HEP Phenomenology·hep-ph

Mon·Aug 17, 2026Monday·August 17, 2026

25 papers—18 primary·7 cross-listed

01
Axion Isocurvature Perturbations Survive the Scaling Evolution of Axion Domain Walls
Naoya Kitajima🇯🇵 · Junseok Lee🇯🇵 · Kai Murai🇯🇵 · Fuminobu Takahashi🇯🇵 · Wen Yin🇯🇵
We revisit the evolution of axion domain walls seeded by inflationary fluctuations. In our previous work, we showed that such domain-wall networks retain superhorizon correlations even after entering the scaling regime. We extend our previous analysis to the case with large initial fluctuations, where many minima of the axion potential are already populated when the axion starts to oscillate. Although the conventional misalignment contribution can have suppressed long-wavelength isocurvature perturbations when many vacua are averaged over, axions produced by domain-wall collapse provide an additional contribution that can dominate when the walls enter the scaling regime before annihilation. In particular, the biased vacuum energy released during wall annihilation inherits the superhorizon correlations of the inflationary fluctuations and transfers them to the axion energy density. We find that sizable isocurvature perturbations can therefore survive even after the walls annihilate. We also discuss generic isocurvature constraints on dark matter produced by domain-wall collapse.
hep-phastro-ph.CO1 citation
02
Gravitational Waves from Dimension-6 Assisted Peccei - Quinn Phase Transitions
Nico Benincasa🇨🇳 · Kristjan Müürsepp🇪🇪
We consider a simple model-independent extension of the minimal KSVZ axion model, augmenting the Peccei - Quinn effective potential with a dimension-6 operator invariant under the Peccei - Quinn symmetry. We show that this operator can trigger a first-order phase transition and study its cosmological consequences. We map out the parameter space, consistent with present observational constraints, in which the phase transition produces a gravitational wave signal observable at current and future interferometers, and we investigate the resulting dark matter phenomenology. Finally, we present specific ultraviolet completions that generate the dimension-6 operator, each leading to distinct phenomenological signatures, which motivates our model-independent approach.
hep-phastro-ph.CO0 citations
03
Beyond $Δ m^{2}$ : Absolute Mass Sensitivity in Neutrino Oscillations
Gustavo F. S. Alves🇺🇸 · André L. C. de Gouvêa🇺🇸 · Joshua Kaler🇺🇸 · Shirley Weishi Li🇺🇸 · Pedro A. N. Machado🇺🇸
Conventional wisdom says that neutrino oscillations measure only mass-squared differences and not the absolute neutrino mass scale. This is true, however, only at leading order in the expansion parameters $m_{i} / E$ , the ratios of the neutrino masses $m_{i}$ ( $i = 1, 2, 3$ ) to the neutrino energy $E$ . At next-to-leading order, the oscillation phase includes terms proportional to $m_{i}^{4} - m_{j}^{4} = Δ m_{ij}^{2} (m_{i}^{2} + m_{j}^{2})$ , and is therefore sensitive to the absolute mass scale. In this paper, we derive the next-to-leading-order corrections using a wave-packet treatment and taking into account the neutrino-production kinematics. We then apply this result to reactor antineutrinos and find that the JUNO experiment is sensitive to neutrino masses of a few hundred keV. While not competitive with existing bounds from beta decay, electron capture, and cosmology, neutrino oscillations provide a novel, complementary probe of the neutrino mass scale, with sensitivity to a different combination of neutrino masses.
hep-phhep-ex0 citations
04
Strong $C P$ and Quark Mass Hierarchies from Modular Invariance
Xiang-Gan Liu🇺🇸 · Michael Ratz🇺🇸 · Alexander Stewart🇺🇸
The strong $C P$ problem and quark mass hierarchies can probe the same ultraviolet structure. We show this by extending modular strong- $C P$ solutions to non-Abelian finite modular symmetries. This reveals a previously overlooked modular-anomaly condition from the finite representations. Regularity removes the dependence of the QCD angle on the $C P$ -breaking modulus, yielding $θ ˉ = 0$ . For positive modular weight, it also forces the quark Yukawa determinant to vanish at the cusp. This leads to pronounced mass hierarchies among the quarks. We further stress that modular symmetries act as R-symmetries. Under moderate additional assumptions, this renders the QCD angle independent of the dilaton. An explicit model illustrates the mechanism.
