Bulletin of the American Physical Society
4th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 59, Number 10
Tuesday–Saturday, October 7–11, 2014; Waikoloa, Hawaii
Session FL: Mini-Symposium on Nuclear Matter in Neutron Stars III (Experimental Prospects on Strangeness) |
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Chair: Satoshi Nakamura, Tohoku University Room: Kona 4 |
Friday, October 10, 2014 9:00AM - 9:15AM |
FL.00001: Detailed simulation study of the electro-production of Lambda hypernuclei at Jefferson Lab Manami Fujita In the JLab E05-115 experiment, (e,e' K$^{+}$) reaction of $\Lambda$ hypernuclei, our group observed mass spectra of $\Lambda$ hypernuclei for A=1$\sim$52. To reconstruct the missing mass of these hypernuclei, a conversion of the information such as particle momenta and angles at the focal planes to those of particles at the target point requires the inverse transfer matrix. The inverse transfer matrix is obtained at first by means of TOSCA(3 dimentional magnetic field calculation code) and Geant4 simulation. The inverse transfer matrix is optimized reproducing the degined resolution ($\delta p/p \sim 10^{-4}$) due to imperfectness of the models. It is crucial to estimate the systematic error caused by this optimization procedures. We developed a full Monte Carlo simulation code and generated dummy data with an arbitrary given hypernuclear masses. The code for the real data analysis was applied to the dummy data in order to estimate the systematic error. The realistic Monte Carlo simulation is also important for the design of the next experiment at JLab. We plan to extend the measurement mass number up to A=208. Realistic simulation of the background rates in scattered electron detector system and optimization of the setup will be discussed in the presentation. [Preview Abstract] |
Friday, October 10, 2014 9:15AM - 9:30AM |
FL.00002: A new method of background suppression for the hypernucleus study at MAMI Yuta Takahashi We started the hypernuclear decay-pion spectroscopy with electron beam at the MAINZ Microtron MAMI-C since 2011. In this experiment, we measure pion momenta from hypernuclei stopped in the target with a 10$^{-4}$ resolution to determine masses of light hypernuclei with an accuracy of $\sim$30 keV. In the previous experiment (2012), we improved the signal to noise ratio by installing a new Pb shield and aerogel Cherenkov detectors in the Kaon spectrometer (Kaos) which tags hyperon generation. We successfully observed a pion peak from two-body weak decay of stopped $^4_{\Lambda}$H, and evaluated B$_{\Lambda}$ and the mass with an accuracy of $\sim$110 keV including both statistical and systematic errors. However, a pion background from the quasi-free hyperon (QFBG) prevented us from observation of other hypernuclei with less yield. Since QFBG cannot be rejected by the K$^+$ tagging, a new method to suppress QFBG is necessary. The generation positions of the pions from QFBG are mainly distributed out of the target while pions from hypernuclei were generated in the target. Therefore a new tungsten heavy-alloy absorber to stop the pions from QFBG was newly installed for the beam time in May-June 2014. I will present the design principle of the absorber and its performance achieved. [Preview Abstract] |
Friday, October 10, 2014 9:30AM - 9:45AM |
FL.00003: Performance evaluation of the Scattered particle Fiber Tracker for J-PARC E10 experiment Yoshiyuki Nakada, Atsushi Sakaguchi, Shuhei H. Hayakawa, Manami Nakagawa, Kenichiro Oue, Tomonari Hayakawa, Koji Miwa, Ryotaro Honda, Yuya Akazawa, Hitoshi Sugimura, Shoichi Hasegawa J-PARC E10 experiment was proposed to produce the neutron-rich $\Lambda$-hypernucleus $^6_\Lambda \mathrm{H}$ by using the $^6 \mathrm{Li(\pi^-, K^+)}$ reaction at $1.2~\mathrm{GeV}/c$ and to study its structure. The experiment was performed at the K1.8 beam line of J-PARC Hadron Experimental Facility. The Scattered particle Fiber Tracker (SFT) is a scintillating fiber tracker which was newly installed just downstream the target. In this experiment we required high intensity $\pi^-$ beams of typically $1.4 \times 10^7~\mathrm{\pi/spill}$. So, we replace a tracking wire chamber with SFT to obtain more precise timing information and higher rate tolerance. SFT has $x,~u,~v$-planes constructed by scintillating fibers. The light signals from the scintillating fibers are read out by Multi Pixel Photon Counters (MPPCs). The Extended Analogue SiPM ReadOut Chip (EASIROC) system was used as readout electronics. The multi-hit TDC program has introduced in FPGA of the EASIROC system. We analyzed the time information of SFT and studied the influence of high counting rate upon the performance of SFT using the data of the E10 experiment. We report the results of the analysis. [Preview Abstract] |
