The B - L scotogenic models for Dirac neutrino masses

Energy Technology Data Exchange (ETDEWEB)

Wang, Weijian [North China Electric Power University, Department of Physics, Baoding (China); Wang, Ruihong [Hebei Agricultural University, College of Information Science and Technology, Baoding (China); Han, Zhi-Long [University of Jinan, School of Physics and Technology, Jinan, Shandong (China); Han, Jin-Zhong [Zhoukou Normal University, School of Physics and Telecommunications Engineering, Zhoukou, Henan (China)

2017-12-15

We construct the one-loop and two-loop scotogenic models for Dirac neutrino mass generation in the context of U(1){sub B-L} extensions of standard model. It is indicated that the total number of intermediate fermion singlets is uniquely fixed by the anomaly free condition and the new particles may have exotic B - L charges so that the direct SM Yukawa mass term anti ν{sub L}ν{sub R}φ{sup 0} and the Majorana mass term (m{sub N}/2)ν{sub R}{sup C}ν{sub R} are naturally forbidden. After the spontaneous breaking of the U(1){sub B-L} symmetry, the discrete Z{sub 2} or Z{sub 3} symmetry appears as the residual symmetry and gives rise to the stability of intermediate fields as DM candidates. Phenomenological aspects of lepton flavor violation, DM, leptogenesis and LHC signatures are discussed. (orig.)

Symplectic symmetry of the neutrino mass for many neutrino flavors

International Nuclear Information System (INIS)

Oeztuerk, N.; Ankara Univ.

2001-01-01

The algebraic structure of the neutrino mass Hamiltonian is presented for two neutrino flavors considering both Dirac and Majorana mass terms. It is shown that the algebra is Sp(8) and also discussed how the algebraic structure generalizes for the case of more than two neutrino flavors. (orig.)

Can neutrino-electron scattering tell us whether neutrinos are Dirac or Majorana particles?

International Nuclear Information System (INIS)

Kayser, B.

1988-04-01

There has recently been interest in the possibility that neutrino-electron scattering experiments could determine whether neutrinos are Dirac or Majorana particles by providing information on their electromagnetic structure. We try to explain why studies of neutrino electromagnetic structure actually cannot distinguish between Dirac and Majorana neutrinos. 9 refs

Planck-scale physics and neutrino masses

International Nuclear Information System (INIS)

Akhmedov, E.Kh.; Senjanovic, G.; Berezhiani, Z.G.

1992-05-01

We discuss gravitationally induced masses and mass splittings of Majorana, Zeldovich-Konopinski-Mahmoud and Dirac neutrinos. Among other implications, these effects can provide a solution of the solar neutrino puzzle. In particular, we show how this may work in the 17 keV neutrino picture. (author). 18 refs

Thermal dark matter through the Dirac neutrino portal

Science.gov (United States)

Batell, Brian; Han, Tao; McKeen, David; Haghi, Barmak Shams Es

2018-04-01

We study a simple model of thermal dark matter annihilating to standard model neutrinos via the neutrino portal. A (pseudo-)Dirac sterile neutrino serves as a mediator between the visible and the dark sectors, while an approximate lepton number symmetry allows for a large neutrino Yukawa coupling and, in turn, efficient dark matter annihilation. The dark sector consists of two particles, a Dirac fermion and complex scalar, charged under a symmetry that ensures the stability of the dark matter. A generic prediction of the model is a sterile neutrino with a large active-sterile mixing angle that decays primarily invisibly. We derive existing constraints and future projections from direct detection experiments, colliders, rare meson and tau decays, electroweak precision tests, and small scale structure observations. Along with these phenomenological tests, we investigate the consequences of perturbativity and scalar mass fine tuning on the model parameter space. A simple, conservative scheme to confront the various tests with the thermal relic target is outlined, and we demonstrate that much of the cosmologically-motivated parameter space is already constrained. We also identify new probes of this scenario such as multibody kaon decays and Drell-Yan production of W bosons at the LHC.

Understanding neutrino masses and mixings

Indian Academy of Sciences (India)

various possible oscillation solutions to the solar neutrino puzzle. It seems .... A first hint of this new ingredient came from the observation of Weinberg that if ..... Using the discussion of the above paragraph, the Dirac mass of the neutrino as .... that contributes to charged fermion masses, one can write the quark and lepton.

Gauge Trimming of Neutrino Masses

International Nuclear Information System (INIS)

Chen, Mu-Chun; de Gouvea, Andre; Dobrescu, Bogdan A.

2006-01-01

We show that under a new U(1) gauge symmetry, which is non-anomalous in the presence of one ''right-handed neutrino'' per generation and consistent with the standard model Yukawa couplings, the most general fermion charges are determined in terms of four rational parameters. This generalization of the B-L symmetry with generation-dependent lepton charges leads to neutrino masses induced by operators of high dimensionality. Neutrino masses are thus naturally small without invoking physics at energies above the TeV scale, whether neutrinos are Majorana or Dirac fermions. This ''Leptocratic'' Model predicts the existence of light quasi-sterile neutrinos with consequences for cosmology, and implies that collider experiments may reveal the origin of neutrino masses

Question of neutrino mass

International Nuclear Information System (INIS)

Branco, G.C.; Senjanovic, G.

1978-01-01

We investigate the question of neutrino mass in theories in which neutrinos are four-component Dirac particles. Our analysis is done in the framework of left-right--symmetric theories. The requirement of calculability and natural smallness of neutrino mass leads to the following constraints: (i) left and right charged weak currents must be ''orthogonal'' to each other, and (ii) there should be no W/sub L/-W/sub R/ mixing at the three level. Finally, we exhibit a model in which, due to the existence of an unbroken symmetry of the total Lagrangian, the electron and muon neutrinos remain massless to all orders in perturbation theory

Naturally light Dirac neutrino in Left-Right Symmetric Model

Energy Technology Data Exchange (ETDEWEB)

Borah, Debasish [Department of Physics, Indian Institute of Technology Guwahati, Assam-781039 (India); Dasgupta, Arnab, E-mail: dborah@iitg.ernet.in, E-mail: arnab.d@iopb.res.in [Institute of Physics, HBNI, Sachivalaya Marg, Bhubaneshwar-751005 (India)

2017-06-01

We study the possibility of generating tiny Dirac masses of neutrinos in Left-Right Symmetric Model (LRSM) without requiring the existence of any additional symmetries. The charged fermions acquire masses through a universal seesaw mechanism due to the presence of additional vector like fermions. The neutrinos acquire a one-loop Dirac mass from the same additional vector like charged leptons without requiring any additional discrete symmetries. The model can also be extended by an additional Z {sub 2} symmetry in order to have a scotogenic version of this scenario predicting a stable dark matter candidate. We show that the latest Planck upper bound on the effective number of relativistic degrees of freedom N {sub eff}=3.15 ± 0.23 tightly constrains the right sector gauge boson masses to be heavier than 3.548 TeV . This bound on gauge boson mass also affects the allowed values of right scalar doublet dark matter mass from the requirement of satisfying the Planck bound on dark matter relic abundance. We also discuss the possible implications of such a scenario in charged lepton flavour violation and generating observable electric dipole moment of leptons.

Neutrino masses and family replication

International Nuclear Information System (INIS)

Hung, P.Q.

1999-01-01

The issue of whether or not there is any link between the smallness of the neutrino mass (if present) and the odd or even nature of the number of families is investigated. It is found that, by assuming the existence of right-handed neutrinos (which would imply that neutrinos will have a mass) and a new chiral SU(2) gauge theory, a constraint on the nature of the number of families can be obtained. In addition, a model, based on that extra SU(2), is constructed where it is plausible to have one 'very heavy' fourth neutrino and three almost degenerate light neutrinos whose masses are all of the Dirac type. copyright 1999 The American Physical Society

On the Hierarchy of Neutrino Masses

International Nuclear Information System (INIS)

Jezabek, M.; Urban, P.

2002-01-01

We present a model of neutrino masses combining the seesaw mechanism and strong Dirac mass hierarchy and at the same time exhibiting a significantly reduced hierarchy at the level of active neutrino masses. The heavy Majorana masses are assumed to be degenerate. The suppression of the hierarchy is due to a symmetric and unitary operator R whose role is discussed. The model gives realistic mixing and mass spectrum. The mixing of atmospheric neutrinos is attributed to the charged lepton sector whereas the mixing of solar neutrinos is due to the neutrino sector. Small U e3 is a consequence of the model. The masses of the active neutrinos are given by μ 3 ≅ √(Δm 2 O ) and μ 1 /μ 2 = ≅ tan 2 (θ O ). (author)

Distinguishing Dirac/Majorana sterile neutrinos at the LHC

International Nuclear Information System (INIS)

Dib, Claudio O.; Zhang, Jue

2016-06-01

We study the purely leptonic decays of W ± → e ± e ± μ -+ ν and μ ± μ ± e -+ ν produced at the LHC, induced by sterile neutrinos with mass m N below M W in the intermediate state. Since the final state neutrino escapes detection, one cannot tell whether this process violates lepton number, what would indicate a Majorana character for the intermediate sterile neutrino. Our study shows that when the sterile neutrino mixings with electrons and muons are different enough, one can still discriminate between the Dirac and Majorana character of this intermediate neutrino by simply counting and comparing the above decay rates. After performing collider simulations and statistical analysis, we find that at the 14 TeV LHC with an integrated luminosity of 3000 fb -1 , for two benchmark scenarios m N =20 GeV and 50 GeV, at least a 3σ level of exclusion on the Dirac case can be achieved for disparities as mild as e.g. vertical stroke U Ne vertical stroke 2 <0.7 vertical stroke U Nμ vertical stroke 2 or vertical stroke U Nμ vertical stroke 2 <0.7 vertical stroke U Ne vertical stroke 2 , provided that vertical stroke U Ne vertical stroke 2 , vertical stroke U Nμ vertical stroke 2 are both above ∝2 x 10 -6 .

Search for Dirac and Majorana sterile neutrinos in trilepton events at the LHC

International Nuclear Information System (INIS)

Dib, Claudio O.; Kim, C.S.; Wang, Kechen; Chinese Academy of Sciences, Beijing

2017-03-01

Heavy sterile neutrinos with masses below M_W can induce trilepton events at the 14 TeV LHC through purely leptonic W decays of W"±→e"±e"±μ"-"+ν and μ"±μ"±e"-"+ν where the heavy neutrino will be in an intermediate state on its mass shell. Discovery and exclusion limits for the heavy neutrinos are found using both Cut-and-Count (CC) and a Multi-Variate Analysis (MVA) methods in this study. We also show that it is possible to discriminate between a Dirac and a Majorana heavy neutrino, even when lepton number conservation cannot be directly tested due to unobservability of the final state neutrino. This discrimination is done by exploiting a combined set of kinematic observables that differ between the Majorana vs. Dirac cases. We find that the MVA method can greatly enhance the discovering and discrimination limits in comparison with the CC method. With an integrated luminosity of 3000 fb"-"1, sterile neutrinos can be found with 5σ significance if heavy-to-light neutrino mixings vertical stroke U_N_e vertical stroke "2∝ vertical stroke U_N_μ vertical stroke "2∝10"-"6, while the Majorana vs. Dirac type can be distinguished if vertical stroke U_N_e vertical stroke "2∝ vertical stroke U_N_μ vertical stroke "2∝10"-"5 or even vertical stroke U_N_l vertical stroke "2∝10"-"6 if one of mixing elements can be at least one order of magnitude smaller than the other.

Relic right-handed Dirac neutrinos and implications for detection of cosmic neutrino background

Directory of Open Access Journals (Sweden)

Jue Zhang

2016-02-01

Full Text Available It remains to be determined experimentally if massive neutrinos are Majorana or Dirac particles. In this connection, it has been recently suggested that the detection of cosmic neutrino background of left-handed neutrinos νL and right-handed antineutrinos ν‾R in future experiments of neutrino capture on beta-decaying nuclei (e.g., νe+H3→He3+e− for the PTOLEMY experiment is likely to distinguish between Majorana and Dirac neutrinos, since the capture rate is twice larger in the former case. In this paper, we investigate the possible impact of right-handed neutrinos on the capture rate, assuming that massive neutrinos are Dirac particles and both right-handed neutrinos νR and left-handed antineutrinos ν‾L can be efficiently produced in the early Universe. It turns out that the capture rate can be enhanced at most by 28% due to the presence of relic νR and ν‾L with a total number density of 95 cm−3, which should be compared to the number density 336 cm−3 of cosmic neutrino background. The enhancement has actually been limited by the latest cosmological and astrophysical bounds on the effective number of neutrino generations Neff=3.14−0.43+0.44 at the 95% confidence level. For illustration, two possible scenarios have been proposed for thermal production of right-handed neutrinos in the early Universe.

Geometric phase of neutrinos: Differences between Dirac and Majorana neutrinos

Science.gov (United States)

Capolupo, A.; Giampaolo, S. M.; Hiesmayr, B. C.; Vitiello, G.

2018-05-01

We analyze the non-cyclic geometric phase for neutrinos. We find that the geometric phase and the total phase associated to the mixing phenomenon provide a theoretical tool to distinguish between Dirac and Majorana neutrinos. Our results hold for neutrinos propagating in vacuum and through the matter. We feed the values of the experimental parameters in our formulas in order to make contact with experiments. Although it remains an open question how the geometric phase of neutrinos could be detected, our theoretical results may open new scenarios in the investigation of the neutrino nature.

Search for Dirac and Majorana sterile neutrinos in trilepton events at the LHC

Energy Technology Data Exchange (ETDEWEB)

Dib, Claudio O. [Univ. Tecnica Federico Santa Maria, Valparaiso (Chile). CCTVal y Dept. of Physics; Kim, C.S. [Yonsei Univ., Seoul (Korea, Republic of). Dept. of Physics and IPAP; Wang, Kechen [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Chinese Academy of Sciences, Beijing (China). Center for Future High Energy Physics

2017-03-15

Heavy sterile neutrinos with masses below M{sub W} can induce trilepton events at the 14 TeV LHC through purely leptonic W decays of W{sup ±}→e{sup ±}e{sup ±}μ{sup -+}ν and μ{sup ±}μ{sup ±}e{sup -+}ν where the heavy neutrino will be in an intermediate state on its mass shell. Discovery and exclusion limits for the heavy neutrinos are found using both Cut-and-Count (CC) and a Multi-Variate Analysis (MVA) methods in this study. We also show that it is possible to discriminate between a Dirac and a Majorana heavy neutrino, even when lepton number conservation cannot be directly tested due to unobservability of the final state neutrino. This discrimination is done by exploiting a combined set of kinematic observables that differ between the Majorana vs. Dirac cases. We find that the MVA method can greatly enhance the discovering and discrimination limits in comparison with the CC method. With an integrated luminosity of 3000 fb{sup -1}, sterile neutrinos can be found with 5σ significance if heavy-to-light neutrino mixings vertical stroke U{sub Ne} vertical stroke {sup 2}∝ vertical stroke U{sub Nμ} vertical stroke {sup 2}∝10{sup -6}, while the Majorana vs. Dirac type can be distinguished if vertical stroke U{sub Ne} vertical stroke {sup 2}∝ vertical stroke U{sub Nμ} vertical stroke {sup 2}∝10{sup -5} or even vertical stroke U{sub Nl} vertical stroke {sup 2}∝10{sup -6} if one of mixing elements can be at least one order of magnitude smaller than the other.

17 keV and 30 eV Dirac neutrinos and a techniphoton

International Nuclear Information System (INIS)

Holdom, B.

1985-01-01

We consider four flavors of left-handed Weyl neutrinos forming two Dirac masses, of order 17 keV and 30 eV. The symmetry Lsub(e)+Lsub(tau)-Lsub(μ)-Lsub(lambda) ensures this form of the mass matrix and consistency with experiments. We show how it arises in a technicolor context. The structure of the model can incorporate a techniphoton, an unbroken U(1) gauge symmetry of technifermions, and this makes a 17 keV neutrino cosmologically unstable. (orig.)

Distinguishing Dirac/Majorana sterile neutrinos at the LHC

Energy Technology Data Exchange (ETDEWEB)

Dib, Claudio O. [Univ. Tecnica Federico Santa Maria, Valparaiso (Chile). CCTVal y Dept. of Physics; Kim, C.S. [Yonsei Univ., Seoul (Korea, Republic of). Dept. of Physics and IPAP; Wang, Kechen [Chinese Academy of Sciences, Beijing (China). Inst. of High Energy Physics; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Zhang, Jue [Chinese Academy of Sciences, Beijing (China). Inst. of High Energy Physics

2016-06-15

We study the purely leptonic decays of W{sup ±} → e{sup ±}e{sup ±}μ{sup -+}ν and μ{sup ±}μ{sup ±}e{sup -+}ν produced at the LHC, induced by sterile neutrinos with mass m{sub N} below M{sub W} in the intermediate state. Since the final state neutrino escapes detection, one cannot tell whether this process violates lepton number, what would indicate a Majorana character for the intermediate sterile neutrino. Our study shows that when the sterile neutrino mixings with electrons and muons are different enough, one can still discriminate between the Dirac and Majorana character of this intermediate neutrino by simply counting and comparing the above decay rates. After performing collider simulations and statistical analysis, we find that at the 14 TeV LHC with an integrated luminosity of 3000 fb{sup -1}, for two benchmark scenarios m{sub N}=20 GeV and 50 GeV, at least a 3σ level of exclusion on the Dirac case can be achieved for disparities as mild as e.g. vertical stroke U{sub Ne} vertical stroke {sup 2}<0.7 vertical stroke U{sub Nμ} vertical stroke {sup 2} or vertical stroke U{sub Nμ} vertical stroke {sup 2}<0.7 vertical stroke U{sub Ne} vertical stroke {sup 2}, provided that vertical stroke U{sub Ne} vertical stroke {sup 2}, vertical stroke U{sub Nμ} vertical stroke {sup 2} are both above ∝2 x 10{sup -6}.

Neutrino mass as the probe of intermediate mass scales

International Nuclear Information System (INIS)

Senjanovic, G.

1980-01-01

A discussion of the calculability of neutrino mass is presented. The possibility of neutrinos being either Dirac or Majorana particles is analyzed in detail. Arguments are offered in favor of the Majorana case: the smallness of neutrino mass is linked to the maximality of parity violation in weak interactions. It is shown how the measured value of neutrino mass would probe the existence of an intermediate mass scale, presumably in the TeV region, at which parity is supposed to become a good symmetry. Experimental consequences of the proposed scheme are discussed, in particular the neutrino-less double β decay, where observation would provide a crucial test of the model, and rare muon decays such as μ → eγ and μ → ee anti e. Finally, the embedding of this model in an O(10) grand unified theory is analyzed, with the emphasis on the implications for intermediate mass scales that it offers. It is concluded that the proposed scheme provides a distinct and testable alternative for understanding the smallness of neutrino mass. 4 figures

Neutrino mass as the probe of intermediate mass scales

Energy Technology Data Exchange (ETDEWEB)

Senjanovic, G.

1980-01-01

A discussion of the calculability of neutrino mass is presented. The possibility of neutrinos being either Dirac or Majorana particles is analyzed in detail. Arguments are offered in favor of the Majorana case: the smallness of neutrino mass is linked to the maximality of parity violation in weak interactions. It is shown how the measured value of neutrino mass would probe the existence of an intermediate mass scale, presumably in the TeV region, at which parity is supposed to become a good symmetry. Experimental consequences of the proposed scheme are discussed, in particular the neutrino-less double ..beta.. decay, where observation would provide a crucial test of the model, and rare muon decays such as ..mu.. ..-->.. e..gamma.. and ..mu.. ..-->.. ee anti e. Finally, the embedding of this model in an O(10) grand unified theory is analyzed, with the emphasis on the implications for intermediate mass scales that it offers. It is concluded that the proposed scheme provides a distinct and testable alternative for understanding the smallness of neutrino mass. 4 figures.

Complex scaling and residual flavour symmetry in the neutrino mass ...

Indian Academy of Sciences (India)

Probir Roy

2017-10-09

Oct 9, 2017 ... Leptonic Dirac CP violation must be maximal while atmospheric neutrino mixing need not be exactly maximal. Each of the two Majorana phases, to be probed by the search for 0νββ decay, has to be zero or π and a normal neutrino mass hierarchy is allowed. Keywords. Neutrinos; residual flavour symmetry; ...

Froggatt-Nielsen hierarchy and the neutrino mass matrix

International Nuclear Information System (INIS)

Kamikado, H.; Takasugi, E.

2008-05-01

We study the neutrino mass matrix derived from the seesaw mechanism in which the neutrino Yukawa couplings and the heavy Majorana neutrino mass matrix are controlled by the Froggatt-Nielsen mechanism. In order to obtain the large neutrino mixings, two Froggatt-Nielsen fields are introduced with a complex vacuum expectation values. As a by-product, CP violation is systematically induced even if the order one couplings of FN fields are real. We show several predictions of this model, such as θ 13 , the Dirac CP phase, two Majorana CP phases, the effective mass of the neutrinoless double beta decay and the leptogenesis. The prediction of the branching ratio of μ→eγ is also given in SUSY model. (orig.)

Unified picture for Dirac neutrinos, dark matter, dark energy and matter–antimatter asymmetry

OpenAIRE

Gu, Pei-Hong

2008-01-01

We propose a unified scenario to generate the masses of Dirac neutrinos and cold dark matter at the TeV scale, understand the origin of dark energy and explain the matter-antimatter asymmetry of the universe. This model can lead to significant impact on the Higgs searches at LHC.

Is neutrino produced in standard weak interactions a Dirac or Majorana particle?

International Nuclear Information System (INIS)

Beshtoev, Kh.M.

2010-01-01

This work considers the following problem: what type (Dirac or Majorana) of neutrinos is produced in standard weak interactions? It is concluded that only Dirac neutrinos but not Majorana neutrinos can be produced in these interactions. Then neutrino interacts with W ± and Z bosons but neutrinoless double beta decay is absent. It means that this neutrino will be produced in another type of interaction. Namely, Majorana neutrino will be produced in the interaction which differentiates spin projections but cannot differentiate neutrino (particle) from antineutrino (antiparticle). Then neutrino will interact with W ± bosons and neutrinoless double beta decay will arise. But interaction with Z boson will be absent. Such an interaction has not been discovered yet. Therefore, experiments with very high precision are important to detect the neutrinoless double decays if they are realized in the Nature

Neutrino helicity reversal and fundamental symmetries

International Nuclear Information System (INIS)

Jentschura, U D; Wundt, B J

2014-01-01

A rather elusive helicity reversal occurs in a gedanken experiment in which a massive left-handed Dirac neutrino, traveling at a velocity u < c, is overtaken on a highway by a speeding vehicle (traveling at velocity v with u < v < c). Namely, after passing the neutrino, looking back, one would see a right-handed neutrino (which has never been observed in nature). The Lorentz-invariant mass of the right-handed neutrino is still the same as before the passing. The gedanken experiment thus implies the existence of right-handed, light neutrinos, which are not completely sterile. Furthermore, overtaking a bunch of massive right-handed Dirac neutrinos leads to gradual de-sterilization. We discuss the helicity reversal and the concomitant sterilization and de-sterilization mechanisms by way of an illustrative example calculation, with a special emphasis on massive Dirac and Majorana neutrinos. We contrast the formalism with a modified Dirac neutrino described by a Dirac equation with a pseudoscalar mass term proportional to the fifth current. (paper)

On the possibilities of distinguishing Dirac from Majorana neutrinos

International Nuclear Information System (INIS)

Zralek, M.

1997-01-01

The problem if existing neutrinos are Dirac or Majorana particles is considered in a very pedagogical way. After a few historical remarks we recall the theoretical description of neutral spin 1/2 particles, emphasizing the difference between chirality and helicity which is important in our discussion. Next we describe the properties of neutrinos in the cases when their interactions are given by the standard model and by its extensions (massive neutrinos, right-handed currents, electromagnetic neutrino interaction, interaction with scalar particles). Various processes where the different nature of neutrinos could in principle be visible are reviewed. We clear up misunderstandings which have appeared in last suggestions how to distinguish both types of neutrinos. (author)

Dirac equation for massive neutrinos in a Schwarzschild-de Sitter spacetime from a 5D vacuum

International Nuclear Information System (INIS)

Sánchez, Pablo Alejandro; Anabitarte, Mariano; Bellini, Mauricio

2011-01-01

Starting from a Dirac equation for massless neutrino in a 5D Ricci-flat background metric, we obtain the effective 4D equation for massive neutrino in a Schwarzschild-de Sitter (SdS) background metric from an extended SdS 5D Ricci-flat metric. We use the fact that the spin connection is defined to an accuracy of a vector, so that the covariant derivative of the spinor field is strongly dependent of the background geometry. We show that the mass of the neutrino can be induced from the extra space-like dimension.

Remarks on ''Neutrino masses and mixing angles in a predictive theory of fermion masses''

International Nuclear Information System (INIS)

Lavoura, L.; Silva, J.P.

1994-01-01

In the extension of the Dimopoulos-Hall-Raby model of the fermion mass matrices to the neutrino sector, there is an entry in the up-quark and neutrino Dirac mass matrices which can be assumed to arise from the Yukawa coupling of a 120, instead of a 10 or a 126, of SO(10). Although this assumption leads to an extra undetermined complex parameter in the model, the resulting lepton mixing matrix exhibits the remarkable feature that the ν τ does not mix with the other two neutrinos. Making a reasonable assumption about the extra parameter, we are able to fit the large-mixing-angle MSW solution of the solar-neutrino problem, and we obtain m ντ ∼10 eV, the right mass range to close the Universe. Other possibilities for explaining the solar-neutrino deficit are also discussed

Baryon asymmetry via leptogenesis in a neutrino mass model with complex scaling

International Nuclear Information System (INIS)

Samanta, Rome; Ghosal, Ambar; Chakraborty, Mainak; Roy, Probir

2017-01-01

Baryogenesis via leptogenesis is investigated in a specific model of light neutrino masses and mixing angles. The latter was proposed on the basis of an assumed complex-extended scaling property of the neutrino Majorana mass matrix M ν , derived with a type-1 seesaw from a Dirac mass matrix m D and a heavy singlet neutrino Majorana mass matrix M R . One of its important features, highlighted here, is that there is a common source of the origin of a nonzero θ 13 and the CP violating lepton asymmetry through the imaginary part of m D . The model predicted CP violation to be maximal for the Dirac type and vanishing for the Majorana type. We assume strongly hierarchical mass eigenvalues for M R . The leptonic CP asymmetry parameter ε α 1 mm with lepton flavor α, originating from the decays of the lightest of the heavy neutrinos N 1 (of mass M 1 ) at a temperature T ∼ M 1 , is what matters here with the lepton asymmetries, originating from the decays of N 2,3 , being washed out. The light leptonic and heavy neutrino number densities (normalized to the entropy density) are evolved via Boltzmann equations down to electroweak temperatures to yield a baryon asymmetry through sphaleronic transitions. The effects of flavored vs. unflavored leptogenesis in the three mass regimes (1) M 1 < 10 9 GeV, (2) 10 9 GeV < M 1 < 10 12 GeV and (3) M 1 > 10 12 GeV are numerically worked out for both a normal and an inverted mass ordering of the light neutrinos. Corresponding results on the baryon asymmetry of the universe are obtained, displayed and discussed. For values close to the best-fit points of the input neutrino mass and mixing parameters, obtained from neutrino oscillation experiments, successful baryogenesis is achieved for the mass regime (2) and a normal mass ordering of the light neutrinos with a nonzero θ 13 playing a crucial role. However, the other possibility of an inverted mass ordering for the same mass regime, though disfavored, cannot be excluded. A

A see-saw mechanism with light sterile neutrinos

International Nuclear Information System (INIS)

McKellar, B.H.J.; Garbutt, M.; Stephenson, G.J.; Goldman, T.

2001-01-01

The usual see-saw mechanism for the generation of light neutrino masses is based on the assumption that all of the flavours of right-handed (more properly, sterile) neutrinos are heavy. If the sterile Majorana mass matrix is singular, one or more of the sterile neutrinos will have zero mass before mixing with the active (left-handed) neutrinos and be light after that mixing is introduced In particular, a rank 1 sterile mass matrix leads naturally to two pseudo-Dirac pairs, one very light active Majorana neutrino and one heavy sterile Majorana neutrino. For any pattern of Dirac masses, there exists a region of parameter space in which the two pseudo-Dirac pairs are nearly degenerate in mass. This, in turn, leads to large amplitude mixing of active states as well as mixing into sterile states

Depletion of atmospheric muon-neutrino fluxes and structure of Majorana mass matrix

International Nuclear Information System (INIS)

Tanimoto, Morimitsu; Matsuda, Masahisa

1993-01-01

We study the structures of the Dirac and Majorana mass matrices which give rise to the large lepton mixing expected from the depleted atmospheric muonneutrino flux. In the case that the Majorana mass matrix has a hierarchy for generations, a certain kind of the neutrino Dirac mass matrix with the hierarchical structure leads to the large lepton mixing between the second generation and the third one. Our model-independent analyses serve the model-building of the mass matrices based on the quark-lepton unified theory. (orig.)

Radiationless Zitterbewegung of Dirac particles and mass formula

International Nuclear Information System (INIS)

Noboru Hokkyo.

1987-06-01

The Zitterbewegung of the Dirac particle is given a visual representation by solving the two-component difference form of the Dirac equation. It is seen that the space-time trajectory of a Dirac particle can be pictured as a correlated whole of a network of zigzags of left- and right-handed chiral neutrino-like line elements. These zigzags can feel the curl of the external electromagnetic vector potential and give rise to the spin magnetic interaction, confirming Schroedinger's earlier intuitive picture of the spin as the orbital angular momentum of the Zitterbewegung. The network of zigzags associated with an electron splits and reunites in passing through the slits in the electron beam interference experiment. It is proposed to interpret Nambu's empirical mass formula m n =(n/2)137m e =(n/2)((h/2π)/cL), n=integer, as a radiationless condition for the Zitterbewegung of the hadronic Dirac particle of the linear spatial extension of the order of the classical electron radius L=e 2 /m e c 2 . (author). 20 refs, 4 figs

Baryon asymmetry via leptogenesis in a neutrino mass model with complex scaling

Energy Technology Data Exchange (ETDEWEB)

Samanta, Rome; Ghosal, Ambar [Saha Institute of Nuclear Physics, HBNI, 1/AF Bidhannagar, Kolkata 700064 (India); Chakraborty, Mainak [Centre of Excellence in Theoretical and Mathematical Sciences, SOA University, Khandagiri Square, Bhubaneswar 751030 (India); Roy, Probir, E-mail: rome.samanta@saha.ac.in, E-mail: mainak.chakraborty2@gmail.com, E-mail: probirrana@gmail.com, E-mail: ambar.ghosal@saha.ac.in [Center for Astroparticle Physics and Space Science, Bose Institute, Kolkata 700091 (India)

2017-03-01

Baryogenesis via leptogenesis is investigated in a specific model of light neutrino masses and mixing angles. The latter was proposed on the basis of an assumed complex-extended scaling property of the neutrino Majorana mass matrix M {sub ν}, derived with a type-1 seesaw from a Dirac mass matrix m {sub D} and a heavy singlet neutrino Majorana mass matrix M {sub R} . One of its important features, highlighted here, is that there is a common source of the origin of a nonzero θ{sub 13} and the CP violating lepton asymmetry through the imaginary part of m {sub D} . The model predicted CP violation to be maximal for the Dirac type and vanishing for the Majorana type. We assume strongly hierarchical mass eigenvalues for M {sub R} . The leptonic CP asymmetry parameter ε{sup α}{sub 1} mm with lepton flavor α, originating from the decays of the lightest of the heavy neutrinos N {sub 1} (of mass M {sub 1}) at a temperature T ∼ M {sub 1}, is what matters here with the lepton asymmetries, originating from the decays of N {sub 2,3}, being washed out. The light leptonic and heavy neutrino number densities (normalized to the entropy density) are evolved via Boltzmann equations down to electroweak temperatures to yield a baryon asymmetry through sphaleronic transitions. The effects of flavored vs. unflavored leptogenesis in the three mass regimes (1) M {sub 1} < 10{sup 9} GeV, (2) 10{sup 9} GeV < M {sub 1} < 10{sup 12} GeV and (3) M {sub 1} > 10{sup 12} GeV are numerically worked out for both a normal and an inverted mass ordering of the light neutrinos. Corresponding results on the baryon asymmetry of the universe are obtained, displayed and discussed. For values close to the best-fit points of the input neutrino mass and mixing parameters, obtained from neutrino oscillation experiments, successful baryogenesis is achieved for the mass regime (2) and a normal mass ordering of the light neutrinos with a nonzero θ{sub 13} playing a crucial role. However, the other

Dirac equation in a de Sitter expansion for massive neutrinos from modern Kaluza-Klein theory

International Nuclear Information System (INIS)

Sánchez, Pablo Alejandro; Anabitarte, Mariano; Bellini, Mauricio

2012-01-01

Using the modern Kaluza-Klein theory of gravity (or the Induced Matter theory), we study the Dirac equation for massive neutrinos on a de Sitter background metric from a 5D Riemann-flat (and hence Ricci-flat) extended de Sitter metric, on which is defined the vacuum for test massless 1/2-spin neutral fields minimally coupled to gravity and free of any other interactions. We obtain that the effective 4D masses of the neutrinos can only take three possible values, which are related to the (static) foliation of the fifth and noncompact extra dimension.

EFFECTS OF THE NEUTRINO MASS SPLITTING ON THE NONLINEAR MATTER POWER SPECTRUM

International Nuclear Information System (INIS)

Wagner, Christian; Verde, Licia; Jimenez, Raul

2012-01-01

We have performed cosmological N-body simulations which include the effect of the masses of the individual neutrino species. The simulations were aimed at studying the effect of different neutrino hierarchies on the matter power spectrum. Compared to the linear theory predictions, we find that nonlinearities enhance the effect of hierarchy on the matter power spectrum at mildly nonlinear scales. The maximum difference between the different hierarchies is about 0.5% for a sum of neutrino masses of 0.1 eV. Albeit this is a small effect, it is potentially measurable from upcoming surveys. In combination with neutrinoless double-β decay experiments, this opens up the possibility of using the sky to determine if neutrinos are Majorana or Dirac fermions.

On neutrino and charged lepton masses and mixings: a view from the electroweak-scale right-handed neutrino model

Energy Technology Data Exchange (ETDEWEB)

Hung, P.Q.; Le, Trinh [Department of Physics, University of Virginia,Charlottesville, VA 22904-4714 (United States)

2015-09-01

We present a model of neutrino masses within the framework of the EW-ν{sub R} model in which the experimentally desired form of the PMNS matrix is obtained by applying an A{sub 4} symmetry to the Higgs singlet sector responsible for the neutrino Dirac mass matrix. This mechanism naturally avoids potential conflict with the LHC data which severely constrains the Higgs sector, in particular the Higgs doublets. Moreover, by making a simple ansa{sup ¨}tz we extract M{sub l}M{sub l}{sup †} for the charged lepton sector. A similar ansa{sup ¨}tz is proposed for the quark sector. The sources of masses for the neutrinos are entirely different from those for the charged leptons and for the quarks and this might explain why U{sub PMNS} is very different from V{sub CKM}.

A model for Simpson's 17 keV neutrino

International Nuclear Information System (INIS)

Rajpoot, S.

1992-01-01

Recent studies of β-decay spectra seem to confirm Simpson's earlier findings that the electron neutrinos contain a small (1%) admixture of a 17 keV Dirac neutrino. In this paper an unconventional model with SU(2) L x SU(2) R x U(1) B-1 gauge interactions is presented in which all neutrinos are Dirac particles. Electron and muon neutrinos acquire seesaw Dirac masses of order 10 -3 eV for the MSW solution for the solar neutrino problem. The τ neutrino is identified as Simpson's 17 keV neutrino. Constraints coming from cosmology and particle physics are shown to be satisfied

Neutrino physics

International Nuclear Information System (INIS)

Gil-Botella, I.

2011-01-01

The fundamental properties of neutrinos are reviewed in these lectures. The first part is focused on the basic characteristics of neutrinos in the Standard Model and how neutrinos are detected. Neutrino masses and oscillations are introduced and a summary of the most important experimental results on neutrino oscillations to date is provided. Then, present and future experimental proposals are discussed, including new precision reactor and accelerator experiments. Finally, different approaches for measuring the neutrino mass and the nature (Majorana or Dirac), of neutrinos are reviewed. The detection of neutrinos from supernovae explosions and the information that this measurement can provide are also summarized at the end. (author)

Neutrino physics

CERN Document Server

Hernandez, P.

2016-01-01

This is the writeup of the lectures on neutrino physics delivered at various schools: TASI and Trieste in 2013 and the CERN-Latin American School in 2015. The topics discussed in this lecture include: general properties of neutrinos in the SM, the theory of neutrino masses and mixings (Dirac and Majorana), neutrino oscillations both in vacuum and in matter, as well as an overview of the experimental evidence for neutrino masses and of the prospects in neutrino oscillation physics. We also briefly review the relevance of neutri- nos in leptogenesis and in beyond-the-Standard-Model physics.

A neutrino mass-mixing sum rule from SO(10) and neutrinoless double beta decay

Energy Technology Data Exchange (ETDEWEB)

Buccella, F. [INFN, Sezione di Napoli,Complesso University Monte S. Angelo, I-80126 Napoli (Italy); Chianese, M. [INFN, Sezione di Napoli,Complesso University Monte S. Angelo, I-80126 Napoli (Italy); Dipartimento di Fisica Ettore Pancini, Università di Napoli Federico II,Complesso University Monte S. Angelo, I-80126 Napoli (Italy); Mangano, G. [INFN, Sezione di Napoli,Complesso University Monte S. Angelo, I-80126 Napoli (Italy); Miele, G.; Morisi, S.; Santorelli, P. [INFN, Sezione di Napoli,Complesso University Monte S. Angelo, I-80126 Napoli (Italy); Dipartimento di Fisica Ettore Pancini, Università di Napoli Federico II,Complesso University Monte S. Angelo, I-80126 Napoli (Italy)

2017-04-03

Minimal SO(10) grand unified models provide phenomenological predictions for neutrino mass patterns and mixing. These are the outcome of the interplay of several features, namely: i) the seesaw mechanism; ii) the presence of an intermediate scale where B-L gauge symmetry is broken and the right-handed neutrinos acquire a Majorana mass; iii) a symmetric Dirac neutrino mass matrix whose pattern is close to the up-type quark one. In this framework two natural characteristics emerge. Normal neutrino mass hierarchy is the only allowed, and there is an approximate relation involving both light-neutrino masses and mixing parameters. This differs from what occurring when horizontal flavour symmetries are invoked. In this case, in fact, neutrino mixing or mass relations have been separately obtained in literature. In this paper we discuss an example of such comprehensive mixing-mass relation in a specific realization of SO(10) and, in particular, analyse its impact on the expected neutrinoless double beta decay effective mass parameter 〈m{sub ee}〉, and on the neutrino mass scale. Remarkably a lower limit for the lightest neutrino mass is obtained (m{sub lightest}≳7.5×10{sup −4} eV, at 3 σ level).

Derivation of the formalism for neutrino matter oscillations from the neutrino relativistic field equations

International Nuclear Information System (INIS)

Mannheim, P.D.

1988-01-01

We derive the standard formalism of Mikheyev, Smirnov, and Wolfenstein for the oscillation of neutrinos in matter taking into account the Lorentz and second-quantized structure of the neutrino fields. We consider neutrinos with Dirac or Majorana masses

Neutrino mass priors for cosmology from random matrices

Science.gov (United States)

Long, Andrew J.; Raveri, Marco; Hu, Wayne; Dodelson, Scott

2018-02-01

Cosmological measurements of structure are placing increasingly strong constraints on the sum of the neutrino masses, Σ mν, through Bayesian inference. Because these constraints depend on the choice for the prior probability π (Σ mν), we argue that this prior should be motivated by fundamental physical principles rather than the ad hoc choices that are common in the literature. The first step in this direction is to specify the prior directly at the level of the neutrino mass matrix Mν, since this is the parameter appearing in the Lagrangian of the particle physics theory. Thus by specifying a probability distribution over Mν, and by including the known squared mass splittings, we predict a theoretical probability distribution over Σ mν that we interpret as a Bayesian prior probability π (Σ mν). Assuming a basis-invariant probability distribution on Mν, also known as the anarchy hypothesis, we find that π (Σ mν) peaks close to the smallest Σ mν allowed by the measured mass splittings, roughly 0.06 eV (0.1 eV) for normal (inverted) ordering, due to the phenomenon of eigenvalue repulsion in random matrices. We consider three models for neutrino mass generation: Dirac, Majorana, and Majorana via the seesaw mechanism; differences in the predicted priors π (Σ mν) allow for the possibility of having indications about the physical origin of neutrino masses once sufficient experimental sensitivity is achieved. We present fitting functions for π (Σ mν), which provide a simple means for applying these priors to cosmological constraints on the neutrino masses or marginalizing over their impact on other cosmological parameters.

