tevatron searches for higgs and susy for the andcollaborations dan claes hadronic structure 2007...
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Tevatron Searches for Higgsand SUSY
for the and collaborations
Dan Claes
Hadronic Structure 2007September 3-7
Comenius University Study and Congress CenterModra-Harmónia, Slovakia
Searches for contributions to observed events by Higgs decays as well as new phenomena beyond the Standard Model are intensifying as the Tevatron data set grows. CDF
Main Injector & Recycler
Tevatron
Chicago
p source
Booster
p
p
p p
1.96 TeV
CDF
DØ
Proton-antiproton collider operating at COM energy of 1.96 TeV
Collider Run II Peak Luminosity
Collider Run II Integrated Luminosity
Will run for at least two more years!
~3 fb-1 recorded!
All the results shown today are based on analysis
of 1+ fb-1
4-8 fb-1 by 2009
one in ~1012 events could be a
Higgs boson!
have seenevidence for single top!
gg
tt
t
H
W / Z W / Z
H
q
q
Higgs production at the Tevatron
AllowedAllowed
Higgs self-coupling Higgs self-coupling divergesdiverges
unstable vacuumunstable vacuum
Nature appears to respect gauge invariance masslessness
Through electroweak symmetry breaking within the complex scalar field, V(), of the Higgs
the gauge bosons W,Z acquire mass
and a spin-0 Higgs boson appears,its own mass unspecified
though theoretical considerations do constrain it.
mH < 144 GeV at 95% confidence limit
The latest LEP Electroweak Working Group fit yields a preferred value of:
Direct searches reveal mH > 114.4 GeV/c2 at 95% confidence
A Standard Model Higgs should be LIGHT!
Exc
lud
ed a
t E
xclu
ded
at
LE
PL
EP
mH<135 GeV/c2
mH>135 GeV/c2
• produced with W or Z boson• decay to b quark pair
• direct ggH production• decays to W boson pair
bbWH bbZH
bbZH
WWH
Most sensitive searches:
Analysis Strategy
mH < 135 GeV
WH/ZH WH/ZH + + HH bb bb
mH > 135 GeV
Gluon fusionGluon fusion + + HHWWWW
top, Wbb, Zbb
WW, DY, WZ
BackgroundBackground
H->WWbb
electron/muon
Selection - one or two tagged b-jets - e or with p
T > 15 GeV
- ET > 20 GeV
neutrino
DØ: 4 non-overlapping samples - e or with - 1 “tight” or 2 “loose” b-tags
CDF: 2 exclusive samples using different b-tagging algorithms
Selection: - two acoplanar jets
(exactly 2 – CDF) - ≥ 1 tagged b-jets (CDF) 2 tagged b-jets (DØ) - E
T > 55 GeV (CDF)
50 GeV (DØ)
b jet
ZH bb
b jet
Selection:-require two isolated muons or electrons in Z mass window-one or two tagged b-jets
e,
Look for enhanced production of Zs:
e,
CDF- corrects its b-jets with ET projections
Separate NN trained to rejecttwo main background processes:
Z + jets top pairs1 ‘tight’ b-tag 2 ‘loose’ b-tags
at MH = 115 GeV
95/SM
20.4 exp 1617.8 obs 16
→ hadrons
→ e or
→ e or
same charge
di-lepton massSelection:- 2 isolated leptons (pT > 15 GeV) (electrons and/or muons)- kinematic likelihood selection
ee
e
“flips”: charge mis-identification estimated from data:: solenoid vs toroide: solenoid vs (track,calorimeter)
like-sign!
, m , ET or E T
min
ee e
expected
background
20.6 4.0
18 5
data 19 15 5
WH(160) 0.1 0.2 0.1
95/SM ~ 18for
MH = 160 GeV
L = 1 fb-1
16
Selection:- two isolated leptons- large ET
miss - Less than 2 jets (>15 GeV) CDF If WW comes from a spin-0 Higgs
Higgs:small ( )
W W:large ( )
leptons will tend to align
• Combines sixteen mutually exclusive final states for WH, ZH, WW
- 10.4 SM at mH=115 GeV
- 3.8 SM at mH=160 GeV• Today I’ll report on recent progress
– updated CDF & DZero low & high mass 1+ fb-1 analyses
SUMMER 2006
Combines sixteen mutually exclusive final states for WH, ZH, WW
7.7 SM at mH=115 GeV
1.4 SM at mH=160 GeV
The Standard Model assumes a single complex Higgs doublet generates W/Z masses and a
massive chargeless spin-0 boson, the Higgs, H
Higgs Bosons Beyond the Standard Model
2HDM: 2 Higgs Doublet Models
• Hu/Hd couple to up- and down- type quarks• tan β is the ratio of their vev’s tan β = <Hu>/<Hd>• EWSB results in 4 massive scalar (h, H, H±) and one massive pseudoscalar (A) Higgs bosons ()
Minimal Supersymmetric Model
At large tan enhanced0bb and 0tt couplings
mean large Higgs productionrates at hadron colliders!
