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Mar.1 KEKPH07 Higgs and new particle searches at Tevatron Yukihiro Kato Kinki University (behalf of CDF collaboration)
Mar.1 KEKPH07
Higgs and new particle searches at Tevatron
Yukihiro Kato
Kinki University
(behalf of CDF collaboration)
Mar.1 KEKPH07
Contents
• Higgs
• SUSY
• Technicolor
• High mass particles (b’)
This talk includes the new results since summer 2006
Mar.1 KEKPH07
Tevatron
TeV1.96satcollisions pp
Peak luminosity record 2.89 ×1032 cm-2s (Feb 25, 2007)
Tevatron delivered 165pb-1 in Jan. 2007
Integrated luminosity is 2.4fb-1TevatronCDF
D0
Main injector
Mar.1 KEKPH07
CDF CDF has collected over 2 fb-1
data at Feb. 2007 653pb-1 delivered in FY06, 82% to tape (~5% trigger, ~5% beam conditions )
General purpose detectorsPrecision tracking with silicon vertex detectorGood particle identification (K, )
Mar.1 KEKPH07
On going analyses of the exotic physics at CDF
• Higgs: SM Higgs, non-SM Higgs • SUSY • High mass particles: Z’, W’, RS gravitons, b’
• Leptoquarks: 1st, 2nd, 3rd generation
• Technicolor: Techni-rho
• Others: Diphoton+x, large extra dimension, lepton+photon+x
Mar.1 KEKPH07
Search for Higgs・ SM channels:
WH →νbb, jjbbZH → ννbb, bb, jjbb
H → WW WH → WWW・ Extended Models
H → bbH → bbbb H → H+hf → W+hfhf → W+
Low mass Higgs
High mass Higgs
Mar.1 KEKPH07
WH → νbbEvent selection
・ Identified e/μ, pT > 20GeV
・ Two jets: ET > 15 GeV, |η| < 2.0・ At least one b-tagged jet (>2 tag, 1 tag w/ NN tag)
・ Missing ET > 20 GeV
Dominant backgrounds・ W backgrounds: Wbb, Wcc, Wqq (false b-tag)・ Top backgrounds: single top, tt ・ Multi-jet (non W-QCD)
Data sample: 955 pb-1
Mar.1 KEKPH07
WH → νbb Result
Upper limit on Higgs mass from 110 GeV/c2 to 150 GeV/c2
)pb(3.19.3)H(BR)WH( bbpp
New result with 955 pb-1
Mar.1 KEKPH07
ZH→ννbb
Dominant backgrounds・ Multi-jet (QCD)
・ W/Z + heavy flavor
・ Top
・ Diboson
・ Mistag
Event selection・ Two jets, ET>60, 20 GeV・ Lepton veto・ Missing ET > 70 GeV, cut on direction with two jets・ 1 or 2 b-tags (single/double tag sample)
1 b-tag 2 b-tags
Total B.G 310±40 19.6±3.1
Observed 333 24
ZH (115 GeV) 0.77±0.09 0.25±0.05
WH (115 GeV) 0.64±0.07 0.22±0.04
Number of expected event after the cuts
Data sample: 973 pb-1
Mar.1 KEKPH07
ZH→ννbb
95% C.L. upper limit with
respect to the SM
cross-sections Higgs mass
ZH
Exp.
WH
Exp.
Combined
Exp. Obs.
110 25.5 34.8 14.9 17.8
115 28.4 34.0 15.4 16.0
120 31.7 35.1 16.8 15.6
125 40.5 39.2 20.0 21.4
130 50.0 41.5 22.6 22.8
Sliding dijet mass cut for limit setting
Mar.1 KEKPH07
H → W+W- → ννGood sensitivity of the “high-mass” region (mH > 150GeV)
Vector Boson fusion
gg → H
σ(gg →H0) = 431fb @ Mh=160 GeVBr(H0→WW) = 90% @ Mh=160 GeV
It’s large!
Detector signature: Two opposite-sign leptons Missing transverse energy
Same final state
Mar.1 KEKPH07
H → W+W- → νν
Event selection: Isolated leptons with opposite charge:
pT(1) > 20 GeV, pT
(2) > 10 GeV
16 GeV < M < MH/2 – 5 GeV
# of jet cuts Missing ET > MH/4
Higgs mass dependent event cuts: Relations between pT
(1), pT(2), missing ET
Dominant backgrounds:Diboson (WW, WZ, ZZ)Drell-YanWγ tt
Summary of event selection vs. mH
Data sample: 1fb-1
Mar.1 KEKPH07
H → W+W- → ννA statistically significant
contribution of the Higgs signal is not observed
Look in Δφ(1, 2) distributions
Set a 95% C.L limit
( Histograms include the signal and B.G.)
