Letteratura scientifica selezionata sul tema "LiteBIRD"

We present LiteBIRD, a satellite project dedicated for the detection of the CMB B-mode polarization. The purpose of LiteBIRD is to measure the tensor-to-scalar ratio [Formula: see text] with a precision of [Formula: see text] to test large-single-field slow-roll inflation models by scanning all the sky area for three years at the sun-earth L2 with the sensitivity of 3.2[Formula: see text]K⋅arcmin. We report an overview and the status of the project, including the ongoing detector and systematic studies.

Abstract We present detailed forecasts for the constraints on the characteristics of primordial magnetic fields (PMFs) generated prior to recombination that will be obtained with the LiteBIRD satellite. The constraints are driven by some of the main physical effects of PMFs on the CMB anisotropies: the gravitational effects of magnetically-induced perturbations; the effects on the thermal and ionization history of the Universe; the Faraday rotation imprint on the CMB polarization spectra; and the non-Gaussianities induced in polarization anisotropies. LiteBIRD represents a sensitive probe for PMFs. We explore different levels of complexity, for LiteBIRD data and PMF configurations, accounting for possible degeneracies with primordial gravitational waves from inflation. By exploiting all the physical effects, LiteBIRD will be able to improve the current limit on PMFs at intermediate and large scales coming from Planck. In particular, thanks to its accurate B-mode polarization measurement, LiteBIRD will improve the constraints on infrared configurations for the gravitational effect, giving B n B=-2.9 1 Mpc< 0.8 nG at 95% C.L., potentially opening the possibility to detect nanogauss fields with high significance. We also observe a significant improvement in the limits when marginalized over the spectral index, B n Bmarg 1 Mpc< 2.2 nG at 95 % C.L. From the thermal history effect, which relies mainly on E-mode polarization data, we obtain a significant improvement for all PMF configurations, with the marginalized case, √⟨B 2⟩marg<0.50 nG at 95 % C.L. Faraday rotation constraints will take advantage of the wide frequency coverage of LiteBIRD and the high sensitivity in B modes, improving the limits by orders of magnitude with respect to current results, B n B=-2.9 1 Mpc < 3.2 nG at 95 % C.L. Finally, non-Gaussianities of the B-mode polarization can probe PMFs at the level of 1 nG, again significantly improving the current bounds from Planck. Altogether our forecasts represent a broad collection of complementary probes based on widely tested methodologies, providing conservative limits on PMF characteristics that will be achieved with the LiteBIRD satellite.

Abstract We estimate the efficiency of mitigating the lensing B-mode polarization, the so-called delensing, for the LiteBIRD experiment with multiple external data sets of lensing-mass tracers. The current best bound on the tensor-to-scalar ratio, r, is limited by lensing rather than Galactic foregrounds. Delensing will be a critical step to improve sensitivity to r as measurements of r become more and more limited by lensing. In this paper, we extend the analysis of the recent LiteBIRD forecast paper to include multiple mass tracers, i.e., the CMB lensing maps from LiteBIRD and CMB-S4-like experiment, cosmic infrared background, and galaxy number density from Euclid- and LSST-like survey. We find that multi-tracer delensing will further improve the constraint on r by about 20%. In LiteBIRD, the residual Galactic foregrounds also significantly contribute to uncertainties of the B-modes, and delensing becomes more important if the residual foregrounds are further reduced by an improved component separation method.

Abstract We study the possibility of using the LiteBIRD satellite B-mode survey to constrain models of inflation producing specific features in CMB angular power spectra. We explore a particular model example, i.e. spectator axion-SU(2) gauge field inflation. This model can source parity-violating gravitational waves from the amplification of gauge field fluctuations driven by a pseudoscalar “axionlike” field, rolling for a few e-folds during inflation. The sourced gravitational waves can exceed the vacuum contribution at reionization bump scales by about an order of magnitude and can be comparable to the vacuum contribution at recombination bump scales. We argue that a satellite mission with full sky coverage and access to the reionization bump scales is necessary to understand the origin of the primordial gravitational wave signal and distinguish among two production mechanisms: quantum vacuum fluctuations of spacetime and matter sources during inflation. We present the expected constraints on model parameters from LiteBIRD satellite simulations, which complement and expand previous studies in the literature. We find that LiteBIRD will be able to exclude with high significance standard single-field slow-roll models, such as the Starobinsky model, if the true model is the axion-SU(2) model with a feature at CMB scales. We further investigate the possibility of using the parity-violating signature of the model, such as the TB and EB angular power spectra, to disentangle it from the standard single-field slow-roll scenario. We find that most of the discriminating power of LiteBIRD will reside in BB angular power spectra rather than in TB and EB correlations.

