Search for Dark Photons with Superconducting Radio Frequency Cavities
Not Available
43 PARTICLE ACCELERATORS↗
SEARCH · Engineering Papers
Results for “Extensions of gauge sector”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Search for Dark Photons in Rare $Z$ Boson Decays with the ATLAS Detector
A search for events with a dark photon produced in association with a dark Higgs boson via rare decays of the standard model Z boson is presented, using 139 fb –1 of $\sqrt{s}$ = 13 TeV proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider. The dark boson decays into a pair of dark photons, and at least two of the three dark photons must each decay into a pair of electrons or muons, resulting in at least two same-flavor opposite-charge lepton pairs in the final state. The data are found to be consistent with the background prediction, and upper limits are set on the dark photon’s coupling to the dark Higgs boson times the kinetic mixing between the standard model photon and the dark photon, α D ϵ 2 , in the dark photon mass range of [5, 40] GeV except for the $Υ$ mass window [8.8, 11.1] GeV. This search explores new parameter space not previously excluded by other experiments.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for Millicharged Particles in Proton-Proton Collisions at $\sqrt{s}$ = 13.6 TeV
We report on a search for elementary particles with charges much smaller than the electron charge using a data sample of proton-proton collisions provided by the CERN Large Hadron Collider in 2023–24, corresponding to an integrated luminosity of 124.7 fb −1 at a center-of-mass energy of 13.6 TeV. The analysis presented uses the completed Run 3 milliQan bar detector to set the most stringent constraints to date for particles with charges ≤ 0.24 e and masses ≥ 0.45 GeV.
Extensions of gauge sector↗
Hidden Sectors from Multiple Line Bundles for the B−L$B-L$ MSSM
Abstract We give a formalism for constructing hidden sector bundles as extensions of sums of line bundles in heterotic M‐theory. Although this construction is generic, we present it within the context of the specific Schoen threefold that leads to the physically realistic MSSM model. We discuss the embedding of the line bundles, the existence of the extension bundle, and a number of necessary conditions for the resulting bundle to be slope‐stable and thus supersymmetric. An explicit example is presented, where two line bundles are embedded into the factor of the maximal subgroup of the hidden sector E 8 gauge group, and then enhanced to a non‐Abelian bundle by extension. For this example, there are in fact six inequivalent extension branches, significantly generalizing that space of solutions compared with hidden sectors constructed from a single line bundle.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Search for a Light Higgs Boson in Single-Photon Decays of ϒ ( 1 S ) Using ϒ ( 2 S ) → π + π − ϒ ( 1 S ) Tagging Method
Not Available
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Theory, phenomenology, and experimental avenues for dark showers: a Snowmass 2021 report
In this work, we consider the case of a strongly coupled dark/hidden sector, which extends the Standard Model (SM) by adding an additional non-Abelian gauge group. These extensions generally contain matter fields, much like the SM quarks, and gauge fields similar to the SM gluons. We focus on the exploration of such sectors where the dark particles are produced at the LHC through a portal and undergo rapid hadronization within the dark sector before decaying back, at least in part and potentially with sizeable lifetimes, to SM particles, giving a range of possibly spectacular signatures such as emerging or semi-visible jets. Other, non-QCD-like scenarios leading to soft unclustered energy patterns or glueballs are also discussed. After a review of the theory, existing benchmarks and constraints, this work addresses how to build consistent benchmarks from the underlying physical parameters and present new developments for the PYTHIA Hidden Valley module, along with jet substructure studies. Finally, a series of improved search strategies is presented in order to pave the way for a better exploration of the dark showers at the LHC.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Tree-level Unitarity in $$ \textrm{SU}{(2)}_L\times \textrm{U}{(1)}_Y\times \textrm{U}{(1)}_{Y^{\prime }} $$ Models
Abstract In models with a U(1) gauge extension beyond the Standard Model, one can derive sum rules for the couplings of the theory that are a consequence of tree-level unitarity. In this paper, we provide a comprehensive list of coupling sum rules for a general$$ \textrm{SU}{(2)}_L\times \textrm{U}{(1)}_Y\times \textrm{U}{(1)}_{Y^{\prime }} $$ SU 2 L × U 1 Y × U 1 Y ′ gauge theory coupled to an arbitrary set of fermion and scalar multiplets. These results are of particular interest for models of dark matter that employ an extended gauge sector mediated by a new (dark)Z ′ gauge boson. For the case of a minimal extension of the Standard Model with a$$ \textrm{U}{(1)}_{Y^{\prime }} $$ U 1 Y ′ gauge boson, we clarify the definitions of the weak mixing angle and the electroweakρparameter. We demonstrate the utility of a generalizedρparameter (denoted byρ ′ ) whose definition naturally follows from the unitarity sum rules developed in this paper.
