Fri·Sep 8, 2023Friday·September 8, 2023

1. 01*

   Tetraquark mass relations in quark and diquark models

   Muhammad Naeem Anwar🇬🇧 · Timothy J. Burns🇬🇧

   We present new linear relations among the masses of S-wave tetraquarks with either one flavour ($QQ\bar{Q}\bar{Q}$) or two ($QQ\bar{q}\bar{q}$). Because the relations are sensitive to the hidden-colour, spin, and spatial degrees of freedom, comparison to experimental data can help to reveal the internal structure of tetraquarks, and discriminate among different theoretical models. Depending on the model, the relations are either exact, or valid in perturbation theory, and a thorough comparison with existing literature confirms their validity at the MeV level. Additionally, we explore the connections among tetraquark models, and show how those with effective (quark or diquark) masses are related to dynamical potential models. We also show how the spectrum of diquark models is effectively a limiting case of (more general) quark models, and in particular, that the diquark concept is most relevant in the particular combination $QQ\bar{q}\bar{q}$, where $Q$ is much heavier than $\bar{q}$.

   hep-phhep-exhep-latnucl-thPLB(2023)·10 citations
2. 02*

   Top tree amplitudes for higher order calculations

   John M. Campbell🇺🇸 · R. Keith Ellis🇬🇧

   We present compact analytic results for tree-level amplitudes containing a $t\bar{t}$ pair accompanied by up to four massless partons, $t\bar{t}gg$, $t\bar{t}ggg$, $t\bar{t}gggg$, $t\bar{t}q\bar{q}$, $t\bar{t}q\bar{q}g$, $t\bar{t}q\bar{q}gg$ and $t\bar{t}q\bar{q}{q}^{\prime }{\bar{q}}^{\prime }$. The results, obtained using BCFW on-shell recursion, are based both on previous published results and on the new calculations performed in this paper. These amplitudes are sufficient to calculate the production of a $t\bar{t}$ pair and zero, one, or two light parton jets, with the option to include the tree-level decays $t\to b\nu e^{+}$ and $\bar{t}\to \bar{b}{e}^{-}\bar{\nu }$ efficiently. Our results are part of the NNLO corrections to $t\bar{t}$ production including the decay correlations for on-shell top quarks.

   hep-phJHEP(2023)·6 citations
3. 03*

   On the definition of fragmentation functions and the violation of sum rules

   John Collins🇺🇸 · Ted Rogers🇺🇸

   We point out a problem with the formulation and derivations of sum rules for quark fragmentation functions that impacts their validity in QCD, but which potentially points toward an improved understanding of final states in inclusive hard processes. Fragmentation functions give the distribution of final-state hadrons arising from a parton exiting a hard scattering, and the sum rules for momentum, electric charge, etc express conservation of these quantities. The problem arises from a mismatch between the quark quantum numbers of the initial quark and the fact that all observed final-state hadrons are confined bound states with color zero. We point that, in a confining theory like QCD, the Wilson line in the operator definition of a fragmentation function entails that the final state in a fragmentation function includes a bound state in the external field generated by the Wilson line. We justify this with the aid of general features of string hadronization. The anomalous bound states are restricted to fractional momentum $z=0$. They tend to invalidate sum rules like the one for charge conservation when applied to the fragmentation functions inferred from experimental data, but not the momentum sum rule. We propose to exploit our ideas in future studies as a way to relate the ffs extracted from inclusive cross sections to more detailed non-perturbative descriptions of final state hadronization. We also describe scenarios wherein the traditional sum rules might remain approximately valid with a reasonably high degree of accuracy.

