Detection of UHE tau neutrinos with a surface detector array

1. - Detection of UHE tau neutrinos with a surface detector array M. Iori ,Roma1

2. OUTLINE • Neutrino tau • Detection method → an alternative method • From theory we know… • Neutrino conversion efficiency • Results of tests of a prototype at high altitude (3600m) M. Iori ,Roma1

3. Neutrino tau • Standard acceleration processes in astrophysics rarely produce τ. • e : μ : τ =1:2:0 • In case of oscillation full mixing, the flux ratios evolves towards • e : μ : τ =1:1:1 for a very large range in Δm2 ~ 50%Eντ ντ →CC → τ + h → shower(1) + shower (2) ντ →NC → ντ+ h \→ τ → shower (1) 1st shower:  decays into hadrons (0.64), this shower carries visible Eτ ~ 0.5 Eν 2nd shower: neutrino-nucleon scattering, this shower carries 0.2 Eν Eτ=(1-y)Eν 0.2<y<0.8 <y>=0.25 and Eτ=0.75 Eν CC • Motivation: • μ↔ τoscillation of atmospheric neutrinos well established • No direct evidence for astrophysics τ appearance observed yet M. Iori ,Roma1

4. Could the flavour ratios differ from 1:1:1? • High Energy neutrinos are belived to be produced through the decays π+→μ+ +νμ→ e+ + νμ + νe + νμ produced in pγ,pp,pn interactions. The ratio of the fluxes of neutrinos is expected to be 1:2:0 • if energy losses is considered (radiation) for µ from high energy pion decay → suppression of contribution of muon decay • Then we expect a ratio at source 0:1:0 • Reactor results give each mass eigenvalues contains equal fraction of νμ–ντthen at Earth the ratio is 1:2:2 Ref.J..F. Beacom N.F.Bell, D. Hooper,S.Pakvasa, T.J.Weiler Phys. Rev. D 68 093005 2003 Neutrinos from π and μ decays M. Iori ,Roma1

5. Other scenarios if not 1:1:1 • Neutrino decay(Beacom, Bell, Hooper, Pakvasa& Weiler) • CPT violation(Barenboim& Quigg) • Oscillation to steriles with very tiny delta δm2 (Crocker et al; Berezinskyet al.) • Pseudo-Dirac mixing(Beacom, Bell, Hooper, Learned, Pakvasa& Weiler) • 3+1 or 2+2 models with sterile neutrinos(Dutta, Reno and Sarcevic) • Magnetic moment transitions(Enqvist, Keränen, Maalampi) • Varying mass neutrinos(Fardon, Nelson & Weiner; Hung & Pas) M. Iori ,Roma1

6. Detection methods • UHEC neutrinos E>108 GeV are difficult to be detected: • The atmosphere is transparent → low density • The Earth opaque to them, νinteraction length ≤ 2000 km • Detection by Large Volume detectors → Cerenkov: rate Φshower = NAv ρ∫(dΦν/dE)dEσνA • ντ channel is quite different from νμ • τ will decay and generate a cascade decay vertex and showers are separated by several ten meters at PeV → double bang event. • This signature is constrained by effective volume • Similar to detection techniques used in low energy experiments (Super-K) • Technique with a proven capacity to detect neutrinos (atmospheric) Cascade detection: e, τ Effective volume = instrumented volume Poor pointing accuracy, Good energy resolution Muon tracking: Effective volume >> instrumented Volume Excellent pointing, Poor energy resolution M. Iori ,Roma1

7. ντdetection technique in a large Volume detectors Cascade detection Lτ =49 Eτ m/PeV τ ντ ντ km3 M. Iori ,Roma1

8. Detection methods cont’d 2. Detection by Large Surface detector: • ρair =10-3 g/cm3 hence large acceptance → 104 km3 sr → Auger • Horizontal neutrino shower rate Φshower =NAvρair ∫ (dΦν/dE)dEσνA • If we increase ρ of a factor ~2500 (i.e.rock) we can reduce the acceptance τ → alternative method → M. Iori ,Roma1

