HEP Phenomenology·hep-ph

Fri·Sep 18, 2026Friday·September 18, 2026

34 papers—26 primary·8 cross-listed

01
Testing Higgs-Coupled Minimal Dark Matter with Solar Neutrinos after the LZ High-Recoil Event
Mattia Di Mauro
The LUX-ZEPLIN (LZ) Collaboration has reported a nuclear-recoil candidate at $248$ keV, motivating interpretations in terms of endothermic dark matter (DM). We investigate this signal in Higgs-coupled minimal dark matter (HC-MDM), where the same electroweak interaction responsible for the terrestrial recoil also induces DM capture in the Sun and a potentially observable high-energy neutrino signal. We independently determine the mass splittings required to reproduce the LZ event and perform an improved calculation of Solar capture and post-capture evolution. Our treatment includes natural isotope mixtures, exact inelastic kinematics, nuclear form factors, finite-temperature nuclear motion near kinematic closure, orbital cooling through loop-induced elastic scattering, and an explicit capture--annihilation equilibrium test. The resulting Solar predictions are numerically stable and robust against the astrophysical and nuclear variations considered. For the two thermal benchmarks within the released IceCube DM mass grid, $3_{M} 2_{D}$ and $5_{M} 4_{D}$ , the predicted annihilation rates exceed the mass-matched $W^{+} W^{-}$ IceCube response by factors of approximately $2.2 \times 1 0^{3}$ and $91$ , placing both standard-halo solutions under strong tension within the $W^{+} W^{-}$ response mapping used here. For the heavier representations, whose masses lie above the published $10$ TeV IceCube grid, we construct a response-based extrapolation to higher masses. The $22$ TeV $7_{M} 6_{D}$ benchmark remains in strong tension with IceCube even under our conservative response-loss extrapolation, while the $48$ TeV $9_{M} 8_{D}$ benchmark also remains above the extrapolated response, although much closer to the sensitivity boundary. The $82$ TeV $1 1_{M} 1 0_{D}$ benchmark is response dependent, whereas the $130$ TeV $1 3_{M} 1 2_{D}$ benchmark remains below the extrapolated IceCube sensitivity.
hep-phastro-ph.HEhep-th
02
Interpreting quantum coherence of neutrinos in asymptotically flat spacetimes via effective distances: Solution to the paradoxes of the Leggett-Garg inequality and quantum information quantities
Shan Wu · Shu-Jun Rong
In this work, we propose a notion called effective distance to characterize the essential gravitational effects on quantum coherence of neutrinos. Employing effective distances, we prove that one can always map neutrino-oscillation phases in asymptotically flat spacetimes onto the phases in flat spacetime, which is considered as a nontrivial realization of equivalence principle. Hence, the maximal amount of quantum coherence, quantified by the Leggett-Garg (LG) parameter is independent from background spacetimes, namely, the paradox that the gravitational effects on quantum coherence of neutrinos are measure-dependent (Ettefaghi et al.[1]) does not arise. Following the same route, we preclude the gravitational amplifying or damping of amplitudes of the quantum information quantities for special masses of black holes (Wang et al. [2]). To demonstrate furthermore the independence of quantum coherence from background spacetimes, we examine the proposal using the LG parameter to identify quantum-corrected models of spacetimes. For different emission positions of neutrinos and various quantum parameters, we find no consistent patterns in oscillating LG curves to discriminate a quantum metric from the classical one.
hep-phgr-qc
03
Collective flavor conversion in dense neutrino plasmas
Damiano F. G. Fiorillo
Compact transient sources, such as supernovae (SNe) and neutron star mergers (NSMs), host a population of thermal neutrinos in their inner cores, which decouple from the dense matter as they stream out. Yet, collisionless does not mean free; their density is large enough to mediate collective waves driven by the coherent weak neutrino--neutrino interaction. These collective waves carry little energy, but crucially they transport flavor. Neutrinos thus form a collisionless plasma with flavor transport driven by flavor waves, whose quanta are called flavomons $ψ$ . The wavelength of these flavomons is much shorter than the characteristic scales of SNe and NSMs, so that a brute-force numerical treatment of the neutrino plasma is beyond our capabilities. Yet flavomons cannot be neglected, as the stimulated neutrino decays, schematically $ν_{e} \to ν_{μ} ψ$ , cause a rapid buildup in their population, more conventionally called a flavor instability. We review the theory of the neutrino plasma, and systematically discuss the instabilities leading to flavomon growth, and connect this emerging quasiparticle description with recent advances in numerical neutrino flavor kinetics.
hep-phastro-ph.COastro-ph.HE
04
A phenomenological profile of Higgs portals at future colliders
Maximilian Detering · Christoph Englert · Victor Maura · Tevong You
Should the Higgs boson be found to couple to a hidden dark sector, it will become necessary to determine the nature of the Higgs portal responsible. Could the minimal, marginal Higgs portal operator be distinguished from a Higgs portal interaction involving a higher-dimensional operator? This is unlikely for Higgs portals with on-shell invisible decays to light dark sectors, but for an off-shell Higgs portal above threshold, where the dark sector is too heavy to contribute to the invisible Higgs decay width, we find that the higher-dimensional Higgs portal operators could in principle be differentiated by combining measurements across the integrated programme of HL-LHC, FCC-ee, and FCC-hh. This illustrates the complementarity of precision and high-energy exploration to phenomenologically profile Higgs portal interactions and probe possible connections between the electroweak scale and a hidden universe.