   hep-phhep-thnucl-thPRD(2024)·22 citations
4. 04*

   A few thoughts on $\theta$ and the electric dipole moments

   Ariel Zhitnitsky🇨🇦

   I highlight a few thoughts on the contribution to the dipole moments from the so-called $\theta$ parameter. The dipole moments are known can be generated by $\theta$. In fact, the renowned strong $\mathcal{C}\mathcal{P}$ problem was formulated as a result of non-observation of the dipole moments. What is less known is that there is another parameter of the theory, the ${\theta }_{QED}$ which becomes also a physical and observable parameter of the system when some conditions are met. This claim should be contrasted with conventional (and very naive) viewpoint that the ${\theta }_{\mathrm{QED}}$ is unphysical and unobservable. A specific manifestation of this phenomenon is the so-called Witten effect when the magnetic monopole becomes the dyon with induced electric charge $e^{\prime }=-e\frac{{\theta }_{QED}}{2\pi }$. We argued that the similar arguments suggest that the electric magnetic dipole moment $\mu$ of any microscopical configuration in the background of ${\theta }_{QED}$ generates the electric dipole moment $⟨d_{\mathrm{ind}}⟩$ proportional to ${\theta }_{QED}$, i.e. $⟨d_{\mathrm{ind}}⟩=-\frac{{\theta }_{\mathrm{QED}}\cdot \alpha }{\pi }\mu$. We also argue that many $\mathcal{C}\mathcal{P}$ correlations such as $⟨{\vec{B}}_{\mathrm{ext}}\cdot \vec{E}⟩=-\frac{\alpha {\theta }_{\mathrm{QED}}}{\pi }{\vec{B}}_{\mathrm{ext}}^2$ will be generated in the background of an external magnetic field ${\vec{B}}_{\mathrm{ext}}$ as a result of the same physics.

   hep-phhep-exhep-thPRD(2023)·5 citations
5. 05*

   ${\Lambda }_b\to {\Lambda }_c^{\ast }$ at $1/m_c^2$ heavy quark order

   Vigilante Di Risi🇮🇹 · Davide Iacobacci🇮🇹 · Francesco Sannino🇮🇹

   We systematically compute the ${\Lambda }_b(p,s_b)\to {\Lambda }_c(2595{)}^{+}$ and ${\Lambda }_b(p,s_b)\to {\Lambda }_c(2625{)}^{+}$ form factors within the Heavy Quark Effective Theory (HQET) framework including $\mathcal{O}(1/m_c^2)$. Besides taking into account the Standard Model-like vector and axial contributions, we further determine tensor and pseudo-tensor form factors. Our work constitutes a step forward with respect to previous analyses allowing for a comprehensive study of the matrix element parametrisation stemming from the HQET formalism. Finally, we demonstrate that the resulting form factors agree well with lattice Quantum Chromodynamics (LQCD) determinations stressing the need and relevance of the newly derived $1/m_c^2$ corrections.

   hep-phhep-latPRD(2024)·7 citations
6. 06*

   Evolution of chirality in a multiphoton pair production process

   Chengpeng Yu🇯🇵

   Recent years, multiphoton pair production has become one of the most promising approaches to investigate the Schwinger effect. However, the production and evolution of chirality, a key topic in the study of this effect, has not been thoroughly considered in the context of multiphoton pair production. In this work, as the first step of filling this gap, we used the Dirac-Heisenberg-Wigner formalism to study the production and evolution of chirality in vacuum under the excitation of the spatially homogeneous electric and magnetic fields $\mathbf{E}(t)$ and $\mathbf{B}(t)$ that satisfy $\mathbf{E}(t)\parallel \mathbf{B}(t)$ and are only nonzero in a short time span $0<t<\tau$, which serve as a simplified model of the laser beams in multiphoton pair production experiments. Based on analytical calculation, we discovered that, after the external fields vanish, an oscillation of pseudoscalar condensate occurs in the system, which leads to the suppression of the chirality of the produced fermion pairs; at the same time, it introduces a special fermion energy ${ϵ}_p=\sqrt{3}m$ at which the chiral charge distribution of the fermions maximizes. This novel phenomenon could help us identify different types of products in future multiphoton pair production experiments.

