Dresden, 17-12-2009 Tom Gaisser 1
Atmospheric Neutrinos
Nature’s neutrino beam
Dresden, 17-12-2009 Tom Gaisser 2
Outline• History• Phenomenology
– of the atmospheric neutrino beam– and relation to atmospheric muons
• Hadronic interactions – K/pi ratio– Production of charm
• Atmospheric leptons in neutrino telescopes
Dresden, 17-12-2009 Tom Gaisser 3
The neutrino landscape
Prompt
e
Solar
Lines show atmosphericneutrinos + antineutrinos
Slope = 3.7
RPQM for prompt from charmBugaev et al., PRD58 (1998) 054001Slope = 2.7
Astrophysical neutrinos • harder spectrum• point sources
Atmospheric neutrinos:• background• calibration
Relic SN
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Detect relic from supernovae:
Kaplinghat, Steigman & Walker, PR D62 (2000) 043001
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Stopped below threshold
e interactions
Current limits from Super-K• Limit is from e + p n + e+
• Neutron not detected in current Super-K
• Backgrounds: – atmospheric e and e
– solar e and reactor e
– atmospheric (E < 50 MeV)
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Improvement with tagged neutron
Beacom & Vagins,PRL 93 (2004) 171101
Prescribe gadolinium additive to detect neutrons and select anti-e only
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Atmospheric neutrinos
• Produced by cosmic-ray interactions– Last component of secondary
cosmic radiation to be measured– Close genetic relation with muons
• p + A ± (K±) + other hadrons• ± (K±) ± + ()• ± e± + () + e (e)
e
e
p
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Historical contextDetection of atmospheric neutrinos• Markov (1960) suggests Cherenkov light in deep lake or ocean to detect atmospheric interactions for neutrino physics• Greisen (1960) suggests water Cherenkov detector in deep mine as a neutrino telescope for extraterrestrial neutrinos• First recorded events in deep mines with electronic detectors, 1965: CWI detector (Reines et al.); KGF detector (Menon, Miyake et al.)
Stability of matter: search for proton decay, 1980’s• IMB & Kamioka -- water Cherenkov detectors• KGF, NUSEX, Frejus, Soudan -- iron tracking calorimeters• Principal background is interactions of atmospheric neutrinos• Need to calculate flux of atmospheric neutrinos
Two methods for calculating atmospheric neutrinos:• From muons to parent pions infer neutrinos (Markov & Zheleznykh, 1961; Perkins)• From primaries to , K and to neutrinos (Cowsik, 1965 and most later calculations)• Essential features known since 1961: Markov & Zheleznykh, Zatsepin & Kuz’min• Monte Carlo calculations follow second method
e
background for p-decay
0.1 1 10
e
background for p-decay
0.1 1 10
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Historical context (cont’d)Atmospheric neutrino anomaly - 1986, 1988 …• IMB too few decays (from interactions of ) 1986• Kamioka -like / e-like ratio too small. • Neutrino oscillations first explicitly suggested in 1988 Kamioka paper• IMB stopping / through-going consistent with no oscillations (1992)• Hint of pathlength dependence from Kamioka, Fukuda et al., 1994
Discovery of atmospheric neutrino oscillations by S-K• Super-K: “Evidence for neutrino oscillations” at Neutriino 98• Subsequent increasingly detailed analyses from Super-K:
• Confirming evidence from MACRO, Soudan, K2K, MINOS• Analyses based on ratios comparing to 1D calculations• Compare up vs down
Parallel discovery of oscillations of Solar neutrinos• Homestake 1968-1995, SAGE, Gallex … chemistry counting expts.• Kamioka, Super-K, SNO … higher energy with directionality• e ( , )
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Atmospheric neutrino beam• Cosmic-ray protons
produce neutrinos in atmosphere
• /e ~ 2 for E < GeV• Up-down symmetric• Oscillation theory:
– Characteristic length (E/m2) – related to m2 = m1
2 – m22
– Mixing strength (sin22) • Compare 2 pathlengths
– Upward: 10,000 km– Downward: 10 – 20 km
P( ) = sin22 sin2 1.27 L(km) m2(eV2) E(GeV)( )
e
e
p
Wolfenstein;Mikheyev & Smirnov
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Classes of atmospheric events
Contained (any direction)
-induced (from below)
e (or )
e (or )
Contained eventsPlot is for Super-K but the classification is generic
External events
Dresden, 17-12-2009 Tom Gaisser 12
Super-K atmospheric neutrino data (hep-
ex/0501064)
1489day FC+PC data + 1646day
upward going muon data
CC e CC
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Atmospheric
Flavor state | ) = i Ui | i ), where | i ) is a mass eigenstate
1 0 00 C23 S23
0 -S23 C23
C13 0 S13
0 1 0-S13 0 C13
C12 S12 0-S12 C12 0 0 0 1
U =
“atmospheric” “solar”C13 ~ 1S13 small
, m2 = 2.5 x 10-3 eV2
maximal mixing
Solar neutrinos e {,}, m2 ~ 10-4 eV2
large mixing
3-flavor mixing Yumiko Takenaga, ICRC2007
Dresden, 17-12-2009 Tom Gaisser 14
High-energy atmospheric neutrinos
Primary cosmic-ray spectrum (nucleons)
Nucleons produce
pions
kaons
charmed hadrons
that decay to neutrinos
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Factors in atmospheric beam
For each parent i = ±, K±, charm:
For example, for
Spectrum-weighted moment of hadron production
Branching ratio
moment of decay
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Similar analysis for atmospheric
Account for energy loss
Account for decay
Analytic approximation works well!
