Top pair production in the littlest Higgs model with T-parity

In the framework of the littlest Higgs model with T-parity,we study the top pair production at the next generation colliders like LHC and ILC.We find that the order O(αs) corrections to the standard model top pair production cross section at LHC can be very small and the magnitude is below 1%.However,the magnitude of corrections to the standard model top pair production rate at ILC may be over 5% for reasonable values'of the parameters.Besides this,the corrections to the asymmetry ALR(tt) may be more sizable. Therefore,the top pair production at ILC may serve as a probe of the littlest Higgs model with T-parity,especially the asymmetry ALR(tt).     

TC corrections to tt̄ production at photon colliders in topcolor-assisted multiscale technicolor model

TC(technicolor) corrections to tt? production in high-energy photon-photon collision are calculated in the topcolor-assisted multiscale technicolor(TOPCMTC) model. We find that the contribution of the technipions to the production cross section of the process γγ → tt? is very small. The relative corrections to the production cross section mainly come from the top-pions, which may be observable at future e ⁺ e ^-. linear collider.     

Soft-gluon resummation for pseudoscalar Higgs boson production at hadron colliders

We compute the threshold-resummed cross section for pseudo-scalar MSSM Higgs boson production by gluon fusion at hadron colliders. The calculation is performed at next-to-next-to leading logarithmic accuracy. We present results for both the LHC and Tevatron Run II. We analyze the factorization and renormalization scale dependence of the results, finding that after performing the resummation the corresponding cross section can be computed with an accuracy better than 10%.     

Production of a neutral scalar associated with a photon at the LHC in the topcolorassisted technicolor model

In the context of the topcolor-assisted technicolor (TC2) model, we consider the production of the neutral scalar S(π_t⁰ or h_t⁰) associated with a photon at the LHC and compare our results with those given by the minimal supersymmetric extension of the Standard Model (MSSM). We find that its production cross section is larger or smaller than that of the scalar particle predicted by the MSSM model, depending on the values of the relevant free parameters.     

Single t-Quark Productions via Flavor-Changing Processes in Topcolor-Assisted Technicolor Model at Hadron Colliders

In the framework of topcolor-assisted technicolor （TC2） model, there exist tree-level flavor-changing （FC） couplings, which can result in the loop-level FC coupling tcg. Such tcg coupling can contribute significant clues at the forthcoming Large Hadron Collider （LHC） experiments. In this paper, based on the TC2 model, we study some single t-quark production processes involving tcg coupling at the Tevatron and LHC： pp（pp） → tq （q = u, d, s）, tg. We calculate the cross sections of these processes. The results show that the cross sections at the Tevatron are too small to observe the signal, but at the LHC it can reach a few pb. With the high luminosity, the LHC has considerable capability to find the single t-quark signal produced via some FC processes involving coupling tcg. On the other hand, these processes can also provide some valuable information of the coupling tcg with detailed study of the processes and furthermore provide the reliable evidence to test the TC2 model     

Double diffractive higgs and di-photon production at the Tevatron and LHC

We use the Monte Carlo generator to predict the cross-sections for double diffractive higgs and di-photon production at the Tevatron and LHC. We find that the higgs production cross-section is too small to be observable at Tevatron energies, and even at the LHC observation would be difficult. Double diffractive di-photon production, however, should be observable within one year of Tevatron Run II.     

The Signatures of the Neutral Top-Pion at the NLC and the Tevatron in Topcolor-Assisted MWTC Model

The neutral top-pion π_t⁰ can couple to the gluons and the photons through the top quark triangle-loop. we calculate the corrections of the neutral top-pion π_t⁰ to the tt production cross section in topcolor-assisted multiscale walking technicolor model. We find that, for a heavy neutral top-pion, the corrections are quite significant. For m_t = 175 GeV, 5 GeV ≤ m_t¹ ≤ 20 GeV and M_πt = 350 GeV, the relative correction Δσ/σ₀ is larger than 10% which might be observed at a high-luminosity Tevatron. We further estimate the production cross section of π_t⁰ at the NLC experiment. We find that the production rate is significantly large. The neutral top-pion π_t⁰ may be detected in future e⁺e^- linear collider experiments.     

