Cosmic Rays in the PeV Energy Range: KASCADE-Grande

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1 22nd Texa Sympoium on Relativitic Atrophyic at Stanford Univerity, Dec , 2004 Comic Ray in the PeV Energy Range: KASCADE-Grande A. Haung, W.D. Apel, F. Badea, K. Bekk, J. Blümer, H. Bozdog, K. Daumiller, P. Doll, R. Engel, J. Engler, F. Feßler, H.J. Gil, D. Heck, H.O. Klage, G. Maier, H.J. Mathe, H.J. Mayer, J. Milke, M. Müller, R. Obenland, J. Oehlchläger, S. Otapchenko, S. Plewnia, H. Rebel, H. Schieler, J. Scholz, T. Thouw, H. Ulrich, J. van Buren, A. Weindl, J. Wochele, S. Zagromki Intitut für Kernphyik, Forchungzentrum Karlruhe, Karlruhe, Germany T. Antoni, J.R. Hörandel, M. Roth, M. Stümpert Intitut für Experimentelle Kernphyik, Univerität Karlruhe, Karlruhe, Germany A. Bercuci, I.M. Brancu, B. Mitrica, M. Petcu, O. Sima, G. Toma National Intitute of Phyic and Nuclear Engineering, 7690 Bucharet, Romania M. Bertaina, A. Chiavaa, F. Di Pierro, G. Navarra, S. Valchierotti Dipartimento di Fiica Generale dell Univerità, 125 Torino, Italy M. Brüggemann, P. Buchholz, Y. Kolotaev, S. Over, W. Walkowiak, D. Zimmermann Fachbereich Phyik, Univerität Siegen, Siegen, Germany P.L. Ghia, C. Morello, G.C. Trinchero Itituto di Fiica dello Spazio Interplanetario, CNR, 133 Torino, Italy R. Glatetter, K.-H. Kampert Fachbereich Phyik, Univerität Wuppertal, Wuppertal, Germany A. Rie, J. Zabierowki Soltan Intitute for Nuclear Studie, Lodz, Poland Recent reult from the multi-detector et-up KASCADE on meaurement of comic ray in the energy range of the o called knee (at 3 PeV) are preented. The multidimenional analyi of the air hower data indicate a ditinct knee in the energy pectra of light primary comic ray and an increaing dominance of heavy one toward higher energie. Thi provide, together with the reult of large cale aniotropy tudie, implication for dicriminating atrophyical model of the origin of the knee. To improve the recontruction quality and tatitic at higher energie, where knee-like feature of the heavy primarie are expected at around 0 PeV, KASCADE ha recently been extended by a factor in area to the new experiment KASCADE-Grande. 1. INTRODUCTION The all-particle energy pectrum of comic ray how a ditinctive dicontinuity at few PeV, known a the knee, where the pectral index change from 2.7 to approximately 3.1 (Fig. 1). At that energy direct meaurement are preently hardly poible due to the low flux, but indirect meaurement oberving extenive air hower (EAS) are performed. Atrophyical cenario like the change of the acceleration mechanim at the comic ray ource (upernova remnant, pular, etc.) or effect of the tranport mechanim inide the Galaxy (diffuion with ecape probabilitie) are conceivable for the origin of the knee a well a particle phyic reaon like a new kind of hadronic interaction inide the atmophere or during the tranport through the intertellar medium. Two clae of theorie (diffuion or acceleration baed) predict knee poition occurring at contant rigidity of the particle. On the other hand, the hypothei of new hadronic interaction mechanim at the knee energy, a for example the production of heavy particle in pp colliion, implie an atomic ma dependence of the knee poition. It i obviou that only detailed meaurement and analye of the primary energy pectra for the different incoming particle type can validate or diprove ome of thee model. Depite EAS meaurement with many experimental etup in the lat five decade the origin of the kink i till not clear, a the dientanglement of the threefold problem of etimate of energy and ma plu the undertanding of the air-hower development in the Earth atmophere remain an experimental challenge. For a detailed dicuion of the ubject ee a recent review [1]. The multi-detector ytem KASCADE (KArlruhe Shower Core and Array DEtector) [2] approache thi challenge by meauring a much a poible redundant information from each ingle air-hower event. The multi-detector arrangement allow to meaure the total electron and muon number of the hower eparately uing an array of hielded and unhielded detector at the ame place. Additionally muon denitie at further three muon energy threhold and the hadronic core of the hower by an iron ampling calorimeter are meaured. Recently KASCADE wa extended in area by a factor to the new experiment KASCADE-Grande. KASCADE-Grande allow now a full coverage of the energy range around the knee, including the poible econd knee at around 0 PeV (ee Fig. 1). From KASCADE [2] meaurement we do know that at a few time 15 ev the knee i due to light element [3], that the knee poition depend on the kind of the incoming particle, and that comic ray around the knee arrive our Earth iotropically [4, 5]

