Fri·Mar 8, 2024Friday·March 8, 2024

1. 01*

   Fermion Dark Matter in the Vector Scotogenic Model: A Survey of Signatures

   Paulo Areyuna C.🇨🇱 · Jilberto Zamora-Saa🇨🇱 · Alfonso R. Zerwekh🇨🇱

   In this work, we have studied the Vector Scotogenic Model in the context of the Dark Matter problem. Due to unitarity considerations, we have focused on the scenario with fermion dark matter, finding out that co-annihilations play a fundamental role in achieving dark matter relic abundance. Moreover, the coannihilation effects allow to separate the parameter space into two regions with different phenomenology. In addition, we have studied the detection prospects of these regions separately, focusing on signatures that can appear in lepton flavor violating decays, indirect and direct searches, and the production of these new particles at collider facilities.

   hep-phEPJC(2024)·2 citations
2. 02*

   A Simple Model of Pentaquarks

   Davide Germani🇮🇹 · Farhad Niliani🇮🇹 · Antonio D. Polosa🇮🇹

   We describe pentaquarks as baryo-charmonia with a color octet $c\bar{c}$ core bonded to a color octet three-quark system. Fermi statistics of the light quark cloud allows to describe two pentaquark triplets: a lower one, well supported by experiment, and a higher one with strangeness. For the time being, the lowest line of the strange triplet has been experimentally identified in a $3\sigma$ peak. Data also suggest (at least) two different production mechanisms for pentaquarks. We show how this can be described in the proposed scheme.

   hep-phEPJC(2024)·7 citations
3. 03*

   Energy-Energy Correlation in the back-to-back region at N${}^3$LL+NNLO in QCD

   Ugo Giuseppe Aglietti🇮🇹 · Giancarlo Ferrera🇮🇹

   We consider the Energy-Energy Correlation (EEC) function in high-energy electron-positron annihilation to hadrons. In the back-to-back (two-jet) region, we perform the all-order resummation of the logarithmically-enhanced contributions in QCD perturbation theory up to next-to-next-to-next-to-leading logarithmic (N${}^3$LL) accuracy. Away from the back-to-back region, we consistently combine resummed predictions with the known fixed-order results up to next-to-next-to-leading order (NNLO) and we are able to obtain an accurate fit of the $\mathcal{O}({\alpha }_S^3)$ remainder function from the numerical QCD computation of the full spectrum. All perturbative terms up to order ${\alpha }_S^3$ are included in our calculation and a non-trivial cross-check in the back-to-back region is obtained by comparing the SCET analytic calculation against the corresponding numerical QCD computation. In particular, the values of the $\mathcal{O}({\alpha }_S^3)$ resummation coefficients have been numerically verified. We regularize the Landau singularity of the QCD coupling within the so-called Minimal Prescription and we discuss the reduction of the perturbative scale dependence of distributions at higher orders, as a means to estimate the corresponding residual perturbative uncertainty. Finally, after introducing within a dispersive approach non-perturbative power corrections, we are able to obtain an accurate description of experimental data at LEP and SLC accelerators.

   hep-phPRD(2024)·16 citations
4. 04*

   Estimating the production of dark photons with $\eta$ decay in Ultra-peripheral Collisions

   Wei Kou🇨🇳 · Xurong Chen🇨🇳

   We propose that the signal of dark photons can be found in the decay channel of $\eta$, and that a certain number of events of dark photon leptonic decay can be observed in the double-photon collision process of heavy-ion ultra-peripheral collisions (UPC). We estimate the total cross-section for producing dark photons in ultra-peripheral $PbPb$ collisions at existing and planned future hadron colliders, as well as the number of signal events. Our results support the search for dark photon signals in ultra-peripheral $PbPb$ collisions. We consider the recent signals of $\eta$ decays produced in LHC $pp$ collisions and estimate the number of dark photon events from the same number of $\eta$ decays from CMS. Based on CMS results, we estimate that there will be at least 1000 signal events of dark photons observed for the mass $m_{A^{\prime }}$ less than 500 MeV. In this study, we propose a method using $\eta$ meson decay to search for signs of dark photons at heavy-ion colliders, such as LHC and RHIC.

