HEP Phenomenology·hep-ph

Wed·Sep 16, 2026Wednesday·September 16, 2026

14 papers—9 primary·5 cross-listed

01
Rethinking search signatures: Hadronic decays of GeV-scale feebly coupled particles
Viktor Kryshtal · Maksym Ovchynnikov
Experimental searches for GeV-scale feebly interacting particles commonly target the simplest decay signatures with two charged particles, including hadrons. Hadronic modes often dominate the inclusive decay rate, and their simulation relies extensively on \textsc{Pythia}. Its fragmentation model, calibrated mainly on LEP data, is unreliable in this mass range: it populates symmetry-forbidden states and misidentifies the dominant allowed channels. We construct a simple hadronization model tuned to electromagnetic scattering data and constrained by conservation laws and available exclusive decay calculations, while retaining a common prescription applicable to different particle models. Considering the SHiP experiment as an example, we show that our model shifts the dominant search signature after event selection from two-particle to multiparticle decays, including mixed charged-neutral states. We provide the model in a form that can be readily integrated into \textsc{Pythia}-based experimental simulation frameworks.
hep-ph
02
Reconciling axion quality with post-inflation cosmology
Luca Di Luzio · Samuele Di Valeriano · Marco Nardecchia · Enrico Nardi
We address the axion quality/cosmology tension that often plagues QCD axion models in post-inflationary Peccei-Quinn (PQ) breaking scenarios. In the proposed framework, the PQ symmetry emerges accidentally from an $SU (N)_{L} \times SU (N)_{R}$ gauge symmetry spontaneously broken to $SU (N)_{L + R}$ , and its quality is protected because PQ breaking first appears at operator dimension $N$ . Moreover, the construction avoids the domain-wall problem, ensures that no stable fractionally charged relic survives $SU (N)_{L + R}$ confinement, and remains free of Landau poles below the scale of PQ-breaking operators. The exotic quarks required to generate the PQ anomaly hadronize into unstable mesons and cosmologically stable neutral baryons. However, plausible arguments indicating a strong suppression of baryon formation in $SU (N)$ gauge theories at large $N$ , suggest that their contribution to the dark matter energy density remains subdominant. Combining cosmological constraints with PQ quality and perturbativity requirements yields a viable parameter space in which the axion makes up most of the dark matter and its mass remains predictable.
hep-phhep-th
03
Generalized Detectors at Colliders
Mark Gonzalez · Kyle Lee · Ian Moult
Recent progress in collider physics has reformulated phenomenological questions in terms of detector correlation functions and advanced their theoretical understanding. These advances have primarily focused on correlators of the average null energy operator, $E (n)$ , known as energy correlators. However, colliders have access to a much broader class of detector operators, $E_{R}^{n} (n)$ , which measure powers of the energy on a subset of hadrons $R$ , such as charged hadrons. These generalized detectors are generically not infrared and collinear safe, and their description requires nonperturbative matching between the hadronic detectors measured in the infrared and the partonic detectors used in ultraviolet calculations. We develop a framework for computing their multi-point correlation functions. We introduce universal nonperturbative matching coefficients, termed "detector functions", that implement this infrared-ultraviolet matching. For the $E_{R}^{n}$ operators studied here, these coefficients are represented by energy-weighted moments of single- and multi-hadron fragmentation functions. We present their renormalization group structure, derive QCD factorization theorems for the projected correlators, and compute jet functions through next-to-leading order. In the fixed-coupling pure Yang-Mills limit, we derive the light-ray OPE of hadronic detectors and connect it to the QCD factorization framework. We also identify universal nonperturbative power corrections generated by soft radiation, which are enhanced in the collinear limit and can substantially modify the perturbative angular scaling. A parton shower study finds qualitative agreement with the predicted perturbative and nonperturbative scaling behaviors. Our work significantly broadens the space of detector operators under theoretical control, with potential phenomenological applications.
