Symmetry dictated universal helicity redistribution of Dirac fermions in transport

Helicity is a fundamental property of Dirac fermions. Yet, how it changes in transport processes remains largely mysterious. We uncover, theoretically, the rule of spinor state transformation and consequently universal helicity redistribution in two cases of transport through potentials of electrostatic and mass types, respectively. The former is dictated by Lorentz boost and its complex counterpart in Klein tunneling regime. The latter is governed by an abstract rotation group we identified, which reduces to SO(2) when acting on the plane of effective mass and momentum. This endows an extra structure foliating the Hilbert space of Dirac spinors, establishes miraculously a unified yet latent connection between helicity, Klein tunneling, and Lorentz boost. Our results thus deepen the understanding of relativistic quantum transport, and may open a new window for exotic helicity-based physics and applications in mesoscopic systems.Comment: 6 pages, 4 figure

Low Energy Antimatter Physics

We will review the motivations and the general features of experiments devoted to testing fundamental laws with antimatter at low energies, namely the study of CPT invariance and the Weak Equivalence Principle. A summary of the recent experimental results will be presented

A 16 Parts per Trillion Comparison of the Antiproton-to-Proton q/m Ratios

The Standard Model (SM) of particle physics is both incredibly successful and glaringly incomplete. Among the questions left open is the striking imbalance of matter and antimatter in the observable universe which inspires experiments to compare the fundamental properties of matter/antimatter conjugates with high precision. Our experiments deal with direct investigations of the fundamental properties of protons and antiprotons, performing spectroscopy in advanced cryogenic Penning-trap systems. For instance, we compared the proton/antiproton magnetic moments with 1.5 ppb fractional precision, which improved upon previous best measurements by a factor of >3000. Here we report on a new comparison of the proton/antiproton charge-to-mass ratios with a fractional uncertainty of 16ppt. Our result is based on the combination of four independent long term studies, recorded in a total time span of 1.5 years. We use different measurement methods and experimental setups incorporating different systematic effects. The final result, $-(q/m)_{\mathrm{p}}/(q/m)_{\bar{\mathrm{p}}}$ = $1.000\,000\,000\,003 (16)$, is consistent with the fundamental charge-parity-time (CPT) reversal invariance, and improves the precision of our previous best measurement by a factor of 4.3. The measurement tests the SM at an energy scale of $1.96\cdot10^{-27}\,$GeV (C$.$L$.$ 0.68), and improves 10 coefficients of the Standard Model Extension (SME). Our cyclotron-clock-study also constrains hypothetical interactions mediating violations of the clock weak equivalence principle (WEP$_\text{cc}$) for antimatter to a level of $|\alpha_{g}-1| < 1.8 \cdot 10^{-7}$, and enables the first differential test of the WEP$_\text{cc}$ using antiprotons \cite{hughes1991constraints}. From this interpretation we constrain the differential WEP$_\text{cc}$-violating coefficient to $|\alpha_{g,D}-1|<0.030$

Dealing with T and CPT violations in mixing as well as direct and indirect CP violations for neutral mesons decaying to two vectors

A large number of observables can be constructed from differential decay rate based on the polarization of final state while considering decay of a neutral meson $(P^0 \text{ or } \bar P^0)$ to two vector particles. But all of these observables are not independent to each other since there are only a few independent theoretical parameters controlling the whole dynamics and therefore various relations among observables emerge. In this paper, we have studied the behaviour of observables for neutral meson decaying to two vectors in presence of T and CPT violations in mixing accompanied by both direct and indirect CP violations. We have expressed all of the fourteen unknown theoretical parameters for this scenario in terms observables only and constructed the complete set of thirty four relations among observables whose violation would signify the existence of some new Physics involving direct violation of CPT. In addition, using this formalism we have studied three special cases too: a) SM scenario, b) SM plus direct CP violation c) SM plus T and CPT violation in mixing.Comment: 28 page

O termo CPT do Modelo Padrão Estendido

O setor de calibre do Modelo Padrão Estendido (MPE) tem sido motivação para uma variedade de estudos, especificamente, os termos representativos da simetria CPT. O presente artigo abordará alguns aspectos teóricos da simetria CPT no contexto do MPE. Serão apresentados o setor CPT-ímpar, representado através do termo de Carrol-Field-Jackiw, assim como o setor CPT-par proposto por Colladay e Kostelecky. A exibição destes setores serão realizados com o máximo de detalhes possíveis, tratando das respectivas lagrangianas, bem como das equações de movimento referente a cada um destes

Measurement of Earth's gravitational acceleration on anti-hydrogen with the ALPHA experiment at CERN

