Partial compositeness: From anarchy to symmetry

Physical review. D/Physical review. D. · 2025-09-24

Within the composite Higgs paradigm, partial compositeness has emerged as an elegant mechanism for generating large flavor hierarchies such as are observed in the quark and lepton masses and mixings. This mechanism exploits the strong renormalization group effects of the compositeness dynamics when these are flavor symmetric. Despite its remarkable properties, at this point it is stringently constrained by the body of flavor- and <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mi>C</a:mi> <a:mi>P</a:mi> </a:mrow> </a:math> -violation tests, so that the compositeness scale must be at least <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>O</c:mi> <c:mo stretchy="false">(</c:mo> <c:mn>100</c:mn> <c:mo stretchy="false">)</c:mo> <c:mtext> </c:mtext> <c:mtext> </c:mtext> <c:mi>TeV</c:mi> </c:math> , beyond the direct reach of proposed colliders. On the other hand, composite Higgs theories with flavor-symmetric strong dynamics, but with realistic flavor-violating hierarchies introduced in an manner, can extend the Glashow–Iliopoulos–Maiani mechanism of the standard model and thereby be far less constrained, at the edge of LHC reach and well within reach of future colliders. We show how the best features of both of these types of dynamics can be combined if flavor symmetries of the strong composite dynamics are emergent in the IR near the compositeness scale but absent in the far UV. In this case, flavor hierarchies can be generated by the renormalization group flow in the UV, followed by an IR stage in which the dynamics flows towards accidental flavor and <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mi>C</g:mi> <g:mi>P</g:mi> </g:math> symmetries. We point out how the collider and low-energy phenomenology is significantly impacted by the IR stage. Our analysis includes a discussion of the distinctive features of the small neutrino masses and their large mixings.

Conformal leptogenesis in composite Higgs models

Journal of High Energy Physics · 2025-02-20 · 3 citations

A bstract We study the generation of the baryon asymmetry in Composite Higgs models with partial compositeness of the Standard Model (SM) fermions and heavy right-handed neutrinos, developing for the first time a complete picture of leptogenesis in that setup. The asymmetry is induced by the out of equilibrium decays of the heavy right-handed neutrinos into a plasma of the nearly conformal field theory (CFT), i.e. the deconfined phase of the Composite Higgs dynamics. This exotic mechanism, which we call Conformal Leptogenesis , admits a reliable description in terms of a set of “Boltzmann equations” whose coefficients can be expressed in terms of correlation functions of the CFT. The asymmetry thus generated is subsequently affected by the supercooling resulting from the confining phase transition of the strong Higgs sector as well as by the washout induced by the resonances formed after the transition. Nevertheless, a qualitative description of the latter effects suggests that conformal leptogenesis can successfully reproduce the observed baryon asymmetry in a wide region of parameter space. A distinctive signature of our scenarios is a sizable compositeness for all the generations of SM neutrinos, which is currently consistent with all constraints but may be within reach of future colliders.

Light in the shadows: primordial black holes making dark matter shine

Journal of High Energy Physics · 2025-02-11 · 2 citations

A bstract We consider the possibility of indirect detection of dark sector processes by investigating a novel form of interaction between ambient dark matter (DM) and primordial black holes (PBHs). The basic scenario we envisage is that the ambient DM is “dormant”, i.e., it has interactions with the SM, but its potential for an associated SM signal is not realized for various reasons. We argue that the presence of PBHs with active Hawking radiation (independent of any DM considerations) can act as a catalyst in this regard by overcoming the aforementioned bottlenecks. The central point is that PBHs radiate all types of particles, whether in the standard model (SM) or beyond (BSM), which have a mass at or below their Hawking temperature. The emission of such radiation is “democratic” (up to the particle spin), since it is based on a coupling of sorts of gravitational origin. In particular, such shining of (possibly dark sector) particles onto ambient DM can then activate the latter into giving potentially observable SM signals. We illustrate this general mechanism with two specific models. First, we consider asymmetric DM, which is characterized by an absence of ambient anti-DM, and consequently the absence of DM indirect detection signals. In this case, PBHs can “resurrect” such a signal by radiating anti-DM, which then annihilates with ambient DM in order to give SM particles such as photons. In our second example, we consider the PBH emission of dark gauge bosons which can excite ambient DM into a heavier state (which is, again, not ambient otherwise), this heavier state later decays back into DM and photons. Finally, we demonstrate that we can obtain observable signals of these BSM models from asteroid-mass PBHs (Hawking radiating currently with ~ $$ \mathcal{O}\left(\textrm{MeV}\right) $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>O</mml:mi> <mml:mfenced> <mml:mi>MeV</mml:mi> </mml:mfenced> </mml:math> temperatures) at gamma-ray experiments such as AMEGO-X.

