We present new constraints on sub-GeV dark matter and dark photons from the electron beam-dump experiment E137 conducted at SLAC in 1980-1982. Dark matter interacting with electrons (e.g., via a dark photon) could have been produced in the electron-target collisions and scattered off electrons in the E137 detector, producing the striking, zero-background signature of a high-energy electromagnetic shower that points back to the beam dump. E137 probes new and significant ranges of parameter space, and constrains the well-motivated possibility that invisibly decaying dark photons can explain the $\sim 3.6 σ$ discrepancy between the measured and SM value of the muon anomalous magnetic moment. It also restricts the parameter space in which the relic density of dark matter in these models is obtained from thermal freeze-out. E137 also convincingly demonstrates that (cosmic) backgrounds can be controlled and thus serves as a powerful proof-of-principle for future beam-dump searches for sub-GeV dark matter scattering off electrons in the detector.
Millicharged particles (MCPs) arise in many well-motivated extensions of the Standard Model and are a popular subject for experimental searches. We investigate attenuation of the MCP flux produced at accelerator experiments due to their interactions in the media. Considering, as an example, the dedicated MCP search at SLACmQ, we demonstrate that this effect can significantly affect the final sensitivity to the MCP parameter space leaving its essential part still unexplored. Applying our analysis to the SLACmQ experiment [53], we correct their exclusion bounds in close accordance with Ref. [54]…
Medium-energy electron beam-dump experiments provide an intense sources of secondary muons. These particles can be used to search for muon-coupling light dark scalars that may explain the $(g-2)_μ$ anomaly. We applied this idea to SLAC E137 experiment deriving new exclusion limits and evaluated the expected sensitivity for the planned Jefferson Lab BDX experiment (in case of null result report). The calculation is based on numerical simulations that include a realistic description of secondary muons generation in the dump, dark scalar production, propagation, and decay, and, finally, the decay…
We derive limits on millicharged dark states, as well as particles with electric or magnetic dipole moments, from the number of observed forward electron scattering events at the Big European Bubble Chamber in the 1982 CERN-WA-066 beam dump experiment. The dark states are produced by the 400 GeV proton beam primarily through the decays of mesons produced in the beam dump, and the lack of excess events places bounds extending up to GeV masses. These improve on bounds from all other experiments, in particular CHARM II.
DUNE with its cutting edge technology is designed to study the neutrino science and proton decay physics. This facility can be further exploited for the study of the ground breaking discoveries i.e. origin of matter, unification of forces, dark matter detection etc. In this work we have explored the DUNE potential for capturing the sub-GeV dark matter in viable dark matter parameter space. The scenario of sub-GeV dark matter range requires a light mediator that couples the hidden sector with the standard model. The choice of the mediator will decide the different channels by which dark matter …
A novel mechanism to produce and detect Light Dark Matter in experiments making use of GeV electrons (and positrons) impinging on a thick target (beam-dump) is proposed. The positron-rich environment produced by the electromagnetic shower allows to produce an $A^\prime$ via non-resonant ($e^+ + e^- \to γ+ A^\prime$) and resonant ($e^+ + e^- \to A^\prime$) annihilation on atomic electrons. The latter mechanism, for some selected kinematics, results in a larger sensitivity with respect to limits derived by the commonly used $A^\prime-strahlung$. This idea, applied to Beam Dump Experiments and {\…
In a dedicated run where protons from the Fermilab Booster were delivered directly to the steel beam dump of the Booster Neutrino Beamline (BNB), the MiniBooNE detector was used to search for the production of sub-GeV dark matter particles via vector-boson mediators. The signal searched for was the elastic scattering of dark matter particles off nucleons in the detector mineral oil, with neutrinos being an irreducible background. A review of the experiment, its analysis methods, its results and future perspectives are summarized, demonstrating that beam dump experiments provide a novel and pro…
Search for Sub-GeV Axion-Like Particles at EBES Pilot Run Using 4 GeV Positron Beam at KEK LINAC
Saga University（佐贺大学）；The University of Tokyo（东京大学）；High Energy Accelerator Research Organization (KEK)（高能加速器研究机构（KEK））；Osaka Metropolitan University（大阪公立大学）；Kyushu University（九州大学）；National Institute of Technology, Niihama College（国立高专新居滨高专）
Hidden monopole is a plausible dark matter candidate due to its stability, but its direct experimental search is extremely difficult due to feeble interactions with the standard model particles in the minimal form. Then, we introduce an axion, $a$, connecting the hidden monopole and the standard model particles and examine the current limits and future prospects of direct dark matter searches and beam-dump experiments. We find two parameter regions around $m_a = {\cal O}(10)$ MeV, $f_a = {\cal O}(10^{5})$ GeV and $m_a = {\cal O}(100)$ MeV, $f_a = {\cal O}(10^{4})$ GeV where monopole dark matte…
