Bounding the electromagnetic and weak dipole moments of the tau-lepton in a simplest little Higgs model

From the total cross section for the reaction $e^+e^-\to \tau^+\tau^-\gamma$ at the $Z_1$ pole and in the framework of a simplest little Higgs model (SLHM), we get a limit on the characteristic energy scale of the model $f$, $f \geq 5.4$ $TeV$, which in turn induces bounds on the electromagnetic and weak dipole moments of the tau-lepton. Our bounds on the electromagnetic moments are consistent with the bounds obtained by the L3 and OPAL collaborations for the reaction $e^+e^-\to \tau^+\tau^-\gamma$. We also obtained bounds on the tau weak dipole moments which are consistent with the bounds obtained recently by the DELPHI and ALEPH collaborations from the reaction $e^+e^-\to \tau^+\tau^-$.Comment: 14 pages, 5 figure

Bounds on the electromagnetic dipole moments through the single top production at the CLIC

We obtain bounds on the anomalous magnetic and electric dipole moments of the $t$-quark from a future high-energy and high-luminosity linear electron positron collider, such as the CLIC, with unpolarized and polarized electron beams which are a powerful tool to determine new physics. We consider the processes $\gamma e^- \to \bar t b\nu_e$ ($\gamma$ is the Compton backscattering photon) and $e^+e^- \to e^-\gamma^* e^+ \to \bar t b\nu_e e^+$ ($\gamma^*$ is the Weizsacker-Williams photon) which are one of the most important sources of single top quark production. For the systematic uncertainties of $\delta_{sys}=0\%,\hspace{1mm}5\%$, b-\mbox{tagging efficiency}=0.8, center-of-mass energy of $\sqrt{s}=3\hspace{0.8mm}TeV$, integrated luminosity of ${\cal L}=2\hspace{0.5mm}ab^{-1}$ and $2\sigma\hspace{1mm}(3\sigma)$ C.L. the future $e^+e^-$ collider may put bounds on the electromagnetic dipole moments $\hat a_V$ and $\hat a_A$ of the top quark of the order of ${\cal O}(10^{-2}-10^{-1})$, which are highly competitive with those recently reported in previous studies.Comment: 26 pages, 6 figures. arXiv admin note: text overlap with arXiv:1412.209

Higgs Boson Self-Coupling at High Energy γγ\gamma \gamma Collider

We analyzed the double production and the triple self-coupling of the standard model Higgs boson at future $\gamma \gamma$ collider energies, with the reactions $\gamma\gamma \rightarrow f \bar f HH$ $(f=b, t)$. We evaluated the total cross section for $f\bar fHH$ and calculated the total number of events considering the complete set of Feynman diagrams at tree-level and for different values of the triple coupling $\kappa\lambda_{HHH}$. We have also analyzed the sensitivity for the considered reaction and we show the results as 95% C.L. regions in the $\kappa-M_H$ plane for different values of the center of mass energy and different levels of background. The numerical computation was done for the energies which are expected to be available at a possible Future Linear $\gamma\gamma$ Collider with a center-of-mass energy 500-3000 $GeV$ and luminosities of 1 and $5 ab^{-1}$. We found that the number of events for the process $\gamma\gamma \rightarrow t \bar t HH$, taking into account the decay products of both $t$ and $H$, is small but enough to obtain information on the triple Higgs boson self-coupling in a independent way, complementing other studies on the triple vertex.Comment: 14 pages, 6 figure

Emissivity of neutrinos in supernova in a left-right symmetric model

We calculate the emissivity due to neutrino-pair production in $e^+e^-$ annihilation in the context of a left-right symmetric model in a way that can be used in supernova calculations. We also present some simple estimates which show that such process can act as an efficient energy-loss mechanism in the shocked supernova core. We find that the emissivity is dependent of the mixing angle $\phi$ of the model in the allowed range for this parameter.Comment: 13 pages, 2 figure

Studying the Triple Higgs Self-Coupling Via e+e- --> b bar b HH, t bar t HH at Future Linear e+e- Colliders

We study the triple Higgs self-coupling at future $e^{+}e^{-}$ colliders energies, with the reactions $e^{+}e^{-}\to b \bar b HH$ and $e^{+}e^{-}\to t \bar t HH$. We evaluate the total cross section of $b\bar bHH$, $t\bar tHH$ and calculate the total number of events considering the complete set of Feynman diagrams at tree-level. The sensitivity of the triple Higgs coupling is considered in the Higgs mass range 110-190 $GeV$, for the energy which is expected to be available at a possible Next Linear $e^{+}e^{-}$ Collider with a center-of-mass energy $800, 1000, 1500$ $GeV$ and luminosity 1000 $fb^{-1}$.Comment: 15 pages, 10 figure

Neutral Higgs Boson Pair-Production and Trilinear Self-Couplings in the MSSM at ILC and CLIC Energies

