1.- Introduction
2.- MAMI Accelerator
3.- A2 Real Photon Facility
4.- nGDH DAPHNE
5.- Crystal Ball/TAPS/MainzPT
6.- Conclusions and Outlook
NSTAR 2009WORKSHOP ON THE PHYSICS OF EXCITED NUCLEONS
19 - 22 April 2009
Beijing, China Andreas Thomas
A2- and CBall@MAMI- Collaborations
Recent result from the A2 Real Photon Facility at MAMI
Institut für Kernphysik
Beam Parameter (beam since 1990)• 885MeV, E=0.068MeV • max. 103A cw • h=8 nm rad, v=0.5 nm rad (Beam Focus ~m)• Halo: < 10-5 bei r > 5∙r
• ca. 6000h – 7000h operation / year
MAMI B
Parameter (since 2006)• 1507MeV, E=0.100MeV• max. 100A• h=9 nm rad, v=0.5 nm rad• as MAMI B !
MAMI C 1557MeV (since 2008)
zppaNN
NNA bt cos
Determination of the degree of polarization ofthe electron beam (Moeller Polarimeter);Circularly pol. photons
2.
3. Coherent production of linearly polarizedphotons on a diamond radiator
Moeller triggerCoincidence
eE
eE
Electronbeam
Radiator(Moeller target)
Primarybeam%2.01.8 tp
"Vacoflux" Foil
Production und energy measurement of the Bremsstrahlungs photons
A2 Tagging system (Glasgow,Mainz)1.
Partial reaction channelsInput for PWA to extract resonance parameters
Measurements in 1998 at MAMIwith DAPHNEand Bonn PT
Bonn Polarized target
„Frozen Spin Mode“ Polarization : DNP at high B-Field (2.5 T)
Measurement : very low T )50( mK
´freeze´ up the spin (0.4 Tesla)
relaxation time hT 200
New Technology: horizontal cryostat with integrated solenoid (holding field)
1.2 Kelvin 0.42 Teslaequiv. 780m Cu (100m NbTi)
[C.Bradtke et al., NIM A436, 430 (1999)]Neutron
60 m
m
beam
target
internal superconducting 'ho ld ing coil’liqu id helium from the still
100 m mButanol (C4H9OH)
(C4D9OD)
[Hartmut Dutz, PT Universität Bonn]
[Gerhard Reicherz, PT Ruhr-Universität Bochum]
D-Butanol
Target material [St. Goertz, PT Ruhr-Universität Bochum]
Density and species of the radicals are very important for:
•maximum degree of polarization•polarization build up times
•relaxation timesTrityl-Radikal
Highest Deuteron polarisation due to new doping material with small ESR from Bochum. [W.Meyer et al.]
NN
d
NN
d
NN
d
np0
Reaction channels on deuterium in the MAMI B energy range (< 855MeV):
d
Desintegration
Coherent pion p.
Incoherent pion p.
Coherent eta p.
Incoherent eta p.
Double pion p.
Neutron
Static propertiesof the nuclei:•mass•charge•anomalous magnetic moment
Helicity structureof the deuterons
excitation spectrum
0 100 200 300 400 500 600 700 800 900
-700
-600
-500
-400
-300
-200
-100
0
100
200
300
400
500
0 100 200 300 400 500 600 700 800 900
-600
-400
-200
0
200
400
A.Fix; priv. communication; M.Schwamb et al.; Nucl. Phys. A 696 (2001), 556.
d -> np
d -> pp
d -> nn
coherent d -> pn
-
(b
)
photon energy (MeV)
Sm
edpa
2
22
0
4)()(
Derived 1965 using general asumption:•Lorentz and gauge invariance ->Low energy theorem•causality ->dispersion relation•unitarity ->opt. theorem
[S.B.Gerasimov: Sov.J.Nucl.Phys.2(1966)430][S.D.Drell, A.C.Hearn: Phys.Rev.Lett.16(1966)908]
Gerasimov-Drell-Hearn sum rule (GDH) for nuclei
•Nucleon Nucleon Interaction•Meson Exchange currents •Final State Interaction•Relativistic Effects, Retardation
Model:
0 100 200 300 400 500 600 700 800 900
-700
-600
-500
-400
-300
-200
-100
0
100
200
300
400
500
0 100 200 300 400 500 600 700 800 900
-600
-400
-200
0
200
400
A.Fix; priv. communication; M.Schwamb et al.; Nucl. Phys. A 696 (2001), 556.
