Thu·Apr 11, 2019Thursday·April 11, 2019

1. 01*

   Evidence in favor of Single Parton Scattering mechanism in ${\rm Y}$ and $D$ associated production at the LHC

   Anton Karpishkov🇷🇺 · Maxim Nefedov🇷🇺 · Vladimir Saleev🇷🇺

   Associated production of prompt ${\rm Y}(1S)$ and $D^{+,0}$ mesons has been proposed as a golden channel for the search of Double Parton Scattering, because Single Parton Scattering contribution to the cross-section is believed to be negligible on a basis of leading order calculations in the Collinear Parton Model. We study this process in the leading order approximation of the Parton Reggeization Approach. Hadronization of $b\bar{b}$-pair into bottomonium states is described within framework of the NRQCD-factorization approach while production of $D$ mesons is described in the fragmentation model with scale-dependent fragmentation functions. We have found good agreement with LHCb data for various normalized differential distributions, except for the case of spectra on azimuthal angle differences at the small $\Delta \phi$ values. Crucially, the total cross-section in our Single Parton Scattering model accounts for more than one half of observed cross-section, thus dramatically shrinking the room for Double Parton Scattering mechanism.

   hep-phPRD(2019)·6 citations
2. 02*

   High-energy bremsstrahlung on atoms in a laser field

   P.A. Krachkov🇷🇺 · A. Di Piazza🇩🇪 · A.I. Milstein🇷🇺

   The impact of a laser field on the process of photon radiation by an ultra-relativistic electron in an atomic field is investigated. The angular distribution and the spectrum of the radiated photon are derived. By means of the quasiclassical approximation, the obtained results are exact in the parameters of the laser field and the atomic field. It is shown that the impact of the laser field is significant even for fairly average values of the laser field parameters routinely achievable nowadays. Therefore, an experimental observation of the influence of the laser field on bremsstrahlung in the atomic field is a very feasible task.

   hep-phphysics.atom-phPLB(2019)·15 citations
3. 03*

   Charmonia and Bottomonia in asymmetric magnetized hot nuclear matter

   Rajesh Kumar🇮🇳 · Arvind Kumar🇮🇳

   We investigate the mass-shift of $P$-wave charmonium (${{\chi }_c}_0$, ${{\chi }_c}_1$) and $S$ and $P$-wave bottomonium (${\eta }_b$, ${\rm Y}$, ${{\chi }_b}_0$ and ${{\chi }_b}_1$) states in magnetized hot asymmetric nuclear matter using the unification of QCD sum rules (QCDSR) and chiral $SU(3)$ model. Within QCDSR, we use two approaches, $i.e.$, moment sum rule and Borel sum rule. The magnetic field induced scalar gluon condensate $⟨\frac{{\alpha }_s}{\pi }{G}_{\mu \nu }^a{G^a}^{\mu \nu }⟩$ and the twist-2 gluon operator $⟨\frac{{\alpha }_s}{\pi }{G}_{\mu \sigma }^a{{G^a}_{\nu }}^{\sigma }⟩$ calculated in chiral $SU(3$) model are utilised in QCD sum rules to calculate the in-medium mass-shift of above mesons. The attractive mass-shift of these mesons is observed which is more sensitive to magnetic field in high density regime for charmonium, but less for bottomonium. These results may be helpful to understand the decay of higher quarkonium states to the lower quarkonium states in asymmetric heavy ion collision experiments.

   hep-phCPC(2019)·14 citations
4. 04*

   AAfrag: Interpolation routines for Monte Carlo results on secondary production in proton-proton, proton-nucleus and nucleus-nucleus interactions

   M.Kachelriess🇳🇴 · I.V.Moskalenko🇺🇸 · S.Ostapchenko🇩🇪

   We provide a compilation of predictions of the QGSJET-II-04m model for the production of secondary species (photons, neutrinos, electrons, positrons, and antinucleons) that are covering a wide range of energies of the beam particles in proton-proton, proton-nucleus, nucleus-proton, and nucleus-nucleus reactions. The current version of QGSJET-II-04m has an improved treatment of the production of secondary particles at low energies: the parameters of the hadronization procedure have been fine-tuned, based on a number of recent benchmark experimental data, notably, from the LHCf, LHCb, and NA61 experiments. Our results for the production spectra are made publicly accessible through the interpolation routines AAfrag which are described below. Besides, we comment on the impact of Feynman scaling violation and isospin symmetry effects on antinucleon production.

