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Register a new userLow Scale String Theory Benchmarks for Hidden Photon Dark Matter Interpretations of the XENON1T Anomaly
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An excess of low-energy electronic recoil events over known backgrounds was recently observed in the XENON1T detector, where $285$ events are observed compared to an expected $232 pm 15$ events from the background-only fit to the data in the energy range 1-7 keV. This could be due to the beta decay of an unexpected tritium component, or possibly to new physics. One plausible new physics explanation for the excess is absorption of hidden photon dark matter relics with mass around $2.8$ keV and kinetic mixing of about $10^{-15}$, which can also explain cooling excesses in horizontal-branch (HB) stars. Such small gauge boson masses and couplings can naturally arise from type-IIB low scale string theory. We provide a fit of the XENON1T excess in terms of a minimal low scale type-IIB string theory parameter space and present some benchmark points which provide a good fit to the data. It is also demonstrated how the required transformation properties of the massless spectrum are obtained in intersecting D-brane models.
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The low-energy electronic recoil spectrum in XENON1T provides an intriguing hint for potential new physics. At the same time, observations of horizontal branch stars favor the existence of a small amount of extra cooling compared to the one expected from the Standard Model particle content. In this note, we argue that a hidden photon with a mass of $sim 2.5$ keV and a kinetic mixing of $sim 10^{-15}$ allows for a good fit to both of these excesses. In this scenario, the signal detected in XENON1T is due to the absorption of hidden photon dark matter particles, whereas the anomalous cooling of horizontal branch stars arises from resonant production of hidden photons in the stellar interior.
We present a dark matter model to explain the excess events in the electron recoil data recently reported by the Xenon1T experiment. In our model, dark matter $chi$ annihilates into a pair of on-shell particles $phi$ which subsequently decay into $psi psi$ final state; $psi$ interacts with electron to generate the observed excess events. Due to the mass hierarchy, the velocity of $psi$ can be rather large and can have an extended distribution, which provides a good fit to the electron recoil energy spectrum. We estimated the flux of $psi$ from dark matter annihilations in the galaxy and further determined the interaction cross section which is sizable but small enough to allow $psi$ to penetrate the rocks to reach the underground labs.
The non-observation of dark matter (DM) by direct detection experiments suggests that any new interaction of DM with the Standard Model (SM) should be very weak. One of the simplest scenarios to achieve this is a dark sector that is charged under a new $U(1)_X$ symmetry, which is kinetically mixed with the SM hypercharge $U(1)_Y$. We briefly review the status of such a minimal setup and analyze in a second step how the picture is altered if also SM fields are charged under the new symmetry. We exemplify this for the case of a gauged $U(1)_{L_mu-L_tau}$ and show that this allows for a simultaneous explanation of the $(g-2)_mu$ excess and the DM relic abundance $Omega_{DM}$. Furthermore, we discuss the potential of four-lepton and two-lepton plus missing energy signatures to test such scenarios.
We present direct detection constraints on the absorption of hidden-photon dark matter with particle masses in the range 1.2-30 eV$c^{-2}$ with the DAMIC experiment at SNOLAB. Under the assumption that the local dark matter is entirely constituted of hidden photons, the sensitivity to the kinetic mixing parameter $kappa$ is competitive with constraints from solar emission, reaching a minimum value of 2.2$times$$10^{-14}$ at 17 eV$c^{-2}$. These results are the most stringent direct detection constraints on hidden-photon dark matter in the galactic halo with masses 3-12 eV$c^{-2}$ and the first demonstration of direct experimental sensitivity to ionization signals $<$12 eV from dark matter interactions.
We study a generic model in which the dark sector is composed of a Majorana dark matter $chi_1$, its excited state $chi_2$, both at the electroweak scale, and a light dark photon $Z$ with $m_{Z} sim 10^{-4}$ eV. The light $Z$ enhances the self-scattering elastic cross section $chi_1 chi_1 to chi_1 chi_1$ enough to solve the small scale problems in the $N$-body simulations with the cold dark matter. The dark matter communicates with the SM via kinetic mixing parameterized by $epsilon$. The inelastic scattering process $chi_1 chi_1 to chi_2 chi_2$ followed by the prompt decay $chi_2 to chi_1 Z$ generates energetic $Z$. By setting $delta equiv m_{chi_2} - m_{chi_1} simeq 2.8$ keV and $epsilon sim 10^{-10}$ the excess in the electron-recoil data at the XENON1T experiment can be explained by the dark photoelectric effect. The relic abundance of the dark matter can also be accommodated by the thermal freeze-out mechanism via the annihilation $chi_1 chi_1 (chi_2 chi_2) to Z Z$ with the dark gauge coupling constant $alpha_X sim 10^{-3}$.
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