HEP Phenomenology·hep-ph

Thu·Nov 15, 2018Thursday·November 15, 2018

33 papers—24 primary·9 cross-listed·reconstructed*

01*
Acoplanarity of Lepton Pair to Probe the Electromagnetic Property of Quark Matter
Spencer Klein🇺🇸 · A.H. Mueller🇺🇸 · Bo-Wen Xiao🇨🇳 · Feng Yuan🇺🇸
We investigate the $P_{T}$ -broadening effects in dilepton production through photon-photon scattering in heavy ion collisions. The QED multiple interaction effects with the medium is found to be consistent with a recent observation of low transverse momentum lepton pair from ATLAS collaboration at the LHC. We further comment on the magnetic effects and point out a number of ways to disentangle these two mechanisms. In particular, the rapidity dependence of the $P_{T}$ -broadening effects provide a unique probe to the magnetic effects.
hep-phhep-exnucl-exnucl-thPRL(2019)·77 citations
02*
Addressing Astrophysical and Cosmological Problems With Secretly Asymmetric Dark Matter
Christopher Dessert🇺🇸 · Can Kilic🇺🇸 · Cynthia Trendafilova🇺🇸 · Yuhsin Tsai🇺🇸
We present a simple model of dark matter that can address astrophysical and cosmological puzzles across a wide range of scales. The model is an application of the Secretly Asymmetric Dark Matter mechanism, where several flavors of dark matter are fully asymmetric despite an exact dark matter number symmetry $U (1)_{χ}$ . The dark matter relic abundance arises from these asymmetries, generated in the early universe through right-handed neutrino decays. The $U (1)_{χ}$ is gauged by a massless dark photon, and asymmetries with opposite signs in the different DM flavors result in the formation of bound states. Dark acoustic oscillations in the early universe lead to a suppression in the matter power spectrum for addressing the $σ_{8}$ problem. The dark photon as a relativistic degree of freedom contributes to $Δ N_{e f f}$ , easing the tension between the CMB and late-time $H_{0}$ measurements. Finally, scattering between the bound states after structure formation leads to a flattening of the dark matter distribution at the cores of haloes.
hep-phPRD(2019)·30 citations
03*
$R$ -parity Violating Decays of Wino Chargino and Wino Neutralino LSPs and NLSPs at the LHC
Sebastian Dumitru🇺🇸 · Burt A. Ovrut🇺🇸 · Austin Purves🇺🇸
The $R$ -parity violating decays of both Wino chargino and Wino neutralino LSPs are analyzed within the context of the $B - L$ MSSM "heterotic standard model". These LSPs correspond to statistically determined initial soft supersymmetry breaking parameters which, when evolved using the renormalization group equations, lead to an effective theory satisfying all phenomenological requirements; including the observed electroweak vector boson and Higgs masses. The explicit decay channels of these LSPs into standard model particles, the analytic and numerical decay rates and the associated branching ratios are presented. The decay lengths of these RPV interactions are discussed. It is shown that the vast majority of these decays are "prompt", although a small, but calculable, number correspond to "displaced vertices" of various lengths. It is demonstrated that for a Wino chargino LSP, the NLSP is the Wino neutralino with a mass only slightly higher than the LSP-- and vice-versa. As a consequence, we show that both the Wino chargino and Wino neutralino LSP/NLSP $R$ -parity violating decays should be simultaneously observable at the CERN LHC.
hep-phhep-exJHEP(2019)·21 citations
04*
Towards a precise determination of the scattering amplitudes of the charmed and light-flavor pseudoscalar mesons
Zhi-Hui Guo🇨🇳 · Liuming Liu🇨🇳 · Ulf-G. Meissner🇩🇪 · J. A. Oller🇪🇸 · A. Rusetsky🇩🇪
We study the scattering of the light-flavor pseudoscalar mesons ( $π, K, η$ ) off the ground-state charmed mesons ( $D, D_{s}$ ) within chiral effective field theory. The recent lattice simulation results on various scattering lengths and the finite-volume spectra both in the moving and center-of-mass frames, most of which are obtained at unphysical meson masses, are used to constrain the free parameters in our theory. Explicit formulas to include the $S$ - and $P$ -wave mixing to determine the finite-volume energy levels are provided. After a successful reproduction of the lattice data, we perform a chiral extrapolation to predict the quantities with physical meson masses, including phase shifts, inelasticities, resonance pole positions and the corresponding residues from the scattering of the light pseudoscalar and charmed mesons.
