Standard Model Photon Research Articles

Aspects of nonlinear effect on black hole superradiance

Under some conditions, light boson fields grow exponentially around a rotating black hole, called the superradiance instability. We discuss effects of nonlinear interactions of the boson on the instability. In particular, we focus on the effect of the particle production and show that the growth of the boson cloud may be saturated much before the black hole spin is extracted by the boson cloud, while the nonlinear interactions also induce the boson emission. For application, we revisit the superradiant instability of the standard model photon, axion and hidden photon.

Probing invisible decay of a dark photon at BESIII and a future Super Tau Charm Factory via monophoton searches

We propose to search the monophoton events at the BESIII detector and future Super Tau Charm Factory to probe the sub-GeV dark photon decay into lighter dark matter. We compute the cross section due to the dark photon associated a standard model photon production, and study the corresponding standard model irreducible/reducible backgrounds. By using the data about 17 fb$^{-1}$ collected at the BESIII detector since 2011, we derive new leading limits of the mixing strength $\varepsilon$, $\varepsilon\lesssim(1.1-1.6)\times 10^{-4}$, in the mass range of 0.04 GeV $\lesssim m_{A^\prime} \lesssim$ 3 GeV. With 30 ab$^{-1}$ data, STCF running at $\sqrt{s} = 2$ GeV, can probe $\varepsilon$ down to 5.1$\times 10^{-6}$ when $m_{A^\prime}=1$ GeV. For models of scalar and fermionic light thermal dark matter production via dark photon, we present the constrains on the dimensionless dark matter parameter $y=\varepsilon^2\alpha_D(m_\chi/m_{A^\prime})^4$ as function of the DM mass $m_{\chi}$ at BESIII and future STCF, conventionally assuming the dark coupling constant $\alpha_D=0.5$ and $m_{A^\prime}=3 m_{\chi}$. We find that BESIII can exclude model of scalar, Majorana, and pseudo-Dirac (with a small splitting) DM for the mass region 0.03$\sim$1 GeV, 0.04$\sim$1 GeV and 0.4$\sim$1 GeV respectively. For values $\alpha_D\lesssim 0.005$, combining the results from 2 GeV STCF with 30 ab$^{-1}$ data and BaBar, one can exclude the above three DM models in the mass region 0.001 GeV $\lesssim m_{\chi} \lesssim$ 1 GeV.

Photon-dark photon conversions in extreme background electromagnetic fields

The mixing of photons with light pseudoscalars in the presence of external electromagnetic fields has been used extensively to search for axion-like-particles. A similar effect for dark photon propagating states is usually not considered due to the Landau-Yang theorem. We point out that mixing between photon and dark photon propagating states in background electromagnetic fields can indeed occur, in non-linear QED, through a four-photon vertex by integrating out the electron box diagram. Starting from the Schwinger Lagrangian, we derive the equations of motion for dark photons interacting with the Standard Model photon through gauge kinetic terms. We provide expressions for the perpendicular and parallel refractive indices in series expansions in the critical field strength, valid both in the strong and weak background field limits. We then consider mixing between the photon-dark photon propagating system in the presence of pure electric and magnetic background fields, and work out the probability of conversion when the background fields are homogeneous. We indicate outlines of the calculation in the inhomogeneous case, and finally express our results in the active-sterile basis, where we find that the mixing induced by background fields can lead to corrections to the tree-level mixing in the zero field limit that is usually considered to probe such systems. Our results may find applications for probing photon-dark photon conversions in the vicinity of neutron stars and in table-top petawatt laser experiments.

