Summary of experimental contributions to SMH working group

1. Summary of experimental contributions to SMH working group Craig Buttar

2. SMH Topics • SM benchmarks for LHC startup • PDF uncertainties • MC • Multi-parton and NNLO • Precision Higgs cross-sections • Electroweak corrections for LHC and LC A brief summary of many topics!!

3. SM Benchmarks • W/Z • W/Z as luminosity monitors • Effect of PDFs on W/Z xsects • W-production impact on PDFs (Cooper-Sarkar/Tricoli) • Effect of low-x corrections (Ball, Del Duca) • Uncertainties on DY with MC@NLO (Ferrag) • W-mass

4. The W mass • The W mass measurement is systematically limited, • and theoretical errors play an important role: • Pt distribution of W and Z. • Difference between W and Z important. • Many calculations exist at NLO, but not all public. • Uncertainties discussed → scaling variation not enough. • Experimenters wish list: Several public calculations! • Influence of PDF uncertainties. • Difference between ubar(x) and dbar(x) • at x ≈ 10-3 influence W and Z mass – correlation? • Method of reweighting to be checked – other methods? • Otherwise, impact on W mass: 17 MeV!!! • Effect of ISR and FSR. • FSR dominant effect – correlation between W and Z. • Photos good for evaluating photons within EM-cluster. - and its theoretical uncertainties. Experimental comment: Energy scale may dominate error! T. Petersen, Les Houches, 10th May 2005

5. Uncertainty in total xsect from PDFs Tricoli/Cooper-Sarkar Z rapidity б.B=2.025 ± 0.062 nb W+ rapidity б.B=12.27 ± 0.40 nb W- rapidity б.B=9.08 ± 0.30 nb NLO predictions for dб/dy. B(leptonic) for single W production at the LHC from ZEUS-S 2002 PDFs with uncertainties-( conventional evolution) PDF uncertainties of ~ ±3% in б.B, but ~±5% at central rapidity

6. Study the effect of including the W Rapidity distributions in global PDF Fits by how much can we reduce the PDF errors? Generate data with CTEQ6.1 PDF, pass through ATLFAST detector simulation and then include this pseudo-data in the global ZEUS PDF fit. Central value of prediction shifts and uncertainty is reduced AFTER including W data BEFORE including W data Tricoli/Cooper-Sarkar W+ to lepton rapidity spectrum data generated with CTEQ6.1 PDF compared to predictions from ZEUS PDF AFTER these data are included in the fit W+ to lepton rapidity spectrum data generated with CTEQ6.1 PDF compared to predictions from ZEUS PDF Specifically the low-x gluon shape parameter λ, xg(x) = x –λ , was λ = -.187 ± .046 for the ZEUS PDF before including this pseudo-data It becomes λ = -.155 ± .03 after including the pseudodata

7. Tricoli/Cooper-Sarkar Reconstructed e- Reconstructed e+ MRST02 MRST02 MRST02 MRST02 MRST03 MRST03 MRST03 MRST03 h h Reconstructed e+- e- Asymmetry Reconstructed e- / e+ Ratio h Contrast the prediction of MRST2002 PDFs conventional QCD evolution with those of MRST03 which distrusts the conventional secenario for x< 5 10-3 Y=0 x=5.10-3 Y=2.5 x=5.10-4 Sensitive to low-x effects R.Ball generated with HERWIG 6.505 + NLO K factors, ATLFAST (200k events->6hrs at low lumi LHC

8. Benchmark: Drell-Yan (Ferrag) • Goal: • Limits on the SM predictions • Observables: • Mll, Pt, boost, Dh • MC@NLO: • s computed by 100 GeV bin • 200 GeV < invMass< 2500 GeV • Sources of uncertainties: • -Factorisation and Renormalisation scales • 1/p * m t < m < p* m t • -PDFs • CTEQ6 40+1 pdf1 40 CTEQ6 pdfs Energy scale variation Invariant mass(GeV) Define threoretical uncertainties Study experimental uncertainies

10. MC • MC@NLO • ggH (Davatz, Drozdetski) • qqWW spin correlations (Drollinger) • ggWW (Duhrssen) • Underlying event • Energy extrapolation (Godbole) • Effect of UE in CJV and lepton isolation (Buttar,Clements, Drozdetski) • Tuning PYTHIA 6.2 and 6.3 (Buttar,Moraes,Skands,Sjostrand) • Tuning • Hbb,tbb fragmentation functions (Drollinger, Corcella)

11. MC@NLO vs LO (Herwig) for gg->H->ZZ->4m mH = 250 GeV: effect of kinematic selections on K factor • Normalized to the number of events for 30 fb-1 • NLO: Nevent(selection)=58.7; • LO: Nevent(selection)=25.7 • KNLO/LO = 2.22 (before selection) • KNLO/LO = 2.28 (after selection) • Conclusion: no significant difference A. Drozdetski Blue: NLO Red: K*LO Analysis cuts: 243 < Minv(H) < 257 GeV

12. Jet veto in gg-h with MC@NLO, PYTHIA6.3, HERWIG and CASCADE. G. Davatz Cut ~30GeV in gg->H->WW Differences vary over the pT spectrum: Integrated efficiency over whole pT spectrum and up to a pT Higgs of 80 GeV: Within MC@NLO uncertainty will be estimated changing the scale

