Tue·Oct 16, 2018Tuesday·October 16, 2018

1. 01*

   Non-Perturbative Effects in $\mu \to e\gamma$

   Wouter Dekens🇺🇸 · Elizabeth E. Jenkins🇺🇸 · Aneesh V. Manohar🇺🇸 · Peter Stoffer🇺🇸

   We compute the non-perturbative contribution of semileptonic tensor operators $(\bar{q}{\sigma }^{\mu \nu }q)(\bar{\ell }{\sigma }_{\mu \nu }\ell )$ to the purely leptonic process $\mu \to e\gamma$ and to the electric and magnetic dipole moments of charged leptons by matching onto chiral perturbation theory at low energies. This matching procedure has been used extensively to study semileptonic and leptonic weak decays of hadrons. In this paper, we apply it to observables that contain no strongly interacting external particles. The non-perturbative contribution to $\mu \to e$ processes is used to extract the best current bound on lepton-flavor-violating semileptonic tensor operators, ${\Lambda }_{\text{BSM}}\gtrsim 450$ TeV. We briefly discuss how the same method applies to dark-matter interactions.

   hep-phhep-exnucl-thJHEP(2019)·50 citations
2. 02*

   Response to an External Magnetic Field of the Decay Rate of a Neutral Scalar Field into a Charged Fermion Pair

   Jorge Jaber-Urquiza🇲🇽 · Gabriella Piccinelli🇲🇽 · Angel Sanchez🇲🇽

   In this work we explore the effects of a weak magnetic field on the decay process of a neutral scalar boson into a pair of charged fermions in vacuum. Since the analytical computation of the decay width needs of some approximation, following two different approaches, we study the low and high transverse momentum limits. Our findings indicate that the magnetic field effect depends on the kinematics of the scalar particle.

   hep-phPRD(2019)·10 citations
3. 03*

   Exploring Bosonic Mediator of Interaction at BESIII

   Jun Jiang🇨🇳 · Hao Yang🇨🇳 · Cong-Feng Qiao🇨🇳

   We present a comprehensive investigation on the possibility of the search for new force mediator $X$ boson in $e^{+}{e}^{-}$ collision and $J/\psi$ decay at the BESIII experiment. The typical interactions of $X$ boson coupling to leptons and quarks are explored. The production and decay properties of this $X$ particle, the product/decay chains $e^{+}{e}^{-}\to X\gamma \to e^{+}{e}^{-}\gamma$ and $J/\psi \to X\gamma \to {\mu }^{+}{\mu }^{-}\gamma$, and exclusion limits on the reduced coupling strength parameters as functions of $X$ boson mass are presented. With the data set of tens of fb${}^{-1}{e}^{+}{e}^{-}$ or $10^{10}J/\psi$, we find that the exclusion limits on the coupling strength parameters fall in the range of $10^{-3}\sim 10^{-4}$, depending on $m_X$ assuming the decay width 10 eV$<{\Gamma }_X<$100 eV reasonably, for various hypotheses in the literature. According to our estimation, the search for new force mediator $X$ boson in both $e^{+}{e}^{-}$ collision and $J/\psi$ decay are accessible in nowadays BESIII experiment.

   hep-phhep-exEPJC(2019)·10 citations
4. 04*

   Flavon Stabilization in Models with Discrete Flavor Symmetry

   So Chigusa🇯🇵 · Shinta Kasuya🇯🇵 · Kazunori Nakayama🇯🇵

   We propose a simple mechanism for stabilizing flavon fields with aligned vacuum structure in models with discrete flavor symmetry. The basic idea is that flavons are stabilized by the balance between the negative soft mass and non-renormalizable terms in the potential. We explicitly discuss how our mechanism works in $A_4$ flavor model, and show that the field content is significantly simplified. It also works as a natural solution to the cosmological domain wall problem.

   hep-phPLB(2019)·9 citations
5. 05*

   Compatibility of $A_4$ Flavour Symmetric Minimal Extended Seesaw with $(3+1)$ Neutrino Data

   Neelakshi Sarma🇮🇳 · Kalpana Bora🇮🇳 · Debasish Borah🇮🇳

   Motivated by the recent resurrection of the evidence for an eV scale sterile neutrino from the MiniBooNE experiment, we revisit one of the most minimal seesaw model known as the minimal extended seesaw that gives rise to a $3+1$ light neutrino mass matrix. We consider the presence of $A_4$ flavour symmetry which plays a non-trivial role in generating the structure of the neutrino mass matrix. Considering a diagonal charged lepton mass matrix and generic vacuum alignments of $A_4$ triplet flavons, we classify the resulting mass matrices based on their textures. Keeping aside the disallowed texture zeros based on earlier studies of $3+1$ neutrino textures, we categorise the remaining ones based on texture zeros, $\mu -\tau$ symmetry in the $3\times 3$ block and hybrid textures. After pointing out the origin of such $3+1$ neutrino textures to $A_4$ vacuum alignments, we use the latest $3+1$ neutrino oscillation data and numerically analyse the texture zeros and $\mu -\tau$ symmetric cases. We find that a few of them are allowed from each category predicting interesting correlations between neutrino parameters. We also find that all of these allowed cases prefer normal hierarchical pattern of light neutrino masses over inverted hierarchy.

