Search for new physics in top events with the D0 detector

This review is focused on the search for new processes, performed with top quark events in D{\O}. It presents four updated or new D{\O} results. The two first analyses deal with top production properties: they search for a new heavy resonance decaying to top-antitop. The two last results concern top decay properties: the measurement of the $W$ helicity as a probe of the $tWb$ coupling structure, and the top quark branching ratio to $Wb$. Neither of these measurements reveal any deviation with respect to the standard model predictions.Comment: Submitted for the SUSY07 conference proceeding. 4 pages, LateX, 6 eps figures, 2 LateX style file

Conjugating effects of symbionts and environmental factors on gene expression in deep-sea hydrothermal vent mussels.

International audienceABSTRACT: BACKGROUND: The deep-sea hydrothermal vent mussel Bathymodiolus azoricus harbors thiotrophic and methanotrophic symbiotic bacteria in its gills. While the symbiotic relationship between this hydrothermal mussel and these chemoautotrophic bacteria has been described, the molecular processes involved in the cross-talking between symbionts and host, in the maintenance of the symbiois, in the influence of environmental parameters on gene expression, and in transcriptome variation across individuals remain poorly understood. In an attempt to understand how, and to what extent, this double symbiosis affects host gene expression, we used a transcriptomic approach to identify genes potentially regulated by symbiont characteristics, environmental conditions or both. This study was done on mussels from two contrasting populations. RESULTS: Subtractive libraries allowed the identification of about 1000 genes putatively regulated by symbiosis and/or environmental factors. Microarray analysis showed that 120 genes (3.5% of all genes) were differentially expressed between the Menez Gwen (MG) and Rainbow (Rb) vent fields. The total number of regulated genes in mussels harboring a high versus a low symbiont content did not differ significantly. With regard to the impact of symbiont content, only 1% of all genes were regulated by thiotrophic (SOX) and methanotrophic (MOX) bacteria content in MG mussels whereas 5.6% were regulated in mussels collected at Rb. MOX symbionts also impacted a higher proportion of genes than SOX in both vent fields. When host transcriptome expression was analyzed with respect to symbiont gene expression, it was related to symbiont quantity in each field. CONCLUSIONS: Our study has produced a preliminary description of a transcriptomic response in a hydrothermal vent mussel host of both thiotrophic and methanotrophic symbiotic bacteria. This model can help to identify genes involved in the maintenance of symbiosis or regulated by environmental parameters. Our results provide evidence of symbiont effect on transcriptome regulation, with differences related to type of symbiont, even though the relative percentage of genes involved remains limited. Differences observed between the vent site indicate that environment strongly influences transcriptome regulation and impacts both activity and relative abundance of each symbiont. Among all these genes, those participating in recognition, the immune system, oxidative stress, and energy metabolism constitute new promising targets for extended studies on symbiosis and the effect of environmental parameters on the symbiotic relationships in B. azoricus

Similarity between structural and proxy estimates of brain connectivity.

peer reviewedFunctional magnetic resonance and diffusion weighted imaging have so far made a major contribution to delineation of the brain connectome at the macroscale. While functional connectivity (FC) was shown to be related to structural connectivity (SC) to a certain degree, their spatial overlap is unknown. Even less clear are relations of SC with estimates of connectivity from inter-subject covariance of regional F18-fluorodeoxyglucose uptake (FDGcov) and grey matter volume (GMVcov). Here, we asked to what extent SC underlies three proxy estimates of brain connectivity: FC, FDGcov and GMVcov. Simultaneous PET/MR acquisitions were performed in 56 healthy middle-aged individuals. Similarity between four networks was assessed using Spearman correlation and convergence ratio (CR), a measure of spatial overlap. Spearman correlation coefficient was 0.27 for SC-FC, 0.40 for SC-FDGcov, and 0.15 for SC-GMVcov. Mean CRs were 51% for SC-FC, 48% for SC-FDGcov, and 37% for SC-GMVcov. These results proved to be reproducible and robust against image processing steps. In sum, we found a relevant similarity of SC with FC and FDGcov, while GMVcov consistently showed the weakest similarity. These findings indicate that white matter tracts underlie FDGcov to a similar degree as FC, supporting FDGcov as estimate of functional brain connectivity

Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at √s=0.9 and 2.36 TeV

Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at root s = 0.9 and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive interactions, the average charged-hadron transverse momentum is measured to be 0.46 +/- 0.01 (stat.) +/- 0.01 (syst.) GeV/c at 0.9 TeV and 0.50 +/- 0.01 (stat.) +/- 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between -2.4 and +2.4. At these energies, the measured pseudorapidity densities in the central region, dN(ch)/d eta vertical bar(vertical bar eta vertical bar and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date

