Andrey Korytov, University of Florida Aspen, February 14, 2005 1
Andrey Korytov
QCD Physics at Tevatron(for CDF and D0 Collaborations)
2005 Aspen Winter ConferenceThe High Energy Physics
Andrey Korytov, University of Florida Aspen, February 14, 2005 2
QCD Physics at Tevatron
High PT QCD
Jet production (g and uds)Heavy flavor quark production (t, b, c) – Michael Weber (t), Friday Talk? (b, c?) Vector boson production (W, Z, γ) – Pasha Murat
Low PT QCD
Jet fragmentationHadron spectroscopyUnderlying EventDiffractive physics – Konstantin Goulianos
Andrey Korytov, University of Florida Aspen, February 14, 2005 3
Jets
Jets areJets aremessymessyobjectsobjects
Analyses are not that simple...
Andrey Korytov, University of Florida Aspen, February 14, 2005 4
Jets: concept is vague…
Calorimeter level:calorimeter towers lumped together according to an experimentalist’s favored algorithm
Hadron level:sprays of long lived observable particles
Parton level 2 (resummed pQCD):outgoing parton accompanied by a few soft QCD bremsstrahlung
Parton level 1 (NLO pQCD at Tevatron):outgoing 1 parton or 2 partons lumped together to mimic a particular experimental jet finding algorithm
Andrey Korytov, University of Florida Aspen, February 14, 2005 5
Jets: jet finding algorithms
Cone Algorithm: cluster together calorimeter towers by their “angular” proximity in (η, φ) spacemerging/splitting of overlapping cones is not infrared stable (at NNLO)ad hoc Rsep=1.3 to match theory and exp.Tevatron Run I legacy
MidPoint Cone Algorithm:cone algorithm with modifications improving infrared stability
kT Algorithm:cluster together calorimeter towers by their kT proximityinfrared stable (no splitting/merging)no clusters left out underlying event contribution unclear favored choice at e+e- colliders
Andrey Korytov, University of Florida Aspen, February 14, 2005 6
Jets: jet energy measurements
Jet Energy Resolution (stochastic):
Absolute Scale Uncertainty (systematic):
70% 6%( )
T
T T
EE E GeV
δ≈ ⊕
5%T
T
EE
δ≈
Andrey Korytov, University of Florida Aspen, February 14, 2005 7
Jets: theory
Very large number of diagrams to tackle…• NLO calculations available… • but still very sensitive to scale choices…• NNLO “soon to become available” for many years…
Uncertainties in Parton Density Functions (PDFs)• especially g(x) at large x…
Sample of LO diagrams (2 2)
Andrey Korytov, University of Florida Aspen, February 14, 2005 8
Inclusive jet production
ET spectra different η-bins…
( , )Tp p Jet E Xη+ → +
Andrey Korytov, University of Florida Aspen, February 14, 2005 9
Jets: Inclusive jets in Run I
Run I data and NLO+CTEQ3MCDF: Excess at high ET?Compositness?
Run I data and NLO+CTEQ6MCTEQ6:
• New Data: H1, ZEUS, D0 (vs. η!), CDF• New methods: Systematic errors included• New features: Errors are available
no excess, anymore...
CDF
Andrey Korytov, University of Florida Aspen, February 14, 2005 10
Jets: Inclusive jets in Run II data vs NLO
Quite reasonable agreement with NLO+CTEQ6.1, but...
déjà vu: “high-ET excess” again? ~20% dip at lower ET? (not present in Run I)all within systematic errors...
must beat systematic errors down:
• Theory: PDFs, NNLO?• Experiment: energy scale,
hadronization corrections?
Run II reach
Andrey Korytov, University of Florida Aspen, February 14, 2005 11
Jets: Inclusive jets in Run II vs Run I
· PDF uncertainties largely cancel out· Energy scale errors are really annoying…
CDF
Andrey Korytov, University of Florida Aspen, February 14, 2005 12
Jets: Inclusive jets by D0 and CDF
D0CDF
Andrey Korytov, University of Florida Aspen, February 14, 2005 13
Jets: kT vs Cone algorithm
Cone
Shapes of Data/Theory differ...
