Search for the U ltra H igh E nergy C osmic R ay Sources : the Current S tatus
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Search for theUltra High Energy Cosmic
RaySources : the Current
StatusHang Bae Kim (HanYang University)
High1-2014 KIAS-NCTS Joint Workshop on Particle Physics, String Theory and Cosmol-
ogyFebruary 12, 2014
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Ultra-High-Energy Cosmic Rays
1 particle/km2/century
Ultra-High Energy Cosmic Ray (UHECR)
Energy :1962, E>1020 eV at Vocano Ranch1991, E=3£1020 eV at Fly’s eye(OMG particle) ~ kinetic energy of a baseball with a speed of 100 km/h
Extensive Air Shower (EAS) Extragalactic origin
Where and How can particles reach such extremely high ener-gies?
Cosmic Rays High energy particle from outer space Primarily composed of proton & nuclei Originated from SNe, AGN, … ? Influence on the life
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Production
Propagation
Observation
• Acceleration of charged particles• Decay of superheavy particles
Cosmic background(Microwave, Radio wave, Magnetic fields)
• Energy loss• Secondary CR production• Deflection and Time lag
Atmosphere as calorimeter / scintilla-tor• Composition• Energy• Arrival Direction
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Observation
Detection of EAS• Surface Detector (SD) – e, ¹• Fluorescence Detector (FD) -
UVL• Cherenkov Radiation• Radio wave• Radar reflection
Longitudinal development Lateral distribution
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Pierre Auger Observatory (PAO)
Fluorescence Detector – PMT
Location : Mendoza, Argentina SD : 1600 water Cherenkov detector,
1.5 km spacing, 3000 km2
FD : 24 telescopes in 4 stations
60 k
m
Surface Detector – Water Cherenkov
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Telescope Array (TA)Surface Detector – Plastic Scintillation
Fluorescence Detector – PMT
35km
SD array
FD stationMD
LRBRM
Location : Utah, USA SD : 507 plastic scintillation detector,
1.2 km spacing, 678 km2
FD : 18 telescopes in 3 stations
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JEM-EUSO (planned)
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Signal & Timing
Lateral distribution
S(1000)
Good energy estima-tor
Distance from the shower axis
Energy, Arrival Direction
Fluorescence Detector
Surface Detector
Longitudinal development
Energy Calibrationthrough hybrid events
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CompositionLongitudinal development
Xmax, the depth of shower maximum depends on en-ergy and composition of primary CR particle.
atmospheric depth
Shower maximumXmax, depth of shower maxi-mum
Observed variation of Xmax as a function of en-ergy.
Average longitudinal develop-ment of proton and Fe nucleus obtained from simulation.Proton has larger X_{max} than Fe.
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PropagationEnergy Loss UHECR p, A, γ interact with CMB photons.
The energy of protons as a func-tion of the propagation distance. Modification factor of energy spectrum
Injected spectrum ! Observed spectrum
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PropagationDeflection Magnetic fields ! Deflection and Time lag
Galactic magnetic fieldBG ~ 10-6 GRG~10 kpc
Extragalactic magnetic fieldBEG ~ 10-9 – 10-6 G (very uncertain)
Proton propagation in a magnetic field of 10-9G
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ProductionTop-down : Decay of superheavy particles, Emission from Topological defects
Superheavy particle with long lifetime Emission from topological defects Cosmic origin involves
new (cosmology + particle physics)
Signatures of top-down models• Spectral shape
– No GZK cutoff, flat spectrum• Composition
– Neutrinos and photons are domi-nant
• Arrival Directions– Galactic anisotropy
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ProductionBottom-up : Acceleration of charged particle at astrophysical sites
Maximum attainable energy Acceleration mechanism Diffusive shock accelerationAcceleration site AGN, GRB, …
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Latest Results and IssuesEnergy spectrum
1990s, AGASA reported No GZK cutoff.
HiRes, Auger, TA con-firmed GZK cutoff.
Abu-Zayyad et al. (2013)
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Latest Results and IssuesComposition
PAO : Transition from proton to heavy nuclei- Ad hoc composition model (p, He, N, Fe)
HiRes & TA : Proton
HiRes (Abbasi et al. 2010)
PAO (Abraham et al. 2010)TA (Tameda et al. 2011)
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Latest Results and IssuesArrival directions
AGASA - Isotropy with small clustering
Auger Anisotropy Correlation with AGNs
AGASA (Hayashida et al. 2000) HiRes (Abbasi et al. 2008)
PAO (Abreu et al. 2010)
TA (Abu-Zayyad et al. 2012)
PAO – Correlation with AGN• Low (<10^{19} eV) energy isotropy• Above GZK cutoff, anisotropy confirmed
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Study of Arrival Directions
Experiment Modeling
Observed AD distribution Expected AD distribution
Statistical Comparison
Probability that the observed distribution is ob-tained from the expected distribution
Test Methods - Statistic• Multipole moments, 2D KS, …• KS on the reduced 1D distribution
• Isotropy• Astrophysical Objects
Simulation
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Exposure Function• The detector array does not cover the sky uniformly and we must
consider its efficiency as a function of the arrival direction.• Here we consider only the geometrical efficiency.
