4,682 research outputs found
WIMP Dark Matter Searches With the ATLAS Detector at the LHC
Astronomical and cosmological observations support the existence of invisible matter that can only be detected through its gravitational effects, thus making it very difficult to study. Dark matter makes up about 27% of the known universe. As a matter of fact, one of the main goals of the physics program of the experiments at the Large Hadron Collider of the CERN laboratory is the search of new particles that can explain dark matter. This review discusses both experimental and theoretical aspects of searches for Weakly Interacting Massive Particle candidates for dark matter at the LHC. An updated overview of the various experimental search channels performed by the ATLAS experiment is presented in order to pinpoint complementarity among different types of LHC searches and the interplay between the LHC and direct and indirect dark matter searches
Search for long-lived particles in ATLAS and CMS
The ATLAS and CMS detectors can be used to search for heavy long-lived
particles which might signal physics beyond the Standard Model. Such new states
can be distinguished from Standard Model particles by exploiting their unique
signatures, ranging from multi-leptons and/or jets pro- duction anywhere within
the detector volume, to minimum ionizing particles with low velocity and high
momentum. Here are reviewed the strategies proposed by ATLAS and CMS to search
for these signals, with particular emphasis on possible challenges to the
trigger and detector operations.Comment: Parallel talk at ICHEP08, Philadelphia, USA, July 2008. 4 pages,
LaTeX, 4 pdf figure
Tau Lepton Identification With Graph Neural Networks at Future Electron–Positron Colliders
Efficient and accurate reconstruction and identification of tau lepton decays plays a crucial role in the program of measurements and searches under the study for the future high-energy particle colliders. Leveraging recent advances in machine learning algorithms, which have dramatically improved the state of the art in visual object recognition, we have developed novel tau identification methods that are able to classify tau decays in leptons and hadrons and to discriminate them against QCD jets. We present the methodology and the results of the application at the interesting use case of the IDEA dual-readout calorimeter detector concept proposed for the future FCC-ee electron–positron collider
Minimal dark matter in type III seesaw
We explore the possibility of a new dark matter candidate in the
supersymmetric type III seesaw mechanism where a neutral scalar component of
the Y=0 triplet can be the lightest supersymmetric particle. Its thermal
abundance can be in the right range if non-standard cosmology such as kination
domination is assumed. The enhanced cross-section of the dark matter
annihilation to W+W- can leave detectable astrophysical and cosmological
signals whose current observational data puts a lower bound on the dark matter
mass. The model predicts the existence of a charged scalar almost degenerate
with the dark matter scalar and its lifetime lies between 5.5 cm and 6.3 m. It
provides a novel opportunity of the dark mater mass measurement by identifying
slowly-moving and highly-ionizing tracks in the LHC experiments. If the
ordinary lightest supersymmetric particle is the usual Bino, its decay leads to
clean signatures of same-sign di-lepton and di-charged-scalar associated with
observable displaced vertices which are essentially background-free and can be
fully reconstructed.Comment: 3 figures, 12 pages; An error in the antiproton limit corrected; the
lower bound on the dark matter mass strengthened; references added; typos
correcte
Immunopathological aspects in Human and Bovine Tuberculosis:<br/> - Immunopathological Changes in IRF-8-/- mice during Mycobacterium tuberculosis Infection<br/> - Histopathological and Biomolecular Evaluations in Cattle Tuberculin Skin Test positive slaughtered according to The Regional Eradication Program
Among diseases caused by Mycobacteria, tuberculosis remains an unsolved issue in humans and animals, causing economic and public health repercussions. How the host immune system responds at initial stage of infection is the key factor for progression of disease or for the establishment of latent infection. This thesis is focused on two fundamental aspects in the immunopathology of tuberculosis: firstly, in lungs of IRF-8-/- mice histopathologic alterations in both innate and adaptive immune response were observed, after experimental infection of animals with Mycobacterium tuberculosis (Mtb). Secondly, the presence of mycobacteria in carcass of TST positive cattle was investigated during sporadic cases of bTB in Sardinia. To investigate the immune events histochemistry, immunohistochemistry and molecular analysis have been applied.
