37 research outputs found
Cross-Section Measurement of Virtual Photoproduction of Iso-Triplet Three-Body Hypernucleus, ⋀nn
Missing-mass spectroscopy with the 3H(e, e′K+) reaction was carried out at Jefferson Lab’s (JLab) Hall A in Oct–Nov, 2018. The differential cross section for the 3H(γ∗, K+)Λnn was deduced at ω = Ee − Ee′ = 2.102 GeV and at the forward K+-scattering angle (0° ≤ θγ∗K ≤ 5°) in the laboratory frame. Given typical predicted energies and decay widths, which are (BΛ, Γ) = (−0.25, 0.8) and (−0.55, 4.7) MeV, the cross sections were found to be 11.2 ± 4.8(stat.)+4.1−2.1(sys.) and 18.1 ± 6.8(stat.)+4.2−2.9(sys.) nb/sr, respectively. The obtained result would impose a constraint for interaction models particularly between Λ and neutron by comparing to theoretical calculations
Revealing the short-range structure of the "mirror nuclei" H and He
When protons and neutrons (nucleons) are bound into atomic nuclei, they are
close enough together to feel significant attraction, or repulsion, from the
strong, short-distance part of the nucleon-nucleon interaction. These strong
interactions lead to hard collisions between nucleons, generating pairs of
highly-energetic nucleons referred to as short-range correlations (SRCs). SRCs
are an important but relatively poorly understood part of nuclear structure and
mapping out the strength and isospin structure (neutron-proton vs proton-proton
pairs) of these virtual excitations is thus critical input for modeling a range
of nuclear, particle, and astrophysics measurements. Hitherto measurements used
two-nucleon knockout or ``triple-coincidence'' reactions to measure the
relative contribution of np- and pp-SRCs by knocking out a proton from the SRC
and detecting its partner nucleon (proton or neutron). These measurementsshow
that SRCs are almost exclusively np pairs, but had limited statistics and
required large model-dependent final-state interaction (FSI) corrections. We
report on the first measurement using inclusive scattering from the mirror
nuclei H and He to extract the np/pp ratio of SRCs in the A=3 system.
We obtain a measure of the np/pp SRC ratio that is an order of magnitude more
precise than previous experiments, and find a dramatic deviation from the
near-total np dominance observed in heavy nuclei. This result implies an
unexpected structure in the high-momentum wavefunction for He and H.
Understanding these results will improve our understanding of the short-range
part of the N-N interaction
ATHENA detector proposal - a totally hermetic electron nucleus apparatus proposed for IP6 at the Electron-Ion Collider
ATHENA has been designed as a general purpose detector capable of delivering the full scientific scope of the Electron-Ion Collider. Careful technology choices provide fine tracking and momentum resolution, high performance electromagnetic and hadronic calorimetry, hadron identification over a wide kinematic range, and near-complete hermeticity.This article describes the detector design and its expected performance in the most relevant physics channels. It includes an evaluation of detector technology choices, the technical challenges to realizing the detector and the R&D required to meet those challenges
ATHENA detector proposal — a totally hermetic electron nucleus apparatus proposed for IP6 at the Electron-Ion Collider
ATHENA has been designed as a general purpose detector capable of delivering the full scientific scope of the Electron-Ion Collider. Careful technology choices provide fine tracking and momentum resolution, high performance electromagnetic and hadronic calorimetry, hadron identification over a wide kinematic range, and near-complete hermeticity. This article describes the detector design and its expected performance in the most relevant physics channels. It includes an evaluation of detector technology choices, the technical challenges to realizing the detector and the R&D required to meet those challenges
The cross-section measurement for the ³H(e, e′K⁺)nnΛ reaction
電荷をもたない奇妙な原子核の高精度探索 --ラムダ-中性子-中性子の三体系--. 京都大学プレスリリース. 2022-03-08.The small binding energy of the hypertriton leads to predictions of the non-existence of bound hypernuclei for isotriplet three-body systems such as nnΛ. However, invariant mass spectroscopy at GSI has reported events that may be interpreted as the bound nnΛ state. The nnΛ state was sought by missing-mass spectroscopy via the (e, e′K⁺) reaction at Jefferson Lab’s experimental Hall A. The present experiment has higher sensitivity to the nnΛ-state investigation in terms of better precision by a factor of about three. The analysis shown in this article focuses on the derivation of the reaction cross-section for the ³H(γ*, K⁺)X reaction. Events that were detected in an acceptance, where a Monte Carlo simulation could reproduce the data well (), were analyzed to minimize the systematic uncertainty. No significant structures were observed with the acceptance cuts, and the upper limits of the production cross-section of the nnΛ state were obtained to be 21 and at the confidence level when theoretical predictions of (−BΛ, Γ) = (0.25, 0.8) MeV and (0.55, 4.7) MeV, respectively, were assumed. The cross-section result provides valuable information for examining the existence of nnΛ