arXiv subjects

Y. Endo

Publications and source records attributed to Y. Endo.

At least 19 recordsLinked to original sources

arXiv2025

Analysis of the isotopologues of CS, CCS, CCCS, HCS+, HCCS+, and H2CS in TMC-1 with the QUIJOTE line survey

We performed a detailed analysis of the isotopologues with 13C, 34S, 33S, and 36S of the sulphur-bearing molecules CS, CCS, CCCS,HCS+, HCCS+, and H2CS towards TMC-1 using the QUIJOTE1. The observations were obtained with the Yebes radio telescope. Observations with the IRAM 30m of the most abundant isotopologues of these species are also presented and used to estimate volume densities and to constrain the excitation conditions. We report the first detection in space of C13C34S, CC33S, CCC33S, HC33S+, and HCC34S+. C36S is also detected for the first time in a cold object. We also complemented with maps that provide the spatial distribution of most of these species. Using the available collisional rate coefficients for each species, we modeled the observed line intensities using the large velocity gradient method for the radiative transfer. We report the most complete analysis of the column densities of the CnS family and to compare the abundance ratios of all detected isotopologues. Adopting a T_k for TMC-1 of 9K, we found that n(H2)=0.9-1.5X10^4cm-3 can explain the observed decline in intensity with increasing J. We derived the rot. constants for the C13C34S, CC33S, CCC33S, HC33S+, and HCC34S+ isotopologues from new laboratory data and complemented them with the frequencies of the observed lines. We find that all S isotopologues are consistent with solar isotopic abundance ratios. Accurate 12C/13C abundances were derived and, as previously suggested, the 13C isotopologues of CCS and CCCS show strong abundance anomalies depending on the position of the substituted carbon. Nevertheless, the 12C/13C abundance ratio is practically identical to the solar value for CS, HCS+, and H2CS. We also searched for the isotopologues of other S-bearing molecules. The expected intensities for their 34S and 13C isotopologues are too low to be detected with the present sensitivity of the QUIJOTE, however.

astro-ph.GA↗

arXiv2025

Identification of the interstellar 1-cyano propargyl radical (HCCCHCN) in TMC-1

We report the first detection in interstellar medium of the 1-cyano propargyl radical, HC$_3$HCN. This species is an isomer of the 3-cyano propargyl radical (CH$_2$C$_3$N), which was recently discovered in TMC-1. The 1-cyano propargyl radical was observed in the cold dark cloud TMC-1 using data from the ongoing QUIJOTE line survey, which is being carried out with the Yebes 40m telescope. A total of seven rotational transitions with multiple hyperfine components were detected in the 31.0-50.4 GHz range. We derived a column density of (2.2$\pm$0.2)$\times$10$^{11}$ cm$^{-2}$ and a rotational temperature of 7$\pm$1\,K. The abundance ratio between HC$_3$HCN and CH$_2$C$_3$N is 1.4. The almost equal abundance of these isomers indicates that the two species may be produced in the same reaction with a similar efficiency, probably in the reaction C + CH$_2$CHCN and perhaps also in the reaction C$_2$ + CH$_3$CN and the dissociative recombination with electrons of CH$_2$C$_3$NH$^+$

astro-ph.GA↗

arXiv2024

Discovery of two cyano derivatives of acenaphthylene (C$_{12}$H$_8$) in TMC-1 with the QUIJOTE line survey