Production of the neutral top-pion πt0 in association with a high-pw jet al the LHC

In the framework of the topcolor-assisted technicolor (TC2) model, we study the production of the neutral top-pion πt0 in association with a high-pT jet al the LHC, which proceeds via the partonic processes gg→πt0g, gq→πt0q, qq→πt0g, gb(b)→πt0b(b), and bb→πt0g. We find that it is very challenging to detect the neutral top-pion πt0 via the process pp→πt0 +jet-t-X→tt +jet + X, while the possible signatures of πt0 might be detected via the process pp→πt0 +jet+X→(tc+tc)+jet+X at the LHC.     

Top quark production from black holes at the CERN LHC

LHC is expected to be a top quark factory. If the fundamental Planck scale is near a TeV, then we also expect the top quarks to be produced from black holes via Hawking radiation. In this Letter we calculate the cross sections for top quark production from black holes at the LHC and compare it with the direct top quark cross section via parton fusion processes at next-to-next-to-leading order (NNLO). We find that the top quark production from black holes can be larger or smaller than the pQCD predictions at NNLO depending upon the Planck mass and black hole mass. Hence the observation of very high rates for massive particle production (top quarks, Higgs or supersymmetry) at the LHC may be an useful signature for black hole production.     

Production of a neutral scalar associatedwith a photon at the LHC in the topcolor-assisted technicolor model

In the context of the topcolor-assisted technicolor (TC2) model, we consider the production of the neutral scalar S(π_t⁰ or h_t⁰) associated with a photon at the LHC and compare our results with those given by the minimal supersymmetric extension of the Standard Model (MSSM). We find that its production cross section is larger or smaller than that of the scalar particle predicted by the MSSM model, depending on the values of the relevant free parameters.     

Charged Top-Pion Production at Hadron Colliders

We studied the charged top-pion in the topcolor assisted technicolor model (TC2). If the charged top-pions are heavy, m_πt >m_t+m_b, they will decay mainly via the channel π⁺_t → t \bar{b}. We also calculated the production ofcharged top-pion at the Tevatron and LHC. The cross section can reach to 100 fb at the Tevatron and dozens of pb at the LHC depending on the mass of the top-pion.     

PGB′s Corrections to Top-Quark Production in Topcolor-assisted Multiscale Technicolor Model

In topcolor-assisted multiscale technicolor (TOPCMTC) model.we calculate the corrections of Pseudo Goldstone bosons (technipions,top-pions)to the cross section of the process qq→tt at the Fermilab Tevatron.Our results show that the corrections mainly come form top pions.With reasonable value of the parameters.the correction can increase the total tt production corss section σtt by as much as 17%.This may provide a window to detect tpo-pions.     

Measurement of the tt production cross section in pp collisions at sqrt[s]=1.96 TeV using dilepton events

We report a measurement of the tt production cross section using dilepton events with jets and missing transverse energy in pp collisions at a center-of-mass energy of 1.96 TeV. Using a 197+/-12 pb(-1) data sample recorded by the upgraded Collider Detector at Fermilab, we use two complementary techniques to select candidate events. We compare the number of observed events and selected kinematical distributions with the predictions of the standard model and find good agreement. The combined result of the two techniques yields a tt production cross section of 7.0(+2.4)(-2.1)(stat)+1.6-1.1(syst)+/-0.4(lum) pb.     

Dark matter production at the LHC from black hole remnants

We study dark matter production at CERN LHC from black hole remnants (BHR). We find that the typical mass of these BHR at the LHC is ∼5–10 TeV which is heavier than other dark matter candidates, such as axion, axino, neutralino, etc. We propose the detection of this dark matter via single jet production in the process pp → jet + BHR (dark matter) at CERN LHC. We find that for zero impact parameter partonic collisions, the monojet cross section is not negligible in comparison to the standard model background and is much higher than the other dark matter scenarios studied so far. We also find that dσ/dp _T of jet production in this process increases as p _T increases, whereas in all other dark matter scenarios the dσ/dp _T decreases at CERN LHC. This may provide a useful signature for dark matter detection at the LHC. However, we find that when the impact parameter dependent effect of inelasticity is included, the monojet cross section from the above process becomes much smaller than the standard model background and may not be detectable at the LHC.     

