In hadronic collisions at high energies, the top-quark may be treated as a parton inside a hadron. Top-quark initiated processes become increasingly important since the top-quark luminosity can reach a few percent of the bottom-quark luminosity. In t
he production of a heavy particle $H$ with mass $m_H > m_t$, treating the top-quark as a parton allows us to resum large logarithms $log(m_{H}^{2}/m_{t}^{2}$) arising from collinear splitting in the initial state. We quantify the effect of collinear resummation at the 14-TeV LHC and a future 100-TeV hadron collider, focusing on the top-quark open-flavor process $ggto tbar t H$ in comparison with $tbar t to H$ and $tgrightarrow tH$ at the leading order (LO) in QCD. We employ top-quark parton distribution functions with appropriate collinear subtraction and power counting. We find that (1) Collinear resummation enhances the inclusive production of a heavy particle with $m_Happrox$ 5 TeV (0.5 TeV) by more than a factor of two compared to the open-flavor process at a 100-TeV (14-TeV) collider; (2) Top-quark mass effects are important for scales $m_H$ near the top-quark threshold, where the cross section is largest. We advocate a modification of the ACOT factorization scheme, dubbed m-ACOT, to consistently treat heavy-quark masses in hadronic collisions; (3) The scale uncertainty of the total cross section in m-ACOT is of about 20 percent at the LO. While a higher-order calculation is indispensable for a precise prediction, the LO cross section is well described by the process $tbar tto H$ using an effective factorization scale significantly lower than $m_H$. We illustrate our results by the example of a heavy spin-0 particle. Our main results also apply to the production of particles with spin-1 and 2.
We investigate the prospects of observing a neutral Higgs boson decaying into a pair of $W$ bosons (one real and the other virtual), followed by the $W$ decays into $qq ell u$ or $jjell u$ at the CERN Large Hadron Collider (LHC). Assuming that the mi
ssing transverse energy comes solely from the neutrino in $W$ decay, we can reconstruct the $W$ masses and then the Higgs mass. At the LHC with a center of mass energy ($sqrt{s}$) of 8 TeV and an integrated luminosity ($L$) of 25 fb$^{-1}$, we can potentially establish a $6sigma$ signal. A $5sigma$ discovery of $H to WW^* to jjell u$ for $sqrt{s} = 14$ TeV can be achieved with $L = $ 6 fb$^{-1}$. The discovery of $H to WW$ implies that the recently discovered new boson is a CP-even scalar if its spin is zero. In addition, this channel will provide a good opportunity to study the $HWW$ coupling.
We investigate the prospects for the discovery of massive color-octet vector bosons at the CERN Large Hadron Collider with $sqrt{s} = 14$ TeV. A phenomenological Lagrangian is adopted to evaluate the cross section of a pair of colored vector bosons (
colorons, $tilde{rho}$) decaying into four colored scalar resonances (hyper-pions, $tilde{pi}$), which then decay into eight gluons. We include the dominant physics background from the production of $8g,7g1q, 6g2q$, and $5g3q$, and determine the masses of $tilde{pi}$ and $tilde{rho}$ where discovery is possible. For example, we find that a 5$sigma$ signal can be established for $M_{tilde{pi}} alt 495$ GeV ($M_{tilde{rho}} alt 1650$ GeV). More generally we give the reach of this process for a selection of possible cuts and integrated luminosities.
We investigate the prospects for the discovery of a neutral Higgs boson produced with one bottom quark followed by Higgs decay into a pair of bottom quarks at the CERN Large Hadron Collider (LHC) and the Fermilab Tevatron Collider. We work within the
framework of the minimal supersymmetric standard model. The dominant physics background is calculated with realistic acceptance cuts and efficiencies including the production of $bbbar{b}$, $bar{b}bbar{b}$, $jbbar{b}$ ($j = g, q, bar{q}$; $q = u, d, s, c$), $tbar{t} to bbar{b}jjell u$, and $tbar{t} to bbar{b}jjjj$. Promising results are found for the CP-odd pseudoscalar ($A^0$) and the heavier CP-even scalar ($H^0$) Higgs bosons with masses up to 800 GeV for the LHC with an integrated luminosity ($L$) of 30 fb$^{-1}$ and up to 1 TeV for $L =$ 300 fb$^{-1}$.
