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Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Meson Physics with Crystal Ball at MAMI
Marc UnverzagtInstitute for Nuclear Physics
University MainzPrague, 17th June 2013
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Outline
Crystal Ball Set-up at MAMI
' Cross Sections
Transition Form Factor from →e+e- Revisited
T and F Asymmetry in Photoproduction
Summary
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Outline
Crystal Ball Set-up at MAMI
' Cross Sections
Transition Form Factor from →e+e- Revisited
T and F Asymmetry in Photoproduction
Summary
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Mainz Microtron
Ee-<1604 MeV E<0.1 MeV
High current (110A) High polarisation (85%) Duty factor 100% ~7000 h/year running experiments
ME
SA
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Experiments at MAMIA2: Real Photon Experiments:- Glasgow tagging spectrometer- Crystal Ball / TAPS hermetic photon spectrometer- Meson Factory
A1: Electron Scattering:- focusing magnetic spectrometers- neutron detection, spin precession- Kaon spectrometer (KAOS/A1)
ME
SA
PRISMA/SFB 1044:- Dark Photon Search- El.-weak Mixing Angle
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Real Photons in A2
High energy resolution: E≈2MeV at E
e-=883 MeV
E≈4MeV at E
e-=1558 MeV
Linearly and circularly polarised photon-beamTagging range: 5.1 to 93% of E
→ Maximum energy tagged for E=1604 MeV is 1491 MeV
E=E
0-E
e- Ethr ≈ 1447 MeV
Data form CB@MAMI, CB@ELSA, CLAS, SAPHIR
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
End-Point-Tagger● Installation of EPT during 2012
Same working principle as main tagging spectrometerE≈1445-1595 MeV
E≈ 2.5MeV
Non-permanent installation infront of main Tagger
EPT
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
4-Setup
Crystal Ball: 672 NaI(Tl) crystals 93,3% of total solid angle Each crystal equipped with PMT
E
=2 %
E /GeV 0.25
t = 2.5 ns FWHM
=2 3
=2 3
sin
TAPS: Up to 510 BaF
2 crystals
Polar acceptance: 4-20°
t = 0.5 ns FWHM
E
=0,79 %
E /GeV1,8%
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Targets● LH2/lD2 used for high rate meson production (/')
- Length: 3cm, 5cm, 10cm
● l3He/l4He
● Polarised Butanol/D-Butanol- Transverse and longitudinal polarisation- Lenght: 2 cm- Dynamic Nuclean Polarisation- Max. Polarisation: 90%- Holding filed: 0.44 T - Relaxation time: ~1000h
● Solid Targets
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Outline
Crystal Ball Set-up at MAMI
' Cross Sections
Transition Form Factor from →e+e- Revisited
T and F Asymmetry in Photoproduction
Summary
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
'→00 Invariant Mass
S. Prakhov (UCLA)P. Ott (Mainz)
E=1430±10 MeV E=1450±10 MeV E=1470±10 MeV
E=1490±10 MeV
E=1550±10 MeV
Prelim
inar
y
E=1510±10 MeV
E=1570±10 MeV
E=1530±10 MeV
Prelim
inar
y
Prelim
inar
y
Prelim
inar
y
Prelim
inar
y
Prelim
inar
y
Prelim
inar
y
Prelim
inar
y
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
' Cross Section
S. Prakhov (UCLA)P. Ott (Mainz)
tot
Prelim
inary
E=1450±10 MeV E=1470±10 MeV E=1490±10 MeV E=1510±10 MeV
E=1530±10 MeV E=1550±10 MeV E=1570±10 MeV
Using '→00
Preliminary Preliminary
Preliminary
Preliminary Preliminary
Preliminary Preliminary
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
' Programme
Status now:● EPT successfully in operation● Preliminary result for photoproduction cross section near threshold● Preliminary result for '→00 Dalitz plot (limited statistics)● MC background studies for '→e+e- and first glance at data
DAQ Improvement:● New trigger system (FPGA based)● Faster DAQ PCs
→ Factor of 2 in speed gained● Sep. 2013: Further DAQ upgrade
→ Additional factor of 2 in speed ?
