Axions, grand unification, and string theory are each compelling extensions of the Standard Model. We show that combining these frameworks imposes strong constraints on the QCD axion mass. Using perturbative unitarity arguments and explicit string compactifications—such as those from the Kreuzer-Skarke (KS) type IIB ensemble—we find that the axion mass is favored to lie within the range <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>11</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi><mo>≲</mo><msub><mi>m</mi><mi>a</mi></msub><mo>≲</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>8</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></math>. This range is directly relevant for near-future axion dark matter searches, including ABRACADABRA/DMRadio and CASPEr. We argue that grand unification and the absence of proton decay suggest a compactification volume that keeps the string scale above the unification scale (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><msup><mn>10</mn><mn>16</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>), which in turn limits how heavy the axion can be. The same requirements limit the KS axiverse to have at most <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><mn>47</mn></math> axions. As an additional application of our methodology, we search for axions in the KS axiverse that could explain the recent Dark Energy Spectroscopic Instrument hints of evolving dark energy but find none with high enough decay constant (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mi>a</mi></msub><mo>≳</mo><mn>2.5</mn><mo>×</mo><msup><mn>10</mn><mn>17</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>); we comment on why such high decay constants and low axion masses are difficult to obtain in string compactifications more broadly.

United States

Joshua N. Benabou

Katherine Fraser

United Kingdom

Mario Reig

Benjamin R. Safdi

String theory and grand unification suggest a submicroelectronvolt QCD axion

We study the semileptonic decays of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msubsup><mrow><mi mathvariant="normal">Ξ</mi></mrow><mrow><mi>b</mi></mrow><mrow><msup><mrow><mo stretchy="false">(</mo></mrow><mrow><mo>′</mo></mrow></msup><mo stretchy="false">)</mo></mrow></msubsup><mo stretchy="false">→</mo><msubsup><mrow><mi mathvariant="normal">Ξ</mi></mrow><mrow><mi>c</mi></mrow><mrow><msup><mrow><mo stretchy="false">(</mo></mrow><mrow><mo>′</mo></mrow></msup><mo stretchy="false">)</mo></mrow></msubsup><mo>ℓ</mo><msub><mrow><mover accent="true"><mrow><mi>ν</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover></mrow><mrow><mo>ℓ</mo></mrow></msub></mrow></math> in all lepton channels. To do this, we first obtain the form factors defining these decay modes within the framework of QCD sum rules. Then, using the transition form factors, we compute the decay widths and branching fractions for all lepton channels and compare the results of our calculations with those obtained from other theoretical methods. We also estimate the branching ratios and the ratio of branching fractions at different leptonic channels to provide useful information for future experiments may be planned at different colliders. Such comparison will provide valuable information about the consistency/inconsistency of the Standard Model theory predictions with experimental data in weak semileptonic single heavy baryon decays.

Iran

Z. Neishabouri

Türkiye

K. Azizi

Investigation of the semileptonic decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msubsup><mrow><mi mathvariant="normal">Ξ</mi></mrow><mrow><mi>b</mi></mrow><mrow><msup><mrow><mo stretchy="false">(</mo></mrow><mrow><mo>′</mo></mrow></msup><mo stretchy="false">)</mo></mrow></msubsup><mo stretchy="false">→</mo><msubsup><mrow><mi mathvariant="normal">Ξ</mi></mrow><mrow><mi>c</mi></mrow><mrow><msup><mrow><mo stretchy="false">(</mo></mrow><mrow><mo>′</mo></mrow></msup><mo stretchy="false">)</mo></mrow></msubsup><mo>ℓ</mo><msub><mrow><mover accent="true"><mrow><mi>ν</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover></mrow><mrow><mo>ℓ</mo></mrow></msub></mrow></math>

