Thu·Apr 5, 2018Thursday·April 5, 2018

1. 01*

   Axions in a highly protected gauge symmetry model

   Quentin Bonnefoy🇫🇷 · Emilian Dudas🇫🇷 · Stefan Pokorski🇵🇱

   We study QCD axion or cosmological axion-like particles (ALPs) in a model inspired by the recent interest in 4-dimensional clockwork models, with the global symmetry being accidentally enforced by a gauge abelian quiver with scalar bifundamental fields. For the QCD axion, we analyze the connection between the degree of protection of the axion mass against gravitational corrections, the explanation of the hierarchy $f_a\ll M_P$ and the number of colored fermions needed to generate anomalous couplings to gluons, all linked together by the underlying gauge symmetries. Based on that model and on the comparison with earlier models in the literature, we derive certain general conclusions on QCD axion models that use accidental global symmetries. For the ALPs, assuming that their mass is solely given by gravitational corrections, we identify the parameter space where the decay constant and the mass are consistent with the DM abundance, and we show that this clockwork-inspired model is a particularly economical model for a very light ALP DM candidate.

   hep-phhep-thEPJC(2019)·38 citations
2. 02*

   Anomalous enhancement of the isospin-violating $\Lambda (1405)$ production by a triangle singularity in ${\Lambda }_c\to {\pi }^{+}{\pi }^0{\pi }^0{\Sigma }^0$

   L. R. Dai🇨🇳 · R. Pavao🇪🇸 · S. Sakai🇪🇸 · E. Oset🇪🇸

   The decay of ${\Lambda }_c^{+}$ into ${\pi }^{+}{\pi }^0\Lambda (1405)$ with the $\Lambda (1405)$ decay into ${\pi }^0{\Sigma }^0$ through a triangle diagram is studied. This process is initiated by ${\Lambda }_c^{+}\to {\pi }^{+}{\bar{K}}^{\ast }N$, then the ${\bar{K}}^{\ast }$ decays into $\bar{K}\pi$ and $\bar{K}N$ produce the $\Lambda (1405)$ through a triangle loop containing ${\bar{K}}^{\ast }N\bar{K}$ which develops a singularity around $1890$ MeV. This process is prohibited by the isospin symmetry, but the decay into this channel is enhanced by the contribution of the triangle diagram, which is sensitive to the mass of the internal particles. We find a narrow peak in the ${\pi }^0{\Sigma }^0$ invariant mass distribution, which originates from the $\Lambda (1405)$ amplitude, but is tied to the mass differences between the charged and neutral $\bar{K}$ or $N$ states. The observation of the unavoidable peak of the triangle singularity in the isospin-violating $\Lambda (1405)$ production would provide further support for hadronic molecular picture of the $\Lambda (1405)$ and further information on the $\bar{K}N$ interaction.

   hep-phPRD(2018)·31 citations
3. 03*

   Electric Dipole Moments from CP-Violating Scalar Leptoquark Interactions

   Kaori Fuyuto🇺🇸 · Michael Ramsey-Musolf🇺🇸 · Tianyang Shen🇺🇸

   We analyze the implications of CP-violating scalar leptoquark (LQ) interactions for experimental probes of parity- and time-reversal violating properties of polar molecules. These systems are predominantly sensitive to the electric dipole moment (EDM) of the electron and nuclear-spin-independent (NSID) electron-nucleon interaction. The LQ model can generate both a tree-level NSID interaction as well as the electron EDM at one-loop order. Including both interactions, we find that the NSID interaction can dominate the molecular response. For moderate values of couplings, the current experimental results give roughly two orders of magnitude stronger limits on the electron EDM than one would otherwise infer from a sole-source analysis.

   hep-phhep-exPLB(2019)·46 citations
4. 04*

   Simplified Dark Matter Models

   Enrico Morgante🇩🇪

   I review the construction of Simplified Models for Dark Matter searches. After discussing the philosophy and some simple examples, I turn the attention to the aspect of the theoretical consistency and to the implications of the necessary extensions of these models.

   hep-phAdv.High Energy Phys.(2018)·39 citations
5. 05*

   Fine structure of the cross sections of $e^{+}{e}^{-}$ annihilation near the thresholds of $p\bar{p}$ and $n\bar{n}$ production