We report the discovery in TMC-1 of two cyano derivatives of the PAH acenaphthylene (C$_{12}$H$_8$). We have found two series of lines with the QUIJOTE line survey that we assign to 1-C$_{12}$H$_7$CN and 5-C$_{12}$H$_7$CN. For the 1-isomer, we have detected and assigned 173 rotational transitions with $J$ up to 46 and $K_a$ up to 9, corresponding to 107 independent frequencies. For the 5-isomer, the identification is based on 56 individual lines, corresponding to 117 rotational transitions with $J$ up to 40 and $K_a$ up to 8. Identification of the carriers was achieved through a careful analysis of the derived rotational constants, which permit us to focus on molecules larger than naphthalene but smaller than anthracene and phenanthrene. Moreover, the derived rotational constants indicate that the species are planar; this allows us to discard derivatives of fluorene and acenaphthene, which are non-planar species. Quantum chemical calculations and subsequent chemical synthesis of these molecules, as well as the observation of their rotational transitions in the laboratory, unequivocally support our identifications. We also confirm, via a robust line-by-line detection, the previous claimed detection of 1- and 2- cyanonaphthalene, which were obtained through statistical stacking techniques. The column densities of 1- and 5-cyanoacenaphthylene are (9.5\,$\pm$\,0.9)$\,\times$\,10$^{11}$ cm$^{-2}$, while those of 1- and 2-cyanonapthalene are (5.5\,$\pm$\,0.5)$\,\times$\,10$^{11}$ cm$^{-2}$. Hence, it seems that acenaphthylene could be a factor of 1.7 more abundant than naphthalene. These results support a scenario in which PAHs grow in cold dark clouds based on fused five- and six-membered carbon rings.

astro-ph.GA↗

arXiv2024

The rich interstellar reservoir of dinitriles: Detection of malononitrile and maleonitrile in TMC-1

While the nitrile group is by far the most prevalent one among interstellar molecules, the existence of interstellar dinitriles (molecules containing two -CN groups) has recently been proven. Here we report the discovery of two new dinitriles in the cold dense cloud TMC-1. These newly identified species are malononitrile, CH2(CN)2, and maleonitrile, the Z isomer of NC-CH=CH-CN, which can be seen as the result of substituting two H atoms with two -CN groups in methane and ethylene, respectively. These two molecules were detected using data from the ongoing QUIJOTE line survey of TMC-1 that is being carried out with the Yebes 40m telescope. We derive column densities of 1.8e11 cm-2 and 5.1e10 cm-2 for malononitrile and maleonitrile, respectively. This means that they are eight and three times less abundant than HCC-CH2-CN and (E)-HCC-CH=CH-CN, respectively, which are analog molecules detected in TMC-1 in which one -CN group is converted into a -CCH group. This is in line with previous findings in which -CCH derivatives are more abundant than the -CN counterparts in TMC-1. We examined the potential chemical pathways to these two dinitriles, and we find that while maleonitrile can be efficiently formed through the reaction of CN with CH2CHCN, the formation of malononitrile is not clear because the neutral-neutral reactions that could potentially form it are not feasible under the physical conditions of TMC-1.

astro-ph.GA↗

arXiv2024

Discovery of the interstellar cyanoacetylene radical cation HC$_3$N$^+$

We report the first identification in space of HC$_3$N$^+$, the simplest member of the family of cyanopolyyne cations. Three rotational transitions with half-integer quantum numbers from $J$=7/2 to 11/2 have been observed with the Yebes 40m radio telescope and assigned to HC$_3$N$^+$, which has an inverted $^2\Pi$ ground electronic state. The three rotational transitions exhibit several hyperfine components due to the magnetic and nuclear quadrupole coupling effects of the H and N nuclei. We confidently assign the characteristic rotational spectrum pattern to HC$_3$N$^+$ based on the good agreement between the astronomical and theoretical spectroscopic parameters. We derived a column density of (6.0$\pm$0.6)$\times$10$^{10}$ cm$^{-2}$ and a rotational temperature of 4.5$\pm$1\,K. The abundance ratio between HC$_3$N and HC$_3$N$^+$ is 3200$\pm$320. As found for the larger members of the family of cyanopolyyne cations (HC$_5$N$^+$ and HC$_7$N$^+$), HC$_3$N$^+$ is mainly formed through the reactions of H$_2$ and the cation C$_3$N$^+$ and by the reactions of H$^+$ with HC$_3$N. In the same manner than other cyanopolyyne cations, HC$_3$N$^+$ is mostly destroyed through a reaction with H$_2$ and a dissociative recombination with electrons.