hep-phhep-ex
05
SHiP as a (post-)discovery machine: identifying the diphoton signals' origin
Matei Climescu · Malte Fogde Mikkelsen · Maksym Ovchynnikov
The upcoming SHiP experiment may probe interaction strengths of decaying feebly coupled particles several orders of magnitude below existing limits. In the event of a discovery, it may also reveal the nature of the new particle. This requires identifying its exact production mechanism, which SHiP does not observe directly. We explore whether this mechanism can be inferred from the kinematics of its visible decays. As a benchmark, we consider an axion-like particle (ALP) with a dominant diphoton decay, which may occur for couplings to the $U (1)_{Y}$ and $S U (2)_{L}$ gauge fields. For a known ALP mass, the observed energy and angular distributions depend on the relative magnitude and sign of the couplings and on the unknown lifetime, which we profile independently under each hypothesis. We first determine how the ALP energy and its longitudinal and transverse decay positions distinguish the interactions, assuming perfect reconstruction and accounting for production, propagation, decay, and geometric acceptance. We then include the detector response and reconstruct the diphoton decays using a full simulation of the SHiP electromagnetic calorimeter. Only $2$ -- $4$ reconstructed diphoton events are needed to distinguish the two pure $U (1)_{Y}$ and $S U (2)_{L}$ interactions for ALP masses between $0.2$ and $1 GeV$ . For coupling admixtures, the study assuming perfect reconstruction indicates requirements of several tens to $O (1 0^{2})$ events in favorable regions.
hep-phhep-ex
06
Lukewarm inflation, primordial black holes and gravitational waves
Paulo B. Ferraz · António Torres Manso · João G. Rosa
We show that a secondary period of warm inflation, at temperatures parametrically below the GUT scale, may not only dilute any unwanted thermal relics formed after reheating but also significantly enhance the power spectrum of primordial curvature perturbations on small scales. The latter is nearly scale-invariant over an exponentially large range of comoving scales, resulting in a stochastic gravitational wave background with a nearly constant energy density over a broad range of frequencies and an associated population of sub-solar mass primordial black holes (PBHs). This scenario could, in particular, explain the NANOGrav signal if it persists at much higher frequencies with a comparable magnitude, up to a sharp cut-off, $f_{ma x}$ . The associated PBH mass distribution may exhibit either a peak at a mass $M_{*} \propto f_{ma x}^{- 2}$ or a broad plateaux above this mass threshold, depending on the spectral tilt. Moreover, in this scenario the NANOGrav signal is compatible with a significant fraction of dark matter in PBHs in the asteroid- and planetary-mass ranges.
hep-phastro-ph.COgr-qc
07
Probing Scalar-Induced First-Order Phase Transitions with the Diffuse Supernova Neutrino Background
Sudipta Das · Shamik Niyogi · Manibrata Sen
We investigate the possibility of probing a scalar-induced first-order phase transition (FOPT) inside core-collapse supernovae through the diffuse supernova neutrino background (DSNB). We consider a light scalar coupled to neutrinos that is produced and thermalised in the proto-neutron-star core. This leads to two distinct neutrino components: a prompt contribution from thermally produced scalars and a delayed, spectrally narrow contribution from the decay of coherent scalar excitations due to the FOPT. We study the resulting DSNB signal at Super-Kamiokande, Hyper-Kamiokande, and DUNE, finding a strong dependence on the neutrino mass ordering. The recent Super-Kamiokande data already constrain the scalar parameter space for inverted ordering and quasi-degenerate neutrino masses, while future detectors can significantly improve this sensitivity. Our results demonstrate that DSNB measurements can provide a novel probe of finite-temperature scalar dynamics in core-collapse supernovae.
hep-phastro-ph.CO
08
Lukewarm inflation and the QCD axion
Paulo B. Ferraz · António Torres Manso · João G. Rosa
We show that a late period of warm inflation, at temperatures just above the QCD scale, can dilute the abundance of the QCD axion produced by the misalignment mechanism, thus avoiding the need to fine-tune the initial misalignment angle in scenarios with an axion decay constant close to the GUT scale. We develop a concrete realization of this lukewarm inflation stage involving right-handed neutrinos in 0.1 - 1 GeV mass range and an associated scalar sector, showing that coherent axion oscillations are damped during this period. In this scenario, a previously generated large baryon asymmetry may also be diluted to yield the observed value, and lukewarm inflation is followed by an early-matter era dominated by the lightest right-handed neutrino, before it decays into Standard Model states. This model can be tested via changes to the number of relativistic species and the induced small-scale enhancements of the primordial curvature power spectrum, leading to primordial black holes and scalar-induced gravitational waves.
