HEP Phenomenology·hep-ph
42 papers—28 primary·14 cross-listed·reconstructed*
John F. Donoghue🇺🇸 · Gabriel Menezes🇺🇸
We evaluate the induced value of Newton's constant which would arise in QCD. The ingredients are modern lattice results, perturbation theory and the operator product expansion. The resulting shift in the Planck mass is positive. A scaled-up version of such a theory may be part of a quantum field theory treatment of gravity.
Francisco J. Botella (Valencia U. and IFIC)🇪🇸 · Gustavo C. Branco (Lisbon IST and CFTP)🇵🇹 · Miguel Nebot (Lisbon IST and CFTP)🇵🇹
We show that a simple extension of the Standard Model involving the introduction of vector-like quarks and heavy neutrinos, provides an explanation of the so called B-anomalies in transitions. Vector-like quarks can explain, in the context of a discrete flavour symmetry, all the relevant characteristics of the Cabibbo-Kobayashi-Maskawa sector. It is in this framework that we study the requirements on the masses of the vector like quarks and the heavy neutrinos leading to viable models with sufficient deviations of lepton flavour universality and which simultaneously avoid too large Flavour Changing Neutral Current effects. Related predictions on and transitions are also analysed in detail.
It has been pointed out that a large non-minimal coupling between the Higgs and the Ricci scalar can source higher derivative operators, which may change the predictions of Higgs inflation. A variant, called critical Higgs inflation, employs the near-criticality of the top mass to introduce an inflection point in the potential and lower drastically the value of . We here study whether critical Higgs inflation can occur even if the pre-inflationary initial conditions do not satisfy the slow-roll behaviour (retaining translation and rotation symmetries). A positive answer is found: inflation turns out to be an attractor and therefore no fine-tuning of the initial conditions is necessary. A very large initial Higgs time-derivative (as compared to the potential energy density) is compensated by a moderate increase in the initial field value. These conclusions are reached by solving the exact Higgs equation without using the slow-roll approximation. This also allows us to treat consistently the inflection point, where the standard slow-roll approximation breaks down. Here we make use of an approach that is independent of the UV completion of gravity, by taking initial conditions that always involve sub-planckian energies.
Christoph Englert🇬🇧 · Stefan Hild🇬🇧 · Michael Spannowsky🇬🇧
Gravitational wave detector technology provides high-precision measurement apparatuses that, if combined with a modulated particle source, have the potential to measure and constrain particle interactions in a novel way, by measuring the pressure caused by scattering particle beams off the mirror material. Such a measurement does not rely on tagging a final state. This strategy has the potential to allow us to explore novel ways to constrain the presence of new interactions beyond the Standard Model of Particle Physics and provide additional constraints to poorly understood cross sections in the non-perturbative regime of QCD and Nuclear Physics, which are limiting factors of dark matter and neutrino physics searches. Beyond high-energy physics, if technically feasible, the proposed method to measure nucleon-nucleon interactions can lead to practical applications in material and medical sciences.
Agnieszka Łuszczak🇵🇱 · Wolfgang Schäfer🇵🇱
We calculate cross sections and transverse momentum distributions for the incoherent diffractive production of vector mesons and on heavy nuclei. In distinction to coherent diffraction, the nucleus is allowed to break up, but except for the vector meson no new particles are produced in the reaction. Within the color dipole approach, we derive the multiple scattering expansion of the incoherent diffractive cross section as an expansion over quasielastic scatterings of the color dipole. We also compare our results to the measurement of the ALICE collaboration for incoherent production at and show predictions at . We also briefly discuss a possible contribution to production in peripheral collisions in the centrality class.
Avital Dery🇮🇱 · Claudia Frugiuele🇮🇱 · Yosef Nir🇮🇱
The present upper bound on , the ratio between the electron Yukawa coupling and its Standard Model value, is of . We ask what would be the implications in case that is close to this upper bound. The simplest extension that allows for such enhancement is that of two Higgs doublet models (2HDM) without natural flavor conservation. In this framework, we find the following consequences: (i) Under certain conditions, measuring and would be enough to predict values of Yukawa couplings for other fermions and for the and scalars. (ii) In the case that the scalar potential has a softly broken symmetry, the second Higgs doublet must be light, but if there is hard breaking of the symmetry, the second Higgs doublet can be much heavier than the electroweak scale and still allow the electron Yukawa coupling to be very different from its SM value. (iii) CP must not be violated at a level higher than in both the scalar potential and the Yukawa sector. (iv) LHC searches for resonances constrain this scenario in a significant way. Finally, we study the implications for models where one of the scalar doublets couples only to the first generation, or only to the third generation.
