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Fermilab Joint Experimental-Theoretical Seminar Fermilab, July 25, 2008. New Results for ICHEP2008 from DØ. Aurelio Juste Fermi National Accelerator Laboratory For the DØ Collaboration. Overview. By ICHEP2008 we will have released in calendar year 2008: 37 preliminary results, - PowerPoint PPT Presentation
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New Results for ICHEP2008from DØ
Fermilab Joint Experimental-Theoretical SeminarFermilab, July 25, 2008
Aurelio JusteFermi National Accelerator Laboratory
For the DØ Collaboration
OverviewOverview
• By ICHEP2008 we will have released in calendar year 2008:
• 37 preliminary results,• 30 publications (~1/week).
[34 submitted in CY 2007]
• 81 abstracts submitted to ICHEP.
• This talk will only cover a subset of new results since Moriond 2008 spanning:
• QCD physics• B physics• EW physics• Top physics• Higgs searches• New phenomena searches
http://www-d0.fnal.gov/Run2Physics/WWW/results.htm
Many thanks to my DØ colleagues
for their hard work!!!
2
Many thanks to the Accelerator Division
for such outstanding performance!!!
Results presented in this talk: ~0.7 - 3.0 fb-13
QCD Physics: New ResultsQCD Physics: New Results
Jet Physics• Inclusive jet cross section • Dijet angular distributions• …
Vector Boson(+jets) Physics
• Z pT spectrum
• Measurement of g2 parameter
• Z+jets total/differential cross sections• (W+charm)/(W+jet) cross section ratio• +jets differential cross sections• +heavy-flavor jets differential cross sections• …
arXiv:0802.2400 [hep-ex]
4
Dijet Angular DistributionsDijet Angular Distributions
• Dijet angular distributions in bins of dijet mass:
• First differential cross section measurement at partonic energies >1 TeV!
• Small experimental and theoretical uncertainties.• Sensitive to New Physics (95% CL limits):
Compositeness (=+1): >2.6 TeV
ADD extra-dimensions (n=4): Ms>1.6 TeV
TeV-1 extra-dimensions: Mc>1.4 TeV
Most restrictive limits at the Tevatron!
*
*
21 cos1
cos1)exp(
yydijet
yi = jet rapidity
0.7 fb-1
5
g2 Measurementg2 Measurement
• Z boson differential distributions provide important information on production mechanism.
• Low Z pT region dominated by multiple soft-gluon emissions resummation
• g2 traditionally extracted from Z pT spectrum.
• New experimental technique almost insensitive to dominant systematic uncertainties in previous measurements (lepton energy resolution/efficiency).
BNLY non-perturbative form factor
ResBos
6
g2 Measurementg2 Measurement
• Z boson differential distributions provide important information on production mechanism.
• Low Z pT region dominated by multiple soft-gluon emissions resummation
• g2 traditionally extracted from Z pT spectrum.
• New experimental technique almost insensitive to dominant systematic uncertainties in previous measurements (lepton energy resolution/efficiency).
BNLY non-perturbative form factor
7
g2 Measurementg2 Measurement
• Z boson differential distributions provide important information on production mechanism.
• Low Z pT region dominated by multiple soft-gluon emissions resummation
• g2 traditionally extracted from Z pT spectrum.
• New experimental technique almost insensitive to dominant systematic uncertainties in previous measurements (lepton energy resolution/efficiency).
• Electron and muon channels (2 fb-1):
BNLY non-perturbative form factor
Precision competitive with world average!
