HEP Phenomenology·hep-ph

Thu·Oct 7, 2021Thursday·October 7, 2021

32 papers—20 primary·12 cross-listed·reconstructed*

01*
Photon-photon scattering from a UV-complete gravity QFT
Bob Holdom🇨🇦
Quantum quadratic gravity (QQG) produces a tree-level differential cross section for $γ γ \to γ γ$ that is well-behaved at all energies. From this we can study how the corrections to low energy scattering amplitudes are related to the UV physics, in particular to the exchange of the massive graviparticles. An effective forward scattering amplitude is obtained by separating out the effects of the $t$ -channel graviton pole. This is possible due to the UV-completeness, and even though the Froissart bound is not satisfied. We then consider photon-photon scattering to two graviparticles and a further imaginary contribution to the $γ γ \to γ γ$ forward scattering amplitude. Unitarity without positivity is a key property of QQG and it impacts all our results.
hep-phhep-thJHEP(2022)·20 citations
02*
Flavor isospin waves in one-dimensional axisymmetric neutrino gases
Huaiyu Duan (UNM)🇺🇸 · Joshua D. Martin (LANL)🇺🇸 · Sivaprasad Omanakuttan (UNM)🇺🇸
Flavor oscillations can occur on very short spatial and temporal scales in the dense neutrino media in a core-collapse supernova (CCSN) or binary neutron star merger (BNSM) event. Although the dispersion relations (DRs) of the fast neutrino oscillations can be obtained by linearizing the equations of motion (EoM) before the emergence of any significant flavor conversion, one largely depends on numerical calculations to understand this interesting phenomenon in the nonlinear regime. In this work we demonstrate that there exist nontrivial solutions to the flavor EoM that govern the fast oscillations in one-dimensional axisymmetric neutrino gases. These solutions represent a coherent flavor isospin wave similar to the magnetic spin wave in a lattice of magnetic dipoles. We also compute the DRs of such waves in some example cases which are closely related to the DRs of the fast neutrino oscillations obtained in the linear regime. This result sheds new light on the long-term behavior of fast neutrino oscillations which can have various implications for the CCSN and BNSM events.
hep-phastro-ph.HEnucl-thPRD(2021)·28 citations
03*
Dark Matter Direct Detection of Classical WIMPs
Jodi Cooley🇺🇸
One of the highest priorities in particle physics today is the identification of the constituents of dark matter. This manuscript is a supplement to pedagogical lectures given at the 2021 Les Houches Summer School on Dark Matter. The lectures cover topics related to the direct detection of WIMP dark matter, including the distribution of dark matter, nuclear scattering, backgrounds, planning and designing of experiments and a sampling of planned and ongoing experiments.
hep-phhep-exSciPost Phys.Lect.Notes(2022)·49 citations
04*
Understanding the systematic differences in extractions of the proton electric form factors at low- $Q^{2}$
Jingyi Zhou🇺🇸 · Vladimir Khachatryan🇺🇸 · Haiyan Gao🇺🇸 · Simon Gorbaty🇺🇸 · Douglas W. Higinbotham🇺🇸
Systematic differences exist between values of the proton's electric form factors in the low- $Q^{2}$ region extracted by different experimental and theoretical groups, though they are all making use of basically the same electron-proton scattering data. To try understand the source of these differences, we make use of the analytically well-behaved rational (N=1, M=1) function, a predictive function that can be reasonably used for extrapolations at $Q^{2} \to 0$ . First, we test how well this deceptively simple two-parameter function describes the extremely complex and state-of-the-art dispersively improved chiral effective field theory calculations. Second, we carry out a complete re-analysis of the 34 sets of eletron-proton elastic scattering cross-section data of the Mainz A1 Collaboration with its unconstrained 31 normalization parameters up to $Q^{2} = 0.5 (GeV/c)^{2}$ . We find that subtle shifts in the normalization parameters can result in relatively large changes in the extracted physical qualities. In conclusion, we show that by simply using a well-behaved analytic function, the apparent discrepancy between recent form-factor extractions can be resolved.