Till Martini🇩🇪 · Peter Uwer🇩🇪
In a recent work the authors have presented a general algorithm to extend the Matrix Element Method (MEM) to the hadronic production of coloured partons taking into account next-to-leading-order (NLO) corrections in quantum chromodynamics (QCD). In this article, the general algorithm is applied to the production of single top quarks at the LHC. In particular, the generation of unweighted events following the NLO predictions is presented. Treating these events as the result of a toy experiment we illustrate the first application of the Matrix Element Method at NLO QCD for hadronic jet production. As a concrete example, we study the determination of the top-quark mass. We show that the inclusion of the NLO corrections can lead to sizeable effects compared to the Matrix Element Method relying on leading-order predictions only and that the incorporation of the NLO corrections is mandatory to obtain reliable estimates of the theoretical uncertainties. In addition, we find that measuring the top-quark mass using the MEM in single top-quark production offers an interesting alternative to mass measurements in top-quark pair production.
O.K. Baker🇺🇸 · D.E. Kharzeev🇺🇸
The origin of the apparent thermalization in high-energy collisions is investigated using the data of the ATLAS and CMS Collaborations at the LHC. For this purpose, we analyze the transverse momentum distributions in the following proton-proton collision processes, all at TeV: i) inclusive inelastic collisions; ii) single- and double-diffractive Drell-Yan production ; and iii) Higgs boson production. We confirm the relation between the effective temperature and the hard scattering scale observed at lower energies, and find that it extends even to the Higgs boson production process. In addition we find that the thermal component disappears in diffractive events (even though many charged hadrons are still produced). We discuss the implications of our study for the mechanism of multi-particle production -- in particular, we test the hypothesis about the link between quantum entanglement and thermalization in high-energy collisions.
Juan V. Guerrero🇺🇸 · Alberto Accardi🇺🇸
Experimental data for integrated kaon multiplicities taken at HERMES and COMPASS measurements look incompatible with each other. In this talk, we investigate the effects of hadron masses calculated at leading-order and leading twist at the kinematics of these two experiments. We present evidence that Hadron Mass Corrections can fully reconcile the data for the multiplicity ratio, and can also sizeably reduce the apparent large discrepancy in the case of data. Residual differences in the shape of the latter one remains to be understood.
This talk provides a limited review of SUSY scenarios with the focus on the way electroweak symmetry breaking is achieved and understood under different assumptions. Various aspects of naturalness and their implications are discussed and compared.
E.V. Arbuzova🇷🇺 · A.D. Dolgov🇷🇺
Spontaneous and closely related to it gravitational baryogenesis are critically analyzed. It is shown that the coupling of the curvature scalar to baryonic current, which induces nonzero baryonic asymmetry of the universe, simultaneously leads to higher order gravitational equations, which have exponentially unstable solutions. It is shown that this instability endangers the standard cosmology.
The axial anomaly is responsible for the masses and mixing of the mesons and . An open question is if (and to what extent) it affects also other hadrons. We show that anomalous terms can be important to understand the spectroscopy of the pseudotensor mesons and . In fact, pseudotensor mesons belong to a so-called heterochiral multiplet, for which a quadratic mixing term between nonstrange and strange isoscalar members arises. On the contrary, for so-called homochiral multiplets, such as the ground-state (axial-)vector and tensor mesons, this mixing is not possible, hence one can easily understand why the isoscalar members of these multiplets are almost purely nonstrange and strange, respectively. Moreover, the axial anomaly can be also coupled to baryons (within the mirror assignment), and thus it helps to explain the large decay width and to clarify which baryons are chiral partners.
The aim of present work is to consider in more details recently theoretically observed exotic "color charge glow" effect and possible physical effects related to ensembles of color charged particles on the classical level. We study ways of occurrence of "color charge glow" in arbitrary systems of point massive particles which could be split into elementary configurations like color charges and color dipoles. Also the impact of this effect on dynamics of such systems is studying. For the natural regularization of expressions we consider collisions of particles with given impact factor. We show that with reasonable values of impact factor collisions could be quite of "electrodynamical" (Coloumb-like) regime and the contribution of "glow" turns out to be suppressed in comparison with "electrodynamical" picture. It follows from the analysis of "color echo" effect that this result is still correct if we consider more complicated configurations of particles because hard gluon fields could arise only due to immediate collisions but not as a result of some effects like "color echo".
