MC
Wl, l=e,
W, l
W, l
Bruce Mellado, Munich Workshop