cosmic rays – where are we? supriya das capss, bose institute if i were a young experimentalist, i...

Cosmic Rays – Where are we?Cosmic Rays – Where are we?

Supriya DasSupriya Das

CAPSS, Bose InstituteCAPSS, 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)

Supriya Das CAPSS Seminar, 8th. April 2009 2

• 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.

Cosmic rays, the beginning


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


First UHECR, 1962

Volcano Ranch ArrayNew 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]


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 evenless 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)


Energy spectrum of cosmic rays, have a look at the leg

Knee

AnkleAir Shower


GRAPES

KASCADE

AUGER

Energy spectrum (Contd.)


• JACEE (Japanese-American Cooperative Emulsion Experiment)Series of emulsion experiments, 1979 – 199411 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 exposureHighest energy proton event ~ 800 TeV

• RUNJOB (RUssian Nipp on JOint Balloon) Series of emulsion experiments, 1995 – 199910 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 calorimeter2 balloon flights, 2000-2003, 31 days exposure ~ 7 m2 sr days exposure3rd LDB Antarctic flight scheduled for December 2005

• CREAM (Cosmic Ray Energetics And Mass)Combined Scintillator, Si Charge Detector, W-scintillator calorimeter, TRDOne balloon flight, 2004-2005, 41 days ~ 12 m2 sr days exposureGoal is to fly multiple 100 day (ULDB) flights to build up exposure

A closer look at the “Knee” – direct measurements


• TRACER (Transition Radiation Array for Cosmic Energetic Radiation)

Scintillator-Cherenkov-TRD for 8 ≤ Z ≤ 26Two flights, 1999-2004 ~ 40 m2 sr days exposure

• 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

• CAKE (Cosmic Abundanes below the Knee Energy)

Nuclear track detectors (CR-39, Lexan) to measure 6 ≤ Z ≤ 74One 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)


Results from direct measurements


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 detectorsFocuses for the UHECR

2000 – till date

HiRes (High Resolution Fly’s eye)Air Fluorescence detectors with Mirror-PMT in the desert of UtahFocuses 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

Measurements through air showers


2nd kneeIron knee??Transition from Galactic to ExtraGalactic Cosmic Rays??

knee

2nd knee

ankle

Extend the step, there is much more than just a “knee”


KASCADE

EAS-TOP

N

Ne

Eh

There is a “knee” – no doubt


Knee is due to the light primaries

Chemical composition gets heavier across the knee

Position of the knee vary withprimary elemental groups (but relative abundances heavily depend on the interaction model)

SYBILL

QGSJet

but, look carefully, there is more


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 needmore systematic studies to conclude.

M.J Gramston and A.A. Watson, J. Phys. A 9 (1976) 1199B. 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


Lifeline 2 : phone call to a friend

Need of the hour : Calibration of models with experimental data

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)


Lifeline 2 (contd.)LHCf experiment @ CERN

INTERACTION POINTINTERACTION POINT

IP1 (ATLAS)IP1 (ATLAS)

Beam lineBeam line

Arm#2Arm#2

TungstenTungsten

ScintillatorScintillator

Silicon Silicon microstripsmicrostrips

Arm#1Arm#1

TungstenTungsten

ScintillatorScintillator

Scintillating Scintillating fibersfibers

140 m140 m 140 m140 m

Two independent electromagnetic calorimeters equipped with position sensitive layers, on both sides of IP1 will measure energy and position of γ from π0 decays.

7 TeV + 7 TeV proton collisions at LHC (ECM = 14 TeV) correspond to

ELAB = 1017 eV (ELAB ≈ ECM2/(2mp))


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.


Cosmic ray search and Gamma ray astronomy in India (contd.)

GRAPES, Ooty

Gulmarg Neutron Monitor

TACTIC, Mt. Abu

HEGRO, Panchmari

Hanle

Proposed air shower array

at Darjeeling


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 componentof 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.


GRAPES (Contd.)

Scintillation detectors: (1m2×5cm) Recording timing and pulse height of charged particles400 detectors with 8m separation

Current configuration uses WLS fiber to collect and transport light from scintillator to PMT


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 counters6m


Results from GRAPES


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


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.


BACK-UP


Moon and Sun shadow

Deficit of number of cosmic rays due to shadow

No deficit of cosmic rays at fake region ±8°

Observation of moon and sun shadowis required good angular resolution!!

Moon or Sun

~0.5°

cosmic rays – where are we? supriya das capss, bose institute if i were a young experimentalist, i...

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