• fully parameterized (at tree level) by tanβ, mA
• with radiative corrections that depend on stop mixing
is accessible to the Tevatron provided mH is not too large!
Background rates in 3 final state are very low• measured fake rates for Z or W • tri-photon production extrapolated from di-photon sample
For tan > 1, mH < 200 GeV and mh < 90 GeV
B(h ) 1 and B( H hW ) 1
Fermiophobic Higgs Decaying to 3A production mechanism unique to hadron colliders
Optimizing selection on 3sET > 30, 25, 25 GeV
0 events observed1.1 0.2 expected background
No obvious structure in
diphoton mass spectrum
Optimizing final selection on 3sET > 30, 20, 25 GeV
and pT > 25 GeV rejects background
Process Events
expected direct 3 0.9 0.2
estimated 3 fakes 0.3 0.05
Observed 0
LEP2 limits of 108 GeV/c2 assumed SM coupling hf V V
Fermiophobic Higgs Decaying to 3
Fermiophobic Higgs in 2+ X
XhVVppf
XZWhpp
f )(
1.1 fb-1
Selection: 2 photons (pT > 25 GeV)
mh>92 GeV at 95% CL
Background: , +jet and jet+jet
b (b) bb b(b) Search
g
g
b
b 0
b
gb
0At high tan Br(H/Abb) 90%, but swamped by QCD background
Look for associated production with bs.
Selection:- 3 b-tagged jets- look for a signal in the invariant mass of two leading jets
The shape from double–tagged events ( mis-tagged rate)
Normalized to the
3b-tagged sample outside
the signal mass
window.
ALPGENMC
0.90 fb-1 0.980 fb-1
b (b) bb b(b) Search
CDF found two useful discriminators• m12 (invariant mass, 2 leading jets)
• mdiff = 321 jet
vertex
jet
vertex
jet
vertexMMM
mass of the tracksassigned to jet fromthe displaced vertex
Neutral MSSM Higgs hadMain backgrounds: Z (irreducible),
W+jets, Zee,, mulijet, di-boson
DØ: -channel only
CDF: e, ,e+ channels
• 1 isolated separated from opposite sign hadronic
• isolated e or separated from opposite sign hadronic
• set of 3 NNs discri- minate from jets
• variable-size cone algorithm for
mvis p1
vis p 2
vis p T
• mvis < 20 GeV removes
remaining W background
• T
had
TTTEppH
> 55 GeV
• Ws removed by a cut on the MET projected on the bisector between s.
Neutral MSSM Higgs had
Small excess in CDF’s e+ channel• but < 2 effect• not observed in CDF e channel
While DØ is in good agreement with SM
Neutral MSSM Higgs had
Both experiments give similar results:in the 90<mA<200 GeV region
tan > ~40-60 excludedfor the no-mixing and mh
max benchmarks
~
~
~~
~Particle Name Symbol Spartner Name Symbol gluon g gluino g charged Higgs H+ chargino 1,2
charged weak boson light Higgs h neutralino 1,2,3,4 heavy Higgs Hpseudoscalar Higgs Aneutral weak boson Z photon quark q squark qR,L
lepton l slepton lR,L
SUPERSYMMETRY
0
The Lightest Supersymmetric Particle provides• ET if the LSP is stable and R-parity is conserved• photons and ET if the LSP is a gravitino and NLSP a neutralino• long-lived particles if the LSP decays weakly
SUSY particles are heavy• high pT final state objects
Minimal Supersymmetric SMExtension adding the fewest new particles
• 2 Higgs doublet h0 H0 A0 H+
• and described by 4 parameters M1 U(1) M2 U(2) gaugino mass parameter at EW scalehiggsino mass parametertan ratio of VEV of Higgs doublets
• scalar sector described by MANY mass parameters• different SUSY breaking different class of models
01
~ 1
~
MSSM Assumptions:
• SUSY particles are pair produced• Lightest SUSY particle (LSP) is stable
