Ultra - - high Energy Cosmic Rays high Energy Cosmic Rays

Topic presentation for the KTH course Topic presentation for the KTH course

“Experimental Techniques for Particle Astrophysics “ Experimental Techniques for Particle Astrophysics” ”

Spring 2007 Spring 2007

Jacob Trier Frederiksen, Stockholm Observatory Jacob Trier Frederiksen, Stockholm Observatory

Ultra

Ultra - - high Energy Cosmic Rays high Energy Cosmic Rays

The short version of talk: no news..?

The short version of talk: no news..?

Outline Outline

Brief history of UHECRs Brief history of UHECRs

Science Science

Observation techniques Observation techniques

A few Observatories A few Observatories

Status and future Status and future

A few more observatories A few more observatories

Discussion

Discussion

Brief history of UHECRs

Brief history of UHECRs - - infancy infancy

1912: Victor K. Hess 1912: Victor K. Hess

Discovers cosmic rays in balloon at 5 km Discovers cosmic rays in balloon at 5 km

1938: Pierre Auger 1938: Pierre Auger

zz Inferred capable of observing ~10Inferred capable of observing ~10¹⁵¹⁵eV primary CR. Used two eV primary CR. Used two correlated ground based detectors. Saw CR secondaries from correlated ground based detectors. Saw CR secondaries from an extensive air shower

an extensive air shower

zz

1946: Rossi & Zatsepin 1946: Rossi & Zatsepin

First multi

First multi--detector array to observe extensive air showers, detector array to observe extensive air showers, Russia

Russia

1962: Linsley et al.

1962: Linsley et al.

z

z First UHECR ~ 1.4x10First UHECR ~ 1.4x10²⁰²⁰eV shower detected at Volcano Ranch, eV shower detected at Volcano Ranch, New Mexico (nb: before GZK cut

New Mexico (nb: before GZK cut-off was predicted...)-off was predicted...)

1966: Greisen, Zatsepin, Kuzmin 1966: Greisen, Zatsepin, Kuzmin

zz Predicts energy (GZK) cutPredicts energy (GZK) cut-off @3-off @3--6x106x10¹⁹¹⁹eV from UHECR-eV from UHECR-CMB CMB interaction

interaction –– rather should be viewed actually as suppresionrather should be viewed actually as suppresion

Brief history of UHECRs

Brief history of UHECRs - - recently recently

1991: Fly's Eye I collab 1991: Fly's Eye I collab

z

z Detects the nicknamed Detects the nicknamed “Oh“Oh--my-my-GodGod--ParticleParticle”” at 3·at 3·1010²⁰²⁰eVeV

1994: AGASA 1994: AGASA

zz Detects a 2·Detects a 2·1010²⁰²⁰eV eventeV event

1995: Pierre Auger Collab 1995: Pierre Auger Collab

The Pierre Auger Observatory construction commences The Pierre Auger Observatory construction commences

2005: Auger 2005: Auger

Auger on

Auger on-line and detecting in hybrid mode-line and detecting in hybrid mode

Energy scale

Energy scale

Science

Science – – Energy profile Energy profile

'Solar modulation' Extra-galatic CRs

UHECRs Galatic CRs

Balloon/Satellite Extensive Air Shower (EAS)

'Not possible'

Science

Science – – Energy limit? Energy limit?

GZK

MAX

MA X GZK

Greisen-Zatsepin-Kuzmin, GZK Cut-off (or suppression)

PAIRS

PIONS

Science

Science – – SuperGZK? SuperGZK?

Old physics

New physics

Fermi “bottom-up” acceleration – known objects

Direct super-heavy relic “top-down” acceleration

'Known'/possible accelerators in astrophysics

Science

Science - - directionality? directionality?

SuperGZKs seem

SuperGZKs seem uncorrelated uncorrelated with known HE with known HE - - acceleration objects.

acceleration objects.

SuperGZKs

SuperGZKs isotropically isotropically distributed with distributed with 'reasonable' confidence.

'reasonable' confidence.