   hep-phEPJC(2019)·19 citations
6. 06*

   Test of the $R(D^{(\ast )})$ anomaly at the LHC

   Syuhei Iguro🇯🇵 · Yuji Omura🇯🇵 · Michihisa Takeuchi🇯🇵

   There are discrepancies between the experimental results and the Standard Model predictions, in the lepton flavor universality of the semileptonic $B$ decays: $B\to D^{(\ast )}\ell \nu$. As the new physics interpretations, new charged vector and charged scalar fields, that dominantly couple to the second and third generations, have been widely discussed. In this paper, we study the signals of the new particles at the LHC, and test the interpretations via the direct search for the new resonances. In particular, we see that the $\tau \nu$ resonance search at the LHC has already covered most of the parameter regions favored by the Belle and BaBar experiments. We find that the bound is already stronger than the one from the $B_c$ decay depending on the mass of charged scalar.

   hep-phhep-exPRD(2019)·61 citations
7. 07*

   The QED Radiative Corrections to Chiral Magnetic Effect

   Bo Feng🇨🇳 · De-fu Hou🇨🇳 · Hai-cang Ren🇺🇸

   We study in this paper the radiative corrections to chiral magnetic current at both zero and nonzero temperature. Our motivation is a radiative correction to the matrix element of the anomalous Ward identity in massless QED stemming from a three-loop diagram where the two photons coming from the one-loop anomalous triangle are re-scattered. Through the interplay between the Ward identity and the infrared subtlety of the fermion loop integral, we are able to reproduce the corrections known in literature in a simpler approach and obtain its contribution to the chiral magnetic current at zero temperature. At a nonzero temperature, the infrared subtlety disappeared in a static magnetic field and the three-loop diagram does not contribute to the chiral magnetic current any more. The generalization to all orders of the massless QED and the QCD corrections are discussed.

   hep-phPRD(2019)·17 citations
8. 08*

   Analysis of the strong vertices of ${\Sigma }_{c}N{D}^{\ast }$ and ${\Sigma }_{b}N{B}^{\ast }$ in QCD sum rules

   Guo-Liang Yu🇨🇳 · Rong-Hua Guan🇨🇳 · Zhi-Gang Wang🇨🇳

   The strong coupling constant is an important parameter which can help us to understand the strong decay behaviors of baryons. In our previous work, we have analyzed strong vertices ${\Sigma }_c^{\ast }ND$, ${\Sigma }_b^{\ast }NB$, ${\Sigma }_{c}ND$, ${\Sigma }_{b}NB$ in QCD sum rules. Following these work, we further analyze the strong vertices ${\Sigma }_{c}N{D}^{\ast }$ and ${\Sigma }_{b}N{B}^{\ast }$ using the three-point QCD sum rules under Dirac structures $q/p/{\gamma }_{\alpha }$ and $q/p/p_{\alpha }$. In this work, we first calculate strong form factors considering contributions of the perturbative part and the condensate terms $⟨\overline{q}q⟩$, $⟨\frac{{\alpha }_s}{\pi }GG⟩$ and $⟨\overline{q}{g}_s\sigma Gq⟩$. Then, these form factors are used to fit into analytical functions. According to these functions, we finally determine the values of the strong coupling constants for these two vertices ${\Sigma }_{c}N{D}^{\ast }$ and ${\Sigma }_{b}N{B}^{\ast }$.

   hep-phInt.J.Mod.Phys.A(2019)·5 citations
9. 09*

   Higgs boson structure from the shape of the cross section in exchange processes

   Fernand M Renard🇫🇷

   We show how the Higgs boson exchange processes may indicate the occurence of special Higgs boson structures (substructures or peculiar interactions with dark matter) from a possible modification of the s-dependence of their cross section. We illustrate the simplest example with the ${\mu }^{+}{\mu }^{-}\to f\bar{f}$ process.

   hep-ph0 citations
10. 10*

    One-loop contribution to dark matter-nucleon scattering in the pseudoscalar dark matter model

    Duarte Azevedo🇵🇹 · Mateusz Duch🇵🇱 · Bohdan Grzadkowski🇵🇱 · Da Huang🇵🇱 · Michal Iglicki🇵🇱 · Rui Santos🇵🇹

    Recent dark matter (DM) direct searches place very stringent constraints on the possible DM candidates proposed in extensions of the Standard Model. There are however models where these constraints are avoided. One of the simplest and most striking examples comes from a straightforward Higgs portal pseudoscalar DM model featured with a softly broken $U(1)$ symmetry. In this model the tree-level DM-nucleon scattering cross section vanishes in the limit of zero momentum-transfer. It has also been argued that the leading-order DM-nucleon cross-section appears at the one-loop level. %, which is too small to be constrained experimentally. In this work we have calculated the exact cross-section in the zero momentum-transfer at the leading-order i.e., at the one-loop level of perturbative expansion. We have concluded that, in agreement with expectations, the amplitude for the scattering process is UV finite and approaches zero in the limit of vanishing DM masses. Moreover, we made clear that the finite DM velocity correction at tree-level is subdominant with respect to the one-loop contribution. Based on the analytic formulae, our numerical studies show that, for a typical choice of model parameters, the DM nuclear recoiling cross section is well below $\mathcal{O}(10^{-50}{\mathrm{cm}}^2)$, which indicates that the DM direct detection signal in this model naturally avoids the present strong experimental limits on the cross-section.