hep-ph1 citation
05
Systematic study of fully heavy-flavored tetraquarks $Q_{1} Q_{2} Q ˉ_{1} Q ˉ_{2} (Q_{1; 2} \in {b; c})$ : Mass spectra, threshold analysis, and confrontation with LHC data
André Aimé Atangana Likéné🇨🇭 · Alexis Franck Rothen🇨🇭 · Dieudonné Nga Ongodo🇨🇲 · Germain Hubert Ben-Bolie🇨🇲 · Tobias Golling🇨🇭
Experimental searches for fully heavy tetraquark states are actively pursued at the LHC. The LHCb, CMS, and ATLAS collaborations have investigated fully charmed $cc c ˉ c ˉ$ , mixed $b c b ˉ c ˉ$ , and fully bottom $bb b ˉ b ˉ$ tetraquarks. In particular, narrow structures such as $X (6200)$ , $X (6900)$ , and $X (7300)$ observed in the di- $J / ψ$ mass spectrum have stimulated considerable theoretical interest. We employ a nonrelativistic diquark-antidiquark model to investigate the mass spectra of ground ( $1 S$ ) and excited ( $1 P$ , $2 S$ , $1 D$ , $2 P$ , $3 S$ , and $4 S$ ) fully heavy tetraquark states. The tetraquarks are modeled as color-singlet bound states of axial-vector diquarks and antidiquarks in the $3 ˉ$ and $3$ color representations. The Schrödinger equation is solved numerically using a modified Cornell potential and the three-point central difference method, while spin-dependent interactions are treated nonperturbatively. We investigate a broad range of $J^{P C}$ quantum numbers for $S$ -, $P$ -, and $D$ -wave states. The predicted masses are compared with recent LHC observations and other theoretical calculations, and the stability of the states against strong fall-apart decays is examined. Our results support the interpretation of several observed structures as different excitations of fully charmed tetraquarks and provide useful predictions for their experimental identification.
hep-phPRD(2026)·1 citation
06
Exploring the chiral magnetic effect in Au+Au collisions at $s_{N N} = 7.7 - 200$ GeV through Chiral Anomaly Transport
Zilin Yuan🇨🇳 · Anping Huang🇨🇳 · Guo-Liang Ma🇨🇳 · Mei Huang🇨🇳 · Guannan Xie🇨🇳
High-energy heavy-ion collisions have the potential to create local domains of chirality-imbalanced quarks, reflecting the topological characteristics of quantum chromodynamics. This phenomenon can potentially induce local $P$ and $C P$ violations in the quark-gluon plasma. The Chiral Magnetic Effect (CME) predicts an electric charge separation along the intense magnetic field generated during these collisions, which is typically investigated through charge-dependent azimuthal correlations ( $Δ γ$ ). In this work, we investigate the CME in Au+Au collisions at $s_{N N} = 7.7 - 200$ GeV using a multiphase transport (AMPT) model equipped with a Chiral Anomaly Transport (CAT) module. we employ two independent methods: direct subtraction of the correlator $⟨ N_{p a r t} Δ γ ⟩$ between simulations with zero and finite chiral chemical potential $μ_{5}$ , and the event-shape-selection (ESS) approach. Our results reveal a significant CME signal within the energy range of 11.5-27 GeV and the centrality range of $20 - 50%$ , where the AMPT model aligns well with STAR experimental data. Furthermore, the CME fractions extracted by both methods are consistent within uncertainties across these energies. However, the CME signal disappears at both 7.7 and 200 GeV. These findings underscore that the observability of the CME critically depends on both the dynamic evolution of the magnetic field and the chemical freeze-out time of the partonic phase, which vary significantly with collision energy.