The aim of this review is to describe the field-theoretical foundations of Brout-Englert-Higgs (BEH) physics, and to show how the usual phenomenology arises from it. This requires to give a precise and gauge-invariant meaning to the underlying physics. This is complicated by the fact that concepts like the Higgs vacuum expectation value or the separation between confinement and the BEH effect loose their meaning beyond perturbation theory. This is addressed by carefully constructing the corresponding theory space and the quantum phase diagram. The physical spectrum needs then to be also given in terms of gauge-invariant, i. e. composite, states. Using gauge-invariant perturbation theory, as developed by Froehlich, Morchio, and Strocchi, it is possible to rederive conventional perturbation theory. This derivation explicitly shows why the description of the standard model in terms of the unphysical, gauge-dependent, elementary states of the Higgs and W-bosons and Z-boson, but also of the elementary fermions, is adequate and successful. These are unavoidable consequences of the field theory underlying the standard model, from which the usual picture emerges. The validity of this emergence can only be tested non-perturbatively. Such tests, in particular using lattice gauge theory, will be reviewed as well. They fully confirm the underlying mechanisms. It will be seen that the structure of the standard model is very special, and qualitative changes occur beyond it. The extension beyond the standard model will therefore also be reviewed. Particular attention will be given to structural differences arising for phenomenology. Again, non-perturbative tests of these results will be reviewed. Finally, to make this review self-contained a brief discussion of issues like the triviality and hierarchy problem, and how they fit into a fundamental field-theoretical formulation, is included.
Ansgar Denner🇩🇪 · Jean-Nicolas Lang🇩🇪 · Sandro Uccirati🇮🇹
We present the Recola2 library for the efficient generation and computation of one-loop amplitudes in Beyond-Standard-Model theories. Recola2 is based on Recola, an efficient one-loop amplitude generator for the Standard Model, and Rept1l, a newly developed tool to generate one-loop model files for Recola2 in a fully automated way. Recola2 is able to operate with non-trivial extensions of the SM, e.g. extended Higgs sectors and effective field theories. We discuss first applications to extended Higgs sectors and their renormalization.
J. C. Jiménez🇧🇷 · E. S. Fraga🇧🇷
We investigate protoneutron star matter using the state-of-the-art perturbative equation of state for cold and dense QCD in the presence of a fixed lepton fraction in which both electrons and neutrinos are included. Besides computing the modifications in the equation of state due to the presence of trapped neutrinos, we show that stable strange quark matter has a more restricted parameter space. We also study the possibility of nucleation of unpaired quark matter in the core of protoneutron stars by matching the lepton-rich QCD pressure onto a hadronic equation of state, namely TM1 with trapped neutrinos. Using the inherent dependence of perturbative QCD on the renormalization scale parameter, we provide a measure of the uncertainty in the observables we compute.
P. G. Moreira🇧🇷 · M. L. L. da Silva🇧🇷
The radiative decay of to vector mesons and is calculated in a non-relativistic approach. The results obtained are compared to experimental data to estimate the glue content of . We find a small or nonexistent glue content when our results are compared to the PDG data. However a large glue content for was found when we compared our results to the CLAS data.
Guo-yuan Huang🇨🇳 · Tommy Ohlsson🇸🇪 · Shun Zhou🇨🇳
We investigate possible interactions between neutrinos and massive scalar bosons via (or massive vector bosons via ) and explore the allowed parameter space of the coupling constant (or ) and the scalar (or vector) boson mass (or ) by requiring that these secret neutrino interactions (SNIs) should not spoil the success of Big Bang nucleosynthesis (BBN). Incorporating the SNIs into the evolution of the early Universe in the BBN era, we numerically solve the Boltzmann equations and compare the predictions for the abundances of light elements with observations. It turns out that the constraint on and in the scalar-boson case is rather weak, due to a small number of degrees of freedom. However, in the vector-boson case, the most stringent bound on the coupling at confidence level is obtained for , while the bound becomes much weaker for smaller masses . Moreover, we discuss in some detail how the SNIs affect the cosmological evolution and the abundances of the lightest elements.
