DOCSLIB.ORG

Electron-Positron Pair Production in Inhomogeneous Electromagnetic Fields

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Electron-Positron Pair Production in Inhomogeneous Electromagnetic Fields Christian Kohlfürst Electron-positron pair production in inhomogeneous electromagnetic fields Dissertation zur Erlangung des Doktorgrades der Naturwissenschaften an der Naturwissenschaftlichen Fakultät der Karl-Franzens-Universität Graz Advisor: Univ-Prof. Dr. rer. nat. Reinhard Alkofer Institut für Physik Fachbereich Theoretische Physik 2015 2 Electron-positron pair production in inhomogeneous electromagnetic fields by Christian Kohlfürst Abstract The process of electron-positron pair production is investigated within the phase-space Wigner formalism. The similarities between atomic ionization and pair production for ho- mogeneous, but time-dependent linearly polarized electric fields are examined mainly in the regime of multiphoton absorption (field-dependent threshold, above-threshold pair produc- tion). Characteristic signatures in the particle spectra are identified (effective mass, channel closing). The non-monotonic dependence of the particle yield on the carrier frequency is discussed as well. The investigations are then extended to spatially inhomogeneous electric fields. New effects arising due to the spatial dependence of the effective mass are discussedin terms of a semi-classical interpretation. An increase in the normalized particle yield is found for various field configurations. Pair production in inhomogeneous electric and magnetic fields is also studied. The influence of a time-dependent spatially inhomogeneous magnetic field on the momentum spectrum and the particle yield is investigated. The Lorentz invari- ants are identified to be crucial in order to understand pair production by strong electric fields in the presence of strong magnetic fields. Zusammenfassung Elektron-Positron Paarerzeugung wird mittels des Wigner-Formalismus im Phasenraum untersucht. Die Gemeinsamkeiten von Atomionisation und Paarerzeugung werden dabei für homogene, zeitabhängige, linear polarisierte elektrische Felder im Bereich der Mehr- photonenabsorption untersucht (feldabhängige Produktionsschwelle etc.). Dabei wurden charakteristische Signaturen im Teilchenspektrum gefunden (effektive Masse, Channel Clos- ing). Außerdem wird der nicht-monotone Zusammenhang zwischen Produktionsrate und Feldfrequenz behandelt. Die Untersuchungen werden dann auf räumlich inhomogene Felder erweitert. Neue Effekte, die im Zusammenhang mit einer raumabhängigen effektiven Masse stehen, werden mithilfe semi-klassischer Methoden diskutiert. Ein Anstieg der räumlich normierten Produktionsrate für spezielle Feldkonfigurationen wurde gefunden. Die Unter- suchungen werden um räumlich und zeitlich inhomogene magnetische Felder erweitert, und deren Auswirkungen auf das Teilchenspektrum wird untersucht. Die Lorentzinvarianten werden als ausschlaggebend für die Produktionsrate durch starke elektrische Felder in An- wesenheit von starken magnetischen Feldern identifiziert. 3 4 Acknowledgments I would like to share my deepest gratitude for the help I received over the last years. This thesis would not have been possible without the permanent support of my colleagues, my friends and my parents. Nevertheless, I want to mention some of the “contributors” by name. At first I want to thank my advisor Reinhard Alkofer for ongoing support andgiving me free rein to follow my own ideas. I would also like to thank Holger Gies from the FSU Jena. He had a significant impact on my research and consulting him was always valuable. Additionally, I want to thank Tom Heinzl and colleagues at Plymouth University for their generous hospitality. I take this opportunity to express gratitude to all of the Department faculty members for their help and support. Furthermore, I want to thank the principal