Tue·Apr 3, 2018Tuesday·April 3, 2018

1. 01*

   Low-energy constants of heavy meson effective theory in lattice QCD

   Mohammad H. Alhakami🇸🇦

   We consider effective theory treatment for the lowest-lying $S$- and $P$-wave states of charmed mesons. In our analysis, quantum corrections and contributions from leading chiral and heavy quark symmetry breakings are taken into account. The heavy meson mass expressions have abundance parameters, low-energy constants, in comparison to the measured charmed mesons masses. The experimental and lattice QCD data on charmed meson spectroscopy are used to extract, for the first time, the numerical values of the full set of low-energy constants of the effective chiral Lagrangian. Our results on these parameters can be used for applications on other properties of heavy-light meson systems.

   hep-phhep-latPRD(2018)·3 citations
2. 02*

   MadDM v.3.0: a Comprehensive Tool for Dark Matter Studies

   Federico Ambrogi🇦🇹 · Chiara Arina🇧🇪 · Mihailo Backovic🇧🇪 · Jan Heisig🇩🇪 · Fabio Maltoni🇧🇪 · Luca Mantani🇧🇪 · Olivier Mattelaer🇧🇪 · Gopolang Mohlabeng🇺🇸

   We present MadDM v.3.0, a numerical tool to compute particle dark matter observables in generic new physics models. The new version features a comprehensive and automated framework for dark matter searches at the interface of collider physics, astrophysics and cosmology and is deployed as a plugin of the MadGraph5_aMC@NLO platform, inheriting most of its features. With respect to the previous version, MadDM v.3.0 can now provide predictions for indirect dark matter signatures in astrophysical environments, such as the annihilation cross section at present time and the energy spectra of prompt photons, cosmic rays and neutrinos resulting from dark matter annihilation. MadDM indirect detection features support both $2\to 2$ and $2\to n$ dark matter annihilation processes. In addition, the ability to compare theoretical predictions with experimental constraints is extended by including the Fermi-LAT likelihood for gamma-ray constraints from dwarf spheroidal galaxies and by providing an interface with the nested sampling algorithm PyMultinNest to perform high dimensional parameter scans efficiently. We validate the code for a wide set of dark matter models by comparing the results from MadDM v.3.0 to existing tools and results in the literature.

   hep-phastro-ph.HEPhys.Dark Univ.(2019)·201 citations
3. 03*

   Looking for the left sneutrino LSP with displaced-vertex searches

   Inaki Lara🇪🇸 · Daniel E. Lopez-Fogliani🇦🇷 · Carlos Munoz🇪🇸 · Natsumi Nagata🇯🇵 · Hidetoshi Otono🇯🇵 · Roberto Ruiz de Austri🇪🇸

   We analyze a displaced dilepton signal expected at the LHC for a tau left sneutrino as the lightest supersymmetric particle with a mass in the range $45$-$100$ GeV. The sneutrinos are pair produced via a virtual $W$, $Z$ or $\gamma$ in the $s$ channel and, given the large value of the tau Yukawa coupling, their decays into two dileptons or a dilepton plus missing transverse energy from neutrinos can be significant. The discussion is carried out in the $\mu \nu$SSM, where the presence of $R$-parity violating couplings involving right-handed neutrinos solves the $\mu$ problem and can reproduce the neutrino data. To probe the tau left sneutrinos we compare the predictions of the $\mu \nu$SSM with the ATLAS search for long-lived particles using displaced lepton pairs in $pp$ collisions at $\sqrt{s}=8$ TeV, allowing us to constrain the parameter space of the model. We also consider an optimization of the trigger requirements used in existing displaced-vertex searches by means of a High Level Trigger that exploits tracker information. This optimization is generically useful for a light metastable particle decaying into soft charged leptons. The constraints on the sneutrino turn out to be more stringent. We finally discuss the prospects for the $13$ TeV LHC searches as well as further potential optimizations.

   hep-phPRD(2018)·30 citations
4. 04*

   Magnifying the ATLAS Stealth Stop Splinter: Impact of Spin Correlations and Finite Widths