Neutrino masses and spontaneously broken flavor symmetries

International Nuclear Information System (INIS)

Staudt, Christian

2014-01-01

We study the phenomenology of supersymmetric flavor models. We show how the predictions of models based on spontaneously broken non-Abelian discrete flavor symmetries are altered when we include so-called Kaehler corrections. Furthermore, we discuss anomaly-free discrete R symmetries which are compatible with SU(5) unification. We find a set of symmetries compatible with suppressed Dirac neutrino masses and a unique symmetry consistent with the Weinberg operator. We also study a pseudo-anomalous U(1) R symmetry which explains the fermion mass hierarchies and, when amended with additional singlet fields, ameliorates the fine-tuning problem.

Neutrino seesaw mechanism with texture zeros

International Nuclear Information System (INIS)

Liao, Jiajun; Marfatia, D.; Whisnant, K.

2015-01-01

In the context of the Type I seesaw mechanism, we carry out a systematic study of the constraints that result from zeros in both the Dirac and right-handed Majorana neutrino mass matrices. We find that most constraints can be expressed in the standard form with one or two element/cofactor zeros alone, while there are 9 classes of nonstandard constraints. We show that all the constraints are stable under one-loop renormalization group running from the lightest right-handed neutrino mass scale to the electroweak scale. We study the predictions of the nonstandard constraints for the lightest neutrino mass, Dirac CP phase and neutrinoless double beta decay.

Neutrino mass matrix: Inverted hierarchy and CP violation

International Nuclear Information System (INIS)

Frigerio, Michele; Smirnov, Alexei Yu.

2003-01-01

We reconstruct the neutrino mass matrix in the flavor basis, in the case of an inverted mass hierarchy (ordering), using all available experimental data on neutrino masses and oscillations. We analyze the dependence of the matrix elements m αβ on the CP violating Dirac δ and Majorana ρ and σ phases, for different values of the absolute mass scale. We find that the present data admit various structures of the mass matrix: (i) hierarchical structures with a set of small (zero) elements; (ii) structures with equalities among various groups of elements: e-row and/or μτ-block elements, diagonal and/or off-diagonal elements; (iii) 'democratic' structure. We find the values of phases for which these structures are realized. The mass matrix elements can anticorrelate with flavor: inverted partial or complete flavor alignment is possible. For various structures of the mass matrix we identify the possible underlying symmetry. We find that the mass matrix can be reconstructed completely only in particular cases, provided that the absolute scale of the mass is measured. Generally, the freedom related to the Majorana phase σ will not be removed, thus admitting various types of mass matrix

Neutrino mass?

International Nuclear Information System (INIS)

Kayser, B.

1992-01-01

After arguing that we should be looking for evidence of neutrino mass, we illustrate the possible consequences of neutrino mass and mixing. We then turn to the question of whether neutrinos are their own antiparticles, and to the process which may answer this question: neutrinoless double beta decay. Next, we review the proposed Mikheyev-Smirnov-Wolfenstein solution to the solar neutrino problem, and discuss models which can generate neutrino electromagnetic moments large enough to play a role in the sun. Finally, we consider how the possible 17 keV neutrino, if real, would fit in with everything we know about neutrinos. (orig.)

Massive neutrinos flavor mixing of leptons and neutrino oscillations

CERN Document Server

2015-01-01

Since the discovery of neutrino oscillations neutrino physics has become an interesting field of research in physics. They imply that neutrino must have a small mass and that the neutrinos, coupled to the charged leptons, are mixtures of the mass eigenstates, analogous to the flavor mixing of the quarks. The mixing angles for the quarks are small, but for the leptons two of the mixing angles are large. The masses of the three neutrinos must be very small, less than 1 eV, but from the oscillation experiments we only know the mass differences — the absolute masses are still unknown. Also we do not know, if the masses of the neutrinos are Dirac masses, as the masses of the charged leptons and of the quarks, or whether they are Majorana masses. In this volume, an overview of the present state of research in neutrino physics is given by well-known experimentalists and theorists. The contents — originated from talks and discussions at a recent conference addressing some of the most pressing open questions in n...

Neutrino masses and oscillations

Energy Technology Data Exchange (ETDEWEB)

Smirnov, A Yu

1996-11-01

New effects related to refraction of neutrinos in different media are reviewed and implication of the effects to neutrino mass and mixing are discussed. Patterns of neutrino masses and mixing implied by existing hints/bounds are described. Recent results on neutrino mass generation are presented. They include neutrino masses in SO(10) GUT`s and models with anomalous U(1), generation of neutrino mass via neutrino-neutralino mixing, models of sterile neutrino. (author). 95 refs, 9 figs.

Geometrical neutrino mass hierarchy and a 17-keV ντ

International Nuclear Information System (INIS)

Babu, K.S.; Mohapatra, R.N.

1991-01-01

We present an extension of the singlet majoron gauge model which realizes a novel scheme of geometrical neutrino mass hierarchy proposed recently by Glashow, wherein ν e and ν μ are Majorana particles with m νe ∼m νμ ∼10 -3 eV while ν τ is a Dirac particle with a mass of 17 keV. Our model explains the solar-neutrino deficit via the Mikheyev-Smirnov-Wolfenstein mechanism and accounts for the recently reported anomaly in beta-decay spectra in a natural manner without any undesirable fine tuning of parameters. An interesting consequence of the model is that ν τ is short lived with a lifetime of ∼10 -3-- 10 -1 sec

Common Origin for Neutrino Anarchy and Charged Hierarchies

International Nuclear Information System (INIS)

Agashe, Kaustubh; Okui, Takemichi; Sundrum, Raman

2009-01-01

The generation of exponential flavor hierarchies from extra-dimensional wave function overlaps is reexamined. We find, surprisingly, that the coexistence of anarchic fermion mass matrices with such hierarchies is intrinsic and natural to this setting. The salient features of charged fermion and neutrino masses and mixings can thereby be captured within a single framework. Both Dirac and Majorana neutrinos can be realized. Implications for a variety of weak-scale scenarios, including warped compactification and supersymmetry, are discussed. When the new weak-scale physics is sensitive to the origin of flavor structure, Dirac neutrinos are preferred

Neutrino mass and the solar neutrino problem

International Nuclear Information System (INIS)

Wolfenstein, L.

1987-01-01

Theoretical ideas about neutrino mass based on grand-unified theories are reviewed. These give the see-saw formula in which neutrino mass is inversely proportional to a large mass scale M. For M between 10/sup 11/ and 10/sup 15/ Gev the study of solar neutrinos appears to be the best probe of neutrino masses and mixings

Flipped neutrino emissivity from strange matter

Energy Technology Data Exchange (ETDEWEB)

Goyal, A.; Dutta, S. (Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India))

1994-04-15

Energy loss due to wrong helicity sterile neutrinos through spin flip processes leads to rapid cooling of nascent neutron stars. The observed cooling of neutron stars associated with SN 1987A seems to preclude the existence of Dirac neutrinos with a mass in excess of 20 keV. Assuming that nuclear matter in the core of the neutron star undergoes a phase transition to quark matter leading to a strange star or a neutron star with a strange matter core, we examine the emission of flipped Dirac neutrinos for two dominant processes: quark-neutrino scattering [[ital q]+[nu][sub [minus

The Majorana project: sup 7 sup 6 Ge 0 nu beta beta-decay neutrino mass measurement

CERN Document Server

Aalseth, C E

2002-01-01

Interest in, and the relevance of, next-generation 0 nu beta beta-decay experiments is increasing. Even with nonzero neutrino mass strongly suggested by SNO, Super Kamiokande, and similar experiments sensitive to delta m sup 2 , 0 nu beta beta-decay experiments are still the only way to establish the Dirac or Majorana nature of neutrinos by measuring effective electron neutrino mass, . Various theorists have recently argued in favor of a neutrino mass between 0.01 and 1 eV. The Majorana Project aims to probe this effective neutrino mass range, reaching a sensitivity of 0.02-0.07 eV. The experiment relies entirely on proven technology and has been devised based upon the materials, technology, and data analysis demonstrated to produce the lowest background per kilogram of fiducial germanium. The project plan includes 500 kg of germanium detector material enriched to 85% in sup 7 sup 6 Ge, specialized pulse-acquisition electronics and detector segmentation for background rejection, and underground electroformed ...

Neutrino CP violation and sign of baryon asymmetry in the minimal seesaw model

Science.gov (United States)

Shimizu, Yusuke; Takagi, Kenta; Tanimoto, Morimitsu

2018-03-01

We discuss the correlation between the CP violating Dirac phase of the lepton mixing matrix and the cosmological baryon asymmetry based on the leptogenesis in the minimal seesaw model with two right-handed Majorana neutrinos and the trimaximal mixing for neutrino flavors. The sign of the CP violating Dirac phase at low energy is fixed by the observed cosmological baryon asymmetry since there is only one phase parameter in the model. According to the recent T2K and NOνA data of the CP violation, the Dirac neutrino mass matrix of our model is fixed only for the normal hierarchy of neutrino masses.

Peccei-Quinn symmetry for Dirac seesaw and leptogenesis

Energy Technology Data Exchange (ETDEWEB)

Gu, Pei-Hong [Department of Physics and Astronomy, Shanghai Jiao Tong University,800 Dongchuan Road, Shanghai 200240 (China)

2016-07-04

We extend the DFSZ invisible axion model to simultaneously explain small Dirac neutrino masses and cosmic matter-antimatter asymmetry. After the Peccei-Quinn and electroweak symmetry breaking, the effective Yukawa couplings of the Dirac neutrinos to the standard model Higgs scalar can be highly suppressed by the ratio of the vacuum expectation value of an iso-triplet Higgs scalar over the masses of some heavy gauge-singlet fermions, iso-doublet Higgs scalars or iso-triplet fermions. The iso-triplet fields can carry a zero or nonzero hypercharge. Through the decays of the heavy gauge-singlet fermions, iso-doublet scalars or iso-triplet fermions, we can obtain a lepton asymmetry in the left-handed leptons and an opposite lepton asymmetry in the right-handed neutrinos. Since the right-handed neutrinos do not participate in the sphaleron processes, the left-handed lepton asymmetry can be partially converted to a baryon asymmetry.

Phenomenological analysis of properties of the right-handed Majorana neutrino in the seesaw mechanism

International Nuclear Information System (INIS)

Pan Haijun; Cheng, G.

2002-01-01

As an extension of our previous work in the seesaw mechanism, we analyze the influence of nonzero U e3 on the properties (masses and mixing) of the right-handed Majorana neutrinos in three flavors. The quasidegenerate light neutrinos case is also considered. Assuming the hierarchical Dirac neutrino masses, we find the heavy Majorana neutrino mass spectrum is either hierarchical or partially degenerate if θ 23 ν is large. We show that degenerate right-handed (RH) Majorana masses correspond to a maximal RH mixing angle while hierarchical ones correspond to the RH mixing angles which scale linearly with the mass ratios of the Dirac neutrino masses. An interesting analogue to the behavior of the matter-enhanced neutrino conversion and their difference is presented

Discrete Symmetry Approach to Lepton Flavour, Neutrino Mixing and Leptonic CP Violation, and Neutrino Related Physics Beyond the Standard Theory

OpenAIRE

Girardi, Ivan

2016-01-01

The experimental evidences of neutrino oscillation, caused by non-zero neutrino masses and neutrino mixing, which were obtained in the experiments with solar, atmospheric, accelerator and reactor neutrinos, opened new field of research in elementary particle physics. The principal goal is to understand at fundamental level the mechanism giving rise to non-zero neutrino masses and neutrino mixing. The open fundamental questions include those of the nature — Dirac or Majorana — of massive neutr...

NEUTRINO MASS

OpenAIRE

Kayser, Boris

1988-01-01

This is a review article about the most recent developments on the field of neutrino mass. The first part of the review introduces the idea of neutrino masses and mixing angles, summarizes the most recent experimental data then discusses the experimental prospects and challenges in this area. The second part of the review discusses the implications of these results for particle physics and cosmology, including the origin of neutrino mass, the see-saw mechanism and sequential dominance, and la...

Neutrino mass

International Nuclear Information System (INIS)

Robertson, R.G.H.

1992-01-01

Despite intensive experimental work since the neutrino's existence was proposed by Pauli 60 years ago, and its first observation by Reines and Cowan almost 40 years ago, the neutrino's fundamental properties remain elusive. Among those properties are the masses of the three known flavors, properties under charge conjugation, parity and time-reversal, and static and dynamic electromagnetic moments. Mass is perhaps the most fundamental, as it constrains the other properties. The present status of the search for neutrino mass is briefly reviewed

Neutrino masses and neutrino oscillations

CERN Document Server

Di Lella, L

2000-01-01

These lectures review direct measurements of neutrino masses and the status of neutrino oscillation searches using both natural neutrino sources (the Sun and cosmic rays interacting in the Earth atmosphere) and artificial neutrinos (produced by nuclear reactors and accelerators). Finally, future experiments and plans are presented. (68 refs).

ABSOLUTE NEUTRINO MASSES

DEFF Research Database (Denmark)

Schechter, J.; Shahid, M. N.

2012-01-01

We discuss the possibility of using experiments timing the propagation of neutrino beams over large distances to help determine the absolute masses of the three neutrinos.......We discuss the possibility of using experiments timing the propagation of neutrino beams over large distances to help determine the absolute masses of the three neutrinos....

Leptogenesis and low energy CP-violation in neutrino physics

International Nuclear Information System (INIS)

Pascoli, S.; Petcov, S.T.; Riotto, A.

2007-01-01

Taking into account the recent progress in the understanding of the lepton flavor effects in leptogenesis, we investigate in detail the possibility that the CP-violation necessary for the generation of the baryon asymmetry of the Universe is due exclusively to the Dirac and/or Majorana CP-violating phases in the PMNS neutrino mixing matrix U, and thus is directly related to the low energy CP-violation in the lepton sector (e.g., in neutrino oscillations, etc.). We first derive the conditions of CP-invariance of the neutrino Yukawa couplings λ in the see-saw Lagrangian, and of the complex orthogonal matrix R in the 'orthogonal' parametrization of λ. We show, e.g. that under certain conditions (i) real R and specific CP-conserving values of the Majorana and Dirac phases can imply CP-violation, and (ii) purely imaginary R does not necessarily imply breaking of CP-symmetry. We study in detail the case of hierarchical heavy Majorana neutrino mass spectrum, presenting results for three possible types of light neutrino mass spectrum: (i) normal hierarchical, (ii) inverted hierarchical, and (iii) quasi-degenerate. Results in the alternative case of quasi-degenerate in mass heavy Majorana neutrinos, are also derived. The minimal supersymmetric extension of the standard theory with right-handed Majorana neutrinos and see-saw mechanism of neutrino mass generation is discussed as well. We illustrate the possible correlations between the baryon asymmetry of the Universe and (i) the rephasing invariant J CP controlling the magnitude of CP-violation in neutrino oscillations, or (ii) the effective Majorana mass in neutrinoless double beta decay, in the cases when the only source of CP-violation is respectively the Dirac or the Majorana phases in the neutrino mixing matrix

Searches for heavy neutrinos from Z decays

International Nuclear Information System (INIS)

Abreu, P.; Adam, W.; Adami, F.

1992-01-01

We have searched for possible fourth family heavy neutrinos, pair produced in Z 0 decays, in a sample of about 112 000 hadronic Z 0 final states collected with the DELPHI detector. For all mixing matrix elements we exclude a new Dirac neutrino light than 44.5 GeV at a 95% confidence level, if the neutrino couples to the electron or muon family, and lighter than 44.0 GeV, if the neutrino couples to the tau family. Depending on the values of the mixing element and to which lepton family the neutrino couples, we obtain mass limits up to 46.2 GeV. For all mixing matrix elements we exclude a new Majorana neutrino lighter than 39.0 GeV, if it couples to the electron or the muon family, and lighter than 38.2 GeV, if it couples to the tau family. Depending on the values of the mixing matrix element and to which lepton family the neutrino couples, we obtain mass limits up to 44.7 GeV. We also exclude stable new Dirac neutrinos lighter than 45.0 GeV and new Majorana neutrinos lighter than 39.5 GeV. (orig.)

Neutrinos: in and out of the standard model

Energy Technology Data Exchange (ETDEWEB)

Parke, Stephen; /Fermilab

2006-07-01

The particle physics Standard Model has been tremendously successful in predicting the outcome of a large number of experiments. In this model Neutrinos are massless. Yet recent evidence points to the fact that neutrinos are massive particles with tiny masses compared to the other particles in the Standard Model. These tiny masses allow the neutrinos to change flavor and oscillate. In this series of Lectures, I will review the properties of Neutrinos In the Standard Model and then discuss the physics of Neutrinos Beyond the Standard Model. Topics to be covered include Neutrino Flavor Transformations and Oscillations, Majorana versus Dirac Neutrino Masses, the Seesaw Mechanism and Leptogenesis.

Neutrino mass and the origin of galactic magnetic fields

International Nuclear Information System (INIS)

Enqvist, K.; Semikoz, V.; Shukurov, A.; Sokoloff, D.

1993-01-01

We compare two constraints on the strength of the cosmological primordial magnetic field: the one following from the restrictions on the Dirac neutrino spin flip in the early Universe, and another one based on the galactic dynamo theory for the Milky Way (presuming that the seed magnetic field has a relic origin). Since the magnetic field facilitates transitions between left- and right-handed neutrino states, thereby affecting 4 He production at primordial nucleosynthesis, we can obtain a guaranteed upper limit on the strength of the relic magnetic field in the protogalaxy, B c approx-lt 4x10 -9 --3x10 -13 G, depending on the neutrino magnetic moment, if we adopt the MSW explanation of the GALLEX results. On the other hand, models of the dynamo in the Milky Way indicate that the seed magnetic field should be at least 10 -11 --10 -13 G at the protogalaxy scale L=100 kpc. These upper and lower limiting ranges are marginally consistent provided the electron neutrino mass is below 0.3 eV. The results apply to a relic magnetic field produced in the early Universe by any causal mechanism before the nucleosynthesis

The mass-hierarchy puzzle and the 17-keV neutrino in the context of a universal seesaw model

International Nuclear Information System (INIS)

Papageorgiu, E.; Ranfone, S.

1991-06-01

In the light of renewed evidence for the existence of a 17 keV neutrino, we study the possible mass patterns for the charged and the neutral leptons, in the context of a generalized ''seesaw''-type of model, which implements a horizontal U(1) A Peccei-Quinn symmetry. Under some general assumptions concerning the structure of the mass matrix we find that the mass hierarchy between the first two generations of charged leptons and the third one is explained in terms of the natural scales of the model. At the same time, with the additional assumption of the proportionality of Majorana- and Dirac-type couplings, the spectrum of the neutral leptons contains two very light Majorana neutrinos, such as required by the Mikheyev-Smirnov-Wolfenstein interpretation of the solar neutrino deficit, and the 17 keV ''Simpson'' neutrino. A cosmologically consistent decay mode of this neutrino is into a ν e and the axion. (author)

Neutrino mass sum-rule

Science.gov (United States)

Damanik, Asan

2018-03-01

Neutrino mass sum-rele is a very important research subject from theoretical side because neutrino oscillation experiment only gave us two squared-mass differences and three mixing angles. We review neutrino mass sum-rule in literature that have been reported by many authors and discuss its phenomenological implications.

Flipped neutrino emissivity from strange matter

International Nuclear Information System (INIS)

Goyal, A.; Dutta, S.

1994-01-01

Energy loss due to wrong helicity sterile neutrinos through spin flip processes leads to rapid cooling of nascent neutron stars. The observed cooling of neutron stars associated with SN 1987A seems to preclude the existence of Dirac neutrinos with a mass in excess of 20 keV. Assuming that nuclear matter in the core of the neutron star undergoes a phase transition to quark matter leading to a strange star or a neutron star with a strange matter core, we examine the emission of flipped Dirac neutrinos for two dominant processes: quark-neutrino scattering [q+ν - (bar ν + )→q+ν + (bar ν - )] and the quark neutrino pair bremsstrahlung process [q+q→q+q+ν - bar ν - (ν+bar ν + )]. We determine the composition of quark matter just after core bounce and examine the effect of neutrino degeneracy on the emission rate and mean free path of the wrong helicity neutrinos

Neutrino mass, a status report

International Nuclear Information System (INIS)

Robertson, R.G.H.

1993-01-01

Experimental approaches to neutrino mass include kinematic mass measurements, neutrino oscillation searches at rectors and accelerators, solar neutrinos, atmospheric neutrinos, and single and double beta decay. The solar neutrino results yield fairly strong and consistent indications that neutrino oscillations are occurring. Other evidence for new physics is less consistent and convincing

Sterile neutrinos as dark matter

International Nuclear Information System (INIS)

Dodelson, S.; Widrow, L.M.

1994-01-01

The simplest model that can accommodate a viable nonbaryonic dark matter candidate is the standard electroweak theory with the addition of right-handed (sterile) neutrinos. We consider a single generation of neutrinos with a Dirac mass μ and a Majorana mass M for the right-handed component. If M much-gt μ (standard hot dark matter corresponds to M=0), then sterile neutrinos are produced via oscillations in the early Universe with energy density independent of M. However, M is crucial in determining the large scale structure of the Universe; for M∼100 eV, sterile neutrinos make an excellent warm dark matter candidate

Search for heavy sterile neutrinos in trileptons at the LHC

International Nuclear Information System (INIS)

Dib, Claudio O.; Kim, C.S.; Wang, Kechen; Chinese Academy of Sciences, Beijing

2017-03-01

We present a search strategy for both Dirac and Majorana sterile neutrinos from the purely leptonic decays of W"±→e"±e"±μ"-"+ν and μ"±μ"±e"-"+ν at the 14 TeV LHC. The discovery and exclusion limits for sterile neutrinos are shown using both the Cut-and-Count (CC) and Multi-Variate Analysis (MVA) methods. We also discriminate between Dirac and Majorana sterile neutrinos by exploiting a set of kinematic observables which differ between the Dirac and Majorana cases. We find that the MVA method, compared to the more common CC method, can greatly enhance the discovery and discrimination limits. Two benchmark points with sterile neutrino mass m_N=20 GeV and 50 GeV are tested. For an integrated luminosity of 3000 fb"-"1, sterile neutrinos can be found with 5σ significance if heavy-to-light neutrino mixings vertical stroke U_N_e vertical stroke "2∝ vertical stroke U_N_μ vertical stroke "2∝10"-"6, while Majorana vs. Dirac discrimination can be reached if at least one of the mixings is of order 10"-"5.

Neutrino cosmology

International Nuclear Information System (INIS)

Berstein, J.

1984-01-01

These lectures offer a self-contained review of the role of neutrinos in cosmology. The first part deals with the question 'What is a neutrino.' and describes in a historical context the theoretical ideas and experimental discoveries related to the different types of neutrinos and their properties. The basic differences between the Dirac neutrino and the Majorana neutrino are pointed out and the evidence for different neutrino 'flavours', neutrino mass, and neutrino oscillations is discussed. The second part summarizes current views on cosmology, particularly as they are affected by recent theoretical and experimental advances in high-energy particle physics. Finally, the close relationship between neutrino physics and cosmology is brought out in more detail, to show how cosmological constraints can limit the various theoretical possibilities for neutrinos and, more particularly, how increasing knowledge of neutrino properties can contribute to our understanding of the origin, history, and future of the Universe. The level is that of the beginning graduate student. (orig.)

Massive neutrinos in particle physics and astrophysics

International Nuclear Information System (INIS)

Rosen, S.P.

1986-01-01

The concepts of Majorana and Dirac neutrinos are reviewed from an operational point of view and survey the experimental search for neutrino mass. Also reviewed are the work of Mikheyev and Smirnov on the enhancement of neutrino oscillations via the mechanism of Wolfenstein matter oscillations. Results of an extensive computation of MSW effects in the sun are described. 41 refs., 6 figs

Sterile neutrinos in the early universe

Energy Technology Data Exchange (ETDEWEB)

Malaney, R.A. (Lawrence Livermore National Lab., CA (USA)); Fuller, G.M. (California Univ., San Diego, La Jolla, CA (USA). Dept. of Physics)

1990-11-14

We discuss the role played by right-handed sterile neutrinos in the early universe. We show how well known {sup 4}He constraint on the number of relativistic degrees of freedom at early times limits the equilibration of the right handed neutrino sea with the background plasma. We discuss how this allows interesting constraints to be placed on neutrino properties. In particular, a new limit on the Dirac mass of the neutrino is presented. 12 refs.

Neutrino mass experiments

International Nuclear Information System (INIS)

Robertson, R.G.H.

1989-01-01

The current status of the experimental search for neutrino mass is reviewed, with emphasis on direct kinematic methods. Simpson and Hime report finding new evidence for a 17-keV neutrino in the β decay of 3 H and 35 S. The situation concerning the electron neutrino mass as measured in tritium beta decay has not changed significantly in the last two years. We discuss the ''model independent'' lower limit of 17 eV obtained by the ITEP group in light of existing data on the 3 H-- 3 He mass difference. 42 refs., 1 fig., 1 tab

Leptogenesis and neutrino masses

International Nuclear Information System (INIS)

Pluemacher, M.

2004-01-01

Thermal leptogenesis explains the baryon asymmetry of the universe by the out-of-equilibrium decays of heavy right-handed neutrinos. In the minimal seesaw model this leads to interesting implications for light neutrino properties. In particular, quasi-degenerate light neutrino masses are incompatible with leptogenesis. An upper bound on light neutrino masses of 0.1 eV can be derived, which will be tested by forthcoming laboratory experiments and cosmology. (author)

Introduction to the physics of massive and mixed neutrinos

CERN Document Server

Bilenky, Samoil

2018-01-01

Small neutrino masses are the first signs of new physics beyond the Standard Model of particle physics. Since the first edition of this textbook appeared in 2010, the Nobel Prize has been awarded "for the discovery of neutrino oscillations, which shows that neutrinos have mass". The measurement of the small neutrino mixing angle $\\theta_{13}$ in 2012, launched the precision stage of the investigation of neutrino oscillations. This measurement now allows such fundamental problems as the three-neutrino mass spectrum - is it normal or inverted? – and the $CP$ violation in the lepton sector to be tackled. In order to understand the origin of small neutrino masses, it remains crucial to reveal the nature of neutrinos with definite masses: are they Dirac neutrinos possessing a conserved lepton number, which distinguishes neutrinos and antineutrinos, or are they Majorana neutrinos with identical neutrinos and antineutrinos? Experiments searching for the neutrinoless double beta decay are presently under way to ans...

Neutrino oscillation observables from mass matrix structure

International Nuclear Information System (INIS)

Winter, Walter

2008-01-01

We present a systematic procedure to establish a connection between complex neutrino mass matrix textures and experimental observables, including the Dirac CP phase. In addition, we illustrate how future experimental measurements affect the selection of textures in the (θ 13 ,δ CP )-plane. For the mixing angles, we use generic assumptions motivated by quark-lepton complementarity. We allow for any combination between U l and U ν , as well as we average over all present complex phases. We find that individual textures lead to very different distributions of the observables, such as to large or small leptonic CP violation. In addition, we find that the extended quark-lepton complementarity approach motivates future precision measurements of δ CP at the level of θ C ≅11 deg

Dark matter and neutrino mass from the smallest non-Abelian chiral dark sector

Science.gov (United States)

Berryman, Jeffrey M.; de Gouvêa, André; Kelly, Kevin J.; Zhang, Yue

2017-10-01

All pieces of concrete evidence for phenomena outside the standard model (SM)—neutrino masses and dark matter—are consistent with the existence of new degrees of freedom that interact very weakly, if at all, with those in the SM. We propose that these new degrees of freedom organize themselves into a simple dark sector, a chiral S U (3 )×S U (2 ) gauge theory with the smallest nontrivial fermion content. Similar to the SM, the dark S U (2 ) is spontaneously broken while the dark S U (3 ) confines at low energies. At the renormalizable level, the dark sector contains massless fermions—dark leptons—and stable massive particles—dark protons. We find that dark protons with masses between 10 and 100 TeV satisfy all current cosmological and astrophysical observations concerning dark matter even if dark protons are a symmetric thermal relic. The dark leptons play the role of right-handed neutrinos and allow simple realizations of the seesaw mechanism or the possibility that neutrinos are Dirac fermions. In the latter case, neutrino masses are also parametrically different from charged-fermion masses and the lightest neutrino is predicted to be massless. Since the new "neutrino" and "dark-matter" degrees of freedom interact with one another, these two new-physics phenomena are intertwined. Dark leptons play a nontrivial role in early Universe cosmology while indirect searches for dark matter involve, decisively, dark-matter annihilations into dark leptons. These, in turn, may lead to observable signatures at high-energy neutrino and gamma-ray observatories, especially once one accounts for the potential Sommerfeld enhancement of the annihilation cross section, derived from the low-energy dark-sector effective theory, a possibility we explore quantitatively in some detail.

Neutrino mass from Cosmology

CERN Document Server

Lesgourgues, Julien

2012-01-01

Neutrinos can play an important role in the evolution of the Universe, modifying some of the cosmological observables. In this contribution we summarize the main aspects of cosmological relic neutrinos and we describe how the precision of present cosmological data can be used to learn about neutrino properties, in particular their mass, providing complementary information to beta decay and neutrinoless double-beta decay experiments. We show how the analysis of current cosmological observations, such as the anisotropies of the cosmic microwave background or the distribution of large-scale structure, provides an upper bound on the sum of neutrino masses of order 1 eV or less, with very good perspectives from future cosmological measurements which are expected to be sensitive to neutrino masses well into the sub-eV range.

Model independent bounds on magnetic moments of Majorana neutrinos

International Nuclear Information System (INIS)

Bell, Nicole F.; Gorchtein, Mikhail; Ramsey-Musolf, Michael J.; Vogel, Petr; Wang, Peng

2006-01-01

We analyze the implications of neutrino masses for the magnitude of neutrino magnetic moments. By considering electroweak radiative corrections to the neutrino mass, we derive model-independent naturalness upper bounds on neutrino magnetic moments, μ ν , generated by physics above the electroweak scale. For Dirac neutrinos, the bound is several orders of magnitude more stringent than present experimental limits. However, for Majorana neutrinos the magnetic moment contribution to the mass is Yukawa suppressed. The bounds we derive for magnetic moments of Majorana neutrinos are weaker than present experimental limits if μ ν is generated by new physics at ∼1 TeV, and surpass current experimental sensitivity only for new physics scales >10-100 TeV. The discovery of a neutrino magnetic moment near present limits would thus signify that neutrinos are Majorana particles

General property of neutrino mass matrix and CP-violation

International Nuclear Information System (INIS)

Aizawa, Ichiro; Yasue, Masaki

2005-01-01

It is found that the atmospheric neutrino mixing angle of θ atm is determined to be tanθ atm =Im(B)/Im(C) for B=M ν e ν μ and C=M ν e ν τ , where M ij is the ij element of M ν - bar M ν with M ν as a complex symmetric neutrino mass matrix in the (ν e , ν μ , ν τ )-basis. Another mixing angle, θ 13 , defined as U e3 =sinθ 13 e -iδ is subject to the condition: tan2θ 13 ∝|sinθ atm B+cosθ atm C| and the CP-violating Dirac phase of δ is identical to the phase of sinθ atm B*+cosθ atm C*. The smallest value of |sinθ 13 | is achieved at tanθ atm =-Re(C)/Re(B) that yields the maximal CP-violation and that implies C=-κB* for the maximal atmospheric neutrino mixing of tanθ atm =κ=+/-1. The generic smallness of |sinθ 13 | can be ascribed to the tiny violation of the electron number conservation

Search for heavy sterile neutrinos in trileptons at the LHC

Energy Technology Data Exchange (ETDEWEB)

Dib, Claudio O. [Univ. Tecnica Federico Santa Maria, Valparaiso (Chile). CCTVal y Dept. of Physics; Kim, C.S. [Yonsei Univ., Seoul (Korea, Republic of). Dept. of Physics and IPAP; Wang, Kechen [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Chinese Academy of Sciences, Beijing (China). Center for Future High Energy Physics

2017-03-15

We present a search strategy for both Dirac and Majorana sterile neutrinos from the purely leptonic decays of W{sup ±}→e{sup ±}e{sup ±}μ{sup -+}ν and μ{sup ±}μ{sup ±}e{sup -+}ν at the 14 TeV LHC. The discovery and exclusion limits for sterile neutrinos are shown using both the Cut-and-Count (CC) and Multi-Variate Analysis (MVA) methods. We also discriminate between Dirac and Majorana sterile neutrinos by exploiting a set of kinematic observables which differ between the Dirac and Majorana cases. We find that the MVA method, compared to the more common CC method, can greatly enhance the discovery and discrimination limits. Two benchmark points with sterile neutrino mass m{sub N}=20 GeV and 50 GeV are tested. For an integrated luminosity of 3000 fb{sup -1}, sterile neutrinos can be found with 5σ significance if heavy-to-light neutrino mixings vertical stroke U{sub Ne} vertical stroke {sup 2}∝ vertical stroke U{sub Nμ} vertical stroke {sup 2}∝10{sup -6}, while Majorana vs. Dirac discrimination can be reached if at least one of the mixings is of order 10{sup -5}.

Neutrino mass models and CP violation

International Nuclear Information System (INIS)

Joshipura, Anjan S.

2011-01-01

Theoretical ideas on the origin of (a) neutrino masses (b) neutrino mass hierarchies and (c) leptonic mixing angles are reviewed. Topics discussed include (1) symmetries of neutrino mass matrix and their origin (2) ways to understand the observed patterns of leptonic mixing angles and (3)unified description of neutrino masses and mixing angles in grand unified theories.

Generalized ℤ 2 × ℤ 2 in scaling neutrino Majorana mass matrix and baryogenesis via flavored leptogenesis

Science.gov (United States)

Sinha, Roopam; Samanta, Rome; Ghosal, Ambar

2017-12-01

We investigate the consequences of a generalized ℤ 2 × ℤ 2 symmetry on a scaling neutrino Majorana mass matrix. It enables us to determine definite analytical relations between the mixing angles θ 12 and θ 13, maximal CP violation for the Dirac type and vanishing for the Majorana type. Beside the other testable predictions on the low energy neutrino parameters such as ββ 0ν decay matrix element | M ee | and the light neutrino masses m 1,2,3, the model also has intriguing consequences from the perspective of leptogenesis. With the assumption that the required CP violation for leptogenesis is created by the decay of lightest ( N 1) of the heavy Majorana neutrinos, only τ -flavored leptogenesis scenario is found to be allowed in this model. For a normal (inverted) ordering of light neutrino masses, θ 23 is found be less (greater) than its maximal value, for the final baryon asymmetry Y B to be in the observed range. Besides, an upper and a lower bound on the mass of N 1 have also been estimated. Effect of the heavier neutrinos N 2,3 on final Y B has been worked out subsequently. The predictions of this model will be tested in the experiments such as nEXO, LEGEND, GERDA-II, T2K, NO νA, DUNE etc.

Radiative neutrino mass model with degenerate right-handed neutrinos

International Nuclear Information System (INIS)

Kashiwase, Shoichi; Suematsu, Daijiro

2016-01-01

The radiative neutrino mass model can relate neutrino masses and dark matter at a TeV scale. If we apply this model to thermal leptogenesis, we need to consider resonant leptogenesis at that scale. It requires both finely degenerate masses for the right-handed neutrinos and a tiny neutrino Yukawa coupling. We propose an extension of the model with a U(1) gauge symmetry, in which these conditions are shown to be simultaneously realized through a TeV scale symmetry breaking. Moreover, this extension can bring about a small quartic scalar coupling between the Higgs doublet scalar and an inert doublet scalar which characterizes the radiative neutrino mass generation. It also is the origin of the Z 2 symmetry which guarantees the stability of dark matter. Several assumptions which are independently supposed in the original model are closely connected through this extension. (orig.)

Effects of neutrino oscillation on supernova neutrino. Inverted mass hierarchy

International Nuclear Information System (INIS)

Takahashi, Keitaro; Sato, Katsuhiko

2003-01-01

We study the effects of neutrino oscillation on supernova neutrinos in the case of the inverted mass hierarchy (m 3 1 2 ) as well as the normal mass hierarchy (m 1 2 3 ). Numerical analysis using realistic supernova and presupernova models allows us to investigate quantitatively the possibility to probe neutrino oscillation parameters. We show that information about the mass hierarchy can be obtained if θ 13 is rather large (sin 2 2θ 13 > 10 -3 ) and that θ 13 can be probed effectively by SuperKamiokande if the neutrino mass hierarchy is inverted. Errors due to the uncertainty in the original neutrino spectra and the Earth effect are also discussed. (author)

Signatures of the neutrino mass hierarchy in supernova neutrinos

International Nuclear Information System (INIS)

Chiu, S.H.; Huang, Chu-Ching; Lai, Kwang-Chang

2015-01-01

The undetermined neutrino mass hierarchy may leave an observable imprint on the neutrino fluxes from a core-collapse supernova (SN). The interpretation of the observables, however, is subject to the uncertain SN models and the flavor conversion mechanism of neutrinos in a SN. We attempt to propose a qualitative interpretation of the expected neutrino events at terrestrial detectors, focusing on the accretion phase of the neutrino burst. The flavor conversions due to neutrino self-interaction, the MSW effect, and the Earth regeneration effect are incorporated in the calculation. It leads to several distinct scenarios that are identified by the neutrino mass hierarchies and the collective flavor transitions. Consequences resulting from the variation of incident angles and SN models are also discussed

Current Direct Neutrino Mass Experiments

Directory of Open Access Journals (Sweden)

G. Drexlin

2013-01-01

Full Text Available In this contribution, we review the status and perspectives of direct neutrino mass experiments, which investigate the kinematics of β-decays of specific isotopes (3H, 187Re, 163Ho to derive model-independent information on the averaged electron (antineutrino mass. After discussing the kinematics of β-decay and the determination of the neutrino mass, we give a brief overview of past neutrino mass measurements (SN1987a-ToF studies, Mainz and Troitsk experiments for 3H, cryobolometers for 187Re. We then describe the Karlsruhe Tritium Neutrino (KATRIN experiment currently under construction at Karlsruhe Institute of Technology, which will use the MAC-E-Filter principle to push the sensitivity down to a value of 200 meV (90% C.L.. To do so, many technological challenges have to be solved related to source intensity and stability, as well as precision energy analysis and low background rate close to the kinematic endpoint of tritium β-decay at 18.6 keV. We then review new approaches such as the MARE, ECHO, and Project8 experiments, which offer the promise to perform an independent measurement of the neutrino mass in the sub-eV region. Altogether, the novel methods developed in direct neutrino mass experiments will provide vital information on the absolute mass scale of neutrinos.

PINGU sensitivity to neutrino mass hierarchy

International Nuclear Information System (INIS)

Groß, Andreas

2014-01-01

Determination of the neutrino mass hierarchy (NMH) is among the most fundamental questions in particle physics. Recent measurements of 1) a large mixing angle between the first and the third neutrino mass eigenstates and 2) the first observation of atmospheric neutrino oscillations at tens of GeV with neutrino telescopes, open the intriguing new possibility to exploit matter effects in neutrino oscillation to determine the neutrino mass hierarchy. A further extension of IceCube/DeepCore called PINGU (Precision IceCube Next Generation Upgrade) has been recently envisioned with the ultimate goal to measure neutrino mass hierarchy. PINGU would consist of additional IceCube-like strings of detectors deployed in the deepest and cleanest ice in the center of IceCube. More densely deployed instrumentation would provide a threshold substantially below 10 GeV and enhance the sensitivity to the mass hierarchy signal in atmospheric neutrinos. Here we discuss an estimate of the PINGU sensitivity to the mass hierarchy determined using an approximation with an Asimov dataset and an oscillation parameter fit

Some unsettled questions in the problem of neutrino oscillations

International Nuclear Information System (INIS)

Beshtoev, Kh.M.

2003-01-01

It is noted that the theory of neutrino oscillations can be constructed only in the framework of the particle physics theory where a mass shell conception is presented and then transitions (oscillations) between neutrinos with equal masses are real and between neutrinos with different masses are virtual. There can be three types of neutrino transitions. In the experiments it is necessary to decide the question: which type of neutrino transitions is realized in nature? At present it is supposed that Dirac and Majorana neutrino oscillations can be realized. It is shown that we cannot put Majorana neutrinos in the standard weak interaction theory without violation of the gauge invariance. If we use the Majorana neutrinos then we come to contradiction with the existing experimental data. Then it is obvious that there can be only realized transitions between Dirac neutrinos with different flavors. It is also shown that the mechanism of resonance enhancement of neutrino oscillations in matter cannot be realized without violation of the law of energy-momentum conservation. Though it is supposed that in experiments we see neutrino oscillations, indeed only transitions between neutrinos are registered.To register neutrino oscillations, it is necessary to see second or even higher neutrino oscillation modes in experiments. For this purpose we can use the elliptic character of the Earth orbit at registrations of sun neutrinos. The analysis shows that the SNO experimental results do not confirm smallness of ν e → ν τ transition angle mixing, which was obtained in the CHOOZ experiment. It is also noted that there is contradiction between the SNO, Super-Kamiokande, Homestake and SAGE, and GNO (GALLEX) data. (author)

The {mu} term and neutrino masses

Energy Technology Data Exchange (ETDEWEB)

Chen, Mu-Chun [California Univ., Irvine, CA (United States). Dept. of Physics and Astronomy; Ratz, Michael; Staudt, Christian [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Vaudrevange, Patrick K.S. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2012-06-15

The well-known Giudice-Masiero mechanism explains the presence of a {mu} term of the order of the gravitino mass, but does not explain why the holomorphic mass term is absent in the superpotential. We discuss anomaly-free discrete symmetries which are both compatible with SU(5) unification of matter and the Giudice-Masiero mechanism, i.e. forbid the {mu} term in the superpotential while allowing the necessary Kaehler potential term. We find that these are Z{sup R}{sub M} symmetries with the following properties: (i) M is a multiple of four; (ii) the Higgs bilinear H{sub u} H{sub d} transforms trivially; (iii) the superspace coordinate {theta} has charge M/4 and, accordingly, the superpotential has charge M/2; (iv) dimension five proton decay operators are automatically absent. All Z{sup R}{sub M} symmetries are anomaly-free due to a non-trivial transformation of a Green-Schwarz axion, and, as a consequence, a holomorphic {mu} term appears at the non-perturbative level. There is a unique symmetry that is consistent with the Weinberg operator while there is a class of Z{sup R}{sub M} symmetries which explain suppressed Dirac neutrino masses.