hep-phnucl-exnucl-thPRC(2022)·10 citations
05*
Particle-beam scattering from strong-field QED
Tim Adamo🇬🇧 · Anton Ilderton🇬🇧 · Alexander J. MacLeod🇬🇧
We consider the scattering of probe particles on an ultra-boosted beam of charge, in the case that the fields of the beam are strong and must be treated non-perturbatively. We show that the fields of the ultra-boosted beam act as stochastic plane waves - scattering amplitudes (of elastic scattering, nonlinear Compton and nonlinear Breit-Wheeler) are obtained without approximation by averaging plane wave scattering amplitudes over all possible plane wave parameters. The relevant plane waves are ultra-short and, as such, scattering on ultra-boosted beams does not exhibit the conjectured strong-field behaviour of QED based on the locally constant field approximation.
hep-phhep-thPRD(2021)·20 citations
06*
First steps towards the quantum simulation of jet quenching
João Barata🇪🇸 · Carlos A. Salgado🇪🇸
The leading order $α_{s}$ effect in jet quenching corresponds to the broadening of the jet's transverse momentum, due to the multiple interactions with the underlying medium. A complete understanding of momentum broadening is critical for the success of jet quenching phenomenology. In this talk, we introduce a strategy to quantum simulate single particle momentum broadening in a QCD background medium. We argue that it is, in principle, possible to extract the jet quenching parameter $q^$ from such an algorithm. More importantly, this corresponds to the first step towards simulating full medium induced parton showers, which is far beyond the capabilities of classical computers.
hep-phPoS(2022)·1 citation
07*
NNLO Photon Fragmentation within Antenna Subtraction
Thomas Gehrmann🇨🇭 · Robin Schürmann🇨🇭
We report on our recent progress towards including the photon fragmentation contribution in next-to-next-to-leading order (NNLO) QCD predictions for photon production cross sections. This extension to previous NNLO calculations requires the identification of the photon in singular parton-photon collinear limits. We discuss how these limits can be subtracted within antenna subtraction using fragmentation antenna functions and we outline their integration.
hep-phSciPost Phys.Proc.(2022)·2 citations
08*
Moat Regimes in QCD and their Signatures in Heavy-Ion Collisions
Fabian Rennecke🇩🇪 · Robert D. Pisarski🇺🇸
Dense QCD matter can exhibit spatially modulated regimes. They can be characterized by particles with a moat spectrum, where the minimum of the energy is over a sphere at nonzero momentum. Such a moat regime can either be a precursor for the formation inhomogeneous condensates, or signal a quantum pion liquid. We introduce the quantum pion liquid and discuss the underlying physics of the moat regime based on studies in low-energy models and preliminary results in QCD. Heavy-ion collisions at small beam energies have the potential to reveal the rich phase structure of QCD at low temperature and nonzero density. We show how moat regimes can be discovered through such collisions. Particle production is enhanced at the bottom of the moat, resulting in a peak at nonzero momentum, instead of zero, in the particle spectrum. Particle number correlations can even increase by several orders of magnitude at nonzero momentum in the moat regime.
hep-phnucl-exnucl-thPoS(2022)·22 citations
09*
Looking for monopolium excited states with electromagnetic detectors
Huner Fanchiotti}🇦🇷 · C.A.~García Canal🇦🇷 · Marco Traini🇮🇹 · Vicente Vento🇪🇸
We study the detection of particles with magnetic moment and no charge by using coils and solenoids. The detector uses the Faraday-Lenz law to create a current whose energy is measured. Our development can be applied to any particle with magnetic moment. The neutron is ideal to show our detector scheme for particles with long lifetimes and the result is encouraging. However, our interest lies in the detection of monopolium states which decays much faster than neutrons. The accelerator scenario with a relatively low monopole mass $\sim 1000$ GeV requires the generalization of the scheme to finite lifetimes. We use two descriptions, which we have called Dirac and Schwinger, (also $β$ -coupling), schemes, in our study. The theoretical behavior of excited monopolia in coils teaches us many of their properties. However, their small production cross sections, given the achievable LHC luminosities, makes detection using coils difficult. Therefore, we generalize the discussion to cosmological heavy monopolium. Our scheme becomes useful for those and supplements detectors like MoEDAL and MAPP in distinguishing monopolia from other long lived particles.
