45 research outputs found
Dealing with T and CPT violations in mixing as well as direct and indirect CP violations for neutral mesons decaying to two vectors
A large number of observables can be constructed from differential decay rate
based on the polarization of final state while considering decay of a neutral
meson to two vector particles. But all of these
observables are not independent to each other since there are only a few
independent theoretical parameters controlling the whole dynamics and therefore
various relations among observables emerge. In this paper, we have studied the
behaviour of observables for neutral meson decaying to two vectors in presence
of T and CPT violations in mixing accompanied by both direct and indirect CP
violations. We have expressed all of the fourteen unknown theoretical
parameters for this scenario in terms observables only and constructed the
complete set of thirty four relations among observables whose violation would
signify the existence of some new Physics involving direct violation of CPT. In
addition, using this formalism we have studied three special cases too: a) SM
scenario, b) SM plus direct CP violation c) SM plus T and CPT violation in
mixing.Comment: 28 page
Testing vertex in radiative muon decay
Large numbers of muons will be produced at facilities developed to probe
lepton flavor violating process . We show that by constructing
a suitable asymmetry, radiative muon decay
can also be used to test the vertex at such facilities. The process
has two missing neutrinos in the final state and on integrating their momenta,
the partial differential decay rate shows no radiation-amplitude-zero. We
establish, however, that an easily separable part of the normalized
differential decay rate, odd under the exchange of photon and electron
energies, does have a zero in the case of standard model (SM). This "new type
of zero" has hitherto not been studied in literature. A suitably constructed
asymmetry using this fact, enables a sensitive probe for the vertex
beyond the SM. With a simplistic analysis, we find that the and
conserving dimension four vertex can be probed at with satisfactory significance level.Comment: 9 pages, 4 figure
Using time-dependent indirect asymmetries to measure and violation in - mixing
Quantum field theory, which is the basis for all of particle physics,
requires that all processes respect invariance. It is therefore of
paramount importance to test the validity of conservation. In this
Letter, we show that the time-dependent, indirect asymmetries involving
decays to a eigenstate contain enough information to measure and
violation in - mixing, in addition to the standard
-violating weak phases. Entangled states are not required
(so that this analysis can be carried out at LHCb, as well as at the
factories), penguin pollution need not be neglected, and the measurements can
be made even if the - width difference vanishes.Comment: 10 pages, no figures, changes: removed almost all discussion of what
can and cannot be done with the method of entangled states; explained that
CPT- and T-violating parameters also contribute to CP-violating effects;
reorganized the presentation of the paper; added footnotes and reference
Updated global fit of the ATHDM with heavy scalars
An updated global fit on the parameter-space of the Aligned Two-Higgs-Doublet
model has been performed with the help of the open-source package
\texttt{HEPfit}, assuming the Standard-Model Higgs to be the lightest scalar.
No new sources of CP violation, other than the phase in the CKM matrix of the
Standard Model, have been considered. A similar global fit was previously
performed in Ref. \cite{Eberhardt:2020dat} with a slightly different set of
parameters. Our updated fit incorporates improved analyses of the theoretical
constraints required for positivity of the scalar potential and perturbative
unitarity, additional flavour observables and updated data on direct searches
of heavy scalars at the LHC, Higgs signal strengths and electroweak precision
observables. Although not included in the main fit, the implications of the CDF
measurement of the mass are also discussed.Comment: 41 pages, 15 figure
Constraining Scalar Doublet and Triplet Leptoquarks with Vacuum Stability and Perturbativity
We investigate the constraints on the leptoquark Yukawa couplings and
Higgs-leptoquark quartic couplings for scalar doublet leptoquark ,
scalar triplet leptoquark and their combination with both three
generations and one generation from perturbative unitarity and vacuum
stability. Perturbative unitarity of all the dimensionless couplings have been
studied via one- and two-loop beta-functions. Introduction of new
multiplets in terms of these leptoquarks fabricate Landau poles at two-loop
level in the gauge coupling at GeV and GeV,
respectively for and models with three
generations. However, such Landau pole ceases to exist for and
any of these extensions with both one and two generations till Planck scale.
The Higgs-leptoquark quartic couplings acquire severe constraints to protect
Planck scale perturbativity, whereas leptoquark Yukawa couplings get some upper
bound in order to respect Planck scale stability of Higgs Vacuum. The Higgs
quartic coupling at two-loop constraints the leptoquark Yukawa couplings for
with values with three generations. In the effective potential approach, the
presence of any of these leptoquarks with any number of generations pushes the
metastable vacuum of the Standard Model to the stable region.Comment: 45 pages, 56 figures, 2 table
Investigating the Production of Leptoquarks by Means of Zeros of Amplitude at Photon Electron Collider
Leptoquarks are one of the possible candidates for explaining various
anomalies in flavour physics. Nonetheless, their existence is yet to be
confirmed from experimental side. In this paper we have shown how zeros of
single photon tree-level amplitude can be used to extract information about
leptoquarks in case of - colliders. Small number of standard model
backgrounds keep the signal clean in this kind of colliders. Unlike other
colliders, the zeros of single photon amplitude here depend on as
well as the mass of leptoquark along with its electric charge. We perform a
PYTHIA based simulation for reconstructing the leptoquark from its decay
products of first generation and estimating the background with luminosity of
100 fb. Our analysis is done for all the leptoquarks that can be seen at
- collider with three different masses (70 GeV, 650 GeV and 1 TeV)
and three different centre of momentum energy (200 GeV, 2 TeV and 3 TeV). The
effects of non-monochromatic photons on the zeros of amplitude under laser
backscattering and equivalent photon approximation have also been addressed.Comment: 46 pages, 14 figures, 15 tables, accepted in EPJC. The effects of
non-monochromatic photons have been include