8154831
Composite scalars at CERN LEP: Constraining technicolor theories
LEP I and LEP II data can be used to constrain technicolor models with light, neutral pseudo-NambuGoldstone bosons, P a . We use published limits on branching ratios and cross sections for final states with photons, large missing energy, jet pairs, or bb pairs to constrain the anomalous P a Z 0 Z 0 , P a Z 0 , and P a couplings. From these results, we derive bounds on the size of the technicolor gauge group and the number of technifermion doublets in models such as Low-scale Technicolor.
119418089
Phenomenology of a technicolor model with heavy scalar doublet
Abstract Rather than having a light scalar both break SU(2) × U(1) and give mass to the fermions, as in the standard model, it is possible to use technicolor to do the first while a heavy (∼ 10 TeV) scalar does the second. The impact of such a heavy scalar on FCNC in the Kaon and B-meson systems is explored here.
118611256
Hypercharge-Universal Topcolor
We propose and discuss the phenomenology of a topcolor-assisted technicolor model with a flavor-universal hypercharge sector. After discussing the symmetry-breaking pattern and low-energy effective Lagrangian, we examine various experimental and theoretical constraints, finding that precision electroweak measurements yield the strongest bounds on the model. We perform a combined fit to all available $Z$-pole and LEP2 data and find that the goodness of fit for hypercharge-universal topcolor is comparable to that of the standard model. In contrast, topcolor-assisted technicolor models with a flavor nonuniversal hypercharge sector are markedly disfavored by the data.
18592130
Thinking About Top: Looking Outside The Standard Model ∗
The top quark is by far the heaviest known fermion [1]. In consequence, experiment is just beginning to explore its properties, and some of them may yet prove to be distinctly non-standard. The very size of the top quark’s mass even hints at the possibility of a special role for top in electroweak symmetry breaking. This talk examines the top quark in the context of physics beyond the standard model, and discusses how Run II can help elucidate the true nature of top.
118713106
Technicolor in the LHC Era
LHC searches for the standard model Higgs Boson in \gamma\gamma\ or \tau\tau\ decay modes place strong constraints on the light technipion state predicted in technicolor models that include colored technifermions. Compared with the standard Higgs Boson, the technipions have an enhanced production rate (largely because the technipion decay constant is smaller than the weak scale) and also enhanced branching ratios into di-photon and di-tau final states (largely due to the suppression of WW decays of the technipions). Recent ATLAS and CMS searches for Higgs bosons exclude the presence of technipions with masses from 110 GeV to nearly 2m_t in technicolor models that (a) include colored technifermions (b) feature topcolor dynamics and (c) have technicolor groups with three or more technicolors (N_{TC} > 3).
199660803
The Limits of Custodial Symmetry
We introduce a toy model implementing the proposal of using a custodial symmetry to protect the Z b_L bbar_L coupling from large corrections. This "doublet-extended standard model" adds a weak doublet of fermions (including a heavy partner of the top quark) to the particle content of the standard model in order to implement an O(4) x U(1)_X = SU(2)_L x SU(2)_R x P_LR x U(1)_X symmetry in the top-quark mass generating sector. This symmetry is softly broken to the gauged SU(2)_L x U(1)_Y electroweak symmetry by a Dirac mass M for the new doublet; adjusting the value of M allows us to explore the range of possibilities between the O(4)-symmetric (M to 0) and standard-model-like (M to infinity) limits.
119400873
Chandra Observations of the Transient 7 s X-ray Pulsar AX J1845.0–0258
We present the results of Chandra X-Ray Observatory observations of the transient anomalous X-ray pulsar candidate AX J1845.0-0258 in apparent quiescence. Within the source's error circle, we find a point source and possible counterpart, which we designate CXOU J184454.6-025653. No coherent pulsations are detected, and no extended emission is seen. The source's spectrum is equally well described by a blackbody model of temperature kT ~ 2.0 keV or a power-law model with photon index Γ ~ 1.0. This is considerably harder than was seen for AX J1845.0-0258 during its period of brightening in 1993 (kT ~ 0.6 keV) despite being at least ~13 times fainter. This behavior is opposite to that observed in the case of the established transient AXP, XTE J1810-197. We therefore explore the possibility that CXOU J184454.6-025653 is an unrelated source and that AX J1845.0-0258 remains undetected since 1993, with a flux 260-430 times fainter than at that epoch. If so, this would represent an unprecedented range of variability in AXPs.