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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