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Die Entdeckung Des − Schlüsselexperimente DIE ENTDECKUNG DES Ω der Teilchenphysik Julian Göltz, 5. Dezember 2014 1 ÜBERBLICK . Theorie . Der AGS Beschleuniger . Detektor . Ω− Ereignis . Auswirkungen 2 HISTORISCHE EINORDNUNG AGS bei Höchstenergie 1960 Vorhersage durch Gell-Mann 1962 Erstes Bild des Detektors 1963 Entdeckung des Ω− 1964 1932 1932 1938 1944 1950 1956 1962 1968 1974 1980 1983 1932 1962 1974 1983 Entdeckung des Positrons Entdeckung Myon Entdeckung des Entdeckung Neutrino J/Psi des Gluons 3 STAND DER TEILCHENPHYSIK . 1960: ~30 „Elementarteilchen“ . In kurzer Zeit 50 neue Teilchen gefunden . Entwicklung des SM parallel 4 VORHERSAGE DES Ω− . Grundlage Gruppentheorie SU(3) . The Eightfold Way: 8 Operatoren 5 VORHERSAGE: SUCHE NACH SYMMETRIE . Sortierung der Teilchen nach Masse Isospin: . Neutron, Proton ähnliche Masse: 푚푝 = 938.3푀푒푉 푚푛 = 939.6푀푒푉 . Isospin-Dublett 6 VORHERSAGE: SUCHE NACH SYMMETRIE Δ Σ 7 VORHERSAGE: BARYONEN DEKUPLETT http://en.wikipedia.org/wiki/Eightfold_Way_%28physics%29http://de.wikipedia.org/wiki/Eightfold_Way 8 EXPERIMENT . Leitung von W.B. Fowler, N.P. Samios . Gezielt nach Ω− gesucht . Gerade entstandene Werkzeuge benutzt 11 THEORIE: SYNCHROTRON . Beschleuniger arbeiten mit geladenen Teilchen . Synchrotron: Kreisbeschleuniger mit variablem Magnetfeld Stabile Bahn . Beschleunigung oft durch HF Resonatoren Keine kontinuierlichen Ströme Teilchenpakete (Bunches) 12 THEORIE: SYNCHROTRON . Bunches müssen fokussiert werden: Keine perfekte Injektion Coulomb Abstoßung Nötig für hohe Energien . Transversale Fokussierung Magnetfeldgradienten 13 THEORIE: CONSTANT GRADIENT SYNCHROTRON . Teilchen weiter außen B größer Krümmungsradius kleiner . Teilchen innen B kleiner Krümmungsradius größer ⇒Horizontale Fokussierung 14 THEORIE: CONSTANT GRADIENT SYNCHROTRON Maxwell Gleichungen für Vakuum ⇒ Horizontale Fokussierung bedeutet vertikale Defokussierung Vertikale Fokussierung bedeutet horizontale Defokussierung 15 THEORIE: ALTERNATING GRADIENT SYNCHROTON . Gradientenfelder in Ablenkmagneten: entlang stabiler Bahn gleiche Magnetfeldstärke, aber nicht konstant bei Abweichungen . Konstante Gradienten: alle Ablenkmagneten gleiches Gradientenfeld .Alternierende Gradienten: abwechselnd positive, negative Gradienten in Ablenkmagneten ⇒ abwechselnd Fokussierung/Defokussierung 16 THEORIE: ALTERNATING GRADIENT SYNCHROTON . Magnetfeldgradientenindex: 푟 휕퐵 푛 = − 퐵 휕푟 . Stabile Bahn bei konstantem Gradient: 0 < 푛 < 1 . Keine Beschränkung für alternierende Gradienten . Alternierende Gradienten fokussieren 17 EXPERIMENT: BESCHLEUNIGER . AGS: Alternating Gradient Synchrotron . Protonenbeschleuniger . 800m Umfang . Von 1960-1968 Beschleuniger mit höchster Energie (33GeV) . 3 Nobelpreise 18 BLASENKAMMER . Entwickelt von Donald A. Glaser . Ähnlich zu Nebelkammer . Kein übersättigtes Gas, sondern überhitzte Flüssigkeit http://de.wikipedia.org/wiki/Blasenkammer 19 BLASENKAMMER . Nachteile: . Höhere Vorsichtsmaßnahmen wegen Brennbaren Flüssigkeiten . Extremere Bedingungen (Druck, Temperatur) . Vorteile: . Keine Sekundäreffekte durch schwere Kerne . Höhere Ortsauflösung . Aus heutiger Sicht: . Zu klein . Keine Elektronische Datenauswertung . Datenauslesen zu langsam 20 BLASENKAMMER: PAARBILDUNG Credit: Courtesy of the Lawrence Berkeley Laboratory, the University of California, Berkeley 21 BLASENKAMMER: PIONEN http://teachers.web.cern.ch/teachers/archiv/HST2005/bubble_chambers/BCwebsite/gallery/gal3_chargedpion1.htm 22 EXPERIMENT: DETEKTOR . 