Two-loop electroweak top corrections: are they under control?

The assumption that two-loop top corrections are well approximated by the $O(G_mu^2 mt^4)$ contribution is investigated. It is shown that in the case of the ratio neutral-to-charged current amplitudes at zero momentum transfer the $O(G_mu^2 mt^2 M_Z^2)$ terms are numerically comparable to the $m_t^4$ contribution for realistic values of the top mass. An estimate of the theoretical error due to unknown two-loop top effect is presented for a few observables of LEP interest.Comment: 13 pages, LaTeX using equations, doublespace, cite macros. Hard copies of the paper including one figure are available from [email protected]

Towards precise predictions for Higgs-boson production in the MSSM

We study the production of scalar and pseudoscalar Higgs bosons via gluon fusion and bottom-quark annihilation in the MSSM. Relying on the NNLO-QCD calculation implemented in the public code SusHi, we provide precise predictions for the Higgs-production cross section in six benchmark scenarios compatible with the LHC searches. We also provide a detailed discussion of the sources of theoretical uncertainty in our calculation. We examine the dependence of the cross section on the renormalization and factorization scales, on the precise definition of the Higgs-bottom coupling and on the choice of PDFs, as well as the uncertainties associated to our incomplete knowledge of the SUSY contributions through NNLO. In particular, a potentially large uncertainty originates from uncomputed higher-order QCD corrections to the bottom-quark contributions to gluon fusion.Comment: 62 pages, 24 pdf figures; v2: minor clarifications, improved plot quality, matches published versio

Fermion Virtual Effects in e+e−−>W+W−e^+ e^- -> W^+ W^- Cross Section

We analyse the contribution of new heavy virtual fermions to the $e^+e^- \rightarrow W^+W^-$ cross section. We find that there exists a relevant interplay between trilinear and bilinear oblique corrections. The result strongly depends on the chiral or vector--like nature of the new fermions. As for the chiral case we consider sequential fermions: one obtains substantial deviation from the Standard model prediction, making the effect possibly detectable at $\sqrt{s}=500$ or $1000$ GeV linear colliders. As an example for the vector--like case we take a SUSY extension with heavy charginos and neutralinos: due to cancellation, the final effect turns out to be negligible.Comment: uuencoded, gz-compressed, tar-ed file. 8 pages, 4 EPS figures, uses EPSFIG.ST

Dynamics of Nucleation in the Ising Model

Reactive pathways to nucleation in a three-dimensional Ising model at 60% of the critical temperature are studied using transition path sampling of single spin flip Monte Carlo dynamics. Analysis of the transition state ensemble (TSE) indicates that the critical nuclei are rough and anisotropic. The TSE, projected onto the free energy surface characterized by cluster size, N, and surface area, S, indicates the significance of other variables in addition to these two traditional reaction coordinates for nucleation. The transmission coefficient along N is ~ 0.35, and this reduction of the transmission coefficient from unity is explained in terms of the stochastic nature of the dynamic model.Comment: In press at the Journal of Physical Chemistry B, 7 pages, 8 figure

Vacuum Condensates and Dynamical Mass Generation in Euclidean Yang-Mills Theories

Vacuum condensates of dimension two and their relevance for the dynamical mass generation for gluons in Yang-Mills theories are discussedComment: Talk given at the International Conference on Color Confinement and Hadrons in Quantum Chromodynamics, Confinement 2003, TITech and RIKEN, Tokyo, Japan, July 21-24, 200

Long-term subjective outcomes of barbed reposition pharyngoplasty for obstructive sleep apnea syndrome treatment

Background: The purpose of this study was to evaluate long-term subjective outcomes of barbed reposition pharyngoplasty for obstructive sleep apnea syndrome (OSAS) treatment using a specific questionnaire, the Palate Postoperative Problem Score (PPOPS). Methods: 140 patients who underwent barbed reposition pharyngoplasty (BRP) surgery in the Morgagni Pierantoni Hospital of Forlì, Italy were enrolled in the study. Postoperative outcomes were evaluated in a short- and long-term follow-up using the PPOPS questionnaire. The average period of follow-up was 26 months. All patients received the PPOPS questionnaire by telephone in a period between April and August 2019. Results: 51% of patients complained of swallowing problems after surgery. In 91% of cases, the problem cleared up spontaneously. At the time of the interview, only 9% of patients had a residual swallowing difficult. At the time of PPOPS evaluation, rhinolalia was observed in 8% of patients, whereas nose regurgitation was present in 2% of patients. In 20% of patients, the foreign body sensation was present during follow-up. The value of apnea-hypopnea index (AHI) reduced from the preoperative value of 31.5 to the postoperative value of 11.4. Conclusions: BRP surgery proved to be an effective technique, appreciated by the majority of patients. Use of the PPOPS questionnaire has demonstrated that the BRP technique seems to ensure efficacy and lower morbidity, with few complications after surgery

Translation of Anticancer Efficacy From Nonclinical Models to the Clinic

Mouse cancer models have provided critical insights into tumor biology; however, clinical translation of these findings has been challenging. This perspective posits that factors impacting on successful translation start with limitations in capturing human cancer pathophysiology and end with challenges in generating robust translatable preclinical end points. A comprehensive approach that considers clinically relevant mouse models with both an integrated biomarker strategy and a complementary modeling and simulation effort will strengthen the current oncology drug development paradigm

The Multitude of Molecular Hydrogen Knots in the Helix Nebula

We present HST/NICMOS imaging of the H_2 2.12 \mu m emission in 5 fields in the Helix Nebula ranging in radial distance from 250-450" from the central star. The images reveal arcuate structures with their apexes pointing towards the central star. Comparison of these images with comparable resolution ground based images reveals that the molecular gas is more highly clumped than the ionized gas line tracers. From our images, we determine an average number density of knots in the molecular gas ranging from 162 knots/arcmin^2 in the denser regions to 18 knots/arcmin^2 in the lower density outer regions. Using this new number density, we estimate that the total number of knots in the Helix to be ~23,000 which is a factor of 6.5 larger than previous estimates. The total neutral gas mass in the Helix is 0.35 M_\odot assuming a mass of \~1.5x10^{-5} M_\odot for the individual knots. The H_2 intensity, 5-9x10^{-5} erg s^{-1} cm^{-2} sr^{-1}, remains relatively constant with projected distance from the central star suggesting a heating mechanism for the molecular gas that is distributed almost uniformly in the knots throughout the nebula. The temperature and H_2 2.12 \mu m intensity of the knots can be approximately explained by photodissociation regions (PDRs) in the individual knots; however, theoretical PDR models of PN under-predict the intensities of some knots by a factor of 10.Comment: 26 pages, 3 tables, 10 figures; AJ accepte

A screening mechanism for extra W and Z gauge bosons

We generalize a previous construction of a fermiophobic model to the case of more than one extra $W$ and $Z$ gauge bosons. We focus in particular on the existence of screening configurations and their implication on the gauge boson mass spectrum. One of these configurations allows for the existence of a set of relatively light new gauge bosons, without violation of the quite restrictive bounds coming from the $\rho_{\rm NC}$ parameter. The links with Bess and degenerate Bess models are also discussed. Also the signal given here by this more traditional gauge extension of the SM could help to disentangle it from the towers of Kaluza-Klein states over $W$ and $Z$ gauge bosons in extra dimensions.Comment: 23 pages, 1 figure, extended discussion on precision tests. To appear in International Journal of Modern Physics