50 research outputs found
Testing the Principle of Equivalence by Solar Neutrinos
We discuss the possibility of testing the principle of equivalence with solar
neutrinos. If there exists a violation of the equivalence principle quarks and
leptons with different flavors may not universally couple with gravity. The
method we discuss employs a quantum mechanical phenomenon of neutrino
oscillation to probe into the non-universality of the gravitational couplings
of neutrinos. We develop an appropriate formalism to deal with neutrino
propagation under the weak gravitational fields of the sun in the presence of
the flavor mixing. We point out that solar neutrino observation by the next
generation water Cherenkov detectors can improve the existing bound on
violation of the equivalence principle by 3-4 orders of magnitude if the
nonadiabatic Mikheyev-Smirnov-Wolfenstein mechanism is the solution to the
solar neutrino problem.Comment: Latex, 17 pages + 6 uuencoded postscript figures, KEK-TH-396,
TMUP-HEL-9402 (unnecessary one reference was removed
A Two-Dimensional Model with Chiral Condensates and Cooper Pairs Having QCD-like Phase Structure
We describe how a generalization of the original Gross-Neveu model from U(N)
to O(N) flavor symmetry leads to the appearance of a pairing condensate at high
density, in agreement with the conjectured phenomenon of color
superconductivity in -dimensional QCD. Moreover, the model displays a
rich phase structure which closely resembles the one expected in two-flavor
QCD.Comment: 11 pages, 1 fugure, Presented at TMU-Yale Symposium on Dynamics of
Gauge Fields: An External Activity of APCTP, Tokyo, Japan, 13-15 Dec 199
Dynamical Pion Production via Parametric Resonance from Disoriented Chiral Condensate
We discuss a dynamical mechanism of pion production from disoriented chiral
condensates (DCC). It leads to an explosive production of pions via the
parametric amplification mechanism, which is similar to the reheating mechanism
in inflationary cosmology. Classically, it is related with the instability in
the solutions of the Mathieu equation and we explore the quantum aspects of the
mechanism. We show that nonlinearlities and back reactions can be ignorable for
sufficiently long time under the small amplitude approximations of background
oscillations, which may be appropriate for the late stage of
nonequilibrium phase transition. It allows us to obtain an explicit quantum
state of the produced pions and , the squeezed state of BCS type.
Single particle distributions and two-pion correlation functions are computed
within these approximations. The results obtained illuminate the characteristic
features of multi-pion states produced through the parametric amplification
mechanism. In particular, two-pion correlations of various charge combinations
contain back-to-back correlations which cannot be masked by the identical
particle interference effect.Comment: REVTEX 18 pages and 10 figure
Unity of CP and T Violation in Neutrino Oscillations
In a previous work a simultaneous P- CP[P] and P- T[P] bi-probability plot
was proposed as a useful tool for unified graphical description of CP and T
violation in neutrino oscillation. The ``baseball diamond'' structure of the
plot is understood as a consequence of the approximate CP-CP and the T-CP
relations obeyed by the oscillation probabilities. In this paper, we make a
step forward toward deeper understanding of the unified graphical
representation by showing that these two relations are identical in its
content, suggesting a truly unifying view of CP and T violation in neutrino
oscillations. We suspect that the unity reflects the underlying CPT theorem. We
also present calculation of corrections to the CP-CP and the T-CP relations to
leading order in Delta m^2_{21} / Delta m^2_{31} and s^2_{13}.Comment: 20 references added, version to appear in "Focus Issue on Neutrino
Physics" of New Journal of Physic
Large-Theta(13) Perturbation Theory of Neutrino Oscillation for Long-Baseline Experiments
The Cervera et al. formula, the best known approximate formula of neutrino
oscillation probability for long-baseline experiments, can be regarded as a
second-order perturbative formula with small expansion parameter epsilon \equiv
Delta m^2_{21} / Delta m^2_{31} \simeq 0.03 under the assumption s_{13} \simeq
epsilon. If theta_{13} is large, as suggested by a candidate nu_{e} event at
T2K as well as the recent global analyses, higher order corrections of s_{13}
to the formula would be needed for better accuracy. We compute the corrections
systematically by formulating a perturbative framework by taking theta_{13} as
s_{13} \sim \sqrt{epsilon} \simeq 0.18, which guarantees its validity in a wide
range of theta_{13} below the Chooz limit. We show on general ground that the
correction terms must be of order epsilon^2. Yet, they nicely fill the mismatch
between the approximate and the exact formulas at low energies and relatively
long baselines. General theorems are derived which serve for better
understanding of delta-dependence of the oscillation probability. Some
interesting implications of the large theta_{13} hypothesis are discussed.Comment: Fig.2 added, 23 pages. Matches to the published versio
Parameter Degeneracies in Neutrino Oscillation Measurement of Leptonic CP and T Violation
The measurement of the mixing angle \theta_{13}, sign of \Delta m^2_{13} and
the CP or T violating phase \delta is fraught with ambiguities in neutrino
oscillation. In this paper we give an analytic treatment of the paramater
degeneracies associated with measuring the \nu_\mu -> \nu_e probability and its
CP and/or T conjugates. For CP violation, we give explicit solutions to allow
us to obtain the regions where there exist two-fold and four-fold degeneracies.