hep-ph0 citations
07
Probing the Single Production of First-Generation Singlet Vector-like Leptons at Future $e^{+} e^{-}$ Colliders
Yao-Bei Liu🇨🇳 · Stefano Moretti🇬🇧
We study the single production of first-generation weak-isosinglet vector-like leptons (VLLs) at future $e^{+} e^{-}$ colliders, considering the channels $e^{+} e^{-} \to e^{\pm} E^{\mp}$ with $E^{\pm} \to W^{\pm} ν_{e}$ and $E^{\pm} \to e^{\pm} Z$ . For the heavy VLL masses under consideration, the decay products of the highly boosted $W$ and $Z$ bosons merge into a single fat-jet, providing a powerful handle for signal identification and background suppression. A comprehensive Monte Carlo simulation is carried out at $s = 1$ TeV at the International Linear Collider (ILC) and 1.5 TeV at the Compact Linear Collider (CLIC). The $2 σ$ exclusion and $5 σ$ discovery reaches are determined as functions of the integrated luminosity and the mixing parameter $sin θ_{L}$ for representative benchmark masses. Our results show that future $e^{+} e^{-}$ colliders can effectively probe the first-generation singlet VLL scenario through these channels. The 1 TeV ILC can probe masses up to 900 GeV, while the 1.5 TeV CLIC extends the reach to 1400 GeV, surpassing existing limits from hadron colliders and complementing constraints from electroweak precision measurements.
hep-ph0 citations
08
Simultaneous production of a $W$ boson and a charmed hadron at the LHC in general-mass variable-flavour-number scheme
Ville Alanko · Ilkka Helenius🇫🇮 · Hannu Paukkunen🇫🇮
The simultaneous production of a $W^{\pm}$ boson and a charmed hadron in proton-proton collisions offers a potential probe for constraining the strange quark parton distribution functions (PDFs). We study these processes at next-to-leading order in perturbative Quantum Chromodynamics within the general-mass variable-flavor-number scheme. By considering ratios of cross-section between oppositely charged mesons, uncertainties associated with unphysical scale choices and fragmentation functions are shown to effectively cancel out, leaving the uncertainty originating from the PDFs as the dominant one. By comparing our calculations with CT18A, MSHT20 and NNPDF4.0 PDFs with the recent ATLAS measurement at $s = 13 TeV$ we find that CT18A, which imposes zero strangeness asymmetry, agrees best with the data, while MSHT20 and NNPDF4.0, both of which allow for a non-zero strangeness asymmetry, exhibit greater tension with the ATLAS data. The sensitivity to the strangeness asymmetry is further confirmed by the PDF reweighting methods. We also study the impact of possible intrinsic charm content of the proton finding no significant sensitivity. Finally, we explore the possibility of measuring these processes in proton-lead collisions. With the estimated detector efficiencies and projected luminositites at the high-luminosity LHC, these processes should be visible, yet with a rather limited constraining power for nuclear PDFs.
hep-ph0 citations
09
Nonstandard Solution for Anomaly Cancellation as Seesaw Neutrino Origin in the SM
Zi-Yue Zou🇨🇳 · Chia-Wei Liu🇨🇳 · Zhong-Lv Huang🇨🇳 · Xiao-Gang He🇨🇳
For fixed Standard Model (SM) non-Abelian representations of 15 chiral fermions with arbitrary hypercharges, anomaly cancellation admits the usual assignment and a distinct nonstandard solution. In the latter, the colored exotic quark and exotic lepton weak doublets and exotic lepton singlet have zero hypercharge, whereas the two colored exotic quark singlets carry opposite hypercharges $- q$ and $q$ . The exotic neutral lepton singlets naturally play the role of the heavy neutrinos. The minimal model with two exotic lepton copies gives a rank-two seesaw, the minimal seesaw model, with one massless active neutrino and predicts $m_{β β} = 1.2 - 4.1 meV$ for normal ordering or $15.9 - 48.9 meV$ for inverted ordering. In a direct SM realization, generating exotic quark masses through the SM Higgs mechanism forces the exotic quarks to carry electric charges $\pm 1/2$ . A separate $SU (2)_{L^{'}}$ realization of the nonstandard solution can allow exotic quarks from several TeV to $10 TeV$ with order-one Yukawa couplings. In this model, the charged exotic quarks and leptons carry electric charges $\pm q$ . In both cases, the lightest exotic quark and lepton are stable, but suitable choices of their charges and masses can satisfy experimental constraints.
hep-ph0 citations
10
Pairton: Iterative Reconstruction of Short-Lived Particles
Andreas Hermansen🇨🇭 · Chris Scheulen🇨🇭 · Tobias Golling🇨🇭
We present Pairton, an iterative framework for reconstructing short-lived particles in high-energy collision events. By formulating particle reconstruction as a masked prediction process over graph structures, Pairton learns conditional distributions consistent with a factorised decomposition of decay products and iteratively predicts edges in the adjacency matrix representing particle decay relationships. Leveraging a pairformer-based architecture with dynamically updated pairwise representations, our method incorporates global event consistency. We demonstrate state-of-the-art performance on fully hadronic $t t ˉ$ decays. Pairton provides a general, flexible paradigm for particle reconstruction and can be readily extended to other topologies, bridging ideas from modern generative modelling and high-energy physics.
