Eötvös Loránd University, Physics MSc Detecting neutrinos For the course: Experimental Nuclear and Particle Physics seminar in Eötvös Loránd University instructors: Máté Csanád and Dezső Varga Budapest, 3 october 2011
Brief outline What is a neutrino? Detecting neutrinos First neutrino detectors Today s neutrino detectors The OPERA experiment Outlook
The never seen particle
What is a neutrino? In beta-decay the scientists encountered problems with energy, momentum, and angular momentum conservation laws: n p+ + e +? Wolfgang Pauli (1930): A new particle would explain anomalies: ν Pauli named it as neutron, but that was already engaged by Chadwick, so later it is renamed by Fermi to neutrino
The beta-decay today Neutrinos take part (only) in weak interaction!
The never seen particle?
Reines Cowan experiment (1956) by: Frederick Reines, Clyde Cowan, Nobel Prize: 1995 Main idea: beta-capture
Homestake experiment (from ~1970) by: Raymond Davis, Jr., John N. Bahcall Nobel Prize: 2002 Main idea: solar neutrinos ν e + 37 Cl 37 Ar + e
(Argonne National Laboratory)
Neutrino flavor 1962: L. Lederman, M. Schwartz, and J. Steinberger: muon neutrino! (Nobel Prize: 1988) G. Danby, J.M. Gaillard, Konstantin A. Goulianos, L.M. Lederman, Nari B. Mistry, M. Schwartz, J. Steinberger, (Columbia U. & Brookhaven). Jul 1962. 9pp. Published in Phys.Rev.Lett.9:36-44,1962. TOPCITE = 500+ 2000: Fermilab, DONUT collaboration: tau neutrino! DONUT Collaboration (K. Kodama (Aichi U. of Education) et al.). 12 pp. Published in Phys.Lett. B504 (2001) 218-224 The DONUT experiment has analyzed 203 neutrino interactions recorded in nuclear emulsion targets. A decay search has found evidence of four tau neutrino interactions with an estimated background of 0.34 events
Solar neutrino anomalies The electron neutrinos arriving from the Sun was just third of the number predicted from Standard Solar Model Solution: neutrino oscillation!
More Nobel Prizes Masatoshi Koshiba (~1980): Kamiokande Neutrinos first ever from a supernova: SN1987A (Nobel Prize: 2002)
Today s neutrino detectors
Cherenkov detection One can detect the Cherenkov radiation emitted by electron or muon which is created by neutrino: Super Kamiokande - 50.000 tons of pure water - 11.146 photomultiplier tubes Sudbury Neutrino Observatory (1000 tons of heavy water) (SNO+ is under constr.)
Underwater Cherenkov detection ANTARES 2.5 km under the Mediterranean Sea 12 separate vertical strings of pmt tubes IceCube ~2 km under the Antarctica 86 strings of pmt tubes
Chlorine and gallium detectors One can detect argon or germanium ejected in chlorine or gallium (as in Homestake experiment) Today: SAGE (Soviet-American Gallium Experiment) 71 Ga (ν e, e - ) 71 Ge ~50 tons of liquid gallium Assuming the solar neutrino production rate was constant during the period of data collection, combined analysis of 168 extractions through December 2007 (from 1989!)
The reactions being used are the same as in Reines Cowan experiment: ν e + p+ e+ + n Today: KamLAND (Kamioka Liquid Scintillator Antineutrino Detector) 1.000 tons of mineral oil, benzene and fluorescent chemicals 1.879 photomultiplier tubes Borexino Detectors based on scintillation 300 tons of scintillation liquid 2.200 photomultipliers ~
The OPERA experiment
Oscillation Project with Emulsion-tRacking Apparatus Location: at the underground Gran Sasso Laboratory Neutrino beam: from CERN through Earth s crust Measured: time of flight and distance Previous limit for (v-c)/c: < 2 10-9 from antineutrinos emitted by SN1987A supernova The new measurement: (v-c)/c = (2.48 ± 0.58) 10-5 Can we trust it? Take a look at the details
OPERA experiment The neutrino beam: - almost pure νμ - mesons decay in flight - difficulties
OPERA experiment The detector: - Target: 625 tons - Emulsion film/lead units - Scintillator strips - Photomultipliers
OPERA experiment Time measurement (calibration between CERN and LNGS): - 1 pulse per second signal from polarx GPS receiver to the CTRI measurement system - the rubidium clock generates time signal at CERN and LNGS - time stamps are created at labs - the time stamps can be referenced to PolaRx measurements - then the real time of flight can be calculated - the system was calibrated by GTR50 receiver (The distance measurement is an art too )
OPERA experiment The results (and outlook): distance: ~730 km ± 20 cm time of flight discrepancy: 60.7 ± 14.3 ns? (remainder: the 2011 Nobel Prize is going to be announced tomorrow!)
Thanks for your attention!