Download talk - INFN Bologna

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.”