Tue·Nov 9, 2021Tuesday·November 9, 2021

1. 01*

   Transverse momentum dependent distributions in dijet and heavy hadron pair production at EIC

   Rafael F. del Castillo🇪🇸 · Miguel G. Echevarria🇪🇸 · Yiannis Makris🇮🇹 · Ignazio Scimemi🇪🇸

   We discuss the measurement of gluon transverse momentum distribution (TMD) in dijet and heavy hadron pair (HHP) production in semi-inclusive deep inelastic scattering. The factorization of these processes in impact parameter space shows the appearance of a specific new soft factor matrix element on top of angular a complex valued anomalous dimensions. We show in detail how these features can be treated consistently and we discuss a scale prescription for the evolution kernel of the dijet soft function. As a result we obtain phenomenological predictions for unpolarized and angular modulated cross-sections for the electron-ion collider (EIC) using current available information on unpolarized TMD.

   hep-phhep-exnucl-exnucl-thJHEP(2022)·30 citations
2. 02*

   Thermal production of sexaquarks in heavy-ion collisions

   D. Blaschke (1 and 2 and 3)🇵🇱 · Larissa Bravina (4)🇳🇴 · Kyrill Bugaev (5 and 6)🇺🇦 · Glennys R. Farrar (7)🇺🇸 · Boris Grinyuk (5)🇺🇦 · Oleksii Ivanytskyi (1 and 5)🇵🇱 · Sonia Kabana (8)🇨🇱 · Sergey V. Kuleshov (9 and 10)🇨🇱 · Irina K. Potashnikova (11)🇨🇱 · Violetta Sagun (12 and 5)🇵🇹 · Arkadiy Taranenko (3)🇷🇺 · Oleksandr V. Vitiuk (6)🇺🇦 and 3 other authors

   We present new results on the thermal production yield of a hypothetical state made of six quarks $uuddss$ assuming its production in heavy-ion collisions at the CERN LHC. A state with this quark content and mass low enough to be stable against decay in timescales of the order of the age of the Universe, has been hypothesized by one of us (G.F.) and has been discussed as a possible dark matter candidate. In this work we address for the first time the thermal production rate that can be expected for this state in heavy-ion collisions at colliders. For this estimate we use a thermal model which has been shown to describe accurately the production of hadrons and nuclei in heavy-ion collisions at LHC energy. This estimate is of great relevance for sexaquark searches at colliders as well as for its consideration as a dark matter candidate and for the composition of neutron stars.

   hep-phnucl-thInt.J.Mod.Phys.A(2021)·6 citations
3. 03*

   The $\sin 2{\varphi }_h$ azimuthal asymmetry of pion production in SIDIS within TMD factorization

   Hui Li🇨🇳 · Zhun Lu🇨🇳

   We study the $\sin 2{\varphi }_h$ azimuthal asymmetry of charged and neutral pion productions off the longitudinally polarized nucleon targets in semi-inclusive deeply inelastic scattering (SIDIS) process within the transverse momentum dependent~(TMD) factorization. The asymmetry is contributed by the convolution of the TMD distribution $h_{1L}^{\perp }$ and the Collins fragmentation function $H_1^{\perp }$. We adopt the Wandzura-Wilczek-type~(WW-type) approximation for $h_{1L}^{\perp }$ and two different parametrizations on the nonperturbative part of TMD evolution for $h_{1L}^{\perp }$ and $H_1^{\perp }$. We numerically estimate the asymmetry in the kinematical configurations available at HERMES, CLAS and CLAS12. It is shown that our theoretical calculation can describe the HERMES and CLAS data, except the asymmetry of the ${\pi }^{-}$ production off proton target at HERMES and CLAS. We also find that different choices of the nonperturbative part of TMD evolution lead qualitatively similar results.

   hep-phhep-exEPJC(2022)·6 citations
4. 04*

   Discerning Singlet and Triplet scalars at the electroweak phase transition and Gravitational Wave

   Priyotosh Bandyopadhyay🇮🇳 · Shilpa Jangid🇮🇳

   In this article we examine the prospect of first order phase transition with a Y=0 real $SU(2)$ triplet extension of the Standard Model, which remains odd under $Z_2$, considering the observed Higgs boson mass, perturbative unitarity, dark matter constraints, etc. Especially we investigate the role of Higgs-triplet quartic coupling considering one- and two-loop beta functions and compare the results with the complex singlet extension case. It is observed that at the one-loop level, no solution can be found for both, demanding the Planck scale perturbativity. However, for a much lower scale of $10^4$ GeV, the singlet case predicts first order phase transition consistent with the observed Higgs boson mass. On the contrary, at the two-loop, both the scenarios foresee strongly first order phase transition consistent with the observed Higgs mass with upper bounds of 310, 909 GeV on the triplet and singlet masses, respectively. This puts the triplet in apparent contradiction with the observed dark matter relic bound and thus requires additional field for that. The preferred regions of the parameter space in both cases are identified by benchmark points, that predict the Gravitational Waves with detectable frequencies in the present and future experiments.

   hep-phPRD(2023)·18 citations
5. 05*

   Constraining Scalar Doublet and Triplet Leptoquarks with Vacuum Stability and Perturbativity

   Priyotosh Bandyopadhyay🇮🇳 · Shilpa Jangid🇮🇳 · Anirban Karan🇮🇳

   We investigate the constraints on the leptoquark Yukawa couplings and Higgs-leptoquark quartic couplings for scalar doublet leptoquark ${\tilde{R}}_2$, scalar triplet leptoquark ${\vec{S}}_3$ and their combination with both three generations and one generation from perturbative unitarity and vacuum stability. Perturbative unitarity of all the dimensionless couplings have been studied via one- and two-loop beta-functions. Introduction of new $SU(2)$ multiplets in terms of these leptoquarks fabricate Landau poles at two-loop level in the gauge coupling $g_2$ at $10^{19.7}$ GeV and $10^{14.4}$ GeV, respectively for ${\vec{S}}_3$ and ${\tilde{R}}_2+{\vec{S}}_3$ models with three generations. However, such Landau pole ceases to exist for ${\tilde{R}}_2$ and any of these extensions with both one and two generations till Planck scale. The Higgs-leptoquark quartic couplings acquire severe constraints to protect Planck scale perturbativity, whereas leptoquark Yukawa couplings get some upper bound in order to respect Planck scale stability of Higgs Vacuum. The Higgs quartic coupling at two-loop constraints the leptoquark Yukawa couplings for ${\tilde{R}}_2,{\vec{S}}_3,{\tilde{R}}_2+{\vec{S}}_3$ with values $\lesssim 1.30,3.90,1.00$ with three generations. In the effective potential approach, the presence of any of these leptoquarks with any number of generations pushes the metastable vacuum of the Standard Model to the stable region.

   hep-phEPJC(2022)·20 citations
6. 06*

   Probing charged lepton flavor violation with a positron beam at CEBAF (JLAB)

