Thu·Apr 18, 2019Thursday·April 18, 2019

1. 01*

   TASI lectures on dark matter models and direct detection

   Tongyan Lin🇺🇸

   These lectures provide an introduction to models and direct detection of dark matter. We summarize the general features and motivations for candidates in the full dark matter mass range, and then restrict to the keV-TeV mass window. Candidates in this window can be produced by thermal mechanisms in the standard cosmology, and are an important target for experimental searches. We then turn to sub-GeV dark matter (light dark matter) and dark sectors, an area where many new models and experiments are currently being proposed. We discuss the cosmology of dark sectors, specific portal realizations, and some of the prospects for detection. The final parts of these lectures focus on the theory for direct detection, both reviewing the fundamentals for nuclear recoils of WIMPs and describing new directions for sub-GeV candidates. A version of these lectures was originally presented at the TASI 2018 summer school on "Theory in an Era of Data".

   hep-phastro-ph.COPoS(2019)·318 citations
2. 02*

   Nucleon resonance contributions to unpolarised inclusive electron scattering

   A. N. Hiller Blin🇩🇪 · V. Mokeev🇺🇸 · M. Albaladejo🇺🇸 · C. Fernández-Ramírez🇲🇽 · V. Mathieu🇺🇸 · A. Pilloni🇮🇹 · A.Szczepaniak🇺🇸 · V. D. Burkert🇺🇸 · V. V. Chesnokov🇷🇺 · A. A. Golubenko🇷🇺 · M. Vanderhaeghen🇩🇪

   The first CLAS12 experiments will provide high-precision data on inclusive electron scattering observables at a photon virtuality $Q^2$ ranging from 0.05 GeV${}^2$ to 12 GeV${}^2$ and center-of-mass energies $W$ up to 4 GeV. In view of this endeavour, we present the modeling of the resonant contributions to the inclusive electron scattering observables. As input, we use the existing CLAS electrocoupling results obtained from exclusive meson electroproduction data off protons, and evaluate for the first time the resonant contributions based on the experimental results on the nucleon resonance electroexcitation. The uncertainties are given by the data and duly propagated through a Monte Carlo approach. In this way, we obtain estimates for the resonant contributions, important for insight into the nucleon parton distributions in the resonance region and for the studies of quark-hadron duality.

   hep-phnucl-thPRC(2019)·46 citations
3. 03*

   Electro-weak production of pseudovector C-even heavy quarkonia in electron-positron collisions on Belle II and BES III

   Nikolay Achasov🇷🇺

   It is shown that the molecular model for the X{3872) state contradicts the new experimental data as well as the old ones. It is suggested to study the \chi_{c1} and \chi_{b1} states in the e+e-\to\chi_{c1}/\chi_{b1} reactions.

   hep-phhep-exnucl-exEPJ Web Conf.(2019)·10 citations
4. 04*

   Updated limits on the CP violating $\eta \pi \pi$ and ${\eta }^{\prime }\pi \pi$ couplings derived from the neutron EDM

   Alexey S. Zhevlakov🇷🇺 · Thomas Gutsche🇩🇪 · Valery E. Lyubovitskij🇩🇪

   We complete our derivation of upper limits on the CP violating $\eta \pi \pi$ and ${\eta }^{\prime }\pi \pi$ couplings from an analysis of their two-loop contributions to the neutron electric dipole moment (nEDM). We use a phenomenological Lagrangian approach which is formulated in terms of hadronic degrees of freedom - nucleons and pseudoscalar mesons. The essential part of the Lagrangian contains the CP violating couplings between $\eta ({\eta }^{\prime })$ and pions. Previously, we included photons using minimal substitution in case of the proton and charged pions. Now we extend our Lagrangian by adding the nonminimal couplings, i.e. anomalous magnetic couplings of nucleons with the photon. The obtained numerical upper limits for the $\eta \pi \pi$ and ${\eta }^{\prime }\pi \pi$ couplings $|f_{\eta \pi \pi }(M_{\eta }^2)|<4.4\times 10^{-11}$ and $|f_{{\eta }^{\prime }\pi \pi }(M_{{\eta }^{\prime }}^2)|<3.8\times 10^{-11}$ can be useful for the related, planned experiments at the JLab Eta Factory. Using present experimental limits on the nEDM, we derive upper limits on the CP violating $\bar{\theta }$ parameter of $\bar{\theta }<4.7\times 10^{-10}$.

