HEP Phenomenology·hep-ph

Thu·Oct 8, 2020Thursday·October 8, 2020

27 papers—21 primary·6 cross-listed·reconstructed*

01*
Scalar Dark Matter Candidates -- Revisited
Céline Bœhm🇦🇺 · Xiaoyong Chu🇦🇹 · Jui-Lin Kuo🇦🇹 · Josef Pradler🇦🇹
We revisit the possibility of light scalar dark matter, in the MeV to GeV mass bracket and coupled to electrons through fermion or vector mediators, in light of significant experimental and observational advances that probe new physics below the GeV-scale. We establish new limits from electron colliders and fixed-target beams, and derive the strength of loop-induced processes that are probed by precision physics, among other laboratory probes. In addition, we compute the cooling bound from SN1987A, consider self-scattering, structure formation, and cosmological constraints as well as the limits from dark matter-electron scattering in direct detection experiments. We then show that the combination of constraints largely excludes the possibility that the galactic annihilation of these particles may explain the long-standing INTEGRAL excess of 511 keV photons as observed in the galactic bulge. As caveat to these conclusions we identify the resonant annihilation regime where the vector mediator goes nearly on-shell.
hep-phastro-ph.COPRD(2021)·38 citations
02*
Soft-virtual correction and threshold resummation for $n$ -colorless particles to fourth order in QCD: Part I
Taushif Ahmed🇩🇪 · Ajjath A. H.🇮🇳 · Goutam Das🇩🇪 · Pooja Mukherjee🇮🇳 · V. Ravindran🇮🇳 · Surabhi Tiwari🇮🇳
We present the general form of a universal soft-collinear distribution operator to compute the soft-virtual cross-section to next-to-next-to-next-to-next-to-leading order (N $^{4}$ LO) in QCD for a process with any number of final state colorless particles in hadron colliders. By acting this universal operator on the pure virtual corrections, which need to be computed explicitly for a process, the soft-virtual cross-section can be obtained. The operator is constructed by exploiting the factorization and renormalization group evolution of amplitudes in QCD, and the universality of soft gluon contributions. We also provide the hard coefficient to perform the threshold resummation to next-to-next-to-next-to-leading logarithmic (N $^{3}$ LL) accuracy. Furthermore, we present the approximate analytical results of the soft-virtual cross-sections at N $^{4}$ LO and N $^{3}$ LL for the Higgs boson production through gluon fusion and bottom quark annihilation, and also for the Drell-Yan production at the hadronic collider.
hep-phhep-th30 citations
03*
Rapidity distribution at soft-virtual and beyond for n-colorless particles to N $^{4}$ LO in QCD
Taushif Ahmed🇩🇪 · Ajjath A. H.🇮🇳 · Pooja Mukherjee🇮🇳 · V. Ravindran🇮🇳 · Aparna Sankar🇮🇳
We present a systematic framework to study the threshold contributions of the differential rapidity distribution for the production of any number of colorless particles in the hadronic colliders. This has been achieved based on the universality structure of the soft enhancements associated with the real emissions, along with the factorization property of the differential cross section and the renormalization group invariance. In this formalism, we present a universal soft-collinear operator to compute the soft virtual differential cross section for a generic $2 \to n$ scattering process up to next-to-next-to-next-to-next-to-leading order (N $^{4}$ LO) in perturbative QCD. We also provide a universal operator to perform the threshold resummation to next-to-next-to-next-to-leading logarithmic (N $^{3}$ LL) accuracy. We explicitly present the approximate analytical results of the rapidity distributions at N $^{4}$ LO and N $^{3}$ LL for the Higgs boson production through gluon fusion and bottom quark annihilation, and also for the Drell-Yan production at the hadronic collider. \textcolor{black}{We extend our framework to include the next to threshold contributions for the diagonal partonic channels.