astro-ph.GA↗

arXiv2024

QUIJOTE discovery of the cation radicals HC5N+ and HC7N+

We present the discovery with the QUIJOTE line survey of the cations HC5N+ and HC7N+ in the direction of TMC-1. Seven lines with half-integer quantum numbers from J=25/2-23/2 to 37/2-35/2 have been assigned to HC5N+ and eight lines from J=55/2-53/2 to 71/2-69/2 to HC7N+. Both species have inverted 2Pi ground electronic states with very good estimates for their B0 and AS0 constants based on optical observations. The lines with the lowest J of HC5N+ exhibit multiple components due to the hyperfine structure introduced by the H and N nuclei. However, these different components collapse for the higher J. No hyperfine structure is found for any of the lines of HC7N+. The derived effective rotational and distortion constants for HC5N+ are Beff = 1336.662+/- 0.001 MHz and Deff = 27.4+/-2.6 Hz, while for HC7N+ they are Beff = 567.85036+/-0.00037 MHz and Deff = 4.01+/-0.19 Hz. From the observed intensities, we derived Trot = 5.5+/-0.5K and N = (9.9+/-1.0)x 1010 cm-2 for HC5N+, while we obtained Trot = 8.5+/-0.5K and N = (2.3+/-0.2)x1010 cm-2 for HC7N+. The HC5N/HC5N+, C5N/HC5N+, C5N-/HC5N+, HC7N/HC7N+, HC5N+/HC7N+, and C7N-/HC7N+ abundance ratios are 670+/-80, 4.8+/-0.8, 1.2+/-0.2, 1000+/-150, 4.2+/-0.5, and 2.2+/-0.2, respectively. We have run chemical modelling calculations to investigate the formation and destruction of these new cations. We find that these species are mainly formed through the reactions of H2 and the cations C5N+ and C7N+, and by the reactions of H+ with HC5N and HC7N, while they are mostly destroyed through a reaction with H2 and a dissociative recombination with electrons. Based on the underestimation of the abundances of HC5N+ and HC7N+ by the chemical model by a factor around 20, we suggest that the rate coefficients currently assumed for the reactions of these cations with H2 could be too high by the same factor, something that will be worth investigating.

astro-ph.GA↗

arXiv2024

Laboratory and astronomical discovery of cyanothioketene, NCCHCS, in the cold starless core TMC-1

We present the detection of cyanothioketene, NCCHCS, in the laboratory and toward TMC-1. This transient species was produced through a discharge of a gas mixture of CH2CHCN and CS2 using argon as carrier gas, and its rotational spectrum between 9 and 40 GHz was characterized using a Balle-Flygare narrowband-type Fourier-transform microwave spectrometer. A total of 21 rotational transitions were detected in the laboratory, all of them exhibiting hyperfine structure induced by the spin of the N nucleus. The spectrum for NCCHCS was predicted in the domain of our line surveys using the derived rotational and distortion constants. The detection in the cold starless core TMC-1 was based on the QUIJOTE line survey performed with the Yebes 40m radio telescope. Twenty-three lines were detected with K_a=0, 1, and 2 and J_u=9 up to 14. The derived column density is (1.2+/-0.1)e11 cm-2 for a rotational temperature of 8.5+/-1 K. The abundance ratio of thioketene and its cyano derivative, H2CCS/NCCHCS, is 6.5+/-1.3. Although ketene is more abundant than thioketene by about 15 times, its cyano derivative NCCHCO surprisingly is not detected with a 3sigma upper level to the column density of 3.0e10 cm-2, which results in an abundance ratio H2CCO/NCCHCO > 430. Hence, the chemistry of CN derivatives seems to be more favored for S-bearing than for O-bearing molecules. We carried out chemical modeling calculations and found that the gas-phase neutral-neutral reactions CCN + H2CS and CN + H2CCS could be a source of NCCHCS in TMC-1.

