1 Primakoff Experiments with EIC A. Gasparian NC A&T State University, Greensboro, NC For the PrimEx Collaboration Outline Physics motivation: The first experiment at JLab: 0 lifetime Development of precision technique Results for 0 lifetime Experiments with EIC Summary
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11 Primakoff Experiments with EIC A. Gasparian NC A&T State University, Greensboro, NC For the PrimEx Collaboration Outline Physics motivation: The.
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11
Primakoff Experiments with EIC
A. GasparianNC A&T State University, Greensboro, NC
For the PrimEx Collaboration
Outline
Physics motivation: The first experiment at JLab: 0 lifetime
Development of precision technique Results for 0 lifetime
Experiments with EIC Summary
2
chiral limit: is the limit of vanishing quark masses mq→ 0.
QCD Lagrangian with quark masses set to zero:
qq
s
d
u
q
GgD
GGqiDqqiDqL
LR
s
RRLLoQCD
)1(2
1
2/
4
1
5,
)(
Large global symmetry group:Large global symmetry group:
• Chiral anomalies Mass of η0 P→γγ ( P: π0, η, η׳)
• Quark flavor SU(3) breaking
The mixing of π0, η and η׳
The The 00, , ηη and and ηη’ system provides a rich ’ system provides a rich laboratory to study the symmetry structure of laboratory to study the symmetry structure of
The PrimEx Experimental ProjectThe PrimEx Experimental Project
Experimental program Precision measurements of:
Two-Photon Decay Widths: Γ(0→), Γ(→), Γ(’→)
Transition Form Factors at low Q2 (0.001-0.5 GeV2/c2): F(*→ 0), F(* →), F(* →)
Test of Chiral Symmetry and Anomalies via the Primakoff Effect
66
Physics Outcome
Fundamental input to Physics:
precision test of chiral anomaly predictions determination of quark mass ratio -’ mixing angle 0, and ’ interaction electromagnetic radii is the ’ an approximate Goldstone boson?
7
First experiment: 0 decay width
eVF
mNc 725.7576 23
3220
0→ decay proceeds primarily via the chiral anomaly in QCD. The chiral anomaly prediction is exact for massless quarks:
Corrections to the chiral anomaly prediction: (u-d quark masses and mass differences)
Calculations in NLO ChPT:(J. Goity, at al. Phys. Rev. D66:076014, 2002)Γ(0) = 8.10eV ± 1.0%
~4% higher than LO, uncertainty: less than 1%
Precision measurements of (0→) at the percent level will provide a stringent test of a fundamental prediction of QCD.
0→
Recent calculations in QCD sum rule: (B.L. Ioffe, et al. Phys. Lett. B647, p. 389, 2007)
Γ() is only input parameter 0- mixing includedΓ(0) = 7.93eV ± 1.5%
8
Decay Length Measurements (Direct Method)
1x10-16 sec too small to measure
solution: Create energetic 0 ‘s,
L = vE/m
But, for E= 1000 GeV, Lmean 100 μm very challenging experiment