LHC and the Origin of Neutrino Mass

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Graduate Physics Seminar Monday, 28 February 2011 from 4 PM University of Nova Gorica, Ajdovščina site Auditorium Prof. Dr. Goran Senjanović The Abdus Salam International Centre for Theoretical Physics Trieste, Italy LHC and the origin of neutrino mass Abstract The physics of elementary particles is almost completely governed by symmetries. One particular symmetry stands out: the one between left and right, called parity, probably the first symmetry a child sees. Its maximal breaking in beta decay created a bombshell more than fifty years ago, and ultimately led to the creation of the Standard Model of all interactions (except gravity), whose final crowning confirmation is to be provided by the Large Hadron Collider (LHC) at CERN if successful in its hunt of the Higgs particle. The Standard Model is based on the basic premise of parity being broken always, at all energies, and being broken maximally. I argue, on the contrary, that in nature left-right symmetry is fundamental, and that at the high energies of the LHC one could actually see its restoration in full glory. I show how this is connected to the nature of the neutrino, a mysterious particle that we are still probing, eighty years after its conception and more than half a century after its discovery. I have been involved in the development of the Left-Right symmetric theory from its beginning, and more recently in its role in the possible creation of electrons out of 'nothing' at the LHC, and in neutrinoless double-beta decay. An essential role in this is played by the 'seesaw' mechanism of small neutrino mass, that emerged naturally from the idea of left-right symmetry, and that hopefully could be probed at the LHC. .

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LHC and the Origin of Neutrino Mass§
LHC and the origin of neutrino massx Goran Senjanović International Centre for Theoretical Physics, 34100 Trieste, Italy Abstract It is often said that neutrino mass is a window to a new physics beyond the standard model (SM). This is certainly true if neutrinos are Majorana particles since the SM with Majorana neutrino mass is not a complete theory. The classical text-book test of neutrino Majorana mass, the neutrino-less double beta decay depends on the completion, and thus cannot probe neutrino mass. As pointed out already more than twenty five years ago, the colliders such as Tevatron or LHC offer a hope of probing directly the origin of neutrino Majorana mass through lepton number violating production of like sign lepton pairs. I discuss this in the context of all three types of seesaw mechanism. I then discuss in detail the situation in L − R symmetric theories, which led originally to the seesaw and which incorporate naturally both type I and type II. A WR gauge boson with a mass in a few TeV region could easily dominate neutrino-less double beta decay, and its discovery at LHC would have spectacular signatures of parity restoration and lepton number violation. At the end I give an example of a predictive SU(5) grand unified theory that results in a hybrid type I and III seesaw with a light fermion triplet below TeV scale. 1 Introduction If M is huge, there is no hope of direct observation of new physics. It is often said that large M is more We know that neutrinos are massive but light [1].
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Curriculum Vitae
CURRICULUM VITAE Name: Goran Senjanović Place/Date of Birth: Beograd, Jugoslavia, 9/6/1950 Nationality: Croatian Present Address: Gran Sasso Science Institute, GSSI Viale Francesco Crispi 7, L'Aquila, Italy. International Centre for Theoretical Physics, ICTP Strada Costiera 11, Trieste, Italy. Electronic mail: [email protected] Phone: +39-345-1700994, +385-(0)99-4106944 Foreign Languages: English, Italian, Spanish, French Marital Status: Divorced, one child. Education • BSc University of Beograd, Beograd, Yugoslavia, 1973. • PhD City College of New York, New York, USA, 1978. Positions Held • (1978 -1980): Postdoctoral Research Associate, University of Maryland, Maryland, USA. • (1980 -1982): Assistant Physicist, Brookhaven National Laboratory, Long Island, USA. • (1982 -1987): Associate Physicist, Brookhaven National Laboratory. 1 • (1987- 1993): Professor of Physics, University of Zagreb, Zagreb, Croatia. • (1991 -2013): Research Scientist (staff), International Centre for Theoretical Physics, Trieste, Italy. • (2013 - present) Emeritus Staff Associate, ICTP, Trieste, Italy. • (October 2013 - present) Director of Research, Gran Sasso Science Institute, L'Aquila, Italy Long-term on-leave Positions • (1983 -1984) Institute for Theoretical Physics, Santa Barbara, Califor- nia, USA. • (1984-1985) Virginia State University, Blacksburg, Virginia, USA • (1990 -1991) CERN, Geneva, Switzerland. Professional recognition • ICTP node representative of the EU 5th framework programme \Su- persymmetry and the early Universe" (2000-2004). • ICTP
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Disentangling the Seesaw Mechanism in the Minimal Left-Right Symmetric Model
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Closing Remarks
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363 CERN .Geneva, Switzerland
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