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Gamma-gamma Physics Group Report

A.De RoeckCERN

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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

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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)

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AMEGIC++ for

S. Schumann, F. Kraus

Resolved

Direct

Event generator AMEGIC++

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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!

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Monte Carlo Tuning

JetWeb hep-ph/0210404 http://jetweb.hep.ucl.ac.uk J Butterworth et al

M.Wing

‘fit’ MCparametersto data fromLEP, HERA& Tevatron

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MC Tuning

have to check effects on our backgrounds

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• Update:Use SIMDET + ZVTOP B finder

SM Higgs analyses

P. Niezurawski

81%

1.8%

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Using NLO backgrounds (Jikia…) Fragmentation questions?

Systematics…??

SM Higgs analyses

1 year/84 fb-1

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SM Higgs analyses

events 2900N

events 3370 N

bkg

sig

ccbb

2.3%NN

N

)bb)BR(h(hbb)BR(h(h

bobs

obs

γγΓ

γγΓΔ

Pythia reweighted with NLO cross sectionsZVTOP Tagging optimization still ongoing (presently lower than prev. analysis)

A. Rosca

. fb 80 1-L

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Overlap events1.5 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…

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SM Higgs analyses

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H/A Higgs

D. Asner/J. Gunion(LCWS02)

Need few years to Close the wedge

Need also Europeanstudy

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Low Mass Charged Higgs

V. Martin

Using H decaysFull simulation

Relative lowefficiency after cuts: 2.5 %

What can a PC contribute?

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2HDM model

M. Krawczyk

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M. KrawczykR. Godbole

Invitation

Upcoming initiative…

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CP studies via tt

R. Godbole et al.hep-ph/021136& LCWS02

Construct combinedasymmetries fromintial lepton polarizationand decay lepton charge

Done with realisticspectra etc., but needsstudy with simulation

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Trilinear Gauge couplings in e

D. Anipko

Analyse d2/dp dcose

CompHEP

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Fitting results of the fit of Fitting results of the fit of andand for for ± 1 photon polarization state – single ± 1 photon polarization state – single

and two parameter fit for real (and two parameter fit for real (ee ) mode ) mode

REAL MODE

1 par. fit

ECM = 450 GeV, L = 110 fb-1

J = +1 J = -1

L 1% 0.1% accur. 1% 0.1% accur.

·10-3 3.4 1.0 0.5 9.7 1.1 0.5

·10-3 1.6 1.5 1.5 4.6 4.4 3.82 par. fit

·10-3 5.1 1.1 0.5 9.7 1.1 0.6

·10-3 2.3 1.6 1.6 4.6 4.6 4.6

REAL MODE - pure e-mode, known beam directions

Trilinear Gauge couplings in e

ee WW , , hadronic decay channel/total and differential cross sectionshadronic decay channel/total and differential cross sections

J Sekaric & K. Moenig

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comparison of the single parameter fit for comparison of the single parameter fit for ee , ,

-, and -, and ee--ee++ - colliders - colliders

Ee= 450 GeV

L=110 fb-1

E= 400 GeV

L=110 fb-1

Eee= 500 GeV

L=500 fb-1

L 0.1% 0.1%

·10-4 10 / 9.8 6.7 3.1

·10-4 15 / 5.8 6.0 4.3

sensitivity to WW only! - , ~ 10-3

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Most important processeshep-ph/0103090

Added since then: Non-commutative measurements, e for ED’s,Light gravitinos, Radions, H?, HH+H-?…

Higgs

Susy

Tril/quart.

Top

QCD

Any Volunteers?? Being done/ready promised

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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

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NLC studies overview

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D. Miller Determining the Spin of the H in collisions

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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 colliderfor several yearsif the physics scenario warrants it!

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Luminosity and spectra

Usable in eventsimulation(Telnov/Ohl/Zarnecki)Pandora

For TESLA…

Z=W/2Ebeam

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Cross sections

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B-tagging

IP

B

D

Primary vertex

Secondary vertex

Tertiary vertex

• Reconstruction of the vertex using a topological vertex technique (ZVTOP).

cc

qlight

bb

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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

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The light Higgs

“State of the art””(M. Krawczyk)

All background under control? B-tagging different in ?

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Background studiesFrequently 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 pixelDetector per bunch crossing

Incoherent pair production: essentiallythe same as for e+e-

Coherent pair production: under study

Neutrons?

Will be able to answer this question soon

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Is a photon collider a hadron collider?

•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)

> 80 mrad > 250 mrad

10-20 tracks/event<ET> few GeV, tails up to 20-30 GeV Looks not so bad!(ADR, ST Malo meeting)

Common study withtheorists and NLC groups starting

NO !

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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 !