Hot topics in Neutrino Physics (and much more) Christian Roca Catal´ a Supervised by: Veronika Chobanova Ludwig Maximilian Universit¨ at Christian.Roca@physik.uni-muenchen.de May 15, 2014 1/71
Brief Introduction Neutrino Oscillations Actual Measurements Beyond Back-Up Slides Table of contents Brief Introduction 1 History lecture Are we sure? Neutrino Oscillations 2 Oscillations in vacuum (PMNS matrix) Mass generation mechanism Oscillations in matter (MSW effect) 3 Actual Measurements Mixing angles θ 13 Mass hierarchy ∆ m 2 13 Absolute mass m ν Beyond 4 Sterile neutrino mass Neutrinoless double beta decay Conclusions Neutrino Oscillation Experiments 2/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations History lecture Actual Measurements Are we sure? Beyond Back-Up Slides “I have done a terrible thing, I have postulated a particle that cannot be detected” Wolfgang Ernst Pauli, 1930 Fortunately he was WRONG and neutrinos can be detected and thus, their oscillations ! 3/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations History lecture Actual Measurements Are we sure? Beyond Back-Up Slides Question: Who proposed such idea? Answer: Bruno Pontecorvo in 1957 in analogy to Kaon mixing K 0 ↔ ¯ K 0 . It actually was a revolutionary idea! The first ”Ey! I just met you, detection of neutrino ν e was that and this is crazy, year! but what if... neutrino oscillate? a nobel maybe?” Bruno Pontecorvo 4/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations History lecture Actual Measurements Are we sure? Beyond Back-Up Slides Chronological ordered events (approximately): 1957 Cowan-Reines experiment - detection of ν e 1958 Goldhaber ν helicity exp : only ν e , L and ¯ ν e , R appear 1962 Lederman, Schwartz and Steinberger discover ν µ 1962 Maki, Nakagawa, and Sakata propose ν µ ↔ ν e 1967 Pontecorvo predicts a deficit in solar ν e 1969 Pontecorvo and Gribov calculate the oscillation probability ( ν e , L , ν µ, L ) ↔ (¯ ν e , LR , ¯ ν µ, R ) 1970-72 Homesake exp. indeed measures a deficit in ν e 5/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations History lecture Actual Measurements Are we sure? Beyond Back-Up Slides Solar/Atmospheric neutrinos TOTALLY PROVED ν µ → ν τ (atmospheric) Around 1998 SuperK announced ν e → ν µ,τ (solar) the confirmation Between 1998-2001 MACRO, Kamiokande II SuperKamiokande (evidence) (evidence) SuperKamiokande SNO (confirmation) (confirmation) K2K (further measurements) 6/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations History lecture Actual Measurements Are we sure? Beyond Back-Up Slides Accelerator/Reactor neutrino experiments RECENTLY PROVED ν e → ¯ ¯ ν µ,τ (antineutrino ν µ → ν e (neutrino appearance) disappearance) 19th of July, 2013 T2K 8th of March 2012 Daya Bay announced confirmation with announced the confirmation with 7 . 5 σ C.L 5 . 2 σ C.L MINOS (evidence) KamLAND (evidence) T2K (confirmation) Daya Bay (confirmation) NO ν A (further Double Chooz, RENO measurements) (further measurements) 7/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations Oscillations in vacuum (PMNS matrix) Actual Measurements Mass generation mechanism Beyond Oscillations in matter (MSW effect) Back-Up Slides The meaning of mixing Question: What does define a neutrino state? Answer: Roughly speaking: Weak Eigenstates : produced at weak vertices - Well defined Leptonic Flavour L α ( ν e , ν µ , ν τ ) Mass Eigenstates : determine the propagation through space - Well defined mass m i ( ν 1 , ν 2 , ν 3 ) Weak Eigenstates � = Weak Eigenstates NOTE! We will see that mass eigenstates in vacuum � = mass eigenstates in matter ¡! 