HANDROICA is an anagram of "Hadronica", the Spanish word for
    "Hadronic". Hadrons are the particles inside the atomics nucleus such
    as protons and neutrons. Hadronic physics is a branch of Nuclear and
    Particle Physics that describes the structure and interactions of
    Hadrons. The principles of Quantum Physics and Quantum Field Theory
    are employed to compute the properties of hadrons and the forces
    between them.

    Rodrigo Navarro Perez, Enrique Ruiz Arriola and Jose Enrique Amaro
    Departamento de Fisica Atomica, Molecular y Nuclear.
    Instituto Carlos I de Fisica Teorica y Computacional.
    Universidad de Granada.

    This Android app is a demonstration of the use of Hadronic Physics
    techniques. It is also a demonstration of the computational power of
    smartphones and tablets. The goal is to compute the binding energy of
    the helium nucleus (He-4 isotop) and of nuclear matter (hypotetical
    nucleus with infinite particles) starting with experimental
    information of the interaction between protons and neutrons.

    The input information are the experimental data of neutron-proton
    scattering. A beam of neutrons with some incident energy interact and
    are scattered by a proton (Hidrogen) target, and precise meassurements
    of the number of neutrons for each scattering angle are performed.
    This information can be codified in quantities called "phaseshifts",
    representing the shifts in the phase of the scattered neutron
    wave. Neutrons are described by waves in quantum physics. The wave
    function of a neutron is computed in this app by solving the
    Schroedinger equation. To solve this equation we must know the force
    between neutrons and protons (np), which is represented by a function
    called "the potential energy" or, simply, "the np potential".

    HADRONICA main screen

    In the main screen there are eleven field text
    with parameters that the user can change to control
    some aspects of the calculations.

    The four numbers R0,lambda0,R1,lambda1 in the first column
    are the parameters of the np interaction in the 1S0 channel.

    The four numbers R0,lambda0,R1,lambda1 in the second column
    are the parameters of the np interaction in the 3S1 channel.

    The three numbers in the last row control several aspects of
    the fitting algorithm:

    E_max: is the maximum incident energy entering in the fit

    Tolerance: is the minimum experimental error allowed for the pseudodata

    Resolution: controls when the optimal set of parameters is found.

    The potential parameters are modified inside a loop. For each set of
    parameters we compute the total distance from the theoretical
    phaseshifts to the experimental data until the minimum distance is
    found. In each step of the loop, the parameters are allowed to move
    in a discrete grid. The distance between adjacent points in the grid
    is reduced recursively by one half until the value of the resolution
    is reached. Note that by this procedure one can reach local
    minima. Experimenting with different starting points and different
    resolutions can produce different results.

    The calculation in this app is performed in four stages,
    fired the user by pressing the four buttons A--D.

    Enjoy performing Quantum Physics on your phone

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