SLBparityR 23)1(
•Lightest SUSY particle is
• 5 free parameters
mo common scalar massm1/2 common squark massAo trilinear couplingtansign(
01
~
SUSY Symmetry Breaking SUGRA( ~ 10 11 GeV)
with 0 as Lightest Supersymmetric Particle and bWtcmmmMm
01
~~
Search for: 2 charm jets plus Missing ET
Stop charm + ET
R-parity pair production
Pre-selection: 2 jets, pT > 40(20) GeVLepton, track vetosδφ(jj) < 165o
δφmax δφmin < 120o
δφ(j,ET) > 50o
A=(ETHT)/(ETHT)>0.05ET> 60 GeV
01
~~
mmMbtand
then flavor tag (>= 1 jet)
~
*use Zee+jets tonormalize Zvv+jets
SM process Number of events
W l+jets 20.62 2.34 Z +jets *13.23 1.76 W l +HF (bb, cc) 11.94 1.06 Z +HF (bb, cc) 11.60 0.78 WW,WZ,ZZ 2.70 0.27 t t 2.17 0.07 Single top 1.76 0.05 Z ll(e,,)+jets 0.12 0.09Z ll(e,,)+ HF (bb, cc) 0.09 0.04
Total BKG 64.213.22
Data 66
Stop charm + ET
Finally optimize mass-dependent cuts on HT and P = max + min
For GeV 75 GeV, 13501
~~
mmt
HT>140 P<320
Search for Long-lived Stop
Tracking
Chamber
Electromagnetic
Calorimeter (EM)
Muon
Detector
CDF
Hadronic
Calorimeter
TOFA long-lived, charged massive particle (CHAMP) appears as a “slow” muon.
Some models predict long-lived massive particles due to:– weak coupling (e.g., NLSP in SUSY
models with GMSB)– Kinematic constraints (chargino in SUSY
with AMSB)– New symmetry (gluino in split-SUSY,
LSP stop in ED models)
– High PT, low velocity, highly ionizing “muon”
– Measure velocity () via TOF detector + timing from tracking detector– Calculate mass from momentum and
Data
Control Region
dominated by WGeV pGeV
T4020
Signal RegionGeV p
T40
Search for Long-lived Stop
Exclude stable stop with
m<250 GeV/c2 at 95%CL
• Signal region: no candidates with m>120
• consistent with expected background
Prospino2
Squarks/Gluinos jets + ET
Assuming R-partity is conserved, squarks and gluinos can decay directly into the LSP (0
1).
or cascade down to the LSP
The dominant signature for ppqq, qg, gg + X is jets+ET
At least 3 jets ET > 25 GeV and ET > 25 GeV Separate 2-jet, 3-jet and >3-jet analysis.
Squarks/Gluinos jets + ET
Mgluino < 290 for any Mq
Mgluino < 380
excluded for Mg ~ Mq
1.4 fb-1
A0=0tan = 5<0
~ ~
~
Squarks/Gluinos jets + ET
Mgluino < 402 excluded for Mg~Mq
Mgluino < 309 excluded – any Mq
~ ~
~
0.96 fb-1
A0=0tan = 3<0
Squarks had + jets + ET
0
2~χ
τ -
A0 = 2m0
tan = 15 < 0
enhanced decay
Selection:• 2 or more jets ET > 35 GeV
• ET > 75 GeV • at least one hadronic
Optimization: • ET > 175 GeV • > 325 GeV
T
jet
T
jet
TEEE 21
Squarks had + jets + ET
Predicted YieldsSignal (m0,m½)( 80,160) 4.70.4(100,150) 7.10.6Background 1.7 Data 2
LEP2slepton
searches
LEP2charginosearches
Translating to CL mq
%95@GeV/c 366 2~
Chargino/NeutralinoTrileptons
Production of 1 02 will lead to trilepton final states with ET
perhaps the cleanest signature of supersymmetry.
Dominant backgrounds:Dibosons and Drell-Yan withconverting bremsstrahlung photon
ee+track• Limits set on Br as a
function of mass• Results interpretted within select mSUGRA scenarios
~
qmm ~~
021
~~~
mmm ~
Large and Br
Maximal 3
Chargino/NeutralinoTrileptons
DØ ee+track:Final SelectionSignal: 1-2 eventsBackground: 1 0.3Data: 0
DØ Combined Limit (5 analysis) : 107.0)3( pbBr
2
~/140
1
cGeV m
DØ Combined Limit (14 analysis) : 125.0)3( pbBr
2
~/130
1
cGeV m