hep-phEPJC(2021)·22 citations
04*
Emergent dark energy from unparticles
Michal Artymowski🇮🇱 · Ido Ben-Dayan🇮🇱 · Utkarsh Kumar🇮🇱
A limiting temperature of a species can cause the Universe to asymptote to it yielding a deSitter (dS) phase due to macroscopic emergent behavior. The limiting temperature is generic for theories slightly shifted from their conformal point. We demonstrate such behavior in the example of unparticles/Banks-Zaks theory. The unparticles behave like radiation at high energies reducing the Hubble tension, and a cosmological constant (CC) at low energies yielding a model that follows closely {\Lambda}CDM model but due to collective phenomenon. It is technically natural and avoids the no-dS conjecture. The model is free of the coincidence and initial conditions problems, of scalar fields and of modified gravity.
hep-phastro-ph.COgr-qchep-thPRD(2021)·25 citations
05*
An incorrect pre-asymptotic RG flow of scattering amplitudes in QCD towards the unitarity limit
Adrian Dumitru🇺🇸 · Vladimir Skokov🇺🇸
Scattering amplitudes in QCD exhibit a definite RG flow with energy towards the unitarity limit. In this paper we put forward an evolution equation which allows one to modify continuously the pre-asymptotic RG flow towards "saturation" of Wilson line correlators. It preserves the linearly unstable zero field fixed point and the unitarity limit attractor. We present the evolution equations in a form suitable for efficient numerical solution. Hence, the proposed evolution equation in principle permits phenomenological comparisons of our incorrect pre-asymptotic RG flows to the BK/JIMWLK flow of QCD. Ultimately, it may lead to observational constraints on the approach to unitarity, constraining it to be specifically the one of QCD. However, it appears that single-inclusive particle spectra in the forward region of p+A collisions at RHIC alone do not provide stringent constraints on the evolution.
hep-ph0 citations
06*
Dilepton production through timelike Compton scattering within the $k_{T}$ -factorization approach
G. M. Peccini🇧🇷 · L. S. Moriggi🇧🇷 · M. V. T. Machado🇧🇷
In this work we consider the dilepton production via timelike Compton scattering (TCS) in electron-proton and proton-proton collisions. In particular, the differential cross section in terms of the dilepton invariant mass and rapidity is computed within the $k_{T}$ -factorization approach. Besides, we utilize distinct unintegrated gluon distributions (UGD) in order to compare their impact on the differential cross section of TCS in $pp$ ( $e p$ ) collisions evaluated at the LHC (LHeC), HL-LHC (LHeC), HE-LHC (LHeC) and FCC-hh (eh) center-of-mass energies.
hep-phhep-exPRD(2020)·7 citations
07*
Bethe phase variation due to a non-exponential nuclear amplitude and the possibility of using a $t$ -dependent phase to determine the $ρ$ -parameter from elastic scattering data
P. Grafstrom🇮🇹 · M.G. Ryskin🇷🇺
We evaluate the possible deviation (from the conventional Cahn's result) of the phase between the one-photon-exchange and the `nuclear' high energy $pp$ scattering amplitudes in a small $t \to 0$ region caused by a more complicated (not just $e x p (B t)$ ) behaviour of the nuclear amplitude. Furthermore we look at the possible role of the $t$ -dependence of the $ρ (t) \equiv$ Real/Imaginary amplitude ratio. It turns out that both effects are rather small - much smaller than to have any influence on the experimental accuracy of $ρ (t = 0)$ extracted from the elastic proton-proton scattering data.
hep-ph3 citations
08*
Constraining flavour patterns of scalar leptoquarks in the effective field theory
Marzia Bordone🇩🇪 · Oscar Cata🇩🇪 · Thorsten Feldmann🇩🇪 · Rusa Mandal🇩🇪
We investigate the viability of extending the Standard Model with $S_{1}$ and $S_{3}$ scalar leptoquarks when the flavour structure is parametrized in terms of Froggatt-Nielsen charges. In contrast to a similar analysis with a vector leptoquark, we find essentially two solutions for the charges that fit the experimental constraints, which are dominated by the current tensions in $B$ decays. These two scenarios differ in their estimate of the anomalous magnetic moment of the muon, $(g - 2)$ , but they both predict sizeable contributions to $τ \to μ γ$ , $B ˉ_{s} \to τ^{\pm} μ^{\mp}$ and $B^{+} \to K^{+} τ^{+} μ^{-}$ decays, whose branching ratios are close to the current experimental limits.
