While at Bari Conference (see here), the news was spreading that OPERA Collaboration, a long baseline experiment using muon neutrino beams launched by CERN by CNGS Project, detected a possible Lorentz violating effect. Initially, it started as a rumor in the comment area at Jester’s blog (see here). Then, Tommaso Dorigo provided a full account on his blog well before the Collaboration come out with its results (see here and here) so, he was kindly advised to remove his ill-timed report by his management at CERN. This post, as you can see, is now back and gives, as usual for Tommaso, a very good description of facts. Similarly, you can find good posts about at vixra and Jester’s blog. Meantime, OPERA Collaboration published its paper on arxiv (see here) and, on Friday, gave a seminar at CERN that was broadcast through all the web. Today, we know that they performed very well at the measurement and, after a struggle with the data lasting about three years, they forcefully published the result waiting for all the community to scrutinize it. Indeed, at first it is very difficult to find some drawback in this work and, being all well-trained physicists, it appears quite difficult to expect this. So, the next and more important step is just to have this result replicated or not by independent labs.
It is interesting to note that this experiment was originally conceived to observe neutrino oscillations. What they should observe are tau neutrinos arising from the muon neutrinos coming from CERN. But this has proved really difficult and, after about 16000 events, they were able to get a possible serendipitous discovery. The spokesperson of the Collaboration is Antonio Ereditato and you can find an interview here.
My first impressions about this result were a couple of important points that surely should have been emphasized: It could be the first evidence of a Lorentz-violating effect and string theory could be put in some difficulty if this result should be confirmed. Theories introducing Lorentz-violating terms have been known for years. These are generally connected to possible formulations of quantum gravity and someone claimed them incorrect just because string mainstream needed a perfect Lorentz symmetry. Besides, in the sixties of the last century, tachyons were introduced by Gerald Feinberg (see here). These are particle with an immaginary mass and so, they could never be seen at rest. But their quantum field theory has an instability in the ground state that would change their nature from superluminal to subluminal breaking symmetry. You can realize this immediately if you have in mind a Higgs field. Neutrinos are Fermions but this does not change too much such a conclusion as for these particles a formulation of spin-statistics theorem could be a mess. But even if we accept their existence, a paper today on arxiv by Giovanni Amelino-Camelia, Giulia Gubitosi, Niccoló Loret, Flavio Mercati, Giacomo Rosati and Paolo Lipari (see here) rules them out as a possible explanation for the OPERA effect. This paper and the other by Giacomo Cacciapaglia, Aldo Deandrea, Luca Panizzi (see here) show that a proper analysis should be accomplished using a modified dispersion relation between energy and momenta. This is perfectly in line with the recently proposal for a modified special relativity that has Amelino-Camelia as one of the proponents. Anyhow, as emphasized by these authors, an in-depth scrutiny of the OPERA experiment is in need as the fits seem to point toward a somewhat exotic dispersion relation even if a kind of fit can be found. On the other side, Cacciapaglia&al. seem to find a fit with non-integer exponent putting OPERA result somewhat out of the theoretical proposals of these last years.
From a string theory standpoint, it appears a rather strange situation even if it is possible to propose modified formulations accounting for the Lorentz-violation and the reason relies on the fact that, essentially, one starts from a fully-fledged quantum field theory preserving all the cherished symmetries. We just point out that what appears today in view is a world with no strings and supersymmetry not even in sight but this is a rapidly changing scenario having LHC at full steam.
Finally, this appears the first significant move toward new physics and a great one indeed arising from an important collaboration. With LHC at full power and other labs now tuned, the future appears quite exciting.
