Fri·Apr 19, 2019Friday·April 19, 2019

1. 01*

   No strong $CP$ violation up to the one-loop level in a two-Higgs-doublet model

   P.M. Ferreira🇵🇹 · L. Lavoura🇵🇹

   We put forward a two-Higgs-doublet model, furnished with a $Z_3$ symmetry, wherein $CP$ is conserved in the dimension-four terms of the Lagrangian and is softly broken in the scalar potential. The new particles of our model are one neutral scalar $H$, one neutral pseudoscalar $A$, and two charged scalars $H^{\pm }$. In our model the only locus of $CP$ violation is the CKM matrix. Strong $CP$ violation is absent both at the tree and one-loop levels. We work out the phenomenological constraints on our model, which features flavour-changing neutral Yukawa interactions, showing that the new scalar particles may in some cases be lighter than 500\,GeV.

   hep-phEPJC(2019)·9 citations
2. 02*

   Discovering True Muonium at LHCb

   Xabier Cid Vidal🇪🇸 · Philip Ilten🇬🇧 · Jonathan Plews🇬🇧 · Brian Shuve🇺🇸 · Yotam Soreq🇮🇱

   We study the potential of the LHCb experiment to discover, for the first time, the ${\mu }^{+}{\mu }^{-}$ true muonium bound state. We propose a search for the vector $1^3{S}_1$ state, $\mathcal{T}\mathcal{M}$, which kinetically mixes with the photon and dominantly decays to $e^{+}{e}^{-}$. We demonstrate that a search for $\eta \to \gamma \mathcal{T}\mathcal{M}$, $\mathcal{T}\mathcal{M}\to e^{+}{e}^{-}$ in a displaced vertex can exceed a significance of 5 standard deviations assuming statistical uncertainties. We present two possible searches: an inclusive search for the $e^{+}{e}^{-}$ vertex, and an exclusive search which requires an additional photon and a reconstruction of the $\eta$ mass.

   hep-phhep-exPRD(2019)·39 citations
3. 03*

   Portraying Double Higgs at the Large Hadron Collider

   Jeong Han Kim🇺🇸 · Minho Kim🇰🇷 · Kyoungchul Kong🇺🇸 · Konstantin T. Matchev🇺🇸 · Myeonghun Park🇰🇷

   We examine the discovery potential for double Higgs production at the high luminosity LHC in the final state with two $b$-tagged jets, two leptons and missing transverse momentum. Although this dilepton final state has been considered a difficult channel due to the large backgrounds, we argue that it is possible to obtain sizable signal significance, by adopting a deep learning framework making full use of the relevant kinematics along with the jet images from the Higgs decay. For the relevant number of signal events we obtain a substantial increase in signal sensitivity over existing analyses. We discuss relative improvements at each stage and the correlations among the different input variables for the neutral network. The proposed method can be easily generalized to the semi-leptonic channel of double Higgs production, as well as to other processes with similar final states.

   hep-phhep-exJHEP(2019)·37 citations
4. 04*

   The $\varphi (2170)$ production in the process $\gamma p\to \eta \varphi p$

   Chen-Guang Zhao🇨🇳 · Guan-Ying Wang🇨🇳 · Guan-Nan Li🇨🇳 · En Wang🇨🇳 · De-Min Li🇨🇳

   We have studied the $\gamma p\to \eta \varphi p$ reaction within the effective Lagrangian approach, by considering the contribution of the intermediate state $\varphi (2170)$ production, and the background contributions of $t$-channel ${\pi }^0$ and $\eta$ mesons exchanges with the intermediate states $N$ and $N(1535)$. Our calculations show that there may be a peak, at least a bump structure around 2180 MeV associated to the resonance $\varphi (2170)$ in the $\eta \varphi$ mass distribution. We suggest to search for the resonance $\varphi (2170)$ in this reaction, which would be helpful to shed light on its nature.

   hep-phhep-exPRD(2019)·23 citations
5. 05*

   $B$-hadron fragmentation functions at next-to-next-to-leading order from global analysis of $e^{+}{e}^{-}$ annihilation data

   Maral Salajegheh🇮🇷 · S. Mohammad Moosavi Nejad🇮🇷 · Hamzeh Khanpour🇮🇷 · Bernd A. Kniehl🇩🇪 · Maryam Soleymaninia🇮🇷

