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CR Anisotropy with IceCube

Rasha Abbasi

Paolo Desiati

Juan Carlos Díaz-Vélez

Frank McNally

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CRA 2023

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History

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Anisotropy in IceCube

First observation

1 year of data from 22-string configuration (IC22)

Shown: relative intensity

2010:

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Abbasi et al., “Measurement of the Anisotropy of Cosmic Ray Arrival Directions with IceCube”, Astrophys.J. 718 (2010) L194 (arXiv:1005.2960)

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History

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Anisotropy in IceCube

First observation

Observation at multiple angular scales

1 year of data from 59-string configuration (IC59)

Shown: relative intensity of small-scale structure

2010:

2011:

3

Abbasi et al., “Observation of Anisotropy in the Arrival Directions of Galactic Cosmic Rays at Multiple Angular Scales with IceCube”, Astrophys.J. 740 (2011) 16 (arXiv:1105.2326)

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History

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Anisotropy in IceCube

First observation

Observation at multiple angular scales

Energy dependence

1 year of data from 59-string configuration (IC59)

Shown: significance at median energies of 20 TeV (top) and �400 TeV (bottom)

2010:

2011:�

2012:

4

Abbasi et al., “Observation of Anisotropy in the Galactic Cosmic Ray Arrival Directions at 400 TeV with IceCube”, Astrophys.J. 746 (2012) 33 (arXiv:1109.1017)

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History

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Anisotropy in IceCube

First observation

Observation at multiple angular scales

Energy dependence

Observation with IceTop

3 years of data from 2009-2012 (IC59 - IC86-2011)

Shown: relative intensity at median energies of 400 TeV (top) and �2 PeV (bottom)

2010:

2011:�

2012:

2013:

5

Aartsen et al., “Observation of Cosmic Ray Anisotropy with the IceTop Air Shower Array”, Astrophys.J. 765 (2013) 55 (arXiv:1210.5278)

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History

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Anisotropy in IceCube

First observation

Observation at multiple angular scales

Energy dependence

Observation with IceTop

Six-Year Update

6 years of data from 2009-2015 (IC59 - IC86-2014)

Shown: relative intensity as a function of energy

2010:

2011:�

2012:

2013:

2015:

6

Aartsen et al., “Anisotropy in Cosmic-Ray Arrival Directions in the Southern Hemisphere with Six Years of Data from the IceCube Detector”, Astrophys.J. 826 (2016) no.2 220 (arXiv:1603.01227)

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History

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Anisotropy in IceCube

First observation

Observation at multiple angular scales

Energy dependence

Observation with IceTop

Six-Year Update

Full-Sky with HAWC

5 years of IceCube data, �2 years of HAWC

Shown: relative intensity of small-scale structures at 10 TeV

2010:

2011:�

2012:

2013:

2015:

2019:

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Abeysekara et al., “All-Sky Measurement of the Anisotropy of Cosmic Rays at 10 TeV and Mapping of the Local Interstellar Magnetic Field”, Astrophys.J. 871 (2019) 96 (arXiv:1812.05682)

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Present Day

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11-Year Update

Objective: Revisit 6-year analysis with enhanced tools

Improved statistics: � Eleven years of data� (~700 billion events)

Improved simulation:� Newer, dataset-specific,� increased statistics

Improved systematics:� Shift from detector to� calendar years, stable� detector configuration

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Energy dependence of large-scale anisotropy��(Created from Astrophys.J. 826 (2016) no.2, 220 (arXiv:1603.01227))

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Simulation

Energy Estimation

  • Simulation binned based on number of digital optical modules hit and cosine of reconstructed zenith angle�
  • Median value for each bin shown in plot�
  • Given hits and reconstructed zenith of event, use splined version to determine median energy value�
  • Previous concern: artifacts caused by limited detector-specific simulation�

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IC59 (6-Year Analysis)

