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AI for Particle Physics
Published in Volker Knecht, AI for Physics, 2023
Mario Campanelli, Volker Knecht
Hadronic jets are collimated sprays of particles produced by the formation of hadrons out of quarks and gluons denoted as hadronization. Due to the laws of strong interactions, particles with a color charge (the property leading to strong interactions) cannot live in isolation. At high energies, quarks will radiate gluons, which will produce quark–antiquark or gluon–antigluon pairs, in a process called parton shower. At lower energies, quarks will pick up other quark-antiquark pairs from the vacuum to produce more stable hadrons like pions, kaons, protons, and neutrons, which is what is called hadronization. When the initial quarks or gluons have sufficiently large momenta, the resulting hadrons will be collimated and all emitted in a narrow geometrical cone, the hadronic jet. Its axis, defined by the weighted average of the directions of the particles composing it, is a proxy for the direction of the quark or gluon that created it, and the jet transverse momentum a proxy for that of the initial particle. Defining which particles belong to a jet is not a trivial task, especially in situations where there are several nearby. Several jet clustering algorithms have been developed to, for instance, remove detector noise or calibrate the jets.
Background theory
Published in Michael de Podesta, Understanding the Properties of Matter, 2020
For our purposes, we need to examine the properties of only one of the above fields, the electroweak field. Before leaving the other two fields we note that: The colour field, while existing everywhere, acts only between particles that possess a property called colour charge and it is through this field that quarks interact with one another. As mentioned previously, the forces between quarks are extremely short range 10−15 m, and they thus act only within nuclei. In attempting to understand the properties of matter we ignore any processes that take place within nuclei and treat nuclei as if they were point masses with an electric charge +Ze.The gravitational field acts between all particles that possess mass, but its effects are generally negligible unless the masses involved are large, which will not happen over the length scales that we are interested in. We do however use the fact that particles possess mass, but only to discuss the way in which their motion is affected under the action of electrical forces. In other words we use mass in the sense of inertial mass, but not gravitational mass.
Elementary Particles and Interactions — Overview
Published in K Grotz, H V Klapdor, S S Wilson, The Weak Interaction in Nuclear, Particle and Astrophysics, 2020
K Grotz, H V Klapdor, S S Wilson
The range of the interaction between two fermions is correlated with the mass of the exchange quanta. Massless exchange quanta lead, with certain restrictions (see below), to interactions with infinite range. This is a consequence of the boson propagator. Transformation of this propagator into the coordinate space gives a range function of the Yukawa form for massive bosons (as for the pion); for massless bosons (as for the photon) on the other hand there results an r−1 potential. There are three interactions with massless exchange quanta (see Table 1.4). One of these is the electromagnetic interaction with the photon as exchange quantum. The graviton should also be massless. These two interactions have infinite range and conform with the previously mentioned correspondence between the interaction range and the mass of the exchange quantum. But the short-range strong interaction also can be traced back to the exchange of massless field quanta, gluons. The gluon mediated exchange interaction (colour interaction) takes place between quarks, which have a colour charge with three degrees of freedom (red, green, blue). The apparent contradiction between the short range of the strong interaction and the masslessness of gluons is explained by the fact that the gluons themselves also have a colour charge, and thus interact among themselves (see Subsection 6.1.1). The strong interaction between hadrons is to be understood as a residual interaction of the colour interaction, similar to the van der Waals interaction between molecules, which can be traced back to the electromagnetic interaction.
An ab-initio investigation of the electronic structure, chemical bonding and optical properties of Ba2HgS5 semiconductor
Published in Molecular Physics, 2020
Sikander Azam, Saleem Ayaz Khan, R. Khenata, S. H. Naqib, A. Abdiche, Ş. Uğur, A. Bouhemadou, Xiaotian Wang
In order to study the bonding nature further, we have calculated the electronic charge densities (ECD) in the (1 0 1) plane. These are displayed in Figure 4. The molecular electrostatic potential and electric moments, which arise from the nature of charge density distribution, help one to understand the bonding properties of solids. From the electronic charge density study, it is possible to obtain the knowledge of some obligatory characteristics of the molecule such as the net charges on the atoms, the molecular dipole moment, and the form of the electrostatic potential in the region between the atoms constituting the molecule. As shown in Figure 4, the charge density at each of the S (2.5) sites is significantly higher than those charge densities at the Ba (0.9) and Hg (1.9) atom sites (the charge density value is given in the parentheses). In addition, the plot of the electronic charge density indicate covalent bonding between the Ba, Hg and S atoms, which depends on the Pauling electro-negativity difference between the Ba (0.9) and Hg (1.9) atoms (The electro-negativity value is given in the parenthesis). Most of the charges taking part in the bond formation are accumulated around the S site. The color charge density scale is shown with the blue color (+1.0000) indicating the maximum charge occurring sites.
Effect of cobalt oxide nanoparticles on dielectric properties of a nematic liquid crystal material
Published in Journal of Dispersion Science and Technology, 2021
Depanshu Varshney, Ariba Parveen, Jai Prakash
To measure the and tan δ of 5 CB that is filled in the LC sample cells, we have used LCR meter (E4980A, Keysight, USA) in the frequency range from 20 Hz to 2 MHz with 0 V DC biasing. These dielectric parameters were observed under the effect of AC voltage kept at 500 mV. Polarizing optical micrographs have been captured with the help of polarizing optical microscope (BX53M, Olympus, Japan) aided with color charge-coupled device camera and a desktop system.