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.

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

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.

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

Nonperturbative effects have a small but nontrivial impact on the determination of the strong coupling from hadronic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> decay data. Several approaches have been proposed to take these into account, the two most important of which are the “truncated Operator Product Expansion (OPE)” approach and “Duality Violation (DV)-model” approach. Recently, Pich and Rodríguez-Sánchez have raised a number of criticisms of the latter approach, including, most notably, claims of the existence of (i) a supposed instability with respect to variations of the model for incorporating quark-hadron duality violations, and (ii) an alleged redundancy in the fitting strategy employed in the DV-model approach. In this paper, we investigate these criticisms and show they fail to survive more detailed scrutiny of the mathematical or numerical arguments that underpin them. We also show that, while the redundancy claim does not apply to the DV-model approach, it does, in fact, apply to the truncated OPE approach. In particular, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>α</mi><mi>s</mi></msub></math> value determined in the latter turns out to derive purely from perturbation theory, with no role played by the nonperturbative condensates determined in the rest of the analysis. This leads to the conclusion that a revision of the conventional understanding of what is learned from truncated OPE analyses is necessary and that only very limited self-consistency checks are possible within this framework. These observations raise new, nontrivial issues for the truncated OPE approach.

Brazil

Diogo Boito

United States

Maarten Golterman

Australia

Canada

Kim Maltman

Spain

Santiago Peris

Quark-hadron duality and the determination of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>α</mi><mi>s</mi></msub></math> from hadronic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> decay: Facts vs myths

In previous work we have combined the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>π</mi><mo>−</mo></msup><msup><mi>π</mi><mn>0</mn></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2</mn><msup><mi>π</mi><mo>−</mo></msup><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mn>0</mn></msup></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>π</mi><mo>−</mo></msup><mn>3</mn><msup><mi>π</mi><mn>0</mn></msup></math> spectral data obtained from hadronic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> decays measured by the ALEPH and OPAL experiments, together with electroproduction data for several of the subleading hadronic modes and BABAR data for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover></math> mode to construct an inclusive nonstrange vector spectral function entirely based on experimental data, with no Monte-Carlo generated input. In this paper, we include, for the first time, the Belle <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi><mo stretchy="false">→</mo><msup><mi>π</mi><mo>−</mo></msup><msup><mi>π</mi><mn>0</mn></msup><msub><mi>ν</mi><mi>τ</mi></msub></math> high-statistics decay data to construct a new inclusive nonstrange vector spectral function that combines more of the world’s available data. As no Belle data are at present available for the two <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>4</mn><mi>π</mi></math> modes, this requires a revised data analysis in comparison with our previous work. From the resulting new spectral function, we obtain a new determination of the strong coupling, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>α</mi><mi>s</mi></msub></math>, using our previously developed strategy based on finite-energy sum rules. We find, at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> mass scale, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>α</mi><mi>s</mi></msub><mo stretchy="false">(</mo><msubsup><mi>m</mi><mi>Z</mi><mn>2</mn></msubsup><mo stretchy="false">)</mo><mo>=</mo><mn>0.1159</mn><mo stretchy="false">(</mo><mn>14</mn><mo stretchy="false">)</mo></math>. We discuss the smaller central value and larger error of our new result compared to our previous result, showing the shifts to be due mainly to significant changes in updated HFLAV results for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>π</mi><mo>−</mo></msup><mn>3</mn><msup><mi>π</mi><mn>0</mn></msup></math> decay mode.

Aaron Eiben

Lucas M. Mansur

Strong coupling from hadronic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math>-decay data including <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi><mo stretchy="false">→</mo><msup><mi>π</mi><mo>−</mo></msup><msup><mi>π</mi><mn>0</mn></msup><msub><mi>ν</mi><mi>τ</mi></msub></math> from Belle

A key issue affecting the attempt to reduce the uncertainty on the Standard Model prediction for the muon anomalous magnetic moment is the current discrepancy between lattice-QCD and data-driven results for the hadronic vacuum polarization. Progress on this issue benefits from precise data-driven determinations of the isospin-limit light-quark-connected (lqc) and strange-plus-light-quark-disconnected (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">s</mi><mo>+</mo><mi>lqd</mi></mrow></math>) components of the related RBC/UKQCD windows. In this paper, using a strategy employed previously for the intermediate window, we provide data-driven results for the lqc and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">s</mi><mo>+</mo><mi>lqd</mi></mrow></math> components of the short- and long-distance RBC/UKQCD windows. Comparing these results with those from the lattice, we find significant discrepancies in the lqc parts but good agreement for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">s</mi><mo>+</mo><mi>lqd</mi></mrow></math> components. We also explore the impact of recent CMD-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mtext> </mtext><mtext> </mtext><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math> cross section results, demonstrating that an upward shift in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ρ</mi></math>-peak region of the type seen in the CMD-3 data serves to eliminate the discrepancies for the lqc components without compromising the good agreement between lattice and data-driven <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">s</mi><mo>+</mo><mi>lqd</mi></mrow></math> results.

