### Results of the Telescope Array experiment

Grigory I. Rubtsov

Institute for Nuclear Research of the RAS

ULB Physique Th´eorique seminar

### Outline

I

### Telescope Array experiment

I

### TA physics results on UHECRs

I spectrum

I chemical composition

I search for sources

I search for photons

### Telescope Array Collaboration

T Abu-Zayyad1_{, R Aida}2_{, M Allen}1_{, R Azuma}3_{, E Barcikowski}1_{, JW Belz}1_{, T Benno}4_{, DR Bergman}1_{,}

SA Blake1_{, O Brusova}1_{, R Cady}1_{, BG Cheon}6_{, J Chiba}7_{, M Chikawa}4_{, EJ Cho}6_{, LS Cho}8_{, WR Cho}8_{, F Cohen}9_{,}

K Doura4_{, C Ebeling}1_{, H Fujii}10_{, T Fujii}11_{, T Fukuda}3_{, M Fukushima}**9,22**_{, D Gorbunov}12_{, W Hanlon}1_{, }

K Hayashi3_{, Y Hayashi}11_{, N Hayashida}9_{, K Hibino}13_{, K Hiyama}9_{, K Honda}2_{, G Hughes}5_{, T Iguchi}3_{, }

D Ikeda9_{, K Ikuta}2_{, SJJ Innemee}5_{, N Inoue}14_{, T Ishii}2_{, R Ishimori}3_{, D Ivanov}5_{, S Iwamoto}2_{, CCH Jui}1_{, }

K Kadota15_{, F Kakimoto}3_{, O Kalashev}12_{, T Kanbe}2_{, H Kang}16_{, K Kasahara}17_{, H Kawai}18_{, S Kawakami}11_{, }

S Kawana14_{, E Kido}9_{, BG Kim}19_{, HB Kim}6_{, JH Kim}6_{, JH Kim}20_{, A Kitsugi}9_{, K Kobayashi}7_{, H Koers}21_{, }

Y Kondo9_{, V Kuzmin}12_{, YJ Kwon}8_{, JH Lim}16_{, SI Lim}19_{, S Machida}3_{, K Martens}22_{, J Martineau}1_{, T Matsuda}10_{, }

T Matsuyama11_{, JN Matthews}1_{, M Minamino}11_{, K Miyata}7_{, H Miyauchi}11_{, Y Murano}3_{, T Nakamura}23_{, }

SW Nam19_{, T Nonaka}9_{, S Ogio}11_{, M Ohnishi}9_{, H Ohoka}9_{, T Okuda}11_{, A Oshima}11_{, S Ozawa}17_{, IH Park}19_{, }

D Rodriguez1_{, SY Roh}20_{, G Rubtsov}12_{, D Ryu}20_{, H Sagawa}9_{, N Sakurai}9_{, LM Scott}5_{, PD Shah}1_{, T Shibata}9_{, }

H Shimodaira9_{, BK Shin}6_{, JD Smith}1_{, P Sokolsky}1_{, TJ Sonley}1_{, RW Springer}1_{, BT Stokes}5_{, SR Stratton}5_{, }

S Suzuki10_{, Y Takahashi}9_{, M Takeda}9_{, A Taketa}9_{, M Takita}9_{, Y Tameda}3_{, H Tanaka}11_{, K Tanaka}24_{, }

M Tanaka10_{, JR Thomas}1_{, SB Thomas}1_{, GB Thomson}1_{, P Tinyakov}12,21_{, I Tkachev}12_{, H Tokuno}9_{, T Tomida}2_{, }

R Torii9_{, S Troitsky}12_{, Y Tsunesada}3_{, Y Tsuyuguchi}2_{, Y Uchihori}25_{, S Udo}13_{, H Ukai}2_{, B Van Klaveren}1_{, }

Y Wada14_{, M Wood}1_{, T Yamakawa}9_{, Y Yamakawa}9_{, H Yamaoka}10_{, J Yang}19_{, S Yoshida}18_{, H Yoshii}26_{, Z Zundel}1

*1 _{University of Utah, }2_{University of Yamanashi, }3_{Tokyo Institute of Technology, }4_{Kinki University, }*

*5 _{Rutgers University, }6_{Hanyang University, }7_{Tokyo University of Science, }8_{Yonsei University, }*

