Transcript No Slide Title

Recent Results from DØ
Barbro Åsman
CDF
Stockholm University
For the DØ Collaborations
6 km circumference
DØ
3RD INTERNATIONAL WORKSHOP ON HE INTERCONNECTION BETWEEN
PARTICLE PHYSICS AND COSMOLOGY
University of Oklahoma, Norman , OK, US
May 18-22 2009
Tevatron Accelerator
Excellent performance:
Instantaneous luminosity:
Typical : ~2.8x1032 cm-2s-1
Record : 3.3x1032 cm-2s-1
• Delivered ~6.5 fb-1
• Recorded ~5.7 fb-1
2
The DØ Detector
Multipurpose detector
Central tracking system:
Silicon vertex detector
Fiber tracker
Preshowers
Calorimeters
Muon system
3
Outline
• Introduction
• Bs-Physics
CP Violation
Rare Decay
• W mass and Top mass
• Single Top
• Higgs
• New Phenomena
• Conclusion
4
CP Violation in Bs Decays
Mass eigenstates:
0
s
| BL  = p | B  + q | B 
0
s
0
s
| BH  = p | B   q | B 
0
s
ΔMs = MH  ML  2 M12
assl= Γs/ΔMs tan(φs)
ΔΓs = ΓL  ΓH  2Γ12 cosφs
assl = -(8.4+5.2-6.7)·10-3
assl = 0.002 ± 0.009 ·10-3
asls 


 
 
Γ Bs (t )  f  Γ Bs (t )  f
Γ Bs (t )  f  Γ Bs (t )  f
World Average
assl = +0.02·10-3 in SM
5


CP Violation in
Opposite Side
0
B s
Decay
Reconstructed Side
X
μ(e)
μ+
Bs0  Bs0
B
LT
D-S
ν
π-
φ
K+
a  0.0017  0.0091(stat )
s
sl
assl = -(8.4+5.2-6.7)·10-3
K-
(syst )
0.0012
0.0023
assl = 0.002 ± 0.009 ·10-3
6
Rare Decays:
B(Bs-> μμ) = (3.37±0.31)×10-9
->
0
B s→μ+μ‐
Expect 0 Events at Tevatron
Can be enhanced by New Physics Contributions
7
0
B s→μ+μ‐: Significance & Outlook
RESULT: B(B
0
s
-> m+m-) < 4.3(5.3 ) x 10-8
Expect sensitivity to get
Better.
Detector and analysis
improvements
Expect combined limit
O(10-8) by end of Run II
Significant constraints on New
Physics
8
Masses for W -Top - Higgs
t
W
W
•
•
b
H
W
W
Constraint on SM Higgs mass dominated
by the W mass uncertainty:
Dmt = ±1.2 GeV  DMH = +9/-8 GeV
DMW = ±25 MeV  DMH = +17/-13 GeV
• Measured from template fits to
W transverse mass, lepton pT and MET
distribution
•
Exquisite understanding of the detector
response, noise and pileup required:
~ few MeV for quantities ~40 GeV!
•
Uncertainty currently dominated
by statistics of Z sample used for calibration.
Theoretical uncertainties ~10-15 MeV.
9
W Mass
–W -> eν mode
e+
– Cannot measure ν or W momentum
along beam
Use variables defined in
transverse plane
PTe, MET, mT
mT = √ 2 PTe, MET (1-cos Df)
- Cannot predict analytically
Distributions from parametric
simulation the work goes here!
10
Mass Fits
mZ = 91.185 ± 0.033 GeV (stat)
mW= 80.401 ± 0.023 GeV (stat)
Z mass value from LEP was an input to
electron energy scale calibration, PDG:
mZ = 91.1876 ± 0.0021 GeV
11
Summary of Uncertainties
Source
Experimental
Electron Energy Scale
Electron Energy Resolution Model
Electron Energy Nonlinearity
W and Z Electron energy loss
differences
Recoil Model
Electron Efficiencies
Backgrounds
Experimental Total
W production and decay model
PDF
QED
Boson PT
W model Total
Total
Statistical
TOTAL
smW) MeV mT
smW) MeV PeT smW) MeV ET
34
2
4
4
6
5
2
34
2
6
4
12
6
5
34
3
7
4
20
5
4
35
37
41
9
7
2
12
37
23
44
11
7
5
14
40
27
48
14
9
2
17
44
23
50 12
W Mass Results
•
Single most precise
measurement
• Good agreement with
previous measurements
• Based on 1/6 of the data
13
Top Quark Mass
Dileptons:
• e, m, t -> e or m
6,5 % low background
• e or m + t -> had
3.6 % resonable background
Leptons plus jets:
• e, m, t -> e or m + jets 35 % resonable background
• t -> had + jets
9.5% high background
All jets:
46 % high background
14
Top Mass Measurement
Sophisticated techniques to minimize
statistical and systematic uncertainties.
