Slide 1:
Title page

Slide 2:
Contents

Slide 3:
Introduction to the Higgs Mechanism.

Slide 4: Constraints on the Higgs Mass. Theoretical constraints from
triviality, vacuum and fine tuning are shown in one plot. The other
plot shows the present direct and indirect (mH<157 GeV @ 95% C.L.)
experimental constraints from LEP and the Tevatron.

Slide 5: Tevatron. The Tevatron is working very well and has delivered
6.9fb-1 up to now. Results presented here used up to 5.0fb-1.

Slide 6: The D0 Detector. The D0 detector is a general purpose
detector with excellent coverage over the full eta range up to 4.2 for
the calorimeter. This is complemented with a powerful trigger system.

Slide 7: Tevatron Cross Sections. The total inelastic cross section at
the Tevatron is a factor 2x10^10 higher than the cross section of
single top production. Depending on the mass the Higgs cross section
is expected to be a factor 2-10 lower than the single top cross
section.

Slide 8: Higgs Production & Decay. Low mass Higgs decay mainly into
b-bbar pairs whereas high mass Higgs decay mainly into WW and ZZ
pairs. For high mass Higgs one can exploit the higher gluon fusion
cross section whereas one has to go to the associated production modes
(H together with W or Z) for the low mass Higgs. Vector Boson Fusion production
is exploited as well.


High mass Higgs channels.
=================

Slide 9: For high mass Higgs the H->WW->emu final state is most important
as it has twice the statistics. Hadronic final states are extremely
difficult but are looked at none the less. The most important feature
distinguishing H->WW decays from background is the angular correlation
of the leptons due to the fact that the Higgs is a spin-0
particle. The lepton opening angle is small.

Slide 10: Event selection and S/B ~ 18/669 for ee+emu are shown.

Slide 11: NN Input variables. A neural network is used as final
discriminant. 14 variables, mainly kinematic ones, are used.  This
makes the modelling of the data by the MC an important factor.

Slide 12 & 13: Detour: V+jets. Plots comparing data with
several MC predictions are shown. Conclusion: None of the available
MCs gets all of the distributions right. Solution: Take one MC and
re-weight the distributions to data onservation.  Control regions
are used for comparing MC and data after re-weighting. Wish for
theorists: differential cross sections for signal and background (with
uncertainties).

Slide 14: NN Output Variable. The high NN region contains the bins
with the best S/B.

Slide 15: Limit Setting. As no signal excess is seen the CL_s method
is used to set a limit. (Gaussian) systematics are fit to data using a
profile likelihood. Correlations are taken into account within and
across channels. Example distributions for log-likelihood ratios (LLR)
for signal+background and background-only hypothesis are shown. Data
gives a single LLR ratio. Larger separation of the curves denotes a
higher sensitivity to signal.

Slide 16: The LLR and the resulting 95%C.L. exclusion is shown as a
function of the Higgs mass for the D0 high mass combination. The
expected/observed D0 limit at mH=165GeV is 1.7/1.3.

Slide 17: Additionally the background-subtracted plot of signal (red)
and background expectation (0-line) and data for mH=165GeV is shown as
a function of the NN output variable. The graph includes a ±1sigma
variation (stat + syst) of the background expectation (blue). The data
exhibit a "downward" fluctuation resulting in an observed limit that
is lower than the expected limit (1-sigma).

Low mass Higgs Channels
=================

Slide 18: Low Mass Higgs Channels. There are three main low mass Higgs
Channels, each complementing the other in cross section and
experimental signature.

Slide 19: b-tagging is a common tool for all low mass
channels. Different working points in the efficiency-fake rate plane
are chosen (also a good cross check). Proof of principle: Z->bbbar
peak.

Slide 20: WH->lnubb as example for low mass analyses. 2-jet and 3-jet
final states with single and double b-tag are analysed for final
states with electron or muon. Plots show the b-tagging points, the
2-jet bin without b-tag, with 1 b-tag and with 2 b-tags and the S/B
ratio.

Slide 21: MC for WH. Two plots show a comparison of data with various
MC predictions. Again, none of the MC gives an excellent description
of the data in all variables.

Slide 22: WH->lnubb Neural Net. Example distributions and other
variables used in the NN. Also the NN output variable is shown.

Slide 23: D0 limits from the WH combination. The observed/expected
limit is 6.9/5.1 ("signal-like" fluctuation by about 1-sigma).

Slide 24: ZH->nunubb. Example plots for the 2-jet bin without and with
2 b-tags and the final discriminant coming from the Decision Tree are
shown. The present analysis uses only 2.1fb-1 and is being
updated. Observed/expected limits are 7.5/8.4

Slide 25: ZH->llbb. The analysis has been improved recently to include the
region between the calorimeter cryostats representing an increase of
15% in acceptance for electrons. Shown is the invariant e+e- mass
using those electrons and the final output variable of the boosted
decision tree. The observed/expected limit is 8/9.1.

Combinations, History and Outlook
=======================

Slide 26: D0 Higgs Combination. LLR and exclusion plots are shown for
the D0 combination over the full Higgs mass range (100-200GeV). The
combination is from summer 2009.

Slide 27: Tevatron Higgs Combination Winter 09. The last Tevatron
combination was done for the winter conferences. Results using
0.9-2.7fb-1 were included. The mass region 160 < mH < 170 GeV has been
excluded at 95% C.L.

Slide 28: Higgs Projections 115GeV. History and projection of Higgs
sensitivity from February 2008. An improvement of the analyses beyond
the expectation from only luminosity increase is seen.  

Slide 29: Higgs Projection 160GeV. Analysis improvements seen as well
in the high mass region.

Slide 30: Conclusion. Wishlist for theorists.

Slide 31: Highly controversial slide about the closeness of the rise
or setting of the Higgs.