Abstract We investigate expected constraints on the primordial tensor power spectrum from the future cosmic microwave background polarization experiment LiteBIRD as a test of multi-field inflation, where we specifically consider spectator models as representative examples. We argue that the measurements of the tensor-to-scalar ratio and the tensor spectral index, in combination with the constraints on the scalar spectral index from the Planck observation, are useful in testing multi-field inflation models. We also discuss implications for multi-field inflationary model building.

Abstract We explore the capability of measuring lensing signals in LiteBIRD full-sky polarization maps. With a 30 arcmin beam width and an impressively low polarization noise of 2.16 μK-arcmin, LiteBIRD will be able to measure the full-sky polarization of the cosmic microwave background (CMB) very precisely. This unique sensitivity also enables the reconstruction of a nearly full-sky lensing map using only polarization data, even considering its limited capability to capture small-scale CMB anisotropies. In this paper, we investigate the ability to construct a full-sky lensing measurement in the presence of Galactic foregrounds, finding that several possible biases from Galactic foregrounds should be negligible after component separation by harmonic-space internal linear combination. We find that the signal-to-noise ratio of the lensing is approximately 40 using only polarization data measured over 80% of the sky. This achievement is comparable to Planck's recent lensing measurement with both temperature and polarization and represents a four-fold improvement over Planck's polarization-only lensing measurement. The LiteBIRD lensing map will complement the Planck lensing map and provide several opportunities for cross-correlation science, especially in the northern hemisphere.

ABSTRACT Multifield inflation models and non-Bunch–Davies vacuum initial conditions both predict sizeable non-Gaussian primordial perturbations and anisotropic μ-type spectral distortions of the cosmic microwave background (CMB) blackbody. While CMB anisotropies allow us to probe non-Gaussianity at wavenumbers $k\simeq 0.05\, {\rm Mpc^{-1}}$, μ-distortion anisotropies are related to non-Gaussianity of primordial perturbation modes with much larger wavenumbers, $k\simeq 740\, {\rm Mpc^{-1}}$. Through cross-correlations between CMB and μ-distortion anisotropies, one can therefore shed light on the aforementioned inflation models. We investigate the ability of a future CMB satellite imager like LiteBIRD to measure μT and μE cross-power spectra between anisotropic μ-distortions and CMB temperature and E-mode polarization anisotropies in the presence of foregrounds, and derive LiteBIRD forecasts on ${f_{\rm NL}^\mu (k\simeq 740\, {\rm Mpc^{-1}})}$. We show that μE cross-correlations with CMB polarization provide more constraining power on $f_{\rm NL}^\mu$ than μT cross-correlations in the presence of foregrounds, and the joint combination of μT and μE observables adds further leverage to the detection of small-scale primordial non-Gaussianity. For multifield inflation, we find that LiteBIRD would detect ${f_{\rm NL}^\mu }=4500$ at 5σ significance after foreground removal, and achieve a minimum error of ${\sigma (f_{\rm NL}^\mu =0) \simeq 800}$ at 68 per cent CL by combining CMB temperature and polarization. Due to the huge dynamic range of wavenumbers between CMB and μ-distortion anisotropies, such large $f^\mu _{\rm NL}$ values would still be consistent with current CMB constraints in the case of very mild scale dependence of primordial non-Gaussianity. Anisotropic spectral distortions thus provide a new path, complementary to CMB B-modes, to probe inflation with LiteBIRD.

