Hasil untuk "Elementary particle physics"

Alain Blondel, Christophe Grojean, Patrick Janot et al.

The FCC integrated programme comprises an $\rm e^+e^-$ high-luminosity circular collider that will produce very large samples of data in an energy range $88 \le \sqrt{s} \le 365$ GeV, followed by a high-energy $\rm pp$ machine that, with the current baseline plan, will operate at a collision energy of around 85 TeV and deliver datasets an order of magnitude larger than those of the HL-LHC. This visionary project will allow for transformative measurements across a very broad range of topics, which in almost all cases will exceed in sensitivity the projections of any other proposed facility, and simultaneously provide the best possible opportunity for discovering physics beyond the Standard Model. The highlights of the physics programme are presented, together with discussion on the key attributes of the integrated project that enable the physics reach. It is noted that the baseline programme of FCC-ee, in particular, is both flexible and extendable, and also that the synergy and complementarity of the electron and proton machines, and the sharing of a common infrastructure, provides a remarkably efficient, timely and cost-effective approach to addressing the most pressing open questions in elementary particle physics.

The ATLAS collaboration, G. Aad, E. Aakvaag et al.

Abstract This paper presents a search for supersymmetric particles in models with highly compressed mass spectra, in events consistent with being produced through vector boson fusion. The search uses 140 fb −1 of proton-proton collision data at s $$ \sqrt{s} $$ = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. Events containing at least two jets with a large gap in pseudorapidity, large missing transverse momentum, and no reconstructed leptons are selected. A boosted decision tree is used to separate events consistent with the production of supersymmetric particles from those due to Standard Model backgrounds. The data are found to be consistent with Standard Model predictions. The results are interpreted using simplified models of R-parity-conserving supersymmetry in which the lightest supersymmetric partner is a bino-like neutralino with a mass similar to that of the lightest chargino and second-to-lightest neutralino, both of which are wino-like. Lower limits at 95% confidence level on the masses of next-to-lightest supersymmetric partners in this simplified model are established between 117 and 120 GeV when the lightest supersymmetric partners are within 1 GeV in mass.

Pinghui Mou, Zhengzhou Yan, Guoping Li

In this paper, by treating the cosmological constant as a thermodynamic pressure, we study the thermodynamics and phase transitions of the dyonic AdS black holes in Gauss-Bonnet-Scalar gravity, where the conformal scalar field is considered. In a more general extended phase space, we first verified the first law of black hole thermodynamics, and find that it is always true. Meanwhile, the corresponding Smarr relation is also obtained. Then, we found that this black hole exhibits interesting critical behaviors in six dimensions, i.e., two swallowtails can be observed simultaneously. Interestingly, in a specific parameter space, we observed the small/intermediate/large black hole phase transitions, with the triple point naturally appearing. Additionally, the small/large black hole phase transition, similar to the liquid/gas phase transition of the van der Waals fluids, can also be found in other parameter regions. Moreover, we note that the novel phase structure composed of two separate coexistence curves discovered in the dyonic AdS black holes in Einstein-Born-Infeld gravity disappears in Gauss-Bonnet-Scalar gravity. This suggests that this novel phase structure may be related to gravity theory, and importantly, it is generally observed that the triple point is a universal property of dyonic AdS black holes. On the other hand, we calculated the critical exponents near the critical points and found that they share the same values as in mean field theory. Finally, it is true that these results will provide some deep insights into the interesting thermodynamic properties of the dyonic AdS black holes in the background of conformal scalar fields.

Wen-Cheng Feng, Shu-Mei Jia, Hai-Hui Zhao et al.

The Lobster Eye Imager for Astronomy (LEIA) is the pathfinder of the wide-field X-ray telescope used in the Einstein Probe mission. In this study, we present an image of the Virgo Cluster taken by LEIA in the 0.5–4.5 keV band with an exposure time of ∼17.3 ks in the central region. This extended emission is generally consistent with the results obtained by ROSAT. However, the field is affected by bright point sources due to the instrument’s Point Spread Function (PSF) effect. Through fitting of the LEIA spectrum of the Virgo Cluster, we obtained a temperature of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>2</mn><mo>.</mo><msubsup><mn>1</mn><mrow><mo>−</mo><mn>0.1</mn></mrow><mrow><mo>+</mo><mn>0.3</mn></mrow></msubsup></mrow></semantics></math></inline-formula> keV, which is consistent with the XMM-Newton results (∼2.3 keV). Above 1.6 keV, the spectrum is dominated by the X-ray background. In summary, this study validates LEIA’s extended source imaging and spectral resolution capabilities for the first time.