hep-phJHEP(2021)·41 citations
09*
Fluctuations and thermodynamic geometry of the chiral phase transition
Paolo Castorina🇮🇹 · Daniele Lanteri🇮🇹 · Marco Ruggieri🇨🇳
We study the thermodynamic curvature, $R$ , around the chiral phase transition at finite temperature and chemical potential, within the quark-meson model augmented with meson fluctuations. We study the effect of the fluctuations, pions and $σ$ -meson, on the top of the mean field thermodynamics and how these affect $R$ around the crossover. We find that for small chemical potential the fluctuations enhance the magnitude of $R$ , while they do not affect substantially the thermodynamic geometry in the proximity of the critical endpoint. Moreover, in agreement with previous studies we find that $R$ changes sign in the pseudocritical region, suggesting a change of the nature of interactions at the mesoscopic level from statistically repulsive to attractive. Finally, we find that in the critical region around the critical endpoint $∣ R ∣$ scales with the correlation volume, $∣ R ∣ = K ξ^{3}$ , with $K = O (1)$ , as expected from hyperscaling; far from the critical endpoint the correspondence between $∣ R ∣$ and the correlation volume is not as good as the one we have found at large $μ$ , which is not surprising because at small $μ$ the chiral crossover is quite smooth; nevertheless, we have found that $R$ develops a characteristic peak structure, suggesting that it is still capable to capture the pseudocritical behavior of the condensate.
hep-phhep-thPRD(2021)·10 citations
10*
Lepton sector in modular $A_{4}$ and gauged $U (1)_{R}$ symmetry
Keiko I. Nagao🇯🇵 · Hiroshi Okada🇰🇷
We propose a lepton model under modular $A_{4}$ and gauged $U (1)_{R}$ symmetries, in which the neutrino masses are induced at one-loop level. Thanks to the modular $A_{4}$ symmetry, we have several predictions on the lepton sector, especially, on fixed points of $τ = i, ω \equiv e^{2 π i /3}, i \times \infty$ each of which has remnant symmetry; $Z_{2}$ for $τ = i$ and $Z_{3}$ for $τ = ω, i \infty$ . These points are favored by a string theory and phenomenologically interesting.
hep-phNPB(2022)·44 citations
11*
Gravitational Wave Signatures from Domain Wall and Strong First-Order Phase Transitions in a Two Complex Scalar extension of the Standard Model
Avik Paul🇮🇳 · Upala Mukhopadhyay🇮🇳 · Debasish Majumdar🇮🇳
We consider a simple extension of Standard Model by adding two complex singlet scalars with a $U (1)$ symmetry. A discrete $Z_{2} \times Z_{2}^{'}$ symmetry is imposed in the model and the added scalars acquire a non zero vacuum expectation value (VEV) when the imposed symmetry is broken spontaneously. The real (CP even) parts of the complex scalars mix with the SM Higgs and give three physical mass eigenstates. One of these physical mass eigenstates is attributed to the SM like Higgs boson with mass 125.09 GeV. In the present scenario, domain walls are formed in the early Universe due to the breaking of discrete $Z_{2} \times Z_{2}^{'}$ symmetry. In order to ensure the unstability of the domain wall this discrete symmetry is also explicitly broken by adding a bias potential to the Lagrangian. The unstable annihilating domain walls produce a significant amount of gravitational waves (GWs). In addition, we also explore the possibility of the production of GW emission from the strong first-order phase transition. We calculate the intensities and frequencies of each of such gravitational waves originating from two different phenomena of the early Universe namely annihilating domain walls and strong first-order phase transition. Finally, we investigate the observational signatures from these GWs at the future GW detectors such as ALIA, BBO, DECIGO, LISA, TianQin, Taiji, aLIGO, aLIGO+ and pulsar timing arrays such as SKA, IPTA, EPTA, PPTA, NANOGrav11 and NANOGrav12.5.
