Search For H-dibaryon Research Articles

High resolution spectroscopy of the “ΣN cusp” by using the d(K−, π−) reaction

We present a new proposal, J-PARC E90, to measure a missing-mass spectrum near the ΣN threshold for the d(K−, π−) reactions at 1.4 GeV/c. While many previous experiments support apparent enhancement near the ΣN thresh-old, the dynamical origin of this so-called “ΣN cusp” remains yet unsolved. The enhancement suggests either a cusp structure or a weakly bound state. One of the keys to making it clear is improving the missing-mass resolution and statistics. Our new experiment can achieve the missing-mass resolution of 0.4 MeV in σ using the K1.8 beam line and S-2S spectrometers at J-PARC. Further-more, we can suppress quasi-free background processes with the time projection chamber (HypTPC), which operated nicely for the H-dibaryon search experi-ment (J-PARC E42). The J-PARC E90 aims to extract the scattering length of the ΣN system with isospin T = 1/2 and spin-triplet channels.

High-rate performance of a time projection chamber for an H-dibaryon search experiment at J-PARC

Abstract 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/CH 4 gas mixture (90/10) without a magnetic field. The spatial resolutions on the pad plane are measured to be 400– 700 μ m , which correspond to 230– 300 μ m in a magnetic field of 1 T. We confirmed high tracking capability at beam rates of up to 1 MHz.

Development of a threshold aerogel Cherenkov detector for [formula omitted] separation in the H-dibaryon search at J-PARC

We have developed a new threshold Cherenkov detector for online triggering in the H-dibaryon search experiment at the K1.8 beam line at J-PARC. Silica aerogel radiators with a refractive index of n=1.04 will cover an effective area of 550 × 220 mm2. The Cherenkov detector will be placed in a high magnetic field between two spectrometer magnets. Three prototypes and a real-size mockup module have been tested using pions and protons from photoproduction at SPring-8. For momentum ranging from 1.0 to 1.1 GeV ∕c, a suppression factor of 103 could be achieved for pions, with a factor of 10−2 for proton misidentification.

Measurements of ˄˄ correlation function in heavy-ion collisions at RHIC

The information on the hyperon-hyperon interaction is crucial for our understanding of baryon-baryon interactions in hot and dense medium from high-energy nuclear collisions. In this proceeding we discuss the measurement of the ˄˄ correlation function from the STAR experiment and the status of an H-dibaryon search based on this measurement.

Development of a prototype GEM TPC with a gating grid for an H-dibaryon search experiment at J-PARC

We have developed a prototype TPC (Time Projection Chamber) based on GEMs (Gas Electron Multipliers) with a gating grid for an H-dibaryon search experiment at J-PARC. To investigate its performance, we conducted laboratory tests and a beam test with two kinds of gases, Ar–CH4 (90:10) and Ar–CF4 (95:5), where the former is mainly used for the tests. The hit detection efficiency per pad row was measured to be 98% at the beam rate up to 5×105cpscm2 (counts per second), and 90% at the rate of 3×106cps/cm2. Based on the measured horizontal resolution of 0.19–0.46mm at the drift length of 5–20cm, the horizontal position resolution of better than 0.3mm is estimated in 1T magnetic field for the final experiment. The ion backflow fraction was measured to be 5% and reduced up to 3% by tuning the GEM voltage configuration, at the gain of 1.6×104. The horizontal position distortion due to ion backflow in the gate operation was suppressed within 0.2mm at the beam rates up to 5×105cps/cm2, corresponding to the ion backflow up to 2.7×108s−1cm−1. On the other hand, the distortion with the gate open was measured to be 1.3mm, corresponding to the backflow of 1.3×109s−1cm−1. The distortion in the final experiment is estimated to be 0.3±0.2mm, within the requirement of 1mm. The GEMs have been operated continuously for a comparable period of the final experiment, with average energy deposit rates per unit GEM area of 30 times as high as that expected for the experiment.

Development of a GEM-TPC for H-dibaryon search experiment at J-PARC

We have developed a GEM-TPC for H-dibaryon search at J-PARC E42, which reconstructs charged particles from the H-dibaryon decay in (K−,K+) reaction. Since 106 cps/cm2 K− beams are injected to the TPC, GEMs and a gating grid are adopted to suppress positive ion feedback. The TPC is also designed to have good position resolutions corresponding to the ΛΛ invariant mass resolution of a few MeV/c2. The design of the E42 TPC, and performance evaluations of a prototype TPC are described.

Search for H-dibaryon at J-PARC with a Large Acceptance TPC

H-dibaryon has been predicted as a stable 6-quark color-singlet state. It has been searched for by many experiments but has never been discovered. Recent lattice QCD calculations predict H-dibaryon as a weakly bound or a resonant state close to the  threshold. E224 and E522 experiments at KEK observed peaks in  invariant mass spectra near the threshold in (K - , K + ) reactions, which were statistically not significant. Therefore, we proposed a new experiment E42 at J-PARC. It will measure decay products of  and   p in a (K - , K + ) reaction. We design a large acceptance spectrometer based on a Time Projection Chamber (TPC) immersed in a dipole magnetic field. The TPC surrounds a target to cover nearly 4 acceptance, and accepts K - beams up to 10 6 counts per second. To suppress drift field distortion at high beam rates, we adopt Gas Electron Multipliers (GEMs) for electron amplification and a gating grid. We show an overview of the experiment, the design of the spectrometer, and the R&D status of the TPC prototype.

Study of ΛΛ correlations and search for H-dibaryon with STAR detector at RHIC

The production of large number of multi-strange hyperons per central nucleus–nucleus collision at RHIC allows us to study hyperon–hyperon interactions through measurement of two particle correlation and search for exotic particles like H-dibaryons. In this article, we discuss analysis details for the measurement of ΛΛ correlation in Au+Au collisions at sNN=200GeV. Fits to different potential models are discussed and the extracted scattering length and effective range are also presented. Finally, we report the progress in searching for the H-dibaryon, a six quark state Jaffe (1977) [1], using its weak decay Λpπ from Au+Au collisions at sNN=200GeV.

Strange particle production and an H-dibaryon search in p-A collisions at the AGS

Strange particle production and an H-dibaryon search in p-A collisions at the AGS