   A.I. Milstein🇷🇺 · S.G. Salnikov🇷🇺

   The energy dependence of the cross sections of $p\bar{p}$, $n\bar{n}$, and meson production in $e^{+}{e}^{-}$ annihilation in the vicinity of the $p\bar{p}$ and $n\bar{n}$ thresholds is studied. The proton-neutron mass difference and the $p\bar{p}$ Coulomb interaction are taken into account. The values of the cross sections are very sensitive to the parameters of the optical potential. It is shown that the commonly accepted factorization approach for the account of the Coulomb interaction does not work well enough in the vicinity of the threshold due to the finite size of the optical potential well.

   hep-phnucl-thNPA(2018)·25 citations
6. 06*

   Anomalous triple-gauge-boson interactions in vector-boson pair production with RECOLA2

   Mauro Chiesa🇩🇪 · Ansgar Denner🇩🇪 · Jean-Nicolas Lang🇨🇭

   Diboson production at the LHC is a process of great importance both in the context of tests of the SM and for direct searches for new physics. In this paper we present a phenomenological study of WW, WZ, and ZZ production considering event selections of interest for the anomalous triple-gauge-boson-coupling searches at the LHC: we provide theoretical predictions within the Standard Model at NLO QCD and NLO EW accuracy and study the effect of the anomalous triple-gauge-boson interactions at NLO QCD. For WW and ZZ production, the contribution of the gluon-initiated loop-induced processes is included. Anomalous triple-gauge-boson interactions are parametrized in the EFT framework. This paper is the first application of RECOLA2 in the EFT context.

   hep-phhep-exEPJC(2018)·48 citations
7. 07*

   Conformal Structure of the Heavy Particle EFT Operator Basis

   Andrew Kobach🇺🇸 · Sridip Pal🇺🇸

   An operator basis of an effective theory with a heavy particle, subject to external gauge fields, is spanned by a particular kind of neutral scalar primary of the nonrelativistic conformal group. We calculate the characters that can be used for generating the operators in a non-relativistic effective field theory, which accounts for redundancies from the equations of motion and integration by parts.

   hep-phhep-thPLB(2018)·15 citations
8. 08*

   Neutrino Masses from Outer Space

   Guido D'Amico🇨🇭 · Teresa Hamill🇺🇸 · Nemanja Kaloper🇺🇸

   Neutrinos can gain mass from coupling to an ultralight field in slow roll. When such a field is displaced from its minimum, its vev acts just like the Higgs vev in spontaneous symmetry breaking. Although these masses may eventually vanish, they do it over a very long time. The theory is technically natural, with the ultralight field-dependent part being the right-handed Majorana mass. The mass variation induced by the field correlates with the cosmological evolution. The change of the mass term changes the mixing matrix, and therefore suppresses the fraction of sterile neutrinos at earlier times and increases it at later times. Since the issue of quantum gravity corrections to field theories with large field variations remains open, this framework may give an observational handle on the Weak Gravity Conjecture.

   hep-phastro-ph.COgr-qchep-thPLB(2019)·14 citations
9. 09*

   What if string theory has no de Sitter vacua?

   Ulf H. Danielsson🇸🇪 · Thomas Van Riet🇧🇪

   We present a brief overview of attempts to construct de Sitter vacua in string theory and explain how the results of this 20-year endeavor could point to the fact that string theory harbors no de Sitter vacua at all. Making such a statement is often considered controversial and "bad news for string theory". We discuss how perhaps the opposite can be true.

   ↳ hep-thastro-ph.COhep-phInt.J.Mod.Phys.D(2018)·475 citations
10. 10*

    Gravitational plane waves in Einstein-aether theory

    Jacob Oost🇺🇸 · Madhurima Bhattacharjee🇺🇸 · Anzhong Wang🇺🇸

    In this paper, we systematically study spacetimes of gravitational plane waves in Einstein-aether theory. Due to the presence of the timelike aether vector field, now the problem in general becomes overdetermined. In particular, for the linearly polarized plane waves, there are five independent vacuum Einstein-aether field equations for three unknown functions. Therefore, solutions exist only for particular choices of the four free parameters $c_i$'s of the theory. We find that there exist eight cases, in two of which any form of gravitational plane waves can exist, similar to that in general relativity, while in the other six cases, gravitational plane waves exist only in particular forms. Beyond these eight cases, solutions either do not exist or are trivial (simply representing a Minkowski spacetime with a constant or dynamical aether field.).