80‘‘ Hydrogen Bubble Chamber . Durchmesser 2m . Flüssigkeit: 26K . Genauigkeit: im µm Bereich . Expansion: 15ms, 1.2cm Kolbenbewegung . 2T Magnetfeld http://www.sciencephoto.com/media/658/view 23 24 EXPERIMENT: ABLAUF . AGS schießt auf Wolfram Target – Ablenkung – Fokussierung - diverse Selektionsschritte . An Blasenkammer: Strahl bestimmter Teilchen definierter Energie und variabler Intensität 25 EXPERIMENT: ERSTER ZERFALL 26 EXPERIMENT: ERSTER ZERFALL (0/7) http://en.wikipedia.org/wiki/File:Omega_Baryon.svg 27 EXPERIMENT: ERSTER ZERFALL (1/7) 28 EXPERIMENT: ERSTER ZERFALL (2/7) 29 EXPERIMENT: ERSTER ZERFALL (3/7) 30 EXPERIMENT: ERSTER ZERFALL (4/7) 31 EXPERIMENT: ERSTER ZERFALL (5/7) 32 EXPERIMENT: ERSTER ZERFALL (6/7) 33 EXPERIMENT: ERSTER ZERFALL (7/7) 34 EXPERIMENT: ERSTER ZERFALL 35 EXPERIMENT: DISKUSSION DES ZERFALLS . Analyse beginnt bei Produkten . Beispielhaft: Zerfall von Λ0 . Blasendichte der Protonenspur . Analyse der Produkte ergibt richtige Masse 2 2 . Invariante Masse: 푗 푝푓푖푛,푗 = 푝푉−푇푒푖푙푐ℎ푒푛 = 푚 . Λ0 zeigt nicht auf Ω− Vertex . Iterieren 36 EXPERIMENT: DISKUSSION DES ZERFALLS Eigenschaften des Ω− . großer transversaler Impuls bei Zerfall, kein Zerfall mit Δ푆 = 2 ⇒ neues Teilchen . Lebenszeit: 0.7 ⋅ 10−10s also 푆 = −3 . Masse: (1668-1686)MeV, Vorhersage 1676 MeV 37 EXPERIMENT: ZWEITER ZERFALL 38 EIGENSCHAFTEN DES Ω− AUS HEUTIGER SICHT Masse (1672.45±0.29)MeV Zerfallszeit (8.2±0.11) ⋅ 10−11 s Quarkinhalt sss Zerfallskanäle 횲 퐊− (67.8±0.7) % Ξ0 휋− (23.6±0.7) % Ξ− 휋0 ( 8.6±0.4) % 39 VORHERSAGE: MESONEN OKTETT http://en.wikipedia.org/wiki/Eightfold_Way_%28physics%29 http://de.wikipedia.org/wiki/Eightfold_Way 40 VORHERSAGE: BARYONEN DEKUPLETT http://de.wikipedia.org/wiki/Eightfold_Way 41 AUSWIRKUNGEN . Nobelpreis für Gell-Mann 1969 . Ordnung der 80+ Teilchen . Einführung des Quark Modells und der Farbladung . Formulierung der QCD und des Standardmodells 43 LITERATUR Fowler, W.B. u.a.: Brookhaven national laboratory 80 hydrogen bubble chamber status and plans. In: Nuclear Instruments and Methods 20 (1963), S. 100 – 109 Barnes, V. E. u.a.: Observation of a Hyperon with Strangeness Minus Three. In: Physical Review Letters 12-8 (1964), S. 204–206 Beth, R. A. ; Lasky, C.: The Brookhaven Alternating Gradient Synchrotron. In: Science 128 (1958), S. 1393 – 1401 Chew, G. F. ; Gell-Mann, M. ; Rosenfeld, A. H.: Strongly Interacting Particles. In: Scientific American 210 (1964), Februar, S. 74–93 Ehrlich, R.: Analysis of Bubble Chamber Photographs. In: PHYSNET(2002) Fowler, W. B. ; Samios, N. P.: The Omega-Minus Experiment. In: Scientific American 211 (1964), Oktober, S. 36–45 Glaser, Donald A.: Some Effects of Ionizing Radiation on the Formation of Bubbles in Liquids. In: Phys. Rev. 87 (1952), Aug, S. 665–665 Harigel, G.G.: Bubble Chambers, Technology and Impact on High Energy Physics. In: Bologna 2003, 30 years of bubble chamber physics (2003), S. 342–355 Hinterberger, Frank: Physik der Teilchenbeschleuniger und Ionenoptik. 2. Berlin, Heidelberg : Springer Berlin Heidelberg, 2008 Povh, Bogdan ; Rith, Klaus ; Scholz, Christoph ; Zetsche, Frank ; Rodejohann, Werner: Teilchen und Kerne. 9. Aufl. 2014. Berlin, Heidelberg : Springer Spektrum, 2014. – 253ff S. Wikipedia: Omega baryon. http://en.wikipedia.org/wiki/Omega_ baryon. Version:Oktober 2014 Yao, W.-M. u.a. (Particle Data Group), J. Phys. G 33, 1 (2006) (URL: http://pdg.lbl.gov) 44 45.
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