Investigation of the ¹⁶O(γ, ρ)³H3α reaction at the energies below the meson production threshold
The reaction ¹⁶O(γ, ρ)³H3α induced by bremsstrahlung photons of endpoint energy Emaxγ = 150 MeV has been studied by the method of a diffusion chamber in a magnetic field. The energy dependence of the total cross section has been measured in the energy range from the threshold and has been founded a...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2021
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Afanasiev, S.N. 2023-12-03T13:28:05Z 2023-12-03T13:28:05Z 2021 Investigation of the ¹⁶O(γ, ρ)³H3α reaction at the energies below the meson production threshold / S.N. Afanasiev // Problems of Atomic Science and Technology. — 2021. — № 3. — С. 68-71. — Бібліогр.: 11 назв. — англ. 1562-6016 PACS: 25.20.-x DOI: https://doi.org/10.46813/2021-133-068 https://nasplib.isofts.kiev.ua/handle/123456789/195109 The reaction ¹⁶O(γ, ρ)³H3α induced by bremsstrahlung photons of endpoint energy Emaxγ = 150 MeV has been studied by the method of a diffusion chamber in a magnetic field. The energy dependence of the total cross section has been measured in the energy range from the threshold and has been founded a broad resonance centered at 55 MeV. The rate of decrease in the cross section undergoes a change in the region around 55 MeV. A comparison was made with the cross section for reactions ⁴He(γ, p)³H and ¹²С(γ, р)³H2α. The agreement between the shapes of distributions for the (γ, p)³H reactions is evident and was concluded that the mechanism of interaction of the γ-quantum with the nucleus is similar. The dependence of average kinetic energy of particles on the total kinetic energy was determined. In the whole energy interval, the distribution for a proton is more than the statistical distribution. Distribution of relative energy of the proton and ³H nucleus in their c.m.s. does not agree with the predictions of the mechanism of photon absorption by an α-particle cluster, but at energies above the maximum, it agrees with calculations within the framework of the quasi-deuteron model of photoabsorption. Виконано аналіз подій реакції ¹⁶O(γ, ρ)³H3α, отриманих методом дифузійної камери в магнітному полі на пучці гальмівних фотонів з Eγmax = 150 МеВ. В енергетичній залежності реакції виявлено широкий максимум при Eγ ∼ 55 МеВ. Вище максимуму спостерігається зміна швидкості убування залежності. Виконано порівняння з виходами реакцій ⁴He(γ, p)³H і ¹²С(γ, р)³H2α, і зроблено висновок про подібність механізму взаємодії γ-кванта з ядром. Основну частину енергії забирає протон, причому при Eγ > 55 МеВ відбувається різка зміна залежності відносного вкладу частинок у повну енергію системи T₀. Поведінка залежності розподілу відносної енергії пари p+³H від T₀ не узгоджується з розрахунками в рамках α-кластерного механізму взаємодії γ-кванта з ядром, але при енергії вище максимуму узгоджується з розрахунками в рамках квазідейтронної моделі фотопоглинання. Выполнен анализ событий реакции ¹⁶O(γ, ρ)³H3α, полученных методом диффузионной камеры в магнитном поле на пучке тормозных фотонов с Eγmax = 150 МэВ. В энергетической зависимости реакции обнаружен широкий максимум при Eγ ∼ 55 МэВ. Выше максимума наблюдается изменение скорости убывания зависимости. Выполнено сравнение с выходами реакций ⁴He(γ, p)³H и ¹²С(γ, р)³H2α, и сделан вывод о подобии механизма взаимодействия γ-кванта с ядром. Основную часть энергии уносит протон, причем при Eγ > 55 МэВ происходит скачкообразное изменение зависимости относительного вклада частиц в полную энергию системы T₀. Поведение зависимости распределения относительной энергии пары p+³H от T₀ не согласуется с расчетами в рамках α-кластерного механизма взаимодействия γ-кванта с ядром, но при энергии выше максимума согласуется с расчетами в рамках квазидейтронной модели фотопоглощения. Author is grateful to A.F. Khodyachikh for stimulating discussions and a number of enlightening comments. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Experimental methods and processing of data Investigation of the ¹⁶O(γ, ρ)³H3α reaction at the energies below the meson production threshold Дослідження реакції ¹⁶O(γ, ρ)³H3α при енергіях до порога народження мезонів Исследование реакции ¹⁶O(γ, ρ)³H3α при энергиях до порога рождения мезонов Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Investigation of the ¹⁶O(γ, ρ)³H3α reaction at the energies below the meson production threshold |
| spellingShingle |
Investigation of the ¹⁶O(γ, ρ)³H3α reaction at the energies below the meson production threshold Afanasiev, S.N. Experimental methods and processing of data |
| title_short |
Investigation of the ¹⁶O(γ, ρ)³H3α reaction at the energies below the meson production threshold |
| title_full |
Investigation of the ¹⁶O(γ, ρ)³H3α reaction at the energies below the meson production threshold |
| title_fullStr |
Investigation of the ¹⁶O(γ, ρ)³H3α reaction at the energies below the meson production threshold |
| title_full_unstemmed |
Investigation of the ¹⁶O(γ, ρ)³H3α reaction at the energies below the meson production threshold |
| title_sort |
investigation of the ¹⁶o(γ, ρ)³h3α reaction at the energies below the meson production threshold |
| author |
Afanasiev, S.N. |
| author_facet |
Afanasiev, S.N. |
| topic |
Experimental methods and processing of data |
| topic_facet |
Experimental methods and processing of data |
| publishDate |
2021 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Дослідження реакції ¹⁶O(γ, ρ)³H3α при енергіях до порога народження мезонів Исследование реакции ¹⁶O(γ, ρ)³H3α при энергиях до порога рождения мезонов |
| description |
The reaction ¹⁶O(γ, ρ)³H3α induced by bremsstrahlung photons of endpoint energy Emaxγ = 150 MeV has been studied by the method of a diffusion chamber in a magnetic field. The energy dependence of the total cross section has been measured in the energy range from the threshold and has been founded a broad resonance centered at 55 MeV. The rate of decrease in the cross section undergoes a change in the region around 55 MeV. A comparison was made with the cross section for reactions ⁴He(γ, p)³H and ¹²С(γ, р)³H2α. The agreement between the shapes of distributions for the (γ, p)³H reactions is evident and was concluded that the mechanism of interaction of the γ-quantum with the nucleus is similar. The dependence of average kinetic energy of particles on the total kinetic energy was determined. In the whole energy interval, the distribution for a proton is more than the statistical distribution. Distribution of relative energy of the proton and ³H nucleus in their c.m.s. does not agree with the predictions of the mechanism of photon absorption by an α-particle cluster, but at energies above the maximum, it agrees with calculations within the framework of the quasi-deuteron model of photoabsorption.
Виконано аналіз подій реакції ¹⁶O(γ, ρ)³H3α, отриманих методом дифузійної камери в магнітному полі на пучці гальмівних фотонів з Eγmax = 150 МеВ. В енергетичній залежності реакції виявлено широкий максимум при Eγ ∼ 55 МеВ. Вище максимуму спостерігається зміна швидкості убування залежності. Виконано порівняння з виходами реакцій ⁴He(γ, p)³H і ¹²С(γ, р)³H2α, і зроблено висновок про подібність механізму взаємодії γ-кванта з ядром. Основну частину енергії забирає протон, причому при Eγ > 55 МеВ відбувається різка зміна залежності відносного вкладу частинок у повну енергію системи T₀. Поведінка залежності розподілу відносної енергії пари p+³H від T₀ не узгоджується з розрахунками в рамках α-кластерного механізму взаємодії γ-кванта з ядром, але при енергії вище максимуму узгоджується з розрахунками в рамках квазідейтронної моделі фотопоглинання.