hep-phhep-latEPJC(2019)·89 citations
05*
$η n$ photoproduction and nucleon resonances
Jung-Min Suh🇰🇷 · Sang-Ho Kim🇰🇷 · Hyun-Chul Kim🇰🇷
We present results of a recent work on the reaction mechanism of $η n$ photoproduction off the neutron in the range of $s \approx 1.5 - 1.9$ GeV and discuss the role of various nucleon resonances listed in the Particle Data Group (PDG). We make use of an effective Lagrangian approach combining with a Regge method. The total and helicity-dependent cross sections $σ_{1/2}, σ_{3/2}$ are computed and the numerical results are in good agreement with the A2 experimental data.
hep-phhep-exnucl-exnucl-thSpringer Proc.Phys.(2020)·0 citations
06*
Instanton effects on charmonium states
Ulugbek Yakhshiev🇰🇷 · Hyun-Chul Kim🇰🇷 · Emiko Hiyama🇯🇵
The instanton effects on the charmonium spectrum is discussed in the framework of nonrelativistic potential model. The results from constituent quark model without inclusion of instanton effects is compared with the results for `the potential from constituent quark model + the contribution from the instanton liquid model'. We consider two models with the corresponding instanton potentials and discuss their relevance to explanations of the origin phenomenological parameters used in the nonrelativistic potential models. We also present the universal instanton potential in the parametrized form which can be useful in practical calculations.
hep-phhep-exhep-latPRD(2018)·9 citations
07*
Antishadowing in the rescaling model at x ~ 0.1
A.V. Kotikov🇷🇺 · B.G. Shaikhatdenov🇷🇺 · Pengming Zhang🇨🇳
The antishadowing behavior of the sea and valence quark densities in nuclei is investigated in the framework of the rescaling model at the values x ~ 0.1 of the Bjorken variable x.
hep-ph10 citations
08*
Invisible neutrino decays at the MOMENT experiment
Jian Tang🇨🇳 · TseChun Wang🇨🇳 · Yibing Zhang🇨🇳
We investigate invisible decays of the third neutrino mass eigenstate in future accelerator neutrino experiments using muon-decay beams such as MuOn-decay MEdium baseline NeuTrino beam experiment (MOMENT). MOMENT has an outstanding performance to measure the deficit or excess in the spectra caused by neutrino decays, especially in $ν_{μ}$ and $ν ˉ_{μ}$ disappearance channels. Such an experiment will improve the constraints of the neutrino lifetime $τ_{3}$ . Compared with exclusion limits in the current accelerator neutrino experiments T2K and NOvA under the stable $ν$ assumption, we expect that MOMENT gives the bound of $τ_{3} / m_{3} \geq 1.46 \times 1 0^{- 11}$ ~s/eV at $3 σ$ confidence level, which is better than their recent limits: $τ_{3} / m_{3} \geq 7 \times 1 0^{- 13}$ ~s/eV in NOvA and $τ_{3} / m_{3} \geq 1.41 \times 1 0^{- 12}$ ~s/eV in T2K. The non-decay scenario is expected to be excluded by MOMENT at the $> 3 σ$ confidence level, if the best fit results in T2K and NOvA are confirmed. We further find that reducing systematic uncertainties is slightly more important than the running time. Finally, we find very little correlations between $τ_{3} / m_{3}$ and other oscillation parameters, which point to an advantage of MOMENT to measure $τ_{3} / m_{3}$ .
hep-phJHEP(2019)·25 citations
09*
Tau Polarimetry in B Meson Decays
Rodrigo Alonso🇯🇵 · Jorge Martin Camalich🇪🇸 · Susanne Westhoff🇩🇪
This article summarizes recent developments in $B \to D^{(*)} τ ν$ decays. We explain how to extract the tau lepton's production properties from the kinematics of its decay products. The focus is on hadronic tau decays, which are most sensitive to the tau polarizations. We present new results for effects of new physics in tau polarization observables and quantify the observation prospects at BELLE II.