2.0 fb-1
8
)(04.0(exp)02.063.02 PDFg
PDF uncertainties not included
Photon+Heavy Flavor JetPhoton+Heavy Flavor Jet
• Limited knowledge on heavy-quark (b,c) PDFs.• Is there an “intrinsic charm” (non-perturbative) component of the proton?
arXiv:hep-ph/0701220
ud
c (radiative)c (radiative+intrinsic)
Two different models
9
Photon+Heavy Flavor JetPhoton+Heavy Flavor Jet
• Use +b-tagged jet events:
• Photon purity: ~60-90% depending on pT
• Discriminate between b, c and light jets using information on track impact parameter.
b
bb
b
1.0 fb-1
+b
+b
+b in agreement with NLO QCD (CTEQ6.6)
10
_
Photon+Heavy Flavor JetPhoton+Heavy Flavor Jet 1.0 fb-1
• Use +b-tagged jet events:
Region probed: 0.1<x<0.3, 0.9x103<Q2<2x104 GeV2
c
cc
c
+c
+c
Large discrepancy for +c at high pT
Significant intrinsic charm contribution?11
_
CP Violation in the BS System: New ResultsCP Violation in the BS System: New Results
Weak eigenstates:
Mass eigenstates:
Bs meson allows to probe the entire matrix:
• Time-dependent angular analysis in flavor-tagged Bs J/ decays
• B(Bs Ds(*)Ds
(*))
• CP-violating asymmetry in semileptonic Bs decays
arXiv:0802.2255 [hep-ex]
mixing 00ss BB
Sensitive to New Physics
Not sensitive to New Physics
VERY sensitive to New Physics
12
Asymmetry in Semileptonic Bs DecaysAsymmetry in Semileptonic Bs Decays
Previous DØ measurements:• vs.
time-integrated, no flavor tagging
• vs.
depends on b-fragmentation and Bd asymmetries from B factories
• Combination of both measurements:
1.3 fb-1, PRL 98, 151801 (2007)
1 fb-1, PRD 74, 092001 (2006)
arXiv:hep-ph/0612167
Prediction
13
Asymmetry in Semileptonic Bs DecaysAsymmetry in Semileptonic Bs Decays
•
• Flavor tagging and time-dependent analysis used for Bs-mixing measurement.
• Exploits regular reversal of solenoid/toroid polarities to control systematics.
XDB ss 0
XDBd 0
2.8 fb-1
NEW
Statistics-limited!
arXiv:hep-ph/0612167
Prediction
Significant constraints on CPV phase
expected from combination of
measurements 14
EW Physics: New ResultsEW Physics: New Results
Precision Measurements
• AFB in Z/*ee and sin2Weff
• W charge asymmetry• (ppZ/*+X)B(Z/*)• …
Diboson• Radiation amplitude zero and
anomalous couplings in W• Search for narrow resonances
decaying to Z• ZZ production• …
arXiv:0804.3220 [hep-ex]
arXiv:0807.3367 [hep-ex]
15
ZZ ProductionZZ Production
• The smallest SM diboson cross section:
(ZZ)=1.6 ± 0.1 pb
reality check for New Phenomena searches.• Sensitive to New Physics:
• ZZ 4 leptons• Very small backgrounds, but small BR (~0.4%)
• ZZ llvv• Manageable backgrounds, larger BR (~2.6%)
l=e,
16
ZZllZZll
• Large background from fake MET reduced by constructing an optimized MET variable.
• Build likelihood discriminant against WW background:
• Mee or P(2Z)
• pT(l1)
• Cos(*l-)
• (l1,ll)
2.7 fb-1
17
18
ZZllZZll
• Large background from fake MET reduced by constructing an optimized MET variable.
• Build likelihood discriminant against WW background:
• Mee or P(2Z)
• pT(l1)
• Cos(*l-)
• (l1,ll)
2.7 fb-1
pb )(4.0)(0.19.1)( syststatZZ
Expected Observed
P-value: 1.92x10-2 1.00x10-2
Significance: 2.1 2.3
ZZ4lZZ4l
• Careful optimization of lepton identification criteria and kinematic selections.
• Seven orthogonal channels:• 4e (3 categories)• 4• 2e+2 (3 categories)
• M(Z1)>70 GeV, M(Z2)>50 GeV
1.7 fb-1
Channel 4e 4 2e+2 All channels
Signal 0.45 0.60 1.08 2.13
Total background
0.05 0.0003 0.095 0.14
Observed events 2 1 0 3
19
4-lepton invariant mass (GeV)
Run IIb
ZZ4lZZ4l
• Careful optimization of lepton identification criteria and kinematic selections.