   hep-phhep-thPRD(2023)·6 citations
7. 07*

   Two states for the $\Xi (1820)$ resonance

   R. Molina🇪🇸 · Wei-Hong Liang🇨🇳 · Chu-Wen Xiao🇨🇳 · Zhi-Feng Sun🇨🇳 · E. Oset🇪🇸

   We recall that the chiral unitary approach for the interaction of pseudoscalar mesons with the baryons of the decuplet predicts two states for the $\Xi (1820)$ resonance, one with a narrow width and the other one with a large width. We contrast this fact with the recent BESIII measurement of the $K^{-}\Lambda$ mass distribution in the $\psi (3686)$ decay to $K^{-}\Lambda {\bar{\Xi }}^{+}$, which demands a width much larger than the average of the PDG, and show how the consideration of the two $\Xi (1820)$ states provides a natural explanation to this apparent contradiction.

   hep-phPLB(2024)·16 citations
8. 08*

   $B_c$ to $A$ Transition Form Factors and Semileptonic Decays in Self-consistent Covariant Light-front Approach

   Avijit Hazra🇮🇳 · Thejus Mary S.🇮🇳 · Neelesh Sharma🇮🇳 · Rohit Dhir🇮🇳

   We present a comprehensive analysis of the semileptonic weak decays of $B_c$ meson decaying to axial-vector ($A$) mesons for bottom-conserving and bottom-changing decay modes. We employ self-consistent covariant light-front quark model (CLFQM) that uses type-II correspondence to eliminate inconsistencies in the traditional type-I CLFQM. As a fresh attempt, we test the self-consistency in CLFQM through type-II correspondence for $B_c\to A$ meson transition form factors. We establish that in type-II correspondence the form factors for longitudinal and transverse polarization states are numerically equal and are free from zero-mode contributions, which confirms the self-consistency of type-II correspondence for $B_c\to A$ transition form factors. Furthermore, we ascertain that the problems of inconsistency and violation of covariance of CLFQM within the type-I correspondence are resolved in type-II correspondence for $B_c\to A$ transitions. We thoroughly investigate the effects of self-consistency between type-I and type-II schemes using a comparative analysis. We also study the $q^2$ dependence of the form factors in weak hadronic currents for the whole accessible kinematic range $0⩽q^2⩽q_{max}^2$ for both bottom-conserving as well as bottom-changing transitions. In addition, we extend our analysis to predict the branching ratios of the semileptonic weak decays of $B_c$ meson involving axial-vector meson in the final state to quantify the effects of self-consistency in these decays that were not studied before. We evaluate the lepton mass effect on these branching ratios and various other important physical observables, such as forward-backward asymmetries, lepton-side convexity parameter, asymmetry parameter, and longitudinal polarization asymmetries and fractions. Finally, we obtain the lepton flavor universality ratios for various decays.

   hep-phhep-exEPJC(2024)·6 citations
9. 09*

   Charmonium production in hot magnetized hyperonic matter -- effects of baryonic Dirac sea and pseudoscalar-vector meson mixing

   Amruta Mishra🇮🇳 · Arvind Kumar🇮🇳 · S. P. Misra🇮🇳

   We investigate the medium modifications of the masses of pseudoscalar open charm ($D$ and $\bar{D}$) mesons and the charmonium state ($\psi (3770)$) in hot isospin asymmetric strange hadronic medium in the presence of an external magnetic field within a chiral effective model. The in-medium partial decay widths of $\psi (3770)$ to $D\bar{D}$ mesons are computed from the in-medium masses of the initial and final state mesons. These are computed using two light quark pair creation models - (I) the ${}^3{P}_0$ model and (II) a field theoretical (FT) model of composite hadrons with quark (and antiquark) constituents. The production cross-sections of $\psi (3770)$, arising from scattering of the $D$ and $\bar{D}$ mesons, are computed from the relativistic Breit-Wigner spectral function expressed in terms of the in-medium masses and the decay widths of the charmonium state. The effects of the magnetic field are considered due to the Dirac sea (DS) of the baryons, the mixing of the pseudoscalar and vector meson (PV mixing) and the Landau level contributions for the charged hadrons. The production cross-sections of $\psi (3770)$ arising due to scattering of $D^{+}{D}^{-}(D^0{\bar{D}}^0)$ mesons in the hot magnetized strange hadronic matter are observed to have distinct peak positions, when the magnetic field is large, due to the mass difference of the transverse and longitudinal components of $\psi (3770)$, arising from PV mixing. These can have observable consequences on the dilepton spectra and the production of the charm mesons in ultra-relativistic peripheral heavy ion collision experiments, where the produced magnetic field is huge.