15. Lepton correlations in WW Drollinger Spin correlation Recently added To MC@NLO qq->WW Pythia reweighted to NLO according to Pt-distribution of WW-system -- describes all distributions except lepton correlations  MC@NLO See also qq->WW By Duehrssen,Binoth

16. effect of UE on isolation in H->ZZ->4mA. Drozdetski 10-15% Effect on lepton isolation • PARP(82) = 2.9  PTcut_off = 2.9 GeV – default scenario • PARP(82) = 2.4  PTcut_off = 2.4 GeV – pessimistic scenario • PARP(82) = 3.4  PTcut_off = 3.4 GeV – optimistic scenario Ptch>2.0 PYTHIA 6.2 Ptch>0.5

17. Effect of multiple interaction models on CJV efficiency (MH 160GeV/c2) Clements,Buttar,Moraes 6% effect PYTHIA6.2 The Tuned Model is a fit to experimental data, using a double gaussian matter distribution with a large core radius. Dan Clements – Feb 2005 ATLAS Physics week

18. PYTHIA 6.3 Sjostrand, Skands • Pt-ordering of ISRand FSR • New MI modelCorrelated PDFsColour correlations • Interleaved ISR+MI

19. PYTHIA 6.3 Tuning Moraes/Buttar Preliminary Smooth ISR cut-off Exponential matter density

20. Underlying event and minimum bias: extrapolation to LHC Godbole, Pancheri, Grou and Srivastava New calculation of total xsect using mini-jet modelParameterisation of inelastic for PYTHIA (with error band) Preliminary sinel(LHC)=60mb

21. Hbb fragmentationCorcella/Drollinger Fragmentation function tuned to e+e- data

22. Agenda of Top Quark related sessions during the Workshop (first session) (contact/organiser : Jorgen D’Hondt) General Top Quark session (2): ttbar Frixione/Maltoni (theory), Huston (Tevatron), D’Hondt (LHC) Single-top Dudko (theory), Dudko (Tevatron), Giammanco (LHC) Jets Ellis Polarization Tsuno Specific single-top quark session : Get the optimal ‘Feynman’ observables from D0 and implement them at the LHC, try the DQ-distribution to estimate the W+njet background. Top Quark mass session : Discussion of mass reconstructions. Jet definition session (2): Definition of variables which can quantify a jet definition to reconstruct the kinematics of the complete final state. Top quark systematic session : Try to define a procedure to estimate systematic uncertainties due to ISR/FSR radiation and b-quark fragmentation.

23. Jet definition sessions (1&2) : Aim to define some variables which can identify the quality of jet definitions To reconstruct the kinematics of the full event (several jet densities) Angles (in space!) : a = Σai(jet-parton) Energy : DE = Σ |(Ejet/Eparton)i – 1| Mass : Dm = Σ |Dmi(jet-parton)| Selection efficiency : es (having 4-jets in the final state passing some basic criterion on Et and h) Resolution on energy : A  B/sqrt(E)  C/E First preliminary results (CMS) : Iterative cone R=0.5, Et,minseed=2GeV Heyninck Heyninck eE = A/(A+B) ea = A/(A+B) A B A B a (radian) DE (GeV)

24. First preliminary results (CMS) : comparison jet definitions • IC : R=0.5, Et,minseed=2GeV (no merging or splitting) • MC : R=0.5, Et,minseed=2GeV, overlap thres = 50%, only pairs • kT : D=1 (is basically a cone larger than R=0.5) • General : Calorimeter Towers E-threshold of 1 GeV, ET-scheme ETraw>10GeV, |h|<2.5 Heyninck → Clearly some differencences between cone-like and kT-like definitions Aim : compare these variables for several jet definitions (including : input definition, clustering algorithm, recombination, ...) For several jet densities: single-top (2jets), tt (4jets), ttH (6jets), ttH (8jets) → Giammanco, Heyninck, Schmidt

25. Top quark systematics session : • Aim is to define a procedure to estimate the uncertainties at the LHC (from MC!) • Radiation uncertainties (ISR/FSR) • ISR : tt+1jet is ~40% of inclusive set • (best would be MC@NLO  PY6.3 • and CKKW matching) • syst = change PARP(67) ~ pTmax • between 1 and 4 (or higher for LHC) • LHC → reweight PY6.2 to CompHEP/MadGraph • → check other distributions !! • Problem : large weights, ttH still visible ?? • Solution : select on pt of tt system • FSR : change LQCD in Parton Shower • 2. Colour reconnection • Conservative model to be implemented • Estimate effect on mt Skands, D’Hondt Skands PY 6.3 PY 6.2 factor ~3-4 increase pt of ISR jet

26. The End or is it the start? • Topics will continue after the workshop • Many topics collected on SM benchmark website: http://www.pa.msu.edu/~huston/Les_Houches_2005/Les_Houches_SM.html Final thoughts • Experiments moving to ‘next’ level of study using full simulations and reconstruction • Theory also moving by providing more precise predictions

27. More on • A.N. “Zeppenfeld plot” : effect of ETj3 cut ? (will bring Tuersday evening) • Grazzini-effect of W-polarisation in WW • Low-x: Richard Ball • Single-top • Top—Jorgen

28. Luminosity with W/Z P. Giraud, S.Hassani Analysis with PYTHIA and ATLFAST W-statistical error PYTHIA Z-statistical error PYTHIA Now working with MC@NLO

29. Luminosity with W/Z P. Giraud, S.Hassani For acceptance PYTHIA or MC@NLO will work but for absolute xsect must use MC@NLO

30. Quayle