Neutrino, discovery

L. Lederman (Batavia, Illinois), M. Schwartz (Mountain View, California) and J. Steinberger (Geneva) for the neutrino beam method and the demonstration of the doublet structure of the leptons through the discovery of the muon neutrino. 

M. L. Perl (Stanford) and F. Reines (Irvine, California) pioneering experimental contributions to lepton physics (discovery of the tau particle and detection of the neutrino, respectively). 

Trillions of neutrinos are flying through your body as you read this. Created by the Big Bang, stars, and the collision of cosmic rays with the earth s atmosphere, neutrinos outnumber electrons and protons by 600 million to 1. [For more information, see. Gibbs, W. (1998) A massive discovery. Scientific American. August, 279(2) 18-19.]... 

The longstanding idea of superluminal motion has become subject to renewed interest, due to a number of recent discoveries and observations, as described in a survey by Recami [27]. Thus the squared mass of muon-neutrinos is found to be negative. There are further observations that can be interpreted as superluminal expansions inside quasars, in some galaxies and in galactic objects. Also, so called X-shaped waves have been observed [69] to propagate at a... 

Another kind of particle and another kind of interaction were discovered from a detailed study of beta radioactivity in which electrons with a continuous spectrum of energies are emitted by an unstable nucleus. The corresponding interactions could be viewed as being due to the virtual transmutation of a neutron into a proton, an electron, and a new neutral particle of vanishing mass called the neutrino. The theory provided such a successful systematization of beta decay rate data for several nuclei that the existence of the neutrino was well established more than 20 years before its experimental discovery. The beta decay interaction was very weak even compared to the electron-photon interaction. 

Under Ya.B. s guidance the theory of disc accretion was developed and received recognition and experimental verification. We note that all this work was basically performed before the experimental discoveries. Still awaiting experimental confirmation is the burst of neutrino radiation accompanying the collapse of a star, which Ya.B. examined together with O. Kh. Guseinov... 

Weak Interactions were treated by Pais who, starting from Fermi s original theory, discussed the discovery by Lee and Yang,74 almost 5 years before, of the parity violation by weak interactions, its experimental confirmation,75 the muon-electron universality,76 the idea of an intermediate boson as a mediator of weak interaction, and the two-neutrinos question. 77... 

J. P. Vigier, Charmed quark discovery in anti-neutrino nucleon scattering Lett. Nuovo Cimento 15(2) (Ser. 2), 41 48 (1976). 

Although I will not discuss the subject here, The most important secondary cosmic-ray flux is the atmospheric neutrino beam because of the discovery of neutrino oscillations by Super-Kamiokande (Fukuda el al., 1998). The experimental situation is reviewed by Kajita Totsuka, 2001 and Jung el al., 2001, and the calculations by Gaisser Honda, 2002. 

Despite all these impressive progress, we are still too far from the ultimate theory of everything. I listed some obvious avenues for future research in particle physics and cosmology. If I am allowed to say my personal prejudice, I would say that the flavor problem is beyond our reach for years to come, but our understanding of the law of force may further be advanced by a new discovery of violation of empirical conservation laws. The Majorana nature of neutrino masses and proton decay are just manifestation of violation of lepton and baryon numbers, and in my view there is no fundamental obstacle against these being discovered in future, however remote it might be. 

The theory of baryogenesis requires new physics beyond the standard model. Fortunately, we already have nice hits universality of three gauge couplings, the discovery of a finite neutrino mass, and recent results from WMAP, indicating convincing evidence for the dark matter, presumably some sort of still unknown elementary particles. 

The forthcoming km3 neutrino telescopes are discovery detectors that could widen the knowledge of the Universe. These detectors have high potential to solve questions as the detection of UHECR sources, the investigation of hadronic processes in astrophysical environments or massive dark matter. Strong scientific motivations suggest the construction of two km3 scale detectors in the Northern and the Southern Hemisphere. 

UHECRs are attractive because of their high centre-of mass energy. The proton-nucleon cross section for BH formation is very small compared to other hadronic processes. The neutrino-nucleon cross section for BH formation may be higher than the SM process, thereby giving interest to neutrino interaction. However, rate counting is not sufficient to prove black hole formation in the atmosphere. Discovery of BHs in UHECRs requires discrimination of BH and SM air showers. The extensive air shower (EAS) characteristics of these processes will differ, and with new detector methods and enough statistics expected from the new generation cosmic ray observatories, it may be possible to detect BH-induced EASs. 

It is remarkable that Fermi introduced this essentially correct interaction only two years after the discovery of the neutron and one year after Pauli s hypothesis of the neutrino. Fermi modeled his interaction after QED, with = 7p, but the actual interaction has to be determined by experiment. After a confusing period in which experiments appeared to indicate tensor-type interactions, the so-called V-A theory was developed, which has the remarkable feature of breaking parity invariance. Specifically, one has Fp = 7 (1 — 75), in which the 7 75 part changes sign under a parity transformation. The V-A interaction creates particles with negative helic-ity, which means that, if they have velocities close to the speed of light, their spins are oriented against the direction of motion. 

During his period of study in Germany, Chadwick discovered that j8-rays (electrons) are emitted in a continuous spectrum, at odds with other groups results, and a finding that eventually led to the theory and discovery of the neutrino. While he was in Germany, World War I broke out, and Chadwick was rounded up with other Engfish in the country and interned at Ruhleben. 

The neutrino plays an essential role in the models of elemoitaiy particles and in the theory of the formation and development of the universe. The existrace of the neutrino was predicted by Pauli in 1927 but it was not proven until 1956 when Reines and Cowan detected them in experiments at the Savannah River (USA) nuclear reactor. Since neutrinos are emitted in the j3-decays following fission, nuclear reactors are the most intense neutrino sources on earth. The detector in the discovery experiments consisted of a scintillating solution containing cadmium surrounded by photomultipliers to observe the scintillations which occurred as a consequoice of the following reactions ... 

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