-
A. Ichikawa,
J.K. Ahn, H. Akikawa,
S. Aoki,
K. Arai,
S.Y. Bahk,
K.M. Baik,
B. Bassalleck,
J.H. Chung,
M.S. Chung, [......],
S. Torikai,
N. Ushida,
K. Yamamoto,
N. Yasuda,
J.T. Yang,
C.J. Yoon,
C.S. Yoon,
M. Yosoi,
T. Yoshida,
L. Zhu
[show abstract]
[hide abstract]
ABSTRACT: A hybrid emulsion experiment was carried out to study double-strangeness nuclei produced via Ξ− hyperon capture at rest with the expectation of ten times larger statistics than previous experiments. We have analyzed 5% of the total emulsion and found one “twin-hypernuclei” event involving the emission of two single-Λ hypernuclei and a nuclear fragment from a Ξ− hyperon stopping point. The event is interpreted as the decay of a atomic system to . The species of the Ξ−-atom and the fragmentation products are uniquely identified for the first time for twin-hypernuclei events. Combined with the results from a past hybrid-emulsion experiment, one double-Λ hypernucleus and three twin-hypernuclei events have been found from Ξ− captures on light emulsion nuclei. The ratio of the detected rate of double-Λ hypernuclei to that of twin-hypernuclei is compared with theoretical estimates.
Physics Letters B 05/2013; 500:37-46. · 3.95 Impact Factor
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M. Ukai,
S. Ajimura, H. Akikawa,
D. E. Alburger,
A. Banu,
R. E. Chrien,
G. B. Franklin,
J. Franz,
O. Hashimoto,
T. Hayakawa, [......],
P. Pile,
B. P. Quinn,
A. Rusek,
Y. Sato,
R. Sutter,
H. Takahashi,
L. Tang,
H. Tamura,
K. Tanida,
S. H. Zhou
[show abstract]
[hide abstract]
ABSTRACT: The bound-state level structures of the Λ16O and Λ15N hypernuclei were studied by γ-ray spectroscopy using a germanium detector array (Hyperball) via the 16O (K-,π-γ) reaction. A level scheme for Λ16O was determined from the observation of three γ-ray transitions from the doublet of states (2-,1-) at ~6.7 MeV to the ground-state doublet (1-,0-). The Λ15N hypernuclei were produced via proton emission from unbound states in Λ16O. Three γ rays were observed, and the lifetime of the 1/2+;1 state in Λ15N was measured by the Doppler shift attenuation method. By comparing the experimental results with shell-model calculations, the spin dependence of the ΛN interaction is discussed. In particular, the measured Λ16O ground-state doublet spacing of 26.4±1.6±0.5 keV determines a small but nonzero strength of the ΛN tensor interaction.
Phys. Rev. C. 05/2008; 77(5).
-
T. Watanabe,
J. K. Ahn, H. Akikawa,
S. Aoki,
K. Arai,
S. Y. Bahk,
K. M. Baik,
B. Bassalleck,
J. H. Chung,
M. S. Chung, [......],
D. N. Tovee,
N. Ushida,
K. Yamamoto,
N. Yasuda,
J. T. Yang,
C. J. Yoon,
C. S. Yoon,
M. Yosoi,
T. Yoshida,
L. Zhu
[show abstract]
[hide abstract]
ABSTRACT: An event emitting a Σ- -hyperon from a Ξ- -hyperon nuclear capture at rest has been observed in a hybrid-emulsion experiment. The event has been analyzed as the first
observation of the weak decay of the S = - 2 system.
European Physical Journal A 08/2007; 33(3):265-268. · 2.19 Impact Factor
-
C. J. Yoon, H. Akikawa,
K. Aoki,
Y. Fukao,
H. Funahashi,
M. Hayata,
K. Imai,
K. Miwa,
H. Okada,
N. Saito, [......],
J. K. Ahn,
B. H. Choi,
S. J. Kim,
S. H. Kim,
B. D. Park,
I. G. Park,
J. S. Song,
C. S. Yoon,
K. Tanida,
A. Ohnishi
[show abstract]
[hide abstract]
ABSTRACT: We searched for the H-dibaryon resonance in the ΛΛ invariant mass spectrum obtained by 12C(K
−, K
+
ΛΛX) reactions using a scintillating fiber active target. We observed enhanced ΛΛ production near the threshold, as found in a previous KEK experiment, with improved statistics. Data were compared with the
results of a cascade model calculation including ΛΛ final state interactions consistent with the recently measured binding energy of the double-Λ hypernucleus. No significant enhancements above the levels predicted by the model were observed. The upper limit for the
production cross section of the H-dibaryon with a mass range between the ΛΛ and ΞN threshold is found to be 2.1 μb/sr at a 90% confidence level.
