Probing neutral top-pion via a flavor-changing process γγ→tcˉΠt0\gamma\gamma\to t\bar{c}\Pi_{t}^{0}

In the framework of topcolor-assisted-technicolor model(TC2), we study a flavor-changing neutral top-pion production process $\gamma\gamma\to t\bar{c}\Pi_{t}^{0}$. The study shows that there exists a resonance effect which can enhance the cross section up to a few fb even tens fb. For a yearly luminosity 100 $fb^{-1}$ at future linear colliders, there might be hundreds even thousands events to be produced. On the other hand, the background of such flavor-changing process is very clean due to the GIM mechanism in SM . With such sufficient events and clean background, neutral toppion could be detected at future linear colliders with high center of energy and luminosity. Our study provides a possible way to test TC2 model.Comment: 10 pages, 4 figures,has been accepted by Phys.Rev.

Lepton flavor violation decays τ−→μ−P1P2\tau^-\to \mu^- P_1 P_2 in the topcolor-assisted technicolor model and the littlest Higgs model with TT parity

The new particles predicted by the topcolor-assisted technicolor ($TC2$) model and the littlest Higgs model with T-parity (called $LHT$ model) can induce the lepton flavor violation ($LFV$) couplings at tree level or one loop level, which might generate large contributions to some $LFV$ processes. Taking into account the constraints of the experimental data on the relevant free parameters, we calculate the branching ratios of the $LFV$ decay processes $\tau^-\to\mu^- P_1 P_2$ with $P_1 P_2$ = $\pi^+\pi^-$, $K^+K^-$ and $K^0\bar{K^0}$ in the context of these two kinds of new physics models. We find that the $TC2$ model and the $LHT$ model can indeed produce significant contributions to some of these $LFV$ decay processes.Comment: 24 pages, 7 figure

The productions of the top-pions and top-Higgs associated with the charm quark at the hadron colliders

In the topcolor-assistant technicolor (TC2) model, the typical physical particles, top-pions and top-Higgs, are predicted and the existence of these particles could be regarded as the robust evidence of the model. These particles are accessible at the Tevatron and LHC, and furthermore the flavor-changing(FC) feature of the TC2 model can provide us a unique chance to probe them. In this paper, we study some interesting FC production processes of top-pions and top-Higgs at the Tevatron and LHC, i.e., $c\Pi_{t}^{-}$ and $c\Pi_{t}^{0}(h_{t}^{0})$ productions. We find that the light charged top-pions are not favorable by the Tevatron experiments and the Tevatron has a little capability to probe neutral top-pion and top-Higgs via these FC production processes. At the LHC, however, the cross section can reach the level of $10\sim 100$ pb for $c\Pi_t^-$ production and $10\sim 100$ fb for $c\Pi_t^0(h_t^0)$ production. So one can expect that enough signals could be produced at the LHC experiments. Furthermore, the SM background should be clean due to the FC feature of the processes and the FC decay modes $\Pi_t^-\to b\bar{c}, \Pi_t^0(h_t^0)\to t\bar{c}$ can provide us the typical signal to detect the top-pions and top-Higgs. Therefore, it is hopeful to find the signal of top-pions and top-Higgs with the running of the LHC via these FC processes.Comment: 12 pages, 6 figure

The rare top quark decays t→cVt\to cV in the topcolor-assisted technicolor model

We consider the rare top quark decays in the framework of topcolor-assisted technicolor (TC2) model. We find that the contributions of top-pions and top-Higgs predicted by the TC2 model can enhance the SM branching ratios by as much as 6-9 orders of magnitude. i.e., in the most case, the orders of magnitude of branching ratios are $Br(t\to c g)\sim 10^{-5}$, $Br(t\to c Z)\sim 10^{-5}$, $Br(t\to c \gamma)\sim 10^{-7}$. With the reasonable values of the parameters in TC2 model, such rare top quark decays may be testable in the future experiments. So, rare top quark decays provide us a unique way to test TC2 model.Comment: 14 pages, 4 figure

Search for Top Quark FCNC Couplings in Z' Models at the LHC and CLIC

The top quark is the heaviest particle to date discovered, with a mass close to the electroweak symmetry breaking scale. It is expected that the top quark would be sensitive to the new physics at the TeV scale. One of the most important aspects of the top quark physics can be the investigation of the possible anomalous couplings. Here, we study the top quark flavor changing neutral current (FCNC) couplings via the extra gauge boson Z' at the Large Hadron Collider (LHC) and the Compact Linear Collider (CLIC) energies. We calculate the total cross sections for the signal and the corresponding Standard Model (SM) background processes. For an FCNC mixing parameter x=0.2 and the sequential Z' mass of 1 TeV, we find the single top quark FCNC production cross sections 0.38(1.76) fb at the LHC with sqrt{s_{pp}}=7(14) TeV, respectively. For the resonance production of sequential Z' boson and decays to single top quark at the Compact Linear Collider (CLIC) energies, including the initial state radiation and beamstrahlung effects, we find the cross section 27.96(0.91) fb at sqrt{s_{e^{+}e^{-}}}=1(3) TeV, respectively. We make the analysis to investigate the parameter space (mixing-mass) through various Z' models. It is shown that the results benefit from the flavor tagging.Comment: 20 pages, 17 figures, 6 table

