Air showers in IceCube. Cosmic rays Neutrinos Gamma rays

Transcription

1 Air showers in IceCube Cosmic rays Neutrinos Gamma rays

2 Cosmic rays Cosmic accelerators produce rela9vis9c protons and nuclei (cosmic rays) CR sources (such as SNR, AGN, GRB) are likely neutrino sources Good! Iden<fying CR sources by detec<ng high energy astrophysical neutrinos is a main goal of IceCube Cosmic rays interact in the atmosphere and produce a million to one background/signal in IceCube Problem and opportunity NSF, 04/24/2014 Tom Gaisser 2

3 Neutrinos High- energy neutrinos are produced in the Universe wherever protons etc. interact with gas or light: Near the sources of cosmic rays During propaga<on of cosmic- rays in the CMB But also locally by cosmic- ray interac<ons in the Earth s atmosphere Atmospheric neutrinos are background but also Calibra<on source and Beam for study of neutrino proper9es (e.g. oscilla9ons) NSF, 04/24/2014 Tom Gaisser 3

4 Gamma rays Gamma- rays are a standard probe of high energy astrophysics Cosmic ray sources produce γ- rays in two ways From radia<on by accelerated electrons From decay of π 0 produced by interac<ons of accelerated cosmic- ray protons or nuclei with gas or photons High energy ν are produced only in hadronic collisions: From decay of π/k produced when cosmic rays interact with gas in or near their sources Or from photo- pion produc<on on CMB or EBL Neutrinos are uniquely of hadronic origin NSF, 04/24/2014 Tom Gaisser 4

5 Cosmic ray showers from above Cosmic rays after propagation Neutrinos from cosmic ray sources ν e :ν µ :ν τ = 1:2:0 à 1:1:1 South Pole 2835 m.a.s.l. Neutrinos from all direc9ons Atmospheric muons and neutrinos NSF, 04/24/2014 Tom Gaisser 5

6 Example... Secondary photons and low energy charged par<cles 5 μs TeV muons NSF, 04/24/2014 Tom Gaisser 6

7 Cosmic Rays Energy content of CR determines possible sources of neutrinos Extra- galac9c origin is likely Loca9on of transi9on from galac9c to extra- galac9c affects energy es9mate E 2 dn/de (GeV cm -2 sr -1 s -1 ) protons only electrons positrons antiprotons Energies and rates of the cosmic-ray particles Grigorov Akeno MSU KASCADE Tibet KASCADE-Grande IceTop73 all-particle HiRes1&2 TA2013 Auger2013 Model H4a CREAM all particle Galactic E dn d ln E GeV cm 2 srs 10-8 Fixed target HERA RHIC TEVATRON LHC Extra-Galactic at GeV (10 19 ev) E (GeV / particle) NSF, 04/24/2014 Tom Gaisser 7

8 Neutrinos from sources of CR Galac9c supernova remnants Accelerated par9cles collide with gas in or near sources and produce neutrinos Extra- galac9c sources (e.g. AGN, GRB, ) The next two slides show two generic models Neutrinos likely in the first case, but less likely in the second NSF, 04/24/2014 Tom Gaisser 8

9 Generic model I CR accelera9on occurs in jets AGN or GRB Intense radia9on fields Models assume photo- produc9on: p + γ à Δ + à p + π 0 à p + γ γ p + γ à Δ + à n + π + à n + µ + ν Ideal case ( ~ Waxman- Bahcall limit ) Strong magne9c fields retain protons in jets Neutrons escape, decay to protons & become UHECR Extra- galac9c cosmic rays observed as protons Energy content in neutrinos energy in UHECR This picture disfavored as limits go below W- B /rieger/science.gif Waxman, Bahcall, PRD 59, (1998). Also TKG astro-ph/ v1 NSF, 04/24/2014 Tom Gaisser 9

10 Generic model II UHECR are accelerated in external shocks analogous to SNR See E.G. Berezhko, & mixed composi9on (accelerate whatever is there) Low density of target material à lower level of TeV- PeV neutrino produc9on Diagram from Begelman & Cioffi, Ap.J. (1989) L21 NSF, 04/24/2014 Tom Gaisser 10

