Fri·Feb 26, 2021Friday·February 26, 2021

1. 01*

   Studies of nonresonant Higgs pair production at electron-proton colliders

   Adil Jueid🇰🇷 · Jinheung Kim🇰🇷 · Soojin Lee🇰🇷 · Jeonghyeon Song🇰🇷

   The measurement of the Higgs quartic coupling modifier between a Higgs boson pair and a vector boson pair, ${\kappa }_{2V}$, is expected to be achieved from vector-boson fusion (VBF) production of a Higgs boson pair. However, this process involves another unmeasured parameter, the trilinear Higgs self-coupling modifier ${\kappa }_{\lambda }$. A sensitivity analysis should target both parameters. Since the LHC cannot avoid the gluon fusion pollution, which becomes severe for non-SM ${\kappa }_{\lambda }$, an electron-proton collider is more appropriate for the comprehensive measurement. In this regard, we study the VBF production of a Higgs boson pair in the $b\bar{b}b\bar{b}$ final state at the LHeC and FCC-he. Performing detailed analysis using the simulated dataset, we devise the search strategy specialized at the LHeC and FCC-he and give a prediction for the sensitivity to both ${\kappa }_{2V}$ and ${\kappa }_{\lambda }$. We find that the two electron-proton colliders have high potential: the LHeC has similar exclusion prospects as the HL-LHC; the FCC-he is extremely efficient, excluding the parameter space outside ${\kappa }_{2V}\in [0.8,1.2]$ and ${\kappa }_{\lambda }\in [1,2.5]$ at 95% C.L. for the total luminosity of $10$ ab${}^{-1}$ and 10% uncertainty on the background yields.

   hep-phPLB(2021)·5 citations
2. 02*

   Mixed QCD-EW corrections to $\mathbf{pp}\to \mathbf{\ell }{\mathbf{\nu }}_{\mathbf{\ell }}+\mathbf{X}$ at the LHC

   Luca Buonocore🇨🇭 · Massimiliano Grazzini🇨🇭 · Stefan Kallweit🇮🇹 · Chiara Savoini🇨🇭 · Francesco Tramontano🇮🇹

   We consider the hadroproduction of a massive charged lepton plus the corresponding neutrino through the Drell-Yan mechanism. We present a new computation of the mixed QCD-EW corrections to this process. The cancellation of soft and collinear singularities is achieved by using a formulation of the $q_T$ subtraction formalism derived from the next-to-next-to-leading order QCD calculation for heavy-quark production. For the first time, all the real and virtual contributions due to initial- and final-state radiation are consistently included without any approximation, except for the finite part of the two-loop virtual correction, which is computed in the pole approximation and suitably improved through a reweighting procedure. We demonstrate that our calculation is reliable in both on-shell and off-shell regions, thereby providing the first prediction of the mixed QCD-EW corrections in the entire region of the lepton transverse momentum. The computed corrections are in qualitative agreement with what we obtain in a factorised approach of QCD and EW corrections. At large values of the lepton $p_T$, the mixed QCD-EW corrections are negative and increase in size, to about $-20\%$ with respect to the next-to-leading order QCD result at $p_T=500$GeV.

   hep-phPRD(2021)·64 citations
3. 03*

   Elucidating the effect of intermediate resonances in the quark interaction kernel on the time-like electromagnetic pion form factor

   Ángel S. Miramontes López🇲🇽 · Hèlios Sanchis-Alepuz🇦🇹 · Reinhard Alkofer🇦🇹

   An exploratory study of the time-like pion electromagnetic form factor in a Poincaré-covariant bound state formalism in the isospin symmetric limit is presented. Starting from a quark interaction kernel representing gluon-intermediated interactions for valence-type quarks, non-valence effects are included by introducing pions as explicit degrees of freedom. The two most important qualitative aspects are, in view of the presented study, the opening of the dominant $\rho$-meson decay channel and the presence of a multi-particle branch cut setting in when the two-pion threshold is crossed. Based on a recent respective computation of the quark-photon vertex, the pion electromagnetic form factor for space-like and time-like kinematics is calculated. The obtained results for its absolute value and its phase compare favorably to the available experimental data, and they are analyzed in detail by confronting them to the expectations based on an isospin-symmetric version of a vector-meson dominance model.

   hep-phPRD(2021)·38 citations
4. 04*

   Masses of positive- and negative-parity hadron ground-states, including those with heavy quarks

   Pei-Lin Yin🇨🇳 · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇨🇳 · Jorge Segovia🇪🇸

