dresden, 17-12-2009tom gaisser1 atmospheric neutrinos nature’s neutrino beam

Dresden, 17-12-2009 Tom Gaisser 1

Atmospheric Neutrinos

Nature’s neutrino beam


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


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


Detect relic from supernovae:

Kaplinghat, Steigman & Walker, PR D62 (2000) 043001


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)


Improvement with tagged neutron

Beacom & Vagins,PRL 93 (2004) 171101

Prescribe gadolinium additive to detect neutrons and select anti-e only


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


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


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 ( , )


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


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


Super-K atmospheric neutrino data (hep-

ex/0501064)

1489day FC+PC data + 1646day

upward going muon data

CC e CC


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


High-energy atmospheric neutrinos

Primary cosmic-ray spectrum (nucleons)

Nucleons produce

pions

kaons

charmed hadrons

that decay to neutrinos


Factors in atmospheric beam

For each parent i = ±, K±, charm:

For example, for

Spectrum-weighted moment of hadron production

Branching ratio

moment of decay


Similar analysis for atmospheric

Account for energy loss

Account for decay

Analytic approximation works well!


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


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


Energy-angle dependence by parent

typeNeutrinos

Muons

Plots show fraction of & from ±, K±, charm = 0 = 60o


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


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


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


FNAL E-781 (SELEX)

Large asymmetry of c+ / c

- production in baryon beams:

p c+ favored with hard spectrum in xF


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


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


Prompt and

RQPM

Multiply differential spectrum x E3 to display transition to prompt leptons

Parameterization

QCD range


Experimental challenge:

+

+ + -

prompt

Must measure change of slope of a steep spectrum with low statistics and fluctuations in energy deposited


Detecting neutrinos in H20Proposed by Greisen, Markov in 1960

ANTARES

IceCube

SNO

Super-K

Heritage:• DUMAND• IMB• Kamiokande

Neutrino must interact to be detected


125 m

IceCube: telescope& cosmic-

ray detector

Seattle Tom GaisserJuly 2, 2009 Photo: James Roth 17-12-2007


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


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


Atmospheric and in IceCube

Extended energy reach of km3 detector

Patrick Berkhaus, ICRC 2009Dmitry Chirkin, ICRC 2009Currently limited by systematics

preliminary


Looking for diffuse fluxes above the background of atmospheric

neutrinosSean GrullonParallel session


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


IceCube 40 Juan Antonio Aguilar TeV PA 2009


Jon Dumm, IceCube, ICRC2009


Shadow of the Moon with muons in IceCube


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


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


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


Cosmic-ray physics with IceCube

Photo: James Roth 17/12/07

Use ratio of deep muons to shower size for composition


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)


Drilling operations

6 strings deployed so far this season.18-20 planned.28 tanks installed and freezing


Extras


Electron neutrinos

K+ 0 e e± ( B.R. 5% )

KL0 ± e e ( B.R. 41% )

Kaons important for e

down to ~10 GeV


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


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


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


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


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

dresden, 17-12-2009tom gaisser1 atmospheric neutrinos nature’s neutrino beam

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