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PoS(ICRC2015)810 , , , 4 , 1 5 1 , 9 , 10 , H. Rebel 1 , , B. Mitrica , J. Blümer , 4 http://pos.sissa.it/ 1 3 5 - , 8 12 , C. Grupen , T. Pierog , J. Milke 9 4 1 , G. Toma , K.-H. Kampert , Z. Feng 1 1 14 , M. Bertaina 1 , F. Cossavella 3 , J. Zabierowski 1 , O. Sima , R. Engel , T. Huege , H.J. Mayer , N. Palmieri 1 1 4 1 , K. Bekk 13 2 , R. Glasstetter 1 , P. Doll , A. Chiavassa 3 6 , , J. Wochele 3 , D. Huber 1 11 , H.J. Gils , H.J. Mathes 5 , F.G. Schröder 12 1 , S. Ostapchenko 1 , F. Di Pierro , A. Weindl 7 , E. Cantoni 1 5 , P. Łuczak , S. Schoo , J.C. Arteaga-Velázquez , J.R. Hörandel 4 1 1 1 , H. Ulrich 6 , A. Gherghel-Lascu , V. de Souza 9 , K. Link ˜ 1 ao Paulo, Instituto de Física de São Carlos, Brasil 1 , D. Heck , I.M. Brancus , J. Oehlschläger 1 1 6 , W.D. Apel , H. Schieler 1 ∗ 1 [email protected] Speaker. KASCADE-Grande was a multi-detector array toin measure the individual air energy showers range of of cosmicGrande, rays 10 an upper PeV limit up to to thedetermined. ﬂux 1 of The EeV. ultra-high analysis Based energy is on gamma-rays performed in full bysmall the selecting data fraction primary air of sets cosmic showers secondary rays measured with hadrons is low in by muon gammaresult KASCADE- ray contents on showers due the to to 90% cosmic a C.L. ray upper showers. limitray A to primaries preliminary the will relative intensity be of presented gamma-raysthis with and contribution. respect discussed to with cosmic- limits reported in previous measurements in ∗ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. Institut für Kernphysik, KIT - KarlsruheUniversidad Institute Michoacana, of Inst. Technology, Germany Física y Matemáticas,Dipartimento Morelia, di Mexico Fisica, Università degli StudiInstitut di für Torino, Italy Experimentelle Kernphysik, KIT -Horia Karlsruhe Hulubei Institute National of Institute Technology, Germany of PhysicsOsservatorio and Astroﬁsico Nuclear di Engineering, Torino, INAF Bucharest, Torino, Romania Italy Universidade S Institute of High Energy Physics, Beijing,Fachbereich Physik, China Universität Wuppertal, Germany Department of Physics, Siegen University, Germany Dept. of Astrophysics, Radboud University Nijmegen,National The Centre Netherlands for Nuclear Research, DepartmentFrankfurt of Institute Astrophysics, for Lodz, Advanced Poland Studies (FIAS),Department Frankfurt of am Physics, Main, University Germany of Bucharest, Bucharest, Romania c

