1. Search for h→ at Dzero
刘衍文
中国科大
中国高能物理学会第十届全国粒子物理学术会议
南京, 2008年4月27日

2. Outline Tevatron Higgs search status Dzero detector Higgs→ at Dzero
Photon identification
Preliminary results
Outlook

3. Tevatron
√s = 1.96TeV
36x36,396ns bunch crossing
Record lumi:

4. Luminosity projection
R. Dixon
Feb 2008, P5

5. Getting close …

6. Status of Higgs searches
Dec 14,2007
, channels added
Apr 21,2008
arXiv:
arXiv:

7. The Dzero detector 2T, R=0.7m L=2.7m
Silicon microstrip (SMT) , central fiber tracker(CFT)
Sampling calorimeter, preshower(CPS), finer granularity at 3rd layer of EM,
muon system

8. Fermiophobic higgs in 
Higgs that have zero coupling to fermions, and all decay to boson pairs.
Fermiophobic higgs in 
Fermiophobic scenario
arXiv: v1[hep-ex]
RunIIa data
Higgs decay in SM

9. Photon identification
ET > 25 GeV
97% energy in ECAL
Isolated in ECAL
No track
Use of CPS
“EM-pointing” for selecting the right vertex
“hit-on-road” to reduce electrons
HOR efficiency for photons
Needs to be commissioned for Run2B.
Work in progress.
Very preliminary

10. Artificial Neural Network(ANN)
ANN: Combines a few variables for discrimination power .
Select input variables that are insensitive to the e/ difference – ANN trained with photons can be cross-checked with electrons

11. Input variables

12. The output

13. Background contributions
PRL95,022003(2005) CDF II, 200/pb
PYTHIA/RESBOS/DIPHOX:
similar shapes at high M
QCD  PYTHIA simulation, DIPHOX (NLO for normalization, 20% uncertainty).
j,jj from data (next slides)
e+e- PYTHIA, NNLO cross section for normalization

14. Background estimation (inclusive)

15. Background subtraction ()
Use ONN>0.85 for the classification

16. Preliminary result out of 2.3/fb
Conference note (public) available at
Preliminary result out of 2.3/fb
Dominant uncertainties: DIPHOX cross section :20%, j,jj estimation: 26%.

17. Current limits for  
Contribute to the Tevatron combination.
Very first look, large room for improvements.

18. Plan: instead of conclusion
Determine  from data at side bands
Reduce uncertainties in photon ANN ID
Commission photon ID techniques ,e.g., CPS for high luminosity.
Make an impact at low mass!
An important discovery opportunity!
谢谢大家!