Theoretical Interpretation of a Recent Experimental Investigation of the Photon Rest Mass
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Kroll, N.↗
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Concentric Spherical Cavities and Limits on the Photon Rest Mass
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Kroll, N.↗
Possible reason for the numerical value of the fine-structure constant
A simple picture of the electron emerges if there is a cross section of πλ 2 for vacuum virtual photons to stimulate an isolated electron to emit an additional virtual photon. This reaction mechanism leads to the storage of the rest-mass energy in the surrounding cloud of virtual photons. The Lamb shift can be obtained if one out of every 1/α of the stimulated emissions is preceded by the absorption and re-emission of the incident vacuum virtual photon including the corresponding electron recoil. This suggests a “doorway” cross section of απλ 2 plays a key role in some QED processes. Additional support for this suggestion is obtained via a simple semi-classical picture of Compton scattering. Several speculative semi-classical reaction mechanism choices, including near-field effects, give the anomalous magnetic moment of the free electron. These choices are partially justified by their ability to give the magnetic moment of electrons in hydrogen-like atoms as a function of the atomic number of the corresponding nucleus, close to the correct result. The stimulated-emission process used to obtain the rest-mass energy allows for the possibility that stimulated virtual photons can be exchanged between an electron pair. This exchange can be used to estimate a repulsive force between electrons, and thus allows for a calculation of the fine-structure constant. A result near to the experimental value is obtained with minor modifications to the assumptions that give the rest mass, Lamb shift, and anomalous magnetic moment of the electron. Additional studies are required to confirm or negate the suggestions made here.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Constraints on the photon mass with fast radio bursts
Fast radio bursts (FRBs) are radio bursts characterized by millisecond durations, high Galactic latitude positions, and high dispersion measures. Very recently, the cosmological origin of FRB 150418 has been confirmed by Keane et al., and FRBs are now strong competitors as cosmological probes. The simple sharp feature of the FRB signal is ideal to probe some of the fundamental laws of physics. Here we show that by analyzing the delay time between different frequencies, the FRB data can place stringent upper limits on the rest mass of the photon. For FRB 150418 at z = 0.492, one can potentially reach m{sub γ}⩽5.2×10{sup −47} g, which is 10{sup 20} times smaller than the rest mass of electron and is about 10{sup 3} times smaller than that obtained using other astrophysical sources with the same method.
79 ASTRONOMY AND ASTROPHYSICS↗
Internal Structure of Charged Particles in a GRT Gravitational Model
With the help of an exact solution of the Einstein and Maxwell equations, the internal structure of a multiply connected space of wormhole type with two unclosed static throats leading out of it into two parallel vacuum spaces or into one space is investigated in GRT for a free electric field and dust-like matter. The given geometry is considered as a particle–antiparticle pair with fundamental constants arising in the form of first integrals in the solution of the Cauchy problem – electric charges ±e of opposite sign in the throats and rest mass m{sub 0} – the total gravitational mass of the inner world of the particle in the throat. With the help of the energy conservation law, the unremovable rotation of the internal structure is included and the projection of the angular momentum of which onto the rotation axis is identified with the z-projection of the spin of the charged particle. The radius of 2-Gaussian curvature of the throat R* is identified with the charge radius of the particle, and the z-projection of the magnetic moment and the g-factor are found. The feasibility of the given gravitational model is confirmed by the found condition of independence of the spin quantum number of the electron and the proton s = 1/2 of the charge radius R* and the relativistic rest mass m* of the rotating throat, which is reliably confirmed experimentally, and also by the coincidence with high accuracy of the proton radius calculated in the model R{sub *p} = 0.8412·10{sup –13} cm with the value of the proton charge radius obtained experimentally by measuring the Lamb shift on muonic hydrogen. The electron in the given model also turns out to be a structured particle with radius R{sub *e} = 3.8617·10{sup –11} cm.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Searching for Low-Mass Dark Matter with SuperCDMS Soudan Detectors
