1. Superluminal neutrinos at OPERA (experimental results and phenomenology) Group meeting November 8, 2011 Würzburg, Germany Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAA A A A

2. 2 Preamble  Sept. 22, 2011: OPERA long-baseline experiment has reported v/c-1 ~ 2.5 10 -5 at 6  for    ; 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?

3. 3 Contents  The OPERA time-of-flight measurement  Interpretations, phenomenological observations  Generic constraints on interpretations from the OPERA result itself

4. 4 Neutrino production  Technical layout:  Flavor composition: mostly   Energy spectrum: ~17 GeV (higher than “typical“ beams) (CNGS, IEEE06, Monte Carlo!) (OPERA, arXiv:1109.4897)

5. 5 Time-of-flight measurement (OPERA, arXiv:1109.4897)

6. 6 Known time delays  Found effect ~ 6% of that! [60.7 ns] Interpretation? (OPERA, arXiv:1109.4897)

7. 7 Proton versus neutrino waveforms  1048.5ns – 987.8ns (corrections) = 60.7 ns (OPERA, arXiv:1109.4897) Neutrinos Protons

8. 8 OPERA self-cross checks  Two extractions (two proton waveforms), time dependence monitored Hardly any energy dependence found (OPERA, arXiv:1109.4897)

9. 9 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?

10. 10 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 conclusions  Some flavor or energy dependence of effect? (incl. a bias correction for Fermilab 79; from arXiv:1110.6577)

11. 11 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 )

12. 12 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)

13. 13 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)

14. 14 Consequences (WW, arXiv:1110.0424) Experimental example: Gaussian filter (protons  neutrinos) Theoretical example: Fraction X of superluminal neutrinos Steriles

15. 15 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