   Timothy Cohen🇺🇸 · Walter Hopkins🇺🇸 · Stephanie Majewski🇺🇸 · Bryan Ostdiek🇺🇸

   In this paper, we recast a "stealth stop" search in the notoriously difficult region of the stop-neutralino Simplified Model parameter space for which $m(\tilde{t})-m(\tilde{\chi })\simeq m_t$. The properties of the final state are nearly identical for tops and stops, while the rate for stop pair production is $\mathcal{O}(10\%)$ of that for $t\bar{t}$. Stop searches away from this stealth region have left behind a "splinter" of open parameter space when $m(\tilde{t})\simeq m_t$. Removing this splinter requires surgical precision: the ATLAS constraint on stop pair production reinterpreted here treats the signal as a contaminant to the measurement of the top pair production cross section using data from $\sqrt{s}=7\text{ TeV}$ and $8\text{ TeV}$ in a correlated way to control for some systematic errors. ATLAS fixed $m(\tilde{t})\simeq m_t$ and $m(\tilde{\chi })=1\text{ GeV}$, implying that a careful recasting of these results into the full $m(\tilde{t})-m(\tilde{\chi })$ plane is warranted. We find that the parameter space with $m(\tilde{\chi })\lesssim 55\text{ GeV}$ is excluded for $m(\tilde{t})\simeq m_t$ --- although this search does cover new parameter space, it is unable to fully pull the splinter. Along the way, we review a variety of interesting physical issues in detail: (i) when the two-body width is a good approximation; (ii) what the impact on the total rate from taking the narrow width is a good approximation; (iii) how the production rate is affected when the wrong widths are used; (iv) what role the spin correlations play in the limits. In addition, we provide a guide to using MadGraph for implementing the full production including finite width and spin correlation effects, and we survey a variety of pitfalls one might encounter.

   hep-phhep-exJHEP(2018)·8 citations
5. 05*

   Initial State Radiation Simulation with MadGraph

   Qiang Li🇨🇳 · Qi-Shu Yan🇨🇳

   Initial State Radiation (ISR) effect is implemented in Madgraph using photon structure functions. Detailed examinations are performed against other generators including Whizard, BabayagaNLO and KKMC, for various physics processes at linear colliders such as 240GeV CEPC and 10.58GeV Belle II. ISR effects on new physics searches are also discussed, taking anomalous gauge boson coupling and dark photon as examples. An ISR plugin is made public for wide usage.

   hep-phhep-ex18 citations
6. 06*

   Direct Solution of Integration-by-Parts Systems

   David A. Kosower🇫🇷

   Systems of integration-by-parts identities play an important role in simplifying the higher-loop Feynman integrals that arise in quantum field theory. Solving these systems is equivalent to reducing integrals containing numerator products of irreducible invariants to a small set of master integrals. I present a new approach to solving these systems that finds direct reduction equations for numerator terms of a given Feynman integral. As a particular example of its power, I show how to obtain reduction equations for arbitrary powers of irreducible invariants, along with their solutions.

   hep-phPRD(2018)·71 citations
7. 07*

   Electroweak properties of octet baryons in light-cone quark-diquark model

   Jun Zhang🇨🇳 · Bo-Qiang Ma🇨🇳

   We study the electroweak properties of ground state octet baryons in a relativistic quark-spectator-diquark model, with light-front formalism applied to take relativistic effects into account. Our model provides a consistent picture of the electroweak properties of the ground state octet baryons in the low momentum transfer region. The Melosh-Wigner rotation is applied as the transformation relation between spinors in the instant form and front form. Numerical results are presented for the magnetic moments, weak transition charges and Sachs form factors. Our results are in good agreement with experimental measurements and other theoretical results.

   hep-phPRC(2016)·15 citations
8. 08*

   Assessing the Viability of $A_4$, $S_4$ and $A_5$ Flavour Symmetries for Description of Neutrino Mixing

   S. T. Petcov🇮🇹 · A. V. Titov🇬🇧

   We consider the $A_4$, $S_4$ and $A_5$ discrete lepton flavour symmetries in the case of 3-neutrino mixing, broken down to non-trivial residual symmetries in the charged lepton and neutrino sectors in such a way that at least one of them is a $Z_2$. Such symmetry breaking patterns lead to predictions for some of the three neutrino mixing angles and/or the leptonic Dirac CP violation phase $\delta$ of the neutrino mixing matrix. We assess the viability of these predictions by performing a statistical analysis which uses as an input the latest global data on the neutrino mixing parameters. We find 14 phenomenologically viable cases providing distinct predictions for some of the mixing angles and/or the Dirac phase $\delta$. Employing the current best fit values of the three neutrino mixing angles, we perform a statistical analysis of these cases taking into account the prospective uncertainties in the determination of the mixing angles, planned to be achieved in currently running (Daya Bay) and the next generation (JUNO, T2HK, DUNE) of neutrino oscillation experiments. We find that only six cases would be compatible with these prospective data. We show that this number is likely to be further reduced by a precision measurement of $\delta$.

   hep-phPRD(2018)·73 citations
9. 09*

   Mixed states for mixing neutrinos

   Gabriel Cozzella🇧🇷 · Carlo Giunti🇮🇹

   Here we discuss the description of flavor neutrinos produced or detected in processes which involve more than one neutrino. We show that in these cases flavor neutrinos cannot be separately described by pure states, but require a density matrix description. We consider explicitly the examples of ${\nu }_e$ and ${\bar{\nu }}_{\mu }$ production in ${\mu }^{+}$ decay and ${\nu }_{\mu }$ detection through scattering on electrons. We show that the density matrix which describes a flavor neutrino can be approximated with a density matrix of a pure state only when the differences of the neutrino masses are neglected in the interaction process. In this approximation, the pure states are the standard flavor states and one recovers the standard expression for the neutrino oscillation probability. We discuss also the effects of mixing of the three standard light neutrinos with heavy neutrinos which can be either decoupled because their masses are much larger than the maximum neutrino energy in the neutrino production process or because they are produced and detected incoherently. Finally, we discuss the more complicated case of neutrino-electron elastic scattering, in which the initial and final neutrinos do not have determined flavors, but there is a flavor dependence due to the different contributions of charged-current and neutral-current interactions.

