A5012127200- Quantum Chromodynamics and Particle Interactions
- Nuclear physics research studies
- Particle physics theoretical and experimental studies
- High-Energy Particle Collisions Research
- Atomic and Molecular Physics
- Quantum, superfluid, helium dynamics
- Quantum Mechanics and Applications
- Advanced Chemical Physics Studies
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum chaos and dynamical systems
- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Quantum and Classical Electrodynamics
- Pulsars and Gravitational Waves Research
- Atomic and Subatomic Physics Research
- Advanced NMR Techniques and Applications
- Laser-Matter Interactions and Applications
- Quantum optics and atomic interactions
- Particle Accelerators and Free-Electron Lasers
- Neutrino Physics Research
- Global Energy and Sustainability Research
- Radioactive Decay and Measurement Techniques
- Muon and positron interactions and applications
- Scientific Research and Discoveries
- Quantum Mechanics and Non-Hermitian Physics
Universidad de Los Andes
2015-2024
Forschungszentrum Jülich
2017-2020
Institute of Physics
2017
Jagiellonian University
2017
Universidad de Los Andes
2006-2014
Bhabha Atomic Research Centre
1991-2003
Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati
1996-1997
Universitat de València
1997
Istituto Nazionale di Fisica Nucleare
1996
Johns Hopkins University
1995
A detailed comparison of the expressions for decay widths obtained within semiclassical WKB approximation using different approaches to tunneling problem is performed. The differences between available improved formulas near top and bottom barrier are investigated. Though simple method gives right order magnitude widths, a small number parameters often fitted. need perform fitting procedure remaining consistently framework emphasized in context fission model based calculations. Calculations...
Though the classical treatment of spontaneous decay leads to an exponential law, it is well known that this approximation quantum mechanical result which a non-exponential at very small and large times for narrow states. The non nature however hard establish from experiments. A method recover time evolution unstable states parametrization amplitude fitted data presented. We apply realistic example broad state, sigma meson reveal not valid any state. This derived experiment, shows unique resonances.
Back in the mid-1980s, a new branch of investigation related to interaction eta mesons with nuclei came into existence. It started theoretical prediction possible exotic states and bound by strong later developed an extensive experimental program search for such unstable as well understand underlying via eta-meson producing reactions. The vast literature works that studied various aspects eta-producing reactions π(+)n → ηp, pd (3)Heη, p (6)Li (7)Be η γ (3)He X, name few, had but one...
In this work, we investigate the equilibrium configurations of massive white dwarfs (MWD) in context modified gravity, namely $f(R,L_m)$ where $R$ stands for Ricci scalar and $L_m$ is Lagrangian matter density. We focused on specific case $f(R,L_m) = R/2 + L_m \sigma RL_m$, i.e., have considered a non-minimal coupling between gravity field field, with $\sigma$ being constant. For first time, theory applied to dwarfs, particular study which topic great interest last years. The predict maximum...
The framework to describe natural phenomena at their basics being quantum mechanics, there exist a large number of common global occurring in different branches sciences. One such phenomenon is spontaneous decay. However, its long time behavior experimentally poorly known. Here we show, that by combining two genuine mechanical results, it possible infer on this behavior, directly from data. Specifically, find evidence for nonexponential alpha decay $^{8}\mathrm{Be}$ times experiments.
The concept of phase and dwell times used in tunneling is extended to quantum collisions derive a relation between the time delays scattering. This can be remove near threshold s-wave singularities Wigner-Eisenbud delay amounts an extension reflection strong interactions. Dwell emerges as quantity which gives correct behavior density states metastable state at all energies. fact demonstrated by investigating some recently found mesic nuclei.
The theoretical treatment of alpha-decay by Gamow is revisited investigating the quantum time scales in tunneling. spent an alpha-particle front barrier and traversing it before escape evaluated using microscopic alpha-nucleus potentials. half-life a nucleus shown to correspond alpha knocking barrier. Calculations for medium super heavy nuclei show that from multitude available tunneling definitions, transmission dwell gives bulk lifetime decaying state, most cases.
A consistent description of the $ d \rightarrow$ $^{4}\hspace{-0.03cm}\mbox{He} \eta$ and ($^4$He$\eta$)$_{bound} \rightarrow X cross sections was recently proposed with a broad range real ($V_{0}$) imaginary (W0), $\eta$-$^4$He optical potential parameters leading to good agreement -> 4He eta data. Here we compare predictions model below $\eta$ production threshold, WASA-at-COSY excitation functions for dd 3He N pi reactions put stronger constraints on (V0, W0). The allowed parameter space...
