Physics Beyond the Standard Model

Last Updated May 28, 2026

Physics beyond the Standard Model examines one of the most important facts in contemporary fundamental physics: the Standard Model is extraordinarily successful, but it is not complete. It describes the known elementary particles and their strong, weak, and electromagnetic interactions with remarkable precision, yet it leaves some of the deepest features of reality unexplained. Gravity is not incorporated into the framework. Dark matter and dark energy are not explained by its known particle content. Neutrino masses require physics beyond the minimal Standard Model. The observed matter–antimatter asymmetry of the universe is also far larger than the Standard Model can account for on its own.

This matters because the search for new physics is not a speculative extension of an otherwise finished theory. It is driven by concrete empirical and theoretical gaps. The Standard Model works so well that any proposed extension must respect its successes, but it leaves open questions that are too large to ignore: why neutrinos have mass, what dark matter is, why matter dominates over antimatter, how gravity should be reconciled with quantum theory, whether dark energy is a cosmological constant or something dynamical, and whether the known gauge structure is part of a deeper symmetry. Physics beyond the Standard Model is therefore the organized search for the deeper structure required by the known theory’s incompleteness.

This article develops Physics Beyond the Standard Model as a foundational frontier topic within the Physics knowledge series. It explains why new physics is needed, what the main open problems are, how dark matter, neutrino mass, baryogenesis, unification, hidden sectors, and quantum gravity fit into the broader search, and how experiments at colliders, underground detectors, neutrino facilities, precision experiments, and cosmological surveys constrain possible answers. It also follows the mathematics-first and computation-aware structure used throughout the series while keeping the article body readable. Selected Python and R workflows appear here, while the full GitHub repository contains expanded research-grade computational workflows for parameter scans, relic-density simplified models, exclusion-region logic, cosmological inventory tables, structured metadata, and reproducible BSM modeling workflows.

Why Physics Beyond the Standard Model Matters

Physics beyond the Standard Model matters because the Standard Model is best understood as a stunningly accurate but incomplete framework. It explains a vast range of particle phenomena, but several major empirical facts point beyond it. Gravity does not fit comfortably into the theory. The known Standard Model particles do not explain dark matter. Dark energy is not explained by the Standard Model’s particle content. Neutrino oscillations require nonzero neutrino masses, which are absent from the minimal Standard Model. The observed matter–antimatter asymmetry of the universe requires more than the known sources of CP violation appear able to provide.

This is not merely a matter of theoretical elegance. These are concrete failures of completeness. If most of the matter in galaxies and clusters is dark, if ordinary matter accounts for only a small fraction of the universe’s total energy budget, if neutrinos have mass, and if gravity remains outside the quantum field-theoretic structure of the Standard Model, then the theory cannot be the final account of fundamental physics. The BSM program is therefore not optional. It is the continuation of fundamental physics under the pressure of unresolved evidence.

The significance of BSM physics is also methodological. It forces physicists to search in many directions at once: high-energy colliders, rare decays, precision measurements, neutrino experiments, underground dark-matter detectors, gravitational observations, cosmic surveys, and mathematical consistency. The frontier is not a single road. It is a network of constraints, possibilities, null results, anomalies, and theoretical structures.

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What the Standard Model Explains and What It Does Not

The Standard Model describes the known quarks, leptons, gauge bosons, and Higgs boson, together with the strong, weak, and electromagnetic interactions. It is a quantum field theory organized around gauge symmetry, spontaneous symmetry breaking, and a set of particles whose interactions have been tested with extraordinary precision. The discovery of the Higgs boson completed a major missing piece of the theory and confirmed a central mechanism for electroweak symmetry breaking.

Yet the theory’s success makes its limitations sharper. The Standard Model does not include gravity. It does not explain why the particle masses and mixing angles take the values they do. It does not naturally explain neutrino masses in its minimal form. It does not identify the particle nature of dark matter. It does not explain dark energy. It does not account for the observed baryon asymmetry of the universe. It does not answer whether the known gauge structure is fundamental or part of a larger symmetry.

These shortcomings are the core rationale for BSM physics. The known theory works extremely well, but it leaves behind some of the biggest questions. The challenge is not to discard the Standard Model, but to understand what deeper structure contains it as a limiting or effective theory.

