24 resultados para SIGNATURE
Resumo:
We present a search for the technicolor particles $\rho_{T}$ and $\pi_{T}$ in the process $p\bar{p} \to \rho_{T} \to W\pi_{T}$ at a center of mass energy of $\sqrt{s}=1.96 \mathrm{TeV}$. The search uses a data sample corresponding to approximately $1.9 \mathrm{fb}^{-1}$ of integrated luminosity accumulated by the CDF II detector at the Fermilab Tevatron. The event signature we consider is $W\to \ell\nu$ and $\pi_{T} \to b\bar{b}, b\bar{c}$ or $b\bar{u}$ depending on the $\pi_{T}$ charge. We select events with a single high-$p_T$ electron or muon, large missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with multiple $b$-tagging algorithms. The observed number of events and the invariant mass distributions are consistent with the standard model background expectations, and we exclude a region at 95% confidence level in the $\rho_T$-$\pi_T$ mass plane. As a result, a large fraction of the region $m(\rho_T) = 180$ - $250 \mathrm{GeV}/c^2$ and $m(\pi_T) = 95$ - $145 \mathrm{GeV}/c^2$ is excluded.
Resumo:
We report on the first search for top-quark production via flavor-changing neutral-current (FCNC) interactions in the non-standard-model process u(c)+g -> t using ppbar collision data collected by the CDF II detector. The data set corresponds to an integrated luminosity of 2.2/fb. The candidate events feature the signature of semileptonic top-quark decays and are classified as signal-like or background-like by an artificial neural network trained on simulated events. The observed discriminant distribution is in good agreement with the one predicted by the standard model and provides no evidence for FCNC top-quark production, resulting in a Bayesian upper limit on the production cross section sigma (u(c)+g -> t) u+g) c+g)
Resumo:
We performed a signature-based search for long-lived charged massive particles (CHAMPs) produced in 1.0 $\rm{fb}^{-1}$ of $\bar{p}p$ collisions at $\sqrt{s}=1.96$ TeV, collected with the CDF II detector using a high transverse-momentum ($p_T$) muon trigger. The search used time-of-flight to isolate slowly moving, high-$p_T$ particles. One event passed our selection cuts with an expected background of $1.9 \pm 0.2$ events. We set an upper bound on the production cross section, and, interpreting this result within the context of a stable scalar top quark model, set a lower limit on the particle mass of 249 GeV/$c^2$ at 95% C.L.
Resumo:
We present a signature-based search for anomalous production of events containing a photon, two jets, of which at least one is identified as originating from a b quark, and missing transverse energy. The search uses data corresponding to 2.0/fb of integrated luminosity from p-pbar collisions at a center-of-mass energy of sqrt(s)=1.96 TeV, collected with the CDF II detector at the Fermilab Tevatron. From 6,697,466 events with a photon candidate with transverse energy ET> 25 GeV, we find 617 events with missing transverse energy > 25 GeV and two or more jets with ET> 15 GeV, at least one identified as originating from a b quark, versus an expectation of 607+- 113 events. Increasing the requirement on missing transverse energy to 50 GeV, we find 28 events versus an expectation of 30+-11 events. We find no indications of non-standard-model phenomena.
Resumo:
We have observed the reactions p+pbar --> p+X+pbar, with X being a centrally produced J/psi, psi(2S) or chi_c0, and gamma+gamma --> mu+mu-, in proton- antiproton collisions at sqrt{s} = 1.96 TeV using the Run II Collider Detector at Fermilab. The event signature requires two oppositely charged muons, each with pseudorapidity |eta| mu+mu-. Events with a J/psi and an associated photon candidate are consistent with exclusive chi_c0 production through double pomeron exchange. The exclusive vector meson production is as expected for elastic photo- production, gamma+p --> J/psi(psi(2S)) + p, which is observed here for the first time in hadron-hadron collisions. The cross sections ds/dy(y=0) for p + pbar --> p + X + pbar with X = J/psi, psi(2S) orchi_c0 are 3.92+/-0.62 nb, 0.53+/-0.14 nb, and 75+/-14 nb respectively. The cross section for the continuum, with |eta(mu+/-)|
Resumo:
We present a search for standard model Higgs boson production in association with a W boson in proton-antiproton collisions at a center of mass energy of 1.96 TeV. The search employs data collected with the CDF II detector that correspond to an integrated luminosity of approximately 1.9 inverse fb. We select events consistent with a signature of a single charged lepton, missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with a secondary vertex tagging method, a jet probability tagging method, and a neural network filter. We use kinematic information in an artificial neural network to improve discrimination between signal and background compared to previous analyses. The observed number of events and the neural network output distributions are consistent with the standard model background expectations, and we set 95% confidence level upper limits on the production cross section times branching fraction ranging from 1.2 to 1.1 pb or 7.5 to 102 times the standard model expectation for Higgs boson masses from 110 to $150 GeV/c^2, respectively.
