Hindawi Publishing Corporation Advances in High Energy Physics Volume 2014, Article ID 823127, 4 pages http://dx.doi.org/10.1155/2014/823127

Editorial Neutrino Masses and Oscillations

Elisa Bernardini,1 Leslie Camilleri,2 Vincenzo Flaminio,3 Srubabati Goswami,4 and Seon-Hee Seo5

1 DESY, Platanen Allee 6, 15738 Zeuthen, Germany 2 Columbia University 435 W. 116th Street, New York, NY 10027-7201, USA 3 Physics Department and INFN, Largo Bruno Pontecorvo, 56127 Pisa, Italy 4 Physical Research Laboratory, Navrangpura, Ahmedabad 380009, India 5 Department of Physics and Astronomy, Seoul National University, Republic of Korea

Correspondence should be addressed to Vincenzo Flaminio; [email protected]

Received 17 December 2013; Accepted 17 December 2013; Published 30 March 2014

Copyright © 2014 Elisa Bernardini et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The publication of this article was funded by SCOAP3.

The year 2013 marks the 100th anniversary of the birth of originated a vast number of both experimental and theoreti- Bruno Pontecorvo, who first suggested the possibility that cal developments. neutrinos might have a nonzero mass such that oscillations The original ideas (1957-58) are first considered in this among different neutrino states might occur. Pontecorvo paper. This is followed by the consideration of a later paper constantly pursued this idea, after the discovery of other by Pontecorvo on neutrino oscillations (1967) and by the neutrino flavours, until his death. anticipation of the solar neutrino problem. The article by V. Thisissueisintendedasacontributiontothecelebration Gribov and B. Pontecorvo where for the first time a solid the- of this anniversary, by collecting a number of articles on oretical formulation of neutrino oscillations (1969) was given neutrino masses and neutrino oscillations, both of which is then considered. The general theory of neutrino mixing have been the subject of extensive studies and have seen a and oscillations and proposals of different experiments on tremendous progress over the last decades. the search for neutrino oscillations by S. M. Bilenky and B. The subject of neutrino mass acquires an even bigger int- Pontecorvo (1975–1989) are finally discussed in detail. erest after the recent announcement of the existence of a new The paper “Four-neutrino analysis of 1.5 km baseline reac- boson which is likely to be the elusive Higgs boson. tor antineutrino oscillations” by S. K. Kang et al. describes This represents a beautiful confirmation of several aspects sterile neutrinos which might be discovered in 1.5 km baseline ofthestandardmodel.However,inthepresentformulationof reactor neutrino experiments. Using recent data from RENO the standard model neutrinos are massless, in contradiction and Daya Bay, the authors performed an analysis of sterile 2 with their tiny masses as inferred by oscillation experiments. neutrino search assuming a 3 + 1 scheme with 0.1 eV < 2 2 Some models link this smallness to the existence of very Δ𝑚14 <1eV . They have not found any evidence yet of sterile heavy mass states, thus opening a window on a much higher neutrinos. mass scale. The paper “Phenomenology of MaVaN’s models in reactor Therefore, the issues of neutrino mass and of lepton neutrino data” by M. F. Carneiro and P. C. de Holanda number violation add an unprecedented momentum in the describes a mechanism of mass varying neutrinos (MaVaN’s) quest for new physics beyond the standard model. which connects to the neutrino mass scale with the dark This issue includes the article “Bruno pontecorvo and energy density. The authors studied the phenomenological neutrino oscillations”byS.M.Bilenky,alongtimeclose consequence of MaVaN’s scenarios assuming a normal hier- collaborator of Bruno Pontecorvo, who gives an overview of archy and using the KamLAND data. They also introduced thelargenumberofideasproposedbyPontecorvo,which an Earth’s crust model to compute precisely the density of 2 Advances in High Energy Physics the Earth along the neutrino trajectory. They observed that the three major unknowns in neutrino physics—namely, the new physics is more than a subleading effect and will improve mass hierarchy, the octant of atmospheric mixing angle, and 𝛿 theanalysisinthenearfuturewithsolarneutrinodata. the leptonic CP phase CP in the light of the moderately large In the paper “The MINOS experiment: results and value of 𝜃13 measured by the reactor experiments. The capa- prospects”byJ.J.Evans,theobservationsof]𝜇 and anti-]𝜇 bilities of the current generation long-baseline experiments, disappearance by the long baseline MINOS magnetized iron T2K and NOVA, and the reach of the future experiments experiment are described as well as their study of atmospheric like LBNE, LBNO, and so forth, which can determine these neutrinos. These measurements yielded the most precise quantities with high precision, are also presented. value of the larger neutrino mass splitting and an indication The paper “Measurement of neutrino oscillations with neu- of a nonzero 𝜃13. Future prospects, in particular on the search trino telescopes” by J. Brunner treats the potential of current for sterile neutrinos, are outlined. instruments (IceCube and ANTARES) as well as planned The paper “The NOMAD experiment at CERN”byF.Van- low energy extensions (PINGU and ORCA) in measuring nucci describes an experiment searching for ]𝜇 −]𝜏 and ]𝜇 −]𝑒 neutrino oscillations. While the primary scientific goal of this 2 2 4 oscillations at Δ𝑚 at or above 10 eV /c and the limits that class of experiments is the detection of cosmic neutrinos in were set. In addition it describes the additional measurements the TeV-PeV range, recent calculations have shown interest- that were made possible by the large data sample collected by ing potential in improving experimental measurements