Philipp Berghofer

There is noticeable consensus among physicists and philosophers that only gauge-invariant quantities can be physically real. However, this insight that physical quantities must be gauge-invariant is not well-reflected in standard approaches to particle physics. For instance, each and every elementary field/particle of the Standard Model fails to be gauge-invariant! The main objective of this paper is to offer an accessible, concise, and convincing analysis of why philosophers and physicists should devote more of their energy to working on gauge-invariant approaches. Correspondingly, the thesis of this paper is that pursuing gauge-invariant approaches has several virtues. For instance, gauge-invariant reformulations allow us to make particle physics consistent with the mathematical framework in which it is formulated. This is illustrated by how mathematical theorems such as Elitzur's theorem, the Gribov ambiguity, and Haag's theorem pose problems for standard approaches but are avoided by gauge-invariant approaches.

Patrick Müller, Wilfried Nörtershäuser

The analysis of experimental results with Python often requires writing many code scripts which all need access to the same set of functions. In a common field of research, this set will be nearly the same for many users. The qspec Python package was developed to provide functions for physical formulas, simulations and data analysis routines widely used in laser spectroscopy and related fields. Most functions are compatible with numpy arrays, enabling fast calculations with large samples of data. A multidimensional linear regression algorithm enables a King plot analyses over multiple atomic transitions. A modular framework for constructing lineshape models can be used to fit large sets of spectroscopy data. A simulation module within the package provides user-friendly methods to simulate the coherent time-evolution of atoms in electro-magnetic fields without the need to explicitly derive a Hamiltonian.

R. Loll, G. Fabiano, D. Frattulillo et al.

Quantum gravity is the missing piece in our understanding of the fundamental interactions today. Given recent observational breakthroughs in gravity, providing a quantum theory for what lies beyond general relativity is more urgent than ever. However, the complex history of quantum gravity and the multitude of available approaches can make it difficult to get a grasp of the topic and its main challenges and opportunities. We provide a guided tour of quantum gravity in the form of 30 questions, aimed at a mixed audience of learners and practitioners. The issues covered range from basic motivational and background material to a critical assessment of the status quo and future of the subject. The emphasis is on structural issues and our current understanding of quantum gravity as a quantum field theory of dynamical geometry beyond perturbation theory. We highlight the identification of quantum observables and the development of effective numerical tools as critical to future progress. Corfu Summer Institute 2021 "School and Workshops on Elementary Particle Physics and Gravity" 29 August 9 October 2021 Corfu, Greece

Sergey L. Cherkas, Vladimir L. Kalashnikov

Grassmann variables are used to formally transform a system with constraints into an unconstrained system. As a result, the Schrödinger equation arises instead of the Wheeler–DeWitt one. The Schrödinger equation describes a system’s evolution, but a definition of the scalar product is needed to calculate the mean values of the operators. We suggest an explicit formula for the scalar product related to the Klein–Gordon scalar product. The calculation of the mean values is compared with an etalon method in which a redundant degree of freedom is excluded. Nevertheless, we note that a complete correspondence with the etalon picture is not found. Apparently, the picture with Grassmann variables requires a further understanding of the underlying Hilbert space.

Kyungil Kim, Sangyong Jeon, Chang-Hwan Lee et al.

We study the effects of a bubble configuration in a nucleus on heavy-ion collisions at a few tens and hundreds A MeV. We first investigate the bubble structure of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>206</mn></msup></semantics></math></inline-formula>Hg using the relativistic continuum Hartree–Bogoliubov theory and then study the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>206</mn></msup></semantics></math></inline-formula>Hg + <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>208</mn></msup></semantics></math></inline-formula>Pb and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>206</mn></msup></semantics></math></inline-formula>Hg+<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>206</mn></msup></semantics></math></inline-formula>Hg reactions using the DaeJeon–Boltzmann–Uehling–Uhlenbeck (DJBUU) transport model. To see the role of the bubble structure, we consider the maximum density of the produced nuclear matter, directed flow of neutrons and protons, and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>π</mi><mo>−</mo></msup><mo>/</mo><msup><mi>π</mi><mo>+</mo></msup></mrow></semantics></math></inline-formula> ratio. We observe that the maximum density is smaller with a bubble nucleus, and the directed flow of nucleons and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>π</mi><mo>−</mo></msup><mo>/</mo><msup><mi>π</mi><mo>+</mo></msup></mrow></semantics></math></inline-formula> ratio may depend on the bubble structure.