   We present nonperturbative fragmentation functions (FFs) for bottom-flavored ($B$) hadrons both at next-to-leading (NLO) and, for the first time, at next-to-next-to-leading order (NNLO) in the $\overline{\mathrm{MS}}$ factorization scheme with five massless quark flavors. They are determined by fitting all available experimental data of inclusive single $B$-hadron production in $e^{+}{e}^{-}$ annihilation, from the ALEPH, DELPHI, and OPAL Collaborations at CERN LEP1 and the SLD Collaboration at SLAC SLC. The uncertainties in these FFs as well as in the corresponding observables are estimated using the Hessian approach. We perform comparisons with available NLO sets of $B$-hadron FFs. We apply our new FFs to generate theoretical predictions for the energy distribution of $B$ hadrons produced through the decay of unpolarized or polarized top quarks, to be measured at the CERN LHC.

   hep-phPRD(2019)·45 citations
6. 06*

   Resummation of soft and Coulomb corrections for $t\bar{t}h$ production at the LHC

   Wan-Li Ju🇨🇳 · Li Lin Yang🇨🇳

   In this paper, a combined resummation of soft and Coulomb corrections is performed for the associated production of the Higgs boson with a top quark pair at the LHC. We illustrate the similarities and critical differences between this process and the $t\bar{t}$ production process. We show that up to the next-to-leading power, the total cross section for $t\bar{t}h$ production admits a similar factorization formula in the threshold limit as that for $t\bar{t}$ production. This fact, however, is not expected to hold at higher powers. Based on the factorization formula, we perform the resummation at the improved next-to-leading logarithmic accuracy, and match to the next-to-leading order result. This allows us to give NLL${}^{\prime }$+NLO predictions for the total cross sections at the LHC. We find that the resummation effects enhance the NLO cross sections by about 6\%, and significantly reduce the scale dependence of the theoretical predictions.

   hep-phJHEP(2019)·23 citations
7. 07*

   Proton decay in flux compactifications

   Wilfried Buchmuller🇩🇪 · Ketan M. Patel🇮🇳

   We study proton decay in a six-dimensional orbifold GUT model with gauge group $SO(10)\times U(1{)}_A$. Magnetic $U(1{)}_A$ flux in the compact dimensions determines the multiplicity of quark-lepton generations, and it also breaks supersymmetry by giving universal GUT scale masses to scalar quarks and leptons. The model can successfully account for quark and lepton masses and mixings. Our analysis of proton decay leads to the conclusion that the proton lifetime must be close to the current experimental lower bound. Moreover, we find that the branching ratios for the decay channels $p\to e^{+}{\pi }^0$ and $p\to {\mu }^{+}{\pi }^0$ are of similar size, in fact the latter one can even be dominant. This is due to flavour non-diagonal couplings of heavy vector bosons together with large off-diagonal Higgs couplings, which appears to be a generic feature of flux compactifications.

   hep-phhep-thJHEP(2019)·9 citations
8. 08*

   Nonlinear flavor development of a two-dimensional neutrino gas

   Joshua D. Martin🇺🇸 · Sajad Abbar🇺🇸 · Huaiyu Duan🇺🇸

   We present a numerical survey of the nonlinear flavor development of dense neutrino gases. This study is based on the stationary, two-dimensional ($x$ and $z$), two-beam, monochromatic neutrino line model with a periodic boundary condition along the $x$ direction. Similar to a previous work, we find that small-scale flavor structures can develop in a neutrino gas even if the physical conditions are nearly homogeneous along the $x$ axis initially. The power diffusion from the large-scale to small-scale structures increases with the neutrino density and helps to establish a semi-exponential dependence of the magnitudes of the Fourier moments on the corresponding wave numbers. The overall flavor conversion probabilities in the neutrino gases with small initial sinusoidal perturbations reach certain equilibrium values at large distances which are mainly determined by the neutrino-antineutrino asymmetry. Similar phenomena also exist in a neutrino gas with a localized initial perturbation, albeit only inside an expanding flavor conversion region. Our work suggests that a statistical treatment may be possible for the collective flavor oscillations of a dense neutrino gas in a multi-dimensional environment.

