The Cosmic Ray Anisotropy PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download The Cosmic Ray Anisotropy PDF full book. Access full book title The Cosmic Ray Anisotropy by David Peter Stern. Download full books in PDF and EPUB format.
Author: David Peter Stern
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
Get Book Here
Book Description
Author: David Peter Stern
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 8
Get Book Here
Book Description
Author: Matthew Robert Meehan
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
Although cosmic rays do not point back to their sources, the distribution of their arrival directions can be used to constrain propagation models, study the distribution of their sources, and probe the structure of the local interstellar environment. A small, part-per-mille, anisotropy in the arrival directions of cosmic rays has been measured at both large and small angular scales by many experiments. Diffusion theory predicts a dipole anisotropy, but decades of observations have resulted in measurements at least an order of magnitude below this naive prediction. Solving the cosmic-ray anisotropy problem has proven difficult, in part due to observational biases of ground-based measurements that render physical information about the anisotropy inaccessible. Spaced-based observatories can provide new information to help shed light on the origin of the anisotropy. In particular, they can offer all-sky measurements that constrain the full two-dimensional phase of the anisotropy, while ground-based experiments only measure the anisotropy along right ascension. The first ever search for cosmic-ray proton anisotropy using the Fermi Large Area Telescope (LAT) is presented in this thesis. The LAT's wide field of view, large effective area, and long exposure time have resulted in the largest data set of primary protons recorded by any instrument. A search for cosmic-ray proton anisotropy is performed using eight years of LAT data from 78 GeV to almost 10 TeV in energy. As the first analysis of its kind using LAT data, a custom event selection suitable for an anisotropy search was developed and systematics unique to this measurement were studied for the first time. The final data set, comprised of 179 million protons, is the largest full-sky, single instrument data set studying anisotropy at these energies to date, capable of probing dipole anisotropy below an amplitude of $10^{-3}$. It is also the most sensitive data set to the declination component of the anisotropy of any experiment to date. We measure a dipole amplitude $\delta = 3.9 \times 10^{-4}$ with a p-value of 0.01 (pre-trials) for protons with a minimum energy of 78 GeV. The weak statistical excess makes it difficult to rule out signal or systematic interpretation of the measurement. We therefore discuss various systematic effects that could give rise to the 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 $\delta_{UL}=1.3\times 10^{-3}$ for protons with a minimum energy of 78 GeV and $\delta_{UL}=1.2 \times 10^{-3}$ for protons with a minimum energy of 251 GeV.
Author: Jacquieline Hope Ericksen
Publisher:
ISBN:
Category : Cosmic rays
Languages : en
Pages : 290
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
Anisotropy in the cosmic-ray arrival direction distribution has been well documented over a large energy range, but its origin remains largely a mystery. In the TeV to PeV energy range, the galactic magnetic field thoroughly scatters cosmic rays, but anisotropy at the part-per-mille level and smaller persists, potentially carrying information about nearby cosmic-ray accelerators and the galactic magnetic field. The IceCube Neutrino Observatory was the first detector to observe anisotropy at these energies in the Southern sky. This work uses 318 billion cosmic-ray induced muon events, collected between May 2009 and May 2015 from both the in-ice component of IceCube as well as the surface component, IceTop. The observed global anisotropy features large regions of relative excess and deficit, with amplitudes on the order of $10^{-3}$. While a decomposition of the arrival direction distribution into spherical harmonics shows that most of the power is contained in the low-multipole ($\ell \leq 4$) moments, higher-multipole components are found to be statistically significant down to an angular scale of less than $10^{\circ}$, approaching the angular resolution of the detector. Above 100\,TeV, a change in the topology of the arrival direction distribution is observed, and the anisotropy is characterized by a wide relative deficit whose amplitude increases with primary energy up to at least 5\,PeV, the highest energies currently accessible to IceCube with sufficient event statistics. No time dependence of the large- and small-scale structures is observed in the six-year period covered by this analysis within statistical and systematic uncertainties. Analysis of the energy spectrum and composition in the PeV energy range as a function of sky position is performed with IceTop data over a five-year period using a likelihood-based reconstruction. Both the energy spectrum and the composition distribution are found to be consistent with a single source population over declination bands. This work represents an early attempt at understanding the anisotropy through the study of the spectrum and composition. The high-statistics data set reveals more details on the properties of the anisotropy, potentially able to shed light on the various physical processes responsible for the complex angular structure and energy evolution.
