Thu·Jul 19, 2018Thursday·July 19, 2018

1. 01*

   On the Cutoff Dependence of the Quark Mass Parameter in Angular Ordered Parton Showers

   André H. Hoang🇦🇹 · Simon Plätzer🇦🇹 · Daniel Samitz🇦🇹

   We show that the presence of an infrared cutoff $Q_0$ in the parton shower (PS) evolution for massive quarks implies that the generator quark mass corresponds to a $Q_0$-dependent short-distance mass scheme and is therefore not the pole mass. Our analysis considers an angular ordered parton shower based on the coherent branching formalism for quasi-collinear stable heavy quarks and splitting functions at next-to-leading logarithmic (NLL) order, and it is based on the analysis of the peak of hemisphere jet mass distributions. We show that NLL shower evolution is sufficient to describe the peak jet mass at full next-to-leading order (NLO). We determine the relation of this short-distance mass to the pole mass at NLO. We also show that the shower cut $Q_0$ affects soft radiation in a universal way for massless and quasi-collinear massive quark production. The basis of our analysis is (i) an analytic solution of the PS evolution based on the coherent branching formalism, (ii) an implementation of the infrared cut $Q_0$ of the angular ordered shower into factorized analytic calculations in the framework of Soft-Collinear-Effective-Theory (SCET) and (iii) the dependence of the peak of the jet mass distribution on the shower cut. Numerical comparisons to simulations with the HERWIG 7 event generator confirm our findings. Our analysis provides an important step towards a full understanding concerning the interpretation of top quark mass measurements based on direct reconstruction.

   hep-phhep-exJHEP(2018)·102 citations
2. 02*

   Clockworking FIMPs

   Andreas Goudelis🇫🇷 · Kirtimaan A Mohan🇺🇸 · Dipan Sengupta🇺🇸

   We study freeze-in dark matter production in models that rely on the Clockwork mechanism to suppress the dark matter couplings to the visible sector. We construct viable scalar and fermionic dark matter models within this Clockwork FIMP scenario, with several subtleties that need to be taken into account revealed in the model-building process. We also provide analytic, semi-analytic and numerical results for the diagonalization of Clockwork-type mass matrices and briefly discuss the LHC phenomenology of the corresponding scenarios.

   hep-phJHEP(2018)·39 citations
3. 03*

   Impact of the 125 GeV Higgs boson on the singlet fermion dark matter searches at the LHC

   P. Ko🇰🇷 · Gang Li🇹🇼 · Jinmian Li🇰🇷

   The search for singlet fermion dark matter at high-energy colliders is commonly analyzed with a singlet scalar mediator, which however violates the standard model (SM) gauge invariance, renormalizability and unitarity. These problems can be cured by introducing a mixing between the singlet scalar $s$ and the SM Higgs boson $h$. Thus one has to consider two scalar mediators $h_1$ and $h_2$, where $h_1$ is identified as the discovered 125 GeV Higgs boson. As a specific example, we consider the dark matter (DM) search in the $t\bar{t}+E_T^{\text{miss}}$ channel. According to the masses of dark matter and two scalar mediators, we classify the process into four cases. By investigating the total cross sections and differential distributions, we find that the contribution of the 125~GeV Higgs boson $h_1$ cannot be neglected in all cases and can even dominate once $h_1$ is on-shell in dark matter production. Further, we study the impact of $h_1$ on the LHC bounds of dark matter searches in the hadronic and semileptonic channels with the integrated luminosity of $36{\text{fb}}^{-1}$. Finally we make a brief comment that $h_1$ should be also considered in the vector DM search at high-energy colliders.

   hep-phhep-exPRD(2018)·5 citations
4. 04*

   B-field induced mixing between Langmuir waves and axions

   Luca Visinelli🇨🇳 · Hugo Terças🇵🇹

   We present an analytic study of the dispersion relation for an isotropic magnetized plasma interacting with axions. We provide a quantitative picture of the electromagnetic plasma oscillations in both the ultrarelativistic and nonrelativistic regimes and considering both non-degenerate and degenerate media, accounting for the dispersion curves as a function of the plasma temperature and the ratio of the plasma phase velocity to the characteristic velocity of particles. We include the modifications on the Landau damping of plasma waves induced by the presence of the axion field, and we comment on the effects of damping on subluminal plasma oscillations.