“Unification” of BSM searches and SM measurements: the case of lepton+ and mW

Journal of High Energy Physics · 2025-02-20 · 1 citations

A bstract We develop the idea that the unprecedented precision in Standard Model (SM) measurements, with further improvement at the HL-LHC, enables new searches for physics Beyond the Standard Model (BSM). As an illustration, we demonstrate that the measured kinematic distributions of the ℓ + "Image missing" final state not only determine the mass of the W boson, but are also sensitive to light new physics. Such a search for new physics thus requires a simultaneous fit to the BSM and SM parameters, “unifying” searches and measurements at the LHC and Tevatron. In this paper, we complete the program initiated in our earlier work [1]. In particular, we analyze ( i ) novel decay modes of the W boson with a neutrinophilic invisible scalar or with a heavy neutrino; ( ii ) modified production of W bosons, namely, associated with a hadrophilic invisible Z ′ gauge boson; and ( iii ) scenarios without an on-shell W boson, such as slepton-sneutrino production in the Minimal Supersymmetric Standard Model (MSSM). Here, we complement our previous MSSM analysis in [1] by considering a different kinematic region. Our results highlight that new physics can still be directly discovered at the LHC, including light new physics, via SM precision measurements. Furthermore, we illustrate that such BSM signals are subtle, yet potentially large enough to affect the precision measurements of SM parameters themselves, such as the W boson mass.

Searching for hadronic scale baryonic and dark forces at (g − 2)μ’s lattice-vs-dispersion front

Journal of High Energy Physics · 2025-08-20

A bstract The anomalous magnetic moment of the muon ( a μ ) provides a stringent test of the quantum nature of the Standard Model (SM) and its extensions. To probe beyond the SM physics, one needs to be able to subtract the SM contributions, which consists of a non-perturbative part, namely, the hadronic vacuum polarization (HVP) of the photon. The state of the art is to predominantly use two different methods to extract this HVP: lattice computation, and dispersion relation-based, data-driven method. Thus one can construct different forms of the “ a μ test” which compares the precise measurement of a μ to its theory prediction. Additionally, this opens the possibility for another subtle test, where these two “theory” predictions themselves are compared against each other, which is denoted as the “HVP-test”. This test is particularly sensitive to hadronic scale new physics. Therefore, in this work, we consider an SM extension consisting of a generic, light ~ (100 MeV – 1 GeV) vector boson and study its impact on both tests. We develop a comprehensive formalism for this purpose. We find that in the case of data-driven HVP being used in the a μ test, the new physics contributions effectively cancel for a flavor-universal vector boson. As an illustration of these general results, we consider two benchmark models: i) the dark photon ( A ′ ) and ii) a gauge boson coupled to baryon-number ( B ). Using a combination of these tests, we are able to constrain the parameter space of B and A ′ , complementarily to the existing limits. As a spin-off, our preliminary analysis of the spectrum of the invariant mass of 3 π in events with ISR at the B − factories (BaBar, Belle) manifests the value of such a study in searching for B → 3 π decay, thus motivating a dedicated search by experimental collaborations.

Partial Compositeness: from Anarchy to Symmetry

ArXiv.org · 2025-07-07

Within the Composite Higgs paradigm, Partial Compositeness has emerged as an elegant mechanism for generating large flavor hierarchies such as are observed in the quark and lepton masses and mixings. This mechanism exploits the strong renormalization group effects of the compositeness dynamics when these are {\it not} flavor-symmetric. Despite its remarkable properties, at this point it is stringently constrained by the body of flavor- and CP-violation tests, so that the compositeness scale must be at least $O(100)$ TeV, beyond the direct reach of proposed colliders. On the other hand, Composite Higgs theories with flavor-symmetric strong dynamics, but with realistic flavor-violating hierarchies introduced in an ad hoc manner, can extend the GIM mechanism of the standard model and thereby be far less constrained, at the edge of LHC reach and well within reach of future colliders. We show how the best features of both these types of dynamics can be combined if flavor-symmetries of the strong composite dynamics are emergent in the IR near the compositeness scale but absent in the far UV. In this case, flavor hierarchies can be generated by the renormalization group flow in the UV, followed by an IR stage in which the dynamics flows towards accidental flavor and CP symmetries. We point out how the collider and low-energy phenomenology is significantly impacted by the IR stage. Our analysis includes a discussion of the distinctive features of the small neutrino masses and their large mixings.

