Transcript Searches for New Phenomena at CDF 

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: Diphoton+X
Summary and Outlook
UCLA, March 15th 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
UCLA, 03/15/06
B. Heinemann
H
2
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:




Extra dimensions (G)
New gauge groups (Z’, W’,…)
New fermions (e*, t’, b’, …)
Leptoquarks
 Many flavours
Can show up!


As subtle deviations in precision measurements
In direct searches for new particles
UCLA, 03/15/06
B. Heinemann
3
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:

>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
UCLA, 03/15/06
B. Heinemann
4
What’s Nice about Susy?




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
UCLA, 03/15/06
B. Heinemann
5
CDF and the Tevatron
UCLA, 03/15/06
B. Heinemann
6
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
UCLA, 03/15/06
B. Heinemann
7
Tevatron Luminosity
UCLA, 03/15/06
B. Heinemann
8
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
UCLA, 03/15/06
B. Heinemann
PLUG EM CAL.
CLC
PLUG
HAD
CAL.
9
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%
UCLA, 03/15/06
B. Heinemann
10
Measurement of Final State Objects with CDF
Muon ID :
•Coverage : |h|<1
•ID eff. ~ 90-100%
UCLA, 03/15/06
B. Heinemann
11
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%
UCLA, 03/15/06
B. Heinemann
12
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
UCLA, 03/15/06
B. Heinemann
13
Supersymmetry
UCLA, 03/15/06
B. Heinemann
14
Supersymmetry

~
G
G


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!
UCLA, 03/15/06
B. Heinemann
15
Cross Section (pb)
Sparticle Cross Sections: Tevatron
UCLA, 03/15/06
150 events
produced so
far (1.5 fb-1)
B. Heinemann
T. Plehn, PROSPINO
16
Cross Section (pb)
Sparticle Cross Sections:
LHC
100 events
with 1 fb-1
UCLA, 03/15/06
B. Heinemann
T. Plehn, PROSPINO
17
Cross Section (pb)
Sparticle Cross Sections:
LHC
100 events
with 1 pb-1
100 events
with 1 fb-1
UCLA, 03/15/06
B. Heinemann
T. Plehn, PROSPINO
18
Higgs in the MSSM



Minimal Supersymmetric Standard Model:


2 Higgs-Fields: Parameter tanb=<Hu>/<Hd>
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

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)
UCLA, 03/15/06
B. Heinemann
19
Neutral MSSM Higgs

Production mechanisms:

Experimentally:




bb  A/h/H
gg  A/h/H
pp  b+X  bbb+X
pp  +X  tt +X
UCLA, 03/15/06
B. Heinemann
20
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 pT>10 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
Mass<1.8 GeV
Kinematic cuts against background:



W+jets
Photon+jets
Dijets
UCLA, 03/15/06
B. Heinemann
21
Acceptance and Background


Main background:


No full mass reconstruction possible
for low Higgs pT:



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:


mvis>120 GeV:
8.4±0.9 expected, 11 observed
UCLA, 03/15/06
B. Heinemann
22
MSSM Higgs: Results

CDF pp  A+X tt+X




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!
UCLA, 03/15/06
B. Heinemann
23
3rd generation Squarks



3rd generation is special:


Masses of one can be very
low due to large SM mass
Particularly at high tanb
Direct production or from
gluino decays:


pp bb
~~ or tt~~
pp gg
~ ~ or tttt~~
~ ~ bbbb
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~
~ ~
~ ~
UCLA, 03/15/06
~
B. Heinemann
24
Bottom Squarks



This analysis:


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
UCLA, 03/15/06
B. Heinemann
Exclude new parameter
space in gluino vs.
sbottom mass plane
25
Light Stop-Quark: Motivation


If stop quark is light:
~ ~10
 decay only via t->c
E.g. consistent with relic
density from WMAP data




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:


ET(jet)>35, 25 GeV
ET>55 GeV
UCLA, 03/15/06
B. Heinemann
26
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: 8.3+2.3-1.7
Main background:


Z+ jj -> vvjj
W+jj -> tvjj
UCLA, 03/15/06
B. Heinemann
27
Stop Quark: Result and Future

Due to slight excess in data:

No limit set on stop quark mass yet

Future light stop reach :

LHC:




~
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!