Photon masses in the landscape and the swampland

In effective quantum field theory, a spin-1 vector boson can have a technically natural small mass that does not originate from the Higgs mechanism. For such theories, which may be written in Stückelberg form, there is no point in field space at which the mass is exactly zero. I argue that quantum gravity differs from, and constrains, effective field theory: arbitrarily small Stückelberg masses are forbidden. In particular, the limit in which the mass goes to zero lies at infinite distance in field space, and this distance is correlated with a tower of modes becoming light according to the Swampland Distance Conjecture. Application of Tower or Sublattice variants of the Weak Gravity Conjecture makes this statement more precise: for a spin-1 vector boson with coupling constant e and Stückelberg mass m, local quantum field theory breaks down at energies at or below ΛUV = min((mMPl/e)1/2, e1/3MPl). Combined with phenomenological constraints, this argument implies that the Standard Model photon must be exactly massless. It also implies that much of the parameter space for light dark photons, which are the target of many experimental searches, is compatible only with Higgs and not Stückelberg mass terms. This significantly affects the experimental limits and cosmological histories of such theories. I explain various caveats and weak points of the arguments, including loopholes that could be targets for model-building.

Study of the Dalitz decayJ/ψ→e+e−η

We study the electromagnetic Dalitz decay J/ψ→e+e−η and search for dielectron decays of a dark gauge boson (γ′) in J/ψ→γ′η with the two η decay modes η→γγ and η→π+π−π0 using (1310.6±7.0)×106 J/ψ events collected with the BESIII detector. The branching fraction of J/ψ→e+e−η is measured to be (1.43±0.04(stat)±0.06(syst))×10−5, with a precision that is improved by a factor of 1.5 over the previous BESIII measurement. The corresponding dielectron invariant mass dependent modulus square of the transition form factor is explored for the first time, and the pole mass is determined to be Λ=2.84±0.11(stat)±0.08(syst) GeV/c2. We find no evidence of γ′ production and set 90% confidence level upper limits on the product branching fraction B(J/ψ→γ′η)×B(γ′→e+e−) as well as the kinetic mixing strength between the standard model photon and γ′ in the mass range of 0.01≤mγ′≤2.4 GeV/c2.1 MoreReceived 8 October 2018DOI:https://doi.org/10.1103/PhysRevD.99.012006Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMagnetic momentParticle decaysParticles & Fields

Status of the PADME experiment

Among the theoretical models addressing the dark matter problem, the category based on a secluded sector is attracting increasing interest. The PADME experiment, at the Laboratori Nazionali di Frascati of INFN, is designed to be sensitive to the production of a low mass gauge boson A′ of a new U(1) symmetry holding for dark sector particles and weakly coupled to the Standard Model photon. The DAΦNE Beam-Test Facility at LNF will provide a high intensity, mono-energetic positron beam impinging on a low Z target. The PADME detector will measure with high precision the momentum of the photon, produced along with the A′ boson in e+e− → A′+γ annihilation in the target, thus allowing to measure the A′ mass as the missing mass in the final state. This technique, particularly useful in case of invisible decays of the A′ boson, will be exploited for the first time in a fixed target experiment. Simulation studies predict a sensitivity on the interaction strength (ϵ2 parameter) down to 10−6, in the mass region 1 MeV < MA′ < 23.7 MeV. In this work the physics potential, the experimental strategy and the status of readiness of the experiment will be reviewed.

Search for a dark photon in electroproduced e+e− pairs with the Heavy Photon Search experiment at JLab

The Heavy Photon Search experiment took its first data in a 2015 engineering run at the Thomas Jefferson National Accelerator Facility, searching for a prompt, electro-produced dark photon with a mass between 19 and 81 MeV/$c^2$. A search for a resonance in the $e^{+}e^{-}$ invariant mass distribution, using 1.7 days (1170 nb$^{-1}$) of data, showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the Standard Model photon are set at the level of 6$\times$10$^{-6}$. Future runs with higher luminosity will explore new territory.