    ↳ gr-qcastro-ph.COhep-phhep-thGen.Rel.Grav.(2018)·11 citations
11. 11*

    Statistical Properties of Scale-Invariant Helical Magnetic Fields and Applications to Cosmology

    Axel Brandenburg🇺🇸 · Ruth Durrer🇨🇭 · Tina Kahniashvili🇺🇸 · Sayan Mandal🇺🇸 · Weichen Winston Yin🇺🇸

    We investigate the statistical properties of isotropic, stochastic, Gaussian distributed, helical magnetic fields characterized by different shapes of the energy spectra at large length scales and study the associated realizability condition. We discuss smoothed magnetic fields that are commonly used when the primordial magnetic field is constrained by observational data. We are particularly interested in scale-invariant magnetic fields that can be generated during the inflationary stage by quantum fluctuations. We determine the correlation length of such magnetic fields and relate it to the infrared cutoff of perturbations produced during inflation. We show that this scale determines the observational signatures of the inflationary magnetic fields on the cosmic microwave background. At smaller scales, the scale-invariant spectrum changes with time. It becomes a steeper weak-turbulence spectrum at progressively larger scales. We show numerically that the critical length scale where this happens is the turbulent-diffusive scale, which increases with the square root of time.

    ↳ astro-ph.COgr-qchep-phJCAP(2018)·31 citations
12. 12*

    Dark Matter implications of DAMA/LIBRA-phase2 results

    Sebastian Baum🇸🇪 · Katherine Freese🇸🇪 · Chris Kelso🇺🇸

    Recently, the DAMA/LIBRA collaboration released updated results from their search for the annual modulation signal from Dark Matter (DM) scattering in the detector. Besides approximately doubling the exposure of the DAMA/LIBRA data set, the updated photomultiplier tubes of the experiment allow a lower recoil energy threshold of 1\,keV electron equivalent compared to the previous threshold of 2 keV electron equivalent. We study the compatibility of the observed modulation signal with DM scattering. Due to a conspiracy of multiple effects, the new data at low recoil energies is very powerful for testing the DM hypothesis. We find that canonical (isospin conserving) spin-independent DM-nucleon interactions are no longer a good fit to the observed modulation signal in the standard halo model. The canonical spin-independent case is disfavored by the new data, with best fit points of a DM mass of $\sim 8$GeV, disfavored by $5.2\sigma$, or a mass of $\sim 54$GeV, disfavored by $2.5\sigma$. Allowing for isospin violating spin independent interactions, we find a region with a good fit to the data with suppressed effective couplings to iodine for DM masses of $\sim 10$GeV. We also consider spin-dependent DM-nucleon interactions, which yield good fits for similar DM masses of $\sim 10$GeV or $\sim 45$GeV

    ↳ astro-ph.COhep-phPLB(2019)·76 citations
13. 13*

    Measuring the CP state of tau lepton pairs from Higgs decay at the ILC

    D. Jeans🇯🇵 · G. W. Wilson🇺🇸

    In the Standard Model, the Higgs boson is a CP even state with CP conserving couplings; any deviations from this would be a sign of new physics. These CP properties can be probed by measuring Higgs decays to tau lepton pairs: the transverse correlation between the tau spins depends on CP. This paper develops such an analysis, using full simulation of signal and background events in the International Large Detector concept for the International Linear Collider. We consider Higgs-strahlung events e+ e- -> Z H) in which the Z boson decays to electrons, muons, or hadrons, and the Higgs boson decays to $\tau$ leptons, which then decay either to (pi+ nu) or (pi+ pi0 nu). Assuming 2 ab^{-1} of integrated luminosity at a center-of-mass energy of 250~GeV, the mixing angle psi_CP between even and odd CP components of the tau pair from Higgs boson decays can be measured to a precision of 75~mrad (4.3 deg).

