Recent results from D0 · Recent results from D0 and CDF Paul de Jong And he seemed to suggest that...
Transcript of Recent results from D0 · Recent results from D0 and CDF Paul de Jong And he seemed to suggest that...
Recent results from D0
Paul de Jong
Recent results from D0
Paul de Jong
Request from previous colloquium organizer
Recent results from D0 and CDF
Paul de Jong
Request from new colloquium organizer
Recent results from D0 and CDF
Paul de Jong
And he seemed to suggest that I should also cover:
and highlights from ICHEP04
Recent results from D0 and CDF
Paul de Jong
and highlights from ICHEP04
Nicola CoppolaOctober 1
Tevatron
1985: start of Tevatron
1987: core of CDF in place,jet physics
1988-1989: run 0
1992: core of D0 in place
1992-1995: run 1120 pb-1, √s = 1.8 TeV
1995: announcement oftop quark discovery
Tevatron dates from SppS time, way before LEPAnd the Tevatron is still around…
Main Ring
Tevatron
1
The fate of LEP…
The same cannot besaid of LEP…
2
Fate of the Tevatron: Run 2!
Upgrade for Run 2:
Main ring taken out,main injector constructed
√s: 1.8 à 1.96 TeV
Also 30% higher top cross section
36 x 36 bunches, (i.o. 6 x 6), ∆t = 396 ns (3500 ns)
Factor ~40 increase in total integrated luminosity3
Tevatron
Tevatron Main injector
Recycler
antiproton
accumulator
4
Tevatron
Antiprotons are valuable. Typical store is 100 mA protons + 10 mA antiprotons.
Store takes typically ~24 hours; during that time antiproton stacking iscontinually in progress for next store.
Recycler was intended to save and rescue remaining antiprotons from onestore to the next. Will not work, but recycler now important for antiprotonstorage during stacking.
Most stores end by dumping beams as planned.Sometimes magnet quenches or other failures.
One store ended by an earthquake…
5
Tevatron
One store ended by an earthquake…
SLAC: Hey this is not fair!We demand to see a tornado now!
5
Tevatron
One store ended by an earthquake… in Alaska…
5
Tevatron
Peak luminosity has exceeded1032 cm-2 s-1 (once…)
Both CDF and D0 have accumulatedsome 450 pb-1 up to now
(cf.: 120 pb-1 in run1)
Data taking efficiency ~85%
Backgrounds in D0 are low.CDF has had some radiationincidents and premature agingof tracker (solved).
2-3 interactions/bunch crossing
2002
2003
2004
run 1
6
Tevatron
To put this in perspective, this is the plan:
TODAY
LHC starts
à Doing fine now, but big steps still needed… 7
Detectors
New Silicon DetectorNew Central Drift ChamberNew End Plug CalorimetryExtended muon coverageNew electronics
CDF
DØØ
Silicon Detector2 T solenoid and central fiber trackerSubstantially upgraded muon systemNew electronics
8
Detectors
CDF
D0 calorimeter
D0 muon system9
NIKHEF in D0
NIKHEF (= Nijmegen and Amsterdam) in D0:
hardware: radiation monitors, magnetic field sensors, mechanical supportfor forward proton detector
computing: farm for MC generation and data reprocessing, agenda server,interfacing with GRIDs
simulation and reconstruction software, b-tagging
analysis: Top physicsB productionElectroweak physics with b’s and τ’sHiggs searchExtra dimensionsJet production
3 Ph.D. theses defended, 4 more within one year from now, 5-6 after 2005 10
Recent results
First D0 run II papers have been submitted to and accepted by PRL.Overall some 10 papers in pipeline for submission soon.
Today: some selected recent results from D0 and CDF on:
Electroweak bosons
Heavy B mesons
QCD: Jet production and b-jet production
Top quarks
Higgs searches: understanding backgrounds.
By no means complete: see CDF and D0 web pages11
Searches
I intend not to cover searches for new physics.
Not because it is not interesting,or because Tevatron would not besensitive, but because of lack of time.
Searches for SUSY, leptoquarks,Z’, extra dimensions, … are beingdone.
Limits have been set, significantlyimproving on run 1.
12
Collider physics
Doing hadron collider physics is likepanning for gold
in the Amazon river(and leaving no water unchecked…)
Trigger is crucial for physics
High pT leptons
Jets
Missing ET
Displaced tracks (b,c)
“Easy”
“Hard”
13
Electroweak bosons
W and Z bosons are the standard candles of hadron collider experiments!
