Showing papers on "Elementary particle published in 2021"
TL;DR: In this article, the anomalous magnetic moment of the muon was determined based on ab initio quantum chromodynamics and quantum electrodynamics simulations, and the experimental results were used to discriminate between the measurement of the magnetic moment and the predictions of dispersive methods.
Abstract: The standard model of particle physics describes the vast majority of experiments and observations involving elementary particles. Any deviation from its predictions would be a sign of new, fundamental physics. One long-standing discrepancy concerns the anomalous magnetic moment of the muon, a measure of the magnetic field surrounding that particle. Standard-model predictions1 exhibit disagreement with measurements2 that is tightly scattered around 3.7 standard deviations. Today, theoretical and measurement errors are comparable; however, ongoing and planned experiments aim to reduce the measurement error by a factor of four. Theoretically, the dominant source of error is the leading-order hadronic vacuum polarization (LO-HVP) contribution. For the upcoming measurements, it is essential to evaluate the prediction for this contribution with independent methods and to reduce its uncertainties. The most precise, model-independent determinations so far rely on dispersive techniques, combined with measurements of the cross-section of electron–positron annihilation into hadrons3–6. To eliminate our reliance on these experiments, here we use ab initio quantum chromodynamics (QCD) and quantum electrodynamics simulations to compute the LO-HVP contribution. We reach sufficient precision to discriminate between the measurement of the anomalous magnetic moment of the muon and the predictions of dispersive methods. Our result favours the experimentally measured value over those obtained using the dispersion relation. Moreover, the methods used and developed in this work will enable further increased precision as more powerful computers become available. A precise theoretical computation of the anomalous magnetic moment of the muon based on ab initio quantum chromodynamics and quantum electrodynamics calculations is presented, which favours the existing experimental values.
170 citations
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TL;DR: In this paper, the authors present evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton-proton collision data collected with the LHCb detector at CERN's Large Hadron Collider.
Abstract: The Standard Model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton-proton collision data collected with the LHCb detector at CERN's Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the Standard Model, such as a new fundamental interaction between quarks and leptons.
99 citations
TL;DR: A variety of observations impose upper limits at the nano Gauss level on magnetic fields that are coherent on inter-galactic scales while blazar observations indicate a lower bound ∼10-16G as mentioned in this paper.
Abstract: A variety of observations impose upper limits at the nano Gauss level on magnetic fields that are coherent on inter-galactic scales while blazar observations indicate a lower bound ∼10-16G. Such magnetic fields can play an important astrophysical role, for example at cosmic recombination and during structure formation, and also provide crucial information for particle physics in the early Universe. Magnetic fields with significant energy density could have been produced at the electroweak phase transition. The evolution and survival of magnetic fields produced on sub-horizon scales in the early Universe, however, depends on the magnetic helicity which is related to violation of symmetries in fundamental particle interactions. The generation of magnetic helicity requires new CP violating interactions that can be tested by accelerator experiments via decay channels of the Higgs particle.
61 citations
TL;DR: In this article, a review of the mutual relationship of the BSM particle physics basis of the modern cosmology and the nontrivial features of the corresponding cosmological scenario is presented.
31 citations
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TL;DR: In this article, the authors improved upon previous calculations of dark matter production from primordial black holes (PBH) by consistently including the greybody factors, and by meticulously tracking a system of coupled Boltzmann equations.
Abstract: Hawking evaporation of black holes in the early Universe is expected to copiously produce all kinds of particles, regardless of their charges under the Standard Model gauge group. For this reason, any fundamental particle, known or otherwise, could be produced during the black hole lifetime. This certainly includes dark matter (DM) particles. This paper improves upon previous calculations of DM production from primordial black holes (PBH) by consistently including the greybody factors, and by meticulously tracking a system of coupled Boltzmann equations. We show that the initial PBH densities required to produce the observed relic abundance depend strongly on the DM spin, varying in about $\sim 2$ orders of magnitude between a spin-2 and a scalar DM in the case of non-rotating PBHs. For Kerr PBHs, we have found that the expected enhancement in the production of bosons reduces the initial fraction needed to explain the measurements. We further consider indirect production of DM by assuming the existence of additional and unstable degrees of freedom emitted by the evaporation, which later decay into the DM. For a minimal setup where there is only one heavy particle, we find that the final relic abundance can be increased by at most a factor of $\sim 4$ for a scalar heavy state and a Schwarzschild PBH, or by a factor of $\sim 4.3$ for a spin-2 particle in the case of a Kerr PBH.