The μ term and neutrino masses

International Nuclear Information System (INIS)

Chen, Mu-Chun

2012-06-01

The well-known Giudice-Masiero mechanism explains the presence of a μ term of the order of the gravitino mass, but does not explain why the holomorphic mass term is absent in the superpotential. We discuss anomaly-free discrete symmetries which are both compatible with SU(5) unification of matter and the Giudice-Masiero mechanism, i.e. forbid the μ term in the superpotential while allowing the necessary Kaehler potential term. We find that these are Z R M symmetries with the following properties: (i) M is a multiple of four; (ii) the Higgs bilinear H u H d transforms trivially; (iii) the superspace coordinate θ has charge M/4 and, accordingly, the superpotential has charge M/2; (iv) dimension five proton decay operators are automatically absent. All Z R M symmetries are anomaly-free due to a non-trivial transformation of a Green-Schwarz axion, and, as a consequence, a holomorphic μ term appears at the non-perturbative level. There is a unique symmetry that is consistent with the Weinberg operator while there is a class of Z R M symmetries which explain suppressed Dirac neutrino masses.

Minimalistic Neutrino Mass Model

CERN Document Server

De Gouvêa, A; Gouvea, Andre de

2001-01-01

We consider the simplest model which solves the solar and atmospheric neutrino puzzles, in the sense that it contains the smallest amount of beyond the Standard Model ingredients. The solar neutrino data is accounted for by Planck-mass effects while the atmospheric neutrino anomaly is due to the existence of a single right-handed neutrino at an intermediate mass scale between 10^9 GeV and 10^14 GeV. Even though the neutrino mixing angles are not exactly predicted, they can be naturally large, which agrees well with the current experimental situation. Furthermore, the amount of lepton asymmetry produced in the early universe by the decay of the right-handed neutrino is very predictive and may be enough to explain the current baryon-to-photon ratio if the right-handed neutrinos are produced out of thermal equilibrium. One definitive test for the model is the search for anomalous seasonal effects at Borexino.

Radiative Majorana Neutrino Masses

OpenAIRE

Hou, Wei-Shu; Wong, Gwo-Guang

1994-01-01

We present new radiative mechanisms for generating Majorana neutrino masses, within an extension of the standard model that successfully generates radiative charged lepton masses, order by order, from heavy sequential leptons. Only the new sequential neutral lepton has a right-handed partner, and its Majorana mass provides the seed for Majorana neutrino mass generation. Saturating the cosmological bound of $50$ eV with $m_{\

Neutrino mass from laboratory: contribution of double beta decay to the neutrino mass matrix

International Nuclear Information System (INIS)

Klapdor-Kleingrothaus, H.V.

2001-01-01

Double beta decay is indispensable to solve the question of the neutrino mass matrix together with ν oscillation experiments. The most sensitive experiment - since eight years the HEIDELBERG-MOSCOW experiment in Gran-Sasso - already now, with the experimental limit of ν > < 0.26 eV practically excludes degenerate ν mass scenarios allowing neutrinos as hot dark matter in the universe for the smallangle MSW solution of the solar neutrino problem. It probes cosmological models including hot dark matter already now on the level of future satellite experiments MAP and PLANCK. It further probes many topics of beyond SM physics at the TeV scale. Future experiments should give access to the multi-TeV range and complement on many ways the search for new physics at future colliders like LHC and NLC. For neutrino physics some of them (GENIUS) will allow to test almost all neutrino mass scenarios allowed by the present neutrino oscillation experiments

Azimuthal asymmetry of recoil electrons in neutrino-electron elastic scattering as signature of neutrino nature

Energy Technology Data Exchange (ETDEWEB)

Sobkow, W.; Blaut, A. [University of Wroclaw, Institute of Theoretical Physics, Wroclaw (Poland)

2016-05-15

In this paper, we analyze the theoretically possible scenario beyond the standard model in order to show how the presence of the exotic scalar, tensor, V + A weak interactions in addition to the standard vector-axial (V - A) ones may help to distinguish the Dirac from Majorana neutrinos in the elastic scattering of an (anti)neutrino beam off the unpolarized electrons in the relativistic limit. We assume that the incoming (anti)neutrino beam comes from the polarized muon decay at rest and is the left-right chiral superposition with assigned direction of the transversal spin polarization with respect to the production plane. Our analysis is carried out for the flavour (current) neutrino eigenstates. It means that the transverse neutrino polarization estimates are the same both for the Dirac and Majorana cases. We display that the azimuthal asymmetry in the angular distribution of recoil electrons is generated by the interference terms between the standard and exotic couplings, which are proportional to the transversal (anti)neutrino spin polarization and independent of the neutrino mass. This asymmetry for the Majorana neutrinos is larger than for the Dirac ones. We also indicate the possibility of utilizing the azimuthal asymmetry measurements to search for the new CP-violating phases. Our study is based on the assumption that the possible detector (running for 1 year) has the shape of a flat circular ring, while the intense neutrino source is located in the centre of the ring and polarized perpendicularly to the ring. In addition, the large low-threshold, real-time detector is able to measure with a high resolution both the polar angle and the azimuthal angle of outgoing electron momentum. Our analysis is model-independent and consistent with the current upper limits on the non-standard couplings. (orig.)

Predictions for the neutrino parameters in the minimal gauged U(1){sub L{sub μ-L{sub τ}}} model

Energy Technology Data Exchange (ETDEWEB)

Asai, Kento; Nagata, Natsumi [University of Tokyo, Department of Physics, Bunkyo-ku, Tokyo (Japan); Hamaguchi, Koichi [University of Tokyo, Department of Physics, Bunkyo-ku, Tokyo (Japan); University of Tokyo, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), Kashiwa (Japan)

2017-11-15

We study the structure of the neutrino-mass matrix in the minimal gauged U(1){sub L{sub μ-L{sub τ}}} model, where three right-handed neutrinos are added to the Standard Model in order to obtain non-zero masses for the active neutrinos. Because of the U(1){sub L{sub μ-L{sub τ}}} gauge symmetry, the structure of both Dirac and Majorana mass terms of neutrinos is tightly restricted. In particular, the inverse of the neutrino-mass matrix has zeros in the (μ,μ) and (τ,τ) components, namely, this model offers a symmetric realization of the so-called two-zero-minor structure in the neutrino-mass matrix. Due to these constraints, all the CP phases - the Dirac CP phase δ and the Majorana CP phases α{sub 2} and α{sub 3} - as well as the mass eigenvalues of the light neutrinos m{sub i} are uniquely determined as functions of the neutrino mixing angles θ{sub 12}, θ{sub 23}, and θ{sub 13}, and the squared mass differences Δm{sub 21}{sup 2} and Δm{sub 31}{sup 2}. We find that this model predicts the Dirac CP phase δ to be δ ≅ 1.59π-1.70π (1.54π-1.78π), the sum of the neutrino masses to be sum {sub i}m{sub i} ≅ 0.14-0.22 eV (0.12-0.40 eV), and the effective mass for the neutrinoless double-beta decay to be left angle m{sub ββ} right angle ≅ 0.024-0.055 eV (0.017-0.12 eV) at 1σ (2σ) level, which are totally consistent with the current experimental limits. These predictions can soon be tested in future neutrino experiments. Implications for leptogenesis are also discussed. (orig.)

Introduction to models of neutrino masses and mixings

International Nuclear Information System (INIS)

Joshipura, Anjan S.

2004-01-01

This review contains an introduction to models of neutrino masses for non-experts. Topics discussed are i) different types of neutrino masses ii) structure of neutrino masses and mixing needed to understand neutrino oscillation results iii) mechanism to generate neutrino masses in gauge theories and iv) discussion of generic scenarios proposed to realize the required neutrino mass structures. (author)

Direct neutrino mass measurements

Energy Technology Data Exchange (ETDEWEB)

Weinheimer, Christian, E-mail: weinheimer@uni-muenster.de [Westfaelische Wilhelms-Universitaet, Institut fuer Kernphysik (Germany)

2013-03-15

Direct neutrino mass experiments are complementary to searches for neutrinoless double {beta}-decay and to analyses of cosmological data. The previous tritium beta decay experiments at Mainz and at Troitsk have achieved upper limits on the neutrino mass of about 2 eV/c{sup 2} . The KATRIN experiment under construction will improve the neutrino mass sensitivity down to 200 meV/c{sup 2} by increasing strongly the statistics and-at the same time-reducing the systematic uncertainties. Huge improvements have been made to operate the system extremely stably and at very low background rate. The latter comprises new methods to reject secondary electrons from the walls as well as to avoid and to eject electrons stored in traps. As an alternative to tritium {beta}-decay experiments cryo-bolometers investigating the endpoint region of {sup 187}Re {beta}-decay or the electron capture of {sup 163}Ho are being developed. This article briefly reviews the current status of the direct neutrino mass measurements.

Effects of neutrino degeneracy and of downscatter on neutrino radiation from dense stellar cores

International Nuclear Information System (INIS)

Lichtenstadt, I.; Ron, A.; Sack, N.; Wagschal, J.J.; Bludman, S.A.

1978-01-01

A simplified model is presneted for several stages in the development of a neutronization shell in the inner core of a collapsing star. Neutrino degeneracy severely reduces neutrino emission and downscatter in energy, so that for all but the thinest shell sources, surface emission of an approximately Fermi-Dirac neutrino spectrum obtains. The Neutrino spectrum departs from exact Fermi-Dirac neutrino form only because of the outstreaming of low-energy neutrinos.Downscatter by electrons is helped by neutron scatterers present, but except for reducing the peak neutrino energy by about 30%, electrons play no dramatic part. The neutrino degeneracy inhibits downscatter so that the low-energy window in the Fermi-Dirac distribution leads to little neutrino loss.A simple equilibrium radiation picture emerges in which neutrinos are LTE thermally emitted in the neutronization shell and isotropically coherently scattered by neutrons and by nuclei on the way out of the overlying mantle. The Fermi statistics limit on neutrino flux is probably reached in practice, but is, in most cases, still insufficient for mantle blow-off

LHC and the origin of neutrino mass

International Nuclear Information System (INIS)

Senjanovic, Goran

2008-01-01

It is often said that neutrino mass is a window to a new physics beyond the standard model (SM). This is true if neutrinos are Majorana particles for 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 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 make a case here for this in the context of all three types of seesaw mechanism.

Viability of Dirac phase leptogenesis

International Nuclear Information System (INIS)

Anisimov, Alexey; Blanchet, Steve; Di Bari, Pasquale

2008-01-01

We discuss the conditions for a non-vanishing Dirac phase δ and mixing angle θ 13 , sources of CP violation in neutrino oscillations, to be uniquely responsible for the observed matter–antimatter asymmetry of the Universe through leptogenesis. We show that this scenario, that we call δ-leptogenesis, is viable when the degenerate limit for the heavy right-handed (RH) neutrino spectrum is considered. We derive an interesting joint condition on sinθ 13 and the absolute neutrino mass scale that can be tested in future neutrino oscillation experiments. In the limit of the hierarchical heavy RH neutrino spectrum, we strengthen the previous result that δ-leptogenesis is only very marginally allowed, even when the production from the two heavier RH neutrinos is taken into account. An improved experimental upper bound on sinθ 13 and/or an account of quantum kinetic effects could completely rule out this option in the future. Therefore, δ-leptogenesis can be also regarded as motivation for models with degenerate heavy neutrino spectrum

A simple connection of the (electroweak) anapole moment with the (electroweak) charge radius of a massless left-handed Dirac neutrino

Energy Technology Data Exchange (ETDEWEB)

Rosado, A. [Universidad Autonoma de Puebla, Puebla (Mexico)

2001-04-01

Assuming that the neutrino is a massless left-handed Dirac particle, we show that the neutrino anapole moment and the neutrino charge radius satisfy the simple relation a{sub v} =(r{sup 2}{sub v}) /6, in the context of the Standard Model of the electroweak interactions. We also show that the neutrino electroweak anapole moment a{sub v}l{sup E}W and the neutrino electroweak charge radius (r{sup 2}{sub v}){sup E}W, which have been defined through the v{sub l}l' scattering at the one-loop level and are physical quantities, also obey the relation a{sub v}l{sup E}W =(r{sup 2}{sub v}){sup E}W/6. [Spanish] Suponiendo que el neutrino es una particula de Dirac, sin masa y con helicidad izquierda, mostramos que el momento anapolar a{sub v} y el radio de carga (r{sub v}{sup 2}) del neutrino satisfacen la relacion simple a{sub v} =(r{sup 2}{sub v}) /6, en el contexto del Modelo Estandar de las interacciones electrodebiles. Ademas, mostramos que el momento anapolar electrodebil a{sub v}l{sup E}W y el radio de carga electrodebil (r{sup 2}{sub v}){sup E}W del neutrino, los cuales han sido definidos a traves de la dispersion v{sub l}l' a nivel de un lazo y que son cantidades fisicas, tambien obedecen la relacion a{sub v}l{sup E}W =(r{sup 2}{sub v}){sup E}W/6.

Measurements of neutrino mass

International Nuclear Information System (INIS)

Robertson, R.G.H.

1985-01-01

Direct experimental information of neutrino mass as derived from the study of nuclear and elementary-particle weak decays is reviewed. Topics include tritium beta decay; the 3 He-T mass difference; electron capture decay of 163 Ho and 158 Tb; and limits on massive neutrinos from cosmology. 38 references

Identifying the neutrino mass spectrum from a supernova neutrino burst

International Nuclear Information System (INIS)

Dighe, A.S.; Smirnov, A.Yu.

1999-12-01

We study the role that the future detection of the neutrino burst from a galactic supernova can play in the reconstruction of the neutrino mass spectrum. We consider all possible 3ν mass and flavor spectra which describe the solar and atmospheric neutrino data. For each of these spectra we find the observable effects of the supernova neutrino conversions both in the matter of the star and the earth. We show that studies of the electron neutrino and antineutrino spectra as well as observations of the neutral current effects from supernova will allow us (i) to identify the solar neutrino solution, (ii) to determine the type of mass hierarchy (normal or inverted) and (iii) to probe the mixing vertical bar U e3 vertical bar 2 to values as low as 10 -4 - 10 -3 . (author)

Dirac Mass Dynamics in Multidimensional Nonlocal Parabolic Equations

KAUST Repository

Lorz, Alexander

2011-01-17

Nonlocal Lotka-Volterra models have the property that solutions concentrate as Dirac masses in the limit of small diffusion. Is it possible to describe the dynamics of the limiting concentration points and of the weights of the Dirac masses? What is the long time asymptotics of these Dirac masses? Can several Dirac masses coexist? We will explain how these questions relate to the so-called "constrained Hamilton-Jacobi equation" and how a form of canonical equation can be established. This equation has been established assuming smoothness. Here we build a framework where smooth solutions exist and thus the full theory can be developed rigorously. We also show that our form of canonical equation comes with a kind of Lyapunov functional. Numerical simulations show that the trajectories can exhibit unexpected dynamics well explained by this equation. Our motivation comes from population adaptive evolution a branch of mathematical ecology which models Darwinian evolution. © Taylor & Francis Group, LLC.

Neutrino masses and mixings

International Nuclear Information System (INIS)

Wolfenstein, L.

1991-01-01

Theoretical prejudices, cosmology, and neutrino oscillation experiments all suggest neutrino mass are far below present direct experimental limits. Four interesting scenarios and their implications are discussed: (1) a 17 keV ν τ , (2) a 30 ev ν τ making up the dark matter, (3) a 10 -3 ev ν μ to solve the solar neutrino problem, and (4) a three-neutrino MSW solution

Right-handed neutrinos at CERN LHC and the mechanism of neutrino mass generation

International Nuclear Information System (INIS)

Kersten, Joern; Smirnov, Alexei Yu.

2007-01-01

We consider the possibility to detect right-handed neutrinos, which are mostly singlets of the standard model gauge group, at future accelerators. Substantial mixing of these neutrinos with the active neutrinos requires a cancellation of different contributions to the light neutrino mass matrix at the level of 10 -8 . We discuss possible symmetries behind this cancellation and argue that for three right-handed neutrinos they always lead to conservation of total lepton number. Light neutrino masses can be generated by small perturbations violating these symmetries. In the most general case, LHC physics and the mechanism of neutrino mass generation are essentially decoupled; with additional assumptions, correlations can appear between collider observables and features of the neutrino mass matrix

Texture zero neutrino models and their connection with resonant leptogenesis

Science.gov (United States)

Achelashvili, Avtandil; Tavartkiladze, Zurab

2018-04-01

Within the low scale resonant leptogenesis scenario, the cosmological CP asymmetry may arise by radiative corrections through the charged lepton Yukawa couplings. While in some cases, as one expects, decisive role is played by the λτ coupling, we show that in specific neutrino textures only by inclusion of the λμ the cosmological CP violation is generated at 1-loop level. With the purpose to relate the cosmological CP violation to the leptonic CP phase δ, we consider an extension of MSSM with two right handed neutrinos (RHN), which are degenerate in mass at high scales. Together with this, we first consider two texture zero 3 × 2 Dirac Yukawa matrices of neutrinos. These via see-saw generated neutrino mass matrices augmented by single ΔL = 2 dimension five (d = 5) operator give predictive neutrino sectors with calculable CP asymmetries. The latter is generated through λμ,τ coupling(s) at 1-loop level. Detailed analysis of the leptogenesis is performed. We also revise some one texture zero Dirac Yukawa matrices, considered earlier, and show that addition of a single ΔL = 2, d = 5 entry in the neutrino mass matrices, together with newly computed 1-loop corrections to the CP asymmetries, give nice accommodation of the neutrino sector and desirable amount of the baryon asymmetry via the resonant leptogenesis even for rather low RHN masses (∼few TeV-107 GeV).

Physics of the neutrino mass

International Nuclear Information System (INIS)

Mohapatra, R N

2004-01-01

Recent neutrino oscillation experiments have yielded valuable information on the nature of neutrino masses and mixings and qualify as the first evidence for physics beyond the standard model. Even though we are far from a complete understanding of the new physics implied by them, there are many useful hints. As the next precision era in neutrino physics is about to be launched, we review the physics of neutrino mass: what we have learned and what we are going to learn

Neutrino mass: Recent results

International Nuclear Information System (INIS)

Robertson, R.G.H.

1989-01-01

Some recent developments in the experimental search for neutrino mass are discussed. Simpson and Hime report finding new evidence for a 17-keV neutrino in the β decay of 3 H and 35 S. New data from Los Alamos on the electron neutrino mass as measured in tritium beta decay give an upper limit of 13.5 eV at the 95% confidence level. This result is not consistent with the long-standing ITEP result of 26(5) eV within a ''model-independent'' range of 17 to 40 eV. It now appears that the electron neutrino is not sufficiently massive to close the universe by itself. 38 refs., 1 figs., 2 tabs

Probing the Absolute Mass Scale of Neutrinos

International Nuclear Information System (INIS)

Formaggio, Joseph A.

2011-01-01

The experimental efforts of the Neutrino Physics Group at MIT center primarily around the exploration of neutrino mass and its significance within the context of nuclear physics, particle physics, and cosmology. The group has played a prominent role in the Sudbury Neutrino Observatory, a neutrino experiment dedicated to measure neutrino oscillations from 8B neutrinos created in the sun. The group is now focusing its efforts in the measurement of the neutrino mass directly via the use of tritium beta decay. The MIT group has primary responsibilities in the Karlsruhe Tritium Neutrino mass experiment, expected to begin data taking by 2013. Specifically, the MIT group is responsible for the design and development of the global Monte Carlo framework to be used by the KATRIN collaboration, as well as responsibilities directly associated with the construction of the focal plane detector. In addition, the MIT group is sponsoring a new research endeavor for neutrino mass measurements, known as Project 8, to push beyond the limitations of current neutrino mass experiments.

Neutrino mass textures with maximal CP violation

International Nuclear Information System (INIS)

Aizawa, Ichiro; Kitabayashi, Teruyuki; Yasue, Masaki

2005-01-01

We show three types of neutrino mass textures, which give maximal CP violation as well as maximal atmospheric neutrino mixing. These textures are described by six real mass parameters: one specified by two complex flavor neutrino masses and two constrained ones and the others specified by three complex flavor neutrino masses. In each texture, we calculate mixing angles and masses, which are consistent with observed data, as well as Majorana CP phases

Reconstructing Neutrino Mass Spectrum

OpenAIRE

Smirnov, A. Yu.

1999-01-01

Reconstruction of the neutrino mass spectrum and lepton mixing is one of the fundamental problems of particle physics. In this connection we consider two central topics: (i) the origin of large lepton mixing, (ii) possible existence of new (sterile) neutrino states. We discuss also possible relation between large mixing and existence of sterile neutrinos.

The νMSM, dark matter and neutrino masses

International Nuclear Information System (INIS)

Asaka, Takehiko; Blanchet, Steve; Shaposhnikov, Mikhail

2005-01-01

We investigate an extension of the Minimal Standard Model by right-handed neutrinos (the νMSM) to incorporate neutrino masses consistent with oscillation experiments. Within this theory, the only candidates for dark matter particles are sterile right-handed neutrinos with masses of a few keV. Requiring that these neutrinos explain entirely the (warm) dark matter, we find that their number is at least three. We show that, in the minimal choice of three sterile neutrinos, the mass of the lightest active neutrino is smaller than O(10 -5 ) eV, which excludes the degenerate mass spectra of three active neutrinos and fixes the absolute mass scale of the other two active neutrinos

The Neutrino Mass Window for Baryogenesis

CERN Document Server

Buchmüller, Wilfried; Plümacher, Michael

2003-01-01

Interactions of heavy Majorana neutrinos in the thermal phase of the early universe may be the origin of the cosmological matter-antimatter asymmetry. This mechanism of baryogenesis implies stringent constraints on light and heavy Majorana neutrino masses. We derive an improved upper bound on the CP asymmetry in heavy neutrino decays which, together with the kinetic equations, yields an upper bound on all light neutrino masses of 0.1 eV. Lepton number changing processes at temperatures above the temperature T_B of baryogenesis can erase other, pre-existing contributions to the baryon asymmetry. We find that these washout processes become very efficient if the effective neutrino mass \\tilde{m}_1 is larger than m_* \\simeq 10^{-3} eV. All memory of the initial conditions is then erased. Hence, for neutrino masses in the range from (\\Delta m^2_sol)^{1/2} \\simeq 8*10^{-3} eV to (\\Delta m^2_atm)^{1/2} \\simeq 5*10^{-2} eV, which is suggested by neutrino oscillations, leptogenesis emerges as the unique source of the ...

Neutrino masses and beyond from supersymmetry

International Nuclear Information System (INIS)

Kong, O.C.W.

2004-01-01

A generic form of the supersymmetric SM naturally gives rise to the lepton number violating neutrino masses and mixings, without the need for extra superfields beyond the minimal spectrum. Hence, SUSY can be considered the origin of beyond SM properties of neutrinos. We have developed a formulation under which one can efficiently analyze the model. Various sources of neutrino masses are discussed. Such mass contributions come from lepton number and flavor violating couplings that also give rise to a rich phenomenology of the neutrinos and other leptons, also to be discussed. (author)

Neutrino mass hierarchy and three-flavor spectral splits of supernova neutrinos

International Nuclear Information System (INIS)

Dasgupta, Basudeb; Mirizzi, Alessandro; Tomas, Ricard; Tamborra, Irene

2010-01-01

It was recently realized that three-flavor effects could peculiarly modify the development of spectral splits induced by collective oscillations, for supernova neutrinos emitted during the cooling phase of a protoneutron star. We systematically explore this case, explaining how the impact of these three-flavor effects depends on the ordering of the neutrino masses. In inverted mass hierarchy, the solar mass splitting gives rise to instabilities in regions of the (anti)neutrino energy spectra that were otherwise stable under the leading two-flavor evolution governed by the atmospheric mass splitting and by the 1-3 mixing angle. As a consequence, the high-energy spectral splits found in the electron (anti)neutrino spectra disappear, and are transferred to other flavors. Imperfect adiabaticity leads to smearing of spectral swap features. In normal mass hierarchy, the three-flavor and the two-flavor instabilities act in the same region of the neutrino energy spectrum, leading to only minor departures from the two-flavor treatment.

Remark on natural models of neutrinos

International Nuclear Information System (INIS)

Fujikawa, Kazuo

2005-01-01

We comment on what 't Hooft's naturalness argument implies with regard to a minimal extension of the Standard Model that incorporates right-handed neutrinos with generic mass terms. If this Lagrangian is taken as that of a low energy effective theory, the idea of pseudo-Dirac neutrinos with very small masses is consistent with 't Hooft's naturalness argument. This argument is based on the observation that the right-handed components of neutrinos in the massless limit exhibit an extra enhanced symmetry which is absent in other charged fermions. This enhanced symmetry is reminiscent of the Nambu-Goldstone fermions associated with spontaneously broken supersymmetry. The conventional seesaw scenario gives another natural solution if the ultra-heavy right-handed neutrinos are integrated out in the formulation of a low energy effective theory. (author)

Neutrino mass and mixing in the seesaw playground

International Nuclear Information System (INIS)

King, Stephen F.

2016-01-01

We discuss neutrino mass and mixing in the framework of the classic seesaw mechanism, involving right-handed neutrinos with large Majorana masses, which provides an appealing way to understand the smallness of neutrino masses. However, with many input parameters, the seesaw mechanism is in general not predictive. We focus on natural implementations of the seesaw mechanism, in which large cancellations do not occur, where one of the right-handed neutrinos is dominantly responsible for the atmospheric neutrino mass, while a second right-handed neutrino accounts for the solar neutrino mass, leading to an effective two right-handed neutrino model. We discuss recent attempts to predict lepton mixing and CP violation within such natural frameworks, focusing on the Littlest Seesaw and its distinctive predictions.

Neutrino mass from M theory SO(10)

International Nuclear Information System (INIS)

Acharya, Bobby S.; Bożek, Krzysztof; Romão, Miguel Crispim; King, Stephen F.; Pongkitivanichkul, Chakrit

2016-01-01

We study the origin of neutrino mass from SO(10) arising from M Theory compactified on a G_2-manifold. This is linked to the problem of the breaking of the extra U(1) gauge group, in the SU(5)×U(1) subgroup of SO(10), which we show can achieved via a (generalised) Kolda-Martin mechanism. The resulting neutrino masses arise from a combination of the seesaw mechanism and induced R-parity breaking contributions. The rather complicated neutrino mass matrix is analysed for one neutrino family and it is shown how phenomenologically acceptable neutrino masses can emerge.

Neutrino mass from M theory SO(10)

Energy Technology Data Exchange (ETDEWEB)

Acharya, Bobby S. [Department of Physics, King’s College,WC2R 2LS, London (United Kingdom); International Centre for Theoretical Physics,I-34151 Trieste (Italy); Bożek, Krzysztof [Department of Physics, King’s College,WC2R 2LS, London (United Kingdom); Romão, Miguel Crispim; King, Stephen F. [School of Physics and Astronomy, University of Southampton,SO17 1BJ, Southampton (United Kingdom); Pongkitivanichkul, Chakrit [Department of Physics, King’s College,WC2R 2LS, London (United Kingdom)

2016-11-29

We study the origin of neutrino mass from SO(10) arising from M Theory compactified on a G{sub 2}-manifold. This is linked to the problem of the breaking of the extra U(1) gauge group, in the SU(5)×U(1) subgroup of SO(10), which we show can achieved via a (generalised) Kolda-Martin mechanism. The resulting neutrino masses arise from a combination of the seesaw mechanism and induced R-parity breaking contributions. The rather complicated neutrino mass matrix is analysed for one neutrino family and it is shown how phenomenologically acceptable neutrino masses can emerge.

See-saw enhancement of neutrino mixing due to the right-handed phases

International Nuclear Information System (INIS)

Tanimoto, M.

1994-11-01

We study the see-saw enhancement mechanism in presence of the right-handed phases of the Dirac neutrino mass matrix and the Majorana mass matrix. The enhancement condition given by Smirnov is modified. We point out that the see-saw enhancement could be obtained due to the right-handed phases even if the Majorana matrix is proportional to the unit matrix. We show a realistic Dirac mass matrix which causes the see-saw enhancement. (author)

Introductory talk. 6. Moriond workshop massive neutrinos in particle physics and astrophysics

International Nuclear Information System (INIS)

Rosen, S.P.

1986-01-01

We review the concepts of Majorana and Dirac neutrinos from an operational point of view and survey the experimental search for neutrino mass. We also review the work of Mikheyev and Smirnov on the enhancement of neutrino oscillations via the mechanism of Wolfenstein matter oscillations. Results of an extensive computation of MSW effects in the sun are described. 39 refs., 6 figs

Experimental studies of neutrino oscillations

CERN Document Server

Kajita, Takaaki

2016-01-01

The 2015 Nobel Prize in physics has been awarded to Takaaki Kajita and Arthur McDonald "for the discovery of neutrino oscillations, which shows that neutrinos have mass". Takaaki Kajita of Tokyo University is a Japanese physicist, known for neutrino experiments at the Kamiokande and its successor, Super-Kamiokande. This volume of collected works of Kajita on neutrino oscillations provides a good glimpse into as well as a record of the rise and the role of Asian research in the frontiers of neutrino physics. Japan is now a major force in the study of the 3 families of neutrinos. Much remains to be done to clarify the Dirac vs. Majorana nature of the neutrino, and the cosmological implications of the neutrino. The collected works of Kajita and his Super-Kamiokande group will leave an indelible foot-print in the history of big and better science.

Nonzero θ13 and neutrino masses from the modified tri-bi-maximal neutrino mixing matrix

International Nuclear Information System (INIS)

Damanik, A.

2014-01-01

There are 3 types of neutrino mixing matrices: tri-bi-maximal, bi-maximal and democratic. These 3 types of neutrino mixing matrices predict that the mixing angle θ 13 should be null. Motivated by the recent experimental evidence of nonzero and relatively large θ 13 , we modified the tribimaximal mixing matrix by introducing a simple perturbation matrix into tribimaximal neutrino mixing matrix. In this scenario, we obtained nonzero mixing angle θ 13 =7.9 degrees which is in agreement with the present experimental results. By imposing 2 zeros texture into the obtained neutrino mass matrix from modified tribimaximal mixing matrix, we then have the neutrino mass spectrum in normal hierarchy. Some phenomenological implications are also discussed. It appears that if we use the solar neutrino squared-mass difference to determine the values of neutrino masses, then we cannot have the correct value for the atmospheric squared-mass difference. Conversely, if we use the experimental value of the squared-mass difference to determine the neutrino masses, then we cannot have the correct value for the solar neutrino squared-mass difference

Effects of neutrino oscillation on supernova neutrino: inverted mass hierarchy

International Nuclear Information System (INIS)

Takahashi, Keitaro; Sato, Katsuhiko

2003-01-01

We study the effects of neutrino oscillation on supernova neutrino in the case of the inverted mass hierarchy (m 3 1 2 ). This is an extended study of our previous study where all analyses are performed with normal mass hierarchy (m 1 2 3 ). Numerical analysis using a realistic supernova and presupernova model allow us to discuss quantitatively a possibility to probe neutrino oscillation parameters. We show that we can break partly the degeneracy of the solar neutrino problem (LMA or SMA) and probe the magnitude of θ 13 to some extent by the ratios of high-energy events and low-energy events at SuperKamiokande and SNO and the presence of the Earth effects. Further, if the magnitude of θ 13 is known roughly, we can identify the mass hierarchy

Status of neutrino mass experiments

International Nuclear Information System (INIS)

Fackler, O.

1985-01-01

In 1980 two experiments ignited a fertile field of research - the determination of the neutrino masses. Subsequently, over 35 experiments using a variety of techniques have probed or are probing this question. Primarily the author discuss electron antineutrino (hereafter referred to as neutrino) mass experiments. Section I begins with a discussion of astronomical and terrestrial observations which motivated these experiments. In Section II, the author quote limits from muon and tau mass determinations. These limits are more thoroughly discussed in other paper. The author continues by describing the four approaches used to measure the electron neutrino mass. In Section III, tritium beta decay mass determinations are reviewed. This section includes a general summary of previous experimental results, and discussion of the major ongoing experiments. Section IV offers concluding remarks

Neutrino Physics

CERN Multimedia

CERN. Geneva; Dydak, Friedrich

2001-01-01

Starting from a review of theoretical concepts and experimental results in the early years of neutrino physics after Pauli's 1930 letter, today's double role of the neutrino as a cornerstone of the Standard Model and as a promising probe of physics beyond the Standard Model will be discussed. Topics comprise: - Conventional neutrino beams - Neutrinos as probes of the nucleon structure - Neutrinos from the universe - Dirac or Majorana neutrinos - Neutrino oscillations - MNS matrix - CP violation in the lepton sector - Neutrino factory.

Neutrino Physics

CERN Multimedia

CERN. Geneva. Audiovisual Unit

2002-01-01

Starting from a review of theoretical concepts and experimental results in the early years of neutrino physics after Pauli's 1930 letter, today's double role of the neutrino as a cornerstone of the Standard Model and as a promising probe of physics beyond the Standard Model will be discussed. Topics comprise: - Conventional neutrino beams - Neutrinos as probes of the nucleon structure - Neutrinos from the universe - Dirac or Majorana neutrinos - Neutrino oscillations - MNS matrix - CP violation in the lepton sector - Neutrino factory.

Constraining dynamical neutrino mass generation with cosmological data

Energy Technology Data Exchange (ETDEWEB)

Koksbang, S.M.; Hannestad, S., E-mail: koksbang@phys.au.dk, E-mail: sth@phys.au.dk [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)

2017-09-01

We study models in which neutrino masses are generated dynamically at cosmologically late times. Our study is purely phenomenological and parameterized in terms of three effective parameters characterizing the redshift of mass generation, the width of the transition region, and the present day neutrino mass. We also study the possibility that neutrinos become strongly self-interacting at the time where the mass is generated. We find that in a number of cases, models with large present day neutrino masses are allowed by current CMB, BAO and supernova data. The increase in the allowed mass range makes it possible that a non-zero neutrino mass could be measured in direct detection experiments such as KATRIN. Intriguingly we also find that there are allowed models in which neutrinos become strongly self-interacting around the epoch of recombination.

Leptogenesis. Theory and neutrino masses

Energy Technology Data Exchange (ETDEWEB)

Buchmueller, W.

2012-12-15

After a brief discussion of baryon and lepton number nonconservation, we review the status of thermal leptogenesis with GUT scale neutrino masses, as well as low scale alternatives with keV neutrinos as dark matter and heavy neutrino masses within the reach of the LHC. Recent progress towards a full quantum mechanical description of leptogenesis is described with resonant leptogenesis as an application. Finally, cosmological B-L breaking after inflation is considered as origin of the hot early universe, generating entropy, baryon asymmetry and dark matter.

Neutrino mixing and masses in SO(10) GUTs with hidden sector and flavor symmetries

Energy Technology Data Exchange (ETDEWEB)

Chu, Xiaoyong [International Centre for Theoretical Physics,Strada Costiera 11, I-34100 Trieste (Italy); Smirnov, Alexei Yu. [Max-Planck-Institute for Nuclear Physics,Saupfercheckweg 1, D-69117 Heidelberg (Germany); International Centre for Theoretical Physics,Strada Costiera 11, I-34100 Trieste (Italy)

2016-05-23

We consider the neutrino masses and mixing in the framework of SO(10) GUTs with hidden sector consisting of fermionic and bosonic SO(10) singlets and flavor symmetries. The framework allows to disentangle the CKM physics responsible for the CKM mixing and different mass hierarchies of quarks and leptons and the neutrino new physics which produces smallness of neutrino masses and large lepton mixing. The framework leads naturally to the relation U{sub PMNS}∼V{sub CKM}{sup †}U{sub 0}, where structure of U{sub 0} is determined by the flavor symmetry. The key feature of the framework is that apart from the Dirac mass matrices m{sub D}, the portal mass matrix M{sub D} and the mass matrix of singlets M{sub S} are also involved in generation of the lepton mixing. This opens up new possibilities to realize the flavor symmetries and explain the data. Using A{sub 4}×Z{sub 4} as the flavor group, we systematically explore the flavor structures which can be obtained in this framework depending on field content and symmetry assignments. We formulate additional conditions which lead to U{sub 0}∼U{sub TBM} or U{sub BM}. They include (i) equality (in general, proportionality) of the singlet flavons couplings, (ii) equality of their VEVs; (iii) correlation between VEVs of singlets and triplet, (iv) certain VEV alignment of flavon triplet(s). These features can follow from additional symmetries or be remnants of further unification. Phenomenologically viable schemes with minimal flavon content and minimal number of couplings are constructed.

Absolute values of neutrino masses: status and prospects

International Nuclear Information System (INIS)

Bilenky, S.M.; Giunti, C.; Grifols, J.A.; Masso, E.

2003-01-01

Compelling evidences in favor of neutrino masses and mixing obtained in the last years in Super-Kamiokande, SNO, KamLAND and other neutrino experiments made the physics of massive and mixed neutrinos a frontier field of research in particle physics and astrophysics. There are many open problems in this new field. In this review we consider the problem of the absolute values of neutrino masses, which apparently is the most difficult one from the experimental point of view. We discuss the present limits and the future prospects of β-decay neutrino mass measurements and neutrinoless double-β decay. We consider the important problem of the calculation of nuclear matrix elements of neutrinoless double-β decay and discuss the possibility to check the results of different model calculations of the nuclear matrix elements through their comparison with the experimental data. We discuss the upper bound of the total mass of neutrinos that was obtained recently from the data of the 2dF Galaxy Redshift Survey and other cosmological data and we discuss future prospects of the cosmological measurements of the total mass of neutrinos. We discuss also the possibility to obtain information on neutrino masses from the observation of the ultra high-energy cosmic rays (beyond the GZK cutoff). Finally, we review the main aspects of the physics of core-collapse supernovae, the limits on the absolute values of neutrino masses from the observation of SN1987A neutrinos and the future prospects of supernova neutrino detection

Neutrino masses twenty-five years later

International Nuclear Information System (INIS)

Valle, J.W.F.

2003-01-01

The discovery of neutrino mass marks a turning point in elementary particle physics, with important implications for nuclear and astroparticle physics. Here I give a brief update, where I summarize the current status of three-neutrino oscillation parameters from current solar, atmospheric, reactor and accelerator neutrino data, discuss the case for sterile neutrinos and LSND, and also the importance of tritium and double beta decay experiments probing the absolute scale of neutrino mass. In this opinionated look at the present of neutrino physics, I keep an eye in the future, and a perspective of the past, taking the opportunity to highlight Joe Schechter's pioneering contribution, which I have had the fortune to share, as his PhD student back in the early eighties

Status of neutrino mass experiments

International Nuclear Information System (INIS)

Fackler, O.

1985-12-01

In 1980 two experiments ignited a fertile field of research the determination of the neutrino masses. Subsequently, over 35 experiments using a variety of techniques have probed or are probing this question. Primarily I will discuss electron antineutrino (hereafter referred to as neutrino) mass experiments. However, let me begin in Section I to discuss astronomical and terrestrial observations which motivated these experiments. In Section II, I will quote limits from muon and tau mass determinations. These limits are more thoroughly discussed in other papers. I will continue by describing the four approaches used to measure the electron neutrino mass. In Section III, tritium beta decay mass determinations will be reviewed. This section includes a general summary of previous experimental results, and discussion of the major ongoing experiments. Section IV offers concluding remarks. 24 refs., 24 figs

Neutrino masses in the minimal gauged (B -L ) supersymmetry

Science.gov (United States)

Yan, Yu-Li; Feng, Tai-Fu; Yang, Jin-Lei; Zhang, Hai-Bin; Zhao, Shu-Min; Zhu, Rong-Fei

2018-03-01

We present the radiative corrections to neutrino masses in a minimal supersymmetric extension of the standard model with local U (1 )B -L symmetry. At tree level, three tiny active neutrinos and two nearly massless sterile neutrinos can be obtained through the seesaw mechanism. Considering the one-loop corrections to the neutrino masses, the numerical results indicate that two sterile neutrinos obtain KeV masses and the small active-sterile neutrino mixing angles. The lighter sterile neutrino is a very interesting dark matter candidate in cosmology. Meanwhile, the active neutrinos mixing angles and mass squared differences agree with present experimental data.