   Yulia Furletova🇺🇸 · Sonny Mantry🇺🇸

   The addition of a high intensity 11 GeV polarized positron beam at the Continuous Electron Beam Accelerator Facility (CEBAF) at JLAB would allow for a search of Charged Lepton Flavor Violation (CLFV) via the process $e^{+}N\to {\mu }^{+}X$. The proposed Solenoidal Large Intensity Detector (SoLID) spectrometer, in the configuration with muon chambers, would be ideal for such CLFV searches. Various new physics scenarios, including the phenomenologically convenient Leptoquark (LQ) framework, predict CLFV rates that are within reach of current or planned experiments. A positron beam with instantaneous luminosity, $\mathcal{L}\sim 10^{38}$ cm${}^{-2}$s${}^{-1}$, could improve on existing HERA limits by two or three orders of magnitude. The availability of positron beam polarization would also allow for distentangling CLFV effects mediated by left-handed vs. right-handed LQs.

   hep-phhep-exnucl-exEPJA(2021)·5 citations
7. 07*

   Illuminating long-lived dark vector bosons via exotic Higgs decays at $\sqrt{s}=13\text{TeV}$

   Tamer Elkafrawy🇺🇸 · Marcus Hohlmann🇺🇸 · Teruki Kamon🇺🇸 · Paul Padley🇺🇸 · Hyunyong Kim🇺🇸 · Mehdi Rahmani🇺🇸 · Sven Dildick🇺🇸

   The possibility of producing a measurable long-lived dark $Z$ boson, that is assumed to be produced either via its kinetic mixing with the hypercharge gauge boson or via mixing of the observed 125-GeV Higgs boson with the dark Higgs boson, called Higgs mixing, in Run 2 of the Large Hadron Collider (LHC) is investigated. Displaced dimuons in the final state are considered where each of the $Z$ and the dark $Z$ bosons decays directly to a dimuon. The Higgs production cross sections via gluon-gluon fusion at 13 TeV calculated to a combination of next-to-next-to-next-to-leading order with QCD corrections (N${}^3$LO QCD) and next-to-leading order with electroweak corrections (NLO EW) from the literature are used, while the branching fractions are calculated to NLO by using Monte Carlo simulation in the framework of {\textsc{MadGraph5}}\_aMC@NLO and compared to the available analytical calculations to leading order (LO). Sensitivities of the LHC in Run 2 to such searches are discussed.

   hep-phhep-exPoS(2021)·2 citations
8. 08*

   The Spin-dependent Scattering of Boosted Dark Matter

   Wenyu Wang🇨🇳 · Lei Wu🇨🇳 · Wen-Na Yang🇨🇳 · Bin Zhu🇨🇳

   Boosted dark matter provides a promising approach to probe the light dark matter, whose computational framework in the spin-independent scattering process is well developed. However, the spin-dependent one lacks a unified treatment. The novelty of this paper is to give the first comprehensive derivation of the cross-section for boosted dark matter in spin-dependent scattering. When the transfer momentum is sufficiently large, there is a sizable enhancement to the proton structure factor from the time component. Besides, we find a residue momentum dependence in the quark-nucleon matching procedure, even without a light mediator. Such behavior can enhance the sensitivity compared with conventional contact interaction. We promote this endeavor by deriving direct limits on sub-GeV spin-dependent boosted dark matter through terrestrial data. The numerical results of the boosted structure factor and the non-relativistic structure factor are given explicitly in the paper and it shows that the excluded region of the boosted structure factor is about six orders larger than the non-relativistic structure factor.

   hep-phPRD(2023)·37 citations
9. 09*

   Festina-Lente Bound on Higgs Vacuum Structure and Inflation

   Sung Mook Lee🇰🇷 · Dhong Yeon Cheong🇰🇷 · Sang Chul Hyun🇰🇷 · Seong Chan Park🇰🇷 · Min-Seok Seo🇰🇷

   The recently suggested Festina-Lente (FL) bound provides a lower bound on the masses of $\mathrm{U}(1)$ charged particles in terms of the positive vacuum energy. Since the charged particle masses in the Standard Model (SM) are generated by the Higgs mechanism, the FL bound provides a testbed of consistent Higgs potentials in the current dark energy-dominated universe as well as during inflation. We study the implications of the FL bound on the UV behavior of the Higgs potential for a miniscule vacuum energy, as in the current universe. We also present values of the Hubble parameter and the Higgs vacuum expectation value allowed by the FL bound during inflation, which implies that the Higgs cannot stay at the electroweak scale during this epoch.

   hep-phastro-ph.COgr-qchep-thJHEP(2022)·21 citations
10. 10*

    Cosmological Dependence of Sterile Neutrino Dark Matter With Self-Interacting Neutrinos

    Carlos Chichiri🇺🇸 · Graciela B. Gelmini🇺🇸 · Philip Lu🇺🇸 · Volodymyr Takhistov🇯🇵

    Unexplored interactions of neutrinos could be the key to understanding the nature of the dark matter (DM). In particular, active neutrinos with new self-interactions can produce keV-mass sterile neutrinos that account for the whole of the DM through the Dodelson-Widrow mechanism for a large range of active-sterile mixing values. This production typically occurs before Big-Bang Nucleosynthesis (BBN) in a yet uncharted era of the Universe. We assess how the mixing range for keV-mass sterile neutrino DM is affected by the uncertainty in the early Universe pre-BBN cosmology. This is particularly relevant for identifying the viable parameter space of sterile neutrino searches allowed by all astrophysical limits, as well as for cosmology, since the detection of a sterile neutrino could constitute the first observation of a particle providing information about the pre-BBN epoch. We find that the combined uncertainties in the early Universe cosmology and neutrino interactions significantly expand the allowed parameter space for sterile neutrinos that can constitute the whole of the DM.

    hep-phastro-ph.COastro-ph.HEhep-exJCAP(2022)·24 citations
11. 11*

    Neutrino and Axion Astronomy with Dark Matter Experiments

    Volodymyr Takhistov🇯🇵

    Sensitive dark matter (DM) experiments can be well exploited beyond their designated targets, allowing to explore a breadth of physics topics. As we discuss, future large direct DM detection experiments constitute impressive telescopes, complementary to conventional neutrino detectors. This opens a new window into neutrino astronomy, including puzzles such as the origin of supermassive black holes and topics like supernova forecast. Furthermore, DM experiments can act as effective instruments for multimessenger astronomy. This is well illustrated by exploration of relativistic axions from transient astrophysical sources (e.g. axion star explosions), providing novel signatures as well as possible insights into the axion potential.

    hep-phastro-ph.COastro-ph.HEhep-exJ.Phys.Conf.Ser.(2021)·2 citations
12. 12*

    Equivalent $SU(3{)}_f$ approaches for two-body anti-triplet charmed baryon decays