   hep-phPRD(2019)·16 citations
5. 05*

   Spectral functions of confined particles

   Daniele Binosi🇮🇹 · Ralf-Arno Tripolt🇩🇪

   We determine the gluon and ghost spectral functions along with the analytic structure of the associated propagators from numerical data describing gauge correlators at space-like momenta obtained by either solving the Dyson-Schwinger equations or through lattice simulations. Our novel reconstruction technique shows the expected branch cut for the gluon and the ghost propagator, which, in the gluon case, is supplemented with a pair of complex conjugate poles. Possible implications of the existence of these poles are briefly addressed.

   hep-phhep-lathep-thPLB(2020)·121 citations
6. 06*

   Real-time dynamics of axion particle production due to spontaneous decay of a coherent axion field

   Xu-Guang Huang🇨🇳 · Dmitri E. Kharzeev🇺🇸 · Hidetoshi Taya🇨🇳

   We show that the coherent axion field spontaneously decays by emitting axion particles via quantum tunneling if axion potential has more than one minimum. By employing the $\hslash$-expansion and mean field approximation, we develop a formalism to trace the real-time dynamics of the axion particle production including its backreaction to the coherent axion field. We also present numerical results for the time evolution of various physical quantities including the strength of the coherent axion field, phase-space density of produced axion particles, energy density, and pressure. Phenomenological implications of our results are also discussed.

   hep-phastro-ph.HEgr-qchep-th+1PRD(2020)·5 citations
7. 07*

   Spin-dependent dynamically assisted Schwinger mechanism

   Xu-Guang Huang🇨🇳 · Hidetoshi Taya🇨🇳

   We study electron and positron pair production from the vacuum by a strong slow electric field superimposed by a weak fast electric field pointing in an arbitrary direction as a perturbation (the dynamically assisted Schwinger mechanism). An analytical formula for the production number is derived on the basis of the perturbation theory in the Furry picture. The formula is found to be in good agreement with non-perturbative results obtained by numerically solving the Dirac equation if the perturbation is sufficiently weak and/or is not very slow. We also find analytically/numerically that the Schwinger mechanism becomes spin-dependent if the perturbation has a transverse component with respect to the strong electric field. The number difference between spin up and down particles is strongly suppressed by an exponential of the critical field strength if the frequency of the perturbation is small, while it is only weakly suppressed by powers of the critical field strength if the frequency is large enough. We also find that the spin-imbalance exhibits non-trivial oscillating behaviors in terms of the frequency of the perturbation, the azimuthal angle, and the momentum of produced particles.

   hep-phhep-thnucl-thphysics.plasm-ph+1PRD(2019)·27 citations
8. 08*

   Search for vector-like bottom quark via $Zb$ production at the LHC

   Xue Gong🇨🇳 · Chong-Xing Yue🇨🇳 · Yu-Chen Guo🇨🇳

   Vector-like quarks (VLQs) are predicted in many new physics scenarios beyond the standard model (SM). We consider a search strategy for vector-like bottom quark (VLQ-$B$) at the LHC in a model independent fashion. Our analysis is based on single production of VLQ-$B$ with decaying to the $Zb$ mode. The production cross sections and the signal significance $SS$ are calculated, and the observability of the VLQ-$B$ signal is investigated. Our numerical results show that the possible signals of the VLQ-$B$ with electric charge of $Q_B=-1/3$, which is the $SU(2)$ singlet, might be detected via the process $pp\to B\to Z(\to l^{+}{l}^{-})b$ at the upgraded LHC.

   hep-phPLB(2019)·18 citations
9. 09*

   Angular mode expansion of the Boltzmann equation in the small-angle approximation

