Transcript Polarization transfer mechanism as a possible source of

Polarization transfer mechanism as a
possible source of the polarized
antiprotons
M.A. Chetvertkov1, V.A. Chetvertkova2,
S.B. Nurushev3
1. Moscow State University, Moscow ,Russia
2. Skobelitsyn Institute of nuclear physics, Moscow State
University, Moscow, Russia
3. Institute of high energy physics, Protvino, Russia
Abstract
We suggest to study the polarization transfer mechanism in the inclusive
reaction of the antiproton production by the polarized proton beam. As a basis of the
experimental set-up we foresee the standard source of the unpolarized antiprotons
as it was realized at PS CERN. This scheme should be transformed by three major
modifications: 1) instead of the initial unpolarized proton beam we shall use the
longitudinally ( transversally) polarized proton beam, 2) transform the longitudinal
polarization of the produced antiprotons to the transverse polarization, and 3) build
the polarimeter for the polarized antiprotons of the proper emerges. We assume that
the best place for such research will be AGS at the Brookhaven National Laboratory
having almost all the needed infrastructures. In the case of revealing the large
polarization transfer tensor we may get the new source of the polarized antiprotons. If
this tensor appears to be small but non zero the production of the antiprotons by the
polarized (longitudinally or transversally) proton beam might become beneficial for
the filtering technique.
Contents
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
1. Introduction
2. Experimental evidences for the
polarization transfer mechanism
3. Scheme of producing the unpolarized
antiprotons
4. Proposal of the experiments for measuring
the polarization transfer from protons to
antiprotons
5. Conclusions
1. Introduction
The problem of producing the intense polarized antiproton source with the appropriate
polarization becomes very acute at present. Such interest is instigated by the great potential of
the physics with the polarized antiprotons [PAX(2005)]. Approximately a dozen suggestions
were made about how to get the polarized antiprotons [Krisch (1985)], [Steffens(2008)] but
none of them (exclusion is the filtering technique [Rathmann(2005)]) was experimentally
demonstrated as really working tool.
The following is the list of these suggestions:
1. Polarized antiprotons from the decay in flight of antihyperons
2. Spin filtering of antiprotons by a polarized hydrogen target in a storage ring
3. Stochastic techniques à la “Stochastic Cooling”
4. DNP (Dynamic Nuclear Polarization) in flight using polarized electrons and microwave
radiation
5. Spontaneous Spin-Flip synchrotron radiation
6. Spin-Flip synchrotron radiation induced by X-ray laser2005
7. Polarization by scattering
8. Repeated Stern-Gerlach deflection
9. Polarized antiprotons via the formation of antihydrogen and application of the ABS method
10. Polarizing during storage in a Penning trap
11. Polarizing by Channeling
12. Polarizing through interaction with polarized X-rays from a diamond crystal.
In this presentation we propose the very well known (at low energy) method of producing the
polarized beam - the mechanism of the spin transfer to the secondary particles from the
primary polarized beam. In section 2 we remind the several experiments providing the
evidences for the spin transfer mechanism at low and high energy ranges. In the same
section we make the statement that there is no any theoretical estimate of the spin transfer
tensor from polarized protons to the antiprotons and no any experimental evidence for
measuring such tensors.
Therefore we suggest the experiment at AGS for measuring the spin transfer tensor from
the polarized protons to the secondary antiprotons produced at zero degree. In Section 3
we recall the standard technique of obtaining the unpolarized antiprotons by the
unpolarized primary proton beam according to PS CERN scheme [The Antiproton Source
Rookie Book, 1999, Version 1.1]. Then in Section 4 we modify this scheme to produce the
polarized antiprotons by the polarized proton beam. We also propose the schemes of
measuring the spin transfer tensor at pbar production at zero angle as a function of the
antiproton momentum.
In Conclusions we summarize the results of our study of the possible new source of the
polarized antiprotons.
2. Experimental evidences for the
polarization transfer mechanism
There is no any theoretical or experimental paper
devoted to the direct prediction or proof of the
existence of the polarization transfer mechanism in
the inclusive reaction
p  N  p   X ,
where the arrows indicate the polarization of the
corresponding particle.