Выполнен анализ событий реакции ¹⁶O(γ, ρ)³H3α, полученных методом диффузионной камеры в магнитном поле на пучке тормозных фотонов с Eγmax = 150 МэВ. В энергетической зависимости реакции обнаружен широкий максимум при Eγ ∼ 55 МэВ. Выше максимума наблюдается изменение скорости убывания зависимости. Выполнено сравнение с выходами реакций ⁴He(γ, p)³H и ¹²С(γ, р)³H2α, и сделан вывод о подобии механизма взаимодействия γ-кванта с ядром. Основную часть энергии уносит протон, причем при Eγ > 55 МэВ происходит скачкообразное изменение зависимости относительного вклада частиц в полную энергию системы T₀. Поведение зависимости распределения относительной энергии пары p+³H от T₀ не согласуется с расчетами в рамках α-кластерного механизма взаимодействия γ-кванта с ядром, но при энергии выше максимума согласуется с расчетами в рамках квазидейтронной модели фотопоглощения.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/195109 |
| citation_txt |
Investigation of the ¹⁶O(γ, ρ)³H3α reaction at the energies below the meson production threshold / S.N. Afanasiev // Problems of Atomic Science and Technology. — 2021. — № 3. — С. 68-71. — Бібліогр.: 11 назв. — англ. |
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ISSN 1562-6016. ВАНТ. 2021. № 3(133) 68
EXPERIMENTAL METHODS AND PROCESSING OF DATA
https://doi.org/10.46813/2021-133-068
INVESTIGATION OF THE 16O(, p)3H3 REACTION
AT THE ENERGIES BELOW THE MESON PRODUCTION THRESHOLD
S.N. Afanasiev
National Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine
E-mail: afanserg@kipt.kharkov.ua
The reaction 16O(, p)3H3 induced by bremsstrahlung photons of endpoint energy Emax
γ = 150 MeV has been
studied by the method of a diffusion chamber in a magnetic field. The energy dependence of the total cross section
has been measured in the energy range from the threshold and has been founded a broad resonance centered at
55 MeV. The rate of decrease in the cross section undergoes a change in the region around 55 MeV. A comparison
was made with the cross section for reactions 4He(, p)3H and 12С(, р)3H2. The agreement between the shapes of
distributions for the (, p)3H reactions is evident and was concluded that the mechanism of interaction of the γ-
quantum with the nucleus is similar. The dependence of average kinetic energy of particles on the total kinetic en-
ergy was determined. In the whole energy interval, the distribution for a proton is more than the statistical distribu-
tion. Distribution of relative energy of the proton and 3H nucleus in their c.m.s. does not agree with the predictions
of the mechanism of photon absorption by an α-particle cluster, but at energies above the maximum, it agrees with
calculations within the framework of the quasi-deuteron model of photoabsorption.
PACS: 25.20.-x.
INTRODUCTION
The interest to the investigation of (, N)-
photonuclear reactions is determined by the possibility
of proving the notions about nuclear forces, cluster con-
figurations and meson exchange currents in nuclei. All
these questions are associated with determination of a
reaction mechanism. With an increase in the γ-quantum
energy, a main contribution to the total effective cross
section for absorption of photons given by manyparticle
photoreactions and their analysis is of interest for study-
ing the mechanism of the interactions between photons
with virtual dynamic cluster systems and of the evolu-
tion of the nuclei cascade processes. The reaction in
question may proceed via the direct decay of the nu-
cleus to particles or via a sequential process involving
the formation of excited states nucleus, which subse-
quently decays to two particles. Therefore, the possibil-
ity of extracting a channel with the formation of a defi-
nite excited state of the intermediate nucleus can facili-
tate the determination of the mechanism of interaction
between the γ-quantum and the target nucleus.
In this article, we present results obtained by study-
ing the photodisintegration of oxygen nuclei via the
reaction 16O(, p)3H3 in the energy range from the
reaction threshold up to 150 MeV. A detailed experi-
mental study of this reaction has not been found. How-
ever, we have previously performed a series of works on
four-body photodisintegration of the carbon nucleus –
the reactions 12C(, p)3H2 and 12С(, n)3He2 [1] and
five-particle photodisintegration of the oxygen nucleus
– the reaction 16O(, n)3He3 [2, 3].
It was revealed [1] that within identical energy in-
tervals, the angular distributions for the «mirror»
12C(, p)3H2 and 12С(, n)3He2 reactions have similar
shapes. In [3], an analysis of (γ, n)-reactions on 12C and
16O nuclei was carried out, and a similarity was ob-
served in the energy and angular distributions.
The theoretical and experimental investigations of
the p-3H- and n-3He-correlations are also necessary for
identification of the -cluster mechanism. Such problem
was discussed in [1, 4 - 6] for the 12C(, p)3H2 reaction.
Note that the analysis of the channels becomes compli-
cated because of the possible manifestation of the qua-
sideuteron [1, 6] and -cluster mechanisms [4 - 6] with
the corresponding singularities of the triangular dia-
grams. Such cluster mechanism with rescattering in the
final state was analyzed in only for the energy distribu-
tions of the final particles in the reaction 12C(, p)3H2
and did not give satisfactory description of the experi-
mental data. The analysis of these mechanisms requires
comparison of the experimental data for the energy and
angular distributions and correlations of the final parti-
cles in the «mirror» reactions (, p)3H and (, n)3He on
the 12C and 16O nuclei. At the present time, experimental
data on (, p)3H and (, n)3He reactions are scanty.
