Neutrino physics: experiments The dark side of the Universe, ISAPP, MPIK Heidelberg, May 29/30, 2019 ν νe µ Christian Weinheimer Institut für Kernphysik, Westfälische Wilhelms-Universität Münster [email protected] ν τ A reminder: Neutrinos in the Standard Model of Particle Physics Prof. Dr. Takaaki Kajita Neutrino oscillations: experiments with atmospheric, solar, accelerator and reactor neutrinos Neutrino masses: - cosmology and astrophysics - neutrinoless double β decay - direct neutrino mass experiments Search for sterile neutrinos Coherent neutrino nucleus elastic scattering Prof. Dr. Arthur B. McDonald Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 1 Experimental proof n of neutrinos ν e p e+ 1956: Cowan and Reines: Poltergeist experiment strong νe source: nuclear power reactor: 6 fission (from fission products), E 9 MeV νe ν energy gain / fission: 200 MeV 1 GW thermal power 2 1020 ν/s + Detection reaction: inverse β decay: νe + p n + e (threshold: 1.8 MeV) Signature:a) n: thermalisation by elastic scattering, capture on Cd γ 's b) e+: annihilation 2 γ 's (511 keV) spatial and time-delayed coincidence (nearly background free) measured cross section: (1.1 ± 0.3) 10-43 cm2 figure: Schmitz: Neutrinophysics, Teubner (in good agreement with Fermi`s theory for V-A) Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 2 ν's in the electroweak Standard Model: U(1)SU(2) 12 fundamental fermions 6 left-handed weak isospin dublets: pure weak isospin dublets weak S. Glashow isospin dublets 9 right-handed weak isospin singulets: (no νR in SM) massive leptons in charged S. Weinberg weak currents (CC): - lepton: For masseless particles (ν in SM): P(H = 1) = (1 -v/c))/2 P = -v/c σ Long c ΨL , ΨR have helicity H = -1 p - anti lepton: P(H = 1) = (1 v/c)/2 σ P = v/c A. Salam c p Long ΨR , ΨL have helicity H = +1 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 3 Lagrangian: Interaction part l (d) ν (u) W + W - ν (u) l (d) weak charged current (CC) ν,l, u,d, .. Z 0 ν,l, u,d, .. weak neutral current (NC) l, u,d, .. γ l, u,d, .. em neutral current coupling to electromagnetic current e.m. as in QED:g sin = e Jµ θW o θW = 28.7 coupling of weak interaction coupling of em. interaction, 2“ 2 but there is a term „mW (mZ ) in the denominator of the propagator, see later Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 4 Weakness of weak interaction Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 5 ν cross sections σ s figure: Schmitz: Neutrinophysics, Teubner -fermion scattering cross sections: s = m 2 + 2E m s E ν σ f ν f ν Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 6 LEP: determination of number of neutrino generations LEP: e- + e+ Z0 (γ) e- + e+, µ- + µ+, τ-+ τ+, e l u + u, b i s i d + d, v s + s, c + c, b + b, νe + νe, e l ν + ν , b µ µ i s i + , v ντ ντ n ???? i figure: PDG Exp: full width: Γ = 2495(2) MeV invisible width: Γinvisible = 499(2) MeV partial width = 167.1 MeV N = 2.99 ν Γν ν Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 7 Angular distribution of neutrino-fermion scattering Neutrino-fermion scattering: no angular dependence: y distribution is flat for νl scattering ! Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 8 Angular distribution of antineutrino-fermion scattering Antineutrino-fermion scattering (neglect NC): angular dependence: distribution y distribution is not flat for νl scattering ! Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 9 Christian Weinheimer Christian distributionand y the for for helicitydeducearguements we From Experiment Sea quarkSea fraction expect: expect: ν Average: Average: q = q : ν q with with and but q ν (x) in nucleon is about nucleon 15% is in (x) q = q and (anti)neutrino-nucleon scattering σ ν tot q : ISAPP Heidelberg May 29/30, 2019 May 29/30, Heidelberg ISAPP Deep inelastic inelastic Deep 10 figures: Perkins: Introduction to High Energy Physics, Cambridge Neutrino sources and energy spectra figure: Schmitz: Neutrinophysics, Teubner Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 11 Summary of neutrinos in the Standard Model of particle physics ● ν's are left-handed, charged fermions in CC reactions (W exchange) are also left-handed charged fermion coupling to the Z0 is more complicated (since the Z0 is a superposition of the „hypercharge photon B“ and the W3) ● ν's are massless, since there is no right-handed neutrino to construct a „Dirac mass term“ = - m ΨL ΨR – m ΨR ΨL L ● ν's have very small cross section (due to the large masses of W and Z) Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 12 Neutrino physics: experiments The dark side of the Universe, ISAPP, MPIK Heidelberg, May 29/30, 2019 ν νe µ Christian