Transcript Cosmic Rays – Where are we? Supriya Das CAPSS, Bose Institute If I were a young experimentalist, I would do experimental physics with.

Cosmic Rays – Where are we?
Supriya Das
CAPSS, Bose Institute
If I were a young experimentalist, I would do experimental physics with cosmic rays because they enable
you to reach much higher energies than at the LHC, even if you have to build a 1x1 km2 or 10x10 km2
detector, and even if there’s only one good event per year – that good event will bring something
extraordinary.
- Georges Charpak (Nobel Prize 1992)
Cosmic rays, the beginning
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From 1911 to 1913 Victor F. Hess, an
Austrian-American physicist measured
radiation levels at various altitudes (up to
17,500 ft) in the Earth’s atmosphere,
flying high in balloon.
•
Radiation levels increased with altitude!
•
The enhanced radiation level was
attributed to some kind of radiation
coming from up.
•
For some time the radiation was thought
to be of electromagnetic nature and was
named as “Cosmic Radiation” which later
became “Cosmic Rays”.
•
Won Nobel Prize in 1936.
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CAPSS Seminar, 8th. April 2009
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Low Energy cosmic rays (<1018 eV):
 Origin : solar flares, corona, supernova explosion within our milky way
 the protons, electrons gain energy by successive reflections by magnetic
fields thrown away from the supernova explosions.
- Fermi’s theory of acceleration
 mostly deflected by earth’s magnetic field and absorbed in atmosphere
 ionize the gases in upper atmosphere
 source of Aurora Borealis (northern hemisphere) Aurora Australis
(southern hemisphere)
Fermi’s theory can accelerate up to 1015 eV
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CAPSS Seminar, 8th. April 2009
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First UHECR, 1962
Volcano Ranch Array
New Mexico, US
Twenty 3.3 m2 plastic scintillators covered with 10 cm of lead,
spaced in 147 meters
“Evidence of Primary Cosmic Ray particle with energy 1020 eV”
J. Linsley Phys. Rev. Lett. 10 (1963) 146-148
[The CMBR(1965) and GZK cut-off (1966) was unknown till then]
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CAPSS Seminar, 8th. April 2009
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High Energy Cosmic rays (>1018 eV):
 Origin : inter stellar space, Galactic cosmic rays (GCR), supernova explosions, Active
Galactic Nuclei (AGN), exotic particles
These cosmic rays are deflected very little by magnetic fields in our galaxy and even
less by the field in the inter galactic space – they should give the direction of their
source.
 So far none of the CR >1020 eV points back to any available source.
On the other hand if the source is not close enough to our galaxy (< 100 million light
years or so), collision with the CMB would reduce their energy to 6x1019 eV.
- Greisen-Zatspin-Kuz’min (GZK) cutoff
Well, CR > 1020 eV have been detected by many experiments.
- Cosmic Ray paradox
Conflict : AGASA confirms the existence of UHECR > 1020 eV, but HiRes and Auger
supports GZK suppression.
The cosmic ray energy spectrum above 3 x 1018 eV measured by the Akeno Giant Air Shower Array
– Astroparticle Physics 3 , 105 (1995)
Extension of the Cosmic Ray Energy Spectrum Beyond the Predicted Greisen-Zatsepin-Kuz'min Cutoff
- Phys. Rev., 81,1163 (1998)
Observation of the suppression of the flux of cosmic rays above 4 x 1019 eV
- Phys. Rev. Lett. 101, 061101 (2008)
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CAPSS Seminar, 8th. April 2009
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Energy spectrum of cosmic rays, have a look at the leg
Knee
Air Shower
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CAPSS Seminar, 8th. April 2009
Ankle
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Energy spectrum (Contd.)