Physics↗
A testable hidden-sector model for Dark Matter and neutrino masses
We consider a minimal extension of the Standard Model with a hidden sector charged under a dark local U(1)' gauge group, accounting simultaneously for light neutrino masses and the observed Dark Matter relic abundance. The model contains two copies of right-handed neutrinos which give rise to light neutrino-masses via an extended seesaw mechanism. The presence of a stable Dark-Matter candidate and a massless state naturally arise by requiring the simplest anomaly-free particle content without introducing any extra symmetries. We investigate the phenomenology of the hidden sector considering the U(1)' breaking scale of the order of the electroweak scale. Confronting the thermal history of this hidden-sector model with existing and future constraints from collider, direct and indirect detection experiments provides various possibilities of probing the model in complementary ways as every particle of the dark sector plays a specific cosmological role. Across the identified viable parameter space, a large region predicts a sizable contribution to the effective relativistic degrees-of-freedom in the early Universe that allows to alleviate the recently reported tension between late and early measurements of the Hubble constant.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Dark radiation constraints on portal interactions with hidden sectors
Here, we update dark radiation constraints on millicharged particle (MCP) and gauged baryon-number-minus-lepton-number (B-L) extensions of the Standard Model (SM). In these models, a massive SM gauge singlet mediator couples the SM plasma to additional SM-singlet light degrees of freedom. In the early Universe, these new light particles are populated via the interaction of the SM with the MCP, or the new B-L gauge boson, and act as dark radiation. The presence of dark radiation in the early Universe is tightly constrained by current and upcoming cosmic microwave background (CMB) measurements. We update bounds on MCPs from current measurements of N eff and show that future CMB experiments will be able to rule out or discover the extended MCP model invoked to explain the EDGES anomaly. Our analysis of the gauged B-L model goes beyond previous studies by including quantum-statistical and out-of-equilibrium effects. Further, we account for the finite lifetime of the B-L gauge boson, which boosts the subsequent right-handed neutrino energy density. We also develop a number of approximations and techniques for simplifying and solving the relevant Boltzmann equations. We use our approximations to develop a lower bound on the radiation density in a generic hidden sector with a light relic that is insensitive to the details of the hidden sector, provided the mediator interacts more strongly with the hidden sector than with the SM.
