Transcript Subproject DOE Rev talk v1.0

Higgs Sensitivity Study







Outline
Committee and Charge
Road Map
Event Yields
Dijet Mass Resolution
Extraction of Limit and
discovery limits.
Summary and Schedule
NOTE: We are not yet to the
point where we have final
numbers…please consider the
trends and topics…not
necessarily the specific numbers.
May 23, 2003
From the Higgs-SUSY Working Group Report.
CDF Collaboration Meeting May
2003
Page 1
Committee and Charge

Committee:
Provide an update to the SUSY-Higgs Working Group evaluation
(http://fnth37.fnal.gov/susy.html) of the Tevatron's Standard Model Higgs
search potential. This should be done in coordination with a similar committee
formed by D0. The studies are to be divided by Higgs decay channel with CDF
focusing on WH production and D0 on ZH production. The results of these
studies should be combined, assuming approximately equal detector
performance, producing a determination of the integrated luminosity required for
95% confidence level exclusion limits, 3 sigma and 5 sigma discovery versus
Higgs mass. The studies should use the experience gained by early Run2 CDF
detector performance, simulation of the detector and relevant physics processes
and build on the work reported by the SUSY-Higgs Working group. The
committee should explore analysis techniques that could improve the reach of the
Higgs sensitivity. The studies should assume Tevatron operation at 396ns,
with instantaneous luminosities as high as 4xE32 /cm**2/s .
Tommaso Dorigo, Tom
Junk, Joseph Kroll (cochair), Mario Martinez,
Pete McNamara, Fumi
Ukegawa, Brian Winer
(co-Chair), Weiming Yao

Other workers:
Henri Bachacou, John
Conway, Martin
Hennecke, Jason
Nielsen, Michael Schmitt,
Luca Scodellaro
May 23, 2003
The committee is encouraged to draw upon resources of the CDF
collaboration, especially those individuals with expertise in critical areas. The
Committee's responsibility is to direct and coordinate the preparation of this
study, however it is understood that significant contributions by other members of
our collaboration will be recognized in the final report. A preliminary report
should be prepared by June 1, 2003 with the goal of blessing the document
by the CDF collaboration in the Joint Physics Meeting.
A final combined CDF and D0 document should be ready for public circulation
by the end of June and availability for the Fermilab Accelerator DOE review
expected latter in summer 2003. The final combined report, containing the
work of CDF and D0, will be presented to Ray Orbach, Director of the DOE
Office of Science, who requested that CDF and D0 perform these studies for
him.
CDF Collaboration Meeting May
2003
Page 2
Searching for SM Higgs


Signal Processes:
pp  W / Z  H
 CDF: W  
 D0: Z  
 HSWG: Z     

Background (~irreducible)
W+Jets
pp  Wg , g  bb
 ~ 10' s pb
Decay Channels:
H


tt :

 ~ 5 pb
Single Top
 bb
Cross Section x BR
pp  tb  Wb b
  B(M  110)  0.216 0.25 pb
  B(M  140)  0.090 0.11pb
pp  tt  WbWb

 ~ 1 pb

WZ
pp  WZ  bb
 ~ 1 pb
May 23, 2003
CDF Collaboration Meeting May
2003
Page 3
Detecting the Signal

Backgrounds are from real bb
 Improving B-Tagging helps S / B

Counting Experiment
 Inside a mass window (HSWG)
 Normalization of Bkg Important

Use Kinematic/topological Cuts
 tt: should have extra jets/MET
 Wbb: different jet properties.