Conclusions

Conclusions - - Science Science

Experiments must address (priority):

Experiments must address (priority):

Energy distribution

Energy distribution (GZK or not? Need for new physics?)(GZK or not? Need for new physics?) Directionality

Directionality (Known sources? Or new physics?)(Known sources? Or new physics?) Composition

Composition (protons, (protons, γγs, iron, neutrinos, neutrons etc.?)‏s, iron, neutrinos, neutrons etc.?)‏

EAS EAS – – generic generic

Techniques

Techniques - - Basics Basics

Only one way to Only one way to

measure UHECRs:

measure UHECRs:

For the case of extremely For the case of extremely high energy, only viable high energy, only viable

solution is to detect solution is to detect

EExtensive xtensive AAir ir SShowershowers

...and side effects thereof...

...and side effects thereof...

Techniques

Techniques – – Basics Basics

Two methods used to study extensive air Two methods used to study extensive air

showers (EAS), complementary in strength:

showers (EAS), complementary in strength:

1) Air flourescence detection.

1) Air flourescence detection.

case study:

case study: ““Fly's Eye I + II / HiResFly's Eye I + II / HiRes””..

2) Direct (secondary) particle detection (only E

2) Direct (secondary) particle detection (only E_primprim>10>10¹⁵¹⁵eV). eV).

case study:

case study: ““AGASAAGASA””

Longitudinal distribution,

“Fly's Eye”

Lateral shower distribution, “AGASA”

Techniques

Techniques – – Air flourescence Air flourescence

Fly's Eye I + II Fly's Eye I + II

November 1986

November 1986 –– still running...still running...

Stereo

Stereo-/mono-/mono--scopic view of celestial sphere.scopic view of celestial sphere.

67/36 mirrors, resp 880/646 PMs.

67/36 mirrors, resp 880/646 PMs.

Each focus equiped with 12

Each focus equiped with 12--14 PMs.14 PMs.

“Fly's Eye I & II” / “HiRes”

“Fly's Eye I Buckets of bolts, or, “would you trust this experiment?”

Actually, one of most successful UHECR Experiments!

Techniques

Techniques – – Air flourescence Air flourescence

Fly's Eye I Fly's Eye I

Gets the highest

Gets the highest--ever UHE event in 1991: Eever UHE event in 1991: E_{primaryprimary}=3.2 =3.2 ±± 0.90.9 x 10x 10²⁰²⁰eVeV !!!!!!

GSK limit

Techniques

Techniques – – Air flourescence Air flourescence

Longitudinal detection: Why use for direction Longitudinal detection: Why use for direction

determination??

determination??

Fixes a plane independent of Fixes a plane independent of lateral directional determination lateral directional determination

zz Provides two new numbers: Provides two new numbers:

XX_maxmax, t, t_10/5010/50

zz XX_maxmax in turn used for mass in turn used for mass composition of primary

composition of primary

Fe C p

Techniques

Techniques – – Air flourescence Air flourescence

Calibration concerns:

Calibration concerns:

Flourescence yield in air Flourescence yield in air

NOTE: HiRes vs AGASA...discrepancy. Recent results from SLAC poi

NOTE: HiRes vs AGASA...discrepancy. Recent results from SLAC points to overestimates of nts to overestimates of flux at UHE by HiRes

flux at UHE by HiRes

Calibration of detectors Calibration of detectors

Radiative transfer from beam to detector Radiative transfer from beam to detector

Hadronic interaction model used for longitudinal shower developm Hadronic interaction model used for longitudinal shower developmentent

Measures taken:

Measures taken:

*Narrow filterering in 300

*Narrow filterering in 300-400 nm range (N-400 nm range (N--flourescence)flourescence)

*Code comparison for hadronic models, longitudinal development

*Code comparison for hadronic models, longitudinal development

*Laboratory electron beam measurements (SLAC)

*Laboratory electron beam measurements (SLAC) Calibration of single detectors by pulsars (?)

Calibration of single detectors by pulsars (?)