hep-phcs.LGhep-ex0 citations
11
Enhanced Three-Particle Contribution to Electroweak Penguin $B$ -Meson Decays
Yong-Kang Huang🇨🇳 · Yu-Ming Wang🇨🇳 · Xue-Chen Zhao🇨🇳
We compute for the first time the subleading twist correction to the exclusive rare $b \to {s, d} ℓ^{+} ℓ^{-}$ decays from the three-particle $B$ -meson distribution amplitude at next-to-leading order accuracy by employing the soft-collinear effective theory. This constitutes the last missing ingredient for the complete factorization analysis of the hadronic matrix element of the weak effective Hamiltonian at leading power in the heavy quark expansion. Incorporating further a variety of the next-to-next-to-leading-order QCD corrections to the spectator-scattering amplitude and the weak annihilation topology, we then present the improved field-theoretic predictions for phenomenologically interesting observables in the electroweak penguin $B \to {K, π} ℓ^{+} ℓ^{-}$ decays.
hep-phhep-exhep-lat0 citations
12
Pion and kaon D terms from holographic QCD and coupled-channel dispersion relations
Zhibo Liu🇯🇵
For a spin-zero meson, the exact trace identity relates the D term to the tensor gravitational form factor $A_{M} (t)$ and the total scalar trace $Θ_{M} (t)$ . We study the pion and kaon D terms by combining a holographic tensor form factor with a chiral-dispersive representation of the trace. Its normalization and slope at the origin are obtained from the forward Ward identity and curved-space SU(3) chiral perturbation theory. A two-channel $π π / K K ˉ$ Muskhelishvili--Omnès solution constructed from empirical scattering amplitudes describes the continuation to spacelike momentum. Available lattice-QCD results are shown for comparison. In the chiral limit, saturation of the trace by the normalized explicit quark-mass response gives $D_{π} (0) = - 1/3$ , while the soft-pion theorem gives $D_{π} (0) = - 1$ . This comparison separates the explicit-mass contribution from the remaining chiral scalar response. At physical masses, SU(3) breaking in the chiral matching distinguishes the pion and kaon forward values, and coupled-channel rescattering governs their evolution away from the origin. The kaon D term is less negative than the pion result in the low- $Q^{2}$ spacelike region considered, with the separation decreasing as $Q^{2}$ increases. These form factors provide a low-energy reference for future lattice studies of the tensor and scalar channels.
hep-ph0 citations
13
Jet functions for next-to-leading power factorization
Robin van Bijleveld🇳🇱 · Jaco ter Hoeve🇬🇧 · Eric Laenen🇳🇱 · Coenraad Marinissen🇳🇱 · Leonardo Vernazza🇮🇹 · Guoxing Wang🇫🇷
We discuss the factorization of scattering processes near partonic threshold at next-to-leading power (NLP) in the threshold variable $1 - z$ , with $z \equiv q^{2} / s^$ . We review the general structure of power-suppressed contributions both in Soft-Collinear Effective Theory (SCET) and in a direct QCD approach, and discuss the definition of NLP jet functions as gauge-invariant operator matrix elements in QCD. As a controlled check of the resulting factorization formula, we verify it explicitly at one and two loops for the massive electromagnetic form factor in the limit $m^{2} ≪ s$ , using the method of regions. We conclude by outlining the two challenges that remain for a systematic resummation of NLP logarithms: the treatment of endpoint divergences in SCET convolutions, and the extension of jet functions to radiative processes capable of describing an arbitrary number of soft-gluon emissions -- the latter being the last missing ingredient for exponentiation, given that the purely soft sector is already understood in terms of generalised webs via the replica trick.