H. Bozdog K. Daumiller The 34th International Cosmic Ray Conference, 30 July- 6 August, 2015 The Hague, The Netherlands D. Fuhrmann A. Haungs D. Kang Upper limits on the diffuse gamma-rayswith measured KASCADE-Grande H.O. Klages C. Morello M. Roth G.C. Trinchero KASCADE-Grande Collaboration E-mail: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 PoS(ICRC2015)810 D. Kang was optimized to measure 2 . Therefore, the usual strategy for 700 m 3 − × 10 ∼ . The angular resolution of KASCADE-Grande 2 2 ] array covering an area of 700 east, 110 m above sea level). It operated until the end of 2012 and 2 ◦ north, 8.4 over the whole energy range, so that it will allow us to perform also gamma-ray ◦ ◦ The KASCADE-Grande [ KASCADE-Grande was an extensive air shower experiment located at Karlsruhe Institute of Investigations of the galactic and extragalactic diffuse emission are potentially able to give For the diffuse flux of ultra-high energy gamma radiation, there are two main plausible sources: Extensive air showers are mainly characterized by the total electron number and the total This contribution presents upper limits on the relative intensity of the gamma-ray component ], whereas the same method of the analysis is applied. 1 is better than 0.5 extensive air showers up totions primary located energies on of a 1 hexagonal EeV.electromagnetic It grid and comprised with muonic 37 an shower components. scintillation average spacing detector Eachplastic of of sta- scintillators the 137 covering detector a m stations total for was area the equipped of measurements with 10 of m the searches. Technology (49.1 all components were by now dismantled. 2. The KASCADE-Grande experiment information about the source and propagation ofgamma-rays galactic and cosmic rays. its spectrum The measured thus fluxDirect may of provide diffuse measurements new of insights ultra-high intodifficult energy the due acceleration photons to of by the cosmic low satellite rays. fluxes. orbased This detectors detection balloon-borne using can, experiments the however, be air are accomplished shower by array large technique. area ground- First source is due tostellar decays gas of and neutral dust pions in the produced disktrated by of in the the the collision Galaxy. galactic In of this plane. cosmic-rays case,interactions with The the of inter- predicted second extremely integral one intensity high-energy is is cosmic-rays due concen- ground with to radiation the electromagnetic or 2.7 cascades topological K resulting defects from cosmologicalflux in the microwave of early back- secondary Universe. photons uniformly In distributedsurements this over of case, cosmological the this distances. diffuse results isotropic Therefore, gamma-ray in theergy flux an mea- cosmic-ray might isotropic components. provide information In on addition, thesearching this for ultra-high flux the en- would gamma-ray represent enhancement a from background the for direction experiments of the galactic disk. muon number. In general, muonshadronic are showers are produced produced by in the nucleus-nucleus decayphotoproduction interactions, of whereas processes. in charged The photon kaons ratio showers or only betweennucleus pions, in the interaction which cross processes in is sections very of small, photoproduction in and the order nucleus- of of cosmic rays measured by themore KASCADE-Grande data experiment. sets In of the the analysis,[ gamma-ray nearly simulations five are times used, compared to the one for the result in Ref. Upper limits on the diffuse gamma-rays measured with KASCADE-Grande 1. Introduction searches for primary gamma-rays in extensivefrom air the showers hadronic is background to by discriminate identifying gamma-ray muon-poor primaries extensive air showers. PoS(ICRC2015)810 ] 3 D. Kang . The spectral ◦ - 60 ◦ ]. Showers initiated by for air showers induced 5 6 . The efficiency is defined 1 •rays•rays•rays γγγ

Proton Proton Proton Iron Iron Iron ) ch lg(N 3 eV with zenith angles in the interval 0 18 - 10 14 200 GeV) model has been used for hadronic interactions at low energies. 5 5.5 6 6.5 7 7.5 8 8.5 < 1 0

