83 research outputs found
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
Left-Right Symmetry and the Charged Higgs Bosons at the LHC
The charged Higgs boson sector of the Minimal Manifest Left-Right Symmetric
model (MLRSM) is investigated in the context of LHC discovery search for new
physics beyond Standard Model. We discuss and summarise the main processes
within MLRSM where heavy charged Higgs bosons can be produced at the LHC. We
explore the scenarios where the amplified signals due to relatively light
charged scalars dominate against heavy neutral and charged gauge as
well as heavy neutral Higgs bosons signals which are dumped due to large vacuum
expectation value of the right-handed scalar triplet. In particular,
production processes with one and two doubly charged Higgs bosons are
considered. We further incorporate the decays of those scalars leading to multi
lepton signals at the LHC. Branching ratios for heavy neutrino , and
decay into charged Higgs bosons are calculated. These effects are
substantial enough and cannot be neglected. The tri- and four-lepton final
states for different benchmark points are analysed. Kinematic cuts are chosen
in order to strength the leptonic signals and decrease the Standard Model (SM)
background. The results are presented using di-lepton invariant mass and
lepton-lepton separation distributions for the same sign (SSDL) and opposite
sign (OSDL) di-leptons as well as the charge asymmetry are also discussed. We
have found that for considered MLRSM processes tri-lepton and four-lepton
signals are most important for their detection when compared to the SM
background. Both of the signals can be detected at 14 TeV collisions at the LHC
with integrated luminosity at the level of with doubly charged
Higgs bosons up to approximately 600 GeV. Finally, possible extra contribution
of the charged MLRSM scalar particles to the measured Higgs to di-photon
() decay is computed and pointed out.Comment: FCNC analysis is incorporated while fitting the scalar spectrum.
Light doubly charged scalars are still compatible with FCNC. Accepted in
JHEP. New References and figures are added. The fitted scalar spectrum is
given in detail in appendi
Naturalness, Vacuum Stability and Leptogenesis in the Minimal Seesaw Model
The right-handed neutrinos within the type-I seesaw mechanism can induce
large radiative corrections to the Higgs mass, and naturalness arguments can
then be used to set limits on their mass scale and Yukawa couplings. Driven by
minimality, we consider the presence of two degenerate right-handed neutrinos.
We compare the limits from naturalness with the ones from the stability of the
electroweak vacuum and from lepton flavor violation. Implications from
neutrinoless double beta decay are also discussed and renormalization effects
for the light neutrino parameters are presented. Adding small perturbations to
the degenerate heavy neutrino spectrum allows for successful leptogenesis.Comment: 22 pages, 11 figures; minor changes; version to appear in Phys. Rev.
Constraints on a seesaw model leading to quasidegenerate neutrinos and signatures at the LHC
We consider a variant of TeV scale seesaw models in which three additional
heavy right handed neutrinos are added to the standard model to generate the
quasi-degenerate light neutrinos. This model is theoretically interesting since
it can be fully rebuilt from the experimental data of neutrino oscillations
except for an unknown factor in the Dirac Yukawa coupling. We study the
constrains on this coupling coming from meta-stability of electro-weak vacuum.
Even stronger bound comes from the lepton flavor violating decays on this
model, especially in a heavy neutrino mass scenario which is within the
collider reach. Bestowed with these constrained parameters, we explore the
production and discovery potential coming from these heavy neutrinos at the
~TeV run of Large Hadron Collider. Signatures with tri-lepton final state
together with backgrounds are considered in a realistic simulation.Comment: v2: 21 pages, 5 figures, matches with published versio
Energy extraction from Janis-Newman-Winicour naked singularity
In general, energy extraction methods such as the Penrose process and the
magnetic Penrose process are thought to be reliant on the existence of an
ergoregion. Inside an ergoregion, there are negative energy states that allow a
particle to extract energy and escape to an observer at infinity. In this
paper, we considered the electromagnetic field in the rotating
Janis-Newman-Winicour (JNW) spacetime. This concept is feasible because an
accretion disc forms an electromagnetic field around compact objects. After
that, we briefly examine negative energy orbits and their significance in
energy extraction. The ergoregion is absent in a rotating JNW geometry, but we
show that the effective ergoregion is there. The change in a negative energy
orbit concerning the magnetic field (B), spin parameter (a), and electric
charge (Q) is analyzed. We find that the total energy extraction efficiency
within this process can be around for the rotating JNW naked
singularity.Comment: 11 pages, 18 figure
Naked Singularity as a Possible Source of Ultra-High Energy Cosmic Rays
The source of Ultra-High Energy Cosmic Rays (UHECRs) remains one of the
greatest mysteries in astrophysics. Their possible source can be the galactic
nuclei, where the ultra-high gravity region plays a crucial role. Cosmic rays
are extremely energetic particles that travel through space with energies
exceeding , but their origin is still a mystery despite years of
studies and observations. In view of this, in this work, we studied the
Joshi-Malafarina-Narayan (JMN-1) naked singularity as a natural particle
accelerator. We derived the necessary expressions to find center of mass energy
when two particles collide. We have obtained results showing that center of
mass energy of the two particles will reach to Planck energy scale. This will
form a microscopic black hole which will decay in Hawking radiation, having
energy on the order of from the ultra-high gravity region of Sgr
A*. These outgoing highly energetic particles from the naked singularity could
be the possible sources of UHECRs.Comment: 11 pages, 7 figure
NUMERICAL TRANSIENT HEAT TRANSFER ANALYSIS OF REACTOR FOR MAGNESIUM BASED ALLOY FOR HYDROGEN STORAGE APPLICATION
Metal hydrides are potential hydrogen storage media. They release hydrogen at moderate temperatures and pressures. Magnesium hydride is a promising approach for stationary power system application, due to high hydrogen storage capacity by weight. Magnesium hydride based reactor design is more complex due to high thermal energy release and absorption during hydriding reaction and dehydriding reaction, respectively. In this study, results of a numerical modeling study are presented for a 1.5 kg Magnesium alloy based hydriding reactor. Temperature profile in the reactor is computed by FEM analysis using ANSYS software for hydriding and dehydriding reaction. FEM analysis indicates that the reactor temperature is raised from 200 C to 422 ºC in 20 minutes during the hydriding process. Hence, a “cooling system” is required for maintaining temperature during the hydriding process. During the dehydriding process, maximum temperature drop occurs from 350 C to 189 ºC in 20 minutes. Therefore, an external heat source of 2 kW is required for maintaining the temperature during dehydriding. Details are presented
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