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Else Lytken, March 30, 2006 2
Outline o Introduction to the Tevatron and CDF o CDF search strategieso Selection of results:
o Higgs searcheso SUSY searcheso Other searches:
bump hunting, model-independent
o Conclusions
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The Tevatron
p-p collider located at Fermilab ~ 50 miles from ChicagoRun II started in Spring 2001
anti-protons: electron coolingaccumulation: up to 20 mA/hourRoutine operation of storage rings
Beams collide every 396 ns with s = 1.96 TeVCurrent luminosity record:
1.8*1032 cm-2s-1
26.1 pb-1 in a week
Plan: Take data until 2009, collecting a total of 4-8 fb-1
by end of Run II
_
2km
1mA ~ 1010 p_
^
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Collider Detector @ Fermilab
Had Calorimeter
Muon system
Drift chamber
Em Calorimeter
=0=1 Inner tracker (Si)
Towers 150() x 0.1()
Central:
/E = 13.5%/ET
Extends to ||~3.8
/E = 0.5/E coverage:||< 1.2
Hit res: 140 microns
coverage: ||~2.0IP res: 40 microns
Basic coverage ||<1.0
Extension: ||<1.5
B field: 1.4 T
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PerformanceRun II now mature environment stable operation of acceleratorand detectorsMore than 1fb-1 of data on tapeAnalyses shown here use up to 1fb-1 (< when corrected for running conditions)
10 Run I dataset!
1fb-1
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Leptons and jetsAll searches highly dependent on efficient and reliable object identification
Typical efficiencies: (Jet fake rate ~ 10-3 - 10-4 )
~ 45% at high pT
Calorimeter towers:
Coverage : ||<3.6
Heavy flavour jets (||<1.5) : Identified by tagging soft leptons or secondary vertex.
e Eff: 80-90% ~ 80% 85-95% ~50%
Coverage ||<2 ||<2.8 ||<1.5 ||<1
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New PhysicsThe standard model has been a great success Too many questions blowing in the wind:
hierarchy problem, divergences at high E, how to explain dark matter, etc.
Something else is out there to take over at higher energies.Tevatron is currently the place to search for new high pt physics!
Some of the focus points for CDF searches:SM and Extended higgs sectorSupersymmetry
Extra dimensions (large or universal) New heavy gauge bosons Compositeness Generic signature-based searches – always preparing for
the unexpected!Very extensive program, please check out http://www-cdf.fnal.gov/physics/exotic/exotic.html for more results
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p pNEW PHYSICS
Large Missing Energy
Multi-Leptons
Heavy Flavor Jets
Multi-Photons
Long Lived Massive Particles
(ET, or MET)/
New resonances
What we look for
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Expecting small excesses above SM+ many studies have to rely on predictions from simulation to test standard model prediction
very sensitive to little imperfections (detector material distribution, tracking resolution, etc.)
•Now 2-3 interactions/bunch crossing, and increasing with increasing Tevatron L
σ(W→lν)
σ(tt)mt=175 GeV
Challenges for New Physics
most analyses unbiased searches: Signal regions not looked at until confident in background estimates
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Standard Model Higgs- Higgs is only missing SM particle
needed to gives masses to W, Z, fermions - Higgs-like object necessary for most beyond-SM theories.Direct bound from LEP2: mH >114.4 GeV
Indirect from precision EWK fits: mH <175 GeV (<207 GeV if low mass area excl )
Preferred higgs mass (89 GeV) already excluded
Includes new top mass from TeV:mtop = 172.5±2.3GeV
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Higgs Searches @ TeVatronTevatron strategy:
Low higgs masses: (<135 GeV)
Associated higgs production
WH, ZH, with Hbb
(single higgs dominated by dijet background)
Cross section is few hundred fb-1 and efficiencies a few %
Very challenging
For mHiggs>135 GeV:
gg H with HWW*
cros
s se
ctio
n (p
b)
SM Higgs cross section (HIGLU,V2HV)
pp,s=1.96 TeV-
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WHlbb
Search for resonant mass peak in dijets1 tag: 175±26 expected, 187 observed2 tags: 15 ±3 expected, 14 observed
Same final state also used to set limit fortechni- given mass of techni-
Among best channels for low mass higgs• 1 high pT lepton (e or µ)• MET > 20 GeV• 2 b jets ( at least 1 tagged)Main background: Wbb, Wcc, top
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Light flavormistags
QCD
Top
EWK
ZHbb
MET=145 GeV, dijet mass: 82 GeV
In mass window 80-120 GeV:
SM prediction: 4.36 1.02 events
Observe: 6 events.
