1. MDM October 2004
D MDM General
Martin Kotulla, University Basel

2. Hadron Structure: D+ Magnetic Moment
measurement:
excitation of the D+ and identification of the p0g´p state
or p+g´n (D. Watts)
D(1232) resonance:
first excited state of the nucleon
livetime t ~ s
m(D+) p D g g´ p0
basic principle
M1, (E2), M3 DDg´ transition
M1 sensitive to m(D+)
characteristic
energy distribution of the g´ +
dominant p D g p0 g´ +
small p g g´ p0
coherent addition...
D. Drechsel et al., PRC 64 (2001)
SPS Martin Kotulla, Universität Basel

3. Theory Status new calculation: includes pN rescattering loops
W.-T. Chiang, M. Vanderhaeghen, S. N. Yang, D. Drechsel, hep-ph/
SPS Martin Kotulla, Universität Basel

4. Diagrams
SPS Martin Kotulla, Universität Basel

5. Single Pion (s) Test of new calculation:
total cross section of single pion photoproduction on the proton
SPS Martin Kotulla, Universität Basel

6. Single Pion (angular) Test of new calculation:
angular distribution of single pion photoproduction on the proton
SPS Martin Kotulla, Universität Basel

7. Comparison with old data
M. Kotulla et al., PRL 89 (2002)
new calculation - old data:
„soft photon“ ratio
calculation much closer to old data
SPS Martin Kotulla, Universität Basel

8. Sensitivity Energy Distribution
new calculation - sensitivity I:
sensitivity to energy differential cross section with cut on p0 angle
SPS Martin Kotulla, Universität Basel

9. Sensitivity linear pol.
new calculation - sensitivity II:
sensitivity to angular differential cross section with cut on g´ energy
new calculation - sensitivity III:
sensitivity to beam asymmetry
SPS Martin Kotulla, Universität Basel

10. Sensitivity helicity new calculation - sensitivity IV:
sensitivity to helicity asymmetry
SPS Martin Kotulla, Universität Basel

11. Polarization Linear pol.: 1. run: ca. 330h at 440 MeV
circ. pol. settings:
ca. 52% at 440 MeV
ca. 46% at 400 MeV
ca. 40% at 360 MeV
SPS Martin Kotulla, Universität Basel

12. Experimental Settings
General experience:
MAMI and CB/TAPS/PID fine
first full featured experiment (lost > 1.5 weeks for debugging MWPC ADCs)
pol. peak stability sometimes bad
LH2 and ice
Run settings:
linear polarization: 1. run: ca. 300h at 440 MeV (ca. 38%) 2. run: ca. 180h at 400 MeV (ca. 45%)
circ. polarization: ca. 52% at 440 MeV ca. 46% at 400 MeV ca. 40% at 360 MeV
Trigger: 1. Level CB Sum (20MeV) + TAPS4OR 2. Level M>2 for TAPS4(>30MeV, 2 rings off) + CB45(>20MeV)
SPS Martin Kotulla, Universität Basel

13. Next Run
DAQ :
performance 1. Run: triple ADC read from CB and MWPC 2. Run: only single ADC value read from MWPC (ca. 4% improvement in speed) (CB optional)
Open points :
empty target run at 440 MeV linear pol. setting
SPS Martin Kotulla, Universität Basel

14. Next Run Improve circ. pol. Settings (~500 MeV beam energy):
helicity asymmetry shows promising sensitivity
ca. 72% at 400 MeV (old ca. 46%)
consistency check
no information for beam asymmetry
small cross section (5fold diff. cross section)
SPS Martin Kotulla, Universität Basel

15. SPS 2004 Martin Kotulla, Universität Basel

16. SPS 2004 Martin Kotulla, Universität Basel

17. SPS 2004 Martin Kotulla, Universität Basel

18. SPS 2004 Martin Kotulla, Universität Basel