   hep-phCPC(2024)·0 citations
5. 05*

   Probing the mixing between sterile and tau neutrinos in the SHiP experiment

   Ki-Young Choi🇰🇷 · Sung Hyun Kim🇰🇷 · Yeong Gyun Kim🇰🇷 · Kang Young Lee🇰🇷 · Kyong Sei Lee🇰🇷 · Byung Do Park🇰🇷 · Jong Yoon Sohn🇰🇷 · Seong Moon Yoo🇰🇷 · Chun Sil Yoon🇰🇷

   We study the expected sensitivity to the mixing between sterile and tau neutrinos directly from the tau neutrino disappearance in the high-energy fixed target experiment. Here, the beam energy is large enough to produce tau neutrinos at the target with large luminosity. During their propagation to the detector, tau neutrinos may oscillate into sterile neutrinos. By examining the energy spectrum of the observed tau neutrino events, we can probe the mixing between sterile and tau neutrinos directly. In this paper, we consider Scattering and Neutrino Detector (SND) at SHiP experiment as a showcase, which uses 400 GeV protons from SPS at CERN, and expect to observe 7,300 tau and anti-tau neutrinos from the $2\times 10^{20}$ POT for 5 years operation. Assuming the uncertainty of 10\%, we find the sensitivity $|U_{\tau 4}{|}^2\sim 0.08$\, (90\% CL) for $\Delta m_{41}^2\sim 500{\mathrm{eV}}^2$ with 10\% background to the signal. We also consider a far SND at the end of the SHiP Hidden Sector Decay Spectrometer (HSDS), in which case the sensitivity would be enhanced to $|U_{\tau 4}{|}^2\sim 0.02$. Away from this mass, the sensitivity becomes lower than $|U_{\tau 4}{|}^2\sim 0.15$ for $\Delta m_{41}^2\lesssim 100{\mathrm{eV}}^2$ or $\Delta m_{41}^2\gtrsim 10^4{\mathrm{eV}}^2$.

   hep-phhep-exJHEP(2024)·5 citations
6. 06*

   Possible ${\Sigma }_c^{\ast }\bar{\Sigma }$ molecular states

   Bing Wu🇨🇳 · Xiang-Kun Dong🇩🇪 · Feng-Kun Guo🇨🇳 · Bing-Song Zou🇨🇳

   We investigate the possibility of deuteron-like ${\Sigma }_c^{\ast }\bar{\Sigma }$ bound states within the one-boson-exchange model and systematically analyze the effects of the contact-range ${\delta }^3(\vec{r})$ potential, the tensor term from the vector-meson exchange, and nonlocal potentials due to the dependence on the sum of the initial and final state center-of-mass momenta. We find that the pion-exchange potential including the ${\delta }^3(\vec{r})$ term and the tensor term of the $\rho$-exchange potential exhibit comparable magnitudes but opposite signs for any $S$-wave baryon-antibaryon systems. For the ${\Sigma }_c^{\ast }\bar{\Sigma }$ system, it is most likely to form bound states with mass around 3.7 GeV in the $I(J^P)=0(2^{-})$ and $1(2^{-})$ channels.

   hep-phnucl-thPRD(2024)·3 citations
7. 07*

   Binned top quark spin correlation and polarization observables for the LHC at 13.6 TeV