hep-phhep-ex1 citation
10*
Hierarchy in double SU(2) models
Clara Álvarez-Luna🇪🇸 · José A. R. Cembranos🇪🇸 · Juan José Sanz-Cillero🇪🇸
In this work, we provide a simple model that studies the probability to obtain a given hierarchy between two scales. In particular, we work in a theory with an $S U (2)_{L} \times S U (2)_{H} \times U (1)_{X}$ gauge symmetry and two scalar doublets. By the Coleman-Weinberg mechanism, the gauge bosons and scalars obtain different masses, corresponding to the light and heavy sectors. We analyze the mass ratio of these sectors in order to discuss the hierarchy between them, and we define a probability associated to this hierarchy. We analyze different cases in which one of the sectors is fixed or both of them have free parameters, and also study the effect of including an interaction between them. We conclude that the probability of obtaining very large hierarchies is (logarithmically) small but not negligible.
hep-phPoS(2022)·0 citations
11*
Generalization of Weinberg's Compositeness Relations
Yan Li🇨🇳 · Feng-Kun Guo🇨🇳 · Jin-Yi Pang🇨🇳 · Jia-Jun Wu🇨🇳
We generalize the time-honored Weinberg's compositeness relations by including the range corrections through considering a general form factor. In Weinberg's derivation, he considered the effective range expansion up to $O (p^{2})$ and made two additional approximations: neglecting the non-pole term in the Low equation; approximating the form factor by a constant. We lift the second approximation, and work out an analytic expression for the form factor. For a positive effective range, the form factor is of a single-pole form. An integral representation of the compositeness is obtained and is expected to have a smaller uncertainty than that derived from Weinberg's relations. We also establish an exact relation between the wave function of a bound state and the phase of the scattering amplitude neglecting the non-pole term. The deuteron is analyzed as an example, and the formalism can be applied to other cases where range corrections are important.
hep-phhep-exhep-latnucl-thPRD(2022)·51 citations
12*
Jet Substructure and Multivariate Analysis Aid in Polarization Study of Boosted, Hadronic $W$ Fatjet at the LHC
Atri Dey🇮🇳 · Tousik Samui🇮🇳
Study of polarization of heavy particles is an important branch of research in today's collider studies. The massive $W$ boson has two types of polarization states, which usually are studied via the angular distribution of its decay products. We have studied polarization of hadronic and boosted $W$ boson using jet substructure technique at 14 TeV LHC. Two different methods, viz. N-subjettiness and Soft Drop, were used to find the subjets, which are approximately considered to be the two hadronic decay products of $W$ , inside boosted $W$ jets. These subjets were then used to find the distribution of $p_{θ}$ and $z_{j}$ to prepare the templates of longitudinally and transversely polarized $W$ . We then used these templates to find the fractions of different $W$ polarization in a mixed sample to a relatively good accuracy.
hep-phhep-exEPJC(2023)·9 citations
13*
NNLO QCD corrections to weak boson fusion Higgs boson production in the $H \to b b ˉ$ and $H \to W W^{*} \to 4 l$ decay channels
Konstantin Asteriadis🇺🇸 · Fabrizio Caola🇬🇧 · Kirill Melnikov🇩🇪 · Raoul Röntsch🇨🇭
We compute the next-to-next-to-leading order QCD corrections to Higgs boson production in weak boson fusion followed by its decay to a $b b ˉ$ pair or to a pair of leptonically-decaying $W$ bosons. Our calculation allows us to compute realistic fiducial cross sections and assess the impact of fiducial cuts applied to the Higgs boson decay products on the magnitude of QCD radiative corrections in weak boson fusion.