   hep-phastro-ph.HEnucl-thPRD(2019)·29 citations
9. 09*

   Identifying a Higgsino-like NLSP in the context of a keV-scale gravitino LSP

   Juhi Dutta🇮🇳 · Biswarup Mukhopadhyaya🇮🇳 · Santosh Kumar Rai🇮🇳

   The presence of a Higgsino-like neutralino next-to-lightest sparticle (NLSP) and a keV scale gravitino ($\tilde{G}$) LSP opens up new decay modes of the NLSP, mainly to a Higgs/$Z$ boson and the LSP. Besides, a keV-scale gravitino as a warm dark matter candidate salvages a relatively-light Higgsino-like NLSP from dark matter constraints. We focus on the prospects of observing at least one b jet and two opposite sign leptons with a large missing transverse momenta ($\ge 1b$ $+$ ${\ell }^{+}{\ell }^{-}+/E_T$) signal at the LHC. A distinguishing feature of this scenario is the production of longitudinal $Z$ bosons in neutralino decays, unlike in the case of gauginolike neutralinos, where the $Z$ is mostly transverse. The polarisation information of the parent $Z$ boson gets reflected in the angular distributions of the decay leptons and in some other variables derived therefrom.

   hep-phPRD(2020)·5 citations
10. 10*

    The Polarized Two-Loop Massive Pure Singlet Wilson Coefficient for Deep-Inelastic Scattering

    J. Blümlein🇩🇪 · C.G. Raab🇦🇹 · K. Schönwald🇩🇪

    We calculate the polarized massive two--loop pure singlet Wilson coefficient contributing to the structure functions $g_1(x,Q^2)$ analytically in the whole kinematic region. The Wilson coefficient contains Kummer--elliptic integrals. We derive the representation in the asymptotic region $Q^2\gg m^2$, retaining power corrections, and in the threshold region. The massless Wilson coefficient is recalculated. The corresponding twist--2 corrections to the structure function $g_2(x,Q^2)$ are obtained by the Wandzura--Wilczek relation. Numerical results are presented.

    hep-phhep-exNPB(2019)·29 citations
11. 11*

    Vacuum Decay in Real Time and Imaginary Time Formalisms

    Mark P. Hertzberg🇺🇸 · Masaki Yamada🇺🇸

    We analyze vacuum tunneling in quantum field theory in a general formalism by using the Wigner representation. In the standard instanton formalism, one usually approximates the initial false vacuum state by an eigenstate of the field operator, imposes Dirichlet boundary conditions on the initial field value, and evolves in imaginary time. This approach does not have an obvious physical interpretation. However, an alternative approach does have a physical interpretation: in quantum field theory, tunneling can happen via classical dynamics, seeded by initial quantum fluctuations in both the field and its momentum conjugate, which was recently implemented in Ref. [1]. We show that the Wigner representation is a useful framework to calculate and understand the relationship between these two approaches. We find there are two, related, saddle point approximations for the path integral of the tunneling process: one corresponds to the instanton solution in imaginary time and the other one corresponds to classical dynamics from initial quantum fluctuations in real time. The classical approximation for the dynamics of the latter process is justified only in a system with many degrees of freedom, as can appear in field theory due to high occupancy of nucleated bubbles, while it is not justified in single particle quantum mechanics, as we explain. We mention possible applications of the real time formalism, including tunneling when the instanton vanishes, or when the imaginary time contour deformation is not possible, which may occur in cosmological settings.

    ↳ hep-thastro-ph.COgr-qchep-ph+1PRD(2019)·42 citations
12. 12*

    Effective gauge theories of superfluidity with topological order

    Yuji Hirono🇰🇷 · Yuya Tanizaki🇺🇸

    We discuss the low-energy dynamics of superfluidity with topological order in $(3+1)$ spacetime dimensions. We generalize a topological $BF$ theory by introducing a non-square $K$ matrix, and this generalized $BF$ theory can describe massless Nambu-Goldstone bosons and anyonic statistics between vortices and quasiparticles. We discuss the general structure of discrete and continuous higher-form symmetries in this theory, which can be used to classify quantum phases. We describe how to identify the appearance of topological order in such systems and discuss its relation to a mixed 't Hooft anomaly between discrete higher-form symmetries. We apply this framework to the color-flavor locked phase of dense QCD, which shows anyonic particle-vortex statistics while no topological order appears. An explicit example of superfluidity with topological order is discussed.