   hep-phPRD(2022)·18 citations
5. 05*

   Role of system size on freezeout conditions extracted from transverse momentum spectra of hadrons

   Ajay Kumar Dash🇮🇳 · Ranbir Singh🇮🇳 · Sandeep Chatterjee🇵🇱 · Chitrasen Jena🇮🇳 · Bedangadas Mohanty🇮🇳

   The data on hadron transverse momentum spectra in different centrality classes of p+Pb collisions at ${\sqrt{s}}_{NN}=5.02$ TeV has been analysed to extract the freezeout hypersurface within a simultaneous chemical and kinetic freezeout scenario. The freezeout hypersurface has been extracted for three different freezeout schemes that differ in the way strangeness is treated: i. unified freezeout for all hadrons in complete thermal equilibrium (1FO), ii. unified freezeout for all hadrons with an additional parameter ${\gamma }_S$ which accounts for possible out-of-equilibrium production of strangeness (1FO$+{\gamma }_S$), and iii. separate freezeout for hadrons with and without strangeness content (2FO). Unlike in heavy ion collisions where 2FO performs best in describing the mean hadron yields as well as the transverse momentum spectra, in p+Pb we find that 1FO$+{\gamma }_S$ with one less parameter than 2FO performs better. This confirms expectations from previous analysis on the system size dependence in the freezeout scheme with mean hadron yields: while heavy ion collisions that are dominated by constituent interactions prefer 2FO, smaller collision systems like proton + nucleus and proton + proton collisions with lesser constituent interaction prefer a unified freezeout scheme with varying degree of strangeness equilibration.

   hep-phnucl-thPRC(2018)·4 citations
6. 06*

   The Matrix Element Method at next-to-leading order QCD using the example of single top-quark production at the LHC

   Till Martini🇩🇪

   Analyses in high energy physics aim to put the Standard Model---the commonly accepted theory---to test. For convincing conclusions, analysis methods are needed which offer an unambiguous comparison between data and theory while allowing reliable estimates of uncertainties. The Matrix Element Method (MEM) is a Maximum Likelihood method which is especially tailored for signal searches and parameter estimation at colliders. The MEM has proven to be beneficial due to optimal use of the available information and a clean statistical interpretation of the results. But it has a big drawback: In its original formulation, the likelihood calculation is intrinsically limited to the leading perturbative order in the coupling. Higher-order corrections improve the accuracy of theoretical predictions and allow for unambiguous field-theoretical interpretation of the extracted information. In this work, the MEM incorporating corrections of next-to-leading order (NLO) in QCD by defining event weights suited for the likelihood calculation is presented for the first time. These weights also enable the generation of unweighted events following the cross section calculated at NLO accuracy. The method is demonstrated for top-quark events. The top-quark mass is determined with the MEM at NLO accuracy from the generated events. The extracted estimators are in agreement with the input values from the event generation. Repeating the mass determinations from the same events, without NLO corrections in the predictions, results in biased estimators. These shifts may not be accounted for by estimated theoretical uncertainties rendering the estimation of the theoretical uncertainties unreliable in the leading-order analysis. The results emphasise the importance of the inclusion of NLO corrections into the MEM.

   hep-phhep-ex3 citations
7. 07*

   Two-loop corrections to Starobinsky-Higgs inflation

   D. M. Ghilencea🇷🇴

   Higgs inflation and $R^2$-inflation (Starobinsky model) are two limits of the same quantum model, hereafter called Starobinsky-Higgs. We analyse the two-loop action of the Higgs-like scalar $\varphi$ in the presence of: 1) non-minimal coupling ($\xi$) and 2) quadratic curvature terms. The latter are generated at the quantum level with $\varphi$-dependent couplings ($\tilde{\alpha }$) even if their tree-level couplings ($\alpha$) are tuned to zero. Therefore, the potential always depends on both Higgs field $\varphi$ and scalaron $\rho$, hence multi-field inflation is a quantum consequence. The effects of the quantum (one- and two-loop) corrections on the potential $\hat{W}(\varphi ,\rho )$ and on the spectral index are discussed, showing that the Starobinsky-Higgs model is in general stable in their presence. Two special cases are also considered: first, for a large $\xi$ in the quantum action one can integrate $\varphi$ and generate a "refined" Starobinsky model which contains additional terms ${\xi }^2{R}^2{\ln }^p(\xi |R|/{\mu }^2)$, $p=1,2$ ($\mu$ is the subtraction scale). These generate corrections linear in the scalaron to the "usual" Starobinsky potential and a "running" scalaron mass. Second, for a small fixed Higgs field ${\varphi }^2\ll M_p^2/\xi$ and a vanishing classical coefficient of the $R^2$-term, we show that the "usual" Starobinsky inflation is generated by the quantum corrections alone, for a suitable non-minimal coupling ($\xi$).

