<P>
    Presented dijet masses from dimuon events with each jet b-tagged 
by a soft muon.   Data is from B2M stream and an integrated luminosity
of 40pb-1 from Tom McKibben's BB mixing studies.
</p><p>
My interest in Higgs grew out of Liang-Ping's WZ production work using the 
channel enujj where there is an enhancement at high W(enu)pt (160GeV) which
one might like to interpret as Higgs-WW.  Actually the Wbb QCD background may 
have an enhancement there and the cross section is at least 1000 off the SM
prediction, but I got intrigued enough to ask what D0's limit to lower 
mass Higgs from the H-bb channel was.  We had not looked systematically 
at masses below 200 GeV, so had not even looked for Z-bb which should occur at
a rate 1000 times higher than the Higgs rate.  Ellis recently presented a global 
fit to EW data which indicated a 76 GeV Higgs central value.  I became aware 
of the CDF rumor of a possible H-bb at 120GeV and asked Tom to make the bb dijet 
mass plot to see what our data looked like.   The discovery limit of 
WH with H to double b tagged jets has been estimated by Strange, Marciano,
Willenbrock PRD, 50(1994)4491 to be at the 10fb-1 level so we would 
be a factor 100 below this level of sensitivity. 
</p><p>
Single muon tags would increase the number of candidate events but the dimuon
ntuples produced  by Divitoe is what we had immediately available.
</p><p>
Goal:    H-bb (both b jets muon tagged).  Must also observe Z-bb first since the
only difference will be:
</p><pre>
    #H/#Z = sig(H).BR(H-bb)/(sig(Z).BR(Z-bb) = 1pb(0.85)/7000pb(0.15) = 0.8E-3

Cuts
Clean muon cuts: 3<ptmin<25GeV, IFW4=0 or 1, HFRACT>0.75, abs(t0)<100
ptrel > 1.2  very hard cut to selects bs...should relax 
dimuon angle: no constraint, although all high mass dijet events occur 
with theta > 100 degrees.

Etjet > 8GeV, CAFIX 4 version of jets
No correction has been made to jet energy for muon or neutrino momenta.  Jet
masses have been used and no jet cleaning is done yet.
muon-jet match dR<0.8

Observationn (first pass)
The dijet mass from dimuon events has a cluster of 12 events around 100GeV in 
unlike signs muon tags and 3 events in  like sign (90<Mjj<110GeV).
The peak is narrower than the expected >15% resolution.

What is expected for Z-bb (2 muon tags of unlike sign) rates?

 #Z-bb = L   sig  BR(z-bb)  (Aeff)  btag**2   ptrel**2  BBmixing
        40pb-1 7000pb (0.15) (0.1) (.25)**2 (0.4)**2 (0.75)
       = 30 events
    That is close enough agreement at this stage to try to improve signal.

Predicted Tevatron light Higgs limits from the TEV2000 report and Marciano et al
indicate the best channel is WH with H to bb so we are below discovery 
threshhold by a factor 100.  I'll assume that they are correct about the 
rates and present crudely predicted number of events of H-bb for several
channels:  

	H produced from gg has a cross section of 1pb-1.  The WH rate is 
20% of that.  Stange states that there are 0.3 WH, 0.4 WZ and 0.5 Wbb background 
expected at a Higgs mass of 100GeV if we double tag at run 2 TeV and 
tag W,Z with leptons.

H-bb doubly tagged ( my crude guess )
	1pb x 100pb-1 x BR(bb=0.85) x acc(0.1) x (btag=0.25)**2 x (0.4)**2 (0.75)
		= 0.026 event.  With 1 btag 0.26 events
WH generates above rate divided by 5 but has 100pb-1 sample to work from
	0.012 double tag and 0.1 single tagged events (even before W tag)
        (My rate estimate is at least a factor 50 below SMW, probably mostly
        due to our low acceptance and ptrel requirement.  They also assume 
        btag eff of 0.5)

We have cut harder than needed on ptrel, btag efficiency might be improved and
acceptance may be improved.  If we include mu and electron W tags and 
investigate e tagging of bs we may approach the 0.3 event level.
SMW and TeV2000 reports indicate a 2/1 background to signal however if 
the cross section for H-bb or WH-bb is higher than expected 
we may sensitive enough.  It's worth a look.

Conclusions:

    First look at b tagged dijet masses find a cluster of events at 100GeV
    in unlike sign muon tagged events

    Number of events is within a factor of three of the Z-bb expectation.

    Could imagine a many channel search for H-bb using single and double 
    muon tags which could get within a factor 10 of expected discovery rate.
    (ignoring Wbb QCD background)

    Dijet with soft mu tag trigger for 30pb-1 of run 1c may prove very useful.
</pre>