About helicity conservation in gauge boson scattering at high energy

We remark that the high energy gauge boson scattering processes involving two-body initial and final states, satisfy certain selection rules described as helicity conservation of the \underline{gauge boson} amplitudes (GBHC). These rules are valid at Born level, as well as at the level of the leading and sub-leading 1-loop logarithmic corrections, in both the Standard Model (SM) and the Minimal Supersymmetric Standard Model (MSSM). A "fermionic equivalence" theorem is also proved, which suggests that GBHC is valid at all orders in MSSM at sufficiently high energies, where the mass suppressed contributions are neglected.Comment: 7 pages, 2 figures, version to appear in Phys. Rev. Letter

Vector boson Pair Production at Supercolliders; useful approximate helicity amplitudes

We study vector boson pair production at $LHC$ and $SSC$, taking into account the effects generated by the anomalous vector boson and Higgs couplings induced by the operators ${\cal O}_W$ and ${\cal O}_{UW}$, which are the only dim=6 operators preserving $SU(2)_c$. These operators lead to enhanced production of transverse vector bosons, as opposed to the enhanced production of longitudinal gauge bosons, induced in case M_H\gsim 1\ TeV, by dim=4 terms already existing in the Standard Model lagrangian. For vector boson pair masses larger than $1\ TeV$, we establish very simple approximate expressions for the standard as well as the non-standard helicity amplitudes for $q\bar q$ annihilation and vector boson fusion, which accurately describe the physics. These expressions should simplify the experimental search for such interactions. We finally discuss the observability and the disentangling of these interactions.Comment: 22 pages, 6 figures avaible by air mail upon request , (e-mail [email protected] PM/93-26 THES-TP 93/

Signatures of the anomalous ZγZ\gamma and ZZ production at the lepton and hadron Colliders

The possible form of New Physics (NP) interactions affecting the ZZZ, $ZZ \gamma$ and $Z\gamma \gamma$ vertices, is critically examined. Their signatures and the possibilities to study them, through ZZ and $Z\gamma$ production, at the e^-e^+ Colliders LEP and LC and at the hadronic Colliders Tevatron and LHC, are investigated. Experimental limits obtained or expected on each coupling are collected. A simple theoretical model based on virtual effects due to some heavy fermions is used for acquiring some guidance on the plausible forms of these NP vertices. In such a case specific relations among the various neutral couplings are predicted, which can be experimentally tested and possibly used to constrain the form of the responsible NP structure.Comment: 17 pages and 9 figures, version to appear in Phys. ReV. e-mail: [email protected]

Electron Spectra in the Ionization of Atoms by Neutrinos

For neutrinos of O(10keV) energies, their oscillation lengths are less than a few hundred meters, thereby suggesting the fascinating idea of oscillation experiments of small geometrical size. To help evaluating this idea we calculate the ionization cross sections of H, He, Ne and Xe, using any neutrino flavor, in the few keV energy range. We find that the atomic ionization cross sections per electron are always smaller than the neutrino cross sections off free electrons, approaching it from below as the energy increases to the 100 keV region. At the 10-20 keV range though, atomic binding effects are very important, particularly for the heavier atoms, inducing a factor of two reduction of the Xe ionization cross section, compared to the free electron one.Comment: Typos corrected. Version appeared in Phys. Rev. D70:113008 (2004

Testing the Higgs boson gluonic couplings at LHC

We study Higgs + jet production at hadron colliders in order to look for new physics residual effects possibly described by the $dim=6$ operators {\O}_{GG} and {\widetilde\O}_{GG} which induce anomalous $Hgg$ and $Hggg$ couplings. Two ways for constraining these operators at LHC may be ~useful. The first is based on the total Higgs boson production rate induced by gluon-gluon fusion, in which the main cause of limitations are due to theoretical uncertainties leading to sensitivities of $|d_G|\simeq 3.\times 10^{-4}$ and $|\widetilde{d}_G|\simeq 1.4\times 10^{-3}$ for the corresponding anomalous couplings, in the mass range 100 GeV \lsim \mh \lsim 2~00 GeV. These results imply sensitivity to new physics scales of 51 and 24 TeV respectively. The second way investigated here concerns the shape of the Higgs transverse momentum; for which the theoretical uncertainties are less severe and the limitations are mainly induced by statistics. A simple analysis, based on the ratio of the number of events at large and low $p_T$ at LHC, leads to similar sensitivities, if only the $H\to \gamma \gamma$ decay mode is used. But the sensitivities can now be improved by a factor 2 to 10, depending on the Higgs mass, if the Higgs decay modes to $WW^*$, $ZZ^*$, $WW$, $ZZ$ are also used.Comment: 23 pages and 7 figures, version to appear in Phys.ReV.D. e-mail: [email protected]