hep-phhep-exhep-thnucl-ex+1
04
Eclectic flavour symmetries without flavons
Ferruccio Feruglio · Antonio Marrone
We develop a new framework in which eclectic groups are realised as flavour symmetries without flavons. Focusing on the group $Ω (1)$ , we show that it can be realised as a finite image of the integral Jacobi group, i.e. the semidirect product of $H (Z)$ with $S L (2, Z)$ , acting on two moduli $(τ, z)$ . The Heisenberg subgroup $H (Z)$ leaves the modulus $τ$ unchanged, and its finite image $Δ (27)$ plays the role of the traditional flavour symmetry. We provide the ingredients needed to construct supersymmetric Jacobi-invariant theories, both in globally supersymmetric theories and in supergravity. We develop a realistic model of fermion masses within this framework and formulate a consistent CP symmetry, which can be imposed at the Lagrangian level and broken spontaneously by the moduli. We discuss how the conventional eclectic-flavour description is recovered in an appropriate limit. We also extend this geometric interpretation to the $T^{2} / Z_{4}$ and $T^{2} / Z_{2}$ eclectic building blocks, and clarify why the $T^{2} / Z_{6}$ case is structurally different.
hep-phhep-th
05
Dark Radiation Sticks Together: Dark QCD and the Hubble Tension
Matthew R. Buckley · Nicolas Fernandez · Eric Putney
We introduce a model of dark matter charged under a new confining gauge group akin to the Standard Model's quantum chromodynamics (QCD). The fermionic sector contains both heavy and light quark-like fermions charged under the dark QCD. As the Universe cools, the gauge force confines and dark radiation transitions from free particles to low-mass dark pions. This form of dark radiation behaves as an imperfect fluid with nonzero viscosity. If the confinement occurs at the MeV scale, the model can alleviate the tension between early- and late-time measurements of the Hubble parameter, with a Bayesian posterior of $H_{0} = 71.60 \pm 0.63$ km/s/Mpc and a $3 σ$ residual tension across Planck, ACT, BBN, Pantheon+, DESI DR2, and SH0ES. In the late Universe, the heavy dark matter can evade existing constraints on dark matter self-interactions while containing a rich phenomenology that may be accessible in future observations.
hep-phastro-ph.CO
06
A Casimir bottleneck in primordial large-N baryon formation
Luca Di Luzio · Samuele Di Valeriano · Enrico Nardi
We study baryon $(B)$ formation in the early Universe in a confining $S U (N)$ gauge theory with quarks transforming in the fundamental representation. Casimir scaling of the confining potential implies that, at large $N$ , $B$ formation is hindered by a bottleneck: for small quark clusters, representing the initial stages of $B$ assembly, destruction processes greatly outweigh formation processes. In a $B$ - $B ˉ$ symmetric plasma, the relic density of cosmologically stable $B$ 's is set, for large $N$ , during confinement rather than by annihilation freeze-out. This affects relic-density estimates for $S U (N)$ dark matter models.
hep-phhep-th
07
Multiple-Mediator-Affected Ultra-High-Energy Neutrino Attenuation: Hints for 5D $U (1)_{L_{μ} - L_{τ}}$ in IceCube
Atri Bhattacharya · Ayushi Kaushik · Kenji Nishiwaki
Recent IceCube observations point to the ultra-high energy neutrino flux exhibiting a very soft spectral nature beyond tens of TeV, which is unexpected from the standard cosmic-ray neutrino connection. As a potential explanation for this behaviour, we investigate neutrino self-interactions in an extra-dimensional $U (1)_{L_{μ} - L_{τ}}$ gauge theory, where symmetry breaking leads to a tower of Kaluza-Klein gauge bosons in compactified four dimensions. These multiple gauge bosons may enhance the attenuation of astrophysical neutrinos as they propagate in the C $ν$ B medium. Unlike single-mediator scenarios, for example, which arise from broken $U (1)_{L_{μ} - L_{τ}}$ gauge symmetries in four dimensions, the presence of a Kaluza-Klein tower of mediators produces multiple closely spaced resonances whose interference gives rise to a rich energy-dependent behaviour of the scattering cross-section over a vast range of incident neutrino energies. Alongside $s$ -channel resonances, off-resonant $t$ - and $u$ -channel contributions also become important. We explore the possibility that repeated resonant scattering between astrophysical neutrinos and those in the C $ν$ B, mediated by these new multiple gauge bosons may increasingly attenuate the former at higher energies, thereby addressing the possibility of softening its spectral nature within the consideration of a single power law.