hep-phhep-exJHEP(2022)·21 citations
14*
Dark photon limits from magnetic fields and astrophysical plasmas
Giacomo Marocco🇬🇧
Dark photons may kinetically mix with our photon and modify Maxwell's equations. We examine their impact on the Lorentz force acting on the plasma in astrophysical magnetospheres. Solving the relevant magnetohydrodynamic equations, we show that any dark photon effect is negligible. The existing bound on dark photons with a mass below $1 0^{- 14}$ eV, coming from Pioneer 10 observations of Jupiter's magnetosphere, relies on such an effect and is thus unreliable. To rectify this, we use recent Juno analyses to isolate any dark photon-induced modification of the Jovian magnetic field and hence place a numerically similar limit.
hep-ph16 citations
15*
Effect of non-unitary mixing on the mass hierarchy and CP violation determination at the Protvino to Orca experiment
Daljeet Kaur🇮🇳 · Nafis Rezwan Khan Chowdhury🇪🇸 · Ushak Rahaman🇿🇦
In this paper, we have estimated the neutrino mass ordering and the CP violation sensitivity of the proposed Protvino to Orca (P2O) experiment after 6 years of data-taking. Both unitary and non-unitary $3 \times 3$ neutrino mass mixing have been considered in the simulations. A forecast analysis deriving possible future constraints on non-unitary parameters at P2O have been performed.
hep-phhep-exEPJC(2024)·10 citations
16*
$T_{cc}^{+}$ coupled channel analysis and predictions
M. Albaladejo🇪🇸
A coupled channel analysis of the $D^{*+} D^{0}$ and $D^{* 0} D^{+}$ system is performed to study the doubly charmed $T_{cc}^{+}$ state recently discovered by the LHCb collaboration. We use a simple model for the scattering amplitude that allows us to describe well the experimental spectrum, and obtain the $T_{cc}^{+}$ pole in the coupled channel $T$ -matrix. We find that this bound state has a large molecular component. The isospin ( $I = 0$ or $I = 1$ ) of the state cannot be inferred from the $D^{0} D^{0} π^{+}$ spectrum alone. Therefore, we use the same formalism to predict other $D D π$ spectra. In the case the $T_{cc}^{+}$ has $I = 1$ , we also predict the location of the other two members ( $T_{cc}^{++}$ and $T_{cc}^{0}$ ) of the triplet. Finally, using Heavy-Quark Spin Symmetry, we predict the location of possible heavier $D^{*} D^{*}$ ( $I = 0$ or $I = 1$ ) partners.
hep-phPLB(2022)·130 citations
17*
Non-Decoupling New Particles
Ian Banta🇺🇸 · Timothy Cohen🇺🇸 · Nathaniel Craig🇺🇸 · Xiaochuan Lu🇺🇸 · Dave Sutherland🇮🇹
We initiate the study of a new class of beyond the Standard Model states that we call "Loryons." They have the defining characteristic of being non-decoupling, in the sense that their physical mass is dominated by a contribution from the vacuum expectation value of the Higgs boson. The stakes are high: the discovery of a Loryon would tell us that electroweak symmetry must be non-linearly realized in the effective field theory of the Standard Model. Loryons have their masses bounded from above by perturbative unitarity considerations and thus define a finite parameter space for exploration. After providing a complete catalog of Loryon representations under mild assumptions, we turn to examining the constraints on the parameter space from Higgs couplings measurements, precision electroweak tests, and direct collider searches. We show that most fermionic candidates are already ruled out (with some notable exceptions), while much of the scalar Loryon parameter space is still wide open for discovery.