The OPERA Collaboraton: T. Adam, N. Agafonova, A. Aleksandrov, O. Altinok, P. Alvarez Sanchez, S. Aoki, A. Ariga, T. Ariga, D. Autiero, A. Badertscher, A. Ben Dhahbi, A. Bertolin, C. Bozza, T. Brugiére, F. Brunet, G. Brunetti, S. Buontempo, F. Cavanna, A. Cazes, L. Chaussard, M. Chernyavskiy, V. Chiarella, A. Chukanov, G. Colosimo, M. Crespi, N. D’Ambrosios, Y. Déclais, P. del Amo Sanchez, G. De Lellis, M. De Serio, F. Di Capua, F. Cavanna, A. Di Crescenzo, D. Di Ferdinando, N. Di Marco, S. Dmitrievsky, M. Dracos, D. Duchesneau, S. Dusini, J. Ebert, I. Eftimiopolous, O. Egorov, A. Ereditato, L. S. Esposito, J. Favier, T. Ferber, R. A. Fini, T. Fukuda, A. Garfagnini, G. Giacomelli, C. Girerd, M. Giorgini, M. Giovannozzi, J. Goldberga, C. Göllnitz, L. Goncharova, Y. Gornushkin, G. Grella, F. Griantia, E. Gschewentner, C. Guerin, A. M. Guler, C. Gustavino, K. Hamada, T. Hara, M. Hierholzer, A. Hollnagel, M. Ieva, H. Ishida, K. Ishiguro, K. Jakovcic, C. Jollet, M. Jones, F. Juget, M. Kamiscioglu, J. Kawada, S. H. Kim, M. Kimura, N. Kitagawa, B. Klicek, J. Knuesel, K. Kodama, M. Komatsu, U. Kose, I. Kreslo, C. Lazzaro, J. Lenkeit, A. Ljubicic, A. Longhin, A. Malgin, G. Mandrioli, J. Marteau, T. Matsuo, N. Mauri, A. Mazzoni, E. Medinaceli, F. Meisel, A. Meregaglia, P. Migliozzi, S. Mikado, D. Missiaen, K. Morishima, U. Moser, M. T. Muciaccia, N. Naganawa, T. Naka, M. Nakamura, T. Nakano, Y. Nakatsuka, D. Naumov, V. Nikitina, S. Ogawa, N. Okateva, A. Olchevsky, O. Palamara, A. Paoloni, B. D. Park, I. G. Park, A. Pastore, L. Patrizii, E. Pennacchio, H. Pessard, C. Pistillo, N. Polukhina, M. Pozzato, K. Pretzl, F. Pupilli, R. Rescigno, T. Roganova, H. Rokujo, G. Rosa, I. Rostovtseva, A. Rubbia, A. Russo, O. Sato, Y. Sato, A. Schembri, J. Schuler, L. Scotto Lavina, J. Serrano, A. Sheshukov, H. Shibuya, G. Shoziyoev, S. Simone, M. Sioli, C. Sirignano, G. Sirri, J. S. Song, M. Spinetti, N. Starkov, M. Stellacci, M. Stipcevic, T. Strauss, P. Strolin, S. Takahashi, M. Tenti, F. Terranova, I. Tezuka, V. Tioukov, P. Tolun, T. Tran, S. Tufanli, P. Vilain, M. Vladimirov, L. Votano, J. -L. Vuilleumier, G. Wilquet, B. Wonsak, J. Wurtz, C. S. Yoon, J. Yoshida, Y. Zaitsev, S. Zemskova, & A. Zghiche (2011). Measurement of the neutrino velocity with the OPERA detector in the CNGS
beam arXiv arXiv: 1109.4897v1
Feinberg, G. (1967). Possibility of Faster-Than-Light Particles Physical Review, 159 (5), 1089-1105 DOI: 10.1103/PhysRev.159.1089
Giovanni Amelino-Camelia, Giulia Gubitosi, Niccoló Loret, Flavio Mercati, Giacomo Rosati, & Paolo Lipari (2011). OPERA-reassessing data on the energy dependence of the speed of neutrinos arXiv arXiv: 1109.5172v1
Giacomo Cacciapaglia, Aldo Deandrea, & Luca Panizzi (2011). Superluminal neutrinos in long baseline experiments and SN1987a arXiv arXiv: 1109.4980v1