Fit Dijet Mass distribution
 Help Normalization of Bkg.
 Dijet Mass Resolution Critical
 Understand from data Z
May 23, 2003
bb
PT of bb System GeV/c
CDF Note 6309: Run 1 NN
search for Higgs (Chris Neu)
CDF Collaboration Meeting May
2003
Page 4
Plenty of Publications

We have not been idle in this area
 The CDF Collaboration, Phys. Rev. Lett. 90, 081802 (2003). Search for W'
Boson Decaying to a Top and Bottom Quark Pair in 1.8 TeV p anti-p Collisions
 The CDF Collaboration, Phys. Rev. D65, 091120 (2002) Search for Single-TopQuark Production in p anti-p Collisions at s**(1/2) = 1.8 TeV
 The CDF Collaboration, Phys. Rev. Lett. 84, 5273 (2000) Search for Scalar Top
Quark Production in p anti-p Collisions at s**(1/2) = 1.8 TeV
 The CDF Collaboration, Phys. Rev. Lett. 81, 5748 (1998). Search for Higgs
Bosons Produced in Association with a Vector Boson in p anti-p Collisions at
s**(1/2) = 1.8 TeV
 The CDF Collaboration, Phys. Rev. Lett. 79, 3819 (1997) Search for New
Particles Decaying into b anti-b and Produced in Association with W Bosons
Decaying into e nu and mu nu at the Tevatron
 Plus a series of SUSY Higgs Search papers.
May 23, 2003
CDF Collaboration Meeting May
2003
Page 5
Road Map for Study
Event Yields
• Establish baseline event selection
 Use the Run 2A Winter
Conference Select (Top/EWK)
Dijet Mass Resolution
•What can we achieve?
• Use of Tracking Information
• B Tagging
• Full Corrections for b-quarks
• Estimate Extensions to acceptance.
• Advanced Techniques using full
event information.
• Impact of multiple interactions.
• Explore other selection cuts to
reduce backgrounds…this needs
more work.
• IMPORTANT: We must use every
part of our detector and reducing the
sys. Error on background is key.
Extracting Luminosity
Thresholds
•Establishing thresholds for
95%CL, 3, 5 discovery.
•Use full Mjj Spectrum
•How do we quote the result?
May 23, 2003
CDF Collaboration Meeting May
2003
Page 6
Event Yield~Introduction

Establish a Solid Baseline first:
 Lepton Selection (Winter 2003)
 Loose Jet Selection
 Use Run 2A detector Simulation
 Not perfect…would have preferred a
Run 2B Simulation
 But offline Alg. are tuned for current
detector and L…no time to optimize.

Additional Kinematic Cuts
 Attempt to clean up backgrounds
 Followed approach similar to HSWG
 More optimization possible
 e.g. Variables from CDF6309
May 23, 2003
Lepton Selection:
(CEM, CMUP, CMX)
Winter 2003 Conference Cuts
Missing ET > 20 GeV (raw)
Jet Counting:
ET > 10 GeV (raw)
|hd| < 2.0
Z-Veto: Winter 2003 Top Cuts
Additional Kinematic Cuts:
One Jet ET > 25 GeV
No third Jet ET > 20 GeV
No second Isolated Track
CDF Collaboration Meeting May
2003
Page 7
Event Yield ~ Signal Events

Monte Carlo Sample:
 Alpgen: WH Productions
 MH 110, 115, 120, 130, 140
 500K events at each mass
 All decays W and H.
 Standard Winter 2003
approach for generation and
simulation

Cross Section and BR
 PPHV T.Han, S Willenbrock Phys.
Lett. B273 (1991) 167.
 HDECAY: A.Djouadi,J.Kalinowski,
M. Spira Comp. Phys. Commun
108C (1998) 56
May 23, 2003
CDF Collaboration Meeting May
2003
Page 8
Signal Distributions
ETleadingJet
ETsecond Jet
WH110
WH120
WH140
N jet
May 23, 2003
CDF Collaboration Meeting May
2003
hb,b quarks
Page 9
B-Tagging

Baseline:
 Use Winter 2003 Secvtx
 Uses Beamline…not optimal
 Is “tight” tag for both b’s not
optimal
 Eta range ~ < 1.0
 Additional Requirement that one
of the tags in a jet with ET > 25

