Photoproduction and Decays of Pseudoscalar Mesons in CLAS

M.Amaryan, University of Bochum, December 6, 2011

Photoproduction and Decays of Pseudoscalar Mesons in CLAS

Moskov Amaryan Old Dominion University Norfolk, Virginia, USA

M.Amaryan, University of Bochum, December 6, 2011

Outline

-CLAS setup at JLAB

-Classification of Mesons

-Hadronic decays

-Dalitz decays

-Radiative decays

-Summary

M.Amaryan, University of Bochum, December 6, 2011

Emax ~ 6 GeV Imax ~ 200 mADuty Factor ~ 100% sE/E ~ 2.5 10-5

Beam P ~ 80%Eg(tagged) ~ 0.8- 5.5 GeV

CLAS

JLab Site: The 6 GeV CW Electron Accelerator

M.Amaryan, University of Bochum, December 6, 2011

The CLAS Photon Tagger

M.Amaryan, University of Bochum, December 6, 2011

CEBAF Large Acceptance Spectrometer

Liquid D2 (H2)target +g start counter; e minitorus

Drift chambersargon/CO2 gas, 35,000 cells

Electromagnetic calorimetersLead/scintillator, 1296 PMTs

Torus magnet6 superconducting coils

Gas Cherenkov counterse/p separation, 216 PMTs

Time-of-flight countersplastic scintillators, 684 PMTs

Large angle calorimetersLead/scintillator, 512 PMTs

M.Amaryan, University of Bochum, December 6, 2011

Horizontal cut through the CLAS detector

M.Amaryan, University of Bochum, December 6, 2011

(Reminder)

M.Amaryan, University of Bochum, December 6, 2011

Type S L P J JP

Pseudscalar mesons

0 0 - 0 0-

Axial vector mesons

0 1 + 1 1+

Vector mesons 1 0 - 1 1-

Scalar mesons 1 1 + 0 0+

Tensor mesons 1 1 + 2 2+

Meson Families

J=L+S

P=(-1)L+1

C=(-1)L+S

G=(-1)L+S+I

M.Amaryan, University of Bochum, December 6, 2011

In the SU(3) Group Theory Language

M.Amaryan, University of Bochum, December 6, 2011

OUTLINE - Photoproduction of Pseudoscalar Mesons with CLAS

Radiative Decays

Hadronic Decays

Also Vector Mesons:

M.Amaryan, University of Bochum, December 6, 2011

Missing Mass Distribution

gp pX

Single charged track events identified as a proton

M.Amaryan, University of Bochum, December 6, 2011

Missing Mass

3 charged track events identified as a proton, π+ and π-

π0

η

M.Amaryan, University of Bochum, December 6, 2011

OZI allowed OZI suppressed

Okubo-Zweig-Iizuka Rule

M.Amaryan, University of Bochum, December 6, 2011

ω-ϕ Interference in e+e- annihilation

M.N.Achasovhep-ex/0604051

It depends on production and decay amplitudes of interfering resonances as well as on their relative phases.

How would it look like in photoproduction?

M.Amaryan, University of Bochum, December 6, 2011

OZI Rule Violating Decay of ϕ meson in photoproduction

ω

η

ϕη‘

η‘ ϕ

γ+p = pπ+π-π0

(~2M events)

Hadronic decay

M.Amaryan, University of Bochum, December 6, 2011

G-Parity Violating Decay of φ Meson ?

M=1.021 GeVσ = 0.005 GeV

PDG Exp. limit Br<1.8x10-5

η‘

Φ

f1(1285)

Theory prediction:Br( ) ~3x10-7 Achasov, I.J.M.Phys. A, Vol.7, No. 20(1992, 4825)

M.Amaryan, University of Bochum, December 6, 2011

~340K η’ events and ~1M on tape

~40K events

arXiv:1012.1117v2 [hep-ex]

M.Amaryan, University of Bochum, December 6, 2011

M.Amaryan, University of Bochum, December 6, 2011

not corrected for acceptance

M.Amaryan, University of Bochum, December 6, 2011

M.Amaryan, University of Bochum, December 6, 2011

M.Amaryan, University of Bochum, December 6, 2011

From g11 run only

Adding g12 will reduce stat.err. by factor of two

M.Amaryan, University of Bochum, December 6, 2011

M.Amaryan, University of Bochum, December 6, 2011

Radiative Decay

ρ/

M.Amaryan, University of Bochum, December 6, 2011

Theory:F.Stollenwerk et al.,arXiv:1108.2419v1[nucl-th]

WASA-at-COSY[17]

BNL-AGS[18]

CLAS

η->π+π-γ η’->π+π-γ

Eγ [GeV] Eγ [GeV]

Not corrected

M.Amaryan, University of Bochum, December 6, 2011

Not corrected for acceptance

CLAS

M.Amaryan, University of Bochum, December 6, 2011

Dalitz Decay of Pseudoscalar Mesons

M.Amaryan, University of Bochum, December 6, 2011

M.Amaryan, University of Bochum, December 6, 2011

Summary

-High statistics experimental results on rare and dominant decay modes of pseudoscalar and vector mesons are obtained with CLAS at JLAB.- In some channels CLAS data are exceeding the world statistics -Dalitz decay of etaprime is observed for the first time-Combining data from different world facilities will help to provide high quality and high statistics data-We believe that common efforts of European and US groups related to meson decays will be extremely useful -Thanks for the opportunity to give a seminar in University of Bochum !