Download - Crystal Ball at MAMI
Crystal Ball at MAMI
Daniel Watts, Univ. of Edinburgh (UK)
For the CB@MAMI Collaboration
(mainly involving low cross sections and/or precision measurements)
• Precision spectroscopy of low lying baryon states:
(1232)) from p’p and ’n
(S11(1535)) from p’p reaction
• Threshold meson production: (test of LET/ ChPT):
Strangeness (N →K)
0 photoproduction at threshold
• Ambiguity free amplitude analysis of meson photoproduction
Requires Double polarization measurements:
N→N(); N (,…) channels
• Tests of fundamental symmetries (C,CP,CPT…)
Rare / decays
• In medium properties of hadrons & nuclear physics:
Meson photo production on nuclei
CB@MAMI: Main physics objectives
• 100% duty factor electron microtron
• MAMI-C 1.5 GeV upgrade (2006)
(MAMI-B 0.85 GeV)
• Crystal Ball - A2 hall
(tagged photon beam)
The MAMI facility
One of the MAMI-C magnets
e
Photon Tagger upgrade
Emax
(GeV)
Imax
(s-1MeV-
1)
ΔE
(FWHM(MeV)
Pollin
(%)
Polcir
c
(%)
3.5 ≈ 104 5 70 80
1.5 ≈ 103 15 100 100
5.4 ≈ 104 5 70 80
0.45 ≈ 103 5 100 100
0.81.5
≈ 105 1 70 80
3.0 ≈ 103 30 100 100
Photon beam facilities
Legs
B
C
1976 Conceived1978 -1981SPEAR(Ecm = 3 - 7 GeV)
1982-1986DORIS (Ecm = 9 -10 GeV)
1996-2002 BNL-AGS (Ecm = 1.2 – 1.53 GeV)
2002MAMI (Ecm = 1.2 -1.9 GeV)
Crystal Ball history
Crystal Ball arrives at Frankfurt
Good angular and energy resolution, close to 4 acceptance
Setup at MAMI
Tracker & Particle-ID
Tracker & Particle-ID
~ 1.5o
~ 1.3o
• Two cylindrical wire chambers• 480 anode wires, 320 strips• Adapted from DAPHNE• New MWPC tracker under construction (2006)
2mm thickEJ204 scintillator
320m
m
MWPC & Particle-ID in situ
Good angular and energy resolution, close to 4 acceptance
Setup at MAMI
Tracker & Particle-ID
MAMI Photo GalleryCBwith PMTs
CB
Panoramic view of MAMI setup
TAPS CB
TAPS
Targets at MAMI
Liquid hydrogen (deuterium) target
Liquid 3He target (2006)
Polarised 3He gas target(~2008)
Frozen spin Targetbutanol / deuterated butanol
(~2007)
Apr '05-Jan'06 : MAMI-C upgrade, photon tagger upgrade
'06 onwards : Second production runs E=0.1-1.5 GeV: unpolarized, polarised, nuclear targets
Nov '02: Crystal Ball moved to MainzNov '03: Crystal Ball installed at photon beam at MAMIMar '04: TAPS installedApr '04: MWPC and PID installedMay '04: First test run tests with the complete setupJun'04-Apr '05 : First production runs
CB@MAMI – timetable
E=0.1-0.8 GeV: unpolarized H2 or D2 targets, nuclear targets
Selection of preliminary spectra from first round of
experimentsE= 0.1 – 0.8 GeV
Preliminary analyses: identification
→MeV
→MeV
→→MeV
Preliminary analyses: Ags(0)Ags
coherent 0 photoproduction from nuclei
208Pb
33o
sin ~ 1.22 /D Rm ~ 5.75 fm(Rc ~ 5.50 fm)
E=220 MeV
16O12C 40Ca
4.4 MeV3.7MeV
6.1 MeV
Also see coincident low energy Nuclear Decay Photons !!