*9 _{Institute for Cosmic Ray Research, University of Tokyo, }10_{Institute of Particle and Nuclear Studies, KEK, }*

*11 _{Osaka City University, }12_{Institute for Nuclear Research of the Russian Academy of Sciences, }*

*13 _{Kanagawa University, }14_{Saitama University, }15_{Tokyo City University, }16_{Pusan National University, }*

*17 _{Waseda University, }18_{Chiba University }19_{Ewha Womans University, }20_{Chungnam National University, }*

*21 _{University Libre de Bruxelles, }22_{University of Tokyo, }23_{Kochi University, }24_{Hiroshima City University, }*

### Telescope Array observatory

I 507 SD’s, S = 3m2

I 3 FD’s

### TA surface detector

**solarpanel**

**(120w)**

**wLAN (2.4GHz)**

**electronics**

**box**

**(100Ah)**

**battery**

**+**

**box**

**scintillator**

**GPS**< Surface Detector > • 3m2 (12mm × 2 layers) • PMTs: ET 9123SA × 2 (2cm separation) • WLSF: 1.0mmφ ∼200kg

M. Takeda, JPS meeting, March 2010
< SD Observation Status >
**15947.3 hrs**
**94.2 %**
**16160.7 hrs**
**95.7 %**
**16484.0 hrs**
**97.5 %**
MJD
Observation Time [hr]
Observation Time [hr]
Observation Time [hr]

**Mar’08** **Nov’08** **Nov’09Feb’10**

**Black Rock Mesa**

**Long Ridge**
**Smelter Knoll**
54600 54800 55000 55200
0
10
20
0
10
20
0
10
20 • operation in stable
∼
> 95%
∼
> 16k hours
• wLAN interference
in early stage
• thunder storms
in summer
• maintenance access
in autumn

• low temperature & snow in winter

### SD event example

M. Takeda, JPS meeting, March 2010

< SD Event Example >
2.0
0.2
1.7
22.9
74.6
2.2
1.5
26.3
117.8
2.2
2.4
3.6
1.9
0.3
0.8
0.5
**RUN(50141)** **EVENT(2182)**
**DATE(080531)** **TIME(050737)**
**Log(E[eV])=19.698**η** = 3.542**
**Zenith=36.246[deg] Azimuth= 27.854[deg]**
**Core(9) ChiD(0.09) ChiCS(1.39)**

**1318**
X [m]
Y [m]
**1401**
**1404**
**1608**
**1611**
**1612**
**1613**
**1707**
**1710**
**1711**
**1712**
**1713**
**1803**
**1805**
**1810**
**1811**
0 5000 10000
−10000
−5000
0
0 10000 20000 30000
1
10
102 103 104
Core Distance [m]
Td [nsec]
108
106
104
102
100
Density [m ]
−2
**1812**
**1813**
**1911**
**1912**
**1913**
**1914**
**2012**
**2014**
**2213**
**2313**

Relative Timimg [nsec]

102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 #FADC (raw) 102 103 104 100 10 10 10 4 2 6 Core Distance [m]

< FD Observation Status >
**Nov’07** **Feb’10**
**May’09**
**2506.2 hrs**
**12.4 %**
**2180.4 hrs**
**10.8 %**
Observation Time [hr]
MJD

Observation Time [hr] **Long Ridge**

**Black Rock Mesa**

0 5 10 54400 54600 54800 55000 55200 0 5 10

• Full operation since Nov ’07

• Long Ridge remote operation since May ’09

• ∼> 2.5k hrs

• ∼> 2.1k hrs

### FD event example

M. Takeda, JPS meeting, March 2010

< Atmospheric Monitor (LIDAR, CLF) & LINAC >
**LINAC** **CLF**
**100m** **20.85km**
**LIDAR**
**109e** **(6.4mJ)**
**40MeV**
**@355nm**
**@355nm**
**4mJ** **5mJ**
【back-scat.】 【side-scat.】
【electron shower】

### TA-LINAC: Linear Accelerator @ TA

I Electron accelerator 100 m from TA FD I Rate 0.5 Hz I Energy_{∼ 40 MeV}I Current 10

