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Neutrini da reattore: la misura di θ13

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Gli esperimenti fino al 2003

I nuovi esperimenti

Impact of the CHOOZ (1998) experiment on the mixing matrix

νe disappearance probability: 22

)()(1 LLee νννν τµ −−=P

Evolution of a neutrino produced as ne at distance L from source:

LiEe

LiEe

LiEe eUeUeUL 321 332211)(

−−− ++= νννν

( )LEEieLEEieeLiE eUUeUUUUeL )(33)(2211 13121)( −−−−− ++= µµµµ νν

Remember: for E >> m EmmEE kiki 2

22 −≈−

Ignoring the overall phase exp(–iE1L) :

LE

i

e

LE

i

ee eUUeUUUUL 233222111312

)(Δ−Δ−

++= µµµµ νν

( )LEEieLEEieeLiE eUUeUUUUeL )(33)(2211 13121)( −−−−− ++= ττττ νν

LE

i

e

LE

i

ee eUUeUUUUL 233222111312

)(Δ−Δ−

++= ττττ νν

In the CHOOZ experiment ≈ 3 MeV , L ≈ 1000 m

1(m)(MeV)

)(eV534.22

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L’ esperimento RENO (Reactor Exp. for Neutrino Oscillations)

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Il detector

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Flusso di neutrino e meccanismo di rivelazione

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Selezione eventi

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Fondi

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Risultati

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Analisi Dati

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Errori sistematici

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Double Chooz

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Comparazione risultati

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AGGIORNAMENTO 2013

G.Battistoni 2014

sin2(2θ13) = 0.092±0.017 tan2(θ12) = 0.457+0.040−0.029. Questo corrisponde a θ12 ≡ θsol = 34.06+1.16−0.84° sin2(2θ23) > 0.92 at 90% confidence level, corrispondente a θ23 ≡ θatm = 45±7.1° Δm221 ≡ Δm2sol = 7.59+0.20−0.21×10−5 eV2 |Δm231| ≈ |Δm232| ≡ Δm2atm = 2.43+0.13−0.13×10−3 eV2 δ, α1, α2, e il segno di Δm232 non sono attualmente noti

This effect is only possible for m2 > m1 => Information on mass hierarchy in the m2 m1

system

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Aggiornamento 2015

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This is the first measurement obtained with the completed Daya Bay detector configuration consisting of eight modular antineutrino detectors, providing a total target mass of 160 tonnes. Four detectors located around 300 to 500 m from the reactors measure the initial νe rate from the reactors, while four detectors at around 1.6 km from the reactors observe the subsequent disappearance. The analysis found sin2(2θ13) = 0.084±0.005 from the amplitude of anti-νe disappearance, while the energy dependence of this disappearance provided a measurement of oscillation frequency expressed in terms of the effective mass-squared difference |Δm2ee| = (2.42±0.11) × 10–3 eV2 This is actually related to the two almost-equal neutrino mass-squared differences |Δm232| and |Δm231| = |Δm232 + Δm221|. If the mass hierarchy is normal, then |Δm232| = (2.37±0.11) × 10–3 eV2, while if it is inverted, |Δm232| = (2.47±0.11) × 10–3 eV2.