   A symmetry-preserving treatment of a vector$\times$vector contact interaction is used to compute spectra of ground-state $J^P=0^{\pm },1^{\pm }$ $(f\bar{g})$ mesons, their partner diquark correlations, and $J^P=1/2^{\pm },3/2^{\pm }$ $(fgh)$ baryons, where $f,g,h\in \{u,d,s,c,b\}$. Results for the leptonic decay constants of all mesons are also obtained, including scalar and pseudovector states involving heavy quarks. The spectrum of baryons produced by this chiefly algebraic approach reproduces the 64 masses known empirically or computed using lattice-regularised quantum chromodynamics with an accuracy of 1.4(1.2)%. It also has the richness of states typical of constituent-quark models and predicts many baryon states that have not yet been observed. The study indicates that dynamical, nonpointlike diquark correlations play an important role in all baryons; and, typically, the lightest allowed diquark is the most important component of a baryon's Faddeev amplitude.

   hep-phhep-exhep-latnucl-ex+1EPJC(2021)·66 citations
5. 05*

   The imaginary part of the heavy-quark potential from real-time Yang-Mills dynamics

   Kirill Boguslavski🇦🇹 · Babak S. Kasmaei🇺🇸 · Michael Strickland🇺🇸

   We extract the imaginary part of the heavy-quark potential using classical-statistical simulations of real-time Yang-Mills dynamics in classical thermal equilibrium. The $r$-dependence of the imaginary part of the potential is extracted by measuring the temporal decay of Wilson loops of spatial length $r$. We compare our results to continuum expressions obtained using hard thermal loop theory and to semi-analytic lattice perturbation theory calculations using the hard classical loop formalism. We find that, when plotted as a function of $m_{D}r$, where $m_D$ is the hard classical loop Debye mass, the imaginary part of the heavy-quark potential shows little sensitivity to the lattice spacing at small $m_{D}r\lesssim 1$ and agrees well with the semi-analytic hard classical loop result. For large quark-antiquark separations, we quantify the magnitude of the non-perturbative long-range corrections to the imaginary part of the heavy-quark potential. We present our results for a wide range of temperatures, lattice spacings, and lattice volumes. This work sets the stage for extracting the imaginary part of the heavy-quark potential in an expanding non-equilibrium Yang Mills plasma.

   hep-phhep-latnucl-thJHEP(2021)·12 citations
6. 06*

   Radiative Transitions of Charmoniumlike Exotics in the Dynamical Diquark Model

   Justin M. Gens🇺🇸 · Jesse F. Giron🇺🇸 · Richard F. Lebed🇺🇸

   Using the dynamical diquark model, we calculate the electric-dipole radiative decay widths to $X(3872)$ of the lightest negative-parity exotic candidates, including the four $I=0$, $J^{PC}=1^{--}$ ("$Y$") states. The $O$(100--1000 keV) values obtained test the hypothesis of a common substructure shared by all of these states. We also calculate the magnetic-dipole radiative decay width for $Z_c(4020{)}^0\to \gamma X(3872)$, and find it to be rather smaller ($<$~10 keV) than its predicted value in molecular models.

   hep-phPRD(2021)·10 citations
7. 07*

   $\varphi$-meson lepto-production near threshold and the strangeness $D$-term

   Yoshitaka Hatta🇺🇸 · Mark Strikman🇺🇸

   We present a model of exclusive $\varphi$-meson lepto-production $ep\to e^{\prime }{p}^{\prime }\varphi$ near threshold which features the strangeness gravitational form factors of the proton. We argue that the shape of the differential cross section $d\sigma /dt$ is a sensitive probe of the strangeness D-term of the proton.

   hep-phnucl-exPLB(2021)·44 citations
8. 08*

   A novel determination of non-perturbative contributions to Bjorken sum rule

   Qing Yu🇨🇳 · Xing-Gang Wu🇨🇳 · Hua Zhou🇨🇳 · Xu-Dong Huang (Chongqing U.)🇨🇳

   In the present paper, we first give a detailed study on the pQCD corrections to the leading-twist part of BSR. Previous pQCD corrections to the leading-twist part derived under conventional scale-setting approach up to $\mathcal{O}({\alpha }_s^4)$-level still show strong renormalization scale dependence. The principle of maximum conformality (PMC) provides a systematic way to eliminate conventional renormalization scale-setting ambiguity by determining the accurate ${\alpha }_s$-running behavior of the process with the help of renormalization group equation. Our calculation confirms the PMC prediction satisfies the standard renormalization group invariance, e.g. its fixed-order prediction does scheme-and-scale independent. In low $Q^2$-region, the effective momentum of the process is small and to have a reliable prediction, we adopt four low-energy ${\alpha }_s$ models to do the analysis. Our predictions show that even though the high-twist terms are generally power suppressed in high $Q^2$-region, they shall have sizable contributions in low and intermediate $Q^2$ domain. By using the more accurate scheme-and-scale independent pQCD prediction, we present a novel fit of the non-perturbative high-twist contributions by comparing with the JLab data.

   hep-phEPJC(2021)·11 citations
9. 09*

   Form-factor-independent test of lepton universality in semileptonic heavy meson and baryon decays