Why? (work in progress)
CDF
KTCDF
Andrey Korytov, University of Florida Aspen, February 14, 2005 14
Jets: dijet production
What one might want to look at:MJJ
θcm
∆φ12
…
1 2p p Jet Jet X+ → + +
ET=666 GeV
ET=633 GeV
MJJ=1364 GeV
Andrey Korytov, University of Florida Aspen, February 14, 2005 15
Jets: Dijet production
statistical errors only
Look for narrow resonance peaks in Dijet Mass spectrum—seen none
Data/theory agree—within large systematic errors (jet-energy scale)
Andrey Korytov, University of Florida Aspen, February 14, 2005 16
Jets: Dijet ∆φ12
LO is very poor at ∆φ∼π/2 and ∆φ∼πNLO fixes ∆φ∼π/2, but still no good at ∆φ∼π
Herwig is quite good everywherePythia needs ISR enhancement for ∆φ∼π/2
LO in ∆φ NLO in ∆φ
Andrey Korytov, University of Florida Aspen, February 14, 2005 17
Jets: three-jet production
Many more variables to play with...No surprises...
1 2 3p p Jet Jet Jet X+ → + + +
Andrey Korytov, University of Florida Aspen, February 14, 2005 18
QCD Physics at Tevatron
High PT QCD
Jets production (gluons and light quarks)Heavy flavor quark production (t, b, c) – Michael Weber (top), Friday Talk (b) Vector boson production (W, Z, γ) – Pasha Murat
Low PT QCD
Jet fragmentationHadron spectroscopyUnderlying eventDiffractive physics – Konstantin Goulianos
Andrey Korytov, University of Florida Aspen, February 14, 2005 19
Jet Fragmentation: intrinsically soft QCD
Differential probabilities of gluon emission:
Perturbative methods will NOT work for kT<1 GeV
( )QCDTS
T
TS kk
dkkdkdw
Λ=
/ln92 ,~ παα
k, gluon momentum
kT=k⋅sinθgluon transverse momentum
θ
Cone 0.280
MJJ=82 GeV (lower set)
MJJ=628 GeV (upper set)MJJ=229 GeV (middle set)
DATA (points) vs Herwig/QFL(line)
CDF Preliminary
dN/d
k T
kT (GeV)
1 GeV
From data we know that most particles have kT<1 GeV
ANY HOPE?
2 GeV
kT distribution of particles in jets
THEORY EXPERIMENT
Andrey Korytov, University of Florida Aspen, February 14, 2005 20
Jet Fragmentation: doing it analytically
Jet fragmentation in pQCD:parton shower development: resummed NLL approximations
e.g., MLLA, Modified Leading Log Approximation with single parameter Qeff=Qcutoff=ΛQCD
hadronization: no coherent theory
LPHD, hypothesis of Local Parton Hadron Duality with one parameter KLPHD=Nhadrons/Npartons
MLLA+LPHD:cannot describe all details…but all analytical…does it work at all?
R~1/MJJR~1/QcutoffR~1/Λ~1/mπ~1 fm
Andrey Korytov, University of Florida Aspen, February 14, 2005 21
Jet Fragmentation: data vs resummed pQCD
Charged particles in jetsTwo parameter fit:
Qeff = 230±40 MeV kT-cutoff can be set as low as ~ΛQCD
KLPHD(± ) = 0.56 ± 0.10 number of hadrons ≈ number of partons
particle
jet
px
E=
CDF
Andrey Korytov, University of Florida Aspen, February 14, 2005 22
Jet Fragmentation: Gluon vs Quark jets
Difference of Gluon and Quark jets:r = Nhadrons(gluon jet) / Nhadrons(quark jet)calculations (for partons): various extensions of NLLA (r=1.5-1.7) data: 15+ papers from e+e-, not all self-consistent (r = 1 to 1.5)CDF: r=1.6±0.2
jet coneQ E θ=
Andrey Korytov, University of Florida Aspen, February 14, 2005 23
QCD Physics at Tevatron
High PT QCD
Jets production (gluons and light quarks)Heavy flavor quark production (t, b, c) – Michael Weber (top), Friday Talk (b) Vector boson production (W, Z, γ) – Pasha Murat
Low PT QCD
Jet fragmentationHadron spectroscopyUnderlying eventDiffractive physics – Konstantin Goulianos
Andrey Korytov, University of Florida Aspen, February 14, 2005 24
Hadrons: Λb mass
Tevatron is THE heavy flavor hadron factory (not very clean though...)Secondary vertex trigger allows to fish them outWorld largest sample of Λb
M(Λb)=5619±1.2±1.2 MeV/c2
PDG2002: 5624 ± 9
Andrey Korytov, University of Florida Aspen, February 14, 2005 25
Hadrons: X(3872)
Aug 2003: Belle announced discovery of X(3872) J/ψ π+π−
M=3872.0±0.6 ±0.5 MeVΓ < 2.3 MeVππ masses are always high (>500 MeV)
Confirmed by CDF, D0, BaBar
Interpretation still remains unclear:3D2 charmonium? cc
• too heavy for it (expected M~3810-3840)• also, not seen to decay to χ1γ
M(X)~M(D0)+M(D*0) = 1864.6 + 2006.7 = 3871 MeV• DD* molecule? cu-cu
Quadra-quark? cu-cu
Μ(J/ψ)+Μ(ρ) = 3097+770 = 3867 MeV• ???
