Higgs searches and Top properties at CDF

1
Higgs searches and Top properties at CDF
Takasumi Maruyama (Univ. of Tsukuba)
for CDF collaboration

• Contents
• Direct Higgs searches
• Direct SM Higgs searches
• Direct Higgs searches for MSSM
• Recent results of Top physics (except mass)
• ttbar resonance search, cross section, lifetime,
  etc
• Summary

2
Standard Model Higgs Search
Integrated luminosity (/fb)

• Electro-weak precision data prefer light SM
  Higgs (as
• shown in previous talk, blue-band plot shown
  above)
• ( SUSY requires light Higgs.)
• TeV studies in 1999 and 2003 predicted
• 2 fb-1 95CL exclusion at mH115 GeV/c2
• 5 fb-1 3s evidence at mH115 GeV/c2
• If Higgs mass is small, TeV could compete to LHC.

3
SM Higgs Boson Production and Decay _at_ TeV
Decay Branching Ratios
Production Cross-Sections
bb
WW
4
Direct SM Higgs Search
Associate production (search for Mbb peak)
Direct production (phi of dilepton)
CDF (and D0) have started the hunt (WW
result updated from LP05)
5
SM Higgs Searches at the Tevatron
WH?l?bb (Y.Ishizawa (Univ. of Tsukuba) Ph.D
thesis (2005))

• Select events with
• Identified electron or muon
• ETgt20 GeV, isolated
• Missing ET gt 20 GeV
• Two jets with ? lt 2.0,
• ETgt15 GeV.
• Veto extra jets, Z0, cosmics,
• conversions, extra isolated
• tracks
• At least one b-tag

signal region
control region
control region
All requirements except jets. 1, 3 4-jet bins
are control samples for normalizing backgrounds.
6
WH?l?bb Channel Before and After the B-tag
Before b-jet identification there are different
background composition fraction, but gives higher
statistics test !!
7
WH?l?bb Channel Observed and Expected Limits
8
The gg ? H ? WW- Channel
Signal Process

• Interesting Angular
• Correlation due to
• Scalar nature of Higgs Boson
• Different from SM WW- bg
• decay angular correlation!

9
gg ? H ? WW- Channel ?? Discriminant Variable

• Two leptons, Each with ETgt20 GeV
• Jet Veto to remove t-tbar
• Missing ETgt25 GeV
• Z veto
• mllltmH/2 -- note background depends on test
  mass
• Acceptance is 0.4 including Br2(W?l?) for
  mHgt160 GeV

assuming 160 GeV/c2
10
Summary plot for direct SM Higgs searches
K.Kobayashi (Univ. of Tsukuba) Ph.D (2005)
Same colors correspond to same decay mode !! (We
have 3 lines, for CDF, D0 and theory)
11
Ratio of Limits to SM
Note all are normalized to the theoretical cross
section
12
So How Do We Get There??
Luminosity Equivalent (s/?b)2
Improvement WH?l?bb ZH???bb ZH?llbb
Mass resolution 1.7 1.7 1.7
Continuous b-tag (NN) 1.5 1.5 1.5
Forward b-tag 1.1 1.1 1.1
Forward leptons 1.3 1.0 1.6
Track-only leptons 1.4 1.0 1.6
NN Selection 1.75 1.75 1.0
WH signal in ZH 1.0 2.7 1.0
Product of above 8.9 13.3 7.2
CDFDØ combination 2.0 2.0 2.0
All combined 17.8 26.6 14.4
Start with existing channels, add in ideas with
latest knowledge of how well they work (under
studying)
Expect a factor of 10 luminosity improvement
per channel, and a factor of 2 from CDFDØ
Combination
13
Expected Signal Significance CDFDØ vs Luminosity
Its possible to be lucky or unlucky!
per experiment
per experiment
mH115 GeV assumed
14
Non-SM Higgs A?bb and A?tt

• Supersymmetry (MSSM)
• 2 Higgs doublets gt 5 Higgs bosons h, H, A, H
• High tanb
• A degenerate in mass with h or H
• Cross sections enhanced with tan2b due to
  enhanced coupling to down-type quarks
• Decay into either tt or bb
• BR(A ?tt) 10, BR(A? bb) 90
• Exact values depend on SUSY parameter space
• Experimentally
• pp ? AbX ? bbbX (D0 has result)
• pp ? AX ? tt X (CDF has result)

• C. Balazs, J.L.Diaz-Cruz, H.J.He, T.Tait and C.P.
  Yuan, PRD 59, 055016 (1999)
• M.Carena, S.Mrenna and C.Wagner, PRD 60, 075010
  (1999)
• M.Carena, S.Mrenna and C.Wagner, PRD 62, 055008
  (2000)

