2,501 research outputs found
Two-loop Master Integrals with the Simplified Differential Equations approach
We calculate the complete set of two-loop Master Integrals with two off
mass-shell legs with massless internal propagators, that contribute to
amplitudes of diboson production at the LHC. This is done with the
Simplified Differential Equations approach to Master Integrals, which was
recently proposed by one of the authors.Comment: 4 figures, 6 ancillary files. Version as published in JHE
The Pentabox Master Integrals with the Simplified Differential Equations approach
We present the calculation of massless two-loop Master Integrals relevant to
five-point amplitudes with one off-shell external leg and derive the complete
set of planar Master Integrals with five on-mass-shell legs, that contribute to
many amplitudes of interest at the LHC, as for instance three jet
production, jets etc., based on the Simplified Differential
Equations approach.Comment: Revised version accepted for publication in JHEP. Ancillary files
with results can be downloaded from
https://www.dropbox.com/s/90iiqfcazrhwtso/results.tgz?dl=
Cosmogenic neutrino fluxes under the effect of active-sterile secret interactions
Ultra High Energy cosmogenic neutrinos may represent a unique opportunity to
unveil possible new physics interactions once restricted to the neutrino sector
only. In the present paper we study the observable effects of a secret
active-sterile interactions, mediated by a pseudoscalar, on the expected flux
of cosmogenic neutrinos. The results show that for masses of sterile neutrinos
and pseudoscalars of hundreds MeV, necessary to evade cosmological,
astrophysical and elementary particle constraints, the presence of such new
interactions can significantly change the energy spectrum of cosmogenic
neutrinos at Earth in the energy range from PeV to ZeV. Interestingly, the
distortion of the spectrum results to be detectable at GRAND apparatus if the
scalar mediator mass is around 250 MeV and the UHECRs are dominated by the
proton component. Larger mediator masses or a chemical composition of UHECRs
dominated by heavier nuclei would require much larger cosmic rays apparatus
which might be available in future.Comment: 10 pages, 3 figure
A new approach to analysing HST spatial scans: the transmission spectrum of HD 209458 b
The Wide Field Camera 3 (WFC3) on Hubble Space Telescope (HST) is currently
one of the most widely used instruments for observing exoplanetary atmospheres,
especially with the use of the spatial scanning technique. An increasing number
of exoplanets have been studied using this technique as it enables the
observation of bright targets without saturating the sensitive detectors. In
this work we present a new pipeline for analyzing the data obtained with the
spatial scanning technique, starting from the raw data provided by the
instrument. In addition to commonly used correction techniques, we take into
account the geometric distortions of the instrument, whose impact may become
important when combined to the scanning process. Our approach can improve the
photometric precision for existing data and also push further the limits of the
spatial scanning technique, as it allows the analysis of even longer spatial
scans. As an application of our method and pipeline, we present the results
from a reanalysis of the spatially scanned transit spectrum of HD 209458 b. We
calculate the transit depth per wavelength channel with an average relative
uncertainty of 40 ppm. We interpret the final spectrum with T-Rex, our fully
Bayesian spectral retrieval code, which confirms the presence of water vapor
and clouds in the atmosphere of HD 209458 b. The narrow wavelength range limits
our ability to disentangle the degeneracies between the fitted atmospheric
parameters. Additional data over a broader spectral range are needed to address
this issue.Comment: 13 pages, 15 figures, 7 tables, Accepted for publication in Ap
A Principal Component Analysis-based method to analyse high-resolution spectroscopic data
High-Resolution Spectroscopy (HRS) has been used to study the composition and
dynamics of exoplanetary atmospheres. In particular, the spectrometer CRIRES
installed on the ESO-VLT has been used to record high-resolution spectra in the
Near-IR of gaseous exoplanets. Here we present a new automatic pipeline to
analyze CRIRES data-sets. Said pipeline is based on a novel use of Principal
Component Analysis (PCA) and Cross-Correlation Function (CCF). The exoplanetary
atmosphere is modeled with the -REx code using opacities at high
temperature from the ExoMol project. In this work, we tested our analysis tools
on the detection of CO and HO in the atmospheres of the hot-Jupiters
HD209458b and HD189733b. The results of our pipeline are in agreement with
previous results in the literature and other techniques.Comment: 14 pages, 12 figures, 2 tables, published in Ap
Quantum Topological Invariants, Gravitational Instantons and the Topological Embedding
Certain topological invariants of the moduli space of gravitational
instantons are defined and studied. Several amplitudes of two and four
dimensional topological gravity are computed. A notion of puncture in four
dimensions, that is particularly meaningful in the class of Weyl instantons, is
introduced. The topological embedding, a theoretical framework for constructing
physical amplitudes that are well-defined order by order in perturbation theory
around instantons, is explicitly applied to the computation of the correlation
functions of Dirac fermions in a punctured gravitational background, as well as
to the most general QED and QCD amplitude. Various alternatives are worked out,
discussed and compared. The quantum background affects the propagation by
generating a certain effective ``quantum'' metric. The topological embedding
could represent a new chapter of quantum field theory.Comment: LaTeX, 18 pages, no figur
Slow and fast collective neutrino oscillations: Invariants and reciprocity
The flavor evolution of a neutrino gas can show ''slow'' or ''fast''
collective motion. In terms of the usual Bloch vectors to describe the
mean-field density matrices of a homogeneous neutrino gas, the slow two-flavor
equations of motion (EOMs) are
,
where , , is a unit vector in the mass direction in
flavor space, and . For an
axisymmetric angle distribution, the fast EOMs are
, where
is the Bloch vector for lepton number, is the
velocity along the symmetry axis, , and
. We discuss similarities and differences
between these generic cases. Both systems can have pendulum-like instabilities
(soliton solutions), both have similar Gaudin invariants, and both are
integrable in the classical and quantum case. Describing fast oscillations in a
frame comoving with (which itself may execute pendulum-like
motions) leads to transformed EOMs that are equivalent to an abstract slow
system. These conclusions carry over to three flavors.Comment: 16 pages; typo below Eq. (5) and in Eq. (47) correcte
Bump-hunting in the diffuse flux of high-energy cosmic neutrinos
The origin of the bulk of the high-energy astrophysical neutrinos seen by
IceCube, with TeV--PeV energies, is unknown. If they are made in photohadronic,
i.e., proton-photon, interactions in astrophysical sources, this may manifest
as a bump-like feature in their diffuse flux, centered around a characteristic
energy. We search for evidence of this feature, allowing for variety in its
shape and size, in 7.5 years of High-Energy Starting Events (HESE) collected by
the IceCube neutrino telescope, and make forecasts using larger data samples
from upcoming neutrino telescopes. Present-day data reveals no evidence of
bump-like features, which allows us to constrain candidate populations of
photohadronic neutrino sources. Near-future forecasts show promising potential
for stringent constraints or decisive discovery of bump-like features. Our
results provide new insight into the origins of high-energy astrophysical
neutrinos, complementing those from point-source searches.Comment: 29 pages, 13 figure
- …