hep-phastro-ph.HE
08
Composite dark matter at the LHC
Alan S. Cornell · Louie Corpe · Aldo Deandrea · Benjamin Fuks · Taylor Murphy · Clarisse Prat
We investigate a composite-inspired model in which a scalar dark matter candidate couples to third-generation quarks through a non-minimal set of coloured vector-like fermions, as motivated by partial compositeness. The simultaneous presence of several mediator states leads to a richer phenomenology than conventional single-mediator descriptions, and we confront the framework with the observed relic abundance, direct-detection and indirect-detection constraints, as well as data from the Large Hadron Collider. At colliders, we compare the sensitivity of dedicated new-physics searches with that of unfolded measurements of Standard Model processes, and we assess the impact of higher-order corrections on the different production mechanisms. We find that dedicated searches generally provide the strongest collider exclusions, while unfolded measurements offer complementary sensitivity. Direct detection becomes increasingly powerful as the interaction strength grows and can become the dominant constraint. This broader complementarity arises because collider data directly test the production and decay of the coloured mediators, whereas cosmological and astroparticle observables constrain the interactions governing dark-matter abundance, scattering and annihilation. Although present constraints significantly restrict the model, viable regions compatible with the observed dark-matter abundance remain.
hep-phhep-ex
09
Enhanced Standard Model bound on charm CP violation from QCD penguins
Ali Mohamed · Maria Laura Piscopo
We investigate the impact of QCD penguin operators on direct CP violation in singly Cabibbo-suppressed $D^{0}$ decays within the framework of light-cone sum rules (LCSR) using pion and kaon light-cone distribution amplitudes. We determine, for the first time, the hadronic matrix elements of the QCD penguin operators for $D^{0} \to K^{+} K^{-}$ and $D^{0} \to π^{+} π^{-}$ at leading order in $α_{s}$ , employing a three-point correlation function with an artificial momentum to avoid unphysical parasitic cuts. We also compute the matrix elements of the current-current operators using the same framework and compare them with previous LCSR results. We find that the scalar penguin operators $Q_{5}$ and $Q_{6}$ can have substantially enhanced matrix elements. We identify two sources of enhancement: quark-condensate contributions, which arise already at tree level and are therefore enhanced by a relative factor of $16 π^{2}$ compared to the remaining, loop-induced terms in the sum rule; and an annihilation-type contribution from the $u ˉ u$ component of these operators, which enters already through twist-three light-cone distribution amplitudes and is of comparable magnitude. While the impact of QCD penguin operators on the branching ratios is negligible, they can enhance the magnitude of the ``penguin-to-tree'' amplitude ratios relevant for direct CP violation. The relevant strong phases, however, remain largely unconstrained within the accuracy of our framework. Assuming maximal relative strong phases, we find that the corresponding upper bound on the Standard Model contribution to charm CP violation can be enhanced compared to estimates based on the current-current operators alone, reducing the gap with the experimental measurement.
hep-ph
10
Adaptive detection of Rabi signals under composite hypotheses
So Chigusa
Motivated by searches for weak coherent drives, we formulate repeated quantum sensing with a fixed shot budget as an asymmetric composite hypothesis test. Taking Rabi sensing as a concrete example, we benchmark detection power, sensitivity, and Type-II error exponents in the resonant case with unknown signal amplitude and phase. We compare non-adaptive population and transverse readouts with a myopic Bayesian policy that selects each projective axis by maximizing the expected information gain in one step. The common decision statistic is a log Bayes factor, with a policy specific threshold calibrated under the null to enforce a common Type-I error. A weak signal expansion shows that population readout is phase independent but quadratic in amplitude, giving $n^{- 1/4}$ sensitivity, whereas transverse readout is linear in amplitude and permits $n^{- 1/2}$ sensitivity without adaptation, but is phase-dependent. In Monte Carlo pseudoexperiments, the adaptive policy exploits posterior information about the unknown direction to guide subsequent readouts; its sensitivity is consistent with $n^{- 1/2}$ over the simulated large $n$ range and, at the largest simulated shot counts, outperforms the fixed transverse schedules. Its phase-averaged effective Type-II exponent also exceeds the non-adaptive references over the simulated range. These results demonstrate the finite budget value of exploiting nuisance parameter information under calibrated false positive control.
