共查询到20条相似文献,搜索用时 625 毫秒
1.
A. E. Bernardini 《International Journal of Theoretical Physics》2007,46(6):1562-1569
We shall proceed with the construction of normalizable Dirac wave packets for fermionic particles (neutrinos) with dynamics governed by a “modified” Dirac equation with a non-minimal coupling with an external
magnetic field. We are not only interested on the analytic solutions of the “modified” Dirac wave equation but also on the
construction of Dirac wave packets which can be used for describing the dynamics of some observable physical quantities which
are relevant in the context of the quantum oscillation phenomena. To conclude, we discuss qualitatively the applicability
of this formal construction in the treatment of chiral (and flavor) oscillations in the theoretical context of neutrino physics.
PACS numbers: 02.30.Cj, 03.65.Pm 相似文献
2.
3.
Kh. M. Beshtoev 《Physics of Particles and Nuclei Letters》2009,6(5):397-402
Usually it is supposed that Majorana neutrino produced in the superposition state χ
L
= ν
L
+ (ν
L
)
c
and then follows the neutrinoless double beta decay. But since the standard weak interactions are chiral invariant then neutrino
at production has definite helicity (ν
L
and (ν
L
)
c
have opposite spirality). Then these neutrinos are separately produced and their superposition state cannot appear. Thus
we see that for unsuitable helicity the neutrinoless double β decay is not possible even if it is supposed that neutrino is
a Majorana particle (i.e. there is not a lepton number which is conserved). Also transition of Majorana neutrino ν
L
into antineutrino (ν
L
)
c
at their oscillations is forbidden since helicity in vacuum holds. Transition Majora neutrino ν
L
into (ν
R
)
c
(i.e., ν
L
→ (ν
R
)
c
) at oscillations is unobserved since it is supposed that mass of (ν
R
)
c
is very big. If neutrino is a Dirac particle there can be transition of ν
L
neutrino into (sterile) antineutrino $
\bar v_R
$
\bar v_R
(i.e., ν
L
→ $
\bar v_R
$
\bar v_R
) at neutrino oscillations if there takes place double violation of lepton number. It is necessary also to remark that introducing
of a Majorana neutrino implies violation of global and local gauge invariance in the standard weak interactions. 相似文献
4.
5.
Neutrinos with magnetic moment experience chirality flips while scattering off charged particles. It is known that if neutrino
is a Dirac fermion, then such chirality flips lead to the production of sterile right-handed neutrinos inside the core of
a star during the stellar collapse, which may facilitate the supernova explosion and modify the supernova neutrino signal.
In the present paper we reexamine the production of right-handed neutrinos during the collapse using a dynamical model of
the collapse. We refine the estimates of the values of the Dirac magnetic moment which are necessary to substantially alter
the supernova dynamics and neutrno signal. It is argued in particular that Super-Kamiokande will be sensitive at least to
μ
ν Dirac = 10−13μB in case of a galactic supernova explosion. Also we briefly discuss the case of Majorana neutrino magnetic moment. It is pointed
out that in the inner supernova core spin flips may quickly equilibrate electron neutrinos with nonelectron antineutrinos
if μ
ν Majorana ≳ 10−12μB. This may lead to various consequences for supernova physics. 相似文献
6.
Kh. M. Beshtoev 《Physics of Particles and Nuclei Letters》2007,4(6):471-476
In the standard theory of neutrino oscillations, it is supposed that physically observed neutrino states ν
e
, νμ, ντ, have no definite masses, that they are initially produced as a mixture of the ν1, ν2, ν3 neutrino states (i.e., they are produced as a wave packet), and that neutrino oscillations are the real ones. Then, this
wave packet must decompose at a definite distance into constituent parts and neutrino oscillations must disappear. It was
shown that these suppositions lead to violation of the law of energy and momentum conservation. An alternative scheme of neutrino
oscillations obtained within the framework of particle physics has been considered, where the above mentioned shortcomings
are absent, the oscillations of neutrinos with equal masses are the real ones, and the oscillations of neutrinos with different
masses are the virtual ones. Expressions for probabilities of neutrino transitions (oscillations) in the alternative (corrected)
scheme are given.
The text was submitted by the author in English. 相似文献
7.
Y. Koide 《The European Physical Journal C - Particles and Fields》2007,52(3):617-623
Stimulated by Ma’s idea, which explains the tribimaximal neutrino mixing by assuming an A4 flavor symmetry, a lepton mass matrix model is investigated. A Frogatt–Nielsen-type model is assumed, and the flavor structures
of the masses and mixing are caused by the VEVs of SU(2)L singlet scalars φi
u and φi
d (i=1,2,3), which are assigned to 3
and (1
,1
’,1
”) of A4, respectively. Possible charged lepton and neutrino mass spectra and mixing are investigated. 相似文献
8.