Neutrino`s helicity in a gravitational field; Helicite des neutrinos dans un champ gravitationnel

Energy Technology Data Exchange (ETDEWEB)

Pansart, J.P.

1996-12-31

By using approximated solutions of Dirac`s equation, we show that there is no helicity reversal for light neutrinos in the Schwarzschild metric nor in an expanding universe. The actual coupling between a particle spin and the angular momentum of a heavy rotating body induces a possible helicity reversal but with an unobservable probability proportional to m{sup 2}{sub p} / E{sup 2}, where m{sub p} is the particle mass and E its energy. In these calculations, the helicity is defined through the spin orientation with respect to the current and not with respect to the linear momentum. This definition gives simple expressions and is equal to the usual definition in the case of a flat space. (N.T.). 10 refs.

A light Zeldovich-Konopinski-Mahmoud neutrino with a large magnetic moment

International Nuclear Information System (INIS)

Ecker, G.; Grimus, W.; Neufeld, H.

1989-08-01

We propose a non-Abelian extension of a Zeldovich-Konopinski-Mahmoud lepton number symmetry which gives rise to a naturally light Dirac neutrino with a magnetic moment of O(10 -11 μ B ). The neutrino mass appears first at the two-loop level and is well below the experimental upper bound. 13 refs., 3.figs. (Authors)

Direct measurements of neutrino mass

International Nuclear Information System (INIS)

Robertson, R.G.H.

1991-01-01

Some recent developments in the experimental search for neutrino mass are discussed. New data from Los Alamos on the electron neutrino mass as measured in tritium beta decay give an upper limit of 9.3 eV at the 95% confidence level. This result is not consistent with the long-standing ITEP result of 26(5) eV within a ''model-independent'' range of 17 to 40 eV. It now appears that the electron neutrino is not sufficiently massive to close the universe by itself. Hime and Jelley report finding new evidence for a 17-keV neutrino in the Β decay of 35 S and 63 Ni. Many other experiments are being reported and the situation is still unresolved. 56 refs., 1 fig., 3 tabs

Majorana neutrino transition magnetic moment in a variant of Zee model with horizontal symmetry

International Nuclear Information System (INIS)

Dhar, Jyoti; Dev, S.

1992-01-01

A SU(2) H symmetric variant of Zee model of lepton flavour violation is presented and is shown to lead to neutrino transition magnetic moment of the order required to explain the solar neutrino deficit and the possible anticorrelation of solar neutrino flux with sunspot activity via VVO mechanism. The use of horizontal symmetry leads to totally degenerate neutrino states which may be combined to form a ZKM Dirac neutrino with naturally small mass. (author). 22 refs., 1 fig

Systems of neutrinos with mass

International Nuclear Information System (INIS)

Groot, S.R. de

1984-01-01

From the formalism of relativistic kinetic theory and the weak interaction Lagrangian the volume viscosity of a massive neutrino system is derived. Its value is calculated as a function of the neutrino mass and the temperature. Its role in the way of expanding or contraction of neutrino clouds in the universe is discussed. (Author) [pt

Neutrino mass matrix and hierarchy

International Nuclear Information System (INIS)

Kaus, Peter; Meshkov, Sydney

2003-01-01

We build a model to describe neutrinos based on strict hierarchy, incorporating as much as possible, the latest known data, for Δsol and Δatm, and for the mixing angles determined from neutrino oscillation experiments, including that from KamLAND. Since the hierarchy assumption is a statement about mass ratios, it lets us obtain all three neutrino masses. We obtain a mass matrix, Mν and a mixing matrix, U, where both Mν and U are given in terms of powers of Λ, the analog of the Cabibbo angle λ in the Wolfenstein representation, and two parameters, ρ and κ, each of order one. The expansion parameter, Λ, is defined by Λ2 = m2/m3 = √(Δsol/Δatm) ≅ 0.16, and ρ expresses our ignorance of the lightest neutrino mass m1, (m1 ρΛ4m3), while κ scales s13 to the experimental upper limit, s13 = κΛ2 ≅ 0.16κ. These matrices are similar in structure to those for the quark and lepton families, but with Λ about 1.6 times larger than the λ for the quarks and charged leptons. The upper limit for the effective neutrino mass in double β-decay experiments is 4 x 10-3eV if s13 = 0 and 6 x 10-3eV if s13 is maximal. The model, which is fairly unique, given the hierarchy assumption and the data, is compared to supersymmetric extension and texture zero models of mass generation

Neutrino oscillations and the seesaw origin of neutrino mass

Energy Technology Data Exchange (ETDEWEB)

Miranda, O.G., E-mail: omr@fis.cinvestav.mx [Departamento de Física, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. Postal 14-740, 07000 Mexico, Distrito Federal (Mexico); Valle, J.W.F. [AHEP Group, Institut de Física Corpuscular – C.S.I.C./Universitat de València, Parc Cientific de Paterna, C/Catedratico José Beltrán, 2, E-46980 Paterna (València) (Spain)

2016-07-15

The historical discovery of neutrino oscillations using solar and atmospheric neutrinos, and subsequent accelerator and reactor studies, has brought neutrino physics to the precision era. We note that CP effects in oscillation phenomena could be difficult to extract in the presence of unitarity violation. As a result upcoming dedicated leptonic CP violation studies should take into account the non-unitarity of the lepton mixing matrix. Restricting non-unitarity will shed light on the seesaw scale, and thereby guide us towards the new physics responsible for neutrino mass generation.

The IBM neutrino-mass experiment

International Nuclear Information System (INIS)

Clark, G.J.; Frisch, M.A.; Chaudhari, P.; Bregman, M.F.

1985-01-01

IBM is undertaking an experiment to measure the electron anti-neutrino mass. A high precision measurement of the tritium Β-decay spectrum near the end point is used to infer the neutrino mass. Electron energies are measured using a large spherical retarding grid analyzer. We are placing particular emphasis on understanding the complications introduced by solid state effects in the source

The IBM neutrino-mass experiment

International Nuclear Information System (INIS)

Clark, G.J.; Frisch, M.A.; Chaudhari, P.; Bregman, M.F.

1985-01-01

IBM is undertaking an experiment to measure the electron anti-neutrino mass. A high precision measurement of the tritium β-decay spectrum near the end point is used to infer the neutrino mass. Electron energies are measured using a large spherical retarding grid analyzer. They are placing particular emphasis on understanding the complications introduced by solid state effects in the source

Looking for Cosmic Neutrino Background

Directory of Open Access Journals (Sweden)

Chiaki eYanagisawa

2014-06-01

Full Text Available Since the discovery of neutrino oscillation in atmospheric neutrinos by the Super-Kamiokande experiment in 1998, study of neutrinos has been one of exciting fields in high-energy physics. All the mixing angles were measured. Quests for 1 measurements of the remaining parameters, the lightest neutrino mass, the CP violating phase(s, and the sign of mass splitting between the mass eigenstates m3 and m1, and 2 better measurements to determine whether the mixing angle theta23 is less than pi/4, are in progress in a well-controlled manner. Determining the nature of neutrinos, whether they are Dirac or Majorana particles is also in progress with continuous improvement. On the other hand, although the ideas of detecting cosmic neutrino background have been discussed since 1960s, there has not been a serious concerted effort to achieve this goal. One of the reasons is that it is extremely difficult to detect such low energy neutrinos from the Big Bang. While there has been tremendous accumulation of information on Cosmic Microwave Background since its discovery in 1965, there is no direct evidence for Cosmic Neutrino Background. The importance of detecting Cosmic Neutrino Background is that, although detailed studies of Big Bang Nucleosynthesis and Cosmic Microwave Background give information of the early Universe at ~a few minutes old and ~300 k years old, respectively, observation of Cosmic Neutrino Background allows us to study the early Universe at $sim$ 1 sec old. This article reviews progress made in the past 50 years on detection methods of Cosmic Neutrino Background.

Fermion masses and mixings in the 3-3-1 model with right-handed neutrinos based on the S{sub 3} flavor symmetry

Energy Technology Data Exchange (ETDEWEB)

Hernandez, A.E.C. [Universidad Tecnica Federico Santa Maria, Valparaiso (Chile); Martinez, R.; Ochoa, F. [Universidad Nacional de Colombia, Departamento de Fisica, Bogota (Colombia)

2016-11-15

We propose a 3-3-1 model where the SU(3){sub C} x SU(3){sub L} x U(1){sub X} symmetry is extended by S{sub 3} x Z{sub 3} x Z{sub 3}{sup '} x Z{sub 8} x Z{sub 16} and the scalar spectrum is enlarged by extra SU(3){sub L} singlet scalar fields. The model successfully describes the observed SM fermion mass and mixing pattern. In this framework, the light active neutrino masses arise via an inverse seesaw mechanism and the observed charged fermion mass and quark mixing hierarchy is a consequence of the Z{sub 3} x Z{sub 3}{sup '} x Z{sub 8} x Z{sub 16} symmetry breaking at very high energy. The obtained physical observables for both quark and lepton sectors are compatible with their experimental values. The model predicts the effective Majorana neutrino mass parameter of neutrinoless double beta decay to be m{sub ββ} = 4 and 48 meV for the normal and the inverted neutrino spectra, respectively. Furthermore, we found a leptonic Dirac CP-violating phase close to (π)/(2) and a Jarlskog invariant close to about 3 x 10{sup -2} for both normal and inverted neutrino mass hierarchy. (orig.)

Identifying the neutrino mass hierarchy with supernova neutrinos

International Nuclear Information System (INIS)

Tomas, Ricard

2006-01-01

We review how a high-statistics observation of the neutrino signal from a future galactic core-collapse supernova (SN) may be used to discriminate between different neutrino mixing scenarios. We discuss two complementary methods that allow for the positive identification of the mass hierarchy without knowledge of the emitted neutrino fluxes, provided that the 13-mixing angle is large, sin 2 θ 13 -5 . These two approaches are the observation of modulations in the neutrino spectra by Earth matter effects or by the passage of shock waves through the SN envelope. If the value of the 13-mixing angle is unknown, using additionally the information encoded in the prompt neutronization ν e burst-a robust feature found in all modern SN simulations-can be sufficient to fix both the neutrino hierarchy and to decide whether θ 13 is 'small' or 'large'

Neutrino mass spectrum with υμ → υs oscillations of atmospheric neutrinos

International Nuclear Information System (INIS)

Liu, Q.Y.; Smirnov, A.Yu.

1998-02-01

We consider the ''standard'' spectrum of the active neutrinos (characterized by strong mass hierarchy and small mixing) with additional sterile, υ s . The sterile neutrino mixes strongly with the muon neutrino, so that υ μ ↔ υ s oscillations solve the atmospheric neutrino problem. We show that the parametric enhancement of the υ μ ↔ υ s oscillations occurs for the high energy atmospheric neutrinos which cross the core of the Earth. This can be relevant for the anomaly observed by the MACRO experiment. Solar neutrinos are converted both to υ μ and υ s . The heaviest neutrino (approx. υ τ ) may compose the hot dark matter of the Universe. Phenomenology of this scenario is elaborated and crucial experimental signatures are identified. We also discuss properties of the underlying neutrino mass matrix. (author)

New light Higgs boson and short-baseline neutrino anomalies

Science.gov (United States)

Asaadi, J.; Church, E.; Guenette, R.; Jones, B. J. P.; Szelc, A. M.

2018-04-01

The low-energy excesses observed by the MiniBooNE experiment have, to date, defied a convincing explanation under the standard model even with accommodation for nonzero neutrino mass. In this paper we explore a new oscillation mechanism to explain these anomalies, invoking a light neutrinophilic Higgs boson, conceived to induce a low Dirac neutrino mass in accord with experimental limits. Beam neutrinos forward scattering off of a locally overdense relic neutrino background give rise to a novel matter effect with an energy-specific resonance. An enhanced oscillation around this resonance peak produces flavor transitions which are highly consistent with the MiniBooNE neutrino- and antineutrino-mode data sets. The model provides substantially improved χ2 values beyond either the no-oscillation hypothesis or the more commonly explored 3 +1 sterile neutrino hypothesis. This mechanism would introduce distinctive signatures at each baseline in the upcoming short-baseline neutrino program at Fermilab, presenting opportunities for further exploration.

Leptoquarks: Neutrino masses and related accelerator signals

International Nuclear Information System (INIS)

Aristizabal Sierra, D.; Hirsch, M.; Kovalenko, S. G.

2008-01-01

Leptoquark-Higgs interactions induce mixing between leptoquark (LQ) states with different chiralities once the electroweak symmetry is broken. In such LQ models Majorana neutrino masses are generated at 1-loop order. Here we calculate the neutrino mass matrix and explore the constraints on the parameter space enforced by the assumption that LQ-loops explain current neutrino oscillation data. LQs will be produced at the CERN LHC, if their masses are at or below the TeV scale. Since the fermionic decays of LQs are governed by the same Yukawa couplings, which are responsible for the nontrivial neutrino mass matrix, several decay branching ratios of LQ states can be predicted from measured neutrino data. Especially interesting is that large lepton flavor violating rates in muon and tau final states are expected. In addition, the model predicts that, if kinematically possible, heavier LQs decay into lighter ones plus either a standard model Higgs boson or a Z 0 /W ± gauge boson. Thus, experiments at the LHC might be able to exclude the LQ mechanism as an explanation of neutrino data.

Neutrino masses and mixing

International Nuclear Information System (INIS)

Fogli, G.

1998-01-01

The paper presents an analysis of the solar neutrino problem in terms of both Mikheyev-Smirnov-Wolfenstein (MSW) and vacuum neutrino oscillations, with the inclusion of the data collected by the SuperKamiokande experiment during 306.3 days of operation. In particular, the observed energy spectrum of the recoil electrons from 8 B neutrino scattering is discussed in detail and used to constrain the mass-mixing parameter space. Going to the atmospheric neutrino anomaly, the paper performs both a two- and three-flavor analysis of the most recent SuperKamiokande atmospheric neutrino data. The variations of the zenith distributions of ν events in the presence of flavor oscillations are investigated. It is seen that fits to the SK data, with and without the addition of the CHOOZ constrains, strongly limit the parameter space. Detailed bounds in triangle graphs are reported

Supernova signatures of neutrino mass ordering

Science.gov (United States)

Scholberg, Kate

2018-01-01

A suite of detectors around the world is poised to measure the flavor-energy-time evolution of the ten-second burst of neutrinos from a core-collapse supernova occurring in the Milky Way or nearby. Next-generation detectors to be built in the next decade will have enhanced flavor sensitivity and statistics. Not only will the observation of this burst allow us to peer inside the dense matter of the extreme event and learn about the collapse processes and the birth of the remnant, but the neutrinos will bring information about neutrino properties themselves. This review surveys some of the physical signatures that the currently-unknown neutrino mass pattern will imprint on the observed neutrino events at Earth, emphasizing the most robust and least model-dependent signatures of mass ordering.

CP violation and neutrino masses and mixings from quark mass hierarchies

International Nuclear Information System (INIS)

Buchmueller, W.; Covi, L.; Emmanuel-Costa, D.; Wiesenfeldt, S.

2007-10-01

We study the connection between quark and lepton mass matrices in a supersymmetric SO(10) GUT model in six dimensions, compactified on an orbifold. The physical quarks and leptons are mixtures of brane and bulk states. This leads to a characteristic pattern of mass matrices and high-energy CP violating phases. The hierarchy of up and down quark masses determines the CKM matrix and most charged lepton and neutrino masses and mixings. The small hierarchy of neutrino masses is a consequence of the mismatch of the up and down quark mass hierarchies. The effective CP violating phases in the quark sector, neutrino oscillations and leptogenesis are unrelated. In the neutrino sector we can accomodate naturally sin θ 23 ∝1, sin θ 13 1 2 ∝√(Δm 2 sol ) 3 ∝√(Δm 2 atm ). (orig.)

CP violation and neutrino masses and mixings from quark mass hierarchies

International Nuclear Information System (INIS)

Buchmueller, Wilfried; Covi, Laura; Emmanuel-Costa, David; Wiesenfeldt, Soeren

2007-01-01

We study the connection between quark and lepton mass matrices in a supersymmetric SO(10) GUT model in six dimensions, compactified on an orbifold. The physical quarks and leptons are mixtures of brane and bulk states. This leads to a characteristic pattern of mass matrices and high-energy CP violating phases. The hierarchy of up and down quark masses determines the CKM matrix and most charged lepton and neutrino masses and mixings. The small hierarchy of neutrino masses is a consequence of the mismatch of the up and down quark mass hierarchies. The effective CP violating phases in the quark sector, neutrino oscillations and leptogenesis are unrelated. In the neutrino sector we can accomodate naturally sin θ 23 ∼ 1, sin θ 13 ∼ 1 ∼ 2 ∼ (Δm 2 sol ) 1/2 3 ∼ (Δm 2 atm ) 1/2

Resolving neutrino mass hierarchy from supernova (anti)neutrino-nucleus reactions

Science.gov (United States)

Vale, Deni; Paar, Nils

2015-10-01

Recently a hybrid method has been introduced to determine neutrino mass hierarchy by simultaneous measurements of detector responses induced by antineutrino and neutrino fluxes from accretion and cooling phase of type II supernova. The (anti)neutrino-nucleus cross sections for 12C, 16O, 56Fe and 208Pb are calculated in the framework of relativistic nuclear energy density functional and weak interaction Hamiltonian, while the cross sections for inelastic scattering on free protons in mineral oil and water, p (v¯e,e+)n are obtained using heavy-baryon chiral perturbation theory. The simulations of (anti)neutrino fluxes emitted from a proto-neutron star in a core-collapse supernova include collective and Mikheyev-Smirnov-Wolfenstein effects inside star. It is shown that simultaneous use of ve/v¯e detectors with different target material allow to determine the neutrino mass hierarchy from the ratios of ve/v¯e induced particle emissions. The hybrid method favors detectors with heavier target nuclei (208Pb) for the neutrino sector, while for antineutrinos the use of free protons in mineral oil and water is more appropriate.

Neutrino Masses and Mixings and Astrophysics

Science.gov (United States)

Fuller, George M.

1998-10-01

Here we discuss the implications of light neutrino masses and neutrino flavor/type mixing for dark matter, big bang nucleosynthesis, and models of heavy element nucleosynthesis in super novae. We will also argue the other way and discuss possible constraints on neutrino physics from these astrophysical considerations.

Hiding neutrino mass in modified gravity cosmologies

Energy Technology Data Exchange (ETDEWEB)

Bellomo, Nicola; Bellini, Emilio; Hu, Bin; Jimenez, Raul; Verde, Licia [ICC, University of Barcelona (UB-IEEC), Marti i Franques 1, 08028, Barcelona (Spain); Pena-Garay, Carlos, E-mail: nicola.bellomo@icc.ub.edu, E-mail: emilio.bellini@physics.ox.ac.uk, E-mail: binhu@icc.ub.edu, E-mail: raul.jimenez@icc.ub.edu, E-mail: penya@ific.uv.es, E-mail: liciaverde@icc.ub.edu [Instituto de Fisica Corpuscular, CSIC-UVEG, P.O. 22085, Valencia, 46071 (Spain)

2017-02-01

Cosmological observables show a dependence with the neutrino mass, which is partially degenerate with parameters of extended models of gravity. We study and explore this degeneracy in Horndeski generalized scalar-tensor theories of gravity. Using forecasted cosmic microwave background and galaxy power spectrum datasets, we find that a single parameter in the linear regime of the effective theory dominates the correlation with the total neutrino mass. For any given mass, a particular value of this parameter approximately cancels the power suppression due to the neutrino mass at a given redshift. The extent of the cancellation of this degeneracy depends on the cosmological large-scale structure data used at different redshifts. We constrain the parameters and functions of the effective gravity theory and determine the influence of gravity on the determination of the neutrino mass from present and future surveys.

Neutrino masses and mixing: evidence and implications

International Nuclear Information System (INIS)

Gonzalez-Garcia, M.C.; Nir, Yosef

2003-01-01

Measurements of various features of the fluxes of atmospheric and solar neutrinos have provided evidence for neutrino oscillations and therefore for neutrino masses and mixing. The authors review the phenomenology of neutrino oscillations in vacuum and in matter. They present the existing evidence from solar and atmospheric neutrinos as well as the results from laboratory searches, including the final status of the Liquid Scintillator Neutrino Detector (LSND) experiment. The theoretical inputs that are used to interpret the experimental results are described in terms of neutrino oscillations. The allowed ranges for the mass and mixing parameters are derived in two frameworks: First, each set of observations is analyzed separately in a two-neutrino framework; Second, the data from solar and atmospheric neutrinos are analyzed in a three-active-neutrino framework. The theoretical implications of these results are then discussed, including the existence of new physics, the estimate of the scale of this new physics, and the lessons for grand unified theories, for models of extra dimensions and singlet fermions in the bulk, and for flavor models

Neutrino masses and mixings: Big Bang and Supernova nucleosynthesis and neutrino dark matter

International Nuclear Information System (INIS)

Fuller, George M.

1999-01-01

The existence of small mixings between light active and sterile neutrino species could have implications for Big Bang and Supernova Heavy Element Nucleosynthesis. As well, such mixing would force us to abandon cherished constraints on light neutrino Dark Matter. Two proposed 4-neutrino mass and mixing schemes, for example, can both accomodate existing experimental results and lead to elegant solutions to the neutron-deficit problem for r-Process nucleosynthesis from neutrino-heated supernova ejecta. Each of these solutions is based on matter-enhanced (MSW) active-sterile neutrino transformation. In plausible extensions of these schemes to the early universe, Shi and Fuller have shown that relatively light mass (∼200 eV to ∼10 keV) sterile neutrinos produced via active-sterile MSW conversion can have a ''cold'' energy spectrum. Neutrinos produced in this way circumvent the principal problem of light neutrino dark matter and would be, essentially, Cold Dark Matter

Towards absolute neutrino masses

Energy Technology Data Exchange (ETDEWEB)

Vogel, Petr [Kellogg Radiation Laboratory 106-38, Caltech, Pasadena, CA 91125 (United States)

2007-06-15

Various ways of determining the absolute neutrino masses are briefly reviewed and their sensitivities compared. The apparent tension between the announced but unconfirmed observation of the 0{nu}{beta}{beta} decay and the neutrino mass upper limit based on observational cosmology is used as an example of what could happen eventually. The possibility of a 'nonstandard' mechanism of the 0{nu}{beta}{beta} decay is stressed and the ways of deciding which of the possible mechanisms is actually operational are described. The importance of the 0{nu}{beta}{beta} nuclear matrix elements is discussed and their uncertainty estimated.

Neutrino mass hierarchy determination via atmospheric neutrinos with future detectors

International Nuclear Information System (INIS)

Gandhi, Raj; Ghoshal, Pomita; Goswami, Srubabati; Mehta, Poonam; Sankar, S Uma; Shalgar, Shashank

2008-01-01

The issue of determining the neutrino mass hierarchy is one of the outstanding questions in neutrino physics. We consider the potential of hierarchy determination using atmospheric neutrinos as the source in three different proposed future detectors: A large Iron Calorimeter detector, a megaton Water Cerenkov detector and a large-mass Liquid Argon detector. If the mixing angle θ 13 is about 10 deg. (close to CHOOZ upper bound), the hierarchy sensitivity is essentially determined by resonant matter effects. To maximize the potential of these effects in atmospheric neutrinos, charge discrimination capability in the detector is desirable. Hence, detectors with this capability have an advantage in hierarchy determination. We compare and contrast the performance of the above three detectors in this respect. We perform a realistic analysis of the above future detectors for atmospheric neutrinos and show that it is possible to achieve a significant hierarchy sensitivity if the detector characteristics are favourable. Note: The abstract has been modified from its original form to incorporate suggestions received during the conference. The poster is being submitted in its original form.

Probing Neutrino Mass Hierarchy with Supernova

International Nuclear Information System (INIS)

Chakraborty, Sovan

2013-01-01

The rise time of electron antineutrino lightcurve from a Galactic supernova (SN), observable at the IceCube Cherenkov detector, can provide signature of the neutrino mass hierarchy at “large” 1-3 leptonic mixing angle ϑ 13 . In the early accretion phase of the SN, the neutrino oscillations are nontrivial. Due to the matter suppression of collective effects at these early post bounce times, only the MSW resonances in the outer layers of the SN influence the neutrino flux. When the oscillations are taken into account, the signal in IceCube shows sufficiently fast rise time for the inverted mass hierarchy compared to the normal hierarchy. An investigation with an extensive set of stellar core-collapse simulations, provides both qualitative and quantitative robustness of these features. Thus opening another avenue to explore the neutrino mass hierarchy with the rise time of a supernova burst

Neutrino masses in astrophysics and cosmology

International Nuclear Information System (INIS)

Raffelt, G.G.

1996-01-01

Astrophysical and cosmological arguments and observations give us the most restrictive constraints on neutrino masses, electromagnetic couplings, and other properties. Conversely, massive neutrinos would contribute to the cosmic dark-matter density and would play an important role for the formation of structure in the universe. Neutrino oscillations may well solve the solar neutrino problem, and can have a significant impact on supernova physics. (author) 14 figs., tabs., 33 refs

Neutrino masses in astrophysics and cosmology

Energy Technology Data Exchange (ETDEWEB)

Raffelt, G G [Max-Planck-Institut fuer Physik, Muenchen (Germany)

1996-11-01

Astrophysical and cosmological arguments and observations give us the most restrictive constraints on neutrino masses, electromagnetic couplings, and other properties. Conversely, massive neutrinos would contribute to the cosmic dark-matter density and would play an important role for the formation of structure in the universe. Neutrino oscillations may well solve the solar neutrino problem, and can have a significant impact on supernova physics. (author) 14 figs., tabs., 33 refs.

Hierarchical Neutrino Masses and Mixing in Flipped-SU(5)

CERN Document Server

Rizos, J

2010-01-01

We consider the problem of neutrino masses and mixing in the framework of flipped SU(5). The right-handed neutrino mass, generated through the operation of a seesaw mechanism by a sector of gauge singlets, leads naturally, at a subsequent level, to the standard seesaw mechanism resulting into three light neutrino states with masses of the desired phenomenological order of magnitude. In this framework we study simple Ansatze for the singlet couplings for which hierarchical neutrino masses emerge naturally, parametrized in terms of the Cabbibo parameter. The resulting neutrino mixing matrices are characterized by a hierarchical structure, in which theta-(13) is always predicted to be the smallest. Finally, we discuss a possible factorized parametrization of the neutrino mass that, in addition to Cabbibo mixing, encodes also mixing due to the singlet sector.

Seesaw neutrinos from the heterotic string

International Nuclear Information System (INIS)

Buchmueller, W.; Hamaguchi, K.; Ramos-Sanchez, S.; Ratz, M.

2007-03-01

We study the possibility of realizing the neutrino seesaw mechanism in the E 8 x E 8 heterotic string. In particular, we consider its Z 6 orbifold compactifications leading to the supersymmetric standard model gauge group and matter content. We find that these models possess all the necessary ingredients for the seesaw mechanism, including the required Dirac Yukawa couplings and large Majorana mass terms. We argue that this situation is quite common in heterotic orbifolds. In contrast to the conventional seesaw of grand unified theories (GUTs), no large GUT representations are needed to generate the Majorana mass terms. The total number of right-handed neutrinos can be very large, up to O(100). (orig.)

JUNO. Determination of the neutrino mass hierarchy using reactor neutrinos

Energy Technology Data Exchange (ETDEWEB)

Wonsak, Bjoern [Hamburg University, Inst. Exp. Phys., Hamburg (Germany)

2015-07-01

The Jiangmen Underground Neutrino Observatory (JUNO) is a medium-baseline reactor neutrino experiment located in China. Its aim is to determine the neutrino mass hierarchy at more than 3 sigma significance after six years of data taking by using a 20kt liquid scintillator detector. To achieve this goal, an energy resolution of less than 3%/√(E) is necessary, creating strict requirements on the detector design and the liquid scintillator. Moreover, JUNO will be the only experiment in the near future able to measure the solar mixing parameters with a precision of better than 1%. This is at the same level as our current knowledge on flavour mixing in the quark sector, marking an important milestone of neutrino physics. In addition, supernova neutrinos, geo-neutrinos, sterile neutrinos as well as solar and atmospheric neutrinos can be studied. JUNO was approved in 2013 and the construction of the underground facility started early this year. In this talk the status of the experiment and its prospects is discussed.

Neutrino Masses from Neutral Top Partners

CERN Document Server

Batell, Brian

2015-01-01

We present theories of `Natural Neutrinos' in which neutral fermionic top partner fields are simultaneously the right-handed neutrinos (RHN), linking seemingly disparate aspects of the Standard Model structure: a) The RHN top partners are responsible for the observed small neutrino masses, b) They help ameliorate the tuning in the weak scale and address the little hierarchy problem, and c) The factor of $3$ arising from $N_c$ in the top-loop Higgs mass corrections is countered by a factor $3$ from the number of vector-like generations of RHN. The RHN top partners may arise in pseudo-Nambu-Goldstone-Boson (pNGB) Higgs models such as the Twin Higgs, as well as more general Composite, Little, and Orbifold Higgs scenarios, and three simple example models are presented. This framework firmly predicts a TeV-scale seesaw, as the RHN masses are bounded to be below the TeV scale by naturalness. The generation of light neutrino masses relies on a collective breaking of lepton number, allowing for comparatively large ne...

Neutrino masses and their ordering: global data, priors and models

Science.gov (United States)

Gariazzo, S.; Archidiacono, M.; de Salas, P. F.; Mena, O.; Ternes, C. A.; Tórtola, M.

2018-03-01

We present a full Bayesian analysis of the combination of current neutrino oscillation, neutrinoless double beta decay and Cosmic Microwave Background observations. Our major goal is to carefully investigate the possibility to single out one neutrino mass ordering, namely Normal Ordering or Inverted Ordering, with current data. Two possible parametrizations (three neutrino masses versus the lightest neutrino mass plus the two oscillation mass splittings) and priors (linear versus logarithmic) are exhaustively examined. We find that the preference for NO is only driven by neutrino oscillation data. Moreover, the values of the Bayes factor indicate that the evidence for NO is strong only when the scan is performed over the three neutrino masses with logarithmic priors; for every other combination of parameterization and prior, the preference for NO is only weak. As a by-product of our Bayesian analyses, we are able to (a) compare the Bayesian bounds on the neutrino mixing parameters to those obtained by means of frequentist approaches, finding a very good agreement; (b) determine that the lightest neutrino mass plus the two mass splittings parametrization, motivated by the physical observables, is strongly preferred over the three neutrino mass eigenstates scan and (c) find that logarithmic priors guarantee a weakly-to-moderately more efficient sampling of the parameter space. These results establish the optimal strategy to successfully explore the neutrino parameter space, based on the use of the oscillation mass splittings and a logarithmic prior on the lightest neutrino mass, when combining neutrino oscillation data with cosmology and neutrinoless double beta decay. We also show that the limits on the total neutrino mass ∑ mν can change dramatically when moving from one prior to the other. These results have profound implications for future studies on the neutrino mass ordering, as they crucially state the need for self-consistent analyses which explore the

Reconstructing neutrino properties from collider experiments in a Higgs triplet neutrino mass model

International Nuclear Information System (INIS)

Aristizabal Sierra, D.; Hirsch, M.; Valle, J. W. F.; Villanova del Moral, A.

2003-01-01

We extend the minimal supersymmetric standard model with bilinear R-parity violation to include a pair of Higgs triplet superfields. The neutral components of the Higgs triplets develop small vacuum expectation values (VEVs) quadratic in the bilinear R-parity breaking parameters. In this scheme the atmospheric neutrino mass scale arises from bilinear R-parity breaking while for reasonable values of parameters the solar neutrino mass scale is generated from the small Higgs triplet VEVs. We calculate neutrino masses and mixing angles in this model and show how the model can be tested at future colliders. The branching ratios of the doubly charged triplet decays are related to the solar neutrino angle via a simple formula

Neutrino mass hierarchy and matter effects

OpenAIRE

Smirnov, Alexei Yu.

2013-01-01

Matter effects modify the mixing and the effective masses of neutrinos in a way which depends on the neutrino mass hierarchy. Consequently, for normal and inverted hierarchies the oscillations and flavor conversion results are different. Sensitivity to the mass hierarchy appears whenever the matter effects on the 1-3 mixing and mass splitting become substantial. This happens in supernovae in wide energy range and in the matter of the Earth. The Earth density profile is a multi-layer medium wh...

Mass of neutrino and particle physics

CERN Document Server

Yanagida, T

2003-01-01

We give a brief review on the seesaw mechanism in a grand unified theory which predicts small neutrino masses. In the seesaw mechanism the lepton-number conservation is broken and neutrinos have Majorana type masses. We also explain why the lepton-number nonconservation can be an origin of the baryon-number asymmetry in the present universe. (author)

Neutrino masses in flipped SU(5)

Energy Technology Data Exchange (ETDEWEB)

Abel, S.A. (Bristol Univ. (UK). H.H. Wills Physics Lab.)

1990-01-04

It is demonstrated that the, recently proposed, SU(5)xU(1) unification scheme is one of only a small number of the current candidates that allows, in its parameter space, the possibility of heavy neutrinos. This is due to the fact that the usual GIM suppression mechanism does not operate, leading to fast decays of heavy tau neutrinos of the form {nu}{yields}{nu}{gamma}, with an estimated lifetime of O(1 yr) for a tau neutrino mass of 1 MeV. Using well known cosmological arguments, based on the observed 3 K background radiation, the mass of the electron neutrino is constrained to be either greater than O(1 eV), or less than the usual limit of O(10{sup -2} eV). (orig.).

A three-parameter neutrino mass matrix with maximal CP violation

International Nuclear Information System (INIS)

Grimus, W.; Lavoura, L.

2009-01-01

Using the seesaw mechanism, we construct a model for the light-neutrino Majorana mass matrix which yields trimaximal lepton mixing together with maximal CP violation and maximal atmospheric-neutrino mixing. We demonstrate that, in our model, the light-neutrino mass matrix retains its form under the one-loop renormalization-group evolution. With our neutrino mass matrix, the absolute neutrino mass scale is a function of |U e3 | and of the atmospheric mass-squared difference. We study the effective mass in neutrinoless ββ decay as a function of |U e3 |, showing that it contains a fourfold ambiguity

Baryogenesis and neutrino masses

International Nuclear Information System (INIS)

Peccei, R.D.

1992-01-01

The erasure of any preexisting B+L asymmetry in the universe in its late stages suggests that the B asymmetry observed today either originated at the electroweak scale or it arose from an original L asymmetry. For the latter case to be viable either neutrino masses are much below the eV scale or the L asymmetry itself is generated at an intermediate scale. Several features of the generation of a B asymmetry via an L asymmetry are discussed, including the interesting possibility that the present baryon asymmetry in the universe originates as a result of CP violating phases in the neutrino mass matrix

Constraining the lightest neutrino mass and mee from general ...

Indian Academy of Sciences (India)

surements. For example, neutrino oscillation experiments provide no clue regarding the absolute neutrino mass scale and the related issue of the neutrino mass hierarchy. Another important issue which needs to be taken note of is regarding the rather small neu- trino masses as compared to their charged counterparts.

Neutrino Mass Matrix Textures: A Data-driven Approach

CERN Document Server

Bertuzzo, E; Machado, P A N

2013-01-01

We analyze the neutrino mass matrix entries and their correlations in a probabilistic fashion, constructing probability distribution functions using the latest results from neutrino oscillation fits. Two cases are considered: the standard three neutrino scenario as well as the inclusion of a new sterile neutrino that potentially explains the reactor and gallium anomalies. We discuss the current limits and future perspectives on the mass matrix elements that can be useful for model building.

Ghost basis for neutrino

International Nuclear Information System (INIS)

Novello, M.

1976-07-01

A class of solutions of DIRAC'S equation in gravitational fields for ghost neutrinos is given. Comments are restricted to the neutrino cosmological model recently found by M. Novello e I.D. Soares [pt

Objective Bayesian analysis of neutrino masses and hierarchy

Science.gov (United States)

Heavens, Alan F.; Sellentin, Elena

2018-04-01

Given the precision of current neutrino data, priors still impact noticeably the constraints on neutrino masses and their hierarchy. To avoid our understanding of neutrinos being driven by prior assumptions, we construct a prior that is mathematically minimally informative. Using the constructed uninformative prior, we find that the normal hierarchy is favoured but with inconclusive posterior odds of 5.1:1. Better data is hence needed before the neutrino masses and their hierarchy can be well constrained. We find that the next decade of cosmological data should provide conclusive evidence if the normal hierarchy with negligible minimum mass is correct, and if the uncertainty in the sum of neutrino masses drops below 0.025 eV. On the other hand, if neutrinos obey the inverted hierarchy, achieving strong evidence will be difficult with the same uncertainties. Our uninformative prior was constructed from principles of the Objective Bayesian approach. The prior is called a reference prior and is minimally informative in the specific sense that the information gain after collection of data is maximised. The prior is computed for the combination of neutrino oscillation data and cosmological data and still applies if the data improve.

Calculation of the decay rate of tachyonic neutrinos against charged-lepton-pair and neutrino-pair Cerenkov radiation

Science.gov (United States)

Jentschura, Ulrich D.; Nándori, István; Ehrlich, Robert

2017-10-01

We consider in detail the calculation of the decay rate of high-energy superluminal neutrinos against (charged) lepton pair Cerenkov radiation, and neutrino pair Cerenkov radiation, i.e., against the decay channels ν \\to ν {e}+ {e}- and ν \\to ν \\overline{ν } ν . Under the hypothesis of a tachyonic nature of neutrinos, these decay channels put constraints on the lifetime of high-energy neutrinos for terrestrial experiments as well as on cosmic scales. For the oncoming neutrino, we use the Lorentz-covariant tachyonic relation {E}ν =\\sqrt{{p}2-{m}ν 2}, where m ν is the tachyonic mass parameter. We derive both threshold conditions as well as on decay and energy loss rates, using the plane-wave fundamental bispinor solutions of the tachyonic Dirac equation. Various intricacies of rest frame versus lab frame calculations are highlighted. The results are compared to the observations of high-energy IceCube neutrinos of cosmological origin.

Hierarchical neutrino masses and mixing in flipped-SU(5)

Energy Technology Data Exchange (ETDEWEB)

Rizos, J. [Physics Department, University of Ioannina, 45110 Ioannina (Greece); Tamvakis, K., E-mail: tamvakis@uoi.g [Physics Department, University of Ioannina, 45110 Ioannina (Greece); Physics Department, CERN, CH-1211, Geneva 23 (Switzerland)

2010-02-22

We consider the problem of neutrino masses and mixing in the framework of flipped SU(5). The right-handed neutrino mass, generated through the operation of a seesaw mechanism by a sector of gauge singlets, leads naturally, at a subsequent level, to the standard seesaw mechanism resulting into three light neutrino states with masses of the desired phenomenological order of magnitude. In this framework we study simple Ansaetze for the singlet couplings for which hierarchical neutrino masses emerge naturally as lambda{sup n}:lambda:1 or lambda{sup n}:lambda{sup 2}:1, parametrized in terms of the Cabbibo parameter. The resulting neutrino mixing matrices are characterized by a hierarchical structure, in which theta{sub 13} is always predicted to be the smallest. Finally, we discuss a possible factorized parametrization of the neutrino mass that, in addition to Cabbibo mixing, encodes also mixing due to the singlet sector.

Finding Mass Constraints Through Third Neutrino Mass Eigenstate Decay

Science.gov (United States)

Gangolli, Nakul; de Gouvêa, André; Kelly, Kevin

2018-01-01

In this paper we aim to constrain the decay parameter for the third neutrino mass utilizing already accepted constraints on the other mixing parameters from the Pontecorvo-Maki-Nakagawa-Sakata matrix (PMNS). The main purpose of this project is to determine the parameters that will allow the Jiangmen Underground Neutrino Observatory (JUNO) to observe a decay parameter with some statistical significance. Another goal is to determine the parameters that JUNO could detect in the case that the third neutrino mass is lighter than the first two neutrino species. We also replicate the results that were found in the JUNO Conceptual Design Report (CDR). By utilizing Χ2-squared analysis constraints have been put on the mixing angles, mass squared differences, and the third neutrino decay parameter. These statistical tests take into account background noise and normalization corrections and thus the finalized bounds are a good approximation for the true bounds that JUNO can detect. If the decay parameter is not included in our models, the 99% confidence interval lies within The bounds 0s to 2.80x10-12s. However, if we account for a decay parameter of 3x10-5 ev2, then 99% confidence interval lies within 8.73x10-12s to 8.73x10-11s.

Coherent neutrino interactions in a dense medium

International Nuclear Information System (INIS)

Kiers, K.; Weiss, N.

1997-01-01

Motivated by the effect of matter on neutrino oscillations (the MSW effect) we study in more detail the propagation of neutrinos in a dense medium. The dispersion relation for massive neutrinos in a medium is known to have a minimum at nonzero momentum p∼G F ρ/√(2). We study in detail the origin and consequences of this dispersion relation for both Dirac and Majorana neutrinos both in a toy model with only neutral currents and a single neutrino flavor and in a realistic open-quotes standard modelclose quotes with two neutrino flavors. We find that for a range of neutrino momenta near the minimum of the dispersion relation, Dirac neutrinos are trapped by their coherent interactions with the medium. This effect does not lead to the trapping of Majorana neutrinos. copyright 1997 The American Physical Society

Hybrid method to resolve the neutrino mass hierarchy by supernova (anti)neutrino induced reactions

Science.gov (United States)

Vale, D.; Rauscher, T.; Paar, N.

