Transcript Searches for New Phenomena at CDF 

Searches for New Phenomena at CDF
Beate Heinemann, University of Liverpool
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


Introduction
Supersymmetry:




Higgs
Squarks and Gluinos
Charginos and Neutralinos
Indirect search: Bsmm
Signature Based:


Dilepton and Diphoton
Diphoton+X
Summary and Outlook
UC San Diego, March 14th 2006
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
UCSD, 03/14/06
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H
2
What is Beyond the SM?
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Many good reasons to believe there is as yet unknown
physics beyond the SM
Many possible new particles/theories:

Supersymmetry:

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

Extra dimensions (G)
New gauge groups (Z’, W’,…)
New fermions (e*, t’, b’, …)
Leptoquarks
 Many flavours
Can show up!

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As subtle deviations in precision measurements
In direct searches for new particles
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The Standard Model


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

only accounts for 4% of matter in Universe

No candidate for Cold Dark Matter (≈25%)
cannot explain large mass hierarchy in
fermion sector:

>10 orders of magnitude
does not allow grand unification:

electroweak and strong interactions do not
unify
Hubble Constant
There is a Lot Unknown
has large radiative corrections in Higgs
sector

Matter Density
require fine-tuning of parameters
Cannot explain matter-antimatter
asymmetry?
SM
Supersymmetry can solve three
of these problems
UCSD, 03/14/06
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What’s Nice about Susy?
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Unifications of forces possible
Dark matter candidate exists:

With SUSY
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
UCSD, 03/14/06
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CDF and the Tevatron
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Tevatron Run II


World’s highest energy collider
Tevatron Accelerator:
Run II
√s(TeV)
Dt(ns) L(cm-2 s-1)
1.96
396
_
p
p
1.7x1032
Key parameter: N= • Ldt

Integrated luminosity >1.5 fb-1 by
now:


CDF data taking efficiency about
83%
Delivered: 1.6 fb-1
Recorded: 1.3 fb-1
Integrate Ldt=4-8 fb-1 by 2009
UCSD, 03/14/06
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Tevatron Luminosity
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Measurement of Final State Objects with CDF
MUON CHAMBERS
h = 1.0
CENTRAL HAD CALORIMETER
END
WALL
HAD CAL.
CENTRAL EM CALORIMETER
SOLENOID
h = 2.0
h = 3.0
Silicon
Vertex
Detector
CENTRAL OUTER TRACKER
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PLUG EM CAL.
CLC
PLUG
HAD
CAL.
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Measurement of Final State Objects with CDF
Electron ID :
•Coverage : |h|<3.6
•|h|<2 (w/ trk)
•ID eff. ~ 80-90%
Photon ID :
•Coverage : |h|<2.8
•ID eff. ~ 80%
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Measurement of Final State Objects with CDF
Muon ID :
•Coverage : |h|<1
•ID eff. ~ 90-100%
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Measurement of Final State Objects with CDF
th ID
t cone
isolation
Tau ID :
•Narrow iso. cluster
•Low # tracks
• p0 identification
•Coverage : |h|<1
•ID eff. ~ 46%
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Measurement of Final State Objects with CDF
b
Jet ID :
do
•Cluster of CAL towers
Lxy
•Coverage : |h|<3.6
y
z
Heavy Flavor Jet Tagging :
x
•Id HF jets via semi-leptonic
decay
•Find soft lepton in jets
•Coverage : |h|<1
•Id HF jets via finding displaced
vertex
•Coverage : |h|<1.5
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Supersymmetry
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Supersymmetry

