1 HERA and the LHC Report on the workshop on HERA  LHC A. De Roeck/CERN HEP-MAD07 Madagascar September 2007  Overview & Highlights of the Workshop  The continuation of the Workshop…

2  Next Meetings: 29 Oct- 2 working groups  May : plenary meetings History of the Workshop

3 The LHC Machine and Experiments pp collisions at 14 TeV LHCf totem (moedal) Luminosity First phase 2  cm -2 s -1 High lumi phase cm -2 s -1 First data expected in summer 2008

4 Workshop Goals ~60 from Hera ~50 from LHC ~50 theory (>160 March 2007 DESY

5 Proceedings of the first Workshop

6 QCD at the LHC CMS experiment At the LHC

7 Jets!

8 Systematics on Jet Measurements

9 Jet Measurements Contact interactions

10 Prompt Photon Production

11 Shape Variables

12 The Underlying Event

13 Study of the Underlying Event at the LHC

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15 MC - Tools S. Gieseke, F. Krauss, T. Kluge, P. Bartalini, P. Robbe, S. Chekanov Multijets & final states Underlying events, un-integrated pdfs L. Lonnblad, G. Zanderighi, C. Gwenlan, N. Tuning, S. Banerjee, Ch. Risler, D. Traynor Structure functions and parton distributions S. Forte, S. Moch, M. Dittmar, A. Glazov M. Botje Diffraction M. Diehl, V. Khoze M. Arneodo, P. Newman, A. Bruni, B. Cox, R. Orava Heavy quarks: B quark pdfs of the proton, fragmentation fct, u-pdfs M. Cacciari,H. Spiesberger, A. Dainese, A. Geiser, K. Lipka,U. Uwer Working Groups of the workshop

16 Parton Density functions Collinear PDFs Simple spread of existing PDFs gives up to 10% uncertainty on Higgs cross section

17 Parton Density functions Collinear PDFs Unintegrated PDFs Large k T effects may affect Higgs searches/measurements

18 Parton Density functions Collinear PDFs Unintegrated PDFs Diffractive and Generalized PDFs All these PDFs can be addressed at HERA via  inclusive,  semi-inclusive,  diffractive,  vector meson  DVCS …measurements

19 PDFs & ADD extra dimensions: di-jet final state Reduction of the sensitivity due to PDF uncertainty (CTEQ6) Graviton exchange contributions reduce the cross section (interference) S. Ferrag

20 PDFS and ADD/RS: Di-lepton final states Kumar et al. hep/  Q 2 = 1 TeV  7.5% uncertainty  Q 2 = 1.5 TeV  12.5% uncertainty  Can get to >30% for large masses! Using MRST set ADDRS

21 PDFs are important!! Tevatron: mid 90’s ?  New Physics? …or PDFs?

22 LHC Kinematics/QCD evolution Evolution of PDFs to high Q2 & low x important at the LHC Precision? Level of approximation? CCFM/BFKL?, non-linear effects?  Test it at HERA Is this a region of “safe –x”??? ?

23 Example W, Z production  Theoretical uncertainty small but how well do we know the parton distributions?

24 W prod. at LHC without HERA:W prod. at LHC including HERA PDFs including HERA: PDFs without HERA: ~ 3.5 % ~ 16 % <x<0.1 HERA Impact on the LHC  PDF uncertainty will be the dominant error!

25 Impact of Future HERA Data  Improvement in PDF precision with projected 700 fb -1 of data in HERA-II  Includes jets in DIS and  p  Note: only HERA (ZEUS) data are used in the fits Gwenlan Cooper-Sarkar Targett-Adams hep-ph/

26 from C. Gwenlan, A. Cooper-Sarkar, C. Targett-Adams high statistics from HERA II is important (assumed 700 pb -1 ) Using jets together with F 2 (at large Q 2 ) quark and gluon uncertainties Error on LHC jet xsection reduced !!! PDF Uncertainties: Improvements

27 From M. Cooper-Sakar, C. Gwenlan and S. Glazov Much reduced uncertainties.... Model independent analysis of data desirable get THE HERA – PDF !!!!! ● Combined PDF fit to H1& ZEUS ● Average H1&ZEUS data sets Average HERA data A request from the 2005 workshop…

28 PDFs: E.g. MRST/CTEQ differences YES: F L can referee the gluon distribution! F L is like F 2 : little theoretical ambiguity (compared to e.g. F 2 C ) H. Stenzel R. Thorne Need to lower the energy of proton or electron beam for this measurement Can we know more by the time of the LHC startup? Strong case made during HERA-LHC Workshops 2004/2005

29 Prospects for Measuring F L Detailed study for H1, with 2 lower proton beam energy settings F L can referee between MRST and CTEQ gluons F L is gluon driven F L measurement at HERA in 2007 ! 2 lower energy settings CTEQ MRST Feltesse/Klein et al

30 CTEQ6.1  CTEQ6.5 Parton Distribution “Evolution” Heavy flavours treatement in PDFs! Any claim that we know the W,Z cross sections with a precision of a few % should be taken with care

31 Study of the impact of intrinsic charm Still an open issue

32 Using NLO PDFs for (LO) LHC MC’s? Proposal by J. Huston et al

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35 PDF determination at LHC WG1 convenors: Should form a “group” from ATLAS, CMS, LHCb, ALICE, H1, ZEUS and theoretical PDF experts Also jets, photons,… See Eg. M. Cooper-Sarkar et al.