28 citations
TL;DR: CosmoBit as mentioned in this paper is a module within the open-source GAMBIT software framework for exploring connections between cosmology and particle physics with joint global fits, such as models of inflation, modifications of the effective number of relativistic degrees of freedom, exotic energy injection from annihilating or decaying dark matter, and variations of the properties of elementary particles such as neutrino masses.
Abstract: We introduce CosmoBit, a module within the open-source GAMBIT software framework for exploring connections between cosmology and particle physics with joint global fits. CosmoBit provides a flexible framework for studying various scenarios beyond ΛCDM, such as models of inflation, modifications of the effective number of relativistic degrees of freedom, exotic energy injection from annihilating or decaying dark matter, and variations of the properties of elementary particles such as neutrino masses and the lifetime of the neutron. Many observables and likelihoods in CosmoBit are computed via interfaces to AlterBBN, CLASS, DarkAges, MontePython, MultiModeCode, and plc. This makes it possible to apply a wide range of constraints from large-scale structure, Type Ia supernovae, Big Bang Nucleosynthesis and the cosmic microwave background. Parameter scans can be performed using the many different statistical sampling algorithms available within the GAMBIT framework, and results can be combined with calculations from other GAMBIT modules focused on particle physics and dark matter. We include extensive validation plots and a first application to scenarios with non-standard relativistic degrees of freedom and neutrino temperature, showing that the corresponding constraint on the sum of neutrino masses is much weaker than in the standard scenario.
19 citations
TL;DR: In this article, the relationship between the condensed matter axion and a collective spin-wave excitation in an anti-ferromagnetic insulator at the quantum level is discussed.
Abstract: The QCD axion or axion-like particles are candidates of dark matter of the universe. On the other hand, axion-like excitations exist in certain condensed matter systems, which implies that there can be interactions of dark matter particles with condensed matter axions. We discuss the relationship between the condensed matter axion and a collective spin-wave excitation in an anti-ferromagnetic insulator at the quantum level. The conversion rate of the light dark matter, such as the elementary particle axion or hidden photon, into the condensed matter axion is estimated for the discovery of the dark matter signals.
18 citations
TL;DR: In this paper, it was shown that SUSY can be realized at the edge of the Moore-Read quantum Hall state in the absence or presence of edge reconstruction, allowing for their unified description.
Abstract: Supersymmetry (SUSY) relating bosons and fermions plays an important role in unifying different fundamental interactions in particle physics. Since no superpartners of elementary particles have been observed, SUSY, if present, must be broken at low-energy. This makes it important to understand how SUSY is realized and broken, and study their consequences. We show that an $\mathcal{N}=(1,0)$ SUSY, arguably the simplest type, can be realized at the edge of the Moore-Read quantum Hall state. Depending on the absence or presence of edge reconstruction, both SUSY-preserving and SUSY broken phases can be realized in the same system, allowing for their unified description. The significance of the gapless fermionic Goldstino mode in the SUSY broken phase is discussed.
17 citations
TL;DR: In this paper, the authors studied the nonequilibrium dynamics of the false vacuum in a quantum Ising chain and in an XXZ ladder and found that the numerical results agree with the theoretical prediction that the decay rate is exponentially small in the inverse of the longitudinal field.