   Werner Bernreuther🇩🇪 · Long Chen🇨🇳 · Zong-Guo Si🇨🇳

   We consider top-antitop quark $(t\bar{t})$ production at the Large Hadron Collider (LHC) with subsequent decays into dileptonic final states. We use and investigate a set of leptonic angular correlations and distributions with which all the independent coefficient functions of the top-spin dependent parts of the $t\bar{t}$ production spin density matrices can be experimentally probed. We compute these observables for the LHC center-of-mass energy 13.6 TeV within the Standard Model at next-to-leading order in the QCD coupling including the mixed QCD-weak corrections. We determine also the $t\bar{t}$ charge asymmetry where we take in addition also the mixed QCD-QED corrections into account. In addition we analyze and compute possible new physics (NP) effects on these observables in terms of a gauge-invariant effective Lagrangian that contains the operators up to mass dimension six that are relevant for hadronic $(t\bar{t})$ production. First we compute our observables inclusive in phase space. In order to investigate which region in phase space has, for a specific observable, a high NP sensitivity, we determine our observables also in two-dimensional $(M_{t\bar{t}},\cos {\theta }_t^{\ast })$ bins, where $M_{t\bar{t}}$ denotes the $t\bar{t}$ invariant mass and ${\theta }_t^{\ast }$ is the top-quark scattering angle in the $t\bar{t}$ zero-momentum frame.

   hep-phhep-exPRD(2024)·7 citations
8. 08*

   Dynamic critical behavior of the chiral phase transition from the real-time functional renormalization group

   Johannes V. Roth🇩🇪 · Yunxin Ye🇩🇪 · Sören Schlichting🇩🇪 · Lorenz von Smekal🇩🇪

   In the chiral limit the complicated many-body dynamics around the second-order chiral phase transition of two-flavor QCD can be understood by appealing to universality. We present a novel formulation of the real-time functional renormalization group that describes the stochastic hydrodynamic equations of motion for systems in the same dynamic universality class, which corresponds to Model G in the Halperin-Hohenberg classification. Our approach preserves all relevant symmetries of such systems with reversible mode couplings. We show that the calculations indeed produce the non-trivial value $z=d/2$ for the dynamic critical exponent, where $d$ is the number of spatial dimensions. From the momentum and temperature dependence of the diffusion coefficient of the conserved charge densities, we extract the dimensionless universal scaling function.

   hep-phJHEP(2025)·19 citations
9. 09*

   Next-to-eikonal corrections to dijet production in Deep Inelastic Scattering in the dilute limit of the Color Glass Condensate

   Pedro Agostini🇵🇱 · Tolga Altinoluk🇵🇱 · Néstor Armesto🇪🇸

   We analyze the effects of next-to-eikonal corrections on dijet production in Deep Inelastic Scattering off nuclear targets in the framework of the Color Glass Condensate. They require the knowledge of correlators of fields in the target beyond those computed in the standard McLerran-Venugopalan model, specifically those between transverse and boost-enhanced components, and of the recoil of the fields. We neglect the latter, while for the former we develop a linear model valid for large nuclei. We considered the unpolarized cross sections for dijet production in the approximation of a homogenous dilute nucleus, obtaining simple analytic expressions for the cross sections at nex-to-eikonal accuracy, valid in the limit of total dijet momentum and dijet momentum imbalance larger than the saturation scale of the nucleus. We perform a numerical study of the results at energies of the Electron Ion Collider, finding $\mathcal{O}(10\%)$ effects in the cross sections at large total momentum. We also analyze the azimuthal asymmetries between total momentum and imbalance, finding that non-eikonal corrections induce odd azimuthal harmonics for the situation of jets with equal momentum fractions from the virtual photon, where they are absent in the eikonal approximation. Finally, in the eikonal approximation we have compared the results of our analytic expansion valid in the dilute limit of the target, and the full Color Glass Condensate results in the McLerran-Venugopalan model and their correlation limit. Our analytic expressions match the correlation limit ones in the region where both should be simultaneously valid and reproduce very well the full Color Glass Condensate results in its validity region.

   hep-phnucl-thJHEP(2024)·25 citations
10. 10*

    $B$-meson production at forward rapidities in $pp$ collisions at the LHC: Estimating the intrinsic bottom contribution