astro-ph.GA↗

arXiv2023

Laboratory and astronomical discovery of the cyanovinyl radical H2CCCN

We report the first laboratory and interstellar detection of the alpha-cyano vinyl radical (H2CCCN). This species was produced in the laboratory by an electric discharge of a gas mixture of vinyl cyanide, CH2CHCN, and Ne, and its rotational spectrum was characterized using a Balle-Flygare narrowband-type Fourier-transform microwave spectrometer operating in the frequency region of 8-40 GHz. The observed spectrum shows a complex structure due to tunneling splittings between two torsional sublevels of the ground vibronic state, 0+ and 0-, derived from a large-amplitude inversion motion. In addition, the presence of two equivalent hydrogen nuclei makes necessary to discern between ortho- and para-H2CCCN. A least squares analysis reproduces the observed transition frequencies with a standard deviation of ca. 3 kHz. Using the laboratory predictions, this radical is detected in the cold dark cloud TMC-1 using the Yebes 40m telescope and the QUIJOTE line survey. The 404-303 and 505-404 rotational transitions, composed of several hyperfine components, were observed in the 31.0-50.4 GHz range. Adopting a rotational temperature of 6K we derive a column density of (1.4+/-0.2)e11 cm-2 and (1.1+/-0.2)e11 cm-2 for ortho-H2CCCN and para-H2CCCN, respectively. The reactions C + CH3CN, and perhaps also N + CH2CCH, emerge as the most likely routes to H2CCCN in TMC-1.

astro-ph.GA↗

arXiv2023

The magnesium paradigm in IRC+10216: Discovery of MgC$_4$H$^+$, MgC$_3$N$^+$, MgC$_6$H$^+$, and MgC$_5$N$^+$

We found four series of harmonically related lines in IRC\,+10216 with the Yebes\,40m and IRAM\,30m telescopes. The first series corresponds to a molecule with a rotational constant, $B$, of 1448.5994$\pm$0.0013 MHz and a distortion constant, $D$, of 63.45$\pm$1.15 Hz and covers upper quantum numbers from $J_u$=11 up to 33 (B1449). The second series is fitted with $B$=1446.9380$\pm$0.0098 MHz and $D$=91$\pm$23 Hz and covers upper quantum numbers from $J_u$=11 up to 17 (B1447). The third series is fitted with $B$=598.7495$\pm$0.0011 MHz and D=6.13$\pm$0.43 Hz and covers quantum numbers from $J_u$=26 up to 41 (B599). Finally, the frequencies of the last series of lines can be reproduced with $B$=594.3176$\pm$0.0026 MHz and $D$=4.92$\pm$1.16 Hz (B594). The large values of $D$ point toward four metal-bearing carriers. After exploring all plausible candidates containing Na, Al, Mg, and other metals, our ab initio calculations indicate that the cations MgC$_4$H$^+$, MgC$_3$N$^+$, MgC$_6$H$^+$, and MgC$_5$N$^+$ must be the carriers of B1449, B1447, B599, and B594, respectively. These cations could be formed by the radiative association of Mg$^+$ with C$_4$H, C$_3$N, C$_6$H, and C$_5$N, respectively. We calculated the radiative association rate coefficient of Mg$^+$ with C$_4$H, C$_3$N, C$_6$H, and C$_5$N and incorporated them in our chemical model. The results confirm that the Mg-bearing cations can be formed through these radiative association reactions in the outer layers of IRC\,+10216. This is the first time that cationic metal-bearing species have been found in space. These results provide a new paradigm on the reactivity of ionized metals with abundant radicals and open the door for further characterization of similar species in metal-rich astrophysical environments.

astro-ph.GA↗

arXiv2023

Discovery of two metallic cyanoacetylides in IRC+10216: HMgCCCN and NaCCCN

We report on the detection of a series of six lines in the ultra-deep Q-band integration toward IRC+10216 carried out with the Yebes 40m telescope, which are in harmonic relation with integer quantum numbers J from 12 to 18. After a detailed analysis of all possible carriers, guided by high-level quantum chemical calculations, we conclude that the lines belong to HMgCCCN, named hydromagnesium cyanoacetylide. The rotational temperature and column density derived for HMgCCCN are 17.1 +/- 2.8K and (3.0 +/- 0.6) e12 cm-2, respectively. The observed abundance ratio between MgCCCN and HMgCCCN is 3. In addition, we report the discovery in space, also toward IRC+10216, of sodium cyanoacetylide, NaCCCN, for which accurate laboratory data are available. For this species we derive a rotational temperature of 13.5 +/- 1.7K and a column density of (1.2 +/- 0.2) e11 cm-2.