2016-02-01

We introduce a hybrid method to determine the neutrino mass hierarchy by simultaneous measurements of responses of at least two detectors to antineutrino and neutrino fluxes from accretion and cooling phases of core-collapse supernovae. The (anti)neutrino-nucleus cross sections for 56Fe and 208Pb are calculated in the framework of the relativistic nuclear energy density functional and weak interaction Hamiltonian, while the cross sections for inelastic scattering on free protons p(bar nue,e+)n are obtained using heavy-baryon chiral perturbation theory. The modelling of (anti)neutrino fluxes emitted from a protoneutron star in a core-collapse supernova include collective and Mikheyev-Smirnov-Wolfenstein effects inside the exploding star. The particle emission rates from the elementary decay modes of the daughter nuclei are calculated for normal and inverted neutrino mass hierarchy. It is shown that simultaneous use of (anti)neutrino detectors with different target material allows to determine the neutrino mass hierarchy from the ratios of νe- and bar nue-induced particle emissions. This hybrid method favors neutrinos from the supernova cooling phase and the implementation of detectors with heavier target nuclei (208Pb) for the neutrino sector, while for antineutrinos the use of free protons in mineral oil or water is the appropriate choice.

Neutrino mass and mixing, and non-accelerator experiments

International Nuclear Information System (INIS)

Robertson, R.G.H.

1992-01-01

We review the current status of experimental knowledge about neutrinos derived from kinematic mass measurements, neutrino oscillation searches at reactors and accelerators, solar neutrinos, atmospheric neutrinos, and single and double beta decay. The solar neutrino results yield fairly strong and consistent indication that neutrino oscillations are occurring. Other evidence for new physics is less consistent and convincing

The experimental status of neutrino masses and mixings

International Nuclear Information System (INIS)

Robertson, R.G.H.

1992-01-01

We review the current status of experimental knowledge about neutrinos derived from kinematic mass measurements, neutrino oscillation searches at reactors and accelerators, solar neutrinos, atmospheric neutrinos, and single and double beta decay. The solar neutrino results yield fairly strong and consistent indications that neutrino oscillations are occurring. Other evidence for new physics is less consistent and convincing

Leptoquarks and neutrino masses at the LHC

Energy Technology Data Exchange (ETDEWEB)

Fileviez Perez, Pavel [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)], E-mail: fileviez@physics.wisc.edu; Han Tao [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Li Tong [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Department of Physics, Nankai University, Tianjin 300071 (China); Center for High Energy Physics, Peking University, Beijing 100871 (China); Ramsey-Musolf, Michael J. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States)

2009-09-21

The properties of light leptoquarks predicted in the context of a simple grand unified theory and their observability at the LHC are investigated. The SU(5) symmetry of the theory implies that the leptoquark couplings to matter are related to the neutrino mass matrix. We study the resulting connection between neutrino masses and mixing parameters and the leptoquark decays, and show that different light neutrino hierarchies imply distinctive leptoquark decay signatures. We also discuss low-energy constraints implied by searches for charged lepton flavour violation, studies of meson decays, and electroweak precision data. We perform a detailed parton-level study of the leptoquark signals and the Standard Model backgrounds at the LHC. With the clean final states containing a di-lepton plus two jets, the QCD production of the leptoquark pair can be observed for a leptoquark mass of one TeV and beyond. By examining the lepton flavor structure of the observed events, one could further test the model predictions related to the neutrino mass spectrum. In particular, b-flavor tagging will be useful in distinguishing the neutrino mass pattern and possibly probing an unknown Majorana phase in the Inverted Hierarchy or the Quasi-Degenerate scenario. Electroweak associated production of the leptoquark doublet can also be useful in identifying the quantum numbers of the leptoquarks and distinguishing between the neutrino mass spectra, even though the corresponding event rates are smaller than for QCD production. We find that with only the clean channel of {mu}+E/{sub T}+jets, one could expect an observable signal for a leptoquark masses of about 600 GeV or higher.

Leptoquarks and neutrino masses at the LHC

International Nuclear Information System (INIS)

Fileviez Perez, Pavel; Han Tao; Li Tong; Ramsey-Musolf, Michael J.

2009-01-01

The properties of light leptoquarks predicted in the context of a simple grand unified theory and their observability at the LHC are investigated. The SU(5) symmetry of the theory implies that the leptoquark couplings to matter are related to the neutrino mass matrix. We study the resulting connection between neutrino masses and mixing parameters and the leptoquark decays, and show that different light neutrino hierarchies imply distinctive leptoquark decay signatures. We also discuss low-energy constraints implied by searches for charged lepton flavour violation, studies of meson decays, and electroweak precision data. We perform a detailed parton-level study of the leptoquark signals and the Standard Model backgrounds at the LHC. With the clean final states containing a di-lepton plus two jets, the QCD production of the leptoquark pair can be observed for a leptoquark mass of one TeV and beyond. By examining the lepton flavor structure of the observed events, one could further test the model predictions related to the neutrino mass spectrum. In particular, b-flavor tagging will be useful in distinguishing the neutrino mass pattern and possibly probing an unknown Majorana phase in the Inverted Hierarchy or the Quasi-Degenerate scenario. Electroweak associated production of the leptoquark doublet can also be useful in identifying the quantum numbers of the leptoquarks and distinguishing between the neutrino mass spectra, even though the corresponding event rates are smaller than for QCD production. We find that with only the clean channel of μ+E/ T +jets, one could expect an observable signal for a leptoquark masses of about 600 GeV or higher.

Neutrino Physics without Neutrinos: Recent results from the NEMO-3 experiment and plans for SuperNEMO

CERN Multimedia

CERN. Geneva

2015-01-01

The observation of neutrino oscillations has proved that neutrinos have mass. This discovery has renewed and strengthened the interest in neutrinoless double beta decay experiments which provide the only practical way to determine whether neutrinos are Majorana or Dirac particles. The recently completed NEMO-3 experiment, located in the Laboratoire Souterrain de Modane in the Frejus Tunnel, was an experiment searching for neutrinoless double beta decays using a powerful technique for detecting a two-electron final state by employing an apparatus combining tracking, calorimetry, and the time-of-flight measurements. We will present latest results from NEMO-3 and will discuss the status of SuperNEMO, the next generation experiment that will exploit the same experimental technique to extend the sensitivity of the current search.

Comments on reconstruction and origins of the neutrino mass spectrum

International Nuclear Information System (INIS)

Smirnov, A.Yu.

2000-01-01

There are two main issues in the present day neutrino physics: (i) Reconstruction of the neutrino mass (and flavor) spectrum and (ii) Identification of origin of the neutrino mass and mixing, or in other terms, implications of the neutrino data for the fundamental theory. Present status and perspectives of the reconstruction are summarized. We comment on the see-saw and the 'bulk-brane' mechanisms of neutrino mass generation

Pattern of neutrino mixing in grand unified theories

International Nuclear Information System (INIS)

Milton, K.; Tanaka, K.

1981-01-01

It was found previously in SO(10) grand unified theories that if the neutrinos have a Dirac mass and a right-handed Majorana mass (approx. 10 15 GeV) but no left-handed Majorana mass, there is small ν/sub e/ mixing but ν/sub μ/ - ν/sub tau/ mixing can be substantial. This problem is reexamined on the basis of a formalism that assumes that the up, down, lepton, and neutrino mass matrices arise from a single complex 10 and a single 126 Higgs boson. This formalism determines the Majorana mass matrix in terms of quark mass matrices. Adopting three different sets of quark mass matrices that produce acceptable fermion mass ratios and Cabbibo mixing produces results consistent with the above; however, in the optimum case, ν/sub e/ - ν/sub μ/ mixing can be of the order of the Cabbibo angle

Determining the neutrino mass hierarchy with cosmology

International Nuclear Information System (INIS)

De Bernardis, Francesco; Kitching, Thomas D.; Heavens, Alan; Melchiorri, Alessandro

2009-01-01

The combination of current large-scale structure and cosmic microwave background anisotropies data can place strong constraints on the sum of the neutrino masses. Here we show that future cosmic shear experiments, in combination with cosmic microwave background constraints, can provide the statistical accuracy required to answer questions about differences in the mass of individual neutrino species. Allowing for the possibility that masses are nondegenerate we combine Fisher matrix forecasts for a weak lensing survey like Euclid with those for the forthcoming Planck experiment. Under the assumption that neutrino mass splitting is described by a normal hierarchy we find that the combination Planck and Euclid will possibly reach enough sensitivity to put a constraint on the mass of a single species. Using a Bayesian evidence calculation we find that such future experiments could provide strong evidence for either a normal or an inverted neutrino hierarchy. Finally we show that if a particular neutrino hierarchy is assumed then this could bias cosmological parameter constraints, for example, the dark energy equation of state parameter, by > or approx. 1σ, and the sum of masses by 2.3σ. We finally discuss the impact of uncertainties on the theoretical modeling of nonlinearities. The results presented in this analysis are obtained under an approximation to the nonlinear power spectrum. This significant source of uncertainty needs to be addressed in future work.

Probing neutrino mass hierarchy by comparing the charged-current and neutral-current interaction rates of supernova neutrinos

Energy Technology Data Exchange (ETDEWEB)

Lai, Kwang-Chang [Center for General Education, Chang Gung University,Kwei-Shan, Taoyuan, 333, Taiwan (China); Leung Center for Cosmology and Particle Astrophysics (LeCosPA), National Taiwan University, Taipei, 106, Taiwan (China); Lee, Fei-Fan [Institute of Physics, National Chiao Tung University,Hsinchu, 300, Taiwan (China); Lee, Feng-Shiuh [Department of Electrophysics, National Chiao Tung University,Hsinchu, 300, Taiwan (China); Lin, Guey-Lin [Leung Center for Cosmology and Particle Astrophysics (LeCosPA), National Taiwan University, Taipei, 106, Taiwan (China); Institute of Physics, National Chiao Tung University,Hsinchu, 300, Taiwan (China); Liu, Tsung-Che [Leung Center for Cosmology and Particle Astrophysics (LeCosPA), National Taiwan University, Taipei, 106, Taiwan (China); Yang, Yi [Department of Electrophysics, National Chiao Tung University,Hsinchu, 300, Taiwan (China)

2016-07-22

The neutrino mass hierarchy is one of the neutrino fundamental properties yet to be determined. We introduce a method to determine neutrino mass hierarchy by comparing the interaction rate of neutral current (NC) interactions, ν(ν-bar)+p→ν(ν-bar)+p, and inverse beta decays (IBD), ν-bar{sub e}+p→n+e{sup +}, of supernova neutrinos in scintillation detectors. Neutrino flavor conversions inside the supernova are sensitive to neutrino mass hierarchy. Due to Mikheyev-Smirnov-Wolfenstein effects, the full swapping of ν-bar{sub e} flux with the ν-bar{sub x} (x=μ, τ) one occurs in the inverted hierarchy, while such a swapping does not occur in the normal hierarchy. As a result, more high energy IBD events occur in the detector for the inverted hierarchy than the high energy IBD events in the normal hierarchy. By comparing IBD interaction rate with the mass hierarchy independent NC interaction rate, one can determine the neutrino mass hierarchy.

Probing neutrino mass hierarchy by comparing the charged-current and neutral-current interaction rates of supernova neutrinos

Science.gov (United States)

Lai, Kwang-Chang; Lee, Fei-Fan; Lee, Feng-Shiuh; Lin, Guey-Lin; Liu, Tsung-Che; Yang, Yi

2016-07-01

The neutrino mass hierarchy is one of the neutrino fundamental properties yet to be determined. We introduce a method to determine neutrino mass hierarchy by comparing the interaction rate of neutral current (NC) interactions, ν(bar nu) + p → ν(bar nu) + p, and inverse beta decays (IBD), bar nue + p → n + e+, of supernova neutrinos in scintillation detectors. Neutrino flavor conversions inside the supernova are sensitive to neutrino mass hierarchy. Due to Mikheyev-Smirnov-Wolfenstein effects, the full swapping of bar nue flux with the bar nux (x = μ, τ) one occurs in the inverted hierarchy, while such a swapping does not occur in the normal hierarchy. As a result, more high energy IBD events occur in the detector for the inverted hierarchy than the high energy IBD events in the normal hierarchy. By comparing IBD interaction rate with the mass hierarchy independent NC interaction rate, one can determine the neutrino mass hierarchy.

Probing neutrino mass hierarchy by comparing the charged-current and neutral-current interaction rates of supernova neutrinos

International Nuclear Information System (INIS)

Lai, Kwang-Chang; Lee, Fei-Fan; Lee, Feng-Shiuh; Lin, Guey-Lin; Liu, Tsung-Che; Yang, Yi

2016-01-01

The neutrino mass hierarchy is one of the neutrino fundamental properties yet to be determined. We introduce a method to determine neutrino mass hierarchy by comparing the interaction rate of neutral current (NC) interactions, ν(ν-bar)+p→ν(ν-bar)+p, and inverse beta decays (IBD), ν-bar_e+p→n+e"+, of supernova neutrinos in scintillation detectors. Neutrino flavor conversions inside the supernova are sensitive to neutrino mass hierarchy. Due to Mikheyev-Smirnov-Wolfenstein effects, the full swapping of ν-bar_e flux with the ν-bar_x (x=μ, τ) one occurs in the inverted hierarchy, while such a swapping does not occur in the normal hierarchy. As a result, more high energy IBD events occur in the detector for the inverted hierarchy than the high energy IBD events in the normal hierarchy. By comparing IBD interaction rate with the mass hierarchy independent NC interaction rate, one can determine the neutrino mass hierarchy.

Hybrid method to resolve the neutrino mass hierarchy by supernova (anti)neutrino induced reactions

Energy Technology Data Exchange (ETDEWEB)

Vale, D. [Department of Physics, Faculty of Science, University of Zagreb, Bijenička c. 32, HR-10000 Zagreb (Croatia); Rauscher, T. [Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Paar, N., E-mail: dvale@phy.hr, E-mail: Thomas.Rauscher@unibas.ch, E-mail: npaar@phy.hr [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

2016-02-01

We introduce a hybrid method to determine the neutrino mass hierarchy by simultaneous measurements of responses of at least two detectors to antineutrino and neutrino fluxes from accretion and cooling phases of core-collapse supernovae. The (anti)neutrino-nucleus cross sections for {sup 56}Fe and {sup 208}Pb are calculated in the framework of the relativistic nuclear energy density functional and weak interaction Hamiltonian, while the cross sections for inelastic scattering on free protons p(ν-bar {sub e},e{sup +})n are obtained using heavy-baryon chiral perturbation theory. The modelling of (anti)neutrino fluxes emitted from a protoneutron star in a core-collapse supernova include collective and Mikheyev-Smirnov-Wolfenstein effects inside the exploding star. The particle emission rates from the elementary decay modes of the daughter nuclei are calculated for normal and inverted neutrino mass hierarchy. It is shown that simultaneous use of (anti)neutrino detectors with different target material allows to determine the neutrino mass hierarchy from the ratios of ν{sub e}- and ν-bar {sub e}-induced particle emissions. This hybrid method favors neutrinos from the supernova cooling phase and the implementation of detectors with heavier target nuclei ({sup 208}Pb) for the neutrino sector, while for antineutrinos the use of free protons in mineral oil or water is the appropriate choice.

Direct search for neutrino mass and anomaly in the tritium beta-spectrum: Status of 'Troitsk neutrino mass' experiment

International Nuclear Information System (INIS)

Lobashev, V.M.; Aseev, V.N.; Belesev, A.I.; Berlev, A.I.; Geraskin, E.V.; Golubev, A.A.; Kazachenko, O.V.; Kuznetsov, Yu.E.; Ostroumov, R.P.; Rivkis, L.A.; Stern, B.E.; Titov, N.A.; Zadoroghny, C.V.; Zakharov, Yu.I.

2000-01-01

Results of the 'Troitsk ν-mass' experiment on search for the neutrino rest mass in the tritium beta-decay are presented. New data on the time dependence of the anomalous, bump-like structure at the end of the beta spectrum reported earlier are discussed. Possible systematics is considered in view of contradiction of 'Troitsk nu-mass' observation with those of 'Mainz neutrino' set-up. An upper limit for electron antineutrino rest mass remains at m ν 2 at 95% C.L

Unification of gauge couplings in radiative neutrino mass models

DEFF Research Database (Denmark)

Hagedorn, Claudia; Ohlsson, Tommy; Riad, Stella

2016-01-01

masses at one-loop level and (III) models with particles in the adjoint representation of SU(3). In class (I), gauge couplings unify in a few models and adding dark matter amplifies the chances for unification. In class (II), about a quarter of the models admits gauge coupling unification. In class (III......We investigate the possibility of gauge coupling unification in various radiative neutrino mass models, which generate neutrino masses at one- and/or two-loop level. Renormalization group running of gauge couplings is performed analytically and numerically at one- and two-loop order, respectively....... We study three representative classes of radiative neutrino mass models: (I) minimal ultraviolet completions of the dimension-7 ΔL = 2 operators which generate neutrino masses at one- and/or two-loop level without and with dark matter candidates, (II) models with dark matter which lead to neutrino...

Gravity wave and neutrino bursts from stellar collapse: A sensitive test of neutrino masses

International Nuclear Information System (INIS)

Arnaud, N.; Barsuglia, M.; Bizouard, M.A.; Cavalier, F.; Davier, M.; Hello, P.; Pradier, T.

2002-01-01

New methods are proposed with the goal to determine absolute neutrino masses from the simultaneous observation of the bursts of neutrinos and gravitational waves emitted during a stellar collapse. It is shown that the neutronization electron neutrino flash and the maximum amplitude of the gravitational wave signal are tightly synchronized with the bounce occurring at the end of the core collapse on a time scale better than 1 ms. The existing underground neutrino detectors (SuperKamiokande, SNO,...) and the gravity wave antennas soon to operate (LIGO, VIRGO,...) are well matched in their performance for detecting galactic supernovae and for making use of the proposed approach. Several methods are described, which apply to the different scenarios depending on neutrino mixing. Given the present knowledge on neutrino oscillations, the methods proposed are sensitive to a mass range where neutrinos would essentially be mass degenerate. The 95% C.L. upper limit which can be achieved varies from 0.75 eV/c 2 for large ν e survival probabilities to 1.1 eV/c 2 when in practice all ν e 's convert into ν μ 's or ν τ 's. The sensitivity is nearly independent of the supernova distance

Probing neutrino mass hierarchy by comparing the charged-current and neutral-current interaction rates of supernova neutrinos

OpenAIRE

Lai, Kwang-Chang; Lee, Fei-Fan; Lee, Feng-Shiuh; Lin, Guey-Lin; Liu, Tsung-Che; Yang, Yi

2016-01-01

The neutrino mass hierarchy is one of the neutrino fundamental properties yet to be determined. We introduce a method to determine neutrino mass hierarchy by comparing the interaction rate of neutral current (NC) interactions, $\

Neutrino mass in flavor dependent gauged lepton model

Science.gov (United States)

Nomura, Takaaki; Okada, Hiroshi

2018-03-01

We study a neutrino model introducing an additional nontrivial gauged lepton symmetry where the neutrino masses are induced at two-loop level, while the first and second charged-leptons of the standard model are done at one-loop level. As a result of the model structure, we can predict one massless active neutrino, and there is a dark matter candidate. Then we discuss the neutrino mass matrix, muon anomalous magnetic moment, lepton flavor violations, oblique parameters, and relic density of dark matter, taking into account the experimental constraints.

Radiative stability of neutrino-mass textures

Indian Academy of Sciences (India)

physics pp. 647-650. Radiative stability of neutrino-mass textures. M K PARIDA ... A major challenge to particle physics at present is the theoretical understanding of ... A possible origin of two large neutrino mixings for /e -/μ and /μ -/г but small.

Prospects for cosmic neutrino detection in tritium experiments in the case of hierarchical neutrino masses

International Nuclear Information System (INIS)

Blennow, Mattias

2008-01-01

We discuss the effects of neutrino mixing and the neutrino mass hierarchy when considering the capture of the cosmic neutrino background (CNB) on radioactive nuclei. The implications of mixing and hierarchy at future generations of tritium decay experiments are considered. We find that the CNB should be detectable at these experiments provided that the resolution for the kinetic energy of the outgoing electron can be pushed to a few 0.01 eV for the scenario with inverted neutrino mass hierarchy, about an order of magnitude better than that of the upcoming KATRIN experiment. Another order of magnitude improvement is needed in the case of normal neutrino mass hierarchy. We also note that mixing effects generally make the prospects for CNB detection worse due to an increased maximum energy of the normal beta decay background

Lepton mixing and cancellation of the Dirac mass hierarchy in SO(10) GUTs with flavor symmetries T7 and Σ(81)

International Nuclear Information System (INIS)

Hagedorn, Claudia; Schmidt, Michael A.; Smirnov, Alexei Yu.

2009-01-01

In SO(10) grand unified theories the hierarchy which is present in the Dirac mass term of the neutrinos is generically as strong as the one in the up-type quark mass term. We propose a mechanism to partially or completely cancel this hierarchy in the light neutrino mass matrix in the seesaw context. The two main ingredients of the cancellation mechanism are the existence of three fermionic gauge singlets and of a discrete flavor symmetry G f which is broken at a higher scale than SO(10). Two realizations of the cancellation mechanism are presented. The realization based on the Frobenius group T 7 ≅Z 7 xZ 3 leads to a partial cancellation of the hierarchy and relates maximal 2-3 lepton mixing with the geometric hierarchy of the up-quark masses. In the realization with the group Σ(81) the cancellation is complete and tribimaximal lepton mixing is reproduced at the lowest order. In both cases, to fully accommodate the leptonic data we take into account additional effects such as effects of higher-dimensional operators involving more than one flavon. The heavy neutral fermion mass spectra are considered. For both realizations we analyze the flavon potential at the renormalizable level as well as ways to generate the Cabibbo angle.

Production of heavy neutrino in next-to-leading order QCD at the LHC and beyond

International Nuclear Information System (INIS)

Das, Arindam; Konar, Partha; Majhi, Swapan

2016-01-01

Majorana and pseudo-Dirac heavy neutrinos are introduced into the type-I and inverse seesaw models, respectively, in explaining the naturally small neutrino mass. TeV scale heavy neutrinos can also be accommodated to have a sizable mixing with the Standard Model light neutrinos, through which they can be produced and detected at the high energy colliders. In this paper we consider the Next-to-Leading Order QCD corrections to the heavy neutrino production, and study the scale variation in cross-sections as well as the kinematic distributions with different final states at 14 TeV LHC and also in the context of 100 TeV hadron collider. The repertoire of the Majorana neutrino is realized through the characteristic signature of the same-sign dilepton pair, whereas, due to a small lepton number violation, the pseudo-Dirac heavy neutrino can manifest the trileptons associated with missing energy in the final state. Using the √s=8 TeV, 20.3 fb"−"1 and 19.7 fb"−"1 data at the ATLAS and CMS respectively, we obtain prospective scale dependent upper bounds of the light-heavy neutrino mixing angles for the Majorana heavy neutrinos at the 14 TeV LHC and 100 TeV collider. Further exploiting a recent study on the anomalous multilepton search by CMS at √s=8 TeV with 19.5 fb"−"1 data, we also obtain the prospective scale dependent upper bounds on the mixing angles for the pseudo-Dirac neutrinos. We thus project a scale dependent prospective reach using the NLO processes at the 14 TeV LHC.

A comprehensive study of neutrino spin-flavour conversion in supernovae and the neutrino mass hierarchy

Science.gov (United States)

Ando, Shin'ichiro; Sato, Katsuhiko

2003-10-01

Resonant spin-flavour (RSF) conversions of supernova neutrinos, which are induced by the interaction between the nonzero neutrino magnetic moment and supernova magnetic fields, are studied for both normal and inverted mass hierarchy. As the case for the pure matter-induced neutrino oscillation (Mikheyev–Smirnov–Wolfenstein (MSW) effect), we find that the RSF transitions are strongly dependent on the neutrino mass hierarchy as well as the value of θ13. Flavour conversions are solved numerically for various neutrino parameter sets, with the presupernova profile calculated by Woosley and Weaver. In particular, it is very interesting that the RSF-induced νe→bar nue transition occurs if the following conditions are all satisfied: the value of μνB (μν is the neutrino magnetic moment and B is the magnetic field strength) is sufficiently strong, the neutrino mass hierarchy is inverted, and the value of θ13 is large enough to induce adiabatic MSW resonance. In this case, the strong peak due to the original νe emitted from the neutronization burst would exist in the time profile of the neutrino events detected at the Super-Kamiokande detector. If this peak were observed in reality, it would provide fruitful information on the neutrino properties. On the other hand, the characteristics of the neutrino spectra are also different between the neutrino models, but we find that there remains degeneracy among several models. Dependence on presupernova models is also discussed.

Phenomenological study of extended seesaw model for light sterile neutrino

International Nuclear Information System (INIS)

Nath, Newton; Ghosh, Monojit; Goswami, Srubabati; Gupta, Shivani

2017-01-01

We study the zero textures of the Yukawa matrices in the minimal extended type-I seesaw (MES) model which can give rise to ∼ eV scale sterile neutrinos. In this model, three right handed neutrinos and one extra singlet S are added to generate a light sterile neutrino. The light neutrino mass matrix for the active neutrinos, m ν , depends on the Dirac neutrino mass matrix (M D ), Majorana neutrino mass matrix (M R ) and the mass matrix (M S ) coupling the right handed neutrinos and the singlet. The model predicts one of the light neutrino masses to vanish. We systematically investigate the zero textures in M D and observe that maximum five zeros in M D can lead to viable zero textures in m ν . For this study we consider four different forms for M R (one diagonal and three off diagonal) and two different forms of (M S ) containing one zero. Remarkably we obtain only two allowed forms of m ν (m eτ =0 and m ττ =0) having inverted hierarchical mass spectrum. We re-analyze the phenomenological implications of these two allowed textures of m ν in the light of recent neutrino oscillation data. In the context of the MES model, we also express the low energy mass matrix, the mass of the sterile neutrino and the active-sterile mixing in terms of the parameters of the allowed Yukawa matrices. The MES model leads to some extra correlations which disallow some of the Yukawa textures obtained earlier, even though they give allowed one-zero forms of m ν . We show that the allowed textures in our study can be realized in a simple way in a model based on MES mechanism with a discrete Abelian flavor symmetry group Z 8 ×Z 2 .

The high mass frontier: limits on heavy neutrinos

International Nuclear Information System (INIS)

Gronau, M.

1984-01-01

The theoretical motivation for a search for heavy neutrinos is discussed followed by the presentation of typical model dependent expectations for the mixing of the latter with ordinary neutrinos. Present mass and mixing limits on such heavy neutral leptons are based on search for secondary peaks in π and K leptonic decays and on the absence of neutrino decay signatures in neutrino beams from conventional sources and beam dumps. While these limits are quite poor for masses above 1 GeV, we describe methods to extend the limits to masses in the many GeV region. Such limits may be derived from search in b decays, high statistics neutrino experiments, search in ep colliders, W and Z decays and finally - decays of very heavy gauge bosons (if such exist in the TeV region) when produced in multi-TeV pp and antipp colliders

Quantum treatment of neutrino in background matter

International Nuclear Information System (INIS)

Studenikin, A I

2006-01-01

Motivated by the need of elaboration of the quantum theory of the spin light of neutrino in matter (SLν), we have studied in more detail the exact solutions of the Dirac equation for neutrinos moving in background matter. These exact neutrino wavefunctions form a basis for a rather powerful method of investigation of different neutrino processes in matter, which is similar to the Furry representation of quantum electrodynamics in external fields. Within this method we also derive the corresponding Dirac equation for an electron moving in matter and consider the electromagnetic radiation ('spin light of electron in matter' (SLe)) that can be emitted by the electron in this case

Cosmological and astrophysical neutrino mass measurements

DEFF Research Database (Denmark)

Abazajian, K.N.; Calabrese, E.; Cooray, A.

2011-01-01

Cosmological and astrophysical measurements provide powerful constraints on neutrino masses complementary to those from accelerators and reactors. Here we provide a guide to these different probes, for each explaining its physical basis, underlying assumptions, current and future reach.......Cosmological and astrophysical measurements provide powerful constraints on neutrino masses complementary to those from accelerators and reactors. Here we provide a guide to these different probes, for each explaining its physical basis, underlying assumptions, current and future reach....

The Mainz Neutrino Mass Experiment

Czech Academy of Sciences Publication Activity Database

Kraus, C.; Bornschein, L.; Bonn, J.; Bornschein, B.; Flatt, B.; Kovalík, Alojz; Müller, B.; Otten, EW; Schall, JP.; Thummler, T.; Weinheimer, C.

2005-01-01

Roč. 143, - (2005), s. 143 ISSN 0920-5632. [International Conference on Neutrino Physics and Astrophysics /21./. Paříž, 14.06.2004-19.06.2004] R&D Projects: GA MŠk 1P04LA213 Institutional research plan: CEZ:AV0Z10480505 Keywords : neutrino mass * tritium beta decay Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 0.875, year: 2005

Neutrino mass textures from F-theory

CERN Document Server

Antoniadis, I

2013-01-01

Experimental data on the neutrino mixing and masses strongly suggest an underlying approximate symmetry of the relevant Yukawa superpotential terms. Intensive phenomenological explorations during the last decade indicate that permutation symmetries such as S_4, A_4 and their subgroups, under certain assumptions and vacuum alignments, predict neutrino mass textures compatible with such data. Motivated by these findings, in the present work we analyse the neutrino properties in F-theory GUT models derived in the framework of the maximal underlying E_8 symmetry in the elliptic fibration. More specifically, we consider local F-SU(5) GUT models and study in detail spectral cover geometries with monodromies associated to the finite symmetries S_4, A_4 and their transitive subgroups, including the dihedral group D_4 and Z_2 X Z_2. We discuss various issues that emerge in the implementation of S_4, A_4 neutrino models in the F-theory context and suggest how these can be resolved. Realistic models are presented for th...

Lepton-number-charged scalars and neutrino beamstrahlung

Science.gov (United States)

Berryman, Jeffrey M.; de Gouvêa, André; Kelly, Kevin J.; Zhang, Yue

2018-04-01

Experimentally, baryon number minus lepton number, B -L , appears to be a good global symmetry of nature. We explore the consequences of the existence of gauge-singlet scalar fields charged under B -L -dubbed lepton-number-charged scalars (LeNCSs)—and postulate that these couple to the standard model degrees of freedom in such a way that B -L is conserved even at the nonrenormalizable level. In this framework, neutrinos are Dirac fermions. Including only the lowest mass-dimension effective operators, some of the LeNCSs couple predominantly to neutrinos and may be produced in terrestrial neutrino experiments. We examine several existing constraints from particle physics, astrophysics, and cosmology to the existence of a LeNCS carrying B -L charge equal to two, and discuss the emission of LeNCSs via "neutrino beamstrahlung," which occurs every once in a while when neutrinos scatter off of ordinary matter. We identify regions of the parameter space where existing and future neutrino experiments, including the Deep Underground Neutrino Experiment, are at the frontier of searches for such new phenomena.

Search for long-lived massive neutrinos in Z decays

International Nuclear Information System (INIS)

Jung, C.K.; Van Kooten, R.; Abrams, G.S.; Adolphsen, C.E.; Averill, D.; Ballam, J.; Barish, B.C.; Barklow, T.; Barnett, B.A.; Bartelt, J.; Bethke, S.; Blockus, D.; Bonvicini, G.; Boyarski, A.; Brabson, B.; Breakstone, A.; Bulos, F.; Burchat, P.R.; Burke, D.L.; Cence, R.J.; Chapman, J.; Chmeissani, M.; Cords, D.; Coupal, D.P.; Dauncey, P.; DeStaebler, H.C.; Dorfan, D.E.; Dorfan, J.M.; Drewer, D.C.; Elia, R.; Feldman, G.J.; Fernandes, D.; Field, R.C.; Ford, W.T.; Fordham, C.; Frey, R.; Fujino, D.; Gan, K.K.; Gatto, C.; Gero, E.; Gidal, G.; Glanzman, T.; Goldhaber, G.; Gomez Cadenas, J.J.; Gratta, G.; Grindhammer, G.; Grosse-Wiesmann, P.; Hanson, G.; Harr, R.; Harral, B.; Harris, F.A.; Hawkes, C.M.; Hayes, K.; Hearty, C.; Heusch, C.A.; Hildreth, M.D.; Himel, T.; Hinshaw, D.A.; Hong, S.J.; Hutchinson, D.; Hylen, J.; Innes, W.R.; Jacobsen, R.G.; Jaros, J.A.; Kadyk, J.A.; Kent, J.; King, M.; Klein, S.R.; Koetke, D.S.; Komamiya, S.; Koska, W.; Kowalski, L.A.; Kozanecki, W.; Kral, J.F.; Kuhlen, M.; Labarga, L.; Lankford, A.J.; Larsen, R.R.; Le Diberder, F.; Levi, M.E.; Litke, A.M.; Lou, X.C.; Lueth, V.; McKenna, J.A.; Matthews, J.A.J.; Mattison, T.; Milliken, B.D.; Moffeit, K.C.; Munger, C.T.; Murray, W.N.; Nash, J.; Ogren, H.; O'Shaughnessy, K.F.; Parker, S.I.; Peck, C.; Perl, M.L.; Perrier, F.; Petradza, M.; Pitthan, R.; Porter, F.C.; Rankin, P.; Riles, K.; Rouse, F.R.; Rust, D.R.; Sadrozinski, H.F.W.; Schaad, M.W.; Schumm, B.A.; Seiden, A.; Smith, J.G.; Snyder, A.; Soderstrom, E.; Stoker, D.P.; Stroynowski, R.; Swartz, M.; Thun, R.; Trilling, G.H.; Voruganti, P.; Wagner, S.R.; Watson, S.; Weber, P.; Weigend, A.; Weinstein, A.J.; Weir, A.J.; Wicklund, E.; Woods, M.; Wu, D.Y.; Yurko, M.; Zaccardelli, C.; von Zanthier, C.

1990-01-01

We search for events in the Mark II detector at SLAC Linear Collider with the topology of a Z boson decaying into a pair of long-lived massive particles. No events that are consistent with the search hypothesis are found. Interpreting the long-lived particle as a sequential Dirac neutrino ν 4 of the fourth generation, we exclude at the 95% confidence level a significant range of mixing-matrix elements of ν 4 to other-generation neutrinos for a ν 4 mass from 10 to 43 GeV/c 2

Cosmology and the neutrino mass ordering

DEFF Research Database (Denmark)

Hannestad, Steen; Schwetz, Thomas

2016-01-01

We propose a simple method to quantify a possible exclusion of the inverted neutrino mass ordering from cosmological bounds on the sum of the neutrino masses. The method is based on Bayesian inference and allows for a calculation of the posterior odds of normal versus inverted ordering. We apply...... the method for a specific set of current data from Planck CMB data and large-scale structure surveys, providing an upper bound on the sum of neutrino masses of 0.14 eV at 95% CL. With this analysis we obtain posterior odds for normal versus inverted ordering of about 2:1. If cosmological data is combined...... with data from oscillation experiments the odds reduce to about 3:2. For an exclusion of the inverted ordering from cosmology at more than 95% CL, an accuracy of better than 0.02 eV is needed for the sum. We demonstrate that such a value could be reached with planned observations of large scale structure...

The neutrino masses in SO(10) grand unified theory

International Nuclear Information System (INIS)

Leontaris, G.K.; Vergados, J.D.; Ioannina Univ.

1987-01-01

The neutrino masses and mixing are investigated in an SO(10) model in which the ten-dimensional and 126-dimensional representations are allowed to obtain vacuum expectation values. The parameters specifying the heavy Majorana neutrino mass matrix are constrained from the cosmological bound of light neutrino masses and the limits from ν μ ↔ ν τ oscillations. The implications of our model on 0ν-ββ decay and muon-number violating processes are explored. (orig.)

Noncommutativity into Dirac Equation with mass dependent on the position

International Nuclear Information System (INIS)

Bastos, Samuel Batista; Almeida, Carlos Alberto Santos; Nunes, Luciana Angelica da Silva

2013-01-01

Full text: In recent years, there is growing interest in the study of theories in non-commutative spaces. Non-commutative fields theories are related with compactifications of M theory, string theory and the quantum Hall effect. Moreover, the role of the non-commutativity of theories of a particle finds large applications when analyzed in scenarios of quantum mechanics and relativistic quantum mechanics. In these contexts investigations on the Schrodinger and Dirac equations with mass depending on the position (MDP) has attracted much attention in the literature. Systems endowed with MDP models are useful for the study of many physical problems. In particular, they are used to study the energy density in problems of many bodies, determining the electronic properties of semiconductor heterostructures and also to describe the properties of heterojunctions and quantum dots. In particular, the investigation of relativistic effects it is important for systems containing heavy atoms or doping by heavy ions. For these types of materials, the study of the properties of the Dirac equation, in the case where the mass becomes variable is of great interest. In this paper, we seek for the non-relativistic limit of the Dirac Hamiltonian in the context of a theory of effective mass, through a Foldy-Wouthuysen transformation. We analyse the Dirac equation with mass dependent on the position, in a smooth step shape mass distribution, in non-commutative space (NC). This potential type kink was recently discussed by several authors in the commutative context and now we present our results in the non-commutative context. (author)

Neutrino mass and physics beyond the Standard Model; Masse des Neutrinos et Physique au-dela du Modele Standard

Energy Technology Data Exchange (ETDEWEB)

Hosteins, P

2007-09-15

The purpose of this thesis is to study, in the neutrino sector, the flavour structures at high energy. The work is divided into two main parts. The first part is dedicated to the well known mechanism to produce small neutrino masses: the seesaw mechanism, which implies the existence of massive particles whose decays violate lepton number. Therefore this mechanism can also be used to generate a net baryon number in the early universe and explain the cosmological observation of the asymmetry between matter and antimatter. However, it is often non-trivial to fulfill the constraints coming at the same time from neutrino oscillations and cosmological experiments, at least in frameworks where the couplings can be somehow constrained, like some Grand Unification models. Therefore we devoted the first part to the study of a certain class of seesaw mechanism which can be found in the context of SO(10) theories for example. We introduce a method to extract the mass matrix of the heavy right-handed neutrinos and explore the phenomenological consequences of this quantity, mainly concerning the production of a sufficient baryon asymmetry. When trying to identify the underlying symmetry governing the mixings between the different generations, we see that there is a puzzling difference between the quark and the lepton sectors. However, the quark and lepton parameters have to be compared at the scale of the flavour symmetry breaking, therefore we have to make them run to the appropriate scale. Thus, it is worthwhile investigating models where quantum corrections allow an approximate unification of quark and lepton mixings. This is why the other part of the thesis investigates the running of the effective neutrino mass operator in models with an extra compact dimension, where quantum corrections to the neutrino masses and mixings can be potentially large due to the multiplicity of states.

Large νμ-ντ mixing and the structure of right-handed Majorana mass matrix

International Nuclear Information System (INIS)

Matsuda, Masahisa

1993-01-01

Recent solar neutrino and atmospheric neutrino experiment suggest the existence of the large lepton mixing among 2nd and 3rd generation neutrino. This fact gives the important information on the structure of right-handed Majorana neutrino. It is shown that, if we assume that the neutrino Dirac mass matrix is similar to the mass matrix of the up-quark sector, the large lepton mixing among the 2nd and the 3rd generation requires the hierarchical structure of the Majorana mass matrix. This model-independent analyses serve the model-building of the mass matrices based on the quark-lepton unified theory. (author)

Neutrino Majorana masses from string theory instanton effects

International Nuclear Information System (INIS)

Ibanez, Luis E.; Uranga, Angel M.

2007-01-01

Finding a plausible origin for right-handed neutrino Majorana masses in semirealistic compactifications of string theory remains one of the most difficult problems in string phenomenology. We argue that right-handed neutrino Majorana masses are induced by non-perturbative instanton effects in certain classes of string compactifications in which the U(1) B-L gauge boson has a Stueckelberg mass. The induced operators are of the form e -U ν R ν R where U is a closed string modulus whose imaginary part transforms appropriately under B-L. This mass term may be quite large since this is not a gauge instanton and Re U is not directly related to SM gauge couplings. Thus the size of the induced right-handed neutrino masses could be a few orders of magnitude below the string scale, as phenomenologically required. It is also argued that this origin for neutrino masses would predict the existence of R-parity in SUSY versions of the SM. Finally we comment on other phenomenological applications of similar instanton effects, like the generation of a μ-term, or of Yukawa couplings forbidden in perturbation theory

Neutrino Mixing and Masses from a Minimum Principle

CERN Document Server

Alonso, R; Isidori, G; Maiani, L

2013-01-01

We analyze the structure of quark and lepton mass matrices under the hypothesis that they are determined from a minimum principle applied to a generic potential invariant under the $\\left[SU(3)\\right]^5\\otimes \\mathcal O(3)$ flavor symmetry, acting on Standard Model fermions and right-handed neutrinos. Unlike the quark case, we show that hierarchical masses for charged leptons are naturally accompanied by degenerate Majorana neutrinos with one mixing angle close to maximal, a second potentially large, a third one necessarily small, and one maximal relative Majorana phase. Adding small perturbations the predicted structure for the neutrino mass matrix is in excellent agreement with present observations and could be tested in the near future via neutrino-less double beta decay and cosmological measurements. The generalization of these results to arbitrary sew-saw models is also discussed.

