Detectors for astroparticle physics Teresa Marrodán Undagoitia marrodan@physik.uzh.ch Universität Zürich Kern und Teilchenphysik II, Zürich 07.05.2010 Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 1 / 32
Outline 1 Liquid xenon for dark matter search 2 Water Cherenkov detectors as neutrino observatory 3 Cherenkov telescopes for gamma astronomy Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 2 / 32
Outline 1 Liquid xenon for dark matter search 2 Water Cherenkov detectors as neutrino observatory 3 Cherenkov telescopes for gamma astronomy Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 3 / 32
Dark matter indications from astronomy Star rotation curves Measurement: 21 cm H-line Dark matter halo explanation Bullet cluster Indirect dark matter evidence Baryonic matter in red (X-rays) Matter distribution in blue (gravitational lensing) Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 4 / 32
Dark matter particle candidates WIMP (Weakly Interacting Massive Particle) DM particle candidates: Theories beyond the standard model predict new particles, the lightest is a dark matter candidate Example: Neutralino χ of Supersymmetry Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 5 / 32
WIMP search Indirect detection Direct detection Production at LHC χχ e+ e, pp χn χn p + p + a lot χ Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 6 / 32
Direct detection WIMP Detection via scatter off nuclei Reaction rate: R = N φ(e)σ(e)de N: number of target atoms φ(e): flux of dark matter σ(e): cross section Recoiling energy: E R = m N m χ m N +m χ m χ v 2 m N : mass of the target nuclei m χ : WIMP mass v: WIMP velocity Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 7 / 32
Xenon as detection medium Detection via scatter off nuclei Self-shielding High stopping power 178 nm UV photons No wavelength-shifter Simple cryogenics 180 K = - 93 Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 8 / 32
Scintillation in xenon Nuclear recoil Ionization: N + + N N + and e s N + 2 N + 2 + e N** + N N * Excitation: N + 2 + e N* 2 N ** N * + heat N * +N N* 2 N* 2 2N + hν N* 2 2N + hν singlet 3 ns triplet 25 ns singlet 3 ns triplet 25 ns Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 9 / 32
Two phase noble gas TPC Scintillation signal (S1) Charges drift to the liquid-gas surface Proportional signal (S2) Electron recombination is stronger for nuclear recoils Electron- / nuclear recoil discrimination Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 10 / 32
XENON experiment XENON100: 65 kg active volume Currently taking science data Laboratori Nazionali del Gran Sasso (Italy) 3 500 m.w.e. shielding from cosmic rays Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 11 / 32
XENON100 detector 30 cm drift length and 30 cm 165 kg total (30-50 kg fiducial volume) Shield: copper, polyethylene and led Material screening and selection Cooling outside the shield Active liquid xenon veto 1 inch PMTs 30 cm meshes Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 12 / 32
XENON100 detector 30 cm drift length and 30 cm 165 kg total (30-50 kg fiducial volume) Shield: copper, polyethylene and led Material screening and selection Cooling outside the shield Active liquid xenon veto 1 inch PMTs Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics 30 cm meshes Zürich 07.05.2010 13 / 32
Response to different types of particles AmBe neutron source Gamma ray sources Neutrons loose energy producing nuclear recoils Pair production, Compton effect and photoabsorption Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 14 / 32
Dark matter data Calibration data Background data (11.2 days) Band determination using: 60 Co and AmBe data No nuclear recoils in the expected region Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 15 / 32
Limit on the mass and cross section of WIMPs Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 16 / 32
Outline 1 Liquid xenon for dark matter search 2 Water Cherenkov detectors as neutrino observatory 3 Cherenkov telescopes for gamma astronomy Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 17 / 32
Cherenkov effect Charged particles which move faster than the speed of light in the medium v > c n emit Cherenkov light Cherenkov angle: cos θ = 1 βn Threshold for different particles: E thr = n n 2 1 m 0c 2 In water (n = 1.3): Particle Threshold [MeV] e ± 0.77 µ ± 159 π ± 210 Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 18 / 32
Size: 41 m height and 39 m Mass: 50 ktons of pure water 22 kton fiducial mass 11 000 photosensors of 0.5 m 1 000 m underground Kamioka mine (Japan) Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 19 / 32
Cherenkov rings in Superkamiokande I 1 GeV muon 600 MeV electron Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 20 / 32
Proton decay in Superkamiokande Original motivation to build Kamiokande Process predicted by GUT : Grand Unified Theories Clear identification of the decay p e + π 0 Limit on the proton lifetime: τ(p e + π 0 ) 8.2 10 33 y (90% C.L.) Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 21 / 32
Cherenkov rings in Superkamiokande II Multi-ring event Through-going muon Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 22 / 32
Atmospheric neutrinos Atmospheric neutrinos are produced in cosmic ray showers: a primary proton hits the top of the atmosphere and a shower of particles is created including π s and µ s. π µ ν µ µ e ν e ν µ Detection: neutral current reaction: ν x (ν x ) e ν x (ν x ) e with x = e, µ, τ Detection: charged current reactions: ν e p ne + ν e 16 O 16 F e ν e 16 O 16 N e + + ν µ and ν τ charged current reactions Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 23 / 32
Neutrino oscillations ν e, ν µ and ν τ : flavour eigenstates ν 1, ν 2 and ν 3 : mass eigenstates ( ) Survival probability: P e µ = sin 2 2θ sin 2 m 2 L 4E sin 2 2θ: mixing of neutrino flavours m 2 : splitting of neutrino mass eigenstates L: propagation distance E: neutrino energy the amount of neutrinos expected depends on their angle (length of the path through the atmosphere) and on their energy Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 24 / 32
Atmospheric neutrino results Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 25 / 32
Outline 1 Liquid xenon for dark matter search 2 Water Cherenkov detectors as neutrino observatory 3 Cherenkov telescopes for gamma astronomy Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 26 / 32
Gamma astronomy with Cherenkov telescopes Energy region: 0.05 50 TeV Gamma rays: no charge not affected by magnetic fields Physics: Pulsar wind nebula (crab) Active galactive nuclei (AGNs) Supernova remnants Pulsars Binary systems Gamma ray burst?... Results can be correlated with other wavelengths (e.g. radio, optical, X-ray...) Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 27 / 32
Imaging Cherenkov telescope Detection of particle cascades in the atmosphere Atmosphere as calorimeter Cherenkov-Light (1 5 ns) Statistical analysis of the shower images Large effective area Several experiments arround the world: Veritas, HESS, MAGIC Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 28 / 32
The MAGIC telescopes Two telescopes: stereo mode Mirrors of 17 m diameter Cameras using photomultiplier tubes Light construction: 65 t each Complete rotation in 30 seconds Location: La Palma (Canary islands) Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 29 / 32
Showers in the MAGIC-1 telescope > 99% of cosmic rays are hadrons Electromagnetic showers have to be distinguished from hadronic showers Image analysis is used for discrimination Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 30 / 32
MAGIC result (example) Makarian 501 Close blazar (type of AGN) Data from May - July 2005 High flux variation (double in few minutes) Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 31 / 32
More information: XENON100: http://xenon.astro.columbia.edu/xenon100.html Superkamiokande: http://www-sk.icrr.u-tokyo.ac.jp/sk/index-e.html MAGIC: http://wwwmagic.mppmu.mpg.de/ Teresa Marrodán Undagoitia (UZH) Detectors for astroparticle physics Zürich 07.05.2010 32 / 32