    Yuri N. Lima🇧🇷 · Victor P. Goncalves🇧🇷 · André V. Giannini🇧🇷

    The production of $B$ mesons at forward rapidities is strongly sensitive to the behavior of the gluon and bottom distribution functions for small and large values of the Bjorken - $x$ variable. In this exploratory study, we estimate the cross - section for the $B^{\pm }$ meson production in the kinematic range probed by the LHCb detector and that will be analyzed by the future Forward Physics Facility (FPF) considering the hybrid formalism, the solution of the running coupling Balitsky - Kovchegov equation and distinct descriptions for the bottom distribution function. We assume an ansatz for the intrinsic bottom component in the proton wave function, and estimate its impact on the transverse momentum, rapidity and Feynman - $x$ distributions. Our results indicate that the presence of an intrinsic bottom strongly modifies the magnitude of the cross - section at ultra - forward rapidities ($y\ge 6$), which implies an enhancement of the $B^{\pm }$ production at the FPF. Possible implications on the prompt neutrino flux at ultra-high energies are also briefly discussed.

    hep-phhep-exEPJC(2024)·3 citations
11. 11*

    Leptoquark-Mediated Two-Loop Neutrino Mass in Unified Theory

    Kevin Hinze🇨🇭 · Shaikh Saad🇨🇭

    Scalar leptoquarks naturally arise within unified theories, offering a promising avenue for addressing one of the most significant challenges of the Standard Model--the existence of non-zero neutrino masses. In this work, we present a unified theory based on the SU(5) gauge group, where neutrino mass appears at the two-loop level via the propagation of scalar leptoquarks. Due to the unified framework, the charged fermion and neutrino masses and mixings are entangled and determined by a common set of Yukawa couplings. These exotic particles not only shed light on the neutrino mass generation mechanism but also help to achieve the unification of gauge couplings and are expected to lead to substantial lepton flavor violating rates, offering tangible opportunities for experimental verification. Reproducing the observed neutrino mass scale necessitates that a set of leptoquarks reside a few orders of magnitude below the unification scale--a specific feature of the proposed scenario. Moreover, maximizing the unification scale implies TeV scale new physics states, making them accessible at colliders. The diverse roles that leptoquarks play highlight the elegance and predictive ability of the proposed unified model.

    hep-phPLB(2024)·7 citations
12. 12*

    Prospects for Heavy Neutral Lepton Searches at Short and Medium Baseline Reactor Experiments

    N. van Remortel🇧🇪 · M. Colomer Molla🇧🇪 · B. Clerbaux🇧🇪 · A. De Roeck🇨🇭 · M. Drewes🇧🇪 · R. Keloth🇧🇪 · H. Sfar🇧🇪 · S. Vercaemer🇧🇪 · M. Verstraeten🇧🇪

    Heavy neutrinos with masses in the MeV range can in principle simultaneously explain the light neutrino masses and the origin of baryonic matter in the universe. The strongest constraints on their properties come from their potential impact on the formation of light elements in the early universe. Since these constraints rely on assumptions about the cosmic history, independent checks in the laboratory are highly desirable. In this paper, we discuss the opportunity to search for heavy neutrinos within the MeV mass range in short and medium baseline reactor neutrino experiments, using the SoLid, JUNO and TAO experiments as examples. These experiments can give the currently strongest upper bound on the mixing between the light electron neutrinos and the heavy neutrino in the 2-9 MeV mass range.

    hep-phJHEP(2024)·6 citations
13. 13*

    Birdtracks of Exotic SU(N) Color Structures

    Thorsten Ohl (University of Würzburg)🇩🇪

    I introduce a systematic procedure for constructing complete and independent sets of interactions of fields transforming under exotic representations of SU(N), in particular the SU(3) gauge group of QCD. It uncovers errors in previous results, starting with interactions of four fields including a single sextet.

