<p>We report on a search for axion dark matter in the frequency range near 5.9 GHz, conducted using the haloscope technique. The experiment employed an 8-cell microwave resonator designed to extend the accessible frequency range by a multifold factor relative to conventional single-cell configurations, while maintaining a large detection volume. To enhance sensitivity, a flux-driven Josephson parametric amplifier operating near the quantum noise limit was utilized, together with a sideband-summing method that coherently combines mirrored spectral components generated by the Josephson parametric amplifier. Data were acquired over the frequency range 5.83–5.94 GHz. With no statistically significant excess observed, we exclude axion-photon couplings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>g</mi></mrow><mrow><mi>a</mi><mi>γ</mi><mi>γ</mi></mrow></msub></mrow></math> down to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1.2</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>14</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mrow><msup><mrow><mi>GeV</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></mrow></math> at a 90% confidence level. The achieved sensitivity approaches the Kim-Shifman-Vainshtein-Zakharov benchmark prediction, setting the most stringent limits to date in this range.</p>

South Korea

Saebyeok Ahn

Çağlar Kutlu

Soohyung Lee

SungWoo Youn

Sergey V. Uchaikin

Sungjae Bae

Sweden

Junu Jeong

Japan

Arjan F. van Loo

Yasunobu Nakamura

Seongjeong Oh

Jihn E. Kim

Yannis K. Semertzidis

Probing Kim-Shifman-Vainshtein-Zakharov Axion Dark Matter near 5.9 GHz Using an 8-Cell Cavity Haloscope

<p>Axions, originally proposed to resolve the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math> problem in the strong interaction, remain a leading dark matter candidate. While cavity haloscopes offer the most sensitive technique for detecting axions, searches have largely been limited to masses below <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>10</mn><mtext> </mtext><mtext> </mtext><mi>μeV</mi></mrow></math>. We report a sensitive search for axion dark matter with masses around <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>21</mn><mtext> </mtext><mtext> </mtext><mi>μeV</mi></mrow></math>, utilizing the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>TM</mi></mrow><mrow><mn>020</mn></mrow></msub></mrow></math> mode of a cylindrical cavity equipped with an innovative tuning mechanism. Our search achieved a sensitivity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1.7</mn><mo>×</mo></math> the Kim-Shifman-Vainshtein-Zakharov benchmark over a 100-MHz range, representing a significant advance in this mass range. These results demonstrate that higher-order modes provide a viable strategy for extending haloscope searches into previously unexplored higher-mass regions.</p>

Germany

Younggeun Kim

Jinsu Kim

Seonjeong Oh

Taehyeon Seong

Sergey Uchaikin

Axion Dark Matter Search with Sensitivity near the Kim-Shifman-Vainshtein-Zakharov Benchmark Using the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>TM</mi></mrow><mrow><mn>020</mn></mrow></msub></mrow></math> Mode

It has been known for some time that the cosmological bound on the invisible axion scale can be avoided by an early phase of strong QCD. While most approaches rely on theories where the strong coupling constant is determined through the expectation value of some scalar field, we show that this mechanism can also be implemented into the benchmark Kim-Shifman-Vainshtein-Zakharov and Dine-Fischler-Srednicki-Zhitnitsky models when the early phase of strong QCD emerges by the modification of the running coupling during inflation. For both models the physics that are responsible for making QCD strong do not displace the axions minimum by too much, so that the efficiency of the relaxation is controlled by parameters of the theory and the number of inflationary <math><mi>e</mi></math>-folds. In particular, we consider the case of very efficient relaxation where the axion abundance is dominated by inflationary quantum and postinflationary thermal fluctuations. Within this situation we identify the parameter space compatible with all cosmological constrains and derive conditions on the reheating temperature and the QCD scale during inflation that result in the axion making up all the dark matter. Because of duality below the Peccei-Quinn scale and a minor influence of the Kim-Shifman-Vainshtein-Zakharov and Dine-Fischler-Srednicki-Zhitnitsky fields on the running, our findings also apply to a minimal two-form implementation of the axion.