We study pair-production as well as the triple self-couplings of the neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) at the Future International Linear $e^{+}e^{-}$ Collider (ILC) and Compact Linear Collider (CLIC). The analysis is based on the reactions $e^{+}e^{-}\to b \bar b h_ih_i, t \bar t h_ih_i$ with $h_i=h, H, A$. We evaluate the total cross-section for both $b\bar bh_ih_i$, $t\bar th_ih_i$ and calculate the total number of events considering the complete set of Feynman diagrams at tree-level. We vary the triple couplings $\kappa\lambda_{hhh}$, $\kappa\lambda_{Hhh}$, $\kappa\lambda_{hAA}$, $\kappa\lambda_{HAA}$, $\kappa\lambda_{hHH}$ and $\kappa\lambda_{HHH}$ within the range $\kappa=-1$ and +2. The numerical computation is done for the energies expected at the ILC with a center-of-mass energy 500, 1000, 1600 $GeV$ and a luminosity 1000 $fb^{-1}$. The channels $e^{+}e^{-}\to b \bar b h_ih_i$ and $e^{+}e^{-}\to t \bar t h_ih_i$ are also discussed to a center-of-mass energy of 3 $TeV$ and luminosities of 1000 $fb^{-1}$ and 5000 $fb^{-1}$.Comment: 26 pages, 11 figure

Higgs bosons production and decay at future e+e−e^+e^- linear colliders as a probe of the B-L model

We study the phenomenology of the light and heavy Higgs boson production and decay in the context of a $U(1)_{B-L}$ extension of the Standard Model with an additional $Z'$ boson at future $e^+e^-$ linear colliders with center-of-mass energies of $\sqrt{s}=500-3000\hspace{0.8mm}GeV$ and integrated luminosities of ${\cal L}=500-2000\hspace{0.8mm}fb^{-1}$. The study includes the processes $e^{+}e^{-}\rightarrow (Z, Z') \to Zh$ and $e^{+}e^{-}\rightarrow (Z, Z') \to ZH$, considering both the resonant and non-resonant effects. We find that the total number of expected $Zh$ and $ZH$ events can reach 909,124 and 97,487, respectively, which is a very optimistic scenario and thus it would be possible to perform precision measurements for both Higgs bosons $h$ and $H$, as well as for the $Z'$ boson in future high-energy and high-luminosity $e^+e^-$ colliders experiments. Our study complements other studies on the B-L model and on the Higgs-strahlung processes $e^{+}e^{-}\rightarrow (Z, Z') \to Zh$ and $e^{+}e^{-}\rightarrow (Z, Z') \to ZH$.Comment: 39 pages, 15 figures; To be published in The Journal of Physics G: Nuclear and Particle Physics. arXiv admin note: substantial text overlap with arXiv:1506.07575; text overlap with arXiv:1106.4462 by other author

Model-independent sensibility studies for the anomalous dipole moments of the ντ\nu_\tau at the CLIC based γe−\gamma e^- colliders

To improve the theoretical prediction of the anomalous dipole moments of the $\tau$-neutrino, we have carried out a study through the process $\gamma e^- \to \tau \bar\nu_\tau \nu_e$, which represents an excellent and useful option in determination of these anomalous parameters. To study the potential of the process $\gamma e^- \to \tau \bar\nu_\tau \nu_e$, we apply a future high-energy and high-luminosity linear electron-positron collider, such as the CLIC, with $\sqrt{s}=380, 1500, 3000\hspace{0.8mm}GeV$ and ${\cal L}=10, 50, 100, 200, 500, 1000, 1500, 2000, 3000\hspace{0.8mm}fb^{-1}$, and we consider systematic uncertainties of $\delta_{sys}=0, 5, 10\%$. With these elements, we present a comprehensive and detailed sensitivity study on the total cross-section of the process $\gamma e^- \to \tau \bar\nu_\tau \nu_e$, as well as on the dipole moments $\mu_{\nu_\tau}$ and $d_{\nu_\tau}$ at the $95\%$ C.L., showing the feasibility of such process at the CLIC at the $\gamma e^-$ mode with unpolarized and polarized electron beams.Comment: 28 pages, 15 figure

Limits on the quartic couplings ZγγγZ\gamma\gamma\gamma and ZZγγZZ\gamma\gamma from e+e−e^+e^- colliders

We obtain limits on the quartic neutral gauge bosons couplings $Z\gamma\gamma\gamma$ and $ZZ\gamma\gamma$ using LEP 2 data published by the L3 Collaboration on the reactions $e^+e^-\to \gamma\gamma\gamma, Z\gamma\gamma$. We also obtain $95 \%$ C. L. limits on these couplings at the future linear colliders energies. The LEP 2 data induce limits of order $10^{-5}$ $GeV^{-4}$ for the $Z\gamma\gamma\gamma$ couplings and of order $10^{-3}$ $GeV^{-2}$ for the $ZZ\gamma\gamma$ couplings, which are still above the respective Standard Model predictions. Future $e^+e^-$ linear colliders may improve these limits by one or two orders of magnitude.Comment: 13 pages, 7 figures. This article has been accepted for publication in Physical Review

Bounding the Number of Light Neutrinos Species in a Left-Right Symmetric Model

Using the experimental values for the rates $R^{LEP} _{exp}=\Gamma_{inv}/\Gamma_{l\bar l}=5.942\pm 0.016$, $R^{Giga-Z_1}=\Gamma_{inv}/\Gamma_{l\bar l}=5.942\pm 0.012$ (most conservative) and $R^{Giga-Z_1}=\Gamma_{inv}/\Gamma_{l\bar l}=5.942\pm 0.006$ (most optimistic) we derive constraints on the number of neutrinos light species $(N_\nu)_{LRSM}$ with the invisible width method in the framework of a left-right symmetric model (LRSM) as a function of the LR mixing angle $\phi$. Using the LEP result for $N_\nu$ we may place a bound on this angle, $-1.6\times 10^{-3}\leq\phi \leq 1.1\times 10^{-3}$, which is stronger than those obtained in previous studies of the LRSM.Comment: 8 pages, 3 figure