Clearly we must
 Use event-by-event vertex
 Have a loose tag for second leg
 JETPRB (More Later)
 extend to higher eta?
 More Later
 …other good ideas
May 23, 2003
CDF Collaboration Meeting May
2003
Page 10
Summary of Signal Yields
Mass
110
115
120
130
140

0.216
0.186
0.160
0.199
0.090
BR lvbb
0.257
0.244
0.226
0.176
0.115
1 Lepton
0.24
0.24
0.24
0.25
0.25
MET
0.89
0.89
0.89
0.89
0.89
Z Veto
0.99
0.99
0.99
0.99
0.99
Loose Jet
0.77
0.77
0.79
0.80
0.80
Kinematic
0.84
0.84
0.84
0.84
0.82
#/fb-1
7.3
5.95
4.9
2.9
1.4
≥1 B-Tag
0.48*0.87
0.49*0.87
0.50*0.87
0.50*0.89
0.50*0.90
#/fb-1
3.07
2.5
2.1
1.3
0.64
2 B-Tag
0.18
0.18
0.18
0.18
0.20
#/fb-1
0.65
0.51
0.44
0.25
0.142
May 23, 2003
CDF Collaboration Meeting May
2003
Page 11
Yields
Don’t run screaming from the room…yet.
There are a lot of improvements that are possible on these
numbers:
e.g. extended lepton coverage
loose b-tagging.
etc.
This is just a (low) reference point to work from
…More details after looking at the backgrounds.
May 23, 2003
CDF Collaboration Meeting May
2003
Page 12
Event Yields ~ Backgrounds

Monte Carlo:
 Relied on much of the
background Monte Carlo
generated for the top group for
the winter conferences.
 ttbar
 Alpgen, Herwig, Pythia
 Wbb, Wcc
 Alpgen
 WZ
 Alpgen
 Single Top
 Pythia
May 23, 2003
CDF Collaboration Meeting May
2003
Page 13
Background Distributions
ETleadingJet
ETsecond Jet
Wbb
ttbar
W*  tb
N jet
May 23, 2003
CDF Collaboration Meeting May
2003
hb,b quarks
Page 14
Summary of Background Yields
Mass
Ttbar
Wbb
Wcc
W*
WZ

6.5
To Data
To Data
0.88
3.2
BR lvjjjj
0.33
0.33
0.33
1 Lepton
0.27
0.22
0.12
MET
0.91
0.91
0.89
0.89
Z Veto
0.94
0.99
0.99
0.91
Loose Jet
0.49
0.25
0.74
0.52
Kinematic
0.49
0.58
0.83
0.78
#/fb-1
111
132.
33
70.1
1 B-Tag
0.46*0.91
0.40*0.82
0.46*0.92
0.09*0.83
#/fb-1
46.4
53.50
13.4
13.9
5.3
2 B-Tag
0.15
0.18
0.023
0.17
0.10
#/fb-1
7.7
9.6
0.31
2.5
0.70
May 23, 2003
179
CDF Collaboration Meeting May
2003
Page 15
Event Yield ~ Extensions/Improvements
Improve S/B
Improve Acceptance

Lepton Coverage

 Include Plug Electrons
 Include Muons in the IMU
 Tau’s
 Isolated Tracks

B-Tagging
May 23, 2003
 Beat down individual
backgrounds.
 Avoid Shaping the Mjj


 Loose tagging
 Extension to higher h
 Can we get away with a
single tag?
Kinematic Selection
Improve Mjj…more later.
Techniques
 Neural Networks
 Recent Analysis got an
effective 30% increase in Lum.
We have investigated some of
these…but it is a never ending list of
ideas.
CDF Collaboration Meeting May
2003
Page 16
Primary Lepton (h) Coverage

Looking for electrons in the plug
and muons in the IMU/BMU.
 The HWG Report assumed coverage
out to |h|<2.0
 We will have to do this.

