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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. Lines show atmospheric
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Atmospheric Neutrinos Nature’s neutrino beam Tom Gaisser
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 Tom Gaisser
Lines show atmospheric neutrinos + antineutrinos • Astrophysical neutrinos • harder spectrum • point sources nm ne Solar n RPQM for prompt n from charm Bugaev et al., PRD58 (1998) 054001 Slope = 2.7 Prompt n Slope = 3.7 The neutrino landscape • Atmospheric neutrinos: • background • calibration Relic SN n Tom Gaisser
Detect relic n from supernovae: Kaplinghat, Steigman & Walker, PR D62 (2000) 043001 Tom Gaisser
Stopped m below threshold ne interactions Current limits from Super-K • Limit is from ne + p n + e+ • Neutron not detected in current Super-K • Backgrounds: • atmospheric ne and ne • solar ne and reactor ne • atmospheric nm m (Em < 50 MeV) Tom Gaisser
Improvement with tagged neutron Beacom & Vagins, PRL 93 (2004) 171101 Prescribe gadolinium additive to detect neutrons and select anti-ne only Tom Gaisser
p p m e ne nm nm Atmospheric neutrinos • Produced by cosmic-ray interactions • Last component of secondary cosmic radiation to be measured • Close genetic relation with muons • p + A p± (K±) + other hadrons • p± (K±) m± + nm (nm) • m± e± + nm (nm) + ne (ne) Tom Gaisser
Historical context • Detection of atmospheric neutrinos • Markov (1960) suggests Cherenkov light in deep lake or ocean to • detect atmospheric n 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.) • Two methods for calculating atmospheric neutrinos: • From muons to parent pions infer neutrinos (Markov & Zheleznykh, 1961; Perkins) • From primaries to p, K and m to neutrinos (Cowsik, 1965 and most later calculations) • Essential features known since 1961: Markov & Zheleznykh, Zatsepin & Kuz’min • Monte Carlo calculations follow second method • 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 Tom Gaisser
Historical context (cont’d) • Atmospheric neutrino anomaly - 1986, 1988 … • IMB too few m decays (from interactions of nm) 1986 • Kamioka m-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: nm nt • 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 • ne ( nm, nt ) Tom Gaisser
p p m e nm ne nm ( ) 1.27 L(km) dm2(eV2) En(GeV) P(nmnt) = sin22q sin2 Atmospheric neutrino beam • Cosmic-ray protons produce neutrinos in atmosphere • nm/ne ~ 2 for En < GeV • Up-down symmetric • Oscillation theory: • Characteristic length (E/dm2) • related to dm2 =m12 – m22 • Mixing strength (sin22q) • Compare 2 pathlengths • Upward: 10,000 km • Downward: 10 – 20 km Wolfenstein; Mikheyev & Smirnov Tom Gaisser
e (or m) ne (or nm) nm Classes of atmospheric n events m Contained (any direction) n-induced m (from below) External events Plot is for Super-K but the classification is generic Contained events Tom Gaisser
Super-K atmospheric neutrino data (hep-ex/0501064) CC ne CC nm 1489day FC+PC data + 1646day upward going muon data Tom Gaisser
0 0 • 0 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 ~ 1 S13 small Atmospheric n nm nt, dm2 = 2.5 x 10-3 eV2 maximal mixing Solar neutrinos ne{nm,nt}, dm2 ~ 10-4 eV2 large mixing Yumiko Takenaga, ICRC2007 3-flavor mixing Flavor state | na ) = Si Uai | ni ), where | ni ) is a mass eigenstate Tom Gaisser
Primary cosmic-ray spectrum (nucleons) Nucleons produce pions kaons charmed hadrons that decay to neutrinos High-energy atmospheric neutrinos Tom Gaisser
Branching ratio moment of decay Spectrum-weighted moment of hadron production For example, for Factors in atmospheric n beam For each parent i = p±, K±, charm: Tom Gaisser
Account for m energy loss Account for m decay Similar analysis for atmosphericm Analytic approximation works well! Tom Gaisser
Energy spectrum of atmospheric muons and neutrinos • At low energy, Fn,m has same spectral index at production as primary spectrum • Fn,m becomes steeper by one power of energy at high energy • Critical energy depends on zenith angle: Ecritical = ei / cosq Tom Gaisser