• Clear diffraction patterns for 208Pb, 40Ca, 16O, 12C
d/dA2(q/k)P32|F
m(q)|2sin2
• Matter form factor, properties in the medium
C. Tarbert, D. Watts
Photon Asymmetry :
)2cos(1)(),(
p
d
d
d
d
Preliminary analyses: (, p)0
A. Starostin
• High statistics measurement
• With beam polarisation → , circ
~5% of total s
tatistic
s
Preliminary analyses: p(,p)
dependence ofyield (not acc. corrected)
F.Zehr
Preliminary analyses: p(,p)to measure
p p
´
p
p
´
p p
´
+
+
coherent addition...
small
dominant
MAMI pilot measurement with TAPS onlyM. Kotulla et al., PRL 89 (2002) 272001
• 100 in statistics • measure beam polarisation observables • Both p0 and n+ decay of +
=5p=3p=1p
= 0.79p
=3p
p(,p)to measure
Future planswith MAMI-C
E= 0.1 – 1.5 GeV
Double-polarisation in pseudo-scalar meson photoproduction
Polarisation of
target recoil
Observable
p → p 0 p → p
n → n 0 n → n
Circularly polarised photons + longitudinally polarised protons (or neutrons)
Deuterated butanol frozen spin target
Butanol frozen spin target
Beam-target observable: E
Previous E measurement for p → p 0 led to significant revision of helicity amplitudes for D13(1520) [ PRL 88, 232002 (2002)]
Neutron targets: different resonance contributions, isospin structure
Also get channels – mechanisms, contributions to GDH integrand
Expected data accuracy10o
E±10 MeV250 hrs
p → p 0
=90o
n → n 0
=90o
E
E(MeV) E(MeV)
Variable well suited to studies of Roper resonance ( P11(1440) )
p → p 0 p → n +
linearly polarised photons + longitudinally polarised protons
Beam-target observable: G
Expected Data accuracy10o
E±10 MeV600 hrs
Beam-Recoil Observables: Cx, OX, T, P
Graphite sheet(~7cm thick)
TAPS
Crystal Ball
beam
Hydrogen target cell
Initial path of proton Polarimeter acceptance : ±20o polar angle (target at centre)Most events suffer only coulomb scattering
Useful scattered eventSelect events with scattering angleslarger than ~10 degrees : arising from nuclear interaction
n() =no(){1+A()[Pycos()–Pxsin()]
Beam-Recoil Observables- p()p
300 hrs Ee=0.85 GeV
500 hrs Ee=1.5 GeV
(cm)=130o
~4 detector system
Very good neutral (and charged) particle detection capabilities
Excellent properties of MAMI beam
Availability of polarized targets
Recoil nucleon polarimetry possibilities
High quality data for meson photoproduction for E up to ~1.5 GeV can be expected
Summary
J.Brudvik, J. Goetz, B.M.K.Nefkens, S.N.Prakhov, A.Starostin, I. Saurez, University of California, Los Angeles, CA, USA
J.Ahrens, H.J.Arends, D.Drechsel, D.Krambrich, M.Rost, S.Scherer, A.Thomas, L.Tiator, D. von Harrach and Th.Walcher Institut fur Kernphysik, University of Mainz, Germany
R. Beck, M. Lang, A. Nikolaev, S. Schumann, M. unverzagt, Helmholtz-Institut fur strahlen und Kernphysik, Universitat Bonn, Germany
S.Altieri, A.Braghieri, P.Pedroni, A.Panzeri and T.Pinelli INFN Sezione di Pavia and DFNT University of Pavia, Italy
J.R.M.Annand, R.Codling, E.Downie, D.Glazier, J. Kellie, K.Livingston, J.McGeorge, I.J.D.MacGregor, R. Owens D.Protopopescu and G.Rosner Department of Physics and Astronomy, University of Glasgow, Glasgow, UK
C.Bennhold and W.Briscoe George Washington University, Washington, USA
S.Cherepnya, L.Fil'kov, and V.Kashevarow Lebedev Physical Institute, Moscow, Russia
V.Bekrenev, S.Kruglov, A.Koulbardis, and N.Kozlenko Petersburg Nuclear Physics Institute, Gatchina, Russia