Rakesh Ranjan Sahoo, Kamal Lochan Mahanta, Saibal Ray

We obtain exact solutions to the field equations for five-dimensional locally rotationally symmetric (LRS) Bianchi type-I spacetime in the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></semantics></math></inline-formula> theory of gravity, where specifically, the following three cases are considered: (i) <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo><mo>=</mo><mi>μ</mi><mo>(</mo><mi>R</mi><mo>+</mo><mi>T</mi><mo>)</mo></mrow></semantics></math></inline-formula>, (ii) <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow><mo>=</mo><mi>R</mi><mi>μ</mi><mo>+</mo><mi>R</mi><mi>T</mi><msup><mi>μ</mi><mn>2</mn></msup></mrow></semantics></math></inline-formula>, and (iii) <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow><mo>=</mo><mi>R</mi><mo>+</mo><mi>μ</mi><msup><mi>R</mi><mn>2</mn></msup><mo>+</mo><mi>μ</mi><mi>T</mi></mrow></semantics></math></inline-formula>, where <i>R</i> and <i>T</i>, respectively, are the Ricci scalar and trace of the energy–momentum tensor. It is found that the equation of state (EOS) parameter <i>w</i> is governed by the parameter <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>μ</mi></semantics></math></inline-formula> involved in the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>)</mo></mrow></semantics></math></inline-formula> expressions. We fine-tune the parameter <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>μ</mi></semantics></math></inline-formula> to obtain the effect of phantom energy in the model. However, we also restrict this parameter to obtain a stable model of the universe.

Kongjun Zhang, Longbiao Li, Zhibin Zhang et al.

In this paper, we present a sample of 21 repeating fast radio bursts (FRBs) detected by different radio instruments before September 2021. Using the Anderson–Darling test, we compared the distributions of extra-Galactic dispersion measure (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>D</mi><msub><mi>M</mi><mi mathvariant="normal">E</mi></msub></mrow></semantics></math></inline-formula>) of non-repeating FRBs, repeating FRBs and all FRBs. It was found that the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>D</mi><msub><mi>M</mi><mi mathvariant="normal">E</mi></msub></mrow></semantics></math></inline-formula> values of three sub-samples are log-normally distributed. The <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>D</mi><msub><mi>M</mi><mi mathvariant="normal">E</mi></msub></mrow></semantics></math></inline-formula> of repeaters and non-repeaters were drawn from a different distribution on basis of the Mann–Whitney–Wilcoxon test. In addition, assuming that the non-repeating FRBs identified currently may be potentially repeators, i.e., the repeating FRBs to be universal and representative, one can utilize the averaged fluence of repeating FRBs as an indication from which to derive an apparent intensity distribution function (IDF) with a power-law index of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>a</mi><mn>1</mn></msub><mo>=</mo></mrow></semantics></math></inline-formula><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.10</mn><mo>±</mo><mn>0.14</mn></mrow></semantics></math></inline-formula> (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>a</mi><mn>2</mn></msub><mo>=</mo></mrow></semantics></math></inline-formula><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.01</mn><mo>±</mo><mn>0.16</mn></mrow></semantics></math></inline-formula>, the observed fluence as a statistical variant), which is in good agreement with the previous IDF of 16 non-repeating FRBs found by Li et al. Based on the above statistics of repeating and non-repeating FRBs, we propose that both types of FRBs may have different cosmological origins, spatial distributions and circum-burst environments. Interestingly, the differential luminosity distributions of repeating and non-repeating FRBs can also be well described by a broken power-law function with the same power-law index of −1.4.