EXPERIMENTAL PROCEDURE
The results given here were obtained by using a dif-
fusion chamber [7] placed in a magnetic field and ex-
posed to a beam of bremsstrahlung photons, their end-
point energy being 150 MeV.
For a further treatment, we selected five-prong stars
whose tracks were associated with two single charged
particles and three doubly charged particles. Oxygen
nucleus photodisintegration events was easily separated
visually. Low pressure in the chamber and target and
detector matching made possible to investigate reaction
from reaction threshold. The measurement error of the
momentum of particles depended on the momentum
value itself and the particle track length, and varied
from 3 to 10%. The energy of stopped -particles was
determined from the range/energy ratio.
Events were identified after the measurement based
on momentum balance. In the experiment, the axis OX
was directed along the beam of γ-quanta. Boundary
ISSN 1562-6016. ВАНТ. 2021. № 3(133) 69
conditions were imposed on the quantities PX
i, Py
i,
and Pz
i, where PX(Y,Z)
i are the components of the three-
dimensional momentum of the i-th final particle. The γ-
quantum energy Eγ was determined as the sum of the
kinetic energies of final i-particles and the reaction
threshold. A distinctly pronounced peak in region 0 cor-
responded to events of the examined reaction. The en-
ergy and momentum conservation laws allowed the
measurement results obtained for one of the tracks,
which turned out to be the worst in comparison with the
results obtained for all other tracks, to be made more
exact.
Because of an insufficient length of the projection of
a track onto the median plane, we were unable to meas-
ure, with the required precision, the kinematical pa-
rameters of particles that did not stop in the chamber
fiducial volume and which escaped from it at an angle
smaller than 50 with respect to the vector of the mag-
netic-field strength. For events not processed for this
reason, we introduced a geometric correction calculated
under the assumption of an isotropic distribution with
respect to the azimuthal angle since the photon beam
was unpolarized.
EXPERIMENTAL RESULTS
We have measured dependence of the number of
events for the reaction 16O(, p)3H3 in the photon en-
ergy range from the reaction threshold up to 150 MeV
with a step of 2 MeV. The results are shown in Fig. 1,a
by solid circles placed at the midpoint of a step. The
displayed errors are purely statistical.
50 75 100 125
0,1
1
10
50 75 100 125
0
20
40
60
b)
16O(,pt)3
12C(,pt)2
4He(,pt)
E
, MeV
a)
nu
m
be
r o
f e
ve
nt
s
16O(,pt)3
Fig. 1. Dependence of the number of events for
the reaction 16O(, p)3H3 (solid circles) as a function
of the photon energy. The histogram and open circles
represent, respectively, the experimental results
reported in [8] on the reaction 4He(, p)3H
and in [9] on the reaction 12С(, р)3H2
The measured energy dependence of the number of
events exhibits a broad resonance centered at 55 MeV.
The rate of decrease in the energy dependence under-
goes a change in the region around 55 MeV. A similar
irregularity in the region of this energy value was previ-
ously observed in the reactions 4He(, p)3H [8] and
12С(, р)3H2 [9].
In Fig. 1,b, the energy dependence for the reaction in
question is contrasted against the energy dependence of
the cross section measured for the reactions 4He(, p)3H
(histogram) and 12С(, р)3H2 (open circles) at an en-
ergy more 55 MeV. The results normalize in the region
around 55 MeV. The experimental curves have the same
slope. The change in the rate of decrease in the cross
section at around 55 MeV may possibly be due to a
transition from the mechanism of direct nucleon knock-
out to the pair-absorption mechanism [1].
In Fig. 2 the dependence of the average kinetic en-
ergy Taver of the final particles on the total kinetic en-
ergy T0 is depicted. The latter equals T0 = Eγ − Q, where
Q is the reaction threshold (Q = 34.302 MeV). The
value T0 20 MeV corresponds to the position of the
maximum of the reaction yield at Eγ 55 MeV and will
be used further as the boundaries of the intervals in the
analyze of events.