12/2006: pages 121-126;
-
M Ukai,
S Ajimura, H Akikawa,
D E Alburger,
A Banu,
R E Chrien,
G B Franklin,
J Franz,
O Hashimoto,
T Hayakawa, [......],
B P Quinn,
A Rusek,
Y Sato,
R Sutter,
H Takahashi,
L Tang,
H Tamura,
K Tanida,
L Yuan,
S H Zhou
[show abstract]
[hide abstract]
ABSTRACT: We have observed two gamma-ray transitions in (16)(Lambda)O from the 6.6 MeV excited 1(-)(2) state to both ground-state spin-doublet members (1(-)(1),0(-)) by the (K-,pi(-)gamma) reaction. We have obtained the ground-state doublet spacing to be 26.4+/-1.6(stat)+/-0.5(syst) keV and the excitation energy of the 1(-)(2) state to be 6561.7+/-1.1(stat)+/-1.7(syst) keV. The ground-state doublet spacing provides a small but nonzero strength of the tensor interaction between a Lambda and a nucleon. This is the first experimental result on the LambdaN tensor interaction.
Physical Review Letters 01/2005; 93(23):232501. · 7.37 Impact Factor
-
J.K. Ahn, H. Akikawa,
J. Arvieux,
B. Bassalleck,
M.S. Chung,
H. En'yo,
T. Fukuda,
H. Funahashi,
S.V. Golovkin,
A.M. Gorin, [......],
A. Sato,
H.D. Sato,
K.S. Sim,
T. Tabaru,
F. Takeutchi,
P. Trusty,
H. Torii,
K. Yamamoto,
S. Yokkaichi,
M. Yoshida
[show abstract]
[hide abstract]
ABSTRACT: An active target with plastic scintillating fibers has been
constructed. This active target serves as a production target of
hyperons, as well as a scattering target, and works as a 4π-detector
for charged particles. This system is designed for measurements of
hyperon-proton scattering for hyperon momenta of several hundred MeV/c.
A spectrometer system for the incident beam and outgoing particles of
the hyperon production reaction is linked with this target-detector in
order to provide triggers for the imaging device of this detector
system. As a control of this detector, the decay constant of the Σ
<sup>-</sup> hyperon has been evaluated
IEEE Transactions on Nuclear Science 05/2002; · 1.45 Impact Factor
-
H. Kohri,
S. Ajimura,
H. Hayakawa,
T. Kishimoto,
K. Matsuoka,
S. Minami,
Y. S. Miyake,
T. Mori,
K. Morikubo,
E. Saji, [......],
H. Outa,
L. Gan,
L. Tang,
L. Yuan,
J. Nakano,
T. Tamagawa,
K. Tanida,
R. Sawafta,
H. Tamura, H. Akikawa
[show abstract]
[hide abstract]
ABSTRACT: The Λ13C hypernucleus was studied by measuring γ rays in coincidence with the 13C(K-,π-) reaction. γ rays from the 1/2- and 3/2- states, which are the partners of the spin-orbit doublet states with a predominant configuration of [12Cg.s.(0+)⊗pΛ], to the ground state were measured. The splitting of the states was found to be ΔE(1/2--3/2-)=+152±54(stat)±36(syst) keV. This value is 20–30 times smaller than that of single particle states in nuclei around this mass region. The jΛ=lΛ-1/2[(p1/2)Λ] state appeared higher in energy, as in normal nuclei. The value gives new insight into the YN interaction. The excitation energies of the 1/2- and 3/2- states were obtained as 10.982±0.031(stat)±0.056(syst) and 10.830±0.031(stat)±0.056(syst) MeV, respectively. We also observed γ rays from the 3/2+ state, which has a [12C(2+)⊗sΛ] configuration, to the ground state in Λ13C. The excitation energy of the 3/2+ state was obtained as 4.880±0.010(stat)±0.017(syst) MeV. Nuclear γ rays with energies of 4.438 and 15.100 MeV had similar yields, which suggests that a quasifree knockout of a Λ particle is dominant in highly excited regions.