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Simulation

Energy Estimation

  • Simulation binned based on number of digital optical modules hit and cosine of reconstructed zenith angle�
  • Median value for each bin shown in plot�
  • Given hits and reconstructed zenith of event, use splined version to determine median energy value�
  • Previous concern: artifacts caused by limited detector-specific simulation�

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IC79 (6-Year Analysis)

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Simulation

Energy Estimation

  • Simulation binned based on number of digital optical modules hit and cosine of reconstructed zenith angle�
  • Median value for each bin shown in plot�
  • Given hits and reconstructed zenith of event, use splined version to determine median energy value�
  • Previous concern: limited detector-specific simulation�
  • New simulation: events that pass SMT08 trigger, IC86 only (splined version shown)�

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IC86 (11-Year Analysis)

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Simulation

Energy Estimation

  • Simulation binned based on number of digital optical modules hit and cosine of reconstructed zenith angle�
  • Median value for each bin shown in plot�
  • Given hits and reconstructed zenith of event, use splined version to determine median energy value�
  • Note: wide, correlated energy bins�����

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Statistics/Simulation

Energy Dependence

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6-year

11-year

IceCube Preliminary

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Statistics/Simulation

Energy Dependence

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6-year

11-year

IceCube Preliminary

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Statistics/Simulation

Energy Dependence

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6-year

11-year

IceCube Preliminary

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Statistics/Simulation

Energy Dependence

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6-year

11-year

IceCube Preliminary

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Statistics/Simulation

Energy Dependence

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6-year

11-year

IceCube Preliminary

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Statistics/Simulation

Energy Dependence

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6-year

11-year

IceCube Preliminary

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Statistics/Simulation

Energy Dependence

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6-year

11-year

IceCube Preliminary

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Statistics/Simulation

Energy Dependence

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6-year

11-year

IceCube Preliminary

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Statistics/Simulation

Energy Dependence

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6-year

11-year

IceCube Preliminary

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Statistics/Simulation

High-Energy Significance

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6-year

11-year

IceCube Preliminary

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Statistics/Simulation

High-Energy Significance

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6-year

11-year

IceCube Preliminary

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Statistics/Simulation

Dipole Phase & Amplitude

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Reconstructed R.A. component of the dipole amplitude and phase including other experiments (adopted from Ahlers & Mertsch 2017). The results shown are from Abeysekara et al. (2018b), Chiavassa et al. (2015), Alekseenko et al. (2009), Aglietta et al. (2009), Ambrosio et al. (2003), Guillian et al. (2007), �Abdo et al. (2009), Bartoli et al. (2015), Amenomori et al. (2005), and Aartsen et al. (2013, 2016), A. Aab et al (2020), W. Gao et al (2021).

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Statistics/Simulation

Summary

  • New simulation and statistics only slightly change energy maps�
  • Transition still occurs around 100 TeV�
  • Structure at highest energy now consistent with other PeV measurements�
  • Phase and amplitude of best-fit dipole consistent with other experiments�����

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Statistics

Large- and Small-Scale Structure

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Relative Intensity

Six Years

Eleven Years

Large-Scale Structure

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Small-Scale Structure

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IceCube Preliminary

IceCube Preliminary

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Statistics

Large- and Small-Scale Structure

  • Concern: traditional maps with all data show the conflicting overlay of two structures�
  • New approach: large- and small-scale structure maps for low- and high-energy collections�

29% overlap

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Relative Intensity

Six Years

Eleven Years

Large-Scale Structure

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Small-Scale Structure

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IceCube Preliminary

IceCube Preliminary

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Statistics

Large- and Small-Scale Structure

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Relative Intensity

Low Energy

High Energy

Large-Scale Structure

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Small-Scale Structure

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IceCube Preliminary

IceCube Preliminary

IceCube Preliminary

IceCube Preliminary

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Statistics

Large- and Small-Scale Structure

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Significance

Low Energy

High Energy

Large-Scale Structure

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Small-Scale Structure

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IceCube Preliminary

IceCube Preliminary

IceCube Preliminary

IceCube Preliminary

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Statistics

Angular Power Spectrum

Uncertainties:

statistical

systematic

Previous 2σ noise limit

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Statistics/Simulation

Angular Power Spectrum

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Statistics/Simulation

Angular Power Spectrum

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Statistics/Simulation

Angular Power Spectrum

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Statistics/Simulation

Angular Power Spectrum

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Statistics/Simulation

Angular Power Spectrum

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Statistics/Simulation

Angular Power Spectrum

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Statistics/Simulation

Angular Power Spectrum

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Statistics/Simulation

Angular Power Spectrum

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Statistics/Simulation

Angular Power Spectrum

Alternative visualization�Display amplitude of select multipole moments as a function of energy

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Systematics

Time Dependence

Goal: look for time-dependence of sidereal signal�

  • One-dimensional projection of relative intensity along right ascension, by detector year
  • Six-year sample, all events included

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Systematics

Time Dependence

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Systematics

Time Dependence

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IceCube Preliminary

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Summary

Results

  • Update analysis features improved statistics, simulation, and systematics�
  • Structures in large-scale, small-scale, and energy-split maps appear consistent, with higher significance�
  • Dipole phase and amplitude consistent with measurements from other experiments�
  • New energy-dependent views of the angular power spectrum�
  • Time-dependent trend possible in some right ascension bins

Upcoming Work

  • Time modulation, anti- and extended sidereal frames�
  • Anisotropy in IceTop�
  • Joint IceTop / TALE analysis�
  • Joint in-ice / HAWC analysis�
  • Spectral anisotropy�
  • Rigidity-dependence of anisotropy

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Coauthors

Undergraduate Personnel

  • Mercer�Christina Cochling�Alexis Hardy�Emily Schmidt�Alex Simmons�Andrew Thorpe�
  • Loyola�Katherine “Jo” Gruchot�Andrew Moy�Will Hays �Joe Summers �Grace Bratude�Gunwati Agrawal�Savannah Lehrman�
  • UW-Madison�Hannah Woodward �(Summer 2020 REU)�(University of Virginia)
  • Mercer�Angular power spectrum�Event rate analysis�Time gap analysis�Systematic checks across detector seasons�Energy estimation and true energy distributions�
  • Loyola�Anisotropy time dependence
  • Anisotropy time/energy dependence
  • Events livetime/rates
  • IceTop simulation/Data comparison
  • IceTop Data processing/analysis �IceTop Data processing/analysis �IceTop Data processing/analysis
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  • UW-Madison�Extended- and anti-sidereal distributions
  • Comparing detector and calendar years

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Backup Slides

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Improved Systematics

Review: Yearly Variation�

  • Consider four time frames:� (hrs/day) (days/year)
    • Anti-sidereal 24:04 364
    • Solar 24:00 365
    • Sidereal 23:56 366
    • Extended-sidereal 23:52 377�
  • What is the mutual influence of the signals in the solar and sidereal frames?�
  • Anti-sidereal: effect of solar on sidereal
  • Extended-sidereal: effect of sidereal on solar

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Improved Systematics: Calendar Years

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  • Signal due to annual orbit should cancel out over a solar year�
    • Systematic uncertainty in sidereal signal derived from anti-sidereal frame�
  • “Detector years” inconsistent in size�
  • Consistent detector configuration: systematic uncertainty calculated using calendar years�
    • Shown: IC86-2011
    • Amplitude ~100x smaller than sidereal

IceCube Preliminary

One-dimensional projection in RA of relative intensity in the anti-sidereal frame. The amplitude of a best-fit dipole (blue curve) is used as the systematic uncertainty for the sidereal signal in the corresponding year.

Andrew Moy

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Systematics

Angular Power Spectrum

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Statistics/Simulation

Dipole Phase & Amplitude

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Six Years

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Statistics/Simulation

Dipole Phase & Amplitude

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Eleven Years

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