_{− 250pC/pulse}

T.Shibata, UHECR-2010, Nagoya Fist run: September 2010

### Telescope Array physics objectives

Study of UHECR E_{& 10}18 _{eV}

I Spectrum

I Chemical composition

I Search for sources

I Search for photons and neutrino

I Hadronic interactions properties

### TA physics results

I I. UHECR spectrum

I II. Chemical composition by XMAX stereo

I III. Search for cosmic ray sources

### GZK effect

Greisen, 1966; Zatsepin, Kuzmin, 1966

Cut-off predicted for E_{& 10}19.7eV.
p + γ_{2.7K}_{→ n + π}+

→ p + π0

AGASA spectrum, 2003

Takeda, M. et al., Astropart. Phys 19(2003)

I Expected 1.9 event I Observed 11 events

### Cut-off observation by HiRES

Monocular: Quarks’06; PRL 100 (2008) Stereo: Astropart. Phys. 32 (2010)

### Pierre Auger spectrum

### Telescope Array spectrum

TA measures spectrum by three techniques:

I Middle Drum fluorescence detector (FD) mono

I Surface detector (SD)

### Monocular spectrum from Middle Drum (MD) detector

I MD uses 14 refurbish HiRes-1 telescopes.

I TAMD mono processing is identical to HiRes-1 monocular data analysis

I same program set

I same “average” atmospheric model

I same event selection, cuts

I Differences:

I telescope location and pointing directions

I Thresholds (∼ 20% lower than HiRes-1)

I Exposure is calculated with Monte-Carlo

**Jui, ICRC 2009**

10

**MD Spectrum**

### Surface detector spectrum

Dataset:

I Geometrical cuts:

I θ < 45◦

I core inside the array, distance to border > 1200 m

I Cuts on reconstruction quality:

I number of detectors hit >= 4

I χ2/d.o.f < 4.0

I pointing direction resolution < 5◦

I fractional S800 uncertainty < 0.25

I 1.75 years, 6264 events after cuts

### Energy scale normalization

I SD energy: CORSIKA QGSJET-II full MC

I FD energy: MD mono, BRM, LR hybrid

I Result: E = E_{SD}/1.27

### TA surface detector spectrum

### GZK cut-off statistical significance

### Surface detector, MD mono and hybrid spectra

Note: SD energy normalized by 27%

### Comparison with AGASA, HiRes, Auger

### Spectrum summary

I Cut-off is observed by HiRES and confirmed by Pierre Auger and Telescope Array experiments

I GZK process in not questioned, but it’s contribution to cut-off is unknown due to unknown spectrum and composition at the sources

I One may probe E > 1020 eV physics by looking at GZK secondaries: photons and neutrinos

### Auger/HiRES XMAX results

Auger Phys.Rev.Lett.104.091101**E [eV]**

**18**

**10**

**19**

**10**

**]**

**2**

**> [g/cm**

**max**

**<X**

**650**

**700**

**750**

**800**

**850**proton iron

**QGSJET01**

**QGSJETII**

**Sibyll2.1**

**EPOSv1.99**

**E [eV]**

**18**

**10**

**19**

**10**

**]**

**2**

**) [g/cm**

**max**

**RMS(X**

**0**

**10**

**20**

**30**

**40**

**50**

**60**

**70**

_{proton}iron HiRES Phys.Rev.Lett.104.161101

### Yakutsk array result on chemical composition

0.5 1 1.5 2 ΡΜ obs ΡΜ sim, p 0 2 4 6 8 Number of events EPOS p 0.5 1 1.5 ΡΜ obs ΡΜ sim, Fe 0 2 4 6 8 Number of events EPOS Fe 0.29_{≤ }

_{Fe}

_{≤ 0.68 (95%CL),}E > 1019 eV Glushkov et al, JETP Letters 87:190-194,2008

### Possible interpretation of Auger result

’The disappointing model’

10 17 10 18 10 19 10 20 10 23 10 24 E m ax =4 EeV g =2.3, d=40 Mpc E 3 J( E ) , e V 2 m -2 se c -1 st e r -1 E, eV Auger 09 r e ct i lin e a r K o lm . d if fu si o n protons 10 17 10 18 10 19 10 20 10 23 10 24 E m ax =4 EeV g =2.3, d=40 Mpc E 3 J( E ) , e V 2 m -2 se c -1 st e r -1 E, eV Auger 09 r e ct i lin e a r K o lm . d if fu si o n nuclei protons