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Dark Matter

Dark matter is one of the strongest motivations for new physics. Observations of galaxies, galaxy clusters, gravitational lensing, cosmic microwave background structure, and large-scale structure all indicate that there is more gravitating matter than can be explained by ordinary visible matter. NASA’s current public summaries describe the cosmic inventory as roughly 5 percent ordinary or visible matter, 27 percent dark matter, and 68 percent dark energy. The Standard Model contains no known particle that can serve as the dominant cold dark matter candidate in the usual cosmological sense.

This is why dark matter drives a wide range of BSM models: weakly interacting massive particles, axions, sterile neutrinos, hidden-sector particles, dark photons, asymmetric dark matter, ultralight fields, primordial black holes, and other candidates. The diversity of models reflects the fact that dark matter is gravitationally well motivated but microscopically unidentified. Its existence is strongly inferred, but its particle or field nature remains unknown.

The search for dark matter also shows how BSM physics extends far beyond colliders. Direct-detection experiments look for scattering events in low-background environments. Indirect-detection searches look for astrophysical products of dark-matter annihilation or decay. Collider experiments search for missing energy, displaced signatures, or mediator particles. Cosmological surveys constrain how dark matter clusters, streams, and affects structure formation. Dark matter is therefore both a particle-physics problem and a cosmological problem.

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Neutrino Mass and Mixing

Neutrino mass is another decisive sign of physics beyond the minimal Standard Model. Neutrino oscillation phenomena require that neutrino flavor states mix and that at least two neutrino mass eigenstates have nonzero mass. This is not a small conceptual detail. It means that the minimal version of the Standard Model must be extended.

Neutrino mass points toward new structure: right-handed neutrinos, Majorana masses, seesaw mechanisms, sterile neutrinos, or other extensions of the fermion sector. It also connects particle physics to cosmology, because neutrino masses affect structure formation, cosmic background evolution, and early-universe physics. Neutrino experiments therefore occupy a special place in BSM research: they are already beyond the minimal Standard Model, yet the full mechanism behind their masses remains unknown.

This is one of the clearest cases where experiment has forced theory to expand. The question is no longer whether neutrino physics points beyond the minimal Standard Model. The question is what kind of new physics it requires.

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Matter–Antimatter Asymmetry and CP Violation

The observable universe is overwhelmingly made of matter rather than equal parts matter and antimatter. This fact is one of the deepest unsolved problems in physics because the Standard Model does not appear to provide enough CP violation to generate the observed asymmetry. In broad terms, baryogenesis requires conditions that allow a matter excess to form in the early universe, including baryon-number violation, C and CP violation, and departure from thermal equilibrium. The known Standard Model ingredients do not seem sufficient.

This matters because baryogenesis is not a peripheral detail. It is a question about why ordinary material existence is possible at all. If the early universe had remained matter–antimatter symmetric in the relevant sense, much of the familiar universe would not exist as it does. BSM physics is therefore partly a search for the deeper mechanism that tipped the balance.

Possible answers include new CP-violating sectors, electroweak baryogenesis variants, leptogenesis linked to neutrino physics, heavy right-handed neutrinos, scalar-sector extensions, or more exotic frameworks. The matter–antimatter problem illustrates how particle physics, cosmology, and the history of the early universe are inseparable.

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Hidden Sectors and Weakly Interacting Particles

One of the most active BSM ideas today is that new physics may exist in hidden or weakly coupled sectors that interact only feebly with ordinary matter. Such sectors may contain particles that are difficult to produce, rare to decay, long-lived, or visible only through displaced vertices, missing energy, rare processes, or small deviations from Standard Model expectations.

This matters because new physics may have escaped detection not because it is absent, but because it is weakly coupled, long-lived, low mass, or hidden behind difficult experimental signatures. The frontier is not only at higher energy. It is also at lower coupling, longer lifetime, greater precision, and more elusive signal structure. Experiments such as FASER, SHiP, MoEDAL-MAPP, fixed-target facilities, rare-decay searches, and precision experiments reflect this broader strategy.

The hidden-sector idea changes the experimental imagination of BSM physics. It warns against assuming that new particles must appear as obvious heavy resonances. They may appear instead as rare decays, subtle branching-ratio shifts, displaced signatures, feeble interactions, or cosmological effects.

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Supersymmetry, Unification, and Naturalness

Supersymmetry and grand unification remain among the most influential BSM ideas, even though no decisive direct evidence for them has yet appeared. Supersymmetry proposes a relationship between bosons and fermions and historically offered possible solutions to the hierarchy problem, dark-matter candidates, and gauge-coupling unification. Grand unified theories attempt to embed the Standard Model gauge structure into a larger symmetry, suggesting that the strong, weak, and electromagnetic interactions may arise from a deeper common framework at high energy.