    Y.K. Hsiao🇨🇳 · Y.L. Wang🇨🇳 · H.J. Zhao🇨🇳

    For the two-body ${\mathbf{B}}_c\to \mathbf{B}M$ decays, where ${\mathbf{B}}_c$ denotes the anti-triplet charm baryon and $\mathbf{B}(M)$ the octet baryon (meson), there exist two theoretical studies based on the $SU(3)$ flavor [$SU(3{)}_f$] symmetry. One is the irreducible $SU(3{)}_f$ approach (IRA). In the irreducible $SU(3{)}_f$ representation, the effective Hamiltonian related to the initial and final states forms the amplitudes for ${\mathbf{B}}_c\to \mathbf{B}M$. The other is the topological-diagram approach (TDA), where the $W$-boson emission and $W$-boson exchange topologies are drawn and parameterized for the decays. As required by the group theoretical consideration, we present the same number of the IRA and TDA amplitudes. We can hence relate the two kinds of the amplitudes, and demonstrate the equivalence of the two $SU(3{)}_f$ approaches. We find a specific $W$-boson exchange topology only contributing to ${\Xi }_c^0\to \mathbf{B}M$. Denoted by $E_M$, it plays a key role in explaining $\mathcal{B}({\Xi }_c^0\to {\Lambda }^0{K}_S^0,{\Sigma }^0{K}_S^0,{\Sigma }^{+}{K}^{-})$. We consider that ${\Lambda }_c^{+}\to n{\pi }^{+}$ and ${\Lambda }_c^{+}\to p{\pi }^0$ proceed through the constructive and destructive interfering effects, respectively, which leads to $\mathcal{B}({\Lambda }_c^{+}\to n{\pi }^{+})\gg \mathcal{B}({\Lambda }_c^{+}\to p{\pi }^0)$ in agreement with the data. With the exact and broken $SU(3{)}_f$ symmetries, we predict the branching fractions of ${\mathbf{B}}_c\to \mathbf{B}M$ to be tested by future measurements.

    hep-phhep-exJHEP(2022)·31 citations
13. 13*

    Charmless $B_s\to VS$ Decays in PQCD Approach

    Zhao-Wu Liu🇨🇳 · Zhi-Tian Zou🇨🇳 · Ying Li🇨🇳 · Xin Liu🇨🇳 · Jie Wang🇨🇳

    In this work, we investigate the $B_s\to VS$ decays in the perturbative QCD approach, where $V$ and $S$ denote the vector meson and scalar meson respectively. Based on the two-quark structure, considering two different scenarios for describing the scalar mesons, we calculate the branching fractions and the direct $CP$ asymmetries of all $B_s\to VS$ decays. Most branching fractions are predicted to be at $10^{-7}$ to $10^{-5}$, which could be measured in the LHCb and Belle-II experiments, especially for these color-allowed $B_s\to \kappa (800)(K_0^{\ast }(1430))K^{\ast }$ decays. It is found that the branching fractions of $B_s\to K_0^{\ast 0}(1430){\bar{K}}^{\ast 0}$ and $B_s\to K_0^{\ast +}(1430){\bar{K}}^{\ast -}$ are very sensitive to the scenarios, which can be used to determine whether $K_0^{\ast 0}(1430)$ belongs to the ground state or the first excited state, if the data were available. We also note that some decays have large direct $CP$ asymmetries, some of which are also sensitive to the scenarios, such as the $B_s\to a_0^{+}(1450)K^{\ast -}$ and the $B_s\to f_0(1500)K^{\ast 0}$ decays. Since the experimental measurements of $B_s\to VS$ decays are on the way, combined with the available data in the future, we expect the theoretical predictions will shed light on the structure of the scalar mesons.

    hep-phEPJC(2022)·8 citations
14. 14*

    LUXE: A new experiment to study non-perturbative QED in electron-laser and photon-laser collisions

    Shan Huang (for the LUXE Collaboration)🇮🇱

    LUXE (Laser Und XFEL Experiment) is a new experiment in planning at DESY Hamburg using the electron beam of the European XFEL. LUXE is intended to study collisions between a high-intensity optical laser and 16.5 GeV electrons from the XFEL electron beam, as well as collisions between the optical laser and high-energy secondary photons. The physics objective of LUXE are processes of quantum electrodynamics (QED) at the strong-field frontier, where the electromagnetic field of the laser is above the Schwinger limit. In this regime, QED is non-perturbative. This manifests itself in the creation of physical electron-positron pairs from the QED vacuum, similar to Hawking radiation from black holes. LUXE intends to measure the positron production rate in an unprecedented laser intensity regime. An overview of the LUXE experimental setup and its challenges will be given, followed by a discussion of the expected physics reach in the context of testing QED in the non-perturbative regime.

    hep-phhep-exphysics.ins-detphysics.opticsPoS(2022)·0 citations
15. 15*

    Gauge Parameter Independence of the Higgs Pole Mass in the Multi-Higgs model

    Chungku Kim🇰🇷

    e have investigated the gauge parameter dependence of the Higgs pole masses in the multi-Higgs model in two different types of the gauge fixing conditions. It turns out that the Higgs pole masses of the multi-Higgs model when expressed in terms of the Lagrangian parameters, are independent of the gauge parameter for both cases.

    hep-phJ.Korean Phys.Soc.(2020)·1 citation
16. 16*

    A Tale of Invisibility: Constraints on New Physics in $b\to s\nu \nu$

    Tobias Felkl🇦🇺 · Sze Lok Li🇺🇸 · Michael A. Schmidt🇦🇺

    The Belle II experiment will measure the rare decays $B\to K\nu \nu$ and $B\to K^{\ast }\nu \nu$ with increased sensitivity which can hence be expected to serve as a very efficient probe of new physics. We calculate the relevant branching ratios in low-energy effective field theory (LEFT) including an arbitrary number of massive sterile neutrinos and discuss the expected sensitivity to the different operators. We also take into account the longitudinal polarisation fraction $F_L$ and the inclusive decay rate $B\to X_s\nu \nu$. In our investigation we consider new physics dominantly contributing to one and two operators both for massless and massive (sterile) neutrinos. Our results show a powerful interplay of the exclusive decay rates $B\to K\nu \nu$ and $B\to K^{\ast }\nu \nu$, and a surprisingly large sensitivity of the inclusive decay mode to vector operators even under conservative assumptions about its uncertainty. Furthermore, the sensitivity of $F_L$ is competitive with the branching ratio of $B\to K^{\ast }\nu \nu$ in the search for new physics contributing to scalar operators and thus also complementary to $B\to K\nu \nu$ and $B\to X_s\nu \nu$.

    hep-phJHEP(2021)·54 citations
17. 17*

    Electroweak phase transition and gravitational waves in a two-component dark matter model

    Ahmad Mohamadnejad🇮🇷

    We investigate an extension of the Standard Model (SM) with two candidates for dark matter (DM). One of them is a real scalar field and the other is an Abelian gauge field. Except for these two, there is another beyond SM field which has unit charge under a dark $U_D(1)$ gauge symmetry. The model is classically scale invariant and the electroweak symmetry breaks because of the loop effects. Although SM is extended with a new dark symmetry and three fields, because of scale invariance, the parameter space is strictly restricted compared to other two-component DM models. We study both DM phenomenology and electroweak phase transition and show that there are some points in the parameter space of the model consistent with DM relic density and direct detection constraints, while at the same time can lead to first order electroweak phase transition. The gravitational waves produced during the phase transition could be probed by future space-based interferometers such as Laser Interferometer Space Antenna (LISA) and Big Bang Observer (BBO).