SuperCDMS is a direct-detection dark matter (DM) experiment that uses cryogenically cooled germanium and silicon detectors to search for interac- tions between DM particles and detector nuclei, and in this thesis I describe my contributions to the experiment. I start with a brief review of DM and motivate the possibility of its de- tection in underground laboratories with sensitive detectors, and I review the SuperCDMS detector fundamentals. Then I focus on detector develop- ment for the future generation of the experiment, which will deploy an array of detectors at SNOLAB in Sudbury, Canada. Specifically I describe char- acterization of prototype detectors from surface facility testing, and discuss measurements of critical values that determine the detectors’ sensitivity to DM particles, such as the baseline resolution and the phonon collection ef- ficiency. I also describe analysis techniques developed to measure intrinsic detector noise in a high radiation environment such as a surface test facility. In the final chapters I describe a DM search analysis using four months of data from operation of SuperCDMS detectors in the Soudan Mine in northern Minnesota. I discuss how a particular detector operating mode, called CDMSlite, lowers the energy threshold of the detectors in order to improve the sensitivity to low-mass DM particles. I also present new analysis techniques that optimize the sensitivity to low-mass DM particles, including noise discrimination with multivariate classifiers, instrumental background modeling, and a profile likelihood signal and background fitting approach. In this analysis we set an upper limit on the DM-nucleon scattering cross section in germanium that is a factor of 2.5 improvement over the previous CDMSlite result for a DM mass that is five times the proton rest mass.
79 ASTRONOMY AND ASTROPHYSICS↗
AGILE Observations of the Gravitational-wave Source GW170104
The LIGO/Virgo Collaboration (LVC) detected on 2017 January 4 a significant gravitational-wave (GW) event (now named GW170104). We report in this Letter the main results obtained from the analysis of hard X-ray and gamma-ray data of the AGILE mission that repeatedly observed the GW170104 localization region (LR). At the LVC detection time T {sub 0} AGILE observed about 36% of the LR. The gamma-ray imaging detector did not reveal any significant emission in the energy range 50 MeV–30 GeV. Furthermore, no significant gamma-ray transients were detected in the LR that was repeatedly exposed over timescales of minutes, hours, and days. We also searched for transient emission using data near T {sub 0} of the omnidirectional detector MCAL operating in the energy band 0.4–100 MeV. A refined analysis of MCAL data shows the existence of a weak event (that we call “E2”) with a signal-to-noise ratio of 4.4 σ lasting about 32 ms and occurring 0.46 ± 0.05 s before T {sub 0}. A study of the MCAL background and of the false-alarm rate of E2 leads to the determination of a post-trial significance between 2.4σ and 2.7σ for a temporal coincidence with GW170104. We note that E2 has characteristics similar to those detected from the weak precursor of GRB 090510. The candidate event E2 is worth consideration for simultaneous detection by other satellites. If associated with GW170104, it shows emission in the MeV band of a short burst preceding the final coalescence by 0.46 s and involving ∼10{sup −7} of the total rest mass energy of the system.
79 ASTRONOMY AND ASTROPHYSICS↗
THE INTERNAL STRUCTURE OF OVERPRESSURED, MAGNETIZED, RELATIVISTIC JETS
This work presents the first characterization of the internal structure of overpressured, steady superfast-magnetosonic relativistic jets in connection with their dominant type of energy. To this aim, relativistic magnetohydrodynamic simulations of different jet models threaded by a helical magnetic field have been analyzed covering a wide region in the magnetosonic Mach number–specific internal energy plane. The merit of this plane is that models dominated by different types of energy (internal energy: hot jets; rest-mass energy: kinetically dominated jets; magnetic energy: Poynting-flux-dominated jets) occupy well-separated regions. The analyzed models also cover a wide range of magnetizations. Models dominated by the internal energy (i.e., hot models, or Poynting-flux-dominated jets with magnetizations larger than but close to one) have a rich internal structure characterized by a series of recollimation shocks and present the largest variations in the flow Lorentz factor (and internal energy density). Conversely, in kinetically dominated models, there is not much internal or magnetic energy to be converted into kinetic, and the jets are featureless with small variations in the flow Lorentz factor. The presence of a significant toroidal magnetic field threading the jet produces large gradients in the transversal profile of the internal energy density. Poynting-flux-dominated models with high magnetization (≈10 or larger) are prone to be unstable against magnetic pinch modes, which sets limits on the expected magnetization in parsec-scale active galactic nucleus jets or constrains their magnetic field configuration.