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Kolmogorov-Smirnov TestComparison of two one-dimensional distributions• Kolmogorov-Smirnov statistic
Cumulative probability distribution
KS statistic
• Probability that the observed distribution isobtained from the expected distribution
Kuiper statisticAnderson-Darling statis-tic
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RA, DEC Distribution2D Distribution
1D Distribution
Observed Data (TA, E≥1 EeV) Simulation Data (Isotropic)
RA Distribution DEC Distribution
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Auto-Angular Distance Distr. (AADD)
clustered isotropic
Caution: AADD is not an independent sampling.Probability(D) must be obtained from simulation.
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Correl. Angular Distance Distr. (CADD)
correlated isotropic
H.B.K, J. Kim, JCAP 1103, 006 (2011)
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Super-Heavy Dark Matter (SHDM) Model
• UHECR flux is obtained by the line-of-sight integration of the UHECR luminosity function L(R), which is proportional to the DM density ρ(R).
• Galactic DM contribution / Extragalactic DM contribution
• Galactic DM contribution
UHECR Luminosity
Dark Matter Profile
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Super-Heavy Dark Matter (SHDM) Model
Unfavorable
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AGN ModelHypothesis : UHECRs are composed of
• AGN contribution,fraction fA
• Background (isotropic) contribution,fraction 1-fA
Selection of UHECR data• Energy cut • We take
Selection of AGN• Distance cut• We take
Notes• The fraction f depends on Ec and dc.
PAO-AGN
H.B.K, J. Kim, JCAP 1103, 006 (2011)IJMPD 22, 1350045 (2013)
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UHECR flux from AGN
For simplicity, we assume the universality of AGN.
Expected flux• AGN contribution
fraction fA,• Isotropic component
fraction 1-fA,
AGN Model
UHECR Luminos-ity
Dis-tance
Smear-ing
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AGN Model
The cumulative probability distribution of CADD using the AGN reference set
Steep rise of CPD near µ=0 means the strong correlation at small angles.
PAO data are not consistent with isotropy, meaning that they are much more correlated with AGNs than isotropic distri-bution.
PAO data are not consistent ei-ther with the hypothesis that they are completely from AGNs.
Adding isotropic component can make the consistency im-proved.
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Consistent with the simple AGN model when enough isotropic component is added.
Cf. Fiducial value of f
AGN ModelPAO
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Point-wise Anisotropy Idea – Sweep the whole sky and perform the
point-wise comparison to the isotropic distribu-tion (Comparison method: CADD with a point reference)
Features of PAO AD anisotropy• One prominent excess region around Centaurus A• One void region near the south pole
Excess
Deficit
H.B.KMPLA 28, 1350075 (2013)
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Features of TA AD anisotropy• No prominent excess region• Broad hot spot• One void region near the north pole
Hot spot ?
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Cen A as a UHECR source Centaurus A is a nearby strong source of radio waves to γ-rays.
Modeling Centaurus A as a point source of UHECRs
H.B.K, ApJ 764, 121 (2013)
Centaurus A contribution + Isotropic backgroundthe Cen A fractionthe smearing angle
M87
Centaurus A
The PAO data show the cluster-ing of UHECRs around Centaurus A.
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Cen A as a UHECR source
Among 69 UHECR observed by PAO,about 10 (6 ~ 17) UHECR can be attrib-uted to Cen A contribution.
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Cen A as a UHECR source Incorporation of Void structure
H.B.K, JKPS 62, 708 (2013)
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Centaurus A – a UHECR source
Estimate of intergalactic magnetic fields from the deflection angles
By using UHECRs around Centaurus A, the estimate of IGMF is
• Without voids – 10 UHECRs • With voids – 18 UHECRs
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Composition and GMF Influence
Lorentz force equation
GMF model – Prouza-Smida (2003) model• Fit to observed Faraday rotations• Disk field• Toroidal field• Poloidal field
The deflection map of UHECR in the PS modelfor Z=1 (proton).
The Galactic plane sectionof the disk field of the PS model
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Composition and GMF Influence
The deflections of arrival directions of 69 UHECRs detected by the PAO, due to the GMF, computed using the PS model, when UHECRs are protons (Left), or iron nuclei (Right). Red circles mark the arrival directions de-tected at the earth, and black bullets connected by yellow lines mark the arrival directions before UHECR en-ter the GMF .The blue square marks the direction of Centaurus A.
If all UHECRs are protons, the clustering around Centaurus A isnot altered significantly.
If all UHECRs are iron nuclei, the clustering around Centaurus A may be a fake due to the GMF.
H.B.K, JKPS 63, 135 (2013)
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Summary• After 100 years of research, the origin of cosmic rays is still an
open question, with a degree of uncertainty increasing with energy.
• Statistically meaningful data have been accumulated, but not yet conclusive about composition and arrival directions.
• Statistical methods to compare two distributions of UHECR ar-rival directions.
– 2D → 1D reduction : CADD– KS or KP test
• Point-wise anisotropy and point source search• Centaurus A seems to be a strong source of UHECRs.
– Estimate of IGMF : – The influence of GMF may tell something about composition.– Beginning of cosmic ray astronomy?
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New Window to the skyGalileo’s telescope
Jansky’s radio antenna
Penzias & Wilson’s antenna
Planck satellite
Tycho’s Mural quadrant Herschel’s telescope Hubble’s telescope
Hubble Space Telescope
Chandra X-ray telescope