↳ quant-phhep-ph
11
CMB-HD Foregrounds: Simulations, Source Detection, and Foreground Removal
Amanda MacInnis · Joshua Ange · Neelima Sehgal · Joshua A. Kable · Isabelle Blackstad
We present simulations of the microwave sky at 2.5 arcsecond resolution over 100 square degrees, generated from existing full-sky, lower-resolution simulations, and use them to demonstrate extragalactic foreground removal for a CMB-HD survey. Our cleaning method detects and removes the cosmic infrared background and radio galaxies, yielding source catalogs that are 95% complete down to flux limits of 0.008 and 0.04 mJy at 90 and 148 GHz, respectively. It also identifies and removes galaxy clusters via the thermal Sunyaev-Zel'dovich effect, producing a cluster sample that is nearly complete above $M_{500 c} = 5 \times 1 0^{13} M_{⊙}$ . After cleaning, the residual foreground-plus-noise power spectrum of the coadded 90 and 148 GHz temperature map is 50% higher than previous idealized estimates, increasing cosmological parameter uncertainties for an 11-parameter $Λ$ CDM + $N_{eff}$ + $\sum m_{ν}$ + $T_{AGN}$ + $A_{kSZ}$ + $n_{kSZ}$ model by less than 7%. The small impact on cosmological parameters reflects the strong constraining power of CMB polarization, the temperature-polarization cross spectra, and CMB lensing spectra reconstructed from polarization-only estimators, all of which are minimally affected by extragalactic foregrounds. In particular, the survey remains a sensitive probe of light thermal relic particles, achieving $σ (N_{eff}) = 0.0154$ , which can exclude any new species ( $Δ N_{eff} \geq 0.027$ ) with at least 90% confidence. Our simulation and foreground-removal codes are publicly available and should aid the development of analysis pipelines for ultradeep, ultrahigh-resolution microwave surveys.
↳ astro-ph.COhep-ph
12
Making the Great Desert Bloom
Jacques Distler · Andreas Karch
The absence of new physics beyond neutrino masses between the weak scale and the Planck scale is referred to as the great desert. It is often seen as a nightmare scenario for particle physics. Here we argue, by contrast, that the great desert assumption in fact has dramatic implications: it predicts that the Standard Model has a semi-classical AdS $_{4}$ vacuum with CFT $_{3}$ dual and, under reasonable assumptions, must be accompanied by at least one extra dimension significantly larger than Planck length. We also present one plausible candidate CFT $_{3}$ to be ``the" dual to the Standard Model.
↳ hep-thhep-ph
13
Peering Beyond the Veil of Last Scattering: A View of the Universe with CMB Spectral Distortions
Bryce Cyr · Nabila Aghanim · Ethan Baker · Elia Stefano Battistelli · Richard Battye · José Luis Bernal · Jens Chluba · Xavier Coulon · William Coulton · Paolo de Bernardis · Eleonora Di Valentino · Guillem Domènech and 28 other authors
The frequency spectrum of the cosmic microwave background is the most precise blackbody ever measured in nature, with deviations constrained at the level of almost one part per million from the COBE satellite. Nevertheless, departures away from a perfect blackbody are present in standard $Λ$ CDM cosmology, lurking just beneath the surface of our current observational bounds. These spectral distortions provide invaluable information on our thermal history in both the post- and pre-recombination epochs, allowing us to peer beyond last scattering and into the primordial Universe. Here, we present an overview of the underlying physics responsible for generating CMB spectral distortions at all epochs. As an illustration of this rich physics, we review a comprehensive set of mechanisms capable of generating distortions both within and beyond the standard $Λ$ CDM paradigm. We also discuss the information that can be gleaned by going beyond the monopole (sky-averaged) spectrum and exploiting the spatial information present in anisotropic spectral distortions. To supplement our discussion of the diverse science of spectral distortions, we provide an overview of the upcoming and proposed experimental landscape. We highlight that the combination of the TMS, COSMO, and BISOU experiments will provide the first discovery of a monopole $y$ -type distortion within the coming decade. From space, the proposed FOSSIL experiment is forecasted to improve upon the original COBE/FIRAS measurement by roughly three orders of magnitude in sensitivity, bringing with it the detection of the $Λ$ CDM $μ$ -type distortion sourced by the dissipation of small scale acoustic modes in the pre-recombination plasma. With transformational measurements on the horizon, CMB spectral distortions offer a uniquely sensitive probe of the thermal history of the Universe at redshifts $z ≲ 2 \times 1 0^{6}$ .
↳ astro-ph.COastro-ph.IMhep-ph
14
Obtaining tensor-polarized nuclei with spin $S \geq 1$ via spin filtering upon nuclear beam transmission through an unpolarized target (spin dichroism effect)
Sergey Anishchenko · Vladimir Baryshevsky · Alexandra Gurinovich
Upon transmission through an unpolarized target initially unpolarized nuclei with spin $S \geq 1$ acquire tensor polarization due to spin dichroism effect. For nuclei passing several nuclear lengths in the target, the acquired component $p_{z z}$ can reach substantial values of ~0.2-0.8. The beam obtained in this way can be effectively used to study reactions with tensor-polarized nuclei.
↳ nucl-thhep-phnucl-ex