   hep-phhep-exPRD(2018)·10 citations
10. 10*

    Non-hydrodynamic quasinormal modes and equilibration of a baryon dense holographic QGP with a critical point

    Romulo Rougemont (IIP, Brazil)🇧🇷 · Renato Critelli (Sao Paulo U.)🇧🇷 · Jorge Noronha (Sao Paulo U.)🇧🇷

    We compute the homogeneous limit of non-hydrodynamic quasinormal modes (QNM's) of a phenomenologically realistic Einstein-Maxwell-Dilaton (EMD) holographic model for the Quark-Gluon Plasma (QGP) that is able to: i) {\it quantitatively} describe state-of-the-art lattice results for the QCD equation of state and higher order baryon susceptibilities with $2+1$ flavors and physical quark masses up to highest values of the baryon chemical potential currently reached in lattice simulations; ii) describe the nearly perfect fluidity of the strongly coupled QGP produced in ultrarelativistic heavy ion collisions; iii) give a very good description of the bulk viscosity extracted via some recent Bayesian analyzes of hydrodynamical descriptions of heavy ion experimental data. This EMD model has been recently used to predict the location of the QCD critical point in the QCD phase diagram, which was found to be within the reach of upcoming low energy heavy ion collisions. The lowest quasinormal modes of the $SO(3)$ rotationally invariant quintuplet, triplet, and singlet channels evaluated in the present work provide upper bounds for characteristic equilibration times describing how fast the dense medium returns to thermal equilibrium after being subjected to small disturbances. We find that the equilibration times in the different channels come closer to each other at high temperatures, although being well separated at the critical point. Moreover, in most cases, these equilibration times decrease with increasing baryon chemical potential while keeping temperature fixed.

    hep-phhep-thnucl-thPRD(2018)·26 citations
11. 11*

    Realization of Sneutrino Self-interacting Dark Matter in the Focus Point Supersymmetry

    Bin Zhu🇨🇳 · Ran Ding🇨🇳 · Ying Li🇨🇳

    The Lightest Supersymmetric Particle (LSP) is generally regarded as higgsino in focus point supersymmetry (SUSY). Under such circumstance it leads to bileptino LSP when the MSSM is extended by $U(1{)}_{B-L}$ gauge group within the framework of Double Focus Point (DFP) supersymmetry. The bileptino is a copy of higgsino whose partner, bilepton, is used to break $U(1{)}_{B-L}$ gauge symmetry spontaneously. Such scenario, however, is not favored by direct detection since it leads to unacceptable spin-independent cross section when one requires correct self-scattering cross section. We point out that is not necessarily the case even in the presence of light $Z^{\prime }$. The right-handed sneutrino in this model acts as LSP in most of parameter space for non-vanishing soft trilinear coupling $T_{\eta }$. It is thus consistent of the requirement of DFP SUSY without involving any direct detection issue. The corrected relic abundance could be achieved via sneutrino annihilate into pair of bilepton which also serve as light mediator in Self-Interacting Dark Matter (SIDM). Moreover, stringent constraint comes from CMB anisotropies can be evaded by considering retarded decay of right-handed neutrinos. We further stress the need for a large soft trilinear term $T_{\eta }$ in order to generate desirable self-scattering cross section $\sigma /m_{{\tilde{\nu }}_R}$ with moderate Yukawa coupling $Y_{\eta }$. The numerical calculation illustrates that SIDM is reliable in our model from the scales of dwarf galaxy to galaxy cluster.

    hep-phPRD(2018)·5 citations
12. 12*

    A study about the F-estimator for the neutrino mass hierarchy in the JUNO experiment

    Sara Leardini🇮🇹

    At present, it is still unknown whether the correct mass ordering of the neutrino mass eigenstates is either $m_1$, $m_2$, $m_3$ (Normal Hierarchy, NH), or $m_3$, $m_1$, $m_2$ (Inverted Hierarchy, IH). The new analysis method proposed by Stanco et al. (arXiv:1707.07651v3) should fix some issues of the currently most used estimator, $\Delta {\chi }^2$, and make it possible to reach $5\sigma$ measurements in less than six years of data taking with JUNO (Jiangmen Underground Neutrino Observatory) if a degeneracy in the atmospheric mass, $\Delta m_{atm}^2$, is accepted. In this note, the analysis introduced in the paper above was extended to more detailed studies on the dependence of the new F estimator to $\Delta m_{atm}^2$. A fit to the values of the new estimator as a function of $\Delta m_{atm}^2$, calculated for both the true hierarchy and the wrong hierarchy, was performed. The study of the fitting function showed that the average minimum counts, corresponding to the best value for $\Delta m_{atm}^2$, either for the true hierarchy or for the wrong hierarchy, are well separated, and allow to distinguish easily between NH and IH.

