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Search Results: 1 - 10 of 662261 matches for " Raúl A. Brice?o "
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Heavy Meson Masses in the ε-Regime of HMχPT
Raúl A. Briceo
Physics , 2011, DOI: 10.1103/PhysRevD.85.014508
Abstract: The pseudoscalar and vector heavy meson masses are calculated in the \epsilon-regime of Heavy Meson Chiral Perturbation Theory to order \epsilon^4. The results of this calculation will allow the determination of low-energy coefficients (LECs) directly from Lattice QCD calculations of the heavy mesons masses for lattices that satisfy the \epsilon-regime criteria. In particular, the LECs that parametrize the NLO volume dependance of the heavy meson masses are necessary for evaluating the light pseudoscalar meson (\pi, K, \eta) and heavy meson ({D^0, D^+, D^+_s}, {B^-,\bar{B}^0,\bar{B}^0_s}) scattering phase shifts.
Few-body physics
Raúl A. Briceo
Physics , 2014,
Abstract: Few-body hadronic observables play an essential role in a wide number of processes relevant for both particle and nuclear physics. In order for Lattice QCD to offer insight into the interpretation of few-body states, a theoretical infrastructure must be developed to map Euclidean-time correlation functions to the desired Minkowski-time few-body observables. In this talk, I review the formal challenges associated with the studies of such systems via Lattice QCD, as first introduced by Maiani and Testa, and I also review the methodology to circumvent said limitations. The first main example of the latter is the formalism by Luscher to analyze elastic scattering and a second is the method by Lellouch and Luscher to analyze weak decays. I discus recent theoretical generalizations of these frameworks that allow for the determination of scattering amplitudes, resonances, nonlocal contribution to matrix elements, and form factors below and above inelastic thresholds. Finally, I outline outstanding problems, including those that are now beginning to be addressed.
Multichannel 0-to-2 and 1-to-2 transition amplitudes for arbitrary spin particles in a finite volume
Raúl A. Briceo,Maxwell T. Hansen
Physics , 2015, DOI: 10.1103/PhysRevD.92.074509
Abstract: We present a model-independent, non-perturbative relation between finite-volume matrix elements and infinite-volume $\textbf{0}\rightarrow\textbf{2}$ and $\textbf{1}\rightarrow\textbf{2}$ transition amplitudes. Our result accommodates theories in which the final two-particle state is coupled to any number of other two-body channels, with all angular momentum states included. The derivation uses generic, fully relativistic field theory, and is exact up to exponentially suppressed corrections in the lightest particle mass times the box size. This work distinguishes itself from previous studies by accommodating particles with any intrinsic spin. To illustrate the utility of our general result, we discuss how it can be implemented for studies of $N+\mathcal{J}~\rightarrow~(N\pi,N\eta,N\eta',\Sigma K,\Lambda K)$ transitions, where $\mathcal{J}$ is a generic external current. The reduction of rotational symmetry, due to the cubic finite volume, manifests in this example through the mixing of S- and P-waves when the system has nonzero total momentum.
Nuclear Reactions from Lattice QCD
Raúl A. Briceo,Zohreh Davoudi,Thomas C. Luu
Physics , 2014, DOI: 10.1088/0954-3899/42/2/023101
Abstract: One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some of the low- energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.
Relativistic, model-independent, multichannel $2\to2$ transition amplitudes in a finite volume
Raúl A. Briceo,Maxwell T. Hansen
Physics , 2015,
Abstract: We derive formalism for determining $\textbf{2} + \mathcal J \to \textbf{2}$ infinite-volume transition amplitudes from finite-volume matrix elements. Specifically, we present a relativistic, model-independent relation between finite-volume matrix elements of external currents and the physically observable infinite-volume matrix elements involving two-particle asymptotic states. The result presented holds for states composed of two scalar bosons. These can be identical or non-identical and, in the latter case, can be either degenerate or non-degenerate. We further accommodate any number of strongly-coupled two-scalar channels. This formalism will, for example, allow future lattice QCD calculations of the $\rho$-meson form factor, in which the unstable nature of the $\rho$ is rigorously accommodated.