    ↳ hep-thcond-mat.str-elhep-phnucl-thJHEP(2019)·24 citations
13. 13*

    Gravitino condensate in $N=1$ supergravity coupled to the $N=1$ supersymmetric Born-Infeld theory

    Ryotaro Ishikawa🇯🇵 · Sergei V. Ketov🇯🇵

    The $N=1$ supersymmetric Born-Infeld theory coupled to $N=1$ supergravity in four spacetime dimensions is studied in the presence of a cosmological term with spontaneous supersymmetry breaking. The consistency is achieved by compensating a negative contribution to the cosmological term from the Born-Infeld theory by a positive contribution originating from the gravitino condensate. This leads to an identification of the Born-Infeld scale with the supersymmetry breaking scale. The dynamical formation of the gravitino condensate in supergravity is reconsidered and the induced one-loop effective potential is derived. Slow roll cosmological inflation with the gravitino condensate as the inflaton (near the maximum of the effective potential) is viable against the Planck 2018 data and can lead to the inflationary (Hubble) scale as high as $10^{12}$ GeV. Uplifting the Minkowski vacuum (after inflation) to a de Sitter vacuum (dark energy) is possible by the use of the alternative Fayet-Iliopoulos term. Some major physical consequences of our scenario to reheating are briefly discussed also.

    ↳ hep-thgr-qchep-phPTEP(2020)·7 citations
14. 14*

    Phase ambiguity of the measure for continuum Majorana fermions

    Maarten Golterman🇺🇸 · Yigal Shamir🇮🇱

    Integrating over a continuum Majorana fermion formally yields a functional pfaffian. We show that the phase of this pfaffian is ambiguous, as it depends on the choice of basis. This ambiguity is naturally resolved within a non-perturbative lattice definition, allowing us to discuss the relation between the phase of the lattice pfaffian and the effective $\theta$ angle of the theory. We also resolve an apparent paradox regarding the induced $\theta$ angle when a theory of $N$ Dirac fermions in a real representation of the gauge group is re-expressed in terms of $2N$ Majorana fermions. We discuss how all this is reflected in chiral perturbation theory.

    ↳ hep-lathep-phhep-thPRD(2019)·2 citations
15. 15*

    Mean-field potential effects in the cumulants of baryons from central Au+Au collision at $E_{lab}$= 1.23 GeV$/$nucleon

    Yongjia Wang🇨🇳 · Yunxiao Ye🇨🇳 · QIngfeng Li🇨🇳

    The cumulants of baryon multiplicity distribution in relativistic heavy-ion collisions (HICs) have attracted considerable attention recently. It has been conjectured that they may serve as a promising observable to detect the critical end point in the QCD phase diagram, while the cumulants in HICs at intermediate energies have not been widely studied to date. How to interpret the cumulants data at intermediate energies and compare with the data at relativistic energies is now being actively discussed. Both meam-field potential and clustering are highly important to HICs at intermediate energies. In this talk, we discuss these effects on the cumulant ratios of baryon number distributions in Au+Au collisions at beam energies of 1.23 GeV$/$nucleon which have been currently performed by the HADES Collaboration at GSI. Within the newest version of the ultrarelativistic quantum molecular dynamics (UrQMD) model, calculations with different mean field potentials as well as without mean field potential are performed. It is found that the mean field potential enhances fluctuations in the momentum space during the expanding stage, especially in a small rapidity acceptance window. The enhancement of cumulant ratios for free protons is suppressed compared with that for all baryons.

    ↳ nucl-thhep-phAIP Conf.Proc.(2019)·0 citations
16. 16*

    Two-particle angular correlations in heavy ion collisions from a multiphase transport model

    Liu-Yao Zhang🇨🇳 · Jin-Hui Chen🇨🇳 · Zi-Wei Lin🇺🇸 · Yu-Gang Ma🇨🇳 · Song Zhang🇨🇳

    We extend our earlier study on two-particle angular correlations in $pp$ collisions at low transverse momentum ($p_T$) to $p$-Pb, Pb-Pb and Au-Au collisions at RHIC and LHC energies. We mainly use the string melting version of a multiphase transport model with improved quark coalescence for this study. We start from the analysis of ${\pi }^{\pm }$, $K^{\pm }$ and $p$($\bar{p}$) $p_T$ and rapidity distributions at different centralities. We then focus on two-particle angular correlations in $p$-Pb collisions at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}=5.02$ TeV and Pb-Pb collisions at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}=2.76$ TeV. For $p$-Pb collisions, a near side depression in the angular correlation is observed for low $p_T$ proton pairs and $\Lambda$ pairs but not for pion pairs or kaon pairs, similar to our earlier finding for $pp$ collisions at $\sqrt{\mathrm{s}}=7$ TeV. This is also the case for very low multiplicity Pb-Pb and Au-Au collisions. We also find that parton interactions and the improved quark coalescence are mainly responsible for the depression feature in baryon pair angular correlations. However, no such baryon-baryon anti-correlations are observed in Pb-Pb and Au-Au collisions at higher multiplicities. Therefore our results suggest that low $p_T$ baryon-baryon angular anti-correlations have a strong multiplicity dependence.