Friday, October 10, 2014 9:45AM - 10:00AM |
FL.00004: Proposal of an experiment about $\Lambda -n$ interaction via FSI in $\gamma +d$ reaction at ELPH, Tohoku University Masashi Kaneta The experiment of strangeness photo-production, NKS2, has been carried out at Research Center for Electron Photon Science (ELPH), Tohoku University. We had focused on the neutral channel near the threshold and reported $K^{\mathrm{0}}$ and Lambda differential cross section of $\gamma +d$ reaction in that energy region. ELPH started to provide the real photon beam from a 1.3 GeV electron synchrotron after recovering from the damage of the Great East Japan Earthquake. As the prospect of the next experiment, we are planning to measure $\Lambda -n$ interaction via $\gamma +d\to K^{+}+\Lambda +n$. Theoretical studies predict that the $K^{\mathrm{+}}$ cross section enhanced only near the threshold region due to FSI of $\Lambda +n$ in $\gamma +d$ reaction comparing to $\gamma +p$. NKS2 has an acceptance in forward angle and covers almost full kinematic region. The characteristics give us an advantage of experiment, that is, not only $K^{+}$ but also $K^{+}$ Lambda coincidence measurement. Additionally, the gamma beam provided (maximum: 1.25 GeV) is suitable for the strangeness photo production in the threshold region (0.9 GeV in lab). We will present a capability of measurement for $\Lambda +n$ interaction using the NKS2 spectrometer at ELPH. [Preview Abstract] |
Friday, October 10, 2014 10:00AM - 10:15AM |
FL.00005: Isotope Identification in Nuclear Emulsion Plate Kinbara Shinji, Nakazawa Kazuma, Ichikawa Yuichi, Ueno Hideki, Yoshida Junya, Khin Than Tint, Myint Kyaw Soe, Mishina Akihiro, Itoh Hiroki, Endo Yoko, Kobayashi Hidetaka We have to identify nuclide of 10$^{2}$ or more double-hypernuclei in the J-PARC E07 experiment. It is necessary to know nuclear species of daughter isotopes from decay of double-hypernuclei in nuclear emulsion plates for that We identify daughter isotopes by the measurement of energy losses as their track thickness in the emulsion. In theory, the relative values of each nuclide ($^{4}$He,$^{7}$Li,$^{9}$Be,$^{11}$B) of sum of energy-loss for proton in range from stopping point to 100 $\mu$m are 4,8,12,17 times respectively. Track width is measured from stopping point with image processing method. Under the assumption of tracks to be made of many cylinders by length of 1$\mu$m, track ``volume'' given by width is summed up and expected to present differences Furthermore, we have to get alignment parameter between various angles for each nuclide and calibrate track width by using electron beam, because the appearance of track is different depending on the angle of incidence and the depth In this paper, we present the test result of the above PID method applied for protons in emulsion of E373 experiment. [Preview Abstract] |
Friday, October 10, 2014 10:15AM - 10:30AM |
FL.00006: Track following of $\Xi^{-}$hyperons in nuclear emulsion for the E07 experiment Akihiro Mishina, Kazuma Nakazawa, Kaoru Hoshino, Kazunori Itonaga, Junya Yoshida, Khin Than Tint, Myint Kyaw Soe, Shinji Kinbara, Hiroki Itoh, Yoko Endo, Hidetaka Kobayashi, Kaori Umehara, Hiroyuki Yokoyama, Daisuke Nakashima Events of Double-$\Lambda $ and Twin Single-$\Lambda $ Hypernuclei are very important to understand $\Lambda $-$\Lambda $ and $\Xi^{-}$-N interaction. We planned the E07 experiment to find Nuclear mass dependences of them with ten times higher statistics than before. In the experiment, the number of $\Xi^{-}$ hyperon stopping at rest is about ten thousands which is ten times larger than before. Such number of tracks for $\Xi^{-}$ hyperon candidates should be followed in nuclear emulsion plate up to their stopping point. To complete its job within one year, it is necessary for development of automated track following system. The important points for track following is Track connection in plate by plate. To carry out these points, we innovated image processing methods. Especially, we applied pattern match of $K^{-}$ beams for 2nd point. Position accuracy of this method was 1.4 $+$/- 0.8$\mu m. $If we succeed this application in about one minute for a track in each plate, all track following can be finished in one year. [Preview Abstract] |