    hep-phJHEP(2019)·74 citations
11. 11*

    Sound propagation and Mach cone in anisotropic hydrodynamics

    Martin Kirakosyan🇷🇺 · Aleksandr Kovalenko🇷🇺 · Andrey Leonidov🇷🇺

    This letter is based on a kinetic theory approach to anisotropic hydrodynamics. We derive the sound wave equation in anisotropic hydrodynamics and show that a corresponding wave front is ellipsoidal. The phenomenon of Mach cone emission in anisotropic hydrodynamics is studied. It is shown that Mach cone in anisotropic case becomes asymmetric, i. e. in this limit they're two different angles, left and right with respect to the ultrasonic particle direction, which are determined by the direction of ultrasonic particle propagation and the asymmetry coefficient.

    hep-phEPJC(2019)·6 citations
12. 12*

    Unveiling Regions in multi-scale Feynman Integrals using Singularities and Power Geometry

    B. Ananthanarayan🇮🇳 · Abhishek Pal🇺🇸 · S. Ramanan🇮🇳 · Ratan Sarkar🇮🇳

    We introduce a novel approach for solving the problem of identifying regions in the framework of Method of Regions by considering singularities and the associated Landau equations given a multi-scale Feynman diagram. These equations are then analyzed by an expansion in a small threshold parameter via the Power Geometry technique. This effectively leads to the analysis of Newton Polytopes which are evaluated using a Mathematica based convex hull program. Furthermore, the elements of the Gröbner Basis of the Landau Equations give a family of transformations, which when applied, reveal regions like potential and Glauber. Several one-loop and two-loop examples are studied and benchmarked using our algorithm which we call ASPIRE.

    hep-phEPJC(2019)·50 citations
13. 13*

    Dark Matter from a Vector Field in the Fundamental Representation of $SU(2{)}_L$

    Bastian Díaz Sáez🇨🇱 · Felipe Rojas-Abatte🇨🇱 · Alfonso R. Zerwekh🇨🇱

    We explore an extension to the Standard Model which incorporates a vector field in the fundamental representation of $SU(2{)}_L$ as the only non-standard degree of freedom. This kind of field may appear in different scenarios such as Compositness, Gauge-Higgs unification and extradimensional scenarios. We study the model in which a $Z_2$ symmetry is manifest, making the neutral CP-even component of the new vector field a vectorial dark matter candidate. We constraint the parameter space through LEP and LHC data, as well as from current dark matter searches. Additionally, comment on the implications of perturbative unitarity are presented. We find that the model is highly constrained but a small region of the parameter space can provide a viable DM candidate. On the other hand, unitarity demands an UV completion at an scale below 10 TeV. Finally we contrast our predictions on mono-jet, -$Z$, -Higgs production with the ones obtained in the inert Two Higgs Doublet Model.

    hep-phPRD(2019)·27 citations
14. 14*

    A $U(1{)}_R$ inspired inflation model in no-scale Supergravity

    Shaaban Khalil🇪🇬 · Ahmad Moursy🇪🇬 · Abhijit Kumar Saha🇮🇳 · Arunansu Sil🇮🇳

    We consider a cosmological inflation scenario based on a no-scale supergravity sector with $U(1{)}_R$ symmetry. It is shown that a tree level $U(1{)}_R$ symmetric superpotential alone does not lead to a slowly rolling scalar potential. A deformation of this tree level superpotential by including an explicit $R$ symmetry breaking term beyond the renomalizable level is proposed. The resulting potential is found to be similar (but not exactly the same) to the one in Starobinsky inflation model. We emphasize that for successful inflation, with the scalar spectral index $n_s\sim 0.96$ and the tensor-to-scalar ratio $r<0.08$, a correlation between the mass parameters in the superpotential and the vacuum expectation value of the modulus field $T$ in the Kähler potential must be adopted.

    hep-phhep-thPRD(2019)·20 citations
15. 15*

    A Concrete Composite 2-Higgs Doublet Model

    Stefania De Curtis🇮🇹 · Luigi Delle Rose🇮🇹 · Stefano Moretti🇬🇧 · Kei Yagyu🇯🇵

    We consider a Composite Higgs Model (CHM) with two isospin doublet Higgs fields arising as pseudo Nambu-Goldstone bosons from a $\mathrm{SO}(6)\to \mathrm{SO}(4)\times \mathrm{SO}(2)$ breaking. The main focus of this work is to explicitly compute the properties of these Higgses in terms of the fundamental parameters of the composite sector such as masses, Yukawa and gauge couplings of the new spin-1 and spin-1/2 resonances. Concretely, we calculate the Higgs potential at one-loop level through the Coleman-Weinberg mechanism from the explicit breaking of the $\mathrm{SO}(6)$ global symmetry by the partial compositeness of fermions and gauge bosons. We derive then the phenomenological properties of the Higgs states and highlight the main signatures of this Composite 2-Higgs Doublet Model at the Large Hadron Collider, including modifications to the SM-like Higgs couplings as well as production and decay channels of heavier Higgs bosons. We also consider flavour bounds that are typical of CHMs with more than one Higgs doublet.