GRAPES
KASCADE
AUGER
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A closer look at the “Knee” – direct measurements
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JACEE (Japanese-American Cooperative Emulsion Experiment)
Series of emulsion experiments, 1979 – 1994
11 balloon flights, cumulative exposure 644 m2 hrs @ ~ 3.5 – 5.5 g/cm2
Zenith angle acceptance out to tan θ ~ 72-79°  ~80 m2 sr days exposure
Highest energy proton event ~ 800 TeV
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RUNJOB (RUssian Nipp on JOint Balloon)
Series of emulsion experiments, 1995 – 1999
10 balloon flights, cumulative exposure 575 m2 hrs @ ~ 9.0 – 10.7 g/cm2
Highest energy proton event seen at E > 1 PeV
•
ATIC (Advanced Thin Ionization Calorimeter)
Silicon matrix-scintillator-BGO calorimeter
2 balloon flights, 2000-2003, 31 days exposure  ~ 7 m2 sr days exposure
3rd LDB Antarctic flight scheduled for December 2005
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CREAM (Cosmic Ray Energetics And Mass)
Combined Scintillator, Si Charge Detector, W-scintillator calorimeter, TRD
One balloon flight, 2004-2005, 41 days ~ 12 m2 sr days exposure
Goal is to fly multiple 100 day (ULDB) flights to build up exposure
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CAPSS Seminar, 8th. April 2009
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TRACER (Transition Radiation Array for Cosmic Energetic Radiation)
Scintillator-Cherenkov-TRD for 8 ≤ Z ≤ 26
Two flights, 1999-2004  ~ 40 m2 sr days exposure
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TIGER (Trans-Iron Galactic Element Recorder)
Scintillator-Cherenkov-fibre hodoscope to measure Z ≥ 30
Three flights, 1997-2004, 50+ days exposure  ~ 4 m2 sr days exposure
Originally planned as first ULDB instrument; future flights planned
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CAKE (Cosmic Abundanes below the Knee Energy)
Nuclear track detectors (CR-39, Lexan) to measure 6 ≤ Z ≤ 74
One flight, 1999, 22 hours exposure  ~ 0.9 – 1.8 m2 sr days exposure @ 3 – 3.5
g/cm2
Planning to fly larger version on ULDB
ULDB – Ultra Long Duration Balloon (NASA)
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CAPSS Seminar, 8th. April 2009
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Results from direct measurements
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Measurements through air showers
EAS TOP:
Scintillator detector array (1987-2000) in Gran Sasso, Italy.
KASCADE-Grande:
EASTOP reassembled in Karlsruhe, Germany along with a hadron
calorimeter and Muon tracking detector.
1996 – till date
AGASA (Akeno Giant Air Shower Array):
111 surface detectors over 100 km2 with a separation of 1 km between them,
27 underground muon detectors
Focuses for the UHECR
2000 – till date
HiRes (High Resolution Fly’s eye)
Air Fluorescence detectors with Mirror-PMT in the desert of Utah
Focuses on UHECR
Auger Observatory:
Combination of Scintillator detector and water Cerenkov detector as surface
detectors along with fluorescence detectors with an area of 3000 sq. km in Agentina.
First results in 2007
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CAPSS Seminar, 8th. April 2009
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Extend the step, there is much more than just a “knee”
2nd knee
knee
ankle
2nd knee
Iron knee??
Transition from Galactic to ExtraGalactic Cosmic Rays??
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CAPSS Seminar, 8th. April 2009
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There is a “knee” – no doubt
EAS-TOP
SEh
KASCADE
Nm
Ne
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but, look carefully, there is more
Knee is due to the light primaries
Chemical composition gets
heavier across the knee
SYBILL
QGSJet
Position of the knee vary with
primary elemental groups
(but relative abundances heavily depend on the interaction model)
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CAPSS Seminar, 8th. April 2009
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The twins : Correlated air showers
Lot of arguments favouring co-related air showers :
- photodisintegration in the solar photon field
- breakup of relativistic dust grains
- synchrotron gamma ray emission of high energy electrons in the interstellar
magnetic fields
Several studies on the above issues have either yielded negative results or need
more systematic studies to conclude.
M.J Gramston and A.A. Watson, J. Phys. A 9 (1976) 1199
B. McBreen et al., Abstracts of ICRC, 1981
C.L Bhat et al. J. Phys. G 10 (1984) 1771
G. A Medina-Tanco and A.A. Watson, Astroparticle Physics 10 (1999) 157
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Lifeline 2 : phone call to a friend
The depth of the maximum of the
shower Xmax in the atmosphere
depends on energy and type of the
primary particle.
Different hadronic interaction
models give different answers
about the composition of HECR.
Different hadronic interaction models give
different answers for the primary CR energy
estimate.
(for instance, AGASA reports 18% as systematic
uncertainty in energy determination, 10% being
due to the interaction model)
Need of the hour : Calibration of models with experimental data
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CAPSS Seminar, 8th. April 2009
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Lifeline 2 (contd.)
LHCf experiment @ CERN
7 TeV + 7 TeV proton collisions at LHC (ECM = 14 TeV) correspond to
ELAB = 1017 eV (ELAB ≈ ECM2/(2mp))
Arm#1
Tungsten
Scintillator
Scintillating fibers
INTERACTION POINT
IP1 (ATLAS)
140 m
Arm#2
Tungsten
Scintillator
Silicon microstrips
140 m
Beam line
Two independent electromagnetic calorimeters equipped with position sensitive layers, on
both sides of IP1 will measure energy and position of γ from π0 decays.