• Seven orthogonal channels:• 4e (3 categories)• 4• 2e+2 (3 categories)
• M(Z1)>70 GeV, M(Z2)>50 GeV
1.7 fb-1
Channel 4e 4 2e+2 All channels
Signal 0.45 0.60 1.08 2.13
Total background
0.05 0.0003 0.095 0.14
Observed events 2 1 0 3
Expected Observed
P-value: 1.32x10-4 2.94x10-8
Significance: 3.65 5.42
pb )(13.0)(75.1)( 27.186.0 syststatZZ
First observation of ZZ production!!!20
4-lepton invariant mass (GeV)
Run IIb
Top Physics: New ResultsTop Physics: New Results
• Multiple cross section measurements including their combination
• Precise top quark mass measurement in lepton+jets and dilepton channels.
• Top mass extraction from cross section
• Limits on anomalous tbW couplings from single top production
• Model-independent measurement of the W helicity fraction in top quark decays
• Search for W’tb• Search for H± tb• Limits on H± in top quark decays
• …
p
p t
b
W
q
q’
t b
W+
l
X
Production cross-section
Resonant production
Production kinematics
Top Spin Polarization
Top MassW helicity
|Vtb|
Branching Ratios
Rare/ non SM Decays
Anomalous Couplings
CP violation
Top Spin
Top Charge
Top Width
_ _
_
_
21
Top Pair Cross Section and New PhysicsTop Pair Cross Section and New Physics 1.0 fb-1
22
B(H+)=1
• Combine tt cross section measurements in lepton+jets, dilepton and lepton+tau (14 independent channels).
• Precise measurements in different channels allows to place constraints on New Physics.
• tH+b: channels affected differently depending on H+ decay modes.
Tauonic: B(H+)=1• disappearance of l+jets, dilepton• appearance of l+
Leptophobic: B(H+cs)=1• disappearance of l+jets, dilepton
and l+
Tauonic
Leptophobic
23
Top Pair Cross Section and New PhysicsTop Pair Cross Section and New Physics 1.0 fb-1
• Combine tt cross section measurements in lepton+jets, dilepton and lepton+tau (14 independent channels).
• Precise measurements in different channels allows to place constraints on New Physics.
• tH+b: channels affected differently depending on H+ decay modes.
Tauonic: B(H+)=1• disappearance of l+jets, dilepton• appearance of l+
Leptophobic: B(H+cs)=1• disappearance of l+jets, dilepton
and l+
Using top as a tool to look for New Physics
Top Quark MassTop Quark Mass
• Important parameter in precision electroweak analyses.
• Challenges: • Jet energy scale (JES)• Signal modeling• Combinatorics
• Sophisticated techniques to minimize statistical and dominant systematic uncertainties (JES via in-situ calibration in lepton+jets).
GeV (syst) 3.2(stat) 6.39.172 topm
Lepton+jets (2.1 fb-1):
e+ (2.8 fb-1):
GeV (syst) 4.1(stat) 0.12.172 topm
Matrix Element Method:
2.8 fb-1
24
Top Quark MassTop Quark Mass
• Important parameter in precision electroweak analyses.
• Sophisticated techniques to minimize statistical and dominant systematic uncertainties.
• Good agreement between mass from direct reconstruction and cross section measurement.
GeV 5.56.169 topm
2.8 fb-1
Different systematic uncertainties25
• Top couplings to the W boson very interesting!
• Single top production directly sensitive to the tbW interaction: rate and kinematics.
SM: ~ 2.9 pb (SM)
SM:
SM
tbW Interaction: Single ToptbW Interaction: Single Top 0.9 fb-1
26
• Top couplings to the W boson very interesting!
• Single top production directly sensitive to the tbW interaction: rate and kinematics.