    hep-phJHEP(2018)·29 citations
16. 16*

    The GAmmas from Nuclear Decays Hiding from Investigators (GANDHI) Experiment

    Giovanni Benato🇺🇸 · Alexey Drobizhev🇺🇸 · Surjeet Rajendran🇺🇸 · Harikrishnan Ramani🇺🇸

    We propose a high statistics experiment to search for invisible decay modes in nuclear gamma cascades. A radioactive source (such as ${}^{60}$Co or ${}^{24}$Na) that triggers gamma cascades is placed in the middle of a large, hermetically sealed scintillation detector, enabling photon identification with high accuracy. Invisible modes are identified by establishing the absence of a photon in a well-identified gamma cascade. We propose the use of fast scintillators with nanosecond timing resolution, permitting event rates as high as $10^7$ Hz. Our analysis of the feasibility of this setup indicates that branching fractions as small as $10^{-12}-10^{-14}$ can be probed. This experimental protocol benefits from the fact that a search for invisible modes is penalized for weak coupling only in the production of the new particle. If successfully implemented, this experiment is an exquisite probe of particles with mass below $\sim$4 MeV that lie in the poorly constrained supernova "trapping window" that exists between 100 keV - 30 MeV. Such particles have been invoked as mediators between dark matter and nucleons, explain the proton radius and $(g-2{)}_{\mu }$ anomalies and potentially power the shock wave in type II supernovae. The hadronic axion could also be probed with modifications to the proposed setup.

    hep-phnucl-exphysics.ins-detPRD(2019)·19 citations
17. 17*

    Parton Shower and Matching Uncertainties in Top Quark Pair Production with Herwig 7

    Kyle Cormier🇨🇦 · Simon Plätzer🇦🇹 · Christian Reuschle🇺🇸 · Peter Richardson🇨🇭 · Stephen Webster🇬🇧

    We evaluate the theoretical uncertainties in next-to-leading order plus parton shower predictions for top quark pair production and decay in hadronic collisions. Our work is carried out using the Herwig 7 event generator and presents an in-depth study of variations in matching schemes with two systematically different shower algorithms, the traditional angular-ordered and alternative dipole shower. We also present all of the required extensions of the Herwig dipole shower algorithm to properly take into account quark mass effects, as well as its ability to perform top quark decays. The predictions are compared at parton level as well as to LHC data, including in the boosted regime. We find that the regions where predictions with a non-top-quark-specific tune differ drastically from data are plagued by large uncertainties which are consistent between our two shower and matching algorithms.

    hep-phEPJC(2019)·34 citations
18. 18*

    Phenomenology using PARTONS software of Generalized Parton Distribution models built from Light-Front Wave-functions

    Nabil Chouika🇫🇷

    We present a procedure aiming at extending to the full kinematic domain a Generalized Parton Distribution obtained from a finite order truncation in Fock space. This method allows to fulfill both polynomiality and positivity at the same time and can be applied to any given models of Light-front wave-functions. In particular, we illustrate this on a three-body truncated wave-function of the chiral quark soliton model and show how a systematic phenomenology of GPD models based on LFWFs can be achieved with the help of the PARTONS framework, here using DVCS data. This paves the way for a unified phenomenology of GPDs and TMDs at the level of LFWFs, with the final goal of hadron tomography.

    hep-phnucl-thphysics.comp-phPoS(2018)·0 citations
19. 19*

    $U(1{)}_{\chi }$, Seesaw Dark Matter, and Higgs Decay

    Ernest Ma (UC Riverside)🇺🇸

    It has recently been pointed out that the underlying symmetry of dark matter may well be $U(1{)}_{\chi }$ (coming from $SO(10)\to SU(5)\times U(1{)}_{\chi }$) with the dark parity of any given particle determined by $(-1{)}^{Q_{\chi }+2j}$, where $Q_{\chi }$ is its $U(1{)}_{\chi }$ charge and $j$ its spin angular momentum. Armed with this new insight, previous simple models of dark matter are reinterpreted, and a novel idea is proposed that light seesaw dark matter exists in analogy to light neutrinos and is produced by the rare decay of the standard-model Higgs boson.

    hep-phLHEP(2019)·20 citations
20. 20*

    New Insights on an Old Problem: Resummation of the D-parameter

    Andrew J. Larkoski🇺🇸 · Aja Procita🇺🇸

    The $D$-parameter is one of the oldest and most experimentally well-studied hadronic observables for $e^{+}{e}^{-}$ collisions. Nevertheless, unlike other classic observables like the $C$-parameter or thrust, the $D$-parameter has never been resummed throughout its entire singular phase space. Using insights and techniques motivated by modern multi-differential jet substructure calculations, we are able to predict the $D$-parameter distribution with no additional phase space cuts. Our approach is to measure both the $C$- and $D$-parameters on hadronic final states in $e^{+}{e}^{-}$ collisions. We can tune the value of the $C$-parameter with respect to the $D$-parameter to specify simple, physical configurations of final state particles in which to perform calculations. There are three parametric regions that exist: $D\ll C^2\sim 1$, $D\ll C^2\ll 1$, and $D\sim C^2\ll 1$, and we calculate the $D$-parameter in each region separately. In the first two of these three regions, we present all-orders factorization theorems and explicitly demonstrate resummation to next-to-leading logarithmic accuracy. The region in which $D\sim C^2\ll 1$ corresponds to the dijet limit and where the $D$-parameter loses the property of additivity. In this region we introduce a systematically-improvable procedure exploiting properties of conditional probabilities and resum to approximate next-to-leading logarithmic accuracy. The contributions from these regions can be consistently combined, and the value of the $C$-parameter integrated over to produce the cross section for the $D$-parameter. With these results, we match to leading fixed order as proof of principle and compare our resummed and matched prediction to data from LEP.