of this magnetic detector and by its openness. the atmospheric neutrino oscillation parameters, as well as The paper “Evidence and search for sterile neutrinos at in addressing the question of the neutrino mass hierarchy. accelerators”byW.C.LouisdescribesthelongstandingLSND Complementarity with measurements in a long baseline result of an unexpected appearance of anti-]𝑒 events which, neutrino beam is also discussed. if ascribed to anti-]𝜇 to anti-]𝑒 oscillations, could only be The paper “Neutrino oscillations in the atmospheric explained by the existence of a fourth and sterile neutrino parameter region: from the early experiments to the present”by 2 with a mass of about 1 eV/c . The MiniBooNE measurements, G. Giacomelli et al. reviews experimental results on neutrino including an additional unexpected observation of a low oscillations in the atmospheric sector from early experi- energy excess of electromagnetic origin, are also discussed ments, which observed a deficit of muon neutrinos in deep and so are future experiments such as MicroBooNE. underground detectors, to the present, after the availability In the paper “Cyclotrons as drivers for precision neutrino of artificial neutrino beams. Recollections on key results from measurements”byA.Adelmannetal.,theR&Dstatusfor solar neutrino measurements, neutrino telescopes as well as high intensity cyclotrons and proposed searches for sterile on reactor neutrinos are also given. Prospects for the future 2 are briefly given. neutrinos with masses of about 1 eV/c that use them are The paper “Studying the Earth with geoneutrinos”byL. described. The improvements to the sensitivities to CP vio- Ludhova and S. Zavatarelli presents a review on neutrino lation searches in the neutrino sector and the determination geophysics covering all the major recent publications in this of the mass hierarchy through the addition of cyclotrons to field. The authors also discuss the results of an analysis proposed Long Base Line Beams are also described. based on a more refined model for the Mantle compared to The paper “The study of neutrino oscillations with emul- previous literature. They conclude that the current and near sion detectors” by A. Ereditato describes the evolution of future geoneutrino measurements are not sensitive enough to emulsion detectors and their applications to neutrino physics. distinguish different mantle models. Their superb spatial resolution was instrumental in pro- ] The paper “Neutrino oscillations”byG.Bellinietal., viding the first observation of directly produced 𝜏’s in describes the theoretical background of the neutrino oscil- the DONUT experiment followed by the recording by the lation phenomenon. An overview of the different techniques OPERA experiment of ]𝜏 events that appeared in a ]𝜇 beam ] − ] used (or being used) with neutrinos from different sources through 𝜇 𝜏 oscillations. is then given and results are discussed. Open questions and The paper “Nuclear effects in neutrino interactions and perspectives for the future are also finally analyzed. theirimpactonthedeterminationofoscillationparameters” The paper “Cosmic dark radiation and neutrinos”by by O. Benhar and N. Rocco investigates the effects of nuclear M. Archidiacono et al. discusses the possible existence of dynamicsonthemeasuredneutrino-nucleuscrosssection. dark radiation, a weakly interacting component of radia- The theoretical approach based on the impulse approxi- tion, in a cosmological model testable by Planck and other mation and the use of realistic nucleon spectral functions, observational probes. The article reviews the most recent allowing one to describe a variety of reaction mechanisms cosmological results and presents a complete investigation of active in the broad kinematical range covered by neutrino the dark radiation sector with an overview of models that experiments, are reviewed. The extension of this scheme try to explain the presence of dark radiation relating it to to include more complex mechanisms involving the two- sterile neutrinos. An update on cosmological constraints on nucleon current is also discussed. The impact of nuclear neutrino physics and dark radiation properties is also given. effects on the determination of neutrino oscillation parame- The paper “Challenges in double beta decay”byO.Cre- ters is illustrated by analyzing the problem of neutrino energy monesi and M. Pavan gives a critical overview of many reconstruction. experiments on the search for neutrinoless double beta decay The paper “Physics potential of long-baseline experiments” of nuclei. Starting from the consideration that the observation by S. K. Agarwalla reviews the prospect of measuring of neutrino oscillations implies a nonzero neutrino mass, one Advances in High Energy Physics 3 is indeed led to conclude that the neutrinoless double beta theideaofcombiningabolometrictechnique(alreadyused decay of a number of different nuclei is possible, provided in the CUORE experiment) with a light detection technique that neutrinos are Majorana particles. If successful, such in the search for neutrinoless double-beta decay. The bolo- experiments might also provide information on the absolute metric technique allows an extremely good energy resolution mass scale (hierarchy) of neutrinos. The authors describe the while its combination with the scintillation detection offers most recent experiments, the limits so far obtained, and the an ultimate tool for background rejection. The collaboration prospects for the future. has performed preliminary tests on several detectors contain- The paper “Present status and future perspectives of the ing different interesting double-beta emitters, clearly demon- NEXT experiment” by J. J. G. Cadenas et al. describes the strating the excellent background rejection capabilities that status and perspectives of the