MULTI-FLAVOUR PEV NEUTRINO SEARCH LU LU for the IceCube - - PowerPoint PPT Presentation

MULTI-FLAVOUR PEV NEUTRINO SEARCH

LU LU for the IceCube Collaboration, Chiba University, Japan

Fig adapted from L. Mohrmann

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IS THERE A CUT-OFF AT THE END OF ASTROPHYSICAL NEUTRINO SPECTRUM?

Need new analysis to increase sensitivity for PeV neutrinos

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Similar energies injected into Universe! Are CRs and neutrinos produced in the same source?

THE HIGHEST ENERGY FUNDAMENTAL PARTICLES FROM EXTERRITORIAL ORIGIN

*up-mu analysis is also sensitive to through- going numu Through-going track Contained cascades

+

2.6 PeV deposited energy

EHE-PeV* HESE NEW

Uncontained cascades

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MC data data

PEPE: PEV ENERGY PATRICIALLY- CONTAINED EVENTS

The new event selection:

Glashow resonance

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MC

PEPE (uncontained) HESE (contained)

EXAMPLE OF SIGNAL VS BACKGROUND (1/3)

A simple case

Cosmic-ray muon (MC) Signal (MC)

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EXAMPLE OF SIGNAL VS BACKGROUND (2/3)

A difficult case

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Is this a signal? (MC) Signal (MC)

EXAMPLE OF SIGNAL VS BACKGROUND (3/3)

A difficult case

The timing of first arrival photons gives hints on if it is track

• r cascade

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It’s from a cosmic-ray! (MC) Signal (MC)

HOW TO DISTINGUISH SIGNAL AND BACKGROUND? (1/3)

Example: shape of the waveform (risetime)

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Time [ns] Time [ns]

TEST TIMING AND SPATIAL OBSERVABLES FOR SINGLE CASCADE HYPOTHESIS (2/3)

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Time [ns] Time [ns] Time [ns] Time [ns]

data

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Boosted decision tree (BDT): 11 features, e.g., shift of 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

MACHINE-LEARNING FOR CLASSIFICATION (3/3)

signal background

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EVENT RATE FOR SIGNAL AND BACKGROUND

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HESE selects ~20% PeV cascades PEPE selects ~40% PeV cascades

(assuming E-2 spectrum)

Glashow resonance expectation changes rapidly with cut-off energy

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SIGNAL EXPECTATION FOR HESE, PEPE AND EHE-PEV FOR 6 YEARS OF DATA TAKING

We could use > 5 PeV bin as a probe for constraining the cut-off energy

ASIMOV DATASET: PEPE SAMPLE PROVIDES NEW INFORMATION FOR CONSTRAINING CUT-OFF ENERGY

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Assuming Φ = 10−18 × 2.7 × (

𝐹 100𝑈𝑓𝑊)−2.29𝑓−𝐹/2.21𝑄𝑓𝑊𝐻𝑓𝑊−1𝑑𝑛−2𝑡−1

(motived by global analysis ICRC 2015)

The highest sensitivity to the Glashow resonance

PEPE sample:

• 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.

Preliminary

*expect ~5% reduction after fitting quality cut

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Likely to be the event with the highest deposit energy ever seen (sophisticated reconstruction on-going )

It’s brighter than the highest energy up-going track event. On-going studies on the cosmic-ray background

THE HIGHEST ENERGY EVENT

(as also found in EHE)

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data

CONCLUSION

A new event selection, which targets at PeV Energy Partially- contained Events, 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

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Visualise Ic IceCube PeV events with Augmented Reality

Holographic IceCube

Please contact me or go to poster Nu22/board 116, Saturday & Monday