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Title: Connecting low energy leptonic CP violation to leptogenesis

Abstract

It was commonly thought that the observation of low energy leptonic CP-violating phases would not automatically imply the existence of a baryon asymmetry in the leptogenesis scenario. This conclusion does not generically hold when the issue of flavor is relevant and properly taken into account in leptogenesis. We illustrate this point with various examples studying the correlation between the baryon asymmetry and the CP-violating asymmetry in neutrino oscillations and the effective Majorana mass in neutrinoless double beta decay.

Authors:
 [1];  [2];  [3];  [1];  [4]
  1. CERN, Theory Division, Geneva 23, CH-1211 (Switzerland)
  2. (United Kingdom)
  3. SISSA and INFN, Sezione di Trieste, I-34014, Trieste (Italy)
  4. (Italy)
Publication Date:
OSTI Identifier:
21020353
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 8; Other Information: DOI: 10.1103/PhysRevD.75.083511; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; BARYONS; CORRELATIONS; CP INVARIANCE; DOUBLE BETA DECAY; FLAVOR MODEL; NEUTRINO OSCILLATION; REST MASS

Citation Formats

Pascoli, S., IPPP, Dept. of Physics, University of Durham, DH1 3LE, Petcov, S. T., Riotto, Antonio, and INFN, Sezione di Padova, Via Marzolo 8, 35131. Connecting low energy leptonic CP violation to leptogenesis. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.083511.
Pascoli, S., IPPP, Dept. of Physics, University of Durham, DH1 3LE, Petcov, S. T., Riotto, Antonio, & INFN, Sezione di Padova, Via Marzolo 8, 35131. Connecting low energy leptonic CP violation to leptogenesis. United States. doi:10.1103/PHYSREVD.75.083511.
Pascoli, S., IPPP, Dept. of Physics, University of Durham, DH1 3LE, Petcov, S. T., Riotto, Antonio, and INFN, Sezione di Padova, Via Marzolo 8, 35131. Sun . "Connecting low energy leptonic CP violation to leptogenesis". United States. doi:10.1103/PHYSREVD.75.083511.
@article{osti_21020353,
title = {Connecting low energy leptonic CP violation to leptogenesis},
author = {Pascoli, S. and IPPP, Dept. of Physics, University of Durham, DH1 3LE and Petcov, S. T. and Riotto, Antonio and INFN, Sezione di Padova, Via Marzolo 8, 35131},
abstractNote = {It was commonly thought that the observation of low energy leptonic CP-violating phases would not automatically imply the existence of a baryon asymmetry in the leptogenesis scenario. This conclusion does not generically hold when the issue of flavor is relevant and properly taken into account in leptogenesis. We illustrate this point with various examples studying the correlation between the baryon asymmetry and the CP-violating asymmetry in neutrino oscillations and the effective Majorana mass in neutrinoless double beta decay.},
doi = {10.1103/PHYSREVD.75.083511},
journal = {Physical Review. D, Particles Fields},
number = 8,
volume = 75,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • If the baryon asymmetry of the Universe is produced by leptogenesis, CP violation is required in the lepton sector. In the seesaw extension of the standard model with three hierarchical right-handed neutrinos, we show that the baryon asymmetry is insensitive to the Pontecorvo-Maki-Nagakawa-Sakata phases: thermal leptogenesis can work for any value of the observable phases. This result was well known when there were no flavor effects in leptogenesis; we show that it remains true when flavor effects are included.
  • In the minimal left-right symmetric model, there are only two intrinsic CP violating phases to account for all CP violation in both the quark and lepton sectors, if CP is broken spontaneously by the complex phases in the VEV's of the scalar fields. In addition, the left- and right-handed Majorana mass terms for the neutrinos are proportional to each other due to the parity in the model. This is thus a very constrained framework, making the existence of correlations among the CP violation in leptogenesis, neutrino oscillation and neutrinoless double beta decay possible. In these models, CP violation in themore » leptonic sector and CP violation in the quark sector are also related. We find, however, that such connection is rather weak due to the large hierarchy in the bi-doublet VEV required by a realistic quark sector.« less
  • Within the context of the see-saw mechanism, we review the possible connection between the CP-violating phases which appear in the lepton unitary mixing matrix and are measurable in neutrino oscillations and other low-energy processes, with the ones which play a role in the generation of the baryon asymmetry of the universe through the leptogenesis mechanism.
  • It is well-known that for unflavored leptogenesis there is in general no connection between low and high energy CP violation. We stress that for a non-unitary lepton mixing matrix this may not be the case. We give an illustrative example for this connection and show that the non-standard CP phases that are induced by non-unitarity can be responsible for observable effects in neutrino oscillation experiments as well as for the generation of the baryon asymmetry of the Universe.
  • We further study the previously proposed ansatz, Tr(M{sub {nu}})=0, for a prediagonal light Majorana type neutrino mass matrix. If CP violation is neglected this enables one to use the existing data on squared mass differences to estimate (up to a discrete ambiguity) the neutrino masses themselves. If it is assumed that only the conventional CP phase is present, the ansatz enables us to estimate this phase in addition to all three masses. If it is assumed that only the two Majorana CP phases are present, the ansatz enables us to present a one parameter family of solutions for the massesmore » and phases. This enables us to obtain a simple 'global' view of lepton number violation effects. Furthermore using an SO(10) motivation for the ansatz suggests an amusing toy (clone) model in which the heavy neutrinos have the same mixing pattern and mass ratios as the light ones. In this case only their overall mass scale is not known (although it is constrained by the initial motivation). Using this toy model we make a rough estimate of the magnitude of the baryon to photon ratio induced by the leptogenesis mechanism. Solutions close to the CP conserving cases seem to be favored.« less