Yesterday’s sensationToday’s calibrationBackground to Higgs, SUSY, …
14
Electroweak bosons
LEP experiments (and LEP energy group!) have measured Z mass and width.
Use for lepton energy calibration, together with J/ψ and ϒAlso: resolution and efficiency studies
Z à ee
Z à µµ
15
Electroweak bosons
Cross sections: very careful study of efficiencies
à trigger efficienciesà reconstruction and object IDà trackingà selection
And backgrounds…
Luminosity measured with scintillator counters àtotal inelastic cross section
CDF and D0 now agree on value of σinel(not so in run 1…)
6.5% uncertainty
Get everything from data;MC used only for acceptance
16
Tau reconstruction
Most difficult channel: Z à ττ (àµνν + hadrons + ν)
Discriminating variables on tau shower shape and track properties are usedin a neural network.Backgrounds estimated from data: mistags (same-signs vs opposite signs),
W à µν + jets,Z à µµ
Tau reconstruction capability important for H à ττ search 17
Good agreementwith MC, also onother variables
Electroweak bosons
18
Electroweak bosons
Cross sections can now also be computed reliably, up to NNLO:
à A handle on luminosity measurement
19
W Mass
The mass of the W boson is an important Standard Model parameter.
CDF and D0 in Run 1
W à eν and W à µν provide clean final states.
Crucial element: lepton and missing ET energy scale
Statistics is huge:one expt, one finalstate, 150 pb-1 equalsfull LEP 2 sample.
Plot transverse mass:)cos1(22 νν ϕ l
TlTT EEM −=
20
mass
width
W mass outlook
CDF and D0 have worked on the systematics, no mass result yet…
Expect CDF result quite soon (Wàµν, 200 pb-1, stat error 50 MeV, syst 70 ?)D0 by next summer
Goal: 40 MeV total accuracy per experiment for 2 fb-1
Improvement “for free”
Needs work…
21
(example: good descriptionof detector materialin MC crucial forelectron scale…)
W Width
Can measure W width by two methods:
Direct: tail of MT
D0, 177 pb-1 , W à eν: ΓW = 2.01 ± 0.09 ± 0.11 GeV
Indirect: use W/Z cross section ratio
CDF indirect:ΓW = 2.079 ± 0.041 GeV
(SM: 2.092 ± 0.002 GeV)22
As accurate as bestmeasurement to date
Most accurate measurement to date
W charge asymmetry
23
W/Z summary
24
Di-boson production:-gauge couplings-backgrounds to
top/Higgs/SUSY
B physics
25
Heavy B mesons
At the Tevatron, all kinds of B mesons are (copiously) produced: σ(bb) ~ 100 µb
Trigger: D0 relies on muon trigger (good rapidity coverage: good yields)CDF: muon trigger and displaced track trigger
Level 1: very fast trackingLevel 2: add silicon hits to recognize displaced tracks
with high impact parameters
Has revolutionized CDF’s charm and bottom physics program
D0 is commissioning such a trigger, but with emphasis on high pTphysics (top, Higgs, …)
Today: selection of B-physics results: BC, ∆Γ(BS) 26
BC
BC first seen by CDF (1998), 20 events above bg, M = 6.4 ± 0.4 GeVOPAL (1998) saw 2 events, 0.6 ± 0.2 bg
D0: 210 pb-1 used. Look for BC à J/ψµX à µµµXBackground control sample: J/ψ + 1 track
Observe 95 ± 16 candidates(first 5σ observation)
M = 5.95 ± 0.14 ± 0.34 GeV
τ = 0.45 +0.12-0.10 ± 0.12 ps
BackgroundFeed down ψ(2S)Signal modelingMomentum binning
27
Bs lifetime
The Bs and the Bs-bar mix to 2 eigenstates with definite mass and width:∆m = mH – mL > 0, ∆Γ = ΓL - ΓH > 0 (H: heavy; L: light)
∆m governs oscillation frequency; ∆Γ≠0 implies different lifetimes.
The two states are also very nearly CP-eigenstates: L CP-even, H CP-odd.