hep-phhep-exSciPost Phys.Proc.(2019)·6 citations
10*
Gravitational Waves from Walking Technicolor
Kohtaroh Miura🇩🇪 · Hiroshi Ohki🇯🇵 · Saeko Otani🇯🇵 · Koichi Yamawaki🇯🇵
We study gravitational waves from the first-order electroweak phase transition in the $S U (N_{c})$ gauge theory with $N_{f} / N_{c} ≫ 1$ ("large $N_{f}$ QCD") as a candidate for the walking technicolor, which is modeled by the $U (N_{f}) \times U (N_{f})$ linear sigma model with classical scale symmetry (without mass term), particularly for $N_{f} = 8$ ("one-family model"). This model exhibits spontaneous breaking of the scale symmetry as well as the $U (N_{f}) \times U (N_{f})$ radiatively through the Coleman-Weinberg mechanism $a ˋ$ la Gildener-Weinberg, thus giving rise to a light pseudo dilaton (techni-dilaton) to be identified with the 125 GeV Higgs. This model possess a strong first-order electroweak phase transition due to the resultant Coleman-Weinberg type potential. We estimate the bubble nucleation that exhibits an ultra supercooling and then the signal for a stochastic gravitational wave produced via the strong first-order electroweak phase transition. We show that the amplitude can be reached to the expected sensitivities of the LISA.
hep-phastro-ph.HEgr-qcJHEP(2019)·29 citations
11*
Determination of the quantum numbers of $Σ_{b} (6097)^{\pm}$ via their strong decays
T. M. Aliev🇹🇷 · K. Azizi🇹🇷 · Y. Sarac🇹🇷 · H. Sundu🇹🇷
The progresses in the experimental sector have been the harbinger of the observations of many new hadrons. Very recently, LHCb Collaboration announced the observation of two new $Σ_{b} (6097)^{\pm}$ states in the $Λ_{b}^{0} π^{\pm}$ invariant mass distribution, which are considered as the excited states of the ground state $Σ_{b}^{(*)}$ baryon. Though, almost all of the ground state baryons have been observed, having a limited number of excited states observed so far makes them intriguing. Understanding the properties of the excited baryons improve our knowledge on the strong interaction as well as the nature and internal structures of these baryons. To specify the quantum numbers of the $Σ_{b} (6097)^{\pm}$ an analysis on their strong decays to $Λ_{b}^{0}$ and $π^{\pm}$ is performed within the light cone QCD sum rule formalism. To this end, they are considered as possible $1 P$ or $2 S$ excitation of either the ground state $Σ_{b}$ baryon with $J = \frac{1}{2}$ or $Σ_{b}^{*}$ baryon with $J = \frac{3}{2}$ . The corresponding masses are also calculated considering the same scenarios for their quantum numbers. The results of the analyses indicate that the $Σ_{b} (6097)^{\pm}$ baryons are excited $1 P$ baryons having quantum numbers $J^{P} = \frac{3}{2}^{-}$ .
hep-phhep-exhep-latPRD(2019)·38 citations
12*
Gluon fusion into Higgs pairs at NLO QCD and the top mass scheme
Julien Baglio🇩🇪 · Francisco Campanario🇪🇸 · Seraina Glaus🇩🇪 · Margarete Mühlleitner🇩🇪 · Michael Spira🇨🇭 · Juraj Streicher🇩🇪
We present the calculation of the full next-to-leading order (NLO) QCD corrections to Higgs boson pair production via gluon fusion at the LHC, including the exact top-mass dependence in the two-loop virtual and one-loop real corrections. This is the first independent cross-check of the NLO QCD corrections presented in the literature before. Our calculation relies on numerical integrations of Feynman integrals, stabilised with integration-by-parts and a Richardson extrapolation to the narrow width approximation. We present results for the total cross section as well as for the invariant Higgs-pair-mass distribution at the LHC, including for the first time a study of the uncertainty due to the scheme and scale choice for the top mass in the loops.
hep-phhep-exEPJC(2019)·257 citations
13*
$S U (7)$ Unification of Scotogenic Model with Pati-Salam $S U (4)_{c} \otimes S U (2)_{L} \otimes U (1)_{R}$ gauge symmetry
Arnab Dasgupta🇰🇷 · Sin Kyu Kang🇰🇷 · Oleg Popov🇰🇷
In this work we demonstrate how Scotogenic model can arise naturally from an $S U (7)$ grand unified theory. Our model also includes a low scale Pati-Salam $S U (4)_{c} \times S U (2)_{L} \times U (1)_{R}$ symmetry which unifies quarks and leptons. $Z_{2}$ symmetry needed for the realization of Scotogenic scenario is a residual symmetry and not $a d$ $h oc$ . A short fermion masses and dark matter analysis is included.