Sebbene l'interazione gravitazionale tra materia e antimateria sia stata oggetto di speculazione teorica sin dalla scoperta di quest'ultima nel 1928, solo recentemente, per la prima volta, l'esperimento ALPHA al CERN (Anti-hydrogen Laser physics Apparatus) è stato in grado di osservare gli effetti della gravità sugli atomi di antimateria, in particolare sull'anti-idrogeno. Questa misura è un test del principio di equivalenza debole (WEP), un principio fondamentale della teoria della relatività generale di Einstein, che afferma che tutte le masse reagiscono in modo identico alla gravità, indipendentemente dalla loro struttura interna. Per misurare l'accelerazione gravitazionale sull'anti-idrogeno, gli anti-atomi sono stati confinati magneticamente nell'apparato sperimentale di ALPHA e rilasciati sotto un effetto combinato di forze gravitazionali e magnetiche. L'analisi dei dati acquisiti si basa sulla costruzione di una likelihood delle posizioni dei vertici di annichilazione prodotti quando i campi magnetici per il confinamento vengono ridotti e gli atomi di anti-idrogeno escono dalla trappola. Il parametro rilevante di questa likelihood è l'asimmetria tra il numero di anti-atomi rilasciati verso l'alto e il numero di anti-atomi rilasciati verso il basso rispetto al centro della trappola elettromagnetica. Successivamente il parametro dell'accelerazione gravitazionale è ottenuto da una regressione sui dati eseguita utilizzando un modello ricavato dalla simulazione numerica del moto degli anti-atomi nell'esperimento. Questo lavoro comprende la stima delle incertezze statistiche e il trattamento delle incertezze sistematiche. I risultati dell'analisi rivelano che gli atomi di anti-idrogeno si comportano in modo compatibile con l'attrazione gravitazionale tra anti-idrogeno e Terra. Questo esperimento apre la strada a ulteriori ricerche sull'accelerazione gravitazionale terrestre su anti-atomi per effettuare test più precisi del principio di equivalenza debole.Although the gravitational interaction between matter and antimatter has been the subject of theoretical speculation since the discovery of the latter in 1928, only recently, for the first time, the ALPHA experiment at CERN (Anti-hydrogen Laser PHysics Apparatus) was able to observe the effects of gravity on antimatter atoms, namely on anti-hydrogen. This measurement is a test of the weak equivalence principle (WEP), a fundamental principle of Einstein's general theory of relativity, stating that all masses react identically to gravity, independent of their internal structure. In order to measure the gravitational acceleration on anti-hydrogen, anti-hydrogen atoms were magnetically confined in the ALPHA apparatus and released under a combined effect of gravitational and magnetic forces. The analysis of the acquired data is based on the construction of a likelihood of the annihilation vertex positions produced when the confining magnetic fields are lowered and the anti-hydrogen atoms are released. The relevant parameter of this likelihood is the asymmetry between the number of anti-atoms escaping upwards and the number of anti-atoms escaping downwards with respect to the center of the electromagnetic trap. The gravitational acceleration parameter is obtained from a regression on the data using a model obtained from a simulation of the anti-hydrogen motion in the experiment. This work includes the estimation of the statistical uncertainties and the treatment of the systematic uncertainty sources. The analysis results reveal that anti-hydrogen atoms behave in a way that is consistent with gravitational attraction between anti-hydrogen and the Earth. This experiment sets the path for further research on the gravitational acceleration between anti-atoms and the Earth for WEP testing

Symmetries, Conserved Properties, Tensor Representations, and Irreducible Forms in Molecular Quantum Electrodynamics

In the wide realm of applications of quantum electrodynamics, a non-covariant formulation of theory is particularly well suited to describing the interactions of light with molecular matter. The robust framework upon which this formulation is built, fully accounting for the intrinsically quantum nature of both light and the molecular states, enables powerful symmetry principles to be applied. With their origins in the fundamental transformation properties of the electromagnetic field, the application of these principles can readily resolve issues concerning the validity of mechanisms, as well as facilitate the identification of conditions for widely ranging forms of linear and nonlinear optics. Considerations of temporal, structural, and tensorial symmetry offer significant additional advantages in correctly registering chiral forms of interaction. More generally, the implementation of symmetry principles can considerably simplify analysis by reducing the number of independent quantities necessary to relate to experimental results to a minimum. In this account, a variety of such principles are drawn out with reference to applications, including recent advances. Connections are established with parity, duality, angular momentum, continuity equations, conservation laws, chirality, and spectroscopic selection rules. Particular attention is paid to the optical interactions of molecules as they are commonly studied, in fluids and randomly organised media

Quantum formulation for nanoscale optical and material chirality: symmetry issues, space and time parity, and observables

To properly represent the interplay and coupling of optical and material chirality at the photon-molecule or photon-nanoparticle level invites a recognition of quantum facets in the fundamental aspects and mechanisms of light-matter interaction. It is therefore appropriate to cast theory in a general quantum form, one that is applicable to both linear and nonlinear optics as well as various forms of chiroptical interaction including chiral optomechanics. Such a framework, fully accounting for both radiation and matter in quantum terms, facilitates the scrutiny and identification of key issues concerning spatial and temporal parity, scale, dissipation and measurement. Furthermore it fully provides for describing the interactions of light beams with a vortex character, and it leads to the complete identification of symmetry conditions for materials to provide for chiral discrimination. Quantum considerations also lend a distinctive perspective to the very different senses in which other aspects of chirality are recognized in metamaterials. Duly attending to the symmetry principles governing allowed or disallowed forms of chiral discrimination supports an objective appraisal of the experimental possibilities and developing applications

Precision measurement and symmetry properties of metastable hydrogen

Includes bibliographical references.2022 Fall.Hydrogen has been an indispensable system to study during the development of quantum mechanics due to the simplicity of its atomic structure. Hydrogen maintains its utility today as an important tool for determining fundamental values such as the Rydberg and fine structure constants, as well as the proton charge radius. The work described in this thesis aims to use hydrogen for determining the proton Zemach radius, to search for anomalous spin-dependent forces, and to provide means for measuring the degree of parity violation within this simple system. An overview of a 2S1/2 hyperfine interval measurement is described, followed by a description of the apparatus used and finally a discussion of the systematic effects to be characterized. A proposed parity violation experiment is also described