In this study, we investigate the possibility of enhancing the di-jet resonance searches by tagging the final state radiation (FSR) jet using an event-level deep neural network. It is found that solely relying on the 4-momenta of the leading three jets allows the algorithm to achieve good discriminating power that can identify the hardest FSR jet in the signal while rejecting other soft jets. Once the invariant mass is corrected with the tagged FSR jet, the mass resolution of the signal is greatly enhanced, and the sensitivity of the search is also improved by more than 10%. By crafting the input variables carefully, the algorithm introduces minimal mass sculpting for the background, and its applicability extends to a broad mass range. This work proves that FSR jet tagging can potentially enhance di-jet resonance searches, suiting various stages of the physics programmes at the Large Hadron Collider (LHC) and High-Luminosity LHC (HL-LHC).

China

Bingxuan Liu

Yuxuan Shen

Yuanshunzi Sui

Enhancing di-jet resonance searches via a final-state radiation jet tagging algorithm * Bingxuan Liu is supported by Shenzhen Campus of the Sun Yat-sen University under project 74140-12255011, and by the Young Scientists Fund (C Class) of the National Natural Science Foundation of China (12405122). Both Yuxuan Shen and Yuanshunzi Sui are supported by College Students’ Innovative Entrepreneurial Training Plan Program

We investigated the effect of an isospin chemical potential ( $ \mu_{I} $ ) within the quark-meson model, which approximates quantum chromodynamics (QCD) by modeling low-energy phenomena such as chiral symmetry breaking and phase structure under varying conditions of temperature and chemical potential. Using the functional renormalization group (FRG) flow equations, we calculated the phase diagram in the chiral limit within the two-flavor quark-meson model in a finite $ \mu_{I} $ with $\textit{ρ}$ vector meson interactions. Fluctuation effects significantly decrease the critical chemical potential from the mean-field (MF) value $\mu_{I,{\rm MF}} \gt m_\rho$ to a lower value at which the $\textit{ρ}$ vector meson condensates alongside the chiral condensate once the isospin chemical potential exceeds the critical value $ \mu_{I}^{{\rm{crit}}} $ . This $\textit{ρ}$ condensation was investigated numerically for different meson coupling strengths. The $\textit{ρ}$ meson dominated region is delineated from other phases by a second-order phase transition at lower $ \mu_{I} $ and a first-order transition at slightly higher $ \mu_{I} $ .

Mohammed Osman

Defu Hou

Wentao Wang

United States

Hui Zhang

Functional renormalization group study of $\textit{ρ}$ meson condensate at a finite isospin chemical potential in the quark meson model * Supported in part by the National Key Research and Development Program of China (2022YFA1604900). This work is also partly supported by the National Natural Science Foundation of China (NSFC) (12435009, 12275104). Hui Zhang acknowledges the financial support from the Guangdong Major Project of Basic and Applied Basic Research (2020B0301030008) and the National Natural Science Foundation of China (12047523, 12105107)

We discuss dimensional continuation of the massless scalar field theory with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>i</mi><msup><mrow><mi>ϕ</mi></mrow><mrow><mn>5</mn></mrow></msup></mrow></math> interaction term. It preserves the so-called <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">P</mi><mi mathvariant="script">T</mi></mrow></math> symmetry, which acts by <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi><mo stretchy="false">→</mo><mo>−</mo><mi>ϕ</mi></math> accompanied by <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>i</mi><mo stretchy="false">→</mo><mo>−</mo><mi>i</mi></math>. Below its upper critical dimension <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>10</mn><mo>/</mo><mn>3</mn></math>, this theory has interacting infrared fixed points. We argue that the fixed point in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>d</mi><mo>=</mo><mn>2</mn></math> describes the nonunitary minimal conformal model <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>M</mi><mo stretchy="false">(</mo><mn>2</mn><mo>,</mo><mn>7</mn><mo stretchy="false">)</mo></math>. We identify the operators <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>ϕ</mi><mn>2</mn></msup></math> with the Virasoro primaries <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ϕ</mi><mrow><mn>1</mn><mo>,</mo><mn>2</mn></mrow></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ϕ</mi><mrow><mn>1</mn><mo>,</mo><mn>3</mn></mrow></msub></math>, respectively, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>i</mi><msup><mi>ϕ</mi><mn>3</mn></msup></math> with a quasiprimary operator, which is a Virasoro descendant of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ϕ</mi><mrow><mn>1</mn><mo>,</mo><mn>3</mn></mrow></msub></math>. Our identifications appear to be consistent with the operator product expansions and with considerations based on integrability. Using constrained Padé extrapolations, we provide estimates of the critical exponents in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>d</mi><mo>=</mo><mn>3</mn></math>. We also comment on possible lattice descriptions of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>M</mi><mo stretchy="false">(</mo><mn>2</mn><mo>,</mo><mn>7</mn><mo stretchy="false">)</mo></math> and discuss RG flows to and from this conformal field theory (CFT). Finally, we conjecture that the minimal models <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>M</mi><mo stretchy="false">(</mo><mn>2</mn><mo>,</mo><mn>2</mn><mi>n</mi><mo>+</mo><mn>1</mn><mo stretchy="false">)</mo></math> are described by the massless scalar field theories with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>i</mi><msup><mi>ϕ</mi><mrow><mn>2</mn><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msup></math> interaction terms.