   Stefan Groote🇪🇪 · Mikhail A. Ivanov🇷🇺 · Jürgen G. Körner🇩🇪 · Valery E. Lyubovitskij🇩🇪 · Pietro Santorelli🇮🇹 · Chien-Thang Tran🇮🇹

   In the semileptonic decays of heavy mesons and baryons the lepton-mass dependence factors out in the quadratic ${\cos }^2\theta$ coefficient of the differential $\cos \theta$ distribution. We call the corresponding normalized coefficient the convexity parameter. This observation opens the path to a test of lepton universality in semileptonic heavy meson and baryon decays that is independent of form-factor effects. By projecting out the quadratic rate coefficient, dividing out the lepton-mass-dependent factor and restricting the phase space integration to the $\tau$ lepton phase space, one can define optimized partial rates which, in the Standard Model, are the same for all three $(e,\mu ,\tau )$ modes in a given semileptonic decay process. We discuss how the identity is spoiled by New Physics effects. We discuss semileptonic heavy meson decays such as ${\bar{B}}^0\to D^{(\ast )+}{\ell }^{-}{\bar{\nu }}_{\ell }$ and $B_c^{-}\to J/\psi ({\eta }_c){\ell }^{-}{\bar{\nu }}_{\ell }$, and semileptonic heavy baryon decays such as ${\Lambda }_b\to {\Lambda }_c{\ell }^{-}{\bar{\nu }}_{\ell }$ for each $\ell =e,\mu ,\tau$.

   hep-phhep-exPRD(2021)·11 citations
10. 10*

    Heavy Neutrino Searches via Same-sign Lepton Pairs at the Higgs Factory

    Yu Gao🇨🇳 · Kechen Wang🇨🇳

    This paper investigates the $e^{-}{e}^{+}\to Z{h}_1$ sensitivity for Higgs boson's rare decay into heavy neutrinos $h_1\to NN$ at the proposed electron-positron collider, with the focus on multi-lepton final states that contain same-sign lepton pairs. $h_1\to NN$ decay can derive from Higgs boson's mixing with new physics scalar(s) that is complementary to the contribution from active-sterile neutrino mixings. We consider the scenario with a singlet scalar which gives the heavy neutrino mass and has a small mixing with the SM Higgs boson. We analyze the semileptonic, fully leptonic and mixed $NN$ decay scenarios, and categorize the signal on the number of leptons in the final state: ${\ell }^{\pm }{\ell }^{\pm }$ with at least 3 jets, ${\ell }^{\pm }{\ell }^{\pm }\ell$ with at least 2 jets, and $e^{\pm }{e}^{\pm }{\mu }^{\mp }{\mu }^{\mp }$ plus with at least 1 jet, each containing one or two same-sign dilepton system(s). Selection cuts are optimized for the presence of the associated $Z$-boson, which leads to additional backgrounds at the $e^{-}{e}^{+}$ collider. The Standard Model background channels are systematically analyzed. Sensitivity limits on $h_1\to NN$ branching fractions are derived for signals with 2-4 final leptons assuming the heavy neutrino masses are between 10 and 60 GeV. With 240 GeV center-of-mass energy and 5.6 ab${}^{-1}$ design luminosity, $h_1\to NN$ branching fraction can be probed to $2\times 10^{-4}$ in $2\ell$ and $3\ell$ channels, and $6\times 10^{-4}$ in the $4\ell$ channel at $95\%$ confidence level. $3\ell ,4\ell$ channels expect one or fewer background event, and their sensitivities saturate the statistic limit at 5.6 ab${}^{-1}$ luminosity. A same-sign trilepton (${\ell }^{\pm }{\ell }^{\pm }{\ell }^{\pm }$) signal in the $3\ell$ channel is also discussed. Our search strategy provides an approach to discovering the singlet scalar and exploring the origin of neutrino masses at future $e^{-}{e}^{+}$ colliders.

    hep-phPRD(2022)·13 citations
11. 11*

    Six-loop beta functions in general scalar theory

    Alexander Bednyakov🇷🇺 · Andrey Pikelner🇷🇺

    We consider general renormalizable scalar field theory and derive six-loop beta functions for all parameters in d = 4 dimensions within the $\overline{MS}$-scheme. We do not explicitly compute relevant loop integrals but utilize $O(n)$-symmetric model counter-terms available in the literature. We consider dimensionless couplings and parameters with a mass scale, ranging from the trilinear self-coupling to the vacuum energy. We use obtained results to extend renormalization-group equations for several vector, matrix, and tensor models to the six-loop order. Also, we apply our general expressions to derive new contributions to beta functions and anomalous dimensions in the scalar sector of the Two-Higgs-Doublet Model.

    hep-phcond-mat.stat-mechhep-thJHEP(2021)·50 citations
12. 12*

    The three-loop singlet contribution to the massless axial-vector quark form factor

