Frontiers in Contemporary Physics: May 23, 2005

Recent Results From AMANDA and IceCube

Jessica HodgesUniversity of Wisconsin – Madison

for the IceCube Collaboration

Why study neutrinos?

Protons: easily detected, but deflected by magnetic fields. Direction of cosmic ray origin is unknown.

Photons: absorbed by matter and will interact with the microwave and IR backgrounds. Carry directional information.

Neutrinos: not deflected by magnetic fields, therefore they keep their directional information. Low cross-section means they rarely interact and are hard to detect.

p

AMANDA

IceCube

Neutrino ProductionCosmic accelerators that are suspected to produce high energy cosmic rays include:

Gamma Ray Bursts (GRBs)Active Galactic Nuclei (AGNs)Supernova Remnants?

Due to Fermi acceleration, neutrinos are predicted to arrive with an E-2 energy spectrum

Bottom-Up scenariop + (p or ) + X e , + X

e : : = 1 : 2 : 0 at source

e : : = 1 : 1 : 1 at Earth (due to oscillations)

Amundsen-Scott South Pole Station

South PoleDome

Summer camp

AMANDA

road to work

1500 m

2000 m

[not to scale]

Where are we ?

Université de Mons-Hainaut, Mons, BelgiumUniversity Gent, Gent, BelgiumUniversity of Alabama, Tuscaloosa, ALUniversity of California-Berkeley, Berkeley, CA, USAUniversity of California-Irvine, Irvine, CA, USAUniversity of Canterbury, Christchurch, New ZealandUniversity of Delaware, Newark, DE, USAUniversity of Kansas, Lawrence, KS, USAUniversity of Maryland, College Park, MD, USAUniversity of Oxford, Oxford, UKUniversity of Wisconsin-Madison, Madison, WI, USAUniversity of Wisconsin-River Falls, River Falls, WI, USAUppsala Universitet, Uppsala, SwedenUtrecht University, Utrecht, NetherlandsVrije Universiteit Brussel, Brussels, Belgium

Chiba University, Chiba, JapanCTSPS, Clark Atlanta University, Atlanta, GA, USA

DESY, Zeuthen, GermanyHumboldt Universität, Berlin, Germany

Imperial College, London, UKInstitute for Advanced Study, Princeton, NJ, USA

Lawrence Berkeley National Laboratory, Berkeley, CA, USAPennsylvania State University, University Park, PA, USA

Amundsen-Scott Station, AntarcticaSouthern University and A & M College, Baton Rouge, LA, USA

Stockholm Universitet, Stockholm, SwedenUniversität Dortmund, Dortmund, Germany

Universität Mainz, Mainz, GermanyUniversität Wuppertal, Wuppertal, Germany

Université Libre, Brussels, Belgium

IceCube Collaboration

Antarctic Muon and Neutrino Detector Array

AMANDA-B10inner 10 strings302 Optical ModulesOperating from 1997-1999

AMANDA-II19 strings677 Optical ModulesOperating from 2000-now

Trigger Rate ~80 HzPMT noise ~ 1kHz

Optical Module:Down-looking photomultiplier tube enclosed in a pressure

resistant glass sphere

Ice Properties: dust layers exist at different depths

for wavelength = 400 nm,average absorption length = 110 maverage effective scattering length = 20 m

Neutrino Induced Events in the Ice

“Up-going”(from Northern sky)

“Down-going”(from Southern sky)

νμ charged current interactions produce

Cherenkov light along long tracks.Pointing resolution ~ 2 o

Energy resolution ~ 0.3 - 0.4 in log10

(E / TeV)Coverage: 2

νe and ντ charged current interactions and all flavor neutral current interactions induce cascades in the ice.Pointing resolution ~ 30o

Energy resolution ~ 0.1 – 0.2 in log10

(E / TeV)Coverage: 4

Muon Track

Cascade~15 m

Diffuse Neutrino Analysis (TeV – PeV)

“Signal”

downgoing muons and neutrinos

E-3.7E-2

Number of Optical Modules hit (scales with the neutrino energy)

Reconstructed Muon Event:

To select high quality upgoing events, apply cuts to the data based on the observables of the event.

Separate atmospheric and E-2 signal neutrinos with an energy cut. Monte Carlo based sensitivity optimization using the Feldman – Cousins prescription

Diffuse flux = flux from unresolved neutrino sources

Arb

itra

ry u

nit

s

Another Method of Setting a Diffuse νμ Limit

log of the neutrino energy (GeV)

Reconstruct the atmospheric neutrino spectrum and use this to set a diffuse limit

Neural Network Energy Reconstruction

Regularized unfolding gives the energy spectrum

Setting a limit on the diffuse flux of E-2 cosmic neutrinos:This limit corresponds to the highest allowed E-2 cosmic neutrino signal within the the uncertainty of the highest energy bin.

