Dark Photon Model Research Articles

Revisiting dark photon constraints from CMB spectral distortions

Abstract Spectral distortions of the cosmic microwave background (CMB) provide stringent constraints on energy and entropy production in the post-BBN (Big Bang Nucleosynthesis) era. This has been used to constrain dark photon models with COBE/FIRAS and forecast the potential gains with future CMB spectrometers. Here, we revisit these constraints by carefully considering the photon to dark photon conversion process and evolution of the distortion signal. Previous works only included the effect of CMB energy density changes but neglected the change to the photon number density. We clearly define the dark photon distortion signal and show that in contrast to previous analytic estimates the distortion has an opposite sign and a ≃ 1.5 times larger amplitude. We furthermore extend the treatment into the large distortion regime to also cover the redshift range ≃ 2 × 106 − 4 × 107 between the μ-era and the end of BBN using CosmoTherm. This shows that the CMB distortion constraints for dark photon masses in the range 10−4 eV ≲ md ≲ 10−3 eV were significantly underestimated. We demonstrate that in the small distortion regime the distortion caused by photon to dark photon conversion is extremely close to a μ-type distortion independent of the conversion redshift. This opens the possibility to study dark photon models using CMB distortion anisotropies and the correlations with CMB temperature anisotropies as we highlight here.

Complex dark photon dark matter EFT

We construct an effective field theory for complex Stueckelberg dark photon dark matter. Such an effective construction can be realized by writing down a complete set of operators up to dimension six built with the complex dark photon and Standard Model fields. Classifying the effective operators, we find that in order to properly take into account the non-renormalizable nature of an interacting massive vector, the size of the Wilson coefficients should be naturally smaller than naively expected. This can be consistently taken into account by a proper power counting, that we suggest. First we apply this to collider bounds on light dark matter, then to direct detection searches by extending the list of non-relativistic operators to include the case of complex vectors. In the former we correctly find scaling limits for small masses, while in the latter we mostly focus on electric dipole interactions, that are the signatures of this type of dark matter. Simple UV completions that effectively realize the above scenarios are also outlined.

Cosmological implications of Kalb-Ramond-like particles

The Kalb-Ramond field is an antisymmetric, rank-two tensor field which most notably appears in the context of string theory, but has largely been unexplored in the context of cosmology. In this work, motivated by the Kalb-Ramond field in string theory, and antisymmetric tensor fields that emerge in effective field theories ranging from particle physics to condensed matter, we study the primordial production of interacting massive Kalb-Ramond-like-particles (KRLPs). KRLPs contain features of both dark photon and axion models, which can be appreciated via their duality properties. While the massless non-interacting KRLP is dual to a pseudoscalar, and the massive non-interacting KRLP is dual to a pseudovector, the interacting massive KRLP can be distinguished from its scalar and vector counterparts. We study early-universe production of KRLPs via the freeze-in mechanism, considering a ‘dark photon-like’ interaction, an ‘axion-like’ interaction, and a ‘Higgs portal’ interaction, as well as production via cosmological gravitational particle production. We find that as a dark matter candidate, KRLPs can be produced by all of the above mechanisms and account for the relic density of dark matter today for a wide range of masses. Finally, we comment on the potential to obtain both warm and cold dark matter subcomponents, and speculate on observational and experimental prospects.