hep-phJHEP(2022)·59 citations
18*
Dimuons in Neutrino Telescopes: New Predictions and First Search in IceCube
Bei Zhou🇺🇸 · John F. Beacom🇺🇸
Neutrino telescopes allow powerful probes of high-energy astrophysics and particle physics. Their power is increased when they can isolate different event classes, e.g., by flavor, though that is not the only possibility. Here we focus on a new event class for neutrino telescopes: dimuons, two energetic muons from one neutrino interaction. We make new theoretical and observational contributions. For the theoretical part, we calculate dimuon-production cross sections and detection prospects via deep-inelastic scattering (DIS; where we greatly improve upon prior work) and $W$ -boson production (WBP; where we present first results). We show that IceCube should have $≃ 130$ dimuons ( $≃ 6$ from WBP) in its current data and that IceCube-Gen2, with a higher threshold but a larger exposure, could detect $≃ 620$ dimuons ( $≃ 30$ from WBP) in 10 years. These dimuons are almost all produced by atmospheric neutrinos. For the observational part, we perform a simple but conservative analysis of IceCube public data, finding 19 candidate dimuon events. Subsequent to our paper appearing, visual inspection of these events by the IceCube Collaboration revealed that they are not real dimuons, but instead arise from an internal reconstruction error that identifies some single muons crossing the dust layer as two separate muons. To help IceCube and the broader community with future dimuon searches, we include the updated full details of our analysis. Together, these theoretical and observational contributions help open a valuable new direction for neutrino telescopes, one especially important for probing high-energy QCD and new physics.
hep-phastro-ph.HEhep-exPRD(2022)·28 citations
19*
Quark-Gluon Backscattering in the Regge Limit at One-Loop
Arindam Bhattacharya🇺🇸 · Aneesh V. Manohar🇺🇸 · Matthew D. Schwartz🇺🇸
At small momentum transfer, the quark-gluon scattering cross section d{\sigma}/dt has a power-law divergence in the backward scattering region where the outgoing quark is nearly collinear to the incoming gluon. In this Regge limit |t|<< s, the leading behavior of the 2 2 amplitude can be described by the exchange of Glauber quarks. In Soft-Collinear Effective Theory (SCET) at leading power, Glauber quark exchange is given by five non-local Glauber quark operators, of which only one is generated at tree-level. We show that at leading power the QCD amplitude for quark-gluon backscattering at one-loop can be exactly reproduced by SCET using the tree-level Glauber operator. The agreement between QCD and SCET of the ultraviolet, infrared, and rapidity divergences as well as all logarithms, Glauber phases and finite parts for all polarizations of the external gluons is a strong check on the effective theory. We find that the entire one-loop matching vanishes -- there is no correction to the operator generated at tree-level, and the coefficients of the other four operators remain zero at one-loop. This suggests that SCET with Glauber operators may be useful for uncovering new aspects of Regge physics in a systematically improveable way.
hep-phhep-thJHEP(2022)·6 citations
20*
Fuelling the search for light dark matter-electron scattering with spherical proportional counters
Louis Hamaide🇬🇧 · Christopher McCabe🇬🇧
Dark matter (DM) detectors employing a Spherical Proportional Counter (SPC) have demonstrated a single-electron detection threshold and are projected to have small background rates. We explore the sensitivity to DM-electron scattering with SPC detectors in the context of DarkSphere, a proposal for a 300 cm diameter fully-electroformed SPC. SPCs can run with different gases, so we investigate the sensitivity for five targets: helium, neon, xenon, methane, and isobutane. We use tools from quantum chemistry to model the atomic and molecular systems, and calculate the expected DM induced event rates. We find that DarkSphere has the potential to improve current exclusion limits on DM masses above 4 MeV by up to five orders of magnitude. Neon is the best all-round gas target and provides good sensitivity to scenarios with both light and heavy mediators. Gas mixtures, where methane or isobutane is added to a noble gas, can extend the sensitivity at lower masses. Our study highlights the currently untapped potential of SPCs to search for DM-electron scattering in the MeV-to-GeV DM mass range.