Limit on Diffuse E-2 νμ flux: E2 (E) < 2.6 x 10-7 GeV cm-2s-1sr-1

Range: 100 – 300 TeV Data Year: 2000

* Preliminary *

Preliminary

Preliminary

Muon Neutrino Flux Limits

Cascade Diffuse Neutrino Analysis

Nobs = 1 event

Natm = 0.90

Natm ν = 0.06 ± 25%norm

Astroparticle Physics 22 (2004) 127

Sensitive to all three neutrino flavors

+0.69

-0.43

+0.09

-0.04

All flavor limit on diffuse E-2 neutrino flux: E2 (E) < 8.6 x 10-7 GeV cm-2s-1sr-1

Range: 50 TeV – 5 PeV Data Year: 2000

Cuts optimized on topology and energy

PeV – EeV Diffuse Neutrino Analysis

Ultra high energy neutrinos have large cross-sections --> PeV and EeV neutrinos that enter the earth in the Northern Hemisphere are likely to interact before reaching AMANDA

Best detection strategy: Look near the horizon and just above it.True cosmic neutrino events should be very bright (large number of hits in the detector).

Using a neural net trained to distinguish ultra high energy cosmic E-2 events from background:

Limit on Diffuse E-2 neutrino flux: all E

2 (E) < 0.99 x 10-6 GeV cm-2s-1sr-1

Range: 1 PeV – 3 EeV Data Year: 1997

Neutrino Point Source Search

2000 – 2003 Sky Map807 days of livetime3329 upgoing events

(3438 atmospheric events expected)

All events shown are consistent with the atmospheric neutrino background. No extraterrestrial E-2 signal observed.

Two Search Methods:1) Look for clusters of events around a predefined list of neutrino source candidates.

2) Grid search : Shift the grid repeatedly to look for a clustering of events. This allows you to find sources not on the predefined list.

Neutrinos from Gamma Ray Bursts

Background determined on-source / off-time Background determined on-source / off-time

Blinded Window

-1 hour +1 hour10 min

Time of GRB (start of T90

)

97-00 Flux Limit at Earth*: E2Φν≤ 4·10-8 GeV cm-2 s-1 sr-1

00-03 Flux Limit at Earth*: E2Φν≤ 3·10-8 GeV cm-2 s-1 sr-1

Using space and time coincidence leads to a very low background.

Separate analyses are currently underway using both the average Waxman-Bahcall parameters and burst-specific observables.

Year Detector Bursts Background Predicted

Number Observed

Event Upper Limit

1997-2000 B-10 / A-II 312 (BATSE)

1.29 0 1.45

2000-2003 A-II 139(BATSE + IPN)

1.25 0 1.47* Preliminary *

Indirect Dark Matter Search for Neutralinos Gravitationally Trapped in the Sun

Limits on muon flux from the Sun

COLOR CODE:

Disfavored by CDMS II

Will be ruled out when experiments reach 10x current sensitivity

Require greater than 10x current sensitivity to probe

detection

radius

SuperNova Early Warning System

SNEWS is a collaborative effort between Super-K, SNO, LVD, KamLAND, AMANDA, BooNE and several gravitational wave experiments

Bursts of low-energy (MeV) neutrinos from core collapse supernovae

AMANDA detection: - simultaneous increase of all PMT count rates (~10 s) - can detect 90% of SN within 9.4 kpc - less than 15 fakes per year

AMANDA-II

AMANDA-B10

IceCube30 kpc

AMANDA-B10 sees 70% of the galaxy

AMANDA-II sees 90% of the galaxy

IceCube will see out to the LMC

IceCube: The Future

one cubic kilometer

80 strings with 60 Digital Optical Modules per string

Optimized for detection of TeV – PeV neutrinos 17 m vertical spacing of DOMs 125 m between strings

2 IceTop Tanks with 2 Digital Optical Modules above each IceCube string

Estimated completion: 2010

1450 m

2450 m

300

m

AMANDA

~300m for 10 PeV

Event Simulation in IceCube

Very high energy events that saturate AMANDA will be clearly distinguished in IceCube.

muon event

e cascade event

double bang event

E = 10 TeV

E = 375 TeV

Recent Deployment

January 27, 2005First IceCube String Deployed!60 Digital Optical Modules are in the ice

8 IceTop tanks deployed

IceCube Drill Camp

Limits have been set and multi-year AMANDA analyses are getting closer to the Waxman-Bahcall diffuse neutrino upper limit. However, no extraterrestrial neutrino signal has been observed yet.

AMANDA is successful as a proof-of-concept and is the largest neutrino detector in the world. IceCube is under construction.

One IceCube string has been deployed and all DOMs are communicating successfully.

www.icecube.wisc.edu

hodges@icecube.wisc.edu

ConclusionsIceTop

Spring 2005 data event:

Run 872 Event 5945

First IceCube string