Friday, October 10, 2014 10:30AM - 10:45AM |
FL.00007: Establishment of Developing Method for the E07 Experiment Yoko Endo, Kazuma Nakazawa, Kaoru Hoshino, Jyunya Yoshida, Khin Than Tint, Myint Kyaw Soe, Shinji Kinbara, Akihiro Mishina, Hiroki Ito, Hidetaka Kobayashi J-PARC E07 experiment is to understand $\Lambda $-$\Lambda $ interaction by the detection of double-hypernuclei events in nuclear emulsion plate about 10times larger statistics than that in the KEK-PS E373 experiment. We must optimize photographic developing method for E07 experiment. Nuclear emulsion plates for E07 experiment to develop are about 1300 plates of thick type and about 220 plates of thin type. Their size is twice as large as E373 experiment (350 $\times$ 345 mm$^{2})$. It will take 23cycle to develop all of plates. (1 cycle is 8 days.) In order to establish the method, we have to check following issues such as. 1) ``Fog density,'' which disturb analysis, should be 3.0 or less/1000 $\mu$m$^{3}$ Current fog density is 2.25 $\pm$ 0.23/1000 $\mu$m$^{3}$ 2) ``Grain density,'' which corresponds to energy loss of charged particles should be 25 $\sim$ 30/100 $\mu$m. Current grain density is 28.65 $\pm$ 4.86/100 $\mu$m. 3) Uniform sensitivity in nuclear emulsion plates 4) Possibility to develop mass huge amount and large sized emulsion plate In our presentation, I will discuss about tests and their results to establish developing method for the E07 experiment. [Preview Abstract] |
Friday, October 10, 2014 10:45AM - 11:00AM |
FL.00008: Mass production of the large-sized nuclear plate for J-PARC E07 Hiroki Ito, Kazuma Nakazama, Kaoru Hoshino, Jyunya Yoshida, Khin Than Tint, Myint Kyaw Soe, Shinji Kinbara, Akihiro Mishina, Yoko Endo, Hidetaka Kobayashi In J-PARC E07, about 10$^{2}$ double lambda hypernuclei will be detected, which is 10 times or more than that of the KEK PS-E373 experiment. Therefore, it is necessary for large-scale emulsion plates to avoid time-consuming job for exchange emulsion stack in beam exposure. We also use huge amount of emulsion gel with weight of 2.1 t, which is about 3 times' quantity used for E373. Nuclear emulsion plate is made of photographic emulsion gel as a dry film. Melted gel in 40$^{\circ}$C is poured on a thin polystyrene film in the size of 710 $\times$ 700 mm$^{2}$. These sheets were dried slowly for two days in drying cabinet under 28$^{\circ}$C and RH. 75{\%}. After drying, the surface was coated by thin gelatin layer with 0.3 $\mu$m thickness. Regarding the 2nd face, it was poured and coated in the same manner. Finally we dry it well under 25$^{\circ}$C and RH. 60{\%} and cut into four 350 $\times$ 345 mm$^{2}$ plates. We evaluated the performance about these plates. The length of upper, lower, right-hand and left-hand side are 345.08 $\pm$ 0.05 mm, 345.23 $\pm$ 0.13 mm, 350.03 $\pm$ 0.04 mm, and 350.80 $\pm$ 0.05 mm, respectively. The density is 3.676 $\pm$ 0.032 g/cm$^{3}$, enough quality for the experiment. [Preview Abstract] |
Friday, October 10, 2014 11:00AM - 11:15AM |
FL.00009: Event analysis in nuclear emulsion for E07 experiment Myint Kyaw Soe, Kazuma Nakazawa, Johnya Yoshida, Khin Than Tint, Arkihiro Mishina, Shinji Khinbara, Endo Yoko, Itoh Hiro, Hidetaka Kobayashi In near future, the E07 experiment will be carried out for beam exposure at J-PARC to search for double strangeness (S$=$-2) system. We expect to analyze nearly $10^{2}$ or more double-$\Lambda $ hypernuclei and $10^{8}$ single hypernuclei in the E07 experiment. Therefore we have to detect and analyze with the high speed to provide the information of double strangeness system in a suitable time. We are establishing and polishing analysis system with use of typical events detected by Overall-scanning method applied for E373 emulsion. The events with hammer tracks and single hypernuclei are very good samples to validate event analysis. We should calibrate our analysis system to identify the new events. The well-known mass of the $^{8}$Be* was reconstructed from the alpha particles back to back decayed in hammer tracks events applied by kinematic fitting method. All of reconstructed masses for $^{8}$Be* came into one sigma of the mass of $^{8}$Be*(7457.89$+$/-0.75 MeV/c2). Thus we calibrated unambiguously our analysis system and analyzed single hypernuclei events. In my presentation, I will discuss event analysis with the kinematic fitting applied for hammer track events and single hypernuclei events. [Preview Abstract] |
