A high-resolution measurement method based on X-ray microscopy was developed to analyze double-strangeness hypernuclear events with a complex topology in a nuclear emulsion. In a feasibility study ...performed on
α
-decay events in emulsions, the resolution of the X-ray microscopy in the focal plane was found to be 0.2
μ
m
, which shows an improvement by
∼
2.4
times to that of the optical microscopy used for conventional analysis. The extent to which the emulsion underwent modification as a result of X-ray irradiation was also evaluated. The modification mainly occurred in the form of a change in its thickness; however, this affection was adequately small to perform X-ray imaging if the duration of the irradiation was sufficiently short. Stereo imaging with X-ray microscopy improved the resolution by
∼
2.5
times to 0.28
μ
m
along the optical axis compared with the depth of field of the optical microscope, 0.7
μ
m
. We applied the developed method to the study of a double-strangeness hypernuclear event. The uncertainty on the position of the vertex point and the binding energy of the
Ξ
-
and
14
N system was improved from 3
μ
m
to 0.04
μ
m
and
±
3
MeV to
±
0.86
MeV, respectively. The binding energy was deduced to be
-
1.23
±
0.86
MeV
, and this result indicates that a
Ξ
-
atomic state is produced in the observed event.
Abstract
Ξ− atomic X-ray spectroscopy is one of the most useful methods for investigation of the Ξ–nucleus strong interaction. Since the X-ray energy is shifted and/or broadened due to the Ξ–nucleus ...strong interaction compared to those calculated from electromagnetic interaction alone, the measurement of the energy shift, ΔE, and the width, Γ, give us information on the Ξ–nucleus potential. A serious problem in the measurement is the significant background derived from in-flight Ξ− decay. A novel method of identifying stopped Ξ− events using the nuclear emulsion was developed to realize the first Ξ− atomic X-ray spectroscopy experiment as the J-PARC E07 experiment, which also aimed at searching for ΛΛ and Ξ− hypernuclei in the emulsion. The X-rays emitted from Ξ− Br and Ξ− Ag atoms were measured using germanium detectors. No clear peaks were observed in the obtained spectra. However, we succeeded in reducing the background to 1/170 by this method employing coincidence measurements using nuclear emulsion and X-ray detectors.
Abstract
A double-$\Lambda$ hypernucleus, _{\Lambda\Lambda}\mathrm{Be}$, was observed by the J-PARC E07 Collaboration in nuclear emulsions tagged by the ($K^{-}, K^{+}$) reaction. This event was ...interpreted as the production and decay of $ {}_{\Lambda\Lambda}^{\;10}\mathrm{Be}$, _{\Lambda\Lambda}^{\;11}\mathrm{Be}$, or _{\Lambda\Lambda}^{\;12}\mathrm{Be}^{*}$ via $\Xi^{-}$ capture in ^{16}\mathrm{O}$. By assuming capture in the atomic 3D state, the binding energies of two $\Lambda$ hyperons ($B_{\Lambda\Lambda}$) of these double-$\Lambda$ hypernuclei are obtained to be $15.05 \pm 0.11\,\mathrm{MeV}$, $19.07 \pm 0.11\,\mathrm{MeV}$, and $13.68 \pm 0.11\,\mathrm{MeV}$, respectively. Based on the kinematic fitting, _{\Lambda\Lambda}^{\;11}\mathrm{Be}$ is the most likely explanation for the observed event.