Mar.1 KEKPH07
MSSM Higgs →ττMSSM SUSY with minimal Higgs content⇒ Requires two higgs field doublets
H±; A (CP-odd); h, H (CP-even) At tree level defined by mA and tanvu/vd
A couplings to b, t enhanced by ～ tan For large tan, one of the h/H is SM-like and low mass (m<135 GeV), the ot
her almost mass-degenerate with A, similar couplings
Dominant A decays: bb ( ～ 85 － 95%), ( ～ 5 － 15%) bb: larger BR, but need associated b-jets
In the following is used to denote any of A, h, H
Hgg Hbb
search for Higgs →
Mar.1 KEKPH07
MSSM Higgs →ττSignatures are determined by the decay modes of
Mode Fraction (%) comment
ee 3 Large Z/*→ee B.G.
3 Large Z/*→ B.G.
e 6 Low jet backgrounds
ehad 23 golden
had 23 golden
hadhad 41 Challenging (jet B.G)
Z/*→ee Z/*→ Misidentified jet as had (w+jets, multi-jets) Diboson Top pair production
Used in this search
Dominant backgrounds
Mar.1 KEKPH07
MSSM Higgs →ττData sample (992pb-1) : ehad, had from lepton plus track trigger
(one e/ and isolated track pT>5GeV/c) e from di-lepton trigger
Event selection Good isolation lepton with pT
> 10GeV/chad-ID: ET
cl>9 GeV, pT(had) > 15(1p), 20(3p) GeV/c, Mhad <1.8(1p), 2.2(3p) GeV, isolation(track, )(1,2)>0.5 rad Diboson, tt, W+jets suppression Transverse momentum balance between 1, 2, missing ET Soft QCD suppression ・ e/had: |pThad|+|ET
e(pT)|+|mis.ET| > 55 GeV: (3p)
|pThad|+|ETe(pT
)|+|mis.ET| > 45(50)GeV: (1p) had(ehad) ・ e: |ET
e|+|pT| > 30 GeV
3-prong = (3p)1-prong = (1p)
hadronic decay
Mar.1 KEKPH07
MSSM Higgs →ττ
Backgroundsand
observed events
mvis = invariant mass of the visible decay products and missing ET
mA = 160 GeV/c2
No signal evidence for mA = 90 – 250 GeV/c2
mvis distribution
Mar.1 KEKPH07
MSSM Higgs →ττObserved and expected limits at 95% CL
Excluded region in tan vs mA
Results
Mar.1 KEKPH07
Search for SUSY
• Squarks and Gluinos• Charginos + Neutralinos: like-sign dilepton, trilepton
• R-parity violation: multi-lepton, stop, sneutrino
• GMSB: long-lived neutralinos (decays to photon and gravitino)
• Rare decays and stable particles: Bs and Bd →, long-lived particles
Mar.1 KEKPH07
Chargino – Neutralino production
Multi-lepton (trilepton, like-sign dilepton) is a strong tool!
collidershadronatproductionχ~χ~ 021
021 χ~ and χ~ ofdecay leptonic
)undetected and LSPisχ~( 01
Mar.1 KEKPH07
Chargino – Neutralino productionEvent selection and backgrounds
Trilepton isolated three e/, isolated two e/ and one track pT
1, pT2, pT
3,trk (GeV/c) = (20,8,5), (20,5,5), (15,5,4), (5,5,5) missing ET > 15 GeV reject Mass window: M < 20 GeV/c2, 76< M< 106 GeV/c2
Dominant backgrounds – dibosons, Drell-Yan+conversion
Like-sign dilepton Pair of same charge e/ isolated two e/ with ET(pT) > 20 GeV, 10 GeV Missing ET > 15 GeV Z veto ( 66 < M < 116 GeV/c2) Dominant backgrounds – Drell-Yan, diboson, W/Z+1jet
high-pTlow-pT
Mar.1 KEKPH07
Chargino – Neutralino production
Results of event selections
trilepton
Like-sign dilepton
# of observed events are consistent with SM expectations
Mar.1 KEKPH07
Chargino – Neutralino production
(1) mSUGRA: five free parameters (M0, M1/2, A0, tan, sign()),
parameters: M0 = 60 GeV/c2, A0 = 0, tan = 3, >0, 162 < M1/2 < 230 GeV/c2
(2) MSSM with no slepton mixing: keep mSUGRA relations with slepton mixing off (diagonal terms of the mixing matrix
to zero in Softsusy). → enhances the BR of to e/
parameters:(3) MSSM with W/Z decay: keep the relation in below in the MSSM framework.