    T. Gehrmann🇨🇭 · A. Primo🇨🇭

    We compute the three-loop corrections to the quark axial vector form factor in massless QCD, focusing on the pure-singlet contributions where the axial vector current couples to a closed quark loop. Employing the Larin prescription for ${\gamma }_5$, we discuss the UV renormalization of the form factor. The infrared singularity structure of the resulting singlet axial-vector form factor is explained from infrared factorization, defining a finite remainder function.

    hep-phPLB(2021)·18 citations
13. 13*

    Factorization and transverse phase-space parton distributions

    Bin Wu🇨🇭

    We first revisit impact-parameter dependent collisions of ultra-relativistic particles in quantum field theory. Two conditions sufficient for defining an impact-parameter dependent cross section are given, which could be violated in proton-proton collisions. By imposing these conditions, a general formula for the impact-parameter dependent cross section is derived. Then, using soft-collinear effective theory, we derive a factorization formula for the impact-parameter dependent cross section for inclusive hard processes with only colorless final-state products in hadron and nuclear collisions. It entails defining thickness beam functions, which are Fourier transforms of transverse phase-space parton distribution functions. By modelling non-perturbative modes in thickness beam functions of large nuclei in heavy-ion collisions, the factorization formula confirms the cross section in the Glauber model for hard processes. Besides, the factorization formula is verified up to one loop in perturbative QCD for the inclusive Drell-Yan process in quark-antiquark collisions at a finite impact parameter.

    hep-phhep-exnucl-exnucl-thJHEP(2021)·10 citations
14. 14*

    Alice meets Boojums in neutron stars: vortices penetrating two-flavor quark-hadron continuity

    Yuki Fujimoto🇯🇵 · Muneto Nitta🇯🇵

    Alice and Boojums are both representative characters created by Lewis Carroll. We show that they possibly meet in cores of rotating neutron stars. Recent studies of quark-hadron continuity suggest that neutron superfluid matter can connect smoothly to two-flavor symmetric quark matter at high densities. We study how this can be maintained in the presence of the vortices. In the neutron matter, quantized superfluid vortices arise. In the two-flavor dense quark matter, vortices carrying color magnetic fluxes together with fractionally quantized superfluid circulations appear as the most stable configuration, and we call these as the non-Abelian Alice strings. We show that three integer neutron superfluid vortices and three non-Abelian Alice strings of different color magnetic fluxes with total color flux canceled out are joined at a junction called a Boojum.

    hep-phastro-ph.HEcond-mat.supr-conhep-th+1PRD(2021)·12 citations
15. 15*

    Probing doubly charged scalar bosons from the doublet at future high-energy colliders

    Kazuki Enomoto🇯🇵 · Shinya Kanemura🇯🇵 · Kento Katayama🇯🇵

    The isospin doublet scalar field with hypercharge 3/2 is introduced in some new physics models such as tiny neutrino masses. Detecting the doubly charged scalar bosons from the doublet field can be a good probe of such models. However, their collider phenomenology has not been examined sufficiently. We investigate collider signatures of the doubly and singly charged scalar bosons at the LHC for the high-luminosity upgraded option (HL-LHC) by looking at transverse mass distributions etc. With the appropriate kinematical cuts we demonstrate the background reduction in the minimal model in the following two cases depending on the mass of the scalar bosons. (1) The main decay mode of the singly charged scalar bosons is the tau lepton and missing (as well as charm and strange quarks). (2) That is into a top bottom pair. In the both cases, we assume that the doubly charged scalar boson is heavier than the singly charged ones. We conclude that the scalar doublet field with $Y=3/2$ is expected to be detectable at the HL-LHC unless the mass is too large.

    hep-phPRD(2021)·4 citations
16. 16*

    Test of beta and antineutrino spectra symmetry in beta-decay

    S. V. Silaeva🇷🇺 · V. V. Sinev🇷🇺

    The mechanism of beta decay in nature is not understood yet. Mirrored energy spectra of electron and antineutrino can clarify the situation. A special experiment is needed to measure antineutrino spectrum from known beta-decaying isotope to compare it with the beta one. One of ongoing experiments with large volume detector can be chosen to make the experiment. Another possibility is to make a special experiment close to a powerful source of mixture of known beta-decaying isotopes. If sufficient differences in shape will be observed the method of antineutrino spectrum calculation should be revised.

    hep-ph2 citations
17. 17*

    Study of the exclusive reaction $pp\to pp{K}^{\ast 0}{\bar{K}}^{\ast 0}$: $f_2(1950)$ resonance versus diffractive continuum