Weinheimer Institut für Kernphysik, Westfälische Wilhelms-Universität Münster [email protected] ν τ A reminder: Neutrinos in the Standard Model of Particle Physics Prof. Dr. Takaaki Kajita Neutrino oscillations: experiments with atmospheric, solar, accelerator and reactor neutrinos Neutrino masses: - cosmology and astrophysics - neutrinoless double β decay - direct neutrino mass experiments Search for sterile neutrinos Coherent neutrino nucleus elastic scattering Prof. Dr. Arthur B. McDonald Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 13 Atmospheric neutrino anomaly: too few muon neutrinos Interaction of cosmic rays (p,α, ..) in outer atmosphere: π, K,... + + + π µ νµ + e + νµ + νe - - + π µ νµ e- + + νµ νe + / 2 νµ νµ νe νe n o i t a t c e ν e p x e e ν / t / n µ e ν + m i µ r ν e p x e Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 14 Kamioka Nucleon Decay Experiment: KamiokaNDE (II) 3000 t water Cherenov detector to search for proton decay (→ GUT) 16m high, 16m diameter 1000 38cm PMTs at the surface If a charged particle moves faster than speed of light in the medium, polarisation does not follow: → Emission of Cherenkov-light into a cone: cosθ = 1/βn o (→ 42 for H20 assuming β=v/c → 1) → ring structure at wall covered by PMTs Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 15 Atmospheric neutrinos in a water Cherenkov detector Cherenkov cone gives: ● energy ● direction (-) ν ● electron/muon differentiation: muons: sharp ring l+/- electrons: washed-out ring (multiple scattering, em shower) (Super-)Kamiokande Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 16 Physics results of KamiokaNDE II No observation of proton decay → main mission failed but KamiokaNDE II performed extremely well, e.g. - Discovery (together with IMB) of neutrinos from SN1987a → Nobel prize 2002 to Masatoshi Koshiba - confirmation of nuclear burning in the sun by observing solar neutrinos - atmospheric neutrino anomaly: wrong muon neutrinos/electron neutrino ratio & wrong angular distribution Y. Fukuda et al., Phys. Lett. B 335 (1994) 237 → decision to build Super-Kamiokande Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 17 Super-Kamiokande: Start of data taking in April 1996 water Cherenkov detector H20: 50 000 t 40 m high, 40 m 11146 PMTs a 50 cm 1 km overburden in Kamioka Mine, Japan Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 18 Super-Kamiokande's first result at Int. Conf. Neutrino 1998 at Takayama Nobel prize 2015 to Takaaki Kajita Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 19 Angular distribution of and at SK νe νµ θ ν p, α, .. L Expectation no neutrino oscillation Fit νµ → ντ Oszillation R. Wendell – Neutrino 2014 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 20 Angular distribution of and at SK νe νµ Clear deficit of muon neutrinos coming from below, θ (i.e. muon neutrino which travelled a long distance) ν p, α, .. Measurement is compatible to neutrino oscillation: L (detector is nearly blind for ν ) νµ ντ τ „Neutrino oscillation“ with parameters (Δm2 2 ×10-3 eV2. sin2(2θ) 1) Expectation no neutrino oscillation Fit νµ → ντ Oszillation R. Wendell – Neutrino 2014 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 21 Angular distribution of and at SK νe νµ All data sets and analyses (FC, PC, up-going θ µ, NC enhanced): ν compatible with p, α, .. ν ν oscillation L µ τ (Δm2 2 ×10-3 eV2. sin2(2θ) 1) Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 22 Angular distribution of and at SK νe νµ θ Question to think about: ν What is the connection of the expected multi-GeV p, α, .. angular distributions of atmospheric neutrinos L with the red sky at sun rise or sun set ? Expectation no neutrino oscillation Fit νµ → ντ Oszillation R. Wendell – Neutrino 2014 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 23 Neutrino (vacuum) oscillations 1) non-trivial unitary ν mixing matrix U between neutrino flavour states ( ) and mass states ( ): νe νµ ντ ν1 ν2 ν3 d d g s mixin d 3 state 2) a flavour state propagates as a coherent sum of mass states m(νi) if the m(νi) differ neutrino oscillation ν U 1 U * - + µ1 τ1 ντ τ nt + µ ν perime W U 2 U * slit ex µ2 τ2 Triple ν ν + µ U 3 U * W µ3 τ3 creation of a detection of a νµ propagation as coherent ντ via weak interaction superposition of mass states via weak interaction Formula is correct, P but correct derivation (να νβ) needs wave packages or QFT (see E. Akhmedov) Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 24 Neutrino (vacuum) oscillations 2 Flavor case: Probability for an oscillation sin2(2 ) from to (and back) for Θ να νβ an amplitude value of 2 average E/L sin (2θ) = 0.2 in units of the y oscillation length L .