Gianfranco Bertone🇳🇱 · Nassim Bozorgnia🇳🇱 · Jong Soo Kim🇿🇦 · Sebastian Liem🇳🇱 · Christopher McCabe🇬🇧 · Sydney Otten🇩🇪 · Roberto Ruiz de Austri🇪🇸
One of the most promising strategies to identify the nature of dark matter consists in the search for new particles at accelerators and with so-called direct detection experiments. Working within the framework of simplified models, and making use of machine learning tools to speed up statistical inference, we address the question of what we can learn about dark matter from a detection at the LHC and a forthcoming direct detection experiment. We show that with a combination of accelerator and direct detection data, it is possible to identify newly discovered particles as dark matter, by reconstructing their relic density assuming they are weakly interacting massive particles (WIMPs) thermally produced in the early Universe, and demonstrating that it is consistent with the measured dark matter abundance. An inconsistency between these two quantities would instead point either towards additional physics in the dark sector, or towards a non-standard cosmology, with a thermal history substantially different from that of the standard cosmological model.
Abdel Nasser Tawfik (Egyptian Ctr. Theor. Phys., Cairo and WLCAPP, Cairo)🇪🇬
The current status of implementing Tsallis (nonextensive) statistics on high-energy physics is briefly reviewed. The remarkably low freezeout-temperature, which apparently fails to reproduce the first-principle lattice QCD thermodynamics and the measured particle ratios, etc. is discussed. The present work suggests a novel interpretation for the so-called {\it "Tsallis-temperature"}. It is proposed that the low Tsallis-temperature is due to incomplete implementation of Tsallis algebra though exponential and logarithmic functions to the high-energy particle-production. Substituting Tsallis algebra into grand-canonical partition-function of the hadron resonance gas model seems not assuring full incorporation of nonextensivity or correlations in that model. The statistics describing the phase-space volume, the number of states and the possible changes in the elementary cells should be rather modified due to interacting correlated subsystems, of which the phase-space is consisting. Alternatively, two asymptotic properties, each is associated with a scaling function, are utilized to classify a generalized entropy for such a system with large ensemble (produced particles) and strong correlations. Both scaling exponents define equivalence classes for all interacting and noninteracting systems and unambiguously characterize any statistical system in its thermodynamic limit. We conclude that the nature of lattice QCD simulations is apparently extensive and accordingly the Boltzmann-Gibbs statistics is fully fulfilled. Furthermore, we found that the ratios of various particle yields at extreme high and extreme low energies of RHIC-BES is likely nonextensive but not necessarily of Tsallis type.
Michał Czakon🇩🇪 · David Heymes🇬🇧 · Alexander Mitov🇬🇧 · Davide Pagani🇩🇪 · Ioannis Tsinikos🇧🇪 · Marco Zaro🇳🇱
We calculate all main top-quark pair differential distributions at the Tevatron. For the first time Tevatron predictions for this process include all Standard Model corrections through NLO (referred to as complete-NLO) consistently combined with previously computed NNLO QCD corrections. We also assess, for the first time, the impact of dynamical scales on predictions for the latest Tevatron measurements.
Thomas Hambye🇧🇪 · Julian Heeck🇧🇪
We discuss proton and neutron decays involving three leptons in the final state. Some of these modes could constitute the dominant decay channel because they conserve lepton-flavor symmetries that are broken in all usually considered channels. This includes the particularly interesting and rarely discussed and modes. As the relevant effective operators arise at dimension 9 or 10, observation of a three-lepton mode would probe energy scales of order 100 TeV. This allows to connect proton decay to other probes such as rare meson decays or collider physics. UV completions of this scenario involving leptoquarks unavoidably violate lepton flavor universality and could provide an explanation to the recent anomalies observed in meson decays.
In this work we study a predictive model based on a partially unified theory possessing the gauge symmetry of the Pati-Salam group, supplemented by a global Peccei-Quinn symmetry, . A comprehensive analysis of the Higgs potential is carried out in a minimal set-up. The assumed Peccei-Quinn symmetry along with solving the strong CP problem, can provide axion as the dark matter candidate. This minimal set-up with limited number of Yukawa parameters can successfully incorporate the hierarchies in the charged fermion masses and mixings. The automatic existence of the heavy Majorana neutrinos generate the extremely small light neutrino masses through the seesaw mechanism, which is also responsible for producing the observed cosmological matter-antimatter asymmetry of the universe. We find interesting correlation between the low scale neutrino observables and the baryon asymmetry in this model. Baryon number violating nucleon decay processes mediated by the scalar diquarks and leptoquarks in this framework are found to be, ( meson, lepton, antilepton) and . For some choice of the parameters of the theory, these decay rates can be within the observable range. Another baryon number violating process, the neutron-antineutron oscillation can also be in the observable range.