Phys. Rev. C. 02/2002; 65(3).
-
H Akikawa,
S Ajimura,
R E Chrien,
P M Eugenio,
G B Franklin,
J Franz,
L Gang,
K Imai,
P Khaustov,
M May, [......],
J Sasao,
R I Sawafta,
H Schmitt,
H Tamura,
L Tang,
K Tanida,
L Yuan,
S H Zhou,
L H Zhu,
X F Zhu
[show abstract]
[hide abstract]
ABSTRACT: With a germanium detector array (Hyperball), we observed two gamma-ray peaks corresponding to the two transitions (5/2(+)-->1/2(+) and 3/2(+)-->1/2(+)) in the (9)(Lambda)Be hypernucleus which was produced by the 9Be(K-,pi(-)) reaction. The energies of the gamma rays are 3029 +/- 2 +/- 1 keV and 3060 +/- 2 +/- 1 keV. The energy difference was measured to be 31.4(+2.5)(-3.6) keV, which indicates a very small Lambda-spin-dependent spin-orbit force between a Lambda and a nucleon. This is the smallest level splitting by far ever measured in a hypernucleus.
Physical Review Letters 02/2002; 88(8):082501. · 7.37 Impact Factor
-
H Takahashi,
J K Ahn, H Akikawa,
S Aoki,
K Arai,
S Y Bahk,
K M Baik,
B Bassalleck,
J H Chung,
M S Chung, [......],
D N Tovee,
N Ushida,
K Yamamoto,
N Yasuda,
J T Yang,
C J Yoon,
C S Yoon,
M Yosoi,
T Yoshida,
L Zhu
[show abstract]
[hide abstract]
ABSTRACT: A double-hyperfragment event has been found in a hybrid-emulsion experiment. It is identified uniquely as the sequential decay of ( 6)(LambdaLambda)He emitted from a Xi(-) hyperon nuclear capture at rest. The mass of ( 6)(LambdaLambda)He and the Lambda-Lambda interaction energy DeltaB(LambdaLambda) have been measured for the first time devoid of the ambiguities due to the possibilities of excited states. The value of DeltaB(LambdaLambda) is 1.01+/-0.20(+0.18)(-0.11) MeV. This demonstrates that the Lambda-Lambda interaction is weakly attractive.
Physical Review Letters 12/2001; 87(21):212502. · 7.37 Impact Factor
-
J. K. Ahn,
Y. Akaishi, H. Akikawa,
S. Aoki,
K. Arai,
S. Y. Bahk,
K. M. Baik,
B. Bassalleck,
J. H. Chung,
M. S. Chung, [......],
N. Ushida,
K. Yamamoto,
Y. Yamamoto,
N. Yasuda,
J. T. Yang,
C. J. Yoon,
C. S. Yoon,
M. Yosoi,
T. Yoshida,
L. Zhu
[show abstract]
[hide abstract]
ABSTRACT: A hybrid emulsion experiment E373 at KEK has been carried out to study doubly strange nuclear system. By the 8% data analysis of all, one twin single-Λ hypernuclei event and two events of double-Λ hypernucleus have been successfully detected. The twin single-Λ event is uniquely interpreted as Ξ−+14N→Λ5He+Λ5He+4He+n for the first time. In the first double-Λ hypernucleus event, “Demachi-Yanagi,” it is interpreted as Ξ−+12C→ΛΛ10Be∗ (or ΛΛ10Be∗)+t. The second double-Λ hypernucleus event, “NAGARA,” shows a clearly recognized topology and the interpretation is unique as Ξ−+12C→ΛΛ6He+4He+t, ΛΛ6He→Λ5He+π−+p, Λ5He→p+d+2n etc. By the preliminary result of the ΛΛ6He, the attractive ΛΛ interaction has been confirmed with the ΔBΛΛ ∼ 1 MeV. © 2001 American Institute of Physics.
AIP Conference Proceedings. 10/2001; 594(1):180-188.