    hep-phJHEP(2022)·28 citations
18. 18*

    Long-lived Sterile Neutrinos at Belle II in Effective Field Theory

    Guanghui Zhou🇳🇱 · Julian Y. Günther🇩🇪 · Zeren Simon Wang🇹🇼 · Jordy de Vries🇳🇱 · Herbi K. Dreiner🇩🇪

    Large numbers of $\tau$ leptons are produced at Belle II. These could potentially decay into sterile neutrinos that, for the mass range under consideration, are typically long-lived, leading to displaced-vertex signatures. Here, we study a displaced-vertex search sterile-neutrino-extended Standard Model Effective Field Theory. The production and decay of the sterile neutrinos can be realized via either the standard active-sterile neutrino mixing or higher-dimensional operators in the effective Lagrangian. We perform Monte-Carlo simulations to estimate the Belle II sensitivities to such interactions. We find that Belle II can probe non-renormalizable dimension-six operators involving a single sterile neutrino up to a few TeV in the new-physics scale.

    hep-phhep-exJHEP(2022)·41 citations
19. 19*

    Testing the Standard Model with CP-asymmetries in flavour-specific non-leptonic decays

    Tim Gershon🇬🇧 · Alexander Lenz🇩🇪 · Aleksey V. Rusov🇩🇪 · Nicola Skidmore🇬🇧

    Motivated by recent indications that the rates of colour-allowed non-leptonic channels are not in agreement with their Standard Model expectations based on QCD factorisation, we investigate the potential to study CP asymmetries with these decays. In the Standard Model, these flavour-specific decays are sensitive to CP violation in $B_{(s)}^0$--${\bar{B}}_{(s)}^0$ mixing, which is predicted with low uncertainties and can be measured precisely with semileptonic decays. If there are beyond Standard Model contributions to the non-leptonic decay amplitudes, there could be significant enhancements to the CP asymmetries. Measurements of these quantities therefore have potential to identify BSM effects without relying on Standard Model predictions that might be affected by hadronic effects. We discuss the experimental prospects, and note the excellent potential for a precise determination of the CP asymmetry in ${\bar{B}}_s\to D_s^{+}{\pi }^{-}$ decays by the LHCb experiment.

    hep-phPRD(2022)·18 citations
20. 20*

    Initial-state temperature of light meson emission source from squared momentum transfer spectra in high-energy collisions

    Qi Wang🇨🇳 · Fu-Hu Liu🇨🇳 · Khusniddin K. Olimov🇺🇿

    The squared momentum transfer spectra of light mesons, ${\pi }^0$, ${\pi }^{+}$, $\eta$, and ${\rho }^0$, produced in high-energy virtual photon-proton (${\gamma }^{\ast }p$) $\to \mathrm{meson}+\mathrm{nucleon}$ process in electron-proton ($ep$) collisions measured by the CLAS Collaboration are analyzed by the Monte Carlo calculations, where the transfer undergoes from the incident ${\gamma }^{\ast }$ to emitted meson or equivalently from the target proton to emitted nucleon. In the calculations, the Erlang distribution from a multi-source thermal model is used to describe the transverse momentum spectra of emitted particles. Our results show that the average transverse momentum ($⟨p_T⟩$) and the initial-state temperature ($T_i$) increase from lower squared photon virtuality ($Q^2$) and Bjorken variable ($x_B$) to higher one. This renders that the excitation degree of emission source, which is described by $⟨p_T⟩$ and $T_i$, increases with increasing of $Q^2$ and $x_B$.

    hep-phhep-exnucl-exnucl-thFront.in Phys.(2021)·13 citations
21. 21*

    New hadron configuration: The double-gluon hybrid state

    Hua-Xing Chen🇨🇳 · Wei Chen🇨🇳 · Shi-Lin Zhu🇨🇳

    This is the first study on the double-gluon hybrid, which consists of one valence quark and one valence antiquark together with two valence gluons. We concentrate on the one with the exotic quantum number $J^{PC}=2^{+-}$ that conventional $\bar{q}q$ mesons can not reach. We apply QCD sum rule method to evaluate its mass to be $2.26_{-0.25}^{+0.20}$ GeV, and study its possible decay patterns. Especially, its three-meson decay patterns are generally not suppressed severely compared to two-meson decay patterns, so the $S$-wave three-meson decay channels $f_1\omega \pi /f_1\rho \pi$ can be useful in identifying its nature, which is of particular importance to the direct test of QCD in the low energy sector.

    hep-phhep-exhep-latnucl-ex+1PRD(2022)·16 citations
22. 22*

    Explaining the Cabibbo Angle Anomaly

    Claudio Andrea Manzari🇨🇭

    The Cabibbo-Cobayashi-Maskawa (CKM) matrix parametrizes the misalignement between the up- and down-quark mass basis in the Standard Model (SM). The observation of first row CKM unitarity violation has recently emerged as a new anomaly of the SM, known as the "Cabibbo Angle Anomaly" (CAA). With current measurements, comparing the elements $V_{ud}$ and $V_{us}$ extracted from beta and kaon decays respectively, the tension with the SM prediction amounts to $\sim$$3\sigma$. Recently, it has been pointed out that this anomaly can also be seen as a discrepancy in the determination of the Fermi constant from muon decay vs $\beta$ and K decays, once CKM unitarity is assumed. In fact, possible explanations in terms on New Physics fall under two broad classes: contributions to $\beta$ decay and/or to $\mu$ decay. In this proceedings, we discuss these solutions in terms of gauge invariant dimension 6 operators in SMEFT and simplified extensions of the Standard Model. The latter could introduce correlations with other anomalies in the SM, pointing to new and interesting directions for model building.

    hep-phhep-exnucl-thPoS(2022)·3 citations
23. 23*

    Discriminating the heavy jet production mechanisms in associated $Z$ + heavy flavor events at the LHC

    S. P. Baranov🇷🇺 · A. Bermudez Martinez🇩🇪 · H. Jung🇩🇪 · A. V. Lipatov🇷🇺 · M. A. Malyshev🇷🇺 · S. Taheri Monfared🇩🇪

    We reconsider the associated $Z$ boson and charm or beauty jet production at the LHC with paying special attention to the formation dynamics of heavy jets. Two different approaches are studied: first one, where heavy quarks are produced in the hard scattering subprocesses, implemented in the Monte-Carlo generator PEGASUS, and another scenario, where the hard scattering is calculated at NLO with MadGraph5_aMC@NLO and TMD parton shower is included (implemented in the Monte-Carlo generator CASCADE3). We compare the predictions obtained in both schemes with latest experimental data for associated $Z+b$ production cross sections and the relative production rate $\sigma (Z+c)/\sigma (Z+b)$ collected by the ATLAS and CMS Collaborations at $\sqrt{s}=13$~TeV. We introduce two kinematic observables (denoted as $z_b$ and $p_T^{\mathrm{rel}}$) which can be used to discriminate the heavy jet production mechanisms. Using these variables we trace the shape of the simulated $b$-jet events and recommend that these observables be taken into consideration in the forthcoming experimental analyses.

