Superluminal neutrinos at OPERA (experimental results and phenomenology) Group meeting November 8, 2011 Würzburg, Germany Walter Winter Universität Würzburg
Jan 13, 2016
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