SM (f1L=1, rest=0): ~ 2.9 pb
f2L(R)=1, rest=0 : ~ 10.4 pb
SM
f2L(R)=1, rest=0
tbW Interaction: Single ToptbW Interaction: Single Top 0.9 fb-1
27
• Top couplings to the W boson very interesting!
• Single top production directly sensitive to the tbW interaction: rate and kinematics.
SM (f1L=1, rest=0): ~ 2.9 pb
f2L(R)=1, rest=0 : ~ 10.4 pb
• Use same multivariate analysis technique as for the single top production evidence.
arXiv:0807.1692 [hep-ex]
First direct constraints on tbW tensor couplings
tbW Interaction: Single ToptbW Interaction: Single Top 0.9 fb-1
28
• W helicity polarizations in top quark decays:
• Lepton+jets and dilepton final states.• Reconstruct lepton helicity angle:
t
b
W
t
W
b
t
W
b
t
b
W
Left-handed W(W=-1 )
Longitudinal W(W=0 )
Right-handed W(W=+1 )
SM:PRL 100, 062004 (2008)
SM
tbW Interaction: W HelicitytbW Interaction: W Helicity
29
1W+
b
l+
• W helicity polarizations in top quark decays:
• Lepton+jets and dilepton final states.• Reconstruct lepton helicity angle.
• Model independent measurement:
t
b
W
t
W
b
t
W
b
t
b
W
Left-handed W(W=-1 )
Longitudinal W(W=0 )
Right-handed W(W=+1 )
SM:
lepton+jets
tbW Interaction: W HelicitytbW Interaction: W Helicity 2.7 fb-1
SM
Most precise measurement!Further constraints on tbW couplings to follow 30
NEW
1
New Phenomena Searches: New ResultsNew Phenomena Searches: New Results
• Scalar top pair production
• Leptoquarks (1st, 2nd, 3rd generation)
• T-odd quarks in Little Higgs models
• Large extra-dimensions in mono-photon
• Large extra-dimensions in di-EM
• Long-lived particles decaying into ee, • Charged massive stable particles
•
31
Scalar Leptoquarks (3rd Generation)Scalar Leptoquarks (3rd Generation)
• Predicted by a variety of New Physics models (GUTs, Compositeness, etc).
• Couple directly to a quark and a lepton:
• Consider 3rd gen scalar LQ with charge 2/3 or 4/3: LQ+b
• 1 isolated , pT>15 GeV• 1 candidate, pT>15-20 GeV• 2 jet, pT>25(20) GeV; 1 and 2 b-tags
1+2 tags
~ B(LQl+q)
l,
q
l,
q
_
_
_
arXiv:0806.3527 [hep-ex]
1.0 fb-1
Most restrictive limits in this decay channel!32
Acoplanar Jets+METAcoplanar Jets+MET
2 jets, pT>15 GeV
(jet1,jet2) >165o
MET>75 GeV
Optimized cuts on MET and HT
jets
jetTT pH
1st Generation Leptoquarks (=0)
1- = B(LQq)
qqLQLQ
Precision EW
measurements
LEP
Littlest Higgs model (T-parity)HH AqAqQQ
~~~~
2.5 fb-1
Most restrictive direct limits!33
DØ Run II Preliminary
DØ Run II Preliminary
• Gravity diluted in large compactified extra spatial dimensions.
• Tower of Kaluza-Klein gravitons GKK (massive, stable, non-interacting).
• qq + GKK monophoton signature
• pT()>90 GeV, MET>70 GeV
• Backgrounds:• Z(),..• Non-collision
(cosmics, beam-halo)• Exploit fine granularity of the
DØ EM calorimeter and central preshower detector to do “photon pointing”.
Large Extra-Dimensions: mono-photonLarge Extra-Dimensions: mono-photon 2.7 fb-1
34
• Gravity diluted in large compactified extra spatial dimensions.
• Tower of Kaluza-Klein gravitons GKK (massive, stable, non-interacting).
