Hadron Mass Effects in Power Corrections to Event Shapes

We study the effect of hadron masses on the leading power correction of dijet event-shape distributions. We define the transverse velocity operator, that describes the effects of hadron masses. It depends on the "transverse velocity" r, which is different from one only for non-vanishing hadron masses. We find that hadron-mass effects in general break universality. However we provide a simple method to identify universality classes of event shapes with a common power correction. We also compute the anomalous dimension of the power correction and the structure of the corresponding Wilson coefficient, finding a nontrivial result.Comment: 8 pages, 3 figures, 2 tables, to appear in the proceedings of Xth Quark Confinement and the Hadron Spectru

GenEvA (I): A new framework for event generation

We show how many contemporary issues in event generation can be recast in terms of partonic calculations with a matching scale. This framework is called GenEvA, and a key ingredient is a new notion of phase space which avoids the problem of phase space double-counting by construction and includes a built-in definition of a matching scale. This matching scale can be used to smoothly merge any partonic calculation with a parton shower. The best partonic calculation for a given region of phase space can be determined through physics considerations alone, independent of the algorithmic details of the merging. As an explicit example, we construct a positive-weight partonic calculation for e+e- -> n jets at next-to-leading order (NLO) with leading-logarithmic (LL) resummation. We improve on the NLO/LL result by adding additional higher-multiplicity tree-level (LO) calculations to obtain a merged NLO/LO/LL result. These results are implemented using a new phase space generator introduced in a companion paper [arXiv:0801.4028].Comment: 60 pages, 22 figures, v2: corrected typos, added reference

GenEvA (II): A phase space generator from a reweighted parton shower

We introduce a new efficient algorithm for phase space generation. A parton shower is used to distribute events across all of multiplicity, flavor, and phase space, and these events can then be reweighted to any desired analytic distribution. To verify this method, we reproduce the e+e- -> n jets tree-level result of traditional matrix element tools. We also show how to improve tree-level matrix elements automatically with leading-logarithmic resummation. This algorithm is particularly useful in the context of a new framework for event generation called GenEvA. In a companion paper [arXiv:0801.4026], we show how the GenEvA framework can address contemporary issues in event generation.Comment: 54 pages, 20 figures, v2: corrected typos, added reference

Intermediate-Term Risk of Stroke Following Cardiac Procedures in a Nationally Representative Data Set.

BACKGROUND: Studies on stroke risk following cardiac procedures addressed only perioperative and long-term risk following limited higher-risk procedures, were poorly generalizable, and often failed to stratify by stroke type. We calculated stroke risk in the intermediate risk period following cardiac procedures compared with common noncardiac surgeries and medical admissions. METHODS AND RESULTS: The Nationwide Readmissions Database contains readmission data for 49% of US admissions in 2013. We compared age-adjusted stroke readmission rates up to 90 days postdischarge. We used Cox regression to calculate hazard ratios, up to 1 year, of stroke risk comparing transcatheter aortic valve replacement versus surgical aortic valve replacement and coronary artery bypass graft versus percutaneous coronary intervention. Procedures and diagnoses were identified by International Classification of Disease, Ninth Revision, Clinical Modification codes. After cardiac procedures, 90-day ischemic stroke readmission rate was highest after transcatheter aortic valve replacement (2.05%); 90-day hemorrhagic stroke rate was highest after left ventricular assist device placement (0.09%). The hazard ratio for ischemic stroke after transcatheter aortic valve replacement, compared with surgical aortic valve replacement, in fully adjusted Cox models was 1.86 (95% confidence interval, 1.12-3.08; P=0.016) and 6.17 (95% confidence interval, 1.97-19.33; P=0.0018) for hemorrhagic stroke. There was no difference between coronary artery bypass graft and percutaneous coronary intervention. CONCLUSIONS: We demonstrated elevated readmission rates for ischemic and hemorrhagic stroke in the intermediate 30-, 60-, and 90-day risk periods following common cardiac procedures. Furthermore, we found an elevated risk of stroke after transcatheter aortic valve replacement compared with surgical aortic valve replacement up to 1 year

An effective thermodynamic potential from the instanton with Polyakov-loop contributions

We derive an effective thermodynamic potential (Omega_eff) at finite temperature (T>0) and zero quark-chemical potential (mu_R=0), using the singular-gauge instanton solution and Matsubara formula for N_c=3 and N_f=2 in the chiral limit. The momentum-dependent constituent-quark mass is also obtained as a function of T, employing the Harrington-Shepard caloron solution in the large-N_c limit. In addition, we take into account the imaginary quark chemical potential mu_I = A_4, translated as the traced Polayakov-loop (Phi) as an order parameter for the Z(N_c) symmsetry, characterizing the confinement (intact) and deconfinement (spontaneously broken) phases. As a result, we observe the crossover of the chiral (chi) order parameter sigma^2 and Phi. It also turns out that the critical temperature for the deconfinment phase transition, T^Z_c is lowered by about (5-10)% in comparison to the case with a constant constituent-quark mass. This behavior can be understood by considerable effects from the partial chiral restoration and nontrivial QCD vacuum on Phi. Numerical calculations show that the crossover transitions occur at (T^chi_c,T^Z_c) ~ (216,227) MeV.Comment: 15 pages, 7 figure