    ↳ nucl-thhep-phnucl-exPRC(2019)·19 citations
17. 17*

    Emergence of hydrodynamical behavior in expanding quark-gluon plasmas

    Jean-Paul Blaizot🇫🇷 · Li Yan🇨🇳

    We use a set of simple angular moments to solve the Boltzmann equation in the relaxation time approximation for a boost invariant longitudinally expanding gluonic plasma. The transition from the free streaming regime at early time to the hydrodynamic regime at late time is well captured by the first two-moments, corresponding to the monopole and quadrupole components of the momentum distribution, or equivalently to the energy density and the difference between the longitudinal and the transverse pressures. We relate this property to the existence of fixed points in the infinite hierarchy of equations satisfied by the moments. These fixed points are already present in the two-moment truncations and are only moderately affected by the coupling to higher moments. Collisions contribute to a damping of all the non trivial moments. At late time, when the hydrodynamic regime is entered, only the monopole and quadrupole moments are significant and remain strongly coupled, the decay of the quadrupole moment being delayed by the expansion, causing in turn a delay in the full isotropization of the system. The two-moment truncation contains second order viscous hydrodynamics, in its various variants, and third order hydrodynamics, together with explicit values of the relevant transport coefficients, can be easily obtained from the three-moment truncation.

    ↳ nucl-thhep-phnucl-exAnnals Phys.(2020)·76 citations
18. 18*

    Light-meson leptonic decay rates in lattice QCD+QED

    M. Di Carlo🇮🇹 · D. Giusti🇮🇹 · V. Lubicz🇮🇹 · G. Martinelli🇮🇹 · C.T. Sachrajda🇬🇧 · F. Sanfilippo🇮🇹 · S. Simula🇮🇹 · N. Tantalo🇮🇹

    The leading electromagnetic (e.m.) and strong isospin-breaking corrections to the ${\pi }^{+}\to {\mu }^{+}\nu [\gamma ]$ and $K^{+}\to {\mu }^{+}\nu [\gamma ]$ leptonic decay rates are evaluated for the first time on the lattice. The results are obtained using gauge ensembles produced by the European Twisted Mass Collaboration with $N_f=2+1+1$ dynamical quarks. The relative leading-order e.m.~and strong isospin-breaking corrections to the decay rates are 1.53(19)\% for ${\pi }_{\mu 2}$ decays and 0.24(10)\% for $K_{\mu 2}$ decays. Using the experimental values of the ${\pi }_{\mu 2}$ and $K_{\mu 2}$ decay rates and updated lattice QCD results for the pion and kaon decay constants in isosymmetric QCD, we find that the Cabibbo-Kobayashi-Maskawa matrix element $|V_{us}|=0.22538(46)$, reducing by a factor of about $1.8$ the corresponding uncertainty in the Particle Data Group review. Our calculation of $|V_{us}|$ allows also an accurate determination of the first-row CKM unitarity relation $|V_{ud}{|}^2+|V_{us}{|}^2+|V_{ub}{|}^2=0.99988(46)$. Theoretical developments in this paper include a detailed discussion of how QCD can be defined in the full QCD+QED theory and an improved renormalisation procedure in which the bare lattice operators are renormalised non-perturbatively into the (modified) Regularization Independent Momentum subtraction scheme and subsequently matched perturbatively at $O({\alpha }_{em}{\alpha }_s(M_W))$ into the W-regularisation scheme appropriate for these calculations.

    ↳ hep-lathep-exhep-phPRD(2019)·151 citations
19. 19*

    Strong dynamics with matter in multiple representations: SU(4) gauge theory with fundamental and sextet fermions

    Guido Cossu🇬🇧 · Luigi Del Debbio🇬🇧 · Marco Panero🇮🇹 · David Preti🇮🇹

    We present a non-perturbative lattice study of SU(4) gauge theory with two flavors of fermions in the fundamental representation and two in the two-index antisymmetric representation: a theory closely related to a minimal partial-compositeness model for physics beyond the Standard Model, that was proposed by G. Ferretti. We discuss the phase structure of the lattice theory and report results for various observables of interest, including the masses of states obtained from different combinations of valence fermions and the spectrum of the Dirac operator. Finally, we comment on the extension of this type of studies to other partial-compositeness models (including, in particular, one that was recently suggested by H. Gertov et al.), which could admit lighter top-quark partners, highlighting some key features of our lattice simulation algorithm, that make it suitable for such generalizations.