Philip Semrén

We investigate electromagnetic, gravitational, and plasma-related perturbations to the first order on homogeneous and hypersurface orthogonal locally rotationally symmetric (LRS) class II spacetimes. Due to the anisotropic nature of the studied backgrounds, we are able to include a non-zero magnetic field to the zeroth order. As a result of this inclusion, we find interesting interactions between the electromagnetic and gravitational variables already of the first order in the perturbations. The equations governing these perturbations are found by using the Ricci identities, the Bianchi identities, Einstein’s field equations, Maxwell’s equations, particle conservation, and a form of energy-momentum conservation for the plasma components. Using a <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1</mn><mo>+</mo><mn>1</mn><mo>+</mo><mn>2</mn></mrow></semantics></math></inline-formula> covariant split of spacetime, the studied quantities and equations are decomposed with respect to the preferred directions on the background spacetimes. After linearizing the decomposed equations around an LRS background, performing a harmonic decomposition, and imposing the cold magnetohydrodynamic (MHD) limit with a finite electrical resistivity, the system is then reduced to a set of ordinary differential equations in time and some constraints. On solving for some of the harmonic coefficients in terms of the others, the system is found to decouple into two closed and independent subsectors. Through numerical calculations, we then observe some mechanisms for generating magnetic field perturbations, showing some traits similar to previous works using Friedmann–Lemaître–Robertson–Walker (FLRW) backgrounds. Furthermore, beat-like patterns are observed in the short wave length limit due to interference between gravitational waves and plasmonic modes.

David d'Enterria, Marco Drewes, Andrea Giammanco et al.

Opportunities for searches for phenomena beyond the Standard Model (BSM) using heavy-ions beams at high energies are outlined. Different BSM searches proposed in the last years in collisions of heavy ions, mostly at the Large Hadron Collider, are summarized. A few concrete selected cases are reviewed including searches for axion-like particles, anomalous $τ$ electromagnetic moments, magnetic monopoles, and dark photons. Expectations for the achievable sensitivities of these searches in the coming years are given. Studies of CP violation in hot and dense QCD matter and connections to ultrahigh-energy cosmic rays physics are also mentioned.

C. A. J. O'Hare, D. Loomba, K. Altenmüller et al.

Recoil imaging entails the detection of spatially resolved ionization tracks generated by particle interactions. This is a highly sought-after capability in many classes of detector, with broad applications across particle and astroparticle physics. However, at low energies, where ionization signatures are small in size, recoil imaging only seems to be a practical goal for micro-pattern gas detectors. This white paper outlines the physics case for recoil imaging, and puts forward a decadal plan to advance towards the directional detection of low-energy recoils with sensitivity and resolution close to fundamental performance limits. The science case covered includes: the discovery of dark matter into the neutrino fog, directional detection of sub-MeV solar neutrinos, the precision study of coherent-elastic neutrino-nucleus scattering, the detection of solar axions, the measurement of the Migdal effect, X-ray polarimetry, and several other applied physics goals. We also outline the R&D programs necessary to test concepts that are crucial to advance detector performance towards their fundamental limit: single primary electron sensitivity with full 3D spatial resolution at the $\sim$100 micron-scale. These advancements include: the use of negative ion drift, electron counting with high-definition electronic readout, time projection chambers with optical readout, and the possibility for nuclear recoil tracking in high-density gases such as argon. We also discuss the readout and electronics systems needed to scale-up such detectors to the ton-scale and beyond.

Ievgen Dubovyk, Janusz Gluza, Gabor Somogyi

We discuss the Mellin-Barnes representation of complex multidimensional integrals. Experiments frontiered by the High-Luminosity Large Hadron Collider at CERN and future collider projects demand the development of computational methods to achieve the theoretical precision required by experimental setups. In this regard, performing higher-order calculations in perturbative quantum field theory is of paramount importance. The Mellin-Barnes integrals technique has been successfully applied to the analytic and numerical analysis of integrals connected with virtual and real higher-order perturbative corrections to particle scattering. Easy-to-follow examples with the supplemental online material introduce the reader to the construction and the analytic, approximate, and numeric solution of Mellin-Barnes integrals in Euclidean and Minkowskian kinematic regimes. It also includes an overview of the state-of-the-art software packages for manipulating and evaluating Mellin-Barnes integrals. These lecture notes are for advanced students and young researchers to master the theoretical background needed to perform perturbative quantum field theory calculations.

José Ignacio Illana, Alejandro Jiménez Cano

The Standard Model of the electroweak and strong interactions of particle physics is a quantum field theory. Elementary particles are not indivisible `pieces' of matter but energy bundles of fields, whose properties and interactions are a consequence of the principles of symmetry. These lecture notes provide a brief introduction to the construction of the Standard Model from its basic ingredients: Poincaré symmetry, gauge invariance and spontaneous symmetry breaking. The full Lagrangian is derived in detail and the most relevant aspects of the electroweak phenomenology are discussed with special emphasis on the determination of the input parameters and the consistency checks of the model. Some exercises are proposed to fix the main ideas.

