The Pierre Auger Observatory and ultra-high energy neutrinos: upper limits to the diffuse and point source fluxes

Transcription

1 id 068 The Pierre Auger Observatory and ultra-high energy neutrinos: upper limits to the diffuse and point source fluxes Yann Guardincerri1 for the Pierre Auger Collaboration 1 Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina Observatorio Pierre Auger, Av. San Martı n Norte 304, (5613) Malargu e, Argentina Full author list: html 3nd ICRC, Beijing 011 HE.3

2 Identifying neutrinos in data Challenge: identify neutrino showers in a background of nucleonic showers. The discrimination power is enhanced when looking at inclined showers. (1) Inclined showers are mainly regular nucleonic cosmic rays. They interact high in the atmosphere. At ground level there are mainly muons. (, 3,4 and 5) Neutrinos can induce showers close to the ground. 4) double-bang shower initiated by ν τ 1) regular shower initiated by proton muonic component of the shower τ ) deep shower initiated by ν E-M component of the shower 5) down-going shower initiated by ν τ τ detector Two analysis: Earth-skimming (3) Down-going (, 4 and 5) τ 3) up-going shower initiated by ν τ first interaction τ decay Basis of identification criteria: inclined young (deep) shower. / 15

3 The Pierre Auger Observatory: surface detector Array 1600 water Cherenkov stations ( 3000km ) With the SD we can distinguish muonic from electromagnetic shower fronts. Water Cherenkov stations Signals are digitised with 5 ns time resolution signal [VEM] 6 4 PMT 1 μ signal [VEM] PMT time [ns] time [ns] signal [VEM] 6 4 PMT signal [VEM] PMT time [ns] time [ns] signal [VEM] 6 4 PMT 3 E-M signal [VEM] PMT time [ns] time [ns] 3 / 15

4 Identification criteria: inclined showers Elongated footprint Apparent velocity of propagation of shower front at ground along major axis L Vertical shower T ij 0 V c Horizontal shower V c Earth-skimming Elongated event: L/W 5 Signal speed: 0.9 ns m V 0.31 ns m SD(V )< 0.08 ns m Down-going Elongated event: L/W 3 Signal speed: V ns m SD(V ) < 8% V Rec. zenith angle θ 75 4 / 15

5 Identification criteria: deep showers Deep showers induce signals extended in time. Earth-skimming Time over Threshold trigger (ToT): Down-going Area over Peak 13 bins over 0. VEM in a 3µs window + AoP>1.4 ToT fraction>0.6 ToT station Thr station ToT station Thr station ToT Fraction>0.6 ToT Fraction<0.6 MV-Analysis: Fisher discriminating variables AoP of first 4 stations Non linear transformation of them. Asymetry parameter: early AoP - late AoP 5 / 15

6 General neutrino search strategy Two analysis: Earth-skimming and down-going Same approach: blind search procedure 6 / 15

7 Exposure Earth-skimming (3.5 yr of full Auger) s sr] Exposure [cm Down-going ( yr of full Auger) Total CC e CC µ CC τ NC x CC τ Mountains ν energy (ev) / 15

8 Opening the box After unblinding: 0 candidates found in both analysis. We proceed to place an upper limit. 8 / 15

9 Integral limits to diffuse fluxes sr -1 ] s -1 Single flavour neutrino limits (90% CL) -5 Down-going (yr) EarthSkimming (3.5yr) IceCube-40 (333.5 days) -6 Anita-II Rice Exotic Cosmogenic - ƒ(e) [GeV cm E ν energy (ev) k <.8 8 GeV cm s 1 sr 1 in ev < E <.0 19 ev 19 0 k < GeV cm s 1 sr 1 in 1 17 ev < E < 1 0 ev 1 9 / 15

10 Differential limits to diffuse fluxes -5 Single flavour neutrino limits (90% CL) sr -1 ] -6 - ƒ(e) [GeV cm E s Down-going (yr) EarthSkimming (3.5yr) IceCube-40 (333.5 days) Anita-II Exotic Cosmogenic ν energy (ev) / 15

11 Limits to point like sources s -1 ] -5-6 Single flavour neutrino limits (90% CL) Down-going (yr) Earth-skimming (3.5yr) Fixed energy range 17 ev < E < 0 ev ev < E < 19 ev g(e) [GeV cm - E -7-8 Cen A IceCube-40 (375.5 days) Energy range depends on declination Below 17 ev Source declination [deg] Sensitive to potential point sources of UHE neutrinos in a broad range in declination. 11 / 15

12 Limits to Cen A -4-5 Down-going (yr) LUNASKA s -1 ] - g(e) [GeV cm E Earth-skimming (3.5yr) IceCube-40 (375.5 days) Cuoco Kachelriess Anchordoqui ν energy (ev) Expected number of events is bellow 0.1 for current models. 1 / 15

13 Conclusions Method to search for Earth-skimming and down-going UHE neutrinos using the Surface Detector of the Pierre Auger Observatory. Competitive limit to UHE neutrino diffuse flux: Earth-skimming is sensitive to ν τ k <.8 8 GeV cm s 1 sr 1 in ev < E <.0 19 ev Down-going is sensitive to all neutrino flavors. k < GeV cm s 1 sr 1 in 1 17 ev < E < 1 0 ev The surface detector of the Pierre Auger Observatory is sensitive to potential point sources of UHE neutrinos in a broad range in declination. 13 / 15

14 BACK UP SLIDES 14 / 15

15 Expected number of events for two diffuse neutrino flux models and two CenA neutrino flux models. Diffuse flux model Earth-skimming Down-going Cosmogenic Exotic CenA flux model Earth-skimming Down-going Cuoco et al Kachelriess et al / 15