Abstract: The false vacuum decay has been a central theme in physics for half a century with applications to cosmology and to the theory of fundamental interactions. This fascinating phenomenon is even more intriguing when combined with the confinement of elementary particles. Due to the astronomical timescales involved, the research has so far focused on theoretical aspects of this decay. The purpose of this Letter is to show that the false vacuum decay is accessible to current optical experiments as quantum analog simulators of spin chains with confinement of the elementary excitations, which mimic the high energy phenomenology but in one spatial dimension. We study the nonequilibrium dynamics of the false vacuum in a quantum Ising chain and in an XXZ ladder. The false vacuum is the metastable state that arises in the ferromagnetic phase of the model when the symmetry is explicitly broken by a longitudinal field. This state decays through the formation of ``bubbles'' of true vacuum. Using infinite volume time evolving block decimation (iTEBD) simulations, we are able to study the real-time evolution in the thermodynamic limit and measure the decay rate of local observables. We find that the numerical results agree with the theoretical prediction that the decay rate is exponentially small in the inverse of the longitudinal field.
17 citations
TL;DR: In this article, the relationship between the condensed matter axion and a collective spin-wave excitation in an anti-ferromagnetic insulator at the quantum level is discussed.
Abstract: The QCD axion or axion-like particles are candidates of dark matter of the universe. On the other hand, axion-like excitations exist in certain condensed matter systems, which implies that there can be interactions of dark matter particles with condensed matter axions. We discuss the relationship between the condensed matter axion and a collective spin-wave excitation in an anti-ferromagnetic insulator at the quantum level. The conversion rate of the light dark matter, such as the elementary particle axion or hidden photon, into the condensed matter axion is estimated for the discovery of the dark matter signals.
13 citations
TL;DR: The information capacity of the universe has been a topic of great debate since the 1970s and continues to stimulate multiple branches of physics research as discussed by the authors, and it has been shown that each particle in the observable universe contains 1.509 bits of information.
Abstract: The information capacity of the universe has been a topic of great debate since the 1970s and continues to stimulate multiple branches of physics research. Here, we used Shannon’s information theory to estimate the amount of encoded information in all the visible matter in the universe. We achieved this by deriving a detailed formula estimating the total number of particles in the observable universe, known as the Eddington number, and by estimating the amount of information stored by each particle about itself. We determined that each particle in the observable universe contains 1.509 bits of information and there are ∼6 × 1080 bits of information stored in all the matter particles of the observable universe.
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TL;DR: In this paper, a spin-orbit coupling (SOC)-free Z_2 topological phase with unprecedented surface node structures is shown to have strong symmetries, and the symmetry properties of the spin group are analyzed.
Abstract: Symmetry formulated by group theory plays an essential role with respect to the laws of nature, from fundamental particles to condensed matter systems. Here, by combining symmetry analysis and tight-binding model calculations, we elucidate that the crystallographic symmetries of a vast number of magnetic materials with light elements, in which the neglect of relativistic spin-orbit coupling (SOC) is an appropriate approximation, are considerably larger than the conventional magnetic groups. Thus, a symmetry description that involves partially-decoupled spin and spatial rotations, dubbed as spin group, is required. Spin group permits more symmetry operations and thus more energy degeneracies that are disallowed by the magnetic groups. One consequence of the spin group is the new anti-unitary symmetries that protect SOC-free Z_2 topological phases with unprecedented surface node structures. Our work not only manifests the physical reality of materials with weak SOC, but also shed light on the understanding of all solids with and without SOC by a unified group theory.
TL;DR: Weyl fermions have been observed as collective electronic excitations in the strong spin-orbit coupled material tantalum arsenide, TaAs, in this paper, leading to a flurry of experimental and theoretical explorations of Weyl phenomena in materials.
