189 research outputs found
Gluon-induced QCD corrections to pp --> ZZ --> l anti-l l' anti-l'
A calculation of the loop-induced gluon-fusion process gg --> Z(photon)Z(photon) --> l anti-l l' anti-l' is presented, which provides an important background for Higgs boson searches in the H --> ZZ channel at the LHC. We find that the photon contribution is important for Higgs masses below the Z-pair threshold and that the gg-induced process yields a correction of about 15% relative to the NLO QCD prediction for the q anti-q-induced process when only a M(l anti-l), M(l' anti-l') > 5 GeV cut is applied
Neutrino clustering in the Milky Way and beyond
The standard cosmological model predicts the existence of a Cosmic Neutrino Background, which has not yet been observed directly. Some experiments aiming at its detection are currently under development, despite the tiny kinetic energy of the cosmological relic neutrinos, which makes this task incredibly challenging. Since massive neutrinos are attracted by the gravitational potential of our Galaxy, they can cluster locally. Neutrinos should be more abundant at the Earth position than at an average point in the Universe. This fact may enhance the expected event rate in any future experiment. Past calculations of the local neutrino clustering factor only considered a spherical distribution of matter in the Milky Way and neglected the influence of other nearby objects like the Virgo cluster, although recent N-body simulations suggest that the latter may actually be important. In this paper, we adopt a back-tracking technique, well established in the calculation of cosmic rays fluxes, to perform the first three-dimensional calculation of the number density of relic neutrinos at the Solar System, taking into account not only the matter composition of the Milky Way, but also the contribution of the Andromeda galaxy and the Virgo cluster. The effect of Virgo is indeed found to be relevant and to depend non-trivially on the value of the neutrino mass. Our results show that the local neutrino density is enhanced by 0.53% for a neutrino mass of 10 meV, 12% for 50 meV, 50% for 100 meV or 500% for 300 meV
Indication of a fast ejecta fragment in the atomic cloud interacting with the southwestern limb of SN 1006
Context. Supernova remnants interacting with molecular and atomic clouds are interesting X-ray sources for studies of broadband nonthermal emission. X-ray line emission in these systems can be produced by different processes, such as low-energy cosmic rays (LECRs) interacting with the cloud and fast ejecta fragments moving in the cloud. Aims. This paper is aimed at studying the origin of the non-thermal X-ray emission of the southwestern limb of SN 1006 beyond the main shock to determine whether the emission is due to LECRs diffusing in the cloud or to ejecta knots moving into the cloud. Methods. We analyzed the X-ray emission of the southwestern limb of SN 1006, where the remnant interacts with an atomic cloud, using three different X-ray telescopes: NuSTAR, Chandra, and XMM-Newton. We also performed a combined spectro-imaging analysis of this region. Results. Our analysis of the nonthermal X-ray emission of the southwestern limb of SN 1006 interacting with an atomic cloud has led to the detection of an extended X-ray source in the atomic cloud, approximately 2 pc upstream of the shock front. The source is characterized by a hard continuum (described by a power law with photon index Γ ∼ 1.4) and by Ne, Si, and Fe emission lines. The observed flux suggests that the origin of the X-ray emission is not associated with LECRs interacting with the cloud. On the other hand, the spectral properties of the source, together with the detection of an IR counterpart visible with Spitzer-MIPS at 24 μm, are in good agreement with the general expectations for a fast ejecta fragment moving within the atomic cloud. Conclusions. We detected X-ray and IR emission from a possible ejecta fragment, with an approximate radius of 1 × 1017 cm and approximate mass of 10−3 M at about 2 pc out of the shell of SN 1006, in the interaction region between the southwestern limb of the remnant and the atomic cloud
