1 Jul 19, ICRC2017 Busan, Korea CRI125 “TA Spectrum Summary “: Energy Spectrum Measurements With The Telescope Array Detectors Yoshiki Tsunesada Osaka City University for The Telescope Array Collaboration
Millard county, Utah, US BR LR MD 2 507 SDs 3 FD stations TA Detectors • 700 km 2 m k 0 2 • Black Rock • Long Ridge SD Array • Middle Drum 507 counters • TALE - High-elevation FD
3 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 • 3 energy spectra from independent data set • SD: > 10 18.2 eV • BR/LR mono: > 10 17.2 eV • TALE Cherenkov: > 10 15.4 eV MD/TALE FD SD BR/LR
TA 7 years (ICRC2015) 8100 km 2 sr yr 2008/May/11 - 2017/May/11 2008/May/11 - 2017/May/11 4 2014/Jun - 22 months TA 9-Year Exposures [Area * FoV * Time] θ < 45°
5 SD Event Reconstruction Slide by D. Ivanov (U. Utah) NORTH [1200m] --> •The SD array measures the “footprint” of a shower S800 EAST [1200m] --> LDF (AGASA) • Use “S800” as an energy 800m estimator
6 TA SD Energy Scale • 1st energy estimate: A lookup table (S800, θ ) -> E TBL E TBL = f[S800,sec( θ )] X = Secant of zenith angle • Final energy is by scaling E TBL : • • θ ⌧ E TBL � �� • θ = 1 . 27 • E FD hyb ⌧ E TBL � E SD = E TBL / E FD hyb
7 Energy Resolution D. Ivanov, ICRC2015 FD energy systematic uncertainty 21%
8 TA SD 7-Year Spectrum (ICRC2015)
9 TA SD 9-Year Spectrum
10 TA SD “ICRC Spectra” 2011-2017
11 Power-Law Fit log E sup = 19.81 ± 0.04 2 0 . 0 ± 9 6 . 2 E 3.27±0.03 E E 4.63±0.49 log E ank = 18.69 ± 0.02 Nexp (no suppression): 79.8 Nobs: 26 Prob.: 2.2x10 -12 , 6.92 σ
12 TA SD and FD Mono TA ICRC2017 Preliminary
13 “Full-Range” TA Spectrum T. AbuZayyad, CRI126 TA ICRC2017 Preliminary
14 Comparison with Other Experiments
15 Declination Dependence /Spectral Anisotropies? E [eV] 10 19 10 20 10 38 eV 2 km � 2 sr � 1 yr � 1 i 10 37 I. Valinio, Auger ICRC2015 h E 3 J ( E ) � 90.0 � δ < � 49.3 � � 49.3 � δ < � 29.5 � � 29.5 � δ < � 10.0 � � 10.0 � δ < 24.8 � 10 36 18.5 19.0 19.5 20.0 log 10 ( E / eV)
htup://www.telescopearray.org/index.php/research/collaborators 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 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 for energies above 10 EeV. Linear fit is made to both fig than that of the Telescope Array. This effect cannot be explained by adjusting the energy scales of the two exper 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. 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. 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 ) 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 ( 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 spectrum and we have demonstrated that this is not an instrumental effect. In the first 7 years of the TA from 60 EeV to 40 EeV, and the TA spectrum is in a betuer agreement with the Auger spectrum. The 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 [1] R. U. Abbasi et al. [HiRes Collaboration], Phys. Rev. Letu. A [2] A. Aab et al. [Auger Collaboration] JCAP 1508 (2015) 49 shows the configuration of the entire TA detector [5] K. Greisen, Phys. Rev. Letu. 16 (1966) 183 tector consists of the three fluorescence detector (FD) [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 SD effectively covers a 680m of the main TA SD counters, small filled squares cor respond to the TALE infill array counters, and the [15] E. Kido [TA Collaboration], “The TAx4 experiment“ PoS(ICRC2017)510 fields of view of the three TA FD sites: Black Rock 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 between the Auger and TA results. We see a betuer agreement of the TA energy spectrum with the Research; by the U.S. National Science Foundation awards PHY-0601915, PHY-1404495, 16 Declination Dependence 19.59 /Spectrum Anisotropies? (2015R1A2A1A01006870, 2015R1A2A1A15055344, 2016R1A5A1013277, 2007-0093860, 19.85 for declinations from 24.8 to 90 2016R1A2B4014967); by the Russian Academy of Sciences, RFBR grant 16-02-00962a (INR), IISN D. Ivanov, CRI236 (Poster) JP. Lundquist, CRI194 (Jul 18) D. Ivanov, CRI 231 (JUl 18) Ezekiel R. and Edna Watuis Dumke, Willard L. Eccles, and George S. and Dolores Doré Eccles all ] -1 s × -1 Development Board, and the University of Utah through the Office of the Vice President for Re sr × -2 24 10 o o TA SD, -15.0 < < 24.8 δ m × 2 o o Auger SD, -15.7 < < 24.8 J [ eV δ U.S. Air Force. We appreciate the assistance of the State of Utah and Fillmore offices of the BLM in (E rescaled by +16%) o o TA SD, 24.8 < < 90 δ × 3 E advice on a variety of topics. The people and the officials of Mil-lard County, Utah have been a 19 19.2 19.4 19.6 19.8 20 20.2 20.4 log (E/eV) to the Millard County Road Department for their efforts to maintain and clear the roads which get 10 (b) us to our sites. We gratefully acknowledge the contribution from the technical staffs of our home 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 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
17 Conclusions TA 9-year SD/FD data and 3.5 years of TALE FD • Energy spectrum of cosmic rays in 4.7 decades > 10 15.4 eV • 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 - 6.9 σ . 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 D. Ivanov, CRI236 (Poster) JP. Lundquist, CRI194 (Jul 18) D. Ivanov, CRI 231 (JUl 18) TAx4 is of crucial importance.
18 J.P. Lundquist, CRI194 7-YEAR DATA HOTSPOT RESULT Period : 2008 May – 2015 May Tighter Cuts, 20° bin Cuts: # of used detectors >=4 • Zenith angle < 55° • Pointing Error < 10° • Energy >= 57EeV • 𝟑𝟏 ° binning Resulting Data: 109 events HOT COLD 3.4 σ post-trial significance Max significance 5.1σ Energy distribution at this point shows R.A=148.5°, Dec.=44.5° an overall deficit of events 3 (17° from SGP)
Recommend
More recommend