Composite asymmetric dark matter with a dark photon portal

Asymmetric dark matter (ADM) is an attractive framework relating the observed baryon asymmetry of the Universe to the dark matter density. A composite particle in a new strong dynamics is a promising candidate for ADM as the strong dynamics naturally explains the ADM mass in the GeV range. Its large annihilation cross section due to the strong dynamics leaves the asymmetric component to be dominant over the symmetric component. In such composite ADM scenarios, the dark sector has a relatively large entropy density in the early Universe. The large dark sector entropy results in the overclosure of the Universe or at best contradicts with the observations of the cosmic microwave background and the successful Big-Bang Nucleosynthesis. Thus, composite ADM models generically require some portal to transfer the entropy of the dark sector into the Standard Model sector. In this paper, we consider a dark photon portal with a mass in the sub-GeV range and kinetic mixing with the Standard Model photon. We investigate the viable parameter space of the dark photon in detail, which can find broad applications to dark photon portal models. We also provide a simple working example of composite ADM with a dark photon portal. Our model is compatible with thermal leptogenesis and B − L symmetry. By taking into account the derived constraints, we show that the parameter space is largely tested by direct detection experiments.

Constraining photon portal Dark Matter with TEXONO and COHERENT data

Dark Matter may reside in sector without Standard Model (SM) gauge interactions. One way in which such a dark sector can still impact SM particles through non-gravitational interactions is via the “photon portal” in which a dark photon kinetically mixes with the ordinary SM photon. We study the implications of this setup for electron recoil events at TEXONO reactor and nuclear recoil events at the COHERENT experiment. We find that the recent COHERENT data rules out previously allowed regions of parameter space favored by the thermal relic hypothesis for the DM abundance. When mapped onto the DM-electron cross section, we find that COHERENT provides the leading direct constraints for DM masses < 30 MeV.

The calorimeters of the PADME experiment

Abstract The PADME experiment is under construction at the Frascati National Laboratories of INFN to explore the coupling between ordinary and dark matter. This will be done through the detection of Standard Model photons produced in the reaction e + e − → γ A ′ . The measurement of the photons 4-momentum allows to reconstruct the missing mass spectrum of this process, where the A ′ could appear as a peak. To this purpose, two independent electromagnetic calorimeters are used. The layout of the two detectors, and their expected performance measured during prototypes tests, are here presented.

Constraints on light Dark Matter fermions from relic density consideration and Tsallis statistics

The cold dark matter fermions with mass MeV scale, pair produced inside the supernova SN1987A core, can freely stream away from the supernovae and hence contributes to its energy loss rate. Similar type of DM fermions (having similar kind of coupling to the standard model photon), produced from some other sources earlier, could have contributed to the relic density of the Universe. Working in a theory with an effective dark matter-photon coupling (inversely proportional to the scale Λ) in the formalism of Tsallis statistics, we find the dark matter contribution to the relic density and obtain a upper bound on Λ using the experimental bound on the relic density for cold non-baryonic matter i.e. Ωh2 = 0.1186 ± 0.0020. The upper bound obtained from the relic density is shown with the lower bound obtained from the Raffelt’s criterion on the emissibity rate of the supernovae SN1987A energy loss overset{cdot }{varepsilon}left({e}^{+}{e}^{-}to chi overline{chi}right)le {10}^{19} erg g−1s−1 and the optical depth criteria on the free streaming of the dark matter fermion (produced inside the supernovae core). As the deformation parameter q changes from 1.0 (undeformed scenario) to 1.1 (deformed scenario), the relic density bound on Λ is found to vary from ∼ 4.9 × 107 TeV to 1.6 × 108 TeV for a fermion dark matter (χ) of mass mχ = 30 MeV, which is almost10 times more than the lower bound obtained from the SN1987A energy loss rate and the optical depth criteria.

Prospects for indirect detection of frozen-in dark matter

We study observational consequences arising from dark matter (DM) of non-thermal origin, produced by dark freeze-out from a hidden sector heat bath. We assume this heat bath was populated by feebly-coupled mediator particles, produced via a Higgs portal interaction with the Standard Model (SM). The dark sector then attained internal equilibrium with a characteristic temperature different from the SM photon temperature. We find that even if the coupling between the DM and the SM sectors is very weak, the scenario allows for indirect observational signals. We show how the expected strength of these signals depends on the temperature of the hidden sector at DM freeze-out.