Neurocognitive networks: altered by dementia but not working memory training

Functional magnetic resonance imaging (fMRI) studies have reported a link between cognitive performance and large-scale neurocognitive networks (NCN). In dementing disorders altered integrity of these NCN have been reported. As of today, no pharmacological treatments exist to slow down, stop or reverse neuronal cell death causing these altered integrities of NCN and cognitive decline. As a consequence, cognitive training programs have become a popular tool to improve cognitive skills in dementia but also in healthy subjects. Especially, working memory (WM) training was observed to lead to a performance improvement in the trained task but also to generalized improvements in non-trained tasks. Hence, these so-called transfer effects developed into an index of the putative effectiveness of WM training. Despite growing interest in cognitive interventions from academia and industry, the literature reports heterogeneous results on transfer effects. Likewise, there is very little evidence of neural correlates underlying transfer. Accordingly, the effects of WM training on NCN remain understudied. Within this cumulative thesis, project one investigated impairments of NCN in AD and bvFTD, the two most common causes of dementia among patients less than 65 years of age. To this end, simultaneous fMRI and FDG-PET data was acquired enabling the comparison of NCN integrity measures between patient groups, as well as between neuroimaging modalities. In project two, we assessed the effectiveness of WM training in regards to transfer effects in healthy middle-aged participants – an age group directly preceding or equivalent to that seen in early-stage dementia. Hypothesized transfer effect-related neural plasticity was evaluated in terms of change in NCN integrity between pre- and post-training. Equivalent to project one, both fMRI and FDG-PET was used to measure two linked but distinct marker of neural plasticity. The additional assessment of an extensive cognitive test battery captured changes in nearest, near and far transfer tasks. To this end, all training induced changes were contrasted to an active control group. Overall, the thesis aims to assess the applicability of WM training to decrease AD and bvFTD specific NCN integrity impairments. Based on the results achieved within project one, we report significant differences in NCN integrity impairments between AD and bvFTD. We could also show that the pattern of network alterations differed between the neuroimaging modalities, with the fMRI-based NCN showing a generally lower disease specificity. The integrity of the anterior default mode network as measured with FDG-PET alone accurately differentiated between patients with AD and bvFTD. Based on the results obtained in project two, we report the lack of WM training induced neural plasticity in NCN in healthy middle-aged participants. Equivalently, on the behavioural level no near or far transfer effects were observed. Thus, WM training-related gains appear not to generalize to other cognitive domains and only to an extremely limited degree to other WM tasks. Overall, these results discourage the potential applicability of WM training in dementia to decrease NCN integrity impairments. However, looking beyond the concept of transfer as revealed by comparing WM training-induced changes in the active control and experimental group, we see positive effects in form of cognitive improvements in some tasks. Thus, I propose to test WM training along with multiple other cognitive training paradigms to maximize the range of cognitive improvements in patients with a mild cognitive impairment

First look at CKM parameters from early Belle II data

International audienceAfter its commissioning in 2018, the Belle II experiment has started registering first physics data delivered by SuperKEKB in 2019. The Belle II physics program focuses on the search for physics beyond the standard model with precise measurements in the flavour sector. The huge targeted dataset and the B-factory particular collision scheme will help to significantly improve the experimental precision on the three angles of the bd CKM unitarity triangle. These measurements are based on time-dependent CP asymmetry analyses for the angles phi1 and phi2, and on the reconstruction of many B and D hadronic decay modes for phi3. In this proceeding article are reported the first look at these ingredients reconstructed with early Belle II data, and the expected Belle II sensitivity on phi1, phi2 and phi3 with more data

Etude de détecteurs gazeux à micropistes pour le trajectographe de CMS et mesure de la masse du boson W dans l'expérience DELPHI

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Recherche du boson de Higgs standard léger dans le canal WH avec la statistique finale de l'expérience DØ au Tevatron

Le mécanisme de Higgs, introduit en 1964, propose une solution à un problème majeur du modèle standard de la physique des particules : l'origine de la masse. Ce mécanisme prédit l'existence d'un boson scalaire, de masse non prédite par la théorie et qui n'a encore jamais été observé expérimentalement (Juin 2012). Le Tevatron, un accélérateur hadronique basé à Fermi National Accelerator Laboratory près de Chicago, a permis la prise de données à l'aide des deux détecteurs CDF et DØ depuis 1983 jusqu'en septembre 2011. Accumulant une statistique de près de 10fb-1 à analyser. La production associée du Higgs et d'un boson vecteur est le canal principal de recherche pour un Higgs standard léger. A l'aide des données collectées par DØ, nous recherchons ce mode de production. La production du boson de Higgs étant très rare, nous avons développé des techniques sophistiquées de manière à améliorer la sensibilité au signal, telles que l'identification des jets de quarks beaux ou encore des méthodes basées sur des discriminants multivariés. Au final, une approche statistique nous permet de poser une limite supérieure sur le taux de production du Higgs observé (resp. attendu) rapporté aux prédictions du modèle standard. Les résultats obtenus dans le canal WH avec la statistique finale de l'expérience DØ au Tevatron sont de 3.15 (resp. 3.97) pour un boson de Higgs de 115 GeV/C2.Higgs mechanism, introduced in 1964, gives a satisfactory solution to a major problem of the standard model of elementary particles: the origin of the mass. It predicts the existence of the Higgs scalar boson, which mass is not defined by the theory and which has not been discovered experimentally yet (June 2012). The Tevatron, a hadron accelerator based at Fermi National Accelerator Laboratory near Chicago, took data with its two multi-purpose detectors CDF and DØ since 1983 up to september 2011. Leaving about 10 fb-1 of statistics to analyze. Associated production of Higgs and vector gauge boson is the main search channel for a light standard Higgs boson. Using data collected by DØ, we are looking for this production mode taking advantage of sophisticated techniques to improve the signal sensitivity like b-jet identification and multivariate discriminants. In the end, a statistical approach allows us to set an upper limit on the ratio between the observed (resp. expected) Higgs production and its theoretical cross section. The results obtained in the WH channel using 9.7 fb-1 at DØ is 3;15 (resp. 3.96) for a 115 GeV/c2 Higgs boson.STRASBOURG-Bib.electronique 063 (674829902) / SudocSudocFranceF