~
G
G
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SM particles have supersymmetric partners:
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Differ by 1/2 unit in spin
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Sfermions (squarks, selectron, smuon, ...): spin 0
gauginos (chargino, neutralino, gluino,…): spin 1/2
No SUSY particles found as yet:
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SUSY must be broken: breaking mechanism determines phenomenology
More than 100 parameters even in “minimal” models!
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How to look for SUSY
o LSP = lightest neutralino (or sneutrino or stau)
o Typical search : NLSP  LSP + (SM particles), LSP
o
o
undetected : Et
Sensitivity:
o LEP: mNLSP ≈ s /2 ≤ 103.5 GeV
o Tevatron: 100- 500 GeV (depends on particle)
Example topologies:
squarks, gluinos
UCSD, 03/14/06
chargino+neutralino
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GMSB
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Cross Section (pb)
Sparticle Cross Sections: Tevatron
UCSD, 03/14/06
150 events
produced so
far (1.5 fb-1)
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T. Plehn, PROSPINO
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Cross Section (pb)
Sparticle Cross Sections:
LHC
100 events
with 1 fb-1
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T. Plehn, PROSPINO
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Cross Section (pb)
Sparticle Cross Sections:
LHC
100 events
with 1 pb-1
100 events
with 1 fb-1
UCSD, 03/14/06
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T. Plehn, PROSPINO
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Higgs in the MSSM
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Minimal Supersymmetric Standard Model:
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2 Higgs-Fields: Parameter tanb=<Hu>/<Hd>
5 Higgs bosons: h, H, A, H±
Neutral Higgs Boson:
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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

Cross section enhanced with tan2b
 Decay into either tt or bb for mA<300 GeV:
 BR(A tt) ≈ 10%, BR(A bb) ≈ 90%
•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
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Production mechanisms:
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Experimentally:
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bb  A/h/H
gg  A/h/H
pp  b+X  bbb+X
pp  +X  tt +X
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MSSM Higgs: Tau-Selection
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Select ttEvents:
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One t decays to e or m
One t decays to hadrons
Require:
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e or m with pT>10 GeV
Hadronic t:
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Narrow Jet with low multiplicity
1 or 3 tracks in 10o cone
No tracks between 10o and 30o:
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Cone size descreasing with increasing energy
Low p0 multiplicity
Mass<1.8 GeV
Kinematic cuts against background:
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W+jets
Photon+jets
Dijets
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Acceptance and Background
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Main background:
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No full mass reconstruction possible
for low Higgs pT:
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Drell-Yan tt
Indistinguishable signature => Separate
kinematically
Form mass like quantity:
mvis=m(t,e/m,ET)
Good separation between signal and
background
Data mass distribution agrees with SM
expectation:
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mvis>120 GeV:
8.4±0.9 expected, 11 observed
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MSSM Higgs: Results
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CDF pp  A+X tt+X
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Sensitivity at high tanb
Exploting regime beyond LEP
Brandnew result from DØ
 Combined with other mode
 pp  bA+Xbbb+X
Future (L=8 fb-1):

Probe values down to 25-30!
UCSD, 03/14/06
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Generic Squarks and Gluinos
 Squark and Gluino
production:
 jets and Et
 Golden signature at LHC
Jets
~g
~( s  2.0  TeV )
p pq
103
(pb)
Missing Transverse
Energy
Missing Transverse
Energy
1

10-3
10-6

10-9
Phys.Rev.D59:074024,1999
300
( M q~  M g~ ) / 2
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500
Strong interaction => large
production cross section
 for M(g)
~ ≈ 300 GeV/c2:
 1000 event produced
for M(g)
~ ≈ 500 GeV/c2:
700
 1 event produced
(GeV )
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Generic Squarks and Gluinos
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Selection:
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3 jets with ET>125 GeV, 75 GeV
and 25 GeV
Missing ET>165 GeV
HT=∑ jet ET > 350 GeV
Missing ET not along a jet direction:
QCD
 Avoid jet mismeasurements
Background:
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W/Z+jets with Wl or Z
Top
QCD multijets
 Mismeasured jet energies lead to
missing ET
Observe: 3, Expect: 4.1±1.5
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Squark/Gluino Candidate event
4 Jets and large missing ET
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Impact on SUSY
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No evidence for excess of
events:
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Exclude squarks and gluinos
for certain mass values
D0 excluded gluinos up to
230 GeV
CDF:
 Interpretation still ongoing
 Likely similar to D0
Stop and sbottom quarks
are excluded from CDF
analysis