   Jean-Paul Blaizot🇫🇷 · Naoto Tanji🇮🇹

   We use an expansion in angular mode functions in order to solve the Boltzmann equation for a gluon plasma undergoing longitudinal expansion. By comparing with the exact solution obtained numerically by other means we show that the expansion in mode functions converges rapidly for all cases of practical interest, and represents a substantial gain in numerical effort as compared to more standard methods. We contrast the cases of a non expanding plasma and of longitudinally expanding plasmas, and follow in both cases the evolutions towards thermalization. In the latter case, we observe that, although the spherical mode function appears to be well reproduced after some time by a local equilibrium distribution function depending on slowly varying temperature and chemical potential, thereby suggesting thermalization of the system, the longitudinal and transverse pressures take more time to equilibrate. This is because the expansion hinders the relaxation of the first angular mode function. This feature was also observed in a simpler context where the Boltzmann equation is solved in terms of special moments within the relaxation time approximation, and attributed there to the particular coupling between the first two moments of the distribution function. The present analysis confirms this observation in a more realistic setting.

   hep-phnucl-thNPA(2019)·4 citations
10. 10*

    The analytic structure of thermodynamic systems with repulsive interactions

    Kirill Taradiy🇺🇦 · Anton Motornenko🇩🇪 · Volodymyr Vovchenko🇩🇪 · Mark I. Gorenstein🇺🇦 · Horst Stoecker🇩🇪

    Thermodynamic properties of systems with repulsive interactions, are considered in the grand canonical ensemble. The analytic structure of the excluded-volume model in the complex plane of the system chemical potential (fugacity) is elaborated, based on the fact that the pressure function can be given in terms of the Lambert W-function. Even though the excluded volume model has no phase transitions at real values of the chemical potential, it does exhibit a branch cut singularity in the complex plane, thus limiting the convergence range of the Taylor expansion in the chemical potential. Close similarities to analytic properties of the other models with repulsive interactions, such as a cluster expansion model, the mean-field model, and the ideal Fermi gas model, are pointed out. As an example, repulsive baryonic interactions in a hadron gas, with a focus on the fugacity/virial and Taylor expansion methods used in lattice QCD, are presented. The asymptotic behavior of the Fourier expansion coefficients in these various models suggests that the singular part of net baryonic density can to leading order be universally expressed in terms of polylogarithms.

    hep-phhep-latnucl-thPRC(2019)·16 citations
11. 11*

    Lepton flavor universality violation in semileptonic tree level weak transitions

    K. Azizi🇹🇷 · Y. Sarac🇹🇷 · H. Sundu🇹🇷

    The recent deviations of the experimental data on some parameters of the tree-level semileptonic $B$ and $B_c$ mesons decays from the standard model (SM) predictions indicate considerable violations of the lepton flavor universality, and as a result possible new physics (NP) effects. To better understand the possible NP effects it is necessary to study deeply the physical quantities defining these decays from many aspects. The calculations of the physical quantities require the determinations of the hadronic form factors entering the matrix elements of the considered transitions as the main inputs. We calculate the form factors governing the tree-level $B_c\to J/\psi l\nu$ and $B_c\to {\eta }_{c}l\nu$ transitions within the QCD sum rules method. The obtained form factors are used in the calculations of the branching ratios ($BR$s) of the $B_c\to J/\psi l\nu$ and $B_c\to {\eta }_{c}l\nu$ transitions as well as $R(J/\psi )$ and $R({\eta }_c)$. Our result on $R(J/\psi )$ supports the present tension between the SM theory prediction and the experimental data. Our result on $R({\eta }_c)$ can be checked in future experiments.

    hep-phhep-exhep-latPRD(2019)·37 citations
12. 12*

    The ${\chi }_{cJ}$ decay to $\varphi K^{\ast }\bar{K},\varphi h_1(1380)$ testing the nature of axial vector meson resonances