    hep-phhep-exJHEP(2019)·11 citations
21. 21*

    Exclusive LHC physics with heavy ions: SuperChic 3

    L.A. Harland-Lang🇬🇧 · V.A. Khoze🇬🇧 · M.G. Ryskin🇷🇺

    We present results of the updated SuperChic 3 Monte Carlo event generator for central exclusive production. This extends the previous treatment of proton-proton collisions to include heavy ion (pA and AA) beams, for both photon and QCD-initiated production, the first time such a unified treatment of exclusive processes has been presented in a single generator. To achieve this we have developed a theory of the gap survival factor in heavy ion collisions, which allows us to derive some straightforward results about the $A$ scaling of the corresponding cross sections. We compare against the recent ATLAS and CMS measurements of light-by-light scattering at the LHC, in lead-lead collisions. We find that the background from QCD-initiated production is expected to be very small, in contrast to some earlier estimates. We also present results from new photon-initiated processes that can now be generated, namely the production of axion-like particles, monopole pairs and monopolium, top quark pair production, and the inclusion of $W$ loops in light-by-light scattering.

    hep-phhep-exEPJC(2019)·153 citations
22. 22*

    Strong- vs. weak-coupling pictures of jet quenching: a dry run using QED

    Peter Arnold🇺🇸 · Shahin Iqbal🇵🇰 · Tanner Rase🇺🇸

    High-energy partons ($E\gg T$) traveling through a quark-gluon plasma lose energy by splitting via bremsstrahlung and pair production. Regardless of whether or not the quark-gluon plasma itself is strongly coupled, an important question lying at the heart of philosophically different approaches to energy loss is whether the high-energy partons of an in-medium shower can be thought of as a collection of individual particles, or whether their coupling to each other is also so strong that a description as high-energy `particles' is inappropriate. We discuss some possible theorists' tests of this question for simple situations (e.g. an infinite, non-expanding plasma) using thought experiments and first-principles quantum field theory calculations (with some simplifying approximations). The physics of in-medium showers is substantially affected by the Landau-Pomeranchuk-Midgal (LPM) effect, and our proposed tests require use of what might be called `next-to-leading order' LPM results, which account for quantum interference between consecutive splittings. The complete set of such results is not yet available for QCD but is already available for the theory of large-$N_f$ QED. We therefore use large-$N_f$ QED as an example, presenting numerical results as a function of $N_f\alpha$, where $\alpha$ is the strength of the coupling at the relevant high-energy scale characterizing splittings of the high-energy particles.

    hep-phnucl-thJHEP(2019)·20 citations
23. 23*

    New constraints on sterile neutrino dark matter from the Galactic Center

    R. Yunis🇮🇹 · C. R. Argüelles🇦🇷 · N. E. Mavromatos🇬🇧 · A. Moliné🇵🇹 · A. Krut🇮🇹 · J. A. Rueda🇮🇹 · R. Ruffini🇮🇹

    We calculate the most stringent constraints up to date on the parameter space for sterile neutrino warm dark matter models possessing a radiative decay channel into X-rays. These constraints arise from the X-ray flux observations from the Galactic center (central parsec), taken by the XMM and NuSTAR missions. We compare the results obtained from using different dark matter density profiles for the Milky Way, such as NFW, Burkert or Einasto, to that produced by the Ruffini-Argüelles-Rueda (RAR) fermionic model, which has the distinct feature of depending on the particle mass. We show that due to the novel core-halo morphology present in the RAR profile, the allowed particle mass window is narrowed down to $m_s\sim 10-15$ keV, when analyzed within the $\nu$MSM sterile neutrino model. We further discuss on the possible effects in the sterile neutrino parameter-space bounds due to a self-interacting nature of the dark matter candidates.

    ↳ astro-ph.GAastro-ph.COhep-ph7 citations
24. 24*

    HVP contribution of the light quarks to the muon $(g-2)$ including isospin-breaking corrections with Twisted-Mass fermions

    Davide Giusti🇮🇹 · Vittorio Lubicz🇮🇹 · Guido Martinelli🇮🇹 · Francesco Sanfilippo🇮🇹 · Silvano Simula🇮🇹 · Cecilia Tarantino🇮🇹

    We present a preliminary lattice calculation of the leading-order electromagnetic and strong isospin-breaking corrections to the Hadronic Vacuum Polarization (HVP) contribution of the light quarks to the anomalous magnetic moment of the muon. The results are obtained in the quenched-$QED$ approximation using the $QCD$ gauge configurations generated by the European Twisted Mass Collaboration (ETMC) with $N_f=2+1+1$ dynamical quarks, at three values of the lattice spacing varying from $0.089$ to $0.062\text{mbox}fm$, at several lattice volumes and with pion masses in the range $M_{\pi }\simeq 220÷490\text{mbox}MeV$.