Low scale gravity as the source of neutrino masses?

International Nuclear Information System (INIS)

Berezinsky, Veniamin; Narayan, Mohan; Vissani, Francesco

2005-01-01

We address the question whether low-scale gravity alone can generate the neutrino mass matrix needed to accommodate the observed phenomenology. In low-scale gravity the neutrino mass matrix in the flavor basis is characterized by one parameter (the gravity scale M X ) and by an exact or approximate flavor blindness (namely, all elements of the mass matrix are of comparable size). Neutrino masses and mixings are consistent with the observational data for certain values of the matrix elements, but only when the spectrum of mass is inverted or degenerate. For the latter type of spectra the parameter M ee probed in double beta experiments and the mass parameter probed by cosmology are close to existing upper limits

Masses, flavor mix and CP violation

International Nuclear Information System (INIS)

Chaussard, L.

2004-06-01

The author describes the relationships between masses, mixing of flavors and CP violation. This document is divided into 4 chapters: 1) fermions' masses, 2) mixing of flavors and CP violation, 3) beauty physics and 4) neutrino physics. In chapter 1 an attempt is made to explain what is behind the concepts of lepton mass and quark mass. As for neutrinos, the only neutral fermion, Dirac's and Majorana's views are exposed as well as their consequences. Fermion flavors are mixed in the process of mass generation and this mix is responsible for the breaking of CP and T symmetries. In chapter 2 the author shows how the analysis of particle oscillations from neutral mesons (K 0 , D 0 , B d 0 and B s 0 ) and from neutrinos can shed light on CP violation. Chapter 3 is dedicated to the contribution of beauty physics to the determination of the unitary triangle, through the oscillations of beauty mesons. In chapter 4 the author reviews the experimental results obtained recently concerning neutrino mass and neutrino oscillations and draws some perspectives on future neutrino experiments. (A.C.)

Neutrino masses and family symmetry

International Nuclear Information System (INIS)

Grinstein, B.; Preskill, J.; Wise, M.B.

1985-01-01

Neutrino masses in the 100 eV-1 MeV range are permitted if there is a spontaneously broken global family symmetry that allows the heavy neutrinos to decay by Goldstone boson emission with a cosmologically acceptable lifetime. The family symmetry may be either abelian or nonabelian; we present models illustrating both possibilities. If the family symmetry is nonabelian, then the decay tau -> μ + Goldstone boson or tau -> e + Goldstone may have an observable rate. (orig.)

Trinification, the hierarchy problem, and inverse seesaw neutrino masses

International Nuclear Information System (INIS)

Cauet, Christophe; Paes, Heinrich; Wiesenfeldt, Soeren

2011-01-01

In minimal trinification models light neutrino masses can be generated via a radiative seesaw mechanism, where the masses of the right-handed neutrinos originate from loops involving Higgs and fermion fields at the unification scale. This mechanism is absent in models aiming at solving or ameliorating the hierarchy problem, such as low-energy supersymmetry, since the large seesaw scale disappears. In this case, neutrino masses need to be generated via a TeV-scale mechanism. In this paper, we investigate an inverse seesaw mechanism and discuss some phenomenological consequences.

Bilarge neutrino mixing and mass of the lightest neutrino from third generation dominance in a democratic approach

International Nuclear Information System (INIS)

Dermisek, Radovan

2004-01-01

We show that both small mixing in the quark sector and large mixing in the lepton sector can be obtained from a simple assumption of universality of Yukawa couplings and the right-handed neutrino Majorana mass matrix in leading order. We discuss conditions under which bilarge mixing in the lepton sector is achieved with a minimal amount of fine-tuning requirements for possible models. From knowledge of the solar and atmospheric mixing angles we determine the allowed values of sin θ 13 . If embedded into grand unified theories, the third generation Yukawa coupling unification is a generic feature while masses of the first two generations of charged fermions depend on small perturbations. In the neutrino sector, the heavier two neutrinos are model dependent, while the mass of the lightest neutrino in this approach does not depend on perturbations in the leading order. The right-handed neutrino mass scale can be identified with the GUT scale in which case the mass of the lightest neutrino is given as (m top 2 /M GUT )sin 2 θ 23 sin 2 θ 12 in the limit sin θ 13 ≅0. Discussing symmetries we make a connection with hierarchical models and show that the basis independent characteristic of this scenario is a strong dominance of the third generation right-handed neutrino, M 1 ,M 2 -4 M 3 , M 3 =M GUT

Low scale gravity as the source of neutrino masses?

Energy Technology Data Exchange (ETDEWEB)

Berezinsky, Veniamin [INFN, Laboratori Nazionali del Gran Sasso, I-67010 Assergi, AQ (Italy); Narayan, Mohan [INFN, Laboratori Nazionali del Gran Sasso, I-67010 Assergi, AQ (Italy); Vissani, Francesco [INFN, Laboratori Nazionali del Gran Sasso, I-67010 Assergi, AQ (Italy)

2005-04-01

We address the question whether low-scale gravity alone can generate the neutrino mass matrix needed to accommodate the observed phenomenology. In low-scale gravity the neutrino mass matrix in the flavor basis is characterized by one parameter (the gravity scale M{sub X}) and by an exact or approximate flavor blindness (namely, all elements of the mass matrix are of comparable size). Neutrino masses and mixings are consistent with the observational data for certain values of the matrix elements, but only when the spectrum of mass is inverted or degenerate. For the latter type of spectra the parameter M{sub ee} probed in double beta experiments and the mass parameter probed by cosmology are close to existing upper limits.

Phenomenological study of extended seesaw model for light sterile neutrino

Energy Technology Data Exchange (ETDEWEB)

Nath, Newton [Physical Research Laboratory,Navarangpura, Ahmedabad 380 009 (India); Indian Institute of Technology,Gandhinagar, Ahmedabad-382424 (India); Ghosh, Monojit [Department of Physics, Tokyo Metropolitan University,Hachioji, Tokyo 192-0397 (Japan); Goswami, Srubabati [Physical Research Laboratory,Navarangpura, Ahmedabad 380 009 (India); Gupta, Shivani [Center of Excellence for Particle Physics (CoEPP), University of Adelaide,Adelaide SA 5005 (Australia)

2017-03-14

We study the zero textures of the Yukawa matrices in the minimal extended type-I seesaw (MES) model which can give rise to ∼ eV scale sterile neutrinos. In this model, three right handed neutrinos and one extra singlet S are added to generate a light sterile neutrino. The light neutrino mass matrix for the active neutrinos, m{sub ν}, depends on the Dirac neutrino mass matrix (M{sub D}), Majorana neutrino mass matrix (M{sub R}) and the mass matrix (M{sub S}) coupling the right handed neutrinos and the singlet. The model predicts one of the light neutrino masses to vanish. We systematically investigate the zero textures in M{sub D} and observe that maximum five zeros in M{sub D} can lead to viable zero textures in m{sub ν}. For this study we consider four different forms for M{sub R} (one diagonal and three off diagonal) and two different forms of (M{sub S}) containing one zero. Remarkably we obtain only two allowed forms of m{sub ν} (m{sub eτ}=0 and m{sub ττ}=0) having inverted hierarchical mass spectrum. We re-analyze the phenomenological implications of these two allowed textures of m{sub ν} in the light of recent neutrino oscillation data. In the context of the MES model, we also express the low energy mass matrix, the mass of the sterile neutrino and the active-sterile mixing in terms of the parameters of the allowed Yukawa matrices. The MES model leads to some extra correlations which disallow some of the Yukawa textures obtained earlier, even though they give allowed one-zero forms of m{sub ν}. We show that the allowed textures in our study can be realized in a simple way in a model based on MES mechanism with a discrete Abelian flavor symmetry group Z{sub 8}×Z{sub 2}.

Lepton flavour symmetry and the neutrino magnetic moment

International Nuclear Information System (INIS)

Ecker, G.; Grimus, W.

1990-01-01

With the standard model gauge group and the three standard left-handed Weyl neutrinos, two minimal scenarios are investigated where an arbitrary non-abelian lepton flavour symmetry group G H is responsible for a light neutrino with a large magnetic moment. In the first case, with scalar fields carrying lepton flavour, some finetuning is necessary to get a small enough neutrino mass for μ ν = O(10 -11 μ B ). In the second scenario, the introduction of heavy charged gauge singlet fermions with lepton flavour allows for a strictly massless neutrino to one-loop order. In both cases, the interference mechanisms for small m ν and large μ ν is unique, independently of G H . In explicit realizations of the two scenarios, the horizontal groups are found to be non-abelian extensions of a Zeldovich-Konopinski-Mahmoud lepton number symmetry. Only a discrete part of G H is spontaneously broken leading to a light Dirac neutrino with a large magnetic moment. (Authors) 22 refs., 3 figs

Predicting {theta}{sub 13} and the neutrino mass scale from quark lepton mass hierarchies

Energy Technology Data Exchange (ETDEWEB)

Buchmueller, W.; Domcke, V.; Schmitz, K.

2011-11-15

Flavour symmetries of Froggatt-Nielsen type can naturally reconcile the large quark and charged lepton mass hierarchies and the small quark mixing angles with the observed small neutrino mass hierarchies and their large mixing angles. We point out that such a flavour structure, together with the measured neutrino mass squared differences and mixing angles, strongly constrains yet undetermined parameters of the neutrino sector. Treating unknown O(1) parameters as random variables, we obtain surprisingly accurate predictions for the smallest mixing angle, sin{sup 2}2{theta}{sub 13}=0.07{sup +0.11}{sub -0.05}, the smallest neutrino mass, m{sub 1}=2.5{sup +1.7}{sub -1.6} x 10{sup -3} eV, and one Majorana phase, {alpha}{sub 21}/{pi}=1.0{sup +0.2}{sub -0.2}. (orig.)

Neutrino masses and ordering via multimessenger astronomy

DEFF Research Database (Denmark)

Langæble, Kasper; Meroni, Aurora; Sannino, Francesco

2016-01-01

We define the theoretical framework and deduce the conditions under which multi-messenger astronomy can provide useful information about neutrino masses and their ordering. The framework uses time differences between the arrival of neutrinos and the other light messenger, i.e. the graviton, emitted...

Neutrino spectrum of Einstein universes

International Nuclear Information System (INIS)

Holm, C.

1988-01-01

The study of higher-dimensional Kaluza--Klein universes constructed from the unitary groups U/sub N/ is continued. They form Bergmann manifolds of dimension N 2 with Finslerian geometry induced by their hyperspin structure. In this paper Lagrangians for relativistic wave equations, which are generalizations of the Klein--Gordan, Dirac, and Weyl neutrino equations, are formulated. The wave equations are in general of differential order N. The hyperneutrino equation is examined in detail as the simplest example and its discrete symmetries are discussed. It is found that for N = 3 and N>4 TCP and all its constituent symmetries are violated. The boson calculus is used to solve the linear neutrino equation exactly on U/sub N/ and the energy spectra of the neutrino and antineutrino are presented. It is found that the density ratio of negative to positive energy states is unity only for N = 2, producing asymmetry for all higher-dimensional U/sub N/. The neutrino acquires a negligible rest mass of O(10 -31 eV) due to the global curvature of our manifold

Neutrino diffusion and mass ejection in protoneutron stars

International Nuclear Information System (INIS)

Almeida, L. G.; Rodrigues, H.; Portes, D. Jr.; Duarte, S. B.

2010-01-01

We discuss the mass ejection mechanism induced by diffusion of neutrino during the early stage of the protoneutron star cooling. A dynamical calculation is employed in order to determine the amount of matter ejected and the remnant compact object mass. An equation of state considering hadronic and quark phases for the stellar dense matter was used to solve the whole time evolution of the system during the cooling phase. The initial neutrino population was obtained by considering beta equilibrium in the dense stellar matter with confined neutrinos, in the very early period of the deleptonic stage of the nascent pulsar. For specified initial configurations of the protoneutron star, we solve numerically the set of equations of motion together with neutrino diffusion through the dense stellar medium.

NEUTRINO mass textures and the nature of new physics implied by present neutrino data

International Nuclear Information System (INIS)

Mohapatra, R.N.

1997-01-01

If all the indications for neutrino oscillations observed in the solar, atmospheric neutrino data as well as in the LSND experiment are borned out by the ongoing and future experiments, then they severely constrain the neutrino mass texture. In particular, the need for an extra ultra-light sterile neutrino species is hard to avoid. Such an extra neutrino has profound implication not only for physics beyond the standard model but even perhaps for physics beyond conventional grand unification. A scenario involving a parallel (or shadow) universe that interacts with the familiar universe only via the gravitational interactions where the ultra-lightness of the sterile neutrino follows from the same physics that explains the near masslessness of the familiar neutrinos is discussed in the presentation

Neutrino mass constraints from joint cosmological probes.

Science.gov (United States)

Kwan, Juliana

2018-01-01

One of the most promising avenues to come from precision cosmology is the measurement of the sum of neutrino masses in the next 5-10 years. Ongoing imaging surveys, such as the Dark Energy Survey and the Hyper Suprime Cam survey, will cover a substantial volume of the sky and when combined with existing spectroscopic data, are expected to deliver a definitive measurement in the near future. But it is important that the accuracy of theoretical predictions matches the precision of the observational data so that the neutrino mass signal can be properly detected without systematic error. To this end, we have run a suite of high precision, large volume cosmological N-body simulations containing massive neutrinos to quantify their effect on probes of large scale structure such as weak lensing and galaxy clustering. In this talk, I will describe the analytical tools that we have developed to extract the neutrino mass that are capable of fully utilizing the non-linear regime of structure formation. These include predictions for the bias in the clustering of dark matter halos (one of the fundamental ingredients of the halo model) with an error of only a few percent.

Explosive nucleosynthesis in a neutrino-driven core collapse supernova

International Nuclear Information System (INIS)

Fujimoto, Shin-ichiro; Kotake, Kei; Hashimoto, Masa-aki; Ono, Masaomi; Ohnishi, Naofumi

2010-01-01

We investigate explosive nucleosynthesis in a delayed neutrino-driven, supernova explosion aided by standing accretion shock instability (SASI), based on two-dimensional hydrodynamic simulations of the explosion of a 15 M · star. We take into accounts neutrino heating and cooling as well as change in electron fraction due to weak interactions appropriately, in the two-dimensional simulations. We assume the isotropic emission of neutrinos from the neutrino spheres with given luminosities. and the Fermi-Dirac distribution of given temperatures. We find that the stalled shock revives due to the neutrino heating aided by SASI for cases with L νe ≥3.9x10 52 ergss -1 and the as-pherical shock passes through the outer layers of the star (≥10,000 km), with the explosion energies of ∼10 51 ergs.Next we examine abundances and masses of the supernova ejecta. We find that masses of the ejecta and 56 Ni correlate with the neutrino luminosity, and 56 Ni mass is comparable to that observed in SN 1987A. We also find that abundance pattern of the supernova ejecta is similar to that of the solar system, for cases with high explosion energies of >10 51 ergs. We emphasize that 64 Zn, which is underproduced in the spherical case, is abundantly produced in slightly neutron-rich ejecta.

Neutrino-electron scattering with a new source of CP violation

International Nuclear Information System (INIS)

Barranco, J; Delepine, D; Napsuciale, M; Yebra, A

2016-01-01

According to previous works, there is a possibility for increasing the difference between Dirac and Majorana cross section for a neutrino-electron scattering process if we take into account that the neutrino longitudinal polarization can be different from minus one. In this work, we study the difference between Dirac and Majorana scattering process but we introduce an additional effective interaction that depends on complex coupling constants for the neutrinos. Thus, in this more general case, we have two additional parameters, the phase of the neutrino couplings and one parameter ϵ related to the effective coupling of the new interaction. (paper)

Low-scale seesaw and the CP violation in neutrino oscillations

Science.gov (United States)

Penedo, J. T.; Petcov, S. T.; Yanagida, Tsutomu T.

2018-04-01

We consider a version of the low-scale type I seesaw mechanism for generating small neutrino masses, as an alternative to the standard seesaw scenario. It involves two right-handed (RH) neutrinos ν1R and ν2R having a Majorana mass term with mass M, which conserves the lepton charge L. The RH neutrino ν2R has lepton-charge conserving Yukawa couplings gℓ2 to the lepton and Higgs doublet fields, while small lepton-charge breaking effects are assumed to induce tiny lepton-charge violating Yukawa couplings gℓ1 for ν1R, l = e , μ , τ. In this approach the smallness of neutrino masses is related to the smallness of the Yukawa coupling of ν1R and not to the large value of M: the RH neutrinos can have masses in the few GeV to a few TeV range. The Yukawa couplings |gℓ2 | can be much larger than |gℓ1 |, of the order |gℓ2 | ∼10-4-10-2, leading to interesting low-energy phenomenology. We consider a specific realisation of this scenario within the Froggatt-Nielsen approach to fermion masses. In this model the Dirac CP violation phase δ is predicted to have approximately one of the values δ ≃ π / 4 , 3 π / 4, or 5 π / 4 , 7 π / 4, or to lie in a narrow interval around one of these values. The low-energy phenomenology of the considered low-scale seesaw scenario of neutrino mass generation is also briefly discussed.

Limits on neutrino masses from tritium beta decay

CERN Document Server

Bonn, J; Bornschein, L; Flatt, B; Kraus, C V; Otten, E W; Schall, J P; Thuemmler, T; Weinheimer, C

2002-01-01

The presently lowest limit for the mass of the electron neutrino is m nu < 2.2 eV (95 % C.L.) derived from measurements at Mainz up to 1999. The data taken in 2000 are not fully analyzed yet but limits of possible distortions as reported by the Troitsk group can be given. The next generation neutrino mass experiment KATRIN is briefly discussed.

Testing the nature of neutrinos from four-body τ decays

Science.gov (United States)

Yuan, Han; Jiang, Yue; Wang, Tian-hong; Li, Qiang; Wang, Guo-Li

2017-11-01

This paper discusses four-body lepton number violating tau decay. We study the processes {τ }+\\to {e}+{e}+{π }-{\\bar{ν }}τ and {τ }+\\to {e}+{e}+{π }-{ν }e to determine the nature of the neutrino. The first process violates the lepton number by two units, which can only happen through an internal Majorana. The second one conserves the lepton number but violates the lepton flavor, which can take place with both a Majorana neutrino and a Dirac neutrino. We calculate their branching ratio (BR) and differential BR {{d}}{B}{R}/{{{d}}{E}}π to distinguish between the Majorana neutrino and the Dirac neutrino. We also propose an experiment to perform this detection.

Common origin of soft μ−τ and CP breaking in neutrino seesaw and the origin of matter

International Nuclear Information System (INIS)

Ge, Shao-Feng; He, Hong-Jian; Yin, Fu-Rong

2010-01-01

Neutrino oscillation data strongly support μ – τ symmetry as a good approximate flavor symmetry of the neutrino sector, which has to appear in any viable theory for neutrino mass-generation. The μ – τ breaking is not only small, but also the source of Dirac CP-violation. We conjecture that both discrete μ – τ and CP symmetries are fundamental symmetries of the seesaw Lagrangian (respected by interaction terms), and they are only softly broken, arising from a common origin via a unique dimension-3 Majorana mass-term of the heavy right-handed neutrinos. From this conceptually attractive and simple construction, we can predict the soft μ – τ breaking at low energies, leading to quantitative correlations between the apparently two small deviations θ 23 −45° and θ 13 −0°. This nontrivially connects the on-going measurements of mixing angle θ 23 with the upcoming experimental probes of θ 13 . We find that any deviation of θ 23 −45° must put a lower limit on θ 13 . Furthermore, we deduce the low energy Dirac and Majorana CP violations from a common soft-breaking phase associated with μ – τ breaking in the neutrino seesaw. Finally, from the soft CP breaking in neutrino seesaw we derive the cosmological CP violation for the baryon asymmetry via leptogenesis. We fully reconstruct the leptogenesis CP-asymmetry from the low energy Dirac CP phase and establish a direct link between the cosmological CP-violation and the low energy Jarlskog invariant. We predict new lower and upper bounds on the θ 13 mixing angle, 1°∼ 13 ∼ 12 by its group-parameter, and includes the conventional tri-bimaximal mixing as a special case, allowing deviations from it

Constraints on TeV scale Majorana neutrino phenomenology from the vacuum stability of the Higgs

International Nuclear Information System (INIS)

Chakraborthy, Jaydeep; Das, Moumita; Mohanty, Subhendra

2013-01-01

The vacuum stability condition of the Standard Model Higgs potential with mass in the range of 124-127 GeV puts an upper bound on the Dirac mass of the neutrinos. We study this constraint with the right-handed neutrino masses upto TeV scale. The heavy neutrinos contribute to ΔL = 2 processes like neutrinoless double beta decay and same-sign-dilepton production in the colliders. The vacuum stability criterion also restricts the light-heavy neutrino mixing and constrains the branching ratio of lepton flavour violating process, like μ → eγ mediated by the heavy neutrinos. We show that neutrinoless double beta decay with a lifetime ∼ 10 25 years can be observed if the the lightest heavy neutrino mass is R > 3.3 TeV. Finally we show that the observation of same-sign-dileptons (SSD) associated with jets at the LHC needs much larger luminosity than available at present. We have estimated the possible maximum cross-section for this process at the LHC and show that with an integrated luminosity 100 fb 1 it may be possible to observe the SSD signals as long as M R < 400 GeV. (author)

Study of experimentally undetermined neutrino parameters in the light of baryogenesis considering type I and type II Seesaw models

International Nuclear Information System (INIS)

Kalita, Rupam

2017-01-01

We study to connect all the experimentally undetermined neutrino parameters namely lightest neutrino mass, neutrino CP phases and baryon asymmetry of the Universe within the framework of a model where both type I and type II seesaw mechanisms can contribute to tiny neutrino masses. In this work we study the effects of Dirac and Majorana neutrino phases in the origin of matter-antimatter asymmetry through the mechanism of leptogenesis. Type I seesaw mass matrix considered to a tri-bimaximal (TBM) type neutrino mixing which always gives non zero reactor mixing angle. The type II seesaw mass matrix is then considered in such a way that the necessary deviation from TBM mixing and the best fit values of neutrino parameters can be obtained when both type I and type II seesaw contributions are taken into account. We consider different contribution from type I and type II seesaw mechanism to study the effects of neutrino CP phases in the baryon asymmetry of the universe. We further study to connect all these experimentally undetermined neutrino parameters by considering various contribution of type I and type II seesaw. (author)

The neutrino mass hierarchy measurement with a neutrino telescope in the Mediterranean Sea: A feasibility study

Energy Technology Data Exchange (ETDEWEB)

Tsirigotis, A. G. [Physics Laboratory, Hellenic Open University (Greece); Collaboration: KM3NeT Collaboration

2014-11-18

With the measurement of a non zero value of the θ{sub 13} neutrino mixing parameter, interest in neutrinos as source of the baryon asymmetry of the universe has increased. Among the measurements of a rich and varied program in near future neutrino physics is the determination of the mass hierarchy. We present the status of a study of the feasibility of using a densely instrumented undersea neutrino detector to determine the mass hierarchy, utilizing the Mikheyev-Smirnov-Wolfenstein (MSW) effect on atmospheric neutrino oscillations. The detector will use technology developed for KM3NeT. We present the systematic studies of the optimization of a detector in the required 5–10 GeV energy regime. These studies include new tracking and interaction identification algorithms as well as geometrical optimizations of the detector.

Neutrino helicity flips via electroweak interactions

International Nuclear Information System (INIS)

Gaemers, K.J.F.; Gandhi, R.; Lattimer, J.M.; Department of Earth and Space Sciences, State University of New York, Stony Brook, New York 11794)

1989-01-01

Electroweak mechanisms via which neutrinos may flip helicity are examined in detail. Exact and approximate expressions for a variety of flip processes relevant in astrophysics and cosmology, mediated by W, Z, and γ exchange, including their interference, are derived for both Dirac and Majorana neutrinos (with emphasis on the former). It is shown that in general flip and nonflip cross sections differ by more than just a multiplicative factor of m/sub ν/ 2 /4E/sub ν/ 2 contrary to what might be expected and that this additional dependence on helicities can be significant. It is also shown that within the context of the standard model with massive neutrinos, for νe yields νe scattering, σ/sub Z//sup flip//σ/sub γ//sup flip/ ∼ 10 4 , independent of particle masses and energies to a good approximation. As an application, using some general considerations and the fact that the observed bar nu/sub e/ burst from SN 1987A lasted several seconds, these weak-interaction flip cross sections are used to rule out μ and tau neutrino masses above 30 keV. Finally, some other consequences for astrophysics in general and supernovae in particular are briefly discussed

Cosmology in Mirror Twin Higgs and neutrino masses

Science.gov (United States)

Chacko, Zackaria; Craig, Nathaniel; Fox, Patrick J.; Harnik, Roni

2017-07-01

We explore a simple solution to the cosmological challenges of the original Mirror Twin Higgs (MTH) model that leads to interesting implications for experiment. We consider theories in which both the standard model and mirror neutrinos acquire masses through the familiar seesaw mechanism, but with a low right-handed neutrino mass scale of order a few GeV. In these νMTH models, the right-handed neutrinos leave the thermal bath while still relativistic. As the universe expands, these particles eventually become nonrelativistic, and come to dominate the energy density of the universe before decaying. Decays to standard model states are preferred, with the result that the visible sector is left at a higher temperature than the twin sector. Consequently the contribution of the twin sector to the radiation density in the early universe is suppressed, allowing the current bounds on this scenario to be satisfied. However, the energy density in twin radiation remains large enough to be discovered in future cosmic microwave background experiments. In addition, the twin neutrinos are significantly heavier than their standard model counterparts, resulting in a sizable contribution to the overall mass density in neutrinos that can be detected in upcoming experiments designed to probe the large scale structure of the universe.

Constraints on a general 3-generation neutrino mass matrix from neutrino data application to the MSSM with R-parity violation

CERN Document Server

Abada, A

2000-01-01

We consider a general symmetric $(3\\times 3)$ mass matrix for three generations of neutrinos. Imposing the constraints, from the atmospheric neutrino and solar neutrino anomalies as well as from the CHOOZ experiment, on the mass squared differences and on the mixing angles, we identify the ranges of allowed inputs for the 6 matrix elements. We apply our results to Majorana left-handed neutrino masses generated at tree level and through The present experimental results on neutrinos from laboratories, cosmology and astrophysics are implemented to either put bounds on trilinear ($\\lambda_{ijk}, or constrain combinations of products of these couplings.

Neutrino mass, the right-handed interaction and the double beta decay, 1

International Nuclear Information System (INIS)

Doi, Masaru; Kotani, Tsuneyuki; Nishiura, Hiroyuki; Okuda, Kazuko; Takasugi, Eiichi.

1981-01-01

In order to shed light on the important question whether neutrinos are Dirac or Majorana particles, the double β decay is investigated within a general form of weak interaction Hamiltonian. The systematic study is made on the 0 + → J + nuclear transitions for the two-neutrino and neutrinoless modes both in the two-nucleon- and N*-mechanism. It is shown that for the neutrinoless mode, only the 0 + → 0 + transition in the two-nucleon mechanism is allowed if there is no right-handed interaction. When the right-handed interaction gives a sizable contribution, the role of the 0 + → 2 + transition becomes as important as the 0 + → 0 + transition. The comparison of our results with the previous ones is also presented. (author)

A biased review of tau neutrino mass limits

Energy Technology Data Exchange (ETDEWEB)

Duboscq, J.E

2001-04-01

After a quick review of astrophysically relevant limits, I present a summary of MeV scale tau neutrino mass limits derived from accelerator based experiments. I argue that the current published limits appear to be too consistent, and that we therefore cannot conclude that the tau neutrino mass limit is as low as usually claimed. I provide motivational arguments calling into question the assumed statistical properties of the usual maximum likelihood estimators, and provide a prescription for deriving a more robust and understandable mass limit.

arXiv Neutrino Masses from Outer Space

CERN Document Server

D'Amico, Guido; Kaloper, Nemanja

Neutrinos can gain mass from coupling to an ultralight field in slow roll. When such a field is displaced from its minimum, its vev acts just like the Higgs vev in spontaneous symmetry breaking. Although these masses may eventually vanish, they do it over a very long time. The theory is technically natural, with the ultralight field-dependent part being the right-handed Majorana mass. The mass variation induced by the field correlates with the cosmological evolution. The change of the mass term changes the mixing matrix, and therefore suppresses the fraction of sterile neutrinos at earlier times and increases it at later times. Since the issue of quantum gravity corrections to field theories with large field variations remains open, this framework may give an observational handle on the Weak Gravity Conjecture.

Right-handed currents and heavy neutrinos in high energy ep and e+e- scattering

International Nuclear Information System (INIS)

Buchmueller, W.; Greub, C.

1992-03-01

Heavy Dirac or Majorana neutrinos can be produced via right-handed charged currents which occur in extensions of the standard model with SU(2) L x SU(2) R x U(1) B-L gauge symmetry. Low energy processes, Z precision experiments and direct search experiments in pp collisions are consistent with W R bosons heavier than 300 GeV, if the right-handed neutrinos are heavy. We study the production of heavy neutrinos via right-handed currents in e + e - annihilation and ep scattering which appears particularly promising. At HERA heavy neutrinos and W R bosons can be discovered with masses up to 170 GeV and 700 GeV, respectively. (orig.)

Interplay of type I and type II seesaw contributions to neutrino mass

International Nuclear Information System (INIS)

Akhmedov, Evgeny Kh.; Frigerio, Michele

2007-01-01

Type I and type II seesaw contributions to the mass matrix of light neutrinos are inherently related if left-right symmetry is realized at high energy scales. We investigate implications of such a relation for the interpretation of neutrino data. We proved recently that the left-right symmetric seesaw equation has eight solutions, related by a duality property, for the mass matrix of right-handed neutrinos M R . In this paper the eight allowed structures of M R are reconstructed analytically and analyzed numerically in a bottom-up approach. We study the dependence of right-handed neutrino masses on the mass spectrum of light neutrinos, mixing angle θ 13 , leptonic CP violation, scale of left-right symmetry breaking and on the hierarchy in neutrino Yukawa couplings. The structure of the seesaw formula in several specific SO(10) models is explored in the light of the duality. The outcome of leptogenesis may depend crucially on the choice among the allowed structures of M R and on the level crossing between right-handed neutrino masses

Atmospheric neutrino oscillations, θ13 and neutrino mass hierarchy

International Nuclear Information System (INIS)

Bernabeu, J.; Palomares-Ruiz, Sergio; Petcov, S.T.

2003-01-01

We derive predictions for the Nadir angle (θ n ) dependence of the ratio N μ /N e of the rates of the μ-like and e-like multi-GeV events measured in water-Cerenkov detectors in the case of 3-neutrino oscillations of the atmospheric ν e (ν-bar e ) and ν μ (ν-bar μ ), driven by one neutrino mass squared difference, vertical bar Δm 2 31 vertical bar ∼(2.5-3.0)x10 -3 eV 2 >> Δm 2 21 . This ratio is particularly sensitive to the Earth matter effects in the atmospheric neutrino oscillations, and thus to the values of sin 2 θ 13 and sin 2 θ 23 , θ 13 and θ 23 being the neutrino mixing angle limited by CHOOZ and Palo Verde experiments and that responsible for the dominant atmospheric ν μ →ν τ (ν-bar μ →ν-bar τ ) oscillations. It is also sensitive to the type of neutrino mass spectrum which can be with normal (Δm 2 31 >0) or with inverted (Δm 2 31 2 θ 13 > or approx. 0.01, sin 2 θ 23 > or approx. 0.5 and at cosθ n > or approx. 0.4, the Earth matter effects modify substantially the θ n -dependence of the ratio N μ /N e and in a way which cannot be reproduced with sin 2 θ 13 =0 and a different value of sin 2 θ 23 . For normal hierarchy the effects can be as large as ∼25% for cosθ n ∼(0.5-0.8), can reach ∼35% in the Earth core bin cosθ n ∼(0.84-1.0), and might be observable. They are typically by ∼10% smaller in the inverted hierarchy case. An observation of the Earth matter effects in the Nadir angle distribution of the ratio N μ /N e would clearly indicate that sin 2 θ 13 > or approx. 0.01 and sin 2 θ 23 > or approx. 0.50

Verifiable origin of neutrino mass at TeV scale

International Nuclear Information System (INIS)

Ma, Ernest

2002-01-01

The physics responsible for neutrino mass may reside at or below the TeV energy scale. The neutrino mass matrix in the (ν e ν μ ν gt ) basis may then be deduced from future high-energy accelerator experiments. The newly observed excess in the muon anomalous magnetic moment may also be related

Dark matter physics in neutrino specific two Higgs doublet model

Energy Technology Data Exchange (ETDEWEB)

Baek, Seungwon; Nomura, Takaaki [School of Physics, Korea Institute for Advanced Study,85 Hoegiro, Dongdaemun-gu, Seoul 02455 (Korea, Republic of)

2017-03-10

Although the seesaw mechanism is a natural explanation for the small neutrino masses, there are cases when the Majorana mass terms for the right-handed neutrinos are not allowed due to symmetry. In that case, if neutrino-specific Higgs doublet is introduced, neutrinos become Dirac particles and their small masses can be explained by its small VEV. We show that the same symmetry, which we assume a global U(1){sub X}, can also be used to explain the stability of dark matter. In our model, a new singlet scalar breaks the global symmetry spontaneously down to a discrete Z{sub 2} symmetry. The dark matter particle, lightest Z{sub 2}-odd fermion, is stabilized. We discuss the phenomenology of dark matter: relic density, direct detection, and indirect detection. We find that the relic density can be explained by a novel Goldstone boson channel or by resonance channel. In the most region of parameter space considered, the direct detections is suppressed well below the current experimental bound. Our model can be further tested in indirect detection experiments such as FermiLAT gamma ray searches or neutrinoless double beta decay experiments.

Neutrino masses, lepton number violation and unification

CERN Document Server

Barbieri, Riccardo

1980-01-01

Theories with parity as a short-distance symmetry lead rather naturally to a small but non-vanishing nu L/sub 2/ mass. A reference formula for the size of the effect is m/sub nu / approximately=m/sup 2 //M with M a huge Majorana mass of the nu /sub R/ field, associated with the breaking of the group down to SU(3)*SU(2)*U(1) and m a typical quark mass, most likely that of charge 2/3. This is because of the Pati-Salam SU(4) which relates neutrinos with charge 2/3 quarks, and is contained in the prototypes of these theories, SO(10) or E/sub 6/. Ten GeV for m requires M approximately=10/sup 11/ GeV in order to saturate the cosmological bound (m/sub nu / of a few eV). This value is not too far from the currently preferred mass approximately=10/sup 14/ GeV of the superheavy gauge bosons. In view of these concepts, the search for neutrino oscillations appears to be of overwhelming importance. A combined effort in all different kinds of possible experiments (reactors, accelerators, deep mines, and solar neutrino obse...

Testing SO(10)-inspired leptogenesis with low energy neutrino experiments

CERN Document Server

Di Bari, Pasquale

2011-01-01

We extend the results of a previous analysis of ours showing that, when both heavy and light flavour effects are taken into account, successful minimal (type I + thermal) leptogenesis with SO(10)-inspired relations is possible. Barring fine tuned choices of the parameters, these relations enforce a hierarchical RH neutrino mass spectrum that results into a final asymmetry dominantly produced by the next-to-lightest RH neutrino decays (N_2 dominated leptogenesis). We present the constraints on the whole set of low energy neutrino parameters. Allowing a small misalignment between the Dirac basis and the charged lepton basis as in the quark sector, the allowed regions enlarge and the lower bound on the reheating temperature gets relaxed to values as low as ~ 10^10 GeV. It is confirmed that for normal ordering (NO) there are two allowed ranges of values for the lightest neutrino mass: m_1 \\simeq (1-5)\\times 10^-3 eV and m_1\\simeq (0.03-0.1) eV. For m_1\\lesssim 0.01 eV the allowed region in the plane theta_13-thet...

Neutrino mass and physics beyond the Standard Model

International Nuclear Information System (INIS)

Hosteins, P.

2007-09-01

The purpose of this thesis is to study, in the neutrino sector, the flavour structures at high energy. The work is divided into two main parts. The first part is dedicated to the well known mechanism to produce small neutrino masses: the seesaw mechanism, which implies the existence of massive particles whose decays violate lepton number. Therefore this mechanism can also be used to generate a net baryon number in the early universe and explain the cosmological observation of the asymmetry between matter and antimatter. However, it is often non-trivial to fulfill the constraints coming at the same time from neutrino oscillations and cosmological experiments, at least in frameworks where the couplings can be somehow constrained, like some Grand Unification models. Therefore we devoted the first part to the study of a certain class of seesaw mechanism which can be found in the context of SO(10) theories for example. We introduce a method to extract the mass matrix of the heavy right-handed neutrinos and explore the phenomenological consequences of this quantity, mainly concerning the production of a sufficient baryon asymmetry. When trying to identify the underlying symmetry governing the mixings between the different generations, we see that there is a puzzling difference between the quark and the lepton sectors. However, the quark and lepton parameters have to be compared at the scale of the flavour symmetry breaking, therefore we have to make them run to the appropriate scale. Thus, it is worthwhile investigating models where quantum corrections allow an approximate unification of quark and lepton mixings. This is why the other part of the thesis investigates the running of the effective neutrino mass operator in models with an extra compact dimension, where quantum corrections to the neutrino masses and mixings can be potentially large due to the multiplicity of states

Neutrino mixing and lepton CP-phase in neutrino oscillations

International Nuclear Information System (INIS)

Ryzhikh, D.A.; Ter-Martirosyan, K.A.

2001-01-01

One studied oscillations of the Dirac neutrinos belonging to three generations in vacuum with regard to the effect of the lepton CP-breaking phase on them in the matrix of lepton mixing (analogue of the quark CP-phase). In the general form one obtained formulae for probabilities of transition of neutrino of one kind to another at oscillations depending on three angles of mixing and on CP-phase. It was pointed that when measuring oscillation average probabilities of transition of neutrino of one kind to another one might in principle, restore the value of lepton CP-phase. Manifestation of CP-phase in the form of deviation of the values of probabilities of direct neutrino transition from reverse one is the effect practically escaping observation [ru

Fourth standard model family neutrino at future linear colliders

International Nuclear Information System (INIS)

Ciftci, A.K.; Ciftci, R.; Sultansoy, S.

2005-01-01

It is known that flavor democracy favors the existence of the fourth standard model (SM) family. In order to give nonzero masses for the first three-family fermions flavor democracy has to be slightly broken. A parametrization for democracy breaking, which gives the correct values for fundamental fermion masses and, at the same time, predicts quark and lepton Cabibbo-Kobayashi-Maskawa (CKM) matrices in a good agreement with the experimental data, is proposed. The pair productions of the fourth SM family Dirac (ν 4 ) and Majorana (N 1 ) neutrinos at future linear colliders with √(s)=500 GeV, 1 TeV, and 3 TeV are considered. The cross section for the process e + e - →ν 4 ν 4 (N 1 N 1 ) and the branching ratios for possible decay modes of the both neutrinos are determined. The decays of the fourth family neutrinos into muon channels (ν 4 (N 1 )→μ ± W ± ) provide cleanest signature at e + e - colliders. Meanwhile, in our parametrization this channel is dominant. W bosons produced in decays of the fourth family neutrinos will be seen in detector as either di-jets or isolated leptons. As an example, we consider the production of 200 GeV mass fourth family neutrinos at √(s)=500 GeV linear colliders by taking into account di-muon plus four jet events as signatures

Wave-packet treatment of reactor neutrino oscillation experiments and its implications on determining the neutrino mass hierarchy

Energy Technology Data Exchange (ETDEWEB)

Chan, Yat-Long; Chu, M.C.; Xu, Jianyi [The Chinese University of Hong Kong, Department of Physics, Shatin (China); Tsui, Ka Ming [University of Tokyo, RCCN, ICRR, Kashiwa, Chiba (Japan); Wong, Chan Fai [Sun Yat-Sen University, Guangzhou (China)

2016-06-15

We derive the neutrino flavor transition probabilities with the neutrino treated as a wave packet. The decoherence and dispersion effects from the wave-packet treatment show up as damping and phase-shifting of the plane-wave neutrino oscillation patterns. If the energy uncertainty in the initial neutrino wave packet is larger than around 0.01 of the neutrino energy, the decoherence and dispersion effects would degrade the sensitivity of reactor neutrino experiments to mass hierarchy measurement to lower than 3 σ confidence level. (orig.)