Andrei Katsevich

Igor Klebanov

Zimo Sun

Grigory Tarnopolsky

Towards a Quintic Ginzburg-Landau Description of the (2,7) Minimal Model

We explore the detection prospects for a minimal secluded dark matter model, where a fermionic dark matter particle interacts with the Standard Model (SM) via a kinetically mixed dark photon. We focus on scenarios where the dark photon decays visibly, making it a prime target for beam-dump experiments. In this model, the dark matter relic abundance can be achieved by a variety of mechanisms: freeze-in, out-of-equilibrium freeze-out, and secluded freeze-out. We demonstrate that the secluded freeze-out regime in the considered mass range is now entirely excluded by a combination of direct and indirect detection constraints. Moreover, we show that future direct detection and intensity frontier experiments offer complementary sensitivity to this minimal model in the parameter space where the hidden sector never enters equilibrium with the SM. In out-of-equilibrium freeze-out scenarios, nuclear-recoil direct detection experiments can still access signals above the neutrino fog that are mediated by dark photons that are too weakly coupled to be detected in future beam dump experiments. Meanwhile, future beam dump experiments provide a powerful probe of the freeze-in parameter space in this model, which is largely inaccessible to direct detection experiments. Notably, even in the absence of a future observation in direct detection experiments, a dark photon discovery remains possible at SHiP, DUNE, LHCb, and DarkQuest within this minimal dark matter model.

Ahmed Alenezi

Cari Cesarotti

Stefania Gori

Jessie Shelton

Discovery prospects for a minimal dark matter model at cosmic and intensity frontier experiments

We study the QCD axion arising from the 5th component of a bulk U(1) gauge field in a five-dimensional warped grand unified theory, and determine the viable range of the axion decay constant $\textit{f}$ . Unlike flat extra dimensions, where gauge couplings run quickly above the Kaluza-Klein (KK) scale, the logarithmic running in warped geometries permits substantially smaller $\textit{f}$ while preserving perturbative gauge coupling unification. However, bulk tree-level contributions to the gauge coupling — interpreted holographically as CFT renormalization — place a lower bound on $\textit{f}$ . We find that the conventional QCD axion window 10 GeV ≲ $\textit{f}$ ≲ 10 GeV is readily compatible without losing perturbativity, provided the AdS curvature is near the Planck scale. Thus, the 5D warped orbifold GUT naturally accommodates a high-quality QCD axion in a grand unified theory that provides an effective description of string-theoretic warped flux compactifications, admitting complementary geometric and holographic descriptions of the axion.

Gongjun Choi

Tony Gherghetta

An extra-dimensional axion in a 5D warped orbifold GUT

We propose and evaluate a source-equals-detector search for the deexcitation of the long-lived isomer <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi>Ta</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>180</mn><mi mathvariant="normal">m</mi></mrow></mmultiscripts></mrow></math> in natural tantalum (Ta), using a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math>-ray transition-edge-sensor (TES) array. Two capabilities absent in conventional high-purity germanium (HPGe) searches are exploited: (i) near-unity containment of low-energy secondaries [internal-conversion (IC) electrons and characteristic x-rays] and of the nuclear recoil, enabling a calorimetric, event-by-event measurement of the total deposited energy in the absorber; and (ii) a delayed-coincidence tag using the subsequent <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi>Ta</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>180</mn></mrow></mmultiscripts></mrow></math> electron-capture (EC) decay to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi>Hf</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>180</mn></mrow></mmultiscripts></mrow></math>. We evaluate the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mi>σ</mi></math> discovery reach for IC and for dark-matter (DM)-induced deexcitation in two benchmark scenarios: a strongly interacting DM subcomponent and inelastic DM with off diagonal couplings. Using a background model based on intrinsic radioactivity in the Ta absorber and realistic detector performance, we show that arrays with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>N</mi></mrow><mrow><mi>TES</mi></mrow></msub><mo>=</mo><mn>256</mn></mrow></math> and 1,000 pixels can reach the theoretically expected IC half-life within 2.6 yr and 0.66 yr, respectively. For an array with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>N</mi><mi>TES</mi></msub><mo>=</mo><msup><mn>10</mn><mn>4</mn></msup></math> and a five-year exposure, the projected sensitivity to DM-induced de-excitation surpasses limits inferred from HPGe nonobservations of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi>Ta</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>180</mn><mi mathvariant="normal">m</mi></mrow></mmultiscripts></mrow></math> and probes regions of parameter space not covered by current direct-detection experiments.