    hep-phEPJC(2022)·2 citations
24. 24*

    Systematic study of $D_{s0}^{\ast }$(2317) in quark models

    Yue Tan🇨🇳 · Yuheng Wu🇨🇳 · Youchang Yang🇨🇳 · Jialun Ping🇨🇳

    Recently, the BES\uppercase\expandafter{\romannumeral3} Collaboration updated the data for the exotic state, $D_{s0}^{\ast }(2317)$, with a mass of $2318.3\pm 1.2\pm 1.2$ MeV from the positronium annihilation process. Inspired by the experiment, we systematically investigated the $c\bar{q}$ meson family spectrum from the perspectives of two-quark, four-quark, and mixed two-four-quark structures, including $D_s$, $D_s^{\ast }$, $D_{s0}^{\ast }(2317)$, and $D_{s1}(2460)$, with the help of the Gaussian expansion method, which is a very accurate calculation method for few-body systems. We found that with appropriate spin-orbit coupling parameter $a_s$, the chiral quark model can effectively describe both $D_{s0}^{\ast }(2317)$ and $D_{s1}(2460)$. The four-quark calculation shows that the $DK$ state does not form a bound state, but the effective potential calculation shows an attractive interaction between them. Finally, we performed mixed two-four-quark calculations, and the results, with the help of the unquenched effect, show that the energies of $D_{s0}^{\ast }(2317)$ and $D_{s1}(2460)$ are in better agreement with experimental values. Therefore, we conclude that these two particles are good candidates for mixed two-four-quark states.

    hep-phPRD(2025)·10 citations
25. 25*

    Hypermagnetogenesis from axion inflation: Model-independent estimates

    E.V. Gorbar🇺🇦 · K. Schmitz🇨🇭 · O.O. Sobol🇨🇭 · S.I. Vilchinskii🇺🇦

    Axion inflation coupled to the Standard Model (SM) hypercharge gauge sector represents an attractive scenario for the generation of primordial hypermagnetic fields. The description of this scenario is, however, complicated by the Schwinger effect, which gives rise to highly nonlinear dynamics. Hypermagnetogenesis during axion inflation in the absence of nonlinear effects is well studied and known to result in a hypermagnetic energy density that scales like $H^4{e}^{2\pi \xi }/{\xi }^5$, where $\xi$ is proportional to the time derivative of the axion-vector coupling in units of the Hubble rate $H$. In this paper, we generalize this result to the full SM case by consistently taking into account the Schwinger pair production of all SM fermions. To this end, we employ the novel gradient-expansion formalism that we recently developed in [2109.01651], and which is based on a set of vacuum expectation values for bilinear hyperelectromagnetic functions in position space. We parametrize the numerical output of our formalism in terms of three parameters ($\xi$, $H$, and $\Delta$, where the latter accounts for the damping of subhorizon gauge-field modes because of the finite conductivity of the medium) and work out semianalytical fit functions that describe our numerical results with high accuracy. Finally, we validate our results by comparing them to existing estimates in the literature as well as to the explicit numerical results in a specific inflationary model, which leads to good overall agreement. We conclude that the systematic uncertainties in the description of hypermagnetogenesis during axion inflation, which previously spanned up to several orders of magnitude, are now reduced to typically less than 1 order of magnitude, which paves the way for further phenomenological studies.

    hep-phastro-ph.COhep-thPRD(2022)·42 citations
26. 26*

    Top quark effective couplings from top-pair tagged photoproduction in $p{e}^{-}$ collisions

    Antonio O. Bouzas🇲🇽 · F. Larios🇲🇽

    We present a detailed study, at the fast detector simulation level, of top-pair photoproduction in semileptonic mode at the LHeC and FCC-he future colliders. We work in full tree-level QED, not relying on the equivalent-photon approximation, taking into account the complete photoproduction kinematics. This allows us to define three photoproduction regions based on the angular acceptance range of the electron tagger. Those regions provide different degrees of sensitivity to top-quark effective couplings. We focus on the $t\bar{t}\gamma$ dipole couplings and the left-handed vector $tbW$ coupling for which we determine limits at both energies and in different photoproduction regions. We find that the LHeC and FCC-he will yield tight direct bounds on top dipole moments, greatly improving on current direct limits from hadron colliders, and direct limits on the $tbW$ coupling as restrictive as those expected from the HL-LHC. We also consider indirect limits from $b\to s\gamma$ branching ratio and $CP$ asymmetry, that are well known to be very sensitive probes of top electromagnetic dipole moments.

    hep-phPRD(2022)·4 citations
27. 27*

    Gauging lepton flavor SU(3) for the muon $g-2$

    Gonzalo Alonso-Álvarez🇨🇦 · James M. Cline🇨🇦

    Gauging a specific difference of lepton numbers such as $L_{\mu }-L_{\tau }$ is a popular model-building option, which gives rise to economical explanations for the muon anomalous magnetic moment. However, this choice of gauge group seems rather arbitrary, and additional physics is required to reproduce the observed neutrino masses and mixings. We address these shortcomings by embedding $L_{\mu }-L_{\tau }$ in the vectorial SU(3) gauge symmetry of lepton flavor. The vacuum expectation values (VEVs) of scalar fields in the fundamental, six-dimensional and adjoint representations allow for phenomenologically viable lepton and gauge boson masses. The octet scalar gives rise to charged lepton masses, and together with the triplet scalar generates masses for all the leptophilic gauge bosons except for the $L_{\mu }-L_{\tau }$ one. The latter gets its smaller mass from the sextet VEVs, which also generate the neutrino masses, and are determined up to an overall scaling by the observed masses and mixings. The model predicts three heavy neutral leptons at the GeV-TeV scale as well as vectorlike charged lepton partners; it requires the mass of the lightest active neutrino to exceed $10^{-4}$eV, and it naturally provides a resolution of the Cabibbo angle anomaly.

    hep-phJHEP(2022)·11 citations
28. 28*

    Non-resonant new physics search at the LHC for the $b\to c\tau \nu$ anomalies

    Motoi Endo🇯🇵 · Syuhei Iguro🇩🇪 · Teppei Kitahara🇯🇵 · Michihisa Takeuchi🇯🇵 · Ryoutaro Watanabe🇮🇹