Direct searches for Dark Matter (DM) are continuously improving, probing down to lower and lower DM-nucleon interaction cross sections. For strongly-interacting massive particle (SIMP) Dark Matter, however, the accessible cross section is bounded from above due to the stopping effect of the atmosphere, Earth and detector shielding. We present a careful calculation of the SIMP signal rate, focusing on super-heavy DM () for which the standard nuclear-stopping formalism is applicable, and provide code for implementing this calculation numerically. With recent results from the low-threshold CRESST 2017 surface run, we improve the maximum cross section reach of direct detection searches by a factor of around 5000, for DM masses up to . A reanalysis of the longer-exposure, sub-surface CDMS-I results (published in 2002) improves the previous cross section reach by two orders of magnitude, for masses up to . Along with complementary constraints from SIMP capture and annihilation in the Earth and Sun, these improved limits from direct nuclear scattering searches close a number of windows in the SIMP parameter space in the mass range GeV to GeV, of particular interest for heavy DM produced gravitationally at the end of inflation.
Pouya Asadi🇺🇸 · Matthew R. Buckley🇺🇸 · Anthony DiFranzo🇺🇸 · Angelo Monteux🇺🇸 · David Shih🇺🇸
In previous work, we identified an anomalous number of events in the LHC jets+MET searches characterized by low jet multiplicity and low-to-moderate transverse energy variables. Here, we update this analysis with results from a new ATLAS search in the monojet channel which also shows a consistent excess. As before, we find that this "monojet excess" is well-described by the resonant production of a heavy colored state decaying to a quark and a massive invisible particle. In the combined ATLAS and CMS data, we now find a local (global) preference of 3.3 (2.5) for the new physics model over the Standard Model-only hypothesis. As the signal regions containing the excess are systematics-limited, we consider additional cuts to enhance the signal-to-background ratio. We show that binning finer in and requiring the jets to be more central can increase by a factor of .
Luca Di Luzio🇬🇧 · Federico Mescia🇪🇸 · Enrico Nardi🇮🇹 · Paolo Panci🇨🇭 · Robert Ziegler🇨🇭
We propose a class of axion models with generation dependent Peccei-Quinn charges for the known fermions that allow to suppress the axion couplings to nucleons and electrons. Astrophysical limits are thus relaxed, allowing for axion masses up to eV. The axion-photon coupling remains instead sizeable, so that next generation helioscopes will be able to probe this scenario. Astrophobia unavoidably implies flavor violating axion couplings, so that experimental limits on flavour-violating processes can provide complementary probes. The astrophobic axion can be a viable dark matter candidate in the heavy mass window, and can also account for anomalous energy loss in stars.
Joshua Eby🇮🇱 · Peter Suranyi🇺🇸 · L.C.R. Wijewardhana🇺🇸
The method pioneered by Ruffini and Bonazzola (RB) to describe boson stars involves an expansion of the boson field which is linear in creation and annihilation operators. In the nonrelativistic limit, the equation of motion of RB is equivalent to the nonlinear Schrödinger equation. Further, the RB expansion constitutes an exact solution to a non-interacting field theory, and has been used as a reasonable ansatz for an interacting one. In this work, we show how one can go beyond the RB ansatz towards an exact solution of the interacting operator Klein-Gordon equation, which can be solved iteratively to ever higher precision. Our Generalized Ruffini-Bonazzola approach takes into account contributions from nontrivial harmonic dependence of the wavefunction, using a sum of terms with energy , where and is the chemical potential of a single bound axion. The method critically depends on an expansion in a parameter , where is the mass of the boson. In the case of the axion potential, we calculate corrections which are relevant for axion stars in the transition or dense branches of solutions. We find with high precision the local minimum of the mass, , at , where is the axion decay constant. This point marks the crossover from the transition branch to the dense branch of solutions, and a corresponding crossover from structural instability to stability.