Harald Rose

A novel theory of the structure of elementary particles is outlined. The proposed relativistic covariant space-time approach supposes that all massive particles are composite particles formed by massless elementary particles with opposite four-dimensional (4D) helicity. The attraction between two basic particles originates from their mutual 4D density, which depends only on their 4D distance. The approach enables a consistent description of the internal structure of massive elementary particles including the origin of their spin, their mass, and the sign of their charge. The 4D rotational Hamiltonian depends on the hyper-symmetric potential obtained by using the mutual density for the source term of the 4D Poisson equation. The rotational eigenfunctions depend on the 4D radius and on three angles, one of which is imaginary. This angle accounts for the rotation of the time-like axis with respect to the three-dimensional subspace representing a Lorentz transformation. We obtain the wave equation of the basic particles by supposing that they are propagating with the speed of light. Such subatomic massless particles are photons, basic-quarks, and neutrinos, which we assume to be massless if they are free. The results of the analytical calculations show that massive particles can only be stable if the potential is a 4D well trapping the constituents. As a result, we do not need the Higgs field for explaining the origin of the mass. In particular, we show that electrons and positrons are such two-component systems each consisting of two photons. The eigenvalue of the 4D rotational energy determines the mass of the composite particle. We prove the relevance of the novel theory by revisiting the hydrogen atom. The resulting energy eigenvalues depend on three quantum numbers having no degenerated energy states. In particular, it provides the Lamb shift.

L. Zuev, S. Barannikova, V. Danilov et al.

New representations concerning plasticity physics in crystals are discussed. The model of plastic flow is suggested, which can describe its main regularities. With the use of the experimental investigation, it is shown that the plastic flow localization plays the role in the evolution of plastic deformation. Obtained data are explained with the application of the principles of nonequilibrium-systems’ theory. The quasi-particle is introduced for the description of plasticity phenomenon. It is established the relation between plasticity characteristics of metals and their position in Periodic table of the elements. A new model is elaborated to address localized plastic-flow evolution in solids. The basic assumption of the proposed model is that the elementary plasticity acts evolving in the deforming of medium would generate acoustic emission pulses, which interact with the plasticity carriers and initiate new elementary shears. As found experimentally, the macrolocalization of plastic flow involves a variety of autowave processes. To address the phenomenon of localized plastic-flow autowaves, a new quasi-particle called ‘autolocalizon’ is introduced; the criterion of validity of the concept is assessed.

P. Bari

The understanding of the physical processes that lead to the origin of matter in the early Universe, creating both an excess of matter over anti-matter and a dark matter abundance that survived until the present, is one of the most fascinating challenges in modern science. The problem cannot be addressed within our current description of fundamental physics and, therefore, it currently provides a very strong evidence of new physics. Solutions can either reside in a modification of the standard model of elementary particle physics or in a modification of the way we describe gravity, based on general relativity, or at the interface of both. We will mainly discuss the first class of solutions. Traditionally, models that separately explain either the matter-antimatter asymmetry of the Universe or dark matter have been proposed. However, in the last years there has also been an accreted interest and intense activity on scenarios able to provide a unified picture of the origin of matter in the early universe. In this review we discuss some of the main ideas emphasising primarily those models that have more chances to be experimentally tested during next years. Moreover, after a general discussion, we will focus on extensions of the standard model that can also address neutrino masses and mixing. Since this is currently the only evidence of physics beyond the standard model coming directly from particle physics experiments, it is then reasonable that such extensions might also provide a solution to the problem of the origin of matter in the universe. ar X iv :2 10 7. 13 75 0v 2 [ he pph ] 2 7 Se p 20 21

Anirudh Gundhi, C. Steinwachs

We propose an extension of the scalaron-Higgs model by a non-minimal coupling of the Standard Model Higgs boson to the quadratic Ricci scalar resulting in a Higgs-dependent scalaron mass. The model predicts a successful stage of effective single-field Starobinsky inflation. It features a multi-field amplification mechanism leading to a peak in the inflationary power spectrum at small wavelengths which enhances the production of primordial black holes. The extended scalaron-Higgs model unifies inflationary cosmology with elementary particle physics and explains the origin of cold dark matter in terms of primordial black holes without assuming any new particles.