Measurement of the cosmic-ray proton spectrum from 54 GeV to 9.5 TeV with the Fermi Large Area Telescope

Green, David Michael

doi:10.13016/m2zk06

Cited by 2 publications

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“…We also cut on a classification tree-based variable trained to identify accurately reconstructed events. These quality cuts are based on the event selection developed for the Fermi-LAT proton spectral measurement (Green 2016;Green & Hays 2017). Additionally, we required that the LAT was in standard survey mode 4 , and that the rocking angle of the spacecraft was <52°5.…”

Section: Data Setmentioning

confidence: 99%

A Search for Cosmic-ray Proton Anisotropy with the Fermi Large Area Telescope

2019

Preprint

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The Fermi Large Area Telescope (LAT) has amassed a large data set of primary cosmic-ray protons throughout its mission. The LAT's wide field of view and full-sky survey capabilities make it an excellent instrument for studying cosmic-ray anisotropy. As a space-based survey instrument, the LAT is sensitive to anisotropy in both right ascension and declination, while ground-based observations only measure the anisotropy in right ascension. We present the results of the first ever proton anisotropy search using Fermi LAT. The data set uses eight years of data and consists of approximately 179 million protons above 78 GeV, enabling it to probe dipole anisotropy below an amplitude of 10 −3 , resulting in the most stringent limits on the declination dependence of the dipole to date. We measure a dipole amplitude δ = 3.9 ± 1.5 × 10 −4 with a p-value of 0.01 (pre-trials) for protons with a minimum energy of 78 GeV. We discuss various systematic effects that could give rise to a dipole excess and calculate upper limits on the dipole amplitude as a function of minimum energy. The 95% CL upper limit on the dipole amplitude is δ U L = 1.3 × 10 −3 for protons with a minimum energy of 78 GeV and δ U L = 1.2 × 10 −3 for protons with a minimum energy of 251 GeV.

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Section: Data Setmentioning

confidence: 99%

A Search for Cosmic-ray Proton Anisotropy with the Fermi Large Area Telescope

2019

Preprint

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A Search for Cosmic-Ray Proton Anisotropy with the Fermi Large Area Telescope

Ajello

Baldini

Barbiellini

et al. 2019

ApJ

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The Fermi Large Area Telescope (LAT) has amassed a large data set of primary cosmic-ray protons throughout its mission. In fact, it is the largest set of identified cosmic-ray protons ever collected at this energy. The LAT's wide field of view and full-sky survey capabilities make it an excellent instrument for studying cosmic-ray anisotropy. As a space-based survey instrument, the LAT is sensitive to anisotropy in both R.A. and decl., while ground-based observations only measure the anisotropy in R.A. We present the results of the first-ever proton anisotropy search using Fermi LAT. The data set was collected over eight years and consists of approximately 179 million protons above 78 GeV, enabling it to probe dipole anisotropy below an amplitude of 10 −3 , resulting in the most stringent limits on the decl. dependence of the dipole to date. We measure a dipole amplitude δ=3.9±1.5×10 −4 with a p-value of 0.01 (pretrials) for protons with energy greater than 78 GeV. We discuss various systematic effects that could give rise to a dipole excess and calculate upper limits on the dipole amplitude as a function of minimum energy. The 95% confidence level upper limit on the dipole amplitude is δ UL =1.3×10 −3 for protons with energy greater than 78 GeV and δ UL =1.2×10 −3 for protons with energy greater than 251 GeV. Unified Astronomy Thesaurus concepts: Galactic cosmic rays (567); High-energy astrophysics (739) 54 Funded by contract FIRB-2012-RBFR12PM1F from the Italian Ministry of Education, University, and Research (MIUR). 55 This is in contrast to ground-based detectors, which have poor composition resolution. 56 The rocking angle of the instrument (angle between zenith and instrument axis) was 35°for the first year of data taking and increased to 50°thereafter.

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Measurement of the cosmic-ray proton spectrum from 54 GeV to 9.5 TeV with the Fermi Large Area Telescope

Cited by 2 publications

References 0 publications

A Search for Cosmic-ray Proton Anisotropy with the Fermi Large Area Telescope

A Search for Cosmic-ray Proton Anisotropy with the Fermi Large Area Telescope

A Search for Cosmic-Ray Proton Anisotropy with the Fermi Large Area Telescope

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