B.Boillat, B.Krusche and F.Zehr, Institut fur Physik University of Basel, Basel, Ch
P. Drexler, F. Hjelm, M. Kotulla, K. Makonoyi, R.Novotny, M. Thiel and D. Trnka II. Phys. Institut, University of Giessen, Germany
D.Branford, K.Foehl, C.M.Tarbert and D.P.Watts School of Physics, University of Edinburgh, Edinburgh, UK
V.Lisin, R.Kondratiev and A.Polonski Institute for Nuclear Research, Moscow, Russia
J.W. Price California State University, Dominguez hills, CA, USA
D.Hornidge Mount Allison University, Sackville, Canada
P. Grabmayr and T. Hehl Physikalisches Institut Universitat Tubingen, Tubingen, Germany
D.M. Manley Kent State University, Kent, USA
M. Korolija and I. Supek Rudjer Boskovic Institute, Zagreb, Croatia
D. Sober Catholic Catholic University, Washington DC
M. Vanderhaeghen, College of William and Mary, Williamsburg, USA
CB@MAMI
(mainly involving low cross sections and/or precision measurements)
• Precision spectroscopy of low lying baryon states:
(1232)) from p’p and ’n
m(S11(1535)) from p’p reaction
• Threshold meson production: (test of LET/ ChPT):
Strangeness (N →K)
0 photoproduction at threshold
• Ambiguity free amplitude analysis of meson photoproduction
Requires Double polarization measurements:
N→N(); N (,…) channels
• Tests of fundamental symmetries (C,CP,CPT…)
Rare decays
• In medium properties of hadrons:
Meson photo production on nuclei
CB@MAMI: Main physics objectives
• 100 in statistics • measure beam polarisation observables • Both p0 and n+ decay of +
=5p=3p=1p
= 0.79p
=3p
p(,p)to measure
• 4 complex amplitudes – 16 observables in meson photoproduction
• Each double polarisation observable gives different combination of amplitudes
• To fix the 4 amplitudes unambiguously → 8 real quantities
• Cannot choose from the same set
Polarisation of
target recoil
Double-polarisation: theory background
Observable
• Predicted sensitivity to poorly established resonances
• Resonance parameters from quark model (Capstick and Roberts)
Solid – SAIDDashed – background + **** Dotdash- background + **** +N-
3/2(1960)
Dutta, Gao and Lee, PRC 65, 044619 (2002)
Cx’ ( + recoil) – theoretical predictions
P
T
Previous experimental data – SAID database
Data for all CM breakup angles
Ox’ Cx’
Recent JLAB datanot in database
• First determination p(,p)0 in 2002Hall A JLab
• MAID & SAID poor description of new data
Recent Cx’ measurement at JLab
Po
lari
sati
on
tra
nsf
er C
x’
Photon energy (MeV)
The proposed experimental setup
Graphite sheet
TAPS
Crystal Ball
beam
Hydrogen target cell
Initial path of proton Polarimeter acceptance : ±20o polar angle (target at centre)Most events suffer only coulomb scattering
Useful scattered eventSelect events with scattering angleslarger than ~10 degrees : arising from nuclear interaction
n() =no(){1+A()[Pycos()–Pxsin()]
GEANT simulation of polarimeter
No GraphiteWith Graphite scatterer
• Simulation includes realisticsmearing of energy deposits due to experimental energy resolutionand proper cluster finding algorithms
• Finite target size and E resolution included
Angle between N(E,) and TAPS hit
CM) >~130o
E=150 MeVE=200Eg=300E=500E=750E=1000E=1500
Polarimeteracceptance
Nucleon angle in lab (deg)
Pio
n a
ngle
in C
M (
deg)
Kinematic acceptance of polarimeter
p()N
• More forward recoils than for pion production.
