Detecting Earth-Skimming and Mountain-Penetrating Tau Neutrinos G.-L.Lin National Chiao-Tung University, Taiwan ISMD04

Outline Neutrino oscillations and Astrophysical Tau Neutrino Fluxes The Rationale for Detecting Earth- Skimming/Mountain-Penetrating  The Conversion Efficiency for    The Simultaneous Detections of Earth- Skimming and Mountain-Penetrating  The Event Rate Conclusions

Neutrino oscillations and astrophysical  fluxes Although  flux from the source is generally suppressed compared to that of  and e, the oscillation effects make the flux of each flavor comparable at the Earth.

The idea of observing  in view of neutrino oscillations, was suggested sometime ago. Learned and Pakvasa 1995 For a source in a cosmological distance, with e :  :  =1:2:0, the oscillation effects taking place as the neutrinos reach the terrestrial detector make e :  :  =1:1:1. Athar, Jezabek, Yasuda 2000

Tau neutrino fluxes Athar, Tseng and Lin, ICRC 2003

Detecting Earth- Skimming/Mountain-Penetrating  The Rationale

The Earth-skimming detection strategy…. Domokos and Kovesi-Domokos, 1998 Fargion, 1997, 2002 Bertou et al., 2001 Feng et al., 2001 Bottai and Giurgola, 2002 Tseng et al., 2003 Mountain-penetrating idea: Hou and Huang, 2002 Auger, TA,… Ashra-NuTel

   N inelasticity  Energy losses and decays   N only scatters once.  produced near the earth surface.  effective interaction region– 1 tau range! Earth-Skimming  fluorescence Cherenkov

The “effective” tau lepton production probability =Tau Range(R  ) /  N interaction length(  )  R  increases with energy, while  decreases with energy. Hence it is favorable to detect neutrinos of higher energies! Flux?

The calculation of tau lepton range requires the consideration of…

The tau lepton loses its energy in the rock through 4 kinds of interactions: (1). Ionization (  ): the tau lepton excites the atomic electrons. H. A. Bethe 1934 (2). Bremsstrahlung (  ): (3). Pair Production (  ):   A A. A. Petrukhin &V.V. Shestakov, 1968   A R. P. Kokoulin & A. A. Petrukhin, 1971

(4). Photo-nuclear interaction: N X    Basic component F 2 (x,Q 2 ) The nucleus shadowing effect is considered: Brodsky & Lu, 1990; Mueller & Qiu 1986; E665 Collab. Adams et al., 1992; Iyer Dutta, Reno, Sarcevic &Seckel, 2001.

Iyer Dutta, Reno, Sarcevic, & Seckel, 01 Tseng, Yeh, Athar, Huang, Lee, & Lin, 03 Log(E/GeV) Tau lepton range approaches to 20 km in rock. Mountain-penetrating is sufficient!

Mountain-penetrating and Earth-skimming tau neutrinos/tau leptons

The  N interaction length: Gandhi, Quigg, Reno, Sarcevic, 1998

The “effective” tau lepton production probability

The Conversion Efficiency for   

 and  propagations inside the Earth  NC  CC Energy loss  Decay CC  NC

Iong, master thesis, NCTU km in rock

100 km in rock

20 km in rock

100 km in rockminor absorptions

Simultaneous Detection of Mountain-Penetrating and Earth-Skimming  ---sensitive to new physics TeV scale gravity, KK excitations…

Log(E’/eV) E: initial  energy, E’: final  energy, r=Log(E/E’) New physics-- a factor of 10 enhancement on  N Mountain-Penetrating Rough estimate

Log(E’/eV) E: initial  energy, E’: final  energy, r=Log(E/E’) Earth-Skimming Rough estimate

 From 30  100 km, a drastic change on the effect of enhanced  (  N   X)!  Comparison of event rates in 2 medium lengths probes the new physics.

For the mountain-penetrating case: The solid angle is W=20 km L=20 km H=2 km L H Not small O

The Event Rate

Log(E/GeV) AGN  flux from Kalashev, Kuzmin, Semikoz, and Sigl, 03 Tseng et al., 03

Log(E/GeV) GRB  flux from Waxman and Bahcall 1997 Tseng et al., 03

Log(E/GeV) GZK  flux from Engel, Seckel, and Stanev, 01 Tseng et al., 03

Energy & flux AGNGRBGZK eV   eV   eV   eV 1.1   Integrated tau lepton flux in units of km -2 yr -1 sr -1

Energy & Aperture (km 2 sr) AGNGRBGZK eV eV eV eV 290 Effective aperture (A  ) eff required for 1 event/yr, assuming a 10% duty cycle.

Conclusions We have presented the essential features of detecting Earth-skimming and mountain- penetrating . The tau lepton flux already reaches its maximum for a 20 km medium length. This motivates the detections of mountain- penetrating , in addition to the Earth- skimming ones.

Simultaneous detections of mountain-penetrating and Earth-skimming  probes the anomalous  N   X cross section. We give effective aperture required for detecting 1 event/yr assuming a 10% duty cycle.