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The physical properties of candidate neutrino-emitter blazars
No full textContext. The processes governing the production of astrophysical high-energy neutrinos are still a matter of debate, and the sources that originate them remain an open question. Among the putative emitters, active galactic nuclei (AGN) have gained increasing attention in recent years. Blazars, in particular, stand out due to their capability of accelerating particles in environments with external radiation fields. Recent observations suggest that they may play a role in the production of high-energy neutrinos detected by the IceCube observatory.Aims. We studied the physical properties of a subsample of 52 blazars, that have been proposed as candidate neutrino emitters, based on a positional cross-correlation statistical analysis between IceCube hotspots and the Fifth Edition of the Roma BZCat catalog. We provide a first characterization of their central engines and inner physical nature, which may help to explore the potential link with neutrino production.Methods. This study carries out an analysis of the optical spectroscopic properties of a sample of 52 candidate neutrino-emitter blazars, to infer their accretion regime. It is complemented by data at the radio and γ-ray frequencies, which carry the information about the intrinsic power of the relativistic jet. We compared the properties of the sample of candidate neutrino-emitter blazars to other blazar samples from the literature. To this end, we performed statistical tests and also explored, through simulations, the applicability of methods that include limits (censored data) on the quantities of our interest.Results. Overall, the sample of candidate neutrino-emitter blazars displays properties compatible with those of the reference samples. We observe a mild tendency to prefer objects with intense radiation fields (which are typical of radiatively efficient accretors), and high radio power, such as high-excitation radio galaxies (HERGs). Among the blazars in our sample, 24 are detected in γ-rays; they cover various ranges of γ-ray luminosities, compatible with the overall population. Additionally, we show that the statistical tests commonly used in the literature need to be used with caution, as they are highly sensitive to the amount of censored data and the sample size.Key words: black hole physics / line: identification / neutrinos / galaxies: active / gamma rays: galaxies / radio continuum: galaxies⋆⋆ Now at Departament d’Astronomia i Astrofísica, Universitat de València, C/ Dr. Moliner, 50, 46100, Burjassot, València, Spain
Measurements of Higgs boson production with top quarks with the ATLAS detector
No full textThe study of Higgs boson production in association with one or two top quarks offers a unique opportunity to probe the interactions between the two heaviest particles in the Standard Model. This talk presents measurements of key Higgs boson properties - specifically the production cross section and CP nature - in events produced via tH and ttH processes. The results are based on the full Run 2 dataset of proton-proton collisions at \sqrt{s} = 13 TeV, recorded by the ATLAS detector at the LHC
Colliding Ideas - Accelerating Resilience
No full textFreya Blekman is a lead scientist at the German physics laboratory DESY and a Helmholtz Distinguished Professor of Physics at the University of Hamburg. She holds additional chairs as guest professor at Oxford University and Vrije Universiteit Brussel. She works as a particle physicist at CERN, focusing on the use of data from the Large Hadron Collider, collected with the enormous Compact Muon Solenoid (CMS) experiment, to examine undiscovered physics processes and search for new particles. She has led many large international research teams at CERN and CMS, the most prominent probably the start of the physics outreach activities of the CMS Collaboration as the first Physics Communications Officer, and as the first convener of the “Beyond-Two-Generations“ (B2G) physics group, a dedicated physics analysis group focusing on using heavy quarks and W/Z/H bosons to search for new particles.Blekman is an experienced science communicator who has won many prizes for her science and also for science communication. She regularly appears in various media, is multilingual, and is very active on social media with content aimed at the technically inclined public
The post-reactive structures of Leishmania major UDP-sugar pyrophosphorylase provide insights into the product release mechanism