Dresden, 17-12-2009 Tom Gaisser 17
Energy spectrum of atmospheric muons and
neutrinos• At low energy, has same spectral
index at production as primary spectrum
• becomes steeper by one power of energy at high energy
• Critical energy depends on zenith angle:
Ecritical = i / cos
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Neutrinos from kaons
Critical energies determine where spectrum changes, but AK / A and AC / AK determine magnitudes
New information from MINOS relevant to with E > TeV
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Energy-angle dependence by parent
typeNeutrinos
Muons
Plots show fraction of & from ±, K±, charm = 0 = 60o
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1.27
1.37
x
x
TeV +/- with MINOS far detector
• 100 to 400 GeV at depth > TeV at production
• Increase in charge ratio shows– p K+ is important– Forward process– s-quark recombines
with leading di-quark – Similar process for c? Increased contribution from kaons
at high energy
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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 / because kaons dominate
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Atmospheric neutrinos – harder spectrum from kaons?
AMANDA atmospheric neutrinoPhys.Rev D79 (2009) 102005(The blue shaded region is the same as the green band on the right.)
Re-analysis of Super-KGonzalez-Garcia, Maltoni, Rojo JHEP 2007
Dresden, 17-12-2009 Tom Gaisser 23
FNAL E-781 (SELEX)
Large asymmetry of c+ / c
- production in baryon beams:
p c+ favored with hard spectrum in xF
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Signature of charm: dependence
For K < E cos() < c , conventional neutrinos ~ sec() , but “prompt” neutrinos independent of angle
Uncertain charm component most important near the vertical
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Questions:• How much intrinsic charm? (Brodsky et al.)• What is the magnitude of ZNcharm ?
– My analytic estimate: ZNcharm ≈ 5 x 10-4
• Normalized to ISR inclusive spectra in Lykasov et al., arXiv:0909.5061
– RQPM model: ZNcharm ≈ 10-3
• E.V. Bugaev et al., Phys. Rev. D58 (1998) 054001
– Perturbative QCD• Values vary among calculations, generally lower estimates
– Example: ZNcharm ≈ 1.5 x 10-4
• Enberg, Reno & Sarcevic, Phys. Rev. D78 (2008) 043005
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Prompt and
RQPM
Multiply differential spectrum x E3 to display transition to prompt leptons
Parameterization
QCD range
Dresden, 17-12-2009 Tom Gaisser 27
Experimental challenge:
+
+ + -
prompt
Must measure change of slope of a steep spectrum with low statistics and fluctuations in energy deposited
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Detecting neutrinos in H20Proposed by Greisen, Markov in 1960
ANTARES
IceCube
SNO
Super-K
Heritage:• DUMAND• IMB• Kamiokande
Neutrino must interact to be detected
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125 m
IceCube: telescope& cosmic-
ray detector
Seattle Tom GaisserJuly 2, 2009 Photo: James Roth 17-12-2007
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Muons in telescopes
SNO at 6000 m.w.e. depth
Million to 1 background to signal from above. Use Earth as filter; look for neurtinos from below.