36 Finally: Call for a working group/task force/LHC-study group … Interest from theorists/fitters/HERA/ LHC/…?  The PDF + uncertainties …Need to call for a meeting

37 from R. Field Underlying event/multiple interactions  Studies and tunes made on Tevatron/lower energy data  Do the Tevatron tunes work for HERA? Special program to check…  New models on the market that should be tested (new Pythia, Jimmy, Sherpa)

38 Pythia ATLFAST 602 Effect of underlying event on central jet veto in VBF Higgs Uncertainty of the central jet veto efficiency due to UE model; ATLAS. Rapidity of the central jet in Higgs events; CMS; full simulation, L=2x10 33 cm -2 s -1 “bkg. like” behaviour for soft jets; fake jets: pile up+UE+detector H->WW*->2l in qqH prod.

39 Double Parton interactions Not well know what to expect…

40 HERA II analysis (expect factor 10 more), larger kinematic range ➔ Understand b-production mechanism (...remember b-puzzle at the TeVatron...) ➔ NOTE: gluon drives heavy quark PDFs Current H1 (HERA I) analysis From O.Behnke, A. Geiser, A. Meyer, M. Wing beauty charm HERA: Heavy Quark PDFs at large Q 2

41 estimates for ALICE × Nonlinear evolution equation for uPDF: (B alitsky - K ovchegov equation) A. Dainese et al Bottom suppression due to non-linear effects in BK ● Significant effects... ● up to factor of 2 in hot spot scenario ● factorization still ok ? Non-Linear QCD effects at the LHC

42 H gap -jet  Exclusive Higgs Production Exclusive diffractive Higgs production pp  p +H+ p : 2-10 fb SM Cross section ‘stabelized’ during the previous workshop fb MSSM p p beam p’ roman pots dipole Advantages Exclusive:  Jz=0 suppression of gg  bb background  Mass measurement via missing mass E.g. V. Khoze et al M. Boonekamp et al. B. Cox et al. …  M = O( ) GeV P. Landshof: Cross sections can be higher!

43 Central Exclusive Production Kaidalov et al., hep-ph/ fb 1fb MSSM Higgs/high tan  : (30fb -1 )  signal events (after cuts) and O(10) background events  Study correlations between the outgoing protons to analyse the spin-parity structure of the produced boson A way to get information on the spin of the Higgs  ADDED VALUE TO LHC

44 Detectors for Exclusive Higgs Production Low  *: (0.5m): Lumi cm -2 s m: 0.02 <  < /400m: <  < 0.02 RPs in the cold region/needs cryostat redesign Detectors at 420 are needed to access the low  values for low Higgs mass acceptance TOTEM (ATLAS) FP420  Problem: 420m to late for CMS/ATLAS L1 trigger. Trigger on central activity FP420 R&D Project Contacts: A De Roeck/B. Cox

45 Idea to fill gap in rapidity with calorimeter at 135 m in front of TAN ( E ~ TeV and pseudorapidity range 8 – 12 ) Beamline simulation performed Pseudorapidity resolution ~ ( depends on the selected energy rapidity range) Radiation level near the calorimeter at 135 m is reasonable (from studies of ZDC) Tracker in front of calorimeter to improve coordinate resolution (GEM) V.Andreev, A.Bunyatyan, K.Borras, HJU, M.Kapishin, L.Lytkin R. Orava, J. Lamsa Ideas for upgrading forward region

46 MC and other Tools Parton distribution library: –LHAPDF now official carrier of the PDFs Used by LHC experiments in generators HERA pdfs have been added Allows error uncertainty estimates Pion and photon added, particularly for HERA. F2D next? NLOLIB framework for NLO QCD programs –Uniform user interface/interface to HZTOOL –e+e-/ep included, pp can be added HZTOOL/JetWeb/RunMC/Cedar(?) for tunning –All HERA results to be included, some e+e-. Include more pp? RAPGAP, Cascade Monte Carlos for inclusive and diffractive pp Plenty of exchange on other MC tools, leading to new MC tools and comparisons with ep where possible Continuation of the MC4LHC 2003 (and 2006) workshop, concerning MC validation

47 MC Activities

48 Nutshell: Results from HERA/LHC I Parton Distribution Functions –Dialogue/discussion between PDF fitters and community that delivers the data. –Combined data (H1/Zeus Datasets for F2, F2D), measurements of F L at HERA. –Discrepancies between PDFs will be ironed out, eg via to new measurements. Fits with 1-  bands available. –Quantitative estimates for low-x/large-x resummation available –Timescale for the full program 1-2 years, i.e. just in time for the LHC  Will lead to more precise PDFs: maybe factor 2? (personal guess/hope) Diffraction –Improved understanding on the DPE/Higgs production and cross section Final states –Lots of work/progress on underlying events (tuning), gap survival Heavy quarks –Saturation effects measurable at low pt –Heavy quark parton distributions eg. for Higgs cross section calculations. Tools –Tool & generator developments, preparing for LHC startup

49 PDF determination: – Best possible PDF. Ultmate expected precision? Impact on LHC measurements? – Uncertainties on the PDF and QCD evolution – Special PDFs? Diffractive, unintegrated, generalized… Event topologies: – Multiple Interact./Underlying Events: understanding the physics/uncertainties – Higher Order Corrections/verified on HERA data/Jet studies (algorithms..) Reliable Simulations/ Theory/Models – tuning of free parameters to many different measurements – improved calculations/NLO libraries – test alternative approaches (SCET?) HERA/LHC II: what does LHC need? Goals for HERA/LHC II Next Meeting: 29 Oct-2 DESY/Hamburg Keywords: tools, phenomenological progress, and quantitative estimate for the impact of HERA on LHC measurements

50 Backup