Background composition:
QCD normalized in control region:
Jet ET = 100 GeV, tagged
Jet ET = 55 GeVtagged
Select events with• 2 jets (at least 1b-tag)• Missing Et >70 GeV
Candidate event:
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HWW*
Spin 0 higgs: spin of W’s from H back-to-back leptons have small angularseparation and small inv mass
W+ e+
W- e-
• Look for opp sign dileptons + MET>25 GeV• Veto Z mass windowMain bkg: direct WW production
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HWW* resultsSuppress background: Mass cut, Mll<½MH and fit to
No excess observed, overall see 14 events as expected
ee e llTotal bkg
4.5±0.4 6.6±0.6 2.9±0.3 14.0±1.3
HWW 0.11±0.01 0.23±0.01 0.11±0.01 0.44±0.03
Obs 4 5 5 14
150 GeV Higgs
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Higgs Searches: CDF Combined Results
In addition to more data: Several improvements underway to bridge the gap
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SupersymmetryIdea: extend SM with symmetry fermions bosonsIf realized, lots of new particles to be found!
Many attractions: Low scale supersymmetry protects higgs mass, provides dark matter candidate, unification @1016 GeV, and consistent with precision top mass fits
Spin 0 1/2 1 3/2 25 higgses leptons gauge gravitino gravitonh0/h0,H0,A, H± quarks bosons G Gsleptons l gluino gsquarks q gauginos ±
0~
~~
~~
~
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SUSY@TeVatron
Large selection of SUSY models and parametersMost interpretations use minimal models
with tan= vu/vd, m0= scalar mass, m1/2= fermion mass
Non-exluded cross sections small Compared to LHC expectations:
Tevatron
LHC
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SUSY signatures
SUSY searches attractive from experimental point of view due to variety of signatures:
- Missing transverse energy from stable LSP’s
(when R-parity conserved)
- multijets from cascade decays
- multileptons
Lightest SusyParticle
New quantum numberoften assumed conserved
R PB L s ( ) ( )1 3 2 +1 SM
- 1 SUSY
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MET + 3 leptonsExpected signature from chargino-neutralino productionHeavily constrained by LEP: m() >103 GeV
~02
~
1
W*
q
q ~01~
1
W*
~01
~02
Z*
Clean signature very attractive for Tevatron, Main backgrounds: DY+fake lepton/conversion, W(Z/*)
CDF takes advantage of all lepton triggers for maximum sensitivity
1
’
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3 leptons: continued
All observations in agreement with SM predictions
ChannelExample signal
SM expected
Obs
µµ/e +l (0.7 fb-1) 2.3±0.3 1.2±0.2 1
ee+l (0.35 fb-1) 0.5±0.06 0.2±0.05 0
µµ+l (low pt) (0.3 fb-1) 0.2±0.03 0.1±0.03 0
ee+trk (0.6 fb-1) 0.7±0.03 0.5±0.1 1
Stay tuned for updated limits!
(enhanced sensitivity to ’s)
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Like-sign dileptons (704 pb-1)
Signature for leptons, decays of gluinosor other majorana particles leptons
Most problematic background: untagged conversions, Drell-Yan+ and W+
MET>15 GeV to suppress DY
Opp sign leptons Like-sign from conversions
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like-sign resultsCategory Obs Predicted signal
ee 4 2.6 ± 0.4 0.64
eμ 5 3.5 ± 0.6 1.64
µμ 0 0.7 ± 0.1 0.91
Total 9 6.8 ± 1.0 3.19
Interesting excess at high pT
- number of events consistent with background prediction.
Look forward to add more data!
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RP: 4 leptons (350 pb-1)
Assume prompt decay of LSP 4 leptons from decaysAnalysis also looked at 3 leptons
~~
Yukawa term:
ijkLiLjEk
Analysis accepts e and µSensitive to 121 and 122
_
Trilepton control regions
Striking signature, virtually no SM backgroundNo cut on MET or N jets4 Leptons: Expects 1.5±0.2 signal, <0.01 SM, observes 0
Comb. 1210: < 0.21 pb limits 1220 : < 0.11 pb
/
:
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MET + jets: squark and gluinoGeneric squarks and gluinos strongly producedCross section @ Tevatron: ~ a few pb
Expect cascade decaysSignature: lots of MET and 2 jets
• Req. 3 jets and MET>165 GeV
• Bkg dominated by Z + jets
• Check: compare data and QCD MC in jet domimated region
• SM wins again:
Expect 4.10.6 events, observe 3
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Search for StopProduction of 3rd generation sparticles could give us first hintsof SUSY:
Due to larger masses of SM partners, mass eigenstates ofleft- and right- stops can have large mass splitting. lightest stop, t1, lighter than other squarks
CDF looking into severalpossible decay modes: t1 c t1 bl RP modes: t1 b New result also using HT:
mass(LQ3)368 GeV Exclusion also applies to3rd generation LQ
/
~
~~
~~
~ 01
01
Updating!