Dark photon search in the mass range between 1.5 and 3.4 GeV/c2

Using a data set of 2.93 fb−1 taken at a center-of-mass energy s=3.773 GeV with the BESIII detector at the BEPCII collider, we perform a search for an extra U(1) gauge boson, also denoted as a dark photon. We examine the initial state radiation reactions e+e−→e+e−γISR and e+e−→μ+μ−γISR for this search, where the dark photon would appear as an enhancement in the invariant mass distribution of the leptonic pairs. We observe no obvious enhancement in the mass range between 1.5 and 3.4 GeV/c2 and set a 90% confidence level upper limit on the mixing strength of the dark photon and the Standard Model photon. We obtain a competitive limit in the tested mass range.

Search for dark photons using data from CRESST-II Phase 2

Understanding the nature and origin of dark matter is one of the most important challenges for modern particle physics. During the previous decade the sensitivities of direct dark matter searches have improved by several orders of magnitude. These experiments focus their work mainly on the search for dark-matter particles interacting with nuclei (e.g. Weakly Interacting Massive Particles, WIMPs). However, there exists a large variety of different candidates for dark-matter particles. One of these candidates, the so-called dark photon, is a long-lived vector boson with a kinetic mixing to the standard-model photon. In this work we present the preliminary results of our search for dark photons. Using data from the direct dark matter search CRESST-II Phase 2 we can improve the existing constraints for the kinetic mixing for dark-photon masses between 0.3 and 0.5 keV/c2. In addition, we also present projected sensitivities for the next phases of the CRESST-III experiment showing great potential to improve the sensitivity for dark-photon masses below 1 keV.

Dark-photon search using data from CRESST-II Phase 2

Identifying the nature and origin of dark matter is one of the major challenges for modern astro and particle physics. Direct dark-matter searches aim at an observation of dark-matter particles interacting within detectors. The focus of several such searches is on interactions with nuclei as provided e.g. by weakly interacting massive particles. However, there is a variety of dark-matter candidates favoring interactions with electrons rather than with nuclei. One example are dark photons, i.e., long-lived vector particles with a kinetic mixing to standard-model photons. In this work we present constraints on this kinetic mixing based on data from CRESST-II Phase 2 corresponding to an exposure before cuts of 52 kg-days. These constraints improve the existing ones for dark-photon masses between 0.3 and 0.7 keV/c^2.

Dark photons from captured inelastic dark matter annihilation: Charged particle signatures

The dark sector may contain a dark photon that kinetically mixes with the Standard Model photon, allowing dark matter to interact weakly with normal matter. In previous work we analyzed the implications of this scenario for dark matter capture by the Sun. Dark matter will gather in the core of the Sun and annihilate to dark photons. These dark photons travel outwards from the center of the Sun and may decay to produce positrons that can be detected by the Alpha Magnetic Spectrometer (AMS-02) on the ISS. We found that the dark photon parameter space accessible to this analysis is largely constrained by strong limits on the spin-independent WIMP-nucleon cross section from direct detection experiments. In this paper we build upon previous work by considering the case where the dark sector contains two species of Dirac fermion that are nearly degenerate in mass and couple inelastically to the dark photon. We find that for small values of the mass splitting $\Delta \sim 100 ~\text{keV}$, the predicted positron signal at AMS-02 remains largely unchanged from the previously considered elastic case while constraints from direct detection are relaxed, leaving a region of parameter space with dark matter mass $100 ~\text{GeV} \lesssim m_X \lesssim 10 ~\text{TeV}$, dark photon mass $1 ~\text{MeV} \lesssim m_{A'} \lesssim 100 ~\text{MeV}$, and kinetic mixing parameter $10^{-9} \lesssim \varepsilon \lesssim 10^{-8}$ that is untouched by supernova observations and fixed target experiments but where an inelastic dark sector may still be discovered using existing AMS-02 data.