    hep-phhep-thmath-phmath.MPJHEP(2024)·7 citations
14. 14*

    Invariant amplitudes, unpolarized cross sections, and polarization asymmetries in (anti)neutrino-nucleon elastic scattering

    Kaushik Borah🇺🇸 · Minerba Betancourt🇺🇸 · Richard J. Hill🇺🇸 · Thomas Junk🇺🇸 · Oleksandr Tomalak🇺🇸

    At leading order in weak and electromagnetic couplings, cross sections for (anti)neutrino-nucleon elastic scattering are determined by four nucleon form factors that depend on the momentum transfer $Q^2$. Including radiative corrections in the Standard Model and potential new physics contributions beyond the Standard Model, eight invariant amplitudes are possible, depending on both $Q^2$ and the (anti)neutrino energy $E_{\nu }$. We review the definition of these amplitudes and use them to compute both unpolarized and polarized observables including radiative corrections. We show that unpolarized accelerator neutrino cross-section measurements can probe new physics parameter space within the constraints inferred from precision beta decay measurements.

    hep-phhep-exnucl-exnucl-thPRD(2024)·9 citations
15. 15*

    Stability and causality of rest frame modes in second-order spin hydrodynamics

    Asaad Daher🇵🇱 · Wojciech Florkowski🇵🇱 · Radoslaw Ryblewski🇵🇱 · Farid Taghinavaz🇮🇷

    We analyze the low- and high-momentum rest frame modes in the second-order spin hydrodynamics and check the asymptotic causality of the theory. A truncation scheme of the Israel-Stewart formalism derived in our earlier work is proposed that extends the minimal causal formulation. It consists of altogether 40 interconnected relaxation-type dynamical equations -- 16 (24) of them correspond to the independent components of the energy-momentum (spin) tensor. Similarly to previous studies, we find that the stability of the perturbations and asymptotic causality require using the spin equation of state that satisfies the generalized Frenkel condition demanding that the ``electric'' and ``magnetic'' components of the spin density tensor have opposite signs. For low-momentum modes this behavior is similar to that found earlier for the first-order (Navier-Stokes) spin hydrodynamics.

    hep-phmath-phmath.MPnucl-thPRD(2024)·24 citations
16. 16*

    Exclusive production of double light neutral mesons at the $e^{+}{e}^{-}$ colliders

    Junliang Lu🇨🇳 · Cai-Ping Jia🇨🇳 · Yu Jia🇨🇳 · Xiaonu Xiong🇨🇳

    In this work we investigate the exclusive production of a pair of light neutral mesons in $e^{+}{e}^{-}$ annihilation, where the final state bears an even $C$-parity. The production processes can be initiated via the photon fragmentation or the non-fragmentation mechanism. While the fragmentation contribution can be rigorously accounted, the non-fragmentation contributions are calculated within the framework of collinear factorization, where only the leading-twist light-cone distribution amplitudes (LCDAs) of mesons are considered. Mediately solely by the non-fragmentation mechanism, the production rates of double light neutral pseudoscalar mesons are too small to be observed at the commissioning $e^{+}{e}^{-}$ facilities. In contrast, the production rates of a pair of light neutral vector mesons are greatly amplified owing to the significant kinematic enhancement brought by the fragmentation mechanism. It is found that, at $\sqrt{s}=3.77$ GeV, after including the destructive interference between the non-fragmentation and fragmentation contributions, the production rates for $e^{+}{e}^{-}\to {\rho }^0{\rho }^0$ and ${\rho }^0\omega$ can be lowered by about 10\% and 30\% relative to the fragmentation predictions. Future precise measurement of these exclusive double neutral vector meson production channels at {\tt BESIII} experiment may provide useful constraints on the LCDAs of light vector mesons.

