Thu·Jul 18, 2019Thursday·July 18, 2019

1. 01*

   A hadron-quark hybrid model reliable for the EoS in ${\mu }_B\le 400$ MeV

   Akihisa Miyahara🇯🇵 · Masahiro Ishii🇯🇵 · Hiroaki Kouno🇯🇵 · Masanobu Yahiro🇯🇵

   We present a simple version of hadron-quark hybrid (HQH) model in the ${\mu }_B$--$T$ plain, where $T$ is temperature and ${\mu }_B$ is the baryon-number chemical potential. The model is composed of the independent-quark model for quark-gluon states and an improved version of excluded-volume hadron resonance gas (EV-HRG) model for hadronic states. In the improved version of EV-HRG, the pressure has charge conjugation and is obtained by a simple analytic form. The switching function from hadron states to quark-gluon states in the present model has no chemical potential dependence. The simple HQH model is successful in reproducing LQCD results on the transition region of chiral crossover and the EoS in ${\mu }_B\le 400$ MeV. We then predict the chiral-crossover region in $400\le {\mu }_B\le 800$ MeV. We also predict a transition line derived from isentropic trajectories in $0\le {\mu }_B\le 800$ MeV and find that the effect of strangeness neutrality is small there.

   hep-phhep-latPRD(2020)·4 citations
2. 02*

   Freeze-in Axion-like Dark Matter

   Sang Hui Im🇰🇷 · Kwang Sik Jeong🇰🇷

   We present an interesting Higgs portal model where an axion-like particle (ALP) couples to the Standard Model sector only via the Higgs field. The ALP becomes stable due to CP invariance and turns out to be a natural candidate for freeze-in dark matter because its properties are controlled by the perturbative ALP shift symmetry. The portal coupling can be generated non-perturbatively by a hidden confining gauge sector, or radiatively by new leptons charged under the ALP shift symmetry. Such UV completions generally involve a CP violating phase, which makes the ALP unstable and decay through mixing with the Higgs boson, but can be sufficiently suppressed in a natural way by invoking additional symmetries.

   hep-phastro-ph.COPLB(2019)·20 citations
3. 03*

   QCD effective charges and the structure function $F_2$ at small-$x$: Higher twist effects

   D. Hadjimichef🇧🇷 · E. G. S. Luna🇧🇷 · M. Peláez🇺🇾

   We consider the effect of higher twist operators of the Wilson operator product expansion in the structure function $F_2(x,Q^2)$ at small-$x$, taking into account QCD effective charges whose infrared behavior is constrained by a dynamical mass scale. The higher twist corrections are obtained from the renormalon formalism. Our analysis is performed within the conventional framework of next-to-leading order, with the factorization and renormalization scales chosen to be $Q^2$. The infrared properties of QCD are treated in the context of the generalized double-asymptotic-scaling approximation. We show that the corrections to $F_2$ associated with twist-four and twist-six are both necessary and sufficient for a good description of the deep infrared experimental data.

   hep-phhep-exhep-lathep-thPLB(2020)·10 citations
4. 04*

   Complete One-Loop Renormalization of the Higgs-Electroweak Chiral Lagrangian

   Claudius Krause🇺🇸 · Gerhard Buchalla🇩🇪 · Oscar Catà🇩🇪 · Alejandro Celis🇩🇪 · Marc Knecht🇫🇷

   The electroweak sector of the Standard Model can be formulated in a way similar to Chiral Perturbation Theory (ChPT), but extended by a singlet scalar. The resulting effective field theory (EFT) is called Higgs-Electroweak Chiral Lagrangian (EWCh$\mathcal{L}$) and is the most general approach to new physics in the Higgs sector. It solely assumes the pattern of symmetry breaking leading to the three electroweak Goldstone bosons (i.e. massive $W$ and $Z$) and the existence of a Higgs-like scalar particle. The power counting of the EWCh$\mathcal{L}$ is given by a generalization of the momentum expansion of ChPT. It is connected to a loop expansion, making the theory renormalizable order by order in the EFT. I will briefly review the construction of the EWCh$\mathcal{L}$ and its power counting. Then, I will discuss the complete one-loop renormalization of the EWCh$\mathcal{L}$ employing the background-field method and the super-heat-kernel expansion. This computation confirms the power counting assumptions, is consistent with the completeness of the operator basis, and reproduces known results of subsectors in the appropriate limits.