15
CDF search for A-gttt using Mvis
Invariant mass of visible ??- decay
products plus Missing ET
16
Limits on Cross-Section Branching Ratio
? h0, A0 or H0 or a sum of states with similar
masses
17
Interpretations in MSSM Benchmarks
? 200 GeV M2 200 GeV Mgluino 0.8
MSUSY MSUSY 1 TeV, Xt v6 MSUSY (mhmax) MSUSY
2 TeV, Xt 0 (no-mixing)
D0 searched A-gtbbX mode. CDF new result A-gtbbX
coming soon LEP Limits mtop174.3 GeV for
historical reasons.
18
Tau Channel Prospects for the Future
19
Top Quark Properties

• Understanding on top quark properties has been
  largely improved by much higher statistics than
  Run1 (7 times at this winter conferences)
• Any significant deviation from standard model
  prediction could indicate new physics.
• Recent hot topics (pink boxes) are shown at this
  talk

20
Top Production decay
Top pairs via strong interaction
Cacciari et al JHEP 0404068 (2004) Kidonakis et
al PRD 68 114014 (2003)
TeVatron vs1.96 TeV
mt (GeV) -PDF NLOs(pb) PDF -PDF NLOs(pb) PDF -PDF NLOs(pb) PDF
170 6.8 7.8 8.7
175 5.8 6.7 7.4
180 5.0 5.7 6.3
85 qq 15 gg
Top decays to Wb by 100 in SM
21
Top Pair Production Cross Sections

• Cross section is sensitive to both the
• production and decay anomaly.
• The difference of the xs with different
• decay mode is sensitive to the new physics
• such as charged Higgs.
• Cross section is old but also fresh topic.
• CDF measure this with various decay
• mode and techniques (consistent with SM)

22
Does something new produce ttbar?

• This is more direct exotic search on ttbar
  production.
• Search for new massive resonance decaying to top
  pairs such as top-color Z
• Using leptongt4jets (no-btag) sample.
  Likelihood incorporating LO matrix element was
  used to reconstruct Mttbar.
• Constraint top mass 175GeV/c2
• Fix most of SM backgrounds to expected rate
• Use theory prediction of 6.7pb for SM top pair
  production

Interesting fluctuation, 500GeV _at_ 319pb-1
(2005 summer)
23
New results for Mttbar (with 680pb-1)

• Using the 682pb-1, same analysis was done !!
  (same selection, same
• mass fitting). Note previous 318pb-1 data is
  the sub-sample of the full
• dataset.
• No excess was observed at this time. (left
  figure)
• limit on a narrow leptophobic Z (GZ1.2MZ)
  MZgt725 GeV at 95CL

24
kinematics for ttbar events

• So far, Leading-Order MC (such as PYTHIA,
  HERWIG) describes
• kinematics of the ttbar rich data sample well.
• For example, plots below show PT(ttbar), and
  PT(top/anti-top) using
• ttbar kinematic fitter. (same one as the mass
  analysis)
• This is the start point of the precision
  measurement for top quark

25
Top Lifetime (1)

• SM top has t10-24s
• Measuring lifetime
• Helps in confirming SM top
• Sensitive to production mechanism from long lived
  particles
• CDF uses LeptonJets channel with b jet tagged
• Measure lepton impact parameter (d0)

• Backgrounds
• Prompt Wjets, Drell-Yan, Diboson
• Displaced lepton W(Z) decaying to t,
  Semileptonic b,c decays, photon conversion
  (failing filter)
• Calibration use DY near Z resonance to get d0
  resolution

Signal template
26
Top Lifetime (2)

• Observed data prefer 0 mm lifetime (left figure)
• Interpretation to 95 CL.
• Using Feldman-Cousin limit (right plot)
• cttop lt 52.5 mm (tlt1.75x10-13 s) at 95 C.L.

27
Summary (1)

• We have preliminary searches in a great variety
• of channels, most with 300 pb-1 of data
  analyzed for
• 2005. (expect 1000pb-1 results in this
  summer)
• The sensitivity is currently insufficient to
  test
• for presence or absence of a SM Higgs boson
  but we
• will get more data and improve our channels
  with well-
• understood techniques.
• We have tools to estimate the sensitivity, also
  to combine
• them
• MSSM Higgs searches are getting exciting.

SM Higgs Searches
28
Summary (2)

• Top physics are now in the precision measurement
  phase. (more than 7 times statistics of CDF run
  I in this winter.) In this summer, we will have
  1000pb-1 results
• Trying to check many of top properties.
• So far we have no obvious anomalies against SM
  in ttbar rich sample.
• If we have physics beyond Standard Model related
  to top physics, it could be possible to observe
  it before LHC.

