CNRP. Qiang Zhao. Locality of quark-hadron duality and its manifestation in exclusive meson photoproduction reaction above the resonance region. Qiang Zhao Centre for Nuclear and Radiation Physics Department of Physics, University of Surrey, Guildford, U.K.
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Locality of quark-hadron duality and its manifestation in exclusive meson photoproduction reaction
above the resonance region
Centre for Nuclear and Radiation Physics
Department of Physics, University of Surrey, Guildford, U.K.
In collaboration with F.E. Close (Oxford Univ.)
MeNu2004, IHEP, Beijing, Sept. 2, 2004
-- above the resonance region
The electroproduction of N* at low energies and momentum transfers empirically averages smoothly around the scaling curve for nucleon structure function F2(W2,Q2) measured at large momentum transfers for both proton and neutron targets.
Bloom and Gilman, PRD4, 2901 (1971); Close, Gilman and Karliner, PRD6, 2533 (1972); I. Niculescu et al, Phys. Rev. Lett. 85, 1182 (2000); 85, 1186 (2000).
Nachtmann scaling variable:
=2x/[1+(1+4M2 x2 /Q2 )1/2], where x=Q2/2M2
quark model, hadronic model …
Lattice QCD ?
For exclusive scattering processes at high energy and large transverse momentum, the differential cross section for a two-body reaction A + B C + D has a behaviour:
t =(pA–pC)2 =(pB–pD)2
s =(pA+pB)2 =(pC+pD)2
Brodsky and Farrar, PRL31, 1153 (1973); PRD11, 1309 (1975).
Matveev, Muradian and Tavkhelidze, Nuovo Cim. Lett. 7, 719 (1973).
Lepage and Brodsky, PRD22, 2157 (1980).
Other channels are also measured
Anderson et al., PRD14, 679 (1976)
Oscillatory deviations from the scaling behavior of dimensional quark-counting rules above the nucleon resonance region.
Figure from JLab proposal PR94-104 , Gao and Holt (co-spokesperson)
Isgur and Llewellyn Smiths, PRL52, 1080 (1984)
i) The channel-opening of new flavours
Brodsky, De Teramond, PRL 60, 1924 (1988).
ii) Interference between pQCD and sizeable long-range component.
Brodsky, Carlson, and Lipkin, PRD 20, 2278 (1979);
Miller, PRC 66, 032201(R) (2002);
Belitsky, Ji and Yuan, PRL 91, 092003 (2003).
iii) PQCD color transparency effects
Ralston and Pire, PRL 49, 1605 (1982); 61, 1823 (1988).
iv) Restricted locality of quark-hadron duality
Close and Zhao, PRD 66, 054001 (2002); PLB 553, 211(2003);
Zhao and Close, PRL 91, 022004 (2003); work in preparation.
How does the square of sum become the sum of squares? --- Close and Isgur
F1n /F1p =2/3
F1p,n ~1/2 + 3/2
g1 p /F1p =5/9
g1 p,n ~ 1/2 3/2
g1n /F1n =0
Close, Gilman, and Karliner, PRD6, 2533 (1972); Close and Isgur, PLB 509, 81 (2001)
Sum over intermediate states:
where the coherent term (~e1e2) is suppressed due to destructive interferences.
i) At high energies, i.e. in the state degeneracy limit, all terms of N > 0 (L=0, …, N) vanish due to destructive cancellation: (–C22+C20) 0; (3C44–10C42+7C40) 0; …
R(t) : QCR-predicted scaling factor.
Deviation from QCR is expected !
Effective chiral Lagrangian for quark-pseudoscalar meson coupling:
where the vector and axial vector current are:
with the chiral transformation
The quark and meson field in the SU(3) symmetry:
The quark-meson pseudovector coupling:
Manohar and Georgi, NPB 234, 189 (1984); Li, PRD50, 5639 (1994);
Zhao, Al-Khlili, Li and Workman, PRC65, 065204 (2002)
Internal quark correlations are separated out
Resonances of n 2 included in the SU(6)O(3) quark model
Zhao, Al-Khalili, Li and Workman, PRC65, 065204 (2002)
High energy degenerate limit:
The new data are from: Zhu et al., [Jlab Hall A Colla.], PRL91, 022003 (2003).
Further manifestations of Bloom-Gilman duality dimensional quark-counting rules above the nucleon resonance region.
Jeschonnek and Van Orden, PRD 69, 054006 (2004).
Dong and He, NPA720, 174 (2003).
Summary and discussion dimensional quark-counting rules above the nucleon resonance region.
Nonperturbative resonance excitations due to quark correlations, are an important source for deviations from QCR at 2 s1/2 3.5 GeV.
Features distinguishable from other models:
i) The deviations can be dominantly produced by “restrictedly localized” resonance excitations, i.e. the destructive cancellation occurs within states of the same parity.
ii) The deviation pattern need have no simple periodicity.
iii) The Q2 dependence of the deviations would exhibit significant shifts in both magnitude and position.