    ↳ hep-lathep-phEPJC(2019)·50 citations
20. 20*

    Axion-Dilaton Destabilization and the Hubble Tension

    Stephon Alexander🇺🇸 · Evan McDonough🇺🇸

    The discrepancy in measurements of the Hubble constant indicates new physics in dark energy, dark matter, or both. Drawing inspiration from string theory, where axions interact with the other moduli fields, including the dilaton, here we demonstrate that the dynamics of an interacting dilaton and axion naturally realizes the proposal of Early Dark Energy. In this setup, stabilization of the the dilaton is in part due to the axion, and in the early universe the dilaton contributes to dark energy. The combined axion-dilaton system is destabilized when the Hubble constant falls below the mass of the axion, triggering a phase of fast-roll evolution of the dilaton wherein its equation of state is $w=1$, and the early dark energy redshifts away as $a^{-6}$.

    ↳ astro-ph.COgr-qchep-phhep-thPLB(2019)·156 citations
21. 21*

    Cosmic-ray transport from AMS-02 B/C data: benchmark models and interpretation

    Yoann Genolini🇧🇪 · Mathieu Boudaud🇫🇷 · Pedro Ivo Batista🇧🇷 · Sami Caroff🇫🇷 · Laurent Derome🇫🇷 · Julien Lavalle🇫🇷 · Alexandre Marcowith🇫🇷 · David Maurin🇫🇷 · Vincent Poireau🇫🇷 · Vivian Poulin🇫🇷 · Sylvie Rosier🇫🇷 · Pierre Salati🇫🇷 · Pasquale Dario Serpico🇫🇷 · Manuela Vecchi🇧🇷

    This article aims at establishing new benchmark scenarios for Galactic cosmic-ray propagation in the GV-TV rigidity range, based on fits to the AMS-02 B/C data with the USINE v3.5 propagation code. We employ a new fitting procedure, cautiously taking into account data systematic error correlations in different rigidity bins and considering Solar modulation potential and leading nuclear cross-section as nuisance parameters. We delineate specific low, intermediate, and high-rigidity ranges that can be related to both features in the data and peculiar microphysics mechanisms resulting in spectral breaks. We single out a scenario which yields excellent fits to the data and includes all the presumably relevant complexity, the BIG model. This model has two limiting regimes: (i) the SLIM model, a minimal diffusion-only setup, and (ii) the QUAINT model, a convection-reacceleration model where transport is tuned by non-relativistic effects. All models lead to robust predictions in the high-energy regime ($\gtrsim 10$GV), i.e. independent of the propagation scenario: at $1\sigma$, the diffusion slope $\delta$ is $[0.43-0.53]$, whereas $K_{10}$, the diffusion coefficient at 10GV, is $[0.26-0.36]$kpc${}^2$Myr${}^{-1}$; we confirm the robustness of the high-energy break, with a typical value ${\Delta }_h\sim 0.2$. We also find a hint for a similar (reversed) feature at low rigidity around the B/C peak ($\sim 4$GV) which might be related to some effective damping scale in the magnetic turbulence.

    ↳ astro-ph.HEhep-phPRD(2019)·107 citations
22. 22*

    Testing $\Lambda$CDM With Dwarf Galaxy Morphology

    Weishuang Linda Xu🇺🇸 · Lisa Randall🇺🇸

    The leading tensions to the collisionless cold dark matter (CDM) paradigm are the "small-scale controversies", discrepancies between observations at the dwarf-galactic scale and their simulational counterparts. In this work we consider methods to infer 3D morphological information on Local Group dwarf spheroidals, and test the fitness of CDM+hydrodynamics simulations to the observed galaxy shapes. We find that the subpopulation of dwarf galaxies with mass-to-light ratio $\gtrsim 100M_{\odot }/L_{\odot }$ reflects an oblate morphology. This is discrepant with the dwarf galaxies with mass-to-light ratio $\lesssim 100M_{\odot }/L_{\odot }$, which reflect prolate morphologies, and more importantly with simulations of CDM-sourced galaxies which are explicitly prolate. Although more simulations and data are called for, if evidence of oblate pressure-supported stellar distributions persists, we argue that an underlying oblate non-CDM dark matter halo may be required, and present this as motivation for future studies.

    ↳ astro-ph.GAhep-phApJ(2020)·7 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.