Cette thèse est consacrée à l'étude de l'inflation cosmologique, une phase d'expansion accélérée de l'univers primordial qui reste, à ce jour, spéculative. L'observable central de ce travail est le fond diffus cosmologique (CMB), la plus ancienne lumière encore visible aujourd'hui, dont l'étude statistique permet d'inférer des informations cruciales sur la cosmologie. Nous entamons cette étude sur un volet expérimental, avec la préparation du satellite LiteBIRD. Au milieu de la prochaine décennie, ce dernier mesurera la polarisation du CMB à grande échelle avec une précision inédite, permettant ainsi de contraindre la présence d'ondes gravitationnelles primordiales générées durant l'inflation. Pour obtenir une telle sensibilité et éviter tout potentiel effet systématique, une maîtrise parfaite de l'instrument et de l'analyse de donnée est indispensable. Dans ce cadre, nous présentons notre première implémentation du modèle de l'instrument dans une base de données dédiée, ainsi que les outils nécessaires à la production de certains paramètres instrumentaux. Nous avons notamment produit les quaternions qui encodent les informations de pointage et d'orientation de chaque détecteur, et implémenté les faisceaux, les bandes passantes, le modèle de bruit de l'instrument et la spécification du système de lecture.De plus, nous avons mis en place un pipeline complet pour analyser les cartes de polarisation que LiteBIRD fournira. Nous avons testé ce pipeline sur des simulations de l'instrument présentant diverses complexités. L'analyse se décompose en trois étapes. La première étape est la séparation des composantes afin de nettoyer les cartes des avant-plans. Nous avons optimisé une méthode agnostique qui ne nécessite pas de connaissances préalables sur les propriétés des avant-plans. La deuxième étape consiste à estimer les spectres à partir des cartes nettoyées et masquées, pour laquelle nous avons implémenté et testé diverses méthodes non biaisées et quasi optimales. Enfin, nous avons évalué la performance de plusieurs fonctions de vraisemblance pour inférer les paramètres cosmologiques. En plus de contraindre la présence d'ondes gravitationnelles primordiales, cette analyse permettra d'affiner notre compréhension de l'époque de la réionisation, liée au puissant rayonnement émis par la première génération d'étoiles.La troisième partie de cette thèse se concentre sur une étude phénoménologique de l'inflation, en particulier sur un modèle d'inflation qui s'inscrit dans un cadre de physique des particules : le modèle supersymétrique minimal. En collaboration avec des cosmologistes, théoriciens et physiciens des particules, nous avons montré que les données existantes du satellite Planck sont suffisamment précises pour que les erreurs systématiques dans les prédictions du modèle dominent le budget d'erreur dans un exercice d'inférence. Ces erreurs systématiques théoriques sont dues à la non-inclusion des corrections radiatives et à une compréhension imparfaite de la fin de l'inflation. Nous avons donc incorporé les corrections nécessaires et identifié des points dans l'espace des paramètres qui satisfont à la fois les contraintes observationnelles de la physique des particules (comme la masse du Higgs et les recherches directes de SUSY au LHC) et de la cosmologie (comme la fraction de matière noire dans l'univers et les propriétés des perturbations observées par Planck). Ce travail démontre la possibilité d'unifier la description de la physique des particules et de la cosmologie dans un seul modèle cohérent, ouvrant ainsi la voie à une exploration complète de ce cadre
This thesis is devoted to the study of cosmological inflation, a phase of accelerated expansion in the early universe that remains speculative to this day. The central observable for this study is the cosmic microwave background (CMB), the oldest light still visible today, whose statistical study enables cosmological inference.We first approach the study from an experimental perspective, focusing on the preparation of the LiteBIRD satellite. Set to launch in the middle of the next decade, LiteBIRD will measure the large-scale polarisation of the CMB with unprecedented precision, allowing for stringent constraints on the presence of primordial gravitational waves generated during inflation. To achieve the required sensitivity and minimise systematic effects, we must ensure precise control of both the instrument and data analysis. As part of this effort, we have implemented the instrument model in a dedicated database, along with the tools necessary to produce key instrumental parameters. This includes generating quaternions that encode each detector's pointing and orientation information, as well as implementing beam models, bandpasses, the noise model, and the specification of the readout system. Furthermore, we have developed a complete pipeline for analysing the polarisation maps that LiteBIRD will deliver. We have tested this pipeline on realistic simulations of the instrument with various levels of complexity. The analysis pipeline consists of three stages. The first stage involves component separation to remove foreground contamination from the maps. We optimise an agnostic method that does not rely on prior knowledge of the foreground properties. The second stage focuses on estimating power spectra from the cleaned and masked maps. To this end, we have implemented and tested various unbiased and quasi-optimal methods. Finally, we assess the performance of different likelihood functions to infer cosmological parameters. In addition to constraining primordial gravitational waves, this analysis will enhance our understanding of the epoch of reionisation, which is due to the intense radiation from the first generation of stars.In the third section of the thesis, we focus on a phenomenological study of inflation, particularly on a model of inflation situated within a particle physics framework: the minimal supersymmetric model. In collaboration with cosmologists, theorists, and particle physicists, we demonstrate that the existing data from the Planck satellite are already precise enough that systematic errors in the model's predictions dominate the error budget in an inference context. These theoretical systematics arise from the non-inclusion of radiative corrections and an incomplete understanding of the end of inflation. We have included the necessary corrections and identified points in parameter space that satisfy both the observational constraints of particle physics (such as the Higgs mass and direct SUSY searches at the LHC) and cosmology (including the dark matter fraction in the universe and the properties of scalar perturbations as observed by Planck). Our work demonstrates the feasibility of unifying particle physics and cosmology descriptions within a single self-consistent model, paving the way for a comprehensive exploration of the inflationary MSSM or other high-energy physics models