   hep-phastro-ph.COgr-qchep-thPRD(2018)·44 citations
8. 08*

   Revisiting heavy quark radiative energy loss in nuclei within the high-twist approach

   Yi-Lun Du🇨🇳 · Yayun He🇨🇳 · Xin-Nian Wang🇨🇳 · Hongxi Xing🇨🇳 · Hong-Shi Zong🇨🇳

   We revisit the calculation of multiple parton scattering of a heavy quark in nuclei within the framework of recently improved high-twist factorization formalism, in which gauge invariance is ensured by a delicate setup of the initial partons' transverse momenta. We derive a new result for medium modified heavy quark fragmentation functions in deeply inelastic scattering. It is consistent with the previous calculation of light quark energy loss in the massless limit, but leads to a new correction term in the heavy quark case, which vanishes in the soft gluon radiation limit. We show numerically the significance of the new correction term in the calculation of heavy quark energy loss as compared to previous studies and with soft gluon radiation approximation.

   hep-phnucl-thPRD(2018)·11 citations
9. 09*

   Spontaneous $CP$-Violating Electroweak Baryogenesis and Dark Matter from a Complex Singlet Scalar

   Bohdan Grzadkowski🇵🇱 · Da Huang🇵🇱

   CP non-invariance is strongly limited by present experiments, while extra sources of CP-violation are needed for a successful baryogenesis. Motivated by those observations we consider a model which predicts spontaneous violation of CP at high temperature and restoration of CP at present temperature of the Universe. In addition we propose a dark matter (DM) candidate that meets all known properties of DM. Looking for a minimal model that satisfies the above conditions leads us to extending the Standard Model (SM) of fundamental interactions by adding a complex singlet scalar $S$. We impose the $CP$ and $Z_2$ symmetries on the scalar potential. With the complex vacuum expectation value of $S$ at the temperature higher than the EW phase transition, the $CP$ symmetry is spontaneously broken and a strong first-order electro-weak phase transition is easily realized. Introducing a dimension-6 effective operator that gives new complex contributions to the top quark mass, we show that it is easy to yield the observed baryon asymmetry in our Universe. On the other hand, the $CP$ and $Z_2$ symmetries are recovered after the EW phase transition so that the present strong constraints on $CP$ violation can be satisfied and the lighter of $\Re S$ or $\Im S$ can be the dark matter candidate. By scanning the parameter space, we find regions where the model can explain the dark matter relic abundance and the baryon asymmetry simultaneously while satisfying all other experimental constraints. Finally, we discuss the explicit $CP$ symmetry breaking in the scalar potential that can help dynamically eliminate the domains producing the negative baryon asymmetry. It is found that this can be achieved by a tiny explicit $CP$-violating phase of $\mathcal{O}(10^{-15})$.

   hep-phJHEP(2018)·69 citations
10. 10*

    Production of Higgs bosons with large transverse momentum

    Kirill Kudashkin🇩🇪

    Recent results on the Higgs plus jet production is reviewed. We have computed the two-loop amplitudes for $gg\to Hg$, $q\bar{q}\to Hg$ and $qg\to Hq$ at the large Higgs transverse momentum. It was long-missing part of NLO corrections to the Higgs plus jet production above the top mass threshold. This results are combined with the real corrections to produce the Higgs boson transverse momentum distribution at NLO.

    hep-phPoS(2018)·1 citation
11. 11*

    Collective neutrino oscillations with the halo effect in single-angle approximation

    Vincenzo Cirigliano🇺🇸 · Mark Paris🇺🇸 · Shashank Shalgar🇺🇸

    We perform a self-consistent calculation of collective neutrino oscillations including the effect of back scattered neutrinos (Halo effect) in the `single-angle' approximation, within a spherically symmetric supernova model. We find that due to the Halo effect the onset of flavor transformations is pushed to smaller radii, by a few kilometers. The celebrated phenomenon of the spectral split is found to be robust under the present inclusion of the Halo effect.