2 ! 22nd Texa Sympoium on Relativitic Atrophyic at Stanford Univerity, Dec , 2004 ) ev -1 r PROTON RUNJOB +. ' -0/1+ ( ta ,3 DE (9;: H He EGF=H vy ,3 56I JGKDLMLN=O AB DE ( H He EGF=H vy PRQTS no UV WXS I UV WXS II PYZP*[ A -2 ec 16 ) (m 15 & #%$ " E 14 Tevatron LHC KASCADE - G' (*),+ - Pierre A\M]M^ r E_`8^Ga b c;^ nt gy Figure 1: Primary comic ray flux and primary energy range covered by KASCADE-Grande. Reult of the KASCADE data analye are alo hown (ee text). KASCADE-Grande [6, 7], meauring higher energie, will prove, if exitent, the knee correponding to heavy element. Additionally KASCADE could how that no current hadronic interaction model which are unavoidably needed for the interpretation of air hower data, decribe very well comic ray meaurement in the energy range of the knee and above [9]. Thee model uncertaintie are due to the lack of accelerator data at thee energie and epecially for the forward direction of colliion. Multi-detector ytem like KASCADE and KASCADE-Grande offer the poibility of teting and tuning the different hadronic interaction model. With it capabilitie KASCADE-Grande i alo the ideal tetbed for the development and calibration of new air-hower detection technique like the meaurement of EAS radio emiion [8]. 2. THE KASCADE EXPERIMENT The KASCADE experiment [2], located at the Forchungzentrum Karlruhe, Germany, (49 n, 8 e, 1 m a..l.) meaure hower in a primary energy range from 0 TeV to 80 PeV and provide multiparameter meaurement on a large number of obervable concerning electron, muon at 4 energy threhold, and hadron. The main detector component of KASCADE are the Field Array, the Central Detector, and the Muon Tracking Detector. The Field Array meaure the total electron and muon number (E µ > 230 MeV) of the hower eparately uing an array of 252 detector tation containing hielded and unhielded detector at the ame place in a grid of m 2. The excellent time reolution of thee detector allow alo decent invetigation of the arrival direction of the hower in earching large cale aniotropie and, if exitent, comic ray point ource. The Muon Tracking Detector (128 m 2 ) meaure the incidence angle of muon (E µ > 800 MeV) relative to the hower arrival direction. Thee meaurement provide a enitivity to the longitudinal development of the hower. The hadronic core of the hower i meaured by a 300 m 2 iron ampling calorimeter intalled at the KASCADE Central Detector: Three other component - trigger plane (erve alo a timing facility), multiwire proportional chamber (MWPC), and limited treamer tube (LST) - offer additional valuable information on the penetrating muonic component at 490 MeV and 2.4 GeV energy threhold, repectively. The whole KASCADE etup i read out if a certain multiplicity of the array detector tation or of the trigger plane i firing, leading to a trigger rate of 4 Hz. The redundant information of the hower meaured by the Central Detector and the Muon Tracking Detector i predominantly being ued for tet and improvement of the hadronic interaction model

3 y 22nd Texa Sympoium on Relativitic Atrophyic at Stanford Univerity, Dec , 2004 ux Do q {~ˆ,ƒ Šq, ƒ np wx* D qœ Ž 0 } = 8 6 x wx {w Zo de*fxgxh i jxk;e ge lgmzh y coordinate [m] Piccolo Cluter 200 m (# of 18) Grande tation x coordinate [m] npoo qr t uvmwx ozy 200 m 13 m tx {w o Dƒ{ }Mwq tion x wx {w Zo~}Mwq tion 0 m 20m Figure 2: The main detector component of the KASCADE experiment: (the 16 cluter of) Field Array, Muon Tracking Detector and Central Detector. The location of radio antenna i alo diplayed, a well a three tation of the Grande array. 