eötvös loránd university, physics...

Detecting neutrinos

Budapest, 3 october 2011

Gergely Kalmár Eötvös Loránd University, Physics MSc

For the course:

Experimental Nuclear and Particle Physics seminar in Eötvös Loránd University instructors: Máté Csanád and Dezső Varga

What is a neutrino?

Detecting neutrinos

First neutrino detectors

Today’s neutrino detectors

The OPERA experiment

Outlook

Brief outline

Gergely Kalmár ELTE presentation 2011.

The „never seen” particle


In beta-decay the scientists encountered problems with

energy, momentum, and angular momentum conservati-

on laws:

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”

What is a neutrino?


n → p⁺ + e⁻ + ?

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

νe + 37Cl → 37Ar + e⁻

(Argonne National Laboratory)

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…’’

Neutrino flavor


The electron neutrinos arriving from the Sun was just

third of the number predicted from Standard Solar

Model…

Solution: neutrino oscillation!

Solar neutrino anomalies


Masatoshi Koshiba (~1980): Kamiokande

Neutrinos first ever from a supernova: SN1987A

(Nobel Prize: 2002)

More Nobel Prizes…


Today’s neutrino detectors


One can detect the Cherenkov radiation emitted by

electron or muon which is created by neutrino:

Cherenkov detection


Super Kamiokande - 50.000 tons of pure water - 11.146 photomultiplier tubes

Sudbury Neutrino Observatory

(1000 tons of heavy water)

(SNO+ is under constr.)

ANTARES 2.5 km under the Mediterranean Sea 12 separate vertical strings of pmt tubes

Underwater Cherenkov detection


IceCube ~2 km under the Antarctica 86 strings of pmt tubes

One can detect argon or germanium ejected in chlo-

rine or gallium (as in Homestake experiment)

Today: SAGE (Soviet-American Gallium Experiment)

71Ga (νe , e-) 71Ge

~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!)

Chlorine and gallium detectors


The reactions being used are the same as in Reines–

Cowan experiment: νe + 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 300 tons of scintillation liquid 2.200 photomultipliers

Detectors based on scintillation


~

The OPERA experiment


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…

Oscillation Project with Emulsion-tRacking Apparatus


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 referen- ced 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

OPERA experiment


? (remainder: the 2011 Nobel Prize is going to be announced tomorrow!)

Thanks for your attention!


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