    ↳ hep-exhep-phPRD(2018)·57 citations
14. 14*

    AGN outflows as neutrino sources: an observational test

    P. Padovani (1)🇩🇪 · A. Turcati (2)🇩🇪 · E. Resconi (2) ((1) ESO, (2) TUM)🇩🇪

    We test the recently proposed idea that outflows associated with Active Galactic Nuclei (AGN) could be neutrino emitters in two complementary ways. First, we cross-correlate a list of 94 "bona fide" AGN outflows with the most complete and updated repository of IceCube neutrinos currently publicly available, assembled by us for this purpose. It turns out that AGN with outflows matched to an IceCube neutrino have outflow and kinetic energy rates, and bolometric powers larger than those of AGN with outflows not matched to neutrinos. Second, we carry out a statistical analysis on a catalogue of O III 5007 line profiles using a sample of 23,264 AGN at z < 0.4, a sub-sample of which includes mostly possible outflows sources. We find no significant evidence of an association between the AGN and the IceCube events, although we get the smallest p-values (~ 6 and 18 per cent respectively, pre-trial) for relatively high velocities and luminosities. Our results are consistent with a scenario where AGN outflows are neutrino emitters but at present do not provide a significant signal. This can be tested with better statistics and source stacking. A predominant role of AGN outflows in explaining the IceCube data appears in any case to be ruled out.

    ↳ astro-ph.HEastro-ph.GAhep-exhep-phMNRAS(2018)·11 citations
15. 15*

    Dark Matter Effects On Neutron Star Properties

    John Ellis🇬🇧 · Gert Hütsi🇪🇪 · Kristjan Kannike🇪🇪 · Luca Marzola🇪🇪 · Martti Raidal🇪🇪 · Ville Vaskonen🇪🇪

    We study possible effects of a dark matter (DM) core on the maximum mass of a neutron star (NS), on the mass-radius relation and on the NS tidal deformability parameter $\Lambda$. We show that all these quantities would in general be reduced in the presence of a DM core. In particular, our calculations indicate that the presence of a DM core with a mass fraction $\sim 5\%$ could affect significantly the interpretation of these NS data as constraints on the nuclear equation of state (EOS), potentially excluding some EOS models on the basis of the measured mass of PSR J0348+0432, while allowing other EOS models to become consistent with the LIGO/Virgo upper limit on $\Lambda$. Specific scenarios for generating such DM cores are explored in an Appendix.

    ↳ astro-ph.COhep-phnucl-thPRD(2018)·231 citations
16. 16*

    On gravitational-wave echoes from neutron-star binary coalescences

    Paolo Pani🇮🇹 · Valeria Ferrari🇮🇹

    A tentative detection of gravitational-wave echoes in the post-merger signal of GW170817 has been recently claimed at $4.2\sigma$ significance level. It has been speculated that the signal might provide evidence for near-horizon quantum structures in the remnant exotic object. We point out that if the remnant object is an ultracompact neutron star, echoes are expected for objects with radius only slightly smaller than that of an ordinary neutron star. The reported echoes at ~72 Hz are compatible with a toy model of incompressible star with mass approximately $M\in (2,3)M_{\odot }$ and radius close to the Buchdahl limit, R~9GM/(4c^2). If confirmed, low-frequency gravitational-wave echoes would be in tension with all current neutron-star models and would have dramatic implications for nuclear physics and gravity.

    ↳ gr-qcastro-ph.HEhep-phClass.Quant.Grav.(2018)·69 citations
17. 17*

    First direct lattice-QCD calculation of the $x$-dependence of the pion parton distribution function

    Jian-Hui Zhang🇩🇪 · Jiunn-Wei Chen🇹🇼 · Luchang Jin🇺🇸 · Huey-Wen Lin🇺🇸 · Andreas Schäfer🇩🇪 · Yong Zhao🇺🇸

    We present the first direct lattice-QCD calculation of the Bjorken-$x$ dependence of the valence quark distribution of the pion. Using large-momentum effective theory (LaMET), we calculate the boosted pion state with long Wilson link operators. After implementing the one-loop matching and meson mass corrections, our result at $m_{\pi }\approx 310$ MeV is in agreement with those extracted from experimental data as well as from Dyson-Schwinger equation in small $x$ region, but a sizeable discrepancy in the large $x$ region. This discrepancy provides a nice opportunity to systematically study and disentangle the artifacts in the LaMET approach, which will eventually help to discern various existing analyses in the literature.

    ↳ hep-lathep-exhep-phnucl-ex+1PRD(2019)·170 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.