neutrino experiment with a arise from the simultaneous, independent, double readout of Xenon TPC (NEXT), a novel approach to the search for heat and scintillation light. neutrinoless double beta decay which combines the use of a The paper “Present status and future perspectives for the suitable target (xenon) with a refined experimental technique EXO-200 experiment” by G. Gratta and D. Sinclair discusses (a high pressure xenon chamber using electroluminescence the design, construction, and operational details of an exper- and optical readouts) to provide excellent energy resolution iment aiming at the detection of neutrinoless double-beta 136 (0.5% FWHM at 2.5 MeV) and a clean topological signature decay of Xe. The experiment has used 200 kg of liquid 136 (the observation of the two electrons characterizing the decay, xenonenrichedto81%in Xe. They give details of the very which are seen as clear tracks ending in ionization blobs at the good results obtained so far and their significance. They end of the chamber). mention how the excellent performance of the detector The paper “The potential of hybrid pixel detectors in the encourages the concept of a much larger detector to obtain 116 search for the neutrinoless double-beta decay of Cd” by T. improved sensitivity to the possible detection of the neutri- Michel et al. describes the potential benefit of state-of-the- noless decay mode of xenon. art hybrid photon counting pixel detectors—especially the The paper “The Majorana demonstrator neutrinoless Timepix detector—within pixel signal digitization equipped double-beta decay experiment” by J. Gruszko describes the with CdTe sensor layers in the search for the neutrinoless initial stage of an experiment aiming at the detection of neu- 116 76 double-beta decay of Cd. They discuss the background trinoless double-beta decay of Ge. The Majorana demon- reduction potential (against single electrons from beta decays strator uses a 30 kg mixed array of enriched and natural or from Compton scattering) released in the bulk of the detec- germanium detectors. The demonstrator is being assembled tor by track analysis and derive values for the improvement at the 4850-foot level of the Sanford Underground Research of sensitivity with respect to the effective Majorana neutrino Facility in Lead, South Dakota. The array will be situated in mass that might be achieved applying track analysis. a low-background environment and surrounded by passive The paper “Current status and future perspectives of the andactiveshielding.Theauthorsdescribethesciencegoals COBRA experiment” by J. Ebert et al. describes a detector of the Demonstrator and the details of its design. array made of cadmium-zinc-telluride (CdZnTe) semicon- In the paper “Neutrinoless double beta+/EC decays”by + ductor detectors operating at the Gran Sasso Underground J. Maalampi and J. Suhonen various positron emitting 𝛽 Laboratory (LNGS) in Italy, used in the search for the and electron capture (EC) decay modes of neutrinoless 116 neutrinoless double-beta decay of Cd. The experiment is double-beta decay were studied. Nuclear matrix elements for currently investigating the experimental issues of operating various processes have been computed using a QRPA based CdZnTe detectors in low background mode and identifying framework. These were compared with those for double beta potential background components, whilst additional stud- minus decay. Special attention has been paid to the resonant ies are proceeding in surface laboratories. The experiment neutrinoless double electron capture process to investigate currently consists of monolithic, calorimetric detectors of its potential for the understanding of the role of Majorana coplanar grid design (CPG detectors). The article gives an neutrinos in different experiments. overview of the current status of the experiment and future The paper “Lepton flavour violation experiments”byF.Cei perspectives. and D. Nicolo` provides a comprehensive review of past and The paper “Status of the GERDA experiment at the Labor- recent results in the field of lepton flavour violation, both in atori Nazionali del Gran Sasso”byR.BrugneraandA. channels involving muons and taus. They discuss currently Garfagnini describes a search for neutrinoless double-beta operating experiments as well as future projects, with empha- 76 decay of Ge, currently going on at Laboratori Nazionali sis laid on how sensitivity enhancements are accompanied del Gran Sasso in Italy. The experiment has recently reported by improvements in detection techniques. Limitations due to results that are the most sensitive in the decay of this systematic effects are also discussed in detail together with the 2 isotope, reaching values of the order of 0.23–0.39 eV/c for solutions being adopted to overcome them. the effective neutrino Majorana mass. They also describe The paper “Studyofneutrinoreactionsforlowvaluesof 2 the planned increase in sensitivity by using a more massive 𝑄 ”byE.A.PaschosandD.Schallapresentsacalculation 2 (100 kg) Ge detector, accompanied by a substantial back- of the production of pions by neutrinos in the small 𝑄 ground reduction. region using results of PCAC and experimental data. In The paper “Current status and future perspectives of the this kinematic region the contribution of many of the form LUCIFER experiment” by J. W. Beeman et al. describes factors is suppressed. The results for the cross section are used 4 Advances in High Energy Physics to compute the yields in the MiniBooNE experiment. The results can also be useful in determining the background for coherent scattering. Elisa Bernardini Leslie Camilleri Vincenzo Flaminio Srubabati Goswami Seon-Hee Seo Copyright of Advances in High Energy Physics is the property of Hindawi Publishing Corporation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.