    Piotr Lebiedowicz🇵🇱

    We present first predictions of the cross sections and differential distributions for the exclusive reaction $pp\to pp{K}^{\ast 0}{\bar{K}}^{\ast 0}$ contributing to the $K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}$ channel. The amplitudes for the reaction are formulated within the nonperturbative tensor-pomeron approach. We consider separately the $f_2(1950)$ $s$-channel exchange mechanism and the $K^{\ast 0}$ $t/u$-channel exchange mechanism, focusing on their specificities. First mechanism is a candidate for the central diffractive production of tensor glueball and the second one is an irreducible continuum. We adjust parameters of our model, assuming the dominance of pomeron-pomeron fusion, to the WA102 experimental data. We find that including the continuum contribution alone one can describe the WA102 data reasonably well. We present predictions for the reaction $pp\to pp(K^{\ast 0}{\bar{K}}^{\ast 0}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^{-})$ for the ALICE, ATLAS, CMS and LHCb experiments including typical kinematical cuts. We find from our model a cross sections of $\sigma \cong 17-250$ nb for the LHC experiments, depending on the assumed cuts. Absorption effects are included in our analysis.

    hep-phPRD(2021)·10 citations
18. 18*

    Fully coupled functional equations for the quark sector of QCD

    Fei Gao🇩🇪 · Joannis Papavassiliou🇪🇸 · Jan M. Pawlowski🇩🇪

    We present a comprehensive study of the quark sector of $2+1$ flavour QCD, based on a self-consistent treatment of the coupled system of Schwinger-Dyson equations for the quark propagator and the full quark-gluon vertex. The individual form factors of the quark-gluon vertex are expressed in a special tensor basis obtained from a set of gauge-invariant operators. The sole external ingredient used as input to our equations is the Landau gauge gluon propagator with $2+1$ dynamical quark flavours, obtained from studies with Schwinger-Dyson equations, the functional renormalisation group approach, and large volume lattice simulations. The appropriate renormalisation procedure required in order to self-consistently accommodate external inputs stemming from other functional approaches or the lattice is discussed in detail, and the value of the gauge coupling is accurately determined at two vastly separated renormalisation group scales. Our analysis establishes a clear hierarchy among the vertex form factors. We identify only three dominant ones, in agreement with previous results. The components of the quark propagator obtained from our approach are in excellent agreement with the results from Schwinger-Dyson equations, the functional renormalisation group, and lattice QCD simulation, a simple benchmark observable being the chiral condensate in the chiral limit, which is computed as $(245\text{MeV}{)}^3$. The present approach has a wide range of applications, including the self-consistent computation of bound-state properties and finite temperature and density physics, which are briefly discussed.

    hep-phhep-lathep-thnucl-thPRD(2021)·105 citations
19. 19*

    Axial meson exchange and the $Z_c(3900)$ and $Z_{cs}(3985)$ resonances as heavy hadron molecules

    Mao-Jun Yan🇨🇳 · Fang-Zheng Peng🇨🇳 · Mario Sánchez Sánchez🇫🇷 · Manuel Pavon Valderrama🇨🇳

    Early speculations about the existence of heavy hadron molecules were grounded on the idea that light-meson exchanges forces could lead to binding. In analogy to the deuteron, the light-mesons usually considered include the pion, sigma, rho and omega, but not the axial meson $a_1(1260)$. Though it has been argued in the past that the coupling of the axial meson to the nucleons is indeed strong, its mass is considerably heavier than that of the vector mesons and thus its exchange ends up being suppressed. Yet, this is not necessarily the case in heavy hadrons molecules: we find that even though the contribution to binding from the axial meson is modest, it cannot be neglected in the isovector sector where vector meson exchange cancels out. This might provide a natural binding mechanism for molecular candidates such as the $Z_c(3900)$, $Z_c(4020)$ or the more recently observed $Z_{cs}(3985)$. However the $Z_{cs}(3985)$ is more dependent on a mixture of different factors, which (besides axial meson exchange) include $\eta$ exchange and the nature of scalar meson exchange. Together they point towards the existence of two $Z_{cs}(3985)$-like resonances instead of one, while the observations about the role of scalar meson exchange in the $Z_{cs}(3985)$ might be relevant for the $P_{cs}(4459)$. Finally, the combination of axial meson exchange and flavor symmetry breaking effects indicates that the isovector $J^{PC}=0^{++}$ $D^{\ast }{\bar{D}}^{\ast }$ and the strange $J^P=2^{+}$ $D^{\ast }{\bar{D}}_s^{\ast }$ molecules are the most attractive configurations and thus the most likely molecular partners of the $Z_c(3900)$, $Z_c(4020)$ and $Z_{cs}(3985)$.

    hep-phhep-exhep-latnucl-thPRD(2021)·57 citations
20. 20*

    Charmed and bottomed hadronic cross sections from a statistical model

    Gábor Balassa🇭🇺 · György Wolf🇭🇺

    In this work, we extended our statistical model with charmed and bottomed hadrons, and fit the quark creational probabilities for the heavy quarks, using low energy inclusive charmonium and bottomonium data. With the finalized fit for all the relevant types of quarks (up, down, strange, charm, bottom) at the energy range from a few GeV up to a few tens of GeV's, the model is now considered complete. Some examples are also given for proton-proton, pion-proton, and proton-antiproton collisions with charmonium, bottomonium, and open charm hadrons in the final state.