investigators of the Doktoratskolleg “Hadrons in Vacuum, Nuclei and Stars” for giving me the opportunity to participate in the graduate program. I also want to acknowledge the Austrian Science Fund, FWF, for financial support (FWF DK W1203-N16). Additionally, I want to mention the University of Graz’ research core are “Models and Simulation”. My office mates in Graz and Jena played a big role in the last three years, becausewe shared a lot of time together. Working on my PhD was often stressful and demanding, but with your help it was an enjoyable part of my life. Hence, my deepest gratitude to Richard Haider, Valentina Verduci, Milan Vujinovic, Mario Giuliani, Alexander Blinne and Nico Seegert. Besides my office mates, I want to thank Julia Borchardt, Ana Juricic, Ydalia Delgado Mercado, Matthias Blatnik, Hans-Peter Schadler, Pascal Törek, Markus Pak and Alexander Goritschnig. A special thank goes to our football team. It was a pleasure to participate. A note to Anita Ulz, conversations with you are and have always been refreshing and entertaining. A special thanks to Matthias Blatnik for careful proofreading my drafts. Ganz besonderen Dank gebührt meinen Eltern, Hans und Roswitha, für fast auf den Tag genau 26 Jahre vollste Unterstützung. Ein Dankeschön auch an meinen Bruder David, es macht immer wieder Freude mit dir etwas zu unternehmen. Ganz zum Schluss noch einen besonderen Dank an meine Oma Maria, die diese Arbeit leider nicht mehr miterleben konnte. 5 Contents List of Figures 11 List of Tables 12 Notation 13 I Considerations 17 1 Introduction 19 2 Overview 23 2.1 Historical remarks . 23 2.1.1 Electrodynamics . 23 2.1.2 Advances in Laser technology . 25 2.2 Theoretical considerations . 26 2.3 Laser beams . 28 2.4 Mechanisms for pair production . 30 2.5 Quantum kinetic methods . 33 2.6 Particle dynamics . 38 2.7 Objectives . 39 3 Dirac-Heisenberg-Wigner formalism 41 3.1 Wigner operator . 41 3.2 Equations of motion . 42 3.3 Pair production in arbitrary dimensions . 43 3.3.1 Pair production in the plane . 45 3.3.2 Pair production along a line . 51 3.4 Spatially homogeneous fields . 53 3.5 Cylindrically symmetric fields . 55 3.6 Observables . 59 3.7 Classical limit . 63 6 4 Solution strategies and models for the background field 67 4.1 Pseudo-spectral methods . 68 4.2 Pseudo-differential operators . 69 4.2.1 Operator expansion . 70 4.2.2 Full solution . 73 4.2.3 Filtering . 74 4.3 Model for the background field . 75 4.3.1 Parameter scales . 75 4.3.2 Model for the time-dependence . 76 4.3.3 Spatially inhomogeneous background fields . 77 4.3.4 Model for the magnetic field . 78 4.4 Final momentum distribution . 78 4.5 Semi-classical interpretation . 80 II Results 85 5 Multiphoton pair production 87 5.1 Effective mass signatures . 88 5.1.1 Quantum kinetic theory and background field . 88 5.1.2 Concept of an effective mass . 89 5.1.3 Particle yield . 91 5.1.4 Particle momentum distribution . 96 5.2 Pair production at extreme parameter regions . 98 6 Spatially inhomogeneous electric fields 101 6.1 Spatial focusing, full-operator DHW approach and background fields . 101 6.2 Ponderomotive forces for pair production in 3 + 1 dimensions . 102 6.3 Schwinger pair production in strongly localized fields . 110 7 Pair production in electric and magnetic fields 113 7.1 Pair production in the plane: Operator-expanded DHW approach and model for the fields . 113 7.2 Effective field amplitude . .116 7.2.1 Particle distribution . 117 7.2.2 Particle yield . 123 7 8 Summary and Outlook 127 8.1 Summary . 127 8.2 Outlook . 130 III Supplement 131 Appendix 132 Bibliography 199 8 Appendix A Detailed calculations 133 A.1 Equations of motion . 133 A.2 Energy averaging . 136 A.3 Transport equations for QED3+1 . 137 A.4 Transport equations for QED2+1 . 140 A.4.1 Four-Spinor formulation . 140 A.4.2 Two-Spinor formulation . 145 A.5 Transport equations for QED1+1 . 147 A.6 Alternative formulations . 