Calibration of system/mirrors with vertical flashers Calibration of system/mirrors with vertical flashers

Atmospheric radiative transfer monitored continuously with N

Atmospheric radiative transfer monitored continuously with N-lasers-lasers

Fly's Eye I + II

Fly's Eye I + II

Techniques

Techniques – – Air flourescence Air flourescence

Fly's Eye I + II Fly's Eye I + II

Narrow filtering in the Narrow filtering in the

flourescence flourescence

Nitrogen

Nitrogen--bandsbands

Techniques

Techniques – – Air flourescence Air flourescence

Fly's Eye I + II Fly's Eye I + II

Longitudinal development: <X

Longitudinal development: <X_maxmax>, N>, N_ee, σ, σ^p-p-airair

Code comparison for different hadronic interaction models.

Code comparison for different hadronic interaction models.

Accelerator data used for physical 'seed' model Accelerator data used for physical 'seed' model (bold) Extrapolation to post

(bold) Extrapolation to post--accelerator regime, > 10accelerator regime, > 10³³GeV.GeV. ^{\propto X}

LHC

Techniques

Techniques – – Air flourescence Air flourescence

Fly's Eye I + II Fly's Eye I + II

Laboratory calibration; in particular air Laboratory calibration; in particular air

flourescence seems to need a makeover flourescence seems to need a makeover

(SLAC) (SLAC)

Techniques

Techniques – – Particle detection Particle detection

AGASA AGASA

First 'light' in 1990

First 'light' in 1990 –– and running...and running...

111 electron detectors.

111 electron detectors.

27 muon detectors.

27 muon detectors.

Lateral span ~ order 10

Lateral span ~ order 10²² kmkm²²

Plastic scintillator detector

μ γ e

AGASA AGASA

One of the highest AGASA

One of the highest AGASA-UHECRs was seen in 1997: -UHECRs was seen in 1997: EE_{primaryprimary}=1.5 x 10=1.5 x 10²⁰²⁰eVeV

Techniques

Techniques – – Particle detection Particle detection

Techniques

Techniques – – Particle detection Particle detection

Lateral detection: Why used

Lateral detection: Why used “ “ S S

(600) (600) ” ” & &

” ” ρ ρ

(600) (600) ” ” as basis for primary energy estimate?? as basis for primary energy estimate??

Lateral shower density fluctuations lowest at ~600 m from shower

Lateral shower density fluctuations lowest at ~600 m from shower core for all core for all species and all detectors. Empirically and from simulations. Thu

species and all detectors. Empirically and from simulations. Thus the safest s the safest metric for the energy of the primary.

metric for the energy of the primary.

Have a common measure to compare the different radial distributi

Have a common measure to compare the different radial distribution relations for on relations for array in the world (all parametrized in different ways depending

array in the world (all parametrized in different ways depending on detectors, on detectors, temperature, altitude, etc.).

temperature, altitude, etc.).

Calibration concerns:

Calibration concerns:

Calibration of detectors, very low Calibration of detectors, very low fraction of muon energy deposited in fraction of muon energy deposited in plastic scintillators => high uncertainty plastic scintillators => high uncertainty in energy per event.

in energy per event.

Hadronic model used for lateral spread Hadronic model used for lateral spread and deposition in detectors, particular and deposition in detectors, particular concern far from shower core (prev.

concern far from shower core (prev.

slide) slide) ......

Measures taken:

Measures taken:

*Code comparison for hadronic models

*Code comparison for hadronic models (see figures for example)

(see figures for example)

*Re-*Re-rere--rere--evaluation of error sources in evaluation of error sources in measurements, and errors in primary ray measurements, and errors in primary ray energy estimate.

energy estimate.

*...*...

AGASA AGASA

Techniques

Techniques – – Particle detection Particle detection

AGASA - Scintillation

PAO - (simulated) Cherenkov

AGASA AGASA

ReRe--re-re-rere--evalution of sources of evalution of sources of errors and uncertainties in

errors and uncertainties in measurements and energy of measurements and energy of primary (UHE)CR.

primary (UHE)CR.

Basically concludes that their Basically concludes that their measurements are correct, with measurements are correct, with only negligible corrections with only negligible corrections with each re

each re--evaluation.evaluation.