Next ' Production:● EPT installation in beam in summer/fall 2014● Beamtime estimate underway● Measure with x4 speed and longer period● Goal: 400,000 '→00 (Dalitz plot analysis)
~200-300 '→e+e- (Transition Form Factor)
A. Denig, M. Ostrick, P. Ott, S. Prakhov, M. Unverzagt, S. Wagner
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Outline
Crystal Ball Set-up at MAMI
' Cross Sections
Transition Form Factor from →e+e- Revisited
T and F Asymmetry in Photoproduction
Summary
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Previous Analysis of TFFH. Berghäuser et al. (A2-Collaboration), Phys. Rev. B 701 (2011) 562-567.
● Based on kinematic cuts● Small amount of data● Limited photoproduction energy range
-2 = (1.92±0.35stat±0.13syst) GeV-2
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
New Analysis of TFF
● Based on kinematic fitting● 3x more data● Full photoproduction range accessible at MAMI used● 18,000 events (no proton requirement: 22,000 events)
m(e+e-)=45±5 MeV m(e+e-)=285±5 MeVSolid line: Pole-approximation fitNormalisation and as free parameters
PreliminaryPreliminary Preliminary
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
New Result on TFFS. Prakhov, M. Unverzagt et al., to be submitted to Phys. Rev. soon
-2 = (1.95±0.15stat±0.05syst) GeV-2 preliminary
A2, 2011: H. Berghäuser et al., Phys. Rev. B 701 (2011) 562-567.NA60, In-In: R. Arnaldi et al., Phys. Lett. B 677 (2009) 260.TL calculation: C. Terschlüsen, Diploma thesis, University Gießen, 2010.Padé-approximants: R. Escribano, P. Masjuan, P. Sanchez-Puertas, in preparation.
Preliminary
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Outline
Crystal Ball Set-up at MAMI
' Cross Sections
Transition Form Factor from →e+e- Revisited
T and F Asymmetry in Photoproduction
Summary
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Polarisation Observables T and F
● Disentangle Multipoles (complete experiment), perform PWAs● s-d wave interference in T for , isobar models predict zero interference
● Double polarisation observable F not measured yet
Dominated by Born, , Dominated by D13(1520)
Dominated by S11(1535)
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Transverse Target Asymmetry T for
Prelim
inary
Black line: MAID-2003, isobar modelBlue line: MAID-2003, reggeized isobar modelRed line: BG2010-02Green line: SAID
Red points: CB 2010/11Balck points: PHOENICSBock et al., Phys. Rev. Lett. 81, 534 (1998)
Victor Kashevarov(Mainz)
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Double Polarisation Observable F for
Prelim
inary
Black line: MAID-2003, isobar modelBlue line: MAID-2003, reggeized isobar modelRed line: BG2010-02
First time measurement with Crystal Ball!
Victor Kashevarov (Mainz)
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Outline
Crystal Ball Set-up at MAMI
' Cross Sections
Transition Form Factor from →e+e- Revisited
T and F Asymmetry in Photoproduction
Summary
Marc Unverzagt Prague, 17th June 2013MesonNet Workshop
Summary
● ' production at MAMI possible now- Preliminary results on ' photoproduction cross section- First glances on '→00 Dalitz plot and ' Transition Form Factor
● New determination of the Transition Form Factor in →e+e-- More than one order of magnitude more than previous A2 analysis- Soon to be published
● Polarisation observables with Crystal Ball- Precise determintation of Target Asymmetry T (preliminary)- First determination of Double Polarisation Observable F (preliminary)
● 12 years physics programme funded through DFG (SFB 1044)- Broad physics programme including
Light Meson DynamicsTransition Form Factors of pseudoscalar MesonsPolarisation Observables (long. and trans. Pol. target)