   hep-phComput.Phys.Commun.(2019)·76 citations
5. 05*

   Pomeron, nucleon-resonance, and $(0^{+},0^{-},1^{+})$-meson contributions in $\varphi$-meson photoproduction

   Sang-Ho Kim🇰🇷 · Seung-il Nam🇰🇷

   We investigate the reaction mechanism of the $\varphi$-meson photoproduction off the proton target, i.e., $\gamma p\to \varphi p$, up to $\sqrt{s}=2.8$ GeV. For this purpose, we employ an effective Lagrangian approach in the tree-level Born approximation, and we employ various experimental and theoretical inputs. As a theoretical setup, the vectorlike Pomeron ($C=+1$) is taken into account as a parameterized two-gluon exchange contribution. We also consider $f_1(1285)$ axial-vector-meson, ($\pi ,\eta$) pseudoscalar-meson, and ($a_0,f_0$) scalar-meson exchanges in the $t$ channel, in addition to the experimentally confirmed nucleon resonances, such as $N^{\ast }(2000,5/2^{+})$ and $N^{\ast }(2300,1/2^{+})$, for the direct $\varphi$-meson radiations in the $s$ and $u$ channels. We provide numerical results for the total and differential cross sections as well as the spin-density matrices in the Gottfried-Jackson, Adair, and helicity frames. We observe that, together with the universally accepted pomeron contribution, the considered meson and nucleon-resonance contributions play significant roles in reproducing the experimental data for the forward and backward $\varphi$-meson scattering-angle regions, respectively, indicating the nontrivial interferences between mesonic and baryonic contributions.

   hep-phhep-exnucl-exnucl-thPRC(2019)·12 citations
6. 06*

   Heavy Holographic Exotics: Tetraquarks as Efimov States

   Yizhuang Liu🇨🇳 · Maciej A. Nowak🇵🇱 · Ismail Zahed🇺🇸

   We provide a holographic description of non-strange multiquark exotics as compact topological molecules by binding heavy-light mesons to a tunneling configuration in D8-D$\bar{8}$ that is homotopic to the vacuum state with fixed Chern-Simons number. In the tunneling process, the heavy-light mesons transmute to fermions. Their binding is generic and arises from a trade-off between the dipole attraction induced by the Chern-Simons term and the U(1) fermionic repulsion. In the heavy quark limit, the open-flavor tetraquark exotics $QQ\bar{q}\bar{q}$ and $\bar{Q}\bar{Q}qq$, emerge as bound Efimov states in a degenerate multiplet $I{J}^{\pi }=(00^{+},01^{+})$ with opposite intrinsic Chern-Simons numbers $\pm \frac{1}{2}$. The hidden-flavor tetraquark exotics such as $Q\bar{Q}q\bar{q}$, $QQ\bar{Q}\bar{q}$ and $QQ\bar{Q}\bar{Q}$ as compact topological molecules are unbound. Other exotics are also discussed.

   hep-phhep-lathep-thnucl-thPRD(2019)·23 citations
7. 07*

   Structure of light front vacuum sector diagrams

   Philip D. Mannheim🇺🇸 · Peter Lowdon🇫🇷 · Stanley J. Brodsky🇺🇸

   We study the structure of scalar field light front quantization vacuum graphs. In instant time quantization both non-vacuum and vacuum graphs can equivalently be described by either the off-shell four-dimensional Feynman diagram approach or the on-shell three-dimensional Fock space approach, with this being the case since the relevant Feynman diagrams are given entirely by pole terms. This is also the case for light front quantization non-vacuum graphs. However this is the not the case for light front vacuum sector diagrams, since then there are also circle at infinity contributions to Feynman diagrams. These non-pole contributions cause vacuum diagrams to be nonzero and to not be given by a light-front Hamiltonian Fock space analysis. The three-dimensional approach thus fails in the light front vacuum sector. In consequence, the closely related infinite momentum frame approach also fails in the light front vacuum sector.

