Search results for " effective"
showing 10 items of 380 documents
Spectator Effects in the Heavy Quark Effective Theory
1996
We present a complete analysis of the Heavy Quark Effective Theory Lagrangian at order $1/m^2$ in the leading logarithmic approximation, including effects induced by spectator quarks. At this order new correction terms appear in the effective Lagrangian, as four-quark operators containing both heavy and light quark fields. We compute the coefficients of these operators to one-loop order and in the leading-logarithmic approximation. Two of them break the heavy quark spin symmetry and we estimate their contribution to the hyperfine splitting of the heavy mesons in the factorization approximation. We find that they make a positive contribution to the hyperfine splitting of about 10% of the mea…
Resummation prediction on top quark transverse momentum distribution at largepT
2012
We study the factorization and resummation of t-channel top quark transverse momentum distribution at large pT in the SM at both the Tevatron and the LHC with soft-collinear effective theory. The cross section in the threshold region can be factorized into a convolution of hard, jet and soft functions. In particular, we first calculate the NLO soft functions for this process, and give a RG improved cross section by evolving the different functions to a common scale. Our results show that the resummation effects increase the NLO results by about 9%-13% and 4%-9% when the top quark pT is larger than 50 and 70 GeV at the Tevatron and the 8 TeV LHC, respectively. Also, we discuss the scale inde…
Infrared singularities of scattering amplitudes in perturbative QCD
2009
An exact formula is derived for the infrared singularities of dimensionally regularized scattering amplitudes in massless QCD with an arbitrary number of legs, valid at any number of loops. It is based on the conjecture that the anomalous-dimension matrix of n-jet operators in soft-collinear effective theory contains only a single non-trivial color structure, whose coefficient is the cusp anomalous dimension of Wilson loops with light-like segments. Its color-diagonal part is characterized by two anomalous dimensions, which are extracted to three-loop order from known perturbative results for the quark and gluon form factors. This allows us to predict the three-loop coefficients of all 1/ep…
Measurements of the semileptonic decaysB¯→Dℓν¯andB¯→D*ℓν¯using a global fit toDXℓν¯final states
2009
Semileptonic (B) over bar decays to DXl (nu) over bar (l = e or mu) are selected by reconstructing D(0)l and D(+)l combinations from a sample of 230 x 10(6) Y(4S) --> B (B) over bar decays recorded with the BABAR detector at the PEP-II e(+)e(-) collider at SLAC. A global fit to these samples in a three-dimensional space of kinematic variables is used to determine the branching fractions B(B- --> D(0)l (nu) over bar = (2.34 +/- 0.03 +/- 0.13)% and B(B- --> D*(0)l (nu) over bar) = (5.40 +/- 0.02 +/- 0.21)% where the errors are statistical and systematic, respectively. The fit also determines form-factor parameters in a parametrization based on heavy quark effective theory, resulting in rho(2)…
A high statistics lattice calculation of the B-meson binding energy
1996
We present a high statistics lattice calculation of the B--meson binding energy $\overline{\Lambda}$ of the heavy--quark inside the pseudoscalar B--meson. Our numerical results have been obtained from several independent numerical simulations at $\beta=6.0$, $6.2$ and $6.4$, and using, for the meson correlators, the results obtained by the APE group at the same values of $\beta$. Our best estimate, obtained by combining results at different values of $\beta$, is $\overline{\Lambda}=180^{+30}_{-20}$ MeV. For the $\overline{MS}$ running mass, we obtain $\overline{m}_{b}(\overline{m}_{b})=4.15 \pm 0.05 \pm 0.20$ GeV, in reasonable agreement with previous determinations. The systematic error is…
Technical note: Monte Carlo derivation of TG-43 dosimetric parameters for radiation therapy resources and 3M Cs-137 sources
2005
In clinical brachytherapy dosimetry, a detailed dose rate distribution of the radioactive source in water is needed in order to plan for quality treatment. Two Cs-137 sources are considered in this study; the Radiation Therapy Resources 67-800 source (Radiation Therapy Resources Inc., Valencia, CA) and the 3M model 6500/6D6C source. A complete dosimetric dataset for both sources has been obtained by means of the Monte Carlo GEANT4 code. Dose rate distributions are presented in two different ways; following the TG43 formalism and in a 2D rectangular dose rate table. This 2D dose rate table is helpful for the TPS quality control and is fully consistent with the TG43 dose calculation formalism…
Evaluation of dentifrices of complementary and alternative medicinal systems on plaque formation and gingivitis: A randomized controlled clinical tri…
2019
Background Bio-film formation is a natural process in the oral environment, but needs to be controlled through regular brushing in order to prevent the development of caries and periodontal diseases. Material and Methods A wide variety of dentifrices of complementary and alternative medicinal systems are available in the market which claims superior plaque control. A randomized controlled double-blinded concurrent parallel clinical trial was conducted with the objective to evaluate and compare the clinical effectiveness of three commercially available dentifrices of complementary and alternative medicine systems with that of a placebo dentifrice on Gingival Index (GI) and Plaque Index (PI) …
Il principio del non refoulement tra controllo dell'accesso al territorio dell'Unione europea e protezione dei diritti umani
2020
Nonostante il non-refoulement sia un principio cardine del diritto internazionale dei rifugiati, il suo preciso ambito di applicazione e l’esatta individuazione degli obblighi a carico degli Stati sono oggetto di incertezza per la tensione costante tra due opposte tendenze. In quanto espressione di un valore umanitario fondamentale, sono fiorite interpretazioni estensive, ma, in quanto limite al potere sovrano dello Stato di regolare l’accesso al territorio, sono emerse tendenze di segno restrittivo. L’articolo presenta la politica comune di asilo come sottoposta alla stessa tensione e ne descrive per grandi linee gli aspetti che costituiscono un ampliamento della protezione offerta dal dir…
Cost-effectiveness of psychotropic polypharmacy in routine schizophrenia care. Results of the ELAN prospective observational trial
2018
Abstract Aims To analyse the costs and cost-effectiveness of psychotropic polypharmacy in comparison to antipsychotic monotherapy in patients with schizophrenia and schizo-affective disorder under real-world treatment conditions. Methods A prospective observational study including 374 adult psychiatric in-patients with schizophrenia or schizo-affective disorder was conducted. Psychotropic regimen, clinical outcomes, and quality of life were assessed before discharge and after 6, 12, 18, and 24 months. Costs and outcomes of psychotropic polypharmacy in comparison to antipsychotic monotherapy were analysed by means of mixed-effects regression models adjusted for propensity scores. Net-benefit…
Validation of a Modified Version of the Psychological Capital Questionnaire (PCQ12) in Spain
2018
Background : Previous studies have found some limitations and inconsistencies in the functioning of the short Psychological Capital Questionnaire (PCQ12), suggesting the need to improve it. The objective of the current study is to validate a modified version of the PCQ12 in Spain. Method : The sample consists of 792 employees from 42 Spanish organizations. A cross-validation was carried out to test the factorial validity of the modified scale. Reliability and convergent, discriminant, and criterion validity were also tested. Results : The modified PCQ12 showed good psychometric qualities. A four-factor structure showed a better fit to the data than the original second-order structure. Conc…