In Bsà J/ψφ à µµKK the two states can be separated by looking atdecay amplitudes of different polarization states à angular distributions
Theory: ∆Γ/Γ = 0.12 ± 0.05
PDG: ∆Γ/Γ < 0.54 at 95% CL leaving Bs lifetime free (DELPHI, ALEPH,L3)< 0.23 at 95% CL if Bs width equals Bd width
HQET: true to within ~1%(PDG: true to within ~4%)
τs/τd = 0.98 ± 0.07 (D0) (220 pb-1, 337 signal events)0.89 ± 0.07 (CDF) (240 pb-1, 256 signal events)
Run 2 Measurement: (τd from J/ψK*):
28
Bs lifetime
CDF result: ∆Γ/Γ = 0.65 +0.25-0.33
( Γs free)
0.71 +0.24-0.28
( Γs = Γd)
Compatibility with ∆Γ/Γ=0 is 0.3%, compatibility with ∆Γ/Γ=0.12 is 1.2%
Would correspond to ∆mS = 125 +69-55 ps-1
(CKM fit: 18.3 ± 1.6 ps-1)
D0 will have a number soon.(It will be smaller than CDF’s, but for both expts errors are still sizable)
CDF do a multidimensional fitto mass, lifetime and angles
Surprise!very fast Bs oscillations!
29
QCD
30
QCD
Main Interest:
• Very high ET jets: anysigns of quark substructure?Resonances?
• Tevatron gives input to PDFfits in unique region ofx and Q2
• Heavy quark production:just standard model ornew physics?
(Further: diffraction and studies of underlying event models)31
Jet energy scale
The hard part: jet energy scale (cone jets used)
Ejet = (Emeasured – offset)/(response x out-of-cone-correction)
NoiseUnderlying eventOther interactions
Calorimeter property
Showers havefinite size
minimum-bias events
photon+jet events
energy in cones+ MC correction
Often a dominating systematic error
W/Z à jets?
32
Jet production
Fattest event:jet pT = 616 GeVjet-jet mass
= 1206 GeV
Di-jet mass:
33
Jet production
34
CDFDØØ
Data/theory
B-quark production
Run 1 results on b-quark production were a surprise:σ(data) >> σ(NLO QCD)
Experiment wrong?
Theory predictionincomplete?
New physics?
b-quarks
B+ mesons
Theory developments beyond NLO calculations:• MC@NLO: match to parton shower Monte Carlo’s• FONLL: resummed logarithms beyond fixed order calc.• be very very careful in unfolding/manipulating data…
Have brought data and theory in better agreement.But data statistics will improve a lot in run 2…
Stefano Frixionetalked about thishere in March
35
B-quark production
Recent CDF Run 2 result:
Select J/ψ à µµ10-40% are from B decay, look at J/ψ
production vertex
Data and theory agree very well(But theory error needs to decrease!)
MC like PYTHIA has LO ME for FCR
Other production mechanisms hidden in PS
GSP FEX
Disentangle and try to tune PYTHIA36
Top quarks
37
Top quark production
(Also single top production through electroweak processesHowever: cross section ~1 pb, larger backgrounds,
will need >1 fb-1 to observe)38
Top quark production
Why are the cross sectionsfor backgrounds at theLHC 10 times larger thanat the Tevatron,but the cross section fortop production 100 times?
It’s all about x…(and the gluon pdf)àYou need partons with
a certain x
Top quark is on the heavyside for Tevatron…
Still, we get 100 t pairs/week
39
Top quark production
2 leptons, 2 b-jetsmissing ET11% of events
6 jets (of which2 are b-jets)
45% of events
1 lepton, missing ET4 jets (of which 2 b)15% e + jets15% µ + jets15% τ + jets
40
Top quark production
Leptons + jets:- topological variables- b-tags
All hadronic top decays: (at least) 6 jets!
Backgrounds from QCD multijet production
Analysis uses topological variablesand b-tagging in a neural network
2-leptons: clean butsmall statistics
1 b-tag 2 b-tags
Most difficult decay channel:
Most powerful decay ch.
41
Top quark production
Cross section measured to 25% accuracy
42Agrees with NNLO-NNLL prediction
DØØ
CDF
CDF, 162 pb-1: F0 = 0.89 +0.30-0.34 ± 0.17
Top quark decay properties
Test of V-A coupling in top decays: in SM W couples only to LH particlesThis together with angular momentum conservation allows top to decay into LH(negative helicity) or longitudinally-polarized (0 helicity) W bosons
In SM F-=0.30, F0 =0.70, F+ =0
Helicity of W manifests itself indecay product kinematics
D0, 160 pb-1: F+ < 0.24 @ 90% CL
Assuming three-generation CKM matrix unitarity, |Vtb|~1.0
R = BR(t→Wb)/BR(t→Wq) ~1.0
Can measure ratio by checking the b quark content of the top sample decay products
CDF: R = 1.11 ± 0.20 (>0.62 @ 95% CL) D0: R = 0.65 ± 0.32 ± 0.14 43
Is the particle we observe reallythe Standard Model top quark?