These ideas matter because they address several problems at once: gauge-coupling unification, hierarchy questions, dark-matter candidates, proton-decay implications, flavor structure, and broader structural simplicity. They also show how BSM physics is driven not only by empirical gaps but by theoretical pressure toward unification and naturalness.

At the same time, null results matter. The absence of simple, low-energy supersymmetric signatures has constrained many early expectations and shifted attention toward more selective, compressed, hidden, or less minimal models. BSM physics is therefore a field where theoretical beauty must repeatedly face experimental discipline.

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Axions, Dark Photons, and Other Light New Physics

Not all BSM physics lies at very high mass. Many current searches target light new particles such as axions, axion-like particles, dark photons, dark Higgs bosons, sterile neutrinos, and long-lived hidden-sector states. These scenarios are attractive because they can address dark matter, strong CP problems, hidden-sector mediation, or weakly coupled new physics while remaining difficult to detect in traditional high-energy searches.

This broadens the logic of BSM exploration. New physics may appear not through a dramatic heavy resonance but through tiny branching-ratio shifts, displaced decays, coherent low-background signals, oscillatory field effects, rare processes, or astrophysical and cosmological signatures. Flavor physics, precision experiments, fixed-target searches, haloscopes, helioscopes, low-threshold detectors, and low-background underground experiments therefore become central parts of the BSM program.

Light new physics also forces careful thinking about scale. A particle can be light and still profoundly important if its coupling, stability, or cosmological role is right. The search for BSM physics is therefore not simply a race toward higher mass; it is a search across mass, coupling, lifetime, symmetry, and cosmological consequence.

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Gravity, Quantum Gravity, and the Planck Frontier

Perhaps the deepest gap in the Standard Model is gravity. The Standard Model is a quantum field theory of three interactions: strong, weak, and electromagnetic. General relativity, the best theory of gravity, describes gravitation in terms of spacetime geometry rather than as a Standard Model gauge interaction. A truly fundamental account of nature should ultimately explain how quantum fields and gravitational spacetime fit together.

This matters because quantum gravity is not simply another particle to add to the known list. It may require rethinking spacetime, locality, black holes, information, singularities, and the meaning of geometry. String theory, loop-quantum approaches, emergent-gravity ideas, holography, asymptotic safety, causal-set approaches, extra-dimensional models, and black-hole-information research all belong to this broader frontier.

Direct experimental access to Planck-scale physics is extraordinarily difficult, but quantum gravity remains unavoidable as a conceptual gap. BSM physics operates on two levels: empirically pressured near-term extensions such as dark matter and neutrino mass, and more ambitious structural programs aiming at deeper unification of quantum theory and gravity.

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Cosmology as a BSM Laboratory

Modern cosmology is itself a laboratory for BSM physics. The universe’s composition, expansion history, structure formation, relic backgrounds, and early-universe asymmetries all constrain particle physics. Dark matter, dark energy, inflationary physics, neutrino masses, primordial gravitational waves, baryogenesis, and possible time variation in cosmic acceleration all connect cosmological measurement to fundamental theory.

Recent DESI results have strengthened hints that dark energy may evolve over time, though this has not reached the standard discovery threshold. If future data confirm dynamical dark energy, the implications would be significant: the simplest cosmological-constant picture would require revision, and cosmology would place new pressure on fundamental physics. Even without such confirmation, the fact that cosmic surveys can test these questions shows how strongly BSM physics has become linked to precision cosmology.

This matters because the universe constrains particle physics in ways laboratories alone cannot. Structure formation, relic abundances, cosmic microwave background patterns, baryon acoustic oscillations, lensing, expansion history, and early-universe thermodynamics all place pressure on candidate theories. BSM physics is therefore not only the province of colliders. It is embedded in the history and composition of the cosmos.

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How New Physics Is Searched For

New physics is searched for through a broad and increasingly diversified program. Collider experiments look for heavy resonances, missing energy, rare decays, long-lived particles, exotic signatures, and precision deviations. Flavor experiments search for rare processes that may be sensitive to virtual new physics. Neutrino facilities probe oscillations, mass ordering, CP violation, sterile-sector possibilities, and neutrino interactions. Dark-matter detectors search for scattering, absorption, or recoil signatures. Cosmological surveys test expansion history, structure growth, lensing, and relic effects. Precision measurements look for small deviations in magnetic moments, electric dipole moments, atomic transitions, and symmetry tests.