2a. Spin Transfer tensor in Inclusive 0
Production by Transversely Polarized
Protons at 200 GeV/c
[A. Bravar et al., Spin Transfer in Inclusive 0 Production by Transversely
Polarized Protons at 200 GeV/c, Phys. Rev. Lett., vol. 78, number 21, 40034006]
This is the first and only example of non-zero Spin Transfer Mechanism,
experimentally established at 200 GeV/c (which is equivalent to the √S≈20
Gev). The depolarization tensor DNN (Wolfenstein’s parameter)=KN0;N0
(according to the Ann Arbor convention) in the reaction
p   p    X
0
has been measured with the transversely polarized protons at 200 GeV/c over
a wide xF range and a moderate pT (E704 experiment at FNAL). DNN reaches
positive values of about 30% at high xF and pT ~ 1.0 GeV/c. This result proves the
existence of the essential spin transfer mechanism at sufficiently high energy.
.
Figure 3. Depolarization DNN data as a function of pT in
at 200 GeV/c. The errors shown are statistical only.
p   p  0  X
Longitudinal spin transfer of Lambda and
antiLambda in pp collisions at STAR
[Qinghua Xu (Shandong Uni.) for the STAR collaboration
Dubna Spin workshop, September 4, 2009]
3.
Scheme of producing the
unpolarized antiprotons
Scheme of Antiproton Accumulator Complex (AAC), CERN.
[ H. Koziol, S. Maury, Parameter List for the Antiproton Accumulator Complex
(AAC), Edition 1994, CERN, Geneva, Switzerland]
Parameters of the AAC.
Proton and antiproton beam transport lines
at AGS
The best way of doing the measurement of the spin transfer tensor from
the polarized protons to the antiprotons would be this PS CERN
scheme. But PS has no polarized proton beam. Therefore we
think about using the AGS at BNL. But AGS (having the polarized
proton beam) has never built the intense antiproton source.
Therefore we assume that these two schemes may be combined
somewhere. For example, at AGS.
In this scheme we identify the following distinct parts:
1. Slow extraction and transport of the primary proton beam of 26
GeV/c. We label it as the beam transport line-1(BTL-1).
2. After production target the beam transport line for antiprotons.
We label it as BTL-2.
3. The antiproton accumulator AA.
4. Suggestion of the experiments for measuring
the polarization transfer from protons to
antiprotons
at AGS
Parameters of the propane-diol polarized target :
C3H8O2
Density of frozen propane-diol (g/cm3)
1.1
Free hydrogen density(g/cm3)
0.12
Bound protons/free protons
4.2
Radiation length (cm)
45
Polarization build-up time (from zero to
0.8 of the maximum polarization) (min)
20
Target polarization, average during runs (%)
77
Target dimensions (cm)
diameter:
2
length
8.5
:
Effective hydrogen density (g/cm3)
0.085
Temperature (degree K)
0.48
Power dissipation (mW)
50
Microwave frequency (GHz)
70
[ J.C. Raoul, P. Autones, R. Auzolle, Apparatus for Simulations
Measurements of the Polarization and Spin-Rotation Parametrs in HighEnergy Elastic Scattering on Polarized Protons, Nuclear Instruments and
Methods 125 (1975) 585-597 ]
Table 1.
The yields of the negative particles in function of energy
Table 2. The count rate per cycle and the time needed for accumulation of the
scattering events for each energy
[H. Grote, R. Hagedorn and J. Ranft, Atlas of Particle Spectra, CERN, Geneva,
Switzerland, 1970.]
Conclusion
We are not aware of any paper devoted to the theoretical or experimental study of the spin
transfer mechanism from the polarized protons to the inclusively produced at zero degree
antiprotons.
Basing on the several experimental data on the spin-transfer effect in elastic and inclusive
reactions for protons and lambda hyperons we hope that similar effect may exist also for
antiprotons.
We would like to emphasize the importance to fulfill the special experiment for measuring
the polarization transfer tensor KLL in reaction
p  A  p   X
at AGS. Initial proton beam with momentum around 22 GeV/c, longitudinal polarization 70%,
intensity 2·1011 p/cycle, may produces the longitudinally polarized pbar beam at zero degree.
Our estimates show that though such an experiment is difficult but it’s realizable.
Acknowledgements
We would like to thank for stimulating
discussions and helps H. Artru, A.
Efremov, Y. Makdisy, M. Ryskin, D. Sivers
and H. Huang.
And I’m also thankful to the Organizing
Committee and personally to prof. A. V.
Efremov for invitation to this workshop.
Thank you!
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