Cosmic ray electrons and positrons from discrete stochastic sources
The distances that galactic cosmic ray electrons and positrons can travel are
severely limited by energy losses to at most a few kiloparsec, thereby
rendering the local spectrum very sensitive to the exact distribution of
sources in our galactic neighbourhood. However, due to our ignorance of the
exact source distribution, we can only predict the spectrum stochastically. We
argue that even in the case of a large number of sources the central limit
theorem is not applicable, but that the standard deviation for the flux from a
random source is divergent due to a long power law tail of the probability
density. Instead, we compute the expectation value and characterise the scatter
around it by quantiles of the probability density using a generalised central
limit theorem in a fully analytical way. The uncertainty band is asymmetric
about the expectation value and can become quite large for TeV energies. In
particular, the predicted local spectrum is marginally consistent with the
measurements by Fermi-LAT and HESS even without imposing spectral breaks or
cut-offs at source. We conclude that this uncertainty has to be properly
accounted for when predicting electron fluxes above a few hundred GeV from
astrophysical sources.Comment: 16 pages, 8 figures; references and clarifying comment added; to
appear in JCA
Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. I: spectrum and chemical composition
In this paper we investigate the effect of stochasticity in the spatial and
temporal distribution of supernova remnants on the spectrum and chemical
composition of cosmic rays observed at Earth. The calculations are carried out
for different choices of the diffusion coefficient D(E) experienced by cosmic
rays during propagation in the Galaxy. In particular, at high energies we
assume that D(E)\sim E^{\delta}, with and being the
reference scenarios. The large scale distribution of supernova remnants in the
Galaxy is modeled following the distribution of pulsars, with and without
accounting for the spiral structure of the Galaxy. We find that the stochastic
fluctuations induced by the spatial and temporal distribution of supernovae,
together with the effect of spallation of nuclei, lead to mild but sensible
violations of the simple, leaky-box-inspired rule that the spectrum observed at
Earth is with , where
is the slope of the cosmic ray injection spectrum at the sources. Spallation of
nuclei, even with the small rates appropriate for He, may account for slight
differences in spectral slopes between different nuclei, providing a possible
explanation for the recent CREAM observations. For we find that
the slope of the proton and helium spectra are and
respectively at energies above 1 TeV (to be compared with the measured values
of and ). For the hardening of the He
spectra is not observed. We also comment on the effect of time dependence of
the escape of cosmic rays from supernova remnants, and of a possible clustering
of the sources in superbubbles. In a second paper we will discuss the
implications of these different scenarios for the anisotropy of cosmic rays.Comment: 28 pages, To appear in JCA
Sommerfeld Enhancement from Multiple Mediators
We study the Sommerfeld enhancement experienced by a scattering object that
couples to a tower of mediators. This can occur in, e.g., models of secluded
dark matter when the mediator scale is generated naturally by hidden-sector
confinement. Specializing to the case of a confining CFT, we show that
off-resonant values of the enhancement can be increased by ~ 20% for cases of
interest when (i) the (strongly-coupled) CFT admits a weakly-coupled dual
description and (ii) the conformal symmetry holds up to the Planck scale.