   hep-phPoS(2019)·3 citations
5. 05*

   A Dark Hidden-Sector of Dirac fermions at the GeV scale

   M. J. Neves🇧🇷 · J. A. Helaÿel-Neto🇧🇷

   Our contribution sets out to investigate the GeV-scale phenomenology of a model based on an $S{U}_L(2)\times U_Y(1)\times U(1{)}_X$-gauge symmetry. The model accommodates, as a consequence of the symmetry-breaking pattern, a light gauge boson at the GeV-scale or below, allowing then to set up a new low energy physics. The fermion sector includes an exotic candidate to Dark Matter (DM) and the whole fermionic field content yields, as it is mandatory, the cancellation of the chiral anomaly. %In this strict sense, we refer to our proposal as a unified description : two different and exclusive symmetry-breaking patterns are treated with a single Lagrangian density and a common symmetry group. Furthermore, The light gauge boson and the exotic fermion are proposed as candidates to the so-called dark sector of the model that we try to describe in this contribution. The low-energy spectrum exhibits a hidden scalar field with mass fixed at the GeV level in the Higgs sector. We calculate the DM relic density associated with the dark fermion candidate by considering two annihilation processes in which the light gauge boson works as a portal for the DM detection. The observed relic density points to a mass of $3.4$ GeV for the DM fermion, while the light gauge boson mass is $8.0$ GeV. We also investigate the direct detection of DM in the low energy regime and obtain the region of parameters allowed by recent discussions on DM limits. Finally, the correction to the muon magnetic dipole moment is calculated considering the gauge boson mass at the GeV scale or below.

   hep-phhep-th1 citation
6. 06*

   Stellar cooling anomalies and variant axion models

   Ken'ichi Saikawa🇩🇪 · Tsutomu T. Yanagida🇯🇵

   A number of observations of stellar systems show a mild preference for anomalously fast cooling compared with what predicted in the standard theory, which leads to a speculation that there exists an additional energy loss mechanism originated from the emission of axions in stars. We revisit the global analysis of the stellar cooling anomalies by adopting conservative assessments on several systematic uncertainties and find that the significance of the cooling hints becomes weaker but still indicates a non-vanishing axion-electron coupling at around 2.4$\sigma$. With the revised analysis results, we explore the possibility that such excessive energy losses are interpreted in the framework of variant axion models, which require two Higgs doublets and flavor-dependent Peccei-Quinn charge assignments. These models resolve two fundamental issues faced in the traditional KSVZ/DFSZ models by predicting a sizable axion coupling to electrons required to explain the cooling anomalies and at the same time providing a solution to the cosmological domain wall problem. We also find that a specific structure of the axion couplings to electrons and nucleons slightly relaxes the constraint from supernova 1987A and enlarges viable parameter regions compared with the DFSZ models. It is shown that good global fits to the observational data are obtained for axion mass ranges of $0.45\mathrm{meV}\lesssim m_a\lesssim 30\mathrm{meV}$, and that the predicted parameter regions can be probed in the forthcoming helioscope searches.

   hep-phastro-ph.COastro-ph.SRJCAP(2020)·20 citations
7. 07*

   Direct Detection of Spin-(In)dependent Nuclear Scattering of Sub-GeV Dark Matter Using Molecular Excitations

   Rouven Essig🇺🇸 · Jesús Pérez-Ríos🇩🇪 · Harikrishnan Ramani🇺🇸 · Oren Slone🇺🇸

   We propose a novel direct detection concept to search for dark matter with 100~keV to 100~MeV masses. Such dark matter can scatter off molecules in a gas and transfer an $\mathcal{O}(1)$ fraction of its kinetic energy to excite a vibrational and rotational state. The excited ro-vibrational mode relaxes rapidly and produces a spectacular multi-infrared-photon signal, which can be observed with ultrasensitive photodetectors. We discuss in detail a gas target consisting of carbon monoxide molecules, which enable efficient photon emission even at a relatively low temperature and high vapor pressure. The emitted photons have an energy in the range 180~meV to 265~meV. By mixing together carbon monoxide molecules of different isotopes, including those with an odd number of neutrons, we obtain sensitivity to both spin-independent interactions and spin-dependent interactions with the neutron. We also consider hydrogen fluoride, hydrogen bromide, and scandium hydride molecules, which each provide sensitivity to spin-dependent interactions with the proton. The proposed detection concept can be realized with near-term technology and allows for the exploration of orders of magnitude of new dark matter parameter space.

   hep-phastro-ph.COhep-exPhys.Rev.Research.(2019)·58 citations
8. 08*

   Investigating multiple solutions to boundary value problems in constrained minimal and non-minimal SUSY models

