Atmospheric neutrinos with Deep Core In the context of atmospheric neutrinos in IceCube

Outline Atmospheric n in IceCube Zenith-angle dependence measured √ Spectrum of atmospheric nm TBD km3 extends reach to E(nm) ~ TeV Look for new physics What about electron neutrinos? Deep core opens lower-energy window Neutrino oscillation studies Hierarchy? Some comments on signal and background for both low and high energy

Atmospheric n spectrum Comment on charm models RQPM model shown here: (Bugaev et al., 1998) ne crossover at 3 TeV nm crossover at 100 TeV Calculation of Enberg, Reno, Sarcevic (arXiv:0806.0418): nm, ne intensities factor 10 lower crossovers factor of two higher e nm ne m p Neutrino spectrum summed over all directions from below the horizon ( TKG & M Honda, Ann Revs 52, 153, 2002)

Muons in IceCube-22 (2007) Downward atmospheric muons Upward neutrino-induced muons Patrick Berghaus et al., Cosmo-08 and ISVHECRI-08

Muon neutrinos in IC22 6000 /yr expected with point-source cuts

Oscillations + Deep Core = new opportunities < 100 GeV q13 = 0 If sin22q13 = 0.1 nm survival probability nm  nt oscillation probability From Carsten at Utrecht Mena, Mocioiu & Razzaque arXiv:0803.3044v2

Expected in IC80 With deep core Standard IceCube 3.2E5 / yr – 2.7E5 / yr = 50K/yr At trigger level

What about electron neutrinos? They might look like this: Kotoyo Hoshina IC22 But it can also be a muon with a large radiative energy loss

On the other hand muon energy loss is stochastic Strange things can happen For example, here’s the energy loss history of the first TeV random muon simulated with the Lipari-Stanev code: 2 photo-nuclear interactions One low-energy brem

Naïve expectations for rates of atmospheric n Assumptions: Muon neutrinos: full efficiency for m range > 0.5 km (En > 150 GeV) Electron neutrinos: Efficiency for ne from PDD is 0 for En < TeV Note advantage of lowering Eth for ne ~800 ne interactions per km3 yr Spectrum of ne events per km3 yr (perfect eff)

Differential and integral spectrum of atmospheric muons Energy loss: Em (surface) = exp{ b X } · ( Em +e ) - e Set Em = e { exp[ b X ] - 1 } in Integral flux to get depth – intensity curve

High-energy atmospheric neutrinos Primary cosmic-ray spectrum (nucleons) Nucleons produce pions kaons charmed hadrons that decay to neutrinos Kaons produce most nm for 100 GeV < En < 100 TeV Eventually “prompt n” from charm decay dominate, ….but what energy?

Importance of kaons at high E vertical 60 degrees Importance of kaons main source of n > 100 GeV p  K+ + L important Charmed analog important for prompt leptons at higher energy

Neutrinos from kaons Critical energies determine where spectrum changes, but AKn / Apn and ACn / AKn determine magnitudes New information from MINOS relevant to nm with E > TeV

Electron neutrinos K+  p0 ne e± ( B.R. 5% ) KL0  p± ne e ( B.R. 41% ) Kaons important for ne down to ~10 GeV

TeV m+/m- with MINOS far detector 1.27 1.37 x 100 to 400 GeV at depth  > TeV at production Increase in charge ratio shows p  K+ L is important Forward process s-quark recombines with leading di-quark Similar process for Lc? Increased contribution from kaons at high energy

MINOS fit ratios of Z-factors Z-factors assumed constant for E > 10 GeV Energy dependence of charge ratio comes from increasing contribution of kaons in TeV range coupled with fact that charge asymmetry is larger for kaon production than for pion production Same effect larger for nm / nm because kaons dominate

Muon veto of atmospheric n

Vertical neutrino flux: comparison M. Honda et al., PR D70 (2004) 043008 G.D. Barr et al. (Bartol flux) PR D70 (2004) 023006 http://www-pnp.physics.ox.ac.uk/~barr/fluxfiles/ M. Honda et al. PR D75 (2007) 043006

Unfolding SK measurements Gonzalez-Garcia, Maltoni, Rojo JHEP 2007

Atmospheric neutrino spectrum 1.27 1.37 x increased m+/m- charge ratio in MINOS far detector suggests corresponding increase in TeV neutrino flux from contribution of p  K+ L AMANDA atmospheric neutrino arXiv:0902.0675v1

Neutrinos from charm Main source of atmospheric n for En > ?? Gelmini, Gondolo, Varieschi PRD 67, 017301 (2003) Main source of atmospheric n for En > ?? ?? > 20 TeV Large uncertainty!

Angular dependence For eK < E cos(q) < ec , conventional neutrinos ~ sec(q) , but “prompt” neutrinos independent of angle Uncertain charm component most important near the vertical

Muon multiplicity at depth protons Iron Total energy per nucleus

Some comments on m background Atmospheric muons (shape only)

Muon energy spectrum at depth Nm= 7 5.5 4.4 2.0 0.2 0.1 Nm=40 32 25 11 1.2 0.7 Muon energy spectrum at depth Invariant shape for slant depth > ~ 2 km. w. e.

Muon energy spectrum at depth Nm=230 180 145 64 7.1 0.4 Nm=1300 1000 830 370 41 2 Muon energy spectrum at depth

A B Energy deposit per 17 m Todor’s plot: --a single event ~ 300 muons

New Geometries Slightly better performance for highest energy muons coming sideways Best for both highest and intermediate (0.1-10 PeV) energy muons (probably preferred) Drilling of 9 holes in the last season inside a circle with radius of 423 m is possible. The most ambitious geometries possible in the last season are presented above.