Searching for hadronic scale baryonic and dark forces at $(g-2)_\mu$'s lattice-vs-dispersion front

arXiv (Cornell University) · 2024-01-01

The anomalous magnetic moment of the muon ($\,a_{\mu}\,$) provides a stringent test of the quantum nature of the Standard Model (SM) and its extensions. To probe beyond the SM physics, one needs to be able to subtract the SM contributions, which consists of a non-perturbative part, namely, the hadronic vacuum polarization (HVP) of the photon. The state of the art is to predominantly use two different methods to extract this HVP: lattice computation, and dispersion relation-based, data-driven method. Thus one can construct different forms of the ``$a_{\mu}$ test' which compares the precise measurement of $a_{\mu}$ to its theory prediction. Additionally, this opens the possibility for another subtle test, where these two ``theory' predictions themselves are compared against each other, which is denoted as the ``HVP-test'. This test is particularly sensitive to hadronic scale new physics. Therefore, in this work, we consider a SM extension consisting of a generic, light $\sim(100~{\rm MeV}-1~{\rm GeV})$ vector boson and study its impact on both tests. We develop a comprehensive formalism for this purpose. We find that in the case of data-driven HVP being used in the $a_{\mu}$ test, the new physics contributions effectively cancels for a flavor-universal vector boson. As an illustration of these general results, we consider two benchmark models: i)~the dark photon ($\,A'\,$) and ii)~a gauge boson coupled to baryon-number ($\,B\,$). Using a combination of these tests, we are able to constrain the parameter space of $B$ and $A'$, complementarily to the existing limits. As a spin-off, our preliminary analysis of the spectrum of invariant mass of $3\pi$ in events with ISR at the $B-$ factories (BaBar, Belle) manifests the value of such a study in searching for $B\to 3\pi$ decay, thus motivating a dedicated search by experimental collaborations.

Review of Particle Physics

Physical review. D/Physical review. D. · 2024 · 2768 citations

• Particle physics
• Physics
• Nuclear physics

The summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,717 new measurements from 869 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Most of the 120 reviews are updated, including many that are heavily revised. The is divided into two volumes. Volume 1 includes the Summary Tables and 97 review articles. Volume 2 consists of the Particle Listings and contains also 23 reviews that address specific aspects of the data presented in the Listings. The complete (both volumes) is published online on the website of the Particle Data Group () and in a journal. Volume 1 is available in print as the . A with the Summary Tables and essential tables, figures, and equations from selected review articles is available in print, as a web version optimized for use on phones, and as an Android app. The 2024 edition of the Review of Particle Physics should be cited as: S. Navas et al. (Particle Data Group), Phys. Rev. D 110, 030001 (2024) © 2024 2024

Conformal Leptogenesis in Composite Higgs Models

arXiv (Cornell University) · 2024-10-01

We study the generation of the baryon asymmetry in Composite Higgs models with partial compositeness of the Standard Model (SM) fermions and heavy right-handed neutrinos, developing for the first time a complete picture of leptogenesis in that setup. The asymmetry is induced by the out of equilibrium decays of the heavy right-handed neutrinos into a plasma of the nearly conformal field theory (CFT), i.e. the deconfined phase of the Composite Higgs dynamics. This exotic mechanism, which we call Conformal Leptogenesis, admits a reliable description in terms of a set of ``Boltzmann equations'' whose coefficients can be expressed in terms of correlation functions of the CFT. The asymmetry thus generated is subsequently affected by the supercooling resulting from the confining phase transition of the strong Higgs sector as well as by the washout induced by the resonances formed after the transition. Nevertheless, a qualitative description of the latter effects suggests that conformal leptogenesis can successfully reproduce the observed baryon asymmetry in a wide region of parameter space. A distinctive signature of our scenarios is a sizable compositeness for all the generations of SM neutrinos, which is currently consistent with all constraints but may be within reach of future colliders.

A new purpose for the W-boson mass measurement: Searching for New Physics in lepton+MET

Physics Letters B · 2024-06-05 · 3 citations

We show that the mW measurement is a direct probe of New Physics (NP) contributing to ℓ+MET, independently from indirect tests via the electroweak fit. Such NP modifies the kinematic distributions used to extract mW, necessitating a simultaneous fit to mW and NP. This effect can in principle bias the mW measurement, but only to a limited extent for our considered models. Given that, we demonstrate that the agreement at high-precision with SM-predicted shapes results in bounds competitive to, if not exceeding, existing ones for two examples: anomalous W decay involving a Lμ−Lτ gauge boson and ν˜ll˜ production in the MSSM.