   Daniel Meuser🇩🇪 · Alexander Voigt🇩🇪

   We investigate the physical origins of multiple solutions to boundary value problems in the fully constrained MSSM and NMSSM. We derive mathematical criteria that formulate circumstances under which multiple solutions can appear. Finally, we study the validity of the exclusion of the CMSSM in the presence of multiple solutions.

   hep-phEPJC(2019)·2 citations
9. 09*

   Cosmic perturbations, baryon asymmetry and dark matter from the minimal supersymmetric standard model

   Keisuke Harigaya🇺🇸 · Masaki Yamada🇺🇸

   Scalar fields in the minimal supersymmetric standard model may have large field values during inflation. Because of approximate global symmetry, it is plausible that the phase directions of them are nearly massless during inflation and obtain quantum fluctuations, which may be the origin of the cosmic perturbations. If perturbations are produced through Q-ball formation, baryon asymmetry and dark matter can be consistently generated. Significant baryon and dark matter isocurvature perturbations are produced, but they are predicted to nearly compensate each other. The lepton asymmetry is much larger than the baryon asymmetry. The scenario predicts local non-Gaussianity of $f_{\mathrm{NL}}=5/3$. Implication to the mass spectrum of supersymmetric particles is discussed.

   hep-phastro-ph.COPRD(2020)·7 citations
10. 10*

    Unitarity Entropy Bound: Solitons and Instantons

    Gia Dvali🇩🇪

    We show that non-perturbative entities such as solitons and instantons saturate bounds on entropy when the theory saturates unitarity. Simultaneously, the entropy becomes equal to the area of the soliton/instanton. This is strikingly similar to black hole entropy despite absence of gravity. We explain why this similarity is not an accident. We present a formulation that allows to apply the entropy bound to instantons. The new formulation also eliminates apparent violations of the Bekenstein entropy bound by some otherwise-consistent unitary systems. We observe that in QCD, an isolated instanton of fixed size and position violates the entropy bound for strong 't Hooft coupling. At critical 't Hooft coupling the instanton entropy is equal to its area.

    ↳ hep-thgr-qchep-lathep-phFortsch.Phys.(2021)·43 citations
11. 11*

    A Cosmological Higgs Collider

    Shiyun Lu🇨🇳 · Yi Wang🇨🇳 · Zhong-Zhi Xianyu🇺🇸

    The quantum fluctuations of the Higgs field during inflation could be a source of primordial density perturbations through Higgs-dependent inflaton decay. By measuring primordial non-Gaussianities, this so-called Higgs-modulated reheating scenario provides us a unique chance to probe Higgs interactions at extremely high energy scale, which we call the Cosmological Higgs Collider (CHC). We realize CHC in a simple scenario where the inflaton decays into Higgs-portal scalars, taking account of the decay of the Higgs fluctuation amplitude after inflation. We also calculate the CHC signals of Standard Model particles, namely their imprints in the squeezed bispectrum, which can be naturally large. The concept of CHC can be straightforwardly generalized to cosmological isocurvature colliders with other types of isocurvature perturbations.

    ↳ hep-thastro-ph.COhep-phJHEP(2020)·102 citations
12. 12*

    Enhanced nuclear Schiff moment in stable and metastable nuclei

    V.V. Flambaum🇦🇺 · H. Feldmeier🇩🇪

    Nuclei with static intrinsic octupole deformation or a soft octupole vibrational mode lead to strongly enhanced collective nuclear Schiff? moments. Interaction between electrons and these Schiff moments produce enhanced time reversal (T) and parity (P) violating electric dipole moments (EDM) in atoms and molecules. Corresponding experiments may be used to test CP-violation theories predicting T,P-violating nuclear forces and to search for axions. Nuclear octupole deformations are predicted in many short lived isotopes. This paper investigates octupole deformations in stable and very long lifetime nuclei such as 153Eu, 235U, 237Np and 227Ac, which can ease atomic experiments substantially. The estimates of the enhanced Schiff? moments, atomic electric dipole momentsand T, P-odd interaction constants in molecules containing these nuclei are presented.