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Indirect constraint: BS
CDF also looks at Bd
Background estimation: linear extrapolation from sidebands
Normalizing using B+- + K+
Rare decay, BR in SM is ~10-9
Loop diagrams with sparticles (or direct decay if RPV) enhance BR orders of magnitudeComplementary to other SUSY e and µ searches
Important at high tan
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BS : Results
Previous limit:
hep-ph/0507233
Compatible with SM backgrounds:Bs Expect: 0.88±0.30 Observe: 1Bd Expect: 1.86±0.34 Observe: 2
Pink regions are excluded by either theory or experimentsGreen region is the WMAP preferred regionBlue dashed line is the Br(Bs) contourLight blue region excluded by old analysis
Limits with 780 pb-1:Br(Bs)<1.0×10-7 @ 95%CLBr(Bd )<3.0×10-8 @ 95%CL
SUSY with minimalSO(10)
NEW limit:
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MSSM Higgs(es)
Analysis look for: l + hadronsFor m120 GeV:
expect 8.4, observe 11 events
All higgs searches working on updates for Summer
5 higgses to look for: h, H, A, H±
Charged: CDF looks for t H±bNeutral: enhanced production at large tan with h/H/A
hep-ex/0508051
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Bump hunting: Z’Several BSM models predict new heavy gauge bosonsCDF searches for Z’ and W’New result: Z’ e+e- using 819 pb-1
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Result: No signifiant bumpsLowest probability observed occurred in 52% of pseudo experimentsHighest mass event: Mee = 491 GeV/c² !
exclude MZ' <850 GeV
SM-Z'
Scan mass spectrum: 1 GeV steps
For each point: get P(bkg fluctuate data) in mass window given by calorimeter resolution
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Large Extra Dimensions
SM backgrounds: Z+ jets, with Z, W+jets, QCD
Compactified extra dimensions (ADD model) with eff Planck scale MD:
M²Planck ~ RnMD²+n
Search for direct production of gravitons in gG or qG final states
Signature would be mono-jet + METET>150
Expect 265±30 eventsObs: 263
MET>120
MET
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First look for anomously production of dilepton+X events (where X = large MET, jets, leptons, etc)
Can be signature for many models: Extra-D, SUSY, ...
Analysis investigating heavy quark model 3 heavy, down-type quarks Q i , decay to Z/H/WFinal state looks at lot like tt
Signal region: eµ + HT>400 GeV, 2 jets >50 GeV
Event expectation SM: 0.8 , QQ: 0.5, observe 0 Limit: (Q)<0.289 pb for m(Q)=300 GeV
Searching for heavy objects
Bjorken, Pakvasa, Tuan: hep-ph/0206116
HT= ET(e) + pT(µ) + ET(jets) + MET No overflows
-
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Now looking for X Zwhere X = Z’, heavy q, neutralino ...
Signature would be high pT excessof events in Z mass window
(66 Mll 116 GeV/c²)
No observed excess on high pT tail for ee or µµ
More limits on heavy quarks: (Q) <0.17 pb @ 95% CL m(Q) = 300 GeV
and more to come ...
CDF Run II Preliminary (305 pb-1)
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Diphoton + e//Several models predict diphoton signatures: Gauge mediated SUSY models,
excited leptons, fermiphobic higgs, ...Analysis inspired by Run I ee +MET event.
searches have huge backgrounds After requiring X almost no backgrounds Do not have to optimize analysis cuts to particular model
CDF has results on +e/µ and More analyses with +X on the way
Phys.Rev.D59.09002 (1999) by Toback et al.
~
q’
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with 1020 pb-1
All photons pass same ID cutsBackground: fakes + real triphotonsExpectation: 1.9 events, observe 4
No significant excess is observedResults will set limits for several models
First case: l with 683 pb-1
Background: fakes or W / Z Expectation: 5.0 events, observe 2
(ET) > 13 GeV
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LEP
excl
ud
ed
Conclusion- CDF and the Tevatron are in great shape!
- Results are pouring in, many more in the pipeline
- No sign of the New Physics yet
More analyses and more data for Summer could take us from great limits to great discovery(ies)!
Higgs sensitivity for Run II:
8 fb-1: exclude Higgs up to mass of 135 GeV
4 fb-1: exclude Higgs up to ~125 GeV
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Vector Leptoquarks (322 pb-1)
Assuming 3rd gen VLQ decays to b+ - signature: lepton+MET+h+di-jet
Cut on: HT=pT(l)+pT(tau)+pT(jets)+MET > 400 GeV/c
New limit: mass 368 GeV/c2
assuming Br(VLQ3 b) = 100%.