Abstract: Quantum materials hosting Weyl fermions have opened a new era of research in condensed matter physics. First proposed in 1929 in the context of particle physics, Weyl fermions have yet to be observed as elementary particles. In 2015, Weyl fermions were detected as collective electronic excitations in the strong spin–orbit coupled material tantalum arsenide, TaAs. This discovery was followed by a flurry of experimental and theoretical explorations of Weyl phenomena in materials. Weyl materials naturally lend themselves to the exploration of the topological index associated with Weyl fermions and their divergent Berry curvature field, as well as the topological bulk–boundary correspondence, giving rise to protected conducting surface states. Here, we review the broader class of Weyl topological phenomena in materials, starting with the observation of emergent Weyl fermions in the bulk and Fermi arc states on the surface of the TaAs family of crystals by photoemission spectroscopy. We then discuss several exotic optical and magnetic responses observed in these materials, as well as progress in developing related chiral materials. We discuss the conceptual development of high-fold chiral fermions, which generalize Weyl fermions, and we review the observation of high-fold chiral fermion phases by taking the rhodium silicide, RhSi, family of crystals as a prime example. Lastly, we discuss recent advances in Weyl line phases in magnetic topological materials. With this Review, we aim to provide an introduction to the basic concepts underlying Weyl physics in condensed matter, and to representative materials and their electronic structures and topology as revealed by spectroscopic studies. We hope this work serves as a guide for future theoretical and experimental explorations of chiral fermions and related topological quantum systems with potentially enhanced functionalities. Weyl fermions have yet to be observed as elementary particles but can be realized in topological quantum materials. This Review discusses the theoretical and experimental discovery of emergent Weyl fermions, high-fold chiral fermions, topological Weyl lines and related Dirac phases.
10 Mar 2021
TL;DR: In this article, the Frohlich-Morchio-Strocchi mechanism was used to test and confirm this mechanism for fermions on the lattice, and a model which contains vectorial leptons but obeys all other relevant symmetries has been simulated.
Abstract: Strict gauge invariance requires that physical left-handed leptons are actually bound states of the elementary left-handed lepton doublet and the Higgs field within the standard model. That they nonetheless behave almost like pure elementary particles is explained by the Fr\"ohlich-Morchio-Strocchi mechanism. Using lattice gauge theory, we test and confirm this mechanism for fermions. Though, due to the current inaccessibility of non-Abelian gauged Weyl fermions on the lattice, a model which contains vectorial leptons but which obeys all other relevant symmetries has been simulated.
TL;DR: In this paper, a master equation is solved for a driven quantum cyclotron with a QND coupling to a detection oscillator in thermal equilibrium, the latter making this an open quantum system.
Abstract: A quantum cyclotron is one trapped electron or positron that occupies only its lowest cyclotron and spin states. A master equation is solved for a driven quantum cyclotron with a QND (quantum nondemolition) coupling to a detection oscillator in thermal equilibrium, the latter making this an open quantum system. The predicted rate of a cyclotron and spin quantum jumps as a function of drive frequency, for a small coupling between the detection motion and its thermal reservoir, differs sharply from what has been predicted and used for past measurements. The calculation suggests a ten times more precise electron magnetic moment measurement is possible, as needed to investigate current differences between the most precise prediction of the standard model of particle physics, and the most accurate measurement of a property of an elementary particle.
15 Apr 2021
TL;DR: The Higgs boson was discovered at the Large Hadron Collider (LHC) at CERN in 2012 as discussed by the authors, and its mass is a remarkable value, meaning that the underlying state of the Universe, the vacuum, sits very close to the border between stable and metastable.
Abstract: The Higgs boson, a fundamental scalar boson with mass 125 GeV, was discovered at the Large Hadron Collider (LHC) at CERN in 2012. So far, experiments at the LHC have focused on testing the Higgs boson’s couplings to other elementary particles, precision measurements of the Higgs boson’s properties and an initial investigation of the Higgs boson’s self-interaction and shape of the Higgs potential. The Higgs boson mass of 125 GeV is a remarkable value, meaning that the underlying state of the Universe, the vacuum, sits very close to the border between stable and metastable, which may hint at deeper physics beyond the standard model. The Higgs potential also influences ideas about the cosmological constant, the dark energy that drives the accelerating expansion of the Universe, the mysterious dark matter that comprises about 80% of the matter component in the Universe and a possible phase transition in the early Universe that might be responsible for baryogenesis. A detailed study of the Higgs boson is at the centre of the European Strategy for Particle Physics update. Here we review the current understanding of the Higgs boson and discuss the insights expected from present and future experiments. The Higgs boson is central to our understanding of the structure of matter in high-energy particle physics: the origin of mass, stability of the vacuum and key issues in cosmology. Here we review recent progress in experiment and theory and the prospects for future discoveries.