    hep-phPRD(2024)·3 citations
17. 17*

    Scaling of pre-equilibrium dilepton production in QCD Kinetic Theory

    Oscar Garcia-Montero🇩🇪 · Philip Plaschke🇩🇪 · Sören Schlichting🇩🇪

    We use QCD kinetic theory to compute dilepton production coming from the pre-equilibrium phase of the Quark-Gluon Plasma created in high-energy heavy-ion collisions. We demonstrate that the dilepton spectrum exhibits a simple scaling in terms of the specific shear viscosity $\eta /s$ and entropy density $dS/d\zeta \sim {\left(T{\tau }^{1/3}\right)}_{\infty }^{3/2}$, which can be derived from dimensional analysis in the presence of a pre-equilibrium attractor. Based on this scaling we perform event-by-event calculations of in-medium dilepton production and determine the invariant mass range where the pre-equilibrium yield is the leading contribution.

    hep-phnucl-thPRD(2025)·23 citations
18. 18*

    Exotic Hadrons at LHCb

    Daniel Johnson🇬🇧 · Ivan Polyakov🇨🇭 · Tomasz Skwarnicki🇺🇸 · Mengzhen Wang🇮🇹

    It has been five years since the data sample from the LHCb detector, the first experiment optimized for heavy-flavor physics studies at a hadronic collider, was completed. These data led to many major discoveries in exotic hadron spectroscopy, which we review in this article. We supplement the experimental results with a selection of phenomenological interpretations. As the upgraded LHCb detector is expected to collect a larger data sample starting in 2024, the near- and further-future potential of the LHCb program in exotic hadron physics is also discussed.

    ↳ hep-exhep-phAnn.Rev.Nucl.Part.Sci.(2024)·31 citations
19. 19*

    Conformal Symmetry in Quantum Gravity

    Ichiro Oda🇯🇵

    We study the problem of how to derive conformal symmetry in the framework of quantum gravity. We start with a generic gravitational theory which is invariant under both the general coordinate transformation (GCT) and Weyl transformation (or equivalently, local scale transformation), and then construct its BRST formalism by fixing the gauge symmetries by the extended de Donder gauge and scalar gauge conditions. These gauge-fixing conditions are invariant under global $GL(4)$ and global scale transformations. The gauge-fixed and BRST invariant quantum action possesses a huge Poincaré-like $IOSp(10|10)$ global symmetry, from which we can construct an extended conformal symmetry in a flat Minkowski background in the sense that the Lorentz symmetry is replaced with the $GL(4)$ symmetry. Moreover, we construct the conventional conformal symmetry out of this extended symmetry. With a flat Minkowski background $⟨g_{\mu \nu }⟩={\eta }_{\mu \nu }$ and a non-zero scalar field $⟨\varphi ⟩\ne 0$, the $GL(4)$ and global scale symmetries are spontaneously broken to the Lorentz symmetry, thereby proving that the graviton and the dilaton are respectively the corresponding Nambu-Goldstone bosons, and therefore they must be exactly massless at nonperturbative level. One of remarkable aspects in our findings is that in quantum gravity, a derivation of conformal symmetry does not depend on a classical action, and its generators are built from only the gauge-fixing and the FP ghost actions. Finally, we address a generalized Zumino theorem in quantum gravity.

    ↳ hep-thgr-qchep-phEPJC(2024)·11 citations
20. 20*

    Sliding into DM: Determining the local dark matter density and speed distribution using only the local circular speed of the Galaxy

    Patrick G. Staudt🇺🇸 · James S. Bullock🇺🇸 · Michael Boylan-Kolchin🇺🇸 · David Kirkby🇺🇸 · Andrew Wetzel🇺🇸 · Xiaowei Ou🇺🇸