9. An alternative method → Earth skimmed neutrinos * Earth skimming process implies: • neutrino propagation in the Earth during which interacts and regenerates (~10% →see Beacom et al.) • tau propagation in the Earth during which looses energy and decays in the atmosphere after exit from Earth surface .→ upward going air shower emerging from the ground may be detected using the fluorescence light (low duty cycle ~10%) or a directional detector. *J.F.Beacom, D. Fargion, J.L. Feng, E.W. Kolb and E. Zas M. Iori ,Roma1

10. Detection strategy: aim at the horizon • strategy to detect τis aim at the horizon To do that we must have: • direction detection (i.e time of flight) • good geometric acceptance M. Iori ,Roma1

11. Different models evaluate the UHE neutrino flux AGN: galaxies with extremely Energetic processes in the nuclei. They are the most likely source of cosmic rays above 1015 eV. AGNs are thought to be fueled by matter accreting onto black holes. Z-burst:A very high energy (>1021 eV) neutrino interacts with a relic neutrino left over from the Big Bang. This produces showers of particles, some of which are neutrinos. GZK:Any high energy hadron will interact with the cosmic microwave background (CMB). This will eventually lead to the production of neutrinos. The rate at which hadrons interact with the CMB is controlled by the injection spectrum of the hadrons and the characteristics of the universe. The uncertainties in this rate can be as high as 300%. topological defects (TDs) which are relics of symmetry breaking just after the Big Bangexcluded by Auger exp Pune Conf. 2005 M. Iori ,Roma1

12. AGN and GZK Excluded by A-B10 Astr.Phys 22 339 05 AGN AGN integrated flux ~104 km-2 yr-1sr-1 @ Eτ108-1011 GeV GZK is a factor 102 -103 less AGN hep-ph/0011176 GZK GZK mechanism: ⌐ p+ e- + νe p+γcmb→Δ+→n +π+ ∟μ++ν ∟e++νe +νμ JCAP 0404 2004 Cosmological neutrino flux and sensitivity for planned projects M. Iori ,Roma1

13. Search for ντup-going Tau events: • τshower: high multiplicity 10 particles/m2 • 64% hadronic decays n(π)ντ • Curved shower wave front (detected by timing) unlike the plane wavefront of atmospheric showers at large angles • Shower emerging from ground Θ>900 • Decay vertex above the ground Backgrounds: • Horizontal atmospheric shower, p interaction → low multiplicity 0.01 particles /m2 • DIS with pions..muon bundles M. Iori ,Roma1

14. Time structure of tau shower tau decay : shower with particles spreaded in time → curvature radius The shower Max occurs after 3-4 km the decay point μ density in a time window of 500 ns Ordinary hadrons or nuclei (p,Fe..) interact at the top of the atmosphere. Electromagnetic component reduced, muons → plane wavefront M. Iori ,Roma1

15. A comment on acceptance for neutrino showers Geometric Acceptance is function of Array Surface and shower radius mainly hence → • Effective area,A = (a sin(α-β)+2r)(b+2r)dΏ where • Surface of Array, S=axb • r=shower radius of shower at first interaction point • Emerging angle Β =Θzenith-90 ~ 50 • Horizontal array α~0, sinβ~10-2 hence → no emerging showers can be detected, only horizontal → Auger surface detector • Inclined array sin(α-β)~0.6 • Detection and trigger efficiency good → no particular event topology required M. Iori ,Roma1

16. Probability to get an emerging Tau ν interaction length in rock neutrino cross section Τau Range in air Τau Range in rock.behaviour including photonuclear pair and bremsstrahlung The tau flux is determined by ratio tau range to CC neutrino N interaction length Ratio @ 1017-18 eV ~10-3hence ν flux at energy>1017 eV Rdecay =E/mτcτ M. Iori ,Roma1