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CAPSS Seminar, 8th. April 2009
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Cosmic ray search in India
 Ground-based observations in 1920’s and 30’s by D.M. Bose, Vibha Choudhury et al in
Kolkata.
 Balloon-borne observations by Homi Bhabha in Bangalore in early 1940’s.
 Studies on primary cosmic rays and particle interactions with nuclear emulsion stacks
flown on balloon-borne platforms in 1950’s and 60’s.
 Cosmic ray measurements started in Kolar Gold mines (100 km east of Bangalore) in
early 1950’s on particle properties and intensity at various depths underground. Angular
distribution measurements showed the suitability of KGF mines for studies on
atmospheric neutrinos at a depth of ~ nearly 2 km underground.
 An interaction of an atmospheric neutrino in a detector was first observed in KGF in 1964
by a TIFR-Durham U-Osaka CU collaboration, followed very soon by a similar observation
by the UCI-led collaboration in a mine in South Africa. Experiments by the TIFR-Osaka
CU team continued in KGF during the 1970’s and 80’s.
 The first experiment for a search for proton decay was carried out at KGF during the early
1980’s. The mines closed in early 1990’s due to economic reasons.
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CAPSS Seminar, 8th. April 2009
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Cosmic ray search and Gamma ray astronomy in India (contd.)
Gulmarg Neutron Monitor
Hanle
Proposed
air shower array
at Darjeeling
TACTIC, Mt. Abu
HEGRO, Panchmari
GRAPES, Ooty
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CAPSS Seminar, 8th. April 2009
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Gamma Ray Astronomy at PeV EnergieS (GRAPES)
Air shower array at Ooty, Tamilnadu (2,230 m asl, 800 gm/cm2)
400 Plastic scintillator+PMT each with 1 m2 area measure the EM component
of the air showers.
 Measurement of particle density and time of arrival of those provide the energy
and direction of primary particle.
3712 gaseous proportional counters (6m x 0.1m x 0.1m) with total area of 560 m2
detect muons in the air showers.
 Muon measurement provides information on compositions of primary particle. It
also distinguishes between cosmic ray showers and gamma ray showers.
The Flux of muons is sensitive to the solar wind, so could be used to study
various phenomena induced by the solar activities.
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CAPSS Seminar, 8th. April 2009
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GRAPES (Contd.)
Scintillation detectors:
(1m2×5cm)
Recording timing and
pulse height of charged
particles
400 detectors with 8m
separation
Current configuration uses WLS fiber to
collect and transport light from scintillator
to PMT
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CAPSS Seminar, 8th. April 2009
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GRAPES (Contd.)
Muon detectors:
16 detectors with 6m×6m
area (Eμ>1GeV)
Total area of 560m2
Recording the individual track of
muons
4 layers
58 counters
6m
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CAPSS Seminar, 8th. April 2009
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Results from GRAPES
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Proposed air shower array at Darjeeling
Proposed site: Bose institute campus at Mayapuri, Darjeeling (2,194 m asl, 792 gm/cm2)
Scintillator + PMT counters, each of 1m2 , 50 detectors in total
- looks at the same region of sky as GRAPES at Ooty
- small size of array, probably can’t measure the energy
- but can provide the direction
- and possibility of identifying correlated showers at Ooty and Darjeeling
- can also provide a cross check with the results from Ooty
We will start with 7 detectors (6 forming a hexagon and one at the centre)
- most of the components have been procured
- two persons to visit CRL for two months to learn the detector assembly,
testing, operation and DAQ.
- will start setting up the detectors as soon as possible after the visit
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CAPSS Seminar, 8th. April 2009
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Summary and Outlook
 The area of cosmic ray research is 100 years old.
 Many questions about the shape of the energy spectrum, chemical composition
of primary cosmic rays, the existence and source of UHECR etc. are still either
unanswered or the answers need more data to be established.
 More and more experiments involving both direct measurements from balloon
borne observations and indirect measurements through air shower studies
are coming up worldwide.
 Indian involvement to this area of research is about 80 years old, both in direct
and in indirect measurements.
 We, at Bose Institute are involved in collaboration with TIFR and other
institutes in air shower measurements as well as theoretical research in the
area of cosmic ray.
 We are close to start of the construction of the air shower array at Bose Institute
campus at Mayapuri, Darjeeling.
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CAPSS Seminar, 8th. April 2009
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BACK-UP
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Moon and Sun shadow
Moon or Sun
~0.5°
Deficit of number of
cosmic rays due to
shadow
No deficit of cosmic rays at
fake region ±8°
Observation of moon and sun shadow
is required good angular resolution!!
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