    hep-phastro-ph.HEJCAP(2018)·17 citations
12. 12*

    $SU(3)\times SO(10)$ in 6d

    Francisco J. de Anda🇲🇽 · Stephen F. King🇬🇧

    We discuss a simple and elegant $SU(3)\times SO(10)$ family unified gauge theory in 6d compactified on a torus with the orbifold $T_2/Z_2^3$ and supplemented by a $Z_6\times Z_3$ discrete symmetry. The orbifold boundary conditions generate all the desired $SU(3)$ breaking vacuum alignments, including the $(0,1,-1)$ and $(1,3,-1)$ alignments of the Littlest Seesaw model for atmospheric and solar neutrino mixing, as well as the usual $SO(10)$ breaking with doublet-triplet splitting. The absence of driving and messenger fields considerably simplifies the field content of the model. It naturally explains why there are three families of quarks and leptons, and accounts for all their masses, mixing angles and CP phases via rather elegant looking Yukawa and Majorana matrices in the theory basis. The resulting model controls proton decay and allows successful Leptogenesis.

    hep-phJHEP(2018)·21 citations
13. 13*

    Pion distribution amplitude from Euclidean correlation functions: Exploring universality and higher-twist effects

    Gunnar S. Bali🇩🇪 · Vladimir M. Braun🇩🇪 · Benjamin Gläßle🇩🇪 · Meinulf Göckeler🇩🇪 · Michael Gruber🇩🇪 · Fabian Hutzler🇩🇪 · Piotr Korcyl🇩🇪 · Andreas Schäfer🇩🇪 · Philipp Wein🇩🇪 · Jian-Hui Zhang🇩🇪

    Building upon our recent study arXiv:1709.04325, we investigate the feasibility of calculating the pion distribution amplitude from suitably chosen Euclidean correlation functions at large momentum. We demonstrate in this work the advantage of analyzing several correlation functions simultaneously and extracting the pion distribution amplitude from a global fit. This approach also allows us to study higher-twist corrections, which are a major source of systematic error. Our result for the higher-twist parameter ${\delta }_2^{\pi }$ is in good agreement with estimates from QCD sum rules. Another novel element is the use of all-to-all propagators, calculated using stochastic estimators, which enables an additional volume average of the correlation functions, thereby reducing statistical errors.

    ↳ hep-lathep-phPRD(2018)·134 citations
14. 14*

    Non-linear mixing of Bogoliubov modes in a bosonic Josephson junction

    Sofía Martínez-Garaot🇪🇸 · Giulio Pettini🇮🇹 · Michele Modugno🇪🇸

    We revisit the dynamics of a Bose-Einstein condensate in a double-well potential, from the regime of Josephson plasma oscillations to the self-trapping regime, by means of the Bogoliubov quasiparticle projection method. For very small imbalance between left and right wells only the lowest Bogoliubov mode is significantly occupied. In this regime the system performs plasma oscillations at the corresponding frequency, and the evolution of the condensate is characterized by a periodic transfer of population between the ground and the first excited state. As the initial imbalance is increased, more excited modes -- though initially not macroscopically occupied -- get coupled during the evolution of the system. Since their population also varies with time, the frequency spectrum of the imbalance turns out to be still peaked around a single frequency, which is continuously shifted towards lower values. The nonlinear mixing between Bogoliubov modes eventually drives the system into the the self-trapping regime, when the population of the ground state can be transferred completely to the excited states at some time during the evolution. For simplicity, here we consider a one-dimensional setup, but the results are expected to hold also in higher dimensions.

