Searches for New Phenomena at CDF

1
Searches for New Phenomena at CDF

• Beate Heinemann, University of Liverpool

• Introduction
• Supersymmetry
• Higgs
• Squarks and Gluinos
• Charginos and Neutralinos
• Indirect search Bs?mm
• Non-SUSY
• Dilepton Mass Spectrum
• Signatrure DiphotonX
• Summary and Outlook

UCLA, March 15th 2006
2
The Standard Model

• Matter is made out of fermions
• quarks and leptons
• 3 generations
• Forces are carried by Bosons
• Electroweak ?,W,Z
• Strong gluons
• Higgs boson
• Gives mass to particles
• Not found yet

H
3
What is Beyond the SM?

• Many good reasons to believe there is as yet
  unknown physics beyond the SM
• Many possible new particles/theories
• Supersymmetry
• Many flavours
• Extra dimensions (G)
• New gauge groups (Z, W,)
• New fermions (e, t, b, )
• Leptoquarks
• Can show up!
• As subtle deviations in precision measurements
• In direct searches for new particles

4
There is a Lot Unknown

• The Standard Model
• only accounts for 4 of matter in Universe
• No candidate for Cold Dark Matter (25)
• cannot explain large mass hierarchy in fermion
  sector
• gt10 orders of magnitude
• does not allow grand unification
• electroweak and strong interactions do not unify
• has large radiative corrections in Higgs sector
• require fine-tuning of parameters
• Cannot explain matter-antimatter asymmetry?
• Supersymmetry can solve three
• of these problems

Hubble Constant
Matter Density
SM
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Whats Nice about Susy?
With SUSY

• Unifications of forces possible
• Dark matter candidate exists
• The lightest neutral gaugino
• Radiative corrections to Higgs acquire SUSY
  corrections
• No fine-tuning required
• Changes relationship between mW, mtop and mH
• Also consistent with precision measurements of MW
  and mtop

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CDF and the Tevatron
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Tevatron Run II

• Worlds highest energy collider
• Tevatron Accelerator
• Integrated luminosity gt1.5 fb-1 by now
• CDF data taking efficiency about 83
• Integrate ?Ldt4-8 fb-1 by 2009

_
p
p
vs(TeV) Dt(ns) L(cm-2 s-1)
Run II 1.96 396 1.7x1032
Key parameter N? ?Ldt
Delivered 1.6 fb-1 Recorded 1.3 fb-1
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Tevatron Luminosity
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Measurement of Final State Objects with CDF
Measurement of Final State Objects with CDF
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Measurement of Final State Objects with CDF
Measurement of Final State Objects with CDF

• Electron ID
• Coverage hlt3.6
• hlt2 (w/ trk)
• ID eff. 80-90

• Photon ID
• Coverage hlt2.8
• ID eff. 80

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Measurement of Final State Objects with CDF
Measurement of Final State Objects with CDF

• Muon ID
• Coverage hlt1
• ID eff. 90-100

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Measurement of Final State Objects with CDF
Measurement of Final State Objects with CDF

• Tau ID
• Narrow iso. cluster
• Low tracks
• p0 identification
• Coverage hlt1
• ID eff. 46

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Measurement of Final State Objects with CDF

• Jet ID
• Cluster of CAL towers
• Coverage hlt3.6

• Heavy Flavor Jet Tagging
• Id HF jets via semi-leptonic decay
• Find soft lepton in jets
• Coverage hlt1
• Id HF jets via finding displaced vertex
• Coverage hlt1.5

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Supersymmetry
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Supersymmetry

• SM particles have supersymmetric partners
• Differ by 1/2 unit in spin
• Sfermions (squarks, selectron, smuon, ...) spin
  0
• gauginos (chargino, neutralino, gluino,) spin
  1/2
• No SUSY particles found as yet
• SUSY must be broken breaking mechanism
  determines phenomenology
• More than 100 parameters even in minimal models!

