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 MonopolesShould have been produced veryearly 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

E. Witten, Phys. Rev. D30 (1984) 272A. 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 (fewA1057)

• Density 3.5 x 1014g cm-3

NUCLEARITESalias Strange Quark Matter, Strangelets, Quark Bags

• Produced in Early Universe: candidates for cold Dark Matter (DM)

• Searched for in Cosmic radiation reaching the Earth (=v/c 10-3)

EXPERIMENTS MACROMonopoleAstrophysicsand Cosmic RayObservatoryGran Sasso - Italia UndergroundSearch For GUT MMs

SLIMSearch for “Light”Magnetic monopoles

Chacaltaya – Bolivia5230 m a.s.l

Nuclear fragment

Fast MM

SlowMM

1.45 mm

1 mm

0.25 mmCR39

Al

LEXAN

The MACRO track-etch subdetector

Total area: 1263 m2

“Stacks” of ~ 24.5 x 24.5 cm2

SLIM

Bologna, Torino, Univ. Alberta (Canada), Pinstech (Pakistan)

Chacaltaya Lab. (Bolivia), 5230 m a.s.l

Search for LIght Magnetic MonopolesM: 106 – 1012 GeVAIM: 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)

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

10-2

10-4

Ionization ExcitationElastic collisions

Limits on MM Flux

Survival of galactic magnetic fields (~3G)

F 10-15 cm-2 s-1 sr-1

The Extended Parker Bound (EPB)

F 1.2 10-16 cm-2 s-1 sr-1

The Parker bound

Astrophysical limits:

3 10-3

F 10-15( /3 10-3) cm-2 s-1 sr-1 3 10-3

MM: MACRO final results – hep-ex/0207020

g=gD

NUCLEARITESRestricted 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.”