hep-phJHEP(2021)·26 citations
12*
Novel signatures of additional Higgs bosons at the LHC
Tim Stefaniak🇩🇪
We identify two types of well-motivated, so-far experimentally unexplored LHC signatures of extended Higgs sectors: First, Higgs-to-Higgs decay signatures that involve (at least) two Beyond-the-Standard Model (BSM) neutral scalar bosons, $ϕ_{i} \to ϕ_{j} ϕ_{k}$ . These signatures are discussed in the framework of the Two-Real-Singlet-Model (TRSM), which can furthermore exhibit cascades of Higgs-to-Higgs decays leading to multi-Higgs final states. Second, the charged Higgs boson decay to a W boson and a neutral BSM Higgs boson, which can easily become the dominant decay within the Two-Higgs-Doublet-Model (2HDM) parameter space. We provide benchmark scenarios for future experimental studies of these signatures.
hep-phhep-exPoS(2021)·0 citations
13*
Correlators of vector, tensor, and scalar composite vertices of order $O (α_{s}^{2} β_{0})$
S. V. Mikhailov🇷🇺 · N. Volchanskiy🇷🇺
We present analytical results for massless correlators of two vector, tensor, and scalar composite vertices with the Bjorken fractions $x$ and $y$ of order $α_{s}^{2} β_{0}$ of QCD. The structure of these correlators $Π^{V,T,S} (x, y; p^{2})$ and properties of its main elements are discussed in detail. Special attention is paid to verifying the results and comparing them with known particular cases. We apply the correlators to evaluate radiative corrections to the distribution amplitudes of light mesons within the QCD sum rules.
hep-phhep-thJHEP(2020)·5 citations
14*
Assessing the tension between a black hole dominated early universe and leptogenesis
Yuber F. Perez-Gonzalez🇺🇸 · Jessica Turner🇬🇧
We perform the first numerical calculation of the interplay between thermal and black hole induced leptogenesis, demonstrating that the right-handed neutrino surplus produced during the evaporation only partially mitigates the entropy dilution suffered by the thermal component. As such, the intermediate-mass regime of the right-handed neutrinos, $1 0^{6} GeV ≲ M_{N} ≲ 1 0^{9} GeV$ , could not explain the observed baryon asymmetry even for fine-tuned scenarios if there existed a primordial black hole dominated era, consistent with initial black hole masses of $M_{i} ≳ O (1)$ kg. Detection of the gravitational waves emitted from the same primordial black holes would place intermediate-scale thermal leptogenesis under tension.
hep-phastro-ph.COPRD(2021)·86 citations
15*
Causal gravitational waves as a probe of free streaming particles and the expansion of the Universe
Anson Hook🇺🇸 · Gustavo Marques-Tavares🇺🇸 · Davide Racco🇨🇦
The low frequency part of the gravitational wave spectrum generated by local physics, such as a phase transition or parametric resonance, is largely fixed by causality, offering a clean window into the early Universe. In this work, this low frequency end of the spectrum is analyzed with an emphasis on a physical understanding, such as the suppressed production of gravitational waves due to the excitation of an over-damped harmonic oscillator and their enhancement due to being frozen out while outside the horizon. Due to the difference between sub-horizon and super-horizon physics, it is inevitable that there will be a distinct spectral feature that could allow for the direct measurement of the conformal Hubble rate at which the phase transition occurred. As an example, free-streaming particles (such as the gravity waves themselves) present during the phase transition affect the production of super-horizon modes. This leads to a steeper decrease in the spectrum at low frequencies as compared to the well-known causal $k^{3}$ super-horizon scaling of stochastic gravity waves. If a sizable fraction of the energy density is in free-streaming particles, they even lead to the appearance of oscillatory features in the spectrum. If the universe was not radiation dominated when the waves were generated, a similar feature also occurs at the transition between sub-horizon to super-horizon causality. These features are used to show surprising consequences, such as the fact that a period of matter domination following the production of gravity waves actually increases their power spectrum at low frequencies.
