Recent measurements of ultra-high energy cosmic rays and their impact on hadronic interaction modeling

Transcription

1 Recent measurements of ultra-high energy cosmic rays and their impact on hadronic interaction modeling Hans Dembinski KIT Karlsruhe KIT University of the State of Baden-Württemberg and National Large-scale Research Center of the Helmholtz Association

2 Outline 100 TeV 1000 TeV Ultra-high energy cosmic rays direct observation 2 indirect observation (via air showers)

3 Outline Introduction and experiments Energy spectrum Xmax and other mass-sensitive observables Limits on photons/neutrinos p-air cross-section Muon number Hadronic interaction properties air shower observables Bottom line: Air shower experiments can be used to indirectly measure p-air cross-section, elasticity, multiplicity at E > 50 TeV but in a highly model dependent way. 3

4 Air showers ultra-high energy "vertical" showers cosmic ray top of atm osphe re hadrons mesons 0 6 ~ "very inclined" showers e, e,, 4 Bgeo fluorescence light in forward direction also Cherenkov light

5 Cosmic ray measurement FD Fluorescence light Fluorescence yield measured in lab Integrate to get energy Eem µ and ν are invisible weakly model dependent above 1018 ev 5 Longitudinal signal profile

6 Cosmic ray measurement Lateral signal profile at ground Sref SD γ, e, µ SD observes only slice of shower development SD cross-calibrated to FD SD samples lateral density profile of e, µ, and possibly γ, depending on detector type Very inclined showers can be observed if detectors have depth : measure muon component 6 Sref µ E (θ < 60 ) Auger: θ > 60 N19 µ Nµ µ E

7 Experiments 7

8 Experiments above 10 ev 18 Northern Hemisphere HiRes and Telescope array Utah, U.S.A. HiRes (aka Fly's Eye) Telescope Array (Successor of HiRes and AGASA) Southern Hemisphere Pierre Auger Observatory Argentina Pierre Auger Observatory Other experiments: Volcano Ranch, SUGAR, Haverah Park, Yakutsk, AGASA 8

9 HiRes (High Resolution Fly's Eye) Fly's Eye formed by overlapping field of views of fluorescence telescopes Fly's eye I Fly's eye I 67 telescopes 360 field of view 3.4 km Fly's eye II 180 field of view Telescope with PMT camera Monocular operation (HiRes-I) Energy resolution ~27 % Stereo operation (HiRes-II) Western desert of Utah, U.S.A m asl 9 Energy resolution ~20 % ~1/7 exposure of monocular D. Bird et al., Astrophys. J., 1994

10 Pierre Auger Observatory Loma Amarilla AMIGA and Radio R&D FD building Coihueco and HEAT XLF CLF Los Morados SD station 10 m2 Water-Cherenkov detector Fluorescence detector (FD) Los Leones 27 fluorescence telescopes Energy resolution ~10 % Surface detector (SD) Malargüe, Argentina 1400 m asl stations Energy resolution ~(15 20) %

11 Telescope array FD building SD station 3 m2 scintillation detector Fluorescence detector (FD) Middle Drum 14 refurbished HiRes telescopes Energy resolution ~16 % Long Ridge and Black Rock 24 fluorescence telescopes Energy resolution ~8 % Surface detector (SD) Western desert of Utah, U.S.A m asl 507 stations Energy resolution? S. Ogio [TA Collab.]; T. Nonaka [TA Collab.]; D. Ikeda [TA Collab.], ICRC Beijing,

12 Exposure Telescope Array PierreAuger Observatory D.C. Rodriguez [TA Collab.]; F. Salamida [Auger Collab.], ICRC Beijing,

13 Energy spectrum 13

14 Energy spectrum Auger θ < 60 γ = 3.27 γ= γ= F. Salamida [Auger Collab.]; H. Dembinski [Auger Collab.]; D. Ikeda [TA Collab.]; ICRC Beijing, 2011 R.U. Abasi et al., Astropart. Phys., 2005 TA 4.2 flux unfolded of detector effects HiRes Auger 60 < θ < 80 14

15 Energy spectrum TA vs. HiRes Agreement, but not so surprising... Middle drum = refurbished HiRes telescopes Data analyis largely the same Same fluorescence yield 15 TA vs. Auger Fluorescence yields and absolute FD calibration differ Agreement between Auger and TA if energy is rescaled by 16 %