Nobuchika Okada🇺🇸 · Satomi Okada🇯🇵 · Digesh Raut🇺🇸
We propose a grand unified SU(5)U(1) model, where the standard SU(5) grand unified theory is supplemented by minimal seesaw and a right-handed neutrino dark matter with an introduction of a global -parity. In the presence of three right-handed neutrinos (RHNs), the model is free from all gauge and mixed-gravitational anomalies. The SU(5) symmetry is broken into the Standard Model (SM) gauge group at GeV in the standard manner, while the U(1) symmetry breaking occurs at the TeV scale, which generates the TeV-scale mass of the U(1) gauge boson ( boson) and the three Majorana RHNs. A unique -odd RHN is stable and serves as the dark matter (DM) in the present Universe, while the remaining two RHNs work to generate the SM neutrino masses through the minimal seesaw. We investigate the -portal RHN DM scenario in this model context, and find that the constraints from the DM relic abundance and the search results for a boson resonance at the Large Hadron Collider (LHC) are complementary to narrow down the allowed parameter region, which will be fully covered by the future LHC experiments (for the boson mass 5 TeV). We also briefly discuss the successful implementation of Baryogenesis and cosmological inflation scenarios in the present model.
Hiromichi Nishimura🇺🇸 · Robert D. Pisarski🇺🇸 · Vladimir V. Skokov🇺🇸
We study phase transitions in gauge theories at nonzero temperature using matrix models. Our basic assumption is that the effective potential is dominated by double trace terms for the Polyakov loops. As a function of the various parameters, related to terms linear, quadratic, and quartic in the Polyakov loop, the phase diagram exhibits a universal structure. In a large region of this parameter space, there is a continuous phase transition whose order is larger than second. This is a generalization of the phase transition of Gross, Witten, and Wadia (GWW). Depending upon the detailed form of the matrix model, the eigenvalue density and the behavior of the specific heat near the transition differ drastically. We speculate that in the pure gauge theory, that although the deconfining transition is thermodynamically of first order, it can be nevertheless conformally symmetric at infinite .
Thamirys de Oliveira🇧🇷 · Débora P. Menezes🇧🇷 · Marcus B. Pinto🇧🇷 · Francesca Gulminelli🇫🇷
We compare relativistic mean field models with their low density expansion counterparts used to mimic non-relativistic models by consistently expanding the baryonic scalar density in powers of the baryonic number density up to , which goes two orders beyond the order considered in previous works. We show that, due to the non-trivial density dependence of the Dirac mass, the convergence of the expansion is very slow, and the validity of the non-relativistic approximation {\bf is} questionable even at subsaturation densities. In order to analyze the roles played by strangeness and isospin we consider and matter separately. Our results indicate that these degrees of freedom play quite different roles in the expansion mechanism and matter can be better described by low density expansions than matter in general.
Li Yan🇨🇦
The success of hydrodynamics in high energy heavy-ion collisions leads to a flow paradigm, to understand the observed features of harmonic flow in terms of the medium collective expansion regarding initial state geometrical properties. In this review, we present some essential ingredients in the flow paradigm, including the hydrodynamic modeling, the characterization of initial state geometry and the medium response relations. The extension of the flow paradigm to small colliding systems is also discussed.
Mei-Yu Wang🇺🇸 · John F. Cherry🇺🇸 · Shunsaku Horiuchi🇺🇸 · Louis E. Strigari🇺🇸
We examine the bounds on resonantly-produced sterile neutrino dark matter from phase-space densities of Milky Way dwarf spheroidal galaxies (dSphs). The bounds result from a derivation of the dark matter coarse-grained phase-space density from the stellar kinematics, which allows us to explore bounds from some of the most compact dSphs without suffering the resolution limitation from N-body simulations that conventional methods have. We find that the strongest constraints come from very compact dSphs, such as Draco II and Segue 1. We additionally forecast the constraining power of a few dSph candidates that do not yet have associated stellar kinematic data, and show that they can improve the bounds if they are confirmed to be highly dark matter dominated systems. Our results demonstrate that compact dSphs provide important constraints on sterile neutrino dark matter that are comparable to other methods using as Milky Way satellite counts. In particular, if more compact systems are discovered from current or future surveys such as LSST or HSC, it should be possible to test models that explain the 3.5 keV X-ray line signal with a 7.1 keV sterile neutrino particle decay.
