A new method to determine the spin tune is described and tested. In an ideal planar magnetic ring, the spin tune-defined as the number of spin precessions per turn-is given by ν(s)=γG (γ is the ...Lorentz factor, G the gyromagnetic anomaly). At 970 MeV/c, the deuteron spins coherently precess at a frequency of ≈120 kHz in the Cooler Synchrotron COSY. The spin tune is deduced from the up-down asymmetry of deuteron-carbon scattering. In a time interval of 2.6 s, the spin tune was determined with a precision of the order 10^{-8}, and to 1×10^{-10} for a continuous 100 s accelerator cycle. This renders the presented method a new precision tool for accelerator physics; controlling the spin motion of particles to high precision is mandatory, in particular, for the measurement of electric dipole moments of charged particles in a storage ring.
This Letter reports the successful use of feedback from a spin polarization measurement to the revolution frequency of a 0.97 GeV/c bunched and polarized deuteron beam in the Cooler Synchrotron ...(COSY) storage ring in order to control both the precession rate (≈121 kHz) and the phase of the horizontal polarization component. Real time synchronization with a radio frequency (rf) solenoid made possible the rotation of the polarization out of the horizontal plane, yielding a demonstration of the feedback method to manipulate the polarization. In particular, the rotation rate shows a sinusoidal function of the horizontal polarization phase (relative to the rf solenoid), which was controlled to within a 1 standard deviation range of σ=0.21 rad. The minimum possible adjustment was 3.7 mHz out of a revolution frequency of 753 kHz, which changes the precession rate by 26 mrad/s. Such a capability meets a requirement for the use of storage rings to look for an intrinsic electric dipole moment of charged particles.
New precise unpolarised differential cross sections of deuteron–proton elastic scattering have been measured at 16 different deuteron beam momenta between pd=3120.17MeV/c and pd=3204.16MeV/c at the ...COoler SYnchrotron COSY of the Forschungszentrum Jülich. The data, which were taken using the magnetic spectrometer ANKE, cover the equivalent range in proton kinetic energies from Tp=882.2MeV to Tp=918.3MeV. The experimental results are analysed theoretically using the Glauber diffraction model with accurate nucleon–nucleon input. The theoretical cross section at Tp=900MeV agrees very well with the experimental one at low momentum transfers t. There are, however, significant deviations for |t|>0.2(GeV/c)2 that must be investigated further.
An extensive experimental study of near-threshold pion production in diproton reactions is underway at the ANKE-COSY spectrometer (Jülich). The programme is aimed at isolating the four-nucleon-pion ...contact interaction term appearing in the XPT expansions of these processes. This will establish links between pion production and other low energy phenomena within the XPT approach. The first step in the programme was to measure the differential cross-section and the proton analysing power in the $\vec pp \to \left\{ {pp} \right\}{}_s{\pi ^0}$ and $\vec pn \to \left\{ {pp} \right\}{}_s{\pi ^ - }$ reactions over the full angular range. Here {pp}s denotes a diproton, i.e., a two-proton system in a 1S0 state. These data allow a partial wave analysis to be carried out provided that simplifying assumptions are made when applying the Watson theorem. To make the analysis more robust, and independent of the uncertainties in the relative normalization, the spin-correlation coefficients Ax,x and Ay,y in the $\vec n\vec p \to \left\{ {pp} \right\}{}_s{\pi ^ - }$ reaction were measured in a follow-up experiment. The first results of the data analysis are presented and future developments of the programme are outlined.
Values of the proton analysing power, deuteron vector analysing power, and the deuteron-proton spin correlations in the pd → 3He π0/3Hπ+ reactions at 350-360 MeV per nucleon were obtained by using ...polarized beams and target at ANKE-COSY. Data were also obtained on the deuteron-proton spin correlation and proton analysing power at small angles at 600 MeV per nucleon. By combining the extrapolated values of the spin correlations to the forward or backward directions with published measurements of the deuteron tensor analysing powers, the relative phases between the two non-vanishing amplitudes were evaluated.
Recent dibaryon studies at ANKE Tsirkov, D.; Komarov, V.; Azaryan, T. ...
EPJ Web of Conferences,
2019, Letnik:
199
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The recent results of dibaryon studies at ANKE are being presented, along with our plans concerning further studies on the topic. The
D
03
resonance has been observed at ANKE in the coherent
pd
→
pd
...+(
ππ
)
0
channel, accompanied by the ABC effect. An explanation of the ABC effect has been proposed, suggesting to to explain it as a kinematic cumulation of the pion pairs in the
D
03
→
D
12
+
π
→
d
+ (
π
+
π
)
I=0
cascade decay channel due to the predominantly collinear
D
12
decay. Based on this hypothesis, a search for a
D
21
signal in the
pp
→ {
pp
}
s
ππ
reaction is suggested. The
p
-wave dibaryon resonances
3
P
2
and
3
P
0
have been observed at ANKE; for
3
P
0
it is a first experimental observation. Preliminary results for a resonance peak in the
pp
→ {
pp
}
s
π
0
reaction with the mass
m
= 2646 ± 5 MeV and the width
Γ
= 132 ± 14 MeV are being presented. Also we propose to search for the narrow
NN
*(1535) resonance in the
pd
→
pdη
reaction.
The proton analysing power in p→p elastic scattering has been measured at small angles at COSY-ANKE at 796 MeV and five other beam energies between 1.6 and 2.4 GeV using a polarised proton beam. The ...asymmetries obtained by detecting the fast proton in the ANKE forward detector or the slow recoil proton in a silicon tracking telescope are completely consistent. Although the analysing power results agree well with the many published data at 796 MeV, and also with the most recent partial wave solution at this energy, the ANKE data at the higher energies lie well above the predictions of this solution at small angles. An updated phase shift analysis that uses the ANKE results together with the World data leads to a much better description of these new measurements.
This paper describes a time-marking system that enables a measurement of the in-plane (horizontal) polarization of a 0.97−GeV/c deuteron beam circulating in the Cooler Synchrotron (COSY) at the ...Forschungszentrum Jülich. The clock time of each polarimeter event is used to unfold the 120-kHz spin precession and assign events to bins according to the direction of the horizontal polarization. After accumulation for one or more seconds, the down-up scattering asymmetry can be calculated for each direction and matched to a sinusoidal function whose magnitude is proportional to the horizontal polarization. This requires prior knowledge of the spin tune or polarization precession rate. An initial estimate is refined by resorting the events as the spin tune is adjusted across a narrow range and searching for the maximum polarization magnitude. The result is biased toward polarization values that are too large, in part because of statistical fluctuations but also because sinusoidal fits to even random data will produce sizable magnitudes when the phase is left free to vary. An analysis procedure is described that matches the time dependence of the horizontal polarization to templates based on emittance-driven polarization loss while correcting for the positive bias. This information will be used to study ways to extend the horizontal polarization lifetime by correcting spin tune spread using ring sextupole fields and thereby to support the feasibility of searching for an intrinsic electric dipole moment using polarized beams in a storage ring. This paper is a combined effort of the Storage Ring EDM collaboration and the JEDI collaboration.
PDF