hep-phPoS(2019)·1 citation
14*
Hagedorn bag-like model with a crossover transition meets lattice QCD
Volodymyr Vovchenko🇩🇪 · Mark I. Gorenstein🇺🇦 · Carsten Greiner🇩🇪 · Horst Stoecker🇩🇪
Thermodynamic functions, the (higher-order) fluctuations and correlations of conserved charges at $μ_{B} = 0$ , and the Fourier coefficients of net-baryon density at imaginary $μ_{B}$ , are considered in the framework of a Hagedorn bag-like model with a crossover transition. The qualitative behavior of these observables is found to be compatible with lattice QCD results. Fair quantitative description of the lattice data is obtained when quasiparticle-type quarks and gluons with non-zero masses are introduced into the bag spectrum. The equation of state of the model exhibits a smooth and wide crossover transition.
hep-phhep-latnucl-thPRC(2019)·17 citations
15*
Compact Flavour-Exotic Tetraquarks in Large- $N_{c}$ QCD - To Be or Not to Be?
Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇦🇹 · Hagop Sazdjian🇫🇷
We analyse exotic tetraquark mesons - bound states formed by two quarks and two antiquarks - for the specific case of four different quark flavours within the framework of a well-defined limit of quantum chromodynamics characterized by the correlated growth without bound of the number of colour degrees of freedom and approach to zero of the coupling constant of the strong interactions. On the one hand, the assumption that the tetraquarks of the kind defined above show up, as poles in the amplitudes for the scattering of two ordinary mesons with flavour quantum numbers that match those of these tetraquarks, already at lowest possible order in an expansion in inverse powers of the number of colours implies the existence of two types of flavour-exotic tetraquarks, distinguishable by their dominant transitions to two ordinary mesons. On the other hand, we are aware of merely a single, unique colour-singlet arrangement of two quarks and two antiquarks capable of tolerating a compact flavour-exotic tetraquark, a bound state of colour-antisymmetric diquark and antidiquark. In view of these two clearly contradictory observations, we are led to the plausible conclusion that, within the considered limiting case of quantum chromodynamics, a conceivable explanation of the riddle might consist in the non-existence of any flavour-exotic tetraquarks in form of narrow states.
hep-phPoS(2018)·0 citations
16*
Quark-lepton flavored unification
Christopher Smith🇫🇷
The unification of the quark and charged lepton flavor structures is revisited using the tools of Minimal Flavor Violation (MFV). Under that framework, we first identify a unique point in parameter space where flavor universality is maximally violated. Though from the point of view of the usual polynomial MFV expansions, standing close to that point would require unacceptable fine-tunings, it is automatically attained with infinite geometric MFV series. Remarkably, this peculiar point is precisely where the charged lepton Yukawa coupling can be expressed naturally in terms of those of the quarks. The most striking consequence would be that the physical electron field is dominantly the gauge lepton field of the third generation.
hep-phPoS(2019)·0 citations
17*
On the origin of forward-backward multiplicity correlations in $pp$ collisions at ultrarelativistic energies
L.V. Bravina🇳🇴 · J. Bleibel🇩🇪 · E.E. Zabrodin🇳🇴
We study multiplicity correlations of hadrons in forward and backward hemispheres in $pp$ inelastic interactions at energies 200GeV $\leq s \leq$ 13TeV within the microscopic quark-gluon string model. The model correctly describes (i) the almost linear dependence of average multiplicity in one hemisphere on the particle multiplicity in other hemisphere in the center-of-mass frame; (ii) the increase of the slope parameter $b_{cor r}$ with rising collision energy; (iii) the quick falloff of the correlation strength with increase of the midrapidity gap; (iv) saturation of the forward-backward correlations at very high multiplicities. Investigation of the sub-processes on partonic level reveals that these features can be attributed to short-range partonic correlations within a single string and superposition of several sub-processes containing different numbers of soft and hard Pomerons with different mean multiplicities. If the number of Pomerons in the event is fixed, no forward-backward correlations are observed. Predictions are made for the top LHC energy $s = 13$ TeV.
