1 / 12

Coincidence analysis in ANTARES: Potassium-40 and muons

ITEP winter school Feb 12, 2008. Coincidence analysis in ANTARES: Potassium-40 and muons. Dmitry Zaborov (ITEP, Moscow, Russia). Brief overview of ANTARES experiment Potassium-40 calibration technique Adjacent floor coincidences as very basic atmospheric muon signal. Detection principle.

angie
Download Presentation

Coincidence analysis in ANTARES: Potassium-40 and muons

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ITEP winter school Feb 12, 2008 Coincidence analysis in ANTARES:Potassium-40 and muons Dmitry Zaborov (ITEP, Moscow, Russia) Brief overview of ANTARES experiment Potassium-40 calibration technique Adjacent floor coincidences as very basic atmospheric muon signal

  2. Detection principle 3D PMTarray p, a 107  atm  104  atm p m Cherenkov light from m gč  1-100  cosm g 43° Sea floor Hadronic showers from CC/NC interactions can be detected as well angular resolution ~ 0.3º at 10 TeV m effective area ~ 0.1 km2 in TeV range interaction Reconstruction of m trajectory(~ n)from timing and position of PMT hits n D. Zaborov. Coincidence analysis in ANTARES

  3. Horizontal layout Detector layout a storey 12 lines (900 PMTs) 25 storeys / line 3 PMTs/storey 14.5 m 350 m 40 km to shore 100 m Junction box ~70 m Readout cables Sea bed ~ -2500 m D. Zaborov. Coincidence analysis in ANTARES

  4. L1 L3 L2 L5 L12 L7 L8 L6 L4 L11 L10 L9 Current status 10 detector lines +instrumentation line operational (since December 07) (Feb. 2008) seismometer N 42°50’ N 6°10’E IL07 ~ 2 muons/sec ~ 5 neutrino/day (atmospheric) Submarine cable to shore 2 more lines coming soon 100 m Junction box * Cable path is shown only indicatively D. Zaborov. Coincidence analysis in ANTARES

  5. Optical Module:10” PMTin17” glass sphere photon detection Local Control Module(in Ti container): Front-end ASIC, Clock, DAQ/SC,compass/roll/pitch Hydrophone: acoustic positioning Basic detection and calibration elements Optical Beaconwith blue LEDs: timing calibration D. Zaborov. Coincidence analysis in ANTARES

  6. In situ calibration with Potassium-40 High precision (~5%) monitoring of OM efficiencies g Gaussian peak on coincidence plot Rate of correlated coincidences g 15 Hz Cherenkov e- (b decay) 40K MC prediction 13+/-4 Hz (“NIM” angular acceptance) Peak offset 40Ca Mean ≈ 0 RMS 0.7 ns No dependence on bioluminescent activity has been observed - this confirms the single photon character of bioluminescent emission time calibration confirmed D. Zaborov. Coincidence analysis in ANTARES

  7. Example: calibration of Line 8 Three OM sensitivity factors si can be extracted using 3 equations rateij = k * si * sj I,j=1,2,3 factor k gives absolute scale; k can be determined from Monte-Carlo (or, in opposite, used to constrain parameters of Monte-Carlo) Unofficial technical plot * No charge calibration used * No walk correction included OM-OM time offsets determined using K-40 (basically single photoelectrons) w.r.t Dark room calibration (high amplitude laser pulse) Unofficial technical plot D. Zaborov. Coincidence analysis in ANTARES

  8. Time evolution (example) Gradual decrease is probably due to PMT gain drift Steep changes are threshold tunings Time delays seem stable (within our accuracy) Unofficial technical plot K40 runs are taken once a week K40 trigger can run in parallel with other triggers (e.g. GRB trigger ordirectional triggers) and can be even used for physics analysis as is Unofficial technical plot D. Zaborov. Coincidence analysis in ANTARES

  9. Time evolution of average K-40 coincidence rate tuning 2 tuning 2 -> 15.5 Hz tuning 1 start at 12 Hz “degradation” Unofficial technical plot One year of “degradation” could be fully compensated by the tuning * Other Lines show similar behavior D. Zaborov. Coincidence analysis in ANTARES

  10. Delay between adjacent floors (theory) ≈ fixed number for exactly vertical muons a wide distribution in general Δt = L / c ≈ 50 ns to Δt ~ L n / c ~ 70 ns But light hits back of the OM L The most basic signal of physics events in ANTARES Delay between storeys No background No systematic errors from trigger or reconstruction algorithms Δt ~ 0 from D. Zaborov. Coincidence analysis in ANTARES

  11. Adjacent floor coincidences: measurement Integral under the peak ~ muon flux Shape is sensitive to angular acceptance of optical modules and angular distribution of muon flux This plot is preliminary Actual comparison of peak amplitude with Monte Carlo will be made after OM angular acceptance issues are fixed, OM efficiency is well known and all dead time corrections applied Low energy threshold (compared to full reconstruction) The analysis can be repeated for every detector storey separately The effect of muon flux reduction with depth is directly (!) measured D. Zaborov. Coincidence analysis in ANTARES

  12. Summary • A calibration technique using Cherenkov light from Potassium-40 decays in sea water has been developed • Sensitivity of optical modules is now controlled using K-40 • K-40 is also a useful tool for time calibration • A simple but powerful technique for atmospheric muon measurement is developed based on the idea of adjacent floor coincidences • First results allowed to reject one of the models of OM angular acceptance • Depth dependence and absolute normalization of atmospheric muon flux can be extracted using this new approach • Possibility to reject certain hadronic interaction models or (less likely) primary flux models is being investigated • Promising prospects to use adjacent floor coincidences in the trigger D. Zaborov. Coincidence analysis in ANTARES

More Related