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Sparticle Cross Sections Tevatron
Cross Section (pb)
150 events produced so far (1.5 fb-1)
T. Plehn, PROSPINO
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Sparticle Cross SectionsLHC
Cross Section (pb)
100 events with 1 fb-1
T. Plehn, PROSPINO
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Sparticle Cross SectionsLHC
100 events with 1 pb-1
Cross Section (pb)
100 events with 1 fb-1
T. Plehn, PROSPINO
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Higgs in the MSSM

• Minimal Supersymmetric Standard Model
• 2 Higgs-Fields Parameter tanbltHugt/ltHdgt
• 5 Higgs bosons h, H, A, H
• Neutral Higgs Boson
• Pseudoscalar A
• Scalar H, h
• Lightest Higgs (h) very similar to SM
• At high tanß
• A is degenerate in mass with either h or H
• Decay into either tt or bb for mAlt300 GeV
• BR(A ?tt) 10, BR(A? bb) 90
• Cross section enhanced with tan2?

• 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)

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Neutral MSSM Higgs

• Production mechanisms
• bb ? A/h/H
• gg ? A/h/H
• Experimentally
• pp ? ?bX ? bbbX
• pp ? ?X ? tt X

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MSSM Higgs Tau-Selection

• Select t t Events
• One t decays to e or m
• One t decays to hadrons
• Require
• e or m with pTgt10 GeV
• Hadronic t
• Narrow Jet with low multiplicity
• 1 or 3 tracks in 10o cone
• No tracks between 10o and 30o
• Cone size descreasing with increasing energy
• Low p0 multiplicity
• Masslt1.8 GeV
• Kinematic cuts against background
• Wjets
• Photonjets
• Dijets

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Acceptance and Background

• Main background
• Drell-Yan tt
• Indistinguishable signature gt Separate
  kinematically
• No full mass reconstruction possible for low
  Higgs pT
• Form mass like quantity mvism(t,e/m,ET)
• Good separation between signal and background
• Data mass distribution agrees with SM
  expectation
• mvisgt120 GeV
• 8.40.9 expected, 11 observed

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MSSM Higgs Results

• CDF pp ? AX? ttX
• Sensitivity at high tanb
• Exploting regime beyond LEP
• Brandnew result from DØ
• Combined with other mode
• pp ? bAX?bbbX
• Future (L8 fb-1)
• Probe values down to 25-30!

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3rd generation Squarks

• 3rd generation is special
• Masses of one can be very low due to large SM
  mass
• Particularly at high tan?
• Direct production or from gluino decays
• pp ?bb or tt
• pp ?gg ?bbbb or tttt
• Decay of sbottom and stop
• b ?b?0
• Stop depends on mass
• Heavy t ?t?0
• Medium t ?b? ?bW?0
• Light t ?c?0

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Bottom Squarks

• This analysis
• Gluino rather light 200-300 GeV
• BR(g-gtbb)100 assumed
• Spectacular signature
• 4 b-quarks ET
• Require b-jets and ETgt80 GeV

Expect2.60.7 Observe 4
Exclude new parameter space in gluino vs. sbottom
mass plane
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Light Stop-Quark Motivation

• If stop quark is light
• decay only via t-gtcc10
• E.g. consistent with relic density from WMAP data
• Balazs, Carena, Wagner hep-ph/0403224
• WCDM0.11-0.02
• m(t)-m(c10)15-30 GeV/c2
• m(t)lt165 GeV/c2
• Search for 2 charm-jets and large Et
• ET(jet)gt35, 25 GeV
• ETgt55 GeV

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Light Stop-Quark Result

• Charm jets
• Use jet probability to tag charm
• Probability of tracks originating from primary
  vertex
• Improves signal to background ratio
• Signal Efficiency 30
• Background rejection 92
• Data consistent with background estimate
• Observed 11
• Expected 8.32.3-1.7
• Main background
• Z jj -gt vvjj
• Wjj -gt tvjj

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Stop Quark Result and Future