11 Toward a global view of CR Popula9on 1 Galac9c SNR? Popula9on 2 Is it needed? Popula9on 3 Extragalac9c? What sources? Focus: transi9on zone NSF, 04/24/2014 Tom Gaisser 11

12 Primary spectrum from IceTop Phys. Rev. D 88, (2013). Bakh9yar Ruzybayev is lead author sr -1 s -1 ] m [GeV dn de da d dt! 2.7 E 4 10 IceTop 73, SIBYLL 2.1, H4a composition assumption KASCADE-Grande, SIBYLL 2.1 KASCADE, SIBYLL 2.1 GAMMA 2008 Tunka-133 Tibet III, SIBYLL log (E/GeV) GeV sets normaliza9on for PeV ν Directly for background atmospheric ν At sources for astrophysical ν GeV: transi9on from galac9c to extragalac9c Model dependent NSF, 04/24/2014 Tom Gaisser 12

13 Spectrum measured by IceTop 2.67 yrs livetime Δlog 10 E = 0.05 total events above 100 PeV Δlog 10 E = ( )!

14 u Predefine New arrays with 250m and 500 m spacing u Count sta9ons from the New list par9cipa9ng in the event. 250 m spacing: too low threshold m spacing seems op9mal for ~50 PeV threshold 500 m spacing: threshold moves to 100 PeV è too high Note: Auger infill: 85 detectors in two grids of 750m (covering 23.5 km2) and 433m (covering 5.9 km2) spacing. TALE: 100 scin9llator counters at 400m spacing

15 Order of magnitude increase is achievable in Galac9c- extragalac9c transi9on region 4 10 sr -1 s -1 ] m ! dn/de [GeV 2.6 E HEGRA Casa-Mia Tibet III 2008 Kascade 2005 Kascade-Grande 2012 IceTop-26 GAMMA 2008 Tunka AGASA HiRes 1 HiRes 2 TA 2011 Auger Threshold with 300 m tank spacing Primary Energy, E [GeV] NSF, 04/24/2014 Tom Gaisser

16 Multi-messenger paradigm TeVCat γ-ray sources o 13 1 Galactic Plane Northern Hemisphere Southern Hemisphere o Galactic -180 o LBL, IBL, LBL, FRI, FSRQ Globular Cluster, Star Forming Region, Massive Star Cluster Binary PWN Shell, SNR/Molec.Cloud, Composite SNR Starburst Others [TeVCat 14] Slide from Markus Ahlers Markus Ahlers (UW-Madison) Physics Goals March 3, 2014 NSF, 04/24/2014 Tom Gaisser 16

17 IceCube selected sources (13 galac9c SNR etc, 30 extragalac9c ac9ve galaxies, etc.) NSF, 04/24/2014 Tom Gaisser 17

18 Upper limits on selected sources IC Ap.J. 779, 132 (2013) NSF, 04/24/2014 Tom Gaisser 18

19 Compare IceCube limits on ν to TeV photons from ac9ve galaxies 1e+46 1e+45 TeVCat IC40+IC59 limits Luminosity estimate (erg/s) 1e+44 1e+43 1e+42 1e+41 Cen A 1ES M87 1e Red shift z NSF, 04/24/2014 Tom Gaisser 19

20 Follow- up by VERITAS Look for TeV gamma- rays from two HESE events (#5 and #13) Both are star9ng muon tracks with ~ 1 degree resolu9on Event 5 has a Fermi blazar within 2 deg (PKS , z=0.128) Observe each for several hours NSF, 04/24/2014 Tom Gaisser 20

21 3.5 hours on Event ID 5, offset by 0.7 degrees NSEW UL(99%) = 1.55 x10-8 m -2 s -1 above 300 GeV (~ 1.2% Crab) 2.5 hours on Event ID 13 UL(99%) = 2.00 x10-8 m -2 s -1 above 300 GeV (~ 1.6% Crab) Nothing elsewhere in the field(including PKS ) Event ID 5 Event ID 13 Preliminary Preliminary Jamie Holder, IceCube Collabora9on Mtg, Mar. 2014