Measurements of current-voltage (I-V) characteristics a high quality Al/Al2O3/Al junction at temperatures ranging from 3.5 K to 300 have been used extract the barrier properties. Fitting results using Simmons's model led constant value width s ∼ 20.8 Å and continuous increase in height with decreasing temperature. The latter is determine energy band gap temperature dependence average phonon frequency ω = 2.05 × 1013 s−1 Al2O3, which adds confidence precision our measurements. parameters are...
Different models for the nonlocal description of nuclear interaction are compared through a study their effects on half-lives radioactive nuclei decaying by emission alpha particles. The evaluated considering preformed $\ensuremath{\alpha}$ particle ($^{4}\mathrm{He}$ nucleus), which tunnels Coulomb barrier generated its with daughter nucleus. An effective potential obtained from density-dependent double-folding strong between and nucleus within framework is found to decrease as those in...
It is common to study the strong decay of a heavy nucleus as tunneling phenomenon where $\alpha$ ($^4$He) or light nuclear cluster tunnels through Coulomb barrier formed by its interaction with heavier daughter nucleus. The position and width are determined total potential between two nuclei. We examine effects including nonlocality deformation in calculating half-lives, $t_{1/2}$, thereby phenomenological preformation factors several nuclei which have possibility decaying emitting either an...
Evidence and hints, from both the theoretical experimental sides, of exotic baryon resonances with B = S, have been us for last 30 years. The poor status general acceptance these Z* is partly due to prejudice against penta-quark baryons opinion that a proof existence states must be rigorous. This can refer quality amount data gathered, also analytical methods applied in study resonances. It then seems mandatory all possibilities aspects exploited. We do by analysing time delay K+N...
The physical significances and the pros cons involved in usage of different time-delay formalisms are discussed. delay-time matrix introduced by Eisenbud, where only $s$ waves participate a reaction, is general related to definition an angular time delay which shown not be equivalent so-called phase Eisenbud Wigner even for single channel scattering. Whereas expression due Smith derived from time-delayed radial wave packet consistent with lifetime Hermitian, this true any Eisenbud-type...
Rainbow, glory and orbiting scattering are usually described by the properties of classical deflection function related to real part quantum mechanical phase shift or diffractive pattern cross sections. Here we show that case massless spin 0, 1 2 particles from Schwarzschild black holes can be characterized a sudden rise in $|{R}_{l}{|}^{2}$ at critical angular momentum ${l}_{C}$, which corresponds unstable circular orbits these particles. For cases $s=0$, 2, attempt new interpretation...
We calculate cross sections for coherent pion production in nuclei induced by neutrinos and antineutrinos of the electron muon types. The analogies differences between this process related ones photons or $(p,n)$ ${(}^{3}\mathrm{He},t)$ reactions are discussed. is one several occurring intermediate energy neutrinos, to be considered when detecting atmospheric neutrinos. For purpose results shown here can easily extrapolated other energies nuclei.
This paper describes a simple yet accurate technique for the continuous measurement of projectile velocities in plate impact experiments (the velocity is critical parameter interpretation such experiments). The technique, known as laser line sensor (LLVS), uses generator to generate sheet uniform intensity that incident on photodiode at focus collecting lens. amount light reaching diminishes intersects sheet, and so calibration procedure conjunction with high-bandwidth optoelectronic system...
The Fock-Krylov formalism for the calculation of survival probabilities unstable states is revisited paying particular attention to mathematical constraints on density states, Fourier transform which gives amplitude. We show that it not possible construct a corresponding purely exponential probability $P(t)$ and autocorrelation function are shown form pair cosine transforms. This result case Wiener-Khinchin theorem forces be an even time in turn contain factor vanishes at large energies....
A measurement of the Lamb shift 49,881.88(76) GHz in muonic hydrogen conjunction with theoretical estimates proton structure effects was recently used to deduce an accurate but rather small radius proton. Such important understanding fundamental values needs reconfirmation. Using a different approach electromagnetic form factors proton, we obtain new expression for transition energy, $Δ= E_{2P_{{3}/{2}}}^{f=2} - E_{2S_{{1}/{2}}}^{f=1}$, and radius, $r_p = 0.831$ fm.
We probe into the instabilities of microscopic quantum black holes. For this purpose, we study quasinormal modes (QNMs) for a massless scalar perturbation noncommutative geometry inspired Schwarzschild hole. By means sixth order Wentzel–Kramers–Brillouin (WKB) approximation show that widely used WKB method does not converge in critical cases where up at third order. employing inverted potential method, demonstrate are an artifact method. Finally, discuss usefulness asymptotic iteration to find QNMs.