Friday, October 10, 2014 11:15AM - 11:30AM |
FL.00010: Improvement in the speed of alpha-decay track measurement Hidetaka Kobayashi, Kazuma Nakazawa, Jyunya Yoshida, Akihiro Mishina, Shinji Kinbara, Yoko Endo, Hiroki Itoh, Myint Kyaw Soe, Kint Tantint For analysis of double-$\Lambda $ hypernucleus in nuclear emulsion, it is necessary to know shrinkage factor and density of emulsion plate by measuring the track ranges of alpha particles. The kinetic energies of nuclear fragment from double-$\Lambda $ hypernucleus are measured by their ranges in the emulsion, which is dedicated photographic emulsion for nuclear physics. Then we have to reconstruct their original ranges since the emulsion plate shrinks about half in thickness after development. Besides, we have to calibrate range-energy relation because the density depends on the emulsion content of moisture. Therefore we use alpha-rays with monochromatic energy as calibration sources which were emitted from natural Radioisotope such as Thorium series and Uranium series in the emulsion. Technique which performs alpha-tracks measurement by image processing is being studied. In the E07 experiment at J-PARC , quick analysis is required for about alpha tracks on about 100 double-$\Lambda $ hypernuclear events within a few years. At present, we are developing automated range measurement technique instead of traditional manual measurement. Alpha tracks are seen as black, bold lines in micrographs. Image processing program detects such lines and the positions, angles, ranges of them in micrographs. [Preview Abstract] |
(Author Not Attending)
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FL.00011: Particle Identification in Nuclear Emulsion by Measuring Multiple Coulomb Scattering Khin Than Tint, Kazuma Nakazawa, Junya Yoshida, Myint Kyaw Soe, Akihiro Mishina, Shinji Kinbara, Hiroki Itoh, Yoko Endo, Hidetaka Kobayashi We are developing particle identification techniques for single charged particles such as Xi, proton, K and $\pi $ by measuring multiple Coulomb scattering in nuclear emulsion. Nuclear emulsion is the best three dimensional detector for double strangeness (S$=$ -2) nuclear system. We expect to accumulate about 10000 Xi- minus stop events which produce double lambda hypernucleus in J-PARC E07 emulsion counter hybrid experiment. The purpose of this particle identification (PID) in nuclear emulsion is to purify Xi-minus stop events which gives information about production probability of double hypernucleus and branching ratio of decay mode. Amount of scattering parameterized as angular distribution and second difference is inversely proportional to the momentum of particle. We produced several thousands of various charged particle tracks in nuclear emulsion stack via Geant4 simulation. In this talk, PID with some measuring methods for multiple scattering will be discussed by comparing with simulation data and real Xi-minus stop events in KEK- E373 experiment. [Preview Abstract] |
Friday, October 10, 2014 11:45AM - 12:00PM |
FL.00012: Scanning system and image process for double-lambda hypernucleus searching in nuclear emulsion Junya Yoshida, Kazuma Nakazawa, Khin Than Tint, Myint Kyaw Soe, Shinji Kinbara, Akihiro Mishina, Yoko Endo, Hiroki Ito, Hidetaka Kobayashi A new method named ``Overall scanning'' is being developed to search for more events of double --lambda hypernucleus in nuclear emulsion. A computer-controlled optical microscope scans full volume of emulsion layers exhaustively and a high-speed, high-resolution camera takes their sequential microscopic images. Then, an image process picks out ``double--lambda hypernucleus--like shapes'' having multi tracks and 3 vertices stem from production and cascade weak decay of double--lambda hypernucleus. In this talk, I'll present the current status of development and its operation. During test operations by E373's emulsion plates, about 20cc volume of emulsion was scanned so far. It equals a half of an E373's emulsion plate. Some candidates of double-$\Lambda $ hypernuclei and twin single-lambda hypernucleus have been detected. Besides, 10$^3$ single-lambda hypernucleus and 10$^3$ alpha decays were found, which is calibration samples for range-energy relation. [Preview Abstract] |
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