TL;DR: In this paper, a simple Planck-scale model of nature appears to yield the entire standard model of particle physics, including its fundamental constants, and over 100 predictions and tests about physics beyond the standard model are deduced from the conjecture.
Abstract: A simple Planck-scale model of nature appears to yield the entire standard model of particle physics, including its fundamental constants. The conjecture derives from Dirac’s proposal to describe fermions as tethered objects and models elementary particles as rational tangles. The tangle model appears to explain the Dirac equation, the principle of least action, the observed particle spectrum of fermions and bosons, and the three observed gauge interactions with their Lie groups and all their other properties. In a natural way, the specific tangles for each elementary particle define spin, quantum numbers and all other properties. No aspect of the standard model remains unexplained. Rational tangles appear to imply all the observed propagators and interaction vertices in Feynman diagrams. Other propagators or vertices are excluded. The tangle model thus yields each term of the full Lagrangian of the standard model. Over 100 predictions and tests about physics beyond the standard model are deduced from the conjecture. The predictions cover magnetic monopoles, the weak interaction, the quark model, non-perturbative effects, glueballs, effects of gravity, and more. The predictions agree with all observations performed so far. The conjectured tangles for the elementary particles imply specific Planck-scale processes that occur during propagation and at interaction vertices. These processes determine particle masses, mixing angles and coupling constants. Approximate estimates are possible; ways to improve the calculations are pointed out.
TL;DR: In this paper, the authors consider the possibility to discover scalar CP violation at the high-luminosity (HL) phase of the LHC and investigate its currently allowed parameter region.
Abstract: Extra Higgs states appear in various scenarios beyond the current Standard Model of elementary particles. If discovered at the LHC or future colliders, the question will arise whether CP is violated or conserved in the extended scalar sector. An unambiguous probe of (indirect) CP violation would be the observation that one of the extra Higgs particles is an admixture of a CP-even and a CP-odd state. We discuss the possibility to discover scalar CP violation in this way at the high-luminosity (HL) phase of the LHC. We focus on the Two-Higgs Doublet Model of type I, where we investigate its currently allowed parameter region. Considering a benchmark point that is compatible with the current constraints but within reach of the HL-LHC, we study the prospects of determining the CP property of an extra neutral Higgs state H via the angular distribution of final states in the decay H → $$ \tau \overline{\tau} $$
. The analysis is performed at the reconstructed level, making use of a Boosted Decision Tree for efficient signal-background separation and a shape analysis for rejecting a purely CP-even or odd nature of H.
TL;DR: The International Linear Collider (ILC) is currently the most advanced in its program as discussed by the authors, and the physics and project status of the ILC including its energy expandability are reviewed in this article.
Abstract: The discovery of Higgs particle has ushered in a new era of particle physics. Even though the list of members of the standard theory of particle physics is now complete, the shortcomings of the theory became ever more acute. It is generally considered that the best solution to the problems is an electron–positron collider that can study Higgs particle with high precision and high sensitivity; namely, a Higgs factory. Among a few candidates for Higgs factory, the International Linear Collider (ILC) is currently the most advanced in its program. In this article, we review the physics and the project status of the ILC including its energy expandability.
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TL;DR: In this paper, the authors present the over-arching and underlying idea of a "logistic" of time-space, as a process of having proposed new definitions for time and space to then deliver via theoretic modelling more ideal results than achieved by Einstein's special and general relativity, quantum mechanics, and the standard model of particles.
Abstract: This paper, the fifth in a series of 5 papers summarising Temporal Mechanics, presents the over-arching and underlying idea of a “logistic” of time-space, as a process of having proposed new definitions for time and space to then deliver via theoretic modelling more ideal results than achieved by Einstein’s special and general relativity, quantum mechanics, and the standard model of particles, namely delivering the same basic constants and metrics for known particle and associated field phenomena, while then proposing a next step for theoretic development, namely quantum-based and Planck-scaled particle mass and associated gravity; here, Temporal Mechanics is able to derive the lightest particle by understanding how a DIR (destructive interference resonance) of a Planck length would lead to particle formation, and not just particle formation, yet the formulation of a basic Planck scaled theory of gravity, correctly deriving the value of “G” from the elementary particle level, thence offering a model for quantum gravity.