29
Backup slides
30
SECVTX B-tag efficiency

• s/b tradeoff Leptons Missing ET are
  distinctive real
• backgrounds have two b quarks. Single-tag is
  enough.
• Future Combine single and double-tag
  analyses, do a tight-loose
• tag.
• Jet-probability tags are available but not yet
  used in Higgs analyses
• -- more complication for estimating mistags

Mistag rates typically 0.5 for displaced vertex
tags
31
NN Extension of SECVTX B-tag
non-top backgrounds (single-top) after SecVtx ¼
50
Neural Network Signal single-top,
Background , Mistags
(mixed acc. to background estimation)

• Approach
• require SecVtx
• improve purity by including
• long lifetime (also by SecVtx)
• decay length of SecVtx
• D0 of tracks
• large mass
• mass at SecVtx
• pT of tracks w.r.t jet axis
• decay multiplicity
• of tracks
• decay probability into leptons
• of leptons

32
Dijet Mass Resolution Improvements

• Larger jet cones
• track-cluster
• association
• b-specific
• corrections
• Advanced
• techniques
• (NN, hyperball)

Target 10 resolution for two central jets
33
Forward Electrons
Currently plug electrons only used as a Z0
veto in the lvbb channel.
Wbb
Phoenix electrons give 25 extra signal 40 extra
background
?
WH
?
(s/b)forw 0.6(s/b)central Not
optimal to add -- treat as separate channel!
34
Improvement example Lepton Selection

• Forward leptons factor 1.3
• Current analyses use only up to ?lt1.1
• Electrons
• CDF
• Forward electrons used already by other analyses,
  e.g. W charge asymmetry
• Up to ?lt2.8
• Central electrons recently improved efficiency
  from 80 to 90
• Factor 1.34 in acceptance
• Muons
• CDF
• uses only up to hlt1.0
• can be extended since we have detector.

W electron charge asymmetry
PRD 71, 051104 (2005)
75 efficiency
35 lt ETelectron lt 45 GeV
35
EJet Scale Resolution Status / Improvements

• Jet energy scale uncertainty
• precision measurements (Mtop), searches
• now 2.5 uncertainty for jets in top decays
• further improvements
• generators, higher order QCD
• better scale for ET gt 100 GeV region
• complete by end of this year
• Jet energy resolution
• currently 17, goal 10-11
• further improvements
• combine track, calorimeter Info 2
• expand cone size 2
• b-jet specific corrections1-2
• sophisticated algorithms 1-2
• complete by spring 2006

H --gt bb mass (GeV)
36
The Higgs Bosons of the MSSM

• Two Complex Higgs Doublets! Needed to avoid
• anomalies.
• Five Degrees of Freedom plus W,-, Z0
  longitudinal
• polarization states
• Five scalars predicted h, H, A, H, H-
• CP-conserving models h, H are CP-even, A is
  CP-odd
• Independent Parameters
• mA
• tan? ratio of VEVs
• ?
• MSUSY (parameterizes squark, gaugino masses)
• mgluino (comes in via loops)
• Trilinear couplings A (mostly through stop
  mixing)
• Map out Higgs sector phenomenology variations
  of
• all other parameters correspond to a point in
  this space
• And a real prediction mh lt 135GeV Lets
  test it!

37
Couplings of MSSM Higgs Bosons Relative to SM
W and Z couplings to H, h are suppressed relative
to SM (but the sum of squares of h0, H0 couplings
are the SM coupling). Yukawa couplings
(scalar-fermion) can be enhanced
38
Higgs Boson Production Mechanisms

Amplitude ? 1/tan?
Amplitude ? tan?
enhanced!
suppressed!
And many other diagrams
At high tan?, ?(h,AX) ? tan2?
(low tan? and SM case cross-sections too small
to test with current data.)
Amplitude ? tan?
enhanced!
39
Higgs Boson Production and Decay at High tan?

• Interesting feature of many MSSM scenarios (but
  not
• all!)
• mh ,mH ? mA at high tan? (most benchmark
  scenarios..)
• At leading order, ?(A0?bb) and ?(A0???-) are
  both
• proportional to tan2?.
• Decays to W, Z are not enhanced
• and so Br. falls with increasing tan? (even
  at high mA)
• Br(A0 ?bb) 90 and Br(A0???-) 10 almost
• independent of tan? (some gg too).

40
MSSM Higgs Searches
Accepted by PRL, hep-ex/0508051
? 200 GeV M2 200 GeV Mgluino 0.8
MSUSY MSUSY 1 TeV, Xt v6 MSUSY (mhmax) MSUSY
2 TeV, Xt 0 (no-mixing)
CDF Preliminary 310 pb-1
41
Update plan in near future

• All updates aim to have 7001000pb-1
• WH -gt lnubbbar
• Aiming to have results until this May
• ZH -gt nunubbbar
• Aiming to have results around summer
• ZH -gt llbbbar
• They aim to have result in Spring/summer 2006
• H -gt WW
• Spring/Summer 2006
• CDF is very active to get new result !!