A covariant theory of wave packets and its application to the quantum field method of calculation of the probabilities of
neutrino oscillations in vacuum that is based on the technique of macroscopic Feynman diagrams, which describe the processes
of emission and absorption of virtual massive neutrinos ν
i
(i = 1, 2, 3) at macroscopicly separated space-time points, is considered. The effect of flavor oscillations is reduced to an
interference of amplitudes with different vi in an intermediate state. A macroscopic amplitude is calculated that describes
a class of processes which go with nonconservation of leptonic numbers, and statistical averaging of the squared modulus of
this amplitude is performed. The averaged probability of a process with ultrarelativistic neutrino exchange is representable
in the form of an integral of the product of three factors: the flux of massless neutrinos from the source, the differential
cross-section for the interaction of a neutrino with the detector, and a dimensionless factor that describes the flavor transition.
The conditions under which the last factor can be interpreted as the probability of the flavor transition in the conventional
quantummechanical sense are analyzed. 相似文献
9.
10.
Bipin Singh Koranga P. Gaira Vinod Kumar 《International Journal of Theoretical Physics》2011,50(2):413-417
We study the Planck scale effects in the neutrino sector on the asymmetry between T-conjugate oscillation probabilities. ΔP
T
=P(ν
α
→ν
β
)−P(ν
β
→ν
α
), in a three flavor neutrino mixing. In this paper, we discuss some aspect of T violation effects in three flavor neutrino
oscillation. 相似文献
11.
Despite the theory of neutrino oscillations being rather old, some of its basic issues are still being debated in the literature.
We discuss a number of such issues, including the relevance of the “same energy” and “same momentum” assumptions, the role
of quantum-mechanical uncertainty relations in neutrino oscillations, the dependence of the coherence and localization conditions
that ensure the observability of neutrino oscillations on neutrino energy and momentum uncertainties, the question of (in)dependence
of the oscillation probabilities on the neutrino production and detection processes, and the applicability limits of the stationary-source
approximation. We also develop a novel approach to calculation of the oscillation probability in the wave-packet approach,
based on the summation/integration conventions different from the standard one, which allows a new insight into the “same
energy” vs. “same momentum” problem. We also discuss a number of apparently paradoxical features of the theory of neutrino
oscillations.
The text was submitted by the authors in English. 相似文献
12.
In the framework of quantum field theory, we consider the way to construct the one-particle state (with definite 3-momentum)
when particle mixing exists, such as in the case of flavor-neutrino mixing. In the preceding report (Prog. Theor. Phys. 112, 901 (2004)), we have examined the structure of expectation values of the flavor neutrino charges (at time t) with respect to a neutrino-source state prepared at time t′ (earlier than t). When there is no mixing, each of various contributions to the expectation value is equal, in its dominant part, to the
transition probability corresponding to the respective neutrino-production process. On the basis of the assumption that such
an equality holds also in the mixing case, we can find an appropriate form of one-flavor-neutrino state with 3-momentum and
helicity. Along the same way, we examine the boson case when flavor mixing exists. We give remarks on the relation and difference
between the ordinary and the present approaches to flavor oscillation.
The text was submitted by the authors in English. 相似文献
13.
In the standard treatment of particle oscillations the mass eigenstates are implicitly assumed to be scalars and, consequently, the spinorial form of the neutrino wave functions is not included in the calculations. To analyze this additional effect, we discuss the oscillation probability formula obtained by using the Dirac equation as evolution equation for the neutrino mass eigenstates. The initial localization of the spinor state also implies an interference between positive and negative energy components of mass eigenstate wave packets which modifies the standard oscillation probability.Received: 8 April 2004, Revised: 12 July 2004, Published online: 20 October 2004 相似文献
14.
A.K. Sarma 《The European Physical Journal C - Particles and Fields》2006,48(2):625-626
We point out a possible way to settle the issue of the Dirac neutrino mass hierarchy. Constraining the observed baryon asymmetry to the normal hierarchy mass model within the seesaw framework, we look for the possible structure of coveted Dirac neutrino masses. We have found the possible structure of the Dirac neutrino masses to be (λ7,λ2,1)v in terms of the parameter λ=0.3, with v as an overall scale factor. PACS 11.30.Er; 11.30.Fs; 13.35.Hb; 14.60.Pq 相似文献
15.
