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From HERA to LHC. HERA – Tevatron – LHC: The decade of Hadron machines. Peter Schleper University of Hamburg. Strasbourg, March 12 th , 2004. HERA: Elektron-Proton E CMS = 320 GeV. LHC: Proton-Proton E CMS = 14 TeV. HERA – LHC:. QCD. Perturbative approach to QCD. - PowerPoint PPT Presentation
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04
From HERA to LHC
Peter SchleperUniversity of Hamburg
Strasbourg, March 12th , 2004
HERA – Tevatron – LHC: The decade of Hadron machines
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04HERA – LHC:
HERA: Elektron-ProtonECMS = 320 GeV
LHC: Proton-ProtonECMS = 14 TeV
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Perturbative approach to QCDQCD: SU(3) gauge theorynon abelian, self-interacting gluons, strong ! running
coupling
extremely rich phenomenology short distances: s small perturbative calculations
factorisation of short (pert.) and long (non-pert.) scales
A.Bhatti
QCD predictions:•hard inter. (N)NLO•Scale dependences: s(Q2), f(x,Q2)
Precision achievable / needed ?
x = P(q,g) / P(p)x = P(q,g) / P(p)momentum fractionmomentum fractionx-dependence of f(x,Q2)x-dependence of f(x,Q2)not predictednot predicted
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04
Benchmarks for Precision QCD
Comparison NLO / NNLOHiggs production at LHC
Discoveries depend on •input parton distributions•Extrapolation by QCD evol.•higher order calculations•non-pert. effectsfor signal and background
The high energy frontier:Decade of Hadron colliders: HERA, Tevatron, LHC
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04HERA Experiments: H1 & ZEUS
H1 & ZEUS:
•Multi-purpose detectors•2-3 layers silicon tracker•Drift chambers (~60 hits)•Forward: straw tubes•Hermetic calorimeters (Uran-Sz. or Lar) calibration ~ 1.5 %•B-field: 1.5 Tesla•Muon drift chambers•100 Hz data taking•Trigger: 6 GeV for el.
Ee = 27.5 GeVEp = 920 GeV
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04HERA 1 HERA 2
HERA I: 93-2000HERA I: 93-2000100pb-1 e+
15pb-1 e-
HERA II goalsHERA II goals500pb-1 e+500pb-1 e-
e polarisation
Strong focussing by Magnets inside det.
Detector upgrades•Silicon tracking•Forward tracking•trigger
107 multi-hadronic events
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Background reductionFocussing magnets ~1.5 m from
vertex Synchrotron radiation from e-
beam Direct synchr. largely shielded Heating of beam pipe bad dynamic vacuum p-beam scatters on beam gas high bkgr. better shielding & vacuum system
Accumulated Accumulated LuminosityLuminosityAccumulated Accumulated LuminosityLuminosity
Expect: 135 pb-1 in 2004 ~ 1 fb-1 until 2007Background problems solved:
No limit on beam currents from experiments
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Kinematics at HERA and LHC
XX
QCD
MZ
QQ22
QQ22
XX
QQ22
HERA kinematics
Fixed target
Neutral +Charged currents
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04
Deep Inelastic ScatteringNeutral Current: low Q2: q+q high Q2: e-p – e+p ~
q-qCharged Current: e+p: u+c + (1-y2)
(d+s)
-
--
--
Quark densities
highsea,g
Q2
x
q+q-
-high sea quark densityimplies high gluon density
Connection to Quark-Gluon Plasma:Colour Glass Condensate
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04High Q2
– Z interference
W exchangee+ e- NC / CC
– Z interference
W exchangee+ e- NC / CC
NC low Q2: 1/Q4 propagatorHigh Q2: M(Z,W) < Q propagators similar to E-weak unification
q-qbar
x
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Charged Currents _ _
--- (e-p) ~ x (u+c) + (1-y2) x (d+s) _ _--- (e+p) ~ x (u+c) + (1-y2) x (d+s)
e+, 250pb-1
• e-, 250pb-1
Unfolding of parton distributions using CC and NC cross sectionsdifficult to reach very large x>0.7
7000 GeV2
700 GeV2 2500 GeV2
25000 GeV2
Charged currents HERA II
x x
reduced cc cross section
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Gluon densityHERA: Scaling violations, FL ,charm
Tevatron: JetsSlope ~s g(x,Q2)
ET
gg
qg
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Parton Density fitsQCD fits to parton densities
•Fit only inclusive DIS data: theoretically clean (H1,ZEUS,Alekhin)
•Global fits: inclusive DIS, DY, Tevatron: jets, W/Z
more constraints (CTEQ,MRST,…)
Zeus/H1:fit to only HERA data !
similar precisionas global fits
guv
dv
Sea
U
D
G
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Gluon Density: Charm at HERA
depends inLO on gluon
agrees with ZEUS NLO QCD fit
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Gluon Density: FL
NLO: contribution from gluons to FL
HERA IIIlow EP run
H1
xx
FLFL
very sensitive: disfavors MRST
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Jets in -p: HERA
full HERA I luminosityFuture: high x gluon ~ c.f.Tevatron
-PDF & NLO describes data
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04s global
Bethke 2002s from QCD fits
s from hadr. processses
Very impressive success of QCD
Limited everywhere by missing higher orders
NNLO
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Higher Order Calculations
Drell Yan at NNLO
NNLO: building blocks known/calculatedFirst results for DIS, Drell-Yan, Higgs,..Within 1 ? year: 3 jets at LEP, 2-jet pp, 2-jet DIS the only way to precise s, H
Monte Carlo: (the experimentalists view)Since ~5 years: 22,3,4 processes, LO+PSNeeded: NLO + PS for unfolding data !Better: NLO + NLL + PS the only way to precise data
Both need strong support from the community !