Dark photon effects with the kinetic and mass mixing in Z -boson decay processes

Motivated by the most recent measurement of tau polarization in Z→τ+τ− by CMS, we have introduced a new U(1)X gauge boson field X, which can have renormalizable kinetic mixing with the standard model U(1)Y gauge boson field Y. In addition to the kinetic mixing of the dark photon, denoted as σ, there may also be mass mixing introduced by the additional Higgs doublet with a vacuum expectation value participating in U(1)X and electroweak symmetry breaking simultaneously. The interaction of the Z boson with the SM leptons is modified by the introduction of the mixing ratio parameter ε, which quantifies the magnitude of both the mass and kinetic mixing of the dark photon. Initially, we use the tau lepton as an example to explore the Z-boson phenomenology of the dark photon model with both kinetic and mass mixing. The goal is to determine the allowed parameter regions by taking into account constraints from the vector and axial-vector couplings gV,Aτ, the decay branching ratio Br(Z→τ−τ+) and tau-lepton polarization in Z→τ−τ+. We found that the mixing ratio plays important role in the Z-boson features by choosing different ε values. Furthermore, we aim to generalize our analysis from the tau-lepton case to include all fermions by conducting global fits. This allows us to identify viable regions by incorporating relevant fermion constraints and the W/Z mass ratio. Correspondingly, we obtain the fit results with the kinetic mixing parameter σ=0.074±0.021, mixing ratio ε=−1.37±0.46, and dark photon mass mX=275±39 GeV. Our global analysis indicates a preference for a dark photon mass larger than mZ. Published by the American Physical Society 2024

Classes of complete dark photon models constrained by Z-physics

Dark Matter models that employ a vector portal to a dark sector are usually treated as an effective theory that incorporates kinetic mixing of the photon with a new U(1) gauge boson, with the Z boson integrated out. However, a more complete theory must employ the full SU(2)×L U(1)×Y U(1)Y′ gauge group, in which kinetic mixing of the Z boson with the new U(1) gauge boson is taken into account. The importance of the more complete analysis is demonstrated by an example where the parameter space of the effective theory that yields the observed dark matter relic density is in conflict with a suitably defined electroweak ρ parameter that is deduced from a global fit to Z physics data.

Search for Light Dark Matter with the DarkMESA Experiment

The search for Dark Matter is an integral part of New Physics searches, however, Dark Matter has yet to be observed directly. Theoretical models provide a large parameter space for Dark Matter and allow for different properties of the particles. Models incorporating so-called portal interactions, where Dark Matter interacts with Standard Model particles through a mediator particle, are of special interest. Examples for these are Dark Photon and Axion models, which can be studied at low energy accelerator facilities. The DarkMESA experiment is a beam dump experiment located at the upcoming accelerator MESA at the JGU Mainz. The accelerator provides an electron beam of 155 MeV and 150 μA in extracted beam mode, which, along with the high-power beam dump of the P2 experiment, provides an ideal environment for Light Dark Matter searches. To accurately predict the expected reach and the impact of the detector design of the DarkMESA experiment on it with respect to different Dark Matter models, most notably Dark Photon and Axion mediated models, a Geant4 simulation is used. Here, the current status of the simulations is discussed.

Search for direct production of GeV-scale resonances decaying to a pair of muons in proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV

A search for direct production of low-mass dimuon resonances is performed using s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV proton-proton collision data collected by the CMS experiment during the 2017–2018 operation of the CERN LHC with an integrated luminosity of 96.6 fb−1. The search exploits a dedicated high-rate trigger stream that records events with two muons with transverse momenta as low as 3 GeV but does not include the full event information. The search is performed by looking for narrow peaks in the dimuon mass spectrum in the ranges of 1.1–2.6 GeV and 4.2–7.9 GeV. No significant excess of events above the expectation from the standard model background is observed. Model-independent limits on production rates of dimuon resonances within the experimental fiducial acceptance are set. Competitive or world’s best limits are set at 90% confidence level for a minimal dark photon model and for a scenario with two Higgs doublets and an extra complex scalar singlet (2HDM+S). Values of the squared kinetic mixing coefficient ε2 in the dark photon model above 10−6 are excluded over most of the mass range of the search. In the 2HDM+S, values of the mixing angle sin(θH) above 0.08 are excluded over most of the mass range of the search with a fixed ratio of the Higgs doublets vacuum expectation tan β = 0.5.

