neutrino “astronomy”

francis halzen university of wisconsin http://icecube.wisc.edu • introduction

• the rationale for building a km3 neutrino detector

• IceCube: 3 challenges

• drilling • optics of ice • atmospheric muons

• neutrino physics: GeV to 100 TeV

• PeV neutrinos: first evidence for cosmic neutrinos

IceCube.wisc.edu

energy (eV)

n

CMB Radio

flux flux TeV sources

Visible cosmic

rays

rays

- g particle flux

In the Universe GeV Galactic and extragalactic cosmic rays

knee

ankle and GZK feature

cosmic rays

neutrinos produced in interactions of cosmic rays with microwave photons cosmic rays interact with the microwave background p g  n   and p  0

cosmic rays disappear,     neutrinos appear

   {e  e}

6 E  2 10 TeV 1 event per cubic kilometer per year  ...but it points at its source • introduction

• the rationale for building a km3 neutrino detector

• IceCube: 3 challenges

• drilling • optics of ice • atmospheric muons

• neutrino physics: GeV to 100 TeV

• PeV neutrinos: first evidence for cosmic neutrinos

IceCube.wisc.edu shock acceleration (solar flare)

coronal mass ejection  10 GeV particles flows of charged particles result in large B-fields Hillas formula : • accelerator must contain the particles

• dimensional analysis, difficult to satisfy energy (eV)

/ / galactic

cosmic rays / / 10-12 erg cm-3 galactic / cosmic rays/ CMB 10-41 erg/cm3 extragalactic

Radio / / cosmic rays / -19 -3 Visible 3x10 erg cm

flux flux /

410 photons / 3 /

of 2.7 K per cm / rays

or - / g 10-12 erg cm-3 / ~ 0.5 eV cm-3 / / GeV cassiopeia A supernova remnant in X-rays gravitational energy released is trans- formed into acceleration

acceleration when particles cross high B-fields neutrinos from supernova remnants :

molecular clouds as beam dumps Galactic plane in 10 TeV gamma rays :

supernova remnants in star forming regions StandardDeviations Southern Hemisphere

Sky

90° 65° 30°

210° milagro neutral pions 0 + - are observed as + - gamma rays g g n  n 

e+ e- charged pions + - are observed as e g e + neutrinos e+ g  + e ne n n  n   g g

Cygnus region : Milagro

translation of TeV gamma rays into TeV neutrinos :

3 ± 1 n per year in IceCube per source 5s in 5 years of IceCube … IceCube image of our Galaxy > 10 TeV cassiopeia A supernova remnant in X-rays and if the star collapses to a black hole …

 happens in seconds not thousands of years  beamed along the spin axis of the black hole  simulation not image

collapse of massive star produces a

gamma ray burst

spinning black hole

neutrinos are produced in the interactions of fireball protons (cosmic rays) with synchrotron photons

decays to PeV neutrino

decays to cosmic ray

GRB: one neutrino per cosmic ray observed active galaxy particle flows near supermassive black hole

sources accommodating the observed energy budget

Galactic: supernova remnants?

extragalactic: gamma ray bursts? active galaxies?

GRBGZ

GRB GZK

100 Galactic supernovae

10 8 9 events per km2yr neutrinos in coincidence with GRB alerts aligned with SWIFT GRB angular accuracy 0.2 deg energy 109 TeV but…. GRB on probation • introduction

• the rationale for building a km3 neutrino detector

• IceCube: 3 challenges

• drilling • optics of ice • atmospheric muons

• neutrino physics: GeV to 100 TeV

• PeV neutrinos: first evidence for cosmic neutrinos

IceCube.wisc.edu M. Markov B. Pontecorvo 1960

M.Markov : we propose to install detectors deep in a lake or in the sea and to determine the direction of charged particles with the help of Cherenkov radiation. • shielded and optically transparent medium

 Pn   nsn R n



• lattice of photomultipliers n photomultiplier tube

93 TeV muon energy measurement ( > 1 TeV )

convert the amount of light emitted to measurement of the muon energy (number of optical modules, number of photons, dE/dx, …) why did it take so long ? 2000

AMANDA South Pole Dome

1500 m

2000 m Amundsen-Scott South Pole station [not to scale] AMANDA event: muon neutrino neutrino interaction creates muon track n + p   + …

analog signal after 2 km… not pretty architecture of independent DOMs

10 inch pmt

LED flasher board

HV board main board Digital Optical Module (DOM)

… each DOM independently collects light signals like this…

Digitized Waveform

…time stamps them with 2 nanoseconds precision and sends them to a computer that sorts them into muon and neutrino events… IceCube / Deep Core • 5160 optical sensors between 1.5 ~ 2.5 km completed December 2010

