Meson Physics with Crystal Ball at MAMI · 2018. 9. 21. · Meson Physics with Crystal Ball at MAMI Marc Unverzagt Institute for Nuclear Physics University Mainz Prague, 17th June

Marc Unverzagt Prague, 17th June 2013MesonNet Workshop

Meson Physics with Crystal Ball at MAMI

Marc UnverzagtInstitute for Nuclear Physics

University MainzPrague, 17th June 2013


Outline

Crystal Ball Set-up at MAMI

' Cross Sections

Transition Form Factor from →e+e- Revisited

T and F Asymmetry in Photoproduction

Summary


Outline


' Cross Sections



Summary


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


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


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

mailto:CB@MAMI

mailto:CB@ELSA


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


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%


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


Outline


' Cross Sections



Summary


'→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


' 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




' 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


Outline


' Cross Sections



Summary


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


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


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


Outline


' Cross Sections



Summary


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)


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)


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)


Outline


' Cross Sections



Summary


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)

Documents

Meson Physics with Crystal Ball at MAMI · 2018. 9. 21. · Meson Physics with Crystal Ball at MAMI Marc Unverzagt Institute for Nuclear Physics University Mainz Prague, 17th June