We study the purely gravitational signatures of dark matter from the ultralight to the ultraheavy mass range in proposed long-baseline atom gradiometers, focusing on terrestrial designs, such as AION-km and MAGIS-km, as well as space-based concepts, such as MAGIS-space, AEDGE and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>AEDGE</mi><mo>+</mo></mrow></math>. Due to its exceptional acceleration sensitivity and depending on astrophysical backgrounds, a detector similar to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>AEDGE</mi><mo>+</mo></mrow></math> could detect a dark matter subcomponent which constitutes <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>10</mn><mo>%</mo><mo stretchy="false">)</mo></math> of the local dark matter energy density and is populated by compact clumps of mass between <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mn>6</mn></msup><mtext> </mtext><mtext> </mtext><mi>kg</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mn>10</mn></msup><mtext> </mtext><mtext> </mtext><mi>kg</mi></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>25</mn></mrow></msup><msub><mi>M</mi><mo stretchy="false">⊙</mo></msub><mo>≲</mo><mspace linebreak="goodbreak"></mspace><mi>M</mi><mo>≲</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>21</mn></mrow></msup><msub><mi>M</mi><mo stretchy="false">⊙</mo></msub></math>) in an otherwise unexplored region of dark matter model space. Furthermore, because the gravitational observable depends on the relative gravitational time delay measured by spatially separated atomic clouds, we find that atom gradiometers are parametrically more sensitive than laser interferometers, such as LIGO and LISA, to fast-oscillating spacetime perturbations sourced by energy density and pressure fluctuations of ultralight dark matter. Depending on astrophysical backgrounds, a detector akin to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>AEDGE</mi><mo>+</mo></mrow></math> could probe a DM overdensity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>10</mn><mo stretchy="false">)</mo></math> times the local dark matter energy density for masses <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>m</mi><mo>≲</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>17</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></math>.

Leonardo Badurina

Yufeng Du

Vincent S.H. Lee

Yikun Wang

Kathryn M. Zurek

Detecting gravitational signatures of dark matter with atom gradiometers

We present a very detailed derivation of solutions describing hairy black holes within the gravity-coupled Weinberg-Salam theory, which were previously reported in Gervalle and Volkov [Black holes with electroweak hair, <a href="http://dx.doi.org/10.1103/PhysRevLett.133.171402">Phys. Rev. Lett. 133, 171402 (2024)</a>]. These black holes support a strong magnetic field that polarizes the electroweak vacuum and creates a condensate of massive fields carrying superconducting currents along the black hole horizon. The currents, in turn, generate a “corona” of magnetic vortex segments attached to the horizon at both ends. The condensate and corona together constitute the black hole hair. The extremal solutions approach, in the far field, the magnetic Reissner-Nordström configuration, with a total mass that is lower than the total charge, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>M</mi><mo>&lt;</mo><mo stretchy="false">|</mo><mi>Q</mi><mo stretchy="false">|</mo></math>, due to the negative Zeeman energy of the condensate. This makes the removal of the hair energetically unfavorable. The maximally hairy black holes exhibit masses comparable to terrestrial values, with approximately 11% of their total mass stored in the hair. Given that these solutions arise within a well-tested theoretical framework, they are likely to have physical relevance.

France

Romain Gervalle

CERN

Mikhail S. Volkov

Black holes with electroweak hair: The detailed derivation

Correlators at finite density and temperature encode important information about a physical system, such as transport and causality. For a massive gas of particles in the relaxation time approximation of kinetic theory, we provide complete analytic results for all first order transport coefficients, including thermoelectric coefficients. We demonstrate the first complete picture of the complex structure of the correlators as a function of mass, providing an interpretation in terms of the causal structure of light cones. We provide a simple criterion to extract the effective light cone velocity from the cut of the retarded correlator.

Slovenia

Matej Bajec

Alexander Soloviev

Relaxation for massive particles: Transport and causality

We present a new equation of state for QCD in which the temperature <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi></math> and the three chemical potentials for baryon number <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>μ</mi><mi>B</mi></msub></math>, electric charge <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>μ</mi><mi>Q</mi></msub></math>, and strangeness <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>μ</mi><mi>S</mi></msub></math> can be varied independently. This result is based on a generalization of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>T</mi><mo>′</mo></msup></math> expansion scheme, thanks to which the diagonal <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>μ</mi><mi>B</mi></msub></math> extrapolation was pushed up to a baryo-chemical potential <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>μ</mi><mi>B</mi></msub><mo>/</mo><mi>T</mi><mo>∼</mo><mn>3.5</mn></math> for the first time. This considerably extended the coverage of the Taylor expansion, limited to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>μ</mi></mrow><mrow><mi>B</mi></mrow></msub><mo>/</mo><mi>T</mi><mo>&lt;</mo><mn>2.5</mn><mi>–</mi><mn>3</mn></mrow></math>. As a consequence, we are able to offer a substantially larger coverage of the four-dimensional QCD phase diagram as well, compared to previously available Taylor expansion results. Our findings are based on new continuum estimated lattice data on the full set of second- and fourth-order fluctuations.