Probing Topcolor-Assisted Technicolor from Top-Charm Associated Production at LHC

We propose to probe the topcolor-assisted technicolor (TC2) model from the top-charm associated productions at the LHC, which are highly suppressed in the Standard Model. Due to the flavor-changing couplings of the top quark with the scalars (top-pions and top-Higgs) in TC2 model, the top-charm associated productions can occur via both the s-channel and t-channel parton processes by exchanging a scalar field at the LHC. We examined these processes through Monte Carlo simulation and found that they can reach the observable level at the LHC in quite a large part of the parameter space of the TC2 model.Comment: Version to appear in PRD (Rapid Communication

The flavor-changing bottom-strange quark production in the littlest Higgs model with T parity at the ILC

In the littlest Higgs model with T-parity (LHT) the mirror quarks induce the special flavor structures and some new flavor-changing (FC) couplings which could greatly enhance the production rates of the FC processes. We in this paper study some bottom and anti-strange production processes in the LHT model at the International Linear Collider (ILC), i.e., $e^+e^-\rightarrow b\bar{s}$ and $\gamma\gamma\rightarrow b\bar{s}$. The results show that the production rates of these processes are sizeable for the favorable values of the parameters. Therefore, it is quite possible to test the LHT model or make some constrains on the relevant parameters of the LHT through the detection of these processes at the ILC.Comment: 12 pages, 8 figure

The improvement of Pd nanoclusters electro-catalytic properties for FAO by the addition of Co element

Conference Name:2014 International Conference on Materials Science and Engineering Technology, MSET 2014. Conference Address: Shanghai, China. Time:June 28, 2014 - June 29, 2014.East China University of Science and Technology; Engineering and Industry Technology Institute; Shanghai JiaoTong University; Shanghai University of Engineering ScienceNear-monodisperse Pd and PdCo nanoclusters were synthesized by physical vapor deposition using a plasma-gas-condensation cluster deposition system and tested for catalyzing formic acid oxidation. Under the condition of high vacuum and inert gas, NCs with clean surface and uniform size were obtained. The cyclic voltammetry tests revealed that the electrochemical surface area was increased from 49.7 m2 g-1 to 51.7 m2 g-1 and the peak current density of catalyzing FAO was raised from 0.115 mA cm-2 to 0.125 mA cm-2 when about 12wt. % Co element was added. Additionally, the tolerance to CO poisoning of Pd could also be improved by the addition of Co. The result indicated that this method offered a chemical-free way to prepare clean and efficient Pd-based nanoscale catalytics and encouraged deeper exploration for electrochemichal catalytic reactions. ? (2014) Trans Tech Publications, Switzerland

Probing Little Higgs Model in e+ e- --> nu nubar gamma Process

We study the process e+e- -->nu nubar gamma to search for its sensitivity to the extra gauge bosons Z_2, Z_3 and W_2 which are suggested by the little Higgs models. We find that the ILC with sqrt(s)=0.5 TeV and CLIC with sqrt(s)=3 TeV cover different regions of the LHM parameters. We show that this channel can provide accurate determination of the parameters, complementary to measurements of the extra gauge bosons at the coming LHC experiments.Comment: 17 pages, 10 figures, 5 table

Lepton Flavor Violation in Z and Lepton Decays in Supersymmetric Models

The observation of charged lepton flavor non-conservation would be a clear signature of physics beyond the Standard Model. In particular, supersymmetric (SUSY) models introduce mixings in the sneutrino and the charged slepton sectors which could imply flavor-changing processes at rates accessible to upcoming experiments. In this paper we analyze the possibility to observe Z --> lep_I lep_J in the GigaZ option of TESLA at DESY. We show that although models with SUSY masses above the current limits could predict a branching ratio BR(Z --> mu e) accessible to the experiment, they would imply an unobserved rate of mu --> e gamma and thus are excluded. In models with a small mixing angle between the first and the third (or the second and the third) slepton families GigaZ could observe Z --> tau mu (or Z --> tau e) consistently with present bounds on lep_J --> lep_I gamma. In contrast, if the mixing angles between the three slepton families are large the bounds from mu --> e gamma push these processes below the reach of GigaZ. We show that in this case the masses of the three slepton families must be strongly degenerated (with mass differences of order 10^{-3}). We update the limits on the slepton mass insertions delta_{LL,RR,LR} and discuss the correlation between flavor changing and g_mu-2 in SUSY models.Comment: 23 pages, 6 figures. Version to appear in Phys. Rev.