Entering the Kilometer-Square Era of High Energy Neutrino Detection Azriel Goldschmidt INPA Journal Club, LBNL, Berkeley, Nov. 2004

Outline Physics of a km 2 neutrino detector –Driving forces –Neutrino sources The IceCube detector: –Point sources searches The IceCube DAQ: –Timing of PMT pulses –System performance Outlook

Main Goal of a km 2 Neutrino Detector  Observation of high-energy point sources  from our galaxy and…  up to cosmological distances  Observed so far, nuclear energy ~MeV sources:  Sun, steady source: Solar physics, neutrino mixing…  SN 1987A, transient source: Supernova physics, neutrino mass…

Cosmic Rays physics: ions with eV tells us there is SOMETHING to look for! High Energy Photon astronomy: eV tells us WHERE to look Driving Force: Data from Related Fields CGRO Whipple Observatory CR detection

The Advantages of HE Neutrino Astronomy At the highest energies,  astronomy is limited by attenuation (  e + e - ). Cosmic rays (protons, ions) do not point back to the source (due to B fields). p  can “look” inside objects in the universe point back to their sources unaffected by B fields But they do present a challenge for their detection

What we hope to learn from the observation of HE point sources ? oOrigin of Cosmic Rays: “smoking gun” of the Supernova Remnant (SNR) hypothesis oOrigin of the Ultra High Energy Cosmic Rays (UHECR, E CR > eV) which present an “acceleration challenge” oInner workings of the most powerful objects in the Universe such as AGN/Blazars, GRB, SNR, Microquasars…

Cosmic Rays & Neutrinos ? Galactic SNR p  ? p

Supernova Remnants (SNR) Powerful blast waves driven to the interstellar medium by core collapse supernovae. Leading candidate “accelerator” of most galactic CR’s: –Evidence of electron acceleration: non-thermal photon emission and high energy  ’s –SNR power matches CR’s –SN chemical abundances match CR’s (after spallation) Fermi acceleration in the blast waves up to eV for thousands of years after SN explosion, producing a spectrum:

Supernova Remnants (SNR) Proving the CR Hypothesis The “smoking guns” of CR-ions acceleration: 1.A 67.5 MeV peak in the  ray spectrum from    decay  –Searches for the peak are inconclusive so far 2. Neutrinos: Discovery of HE neutrinos from SNR would unequivocally establish the origin of galactic cosmic Rays!

Cosmic Rays & Neutrinos ?

The Challenge of Acceleration to eV Hillas Plot from Cronin, Rev. of Mod. Phys. 71 (1999) A “perfect” accelerator: TEVATRON Top-Down models (super-heavies that decay) avoid acceleration challenge E MAX =  ZBL L B GRB

Evidence that CR’s with E>10 18 eV are Extragalactic >10 18 eV, B(galactic) too small to hold p-Fe No anisotropy observed (from galactic plane) Hardening of spectrum and change in composition signal new component Fly’s Eye (1993) Ankle Spectrum

Ref. Waxman, E. Nuclear Physics B 118 (2003) Estimate of flux from CR flux with cosmological origin Assume each proton interacts once losing a fraction  <1 of the E p  p  p Half the pions (     ) produce neutrinos Half the  energy goes to  Injection energy per logarithmic decade of E:

Estimate of Event Rates from CR flux with cosmological origin Probability of observing a muon (per neutrino) Given by the ratio: muon range / neutrino range For instance, the flux between 100TeV and 100PeV: But life isn’t that easy for the neutrino physicist…

Candidate Sources of post-ankle CR’s and neutrinos AGN = Active Galactic Nuclei GRB = Gamma Ray Bursts Top-Down super-heavies

Gamma Ray Bursts (GRB) Intense bursts of keV~MeV   rays up to ~100 sec long, with variability as short as 1 msec.