   hep-phhep-thPLB(2019)·19 citations
8. 08*

   Dirac shell quark-core model for the study of non-strange baryonic spectroscopy

   Maurizio De Sanctis🇨🇴

   A Dirac shell model is developed for the study of baryon spectroscopy, taking into account the most relevant results of the quark-diquark models. The lack of translational invariance of the shell model is avoided, in the present work, by introducing a scalar-isoscalar fictitious particle that represents the origin of quark shell interaction; in this way the states of the system are eigenstates of the total momentum of the baryon. Only one-particle excitations are considered. A two-quark core takes the place of the diquark, while the third quark is excited to reproduce the baryonic resonances. For the $N(939)$ and $\Delta (1232)$, that represent the ground states of the spectra, the three quarks are considered identical particles and the wave functions are completely antisymmetric. The model is used to calculate the spectra of the $N$ and $\Delta$ resonances and the nucleon magnetic moments. The results are compared to the present experimental data. Due to the presence of the core and to the one-particle excitations, the structure of the obtained spectra is analogous to that given by the quark-diquark models.

   hep-phActa Phys.Polon.B(2019)·1 citation
9. 09*

   From Swampland to Phenomenology and Back

   Masahito Yamazaki🇯🇵

   Swampland conjectures are a set of proposed necessary conditions for a low-energy effective field theory to have a UV completion inside a theory of quantum gravity. Swampland conjectures have interesting phenomenological consequences, and conversely phenomenological considerations are useful guidelines in sharping our understanding of quantum gravity.

   hep-phhep-th5 citations
10. 10*

    EFTs meet Higgs Nonlinearity, Compositeness and (Neutral) Naturalness

    Hao-Lin Li🇨🇳 · Ling-Xiao Xu🇨🇳 · Jiang-Hao Yu🇨🇳 · Shou-Hua Zhu🇨🇳

    Composite Higgs and neutral-naturalness models are popular scenarios in which the Higgs boson is a pseudo Nambu-Goldstone boson, and naturalness problem is addressed by composite top partners. Since the standard model effective field theory (SMEFT) with dimension-six operators cannot fully retain the information of Higgs nonlinearity due to its PNGB nature, we systematically construct low energy Lagrangian in which the information of compositeness and Higgs nonlinearity are encoded in the form factors, the two-point functions in the top sector. We classify naturalness conditions in various scenarios, and first present these form factors in composite neutral naturalness models. After extracting out Higgs effective couplings from these form factors and performing the global fit, we find the value of Higgs top coupling could still be larger than the standard model one if the top quark is embedded in the higher dimensional representations. Also we find the impact of Higgs nonlinearity is enhanced by the large mass splitting between composite states. In this case, pattern of the correlation between the $t\bar{t}h$ and $t\bar{t}hh$ couplings is quite different for the linear and nonlinear Higgs descriptions.

    hep-phJHEP(2019)·17 citations
11. 11*

    A $\nu$ Solution to the Strong CP Problem

    Marcela Carena🇺🇸 · Da Liu🇺🇸 · Jia Liu🇺🇸 · Nausheen R. Shah🇺🇸 · Carlos E. M. Wagner🇺🇸 · Xiao-Ping Wang🇺🇸

    We present a new solution to the strong CP problem in which the imaginary component of the up quark mass, $\mathcal{I}[m_u]$, acquires a tiny, but non-vanishing value. This is achieved via a Dirac seesaw mechanism, which is also responsible for the generation of the small neutrino masses. Consistency with the observed value of the up quark mass is achieved via instanton contributions arising from QCD-like interactions. In this framework, the value of the neutron electric dipole moment is directly related to $\mathcal{I}[m_u]$, which, due to its common origin with the neutrino masses, implies that the neutron electric dipole moment is likely to be measured in the next round of experiments. We also present a supersymmetric extension of this Dirac seesaw model to stabilize the hierarchy among the scalar mass scales involved in this new mechanism.

