In Special Geometry there are two inequivalent notions of “Kodaira type” for a singular fiber: one associated with its local monodromy and one with its Hwang-Oguiso characteristic cycle. When the two Kodaira types are not equal the geometry is subtler and its deformation space gets smaller (“partially frozen” singularities). The paper analyzes the physical interpretation of the Hwang-Oguiso invariant in the context of 4d   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = 2 QFT and describes the surprising phenomena which appear when it does not coincide with the monodromy type. The Hwang-Oguiso multiple fibers are in one-to-one correspondence with the partially frozen singularities in M-theory compactified on a local elliptic K3: a chain of string dualities relates the two geometric set-ups. Paying attention to a few subtleties, this correspondence explains in purely geometric terms how the “same” Kodaira elliptic fiber may have different deformations spaces. The geometric computation of the number of deformations agrees with the physical expectations. At the end we briefly outline the implications of the Hwang-Oguiso invariants for the classification program of 4d   <math> <mi>N</mi> </math>  $$ \mathcal{N} $$  = 2 SCFTs.

China

Sergio Cecotti

Hwang-Oguiso invariants and frozen singularities in special geometry

γ emission probabilities from unbound states in $^{78,80}$Se, populated by a neutron-transfer reaction (<math><mi>d</mi><mo>,</mo><mi>p</mi></math>) on $^{77,79}$Se nuclei in inverse kinematics, were measured by directly detecting reaction residues. Assuming the spin distribution at the respective excitation energy of the unbound state, the cross-sections of the $^{79}$Se(<math><mi>n</mi><mo>,</mo><mi>γ</mi></math>)$^{80}$Se reaction were evaluated using the γ emission probabilities. The surrogate-ratio method with the experimental γ emission probabilities of $^{78,80}$Se was also employed to deduce the cross-sections of $^{79}$Se(<math><mi>n</mi><mo>,</mo><mi>γ</mi></math>) reaction by incorporating the theoretical evaluations of the neutron-capture reaction on the isomeric state in $^{77}$Se. Our two cross-sections are in good agreement with existing nuclear data compilations for the neutron-capture reaction on $^{79}$Se. The presented method contributes to the body of existing knowledge by providing approaches for determining the neutron capture cross-sections of radioactive nuclei at various neutron energies.

Japan

N. Imai

M. Dozono

S. Michimasa

T. Sumikama

S. Ota

S. Hayakawa

South Korea

J.W. Hwang

K. Iribe

C. Iwamoto

S. Kawase

K. Kawata

N. Kitamura

S. Masuoka

K. Nakano

P. Schrock

D. Suzuki

R. Tsunoda

K. Wimmer

D.S. Ahn

O. Beliuskina

N. Chiga

N. Fukuda

E. Ideguchi

K. Kusaka

H. Miki

H. Miyatake

D. Nagae

S. Ohmika

M. Ohtake

H.J. Ong

H. Otsu

H. Sakurai

H. Shimizu

Y. Shimizu

X. Sun

H. Suzuki

M. Takaki

H. Takeda

S. Takeuchi

T. Teranishi

Y. Watanabe

Y.X. Watanabe

K. Yako

H. Yamada

H. Yamaguchi

L. Yang

R. Yanagihara

Y. Yanagisawa

K. Yoshida

S. Shimoura

Neutron capture reaction cross-section of Se through the Se( ) Reaction in Inverse Kinematics

Detailed γ-ray spectroscopy of the exotic neon isotope $^{28}$Ne has been performed for the first time using the one-neutron removal reaction from $^{29}$Ne on a liquid hydrogen target at 240 MeV/nucleon. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for $^{28}$Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the <math><mi>N</mi><mo>=</mo><mn>20</mn></math> and <math><mi>N</mi><mo>=</mo><mn>28</mn></math> shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

H. Wang

M. Yasuda

Y. Kondo

T. Nakamura

United Kingdom

J.A. Tostevin

K. Ogata

T. Otsuka

Spain

A. Poves

N. Shimizu

France

N.L. Achouri

Lebanon

H. Al Falou

Germany

L. Atar

T. Aumann

H. Baba

K. Boretzky

C. Caesar

D. Calvet

H. Chae

A. Corsi

United States

H.L. Crawford

F. Delaunay

A. Delbart

Q. Deshayes

Hungary

Zs. Dombrádi

Netherlands

C. Douma

Z. Elekes

P. Fallon

Croatia

I. Gašparić

J.M. Gheller

J. Gibelin

A. Gillibert

M.N. Harakeh

A. Hirayama

C.R. Hoffman

M. Holl

A. Horvat

Á. Horváth

T. Isobe

J. Kahlbow

N. Kalantar-Nayestanaki

S. Kim

K. Kisamori

T. Kobayashi

D. Körper

S. Koyama

I. Kuti

V. Lapoux

Sweden

S. Lindberg

F.M. Marqués

J. Mayer

K. Miki

T. Murakami

M.A. Najafi

N. Nakatsuka

T. Nilsson

A. Obertelli

N.A. Orr

T. Ozaki

V. Panin

S. Paschalis

A. Revel

D. Rossi

A.T. Saito

T. Saito

M. Sasano

H. Sato

Y. Satou

H. Scheit

F. Schindler

M. Shikata

H. Simon

D. Sohler

O. Sorlin

L. Stuhl

M. Tanaka

M. Thoennessen

H. Törnqvist

Y. Togano

T. Tomai

J. Tscheuschner

J. Tsubota

T. Uesaka

Z. Yang

K. Yoneda

Intruder configurations in Ne at the transition into the island of inversion: Detailed structure study of Ne