R. Aloisio, V. Berezinsky, A. Gazizov arXiv:0907.5194v1

I No GZK-photons, no GZK-neutrino

### Another interpretation of Auger result

R. Engel, 31th ICRC, arXiv:0906.0418v1

**0.2** **0.3 0.4** **1** **2** **3** **4** **5 6**
**]**
**−2**
** [gcm**
**max**
**Mean X**
**720**
**740**
**760**
**780**
**800**
**820**
**840**
**860**
**880**
**900**
**920** cross section
multiplicity
elasticity
**19**
**f**
**0.2** **0.3 0.4** **1** **2** **3** **4** **5 6**
**]**
**−2**
** [gcm**
**max**
**RMS X**
**30**
**40**
**50**
**60**
**70**
**80**
**90**
**100**
**110**
Auger, Phys.Rev.Lett.104.091101

### Auger/HiRES XMAX results

Auger: I Southern hemisphere I Heavy nuclei or cross-section growth HiRES: I Northern hemisphere I Protons dominate## ?

### Telescope Array stereo result

TA data favorprotons

data collection is in progress

### TA XMAX distributions

### TA XMAX distributions

### Auger claim discussion

I HiRES doesn’t see correlations with AGN (2 of 13, bg: 3) Astropart.Phys.30,2008

I Comment by Gorbunov,Tinyakov,Tkachev,Troitsky

JETP Lett.87,2008

I Events do not follow prediction of AGN hypothesis. E.g.

nothing comes from Virgo, while it contains significant fraction of nearby AGNs

I Cen A may be a single source with correlation angle

about 20◦

I AGN correlation requires proton primaries; contradicts with Auger composition results due to large deflection of nuclei in Galactic magnetic field

### Pierre Auger claim discussion: Cen A

20 40 60 80 100

distance from Cen A, deg

-5 -4 -3 -2 -1 0 Log 10 P

The Monte-Carlo probability P to have the observed number of events in a circle of a given radius around Cen A on the celestial sphere, out of the 27 events of the Auger sample. Gorbunov,Tinyakov,Tkachev,Troitsky, arXiv:0804.1088

### Auger AGN correlation update

Pierre Auger collaboration, Astropart. Phys. 34 (2010)
Before publication date: 9/13 correlate. Background: 2.7_{± 1.6}
After publication date: 12/42 correlate. Background: 8.9_{± 3.0}

### Auger Centaurus A update

Pierre Auger collaboration, Astropart. Phys. 34 (2010)

I Cen A may be a source

### TA result on AGN correlation

### TA result on AGN correlation

correlate: 6 of 15, bg: 3.6

### TA Autocorrelation analysis

### TA Autocorrelation analysis

### TA correlations with LSS

### TA correlations with LSS

### TA LSS: result of the statistical tests

### TA LSS: result of the statistical tests

### Sources summary

I Correlations with AGN: 6/15 correlate; compatible with background;

I No significant clustering at E > 10 EeV and E > 40 EeV;

I Data with E > 40 EeV are compatible both with structure and isotropy;

I Data with E > 57 EeV are compatible with structure and incompatible with isotropy at 95% CL;

### Photon search techniques

Photon-sensitive parameter:

AGASA, Yakutsk muon density (strongest discrimination)

Pierre Auger SD shower front curvature and thinkness

Pierre Auger hybrid XMAX

### Shower front curvature

deep shower maximum = curved front

I We use Linsley’s shower front curvature parameter “a” as a composition sensitive parameter

### TA SD photon search

Dataset:

I Data collected by SD from 2008-05-11 to 2009-10-08
I Geometrical exposure for θ_{∈ [θ}1, θ2]:

Ageom= 2346× (sin2θ2− sin2θ1) km2 sr yr

Cuts for photon search:

I Number of detectors triggered is 7 or more

I Shower core distance to array boundary is larger than 1 separation unit (1200 m)

### Front curvature example

8.5 8.6 8.7 8.8 8.9 9 9.1 9.2 9.3 9.4 9.5 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 front delay [1200m]; core distance [1200m] Fit data Average photon### Linsley curvature “a”: data vs photon MC