Andrey Korytov, University of Florida Aspen, February 14, 2005 26
Hadrons: X(3872) at CDF
M=3871.3±0.7 ±0.4 MeVΜ(ππ) invariant masses are all high (>500 MeV)high yield:
• ~1/8 of ψ(2S)• ~85% are prompt, not B-decays!
Andrey Korytov, University of Florida Aspen, February 14, 2005 27
Hadrons: pentaquarksPenta-quark states predicted byDiakonov, Petrov, Polyakov(1997):Θ+ : uuddsMass ~ 1530 MeVWidth ~ 15 MeV Decays equally to nK+ and pK0
10 experiments report evidence: see above3 experiments report no observation: HERA-B, PHENIX, BES
In addition,
NA49 at SPS/CERN (pp collider, Ecm = 17.2 GeV): ssddu(1862)
H1 at HERA ep collider: D*- p state: Θc=uuddc(3099)
/ / /3/ 2 π++ −− + − + −Ξ →Ξ
STATISTICAL SIGNIFICANCE VARIES FROM ~4σ to ~8σ
Andrey Korytov, University of Florida Aspen, February 14, 2005 28
Hadrons: Ξ–hyperon track sample at CDF
• CDF developed tracking of long lived hyperons (Ξ and Ω) in the SVX detector
Two Track Trigger Jet 20 Trigger
]2[GeV/c1.24 1.26 1.28 1.3 1.32 1.34 1.36 1.38
2N
/ 2
MeV
/c
0
2000
4000
6000
8000
CDF Run II Preliminary
]2[GeV/c1.24 1.26 1.28 1.3 1.32 1.34 1.36 1.38
2N
/ 2
MeV
/c
0
2000
4000
6000
8000
)πΛM(
-πΛ+πΛ
-1L = 220pb
track found in SVX
N=36,000
Ξ
]2[GeV/c1.25 1.30 1.35 1.40
2N
/ 2
MeV
/c0
500
1000
CDF Run II Preliminary
]2[GeV/c1.25 1.30 1.35 1.40
2N
/ 2
MeV
/c0
500
1000
)-πΛM(
-πΛ+πΛ
-1L~220pb track found in SVXΞ
Two Track Trigger: NTTT ~ 18 times larger than NA49 dataJet20 Trigger: NJet20 ~ 2 times larger than NA49 data
Andrey Korytov, University of Florida Aspen, February 14, 2005 29
Hadrons: Ξ-- (1860) is not found at CDF
TTT Jet20
~0.21<0.0757+/-51Ξ−π+
~0.45<0.0847+/-70Ξ−π+/−
~0.24<0.04-54+/-47Ξ−π−
R(Ξ1860/Ξ1530) NA49R(Ξ1860/Ξ1530) U. L. 95% C.L.
