EeV Neutrinos in UHECR Surface Detector Arrays:

Transcription

1 EeV Neutrinos in UHECR Surface Detector Arrays: OBSERVATORY Challenges & Opportunities Karl-Heinz Kampert Bergische Universität Wuppertal High-Energy neutrino and cosmic ray astrophysics - The way forward Weizmann Institute of Science January -15, HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

2 The Is UHECR-Flux-Suppression this the GZK-Effect? 18 E[eV] 19 arxiv: Update from: PRL 1, 0611 (008), Physics Letters B 685 (0) 39 0 )) s -1 sr -1 ev γ1=3.9 * Eankle= ev γ=.60 * E50% = ev 54 OBSERVATORY - J /(m ( E log 3 apple Is this the GZK-effect... J(E;E > E a ) µ E g log E log E 1/? 1 + exp log W c.5 g g Auger (ICRC 015 preliminary) log (E/eV) combined from: infill+hybrid+vertical+inclined events HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

3 Cosmogenic Neutrinos Recall: If flux suppression above 5 19 ev is due to GZK-effect: expect cosmogenic neutrinos & photons as smoking gun Additional benefit: UHE neutrino physics If due to source exhaustion: neutrinos & photons strongly suppressed 3 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

4 EeV ν s and γ s : Smoking gun of GZK-effect p + CMB!!! n + +! EeV! p + 0! EeV -4 p, best fit with Fermi-LAT bound (Ahlers) KHK, Unger, APP 35 (01) s -1 sr -1 ] - dn/de [ GeV cm E p, FRII & SFR, E = max 0 Fe, FRII & SFR, E max =6 x ev (B. Sarkar) ev (B. Sarkar) p & mixed, SFR & GRB, E =Z x - max GZK-Fe GZK-p ev (Kotera) TopDown models GZK-p GZK-Fe E ν [ev] Note, these calculations assume that the flux suppression is caused solely by the GZK-effect ec?on+in+eev+range+may+provide+complementary+informa?on+to+direct+u 4 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

5 Exhausted UHECR Sources Taylor, Ahlers, Hooper; PRD 9 (015) present upper limits by Auger 1 n = 0 / proton only n = 3/mixed n = 0/mixed ARA-37 (3yr) ARA (3yrs) E J [ev cm s 1 sr 1 ] 0 1 n = n = 3/mixed 6/mixed } maximum energy scenarios that describe UHECR spectra and composition E [ev] Cosmogenic neutrino fluxes may be down by ~ orders of magnitudes for exhausted sources!! 5 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

6 Inclined+showers+ Search for EeV Neutrinos &+UHE+neutrinos+ in inclined showers Protons+&+nuclei+ini?ate+showers+ high+in+the+atmosphere.++ Shower+front+at+ground:++ mainly+composed+of+muons+ electromagne?c+component+ absorbed+in+atmosphere.+ Neutrinos+can+ini?ate+ deep + showers+close+to+ground.+ Shower+front+at+ground:+ electromagne?c+++muonic+ components+ Searching+for+neutrinos+ + searching+for+inclined+showers+ +with+electromagne?c+component+ ν τ$ 6+ 6 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

7 Particle Detectors and Radio Antennas This talk: Particle Detectors at the surface: Auger and beyond Optical detection by Fluorescence Telescopes not covered (lower exposure because of duty cycle) Next Talk by Jörg Hörandel: Potential of radio detection at the surface 7 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

8 Surface Detector Station+ Surface+Detector+(SD)+sta?ons! Sensi?ve+to+inclined+showers.++ x Not+directly+sensi?ve+to+electromagne?c+and+muonic+components.+! Can+measure+the+?me+structure+of+the+signals+induced+by+electrons+and+muons+ 3.6 x 1. = 4.3 m detector area in horizontal direction. Great advantage of WCD! GPS Communications antenna electronics Solar panels 3 photomultiplier tubes Signals+are+digi?zed+with+ 5+ns+?me+resolu?on++ Battery box VEM+ FADC(trace( Example+of+signal+ induced+by+a+muon+ plastic tank 1 tons of purified water t+(ns) HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

9 Identifying νs in surface detector data With+the+SD,+we+can+dis?nguish+muonic+from+electromagne?c+shower+fronts+ (using+the+?me+structure+of+the+signals+in+the+water+cherenkov+sta?ons).+ old shower new shower signal [VEM] signal [VEM] signal [VEM] time [ns] 6 4 PMT 1 PMT time [ns] 6 4 PMT time [ns] 5 EeV, distance to shower axis ~1km zenith angle ~80 signal [VEM] signal [VEM] signal [VEM] PMT time [ns] PMT time [ns] PMT time [ns] 5 EeV, distance to shower axis ~1km zenith angle ~ 9 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15,