   hep-phnucl-thPRD(2024)·17 citations
10. 10*

    Vacuum Stability and Electroweak Precision in the Two Higgs Doublet Model with Vector-Like Quarks

    Kivanc Y. Cingiloglu🇨🇦 · Mariana Frank🇨🇦

    We present a comprehensive analysis of the vacuum stability of the Two-Higgs Doublet Model, for both Type-I and Type-II, augmented by vector-like quarks in either singlet, doublet or triplet representations. We review the model briefly before introducing the extra fermionic states and their interactions, and impose restrictions on the parameters coming both from theoretical considerations and experimental bounds. We then study the renormalization group equation evolution of the parameters of the model in order to isolate the parameter regions that satisfy vacuum stability requirements. We then add the electroweak precision observables to insure that the resulting parameter space is consistent with the data. We include complete expressions for the renormalization group equations and the S and T parameters used. Finally we summarize the effects of various vector-like quark representations on the parameter space. We indicate the regions constrained, highlighting the differences between representations in Type-I and Type-II, and pinpoint the effects of the interplay between the extended model and the additional fermions.

    hep-phPRD(2024)·9 citations
11. 11*

    Constraining light dark matter and mediator with $B^{+}\to K^{+}\nu \bar{\nu }$ data

    Murat Abdughani🇨🇳 · Yakefu Reyimuaji🇨🇳

    We study the decay of $B^{+}$ meson into $K^{+}$ plus a light mediator $\varphi$, which subsequently decays into a dark matter pair, $\bar{\chi }\chi$. Integrating constraints from DM relic density, direct detection, collider data and $B$-physics, alongside the recently reported results form Belle II experiment, we analyze the couplings between the mediator, standard model fermions, and the dark matter particles. Our results indicate that if the decay process $\varphi \to \bar{\chi }\chi$ is kinematically allowed, i.e. $m_{\varphi }>2m_{\chi }$, then the mediator mass must be constrained within 0.35 GeV $\lesssim m_{\varphi }\lesssim$ 3 GeV. Conversely, if $m_{\varphi }<2m_{\chi }$, the mediator $m_{\varphi }$ is long-lived relative to the detector size, and the only allowed decay channel is $\varphi \to e^{+}{e}^{-}$.

    hep-phPRD(2024)·27 citations
12. 12*

    Search for nonextensivity in electron-proton interactions at $\sqrt{s}$ = 300 GeV

    Soumya Sarkar🇮🇳 · R. Aggarwal🇮🇳 · M. Kaur🇮🇳

    Study of canonical entropy in electron-proton interactions at $\sqrt{s}$ = 300 GeV is presented. The precision data collected by the H1 experiment at the HERA in different ranges of invariant hadronic mass $W$ and the squared four-momentum exchange $Q^2$ in $ep$ interactions have been analyzed in the ensemble theory approach. The canonical partition function relates to the multiplicity distribution which is often studied in collider experiments. We use the canonical ensemble partition function to explore the dynamics of hadron production in $ep$ interactions by devising different methods to find the entropic parameter and the collision temperature. The inverse slope of the transverse momentum spectrum of produced hadrons also relates to the temperature. In the recent past, the CMS, ATLAS and ALICE experiments at the LHC have studied the charged hadron transverse momentum and particle distributions in proton-proton and proton-nucleus interactions by using the Tsallis function within this approach. A detailed investigation into the role of the system volume and relation amongst different dynamical parameters reveals interesting results.

    hep-phnucl-thPRD(2024)·1 citation
13. 13*

    The decay $B\to K+\nu +\bar{\nu }$ at Belle II and a massless bino in R-parity-violating supersymmetry