    ↳ hep-lathep-exhep-phPoS(2018)·10 citations
25. 25*

    $B_c$ mesons and their properties on the light front

    Shuo Tang🇺🇸 · Yang Li🇺🇸 · Pieter Maris🇺🇸 · James P. Vary🇺🇸

    We investigate the unequal mass relativistic bound state system, the $B_c$ mesons, in a light-front Hamiltonian formalism. We adopt an effective Hamiltonian based on soft-wall light-front holography, together with a longitudinal confinement that was first introduced for heavy quarkonium. We also include the one gluon-exchange interaction with a running coupling, which produces the spin structure. We present the mass spectrum and light-front wave functions. We also use the light-front wave functions to calculate decay constants, charge and momentum densities, as well as distribution amplitudes. The results are compared with experiments and other theoretical approaches, all of which are in reasonable agreement.

    ↳ nucl-thhep-phPRD(2018)·67 citations
26. 26*

    Exploring Nuclear Effects in Neutrino-Nucleus Interactions Using Measurements of Transverse Kinematic Imbalance from T2K and MINERvA

    Stephen Dolan🇫🇷

    Predictions from widely-used neutrino-nucleus interaction event generators are compared to measurements of transverse kinematic imbalances, made by both the T2K and MINERvA experiments, to allow a joint characterisation of the nuclear physics processes responsible for some of the largest uncertainties in measurements of neutrino oscillations. The role of nucleon-nucleon correlations, initial state nucleon Fermi motion and hadronic re-interactions inside the nuclear medium are explored and areas requiring more theoretical input are identified.

    ↳ hep-exhep-ph36 citations
27. 27*

    A pseudo-conformal structure in dense baryonic matter

    Yong-Liang Ma🇨🇳 · Mannque Rho🇫🇷

    We clarify and extend further the idea developed in \cite{PKLMR,MLPR} that baryonic matter at high density has an emergent "pseudo-conformal symmetry." It is argued that as baryonic density exceeds $n\simeq n_{1/2}\gtrsim 2n_0$, a topology change mimicking the baryon-quark continuity takes place at $n_{1/2}$. In terms of skyrmions, this corresponds to the transition from skyrmions to half-skyrmions and impacts on the equation of state of dense baryonic matter. The emergence in medium at $n_{1/2}$ of parity-doublet symmetry -- which is invisible in QCD in matter-free vacuum -- plays the crucial role. The consequence of the topology change is that massive compact stars carry the "pseudo-conformal sound velocity" $v_s^2/c^2\approx 1/3$ at $n\text{gsim}{n}_{1/2}$ signaling a precursor to precocious emergence of scale symmetry as well as {a} local symmetry hidden in QCD in the matter-free vacuum. A highly significant prediction of this work is that the topology change density from normal matter to half-skyrmion matter, up-to-date inaccessible either by QCD proper or by terrestrial experiments, could possibly be pinned down within the range $2<n_{1/2}/n_0<4$, commensurate with the range expected for a continuous hadrons-to-quarks/gluons transition.

    ↳ nucl-thhep-phPRD(2019)·26 citations
28. 28*

    Recent theoretical results for electromagnetically induced ultraperipheral reactions of heavy ions

    Antoni Szczurek🇵🇱

    We briefly review our works on ultraperipheral heavy ion collisions. We discuss both $\gamma \gamma$ and rescattering of hadronic photon fluctuation induced by one nucleus in the collision partner. Production of one and two leptonic and pionic and $p\bar{p}$ pairs is discussed as an example of photon-photon processes. The production of single vector mesons (${\rho }^0$ or $J/\psi$) is an example of the second category. The double-scattering mechanisms of two ${\rho }^0$ meson production is discussed in addition.

    ↳ nucl-thhep-ph2 citations
29. 29*

    Split Supersymmetry Breaking from Stuckelberg Mixing of Multiple U(1)'s

    Ghazaal Ghaffari🇮🇷 · Mahdi Torabian🇮🇷

    We show that multiple Abelian sectors with Stuckelberg mass-mixing simply break supersymmetry via Fayet-Iliopoulos D-terms and straightforwardly mediate it to the other sectors. This mechanism naturally realizes a split supersymmetry spectrum for soft parameters. Scalar squared-masses (holomorphic and non-holomorphic) are induced through sizable portals and are not suppressed. Gaugino masses, a-terms and a mu-like term are generated by higher-dimensional operators and are suppressed. The hypercharge is mixed with extra U(1)'s, it's D-term in non-vanishing and supersymmetry is broken in the visible sector too. Scalar tachyonic directions are removed by unsuppressed interactions and hypercharge is preserved as supersymmetry is broken. Moreover, if a singlet chiral field is charged under additional $U(1)$'s proportional to its hypercharge, new interaction terms in the Kahler potential and the superpotential are added through Stuckelberg compensation. In this case supersymmetry is broken via F-terms or mixed F and D-terms.