0.8 0.6 0.4 0.2 ] (E Efficiency 4 Trigger and reconstruction efficiency as a function of the number of charged particles for air eV. However, for showers induced by photon primaries the full efficiency is higher due to the The FLUKA [ An essentail part of the present analysis is the Monte-Carlo simulation of the experiment. The trigger and reconstruction efficiency of KASCADE-Grande as a function of the shower 16 High-energy interactions were treated with different models QGSJETII-2 [ program has been used,individual applying detectors, hadronic all interaction secondary models.detector simulation particles program To using at the determine GEANT the package. thesuch ground The signals as predicted level e.g. observables in at are the ground the number level, passed of electrons, through muons a and photons complete are then compared to the measurements. by the ratio of thearea, number in of which the events binomial in statistical thereconstructed errors core reconstructed are positions, area used. i.e. to Efficiencies events falling above the outside oneFull the number are selected efficiency of due area is can to reached events be cuts at in reconstructed on the inside. the the number true of charged particles of around 10 For the simulation of the physical processes in the air shower development the CORSIKA [ size, i.e. the number of charged particles, is demonstrated in Fig. 3. Gamma and cosmic ray simulations primary photons, protons, He,covered the CNO, energy Si range of and 10 ironindex in nuclei the simulations have was -2 been andof for simulated. showers the analysis was it generated The is for weighted simulations each to particle a type. slope of -3. The same number 3.1 Efficiency by protons and iron primary10 particles, which approximately corresponds to a primary energy of Figure 1: showers induced by photons, protons and iron primaries. Upper limits on the diffuse gamma-rays measured with KASCADE-Grande PoS(ICRC2015)810 ) is (4.1) ch N D. Kang . This selection 2 to ensure full efficiency. ◦ ) and charged particles lg( events for a measurement time of µ 7 N ] and the efficiency for gamma-ray , 10 7 using the method of constant intensity 1 ◦ + × β 7 . − γ CR E E 4 γ ε 90 tot N N around the center of the array to avoid large reconstruction < 2 γ I CR I ] 7 CR I / γ I . The simulated gamma-ray showers are superimposed as well. The blue data points 2 , is estimated by [ Since gamma-ray induced air showers are notable for their lack of muons, compared to hadronic The selection of muon-poor showers is indicated by the straight line in Fig. No possible excess of events consistent with a gamma-ray signal was seen in the data. Hence, Assuming that all events passing the gamma-ray selections are indeed gamma-rays, the 90% For this analysis full data sets taken from 2003 to 2012 were used, where only successfully A scattered diagram of the observed number of muons lg( CR I ]. / 6 γ showers, we select amuons, data i.e., sample we therefore enriched takesubtracted in a from photon the more event conservative showers number way by below in the rejecting which cut line. the showers expected containing background is not we assume that allgamma-ray events fraction below of the the selectionof cosmic line observed rays. are events, background applying We and estimate standard the set statistical 90% upper methods C.L. limits [ upper on limit the on theupper limit number on the fractionI of the gamma-ray integral flux relative to the cosmic-ray integral flux, [ is motivated by the simulatedevents below gamma-rays the and straight its line1060 optimization were out is taken of into still a total consideration under of formainly investigation. 17 further due millions analysis. events. to The In primary They the photons amount regionto because below to electron air this ratio. line showers the induced events by are heavy expected to nuclei be show a4.3 larger Upper muon limit of detection. indicate the whole experimental dataevents. set, The whereas shower size the is red corrected one to a illustrate zenith the angle simulated of gamma-ray 20 errors at the edges of the detector field. The zenith angle is smaller than 40 reconstructed and precisely measuredare events inside a were circular selected. area of 152,214 The m core positions of the showers Upper limits on the diffuse gamma-rays measured with KASCADE-Grande missing muon trigger at largethe distances. Grande The array. limit at high energies is due to the4. restricted area The of analysis and result 4.1 Selection of data After applying all quality cuts, we obtained in total ca. 1 ca. 1865 days. 4.2 Gamma hadron discrimination shown in Fig. PoS(ICRC2015)810 . ch CR CR I N E / γ I D. Kang ) 17 4 PeV). − 10 > 1.19 8.51 8.64 8.32 3.89 γ × < < < < < ( E is the efficiency for γ I γ ε 5 4 3 2 2 9.0 = 3.0, − − − − − β 10 10 10 10 10 CR 8.5 I × × × × × and number of charged particles / ) γ is the 90% C.L. upper limit on the I bin using the resulting Gaussian , are given in the unit of TeV. µ γ γ 1.88 6.79 2.08 1.03 2.48 N I 8.0 -rays ch E ( < < < < < γ N simulated 7.5 4 4 4 5 5 10 10 10 10 10 . γ × × × × × 1 7.0 E − ) sr eV. ch 1 1.38 3.29 8.30 1.98 2.92 − 5 6.5 16 s 2 lg(N 4 4 5 5 5 10 − 6.0 10 10 10 10 10 × CR × × × × × E 5.5 5.0 90 , and the mean gamma-ray energy, N 358 3.21 Exp. data is the integral cosmic-ray spectral index ( CR 4.5 E β 6 10 5 4 3 8 7 6