Unitarity Constraints for New Physics Induced by dim-6 Operators

We compute the helicity amplitudes for boson-boson scattering at high energy due to the operators \O_{B\Phi}, \O_{W\Phi} and \O_{UB}, and we derive the corresponding unitarity bounds. Thus, we provide relations between the couplings of these operators and the corresponding New Physics thresholds, where either unitarity is saturated or new degrees of freedom are excited. We compare the results with those previously obtained for the operators \O_W and \O_{UW} and we discuss their implications for direct and indirect tests at present and future colliders. The present treatment completes the study of the unitarity constraints for all blind bosonic operators.Comment: 41 pages, latex file. PM 94-28 THES-TP 94-0

Probing Anomalous Wtb Coupling via Single Top Production at TeV Energy γ\gamma e Colliders

Results of complete tree level calculations of the single top production reaction $\gamma e \to \nu \bar{t} b$ at the Next Linear Collider, including the contribution of anomalous operators to the Wtb coupling are presented. The sensitivity for probing the structure of the Wtb coupling in a model independent way is analyzed and found to be significantly higher than for comparable measurements at the Tevatron.Comment: 10 Latex pages including 1 ps-figure and 3 eps-figure

Investigation of the nuetralino pair production at LHC

In this article, we investigate the Drell-Yan process of the light neutralino pair $\widetilde{\chi}_{i}^{0}\widetilde{\chi}_{j}^{0}$ ($i,j=1,2$) productions at proton-proton collisions and we present the general formulate for the differential cross sections. We conduct an extensive examination of the dependence of the total cross section of the subprocesses $q \bar q \to \widetilde \chi_{i}^{0}\widetilde\chi_{j}^{0}$ on the beam energy, on the mass of the squarks and also on the $M_2$ gaugino for the three extremely different scenarios. For all three cases, the outcomes are as follows. The dependence of the total cross section of the subprocesses $q \bar q \to \widetilde \chi_{i}^{0} \widetilde \chi_{j}^{0}$ on the beam energy is dominated by one of the subprocesses, $q \bar q \to \widetilde \chi_{1}^{0} \widetilde \chi_{2}^{0}$. On the other hand, the dependence of the total cross section of the subprocesses $q \bar q \to \widetilde \chi_{i}^{0} \widetilde \chi_{j}^{0}$ on the mass of the squarks is dominated by one of the subprocesses, $q \bar q \to \widetilde \chi_{1}^{0} \widetilde \chi_{2}^{0}$. We derive there from that our findings may lead to new insights relating to experimental investigations and these dependencies may be used as bases of an experimental research for the neutralino pair at LHC.Comment: 38pp, 22 figures, ReVTeX4, (Baku State University, Azerbaijan, and Erciyes University, Kayseri, Turkey

The processes e−e+→γγ,Zγ,ZZe^-e^+\to\gamma\gamma, Z \gamma, ZZ in SM and MSSM

We present the results of a complete analysis of the one loop electroweak corrections to $e^-e^+\to\gamma\gamma, ~Z\gamma, ~ZZ$ in the Standard (SM) and the Minimal Supersymmetric Standard Model (MSSM). A special emphasis is put on the high energy behaviour of the various helicity amplitudes and the way the logarithmic structure is generated. The large magnitude of these effects, which induce striking differences between the SM and MSSM cases at high energies, offers the possibility of making global tests which could check the consistency of these models, and even decide whether any additional new physics is required.Comment: Short version (16 pages and 9 figures) of the paper hep-ph/0207273, to appear in Phy.Rev.D. e-mail: [email protected]