cosmological neutrinos↗
Sparticle spectroscopy and dark matter in a U(1) B-L extension of MSSM
We consider a class of SUSY models in which the MSSM gauge group is supplemented with a gauged U(1) B-L symmetry and a global U(1) R symmetry. This extension introduces only electrically neutral states, and the new SUSY partners effectively double the number of states in the neutralino sector that now includes a blino (from B - L) and singlino from a gauge singlet superfield. If the DM density is saturated by a LSP neutralino, the model yields quite a rich phenomenology depending on the DM composition. The LSP relic density constraint provides a lower bound on the stop and gluino masses of about 3 TeV and 4 TeV respectively, which is testable in the near future collider experiments such as HL-LHC.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
$\mathrm{FIMP}$ dark matter in heterotic $\mathrm{M}$-theory
Within the context of N = 1 supersymmetric heterotic M-theory, we present a “freeze-in” mechanism for producing dark matter via a “moduli portal” between the observable and hidden sectors. It is assumed that the observable sector consists of the MSSM or some physically acceptable extension of it, while the hidden sector is chosen to satisfy all physical and mathematical constraints. Dark matter production processes are examined for two fundamental types of hidden sectors; those whose gauge bundle structure group contains an anomalous U(1) and those whose structure group is non-Abelian and anomaly free. The couplings of the dilaton and the “universal” modulus to all fields of the observable and hidden sectors are presented and analyzed. These interactions are then combined to produce a moduli portal from a thermal bath of observable sector particles to the hidden sector. These processes are then analyzed for both anomalous and non-anomalous cases. It is shown that only the uncharged hidden sector matter scalars can play the role of dark matter and that these are predominantly produced during the “reheating” epoch on the observable sector. Within the context of both an anomalous and non-anomalous hidden sector, we calculated the dark matter “relic density”. We show that in both cases, for a wide choice of moduli vacua, one can correctly predict the observed relic density. For the anomalous U(1) case, we choose a specific physically acceptable vacuum within the context of the B - L MSSM and show that one precisely obtains the measured dark matter relic abundance.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Large N-ightmare dark matter
A dark QCD sector is a relatively minimal extension of the Standard Model (SM) that admits Dark Matter (DM) candidates, but requires no portal to the visible sector beyond gravitational interactions: a "nightmare scenario" for DM detection. Here, we consider a secluded dark sector containing a single flavor of light, vector-like dark quark gauged under (N). In the large-N limit, this single-flavor theory becomes highly predictive, generating two DM candidates whose masses and dynamics are described by few parameters: a light quark-antiquark bound state, the dark analog of the η' meson, and a heavy bound state of N quarks, the dark analog of the Δ ++ baryon. We show that the latter may freeze-in with an abundance independent of the confinement scale, forming DM-like relics for N ≲ 10, while the former may generate DM via cannibalization and freeze-out. We study the interplay of this two-component DM system, and determine the characteristic ranges of the confinement scale, dark-visible sector temperature ratio, and N that admit non-excluded DM, once effects of self-interaction constraints and bounds on effective degrees of freedom at the BBN and CMB epochs are included.
79 ASTRONOMY AND ASTROPHYSICS↗
Discovering Elusive Dynamics Across Frontiers (Final Technical Report)
Profound puzzles, such as the nature of dark matter, the origins of the electroweak scale, the mechanism behind the small neutrino mass, and the strong CP problem, suggested new physics beyond the Standard Model and drove the particle physics program in search of the associated new particles. Despite extensive searches, conventional realizations of new physics have not yet provided conclusive evidence. This raised the serious possibility that new dynamics might be more elusive, perhaps due to a richer gauge and matter structure than previously considered. Notably, the existence of dark matter and advancements in understanding the naturalness problem urged exploration into sectors with complex gauge and matter structures. Through experiments like the LHC, DUNE, and small-scale experiments, the robust US HEP program played a critical role in pursuing these well-motivated but under-explored scenarios for new physics. I explored these physics opportunities in depth, focusing on novel searches and significant improvements in parameter space coverage. The elusive dynamics revealed rich information about the underlying theory and were essential in identifying observable opportunities. Understanding the observable consequences required a deep comprehension of the theory, which I also developed. The proposal included essential components aimed at coherently increasing our knowledge in well-motivated elusive dynamics models. Through research on high-quality axions, composite neutrinos, the Higgs boson as a portal to hidden strong dynamics, and new scalar potentials to generate alternative electroweak phase transitions, I focused on identifying new signatures and parameter regions in plausible elusive dynamics models. The exploration emphasized generic possibilities motivated by broad classes of elusive dynamics models. These signatures were not effectively probed previously due to various challenges such as triggering, background suppression, or experimental design. My research involved close interaction with experimental colleagues to overcome these difficulties, leveraging new theoretical and experimental possibilities. These efforts included identifying new observables such as timing information and substructure in calorimetries, new multiple-hit techniques, new scattering events, and new resonance searches in liquid argon detectors. This work created a positive feedback loop: theory and experimental work inspired each other, revealing new exciting opportunities that supported both programs.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Gauge hierarchy from electroweak vacuum metastability