    hep-phhep-exPRD(2019)·17 citations
12. 12*

    Interference effects in LNV and LFV semileptonic decays: the Majorana hypothesis

    A. Abada🇫🇷 · C. Hati🇫🇷 · X. Marcano🇫🇷 · A.M. Teixeira🇫🇷

    In the case where the Standard Model is extended by one heavy Majorana fermion, the branching fractions of semileptonic meson decays into same-sign and opposite-sign dileptons are expected to be of the same order. As we discuss here, this need not be the case in extensions by at least two sterile fermions, due to the possible destructive and constructive interferences that might arise. Depending on the $CP$ violating phases, one can have an enhancement of the lepton number violating modes and suppression of the lepton number conserving ones (and vice-versa). We explore for the first time the interference effects in semileptonic decays, and illustrate them for a future observation of kaon decays at NA62. We also argue that a non-observation of a given mode need not be interpreted in terms of reduced active-sterile mixings, but that it could instead be understood in terms of interference effects due to the presence of several sterile states; in particular, for different-flavour final state charged leptons, observing a lepton number conserving process and not a lepton number violating one does not rule out that the mediators are Majorana fermions.

    hep-phhep-exJHEP(2019)·47 citations
13. 13*

    Studying nucleon structure via Double Deeply Virtual Compton Scattering (DDVCS)

    Shengying Zhao🇫🇷

    Study of the structure and dynamics of the nucleon has been deeply renewed with the advent of a parameterization of the partonic structure of the nucleon in terms of the Generalized Parton Distributions (GPDs). Encoding the correlations between the elementary constituents of the nucleon, GPDs allow a 3-dimensional imaging of the nucleon from the dynamical link between the transverse position and the longitudinal momentum of partons. Double Deeply Virtual Compton Scattering (DDVCS) corresponds to the scattering from the nucleon of a virtual photon that finally generates a lepton pair, where the final leptons can be either an electron or a muon pair. The virtuality of the final photon allows to investigate in a decorrelated way the initial and transferred momentum dependences of the GPDs. This unique feature of DDVCS is of relevance, among others, for the determination of the transverse parton densities and the distribution of nuclear forces. This proceeding discusses preliminary model-predicted DDVCS experimental projections at JLab12 and indicates the impact of potential DDVCS experiments.

    hep-phnucl-exPoS(2019)·5 citations
14. 14*

    Too Big To Fail in Light of Gaia

    Manoj Kaplinghat🇺🇸 · Mauro Valli🇺🇸 · Hai-Bo Yu🇺🇸

    We point out an anti-correlation between the central dark matter (DM) densities of the bright Milky Way dwarf spheroidal galaxies (dSphs) and their orbital pericenter distances inferred from Gaia data. The dSphs that have not come close to the Milky Way center (like Fornax, Carina and Sextans) are less dense in DM than those that have come closer (like Draco and Ursa Minor). The same anti-correlation cannot be inferred for the ultra-faint dSphs due to large scatter. Including ultra-faints, a trend that dSphs with more extended stellar distributions tend to have lower DM densities emerges. A fresh look at solutions to the too-big-to-fail problem is warranted in light of these observations.

    ↳ astro-ph.GAastro-ph.COhep-phMNRAS(2019)·133 citations
15. 15*

    Tentative evidence of spatially extended GeV emission from SS433/W50

    Xiao-Na Sun🇨🇳 · Rui-Zhi Yang🇩🇪 · Bing Liu🇨🇳 · Shao-Qiang Xi🇨🇳 · Xiang-Yu Wang🇨🇳

    We analyze 10 years of Fermi-LAT data towards the SS433/W50 region. With the latest source catalog and diffuse background models, the gamma-ray excess from SS433/W50 is detected with a significance of 6{\sigma} in the photon energy range of 500 MeV - 10 GeV. Our analysis indicates that an extended flat disk morphology is preferred over a point-source description, suggesting that the GeV emission region is much larger than that of the TeV emission detected by HAWC. The size of the GeV emission is instead consistent with the extent of the radio nebula W50, a supernova remnant being distorted by the jets, so we suggest that the GeV emission may originate from this supernova remnant. The spectral result of the GeV emission is also consistent with an supernova remnant origin. We also derive the GeV flux upper limits on the TeV emission region, which put moderate constrains on the leptonic models to explain the multiwavelength data.