Ahmed Abuali

Germany

Szabolcs Borsányi

Hungary

Zoltán Fodor

Johannes Jahan

Micheal Kahangirwe

Italy

Paolo Parotto

Attila Pásztor

Claudia Ratti

Hitansh Shah

Seth A. Trabulsi

New 4D lattice QCD equation of state: Extended density coverage from a generalized <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>T</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math> expansion

The ambitious physics program planned for the Future Circular Collider electron-positron phase imposes stringent constraints on detector performance. This study systematically investigates how different detector configurations impact jet flavor identification and their effects on high-profile physics analyses. Using Higgs boson coupling measurements and searches for invisible Higgs decays as benchmarks, we evaluate the sensitivity of these analyses to variations in tracker and calorimeter detector properties. We examine modifications to single-point resolution, material budget, silicon layer placement, and particle identification capabilities, quantifying their effects on flavor-tagging performance. Additionally, we present the first comprehensive study of Higgs-to-invisible decay detection using full detector simulation, providing insights for optimizing detector designs at lepton colliders.

Haider Abidi

Ketevi A. Assamagan

Diallo Boye

Elizabeth Brost

Viviana Cavaliere

Anna E. Connelly

George Iakovidis

Ang Li

Marc-André Pleier

Andrea Sciandra

Scott Snyder

Robert Szafron

Abraham Tishelman-Charny

Iza Veliscek

Michele Selvaggi

FCC feasibility studies: Impact of tracker- and calorimeter-detector performance on jet flavor identification and Higgs physics analyses

A metric on the space of collider physics data enables analysis of its geometrical properties, like dimensionality or curvature, as well as quantifying the density with which a finite, discrete ensemble of data samples the space. We provide the first systematically-improvable precision calculations on this dataspace, presenting predictions resummed to next-to-leading logarithmic accuracy, using the spectral energy mover’s distance (SEMD) as its metric. This is accomplished by demonstration of factorization of soft and collinear contributions to the metric at leading power and renormalization group evolution of the single-scale functions that are present in the factorization theorem. As applications of this general framework, we calculate the two-point correlator between pairs of jets on the dataspace, and the measure of the non-Gaussian fluctuations in a finite dataset. For the non-Gaussianities, our calculations validate the existence of a universal structure that had been previously observed in simulated data. As by-products of this analysis, we also calculate the two-loop anomalous dimension of the SEMD metric and show that the original energy mover’s distance metric is identical to the SEMD through next-to-next-to-leading logarithmic accuracy.

Andrew J. Larkoski

Factorization for collider dataspace correlators

We develop a novel holographic dictionary for the thermodynamics of black holes with Lifshitz and hyperscaling violating asymptotics, generalizing the dictionary for anti—de Sitter black holes. Using our dictionary we show that the holographic Euler equation is dual to a generalized Smarr formula for these black holes, and we find a precise match between the extended bulk and boundary first law. Notably, the dictionary for the central charge appearing in the Euler relation depends on the hyperscaling violating parameter, but not on the Lifshitz dynamical exponent.

Austria

Wan Cong

Czechia

David Kubizňák

Canada

Robert B. Mann

Netherlands

Manus R. Visser

Holographic dictionary for Lifshitz and hyperscaling violating black holes

Masses, magnetic moments, and color-spin structures of nonstrange and strange tetraquarks with two heavy quarks are systematically studied in a QCD string picture with a chromomagnetic interaction. Our mass computations, combined with weak and radiative decays, indicate that there are two doubly heavy tetraquarks, the bottom-charmed tetraquark <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mrow><mi>c</mi><mi>b</mi></mrow></msub><mo stretchy="false">(</mo><mn>7173</mn><mo>,</mo><mn>0</mn><msup><mn>1</mn><mo>+</mo></msup><msup><mo stretchy="false">)</mo><mn>0</mn></msup></math> and the doubly bottom tetraquark <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mrow><mi>b</mi><mi>b</mi></mrow></msub><mo stretchy="false">(</mo><mn>10406</mn><mo>,</mo><mn>0</mn><msup><mn>1</mn><mo>+</mo></msup><msup><mo stretchy="false">)</mo><mo>−</mo></msup></math>, that are stable against strong decay, having lifetimes of 0.069 and 326 fs, respectively. Magnetic moments are also computed and are found to be sensitive to chromomagnetic mixing of the color-spin configurations of these tetraquarks, making them a valuable probe to experimentally detect the nontrivial color configuration <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mn>6</mn><mi>c</mi></msub><mo stretchy="false">⊗</mo><msub><mover accent="true"><mn>6</mn><mo stretchy="false">¯</mo></mover><mi>c</mi></msub></math>.