79 ASTRONOMY AND ASTROPHYSICS↗
Various Applications of Precision Low-Energy Nuclear Electron Spectrometry in the KATRIN Tritium Neutrino Project
The energy scale of the main spectrometer in the KATRIN tritium project is required to remain stable within ±60 meV at an electron energy of 18.6 keV for two months in order to reach the intended sensitivity of 0.2 eV for the rest mass of the electron antineutrino. A natural source of reference electrons with an energy of 17824.3 ± 0.5 eV based on K -conversion electrons of the 32-keV nuclear γ-transition in {sup 83m}Kr from the decay of parent {sup 83}Rb was developed for this purpose using precision low-energy nuclear electron spectrometry. The spectroscopic parameters of {sup 83m}Kr/{sup 83}Rb sources fabricated by ion implantation into polycrystalline platinum foils were significantly better than the parameters of vacuum-deposited sources. A large-scale study of the influence of the physicochemical environment of atoms of different radioisotopes in various matrices of vacuum-deposited and implanted radioactive sources on the energy of emitted conversion and Auger electrons and on the structure of the corresponding energy spectra was conducted in the process. The possibility of application of photoelectron sources with a metallic converter as sources of reference electrons for the KATRIN project was also considered.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
UNBOUND DEBRIS STREAMS AND REMNANTS RESULTING FROM THE TIDAL DISRUPTIONS OF STARS BY SUPERMASSIVE BLACK HOLES
The kinetic energy of a star in orbit about a supermassive black hole is a significant fraction of its rest mass energy when its periapse is comparable to its tidal radius. Upon its destruction, a fraction of this energy is extracted and injected into the stellar debris, half of which becomes unbound from the black hole, with the fastest material moving at ∼0.03c. In this paper, we present a formalism for determining the fate of these unbound debris streams (UDSs) as they depart from the black hole and interact with the surrounding gas. As the density and velocity varies along the length of a UDS, we find that hydrodynamical drag quickly shapes UDSs into loop-like structures, with the densest portions of the streams leading portions of lower density. As UDSs travel outwards, their drag against the ISM increases quadratically with distance, which causes UDSs to deposit their momentum and energy into the ambient medium before the surrounding shocked ISM has a chance to cool. This sudden injection of ∼10{sup 50} erg into the ambient medium generates a Sedov-like unbound debris remnant (UDR) that mimics supernova remnants (SNRs) in energetics and appearance, accelerates particles which will produce cosmic rays and synchrotron emission, and provides momentum feedback into the molecular clouds surrounding a black hole. We estimate that a few of these UDRs might be present within a couple degrees of the Galactic Center masquerading as SNRs, and that the UDR scenario is a plausible explanation for Sgr A east.