TL;DR: In this article, the authors justify and extend the standard model of elementary particle physics by generalizing the theory of relativity and quantum mechanics, and define particle states in terms of modulations of wave functions at the smallest possible scale in space-time.
Abstract: We justify and extend the standard model of elementary particle physics by generalizing the theory of relativity and quantum mechanics. The usual assumption that space and time are continuous implies, indeed, that it should be possible to measure arbitrarily small intervals of space and time, but we ignore if that is true or not. It is thus more realistic to consider an extremely small “quantum of length” of yet unknown value a. It is only required to be a universal constant for all inertial frames, like c and h. This yields a logically consistent theory and accounts for elementary particles by means of four new quantum numbers. They define “particle states” in terms of modulations of wave functions at the smallest possible scale in space-time. The resulting classification of elementary particles accounts also for dark matter. Antiparticles are redefined, without needing negative energy states and recently observed “anomalies” can be explained.
01 Jan 2021
TL;DR: In this paper, the Rotating Lepton Model (RLM) of elementary particles in conjunction with special relativity and the de Broglie equation were used to compute analytically the masses of neutrinos from the mass of composite particles, such as hadrons.
Abstract: We use the Rotating Lepton Model (RLM) of elementary particles in conjunction with special relativity and the de Broglie equation to compute analytically the masses of neutrinos from the masses of composite particles, such as hadrons, in the structures of which neutrinos have been recently shown to participate In this way, three distinct neutrino masses are computed which are in good agreement with the values obtained experimentally at Superkamiokande for the three neutrino flavors of the Normal Hierarchy
TL;DR: In this paper, the Standard Model of particle physics requires nine lepton and quark masses as inputs, but does not incorporate neutrino masses required by neutrinos oscillation observations.
Abstract: The Standard Model of particle physics requires nine lepton and quark masses as inputs, but does not incorporate neutrino masses required by neutrino oscillation observations. This analysis addresses these problems, explaining Standard Model particle masses by describing fundamental particles as solutions of Einstein’s equations, with radii 1/4 their Compton wavelength and half of any charge on rotating particles located on the surface at each end of the axis of rotation. The analysis relates quark and lepton masses to electron charge and mass, and identifies neutrino masses consistent with neutrino oscillation observations.
TL;DR: In this article, the current state-of-the-art experimental results recently obtained in searches for new neutral and charged Higgs bosons with a partial or full Run-2 dataset are summarized.
Abstract: One doublet of complex scalar fields is the minimal content of the Higgs sector in order to achieve spontaneous electroweak symmetry breaking and, in turn, to generate the masses of fundamental particles in the Standard Model. However, several theories beyond the Standard Model predict a nonminimal Higgs sector and introduce additional singlets, doublets or even higher-order weak isospin representations, thereby yielding additional Higgs bosons. With its high proton–proton collision energy (13 TeV during Run-2), the Large Hadron Collider opens a new window towards the exploration of extended Higgs sectors. This review article summarises the current state-of-the-art experimental results recently obtained in searches for new neutral and charged Higgs bosons with a partial or full Run-2 dataset.
TL;DR: In this article, the anisotropic flow of photons calculated using hydrodynamical model framework for different collision systems and beam energies is reviewed and some new ideas which can be valuable for understanding direct photon puzzle.
Abstract: Electromagnetic radiations are one of the potential probes to study the initial state of the hot and dense quark-gluon plasma (QGP) produced during the collision of heavy nuclei at relativistic energies. Photons are emitted throughout the lifetime of the evolving system and carry undistorted information from the production point to the detector. The observation of large anisotropic flow of charged particles provides a strong confirmation of QGP formation and collective behaviour of the produced matter in these collisions. However, the theoretical model calculations which explain the hadronic spectra and anisotropic flow successfully, underpredict the experimental data of elliptic as well as triangular flow of photons by a large margin. This discrepancy between data and theory results is known as direct photon puzzle. In this article, we review the anisotropic flow of photons calculated using hydrodynamical model framework for different collision systems and beam energies. In addition, we propose some new ideas which can be valuable for understanding direct photon puzzle.