Charmed Baryon Spectroscopy from Lattice QCD with $N_f=2+1+1$ flavors
Raúl A. Briceo,Daniel Bolton,Huey-Wen Lin
Physics , 2011,
Abstract: We present preliminary results of the calculation of the positive-parity ground state charm baryon spectrum using of N_f=2+1+1$ dynamical quarks. The calculation uses a relativistic heavy-quark action for the valence charm quark, clover-Wilson fermions for the valence light quarks and HISQ sea quarks. The spectrum is calculated with a lightest pion mass around 220 MeV and two lattice spacings ($a\sim0.12$ fm and 0.09 fm) are used to extrapolate to continuum limit. Our preliminary results are consistent with the currently measured baryon spectrum, except for the isospin-averaged $J=1/2$ $\Xi_{cc}$ which is approximately $2 \sigma$ above the SELEX observed value. We predict the yet-to-be-discovered double and triple-charm baryons $\Xi_{cc}^*$, $\Omega_{cc}$, $\Omega_{cc}^*$, $\Omega_{ccc}$ to have masses 3665(42)(29) MeV, 3694(40)(45) MeV, 3739(35)(21) MeV and 4782(24)(28) MeV, respectively.
Multichannel one-to-two transition amplitudes in a finite volume
Raúl A. Briceo,Maxwell T. Hansen,André Walker-Loud
Physics , 2015,
Abstract: We derive a model-independent expression for finite-volume matrix elements. Specifically, we present a relativistic, non-perturbative analysis of the matrix element of an external current between a one-scalar in-state and a two-scalar out-state. Our result, which is valid for energies below higher-particle inelastic thresholds, generalizes the Lellouch-Luscher formula in two ways: we allow the external current to inject arbitrary momentum into the system and we allow for the final state to be composed an arbitrary number of strongly coupled two-particle states with arbitrary partial waves (including partial-wave mixing induced by the volume). We also illustrate how our general result can be applied to some key examples, such as heavy meson decays and meson photo production. Finally, we point out complications that arise involving unstable resonance states, such as $B\rightarrow K^*\ell^+\ell^-$ when staggered or mixed-action/partially-quenched calculations are performed.
Multichannel one-to-two transition amplitudes in a finite volume
Raúl A. Briceo,Maxwell T. Hansen,André Walker-Loud
Physics , 2014, DOI: 10.1103/PhysRevD.91.034501
Abstract: We perform a model-independent, non-perturbative investigation of two-point and three-point finite-volume correlation functions in the energy regime where two-particle states can go on-shell. We study three-point functions involving a single incoming particle and an outgoing two-particle state, relevant, for example, for studies of meson decays (e.g., B-to-pi Kll) or meson photo production (e.g., pi gamma-to-pi pi). We observe that, while the spectrum solely depends on the on-shell scattering amplitude, the correlation functions also depend on off-shell amplitudes. The main result of this work is a generalization of the Lellouch-Luscher formula relating matrix elements of currents in finite and infinite spatial volumes. We extend that work by considering a theory with multiple, strongly-coupled channels and by accommodating external currents which inject arbitrary four-momentum as well as arbitrary angular momentum. The result is exact up to exponentially suppressed corrections governed by the pion mass times the box size. We also apply our master equation to various examples, including the two processes mentioned above as well as examples where the final state is an admixture of two open channels.
Mediciones GPS NTRIP: una nueva alternativa para el posicionamiento preciso en Venezuela GPS NTRIP observations: A new alternative for precise positioning in Venezuela
A Briceo,L Mass,I Rubí,V Cioce
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2009,
Abstract: Las nuevas tendencias en materia de posicionamiento GNSS ofrecen a los usuarios de las geociencias una poderosa e innovadora herramienta para la determinación de coordenadas precisas, útiles para diversas aplicaciones de acuerdo a la calidad esperada de los resultados. La medición en tiempo real ha sido uno de los tópicos más beneficiados con este avance tecnológico, surgiendo así el NTRIP. Con la renovación y adecuación instrumental en la estación SIRGAS-REGVEN Maracaibo, se inició la transmisión de correcciones diferenciales bajo esta modalidad a través del IGS, siendo posible la medición en tiempo real de forma simple y menos compleja en campo, de forma gratuita y abierta para todo usuario. Adicionalmente la masificación en el uso de la Internet en Venezuela, crea las condiciones ideales para la activación de otras estaciones de la red permanente