IceCube Calibration Overview Kurt Woschnagg University of California, Berkeley MANTS 2009 Berlin, 25 September identical sensors in ultraclean, stable ice

  geometry timing charge ice properties: scattering, absorption, hole ice Low level High level track pointing event energy efficiency Database

Geometry calibration Stage 1 Requirement: position of every DOM known to 1 m Absolute surface coordinates

Geometry calibration Stage 1 tower base plate pressure sensors bottom DOM (defines string depth) water surface well depth string depth in water How deep? How straight?

Geometry calibration Stage 2 L dD Gaussian fit t (ns) z [m] Distance between DOMs [m] z=0 Hyperbola fit Flash all horizontal LEDs and look at photon arrival times at receiving DOMs t 0 = a - b·d Relative depth adjustments

Geometry calibration Stage 2

Timing calibration Requirement: single-photon timing resolution < 5 ns RAPcal – run by DAQ every few seconds – synchronizes local clocks with master clock IceTop In-ice DOMs for 76 OMs monitored for every run:

Timing calibration: verification with flashers

Timing calibration: verification with muons Reconstruct muon tracks without DOM i. Look at time residuals for DOM i for nearby (<10 m) tracks:

Charge calibration Translate digitized waveform signal (V) to number of photo-electrons (pe) DOMcal – DOM-resident calibration software – runs regularly (~every few weeks) PMT gain as function of HV Analog frontend gains and offsets Discriminator thresholds Digitizer sampling speed PMT transit time

Charge calibration: PMT linearity & saturation Saturation curves measured in-situ with flasher data Need DOM-specific saturation curves Pre-deployment lab measurements (at low gain)

PMT and DOM efficiency Lab measurements & Golden DOMs

Understanding the ice “Three feet of ice does not result from one day of cold weather” Chinese proverb The deepest IceCube ice is 100,000 years old

What is the scattering/absorption length? Understanding the ice

What is the scattering/absorption length? “Answer the question, jerk!” John McEnroe Understanding the ice

What is the scattering/absorption length? “Answer the question, jerk!” John McEnroe Understanding the ice

What is the scattering/absorption length? “Answer the question, jerk!” John McEnroe “You can not be serious!” John McEnroe Understanding the ice

Ice properties ↔ dust concentration ↔ climate Dome Fuji (Japan) South Pole (US) Vostok (Russia)

The dust layers are not completely horizontal Understanding the ice

There may be shear in the deep ice – Geometry changes over time The “hole ice” is different from the “bulk ice” – Air bubbles make acceptance more isotropic Understanding the ice “hole ice” (trapped bubbles)

Calibration instrumentation LED flasher boards “Standard Candle” lasers Dust loggers Bubble cameras Transmissometers Pressure sensors Thermistors Golden DOMs 65cm65cm

Energy calibration

Energy calibration: Standard Candles Nitrogen laser Calibrated output Cherenkov cone

Energy calibration flashers SC I SC II cascade energy* EeV PeVTeVGeV *applying rule-of-thumb: 10 5 photons/GeV depends on brightness setting, # of LEDs, pulse width overlapping energy region useful for cross-calibration

Pointing accuracy “calibration” 1. IceTop coincidences Mismatch angle between IceTop and in-ice reconstructed track 2. Moon shadow

IceCube calibration summary Low-level calibrations Geometry, timing – mature, understood (lots of experience from AMANDA) Waveforms/charge – basics (SPE) understood – more work needed as complex NPE waveforms included Ice – description more detailed than simulation can handle High-level calibrations Energy calibration – have special devices, depends on low-level calibration