    Zeren Simon Wang🇹🇼 · Herbert K. Dreiner🇩🇪 · Julian Y. Günther🇩🇪

    Recently, \texttt{Belle II} announced evidence for the decay $B^{+}\to K^{+}+\nu +\bar{\nu }$ at the $3.5\sigma$ significance, and measured the corresponding decay branching ratio to be $2.7\sigma$ above the Standard Model prediction. Here, we provide a theoretical explanation based on a massless bino in R-parity-violating (RPV) supersymmetry. With a single non-vanishing RPV coupling ${\lambda }_{i23/i32}^{\prime }$, ${\lambda }_{i13/i33}^{\prime }$, or ${\lambda }_{i12/i22}^{\prime }$, where $i=1,2,3$, the decay $B^{+}\to K^{+}+\stackrel{(-)}{{\nu }_i}+{\tilde{\chi }}_1^0$ can be induced, which would lead to the same signature as $B^{+}\to K^{+}+\nu +\bar{\nu }$. Taking into account both theoretical and experimental uncertainties, we derive the regions of the parameter space spanned by the RPV couplings and sfermion masses that could accommodate the new measurement at various significance levels and obey the existing bounds simultaneously.

    hep-phEPJC(2025)·46 citations
14. 14*

    Deuterium spectroscopy for enhanced bounds on physics beyond the Standard Model

    Robert M. Potvliege🇬🇧 · Adair Nicolson🇬🇧 · Matthew P. A. Jones🇬🇧 · Michael Spannowsky🇬🇧

    We consider the impact of combining precision spectroscopic measurements made in atomic hydrogen with similar measurements made in atomic deuterium on the search for physics beyond the Standard Model. Specifically we consider the wide class of models that can be described by an effective Yukawa-type interaction between the nucleus and the electron. We find that it is possible to set bounds on new light-mass bosons that are orders of magnitude more sensitive than those set using a single isotope only, provided the interaction couples differently to the deuteron and proton. Further enhancements of these bounds by an order of magnitude or more would be made possible by extending the current measurements of the isotope shift of the 1s${}_{1/2}$-2s${}_{1/2}$ transition frequency to that of a transition between the 2s${}_{1/2}$ state and a Rydberg s-state.

    hep-phphysics.atom-phPRA(2023)·19 citations
15. 15*

    Soft Theorem to Three Loops in QCD and $\mathcal{N}=4$ Super Yang-Mills Theory

    Wen Chen🇨🇳 · Ming-xing Luo🇨🇳 · Tong-Zhi Yang🇨🇭 · Hua Xing Zhu🇨🇳

    The soft theorem states that scattering amplitude in gauge theory with a soft gauge-boson emission can be factorized into a hard scattering amplitude and a soft factor. In this paper, we present calculations of the soft factor for processes involving two hard colored partons, up to three loops in QCD. To accomplish this, we developed a systematic method for recursively calculating relevant Feynman integrals using the Feynman-Parameter representation. Our results constitute an important ingredient for the subtraction of infrared singularities at N${}^4$LO in perturbative QCD. Using the principle of leading transcendentality between QCD and $\mathcal{N}=4$ super Yang-Mills theory, we determine the soft factor in the latter case to three loops with full-color dependence. As a by-product, we also obtain the finite constant $f_2^{(3)}$ in the Bern-Dixon-Smirnov ansatz analytically, which was previously known numerically only.

    hep-phhep-thJHEP(2024)·24 citations
16. 16*

    Anomalies in Particle Physics

    Andreas Crivellin🇨🇭 · Bruce Mellado🇿🇦

    The currently accepted mathematical description of the fundamental constituents and interactions of matter is the Standard Model of particle physics. Its last missing particle, the famous Higgs boson, was observed at the Large Hadron Collider at CERN in 2012. However, it is clear that the Standard Model cannot be the ultimate theory of Nature, and e.g. cannot account for Dark Matter or non-vanishing neutrino masses (and does not include gravity). In fact, searches for physics beyond the SM have been intensified since the Higgs boson discovery. In this article, we review the hints for new physics, called ``anomalies'', obtained in particle physics experiments within the last years. We consider both direct high-energy searches for new resonances at the LHC and indirect low-energy precision experiments. These anomalies range from the nuclear scale (approximately the mass of the proton) to the electroweak scale (i.e. the mass of the Higgs boson) to the TeV scale (the highest scale directly accessible at the LHC), therefore spanning over four orders of magnitude. After discussing the experimental and theoretical status of the anomalies, we summarize possible explanations in terms of new particles and new interactions. In particular, new Higgs bosons and leptoquarks are promising candidates. Discovery prospects and implications for future colliders are discussed.