0◦_{− 30}◦

**h_gm**

**Entries**

**3758**

**Mean**

**0.8287**

**RMS**

**0.2954**

**Underflow 0.1609**

**Overflow 0.3217**

**a**

**0**

**0.20.40.6**

**0.8**

**1**

**1.21.4**

**1.61.8**

**2**

**0**

**20**

**40**

**60**

**80**

**100**

**120**

**140**

**h_gm**

**Entries**

**3758**

**Mean**

**0.8287**

**RMS**

**0.2954**

**Underflow 0.1609**

**Overflow 0.3217**

**h_dt**

**Entries**

**604**

**Mean**

**0.5789**

**RMS**

**0.2067**

**Underflow 0**

**Overflow**

**0**

**h_dt**

**Entries**

**604**

**Mean**

**0.5789**

**RMS**

**0.2067**

**Underflow 0**

**Overflow**

**0**45◦

_{− 60}◦

**h_gm**

**Entries**

**3761**

**Mean**

**0.738**

**RMS**

**0.2737**

**Underflow 0**

**Overflow 1.881**

**a**

**0**

**0.20.40.6**

**0.8**

**1**

**1.21.4**

**1.61.8**

**2**

**0**

**20**

**40**

**60**

**80**

**100**

**120**

**140**

**h_gm**

**Entries**

**3761**

**Mean**

**0.738**

**RMS**

**0.2737**

**Underflow 0**

**Overflow 1.881**

**h_dt**

**Entries**

**335**

**Mean**

**0.3463**

**RMS**

**0.1108**

**Underflow 0**

**Overflow**

**0**

**h_dt**

**Entries**

**335**

**Mean**

**0.3463**

**RMS**

**0.1108**

**Underflow 0**

**Overflow**

**0**30◦

_{− 45}◦

**h_gm**

**Entries**

**8804**

**Mean**

**0.7766**

**RMS**

**0.2726**

**Underflow 0.1037**

**Overflow 0.3111**

**a**

**0**

**0.20.40.60.8**

**1**

**1.21.41.61.8**

**2**

**0**

**20**

**40**

**60**

**80**

**100**

**120**

**140**

**h_gm**

**Entries**

**8804**

**Mean**

**0.7766**

**RMS**

**0.2726**

**Underflow 0.1037**

**Overflow 0.3111**

**h_dt**

**Entries**

**456**

**Mean**

**0.4881**

**RMS**

**0.1685**

**Underflow 0**

**Overflow**

**0**

**h_dt**

**Entries**

**456**

**Mean**

**0.4881**

**RMS**

**0.1685**

**Underflow 0**

**Overflow**

**0**E

_{γ}> 1019 eV data photon MC, E−2 spectrum

### Event-by-event method

I For each event with curvature a_{obs} we select photon MC
events compatible by arrival direction and S_{800}.

I We calculate curvature distribution function f_{γ}(a) for MC
photons
I Let’s define
C =
aobs
Z
−∞
f_{γ}(a)da
I C is defined event-by-event

I For gamma events,_{C is uniformly distributed between 0}
and 1 (independently of the photon primary spectrum).