del país (REMOS), con lo cual se estaría fortaleciendo la infraestructura geodésica en beneficio del colectivo. Aunque en a os anteriores ya se habían realizado observaciones GPS con NTRIP de forma experimental, es en esta ocasión cuando se evalúa formalmente esta herramienta para el posicionamiento preciso. En tal sentido, se planificaron y ejecutaron observaciones GPS de tipo estático diferencial postprocesado sobre una serie de estaciones localizadas a distancias variables con respecto a la estación MARA, adicionalmente, los mismos puntos fueron ocupados en modo tiempo real NTRIP con una y doble frecuencia, permitiendo de esta manera efectuar comparaciones entre las determinaciones y evaluar los diversos efectos que sobre ellas influyen en términos de precisión y exactitud. Este trabajo describe los diversos ensayos realizados así como los resultados obtenidos, los cuales se ubicaron entre ±2 y ±5cm para la componente horizontal. De esta manera se espera ofrecer a la comunidad geodésica nacional, respuestas concretas sobre las bondades y limitaciones del NTRIP. Innovating developments and technologies at satellite positioning GNSS gives an increasing geosciences community a powerful tool for precise coordinate determination at a great application range in function of quality needed. Real time observations in combination with NTRIP services for broadcasting the differential corrections have been accepted at a great branch of applications. SIRGAS-REGVEN GPS permanent station Maracaibo (MARA) recently has been accommodated with newer equipment allowing transmission of corrections issued via NTRIP by the Internet. Receiving the transmissions freely (only handy flat rates apply), real time applications got ava
La mutacion H63D del gen HFE se asocia con un riesgo aumentado de carcinoma hepatocelular The H63D mutation of the HFE gene is related to the risk of hepatocellular carcinoma
P. Ropero,O. Briceo,G. López Alonso,J. A. G.-Agúndez
Revista Espa?ola de Enfermedades Digestivas , 2007,
Abstract: Objetivo: comprobar si las mutaciones del gen HFE, que pueden inducir sobrecarga hepática de hierro, guardan relación con el riesgo de desarrollar carcinoma hepatocelular (CHC) en sujetos predispuestos a sufrir este tumor. Material y métodos: se han incluido 196 pacientes (161 varones) diagnosticados de CHC. Ninguno estaba diagnosticado de hemocromatosis. El grupo control estaba constituido por 181 sujetos sanos. Todos los sujetos eran espa oles de raza blanca.Las mutaciones C282Y y H63D del gen HFE se identificaron mediante reacción en cadena de polimerasa (PCR) sobre ADN genómico leucocitario utilizando enzimas de restricción específicas. Resultados (casos/controles): 1. Distribución genotípica: a) mutación C282Y: 1/0 homocigotos, 12/23 heterocigotos, 183/158 normales (p = 0,07, n.s.); y b) mutación H63D: 9/5 homocigotos, 85/52 heterocigotos, 102/124 normales (odds ratio 2,00, IC95% 1,29-3,12, p = 0,002). Cuatro casos y seis controles eran heterocigotos compuestos. 2. Frecuencias alélicas: a) mutación C282Y: normales 378/339, mutados 14/23 (p = 0,11, n.s.); b) mutación H63D: normales 289/300; mutados 103/62 (odds ratio 1,72, IC95% 1,19-2,50, p = 0,004). No se observaron diferencias en relación con el sexo, la edad o la etiología (VHC, VHB, etílica o mixta) de la hepatopatía previa. Conclusiones: la mutación C282Y no guarda relación con el riesgo de desarrollar CHC en sujetos sin hemocromatosis conocida. La posesión de la mutación H63D se asocia con un riesgo aumentado de desarrollar CHC independientemente de la etiología de la hepatopatía crónica subyacente. Aim: to disclose whether mutations in the HFE gene inducing liver iron overload are related to the risk of hepatocellular carcinoma (HCC) in otherwise predisposed patients. Patients and methods: one hundred and ninety-six patients (161 males) diagnosed with HCC and 181 healthy controls were included in the study. All subjects were white Spaniards. C282Y and H63D mutations in the HFE gene were identified in leucocyte genomic DNA using a polymerase chain reaction (PCR) and specific restriction enzymes. Results (cases/controls): 1. Genotype distribution: a) C282Y mutation: homozygotes 1/0, heterozygotes 12/23, wild type 183/158 (p = 0.07, non significant); b) H63D mutation: homozygotes 9/5, heterozygotes 85/52, wild type 102/124 (0dds ratio 2.00, 95% C.I. 1.29-3.12, p = 0.002. Four cases and 6 controls were carriers of heterozygous mixed genotypes. 2. Allele frequencies: a) C282Y mutation: wild type allele 378/339, mutated allele 14/23 (p = 0.11, non significant); b) H63D mutation: wild type allele 2
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