3. THE KASCADE-GRANDE EXPERIMENT The multi-detector concept of the KASCADE experiment ha been tranlated to higher primary energie through KASCADE-Grande []. The 37 tation of the Grande Array (Fig. 3) extend the comic ray meaurement up to primary energie of 1 EeV. The Grande tation, m 2 of platic cintillator detector each, are paced at approximative 130 m covering a total area of 0.5 km 2. There are 16 cintillator heet in a tation read out by 16 high gain photomultiplier; 4 of the cintillator are read out alo by 4 low gain PM. The covered dynamic range i up to 3000 mip/m 2. A trigger ignal i build when 7 tation in a hexagon (trigger cluter, ee Fig. 3) are fired. Therefore, the Grande Array conit of 18 hexagon with a total trigger rate of 0.5 Hz. Additionally to the Grande Array a compact array, named Piccolo, ha been build in order to provide a fat trigger to KASCADE enuring joint meaurement for hower with core located far from the KASCADE array. The Piccolo array conit of 8 tation with 11 m 2 platic cintillator each, ditributed over an area of 360 m 2. One tation contain 12 platic cintillator organized in 6 module; 3 module Figure 3: Sketch of the KASCADE-Grande experiment. form a o-called electronic tation providing ADC and TDC ignal. A Piccolo trigger i built and ent to KASCADE and Grande when at leat 7 out of the 48 module of Piccolo are fired. Such a logical condition lead to a trigger rate of 0.3 Hz. To improve further the data quality a elftriggering, dead-time free FADC-baed DAQ ytem will be implemented in order to record the full time evolution of energy depoit in the Grande tation at an effective ampling rate of 250 MHz and high reolution of 12 bit in two gain range [11]. Thi will lead to an intrinic electron-muon eparation of the data ignal at the Grande Array. 4. KASCADE RESULTS Search for aniotropie and point ource: Invetigation of aniotropie in the arrival direction of the comic ray give additional information on the comic ray origin and of their propagation. Depending on the model of the origin of the knee and on the aumed tructure of the galactic magnetic field one expect large-cale aniotropie on a cale of 4 to 2 in the energy region of the knee. The limit of large-cale aniotropy analyzing the KASCADE data are determined to be between 3 at 0.7 PeV primary energy and 2 at 6 PeV [4]. Thee limit were obtained by invetigation of the Rayleigh amplitude and phae of the firt harmonic. Taking into account poible nearby ource of galactic comic ray like the Vela Supernova remnant [15] the limit of KASCADE already exclude particular model prediction. But for a complete picture the invetigation

4 š 22nd Texa Sympoium on Relativitic Atrophyic at Stanford Univerity, Dec , 2004 lg N e Θ < 1 8 o œ Ÿž X X G œd M X Xœ QGSJET Xœ SIBYLL lg N tr µ Figure 4: Two dimenional electron (N e) v. muon (Nµ tr = number of muon in m core ditance) number pectrum meaured by the KASCADE array. The line diplay the mot probable value for proton and iron primarie obtained by CORSIKA imulation employing different hadronic interaction model. have to be performed with air hower ample of the different ma group which need a higher tatitical accuracy in meaurement. Some interet for looking to point ource in the KASCADE data ample arie from the poibility of unknown near-by ource, where the deflection of the charged comic ray would be mall or by ource emitting neutral particle like high-energy gamma or neutron. Due to their mall decay length the latter one are of interet for near-by ource only. Invetigated were the full ample of air hower a well a a ample of muon-poor hower which i a ample with an enhanced number of candidate of γ-ray induced event. No ignificant exce wa found in both ample [5]. With a imilarly obtained ample of enhanced gamma candidate an analye wa performed to etimate limit on the diffue high-energy gamma ray flux in the energy range from 0.3 to PeV [16]. The limit are found to be cloe to the theoretically predicted diffue γ-ray pectra from [17]. Energy pectra of individual ma group: The KASCADE data analye aim to recontruct the energy pectra of individual ma group taking into account not only different hower obervable, but alo their correlation on an event-by-event bai. The content of each cell of the two-dimenional pectrum of recontructed electron number v. muon number (Fig. 4) i the um of contribution from the individual primary element. Hence the invere problem g(y) = K(y, x)p(x)dx with y = (N e, Nµ tr ) and x = (E, A) ha to be olved. Thi problem reult in a ytem of coupled Fredholm integral equation of the form dj d lg N e = d lg Nµ tr + A d J A d lg E pa(lg Ne, lg N tr µ lg E) d lg E of ho % where the probability p A i a further integral with the kernel function k A = r A ɛ A A factorized into three part. The quantity