39 research outputs found
Electron-neutrino scattering off nuclei from two different theoretical perspectives
We analyze charged-current electron-neutrino cross sections on Carbon. We
consider two different theoretical approaches, on one hand the Continuum Random
Phase Approximation (CRPA) which allows a description of giant resonances and
quasielastic excitations, on the other hand the RPA-based calculations which
are able to describe multinucleon emission and coherent and incoherent pion
production as well as quasielastic excitations. We compare the two approaches
in the genuine quasielastic channel, and find a satisfactory agreement between
them at large energies while at low energies the collective giant resonances
show up only in the CRPA approach. We also compare electron-neutrino cross
sections with the corresponding muon-neutrino ones in order to investigate the
impact of the different charged-lepton masses. Finally, restricting to the
RPA-based approach we compare the sum of quasielastic, multinucleon emission,
coherent and incoherent one-pion production cross sections (folded with the
electron-neutrino T2K flux) with the charged-current inclusive
electron-neutrino differential cross sections on Carbon measured by T2K. We
find a good agreement with the data. The multinucleon component is needed in
order to reproduce the T2K electron-neutrino inclusive cross sections
Quasielastic electron- and neutrino-nucleus scattering in a continuum random phase approximation approach
We present a continuum random phase approximation approach to study electron-
and neutrino-nucleus scattering cross sections, in the kinematic region where
quasielastic scattering is the dominant process. We show the validity of the
formalism by confronting inclusive () cross sections with the available
data. We calculate flux-folded cross sections for charged-current quasielastic
antineutrino scattering off C and compare them with the MiniBooNE
cross-section measurements. We pay special emphasis to the contribution of
low-energy nuclear excitations in the signal of accelerator-based
neutrino-oscillation experiments.Comment: 5 pages, 5 figures. Contribution to the proceedings of the 16th
International Workshop on Neutrino Factories and Future Neutrino Beam
Facilities (NUFACT-2014
Impact of low-energy nuclear excitations on neutrino-nucleus scattering at MiniBooNE and T2K kinematics
[Background] Meticulous modeling of neutrino-nucleus interactions is
essential to achieve the unprecedented precision goals of present and future
accelerator-based neutrino-oscillation experiments. [Purpose] Confront our
calculations of charged-current quasielastic cross section with the
measurements of MiniBooNE and T2K, and to quantitatively investigate the role
of nuclear-structure effects, in particular, low-energy nuclear excitations in
forward muon scattering. [Method] The model takes the mean-field (MF) approach
as the starting point, and solves Hartree-Fock (HF) equations using a Skyrme
(SkE2) nucleon-nucleon interaction. Long-range nuclear correlations are taken
into account by means of the continuum random-phase approximation (CRPA)
framework. [Results] We present our calculations on flux-folded double
differential, and flux-unfolded total cross sections off C and compare
them with MiniBooNE and (off-axis) T2K measurements. We discuss the importance
of low-energy nuclear excitations for the forward bins. [Conclusions] The CRPA
predictions describe the gross features of the measured cross sections. They
underpredict the data (more in the neutrino than in the antineutrino case)
because of the absence of processes beyond pure quasielastic scattering in our
model. At very forward muon scattering, low-energy nuclear excitations ( 50 MeV) account for nearly 50% of the flux-folded cross section.Comment: 8 pages, 9 figures. Version published in Physical Review
Impact of low-energy nuclear excitations on neutrino-nucleus scattering at MiniBooNE and T2K kinematics
Low-energy excitations and quasielastic contribution to electron-nucleus and neutrino-nucleus scattering in the continuum random-phase approximation
CONCERTO: Extracting the power spectrum of the [C II ] emission line
CONCERTO is the first experiment to perform a [CII] line intensity mapping
survey to target . Measuring the [CII] power spectrum allows us to study
the role of dusty star-forming galaxies in the star formation history during
the Reionization and post-Reionization. The main obstacle to this measurement
is the contamination by bright foregrounds. We evaluate our ability to retrieve
the [CII] signal in mock observations using the Simulated Infrared Dusty
Extragalactic Sky. We compared two methods for dealing with the dust continuum
emission from galaxies: the standard PCA and the arPLS method. For line
interlopers, the strategy relies on masking low-redshift galaxies using
external catalogues. As we do not have observations of CO or classical CO
proxies ,we relied on the COSMOS stellar mass catalogue. To measure the power
spectrum of masked data, we adapted the P of K EstimatoR and discuss its use on
LIM data. The arPLS method achieves a reduction of the continuum background to
a sub-dominant level of the [CII] at z=7 by a factor of>70. When using PCA,
this factor is only 0.7. The masking lowers the power amplitude of line
contamination down to This residual level is dominated
by faint undetected sources. For our [CII] model, this results in a detection
at z = 5.2 with a power ratio [CII]/(residual interlopers) = for a
22 % area survey loss. However, at z = 7, [C II ] / (residual interlopers). Thanks to the large area covered by SIDES-Uchuu, we show that the
power amplitude of line residuals varies by 12-15% for z=5.2-7. We present an
end-to-end simulation of the extragalactic foreground removal that we ran to
detect the [CII] at high redshift via its power spectrum. We show that dust
continuum emission are not a limiting foreground for [CII] LIM. Residual CO and
[CI] limits our ability to measure the [CII] power spectrum at z>7.Comment: 15 pages, 12 figures, to be published in Astronomy & Astrophysic
Genetic variability and the classification of hepatitis E virus