A 3-3-1 model with right-handed neutrinos based on the Δ (27) family symmetry

Energy Technology Data Exchange (ETDEWEB)

Hernandez, A.E.C. [Universidad Tecnica Federico Santa Maria and Centro Cienti fico-Tecnologico de Valparaiso, Valparaiso (Chile); Long, H.N. [Vietnam Academy of Science and Technology, Institute of Physics, Hanoi (Viet Nam); Vien, V.V. [Duy Tan University, Institute of Research and Development, Da Nang City (Viet Nam); Tay Nguyen University, Department of Physics, Buon Ma Thuot, DakLak (Viet Nam)

2016-05-15

We present the first multiscalar singlet extension of the original 3-3-1 model with right-handed neutrinos, based on the Δ (27) family symmetry, supplemented by the Z{sub 4} x Z{sub 8} x Z{sub 14} flavor group, consistent with current low energy fermion flavor data. In the model under consideration, the light active neutrino masses are generated from a double seesaw mechanism and the observed pattern of charged fermion masses and quark mixing angles is caused by the breaking of the Δ (27) x Z{sub 4} x Z{sub 8} x Z{sub 14} discrete group at very high energy. Our model has only 14 effective free parameters, which are fitted to reproduce the experimental values of the 18 physical observables in the quark and lepton sectors. The obtained physical observables for the quark sector agree with their experimental values, whereas those for the lepton sector also do, only for the inverted neutrino mass hierarchy. The normal neutrino mass hierarchy scenario of the model is disfavored by the neutrino oscillation experimental data. We find an effective Majorana neutrino mass parameter of neutrinoless double beta decay of m{sub ββ} = 22 meV, a leptonic Dirac CP violating phase of 34 {sup circle}, and a Jarlskog invariant of about 10{sup -2} for the inverted neutrino mass spectrum. (orig.)

Direct measurements of neutrino masses

Energy Technology Data Exchange (ETDEWEB)

Holzschuh, E [Zurich Univ. (Switzerland). Inst. fuer Physik

1996-11-01

The direct measurements have so far given no indication for a nonzero (positive) mass of any of the three known neutrinos. The experiments measuring the tau and the muon neutrino are good shape. The tritium experiments are in an unfortunate situation. It is unclear to me whether the problems are experimental or theoretical or a combination of both. The electronic final states distribution have been calculated, but the results have never been tested experimentally. The most important question to be answered is about the validity of the sudden approximation. (author) 9 figs., 2 tabs., 16 refs.

Constraining neutrino mass from neutrinoless double beta decay

Science.gov (United States)

Dev, P. S. Bhupal; Goswami, Srubabati; Mitra, Manimala; Rodejohann, Werner

2013-11-01

We study the implications of the recent results on neutrinoless double beta decay (0νββ) from GERDA-I (Ge76) and KamLAND-Zen+EXO-200 (Xe136) and the upper limit on the sum of light neutrino masses from Planck. We show that the upper limits on the effective neutrino mass from Xe136 are stronger than those from Ge76 for most of the recent calculations of the nuclear matrix elements (NMEs). We also analyze the compatibility of these limits with the claimed observation in Ge76 and show that while the updated claim value is still compatible with the recent GERDA limit as well as the individual Xe136 limits for a few NME calculations, it is inconsistent with the combined Xe136 limit for all but one NME. Imposing the most stringent limit from Planck, we find that the canonical light neutrino contribution cannot saturate the current limit, irrespective of the NME uncertainties. Saturation can be reached by inclusion of the right-handed (RH) neutrino contributions in TeV-scale left-right symmetric models with type-II seesaw. This imposes a lower limit on the lightest neutrino mass. Using the 0νββ bounds, we also derive correlated constraints in the RH sector, complimentary to those from direct searches at the LHC.

Relaxing neutrino mass bounds by a running cosmological constant

Energy Technology Data Exchange (ETDEWEB)

Bauer, F.; Schrempp, L.

2007-11-15

We establish an indirect link between relic neutrinos and the dark energy sector which originates from the vacuum energy contributions of the neutrino quantum fields. Via renormalization group effects they induce a running of the cosmological constant with time which dynamically influences the evolution of the cosmic neutrino background. We demonstrate that the resulting reduction of the relic neutrino abundance allows to largely evade current cosmological neutrino mass bounds and discuss how the scenario might be probed by the help of future large scale structure surveys and Planck data. (orig.)

Relaxing neutrino mass bounds by a running cosmological constant

International Nuclear Information System (INIS)

Bauer, F.; Schrempp, L.

2007-11-01

We establish an indirect link between relic neutrinos and the dark energy sector which originates from the vacuum energy contributions of the neutrino quantum fields. Via renormalization group effects they induce a running of the cosmological constant with time which dynamically influences the evolution of the cosmic neutrino background. We demonstrate that the resulting reduction of the relic neutrino abundance allows to largely evade current cosmological neutrino mass bounds and discuss how the scenario might be probed by the help of future large scale structure surveys and Planck data. (orig.)

152nd International School of Physics "Enrico Fermi": Neutrino Physics

CERN Document Server

Declais, Y; Strolin, P; Zanotti, L; Società Italiana di Fisica. Bologna. Scuola internazionale di fisica "Enrico Fermi"; International School of Physics "Enrico Fermi": Neutrino Physics; Scuola Internazionale di Fisica "Enrico Fermi" : Phisica dei neutrini

2003-01-01

Neutrino physics contributed in an fundamental way to the progress of science, opening important windows of knowledge in elementary particle physics, as well in astrophysics and cosmology. Substantial experimental efforts are presently dedicated to improve our knowledge on neutrino properties as, in fact, we don't know yet some of the basic ones. Although very significant steps forward have been done, neutrino masses and mixings still remain largely unknown and constitute an important field for future research. Are neutrinos Majorana or Dirac particles? Have they a magnetic moment? Historically, studies on weak processes and, therefore, on neutrino physics, provided first the Fermi theory of weak interactions and then the V-A theory. Finally, the observation of weak neutral currents provided the first experimental evidence for unification of weak and electromagnetic interactions by the so called "Standard Model' of elementary particles. In addition to the results obtained from the measurement of the solar neu...

Sum rules for neutrino oscillations

International Nuclear Information System (INIS)

Kobzarev, I.Yu.; Martemyanov, B.V.; Okun, L.B.; Schepkin, M.G.

1981-01-01

Sum rules for neutrino oscillations are obtained. The derivation of the general form of the s matrix for two stage process lsub(i)sup(-)→ν→lsub(k)sup(+-) (where lsub(i)sup(-)e, μ, tau, ... are initial leptons with flavor i and lsub(k)sup(+-) is final lepton) is presented. The consideration of two stage process lsub(i)sup(-)→ν→lsub(k)sup(+-) gives the possibility to take into account neutrino masses and to obtain the expressions for the oscillating cross sections. In the case of Dirac and left-handed Majorana neutrino is obtained the sum rule for the quantities 1/Vsub(K)σ(lsub(i)sup(-)→lsub(K)sup(+-)), (where Vsub(K) is a velocity of lsub(K)). In the left-handed Majorana neutrino case there is an additional antineutrino admixture leading to lsub(i)sup(-)→lsub(K)sup(+) process. Both components (neutrino and antineutrino) oscillate independently. The sums Σsub(K)1/Vsub(k)σ(lsub(i)sup(-) - lsub(K)sup(+-) then oscillate due to the presence of left-handed antineutrinos and right-handed neutrinos which do not take part in weak interactions. If right-handed currents are added sum rules analogous to considered above may be obtained. All conclusions are valid in the general case when CP is not conserved [ru

Neutrino masses from U(1) symmetries and the Super-Kamiokande data

CERN Document Server

Lola, S; Lola, Smaragda; Ross, Graham G.

1999-01-01

Motivated by the Super-Kamiokande data, we revisit models with U(1) symmetries and discuss the origin of neutrino masses and mixings in such theories. We show that, in models with just three light neutrinos and a hierarchy of neutrino masses, large (2-3) mixing fixes the lepton doublet U(1) charges and is thus related to the structure of the charged lepton mass matrix. We discuss the fermion mass structure that follows from the abelian family symmetry with an extended gauge group. Requiring that the quark and lepton masses be ordered by the family symmetry, we identify the most promising scheme. This requires large, but not necessarily maximal, mixing in the mu tau sector and gives e mu mixing in the range that is required for the small angle solution of the solar neutrino deficit.

Anatomy of Higgs mass in supersymmetric inverse seesaw models

Energy Technology Data Exchange (ETDEWEB)

Chun, Eung Jin, E-mail: ejchun@kias.re.kr [Korea Institute for Advanced Study, Seoul 130-722 (Korea, Republic of); Mummidi, V. Suryanarayana, E-mail: soori9@cts.iisc.ernet.in [Centre for High Energy Physics, Indian Institute of Science, Bangalore 560012 (India); Vempati, Sudhir K., E-mail: vempati@cts.iisc.ernet.in [Centre for High Energy Physics, Indian Institute of Science, Bangalore 560012 (India)

2014-09-07

We compute the one loop corrections to the CP-even Higgs mass matrix in the supersymmetric inverse seesaw model to single out the different cases where the radiative corrections from the neutrino sector could become important. It is found that there could be a significant enhancement in the Higgs mass even for Dirac neutrino masses of O(30) GeV if the left-handed sneutrino soft mass is comparable or larger than the right-handed neutrino mass. In the case where right-handed neutrino masses are significantly larger than the supersymmetry breaking scale, the corrections can utmost account to an upward shift of 3 GeV. For very heavy multi TeV sneutrinos, the corrections replicate the stop corrections at 1-loop. We further show that general gauge mediation with inverse seesaw model naturally accommodates a 125 GeV Higgs with TeV scale stops.

Neutrino masses

Energy Technology Data Exchange (ETDEWEB)

Anon.

1986-04-15

Postulated in the early days of quantum mechanics by Wolfgang Pauli to make energy-momentum conservation in nuclear beta decay come out right, the neutrino has never strayed far from physicists' attention. The Moriond Workshop on Massive Neutrinos in Particle Physics and Astrophysics held recently in the French Alps showed that more than half a century after Pauli's prediction, the neutrino stubbornly refuses to yield up all its secrets.

Experiment for a precision neutrino mass measurement

International Nuclear Information System (INIS)

Fackler, O.; Mugge, M.; Sticker, H.; Woerner, R.

1984-04-01

We describe an experiment which is designed to determine the electron neutrino mass to better than 2 eV. Key features of the experiment are a high activity frozen tritium source and a high resolution electrostatic spectrometer designed to make a careful measurement of the tritium beta decay end point spectrum. The goal is to determine the neutrino mass to better than 1 eV statistically in a four day run. A series of these runs will allow study of potential systematics. The construction phase is nearly complete and preliminary data will be taken in late spring

Experimental tests for the Babu-Zee two-loop model of Majorana neutrino masses

International Nuclear Information System (INIS)

Sierra, Diego Aristizabal; Hirsch, Martin

2006-01-01

The smallness of the observed neutrino masses might have a radiative origin. Here we revisit a specific two-loop model of neutrino mass, independently proposed by Babu and Zee. We point out that current constraints from neutrino data can be used to derive strict lower limits on the branching ratio of flavour changing charged lepton decays, such as μ→eγ. Non-observation of Br(μ→eγ) at the level of 10 -13 would rule out singly charged scalar masses smaller than 590 GeV (5.04 TeV) in case of normal (inverse) neutrino mass hierarchy. Conversely, decay branching ratios of the non-standard scalars of the model can be fixed by the measured neutrino angles (and mass scale). Thus, if the scalars of the model are light enough to be produced at the LHC or ILC, measuring their decay properties would serve as a direct test of the model as the origin of neutrino masses

Experimental tests for the Babu-Zee two-loop model of Majorana neutrino masses

International Nuclear Information System (INIS)

Aristizabal, D.

2006-01-01

Abstract: The smallness of the observed neutrino masses might have a radiative origin. Here we revisit a specific two-loop model of neutrino mass, independently proposed by Babu and Zee. We point out that current constraints from neutrino data can be used to derive strict lower limits on the branching ratio of flavour changing charged lepton decays, such as μ → e γ. Non-observation of Br(μ → e γ) at the level of 10 -13 would rule out singly charged scalar masses smaller than 590 GeV (5.04 TeV) in case of normal (inverse) neutrino mass hierarchy. Conversely, decay branching ratios of the non-standard scalars of the model can be fixed by the measured neutrino angles (and mass scale). Thus, if the scalars of the model are light enough to be produced at the LHC or ILC, measuring their decay properties would serve as a direct test of the model as the origin of neutrino masses. (author)

Disappearing neutrinos at KamLAND suport the case for neutrino mass

CERN Multimedia

Johnson, G

2002-01-01

Measurements from KamLAND, show that anti-neutrinos emanating from nearby nuclear reactors are "disappearing," which indicates they have mass and can oscillate or change from one type to another (2 pages)

Knitting neutrino mass textures with or without Tri-Bi maximal mixing

Energy Technology Data Exchange (ETDEWEB)

Leontaris, G.K., E-mail: leonta@uoi.gr [Theoretical Physics Division, Ioannina University, GR-45110 Ioannina (Greece); Vlachos, N.D. [Theoretical Physics Division, Aristotle University, GR-54124 Thessaloniki (Greece)

2011-08-03

The solar and baseline neutrino oscillation data suggest bimaximal neutrino mixing among the first two generations, and trimaximal mixing between all three neutrino flavors. It has been conjectured that this indicates the existence of an underlying symmetry for the leptonic fermion mass textures. The experimentally measured quantities, however, are associated to the latter indirectly and in a rather complicated way through the mixing matrices of the charged leptons and neutrinos. Motivated by these facts, we derive exact analytical expressions which directly link the charged lepton and neutrino mass and mixing parameters to measured quantities and obtain constraints on the parameter space. We discuss deviations from Tri-Bi mixing matrices and present minimal extensions of the Harrison, Perkins and Scott matrices capable of interpreting all neutrino data.

Experimental conditions for determination of the neutrino mass hierarchy with reactor antineutrinos

Directory of Open Access Journals (Sweden)

Myoung Youl Pac

2016-01-01

Full Text Available This article reports the optimized experimental requirements to determine neutrino mass hierarchy using electron antineutrinos (ν¯e generated in a nuclear reactor. The features of the neutrino mass hierarchy can be extracted from the |Δm312| and |Δm322| oscillations by applying the Fourier sine and cosine transforms to the L/E spectrum. To determine the neutrino mass hierarchy above 90% probability, the requirements on the energy resolution as a function of the baseline are studied at sin2⁡2θ13=0.1. If the energy resolution of the neutrino detector is less than 0.04/Eν and the determination probability obtained from Bayes' theorem is above 90%, the detector needs to be located around 48–53 km from the reactor(s to measure the energy spectrum of ν¯e. These results will be helpful for setting up an experiment to determine the neutrino mass hierarchy, which is an important problem in neutrino physics.

Neutrino masses at v3/2

International Nuclear Information System (INIS)

Arkani-Hamed, Nima; Hall, Lawrence; Murayama, Hitoshi; Smith, David; Weiner, Neal

2000-01-01

Theories in which neutrino masses are generated by a conventional see-saw mechanism generically yield masses which are O(v 2 ) in units where M Pl = 1, which is naively too small to explain the results from SuperKamiokande. In supersymmetric theories with gravity mediated supersymmetry breaking, the fundamental small parameter is not v/M Pl , but m I /M Pl , where m I is the scale of supersymmetry breaking in the hidden sector. We note that m I 3 /M Pl 2 is only slightly too large to explain SuperKamiokande, and present two models that achieve neutrino masses at this order in m I , one of which has an additional suppression λ τ 2 , while the other has additional suppression arising from a loop factor. The latter model shares a great deal of phenomenology with a class of models previously explored, including the possibility of viable sneutrino dark matter

Neutrino masses

International Nuclear Information System (INIS)

Anon.

1986-01-01

Postulated in the early days of quantum mechanics by Wolfgang Pauli to make energy-momentum conservation in nuclear beta decay come out right, the neutrino has never strayed far from physicists' attention. The Moriond Workshop on Massive Neutrinos in Particle Physics and Astrophysics held recently in the French Alps showed that more than half a century after Pauli's prediction, the neutrino stubbornly refuses to yield up all its secrets

Neutrino masses in RPV models with two pairs of Higgs doublets

Energy Technology Data Exchange (ETDEWEB)

Grossman, Yuval [Laboratory for Elementary-Particle Physics, Cornell University,Ithaca, N.Y. (United States); Peset, Clara [Institut de Fisica d’Altes Energies (IFAE), Universitat Autònoma de Barcelona,08193 Bellaterra, Barcelona (Spain)

2014-04-07

We study the generation of neutrino masses and mixing in supersymmetric R-parity violating models containing two pairs of Higgs doublets. In these models, new RPV terms H^{sub D{sub 1}}H^{sub D{sub 2}}E^ arise in the superpotential, as well as new soft terms. Such terms give new contributions to neutrino masses. We identify the different parameters and suppression/enhancement factors that control each of these contributions. At tree level, just like in the MSSM, only one neutrino acquires a mass due to neutrino-neutralino mixing. There are no new one loop effects. We study the two loop contributions and find the conditions under which they can be important.

Shedding light on neutrino masses with dark forces

Energy Technology Data Exchange (ETDEWEB)

Batell, Brian [Pittsburgh Particle Physics, Astrophysics, and Cosmology Center,Department of Physics and Astronomy, University of Pittsburgh, PA 15260 (United States); Pospelov, Maxim [Perimeter Institute for Theoretical Physics,Waterloo, ON N2J 2W9 (Canada); Department of Physics and Astronomy, University of Victoria,Victoria, BC V8P 5C2 (Canada); Shuve, Brian [SLAC National Accelerator Laboratory,2575 Sand Hill Road, Menlo Park, CA 94025 (United States)

2016-08-08

Heavy right-handed neutrinos, N, provide the simplest explanation for the origin of light neutrino masses and mixings. If M{sub N} is at or below the weak scale, direct experimental discovery of these states is possible at accelerator experiments such as the LHC or new dedicated beam dump experiments; in these experiments, N decays after traversing a macroscopic distance from the collision point. The experimental sensitivity to right-handed neutrinos is significantly enhanced if there is a new “dark” gauge force connecting them to the Standard Model (SM), and detection of N can be the primary discovery mode for the new dark force itself. We take the well-motivated example of a B−L gauge symmetry and analyze the sensitivity to displaced decays of N produced via the new gauge interaction in two experiments: the LHC and the proposed SHiP beam dump experiment. In the most favorable case in which the mediator can be produced on-shell and decays to right handed neutrinos (pp→X+V{sub B−L}→X+NN), the sensitivity reach is controlled by the square of the B−L gauge coupling. We demonstrate that these experiments could access neutrino parameters responsible for the observed SM neutrino masses and mixings in the most straightforward implementation of the see-saw mechanism.

Earth Effects and Mass Hierarchy with Supernova Neutrinos

International Nuclear Information System (INIS)

Dasgupta, Basudeb

2009-01-01

Collective neutrino flavor transformations take place deep inside a supernova if the neutrino mass hierarchy is inverted, even for extremely small values of θ 13 . We show that the presence (or absence) of Earth matter effects in antineutrino signal is directly related to the absence (or presence) of these collective effects, when the mixing angle θ 13 is small. Thus a neutrino signal from a galactic supernova may enable us to distinguish between the hierarchies even for small values of θ 13 .

Deconstructing the neutrino mass constraint from galaxy redshift surveys

Science.gov (United States)

Boyle, Aoife; Komatsu, Eiichiro

2018-03-01

The total mass of neutrinos can be constrained in a number of ways using galaxy redshift surveys. Massive neutrinos modify the expansion rate of the Universe, which can be measured using baryon acoustic oscillations (BAOs) or the Alcock-Paczynski (AP) test. Massive neutrinos also change the structure growth rate and the amplitude of the matter power spectrum, which can be measured using redshift-space distortions (RSD). We use the Fisher matrix formalism to disentangle these information sources, to provide projected neutrino mass constraints from each of these probes alone and to determine how sensitive each is to the assumed cosmological model. We isolate the distinctive effect of neutrino free-streaming on the matter power spectrum and structure growth rate as a signal unique to massive neutrinos that can provide the most robust constraints, which are relatively insensitive to extensions to the cosmological model beyond ΛCDM . We also provide forecasted constraints using all of the information contained in the observed galaxy power spectrum combined, and show that these maximally optimistic constraints are primarily limited by the accuracy to which the optical depth of the cosmic microwave background, τ, is known.

Flavor versus mass eigenstates in neutrino asymmetries: implications for cosmology

Energy Technology Data Exchange (ETDEWEB)

Barenboim, Gabriela [Universitat de Valencia-CSIC, Departament de Fisica Teorica y IFIC, Burjassot (Spain); Kinney, William H. [University at Buffalo, Department of Physics, Buffalo, NY (United States); Park, Wan-Il [Universitat de Valencia-CSIC, Departament de Fisica Teorica y IFIC, Burjassot (Spain); Chonbuk National University, Division of Science Education and Institute of Fusion Science, Jeonju (Korea, Republic of)

2017-09-15

We show that, if they exist, lepton number asymmetries (L{sub α}) of neutrino flavors should be distinguished from the ones (L{sub i}) of mass eigenstates, since Big Bang Nucleosynthesis (BBN) bounds on the flavor eigenstates cannot be directly applied to the mass eigenstates. Similarly, Cosmic Microwave Background (CMB) constraints on the mass eigenstates do not directly constrain flavor asymmetries. Due to the difference of mass and flavor eigenstates, the cosmological constraint on the asymmetries of neutrino flavors can be much stronger than the conventional expectation, but they are not uniquely determined unless at least the asymmetry of the heaviest neutrino is well constrained. The cosmological constraint on L{sub i} for a specific case is presented as an illustration. (orig.)

Double beta decay and majorana neutrinos. Right-handed currents or nonzero masses

International Nuclear Information System (INIS)

Rosen, S.P.; Perlmutter, A.

1981-01-01

This chapter describes some new developments concerning the mechanism for lepton number nonconservation in no-neutrino double beta decay. Explains that lepton number nonconservation in no-neutrino double beta decay comes about either because both left- and right-handed components of a Majorano neutrino are coupled to the electron in the weak leptonic current, or because the neutrino has nonzero mass. Shows that while nuclear ground-state to ground-state transitions arise from right-handed currents and from neutrino mass terms, transitions to low-lying excited states with J /SUP P/ =2 + can arise only from right-handed currents. Emphasizes that the possibilities of detecting small admixtures of right-handed currents, and of setting limits on neutrino masses that are either very small or very large, make double beta decay a most rewarding phenomenon to study

Search for indications of the neutrino mass hierarchy using IceCube/DeepCore

Energy Technology Data Exchange (ETDEWEB)

Leuermann, Martin; Vehring, Markus; Wallraff, Marius; Wiebusch, Christopher [III. Physikalisches Institut B, RWTH Aachen (Germany); Collaboration: IceCube-Collaboration

2016-07-01

In 2015, the Nobel prize in physics was awarded for ''the discovery of neutrino oscillations, which shows that neutrinos have mass'', showing the high relevance of neutrino masses for modern particle physics. However, the ordering of the three neutrino masses is still unknown and is often referred to as neutrino mass hierarchy. Its measurement is a major goal for future experiments. One strategy is to measure matter effects in the oscillation pattern of atmospheric neutrinos e.g. as proposed for the PINGU extension of the IceCube neutrino observatory. Already now, the IceCube/DeepCore detector at the Geographic South Pole can be used to search for this signature. In this talk, we present an analysis based on data taken between 2011 and 2015. Due to recent improvements in the detector's reconstruction performance and the quality of the data selection, a measurement on the significance level of 1 sigma is expected.

Direct bounds on the tau neutrino mass from LEP

International Nuclear Information System (INIS)

Passalacqua, L.

1996-11-01

A review of direct bounds on the mass of the tau neutrino obtained at the LEP collider is presented. In addition to published results it includes preliminary results presented at recent conferences and new results presented at the 1996 Tau Workshop. The different techniques and decay modes employed by the ALEPH, DELPHI and OPAL collaborations are compared. The impact of the theoretical modelling of tau decays is also discussed. The most stringent 95 % CL limit on the tau neutrino mass is now obtained by a preliminary ALEPH analysis which combines the results from τ → 5 π ± (π 0 ) v τ and τ → 3 π ± v τ decays. This bound constraints the mass of the tau neutrino below 18.2 M e V / c 2

Neutrino mass and the reionization history of the Universe

International Nuclear Information System (INIS)

Popa, L.A.; Burigana, C.; Mandolesi, N.

2005-01-01

We investigate the role of a HDM component in the form of the three massive neutrino flavors for the reionization history of the Universe. Assuming a flat background cosmology described by the best fit power low ΛCDM model with WMAP data (Ω b h 2 =0.024, Ω m h 2 =0.14, h=0.72), we analyze the role of the neutrino mass for the properties of the gas in the intergalactic medium (IGM), showing that the temporal evolution of the hydrogen and helium ionization fractions are sensitive to the neutrino mass, with important implications for the CMB anisotropy and polarization angular power spectra

An origin for small neutrino masses in the NMSSM

International Nuclear Information System (INIS)

Abada, Asmaa; Moreau, Gregory

2006-01-01

We consider the Next to Minimal Supersymmetric Standard Model (NMSSM) which provides a natural solution to the so-called μ problem by introducing a new gauge-singlet superfield S. We realize that a mechanism of neutrino mass suppression arises, based on the R-parity violating bilinear terms μ i L i H u mixing neutrinos and higgsinos, offering thus an original approach to the neutrino mass problem (connected to the solution for the μ problem). We generate realistic (Majorana) neutrino mass values without requiring any strong hierarchy amongst the fundamental parameters, in contrast with the alternative models. In particular, the ratio μ i /μ can reach ∼ 10 -1 , unlike in the MSSM where it has to be much smaller than unity. We check that the obtained parameters also satisfy the collider constraints and internal consistencies of the NMSSM. The price to pay for this new cancellation-type mechanism of neutrino mass reduction is a certain fine tuning, which get significantly improved in some regions of parameter space. Besides, we discuss the feasibility of our scenario when the R-parity violating bilinear terms have a common origin with the μ term, namely when those are generated via a VEV of the S scalar component from the couplings λ i SL i H u . Finally, we make comments on some specific phenomenology of the NMSSM in the presence of R-parity violating bilinear terms

Neutrino-antineutrino asymmetry around rotating black holes

Indian Academy of Sciences (India)

important effects and hence can be constrained by Big Bang nucleosynthesis and power spectrum of cosmic microwave background, it becomes an important issue by itself to study new mechanisms which can generate neutrino asymmetry specially in the present epoch. When Dirac neutrinos propagate in gravitational ...

Application of a Lorentz transformation in six dimensions to an extension of dirac equation

International Nuclear Information System (INIS)

Sabry, A.A.

2000-01-01

On applying a six dimensional Lorentz transformation (by adding three time components to the usual 3 space components) a covariant extended Dirac equation in this six dimensional space is suggested. From the free field solution of the extended equation we obtained four solutions for E , the first component of energy which depends on very big masses M and M 0 . The observed masses of the leptons and their corresponding neutrinos satisfying the same free field equation, can then be obtained on using second quantisation procedures on the field operators

Compromise between neutrino masses and collider signatures in the type-II seesaw model

International Nuclear Information System (INIS)

Chao Wei; Luo Shu; Xing Zhizhong; Zhou Shun

2008-01-01

A natural extension of the standard SU(2) L xU(1) Y gauge model to accommodate massive neutrinos is to introduce one Higgs triplet and three right-handed Majorana neutrinos, leading to a 6x6 neutrino mass matrix which contains three 3x3 submatrices, M L , M D and M R . We show that three light Majorana neutrinos (i.e., the mass eigenstates of ν e , ν μ , and ν τ ) are exactly massless in this model, if and only if M L =M D M R -1 M D T exactly holds. This no-go theorem implies that small but nonvanishing neutrino masses may result from a significant but incomplete cancellation between M L and M D M R -1 M D T terms in the Type-II seesaw formula, provided three right-handed Majorana neutrinos are of O(1) TeV and experimentally detectable at the LHC. We propose three simple Type-II seesaw scenarios with the A 4 xU(1) X flavor symmetry and its explicit breaking to interpret the observed neutrino mass spectrum and neutrino mixing pattern. Such a TeV-scale neutrino model can be tested in two complementary ways: (1) searching for possible collider signatures of lepton number violation induced by the right-handed Majorana neutrinos and doubly-charged Higgs particles; and (2) searching for possible consequences of unitarity violation of the 3x3 neutrino mixing matrix in the future long-baseline neutrino oscillation experiments

Neutrino mass constraints on β decay

International Nuclear Information System (INIS)

Ito, Takeyasu M.; Prezeau, Gary

2005-01-01

Using the general connection between the upper limit on the neutrino mass and the upper limits on certain types of non-standard-model interactions that can generate loop corrections to the neutrino mass, we derive constraints on some non-standard-model d→ue - ν interactions. When cast into limits on n→pe - ν coupling constants, our results yield constraints on scalar and tensor weak interactions improved by more than an order of magnitude over the current experimental limits. When combined with the existing limits, our results yield vertical bar C S /C V vertical bar or approx. 5x10 -3 , vertical bar C S ' /C V vertical bar or approx. 5x10 -3 , vertical bar C T /C A vertical bar -2 , and vertical bar C T ' /C A vertical bar -2

Some aspects of chirality: Fermion masses and chiral p-forms

Energy Technology Data Exchange (ETDEWEB)

Kleppe, A

1997-05-01

The properties of fermion mass matrices are investigated from different points of view, both within the minimal Standard Model and in extensions of the model. It is shown how mass matrix invariants are used to define the measurables of the quark mixing matrix as invariant functions of the mass matrices. One model is presented where the family pattern is suggested to originate from a kind of mass scaling. A Lagrangian density is defined for an entire charge sector, such that the existence of a Dirac field with mass m{sub 0} implies the existence of other Dirac fields where the corresponding quanta have masses Rm{sub 0}, R{sup 2}m{sub 0}, .. which are obtained by a discrete scale transformation. This suggests a certain type of democratic fermion mass matrices. Also extensions of the minimal Standard Model are investigated, obtained by including right-handed neutrinos in the model. The Standard Model extended by two right-handed neutrinos gives rise to a mass spectrum with two massive and three massless neutrinos. The phenomenological consequences of this model are discussed. The neutrino mass matrix in such a scheme has what is defined as a democratic texture. They are studied for the cases with two and three right-handed neutrinos, resp. The chiral fields that we find in the Standard Model have certain similarities with self-dual fields. Among other things, both chiral and self-dual fields suffer species doubling on the lattice. Chiral p-forms are self-dual fields that appear in twice odd dimensions. Chiral p-forms violate manifest covariance, in the same sense as manifest covariance is violated by non-covariant gauges in electrodynamics. It is shown that a covariant action can nevertheless be formulated for chiral p-forms, by introducing an infinite set of gauge fields in a carefully controlled way.

Some aspects of chirality: Fermion masses and chiral p-forms

International Nuclear Information System (INIS)

Kleppe, A.

1997-05-01

The properties of fermion mass matrices are investigated from different points of view, both within the minimal Standard Model and in extensions of the model. It is shown how mass matrix invariants are used to define the measurables of the quark mixing matrix as invariant functions of the mass matrices. One model is presented where the family pattern is suggested to originate from a kind of mass scaling. A Lagrangian density is defined for an entire charge sector, such that the existence of a Dirac field with mass m 0 implies the existence of other Dirac fields where the corresponding quanta have masses Rm 0 , R 2 m 0 , .. which are obtained by a discrete scale transformation. This suggests a certain type of democratic fermion mass matrices. Also extensions of the minimal Standard Model are investigated, obtained by including right-handed neutrinos in the model. The Standard Model extended by two right-handed neutrinos gives rise to a mass spectrum with two massive and three massless neutrinos. The phenomenological consequences of this model are discussed. The neutrino mass matrix in such a scheme has what is defined as a democratic texture. They are studied for the cases with two and three right-handed neutrinos, resp. The chiral fields that we find in the Standard Model have certain similarities with self-dual fields. Among other things, both chiral and self-dual fields suffer species doubling on the lattice. Chiral p-forms are self-dual fields that appear in twice odd dimensions. Chiral p-forms violate manifest covariance, in the same sense as manifest covariance is violated by non-covariant gauges in electrodynamics. It is shown that a covariant action can nevertheless be formulated for chiral p-forms, by introducing an infinite set of gauge fields in a carefully controlled way

Constraints on singlet right-handed neutrinos coming from the Z0-width

International Nuclear Information System (INIS)

Escobar, C.O.; Peres, O.L.G.; Pleitez, V.

1992-12-01

The constraints on masses and missing angles imposed by the measured Z 0 invisible width, in a model in which a singlet right-handed neutrino mixes with all the Standard model neutrinos are studied. If neutrinos are massive an important question to be answered concerns the way the Z-pole observables constraint their masses and mixing parameters. In particular the measured Z-invisible width, Γ inv , implies that the number of families is compatible with three. On the other hand, it is well known that this number need not to be an integer number if right-handed neutrinos transformed as singlets under SU(2) L x U(1) Y are added to the particle content of the theory. Experimental searches for sequential neutron leptons beyond the three generations exclude stable Dirac neutrinos below 41.8 GeV and stable Majorana neutrinos below 34.8 GeV. For the unstable cases these values are 46,4 and 45.1 GeV respectively. However, it is worth stressing that these limits are valid for sequential leptons and do not apply to the case of singlets of right-handed neutrinos. Here we will consider the simplest extension of the standard electroweak model with the addition of the one right-handed singlet neutral fermion, resulting in 4 physical neutrinos two of them massless and two massive ones. (author)

Can the neutrino mass be measured using /sup 163/Ho electron capture

International Nuclear Information System (INIS)

Bennett, C.L.

1985-01-01

The safest limit on the neutrino mass comes from allowing the interference amplitude to be a free parameter in a fit to Springer's inner bremsstrahlung data while fixing the Q value to its upper limit based on the results of the relative capture rates from F. Hartmann's data. Since /sup 163/Ho was the most promising electron capture candidate for a neutrino mass detector, it is unlikely that electron capture will ever compete with tritium beta decay in terms of sensitivity to neutrino mass. The best fundamental thing that can be said is that the limit of the difference in the mass of the neutrino and its anti-particle is smaller in absolute value than for any other fermion anti-fermion pair

Neutrino Mass and Flavour Models

International Nuclear Information System (INIS)

King, Stephen F.

2010-01-01

We survey some of the recent promising developments in the search for the theory behind neutrino mass and tri-bimaximal mixing, and indeed all fermion masses and mixing. We focus in particular on models with discrete family symmetry and unification, and show how such models can also solve the SUSY flavour and CP problems. We also discuss the theoretical implications of the measurement of a non-zero reactor angle, as hinted at by recent experimental measurements.

Common origin of μ-τ and CP breaking in the neutrino seesaw, baryon asymmetry, and hidden flavor symmetry

International Nuclear Information System (INIS)

He Hongjian; Yin Furong

2011-01-01

We conjecture that all CP violations (both Dirac and Majorana types) arise from a common origin in the neutrino seesaw. With this conceptually attractive and simple conjecture, we deduce that μ-τ breaking shares the common origin with all CP violations. We study the common origin of μ-τ and CP breaking in the Dirac mass matrix of seesaw Lagrangian (with right-handed neutrinos being μ-τ blind), which uniquely leads to inverted mass ordering of light neutrinos. We then predict a very different correlation between the two small μ-τ breaking observables θ 13 -0 deg. and θ 23 -45 deg., which can saturate the present experimental upper limit on θ 13 . This will be tested against our previous normal mass-ordering scheme by the ongoing oscillation experiments. We also analyze the correlations of θ 13 with Jarlskog invariant and neutrinoless ββ-decay observable. From the common origin of CP and μ-τ breaking in the neutrino seesaw, we establish a direct link between the low energy CP violations and the cosmological CP violation for baryon asymmetry. With these we further predict a lower bound on θ 13 , supporting the ongoing probes of θ 13 at Daya Bay, Double Chooz, and RENO experiments. Finally, we analyze the general model-independent Z 2 x Z 2 symmetry structure of the light neutrino sector, and map it into the seesaw sector, where one of the Z 2 's corresponds to the μ-τ symmetry Z 2 μτ and another the hidden symmetry Z 2 s (revealed in our previous work) which dictates the solar mixing angle θ 12 . We derive the physical consequences of this Z 2 s and its possible partial violation in the presence of μ-τ breaking (with or without the neutrino seesaw), regarding the θ 12 determination and the correlation between μ-τ breaking observables.

Neutrino masses, scale-dependent growth, and redshift-space distortions

Energy Technology Data Exchange (ETDEWEB)

Hernández, Oscar F., E-mail: oscarh@physics.mcgill.ca [Marianopolis College, 4873 Westmount Ave., Westmount, QC H3Y 1X9 (Canada)

2017-06-01

Massive neutrinos leave a unique signature in the large scale clustering of matter. We investigate the wavenumber dependence of the growth factor arising from neutrino masses and use a Fisher analysis to determine the aspects of a galaxy survey needed to measure this scale dependence.

Neutrino mass and mixing – status

Indian Academy of Sciences (India)

be specific, a Majorana mass term for neutrinos, together with the mass term for charged leptons: LM = −. 1 .... hierarchy, respectively (see refs [5,6] for details and references). Parameter ... In figure 3 we show the region in the sin2 θ13–δ plane indicated by T2K ..... and 40 m and the precise rate measurement from Bugey4.

Double beta decay and neutrino mass models

Energy Technology Data Exchange (ETDEWEB)

Helo, J.C. [Universidad Técnica Federico Santa María, Centro-Científico-Tecnológico de Valparaíso, Casilla 110-V, Valparaíso (Chile); Hirsch, M. [AHEP Group, Instituto de Física Corpuscular - C.S.I.C./Universitat de València, Edificio de Institutos de Paterna, Apartado 22085, E-46071 València (Spain); Ota, T. [Department of Physics, Saitama University, Shimo-Okubo 255, 338-8570 Saitama-Sakura (Japan); Santos, F.A. Pereira dos [Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro,Rua Marquês de São Vicente 225, 22451-900 Gávea, Rio de Janeiro (Brazil)

2015-05-19

Neutrinoless double beta decay allows to constrain lepton number violating extensions of the standard model. If neutrinos are Majorana particles, the mass mechanism will always contribute to the decay rate, however, it is not a priori guaranteed to be the dominant contribution in all models. Here, we discuss whether the mass mechanism dominates or not from the theory point of view. We classify all possible (scalar-mediated) short-range contributions to the decay rate according to the loop level, at which the corresponding models will generate Majorana neutrino masses, and discuss the expected relative size of the different contributions to the decay rate in each class. Our discussion is general for models based on the SM group but does not cover models with an extended gauge. We also work out the phenomenology of one concrete 2-loop model in which both, mass mechanism and short-range diagram, might lead to competitive contributions, in some detail.

Leptogenesis in a neutrino mass model coupled with inflaton

Directory of Open Access Journals (Sweden)

Daijiro Suematsu

2016-09-01

Full Text Available We propose a scenario for the generation of baryon number asymmetry based on the inflaton decay in a radiative neutrino mass model extended with singlet scalars. In this scenario, lepton number asymmetry is produced through the decay of non-thermal right-handed neutrinos caused from the inflaton decay. Since the amount of non-thermal right-handed neutrinos could be much larger than the thermal ones, the scenario could work without any resonance effect for rather low reheating temperature. Sufficient baryon number asymmetry can be generated for much lighter right-handed neutrinos compared with the Davidson–Ibarra bound.

Neutrino Mass Models: impact of non-zero reactor angle

International Nuclear Information System (INIS)

King, Stephen F.

2011-01-01

In this talk neutrino mass models are reviewed and the impact of a non-zero reactor angle and other deviations from tri-bi maximal mixing are discussed. We propose some benchmark models, where the only way to discriminate between them is by high precision neutrino oscillation experiments.

Prospects for experiments on neutrino masses and mixing via neutrino oscillations at future accelerators

International Nuclear Information System (INIS)

Lanou, R.E. Jr.

1982-01-01

A study is made of the requirements necessary for improvement in our knowledge of limits in mass and mixing parameters for neutrinos via oscillation phenomena at accelerators. It is concluded that increased neutrino event rate (flux x energy) at modest energy machines (e.g., AGS and LAMPF) is the single most important requirement. This will permit smaller E/L ratios and refinement of systematics

Models of neutrino mass and mixing

International Nuclear Information System (INIS)

Ma, Ernest

2000-01-01

There are two basic theoretical approaches to obtaining neutrino mass and mixing. In the minimalist approach, one adds just enough new stuff to the Minimal Standard Model to get m ν ≠0 and U αi ≠1. In the holistic approach, one uses a general framework or principle to enlarge the Minimal Standard Model such that, among other things, m ν ≠0 and U αi ≠1. In both cases, there are important side effects besides neutrino oscillations. I discuss a number of examples, including the possibility of leptogenesis from R parity nonconservation in supersymmetry

Theoretical estimates of supernova-neutrino cross sections for the stable even-even lead isotopes: Charged-current reactions

Science.gov (United States)

Almosly, W.; Carlsson, B. G.; Suhonen, J.; Toivanen, J.; Ydrefors, E.