22 Air showers from cosmic γ- rays SEARCH FOR GALACTIC PeV GAMMA RAYS WITH THE... PHYSICAL REVIEW D 87, (2013) -60 Declination (degrees) ) -2 HI column density (cm Right Ascension (degrees) FIG. 8 (color online). Equatorial map of the 268 candidate gamma-ray events of the IC40 data set superimposed on HI column densities based on Ref. [14]. The dotted black curve encloses the source region, defined as within 10 of the Galactic plane. Signature: few µ in deep IceCube in coincident events Search with present IceCube limited by narrow aperture for coincident events (<30 o zenith) and high energy threshold Larger aperture would allow beper sky coverage (closer to Galac9c center) ID of muons at the surface improves sensi9vity NSF, 04/24/2014 Tom Gaisser 22

23 Cosmic- ray neutrinos (aka atmospheric neutrinos) Atmospheric neutrinos produced in air showers above IceCube Conven9onal ν (from K and π decay) Prompt ν (from decay of charm) Muons produced in the same shower as ν provide a par9al self- veto in Southern sky IceTop also provides a par9al veto NSF, 04/24/2014 Tom Gaisser 23

24 Atmospheric neutrino self veto Two cases 1. Stefan Schönert et al. Phys. Rev. D79 (2009) Can be evaluated analy9cally 2. Veto by an unrelated μ - - also applies to ν e Requires Monte Carlo or numerical integra9on NSF, 04/24/2014 Tom Gaisser 24

25 Angular/energy dependence Analy9c calcula9on: Applies to ν µ only For E ν > 100 TeV Passing rate < 10% for cosθ > % of downward phase space Even beper at higher E Works best at modest depth Schönert et al. PR D79 (2009) Feb Tom Gaisser 25

26 Surface veto needed to enhance ν µ signal star9ng in ice Astrophysical ν µ Good poin9ng Higher rate (due to large target) This event is vetoed in HESE analysis µ NSF, 04/24/2014 Tom Gaisser 26

27 Yields: Veto concept Use Monte Carlo simula9ons Extend to higher energies numerically Response (ν): Passing rate: P ν (E ν,θ)=σ A Y ν (A, E 0,E ν,θ) and Y µ (A, E 0,E µ,θ) R(A, E 0,E ν,θ)=φ A (E 0 ) Y ν (A, E 0,E µ,θ) de 0 R ν (A, E 0, E ν,θ) P(veto = {no}) Check against full Monte Carlo and extrapolate to E ν > PeV 17- Feb Tom Gaisser 27

28 Neutrino self- veto E 3 Φν [GeV 2 cm 2 sr 1 s 1 ] E 3 Φν [GeV 2 cm 2 sr 1 s 1 ] TeV 10 TeV 100 TeV Conventional ν µ TeV ν e 10 TeV 100 TeV ν µ Conventional ν e cos θ Total flux After veto cos θ E 3 Φν [GeV 2 cm 2 sr 1 s 1 ] Prompt ν µ (solid) and ν e (dashed) 100 TeV 10 TeV 1TeV Prompt ν µ and ν e cos θ TKG, Jero, Karle, van Santen 17- Feb Tom Gaisser 28

29 Comparison with full MC Conven9onal neutrinos Prompt neutrinos ν µ ν e Passing rate Passing rate ν µ ν e Neutrino energy [GeV] 0.13 Passing rate Passing rate ν µ ν e Neutrino energy [GeV] 0.33 ν µ 0.13 ν e 17- Feb Tom Gaisser 29

30 Surface veto example (Event 28) NSF, 04/24/2014 Tom Gaisser 30

31 3 yrs Declination (degrees) 80 Showers Tracks 60 Earth shadow neutrinos suppressed Sketch of atmospheric ν self veto region -80 Atmospheric µ (or ν) Deposited EM-Equivalent Energy in Detector (TeV) 17- Feb Tom Gaisser 31

32 Aperture for coincident events: ν, γ, cosmic rays 0.26 km2 sr ~ 10 km2 sr IceTop Here: 120 strings 1450 m 1.35 to 2.7 km 80 DOMs/string 300 m spacing 2450 m NSF, 04/24/2014 Tom Gaisser 32 IceCube Collaboration Meeting Banff, Alberta, Canada-March 2014 Wisconsin IceCube Particle Astrophysics Center, WIPAC!