hep-phastro-ph.CO
09
Resonant Di-Higgs Searches in $b b ˉ τ^{+} τ^{-}$ at HL-LHC: Supersymmetry versus Compositeness Benchmarks
Atri Dey · Carl Johan Konigsson · Stefano Moretti · Luigi Delle Rose · Luca Panizzi · Stefania De Curtis
We explore the scope of the High-Luminosity Large Hadron Collider (HL-LHC) in testing Standard Model (SM) di-Higgs production and decay into $2 b 2 τ$ final states in the context of two viable theories of the Electro-Weak (EW) scale: Supersymmetry and Compositeness. Specifically, we target minimal model realisations of these two scenarios that enable the resonant process $g g \to H \to hh \to b b ˉ τ^{+} τ^{-}$ , where $h$ is the SM-like Higgs state and $H$ a heavier CP-even companion, with the $τ$ 's decaying hadronically. This is realised within the Next-to-Minimal Supersymmetric SM and the Composite 2-Higgs Doublet Model, respectively. Using two illustrative benchmark points, after performing a thorough detector-level Monte Carlo (MC) analysis exploiting new observables, we show that, in the former case, there is more moderate sensitivity, owing to large backgrounds, whereas, in the latter case, substantial scope for discovery exists, in a background free environment.
hep-ph
10
Generalized parton distributions: Theory meets experiment
Yuxun Guo · Xiangdong Ji · Yao Ji · Jialu Zhang
Over the past three decades, generalized parton distributions (GPDs) have emerged as one of the most active and important areas of research in nucleon structure and quantum chromodynamics (QCD). Since the last comprehensive review two decades ago, substantial progress has been made in experimental measurements of hard exclusive processes, such as deeply virtual Compton scattering and near-threshold $J / ψ$ production, as well as in increasingly sophisticated phenomenological analyses of GPDs that enable three-dimensional nucleon tomography. Theoretical advances in perturbative coefficient functions, scale evolutions, and kinematic and power corrections have considerably improved the precision of GPD phenomenology, while new hard exclusive processes for probing GPDs have been explored. More interestingly, lattice QCD can now directly access GPDs at fixed parton momentum fractions $x$ and skewness $ξ$ through large-momentum expansions, in addition to the traditional calculations of their moments, or generalized form factors. Significant progress has also been made in exploring the QCD energy-momentum tensor that encodes fundamental information on the nucleon's mass distribution, complete spin structure, and spatial distributions of momentum current and color-Lorentz forces acting on quarks and gluons.
hep-phhep-exhep-latnucl-ex+1
11
T-odd Effect from Two-Photon Exchange in SIDIS at Low Transverse Momentum
J.P. Ma · G.P. Zhang
We study T-odd effects through two-photon exchange in semi-inclusive deeply inelastic scattering in the kinematic region where the produced hadron has a low transverse momentum. The absorptive part of lepton-quark scattering amplitude is calculated. Transverse momentum dependent factorization is performed with the absorptive part. Although the absorptive part is divergent, the physical results, i.e., the obtained differential cross-section, is finite. Including the T-odd effects, the differential cross section receives new contributions which have different angular dependence than that obtained with one-photon exchange. Certain asymmetries can be introduced to detect the T-odd effects. Our results here are not only relevant to detecting new effect beyond the one-photon approximation in the process but also relevant to searching for new physics at lepton-proton colliders.
hep-phhep-ex
12
Higher twists in QCD
W. Melnitchouk
Higher twists in deep-inelastic scattering (DIS) and related hard scattering processes provide a unique window on nonperturbative QCD dynamics, encoding quark-gluon correlations and multiparton interactions beyond the leading-twist parton model. We present an overview of the theoretical foundations of higher twists in QCD, based on the operator product expansion, and discuss their intimate connection with quark-hadron duality in the transition between the resonance and scaling regimes. We review the phenomenology of higher-twist effects in unpolarized and polarized DIS, emphasizing their extraction from precision data through modern global QCD analyses that simultaneously determine both leading-twist parton distribution functions and higher-twist contributions. Finally, we discuss recent developments in the study of higher twists in semi-inclusive and exclusive reactions, and conclude by highlighting future opportunities to study QCD dynamics beyond leading twist at Jefferson Lab and the Electron-Ion Collider that promise to deepen our understanding of hadron structure.
hep-phhep-exnucl-th
13
Strange Two-Photon Exchange in Time-Like Electromagnetic Form Factors
Xu Cao · Yong-Hui Lin · Hai-Qing Zhou
While two-photon exchange (TPE) effects in space-like nucleon electromagnetic form factors have been extensively studied for over two decades, their manifestations in the time-like region have yet to be definitively established. We propose the isospin-violating decay $J / ψ \to Σ ˉ^{0} Λ$ and its charge-conjugate process as a sensitive probe of TPE contributions to time-like hyperon electromagnetic form factors. This channel provides a clean laboratory for isolating TPE effects through sensitive and robust polarization and spin-correlation observables, which are particularly enhanced by the $Λ$ - $Σ^{0}$ mass splitting. Combining a dispersion-relation analysis of the one-photon-exchange contribution with explicit loop calculations of the TPE amplitudes, we perform a quantitative study of TPE effects in the threshold region. Our results demonstrate that the considered observables can provide unambiguous signatures of TPE contributions and present predictions for their size together with the associated theoretical uncertainties.
