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V^ Proceedings of the 3Rd Workshop on BALLOON-BORNE EXPERIMENTS with SUPERCONDUCTING MAGNET SPECTROMETERS" /> KEK-PR0C--92- JP9304099 ^ ,-*.«?* ?*! S-;V^ " > Proceedings of the 3rd Workshop on BALLOON-BORNE EXPERIMENTS WITH SUPERCONDUCTING MAGNET SPECTROMETERS held at National Laboratory for High Energy Physics (KEK) February 24-25, 1992 Edited by Akira Yamamoto [ r National Laboratory for High Energy Physics, 1992 KEK Reports are available from: Technical Information & Library National Laboratory for High Energy Physics 1-1 Oho, Tsukuba-shi Ibaraki-ken, 305 JAPAN Phone: 0298-64-1171 Telex: 3652-534 (Domestic) (0)3652-534 (International) Fax: 0298-64-4604 Cable: KEKOHO II '•J % Foreword The Third Work Shop on Balloon Borne Experiment with a Superconducting Magnet Spectrometer was held at National Laboratory for High Energy Physics (KEK), Tsukuba, Japan on February 24 - 25, 1992. The workshop was supported by a Grant for Joint Research under The Monbusho International Scientific Research Program (No. 02044151). Two invited review talks were presented on " Progress of Measurement of Cosmic Ray Antiprotons and Search for Primordial Antimatter" and on " High Rate Data Acquisition System in Balloon Borne Experiments." The main effort for this workshop was focused on the progress of the BESS (Balloon Borne Experiment with a Superconducting Spectrometer) experiment and on the scope for scientific investigation with the BESS detector. The progress was reviewed and further investigation was discussed for the BESS further scientific collaboration among Univ. of Tokyo, Kobe University, KEK, ISAS and NMSU. The 30 scientists and engineers participated to the workshop and there were extensive discussions to verify and to complete the BESS detector to be launched in Canada, this summer. New technologies for future balloon and space experiments were also discussed on triggering by using Neural Network and on Scientific investigation with Japanese Experimental Module (JEM) on the Space Station. The proceedings contains reports based on the talks given in the workshop and the proceedings may also be a progress report of the BESS collaboration. We would thank the Ministry of Education, Science and Culture for the Grant to support the BESS experiment. We deeply appreciate Prof. H. Sugawara, Director General of KEK, and Prof. S. Iwata, Director of Physics Division, for their continuous encouragements. Finally we would thank Mrs. S. Tanaka for her kind help to organize the workshop and to edit the proceedings. March 1992 Akira Yamamoto Editor V ~r CONTENTS Workshop Program ix 1. Plenary talks Measurement of Cosmic-ray Antiprotons and R. Golden 3 Search for Primordial Antimatter Progress of the BESS Experiment A. Yamamoto 9 2. BESS Detector Development Progress of Superconducting magnet Y. Makida 17 Progress of JET Chamber T. Yoshida 23 Progress of Inner and Outer Drift Chambers K. Yoshimura 33 Progress of Time-of-Flight Counters M. Nozaki 45 Mechanical Analysis for the BESS Structure H. Yamaoka 51 3. A Plenary Talk High Rate Data Acquisition System in B. Kimbell 61 Balloon Borne Experiments 4. BESS Electronics and Data Acquisition System Progress of Electronics K. Anraku 73 Progressof Data Acquisition System I. Ueda 81 Progress of Triggers System T. Saeki 87 Discussion Multi Track Triggers R. Golden 97 5. Technologies for Future Projects Track Trigger Using Neural System K. Taruma 103 Space Environment MonitoringSystem T. Doke 113 on the Space Station for common use in JEM Appendix 1 Antiproton and Antimatter: A Balloon S. Onto 127 Experiment with Model Solenoid Appendix 2 Bess Technical Drawings J.Suzuki 143 K. Tanaka Appendix 3 List of Participants 173 \1 THE 3RD WORKSHOP ON BALLOON-BORNE EXPERIMENTS WITH SUPERCONDUCTING MAGNET SPECTROMETERS to be held at KEK National Laboratory for High Energy Physics Meeting Room, 1st floor, Main Laboratory Feb., 24 - 25, 1992 *****pe5_ 24, (Mon,)***** [Plenary Talks] 10:30 Opening Address S. Orito (U. Tokyo) 10:40 Measurement of Cosmic-ray Antiprotons and R. Golden (NMSU) Search for Primordial Antimatter (Invited Talk) 11:40 The BESS status A. Yamamoto (KEK) 12:15 Lunch Break [BESS Detector Development] 13:15 BESS Tour at Experimental Hall 14:30 Progress of Superconducting Magnet Y. Makida (KEK) 15:00 Progress of JET Chamber T. Yoshida (U. Tokyo) 15:30 Coffee Break 15:45 Progress of Inner and Outer Drift Chambers K. Yoshimura (U. Tokyo) 16:15 Progress of Time-of-Flight Counters M. Nozaki (Kobe U,) 16:45 Mechanical Analysis for the BESS Structure H. Yamaoka (KEK) 17:15 Adjourn 18:00 Dinner at Ichinoya IX I" Plenary Talks & ~n Measurement of Cosmic-Ray Antiprotons and the Search for Primordial Antimatter R. Golden Introduction: Since we are all working hard on instruments to measure antiprotons and to search for primordial antimatter, it might be useful to step back from the hardware and look once again at the basic physics that motivated us in the beginning. In this talk we will review the various processes that could generate antimatter for us to study. We will also