Fri·Mar 9, 2018Friday·March 9, 2018

1. 01*

   BSMPT - Beyond the Standard Model Phase Transitions -A Tool for the Electroweak Phase Transition in Extended Higgs Sectors

   Philipp Basler🇩🇪 · Margarete Muhlleitner🇩🇪

   We provide the C++ tool BSMPT for calculating the strength of the electroweak phase transition in extended Higgs sectors. This relies on the loop-corrected effective potential at finite temperature including daisy resummation of the bosonic masses. The program allows to compute the vacuum expectation value (VEV) $v$ of the potential as a function of the temperature, and in particular the critical VEV $v_c$ at the temperature $T_c$ where the phase transition takes place. In addition, the loop-corrected trilinear Higgs self-couplings are provided. We apply an 'on-shell' renormalization scheme in the sense that the loop-corrected masses and mixing angles are required to be equal to their tree-level input values. This allows for efficient scans in the parameter space of the models. The models implemented so far are the CP-conserving and the CP-violating 2-Higgs-Doublet Models (2HDM) and the Next-to-Minimal 2HDM (N2HDM). The program structure is such that the user can easily implement further models. Our tool can be used for the investigation of electroweak baryogenesis in models with extended Higgs sectors and the related Higgs self-couplings. The combination with parameter scans in the respective models allows to study the impact on collider phenomenology and to make a link between collider phenomenology and cosmology. The program package can be downloaded at: https://github.com/phbasler/BSMPT.

   hep-phComput.Phys.Commun.(2019)·122 citations
2. 02*

   LHC Phenomenology of Dark Matter with a Color-Octet Partner

   Alessandro Davoli🇮🇹 · Andrea De Simone🇮🇹 · Thomas Jacques🇮🇹 · Alessandro Morandini🇮🇹

   Colored dark sectors where the dark matter particle is accompanied by colored partners have recently attracted theoretical and phenomenological interest. We explore the possibility that the dark sector consists of the dark matter particle and a color-octet partner, where the interaction with the Standard Model is governed by an effective operator involving gluons. The resulting interactions resemble the color analogues of electric and magnetic dipole moments. Although many phenomenological features of this kind of model only depend on the group representation of the partner under SU(3)${}_c$, we point out that interesting collider signatures such as $R$-hadrons are indeed controlled by the interaction operator between the dark and visible sector. We perform a study of the current constraints and future reach of LHC searches, where the complementarity between different possible signals is highlighted and exploited.

   hep-phJHEP(2018)·13 citations
3. 03*

   Looking for Galactic Diffuse Dark Matter in INO-MagICAL Detector

   Sanjib Kumar Agarwalla🇮🇳 · Amina Khatun🇮🇳 · Ranjan Laha🇺🇸

   The Weakly Interacting Massive Particle (WIMP) is a popular particle physics candidate for the dark matter (DM). It can annihilate and/or decay to neutrino and antineutrino pair. The proposed 50 kt Magnetized Iron CALorimeter (MagICAL) detector at the India-based Neutrino Observatory (INO) can observe these pairs over the conventional atmospheric neutrino and antineutrino fluxes. If we do not see any excess of events in ten years, then INO-Magical can place competitive limits on self-annihilation cross-section ($⟨\sigma v⟩$) and decay lifetime ($\tau$) of dark matter at 90\% C.L.: $⟨\sigma v⟩\le 1.87\times 10^{-24}$ cm${}^3$ s${}^{-1}$ and $\tau \ge 4.8\times 10^{24}$ s for $m_{\chi }$ = 10 GeV assuming the NFW as DM density profile.

   hep-phhep-exphysics.ins-detPoS(2018)·0 citations
4. 04*

   Exponentially Light Dark Matter from Coannihilation

   Raffaele Tito D'Agnolo🇺🇸 · Cristina Mondino🇺🇸 · Joshua T. Ruderman🇺🇸 · Po-Jen Wang🇺🇸