The Fireball Phenomenology: GRB- Connection

GRB’s (continued) Maximum proton energies of eV attainable: possible source of post-ankle CR’s. Energy injection similar to the post-ankle CR’s. Detection in coincidence (time and direction) of neutrinos and  rays (from satellite measurements) reduces background dramatically. And an “extra bonus”: Tests of Relativity…

Arrival Times of &  from GRBs: Concept: Measure  t  =t -t  with ~1sec precision Test of Lorentz Invariance:Test of Lorentz Invariance: Is v =  v   c  e.g. D source ~100Mpc and  t  < 1sec  v  v    (Mass effect negligible: D source ~100Mpc, m ~1eV, E ~TeV   t  ~nsec) Weak equivalence Principle:Weak equivalence Principle: “space-time is endowed with a metric and the world lines of uncharged test bodies are geodesics of that metric”. Test that photons and neutrinos are affected equally by the galaxy gravitational potential:   level test possible for  t  <~1sec

Challenges and Opportunities for the “  Observers” Discovery of HE  sources (above a “diffuse” flux). Establish/discover the source(s) of CR’s: SNRs? Solutions to the UHECR (post-ankle) problems: –Are GRB’s responsible for UHECR acceleration? –Or are AGN’s responsible? –Something more exotic? Neutrino emission signals hadronic processes: –Set constraints on astrophysical models of sources. –Or, rule out specific source models. Explore the neutrino sky for the unexpected

 Cerenkov light Detector interaction Neutrino Detection

Amundsen-Scott South Pole station South Pole Dome Summer camp AMANDA road to work 1500 m 2000 m [not to scale]

InIce 80 strings 60 OMs/string 17 m vertical spacing 125 m between strings IceTop 160 tanks frozen-water tanks 2 OMs / tank IceTop 1200 m AMANDA IceCube

Muon Angular Resolution of IceCube from MC Mean angle between  and    /TeV) 0.7 From below From above

downgoing  ’s rejected cos  A eff / km 2 Effective Area of IceCube At the large energy the Earth is not fully transparent, eg 50% lost at 1PeV

AMANDA Search for Neutrino Point Sources 922 events Highest: 3.41 Above 3σ: 1 σ significance map Highest: 3.6 Above 3σ: 2  No excess in significance beyond randomly expected Scrambled in azimuthal direction! PRELIMINARY equatorial coordinates

Point Source Search: Past, Present and Future… integrated above 10 GeV, E -2 signal 1997 : Ap.J. 583, 1040 (2003) 2000 : PRL 92, (2004) IceCube expectation: Astr. Phys 20, 507 (2004) Average flux upper limit [cm -2 s -1 ] sin  AMANDA-B10 AMANDA-II Completed IceCube 1/2 year expected Preliminary  declination  0 o   90 o  Arbitrary units

The High-Energy Sky Today (E > 1GeV) No observation yet of HE neutrino sources Null results in searches for GRB neutrinos (in coincidence)

The IceCube DAQ Concept GPS 1.Digital Optical Module: Detects photons Collects data autonomously Self calibrating Communicates digitally Free running stable clock 2.Cable 1 to 3.4km (copper): Brings power to 2 DOMs 1Mbaud communications 3.Surface DAQ (one custom card): Network of computers Software trigger & event builder No real time functions (1 exception)

LBNL Role in IceCube Design & Construction DAQ –Hardware –Software System software architecture

 Self-triggers on PMT pulse  Captures waveforms with  250 MHz first 500 ns  40 MHz over 5000 ns  Dynamic range  200 PE over 15 ns  2000 PE over 5000 ns  Time-stamps each pulse  r.m.s. < 5 nsec  Dead time < 1 %  Noise rate < 1000 Hz  Calibration devices: –UV & blue LEDs –electrical pulsers mu metal cage PMT penetratorHV board flasher board DOM main board pressure sphere optical gel delay board 33 cm The DOM (Digital Optical Module)

DOM main board (DOM MB)

