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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 mA
Duty 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 !