3rd generation is special…
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3rd generation Squarks
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3rd generation is special:
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Masses of one can be very
low due to large SM mass
Particularly at high tanb
Direct production or from
gluino decays:
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pp bb
~~ or tt~~
pp gg
~ ~ or tttt~~
~ ~ bbbb
Decay of sbottom and stop:
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b b0
Stop depends on mass:
~ Heavy:
~ t t0
 Medium: t b± bW0
 Light: t ~c0~
~ ~
~ ~
UCSD, 03/14/06
~
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Bottom Squarks
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This analysis:
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Gluino rather light: 200-300 GeV
~ ~
BR(g->bb)=100%
assumed
Spectacular signature:

4 b-quarks + ET
Require b-jets and ET>80 GeV
Expect:2.6±0.7
Observe: 4
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Exclude new parameter
space in gluino vs.
sbottom mass plane
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Light Stop-Quark: Motivation
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If stop quark is light:
~ ~10
 decay only via t->c
E.g. consistent with relic
density from WMAP data
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Balazs, Carena, Wagner: hepph/0403224
WCDM0.110.02
m(t)-m(
~ ~ 10)≈15-30 GeV/c2
2
 m(t)<165
GeV/c
~
Search for 2 charm-jets and
large Et:
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
ET(jet)>35, 25 GeV
ET>55 GeV
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Light Stop-Quark: Result
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Charm jets:
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Use “jet probability” to tag charm:
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Probability of tracks originating from
primary vertex
Improves signal to background ratio:
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Signal Efficiency: 30%
Background rejection: 92%
Data consistent with background
estimate
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Observed: 11
Expected: 8.3+2.3-1.7
Main background:
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Z+ jj -> vvjj
W+jj -> tvjj
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Stop Quark: Result and Future

Due to slight excess in data:
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No limit set on stop quark mass yet
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Future light stop reach :
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LHC:

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

~
L=1 fb-1: m(t)<160
GeV/c2
L=4 fb-1: m(t)<180
GeV/c2
~
Direct production will be tough to trigger
But gluino decay to stop and top yields
striking signature!
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Two W’s, two b-quarks, two c-quarks and
missing ET
If m(g)>m(t)+m(t)
UCSD, 03/14/06
~
~
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Charginos and Neutralinos
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Charginos and Neutralionos:
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SUSY partners of W, Z, photon,
Higgs
Mixed states of those
Signature:

~
3 leptons +
Recent analyses
Et 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
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

