Supernova Neutrinos

that a 4 GeV electron machine was ercise, with contributions in exper lishment of a body analogous to scientifically inappropriate. To ex tise and material from other inter ECFA, the European Committee for plore the furthest frontiers of nu ested nations, much along the lines Future Accelerators, established in clear science, a continuous acceler of the HERA electron-proton collid the early 60s as an independent ator, going beyond CEBAF ener er now nearing completion at the 'mini-parliament' of particle physi gies, attaining 10-15 GeV, would German DESY Laboratory in Ham cists and which has played a major be a better bet. burg. role in the emergence of all Eu Although catalysed in France, To provide a platform for major rope's subsequent major particle the group envisaged the new pro European nuclear physics projects, physics projects. ject as an essentially European ex the group recommended the estab Supernova neutrinos For more than twenty years, physi 'only' about one per cent of this cists have anticipated that the enormous figure. The difference In the first part of his in-depth gravitational collapse of Type II su must come out in some invisible article on the 1987 supernova pernovae, forming neutron stars or form, either neutrinos or gravita (SN 1987A - April issue, black holes, are also copious tional waves. Numerous arguments page 1), David Schramm of sources of neutrinos. have shown that gravitational radi the University of Chicago and As explained in the first part of ation can only carry about one per the NASA/Fermilab Astro this article, massive stars evolve to cent of this, so that the bulk of the physics Centre reviewed the about 1.4 solar mass iron cores energy is released as neutrinos. background to supernovae, surrounded by layers of silicon, ox It is also well established that for the composition of massive ygen, neon, carbon, helium and hy densities greater than about 2 x stars and the optical history drogen. The core of such an object 1011 g per cc, the collapsing core ofSN 1987A and speculated will inevitably collapse, but the de is no longer transparent to neutri on what the 1987 remnant tails of how this collapse produces nos. For electron neutrinos, the might be. a neutron star or a black hole and 'neutrinosphere' source tempera In such a Type II super how the outer material is spewed ture corresponds to an average nova, gravitational pressure out in a supernova outburst are still particle energy around 10 MeV. crushes the atoms of the matters of much debate. Because of the significant masses star's interior producing neu The two most popular scenarios of the muon and the tau lepton, tron matter, or even a black are either a prompt direct shock muon- and tau-type neutrinos and hole, and releasing an intense caused by the bounce of the col their antiparticles only interact at burst of neutrinos. 1987 was lapsing iron core when it hits in these temperatures via neutral rath the first time that physicists compressible nuclear matter densi er than charged current weak inter were equipped (but not en ties, or a delayed shock resulting actions, so their neutrinosphere is tirely ready!) to intercept from neutrinos emitted by material deeper inside the core, and their these particles, and in the se subsequently falling on the baby spectra are correspondingly hotter cond part of his article, David neutron star and driving off the than those of the electron neutrino. Schramm covers the remarka outer mantle. The electron antineutrino opacity ble new insights from the Regardless of these details, will initially be governed by charged science of supernova neutrino compressing about 1.4 solar current scattering off protons, but astronomy, born on 23 Fe masses of neutrons into a dense as the protons disappear, neutral bruary 1987. star releases about 1053 ergs, current effects come into their while the total light and kinetic en own. Thus the temperature of elec ergy of a supernova outburst is tron-type antineutrinos changes 18 CERN Courier, May 1990 SCINTILLATING FIBRES? XP4702 reads them out 64 at a time! Ske (X) 40 mA/W at 400 nm First of a new family, the XP4702 extends G 106 at 1400 V tr 4.8 ns at 1400 V PMT talents into the realm of spatial as well output segmented last dynode, 8x8 matrix of 64 as time resolution. Combined in a single independent 2.54 mm x 2.54 mm elements crosstalk <5% (scanned by 50 \im light spot) envelope, 64 ten-stage multipliers with long-life CuBe dynodes produce an 8x8 XP4702 opens new opportunities in fibre mosaic of discrete pixels. With uniform readout hodoscopy, calorimetry and channel-to-channel gain and transit-time. coarse imaging. Reference: NIM A269 The common anode supplies an (1988) 246-260. additional signal that can be used Fibres courtesy of Optectron, France. For more information contact: Philips Components, for amplitude analysis or triggering. Building BAF2, 5600 MD Eindhoven, The Netherlands. Telex 35000 phtcnl/nl jeveo. STILL SETTING THE STANDARD lllllllllllllllllllllllllllll PHILIPS esigned for applications from the Daudio to the microwave range, the dual- function SNA-6 handles spectrum analysis from 50 Hz to 3.2 GHz, The instrument's excellent dynamic range and accuracy permit analysis of densely spaced line spectra. The narro west analyzer filter (3 Hz bandwidth) allows detection of extremely low amplitude a. c. line interference superimposed on a 3 GHz carrier.This is just one benefit of the low-noise synthesizer oscillator. • More information about the SNA-6 • Please arrange for a sales engineer to call The SNA-6 also sets new standards in scalar network analysis. The 0.1 Hz resolution synthesizer can be tuned across the entire frequency Name range without skips or phase hits. The same synthesizer also provides the signal for the tracking generator. When testing active two-port networks, the gain/attenuation vs. frequency can be determined from Company +30 to -140 dBm and 100 kHz to 3.2 GHz with excellent precision. You can use our bar code reader or your PC with our software for remote control applications on the IEEE 488/IEC 625 bus. Street You will also be impressed by the versatile evaluation functions and hardcopy capabilities of the SNA-6. Town/postcode For more information about the state-of-the-art SNA-6 from Wandel & Goltermann, please fill out and send in the coupon below. Telephone no, Wandel &Goltermann (Schweiz) AG Postfach, 3018 Bern 18, Telefon 031-55 6544, Wandel & Goltermann LLJJ Fax 031-55 4707, Telex 912350 wgch Electronic Measurement Technology wl i from that of electron neutrinos to that of muon- and tau-neutrinos. The peak energies of the emitted neutrinos are very insensitive to model parameters - electron neu trino temperature and energy around 3 and 10 MeV respectively, and temperature and energy of the other neutrino types around 6 and 20 MeV. Starting out with charged current interactions and ending with only neutral currents, the time- averaged electron antineutrino tem perature is about 4.5 MeV with an energy of about 15 MeV. A collapsing core has some 1057 protons that are converted to neu trons with release of electron neu trinos to form a neutron star. Each of these neutrinos carries away on the average 10 MeV, supplying in total about 1.3 x 1052 ergs, not more than about ten per cent of the energy release. The remaining neu trinos (of all types) come from ther mal processes such as electron-po sitron annihilation into neutrino-antineutrino pairs, muon- and tau- type neutrino production occurring only via neutral currents. The reali zation in the 1970s that the signifi cant neutrino energy release comes via neutral currents was an import ant advance in understanding. Simple arguments give estimates Energy and timing of the supernova neutrino counts from the Japanese Kamioka and the The initial neutronization burst of for the counting rates expected for Irvine/Michigan/Brookhav en (1MB) detectors. electron neutrinos is much earlier large shielded detectors such as (after less than a hundredth of a se the 6000 tons of water of the Ir- cond), with the bulk of the flux sub vine/Michigan/Brookhaven team (some 50 kps) to the Large Magel sequently being emitted during and the 2200 tons of water in the lanic Cloud where SN 1987A was several seconds of diffusion. More Japanese Kamiokande detector. born to yield about 11 counts for than half of the thermal neutrinos Such underground detectors are the Kamioka detector, and for the are released in the first one or two mainly sensitive to the reaction Mont Blanc detector with its 0.09 seconds, the remainder coming out where an incoming electron anti- kilotons (of hydrocarbon scintillator over the next few tens of seconds neutrino converts a proton into a rather than water) about 0.6 as the hot newborn neutron star neutron, releasing a positron. counts. 1MB is a little more difficult cools down to become a standard Prior to SN 1987A, estimates because its threshold is not below cold neutron star. Detailed models were made for a supernova in the the peak electron antineutrino suggest that because of neutral centre of our galaxy at about 10 ki- counting rate, however a reasona currents the thermal processes do loparsecs (30,000 light years). ble estimate, using efficiencies, not favour any particular neutrino These can be reduced by the thresholds, etc. gives some seven species. square of the increased distance counts. CERN Courier, May 1990 21 CORNING FRANCE OPTICAL DIVISION DIVISION OPTIQUE 44, avenue de Valvins 77210 AVON - FRANCE Tel.: 33-1 60 72 50 00 Telex: 690 562 CORFOPH Fax: 33-1 60 72 18 30 The worldwide specialist in glasses for Cherenkov counters.

Load more