Emmanouil Koutsangelas

Removing the cosmological bound on the axion scale in the Kim-Shifman-Vainshtein-Zakharov and Dine-Fischler-Srednicki-Zhitnitsky models

In this paper we investigate the <math><msub><mrow><mo>(</mo><mi>g</mi><mo>−</mo><mn>2</mn><mo>)</mo></mrow><mrow><mi>μ</mi></mrow></msub></math> discrepancy in the context of the R-parity conserving next-to-minimal supersymmetric Standard Model plus right-handed neutrinos superfields. The model has the ability to reproduce neutrino physics data and includes the interesting possibility to have the right-handed sneutrino as the lightest supersymmetric particle and a viable dark matter candidate. Since right-handed sneutrinos are singlets, no new contributions for <math><mi>δ</mi><msub><mrow><mi>a</mi></mrow><mrow><mi>μ</mi></mrow></msub></math> with respect to the MSSM and NMSSM are present. However, the possibility to have the right-handed sneutrino as the lightest supersymmetric particle opens new ways to escape Large Hadron Collider and direct detection constraints. In particular, we find that dark matter masses within <math><mn>10</mn><mo>≲</mo><msub><mrow><mi>m</mi></mrow><mrow><msub><mrow><mover><mrow><mi>ν</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mi>R</mi></mrow></msub></mrow></msub><mo>≲</mo><mn>600</mn></math> GeV are fully compatible with current experimental constraints. Remarkably, not only spectra with light sleptons are needed, but we obtain solutions with <math><msub><mrow><mi>m</mi></mrow><mrow><mover><mrow><mi>μ</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow></msub><mo>≳</mo><mn>600</mn></math> GeV in the entire dark matter mass range that could be probed by new <math><msub><mrow><mo>(</mo><mi>g</mi><mo>−</mo><mn>2</mn><mo>)</mo></mrow><mrow><mi>μ</mi></mrow></msub></math> data in the near future. In addition, dark matter direct detection experiments will be able to explore a sizable portion of the allowed parameter space with <math><msub><mrow><mi>m</mi></mrow><mrow><msub><mrow><mover><mrow><mi>ν</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mi>R</mi></mrow></msub></mrow></msub><mo>≲</mo><mn>300</mn></math> GeV, while indirect detection experiments will be able to probe a much smaller fraction within <math><mn>200</mn><mo>≲</mo><msub><mrow><mi>m</mi></mrow><mrow><msub><mrow><mover><mrow><mi>ν</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mi>R</mi></mrow></msub></mrow></msub><mo>≲</mo><mn>350</mn></math> GeV.

South Africa

Jong Soo Kim

Argentina

Daniel E. López-Fogliani

Andres D. Perez

Spain

Roberto Ruiz de Austri

The new ( −2) And Right-handed Sneutrino Dark Matter

We consider dark sectors with spontaneously broken gauge symmetries, where cascade decays of the dark sector fields naturally produce multi-Higgs boson final states along with dark matter. Our study focuses on two and three Higgs boson final states with missing energy using a multivariate analysis with boosted decision trees. We find that the di-Higgs boson channel is quite promising for the <math><mover><mi>b</mi><mo>¯</mo></mover><mi>b</mi><mo>+</mo><mi>γ</mi><mi>γ</mi></math> and <math><mover><mi>b</mi><mo>¯</mo></mover><mi>b</mi><mo>+</mo><mover><mo>ℓ</mo><mo>¯</mo></mover><mo>ℓ</mo></math> decay modes. The tri-Higgs boson final state with missing energy, on the other hand, appears to be beyond the reach of the LHC in analogous channels. This may change when fully hadronic Higgs boson decays are considered.

Philippines

Marvin Flores

Italy

Christian Gross

Finland

Oleg Lebedev

Subhadeep Mondal

Multi-Higgs boson probes of the dark sector

We test the impact of the ATLAS and CMS multilepton searches performed at the LHC with 8 as well as 13 TeV center-of-mass energy (using only the pre-2018 results) on the chargino and neutralino sector of the next-to-minimal supersymmetric Standard Model (NMSSM). Our purpose consists in analyzing the actual reach of these searches for a full model and in emphasizing effects beyond the minimal supersymmetric Standard Model (MSSM) that affect the performance of current (MSSM-inspired) electroweakino searches. To this end, we consider several scenarios characterizing specific features of the NMSSM electroweakino sector. We then perform a detailed collider study, generating Monte Carlo events through pythia and testing against current LHC constraints implemented in the public tool checkmate. We find e.g., that supersymmetric decay chains involving intermediate singlino or Higgs-singlet states can modify the naive MSSM-like picture of the constraints by inducing final states with softer or less easily identifiable SM particles—reversely, a compressed configuration with singlino next-to-lightest supersymmetric particle occasionally induces final states that are rich with photons, which could provide complementary search channels.