• 10 GeV to infinity

• ~ 0.5 degree on-line < 0.3 degree off line

• < 15% energy resolution

Digital Optical Module (DOM) each DOM is independent: continuously sends time- stamped wave forms

89 TeV

43 • introduction

• the rationale for building a km3 neutrino detector

• IceCube: 3 challenges

• drilling • optics of ice • atmospheric muons

• neutrino physics: GeV to 100 TeV

• PeV neutrinos: first evidence for cosmic neutrinos

IceCube.wisc.edu IceCube Site

nozzle delivers  • 200 gallons per minute • 7 Mpa • 90 degree C  4.8 megawatt heating plant drilling and deployment drill hole and install 60 DOMs in less than two days to 2.5 km

46 absorption length  220m 

most transparent solid in Nature...or laboratory scattering length  47m 

… you looked at 10msec of data ! muons detected per year:

• atmospheric*  ~ 1011

• atmospheric** n   ~ 105

• cosmic n   ~ 10

* 2700 per second ** 1 every 6 minutes … on to IceCube science we measure the flux of atmospheric muons and neutrinos at higher energies and with better statistics than previous experiments. Any deviations from what is expected is new neutrino physics or new astrophysics. We just look for surprises. • introduction

• the rationale for building a km3 neutrino detector

• IceCube: 3 challenges

• drilling • optics of ice • atmospheric muons

• neutrino physics: GeV to 100 TeV

• PeV neutrinos: first evidence for cosmic neutrinos

IceCube.wisc.edu the atmospheric neutrino “background”

but also up to 100 TeV neutrinos for … particle physics … radiography of the Earth … … calibration !

• cosmic neutrinos: energy > 100 TeV

• atmospheric background: 1~2 events per year

atmospheric neutrino spectrum oscillations in DeepCore [energy ~30 GeV; 5.6 sigma]

Vertical Horizontal

57 measured at 10X higher energy IceCube/DeepCore: atmospheric and sterile sensitivity

Lsterile potential sterile neutrino limits

Esmaili et al, JCAP 1211, 057 • introduction

• the rationale for building a km3 neutrino detector

• IceCube: 3 challenges

• drilling • optics of ice • atmospheric muons

• neutrino physics: GeV to 100 TeV

• PeV neutrinos: first evidence for cosmic neutrinos

IceCube.wisc.edu cosmic rays interact with the microwave background p g  n   and p  0

     cosmic rays disappear, neutrinos appear

   {e  e}

6 E  2 10 TeV ~1 event per cubed kilometer per year 

GZK neutrinos: > 41,000 photons near the horizon

number of channels > 300

unblinding: 2 events in the signal region

tracks and showers

• energy

1,070 TeV 1,210 TeV (15% resolution)

• showers • downgoing • not atmospheric

 flux at present level of diffuse limit

 largest bkgd: atmospheric charm < 3 sigma

digital optical module 44 on string 20 only

GRBGZ

GRB GZK

100 Galactic supernovae

10 8 9 events per km2yr search for a diffuse cosmic neutrino flux

atmospheric charm

cosmic highest energy event

86 • find more contained events (420 Mton)

no simulation: • total calorimetry tag muons in the veto

region and see what • complete sky coverage fraction is vetoed by

the layer of detectors • flavor determined below

• some will be muon neutrinos with good angular resolution loss in statistics is compensated by event definition

total charge collected by PMTs of events with interaction inside the detector

E2Φ(E) = (3.6±1.2)·10−8 GeVcm−2s−1sr−1

atmospheric n and  100 TeV n

• 28 events • poisson excess 4.3 sigma

atm. background: up neutrinos 4.6 muons 6

down

atmospheric muon (blue) + neutrino (red) background + astrophysical E2Φ(E) =(3.6±1.2)·10−8 GeVcm−2s−1sr−1

energy deposited in the detector zenith angle

increase in threshold not important (in the region where atmospheric background dominates)

Effective volumes DecaCube (1/2/3) IceCube DeepCore Spacing 1 (120m): IceCube (1 km3) + 98 strings (1,3 km3) = 2.3 km3

Spacing 2 (240m): IceCube (1 km3) + 99 strings (5,3 km3) = 6.3 km3

Spacing 3 (360m): IceCube (1 km3) + 95 strings (11,6 km3)

= 12.6 km3 “It is not wise to speculate before the data.” Sherlock Holmes

“If statistics matters, do a better experiment.” Rutherford

• we have another year of data

• we will do a better analysis, this one was…. • ….blind (literally) 39 Institutions ~220 collaborators

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