Many analyses to cover full phase
space:
 10
~

1

Low tanb:
 2e+e/m
 2m+e/m
 mee/m
~
p
p
~
 20

~
 10
High tanb:
 2e+isolated track
 Sensitive to one-prong tau-decay

Other requirements:
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Dilepton mass >15 GeV and not
within Z mass range
Less than 2 jets
Significant ET
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Trileptons: Blind Analyses
Analysis
Expected
background
Example
SUSY
Data
Trilepton (mm+l)
0.640.18
1.60.2
1
Trilepton (me+l)
0.780.13
1.00.2
0
Trilepton (ee+l)
0.170.05
0.50.1
0
Dielectron+track
0.490.14
1.20.1
1
Trilepton(mm+l)
0.130.03
0.12+-0.02
0
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Trileptons: Result
Analysis
Expected
background
Example
SUSY
Data
Trilepton (mm+l)
0.640.18
1.60.2
1
Trilepton (me+l)
0.780.13
1.00.2
0
Trilepton (ee+l)
0.170.05
0.50.1
0
Dielectron+track
0.490.14
1.20.1
1
Trilepton(mm+l)
0.130.03
0.12+-0.02
0
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Trileptons: Result
Analysis
Expected
background
Example
SUSY
Data
Trilepton (mm+l)
0.640.18
1.60.2
1
Trilepton (me+l)
0.780.13
1.00.2
0
Trilepton (ee+l)
0.170.05
0.50.1
0
Dielectron+track
0.490.14
1.20.1
1
Trilepton(mm+l)
0.130.03
0.12+-0.02
0
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Trileptons: Result
Analysis
Expected
background
Example
SUSY
Data
Trilepton (mm+l)
0.640.18
1.60.2
1
Trilepton (me+l)
0.780.13
1.00.2
0
Trilepton (ee+l)
0.170.05
0.50.1
0
Dielectron+track
0.490.14
1.20.1
1
Trilepton(mm+l)
0.130.03
0.12+-0.02
0
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Trileptons: Result
Analysis
Expected
background
Example
SUSY
Data
Trilepton (mm+l)
0.640.18
1.60.2
1
Trilepton (me+l)
0.780.13
1.00.2
0
Trilepton (ee+l)
0.170.05
0.50.1
0
Dielectron+track
0.490.14
1.20.1
1
Trilepton(mm+l)
0.130.03
0.12+-0.02
0
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Trileptons: Result
Analysis
Expected
background
Example
SUSY
Data
Trilepton (mm+l)
0.640.18
1.60.2
1
Trilepton (me+l)
0.780.13
1.00.2
0
Trilepton (ee+l)
0.170.05
0.50.1
0
Dielectron+track
0.490.14
1.20.1
1
Trilepton(mm+l)
0.130.03
0.12+-0.02
0
Still no SUSY!
Will need to set
limit
UCSD, 03/14/06
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3-muon Event
MET
CMIO
CMUP
CMX
UCSD, 03/14/06
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
Rare Decay: Bsmm
SM
heavily
BRrate
( Bs 
m m suppressed:
)  (3.5  0.9)  10


9
(Buchalla & Buras, Misiak & Urban)


SUSY rate may be enhanced:
(Babu, Kolda: hep-ph/9909476+ many more)
Related to Dark Matter cross section (in one of
S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033
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
UCSD, 03/14/06
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Bs


m m
vs. Trileptons
A.Dedes, S. Mrenna, U. Nierste, P. Richardson hep-ph/0507233
1x10-7
Trileptons: 2fb-1
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


Indirect Search: Bs->mm
Preselection:
 Two muons with pT>1.5 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 >0.99
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Bs->mm :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->mm)<1.5 x 10-7 at 90%C.L.
 Combined with D0:
 BR(Bs->mm)<1.2 x 10-7 at 90%C.L.
 Future:
 Probe values of 2x10-8
UCSD, 03/14/06
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Impact of


Bsm m
A.Dedes, S. Mrenna, U. Nierste, P. Richardson hep-ph/0507233
limits: Now
S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033
 Starting to constrain MSSM parameter space
UCSD, 03/14/06
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47
Impact of Bs


m m
A.Dedes, S. Mrenna, U. Nierste, P. Richardson hep-ph/0507233

limits: L=8
-1
fb
S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033
Tevatron will severely constrain parameter space
UCSD, 03/14/06
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Impact of


Bsm m
A.Dedes, S. Mrenna, U. Nierste, P. Richardson hep-ph/0507233
limits: LHC
S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033
 LHC will probe SM value with about 100 fb-1
UCSD, 03/14/06
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Signature Driven Searches
 All SUSY searches cover unique signatures,
e.g. I showed direct searches:
 Three lepton and missing ET
 3 jets and missing ET
 2 b--jets or c-jets and missing ET
 However, can also search really model
independent to make sure we don’t miss
anything! Examples:
 Dilepton or diphoton invariant mass
 Diphoton+X
UCSD, 03/14/06
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High Mass Dileptons and Diphotons
Standard Model high mass production:
New physics at high mass:
 Resonance signature:  Tail Enhancement:
 Spin-1: Z’, W’
 Spin-2: Randall-Sundrum
(RS) Graviton
 Spin-0: Higgs, Sneutrino
UCSD, 03/14/06
 Contact Interactions
 Large Extra Dimension
B. Heinemann
(Arkhani-Hamed,
Dimopoulos, Dvali)
51
Dielectron and Diphoton Mass
Spectra
 Dielectron mass
spectrum and diphoton
mass distributions
ee
 Data agree well with
Standard Model
spectrum
 No evidence for
 mass peak
 deviation in tail
UCSD, 03/14/06