hep-phhep-exnucl-thPLB(2018)·12 citations
18*
Improved local-constant-field approximation for strong-field QED codes
A. Di Piazza🇩🇪 · M. Tamburini🇩🇪 · S. Meuren🇺🇸 · C. H. Keitel🇩🇪
The local-constant-field approximation (LCFA) is an essential theoretical tool for investigating strong-field QED phenomena in background electromagnetic fields with complex spacetime structure. In our previous work [Phys.~Rev.~A~\textbf{98}, 012134 (2018)] we have analyzed the shortcomings of the LCFA in nonlinear Compton scattering at low emitted photon energies for the case of a background plane-wave field. Here, we generalize that analysis to background fields, which can feature a virtually arbitrary spacetime structure. In addition, we provide an explicit and simple implementation of an improved expression of the nonlinear Compton scattering differential probability that solves the main shortcomings of the standard LCFA in the infrared region, and is suitable for background electromagnetic fields with arbitrary spacetime structure such as those occurring in particle-in-cell simulations. Finally, we carry out a systematic procedure to calculate the probability of nonlinear Compton scattering per unit of emitted photon light-cone energy and of nonlinear Breit-Wheeler pair production per unit of produced positron light-cone energy beyond the LCFA in a plane-wave background field, which allows us to identify the limits of validity of this approximation quantitatively.
hep-phphysics.plasm-phPRA(2019)·129 citations
19*
Nuclear Parton Distributions from Neural Networks
Rabah Abdul Khalek🇳🇱 · Jacob J. Ethier🇳🇱 · Juan Rojo🇳🇱
In this contribution we present a status report on the recent progress towards an analysis of nuclear parton distribution functions (nPDFs) using the NNPDF methodology. We discuss how the NNPDF fitting approach can be extended to account for the dependence on the atomic mass number $A$ , and introduce novel algorithms to improve the training of the neural network parameters within the NNPDF framework. Finally, we present preliminary results of a nPDF fit to neutral current deep-inelastic lepton-nucleus scattering data, and demonstrate how one can validate the new fitting methodology by means of closure tests.
hep-phActa Phys.Polon.Supp.(2019)·4 citations
20*
Emergent/Composite axions
Pascal Anastasopoulos🇦🇹 · Panagiotis Betzios🇬🇷 · Massimo Bianchi🇮🇹 · Dario Consoli🇦🇹 · Elias Kiritsis🇬🇷
Hidden theories coupled to the SM may provide emergent axions, that are composites/bound-states of the hidden fields. This is motivated by paradigms emerging from the AdS/CFT correspondence but it is a more general phenomenon. We explore the general setup and find that UV-sourced interactions of instanton densities give rise to emergent axions in the IR. We study the general properties of such axions and argue that they are generically different from both fundamental and composite axions that have been studied so far.
hep-phhep-thJHEP(2019)·26 citations
21*
Non-resonant Leptoquark with multigeneration couplings to $μμ j j$ and $μν j j$ at LHC
Ezequiel Alvarez🇦🇷 · Manuel Szewc🇦🇷
CMS has recently reported a moderate excess in the $μν j j$ final state in a second generation Leptoquark search, but they have disregarded it because the excess is not present in the $μμ j j$ final state and because they do not observe the expected resonant peak in the distributions. As a proof of concept we show that a simple Leptoquark model including second and third generation couplings with non-negligible single- and non-resonant production in addition to usual pair production could explain the data: excess ( $μν j j$ ), lack of excess ( $μμ j j$ ) and missing peak in the distributions; while being in agreement with collider constraints. We take this result and analysis as a starting point of a reconsideration of the ATLAS and CMS second generation Leptoquark searches. We also discuss which would be the consequences and modifications that should be performed in the searches to test if this deviation would correspond to a New Physics signal. We observe that low-energy flavor constraints can be avoided by adding heavier particles to the model.