20 40 60 80 100
0
2
4
6
20 40 60 80 100
0
20
40
60
80
0 10 20
0
2
4
6
0 10 20
0
20
40
60
80
Tav
, M
eV
T0, MeV
b)
a)
Fig. 2. Dependence of the average kinetic energy
of the final particles on the total kinetic energy:
the squares correspond to proton, triangles
for the 3H nuclei and circles for -particles
The average energy Taver was calculated for the par-
ticles with the energy falling within a 1 MeV interval of
the total kinetic energy. The circles are plotted at the
centers of intervals. The histogram step equals 1 MeV in
the energy interval T0 < 20 MeV (open circles) and
5 MeV in the energy interval T0 > 20 MeV (solid cir-
cles). The squares show the distribution of Taver for the
proton (see Fig. 2,a), triangles for the 3H nuclei (see
Fig. 2,b), and circles for -particles (see Fig. 2,b).
a
a
b
b
ISSN 1562-6016. ВАНТ. 2021. № 3(133) 70
Due to the inseparability of -particles, the figure shows
the average value for three -particles.
The dependences of the average kinetic energy was
approximated by the linear functions and the results of
these fits are given in the second and third columns of
the table for all final particles.
Dependence of the relative contributions of the average
kinetic energy of particles on T0
Energy T0 < 20 MeV T0 > 20 MeV
Taver
p 0.50 0.02 0.90 0.01
Taver
3H 0.11 0.01 0.04 0.01
Taver
0.13 0.01 0.02 0.01
Assuming a statistical distribution of energy be-
tween particles, we can calculate the average energy
carried away by each particle as a function of T0 [10]
av
0
A-MT T
(n-1) A
, (1)
where A and M are the atomic numbers of the target
nucleus and the researched particle, respectively; and n
is the number of particles in the final state.
In this reaction, the values of calculation by eq. (1)
correspond: for the proton – 0.23, for the 3H nuclei – 0.2,
and for -particles – 0.19 (should be remembered that
there are three α-particles in the final state).
In the whole energy interval, the experimental dis-
tribution of Taver does not correspond to the statistical
distribution, which testifies to the indirect decay of the
excited oxygen nucleus. Note the sharp change in the
dependence at T0 > 20 MeV, main part of the energy is
carried away by the proton. The low rate of change in
the dependence of distributions for other particles may
indicate that they are decay products of intermediate
excited states.
Qualitatively, such a behavior can be explained by a
similarity of the mechanism of interaction between a γ-
quantum and the target nucleus: the interaction takes
place with a virtual quasiparticle that includes a proton
as one of its components.
It seems interesting to study the correlation in the
p+3H system, which can be interpreted as a virtual -
particle. If a photon is absorbed by a -particle, then
one can expect that the energy of the relative motion of
the p+3H pair will account for most of the total kinetic
energy in the final state T0.
The kinetic energy of the relative motion of the pro-
ton and the 3H nuclei in their c.m.s. is
Ex(p3H)= Meff
p3H – (mp + m3H), (2)
where Meff
p3H is the effective mass of two particles and
mp, m3H are the masses of the p and 3H respectively.
It forms a part of the relative energies
3
x
0
E (p H)з =
T
. (3)
The distribution of events for T0 < 20 MeV interval
is shown in Fig. 3,a by open circles and for T0 >
20 MeV by solid circles (Fig. 3,b).
The distribution structure changes significantly. On
the first region, the distribution is practically symmetric
with respect to 0.4, and on the second, the distribution
maximum shifts to η0.75. A similar change was ob-
served for the p3H system and in the reaction
12С(, р)3H2 [11] previously. Therefore, for a qualita-
tive comparison, the following are theoretical calcula-
tions performed for the four-particle photodisintegration
of the carbon nucleus. The calculated curve was normal-
ized to the area under the experimental curve.
0,00 0,25 0,50 0,75 1,00
0
25
50
75
0
20
40
3
2
1
nu
m
be
r o
f e
ve
nt
s
, a.u.
b)
3
2
1a)
Fig. 3. Function of distribution in relative energy
of a proton and the 3H nuclei. The notation for the
curves is explained in the main body of the text
The results of the calculation performed on the basis
of the -particle model of the nucleus [5, 6] predicted
that the maximum of this distribution curve lies at a
value η close to unity, which indicates that a proton and
the 3H nuclei fly out mainly in opposite directions.