Techniques

Techniques – – Particle detection Particle detection

Techniques

Techniques - - Pierre Auger Observatory Pierre Auger Observatory

The best of both/all worlds:

The best of both/all worlds:

+ =

Last week, status: 75% surface detectors installed Copy Fly's Eyes

AGASA do., but water-Cherenkov instead gives better resolution in muon- detection

EXTENSIVE AIR SHOWER

CHERENKOV RADIATION (not detect. By PAO) PARTICLE SHOWER

AIR FLOURESCENCE UHECR - Incoming!!!

Surface (lateral) arrays Angular (longitudinal) array

Muons Electrons

Flourescence GEOMETRY:

SIGNAL:

Techniques

Techniques - - Pierre Auger Observatory Pierre Auger Observatory

Techniques

Techniques - - Pierre Auger Observatory Pierre Auger Observatory

After first light from PAO, and at present, the UHECR curve is still a statistical mess. No fit.

Ouch. GZK

Techniques

Techniques - - a new a new “ “ AMBER AMBER ” ” array array

AMBER =

AMBER = AAirir--shower shower MMicrowave icrowave BBremsstrahlung remsstrahlung EExperimental xperimental RRadiometeradiometer Complementary technique

Complementary technique AllAll--weather, 24/7weather, 24/7

Reasonably cheap Reasonably cheap

Seems highly coherent Seems highly coherent Likely close to calorimetric Likely close to calorimetric

Plasma effects and polarization Plasma effects and polarization

Techniques

Techniques - - a new a new “ “ AMBER AMBER ” ” array array

.. so now PAO might look like this in a .. so now PAO might look like this in a

few years:

few years:

EXTENSIVE AIR SHOWER

CHERENKOV RADIATION PARTICLE SHOWER

AIR FLOURESCENCE

UHECR - Incoming!!!

Surface (lateral) arrays Angular (longitudinal) array

Muons Electrons Cherenkov

Flourescence GEOMETRY:

SIGNAL:

Techniques

Techniques - - Pierre Auger Observatory Pierre Auger Observatory

MBR (radio)

Bremsstrahlung

schematically..

schematically..

Future

Future - - Observatories Observatories

EUSO

EUSO - - “ “ Extreme Universe Space Extreme Universe Space Observatory

Observatory ” ” , ESA, status: proposal , ESA, status: proposal

(?). (?).

Future

Future - - Observatories Observatories

OWL OWL - - “ “ Orbiting Wide Orbiting Wide - - angle Light angle Light collectors

collectors ” ” , NASA, status: proposal. , NASA, status: proposal.

(OverWhelmingly Large....

(OverWhelmingly Large....☺☺))‏‏

Status and Future Status and Future

“ “ Bigger is better Bigger is better ” ” ...? ...?

Fine.

Notes / questions Notes / questions

Gamma

Gamma-rays vs. hadrons and neutrinos?-rays vs. hadrons and neutrinos?

Might be determined from

Might be determined from pairpair--production on production on the g

the geomagnetic eomagnetic field which would introduce field which would introduce anisotropy in the distribution accordingly anisotropy in the distribution accordingly (decrease in flux at high energies).

(decrease in flux at high energies).

Might also be

Might also be LandauLandau--PomeranchukPomeranchuk--MigdalMigdal effect which reduces Bethe

effect which reduces Bethe--Heitler cross Heitler cross section for pair

section for pair--production (increase in flux at production (increase in flux at high energies).

high energies).

See figure to the right for comparative study of See figure to the right for comparative study of these effects on gamma

these effects on gamma--ray shower ray shower development.

development.

This distinction requires extravagant amounts This distinction requires extravagant amounts of HE data

of HE data --though...though...

Plastic scintillators??

Plastic scintillators??

What is the difference between the muon

What is the difference between the muon--and and electron PS detectors on AGASA

electron PS detectors on AGASA ––besides besides the surface area?

the surface area?

Why this Earth background??

Why this Earth background??

Because its pretty

Because its pretty ––and because cosmic rays and because cosmic rays are believed to play a role (perhaps

are believed to play a role (perhaps ––though –though – not essential) in cloud formation and

not essential) in cloud formation and condensation physics and therefore in the condensation physics and therefore in the temperature budget og the planet.

temperature budget og the planet.