hep-phhep-exPRD(2019)·10 citations
22*
Planck mass and inflation as consequences of dynamically broken scale invariance
Jisuke Kubo🇩🇪 · Manfred Lindner🇩🇪 · Kai Schmitz🇮🇹 · Masatoshi Yamada🇩🇪
Classical scale invariance represents a promising framework for model building beyond the Standard Model. However, once coupled to gravity, any scale-invariant microscopic model requires an explanation for the origin of the Planck mass. In this paper, we provide a minimal example for such a mechanism and show how the Planck mass can be dynamically generated in a strongly coupled gauge sector. We consider the case of hidden SU(N_c) gauge interactions that link the Planck mass to the condensation of a scalar bilinear operator that is nonminimally coupled to curvature. The effective theory at energies below the Planck mass contains two scalar fields: the pseudo-Nambu--Goldstone boson of spontaneously broken scale invariance (the dilaton) and a gravitational scalar degree of freedom that originates from the R^2 term in the effective action (the scalaron). We compute the effective potential for the coupled dilaton-scalaron system at one-loop order and demonstrate that it can be used to successfully realize a stage of slow-roll inflation in the early Universe. Remarkably enough, our predictions for the primordial scalar and tensor power spectra interpolate between those of standard R^2 inflation and linear chaotic inflation. For comparatively small gravitational couplings, we thus obtain a spectral index n_s ~= 0.97 and a tensor-to-scalar ratio as large as r ~= 0.08.
hep-phastro-ph.COgr-qchep-thPRD(2019)·56 citations
23*
Singleton Portals to the Twin Sector
Fady Bishara🇩🇪 · Christopher B. Verhaaren🇺🇸
The mirror twin Higgs framework allows for a natural Higgs mass while being consistent with collider bounds on colored symmetry partners to standard model quarks. This mechanism relies crucially on a discrete symmetry which relates each standard model field to a mirror partner. These partners are charged under gauge groups identical to, but distinct from, those in the standard model. The minimal twin Higgs scenario provides only one low-energy connection between the visible and twin sectors, the light Higgs boson. We present a new class of portals connecting the two sectors, using fields that have 'no twin' partner under the discrete symmetry. Scalar, fermion, and vector states may provide such 'singleton' portals, each with unique features and experimental signatures. The vector portal, in particular, provides a variety of renormalizable interactions relevant for the LHC. We provide concrete constructions of these portals and determine their phenomenology and opportunities to probe the twin sector at the LHC. We also sketch a scenario in which the structure of the twin sector itself can be tested.
hep-phJHEP(2019)·24 citations
24*
Dynamics of a tensor polarization of particles and nuclei and its influence on the spin motion in external fields
Alexander J. Silenko🇷🇺
The tensor polarization of particles and nuclei is constant in a coordinate system rotating with the same angular velocity as the spin. In the laboratory frame, it rotates with this angular velocity. The general equation defining the evolution of the tensor polarization is derived. An explicit form of the dynamics of this polarization is given in the case when the angular velocity of the spin precession is constant and vertical. It is shown that the spin tensor interactions result in mutual transformations of the vector and tensor polarizations. These interactions can influence the spin motion.
hep-phEPJ Web Conf.(2019)·0 citations
25*
Nuclear Matrix Elements for Neutrinoless Double Beta Decay from Lattice QCD
W. Detmold🇺🇸 · D.J. Murphy🇺🇸
While neutrino oscillation experiments have demonstrated that neutrinos have small, nonzero masses, much remains unknown about their properties and decay modes. One potential decay mode --- neutrinoless double beta decay ( $0 ν β β$ ) --- is a particularly interesting target of experimental searches, since its observation would imply that the neutrino is a Majorana particle, demonstrate that lepton number conservation is violated in nature, and give further constraints on the neutrino masses and mixing angles. Relating experimental constraints on $0 ν β β$ decay rates to the neutrino masses, however, requires theoretical input in the form of non-perturbative nuclear matrix elements which remain difficult to calculate reliably. In this talk we will discuss progress towards first-principles calculations of relevant nuclear matrix elements using lattice QCD and effective field theory techniques, assuming neutrinoless double beta decay mediated by a light Majorana neutrino. We will show preliminary results for the $π^{-} \to π^{+} e^{-} e^{-}$ transition amplitude computed on a $1 6^{3} \times 32$ domain wall fermion lattice with a pion mass of 420 MeV, and discuss improved methods applicable to general lattice calculations of $0 ν β β$ decay amplitudes.