-
J K Ahn,
S Ajimura, H Akikawa,
B Bassalleck,
A Berdoz,
D Carman,
R E Chrien,
C A Davis,
P Eugenio,
H Fischer, [......],
R A Schumacher,
M Sekimoto,
K Shileev,
Y Shimizu,
R Sutter,
T Tamagawa,
L Tang,
K Tanida,
K Yamamoto,
L Yuan
[show abstract]
[hide abstract]
ABSTRACT: An experiment demonstrating the production of double-Lambda hypernuclei in (K(-),K(+)) reactions on (9)Be was carried out at the D6 line in the BNL alternating-gradient synchrotron. The technique was the observation of pions produced in sequential mesonic weak decay, each pion associated with one unit of strangeness change. The results indicate the production of a significant number of the double hypernucleus (4)(double Lambda)H and the twin hypernuclei (4)(Lambda)H and (3)(Lambda)H. The relevant decay chains are discussed and a simple model of the production mechanism is presented. An implication of this experiment is that the existence of an S = -2 dibaryon more than a few MeV below the double Lambda mass is unlikely.
Physical Review Letters 10/2001; 87(13):132504. · 7.37 Impact Factor
-
K Tanida,
H Tamura,
D Abe, H Akikawa,
K Araki,
H Bhang,
T Endo,
Y Fujii,
T Fukuda,
O Hashimoto, [......],
J Sasao,
Y Sato,
S Satoh,
R I Sawafta,
M Sekimoto,
T Takahashi,
L Tang,
H H Xia,
S H Zhou,
L H Zhu
[show abstract]
[hide abstract]
ABSTRACT: We report on the first measurement of a hypernuclear gamma-transition probability. gamma rays emitted in the E2(5/2(+)-->1/2(+)) transition of (7)(Lambda)Li were detected by a large-acceptance germanium detector array (Hyperball), and the lifetime of the parent state ( 5/2(+)) was determined by the Doppler shift attenuation method. The obtained result, 5.8(+0.9)(-0.7)+/-0.7 ps, was then converted into the reduced transition probability [ B(E2)] to be B(E2;5/2(+)-->1/2(+)) = 3.6+/-0.5(+0.5)(-0.4) e(2) fm(4). Compared with the B(E2) of the corresponding E2(3(+)-->1(+)) transition in the 6Li nucleus, our result gives evidence that the size of the 6Li core in (7)(Lambda)Li is smaller than the 6Li nucleus in the free space.
Physical Review Letters 03/2001; 86(10):1982-5. · 7.37 Impact Factor
-
H Tamura,
K Tanida,
D Abe, H Akikawa,
K Araki,
H Bhang,
T Endo,
Y Fujii,
T Fukuda,
O Hashimoto, [......],
J Sasao,
Y Sato,
S Satoh,
R I Sawafta,
M Sekimoto,
T Takahashi,
L Tang,
H H Xia,
S H Zhou,
L H Zhu
[show abstract]
[hide abstract]
ABSTRACT: Using a large-acceptance germanium detector array (Hyperball), we have observed a spin-flip M1 gamma transition between the ground-state spin doublet of (7)(Lambda)Li (3/2(+)-->1/2(+)). The observed energy of 691.7+/-0.6(stat)+/-1.0(syst) keV provides crucial information on the strength of the spin-spin interaction between a Lambda and a nucleon. This is the first observation of well-identified hypernuclear gamma transitions using germanium detectors.
