83 research outputs found

    Beautiful Mirrors at the LHC

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    We explore the "Beautiful Mirrors" model, which aims to explain the measured value of AFBbA^b_{FB}, discrepant at the 2.9σ2.9\sigma level. This scenario introduces vector-like quarks which mix with the bottom, subtly affecting its coupling to the ZZ. The spectrum of the new particles consists of two bottom-like quarks and a charge -4/3 quark, all of which have electroweak interactions with the third generation. We explore the phenomenology and discovery reach for these new particles at the LHC, exploring single mirror quark production modes whose rates are proportional to the same mixing parameters which resolve the AFBbA_{FB}^b anomaly. We find that for mirror quark masses â‰Č500GeV,a14TeVLHCwith300fb−1\lesssim 500 GeV, a 14 TeV LHC with 300 {\rm fb}^{-1} is required to reasonably establish the scenario and extract the relevant mixing parameters.Comment: version to be published in JHE

    Covariant Description of Flavor Conversion in the LHC Era

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    A simple covariant formalism to describe flavor and CP violation in the left-handed quark sector in a model independent way is provided. The introduction of a covariant basis, which makes the standard model approximate symmetry structure manifest, leads to a physical and transparent picture of flavor conversion processes. Our method is particularly useful to derive robust bounds on models with arbitrary mechanisms of alignment. Known constraints on flavor violation in the K and D systems are reproduced in a straightforward manner. Assumptions-free limits, based on top flavor violation at the LHC, are then obtained. In the absence of signal, with 100 fb^{-1} of data, the LHC will exclude weakly coupled (strongly coupled) new physics up to a scale of 0.6 TeV (7.6 TeV), while at present no general constraint can be set related to Delta t=1 processes. LHC data will constrain Delta F=2 contributions via same-sign tops signal, with a model independent exclusion region of 0.08 TeV (1.0 TeV). However, in this case, stronger bounds are found from the study of CP violation in D-bar D mixing with a scale of 0.57 TeV (7.2 TeV). In addition, we apply our analysis to models of supersymmetry and warped extra dimension. The minimal flavor violation framework is also discussed, where the formalism allows to distinguish between the linear and generic non-linear limits within this class of models.Comment: 24 pages, 6 figures. Some corrections and clarifications; references added. Matches published versio

    Anomalous tqÎłtq\gamma coupling effects in exclusive radiative B-meson decays

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    The top-quark FCNC processes will be searched for at the CERN LHC, which are correlated with the B-meson decays. In this paper, we study the effects of top-quark anomalous interactions tqÎłtq\gamma in the exclusive radiative B→K∗γB\to K^*\gamma and Bâ†’ÏÎłB\to\rho\gamma decays. With the current experimental data of the branching ratios, the direct CP and the isospin asymmetries, bounds on the coupling ÎștcRÎł\kappa_{tcR}^{\gamma} from B→K∗γB\to K^*\gamma and ÎștuRÎł\kappa_{tuR}^{\gamma} from Bâ†’ÏÎłB\to \rho\gamma decays are derived, respectively. The bound on ∣ÎștcRγ∣|\kappa_{tcR}^{\gamma}| from B(B→K∗γ){\mathcal B}(B\to K^{*}\gamma) is generally compatible with that from B(B→XsÎł){\mathcal B}(B\to X_{s}\gamma). However, the isospin asymmetry Δ(K∗γ)\Delta(K^{*}\gamma) further restrict the phase of ÎștcRÎł\kappa_{tcR}^{\gamma}, and the combined bound results in the upper limit, B(t→cÎł)<0.21\mathcal B(t\to c\gamma)<0.21%, which is lower than the CDF result. For real ÎștcRÎł\kappa_{tcR}^{\gamma}, the upper bound on B(t→cÎł)\mathcal B(t\to c\gamma) is about of the same order as the 5σ5\sigma discovery potential of ATLAS with an integrated luminosity of 10fb−110 {\rm fb}^{-1}. For Bâ†’ÏÎłB\to\rho\gamma decays, the NP contribution is enhanced by a large CKM factor ∣Vud/Vtd∣|V_{ud}/V_{td}|, and the constraint on tuÎłtu\gamma coupling is rather restrictive, B(t→uÎł)<1.44×10−5\mathcal B(t\to u\gamma)<1.44\times 10^{-5}. With refined measurements to be available at the LHCb and the future super-B factories, we can get close correlations between B→VÎłB\to V \gamma and the rare t→qÎłt\to q\gamma decays, which will be studied directly at the LHC ATLAS and CMS.Comment: 25 pages, 15 figures, pdflate

    Genetic Polymorphisms and Drug Susceptibility in Four Isolates of Leishmania tropica Obtained from Canadian Soldiers Returning from Afghanistan

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    Cutaneous leishmaniasis (CL) is a vector-borne parasitic disease transmitted by the bite of sandflies, resulting in sores on the skin. No vaccines are available, and treatment relies on chemotherapy. CL has been frequently diagnosed in military personnel deployed to Afghanistan and returning from duty. The parasites isolated from Canadian soldiers were characterized by pulsed field gels and by sequencing conserved genes and were identified as Leishmania tropica. In contrast to other Leishmania species, high allelic polymorphisms were observed at several genetic loci for the L. tropica isolates that were characterized. In vitro susceptibility testing in macrophages showed that all isolates, despite their genetic heterogeneity, were sensitive to most antileishmanial drugs (antimonials, miltefosine, amphotericin B, paromomycin) but were insensitive to fluconazole. This study suggests a number of therapeutic regimens for treating cutaneous leishmaniasis caused by L. tropica among patients and soldiers returning from Afghanistan. Canadian soldiers from this study were successfully treated with miltefosine

