Neutrino and Astro Particle Physics

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1 Neutrino and Astro Particle Physics Non-accelerator based experiments - Proton decay - Solar neutrino s Neutrino oscillation experiments Astro Particle Physics - Cosmic ray experiments: Pierre Auger - Antares/KM3NET Proton Decay: matter known to us would eventually turn into radiation if protons would decay. Proton Decay Popular field of research in Interesting outlook of material Universe in (far) future Postulated decay time constant: ~ year So: take protons: 10 decays per year Process: p e + + π 0 π 0 2 γ (decay time: s)

2 γ γ e+ π 0 proton γ γ Proton decay. The proton would decay into a (neutral) pion and a positron. The pion decays instantaneously into two gammas, and the positron annihilates with an electron from the surrounding material after being stopped. All four gamma s interact with the surrounding material; the gammas from the electron-positron decay a bit later. The gamma s produce rapid electrons in the surrounding material causing detectable Cerenkov light. Height: 41.4 m Dia.: 39.3 m Contains 50,000 tons pure H 2 O 1000 m underground 11,146 photomultipliers The (super) Kamiokande experiment contains tons of (ultra pure) water. The Cerenkov light is recorded by some (large diameter) photomultipliers. No proton decays have been observed: the experiment has concluded that the proton lifetime exceeds year.

3 The Solar neutrino deficit Allthough no decaying protons have been observed, solar neutrino s were observed. In the Sun, the main energy is generated in a sequence starting with proton-proton fusion. This reaction results in a deuterium nucleus, a positron and an electron-neutrino ν e. The total power, emitted by the sun, is well-known. Assuming known nuclear processes, the neutrino flux at Earth can be calculated rather well. In all experiments, only a fraction ( ) of this expected flux was observed.

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5 Surprise: Supernova 1987A 11 neutrinos measured in Kamiokande in 1 s Supernova 1987A In 1987, Kamiokande recorded within a period of 2 s, 11 neutrinos, to the surprise of the watching crew. It turned out to be caused by Supernova 1987A, as confirmed by optical telescopes. Neutrinos were also observed by other (proton decay & solar neutrino) experiments. The spread in the arrival time suggested that neutrinos might have a small mass. This is in line with the postulation of neutrino oscillation, which could explain the neutrino deficit. With the Sudbury Neutrino Observatory, the difference between muon, electron and tau neutrinos could be observed. After 2001 it was found that 35 % of the observed solar neutrinos were electron-neutrinos, and the rest were muon or tau neutrinos. The total number agreed quite well with the original rate estimates from to solar (nuclear) power.

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7 Muon event in SuperKamiokande. The arrival time of the light signal is indicated by the color. Red: early, blue: late. Since 2000, neutrino oscillations are measured using accelerator-made neutrinos.

8 New experiments: measure neutrino oscllations with neutrinos made in accelerators A beam of neutrinos is made in the JPARC accelerator in Tokai, Japan. The neutrinos are directed into the Earth crust towards SuperKamiokande, 295 km downstream. By pulsing the beam, the arrival time of the neutrinos at Kamiokande is known, and background can be suppressed.

9 Schematic view of the generator of the neutrino beam. Protons (E = 12 GeV) are directed onto a target. The produced positive pions are focused and decay into a muon and a muon neutrino. The neutrino beam is monitored with the near neutrino detector, see below.

10 With the knowledge of the beam geometry and beam composition, obtained from the near detector, the intensity of the beam at Kamiokande can be calculated. Neutrino oscillation has been confirmed. OPERA detector in Gran Sasso Stack of Pb plates with film emulsion!

11 The neutrinos interact with Pb plates. Muon tracks are recorded by gas detectors, with fotographic emulsion in between. This provides precise analysis off-line later, and one can distinguish between ν τ, ν µ and ν µ. Neutrino detector in GranSasso, Italy. It consists of a stack of Pb absorbers, gas-filled detectors and photographic emulsion for a high-precision reconstruction if the neutrino event. In Europa, neutrinos created at CERN, are directed to the OPERA experiment in GranSasso, Italy.