Florian Domingo

Víctor Martín Lozano

Pablo Martín-Ramiro

Confronting the neutralino and chargino sector of the NMSSM with the multilepton searches at the LHC

Several ideas exist on how the stringent mass limits from LHC on new colored particles can be avoided. One idea are the so-called “stealth” scenarios in which missing transversal energy (<math><msub><mi>E</mi><mi>T</mi></msub></math>) is avoided due a peculiar mass configuration. It is usually assumed that the cascade decay of the dominantly produced colored particle finishes in a two-body decay, where this mass configuration leads to a very small amount of <math><msub><mi>E</mi><mi>T</mi></msub></math>. We discuss here the potential impact of other decay channels, either loop-induced or via off-shell mediators. It is shown that those channels already become important even for moderate branching ratios of 10%. Larger branching ratios, in particular, into a photon can completely wash out all benefits of the stealth setup. We discuss this in a model-independent form, but also at the simplest supersymmetry stealth scenario which can be realized in the next-to-minimal supersymmetric standard model.

Manuel E. Krauss

Florian Staub

Illuminating stealth scenarios at the LHC

We investigate the discovery potential of a Stealth SUSY scenario involving squark decays by reconstructing the lightest neutralino decay products using a large-radius jet containing a high transverse momentum photon. Requirements on the event topology, such as photon and large-radius jet multiplicity result in less background than signal. We also estimated the sensitivity of our analysis and found that it has a better exclusion potential compared to the strongest existing search for the specific benchmark points considered here.

Deepak Kar

Constraining Stealth SUSY with illuminated fat jets at the LHC

We analyze the constraints on models of WIMP dark matter that can be derived from upper bounds on the “monojet” cross section at the LHC. These constraints were originally interpreted in the context of an effective field theory (EFT) where the Standard Model is extended by a dimension-6 operator whose coefficient is <math><mrow><mn>1</mn><mo>/</mo><msup><mrow><mi>Λ</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math>. We show that combining the 8 TeV data of the ATLAS and CMS collaborations improves the bounds only slightly. We then analyze this final state in the context of simplified models with an <math><mi>s</mi></math>-channel mediator. We show that if the decay width of the mediator is small, these simplified models can be accurately modeled by the effective field theory only if the mediator mass is above 5 TeV. Finally, we point out that even if the EFT accurately describes the <math><mi>O</mi><mo>(</mo><msup><mi>Λ</mi><mrow><mo>−</mo><mn>2</mn></mrow></msup><mo>)</mo></math> contributions to the matrix element, for values of <math><mi>Λ</mi></math> near the current bound it receives significant contributions of order <math><msup><mi>Λ</mi><mrow><mo>−</mo><mn>4</mn></mrow></msup></math>; in the context of simplified models, these correspond to diagrams where two mediators are exchanged. This observation challenges the internal consistency of the EFT description since dimension-8 operators, which would also contribute to <math><mi>O</mi><mo>(</mo><msup><mi>Λ</mi><mrow><mo>−</mo><mn>4</mn></mrow></msup><mo>)</mo></math> to the matrix element, are not included.

Swasti Belwal

Manuel Drees

Analysis of the bounds on dark matter models from monojet searches at the LHC

We consider pair-production of electroweakinos promptly decaying to light gravitinos in general gauge mediation scenarios within the minimal supersymmetric standard model. Typically the presence of photons and missing transverse momentum is the key signature for this kind of scenarios. We highlight where LHC analyses which have originally been designed to probe different scenarios provide complementary constraints with respect to the dedicated searches and we present the constraints on the parameter space.

Probing the electroweakino sector of general gauge mediation at the LHC