Wei Liao 《The European Physical Journal C - Particles and Fields》2008,57(4):763-768
We consider the non-standard matter effect in flavor conversion of neutrinos crossing the core of the Earth. We show that
oscillations of core-crossing neutrinos with E≳0.5 GeV can well be described by first order perturbation theory. We show that due to the non-standard matter effect a varying
chemical composition in the Earth can modify the neutrino flavor conversion by 100%. The effects of CP violating phases in
non-standard neutral current interactions are emphasized in particular. 相似文献
16.
Maury Goodman 《Pramana》2004,62(2):229-240
Following incredible recent progress in understanding neutrino oscillations, many new ambitious experiments are being planned
to study neutrino properties. The most important may be to find a non-zero value of θ13. The most promising way to do this appears to be to measurev
μ →v
e oscillations with anE/L near Δm
atmo
2
. Future neutrino experiments are great. 相似文献
17.
Mattias Blennow Davide Meloni Tommy Ohlsson Francesco Terranova Mattias Westerberg 《The European Physical Journal C - Particles and Fields》2008,56(4):529-536
We investigate the implications of non-standard interactions on neutrino oscillations in the OPERA experiment. In particular,
we study the non-standard interaction parameter ε
μ
τ
. We show that the OPERA experiment has a unique opportunity to reduce the allowed region for this parameter compared with
other experiments such as the MINOS experiment, mostly due to the higher neutrino energies in the CNGS beam compared to the
NuMI beam. We find that OPERA is mainly sensitive to a combination of standard and non-standard parameters and that a resulting
anti-resonance effect could suppress the expected number of events. Furthermore, we show that running OPERA for five years
each with neutrinos and anti-neutrinos would help in resolving the degeneracy between the standard parameters and ε
μ
τ
. This scenario is significantly better than the scenario with a simple doubling of the statistics by running with neutrinos
for ten years. 相似文献
18.
We consider several subtle aspects of the theory of neutrino oscillations which have been under discussion recently. We show
that the S-matrix formalism of quantum field theory can adequately describe neutrino oscillations if correct physics conditions are
imposed. This includes space-time localization of the neutrino production and detection processes. Space-time diagrams are
introduced, which characterize this localization and illustrate the coherence issues of neutrino oscillations. We discuss
two approaches to calculations of the transition amplitudes, which allow different physics interpretations: (i) using configuration-space
wave packets for the involved particles, which leads to approximate conservation laws for their mean energies and momenta;
(ii) calculating first a plane-wave amplitude of the process, which exhibits exact energy-momentum conservation, and then
convoluting it with the momentum-space wave packets of the involved particles. We show that these two approaches are equivalent.
Kinematic entanglement (which is invoked to ensure exact energy-momentum conservation in neutrino oscillations) and subsequent
disentanglement of the neutrinos and recoiling states are in fact irrelevant when the wave packets are considered. We demonstrate
that the contribution of the recoil particle to the oscillation phase is negligible provided that the coherence conditions
for neutrino production and detection are satisfied. Unlike in the previous situation, the phases of both neutrinos from Z
0 decay are important, leading to a realization of the Einstein-Podolsky-Rosen paradox. 相似文献
19.
J. Ellis G.K. Leontaris S. Lola D.V. Nanopoulos 《The European Physical Journal C - Particles and Fields》1999,9(3):389-408
Motivated by the Super-Kamiokande atmospheric neutrino data, we discuss possible textures for Majorana and Dirac neutrino
masses within the see-saw framework. There are two main purposes of this paper: first, to gain intuition into this area from
a purely phenomenological analysis, and second, to explore to what extent it may be realized in a specific model. We comment
initially on the simplified two-generation case, emphasizing that large mixing is not incompatible with a large hierarchy
of mass eigenvalues. We also emphasize that renormalization-group effects may amplify neutrino mixing, and we present semi-analytic
expressions for estimating this amplification. Several examples are then given of three-family neutrino mass textures, which
may also accommodate the persistent solar neutrino deficit, with different assumptions for the neutrino Dirac mass matrices.
We comment on a few features of neutrino mass textures arising in models with a U(1) flavour symmetry. Finally, we discuss the possible pattern of neutrino masses in a “realistic” flipped SU(5) model derived from string theory, illustrating how a desirable pattern of mixing may emerge. Both small- or large-angle
MSW solutions are possible, while a hierarchy of neutrino masses appears more natural than near-degeneracy. This model contains
some unanticipated features that may be relevant in other models also: The neutrino Dirac matrices may not be related closely
to the quark mass matrices, and the heavy Majorana states may include extra gauge-singlet fields.
Received: 6 November 1998 / Published online: 18 June 1999 相似文献
20.
A SU(2)
H
symmetric variant of Zee model of lepton flavor 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. 相似文献