17. Charged particles as function of the depth of the shower Gaisser_Hillas distribution total γ μ e π • Laundau-Pomeranchuck-Migdal effect • retards the development of em component • M.T.Dova astro-ph/0505583 τ→ πππντ At large depth muons constant and electrons drop; at 3 km electrons/muons ~100 M. Iori ,Roma1

18. The neutrino conversion efficiency, ε in the Earth crust we computed the probability for τ of energy E to survive for a slant depth x inside the crust of Earth and converting to τ within [x, x+dx] e(-x/λν) dx/λν (int.length,λν=1/NAσρ) The probability for a tau lepton of energy E’ to survive for a slant depth L-x inside the Earth crust and exit the crust with the energy Eτincluding the energy loss. • The neutrino conversion efficiency :ε=∫ e(-x/λν) e(L-x/λτ) dx/λν is convolutedwith decay length and longitudinal shower development and neutrino flux 1/E2 gives : M. Iori ,Roma1

19. The τ sample versus θ and εfor Eν = 108 -1011 GeV Tau decay length from ground Toy MonteCarlo events with at least 10 part/m2 on the array and L= 200-300 km Detector at 8 km ε ~ 1.0 – 1.5% L ντ L= 250 500 km To detect τ shower requiring at least 10 part/m2 it must decay at 4-5 km from the ground level 92.50 95.00 Colors: nu interactions where tau reaches the ground with shower max L in rock (km) M. Iori ,Roma1

20. ε as function of detector distance and L for Eν = 108 -1011 GeV 92.50 950 ±200 conversion efficiency εversus L at different detector distances L bin=100 km Detector aperture A=∫ΩSeffcos(θ-α)dΩ=Seff 0.15 km2 sr M. Iori ,Roma1

21. Rate calculation Assuming a neutrino energy spectrum following a power law Φ(E) ~ 10-6/E2 (Gev-1cm-2s-1sr-1) ∫Φ(E)dE ~ 3x103(km-2yr-1sr-1) integrated between 108 – 1011 GeV N τshower = ∫Φ(E)Pdet τau(E)dEdtdAdΏBr= 50 x 0.15x 0.64 ~ 4.8 (km-2yr-1) or a upper flux limit for a spectrum Φ(E) ~ 10-7/E2 *(single tower → 1.6) **No tau regeneration taken into account M. Iori ,Roma1

22. Predictions for Auger and future experiments: Ice-Cube and Nemo Auger fluorescence Guzzo et al hep-ph/0312119 Bugaev et al. astro-ph/0311086 M. Iori ,Roma1

23. Results from Corsika 6.204tau shower 5x1018 eV particle μ,e γtau shower density and momentum at the detector level M. Iori ,Roma1

24. Determination of Mountain slope β=Θ-90 The slope of the mountain slope, θ angle and L M. Iori ,Roma1

25. Performances studies of the array The unit of the array • How many tower? • Angular resolution: 0.50 (core inside the array) • Duty cycle 100% • We can improve the acceptance if we put 2 modules close • separate em component by lead layer under study 60 cm Number hits versus number towers >500 tower no large improvementsin density lead M. Iori ,Roma1

26. From Décor-Nevod at large zenith angle 10-9 10-4 Albedo muon intensity Muon intensity O. Saavedra talk at Cosmic Ray Physics Workshop Moscow 17 Oct 2005 10-5 Bundles ~ 10-5 m-2 s-1 sr-1 M. Iori ,Roma1

27. Trigger 1 To define a trigger we have to remind • Electrons do not escape at that energies • Muons from νµ do not produce visible signal • Neutrino related showers can be easily distinguished from those induced by hadrons in high atmosphere by multiplicity • Muon bundles high multiplicity small area ~10-5 m-2 s-1 sr-1 1st Level record data bank (TDC charge flag etc..) 2nd Level select up-ward tracks 3rd Level multiplicity logic with a coincidence gate (~10µs) M. Iori ,Roma1