hep-phastro-ph.COgr-qcJHEP(2021)·113 citations
16*
Parameter Estimation using Neural Networks in the Presence of Detector Effects
Anders Andreassen🇺🇸 · Shih-Chieh Hsu🇺🇸 · Benjamin Nachman🇺🇸 · Natchanon Suaysom🇺🇸 · Adi Suresh🇺🇸
Histogram-based template fits are the main technique used for estimating parameters of high energy physics Monte Carlo generators. Parametrized neural network reweighting can be used to extend this fitting procedure to many dimensions and does not require binning. If the fit is to be performed using reconstructed data, then expensive detector simulations must be used for training the neural networks. We introduce a new two-level fitting approach that only requires one dataset with detector simulation and then a set of additional generation-level datasets without detector effects included. This Simulation-level fit based on Reweighting Generator-level events with Neural networks (SRGN) is demonstrated using simulated datasets for a variety of examples including a simple Gaussian random variable, parton shower tuning, and the top quark mass extraction.
hep-phhep-exphysics.data-anstat.MLPRD(2021)·16 citations
17*
Quantum simulation of open quantum systems in heavy-ion collisions
Wibe A. de Jong🇺🇸 · Mekena Metcalf🇺🇸 · James Mulligan🇺🇸 · Mateusz Płoskoń🇺🇸 · Felix Ringer🇺🇸 · Xiaojun Yao🇺🇸
We present a framework to simulate the dynamics of hard probes such as heavy quarks or jets in a hot, strongly-coupled quark-gluon plasma (QGP) on a quantum computer. Hard probes in the QGP can be treated as open quantum systems governed in the Markovian limit by the Lindblad equation. However, due to large computational costs, most current phenomenological calculations of hard probes evolving in the QGP use semiclassical approximations of the quantum evolution. Quantum computation can mitigate these costs, and offers the potential for a fully quantum treatment with exponential speedup over classical techniques. We report a simplified demonstration of our framework on IBM Q quantum devices, and apply the Random Identity Insertion Method (RIIM) to account for CNOT depolarization noise, in addition to measurement error mitigation. Our work demonstrates the feasibility of simulating open quantum systems on current and near-term quantum devices, which is of broad relevance to applications in nuclear physics, quantum information, and other fields.
hep-phhep-exnucl-exnucl-th+1PRD(2021)·68 citations
18*
New Constraints on the Mass of Fermionic Dark Matter from Dwarf Spheroidal Galaxies
James Alvey🇬🇧 · Nashwan Sabti🇬🇧 · Victoria Tiki🇳🇱 · Diego Blas🇬🇧 · Kyrylo Bondarenko🇨🇭 · Alexey Boyarsky🇳🇱 · Miguel Escudero🇬🇧 · Malcolm Fairbairn🇬🇧 · Matthew Orkney🇬🇧 · Justin I. Read🇬🇧
Dwarf spheroidal galaxies are excellent systems to probe the nature of fermionic dark matter due to their high observed dark matter phase-space density. In this work, we review, revise and improve upon previous phase-space considerations to obtain lower bounds on the mass of fermionic dark matter particles. The refinement in the results compared to previous works is realised particularly due to a significantly improved Jeans analysis of the galaxies. We discuss two methods to obtain phase-space bounds on the dark matter mass, one model-independent bound based on Pauli's principle, and the other derived from an application of Liouville's theorem. As benchmark examples for the latter case, we derive constraints for thermally decoupled particles and (non-)resonantly produced sterile neutrinos. Using the Pauli principle, we report a model-independent lower bound of $m \geq 0.18 keV$ at 68% CL and $m \geq 0.13 keV$ at 95% CL. For relativistically decoupled thermal relics, this bound is strengthened to $m \geq 0.59 keV$ at 68% CL and $m \geq 0.41 keV$ at 95% CL, whilst for non-resonantly produced sterile neutrinos the constraint is $m \geq 2.80 keV$ at 68% CL and $m \geq 1.74 keV$ at 95% CL. Finally, the phase-space bounds on resonantly produced sterile neutrinos are compared with complementary limits from X-ray, Lyman- $α$ and Big Bang Nucleosynthesis observations.