Estimated the increase in the
acceptance
 Look where the HEPG level lepton
from W decay fell in the detector.
 Ratio of the leptons that fall in our
current coverage (CEM,CMUP,CMX)
to the ones that fell in Plug (|h|<2.0)
and IMU (|h|<2.0).
May 23, 2003
WH
De
CDF Collaboration Meeting May
2003
tt
Wbb W*
27% 26% 35% 28%
Page 17
Primary Lepton Type

Consider other lepton
signatures.
 Hadronic Tau Decays of W
 Isolated Tracks
 Leptons that have failed our
standard cuts, and taus.

Taus:
 Purity Good.
 Efficiency not as high

Isolated Tracks
 PT>15 Isol < 1.0 (R=0.4)
 MET > 35 GeV
 WH Acceptance Increase: 44%
(MH = 120 GeV/c2)
Note: If these samples have lower S/B,
we can combine them as a separate
May 23, 2003
CDF Collaboration Meeting May
Page 18
channel
in
the
end.
2003
B-Tagging ~ Loose Tagging (|h|<~1)



We want the tagging on
the second leg to be
loose.
We have parameterized
the OR between Secvtx
and JETPRB.
We are in the progress
of investigating the
impact on all the signal
and backgrounds.
 Signal Double Tag:
Factor of 1.45 to 2.0
May 23, 2003
CDF Collaboration Meeting May
2003
Page 19
B-Tagging ~ Extended (1<|h|<2)

The HSWG Report
assume b-tagging out to
|h|<2.0.
 Our current algorithms
drop off rapidly after ~1.0
to 1.1.

Based on the distribution
of the b-quarks in the
events there is acceptance
to be gained.
 We are trying to quantify

Of course we have not yet
developed such an
algorithm…how we do it is
a harder question.
May 23, 2003
CDF Collaboration Meeting May
2003
Page 20
Impact of Multiple Interactions

On the debit side, we must
accomplish all this in an environment
of many multiple interactions per
crossing.
 This will involve reoptimizing track
reconstruction, b-tagging, lepton-ID,
and general event selection (e.g. extra
jet veto)

What we have done is try to identify
where things go bad.
 Monte Carlo Datasets with multiple
interactions.
 The MC may not have the proper
tuning but we can look at trends.
 Used our standard reconstruction,
tagging, etc. which is tuned at low
luminosity.

4 1032 cm2s 1
The degradation that we see is worse
than it will be after reoptimizing for
that environment.
May 23, 2003
CDF Collaboration Meeting May
2003
Page 21
Impact of Multiple Interactions

Monte Carlo:
Kept standard event
reconstruction and event
selection:

 Pythia WH ebb Production
 Added minimum bias
interactions using “mbr”
Except jet veto…more in
 Samples with 0,2,4,6,8, and 10
a minute.
additional minimum bias.
SecVtx Tagging
0 MB
2 MB
4 MB
6 MB
8MB
10 MB
Taggable
Jets
81.8% 79.9% 78.3%
77.2%
76.6%
73.5%
+Tag Rate
50.0% 47.8% 45.8%
47.2%
43.7%
41.6%
Tag Rate
1.8%
1.9%
1.8%
1.5%
1.7%
1.9%
Tagging Rates are per taggable Jet… We will need to reoptimize the tagging!
May 23, 2003
CDF Collaboration Meeting May
2003
Page 22
Example of Changing our Approach



One of the kinematic cuts is the removal of events with a third
jet with ET > 20 GeV. (Part of Full Jet Selection Below)
This will clearly be sensitive to extra events.
Demand Veto Jet is consistent with Lepton Primary Vertex by
looking at the z0 of tracks in the jets.
Several Competing effects in the Jet selection.
Jet Selection 0 MB 2 MB
4 MB 6 MB
8 MB
(inc Jet Veto)
10 MB
No Track Info 66%
R=1.0
67%
65%
57%
45%
31%
No Track Info 70%
R=0.4
70%
70%
71%
69%
70%
Using Track
Info. R=0.4
74%
75%
78%
78%
82%
May 23, 2003
72%
CDF Collaboration Meeting May
2003
Page 23
Impact of Multiple Interactions

We have examined a variety of scenarios…here is one
example table.
Degradation Primarily Cal Isolation
May 23, 2003
CDF Collaboration Meeting May
2003
Page 24
Dijet Mass Resolution

Dijet Mass “peak” is important
 Excellent Resolution is essential
 Counting events in a window
 Fitting Mjj
 Use as much information as
possible.