hep-ph0 citations
14
NNLO QCD corrections to $W W γ$ production at the LHC
Paolo Garbarino🇨🇭 · Massimiliano Grazzini🇨🇭 · Stefan Kallweit🇨🇭
Triboson production processes are crucial to study quartic gauge-boson couplings. We present the computation of the radiative corrections to $W W γ$ production at the next-to-next-to-leading order (NNLO) in QCD. The leptonic decays of the $W$ bosons and off-shell effects are fully included. The calculation is exact, apart from the finite part of the two-loop amplitudes, which is evaluated in a soft-photon approximation. We validate our approach by using $Z γ$ production as a reference process, where we take advantage of the availability of the exact two-loop amplitudes to derive a conservative error estimate for our approximation, and then apply it to $W W γ$ production. For typical selection cuts, at the centre-of-mass energy $s = 13$ TeV, the NNLO corrections increase the next-to-leading order (NLO) result by about $16%$ , and the perturbative uncertainties are reduced to the $\pm 4%$ level. The uncertainty from the soft approximation turns out to be at the few per mille level, largely subdominant compared to the residual perturbative uncertainties, both for the fiducial cross section and the most relevant differential distributions.
hep-phhep-ex0 citations
15
Understanding the enhanced $ϕ η^{'}$ decay mode of the $ϕ (2170)$ through strange-meson loops
Qin-Song Zhou🇨🇳 · Jun-Zhang Wang🇨🇳 · Dan Guo🇨🇳
The nature of the strangeonium-like $ϕ (2170)$ remains controversial. Recent measurements of $e^{+} e^{-} \to ϕ η^{(')}$ reveal a striking puzzle: a broad $ϕ (2170)$ -like structure appears in the $ϕ η^{'}$ channel but not in $ϕ η$ , despite the strong phase-space suppression of $ϕ η^{'}$ . We investigate this unexpectedly large $ϕ η^{'}$ decay fraction within the excited-strangeonium assignment. A combined analysis of the $e^{+} e^{-} \to ϕ η$ and $e^{+} e^{-} \to ϕ η^{'}$ cross sections is performed by including short-distance amplitudes from vacuum quark-pair creation and long-distance transitions mediated by strange-meson loops. The short-distance mechanism predicts too small a $ϕ η^{'} / ϕ η$ strength ratio to explain the data. In contrast, strange-meson loops naturally enhance this ratio because the SU(3)-flavor factor at the $K^{(*)} K^{(*)} η^{(')}$ vertex suppresses the transition to $ϕ η$ relative to $ϕ η^{'}$ . The resulting overall description of both cross sections supports an important role for long-distance dynamics in hidden-strangeness decays of excited vector strangeonia. More intriguingly, although the excited strangeonium contributions have been included, the current high-precision $ϕ η$ data still favor the existence of an extra narrow vector state near $2.15 GeV$ with a width of about $25 MeV$ . If confirmed, it would be a promising exotic-hadron candidate in the light-vector sector. Furthermore, we test $Γ (Y \to ϕ η) /Γ (Y \to ϕ η^{'}) = 0.25$ , $1$ , and $4$ as fit inputs and obtain similarly good descriptions of the cross sections in all three cases. The present data therefore do not allow this ratio to discriminate among different internal configurations of the narrow state.
hep-phhep-ex0 citations
16
Improving lepton flavour universality tests with $K_{L}$ decays
G. D'Ambrosio🇮🇹 · A.M. Iyer🇮🇳 · F. Mahmoudi🇫🇷 · S. Neshatpour🇫🇷
Rare kaon decays provide sensitive probes of the flavour structure of the Standard Model and of possible new physics. We perform a global analysis incorporating recent experimental results and updated Standard Model predictions, including the latest measurement of $K^{+} \to π^{+} ν ν ˉ$ and lepton flavour universality observables in $K^{+} \to π^{+} ℓ^{+} ℓ^{-}$ . The fit favours a best-fit point close to the Standard Model, while a second local minimum remains phenomenologically relevant. We define benchmark scenarios associated with these two regions and investigate the prospective sensitivity of NA62 and KOTO-II to the new physics parameter space. We consider projected measurements of $K^{+} \to π^{+} ν ν ˉ$ and lepton flavour universality observables in $K^{+} \to π^{+} ℓ^{+} ℓ^{-}$ at NA62, and of $K_{L} \to π^{0} ν ν ˉ$ , $K_{L} \to π^{0} e^{+} e^{-}$ , and $K_{L} \to π^{0} μ^{+} μ^{-}$ at KOTO-II. We find that KOTO-II has significant potential to probe and discriminate between the viable new physics scenarios, with NA62 providing complementary sensitivity.
