The Search for bb(h/H/A)→bbbb

Andy Haas – Columbia University

D0 Winter Physics Workshop

February 28, 2005

Presented on behalf of the “bbh p14” group:

Jyothsna Rani, Avto Kharchilava, and myself

with contributions from:

Marine Michaut, Boris Tuchming, and Tim Scanlon

Higgseses in Supersymmetry

Higgs fields come in pairs

Gotta cancel those quantum anomalies!

5 Higgs bosons : h, H, A, H+, H-

tanB = Hu / Hd

At tanB=~50, coupling of A to b = A to t

Cross-sections for bbh grow like tan2B !

h is predicted to be light, <~135 GeV

LEP limits on Higgs mass -- 92 GeV
(not the usual 114 GeV like in the SM...)

LEP limits are much looser (~50 GeV) if
CP-violation is allowed in the Higgs sector...
this talk assumes CP-conserving Higgses !

H

h

A

total

At high tanB (>~20),
the A is degenerate with the h,H:

cs(A) =~ cs(h/H)

width(A) =~ width(h/H)

m(A) =~ m(h/H)

BR(A→bb)=~BR(h/H→bb) =~ 90%

Higgs Mass (GeV)

tanB = 30

Signal at NLO

Cross-section (fb)

Cross-section (fb)

There are two ways to calculate the signal production:

bbh (4-flavor scheme)

bh (5-flavor scheme) : use b-PDF

Both methods now agree at NLO

PDF errors are also in agreement

The central values
and the uncertainties
from renormalization
and factorization scale
both agree well !

Data / Triggering

Custom multi-jet triggers (v9-v12) used from Nov. 2002 – June 2004

L1: CJT(3, 5 GeV)

L2: L2J(3, 8 GeV), HT >50 GeV

Each triggerlist had new L3 criteria, as we tightened and improved them to remain within rate limits and retain efficiency
L3J(3, 15 GeV)(2, 25 GeV) in |eta|< 3.0
Jets use 0.5 cone, L3Nada, CalCalib, and
PVZ to correct jet ET and eta
Require good L3 PV with |z|<35cm

260pb-1, after bad runs/lumblocks

Skim (87.5 Million events) :
1 jet>20, 3>15 GeV, |eta|<2.6, cone=0.5

Level 1 : CJT(3,5)

Simulation

Trigger efficiencies measured using data:
> mu-based unbiased trigger for L1/L2
> special CJT(3,5) run for L3

68-80% efficient for mA of 90-150 GeV

v12:

Analysis Method

Signal:

3 or more b-tagged jets

Invariant mass of leading jets is
peaked at mA

Backgrounds:

Determined from data !

Shape estimated from the
double b-tagged data sample

Normalized outside the “signal region”

Also modeled in MC as a cross-check

“fakes”: all light-quark/gluons (data)

“heavy flavor”: (ALPGEN)
bbj(j), ccj(j), bbcc, cccc, bbbb

“other”: tt, Z(→bb)+jets (Pythia)

Events with
>=3 b-tagged jets

“Signal window”

Triple b-tagged Background

Full multi-jet

data sample

Calculate TRF

(ET & 3 Regions of )

Apply TRF to
un-b-tagged jets

Triple b-tagged
background shape

Double b-tagged
data sample

Tag-rate-function (TRF)

Background is completely determined from data !

Triple b-tagged
background

Fit outside the
signal region to data

|eta|<1.1

Jet pT (GeV)

Cross-check Using Double b-tagged Data

Full multi-jet

data sample

Calculate TRF

(ET & 3 Regions of )

Apply TRF to
un-b-tagged jets

Double b-tagged
background

Full multi-jet

data sample

Double b-tagged

data sample

Compare

Contribution from “heavy-flavor” MC

Good agreement in shape.

Normalization of “heavy-flavor” MC agrees to within 10%.

TRF is iteratively corrected for “heavy-flavor”
in the un-b-tagged data sample

MC Cross-checks

Double b-tag

Triple b-tag

Di-jet mass of leading b-tagged jets (GeV)

Monte Carlo accurately predicts
many other distributions in the
double b-tagged data as well.

g->bb !

Monte Carlo predicts a background
shape and normalization in good
agreement with the triple b-tagged data.

Limits

Signal efficiency uncertainty (21%):
b-tagging (15%)
Trigger (9%)
JES (8%)
Luminosity (6.5%)
NLO kinematics (5%)
Jet reco/ID (4%)
Jet energy resolution (1%)

Background shape/norm. uncertainty (3%):
TRF shape (2%)
Statistics outside signal region (1%)
Width of signal region (1%)

Limits set using CLS method (TLimit)

For each mA, set a cross-section limit

Interpret in MSSM at tree-level, assuming tan2B cross-section enhancement

PDF+scale uncertainty

MSSM Beyond Tree-Level

Supersymmetric loop corrections are calculated using “CPSuperH”

Production doesn't scale like tan2B...
can be faster or slower depending on the supersymmetric model and its parameters

We set limits on tanB vs. mA in two of the “benchmark scenarios”:

no mixing and maximal mixing in the stop-quark sector

Pictures

Conclusions / Future

You have approved these preliminary results to be shown at conferences

Our PRL is in EB review

With no analysis improvements, can exclude down to tanB=40 with 4fb-1

We look forward to a much improved p17 analysis

Inclusion of more data and triggers

A new focus on b-tagging

Neural network?

We're keeping an eye on our competitors...

Int. Lum. in pb-1

Expected tree-level tanB limits

D0 bbh(→bb), 260pb-1

CDF bbh(→)

Backup Slides

Mass splitting, weighted by cross-section

Andy Haas

2004-07-07T15:59:13