Standard Model Research Articles

How many new particles do we need?

The Standard Model of particle physics (SM) and Einstein general relativity are extremely successful in describing almost all phenomena observed in Nature so far, spanning distances from a fraction of Fermi to thousands of megaparsec (Mpc). In this review article, the author deliberates on the question formulated in the title, given that the SM does not allow neutrino oscillations, does not have a candidate for dark matter in the Universe, and does not explain the observed cosmological dominance of matter over antimatter.

Euclid. I. Overview of the Euclid mission

The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. is a medium-class mission in the Cosmic Vision 2015--2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14\,000\,deg$^2$ of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance.

Study of angular observables in exclusive semileptonic Bc decays

In this work, we investigate angular observables such as the longitudinal polarization of charged leptons, τ-polarization, and forward-backward asymmetry in semileptonic Bc decays. Additionally, we provide predictions for lepton flavor violating observables, the R ratios in the decay channels Bc→ηc(J/ψ)lνl and Bc→D(D*)lνl across the entire q2 region. Our analysis is conducted within the relativistic independent quark model, focusing on the potential model-dependent aspects of these observables. We compare our model predictions with existing lattice predictions, highlighting the strong applicability of our framework in describing Bc decays. Considering the forthcoming experimental upgrades and the Run 3 data results on Bc meson decays, rapid confirmation of these quantities could indicate significant discoveries of physics beyond the Standard Model. This may open up new avenues for understanding the complex flavor dynamics in heavy meson decays. Published by the American Physical Society 2024

Error analysis model-driven workflow for self-calibration stitching testing of X-ray flat surfaces

Self-calibration stitching test is widely utilized for testing X-ray flat surfaces. Various factors, including environment disturbances, motion errors, misalignments, overlapping ratios, and sub-aperture sizes can affect the accuracy. Previous studies have shown that motion errors can introduce slope errors in the test surface, and higher overlapping ratios can increase the test error. However, these error analyses have not been comprehensive or quantitatively sufficient for practical applications. For X-ray flat surfaces with specific accuracy requirements, the necessary control levels for error sources and the optimal test parameters remain unclear. To this end, an error analysis model-driven workflow for self-calibration stitching testing of X-ray flat surfaces is proposed. This model allows for the systematic evaluation of how different error sources and test parameters affect test accuracy. Further, it can guide the determination of the control levels of error sources and test parameters, moving beyond the reliance on empirical experience as seen in previous studies. A flat X-ray mirror with clear aperture of 250 mm × 30 mm and 0.2 nm (50 nrad) RMS accuracy requirement was utilized to demonstrate the procedures of the workflow. Verification experiments demonstrated that this workflow can serve as a standard model for evaluating test accuracy and guiding test procedures to achieve the desired accuracy in self-calibration stitching of X-ray flat mirrors.

Relic density and temperature evolution of a light dark sector

We have developed a set of four fully coupled Boltzmann equations to precisely determine the relic density and temperature of dark matter by including three distinct sectors: dark matter, light scalar, and standard model sectors. The intricacies of heat transfer between dark matter (DM) and the standard model sector through a light scalar particle are explored, inspired by stringent experimental constraints on the scalar-Higgs mixing angle and the DM-scalar coupling. Three distinct sectors emerge prior to DM freeze-out, requiring fully coupled Boltzmann equations to accurately compute relic density. Investigation of forbidden, resonance, and secluded DM scenarios demonstrates significant deviations between established methods and the novel approach with fully coupled Boltzmann equations. Despite increased computational demands, this emphasizes the need for improved precision in relic density calculations, underlining the importance of incorporating these equations in comprehensive analyses. Published by the American Physical Society 2024

Freeze-in as a complementary process to freeze-out

There are many extensions of the Standard Model with a dark matter (DM) candidate obtained via the freeze-out mechanism. It can happen that after all experimental and theoretical constraints are taken into account, all parameter points have a relic density below the experimentally measured value. This means that the models solve only partially the DM problem, and at least one more candidate is needed. In this work we show that it is possible to further extend the model with a DM candidate obtained via the freeze-in mechanism to be in agreement with the relic density experimental measurement. Once the relic density problem is solved with this addition, new questions are raised. This new model with at least two DM candidates could have a freeze-out undetectable DM particle both in direct and indirect detection. This could happen if the freeze-out DM particle would have a very low density. Hence, a collider DM hint via excess in the missing energy with no correspondence in direct and indirect detection experiments, could signal the existence of a Feebly Interacting Massive Particle (FIMP). Conversely, if a DM particle is found and a particular model can explain all observables except the correct relic density, an extension with an extra FIMP would solve the problem. The freeze-in DM candidate, due to the small portal couplings, will not change the remaining phenomenology.