Curve 1 shows the calculation [5] in the model of di-
rect absorption of a γ-quantum by -particle with a fur-
ther emission of p and 3H. In [6] we can single out the
following stages of the reaction: a virtual decay of the
12С nucleus to an -particle cluster and core in the
ground state; photon absorption by the cluster; and clus-
ter scattering on the core, where by the core goes over to
the ground state. Curve 2 represents the results in this
model. The curve 3 corresponds to the calculation [1]
within the quasi-deuteron model. The excitation energy
of the intermediate nucleus is sufficiently high for nu-
cleon knockout from the s-shell to be possible.
Curve 3 describes satisfactorily the experimental
data at T0 > 20 MeV.
CONCLUSIONS
The reaction 16O(,p)3H3 was studied with the aid
of a diffusion chamber placed in a magnetic field and
irradiated with bremsstrahlung photons of endpoint en-
ergy E
max = 150 MeV. The energy dependence of the
total cross section has been measured in the energy
range from the threshold reaction. The measured cross
section exhibits a broad resonance centered at 55 MeV.
The rate of decrease in the cross section undergoes a
a
b
ISSN 1562-6016. ВАНТ. 2021. № 3(133) 71
change in the region around 55 MeV. Above the maxi-
mum, a comparison is made with the cross-section of
reactions 4He(, p)3H and 12С(, р)3H2.
Dependence of the average kinetic energy of the fi-
nal particles on the total kinetic energy T0 = Eγ Q have
been measured. A jumplike change in the parameters of
the linear approximation was found at energies
T0 20 MeV. The proton carries main part of the en-
ergy away.
Distribution of relative energy of the proton and 3H
nucleus in their c.m.s. does not agree with the predic-
tions of the mechanism of photon absorption by an
-particle cluster, but at energies T0 > 20 MeV it agrees
with calculations within the framework of the quasi-
deuteron model of photoabsorption.
ACKNOWLEDGEMENTS
Author is grateful to A.F. Khodyachikh for stimulat-
ing discussions and a number of enlightening comments.
REFERENCES
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Article received 25.02.2021
ИССЛЕДОВАНИЕ РЕАКЦИИ 16O(, p)3H3 ПРИ ЭНЕРГИЯХ ДО ПОРОГА РОЖДЕНИЯ МЕЗОНОВ
С.Н. Афанасьев
Выполнен анализ событий реакции 16O(, p)3H3, полученных методом диффузионной камеры в магнит-
ном поле на пучке тормозных фотонов с E
макс = 150 МэВ. В энергетической зависимости реакции обнару-
жен широкий максимум при E55 МэВ. Выше максимума наблюдается изменение скорости убывания зави-
симости. Выполнено сравнение с выходами реакций 4He(, p)3H и 12С(, р)3H2, и сделан вывод о подобии
механизма взаимодействия γ-кванта с ядром. Основную часть энергии уносит протон, причем при
E > 55 МэВ происходит скачкообразное изменение зависимости относительного вклада частиц в полную
энергию системы T0. Поведение зависимости распределения относительной энергии пары p+3H от T0 не со-
гласуется с расчетами в рамках -кластерного механизма взаимодействия γ-кванта с ядром, но при энергии
выше максимума согласуется с расчетами в рамках квазидейтронной модели фотопоглощения.
ДОСЛІДЖЕННЯ РЕАКЦІЇ 16O(, p)3H3 ПРИ ЕНЕРГІЯХ ДО ПОРОГА НАРОДЖЕННЯ МЕЗОНІВ
С.М. Афанасьєв
Виконано аналіз подій реакції 16O(, p)3H3, отриманих методом дифузійної камери в магнітному полі на
пучці гальмівних фотонів з E
макс = 150 МеВ. В енергетичній залежності реакції виявлено широкий макси-
мум при E 55 МеВ. Вище максимуму спостерігається зміна швидкості убування залежності. Виконано
порівняння з виходами реакцій 4He(, p)3H і 12С(, р)3H2, і зроблено висновок про подібність механізму
взаємодії γ-кванта з ядром. Основну частину енергії забирає протон, причому при E > 55 МеВ відбувається
різка зміна залежності відносного вкладу частинок у повну енергію системи T0. Поведінка залежності роз-
поділу відносної енергії пари p+3H від T0 не узгоджується з розрахунками в рамках -кластерного механізму
взаємодії -кванта з ядром, але при енергії вище максимуму узгоджується з розрахунками в рамках квазідей-
тронної моделі фотопоглинання.
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