State of the art:•data unfolded with LO+PS monte carlo•results compared to NLO (+NLL) + hadr.cor.(LO+PS monte carlo)
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Higgs Production at LHCBenchmark test for status of QCD calculations
Higher orders Parton densities
uncertainty ~ 10 % uncertainty ~ 10 %
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04
Beauty & Charm Production
Beauty: Problem for QCD ?Tevatron: data/theory ~3 … now much
lessHERA: data/theory ~3 …. now …LEP-data/theory ~ 3 …. still highCharm:Tevatron slightly highHERA and LEP- ~o.k.
•2 (3) scale problem: Mb, PTb, (Q2)
•HERA/LEP- : Mb ~ PTb small,
Experimentally difficult: S/B ~ 1000
•B as part of gamma structure ?
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Beauty at HERAExp difficult: low PT jets, S/B ~ 1000Comparison data/theorieFormer: extrapolation of data to parton level and full phase space with LO+PS monte carloNow: data as is, apply hadronisation corr. to NLO in
visible phase space
Deep inelastic
Now agreement with NLO
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Beauty at HERA
Photoproduction
Data still slightly above NLO, but main effect found:LO+PS differs from NLO invisible part of PS.
b
b
b
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Event Shapes at HERA
New: resummed calculationsfits to both means and shapes
(H1)NLO + PC NLO + NLL NLO + NLL + PC
Jet Broadening
Dokshitzer-Webber ansatz:0 = effective s below
approx. for hadronisation
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Event Shapes at HERA
All event shapeswell described byNLO + NLL + PC
Old result without resummation
Fit to shapes
Resummation + power correction very successful at HERA
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Parton DynamicsDGLAP factorisation: integrated over trans. momentum f(x,Q2) expected to fail when Q~KT
un-integrated PDFs: f(x,Q2,KT) BFKL,CCFM evolution
Selection: 2jets, unbalance
NLO 3jNLO 2j
Important at low –xHigh parton density
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04HERA 2
HERA IHERA I100pb-1 e+
15pb-1 e-
HERA IIHERA II500pb-1 e+500pb-1 e-expected
10 % error for Q2 > 16.000 GeV2
you can never have enough luminosityto beat 1/Q^4 and (1-x)^3-Z interference:
e- constructive / e+ destructive
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04
helicitysuppression
e+ beam polarisationFeb 0360 %
Neutral current Charged current
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Conclusion
s: higher orders vital
Now: uncert. ~ 3 %NNLO: 1-2 % possible
Overall: QCD at HERA is in excellent shape
Beauty puzzle:• Much better agreement with
theorie• Lack of good Monte Carlos• NLO Monte Carlo LHC
Ready for LHC ?not quite, but Tevatron RUN II, HERA II, THEORY…
Parton distributions:• pp H: uncert. 10 %• Requires new data from Tevatron/DY/HERA
Much progress in resummat., power corr., diffraction
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Benchmarks for Precision QCD
as determinations: how good ?
Alpha_s figure
Standard Model Supersymmetry
Zoom into SUSY
Highest possible precision is vital !
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Power Corrections at LEPDokshitzer-Webber
ansatz:0 = effective s below
approx. for hadronisation
shapes well described
Fit to mean values Fit to shapes
s = 0.1207 no consistent s
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Charm at HERA
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Gluon Density: FL
Longitudinal structure function
xgF sL
H1 prel
•simulation
simulation of low Ep data [~ 460, 575, 920 GeV]
HERA II
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Diffraction: factorization
Hard scattering: Q2 largeFactorisation in diffract. PDF and partonic
No colourexchange from Proton Soft QCD ?
should follow DGLAP QCD evolution with Q2
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Diffraction in NLO QCD
NLO QCD fits toincl dataSame as in standard QCD fits to DIS
PDF(x,Q2) for fixed Proton momentum
Large gluon contribution
Use diffr. PDF to predict jet) , (charm)
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Diffraction in NLO QCD
•NLO QCD fit to inclusive data describes jet and charm•successful test of hard scattering factorisation
Jets Charm
Current state: ~ all hard diffractive processes at HERAare described by NLO QCD
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Skewed partonse.g.: DVCS (deeply virtual compton
scattering) correlation between initial quarks and gluons
NLO successful
Factorisation for large Q2
f(x1,x2,Q2)
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04
Inclusive jets: well described by NLO QCD
eventshapes& QCDresummed
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Tevatron Jets•Run I: 100 pb-1
•Run II: 200 pb-1 recorded• first prelim. results CDF: 85 pb**-1, D0: 34 pb**-1
Jet algorithms:Run I: cone, KT (D0)RUN II: also modified cone algor: midpoint algor.: additional seed allowed between found jets (P recomb. scheme, instead E)
CDF cone
D0 KT
differences cone/ KT due to hadr. corrections
Run I
gluon density not constrained at high x
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Peter SchleperFrom HERA to LHC
Strasbourg, March 04Proton Structuremany unknowns: uv, dv, us, ds, s, gmany processes: DIS,Drell-Yan,Tevatron
Predictions depend on•QCD evolution•PDF’s at low Q2