48 research outputs found
Collider signals of a composite Higgs in the Standard Model with four generations
Recent fits of electroweak precision data to the Standard Model (SM) with a
4th sequential family (SM4) point to a possible "three-prong composite
solution": (1) the Higgs mass is at the TeV-scale, (2) the masses of the 4th
family quarks t',b' are of O(500) GeV and (3) the mixing angle between the 4th
and 3rd generation quarks is of the order of the Cabibbo angle, \theta_{34} ~
O(0.1). Such a manifestation of the SM4 is of particular interest as it may
suggest that the Higgs is a composite state, predominantly of the 4th
generation heavy quarks. Motivated by the above, we show that the three-prong
composite solution to the SM4 can have interesting new implications for Higgs
phenomenology. For example, the Higgs can decay to a single heavy 4th
generation quark via the 3-body decays (through an off-shell t' or b') H ->
t'(bar) t'* -> t'(bar) b W+ and H -> b'(bar) b'* -> b'(bar) t W-. These flavor
diagonal decays can be dramatically enhanced at the LHC (by several orders of
magnitudes) due to the large width effects of the resonating heavy Higgs in the
processes gg -> H -> t'(bar) t'* -> t'(bar) b W+ and gg -> H -> b'(bar) b'* ->
b'(bar) t W-, thus yielding a viable signal above the corresponding continuum
QCD production rates. In addition, the Higgs can decay to a single t' and b' in
the loop-generated flavor changing (FC) channels H -> b' b(bar), t' t(bar).
These FC decays are essentially "GIM-free" and can, therefore, have branching
ratios as large as 10^{-4} - 10^{-3}.Comment: As published in Phys.Lett.B688:195-201,201
Enhancement of CP Violation in B^+- to K_i^+- D^0 By Resonant Effects
Resonance width effects in charged decays to neutral mesons and
excited kaon states around 1400 MeV are shown to lead to large calculable
final state phases. asymmetries are defined for any charged decay to
three pseudoscalar mesons involving intermediate overlapping resonance states.
Asymmetries up to about 10 are found in .
Decay distributions can be used to determine the weak phase of the
Cabibbo-Kobayashi-Maskawa (CKM) matrix. No separation of the contributions from
individual resonances is required.Comment: 11 page
Experimental Constraints on Scharm-Stop Flavor Mixing and Implications in Top-quark FCNC Processes
We examine experimental constraints on scharm-stop flavor mixing in the
minimal supersymmetric standard model, which arise from the experimental bounds
on squark and Higgs boson masses, the precision measurements of W-boson mass
and the effective weak mixing angle, as well as the experimental data on
B_s-\bar B_s mixing and b -> s gamma. We find that the combined analysis can
put rather stringent constraints on \tilde{c}_L-\tilde{t}_L and
\tilde{c}_L-\tilde{t}_R mixings. As an illustration for the effects of such
constraints, we examine various top-quark flavor-changing neutral-current
processes induced by scharm-stop mixings at the LHC and find that their maximal
rates are significantly lowered.Comment: B_s mass difference constraint added (version in PRD, rapid
communication