• Due to slight excess in data
• No limit set on stop quark mass yet
• Future light stop reach
• L1 fb-1 m(t)lt160 GeV/c2
• L4 fb-1 m(t)lt180 GeV/c2
• LHC
• Direct production will be tough to trigger
• But gluino decay to stop and top yields striking
  signature!
• Two Ws, two b-quarks, two c-quarks and missing
  ET
• If m(g)gtm(t)m(t)

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Charginos and Neutralinos

• Charginos and Neutralionos
• SUSY partners of W, Z, photon, Higgs
• Mixed states of those
• Signature
• 3 leptons
• Recent analyses of EWK precision data
• J. Ellis, S. Heinemeyer, K. Olive, G. Weiglein
• hep-ph/0411216
• Light SUSY preferred

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3 leptons
Et

• Many analyses to cover full phase space
• Low tan?
• 2ee/m
• 2me/m
• mee/m
• High tan?
• 2eisolated track
• Sensitive to one-prong tau-decay
• Other requirements
• Dilepton mass gt15 GeV and not within Z mass range
• Less than 2 jets
• Significant ET

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Trileptons Result
Analysis Expected background Example SUSY Data
Trilepton (??l) 0.64?0.18 1.6?0.2 1
Trilepton (?el) 0.78?0.13 1.0?0.2 0
Trilepton (eel) 0.17?0.05 0.5?0.1 0
Dielectrontrack 0.49?0.14 1.2?0.1 1
Trilepton(??l) 0.13?0.03 0.12-0.02 0
Still no SUSY! Will need to set limit
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3-muon Event
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Rare Decay Bs?mm-

• SM rate heavily suppressed
• SUSY rate may be enhanced
• Related to Dark Matter cross section (in one of 3
  cosmologically interesting regions)
• Recently gained a lot of attention in WMAP data
  SUSY analyses, see e.g.
• B. Allanach, C. Lester hep/ph-0507383
• J. Ellis et al., hep-ph/0504196
• S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033
• R. Dermisek et al., hep-ph/0507233

(Buchalla Buras, Misiak Urban)
(Babu, Kolda hep-ph/9909476 many more)
S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033
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Bs?mm- vs. Trileptons
A.Dedes, S. Mrenna, U. Nierste, P. Richardson
hep-ph/0507233
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Indirect Search Bs-gtmm

• Preselection
• Two muons with pTgt1.5 GeV/c
• Dimuon vertex displaced from primary
• Identify variables that separate signal from
  background
• Decay length ?
• Points towards primary vertex
• Isolated from other tracks
• Construct likelihood of variables
• Excellent separation
• Cut at likelihood ratio gt0.99

36
Bs-gtmm Result and Future

• Result
• 0 events observed
• Backgrounds
• 0.81 0.12 for (CMU-CMU)
• 0.66 0.13 for (CMU-CMX)
• Branching Ratio
• CDF
• BR(Bs-gtmm)lt1.5 x 10-7 at 90C.L.
• Combined with D0
• BR(Bs-gtmm)lt1.2 x 10-7 at 90C.L.
• Future
• Probe values of 2x10-8

37
Impact of Bs?mm- limits Now
S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033
A.Dedes, S. Mrenna, U. Nierste, P. Richardson
hep-ph/0507233

• Starting to constrain MSSM parameter space

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Impact of Bs?mm- limits L8 fb-1
S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033
A.Dedes, S. Mrenna, U. Nierste, P. Richardson
hep-ph/0507233

• Tevatron will severely constrain parameter space

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Impact of Bs?mm- limits LHC
S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033
A.Dedes, S. Mrenna, U. Nierste, P. Richardson
hep-ph/0507233

• LHC will probe SM value with about 100 fb-1

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Non-Susy Searches
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High Mass Dileptons
Standard Model high mass dilepton production
New physics at high mass

• Resonance signature
• Spin-1 Z, W
• Spin-2 Randall-Sundrum (RS) Graviton
• Spin-0 Higgs, Sneutrino

• Tail Enhancement
• Contact Interactions
• Large Extra Dimension (Arkhani-Hamed, Dimopoulos,
  Dvali)

42
Z?ee Search

• Dielectron mass spectrum and angular
  distribution
• 2D analysis improves sensitivity
• Data agree well with Standard Model spectrum
• No evidence for mass peak