hep-phastro-ph.COastro-ph.GAMNRAS(2021)·84 citations
19*
Superheavy Dark Matter from String Theory
Rouzbeh Allahverdi🇺🇸 · Igor Broeckel🇮🇹 · Michele Cicoli🇮🇹 · Jacek K. Osiński🇺🇸
Explicit string models which can realize inflation and low-energy supersymmetry are notoriously difficult to achieve. Given that sequestering requires very specific configurations, supersymmetric particles are in general expected to be very heavy implying that the neutralino dark matter should be overproduced in a standard thermal history. However, in this paper we point out that this is generically not the case since early matter domination driven by string moduli can dilute the dark matter abundance down to the observed value. We argue that generic features of string compactifications, namely a high supersymmetry breaking scale and late time epochs of modulus domination, might imply superheavy neutralino dark matter with mass around $1 0^{10} - 1 0^{11}$ GeV. Interestingly, this is the right range to explain the recent detection of ultra-high-energy neutrinos by IceCube and ANITA via dark matter decay.
hep-phastro-ph.COgr-qchep-thJHEP(2021)·30 citations
20*
Characterizing Dark Matter Signals with Missing Momentum Experiments
Nikita Blinov🇺🇸 · Gordan Krnjaic🇺🇸 · Douglas Tuckler🇨🇦
Fixed target missing-momentum experiments such as LDMX and M $^{3}$ are powerful probes of light dark matter and other light, weakly coupled particles beyond the Standard Model (SM). Such experiments involve $\sim$ 10 GeV beam particles whose energy and momentum are individually measured before and after passing through a suitably thin target. If new states are radiatively produced in the target, the recoiling beam particle loses a large fraction of its initial momentum, and no SM particles are observed in a downstream veto detector. We explore how such experiments can use kinematic variables and experimental parameters, such as beam energy and polarization, to measure properties of the radiated particles and discriminate between models if a signal is discovered. In particular, the transverse momentum of recoiling particles is shown to be a powerful tool to measure the masses of new radiated states, offering significantly better discriminating ability compared to the recoil energy alone. We further illustrate how variations in beam energy, polarization, and lepton flavor (i.e., electron or muon) can be used to disentangle the possible the Lorentz structure of the new interactions.
hep-phhep-exPRD(2021)·12 citations
21*
Large $N$ -ightmare Dark Matter
Logan Morrison🇺🇸 · Stefano Profumo🇺🇸 · Dean J. Robinson🇺🇸
A dark QCD sector is a relatively minimal extension of the Standard Model (SM) that admits Dark Matter (DM) candidates but requires no portal to the visible sector beyond gravitational interactions: A "nightmare scenario" for DM detection. We consider a secluded dark sector containing a single flavor of light, vector-like dark quark gauged under $S U (N)$ . In the large- $N$ limit, this single-flavor theory becomes highly predictive, generating two DM candidates whose masses and dynamics are described by few parameters: A light quark-antiquark bound state, the dark analog of the $η^{'}$ meson, and a heavy bound state of $N$ quarks, the dark analog of the $Δ^{++}$ baryon. We show that the latter may freeze-in with an abundance independent of the confinement scale, forming DM-like relics for $N ≲ 10$ , while the former may generate DM via cannibalization and freeze-out. We study the interplay of this two-component DM system and determine the characteristic ranges of the confinement scale, dark-visible sector temperature ratio, and $N$ that admit non-excluded DM, once the effects of self-interaction constraints and bounds on effective degrees of freedom at the BBN and CMB epochs are included.
hep-phastro-ph.COastro-ph.HEJCAP(2021)·16 citations
22*
The Positive-Parity Baryon Spectrum and the Role of Hybrid Baryons
Tanjib Khan🇺🇸 · David Richards🇺🇸 · Frank Winter🇺🇸
We calculate the low-lying spectra for the positive-parity $Δ$ and $N$ at two pion masses of 358 and 278 MeV using an isotropic clover action with two degenerate light-quaark and one strange-quark flavors through the application of the generalized variational method within the distillation framework. The spectrum exhibits the general features observed in previous calculations using an anisotropic clover lattice, with a counting of states at least as rich as the quark model. Furthermore, we identify states that are hybrid in nature, where gluonic degrees of freedom play a structural role, indicatinng that such states appear a feature of the excited baryon spectrum, irrespective of the lattice action, or the precise details of the smearing of the lattice interpolating operators used to identify such states.