The most ambitious challenge in Experimental Cosmology today is the preci- sion measurement of the polarized signal of the Cosmic Microwave Background (CMB). CMB was discovered in 1967 by Penzias and Wilson. It is a snapshot of the primordial universe and represents an essential source of information about all epochs of the universe. This experimental thesis concerns the study of polarization measurement techniques and the development of a new superconducting magnetic bearing to continuously rotate a cryogenic half-wave plate (HWP). The chapter 1 of this thesis focuses on the fundamentals of the cold dark matter model (ΛCDM) which is a parametrization of the Big Bang cosmo- logical model. It describes the constituents and the evolution of the universe. The ΛCDM model can be extended by adding cosmological inflation, a short period of exponential expansion in the very early universe. Inflation’s basic predictions regarding the universe large-scale geometry and structure have been borne out by cosmological measurements to date. Inflation makes an additional prediction as the existence of a background of gravitational waves, or tensor mode perturbations. At the recombination epoch, the inflationary gravitational waves (IGW) contribute to the anisotropy of the CMB in both total intensity and linear polarization, discussed deeply in the second part of the first chapter. The amplitude of tensors is conventionally parameterized by r, the tensor-to-scalar ratio at a fiducial scale, and its trace in the CMB polarization is a direct measure of the energy scale of inflation. Theoretical predictions of the value of r cover a very wide range. Conversely, a measurement of r can discriminate between models of inflation. The current upper limit is r < 0.06 at 95% confidence. The chapter 2 presents the Large-Scale Polarization Explorer (LSPE), an experiment composed of two instruments (the ground-based telescope STRIP and the balloon-borne counterpart SWIPE) which aims to measure the polarization of the CMB at large angular scale with a goal of r = 0.01. This thesis is mainly focused on the development of few important subsystems of SWIPE balloon. The detection of this tiny signal requires a very large array of polarization-sensitive detectors coupled to an imaging optical system, to obtain a wide field of view, thus maximizing the mapping speed. SWIPE will focus the incoming radiation on two large curved focal planes (at a temperature of 0.3 K) hosting 326 multi-mode pixels with Transition Edge Sensor (TES) thermistors, divided in the 3 frequency bands: 145GHz (30% bandwidth), 210GHz (20% bandwidth) and 240GHz (10% bandwidth). Chapter 3 describes the tests performed on the multi-mode pixel assembly. A custom cryogenic neoprene absorber was developed to reduce the background on the detector at a level similar to the one expected in flight, allowing to measure the main beam of the pixel assembly. The measured FWHM of the pixel assembly is 21°, slightly narrower than the expected one (24°), due to vignetting produced by the filters stack. Unfortunately this CMB polarization signal is well below the level of un- polarized foregrounds. This makes systematic errors due to temperature-to-polarization leakage particularly detrimental. Polarization modulators offer a solution to separate the polarized signal of interest from these unpolarized foregrounds. Many polarization modulation schemes exist, and a rapidly-rotating half-wave plate (HWP) is one of the most promising. The working principle of a polarimeter is discussed in chapter 4, where there is also an analysis of the main systematics introduced by a rotating HWP, particularly focused on HWP spurious signals and HWP wobbling. Chapter 5 is focused on the SWIPE polarization modulator unit which op- erates at 1.6 K to reduce the background on the detector produced by the HWP emission. On the other hand rotating an object at cryogenic temperature is not trivial, in particular because the dissipation becomes an issue. The technology adopted is based on a superconducting magnetic bearing (SMB) which can significantly reduce the friction. After introducing the basics of superconductivity, the baseline design is described. A large number of tests were performed on a room temperature mockup to optimize the motor configuration while room and cryogenic temperature tests were performed on the clamp mechanism (necessary to hold the bearing at room temperature and release it below the superconductive transition). The total heat load expected from the polarization modulator unit is < 25 mW. This value has to be confirmed during cryogenic test of the whole system which is not performed yet due to delays in the cryostat fabrication. The expected heat load from the polarization modulator represents less than 15% of the total heat load on the superfluid He reservoir, and is fully compatible with the operation of the instrument. Finally, chapter 6 presents LiteBIRD mission and the development of both polarization modulators of the medium and high frequency instruments. LiteBIRD is the next generation spacecraft [5], expected to be operative in ∼ 10 years, and will map CMB polarization 20 times deeper than Planck, with a total error of δr < 0.001, conservatively assuming equal contributions of statis- tical error, systematic error, and margin. The use of 3 continuously rotating HWPs (for the 3 telescopes of LiteBIRD) mitigates important systematic errors already observed in Planck data. Their development is more challenging than for SWIPE due to the spacecraft requirements and the Technology Readiness Level (TRL) required. A scaled baseline design and an optimized configuration are discussed. We find that the optimized one will meet the power budget with a 100% of margin.