    hep-phphysics.data-an0 citations
13. 13*

    Dark SU(2) Antecedents of the U(1) Higgs Model

    Ernest Ma (UC Riverside and HKUST-JCIAS)🇺🇸

    The original spontaneously broken U(1) gauge model with one complex Higgs scalar field has been known in recent years as a possible prototype dark-matter model. Its antecedents in the context of SU(2) are discussed. Three specific examples are described, with one dubbed "quantum scotodynamics".

    hep-phLHEP(2018)·3 citations
14. 14*

    Threshold Effects and the Line Shape of the X(3872) in Effective Field Theory

    M. Schmidt🇩🇪 · M. Jansen🇩🇪 · H.-W. Hammer🇩🇪

    Latest measurements suggest that the X(3872) mass lies less than 200 keV away from the D0-Dbar0* threshold, reenforcing its interpretation as a loosely-bound mesonic molecule. This observation implies that in processes like D0-Dbar0-pi0 production, threshold effects could disguise the actual pole position of the X(3872). We propose a new effective field theory with D0, Dbar0 and pi0 degrees of freedom for the X(3872), considering Galilean invariance to be an exact symmetry. The D0* enters as a D0-pi0 p-wave resonance, allowing for a comprehensive study of the influence of pion interactions on the X(3872) width. We calculate relations between the mass of the X(3872), its width, and its line shape in D0-Dbar0-pi0 production up to next-to-leading order. Our results provide a tool for the extraction of the X(3872) pole position from the experimental data near threshold.

    hep-phPRD(2018)·22 citations
15. 15*

    Boosted Higgs-pair production associated with large $E_T^{miss}$: a signal of $Z^{\prime }$

    Chuan-Ren Chen🇹🇼 · Yu-Xiang Lin🇹🇼 · Hsien-Chih Wu🇹🇼 · Jason Yue🇹🇼

    Non-resonant production of Higgs-pair via heavy intermediate states may be a distinctive signature for extended discrete symmetries when accompaied by large missing transvers energy. We discuss $T$-parity as an example of such symmetry within the Littlest Higgs Model, where a new heavy gauge boson $Z^{\prime }$, the $T$-odd partner of SM $Z$-boson, predominately decays into to a Higgs boson and a dark matter candidate $\chi$. In essence, $T$-parity stablises simultaneously both the Higgs mass and the dark matter. Production via $pp\to Z^{\prime }{Z}^{\prime }\to 2h2\chi$ may therefore yield important clues about symmetries connecting the Higgs and dark sectors. This paper makes a case for the search for this channel at the LHC by studying its discovery potential. It is demonstrated that in situations where a large $Z^{\prime }-\chi$ mass gap results in a boosted topology, the jet-substructure technique can be leveraged to reach the required significance for discovery in the $2h\to 2\gamma 2b$ decay mode.

    hep-ph3 citations
16. 16*

    The NRQED Hamiltonian and photon-exchange interaction up to $m{\alpha }^8$ order

    Wanping Zhou🇨🇳 · Xuesong Mei🇨🇳 · Haoxue Qiao🇨🇳

    We derive the effective Hamiltonian of the Nonrelativistic Quantum Electrodynamic up to $m{\alpha }^8$ by using scattering matching approach. At $m{\alpha }^6$ order, these results are coincide with Pachucki's, which is obtained by applying Foldy-Wouthuysen transformation. And by using the NRQED Hamiltonian, we derive the photon-exchange interaction in non-retarded approximation and the retardation correction up to $m{\alpha }^8$. The energy shift of the photon-exchange interaction is obtained by studying the pole of the total Green function.

    hep-ph0 citations
17. 17*

    Reflective scattering mode interpretation

    S.M. Troshin🇷🇺 · N.E. Tyurin🇷🇺

    This note is devoted to discussion of the reflective scattering mode. This mode connection to the color conducting medium formed under hadron collisions is proposed.

    hep-ph0 citations
18. 18*

    The decays $B_c\to J/\psi +\bar{\ell }{\nu }_{\ell }$ and $B_c\to J/\psi +\pi (K)$ in covariant confined quark model

    Aidos Issadykov🇷🇺 · Mikhail A. Ivanov🇷🇺

    In the wake of the recent measurements of the decays $B_c\to J/\psi \pi (K)$ and $B_c\to J/\psi \ell {\nu }_{\ell }$ reported by the LHCb Collaboration we calculate the form factors for the $B_c\to J/\psi$ and $B_c\to {\eta }_c$ transitions in full kinematical region within covariant confined quark model. Then we use the calculated form factors to evaluate the partial decay widths of the above-mentioned semileptonic and nonleptonic decays of the $B_c$ meson. We find that the theoretical predictions on the ratios of ${\mathcal{R}}_{K^{+}/{\pi }^{+}}$ and ${\mathcal{R}}_{{\pi }^{+}/{\mu }^{+}\nu }$ are in good agreement with last LHCb-data. However, the prediction for the ${\mathcal{R}}_{J/\psi }$ is found to be underestimated.