This matters because there is no single guaranteed route to discovery. The field advances through complementarity. A null result in one region may constrain a model but open attention to another region. A collider result may be interpreted alongside cosmological bounds. A rare-decay constraint may limit a hidden-sector portal. A neutrino measurement may reshape baryogenesis scenarios. BSM physics is therefore both experimental and inferential: it builds knowledge by narrowing parameter space, comparing hypotheses, and linking results across domains.

The field’s maturity is visible in its methodological pluralism. High energy, high intensity, high precision, low background, long exposure, and large survey volume all function as discovery strategies.

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Mathematical Lens

A mathematics-first treatment of BSM physics begins with the recognition that the Standard Model is itself a highly structured quantum field theory. Most extensions alter one or more key elements: field content, symmetry structure, coupling pattern, mass spectrum, vacuum structure, flavor structure, or spacetime framework.

A compact reminder of the Standard Model gauge structure is:

Grand unified models embed this group into a larger symmetry. Hidden-sector models may add new gauge factors or portal interactions. Neutrino-mass extensions often add new fermionic states or mass terms beyond the minimal structure. Dark-matter frameworks often add stable or long-lived fields with suppressed couplings to visible matter.

A common relic-density intuition for thermal dark matter is that abundance is inversely related, at rough scaling level, to annihilation efficiency:

where \(\Omega_{\chi} h^2\) is the dark-matter density contribution and \(\langle \sigma v \rangle\) is a thermally averaged annihilation quantity. This is not a full derivation, but it is one of the most useful compact relations in BSM phenomenology because it links particle interaction strength to cosmological abundance.

Portal models often express communication between a hidden sector and the Standard Model through simple interaction terms. A schematic Higgs-portal term can be written as:

where \(H\) is the Standard Model Higgs field, \(S\) is a new scalar field, and \(\lambda_{HS}\) controls the coupling strength between sectors. The point is not that this term solves BSM physics by itself, but that the frontier is mathematically organized through symmetry, scale, coupling, stability, and cosmological abundance.

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Variables, Units, and Interpretation

BSM physics is full of quantities whose meaning depends on both particle physics and cosmology. The table below summarizes several useful variables and conceptual roles.

The table illustrates why BSM physics is both theoretical and empirical. A candidate field, coupling, mass scale, or symmetry structure becomes scientifically meaningful only when it is connected to measurable consequences and constrained by evidence.

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Worked Example: Relic-Density-Style Scaling

A compact way to illustrate BSM logic is to consider a thermal dark-matter candidate \(\chi\). If its annihilation cross section is too small, too much dark matter remains after freeze-out. If annihilation is too strong, too little remains. At rough scaling level, one writes:

This relation is useful because it shows how cosmology constrains particle properties. Dark matter is not only a galactic-dynamics problem. It is also a relic-abundance problem. A viable BSM model must often satisfy laboratory constraints and cosmological constraints at the same time.

The example captures one of the central habits of BSM reasoning: microscopic particle properties and large-scale cosmic observables are deeply linked. A coupling constant, mediator mass, or annihilation rate can change the predicted cosmic abundance. Conversely, the observed cosmic abundance can constrain particle models long before a particle is directly detected.

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Computational Modeling

Computational modeling is central to BSM physics because the field is organized around parameter spaces, likelihoods, constraints, exclusion regions, sensitivity curves, relic-density estimates, and multi-experiment comparison. Even simple simplified models can clarify the logic of BSM reasoning: define a candidate, specify a coupling or interaction strength, compute an observable, compare with a constraint, and map viable regions.

The article body includes only selected Python and R workflows so the conceptual discussion remains readable. The accompanying GitHub repository expands these examples into a larger set of research-style scaffolds, including relic-density scaling, parameter scans, likelihood-style simplified models, cosmic inventory tables, dark-sector metadata, SQL schemas, Julia numerical examples, C++ parameter-scan utilities, Fortran table generation, Rust command-line tools, C examples, and reproducibility documentation.

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Python Workflow: Relic-Density-Style Scaling

The following Python workflow illustrates inverse relic-density-style scaling in a simplified way. It does not compute a full Boltzmann solution; instead, it makes visible the core intuition that larger annihilation efficiency generally corresponds to lower remaining abundance in simple thermal-relic reasoning.

