Measurement of differential cross sections for Σ⁺p elastic scattering in the momentum range 0.44–0.80 GeV/c

クォーク間の「芯」をとらえた --物質が安定して存在できる理由の理解に貢献--. 京都大学プレスリリース. 2022-09-05.We performed a novel Σ⁺+p scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 Σ⁺+p elastic scattering events were identified from 4.9 × 10⁷ tagged Σ⁺+ particles in the Σ⁺+ momentum range 0.44-0.80 GeV/c. The differential cross sections of the Σ⁺+p elastic scattering were derived with much better precision than in previous experiments. The obtained differential cross sections were approximately 2 mb/sr or less, which were not as large as those predicted by the fss2 and FSS models based on the quark cluster model in the short-range region. By performing phase-shift analyses for the obtained differential cross sections, we experimentally derived the phase shifts of the ³S₁ and ¹P₁ channels for the first time. The phase shift of the ³S₁ channel, where a large repulsive core was predicted owing to the Pauli effect between quarks, was evaluated as 20° < |δ₃S₁| < 35°. If the sign of δ₃S₁ is assumed to be negative, the interaction in this channel is moderately repulsive, as the Nijmegen extended-sort-core models predicted

Σp\Sigma p scattering experiment at J-PARC – results of commissioning run

International audienceThe Σp scattering experiment has just been started at J-PARC this year (2018). We made ”Σ beam factory” a reality where a beam with an intensity of more than 5 × 105 Σ− beam per day could be produced by using 20 M/spill π− beam. The CATCH system, which is a dedicated system to detect recoil proton from the Σp scattering, operated stably under the high counting rate, and its successful operation was confirmed by identifying the pp scattering events in J-PARC. In the June beam time, the production run of the Σ− p scattering was carried out for 2 days, which was just 10% of the requested beam time. The remaining beam time of the Σ− p channel and the Σ+ p channel will take place in the spring of 2019

Operation of Multi-MPPC System for Cylindrical Scintillation Fiber Tracker

International audienceAlthough 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

Observation of Coulomb-Assisted Nuclear Bound State of Ξ\Xi−^−–14^{14}N System

In an emulsion-counter hybrid experiment performed at J-PARC, a $\Xi^-$ absorption event was observed which decayed into twin single-$\Lambda$ hypernuclei. Kinematic calculations enabled a unique identification of the reaction process as $\Xi^{-} + ^{14}$N$\ \rightarrow\ ^{10}_\Lambda$Be + $^5_\Lambda$He. For the binding energy of the $\Xi^{-}$ hyperon in the $\Xi^-$-$^{14}$N system a value of $1.27 \pm 0.21$ MeV was deduced. The energy level of $\Xi^-$ is likely a nuclear $1p$ state which indicates a weak ${\Xi}N$-$\Lambda\Lambda$ coupling

Study of Λ\Lambda Identification Method by the π−p→K0Λ\pi ^{ - }p \to K^{0}\Lambda Reaction for a Λp\Lambda p Scattering Experiment at J-PARC

International audienceThe $\pi ^{ - }p \to K^{0}\Lambda$ reaction is an important elementary process to produce $\Lambda$ from a proton target and is a key for a $\Lambda p$ scattering experiment where the momentum of $\Lambda$ should be tagged from the missing momentum of the $(\pi ^{ - },K^{0})$ reaction. However, the $(\pi ^{ - },K^{0})$ spectroscopy method has not been established yet due to the difficulty of the K^0 detection. Therefore, we have proposed a new K^0 detection method where $\pi ^{ + }$ and $i^{ - }$ from the K^0 decay are measured by a forward magnetic spectrometer and a detector cluster surrounding the target, respectively. The feasibility of the K^0 detection method was confirmed by analyzing the J-PARC E40 data taken with such a detector system. In the analysis, $\Lambda$’s were successfully identified in the missing mass spectrum of the $\pi ^{ - }p \to K^{0}X$ reaction

Measurement of differential cross sections for Σ+p\Sigma^+p elastic scattering in the momentum range 0.44-0.80 GeV/c

We performed a novel $\Sigma^+ p$ scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 $\Sigma^+ p$ elastic scattering events were identified from $4.9 \times 10^7$ tagged $\Sigma^+$ particles in the $\Sigma^+$ momentum range 0.44 -- 0.80 GeV/$c$. The differential cross sections of the $\Sigma^+ p$ elastic scattering were derived with much better precision than in previous experiments. The obtained differential cross sections were approximately 2 mb/sr or less, which were not as large as those predicted by the fss2 and FSS models based on the quark cluster model in the short-range region. By performing phase-shift analyses for the obtained differential cross sections, we experimentally derived the phase shifts of the $^3 S_1$ and $^1 P_1$ channels for the first time. The phase shift of the $^3 S_1$ channel, where a large repulsive core was predicted owing to the Pauli effect between quarks, was evaluated as $20^\circ<|\delta_{^3S_1}|<35^\circ$. If the sign of $\delta_{^3S_1}$ is assumed to be negative, the interaction in this channel is moderately repulsive, as the Nijmegen extended-sort-core models predicted

Establishment of a modern experimental technique of a Σp\Sigma p scattering experiment at J-PARC

International audienceA 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

Precise measurement of differential cross sections of the Σ−p→Λn\Sigma^-p \to \Lambda n reaction in momentum range 470-650 MeV/c/c

International audienceThe differential cross sections of the Σ-p→Λn reaction were measured accurately for the Σ- momentum (pΣ) 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 470&lt;pΣ(MeV/c)&lt;550 and 550&lt;pΣ(MeV/c)&lt;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

Measurement of the differential cross sections of the Σ−p\Sigma^-p elastic scattering in momentum range 470 to 850 MeV/c

International audienceA high statistics Σp scattering experiment is performed at the J-PARC Hadron Experimental Facility. Momentum-tagged Σ−s running in a liquid hydrogen target are accumulated by detecting the π−p→K+Σ− reaction with a high intensity π− beam of 20 M/spill. The differential cross sections of the Σ−p elastic scattering were derived with a drastically improved accuracy by identifying approximately 4500 events from 1.72×107Σ−. The derived differential cross section shows a clear forward-peaking angular distribution for a Σ− momentum range from 470 to 850 MeV/c. The accurate data will impose a strong constraint on the theoretical models of the baryon-baryon interactions