Two W’s, two b-quarks, two c-quarks and
missing ET
If m(g)>m(t)+m(t)
UCLA, 03/15/06
~
~
B. Heinemann
28
Charginos and Neutralinos



Charginos and Neutralionos:


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
UCLA, 03/15/06
B. Heinemann
29
3 leptons + Et






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:



Dilepton mass >15 GeV and not
within Z mass range
Less than 2 jets
Significant ET
UCLA, 03/15/06
B. Heinemann
30
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
UCLA, 03/15/06
B. Heinemann
31
3-muon Event
MET
CMIO
CMUP
CMX
UCLA, 03/15/06
B. Heinemann
32

Rare Decay: Bsm+mSM
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
UCLA, 03/15/06
B. Heinemann
33
Bs
+
m m
vs. Trileptons
A.Dedes, S. Mrenna, U. Nierste, P. Richardson hep-ph/0507233
1x10-7
Trileptons: 2fb-1
UCLA, 03/15/06
B. Heinemann
34



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
UCLA, 03/15/06
B. Heinemann
35
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
UCLA, 03/15/06
B. Heinemann
36
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
UCLA, 03/15/06
B. Heinemann
37
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
UCLA, 03/15/06
B. Heinemann
38
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
UCLA, 03/15/06
B. Heinemann
39
Non-Susy Searches
High Mass Dileptons
Standard Model high mass dilepton production:
New physics at high mass:
 Resonance signature:  Tail Enhancement:
 Spin-1: Z’, W’
 Spin-2: Randall-Sundrum
(RS) Graviton
 Spin-0: Higgs, Sneutrino
UCLA, 03/15/06
 Contact Interactions
 Large Extra Dimension
B. Heinemann
(Arkhani-Hamed,
Dimopoulos, Dvali)
41
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
UCLA, 03/15/06
B. Heinemann
42
Z´ee Signal Examples

Angular distribution has different sensitivity for different Z’ models
UCLA, 03/15/06
B. Heinemann
43
Limits on New Physics
 Mass peak search:
Model
ZSM
Z
Z
Zh
Mass limit
(GeV/c2)
860
735 725 745
ZI
ZN
Zsec
650 710 675
 Tail enhancement: contact interaction
UCLA, 03/15/06
B. Heinemann
44
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 don’t miss
anything!
 Diphoton+X
UCLA, 03/15/06
B. Heinemann
45
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
UCLA, 03/15/06
=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
B. Heinemann
46
Diphoton+X: Invariant Mass


Kinematic distributions also agree well with background
prediction
Triphoton analysis first physics result with >1 fb-1 of data!
UCLA, 03/15/06
B. Heinemann
47
Summary and Outlook


CDF and Tevatron running great!



Most analyses based on up to 350750 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



more than 1 fb-1!
Tevatron most powerful tool today:
 provide world’s best constraints on
nearly anything that is being
searched for
LHC will be very powerful in the
future
It is an exciting time
UCLA, 03/15/06
B. Heinemann
48
Backup Slides
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
UCLA, 03/15/06
B. Heinemann
50
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
UCLA, 03/15/06
B. Heinemann
51
Tevatron: Future
UCLA, 03/15/06
B. Heinemann
52
SUSY Particles
gravitino
UCLA, 03/15/06
B. Heinemann
53
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.
UCLA, 03/15/06
B. Heinemann
54
Future High Energy Colliders
LHC (2007-?)
ILC (>2020?)
+
e
p
p
√s=14 TeV
UCLA, 03/15/06
e√s=0.5-1 TeV
B. Heinemann
55
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
UCLA, 03/15/06
B. Heinemann
56
Randall-Sundrum Graviton
 Analysis:
 2 photon mass spectrum
 Backgrounds:
 direct diphoton production
 Jets: p0
 Data consistent with
background
UCLA, 03/15/06
B. Heinemann
57


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)
UCLA, 03/15/06
B. Heinemann
58