   Dark matter may be a thermal relic whose abundance is set by mutual annihilations among multiple species. Traditionally, this coannihilation scenario has been applied to weak scale dark matter that is highly degenerate with other states. We show that coannihilation among states with split masses points to dark matter that is exponentially lighter than the weak scale, down to the keV scale. We highlight the regime where dark matter does not participate in the annihilations that dilute its number density. In this "sterile coannihilation" limit, the dark matter relic density is independent of its couplings, implying a broad parameter space of thermal relic targets for future experiments. Light dark matter from coannihilation evades stringent bounds from the cosmic microwave background, but will be tested by future direct detection, fixed target, and long-lived particle experiments.

   hep-phJHEP(2018)·77 citations
5. 05*

   Study of the $s-\bar{s}$ asymmetry in the proton

   Muhammad Goharipour🇮🇷

   The study of $s-\bar{s}$ asymmetry is essential to better understand of the structure of nucleon and also the perturbative and nonperturbative mechanisms for sea quark generation. Actually, the nature and dynamical origins of this asymmetry have always been an interesting subject to research both experimentally and theoretically. One of the most powerful models can lead to $s-\bar{s}$ asymmetry is the meson-baryon model (MBM). In this work, using a simplified configuration of this model suggested by Pumplin, we calculate the $s-\bar{s}$ asymmetry for different values of cutoff parameter $\Lambda$, to study the dependence of model to this parameter and also to estimate the theoretical uncertainty imposed on the results due to its uncertainty. Then, we study the evolution of distributions obtained both at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) using different evolution schemes. It is shown that the evolution of the intrinsic quark distributions from a low initial scale, as suggested by Chang and Pang, is not a good choice at NNLO using variable flavor number scheme (VFNS).

   hep-phNPA(2018)·3 citations
6. 06*

   Heavy-Light Mesons in the Non-Relativistic Quark Model Using Laplace Transformation Method

   M. Abu-Shady🇪🇬 · E. M. Khokha🇪🇬

   An analytic solution of the N-dimensional radial Schrödinger equation with the mixture of vector and scalar potentials via the Laplace transformation method (LTM) is studied. The present potential is extended to include the spin hyperfine, spin-orbit and tensor interactions. The energy eigenvalues and the corresponding eigenfunctions have been determined in the N-dimensional space. The present results are employed to study the different properties of the heavy-light mesons. The masses of the scalar, vector, pseudoscalar and pseudovector of B, Bs, D and Ds mesons have been calculated in the three dimensional space. The effect of the dimensional number space is studied on the masses of the heavy-light mesons. We find that the meson mass increases with increasing dimensional space. The decay constants of the pseudoscalar and vector mesons have been computed. In addition, the leptonic decay widths and branching ratio for the B+, D+ and Ds+ mesons have been studied. Therefore, the present method with the present potential gives good results which are in good agreement with experimental data and are improved in comparison with recently theoretical works.

   hep-phAdv.High Energy Phys.(2018)·24 citations
7. 07*

   Signature of Lepton flavor universality violation in $B_s\to D_s\tau \nu$ semileptonic decays

   Rupak Dutta🇮🇳 · Rajeev N🇮🇳

   Deviation from the standard model prediction is observed in many semileptonic $B$ decays mediated via $b\to c$ charged current interactions. In particular, current experimental measurements of the ratio of branching ratio $R_D$ and $R_{D^{\ast }}$ in $B\to D^{(\ast )}l\nu$ decays disagree with standard model expectations at the level of about $4.1\sigma$. Moreover, recent measurement of the ratio of branching ratio $R_{J/\Psi }$ by LHCb, where $R_{J/\Psi }=\mathcal{B}(B_c\to J/\Psi \tau \nu )/\mathcal{B}(B_c\to J/\Psi \mu \nu )$, is more than $2\sigma$ away from the standard model prediction. In this context, we consider an effective Lagrangian in the presence of vector and scalar new physics couplings to study the implications of $R_D$ and $R_{D^{\ast }}$ anomalies in $B_s\to D_s\tau \nu$ decays. We give prediction of several observables such as branching ratio, ratio of branching ratio, forward backward asymmetry parameter, $\tau$ polarization fraction, and the convexity parameter for the $B_s\to D_s\tau \nu$ decays within the standard model and within various new physics scenarios.

   hep-phPRD(2018)·30 citations
8. 08*

   Signs of Dark Matter at 21-cm?