Searches for new physics below twice the electron mass with GERDA

A search for full energy depositions from bosonic keV-scale dark matter candidates of masses between 65 and 1021 keV has been performed with data collected during Phase II of the GERmanium Detector Array (Gerda) experiment. Our analysis includes direct dark matter absorption as well as dark Compton scattering. With a total exposure of 105.5 kg years, no evidence for a signal above the background has been observed. The resulting exclusion limits deduced with either Bayesian or Frequentist statistics are the most stringent direct constraints in the major part of the 140–1021 keV mass range. As an example, at a mass of 150 keV the dimensionless coupling of dark photons and axion-like particles to electrons has been constrained to α′/α<8.7×10-24\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha '/\\alpha <8.7~\ imes 10^{-24}$$\\end{document} and gae<3.3×10-12\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g_\ extrm{ae}<3.3~\ imes 10^{-12}$$\\end{document} at 90% credible interval (CI), respectively. Additionally, a search for peak-like signals from beyond the Standard Model decays of nucleons and electrons is performed. We find for the inclusive decay of a single neutron in 76\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{76}$$\\end{document}Ge a lower lifetime limit of τn>1.5×1024\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ au _\ extrm{n} > 1.5 \ imes 10^{24}$$\\end{document} years and for a proton τp>1.3×1024\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ au _\ extrm{p} > 1.3 \ imes 10^{24}$$\\end{document} years at 90% CI. For the electron decay e-→νeγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$e^\ ext {-} \\rightarrow \ u _\ extrm{e} \\gamma $$\\end{document} a lower limit of τe>5.4×1025\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ au _\ extrm{e} > 5.4\ imes 10^{25}$$\\end{document} years at 90% CI has been determined.

Apparent Parity Violation in the Observed Galaxy Trispectrum

Recent measurements of the four-point correlation function in large-scale galaxy surveys have found apparent evidence of parity violation in the distribution of galaxies. This cannot happen via dynamical gravitational effects in general relativity. If such a violation arose from physics in the early Universe it could indicate important new physics beyond the standard model, and would be at odds with most models of inflation. It is therefore now timely to consider the galaxy trispectrum in more detail. While the four-point correlation function, or equivalently the trispectrum, its Fourier counterpart, is parity invariant, the trispectrum must take redshift-space distortions into account. Although the standard Newtonian correction also respects parity invariance, we show that subleading relativistic corrections do not. We demonstrate that these can be significant at intermediate linear scales and are dominant over the Newtonian parity-invariant part around the equality scale and above. Therefore when the galaxy four-point correlation function, we should expect to detect parity violation on large scales. Published by the American Physical Society 2024

Structural Equation Models to Infer Relationships between Energy-related Blood Metabolites and Milk Daily Energy Output in Holstein Cows.

During lactation, high-yielding cows experience metabolic disturbances due to milk production. Metabolic monitoring offers valuable insights into how cows manage these challenges throughout the lactation period, making it a topic of considerable interest to breeders. In this study, we used Bayesian networks to uncover potential dependencies among various energy-related blood metabolites, i.e. glucose, urea, Beta-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), cholesterol (CHOL), and daily milk energy output (dMEO) in 1,254 Holstein cows. The inferred causal structure was then incorporated into structural equation models (SEM) to estimate heritabilities and additive genetic correlations among these phenotypes using both pedigree and genotypes from a 100k chip. Dependencies among traits were determined using the Hill Climbing algorithm, implemented with the posterior distribution of the residuals obtained from standard multiple trait model (MTM). These identified relationships were then used to construct the SEM, considering both direct and indirect relationships. The relevant dependencies and path coefficients obtained, expressed in units of measurement variation of 1σ, were as follows: dMEO → CHOL (0.181), dMEO → BHB (-0.149), dMEO → urea (0.038), glucose → BHB (-0.55), glucose → urea (-0.194), CHOL → urea (0.175), BHB → urea (-0.049), and NEFA → urea (-0.097). Heritabilities for traits of concern obtained with SEM ranged from 0.09 to 0.2. Genetic correlations with a minimum 95 % probability (P) of the posterior mean being > 0 for positive means or < 0 for negative means include those between dMEO and glucose (-0.583, P = 100), dMEO and BHB (0.349, P = 99), glucose and CHOL (0.325, P = 100), glucose and NEFA (-0.388, P = 100), and NEFA and BHB (0.759, P = 100). The results of this analysis revealed the existence of recursive relationships among the energy-related blood metabolites and dMEO. Understanding these connections is paramount for establishing effective genetic selection strategies, enhancing production and animal welfare.