No full textBiosynthesis of the nucleotide sugars UDP-glucose (UDP-Glc) and UDP-galactose (UDP-Gal) is intimately connected and essential for the viability of trypanosomatid parasites. In the genus Leishmania, it is controlled by the UDP-glucose pyrophosphorylase (UGP) and UDP-sugar pyrophosphorylase (USP). In contrast to UGP, USP has a broad substrate specificity and may generate several UDP-sugars in vitro, including UDP-Glc and UDP-Gal. This enzyme, present in protozoan parasites (including Leishmania species and Trypanosoma cruzi) and in plants, most likely plays a role in salvaging monosaccharides. In order to gain a detailed mechanistic understanding of USPs, we determined high-resolution X-ray structures of Leishmania major USP (LmUSP) in post-reactive states. Several positions of the byproduct pyrophosphate (PPi) were identified and revealed a product release channel in the forward reaction, as well as the geometries of post-reactive Michaelis product complexes. The conformational changes of functional loops (hinge loop-1, hinge loop-2, and the nucleotide-binding loop) showed dynamic effects accompanying the product release process. Structural information about the post-reactive states of LmUSP also includes the metastable binding position of a magnesium (Mg2+) ion in the active site. The proposed product release mechanism was substantiated by molecular dynamics simulations and can serve as a model for other UDP-sugar pyrophosphorylases
Two residues reprogram immunity receptors for nitrogen-fixing symbiosis
No full textReceptor signalling determines cellular responses and is crucial for defining specific biological outcomes. In legume root cells, highly similar and structurally conserved chitin and Nod factor receptor kinases activate immune or symbiotic pathways, respectively, when chitinous ligands are perceived1. Here we show that specific amino acid residues in the intracellular part of the Nod factor receptor NFR1 control signalling specificity and enable the distinction of immune and symbiotic responses. Functional investigation of CERK6, NFR1 and receptor variants thereof revealed a conserved motif that we term Symbiosis Determinant 1 in the juxtamembrane region of the kinase domain, which is key for symbiotic signalling. We show that two residues in Symbiosis Determinant 1 are indispensable hallmarks of NFR1-type receptors and are sufficient to convert Lotus CERK6 and barley RLK4 kinase outputs to enable symbiotic signalling in Lotus japonicus
PDFs from ep colliders: From current to ultimate pictureFrom current to ultimate picture
No full textCosmic-ray acceleration and escape from supernova remnant W44 as probed by Fermi-LAT and MAGIC
No full textContext. The supernova remnant (SNR) W44 and its surroundings are a prime target for studying the acceleration of cosmic rays (CRs). Several previous studies established an extended gamma-ray emission that is set apart from the radio shell of W44. This emission is thought to originate from escaped high-energy CRs that interact with a surrounding dense molecular cloud complex.Aims. We present a detailed analysis of Fermi-LAT data with an emphasis on the spatial and spectral properties of W44 and its surroundings. We also report the results of the observations performed with the MAGIC telescopes of the northwestern region of W44. Finally, we present an interpretation model to explain the gamma-ray emission of the SNR and its surroundings.Methods. We first performed a detailed spatial analysis of 12 years of Fermi-LAT data at energies above 1 GeV, in order to exploit the better angular resolution, while we set a threshold of 100 MeV for the spectral analysis. We performed a likelihood analysis of 174 hours of MAGIC data above 130 GeV using the spatial information obtained with Fermi-LAT.Results. The combined spectra of Fermi-LAT and MAGIC, extending from 100 MeV to several TeV, were used to derive constraints on the escape of CRs. Using a time-dependent model to describe the particle acceleration and escape from the SNR, we show that the maximum energy of the accelerated particles has to be ≃40 GeV. However, our gamma-ray data suggest that a small number of lower-energy particles also needs to escape. We propose a novel model, the broken-shock scenario, to account for this effect and explain the gamma-ray emission.Key words: acceleration of particles / diffusion / cosmic rays / ISM: supernova remnants / gamma rays: genera
Observation and differential measurement of electroweak production of one photon and two jets in pp collision at 13 TeV in CMS detector
No full textWe present the first observation of electroweak production of a photon in association with two forward jets in proton-proton collisions using 13 TeV data recorded by the CMS experiment corresponding to an integrated luminosity of 138 fb-1 The analysis is performed in a region enriched with vector boson fusion (VBF) production, with a requirement on the transverse momentum of the leading photon to exceed 200 GeV. The cross section is measured in the VBF fiducial region, at a significance concerning the null hypothesis that exceeds five standard deviations, and in agreement with the standard model prediction. Differential cross sections are measured as a function of various observables. Limits are set on effective field theory operators that contribute to the WWy vertex at dimension-six. The 95% confidence intervals for cW and cHWB are [0.11, 0.16] and [-1.6, 1.5], respectively