Inferring new physics characteristics from the muon anomalous magnetic moment discrepancy
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Data
2022-11-18
Autores
Cemin, Marcello Vinícius Hallas
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Universidade Estadual Paulista (Unesp)
Resumo
Após uma rápida revisão do Modelo Padrão da Física de Partículas, nós definimos o momento de dipolo magnético anômalo do múon em termos dos fatores de forma. Desse modo, utilizando teoria de perturbação, calculamos a contribuição a 1-loop da eletrodinâmica quântica e da teoria eletrofraca. Citamos os valores encontrados na literatura para ordens superiores e com isso temos então a previsão teórica do Modelo Padrão para o momento de dipolo magnético anômalo do múon. Discutimos a física por trás dos últimos experimentos dedicados a medir o momento magnético anômalo do múon, e vemos que o resultado obtido difere do teórico por 4.2$\sigma$, o que pode indicar a presença de nova física. Como apenas a adição de novos bósons ou novos férmions sozinhos não é capaz de explicar tal discrepância, olhamos para a possibilidade de ao adicionarmos novos bósons, juntamente com novos férmions, obtermos contribuições que possam explicar a discrepância entre teoria e experimento. Em específico olhamos para o modelo 3-3-1 com um lepton pesado e carregado e concluímos que a contribuição da nova física só pode vir através do setor escalar visto que a adição dos novos bósons e férmions com tais interações trariam contribuições ainda menores que as do Modelo Padrão para o momento de dipolo magnético do múon. Finalmente, consideramos interações gerais para partículas escalares neutras e carregadas e concluímos que, em princípio, elas podem contribuir para o momento magnético anômalo do múon.
After a quick review of the Standard Model of Particle Physics, we define the anomalous magnetic dipole moment of the muon in terms of the form factors. In this way, using perturbation theory, we calculate the 1-loop contribution from quantum electrodynamics and also from electroweak theory. We quote the values found in the literature for higher orders and with that, we have the theoretical prediction of the Standard Model for the anomalous magnetic dipole moment of the muon. We discussed the physics behind the last experiments dedicated to measuring the anomalous magnetic moment of the muon and see that the result obtained differs from the theoretical one by 4.2$\sigma$, which may indicate the presence of new physics. Since the addition of new bosons or new fermions alone is not able to explain such a discrepancy, we look at the possibility that by adding new bosons, together with new fermions, we can obtain contributions that can explain the discrepancy between theory and experiment. Specifically, we look at the 3-3-1 model with a heavy charged lepton and conclude that the contribution of the new physics can only come through the scalar sector since the addition of new bosons and fermions with such interactions would bring even smaller contributions than those of the Standard Model to the magnetic dipole moment of the muon. Finally, we consider general interactions for neutral and charged scalar particles and conclude that, in principle, they can contribute to the muon anomalous magnetic moment.
After a quick review of the Standard Model of Particle Physics, we define the anomalous magnetic dipole moment of the muon in terms of the form factors. In this way, using perturbation theory, we calculate the 1-loop contribution from quantum electrodynamics and also from electroweak theory. We quote the values found in the literature for higher orders and with that, we have the theoretical prediction of the Standard Model for the anomalous magnetic dipole moment of the muon. We discussed the physics behind the last experiments dedicated to measuring the anomalous magnetic moment of the muon and see that the result obtained differs from the theoretical one by 4.2$\sigma$, which may indicate the presence of new physics. Since the addition of new bosons or new fermions alone is not able to explain such a discrepancy, we look at the possibility that by adding new bosons, together with new fermions, we can obtain contributions that can explain the discrepancy between theory and experiment. Specifically, we look at the 3-3-1 model with a heavy charged lepton and conclude that the contribution of the new physics can only come through the scalar sector since the addition of new bosons and fermions with such interactions would bring even smaller contributions than those of the Standard Model to the magnetic dipole moment of the muon. Finally, we consider general interactions for neutral and charged scalar particles and conclude that, in principle, they can contribute to the muon anomalous magnetic moment.
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Palavras-chave
Modelo padrão (Física nuclear), Partículas (Física nuclear), Muons