Peter Schleper From HERA to LHC Strasbourg, March 04 1 From HERA to LHC Peter Schleper University of Hamburg Strasbourg, March 12 th, 2004 HERA – Tevatron

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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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Strasbourg, March 04HERA – LHC:

HERA: Elektron-ProtonECMS = 320 GeV

LHC: Proton-ProtonECMS = 14 TeV

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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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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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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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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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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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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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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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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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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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Strasbourg, March 04Gluon densityHERA: Scaling violations, FL ,charm

Tevatron: JetsSlope ~s g(x,Q2)

ET

gg

qg

qq

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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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Strasbourg, March 04Gluon Density: Charm at HERA

depends inLO on gluon

agrees with ZEUS NLO QCD fit

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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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Strasbourg, March 04Jets in -p: HERA

full HERA I luminosityFuture: high x gluon ~ c.f.Tevatron

-PDF & NLO describes data

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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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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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Strasbourg, March 04Higgs Production at LHCBenchmark test for status of QCD calculations

Higher orders Parton densities

uncertainty ~ 10 % uncertainty ~ 10 %

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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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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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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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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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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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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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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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helicitysuppression

e+ beam polarisationFeb 0360 %

Neutral current Charged current

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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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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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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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Strasbourg, March 04Charm at HERA

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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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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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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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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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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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Inclusive jets: well described by NLO QCD

eventshapes& QCDresummed

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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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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

Documents

Peter Schleper From HERA to LHC Strasbourg, March 04 1 From HERA to LHC Peter Schleper University of Hamburg Strasbourg, March 12 th, 2004 HERA – Tevatron