Abstract
Bound systems of $\Xi^-$–$^{14}_{}{\rm N}$ are studied via $\Xi^-$ capture at rest followed by emission of a twin single-$\Lambda$ hypernucleus in the emulsion detectors. Two events forming ...extremely deep $\Xi^-$ bound states were obtained by analysis of a hybrid method in the E07 experiment at J-PARC and reanalysis of the E373 experiment at KEK-PS. The decay mode of one event was assigned as $\Xi^-+^{14}\!\,\!\!{\rm N}\to^{5}_{\Lambda}\!\!\!{\rm He} + ^{5}_{\Lambda}\!\!{\rm He} + ^{4}\!\!{\rm He} + \mathrm{n}$. Since there are no excited states for daughter particles, the binding energy of the $\Xi^-$ hyperon, $B_{\Xi^-}$, in the $^{14}_{}{\rm N}$ nucleus was uniquely determined to be $6.27 \pm 0.27$ MeV. Another $\Xi^-$–$^{14}_{}{\rm N}$ system via the decay $^{9}_{\Lambda}{\rm Be} + ^{5}_{\Lambda}\!\!\!{\rm He} + \mathrm{n}$ brings a $B_{\Xi^-}$ value, $8.00 \pm 0.77$ MeV or $4.96 \pm 0.77$ MeV, where the two possible values of $B_{\Xi^-}$ correspond to the ground and the excited states of the daughter $^{9}_{\Lambda}{\rm Be}$ nucleus, respectively. Because the $B_{\Xi^-}$ values are larger than those of the previously reported events (KISO and IBUKI), which are both interpreted as the nuclear $1p$ state of the $\Xi^-$–$^{14}_{}{\rm N}$ system, these new events give the first indication of the nuclear $1s$ state of the $\Xi$ hypernucleus, $^{15}_{\Xi}{\rm C}$.
PTEP 2021 (2021) 7, 073D02 Bound-systems of $\Xi^-$--$^{14}_{}{\rm N}$ are studied via $\Xi^-$ capture
at rest followed by emission of a twin single-$\Lambda$ hypernucleus in the
emulsion detectors. ...Two events forming extremely deep $\Xi^-$ bound states were
obtained by analysis of a hybrid method in the E07 experiment at J-PARC and
reanalysis of the E373 experiment at KEK-PS. The decay mode of one event was
assigned as $\Xi^-+^{14}_{}{\rm N}\to^{5}_{\Lambda}{\rm
He}$+$^{5}_{\Lambda}{\rm He}$+$^{4}_{}{\rm He}$+n. Since there are no excited
states for daughter particles, the binding energy of the $\Xi^-$ hyperon,
$B_{\Xi^-}$, in $^{14}_{}{\rm N}$ nucleus was uniquely determined to be 6.27
$\pm$ 0.27 MeV. Another $\Xi^-$--$^{14}_{}{\rm N}$ system via the decay
$^{9}_{\Lambda}{\rm Be}$ + $^{5}_{\Lambda}{\rm He}$ + n brings a $B_{\Xi^-}$
value, 8.00 $\pm$ 0.77 MeV or 4.96 $\pm$ 0.77 MeV, where the two possible
values of $B_{\Xi^-}$ correspond to the ground and the excited states of the
daughter $^{9}_{\Lambda}{\rm Be}$ nucleus, respectively. Because the
$B_{\Xi^-}$ values are larger than those of the previously reported events
(KISO and IBUKI), which are both interpreted as the nuclear $1p$ state of the
$\Xi^-$--$^{14}_{}{\rm N}$ system, these new events give the first indication
of the nuclear $1s$ state of the $\Xi$ hypernucleus, $^{15}_{\Xi}{\rm C}$.
Phys. Rev. Lett. 126, 062501 (2021) In an emulsion-counter hybrid experiment performed at J-PARC, a $\Xi^-$
absorption event was observed which decayed into twin single-$\Lambda$
hypernuclei. ...Kinematic calculations enabled a unique identification of the
reaction process as $\Xi^{-} + ^{14}$N$\ \rightarrow\ ^{10}_\Lambda$Be +
$^5_\Lambda$He. For the binding energy of the $\Xi^{-}$ hyperon in the
$\Xi^-$-$^{14}$N system a value of $1.27 \pm 0.21$ MeV was deduced. The energy
level of $\Xi^-$ is likely a nuclear $1p$ state which indicates a weak
${\Xi}N$-$\Lambda\Lambda$ coupling.