16 FD energy scale R. Pesce [Auger Collab.], ICRC Beijing, 2011 T. Abu-Zayyad [TA Collab.], ICRC Beijing, 2011 Telescope Array Auger Lab measurements of fluorescence yield Auger observed difference is well within estimated sys. uncertainty of E-scale TA 16

17 Observables related to mass composition 17

18 Depth of shower maximum Xmax Shower maximum Xmax of proton showers compared to iron showers... develops deeper on average... fluctuates more CORSIKA simulation p Fe depend on hadronic interaction model X0 γ Heck et al., FZKA6019, 1998 Photons behave like super-light hadrons: very deep showers, muon poor 18

19 Field of view bias R. Ulrich [Auger Collab.], ICRC Beijing, 2011 Toy Monte-Carlo Field of view of FD telescopes does not cover full Xmax range for all shower geometries 19

20 Field of view bias R. Ulrich [Auger Collab.], ICRC Beijing, 2011 Toy Monte-Carlo Not all shower geometries allow to observe the full Xmax range HiRes and TA approach Do not correct bias Apply detector simulation to generator-level prediction to be consistent Results are detector dependent 20

21 Field of view bias R. Ulrich [Auger Collab.], ICRC Beijing, 2011 Toy Monte-Carlo Auger approach Select only shower geometries that cover full Xmax range Compare measurement directly with generator-level prediction Results are detector independent 21

22 Mean Xmax P. Facal San Luis [Auger Collab.]; Y. Tameda [TA Collab.], ICRC Beijing, 2011 R.U. Abbasi et al., Astrophys. J., 2005 Auger p Fe HiRes p TA p Fe Fe 22

23 Mean Xmax P. Facal San Luis [Auger Collab.]; Y. Tameda [TA Collab.], ICRC Beijing, 2011 R.U. Abbasi et al., Astrophys. J., 2005 Auger p QGSJet-II Fe HiRes p TA p Fe Fe 23

24 Xmax fluctuations Auger p P. Facal San Luis [Auger Collab.], ICRC Beijing, 2011 R.U. Abbasi et al., Astrophys. J., 2005 HiRes p Fe Fe Detector resolution subtracted from data σres 27 g cm-2 σres 18 g cm-2 Variance of distribution in each bin 24 Detector resolution folded into prediction Fit of truncated Gaussian to suppress long tails

25 Xmax fluctuations P. Facal San Luis [Auger Collab.], ICRC Beijing, 2011 R.U. Abbasi et al., Astrophys. J., 2005 QGSJet-II Auger p HiRes p Fe Fe Detector resolution subtracted from data σres 27 g cm-2 σres 18 g cm-2 Variance of distribution in each bin 25 Detector resolution folded into prediction Fit of truncated Gaussian to suppress long tails

26 Auger: X D. Garcia-Gamez [Auger Collab.], ICRC Beijing, 2011 µ max is Geometrical (optical) model of muon propagation Good approximation for ax z fro nt shower plane front tg 26 production point sh ow er sh ow er pl an e r µ Muon production depth SD station SD station muon trace Auger event E ~ 94 EeV θ ~ 59

27 Auger: Mass observables SD observables muon production depth inclination angle with largest rise time asymmetry FD observables 27 D. Garcia-Pinto [Auger Collab.], ICRC Beijing, 2011

28 Searches for photons and neutrinos (very briefly) 28

29 Photon limits M. Settimo [Auger Collab.]; G.I. Rubtsov [TA Collab.], ICRC Beijing, 2011 Photons develop deeper larger Xmax and front curvature Photons muon poor smaller signal deposited in SD, larger signal rise time Auger below 1019 ev: Hybrid analysis, combining Xmax and TA: SD analysis, using front curvature proton shower photon shower Auger above 1019 ev: SD analysis, combining rise time and front curvature 29

30 Photon limits M. Settimo [Auger Collab.]; G.I. Rubtsov [TA Collab.], ICRC Beijing, 2011 Gelmini et al., 2007 Ellis et al., 2006 SD: Astrop. Phys. 29, 2008 Auger Hybrid 2009: Astrop. Phys. 31, 2009 A (AGASA), Shinozaki et al., 2002 Y (Yakutsk), Glushkov et al.,

31 Neutrino limits Y.Guardincerri [Auger Collab.], ICRC Beijing, 2011 Similar techniques as for photon search, but look for horizontal deep showers Auger SD assumptions: ν-flux µ E-2 νe:νµ:ντ = 1:1:1 ν-exposure computed from simulations 31

