5,809 research outputs found
TeV Scale Left-Right Symmetry and Large Mixing Effects in Neutrinoless Double Beta Decay
We analyze various contributions to neutrinoless double beta decay
() in a TeV-scale Left-Right Symmetric Model (LRSM) for type-I
seesaw dominance. We find that the momentum-dependent effects due to
exchange (-diagram) and mixing (-diagram) could give
dominant contributions to the amplitude in a wide range of the
LRSM parameter space. In particular, for a relatively large mixing,
the -contribution by itself could saturate the current experimental limit
on the half-life, thereby providing stringent constraints on
the relevant LRSM parameters, complementary to the indirect constraints derived
from lepton flavor violating observables. In a simplified scenario parametrized
by a single light-heavy neutrino mixing, the inclusion of the and
contributions leads to significantly improved
constraints on the light-heavy neutrino mixing as well as on the
mixing parameters. We also present a concrete TeV-scale LRSM setup, where the
mixing effects are manifestly enhanced, and discuss the interplay between
, lepton flavor violation and electric dipole moment
constraints.Comment: 33 pages, 7 figures, 2 table
Laser phase modulation approaches towards ensemble quantum computing
Selective control of decoherence is demonstrated for a multilevel system by
generalizing the instantaneous phase of any chirped pulse as individual terms
of a Taylor series expansion. In the case of a simple two-level system, all odd
terms in the series lead to population inversion while the even terms lead to
self-induced transparency. These results also hold for multiphoton transitions
that do not have any lower-order photon resonance or any intermediate virtual
state dynamics within the laser pulse-width. Such results form the basis of a
robustly implementable CNOT gate.Comment: 10 pages, 4 figures, PRL (accepted
On trapped surface formation in gravitational collapse II
Further to our consideration on trapped surfaces in gravitational collapse,
where pressures were allowed to be negative while satisfying weak energy
condition to avoid trapped surface formation, we discuss here several other
attempts of similar nature in this direction. Certain astrophysical aspects are
pointed out towards examining the physical realization of such a possibility in
realistic gravitational collapse
Constraining Neutrino Mass from Neutrinoless Double Beta Decay
We re-analyze the compatibility of the claimed observation of neutrinoless
double beta decay () in Ge with the new limits on the
half-life of Xe from EXO-200 and KamLAND-Zen. Including recent
calculations of the nuclear matrix elements (NMEs), we show that while the
claim in Ge is still compatible with the individual limits from
Xe, it is inconsistent with the KamLAND-Zen+EXO-200 combined limit for
all but one NME calculations. After imposing the most stringent upper limit on
the sum of light neutrino masses from Planck, we find that the canonical light
neutrino contribution cannot satisfy the claimed signature or
saturate the current limit, irrespective of the NME uncertainties. However,
inclusion of the heavy neutrino contributions, arising naturally in TeV-scale
Left-Right symmetric models, can saturate the current limit of
. In a type-II seesaw framework, this imposes a lower limit on
the lightest neutrino mass. Depending on the mass hierarchy, we obtain this
limit to be in the range of 0.07 - 4 meV for a typical choice of the
right-handed (RH) gauge boson and RH neutrino masses relevant for their
collider searches. Using the bounds, we also derive correlated
constraints in the RH sector, complimentary to those from the LHC.Comment: 6 pages, 4 figures, 3 tables; updated version including GERDA
results; Figure 4 and Tables II and III adde
The Scalar Triplet Contribution to Lepton Flavour Violation and Neutrinoless Double Beta Decay in Left-Right Symmetric Model
We analyse in detail the scalar triplet contribution to the low-energy lepton
flavour violating (LFV) and lepton number violating (LNV) processes within a
TeV-scale left-right symmetric framework. We show that in both type-I and
type-II seesaw dominance for the light neutrino masses, the triplet of mass
comparable to or smaller than the largest right-handed neutrino mass scale can
give sizeable contribution to the LFV processes, except in the quasi-degenerate
limit of light neutrino masses, where a suppression can occur due to
cancellations. In particular, a moderate value of the heaviest neutrino to
scalar triplet mass ratio is still experimentally
allowed and can be explored in the future LFV experiments. Similarly, the
contribution of a relatively light triplet to the LNV process of neutrinoless
double beta decay could be significant, disfavouring a part of the model
parameter space otherwise allowed by LFV constraints. Nevertheless, we find
regions of parameter space consistent with both LFV and LNV searches, for which
the values of the total effective neutrino mass can be accessible to the next
generation ton-scale experiments. Such light triplets can also be directly
searched for at the LHC, thus providing a complementary probe of this scenario.
Finally, we also study the implications of the triplet contribution for the
left-right symmetric model interpretation of the recent diboson anomaly at the
LHC.Comment: 28 pages, 17 figures; minor changes, version to appear in JHE
Solar neutrinos and 1-3 leptonic mixing
Effects of the 1-3 leptonic mixing on the solar neutrino observables are
studied and the signatures of non-zero are identified. For this
we have re-derived the formula for -survival probability including all
relevant corrections and constructed the iso-contours of observables in the
plane. Analysis of the solar neutrino
data gives (90% C.L.) for
eV. The combination of the ratio CC/NC at
SNO and gallium production rate selects
(). The global fit of all oscillation data leads to zero best value of
. The sensitivity ( error) of future solar
neutrino studies to can be improved down to 0.01 - 0.02 by
precise measurements of the pp-neutrino flux and the CC/NC ratio as well as
spectrum distortion at high ( MeV) energies. Combination of experimental
results sensitive to the low and high energy parts of the solar neutrino
spectrum resolves the degeneracy of angles and .
Comparison of as well as measured in
the solar neutrinos and in the reactor/accelerator experiments may reveal new
effects which can not be seen otherwise.Comment: 36 pages, latex, 10 figures. Analysis and figures are updated with
new (salt phase II) SNO results, several clarifications added, typos
correcte
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