Dijet Mass Group
 A lot of work
 Including tracking information, etc.


It’s all about the Jet Corrections.
Good Test Sample:
Z  bb
May 23, 2003
CDF Collaboration Meeting May
2003
Page 25
Including Other information

Dijet Mass Group has been working hard developing
algorithms which correct the energy using tracking
information.
From a talk by Steve Kuhlmann at a Higgs Working Group Meeting
Cone 0.4 Mass
Raw,Ave,TraV2
Cone 0.4 Mass
Res
Raw,Ave,TraV2
Cone 1.0
Mass
Raw,Ave,TraV2
Cone 1.0
Mass Res
Raw,Ave,TraV2
Z->uu
120
83,116,109
GeV
19,18,12
%
100,121,120
GeV
13,12,10
%
Z->bb
120
76,105,102
GeV
23,22,15
%
92,110,112
GeV
16,16,13
%
Mbb = 120 GeV
May 23, 2003
Jets in the central and no b-specific corrections.
CDF Collaboration Meeting May
2003
Page 26
Incorporation Corrections for b-quarks

We have studied corrections
that are derived on WH events
considering the b-quark jets in
these events.
Jets
matched to
b-quarks
 These corrections are applied on
top of the tracking corrections from
the dijet mass group.
 Cone Size R=0.4
 But look at tracks R=1.0
 Use Charge Fraction and ET

In principle we could derive
these as a function of MH
May 23, 2003
Central – Central Jets so tracking
info can be used on both jets.
CDF Collaboration Meeting May
2003
  11 %
Page 27
B-Jets in Plug
Central – Plug B-Jets
  12 %
May 23, 2003
Plug – Plug B-Jets
Second Gaussian larger
CDF Collaboration Meeting May
2003
Page 28
Other Interesting Approach


Do other event quantities help?
“Hyperball Method” (CDF-6450)
Note: No H1 Correction Here
 Tommaso Dorigo and Luca
Scordellaro

Use N Kinematic Variables
 e.g. D j MET M j MTj etc.
 Determine the average mass
reconstruction error for small
regions of N-dimensional space
~ 10 %

DM (x )
 Use this to correct events that fall
in that region of phase space
M
corr
jj



( x)  M jj ( x)  DM ( x)
May 23, 2003
Must Avoid Shaping Peak in Bkg.
Test on data. (e.g. Z
CDF Collaboration Meeting May
2003
bb)
Page 29
Extracting Luminosity Thresholds

To quantify our sensitivity we would like to know how much
luminosity is required to:
 Exclude (95% CL) the existence of the SM Higgs at the certain mass.
 This is based on the theoretical cross section.
 Observe a 3 excess of events.
 Consistent with having a higgs decay (i.e. mass “bump”).
 Observe a 5 excess of events.

We want a method that can easily “sum” over different
channels and CDF and Dzero data.
 Note: it will be extremely difficult to see 3 or 5 excesses in individual
channels for individual experiments
 Rough “Rule of Thumb”…multiply the L-Threshold by 4.
May 23, 2003
CDF Collaboration Meeting May
2003
Page 30
Method

Statistical Analysis Using Pseudoexperiments
 Input:
 Predicted Event Yield for each background source and signal
 Dijet Mass Distribution. (Binned)
o We are using the shape information
 Scan through Integrated Luminosity.
 At each Luminosity, generate a large number of pseudoexperiments
both with and without signal.
 For each pseudoexperiment ask “Do we find a N excess or 95% CL”
 Keep Track of the Fraction of pseudoexperiments that satisfy the condition

