Unbound states studied by direct reactions Wolski, R; Golovkov, M S; Grigorenko, L V ...
Journal of physics. Conference series,
05/2008, Letnik:
111, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The t(6He,8He)p t(8He,10He)p reactions were studied in experiments with 25A MeV 6He beam and 27.4A MeV 8He beams and an unique tritium gas target. Results on the 8He and 10He excitation energy ...spectra are presented. The 8He spectrum exhibits 3 states, apart of the ground state and known (2+) state at 3.6 MeV, the third state is seen at 5.4 MeV. A tentative assignment 1+ is proposed for this structure. The 10He spectrum shows no event at the excitation energy below 3 MeV what is in contradiction with the earlier reports on this nucleus. A high statistics of α-n coincidence events collected for the 8He beam run has been subjected to analysis in order search for the bound tetraneutron. The search produced a negative result.
Three-body continuum
p-p-
α for the charge exchange reaction
1
H(
6
Li,
6
Be)
n
is studied in detail. The data are obtained with a high volume of statistics (approximately 4.7 million events), making ...it possible to analyze three-particle correlations. Detailed information about the structure of
6
Ве and the reaction is obtained as a result.
The proton and deuteron pickup reactions 2H(10Be,3He)9Li and 2H(10Be,4He)8Li radioactive beam produced by the new fragment separator ACCULINNA-2 at FLNR, JINR\@. These measurements were initially ...motivated as test reactions intended for the elucidation of results obtained in the study of the extremely neutron-rich 7H and 6H systems created in the 2H(10Be,3He)9Li and 2H(10Be,4He)8Li reactions using the same setup. In the 2H(10Be,3He)9Li reaction the 9Li ground-state (\(3/2^-\)) and its first excited state (2.69MeV, \(1/2^-\)) were identified in the low-energy region of its excitation spectrum. The differential cross sections for the 9Li g.~s.) population were extracted at forward center-of-mass angles (\(3^\circ-13^\circ\)) and compared with the FRESCO calculations. Spectroscopic factor of \(\sim 1.7\), derived by a model for the 10Be\( = p +\)9Li(g.s.) clustering was found in accord with the experimental data. The energy spectrum of 8Li populated in the 2H(10Be,4He)8Li reaction shows the strong peak which corresponds to excitation of the second excited state of 8Li (2.25 MeV, \(3^+\)). The fact that the ground and the first excited states of 8Li were not observed is fully consistent with Shell-Model calculations carried out for the 10Be g.\,s. and 8Li level structure applying momentum selection rules.
New experimental measurements of the total reaction cross sections for the
6
He +
nat
Si and
9
Li +
nat
Si processes in the energy range of 5 to 40 A MeV are presented. A modified transmission method ...based on high-efficiency detection of prompt n–γ radiation has been used in the experiment. A bump is observed for the first time in the energy dependence σ
R
(
E
) at
E
∼ 10–30 A MeV for the
9
Li +
nat
Si reaction, and existence of the bump in σ
R
(
E
) at
E
∼ 10–20 A MeV first observed in the standard transmission experiments is experimentally confirmed for the
6
He +
nat
Si reaction. Theoretical analysis of the measured
6
He +
nat
Si and
9
Li +
nat
Si reaction cross sections is performed within the microscopic double folding model. Disagreement is observed between the experimental and theoretical cross sections in the region of the bump at the energies of 10 to 20 A MeV, which requires further study.
The analyzing powers for proton elastic scattering (
p
A
→
p
X
) and neutron charge exchange (
n
A
→
p
X
) reactions on nuclei have been measured on
C
,
CH
,
C
H
2
and
Cu
targets at incident neutron ...momenta 3.0–4.2 GeV/c by detecting one charged particle in forward direction. The polarized neutron measurements are the first of their kind. The experiment was performed using the Nuclotron accelerator in JINR Dubna, where polarized neutrons and protons were obtained from break-up of a polarized deuteron beam which has a maximum momentum of 13 GeV/c. The polarimeter ALPOM2 was used to obtain the analyzing power dependence on the transverse momentum of the final-state nucleon. These data have been used to estimate the figure of merit of a proposed experiment at Jefferson Laboratory to measure the recoiling neutron polarization in the quasi-elastic
2
H
(
e
,
e
′
n
)
reaction, which yields information on the charge and magnetic elastic form factors of the neutron.
Abstract
The analyzing powers for neutron charge exchange
nA
→
pX
reactions on nuclei have been measured on C, CH2 and Cu targets at incident neutron momenta 3.0 - 4.2 GeV/c by detecting one charged ...particle in forward direction. The polarized neutron measurements are the first of their kind. The experiment was performed using the Nuclotron accelerator in JINR Dubna, where polarized neutrons and protons were obtained from breakup of a polarized deuteron beam which has a maximum momentum of 13 GeV/c. The polarimeter ALPOM2 was used to obtain the analyzing power dependence on the transverse momentum of the final-state nucleon. These data have been used to estimate the figure of merit of a proposed experiment at Jefferson Laboratory to measure the recoiling neutron polarization in the quasi-elastic
2
H
(
e
,
e
′
n
) reaction, which yields information on the charge and magnetic elastic form factors of the neutron.
The reaction p + CH2→ forward charge particle + X is used for this aim traditionally. Analyzing power of this reaction falls off as 1 p, where p is the laboratory momentum. At the proton momenta of ...order 8 GeV c, which are expected at the JLab experiment, the low analyzing power creates problems for off-line analysis of data. On the other hand, it is well known that the reaction p+p → p+p has the much more analyzing power. So, the calorimeter is predestinated for suppression of inelastic events in this reaction. In the report it is shown that the problem is solved quite well.
Quest for the He nucleus Chudoba, V; Fomichev, A S; Golovkov, M S ...
The European physical journal. ST, Special topics,
2008, Letnik:
162
Journal Article
Recenzirano
The spectrum of 10He was studied by means of the 3H(8He, p)mlle reaction at a laboratory energy of 25 MeV/A and small center-of-mass angles. Missing mass spectrum of 10He was derived from the ...obtained p-8He coincidence. A resolution of 0.7 MeV was achieved in this spectrum for the measured 10He energy. Most likely, a well isolated group of 10 events detected between 2 and 5 MeV and showing a maximum at about 3 MeV in the spectrum of the present work exhibits the 10He g.s. resonance.
The ^{7}H system was populated in the ^{2}H(^{8}He,^{3}He)^{7}H reaction with a 26 AMeV ^{8}He beam. The ^{7}H missing mass energy spectrum, the ^{3}H energy and angular distributions in the ^{7}H ...decay frame were reconstructed. The ^{7}H missing mass spectrum shows a peak, which can be interpreted either as unresolved 5/2^{+} and 3/2^{+} doublet or one of these states at 6.5(5) MeV. The data also provide indications of the 1/2^{+} ground state of ^{7}H located at 1.8(5) MeV with quite a low population cross section of ∼25 μb/sr within angular range θ_{c.m.}≃(17°-27°).
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