   Rennan Barkana🇮🇱 · Nadav Joseph Outmezguine🇮🇱 · Diego Redigolo🇮🇱 · Tomer Volansky🇮🇱

   Recently the EDGES collaboration reported an anomalous absorption signal in the sky-averaged 21-cm spectrum around $z=17$. Such a signal may be understood as an indication for an unexpected cooling of the hydrogen gas during or prior to the so called Cosmic Dawn era. Here we explore the possibility that dark matter cooled the gas through velocity-dependent, Rutherford-like interactions. We argue that such interactions require a light mediator that is highly constrained by 5th force experiments and limits from stellar cooling. Consequently, only a hidden or the visible photon can in principle mediate such a force. Neutral hydrogen thus plays a sub-leading role and the cooling occurs via the residual free electrons and protons. We find that these two scenarios are strongly constrained by the predicted dark matter self-interactions and by limits on millicharged dark matter respectively. We conclude that the 21-cm absorption line is unlikely to be the result of gas cooling via the scattering with a dominant component of the dark matter. An order 1\% subcomponent of millicharged dark matter remains a viable explanation.

   hep-phastro-ph.COPRD(2018)·271 citations
9. 09*

   A Holographic Description of Colour Superconductivity

   Kazem Bitaghsir Fadafan🇮🇷 · Jesus Cruz Rojas🇬🇧 · Nick Evans🇬🇧

   The difficulty of describing the gauge dependent bi-quark condensate in the QCD colour superconducting phase has made it hard to construct a holographic dual of the state. To side step this problem, we argue that near the chiral restoration transition in the temperature-chemical potential plane, the strongly coupled gluons are likely completely gapped so that the colour quantum numbers of the quarks can be thought of below that gap as global indices. A standard AdS-superconductor model can then be used to analyze the fermionic gap formation. We investigate the role of four-fermion interactions, which might be used to include the gapped QCD interactions, on the vacuum and metastable vacua of the model. It turns out to be easiest to simply relate the standard interaction of the holographic superconductor to the strength of the gapped gluons. The result is a holographic description of the QCD colour superconducting phase diagram. We take a first look at how quark mass enters and causes a transition between the colour flavour locked phase and the 2SC phase.

   hep-phhep-thPRD(2018)·41 citations
10. 10*

    Heavy-to-light scalar form factors from Muskhelishvili-Omnès dispersion relations

    De-Liang Yao🇪🇸 · P. Fernandez-Soler🇪🇸 · M. Albaladejo🇪🇸 · F.-K. Guo🇨🇳 · J. Nieves🇪🇸

    By solving the Muskhelishvili-Omnès integral equations, the scalar form factors of the semileptonic heavy meson decays $D\to \pi \bar{\ell }{\nu }_{\ell }$, $D\to \bar{K}\bar{\ell }{\nu }_{\ell }$, $\bar{B}\to \pi \ell {\bar{\nu }}_{\ell }$ and ${\bar{B}}_s\to K\ell {\bar{\nu }}_{\ell }$ are simultaneously studied. As input, we employ unitarized heavy meson-Goldstone boson chiral coupled-channel amplitudes for the energy regions not far from thresholds, while, at high energies, adequate asymptotic conditions are imposed. The scalar form factors are expressed in terms of Omnès matrices multiplied by vector polynomials, which contain some undetermined dispersive subtraction constants. We make use of heavy quark and chiral symmetries to constrain these constants, which are fitted to lattice QCD results both in the charm and the bottom sectors, and in this latter sector to the light-cone sum rule predictions close to $q^2=0$ as well. We find a good simultaneous description of the scalar form factors for the four semileptonic decay reactions. From this combined fit, and taking advantage that scalar and vector form factors are equal at $q^2=0$, we obtain $|V_{cd}|=0.244\pm 0.022$, $|V_{cs}|=0.945\pm 0.041$ and $|V_{ub}|=(4.3\pm 0.7)\times 10^{-3}$ for the involved Cabibbo-Kobayashi-Maskawa (CKM) matrix elements. In addition, we predict the following vector form factors at $q^2=0$: $|f_{+}^{D\to \eta }(0)|=0.01\pm 0.05$, $|f_{+}^{D_s\to K}(0)|=0.50\pm 0.08$, $|f_{+}^{D_s\to \eta }(0)|=0.73\pm 0.03$ and $|f_{+}^{\bar{B}\to \eta }(0)|=0.82\pm 0.08$, which might serve as alternatives to determine the CKM elements when experimental measurements of the corresponding differential decay rates become available. Finally, we predict the different form factors above the $q^2-$regions accessible in the semileptonic decays, up to moderate energies amenable to be described using the unitarized coupled-channel chiral approach.