There are broadly three channels to probe axion-like particles (ALPs) produced in the laboratory: through their subsequent decay to Standard Model (SM) particles, their scattering with SM particles, or their subsequent conversion to photons. Decay and scattering are the most commonly explored channels in beam-dump type experiments, while conversion has typically been utilized by light-shining-through-wall (LSW) experiments. A new class of experiments, dubbed PASSAT (Particle Accelerator helioScopes for Slim Axion-like-particle deTection), has been proposed to make use of the ALP-to-photon conv…
The exploration of long-lived particles in the MeV-GeV region is a formidable task but it may provide us a unique access to dark sectors. Fixed-target facilities with sufficiently energetic and intense proton beams are an ideal tool for this challenge. In this work we show that the production rate of Axion-Like-Particles (ALPs) coupled pre-dominantly to photons receives a significant contribution from daughter-photons of secondary $π^0$ and $η$ mesons created in the proton shower. We carefully compare the PYTHIA simulated spectra of such secondaries to experimental literature, compute the ALP …
High energy positron annihilation is a viable mechanism to produce dark photons ($A^\prime$). This reaction plays a significant role in beam-dump experiments using experiments using multi-GeV electron-beams on thick targets by enhancing the sensitivity to $A^\prime$ production. The positrons produced by the electromagnetic shower can produce an $A^\prime$ via non-resonant ($e^+ + e^- \to γ+ A^\prime$) and resonant ($e^+ + e^- \to A^\prime$) annihilation on atomic electrons. For visible decays, the contribution of resonant annihilation results in a larger sensitivity with respect to limits deri…
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 work 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, a…
$L_μ-L_τ$ gauge bosons in beam dumps and supernovae
York University（约克大学）；Fermi National Accelerator Laboratory（费米国家加速器实验室）；Texas A&M University（德克萨斯农工大学）；California Institute of Technology（加州理工学院）；CERN（欧洲核子研究组织）；University of Cincinnati（辛辛那提大学）
While the QCD axion is often considered to be necessarily light ($\lesssim$ eV), recent work has opened a viable and interesting parameter space for heavy axions, which solve both the Strong CP and the axion Quality Problems. These well-motivated heavy axions, as well as the generic axion-like-particles, call for explorations in the GeV mass realm at collider and beam dump environments. The primary upcoming neutrino experiment, Deep Underground Neutrino Experiment (DUNE), is simultaneously also a powerful beam dump experiment, enabled by its multipurpose Near Detector (ND) complex. In this stu…
A search for sub-GeV dark matter produced from collisions of the Fermilab 8 GeV Booster protons with a steel beam dump was performed by the MiniBooNE-DM Collaboration using data from $1.86 \times 10^{20}$ protons on target in a dedicated run. The MiniBooNE detector, consisting of 818 tons of mineral oil and located 490 meters downstream of the beam dump, is sensitive to a variety of dark matter initiated scattering reactions. Three dark matter interactions are considered for this analysis: elastic scattering off nucleons, inelastic neutral pion production, and elastic scattering off electrons.…
We present a model based on a $U(1)_{T3R}$ extension of the Standard Model. The model addresses the mass hierarchy between the third generation and the first two generation fermions. $U(1)_{T3R}$ is spontaneously broken at $\sim 1-10$ GeV. The model contains a sub-GeV dark matter candidate and two sub-GeV light scalar and vector mediators. The model explains the thermal dark matter abundance, measurements of the muon g-2 and $R_{K^{(\ast)}}$ anomalies. The model can be probed at the LHC, FASER, dark matter experiments and various beam-dump based neutrino facilities, e.g., COHERENT, CCM, MicroB…
NO LESS: Novel Opportunities for Light Exotic Searches at the SPS
Max-Planck-Institut für Physik (Werner-Heisenberg-Institut)（马克斯·普朗克物理研究所）；Lancaster University（兰卡斯特大学）；Technical University of Munich, TUM School of Natural Sciences, Physics Department, Chair for Data Science in Physics（慕尼黑工业大学）；Laboratori Nazionali di Frascati dell’INFN（意大利国家核物理研究所弗朗卡蒂国家实验室）
Precision cosmology provides a sensitive probe of extremely weakly coupled states due to thermal freeze-in production, with subsequent decays impacting physics during well-tested cosmological epochs. We explore the cosmological implications of the freeze-in production of a new scalar $S$ via the super-renormalizable Higgs portal. If the mass of $S$ is at or below the electroweak scale, peak freeze-in production occurs during the electroweak epoch. We improve the calculation of the freeze-in abundance by including all relevant QCD and electroweak production channels. The resulting abundance and…