    ↳ hep-thhep-phPLB(2019)·1 citation
30. 30*

    Follow-up on non-leptonic kaon decays at large $N_c$

    Fernando Romero-López🇪🇸 · Andrea Donini🇪🇸 · Pilar Hernández🇪🇸 · Carlos Pena🇪🇸

    We report on the status of our dynamical simulations of a $SU(N_c)$ gauge theory with $N_c=3-6$ and $N_f=4$ fundamental fermions. These ensembles can be used to study the Large $N_c$ scaling of weak matrix elements in the GIM limit $m_c=m_u$, that might shed some light on the origin of the $\Delta I=1/2$ rule. We present preliminary results for the $K\to \pi$ matrix elements in the $N_c=3$ dynamical simulations, where we observe a significant effect of the quark loops that goes in the direction of enhancing the ratio of $A_0/A_2$ amplitudes. Finally, we present the relevant NLO Chiral Perturbation Theory predictions for the relation between $K\to \pi$ and $K\to \pi \pi$ amplitudes in the light charm limit.

    ↳ hep-lathep-phPoS(2018)·4 citations
31. 31*

    Testing velocity-dependent CPT-violating gravitational forces with radio pulsars

    Lijing Shao🇨🇳 · Quentin G. Bailey🇺🇸

    In the spirit of effective field theory, the Standard-Model Extension (SME) provides a comprehensive framework to systematically probe the possibility of Lorentz/CPT violation. In the pure gravity sector, operators with mass dimension larger than 4, while in general being advantageous to short-range experiments, are hard to investigate with systems of astronomical size. However, there is exception if the leading-order effects are CPT-violating and velocity-dependent. Here we study the lowest-order operators in the pure gravity sector that violate the CPT symmetry with carefully chosen relativistic binary pulsar systems. Applying the existing analytical results to the dynamics of a binary orbit, we put constraints on various coefficients for Lorentz/CPT violation with mass dimension 5. These constraints, being derived from the post-Newtonian dynamics for the first time, are complementary to those obtained from the kinematics in the propagation of gravitational waves.

    ↳ gr-qcastro-ph.HEhep-phPRD(2018)·39 citations
32. 32*

    Forecast on lepton asymmetry from future CMB experiments

    Alexander Bonilla🇧🇷 · Rafael C. Nunes🇧🇷 · Everton M. C. Abreu🇧🇷

    We consider a cosmological lepton asymmetry in the form of neutrinos and impose new expected sensitivities on such asymmetry through the degeneracy parameter (${\xi }_{\nu }$) by using some future CMB experiment configurations, such as CORE and CMB-S4. Taking the default scenario with three neutrino states, we find ${\xi }_{\mu }=0.05\pm 0.10(\pm 0.04)$, from CORE (CMB-S4) at 95 percent CL, respectively. Also, within this scenario, we evaluate the neutrino mass scale, obtaining that the normal hierarchy mass scheme is privileged. Our results are an update concerning on the cosmological lepton asymmetry and the neutrino mass scale within this context, from which can bring a perspective on the null hypothesis for ${\xi }_{\nu }$ (and its effects on $\Delta N_{\mathrm{eff}}$), where perhaps, \textbf{${\xi }_{\nu }$} may take a non-null value up to 95 percent CL from future experiments such as CMB-S4. Sensitivity results for CMB-S4 obtained here not including all expected systematic errors.

    ↳ astro-ph.COgr-qchep-phMNRAS(2019)·13 citations
33. 33*

    Magnetized orbifolds and localized flux

    Wilfried Buchmuller🇩🇪 · Markus Dierigl🇳🇱 · Yoshiyuki Tatsuta🇩🇪

    Magnetized orbifolds play an important role in compactifications of string theories and higher-dimensional field theories to four dimensions. Magnetic flux leads to chiral fermions, it can be a source of supersymmetry breaking and it is an important ingredient of moduli stabilization. Flux quantization on orbifolds is subtle due to the orbifold singularities. Generically, Wilson line integrals around these singularities are non-trivial, which can be interpreted as localized flux. As a consequence, flux densities on orbifolds can take the same values as on tori. We determine the transition functions for the flux vector bundle on the orbifold $T^2/{\mathbb{Z}}_2$ and the related twisted boundary conditions of zero-mode wave functions. We also construct "untwisted" zero-mode functions that are obtained for singular vector fields related to the Green's function on a torus, and we discuss the connection between zeros of the wave functions and localized flux. Twisted and untwisted zero-mode functions are related by a singular gauge transformation.

    ↳ hep-thhep-phAnnals Phys.(2019)·15 citations
34. 34*

    Electroweak relaxation of cosmological hierarchy

    Shao-Jiang Wang🇺🇸

    A simple model for the late-time cosmic acceleration problem is presented in the Starobinsky inflation with a negative bare cosmological constant as well as a nonminimal coupling to the Higgs boson. After electroweak symmetry breaking, the Starobinsky inflaton has been frozen until very recently, becoming a thawing quintessence, and a comparable magnitude to the observed dark energy density can be achieved without fine-tuning. Our proposal essentially reduces the cosmological constant problem into the electroweak hierarchy problem, and its late-time behaviour is also consistent with the recently proposed swampland criteria.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2019)·67 citations
35. 35*

    Phenomenological Consequences of the Refined Swampland Conjecture

    Hajime Fukuda🇯🇵 · Ryo Saito🇯🇵 · Satoshi Shirai🇯🇵 · Masahito Yamazaki🇯🇵

    We discuss phenomenological consequences of the recently-introduced refinements of the de Sitter swampland conjecture. The conjecture constraints the first and the second derivatives of the scalar potential in terms of two $O(1)$ constants $c$ and $c^{\prime }$, leading to interesting constraints on particle phenomenology, especially inflationary model building. Our work can also be regarded as bottom-up constraints on the values of $c$ and $c^{\prime }$.