32 p-air cross section 32

33 Auger method: Xmax tail R. Ulrich [Auger Collab.], ICRC Beijing, 2011 = But: Can only observe Xmax with possibly mixed composition Idea Use tail of Xmax distribution CONEX simulation Photons < 0.5 % CONEX simulation 33

34 Auger method: Xmax tail Fit Xmax tail with exponential distribution in energy range ev to obtain slope R. Ulrich [Auger Collab.], ICRC Beijing, 2011 Shift in simulations up and down to get mapping Then invert this mapping to get from measured CONEX simulation 34

35 p-air cross-section R. Ulrich [Auger Collab.], ICRC Beijing, 2011 K. Belov [HiRes Collab.], ICRC Mexico, 2007 Auger 57 TeV HiRes 78 TeV 35

36 Muon content 36

37 Very inclined events Auger E = ev 1/4 of all events are very inclined Auger remains efficient up to 37 3ToT vertical trigger 4C1 inclined trigger

38 G. Rodríguez [Auger Collab.], ICRC Beijing, 2011 Muon scale N19 Auger Reconstruction of muon scale N19 scale factor universal lateral profile Hybrid events σ[n19]/n19 < 24 % Muon excess wrt p QGSJet-II at 1019 ev bias of N19 < 3 % 38

39 Auger: Muon excess J. Allen [Auger Collab.], ICRC Beijing, 2011 Auger Multivariate muon jump method Shower universality method Simulation matching method N19 method Simulation matching method using SENECA N19 p QGSJet-II 39

40 T. Abu-Zayyad [TA Collab.], ICRC Beijing, 2011 Muon excess in TA? ESD from COSMOS simulation Cross-calibration plot From cross-calibration of TA hybrids SD Ground signal S800 larger than expected from COSMOS proton simulations 40 FD

41 Air shower observables and Hadronic interactions 41

42 Hadronic interactions R. Ulrich, R. Engel, M. Unger, Phys. Rev. D, 2011 Investigate connection Xmax, Ne, Nµ (Mean, Fluctuation) cross-section, multiplicity, elasticity, A Nµ can be observed with SD at θ > 60 and dedicated muon detectors (e.g. AMIGA) Xmax RMS(Xmax) Ne RMS(Ne) Nµ RMS(Nµ) X-section, multiplicity, elasticity X-section X-section, multiplicity, elasticity X-section, multiplicity π+/- to π0 ratio, multiplicity elasticity CONEX proton simulation with modified version of SIBYLL Challenge: and changing with E effect needs to be modeled, too 42 f19 energy dependent scale factor

43 Summary Energy spectrum (HiRes, Auger, TA) +++ Agreement within systematic uncertainty of energy scale Cross-calibration desirable, need world-average of fluorescence yield Mass composition (HiRes, Auger, TA) ++/ Consistency between Auger FD and Auger SD Discrepancy between HiRes (possibly TA) and Auger! Analysis/Interpretation issue? Limits on photons/neutrinos (HiRes, Auger, TA) +++ p-air cross-section (HiRes, Auger) ++ Muon number (Auger) ++ Large muon excess in data for any mass assumption/model, TA also sees hints Hadronic interaction properties: cross-section, elasticity, multiplicity Only indirect measurement with significant model dependency Best observables 43

44 Backup 44

45 Hadronic model influence 45 proton iron proton iron

46 Hadronic model influence 46 proton iron proton iron

47 Anisotropy 47

48 Anisotropy 48

49 Pierre Auger Observatory ( ) ev AMIGA Auger stations with 750 m spacing Buried 30 m2 scintillation detectors (muon counters) Standard array 1500 m spacing 49

50 Pierre Auger Observatory ( ) ev HEAT Tiltable Auger FD telescopes Elevated field of view from 30 to 60 Double time resolution HEAT HEAT Coihueco Coihueco Standard array 1500 m spacing 50

51 Improved calibration techiques Electron light source at Telescope array site 40 MeV electron beam pulse as seen by TA telescope 51

52 FD energy scale Fluorescence yield New AIRFLY measurements σsys ~ 4 % Experiments should decide on world average Experiments should cross-calibrate using common light source MC corrections 52 F. Arqueros et al. ICRC 2011, Beijing