hep-ph0 citations
17
Vector-Like Fermions at FCC-ee: NLO Higgs-Strahlung Signatures and Constraints
Carlo Marzo🇪🇪 · Vinicius Padovani🇪🇪 · Daniele Rizzo🇪🇪
We compute the one-loop effects of vector-like fermions (VLFs) on the Higgs-strahlung cross-section, the flagship precision observable of future $e^{+} e^{-}$ Higgs factories such as FCC-ee. We consider four benchmark extensions of the Standard Model (SM): two in which a VL quark (VLQ) or VL lepton (VLL) doublet, together with its singlet partners, couples to the Higgs boson through purely internal Yukawa interactions, and two in which a single VL singlet mixes directly with the third-generation charged lepton or neutrino. Working throughout in the on-shell renormalization scheme and imposing perturbativity bounds on the relevant couplings under renormalization-group (RG) running, we compute both the universal self-energy and the non-universal vertex contributions to the Higgs-strahlung amplitude at one loop, together with the oblique parameters $S$ and $T$ and the $H \to γ γ$ rate as complementary cross-checks. In the two Yukawa-driven scenarios, we find that a sizable fraction of the parameter space still allowed by current LHC searches produces shifts in $σ (Z H)$ at or above the per-mille sensitivity envisioned for FCC-ee, offering a radiative probe of these couplings. In the two mixing-driven scenarios, existing electroweak-precision bounds on the relevant mixing angles already preclude an observable effect, although we characterize the underlying loop dynamics in full generality for future reference. These results identify the VL Yukawa couplings, rather than any residual mixing with the SM fermions, as the more promising target for Higgs-strahlung precision measurements at a future $e^{+} e^{-}$ collider.
hep-phhep-th0 citations
18
Blazar Boosted Dark Matter in IceCube
Alberto M. Gago🇵🇪 · Jaime Hoefken Zink🇵🇱 · Joel Jones-Pérez🇵🇪 · Gabriel D. Zapata🇵🇪
We study the sensitivity of IceCube to blazar-boosted dark matter in a fermionic dark matter model with a massive vector mediator coupling to quarks. To this aim, we compute the diffuse flux arising from a sample of 324 blazars with proton spectra inferred from multiwavelength observations, adopting conservative dark matter spike profiles around the central supermassive black holes and consistently accounting for attenuation effects during propagation through the Earth. The dark matter-nucleon scattering cross section is evaluated by including elastic, resonant single pion production, and deep inelastic contributions, with particular emphasis on resonant single-pion production channels in order to smoothly cover the transition between the elastic and deep inelastic regimes. Using IceCube neutrino data, we derive constraints on the parameter space of the model and show that this detection strategy can surpass the sensitivity of conventional direct-detection experiments for dark matter masses below $\sim 1$ GeV. We find that the signal is dominated by deep inelastic scattering and is therefore more sensitive to comparatively heavy mediators, while resonance processes provide a reduction of the event rate, reaching up to about $9%$ near the experimental threshold. Our results demonstrate that IceCube constitutes a powerful probe of sub-GeV dark matter scenarios through the observation of blazar-boosted dark matter.
hep-phastro-ph.HE0 citations
19
Unknown Unknowns: Model Misspecification in Machine Learning for Physics
Juan Cruz-Martinez🇪🇸 · Carolina Cuesta-Lazaro🇺🇸 · Alexander Held🇺🇸 · Michael Kagan🇺🇸
Machine learning is now a central tool for solving inverse problems in particle physics and astronomy. Models are trained on simulation and deployed on real data, raising the question not just of whether they fit, but of whether they are wrong in ways we did not anticipate: the unknown unknowns. This challenge of model misspecification is not unique to machine learning. In physics, misspecification is sometimes exactly what we want to find: new discoveries appear as failures of existing models. At other times, we want such effects absorbed into the analysis without biasing the measurement. A robust analysis is one that absorbs the misspecifications we are not interested in, while preserving sensitivity to the ones we are. Machine learning can both amplify misspecification and provide new tools to address it. We discuss the challenges of model misspecification, diagnostics for detecting it, and strategies for mitigation. No single diagnostic can confirm that a model is correctly specified: detection and mitigation are two halves of an iterative loop, in which a battery of complementary diagnostics is applied, the model is updated, and the process repeated. Robustness against unknown unknowns is ultimately less about any single technique than about a disposition: a willingness to suspect one's own model, and to design analyses that can survive being wrong in ways one did not anticipate.