    hep-phhep-exhep-lathep-th+1Nature Rev.Phys.(2024)·88 citations
17. 17*

    Neutron star cooling with lepton-flavor-violating axions

    Hong-Yi Zhang🇺🇸 · Ray Hagimoto🇺🇸 · Andrew J. Long🇺🇸

    The cores of dense stars are a powerful laboratory for studying feebly coupled particles such as axions. Some of the strongest constraints on axionlike particles and their couplings to ordinary matter derive from considerations of stellar axion emission. In this work we study the radiation of axionlike particles from degenerate neutron star matter via a lepton-flavor-violating coupling that leads to muon-electron conversion when an axion is emitted. We calculate the axion emission rate per unit volume (emissivity) and by comparing with the rate of neutrino emission, we infer upper limits on the lepton-flavor-violating coupling that are at the level of $|g_{ae\mu }|\lesssim 10^{-6}$. For the hotter environment of a supernova, such as SN 1987A, the axion emission rate is enhanced and the limit is stronger, at the level of $|g_{ae\mu }|\lesssim 10^{-11}$, competitive with laboratory limits. Interestingly, our derivation of the axion emissivity reveals that axion emission via the lepton-flavor-violating coupling is suppressed relative to the familiar lepton-flavor-preserving channels by the square of the plasma temperature to muon mass ratio, which is responsible for the relatively weaker limits.

    hep-phastro-ph.HEPRD(2024)·18 citations
18. 18*

    A novel approach to the global analysis of proton form factors in elastic electron-proton scattering

    Craig McRae🇨🇦 · P. G. Blunden🇨🇦

    We present a novel method for the global analysis of elastic electron-proton scattering when combining data sets from experiments with different overall normalization uncertainties. The method is a modification of one employed by the NNPDF collaboration in the fitting of parton distribution data. This method is an alternative to the 'penalty trick' method traditionally employed in global fits to proton electric and magnetic form factors, while avoiding the biases inherent in that approach. We discuss issues that arise when extending the method to nonlinear models. For data with $Q^2>1$ GeV${}^2$ we find relatively minor differences to traditional model fits when the normalization uncertainties from different experiments are correctly accounted for. We discuss implications of this method for the well-known discrepancy between the form factor ratio $G_E/G_M$ extracted from the Rosenbluth and polarization transfer techniques.

    hep-phnucl-exnucl-thPRC(2024)·4 citations
19. 19*

    Quantization of Axion-Gauge Couplings and Non-Invertible Higher Symmetries

    Yichul Choi🇺🇸 · Matthew Forslund🇺🇸 · Ho Tat Lam🇩🇪 · Shu-Heng Shao🇺🇸

    We derive model-independent quantization conditions on the axion couplings (sometimes known as the anomaly coefficients) to the Standard Model gauge group $[SU(3)\times SU(2)\times U(1{)}_Y]/{\mathbb{Z}}_q$ with $q=1,2,3,6$. Using these quantization conditions, we prove that any QCD axion model to the right of the $E/N=8/3$ line on the $|g_{a\gamma \gamma }|$-$m_a$ plot must necessarily face the axion domain wall problem in a post-inflationary scenario. We further demonstrate the higher-group and non-invertible global symmetries in the Standard Model coupled to a single axion. These generalized global symmetries lead to universal bounds on the axion string tension and the monopole mass. If the axion were discovered in the future, our quantization conditions could be used to constrain the global form of the Standard Model gauge group.