Physical Review Letters 06/2000; 84(26 Pt 1):5963-6. · 7.37 Impact Factor
-
J.K. Ahn, H. Akikawa,
J. Arvieux,
B. Bassalleck,
M.S. Chung,
H. En'yo,
T. Fukuda,
H. Funahashi,
S.V. Golovkin,
A.M. Gorin, [......],
A. Sato,
H.D. Sato,
K.S. Sim,
T. Tabaru,
F. Takeutchi,
P. Tlusty,
H. Torii,
K. Yamamoto,
S. Yokkaichi,
M. Yoshida
[show abstract]
[hide abstract]
ABSTRACT: An active target with plastic scintillating fibers has been
constructed. This active target served as a production target of
hyperons as well as a scattering target, and worked as a 4π-detector
for charged particles. This system is designed for measurement of
hyperon-proton scattering for the hyperon momenta of several hundred
MeV/c. A spectrometer system for the incident beam and outgoing
particles of the hyperon production reaction is linked with this
target-detector in order to provide triggers for the imaging device of
this detector system. The decay constant of the Σ hyperon has been
evaluated
Nuclear Science Symposium Conference Record, 2000 IEEE; 02/2000
-
H Takahashi, H Akikawa,
S Aoki,
A Ichikawa,
M Ieiri,
K Imai,
H Kanda,
Y Kondo,
K Nakazawa,
J.T Rhee,
J Tojo,
K Yamamoto,
T Yoshida
[show abstract]
[hide abstract]
ABSTRACT: Scintillating-fiber-block detectors have been constructed using square fibers for the KEK-PS E373 experiment, which searches for double-strangeness nuclei. The main aim of the detector is to measure the energies of protons and pions produced from decay of double- or single-hypernuclei using their ranges. It is also used to detect Λ hyperons or the H-dibaryon, and to make event selection. The performance of the detectors was studied with low-energy proton and pion beams as well as minimum-ionizing particles. The energy resolution determined by the range measurements was for 's and for protons. The excellent capability of π/p separation has been also demonstrated.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 483(3):689-697. · 1.21 Impact Factor
-
H Tamura,
K Tanida,
D Abe, H Akikawa,
K Araki,
H Bhang,
T Endo,
Y Fujii,
T Fukuda,
O Hashimoto, [......],
J Sasao,
Y Sato,
S Satoh,
R Sawafta,
M Sekimoto,
T Takahashi,
L Tang,
H.H Xia,
S.H Zhou,
L.H Zhu
[show abstract]
[hide abstract]
ABSTRACT: We report on the first observation of hypernuclear γ transitions using germanium detectors. Using a large-acceptance Ge detector system, we observed two γ transitions in Λ7Li, the spin-flip transition at 689±4keV and the transition at 2050±2 keV (preliminary). The strength of the ΛN spin-spin interaction is derived from the energy of the former transition. As for the latter transition, B(E2) was measured to be 3.9±0.6±0.4 e2fm4 (preliminary), which indicates a shrinkage of the nuclear size of Λ7Li from 6Li and confirms “glue-like role” of Λ.
Nuclear Physics A. 670:249-256.
-
M. Ukai,
S. Ajimura, H. Akikawa,
D. E. Alburger,
A. Banu,
R. E. Chrien,
G. B. Franklin,
J. Franz,
O. Hashimoto,
T. Hayakawa, [......],
B. P. Quinn,
A. Rusek,
Y. Sato,
R. Sutter,
H. Takahashi,
L. Tang,
H. Tamura,
K. Tanida,
L. Yuan,
S. H. Zhou
[show abstract]
[hide abstract]
ABSTRACT: In a γ-ray spectroscopy experiment with the (K-,π-) reaction on a 10B target, we have observed the 7/2+→5/2+ spin-flip M1 transition in Λ7Li via γ-γ coincidence with the 5/2+→1/2+E2 transition. This is the first successful γ-γ coincidence measurement for hypernuclei. The measured M1 γ-ray energy is 470.8±1.9(stat)±0.6(syst) keV. The spacing of the 7/2+,5/2+ doublet is consistently explained using the strengths of the spin-spin, Λ-spin-orbit, and tensor interactions obtained from previous γ-spectroscopy experiments.
Phys. Rev. C. 73(1).
-
-
D. Abe, H Akikawa,
K Araki,
H. Bhang,
T Endo,
Y Fujii,
T Fukuda,
O Hashimoto,
H Hotchi,
K Imai,
Y Kakiguchi,
J H Kim,
Y D Kim,
H Tamura,
K Tanida
-
K. Adcox,
S.S. Adler,
M. Aizama,
N.N. Ajitanand,
Y. Akiba, H. Akikawa,
J. Alexander,
A. Al-Jamel,
M. Allen,
G. Alley, [......],
S. Yokkaichi,
Y. Yokota,
S. Yoneyama,
G.R. Young,
I.E. Yushmanov,
W.A. Zajc,
C. Zhang,
L. Zhang,
Z. Zhang,
S. Zhou
[show abstract]
[hide abstract]
ABSTRACT: The PHENIX detector is designed to perform a broad study of A–A, p–A, and p–p collisions to investigate nuclear matter under extreme conditions. A wide variety of probes, sensitive to all timescales, are used to study systematic variations with species and energy as well as to measure the spin structure of the nucleon. Designing for the needs of the heavy-ion and polarized-proton programs has produced a detector with unparalleled capabilities. PHENIX measures electron and muon pairs, photons, and hadrons with excellent energy and momentum resolution. The detector consists of a large number of subsystems that are discussed in other papers in this volume. The overall design parameters of the detector are presented.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