Unbound states in <math><mmultiscripts><mrow><mi>C</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>17</mn></mrow></mmultiscripts></math> were investigated via one-neutron removal from a <math><mmultiscripts><mrow><mi>C</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>18</mn></mrow></mmultiscripts></math> beam at an energy of 245 MeV/nucleon on a carbon target. The energy spectrum of <math><mmultiscripts><mrow><mi>C</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>17</mn></mrow></mmultiscripts></math>, above the single-neutron decay threshold, was reconstructed using invariant mass spectroscopy from the measured momenta of the <math><mmultiscripts><mrow><mi>C</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>16</mn></mrow></mmultiscripts></math> fragment and neutron, and was found to exhibit resonances at <math><msub><mrow><mi>E</mi></mrow><mrow><mtext>r</mtext></mrow></msub></math>=0.52(2), 0.77(2), 1.36(1), 1.91(1), 2.22(3) and 3.20(1) MeV. The resonance at <math><msub><mrow><mi>E</mi></mrow><mrow><mtext>r</mtext></mrow></msub></math>=0.77(2) MeV [<math><msub><mrow><mi>E</mi></mrow><mrow><mi>x</mi></mrow></msub></math>=1.51(3) MeV] was provisionally assigned as the second <math><mn>5</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msup></math> state. The two resonances at <math><msub><mrow><mi>E</mi></mrow><mrow><mtext>r</mtext></mrow></msub></math>=1.91(1) and 3.20(1) MeV [<math><msub><mrow><mi>E</mi></mrow><mrow><mi>x</mi></mrow></msub></math>=2.65(2) and 3.94(2) MeV] were identified, through comparison of the energies, cross sections and momentum distributions with shell-model and eikonal reaction calculations, as p-shell hole states with spin-parities <math><mn>1</mn><mo>/</mo><msubsup><mrow><mn>2</mn></mrow><mrow><mn>1</mn></mrow><mrow><mo>−</mo></mrow></msubsup></math> and <math><mn>3</mn><mo>/</mo><msubsup><mrow><mn>2</mn></mrow><mrow><mn>1</mn></mrow><mrow><mo>−</mo></mrow></msubsup></math>, respectively. A detailed comparison was made with the results obtained using a range of shell-model interactions. The YSOX shell-model Hamiltonian, the cross-shell part of which is based on the monopole-based universal interaction, was found to provide a very good description of the present results and those for the neighbouring odd-A carbon isotopes – in particular for the negative parity cross-shell states.

P. Doornenbal

N. Inabe

D. Kameda

D. Kanno

N. Kobayashi

T. Kubo

S. Leblond

J. Lee

R. Minakata

T. Motobayashi

D. Murai

K. Muto

T. Nakashima

A. Navin

S. Nishi

S. Ogoshi

K. Takahashi

R. Tanaka

A.G. Tuff

M. Vandebrouck

Unbound states in C and - Shell-model Interactions

Corrigendum to “Single-neutron knockout from 20 C and the structure of 19 C” [Phys. Lett. B 769 (2017) 503–508]

The low-lying unbound level structure of the halo nucleus 19 C has been investigated using single-neutron knockout from 20 C on a carbon target at 280 MeV/nucleon. The invariant mass spectrum, derived from the momenta of the forward going beam velocity 18 C fragment and neutrons, was found to be dominated by a very narrow near threshold ( Erel=0.036(1) MeV) peak. Two less strongly populated resonance-like features were also observed at Erel=0.84(4)Â andÂ 2.31(3) MeV, both of which exhibit characteristics consistent with neutron p -shell hole states. Comparisons of the energies, measured cross sections and parallel momentum distributions to the results of shell-model and eikonal reaction calculations lead to spin-parity assignments of 5/21+ and 1/21â for the levels at Ex=0.62(9)Â andÂ 2.89(10) MeV with Sn=0.58(9) MeV. Spectroscopic factors were also deduced and found to be in reasonable accord with shell-model calculations. The valence neutron configuration of the 20 C ground state is thus seen to include, in addition to the known 1s1/22 component, a significant 0d5/22 contribution. The level scheme of 19 C, including significantly the 1/21â cross-shell state, is well accounted for by the YSOX shell-model interaction developed from the monopole-based universal interaction.

Single-neutron knockout from 20 C and the structure of 19 C

The interaction cross sections ( ÏI ) of the very neutron-rich carbon isotopes 19 C, 20 C and 22 C have been measured on a carbon target at 307, 280, and 235 MeV/nucleon, respectively. A ÏI of 1.280Â±0.023Â b was obtained for 22 C, significantly larger than for 19,20 C, supporting the halo character of 22 C. A 22 C root-mean-squared matter radius of 3.44Â±0.08Â fm was deduced using a four-body Glauber reaction model. This value is smaller than an earlier estimate (of 5.4Â±0.9Â fm ) derived from a ÏI measurement on a hydrogen target at 40 MeV/nucleon. These new, higher-precision ÏI data provide stronger constraints for assessing the consistency of theories describing weakly bound nuclei.

Interaction cross section study of the two-neutron halo nucleus 22 C

One-neutron knockout from 24 O leading to the first excited state in 23 O has been measured for a proton target at a beam energy of 62 MeV/nucleon. The decay energy spectrum of the neutron unbound state of 23 O was reconstructed from the measured four momenta of the 22 O fragment and emitted neutron. A sharp peak was found at Edecay=50±3 keV , corresponding to an excited state in 23 O at 2.78±0.11 MeV , as observed in previous measurements. The longitudinal momentum distribution for this state was consistent with d -wave neutron knockout, providing support for a Jπ assignment of 5/2+ . The associated spectroscopic factor was deduced to be C2S(0d5/2)=4.1±0.4 by comparing the measured cross section ( σ−1nexp=61±6 mb ) with a distorted wave impulse approximation calculation. Such a large occupancy for the neutron 0d5/2 orbital is in line with the N=16 shell closure in 24 O.