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.
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.
118658638
Top triangle moose: Combining Higgsless and topcolor mechanisms for mass generation
We present the details of a deconstructed model that incorporates both Higgsless and top-color mechanisms. The model alleviates the tension between obtaining the correct top quark mass and keeping {delta}{rho} small that exists in many Higgsless models. It does so by singling out the top quark mass generation as arising from a Yukawa coupling to an effective top Higgs which develops a small vacuum expectation value, while electroweak symmetry breaking results largely from a Higgsless mechanism. As a result, the heavy partners of the SM fermions can be light enough to be seen at the LHC. After presenting the model, we detail the phenomenology, showing that for a broad range of masses, these heavy fermions are discoverable at the LHC.
118671365
Technipion Limits from LHC Higgs Searches
LHC searches for the standard model Higgs Boson in di-photon or di-tau decay modes place strong constraints on the light top-pion state predicted in technicolor models that include colored technifermions. Compared with the standard Higgs Boson, the top-pions 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). These factors combine to make the technipions more visible in both channels than a standard model Higgs would be. Hence, the recent ATLAS and CMS searches for Higgs bosons exclude the presence of technipions with masses from 110 GeV to nearly twice the top-quark mass in technicolor models that (a) include colored technifermions (b) feature topcolor dynamics and (c) have technicolor groups with three or more technicolors. For certain models, the limits also apply out to higher technipion masses or down to the minimum number of technicolors. The limits may be softened somewhat in models where extended technicolor plays a significant role in producing the top quark's mass. Additional LHC data on di-tau and di-photon final states will be extremely valuable in further exploring technicolor parameter space.
118524954
Deconstructed Higgsless Models at LHC: The Top Triangle Moose
We describe a deconstructed Higgsless model in which electroweak symmetry breaking results largely from a Higgsless mechanism while the top quark mass is generated by a topcolor mechanism. The top quark mass arises from a Yukawa coupling to an effective top-Higgs which develops a small vacuum expectation value. Both the heavy partners of the electoweak gauge bosons and those for the SM fermions can be light enough to be visible at LHC.
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.
13920958
Development of large area polycrystalline diamond detectors for fast timing application of high-energy heavy-ion beams
We have studied the effects of electrode fabrication and detector capacitance on the time resolution of large area electronic grade polycrystalline chemical vapour deposited diamond sensors that are suitable for time of flight measurements of heavy ions at relativistic velocities. Sensors were prepared both in house, with Al or Au metal contacts, and commercially fabricated with Au/diamond-like carbon contacts. He, Ar and a mixture of Ne and O beams at 16.3, 33.5 and 21-23 MeV/u, respectively were used on these devices whilst arranged in transmission geometry. Signal processing only began over one meter away from the sensors. The present approach, where we have large-area/large capacitance multi-strip detectors with processing electronics at some distance from the target, is compatible with anticipated space limitations in particle- identification and tracking setups at existing and planned nuclear fragmentation facilities. In a systematic study under these conditions, we demonstrate that the time resolution is limited by detector capacitance and energy deposition in the sensors. An intrinsic time resolution σ = (44±5) ps was achieved for a diamond detector of ∼ 14 pF capacitance. We conclude that, once further refinements are made, a large area time of flight detection system using polycrystalline diamond detectors would be able to provide time resolutions better than 40 ps, approaching the requirement for particle-identification in relativistic fragmentation experiments, such as those at the facility for antiproton and ion research, FAIR. © 2012 IOP Publishing Ltd and Sissa Medialab srl.
88510456
Experimental study of β -delayed proton decay of Al 23 for nucleosynthesis in novae
The {beta}-delayed {gamma} and proton decay of {sup 23}Al has been studied with an alternative detector setup at the focal plane of the momentum achromat recoil separator MARS at Texas A and M University. We could detect protons down to an energy of 200 keV and determine the corresponding branching ratios. Contrary to results of previous {beta}-decay studies, no strong proton intensity from the decay of the isobaric analog state (IAS) of the {sup 23}Al ground state at E{sub x}=7803 keV in {sup 23}Mg was observed. Instead we assign the observed low-energy group E{sub p,c.m.}=206 keV to the decay from a state that is 16 keV below the IAS. We measured both proton and gamma branches from the decay of this state at E{sub x}=7787 keV in {sup 23}Mg, which is a very rare case in the literature. Combining our data with its measured lifetime, we determine its resonance strength to be {omega}{gamma}=1.4{sub -0.4}{sup +0.5} meV. The value is in agreement with older direct measurements, but disagrees with a recent direct measurement. This state is the most important resonance for the radiative proton capture {sup 22}Na(p,{gamma}){sup 23}Mg in some astrophysical environments, such as novae.