d -> np
d -> pp
d -> nn
coherent d -> pn
-
(b
)
photon energy (MeV)
[H. Arenhövel, et al., Phys. Rev. Lett. 93 (2004) 202301]
IGDH= 0.65b
Helicity dependent deuteron photodesintegration[Arenhövel et al. , Physics Letters B 407 (1997) 1-7]
(1232)-resonance(Spin3/2)
The resonance can better be excited if the inital spins are parallel at 300MeV
proton (neutron)(Spin 1/2)
uud
„Flip of a single quark“:p >> a
a >> p
photon (Spin 1)
photon (Spin 1)
P N3S1 deuteron ground state
(Spin 1)
P N1S0 resonant state at 68KeV
(Spin 0)The resonant 1S0 state can only be reached if the inital spins are
antiparallel at energies close to break-up threshold (2-3MeV)
New precission data set to determine the deuteron-GDH-sumrule above -threshold [Phys. Letters B 672(2009)328-332
Model AFS
Partial reaction channels and polarisation observables deliver more informationto improve the deuteron models and our knowledge on the neutron.(Better Models are needed.)
Sm
edap
2
22
0
4)()(
Gerasimov-Drell-Hearn sum rule (GDH) for nuclei
Photon Nucleon
1 S
a
p
Deuteron
3Helium
P N
P P N
P(Neutron) ~ 0.92 P(Deuteron)
..exp effnuclpGDH
nGDH
d IIII
'..exp effnucl
pGDH
nGDH
he IIII 1.0
Partial reaction channels on
quasifree neutron
GDH-Integralwith small
systematic error
IGDH [b]
proton 204
neutron 233deuteron 0.653helium 497
Deuterated Butanolwas used as target material in 98 (pilot exp.) and 2003
New Exp. In May 2009 on 3Helium
4 photon Spectrometer @ MAMI
TAPS:364 BaF2 detectorsMax. kin. energy:+- : 180 MeVK+- : 280 MeVP : 360 MeV
Crystal Ball:672 NaJ detectorsMax. kin. energy:+- : 233MeV+- : 240 MeVK+- : 341 MeVP : 425 MeV
Vertex detector:2 Cylindr. MWPCs480 wires, 320stripes
PID detector:24 thin plastic detectors
Transverse
And
Longitudinal
Internal
Holding coil
Polarized Target for Crystal Ball
Tagged CW photon beam 4- detector
Frozen spin target (20mKelvin, 5Tesla)Pproton ~ 95%Pdeuteron~70%All directions of polarization
sec107
New 3He4He-Dilution refrigerator(in collaboration with JINR Dubna)
Beam Target
Photoproduction with polarized beam and polarized target
EPGPP
PPTP
FPHPP
Pd
d
d
d
circlinz
liny
circlinx
lin
unpol
2sin
2cos
2sin
2cos1
EGP
PTP
FHP
dd
P
PPP
z
y
x
unpol
circlinlinunpol
- -
- -
- -
- -
4,
4
2,0 Target
Beam
+ Recoil observables [D.Watts, M.Sikora] Wed.,Session6
Conclusion and Outlook
Data from ‚Crystal Ball‘ detector in combination with TAPS and further detectors at MAMI B (882MeV) and MAMI C (1557MeV) are under analysis. Publications 2009:Dalitz Plot Parameter 0η-production, Measurement -mass, rare -decaysMDM, Helicty asymmetries
MAMI C is delivering polarised beam with now 1557 MeV and high Intensity for the experiments since 2008
New precission data set from the neutron-GDH-experiment with ‚DAPHNE‘ detector and is published [Phys. Letters B 672(2009)328-332]Paper on Helicity Dependent Deuteron Photodisintegration between 160 and 480 MeV and single pion production up to 800 MeV is under preparation.
Future: In A2 we continue to do double polarised experiments with polarised beam, polarised targets (3Helium 5/2009 H,D-Butanol 12/2009) and recoil-polarimeter.
Neutron (D,3He)
Theoretical description
Proton (Frozen Spin)
Threshold, Transverse, Complete exp.