    ↳ cond-mat.quant-gashep-phquant-phPRA(2018)·4 citations
15. 15*

    Radiative transitions of doubly charmed baryons in lattice QCD

    H. Bahtiyar🇹🇷 · K. U. Can🇯🇵 · G. Erkol🇹🇷 · M. Oka🇯🇵 · T. T. Takahashi🇯🇵

    We evaluate the spin-$3/2\to$ spin-$1/2$ electromagnetic transitions of the doubly charmed baryons on 2+1 flavor, $32^3\times 64$ PACS-CS lattices with a pion mass of $156(9)$ MeV/c${}^2$. A relativistic heavy quark action is employed to minimize the associated systematic errors on charm-quark observables. We extract the magnetic dipole, $M1$, and the electric quadrupole, $E2$, transition form factors. In order to make a reliable estimate of the $M1$ form factor, we carry out an analysis by including the effect of excited-state contributions. We find that the $M1$ transition is dominant and light degrees of freedom ($u/d$- or $s$-quark) play the leading role. $E2$ form factors, on the other hand, are found to be negligibly small, which in turn, have minimal effect on the helicity and transition amplitudes. We predict the decay widths and lifetimes of ${\Xi }_{cc}^{\ast +,++}$ and ${\Omega }_{cc}^{\ast +}$ based on our results. Finite size effects on these ensembles are expected to be around 1\%. Differences in kinematical and dynamical factors with respect to the $N\gamma \to \Delta$ transition are discussed and compared to non-lattice determinations as well keeping possible systematic artifacts in mind. A comparison to ${\Omega }_c\gamma \to {\Omega }_c^{\ast }$ transition and a discussion on systematic errors related to the choice of heavy quark action are also given. Results we present here are particularly suggestive for experimental facilities such as LHCb, PANDA, Belle II and BESIII to search for further states.

    ↳ hep-lathep-phPRD(2018)·38 citations
16. 16*

    A New Model for Calculating the Ground and Excited States Masses Spectra of Doubly Heavy Baryons

    Neda Mohajery🇮🇷 · Nasrin Salehi🇮🇷 · Hassan Hassanabadi🇮🇷

    In this study, since the doubly heavy baryons masses are experimentally unknown (except and ), we present the ground state masses and the positive and negative parity excited state masses of doubly heavy baryons. For this purpose, we have solved the six-dimensional hyperradial Schrödinger equation analytically for three particles under the hypercentral potential by using the ansatz approach. In this paper the hypercentral potential is regarded as a combination of the color Coulomb plus linear confining term and the six-dimensional harmonic oscillator potential. We also added the first order correction and the spin-dependent part contains three types of interaction terms (the spin-spin term, spin-orbit term and tensor term) to the hypercentral potential. Our obtained masses for the radial excited states and orbital excited states of , , , , and systems are compared with other theoretical reports, which could be a beneficial tool for the interpretation of experimentally unknown doubly heavy baryons spectrum.

    ↳ nucl-thhep-phAdv.High Energy Phys.(2018)·12 citations
17. 17*

    Detecting Domain Walls in Laboratory Experiments

    Claudio Llinares🇬🇧 · Philippe Brax🇫🇷

    The inherently unstable nature of domain walls makes their detection in laboratory experiments extremely challenging. We propose a method to stabilise domain walls in a particular modified gravity model inside a cavity. We suggest two ways in which the walls could be detected once stabilized: studying the trajectories of Ultra Cold Neutrons (UCN's) either via the deflection angle of a neutron beam induced by the attraction towards the wall or through the time difference of these particles passing through the wall. We give realistic estimates for these effects and expect that they should be detectable experimentally.

    ↳ astro-ph.COgr-qchep-phPRL(2019)·18 citations
18. 18*

    Anti-Gravitating Brane-World Solutions for a de Sitter Brane in Scalar-Tensor Gravity

    Panagiota Kanti🇬🇷 · Theodoros Nakas🇬🇷 · Nikolaos Pappas🇬🇷

    In the context of a five-dimensional theory with a scalar field non-minimally-coupled to gravity, we look for solutions that describe novel black-string or maximally-symmetric solutions in the bulk. The brane line-element is found to describe a Schwarzschild-(Anti)-de Sitter spacetime, and, here, we choose to study solutions with a positive four-dimensional cosmological constant. We consider two different forms of the coupling function of the scalar field to the bulk scalar curvature, a linear and a quadratic one. In the linear case, we find solutions where the theory, close to our brane, mimics an ordinary gravitational theory with a minimally-coupled scalar field giving rise to an exponentially decreasing warp factor in the absence of a negative bulk cosmological constant. The solution is characterised by the presence of a normal gravity regime around our brane and an anti-gravitating regime away from it. In the quadratic case, there is no normal-gravity regime at all, however, scalar field and energy-momentum tensor components are well-defined and an exponentially decreasing warp factor emerges again. We demonstrate that, in the context of this theory, the emergence of a positive cosmological constant on our brane is always accompanied by an anti-gravitating regime in the five-dimensional bulk.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2018)·18 citations
19. 19*