IRF-8 KO mice Mtb-infected showed severe tissue damage in the lungs correlated with an uncontrolled growth of granulomas. In addition, in these animals, an altered inflammatory exudate was observed, constituted by a large number of neutrophils with poor recruitment of lymphocytes, resulting in a higher susceptibility to Mtb infection.
In TST cattle, discovering mycobacteria within the carcass using collateral diagnostic methods (histopathology and PCR) have increased the diagnosis of infection of 5% in post-mortem examination.
Therefore, for different purposes, investigating the immunopathology in tuberculosis in humans and cattle is even more important in order to perform an earlier diagnosis, aimed to improve better treatment and eradication of disease
Fast Neural Network Inference on FPGAs for Triggering on Long-Lived Particles at Colliders
Experimental particle physics demands a sophisticated trigger and acquisition
system capable to efficiently retain the collisions of interest for further
investigation. Heterogeneous computing with the employment of FPGA cards may
emerge as a trending technology for the triggering strategy of the upcoming
high-luminosity program of the Large Hadron Collider at CERN. In this context,
we present two machine-learning algorithms for selecting events where neutral
long-lived particles decay within the detector volume studying their accuracy
and inference time when accelerated on commercially available Xilinx FPGA
accelerator cards. The inference time is also confronted with a CPU- and
GPU-based hardware setup. The proposed new algorithms are proven efficient for
the considered benchmark physics scenario and their accuracy is found to not
degrade when accelerated on the FPGA cards. The results indicate that all
tested architectures fit within the latency requirements of a second-level
trigger farm and that exploiting accelerator technologies for real-time
processing of particle-physics collisions is a promising research field that
deserves additional investigations, in particular with machine-learning models
with a large number of trainable parameters.Comment: 12 pages, 9 figures, 2 table
Interferon regulatory factor 8-deficiency determines massive neutrophil recruitment but T cell defect in fast growing granulomas during tuberculosis
Following Mycobacterium tuberculosis (Mtb) infection, immune cell recruitment in lungs is pivotal in establishing protective immunity through granuloma formation and neogenesis of lymphoid structures (LS). Interferon regulatory factor-8 (IRF-8) plays an important role in host defense against Mtb, although the mechanisms driving anti-mycobacterial immunity remain unclear. In this study, IRF-8 deficient mice (IRF-8−/−) were aerogenously infected with a low-dose Mtb Erdman virulent strain and the course of infection was compared with that induced in wild-type (WT-B6) counterparts. Tuberculosis (TB) progression was examined in both groups using pathological, microbiological and immunological parameters. Following Mtb exposure, the bacterial load in lungs and spleens progressed comparably in the two groups for two weeks, after which IRF-8−/− mice developed a fatal acute TB whereas in WT-B6 the disease reached a chronic stage. In lungs of IRF-8−/−, uncontrolled growth of pulmonary granulomas and impaired development of LS were observed, associated with unbalanced homeostatic chemokines, progressive loss of infiltrating T lymphocytes and massive prevalence of neutrophils at late infection stages. Our data define IRF-8 as an essential factor for the maintenance of proper immune cell recruitment in granulomas and LS required to restrain Mtb infection. Moreover, IRF-8−/− mice, relying on a common human and mouse genetic mutation linked to susceptibility/severity of mycobacterial diseases, represent a valuable model of acute TB for comparative studies with chronically-infected congenic WT-B6 for dissecting protective and pathological immune reactions
Measurement of W Polarisation at LEP
The three different helicity states of W bosons produced in the reaction e+
e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W
decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to
measure the polarisation of W bosons, and its dependence on the W boson
production angle. The fraction of longitudinally polarised W bosons is measured
to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and
the second systematic, in agreement with the Standard Model expectation
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