Detecting neutrinos. Gergely Kalmár. For the course: Experimental Nuclear and Particle Physics seminar. Eötvös Loránd University, Physics MSc

Transcription

1 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

2 Brief outline What is a neutrino? Detecting neutrinos First neutrino detectors Today s neutrino detectors The OPERA experiment Outlook

3 The never seen particle

4 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

5 The beta-decay today Neutrinos take part (only) in weak interaction!

6 The never seen particle?

7 Reines Cowan experiment (1956) by: Frederick Reines, Clyde Cowan, Nobel Prize: 1995 Main idea: beta-capture

8 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

9 (Argonne National Laboratory)

10 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 pp. Published in Phys.Rev.Lett.9:36-44,1962. TOPCITE = : Fermilab, DONUT collaboration: tau neutrino! DONUT Collaboration (K. Kodama (Aichi U. of Education) et al.). 12 pp. Published in Phys.Lett. B504 (2001) 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

11 Solar neutrino anomalies The electron neutrinos arriving from the Sun was just third of the number predicted from Standard Solar Model Solution: neutrino oscillation!

12 More Nobel Prizes Masatoshi Koshiba (~1980): Kamiokande Neutrinos first ever from a supernova: SN1987A (Nobel Prize: 2002)

13 Today s neutrino detectors

14 Cherenkov detection One can detect the Cherenkov radiation emitted by electron or muon which is created by neutrino: Super Kamiokande tons of pure water photomultiplier tubes Sudbury Neutrino Observatory (1000 tons of heavy water) (SNO+ is under constr.)

15 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

16 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!)

17 The reactions being used are the same as in Reines Cowan experiment: ν e + p+ e+ + n Today: KamLAND (Kamioka Liquid Scintillator Antineutrino Detector) tons of mineral oil, benzene and fluorescent chemicals photomultiplier tubes Borexino Detectors based on scintillation 300 tons of scintillation liquid photomultipliers ~

18 The OPERA experiment

19 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: < 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

20 OPERA experiment The neutrino beam: - almost pure νμ - mesons decay in flight - difficulties

21 OPERA experiment The detector: - Target: 625 tons - Emulsion film/lead units - Scintillator strips - Photomultipliers

22 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 )

23 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!)

24 Thanks for your attention!