4.0

µ lg(N ) tot N ). Therefore, they are calculated for a fixed is the 90% C.L. upper limit on the number of detected events, ch ) displays the measurements on the gamma-ray fraction as a function of energy, includ- N 90 ch 3 N N are summarized in Table 1. To determine upper limits to the integral flux of gamma-rays 6.5 6.19 7 85537 351 8.72 7.5 9640 214 2.21 8 1239 122 5.31 8.5 165 78 1.13 Scatter distribution of the measured number of muons lg Results of the search for diffuse ultra-high energy gamma-rays at different threshold values of lg( > > > > > ch are the mean energies of cosmic-ray and gamma-ray, respectively, which produce the same ]. The flux limits are also given in Table 1. , superimposed with simulated gamma-ray showers. The green line indicates the selection criteria for N ) γ 8 Figure where The results of the search for diffuse ultra-high energy gamma-rays for different threshold val- E ch N ( ing this work, for thethe energy first range results of in 10 the PeV energy range up above to 5 300 PeV. The limits presented here represent The mean cosmic-ray energy, Table 1: lg the subset of the muon-poor showers. is the 90% C.L. upperintegral limit gamma-ray flux on in the the integral unit gamma-ray of fraction, photons cm and Figure 2: Upper limits on the diffuse gamma-rays measured with KASCADE-Grande gamma-ray detection, and shower size ( at fixed gamma-ray energies, we useRef. measurements [ of the all-particle primary energy spectrum of ues of and function. PoS(ICRC2015)810 ]; 14 D. Kang 6 10 ] and with theoretical 13 , 5 12 10 ] of the KASCADE experiment 10 4 . The lines are the IceCube excess models 4 10 6 are upper limits, except the one from MSU [ ] in Fig. (TeV) 4 γ 3 11 E 10 GRAPES3 (Minamino et al. 2009) GRAPES3 (Minamino et al. MSU (Fomin et al. 2013) KASCADE, Ref. [10] KASCADE-Grande, this work CASA-MIA (ChantellCASA-MIA et al. 1997) (AgliettaEAS-TOP et al. 1996) (AharonianHEGRA et al. 2002) (Karle etHEGRA al. 1995) UMC (Cassiday et al. 1991) 2 10 for 13.8 PeV. These stringent limits are the first results in the energy range 5 − 10

1 10 -1 -5 -6 -2 -3 -4

10 CR 10 10 10 10 10 γ I /I 88 . Fraction of gamma-rays relative to the cosmic rays. The red stars represent the results from 1 20 kpc in the galactic plane. It might hence set some constrains on the distance of sources < < It should be noted that all values in Fig. These results are compared with other previous experiments [ Using full data sets measured by the KASCADE-Grande experiment, the 90%The C.L. best upper upper limit to the fraction of the gamma-ray to the cosmic-ray flux is obtained: CR I / γ curves by a specific IceCube excess model [ with more data are compatible withfrom the theoretical prediction of the IceCubefor excess the model IceCube coming Excess. Details will be described elsewhere in a forthcoming publication. coming from different distances ofalso sources responsible for of primary neutrinos gamma-rays. in The the updated galaxy, results where [ these neutrinos are limits to the diffuse fluxPeV of are ultra-high determined energy by selecting gamma-rays showers for with the low energy muon range contents. ofI 10 PeV to 300 above 10 PeV, and mightsearch constrain for the a galactic limit disk to enhancement of the cosmic background rays. rate Comparison of of these muon-poor experimental showers upper in the Figure 3: KASCADE-Grande. This reported positive signal seems to be disproved by the presented results. 5. Conclusion Upper limits on the diffuse gamma-rays measured with KASCADE-Grande PoS(ICRC2015)810 D. Kang 6 10 5 ]. It should be mentioned that this might 10 9 7 4 Pierre Auger (SettimoPierre et al. 2013) 2013) IceCube excess model (Ahlers&Murase (Ahlers&Murase 2013) IceCube excess model, 8.5kpc (Ahlers&Murase 2013) IceCube excess model, 20kpc (Ahlers&Murase 2013) IceCube excess model, 30kpc CASA-MIA (ChantellCASA-MIA et al. 1997) (AgliettaEAS-TOP et al. 1996) MSU (Fomin et al. 2013) KASCADE, Ref. [10] KASCADE-Grande, this work 10 Energy(TeV) 3 ] of the original KASCADE experiment are updated by including 10 10 ]. 11 2 10 -11 -19 -15 -16 -17 -18 -12 -13 -14

