Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 1 Experimental Tests of Peter Schleper University of Hamburg European Conference on High Energy Physics Aachen, July 17, 2003 Many thanks to: C.Berger, S.Bethke, A.Bhatti, R.Galik, V.Jain, H.Jung, M.Klein, T.Kluge, M.Martinez, P.Newman, R.Nisius, T.Schoerner, H.Stenzel, A.Tapper, T.Wengler, M.Wobisch, P.Zerwas, , session speakers and organizers. Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 2 Perturbative approach to QCD QCD: SU(3) gauge theory non 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 (Q 2 ), f(x,Q 2 ) Precision achievable / needed ? Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 3 Benchmarks for Precision QCD a s determinations: how good ? Alpha_s figure Standard ModelSupersymmetry Zoom into SUSY Highest possible precision is vital ! Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 4 Benchmarks for Precision QCD Comparison NLO / NNLO Higgs production at LHC Discoveries depend on input parton distributions higher order calculations non-pert. effects for signal and background The high energy frontier: Decade of Hadron colliders: Tevatron,HERA,LHC Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 5 Whats New ? Better Theory Fixed order: NLO NNLO All orders: resummed calculations factorisation theorems New Data LEP: close to final precision HERA I: close to final High Q2 data Tevatron: first Run II data Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 6 Event Shapes at LEP Event shapes: thrust, jet broadening, 3-jet parameter, C parameter, jet mass New results from LEP1,2, rad events (L3) e+e+ e-e- Z/ * q q g Cleanest measurements for s at LEP: (Z hadr.), decays NLO resummed calculations Energy dependence, corrected for hadronisation with MC Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 7 Event Shapes at LEP New LEP average for s Refined treatment of correlated errors Running of s Still: cleanest measurements for s at LEP: (Z hadr.), decays prel. largest error: scale uncert. Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 8 Power Corrections at LEP Dokshitzer-Webber ansatz: 0 = effective s below approx. for hadronisation shapes well described Fit to mean valuesFit to shapes s = no consistent s Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 9 Event Shapes at HERA New: resummed calculations fits to both means and shapes (H1) NLO + PC NLO + NLLNLO + NLL + PC Jet Broadening Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 10 Event Shapes at HERA All event shapes well described by NLO + NLL + PC Old result without resummation Fit to shapes Resummation + power correction very successful at HERA Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 11 Proton Structure many unknowns: u v, d v, u s, d s, s, g many processes: DIS,Drell-Yan,Tevatron Predictions depend on QCD evolution PDFs at low Q 2 Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 12 Deep Inelastic Scattering Neutral Current: low Q2: q+q high Q2: e - p e + p ~ q-q Charged Current: e+p: u+c + (1-y 2 )(d+s) Quark densities high sea,g x Q2Q2 xx q+q - q-q - Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 13 Gluon density HERA: Scaling violations, F L,charm Tevatron: Jets Slope ~ s g(x,Q 2 ) ETET gg qg qq Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 14 Tevatron 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, K T (D0) RUN II: also modified cone algor: midpoint algor.: additional seed allowed between found jets (P recomb. scheme, instead E) CDF cone D0 K T differences cone/ K T due to hadr. corrections Run I gluon density not constrained at high x Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 15 Tevatron Run II: D0 Jet-Jet mass Inclusive jets di-jet mass Calor. Energy scale error dominates midpoint algor. PTPT Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 16 Tevatron Run II: CDF incl. cone algor. from Run I (P T, ) Run II / Run I 5% E-scale PDF error close to Run I quality get high x gluon search Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 17 Parton Density fits QCD 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 precision as global fits g uvuv dvdv Sea U D G Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 18 Gluon Density: Charm at HERA depends in LO on gluon agrees with ZEUS NLO QCD fit Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 19 Gluon Density: F L NLO: contribution from gluons to F L HERA III low E P run H1 xx FLFL FLFL very sensitive: disfavors MRST Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 20 Multijet: LEP 4-jet Aleph 4 jet rate and angular correlations NLO + resummed (small scale variation) s = (stat) (sys) Colour factors Very small scale error ! Accidental ? Different error treatment: syst: Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 21 Photon Structure from LEP Albino, Klasen & Soldner Rembold, hep-ph/ Scale dependence of -structure Jet production (OPAL) Confirmation of partonic deconvolution of from R. Nisius Q2Q2 ETET Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 22 L3: at high PT full LEP II data: access to very high PT particles/jets earlier reported: excess in 0 New: +, -New: incl.jet data Huge effect: needs confirmation by other experiments Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 23 Jets in -p: HERA full HERA I luminosity Future: high x gluon ~ c.f.Tevatron -PDF & NLO describes data Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 24 s global Bethke 2002 s from QCD