We present a new measurement of the Λ4H hypernuclear lifetime using in-flight K− + 4He → Λ4H + π0 reaction at the J-PARC hadron facility. We demonstrate, for the first time, the effective selection ...of the hypernuclear bound state using only the γ-ray energy decayed from π0. This opens the possibility for a systematic study of isospin partner hypernuclei through comparison with data from (K−, π−) reaction. As the first application of this method, our result for the Λ4H lifetime, τ(HΛ4)=206±8(stat.)±12(syst.)ps, is one of the most precise measurements to date. We are also preparing to measure the lifetime of the hypertriton (Λ3H) using the same setup in the near future.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Superconducting Kaon Spectrometer (SKS) system has been constructed at the J-PARC K1.8 beam line. With all detectors being operational since October, 2009, a series of commissioning data have ...been taken successfully such that the SKS system performance could be assessed. In particular, the (π−, p) elastic scattering and the P(π−, K+)Σ− reaction were used for this purpose with the beam momentum of 0.5 GeV/c and 1.25 GeV/c, respectively. The measured resolution of Σ− missing mass was 1.7 MeV/c2(FWHM) corresponding to 3.3 MeV/c (FWHM) momentum resolution of the SKS system. Overall, the SKS system showed an expected performance which proved the readiness for the first physics experiment at the K1.8 beam line.
We have developed a gas electron multiplier (GEM)-based time projection chamber (TPC) for the H-dibaryon search experiment at J-PARC. High-rate K− beam particles enter a TPC gas volume of ...approximately 0.2 m3, in a direction perpendicular to the electric field. A long-rectangular hollow section is located inside the TPC volume to accommodate a diamond target. We commissioned the TPC using 230-MeV protons with beam rates of up to 1 MHz. The TPC data acquisition system collected 5768 pad signals in full readout mode, with almost 100% efficiency, at a preset trigger rate of 230 Hz. We operated the TPC in an Ar/CH4 gas mixture (90/10) without a magnetic field. The spatial resolutions on the pad plane are measured to be 400–700μm, which correspond to 230–300μm in a magnetic field of 1 T. We confirmed high tracking capability at beam rates of up to 1 MHz.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract
The J-PARC E16 experiment measures mass spectra of low-mass vector mesons,
ρ
,
ω
, and
ϕ
, in nuclei via
e
+
e
-
decays. Vector mesons are produced in
p
A reactions. A spectrometer with ...a large acceptance and a high-intensity beam up to 1
× 10
10
protons per ∼2-sec duration pulse are utilized to collect a sufficient number
of vector mesons. We have developed a spectrometer, which has two types of electron
identification detectors: a hadron blind detector (HBD) and a lead-glass calorimeter.
Commissioning runs have been performed at the J-PARC high-momentum beam line. The HBD
successfully observed on average 11 ± 1 photoelectrons for an incident electron. We achieved
the pion rejection of 0.9 ± 0.2% with the electron detection efficiency of 61 ± 4% for
the HBD, which was consistent of the expected performance.
We have proposed an experiment for studying charmed baryons via the p( pi super(-),D super(*-))p( pi -,D*-) reaction at the J-PARC high-momentum beam line. Charmed baryons will be measured by a ...missing mass method. Scattered D super(*-)D*- will be reconstructed by detecting its decay chain of D*- arrow right Dmacr0 pi - arrow right K+ pi - pi -. We designed a Ring Imaging Cherenkov (RICH) counter with two radiators, aerogel and C sub(4)F sub(10)C4F10 of refractive indices 1.04 and 1.00137, respectively, in order to identify pions and kaons in a wide momentum range from 2 to 16 GeV/c . Spherical mirrors will be used to focus Cherenkov photons to the photon sensor alloys. The performance of the designed RICH counter is evaluated by a Monte-Carlo simulation based on GEANT4. Detection efficiency for scattered particles averaged over pi and K is found to be 99%. Wrong particle identification ratios of pions and protons to kaons are 0.1% and 0.14%, respectively. The background level in the inclusive p( pi super(-),D super(*-))p( pi -,D*-) spectrum increases only 5% due to the wrong identifications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A high statistics ∑p scattering experiment has been performed at the K1.8 beamline in the J-PARC Hadron Experimental Facility. Data for momentum-tagged ∑− beam running in a liquid hydrogen target ...were accumulated by detecting the π−p→K+∑− reaction with a high intensity π− beam of 20 M/spill. The number of the Σ− beam was about 1.7 × 107 in total. The ∑−ρ elastic scattering and the ∑−p → Λn inelastic scattering events were successfully observed with about 100 times larger statistics than that in past experiments.
The heavy quark baryon spectroscopy is a key way to understand what the building block of hadrons is. The diquark correlation which is expectedly an essential degree of freedom to describe the hadron ...structure can be investigated from the spectroscopy of charmed baryons. An experiment to observe and investigate the charmed baryons was proposed at the J-PARC high- momentum beam line. The missing mass spectroscopy experiment via the π− p → Y*+c D*− reaction at 20 GeV/c will be performed for the systematic measurement of the excitation energy, the production rates and the decay products of charmed baryons. In addition, the properties of the strange baryons can also be measured systematically by using the same experimental setup. From the systematic study of both charmed baryons and hyperons, the diquark correlation can be revealed which is expectedly an essential degree of freedom to describe the hadron structure.
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