149 A.7 Vacuum initial conditions . 154 A.8 Carrier Envelope Phase in the multiphoton regime . 156 A.9 Relativistic Lorentz force . 157 B Additional tables and figures 159 B.1 Figures . 159 B.1.1 Particle yield for homogeneous fields . 159 B.1.2 Carrier Envelope Phase regime . 160 B.1.3 Short pulsed, time-symmetric magnetic field . 160 B.1.4 Long pulsed, time-symmetric magnetic field . 164 B.1.5 Time-antisymmetric magnetic field . 167 B.2 Tables . 172 C Matlab solver 191 C.1 Code . 191 C.1.1 main.m . 191 C.1.2 Dgl.m . 194 C.2 Example calculations . 196 C.3 Parameter tables . 198 9 List of Figures Figure 2-1 Schematic picture displaying pair production via light-light interaction. 29 Figure 2-2 Schematic view of a transverse electromagnetic mode. 30 Figure 2-3 Pictorial description of the Schwinger effect. 31 Figure 2-4 Pictorial description of (multi)photon absorption. 32 Figure 2-5 Pictorial description of above-threshold pair production and the dy- namically assisted Schwinger effect. 32 Figure 2-6 Illustration of the number of non-trivial Wigner components depending on the dimension of the problem. 37 Figure 2-7 Illustration of the difference in the number of non-trivial Wigner com- ponents for ordinary and cylindrically symmetric problems. 37 Figure 4-1 Demonstration of particle-, charge-, positron- and electron distribution. 79 Figure 4-2 Final particle distribution in case of a single-peaked, homogeneous electric field. 80 Figure 4-3 2D picture of the distribution function for a single-peaked, inhomoge- neous electric field. 81 Figure 4-4 Modified particle distribution function demonstrating particle self- bunching. 82 Figure 4-5 Final particle distribution in case of a double-peaked, homogeneous background field. 83 Figure 4-6 2D picture of the distribution function for a double-peaked, inhomo- geneous electric field. 83 Figure 5-1 Particle yield as a function of the field frequency. 88 Figure 5-2 Momentum spectrum for Schwinger and multiphoton pair production. 91 Figure 5-3 Particle yield as a function of the field frequency in the multiphoton regime. 92 Figure 5-4.
Load more

Recommended publications
  • Arxiv:1904.10313V3 [Gr-Qc] 22 Oct 2020 PACS Numbers: Keywords: Entropy, Holographic Principle and CCDM Models
    Thermodynamic constraints on matter creation models R. Valentim∗ Departamento de F´ısica, Instituto de Ci^enciasAmbientais, Qu´ımicas e Farmac^euticas - ICAQF, Universidade Federal de S~aoPaulo (UNIFESP) Unidade Jos´eAlencar, Rua S~aoNicolau No. 210, 09913-030 { Diadema, SP, Brazil J. F. Jesusy Universidade Estadual Paulista (UNESP), C^ampusExperimental de Itapeva Rua Geraldo Alckmin 519, 18409-010, Vila N. Sra. de F´atima,Itapeva, SP, Brazil and Universidade Estadual Paulista (UNESP), Faculdade de Engenharia de Guaratinguet´a Departamento de F´ısica e Qu´ımica, Av. Dr. Ariberto Pereira da Cunha 333, 12516-410 - Guaratinguet´a,SP, Brazil Abstract Entropy is a fundamental concept from Thermodynamics and it can be used to study models on context of Creation Cold Dark Matter (CCDM). From conditions on the first (S_ 0)1 and ≥ second order (S¨ < 0) time derivatives of total entropy in the initial expansion of Sitter through the radiation and matter eras until the end of Sitter expansion, it is possible to estimate the intervals of parameters. The total entropy (St) is calculated as sum of the entropy at all eras (Sγ and Sm) plus the entropy of the event horizon (Sh). This term derives from the Holographic Principle where it suggests that all information is contained on the observable horizon. The main feature of this method for these models are that thermodynamic equilibrium is reached in a final de Sitter era. Total entropy of the universe is calculated with three terms: apparent horizon (Sh), entropy of matter (Sm) and entropy of radiation (Sγ). This analysis allows to estimate intervals of parameters of CCDM models.
