1. SPIN-04
Results for the Asymmetry Measurement in the Elastic Pion-Proton Scattering at 1.78 and 2.07 GeV/c. I.G. Alekseev, P.E. Budkovsky, V.P. Kanavets, L.I. Koroleva, B.V. Morozov, V.M. Nesterov, V.V. Ryltsov, D.N. Svirida, A.D. Sulimov, V.V. Zhurkin. Institute for Theoretical and Experimental Physics, B. Cheremushkinskaya 25, Moscow, , Russia. Tel: 7(095) , Fax: 7(095) , Yu.A. Beloglazov, E.A. Filimonov, A.I. Kovalev, S.P. Kruglov, D.V. Novinsky, V.A. Shchedrov, V.V. Sumachev, V.Yu. Trautman. Petersburg Nuclear Physics Institute, Gatchina, Leningrad district, , Russia. N.A. Bazhanov, E.I. Bunyatova Joint Institute for Nuclear Research, Dubna, Moscow district, , Russia.
Dima Svirida (ITEP)

2. 3 clusters of resonances  3 peaks in total crossection
Preface
SPIN-04
New data on polarization (asymmetry)
Backward hemisphere, 1.78 & 2.07 GeV/c
The latest experiment in the series of the polarization parameter measurements by ITEP-PNPI collaboration in the last decade
Available momentum range ( ) GeV/c
 65 % of light quark resonances,
3 clusters of resonances  3 peaks in total crossection
MAIN GOAL:
Data for the UNAMBIGUOUS RECONSTRUCTION of the elastic p scattering amplitudes by PWA
PHYSICS INTEREST to the LIGHT BARYON SPECTROSCOPY is enhanced by the observation of :
resonance clusters with masses 1.7 and 1.9 GeV/c2
resonances with negative parity in 1.9 GeV/c2 peak
parity doublets in these clusters
missing resonances near 2 GeV/c2
which do not fit well the constituent quark model
Dima Svirida (ITEP)

3. SPIN-04 Background Experiment Dima Svirida (ITEP)
Light baryon resonances in the latest PDG are based mainly on PWA’s KH80 and CMB80, both performed more than two decades ago.
More recent analyses by VPI/GWU group did not revealed 4 of 13 resonances in clusters
New data on polarization in p and spin rotation parameters do not confirm KH80 and CMB80 in the backward scattering region
Experiment
PRESENT MEASUREMENTS:
p, cm=( )o, P=1.78 GeV/c
cm=( )o, P=2.07 GeV/c
No experimental information up to now
Main difficulty: small crossection in the explored domain
Notable background
Its careful subtraction
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4. SPIN-04 Experimental Setup Dima Svirida (ITEP) MAIN ELEMENTS: TARGET:
Vertically polarized proton target PT
4 sets of wire chambers for tracking
Trigger scintillation counters
Beam Arm
Pion Beam
Proton Arm
Pion Arm I
TARGET:
Cylinder 30mm, h=30mm, propanediole C3H8O2, free proton density 10 %
Magnetic field 2.5 T
3He evaporation type cryostat at 0.5 K
Dynamic nuclear orientation
Polarization (70-80) %, measurement accuracy 2 %
Sign reverse once per day
Pion Arm II
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5. SPIN-04 Data Processing 1 Dima Svirida (ITEP)
ELASTIC EVENT SELECTION:
Coplanarity and kinematic correlation  joint 2 criterion:
 ,  – deviations from the elastic kinematics
 and  – distribution widths
Optimal cut (minimal statistic error) 2cut< 3
Additional background suppression by momentum analysis  factor 2 in S/B ratio
NORMALIZATION:
Using 2 distribution wing (quasielastic background)
Using beam particle counts
The results of both are well concordant
2 <3
Quasielastic
20< 2 <80
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6. SPIN-04 Data Processing 2 Dima Svirida (ITEP)
TWO DIFFERENT METHODS TO GET  ,  :
Using polarization information to subtract unpolarized background
Using  distribution after cut in  and vice versa
In both methods gaussian fit for the peak + polynomial for the background
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7. Results: Asymmetry P at 1.78 GeV/c in p
SPIN-04
Correspondence to CMB80 and VPI/GWU recent analysis
Significant deviation from KH80
Agreement with our previous data
cm
Dima Svirida (ITEP)

8. Results: Asymmetry P at 2.07 GeV/c in p
SPIN-04
Best agreement with VPI analysis SM90
Significant deviation from CMB80 and FA02
Contradiction to KH80
Agreement with previous data
cm
Dima Svirida (ITEP)

9. Conclusion
SPIN-04
New polarization parameter data require NEW GLOBAL TYPE PWA, for example resurrection of KH80 analysis
Acknowledgements
Our thanks to Professor G.Hoehler for very interesting and fruitful discussion
We are grateful to the ITEP accelerator team for providing us with the excellent beam conditions and to ITEP cryogenic laboratory for supply with liquid helium and nitrogen.
This work was partially supported by the Russian Fund for Basic Research grant and Russian State Scientific Program "Fundamental Nuclear Physics".
GREAT THANKS to the organizers of this interesting conference ! ! !
Dima Svirida (ITEP)