Author: David Peter Stern
Publisher:
ISBN:
Category : Cosmic rays
Languages : en
Pages : 24
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
Cosmic rays in the TeV to PeV energy range are believed to originate in our galaxy, possibly in local astrophysical accelerators such as supernova remnants. After escaping from their sources, cosmic rays propagate through the interstellar medium where they scatter off turbulences in the Galactic magnetic field. This scattering process efficiently isotropizes the trajectories of cosmic rays before their arrival at Earth. However, it is predicted that a dipolar anisotropy with per-mille amplitude or lower should subsist in their arrival directions. Such an anisotropy was observed for the first time at TeV energies by detectors in the northern hemisphere, and its study revealed the presence of both large angular scale structure (usually interpreted as the aforementioned dipole produced by cosmic-ray diffusion) and anisotropy with smaller angular size and amplitude. Large-scale anisotropy at TeV energies in the southern hemisphere was detected for the first time using data from IceCube, a cubic-kilometer neutrino detector that is sensitive to muons created in the interaction of cosmic rays with the atmosphere. The orientation of the large-scale component is consistent with that observed in the north. In this work, results from three analyses are presented which expand the study of cosmic-ray anisotropy in the southern sky and are aimed at characterizing its evolution as a function of angular scale, energy, and time. Data from three cosmic-ray detectors are used: IceCube, its predecessor experiment AMANDA, and the IceTop air-shower array, all located at the South Pole. Significant anisotropy is observed over a wide range of angular scales (from large-scale to few-degrees structure), and energies (from 20 TeV to 2 PeV.) The relative amplitude of the large-scale anisotropy is 8́ơ 10-3, while smaller structures have amplitudes of the order of 10-4. No significant variation is observed in the TeV anisotropy pattern over the 12-year period considered in this work. These studies provide a complete picture of the cosmic-ray anisotropy in the southern sky at TeV and PeV energies. The coordinated study of the three main cosmic-ray observables (spectrum, composition, and anisotropy) will provide information about the origin of these particles and the environment through which they propagate.
Author: Pierre Sokolsky
Publisher: CRC Press
ISBN: 0429979282
Category : Science
Languages : en
Pages : 165
Get Book Here
Book Description
Cosmic ray physics has recently attracted a great deal of attention from the high energy physics community because of the discovery of new sources and the advent of new techniques. The result of a series of lectures prepared for graduate students and postdoctoral researchers, this book is a general introduction to experimental techniques and results in the field of ultrahigh energy cosmic rays. It succinctly summarizes the rapidly developing field, and provides modern results that include data from newer detectors. Combining experiment and theory, the text explores the results of a single, easy-to-understand experiment to tie together various issues involved in the physics of ultrahigh energy cosmic rays.
Author: Pedram Boghrat
Publisher:
ISBN:
Category :
Languages : en
Pages : 222
Get Book Here
Book Description
Author: Elizabeth J. Wills
Publisher:
ISBN:
Category : Anisotropy
Languages : en
Pages : 181
Get Book Here
Book Description
In the hundred years that have followed the discovery of cosmic rays, more about them remains unknown than known. Many concerted efforts are currently underway to detect cosmic rays using a variety of detection methods in space, on the surface of Earth, and deep underground. Of the many remaining mysteries, the one addressed in this work is the anisotropy in arrival directions of the cosmic rays incident on the atmosphere. This behaviour has been observed in both hemispheres of the planet, at high significance, from 1 TeV - 1 EeV energy ranges, at angular scales from 5 degrees to 180 degrees, and displays no time variation. It is measured consistently as a 0.1% over- and under-fluctuation. This work presents the first neutrino analysis of cosmic ray arrival directions so far, specifically, in the northern hemisphere. The analysis is done with an atmospheric neutrino dataset which was specifically designed for this analysis and composed of neutrinos detected by the IceCube South Pole Neutrino Observatory from 2011-2016. The goal of the search was to detect cosmic ray anisotropy as observed in atmospheric muons, but this time, in atmospheric neutrinos. To this end, a new atmospheric neutrino dataset was created using machine learning, aiming to increase data acceptance rates by optimizing sacrifices in purity and angular acceptance. The standard analysis techniques were carried out, along with a new log-likelihood method developed to improve sensitivity in a lower-statistics realm. While no signal was detected in this analysis, the analysis methodology has been developed and tested. We project that with a total of twelve years of IceCube data will be required to be sensitive to a dipole anisotropy at the level previously reported by the Tibet-AS[gamma] Collaboration. Detection of cosmic ray anisotropy in the neutrino channel would allow for verification of known cosmic ray shower physics, and particle propagation. The neutrinos could allow us to probe the anisotropy in a new way. If the signal deviates, there could be new physics to discover. The method and data selection are developed, and in several years, new developments will be made towards unraveling the mystery of cosmic ray anisotropy with neutrinos.