    hep-phnucl-thEPJA(2020)·6 citations
21. 21*

    Investigating the parton shower model in PYTHIA8 with pp collision data at $\surd s=13TeV$

    S.K.Kundu🇮🇳 · T.Sarkar🇹🇼 · M.Maity🇮🇳

    Understanding the production of quarks and gluons in high energy collisions and their evolution is a very active area of investigation. Monte carlo event generator PYTHIA8 uses the parton shower model to simulate such collisions and is optimized using experimental observations. Recent measurements of event shape variables and differential jet cross-sections in pp collisions at $\surd s=13TeV$ at the Large Hadron Collider have been used to investigate further the parton shower model as used in PYTHIA8.

    hep-ph0 citations
22. 22*

    Angular Distributions, Polarization Observables, Spin Density Matrices and Statistical Tensors in Photoproduction of Two Pseudoscalar Mesons off a Nucleon

    Hiram G. Menendez Santiago🇺🇸

    In two meson photoproduction off a nucleon, for the case in which two of the three final state hadrons are products of the decay of an intermediate resonance, general expressions for its decay distribution and for polarization observables are derived in a model independent way. These are functions of either the spin density matrix elements (SDME's) or statistical tensors of the resonance, and the angles of its decay products. The expressions are general enough that it also describes cases where more than one resonance of arbitrary quantum numbers contributes, including interference effects. They can therefore be used to extract the SDME's or statistical tensors of the resonances that contribute to the reaction.

    hep-phnucl-th0 citations
23. 23*

    Consistent treatment of axions in the weak chiral Lagrangian

    Martin Bauer (U. Durham)🇬🇧 · Matthias Neubert (U. Mainz)🇩🇪 · Sophie Renner (SISSA)🇮🇹 · Marvin Schnubel (U. Mainz)🇩🇪 · Andrea Thamm (U. Melbourne)🇦🇺

    We present a consistent implementation of weak decays involving an axion or axion-like particle in the context of an effective chiral Lagrangian. We argue that previous treatments of such processes have used an incorrect representation of the flavor-changing quark currents in the chiral theory. As an application, we derive model-independent results for the decays $K^{-}\to {\pi }^{-}a$ and ${\pi }^{-}\to e^{-}{\bar{\nu }}_{e}a$ at leading order in the chiral expansion and for arbitrary axion couplings and mass. In particular, we find that the $K^{-}\to {\pi }^{-}a$ branching ratio is almost 40 times larger than previously estimated.

    hep-phPRL(2021)·124 citations
24. 24*

    Hidden physics in pion and some other meson decays

    M. M. Guzzo🇧🇷 · L. J. F. Leite🇧🇷 · S. W. P. Novelo🇧🇷 · O. L. G. Peres🇧🇷 · V. Pleitez🇧🇷

    It has been commonly assumed that pseudoscalar contributions to the leptonic decay of charged mesons, like pions and kaons, is strongly constrained due to the helicity suppression present in the ratio $R_{l/l^{\prime }}=\Gamma (P\to l\nu [\gamma ])/\Gamma (P\to l^{\prime }\nu [\gamma ])$, where $P$ are the charged pseudoscalar meson and $l,l^{\prime }=e,\mu ,\tau$. Here we show that if the effective couplings are proportional to the corresponding charged lepton masses (and also the PMNS matrix), the constraints from $R_{l/l^{\prime }}$ are entirely avoided, and a rather new large allowed region is permitted in the parameter space. In the case of the electron, we found a non-trivial region in the range $10^{-4}\lesssim (G^{\eta }/G_F)\lesssim 10^{-3}$, where $G^{\eta }$ is the effective pseudoscalar coupling associated with a novel charged scalar field, $\eta$, and $G_F$ is the Fermi constant. Furthermore, we show that this dependence of the pseudoscalar couplings on the charged lepton masses can naturally be associated with a critical class beyond the standard model physics, namely models without (leptonic) flavor-changing neutral currents in the scalar sector. The most known examples are the models that satisfy the so-called Glashow-Weinberg-Paschos theorem. Finally, we also point out that, in those cases, the decay rate is degenerated with the Standard Model prediction, possibly hiding the new physics effects in those decays.

    hep-phPRD(2023)·3 citations
25. 25*

    The invariant space of multi-Higgs doublet models

    M. P. Bento🇵🇹

    In a model with more than one scalar doublet, the parameter space encloses both physical and unphysical information. Invariant theory provides a detailed description of the counting and characterization of the physical parameter space. The Hilbert series for the 3HDM is computed for the first time using partition analysis, in particular Omega calculus, giving rise to the possibility of a full description of its physical parameters. A rigorous counting of the physical parameters is given for the full class of models with $N$ scalar doublets as well as a decomposition of the Lagrangian into irreducible representations of $\mathrm{SU}(N)$. For the first time we derive a basis-invariant technique for counting parameters in a Lagrangian with both basis-invariant redundancies and global symmetries.