    On the $a$-theorem in the Conformal Window

    Vladimir Prochazka🇸🇪 · Roman Zwicky🇬🇧

    We show that for four dimensional gauge theories in the conformal window, the Euler anomaly, known as the $a$-function, can be computed from a $2$-point function of the trace of the energy momentum tensor making it more amenable to lattice simulations. Concretely, we derive an expression for the $a$-function as an integral over the renormalisation scale of quantities related to $2$- and $3$-point functions of the trace of the energy momentum tensor.The crucial ingredients are that the square of the field strength tensor is an exactly marginal operator at the Gaussian fixed point and that the relevant $3$-point correlation function is finite when resummed to all orders. This allows us to define a scheme for which the $3$-point contribution vanishes, thereby explicitly establishing the strong version of the $a$-theorem for this class of theories.

    ↳ hep-thhep-lathep-phPRD(2019)·2 citations
20. 20*

    Unitarity constraint on the Kähler curvature

    Yohei Ema🇯🇵 · Ryuichiro Kitano🇯🇵 · Takahiro Terada🇯🇵

    In supersymmetric theories, the signs of quartic terms in the Kähler potential control the stability of non-supersymmetric field configurations. In particular, in supersymmetric inflation models, the signs are important for the stability of an inflationary trajectory as well as for the prediction of the spectral index. In this paper, we clarify what properties of a UV theory determine the sign from unitarity arguments of scattering amplitudes. As non-trivial examples, we discuss the sign of a four-meson term in large $N$ supersymmetric gauge theories and also those of the quartic terms obtained in the intersecting D-brane models in superstring theory. The UV origins of inflationary models and supersymmetry breaking models are constrained by this discussion.

    ↳ hep-thhep-phJHEP(2018)·9 citations
21. 21*

    Full 3D Numerical Relativity Simulations of Neutron Star -- Boson Star Collisions with BAM

    Tim Dietrich🇳🇱 · Serguei Ossokine🇩🇪 · Katy Clough🇩🇪

    With the first direct detections of gravitational waves (GWs) from the coalescence of compact binaries observed by the advanced LIGO and VIRGO interferometers, the era of GW astronomy has begun. Whilst there is strong evidence that the observed GWs are connected to the merger of two black holes (BH) or two neutron stars (NS), future detections may present a less consistent picture. Indeed, the possibility that the observed GW signal was created by a merger of exotic compact objects (ECOs) such as boson stars (BS) or axion stars (AS) has not yet been fully excluded. For a detailed understanding of the late stages of the coalescence full 3D numerical relativity simulations are essential. In this paper, we extend the infrastructure of the numerical relativity code BAM, to permit the simultaneous simulation of baryonic matter with bosonic scalar fields, thus enabling the study of BS-BS, BS-NS, and BS-BH mergers. We present a large number of single star evolutions to test the newly implemented routines, and to quantify the numerical challenges of such simulations, which we find to partially differ from the default NS case. We also compare head-on BS-BS simulations with independent numerical relativity codes, namely the SpEC and the GRChombo codes, and find good general agreement. Finally, we present what are, to the best of our knowledge, the first full NR simulations of BS-NS mergers, a first step towards identifying the hallmarks of BS-NS interactions in the strong gravity regime, as well as possible GW and electromagnetic observables.

    ↳ gr-qcastro-ph.HEhep-phClass.Quant.Grav.(2019)·49 citations
22. 22*

    Gravitational wave forest from string axiverse

    Naoya Kitajima🇯🇵 · Jiro Soda🇯🇵 · Yuko Urakawa🇯🇵

    Axions predicted in string theory may have a scalar potential which has a much shallower potential region than the conventional cosine potential. We first show that axions which were located at such shallow potential regions generically undergo prominent resonance instabilities: the well-known narrow resonance and/or the flapping resonance, which has not been well investigated. We also study non-linear dynamics of axions caused by these resonance instabilities based on lattice simulation. We find that string axions in various mass ranges generate gravitational waves (GWs) with peaks at various frequencies determined by the mass scales, dubbed the GW forest. This may allow us to explore string axiverse through future multi-frequency GW observations. We also investigate GWs produced by the axion which accounts for present dark matter component.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2018)·85 citations
23. 23*