Dark matter-electron interactions in materials beyond the dark photon model

The search for sub-GeV dark matter (DM) particles via electronic transitions in underground detectors attracted much theoretical and experimental interest in the past few years. A still open question in this field is whether experimental results can in general be interpreted in a framework where the response of detector materials to an external DM probe is described by a single ionisation or crystal form factor, as expected for the so-called dark photon model. Here, ionisation and crystal form factors are examples of material response functions: interaction-specific integrals of the initial and final state electron wave functions. In this work, we address this question through a systematic classification of the material response functions induced by a wide range of models for spin-0, spin-1/2 and spin-1 DM. We find several examples for which an accurate description of the electronic transition rate at DM direct detection experiments requires material response functions that go beyond those expected for the dark photon model. This concretely illustrates the limitations of a framework that is entirely based on the standard ionisation and crystal form factors, and points towards the need for the general response-function-based formalism we pushed forward recently [1,2]. For the models that require non-standard atomic and crystal response functions, we use the response functions of [1,2] to calculate the DM-induced electronic transition rate in atomic and crystal detectors, and to present 90% confidence level exclusion limits on the strength of the DM-electron interaction from the null results reported by XENON10, XENON1T, EDELWEISS and SENSEI.

Extended calculation of electronic excitations for direct detection of dark matter

Direct detection experiments utilizing electronic excitations are spearheading the search for light, sub-GeV, dark matter (DM). It is thus crucial to have accurate predictions for any DM-electron interaction rate in this regime. EXCEED-DM (EXtended Calculation of Electronic Excitations for Direct detection of Dark Matter) computes DM-electron interaction rates with inputs from a variety of ab initio electronic structure calculations. The purpose of this manuscript is two-fold: to familiarize the user with the formalism and inputs of EXCEED-DM, and perform novel calculations to showcase what EXCEED-DM is capable of. We perform four calculations which extend previous results: the scattering rate in the dark photon model, screened with the numerically computed dielectric function, the scattering rate with an interaction potential dependent on the electron velocity, an extended absorption calculation for scalar, pseudoscalar, and vector DM, and the annual modulation of the scattering rate in the dark photon model.

Probing New Gauge Forces with a High-Energy Muon Beam Dump.

We propose a new beam-dump experiment at a future TeV-scale muon collider. A beam dump would be an economical and effective way to increase the discovery potential of the collider complex in a complementary regime. In this Letter, we consider vector models such as the dark photon and L_{μ}-L_{τ} gauge boson as new physics candidates and explore which novel regions of parameter space can be probed with a muon beam dump. We find that for the dark photon model, we gain sensitivity in the moderate mass (MeV-GeV) range at both higher and lower couplings compared to existing and proposed experiments, and gain access to previously untouched areas of parameter space of the L_{μ}-L_{τ} model.

Investigating the collinear splitting effects of boosted dark matter at neutrino detectors

We study the probing prospects of cosmic ray boosted dark matter (DM) in the framework of simplified electron-philic dark photon model. Focusing on the dark matter and dark photon masses around keV ~ MeV scale, we consider the bounds obtained from the XENON1T and Super-K experiments. The electron bound state effects are treated carefully in calculating the XENON1T constraint. As for the detection at neutrino detector where the energy threshold is relatively higher, the large logarithmic effects induced by the scale hierarchy between the masses and momentum transfer are considered by introducing the DM parton distribution function (PDF). The logarithmic effects will reduce the electron recoil rate for DM scattering in neutrino detectors. Moreover, we find the DUNE and JUNO experiments provide high sensitivities for probing the dark photon component in the DM PDF through the dark Compton process. We also check the Bullet Cluster constraint on the DM self-scattering cross section.

Particle dispersion in the classical vector dark matter background

Interactions with a background medium modify in general the dispersion relation and canonical normalization of propagating particles. This can have an important phenomenological consequence when considering light dark matter coupling to quarks and leptons. In this paper, we address this issue in the vector dark matter background with the randomly distributed polarizations or a fixed polarization to the single direction. The observations associated with particle dispersion can give constraints on new light Abelian gauge boson models. Considering the solar neutrino transition and the electron mass measurement, stringent bounds can be put on the gauged $L_\mu - L_\tau$ model and the dark photon model. Moreover, the classical vector field turns out to induce drastic changes in the particle normalization, which rule out a significant parameter region of the generic vector dark matter model.

Is the W-boson mass enhanced by the axion-like particle, dark photon, or chameleon dark energy?