    Sheng-Juan Jiang🇨🇳 · S. Sakai🇨🇳 · Wei-Hong Liang🇨🇳 · E. Oset🇪🇸

    We perform a theoretical study of the ${\chi }_{cJ}\to \varphi K^{\ast }\bar{K}\to \varphi K\pi \bar{K}$ reaction taking into account the $K^{\ast }\bar{K}$ final state interaction, which in the chiral unitary approach is responsible, together with its coupled channels, for the formation of the low lying axial vector mesons, in this case the $h_1(1380)$ given the selection of quantum numbers. Based on this picture we can easily explain why in the ${\chi }_{c0}$ decay the $h_1(1380)$ resonance is not produced, and, in the case of ${\chi }_{c1}$ and ${\chi }_{c2}$ decay, why a dip in the $K^{+}{\pi }^0{K}^{-}$ mass distribution appears in the 1550-1600 MeV region, that in our picture comes from a destructive interference between the tree level mechanism and the rescattering that generates the $h_1(1380)$ state. Such a dip is not reproduced in pictures where the nominal $h_1(1380)$ signal is added incoherently to a background, which provides support to the picture where the resonance appears from rescattering of vector-pseudoscalar components.

    hep-phhep-exPLB(2019)·13 citations
13. 13*

    Event-Based Transverse Momentum Resummation

    Thomas Becher🇨🇭 · Monika Hager🇨🇭

    We have developed a framework for automated transverse momentum resummation for arbitrary electroweak final states based on reweighting tree-level events. It is fully differential in the kinematics of the electroweak final states, which facilitates a straightforward analysis of arbitrary observables in the small transverse momentum region. We have implemented the resummation at next-to-next-to-leading logarithmic accuracy and match to next-to-leading fixed-order results using the event generator MadGraph5_aMC@NLO. Results for $Z$ and $W$ boson production with leptonic decay as well as $WZ$ production are presented. We compare to experimental measurements for the transverse momentum and the angular observable ${\varphi }^{\ast }$.

    hep-phEPJC(2019)·38 citations
14. 14*

    Axion superradiance in rotating neutron stars

    Francesca V. Day🇬🇧 · Jamie I. McDonald🇩🇪

    It is a well-known fact that compact gravitating objects admit bound state configurations for massive bosonic fields. In this work we describe a new class of superradiant instabilities of axion bound states in neutron star magnetospheres. The instability arises from the mixing of axion and photon modes in the magnetic field of the neutron star which extract energy from the rotating magnetosphere. Unlike for black holes, where the dissipation required for superradiance is provided by an absorbative horizon, the non-hermitian dynamics in this paper come from the resistivity in the stellar magnetosphere arising from a finite bulk conductivity. The axion field mixes with photon modes which superradiantly scatter off the magnetosphere, extracting rotational energy which is then deposited back into the axion sector leading to an instability. We derive the superradiant eigenfrequencies for the axion-photon system using quantum mechanical perturbation theory on the axion boundstate, drawing an analogy with atomic selection rules. We then compare the characteristic time scale of the instability to the spin-down measurements of pulsars which limit the allowed rate of angular momentum extraction from neutron stars.

    hep-phastro-ph.HEgr-qcJCAP(2019)·75 citations
15. 15*

    Relaxing the $W^{\prime }$ constraint on compactified extra-dimension

    Mathew Thomas Arun🇮🇳

    It has been known for some time that the inclusion of brane fluctuations, namely branons, helps in the suppression of KK-mode couplings to brane localised matter fields. In this paper we study the constraint on brane tension and compactification scale for such models using the results from the direct search of $W^{\prime }$ at 13 TeV LHC, with an integrated luminosity of $36.1f{b}^{-1}$, in the case for which branon forms the entire cold dark matter. Unlike the rigid brane scenario, where the compactification scale gets constrained to $\frac{1}{R}\gtrsim 5.2$ TeV, here we show that compactification scales as small as $\sim 1$ TeV are allowed for brane tensions of similar strength.