    [Show full text]
  • European Astroparticle Physics Strategy 2017-2026 Astroparticle Physics European Consortium
    European Astroparticle Physics Strategy 2017-2026 Astroparticle Physics European Consortium August 2017 European Astroparticle Physics Strategy 2017-2026 www.appec.org Executive Summary Astroparticle physics is the fascinating field of research long-standing mysteries such as the true nature of Dark at the intersection of astronomy, particle physics and Matter and Dark Energy, the intricacies of neutrinos cosmology. It simultaneously addresses challenging and the occurrence (or non-occurrence) of proton questions relating to the micro-cosmos (the world decay. of elementary particles and their fundamental interactions) and the macro-cosmos (the world of The field of astroparticle physics has quickly celestial objects and their evolution) and, as a result, established itself as an extremely successful endeavour. is well-placed to advance our understanding of the Since 2001 four Nobel Prizes (2002, 2006, 2011 and Universe beyond the Standard Model of particle physics 2015) have been awarded to astroparticle physics and and the Big Bang Model of cosmology. the recent – revolutionary – first direct detections of gravitational waves is literally opening an entirely new One of its paths is targeted at a better understanding and exhilarating window onto our Universe. We look of cataclysmic events such as: supernovas – the titanic forward to an equally exciting and productive future. explosions marking the final evolutionary stage of massive stars; mergers of multi-solar-mass black-hole Many of the next generation of astroparticle physics or neutron-star binaries; and, most compelling of all, research infrastructures require substantial capital the violent birth and subsequent evolution of our infant investment and, for Europe to remain competitive Universe.
    [Show full text]
  • A Study of the Effects of Pair Production and Axionlike Particle
    Washington University in St. Louis Washington University Open Scholarship Arts & Sciences Electronic Theses and Dissertations Arts & Sciences Summer 8-15-2016 A Study of the Effects of Pair Production and Axionlike Particle Oscillations on Very High Energy Gamma Rays from the Crab Pulsar Avery Michael Archer Washington University in St. Louis Follow this and additional works at: https://openscholarship.wustl.edu/art_sci_etds Recommended Citation Archer, Avery Michael, "A Study of the Effects of Pair Production and Axionlike Particle Oscillations on Very High Energy Gamma Rays from the Crab Pulsar" (2016). Arts & Sciences Electronic Theses and Dissertations. 828. https://openscholarship.wustl.edu/art_sci_etds/828 This Dissertation is brought to you for free and open access by the Arts & Sciences at Washington University Open Scholarship. It has been accepted for inclusion in Arts & Sciences Electronic Theses and Dissertations by an authorized administrator of Washington University Open Scholarship. For more information, please contact [email protected]. WASHINGTON UNIVERSITY IN ST. LOUIS Department of Physics Dissertation Examination Committee: James Buckley, Chair Francesc Ferrer Viktor Gruev Henric Krawzcynski Michael Ogilvie A Study of the Effects of Pair Production and Axionlike Particle Oscillations on Very High Energy Gamma Rays from the Crab Pulsar by Avery Michael Archer A dissertation presented to the Graduate School of Arts and Sciences of Washington University in partial fulfillment of the requirements for the degree of Doctor of Philosophy August 2016 Saint Louis, Missouri copyright by Avery Michael Archer 2016 Contents List of Tablesv List of Figures vi Acknowledgments xvi Abstract xix 1 Introduction1 1.1 Gamma-Ray Astronomy............................. 1 1.2 Pulsars......................................