    hep-phEPJC(2018)·17 citations
11. 11*

    Comment on "Hearing the signal of dark sectors with gravitational wave detectors" [Phys. Rev. D 94, no. 10, 103519 (2016)]

    Da Huang🇵🇱 · Bo-Qiang Lu🇨🇳

    We revisit the calculation of the gravitational wave spectra generated in a classically scale-invariant $SU(2)$ gauge sector with a scalar field in the adjoint representation, as discussed by J.~Jaeckel, et al. The finite-temperature potential at 1-loop level can induce a strong first-order phase transition, during which gravitational waves can be generated. With the accurate numerical computation of the on-shell Euclidean actions of the nucleation bubbles, we find that the triangle approximation employed by J.~Jaeckel, et al. strongly distorts the actual potential near its maximum and thus greatly underestimates the action values. As a result, the gravitational wave spectra predicted by J.~Jaeckel, et al deviate significantly from the exact ones in peak frequencies and shapes.

    hep-phPRD(2018)·4 citations
12. 12*

    Meson properties and phase diagrams in a SU(3) nlPNJL model with lQCD-inspired form factors

    J. P. Carlomagno🇦🇷

    We study the features of a nonlocal SU(3) Polyakov-Nambu-Jona-Lasinio model that includes wave function renormalization. Model parameters are determined from vacuum phenomenology considering lattice QCD-inspired nonlocal form factors. Within this framework we analyze the properties of light scalar and pseudoscalar mesons at finite temperature and chemical potential determining characteristics of deconfinement and chiral restoration transitions.

    hep-phPRD(2018)·11 citations
13. 13*

    The EDGES 21 cm Anomaly and Properties of Dark Matter

    Sean Fraser🇪🇪 · Andi Hektor🇪🇪 · Gert Hütsi🇪🇪 · Kristjan Kannike🇪🇪 · Carlo Marzo🇪🇪 · Luca Marzola🇪🇪 · Christian Spethmann🇪🇪 · Antonio Racioppi🇪🇪 · Martti Raidal🇪🇪 · Ville Vaskonen🇪🇪 · Hardi Veermäe🇪🇪

    The recently claimed anomaly in the measurement of the 21 cm hydrogen absorption signal by EDGES at $z\sim 17$, if cosmological, requires the existence of new physics. The possible attempts to resolve the anomaly rely on either (i) cooling the hydrogen gas via new dark matter-hydrogen interactions or (ii) modifying the soft photon background beyond the standard CMB one, as possibly suggested also by the ARCADE~2 excess. We argue that solutions belonging to the first class are generally in tension with cosmological dark matter probes once simple dark sector models are considered. Therefore, we propose soft photon emission by light dark matter as a natural solution to the 21 cm anomaly, studying a few realizations of this scenario. We find that the signal singles out a photophilic dark matter candidate characterised by an enhanced collective decay mechanism, such as axion mini-clusters.

    hep-phastro-ph.HEPLB(2018)·184 citations
14. 14*

    Updated Global SMEFT Fit to Higgs, Diboson and Electroweak Data

    John Ellis🇬🇧 · Christopher W. Murphy🇺🇸 · Verónica Sanz🇬🇧 · Tevong You🇬🇧

    The ATLAS and CMS collaborations have recently released significant new data on Higgs and diboson production in LHC Run 2. Measurements of Higgs properties have improved in many channels, while kinematic information for $h\to \gamma \gamma$ and $h\to ZZ$ can now be more accurately incorporated in fits using the STXS method, and $W^{+}{W}^{-}$ diboson production at high $p_T$ gives new sensitivity to deviations from the Standard Model. We have performed an updated global fit to precision electroweak data, $W^{+}{W}^{-}$ measurements at LEP, and Higgs and diboson data from Runs 1 and 2 of the LHC in the framework of the Standard Model Effective Field Theory (SMEFT), allowing all coefficients to vary across the combined dataset, and present the results in both the Warsaw and SILH operator bases. We exhibit the improvement in the constraints on operator coefficients provided by the LHC Run 2 data, and discuss the correlations between them. We also explore the constraints our fit results impose on several models of physics beyond the Standard Model, including models that contribute to the operator coefficients at the tree level and stops in the MSSM that contribute via loops.