    hep-phhep-thPRL(2024)·80 citations
20. 20*

    Axion-Gauge Coupling Quantization with a Twist

    Matthew Reece🇺🇸

    The possible couplings of an axion to gauge fields depend on the global structure of the gauge group. If the Standard Model gauge group is minimal, or equivalently if fractionally charged color-singlet particles are forbidden, then the QCD axion's Chern-Simons couplings to photons and gluons obey correlated quantization conditions. Specifically, the photon coupling can have a fractional part which is a multiple of 1/3, but which is determined by the gluon coupling. A consequence of this result is that, among all theories with a minimal gauge group and minimal axion coupling to gluons, the smallest possible axion-photon amplitude $|g_{a\gamma \gamma }|$ arises for $E/N=8/3$. This provides a new motivation for experiments targeting this axion-photon coupling.

    hep-phhep-thJHEP(2023)·44 citations
21. 21*

    Prospects for $\gamma$-ray observations of the Perseus galaxy cluster with the Cherenkov Telescope Array

    The Cherenkov Telescope Array Consortium: K. Abe🇯🇵 · S. Abe🇯🇵 · F. Acero🇫🇷 · A. Acharyya🇺🇸 · R. Adam🇫🇷 · A. Aguasca-Cabot🇪🇸 · I. Agudo🇪🇸 · A. Aguirre-Santaella🇪🇸 · J. Alfaro🇨🇱 · R. Alfaro🇲🇽 · N. Alvarez-Crespo🇪🇸 · R. Alves Batista🇪🇸 and 553 other authors

    Galaxy clusters are expected to be dark matter (DM) reservoirs and storage rooms for the cosmic-ray protons (CRp) that accumulate along the cluster's formation history. Accordingly, they are excellent targets to search for signals of DM annihilation and decay at gamma-ray energies and are predicted to be sources of large-scale gamma-ray emission due to hadronic interactions in the intracluster medium. We estimate the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse gamma-ray emission from the Perseus galaxy cluster. We perform a detailed spatial and spectral modelling of the expected signal for the DM and the CRp components. For each, we compute the expected CTA sensitivity. The observing strategy of Perseus is also discussed. In the absence of a diffuse signal (non-detection), CTA should constrain the CRp to thermal energy ratio within the radius $R_{500}$ down to about $X_{500}<3\times 10^{-3}$, for a spatial CRp distribution that follows the thermal gas and a CRp spectral index ${\alpha }_{\mathrm{CRp}}=2.3$. Under the optimistic assumption of a pure hadronic origin of the Perseus radio mini-halo and depending on the assumed magnetic field profile, CTA should measure ${\alpha }_{\mathrm{CRp}}$ down to about $\Delta {\alpha }_{\mathrm{CRp}}\simeq 0.1$ and the CRp spatial distribution with 10% precision. Regarding DM, CTA should improve the current ground-based gamma-ray DM limits from clusters observations on the velocity-averaged annihilation cross-section by a factor of up to $\sim 5$, depending on the modelling of DM halo substructure. In the case of decay of DM particles, CTA will explore a new region of the parameter space, reaching models with ${\tau }_{\chi }>10^{27}$s for DM masses above 1 TeV. These constraints will provide unprecedented sensitivity to the physics of both CRp acceleration and transport at cluster scale and to TeV DM particle models, especially in the decay scenario.

    ↳ astro-ph.HEastro-ph.COhep-phJCAP(2024)·22 citations
22. 22*

    Rapid neutron star cooling triggered by dark matter

    Afonso Ávila🇵🇹 · Edoardo Giangrandi🇵🇹 · Violetta Sagun🇵🇹 · Oleksii Ivanytskyi🇵🇱 · Constança Providência🇵🇹

    We study the effect of asymmetric fermionic dark matter (DM) on the thermal evolution of neutron stars (NSs). No interaction between DM and baryonic matter is assumed, except the gravitational one. Using the two-fluid formalism, we show that DM accumulated in the core of a star pulls inwards the outer baryonic layers of the star, increasing the baryonic density in the NS core. As a result, it significantly affects the star's thermal evolution by triggering an early onset of the direct Urca process and modifying the photon emission from the surface caused by the decrease of the radius. Thus, due to the gravitational pull of DM, the direct Urca process becomes kinematically allowed for stars with lower masses. Based on these results, we discuss the importance of NS observations at different distances from the Galactic center. Since the DM distribution peaks towards the Galactic center, NSs in this region are expected to contain higher DM fractions that could lead to a different cooling behavior.