r A decribe the hower fluctuation, i.e. the ditribution of electron and muon number for given primary energy and ma. The quantity ɛ A decribe the trigger efficiency of the experiment, and A decribe the recontruction probabilitie, i.e. the ditribution of recontructed N e and Nµ tr for given true number of electron and muon. The probabilitie p A are obtained by Monte Carlo imulation on bai of two different hadronic interaction model (QGSJET 01 [18], SIBYLL 2.1 [19]) a option embedded in CORSIKA [20]. By applying the above decribed procedure (with the aumption of five primary ma group, only) to the experimental data energy pectra are obtained a diplayed in Fig. 1. The reulting pectra for primary oxygen, ilicon, and iron are added in the figure for a better viibility. A knee like feature i clearly viible in the all particle pectrum, which i the um of the unfolded ingle ma group pectra, a well a in the pectra of primary proton and helium. Thi demontrate that the elemental compoition of comic ray i dominated by the light component below the knee and by a heavy component above the knee feature. Thu, the knee feature originate from a decreaing flux of the light primary particle. Inaccuracie of hadronic interaction model: Comparing the unfolding reult baed on the two different hadronic interaction model, the model dependence when interpreting the data i obviou. Modeling the hadronic interaction underlie aumption from particle phyic theory and extrapolation reulting in large uncertaintie, which are reflected by the dicrepancie of the reult preented here. In Fig. 4 the prediction of the N e and Nµ tr correlation for the two model are overlayed to the meaured ditribution in cae of proton and iron primarie. It i remarkable that all four line have a more or le parallel lope which i different from the data ditribution. There, the knee i viible a kink to a flatter N e -Nµ tr dependence above lg Nµ tr 4.2. The heavier primary contribution on the reult baed on the SIBYLL model i due to prediction of a maller ratio of muon to electron number for all primarie. Comparing the reidual of the unfolded two dimenional ditribution for the different model with the initial data et we conclude [9] that at lower energie the SIBYLL model and at higher energie the QGSJET model are able to decribe the correlation conitently, but none of the preent model give a contenting decription of the whole data et. Crucial parameter in the modeling of hadronic interaction model which can be reponible for thee inconitencie are the total nucleu-air cro-ection and the part of the inelatic and diffractive cro ection leading to hift of the poition of the hower maximum in the atmophere and, therefore, to a

5 ½ ¼»º íîê ì ê y 22nd Texa Sympoium on Relativitic Atrophyic at Stanford Univerity, Dec , 2004 y [m -2 ] ¾½  ÁÃÄ À Á ¾ 3 2 Å Æ~ÇXÈ6ÆZÉ E ~Ó XÏ= Ð Í ;Î Ï8 Í;Ð ª«= D ID KASCADE KASCADE Grande Ñ Ð Ò MÎ ŸÎ Ï8 Í;Ð 1-1 Å Æ~ÇXÈ6ÆZÉ E ÊÌËMÍ ;Î X XÏ8 Í Ð Figure 6: Comparion between KASCADE and KASCADE-Grande data for a combined tet-run = *± ² ³Ÿµ %Ḑ¹ 8² [m] ëëì í 1 4/7 Û Ü Ý gger Figure 5: Particle denitie in the different detector type of KASCADE-Grande meaured for a ingle event. change of the muon and electron number a well a to their correlation on ingle air hower bai. The multiplicity of the pion generation at all energie at the hadronic interaction during the air hower development i alo a emi-free parameter in the air-hower modeling a accelerator data have till large uncertaintie [12]. 5. FIRST MEASUREMENTS WITH KASCADE-GRADE Fig. 5 how, for a ingle event, the lateral ditribution of electron and muon recontructed with KAS- CADE and the charge particle denitie meaured by the Grande tation. Thi example illutrate the capabilitie of KASCADE-Grande and the high quality of the data. The KASCADE-Grande recontruction procedure follow iterative tep: hower core poition, angle-of-incidence, and total number of charged particle are etimated from Grande Array data; the muon denitie and with that the recontruction of the total muon number i provided by the KASCADE muon detector. The recontruction accuracy of the hower core poition and direction i in the order of 4 m (13 m) and 0.18 (0.32 ) with 68% (95%) confidence level for proton and iron hower at 0 PeV primary energy and 22 zenith angle [13]. The tatitical uncertainty of the hower ize are around 