↳ hep-lathep-phnucl-thPRD(2021)·26 citations
23*
Quantum parity conservation in planar quantum electrodynamics
O.M. Del Cima🇧🇷 · D.H.T. Franco🇧🇷 · L.S. Lima🇧🇷 · E.S. Miranda🇧🇷
Quantum parity conservation is verified at all orders in perturbation theory for a massless parity-even $U (1) \times U (1)$ planar quantum electrodynamics (QED $_{3}$ ) model. The presence of two massless fermions requires the Lowenstein-Zimmermann (LZ) subtraction scheme, in the framework of the Bogoliubov-Parasiuk-Hepp-Zimmermann-Lowenstein (BPHZL) renormalization method, in order to subtract the infrared divergences induced by the ultraviolet subtractions at 1- and 2-loops, however thanks to the superrenormalizability of the model the ultraviolet divergences are bounded up to 2-loops. Finally, it is proved that the BPHZL renormalization method preserves parity for the model taken into consideration, contrary to what happens to the ordinary massless parity-even $U (1)$ QED $_{3}$ .
↳ hep-thcond-mat.str-elhep-phmath-ph+2Int.J.Theor.Phys.(2021)·7 citations
24*
Large anisotropies of the stochastic gravitational wave background from cosmic domain walls
Jing Liu🇨🇳 · Rong-Gen Cai🇨🇳 · Zong-Kuan Guo🇨🇳
We investigate the stochastic gravitational wave background (SGWB) from cosmic domain walls (DWs) caused by quantum fluctuations of a light scalar field $ϕ$ during inflation. Perturbations of $ϕ$ remain almost constant after leaving the Hubble horizon. The probabilities of the two domains depend on the averaged value of $ϕ$ at each large scale region, leading to large scale perturbations of DW energy density and large anisotropies in the SGWB. We find that the angular power spectrum is scale-invariant and at least of the order of $1 0^{- 2}$ , which is expected to be detected by future gravitational-wave (GW) detectors. Since we have not detected primordial GWs yet, anisotropies of the SGWB could help us to verify the rationality of inflation and determine the energy scale of inflation.
↳ astro-ph.COgr-qchep-phPRL(2021)·47 citations
25*
Observing primordial magnetic fields through Dark Matter
Sabir Ramazanov🇨🇿 · Federico R. Urban🇨🇿 · Alexander Vikman🇨🇿
Primordial magnetic fields are often thought to be the early Universe seeds that have bloomed into what we observe today as galactic and extra-galactic magnetic fields. Owing to their minuscule strength, primordial magnetic fields are very hard to detect in cosmological and astrophysical observations. We show how this changes if a part of neutral Dark Matter has a magnetic susceptibility. In this way, by studying Dark Matter one can obtain information about the properties of primordial magnetic fields, even if the latter have a comoving amplitude $B_{0} ≲ 0.01 \mbox n G$ . In our model Dark Matter is a stable singlet scalar $χ$ , which interacts with electromagnetism through the Rayleigh operator as $χ^{2} F_{μν} F^{μν} / Λ^{2}$ . For primordial magnetic fields present in the early Universe this operator forces the $Z_{2}$ -symmetry of the model to be spontaneously broken. Later, when the primordial magnetic field redshifts below a critical value, the symmetry is restored through an "inverse phase transition". At that point the field $χ$ begins to oscillate and acts as a "magnetomorphic" Dark Matter component, inheriting the properties of the primordial magnetic field space distribution. In particular, for a nearly flat spectrum of magnetic field fluctuations, the scalar $χ$ carries a statistically anisotropic isocurvature mode. We discuss the parameter space of the model and consider the possibility that the bulk of the Dark Matter is composed of the same particles $χ$ produced via the freeze-in mechanism.
