Search

The differential cross sections of the Σ^{-}p→Λn reaction were measured accurately for the Σ^{-} momentum (p_{Σ}) ranging from 470 to 650 MeV/c at the J-PARC Hadron Experimental Facility. Precise angular information about the Σ^{-}p→Λn reaction was obtained for the first time by detecting approximately 100 reaction events at each angular step of Δcosθ=0.1. The obtained differential cross sections show a slightly forward-peaking structure in the measured momentum regions. The cross sections integrated for -0.7≤cosθ≤1.0 were obtained as 22.5±0.68 [statistical error(stat.)] ±0.65 [systematic error(syst.)] mb and 15.8±0.83(stat)±0.52(syst) mb for 470p_{Σ}(MeV/c)550 and 550p_{Σ}(MeV/c)650, respectively. These results show a drastic improvement compared with past measurements of the hyperon-proton scattering experiments. They will play essential roles in updating the theoretical models of the baryon-baryon interactions.

A new hyperon-proton scattering experiment, dubbed J-PARC E40, was performed to measure differential cross sections of the Σ+p, Σ−p elastic scatterings and the Σ−p → Λn scattering by identifying a lot of Σ particles in the momentum ranging from 0.4 to 0.8 GeV/c produced by the π±p → K+Σ± reactions. We successfully measured the differential cross sections of these three channels with a drastically improved accuracy with a fine angular step. These new data will become important experimental constraints to improve the theories of the two-body baryon-baryon interactions. Following this success, we proposed a new experiment to measure the differential cross sections and spin observables by using a highly polarized Λ beam for providing quantitative information on the ΛN interaction. The results of three Σp channels and future prospects of the Λp scattering experiment are described.

International audience; A part of the experiment was performed in 2018 and 2019 in J-PARC. As a result of analyzing the collected data, the \(\Sigma ^{ - }\) production and the \(\Sigma ^{ - }p\) scattering reaction have been identified. It means that our new measurement and analysis method are successfully working well. Analysis for deriving the differential cross section of the \(\Sigma p\) scattering is on going.

International audience; Although more detailed analysis for deriving the cross section of \(\Sigma p\) scattering is necessary to derive the cross section of \(\Sigma p\) scattering, we have confirmed that CFT has enough angular resolution of tracking and energy resolution in order for the identification of the scattering events and particles.

International audience; In order to test theoretical frameworks of the baryon–baryon (BB) interactions and to confirm the “Pauli effect between quarks” for the first time, we have proposed an experiment (J-PARC E40) to measure low-energy hyperon–proton scattering cross sections of the Σ^+p, Σ^−p elastic scatterings and the Σ^−p → Λn inelastic scattering in the momentum range of 400 < p (MeV/c) < 700 in the laboratory system. Experimentally, we detect two successive reactions of the Σ production (π^±p → K^+Σ^±) and the Σp scattering (Σp → Σp) in the same liquid hydrogen target. The former is measured with two magnetic spectrometers, and the latter with a scattered proton detector (CATCH). By using a high intensity π beam, we estimate that more than 10,000 scattering events can be identified. In this experiment, we aim to provide good quality scattering data to test the theoretical models of the BB interaction.

The Θ(+) pentaquark baryon was searched for via the π(-)p→K(-)X reaction with a missing mass resolution of 1.4 MeV/c(2) (FWHM) at the Japan Proton Accelerator Research Complex (J-PARC). π(-) meson beams were incident on the liquid hydrogen target with a beam momentum of 1.92 GeV/c. No peak structure corresponding to the Θ(+) mass was observed. The upper limit of the production cross section averaged over the scattering angle of 2° to 15° in the laboratory frame is obtained to be 0.26 μb/sr in the mass region of 1.51-1.55 GeV/c(2). The upper limit of the Θ(+) decay width is obtained to be 0.72 and 3.1 MeV for J(Θ)(P)=1/2(+) and J(Θ)(P)=1/2(-), respectively, using the effective Lagrangian approach.

The Theta+ was searched for via the K+p -> pi+X reaction using the 1.2 GeV/c K+ beam at the K6 beam line of the KEK-PS 12 GeV Proton Synchrotron. In the missing mass spectrum of the K+p -> pi+X reaction, no clear peak structure was observed. Therefore a 90 % C.L. upper limit of 3.5 ub/sr was derived for the differential cross section averaged over 2degree to 22degree in the laboratory frame of the K+p -> pi+Theta+ reaction. This upper limit is much smaller than the theoretical calculation for the t-channel process where a K0* is exchanged. From the present result, either the t-channel process is excluded or the coupling constant of g_{K*N\Theta} is quite small.

Occipitofrontal circumference (OFC) is one of the few physical findings in autism that varies significantly from the norm and is distinct and measurable. As part of a study of genetic heterogeneity of autism, we scrutinized data from a large sample of patients with idiopathic autism (N = 137), using OFC as the categorizing variable. The OFC standard deviation (OFCSD) values of the autistic propositi (0.61+/-1.6) varied significantly from that of the normal population (0.0+/-1.0), (P0.001). Comparison of the macrocephalic (OFCSD2.0, N = 32) with the normocephalic individuals (-2 SDOFCSD+2 SD, N = 95) showed no significant differences in sex ratio, morphological status, IQ, seizure prevalence, or recurrence risks. The macrocephalic individuals were slightly less apt than those with normocephaly to have a family history of Attention Deficit Hyperactivity Disorder (ADHD) (P0.05). Each clinical subgroup of autism propositi, defined on the basis of phenotypic status, type of onset, seizure history, or IQ, had a higher than normal mean OFC indicating that macrocephaly is an independent clinical trait in autism. As in the non-autistic population, macrocephaly was highly familial with 45% of the macrocephalic and 37% of the normocephalic propositi having at least one macrocephalic parent. Microcephaly, however, was an independent significant variable that predicted the presence of other phenotypic or genetic traits and outcome. The microcephalic patients were more likely to have abnormal physical morphology, structural brain malformations, lower IQ, and seizures. Their sex ratio was closer to normal, and their relatives had a higher incidence of seizures.