↳ physics.data-anastro-ph.COastro-ph.GAcs.LG+21 citation
20
Contrastive Learning for Interpretable Anomaly Detection at Collider Experiments
Haoyi Jia🇺🇸 · Sagar Addepalli🇺🇸 · Julia Gonski🇺🇸
Generic event-level anomaly detection for collider physics has two recurring problems: anomaly scores are hard to interpret, and they correlate strongly with energy scale and object multiplicity. We present Organized Representation via Contrastive learning for Anomaly detection (ORCA), a two-stage framework that first learns an embedding space via supervised contrastive learning across a diverse set of physics processes, then runs a standard autoencoder in that space to generate event-level anomaly scores. On a simulated dataset consistent with conditions at the High-Luminosity Large Hadron Collider, ORCA delivers significant gains in both breadth and depth of sensitivity to new physics signals with respect to a baseline autoencoder architecture. Beyond improved sensitivity, the contrastive embedding makes the anomalous sample interpretable: because known processes occupy distinct regions of the space, a maximum-likelihood template fit to the embedding distributions can attribute events in an anomalous sample to template physics processes with quantified uncertainties. We demonstrate that the fit accurately recovers injected signal yields, including for signals excluded from the training of the embedding, and characterizes signals absent from the template library through the known processes they most resemble. These results establish ORCA as a route to interpretable anomaly detection-based searches at colliders, where the embedding geometry carries higher dimensional physics information compared to standard one-dimensional output fits, enhancing downstream statistical analysis.
↳ cs.LGhep-exhep-ph1 citation
21
Efficient Hamiltonian Truncation: Fast Matrix Construction and Quantum Krylov Diagonalization
Rachel Houtz🇺🇸 · Marco Knipfer🇺🇸 · Konstantin Matchev🇺🇸 · Alexander Roman🇺🇸 · Mia West🇺🇸
Hamiltonian truncation offers a nonperturbative route to quantum field theory, yet its accuracy is limited by the rapid expansion of the truncated Hilbert space, which drives up computational cost. We tackle this bottleneck with a hybrid strategy that pairs classical and quantum algorithms: 1) we develop an efficient basis-generation scheme built on integer partitions; 2) we speed up the construction of the sparse Hamiltonian matrix using symmetry-aware algorithms; and 3) we explore quantum Krylov diagonalization as a route to the low-lying spectrum. Benchmarking against the free massive scalar and $ϕ^{4}$ theories in two spacetime dimensions, we achieve substantial gains in the computational efficiency of Hamiltonian truncation and chart a path toward future quantum implementations.
↳ quant-phhep-lathep-phhep-th0 citations
22
Bayesian inference of event-by-event collision geometry from charged-particle multiplicity in heavy-ion collisions
Yige Huang🇨🇳 · Fu-Peng Li🇨🇳 · Hanwen Feng🇨🇳 · Nu Xu🇨🇳
We propose the Inference-driven Participant Determination (IPD) method, a Bayesian framework for inferring event-by-event posterior distributions of the number of participants ( $N_{part}$ ) and binary collisions ( $N_{coll}$ ) from final-state charged-particle multiplicities in relativistic heavy-ion collisions. The joint distribution of $(N_{part}, N_{coll})$ obtained from the Monte-Carlo Glauber model is used as the prior, while negative binomial distributions calibrated to charged-particle multiplicity fluctuations define the likelihood. This approach replaces conventional hard-cut centrality classification with a probabilistic assignment based on $N_{part}$ , making the multiplicity--geometry smearing explicit and reducing the impact of volume fluctuations on downstream observables. A closure test using an UrQMD-MCG hybrid model at $s_{N N} = 19.6$ ~GeV shows that the method yields well-calibrated posterior distributions with negligible bias and improves the reconstruction of net-proton cumulants relative to conventional multiplicity-based centrality selection.