79 ASTRONOMY AND ASTROPHYSICS↗
Test of Weak Equivalence Principle with the Multi-band Timing of the Crab Pulsar
The Weak Equivalent Principle (WEP) can be tested through the parameterized post-Newtonian parameter γ, representing the space curvature produced by unit rest mass. The parameter γ in turn has been constrained by comparing the arrival times of photons originating in distant transient events, such as gamma-ray bursts, fast radio bursts, and giant pulses of pulsars. Those measurements normally correspond to an individual burst event with very limited energy bands and signal-to-noise ratios (S/Ns). In this paper, the discrepancy in the pulse arrival times of the Crab Pulsar between different energy bands is obtained by the phase difference between corresponding pulse profiles. This allows us to compare the pulse arrival times at the largest energy band differences, between radio and optical, radio and X-ray, and radio and gamma-ray respectively. Because the pulse profiles are generated by phase-folding thousands of individual pulses, the time discrepancies between two energy bands are actually measured from thousands of events at each energy band, which corresponds to a much higher S/N. The upper limit of the γ discrepancy set by such an extensively observed and well-modeled source is as follows: γ{sub radio}--γ{sub γ-ray}<3.28×10{sup −9} at the energy difference of E{sub γ-ray}/E{sub radio}∼10{sup 13}, γ{sub radio}--γ{sub X-ray}<4.01×10{sup −9} at the energy difference of E{sub X-ray}/E{sub radio}∼10{sup 9}, γ{sub radio}--γ{sub optical}<2.63×10{sup −9} at E{sub optical}/E{sub radio}∼10{sup 5}, and γ{sub optical}--γ{sub γ-ray}<3.03×10{sup −10} at E{sub γ-ray}/E{sub optical}∼10{sup 8}. This actually measures the arrival times of freely falling photons in the gravitational field of the Milky Way with the largest amount of events and with data of the highest S/N, which tests WEP at energy band differences that have never been reached before.
79 ASTRONOMY AND ASTROPHYSICS↗
Direct neutrino-mass measurement based on 259 days of KATRIN data
That neutrinos carry a nonvanishing rest mass is evidence of physics beyond the Standard Model of elementary particles. Their absolute mass holds relevance in fields from particle physics to cosmology. We report on the search for the effective electron antineutrino mass with the KATRIN experiment. KATRIN performs precision spectroscopy of the tritium β-decay close to the kinematic endpoint. On the basis of the first five measurement campaigns, we derived a best-fit value of $m^{2}_{v} = -0.14^{+0.13}_{-0.15}$ eV 2 , resulting in an upper limit of m ν < 0.45 eV at 90% confidence level. Stemming from 36 million electrons collected in 259 measurement days, a substantial reduction of the background level, and improved systematic uncertainties, this result tightens KATRIN’s previous bound by a factor of almost two.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
The Kinetic-Energy–Momentum–Mass 5-Flux of a Baryon Fluid in Bargmann Spacetimes
A Bargmann spacetime is a constrained five-dimensional setting that, while introducing no new physical degrees of freedom beyond those of ordinary four-dimensional spacetime, permits Galilei physics to be expressed with a tensor formalism that respects the distinction between mass and energy while affording the conceptual and technical advantages of a spacetime metric. This framework offers a route to a strong-field ‘Galilei general relativity’ approximating the usual Poincaré general relativity introduced by Einstein. In preparation for modeling core-collapse supernovae, where such an approximation would be useful, this work generalizes the kinetic-energy–momentum–mass 5-flux 𝒯 and its associated spacetime tensor law from a simple fluid of constant particle mass to a baryon fluid whose multiple nuclear species can interconvert rest mass and internal energy. The spacetime tensor law on Bargmann–Galilei spacetime 𝐵𝒢 and its decompositions relative to comoving (‘Lagrangian’) and fiducial (‘Eulerian’) observers are derived in detail. The formalism is rendered more suitable for core-collapse supernova modeling by an extension from strict 𝐵𝒢 to a regime that might be denoted as 𝐵𝒢+: microscopically Poincaré yet macroscopically Galilei. This extension accommodates energy generation by nuclear composition changes and allows comoving energy density and pressure to contribute relative to mass density, while preserving the simplifications of Galilei bulk fluid flow and the streamlined geometry governed by the Bargmann–Galilei spacetime metric.