B. Heinemann
52
Limits on New Physics
 Mass peak search examples:
Model
ZSM
Z
Z
Zh
Mass limit
(GeV/c2)
860
735
725
745
 Tail enhancement: contact interaction
Probing New Physics
- Directly up to 0.9 TeV
- Indirectly up to 5-8 TeV
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Signature: Diphoton+X
 Search for any objects
produced in association
with 2 photons
 Electron, muon, tau
 Photon
 Jet
 Missing ET
SM
 Data consistent with
background prediction
UCSD, 03/14/06
=e,m,
Data
+e
4.50.8
2
m
0.50.1
0

1.90.6
4
ET
0.30.1
0
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Diphoton+X: Invariant Mass


Kinematic distributions also agree well with background
prediction
Triphoton analysis first physics result with >1 fb-1 of data!
UCSD, 03/14/06
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Dirac Magnetic Monopole
•Bends in the wrong plane ( high pt)
•Large ionization in scint (>500 Mips!)
•Large dE/dx in drift chamber
mmonopole > 350 GeV/c2
UCSD, 03/14/06
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Summary and Outlook



CDF and Tevatron running great!


more than 1 fb-1!
Often world’s best constraints
Many unique searches of SUSY,
Higgs and new signatures
Most analyses based on up to 350
pb-1


Will analyse 1 fb-1 by summer 2006
Anticipate 4.4-8.6 fb-1 by 2009
If Tevatron finds no new physics it
will provide further important
constraints

And hopefully LHC will then do the
job
UCSD, 03/14/06
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GMSB: +Et


Assume~01 is NLSP:
~
 Decay to G+
 G~ light: m ≈ 1 keV
 Inspired by CDF ee+Et
event in Run I
 SM exp.: 10-6
D0 (CDF) Inclusive search:
 2 photons: Et > 20 (13) GeV
 Et > 40 (45) GeV
Exp.
Obs.
~+ )
m(
1
D0
2.5±0.5
1
>192 GeV
CDF
0.3±0.1
0
>168 GeV
D0+CDF: m(+1)> 209 GeV/c2
UCSD, 03/14/06
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Tevatron: Future
UCSD, 03/14/06
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Backup Slides
SUSY Particles
gravitino
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Z´ee Signal Examples

Angular distribution has different sensitivity for different Z’
models
UCSD, 03/14/06
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

Extra Dimensions
Attempt to solve hierarchy problem by introducing extra
dimensions at TeV scale
KK
ADD-model:






n ED’s large: 100mm-1fm
M2
PL
~
Rn
MS
q
n+2 (n=2-7)
Kaluza-Klein-tower of Gravitons continuum
Interfere with SM diagrams: =±1 (Hewett)
_
q
ee,
mm,

Randall Sundrum:



Gravity propagates in single curved ED
ED small 1/MPl=10-35 m
Large spacing between KK-excitations
 resolve resonances
Signatures at Tevatron:

Virtual exchange:
 2 leptons, photons, W’s, Z’s, etc.
 BR(G->)=2xBR(G->ll)
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Randall-Sundrum Graviton
 Analysis:
 2 photon mass spectrum
 Backgrounds:
 direct diphoton production
 Jets: p0
 Data consistent with
background
 Relevant parameters:
 Coupling: k/MPl
 Mass of 1st KK-mode
UCSD, 03/14/06
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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: ,h,, I
SM-like couplings (toy model)
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
UCSD, 03/14/06
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Future High Energy Colliders
LHC (2007-?)
ILC (>2020?)
+
e
p
p
√s=14 TeV
UCSD, 03/14/06
e√s=0.5-1 TeV
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