152 research outputs found
Beam polarization effects in the radiative production of lightest neutralinos in collisions in supersymmetric grand unified models
We study the production of the lightest neutralinos in the process in supersymmetric grand unified models
for the International Linear Collider Energies with longitudinally polarized
beams. We consider cases where the standard model gauge group is unified into
the grand unified gauge groups SU(5), or SO(10). We have carried out a
comprehensive study of this process in the SU(5) and SO(10) grand unified
theories which includes the QED radiative corrections. We compare and contrast
the dependence of the signal cross section on the grand unified gauge group,
and on the different representations of the grand unified gauge group, when the
the electron and positron beams are longitudinally polarized. To assess the
feasibility of experimentally observing the radiative production process, we
have also considered in detail the background to this process coming from the
radiative neutrino production process
with longitudinally polarized electron and positron beams. In addition we have
also considered the supersymmetric background coming from the radiative
production of scalar neutrinos in the process with longitudinally polarized beams. The process can be a
major background to the radiative production of neutralinos when the scalar
neutrinos decay invisibly.Comment: 26 pages, 18 figures; typos and misprints corrected; results and
conclusions unchanged; this paper is a sequel to and draws material from the
paper arXiv:1210.647
Distinguishing Signatures of top-and bottom-type heavy vectorlike quarks at the LHC
An SU(2) vectorlike singlet quark with a charge either +2/3 (t') or -1/3 (b')
is predicted in many extensions of the Standard Model. The mixing of these
quarks with the top or bottom lead to Flavor Changing Yukawa Interactions and
Neutral Current. The decay modes of the heavier mass eigenstates are therefore
different from the Standard Model type chiral quarks. The Large Hadron Collider
(LHC) will provide an ideal environment to look for the signals of these exotic
quarks. Considering all decays, including those involving Z- and Yukawa
interactions, we show how one can distinguish between t' and b' from ratios of
event rates with different lepton multiplicities. The ability to reconstruct
the Higgs boson with a mass around 125.5 GeV plays an important role in such
differentiation.Comment: 18 pages, 10 figure
Anomalous Triple Gauge Vertices at the Large Hadron-Electron Collider
At a high energy collider, such as the Large Hadron-Electron Collider
(LHeC) which is being planned at CERN, one can access the vertex
exclusively in charged current events with a radiated photon, with no
interference from the vertex. We find that the azimuthal angle between
the jet and the missing momentum in each charged current event is a sensitive
probe of anomalous couplings, and show that for quite reasonable
values of integrated luminosity, the LHeC can extend the discovery reach for
these couplings beyond all present experimental bounds.Comment: 11 pages, LaTeX2e, 5 EPS figure
Seeking the CP-odd Higgs via
We show that the decay rates of the Higgs boson to a pseudoscalar quarkonium
and a pair of leptons, (), can be
substantially enhanced in a scenario with two Higgs doublets with a softly
broken symmetry (2HDM) when the CP-odd Higgs A is light, i.e.
. Depending on the type of 2HDM the enhancement of
with respect to its Standard Model
value can be an order of magnitude larger, i.e.
. The decays could
therefore provide an efficient channel to investigate the presence of a light
CP-odd Higgs and help to disentangle among various 2HDM scenarios.Comment: 19 pages, 6 figure
Generalized top-spin analysis and new physics in collisions with beam polarization
A generalized top-spin analysis proposed some time ago in the context of
Standard Model and subsequently studied in varying contexts is now applied
primarily to the case of with transversely
polarized beams. This extends our recent work with new physics couplings of
scalar () and tensor () types. We carry out a comprehensive analysis
assuming only the electron beam to be transversely polarized, which is
sufficient to probe these interactions, and also eliminates any azimuthal
angular dependence due to standard model or new physics of vector () and
axial-vector () type interactions. We then consider new physics of general
four-Fermi type of and type with both beams transversely polarized and
discuss implications with longitudinal polarization as well. The generalized
spin bases are all investigated in the presence of either longitudinal or
transverse beam polarization to look for appreciable deviation from the SM
prediction in case of the new physics. 90% confidence level limits are obtained
on the interactions for the generalized spin bases with realistic integrated
luminosity. In order to achieve this we present a general discussion based on
helicity amplitudes and derive a general transformation matrix that enables us
to treat the spin basis. We find that beamline basis combined with transverse
polarization provides an excellent window of opportunity both for , and
, new physics, followed by the off diagonal basis. The helicity basis is
shown to be the best in case of longitudinal polarization to look for new
physics effectsdue to and .Comment: 21 pages using revtex4-
Invisible decays of the lightest Higgs boson in supersymmetric models
We consider supersymmetric models in which the lightest Higgs scalar can
decay invisibly consistent with the constraints on the ~GeV state
discovered at the CERN LHC. We consider the invisible decay in the minimal
supersymmetric standard model~(MSSM), as well its extension containing an
additional chiral singlet superfield, the so-called next-to-minimal or
nonminimal supersymmetric standard model~(NMSSM).We consider the case of MSSM
with both universal as well as nonuniversal gaugino masses at the grand unified
scale, and find that only an grand unified model with unnaturally large
representation can give rise to sufficiently light neutralinos which can
possibly lead to the invisible decay . Following this, we consider the case of NMSSM in detail, where also
we find that it is not possible to have the invisible decay of the lightest
Higgs scalar with universal gaugino masses at the grand unified scale. We
delineate the regions of the NMSSM parameter space where it is possible to have
the lightest Higgs boson to have a mass of about GeV, and then
concentrate on the region where this Higgs can decay into light neutralinos,
with the soft gaugino masses and as two independent parameters,
unconstrained by grand unification. We also consider, simultaneously, the other
important invisible Higgs decay channel in the NMSSM, namely the decay into the
lightest CP odd scalars, , which is studied in detail. With
the invisible Higgs branching ratio being constrained by the present LHC
results, we find that ~GeV and ~GeV is disfavored in
NMSSM for fixed values of the other input parameters. The dependence of our
results on the parameters of NMSSM is discussed in detail.Comment: 20 pages, 14 figures, to appear in Physical Review
Chromium translocation, concentration and its phytotoxic impacts in in vivo grown seedlings of Sesbania sesban L. Merrill.
The present in vivo pot culture study showed hexavalent chromium (Cr+6) induced phytotoxic impacts and its translocation potential in 21 days old sesban (Sesbania sesban L. Merrill.) seedlings. Cr+6 showed significant growth retardation in 21 days old sesban (Sesbania sesban L. Merrill.) seedlings. Germination of seeds at 10,000 mg L−1 of Cr+6 exhibit 80% inhibition in germination. Seedling survival was 67% after 7 days of seedling exposure to 300 mg kg−1 of Cr+6. Shoot phytotoxicity was enhanced from 6% to 31% with elevated supply of Cr+6 from 10 mg kg−1 to 300 mg kg−1. Elevated supply of Cr+6 exhibited increasing and decreasing trends in % phytotoxicity and seedling tolerance index, respectively. Elevated supply of chromium showed decreased chlorophyll and catalase activities. Peroxidase activities in roots and leaves were significantly higher at increased supply of Cr+6. Cr bioconcentration in roots was nearly 10 times more than stems whereas leaves showed nearly double accumulation than stems. Tissue specific chromium bioaccumulation showed 53 and 12 times more in roots and shoots respectively at 300 mg kg−1 Cr+6 than control. The present study reveals potential of sesban for effective Cr translocation from roots to shoots as evident from their translocation factor and Total Accumulation Rate values
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