Cardall, Christian [ORNL] (ORCID:000000020086105X)↗
Geometric and thermodynamic characterization of binary neutron star accretion discs
Accretion disks formed in binary neutron star mergers play a central role in many astrophysical processes of interest, including the launching of relativistic jets or the ejection of neutron-rich matter hosting heavy element nucleosynthesis. In this work we analyze in detail the properties of accretion disks from 44 ab initio binary neutron star merger simulations for a large set of nuclear equations of state, binary mass ratios, and remnant fates, with the aim of furnishing reliable initial conditions for disk simulations and a comprehensive characterization of their properties. We find that the disks have a significant thermal support, with an aspect ratio decreasing with the mass ratio of the binary from ~0.7 to 0.3. Even if the disk sample spans a broad range in mass and angular momentum, their ratio is independent from the equation of state and from the mass ratio. This can be traced back to the rotational profile of the disk, characterized by a constant specific angular momentum (as opposed to a Keplerian one) of 3 – 5×10 16 cm 2 s –1 . The profiles of the entropy per baryon and of the electron fraction depend on the mass ratio of the binary. For more symmetric binaries, they follow a sigmoidal distribution as a function of the rest mass density, for which we provide a detailed description and a fit. Furthermore, the disk properties discussed in this work can be used as a robust set of initial conditions for future long-term simulations of accretion disks from binary neutron star mergers, posing the basis for progress in the quantitative study of the outflow properties.
79 ASTRONOMY AND ASTROPHYSICS↗
Troubles with global monopoles in quantum gravity
A theory with a global [Formula: see text] symmetry broken at a scale [Formula: see text] admits topological configurations: global monopoles realized by Goldstone fields winding around the core of false vacuum. One may expect them to behave as heavy, big composite objects, difficult to make and therefore mostly harmless. However, after gravity is turned on, as long as Equivalence Principle holds, one finds that global monopoles have a negative mass, [Formula: see text], where [Formula: see text] is the field theory coupling. This could catalyze an instability in the space of a global monopole, by the production of additional global monopole–antimonopole pairs along with normal particles, leading to energy production ab nihilo, if the pair energy is dominated by their negative rest masses. In a theory with unbroken local Poincaré symmetry, this could lead to a divergent ‘decay rate’ of the global monopole configurations.
Astronomy & Astrophysics↗
A New Approach for Calculating the Alpha-Decay Half-Life for the Heavy and Super-heavy Elements and an Exact A Priori Result for Beyllium-8
A new general method for calculating the alpha decay half-life is presented. The method predicts an a priori exact value for the beryllium-8 half-life. Beryllium-8 is an exception to the current alpha decay theory captured in the Geiger-Nuttal law. The new method predicts the beryllium-8 alpha half-life using only constants and measured isotopic mass. The method also reliably predicts all the heavier isotope alpha decay half-lives consistent with the Geiger-Nuttal law. With respect to current theory, the inability of the Geiger-Nuttal Law to predict the alpha-decay half-life in the case of beryllium-8 has led to consideration of other decay mechanisms for this isotope, such as fission for example. One result is that given the consistency of the new method presented here for all isotopes including an exact a priori result for beryllium-8, the evidence strongly suggests that the beryllium-8 decay is in fact an alpha decay. A second result is that the method definitively demonstrates that the entire rest mass of the two helium-4 electrons is converted to energy in the decay process and this energy becomes part of the emitted alpha particle kinetic energy.