8/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations Oscillations in vacuum (PMNS matrix) Actual Measurements Mass generation mechanism Beyond Oscillations in matter (MSW effect) Back-Up Slides Quantum Mechanical framework: General problem From flavour ES to mass ES: U change of basis in Hilbert space: � | ν α ( t ) � = U α i | ν i ( t ) � i � U † | ν i ( t ) � = i α | ν α ( t ) � i α : flavour ES, i : mass ES Question: How do | ν i ( t ) � propagate? Answer: Mass eigenstates propagate as usual eigenstates of H : − im 2 i | ν i ( t ) � = e − iHt | ν i ( 0 ) � = e 2 E L | ν i ( 0 ) � 9/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations Oscillations in vacuum (PMNS matrix) Actual Measurements Mass generation mechanism Beyond Oscillations in matter (MSW effect) Back-Up Slides Oscillation paradox Question: Where is the paradox? Answer: Follow theses steps to blow your mind: Flavour ES as a superposition of mass ES (a) Mass ES can be written as well as a composition of flavour ES (b) A pure flavour ES can be written as a superposition of other flavours (c) 10/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations Oscillations in vacuum (PMNS matrix) Actual Measurements Mass generation mechanism Beyond Oscillations in matter (MSW effect) Back-Up Slides Question: What is the solution? Answer: INTERFERENCE . The ν a carried by ν 1 , 2 inside ν e must have opposite phase. They interfere destructively and give a null net contribution to the total flavour. Conclusion ν e has a latent ν a component not seen due to particular phase . During propagation the phase difference changes and the cancellation disappears . This leads to an appearance of ν a component on a pure ν e state. 11/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations Oscillations in vacuum (PMNS matrix) Actual Measurements Mass generation mechanism Beyond Oscillations in matter (MSW effect) Back-Up Slides Overview of vacuum oscillations Evolution of mass ES: Proportion of ν 1 , 2 given at the production point by θ ν 1 , 2 propagate independently . Phase diff. given by m 1 , 2 Mass ES admixtures NEVER change . No ν 1 ↔ ν 2 transitions Flavour comp. of mass ES NEVER changes : given by θ In summary: image (c) is constant over all the travel Question: Then, how do ν mix? Answer: The relative phase ∆ m 2 ij / 2 E creates a cons/des interference of the flavour comp. in ν i , j . Then the initial state is effectively oscillating between flavours. 12/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations Oscillations in vacuum (PMNS matrix) Actual Measurements Mass generation mechanism Beyond Oscillations in matter (MSW effect) Back-Up Slides Quantum Mechanical framework: 2 Generations Question: Why is it important? Answer: Although there are 3 families, in many experiments we effectively have important mixing among 2 families Form of the unitary matrix U We can describe it as general rotation matrix with an unknown mixing angle θ : � � � � � � | ν α � cos θ sin θ | ν 1 � = · | ν β � − sin θ cos θ | ν 2 � � �� � U The mixing angle θ � = 0 for the oscillations to exist. 13/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations Oscillations in vacuum (PMNS matrix) Actual Measurements Mass generation mechanism Beyond Oscillations in matter (MSW effect) Back-Up Slides Question: What are the transition probabilities? Answer: Depend on m 2 12 and the oscillation angle θ P α → β = sin 2 2 θ sin 2 (∆ 12 L ) P α → α = 1 − sin 2 2 θ sin 2 (∆ 12 L ) DO NOT DEPEND ON ABS. VALUE OF m i NOTE! Explicit calculations at the Back-Up slides 14/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
Brief Introduction Neutrino Oscillations Oscillations in vacuum (PMNS matrix) Actual Measurements Mass generation mechanism Beyond Oscillations in matter (MSW effect) Back-Up Slides Quantum Mechanical framework: 3 Generations Question: What are the main differences? Answer: 3 mixtures among 12, 13 and 23 with their respective mixing angles. PMNS Matrix � 1 � � � s 13 e − i δ 0 0 c 13 0 c 12 s 12 0 · − s 12 U = 0 c 23 s 23 · 0 1 0 c 12 0 · − s 13 e i δ − s 23 0 c 23 0 c 13 0 0 1 c ij = cos θ ij and s ij = sin θ ij 1 0 0 θ ij are the mix. angles e i α 1 / 2 · 0 0 δ CP Violation phase e i α 2 / 2 0 0 α 1 , α 2 Majorana Phase 15/71 Christian Roca Catal´ a Selected Topics in Elementary Particle Physics
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