We perform hybrid Monte Carlo simulation of lattice QCD with optimal domain-wall quarks on the lattice with lattice spacing fm, and generate a gauge ensemble with physical and quarks, and pion mass MeV. Using 2-quark (meson) and 3-quark (baryon) interpolating operators, the mass spectra of the lowest-lying states containing and quarks ( and ) are extracted \cite{Chen:2017kxr}, which turn out in good agreement with the high energy experimental values, together with the predictions of the charmed baryons which have not been observed in experiments. For the five new narrow states observed by the LHCb Collaboration \cite{Aaij:2017nav}, the lowest-lying agrees with our predicted mass MeV of the lowest-lying with . This implies that the of is .
Alexandru Dima🇮🇹 · Filippo Vernizzi🇫🇷
Screening mechanisms are essential features of dark energy models mediating a fifth force on large scales. We study the regime of strong scalar field nonlinearities, known as Vainshtein screening, in the most general scalar-tensor theories propagating a single scalar degree of freedom. We first develop an effective approach to parameterize cosmological perturbations beyond linear order for these theories. In the quasi-static limit, the fully nonlinear effective Lagrangian contains six independent terms, one of which starts at cubic order in perturbations. We compute the two gravitational potentials around a spherical body. Outside and near the body, screening reproduces standard gravity, with a modified gravitational coupling. Inside the body, the two potentials are different and depend on the density profile, signalling the breaking of the Vainshtein screening. We provide the most general expressions for these modifications, revising and extending previous results. We apply our findings to show that the combination of the GW170817 event, the Hulse-Taylor pulsar and stellar structure physics, constrain the parameters of these general theories at the level of , and of GLPV theories at the level of .
In this work, we study the key role of generic Effective Field Theory (EFT) framework to quantify the correlation functions in a quasi de Sitter background for an arbitrary initial choice of the quantum vacuum state. We perform the computation in unitary gauge, in which we apply the Stckelberg trick in lowest dimensional EFT operators which are broken under time diffeomorphism. In particular, using this non-linear realization of broken time diffeomorphism and truncating the action by considering the contribution from two derivative terms in the metric, we compute the two-point and three-point correlations from scalar perturbations and two-point correlation from tensor perturbations to quantify the quantum fluctuations observed in the Cosmic Microwave Background (CMB) map. We also use equilateral limit and squeezed limit configurations for the scalar three-point correlations in Fourier space. To give future predictions from EFT setup and to check the consistency of our derived results for correlations, we use the results obtained from all classes of the canonical single-field and general single-field model. This analysis helps us to fix the coefficients of the relevant operators in EFT in terms of the slow-roll parameters and effective sound speed. Finally, using CMB observations from Planck we constrain all these coefficients of EFT operators for the single-field slow-roll inflationary paradigm.
Akshay Ghalsasi🇺🇸 · Matthew McQuinn🇺🇸
A component of the dark matter could consist of two darkly charged particles with a large mass ratio and a massless force carrier. This `atomic' dark sector could behave much like the baryonic sector, cooling and fragmenting down to stellar-mass or smaller scales. Past studies have shown that cosmic microwave background and large-scale structure constraints rule out of the dark matter to behave in this manner. However, we show that, even with percent level mass fractions, a dark atomic sector could affect some extragalactic and galactic observables. We track the cooling and merger history of an atomic dark component for much of the interesting parameter space. Unlike the baryons, where stellar feedback (driven by nuclear physics) delays the formation and growth of galaxies, cooling dark atomic gas typically results in disks forming earlier, leaving more time for their destruction via mergers. Rather than disks in Milky Way sized halos, we find the end product is typically spheroidal structures on galactic scales or dark atom fragments distributed on halo scales. This result contrasts with previous studies, which had assumed that the dark atoms would result in dark disks. Furthermore the dark atoms condense into dense clumps, analogous to how the baryons fragment on solar-mass scales. We estimate the size of these dark clumps, and use these estimates to show that viable atomic dark matter parameter space is ruled out by stellar microlensing, by the half-light radii of ultra-faint dwarf galaxies, and by Milky Way mass-to-light inferences.