# of eventsChannel(TTT)
Andrey Korytov, University of Florida Aspen, February 14, 2005 30
Hadrons: Pentaquark Searches
CDF Collaboration have searched for Θ⁺, Θc⁰, Ξ3/2
No evidence for these states have been found
Andrey Korytov, University of Florida Aspen, February 14, 2005 31
QCD Physics at Tevatron
High PT QCD
Jets production (gluons and light quarks)Heavy flavor quark production (t, b, c) – Michael Weber (top), Friday Talk (b) Vector boson production (W, Z, γ) – Pasha Murat
Low PT QCD
Jet fragmentationHadron spectroscopyUnderlying eventDiffractive physics – Konstantin Goulianos
Andrey Korytov, University of Florida Aspen, February 14, 2005 32
Underlying Event: introductory remarks
Underlying Event (UE) ≈(whole event) – (hard part), i.e.:
--initial state radiationmultiple parton interactionsproton remnantsnot completely independent from the hard scattering part…
Whole Event: hard scattered partonsfinal state radiationinitial state radiationmulti-parton interactions, if anyproton remnantswhole thing is entangled with color connections…
UE Physics is poorly understood:MC Generators implement UE
differently (many parameters)even when tuned to current data,
MC predictions for LHC vary wildly (factor of 3)
UE event pollutes many analyses (source of systematic errors)
Andrey Korytov, University of Florida Aspen, February 14, 2005 33
Underlying Event: studies with charged tracks
Leading Jet ∆φ
“Transverse” “Transverse”
“transverse” particlesas a probe of the underlying event
ET(jet) Charged tracks:
• d2N/dφdη• d3N/dφdηdPT
• d2ET/dφdη
Charged Particle Density: dN/dηdφ
0.1
1.0
10.0
0 30 60 90 120 150 180 210 240 270 300 330 360
∆φ (degrees)
Cha
rged
Par
ticle
Den
sity
Back-to-BackLeading JetMin-Bias
CDF Preliminarydata uncorrected
Charged Particles (|η|<1.0, PT>0.5 GeV/c)
30 < ET(jet#1) < 70 GeV
"Transverse" Region
Jet#1
Min-Bias0.25 per unit η-φ
Run II
Andrey Korytov, University of Florida Aspen, February 14, 2005 34
Underlying Event: default Pythia and Herwig
Default Pythia and Herwig fail to reproduce data one way or another, e.g.:
Pythia 6.206 underestimates number of tracks in transverse direction…
Herwig 6.4 gives too soft spectrum for particles in transverse direction, especially in events with small ET jets (missing MPI now have been added)
"Transverse" Charged Particle Density: dN/dηdφ
0.00
0.25
0.50
0.75
1.00
0 5 10 15 20 25 30 35 40 45 50PT(charged jet#1) (GeV/c)
"Tra
nsve
rse"
Cha
rged
Den
sity
CTEQ3L CTEQ4L CTEQ5L CDF Min-Bias CDF JET20
1.8 TeV |η|<1.0 PT>0.5 GeV
Pythia 6.206 (default)MSTP(82)=1
PARP(81) = 1.9 GeV/c
CDF Datadata uncorrectedtheory corrected
Charged Particle Density
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
0 2 4 6 8 10 12 14
PT (GeV/c)
Cha
rged
Den
sity
dN
/dηdφ
dPT
(1/G
eV/c
)
|η|<1CDF Preliminary
Min-Bias Data, 1.8 TeV
HW "Soft" Min-Biasat 0.63, 1.8, and 14 TeV
Andrey Korytov, University of Florida Aspen, February 14, 2005 35
UE: tune Pythia to match CDF data
Pythia: CDF Tune A vs. Default 6.206
• Enhanced Initial State Radiation (ISR)
• Smoothed out probability of Multi-Parton Interactions (MPI) vs. impact
• MPIs are more likely to produce gluons than quark-antiquark pairsand MPI gluons are more likely to have color connection to p-pbar remnants
• …
Andrey Korytov, University of Florida Aspen, February 14, 2005 36
UE: Pythia Tune A at work
"Transverse" Charged PTsum Density: dPTsum/dηdφ
0.00
0.25
0.50
0.75
1.00
1.25
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
PT(charged jet#1) (GeV/c)
"Tra
nsve
rse"
PTs
um D
ensi
ty (G
eV)
CDF Run 1 Min-BiasCDF Run 1 JET20CDF Run 2PY Tune A
CDF Preliminarydata uncorrectedtheory corrected
|η|<1.0 PT>0.5 GeV/c
"Transverse" Charged Particle Density
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
0 2 4 6 8 10 12 14 16 18 20
PT(charged) (GeV/c)
Cha
rged
Den
sity
d3 N
/dη d
φdP
T(1
/GeV
/c)
CDF Preliminarydata uncorrectedtheory corrected
PYTHIA Tune A 1.96 TeV
30 < PT(chgjet#1) < 70 GeV/c
70 < PT(chgjet#1) < 95 GeV/c
"Transverse" Charged Particle Density: dN/dηdφ
0.00
0.25
0.50
0.75
1.00
1.25
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
PT(charged jet#1) (GeV/c)
"Tra
nsve
rse"
Cha
rged
Den
sity
CDF Run 1 Min-BiasCDF Run 1 JET20CDF Run 2PY Tune A
|η|<1.0 PT>0.5 GeV/c
CDF Preliminarydata uncorrectedtheory corrected
Andrey Korytov, University of Florida Aspen, February 14, 2005 37
Summary
High PT QCD
– all checks within systematic errors– we must beat systematic errors down to move towards
precision QCD measurements
Low PT QCD
– interesting developments despite all the challenges for applying pQCD in this domain
Progmatic
– new physics is likely to be born in a QCD process– QCD is likely to be the nastiest background for the Signal– we’d better tame this beast...
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