The GDH collaborationJ.Ahrens9,S.Altieri15,16,J.R.M.Annand6,G.Anton3,H.-J.Arends9,K.Aulenbacher9,R.Beck9, C.Bradtke1,A.Braghieri15,N.Degrande4, N.d'Hose5, H.Dutz2, S.Goertz1, P.Grabmayr17, K.Hansen8, J.Harmsen1, S.Hasegawa13,T.Hasegawa11, E.Heid9, K.Helbing3, H.Holvoet4, L.VanHoorebeke4, N.Horikawa14,T.Iwata13, P.Jennewein9, T.Kageya14, B.Kiel2,F.Klein2, R.Kondratiev12,K.Kossert7,J.Krimmer17,M.Lang9,B.Lannoy4,R.Leukel9,V.Lisin12,T.Matsuda11,J.C.McGeorge6,A.Meier1,D.Menze2,W.Meyer1,T.Michel3,J.Naumann3, A.Panzeri15,16, P.Pedroni15,T.Pinelli15,16,I.Preobrajenski9,12,E.Radtke1,E.Reichert10,G.Reicherz1,Ch.Rohlof2, G.Rosner6, D.Ryckbosch4,F.Sadiq6,M.Sauer17,B.Schoch2, M.Schumacher7, B.Seitz7, T.Speckner3,M.Steigerwald9, N.Takabayashi13, G.Tamas9, A.Thomas9, R.van de Vyver4, A.Wakai14, W.Weihofen7, F.Wissmann7, F.Zapadtka7, G.Zeitler3
1Institute of Experimental Physics, Ruhr-University, Bochum, Germany 2 Physics Institute, University of Bonn, Germany 3 Physics Institute, University of Erlangen-Nuernberg, Erlangen, Germany 4 Nuclear Physics Laboratory, Gent, Belgium 5 CEA Saclay, DSM/DAPNIA/SPhN, Gif-sur-Yvette, France 6 Department of Physics & Astronomy, University of Glasgow, U.K. 7 II.Physics Institute, University of Goettingen, Germany 8 Department of Physics, University of Lund, Sweden 9,10 Institute of Nucl. Physics and Inst. of Physics, University of Mainz, Germany 11 Faculty of Engineering, Miyazaki University, Miyazaki, Japan 12 INR, Academy of Science, Moscow, Russia 13,14 Department of Physics and CIRSE, Nagoya University, Nagoya, Japan 15,16 INFN Sezione di Pavia and Dept. of Nucl. Physics of the University , Pavia, Italy 17 Physics Institute, University of Tuebingen, Germany
Data set with high statistics for and production [F.Zehr, S.Schumann]
p p00
Rot TAPS DatenKurven:ChPT
Strahl Target
Photoproduction of pseudoscalar ‘, K with polarised beam and target
EPGPP
PPTP
FPHPP
Pd
d
d
d
circlinz
liny
circlinx
lin
unpol
2sin
2cos
2sin
2cos1
EGP
PTP
FHP
dd
P
PPP
z
y
x
unpol
circlinlinunpol
- -
- -
- -
- -
4,
4
2,0 Target
Beam
Pion Photoproduction with Polarized Beam and Polarized Target
N N
1 NlL l
Angular momentum and parity conservation
)()()( NJRJNJ PPP
Parity
Multipole components of the electromagnetic radiation
EL, ML
21
21 lJL
lL
lL
lL
lL
11
1
)1()1(
1)1()1(EL :
ML :
Multipole amplitudes:
llll MMEE ,,,
21lJ
21lJ
ll ME ,JIl 2,2
Angular momentum
Connection between and andMultipoles and Resonances
21 2
3
1 lL
21
23
............2*
221
11*
110
}Re{6
}Re{638
22
222
MEEM
MMEEE
kq
Photon Photon Total Pion Multipole Resonance ContributionL Multipole J P l Amplitude to
1 E1 1/2 - 0 E0+ S11 -
3/2 - 2 E2- D13 +
M1 1/2 + 1 M1- P11 -
3/2 + 1 M1+ P33 +
2 E2 3/2 + 1 E1+ P33 -
5/2 + 3 E3- F15 +
M2 3/2 - 2 M2- D13 -
5/2 - 2 M2+ D15 +
N N
l
JIl 2,2
-prod.->Deformation
p p
E[MeV]
b]
MAID2000
[Phys. Rev. Lett. 84, 5950 (2000)]
200 300 400 500
0
50
100
150
200
250
300
350 -2.5% 0% +2.5% GDH98
p n
E[MeV]200 300 400 500
-150
-100
-50
0
50
100
150
200
-2.5% 0% +2.5% GDH98
[Phys. Rev. Lett. 88 (2002) 232002]
2nd Resonance regionD13Resonance Parameters 20% changed
Connection between and andMultipoles and Resonances
21 2
3
1 lL
21
23
............2*
221
11*
110
}Re{6
}Re{638
22
222
MEEM
MMEEE
kq
Photon Photon Total Pion Multipole Resonance ContributionL Multipole J P l Amplitude to
1 E1 1/2 - 0 E0+ S11 -
3/2 - 2 E2- D13 +
M1 1/2 + 1 M1- P11 -
3/2 + 1 M1+ P33 +
2 E2 3/2 + 1 E1+ P33 -
5/2 + 3 E3- F15 +
M2 3/2 - 2 M2- D13 -
5/2 - 2 M2+ D15 +
N N
l
JIl 2,2