    ↳ hep-thastro-ph.COhep-phPRD(2019)·66 citations
36. 36*

    Effects of $\Delta (1905)5/2^{+}$ on $K^{\ast }\Sigma$ photoproduction

    A. C. Wang🇨🇳 · W. L. Wang🇨🇳 · F. Huang🇨🇳

    The two-channel photoproductions of $\gamma p\to K^{\ast +}{\Sigma }^0$ and $\gamma p\to K^{\ast 0}{\Sigma }^{+}$ are investigated based on an effective Lagrangian approach at the tree-level Born approximation. In addition to the $t$-channel $K$, $\kappa$, $K^{\ast }$ exchanges, the $s$-channel nucleon ($N$) and $\Delta$ exchanges, the $u$-channel $\Lambda$, $\Sigma$, ${\Sigma }^{\ast }$ exchanges, and the generalized contact term, we try to take into account the minimum number of baryon resonances in constructing the reaction amplitudes to describe the experimental data. It is found that by including the $\Delta (1905)5/2^{+}$ resonance with its mass, width, and helicity amplitudes taken from the Review of Particle Physics [Particle Data Group, C. Patrignani {\it et al.}, Chin. Phys. C {\bf 40}, 100001 (2016)], the calculated differential and total cross sections for these two reactions are in good agreement with the experimental data. An analysis of the reaction mechanisms shows that the cross sections of $\gamma p\to K^{\ast +}{\Sigma }^0$ are dominated by the $s$-channel $\Delta (1905)5/2^{+}$ exchange at low energies and $t$-channel $K^{\ast }$ exchange at high energies, with the $s$-channel $\Delta$ exchange providing significant contributions in the near-threshold region. For $\gamma p\to K^{\ast 0}{\Sigma }^{+}$, the angular dependences are dominated by the $t$-channel $K$ exchange at forward angles and the $u$-channel ${\Sigma }^{\ast }$ exchange at backward angles, with the $s$-channel $\Delta$ and $\Delta (1905)5/2^{+}$ exchanges making considerable contributions at low energies. Predictions are given for the beam, target, and recoil asymmetries for both reactions.

    ↳ nucl-thhep-phPRC(2018)·29 citations
37. 37*

    The r-mode instability windows of strange stars

    Yu-Bin Wang🇨🇳 · Xia Zhou🇨🇳 · Na Wang🇨🇳 · Xiong-Wei Liu🇨🇳

    With the constraint from gravitational wave emission of a binary merger system (GW170817) and two-solar-mass pulsar observations, we investigate the r-mode instability windows of strange stars with unpaired and color-flavor-locked phase strange quark matter. Shear viscosities due to surface rubbing and electron-electron scattering are taken into account in this work. The results show that the effects of the equation of state of unpaired strange quark matter are only dominant at low temperature, but do not have significant effects on strange stars in the color-flavor-locked phase. A color-flavor-locked phase strange star, which is surrounded by an insulating nuclear crust, seems to be consistent with observational data of young pulsars. We find that an additional enhanced dissipation mechanisms might exist in SAX J1808.4-3658. Fast spinning young pulsar PSR J0537-6910 is a primary source for detecting gravitational waves from a rotating strange star, and young pulsars might be strange stars with color-flavor-locked phase strange quark matter.

    ↳ astro-ph.HEhep-phRes.Astron.Astrophys.(2019)·7 citations
38. 38*

    Explanation of Detailed Spectral Properties of FRBs by Axion Star Model

    Aiichi Iwazaki🇯🇵

    We have proposed a generation mechanism of non repeating ( repeating ) fast radio bursts: They arise by axion star collisions with neutron stars ( accretion disks of galactic black holes ). The axion star as coherent state of axions with mass $m_a$ generates homogeneous electric field oscillating with frequency $m_a/2\pi$ under strong magnetic fields. The field makes electrons coherently oscillate and emit the coherent dipole radiations ( FRBs ). The radiations stop when thermal fluctuations produced by the oscillation disturb the coherent oscillations. Thus, the duration of the FRBs is determined by the time scale of the thermalization; it is much shorter than $1$ms. Line spectra of the dipole radiations are broadened by the thermal effects. The thermally broaden spectra have a feature that the bandwidths $\delta \nu$ are proportional to their center frequencies ${\nu }_c$. The presence of various center frequencies ( $1.2$GHz$\sim$$7$GHz ) in repeating FRB 121102 is attributed to Doppler shifts owing to the various relativistic velocities of the accretion disk. On the other hand, non repeating FRBs do not show such variety of the center frequencies. They come from the surfaces of neutron stars. The Doppler shift also makes the durations of the bursts with higher frequencies become shorter. Because the magnetic fields of the neutron stars are supposed to be stronger than those of the accretion disks, the peak flux densities of non repeating FRBs are larger than those of repeating FRB 121102. The strong magnetic fields of the neutron stars also lead to much wide bandwidths of non repeating FRBs, which are over the extent of the receiver frequency range. The spectral features of the recently discovered new repeating FRB 180814.J0422+75 are coincident with our general analyses of the repeating FRB 121102.

    ↳ astro-ph.HEhep-phPTEP(2020)·8 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.