    hep-phPLB(2018)·67 citations
19. 19*

    $D$ wave charmonia

    Dian-Yong Chen🇨🇳 · Cheng-Qun Pang🇨🇳 · Jun He🇨🇳 · Zhi-Yong Zhou🇨🇳

    Inspired by the recent observations of the vector charmonium-like states at BES III Collaboration and $\psi (3842)$ at LHCb Collaboration, we comb the $D$ wave charmonium state in the present work. We first evaluate the possibility of $Y(4320)$ as $\psi (3^3{D}_1)$ by investigating its open charm decays in quark-pair creation model and we find the width of $Y(4320)$ can be reproduced in a reasonable parameter range. Moreover, we take $\psi (3770)$, $\psi (4160)$ and $Y(4320)$ as the scale of $1D$, $2D$ and $3D$ charmonia to estimate the open charm decays of other $D$ wave charmonia. The total and partial widths of $D$ wave charmonium states have been predicted, which could be tested by further measurements at LHCb and Belle II Collaborations.

    hep-phhep-exPRD(2019)·6 citations
20. 20*

    Anisotropic equation of state of charged and neutral vector boson gases in a constant magnetic field. Astrophysical implications

    G. Quintero Angulo🇨🇺 · A. Pérez Martínez🇨🇺 · H. Pérez Rojas🇨🇺

    We obtain the pressures and equations of state (EoS) of charged and neutral vector boson gases in a constant magnetic field. The axial symmetry imposed to the system by the field splits the pressures in the parallel and perpendicular directions along the magnetic axis, and this leads to anisotropic equations of state. The values of pressures and energy densities are in the order of those of Fermi gases in compact objects. This opens the possibility to the existence of magnetized boson stars. Under certain conditions, the perpendicular pressure might be negative imposing a bound to the stability of the star. Other implications of negative pressures are also discussed.

    hep-phAstron.Nachr./AN.2017.201713448·0 citations
21. 21*

    Dark Sectors at the Fermilab SeaQuest Experiment

    Asher Berlin🇺🇸 · Stefania Gori🇺🇸 · Philip Schuster🇺🇸 · Natalia Toro🇺🇸

    We analyze the unique capability of the existing SeaQuest experiment at Fermilab to discover well-motivated dark sector physics by measuring displaced electron, photon, and hadron decay signals behind a compact shield. A planned installation of a refurbished electromagnetic calorimeter could provide powerful new sensitivity to GeV-scale vectors, dark Higgs bosons, scalars, axions, and inelastic and strongly interacting dark matter models. This sensitivity is both comparable and complementary to NA62, SHiP, and FASER. SeaQuest's ability to collect data now and over the next few years provides an especially exciting opportunity.

    hep-phhep-exPRD(2018)·241 citations
22. 22*

    Dualities in dense quark matter with isospin, chiral and chiral isospin imbalance in the framework of the large-N${}_c$ limit of the NJL${}_4$ model

    T. G. Khunjua🇷🇺 · K. G. Klimenko🇷🇺 · R. N. Zhokhov🇷🇺

    In this paper the phase structure of the dense quark matter has been investigated in the presence of baryon ${\mu }_B$, isospin ${\mu }_I$, chiral ${\mu }_5$ and chiral isospin ${\mu }_{I5}$ chemical potentials in the framework of Nambu--Jona-Lasinio model. It has been shown that in the large-$N_c$ limit ($N_c$ is the number of quark colours) there exist three duality correspondences in the model. The first duality is between the chiral symmetry breaking and the charged pion condensation phenomena. And there are two new dualities that hold only for chiral symmetry breaking and charged pion condensation phenomena separately. It was shown that at nonzero chiral ${\mu }_5$ chemical potential chiral isospin ${\mu }_{I5}$ chemical potential can generate charged pion condensation in dense quark matter even with zero ${\mu }_I$. But ${\mu }_5$ alone (in absence of ${\mu }_{I5}$ chemical potential) can generate this phase but not as powerfully as ${\mu }_{I5}$ does and only at comparatively low baryon densities.

    hep-phhep-thPRD(2018)·50 citations
23. 23*

    Equipartition Dark Energy

    Weipeng Lin🇨🇳 · Zhiqi Huang🇨🇳 · Yiming Hu🇨🇳 · Shuang Wang🇨🇳 · Yi-Jung Yang🇹🇼

    We explain dark energy with equipartition theorem in string landscape.