hep-ph
14
Clarifying the puzzling mass shift of the $ψ (4160)$ via a reanalysis of $R$ -value data with unquenched charmonium spectroscopy
Tian-Cai Peng · Xiang Liu
The long-standing upward shift of the extracted $ψ (4160)$ mass, from about $4.16$ ~GeV to $4.19$ ~GeV in later analyses, remains a puzzling issue in charmonium spectroscopy. In our previous study, this problem was investigated through the $B^{+} \to K^{+} μ^{+} μ^{-}$ process within an unquenched charmonium framework, where the lower-mass $ψ (4160)$ assignment was found to be compatible with the data. Here we revisit the BESII $R$ -value data, which played an important role in the historical extraction of the higher $ψ (4160)$ mass, and provide an independent examination. In contrast to the conventional quenched picture with $ψ (4040)$ , $ψ (4160)$ , and $ψ (4415)$ , the unquenched vector-charmonium spectrum contains six states: $ψ (4040)$ , $ψ (4160)$ , $ψ (4220)$ , $ψ (4380)$ , $ψ (4415)$ , and $ψ (4500)$ . Including these states together with the near-threshold $ψ (3770)$ , we find that the BESII $R$ -value line shape can be well reproduced over the full energy range while retaining the lower-mass $ψ (4160)$ assignment. The enhancement around $4.19$ ~GeV then arises from the coherent interplay among the nearby $ψ (4040)$ , $ψ (4160)$ , and $ψ (4220)$ amplitudes, rather than requiring an upward shift of the $ψ (4160)$ mass itself. The additional higher states also naturally describe the line-shape structure in the $4.4$ ~GeV region. We further show that the seven-resonance coherent amplitude contains six complex zeros, yielding $2^{6} = 64$ mathematically equivalent solutions with identical line shapes but substantially different di-electron widths and relative phases. Comparing these solutions with available experimental information and representative unquenched charmonium predictions, we provide a qualitative assessment of their phenomenological consistency and highlight several solutions that appear more compatible with present information.
hep-phhep-ex
15
Neutralino Dark Matter in SU(5) after H.E.S.S. and Direct-Detection Searches
M. Adeel Ajaib · Fariha Nasir
We examine the impact of gamma-ray line and direct-detection searches on neutralino dark matter in supersymmetric SU(5) with non-universal gaugino masses. Under the assumption that neutralinos constitute all halo dark matter, a nearly pure wino benchmark at 1 TeV is essentially excluded by the H.E.S.S. line limits for both cusped and cored density profiles. Higgsino and wino-Higgsino benchmarks are independently excluded by direct detection. In contrast, a bino benchmark near thermal saturation combines suppressed present-day line emission with scattering below the displayed experimental limits. Mixed bino-wino solutions illustrate the complementarity of the two searches and the dependence of the line interpretation on the Galactic halo profile. We relate these results to the GUT-scale gaugino hierarchy and the SU(5) scalar and Higgs boundary conditions. Thermally underabundant solutions require additional production to realize the full-density assumption. Comparing the calculated signals with published electroweakino predictions, we identify the spectrum-dependent corrections and collider tests needed to determine the surviving parameter space.
hep-ph
16
Hidden charm pentaquarks and the nature of $P_{c}$ states observed at LHCb
Zhi-Biao Liang · Jun-Jie Liu · Mu-Yang Chen · Xian-Hui Zhong
We carry out a unified study of the low-lying $1 S$ -wave compact states and hadronic molecules composed of hidden charm pentaquarks $q q q c c ˉ$ ( $q = u, d$ ) within a semirelativistic potential quark model. Apart from the linear confinement and one-gluon exchange potential between quarks and/or antiquarks, one-boson exchange potential is also included for baryon and meson clusters within the pentaquark system. We also evaluate the fall-apart decays by combining the obtained spectra within the quark exchange model. It is found that the $P_{c} (4312)^{+}$ , $P_{c} (4440)^{+}$ , and $P_{c} (4457)^{+}$ observed by the LHCb Collaboration in 2019 can be well explained by the hadronic molecules of $[Σ_{c} D ˉ]_{1/ 2^{-}}^{1/2} (4318)$ , $[Σ_{c} D ˉ^{*}]_{1/ 2^{-}}^{1/2} (4437)$ , and $[Σ_{c} D ˉ^{*}]_{3/ 2^{-}}^{1/2} (4458)$ , respectively. Meanwhile, $P_{c} (4380)^{+}$ reported by LHCb in 2015 may be assigned as the molecule $[Σ_{c}^{*} D ˉ]_{3/ 2^{-}}^{1/2} (4382)$ , except that it turns to be a narrow state other than a broad one shown by the experimental data. Our study shows that the $σ$ - and $ρ$ -meson exchanges are crucial for the formation of $Σ_{c}^{(*)} D ˉ^{(*)}$ bound states with isospin $I = 1/2$ . Depending on the potential strength of the $σ$ exchange, there may exist very shallow bound states of $Λ_{c} D ˉ^{(*)}$ with isospin $I = 1/2$ and $Σ_{c}^{(*)} D ˉ^{(*)}$ with isospin $I = 3/2$ . Our study may provide useful information for further exploring the hidden-charm pentaquarks in future experiments.