We argue that quaternions form a natural language for the description of quantum-mechanical wavefunctions with spin. We use the quaternionic spinor formalism which is in one-to-one correspondence with the usual spinor language. No unphysical degrees of freedom are admitted, in contrast to the majority of literature on quaternions. In this paper we first build a Dirac Lagrangian in the quaternionic form, derive the Dirac equation and take the non-relativistic limit to find the Schrödinger's equation. We show that the quaternionic formalism is a natural choice to start with, while in the transition to the non-interacting non-relativistic limit the quaternionic description effectively reduces to the regular complex wavefunction language. We provide an easy to use grammar for switching between the ordinary spinor language and the description in terms of quaternions. As an illustration of the broader range of the formalism, we also derive the Maxwell's equation from the quaternionic Lagrangian of Quantum Electrodynamics. In order to derive the equations of motion, we develop the variational calculus appropriate for this formalism.
We present a general approach for modelling the small-scale suppression in the linear matter power spectrum induced by the presence of non-cold dark matter. We show that the new parametrisation accurately describes a large variety of non-thermal scenarios, removing the need to individually test each of them. We discuss the first astrophysical constraints on its free parameters and we outline the next steps for pursuing a full statistical data analysis.
Stefano Bolognesi🇮🇹 · Kenichi Konishi🇮🇹 · Mikhail Shifman🇺🇸
We consider Yang-Mills theory with massless chiral fermions in a complex representation of the gauge group. The main emphasis is on the so-called hybrid psi-chi-eta model. The possible patterns of realization of the continuous chiral flavor symmetry are discussed. We argue that the chiral symmetry is broken in conjunction with a dynamical Higgsing of the gauge group (complete or partial) by bi-fermion condensates. As a result a color-flavor locked symmetry is preserved. The 't Hooft anomaly matching proceeds via saturation of triangles by massless composite fermions or, in a mixed mode, i.e., also by the "weakly" coupled fermions associated with dynamical Abelianization, supplemented by a number of Nambu-Goldstone mesons. Gauge-singlet condensates are of the multifermion type and, though it cannot be excluded, the chiral symmetry realization via such gauge invariant condensates is more contrived (requires a number of four-fermion condensates simultaneously and, even so, problems remain), and less plausible. We conclude that in the model at hand, chiral flavor symmetry implies dynamical Higgsing by bifermion condensates.
Lucas F. Secco🇺🇸 · Amanda Farah🇺🇸 · Bhuvnesh Jain🇺🇸 · Susmita Adhikari🇺🇸 · Arka Banerjee🇺🇸 · Neal Dalal🇺🇸
Self-Interacting Dark Matter (SIDM) has long been proposed as a solution to small scale problems posed by standard Cold Dark Matter (CDM). We use numerical simulations to study the effect of dark matter interactions on the morphology of disk galaxies falling into galaxy clusters. The effective drag force on dark matter leads to offsets of the stellar disk with respect to the surrounding halo, causing distortions in the disk. For anisotropic scattering cross-sections of 0.5 and 1.0, we show that potentially observable warps, asymmetries, and thickening of the disk occur in simulations. We discuss observational tests of SIDM with galaxy surveys and more realistic simulations needed to obtain detailed predictions.
Andrea Addazi🇨🇳 · Pisin Chen🇹🇼 · Antonino Marciano🇨🇳
We discuss how inflation can emerge from a four-fermion interaction induced by torsion. Inflation can arise from coupling torsion to Standard Model fermions, without any need of introducing new scalar particles beyond the Standard Model. Within this picture, the inflaton field can be a composite field of the SM-particles and arises from a Nambu-Jona-Lasinio mechanism in curved space-time, non-minimally coupled with the Ricci scalar. The model we specify predicts small value of the r-parameter, namely , which nonetheless would be detectable by the next generation of experiments, including BICEP 3 and the AliCPT projects.
Tommi Markkanen🇬🇧 · Tommi Tenkanen🇬🇧 · Ville Vaskonen🇪🇪 · Hardi Veermäe🇪🇪
We study models of quartic inflation where the inflaton field is coupled non-minimally to gravity, , and perform a study of quantum corrections in curved space-time at one-loop level. We specifically focus on comparing results between the metric and Palatini theories of gravity. Transformation from the Jordan to the Einstein frame gives different results for the two formulations and by using an effective field theory expansion we derive the appropriate -functions and the renormalisation group improved effective potentials in curved space for both cases in the Einstein frame. In particular, we show that in both formalisms the Einstein frame depends on the order of perturbation theory but that the flatness of the potential is unaltered by quantum corrections.
* 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.