    We use FIRE-2 zoom simulations of Milky Way size disk galaxies to derive easy-to-use relationships between the observed circular speed of the Galaxy at the Solar location, $v_{\mathrm{c}}$, and dark matter properties of relevance for direct detection experiments: the dark matter density, the dark matter velocity dispersion, and the speed distribution of dark matter particles near the Solar location. We find that both the local dark matter density and 3D velocity dispersion follow tight power laws with $v_{\mathrm{c}}$. Using this relation together with the observed circular speed of the Milky Way at the Solar radius, we infer the local dark matter density and velocity dispersion near the Sun to be $\rho =0.42\pm 0.06\mathrm{GeV}\mathrm{c}{\mathrm{m}}^{-3}$ and ${\sigma }_{3D}=280_{-18}^{+19}\mathrm{km}{\mathrm{s}}^{-1}$. We also find that the distribution of dark matter particle speeds is well-described by a modified Maxwellian with two shape parameters, both of which correlate with the observed $v_{\mathrm{c}}$. We use that modified Maxwellian to predict the speed distribution of dark matter near the Sun and find that it peaks at a most probable speed of $257\mathrm{km}{\mathrm{s}}^{-1}$ and begins to truncate sharply above $470\mathrm{km}{\mathrm{s}}^{-1}$. This peak speed is somewhat higher than expected from the standard halo model, and the truncation occurs well below the formal escape speed to infinity, with fewer very-high-speed particles than assumed in the standard halo model.

    ↳ astro-ph.GAastro-ph.COhep-phJCAP(2024)·18 citations
21. 21*

    The stochastic relativistic advection diffusion equation from the Metropolis algorithm

    Gokce Basar🇺🇸 · Jay Bhambure🇺🇸 · Rajeev Singh🇺🇸 · Derek Teaney🇺🇸

    We study an approach to simulating the stochastic relativistic advection-diffusion equation based on the Metropolis algorithm. We show that the dissipative dynamics of the boosted fluctuating fluid can be simulated by making random transfers of charge between fluid cells, interspersed with ideal hydrodynamic time steps. The random charge transfers are accepted or rejected in a Metropolis step using the entropy as a statistical weight. This procedure reproduces the expected strains of dissipative relativistic hydrodynamics in a specific (and non-covariant) hydrodynamic frame known as the density frame. Numerical results, both with and without noise, are presented and compared to relativistic kinetics and analytical expectations. An all order resummation of the density frame gradient expansion reproduces the covariant dynamics in a specific model. In contrast to all other numerical approaches to relativistic dissipative fluids, the dissipative fluid formalism presented here is strictly first order in gradients and has no non-hydrodynamic modes. The physical naturalness and simplicity of the Metropolis algorithm, together with its convergence properties, make it a promising tool for simulating stochastic relativistic fluids in heavy ion collisions and for critical phenomena in the relativistic domain.

    ↳ nucl-thcond-mat.otherhep-phhep-thPRC(2024)·32 citations
22. 22*

    Testing scale-invariant inflation against cosmological data

    Chiara Cecchini🇮🇹 · Mariaveronica De Angelis🇬🇧 · William Giarè🇬🇧 · Massimiliano Rinaldi🇮🇹 · Sunny Vagnozzi🇮🇹

    There is solid theoretical and observational motivation behind the idea of scale-invariance as a fundamental symmetry of Nature. We consider a recently proposed classically scale-invariant inflationary model, quadratic in curvature and featuring a scalar field non-minimally coupled to gravity. We go beyond earlier analytical studies, which showed that the model predicts inflationary observables in qualitative agreement with data, by solving the full two-field dynamics of the system -- this allows us to corroborate previous analytical findings and set robust constraints on the model's parameters using the latest Cosmic Microwave Background (CMB) data from Planck and BICEP/Keck. We demonstrate that scale-invariance constrains the two-field trajectory such that the effective dynamics are that of a single field, resulting in vanishing entropy perturbations and protecting the model from destabilization effects. We derive tight upper limits on the non-minimal coupling strength, excluding conformal coupling at high significance. By explicitly sampling over them, we demonstrate an overall insensitivity to initial conditions. We argue that the model \textit{predicts} a minimal level of primordial tensor modes set by $r\gtrsim 0.003$, well within the reach of next-generation CMB experiments. These will therefore provide a litmus test of scale-invariant inflation, and we comment on the possibility of distinguishing the model from Starobinsky and $\alpha$-attractor inflation. Overall, we argue that scale-invariant inflation is in excellent health, and possesses features which make it an interesting benchmark for tests of inflation from future CMB data.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2024)·28 citations
23. 23*