"""
Relic-Density-Style Scaling

This workflow illustrates a simplified BSM intuition:

    Omega_chi h^2 ∝ 1 / <sigma v>

where:
    Omega_chi h^2 = schematic dark-matter abundance contribution
    <sigma v> = thermally averaged annihilation quantity

This is not a full relic-density calculation. It is a transparent
simplified model for showing how abundance can scale inversely with
annihilation efficiency.
"""

import numpy as np
import pandas as pd


def relic_density_scaling(
    sigma_v: np.ndarray,
    normalization: float = 1.0,
) -> np.ndarray:
    """
    Compute schematic inverse relic-density scaling.

    Parameters
    ----------
    sigma_v:
        Thermally averaged annihilation quantity in schematic units.
    normalization:
        Arbitrary normalization constant for illustrative scaling.

    Returns
    -------
    np.ndarray
        Schematic relic abundance values.
    """
    if np.any(sigma_v <= 0):
        raise ValueError("All sigma_v values must be positive.")

    return normalization / sigma_v


def main() -> None:
    """
    Generate a small table of annihilation strength and abundance.
    """
    sigma_v = np.logspace(-28, -24, 9)
    omega = relic_density_scaling(sigma_v, normalization=1e-26)

    table = pd.DataFrame(
        {
            "sigma_v_schematic": sigma_v,
            "omega_chi_h2_schematic": omega,
        }
    )

    print("Illustrative inverse relic-density-style scaling")
    print(table.to_string(index=False))


if __name__ == "__main__":
    main()

This workflow shows the computational structure behind a recurring BSM idea: particle-scale interaction strength and cosmological abundance are linked. More realistic workflows require Boltzmann equations, temperature dependence, coannihilation, thresholds, degrees of freedom, and observational constraints, but the simple scaling is useful for intuition.

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R Workflow: Cosmic Inventory and BSM Motivation

R is useful for summarizing cosmological fractions, comparing candidate model classes, and organizing uncertainty-rich parameter spaces. The following workflow represents the broad cosmic inventory that motivates BSM physics and computes the fraction of the universe not explained by ordinary visible matter.

# Cosmic Inventory and BSM Motivation
#
# This workflow summarizes a broad cosmological motivation for
# beyond-the-Standard-Model physics:
#
#   ordinary matter ≈ 5%
#   dark matter ≈ 27%
#   dark energy ≈ 68%
#
# The values are rounded public-summary values, useful for
# conceptual and educational comparison.

library(tibble)
library(dplyr)

cosmic_inventory <- tibble(
  component = c("Ordinary matter", "Dark matter", "Dark energy"),
  fraction_percent = c(5, 27, 68)
)

summary_table <- cosmic_inventory %>%
  summarise(
    ordinary_matter_percent =
      fraction_percent[component == "Ordinary matter"],
    nonordinary_component_percent =
      sum(fraction_percent[component != "Ordinary matter"]),
    dark_sector_percent =
      sum(fraction_percent[component %in% c("Dark matter", "Dark energy")])
  )

print(cosmic_inventory)
print(summary_table)

This workflow makes visible one of the simplest reasons BSM physics remains central. The known Standard Model matter content accounts for the ordinary matter sector, but the dominant cosmic components remain unexplained at the fundamental level.

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GitHub Repository

The article body includes only selected computational examples so the conceptual and theoretical argument remains readable. The full repository contains the expanded computational infrastructure: Python relic-density scaling, R cosmic-inventory summaries, Julia freeze-out simplified dynamics, C++ parameter-scan loops, Fortran scaling tables, SQL model and experiment metadata, Rust command-line utilities, C likelihood-style examples, documentation, and reproducible sample data.

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From BSM Searches to the Future of Fundamental Physics

Physics beyond the Standard Model is best understood as the organized search for the deeper structure required by known gaps in current theory. Dark matter, neutrino mass, baryogenesis, gravity, dark energy, hidden sectors, and unification all provide reasons to expect that the Standard Model is not final. The evidence comes from different directions: particle experiments, cosmology, astrophysics, precision measurements, and theoretical consistency.

This is why BSM physics belongs centrally within the Physics knowledge series. It is not only about speculative model-building. It is about the unfinished business of fundamental science. The Standard Model remains one of the greatest achievements in physics, but its incompleteness is now part of its meaning. Its success defines the boundary from which deeper physics must begin.