07 ISOTOPE AND RADIATION SOURCES↗
D 3 -creatine dilution for skeletal muscle mass measurement: historical development and current status
The French chemist Michel Eugène Chevreul discovered creatine in meat two centuries ago. Extensive biochemical and physiological studies of this organic molecule followed with confirmation that creatine is found within the cytoplasm and mitochondria of human skeletal muscles. Two groups of investigators exploited these relationships five decades ago by first estimating the creatine pool size in vivo with 14 C and 15 N labelled isotopes. Skeletal muscle mass (kg) was then calculated by dividing the creatine pool size (g) by muscle creatine concentration (g/kg) measured on a single muscle biopsy or estimated from the literature. This approach for quantifying skeletal muscle mass is generating renewed interest with the recent introduction of a practical stable isotope (creatine-(methyl-d 3 )) dilution method for estimating the creatine pool size across the full human lifespan. The need for a muscle biopsy has been eliminated by assuming a constant value for whole-body skeletal muscle creatine concentration of 4.3 g/kg wet weight. The current single compartment model of estimating creatine pool size and skeletal muscle mass rests on four main assumptions: tracer absorption is complete; tracer is all retained; tracer is distributed solely in skeletal muscle; and skeletal muscle creatine concentration is known and constant. Three of these assumptions are false to varying degrees. Not all tracer is retained with urinary isotope losses ranging from 0% to 9%; an empirical equation requiring further validation is used to correct for spillage. Not all tracer is distributed in skeletal muscle with non-muscle creatine sources ranging from 2% to 10% with a definitive value lacking. Lastly, skeletal muscle creatine concentration is not constant and varies between muscles (e.g. 3.89–4.62 g/kg), with diets (e.g. vegetarian and omnivore), across age groups (e.g. middle-age, ~4.5 g/kg; old-age, 4.0 g/kg), activity levels (e.g. athletes, ~5 g/kg) and in disease states (e.g. muscular dystrophies, <3 g/kg). Some of the variability in skeletal muscle creatine concentrations can be attributed to heterogeneity in the proportions of wet skeletal muscle as myofibres, connective tissues, and fat. These observations raise serious concerns regarding the accuracy of the deuterated-creatine dilution method for estimating total body skeletal muscle mass as now defined by cadaver analyses of whole wet tissues and in vivo approaches such as magnetic resonance imaging. A new framework is needed in thinking about how this potentially valuable method for measuring the creatine pool size in vivo can be used in the future to study skeletal muscle biology in health and disease.
body composition↗
Understanding hadronic interactions using advanced reconstruction techniques
ProtoDUNE-SP served as the prototype of the future Deep Underground Neutrino Experiment (DUNE). With a total liquid argon mass of 0.77 kt, it stood as the most extensive monolithic single-phase Liquid Argon Time Projection Chamber (LArTPC) ever constructed. Strategically located and operated at CERN, ProtoDUNE-SP benefited from a specialized charged-particle test beam, offering a momentum range of 0.3 - 7 GeV/c. This setup provided a unique opportunity to conduct in-depth studies on hadronic interactions within argon. Hadronic interactions play a fundamental role in neutrino physics, particularly in the intricacies of neutrino detection. We depend on analyzing the outcomes of these interactions to accurately determine both the flavor and energy of the interacting neutrinos. Pions, as one of the primary byproducts of neutrino interactions, are crucial for understanding the overall dynamics and kinematics of these processes. Accurately characterizing and understanding the interaction of pions with argon can significantly enhance the precision of neutrino simulations and measurements.Being a Liquid Argon Time Projection Chamber (LArTPC), ProtoDUNE-SP is distinguished by its ability to produce high-definition images of charged particles as they traverse through the detector's active volume. Yet, accurately reconstructing these particle interactions and determining their kinematic attributes remains a challenging task. The successes of deep learning in diverse domains, especially in image recognition, provide a promising approach for addressing this challenge in ProtoDUNE. This thesis discusses a measurement of the Piplus - argon inelastic cross section in the energy range of 2400 to 3000 MeV, using data taken by protoDUNE during the fall of 2018. Additionally, panoptic segmentation, a machine learning technique, is introduced and validated through its application in the reconstruction of the neutral pion rest mass. The aim is to showcase how these advanced methods can enhance the quality of event reconstruction.
Sarasty Segura, Carlos Eduardo↗