NLO Corrections of HTC Π0 and Π+Π- Pair Production at ILC in TC2 Model

As well known, if the Higgs boson were not observed at LHC, the technicolor model would be the most favorable candidate responsible for the symmetry breaking. To overcome some defects in the previous model, some extended versions have been proposed. In the TC2 model typical signature is existence of heavy H_TC and technipion Π. A direct proof of validity of the model is to produce them at accelerator. Thus we study the production rates of e⁺ e^- → H_TCΠ⁰ and e⁺ e^- → Π⁺ Π^- at ILC in the topcolor-assisted technicolor (TC2) model. In fact, there is a flood of models belonging to new physics, which can result in products withcharacteristics similar to H_TC+Π of the TC2 model. Therefore to distinguish this model from others one may need to investigate some details by calculating the cross section to NLO. We indeed find that the NLO corrections are significant, namely the ratio δ ≡ (σ_NLO- σ_LO)/σ_LO in e⁺ e^- → H_TC Π⁰ exceeds 100% within a plausible parameter space.     

$W^{\pm}\pi_t^{\mp}$ Associated Production at Large Hadron Collider

In this paper we calculate the production of a charged top pion in association with a $W$ boson at the CERN Large Hadron Collider (LHC) in the context of the topcolor assisted technicolor model. We find that the cross section of $pp \rightarrow b\bar{b} \rightarrow W^{\pm}\pi_t^{\mp}$ is roughly corresponding to the result of the process $pp \rightarrow b\bar{b} \rightarrow W^{\pm}H^{\mp}$ in the minimal supersymmetric standard model, and for reasonable ranges of the parameters, the cross section can reach a few hundred fb. The $W^{\pm}\pi_t^{\mp}$ signal should be clearly visible at LHC unless $\pi_t^{\pm}$ is very heavy.     

Associate Higgs and gauge boson production at hadron colliders in a model with vector resonances

Motivated by new models of dynamical electroweak symmetry breaking that predict a light composite Higgs boson, we build an effective Lagrangian which describes the standard model (with a light Higgs) and vector resonances. We compute the cross section for the associate production of a Higgs and a gauge boson. For some values of model parameters we find that the cross section is significantly enhanced with respect to the standard model. This enhancement is similar at the LHC (large hadron collider) and the Tevatron for the same range of resonance mass. PACS 12.60.Nz     

The Effects of Simplest Little Higgs Model on the Spin Correlations in the Top Quark Pair Production at the LHC and ILC

In the simplest little Higgs model (SLH), we study the spin correlations in the top quark pair production at the LHC and ILC. We find that the SLH always suppresses the tt spin correlations compared to the SM values. At the LHC, the suppression can be over 10% for m_Z' < 750 GeV. The SLH prediction value is outside the 1σ range of the experimental data from ATLAS, and within 1σ range of the experimental data from CMS. At the ILC, the SLH can sizably suppress the tt spin correlation for m_Z' approaching the center-of-mass energy √s. For example, the maximal suppression can reach -22.5%, -14.5%, and -9.5% for √s=500 GeV, 800 GeV, and 1000 GeV, respectively. Therefore, the tt spin correlation at the ILC can be a sensitive probe for the SLH.     

Measurement of B(t --> Wb)/B(t--> Wq) at the collider detector at fermilab

We present a measurement of the ratio of top-quark branching fractions R = B(t --> Wb)/B(t --> Wq), where q can be a b, s, or a d quark, using lepton-plus-jets and dilepton data sets with an integrated luminosity of approximately 162 pb(-1) collected with the Collider Detector at Fermilab during Run II of the Tevatron. The measurement is derived from the relative numbers of tt events with different multiplicity of identified secondary vertices. We set a lower limit of R > 0.61 at 95% confidence level.     

Little Higgs models and single top production at the LHC

We investigate the corrections of the “littlest” Higgs (LH) model and the SU(3) simple group model to single top production at the CERN Large Hadron Collider (LHC). We find that the new gauge bosons W_H ^± predicted by the LH model can generate significant contributions to single top production via the s-channel process. The correction terms for the tree-level Wqq’ couplings coming from the SU(3) simple group model can give large contributions to the cross sections of the t-channel single top production process. We expect that the effects of the LH model and the SU(3) simple group model on single top production can be detected at the LHC experiments.