DOM MB Block diagram FPGA CPU CPLD Flash PMT Power SDRAM ATWD fADCDAC Monitor & Control LPF LC x16 x2 x0.25 Flasher Board Pulser DACs & ADCs Corning Frequency Ctl 4Mb 16Mb +/-5V, 3.3V, 2.5V, 1.8V 64 Bytes Trigger (2) ADC Oscillator 20 MHz 40 MHz MUX (n+1) (n–1) DOR OB-LED x 2.6 x 9 10b 8b 32b 16b 8b 8b, 10b, 12b DP Ram 1 megabaud DC-DC Configuration Device 8Mbit Delay

DOM MB Reliability The challenge: –No possibility of repair after deployment –15 yr detector lifetime required Our approach: –Parts selection with reliability as a first priority –Selection of manufacturers (board+assembly) –Extensive testing including accelerated stress

Accelerated screening test with thermal cycles and vibration time Temp and vib

Burn-in, cold and interfaces tests 500 DOM Main Boards produced and tested at LBNL from 6/04 to 10/04 !

10” PMT Hamatsu Fully assembled & tested DOMs are already in their way to South Pole for deployment in January 2005

Calibrating Clocks with nsec Timing over 3.4km long “phone wires” ~5,000 “phones” with –Varying cable lengths (depth & position) –Transit time for 3.4 km twisted pair: ~17  s –Rise-time after propagation ~ 2  s (~1/t) The solution: –High-stability local clock:  f/f ~ 6 x /s ! –Frequent (1 every 10sec) calibrations –Cable delay measurement in situ

Reciprocal Active Pulsing Relates the local DOM oscillator to GPS time This method works when there is symmetry between the up & down pulses This, in turn, requires equivalent electronics on the surface and the DOM

Time Resolution Measured with Laser Source: 100 DOMs in a Freezer (-40C) D. Chirkin Nov 2004  t = 2.37 ns

Demonstration of the DOM Concept in the Ice Prototype: String-18 Deployed at South Pole in 2000 (41 DOMs) Used for development, test and demonstration Detection of cosmic ray muonsDetection of cosmic ray muons Data MC

Speed of Muons from the Prototype String Multiplicity => 8 Slope = 0.984

Muon Reconstruction with Prototype DOM String Uses reduced effective speed of light to account for scattering Higher multiplicities select muons more parallel to the string

IceCube 80-String Deployment Plan Jan-Feb 2005 Deploy 4 strings Dec-Feb 2006 Deploy 12 strings Nov-Feb 2007 Deploy 16 strings Nov-Feb 2008 Deploy 18 strings Nov-Feb 2009 Deploy 18 strings Nov-Feb 2010 Deploy 2+10 strings

Systems at Pole (or on the way) for the first 4 Strings’ deployment Hose-reel with hose, Physical Sciences Laboratory UW-Madison (Nov 2003) Hose-reel at South Pole (Jan 2004)

P.O.H:“The first part of the summer season has been very cold -44 to -57 C…it is not possible to unload the planes in a normal way from the back with tractors because you get lots of small ice particles from condensation behind the engines. You are not able to see anything back of the plane… to unload the cargo one has a combat procedure: stop the plane, open up the back, release the pallets with cargo, accelerate the plane so the pallets with the cargo move out of the plane onto the snow. It is a very fast but sensitive equipment should not be unloaded this way. “ “Last week about 130 (out of 220) people went to the doctor due to the flu or a very heavy cold.” (our guys are OK already) News Flashes 11/11/04 –yesterday-

In Summary… The neutrino sky holds the potential for important discoveries from CR’s origin to the physics of GRBs and AGNs IceCube experiment is on track: –Funded km 3 detector at the South Pole –Working prototype –Drilling and deployment starts in January Major LBNL Role …the next 5-10 years…

GLAST 2007 SWIFT Nov 2004 Auger 2005 (South) IceCube VERITAS 2006