    hep-phhep-exJHEP(2018)·313 citations
15. 15*

    Dipole portal to heavy neutral leptons

    Gabriel Magill🇨🇦 · Ryan Plestid🇨🇦 · Maxim Pospelov🇨🇦 · Yu-Dai Tsai🇺🇸

    We consider generic neutrino dipole portals between left-handed neutrinos, photons, and right-handed heavy neutral leptons (HNL) with Dirac masses. The dominance of this portal significantly alters the conventional phenomenology of HNLs. We derive a comprehensive set of constraints on the dipole portal to HNLs by utilizing data from LEP, LHC, MiniBooNE, LSND as well as observations of Supernova 1987A and consistency of the standard Big Bang Nucleosynthesis. We calculate projected sensitivities from the proposed high-intensity SHiP beam dump experiment, and the ongoing experiments at the Short-Baseline Neutrino facility at Fermilab. Dipole mediated Primakoff neutrino upscattering and Dalitz-like meson decays are found to be the main production mechanisms in most of the parametric regime under consideration. Proposed explanations of LSND and MiniBooNE anomalies based on HNLs with dipole-induced decays are found to be severely constrained, or to be tested in the future experiments.

    hep-phhep-exPRD(2018)·204 citations
16. 16*

    Cosmological Signatures of a Mirror Twin Higgs

    Zackaria Chacko🇺🇸 · David Curtin🇨🇦 · Michael Geller🇺🇸 · Yuhsin Tsai🇺🇸

    We explore the cosmological signatures associated with the twin baryons, electrons, photons and neutrinos in the Mirror Twin Higgs framework. We consider a scenario in which the twin baryons constitute a subcomponent of dark matter, and the contribution of the twin photon and neutrinos to dark radiation is suppressed due to late asymmetric reheating, but remains large enough to be detected in future cosmic microwave background (CMB) experiments. We show that this framework can lead to distinctive signals in large scale structure and in the cosmic microwave background. Baryon acoustic oscillations in the mirror sector prior to recombination lead to a suppression of structure on large scales, and leave a residual oscillatory pattern in the matter power spectrum. This pattern depends sensitively on the relative abundances and ionization energies of both twin hydrogen and helium, and is therefore characteristic of this class of models. Although both mirror photons and neutrinos constitute dark radiation in the early universe, their effects on the CMB are distinct. This is because prior to recombination the twin neutrinos free stream, while the twin photons are prevented from free streaming by scattering off twin electrons. In the Mirror Twin Higgs framework the relative contributions of these two species to the energy density in dark radiation is predicted, leading to testable effects in the CMB. These highly distinctive cosmological signatures may allow this class of models to be discovered, and distinguished from more general dark sectors.

    hep-phJHEP(2018)·121 citations
17. 17*

    Search for Boosted Dark Matter at ProtoDUNE

    Animesh Chatterjee🇺🇸 · Albert De Roeck🇨🇭 · Doojin Kim🇨🇭 · Zahra Gh. Moghaddam🇨🇭 · Jong-Chul Park🇰🇷 · Seodong Shin🇺🇸 · Leigh H. Whitehead🇨🇭 · Jaehoon Yu🇺🇸

    We propose the first experimental test of the inelastic boosted dark matter hypothesis, capitalizing on the new physics potential with the imminent data taking of the ProtoDUNE detectors. More specifically, we explore various experimental signatures at the cosmic frontier, arising in boosted dark matter scenarios, i.e., relativistic, inelastic scattering of boosted dark matter often created by the annihilation of its heavier component which usually comprises of the dominant relic abundance. Although features are unique enough to isolate signal events from potential backgrounds, vetoing a vast amount of cosmic background is rather challenging as the detectors are located on the ground. We argue, with a careful estimate, that such backgrounds nevertheless can be well under control by performing dedicated analyses after data acquisition. We then discuss some phenomenological studies which can be achieved with ProtoDUNE, employing a dark photon scenario as our benchmark dark-sector model.