Japan

A. Gando

K. Ichimura

K. Ishidoshiro

T. Kikuchi

T. Kishimoto

A. Takeuchi

R. Sato

R. Smith

Probing internal conversion and dark-matter-induced deexcitation of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi>Ta</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>180</mn><mi mathvariant="normal">m</mi></mrow></mmultiscripts></mrow></math> with a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math>-ray TES array

We report the refined dark-photon exclusion bound from Dark SRF’s pathfinder run. Our new result is driven by improved theoretical modeling of frequency instability in high-quality resonant experiments. Our analysis leads to a constraint that is an order of magnitude stronger than previously reported (corresponding to a signal-to-noise ratio that is 4 orders of magnitude larger). This result represents the world-leading constraint on non-dark-matter dark photons over a wide range of masses below <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>6</mn><mtext> </mtext><mtext> </mtext><mi mathvariant="normal">μ</mi><mi>eV</mi></math> and translates to the best laboratory-based limit on the photon mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>γ</mi></mrow></msub><mo>&lt;</mo><mn>2.9</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>48</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi mathvariant="normal">g</mi></mrow></math>.

Saarik Kalia

Zhen Liu

Bianca Giaccone

Oleksandr Melnychuk

Roman Pilipenko

Asher Berlin

Anson Hook

Sergey Belomestnykh

Crispin Contreras-Martinez

Daniil Frolov

Timergali Khabiboulline

Yuriy Pischalnikov

Sam Posen

Oleg Pronitchev

Vyacheslav Yakovlev

Anna Grassellino

Roni Harnik

Alexander Romanenko

Improved Dark Photon Sensitivity from a Superconducting-Radio-Frequency-Cavity Experiment

We study the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>ϕ</mi><mi>η</mi><msup><mi>π</mi><mn>0</mn></msup></math> reaction measured recently by the BESIII Collaboration with high precision, paying attention to three important aspects: (1) the production of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>a</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>980</mn><mo stretchy="false">)</mo></math> in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>π</mi><mn>0</mn></msup><mi>η</mi></math> mass distributions, with the typical narrow width observed in isospin violating processes; (2) the origin of two peaks in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi><msup><mi>π</mi><mn>0</mn></msup></math> mass distributions that were branded as “non-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math>” contribution in the experimental analysis; (3) the existence of two triangle mechanisms developing a triangle singularity at the same energy where the non-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math> contribution peaks in the experiment. However, we also show that the strength of these peaks is very small relative to the observed ones, a feature that is tied to the experimental technique used to identify the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math> looking at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup></math> in a narrow window of invariant mass around the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math> mass. We suggest that these triangle singularities could be observed with other methods to identify the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math>.

Hai-Peng Li

Wei-Hong Liang

Chu-Wen Xiao

Spain

Eulogio Oset

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>a</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>980</mn><mo stretchy="false">)</mo></math> production, triangle singularity, and non-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi></math> background in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>ϕ</mi><mi>η</mi><msup><mi>π</mi><mn>0</mn></msup></math> reaction

A correction to this paper has been published: https://doi.org/10.1007/JHEP01(2025)012

Lance Dixon

Shuo Xin

Erratum to: A two-loop four-point form factor at function level

Conventional Lagrangian formulations of gauge and gravity theories emphasize compactness and off-shell symmetry. This often obscures the structure of on-shell physical observables. In this work, we present a constructive framework that elevates gauge-invariant scattering amplitudes to the defining data for quantum field theory actions, including effective field theories. Focusing on double-copy theories, we promote color-dual amplitude numerators to quantum operators. This enables the systematic identification of novel local operator content at each multiplicity and the construction of double-copy-compatible actions. By applying this framework to the well-established double-copy relationship between Einstein gravity and Yang-Mills theory, which holds for all-multiplicity tree-level amplitudes, we demonstrate a systematic path to constructing the operator expansion of $$ \sqrt{-g}R $$ from factorized gauge-theory components. This clarifies how gravitational interactions can be understood as emerging from simpler gauge-theoretic structures at the action level. This formalism extends color-kinematics duality from amplitude data to operator constructions, naturally realizing the double copy at the level of actions and asymptotic quantum states. We illustrate the method with Yang-Mills theory, Einstein gravity, and its application to generating higher-derivative operators inspired by Z-theory and open superstring amplitudes. This work provides a concrete bridge between structured amplitudes and effective actions, offering a physically grounded alternative to traditional EFT basis-building. It reveals at the operator level deep structural connections between gauge theory and gravity (connections long recognized in scattering amplitudes) from fundamental interactions to their quantum state descriptions and higher-derivative extensions.

John Carrasco

Suna Zekioğlu

The double copy effective action: a quantum (chromodynamics) approach to space-time