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Primary nuclei (He, C, O, Ne, Mg, Si, ...) are thought to be mainly produced and accelerated in astrophysical sources such as the supernova. Secondary nuclei (Li, Be, B, ...) are mostly produced by interactions of primary nuclei with the interstellar medium. Precise knowledge of the secondary-to-primary flux ratio, like B/C, is essential in the understanding of cosmic ray propagation. This thesis presents the first precision measurements of the heavy cosmic ray fluorine (F), sodium (Na), and aluminum (Al) fluxes in the rigidity range from 2.15 GV to 3.0 TV, based on data collected by the Alpha Magnetic Spectrometer (AMS) during the first 8.5 years of operation. The F flux is believed to be the only pure secondary flux between oxygen and silicon, and Na and Al fluxes are thought to be produced both in astrophysical sources and by the collisions of heavier nuclei with the interstellar medium.
The Alpha Magnetic Spectrometer (AMS) is a particle detector installed on the International Space Station; it starts to record data since May 2011. The experiment aims to identify the nature of charged cosmic rays and photons and measure their fluxes in the energy range of GeV to TeV. These measurements enable us to refine the cosmic ray propagation models, to perform indirect research of dark matter and to search for primordial antimatter (anti-helium). In this context, the data of the first years have been utilized to measure the electron flux and lepton flux (electron + positron) in the energy range of 0.5 GeV to 700 GeV. Identification of electrons requires an electrons / protons separation power of the order of 104, which is acquired by combining the information from different sub-detectors of AMS, in particular the electromagnetic calorimeter (ECAL), the tracker and the transition radiation detector (TRD). In this analysis, the numbers of electrons and leptons are estimated by fitting the distribution of the ECAL estimator and are verified using the TRD estimator: 11 million leptons are selected and analyzed. The systematic uncertainties are determined by changing the selection cuts and the fit procedure. The geometric acceptance of the detector and the selection efficiency are estimated thanks to simulated data. The differences observed on the control samples from data allow to correct the simulation. The systematic uncertainty associated to this correction is estimated by varying the control samples. In total, at 100 GeV (resp. 700 GeV), the statistic uncertainty of the lepton flux is 2% (30%) and the systematic uncertainty is 3% (40%). As the flux generally follows a power law as a function of energy, it is important to control the energy calibration. We have controlled in-situ the measurement of energy in the ECAL by comparing the electrons from flight data and from test beams, using in particular the E/p variable where p is momentum measured by the tracker. A second method of absolute calibration at low energy, independent from the tracker, is developed based on the geomagnetic cutoff effect. Two models of geomagnetic cutoff prediction, the Störmer approximation and the IGRF model, have been tested and compared. These two methods allow to control the energy calibration to a precision of 2% and to verify the stability of the ECAL performance with time.
Precise measurements of primary cosmic ray Neon, Magnesium and Silicon flux is important to understand the origins and propagation properties of heavy elements in the Galaxy. This thesis presents the measurements of Neon, Magnesium, and Silicon flux in the rigidity (momentum per unit charge) range from 2.15 GV to 3 TV, with 5.6 million Ne, Mg, and Si nuclei events collected during 7 years of AMS operation (2011- 2018). The three fluxes show identical rigidity dependence above 86.5 GV, deviating from a single power law and hardening at high rigidity above 200 GV. Surprisingly, the rigidity dependence of Neon, Magnesium, and Silicon flux is different from the rigidity dependence of primary nuclei Helium, Carbon and Oxygen, even though the two groups are both primaries produced at cosmic rays sources.
A precision measurement of the Boron to Carbon ratio in cosmic rays is carried out in the range 1 GeV/n to 670 GeV/n using the first 30 months of flight data of AMS-02 located on the International Space Station. Above 20 GeV/n, it is the first accurate measurement. About 5 million clean Boron and Carbon nuclei are identified. The experimental and analysis challenges in achieving a high precision measurement are addressed. Boron is exclusively produced as a secondary particle by spallation from primary elements like Carbon in collisions with interstellar medium. The unprecedented precision and energy range of this measurement deepen the knowledge of cosmic ray propagation. Using this measurement, the diffusion coefficient in Gal-Prop model is determined to be (6.05 ± 0.05)10^28 cm2/s, and the Alfven velocity is (33.9 ± 1.0) km/s. This makes the prediction of secondary anti-proton background in dark matter search one order of magnitude more accurate.