28. Trigger 2 detector • Event trigger logic: • Sub-array → µ bundles flag • Event by multiple sub-array • Rate Level 1: 10-2 Hz each tower • zenith angle 930 • Rate Level 2: 10-3 Hz each tower • Cut on charge to select up-ward and down ward • tracks -> 10-6 Hz only up-ward tracks • Rate Level 3: NCMRateL2x(RateL2xgate)M = 10-24 Hz • Sinlge tower at 930 measures a flux of ~10-7 cm-2 s-1 sr-1 Sub-array M. Iori ,Roma1

29. Electronics board M. Iori ,Roma1

30. Test performed with a prototype at Jungfraujoch Station (3600 m)Switzerland Field of view Up-going tracks Time of flight M. Iori ,Roma1

31. Preliminary results (April 05) from 2 towers Tower1 Tower2 950 3 cm Lead in front tile2 of Tower2 (yellow plot) ADC tile1 vs tile2 Tower1 Tower2 1000 M. Iori ,Roma1

32. Time resolution central region, -3ns to +3ns Signal region, ±3ns tile C1 tile C2 time resolution M. Iori ,Roma1

33. The tiles M. Iori ,Roma1

34. Preliminary test results at Jungfraujoch Station Flux measured at Jungfraujoch Station 3600 m P>30 MeV/c • Decor experiment P>7 GeV/c at sea level • M. Iori ,Roma1

35. 活动星系核、暴、GZK, TD, Z-burst等 西部高山后面的宇宙超高能中微子天文学 CRTNT proposal Z. Cao. M.A. Huang, P. Sokolsky Y. Hu Astro-ph/0411677 超高能 电子中微子 μ中微子 中 微 子 τ中微子 振 荡 效 应 荧光/契伦科夫光 空气簇射 x16 AGN event rate: 8~10 event/yr using 16 telescopes τ中微子大气荧光/C光 成像望远镜 3m M. Iori ,Roma1 2.5m

36. Conclusions • Conventional horizontal arrays are not optimally adapted to Earth skimming events • → a new strategy to be considered is: • to aim at the horizon and detect the direction of the shower by time of flight M. Iori ,Roma1

37. R&D 1- development of the electronic board with high resolution TDC (ACAM) and MATACQ chip to sample the signal al High Frequency ( 1GHz sampling) (see http://www.caen.it/nuclear/product.php?mod=V1729) 2- buy 20-30 PM's and 10-15 solar Power supplies 3- design the mechanics to move within 15 deg in zenith each tower and the pointing system 4- define material to be used to built the detector (alluminium, PVC and possible stress due to gradient of the temperature) 5- study an other PM reading (fibers?) to improve the separation of up-ward down-ward tracks 6- study possible part id (by lead + 5 mm scintillator plate read by fibers+PM 4ch) and the signal shape to separate PID 8- Study Trigger by MC, how store the data and its managment 7- built 10-15 towers and move them at the final destination to test the system wireless device (GPS-GSM Motorola12+) and Daq. test the longitudinal as well as transversal time resolution M. Iori ,Roma1

38. setup M. Iori ,Roma1

39. Cost estimate M. Iori ,Roma1

40. Neutrino cross section Making measurements at different θ angle we can estimate σν neutrino R2 • R= Φτ (E)/Φν (E)=∫0L dz∫NρdEν (dσcc /dEτ)e-zNρσ • R1/R2 ≈ (1- e-L1Nρσ)/ (1- e-L2Nρσ) • <σ>=ln(R1-R2 )/Nρ(L2– L1 ) 1017 ≤Eν≤1020 eV R1 Neutrino cross section M. Iori ,Roma1

41. MC Trigger studies and array • Improve e/mu ID (i.e. preshower) and define final version • Front-end configuration/trigger • Mechanics • Test PMT as function of temperature • Test Solar power system Hip-55172 Sanyo 55Watts 17V/3.3A • Test on wireless lan devices (ADlink) • Test prototype on site M. Iori ,Roma1