Heavy Quarkonium in a weakly-coupled quark-gluon plasma below the melting temperature

We calculate the heavy quarkonium energy levels and decay widths in a quark-gluon plasma, whose temperature T and screening mass m_D satisfy the hierarchy m alpha_s >> T >> m alpha_s^2 >> m_D (m being the heavy-quark mass), at order m alpha_s^5. We first sequentially integrate out the scales m, m alpha_s and T, and, next, we carry out the calculations in the resulting effective theory using techniques of integration by regions. A collinear region is identified, which contributes at this order. We also discuss the implications of our results concerning heavy quarkonium suppression in heavy ion collisions.Comment: 25 pages, 2 figure

Bethe--Salpeter equation in QCD

We extend to regular QCD the derivation of a confining $q \bar{q}$ Bethe--Salpeter equation previously given for the simplest model of scalar QCD in which quarks are treated as spinless particles. We start from the same assumptions on the Wilson loop integral already adopted in the derivation of a semirelativistic heavy quark potential. We show that, by standard approximations, an effective meson squared mass operator can be obtained from our BS kernel and that, from this, by ${1\over m^2}$ expansion the corresponding Wilson loop potential can be reobtained, spin--dependent and velocity--dependent terms included. We also show that, on the contrary, neglecting spin--dependent terms, relativistic flux tube model is reproduced.Comment: 23 pages, revte

OntoWebML: A Knowledge Base Management System for WSML Ontologies

This paper addresses the topic of defining a knowledge base system for representing and managing ontologies according to the WSMO conceptual model. We propose a software engineering approach to this problem, by implementing: (i) the relational model for ontologies that corresponds to the WSML representation of WSMO; (ii) the usage of a well known Web modeling language called WebML, extended by a set of new components for exploiting ontological contents in Web services and Web applications design; and (iii) a Web-based content management system for ontologies editing and reasoning, implemented using the abovementioned software engineering approach

Long-term results of iliac aneurysm repair with iliac branched endograft. A 5-year experience on 100 consecutive cases

Background: Iliac branch device (IBD) technique has been introduced as an appealing and effective solution to avoid complications occurring during repair of aorto-iliac aneurysm with extensive iliac involvement. Nevertheless, no large series with long-term follow-up of IBD are available. The aim of this study was to analyse safety and long-term efficacy of IBD in a consecutive series of patients.Methods: Between 2006 and 2011, 100 consecutive patients were enrolled in a prospective database on IBD. Indications included unilateral or bilateral common iliac artery aneurysms combined or not with abdominal aneurysms. Patients were routinely followed up with computed tomography. Data were reported according to the Kaplan-Meier method.Results: There were 96 males, mean age 74.1 years. Preoperative median common iliac aneurysm diameter was 40 mm (interquartile range (IQR): 35-44 mm). Sixty-seven patients had abdominal aortic aneurysm >35 mm (IQR: 40-57 mm) associated with iliac aneurysm. Eleven patients presented hypogastric aneurysm. Twelve patients underwent isolated iliac repair with IBD and 88 patients received associated endovascular aortic repair. Periprocedural technical success rate was 95%, with no mortality. Two patients experienced external iliac occlusion in the first month. At a median follow-up of 21 months (range 1-60) aneurysm growth >3 mm was detected in four iliac (4%) arteries. Iliac endoleak (one type III and two distal type I) developed in three patients and buttock claudication in four patients. Estimated patency rate of internal iliac branch was 91.4% at 1 and 5 years. Freedom from any reintervention rate was 90% at 1 year and 81.4% at 5 years. No late ruptures occurred.Conclusions: Long-term results show that IBD use can ensure persistent iliac aneurysm exclusion at 5 years, with low risk of reintervention. This technique can be considered as a first endovascular option in patients with extensive iliac aneurysm disease and favourable anatomy. (C) 2011 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved

Bottonium mass - evaluation using renormalon cancellation

We present a method of calculating the bottonium mass M[Upsilon(1S)] = [2 mb + E(b barb)]. The binding energy is separated into the soft and ultrasoft components E(b barb)=[E(s)+E(us)] by requiring the reproduction of the correct residue parameter value of the renormalon singularity for the renormalon cancellation in the sum [2 mb + E(s)]. The Borel resummation is then performed separately for (2 mb) and E(s), using the infrared safe MSbar mass [bar mb] as input. E(us) is estimated. Comparing the result with the measured value of M[Upsilon(1S)], the extracted value of the quark mass is [bar mb](mu=[bar mb]) = 4.241 +- 0.068 GeV (for the central value alphas(MZ)=0.1180). This value of [bar mb] is close to the earlier values obtained from the QCD spectral sum rules, but lower than from pQCD evaluations without the renormalon structure for heavy quarkonia.Comment: 4 pages, uses espcrc2.sty, presented at QCD0

A first estimate of triply heavy baryon masses from the pNRQCD perturbative static potential

Within pNRQCD we compute the masses of spin-averaged triply heavy baryons using the now-available NNLO pNRQCD potentials and three-body variational approach. We focus in particular on the role of the purely three-body interaction in perturbation theory. This we find to be reasonably small and of the order 25 MeV Our prediction for the Omega_ccc baryon mass is 4900(250) in keeping with other approaches. We propose to search for this hitherto unobserved state at B factories by examining the end point of the recoil spectrum against triple charm.Comment: 18 figures, 21 page

The spin-orbit potential and Poincar\'e invariance in finite temperature pNRQCD

Heavy quarkonium at finite temperature has been the subject of intense theoretical studies, for it provides a potentially clean probe of the quark-gluon plasma. Recent studies have made use of effective field theories to exploit in a systematic manner the hierarchy of energy scales that characterize the system. In the case of a quarkonium in a medium whose temperature is smaller than the typical momentum transfer in the bound state but larger than its energy, the suitable effective field theory is pNRQCD_HTL, where degrees of freedom with energy or momentum larger than the binding energy have been integrated out. Thermal effects are expected to break Poincar\'e invariance, which, at zero temperature, manifests itself in a set of exact relations between the matching coefficients of the effective field theory. In the paper, we evaluate the leading-order thermal corrections to the spin-orbit potentials of pNRQCD_HTL and show that Poincar\'e invariance is indeed violated.Comment: 17 page, 4 figures. Version published on JHE