Genessa Benton

United Kingdom

Alexander Keshavarzi

Data-driven results for light-quark connected and strange-plus-disconnected hadronic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>g</mi><mo>−</mo><mn>2</mn></mrow></math> short- and long-distance windows

A number of discrepancies have emerged between lattice computations and data-driven dispersive evaluations of the RBC/UKQCD intermediate-window-hadronic contribution to the muon anomalous magnetic moment. It is therefore interesting to obtain data-driven estimates for the light-quark-connected and strange-plus-disconnected components of this window quantity, allowing for a more detailed comparison between the lattice and data-driven approaches. The aim of this paper is to provide these estimates, extending the analysis to several other window quantities, including two windows designed to focus on the region in which the two-pion contribution is dominant. Clear discrepancies are observed for all light-quark-connected contributions considered, while good agreement with lattice results is found for strange-plus-disconnected contributions to the quantities for which corresponding lattice results exist. The largest of these discrepancies is that for the RBC/UKQCD intermediate window, where, as previously reported, our data-driven result, <math><msubsup><mi>a</mi><mi>μ</mi><mrow><mi>W</mi><mn>1</mn><mo>,</mo><mrow><mi>lqc</mi></mrow></mrow></msubsup><mo>=</mo><mn>198.9</mn><mo>(</mo><mn>1.1</mn><mo>)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>10</mn></mrow></msup></math>, is in significant tension with the results of 8 different recent lattice determinations. Our strategy is the same as recently employed in obtaining data-driven estimates for the light-quark-connected and strange-plus-disconnected components of the full leading-order hadronic vacuum polarization contribution to the muon anomalous magnetic moment. Updated versions of those earlier results are also presented, for completeness.

Data-driven estimates for light-quark-connected and strange-plus-disconnected hadronic <math><mi>g</mi><mo>−</mo><mn>2</mn></math> window quantities

We present the first data-driven result for <math><mrow><msubsup><mrow><mi>a</mi></mrow><mrow><mi>μ</mi></mrow><mrow><mi>win</mi><mo>,</mo><mi>lqc</mi></mrow></msubsup></mrow></math>, the isospin-limit light-quark connected component of the intermediate-window Hadronic-vacuum-polarization contribution to the muon anomalous magnetic moment. Our result, <math><mrow><mo>(</mo><mn>198.8</mn><mo>±</mo><mn>1.1</mn><mo>)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>10</mn></mrow></msup></mrow></math>, is in significant tension with eight recent mutually compatible high-precision lattice-QCD determinations, and provides enhanced evidence for a puzzling discrepancy between lattice and data-driven determinations of the intermediate-window quantity, one driven largely by a difference in the light-quark connected component.

Data-Driven Determination of the Light-Quark Connected Component of the Intermediate-Window Contribution to the Muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math>

Using standard mathematical methods for asymptotic series and the large-<math><mrow><msub><mrow><mi>β</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></math> approximation, we define a minimum distance between the fixed-order perturbative series and the contour-improved perturbative series in the strong coupling <math><msub><mi>α</mi><mi>s</mi></msub></math> for finite-energy sum rules as applied to hadronic <math><mi>τ</mi></math> decays. This distance is similar, but not identical, to the asymptotic separation of Hoang and Regner, which is defined in terms of the difference of the two series after Borel resummation. Our results confirm a nonzero nonperturbative result in <math><msub><mi>α</mi><mi>s</mi></msub></math> for this minimum distance as a measure of the intrinsic difference between the two series, as well as a conflict with the operator product expansion for contour-improved perturbation theory.

Difference between fixed-order and contour-improved perturbation theory

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

We describe how recent determinations of exclusive-mode contributions to <math><msubsup><mi>a</mi><mi>μ</mi><mrow><mi>LO</mi><mo>,</mo><mi>HVP</mi></mrow></msubsup></math>, the leading-order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon, can be used to provide, up to small electromagnetic (EM) corrections accessible from the lattice, a data-based dispersive determination of <math><mrow><msubsup><mrow><mi>a</mi></mrow><mrow><mi>μ</mi></mrow><mrow><mtext>lqc</mtext><mo>;</mo><mi>IL</mi></mrow></msubsup></mrow></math>, the isospin-limit, light-quark-connected contribution to <math><msubsup><mi>a</mi><mi>μ</mi><mrow><mi>LO</mi><mo>,</mo><mi>HVP</mi></mrow></msubsup></math>. Such a determination is of interest in view of the existence of a number of lattice results for this quantity, emerging evidence for a tension between lattice and dispersive determinations of <math><msubsup><mi>a</mi><mi>μ</mi><mrow><mi>LO</mi><mo>,</mo><mi>HVP</mi></mrow></msubsup></math>, and the desire to clarify the source of this tension. Taking as input for the small EM correction that must be applied to the purely data-driven dispersive determination the result <math><mo>−</mo><mn>0.93</mn><mo>(</mo><mn>58</mn><mo>)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>10</mn></mrow></msup></math> obtained in a recent BMW lattice study, we find <math><msubsup><mi>a</mi><mi>μ</mi><mrow><mtext>lqc</mtext><mo>;</mo><mi>IL</mi></mrow></msubsup></math> to be <math><mn>635.0</mn><mo>(</mo><mn>2.7</mn><mo>)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>10</mn></mrow></msup></math> if the results of Keshavarzi, Nomura, and Teubner are used for the exclusive-mode contributions and <math><mn>638.4</mn><mo>(</mo><mn>4.1</mn><mo>)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>10</mn></mrow></msup></math> if instead those of Davier, Höcker, Malaescu, and Zhang are used.

Data-based determination of the isospin-limit light-quark-connected contribution to the anomalous magnetic moment of the muon