Single Top Quark Production via FCNC Couplings at Hadron Colliders

We calculate single top-quark production at hadron colliders via the chromo-magnetic flavor-changing neutral current couplings $\bar tcg$ and $\bar tug$. We find that the strength for the anomalous $\bar tcg$ ($\bar tug$) coupling may be probed to $\kappa_c / \Lambda = 0.092 {TeV}^{-1}$ ($\kappa_u / \Lambda = 0.026 {TeV}^{-1}$) at the Tevatron with $2 {fb}^{-1}$ of data and $\kappa_c / \Lambda = 0.013 {TeV}^{-1}$ ($\kappa_u / \Lambda = 0.0061 {TeV}^{-1}$) at the LHC with $10 {fb}^{-1}$ of data. The two couplings may be distinguished by a comparision of the single top signal with the direct top and top decay signals for these couplings.Comment: 18 pages, 6 figures, 3 table

Top-Charm Associated Production in High Energy e+e−e^+e^- Collisions

The possibility of exploring the flavor changing neutral current $tcZ/tc\gamma$ couplings in the production vertex for the reaction \epem\to t\bar c + \bar tc is examined. Using a model independent parameterization for the effective Lagrangian to describe the most general three-point interactions, production cross sections are found to be relatively small at LEP II, but potentially sizeable at higher energy \epem colliders. The kinematic characteristics of the signal are studied and a set of cuts are devised for clean separation of the signal from background. The resulting sensitivity to anomalous flavor changing couplings at LEP II with an integrated luminosity of $4\times 500$ pb$^{-1}$ is found to be comparable to their present indirect constraints from loop processes, while at higher energy colliders with $0.5-1$ TeV center-of-mass energy and 50-200 fb$^{-1}$ luminosity, one expects to reach a sensitivity at or below the percentage level.Comment: Latex, 22 page

Top-quark rare decay t→cht\to c h in R-parity-violating SUSY

The flavor-changing top-quark decay $t\to c h$, where $h$ is the lightest CP-even Higgs boson in the minimal supersymmetric standard model, is examined in the R-parity-violating supersymmetric model. Within the existing bounds on the relevant R-parity-violating couplings, the branching fraction for $t\to c h$ can be as large as about $10^{-5}$ in some part of the parameter space.Comment: version to appear in Phys. Lett.

Flavor changing single top quark production channels at e^+e^- colliders in the effective Lagrangian description

We perform a global analysis of the sensitivity of LEP2 and e^+e^- colliders with a c.m. energy in the range 500 - 2000 GeV to new flavor-changing single top quark production in the effective Lagrangian approach. The processes considered are sensitive to new flavor-changing effective vertices such as Ztc, htc, four-Fermi tcee contact terms as well as a right-handed Wtb coupling. We show that e^+ e^- colliders are most sensitive to the physics responsible for the contact tcee vertices. For example, it is found that the recent data from the 189 GeV LEP2 run can be used to rule out any new flavor physics that can generate these four-Fermi operators up to energy scales of \Lambda > 0.7 - 1.4 TeV, depending on the type of the four-Fermi interaction. We also show that a corresponding limit of \Lambda > 1.3 - 2.5 and \Lambda > 17 - 27 TeV can be reached at the future 200 GeV LEP2 run and a 1000 GeV e^+e^- collider, respectively. We note that these limits are much stronger than the typical limits which can be placed on flavor diagonal four-Fermi couplings. Similar results hold for \mu^+\mu^- colliders and for tu(bar) associated production. Finally we briefly comment on the necessity of measuring all flavor-changing effective vertices as they can be produced by different types of heavy physics.Comment: 34 pages, plain latex, 7 figures embadded in the text using epsfig. Added new references and discussions regarding their relevance to the paper. Added more comments on the comparison between flavor-changing and flavor-diagonal contact terms and on the importance of measuring the Ztc verte

