【實用教育app】HANDROICA|最夯免費app

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.

Spain

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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