    hep-phJHEP(2021)·10 citations
26. 26*

    Survival of the Fittest: Numerical Modeling of Supernova 2014C

    Felipe Vargas · Fabio De Colle · Daniel Brethauer · Raffaella Margutti🇺🇸 · Cristian G. Bernal

    Initially classified as a supernova (SN) type Ib, $\sim$ 100 days after the explosion SN\,2014C made a transition to a SN type II, presenting a gradual increase in the H$\alpha$ emission. This has been interpreted as evidence of interaction between the supernova shock wave and a massive shell previously ejected from the progenitor star. In this paper, we present numerical simulations of the propagation of the SN shock through the progenitor star and its wind, as well as the interaction of the SN ejecta with the massive shell. To determine with high precision the structure and location of the shell, we couple a genetic algorithm to a hydrodynamic and a bremsstrahlung radiation transfer code. We iteratively modify the density stratification and location of the shell by minimizing the variance between X-ray observations and synthetic predictions computed from the numerical model. By assuming spherical symmetry, we found that the shell has a mass of 2.6 M${}_{\odot }$, extends from 1.6 $\times 10^{16}$ cm to $1.87\times 10^{17}$ cm, implying that it was ejected $\sim 60/(v_w/100\mathrm{km}{\mathrm{s}}^{-1})$ yrs before the SN explosion, and has a density stratification decaying as $\sim r^{-3}$. We found that the product of metallicity by the ionization fraction (due to photo-ionization by the post-shock X-ray emission) %and/or the SN UV radiation is $\sim$ 0.5. Finally, we predict that, if the density stratification follows the same power-law behaviour, the SN will break out from the shell by mid 2022, i.e. 8.5 years after explosion.

    ↳ astro-ph.HEcs.NAhep-phmath.NAApJ(2022)·9 citations
27. 27*

    Pair production in asymmetric Sauter potential well

    Adiljan Sawut🇨🇳 · Sayipjamal Dulat🇨🇳 · B. S. Xie🇨🇳

    Electron-positron pair production in asymmetric Sauter potential well is studied, where the potential well has been built as the width of the right edge fixed but the left side of the well is changeable at different values. We study the momentum spectrum, the location distribution and the total pair numbers in this case of asymmetric potential well and compare them with the symmetric case. The relationship between created electron energy, the level energy in the bound states and the photon energy in the symmetric potential well is used to the studied problem for the created electrons in the asymmetric potential well and its validity is confirmed by this approximation. By the location distribution of the electrons we have also shown the reason why the momentum spectrum has an optimization in the asymmetric well compared with the symmetric one.

    ↳ quant-phhep-phPhys.Scripta(2021)·4 citations
28. 28*

    Running vacuum against the $H_0$ and ${\sigma }_8$ tensions

    Joan Sola🇪🇸 · Adria Gomez-Valent🇩🇪 · Javier de Cruz Perez🇪🇸 · Cristian Moreno-Pulido🇪🇸

    The cosmological term, $\Lambda$, was introduced $104$ years ago by Einstein in his gravitational field equations. Whether $\Lambda$ is a rigid quantity or a dynamical variable in cosmology has been a matter of debate for many years, especially after the introduction of the general notion of dark energy (DE). $\Lambda$ is associated to the vacuum energy density, ${\rho }_{\mathrm{vac}}$, and one may expect that it evolves slowly with the cosmological expansion. Herein we present a devoted study testing this possibility using the promising class of running vacuum models (RVM's). We use a large string $SNIa+BAO+H(z)+LSS+CMB$ of modern cosmological data, in which for the first time the CMB part involves the full Planck 2018 likelihood for these models. We test the dependence of the results on the threshold redshift $z_{\ast }$ at which the vacuum dynamics is activated in the recent past and find positive signals up to $\sim 4.0\sigma$ for $z_{\ast }\simeq 1$. The RVM's prove very competitive against the standard $\Lambda$CDM model and give a handle for solving the ${\sigma }_8$ tension and alleviating the $H_0$ one.

    ↳ astro-ph.COgr-qchep-phhep-thEPL(2021)·146 citations
29. 29*

    Superstring Backgrounds in String Geometry

    Masaki Honda🇯🇵 · Matsuo Sato🇯🇵 · Taiki Tohshima🇯🇵

    String geometry theory is a candidate of the non-perturbative formulation of string theory. In order to determine the string vacuum, we need to clarify how superstring backgrounds are described in string geometry theory. In this paper, we show that all the type IIA, IIB, SO(32) type I, and SO(32) and $E_8\times E_8$ heterotic superstring backgrounds are embedded in configurations of the fields of a single string geometry model. Especially, we show that the configurations satisfy the equations of motion of the string geometry model in ${\alpha }^{\prime }\to 0$ if and only if the embedded string backgrounds satisfy the equations of motion of the supergravities, respectively. This means that classical dynamics of the string backgrounds are described as a part of classical dynamics in string geometry theory. Furthermore, we define an energy of the configurations in the string geometry model because they do not depend on the string geometry time. A string background can be determined by minimizing the energy.