hep-phhep-ex
17
FLARE: an open-source data workflow orchestration tool
Cameron Cooper Harris · Aman Desai · Paul Jackson
Flare is an open-source Python-based data workflow orchestration tool powered by b2luigi. It automates the workflow of Monte Carlo (MC) generators inside the Key4HEP stack, such as Whizard, MadGraph5 and Pythia8, together with fast detector simulation using Delphes. It also automates the Future Circular Collider (FCC) physics analysis software workflow. These workflows are combined, giving a user an automated pipeline from MC production to final FCCAnalyses histograms. With its customisation options and Python API, Flare simplifies executing FCC-ee analyses, especially when custom MC events are required.
hep-ph
18
Measure of the kaon structure: generalized valence quark distribution functions and form factors
H. Nematollahi · K. Azizi
We investigate the structure of the $K^{+}$ meson through calculating its valence-quark (anti quark) generalized parton distribution functions (GPDs) and form factors (FFs). For this purpose, we use a theoretical framework which is based on the exponential representation scheme (ERS). In this scheme the valence-quark GPDs of the light mesons, including the kaon, are considered as the valence quark distribution function crossed by the exponential of a profile function, at zero skewness. We apply the modified chiral quark model ( $χ QM$ ) to obtain the input valence distribution functions of the kaon in above scheme and calculate its valence GPDs. The kaon's electromagnetic and gravitational form factors are also determined and compared with existing experimental data and the results of some theoretical and phenomenological models.
hep-phhep-exhep-lat
19
Colour sextet baryons in composite Higgs models
Manuel Kunkel
Composite Higgs models with underlying fermionic descriptions predict a rich spectrum beyond the Standard Model. Besides the colour triplet fermionic resonances that act as top partners, also exotically coloured baryons can appear. In this contribution we summarise the phenomenology of colour sextet baryons. The dominant decay channel proceeds via a colour octet scalar, resulting in pair production signatures with four or six top quarks. In an alternative mass hierarchy, the sextets produce bottom quarks and a collider-stable colour singlet. We derive recasting bounds on the sextet mass, which reach up to $2.64$ TeV.
hep-ph
20
New massive resonances at the LHC
Rosy Caliri
We investigate composite Higgs models arising from a gauge-fermionic UV completion with partial compositeness, where the Higgs boson emerges as a pseudo-Nambu-Goldstone boson (pNGB), and top-partners appear as bound states of three hyperfermions, with $SU (2)_{L} \times SU (2)_{R}$ as the unbroken global subgroup. A bunch of new bound states is predicted by composite Higgs models: spin-0, spin-1/2 and spin-1 resonances. In this work we focus on the phenomenology of the spin-1 resonances. We demonstrate that a generic prediction of these models is the existence of two neutral and one charged spin-1 resonances, which mix significantly with the SM gauge bosons. This mixing allows their single production in Drell-Yan processes at the LHC. We study the LHC phenomenology of these states and identify scenarios where their masses could be as low as $1.5 TeV$ , consistent with the existing LHC data.
hep-ph
21
Study of the $e^{+} e^{-} \to ϕ K^{+} K^{-}$ reaction within triangle dynamics and its implications for the $ϕ (2170)$
Xiang Wei · Cheng Chen · Si-Wei Liu · Zu-Xin Cai · Gang Li · Xiao-Hai Liu · Ju-Jun Xie
We revisit the $e^{+} e^{-} \to ϕ π^{+} π^{-}$ reaction within the $K_{1}$ - $K ˉ$ - $K$ triangle dynamics framework, in which the $e^{+} e^{-}$ pair annihilates through one-photon exchange approximation to produce a $K_{1} K ˉ$ pair, followed by the $K_{1} \to ϕ K$ decay and the final-state $K K ˉ \to π^{+} π^{-}$ rescattering. With the same theoretical formalism and model parameters, the $e^{+} e^{-} \to ϕ K^{+} K^{-}$ reaction is investigated, and it is found that the predicted total cross sections for the $e^{+} e^{-} \to ϕ K^{+} K^{-}$ reaction are in good agreement with the existing BESIII measurements. Our study shows that the triangle singularity in the $ϕ K^{+} K^{-}$ channel is strongly suppressed, because the higher $K^{+} K^{-}$ mass threshold shifts the kinematics away from the triangle singularity condition and the phase space near the $K_{1} K ˉ$ threshold is very limited. Moreover, the interference between the tree-level and loop amplitudes eliminates the remaining signal. These combined effects naturally explain the absence of a distinct $ϕ (2170)$ signal in the $e^{+} e^{-} \to ϕ K^{+} K^{-}$ reaction, provide a strong test of the model, and reinforce the picture that both reactions are governed by the same underlying mechanism, in which the $ϕ (2170)$ state is produced in the $e^{+} e^{-}$ annihilation from the $K_{1}$ - $K ˉ$ - $K$ triangle loop.