10 Identifying νs in surface detector data From+the+observa?onal+point+of+ view,+signals+extended+in+?me:+ Trace+example:+ToT+trigger+&+large+AoP+ Induce+Time&over&Threshold+ (ToT)+triggers+in+the+SD+ sta?ons and/or+ Defini?on+of+Area&over&Peak+(AoP)+ Have+large+Area&over&Peak+ value+(aop+ +1+muonic+front)+ Searching+for+neutrinos+ + Searching+for+inclined+showers+with+sta?ons++ with+tot+triggers+and/or+large+aop+ 9+ HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

11 Sensi?vity+to+all+flavours+&+channels+ EAS are sensitive to all ν flavors and channels + 11 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

12 Selection of inclined showers: 3 Observables 3+observables+ (1)+Elongated+footprint+ WW Δt ij d ij Main axis Figure 5: Schematic view of the footprint of a shower triggering the Parameters: L/W, <v>, RMS(v) LL ()+Apparent+velocity+V+of+propaga?on+of++ shower+front+at+ground+along+major+axis+l+ Ver?cal+shower V+>>+c+ Horizontal+shower V+ +c+ (3)+Reconstructed+θ$ Downward-going Downward-going Selection Earth-skimming (ES) ν high angle (DGH) low angle (DGL) Flavours and interactions ν τ CC ν e ; ν μ ; ν τ CC & NC ν e ; ν μ ; ν τ CC & NC Angular range θ >75 L/W θ > 90 >3 θ ð75 ; 90 Þ θ ð60 ; 75 Þ N of stations (N st ) L/W N>5 st 3 N st 4 N st 4 Inclined showers θ rec > 75 L=W > 5 L=W > 3 hvi ð0.9; 0.31Þ m ns 1 hvi < m ns 1 rmsðvþ < 0.08 m ns 1 rmsðvþ=hvi < 0.08 θ rec ð58.5 ; 76.5 Þ 1 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

13 ν Identification: Earth Skimming Events 3 Training data Search data Monte Carlo ν τ <AoP> AoP > 1.83 ~ 90% of ν-events selected ν τ candidate region 1 Note: ν-searches not limited by background! (cut set to 1 background event per 50 yrs) <AoP> AoP: Area over peak 13 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

14 ν Identification: Down Going (75-90 ) Events 4 AoP of stations along with other observables constructed from AoP combined in a Fisher linear discriminant Training data Search data Monte Carlo ν 3 Fisher > ν candidate region ~ 90% of ν-events selected again: allow 1 background event per 50 yrs Fisher value 14 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

15 Exposure: Earth Skimming ντ τ Exposure:++ 1. Tau+neutrino+propaga?on+and+tau+ Earth&skimming+ν produc?on:+ + τ Dedicated+MC+for+propaga?on+of+ 1. Tau+neutrino+propaga?on+and+tau+ ν τ +through+the+earth+producing+ produc?on:+ emerging+tau+leptons.++ Convolute+with+probability+of+tau+ Dedicated+MC+for+propaga?on+of+ decay+in+the+atmos.+(exponen?al)+ ν τ +through+the+earth+producing+. Tau+decay+products+obtained+with+ emerging+tau+leptons.++ TAUOLA+generator:++ Convolute+with+probability+of+tau+ All+decays+included++ decay+in+the+atmos.+(exponen?al)+. Tau+decay+products+obtained+with+ 17%+BR+to+muons+which+are+not+ TAUOLA+generator:++ detected+ 3. Shower+induced+by+tau+decay+ All+decays+included++ products+simulated+with+aires+ 17%+BR+to+muons+which+are+not+ detected+ 4. Detector+simula?on+performed+ 3. Shower+induced+by+tau+decay+ with+auger+offline+package+ products+simulated+with+aires Detector+simula?on+performed+ with+auger+offline+package+ + Events E ντ = ev - Energy spectra of emerging τ θ = 90.1 deg. θ = 91. deg. θ = 94.8 deg log (E /ev) τ. TAUOLA 1. ν τ PROPAGATION 4. OFFLINE 3. AIRES Mean Mean Mean HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15,