Intelligent clean-in-place (CIP) system in beverage (healthy water) cleaner production

In food and beverage production, maintaining cleanliness is paramount, despite the emphasis placed on it, food safety incidents due to incomplete CIP still occur frequently. This study used the cleaner production of a beverage (healthy water) as a model. An intelligent CIP system employs advanced technologies such as automation, big data, and digital twin to standardize CIP-related data through modeling. Comprehensive management of the CIP process at all levels—from operators to supervisors and managers—is achieved through access control. The digital twin system ensures effective CIP execution by comparing real-time data from automated operations with standard model data. Full traceability and post-event review of CIP activities are realized through CIP order management, while big data analysis quickly identifies problem areas for continuous improvement. This approach ensures the entire CIP process is error-free, fully transparent, traceable, continuously optimized, and conducive to cleaner production.

Searching for exotic Higgs bosons from top quark decays at the HL-LHC

Exotic spin-0 states with unusual couplings with the gauge and matter fields of the Standard Model are worth exploring at the CERN LHC. Though our approach is largely model independent, we take inspiration from flavor models based on some discrete symmetries which predict a set of a scalar and a pseudoscalar having purely off-diagonal Yukawa interactions with quarks and leptons. In a previous paper, some of us explored how to decipher such exotic scalar and pseudoscalar states whose off-diagonal Yukawa couplings involve light quarks. In this work we follow a complementary path and focus on the Yukawa couplings that necessarily involve a top quark. If one such spin-0 state is lighter than the top quark, then the rare decay of the latter, on account of the high yield of the tt¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$t\\bar{t}$$\\end{document} events, could provide a potential hunting ground of those exotic states particularly during the high luminosity phase of the LHC run. We carry out an exhaustive collider analysis of some promising signatures of those exotic states using sophisticated Machine Learning techniques and obtain considerable signal significance.

Unconventional Monetary Policy Response to Covid-19 and Its Impact on Inflation in Morocco

This study explores the impact of unconventional monetary policy on Morocco’s economy during the Covid-19 pandemic. We used a hybrid model combining a financial dynamic stochastic general equilibrium (DSGE) model with a standard epidemiology model, enabling us to consider both economic and epidemiological factors. Our results indicate that unconventional monetary policy cannot fully mitigate the adverse effects of a pandemic, except for an exogenous increase in Central Bank claims. We also found that Morocco’s high inflation is partly due to Bank Al-Maghrib’s unconventional monetary measures in response to the pandemic. Our research underscores the importance of monetary authorities balancing the benefits and risks of unconventional monetary policy. While it can stimulate the economy during crises, it should be used judiciously to avoid long-term negative effects. Incorporating epidemiological factors into macroeconomic models is crucial for understanding the intricate interplay between the economy and public health crises.

An efficient physics-dimension-based reduction method for computing frequency response functions of viscoelastically damped systems

The frequency response functions (FRFs) are of critical interest to dynamic problems, however, they suffer from computational challenges for viscoelastically damped systems. In this paper, a physics-space-based reduction method is proposed for predicting the FRFs of large-scale viscoelastically damped systems involving the standard linear solid model. A physics-dimension subspace is constructed based on original system matrices and viscoelastic parameters, which can be easily generated by using a recursive manner. A projection basis generation algorithm is then developed to generate a standard orthonormal basis within the physics-dimension subspace. With the help of the standard orthonormal basis and the moment-matching-based reduction method, a physics-space-based reduction method is proposed for efficiently predicting the FRFs of large-scale viscoelastically damped systems. Unlike the widely used state-space reduction method, the reduced system of the proposed method can preserve system’s physical structure so that the physical meaning can be captured. Using both theoretical and numerical analyses, the proposed physics-space-based method is more accurate and efficient than the state-space-based reduction method.

One-point statistics in various cosmic environments in the presence of massive neutrinos

Abstract Studying the structures (halos and galaxies) within the cosmic environments (void, sheet, filament, and node) where they reside is an ongoing attempt in cosmological studies. The link between the properties of structures and the cosmic environments may help to unravel the nature of the dark sector of the Universe. In this paper, we study the cosmic web environments from the spatial pattern perspective in the context of ΛCDM and νΛCDM as an example of an extension to the vanilla model. To do this, we use the T-web classification method and classify the cosmic environments for the catalogues from the gevolution N-body simulations for ΛCDM and νΛCDM cosmology. Then, we compute the first nearest neighbour cumulative distribution function, spherical contact cumulative distribution function, and J-function for every cosmic environment. In the context of the standard model, the results indicate that these functions can differentiate the various cosmic environments. In association with distinguishing between extensions of the standard model of cosmologies, these functions within the cosmic environment seem beneficial as a complementary probe.

Dark matter phenomenology in 2HDMS in light of the 95 GeV excess

The Two Higgs Doublet model extended with a complex scalar singlet (2HDMS) is a well-motivated Beyond Standard Model candidate addressing several open problems of nature. In this work, we focus on the dark matter (DM) phenomenology of the complex scalar singlet where the real part of the complex scalar obtains a vacuum expectation value. The model is characterized by an enlarged Higgs spectrum comprising six physical Higgs bosons and a pseudoscalar DM candidate. We address the impact of accommodating the 95 GeV excess on the 2HDMS parameter space and DM observables after including all theoretical and experimental constraints. Finally, we look into the prospects of this scenario at HL-LHC and future lepton colliders for a representative benchmark.

