24 research outputs found
Neutron-proton analyzing power at 12 MeV and inconsistencies in parametrizations of nucleon-nucleon data
We present the most accurate and complete data set for the analyzing power
Ay(theta) in neutron-proton scattering. The experimental data were corrected
for the effects of multiple scattering, both in the center detector and in the
neutron detectors. The final data at En = 12.0 MeV deviate considerably from
the predictions of nucleon-nucleon phase-shift analyses and potential models.
The impact of the new data on the value of the charged pion-nucleon coupling
constant is discussed in a model study.Comment: Six pages, four figures, one table, to be published in Physics
Letters
A New Measurement of the 1S0 Neutron-Neutron Scattering Length using the Neutron-Proton Scattering Length as a Standard
The present paper reports high-accuracy cross-section data for the 2H(n,nnp)
reaction in the neutron-proton (np) and neutron-neutron (nn)
final-state-interaction (FSI) regions at an incident mean neutron energy of
13.0 MeV. These data were analyzed with rigorous three-nucleon calculations to
determine the 1S0 np and nn scattering lengths, a_np and a_nn. Our results are
a_nn = -18.7 +/- 0.6 fm and a_np = -23.5 +/- 0.8 fm. Since our value for a_np
obtained from neutron-deuteron (nd) breakup agrees with that from free np
scattering, we conclude that our investigation of the nn FSI done
simultaneously and under identical conditions gives the correct value for a_nn.
Our value for a_nn is in agreement with that obtained in pion-deuteron capture
measurements but disagrees with values obtained from earlier nd breakup
studies.Comment: 4 pages and 3 figure
Combined pre-supernova alert system with KamLAND and Super-Kamiokande
Preceding a core-collapse supernova (CCSN), various processes produce an increasing amount of neutrinos of all flavors characterized by mounting energies from the interior of massive stars. Among them, the electron antineutrinos are potentially detectable by terrestrial neutrino experiments such as KamLAND and Super-Kamiokande (SK) via inverse beta decay interactions. Once these pre-supernova (pre-SN) neutrinos are observed, an early warning of the upcoming CCSN can be provided. In light of this, KamLAND and SK, both located in the Kamioka mine in Japan, have been monitoring pre-SN neutrinos since 2015 and 2021, respectively. Recently, we performed a joint study between KamLAND and SK on pre-SN neutrino detection. A pre-SN alert system combining the KamLAND detector and the SK detector was developed and put into operation, which can provide a supernova alert to the astrophysics community. Fully leveraging the complementary properties of these two detectors, the combined alert is expected to resolve a pre-SN neutrino signal from a 15 M⊙ star within 510 pc of the Earth at a significance level corresponding to a false alarm rate of no more than 1 per century. For a Betelgeuse-like model with optimistic parameters, it can provide early warnings up to 12 hr in advance
NEUTRON-PROTON ANALYZING POWER DATA AT 7.6, 12.0, 14.1, 16.0, 18.5 MeV
Nous avons mesuré le pouvoir d'analyse neutron-proton Ay(θ) à 7.6, 12.0, 14.1, 16.0 et 18.5 MeV. Cette observable s'avère importante pour déterminer les déphasages 3P0, 1, 2 de la diffusion n-p. Nous comparons les données aux prédictions de 2 analyses en déphasages (dont l'une incorpore les effects BIC) et aux prédictions faites avec les potentiels de Paris et de Bonn.Neutron-Proton Ay(θ) measurements have been made at 7.6, 12.0, 14.1, 16.0, and 18.5 MeV. A sensitivity study establishes the importance of Ay(θ) in determining the 3P0, 1, 2 phase shifts in n-p scattering. The data are compared to the predictions of two phase-shift studies (one of which incorporates CIB effects), and the Paris and Bonn NN potenials