Larger enhancements are possible for lower UV scales due to an increase in the
coupling strength of the tower.Comment: 17p, 2 figures; v2 JHEP version (inconsequential typo fixed,
references added
Absolute electron and positron fluxes from PAMELA/Fermi and Dark Matter
We extract the positron and electron fluxes in the energy range 10 - 100 GeV
by combining the recent data from PAMELA and Fermi LAT. The {\it absolute
positron and electron} fluxes thus obtained are found to obey the power laws:
and respectively, which can be confirmed by the
upcoming data from PAMELA. The positron flux appears to indicate an excess at
energies E\gsim 50 GeV even if the uncertainty in the secondary positron flux
is added to the Galactic positron background. This leaves enough motivation for
considering new physics, such as annihilation or decay of dark matter, as the
origin of positron excess in the cosmic rays.Comment: Accepted by JCA
Benralizumab Reduces Respiratory Exacerbations and Oral Glucocorticosteroid Dose in Patients with Severe Asthma and Eosinophilic Granulomatosis with Polyangiitis
Carlo Mümmler,1 Pontus Mertsch,1 Michaela Barnikel,1 Frank Haubner,2 Ulf Schönermarck,3 Ulrich Grabmaier,4 Hendrik Schulze-Koops,5 Jürgen Behr,1 Nikolaus Kneidinger,1,6 Katrin Milger1 1Department of Medicine V, LMU University Hospital, LMU Munich, Comprehensive Pneumology Center, Member of the German Center of Lung Research (DZL), Munich, Germany; 2Department of Otorhinolaryngology, LMU University Hospital, LMU Munich, Munich, Germany; 3Division of Nephrology, Department of Medicine IV, LMU University Hospital, LMU Munich, Munich, Germany; 4Department of Medicine I, LMU University Hospital, LMU Munich, Munich, Germany; 5Division of Rheumatology and Clinical Immunology, Department of Medicine IV, LMU University Hospital, LMU Munich, Munich, Germany; 6Division of Pulmonology, Department of Internal Medicine, Medical University of Graz, Graz, AustriaCorrespondence: Katrin Milger, Department of Medicine V, LMU University Hospital, Marchioninistr, 15, LMU Munich, Munich, 81377, Germany, Tel +49-89-4400-73071, Email [email protected]: Benralizumab reduces exacerbations and long-term oral glucocorticosteroid (OCS) exposure in patients with severe eosinophilic asthma. In patients with eosinophilic granulomatosis with polyangiitis (EGPA), uncontrolled symptoms and exacerbations of asthma and chronic rhinosinusitis (CRS) are important reasons for continued OCS therapies. We aimed to describe outcomes of patients with severe asthma and EGPA treated with benralizumab in real-life.Methods: We retrospectively analyzed adult patients from the Severe Asthma Unit at LMU Munich diagnosed with severe asthma and EGPA treated with benralizumab, differentiating two groups: Group A, patients with a stable daily OCS dose and diagnosis of EGPA > 6 months ago; and Group B, patients treated with high-dose daily OCS due to recent diagnosis of EGPA < 6 months ago. We compared outcome parameters at baseline and 12 months after initiation of benralizumab, including respiratory exacerbations, daily OCS dose, and lung function.Results: Group A included 17 patients, all receiving OCS therapy and additional immunosuppressants; 15 patients (88%) continued benralizumab for more than 12 months, demonstrating a significant reduction in daily OCS dose and exacerbations while FEV1 increased. Group B included 9 patients, all with high-dose daily OCS and some receiving cyclophosphamide pulse therapy for life-threatening disease. Benralizumab addition during induction was well tolerated. A total of 7/9 (78%) continued benralizumab for more than 12 months and preserved EGPA remission at the 12-month timepoint.Conclusion: In this real-life cohort of patients with severe asthma and EGPA, benralizumab initiation during remission maintenance reduced respiratory exacerbations and daily OCS dose. Benralizumab initiation during remission induction was associated with a high rate of clinical EGPA remission.Keywords: EGPA, asthma, CRS, vasculitis, glucocorticoid, OCS, anti-IL5R, biologics, benralizuma
Secluded Dark Matter Coupled to a Hidden CFT
Models of secluded dark matter offer a variant on the standard WIMP picture
and can modify our expectations for hidden sector phenomenology and detection.
In this work we extend a minimal model of secluded dark matter, comprised of a
U(1)'-charged dark matter candidate, to include a confining hidden-sector CFT.
This provides a technically natural explanation for the hierarchically small
mediator-scale, with hidden-sector confinement generating m_{gamma'}>0.
Furthermore, the thermal history of the universe can differ markedly from the
WIMP picture due to (i) new annihilation channels, (ii) a (potentially) large
number of hidden-sector degrees of freedom, and (iii) a hidden-sector phase
transition at temperatures T << M_{dm} after freeze out. The mediator allows
both the dark matter and the Standard Model to communicate with the CFT, thus
modifying the low-energy phenomenology and cosmic-ray signals from the secluded
sector.Comment: ~50p, 8 figs; v2 JHEP versio
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