The future of fundamental physics may come from a collider anomaly, a neutrino result, a direct-detection signal, a precision deviation, a cosmological survey, a gravitational clue, or a theoretical synthesis that reframes the known structure. BSM physics is the disciplined refusal to mistake an extraordinarily successful effective theory for the end of inquiry.

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Related Articles

• Physics
• Quantum Fields, Particles, and the Standard Model
• Symmetry, Law, and the Search for Physical Order
• Cosmology and the History of the Universe
• Galaxies, Black Holes, and the Large-Scale Universe
• Nuclear Physics and the Energetics of the Atomic Nucleus
• Measurement, Mathematics, and the Structure of Physical Inquiry
• Physics and the Philosophy of Reality
• Data Systems & Analytics
• Systems Modeling

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Further Reading

• CERN (n.d.) The Standard Model. Available at: https://home.cern/science/physics/standard-model (Accessed: 24 April 2026).
• CERN (n.d.) Physics Beyond Colliders. Available at: https://home.cern/science/experiments/physics-beyond-colliders (Accessed: 24 April 2026).
• CERN (n.d.) FASER. Available at: https://home.cern/science/experiments/faser (Accessed: 24 April 2026).
• CERN (n.d.) CERN Neutrino Platform. Available at: https://home.cern/science/experiments/cern-neutrino-platform (Accessed: 24 April 2026).
• Particle Data Group (2025) Review of Particle Physics. Available at: https://pdg.lbl.gov/ (Accessed: 24 April 2026).
• Particle Data Group (2025) Grand Unified Theories. Available at: https://pdg.lbl.gov/2025/reviews/rpp2025-rev-guts.pdf (Accessed: 24 April 2026).
• NASA (2026) Dark Matter. Available at: https://science.nasa.gov/dark-matter/ (Accessed: 24 April 2026).
• NASA (2026) Dark Energy. Available at: https://science.nasa.gov/dark-energy/ (Accessed: 24 April 2026).
• NASA (2026) The Universe’s Building Blocks. Available at: https://science.nasa.gov/universe/overview/building-blocks/ (Accessed: 24 April 2026).
• Berkeley Lab / DESI (2025) New DESI Results Strengthen Hints That Dark Energy May Evolve. Available at: https://newscenter.lbl.gov/2025/03/19/new-desi-results-strengthen-hints-that-dark-energy-may-evolve/ (Accessed: 24 April 2026).

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References

• Berkeley Lab / DESI (2025) New DESI Results Strengthen Hints That Dark Energy May Evolve. Available at: https://newscenter.lbl.gov/2025/03/19/new-desi-results-strengthen-hints-that-dark-energy-may-evolve/ (Accessed: 24 April 2026).
• CERN (n.d.) The Standard Model. Available at: https://home.cern/science/physics/standard-model (Accessed: 24 April 2026).
• CERN (n.d.) Physics Beyond Colliders. Available at: https://home.cern/science/experiments/physics-beyond-colliders (Accessed: 24 April 2026).
• CERN (n.d.) FASER. Available at: https://home.cern/science/experiments/faser (Accessed: 24 April 2026).
• CERN (n.d.) CERN Neutrino Platform. Available at: https://home.cern/science/experiments/cern-neutrino-platform (Accessed: 24 April 2026).
• CERN (2025) A New Piece in the Matter–Antimatter Puzzle. Available at: https://home.cern/news/press-release/physics/new-piece-matter-antimatter-puzzle (Accessed: 24 April 2026).
• NASA (2026) Dark Matter. Available at: https://science.nasa.gov/dark-matter/ (Accessed: 24 April 2026).
• NASA (2026) Dark Energy. Available at: https://science.nasa.gov/dark-energy/ (Accessed: 24 April 2026).
• NASA (2026) The Universe’s Building Blocks. Available at: https://science.nasa.gov/universe/overview/building-blocks/ (Accessed: 24 April 2026).
• Particle Data Group (2025) Review of Particle Physics. Available at: https://pdg.lbl.gov/ (Accessed: 24 April 2026).
• Particle Data Group (2025) Grand Unified Theories. Available at: https://pdg.lbl.gov/2025/reviews/rpp2025-rev-guts.pdf (Accessed: 24 April 2026).
• Reuters (2025) Evidence Mounts That Universe’s Dark Energy Is Changing Over Time. Available at: https://www.reuters.com/science/evidence-mounts-that-universes-dark-energy-is-changing-over-time-2025-03-19/ (Accessed: 24 April 2026).