• Almost all recoils are incident on polarimeter up to ~0.8 GeV
Eg=720Eg=820Eg=920Eg=1520
Lab nucleon angle (degrees)
CM
a
ng
le (
deg
rees)
Polarimeter acceptance
Kinematic acceptance of polarimeter
p()N
Cx’ – Extraction and expected accuracy
Plot difference in distributions for two helicity states (cut on region of with reasonable A())
Left with simple sin() Dependence. Extract Px
0 180 360
Photon energy (MeV)
Cx’
P=0.7, E=±25MeV, =130±10
~ 1 b/sr → Cx ~ 0.015
~ 0.1 b/sr → Cx ~0.05
Greatly improved data quality
• Measure direction of nucleon before and after the scatterer with sufficient accuracy to determine an analysing reaction has taken place.
Polarimetry basics
For incident protons also have multiple (coulomb) scattering
scat=5-20o
scat
• Magnetic dipole moments:
(1232) from p’p and ’n
S11(1535) from p’p) reaction
• Threshold meson production: (test of LET/ ChPT):
Strangeness (N →K)
0 photoproduction at threshold
• Double polarization measurements: (properties of baryon resonances/GDH)
N→N(); N (,…) channels
• Mass of -meson and rare decays
• Meson photo production on nuclei: medium mod., nuclear properties
CB@MAMI: Future programme
• 4 complex amplitudes →16 observables in meson photoproduction
→ need 8 well chosen measurements to fix the 4 amplitudes
• Each double polarisation observable gives a different combination of amplitudes
Polarisation of
target recoil
Double-polarisation in pseudo-scalar
meson photoproduction
Observable
MWPC tracker
~ 1.5o
~ 1.3o
• Adapted from MWPCs used with the DAPHNE detector
• New dedicated MWPC tracker under construction(Complete early 2006)
Scattered nucleon detection in TAPS
• 1 TAPS block ~ position resolution for hit
• TAPS~0.9m from scatterer
N
Straight through10o scatter20o scatter
Detrimental side-effects of scatterer material
• To hit polarimeter TN>100 MeV in (p,)N above the
• Proton energy loss
<10 MeV for Tp>100 MeV.
• Multiple scattering
<1o FWHM for Tp>100 MeV
• 0.37 radiation lengths conversion ~ 30%
Tp incident proton (MeV)
Tp e
xit
pro
ton
(M
eV
)
Tp after graphiteEnergy loss
0
0.5
1
1.5
2
2.5
3
0 200 400 600 800 1000 1200
Series1
Coulomb scattering
Proton energy (MeV)FW
HM
scatt
eri
ng
an
gle
(d
eg
)
1976 Conceived1978 -1981SPEAR(Ecm = 3 - 7 GeV) spectroscopyradiative decays decaysD decays, → f
1982-1986DORIS (Ecm = 9 -10 GeV)Y spectroscopyradiative decays
1996-2002 BNL-AGS (Ecm = 1.2 – 1.53 GeV) decays, medium. mod
2002MAMI (Ecm = 1.2 -1.9 GeV)
Crystal Ball history
24 of 2x10x320mm EJ204 scintillator
24 Hamamatsu =10mm PMT
Particle-ID detector
Small light attenuation
Good separation of p, with little overhead in
material before MWPC and CB
detectors
Hadron Structure: + Magnetic Moment
recent calculation:W.-T. Chiang, M. Vanderhaeghen, S. N. Yang, D. Drechsel, PRC 71,015204 (04)
includes N rescattering loops
Hadron Structure: + Magnetic Moment
Connection between N’N and NN
).(1
'0
' 'factorkin
d
d
EddE
dE
p n
Hadron Structure: + Magnetic Moment
''
1
EdE
dR
M. Kotulla et al., PRL 89 (2002) 272001
TAPS – first
p → p ’ data
)(0.3)(5.1)(2.17.2 model sysstat
=1=7
(units: N)
(units: N)
Hadron Structure: + Magnetic Moment
sensitivity to angular differential cross section with cut on ´ energy
sensitivity to beam asymmetry (linearly polarized photon beam)
N )1(
Good angular and energy resolution, close to 4 acceptance for charged and neutral final states
Setup at MAMI