For the last step we have investigated two approaches
 Bayesian Integration (with a flat prior)
 CLS Frequentist Approach (used at LEP)

Give similar
Results
Methods include external constraints and sys. Errors.
May 23, 2003
CDF Collaboration Meeting May
2003
Page 31
…50% of Experiments…




Where do we set the
Luminosity threshold for a
given higgs mass?
To set a threshold we must
define that threshold as
requiring X% of the
pseudoexperiments satisfy
the condition (e.g. 3 excess)
The HSWG Report required
50% of the
pseudoexperiments satisfy
the condition.
It does matter.
May 23, 2003
CDF Collaboration Meeting May
2003
95 %
3
5
50 %
Page 32
Explore Sensitivity to Various Effect

These methods allow us
to explore our sensitivity
to various effects.
Impact of Dijet Mass Resolution
 Dijet Mass Resolution
 Uncertainty on background.
 Different event selection.
May 23, 2003
CDF Collaboration Meeting May
2003
Page 33
Impact of Systematics

Important conclusion: When the S/B is very low we need to
tightly control the systematic error on the backgrounds
(normalization and shape.)
10%
May 23, 2003
CDF Collaboration Meeting May
2003
Page 34
Combining with Dzero

The method is setup so that we can “easily” combine the
results with Dzero.
 Each experiment would provide the expected Mjj distributions and
the distributions from data.
 The method uses likelihoods so it can combine the two
experiments.
 Need to think carefully about the common systematic errors.

As mentioned earlier Dzero is working on the ZH channel.
We plan to combine our results using this approach.
May 23, 2003
CDF Collaboration Meeting May
2003
Page 35
Summary and Schedule

We have attacked the WH channel search for the SM higgs
boson on three major fronts:
 Event Yields including B-Tagging:
 One Conclusion: We must use every part of the detector and every
handle possible to increase the event yield.
 Dijet Mass Resolution:
 One Conclusion: This is perhaps where we “win” the fastest.
 Luminosity Thresholds:
 One Conclusion: Life is really hard sometimes.

Remember that we will be looking for the higgs as we
accumulate data.
 Setting Limits as we go.
 Our techniques will become more refined.
May 23, 2003
CDF Collaboration Meeting May
2003
Page 36
Summary and Schedule

Schedule:
 Planned to “Prebless” at June 6th Joint Physics Mtg.
 Had planned on May 30th but we need more time.
 Bless at June 20th
 Will include ZH study from DZero.
 Meeting with Ray Orbach on June 24th at 1 pm.
 Hey that gives us the morning to work right?

Having a definitive statement for Orbach is not possible.
 We can’t precisely predict what our abilities will be 5 years from now.
 We can communicate to him our general level of our sensitivity and
relate the critical issues.
 We should emphasize our understanding of the problem only gets
better with time and data!
May 23, 2003
CDF Collaboration Meeting May
2003
Page 37
Final Comments

The top discovery in Run I took several years and an
enormous amount of work.
 It was a complicated analysis in several different channels.
 Our reach was much higher than we expected at the start of the Run 1.
 Our ability to measure the top mass was much better than we expected
at the start of the Run 1.
 To a great extend it was not that sensitive to systematic errors.

The higgs search is much more complicated than the top
analysis.
 Primarily due to the poor S/B.
 Bringing in many more “channels” to increase acceptance.
 We will probably be sensitive to systematic errors.
 …hopefully our reach will be better than we think…
May 23, 2003
CDF Collaboration Meeting May
2003
Page 38
Final Thought
I’m confident that given the data and
the time, the collaboration will find a
way to squeeze the most sensitivity out
of our data sample…we have very
creative people on this collaboration
and that is perhaps our biggest asset.
May 23, 2003
CDF Collaboration Meeting May
2003
Page 39