43
Z?ee Signal Examples

• Angular distribution has different sensitivity
  for different Z models

44
Limits on New Physics

• Mass peak search
• Tail enhancement contact interaction

Model ZSM Z? Z? Z? ZI ZN Zsec
Mass limit (GeV/c2) 860 735 725 745 650 710 675
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Signature Based Searches

• All searches cover unique signatures, e.g.
• Three lepton and missing ET
• B- or c-jets and missing ET
• 2 b--jets or c-jets and missing ET
• Dilepton invariant mass
• However, can also search really model independent
  to make sure we dont miss anything!
• DiphotonX

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Signature DiphotonX

• Search for any objects produced in association
  with 2 photons
• Electron, muon, tau
• Photon
• Jet
• Missing ET
• Data consistent with background prediction

e,m,g
SM Data
??e 4.5?0.8 2
???? 0.5?0.1 0
???? 1.9?0.6 4
???ET 0.3?0.1 0
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DiphotonX Invariant Mass

• Kinematic distributions also agree well with
  background prediction
• Triphoton analysis first physics result with gt1
  fb-1 of data!

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Summary and Outlook

• CDF and Tevatron running great!
• Most analyses based on up to 350-750 pb-1
• Will analyze 1 fb-1 by summer 2006
• Anticipate 4.4-8.6 fb-1 by 2009
• Searches probe Nature in new, unique way
• Tevatron most powerful tool today
• provide worlds best constraints on nearly
  anything that is being searched for
• LHC will be very powerful in the future
• It is an exciting time

more than 1 fb-1!
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Backup Slides
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Dirac Magnetic Monopole

• Bends in the wrong plane (? high pt)
• Large ionization in scint (gt500 Mips!)
• Large dE/dx in drift chamber

TOF trigger designed specifically for monopole
search
mmonopole gt 350 GeV/c2
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GMSB ggEt

• Assume c01 is NLSP
• Decay to Gg
• G light m 1 keV
• Inspired by CDF eeggEt
• event in Run I
• SM exp. 10-6
• D0 (CDF) Inclusive search
• 2 photons Et gt 20 (13) GeV
• Et gt 40 (45) GeV

Exp. Obs. m(c1)
D0 2.50.5 1 gt192 GeV
CDF 0.30.1 0 gt168 GeV
D0CDF m(c1)gt 209 GeV/c2
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Tevatron Future
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SUSY Particles
gravitino
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Neutral Spin-1 Bosons Z

• 2 high-PT electrons, muons, taus
• Data agree with BG (Drell-Yan)
• Interpret in Z models
• E6-models y, h, c, I
• SM-like couplings (toy model)

55
Future High Energy Colliders
LHC (2007-?)

• ILC (gt2020?)

p
e
p
e-
vs0.5-1 TeV
vs14 TeV
56
Randall-Sundrum Graviton

• Analysis
• 2 photon mass spectrum
• Backgrounds
• direct diphoton production
• Jets ?0???
• Data consistent with background
• Relevant parameters
• Coupling k/MPl
• Mass of 1st KK-mode

57
Randall-Sundrum Graviton

• Analysis
• 2 photon mass spectrum
• Backgrounds
• direct diphoton production
• Jets ?0???
• Data consistent with background

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Extra Dimensions

• Attempt to solve hierarchy problem by introducing
  extra dimensions at TeV scale
• ADD-model
• n EDs large 100mm-1fm
• M2PL Rn MSn2 (n2-7)
• Kaluza-Klein-tower of Gravitons ?continuum
• Interfere with SM diagrams l1 (Hewett)
• Randall Sundrum
• Gravity propagates in single curved ED
• ED small 1/MPl10-35 m
• Large spacing between KK-excitations
• ? resolve resonances
• Signatures at Tevatron
• Virtual exchange
• 2 leptons, photons, Ws, Zs, etc.
• BR(G-gtgg)2xBR(G-gtll)

KK
ee, mm, gg
q
_
q