Results Jonas M uller - slac.stanford.edu · Jonas M uller for the CBELSA/TAPS collaboration...
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Motivation Baryon- spectroscopy Polarisation- observables Experiment Setup Data selection Results → γ → p → pπ 0 → γ → p → pη → γ → p → pπ 0 π 0 CB-ELSA Measurement of the double polarisation observable E in the reactions - → γ - → p → pη and - → γ - → p → pπ 0 Jonas M¨ uller for the CBELSA/TAPS collaboration Helmholtz-Institut f¨ ur Strahlen- und Kernphysik supported by SFB/TR16 13. June 2011 1 / 16
Transcript of Results Jonas M uller - slac.stanford.edu · Jonas M uller for the CBELSA/TAPS collaboration...
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Measurement of the double polarisationobservable E in the reactions−→γ −→p → pη and −→γ −→p → pπ0
Jonas Muller
for the CBELSA/TAPS collaboration
Helmholtz-Institut fur Strahlen- undKernphysik
supported by SFB/TR16
13. June 2011
1 / 16
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Table of contents
1 MotivationBaryon spectroscopyPolarisation observables
2 ExperimentSetupData selection
3 Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→ pπ0π0
2 / 16
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Baryon spectroscopy
With the CBELSA/TAPS experiment we want to understand
the spectrum and properties of baryons.
[GeV]γE0 0.5 1 1.5 2 2.5 3
bµ/σ
1
10
210
[GeV]s1 1.5 2 2.5
γp→ X
γp→ pπ+π−
γp→ pπ0π0
γp→ pπ0
γp→ pη
γp→ K+Λ
3 / 16
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Baryon spectroscopy
Experimentally:
Broad, overlapping resonances
N∗ → Nπ, ∆∗ → Nπ N∗ → Nη
Important:
Measurement of different final states
Measurement of polarisation observables (unambigious PWA)
4 / 16
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Polarisation observablesBeam asymmetry Σ in γp→ pη
Predictions for E in −→γ −→p → pη
5 / 16
— BoGa-PWA
· · · η-MAID
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Polarisation observables
Single pseudoscalar meson photoproductionComplete experiment: 8 well chosen observables out of 16
dσ
dΩ(θ, φ) =
dσ
dΩ(θ) · [1 − p
linγ Σ(θ) cos(2φ)
+ px ·(−plinγ H(θ) sin(2φ) + p
circγ F (θ)
)− py ·
(+p
linγ P (θ) cos(2φ) − T (θ)
)− pz ·
(−plinγ G(θ) sin(2φ) + p
circγ E(θ)
)]
Photon pol. Target pol. axisx y z
unpolarised σ - T -linearly −Σ H −P −G
circularly - F - −E
E =σ1/2 − σ3/2
σ1/2 + σ3/2
=1
Pγ · Pz· 1
fdil·N1/2 −N3/2
N1/2 +N3/2
6 / 16
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Crystal Barrel/TAPS @ ELSA
7 / 16
Eγ = E0 − Ee−
Crystal Barrel
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Polarised target and beam
8 / 16
Frozen spin butanol target
longitudinally polarised protonswithin butanol
mean polarisation ≈ 70%
Bradtke et. al
Beam polarisation
circularly polarised photons viabremsstrahlung of long. pol. e−
mean e− pol. ≈ 65% at 2.4GeV
Helicity transfer
e / EγE0 0.2 0.4 0.6 0.8 1
e /
Pγ
P
0
0.2
0.4
0.6
0.8
1
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Data selection−→γ −→p → pπ0/pη
Final states:−→γ −→p → pγγ
Invariant meson mass spectrum
Applied cuts:
charge
coplanarity
calculated proton mass
meson mass
time background subtraction
Coplanarity between meson and baryon
Missing baryon mass
9 / 16
−→γ −→p → pη
φmeson − φbaryon
−→γ −→p → pη
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Dilution factor determination
Effective dilution factor:
fdil =Nbutanol −Ncarbon
Nbutanol
mass [MeV]400 600 800 1000 1200 1400 16000
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000=1100 MeVγE
10 / 16
ButanolHydrogenCarbonHydrogen + Carbon
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Polarised events
Helicity difference in calculated missing baryon massfor π0 events
Differenz_pyEntries 658562Mean 971RMS 227.5
missing mass [MeV]0 200 400 600 800 1000 1200 1400 1600 1800
#
-5000
-4000
-3000
-2000
-1000
0
Differenz_pyEntries 658562Mean 971RMS 227.5
11 / 16
Butanol:N 1
2−N 3
2
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
−→γ −→p → pπ0
π0 count rate difference
12 / 16
M. Gottschall
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
E for −→γ −→p → pπ0
E =1
Pγ · Pz· 1
fdil· N1/2 −N3/2
N1/2 +N3/2
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
550
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
950
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1350
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1750
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
650
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1050
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1450
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1850
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
750
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1150
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1550
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1950
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
850
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1250
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1650
θcos-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
2050
E
cos θπ0
1
0
-11
0
-11
0
-11
0
-1-1 0 1 -1 0 1 -1 0 1 -1 0 1
— Maid — Said — BnGa13 / 16
M. Gottschall
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
−→γ −→p → pηη count rate difference
Important information for partial wave analyses
14 / 16
S11(1535)
P11(1710)?P13(1720)?
[MeV]γ
E
0 500 1000 1500 2000 2500-5
0
5
10
15
20
25
30Maid
Said
BnGa
BnGaCur
b]µ[3/2
σ- 1/2
σ
N 12−N 3
2
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
−→γ −→p → pπ0π0
Count rate difference in π0π0 photoproductionCBELSA/TAPS data, E: ~γ~p → pπ0π0
(D.Piontek, Bonn)
[Mev]γE400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
2000
1000
0
−1000
−2000
−3000
−4000
∆C
ount N1/2 − N3/2
very preliminary
−8
−6
−4
−2
0
2
4σ(3/2), µb
0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5
E(γ), GeV
σ (1/2) −
very preliminaryPWA
sol 1 (l=0)
sol 2 (l=2)
cos θp-distributions:
⇔ Statistics needs to be improved !!
pπ0η-channel: statistics even worse
Additional data needed
for the double meson channels:
- High mass N∗ and ∆∗-resonances
- Cascade decays via other baryonand meson resonances
15 / 16
D. Piontek
Motivation
Baryon-spectroscopy
Polarisation-observables
Experiment
Setup
Data selection
Results→γ→p→ pπ0
→γ→p→ pη
→γ→p→
pπ0π0
CB-ELSA
Summary
Double polarisation data have been takenwith the Crystal Barrel/TAPS experiment:
Polarisation observable E currently analysedfor different channels
Measurements for different polarisation observablesare ongoing
Preliminary results show clear deviationfrom current PWA analyses
The results will be important input for PWAand lead us one step closer to the complete experiment.
16 / 16
funded within
SFB/TR16