The $W$-boson mass ($m_{W}=80.4335 \pm 0.0094 \mathrm{GeV}$) measured by the Collider Detector at Fermilab collaboration is greater than the standard model (SM) prediction at a confidence level of $7\sigma$, strongly suggesting the presence of new particles or fields. In the literature, various new particles and/or fields have been introduced to explain the astrophysical and experimental data, and their presence, in principle, may also enhance the $W$-boson mass. In this study, we investigate axion-like particle (ALP), dark photon (DP), and chameleon dark energy (DE) models for a solution to the $W$-boson mass excess. We find that the ALP and DP interpretations have been significantly narrowed down by global electroweak fits. The possibility of attributing the $W-$boson mass anomaly to the chameleon DE is ruled out by other experiments.

Unitarity constraints and collider searches for dark photons

Dark photons are predicted by various new physics models, and are being intensively studied in a variety of experiments. In the first part of this paper, we obtain partial wave unitarity constraints on the dark photon parameter space from the allowed $VV\rightarrow VV$ scattering processes in the limit of large center-of-mass energy, where $V=W,Z$. In the second part of the paper, searches are performed using the expected differential rates with a realistic detector simulation including a comprehensive set of background processes on dilepton and dilepton plus a photon events at the High Luminosity LHC. In these searches, sensitive differential distributions are used in an optimized way to determine the sensitivity to dark photon parameter space. It is shown that remarkable sensitivity to the dark photon model is achieved and kinetic mixing strength can be probed down to $(1.4-10)\times 10^{-4}$ for dark photon mass between $15$ GeV to $2$ TeV. We also investigate the sensitivity of a future muon collider suggested by the Muon Accelerator Program (MAP) to the dark photon model at different center-of-mass energies. It is shown that a future muon collider is able to reach a sensitivity to kinetic mixing at the order of $10^{-4}$.

Hadrophilic dark sectors at the Forward Physics Facility

Models with light dark sector and dark matter particles motivate qualitatively new collider searches. Here we carry out a comprehensive study of hadrophilic models with U(1)$_B$ and U(1)$_{B-3L_{\tau}}$ gauge bosons coupled to light dark matter. The new mediator particles in these models couple to quarks, but have suppressed couplings to leptons, providing a useful foil to the well-studied dark photon models. We consider current bounds from accelerator and collider searches, rare anomaly-induced decays, neutrino non-standard interactions, and dark matter direct detection. Despite the many existing constraints, these models predict a range of new signatures that can be seen in current and near future experiments, including dark gauge boson decays to the hadronic final states $\pi^+ \pi^- \pi^0$, $\pi^0 \gamma$, $K^+ K^-$, and $K_S K_L$ in FASER at LHC Run 3, enhancements of $\nu_{\tau}$ scattering rates in far-forward neutrino detectors, and thermal dark matter scattering in FLArE in the HL-LHC era. These models therefore motivate an array of different experiments in the far-forward region at the LHC, as could be accommodated in the proposed Forward Physics Facility.

Constraining time dependent dark matter signals from the Sun

Dark matter (DM) particles captured by the Sun can produce high-energy electrons outside the Sun through annihilating into meta-stable mediators. The corresponding cosmic-ray electron signals observed by the space-based experiments will be time dependent due to the orbital motion of the space-based detectors. The shape of this time dependence is predictable given the orbital information of the detectors. Since the high-energy CR electron (with energy E > 100 GeV) fluxes are expected to be constant in time, non-observation of such time variation can be used to place upper limits on the DM annihilation cross section. We analyze the time dependence of dark matter cosmic-ray signals in three space-based experiments: AMS-02, DAMPE and CALET. Under the assumption that no time dependent signal is observed, we derive the 95% C.L. exclusion limits on the signal strength from the current data. We map our limits onto the parameter space of the dark photon model and find that the constraints are comparable with that derived from the supernova SN1987A.