    ↳ astro-ph.COgr-qchep-phhep-th0 citations
24. 24*

    Dark Matter Distribution Induced by a Cosmic String Wake in the Nonlinear Regime

    Disrael Cunha🇨🇦 · Joachim Harnois-Deraps🇬🇧 · Robert Brandenberger🇨🇦 · Adam Amara🇨🇭 · Alexandre Refregier🇨🇭

    We study the distribution of dark matter in the nonlinear regime in a model in which the primordial fluctuations include, in addition to the dominant primordial Gaussian fluctuations generated by the standard $\Lambda CDM$ cosmological model, the effects of a cosmic string wake set up at the time of equal matter and radiation, making use of cosmological $N$-body simulations. At early times the string wake leads to a planar overdensity of dark matter. We study how this non-Gaussian pattern of a cosmic string wake evolves in the presence of the Gaussian perturbations, making use of wavelet and ridgelet-like statistics specifically designed to extract string wake signals. At late times the Gaussian fluctuations disrupt the string wake. We find that for a string tension of $G\mu =10^{-7}$, a value just below the current observational limit, the effects of a string wake can be identified in the dark matter distribution, using the current level of the statistical analysis, down to a redshift of $z=10$.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2018)·17 citations
25. 25*

    SENSEI: First Direct-Detection Constraints on sub-GeV Dark Matter from a Surface Run

    The SENSEI Collaboration: Michael Crisler🇺🇸 · Rouven Essig🇺🇸 · Juan Estrada🇺🇸 · Guillermo Fernandez🇺🇸 · Javier Tiffenberg🇺🇸 · Miguel Sofo Haro🇺🇸 · Tomer Volansky🇮🇱 · Tien-Tien Yu🇺🇸

    The Sub-Electron-Noise Skipper CCD Experimental Instrument (SENSEI) uses the recently developed Skipper-CCD technology to search for electron recoils from the interaction of sub-GeV dark matter particles with electrons in silicon. We report first results from a prototype SENSEI detector, which collected 0.019 gram-days of commissioning data above ground at Fermi National Accelerator Laboratory. These commissioning data are sufficient to set new direct-detection constraints for dark matter particles with masses between ~500 keV and 4 MeV. Moreover, since these data were taken on the surface, they disfavor previously allowed strongly interacting dark matter particles with masses between ~500 keV and a few hundred MeV. We discuss the implications of these data for several dark matter candidates, including one model proposed to explain the anomalously large 21-cm signal observed by the EDGES Collaboration. SENSEI is the first experiment dedicated to the search for electron recoils from dark matter, and these results demonstrate the power of the Skipper-CCD technology for dark matter searches.

    ↳ hep-exastro-ph.COhep-phPRL(2018)·259 citations
26. 26*

    Gravitational Friedel oscillations in higher-derivative and infinite-derivative gravity?

    Jens Boos🇨🇦

    When a positively charged impurity is placed inside a cold metal, the resulting charge density around that object exhibits characteristic ripples to negative values, known as Friedel oscillations. In this essay, we describe a somewhat analogous effect in (i) linearized higher-derivative gravity and (ii) linearized infinite-derivative "ghost-free" gravity: when a gravitational impurity (point particle) is placed in Minkowski vacuum, the local energy density $\rho \equiv G{}_{\mu \nu }\xi {}^{\mu }\xi {}^{\nu }$ (with $\xi ={\partial }_t$) exhibits oscillations to negative values. The wavelength of these oscillations is roughly given by (i) the Pauli--Villars regularization scale and (ii) the scale of non-locality. We hence dub this phenomenon gravitational Friedel oscillations.

    ↳ gr-qccond-mat.otherhep-phInt.J.Mod.Phys.D(2018)·24 citations
27. 27*

    A pseudo-conformal equation of state in compact-star matter from topology change and hidden symmetries of QCD

    Yong-Liang Ma🇨🇳 · Hyun Kyu Lee🇰🇷 · Won-Gi Paeng🇰🇷 · Mannque Rho🇫🇷

    We construct a new effective field theory approach to the equation of state (EoS), dubbed pseudo-confomal model "PCM," for nuclear and compact star matter entirely in terms of effective hadron degrees of freedom. The possible transition at $n\sim (2-4)n_0$ (where $n_0$ is the normal nuclear matter density) from hadron degrees of freedom to strongly-coupled quark degrees of freedom, giving rise to a soft-to-hard changeover in the EoS that can accommodate the massive stars observed, is effectuated by the topology change at $n_{1/2}\text{gsim}2n_0$ from skyrmions to half-skyrmions without involving local order-parameter fields. The mechanism exploits possible emergence of hidden scale and local symmetries of QCD at high density, leading to a precocious "pseudo-conformal" sound velocity $v_s^2=1/3$ (in unit of $c=1$) for $n\text{gsim}3n_0$. The resulting prediction signals a drastic departure from standard nuclear many-body theory in the density regime involved in the massive stars. We suggest that the tidal deformability implemented in gravitational waves coming from coalescing neutron stars in LIGO/Virgo-type observations could pin down the location of the topology change density $n_{1/2}$.

