Are There Hints of Light Stops in Recent Higgs Search Results?

The recent discovery at the LHC by the CMS and ATLAS collaborations of the Higgs boson presents, at long last, direct probes of the mechanism for electroweak symmetry breaking. While it is clear from the observations that the new particle plays some role in this process, it is not yet apparent whether the couplings and widths of the observed particle match those predicted by the Standard Model. In this paper, we perform a global fit of the Higgs results from the LHC and Tevatron. While these results could be subject to as-yet-unknown systematics, we find that the data are significantly better fit by a Higgs with a suppressed width to gluon-gluon and an enhanced width to gamma gamma, relative to the predictions of the Standard Model. After considering a variety of new physics scenarios which could potenially modify these widths, we find that the most promising possibility is the addition of a new colored, charged particle, with a large coupling to the Higgs. Of particular interest is a light, and highly mixed, stop, which we show can provide the required alterations to the combination of gg and gamma gamma widths.Comment: 6 pages, 5 figure

The Gaugephobic Higgs

We present a class of models that contains Randall-Sundrum and Higgsless models as limiting cases. Over a wide range of the parameter space WW scattering is mainly unitarized by Kaluza-Klein partners of the W and Z, and the Higgs particle has suppressed couplings to the gauge bosons. Such a gaugephobic Higgs can be significantly lighter than the 114 GeV LEP bound for a standard Higgs, or heavier than the theoretical upper bound. These models predict a suppressed single top production rate and unconventional Higgs phenomenology at the LHC: the Higgs production rates will be suppressed and the Higgs branching fractions modified. However, the more difficult the Higgs search at the LHC is, the easier the search for other light resonances (like Z', W', t', exotic fermions) will be.Comment: 20 pages, 3 figure

Next-to-leading order QCD predictions for A0Z0A^0Z^0 associated production at the CERN Large Hadron Collider

We present the calculations of the complete next-to-leading order (NLO) QCD corrections (including supersymmetric QCD) to the inclusive total cross sections of the associated production processes $pp\to A^0Z^0+X$ in the Minimal Supersymmetric Standard Model at the CERN Large Hadron Collider. Both the dimensional regularization scheme and the dimensional reduction scheme are used to organize the calculations which yield the same NLO rates. The NLO correction can either enhance or reduce the total cross sections, but it generally efficiently reduces the dependence of the total cross sections on the renormalization/factorization scale. We also examine the uncertainty of the total cross sections due to the parton distribution function uncertainties.Comment: 53 pages, 20 figures; the alpha_s in Eq.(70) is now evaluated at M_SUSY scale, not the \mu_r scale; numerical results updated, typos corrected; version to appear in PR

Intermolecular interactions in the TMEM16A dimer controlling channel activity

TMEM16A and TMEM16B are plasma membrane proteins with Ca2+ -dependent Cl- channel function. By replacing the carboxy-terminus of TMEM16A with the equivalent region of TMEM16B, we obtained channels with potentiation of channel activity. Progressive shortening of the chimeric region restricted the "activating domain" to a short sequence close to the last transmembrane domain and led to TMEM16A channels with high activity at very low intracellular Ca2+ concentrations. To elucidate the molecular mechanism underlying this effect, we carried out experiments based on double chimeras, Forster resonance energy transfer, and intermolecular cross-linking. We also modeled TMEM16A structure using the Nectria haematococca TMEM16 protein as template. Our results indicate that the enhanced activity in chimeric channels is due to altered interaction between the carboxy-terminus and the first intracellular loop in the TMEM16A homo-dimer. Mimicking this perturbation with a small molecule could be the basis for a pharmacological stimulation of TMEM16A-dependent Cl- transport

An Agent-Based Model of Collective Emotions in Online Communities

We develop a agent-based framework to model the emergence of collective emotions, which is applied to online communities. Agents individual emotions are described by their valence and arousal. Using the concept of Brownian agents, these variables change according to a stochastic dynamics, which also considers the feedback from online communication. Agents generate emotional information, which is stored and distributed in a field modeling the online medium. This field affects the emotional states of agents in a non-linear manner. We derive conditions for the emergence of collective emotions, observable in a bimodal valence distribution. Dependent on a saturated or a superlinear feedback between the information field and the agent's arousal, we further identify scenarios where collective emotions only appear once or in a repeated manner. The analytical results are illustrated by agent-based computer simulations. Our framework provides testable hypotheses about the emergence of collective emotions, which can be verified by data from online communities.Comment: European Physical Journal B (in press), version 2 with extended introduction, clarification