Leptons + jets RunIIa :
171.5 ± 1.4 (stat) ± 1.8 (syst)
with 1.0 fb-1
Lepton + jets RunIIb:
174.8 ± 1.0 (stat) ± 1.6 (syst)
with 2.6 fb-1
Electron + muon RunIIa: 171.7 ± 6.4 (stat) ± 2.5 (syst)
with 1.0 fb-1
Electron + muon RunIIb: 176.1 ± 3.9 (stat) ± 2.7 (syst)
with 2.6 fb-1
ee, mm, l + track RunIIa:
with 1.0 fb-1
174.2 ± 6.0 (stat) ± 2.3 (syst)
15
Top Mass Combined Measurement
Goal to reach an error below 1 GeV
16
Observation of Single Top
Direct access to the Wtb coupling
Overall rate and ratio between
s -and t-channels are sensitive to NP•
Experimental challenge:
-cross section ~x2 lower than ttbar
-large backgrounds from W+2 jets
-S/B ~1/200 before b-tagging
-Need multivariate techniques to
extract signal.
17
Observation of Single Top
s (pp -> tb + X, tbq + X) = 3.94 ± 0.88 pb
| Vtb | > 0.78 at 95 % C.L.
| f1L Vtb | = 1.07 ± 0.12
where is f1L the strength of the
left-handed Wtb coupling
Submitted to PRL (2009), hep-ex/0903.0850
18
Top Resonances?
Seach for X -> tt
0.35 TeV < MX< 1.2 TeV
Width RX = 0.012 MX
Signal: Lepton, MET, ≥3 jets, ≥1b-tag
19
Higgs Search
…and more!
•
Current experimental information :
•
• SM LEP direct search: mH>114 GeV
• SM indirect constraint: mH<168 GeV
 Tevatron is sensitive over whole
“interesting” mass range.
•
•
Main production mechanisms:
• Gluon fusion ggH
• Associated production , WH and ZH:
Dominant decay channels:
• mH<135 GeV: Hbb
• mH>135 GeV: HWW(*)
Search strategy:
• Low mass region:
WHlnbb, ZH l+l-bb, ZHnnbb
• High mass region:
20
ggHWW(*) l+nl’-n
Higgs Channels
Channel
Data Eoch
WH -> lnbb, ST/DT, W+2 jets
WH -> lnbb , ST/DT,W+3 jets
WH -> tnbb
H + X -> ttbb/qqtt
ZH-> nnbb, DT
ZH -> e+e-bb , ST/DT
ZH->mmbb, ,ST/DT
ZH-> e+e- , ST/DT
ZH->mm-bb, ST/DT
ZH->m±+track, ST/DT
WH-> WW+WWH->WW+WH->W+W-(mm)
H->W+W-(em)
H->W+W-(e+e-)
H->gg
ttH ->ttbb
RunIIa+RunIIb
RunIIa+RunIIb
RunIIa
RunIIa
RunIIa+RunIIb
RunIIa
RunIIa
RunIIb
RunIIb
RunIIa+RunIIb
RunIIa
RunIIb
RunIIa+RunIIb
RunIIa+RunIIb
RunIIa+RunIIb
RunIIa+RunIIb
RunIIa+RunIIb
L (fb-1)
2.7
2.7
0.9
1.0
2.1
1.1
1.1
3.1
3.1
4.2
1.1
2.5
3.0
4.2
4.2
4.2
2.1
Final variable
#Sub
Ch
NN discriminant
8
Dijet Mass
8
Dijet Mass
5
NN discriminant
1
DTree discriminant
2
NN discriminant
2
DTree discriminant
2
DTree discriminant
6
DTree discriminant
2
DTree discriminant
2
2-D Likelihood
3
1-D Likelihood
3
NN discriminant
1
NN discriminant
1
NN discriminant
1
Di-photon Mass
1
Scaled HT
12
TOTAL Sub-Channels 60
21
Higgs Limits
22
Higgs Limits
23
SUSY Higgs
Minimal Supersymmetric Standard Model (MSSM):
5 Physical Higgs bosons :
0
0
0
3 Neutral: (A , h and H ) → 0
2 Charged: H
Two parameters to calculate Higgs masses and couplings at tree level
mA
tan = ratio of vacuum expectation values of two Higgs fields
DØ search:
•
MSSM at large tan:
•
•
•
b, t
b, t
0={h0/H0,A0} nearly degenerated in mass
Coupling to b, t enhanced (tan)  s+X  2 x tan2
BR(0bb)~90%, BR(0t+t-)~10%
t
t
24
0 -> bb / 0 > tt
Φ0->bb too hard due to QCD processes:
•Look for Φ0b->bbb in triple‐tagged events
to reduce background
Combination with analysis on earlier data:
Exclusion region in the tanβ‐mA plane
• 0 > tt has lower BR,
but higher cross section
•Inclusive decays:  -> τeτμ, τhτμ, τhτe
•Challenge: hadronic τ -decay ID
25
NMSSM h -> aa Search
- h -> bb branching ratio reduced
- h decays mainly to pair of pseudo-scalor Higgs a : h ->aa
-LEP search sets limit: Mh > 82 Gev
For Masses 2Mm < Ma < 2Mt
- BR(a->mm) ~ 100%: 4 m final state
- signature: two pair of extremely
collinear m due to low Ma
-Require “companion-track” for each of
two muon → m isolation for pair.