The classification of hepatitis E virus (HEV) variants is currently in transition without agreed definitions for genotypes and subtypes or for deeper taxonomic groupings into species and genera that could incorporate more recently characterized viruses assigned to the Hepeviridae family that infect birds, bats, rodents, and fish. These conflicts arise because of differences in the viruses and genomic regions compared and in the methodology used. We have reexamined published sequences and found that synonymous substitutions were saturated in comparisons between and within virus genotypes. Analysis of complete genome sequences or concatenated ORF1/ORF2 amino acid sequences indicated that HEV variants most closely related to those infecting humans can be consistently divided into six genotypes (types 1 to 4 and two additional genotypes from wild boar). Variants isolated from rabbits, closely related to genotype 3, occupy an intermediate position. No consistent criteria could be defined for the assignment of virus subtypes. Analysis of amino acid sequences from these viruses with the more divergent variants from chickens, bats, and rodents in three conserved subgenomic regions (residues 1 to 452 or 974 to 1534 of ORF1 or residues 105 to 458 of ORF2) provided consistent support for a division into 4 groups, corresponding to HEV variants infecting humans and pigs, those infecting rats and ferrets, those from bats, and those from chickens. This approach may form the basis for a future genetic classification of HEV into four species, with the more divergent HEV-like virus from fish (cutthroat trout virus) representing a second genus
CONCERTO: High-fidelity simulation of millimeter line emissions of galaxies and [CII] intensity mapping
The intensity mapping of the [CII] 158-μm line redshifted to the submillimeter window is a promising probe of the za>4 star formation and its spatial distribution into large-scale structures. To prepare the first-generation experiments (e.g., CONCERTO), we need realistic simulations of the submillimeter extragalactic sky in spectroscopy. We present a new version of the simulated infrared dusty extragalactic sky (SIDES) model including the main submillimeter lines around 1 mm (CO, [CII], [CI]). This approach successfully reproduces the observed line luminosity functions. We then use our simulation to generate CONCERTO-like cubes (125-305 GHz) and forecast the power spectra of the fluctuations caused by the various astrophysical components at those frequencies. Depending on our assumptions on the relation between the star formation rate and [CII] luminosity, and the star formation history, our predictions of the za∼6 [CII] power spectrum vary by two orders of magnitude. This highlights how uncertain the predictions are and how important future measurements will be to improve our understanding of this early epoch. SIDES can reproduce the CO shot noise recently measured at a4;100 GHz by the millimeter-wavelength intensity mapping experiment (mmIME). Finally, we compare the contribution of the different astrophysical components at various redshifts to the power spectra. The continuum is by far the brightest, by a factor of three to 100, depending on the frequency. At 300 GHz, the CO foreground power spectrum is higher than the [CII] one for our base scenario. At lower frequencies, the contrast between [CII] and extragalactic foregrounds is even worse. Masking the known galaxies from deep surveys should allow us to reduce the foregrounds to 20% of the [CII] power spectrum up to z∼ 6.5. However, this masking method will not be sufficient at higher redshifts. The code and the products of our simulation are released publicly, and can be used for both intensity mapping experiments and submillimeter continuum and line surveys
CONCERTO: Simulating the CO, [CII], and [CI] line emission of galaxies in a 117 deg2 field and the impact of field-to-field variance
In the submillimeter regime, spectral line scans and line intensity mapping (LIM) are new promising probes for the cold gas content and star formation rate of galaxies across cosmic time. However, both of these two measurements suffer from field-to-field variance. We study the effect of field-to-field variance on the predicted CO and [CII] power spectra from future LIM experiments such as CONCERTO, as well as on the line luminosity functions (LFs) and the cosmic molecular gas mass density that are currently derived from spectral line scans. We combined a 117 deg2 dark matter lightcone from the Uchuu cosmological simulation with the simulated infrared dusty extragalactic sky (SIDES) approach. The clustering of the dusty galaxies in the SIDES-Uchuu product is validated by reproducing the cosmic infrared background anisotropies measured by Herschel and Planck. We find that in order to constrain the CO LF with an uncertainty below 20%, we need survey sizes of at least 0.1 deg2. Furthermore, accounting for the field-to-field variance using only the Poisson variance can underestimate the total variance by up to 80%. The lower the luminosity is and the larger the survey size is, the higher the level of underestimate. At z < 3, the impact of field-to-field variance on the cosmic molecular gas density can be as high as 40% for the 4.6 arcmin2 field, but drops below 10% for areas larger than 0.2 deg2. However, at z > 3 the variance decreases more slowly with survey size and for example drops below 10% for 1 deg2 fields. Finally, we find that the CO and [CII] LIM power spectra can vary by up to 50% in 1 deg2 fields. This limits the accuracy of the constraints provided by the first 1 deg2 surveys. In addition the level of the shot noise power is always dominated by the sources that are just below the detection thresholds, which limits its potential for deriving number densities of faint [CII] emitters. We provide an analytical formula to estimate the field-to-field variance of current or future LIM experiments given their observed frequency and survey size. The underlying code to derive the field-to-field variance and the full SIDES-Uchuu products (catalogs, cubes, and maps) are publicly available
Modeling nuclear effects for neutrino-nucleus scattering in the Few-GeV region
Accelerator-based neutrino oscillation experiments rely on the description of neutrino interactions with bound nucleons inside atomic nuclei. Neutrino fluxes used in modern experiments (T2K, NOvA) are peaked in the 0.5–5 GeV energy region where one can identify contributions from multiple interaction channels and various nuclear effects. The neutrino-nucleus cross sections in this region are known with a precision not exceeding 20% and have to be investigated further in pursue to reduce systematic errors in oscillation measurements. The concept of Monte Carlo neutrino event generators, which provide essential cross section expectations for oscillation experiments, is examplified by NuWro, the generator developed at the University of Wroclaw. We discuss various implementations of nuclear effects on top of the factorization framework used to describe neutrino-nucleus scattering, focusing specifically on possible generator development using more sophisticated microscopic models