    Tensor bispectrum mediated by an excited scalar field during inflation

    Zhi-Zhang Peng🇨🇳 · Cheng-Jun Fang🇨🇳 · Zong-Kuan Guo🇨🇳

    We calculate the tensor bispectrum mediated by an excited scalar field during inflation and find that the bispectrum peaks in the squeezed configuration, which is different from that of gravitational waves induced by enhanced curvature perturbations re-entering the horizon in the radiation-dominated era. Measuring the bispectrum provides a promising way to distinguish the stochastic gravitational-wave background generated during inflation from that generated after inflation.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2024)·5 citations
24. 24*

    Superhorizon Curvature Perturbations Are Protected against One-Loop Corrections

    Keisuke Inomata🇺🇸

    We examine one-loop corrections from small-scale curvature perturbations to the superhorizon-limit ones in single-field inflation models, which have recently caused controversy. We consider the case where the Universe experiences transitions of slow-roll (SR) $\to$ intermediate period $\to$ SR. The intermediate period can be an ultra-slow-roll period or a resonant amplification period, either of which enhances small-scale curvature perturbations. We assume that the superhorizon curvature perturbations are conserved at least during each of the SR periods. Within this framework, we show that the superhorizon curvature perturbations during the first and the second SR periods coincide at one-loop level in the slow-roll limit.

    ↳ astro-ph.COgr-qchep-phhep-thPRL(2024)·49 citations
25. 25*

    Circles and Triangles, the NLSM and Tr(${\Phi }^3$)

    Nima Arkani-Hamed🇺🇸 · Carolina Figueiredo🇺🇸

    A surprising connection has recently been made between the amplitudes for Tr(${\Phi }^3$) theory and the non-linear sigma model (NLSM). A simple shift of kinematic variables naturally suggested by the associahedron/stringy representation of Tr$({\Phi }^3$) theory yields pion amplitudes at all loops. In this note we provide an elementary motivation and proof for this link going in the opposite direction, starting from the non-linear sigma model and discovering its formulation as a sum over triangulations of surfaces with simple numerator factors. This uses an ancient connection between "circles" and "triangles", interpreting the equation $y=\sqrt{1-x^2}$ both as parametrizing points on a circle as well as generating the number of triangulations of polygons. A further simplification of the numerator factors exposes them as arising from the kinematically shifted Tr(${\Phi }^3$) theory, and gives rise to novel tropical representations of NLSM amplitudes. The connection to Tr$({\Phi }^3)$ theory defines a natural notion of "surface-soft limit" intrinsic to curves on surfaces. Remarkably, with this definition, the soft limit of pion amplitudes vanishes directly at the level of the integrand, via obvious pairwise cancellations. We also give simple, explicit expressions for the multi-soft factors for tree and loop-level integrands in the limit as any number of pions are taken "surface-soft".

    ↳ hep-thhep-phJHEP(2025)·44 citations
26. 26*

    Non-Invertible Symmetries, Anomalies and Scattering Amplitudes

    Christian Copetti🇬🇧 · Lucia Cordova🇨🇭 · Shota Komatsu🇨🇭

    We show that crossing symmetry of S-matrices is modified in certain theories with non-invertible symmetries or anomalies. Focusing on integrable flows to gapped phases in two dimensions, we find that S-matrices derived previously from the bootstrap approach are incompatible with non-invertible symmetries along the flow. We present consistent alternatives, which however violate standard crossing symmetry and obey modified rules dictated by fusion categories. We extend these rules to theories with discrete anomalies.

    ↳ hep-thcond-mat.str-elhep-phPRL(2024)·47 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.