1. Doug Cowen, Tyce DeYoung, Soeb Razzaque April 25, 2006 A Novel Tau Signature in Neutrino Telescopes UHE Tau Neutrino Workshop Beijing, China

2. April 25, 2006UHE Tau Neutrino Workshop Classic Tau Signature “Double Bang” Learned & Pakvasa 1995 ν N interaction Tau lepton track ~50 m/PeV (neglecting energy loss) Tau decay

3. April 25, 2006UHE Tau Neutrino Workshop Energy Windows by Flavor (supernovæ) showers vs. tracks full flavor ID Neutrino flavor   e Log(ENERGY/eV) 1218 156 219 e

4. April 25, 2006UHE Tau Neutrino Workshop Alternative Signature “Lollipop” – half double bang Beacom, Bell, Hooper, Pakvasa & Weiler Dim track Stops in a big cascade (starting tracks dominated by BG)

5. April 25, 2006UHE Tau Neutrino Workshop Tau Decay Modes Decay mode Branching fraction τ → ν τ + e + ν e 17.8% τ → ν τ + X (hadronic)~65% τ → ν τ + μ + ν μ 17.4% double bang / lollipop

6. April 25, 2006UHE Tau Neutrino Workshop Energy Losses ionization stochastic losses Particles are detected in neutrino telescopes through energy deposited in the detector Stochastic energy loss mechanisms: Bremsstrahlung pair production Photonuclear interactions

7. April 25, 2006UHE Tau Neutrino Workshop Energy Loss Rates Taus are much dimmer than muons Bremsstrahlung, pair production suppressed by particle mass At E = 1 PeV: 1 EeV: β μ ~ 5 · 10 -6 7 · 10 -6 β τ ~ 3.5 · 10 -7 9 · 10 -7

8. Muons are brighter than taus τ μ → track suddenly brightens Can we see it?

9. April 25, 2006UHE Tau Neutrino Workshop Muonic Tau Decay τ → ν τ + μ + ν μ Muon energy spectrum in the lab frame: where Average muon energy (Perl 1992)

10. April 25, 2006UHE Tau Neutrino Workshop Flavor Dependence Muons lose energy by pair production (& brems) Taus lose through photonuclear interactions μ τ Dutta, Reno, Sarcevic, and Seckel

11. April 25, 2006UHE Tau Neutrino Workshop Energy Loss Mechanisms Bremsstrahlung Pair production Photonuclear interactions l l l l l l γ e+e+ e-e- hadronic shower ( = μ,τ) l EM showers

12. April 25, 2006UHE Tau Neutrino Workshop Hadronic Light Yield Hadronic showers emit 65-85% of the light of an electromagnetic shower of the same energy M. Kowalski

13. April 25, 2006UHE Tau Neutrino Workshop Are Photonuclear Losses Quasi-Continuous? Very high energy muons emit pairs, brems so frequently they cannot be resolved → Increase overall track brightness Tau losses dominated by photonuclear interactions – fewer, brighter events If they blur together, increase track brightness If they’re distinct, won’t increase “baseline” track brightness (may reduce event rates)

14. April 25, 2006UHE Tau Neutrino Workshop Photonuclear Energy Loss soft component total photonuclear energy loss hard component Bugaev & Shlepin

15. April 25, 2006UHE Tau Neutrino Workshop Photonuclear Spectra soft component hard component 1 EeV 1 PeV 10 PeV 100 PeV 1 EeV 1 PeV Peak at 10 -2 E l Bugaev & Shlepin = E shower / E τ

16. April 25, 2006UHE Tau Neutrino Workshop Quasi-Continuous? Soft component clearly continuous Hard component: At 1 PeV, → 30 TeV Mean free path ~ 5 km At 1 EeV, mean free path ~ 200 m

17. April 25, 2006UHE Tau Neutrino Workshop Brightness Ratio 4.3–6.12.5–5.05.2–6.94.1–6.9 0.63–0.790.40–0.700.72–0.840.61–0.84 Quasi-Continuous Non-Continuous PeV EeV PeV EeV Ratio: ∆(log 10 ): Detector resolutions (in log 10 E): AMANDA: 0.5 ANTARES: 0.3–0.4 (Carr & Hallewell) (ICRC 2003)

18. April 25, 2006UHE Tau Neutrino Workshop Low Energy Taus? 1 TeV tau “track:”5 cm Impossible! ν τ → τ + X μ + ν μ + ν τ Two neutrinos take 2/3 the energy → dim track Compare energy of hadronic shower to energy of muon track? Need to worry about NC/ ν e background! MC studies in progress…