11 research outputs found
Baseline-dependent neutrino oscillations with extra-dimensional shortcuts
In extra-dimensional scenarios oscillations between active and sterile
neutrinos can be governed by a new resonance in the oscillation amplitude. This
resonance results when cancelation occurs between two phase differences, the
usual kinematic one coming from the neutrino mass-squared difference, and a
geometric one coming from the difference in travel times of the sterile
neutrino through the bulk relative to the active neutrino confined to the
brane. In this work we introduce a specific metric for the brane-bulk system,
from which we explicitly derive extra-dimensional geodesics for the sterile
neutrino, and ultimately the oscillation probability of the active-sterile
two-state system. We find that for an asymmetrically-warped metric, the
resonance condition involves both the neutrino energy E and the travel distance
L on the brane. In other words, the resonant energy may be viewed as
baseline-dependent. We show that to a good approximation, the resonance
condition is not on E or on L, but rather on the product LE. The model is rich
in implications, including the possibility of multiple solutions to the
resonance condition, with ramifications for existing data sets, e.g., LSND and
MiniBooNE. Some phenomenology with these brane-bulk resonances is discussed.Comment: 20 pages, 5 figure
Closed timelike curves in asymmetrically warped brane universes
In asymmetrically warped spacetimes different warp factors are assigned to
space and to time. We discuss causality properties of these warped brane
universes and argue that scenarios with two extra dimensions may allow for
timelike curves which can be closed via paths in the extra-dimensional bulk. In
particular, necessary and sufficient conditions on the metric for the existence
of closed timelike curves are presented. We find a six-dimensional warped
metric which satisfies the CTC conditions, and where the null, weak and
dominant energy conditions are satisfied on the brane (although only the former
remains satisfied in the bulk). Such scenarios are interesting, since they open
the possibility of experimentally testing the chronology protection conjecture
by manipulating on our brane initial conditions of gravitons or hypothetical
gauge-singlet fermions (sterile neutrinos) which then propagate in the extra
dimensions.Comment: 24 pages, 2 figures; major corrections: CTC metric generalized from
5D to 6D, the new 6D metric satisfies the conclusions attributed
(incorrectly) to the 5D metric in v
Causality-Violating Higgs Singlets at the LHC
We construct a simple class of compactified five-dimensional metrics which
admits closed timelike curves (CTCs), and derive the resulting CTCs as analytic
solutions to the geodesic equations of motion. The associated Einstein tensor
satisfies all the null, weak, strong and dominant energy conditions. In
particular, no negative-energy "tachyonic" matter is required. In
extra-dimensional models where gauge charges are bound to our brane, it is the
Kaluza-Klein (KK) modes of gauge-singlets that may travel through the CTCs.
From our brane point of view, many of these KK modes would appear to travel
backward in time. We give a simple model in which time-traveling Higgs singlets
can be produced by the LHC, either from decay of the Standard Model (SM) Higgs
or through mixing with the SM Higgs. The signature of these time-traveling
singlets is a secondary decay vertex pre-appearing before the primary vertex
which produced them. The two vertices are correlated by momentum conservation.
We demonstrate that pre-appearing vertices in the Higgs singlet-doublet mixing
model may well be observable at the LHC.Comment: 55 pages, 5 figures, v4: Version updated to include in single
manuscript the contents of Erratum [Phys. Rev. D 88, 069901(E) (2013)], Reply
[Phys. Rev. D 88, 068702 (2013)], Comment [Phys. Rev. D 88, 068701 (2013),
arXiv:1302.1711], and original published article [Phys. Rev. D 87, 045004
(2013), arXiv:1103.1373]. Positive conclusions remain unchange
Recommended from our members
The Kemmer-Duffin-Petiau formalism and intermediate-energy deuteron-nucleus scattering
The spin-1 Kemmer-Duffin-Petiau (KDP) equations are described and applied to deuteron-nucleus scattering. Comparison with d + /sup 58/Ni elastic scattering data at 400 MeV shows that the KDP model; reproduces experimental spin observables very well. 11 refs., 1 fig
Sterile-active neutrino oscillations and shortcuts in the extra dimension
We discuss a possible new resonance in active-sterile neutrino oscillations
arising in theories with large extra dimensions. Fluctuations in the brane
effectively increase the path-length of active neutrinos relative to the
path-length of sterile neutrinos through the extra-dimensional bulk. Well below
the resonance, the standard oscillation formulas apply. Well above the
resonance, active-sterile oscillations are suppressed. We show that a resonance
energy in the range of 30-400 MeV allows an explanation of all neutrino
oscillation data, including LSND data, in a consistent four-neutrino model. A
high resonance energy implies an enhanced signal in MiniBooNE. A low resonance
energy implies a distorted energy spectrum in LSND, and an enhanced v_mu
depletion from a stopped-pion source. The numerical value of the resonance
energy may be related back to the geometric aspects of the brane world. Some
astrophysical and cosmological consequences of the brane-bulk resonance are
briefly sketched.Comment: 26 pages, 6 figures, predictions for v_mu disappearance at SNS added,
version to appear in PR