    hep-phAdv.High Energy Phys.(2022)·1 citation
16. 16*

    Causality, unitarity thresholds, anomalous thresholds and infrared singularities from the loop-tree duality at higher orders

    J. Jesús Aguilera-Verdugo🇪🇸 · Félix Driencourt-Mangin🇪🇸 · Judith Plenter🇪🇸 · Selomit Ramírez-Uribe🇪🇸 · Germán Rodrigo🇪🇸 · Germán F. R. Sborlini🇪🇸 · William J. Torres Bobadilla🇪🇸 · Szymon Tracz🇪🇸

    We present the first comprehensive analysis of the unitarity thresholds and anomalous thresholds of scattering amplitudes at two loops and beyond based on the loop-tree duality, and show how non-causal unphysical thresholds are locally cancelled in an efficient way when the forest of all the dual on-shell cuts is considered as one. We also prove that soft and collinear singularities at two loops and beyond are restricted to a compact region of the loop three-momenta, which is a necessary condition for implementing a local cancellation of loop infrared singularities with the ones appearing in real emission; without relying on a subtraction formalism.

    hep-phhep-thJHEP(2019)·70 citations
17. 17*

    Update on the b->s anomalies

    A. Arbey🇫🇷 · T. Hurth🇩🇪 · F. Mahmoudi🇫🇷 · D. Martinez Santos🇪🇸 · S. Neshatpour🇪🇸

    We present a brief update of our model-independent analyses of the b->s data presented in the articles published in Phys. Rev. D96 (2017) 095034 and Phys. Rev. D98 (2018) 095027 based on new data on R_K by LHCb, on R_{K^*} by Belle, and on B_{s,d}-> mu^+ mu^- by ATLAS.

    hep-phPRD(2019)·140 citations
18. 18*

    The Weak Scale from Weak Gravity

    Nathaniel Craig🇺🇸 · Isabel Garcia Garcia🇺🇸 · Seth Koren🇺🇸

    We explore the prospects for bounding the weak scale using the weak gravity conjecture (WGC), addressing the hierarchy problem by violating the expectations of effective field theory. Building on earlier work by Cheung and Remmen, we construct models in which a super-extremal particle satisfying the electric WGC for a new Abelian gauge group obtains some of its mass from the Higgs, setting an upper bound on the weak scale as other UV-insensitive parameters are held fixed. Avoiding undue sensitivity of the weak scale to the parameters entering the bound implies that the super-extremal particle must lie at or below the weak scale. While the magnetic version of the conjecture implies additional physics entering around the same scale, we demonstrate that this need not correspond to a cutoff for the Higgs potential or otherwise trivialize the bound. We stress that linking the WGC to the weak scale necessarily involves new light particles coupled to the Higgs, implying a variety of experimentally accessible signatures including invisible Higgs decays and radiative corrections in the electroweak sector. These models also give rise to natural dark matter candidates, providing additional paths to discovery. In particular, collective effects in the dark matter plasma may provide a telltale sign of the Abelian gauge group responsible for bounding the weak scale.

    hep-phhep-thJHEP(2019)·33 citations
19. 19*

    Consistency of local and astrophysical tests of the stability of fundamental constants

    C. J. A. P. Martins🇵🇹 · M. Vila Miñana🇪🇸

    Tests of the stability of nature's fundamental constants are one of the cornerstones of the ongoing search for the new physics which is required to explain the recent acceleration of the universe. The two main settings for these tests are high-resolution spectroscopy of astrophysical systems (mainly in low-density absorption clouds along the line of sight of bright quasars) and laboratory comparisons of pairs of atomic clocks. Here we use standard chi-square techniques to perform a global analysis of all currently available data, studying both the consistency of tests of stability of different constants (specifically the fine-structure constant $\alpha$, the proton-to-electron mass ratio $\mu$ and the proton gyromagnetic ratio $g_p$) and the consistency between local laboratory and astrophysical tests. We start by doing a model-independent analysis (studying the internal consistency of the various available datasets) but also explore specific phenomenological models motivated by string theory and grand unification. Overall there is weak (one to two sigma) evidence of variations, at the level of up to a few parts per million, and reasonable agreement between laboratory and astrophysical tests. This result holds even if one removes from the analysis the Webb {\it et al.} archival dataset of $\alpha$ measurements. Forthcoming astrophysical facilities, such as the ESPRESSO spectrograph, should be able to confirm or rule out these hints.