Large Extra-Dimensions: mono-photonLarge Extra-Dimensions: mono-photon 2.7 fb-1
35Improve upon LEP limits for nd>4
• qq + GKK monophoton signature
• pT()>90 GeV, MET>70 GeV
• Backgrounds:• Z(),..• Non-collision
(cosmics, beam-halo)• Exploit fine granularity of the
EM calorimeter and central preshower detector to do “photon pointing”.
• Gravity diluted in large compactified extra spatial dimensions.
• Tower of Kaluza-Klein gravitons GKK (massive, stable, non-interacting).
• Di-EM (ee,) final state signature.• Exploit di-EM mass and cos(*) distributions.
Large Extra-Dimensions: ee, Large Extra-Dimensions: ee, 1.0 fb-1
Virtual GKK exchange
36
DØ Run II Preliminary
Interference!
DØ Run II Preliminary
Most restrictive limits at the Tevatron!
Charged Massive Stable ParticlesCharged Massive Stable Particles
• Charged: leaves track in detector
Massive: long time-of-flight, heavily ionizing
“Stable” = long-lived signal in muon system
• Search for dimuon-like signature with long time-of-flight. Exploit timing information from muon scintillator system (resolution: ~2.5 ns)
Gaugino-like
chargino 185 GeV
1.1 fb-1
Most restrictive limits at the Tevatron37
DØ Run II Preliminary
DØ Run II Preliminary
Higgs Searches Beyond the SMHiggs Searches Beyond the SM
• Within a generic (Type II) 2HDM: u and d couple respectively to up- and down-type fermions; tan=vu/vd.• After EWSB: four massive scalars (h0,H0,H±) and one pseudo-scalar (A0)
• MSSM at large tan:• 0={h0/H0,A0} nearly degenerated in mass• Coupling to b, enhanced (tan)
• b(b)+0bbb(b)• b(b)+0hadb(b)• 0
Significant increase in production rate: +X 2 x tan2BR(0bb)~90%, BR(0+-)~10%
38
NEW
NEW
NEW
b(b)+0bbb(b)b(b)+0bbb(b)
• Experimental signature:• 3, 4 or 5 jets; 3 b-tags• Select on likelihood discriminant (mass
information not used).• Invariant mass of leading two jets peaks
at M
• Backgrounds dominated by heavy flavor-enriched QCD multijets:
• Shape extracted from 2-tag sample• Rate normalized outside the “signal region”
• Run IIb preliminary result combined with Run IIa (1 fb-1) publication.
bb
2.6 fb-1
39Most restrictive limits at the Tevatron!
2
T
vis pppM
• Lower BR but also lower backgrounds.
• Typical experimental signature (had):• 1 isolated , pT>10 GeV• 1 candidate, pT>15(20) GeV
• Main background: Z+- • Visible mass:
• Combination of four channels:• Run IIa (1.0 fb-1): had, ehad, e
• Run IIb (1.2 fb-1) : had
00 2.2 fb-1
40Work ongoing to combine the three analyses
SM Higgs Searches: New ResultsSM Higgs Searches: New Results
• Major effort underway to continue to improve sensitivity:
• Adding channels,• Optimized object identification/resolution• Optimized selections and signal-to-bckg
discrimination, and of course,• Adding more luminosity!
• WHlbb• WHbb• ZHllbb• ttHlbjjbbb• H• HWW•
Added for the first time
41
…and more!
WHlbbWHlbb
42
• One of the most sensitive channels in the ~110-130 GeV mass range.
• Consider 8 independent channels:• e+jets, +jets• 2, 3 jets• 1, 2 b-tags (NN-based)
• Main background: W+HF jets, tt• Dijet mass multivariate discriminants
WHlbbWHlbb
• One of the most sensitive channels in the ~110-130 GeV mass range.
• Consider 8 independent channels:• e+jets, +jets• 2, 3 jets• 1, 2 b-tags (NN-based)
• Main background: W+HF jets, tt• Dijet mass multivariate discriminants
• ~20% improvement in limit re-analyzing same dataset (1.1 fb-1) for publication.
• Input to Tevatron combination w/ 1.7 fb-1:
expected limit: 8.5 x SM.
