Gamma-gamma Physics Group Report

1. Gamma-gamma Physics Group Report De Roeck CERN

2. This meeting Sessions • Gamma gamma session (3 talks) (including a Report from LCWS02 by M Krawczyk) • Common session with QCD (1 talk) • Common session with Higgs (6 talks) • Common session with EW ( 2 talks) • Jeju Photon Collider option discussion (Higgs group) • Physics case for PC has confirmed/strengthened (Higgs properties measurements/Heavy Higgs production) • Must do appropriate R&D to keep the possibility of a PC

3. Studies Reach Maturity • Aim: Level of detail in  as good or better than in e+e- • SIMDET simulation (~e+e- detector/ see K. Moenig). Brahms? • Real Luminosity spectra/polarization used • B search using ZVTOP • Adding overlap events • QCD backgrounds in NLO • QCD Monte Carlo tuning to existing data • Cross checks for key processes (Higgs production) • Direct contact & exchange with the NLC studies/exchange tools • More work still needed on • Luminosity/polarisation measurement (& corresponding syst.) • Final design of IP/vertex detectors ( backgrounds)

4. AMEGIC++ for  S. Schumann, F. Kraus Event generator AMEGIC++ Resolved Direct

5. AMEGIC++ for  • Matching ME to parton showers • NLO • Underlying event structure • Hadronization and fragmentation • Specific for : Photon decomposition & structure Expect first version (for lepton final states) next month/ Hadrons early next year. !Useful for background studies to Higgs!

6. Monte Carlo Tuning M.Wing ‘fit’ MC parameters to data from LEP, HERA & Tevatron JetWeb hep-ph/0210404 http://jetweb.hep.ucl.ac.uk J Butterworth et al

7. MC Tuning  have to check effects on our backgrounds

9. SM Higgs analyses • Update:Use SIMDET + ZVTOP B finder P. Niezurawski 81% 1.8%

10. SM Higgs analyses 1 year/84 fb-1 Systematics…?? Using NLO backgrounds (Jikia…) Fragmentation questions?

11. SM Higgs analyses A. Rosca Pythia reweighted with NLO cross sections ZVTOP Tagging optimization still ongoing (presently lower than prev. analysis)

12. Overlap events • 1.5 central high energy  events for L(z > 0.8zmax) • ~ 1.1 .1034 cm-2 s-1 • Files for TESLA have been prepared/SIMDET adapted to use overlays • e+e- and  files • So far catalogued on the CLIC page • //clicphysics.web.cern.ch/CLICphysics • 200 & 500 GeV files available  file contains 5000 events • Selection events: W2 > 5 GeV2 , • tracks: Pt> 150 MeV, •  > 80 mrad • photon polarization not taken into account Effect on the measurement? Work in progress…

13. SM Higgs analyses

14. H/A Higgs D. Asner/J. Gunion (LCWS02) Need few years to Close the wedge Need also European study

15. Low Mass Charged Higgs V. Martin Using H  decays Full simulation Relative low efficiency after cuts: 2.5 % What can a PC contribute?

16. 2HDM model M. Krawczyk

17. Upcoming initiative… M. Krawczyk R. Godbole Invitation

18. CP studies via tt R. Godbole et al. hep-ph/021136 & LCWS02 Construct combined asymmetries from intial lepton polarization and decay lepton charge Done with realistic spectra etc., but needs study with simulation

19. Trilinear Gauge couplings in e D. Anipko Analyse d2/dp dcose CompHEP

20. Trilinear Gauge couplings in e J Sekaric & K. Moenig • Fitting results of the fit of andfor ± 1 photon polarization state – single and two parameter fit for real (e ) mode • REAL MODE - pure e-mode, known beam directions e W , hadronic decay channel/total and differential cross sections

21. comparison of the single parameter fit for e ,  -, and e-e+ - colliders • sensitivity to WW only! -  ,~ 10-3

22. Most important processes hep-ph/0103090    •    •    Higgs Susy Tril/quart. Top QCD Added since then: Non-commutative measurements,  e for ED’s, Light gravitinos, Radions,  H?,  HH+H-?… • Being done/ready • promised Any Volunteers??

23. Plans • Finalize current analyses, particularly higgs sector • If IP studies in near future will require changes need to know this asap • High priority to start H/A & SUSY particle analysis, CP studies • Use synergy with NLC group/exchange of tools • Indian group starts studying ED’s in  and e (R. Godbole et al.). Expect first results by Amsterdam • Additional meeting before Amsterdam: February 13 @ CERN • Plan to write up summary of the PC studies for Amsterdam • At Amsterdam: Plan a panel discussion on a PC collider

24. NLC studies overview

25. D. Miller Determining the Spin of the H in  collisions

26. H/A higgs Can a photon collider close the wedge? Cross section gets small For M(H/A) > 600 GeV J.Gunion: 2-4 years needed CP studies Expect need to run of photon collider for several years if the physics scenario warrants it!

27. Luminosity and spectra Usable in event simulation (Telnov/Ohl/Zarnecki) Pandora For TESLA… Z=W/2Ebeam

28. Cross sections

29. B-tagging • Reconstruction of the vertex using a topological vertex technique (ZVTOP). IP Primary vertex Secondary vertex Tertiary vertex B D

30. The photon collider case • Advantages • Large cross sections (e.g. WW production cactor 20-40 times) • Large circular polarization e-e- beams (~80%)   (90-95% in peak) • Linear polarization (CP filter) • Extended kinematic range for some new particles • S-channel production for H,… /association e.g. slepton  lepton+0 • Sometimes different couplings probed (no “Z” effects) • Issues • Luminosity spectrum spread (not monochromatic, but much better than LHC). How precise can we measure the spectrum/luminosity? • Luminosity typically factor 3 lower compared to e+e-(but yet not at limit) • Needs R&D to proof it works as expected.  plans • More complicated IR • Debate of backgrounds and its implication on detector not yet finalized • Only few processes so far studied in (almost) all experimental details, most important one   Higgs

31. The light Higgs “State of the art”” (M. Krawczyk) All background under control? B-tagging different in ?

32. Background studies Frequently asked question: same b-tagging efficiency as in e+e- case? K. Moenig et al.: backgrounds studied for TESLA IP layout Study beam related background # of hits in the layers of the pixel Detector per bunch crossing Incoherent pair production: essentially the same as for e+e- Coherent pair production: under study Neutrons? Will be able to answer this question soon

33. Is a photon collider a hadron collider? NO ! • The QCD background in a  collider can be large • Eg. for Lgeom ~ 1035 cm-2 s-1, 400 nb  cross section •  3  events/bunch crossing • Many events boosted and/or low mass: no problems • V. Telnov (TESLA TDR appendix): 1.5 central high energy  events • for L(z > 0.8zmax) ~ 1.1 .1034 cm-2 s-1 # of jets (Et > 5 GeV) 10-20 tracks/event <ET> few GeV, tails up to 20-30 GeV Looks not so bad! (ADR, ST Malo meeting) Common study with theorists and NLC groups starting  > 80 mrad  > 250 mrad

34. R&D program Europe: R&D for lasers in IP (10% size prototype cavity planned) US: Laser development at LLNL Plan for SLC photon collider testbed at SLAC (means reactiviating SLC/ Workshop at SLAC Nov 21-23 ‘02 Conclusion: Photon collider will enrich the program of an e+e- machine We cannot afford NOT to study it !