The neutrino physics program at the LHC, which will soon be initiated by the FASER experiment, will provide unique opportunities for precision studies of neutrino interaction vertices at high energies. This will also open up the possibility to search for beyond the standard model (BSM) particles produced in such interactions in the specific high-energy neutrino beam-dump experiment. In this study, we illustrate the prospects for such searches in models with the dipole or $Z^\prime$ portal to GeV-scale heavy neutral leptons. To this end, we employ both the standard signature of new physics that…
University of Texas at Arlington（阿灵顿得克萨斯大学）；Fermi National Accelerator Laboratory（费米国家加速器实验室）；Washington University（华盛顿大学）；Texas A&M University（德克萨斯农工大学）；Department of Physics & Astronomy, University of California, Riverside（加州大学河滨分校物理与天文学系）；Brookhaven National Laboratory（布鲁克海文国家实验室）；Nanjing Normal University（南京师范大学）；Institute for Basic Science (IBS)（韩国基础科学研究所）；University of South Dakota（南达科他大学）；Seoul National University（首尔大学）；Kyungpook National University（庆北国立大学）；University of Chicago（芝加哥大学）；University of Pittsburgh（匹兹堡大学）；Korea University Sejong Campus（韩国大学世宗校区）；Chungnam National University（忠南国立大学）；South Dakota School of Mines and Technology（南达科他矿业理工学院）；University of Maryland, College Park（马里兰大学帕克分校）；Jeonbuk National University（全北国立大学）；Northwestern University（西北大学）
Experimental searches for Axion-Like Particles (ALPs) which couple to the electroweak bosons span over a wide range of ALP masses, from MeV searches at beam-dump experiments, to TeV searches at the LHC. Here we examine an interesting range of parameter space in which the ALP couples only to hypercharge. In the GeV to hundreds of GeV mass range, the contribution of an ALP to light by light scattering can be significant. By making simple kinematic cuts, we show that the ILC running at $\sqrt{s} = 250\,\rm{GeV}$ or $\sqrt{s} = 500\,\rm{GeV}$ can discover ALPs in this range of masses with signific…
We propose the operation of \textbf{LEvEL}, the Low-Energy Neutrino Experiment at the LHC, a neutrino detector near the Large Hadron Collider Beam Dump. Such a detector is capable of exploring an intense, low-energy neutrino flux and can measure neutrino cross sections that have previously never been observed. These cross sections can inform other future neutrino experiments, such as those aiming to observe neutrinos from supernovae, allowing such measurements to accomplish their fundamental physics goals. We perform detailed simulations to determine neutrino production at the LHC beam dump, a…
The goal of FASER, ForwArd Search ExpeRiment at the LHC, is to discover light, weakly-interacting particles with a small and inexpensive detector placed in the far-forward region of ATLAS or CMS. A promising location in an unused service tunnel 480 m downstream of the ATLAS interaction point (IP) has been identified. Previous studies have found that FASER has significant discovery potential for new particles produced at the IP, including dark photons, dark Higgs bosons, and heavy neutral leptons. In this study, we explore a qualitatively different, `beam dump' capability of FASER, in which the…
Prying Open the Dark Sector Window with SBND Off-Target Mode
Fermi National Accelerator Laboratory（费米国家加速器实验室）；University of Pittsburgh（匹兹堡大学）；CERN（欧洲核子研究中心）；Northwestern University（西北大学）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）
The origin of neutrino mass is a big unsolved problem of the Standard Model (SM) that motivate us to consider beyond the SM (BSM) scenarios where SM-singlet right-handed neutrinos (RHNs) are introduced to explain the origin of the light neutrino masses through the seesaw mechanism. There is a variety of ways which could lead us to this goal and one of them is a general U$(1)$ extension of the SM. In this scenario, three SM-singlet RHNs are introduced to cancel the gauge and mixed gauge gravity anomalies. After anomaly cancellation, we notice that the left- and right-handed charged fermions are…
A search for sub-GeV dark matter production mediated by a new vector boson $A'$, called dark photon, is performed by the NA64 experiment in missing energy events from 100 GeV electron interactions in an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with $2.84\times10^{11}$ electrons on target no evidence of such a process has been found. The most stringent constraints on the $A'$ mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range $\lesssim 0.2$ GeV are derived, thus demons…
We investigate a dark sector containing a pair of light non-degenerate scalar particles, with masses in the MeV-GeV range, coupled to the visible sector through heavier mediators. The heaviest dark state is long-lived, and its decays offer new testable signals. We analyze the prospects for detection with the proposed beam-dump facility SHiP, and the proposed LHC experiments FASER and MATHUSLA. Moreover, we consider bounds from the beam-dump experiment CHARM and from colliders (LEP, LHC and BaBar). We present our results both in terms of an effective field theory, where the heavy mediators have…
Cornering MeV-GeV Axions and Dark Photons with LDMX
SLAC National Accelerator Laboratory（斯坦福直线加速器中心）；Department of Physics, Stanford University（斯坦福大学物理系）；Leinweber Institute for Theoretical Physics（莱因韦伯理论物理研究所）