hep-phastro-ph.COhep-exPRD(2023)·23 citations
21*
An Analytic Treatment of Underdamped Axionic Blue Isocurvature Perturbations
Daniel J. H. Chung🇺🇸 · Sai Chaitanya Tadepalli🇺🇸
Previous computations of strongly blue tilted axionic isocurvature spectra were computed in the parametric region in which the lightest time-dependent mass is smaller than the Hubble expansion rate during inflation, leading to an overdamped time evolution. Here we present the strongly blue tilted axionic isocurvature spectrum in an underdamped time evolution parametric regime. Somewhat surprisingly, there exist parametric regions with a strong resonant spectral behavior that leads to a rich isocurvature spectral shape. We focus on computing this resonant spectrum analytically in a large parametric region amenable to such computations. Because the spectrum is sensitive to nonperturbative classical field dynamics, a wide variety of analytic techniques are used including a time-space effective potential obtained by integrating out high frequency fluctuations.
↳ astro-ph.COhep-phPRD(2022)·22 citations
22*
Triangulating Black Hole Forming Stellar Collapses through Neutrinos
Lila Sarfati🇩🇰 · Rasmus S. L. Hansen🇩🇰 · Irene Tamborra🇩🇰
In the event of a black hole (BH) forming stellar collapse, the neutrino signal should terminate abruptly at the moment of BH formation, after a phase of steady accretion. Since neutrinos are expected to reach Earth hours before the electromagnetic signal, the combined detection of the neutrino burst through multiple neutrino telescopes could allow to promptly determine the angular location of a nearby stellar collapse in the sky with high precision. In this paper, we contrast the triangulation pointing procedure that relies on the rise time of the neutrino curve, often considered in the literature, to the one that takes advantage of the cutoff of the neutrino curve at the moment of BH formation. By forecasting the neutrino signal expected in the IceCube Neutrino Observatory, Hyper-Kamiokande and DUNE, we devise a strategy to optimize the identification of the rise and cutoff time of the neutrino curve. We show that the triangulation method developed by employing the end tail of the neutrino curve allows to achieve at least one order of magnitude improvement in the pointing precision for a galactic burst, while being insensitive to the neutrino mixing scenario. The triangulation pointing method based on the cutoff of the neutrino curve will also guarantee a better performance for BH forming collapses occurring beyond our own Galaxy.
↳ astro-ph.HEhep-phPRD(2022)·8 citations
23*
Phenomenological developments for event-by-event fluctuations of conserved charges
Volodymyr Vovchenko🇺🇸
A brief overview of the recent developments concerning theoretical description of event-by-event fluctuations in heavy-ion collisions is presented, with an emphasis on the role of exact conservation laws and calculations based on relativistic hydrodynamics.
↳ nucl-thhep-phPoS(2022)·8 citations
24*
Exploration of interacting dynamical dark energy model with interaction term including the equation-of-state parameter: alleviation of the $H_{0}$ tension
Rui-Yun Guo🇨🇳 · Lu Feng🇨🇳 · Tian-Ying Yao🇨🇳 · Xing-Yu Chen🇨🇳
We explore a scenario of interacting dynamical dark energy model with the interaction term $Q$ including the varying equation-of-state parameter $w$ . Using the data combination of the cosmic microwave background, the baryon acoustic oscillation, and the type Ia supernovae, to global fit the interacting dynamical dark energy model, we find that adding a factor of the varying $w$ in the function of $Q$ can change correlations between the coupling constant $β$ and other parameters, and then has a huge impact on the fitting result of $β$ . In this model, the fitting value of $H_{0}$ is lower at the $3.54 σ$ level than the direct measurement value of $H_{0}$ . Comparing to the case of interacting dynamical dark energy model with $Q$ excluding $w$ , the model with $Q$ including the constant $w$ is more favored by the current mainstream observation. To obtain higher fitting values of $H_{0}$ and narrow the discrepancy of $H_{0}$ between different observations, additional parameters including the effective number of relativistic species, the total neutrino mass, and massive sterile neutrinos are considered in the interacting dynamical dark energy cosmology. We find that the $H_{0}$ tension can be further reduced in these models, but is still at the about $3 σ$ level.