    [Show full text]
  • FRW Type Cosmologies with Adiabatic Matter Creation
    Brown-HET-991 March 1995 FRW Type Cosmologies with Adiabatic Matter Creation J. A. S. Lima1,2, A. S. M. Germano2 and L. R. W. Abramo1 1 Physics Department, Brown University, Providence, RI 02912,USA. 2 Departamento de F´ısica Te´orica e Experimental, Universidade Federal do Rio Grande do Norte, 59072 - 970, Natal, RN, Brazil. Abstract Some properties of cosmological models with matter creation are inves- tigated in the framework of the Friedman-Robertson-Walker (FRW) line element. For adiabatic matter creation, as developed by Prigogine arXiv:gr-qc/9511006v1 2 Nov 1995 and coworkers, we derive a simple expression relating the particle num- ber density n and energy density ρ which holds regardless of the mat- ter creation rate. The conditions to generate inflation are discussed and by considering the natural phenomenological matter creation rate ψ = 3βnH, where β is a pure number of the order of unity and H is the Hubble parameter, a minimally modified hot big-bang model is proposed. The dynamic properties of such models can be deduced from the standard ones simply by replacing the adiabatic index γ of the equation of state by an effective parameter γ∗ = γ(1 β). The − thermodynamic behavior is determined and it is also shown that ages large enough to agree with observations are obtained even given the high values of H suggested by recent measurements. 1 Introduction The origin of the material content (matter plus radiation) filling the presently observed universe remains one of the most fascinating unsolved mysteries in cosmology even though many authors worked out to understand the matter creation process and its effects on the evolution of the universe [1-27].
    [Show full text]
  • 7. Gamma and X-Ray Interactions in Matter
    Photon interactions in matter Gamma- and X-Ray • Compton effect • Photoelectric effect Interactions in Matter • Pair production • Rayleigh (coherent) scattering Chapter 7 • Photonuclear interactions F.A. Attix, Introduction to Radiological Kinematics Physics and Radiation Dosimetry Interaction cross sections Energy-transfer cross sections Mass attenuation coefficients 1 2 Compton interaction A.H. Compton • Inelastic photon scattering by an electron • Arthur Holly Compton (September 10, 1892 – March 15, 1962) • Main assumption: the electron struck by the • Received Nobel prize in physics 1927 for incoming photon is unbound and stationary his discovery of the Compton effect – The largest contribution from binding is under • Was a key figure in the Manhattan Project, condition of high Z, low energy and creation of first nuclear reactor, which went critical in December 1942 – Under these conditions photoelectric effect is dominant Born and buried in • Consider two aspects: kinematics and cross Wooster, OH http://en.wikipedia.org/wiki/Arthur_Compton sections http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GRid=22551 3 4 Compton interaction: Kinematics Compton interaction: Kinematics • An earlier theory of -ray scattering by Thomson, based on observations only at low energies, predicted that the scattered photon should always have the same energy as the incident one, regardless of h or • The failure of the Thomson theory to describe high-energy photon scattering necessitated the • Inelastic collision • After the collision the electron departs
    [Show full text]
  • Arxiv:1809.04815V2 [Physics.Hist-Ph] 28 Jan 2020
    Who discovered positron annihilation? Tim Dunker∗ (Dated: 29 January 2020) In the early 1930s, the positron, pair production, and, at last, positron annihila- tion were discovered. Over the years, several scientists have been credited with the discovery of the annihilation radiation. Commonly, Thibaud and Joliot have received credit for the discovery of positron annihilation. A conversation between Werner Heisenberg and Theodor Heiting prompted me to examine relevant publi- cations, when these were submitted and published, and how experimental results were interpreted in the relevant articles. I argue that it was Theodor Heiting— usually not mentioned at all in relevant publications—who discovered positron annihilation, and that he should receive proper credit. arXiv:1809.04815v2 [physics.hist-ph] 28 Jan 2020 ∗ tdu {at} justervesenet {dot} no 2 I. INTRODUCTION There is no doubt that the positron was discovered by Carl D. Anderson (e.g. Anderson, 1932; Hanson, 1961; Leone and Robotti, 2012) after its theoretical prediction by Paul A. M. Dirac (Dirac, 1928, 1931). Further, it is undoubted that Patrick M. S. Blackett and Giovanni P. S. Occhialini discovered pair production by taking photographs of electrons and positrons created from cosmic rays in a Wilson cloud chamber (Blackett and Occhialini, 1933). The answer to the question who experimentally discovered the reverse process—positron annihilation—has been less clear. Usually, Frédéric Joliot and Jean Thibaud receive credit for its discovery (e.g., Roqué, 1997, p. 110). Several of their contemporaries were enganged in similar research. In a letter correspondence with Werner Heisenberg Heiting and Heisenberg (1952), Theodor Heiting (see Appendix A for a rudimentary biography) claimed that it was he who discovered positron annihilation.