↳ nucl-thhep-phphysics.data-an0 citations
23
Neural network maximum entropy framework for distribution reconstruction in heavy-ion collisions
Qian-Ru Lin🇨🇳 · Fu-Peng Li🇨🇳 · YiGe Huang🇨🇳 · Long-Gang Pang🇨🇳
We develop a neural-network maximum-entropy (NN+MaxEnt) framework for reconstructing probability distributions from limited observables in heavy-ion collisions. The method combines flexible neural-network representations with Shannon-entropy regularization, preserving positivity and normalization without assuming a fixed analytic form. After validation with Gaussian, Poisson, and mixed-Poisson closure tests, we apply the framework to two physics-motivated inverse problems: an effective multiplicity reconstruction constrained by functional renormalization group cumulants, used as a closure test, and the conditional jet-energy-loss distribution extracted from single-inclusive jet $R_{AA}$ data in Pb+Pb collisions at $s_{N N} = 2.76$ ~TeV. For the fRG closure test, NN+MaxEnt accurately reproduces the imposed cumulants and yields distributions consistent with conventional MaxEnt solutions. For jets, the reconstructed energy-loss distributions reproduce the measured $R_{AA}$ ; at an initial jet momentum $x = 50 GeV$ , the conditional mean energy loss is $⟨ Δ p_{T} ⟩ ≃ 11.8 GeV$ , with a central $16 - 84%$ interval of $9.0 - 15.0 GeV$ . The extracted energy-loss profile is qualitatively consistent with Bayesian MCMC and LBT results. NN+MaxEnt thus provides a flexible, less ansatz-dependent framework for regularized distribution reconstruction from observables connected to the underlying distribution through differentiable forward maps.
↳ nucl-thhep-ph0 citations
24
Dirac, Majorana, and Weyl Spinors in Arbitrary Dimension and Signature
Jan Hajer🇵🇹
Fermionic field types in arbitrary signature are often inferred from complex Spin representations alone, which obscures distinctions associated with real structures, disconnected spacetime reflections, and action-level bilinear constraints. We give a convention-explicit classification that treats the full real Clifford algebra and its even subalgebra separately, thereby distinguishing pinors from spinors and Pin-equivariant Majorana-type structures from structures that are only Spin-equivariant. Adjoint, complex-conjugation, and transposition intertwiners are combined with elementary and collective reflection lifts into a unified sign calculus. The resulting local Clifford classification is organised into thirty-two periodicity sectors determined by the Bott class and the total dimension modulo eight, without including theory-dependent gauge, anomaly, or global constraints. For each sector, we identify the available Dirac, Weyl, Majorana, symplectic Majorana, Majorana-Weyl, and symplectic Majorana-Weyl fields. The existence of an invariant pairing is distinguished from intertwiner compatibility, Grassmann and chiral selection rules, covariant index contraction, and Hermiticity of local bilinear operators.
↳ hep-thhep-ph0 citations
25
Asymptotic flatness beyond General Relativity
David Maibach🇩🇪
The asymptotic symmetry group of asymptotically flat spacetimes gives rise to balance flux equations that constrain, fully non-perturbatively, the asymptotic strain measured by gravitational-wave detectors. Such constraints are sharp tools for identifying features such as the memory effect. As detector sensitivities improve, it becomes imperative to place the most promising beyond-GR candidates on the same footing. Whether the asymptotically flat framework applies to such theories at all is far from obvious and requires careful analysis of the additional degrees of freedom reaching future null infinity. In this work, we address this question. We integrate the Bondi-Sachs hierarchy in the presence of an arbitrary stress-energy tensor and extract the falloff conditions its components must satisfy for the standard metric decay to close. We then feed the most general scalar-vector-tensor theory with second-order equations of motion through this framework. Recasting the field equations in the effective Einstein form $G_{μν} = T_{μν}^{eff} / G_{4} (Φ, X)$ and evaluating every operator of $L_{i}$ against the falloff table, we condense the outcome into a constraint table for the coupling functionals and their derivatives at the asymptotic vacuum, sharpened by the scalar and vector equations of motion and vacuum stability. Remarkably few conditions survive. The scalar potential must vanish to cubic order at the asymptotic vacuum, the asymptotic Newton constant must be finite and positive, the scalar and vector modes must be canonically normalized, and the conformally coupled sector carries a frame subtlety. Every other coupling functional is protected by the structure of the theory. The constraint table thus provides a diagnostic for screening beyond-GR models against asymptotic flatness and establishes the BMS group as the asymptotic symmetry group across the entire admissible SVT class.
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first authorsco-authorsvia INSPIRE