The HPS electromagnetic calorimeter

The Heavy Photon Search experiment (HPS) is searching for a new gauge boson, the so-called “heavy photon.” Through its kinetic mixing with the Standard Model photon, this particle could decay into an electron-positron pair. It would then be detectable as a narrow peak in the invariant mass spectrum of such pairs, or, depending on its lifetime, by a decay downstream of the production target. The HPS experiment is installed in Hall-B of Jefferson Lab. This article presents the design and performance of one of the two detectors of the experiment, the electromagnetic calorimeter, during the runs performed in 2015–2016. The calorimeter's main purpose is to provide a fast trigger and reduce the copious background from electromagnetic processes through matching with a tracking detector. The detector is a homogeneous calorimeter, made of 442 lead-tungstate (PbWO4) scintillating crystals, each read out by an avalanche photodiode coupled to a custom trans-impedance amplifier.

The HPS experiment at JLab

Many Beyond-Standard-Model theories predict a new massive gauge boson, such as a “dark” or “heavy photon”. The heavy photon is expected to mix with the Standard Model photon through kinetic mixing and therefore have a small coupling to electric charge. The Heavy Photon Search (HPS) experiment is searching for a heavy photon at the Thomas Jefferson National Accelerator Facility (JLab), in the mass range 20-500 MeV/c2 . In particular HPS looks for the e + e − decay channel of heavy photons radiated by electron Bremsstrahlung, employing both an invariant mass search and detached vertexing techniques. The experiment employs a compact forward spectrometer comprising silicon microstrip detectors for vertexing and tracking and an electromagnetic calorimeter for particle identification and triggering. HPS took data successfully in 2015 and 2016 at 1.05 GeV and 2.3 GeV beam energies, respectively. First results are expected to be presented soon.

Light chiral dark sector

An interesting possibility for dark matter is a scalar particle of mass of order 10 MeV-1 GeV, interacting with a U(1) gauge boson (dark photon) which mixes with the photon. We present a simple and natural model realizing this possibility. The dark matter arises as a composite pseudo Nambu-Goldstone boson (dark pion) in a non-Abelian gauge sector, which also gives a mass to the dark photon. For a fixed non-Abelian gauge group, SU(N), and a U(1) charge of the constituent dark quarks, the model has only three free parameters: the dynamical scale of the non-Abelian gauge theory, the gauge coupling of the dark photon, and the mixing parameter between the dark and standard model photons. In particular, the gauge symmetry of the model does not allow any mass term for the dark quarks, and stability of the dark pion is understood as a result of an accidental global symmetry. The model has a significant parameter space in which thermal relic dark pions comprise all of the dark matter, consistently with all experimental and cosmological constraints. In a corner of the parameter space, the discrepancy of the muon g-2 between experiments and the standard model prediction can also be ameliorated due to a loop contribution of the dark photon. Smoking-gun signatures of the model include a monophoton signal from the e+ e- collision into a photon and a "dark rho meson." Observation of two processes in e+ e- collision, the mode into the dark photon and that into the dark rho meson, would provide strong evidence for the model.

Detecting Topological Defect Dark Matter Using Coherent Laser Ranging System.

In the last few decades, optical frequency combs with high intensity, broad optical bandwidth, and directly traceable discrete wavelengths have triggered rapid developments in distance metrology. However, optical frequency combs to date have been limited to determine the absolute distance to an object (such as satellite missions). We propose a scheme for the detection of topological defect dark matter using a coherent laser ranging system composed of dual-combs and an optical clock via nongravitational signatures. The dark matter field, which comprises a defect, may interact with standard model particles, including quarks and photons, resulting in the alteration of their masses. Thus, a topological defect may function as a dielectric material with a distinctive frequency-depend index of refraction, which would cause the time delay of a periodic extraterrestrial or terrestrial light. When a topological defect passes through the Earth, the optical path of long-distance vacuum path is altered, this change in optical path can be detected through the coherent laser ranging system. Compared to continuous wavelength(cw) laser interferometry methods, dual-comb interferometry in our scheme excludes systematic misjudgement by measuring the absolute optical path length.