Gamma-gamma Physics Group Report De Roeck CERN
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
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)
AMEGIC++ for S. Schumann, F. Kraus Event generator AMEGIC++ Resolved Direct
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!
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
MC Tuning have to check effects on our backgrounds
SM Higgs analyses • Update:Use SIMDET + ZVTOP B finder P. Niezurawski 81% 1.8%
SM Higgs analyses 1 year/84 fb-1 Systematics…?? Using NLO backgrounds (Jikia…) Fragmentation questions?
SM Higgs analyses A. Rosca Pythia reweighted with NLO cross sections ZVTOP Tagging optimization still ongoing (presently lower than prev. analysis)
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…
H/A Higgs D. Asner/J. Gunion (LCWS02) Need few years to Close the wedge Need also European study
Low Mass Charged Higgs V. Martin Using H decays Full simulation Relative low efficiency after cuts: 2.5 % What can a PC contribute?
2HDM model M. Krawczyk
Upcoming initiative… M. Krawczyk R. Godbole Invitation
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
Trilinear Gauge couplings in e D. Anipko Analyse d2/dp dcose CompHEP
Trilinear Gauge couplings in e J Sekaric & K. Moenig • Fitting results of the fit of andfor ± 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
comparison of the single parameter fit for e , -, and e-e+ - colliders • sensitivity to WW only! - ,~ 10-3
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?, HH+H-?… • Being done/ready • promised Any Volunteers??
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
D. Miller Determining the Spin of the H in collisions
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!
Luminosity and spectra Usable in event simulation (Telnov/Ohl/Zarnecki) Pandora For TESLA… Z=W/2Ebeam
B-tagging • Reconstruction of the vertex using a topological vertex technique (ZVTOP). IP Primary vertex Secondary vertex Tertiary vertex B D
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
The light Higgs “State of the art”” (M. Krawczyk) All background under control? B-tagging different in ?
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
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
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 !