15% for both, the total number of electron and muon. The critical point of the KASCADE-Grande recontruction i the etimation of the muon number due to the limited ampling of the muon lateral ditribution by the KASCADE muon detector. The ytematic uncertainty for the muon number depend on the radial /7 ÛTÜ Ý gger p (N µ >0) Fe XØÙ4Ú >19 0% Þ,ßßXà á ient above 2x 16 ev Ô,Õ,Õ,Ö Ô,Õ 0m 2 <42 o â~ã%ä mary åæ=å ã ç y lg(e 0 /Gåè6é Figure 7: Efficiency of the Grande array (detail ee text). range of the data meaured by the KASCADE array and the choen lateral ditribution function. At the KASCADE experiment, the two-dimenional ditribution hower ize - truncated number of muon played the fundamental role in recontruction of energy pectra of ingle ma group. In Figure 6 the correlation of thee two hower ize for both cae KASCADE and KASCADE-Grande meaurement are compared for a 1-day tet-run. For the ame run time, due to it time larger area compared with KASCADE, the Grande Array ee a ignificant number of hower at primary energie time higher. Hence, Figure 6 illutrate the capability of KASCADE-Grande to perform an unfolding procedure like in KASCADE. Figure 7 how the efficiency characteritic of the KASCADE-Grande array. For internal tet of the detector tation a 4/7 trigger i performed at the hexagon. The efficiency of the 7/7 trigger are alo

6 22nd Texa Sympoium on Relativitic Atrophyic at Stanford Univerity, Dec , 2004 hown which i only mall decreaing if additionally i required that the muon number ha to be recontructed with the information of the muon detector of the original KASCADE array. To reduce efficiently the amount of data a oftware cut will be applied with the requirement of at leat 20 Grande tation (NGRS > 19) have to be fired. A hundred percent efficiency i than reached for all primary particle type for energie above 2 16 ev, providing till a large overlap with the KASCADE energy range. The limit at high energie for Grande i due to the limitation in area and not aturation of the detector, a even at primary energy of 18 ev only one tation in average i aturated. 6. CONCLUSIONS The extenion of KASCADE to the KASCADE- Grande experiment, acceing higher primary energie, i expected to prove the exitence of a knee-like tructure correponding to heavy element. KASCADE-Grande keep the multi-detector concept for tuning different interaction model at primary energie up to 18 ev. KASCADE-grande alo provide the perfect environment detecting radio emiion in extenive air hower. Thi i the aim of the LOPES project and ubject of a further paper in thee proceeding [8]. Acknowledgment KASCADE-Grande i upported by the Minitry for Reearch and Education of Germany, the INFN of Italy, the Polih State Committee for Scientific Reearch (KBN grant for ) and the Romanian National Academy for Science, Reearch and Technology. [2] T. Antoni et al. - KASCADE collab., Nucl. Intr. Meth. A 513 (2003) 429. [3] T. Antoni et al. - KASCADE collab., Atrop. Phy. 16 (2002) 373. [4] T. Antoni et al. - KASCADE collab., Atrophy. J. 604 (2004) 687. [5] T. Antoni et al. - KASCADE collab., Atrophy. J. 608 (2004) 865. [6] G. Navarra et al. - KASCADE-Grande collab., Nucl. Intr. Meth. A 518 (2004) 207. [7] A. Haung et al. - KASCADE-Grande collab., Proc. of 28 th ICRC, Tukuba, Japan (2003) p.985. [8] A. Haung et al. - LOPES collab., thee proceeding. [9] H. Ulrich et al. - KASCADE Coll., Europ. J. C (2004) DOI.1140/epjcd/ [] A.F. Badea et al. - KASCADE-Grande collab., Nucl. Phy. B (Proc. Suppl.) 136 (2004) 384. [11] W. Walkowiak et al. - KASCADE-Grande collab., A FADC-baed Data Acquiition Sytem for the KASCADE-Grande Experiment, Proc. of IEEE Nuclear Science Sympoium, Rome [12] R. Engel, Nucl. Phy. B (Proc. Suppl.) 122 (2003) 437. [13] R. Glatetter et al. - KASCADE-Grande collab., Proc. of 28 th ICRC, Tukuba, Japan (2003) p.781. [14] S.N. Vernov et al., Can. J. Phy. 46 (1968) 241. [15] V. Ptukin, Adv. in Space Re. 19 (1996) 697. [16] G. Schatz et al. - KASCADE Coll., Proc. of 28 th ICRC, Tukuba, Japan (2003) p [17] F.A. Aharonian, A.M. Atoyan, Atron. Atrophy. 362 (2000) 937. [18] N.N. Kalmykov, S.S. Otapchenko, Phy. Atom. Nucl. 56 (1993) 346. [19] R. Engel et al., 26 th ICRC, Salt Lake City, Utah 1 (1999) p.415. [20] D. Heck et al., Report FZKA 6019, Forchungzentrum Karlruhe (1998). Reference [1] A. Haung, H. Rebel, M. Roth, Rep. Prog. Phy. 66 (2003)