    ↳ astro-ph.HEgr-qchep-phnucl-thMNRAS(2024)·29 citations
23. 23*

    The Monodromic Axion-Photon Coupling

    Prateek Agrawal🇬🇧 · Arthur Platschorre🇬🇧

    We consider the general form of the axion coupling to photons in the axion-Maxwell theory. On general grounds this coupling takes the form of a monodromic function of the axion, which we call $g(a)$, multiplying the Chern-Pontryagin density $F\tilde{F}$ of the photon. We show that the non-linearity of $g(a)$ is a spurion for the shift symmetry of the axion. In this context, when $g(a)\ne \mathbb{Z}a$, the linearized coupling of the axion $g^{\prime }(a)$ is not quantized and there is a correlated mass term for the axion. Singularities in $g(a)$ due to the fast rearrangement of degrees of freedom are shown to have corresponding cusps and singularities in the axion potential. We derive the general form of $g(a)$ for the QCD axion, axions with perturbatively broken shift symmetries and axions descending from extra dimensions. In all cases, we show that there is a uniform general form of the monodromic function $g(a)$ and it is connected to the axion potential.

    ↳ hep-thhep-phJHEP(2024)·28 citations
24. 24*

    Accelerated expansion of an open universe, and string theory realizations

    David Andriot🇫🇷 · Dimitrios Tsimpis🇫🇷 · Timm Wrase🇺🇸

    Recently, many works have tried to realize cosmological accelerated expansion in string theory models in the asymptotic regions of field space, with a typical scalar potential $V(\phi )$ having an exponential fall-off $e^{-\gamma \phi }$. Those attempts have been plagued by the fact that $V$ is too steep, namely $\gamma \ge 2/\sqrt{d-2}$ in a $d$-dimensional spacetime. We revisit the corresponding dynamical system for arbitrary $d$ and $\gamma$, and show that for an open universe ($k=-1$), there exists a new stable fixed point $P_1$ precisely if $\gamma >2/\sqrt{d-2}$. Building on the recent work arXiv:2210.10813, we show in addition that cosmological solutions asymptoting to $P_1$ exhibit accelerated expansion in various fashions (semi-eternal, eternal, transient with parametrically controlled number of e-folds, or rollercoaster). We finally present realizations in string theory of these cosmological models with asymptotically accelerating solutions, for $d=4$ or $d=10$. We also show that these solutions do not admit a cosmological event horizon, and discuss the possibility of this being a generic feature of quantum gravity.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2023)·46 citations
25. 25*

    The two-mode puzzle: Confronting self-interacting neutrinos with the full shape of the galaxy power spectrum

    David Camarena🇺🇸 · Francis-Yan Cyr-Racine🇺🇸 · John Houghteling🇺🇸

    A cosmological scenario in which the onset of neutrino free streaming in the early Universe is delayed until close to the epoch of matter-radiation equality has been shown to provide a good fit to some cosmic microwave background (CMB) data, while being somewhat disfavored by Planck CMB polarization data. To clarify this situation, we investigate in this paper CMB-independent constraints on this scenario from the Full Shape of the galaxy power spectrum. Although this scenario predicts significant changes to the linear matter power spectrum, we find that it can provide a good fit to the galaxy power spectrum data. Interestingly, we show that the data display a modest preference for a delayed onset of neutrino free streaming over the standard model of cosmology, which is driven by the galaxy power spectrum data on mildly non-linear scales. This conclusion is supported by both profile likelihood and Bayesian exploration analyses, showing robustness of the results. Compared to the standard cosmological paradigm, this scenario predicts a significant suppression of structure on subgalactic scales. While our analysis relies on the simplest cosmological representation of neutrino self-interactions, we argue that this persistent - and somehow consistent - picture in which neutrino free streaming is delayed motivates the exploration of particle models capable of reconciling all CMB, large-scale structure, and laboratory data.

    ↳ astro-ph.COhep-phPRD(2023)·47 citations

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