    Motivated by the $b\to c\tau \overline{\nu }$ anomalies, we study non-resonant searches for new physics at the large hadron collider (LHC) by considering final states with an energetic and hadronically decaying $\tau$ lepton, a $b$-jet and large missing transverse momentum ($pp\to {\tau }_h\overline{b}+E_{\mathrm{T}}^{\mathrm{miss}}$). Such searches can be useful to probe new physics contributions to $b\to c\tau \overline{\nu }$. They are analyzed not only within the dimension-six effective field theory (EFT) but also in explicit leptoquark (LQ) models with the LQ non-decoupled. The former is realized by taking a limit of large LQ mass in the latter. It is clarified that the LHC sensitivity is sensitive to the LQ mass for $O(1)$ TeV even in the search of $pp\to {\tau }_h\overline{b}+E_{\mathrm{T}}^{\mathrm{miss}}$. Although the LQ models provide a weaker sensitivity than the EFT limit, it is found that the non-resonant search of $pp\to {\tau }_h\overline{b}+E_{\mathrm{T}}^{\mathrm{miss}}$ can improve the sensitivity by $\approx 40\%$ versus a conventional mono-$\tau$ search ($pp\to {\tau }_h+E_{\mathrm{T}}^{\mathrm{miss}}$) in the whole LQ mass region. Consequently, it is expected that most of the parameter regions suggested by the $b\to c\tau \overline{\nu }$ anomalies can be probed at the HL-LHC. Also, it is shown that ${\text{R}}_2$ LQ scenario is accessible entirely once the LHC Run 2 data are analyzed. In addition, we discuss a charge selection of ${\tau }_h$ to further suppress the standard-model background, and investigate the angular correlations among $b,\tau$ and the missing transverse momentum to discriminate the LQ scenarios.

    hep-phhep-exJHEP(2022)·41 citations
29. 29*

    Numerical study of multiparticle production in ${\varphi }^4$ theory: comparison with analytic results

    S.V. Demidov🇷🇺 · B.R. Farkhtdinov🇷🇺 · D.G. Levkov🇷🇺

    We develop a numerical method to compute the probabilities of multiparticle production in weakly coupled scalar theories. Our technique is based on D.T. Son's semiclassical method of singular solutions. Applying it to the process $1\to n$ in the unbroken four-dimensional $\lambda {\varphi }^4$ theory, we reproduce the known results at $1\ll n\ll {\lambda }^{-1}$.

    hep-phhep-thPisma Zh.Eksp.Teor.Fiz.(2021)·5 citations
30. 30*

    Uehling potential and lowest-order corrections on vacuum polarization to the cross sections of some QED processes

    Alexei M. Frolov🇨🇦

    Properties and different representations of the Uehling potential are investigated. Based on these properties and by using our formulas for the Fourier transform of the Uehling potential we have developed the new analytical, logically closed and physically transparent procedure which can be used to evaluate the lowest-order vacuum polarization correction to the cross sections of a number of QED processes, including the Mott electron scattering, bremsstrahlung, creation and/or annihilation of the $(e^{-},e^{+})-$pair in the field of a heavy Coulomb center, e.g., atomic nucleus.

    hep-phhep-thEPJA(2021)·4 citations
31. 31*

    Analytic non-homogeneous condensates in the $(2+1)$-dimensional Yang-Mills-Higgs-Chern-Simons theory at finite density

    Fabrizio Canfora🇨🇱 · Daniel Flores-Alfonso🇲🇽 · Marcela Lagos🇨🇱 · Aldo Vera🇨🇱

    We construct the first analytic examples of non-homogeneous condensates in the Georgi-Glashow model at finite density in $(2+1)$ dimensions. The non-homogeneous condensates, which live within a cylinder of finite spatial volume, possess a novel topological charge that prevents them from decaying in the trivial vacuum. Also the non-Abelian magnetic flux can be computed explicitly. These solutions exist for constant and non-constant Higgs profile and, depending on the length of the cylinder, finite density transitions occur. In the case in which the Higgs profile is not constant, the full system of coupled field equations reduce to the Lamé equation for the gauge field (the Higgs field being an elliptic function). For large values of this length, the energetically favored configuration is the one with a constant Higgs profile, while, for small values, it is the one with non-constant Higgs profile. The non-Abelian Chern-Simons term can also be included without spoiling the integrability properties of these configurations. Finally, we study the stability of the solutions under a particular type of perturbations.

    ↳ hep-thhep-phPRD(2021)·7 citations
32. 32*

    Soliton boson stars, Q-balls and the causal Buchdahl bound

    Mateja Bošković🇮🇹 · Enrico Barausse🇮🇹

    Self-gravitating non-topological solitons whose potential admits multiple vacua are promising candidates for exotic compact objects. Such objects can arise in several extensions of the Standard Model and could be produced in the early Universe. In this work, we focus on objects made from complex scalars (gravitating Q-balls/soliton boson stars), deriving analytic solutions in spherical symmetry and comparing them with fully numerical ones. In the high-compactness limit we find that these objects present an effectively linear equation of state, thus saturating the Buchdahl limit with the causality constraint. Far from that limit, these objects behave either as flat space-time Q-balls or (in the low-compactness limit) as mini boson stars stabilized by quantum pressure. We establish the robustness of this picture by analyzing a variety of potentials (including cosine, quartic and sextic ones).

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2022)·47 citations
33. 33*

    Constraints on the number of X-ray Pulsars in IC 10 from a deep XMM-Newton Observation

    Jun Yang🇺🇸 · Silas G. T. Laycock🇺🇸 · Daniel R. Wik🇺🇸

    We report the most sensitive search yet for X-ray pulsars in the dwarf starburst galaxy IC 10, which is known to contain a population of young high mass X-ray binaries. We searched for pulsations in 207 point-like X-ray sources in the direction of IC 10 by a 2012 \xmm~observation with a total exposure time of 134.5 ks. Pulsation searches in faint objects can be sensitive to the energy bands of the light curves, and the source and background extraction areas. We analyzed separately the PN and MOS barycenter corrected 0.2-12 keV data, with good time interval filtering. Different schemes for source and background extraction were compared, and the search was repeated in the narrower 0.5-8 keV energy band to increase the signal-to-noise ratio. For the most conservative parameters, 5 point sources produced significant peaks in the Lomb-Scargle periodogram (99\% significance, single trial, assuming white noise). A similar number of different candidates result from alternative analyses. A $\sim$4100 s period seen in all 3 instruments for the black hole (BH) + Wolf-Rayet (WR) binary IC 10 X-1 is probably due to red noise of astrophysical origin. Considering the periods, luminosities, and spatial distribution of the pulsar candidates in the direction of IC 10, they do not belong to the same distribution as the ones in the Magellanic Clouds and Milky Way. This result holds even if the candidates are spurious, since if the Small Magellanic Cloud were placed at the distance of IC 10, we would expect to see $\sim$5 pulsars at $L_x>10^{36}$ \lx ~inside the $D_{25}$ contour, and their periods would be of order 100 seconds, rather than the mostly $\sim$1 s periods for the candidates reported here, which lie outside the main body of the galaxy.