    ↳ hep-thgr-qchep-phAdv.High Energy Phys.(2021)·10 citations
30. 30*

    $Z_N$ symmetry in $SU(N)$ gauge theories

    Minati Biswal🇮🇳 · Sanatan Digal🇮🇳 · Vinod Mamale🇮🇳 · Sabiar Shaikh🇮🇳

    We study $Z_N$ symmetry in $SU(N)$ gauge theories in the presence of matter fields in the fundamental representation, by restricting the lattice partition function integration to matter fields which are uniform in spatial directions and gauge fields with vanishing spatial components. In this approximation the gauge matter field interaction effectively reduces to a 1-dimensional gauged chain. This makes analytical calculations of the matter field contribution to the Polyakov loop free energy possible. We show that in the limit of large number of temporal sites the explicit breaking of $Z_N$ symmetry in this free energy vanishes, driven by dominance of the density of states. We argue that the spatial links as well as the spatial modes of the matter fields determine the boundaries separating regions where $Z_N$ symmetry is realised from rest of the phase diagram.

    ↳ hep-lathep-phnucl-thInt.J.Mod.Phys.A(2022)·2 citations
31. 31*

    Transverse charge density and the radius of the proton

    Alexander V. Gramolin🇺🇸 · Rebecca L. Russell🇺🇸

    A puzzling discrepancy exists between the values of the proton charge radius obtained using different experimental techniques: elastic electron-proton scattering and spectroscopy of electronic and muonic hydrogen. The proton radius is defined through the slope of the electric form factor, $G_E(Q^2)$, at zero four-momentum transfer, which is inaccessible in scattering experiments. We propose a novel method for extracting the proton radius from scattering data over a broad $Q^2$ range rather than attempting to directly determine the slope of $G_E$ at $Q^2=0$. This method relates the radius of the proton to its transverse charge density, which is the two-dimensional Fourier transform of the Dirac form factor, $F_1(Q^2)$. We apply our method to reanalyze the extensive data obtained by the A1 Collaboration [J. C. Bernauer et al., Phys. Rev. Lett. 105, 242001 (2010)] and extract a radius value, $r_E=0.889(5{)}_{\text{stat}}(5{)}_{\text{syst}}(4{)}_{\text{model}}\text{fm}$, that is consistent with the original result. We also provide new parametrizations for the Dirac and Pauli form factors and the transverse charge and magnetization densities of the proton. Our reanalysis shows that the proton radius discrepancy cannot be explained by issues with fitting and extrapolating the A1 data to $Q^2=0$.

    ↳ nucl-exhep-exhep-phnucl-thPRD(2022)·18 citations
32. 32*

    A Mathematical Construction of an E6 Grand Unified Theory

    Anthony Britto🇩🇪

    Of the five exceptional groups, ${\mathrm{E}}_6$ is considered the most attractive for unification due to the following reasons: (i) it contains both $\mathrm{Spin}(10)\times \mathrm{U}(1)$ and $\mathrm{SU}(3)\times \mathrm{SU}(3)\times \mathrm{SU}(3)$ as maximal subgroups, each of which admit embeddings of the Standard Model; (ii) uniquely among the exceptional groups, it admits complex representations; in particular, its 27 dimensional fundamental representation accommodates one generation of left-handed fermions under the usual charge assignments; (iii) all of its representations are anomaly-free. In this master's thesis, written in the spirit of Baez and Huerta's "The Algebra of Grand Unified Theories", we rigorously show how an ${\mathrm{E}}_6$ grand unified theory is mathematically constructed. Our modest contribution to the literature includes an explicit check that that ${\mathbb{Z}}_4$ kernel of the homomorphism $\mathrm{Spin}(10)\times \mathrm{U}(1)\to {\mathrm{E}}_6$ acts trivially on every fermion; we also formulate symmetry breaking, in particular the symmetry breaking of the exotic ${\mathrm{E}}_6$ fermions under $\mathrm{Spin}(10)\to \mathrm{SU}(5)$, using a different approach than the usual Dynkin diagrams: we explicitly embedded $\mathfrak{su}(5)\hookrightarrow \mathfrak{so}(10)\cong \mathfrak{spin}(10)$ and solve the related eigenvalue problem. Phenomenological aspects of grand unified theories are also discussed.

    ↳ hep-thhep-phmath.RT0 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.