    ↳ nucl-thastro-ph.HEhep-phSCPMA(2019)·24 citations
28. 28*

    The Non-Quenching of $g_A$ in Nuclei and Emergent Scale Symmetry in Dense Baryonic Matter

    Yan-Ling Li🇨🇳 · Yong-Liang Ma🇨🇳 · Mannque Rho🇫🇷

    How the axial coupling constant $g_A$ in nuclear Gamow-Teller transitions described in shell model gets "quenched" to a universal constant close to 1 can be explained by nuclear correlations in Fermi-liquid fixed point theory using a scale-symmetric chiral Lagrangian supplemented with hidden local symmetric vector mesons. Contrary to what one might naively suspect -- and has been discussed in some circles, there is no fundamental quenching at nuclear matter density due to QCD condensates. When the density of many-body systems treated with the same Lagrangian increases beyond the density $n=n_{1/2}\text{gsim}2n_0$ (where $n_0$ is the normal nuclear matter density) at which skyrmions representing baryons fractionize to half-skyrmions, with the $\rho$ meson driven toward the vector manifestation fixed point and a scalar meson $\sigma$ driven to the dilaton-limit fixed point with the nucleons parity-doubled, the dense matter supports the "pseudo-conformal" sound velocity for $n\text{gsim}{n}_{1/2}$ while the trace of the energy momentum tensor remains non-vanishing. A plausible interpretation is that this signals the emergence of scale symmetry not explicitly present or hidden in QCD in the vacuum. The fundamental constant $g_A$, unaffected by QCD condensates for $n<n_{1/2}$, does go to 1 as the dilaton-limit fixed point is approached before arriving at chiral restoration, but it is not directly related to the "quenched $g_A$" in nuclei which can be explained as a Fermi-liquid fixed point quantity. The mechanism that produces a precocious pseudo-conformal sound velocity is expected to impact on the tidal deformability $\Lambda$ in gravity waves from coalescing neutron stars.

    ↳ nucl-thhep-phPRC(2018)·12 citations
29. 29*

    The 1.5 Ms Observing Campaign on IRAS 13224-3809: X-ray Spectral Analysis I

    J. Jiang · M. L. Parker · A. C. Fabian🇬🇧 · W. N. Alston · D. J. K. Buisson · E. M. Cackett · C.-Y. Chiang · T. Dauser · L. C. Gallo · J. A. García · F. A. Harrison · A. M. Lohfink and 7 other authors

    We present a detailed spectral analysis of the recent 1.5\,Ms XMM-Newton observing campaign on the narrow line Seyfert 1 galaxy IRAS~13224$-$3809, taken simultaneously with 500\,ks of NuSTAR data. The X-ray lightcurve shows three flux peaks, registering at about 100 times the minimum flux seen during the campaign, and rapid variability with a time scale of kiloseconds. The spectra are well fit with a primary powerlaw continuum, two relativistic-blurred reflection components from the inner accretion disk with very high iron abundance, and a simple blackbody-shaped model for the remaining soft excess. The spectral variability is dominated by the power law continuum from a corona region within a few gravitational radii from the black hole. Additionally, blueshifted Ne \textsc{x}, Mg \textsc{xii}, Si \textsc{xiv} and S \textsc{xvi} absorption lines are identified in the stacked low-flux spectrum, confirming the presence of a highly ionized outflow with velocity up to $v=0.267$ and $0.225$\,c. We fit the absorption features with \texttt{xstar} models and find a relatively constant velocity outflow through the whole observation. Finally, we replace the \texttt{bbody} and supersolar abundance reflection models by fitting the soft excess successfully with the extended reflection model \texttt{relxillD}, which allows for higher densities than the standard \texttt{relxill} model. This returns a disk electron density $n_{\mathrm{e}}>10^{18.7}$\,cm${}^{-3}$ and lowers the iron abundance from $Z_{\mathrm{Fe}}=24_{-4}^{+3}{Z}_{\odot }$ with $n_{\mathrm{e}}\equiv 10^{15}$\,cm${}^{-3}$ to $Z_{\mathrm{Fe}}=6.6_{-2.1}^{+0.8}{Z}_{\odot }$.

    ↳ astro-ph.HEhep-phMNRAS(2018)·93 citations
30. 30*

    Inflation in the Mixed Higgs-$R^2$ Model

    Minxi He🇯🇵 · Alexei A. Starobinsky🇯🇵 · Jun'ichi Yokoyama🇯🇵

    We analyze a two-field inflationary model consisting of the Ricci scalar squared ($R^2$) term and the standard Higgs field non-minimally coupled to gravity in addition to the Einstein $R$ term. Detailed analysis of the power spectrum of this model with mass hierarchy is presented, and we find that one can describe this model as an effective single-field model in the slow-roll regime with a modified sound speed. The scalar spectral index predicted by this model coincides with those given by the $R^2$ inflation and the Higgs inflation implying that there is a close relation between this model and the $R^2$ inflation already in the original (Jordan) frame. For a typical value of the self-coupling of the standard Higgs field at the high energy scale of inflation, the role of the Higgs field in parameter space involved is to modify the scalaron mass, so that the original mass parameter in the $R^2$ inflation can deviate from its standard value when non-minimal coupling between the Ricci scalar and the Higgs field is large enough.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2018)·131 citations
31. 31*