16 Acceptance and Uncertainties 18 s sr ] 17 ES Earth-Skimming ντ dominates exposure (loss at higher energies due to τ decays high in the atmosphere) Exposure [ cm DGH DGL Combined (1 Jan 04-0 Jun 13) Earth-Skimming Relative contribution to expected event rate: Earth Skimming: ~84% Down Going (75-90 ) ~ 14% Down Going (60-75 ) ~ % Downward-going 75 < θ < 90 deg. Downward-going 60 < θ < 75 deg E ν [ev] 19 0 Source of systematic Combined uncertainty band Simulations +4%, -3% cross section & E-loss +34%, -8% Topography +15%, 0% Total +37%, -8% 16 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

17 EeV Neutrino Limits Auger Collaboration, PRD 91, (015) Single flavour, 90% C.L. s -1 sr -1 ] 5 6 IceCube 013 (x 1/3) [30] Auger (this (015) work) ANITA-II 0 (x 1/3) [9] Cosmogenic ν models p, Fermi-LAT best-fit (Ahlers ') [33] p, Fermi-LAT 99% CL band [33] p, FRII & SFR (Kampert '1) [31] Fe, FRII & SFR (Kampert '1) [31] p or mixed, SFR & GRB (Kotera ') [9] Waxman-Bahcall '01 [13] - dn/de [ GeV cm E E ν [ev] HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

18 EeV Neutrino Limits Single flavour, 90% C.L. -5 IceCube 013 (x 1/3) [30] ] sr -1-6 Auger (this (015) work) ANITA-II 0 (x 1/3) [9] Auger Collaboration, PRD 91, (015) Cosmogenic ν models p, Fermi-LAT best-fit (Ahlers ') [33] p, Fermi-LAT 99% CL band (Ahlers ') [33] p, FRII & SFR (Kampert '1) [31] - s -1 dn/de [ GeV cm E Waxman-Bahcall '01 [13] E ν [ev] Would have expected to see 1-7 GZK neutrinos (for different models), have seen none Neutrino upper limits start to constrain cosmogenic neutrino fluxes of p-sources 18 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

19 EeV Neutrino Limits Single flavour, 90% C.L. -5 IceCube 013 (x 1/3) [30] Cosmogenic ν models Auger Collaboration, PRD 91, (015) Auger (this (015) work) Fe, FRII & SFR (Kampert '1) [31] ] sr -1-6 ANITA-II 0 (x 1/3) [9] p or mixed, SFR & GRB (Kotera ') [9] - s -1 Waxman-Bahcall '01 [13] dn/de [ GeV cm -7-8 E E ν [ev] Cosmogenic Neutrino Models with mixed/heavy primaries still below present upper limits 19 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

20 EeV Neutrino Limits Challenge GZK J. Heinze et al., ApJ 016 preliminary exclusion limits from IceCube expected ν-fluxes if flux suppression of TA is due to GZK-effect Pure Figure 4. proton All-flavor flux of with cosmogenic GZK neutrinossuppression predicted by the 3D fit to challenged by upper limits to neutrino fluxes 0 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

21 Where could we get with Auger and beyond? Present data represent 3 yrs (4.5 yrs) of full SD array and run into 013 if no ν are observed, limits will go down by factor ~ rule out high flux models Single flavour, 90% C.L. -5 IceCube 013 (x 1/3) [30] ] sr -1 s -1 - dn/de [ GeV cm Auger (this work) ANITA-II 0 (x 1/3) [9] Cosmogenic ν models p, Fermi-LAT best-fit (Ahlers ') [33] p, Fermi-LAT 99% CL band (Ahlers ') [33] p, FRII & SFR (Kampert '1) [31] Waxman-Bahcall '01 [13] Moreover: exploit new trigger for better sensitivity at lower E E ν [ev] energies and use data of infill array (low exposure, however) a next generation CR-Observatory would reach down to Fe/mixed composition scenarios 1 HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017

22 What, if we observe a Neutrino? Energy estimate of a ν candidate: Only the energy of the ν-induced shower (Eshower) can be reconstructed ν flavour cannot be determined & Eshower depends on flavour At best a lower bound to E ν, because E ν > Eshower ν can interact anywhere in atmosphere: Eshower determination should include shower age No algorithm including age exists so far Angular reconstruction of quasi-horizontal events: Not optimised for deeply penetrating & very inclined showers (> 80 ) Angular resolution ~ 1- Identification of up-going shower would indicate tau neutrino primary Conservative statement: Auger = discovery experiment (a counter of UHE neutrinos) HE Neutrinos and UHECR - The way forward: Weizmann Institute, Jan. -15, 017