    [Show full text]
  • Pkoduction of RELATIVISTIC ANTIHYDROGEN ATOMS by PAIR PRODUCTION with POSITRON CAPTURE*
    SLAC-PUB-5850 May 1993 (T/E) PkODUCTION OF RELATIVISTIC ANTIHYDROGEN ATOMS BY PAIR PRODUCTION WITH POSITRON CAPTURE* Charles T. Munger and Stanley J. Brodsky Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 .~ and _- Ivan Schmidt _ _.._ Universidad Federico Santa Maria _. - .Casilla. 11 O-V, Valparaiso, Chile . ABSTRACT A beam of relativistic antihydrogen atoms-the bound state (Fe+)-can be created by circulating the beam of an antiproton storage ring through an internal gas target . An antiproton that passes through the Coulomb field of a nucleus of charge 2 will create e+e- pairs, and antihydrogen will form when a positron is created in a bound rather than a continuum state about the antiproton. The - cross section for this process is calculated to be N 4Z2 pb for antiproton momenta above 6 GeV/c. The gas target of Fermilab Accumulator experiment E760 has already produced an unobserved N 34 antihydrogen atoms, and a sample of _ N 760 is expected in 1995 from the successor experiment E835. No other source of antihydrogen exists. A simple method for detecting relativistic antihydrogen , - is -proposed and a method outlined of measuring the antihydrogen Lamb shift .g- ‘,. to N 1%. Submitted to Physical Review D *Work supported in part by Department of Energy contract DE-AC03-76SF00515 fSLAC’1 and in Dart bv Fondo National de InvestiPaci6n Cientifica v TecnoMcica. Chile. I. INTRODUCTION Antihydrogen, the simplest atomic bound state of antimatter, rf =, (e+$, has never. been observed. A 1on g- sought goal of atomic physics is to produce sufficient numbers of antihydrogen atoms to confirm the CPT invariance of bound states in quantum electrodynamics; for example, by verifying the equivalence of the+&/2 - 2.Py2 Lamb shifts of H and I?.
    [Show full text]
  • Electron-Positron Pairs in Physics and Astrophysics
    Electron-positron pairs in physics and astrophysics: from heavy nuclei to black holes Remo Ruffini1,2,3, Gregory Vereshchagin1 and She-Sheng Xue1 1 ICRANet and ICRA, p.le della Repubblica 10, 65100 Pescara, Italy, 2 Dip. di Fisica, Universit`adi Roma “La Sapienza”, Piazzale Aldo Moro 5, I-00185 Roma, Italy, 3 ICRANet, Universit´ede Nice Sophia Antipolis, Grand Chˆateau, BP 2135, 28, avenue de Valrose, 06103 NICE CEDEX 2, France. Abstract Due to the interaction of physics and astrophysics we are witnessing in these years a splendid synthesis of theoretical, experimental and observational results originating from three fundamental physical processes. They were originally proposed by Dirac, by Breit and Wheeler and by Sauter, Heisenberg, Euler and Schwinger. For almost seventy years they have all three been followed by a continued effort of experimental verification on Earth-based experiments. The Dirac process, e+e 2γ, has been by − → far the most successful. It has obtained extremely accurate experimental verification and has led as well to an enormous number of new physics in possibly one of the most fruitful experimental avenues by introduction of storage rings in Frascati and followed by the largest accelerators worldwide: DESY, SLAC etc. The Breit–Wheeler process, 2γ e+e , although conceptually simple, being the inverse process of the Dirac one, → − has been by far one of the most difficult to be verified experimentally. Only recently, through the technology based on free electron X-ray laser and its numerous applications in Earth-based experiments, some first indications of its possible verification have been reached. The vacuum polarization process in strong electromagnetic field, pioneered by Sauter, Heisenberg, Euler and Schwinger, introduced the concept of critical electric 2 3 field Ec = mec /(e ).