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 Tom Gaisser
Energy-angle dependence by parent type Neutrinos Muons Plots show fraction of n & m from p±, K±, charm q = 0 q = 60o Tom Gaisser
x 1.37 x 1.27 TeV m+/m- with MINOS far detector • 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 Tom Gaisser
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 MINOS fit ratios of Z-factors Tom Gaisser
Atmospheric neutrinos – harder spectrum from kaons? Re-analysis of Super-K Gonzalez-Garcia, Maltoni, Rojo JHEP 2007 AMANDA atmospheric neutrino Phys.Rev D79 (2009) 102005 (The blue shaded region is the same as the green band on the right.) Tom Gaisser
FNAL E-781 (SELEX) Large asymmetry of Lc+ / Lc- production in baryon beams: p Lc+ favored with hard spectrum in xF Tom Gaisser
Signature of charm: q 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 Tom Gaisser
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 Tom Gaisser
RQPM Parameterization QCD range Multiply differential spectrum x E3 to display transition to prompt leptons Prompt m and n Tom Gaisser
m+ + m- nm + nm prompt Experimental challenge: Must measure change of slope of a steep spectrum with low statistics and fluctuations in energy deposited Tom Gaisser
Detecting neutrinos in H20Proposed by Greisen, Markov in 1960 • Heritage: • DUMAND • IMB • Kamiokande Super-K ANTARES SNO Neutrino must interact to be detected IceCube Tom Gaisser
125 m IceCube: n telescope& cosmic-ray detector Seattle Tom Gaisser July 2, 2009 Tom Gaisser Photo: James Roth 17-12-2007
Million to 1 background to signal from above. Use Earth as filter; look for neurtinos from below. Muons in n telescopes Downward atmospheric muons Neutrino-induced muons from all directions SNO at 6000 m.w.e. depth Tom Gaisser
Muons in IceCube Downward atmospheric muons Neutrino-induced muons from all directions IceCube P. Berghaus et al., ISVHECRI-08 also HE1.5 ~75° for deepest Mediterranean site Crossover at ~85° for shallow detectors Tom Gaisser 31
preliminary Atmospheric m and n in IceCubeExtended energy reach of km3 detector Dmitry Chirkin, ICRC 2009 Currently limited by systematics Patrick Berkhaus, ICRC 2009 Tom Gaisser
Looking for diffuse fluxes above the background of atmospheric neutrinos Sean Grullon Parallel session Tom Gaisser
+75° +60° +45° +30° +15° 24h 0h -15° -30° -45° -log10 p -log10 p R. Lauer, Heidelberg Workshop, Jan09 arXiv:0903.5434 Paper accepted for PRL 9 November 2009 Tom Gaisser
IceCube 40 Juan Antonio Aguilar TeV PA 2009 Tom Gaisser
Jon Dumm, IceCube, ICRC2009 Tom Gaisser
Shadow of the Moon with muons in IceCube Tom Gaisser
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 Tom Gaisser
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 n from same direction in Dt • 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 Tom Gaisser
pion decay probability 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 Tom Gaisser
Cosmic-ray physics with IceCube Use ratio of deep muons to shower size for composition Tom Gaisser Photo: James Roth 17/12/07
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) Tom Gaisser
Drilling operations 6 strings deployed so far this season. 18-20 planned. 28 tanks installed and freezing Tom Gaisser
Extras Tom Gaisser
Electron neutrinos K+ p0ne e± ( B.R. 5% ) KL0 p±ne e( B.R. 41% ) Kaons important for ne down to ~10 GeV Tom Gaisser
Uncertainty in atmospheric n • 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 Tom Gaisser
A C B C/A B/A Comparison of 3 calculations used by Super-K( Note: En > 100 MeV in most calculations) Y. Ashi et al. (Super-K Collaboration) Phys. Rev. D71 (2005) 112005 Tom Gaisser
Low energy (10 – 100 MeV ) Note: most neutrinos with En < 50 MeV are from decay of muons stopped in atmosphere Gaisser & Stanev, Proc 24th ICRC, Rome (1995) Tom Gaisser
Calculations of anti-ne background 10-100 MeV • Note dependence • on phase of solar • cycle: • 10 – 20% variation • similar to response • of neutron monitors FLUKA10-100 MeV Battistoni et al.(2004): http://www.mi.infn.it/~battist/neutrino.html Tom Gaisser