    ↳ astro-ph.HEhep-phAstron.Nachr.(2019)·1 citation
34. 34*

    Perspectives in Small Systems : Heavy Quarks and HBT Radii

    Debasish Das🇮🇳

    Recent observations of QGP-like phenomena in small collision systems like p+p and p+A collisions have questioned our understanding of the basic paradigms of high energy heavy-ion physics. A brief discussion of these new aspects in small systems which in turn influence our understanding of hard probes like heavy quarks has been provided. Furthermore, a closer observation of the two-particle Hanbury-Brown Twiss (HBT) interferometry measurements provide new insights in our understanding of medium-like phenomena in small systems. An outlook of future goals and measurements is also made.

    ↳ nucl-exhep-exhep-phnucl-thNPA(2021)·4 citations
35. 35*

    Varying fundamental constants and dark energy in the ESPRESSO era

    C. J. A. P. Martins🇵🇹

    The observational evidence for the recent acceleration of the universe shows that canonical theories of cosmology and particle physics are incomplete and that new physics is out there, waiting to be discovered. A compelling task for astrophysical facilities is to search for, identify and ultimately characterize this new physics. I present very recent developments in tests of the stability of nature's fundamental constants, as well as their impact on physics paradigms beyond the standard model. Specifically I discuss new observational constraints at low redshifts and at the BBN epoch, and highlight their different implications for canonical quintessence-type models and for non-canonical string-theory inspired models. Finally I also present new forecasts, based on realistic simulated data, of the gains in sensitivity for these constraints expected from ELT-HIRES, on its own and in combination with Euclid.

    ↳ astro-ph.COgr-qchep-ph1 citation
36. 36*

    Lattice gauge symmetry in neural networks

    Matteo Favoni🇦🇹 · Andreas Ipp🇦🇹 · David I. Müller🇦🇹 · Daniel Schuh🇦🇹

    We review a novel neural network architecture called lattice gauge equivariant convolutional neural networks (L-CNNs), which can be applied to generic machine learning problems in lattice gauge theory while exactly preserving gauge symmetry. We discuss the concept of gauge equivariance which we use to explicitly construct a gauge equivariant convolutional layer and a bilinear layer. The performance of L-CNNs and non-equivariant CNNs is compared using seemingly simple non-linear regression tasks, where L-CNNs demonstrate generalizability and achieve a high degree of accuracy in their predictions compared to their non-equivariant counterparts.

    ↳ hep-latcs.LGhep-phhep-th+1PoS(2022)·5 citations
37. 37*

    Constrained Superfields in Dynamical Background

    Shuntaro Aoki🇰🇷 · Takahiro Terada🇰🇷

    We study the nonlinear realization of supersymmetry in a dynamical/cosmological background in which derivative terms like kinetic terms are finite. Starting from linearly realized theories, we integrate out heavy modes without neglecting derivative terms to obtain algebraic constraints on superfields. Thanks to the supersymmetry breaking contribution by the kinetic energy, the validity of constrained superfields can be extended to cosmological regimes and phenomena such as reheating after inflation, kinetic-energy domination, and the kinetic and standard misalignment of axion.

    ↳ hep-thastro-ph.COhep-phJHEP(2022)·3 citations
38. 38*

    WISPLC: Search for Dark Matter with LC Circuit

    Zhongyue Zhang🇩🇪 · Oindrila Ghosh🇩🇪 · Dieter Horns🇩🇪

    The focus on dark matter search has expanded to include low-mass particles such as axions or axion-like particles, and novel theoretical schemes extending the phenomenological landscape, within QCD and beyond, also garnered additional interest in recent decades. Assuming dark matter is composed of axions, in presence of a solenoidal magnetic field, they induce a displacement current that gives rise to a toroidal magnetic field. The Weakly Interacting Slender Particle detection with LC circuit (WISPLC) is a precision direct detection experiment that will search for light dark matter candidates such as axion-like particles in parts of the parameter space previously unexplored. We present two detection schemes of the signal in a pickup loop capturing the flux of this toroidal magnetic field. WISPLC operates in a broadband and a resonant scheme where a LC circuit is used to enhance the signal with an expected Q factor $\sim 10^4$. Taking into account the irreducible flux noise of the detector, we estimate the sensitivity of the experiment in the axion mass range between $10^{-11}$ eV and $10^{-6}$ eV to reach a detectable axion-photon coupling of $g_{a\gamma \gamma }\approx 10^{-15}{\mathrm{GeV}}^{-1}$, making it possible to probe mass ranges corresponding to ultralight axions motivated by string theory. The WISPLC experiment is fully funded and currently in the construction phase.

    ↳ hep-exastro-ph.COhep-phPRD(2022)·54 citations
39. 39*

    Overview of lattice calculations of the $x$-dependence of PDFs, GPDs and TMDs

    Krzysztof Cichy🇵🇱

    For a long time, lattice QCD was unable to address the $x$-dependence of partonic distributions, direct access to which is impossible in Euclidean spacetime. Recent years have brought a breakthrough for such calculations when it was realized that partonic light-cone correlations can be accessed through spatial correlations computable on the lattice. Appropriately devised observables can be factorized into physical PDFs via a perturbative procedure called matching, analogous to the standard factorization of experimental cross sections. In this short review, aimed at a broader high-energy and nuclear physics community, we discuss the recent highlights of this research program. Key concepts are outlined, followed by a case study illustrating the typical stage of current lattice extractions and by a brief review of the most recent explorations. We finalize with a number of messages for the prospects of lattice determinations of partonic structure.

    ↳ hep-lathep-exhep-phnucl-thEPJ Web Conf.(2022)·40 citations
40. 40*

    Asymptotic freedom and safety in quantum gravity

    Saswato Sen🇩🇪 · Christof Wetterich🇩🇪 · Masatoshi Yamada🇩🇪

    We compute non-perturbative flow equations for the couplings of quantum gravity in fourth order of a derivative expansion. The gauge invariant functional flow equation for arbitrary metrics allows us to extract $\beta$-functions for all couplings. In our truncation we find two fixed points. One corresponds to asymptotically free higher derivative gravity, the other is an extension of the asymptotically safe fixed point in the Einstein-Hilbert truncation or extensions thereof. The infrared limit of the flow equations entails only unobservably small modifications of Einstein gravity coupled to a scalar field. Quantum gravity can be asymptotically free, based on a flow trajectory from the corresponding ultraviolet fixed point to the infrared region. This flow can also be realized by a scaling solution for varying values of a scalar field. As an alternative possibility, quantum gravity can be realized by asymptotic safety at the other fixed point. There may exist a critical trajectory between the two fixed points, starting in the extreme ultraviolet from asymptotic freedom. We compute critical exponents and determine the number of relevant parameters for the two fixed points. Evaluating the flow equation for constant scalar fields yields the universal gravitational contribution to the effective potential for the scalars.