    [Show full text]
  • Universe Model Multicomponent
    We can’t solve problems by using the same kind of thinking we used when we created them. Albert Einstein WORLD – UNIVERSE MODEL MULTICOMPONENT DARK MATTER COSMIC GAMMA-RAY BACKGROUND Vladimir S. Netchitailo Biolase Inc., 4 Cromwell, Irvine CA 92618, USA. [email protected] ABSTRACT World – Universe Model is based on two fundamental parameters in various rational exponents: Fine-structure constant α, and dimensionless quantity Q. While α is constant, Q increases with time, and is in fact a measure of the size and the age of the World. The Model makes predictions pertaining to masses of dark matter (DM) particles and explains the diffuse cosmic gamma-ray background radiation as the sum of contributions of multicomponent self-interacting dark matter annihilation. The signatures of DM particles annihilation with predicted masses of 1.3 TeV, 9.6 GeV, 70 MeV, 340 keV, and 3.7 keV, which are calculated independently of astrophysical uncertainties, are found in spectra of the diffuse gamma-ray background and the emission of various macroobjects in the World. The correlation between different emission lines in spectra of macroobjects is connected to their structure, which depends on the composition of the core and surrounding shells made up of DM particles. Thus the diversity of Very High Energy (VHE) gamma-ray sources in the World has a clear explanation. 1 1. INTRODUCTION In 1937, Paul Dirac proposed a new basis for cosmology: the hypothesis of a time varying gravitational “constant” [1]. In 1974, Dirac added a mechanism of continuous creation of matter in the World [2]: One might assume that nucleons are created uniformly throughout space, and thus mainly in intergalactic space.
    [Show full text]
  • Worldline Sphaleron for Thermal Schwinger Pair Production
    IMPERIAL-TP-2018-OG-1 HIP-2018-17-TH Worldline sphaleron for thermal Schwinger pair production Oliver Gould,1, 2, ∗ Arttu Rajantie,1, y and Cheng Xie1, z 1Department of Physics, Imperial College London, SW7 2AZ, UK 2Helsinki Institute of Physics, University of Helsinki, FI-00014, Finland (Dated: August 24, 2018) With increasing temperatures, Schwinger pair production changes from a quantum tunnelling to a classical, thermal process, determined by a worldline sphaleron. We show this and calculate the corresponding rate of pair production for both spinor and scalar quantum electrodynamics, including the semiclassical prefactor. For electron-positron pair production from a thermal bath of photons and in the presence of an electric field, the rate we derive is faster than both perturbative photon fusion and the zero temperature Schwinger process. We work to all-orders in the coupling and hence our results are also relevant to the pair production of (strongly coupled) magnetic monopoles in heavy-ion collisions. I. INTRODUCTION Schwinger rate, Γ(E; T ), takes the form, 1 In non-Abelian gauge theories, sphaleron processes, X Γ(E; T ) = c h(J · A)ni; (1) or thermal over-barrier transitions, have long been un- n derstood to dominate over quantum tunnelling transi- n=0 1 tions at high enough temperatures [1{4] . The same is where E is the magnitude of the electric field and T is true, for example, in gravitational theories [5]. On the the temperature. The leading term, c0, gives the one loop other hand, sphalerons have been conspicuously absent result, that of Schwinger [6], at zero temperature.