touch on the implications of various possible findings. Then we will review what is known at this time. Finally, I will close by summarizing what physics issues the first flight of BESS might address. Why do we study "cosmic" antimatter? The role of antimatter in the creation and evolution of the Universe is not understood because there is very little data to help us build a detailed description of what happened. We do know, however, that tne fundamental interactions conserve baryons, at least to a very high degree in our present environment. Because of this conservation of baryons, there is much reason to believe that the big-bang was symmetric. But, as we shall see, both the symmetric and non- symmetric big bang theories have problems. The "smooth - symmetric" big bang was the first proposed model. In this model, the universe expanded and cooled reaching a point where the average photon energy decreased to about 1 GeV. At this point, the universe would have consisted of a "gas" containing roughly equal numbers of protons, antiprotons and photons. As the temperature dropped further, the protons and antiprotons would be "frozen out" with photon-photon collisions no longer able to create new baryon-anti baryon pairs. From this point on, protons and antiprotons would annihilate finally reducing the density until the mean-time between chance encounters approaches the age of the universe. The resulting universe would be very diffuse and have a very high photon/baryon ratio (about 1018:1). The formation of stars and galaxies, etc., would be extremely unlikely. Clearly our universe began differently...but how can we change the smooth-symmetric picture into something more workable? We could just make the ad-hoc assumption that the initial baryon number of the universe was not zero. But this is unsatisfactory to most persons because it postulates that one type of matter was preferred over another. During the 1960's a number of persons investigated other possible separation mechanisms (electromagnetic, etc.) which could separate the universe into domains alternating between matter and antimatter in their dominant form. Unfortunately none of these mechanisms found wide-spread acceptance. Another class of theories follows the same beginnings as the smooth- symmetric big bang but at some point before the proton-anti proton freeze-out, another process intervenes. In general, this other process involves heavier particles (perhaps even the 101* GeV GUTS vector bosons). These heavier particles and their antiparticles undergo a baryon non-conserving decay, with a higher decay rate for the anti-particle that for the particle of ordinary matter. The net result is that there are more "parents" who will give rise to protons than there are "parents" that can give rise to antiprotons. Note that this process involves both baryon non-conservation (which has NEVER been observed) and CP violation (which has been observed in weak interactions). Many people are disturbed by the requirement in this theory for baryon non-conservation. In addition this class of theories still requires that one type of matter be preferred over another. In an attempt to overcome the last objective, Floyd Stecker has proposed that the CP violation be regional, with some portions the universe having preference for matter and other portions having a preference for antimatter. This leads to a universe organized into domains of matter and antimatter but no one knows what the size of these domains might be. There are other processes taking place in the universe that also produce antimatter. Some of these are less exotic than others, but in each case, the rarity of antimatter in our part of the universe, may allow us to study these processes by observing their antimatter by-products in cosmic rays. These processes include: Production of p and e+ by cosmic ray interactions Possible pair-production near black holes (the Hawking effect) Production of antimatter in other exotic environments Possible production by decay of super heavy particles What can we learn by photon-related observations? Visual observations of stars, etc., do not give useful information regarding the possible presence of antimatter. This is because visual photons are generated by th. .rial and atomic processes. The light emitted by these processes has the same spectra whether the material involved is matter or antimatter. However, X and Y - ray spectra can be useful. In the X-ray region, annihilation of e+ and e" gives rise to a X-rays of 0.51 MeV energy. Broadening of this line emission should be quite small, arising only from bulk motion of the annihilation region. Annihilation of p and protons gives rise to meson production. In particular, n° mesons which decay in to two 70-MeV y - rays. Unfortunately, in this case the rc° can be produced with a wide range of energies. The resulting y - ray spectrum is quite broad. Because of the broad spectrum, and the existence of alternate ways for producing jt° , unambiguous recognition of p - p annihilation would be difficult.
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