12 Cosmic Ray experiments Cosmic rays come to us, mostly in the form of protons and nuclii. They start to interact in the upper regions of our atmosphere, and create a shower of particles due to interactions with atoms and molecules in the air. Muons, created in the shower, live long enough to have a fair chance to reach the Earth surface. As a rule of thumb: on average, at sea level, a horizontal square cm 2 is crossed by a minimum-ionizing particle once per minute. In fact, the earth atmosphere acts as a leaking (hadron) calorimeter.

13 The energy associated with cosmic ray showers (originated by a single incident proton or nucleus). At around ev, the rate is higher than the expected value from a fitted double-exponential relation. Note the existence of extremely energetic events, exceeding an energy of 10 Joule!

14 The Auger Observatory 1400 m height 875 g/cm 2 Total area ~3000 km 2 Low population density Good atmospheric conditions (clouds, aerosol) 1600 water tanks 1.5 km spacing 24 fluorescence telescopes, 6 in each of 4 buildings The state-of-the-art cosmic ray experiment is the Pierre Auger Observatory in Argentina. On a deserted pampa the sky is being monitored on Cerenkov light by means of for stations. Distributed over the surface, Cherenkov light is detected in 1600 tanks containing 12 m 3 pure water. Water Tank in the Pampa Communication antenna GPS antenna Electronics enclosure 40 MHz FADC, local triggers, 10 Watts Solar Panel Battery box three 9 PMTs Plastic tank with 12 tons of water

15 Example Event A hybrid event Zenith angle ~ 30º, Energy ~ 8 EeV Lateral density distribution Flash ADC traces Typical event in the watertanks. From the weighted signal distribution and the arrival time of the signals the parameters of the shower can be obtained. Fluorescence Telescope Spherical mirror (R=3.4 m) Camera with 440 PMTs The Sky telescope: an assembly of mirrors and photomultipliers.

16 Fluorescence detection: Calorimetry Fly s eye Typical shower measured with the Sky telescope. The atmosphere acts as calorimeter. Highest Energy Events AGN Catalog: Veron-Cetty Veron 318 AGNs in field of view observatory Centaurus A Result of Pierre-Auger: the sources of high-energy cosmic rays. There is no flat distribution over the hemisphere.

17 Astro Particle Physics: Neutrino physics Waarom? reistijd afbuiging absorptie p ν γ - We can not travel to interesting sources light years away and do lab tests there; - Charged particles travelling through the cosmos are bended off in magnetic fields (and loose energy) - Photons and gamma s are absorbed by interstellar material Cosmic neutrinos are an interesting source of knowledge

18 omringend licht ν µ p n p + π + π 0 γ materie Neutrino telescoop: oorsprong kosmische straling ontstaan & kompositie relativistische stralen werking kosmische deeltjesversnellers zwart gat KM 3 Neutrino Telescoop neutrino detectie neutrino muon golffront ~100 m interactie ~ km muon reist met de lichtsnelheid (300,000 km/s) detectie Cherenkov licht ns km Detection of neutrinos with water: conversion into fast electron or muon (or tau). The speed of this particle exceeds the speed of light in water: Cerenkov radiation (UV blue light).

19 12 x 25 = 300 detection units Optical beacon timing calibration 10 PMT photon detection Electronics readout Hydrophone acoustic positioning ~1 m titanium frame mechanical support Essentially: pulled-up strings equipped with triplets of wide-area photomultipliers. They are oriented such that the Cerenkov light from muons and electrons moving UP, is detected. So neutrinos coming up, after passing through the Earth, are detected. ~200 persons 6 countries ~40 km off the coast near Toulon 12 lines ~2.5 km 500 m 250 Atm. ~200x200 m2 25 storeys / line

20 The future: KM3Net