astro-ph.GA↗

arXiv2022

Discovery of C5H+ and detection of C3H+ in TMC-1 with the QUIJOTE line survey

We report the discovery of the C5H+ cation toward TMC-1 with the QUIJOTE line survey. Four lines from J=7-6 up to J=10-9 have been identified in perfect harmonic frequency relation that can be fit with B=2411.94397 +/-0.00055 MHz and D=138+/-3 Hz. The standard deviation of the fit is 4.4 kHz. After discarding potential candidates, C5H- among them, we conclude that the carrier is C5H+, for which accurate ab initio calculations provide B=2410.3 MHz. We also report for the first time in a cold starless core the detection of the C3H+ cation. The column densities we derive for C5H+ and C3H+ are (8.8+/-0.5)e10 cm-2 and (2.4+/-0.2)e10 cm-2, respectively. Hence, the C5H+/C3H+ abundance ratio is 3.7+/-0.5. The fact that C5H+ is more abundant than C3H+ is well explained by dedicated chemical models and is due to the slow reactivity of C5H+ with H2, while C3H+ reacts with H2.

astro-ph.GA↗

arXiv2021

Discovery of the elusive thioketenylium, HCCS+, in TMC-1

We report the detection in TMC-1 of the cation HCCS+ (3Sigma-), which is the protonated form of the widespread radical CCS. This is the first time that a protonated radical has been detected in a cold dark cloud. Twenty-six hyperfine components from twelve rotational transitions have been observed with the Yebes 40m and IRAM 30m radio telescopes. We confidently assign the characteristic rotational spectrum pattern to HCCS+ based on the good agreement between the astronomical and theoretical spectroscopic parameters. The column density of HCCS+ is (1.1+/-0.1)e12 cm-2, and the CCS/HCCS+ abundance ratio is 50+/-10, which is very similar to that of CS/HCS+ (35+/-8) and CCCS/HCCCS+ (65+/-20). From a state-of-the-art gas-phase chemical model, we conclude that HCCS+ is mostly formed by reactions of proton transfer from abundant cations such as HCO+, H3O+, and H3+ to the radical CCS.

astro-ph.GA↗

arXiv2021

Laboratory observation and astronomical search of 1-cyano propargyl radical, HCCCHCN

The reaction between carbon atoms and vinyl cyanide, CH2CHCN, is a formation route to interstellar 3-cyano propargyl radical, CH2C3N, a species that has recently been discovered in space. The 1-cyano propargyl radical (HC3HCN), an isomer of CH2C3N, is predicted to be produced in the same reaction at least twice more effciently than CH2C3N. Hence, HC3HCN is a plausible candidate to be observed in space as well. We aim to generate the HC3HCN radical in the gas phase in order to investigate its rotational spectrum. The derived spectroscopic parameters for this species will be used to obtain reliable frequency predictions to support its detection in space.The HC3HCN radical was produced by an electric discharge, and its rotational spectrum was characterized using a Balle-Flygare narrowband-type Fourier-transform microwave spectrometer operating in the frequency region of 4-40 GHz. The spectral analysis was supported by high-level ab initio calculations. A total of 193 hyperfine components that originated from 12 rotational transitions, a- and b-type, were measured for the HC3HCN radical. The analysis allowed us to accurately determine 22 molecular constants, including rotational and centrifugal distortion constants as well as the fine and hyperfine constants. Transition frequency predictions were used to search for the HC3HCN radical in TMC-1 using the QUIJOTE survey between 30.1-50.4 GHz. We do not detect HC3HCN in TMC-1 and derive a 3sigma upper limit to its column density of 6.0e11 cm-2.