Not Available
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Dark C P violation and gauged lepton or baryon number for electroweak baryogenesis
We explore the generation of the baryon asymmetry in an extension of the standard model where the lepton number is promoted to a U(1)ℓ gauge symmetry with an associated Z' gauge boson. This is based on a novel electroweak baryogenesis mechanism first proposed by us in Ref. Extra fermionic degrees of freedom, including a fermionic dark matter χ, are introduced in the dark sector for anomaly cancellation. The lepton number is spontaneously broken at high scale and the effective theory, containing the standard model, the Z', the fermionic dark matter, and an additional complex scalar field S, violates CP in the dark sector. The complex scalar field couples to the Higgs portal and is essential in enabling a strong first order phase transition. Dark CP violation is diffused in front of the bubble walls and creates a chiral asymmetry for χ, which in turn creates a chemical potential for the standard model leptons. Weak sphalerons are then in charge of transforming the net lepton charge asymmetry into net baryon number. We explore the model phenomenology related to the leptophilic Z', the dark matter candidate, the Higgs boson, and the additional scalar, as well as implications for electric dipole moments. We also discuss the case when baryon number U(1)B is promoted to a gauge symmetry, and discuss electroweak baryogenesis and its corresponding phenomenology.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
New physics in multi-lepton tau decays
Dark particles with lepton-flavor-violating couplings to the tau lepton can induce rare neutrinoless $τ$ decays with large final state multiplicities. We study models where transitions of the type $τ^\pm\to \ell^\pm\,ϕ$, with $ϕ$ a light new particle, initiate a chain of decays in the dark sector that terminate with decays into electrons, muons, or pions. These decay cascades appear as rare five or even seven-body $τ$ decays with multiple reconstructable resonances. We survey several representative models: kinetically mixed dark photon, gauged $L_i-L_j$ models, and other more exotic charge assignments such as chiral $U(1)'$ extensions of the Standard Model. The main new ingredient is the possibility of flavor violation at very high scales. In these models, a number of channels that have not yet been searched for experimentally, such as $τ\to 5μ$, $τ\to 3μ\,2e$, $τ\to μ\,4e$, and hadronic channels like $τ\to μ\,4π$, typically dominate over the previously-considered signatures such as $τ\to 3μ$. While some of the models, such as the gauged $L_i-L_j$ ones, also contain more challenging channels with missing energy due to decays to neutrinos, they can still be searched for via fully visible channels.
Ema, Yohei [Florida U.]↗
Breaking mirror twin color
We investigate simple extensions of the Mirror Twin Higgs model in which the twin color gauge symmetry and the discrete Z2 mirror symmetry are spontaneously broken. This is accomplished in a minimal way by introducing a single new colored triplet, sextet, or octet scalar field and its twin along with a suitable scalar potential. This spontaneous Z2 breaking allows for a phenomenologically viable alignment of the electroweak vacuum, and leads to dramatic differences between the visible and mirror sectors with regard to the residual gauge symmetries at low energies, color confinement scales, and particle spectra. In particular, several of our models feature a remnant SU(2) or SO(3) twin color gauge symmetry with a very low confinement scale in comparison to ΛQCD. Furthermore, couplings between the colored scalar and matter provide a new dynamical source of twin fermion masses, and due to the mirror symmetry, these lead to a variety of correlated visible sector effects that can be probed through precision measurements and collider searches.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Microstate geometries from gauged supergravity in three dimensions
The most detailed constructions of microstate geometries, and particularly of superstrata, are done using $\mathcal{N}$ = (1, 0) supergravity coupled to two anti-self-dual tensor multiplets in six dimensions. We show that an important sub-sector of this theory has a consistent truncation to a particular gauged supergravity in three dimensions. Our consistent truncation is closely related to those recently laid out by Samtleben and Sarioglu, which enables us to develop complete uplift formulae from the three-dimensional theory to six dimensions. We also find a new family of multi-mode superstrata, indexed by two arbitrary holomorphic functions of one complex variable, that live within our consistent truncation and use this family to provide extensive tests of our consistent truncation. We discuss some of the future applications of having an intrinsically three-dimensional formulation of a significant class of microstate geometries.
79 ASTRONOMY AND ASTROPHYSICS↗