fits s from hadr. processses Very impressive success of QCD Limited everywhere by missing higher orders Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 25 Higher Order Calculations Drell Yan at NNLO NNLO: building blocks known/calculated First 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: 2 2,3,4 processes, LO+PS Needed: 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) Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 26 Higgs Production at LHC Benchmark test for status of QCD calculations Higher orders Parton densities uncertainty ~ 10 % Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 27 Beauty & Charm Production Beauty: Problem for QCD ? Tevatron: data/theory ~3 HERA: data/theory ~3 LEP- data/theory ~ 3 Charm: Tevatron slightly high HERA and LEP- ~o.k. 2 (3) scale problem: M b, P Tb, (Q2) HERA/LEP- : M b ~ P Tb small, Experimentally difficult: S/B ~ 1000 B as part of gamma structure ? Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 28 Charm & Beauty at Tevatron CDF: charm, 5.8 pb -1, but new silicon trigger theory factor 1.7 low Nason & Cacciari hep-ph/ New D0 silicon tracker first beauty results from Run II LO Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 29 Beauty at Tevatron Previous excess partially explained by: resummation of ln(P T /M b ) data: jet with b theory: b only Now: data/theory ~ 1.6 Exclusive B Production Update to more recent fragmentation functions Now: data/theory ~ 1.7 Problem partially solved Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 30 Beauty at HERA Exp difficult: low PT jets, S/B ~ 1000 Comparison data/theorie Former: extrapolation of data to parton level and full phase space with LO+PS monte carlo Now: data as is, apply hadronisation corr. to NLO in visible phase space Deep inelastic Now agreement with NLO Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 31 Beauty at HERA Photoproduction Data still slightly above NLO, but main effect found: LO+PS differs from NLO invisible part of PS. b b b Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 32 Charm & Beauty in at LEP New data L3: full LEP 2 data Delphi: first analysis (K in RICH) Confirmation of previous results Charm o.k., beauty low no explanation yet Direct Process Single resolved process Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 33 Parton Dynamics DGLAP factorisation: integrated over trans. momentum f(x,Q 2 ) expected to fail when Q~K T un-integrated PDFs: f(x,Q 2,K T ) BFKL,CCFM evolution Selection: 2jets, unbalance NLO 3j NLO 2j Important at low x High parton density Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 34 Low x physics: LEP * * scattering: 2 hard scales test case for BFKL dynamics L3 OPAL Q 2 to 10Q 2 for LO, Q 2 to 4Q 2 for NLO BFKL in LO BFKL in NLO Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 35 Diffraction: factorization Hard scattering: Q2 large Factorisation in diffract. PDF and partonic No colour exchange from Proton Soft QCD ? should follow DGLAP QCD evolution with Q 2 Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 36 Diffraction in NLO QCD NLO QCD fits to incl data Same as in standard QCD fits to DIS PDF(x,Q2) for fixed Proton momentum Large gluon contribution Use diffr. PDF to predict jet), (charm) Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 37 Diffraction in NLO QCD NLO QCD fit to inclusive data describes jet and charm successful test of hard scattering factorisation JetsCharm Current state: ~ all hard diffractive processes at HERA are described by NLO QCD Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 38 Skewed partons e.g.: DVCS (deeply virtual compton scattering) correlation between initial quarks and gluons NLO successful Factorisation for large Q 2 f(x 1,x 2,Q 2 ) Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 39 Spin Parton Distributions proton spin: = ( u v + d v + q sea ) + g + Lq + Lg Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 40 Spin Parton Distributions NLO QCD fit Compass Experiment: data taking started 2002 first results on particle production gluon density from *g cc X soon Next: Gluon distribution well determined: u, d Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 41 Pentaquarks: I LEPS: n K - K + n hep-ex/ beam up to 2.4 GeV Mass(K + n) from K - recoil background from comparison n and p Evidence from 3 experiments: LEPS,DIANA,CLAS DIANA: K + n K 0 p hep-ex/ In Xe bubble chamber Mass(K + n) from K - recoil Claim: 4.6 evidence M(K 0 p) Claim: 4.4 evidence Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 42 Pentaquarks: 2 CLAS: d K + K - p n Claim 5.8 observation 3 experiments taken together: Observation of a new state (although size of effect in each experiment can be debated) mass consistent: MeV width smaller than exp. resolution (1020 MeV) Interpretation: Bound system of uudds - Related to di-baryon, 4-quark states - 1.Constituent Quark Model 2.Chiral symmetry breaking : Prediction from Diakonov, Petrov,Polyakov: decuplet of strange 5-quark systems M =1530 MeV, < 15 MeV hep-ph/ Peter Schleper Exp. Tests of QCD EPS 2003, Aachen 43 Conclusion s : higher orders vital Now: uncert. ~ 3 % NNLO: 1-2 % possible Overall: QCD is in excellent shape Beauty puzzle: Tevatron and HERA slighty high, but much better with new calculations/observables Lecture for LEP ? 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 L3 Huge excess seen, needs to be confirmed Much progress in resummat., power corr., diffraction, spin,