Beam polarization effects in the radiative production of lightest neutralinos in e+e−e^+ e^- collisions in supersymmetric grand unified models

We study the production of the lightest neutralinos in the process $e^+ e^- \rightarrow \chi_1^0 \chi_1^0 \gamma$ 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 $e^+ e^- \rightarrow \nu \bar\nu \gamma$ 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 $e^+ e^- \rightarrow \tilde \nu \tilde\nu^* \gamma$ 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 $ep$ collider, such as the Large Hadron-Electron Collider (LHeC) which is being planned at CERN, one can access the $WW\gamma$ vertex exclusively in charged current events with a radiated photon, with no interference from the $WWZ$ 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 $WW\gamma$ 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 h→ηc,bℓ+ℓ−h\rightarrow \eta_{c,b}\ell^+\ell^-

We show that the decay rates of the Higgs boson to a pseudoscalar quarkonium and a pair of leptons, $h\to P\ell^+\ell^-$ ($P\in\{\eta_c,\eta_b\}$), can be substantially enhanced in a scenario with two Higgs doublets with a softly broken $\mathbb{Z}_2$ symmetry (2HDM) when the CP-odd Higgs A is light, i.e. $m_A\lesssim m_h$. Depending on the type of 2HDM the enhancement of $\mathcal{B}(h\to \eta_{c,b}\tau^+\tau^-)$ with respect to its Standard Model value can be an order of magnitude larger, i.e. $\mathcal{O}(10^{-6}\div10^{-5})$. The decays $h\to P\ell^+\ell^-$ could therefore provide an efficient channel to investigate the presence of a light CP-odd Higgs $A$ and help to disentangle among various 2HDM scenarios.Comment: 19 pages, 6 figure

Generalized top-spin analysis and new physics in e+e−e^{+} e^{-} 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 $e^+e^-\rightarrow t\bar{t}$ with transversely polarized beams. This extends our recent work with new physics couplings of scalar ($S$) and tensor ($T$) 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 ($V$) and axial-vector ($A$) type interactions. We then consider new physics of general four-Fermi type of $V$ and $A$ 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 $S$, $T$ and $V$, $A$ 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 $V$ and $A$.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 $126$~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 $E_6$ grand unified model with unnaturally large representation can give rise to sufficiently light neutralinos which can possibly lead to the invisible decay $h^0 \rightarrow \tilde \chi_1^0 \tilde \chi_1^0$. 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 $126$ GeV, and then concentrate on the region where this Higgs can decay into light neutralinos, with the soft gaugino masses $M_1$ and $M_2$ 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, $h_1 \to a_1 a_1$, which is studied in detail. With the invisible Higgs branching ratio being constrained by the present LHC results, we find that $\mu_{eff} < 170$~GeV and $M_1 < 80$~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