Top quark decay properties
Test of V-A coupling in top decays: in SM W couples only to LH particlesThis together with angular momentum conservation allows top to decay into LH(negative helicity) or longitudinally-polarized (0 helicity) W bosons
In SM F-=0.30, F0 =0.70, F+ =0
Helicity of W manifests itself indecay product kinematics
CDF, 162 pb-1: F0 = 0.89 +0.30-0.34 ± 0.17 D0, 160 pb-1: F+ < 0.24 @ 90% CL
Assuming three-generation CKM matrix unitarity, |Vtb|~1.0
R = BR(t→Wb)/BR(t→Wq) ~1.0
Can measure ratio by checking the b quark content of the top sample decay products
CDF: R = 1.11 ± 0.20 (>0.62 @ 95% CL) D0: R = 0.65 ± 0.32 ± 0.14 43
Top quark mass
Run 1 only:
New in 2004 !
Matrix ElementMethod
Fundamental SM parameterTop mass together with EW data constrain Higgs mass
44
Top quark mass
Using Run I l+jets events (125 pb-1) DØØ developed the “matrix element method”
Detailed knowledge of top quark decay and detector response is required à event by event likelihood calculated vs mt
Phase space x LO ME PDFs Probability for observable x when y was produced (Ex: quark ET → jet ET)
45
stat. error5.6 à 3.6 GeV
syst. error5.5 à 3.9 GeV
Top quark mass
Run 2 only:
} Methods are close to theMatrix Element Method
Systematic error (mainly jet energy scale)
is becoming limiting accuracy factor
46
Top quark mass
Outlook:
Jet energy scale: W constraint helps for light jetsb-quark jets? Look for Z à bb
Stated goal for run 2 is 2.5 GeV per experiment.
Needs appropriate trigger. Trying to improve current triggers and use displaced track trigger.
47
The road to the Higgs…
48
Higgs search
If nature has indeed used the Higgs mechanism to generate mass, there isvery likely at least one light Higgs boson.
(The Standard Model needs a Higgs boson.Electroweak data indicates that it is light: 114+69
-45 GeV
SUSY models: MSSM and NMSSM want a light h)
The Tevatron may be in a position to discover it, or exclude its existenceover a sizable mass range.
It needs: luminosity (>2 fb-1)optimal techniques to separate signal and backgroundgood understanding of the background
Now is the time to study this
49
Higgs search
SM dominating decay modesMay be different in SUSY
gg à H à bb swamped by backgroundTry to see Z à bb first.
gg à H à WW feasible for MH > 140 GeV
WH and ZH are our best SM Higgs bets:H à bbZ à 2 leptons or 2 neutrino’sW à lepton + neutrino
ttH too small
bbH and H à ττ could be enhanced in SUSY
Backgrounds: W/Z+light jetsW/Z+bb
50Also important at the LHC…
Wqq and Wbb
51
MCFM is a NLO Monte Carlo for Wqq and Wbb but no interface to PS
MC@NLO is a NLO MC interfaced to PS but cannot yet do W+jets
ALPGEN/MADGRAPH can do Wqq and Wbb matched to PS but only at LO
Can use with total rate scaled to NLO or use MCFM
D0 analysis for Wbb: 174 pb-1
MC = (ALPGEN+PYTHIA)*0.95 à MC does a decent job
Outlook
52
Outlook
Ambitious luminosityplans:
4-8 fb-1 by 2009
Tevatron likely torun until madeobsolete by LHC
53
Outlook
Layer 0
If Layer 1is dead andno Layer 0
Impact parameterresolution
Inner layer ofsilicon detectoris expected to dieafter ~4 fb-1
Also: relativelyfar from beam
In 2005 D0 intends to install a Layer 0 forits silicon detector, at R=1.6 cm from beam,inside current detector.
In addition: trigger system upgrade.54
Connection with LHC
Does all this matter for LHC physics?
What we get out of it: doing physics at the CURRENT high E frontierexperience in commissioning, computing, analysis
What the LHC physics gets out of it:
àPDF’s, jet algorithms in practice, tests of ME-PS matching, underlyingevent models and tunes, hadronization, b-tagging strategies, massresolution optimization, tau reconstruction, backgrounds, better MC’s,impact on the physics landscape and constraints on beyond SM models,….
55th and final slide…
Haringtijd…