Effects of degraded durability on the long-term stability of in-service slopes with reinforced concreted support structures

Engineering slope stability issues typically exhibit the impact of deteriorating durability on the susceptibility of slopes to failure. A thorough investigation was essential to explore theoretical and experimental aspects of slope durability degradation and its implications on long-term stability. Hence, a durability model was developed to accommodate slope stabilization using reinforced concrete (RC) support structures. This model was grounded in classical durability principles for RC structures. Subsequently, a model test was conducted to compare the responses of a standard slope model with a weakened counterpart subjected to environmental impacts. According to the proposed methodology for slope durability and stability, a case study involving future durability and stability predictions was performed. It was found that the theoretical solutions for the carbonation or neutralization (CN) velocity, depth, and penetration time agreed well with model test results. The slope surface displacements of the weakened slope with deteriorating coefficients between 0.6 and 0.9 were 4 to 8 times those of the standard slope, demonstrating significant degradation in stability. The case study indicated a steady reduction in the safety factor, at a rate of 2.3 to 2.4‰ per year throughout the slope’s service life. Finite-element-based predictions also suggested the potential for corrosion of slope anchor bolts within 20 years and breakage within 30 years, at an average rate of 7.5‰ per year in the ultimate bearing capacity. These findings highlight the need for timely maintenance and reinforcement interventions to ensure the long-term durability of operational slopes.

Amplitude factorization in the electroweak standard model

Amplitude factorization in the electroweak standard model

Re-assessing special aspects of Dirac fermions in presence of Lorentz-symmetry violation

This paper focuses on additional inspections concerning the fermionic sector of the Standard Model Extension (SME). In this context, our main effort in this contribution is to investigate effects of Lorentz-symmetry violation (LSV) on the Klein Paradox, the Zitterbewegung and its phenomenology in connection to Condensed Matter Physics, Atomic Physics, and Astrophysics. Finally, we discuss a particular realization of LSV in the Dirac equation, considering an asymmetry between space and time due to a scale factor present in the linear momentum of the fermion, but which does not touch its time derivative. We go further and extend the implications of this asymmetry in the situation the scale factor becomes space–time dependent to compute its influence on the kinematics of the Compton effect with the extended dispersion relation for the fermion that scatters the photon.

Private ownership in monopolistic competition models

Motivated by empirical evidence, I study the properties of a monopolistic competition model with private ownership. Toward that goal, I consider a monopolistic competition model with additive preferences, homogeneous workers and homogeneous firms. I then introduce in such a standard framework a single additional ingredient: private ownership. Private ownership means that each firm is owned and managed by a single household called the entrepreneur, and this entrepreneur receives profits as sole revenues. In turn, private ownership changes the nature of entry. Free entry in the industry is no longer satisfied. Rather, the number of firms is now determined through occupational choice. Armed with this new framework, I provide a full characterization of a market equilibrium, and compare it to the standard model with collective ownership and free entry. Notably, I find new results concerning optimality, the transmission of aggregate shocks and the ability of the new model to replicate well-established empirical facts.

Dark branes for dark matter

We propose a setup for the origin of dark matter based on spacetime with a warped extra dimension and three branes: the Planck brane, the TeV brane, at a (few) TeV scale ρT, and a dark brane, at a (sub-)GeV scale ρ1≲100 GeV≪ρT. The Standard Model (SM) is localized in the TeV brane, thus solving the Higgs hierarchy problem, while the dark matter χ, a Dirac fermion with mass mχ&lt;ρ1, is localized in the dark brane. The radion, with mass mr&lt;mχ, interacts strongly [∼mχ/ρ1∼O(1)] with dark matter and very weakly (∼mfρ1/ρT2≪1) with the Standard Model matter f. The generic conflict between the bounds on its detection signatures and its proper relic abundance is avoided as dark matter annihilation is p-wave suppressed. The former is determined by its very weak interactions with the SM and the latter by its much stronger annihilation into radions. Therefore, there is a vast range in the dark matter’s parameter space where the correct relic abundance is achieved consistently with the existing bounds. Moreover, for the dark brane with ρ1≲3 GeV, a confinement/deconfinement first order phase transition, where the radion condensates, produces a stochastic gravitational wave background at the nanohertz frequencies, which can be identified with the signal detected by the Pulsar Timing Array (PTA) experiments. In the PTA window, for 0.15≲mχ≲2 GeV the relic abundance is reproduced and all constraints are satisfied. Published by the American Physical Society 2024