parameters:
SUSY scenarios for this analyses
candidate.CDM and LSP theisχ~01
)χ~2M()χ~M()χ~M( 01
021
) Br(W )χ~νχ~Br( 011 ν ) Br(Z )χ~χ~Br( 00
102
)χ~2M(~)χ~M(~)χ~ M(0, 3,tan 011
02
μβ
021 χ~,χ~
Acceptance of high-pT sample
Mar.1 KEKPH07
Chargino – Neutralino production
mSUGRA
no slepton mixing with W/Z decay
MSSM
The excluded cross section limit vs. chargino mass
Mar.1 KEKPH07
GMSB (Gauge Mediated Supersymmetry Breaking models)
G~
χ~01
Neutralino can be have a long life(free parameter). The lightest neutralino is NLSP. LSP is gravitino. NLSP decays to photons and missing ET(gravitino).
The arrival time is different from prompt and decay
Compare arrival time of photons in the +missing ET+jets events
Feynman diagram for GMSB processes
Monte Carlo simulation
Mar.1 KEKPH07
Dominant backgrounds Collision photon: W→eν, +jet+fake missing ET,
2jets+fake missing ET, jets fake Non-collision photon: cosmic rays, beam effect
Selection criteria IDET > 30 GeV, ||<1.1 Missing ET > 40 GeV Jet ET > 35 GeV(missing ET, jet) > 1.0 2.0 < tarrival < 10ns Cosmic rejection Collision fiducial
G~
χ~01
Data sample: 570pb-1
Observed : 2 events# of backgrounds: 1.3±0.7
Mar.1 KEKPH07
G~
χ~01
The expected and observed 95% C.L. cross section limit
The exclude region in the neutralino lifetime and mass space
Mar.1 KEKPH07
Technicolor
Technicolor model:・ New interaction to induce spontaneous sym
metry breaking of the gauge theory.
・ At Tevatron energy, new particle (ρT) could be produced.
bbWpp ν 0TT
Search for W+2jet (b-tag) signature
・ isolated e/μ with ET(pT) > 20 GeV・ missing ET > 25 GeV・ two jets with ET > 20GeV, |η| < 2.0・ b-tag: one tag with NN, double tag w/o NNData sample: 955 pb-1
Mar.1 KEKPH07
TechnicolorDataset agree with B.G.
Backgrounds:・ W/Z + heavy flavors・ tt production・ diboson production・ Non-W QCD・ mistag
1 tag w/ NN
2 tag w/o NN
Mar.1 KEKPH07
b’b’ → bZbZ → bbqq
Search for new particledecaying to Z0
→ b’ quark may have a large branching ratio to bZ0
Event selection・ At least one pair of e/μ with pT>20 GeV・ Z mass window 81 < M< 101 GeV・ # of jets (with ET>30 GeV, |η| <2) 3≧
Target range of b’150 < mb’ < 350 GeV
Backgrounds: ・ Z0 + jets・ Diboson (WZ, ZZ) + jets・ tt + jets ・ QCD multi-jet
Data sample: 1055 pb-1
Mar.1 KEKPH07
b’b’ → bZbZ → bbqqData compared to the Z0+jets B.G
(J30T = scalar sum of ET’s of all jets)
No significant excess
Set cross section limit
mb’ > 270 GeV( BR(b’→ bZ0) = 100 % )
Mar.1 KEKPH07
summary
• Tevatron and CDF are working well.
• CDF has collected the over 2fb-1 data
• CDF has been exploring the new phenomena using ~ 1fb-1 data.
• Please expect the interesting results of the new particles searches at summer conference.
Mar.1 KEKPH07
Backup slides
Mar.1 KEKPH07
By A. Anastassov
Mar.1 KEKPH07
Expected 95% C.L limits
Run same likelihood procedure using “pseudoexperiments”
i. Replace Nobs in each channel with a Poisson fluctuated value with mean equal to the total expected background.
ii. Replace the kinematic distribution with one randomly constructed from the above Poisson number, and the total background distribution.
iii. Replace the Gaussian constrained background values in the likelihood function with a Gaussian fluctuated value with mean equal to that background value. The error are left the same.
iv. Repeat many times.