    Anomalous tqZtqZ coupling effects in rare B- and K-meson decays

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    As a top-factory, the LHC is performing a direct study of top-quark anomalous FCNC couplings, which are, however, correlated closely with the rare B- and K-meson decays. In this paper, we study the effects of anomalous tqZtqZ (with q=u,cq=u,c) couplings in the rare decays Bs,d→Ό+Ό−B_{s,d}\to \mu^+\mu^-, B→XsΜΜˉB\to X_s \nu \bar\nu, B→K(∗)ΜΜˉB\to K^{(*)}\nu \bar\nu, K+→π+ΜΜˉK^+\to \pi^+ \nu \bar\nu, and KL→π0ΜΜˉK_L\to \pi^0 \nu \bar\nu. With the up-to-date experimental bounds on the branching ratios of these channels, constraints on the left-handed anomalous couplings XctLX_{ct}^L and XutLX_{ut}^L are derived, respectively. With these low-energy constraints taken into account, we find that, for real couplings XctLX_{ct}^L and XutLX_{ut}^L, the indirect upper bounds on B(t→qZ)\mathcal B(t\to qZ) are much lower than that from the D0 collaboration, but are still compatible with the 5σ5\sigma discovery potential of ATLAS with an integrated luminosity of 10fb−110 {\rm fb}^{-1}. With refined measurements to be available at the LHCb, the future super-B factories, the NA62 at CERN, and the KOTO at J-PARC, closer correlations between the t→qZt\to qZ and the rare B- and K-meson decays are expected in the near future, which will be helpful for the searches of the top-quark FCNC decays at the LHC.Comment: 25 pages, 18 figures, 4 tables; More references added, version published in JHE

    Potential toxic elements in stream sediments, soils and waters in an abandoned radium mine (central Portugal)

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    The Alto da Vårzea radium mine (AV) exploited ore and U-bearing minerals, such as autunite and torbernite. The mine was exploited underground from 1911 to 1922, closed in 1946 without restoration, and actually a commercial area is deployed. Stream sediments, soils and water samples were collected between 2008 and 2009. Stream sediments are mainly contaminated in As, Th, U and W, which is related to the AV radium mine. The PTEs, As, Co, Cr, Sr, Th, U, W, Zn, and electrical conductivity reached the highest values in soils collected inside the mine influence. Soils are contaminated with As and U and must not be used for any purpose. Most waters have pH values ranging from 4.3 to 6.8 and are poorly mineralized (EC = 41-186 ”S/cm; TDS = 33-172 mg/L). Groundwater contains the highest Cu, Cr and Pb contents. Arsenic occurs predominantly as H2(AsO4)- and H(AsO4)2-. Waters are saturated in goethite, haematite and some of them also in lepidocrocite and ferrihydrite, which adsorbs As (V). Lead is divalent in waters collected during the warm season, being mobile in these waters. Thorium occurs mainly as Th(OH)3(CO3)-, Th(OH)2(CO3) and Th(OH)2(CO3) 22- , which increase water Th contents. Uranium occurs predominantly as UO2CO3, but CaUO2(CO3) 32- and CaUO2(CO3)3 also occur, decreasing its mobility in water. The waters are contaminated in NO2-, Mn, Cu, As, Pb and U and must not be used for human consumption and in agricultural activities. The water contamination is mainly associated with the old radium mine and human activities. A restoration of the mining area with PTE monitoring is necessary to avoid a public hazard.Thanks are due to Prof. Joao Coutinho for the determination of organic matter and cation exchange capacity in samples of stream sediments and soils and A. Rodrigues for the water analyses, EDM for some information on the Alto da Varzea mine area. This study had the support of Portuguese Fundacao para a Ciencia e Tecnologia (FCT), through the strategic projects UID/GEO/04035/2013 and UID/MAR/04292/2013 (MARE).info:eu-repo/semantics/publishedVersio

    The ancient history of the structure of ribonuclease P and the early origins of Archaea

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    Oxidative protein labeling in mass-spectrometry-based proteomics

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    Oxidation of proteins and peptides is a common phenomenon, and can be employed as a labeling technique for mass-spectrometry-based proteomics. Nonspecific oxidative labeling methods can modify almost any amino acid residue in a protein or only surface-exposed regions. Specific agents may label reactive functional groups in amino acids, primarily cysteine, methionine, tyrosine, and tryptophan. Nonspecific radical intermediates (reactive oxygen, nitrogen, or halogen species) can be produced by chemical, photochemical, electrochemical, or enzymatic methods. More targeted oxidation can be achieved by chemical reagents but also by direct electrochemical oxidation, which opens the way to instrumental labeling methods. Oxidative labeling of amino acids in the context of liquid chromatography(LC)–mass spectrometry (MS) based proteomics allows for differential LC separation, improved MS ionization, and label-specific fragmentation and detection. Oxidation of proteins can create new reactive groups which are useful for secondary, more conventional derivatization reactions with, e.g., fluorescent labels. This review summarizes reactions of oxidizing agents with peptides and proteins, the corresponding methodologies and instrumentation, and the major, innovative applications of oxidative protein labeling described in selected literature from the last decade
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