hep-ph
22
Paired charmonium and bottomonium production in rare exclusive decays of Z boson
F. A. Martynenko · A. P. Martynenko · A. A. Skakun
The processes of paired charmonium and bottomonium production in Z-boson decays are investigated within the relativistic quark model. Various decay mechanisms are examined, and relativistic decay amplitudes are constructed, taking into account the relative momenta of heavy quarks. Decay widths are calculated for various mechanisms in the nonrelativistic approximation and taking into account relativistic corrections.
hep-ph
23
On the Maximal CP Violation in Leptogenesis with Two Right Handed Neutrinos
Swapnil Dutta
We present a generalized exact analytical expression for the upper bound on the CP-violating decay asymmetry in the case of standard vanilla leptogenesis within the minimal type-I seesaw with two Right Handed Neutrinos (RHNs) case scenario as a function of the effective neutrino mass in the hierarchical limit. We derive the bound using a novel analytical treatment of the roots of a quartic equation arising from the conditions for successful leptogenesis, in which the CP asymmetry, effective neutrino mass, and other physical quantities enter as parameters. We find that the upper bound on CP asymmetry is a monotonically increasing function of the effective neutrino mass, asymptotically saturating to a global maximum at the large effective mass regime. We find that our exact analytical expression of the upper bound as a function of the effective neutrino mass is smaller than the previous analytical results in the literature. We also find that the global maximum on CP asymmetry with two RHNs obtained at the large effective mass regime is less than the Davidson-Ibarra bound corresponding to the standard vanilla leptogenesis scenario with three RHNs, leading to a more stringent bound on the lightest RHN mass for the scenario with two RHNs, as expected from some previous results in literature. We find that the deviation from the standard Davidson-Ibarra bound becomes most dramatic for inverted neutrino mass hierarchy, by nearly two orders of magnitude.
hep-ph
24
Stasis Combs: Gravitational-Wave Signatures of Recurrent Cosmological Stasis
Gabriela Barenboim · Anne-Katherine Burns
Cosmological stasis can recur multiple times, and each occurrence imprints a characteristic feature on the inflationary gravitational wave background (IGWB). We extend the single-epoch spectral template to an arbitrary number $N$ of consecutive stasis epochs, deriving a closed-form $N$ -epoch piecewise template that factorizes cleanly: the amplitude steps at each break are determined entirely by the local equation of state $w_{s}^{(i)}$ of that epoch, while the inter-epoch plateau levels encode the accumulated spectral tilt from all prior epochs. Each resolved spectral feature yields an independent test of the Bessel-function consistency relation $C^{2} = C^{2} (α)$ established in~\cite{BarenboimBurns:paper1}, and the probability that $N$ such tests are simultaneously satisfied by a non-stasis spectrum falls sharply with $N$ , making a confirmed multi-epoch comb the strongest available discriminator against constant- $w$ alternatives. We apply the formalism to the triple-stasis scenario of~\cite{Dienes:2023ziv}, which chains three pairwise stasis mechanisms (matter/radiation, vacuum-energy/matter, vacuum-energy/radiation) sequentially. For each block we derive the conditions under which the epoch lies within the template's validity range $w_{s} > - 1/3$ . We show that the Fig.~3 benchmark of~\cite{Dienes:2023ziv} falls outside this range and identify parameter choices that are both physically realizable and accessible to the template. We validate the inter-plateau ratio predictions numerically for representative two- and three-block chains, and work out the touching-epoch limit in which consecutive blocks share a break frequency without an intervening radiation-dominated interval. Finally, we discuss the detectability of a variety of multi-epoch stasis scenarios and give the minimum detectable tensor-to-scalar ratio as a function of the number of recurrent stasis epochs.
hep-phastro-ph.COgr-qc
25
Comparing theoretical descriptions of Drell-Yan angular coefficients
Nikita Gramotkov · Oleg Teryaev
A quantitative comparison of the predictions of three theoretical descriptions (TMD, pQCD and geometrical) of the angular coefficients in Drell-Yan Z-boson production with new experimental data on angular coefficients obtained by the ATLAS, CMS and LHCb collaborations has been performed. In the central rapidity region at low- $Q_{T}$ , the TMD calculation provides a better description of the $A_{0}$ and $A_{2}$ coefficients among the descriptions considered. The differences between the approaches are less pronounced for $A_{1}$ , $A_{3}$ and $A_{4}$ coefficients. The results identify $A_{0}$ , $A_{2}$ and the Lam--Tung relation as the most sensitive observables at low-QT and illustrate the domains of applicability of the three descriptions.