↳ hep-lathep-phPoS(2019)·17 citations
26*
Trading kinetic energy: How late kinetic decoupling of dark matter changes $N_{eff}$
James A. D. Diacoumis🇦🇺 · Yvonne Y. Y. Wong🇦🇺
Elastic scattering between dark matter particles and a relativistic species such as photons or neutrinos leads to a transfer of energy from the latter due to their intrinsically different temperature scaling relations. In this work, we point out that this siphoning of energy from the radiation bath manifests as a change in the effective number of neutrinos $N_{eff}$ , and compute the expected shift $Δ N_{eff}$ for dark matter-photon and dark matter-neutrino elastic scattering as a function of the dark matter mass $m_{ψ}$ and scattering cross section $σ_{ψ - X}$ . For $(m_{ψ}, σ_{ψ - X})$ -parameter regions already explored by nonlinear probes such as the Lyman- $α$ forest through collisional and/or free-streaming damping, we find shifts of $∣Δ N_{eff} ∣ ≃ O (1 0^{- 2})$ , which may be within the reach of the proposed CMB-S4 experiment. For most of the as-yet-unexplored parameter space, however, we expect $∣Δ N_{eff} ∣ ≲ O (1 0^{- 3})$ . An ideal 21 cm tomography survey of the dark ages limited only by cosmic variance is potentially sensitive to $∣Δ N_{eff} ∣ ≃ O (1 0^{- 6})$ , in which case dark matter masses up to $m_{ψ} \sim 10 MeV$ may be probed via their effect on $N_{eff}$ .
↳ astro-ph.COhep-phJCAP(2019)·9 citations
27*
Finite-size scaling for four-dimensional Higgs-Yukawa model near the Gaussian fixed point
David Y.-J Chu🇹🇼 · Karl Jansen🇩🇪 · Bastian Knippschild🇩🇪 · C.-J. David Lin🇹🇼
We analyse finite-size scaling behaviour of a four-dimensional Higgs-Yukawa model near the Gaussian infrared fixed point. Through improving the mean-field scaling laws by solving one-loop renormalisation group equations, the triviality property of this model can be manifested in the volume-dependence of moments of the scalar-field zero mode. The scaling formulae for the moments are derived in this work with the inclusion of the leading-logarithmic corrections. To test these formulae, we confront them with data from lattice simulations in a simpler model, namely the O(4) pure scalar theory, and find numerical evidence of good agreement. Our results of the finite-size scaling can in principle be employed to establish triviality of Higgs-Yukawa models, or to search for alternative scenarios in studying their fixed-point structure, if sufficiently large lattices can be reached.
↳ hep-lathep-phJHEP(2019)·5 citations
28*
The Spectrum of the Axion Dark Sector, Cosmological Observable and Black Hole Superradiance Constraints
Matthew J. Stott🇬🇧
Consistent frameworks of quantum gravity often predict the existence of large numbers of ultralight pseudoscalar degrees of freedom, forming the phenomenological landscape of the String Axiverse. The complexity of the extra-dimensional compactification manifolds and vacua determine that these fields could possess parameters with cosmologically significant scales, which span many decades. Astrophysical observations of stellar binary and supermassive black hole systems can be used to exclude the existence of certain ultralight massive bosons, via the superradiance phenomenon. In this work it is shown how these measurements can be used to constrain properties of statistical distributions for the masses of multiple bosonic field theories, inspired by axion field alignment models and an explicit realisation of the string axiverse in M-theory. Such a methodology can exclude $N_{ax} \geq 30$ axion-like fields with a range of mass distribution widths and central values spanning many orders of magnitude, covering axion phenomenologies important to the dark sector and grand unified theories. This is demonstrated for several examples of axions in string theory and M-theory, where the mass distributions in certain cases take universal forms found in random matrix theory.
↳ hep-thhep-phPoS(2019)·1 citation
29*
Decaying Dark Matter in Halos of Primordial Black Holes
Florian Kuhnel🇸🇪 · Tommy Ohlsson🇸🇪
We investigate photon signatures of general decaying dark-matter particles in halos of primordial black holes. We derive the halo-profile density and the total decay rate for these combined dark-matter scenarios. For the case of axion-like particles of masses below $O (1)$ keV, we find strong bounds on the decay constant which are several orders of magnitude stronger than the strongest existing bounds, for all halo masses above $O (1 0^{- 5})$ solar masses. Using future X-ray measurements, it will be possible to push these bounds on such combined dark-matter scenarios even further.