Cosmology’s journey to the present day has been a long one. This book outlines the latest research on modern cosmology and related topics from world-class experts. Through it, readers will learn how multi-disciplinary approaches and technologies are used to search the unknown and how we arrived at the knowledge used and assumptions made by cosmologists today. The book is organized into four parts, each exploring a theme that has troubled humankind for centuries. Since the dawn of time, looking at the sky, humans have tried to understand their origin, the laws governing it, and what influence it all has on human life. In most ancient civilizations, astronomers embodied the power of knowledge. This knowledge was not compartmentalized, and scientists often found philosophical implications within their quests, many of which destroyed the borders between the natural sciences. Even now, as observers and scientists continue to use conjecture to generate theoretical assumptions and laws that then have to be confirmed experimentally, said theoretical and experimental searches are being linked to philosophical thinking and artistic representation, as they were up until the 18th century. This multi-disciplinary book will appeal to anyone with an interest in the fields of Astronomy, Cosmology or Physics.
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The AMS-02 experiment is a particle detector installed on the International Space Station (ISS) since May 2011, which measures the characteristics of the cosmic rays to bring answers to the problematics risen by the astroparticle physics since a few decades, in particular the study of dark matter and the search of antimatter. The phenomenological aspects of the physics of cosmic rays are reviewed in a first part. A second one describes the in-flight performances of the different subdetectors of AMS-02, in particular the electromagnetic calorimeter. It is shown, using particles at the ionizing minimum (MIPs), accounting for the main part of cosmic rays, that the calorimeter works as expected, and we find the same performances as on ground. This study is used to follow in time the evolution of the detector performances. It also allows to develop a charge estimator for the nuclei using the calorimeter. A third and final part, deals with the determination of the positronic fraction. The main difficulty of this measurement is to identify the positrons by rejecting the protons thanks to the characteristics of the showers in the calorimeter. After having defined variables relevant for this separation, we build an estimator using a multivariate analysis and Monte-Carlo simulations of electrons for the higher energies. Above 100 GeV, we obtain a rejection factor of about 10 000 at a 90% efficiency. After having estimated the charge confusion, this estimator, finally, allows us to determine the positronic ratio for the first 18 months of data and energies ranging from 1.5 to 350 GeV.
In 1912 Victor Franz Hess made the revolutionary discovery that ionizing radiation is incident upon the Earth from outer space. He showed with ground-based and balloon-borne detectors that the intensity of the radiation did not change significantly between day and night. Consequently, the sun could not be regarded as the sources of this radiation and the question of its origin remained unanswered. Today, almost one hundred years later the question of the origin of the cosmic radiation still remains a mystery.Hess' discovery has given an enormous impetus to large areas of science, in particular to physics, and has played a major role in the formation of our current understanding of universal evolution. For example, the development of new fields of research such as elementary particle physics, modern astrophysics and cosmology are direct consequences of this discovery. Over the years the field of cosmic ray research has evolved in various directions: Firstly, the field of particle physics that was initiated by the discovery of many so-called elementary particles in the cosmic radiation. There is a strong trend from the accelerator physics community to reenter the field of cosmic ray physics, now under the name of astroparticle physics. Secondly, an important branch of cosmic ray physics that has rapidly evolved in conjunction with space exploration concerns the low energy portion of the cosmic ray spectrum. Thirdly, the branch of research that is concerned with the origin, acceleration and propagation of the cosmic radiation represents a great challenge for astrophysics, astronomy and cosmology. Presently very popular fields of research have rapidly evolved, such as high-energy gamma ray and neutrino astronomy. In addition, high-energy neutrino astronomy may soon initiate as a likely spin-off neutrino tomography of the Earth and thus open a unique new branch of geophysical research of the interior of the Earth. Finally, of considerable interest are the biological and medical aspects of the cosmic radiation because of it ionizing character and the inevitable irradiation to which we are exposed. This book is a reference manual for researchers and students of cosmic ray physics and associated fields and phenomena. It is not intended to be a tutorial. However, the book contains an adequate amount of background materials that its content should be useful to a broad community of scientists and professionals. The present book contains chiefly a data collection in compact form that covers the cosmic radiation in the vicinity of the Earth, in the Earth's atmosphere, at sea level and underground. Included are predominantly experimental but also theoretical data. In addition the book contains related data, definitions and important relations. The aim of this book is to offer the reader in a single volume a readily available comprehensive set of data that will save him the need of frequent time consuming literature searches.