↳ gr-qcastro-ph.COhep-phJCAP(2021)·33 citations
25*
Can we detect the quantum nature of weak gravitational fields?
Francesco Coradeschi🇮🇹 · Antonia Micol Frassino🇪🇸 · Thiago Guerreiro🇧🇷 · Jennifer Rittenhouse West🇺🇸 · Enrico Junior Schioppa🇮🇹
A theoretical framework for the quantization of gravity has been an elusive Holy Grail since the birth of quantum theory and general relativity. While generations of scientists have attempted solutions to this deep riddle, an alternative path built upon the idea that experimental evidence could determine whether gravity is quantized has been decades in the making. The possibility of an experimental answer to the question of the quantization of gravity is of renewed interest in the era of gravitational wave detectors. We review and investigate an important subset of phenomenological quantum gravity, detecting quantum signatures of weak gravitational fields in table-top experiments and interferometers.
↳ gr-qchep-phquant-phUniverse(2021)·19 citations
26*
Modelling the Data at the LHC
Efe Yazgan (for the ATLAS and CMS Collaborations)🇹🇼
Measurements at hadron colliders rely on large scale quantum chromodynamics (QCD) Monte Carlo (MC) production for interpretation of the data. MC simulations allow testing Standard Model (SM) with more accurate and precise calculations to understand perturbative QCD as well as electroweak effects, and extrapolations of the irreducible backgrounds to signal phase-space regions for new physics searches or for the measurements of rare SM processes. In the MC codes, there are many pieces, approximations, and parameters and settings to compare to the data and tune. Precise experimental measurements at the LHC require similar level of precision in theoretical calculations. Cross sections measured at the LHC both by ATLAS and CMS experiments cover more than 14 orders of magnitude. So far, SM cross section predictions are found to be in very good agreement with the data. These cross sections are measured at different pp collision energies and compared to prediction up to next-to-next-to-leading order (NNLO) for many processes, and recently up to N $^{3}$ LO for some of them. In this note, a few measurements relevant to data modelling are discussed.
↳ hep-exhep-phPoS(2022)·0 citations
27*
Palatini approach and large-scale magnetogenesis
Massimo Giovannini🇨🇭
Large-scale magnetogenesis is analyzed within the Palatini approach when the gravitational action is supplemented by a contribution that is nonlinear in the Einstein-Hilbert term. While the addition of the nonlinear terms does not affect the scalar modes of the geometry during the inflationary phase, the tensor-to-scalar ratio is nonetheless suppressed. In this context it is plausible to have a stiff phase following the standard inflationary stage provided the potential has a quintessential form. The large-scale magnetic fields can even be a fraction of the nG over typical length scales of the order of the Mpc prior to the gravitational collapse of the protogalaxy.
↳ hep-thastro-ph.COgr-qchep-phJCAP(2021)·8 citations
28*
Primordial Black Holes as Dark Matter Candidates
Bernard Carr🇬🇧 · Florian Kuhnel🇩🇪
We review the formation and evaporation of primordial black holes (PBHs) and their possible contribution to dark matter. Various constraints suggest they could only provide most of it in the mass windows $1 0^{17}$ - $1 0^{23}$ g or $10$ - $1 0^{2} M_{⊙}$ , with the last possibility perhaps being suggested by the LIGO/Virgo observations. However, PBHs could have important consequences even if they have a low cosmological density. Sufficiently large ones might generate cosmic structures and provide seeds for the supermassive black holes in galactic nuclei. Planck-mass relics of PBH evaporations or stupendously large black holes bigger than $1 0^{12} M_{⊙}$ could also be an interesting dark component.