astro-ph.GA↗

arXiv2021

The sulphur saga in TMC-1: Discovery of HCSCN and HCSCCH

We report the detection, for the first time in space, of cyano thioformaldehyde (HCSCN) and propynethial (HCSCCH) towards the starless core TMC-1. Cyano thioformaldehyde presents a series of prominent a- and b-type lines, which are the strongest previously unassigned features in our Q-band line survey of TMC-1. Remarkably, HCSCN is four times more abundant than cyano formaldehyde (HCOCN). On the other hand, HCSCCH is five times less abundant than propynal (HCOCCH). Surprisingly, we find an abundance ratio HCSCCH/HCSCN of 0.25, in contrast with most other ethynyl-cyanide pairs of molecules for which the CCH-bearing species is more abundant than the CN-bearing one. We discuss the formation of these molecules in terms of neutral-neutral reactions of S atoms with CH2CCH and CH2CN radicals as well as of CCH and CN radicals with H2CS. The calculated abundances for the sulphur-bearing species are, however, significantly below the observed values, which points to an underestimation of the abundance of atomic sulphur in the model or to missing formation reactions, such as ion-neutral reactions.

astro-ph.GA↗

arXiv2021

First observation of a nuclear $s$-state of $\Xi$ hypernucleus, $^{15}_{\Xi}{\rm C}$

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, $^{15}_{\Xi}{\rm C}$.

nucl-ex↗

arXiv2021

Space and laboratory discovery of HC3S+

We report the detection in TMC-1 of the protonated form of C3S. The discovery of the cation HC3S+ was carried through the observation of four harmonically related lines in the Q band using the Yebes 40m radiotelescope, and is supported by accurate ab initio calculations and laboratory measurements of its rotational spectrum. We derive a column density N(HC3S+) = (2.0 +/- 0.5)e11 cm-2, which translates to an abundance ratio C3S/HC3S+ of 65 +/- 20. This ratio is comparable to the CS/HCS+ ratio (35 +/- 8) and is a factor of about ten larger than the C3O/HC3O+ ratio previously found in the same source. However, the abundance ratio HC3O+/HC3S+ is 1.0 +/- 0.5, while C3O/C3S is just 0.11. We also searched for protonated C2S in TMC-1, based on ab initio calculations of its spectroscopic parameters, and derive a 3sigma upper limit of N(HC2S+) < 9e11 cm-2 and a C2S/HC2S+ > 60. The observational results are compared with a state-of-the-art gas-phase chemical model and conclude that HC3S+ is mostly formed through several pathways: proton transfer to C3S, reaction of S+ with c-C3H2, and reaction between neutral atomic sulfur and the ion C3H3+.

astro-ph.GA↗

arXiv2021

Discovery of the acetyl cation, CH3CO+, in space and in the laboratory

Using the Yebes 40m and IRAM 30m radiotelescopes, we detected two series of harmonically related lines in space that can be fitted to a symmetric rotor. The lines have been seen towards the cold dense cores TMC-1, L483, L1527, and L1544. High level of theory ab initio calculations indicate that the best possible candidate is the acetyl cation, CH3CO+, which is the most stable product resulting from the protonation of ketene. We have produced this species in the laboratory and observed its rotational transitions Ju = 10 up to Ju = 27. Hence, we report the discovery of CH3CO+ in space based on our observations, theoretical calculations, and laboratory experiments. The derived rotational and distortion constants allow us to predict the spectrum of CH3CO+ with high accuracy up to 500 GHz. We derive an abundance ratio N(H2CCO)/N(CH3CO+) = 44. The high abundance of the protonated form of H2CCO is due to the high proton affinity of the neutral species. The other isomer, H2CCOH+, is found to be 178.9 kJ/mol above CH3CO+. The observed intensity ratio between the K=0 and K=1 lines, 2.2, strongly suggests that the A and E symmetry states have suffered interconversion processes due to collisions with H and/or H2, or during their formation through the reaction of H3+ with H2CCO.

astro-ph.GA↗

arXiv2020

Observation of Coulomb-assisted nuclear bound state of $\Xi^-$-$^{14}$N system

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.

nucl-ex↗