CB TAPS October 2004

´ Photoproductionoff the Nucleon

Martin Kotulla

Perspectives: ‘

excitation region close to w=2 GeV:

density of resonances increases

very few channels studied ()

‘ is a promising channel (only a few partial waves contribute at threshold), isospin filter

excitation region close to 2 GeV:

P13 (1900) [*], F17 (1990) [**], F15 (2000) [**], D13 (2080) [**], S11 (2090) [*], P11 (2100) [*]

biggest ‘ coupling: S. Capstick and W. Roberts, PRD 49 (1994) 4570 D13 (2080) [**] and S11 (2090) [*]

Meson 2004 Martin Kotulla, University Basel

Status: ‘

Meson 2004 Martin Kotulla, University Basel

Interpretation:

R. Plötzke et al., PLB 444 (1998) 555S11(1900) and P11 (1990)

J. Barth et al., NPA 691 (2001) 374Regge exchangeS11 close to threshold

Chiang et al., PRC 68 (2003) 045202S11 (P1X ) and Regge exchange

Z. Li J.Phys. G 23 (1997) 1127, Sibirtsev et al., nucl-th/0303044

t-channel exchange () subtreshold S11(1535)

and many contradicting interpretations

Published data:

total cross sections from old bubble chamber experiments

SAPHIR: two data sets including angular distributions,

‘ Models

Meson 2004 Martin Kotulla, University Basel

Sibirtsev, Elster, Krewald, Speth nucl-th/0303044 (2003) eff. Langragian model

t-channel exchange (dashed)

t-channel + S11(1535)

Ploetzke et al., PLB444 (1998) 555 J.Link et al. PHD thesis (unpublished)

Identification

Meson 2004 Martin Kotulla, University Basel

2fi

2

fi2X ppEEM

neglect

final

,

initial

pp

p ‘ p : threshold (1447MeV) up to 2530 MeV

‘ identification: ‘ 2 6

‘ 2 10 missing mass

preliminary results: ca 50% of full data set

calibrations not final

kinematic fit to increase resolution

cross section: cross sections determined by fit of the invariant mass

individualy in each bin of the angular distributions

‘ Models

Meson 2004 Martin Kotulla, University Basel

Chiang et al., PRC 68 (2003) 045202 reggeized model

S11(1950) necessary for interference

additional P1X(1950) possibledashed: reggeized t-channeldotted: S11(1950) onlysolid: regge and S11(1950) dashed dotted: t-channel

Ploetzke et al., PLB444 (1998) 555

‘ Models

Meson 2004 Martin Kotulla, University Basel

Chiang et al., PRC 68 (2003) 045202 polarization observables

sensitivity to resonances at E=1.59GeVsolid: regge and S11(1950) dashed: regge and S11(1950) and P11(1950) dotted: regge and S11(1950) and P13(1950)

might be changed if additonal D wave contributes (like in the case of )

longitudinally pol. target:G very sensitive to P1X resonances (but pol.)„GDH“ E

‘ on deuterium

Meson 2004 Martin Kotulla, University Basel

p ‘ p : threshold 1447MeV

with 1500MeV electron beam energy: additional tagger for high photon beam energies necessary

d ‘ X : threshold at 1202 MeV

neutron data has been measured at ELSA with CBTAPS(rough cross section on neutron)

study of ‘ FSI (‘ N interaction)

A. Sibirtsev et al., PRC 65, 044007 (2002)

J.Weiss et al., EPJ A 11, 371 (2001)