Picture shows the event distribution in our wire chambers


the three-nucleon force

CE80: spin correlation coefficients in p+d elastic scattering

The experiment used a vector and tensorpolarized deuteron target and a polarized stored proton beam. Data have been taken at incident proton energies of 135 and 200 MeV. The data are compared to Faddeev calculations with and without three body force.
B. v.Przewoski, submitted to Phys. Rev. C

CE64: spin observables in pd breakup

Using a polarized deuteron beam and a polarized hydrogen target, pd breakup was studied at 270 MeV deuteron energy (corresponds to 135 MeV protons). The analysis of the data for the s0-called axial observables, that are parity-forbidden in elastic scattering constituted the thesis topic of T.J. Whitaker.
Axial observables..., H.O. Meyer et al., submitted to Phys. Rev. Lett.

pion production with polarized collision partners

ce44, ce64: neutral pion production in pp collisions

The original goal of this experiment was to measure the spin-dependent total cross sections Deltasigma_T/sigma_tot and Deltasigma_L/sigma_tot, using A polarized internal atomic hydrogen target and a stored, polarized beam. This is sufficient to determine certain constraints on the partial waves of the reaction.
H.O. Meyer et al., Phys. Rev. Letters, 81, 3096 (1998)
H.O. Meyer et al., Phys. Rev. Lett. 83, 5439 (1999)

It was soon realized, that the experiment performed so well that all possible polarization observables everywhere in pase space could be determined. A measurement at four bombarding energies between 325 and 400 MeV then determines all partial waves that are relevant in the first 100 MeV above threshold.
H.O. Meyer et al., Phys. Rev. C63, 064002 (2001)

An interesting side-issue concerned the longitudinal analyzing power, measured either with the target or the beam longitudinally polarized. This observables is zero by parity conservation if there are only two particles in the final state. It turned out that for pion production with a three-body final state, the longitudinal analyzing power can be as large as the transverse one.
H.O. Meyer et al., Phys. Lett. B480, 7 (2000)

ce72, ce73: charged pion production in pp collisions

Concurrently with the observation of neutral pions, it was possible to also register charged pion production. These reaction channels were the domain of the Pittsburgh contingent, and Wilfried Daehnick worked on the analysis of these experiments until his untimely death.
p+p -> p+n+pi+ :
Swapan K. Saha et al.,Phys. Lett. B461, 175 (1999)
W.W. Daehnick et al., Phys. Rev. C65, 024003 (2002)
p+p -> d+pi+ :
B. v. Przewoski et al., Phys. Rev. C61, 064604 (2000)
data: p+p -> d+pi+

ce79: pion production in pd collisions

This is a measurement of spin correlation coefficients in pd-->tpi+ between 220 and 270 MeV. The involvement of pion production with its large momentum transfer would test the nuclear interaction at short distances where three-nucleon effects should be largest.
Status: analysis (June 2004)

pp elastic scattering

A measurement of analyzing power\and spin correlation coefficients in pp elastic scattering was the commissioning experiment for the PINTEX setup, demonstrating that an internal polarized atomic target enhanced by a storage cell is not only feasible, but makes measurements of spin correlation parameters with unprecedented accuracy possible. The first measurement (ce35) was limited to forward angles (4.5 - 17.5 degrees) and one energy (200 MeV).
W. Haeberli et al., Phys. Rev. C 55 (1997) pp. 597-613
data: pp scattering (ce35)
Later, full angular distributions and a measurement of the Azz correlation coefficient was added.
F. Rathmann, Phys. Rev. C58, 658 (1998)
B. Lorentz, Phys. Rev. C61, 054002 (2000)
After mastering the problems associated with changing the energy of a stored polarized beam, the energy range from 200 to 450 MeV was mapped out (ce42).
B.v. Przewoski, Phys. Rev. C58, 1897 (1998)
data: pp scattering (ce42)
A new mathematical method, based on 'diagonal scaling' was invented to reduce the measured yields to the observables.
H.O. Meyer, Phys. Rev. C 56, 2074 (1997)

polarization of the stored beam

polarization calibration

The knowledge of the polarization of stored protons was based on a single, well-measured analyzing power in pp scattering. This calibration point was measured concurrently with p+12C scattering. At the calibration energy p+12C scattering exhibits a point in energy and angle where the analyzing power is exactly unity, which can be used as an absolute reference.
B. von Przewoski, Phys. Rev. C44, 44 (1991)
Exporting the calibration to all beam energies accessible in a ring is another benefit of the storage ring environment.
R.E. Pollock, Phys. Rev. E55, 7606 (1997)

polarization lifetime

Usually, the lifetime of the polarization of the stored beam is much longer than the lifetime of the beam itself. Near a depolarizing resonance, however, polarization lifetime becomes measurable. This was studied for an intrinsic resonance (ce55), as well as for an induced (by an RF solenoid) resonance.
H.O. Meyer, Phys. Rev. E56, 3578 (1997)
B.v.Przewoski, Review of Scientific Instruments 69, 3146 (1998)

lifetime of vector and tensor polarization

Interestingly, the lifetime of the tensor and vector polarization of a stored deuteron beam is not the same. This was studied with a deuteron beam that had both kinds of polarization at the same time.
B. v.Przewoski, Phys. Rev. E68, 046501 (2003)

polarization of the target

CE70: polarized molecules?

The atoms in a polarized target recombine to some degree. Do the resulting molecules retain some polarization? (the answer is yes). This was studied in a dedicated experiment, nicknamed 'polmol'.
T. Wise, Phys. Rev. Lett. 87, 042701 (2001)

spin exchange in dense, polarized deuterium gas

In a dense deuterium target collisions between the target atoms leads to spin exchange which in turn may affect the polarization of the target. This effect is significant for tensor polarization and has been observed during ce80.
B. v.Przewoski, Phys. Rev. A68, 042705 (2003)

storage cell in ring

Test of a Windowless Storage Cell Target in a Proton Storage Ring
M.A. Ross, Nucl. Instr. Meth. A326, 424 (1993)
Performance of a Polarized-Hydrogen Storage Cell Target
M.A. Ross, Nucl. Instr. Meth. A344, 307 (1994)
Effect of a Polarized Hydrogen Target on the Polarization of a Stored Proton Beam
H. O. Meyer, Phys. Rev. E50, 1485 (1994)

Last modified: June 2004 by H.O. Meyer