MULTI-FLAVOUR PEV NEUTRINO SEARCH LU LU for the IceCube Collaboration, Chiba University, Japan
IS THERE A CUT-OFF AT THE END OF ? ASTROPHYSICAL NEUTRINO Similar energies injected into SPECTRUM? Universe! Are CRs and neutrinos produced in the same source ? Need new analysis to Fig adapted from L. Mohrmann increase sensitivity for PeV neutrinos 2
THE HIGHEST ENERGY FUNDAMENTAL PARTICLES FROM EXTERRITORIAL ORIGIN EHE-PeV* HESE NEW data data MC 2.6 PeV deposited energy + Through-going track Contained cascades Uncontained cascades *up-mu analysis is also sensitive to through- 3 going numu
The new event selection: PEPE: PEV ENERGY PATRICIALLY- CONTAINED EVENTS Glashow resonance PEPE (uncontained) HESE (contained) MC 4
EXAMPLE OF SIGNAL VS BACKGROUND (1/3) A simple case Cosmic-ray muon (MC) Signal (MC) 5
EXAMPLE OF SIGNAL VS BACKGROUND (2/3) A difficult case Is this a signal ? (MC) Signal (MC) 6
EXAMPLE OF SIGNAL VS BACKGROUND (3/3) A difficult case It’s from a cosmic -ray! (MC) Signal (MC) The timing of first arrival photons gives hints on if it is track or cascade 7
HOW TO DISTINGUISH SIGNAL AND BACKGROUND? (1/3) Example: shape of the waveform (risetime) Time [ns] Time [ns] 8
TEST TIMING AND SPATIAL OBSERVABLES FOR SINGLE CASCADE HYPOTHESIS (2/3) Time [ns] Time [ns] data 9 Time [ns] 9 Time [ns]
MACHINE-LEARNING FOR CLASSIFICATION (3/3) Boosted decision tree (BDT): background 11 features, e.g., shift of signal centre of weight in z direction (CRs down- going), risetime, signal brightness… Signal : 1-10 PeV nue Selection: not in HESE, not in EHE-PeV. Focus is on Glashow resonance 10
EVENT RATE FOR SIGNAL AND BACKGROUND (assuming E -2 spectrum) HESE selects PEPE ~20% PeV selects cascades ~40% PeV cascades 11
SIGNAL EXPECTATION FOR HESE, PEPE AND EHE-PEV FOR 6 YEARS OF DATA TAKING Glashow resonance expectation changes rapidly with cut-off energy We could use > 5 PeV bin as a probe for constraining the cut-off energy 12
ASIMOV DATASET: PEPE SAMPLE PROVIDES NEW INFORMATION FOR CONSTRAINING CUT-OFF ENERGY Assuming Φ = 10 −18 × 2.7 × ( 𝐹 100𝑈𝑓𝑊 ) −2.29 𝑓 −𝐹/2.21𝑄𝑓𝑊 𝐻𝑓𝑊 −1 𝑑𝑛 −2 𝑡 −1 (motived by global analysis ICRC 2015) 13
The highest sensitivity to the Glashow resonance PEPE sample: Preliminary • Passed internal data challenge • There is no overlap between PEPE and HESE • ~a factor of 2 sensitivity for the Glashow energy compared to HESE • The highest energy event shown in the next slide (from 4.6 years of data) • Analysis in progress • Spectrum fitting results will be shown @TeVPA. 14 *expect ~5% reduction after fitting quality cut
THE HIGHEST ENERGY EVENT Likely to be the event with the highest deposit energy ever seen (sophisticated reconstruction on-going ) (as also found in EHE) It’s brighter than the highest energy up-going track event. On-going studies on the data cosmic-ray background 15
CONCLUSION A new event selection, which targets at P eV E nergy P artially- contained E vents, has been developed. At Glashow resonance energy bin, the effective area of PEPE is ~ x2 of HESE. There is no overlap between HESE and PEPE sample. Cut-off and spectrum fits will be available soon for the combined sample HESE + PEPE + EHE-PeV 16
Holographic IceCube Visualise Ic IceCube PeV events with Augmented Reality Please contact me or go to poster Nu22/board 116, Saturday & Monday
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