TL;DR: The Higgs boson was discovered at CERN in 2012 with mass 125 GeV, a mass that turned out to be a remarkable choice of Nature as discussed by the authors, and it is closely linked to the mechanism that gives mass to the W and Z gauge bosons that mediate the weak interactions and to the charged fermions.
Abstract: The Higgs boson, a fundamental scalar, was discovered at CERN in 2012 with mass 125 GeV, a mass that turned out to be a remarkable choice of Nature. In the Standard Model of particle physics, the Higgs boson is closely linked to the mechanism that gives mass to the W and Z gauge bosons that mediate the weak interactions and to the charged fermions. Following discovery of the Higgs boson, present measurements at the Large Hadron Collider are focused on testing the Higgs boson's couplings to other elementary particles, precision measurements of the Higgs boson's properties and initial investigation of the Higgs boson's self-interaction and shape of the Higgs potential. With the Higgs boson mass of 125 GeV the vacuum sits very close to the border of stable and metastable, which may be a hint to deeper physics beyond the Standard Model. The Higgs potential also plays an important role in ideas about the cosmological constant or dark energy that drives the accelerating expansion of the Universe, the mysterious dark matter that comprises about 80% of the matter component in the Universe, as well as a possible phase transition in the early Universe that might be responsible for baryogenesis. Detailed study of the Higgs boson is at the centre of the recent European Strategy for Particle Physics update. Here we review the present status of this physics and discuss the new insights expected from present and future experiments.
CERN1
TL;DR: In this paper, a guide-field along the accelerator, typically provided by sets of different types of magnets, ensures the charged particles stay within the transverse boundaries of the beam pipe, near its center, travelling on the wanted trajectory.
Abstract: While charged particle accelerators have their origin in the research related to fundamental and high-energy physics, they expanded their applications to many other fields of applied research in physics, material science, biology, chemistry, and medical science, including the treatment of patients, to name some. However, in all types of accelerators assembles of charged particles, e.g., electrons, protons, ions, sometimes their antimatter partners positrons or p-bars (anti-protons) are accelerated to a desired energy, typically in an evacuated, metallic tube, called beam pipe. The acceleration is performed by providing an electric field of high gradient to the charged particle assemble in the direction of motion. In most cases this is performed by resonant radio-frequency (RF) cavities, which are fed by a high-power RF source. However, new acceleration schemes using high power lasers, plasma wakefields, etc. are also studied these days. A guide-field along the accelerator, typically provided by sets of different types of magnets, ensures the charged particles stay within the transverse boundaries of the beam pipe, near its center, travelling on the wanted trajectory. Accelerating elementary particles, like electrons, or quasi-elementary particles, like protons, to very high energies (GeV range) results their velocity $v$ to be close to speed-of-light $c$ , typically expressed as relative velocity $\beta=v/c\approx 1$ , and any further acceleration manifests in a gain of momentum $p=\gamma m_{0}v$ , with $\gamma=1/\sqrt{1-\beta^{2}}$ being the Lorentz factor and $m_{0}$ being the mass of the particle at rest, 0.511 MeV and 938.26 MeV for electron and proton, respectively. The use of resonant RF cavities for the acceleration, causes the particles to form bunches, which fill a longitudinal range of typically a few millimeters up to some meters, depending on $f_{RF}, \gamma$ and other factors. This means, the large number of charged particles in the accelerator are not uniformly distributed along the beam-line but appear in bunches of typical $N=10^{8}-10^{11}$ particles per bunch, and the minimum space between the center of those bunches is defined by the RF bucket length, given by the wavelength $\lambda_{RF}=v/f_{RF}$ of the RF system.
Journal Article•
TL;DR: In this paper, the SU(2) theory was investigated in one dimension with two color degrees of freedom. But the SU (2) model is a non-Abelian model and the spectrum contains not only meson-type states, made of one valence fermion and two valence antifermions, but also baryon type states composed of only valence Fermions.