    [Show full text]
  • Gamma-Ray Pulsars: Models and Predictions
    Gamma-Ray Pulsars: Models and Predictions Alice K. Harding NASA Goddard Space Flight Center, Greenbelt MD 20771, USA Abstract. Pulsed emission from γ-ray pulsars originates inside the magnetosphere, from radiation by charged particles accelerated near the magnetic poles or in the outer gaps. In polar cap models, the high energy spectrum is cut off by magnetic pair production above an energy that is dependent on the local magnetic field strength. While most young pulsars with surface fields in the range B =1012 1013 G are expected to have high energy cutoffs around several GeV, the gamma-ray− spectra of old pulsars having lower surface fields may extend to 50 GeV. Although the gamma- ray emission of older pulsars is weaker, detecting pulsed emission at high energies from nearby sources would be an important confirmation of polar cap models. Outer gap models predict more gradual high-energy turnovers at around 10 GeV, but also predict an inverse Compton component extending to TeV energies. Detection of pulsed TeV emission, which would not survive attenuation at the polar caps, is thus an important test of outer gap models. Next-generation gamma-ray telescopes sensitive to GeV-TeV emission will provide critical tests of pulsar acceleration and emission mechanisms. INTRODUCTION The last decade has seen a large increase in the number of detected γ-ray pulsars. At GeV energies, the number has grown from two to at least six (and possibly nine) pulsar detections by the EGRET telescope on the Compton Gamma Ray Obser- vatory (CGRO) (Thompson 2000). However, even with the advance of imaging Cherenkov telescopes in both northern and southern hemispheres, the number of detections of pulsed emission at energies above 20 GeV (Weekes et al.
    [Show full text]
  • Searches for Leptophilic Dark Matter with Astrophysical Experiments
    . Searches for leptophilic dark matter with astrophysical experiments . Von der Fakult¨atf¨urMathematik, Informatik und Naturwissenschaften der RWTH Aachen University zur Erlangung des akademischen Grades einer Doktorin der Naturwissenschaften genehmigte Dissertation vorgelegt von M. Sc. Leila Ali Cavasonza aus Finale Ligure, Savona, Italien Berichter: Universit¨atsprofessorDr. rer. nat. Michael Kr¨amer Universit¨atsprofessorDr. rer. nat. Stefan Schael Tag der m¨undlichen Pr¨ufung: 13.05.16 Diese Dissertation ist auf den Internetseiten der Universit¨atsbibliothekonline verf¨ugbar RWTH Aachen University Leila Ali Cavasonza Institut f¨urTheoretische Teilchenphysik und Kosmologie Searches for leptophilic dark matter with astrophysical experiments PhD Thesis February 2016 Supervisors: Prof. Dr. Michael Kr¨amer Prof. Dr. Stefan Schael Zusammenfassung Suche nach leptophilischer dunkler Materie mit astrophysikalischen Experimenten Die Natur der dunklen Materie (DM) zu verstehen ist eines der wichtigsten Ziele der Teilchen- und Astroteilchenphysik. Große experimentelle Anstrengungen werden un- ternommen, um die dunkle Materie nachzuweisen, in der Annahme, dass sie neben der Gravitationswechselwirkung eine weitere Wechselwirkung mit gew¨ohnlicher Materie hat. Die dunkle Materie in unserer Galaxie k¨onnte gew¨ohnliche Teilchen durch An- nihilationsprozesse erzeugen und der kosmischen Strahlung einen zus¨atzlichen Beitrag hinzuf¨ugen.Deswegen sind pr¨aziseMessungen der Fl¨ussekosmischer Strahlung ¨außerst wichtig. Das AMS-02 Experiment misst die
    [Show full text]