↳ astro-ph.COgr-qchep-phEPJC(2019)·3 citations
30*
The quest for $μ \to e γ$ : present and future
Francesco Renga (for the MEG Collaboration)🇮🇹
The quest for $μ \to e γ$ is one of the most important endeavors to search for New Physics beyond the Standard Model. In this talk I will review the current status of the experimental searches by the MEG Collaboration at PSI. I will also present a study of the experimental limiting factors that will define the ultimate performances, and hence the sensitivity, in the search for $μ \to e γ$ with continuous muon beams of extremely high rate (one or even two orders of magnitude larger than the present beams), whose construction is under consideration for the next decade.
↳ hep-exhep-phphysics.ins-detHyperfine Interact.(2018)·38 citations
31*
Primordial Circular Polarization in the Cosmic Microwave Background
Stephon Alexander🇺🇸 · Evan McDonough🇺🇸
Circular ("V-mode") polarization is expected to be vanishing in the CMB, since it is not produced in Thomson scattering. However, considering that the conventional CMB anisotropies are generated via an early universe mechanism such as inflation or a bouncing scenario, it is possible that circular polarization could be primordially produced and survive to the surface of last scattering. We study this in detail, and find a large class of inflationary models that produce a nearly scale invariant spectrum of scalar V-mode anisotropies. We study the inflationary production and subsequent evolution via the Boltzmann hierarchy, and show that V-mode polarization present in the CMB is suppressed by a factor of at least $1 0^{1 0^{20}}$ relative to the primordial $V$ , consistent with expectation of negligible V-mode polarization from inflation. We consider alternative possibilities for sourcing $V$ primordially, such as the V-mode polarization induced by circularly polarized primordial gravitational waves, or producing $V$ after inflation, via new interactions at recombination.
↳ astro-ph.COgr-qchep-phhep-thPLB(2018)·15 citations
32*
Scale-invariant alternatives to general relativity. III. The inflation--dark-energy connection
Santiago Casas🇫🇷 · Georgios K. Karananas🇩🇪 · Martin Pauly🇩🇪 · Javier Rubio🇩🇪
We discuss the cosmological phenomenology of biscalar-tensor models displaying a maximally symmetric Einstein-frame kinetic sector and constructed on the basis of scale symmetry and volume-preserving diffeomorphisms. These theories contain a single dimensionful parameter $Λ_{0}$ -associated with the invariance under the aforementioned restricted coordinate transformations-and a massless dilaton field. At large field values these scenarios lead to inflation with no generation of isocurvature perturbations. The corresponding predictions depend only on two dimensionless parameters, which characterize the curvature of the field--manifold and the leading order behavior of the inflationary potential. For $Λ_{0} = 0$ the scale symmetry is unbroken and the dilaton admits only derivative couplings to matter, evading all fifth force constraints. For $Λ_{0} \neq = 0$ the field acquires a run-away potential that can support a dark energy dominated era at late times. We confront a minimalistic realization of this appealing framework with present data sets. The impact of possible consistency relations among the early and late Universe dynamics that could appear within this setting is also discussed.
↳ astro-ph.COgr-qchep-phPRD(2019)·42 citations
33*
Constraints on Decaying Dark Matter from the Isotropic Gamma-Ray Background
Carlos Blanco🇺🇸 · Dan Hooper🇺🇸
If the dark matter is unstable, the decay of these particles throughout the universe and in the halo of the Milky Way could contribute significantly to the isotropic gamma-ray background (IGRB) as measured by Fermi. In this article, we calculate the high-latitude gamma-ray flux resulting from dark matter decay for a wide range of channels and masses, including all contributions from inverse Compton scattering and accounting for the production and full evolution of cosmological electromagnetic cascades. We also make use of recent multi-wavelength analyses that constrain the astrophysical contributions to the IGRB, enabling us to more strongly restrict the presence any component arising from decaying dark matter. Over a wide range of decay channels and masses (from GeV to EeV and above), we derive stringent lower limits on the dark matter's lifetime, generally in the range of $τ \sim (1 - 5) \times 1 0^{28}$ s.
↳ astro-ph.HEastro-ph.COastro-ph.GAhep-phJCAP(2019)·123 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.