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Look in the Bs and Bd Signal Window
LR > 0.99
CMU-CMU Channel: Expect Observed ProbBs 0.88±0.30 1 67%Bd 1.86±0.34 2 63%
CMU-CMX Channel: Expect Observed ProbBs 0.39±0.21 0 68%Bd 0.59±0.21 0 55%
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High mass ee event
run: 202771, event: 8309309
central-central
Mee = 491 GeV/c2
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More Z’ Other analysis also exploring angular information: Z’ would interfere with Z/ look for change in expected shape of cos(*) for Mee > 200 GeV.Observation: 120 events, 115±19 expected similar mass limit with 450 pb-1
Testing angular shape
hep-ex/0602045
angle(incomming quarks, electrons)cos(*) in Colling-Soper frameminimize ambiguity in incomming q Pt
e
e
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New top mass and the MSSM
Plot from: http://quark.phy.bnl.gov/~heinemey/uni/plots/
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More on MSSM higgs
•Br(bb)~90%
• gg,bbbb: need to overcome large QCD BG
•Br()~10%
• gg,bb overcome much smaller SM BG
Projection:
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CDF Trigger System• Rate of incoming events:
– Every 396 ns• Design specs: maximum
rate of accepting events:– L1: 50 kHz– L2: 300 Hz– L3: 30 Hz
• L2 currently is the bottleneck – Exceeded design specs to
operate at 380 Hz
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Shutdown 2006
Detectors:Various maintenance and repairs +
CDF: Final Run II b upgrades: New TDC’s, upgrades to tracktriggers and hardware event builder.
D0: Add innermost Si layer + upgrades to track and calorimetertriggers
We are currently in a long showdown for maintenance of TeVExpected duration: March- June
Plenty of time
On trackPotentially tricky
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Tagging B-jetsTagging B-jetsTagging jets with the SecVtx algorithm is a powerful way of selecting b-jets
Jet is tagged:• decay length Lxy/Lxy > 7• Lxy>0 identifies real heavy flavor jet
Tagged jet
Prim. vertex
2nd vertexLxy>0
• Currently using the tight tagger
• Development of a “forward b-jet tagging” is in progress to increase acceptance
• Mistag rate is ~1%
–Double-sided silicon microstrips: 800k channels!
–r ~1.5 cm out to ~50 cm
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Jet reconstruction Final state partons are revealed through collimated flows of hadrons called jets
Need to have common and unambiguous definition used for theory and experiments. Jet reconstruction algorithms: - infrared and collinear safe - jet direction = parent parton direction
Two main types of jet algorithms:- Cone Algorithm JETCLU (Run I like) and MIDPOINT - KT algorithm
Measurements at hadron level Theory prediction parton level
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• COT Aging - Fully Recovered– Aging due to hydrocarbons
coating sense wires– Fixed by adding Oxygen– Fully recovered May 2004– 99.7% working!
• Silicon detector lifetime is a complex issue involving
• ~93% powered; ~84% working + 4% recoverable in offline
• Secondary vertex trigger requires 4 layers: 21 out of 24 wedges
COT Gain vs. Time
Jan.2002 Aug.2005
May 2004
Lifetime 0 10 fb-1 20 fb-1 30 fb-1 40
Predicted Silicon Lifetime
8 fb-1
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Electron CoolingRecycler: 3.3 km in circumferenceStore antiprotons at 8 GeVMix pbars with 4.3 GeV electron beam reduce longitudinal emittance(Coulomb scattering until thermal equilibrium)
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• Rp (R-parity) conserving– Lightest Supersymmetric Particle (LSP) is stable, escapes
detector (undetected)– Results in large ET
Miss
• striking exp. Signature• (Rp violating signatures)
– Often include lepton flavor violating decaysBreaking Models:• mSugra: supergravity-inspired
– Best-studied model, 5 parameters
• GMSB-motivated signatures– LSP: Gravitino, various next-LSP (NLSP)
• Experimentally: photons!• Run 1 CDF eET
Miss
• AMSB-motivated signatures– Long-lived particles, soft pions– Very hard at hadron colliders
G~~01
120 , , , tan ,sign( )m m A
0 0 122 1 1
122 0.8gm m m m m
sLBPR 2)(3)1(
2222~
2~
2~
2~
2~ )cot(4)(
2
12,1
ttttttt AmmmmmmRLRL
Lightest squark:
)tanhigh(~
),tanlow(~11 bt
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e+, pT = 41 GeV
MET, 45 GeV
CDF Trilepton events
CMIOMET
CMUP
CMX
Mass OS1 41.6 GeV
Mass OS2 27.0 GeV
Jet ET = 50 GeVpT = 4 GeV
e-, pT = 12 GeV