    ↳ hep-thgr-qchep-phJHEP(2022)·37 citations
41. 41*

    Outer Automorphism Anomalies

    Brian Henning🇨🇭 · Xiaochuan Lu🇺🇸 · Tom Melia🇯🇵 · Hitoshi Murayama🇺🇸

    We discuss anomalies associated with outer automorphisms in gauge theories based on classical groups, namely charge conjugations for $SU(N)$ and parities for $SO(2r)$. We emphasize the inequivalence (yet related by a flavor transformation) between two versions of charge conjugation for $SU(2k)$, $SO(2r)$, and $E_6$ symmetries. The subgroups that commute with the outer automorphisms are identified. Some charge conjugations can lead to a paradox, which is resolved by the observation that they are anomalous and hence not symmetries. We then discuss anomaly matching conditions that involve the charge conjugations or parities. Interesting examples are given where the charge conjugation is spontaneously broken.

    ↳ hep-thhep-phJHEP(2022)·19 citations
42. 42*

    Stasis in an Expanding Universe: A Recipe for Stable Mixed-Component Cosmological Eras

    Keith R. Dienes🇺🇸 · Lucien Heurtier🇬🇧 · Fei Huang🇨🇳 · Doojin Kim🇺🇸 · Tim M.P. Tait🇺🇸 · Brooks Thomas🇺🇸

    One signature of an expanding universe is the time-variation of the cosmological abundances of its different components. For example, a radiation-dominated universe inevitably gives way to a matter-dominated universe, and critical moments such as matter-radiation equality are fleeting. In this paper, we point out that this lore is not always correct, and that it is possible to obtain a form of "stasis" in which the relative cosmological abundances ${\Omega }_i$ of the different components remain unchanged over extended cosmological epochs, even as the universe expands. Moreover, we demonstrate that such situations are not fine-tuned, but are actually global attractors within certain cosmological frameworks, with the universe naturally evolving towards such long-lasting periods of stasis for a wide variety of initial conditions. The existence of this kind of stasis therefore gives rise to a host of new theoretical possibilities across the entire cosmological timeline, ranging from potential implications for primordial density perturbations, dark-matter production, and structure formation all the way to early reheating, early matter-dominated eras, and even the age of the universe.

    ↳ astro-ph.COhep-phPRD(2022)·44 citations
43. 43*

    Faking Gauge Coupling Unification in String Theory

    James Halverson🇺🇸 · Benjamin Sung🇺🇸

    Gauge coupling unification misleads infrared observers if new gauge bosons do not simultaneously come into the spectrum. Though easy to engineer in gauge theory, the situation in string theory is nuanced, due to moduli dependence. We study the possibility of faking gauge coupling unification in the context of $4$d F-theory compactifications. Specifically, we formulate a sufficient condition that we call a strong calibration, under which seven-brane gauge couplings on homologically distinct divisors become equal at codimension one in Kähler moduli space. We prove that a strong calibration is preserved under appropriate topological transitions and that a pair of non-intersecting divisors each admitting a contraction can always be strongly calibrated. Within the Tree ensemble, we find that $\approx 77.12\%$ of pairs of intersecting toric divisors can be strongly calibrated and $\approx 3.22\%$ can never be calibrated. Physically, this means that gauge coupling unification can be faked in most cases that we study, but in others it cannot, which is surprising from a gauge theoretic perspective.

    ↳ hep-thhep-phmath.AGPRD(2022)·1 citation
44. 44*

    Primordial gravitational waves from NANOGrav: a broken power-law approach

    Micol Benetti🇮🇹 · Leila Lobato Graef🇧🇷 · Sunny Vagnozzi🇬🇧

    We revisit the possibility that the stochastic common-spectrum process recently detected by the NANOGrav pulsar timing array experiment could be due to primordial gravitational waves (GWs). A naïve extrapolation down to interferometer scales of the blue GW spectrum required to explain NANOGrav consistently with Cosmic Microwave Background (CMB) observations would strongly violate upper limits on the stochastic GW background (SGWB) amplitude from LIGO/Virgo. In combination with the fact that there are over 19 decades in frequency between CMB and interferometer scales, this motivates us to move beyond the commonly adopted approximation of a pure power-law GW spectrum. We consider a broken power-law parametrization for the SGWB spectrum, which turns from blue to red above the break frequency: while phenomenological, this choice maps to various well-motivated early-Universe models, including scenarios featuring non-instantaneous reheating or a non-standard background expansion following reheating. After a detailed discussion of the contribution of the resulting SGWB to the early-Universe radiation energy density, we constrain the broken power-law model against a wide variety of multi-frequency cosmological and GW observations. We find that this phenomenological model is able to explain the NANOGrav signal while remaining in agreement with upper limits on the tensor-to-scalar ratio on CMB scales, Big Bang Nucleosynthesis constraints on the early-Universe radiation energy density, and upper limits on the SGWB amplitude on interferometer scales. We briefly discuss the very bright prospects for testing this model with next-generation probes across the GW frequency landscape, which motivate further exploring connections to specific well-motivated early-Universe models.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2022)·175 citations
45. 45*

    The World in a Grain of Sand: Condensing the String Vacuum Degeneracy

    Yang-Hui He🇬🇧 · Shailesh Lal🇵🇹 · M. Zaid Zaz🇺🇸

    We propose a novel approach toward the vacuum degeneracy problem of the string landscape, by finding an efficient measure of similarity amongst compactification scenarios. Using a class of some one million Calabi-Yau manifolds as concrete examples, the paradigm of few-shot machine-learning and Siamese Neural Networks represents them as points in R(3) where the similarity score between two manifolds is the Euclidean distance between their R(3) representatives. Using these methods, we can compress the search space for exceedingly rare manifolds to within one percent of the original data by training on only a few hundred data points. We also demonstrate how these methods may be applied to characterize `typicality' for vacuum representatives.

    ↳ hep-thhep-phmath.AGPLB(2024)·12 citations
46. 46*

    On the evaluation of the Appell $F_2$ double hypergeometric function

    B. Ananthanarayan🇮🇳 · Souvik Bera🇮🇳 · S. Friot🇫🇷 · O. Marichev🇺🇸 · Tanay Pathak🇮🇳

    The transformation theory of the Appell $F_2(a,b_1,b_2;c_1,c_2;x,y)$ double hypergeometric function is used to obtain a set of series representations of $F_2$ which provide an efficient way to evaluate $F_2$ for real values of its arguments $x$ and $y$ and generic complex values of its parameters $a,b_1,b_2,c_1$ and $c_2$ (i.e. in the nonlogarithmic case). This study rests on a classical approach where the usual double series representation of $F_2$ and other double hypergeometric series that appear in the intermediate steps of the calculations are written as infinite sums of one variable hypergeometric series, such as the Gauss ${}_2{F}_1$ or the ${}_3{F}_2$, various linear transformations of the latter being then applied to derive known and new formulas. Using the three well-known Euler transformations of $F_2$ on these results allows us to obtain a total of 44 series which form the basis of the Mathematica package AppellF2, dedicated to the evaluation of $F_2$. A brief description of the package and of the numerical analysis that we have performed to test it are also presented.

    ↳ math.CAhep-phhep-thmath-ph+1Comput.Phys.Commun.(2023)·31 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.