Superluminal neutrinos at OPERA(experimental results and phenomenology)

Group meetingNovember 8, 2011Würzburg, Germany

Walter WinterUniversität Würzburg

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Preamble

Sept. 22, 2011: OPERA long-baseline experiment has reported v/c-1 ~ 2.5 10-5 at 6for ; 60.7ns faster than light over 730km baseline)

Since then (Nov. 7): 129 papers discussing that ~ 2.8/calender day

Why so striking? Probably systematical error not accounted for, but if confirmed, evidence for Lorentz invariance violation? One of the major breakthroughs of this century?

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Contents

The OPERA time-of-flight measurement Interpretations, phenomenological

observations Generic constraints on interpretations

from the OPERA result itself

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Neutrino production

Technical layout:

Flavor composition: mostly

Energy spectrum:<E> ~17 GeV(higher than “typical“ beams)

(CNGS, IEEE06, Monte Carlo!)

(OPERA, arXiv:1109.4897)

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Time-of-flight measurement

(OPERA, arXiv:1109.4897)

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Known time delays

Found effect ~ 6% of that! [60.7 ns] Interpretation?

(OP

ER

A, arX

iv:1109.4897)

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Proton versus neutrino waveforms

1048.5ns – 987.8ns (corrections) = 60.7 ns

(OPERA, arXiv:1109.4897)

Neutrinos

Protons

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OPERA self-cross checks

Two extractions (two proton waveforms),time dependencemonitored

Hardly any energy

dependence found

(OPERA, arXiv:1109.4897)

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Possible interpretations?

Lorentz invariance violation (e. g. different dispersion relation)?

Environment-dependent effect? Sterile neutrinos, such as taking shortcuts

through an extra dimension? Experimental effect, not accounted for?

Unknown systematics? Problem with statistics treatment? S. Parke: Most stringent test of the GPS

system?

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Phenomenological observations

SN 1987A neutrinos obviously without significant advance (E ~ 10 MeV; electron s)

MINOS and other experiments measuring in the same energy range without significant conclusionsSome flavor or

energy dependence of effect?

(incl. a bias correction for Fermilab 79; from arXiv:1110.6577)

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Theoretical observations

Neutrino oscillations (not flavor mixing!) between two mass eigenstates with very different velocities average out[however: not observed at OPERA …]

Cohen-Glashow bound (next week)Sterile neutrino easiest workaround?Can also “tune“ the energy easily (well known

for matter effects in neutrino oscillations; see e.g. arXiv:1110.4871)

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Experimental observations

The proton and neutrino waveforms may not be the same

E.g. some averaging in the beam current transformer affects leading and trailing edges

(arXiv:1110.0595)

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What can we learn from OPERA data?

However: not only leading an trailing edges match, also complicated proton waveform at “plateau“

Example: Exaggerated 200ns Gaussian filter (blue, dotted) affects g.o.f.

Consequence:any effect which deteriorates proton waveform decreases g.o.f. (WW, arXiv:1110.0424)

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Consequences

(WW, arXiv:1110.0424)

Experimental example:Gaussian filter (protons neutrinos)

Theoretical example:Fraction X of superluminal neutrinos

Steriles

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Summary

OPERA result striking Challenging to find a good interpretation

because Cohen-Glashow bound Energy-dependent effect? Proton waveform reproduced

More on theoretical matters: Martin Krauss, next week