    Conversion of Gravitons into Dark Photons in Cosmological Dark Magnetic Fields

    Emi Masaki🇯🇵 · Jiro Soda🇯🇵

    It is well known that gravitons can convert into photons, and vice versa, in the presence of cosmological magnetic fields. We study this conversion process in the context of atomic dark matter scenario. In this scenario, we can expect cosmological dark magnetic fields, which are free from the stringent constraint from the cosmic microwave observations. We find that gravitons can effectively convert into dark photons in the presence of cosmological dark magnetic fields. The graviton-dark photon conversion effect may open up a new window for ultra high frequency gravitational waves.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2018)·17 citations
32. 32*

    Quantum no-scale regimes and moduli dynamics

    Thibaut Coudarchet🇫🇷 · Herve Partouche🇫🇷

    We analyze quantum no-scale regimes (QNSR) in perturbative heterotic string compactified on tori, with total spontaneous breaking of supersymmetry. We show that for marginal deformations initially at any point in moduli space, the dynamics of a flat, homogeneous and isotropic universe can always be attracted to a QNSR. This happens independently of the characteristics of the 1-loop effective potential $V_{1-loop}$, which can be initially positive, negative or vanishing, and maximal, minimal or at a saddle point. In all cases, the classical no-scale structure is restored at the quantum level, during the cosmological evolution. This is shown analytically by considering moduli evolutions entirely in the vicinity of their initial values. Global attractor mechanisms are analyzed numerically and depend drastically on the sign of $V_{1-loop}$. We find that all initially expanding cosmological evolutions along which $V_{1-loop}$ is positive are attracted to the QNSR describing a flat, ever-expanding universe. On the contrary, when $V_{1-loop}$ can reach negative values, the expansion comes to a halt and the universe eventually collapses into a Big Crunch, unless the initial conditions are tuned in a tiny region of the phase space. This suggests that flat, ever-expanding universes with positive potentials are way more natural than their counterparts with negative potentials.

    ↳ hep-thgr-qchep-phNPB(2018)·32 citations
33. 33*

    Medium-induced gluon emission via transverse and longitudinal scattering in dense nuclear matter

    Le Zhang🇨🇳 · De-Fu Hou🇨🇳 · Guang-You Qin🇨🇳

    We study the medium-induced gluon emission from a hard quark jet traversing the dense nuclear matter within the framework of deep inelastic scattering off a large nucleus. We extend the previous work and compute the single gluon emission spectrum including both transverse and longitudinal momentum exchanges between the hard jet parton and the medium constituents. On the other hand, with only transverse scattering and using static scattering centers for the traversed medium, our induced gluon emission spectrum in the soft gluon limit reduces to the Gyulassy-Levai-Vitev one-rescattering-one-emission formula.

    ↳ nucl-thhep-phnucl-exPRC(2018)·9 citations
34. 34*

    Odd-parity stability of hairy black holes in $U(1)$ gauge-invariant scalar-vector-tensor theories

    Lavinia Heisenberg🇨🇭 · Ryotaro Kase🇯🇵 · Shinji Tsujikawa🇯🇵

    In scalar-vector-tensor theories with $U(1)$ gauge invariance, it was recently shown that there exists a new type of hairy black hole (BH) solutions induced by a cubic-order scalar-vector interaction. In this paper, we derive conditions for the absence of ghosts and Laplacian instabilities against odd-parity perturbations on a static and spherically symmetric background for most general $U(1)$ gauge-invariant scalar-vector-tensor theories with second-order equations of motion. We apply those conditions to hairy BH solutions arising from the cubic-order coupling and show that the odd-parity stability in the gravity sector is always ensured outside the event horizon with the speed of gravity equivalent to that of light. We also study the case in which quartic-order interactions are present in addition to the cubic coupling and obtain conditions under which black holes are stable against odd-parity perturbations.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2018)·18 citations
35. 35*

    Event patterns from negative pion spectra in proton-proton and nucleus-nucleus collisions at SPS

    Ya-Hui Chen🇨🇳 · Fu-Hu Liu🇨🇳 · Edward K. Sarkisyan-Grinbaum🇨🇭

    Rapidity-dependent transverse momentum spectra of negatively charged pions measured at different rapidities in proton-proton collisions at the Super Proton Synchrotron (SPS) at various energies within its Beam Energy Scan (BES) program are investigated by using one- and two-component standard distributions where the chemical potential and spin property of particles are implemented. The rapidity spectra are described by a double-Gaussian distribution. At the stage of kinetic freeze-out, the event patterns are structured by the scatter plots in the three-dimensional subspaces of velocity, momentum and rapidity. The results of the studies of the rapidity-independent transverse mass spectra measured at mid-rapidity in proton-proton collisions are compared with those based on the similar transverse mass spectra measured in the most central beryllium-beryllium, argon-scandium and lead-lead collisions from the SPS at its BES energies.

    ↳ nucl-thhep-exhep-phnucl-exCPC(2018)·4 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.