IF:
Cross section of ~ 1000 fb
Mh =120 GeV
BR(h-> aa) ~ 1
BR(aa -> mm) > 10% exluded 95% CL
26
NMSSM h -> aa Search
For Masses 2Mt < Ma < 2Mb
Decays mainly to t pairs
- 2m2t final state : one pair of collinear m
large MET from a → tt decay
Select back-to-back mm- and tt-paired
topologies
27
SUSY Searches
Chargino/Neutralino
• Clean multi-lepton+MET
signature, but:
• low sxBR (<0.1 pb)
• low pT leptons (<8 GeV)
• Challenges: lepton ID at low pT
28
SUSY Searches
•
•
Pair production of q,g with decays
involving multi-jets + MET.
Critical to understand tail of MET
distribution.
29
Model Independent Search
Look for discrepancies between data and expactions
VISTA
-Event counts in many final states
-Shapes of many kinematic
variables
High PT isolated lepton
4/180 channels with disagreement
m±MET + 2 jets
9.3 s
m±gMET + 1 jet
6.6 s
mmMET (OS)
4.4 s
mmg (OS)
4.4 s
30
Model Independent Search
Sleuth
-Focus on tail of SPT for each final
state
5/44 distributions with some
discrepancy
-Search for excesses
1/ 44 with significant discrepancy
probably bad m resolution
31
Tau Sneutrinos (RPV)
e-
q
Look for high PT isolated lepton
pair
Assume that nt is the LSP
~
n
Assume that all RPV couplings
are zero except l’311, l321=l312
¯
q
m+
Limits on s*BR give nt mass
limits for different values of l
32
Conclusions
•
Run II physics program in full swing.
•
Excellent performance of the accelerator and CDF and DØ detectors.
•
Expect more than 8 fb-1 by the end of the run.
Analyzed luminosity will increase by a factor of ~2.5-7.
•
Physics reach further expanded by analysis improvements.
•
Establish benchmarks in analysis techniques for the LHC era.
• Prospects for discoveries remain open.
33
Charge Massive Stable Particles
Charge Massive Stable Particles CMSPs or Champs
-”stable” -> lifetimes > ~10-8 sec
-Extension of the SM
--> stop, stau or chargino in some SUSY models
-> possibly long-lived if mass difference to decay product
e.g. chargino neutralino + X and neutralino is LSP
CMSPs may appear as "slow" moving muons.
Striking signature:
- isolated high pT muons
- use timing in muon system (D0) or central track TOF
- the di-muon mass can also provide discrimination
34
CMSP
- pair-production limits:
σ∼ 40 fb for M~ 200 GeV
- SUSY limits model dependent
no stau limit
m~ + > 171
c1
higgsino-like
m ~ + > 206 guagino-like
c1
35
D0: 2 isolated μ pT>20 GeV
- |φμμ+θμμ−2π| > 0.05 plus timing
cuts to reject cosmic ray muons
- backgrounds determined from
36
Fermiophobic Higgs Search
-Higgs mainly couples to bosons ->
branching ratio to fermion supressed
- Decays to g or W
37
WH-> WWW*-> l±nl±n+X
Likelihood discriminant used to separate
ee
signal from backgrounds:
Data: 19 events
Bckg: 20.4 ± 4.0
- physics: WZ -> lnll with lost lepton from Z
- QCD b-jets, punch-throughs, g -> e
- Charge flips: maily from Z/g* -> ll
mm
Data: 5 events
Bckg: 5.0 ± 2.5
em
Data: 15 events
Bckg: 18.0 ± 2.8
38
H-> gg
Search for di-photon mass peak
Mass resolution ~ 3 GeV / c2
Looser selection PTgg > 35 GeV/c
Backgrounds from MC and Data
No excess observed:
Excluded MH<102.5 GeV /C2 @ 95 CL
39