Downward atmospheric muons
Neutrino-induced muons from all directions
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Muons in IceCubeDownward atmospheric muons
Neutrino-induced muons from all directions
P. Berghaus et al., ISVHECRI-08 also HE1.5
IceCube
Crossover at ~85° for shallow detectors
~75° for deepest Mediterranean site
Dresden, 17-12-2009 Tom Gaisser 32
Atmospheric and in IceCube
Extended energy reach of km3 detector
Patrick Berkhaus, ICRC 2009Dmitry Chirkin, ICRC 2009Currently limited by systematics
preliminary
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Looking for diffuse fluxes above the background of atmospheric
neutrinosSean GrullonParallel session
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0h24h
+30°
+15°
+45°
+60°+75°
-15°
-30°
-45°
-log 1
0 p
-log 1
0 p
R. Lauer, Heidelberg Workshop, Jan09 arXiv:0903.5434
Paper accepted for PRL 9 November 2009
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IceCube 40 Juan Antonio Aguilar TeV PA 2009
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Jon Dumm, IceCube, ICRC2009
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Shadow of the Moon with muons in IceCube
Dresden, 17-12-2009 Tom Gaisser 38
Cosmic-ray anisotropy with IceCube muons
Compare IceCube measurements of the Southern sky with previous results in the North
Abbasi, Desiati for IceCube at ICRC2009
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Monitoring the Universe• Look for correlation with variable sources
– e.g. AGN flares• Externally triggered searches (GRB)• Neutrino alerts (e.g. optical follow-up)
– 2 or more from same direction in t• Alerts to ROTSE-III from IceCube since Oct. 2008• Alerts to TAROT from Antares since May 2009
– Sudden excess in counting rate (IceCube)• Send SN alert to SNEWS
• Monitoring rates in surface detectors– IceTop, Auger– Solar particle events, modulation of galactic cosmic
rays
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Deep muons as a probe of weather in the stratosphere
• Barrett et al.• MACRO• MINOS far detector
– Sudden stratospheric warmings observed• IceCube
– Interesting because of unique seasonal features of the upper atmosphere over Antarctica related to ozone hole
• Decay probability ~ T: – h0 ~ RT
pion decay probability
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Dresden, 17-12-2009 Tom Gaisser 42
Cosmic-ray physics with IceCube
Photo: James Roth 17/12/07
Use ratio of deep muons to shower size for composition
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Cosmic-ray physics with IceCube
• Goal:– Composition,
& spectrum– 1015 – 1018 eV– Use
coincident events
– Look for transition to extra-galactic cosmic rays IceTop 59
(plus 14 stations installed 09/10)
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Drilling operations
6 strings deployed so far this season.18-20 planned.28 tanks installed and freezing
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Extras
Dresden, 17-12-2009 Tom Gaisser 46
Electron neutrinos
K+ 0 e e± ( B.R. 5% )
KL0 ± e e ( B.R. 41% )
Kaons important for e
down to ~10 GeV
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Uncertainty in atmospheric
• Any uncertainty in atmospheric neutrino background limits sensitivity of search for diffuse supernova neutrino background
• Primarily interested in shape– Steep spectrum for DSNB as compared
to– Hard spectrum of atmospheric
neutrinos
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Comparison of 3 calculations used by Super-
K
( Note: E > 100 MeV in most calculations)
ACB
C/A
B/A
Y. Ashi et al. (Super-K Collaboration) Phys. Rev. D71 (2005) 112005
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Low energy (10 – 100 MeV )
Gaisser & Stanev, Proc 24th ICRC, Rome (1995)
Note: most neutrinos with E < 50 MeV are from decay of muons stopped in atmosphere
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Calculations of anti-e background 10-100 MeV
FLUKA 10-100 MeV Battistoni et al.(2004): http://www.mi.infn.it/~battist/neutrino.html
Note dependence on phase of solar cycle:
• 10 – 20% variation
• similar to response of neutron monitors
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Recent papers on transition from Galactic to extra-Galactic
CR• Source models for extra-galactic CR– E.G. Berezhko
• Acceleration in external AGN shocks: 0809.0734• Implications for composition: 0905.4785
• Propagation from extra-galactic sources: – implications for what is observed at Earth
• D. Allard, 0906.3156• Hooper & Taylor, 0910.1842
• Modeling the end of Galactic CR spectrum– Donato & Medina-Tanco, Astropart. Phys. 32 (2009) 253
• Limit on proton fraction from upper limits on – Neutrino diagnostics of ultrahigh energy cosmic ray
protons, PHYSICAL REVIEW D 79, 083009 (2009), Markus Ahlers, Luis A. Anchordoqui, and Subir Sarkar