hep-ph
26
Investigation of low-lying $Ω_{b} (1 P)$ states in an unquenched coupled-channel framework
Zi-Le Zhang · Si-Qiang Luo · Shuai-Wei Wang · Qin Chang
In this work, we study the unquenched effects on the low-lying $Ω_{b} (1 P)$ states with a coupled-channel equations. We reveal how the unquenched effects affect the $Ω_{b} (1 P)$ spectroscopy and component mixing. The numerical results indicate that the $J^{P} = 1/ 2^{-}$ $Ω_{b} (1 P)$ state dominated by the $j_{ℓ} = 0$ configuration exhibits significant coupled-channel effects due to its $S$ -wave coupling to the $Ξ_{b} K ˉ$ channel, where $j_{ℓ}$ denotes the total angular momentum of the light flavor degrees-of-freedom. In this scenario, the mass of this state may be shifted close to or below the $Ξ_{b} K ˉ$ threshold, making the radiative and isospin-breaking channels kinematically allowed decay processes. The present analysis provides a coupled-channel perspective on the low-lying $Ω_{b} (1 P)$ spectrum and offers guidance for future experimental studies of excited bottom baryons.
hep-phhep-ex
27
Cosmological anatomy of interacting dark energy
Miguel A. Sabogal🇮🇹 · Sunny Vagnozzi🇮🇹 · Eleonora Di Valentino🇬🇧
Interacting dark energy (IDE) models, featuring interactions between dark matter (DM) and dark energy (DE), have received significant renewed interest. However, little attention has been devoted to understanding their genuine cosmological signatures, with comparisons against $Λ$ CDM often carried out at fixed cosmological parameters. Considering the widely studied model with energy exchange rate proportional to the DE density, we carry out a three-level sequence of comparisons, starting from the naïve fixed-parameter comparison, then compensating for shifts in $θ_{s}$ and $z_{eq}$ , and then removing effects due to the modified background. We show that fixing $θ_{s}$ and $z_{eq}$ leads to pre-recombination evolutions of the Weyl potential, photon monopole, and baryon velocity which are nearly identical to their $Λ$ CDM counterparts, and hence virtually indistinguishable Cosmic Microwave Background (CMB) temperature power spectra. Comparing IDE to a non-interacting $w$ CDM model with the same background, we find small scale-dependent signatures in CMB lensing. We find larger differences in the matter power spectrum, reflecting the different values of $Ω_{m}$ resulting from the different partition of the dark sector into DM and DE, with only percent-level differences remaining once we compare $Ω_{m}^{2} P_{m} (k)$ , indicating the importance of high-fidelity determinations of $Ω_{m}$ . Our controlled comparison strategy can be a powerful tool for a wide range of models beyond $Λ$ CDM.
↳ astro-ph.COgr-qchep-ph0 citations
28
Femtoscopic Correlation Functions in Density Operator Representation
Hao-Nan Liu · Duo-Lun Ge · Zhi-Wei Liu · Jun-Xu Lu · Li-Sheng Geng
Femtoscopic correlation functions (CFs) have been increasingly used to extract strong interactions between pairs of unstable particles, but their physical soundness has recently been questioned. To answer this, we formulate CFs at the operator level, with the observed subsystem described by a reduced density operator and subsequent dynamics absorbed into an effective measurement operator. The Koonin-Pratt form is recovered under four well-motivated reductions. The formulation makes explicit that the source-side and interaction-side representations must be consistently matched, and motivates an operational convention in which a measured reference correlation establishes a compatible source--interaction pairing that can be extended to other pairs for CF-to-CF predictions.
↳ quant-phhep-exhep-phnucl-ex+1
29
Projective Origin of the Spin Hydrodynamic Attractor and Its Resurgent repeller
Qi Zhou · Enke Wang
We investigate the projective and resurgent structure of a spin hydrodynamic attractor in Bjorken expansion. We show that the nonlinear spin attractor family is determined by the projective classes of the two dimensional linear solution space, with the attractor and repeller corresponding to two distinguished projective directions and the linear modes ratio generating the full one-parameter transseries tower. We identify the attractor and repeller as complete global solution branches associated with the two distinguished projective directions of the underlying linear solution space. Using the projective transseries structure, we show analytically that the data of repeller are encoded in the Borel-Stokes structure of the attractor expansion. These results provide an explicit analytic realization of resurgence relations that are often extracted through high order expansions and numerical Borel analysis, and yield a unified description of the attractor, the repeller, and their Borel-Stokes connection in minimal causal spin hydrodynamics.
↳ nucl-thhep-phhep-th
30
A Global Overview of Starobinsky Inflation beyond slow-roll with CMB-BAO data
Tarun · Tanmoy Modak · Björn Malte Schäfer
We perform a global analysis of the Starobinsky inflation using most recent CMB data from ACT and SPT together with DESI BAO measurements. By directly solving the equations of motion, we find relatively stronger constraints on the model parameters than those obtained under the slow-roll approximation from the baseline $Λ$ CDM parameters $A_{s}$ and $n_{s}$ . We translate these constraints into limits on the reheating temperature. We also discuss the dependence of the prior choices of the model parameters. Further, the correlation of the model parameters with the BAO parameter $r_{d} h$ is also studied. We further investigate the impact of the global analysis on the dimension-six $R^{3}$ modified Starobinsky model, deriving constraints on its additional parameters. Finally, we also provide parameter limits on the effective inflationary Hubble slow-roll (HSR) and potential slow-roll (PSR) parametrization.