A double-\(\Lambda\) hypernucleus, \({}_{\Lambda\Lambda}\mathrm{Be}\), was observed by the J-PARC E07 collaboration in nuclear emulsions tagged by the \((K^{-},K^{+})\) reaction. This event was ...interpreted as a production and decay of \( {}_{\Lambda\Lambda}^{\;10}\mathrm{Be}\), \({}_{\Lambda\Lambda}^{\;11}\mathrm{Be}\), or \({}_{\Lambda\Lambda}^{\;12}\mathrm{Be}^{*}\) via \(\Xi^{-}\) capture in \({}^{16}\mathrm{O}\). By assuming the capture in the atomic 3D state, the binding energy of two \(\Lambda\) hyperons\(\,\)(\(B_{\Lambda\Lambda}\)) of these double-\(\Lambda\) hypernuclei are obtained to be \(15.05 \pm 0.11\,\mathrm{MeV}\), \(19.07 \pm 0.11\,\mathrm{MeV}\), and \(13.68 \pm 0.11\,\mathrm{MeV}\), respectively. Based on the kinematic fitting, \({}_{\Lambda\Lambda}^{\;11}\mathrm{Be}\) is the most likely explanation for the observed event.
Bound-systems of \(\Xi^-\)--\(^{14}_{}{\rm N}\) are studied via \(\Xi^-\) capture at rest followed by emission of a twin single-\(\Lambda\) hypernucleus in the emulsion detectors. Two events forming ...extremely deep \(\Xi^-\) bound states were obtained by analysis of a hybrid method in the E07 experiment at J-PARC and reanalysis of the E373 experiment at KEK-PS. The decay mode of one event was assigned as \(\Xi^-+^{14}_{}{\rm N}\to^{5}_{\Lambda}{\rm He}\)+\(^{5}_{\Lambda}{\rm He}\)+\(^{4}_{}{\rm He}\)+n. Since there are no excited states for daughter particles, the binding energy of the \(\Xi^-\) hyperon, \(B_{\Xi^-}\), in \(^{14}_{}{\rm N}\) nucleus was uniquely determined to be 6.27 \(\pm\) 0.27 MeV. Another \(\Xi^-\)--\(^{14}_{}{\rm N}\) system via the decay \(^{9}_{\Lambda}{\rm Be}\) + \(^{5}_{\Lambda}{\rm He}\) + n brings a \(B_{\Xi^-}\) value, 8.00 \(\pm\) 0.77 MeV or 4.96 \(\pm\) 0.77 MeV, where the two possible values of \(B_{\Xi^-}\) correspond to the ground and the excited states of the daughter \(^{9}_{\Lambda}{\rm Be}\) nucleus, respectively. Because the \(B_{\Xi^-}\) values are larger than those of the previously reported events (KISO and IBUKI), which are both interpreted as the nuclear \(1p\) state of the \(\Xi^-\)--\(^{14}_{}{\rm N}\) system, these new events give the first indication of the nuclear \(1s\) state of the \(\Xi\) hypernucleus, \(^{15}_{\Xi}{\rm C}\).
In an emulsion-counter hybrid experiment performed at J-PARC, a \(\Xi^-\) absorption event was observed which decayed into twin single-\(\Lambda\) hypernuclei. Kinematic calculations enabled a unique ...identification of the reaction process as \(\Xi^{-} + ^{14}\)N\(\ \rightarrow\ ^{10}_\Lambda\)Be + \(^5_\Lambda\)He. For the binding energy of the \(\Xi^{-}\) hyperon in the \(\Xi^-\)-\(^{14}\)N system a value of \(1.27 \pm 0.21\) MeV was deduced. The energy level of \(\Xi^-\) is likely a nuclear \(1p\) state which indicates a weak \({\Xi}N\)-\(\Lambda\Lambda\) coupling.
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