Abstract: Quantum computers can dramatically enhance current simulation methods. Some of the most promising applications are non-Abelian gauge theories that describe fundamental particle interactions. In particular quantum chromodynamics (QCD), which describes the strong interaction between quarks and gluons that form hadrons such as protons and neutrons, is relying on future quantum computers to perform simulations that are known to be unattainable on classical computers. Here, we present the first quantum computer simulation of a complete non-Abelian gauge theory incorporating both gauge and matter fields. We investigate the SU(2) gauge theory in one dimension - with two color degrees of freedom - as a first important step towards studying QCD. A striking signature of the non-Abelian nature of the model is that the spectrum contains not only meson-type states, made of one valence fermion and one valence antifermion, but also baryon-type states composed of only valence fermions. We performed a quantum computation of the masses of the lightest baryon and meson in the theory on an IBM superconducting platform using a variational quantum eigensolver. Running the full SU(2) theory on current quantum hardware was enabled by a resource-efficient approach that lays out the premises for future quantum simulations of more complex and ultimately sign-problem afflicted models.
Posted Content•
TL;DR: In this article, the authors proposed a model that matches and predicts data across four facets of physics: elementary particles, properties of elementary particles and other objects, cosmology, and astrophysics.
Abstract: This essay shows modeling that - across four facets of physics - matches and predicts data. The facets are elementary particles, properties of elementary particles and other objects, cosmology, and astrophysics. Regarding elementary particles, our modeling matches all known particles and suggests new particles. New particles include zero-charge quark-like particles, a graviton, an inflaton, and other elementary particles. Some models split gravitational fields in ways similar to the splitting of electromagnetic fields into electric fields and magnetic fields. Regarding properties, our modeling suggests a new property - isomer. An isomer is a near copy of a set of most elementary particles. Our modeling includes a parameter that catalogs charge, mass, spin, and other properties. Regarding cosmology and astrophysics, the elementary particles and the new property seem to explain dark matter. Most dark matter has bases in five new isomers of the Standard Model elementary particles. More than eighty percent of dark matter is cold dark matter. Some dark matter has similarities to ordinary matter. Regarding cosmology, our modeling points to a basis for the size of recent increases in the rate of expansion of the universe. Our modeling suggests five eras in the evolution of the universe. Two eras would precede inflation. Regarding astrophysics, our modeling explains ratios of dark matter to ordinary matter. One ratio pertains to densities of the universe. Some ratios pertain to galaxy clusters. Some ratios pertain to galaxies. One ratio pertains to depletion of cosmic microwave background radiation. The modeling seems to offer insight about galaxy formation. That our work seems to explain cosmology data and astrophysics data might confirm some of our work regarding properties and elementary particles. Our modeling has roots in discrete mathematics. Our modeling unites itself and widely-used physics modeling.
01 Jan 2021
TL;DR: In the early 1950s, T.D. Lee and C.N. Yang suggested that the violation of parity symmetry, a radical solution, would solve the θ − τ puzzle as discussed by the authors.
Abstract: This chapter will discuss the discovery of parity nonconservation. In the early 1950s the physics community was faced with a vexing problem, the θ − τ puzzle. There were two elementary particles which, on one set of criteria, mass and lifetime, seemed to be the same particle. On another set of criteria, spin and parity, they seemed to be different particles. Solutions using accepted physics failed to solve the problem. In 1956, T.D. Lee and C.N. Yang suggested that the violation of parity symmetry, a radical solution, would solve the problem. They proposed several experiments that would test their hypothesis. The first, the β decay of oriented nuclei was performed by C.S. Wu and her collaborators. They observed an asymmetry in the decay, more electrons were emitted opposite to the nuclear spin than along the spin direction, thus, demonstrating parity nonconservation. Similar results were obtained in a second set of experiments on π → μ → e decay by Garwin, Lederman, and Weinrich and by Friedman and Telegdi. The question of whether just one of these experiments would have sufficed to demonstrate parity violation will be discussed.