    ↳ nucl-thhep-phphysics.atom-phPRC(2020)·33 citations
13. 13*

    Transverse momentum dependent multiplicities of hadrons produced in DIS at COMPASS

    Andrea Moretti (on behalf of the COMPASS Collaboration)🇮🇹

    The COMPASS Collaboration measured the transverse momentum dependent multiplicities of charged hadrons produced in Deep Inelastic Scattering (DIS) off unpolarized protons. Complementing previous COMPASS measurements obtained with an isoscalar target, the data have been collected in 2016 and 2017 with 160 GeV/$c$ muon beams and a liquid hydrogen target. The multiplicities are studied as a function of the square of the hadron transverse momentum with respect to the virtual photon direction $P_{hT}^2$ in bins of the Bjorken variable $x$, of the photon virtuality $Q^2$ and of the fraction $z$ of the photon energy carried by the hadron. Preliminary results of this analysis, performed on a fraction of the available data sample, are shown here for the first time.

    ↳ hep-exhep-phPoS(2019)·1 citation
14. 14*

    Real-time cosmology with SKA

    Yan Liu🇨🇳 · Jing-Fei Zhang🇨🇳 · Xin Zhang🇨🇳

    In this work, we investigate what role the redshift drift data of Square Kilometre Array (SKA) will play in the cosmological parameter estimation in the future. To test the constraint capability of the redshift drift data of SKA-only, the $\Lambda$CDM model is chosen as a reference model. We find that using the SKA1 mock data, the $\Lambda$CDM model can be loosely constrained, while the model can be well constrained when the SKA2 mock data are used. When the mock data of SKA are combined with the data of the European Extremely Large Telescope (E-ELT), the constraints can be significantly improved almost as good as the data combination of the type Ia supernovae observation (SN), the cosmic microwave background observation (CMB), and the baryon acoustic oscillations observation (BAO). Furthermore, we explore the impact of the redshift drift data of SKA on the basis of SN+CMB+BAO+E-ELT in the $\Lambda$CDM model, the $w$CDM model, the CPL model, and the HDE model. We find that the redshift drift measurement of SKA could help to significantly improve the constraints on dark energy and could break the degeneracy between the cosmological parameters. Therefore, we conclude that redshift-drift observation of SKA would provide a good improvement in the cosmological parameter estimation in the future and has the enormous potential to be one of the most competitive cosmological probes in constraining dark energy.

    ↳ astro-ph.COgr-qchep-phEPJC(2020)·10 citations
15. 15*

    New physics in light of the $H_0$ tension: an alternative view

    Sunny Vagnozzi🇸🇪

    The strong discrepancy between local and inverse distance ladder estimates of the Hubble constant $H_0$ could be pointing towards new physics beyond $\Lambda$CDM. Several attempts to address this tension through new physics rely on extended models, featuring extra free parameters beyond the 6 $\Lambda$CDM parameters. However, marginalizing over extra parameters has the effect of broadening the uncertainties on the inferred parameters, and it is often the case that within these models the $H_0$ tension is addressed due to larger uncertainties rather than a genuine shift in the central value of $H_0$. What happens if a physical theory is able to fix the extra parameters to a specific set of non-standard values? The degrees of freedom of the model are reduced with respect to the standard case where the extra parameters are free to vary. Focusing on the dark energy equation of state $w$ and the effective number of relativistic species $N_{\mathrm{eff}}$, I find that physical theories able to fix $w\approx -1.3$ or $N_{\mathrm{eff}}\approx 3.95$ would lead to an estimate of $H_0$ from CMB, BAO, and SNeIa data in perfect agreement with the local distance ladder estimate, without broadening its uncertainty. These two non-standard models are, from a model-selection perspective, strongly disfavoured with respect to $\Lambda$CDM. However, models that predict $N_{\mathrm{eff}}\approx 3.45$ would be able to bring the tension down to $1.5\sigma$ while only being weakly disfavored with respect to $\Lambda$CDM, whereas models that predict $w\approx -1.1$ would be able to bring the tension down to $2\sigma$ (at the cost of the preference for $\Lambda$CDM being definite). Finally, I estimate dimensionless multipliers relating variations in $H_0$ to variations in $w$ and $N_{\mathrm{eff}}$, which can be used to repeat the analysis of this paper in light of future more precise local distance ladder estimates of $H_0$.