### C: data vs photon MC

0◦_{− 30}◦

**h_gm**

**Entries**

**3758**

**Mean**

**0.5024**

**RMS**

**0.2819**

**Underflow 0**

**Overflow 0.1608**

**C**

**0**

**0.10.20.3**

**0.40.5**

**0.60.7**

**0.80.9**

**1**

**0**

**20**

**40**

**60**

**80**

**100**

**120**

**140**

**160**

**180**

**h_gm**

**Entries**

**3758**

**Mean**

**0.5024**

**RMS**

**0.2819**

**Underflow 0**

**Overflow 0.1608**

**h_dt**

**Entries**

**604**

**Mean**

**0.1847**

**RMS**

**0.1848**

**Underflow 0**

**Overflow**

**0**

**h_dt**

**Entries**

**604**

**Mean**

**0.1847**

**RMS**

**0.1848**

**Underflow 0**

**Overflow**

**0**45◦

_{− 60}◦

**h_gm**

**Entries**

**3761**

**Mean**

**0.5051**

**RMS**

**0.2843**

**Underflow 0**

**Overflow 0.0891**

**C**

**0**

**0.10.20.3**

**0.40.5**

**0.60.7**

**0.80.9**

**1**

**0**

**20**

**40**

**60**

**80**

**100**

**120**

**140**

**160**

**180**

**h_gm**

**Entries**

**3761**

**Mean**

**0.5051**

**RMS**

**0.2843**

**Underflow 0**

**Overflow 0.0891**

**h_dt**

**Entries**

**335**

**Mean**

**0.08868**

**RMS**

**0.09145**

**Underflow**

**0**

**Overflow**

**0**

**h_dt**

**Entries**

**335**

**Mean**

**0.08868**

**RMS**

**0.09145**

**Underflow**

**0**

**Overflow**

**0**30◦

_{− 45}◦

**h_gm**

**Entries**

**8804**

**Mean**

**0.5009**

**RMS**

**0.2806**

**Underflow 0**

**Overflow**

**0**

**C**

**0**

**0.10.20.30.40.50.60.70.80.9**

**1**

**0**

**20**

**40**

**60**

**80**

**100**

**120**

**140**

**160**

**180**

**200**

**h_gm**

**Entries**

**8804**

**Mean**

**0.5009**

**RMS**

**0.2806**

**Underflow 0**

**Overflow**

**0**

**h_dt**

**Entries**

**456**

**Mean**

**0.1196**

**RMS**

**0.1306**

**Underflow 0**

**Overflow**

**0**

**h_dt**

**Entries**

**456**

**Mean**

**0.1196**

**RMS**

**0.1306**

**Underflow 0**

**Overflow**

**0**E

_{γ}> 1019 eV data photon MC, E−2 spectrum

### Calculations

Search region:

I Egamma > 1019 eV 1395 events

I 45◦ < θ < 60◦ 335 events

I C > 0.5 1 event

I Poisson 95% upper limit: _{≤ 5.14 events}

I Total exposure: A_{total}= 158 km2 sr yr

I F_{γ}< 3.3_{· 10}−2 km−2sr−1yr−1 (95% CL)

### Photon flux limits

18 18.5 19 19.5 20 Log EmineV 35.5 36 36.5 37 37.5 38 Log H E 2 F Γ H eV 2 km -2 yr -1 sr -1 LL A A PA PA PA Y Y Y TA TA ICRC**PRELIMINARY**

**PRELIMINARY**

### Photon fraction and flux limits

Fraction limits 18 18.5 19 19.5 20 Log EmineV 0.1 1 10 100 ΕΓ ,% 0.1 1 10 100 A A A PAO-SD PAO-SD PAO-SD HP HP AY Y Y AH PAO-H PAO-H PAO-H PAO-H Y Y Y Flux limits 18 18.5 19 19.5 20 Log EmineV 35.5 36 36.5 37 37.5 38 Log H E 2F Γ H eV 2km -2yr -1sr -1LL A A PA PA PA Y Y Y TA TA ICRC*I GZK prediction:*

**PRELIMINARY**_{γ}< 1% for E > 1019 eV Gelmini,Kalashev,Semikoz, JCAP 0711 (2007)

I Photons may be detected in the near future (depends on astrophysics parameters)

### Constraints on parameters of Superheavy dark matter

21.5 22 22.5 23 Log10HMXeVL -17. -16.5 -16. Log 10 H FSH m -2 sr -1 s -1 L 21.5 22 22.5 23 Log10HMXeVL -17. -16.5 -16. Log 10 H FSH m -2 sr -1 s -1 LF_{SH} – flux of SHDM-produced cosmic rays E > 1020 eV
above thick line – excluded by spectral fits

shaded area – allowed by spectrum and γ limits

⇒SHDM decay may not be the source of all UHECRs

### Lorentz invariance violation tests 1/2

I LIV is proposed by Coleman & Glashow to suppress GZK

process Phys.Rev.D59,1999

I If LI is broken, threshold of GZK reaction may be upshifted
p + γ_{2.7K}_{→ ∆(1232)}

I If we can prove that GZK reaction takes place, we have a constraint on LIV parameters

I One approach to confirm GZK reaction is to observe secondary photons

### Lorentz invariance violation tests 2/2

I If LI is broken for photons in form

ω2= k2+ ξnk2(k/MPl)n

pair production on CMB

γ + γCMB→ e++ e−

may be suppressed by kinematics and photons will propagate through large distances.

I Observed photon flux will contradict existing photon limits
if _{|ξ}1| & 10−14or ξ2 .−10−6.

Galaverni, Sigl, Phys.Rev.Lett.100, 2008

### Conclusions

I TA is a large scale detector operating in the northern hemisphere

I Results on spectrum, composition and anisotropy are presented

I UHECR sources are not yet discovered

I Good chance to detect GZK photons in the midrange

future (3 - 5 years)