    The Scales of the Infrared

    Cesar Gomez🇪🇸 · Raoul Letschka🇪🇸 · Sebastian Zell🇩🇪

    In theories with long-range forces like QED or perturbative gravity, loop corrections lead to vanishing amplitudes. There are two well-known procedures to address these infrared divergences: dressing of asymptotic states and inclusion of soft emission. Although both yield the same IR-finite rates, we point out that they are not equivalent since they encode different infrared scales. In particular, dressing states are independent of the resolution scale of radiation. Instead, they define radiative vacua in the von Neumann space. After a review of these concepts, the goal of this paper is to present a combined formalism that can simultaneously describe both dressing and radiation. This unified approach allows us to tackle the problem of quantum decoherence due to tracing over unresolved radiation. We obtain an IR-finite density matrix with non-vanishing off-diagonal elements and estimate how its purity depends on scattering kinematics and the resolution scale. Along the way, we comment on collinear divergences as well as the connection of large gauge transformations and dressing.

    ↳ hep-thgr-qchep-phquant-phJHEP(2018)·28 citations
24. 24*

    Observational constraints on the tilted spatially-flat and the untilted nonflat $\varphi$CDM dynamical dark energy inflation models

    Chan-Gyung Park🇰🇷 · Bharat Ratra🇺🇸

    We constrain spatially-flat tilted and nonflat untilted scalar field ($\varphi$) dynamical dark energy inflation ($\varphi$CDM) models by using Planck 2015 cosmic microwave background (CMB) anisotropy measurements and recent baryonic acoustic oscillation distance observations, Type Ia supernovae apparent magnitude data, Hubble parameter measurements, and growth rate data. We assume an inverse power-law scalar field potential energy density $V(\varphi )=V_0{\varphi }^{-\alpha }$. We find that the combination of the CMB data with the four non-CMB data sets significantly improves parameter constraints and strengthens the evidence for nonflatness in the nonflat untilted $\varphi$CDM case from $1.8\sigma$ for the CMB measurements only to more than $3.1\sigma$ for the combined data. In the nonflat untilted $\varphi$CDM model current observations favor a spatially closed universe with spatial curvature contributing about two-thirds of a percent of the present cosmological energy budget. The flat tilted $\varphi$CDM model is a 0.4$\sigma$ better fit to the data than is the standard flat tilted $\Lambda$CDM model: current data allow for the possibility that dark energy is dynamical. The nonflat tilted $\varphi$CDM model is in better accord with the Dark Energy Survey bounds on the rms amplitude of mass fluctuations now (${\sigma }_8$) as a function of the nonrelativistic matter density parameter now (${\Omega }_m$) but it does not provide as good a fit to the larger-multipole Planck 2015 CMB anisotropy data as does the standard flat tilted $\Lambda$CDM model. A few cosmological parameter value measurements differ significantly when determined using the tilted flat and the untilted nonflat $\varphi$CDM models, including the cold dark matter density parameter and the reionization optical depth.

    ↳ astro-ph.COgr-qchep-phhep-thApJ(2018)·99 citations
25. 25*

    Proton Isovector Helicity Distribution on the Lattice at Physical Pion Mass

    Huey-Wen Lin🇺🇸 · Jiunn-Wei Chen🇹🇼 · Xiangdong Ji🇨🇳 · Luchang Jin🇺🇸 · Ruizi Li🇺🇸 · Yu-Sheng Liu🇨🇳 · Yi-Bo Yang🇺🇸 · Jian-Hui Zhang🇩🇪 · Yong Zhao🇺🇸

    We present a state-of-the-art calculation of the isovector quark helicity Bjorken-$x$ distribution in the proton using lattice-QCD ensembles at the physical pion mass. We compute quasi-distributions at proton momenta $P_z\in \{2.2,2.6,3.0\}$~GeV on the lattice, and match them systematically to the physical parton distribution using large-momentum effective theory (LaMET). We reach an unprecedented precision through high statistics in simulations, large-momentum proton matrix elements, and control of excited-state contamination. The resulting distribution with combined statistical and systematic errors is in agreement with the latest phenomenological analysis of the spin-dependent experimental data; in particular, $\Delta \bar{u}(x)>\Delta \bar{d}(x)$.

    ↳ hep-lathep-exhep-phnucl-ex+1PRL(2018)·137 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.