↳ astro-ph.COgr-qchep-ph
31
Long-Lived False-vacuum-Trapped Self-Bound Neutron-rich Droplets
Jingdong Shao · Mei Huang
We propose a novel class of anomalous nuclear matter: self-bound, neutron-rich droplets trapped in false vacuum associated with the nuclear liquid-gas phase transition in heavy-ion collisions. During the early stage of the fireball expansion, strongly correlated local clusters dynamically decouple from the bulk medium and are excited into the liquid phase. As the ambient fireball cools rapidly, these clusters are quenched into metastable anomalous droplets with isospin asymmetry from ambient neutron-enrichment. Mechanical equilibrium among nuclear pressure difference, Coulomb repulsion, and surface tension stabilizes droplets at radii of order $O (10)$ fm. Isospin asymmetry induces high potential barrier that suppresses decay channels, yielding long lifetimes. These droplets are expected to exhibit characteristic charge-to-mass ratios distinct from conventional neutron-rich nuclei, providing clear experimental signatures for future heavy-ion collision searches.
↳ nucl-thhep-ph
32
Relativistic Stellar Oscillations from Ultralight Dark Matter
Shanae Oishi · Christopher Reyes · Jeremy Sakstein
Ultra-light dark matter, composed of bosons behaving as classical waves, can resonantly excite stellar oscillations. In this work, we investigate this phenomenon in relativistic stars, showing that $ℓ = 0$ fluid modes can be excited. We derive a framework for calculating the mode amplitude and apply it to neutron stars to predict the associated surface temperature fluctuations; the resulting signal lies beyond current observational sensitivities. We discuss prospects for extending this approach to other compact objects.
↳ gr-qcastro-ph.COastro-ph.HEhep-ph
33
Probing Forward-Backward Multiplicity Correlations and Fluctuations Using the Strongly Intensive Observable $Σ$ in Pb-Pb Collisions at SPS Energies with UrQMD
Ekata Nandy · Subhasis Chattopadhyay
The strongly intensive observable $Σ$ , constructed from charged-pion multiplicities in separated forward (F) and backward (B) pseudorapidity intervals $Δ η$ , is studied within the UrQMD transport model for Pb--Pb collisions at SPS energies. The dependence of $Σ$ on $Δ η$ is investigated as a function of collision energy, centrality, and acceptance to probe the longitudinal structure of multiplicity fluctuations and correlations. For $s_{N N} > 6$ GeV, $Σ$ exhibits a non-monotonic dependence on $Δ η$ , increasing from values near unity at small separation, reaching a maximum at intermediate $Δ η$ , and decreasing towards unity at larger separation. Decomposition into scaled variance and covariance terms shows that this behavior arises from their different $Δ η$ dependences. Calculations with resonance decays switched off show that resonances dominate short-range correlations, while $Σ > 1$ at larger $Δ η$ indicates fluctuations and correlations extending over broader pseudorapidity intervals. The magnitude of $Σ$ , together with its fluctuation and covariance components, increases from central to peripheral collisions, with fluctuations dominating over covariance at large $Δ η$ . As the collision energy increases, the pseudorapidity interval over which $Σ > 1$ persists becomes significantly larger, whereas at lower energies, where resonance dynamics dominate particle production, $Σ$ is nearly independent of $Δ η$ . An acceptance-scaling study reveals deviations from simple binomial scaling in regions of strong correlations. These results demonstrate the sensitivity of $Σ$ to the interplay between multiplicity fluctuations and forward--backward correlations in heavy-ion collisions.
↳ nucl-thhep-ph
34
A comprehensive theory framework for perturbative calculations of $δ_{C}$ in superallowed beta decays
Chien-Yeah Seng
The present high precision determination of $∣ V_{u d} ∣$ from superallowed beta decays of $J^{P} = 0^{+}$ , $T = 1$ nuclei is largely built on top of the ``standard'' calculation of the isospin breaking correction $δ_{C}$ to the Fermi matrix element, which assumes the splitting $δ_{C} = δ_{C 1} + δ_{C 2}$ , where $δ_{C 1}$ and $δ_{C 2}$ represent the ``isospin mixing'' correction and the ``radial mismatch'' correction, respectively. In this paper I show that this formalism violates the rule of nucleon basis independence, similar to the gauge invariance requirement in quantum field theory, therefore its outcome is inevitably subject to uncontrolled systematic errors. I further argue that the perturbative formalism is the only approach that allows the computation of $δ_{C}$ at the precision level required for the test of the Cabibbo unitarity. Advancing from existing literature, I develop the full ``generating function approach'' to compute $δ_{C}$ perturbatively, with connections to nuclear mass splittings and the isospin breaking in nuclear charge radii as theory benchmarks.
↳ nucl-thhep-exhep-phnucl-ex