↳ astro-ph.COhep-phhep-thJCAP(2021)·9 citations
26*
The Mellin moments $⟨ x ⟩$ and $⟨ x^{2} ⟩$ for the pion and kaon from lattice QCD
Constantia Alexandrou🇨🇾 · Simone Bacchio🇨🇾 · Ian Cloet🇺🇸 · Martha Constantinou🇺🇸 · Kyriakos Hadjiyiannakou🇨🇾 · Giannis Koutsou🇨🇾 · Colin Lauer🇺🇸
We present a calculation of the pion quark momentum fraction, $⟨ x ⟩$ , and its third Mellin moment $⟨ x^{2} ⟩$ . We also obtain directly, for the first time, $⟨ x ⟩$ and $⟨ x^{2} ⟩$ for the kaon using local operators. We use an ensemble of two degenerate light, a strange and a charm quark ( $N_{f} = 2 + 1 + 1$ ) of maximally twisted mass fermions with clover improvement. The quark masses are chosen so that they reproduce a pion mass of about 260 MeV, and a kaon mass of 530 MeV. The lattice spacing of the ensemble is 0.093 fm and the lattice has a spatial extent of 3 fm. We analyze several values of the source-sink time separation within the range of $1.12 - 2.23$ fm to study and eliminate excited-states contributions. The necessary renormalization functions are calculated non-perturbatively in the RI $^{'}$ scheme, and are converted to the $MS$ scheme at a scale of 2 GeV. The final values for the momentum fraction are $⟨ x ⟩_{u^{+}}^{π} = 0.261 (3)_{stat} (6)_{syst}$ , $⟨ x ⟩_{u^{+}}^{K} = 0.246 (2)_{stat} (2)_{syst}$ , and $⟨ x ⟩_{s^{+}}^{K} = 0.317 (2)_{stat} (1)_{syst}$ . For the third Mellin moments we find $⟨ x^{2} ⟩_{u^{+}}^{π} = 0.082 (21)_{stat} (17)_{syst}$ , $⟨ x^{2} ⟩_{u^{+}}^{K} = 0.093 (5)_{stat} (3)_{syst}$ , and $⟨ x^{2} ⟩_{s^{+}}^{K} = 0.134 (5)_{stat} (2)_{syst}$ . The reported systematic uncertainties are due to excited-state contamination. We also give the ratio $⟨ x^{2} ⟩ / ⟨ x ⟩$ which is an indication of how quickly the PDFs lose support at large $x$ .
↳ hep-lathep-exhep-phPRD(2021)·35 citations
27*
Primordial black holes and gravitational waves from resonant amplification during inflation
Zihan Zhou🇨🇳 · Jie Jiang🇨🇳 · Yi-Fu Cai🇨🇳 · Misao Sasaki🇯🇵 · Shi Pi🇯🇵
We present a new realization of the resonant production of primordial black holes as well as gravitational waves in a two-stage inflation model consisting of a scalar field \phi with an axion-monodromy-like periodic structure in the potential that governs the first stage and another field \chi with a hilltop-like potential that dominates the second stage. The parametric resonance seeded by the periodic structure at the first stage amplifies the perturbations of both fields inside the Hubble radius. While the evolution of the background trajectory experiences a turn as the oscillatory barrier height increases, the amplified perturbations of \chi remain as they are and contribute to the final curvature perturbation. It turns out that the primordial power spectrum displays a significant resonant peak on small scales, which can lead to an abundant production of primordial black holes. Furthermore, gravitational waves are also generated from the resonantly enhanced field perturbations during inflation, the amplitude of which may be constrained by future gravitational wave interferometers.
↳ astro-ph.COgr-qchep-phhep-thPRD(2020)·149 citations

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