Enhanced long-lived dark photon signals at lifetime frontier detectors

Long-lived particles that are present in many new physics models beyond the standard model, can be searched for in a number of newly proposed lifetime frontier experiments at the LHC. The signals of the long-lived dark photons can be significantly enhanced in a new dark photon model in which dark photons are copiously produced in the hidden radiation process. We investigate the capability of various lifetime frontier detectors in probing the parameter space of this model, including the far forward detectors FACET and FASER, the far transverse detector MATHUSLA, and the precision timing detector CMS-MTD. We find that the accessible parameter space is significantly enlarged by the hidden radiation process so that FACET, MATHUSLA, and CMS-MTD can probe a much larger parameter space than the so-called minimal model. The parameter space probed by FACET is found to be much larger than FASER, which is largely due to the fact that the former has a larger decay volume and is closer to the interaction point. There also exists some parameter space that can be probed both by the far detectors and by precision timing detectors, so that different experiments can be complementary to each other. A brief overview of the lifetime frontier detectors is also given.

Atomic Compton scattering effect on direct dark matter detection

Atomic Compton scattering effect significantly contributes to low-energy electronic recoils below its k-shell energy for the direct dark matter detection. Searches on ADM models, dark photon models, leptophilic dark matter models as well as the conventional WIMPs for background understandings are vitally required to clarify the effect. We employed the relativistic impulse approximation (RIA) together with the ab initio Multi-Configuration Dirac-Fock (MCDF) theory to obtain the atomic Compton scattering for Germanium (Ge) Silicon (Si) and Xenon (Xe) atoms. Comparisons on low momentum transfer regions with our calculations for Ge and Si are achieved. In addition, millicharged dark matter particles estimated by RIA in the atomic ionization for Ge and Xe have been evaluated. A factor-of-two discrepancy on the incoherent-scattering factor (a.k.a. scattering function) near 100 eV/c momentum transfer with the Ge system between our calculation and the latest version of Geant4 (10.07.02) simulation data is observed. Plans on the experimental verification and the perspectives of the atomic Compton scattering effect for the direct detections will be discussed.

Forward experiment sensitivity estimator for the LHC and future hadron colliders

We introduce a numerical package FORward Experiment SEnsitivity Estimator, or $\mathtt{FORESEE}$, that can be used to simulate the expected sensitivity reach of experiments placed in the far-forward direction from the proton-proton interaction point. The simulations can be performed for 14 TeV collision energy characteristic for the LHC, as well as for larger energies; 27 and 100 TeV. In the package, a comprehensive list of validated forward spectra of various SM species is also provided. The capabilities of $\mathtt{FORESEE}$ are illustrated for the popular dark photon and dark Higgs boson models, as well as for the search for light up-philic scalars. For the dark photon portal, we also comment on the complementarity between such searches and dark matter direct detection bounds. Additionally, for the first time, we discuss the prospects for the LLP searches in the proposed future hadron colliders: High-Energy LHC (HE-LHC), Super proton-proton Collider (SppC), and Future Circular Collider (FCC-hh).

Projected sensitivity to sub-GeV dark matter of next-generation semiconductor detectors

We compute the projected sensitivity to dark matter (DM) particles in the sub-GeV mass range of future direct detection experiments using germanium and silicon semiconductor targets. We perform this calculation within the dark photon model for DM-electron interactions using the likelihood ratio as a test statistic, Monte Carlo simulations, and background models that we extract from recent experimental data. We present our results in terms of DM-electron scattering cross section values required to reject the background only hypothesis in favour of the background plus DM signal hypothesis with a statistical significance, Z, corresponding to 3 or 5 standard deviations. We also test the stability of our conclusions under changes in the astrophysical parameters governing the local space and velocity distribution of DM in the Milky Way. In the best-case scenario, when a high-voltage germanium detector with an exposure of 50 kg-year and a CCD silicon detector with an exposure of 1 kg-year and a dark current rate of 1×10−7 counts/pixel/day have simultaneously reported a DM signal, we find that the smallest cross section value compatible with Z=3 (Z=5) is about 4×10−42 cm2 (6×10−42 cm2) for contact interactions, and 2.5×10−41 cm2 (4×10−41 cm2) for long-range interactions. Our sensitivity study extends and refine previous works in terms of background models, statistical methods, and treatment of the underlying astrophysical uncertainties.