    ↳ astro-ph.COgr-qchep-phPRD(2020)·606 citations
16. 16*

    The $XYZ$ states: experimental and theoretical status and perspectives

    Nora Brambilla🇩🇪 · Simon Eidelman🇷🇺 · Christoph Hanhart🇩🇪 · Alexey Nefediev🇷🇺 · Cheng-Ping Shen🇨🇳 · Christopher E. Thomas🇬🇧 · Antonio Vairo🇩🇪 · Chang-Zheng Yuan🇨🇳

    The quark model was formulated in 1964 to classify mesons as bound states made of a quark-antiquark pair, and baryons as bound states made of three quarks. For a long time all known mesons and baryons could be classified within this scheme. Quantum Chromodynamics (QCD), however, in principle also allows the existence of more complex structures, generically called exotic hadrons or simply exotics. These include four-quark hadrons (tetraquarks and hadronic molecules), five-quark hadrons (pentaquarks) and states with active gluonic degrees of freedom (hybrids), and even states of pure glue (glueballs). Exotic hadrons have been systematically searched for in numerous experiments for many years. Remarkably, in the past fifteen years, many new hadrons that do not exhibit the expected properties of ordinary (not exotic) hadrons have been discovered in the quarkonium spectrum. These hadrons are collectively known as $XYZ$ states. Some of them, like the charged states, are undoubtedly exotic. Parallel to the experimental progress, the last decades have also witnessed an enormous theoretical effort to reach a theoretical understanding of the $XYZ$ states. Theoretical approaches include not only phenomenological extensions of the quark model to exotics, but also modern non-relativistic effective field theories and lattice QCD calculations. The present work aims at reviewing the rapid progress in the field of exotic $XYZ$ hadrons over the past few years both in experiments and theory. It concludes with a summary on future prospects and challenges.

    ↳ hep-exhep-lathep-phPhys.Rept.(2020)·1171 citations
17. 17*

    Accelerating the search for Axion-Like Particles with machine learning

    Francesca Day🇬🇧 · Sven Krippendorf🇩🇪

    Machine learning (ML) techniques have been applied with tremendous success in many areas of physics. In this work, we use ML to place bounds on the coupling between photons and axion-like particles (ALPs). This coupling causes ALPs and photons to interconvert in the presence of a background magnetic field. This would lead to modulations in the spectra of point sources shining through the magnetic fields of galaxy clusters. This effect has already been used to place world-leading bounds on the ALP-photon coupling using conventional statistical methods. We train ML classification algorithms on simulated spectra from the Chandra X-ray telescope for a range of point sources and ALP-photon couplings. We then use the response of these algorithms to the real Chandra spectra to place bounds on ALP-photon interactions. We obtain bounds at a similar level to those based on other techniques, but find improvements on an individual source basis. We expect such search techniques to become increasingly important for ALP searches with future telescopes that will offer substantially higher energy resolution.

    ↳ astro-ph.HEhep-phJCAP(2020)·10 citations
18. 18*

    Generalized Brans-Dicke theories in light of evolving dark energy

    Alex Zucca🇨🇦 · Levon Pogosian🇨🇦 · Alessandra Silvestri🇳🇱 · Yuting Wang🇨🇳 · Gong-Bo Zhao🇨🇳

    The expansion history of the Universe reconstructed from a combination of recent data indicates a preference for a changing Dark Energy (DE) density. Moreover, the DE density appears to be increasing with cosmic time, with its equation of state being below -1 on average, and possibly crossing the so-called phantom divide. Scalar-tensor theories, in which the scalar field mediates a force between matter particles, offer a natural framework in which the effective DE equation of state can be less than -1 and cross the phantom barrier. We consider the generalized Brans-Dicke (GBD) class of scalar-tensor theories and reconstruct their Lagrangian given the effective DE density extracted from recent data. Then, given the reconstructed Lagrangian, we solve for the linear perturbations and investigate the characteristic signatures of these reconstructed GBD in the cosmological observables, such as the cosmic microwave background (CMB) anisotropy, the galaxy number counts, and their cross-correlations. In particular, we demonstrate that the Integrated Sachs-Wolfe (ISW) effect probed by the cross-correlation of CMB with the matter distribution can rule out scalar-tensor theories as the explanation of the observed DE dynamics independently from the laboratory and solar system fifth force constraints.

    ↳ astro-ph.COgr-qchep-phPRD(2020)·14 citations
19. 19*

    First-order relativistic hydrodynamics is stable

    Pavel Kovtun🇨🇦

    We study linearized stability in first-order relativistic viscous hydrodynamics in the most general frame. There is a region in the parameter space of transport coefficients where the perturbations of the equilibrium state are stable. This defines a class of stable frames, with the Landau-Lifshitz frame falling outside the class. The existence of stable frames suggests that viscous relativistic fluids may admit a sensible hydrodynamic description in terms of temperature, fluid velocity, and the chemical potential only, i.e. in terms of the same hydrodynamic variables as non-relativistic fluids. Alternatively, it suggests that the Israel-Stewart and similar constructions may be unnecessary for a sensible relativistic hydrodynamic theory.

    ↳ hep-thgr-qchep-phJHEP(2019)·354 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.