Photoproduction of h and h Mesons on the

Photoproduction of h and h‘ Mesons on the Nucleon L. Tiator, Institut für Kernphysik, Universität Mainz v introduction v the MAID project v t-channel exchanges: poles vs. Regge trajectories v D 15(1675) resonance vs. P 11(1675) pentaquark v summary and conclusion

p threshold K threshold nonresonant background: large very small large

motivation for g, and g, ‘ • missing or misidentified resonances • qqq resonances vs. dynamically generated resonances with pp. N or with KS, e. g. S 11(1535) • exotic resonances: Does the Q+ pentaquark exist? if so, it should have a non-strange partner P 11(~1700)

MAID the Mainz-Dubna Unitary Isobar Model K-matrix unitarization phase determined by the Watson theorem, below 2 p threshold relaxed above 2 p threshold

ETA-MAID uses a simpler approach without additional unitarization:

Resonances Breit-Wigner form 8 resonances are included in -MAID : D 13(1520) S 11(1535) S 11(1650) D 15(1675) very important for S most important very important for S F 15(1680) less important D 13(1700) unimportant P 11(1710) important P 13(1720) unimportant

Background Born Terms very small coupling constant:

Vector Meson Exchanges

This description for vector meson exchanges § works fine in the resonance region (W < 2 Ge. V) § but cannot be extended to high energies

Regge Trajectory Exchanges At high s and low t, it is known that meson photoproduction can be well described by Regge trajectories in the t-channel. Replace pole-like propagator With Regge propagator

Vector Meson Exchanges in p hp Fit high-s, low-t data to determine the vector meson couplings g. VNN and k. VNN Data from DESY (1970)

Photoproduction Data available in 2001 Cross sections • MAMI in Mainz Krusche et al. , Phys. Lett. B 358, 40 (1995) • ELSA in Bonn Price et al. , Phys. Rev. C 51, 2283 (1995) • GRAAL, ESRF in Grenoble Renard et al. , Phys. Lett. B 528, 215 (2002) MAMI 95 ELSA 95 GRAAL 02 Beam asymmetry • GRAAL, ESRF in Grenoble Ajaka et al. , Phys. Rev. Lett. 81, 1797 (1998) Kouznetsov (SAID database) GRAAL 98 GRAAL 01 Target asymmetry • PHOENICS, ELSA in Bonn Bock et al. , Phys. Rev. Lett. 81, 534 (1998) ELSA 98

Photoproduction Data after 2001 Cross sections • GRAAL, ESRF in Grenoble Renard et al. , Phys. Lett. B 528, 215 (2002) • CLAS, Jefferson Lab Dugger et al. , Phys. Rev. Lett. 89, 222002 (2002) • CB-ELSA in Bonn Crede et al. , Phys. Rev. Lett. 94, 012004 (2005) GRAAL 02 CLAS 02 BONN 05 preliminary data 2005/06 Cross sections and Beam Asymmetry • GRAAL (ds/d. W and S for proton and neutron) Kouznetsov et al. , N*2005 GRAAL 05 • CB-ELSA (s and ds/d. W for proton and neutron) Jaegle et al. N*2005 BONN 05

Eta-Maid 2001 compared to data from TAPS@Mainz and GRAAL differential cross section photon beam asymmetry

Comparison with the Eta-Maid 2003 Reggeized Model

with std. vector meson poles and hadronic form factors with reggeized vector mesons both models describe very well the proton data

standard w, r + resonances reggeized w, r only reggeized w, r + resonances

The role of the D 15(1675) resonance h. N branching ratios in our 2 models: 17 % for the Eta. Maid with v. m. poles 0. 7 % for the reggeized model

! almost a factor 10

Comparison with preliminary data from GRAAL diff. c. s. and beam asymm. on neutron (priv. comm. S. Kouznetsov, 2006) bump observed around 1650 Me. V -Maid 2001 -Maid without D 15

Comparison with preliminary data from CB-ELSA total c. s. on proton and neutron (I. Jaegle, priv. comm. 2006) - Maid 2001

ETA - MAID 2003 isobar model (update of Eta-Maid 2001) reggeized isobar model (w, r Regge trajectories) (preliminary data from CB-ELSA, I. Jaegle, priv. comm. 2006) only the model with the strong D 15 can describe the neutron data

problems with the D 15(1675) resonance: 1) in the std Eta. Maid model it fits the neutron data very well but needs a large branching ratio of b N = 17 % SU(3)fl for baryon octett gives a prediction of b N= 2. 5 % (Guzey and Polyakov, hep-ph/0512355) 2) in the Regge model the D 15(1675) does not play any important role

effect of a non-strange pentaquark in

quasifree eta photoproduction on the deuteron in collaboration with Alexander Fix ( e. g. A. Fix and H. Arenhövel, Z. Phys. A 359 (1997) 427 ) in impulse approximation: h. NN fsi is negligible NN fsi is larger but only important near threshold input: Eta. Maid with additional pentaquark state P 11(1675)

pentaquark solution

D 15 resonance versus Pentaquark in angular distribution on the neutron both models cannot really describe the differential cross section

Summary on h production Ø The old Eta. Maid 2001 describes new data > 2002 very well Ø D 15 resonance needs a very large h. N branching ratio, to describe the photon asymmetry on the proton this leads to the peak in s(n)/s(p) Ø a non-strange narrow pentaquark state P 11(1675) Fermi averaged in the deuteron would also produce such a peak Ø angular distributions are not yet conclusive

’ Photoproduction Data total cross sections • DESY ABBHHM collaboration, PRC 175 (1968) 1669 AHHM collaboration, 1976, Nucl. Phys. B 108 (1976) 45 • SAPHIR in Bonn R. Ploetzke et al. , PL B 444, 555 (1998) differential cross sections • SAPHIR in Bonn R. Ploetzke et al. , PL B 444, 555 (1998) • JLAB/CLAS M. Dugger et al. , preliminary (2005 -2006) N*2005 Tallahassee and private communication

h photoproduction p h p § Born terms are small and can be neglected (98) (76) (68) § t-channel vector meson Regge trajectories are fixed from p h p § the sharp rise of the total cross section near threshold is similar to p h p and suggests an S 11 resonance threshold

p h p Total Cross Sections total: Regge + S 11 Regge trajectories

comparison of old h‘-Maid with SAPHIR(98) data only S 11 resonance required P 11 or even higher resonances are not really necessary

fit to preliminary JLab/CLAS data (M. Dugger, N*2005 and private comm. )

Summary on h‘ production Ø The new JLab/CLAS data are very accurate and cover a large kinematical range and allow to draw more reliable conclusions Ø Born terms are negligible, gh‘ 2 NN /4 p << 0. 1 Ø a reggeization of the t-channel w, r is clearly necessary in this energy region of E > 1. 7 Ge. V Ø an S 11 resonance at W=1904 Me. V (only 8 Me. V above threshold) plays the dominant role, similar as in production Ø further resonances are needed in order to describe the data: mainly D 13(2080) found at W = 2100 Me. V, weakly P 11 (2100) found at 2083 Me. V and P 13(1900) found at 1926 Me. V