    ↳ astro-ph.COgr-qchep-phPhys.Dark Univ.(2019)·18 citations
20. 20*

    Fitting B/C cosmic-ray data in the AMS-02 era: A cookbook

    L. Derome🇫🇷 · D. Maurin🇫🇷 · P. Salati🇫🇷 · M. Boudaud🇫🇷 · Y. Génolini🇧🇪 · P. Kunzé🇫🇷

    AMS-02 on the International Space Station has been releasing data of unprecedented accuracy. This poses new challenges for their interpretation. We refine the methodology to get a statistically sound determination of the cosmic-ray propagation parameters. We inspect the numerical precision of the model calculation, nuclear cross-section uncertainties, and energy correlations in data systematic errors. We used the 1D diffusion model in USINE. Our ${\chi }^2$ analysis includes a covariance matrix of errors for AMS-02 systematics and nuisance parameters to account for cross-section uncertainties. Mock data were used to validate some of our choices. We show that any mis-modelling of nuclear cross-section values or the energy correlation length of the covariance matrix of errors biases the analysis. It also makes good models (${\chi }_{\min }^2/\mathrm{dof}\approx 1$) appear as excluded (${\chi }_{\min }^2/\mathrm{dof}\gg 1$). We provide a framework to mitigate these effects (AMS-02 data are interpreted in a companion paper). New production cross-section data and the publication by the AMS-02 collaboration of a covariance matrix of errors for each data set would be an important step towards an unbiased view of cosmic-ray propagation in the Galaxy.

    ↳ astro-ph.HEhep-phAstron.Astrophys.(2019)·57 citations
21. 21*

    Probing 21cm cosmology and radiative neutrino decays

    Kareem R. H. A. M. Farrag🇬🇧

    Here we discuss the recent EDGES observation of a excess in its radio profile and how it can be used to constrain radiative neutrino decays.

    ↳ astro-ph.COhep-ph0 citations
22. 22*

    Hadron-Deuteron Correlations and Production of Light Nuclei in Relativistic Heavy-Ion Collisions

    Stanislaw Mrowczynski🇵🇱 · Patrycja Slon🇵🇱

    The production of light nuclei in relativistic heavy-ion collisions is well described by both the thermal model, where light nuclei are in equilibrium with all other hadron species present in a fireball, and by the coalescence model, where light nuclei are formed due to final state interactions after the fireball decays. A method is proposed to falsify one of the models. We suggest to measure a hadron-deuteron correlation function which carries information about the source of the deuterons and allows one to determine whether a deuteron is directly emitted from the fireball or if it is formed afterwards. The $K^{-}-D$ and $p-D$ correlation functions are computed to illustrate the statement.

    ↳ nucl-thhep-phnucl-exActa Phys.Polon.B(2020)·52 citations
23. 23*

    Dark Matter Strikes Back at the Galactic Center

    Rebecca K. Leane🇺🇸 · Tracy R. Slatyer🇺🇸

    Statistical evidence has previously suggested that the Galactic Center GeV Excess (GCE) originates largely from point sources, and not from annihilating dark matter. We examine the impact of unmodeled source populations on identifying the true origin of the GCE using non-Poissonian template fitting (NPTF) methods. In a proof-of-principle example with simulated data, we discover that unmodeled sources in the Fermi Bubbles can lead to a dark matter signal being misattributed to point sources by the NPTF. We discover striking behavior consistent with a mismodeling effect in the real Fermi data, finding that large artificial injected dark matter signals are completely misattributed to point sources. Consequently, we conclude that dark matter may provide a dominant contribution to the GCE after all.

    ↳ astro-ph.HEastro-ph.COhep-phPRL(2019)·166 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.