Resumo:
The impact of Greek-Egyptian bilingualism on language use and linguistic competence is the key issue in this dissertation. The language use in a corpus of 148 Greek notarial contracts is analyzed on phonological, morphological and syntactic levels. The texts were written by bilingual notaries (agoranomoi) in Upper Egypt in the later Hellenistic period. They present, for the most part, very good administrative Greek. On the other hand, their language contains variation and idiosyncrasies that were earlier condemned as ungrammatical and bad Greek, and were not subjected to closer analysis. In order to reach plausible explanations for those phenomena, a thorough research into the sociohistorical and linguistic context was needed before the linguistic analysis. The general linguistic landscape, the population pattern and the status and frequency of Greek literacy in Ptolemaic Egypt in general, and in Upper Egypt in particular, are presented. Through a detailed examination of the notaries themselves (their names, families and handwriting), it became evident that there were one to three persons at the notarial office writing under the signature of one notary. Often the documents under one notary's name were written in the same hand. We get, therefore, exceptionally close to studying idiolects in written material from antiquity. The qualitative linguistic analysis revealed that the notaries made relatively few orthographic mistakes that reflect the ongoing phonological changes and they mastered the morphological forms. The problems arose at the syntactic level, for example, with the pattern of agreement between the noun groups or a noun with its modifiers. The significant structural differences between Greek and Egyptian can be behind the innovative strategies used by some of the notaries. Moreover, certain syntactic structures were clearly transferred from the notaries first language, Egyptian. This is obvious in the relative clause structure. Transfer can be found in other structures, as well, although, we must not forget the influence of parallel Greek structures. Sometimes these can act simultaneously. The interesting linguistic strategies and transfer features come mostly from the hand of one notary, Hermias. Some other notaries show similar patterns, for example, Hermias' cousin, Ammonios. Hermias' texts reveal that he probably spoke Greek more than his predecessors. It is possible to conclude, then, that the notaries of the later generations were more fluently bilingual; their two languages were partly integrated in their minds as an interlanguage combining elements from both languages. The earlier notaries had the two languages functionally separated and they followed the standardized contract formulae more rigidly.
Resumo:
Individuals with inherited deficiency in DNA mismatch repair(MMR) (Lynch syndrome) LS are predisposed to different cancers in a non-random fashion. Endometrial cancer (EC) is the most common extracolonic malignancy in LS. LS represents the best characterized form of hereditary nonpolyposis colorectal carcinoma (HNPCC). Other forms of familial non-polyposis colon cancer exist, including familial colorectal cancer type X (FCCX). This syndrome resembles LS, but MMR gene defects are excluded and the predisposition genes are unknown so far. To address why different organs are differently susceptible to cancer development, we examined molecular similarities and differences in selected cancers whose frequency varies in LS individuals. Tumors that are common (colorectal, endometrial, gastric) and less common (brain, urological) in LS were characterized for MMR protein expression, microsatellite instability (MSI), and by altered DNA methylation. We also studied samples of histologically normal endometrium, endometrial hyperplasia,and cancer for molecular alterations to identify potential markers that could predict malignant transformation in LS and sporadic cases. Our results suggest that brain and kidney tumors follow a different pathway for cancer development than the most common LS related cancers.Our results suggest also that MMR defects are detectable in endometrial tissues from a proportion of LS mutation carriers prior to endometrial cancer development. Traditionally (complex) atypical hyperplasia has been considered critical for progression to malignancy. Our results suggest that complex hyperplasia without atypia is equally important as a precursor lesion of malignancy. Tumor profiles from Egypt were compared with colorectal tumors from Finland to evaluate if there are differences specific to the ethnic origin (East vs.West). Results showed for the first time a distinct genetic and epigenetic signature in the Egyptian CRC marked by high methylation of microsatellite stable tumors associated with advanced stage, and low frequency of Wnt signaling activation, suggesting a novel pathway. DNA samples from FCCX families were studied with genome wide linkage analysis using microsatellite markers. Selected genes from the linked areas were tested for possible mutations that could explain predisposition to a large number of colon adenomas and carcinomas seen in these families. Based on the results from the linkage analysis, a number of areas with tentative linkage were identified in family 20. We narrowed down these areas by additional microsatellite markers to found a mutation in the BMPR1A gene. Sequencing of an additional 17 FCCX families resulted in a BMPR1A mutation frequency of 2/18 families (11%). Clarification of the mechanisms of the differential tumor susceptibility in LS increases the understanding of gene and organ specific targets of MMR deficiency. While it is generally accepted that widespread MMR deficiency and consequent microsatellite instability (MSI) drives tumorigenesis in LS, the timing of molecular alterations is controversial. In particular, it is important to know that alterations may occur several years before cancer formation, at stages that are still histologically regarded as normal. Identification of molecular markers that could predict the risk of malignant transformation may be used to improve surveillance and cancer prevention in genetically predisposed individuals. Significant fractions of families with colorectal and/or endometrial cancer presently lack molecular definition altogether. Our findings expand the phenotypic spectrum of BMPR1A mutations and, for the first time, link FCCX families to the germline mutation of a specific gene. In particular, our observations encourage screening of additional families with FCCX for BMPR1A mutation, which is necessary in obtaining a reliable estimate of the share of BMPR1A-associated cases among all FCCX families worldwide. Clinically, the identification of predisposing mutations enables targeted cancer prevention in proven mutation carriers and thereby reduces cancer morbidity and mortality in the respective families.
Resumo:
To test the reliability of the radiocarbon method for determining root age, we analyzed fine roots (originating from the years 1985 to 1993) from ingrowth cores with known maximum root age (1 to 6 years old). For this purpose, three Scots pine (Pinus sylvestris L.) stands were selected from boreal forests in Finland. We analyzed root 14C age by the radiocarbon method and compared it with the above-mentioned known maximum fine root age. In general, ages determined by the two methods (root 14C age and ingrowth core root maximum age) were in agreement with each other for roots of small diameter (<0.5mm). By contrast, in most of the samples of fine roots of larger diameter (1.5-2mm), the 14C age of root samples of 1987-89 exceeded the ingrowth core root maximum age by 1-10 years. This shows that these roots had received a large amount of older stored carbon from unknown sources in addition to atmospheric CO2 directly from photosynthesis. We conclude that the 14C signature of fine roots, especially those of larger diameter, may not always be indicative of root age, and that further studies are needed concerning the extent of possible root uptake of older carbon and its residence time in roots. Keywords: fine root age, Pinus sylvestris, radiocarbon, root carbon, ingrowth cores, tree ring