    ↳ astro-ph.HEhep-phAstron.Astrophys.(2019)·16 citations
16. 16*

    Systematic Differences due to High Energy Hadronic Interaction Models in Air Shower Simulations in the 100 GeV-100 TeV Range

    R.D. Parsons🇩🇪 · H. Schoorlemmer🇩🇪

    The predictions of hadronic interaction models for cosmic-ray induced air showers contain inherent uncertainties due to limitations of available accelerator data and theoretical understanding in the required energy and rapidity regime. Differences between models are typically evaluated in the range appropriate for cosmic-ray air shower arrays ($10^{15}$-$10^{20}$ eV). However, accurate modelling of charged cosmic-ray measurements with ground based gamma-ray observatories is becoming more and more important. We assess the model predictions on the gross behaviour of measurable air shower parameters in the energy (0.1-100 TeV) and altitude ranges most appropriate for detection by ground-based gamma-ray observatories. We go on to investigate the particle distributions just after the first interaction point, to examine how differences in the micro-physics of the models may compound into differences in the gross air shower behaviour. Differences between the models above 1 TeV are typically less than 10%. However, we find the largest variation in particle densities at ground at the lowest energy tested (100 GeV), resulting from striking differences in the early stages of shower development.

    ↳ astro-ph.HEhep-phPRD(2019)·21 citations
17. 17*

    Dark energy perturbations in $N$-body simulations

    Jeppe Dakin🇩🇰 · Steen Hannestad🇩🇰 · Thomas Tram🇩🇰 · Mischa Knabenhans🇨🇭 · Joachim Stadel🇨🇭

    We present $N$-body simulations which are fully compatible with general relativity, with dark energy consistently included at both the background and perturbation level. We test our approach for dark energy parameterised as both a fluid, and using the parameterised post-Friedmann (PPF) formalism. In most cases, dark energy is very smooth relative to dark matter so that its leading effect on structure formation is the change to the background expansion rate. This can be easily incorporated into Newtonian $N$-body simulations by changing the Friedmann equation. However, dark energy perturbations and relativistic corrections can lead to differences relative to Newtonian $N$-body simulations at the tens of percent level for scales $k<(10^{-3}–10^{-2}){\mathrm{Mpc}}^{-1}$, and given the accuracy of upcoming large scale structure surveys such effects must be included. In this paper we will study both effects in detail and highlight the conditions under which they are important. We also show that our $N$-body simulations exactly reproduce the results of the Boltzmann solver CLASS for all scales which remain linear.

    ↳ astro-ph.COhep-phJCAP(2019)·28 citations
18. 18*

    The Full-Color Two-Loop Four-Gluon Amplitude in $\mathcal{N}=2$ Super-QCD

    Claude Duhr🇨🇭 · Henrik Johansson🇸🇪 · Gregor Kälin🇸🇪 · Gustav Mogull🇸🇪 · Bram Verbeek🇧🇪

    We present the fully integrated form of the two-loop four-gluon amplitude in $\mathcal{N}=2$ supersymmetric quantum chromodynamics with gauge group SU$(N_c)$ and with $N_f$ massless supersymmetric quarks (hypermultiplets) in the fundamental representation. Our result maintains full dependence on $N_c$ and $N_f$, and relies on the existence of a compact integrand representation that exhibits the duality between color and kinematics. Specializing to the $\mathcal{N}=2$ superconformal theory, where $N_f=2N_c$ , we obtain remarkably simple amplitudes that have an analytic structure close to that of $\mathcal{N}=4$ super-Yang-Mills theory, except that now certain lower-weight terms appear. We comment on the corresponding results for other gauge groups.

    ↳ hep-thhep-phPRL(2019)·18 citations
19. 19*

    Testing the nature of dark compact objects: a status report

    Vitor Cardoso🇵🇹 · Paolo Pani🇮🇹

    Very compact objects probe extreme gravitational fields and may be the key to understand outstanding puzzles in fundamental physics. These include the nature of dark matter, the fate of spacetime singularities, or the loss of unitarity in Hawking evaporation. The standard astrophysical description of collapsing objects tells us that massive, dark and compact objects are black holes. Any observation suggesting otherwise would be an indication of beyond-the-standard-model physics. Null results strengthen and quantify the Kerr black hole paradigm. The advent of gravitational-wave astronomy and precise measurements with very long baseline interferometry allow one to finally probe into such foundational issues. We overview the physics of exotic dark compact objects and their observational status, including the observational evidence for black holes with current and future experiments.

    ↳ gr-qcastro-ph.HEhep-phphysics.space-phLiving Rev.Rel.(2019)·1221 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.