We calculate the fractional differences, \Delta \theta / \bar{\theta}, between
the allowed solutions which may be used to compare with the expected
sensitivities of the experiments. For T violation we show that there is always
a complete degeneracy between solutions with positive and negative \Delta
m^2_{13} which arises due to a symmetry and cannot be removed by observing one
neutrino oscillation probability and its T conjugate. Thus, there is always a
four fold parameter degeneracy apart from exceptional points. Explicit
solutions are also given and the fractional differences are computed. The
bi-probability CP/T trajectory diagrams are extensively used to illuminate the
nature of the degeneracies.Comment: 35 pages, Latex, 11 postscript figures, minor correction
Recoilless Resonant Absorption of Monochromatic Neutrino Beam for Measuring Delta m^2_{31} and theta_{13}
We discuss, in the context of precision measurement of Delta m^2_{31} and
theta_{13}, physics capabilities enabled by the recoilless resonant absorption
of monochromatic antineutrino beam enhanced by the M\"ossbauer effect recently
proposed by Raghavan. Under the assumption of small relative systematic error
of a few tenth of percent level between measurement at different detector
locations, we give analytical and numerical estimates of the sensitivities to
Delta m^2_{31} and sin^2 2theta_{13}. The accuracies of determination of them
are enormous; The fractional uncertainty in Delta m^2_{31} achievable by 10
point measurement is 0.6% (2.4%) for sin^2 2theta_{13} = 0.05, and the
uncertainty of sin^2 2theta_{13} is 0.002 (0.008) both at 1 sigma CL with the
optimistic (pessimistic) assumption of systematic error of 0.2% (1%). The
former opens a new possibility of determining the neutrino mass hierarchy by
comparing the measured value of Delta m^2_{31} with the one by accelerator
experiments, while the latter will help resolving the theta_{23} octant
degeneracy.Comment: 23 pages, 3 figures, version to appear in New Journal of Physic
High Energy Cosmic Neutrinos and the Equivalence Principle
Observation of the ultra-high energy neutrinos, in particular, detection of
from cosmologically distant sources like active galactic nuclei
(AGN) opens new possibilities to search for neutrino flavor conversion. We
consider effects of violation of the equivalence principle (VEP) on propagation
of these cosmic neutrinos. Two effects are studied: (1) the oscillations of
neutrinos due to the VEP in the gravitational field of our Galaxy and in the
intergalactic space, (2) the resonance flavor conversion driven by the
gravitational potential of the AGN. We show that the ultra-high energies of the
neutrinos as well as cosmological distances to the AGN, or strong AGN
gravitational potential will allow one to improve the accuracy of test of the
equivalence principle by 21 orders of magnitude for massless or degenerate
neutrinos () and at least by 12 orders of magnitude for
massive neutrinos ().
Experimental signatures of the transitions induced by the VEP are discussed.Comment: 24 pages, revtex, no figures, slightly revised with no change in
conclusio
CP violation effects and high energy neutrinos
This work discusses critically the prospects of measuring CP and T violation
effects in high energy neutrino factories. For this purpose we develop, in the
standard framework with three neutrino flavors, simple expressions for the
oscillation probabilities in matter that are valid for high E_nu. All CP
violating effects vanish as E_nu^(-3) and are very difficult to detect with
high energy neutrinos. A significantly easier task is the determination of the
absolute value |delta| of the phase in the neutrino mixing matrix that controls
the CP and T violation effects, performing precision measurements of the CP and
T conserving part of the oscillation probabilities.Comment: Latex, 46 pages, 15 figure