TA Spectrum Summary : Energy Spectrum Measurements With The - - PowerPoint PPT Presentation

“TA Spectrum Summary “: Energy Spectrum Measurements With The Telescope Array Detectors

Yoshiki Tsunesada Osaka City University for The Telescope Array Collaboration

Jul 19, ICRC2017 Busan, Korea

CRI125

1

TA Detectors

BR LR MD

SD Array 507 counters

2 k m

3 FD stations 507 SDs

• Black Rock
• Long Ridge
• Middle Drum
• TALE - High-elevation FD

2

• 700 km2

Millard county, Utah, US

9-Year TA Operation

• TA detectors in full operation since May 11, 2008 - 9 years.
• TA 9-year spectra from SD and FD
• TALE Cherenkov - 22 months since June 2014

MD/TALE FD BR/LR SD

3

• 3 energy spectra from

independent data set

• SD: > 1018.2 eV
• BR/LR mono: > 1017.2 eV
• TALE Cherenkov: > 1015.4 eV

TA 9-Year Exposures

TA 7 years (ICRC2015)

[Area * FoV * Time]

8100 km2 sr yr

2008/May/11 - 2017/May/11 2008/May/11 - 2017/May/11

θ < 45°

4

2014/Jun - 22 months

NORTH [1200m] --> EAST [1200m] -->

Slide by D. Ivanov (U. Utah)

S800 800m

LDF

(AGASA)

• The SD array measures

the “footprint” of a shower

SD Event Reconstruction

• Use “S800” as an energy

estimator

5

TA SD Energy Scale

• θ
• θ
• X = Secant of zenith angle

ETBL = f[S800,sec(θ)]

• 1st energy estimate: A lookup

table (S800, θ) -> ETBL

• Final energy is by scaling ETBL :

⌧ETBL EFD

• hyb

= 1.27 ESD = ETBL/ ⌧ETBL EFD

• hyb

6

7

Energy Resolution

FD energy systematic uncertainty 21%

• D. Ivanov, ICRC2015

TA SD 7-Year Spectrum (ICRC2015)

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TA SD 9-Year Spectrum

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TA SD “ICRC Spectra” 2011-2017

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Power-Law Fit

logEank = 18.69 ± 0.02

logEsup = 19.81 ± 0.04

E 3.27±0.03 E

2 . 6 9 ± . 2

E 4.63±0.49

Nexp (no suppression): 79.8 Nobs: 26 Prob.: 2.2x10-12, 6.92 σ

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TA SD and FD Mono

TA ICRC2017 Preliminary

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“Full-Range” TA Spectrum

• T. AbuZayyad, CRI126

TA ICRC2017 Preliminary

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Comparison with Other Experiments

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Declination Dependence /Spectral Anisotropies?

18.5 19.0 19.5 20.0

log10(E/eV)

1036 1037 1038

E3J(E) h eV2 km2 sr1 yr1i

90.0  δ < 49.3 49.3  δ < 29.5 29.5  δ < 10.0 10.0  δ < 24.8

1019 1020

E [eV]

• I. Valinio, Auger ICRC2015

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htup://www.telescopearray.org/index.php/research/collaborators

ments are adjusted to use a common energy scale. Above 25 EeV, however, there is a significant discrepancy be tween the two results: the second break point in Pierre Auger spectrum occurs at a significantly lower energy than that of the Telescope Array. This effect cannot be explained by adjusting the energy scales of the two exper we see that the second break point occurs at a lower energy of 40 EeV, in betuer agreement with the Pierre Auger

• result. The difference between the TA low and high declination break points is a 3.9σ effect. Also, we perform

checks of the systematic uncertainties and demonstrate that this is not an instrumental effect.

shows the configuration of the entire TA detector tector consists of the three fluorescence detector (FD) SD effectively covers a 680m energy resolution betuer than 20% [13]. through Grants-in-Aid for Scientific Research on Specially Promoted Research (21000002) “Ex treme Phenomena in the Universe Explored by Highest Energy Cosmic Rays” and for Scientific Research (19104006), and the Inter-University Research Program of the Institute for Cosmic Ray Research; by the U.S. National Science Foundation awards PHY-0601915, PHY-1404495, (2015R1A2A1A01006870, 2015R1A2A1A15055344, 2016R1A5A1013277, 2007-0093860, 2016R1A2B4014967); by the Russian Academy of Sciences, RFBR grant 16-02-00962a (INR), IISN Ezekiel R. and Edna Watuis Dumke, Willard L. Eccles, and George S. and Dolores Doré Eccles all Development Board, and the University of Utah through the Office of the Vice President for Re U.S. Air Force. We appreciate the assistance of the State of Utah and Fillmore offices of the BLM in advice on a variety of topics. The people and the officials of Mil-lard County, Utah have been a to the Millard County Road Department for their efforts to maintain and clear the roads which get us to our sites. We gratefully acknowledge the contribution from the technical staffs of our home [1] R. U. Abbasi et al. [HiRes Collaboration], Phys. Rev. Letu. A [2] A. Aab et al. [Auger Collaboration] JCAP 1508 (2015) 49 [5] K. Greisen, Phys. Rev. Letu. 16 (1966) 183 [6] G. T. Zatsepin and V. A. Kuz’min, Sov. Phys. JETP Letu. 4 (1966) 114. [7] R. U. Abbasi et al. [HiRes Collaboration], Phys. Rev. Letu. 104 (2010) 161101 [8] R. U. Abbasi, M. Abe et al. [TA Collaboration], Astropart. Phys. 64 (2014) 49 [9] A. Aab et al. [Auger Collaboration], Phys. Rev. D 90 (2014) 12, 122006 [10] T. Abu-Zayyad et al. [TA Collaboration], Nucl. Instrum. Meth. A 609 (2009) 227 [11]T. Abu-Zayyad et al. [TA Collaboration], Astropart. Phys. 39-40 (2012) 109 [12] T. Abu-Zayyad et al. [TA Collaboration], Nucl. Instrum. Meth. A 689 (2012) 87 [15] E. Kido [TA Collaboration], “The TAx4 experiment“ PoS(ICRC2017)510