At mH = 115 GeV:
Expected limit: 10.1 x SM (=1.29 pb)Observed limit: 10.7 x SM (=1.37 pb)
1.1 fb-1
43
HH
• Small BR in SM (~0.2%) but one of the most promising channels at the LHC.
It also contributes at the Tevatron!
• Event selection:
2 photons with pT>25 GeV and ||<1.1
[NN-based photon ID]
• Main backgrounds estimated from data:• Direct QCD (~60%)• +j and dijet (jet )
• Use diphoton mass spectrum:
At mH = 115 GeV:
Expected limit: 23.2 x SM (=65.1 fb)Observed limit: 30.8 x SM (=86.5 fb)
Limits improved by x2 since Moriond’08 (2.3 fb-1)
2.7 fb-1
44
1.3 signal events
HWWHWW
• Highest sensitivity channel for mH>130 GeV.
• Main backgrounds:• mH~160 GeV: WW• mH~130 GeV: W+jets
• Low (l,l) because of spin-0 Higgs.
• Capitalize on improvements in lepton identification and multivariate techniques.
At mH = 160 GeV:
Expected limit: 2.4 x SMObserved limit: 2.1 x SM
ee,, e
45
As of Moriond’08…
Moriond’08 Tevatron CombinationMoriond’08 Tevatron Combination
At mH = 160 GeV:
Expected limit: 1.6 x SMObserved limit: 1.1 x SM
Exciting prospects to start excluding in 2008!
46
47
HWWHWW 3.0 fb-1
• First 3.0 fb-1 result at DØ! • Significant improvements since Moriond:
• Lepton ID • Neural Networks• 30% more luminosity
• And the answer is….
48
HWWHWW 3.0 fb-1
Watch for updated Tevatron combination at ICHEP!
• First 3.0 fb-1 result at DØ! • Significant improvements since Moriond:
• Lepton ID • Neural Networks• 30% more luminosity
• And the answer is….will finalize review in ~2 days
ConclusionsConclusions
• 21 new results from DØ discussed here covering a wide range of physics topics.
These represent a fraction of the results from DØ that will be discussed at ICHEP.
• With ~4 fb-1 of data recorded, more to come, and getting smarter by the day on how to most effectively extract the physics information, Tevatron results will continue to resonate for years to come.
• See you in Philadelphia next week!
49
Backup
50
ttH Associated ProductionttH Associated Production
• (ttH)B(Hbb): ~4 fb at mH=115 GeV
• Main background: tt+jets
• Split in 12 independent channels:• e+jets, +jets• 4, ≥5 jets• 1, 2, ≥3 b-tags (NN-based)
and use HT distribution.
SM: t ~ 1
bb
Exp. Signal: ~0.12
Exp. Bckg: ~3.7
Observed: 5
2.1 fb-1
51
• Tiny cross section: ~X fb at mH=115 GeV
• Main background: tt+jets
• Split in 12 independent channels:• e+jets, +jets• 4, ≥5 jets• 1, 2, ≥3 b-tags (NN-based)
and use HT distribution.
Exp. Signal: ~0.12
Exp. Bckg: ~3.7
Observed: 5
SM: t ~ 1
bb
At mH = 115 GeV:
Expected limit: 46.1 x SM (=187 fb)Observed limit: 64.4 x SM (=271 fb)
ttH Associated ProductionttH Associated Production
Still much room for optimization!
jets
jetTT pH
2.1 fb-1
52
53
Top Pair Cross Section and New PhysicsTop Pair Cross Section and New Physics
• Combine tt cross section measurements in lepton+jets, dilepton and lepton+tau (14 independent channels).
• Precise measurements in different channels allows to place constraints on New Physics.
• tH+b: channels affected differently depending on H+ decay modes.
Tauonic: B(H+)=1• disappearance of l+jets, dilepton• appearance of l+
Leptophobic: B(H+cs)=1• disappearance of l+jets, dilepton
and l+
1.0 fb-1
For mt=170 GeV:
Good agreement with the SM prediction