Search

We have investigated real graviton emission in the ADD and RS model of extra dimensions through the photoproduction process pp-> p gamma p-> pGqX at the LHC. We have considered all contributions from the subprocesses gamma q -> G q, where q=u,d,c,s,b,anti-u,anti-d, anti-c, anti-s, anti-b quark. The constraints on model parameters of the ADD and RS model of extra dimensions have been calculated. During numerical calculations we have taken account of 3, 4, 5 and 6 large extra dimensional scenarios. The constraints on RS model parameters have been calculated by considering G -> gamma gamma, e^- e^+, mu^- mu^+ decay channels of the graviton., Comment: 27 pages, 12 figures; final version to appear in PRD

We have examined TeV scale effects of extra spatial dimensions through the processes gamma q-> gamma q where q=u,d,c,s,b, anti-u, anti-d, anti-c, anti-s, anti-b. These processes have been treated in a photon-proton collision via the main reaction pp-> p gamma p-> p gamma qX at the LHC. We have employed equivalent photon approximation for incoming photon beams and performed statistical analysis for various forward detector acceptances., Comment: 17 pages, 5 figures

We investigate the constraints on the anomalous quartic $ZZ\gamma\gamma$ couplings through the process $p p\to p\gamma p\to p \gamma q Z X$ at the LHC. Taking into consideration various forward detector acceptances and integrated LHC luminosities, we find 95% confidence level bounds on the anomalous coupling parameters. We show that the bounds on these couplings are at the order of $10^{-6}GeV^{-2}$ which are about four orders of magnitude more restricted with respect to current experimental bounds., Comment: 15 pages, 4 figures; to be published in PRD

We study the possibility for the process $pp \rightarrow p\gamma p \rightarrow pW^-t(W^+\bar t)X$ with anomalous Wtb couplings in a model independent effective Lagrangian approach at the LHC. We find 95% confidence level bounds on the anomalous coupling parameters for various values of the integrated luminosity. The improved constraints on the anomalous Wtb couplings have been obtained compared to current limits., Comment: 6 figures, To be published in PRD

Capability of medium energy setup of a beta beam experiment to probe new physics contributions to neutrino-W and neutrino-Z couplings are investigated. We employ the effective lagrangian approach of Buchmuller and Wyler and obtain 95% confidence level limits on neutrino couplings to these gauge bosons without assuming the flavor universality of the coupling of neutrinos. We show that a beta beam facility can place 3 to 20 times more restrictive limits than present ones on the deviations from the electron neutrino couplings in the Standard Model., Comment: 22 pages, 10 figures

The constraints on anomalous Higgs boson couplings are investigated through the process $\gamma\gamma \to W^{+}W^{-}H$. Considering the longitudinal and transverse polarization states of the final $W^{+}$ and $W^{-}$ bosons and incoming beam polarizations, we find 95% confidence level limits on the anomalous coupling parameters $\Delta a_{W}$, $b_{W}$ and $\beta_{W}$ with an integrated luminosity of 500 $fb^{-1}$ and $\sqrt{s}$=0.5, 1 TeV energies. We show that initial beam and final state polarizations lead to a significant improvement on the sensitivity limits of the anomalous coupling parameters $b_{W}$ and $\beta_{W}$., Comment: 20 pages, 9 figures

We investigate the physics potential of NuSOnG experiment to probe new physics contributions to Z-neutrino-neutrino couplings in muon-neutrino electron elastic and neutral-current deep-inelastic scattering processes. We employ an effective Lagrangian approach and do not a priori assume universality of the coupling of neutrinos to Z. We obtain 95% C.L. limits on possible universality violating couplings., Comment: LaTeX with 6 figures

We investigate the effects of scalar and vector unparticles on top quark spin correlations via the process $e^{+}e^{-}\to t \bar{t}$. In addition to the Standard Model diagrams, there is a new contribution to top-antitop quark production process mediated by unparticle in the s-channel. It is shown that scalar and vector unparticle contribution leads to a considerable deviation of the top spin correlations from the Standard Model one., Comment: 13 pages, 6 figures

We investigate the virtual effects of vector unparticles in the Moller scattering. We derive the analytic expression for scattering amplitudes with unpolarized beams. We obtain 95% confidence level limits on the unparticle couplings $\lambda_{V}$ and $\lambda_{A}$ with integrated luminosity of $L_{int}=50, 500 fb^{-1}$ and $\sqrt{s}=100, 300$ and 500 GeV energies. We show that limits on $\lambda_{V}$ are more sensitive than $\lambda_{A}$., Comment: 10 pages, 5 figures, 4 tables

We investigate the potential of $e\gamma$ collisions to probe anomalous $Wtb$ couplings via the polarized single top quark production process $e^{+} \gamma \to t \bar{b} \bar{\nu_{e}}$. We find 95% confidence level limits on the anomalous coupling parameters $F_{2L}$ and $F_{2R}$ with an integrated luminosity of $500 fb^{-1}$ and $\sqrt{s}=0.5, 1$ and 1.5 TeV energies. The effects of top quark spin polarization on the anomalous $Wtb$ couplings are discussed. It is shown that polarization leads to a considerable improvement in the sensitivity limits., Comment: published version

We investigate the degree of spin polarization of single top quarks in the $e\gamma$ collision via the process $e^{+} \gamma \to t \bar{b} \bar{\nu_{e}}$ with center of mass energies $\sqrt{s}$=0.5, 1 and 1.5 TeV of the parental linear $e^{+}e^{-}$ collider. Dominant spin fractions and spin asymmetries for the various top quark spin bases are investigated. We show that $e^{+}$-beam direction is the favorite top quark spin decomposition axis. It is found to be comparable with the ones in $pp$ and $ep$ collisions., Comment: 5 pages, 3 figures

We discuss the degree of spin polarization of single top quarks produced via $Wg$ fusion process in $ep$ collision at TESLA+HERAp and CLIC+LHC energies $\sqrt{s}=1.6$ and 5.3 TeV. For $eb \to t \bar{\nu}$ subprocess we show that the top quark spin is completely polarized when the spin basis is chosen in the direction of the incoming positron beam in the rest frame of top quark. A description on how to combine the cross sections of $e^{+}b\to t\bar{\nu}$ and $e^{+}g\to t\bar{b}\bar{\nu}$ processes is given. $e^{+}$-beam direction is taken to be the favorite top quark spin decomposition axis in its rest frame and it is found to be comparable with the ones in $pp$ collision. It is argued that theoretical simplicity and experimental clearness are the advantage of $ep$ collision., Comment: Revised version of Phys. Rev. D69 (2004)034016

We discuss the degree of spin polarization of single top quarks produced via $Wg$ fusion process in $ep$ collision at TESLA+HERAp and CLIC+LHC energies $\sqrt{s}=1.6$ and 5.3 TeV. A description on how to combine the cross sections of $e^{+}b\to t\bar{\nu}$ and $e^{+}g\to t\bar{b}\bar{\nu}$ processes is given. $e^{+}$-beam direction is taken to be the favorite top quark spin decomposition axis in its rest frame and it is found to be comparable with the ones in $pp$ collision. It is argued that theoretical simplicity and experimental clearness are the advantage of $ep$ collision., Comment: 2 eps figures