scope Array (TA) [3]. Although these experiments have vastly different exposures and use generally different detection techniques, all three agree that the cosmic ray spectrum at ultra-high energies has tra-high energies. In the case of Auger, on the other hand, the effects of the propagation are complicat ed by the mixed composition result that is reported by the Auger experiment [9] and by the fact that from 60 EeV to 40 EeV, and the TA spectrum is in a betuer agreement with the Auger spectrum. The

We first check whether the surface detector energy reconstruction has a bias that depends on the comparing the ratio of the SD energy to that of the FD for different slices in energy and zenith

• angle. As Figures 3 shows, no significant SD energy reconstruction biases are seen.

tion (the aperture of the SD depends on the zenith angle only geometrically, as sin(θ)cos(θ)) [13]. To verify this further, we perform the following test. We first note that cutuing on the event declina is equivalent to cutuing on points inside and outside, respectively, of the θ , φ constant declination contour shown in Figure 4a. θ is the zenith and φ is he azimuthal angles

• f the main TA SD counters, small filled squares cor

respond to the TALE infill array counters, and the fields of view of the three TA FD sites: Black Rock

(E/eV)

10

log

19 19.2 19.4 19.6 19.8 20 20.2 20.4

]

• 1

s ×

• 1

sr ×

• 2

m ×

2

J [ eV ×

3

E

24

10

• < 24.8

δ <

• TA SD, -15.0
• < 24.8

δ <

• Auger SD, -15.7
• < 90

δ <

• TA SD, 24.8

(E rescaled by +16%)

Comparison of Auger and TA SD energy spectra in different declination bands. Position of the second break point is different for events below and above the declination of 24.8 . We see a betuer agreement with the Auger when the TA and

(b)

between the Auger and TA results. We see a betuer agreement of the TA energy spectrum with the

19.59

for declinations from 24.8 to 90

19.85

If we move this contour to the right in φ by +90 sets of data are roughly similar. If the spectrum difference is due to the declination only and not be cause of the acceptance or reconstruction biases in θ, φ, then the two spectra should be in a good

for energies above 10 EeV. Linear fit is made to both fig ures, and the result is that the slopes are withing their fit ting uncertainties in both figures, indicating that there are no significant energy reconstruction biases. ) Cutuing on declination above and below 24.8 is equivalent to cutuing on data below and above the solid curve, respectively. ) After moving the solid curve by +90 to the right, cutuing on data below and above the solid line no longer corresponds to cutuing on data sets obtained by selecting events inside and outside of the θ vs φ curve in (

spectrum and we have demonstrated that this is not an instrumental effect. In the first 7 years of the TA SD data, the declination dependence of the second break point was a 3.9 σ effect. A preliminary analysis significance of the effect. The TA X 4 extension detector, which is currently being constructed, [15], is ex

Declination Dependence /Spectrum Anisotropies?

• D. Ivanov, CRI236 (Poster)
• JP. Lundquist, CRI194 (Jul 18)
• D. Ivanov, CRI 231 (JUl 18)

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Conclusions

TA 9-year SD/FD data and 3.5 years of TALE FD

• Energy spectrum of cosmic rays in 4.7 decades > 1015.4eV
• Agreement in the three independent data sets
• Spectral structures
• “ankle” and “knee” (2nd knee) in the lower energies
• Ankle at logE = 18.69
• Suppression at logE = 19.81 - 6.9σ.

Declination dependence?

• Spectra of high/low declination bands look different in the highest energies
• Best agreement with Auger in -15° < δ < 24.8°
• Difference is significant for the northern-sky spectrum and Auger’s
• An implication of spectral anisotropies

TAx4 is of crucial importance.

• D. Ivanov, CRI236 (Poster)
• JP. Lundquist, CRI194 (Jul 18)
• D. Ivanov, CRI 231 (JUl 18)

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7-YEAR DATA HOTSPOT RESULT

3

Max significance 5.1σ R.A=148.5°, Dec.=44.5° (17° from SGP)

𝟑𝟏° binning

Period : 2008 May – 2015 May Cuts:

• # of used detectors >=4
• Zenith angle < 55°
• Pointing Error < 10°
• Energy >= 57EeV

Resulting Data: 109 events

3.4σ post-trial significance

Energy distribution at this point shows an overall deficit of events COLD HOT Tighter Cuts, 20° bin

J.P. Lundquist, CRI194

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90 70 50 30 10 10

30 50 70 90 Declination δ/ 2000 4000 6000 8000 10000 Directional exposure ω(δ)/km2 yr

Auger SD vertical (2004 - 2014) Auger SD inclined (2004 - 2013) Telescope Array SD, θ < 45° (05/2008 - 05/2015) Telescope Array SD, θ < 55° (05/2008 - 05/2015)

Auger-TA Exposures

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