    hep-phhep-exPRD(2018)·53 citations
18. 18*

    Dark halos around neutron stars and gravitational waves

    Ann Nelson🇺🇸 · Sanjay Reddy🇺🇸 · Dake Zhou🇺🇸

    We find that a class of models of MeV-GeV dark matter in which dark matter interacts strongly can be constrained by the observation of gravitational waves from neutron star mergers. Trace amounts of dark matter, either produced during the supernova or accreted later, can alter the structure of neutron stars and influence their tidal polarizability. We focus on models of dark matter interacting by the exchange of light vector gauge bosons that couple to a conserved dark charge. In these models, dark matter accumulated in neutron stars can extend to large radii and enhance their tidal polarizability. Gravitational waves detected from the first binary neutron star merger GW170817 places useful constraints on such not-so compact objects. Dark halos, if present, also predict a greater variability of neutron star tidal polarizabilities than expected for ordinary neutron stars.

    hep-phJCAP(2019)·183 citations
19. 19*

    ${\mathbf{\Omega }}_{\mathbf{b}}^{-}\to ({\mathbf{\Xi }}_{\mathbf{c}}^{+}{\mathbf{K}}^{-}){\mathbf{\pi }}^{-}$ and the ${\mathbf{\Omega }}_{\mathbf{c}}$ states

    V. R. Debastiani🇪🇸 · J. M. Dias🇪🇸 · Wei-Hong Liang🇨🇳 · E. Oset🇪🇸

    We study the weak decay ${\Omega }_b^{-}\to ({\Xi }_c^{+}{K}^{-}){\pi }^{-}$, in view of the narrow ${\Omega }_c$ states recently measured by the LHCb collaboration and later confirmed by the Belle collaboration. The ${\Omega }_c(3050)$ and ${\Omega }_c(3090)$ are described as meson-baryon molecular states, using an extension of the local hidden gauge approach in coupled channels. We investigate the $\Xi D$, ${\Xi }_c\bar{K}$ and ${\Xi }_c^{\prime }\bar{K}$ invariant mass distributions making predictions that could be confronted with future experiments, providing useful information that could help determine the quantum numbers and nature of these states.

    hep-phPRD(2018)·15 citations
20. 20*

    Bounds on dipole moments of tau-neutrino from single photon searches in $SU(4{)}_L\times U(1{)}_X$ model at CLIC and ILC energies

    D. T. Binh🇻🇳 · Vo Van On🇻🇳 · H. N. Long🇻🇳

    We investigate the dipole moments of the tau- neutrino at high-energy and high luminosity at linear electron positron colliders, such as CLIC or ILC through the analysis of the reaction $e^{+}{e}^{-}\to \nu \bar{\nu }\gamma$ in the framework of the $SU(4{)}_L\times U(1{)}_X$ model. The limits on dipole moment were obtained for integrated luminosity of $\mathcal{L}$= 500-2000\, fb${}^{-1}$ and center of mass between 0.5 and 3.0 TeV. The estimated limits for the tau-neutrino magnetic and electric dipole moments are improved by 2-3 orders of magnitude and complement previous studies on the dipole moments.

    hep-phInt.J.Mod.Phys.A(2019)·8 citations
21. 21*

    Higgs Vacuum Decay from Particle Collisions?

    Leopoldo Cuspinera🇬🇧 · Ruth Gregory🇬🇧 · Katie Marshall🇬🇧 · Ian G Moss🇬🇧

    We examine the effect of large extra dimensions on black hole seeded vacuum decay using the Randall-Sundrum model as a prototype for warped extra dimensions. We model the braneworld black hole by a tidal solution, and solve the Higgs equations of motion for the instanton on the brane. Remarkably, the action of the static instanton can be shown to be the difference in the bulk areas of the seed and remnant black holes, and we estimate these areas assuming the black holes are small compared to the bulk AdS radius. Comparing to the Hawking evaporation rate shows that small black hole seeds preferentially catalyse vacuum decay, thus extending our previous results to higher dimensional braneworld scenarios. The parameter ranges do not allow for Standard Model Higgs decay from collider black holes, but they can be relevant for cosmic ray collisions.

