Preamble. Deuteron, as the simplest nuclear system, provides an unique opportunity to observe the short range nucleon-nucleon correlations without obscurity due to influence of the nuclear environment. All the potential models predict that the D-state in the deuteron dominates at relatively large internal deuteron momenta q~0.3-0.7 GeV/c (small distances) while the S-state, which fully dominates at small q, has a node around q=0.4 GeV/c.
It is obvious that at large q this simple picture based on nonrelativistic potential models may be essentially modified by effects of internal nucleon structure. As an example, the proton and neutron in the deuteron may turn into a six-quark system, the effect known as 6-quark bag admixture to the deuteron wave function.
A good way to study deuteron structure is the investigation of the deuteron breakup reactions using both electron and hadron intermediate energy probes. In Impulse Approximation (IA) unpolarized differential cross section of the reaction is proportional to the momentum distribution of nucleons in the deuteron
p(q)=u2(q)+w2(q) where u(q) and w(q) are S and D-state deuteron wave functions,
while polarization observables depends on the ratio of u(q)/w(q). This allows separate study of the S and D-states in the deuteron.
> Unpolarized quasi-elastic breakup pd -->pp(n) and pd -->pn(p) reaction at 1GeV.
The experiment was performed at 1 GeV extracted proton beam of the PNPI synchro cyclotron
using a two-arm detecting system. The system consisted of the forward magnetic spectrometer
(see previous sections) used as a high-momentum arm and an array of scintillation counter
used as a low-momentum arm for detection of the recoil protons and neutrons in coincidence
with the high-momentum arm. The deuteron wave function was investigated up to q~0.5 GeV/c.
A theoretical model developed to describe reaction mechanism contained IA, NN-rescattering
and Delta excitation graphs with full spin-isospin symmetrization included.
It has been found that the deuteron wave function calculated using both Bonn and Paris
potential gives adequate description of the data at all investigated kinematical settings
including the case of backward recoil angles.
References
Study of the deuteron structure in quasi-elastic breakup reaction pd
--> ppn at 1-GeV.
N.P. Aleshin et al. Nucl.Phys.A568, 809-827, 1994.
> Measurement of polarization observables in dp --> pp(n) reaction.
A full set of data on polarization observables was obtained in this experiment in inverse dp ->pp(n) kinematics of the breakup reaction studied up to q=0.44 GeV/c. The experiment was performed at 2 GeV polarized deuteron beam of the Saturne-2 accelerator at Saclay using the spectrometer SPES-4 as a high-momentum arm in coincidence with a recoil detecting system (RS). The SPES-4 spectrometer was equipped with the POMME polarimeter. The RS consisted of a scintillation wall and a proportional chamber tracking system. The RS was a material contribution of the PNPI to the experimental setup.
The experiment was initiated by M.Strikman and L.Franfurt, and proposed for the Saturne machine by S.Belostotski and A.Boudard.
The vector analyzing power Ay, tensor analyzing power Ayy were measured, together with the spin-transfer Dy and polarization P0 coefficients.
The tensor analyzing power Ayy is a sensitive test of IA applicability.
The IA fails to describe the Ayy data above q~0.2 GeV/c. This conclusion is independent on a particular model used for the deuteron wave function.
In order to improve the description of all measured polarization observables the FSI and intermediate Δ-excitation graphs were included.
(For more details see articles "Study of deuteron structure in exclusive breakup reactions "
in "Main Scientific Activities 1971-1996", research report of the High Energy Physics Division, PNPI, 1998)
References
Measurement of polarization observables in d (polarized) + p --> p
(polarized) + p + n reaction at T(d) = 2-GeV.
S.L. Belostotsky et al. Phys.Rev.C56, 50-63, 1997.
> Inclusive deuteron breakup dp -->p'X experiments.
These experiments were performed in JINR (Dubna) and at Saturne (Saclay) in collaboration with PNPI group. The tensor analyzing power T20 (Ayy) and spin-transfer k_0 to the proton produced at the forward angle (0 deg.) were measured. In IA the forward going proton with the momentum larger than half the beam momentum selects processes in which this proton is a spectator. This gives a direct access to polarization state of a nucleon in the deuteron.
In agreement with exclusive data, T20 was found to follow to IA up to q=0.2 GeV/c.
In principle inclusive experiments allow investigations of the deuteron up to very high q~1GeV/c which corresponds to the distances about 0.2fm.
Interpretation of the data obtained, however, is difficult because the IA is not valid at such high q and evaluation of second order corrections is by far not straightforward.
References
Measurement of polarization transfer kappa(0) and tensor analyzing
Power T(20) in the backward elastic d p scattering.
V. Punjabi et al. Phys.Lett.B350, 178-183, 1995.
> Experiments on photodisintegration of the deuteron ed -->epn.
References
Measurement of the analyzing power components in photodisintegration
of the polarized deuteron.
S.I. Mishnev et al. Phys.Lett.B302, 23-28, 1993.
|
|