Integral flux (cm flux Integral sr s ) 10 10 10 10 10 10 10 10

-1 -1 -2 Comparison of integral ﬂux of gamma-rays with previous results and with theoretical curves by The authors would like to thank the members of the engineering and technical staff of the In addition, the results [ Acknowledgments KASCADE-Grande collaboration, who contributed to the success ofGrande the experiment. experiment The is KASCADE- supportedAstroparticle in Physics Germany - by HAP’ funded the bysociation, BMBF the by and Initiative the and by MIUR Networking the and Fundand INAF ’Helmholtz of the of the Alliance Romanian Italy, Helmholtz for the Authority As- Polish for17/2011). Ministry Scientiﬁc J.C.A.V. of Research acknowledges the Science UEFISCDI partial and (PNII-IDEI support Higher grants of Education, 271/2011 CONACyT. and set some constraints on the distance of sources for the IceCube excess. eight years of more data since the publication in Ref. [ limits with the theoretical predictionsat is energies still around required, 10 since PeV. no Thesehadron preliminary theoretical discrimination results predictions and will exist also be so by improved a far by new muon a reconstruction. more careful gamma- Figure 4: an IceCube excess model [ Upper limits on the diffuse gamma-rays measured with KASCADE-Grande PoS(ICRC2015)810 D. Kang (2010) 202 171104 (2011)171104 (2012) 183 A 620 36 107 Nucl. Instr. Meth. Astropart. Phys. Phys. Rev. Lett. 8 (1997) 1805 79 (1996) 71 (2006) 014026 6 (1983) 319 D 74 212 Phys. Rev. Lett. Phys. Rev. Nucl. Instr. Meth. (2015) #0811 these proceedings (2014) [9] G. Schatz et al. KASCADE Collaboration, Proc. 28th Int. Cosmic Ray Conf., Tsukuba, Japan (2003) [1] D. Kang et al. KASCADE-Grande Collaboration, Proc. 24th European Cosmic Ray[2] Symposium, Kiel W.D. Apel et al. KASCADE-Grande Collaboration, [3] D. Heck et al., Rep. FZKA[4] 6019, ForschungszentrumA. Karlsruhe Fassò (1998) et al., CERN-2005-10, INFN/TC-05/11,[5] SLAC-R-773 (2005) S.S. Ostapchenko, [6] W.D. Apel et al. KASCADE-Grande Collaboration, [7] O. Helene, [8] W.D. Apel et al. KASCADE-Grande Collaboration, [10] Z. Feng et al. KASCADE Collaboration, 34th Int. Cosmic Ray Conf.,[11] The Hague,M. The Ahlers Netherlands and K. Murase, arXiv:1309.4077v3[12] (2014) M. Aglietta et al., Astopart. Phys. [13] M.C.Chantell et al., [14] Yu. A. Fomin, arXiv:1307.4988v2 (2013) Upper limits on the diffuse gamma-rays measured with KASCADE-Grande References