Direct Top Quark Production at Hadron Colliders as a Probe of New Physics

We examine the effect of an anomalous flavor changing chromomagnetic moment which allows direct top quark production (two partons combining into an unaccompanied single top quark in the s-channel) at hadron colliders. We consider both t-c-g and t-u-g couplings. We find that the anomalous charm quark coupling parameter $\kappa_c / \Lambda$ can be measured down to $.06 TeV^{-1}(.009 TeV^{-1}$) at the Tevatron with the Main Injector upgrade(LHC). The anomalous up quark coupling parameter $\kappa_u / \Lambda$ can be measured to $.02 TeV^{-1}(.003 TeV^{-1}$) at the Tevatron(LHC).Comment: 14 pages, Latex, requires feynm

Who Smokes in Europe? Data From Twelve European Countries in the TackSHS Survey (2017-2018)

Background: Population data on tobacco use and its determinants require continuous monitoring and careful inter-country comparison. We aimed to provide the most up-to-date estimates on tobacco smoking from a large cross-sectional survey, conducted in selected European countries. Methods: Within the TackSHS Project, a face-to-face survey on smoking was conducted in 2017–2018 in 12 countries: Bulgaria, England, France, Germany, Greece, Ireland, Italy, Latvia, Poland, Portugal, Romania, and Spain, representing around 80% of the 432 million European Union (EU) adult population. In each country, a representative sample of around 1,000 subjects aged 15 years and older was interviewed, for a total of 11,902 participants. Results: Overall, 25.9% of participants were current smokers (31.0% of men and 21.2% of women, P \u3c 0.001), while 16.5% were former smokers. Smoking prevalence ranged from 18.9% in Italy to 37.0% in Bulgaria. It decreased with increasing age (compared to Conclusions: These smoking prevalence estimates represent the most up-to-date evidence in Europe. From them, it can be derived that there are more than 112 million current smokers in the EU-28. Lower socio-economic status is a major determinant of smoking habit in both sexes

Forward pi^0 Production and Associated Transverse Energy Flow in Deep-Inelastic Scattering at HERA

Deep-inelastic positron-proton interactions at low values of Bjorken-x down to x \approx 4.10^-5 which give rise to high transverse momentum pi^0 mesons are studied with the H1 experiment at HERA. The inclusive cross section for pi^0 mesons produced at small angles with respect to the proton remnant (the forward region) is presented as a function of the transverse momentum and energy of the pi^0 and of the four-momentum transfer Q^2 and Bjorken-x. Measurements are also presented of the transverse energy flow in events containing a forward pi^0 meson. Hadronic final state calculations based on QCD models implementing different parton evolution schemes are confronted with the data.Comment: 27 pages, 8 figures and 3 table

The Astropy Problem

The Astropy Project (http://astropy.org) is, in its own words, "a community effort to develop a single core package for Astronomy in Python and foster interoperability between Python astronomy packages." For five years this project has been managed, written, and operated as a grassroots, self-organized, almost entirely volunteer effort while the software is used by the majority of the astronomical community. Despite this, the project has always been and remains to this day effectively unfunded. Further, contributors receive little or no formal recognition for creating and supporting what is now critical software. This paper explores the problem in detail, outlines possible solutions to correct this, and presents a few suggestions on how to address the sustainability of general purpose astronomical software

Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA

An investigation of the hadronic final state in diffractive and non--diffractive deep--inelastic electron--proton scattering at HERA is presented, where diffractive data are selected experimentally by demanding a large gap in pseudo --rapidity around the proton remnant direction. The transverse energy flow in the hadronic final state is evaluated using a set of estimators which quantify topological properties. Using available Monte Carlo QCD calculations, it is demonstrated that the final state in diffractive DIS exhibits the features expected if the interaction is interpreted as the scattering of an electron off a current quark with associated effects of perturbative QCD. A model in which deep--inelastic diffraction is taken to be the exchange of a pomeron with partonic structure is found to reproduce the measurements well. Models for deep--inelastic $ep$ scattering, in which a sizeable diffractive contribution is present because of non--perturbative effects in the production of the hadronic final state, reproduce the general tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil

Search for Single Top Production at LEP

Single top production in e+e- annihilations is searched for in data collected by the L3 detector at centre-of-mass energies from 189 to 209 GeV, corresponding to a total integrated luminosity of 634 pb-1. Investigating hadronic and semileptonic top decays, no evidence of single top production at LEP is obtained and upper limits on the single top cross section as a function of the centre-of-mass energy are derived. Limits on possible anomalous couplings, as well as on the scale of contact interactions responsible for single top production are determined