1. Controlling the Neutral Drell-Yan at high mass
Samir Ferrag
University of Glasgow
ATLAS UK Physics Meeting, Durham, 09-11/01/2008

2. Introduction Context: high mass Dilepton-Analysis with ATLAS:
Standard Model + Detector ---> New Physics (afternoon talk)
Question:
How much do we control the Standard Model ?
Mini-Workshop in Glasgow:
kindly funded by SUPA* and Glasgow Physics Department
Working group:
F. Piccinini, S. Moretti, C. Carloni, C. Sephered, J. Jackson, S. harper, A. Viccini, S. Pozzorini, B. Jantzen, D. Wackeroth and S. Ferrag
Goal:
bring together knowledge of QCD and ElectroWeak theories and apply it to a Dileptons at high mass for the best possible theoretical prediction might be tested with early LHC data
* SUPA for Scottish Universities for Physics Alliance

3. Output (Preliminary) 0- Introduction 1- QCD
1.1- Existing tools and calculations
1.2- Effects of NLO corrections
2-EW
2.1- NLO corrections
2.2- Multiples photons emissions
2.3- Sudakov Logs loop vs Sudakov approx, 2-loops Sudakov
3- Combined effects
parton level + shower level
4- Uncertainties
4.1 PDFs
4.2 Energy scale (QCD, QED)
4.3 Input Scheme
4.4 Others
a-QED+QCD
b-NNNLO…
c-Shower…
5-Summary and Conclusion
5.1- Summary and results
5.2- Conclusion

4. Calculating the Drell-Yan Cross section
Change the W by Z

5. Status of QCD calculation and tools- - - - - -

6. QCD NLO corrections I

7. QCD NLO corrections II

8. EW calculations and tools for Z- -

9. 2-Loop EW Sudakov logs From Virtual Weak boson corrections:
large log EW corrections:
- 1-Loop >> 10%
- 2-Loop >>1%
Asymptotic expansion at high energy for M2W/s << 1
Typical size of the leading 2-loop logarithms:
Strong simplification, process independent treatments
Good precision
Using the 2-loop EW Sudakov logs is a good approximation to
full EW 2-loop calculation

10. Testing the 1-loop EW Sudakov
Preliminary
Comparison 1 Full Loop calculation ZGRAD2 and LO+1-loop Sudakov

11. EW: 2-loop Sudakov Logs Preliminary
2 loop Sudakov calculated and injected into HORACE

12. Combining QCD and EW corrections
At LO, the MC are tuned to agree
@ 0.1% level

13. Corrections on invariant mass
Preliminary
No QCD LL

14. Pt of the lepton pair
Preliminary
No QCD LL

15. Pt of the lepton
Preliminary
No QCD LL

16. Lepton and lepton pair rapidities
Preliminary
No QCD LL
No QCD LL

17. Conclusion Successful interaction experimentalists-theorists
Toward a control of the high mass dileptons and precision predictions
Further work: uncertainties
Results will be injected and used in the ATLAS CSC …