2016-10-01

A detailed study of the charged-current supernova electron neutrino and electron antineutrino scattering off the stable even-mass lead isotopes A =204 , 206, and 208 is reported in this work. The proton-neutron quasiparticle random-phase approximation (pnQRPA) is adopted to construct the nuclear final and initial states. Three different Skyrme interactions are tested for their isospin and spin-isospin properties and then applied to produce (anti)neutrino-nucleus scattering cross sections for (anti)neutrino energies below 80 MeV. Realistic estimates of the nuclear responses to supernova (anti)neutrinos are computed by folding the computed cross sections with a two-parameter Fermi-Dirac distribution of the electron (anti)neutrino energies. The computed cross sections are compared with earlier calculations and the analyses are extended to take into account the effects coming from the neutrino oscillations.

The variability of the gravitational constant and the mass-energy conservation in the Dirac cosmology

International Nuclear Information System (INIS)

Rybak, M.; Krygier, B.; Krempec-Krygier, J.

1985-01-01

The Hubble-Sandage diagrams for the Dirac cosmology have been discussed in the case of the modified dependence of luminosity upon the gravitational parameter G and mass. It is shown that the observational data for galaxies and the brightest quasars can be explained by the Dirac cosmology with the reasonably chosen changes of the gravitational parameter and of mass with the time. 41 refs., 2 figs. (author)

Neutrino mass ordering and μ-τ reflection symmetry breaking

Science.gov (United States)

Xing, Zhi-zhong; Zhu, Jing-yu

2017-12-01

If the neutrino mass spectrum turns out to be m 3case the columns of the 3×3 lepton flavor mixing matrix U should be reordered accordingly, and the resulting pattern U‧ may involve one or two large mixing angles in the standard parametrization or its variations. Since the Majorana neutrino mass matrix remains unchanged in such a mass relabeling, a possible μ-τ reflection symmetry is respected in this connection and its breaking effects are model-independently constrained at the 3σ level by using current experimental data. Supported by National Natural Science Foundation of China (11135009, 11375207)

Born–Infeld condensate as a possible origin of neutrino masses and dark energy

Energy Technology Data Exchange (ETDEWEB)

Addazi, Andrea [Dipartimento di Fisica, Università di L' Aquila, 67010 Coppito AQ (Italy); Laboratori Nazionali del Gran Sasso (INFN), 67010 Assergi AQ (Italy); Capozziello, Salvatore [Dipartimento di Fisica “Ettore Pancini”, Università di Napoli “Federico II”, INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126, Napoli (Italy); INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126, Napoli (Italy); Gran Sasso Science Institute (INFN), Viale F. Crispi 7, I-67100, L' Aquila (Italy); Odintsov, Sergei [Institució Catalana de Recerca i Estudis Avancats (ICREA), Barcelona (Spain); Institut de Ciencies de l' Espai (IEEC-CSIC), Campus UAB, Carrer de Can Magrans, s/n 08193 Cerdanyola del Valles, Barcelona (Spain); Lab. Theor. Cosmology, Tomsk State University of Control Systems and Radioelectronics (TUSUR), 634050 Tomsk (Russian Federation); Tomsk State Pedagogical University, 634061 Tomsk (Russian Federation)

2016-09-10

We discuss the possibility that a Born–Infeld condensate coupled to neutrinos can generate both neutrino masses and an effective cosmological constant. In particular, an effective field theory is provided capable of dynamically realizing the neutrino superfluid phase firstly suggested by Ginzburg and Zharkov. In such a case, neutrinos acquire a mass gap inside the Born–Infeld ether forming a long-range Cooper pair. Phenomenological implications of the approach are also discussed.

Charged-Current Neutrino-Nucleus Scattering off the Even Molybdenum Isotopes

Directory of Open Access Journals (Sweden)

E. Ydrefors

2012-01-01

Full Text Available Neutrinos from supernovae constitute important probes of both the currently unknown supernova mechanisms and of neutrino properties. Reliable information about the nuclear responses to supernova neutrinos is therefore crucial. In this work, we compute the cross sections for the charged-current neutrino-nucleus scattering off the even-even molybdenum isotopes. The nuclear responses to supernova neutrinos are subsequently calculated by folding the cross sections with a Fermi-Dirac distribution.

Determination of absolute neutrino masses from Z-bursts

International Nuclear Information System (INIS)

Fodor, Z.

2001-05-01

Ultrahigh energy neutrinos (UHEν) scatter on cosmological relic neutrinos (Rν) producing Z bosons, which can decay hadronically producing protons (Z-burst). We compare the predicted proton spectrum with the observed ultrahigh energy cosmic ray (UHECR) spectrum and determine the mass of the heaviest Rν via a maximum likelihood analysis. Our mass prediction depends on the origin of the power-like part of the UHECR spectrum: m ν = 2.34 -0.84 +1.29 eV for Galactic halo and 0.26 -0.14 +0.20 eV for extragalactic (EG) origin. The second mass, with a lower bound of 0.06 eV on the 95% confidence level (CL), is compatible with a hierarchical ν mass scenario with the largest mass suggested by the atmospheric ν oscillation. The necessary UHEν flux is compatible with present upper limits and should be detected in the near future. (orig.)

Origins of tiny neutrino mass and large flavor mixings

International Nuclear Information System (INIS)

Haba, Naoyuki

2015-01-01

Active neutrino masses are extremely smaller than those of other quarks and leptons, and there are large flavor mixings in the lepton sector, contrary to the quark sector. They are great mysteries in the standard model, but also excellent hints of new physics beyond the standard model. Thus, questions 'What is an origin of tiny neutrino mass?' and 'What is an origin of large lepton flavor mixings?' are very important. In this paper, we overview various attempts to solve these big questions. (author)

Heavy neutrino signals at large hadron colliders

International Nuclear Information System (INIS)

Aguila, Francisco del; Aguilar-Saavedra, Juan Antonio; Pittau, Roberto

2007-01-01

We study the LHC discovery potential for heavy Majorana neutrino singlets in the process pp → W + → l + N → l + l + jj (l = e, μ) plus its charge conjugate. With a fast detector simulation we show that backgrounds involving two like-sign charged leptons are not negligible and, moreover, they cannot be eliminated with simple sequential kinematical cuts. Using a likelihood analysis it is shown that, for heavy neutrinos coupling only to the muon, LHC has 5σ sensitivity for masses up to 200 GeV in the final state μ ± μ ± jj. This reduction in sensitivity, compared to previous parton-level estimates, is driven by the ∼ 10 2 -10 3 times larger background. Limits are also provided for e ± e ± jj and e ± μ ± jj final states, as well as for Tevatron. For heavy Dirac neutrinos the prospects are worse because backgrounds involving two opposite charge leptons are much larger. For this case, we study the observability of the lepton flavour violating signal e ± μ -+ jj. As a by-product of our analysis, heavy neutrino production has been implemented within the ALPGEN framework

Two old ways to measure the electron-neutrino mass

CERN Document Server

De Rújula, A

2013-01-01

Three decades ago, the measurement of the electron neutrino mass in atomic electron capture (EC) experiments was scrutinized in its two variants: single EC and neutrino-less double EC. For certain isotopes an atomic resonance enormously enhances the expected decay rates. The favoured technique, based on calorimeters as opposed to spectrometers, has the advantage of greatly simplifying the theoretical analysis of the data. After an initial surge of measurements, the EC approach did not seem to be competitive. But very recently, there has been great progress on micro-calorimeters and the measurement of atomic mass differences. Meanwhile, the beta-decay neutrino-mass limits have improved by a factor of 15, and the difficulty of the experiments by the cube of that figure. Can the "calorimetric" EC theory cope with this increased challenge? I answer this question affirmatively. In so doing I briefly review the subject and extensively address some persistent misunderstandings of the underlying quantum physics.

Proposal on electron anti-neutrino mass measurement at INS

International Nuclear Information System (INIS)

Ohshima, Takayoshi.

1981-03-01

Some comment on the proposed experiment, namely the measurement of electron anti-neutrino mass, is described. Various experiments with the measurement of β-ray from tritium have been reported. The precise measurement of the shape of the Kurie plot is required in this kind of experiment. The present experiment aimed at more accurate determination of neutrino mass than any other previous ones. An important point of the present experiment is to reduce the background due to the β-ray from evaporating tritium. The source candidates have low evaporation rate. A double focus √2π air core spectrometer is employed for the measurement of β-ray. The spectrometer was improved to meet the present purpose. The accumulated event rate was expected to be about 10 times higher than Russian experiment. The estimated energy resolution was about 30 eV. The neutrino mass with less than 10 eV accuracy will be obtained. (Kato, T.)

Detecting non-relativistic cosmic neutrinos by capture on tritium: phenomenology and physics potential

Energy Technology Data Exchange (ETDEWEB)

Long, Andrew J.; Lunardini, Cecilia; Sabancilar, Eray, E-mail: andrewjlong@asu.edu, E-mail: Cecilia.Lunardini@asu.edu, E-mail: Eray.Sabancilar@asu.edu [Physics Department, Arizona State University, Tempe, Arizona 85287 (United States)

2014-08-01

We study the physics potential of the detection of the Cosmic Neutrino Background via neutrino capture on tritium, taking the proposed PTOLEMY experiment as a case study. With the projected energy resolution of Δ ∼ 0.15 eV, the experiment will be sensitive to neutrino masses with degenerate spectrum, m{sub 1} ≅ m{sub 2} ≅ m{sub 3} = m{sub ν} ∼> 0.1 eV. These neutrinos are non-relativistic today; detecting them would be a unique opportunity to probe this unexplored kinematical regime. The signature of neutrino capture is a peak in the electron spectrum that is displaced by 2 m{sub ν} above the beta decay endpoint. The signal would exceed the background from beta decay if the energy resolution is Δ ∼< 0.7 m{sub ν} . Interestingly, the total capture rate depends on the origin of the neutrino mass, being Γ{sup D} ≅ 4 and Γ{sup M} ≅ 8 events per year (for a 100 g tritium target) for unclustered Dirac and Majorana neutrinos, respectively. An enhancement of the rate of up to O(1) is expected due to gravitational clustering, with the unique potential to probe the local overdensity of neutrinos. Turning to more exotic neutrino physics, PTOLEMY could be sensitive to a lepton asymmetry, and reveal the eV-scale sterile neutrino that is favored by short baseline oscillation searches. The experiment would also be sensitive to a neutrino lifetime on the order of the age of the universe and break the degeneracy between neutrino mass and lifetime which affects existing bounds.

Acquiring information about neutrino parameters by detecting supernova neutrinos

Science.gov (United States)

Huang, Ming-Yang; Guo, Xin-Heng; Young, Bing-Lin

2010-08-01

We consider the supernova shock effects, the Mikheyev-Smirnov-Wolfenstein effects, the collective effects, and the Earth matter effects in the detection of type II supernova neutrinos on the Earth. It is found that the event number of supernova neutrinos depends on the neutrino mass hierarchy, the neutrino mixing angle θ13, and neutrino masses. Therefore, we propose possible methods to identify the mass hierarchy and acquire information about θ13 and neutrino masses by detecting supernova neutrinos. We apply these methods to some current neutrino experiments.

Mixed Inert scalar triplet dark matter, radiative neutrino masses and leptogenesis

Directory of Open Access Journals (Sweden)

Wen-Bin Lu

2017-11-01

Full Text Available The neutral component of an inert scalar multiplet with hypercharge can provide a stable dark matter particle when its real and imaginary parts have a splitting mass spectrum. Otherwise, a tree-level dark-matter-nucleon scattering mediated by the Z boson will be much above the experimental limit. In this paper we focus on a mixed inert scalar triplet dark matter scenario where a complex scalar triplet with hypercharge can mix with another real scalar triplet without hypercharge through their renormalizable coupling to the standard model Higgs doublet. We consider three specified cases that carry most of the relevant features of the full parameter space: (i the neutral component of the real triplet dominates the dark matter particle, (ii the neutral component of the complex triplet dominates the dark matter particle; and (iii the neutral components of the real and complex triplets equally constitute the dark matter particle. Subject to the dark matter relic abundance and direct detection constraint, we perform a systematic study on the allowed parameter space with particular emphasis on the interplay among triplet-doublet terms and gauge interactions. In the presence of these mixed inert scalar triplets, some heavy Dirac fermions composed of inert fermion doublets can be utilized to generate a tiny Majorana neutrino mass term at one-loop level and realize a successful leptogenesis for explaining the cosmic baryon asymmetry.

A model of radiative neutrino masses. Mixing and a possible fourth generation

International Nuclear Information System (INIS)

Babu, K.S.; Ma, E.; Pantaleone, J.

1989-01-01

We consider the phenomenological consequences of a recently proposed model with four lepton generations such that the three known neutrinos have radiatively induced Majorana masses. Mixing among generations in the presence of a heavy fourth neutrino necessitates a reevaluation of the usual experimental tests of the standard model. One interesting possibility is to have a τ lifetime longer than predicted by the standard three-generation model. Another is to have neutrino masses and mixing angles in the range needed for a natural explanation of the solar-neutrino puzzle in terms of the Mikheyev-Smirnov-Wolfenstein effect. (orig.)

Reduced Dirac equation and Lamb shift as off-mass-shell effect in quantum electrodynamics

International Nuclear Information System (INIS)

Ni Guang-Jiong; Xu Jian-Jun; Lou Sen-Yue

2011-01-01

Based on the accurate experimental data of energy-level differences in hydrogen-like atoms, especially the 1S—2S transitions of hydrogen and deuterium, the necessity of introducing a reduced Dirac equation with reduced mass as the substitution of original electron mass is stressed. Based on new cognition about the essence of special relativity, we provide a reasonable argument for the reduced Dirac equation to have two symmetries, the invariance under the (newly defined) space-time inversion and that under the pure space inversion, in a noninertial frame. By using the reduced Dirac equation and within the framework of quantum electrodynamics in covariant form, the Lamb shift can be evaluated (at one-loop level) as the radiative correction on a bound electron staying in an off-mass-shell state—-a new approach eliminating the infrared divergence. Hence the whole calculation, though with limited accuracy, is simplified, getting rid of all divergences and free of ambiguity. (general)

CLFV and the origin of neutrino masses

Science.gov (United States)

Hambye, Thomas

2014-03-01

The neutrino oscillations constitute the unique absolute guarantee we have at the moment that charged lepton flavor violation (CLFV) processes do exist. Even if the associated rates are in general expected very suppressed, it turns out that this is not always necessarily the case. In the framework of the three basic seesaw models, we review the possibilities of having observable rates. Each seesaw case presenting a quite different CLFV pattern, we show how these observable rates could allow us to distinguish these various possible neutrino mass origins.

CLFV and the origin of neutrino masses

International Nuclear Information System (INIS)

Hambye, Thomas

2014-01-01

The neutrino oscillations constitute the unique absolute guarantee we have at the moment that charged lepton flavor violation (CLFV) processes do exist. Even if the associated rates are in general expected very suppressed, it turns out that this is not always necessarily the case. In the framework of the three basic seesaw models, we review the possibilities of having observable rates. Each seesaw case presenting a quite different CLFV pattern, we show how these observable rates could allow us to distinguish these various possible neutrino mass origins

Implications of neutrino masses and mixing for weak processes

International Nuclear Information System (INIS)

Shrock, R.E.

1981-01-01

A general theory is presented of weak processes involving neutrinos which consistently incorporates the possibility of nonzero neutrino masses and associated lepton mixing. The theory leads to new tests for and bounds on such masses and mixing. These tests make use of (π,K)/sub l2/ decay, nuclear β decay, and μ and tau decays, among others. New experiments at SIN and KEK to apply the tests are mentioned. Further, some implications are discussed for (1) the analysis of the spectral parameters in leptonic decays to determine the Lorentz structure of the weak leptonic couplings; (2) fundamental weak interaction constants such as G/sub μ/, G/sub V/', f/sub π/, f/sub K/, V/sub uq/, q = d or s, m/sub W/, and m/sub Z/; and (3) neutrino propagation

Seesaw induced electroweak scale, the hierarchy problem and sub-eV neutrino masses

International Nuclear Information System (INIS)

Atwood, D.; Bar-Shalom, S.; Soni, A.

2006-01-01

We describe a model for the scalar sector where all interactions occur either at an ultra-high scale, Λ U ∝10 16 -10 19 GeV, or at an intermediate scale, Λ I =10 9 -10 11 GeV. The interaction of physics on these two scales results in an SU(2) Higgs condensate at the electroweak (EW) scale, Λ EW , through a seesaw-like Higgs mechanism, Λ EW ∝Λ I 2 /Λ U , while the breaking of the SM SU(2) x U(1) gauge symmetry occurs at the intermediate scale Λ I . The EW scale is, therefore, not fundamental but is naturally generated in terms of ultra-high energy phenomena and so the hierarchy problem is alleviated. We show that the class of such ''seesaw Higgs'' models predict the existence of sub-eV neutrino masses which are generated through a ''two-step'' seesaw mechanism in terms of the same two ultra-high scales: m ν ∝Λ I 4 /Λ U 3 ∝Λ EW 2 /Λ U . The neutrinos can be either Dirac or Majorana, depending on the structure of the scalar potential. We also show that our seesaw Higgs model can be naturally embedded in theories with tiny extra dimensions of size R∝Λ U -1 ∝10 -16 fm, where the seesaw induced EW scale arises from a violation of a symmetry at a distant brane; in particular, in the scenario presented there are seven tiny extra dimensions. (orig.)

LSND versus MiniBooNE: Sterile neutrinos with energy dependent masses and mixing?

CERN Document Server

Schwetz, Thomas

2008-01-01

Standard active-sterile neutrino oscillations do not provide a satisfactory description of the LSND evidence for neutrino oscillations together with the constraints from MiniBooNE and other null-result short-baseline oscillation experiments. However, if the mass or the mixing of the sterile neutrino depends in an exotic way on its energy all data become consistent. I explore the phenomenological consequences of the assumption that either the mass or the mixing scales with the neutrino energy as $1/E_\

Determination of neutrino mass hierarchy by 21 cm line and CMB B-mode polarization observations

Energy Technology Data Exchange (ETDEWEB)

Oyama, Yoshihiko, E-mail: oyamayo@post.kek.jp [The Graduate University for Advanced Studies (SOKENDAI), 1-1 Oho, Tsukuba 305-0801 (Japan); Shimizu, Akie [The Graduate University for Advanced Studies (SOKENDAI), 1-1 Oho, Tsukuba 305-0801 (Japan); Kohri, Kazunori [The Graduate University for Advanced Studies (SOKENDAI), 1-1 Oho, Tsukuba 305-0801 (Japan); Institute of Particle and Nuclear Studies, KEK, 1-1 Oho, Tsukuba 305-0801 (Japan)

2013-01-29

We focus on the ongoing and future observations for both the 21 cm line and the CMB B-mode polarization produced by a CMB lensing, and study their sensitivities to the effective number of neutrino species, the total neutrino mass, and the neutrino mass hierarchy. We find that combining the CMB observations with future square kilometer arrays optimized for 21 cm line such as Omniscope can determine the neutrino mass hierarchy at 2{sigma}. We also show that a more feasible combination of Planck + POLARBEAR and SKA can strongly improve errors of the bounds on the total neutrino mass and the effective number of neutrino species to be {Delta}{Sigma}m{sub {nu}}{approx}0.12 eV and {Delta}N{sub {nu}}{approx}0.38 at 2{sigma}, respectively.

Neutrinos and the origin of fermion mass structure

International Nuclear Information System (INIS)

Ross, Graham G.

2007-01-01

The pattern of neutrino masses and mixings is characteristically different from those observed in the quark sector. I discuss why this should be the case and what implications this has for the origin of quark and lepton masses, mixings and CP violation

Acquire information about neutrino parameters by detecting supernova neutrinos

OpenAIRE

Huang, Ming-Yang; Guo, Xin-Heng; Young, Bing-Lin

2010-01-01

We consider the supernova shock effects, the Mikheyev-Smirnov-Wolfenstein (MSW) effects, the collective effects, and the Earth matter effects in the detection of type II supernova neutrinos on the Earth. It is found that the event number of supernova neutrinos depends on the neutrino mass hierarchy, the neutrino mixing angle $\\theta_{13}$, and neutrino masses. Therefore, we propose possible methods to identify the mass hierarchy and acquire information about $\\theta_{13}$ and neutrino masses ...

Insights into neutrino decoupling gleaned from considerations of the role of electron mass

Science.gov (United States)

Grohs, E.; Fuller, George M.

2017-10-01

We present calculations showing how electron rest mass influences entropy flow, neutrino decoupling, and Big Bang Nucleosynthesis (BBN) in the early universe. To elucidate this physics and especially the sensitivity of BBN and related epochs to electron mass, we consider a parameter space of rest mass values larger and smaller than the accepted vacuum value. Electromagnetic equilibrium, coupled with the high entropy of the early universe, guarantees that significant numbers of electron-positron pairs are present, and dominate over the number of ionization electrons to temperatures much lower than the vacuum electron rest mass. Scattering between the electrons-positrons and the neutrinos largely controls the flow of entropy from the plasma into the neutrino seas. Moreover, the number density of electron-positron-pair targets can be exponentially sensitive to the effective in-medium electron mass. This entropy flow influences the phasing of scale factor and temperature, the charged current weak-interaction-determined neutron-to-proton ratio, and the spectral distortions in the relic neutrino energy spectra. Our calculations show the sensitivity of the physics of this epoch to three separate effects: finite electron mass, finite-temperature quantum electrodynamic (QED) effects on the plasma equation of state, and Boltzmann neutrino energy transport. The ratio of neutrino to plasma-component energy scales manifests in Cosmic Microwave Background (CMB) observables, namely the baryon density and the radiation energy density, along with the primordial helium and deuterium abundances. Our results demonstrate how the treatment of in-medium electron mass (i.e., QED effects) could translate into an important source of uncertainty in extracting neutrino and beyond-standard-model physics limits from future high-precision CMB data.

Insights into neutrino decoupling gleaned from considerations of the role of electron mass

Directory of Open Access Journals (Sweden)

E. Grohs

2017-10-01

Full Text Available We present calculations showing how electron rest mass influences entropy flow, neutrino decoupling, and Big Bang Nucleosynthesis (BBN in the early universe. To elucidate this physics and especially the sensitivity of BBN and related epochs to electron mass, we consider a parameter space of rest mass values larger and smaller than the accepted vacuum value. Electromagnetic equilibrium, coupled with the high entropy of the early universe, guarantees that significant numbers of electron–positron pairs are present, and dominate over the number of ionization electrons to temperatures much lower than the vacuum electron rest mass. Scattering between the electrons–positrons and the neutrinos largely controls the flow of entropy from the plasma into the neutrino seas. Moreover, the number density of electron–positron-pair targets can be exponentially sensitive to the effective in-medium electron mass. This entropy flow influences the phasing of scale factor and temperature, the charged current weak-interaction-determined neutron-to-proton ratio, and the spectral distortions in the relic neutrino energy spectra. Our calculations show the sensitivity of the physics of this epoch to three separate effects: finite electron mass, finite-temperature quantum electrodynamic (QED effects on the plasma equation of state, and Boltzmann neutrino energy transport. The ratio of neutrino to plasma–component energy scales manifests in Cosmic Microwave Background (CMB observables, namely the baryon density and the radiation energy density, along with the primordial helium and deuterium abundances. Our results demonstrate how the treatment of in-medium electron mass (i.e., QED effects could translate into an important source of uncertainty in extracting neutrino and beyond-standard-model physics limits from future high-precision CMB data.

Neutrino mass matrices with two vanishing cofactors and Fritzsch texture for charged lepton mass matrix

Science.gov (United States)

Wang, Weijian; Guo, Shu-Yuan; Wang, Zhi-Gang

2016-04-01

In this paper, we study the cofactor 2 zero neutrino mass matrices with the Fritzsch-type structure in charged lepton mass matrix (CLMM). In the numerical analysis, we perform a scan over the parameter space of all the 15 possible patterns to get a large sample of viable scattering points. Among the 15 possible patterns, three of them can accommodate the latest lepton mixing and neutrino mass data. We compare the predictions of the allowed patterns with their counterparts with diagonal CLMM. In this case, the severe cosmology bound on the neutrino mass set a strong constraint on the parameter space, rendering two patterns only marginally allowed. The Fritzsch-type CLMM will have impact on the viable parameter space and give rise to different phenomenological predictions. Each allowed pattern predicts the strong correlations between physical variables, which is essential for model selection and can be probed in future experiments. It is found that under the no-diagonal CLMM, the cofactor zeros structure in neutrino mass matrix is unstable as the running of renormalization group (RG) from seesaw scale to the electroweak scale. A way out of the problem is to propose the flavor symmetry under the models with a TeV seesaw scale. The inverse seesaw model and a loop-induced model are given as two examples.

Neutrino mass hierarchy determination for θ13 = 0

International Nuclear Information System (INIS)

Gandhi, Raj; Ghoshal, Pomita; Goswami, Srubabati; Sankar, S. Uma

2010-01-01

We examine the possibility of determining the neutrino mass hierarchy in the limit θ 13 = 0 using atmospheric neutrinos as the source. In this limit, θ 13 driven matter effects are absent so independent measurements of Δ 31 and Δ 32 can, in principle, lead to hierarchy determination. Since their difference is Δ 21 , one needs an experimental arrangement where Δ 21 L/E > or approx. 1 can be achieved. This can be satisfied by atmospheric neutrinos which have a large range of L and E. Still, we find that hierarchy determination in the θ 13 = 0 limit with atmospheric neutrinos is not a realistic possibility, even in conjunction with a beam experiment like T2K or NOνA. We discuss why, and also reiterate the general conditions for hierarchy determination if θ 13 = 0.

The Neutrino Bomb: A New Weapon of Mass Destruction

International Nuclear Information System (INIS)

Broda, E.

1978-01-01

This text was written by E. Broda in a “Supplementary” paper for Pugwash in the year 1978. It is about the neutrino and a general principle of its use as a potential weapon of mass destruction. It ends with a suggestion to convene a Pugwash workshop for dealing with the threat of the neutrino bomb. (zarka)

Double beta decays and neutrino masses

International Nuclear Information System (INIS)

Ejiri, Hiro

2006-01-01

Neutrino-less double beta decays(0νββ) are of great interest for studying the Majorana nature of ν's and the absolute ν-mass scale. The present report is a brief review of the 0νββ studies with emphasis on future experiments with the mass sensitivity of an order of 25∼100 meV and on experimental probes for investigating 0νββ nuclear matrix elements

Measuring the neutrino mass hierarchy with the future KM3NeT/ORCA detector

Energy Technology Data Exchange (ETDEWEB)

Hofestaedt, Jannik

2017-02-22

The neutrino mass hierarchy can be determined by measuring the energy- and zenith-angle-dependent oscillation pattern of few-GeV atmospheric neutrinos that have traversed the Earth. This measurement is the main science goal of KM3NeT/ORCA ('Oscillation Research with Cosmics in the Abyss'), a planned multi-megaton underwater Cherenkov detector in the Mediterranean Sea. A key task is the reconstruction of shower-like events induced by electron neutrinos in charged-current interactions, which substantially affect the neutrino mass hierarchy sensitivity. In this thesis, numerous aspects of the expected neutrino detection performance of the planned ORCA detector are investigated. A new reconstruction algorithm for neutrino-induced shower-like events is developed. Excellent reconstruction accuracies are achieved, with a neutrino energy resolution better than 26%/24%, and a median neutrino direction resolution better than 11 /9 for electron neutrinos/antineutrinos in charged-current interactions with energies above 7 GeV. It is shown that these resolutions are close to the reconstruction accuracy limits imposed by intrinsic fluctuations in the Cherenkov light signatures. These intrinsic resolution limits are based on generic assumptions about event reconstruction in Cherenkov detectors and are derived as part of this thesis. Differences in event reconstruction capabilities between water- and ice-based Cherenkov detectors are discussed. The configuration of existing trigger algorithms is optimised for the ORCA detector. Based on the developed shower reconstruction, a detector optimisation study of the photosensor density is performed. In addition, it is shown that optical background noise in the deep Mediterranean Sea is not expected to compromise the feasibility of the neutrino mass hierarchy measurement with ORCA. Together, these investigations contribute significantly to the estimated neutrino mass hierarchy sensitivity of ORCA published in the 'Letter of

Detection of supernova neutrinos at spallation neutron sources

Science.gov (United States)

Huang, Ming-Yang; Guo, Xin-Heng; Young, Bing-Lin

2016-07-01

After considering supernova shock effects, Mikheyev-Smirnov-Wolfenstein effects, neutrino collective effects, and Earth matter effects, the detection of supernova neutrinos at the China Spallation Neutron Source is studied and the expected numbers of different flavor supernova neutrinos observed through various reaction channels are calculated with the neutrino energy spectra described by the Fermi-Dirac distribution and the “beta fit” distribution respectively. Furthermore, the numerical calculation method of supernova neutrino detection on Earth is applied to some other spallation neutron sources, and the total expected numbers of supernova neutrinos observed through different reactions channels are given. Supported by National Natural Science Foundation of China (11205185, 11175020, 11275025, 11575023)

Hadron collider tests of neutrino mass-generating mechanisms

Science.gov (United States)

Ruiz, Richard Efrain

The Standard Model of particle physics (SM) is presently the best description of nature at small distances and high energies. However, with tiny but nonzero neutrino masses, a Higgs boson mass unstable under radiative corrections, and little guidance on understanding the hierarchy of fermion masses, the SM remains an unsatisfactory description of nature. Well-motivated scenarios that resolve these issues exist but also predict extended gauge (e.g., Left-Right Symmetric Models), scalar (e.g., Supersymmetry), and/or fermion sectors (e.g., Seesaw Models). Hence, discovering such new states would have far-reaching implications. After reviewing basic tenets of the SM and collider physics, several beyond the SM (BSM) scenarios that alleviate these shortcomings are investigated. Emphasis is placed on the production of a heavy Majorana neutrinos at hadron colliders in the context of low-energy, effective theories that simultaneously explain the origin of neutrino masses and their smallness compared to other elementary fermions, the so-called Seesaw Mechanisms. As probes of new physics, rare top quark decays to Higgs bosons in the context of the SM, the Types I and II Two Higgs Doublet Model (2HDM), and the semi-model independent framework of Effective Field Theory (EFT) have also been investigated. Observation prospects and discovery potentials of these models at current and future collider experiments are quantified.

Late time neutrino masses, the LSND experiment, and the cosmic microwave background.

Science.gov (United States)

Chacko, Z; Hall, Lawrence J; Oliver, Steven J; Perelstein, Maxim

2005-03-25

Models with low-scale breaking of global symmetries in the neutrino sector provide an alternative to the seesaw mechanism for understanding why neutrinos are light. Such models can easily incorporate light sterile neutrinos required by the Liquid Scintillator Neutrino Detector experiment. Furthermore, the constraints on the sterile neutrino properties from nucleosynthesis and large-scale structure can be removed due to the nonconventional cosmological evolution of neutrino masses and densities. We present explicit, fully realistic supersymmetric models, and discuss the characteristic signatures predicted in the angular distributions of the cosmic microwave background.

Neutrino masses and b - τ unification in the supersymmetric standard model

International Nuclear Information System (INIS)

Vissani, F.; Smirnov, A.Yu.

1994-05-01

There are several indications that the Majorana masses of the right-handed neutrino components, M R , are at the intermediate scale: M R ∼ (10 10 - 10 12 ) GeV or even lighter. The renormalization effects due to large Yukawa couplings of neutrinos from region of momenta M R G are studied in the supersymmetric standard model. It is shown that neutrino renormalization effect can increase the m b /m τ ratio up to (10/15)%. This strongly disfavors m b - m τ unification for low values of tan β s . Lower bound on M R and tan β from the b - τ unification condition were found. The implications of the results to the see-saw mechanism of the neutrino mass generation are discussed. (author). 17 refs, 4 figs

Models of neutrino masses and baryogenesis

Indian Academy of Sciences (India)

Majorana masses of the neutrino implies lepton number violation and is intimately related to the lepton asymmetry of the universe, which gets related to the baryon asymmetry of the universe in the presence of the sphalerons during the electroweak phase transition. Assuming that the baryon asymmetry of the universe is ...

Determining neutrino mass hierarchy from electron disappearance at a low energy neutrino factory

International Nuclear Information System (INIS)

Raut, Sushant K.

2013-01-01

Reactor neutrino experiments have recently measured the value of θ 13 , to be non-zero and moderately large. This makes the determination of the neutrino mass hierarchy possible. However, our lack of knowledge of δ CP results in a parameter degeneracy, which makes this task difficult. The electron neutrino disappearance probability does not depend on δ CP . Therefore, in principle, it is possible to determine the hierarchy independently of δ CP using this channel. Previous studies of neutrino factories have not considered this channel, because the effect of systematics in electron disappearance is substantial. However, we show that for the moderately large value of θ 13 measured, hierarchy determination is possible in spite of systematic effects. We consider a low energy neutrino factory (LENF) setup with a totally active scintillator detector (TASD) with charge-identification. We optimize the setup in muon energy and baseline, for different allowed values of θ 13 and runtime. We find that a LENF with baseline of around 1300 km and muon energy around 3-4 GeV is well suited for hierarchy determination. For the RENO best-fit value of θ 13 , this setup can determine the hierarchy at 5ω, for all values of δ CP and for both hierarchies. (author)

More is different: Reconciling eV sterile neutrinos with cosmological mass bounds

Directory of Open Access Journals (Sweden)

Yong Tang

2015-11-01

Full Text Available It is generally expected that adding light sterile species would increase the effective number of neutrinos, Neff. In this paper we discuss a scenario that Neff can actually decrease due to the neutrino oscillation effect if sterile neutrinos have self-interactions. We specifically focus on the eV mass range, as suggested by the neutrino anomalies. With large self-interactions, sterile neutrinos are not fully thermalized in the early Universe because of the suppressed effective mixing angle or matter effect. As the Universe cools down, flavor equilibrium between active and sterile species can be reached after big bang nucleosynthesis (BBN epoch, but leading to a decrease of Neff. In such a scenario, we also show that the conflict with cosmological mass bounds on the additional sterile neutrinos can be relaxed further when more light species are introduced. To be consistent with the latest Planck results, at least 3 sterile species are needed.

Multipole electromagnetic moments of neutrino in dispersive medium

International Nuclear Information System (INIS)

Semikov, V.B.; Smorodinskij, Ya.A.; Gosudarstvennyj Komitet po Ispol'zovaniyu Atomnoj Ehnergii SSSR, Moscow

1989-01-01

Four multipole moments for a Dirac and Majorana neutrino in a dispersive medium are calculated viz., the electric monopole (charge), electric dipole, magnetic dipole and anapole dipole moment. For comparison the same quantities are presented in the case of vacuum. The neutrino does not possess an (induced) anapole moment in an isotropic medium; however, in a ferromagnetic such a moment exists and for the Majorana neutrino it is the only electromagnetic cjaracteristic. As an example the cross section for elastic scattering of a Majorana neutrino by nuclei in an isotropic plasma is calculated

Quark-lepton complementarity relation and neutrino mass hierarchy

International Nuclear Information System (INIS)

Ferrandis, Javier; Pakvasa, Sandip

2005-01-01

Latest measurements have revealed that the deviation from a maximal solar mixing angle is approximately the Cabibbo angle [i.e., quark-lepton complementarity (QLC) relation]. We argue that it is not plausible that this deviation from maximality, be it a coincidence or not, comes from the charged lepton mixing. Consequently we have calculated the required corrections to the exactly bimaximal neutrino mass matrix ansatz necessary to account for the solar mass difference and the solar mixing angle. We point out that the relative size of these two corrections depends strongly on the hierarchy case under consideration. We find that the inverted hierarchy case with opposite CP parities, which is known to guarantee the renormalization group equations stability of the solar mixing angle, offers the most plausible scenario for a high-energy origin of a QLC-corrected bimaximal neutrino mass matrix. This possibility may allow us to explain the QLC relation in connection with the origin of the charged fermion mass matrices

Chiral condensate from the twisted mass Dirac operator spectrum

International Nuclear Information System (INIS)

Cichy, Krzysztof; Jansen, Karl; Cyprus Univ., Nicosia

2013-03-01

We present the results of our computation of the chiral condensate with N f =2 and N f =2+1+1 flavours of maximally twisted mass fermions. The condensate is determined from the Dirac operator spectrum, applying the spectral projector method proposed by Giusti and Luescher. We use 3 lattice spacings and several quark masses at each lattice spacing to reliably perform the chiral and continuum extrapolations. We study the effect of the dynamical strange and charm quarks by comparing our results for N f =2 and N f =2+1+1 dynamical flavours.

Determining neutrino mass from the cosmic microwave background alone.

Science.gov (United States)

Kaplinghat, Manoj; Knox, Lloyd; Song, Yong-Seon

2003-12-12

Distortions of cosmic microwave background temperature and polarization maps caused by gravitational lensing, observable with high angular resolution and high sensitivity, can be used to measure the neutrino mass. Assuming two massless species and one with mass m(nu), we forecast sigma(m(nu))=0.15 eV from the Planck satellite and sigma(m(nu))=0.04 eV from observations with twice the angular resolution and approximately 20 times the sensitivity. A detection is likely at this higher sensitivity since the observation of atmospheric neutrino oscillations requires Deltam(2)(nu) greater, similar (0.04 eV)(2).

Unified scenario for composite right-handed neutrinos and dark matter

Science.gov (United States)

Davoudiasl, Hooman; Giardino, Pier Paolo; Neil, Ethan T.; Rinaldi, Enrico

2017-12-01

We entertain the possibility that neutrino masses and dark matter (DM) originate from a common composite dark sector. A minimal effective theory can be constructed based on a dark S U (3 )D interaction with three flavors of massless dark quarks; electroweak symmetry breaking gives masses to the dark quarks. By assigning a Z2 charge to one flavor, a stable "dark kaon" can provide a good thermal relic DM candidate. We find that "dark neutrons" may be identified as right handed Dirac neutrinos. Some level of "neutron-anti-neutron" oscillation in the dark sector can then result in non-zero Majorana masses for light standard model neutrinos. A simple ultraviolet completion is presented, involving additional heavy S U (3 )D-charged particles with electroweak and lepton Yukawa couplings. At our benchmark point, there are "dark pions" that are much lighter than the Higgs and we expect spectacular collider signals arising from the UV framework. This includes the decay of the Higgs boson to τ τ ℓℓ', where ℓ(ℓ') can be any lepton, with displaced vertices. We discuss the observational signatures of this UV framework in dark matter searches and primordial gravitational wave experiments; the latter signature is potentially correlated with the H →τ τ ℓℓ' decay.

Neutrino mass, dark energy, and the linear growth factor

International Nuclear Information System (INIS)

Kiakotou, Angeliki; Lahav, Ofer; Elgaroey, Oystein

2008-01-01

We study the degeneracies between neutrino mass and dark energy as they manifest themselves in cosmological observations. In contradiction to a popular formula in the literature, the suppression of the matter power spectrum caused by massive neutrinos is not just a function of the ratio of neutrino to total mass densities f ν =Ω ν /Ω m , but also each of the densities independently. We also present a fitting formula for the logarithmic growth factor of perturbations in a flat universe, f(z,k;f ν ,w,Ω DE )≅[1-A(k)Ω DE f ν +B(k)f ν 2 -C(k)f ν 3 ]Ω m α (z), where α depends on the dark energy equation of state parameter w. We then discuss cosmological probes where the f factor directly appears: peculiar velocities, redshift distortion, and the integrated Sachs-Wolfe effect. We also modify the approximation of Eisenstein and Hu [Astrophys. J. 511, 5 (1999)] for the power spectrum of fluctuations in the presence of massive neutrinos and provide a revised code [http://www.star.ucl.ac.uk/∼lahav/nu m atter p ower.f].

The Use of Low Temperature Detectors for Direct Measurements of the Mass of the Electron Neutrino

Directory of Open Access Journals (Sweden)

A. Nucciotti

2016-01-01

Full Text Available Recent years have witnessed many exciting breakthroughs in neutrino physics. The detection of neutrino oscillations has proved that neutrinos are massive particles, but the assessment of their absolute mass scale is still an outstanding challenge in today particle physics and cosmology. Since low temperature detectors were first proposed for neutrino physics experiments in 1984, there has been tremendous technical progress: today this technique offers the high energy resolution and scalability required to perform competitive experiments challenging the lowest electron neutrino masses. This paper reviews the thirty-year effort aimed at realizing calorimetric measurements with sub-eV neutrino mass sensitivity using low temperature detectors.

Effect of atmospheric flux uncertainties on the determination of the neutrino mass hierarchy

Directory of Open Access Journals (Sweden)

Sandroos Joakim

2016-01-01

Full Text Available The next generation of large-volume neutrino telescopes will include low-energy subarrays which will be able to measure neutrinos with energies of a few GeV. In this energy range the primary signal below the horizon is neutrinos created by cosmic ray interactions in the atmosphere. The measured event rate will depend on the neutrino mass hierarchy, allowing determination of this quantity to a significance level of about 3.5 sigma within a 5-year period, mostly limited by systematic uncertainties. We present here the impact of the uncertainties on the atmospheric neutrino flux normalization on the determination of the neutrino mass hierarchy. We suggest constraining the systematic uncertainties by including the downgoing neutrino sample, which will increase the significance. This work was performed using simulation data from the low-energy extension to the IceCube detector located at the geographic south pole, PINGU, and is relevant to a wide range of other experiments.

Possibility of experimental detection of the Dirac-Schwinger heavy mass monopoles