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8th Topical Seminar on “Innovative Particle and Radiation Detectors” Siena 21-24 Oct. 2002 CALIBRATION AND SEARCH FOR EXOTIC PARTICLES WITH CR39 AND MAKROFOL NUCLEAR TRACK DETECTORS Vincent TOGO – INFN Bologna Calibration and Search for Exotic Particles with CR39 and Makrofol • Exotic particles in Cosmic Rays • MACRO, SLIM • CR39, Makrofol • Improvements • Calibrations • Results EXOTIC PARTICLES Massive penetrating Particles From Cosmic Rays • Magnetic Monopoles • Nuclearites Magnetic Monopoles Should have been produced very early in the Big Bang Universe. • Elementary magnetic charge: gD Dirac quantization condition: egD = ħc/2 (1931) Grand Unified Theories (GUTs) of electroweak and strong interactions Superheavy MMs: Mass ≥ 1016 GeV . About MMs: Magnetic monopole bibliography, G. Giacomelli et al. hep-ex/0005041 NUCLEARITES alias Strange Quark Matter, Strangelets, Quark Bags E. Witten, Phys. Rev. D30 (1984) 272 A. De Rujula, S. L. Glashow, Nature 312 (1984) 734 •Aggregates of u, d, s quarks • Ground state of nuclear matter • Stable for any barion number A (few <A<1057) • Density 3.5 x 1014 g cm-3 • Produced in Early Universe: candidates for cold Dark Matter (DM) • Searched for in Cosmic radiation reaching the Earth (=v/c 10-3) EXPERIMENTS MACRO Monopole Astrophysics and Cosmic Ray Observatory Gran Sasso - Italia Underground Search For GUT MMs SLIM Search for “Light” Magnetic monopoles Chacaltaya – Bolivia 5230 m a.s.l The MACRO track-etch subdetector Total area: 1263 m2 “Stacks” of ~ 24.5 x 24.5 cm2 m CR39 LEXAN Al Nuclear Fast fragment MM Slow MM 1.45 mm 0.25 mm 1 mm SLIM Bologna, Torino, Univ. Alberta (Canada), Pinstech (Pakistan) Search for LIght Magnetic Monopoles M: 106 – 1012 GeV AIM: Search, at high altitude, of MM and other massive particles with high dE/dx (nuclearites) in Cosmic Radiation. Detector: 400 m2 of nuclear track detectors (24cmx24cm CR39 and Makrofol) Chacaltaya Lab. (Bolivia), 5230 m a.s.l CR39 and MAKROFOL CR39 ® (PPG Industries Inc.) The CR39 plastic is made by polymerization of the dietilenglycol bis allylcarbonate (ADC) Standard INTERCAST CR39: mainly used for sun glasses Improved in order to achieve : • low detection threshold, • high sensitivity in a large range of energy losses, • high quality of the post-etched surface • stability of the sensitivity over long periods of time (several years) [Aging effect] • uniformity of sensitivity for mass-produced sheets In order to achieve these goals, a specific scientific line of production was designed and implemented MAKROFOL® (BAYER) Polycarbonate films • high light transmission, • excellent surface uniformity Passage of a particle in a nuclear track detector SHAPE OF A TRACK Track diameter: D = 2vB[(vT-vB)/(vT+vB)] -1/2 Track length: L = (vT-vB) t Reduced etch rate: p = vT/vB Tracks of 158 A GeV Pb ions in CR39 nuclear track detector 6N NaOH, 700C, 30 h – 20X 6N KOH +10% ethyl alcohol, 700C, 3h-20X Background tracks in CR-39 8N NaOH, 900C, 30 h 6n KOH + 10% ethyl alcohol, 800C, 20 h Tracks of 156 A GeV Pb ions in Makrofol nuclear track detector 6N NaOH, 95 h, 500C 6N KOH + 20% ethyl alcohol, 8 h, 450C CALIBRATION OF CR39 Stacks of CR39 foils + target exposed to 158 A GeV 207 Pb82+ Detection of Pb ions + fragments (5 < Z < 82) Length and base area of tracks in CR39 exposed to Pb ions (158 A GeV) CALIBRATION OF CR39 WITH LEAD ION BEAM - 158 A GeV SPS CERN Cone base area distribution of 158 A GeV Pb ion beam and fragments in Makrofol MM Energy Losses >10-2 10-4<<10-2 10-5<<10-4 Ionization Excitation Elastic collisions Limits on MM Flux Astrophysical limits: The Parker bound Survival of galactic magnetic fields (~3mG) F< 10-15 cm-2 s-1 sr-1 <3 10-3 F< 10-15( /3 10-3) cm-2 s-1 sr-1 >3 10-3 The Extended Parker Bound (EPB) F< 1.2 10-16 cm-2 s-1 sr-1 MM: MACRO final results – hep-ex/0207020 g=gD NUCLEARITES Restricted Energy Loss Signal similar to that of a Magnetic Monopole Nuclearites: MACRO final results Isotropic Flux Flux from above N. BOHR “Une théorie doit être suffisamment insensée pour être vraie.”