    ↳ hep-thhep-phPRD(2019)·16 citations
22. 22*

    Extraction of isoscalar $\pi \pi$ phase-shifts from lattice QCD

    Dehua Guo🇺🇸 · Andrei Alexandru🇺🇸 · Raquel Molina🇧🇷 · Maxim Mai🇺🇸 · Michael Döring🇺🇸

    We conduct a two-flavor ($N_f=2$) lattice QCD calculation of the elastic phase-shifts for pion-pion scattering in the scalar, isoscalar channel (the $\sigma$-meson). The calculation is performed for two quark masses corresponding to a pion mass of $315\text{ MeV}$ and $227\text{ MeV}$. The $\sigma$-meson parameters are extracted using various parametrizations of the scattering amplitude. The results obtained from a chiral unitary parametrization are extrapolated to the physical point and read $M_{\sigma }=(440_{-16}^{+10}(50)-i240(20)(25))\text{ MeV}$, where the uncertainties in the parentheses denote the stochastic and systematic ones. The behavior of the $\sigma$-meson parameters with increasing pion mass is discussed as well.

    ↳ hep-lathep-phnucl-thPRD(2018)·91 citations
23. 23*

    Energy budget of cosmological first-order phase transition in FLRW background

    Rong-Gen Cai🇨🇳 · Shao-Jiang Wang🇨🇳

    We study the hydrodynamics of bubble expansion in cosmological first-order phase transition in the Friedmann-Lema\^ıtre-Robertson-Walker (FLRW) background with probe limit. Different from previous studies for fast first-order phase transition in flat background, we find that, for slow first-order phase transition in FLRW background with a given peculiar velocity of the bubble wall, the efficiency factor of energy transfer into bulk motion of thermal fluid is significantly reduced, thus decreasing the previously-thought dominated contribution from sound wave to the stochastic gravitational-wave background.

    ↳ gr-qcastro-ph.COhep-phSCPMA(2018)·19 citations
24. 24*

    Forecasts for Warm Dark Matter from Photometric Galaxy Surveys

    Jéssica S. Martins🇧🇷 · Rogerio Rosenfeld🇧🇷 · Flavia Sobreira🇧🇷

    We present a Fisher matrix forecast for the sensitivity on the mass of a thermal warm dark matter (WDM) particle from current (DES-like) and future (LSST-like) photometric galaxy surveys using the galaxy angular power spectrum. We model the nonlinear clustering using a modified Halo Model proposed to account for WDM effects. We estimate that from this observable alone a lower bound of $m_{\text{wdm}}>647$\,eV ($m_{\text{wdm}}>126$\,eV) for the LSST (DES) case could be obtained.

    ↳ astro-ph.COhep-phMNRAS(2018)·11 citations
25. 25*

    Multiple spectator condensates from inflation

    Robert J. Hardwick🇬🇧

    We investigate the development of spectator (light test) field condensates due to their quantum fluctuations in a de Sitter inflationary background, making use of the stochastic formalism to describe the system. In this context, a condensate refers to the typical field value found after coarse-graining using the Hubble scale $H$, which can be essential to seed the initial conditions required by various post-inflationary processes. We study models with multiple coupled spectators and for the first time we demonstrate that new forms of stationary solution exist (distinct from the standard exponential form) when the potential is asymmetric. Furthermore, we find a critical value for the inter-field coupling as a function of the number of fields above which the formation of stationary condensates collapses to $H$. Considering some simple two-field example potentials, we are also able to derive a lower limit on the coupling, below which the fluctuations are effectively decoupled, and the standard stationary variance formulae for each field separately can be trusted. These results are all numerically verified by a new publicly available python class (https://github.com/umbralcalc/nfield) to solve the coupled Langevin equations over a large number of fields, realisations and timescales. Further applications of this new tool are also discussed.

    ↳ gr-qchep-phhep-thJCAP(2018)·12 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.