↳ astro-ph.COgr-qchep-phSciPost Phys.Lect.Notes(2022)·292 citations
29*
Towards top-down holographic composite Higgs: minimal coset from maximal supergravity
Daniel Elander🇫🇷 · Maurizio Piai🇬🇧
Within the context of top-down holography, we study a one-parameter family of regular background solutions of maximal gauged supergravity in seven dimensions, dimensionally reduced on a 2-torus. The dual, four-dimensional confining field theory realises the global (spontaneous as well as explicit) symmetry breaking pattern SO(5)->SO(4). We compute the complete mass spectrum for the fluctuations of the 128 bosonic degrees of freedom of the five-dimensional gravity theory, which correspond to scalar, pseudoscalar, vector, axial-vector, and tensor bound states of the dual field theory, and includes particles with exotic SO(4) quantum numbers. We confirm the existence of tachyonic instabilities near the boundaries of the parameter space. We discuss the interplay between explicit and spontaneous symmetry breaking. The SO(5)/SO(4) coset might provide a first step towards the realisation of a calculable framework and ultraviolet completion of minimal composite Higgs models, if the four pseudo-Nambu-Goldstone bosons are identified with the real components of the Higgs doublet in the standard model (SM), and a subgroup of SO(4) with the SU(2)xU(1) SM gauge group. We exhibit an example with an additional localised boundary term that mimics the effect of a weakly-coupled external sector.
↳ hep-thhep-lathep-phJHEP(2022)·20 citations
30*
Fuzzy Dark Matter Candidates from String Theory
Michele Cicoli🇮🇹 · Veronica Guidetti🇩🇪 · Nicole Righi🇩🇪 · Alexander Westphal🇩🇪
String theory has been claimed to give rise to natural fuzzy dark matter candidates in the form of ultralight axions. In this paper we revisit this claim by a detailed study of how moduli stabilisation affects the masses and decay constants of different axion fields which arise in type IIB flux compactifications. We find that obtaining a considerable contribution to the observed dark matter abundance without tuning the axion initial misalignment angle is not a generic feature of 4D string models since it requires a mild violation of the $S f ≲ M_{P}$ bound, where $S$ is the instanton action and $f$ the axion decay constant. Our analysis singles out $C_{4}$ -axions, $C_{2}$ -axions and thraxions as the best candidates to realise fuzzy dark matter in string theory. For all these ultralight axions we provide predictions which can be confronted with present and forthcoming observations.
↳ hep-thastro-ph.COhep-phJHEP(2022)·79 citations
31*
Gravitational soft theorem from emergent soft gauge symmetries
Martin Beneke🇩🇪 · Patrick Hager🇩🇪 · Robert Szafron🇺🇸
We consider and derive the gravitational soft theorem up to the sub-subleading power from the perspective of effective Lagrangians. The emergent soft gauge symmetries of the effective Lagrangian provide a transparent explanation of why soft graviton emission is universal to sub-subleading power, but gauge boson emission is not. They also suggest a physical interpretation of the form of the soft factors in terms of the charges related to the soft transformations and the kinematics of the multipole expansion. The derivation is done directly at Lagrangian level, resulting in an operatorial form of the soft theorems. In order to highlight the differences and similarities of the gauge-theory and gravitational soft theorems, we include an extensive discussion of soft gauge-boson emission from scalar, fermionic and vector matter at subleading power.
↳ hep-thgr-qchep-phJHEP(2022)·27 citations
32*
Nonperturbative effects in the Standard Model with gauged 1-form symmetry
Mohamed M. Anber🇬🇧 · Erich Poppitz🇨🇦
We study the Standard Model with gauged $Z_{N = 2, 3, 6}^{(1)}$ subgroups of its $Z_{6}^{(1)}$ 1-form global symmetry, making the gauge group $\frac{S U ( 3 ) \times S U ( 2 ) \times U ( 1 )}{Z _{N}}$ . We show that, on a finite $T^{3}$ , there are self-dual instantons of fractional topological charge. They mediate baryon- and lepton-number violating processes. We compare their amplitudes to the ones due to the usual BPST-instantons. We find that the small hypercharge coupling suppresses the fractional-instanton contribution, unless the torus size is taken sub-Planckian, or extra matter is added above the weak scale. We also discuss these results in light of the cosmological bounds on the torus size.
↳ hep-thhep-lathep-phJHEP(2021)·39 citations

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