Lessons from Neutrinos in the IceCube Deep Core Array

Lessons from Neutrinos in the IceCube Deep Core Array

Irina Mocioiu Penn State

TeV 2009, July 15 2009

Neutrino Telescopes

- AMANDA/ICECUBE : Cerenkov light in ice (South Pole) - ANTARES, NEMO, NESTOR, etc. : Cerenkov light in water (Mediterranean) - RICE: radio Cerenkov in ice (South Pole) - ANITA: radio Cerenkov from ice (balloon at South Pole) - PIERRE AUGER: air showers (Argentina,...) - ... What to look for? • Point sources • Diffuse fluxes • from astrophysical objects • from cosmic ray interactions • from dark matter annihilation • ... • Correlations with other observations: cosmic rays, gamma rays...

Lessons for Particle Astrophysics Weak interactions -

access to dense, violent envirenoments test mechanism powering astrophysical sources cosmic ray acceleration processes cosmic ray propagation and intergalactic backgrounds ... Lessons for Particle Physics

high energies, beyond those accessible in colliders, etc. weak interactions -

neutrino interaction cross-sections (in Standard Model!) neutrino properties new interactions/particles dark matter ...

How to do it? - measure all you can! - take into account everything you know/can think about! - identify the right observables! • • • • • • •

energy distributions angular distributtions flavour composition better detector techniques smart tricks, unique signatures, etc. very good simulations correlations with other observables: photons, protons, etc.

• can distinguish particle physics from astrophysics effects • learn about both!

Deep Core Array

• motivation: galactic sources, dark matter annihilation galactic center above horizon at South Pole

• need to reduce large cosmic muon background

• dense phototube coverage region

• in the deep ceter region of IceCube

Deep Core Array

Doug Cowen, Nu2008

Deep Core Array

• greatly reduce large cosmic muon background

• 4π coverage look at downgoing events, galactic sources, galactic center

• low energy threshold open up the neutrino energy range from 10 Gev to 100 Gev

• overlap with Super-Kamiokande at low energy and IceCube at high energy

Atmospheric Neutinos Cosmic ray

π+ µ+

∼ 30km e+ ν ¯µ

νe

νµ

Underground

νe ,¯ νe ,, νµ , ν ¯µ ,ντ , ν ¯τ

detector

• background to many searches • Lots of them!

π0

Atmospheric Neutinos Super-Kamiokande: • Expect:

N (νµ+¯ νµ ) ∼2 N (νe+¯ νe )

at low energy

∼isotropic • used zenith angle distributin to prove neutrino oscillations IceCube Deep Core N (ν +¯ ν )

µ ∼ 10 • N (νµ+¯ e νe )

• steep energy spectrum (Eν−3) • νe flux not measured at high energies

Neutrino oscillations: • massive and mixed neutrinos νe produced together with the electron in weak interactions does not have to be one of the definite mass particles ν1 or ν2 νe νµ

!

=

cos θ sin θ − sin θ cos θ

P (να → νβ ) = sin2 2θ sin2

!

ν1 ν2

∆m2L 4E

!

!

= sin2 2θ sin2 1.27

2 − m2 ∆m2 = m ji j i

[∆m2] : eV ,

[L] : km,

[E] : GeV

∆m2L E

!

Summary of Experimental Results • Solar Neutrinos: νe → νx, x = µ, τ + reactor antineutrinos −5 eV2 ' 7.6 × 10 ∆m2 sol

tan2 θsol ' 0.45 • Atmospheric Neutrinos: νµ → νx, x = τ + accelerator neutrinos −3 2 ∆m2 atm ' 2.5 × 10 eV

sin2 2θatm ' 1 • Reactor antineutrinos: ν ¯e 6→ ν ¯e < 0.1 for ∆m2 ∼ 10−3 eV 2 sin2 2θreactor ∼

Three flavors neutrino oscillations c12c13   −s12c23 − c12s23s13eiδ s12s23 − c12c23s13eiδ 

s12c13 c12c23 − s12s23s13eiδ −c12s23 − s12c23s13eiδ

 −iδ s13e  s23c13 

c23c13

2 , ∆m2 = ∆m2 = ∆m ∆m2 atm 32 21 sol

θ12 = θsol , θ13 = θreactor , θ23 = θatm, δ We • • •

want to measure: θ13 hierarchy (sign of ∆m2 atm ) CP violation (δ)

large effort to build new accelerator experiments for this purpose use matter effetcs

Neutrino Oscillations in the IceCube Deep Core tracks: µ like fully contained events Angular distribution: • cos θ ∈ (0, 1) atmosperic flux normalization • cos θ ∈ (−0.9, 0) + main oscillation signal (∆m2 32 , θ23 ) • cos θ ∈ (−1, −0.9) + matter effects (θ13, hierarchy, CP) Energy distribution: • E ≤ 40GeV: neutrino oscillations • 50 GeV ≤ E ≤ 5 TeV atmospheric neutrino flux • E ≥ 10 TeV: Earth density profile

Normal versus inverted mass hierarchy O. Mena, I. M., S. Razzaque, Phys.Rev.D78,093003 (2008)

cosθ ∈ (−1, −0.9)

cosθ ∈ (−0.9, −0.8) Note Eµ ' 0.5Eν

cosθ ∈ (−0.8, −0.7)

Normal versus inverted mass hierarchy • χ2 fit to discriminate between normal and inverted hierarchy Normal H100 Mt yr, Θ23=45é, No systematicsL

Inverted H100 Mt yr, Θ23=45é, No systematicsL

150

50 ∆cp

100

90%

0 -50

95%

99%

0 -50

-100 68%

-100

-150

-150

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 sin22Θ13

90%

50

99%

∆cp

100

150

95% 68%

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 sin22Θ13

Normal versus inverted mass hierarchy • χ2 fit to discriminate between normal and inverted hierarchy Normal H100 Mt yr, Θ23=45é, 10% systematicsL

Inverted H100 Mt yr, Θ23=45é, 10% systematicsL

150

150

100

100

90%

0 -50 -100

50

99%

∆cp

∆cp

50

95% 68%

-150 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 sin22Θ13

0 -50 -100

68%

-150 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 sin22Θ13

How about cascades? • Electromagnetic cascades: ¯e + ντ Tau decay: τ → e + ν νe CC interactions: νe + N → e + X • Hadronic cascades Tau decay: τ → ντ + X ντ NC interactions: ντ + N → ντ + X ντ CC interactions: ντ + N → τ + X νe,µ NC and CC interactions

ντ 1 νµ − νµ νµ − ντ

Oscillation probabilities

0.8

0.6

0.4

0.2

0

5

10

15

20

30 25 Eν [GeV]

35

40

large number of ντ

45

50

Number of shower events for sin22θ 13 = 0.01 and δ = 0 in bin sizes of 5GeV and cν (-1,-0.9) 4500

atm ν e and ν µ->ν e ν τ ->ν e

4000 3500

Number of events

3000 2500 2000 1500 1000 500 0 5

10

15 20 Shower Energy[GeV]

25

30

ντ cascades with G. Giordano and O. Mena

• νµ → ντ → τ → e or hadrons dominates • present world sample of ντ events: 9 (DONUT) • high statistics ντ interactions • first direct evidence for νµ → ντ appearance • ντ interaction cross-section • non-standard interactions of ντ • experience with cascade detection

Outlook IceCube Deep Core • galactic sources, dark matter annihilation • atmospheric neutrinos high statistics, large energy range better understanding of background for other searches • neutrino oscillations mass hierarchy ντ : oscillations, ντ interactions, cascade detection