1,008 research outputs found

    GIADA performance during Rosetta mission scientific operations at comet 67P

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    The Grain Impact Analyser and Dust Accumulator (GIADA) instrument onboard Rosetta studied the dust environment of comet 67P/Churyumov–Gerasimenko from 3.7 au inbound, through perihelion, to 3.8 au outbound, measuring the dust flow and the dynamic properties of individual particles. GIADA is composed of three subsystems: 1) Grain Detection System (GDS); 2) Impact Sensor (IS); and 3) Micro-Balances System (MBS). Monitoring the subsystems’ performance during operations is an important element for the correct calibration of scientific measurements. In this paper, we analyse the GIADA inflight calibration data obtained by internal calibration devices for the three subsystems during the period from 1 August 2014 to 31 October 2015. The calibration data testify a nominal behaviour of the instrument during these fifteen months of mission; the only exception is a minor loss of sensitivity for one of the two GDS receivers, attributed to dust contamination

    Star formation histories in mergers: the spatially resolved properties of the early-stage merger luminous infrared galaxies IC 1623 and NGC 6090

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    The role of major mergers in galaxy evolution is investigated through a detailed characterization of the stellar populations, ionized gas properties and star formation rates (SFR) in the early-stage merger luminous infrared galaxies (LIRGs) IC 1623 W and NGC 6090, by analysing optical integral field spectroscopy and high-resolution Hubble Space Telescope imaging. The spectra were processed with the starlight full spectral fitting code, and the emission lines measured in the residual spectra. The results are compared with non-interacting control spiral galaxies from the Calar Alto Legacy Integral Field Area survey. Merger-induced star formation is extended and recent, as revealed by the young ages (50–80 Myr) and high contributions to light of young stellar populations (50–90 per cent), in agreement with merger simulations in the literature. These early-stage mergers have positive central gradients of the stellar metallicity, with an average ∼0.6 Z⊙. Compared to non-interacting spirals, they have lower central nebular metallicity, and flatter profiles, in agreement with the gas inflow scenario. We find that they are dominated by star formation, although shock excitation cannot be discarded in some regions, where high velocity dispersion is found (170–200 km s−1). The average SFR in these early-stage mergers (∼23–32 M⊙ yr−1) is enhanced with respect to main-sequence Sbc galaxies by factors of 6–9, slightly above the predictions from classical merger simulations, but still possible in about 15 per cent of major galaxy mergers, where U/LIRGs belong

    Theoretical predictions for the direct detection of neutralino dark matter in the NMSSM

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    We analyse the direct detection of neutralino dark matter in the framework of the Next-to-Minimal Supersymmetric Standard Model. After performing a detailed analysis of the parameter space, taking into account all the available constraints from LEPII, we compute the neutralino-nucleon cross section, and compare the results with the sensitivity of detectors. We find that sizable values for the detection cross section, within the reach of dark matter detectors, are attainable in this framework. For example, neutralino-proton cross sections compatible with the sensitivity of present experiments can be obtained due to the exchange of very light Higgses with m_{h_1^0}\lsim 70 GeV. Such Higgses have a significant singlet composition, thus escaping detection and being in agreement with accelerator data. The lightest neutralino in these cases exhibits a large singlino-Higgsino composition, and a mass in the range 50\lsim m_{\tilde\chi_1^0}\lsim 100 GeV.Comment: Final version to appear in JHEP. References added. LaTeX, 53 pages, 23 figure

    Searching for an Invisibly Decaying Higgs Boson in E^+E^-, E-Gamma, and Gamma-Gamma Collisions

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    Higgs bosons can have a substantial ``invisible'' branching ratio in many extensions of the Standard Model, such as models where the Higgs bosons decay predominantly into light or massless weakly interacting Goldstone bosons. In this work, we examine the production mechanisms and backgrounds for invisibly decaying Higgs bosons at the Next Linear e+e−e^+e^- Collider operating in the modes e+e−e^+e^-, eγe\gamma, and γγ\gamma\gamma. We demonstrate that such machine is much more efficient to survey for invisibly decaying Higgs bosons than the Large Hadron Collider at CERN.Comment: (LaTex file, 9 figures in postcript available upon request. MAD/PH/81

    Higgs Scalars in the Minimal Non-minimal Supersymmetric Standard Model

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    We consider the simplest and most economic version among the proposed non-minimal supersymmetric models, in which the Îź\mu-parameter is promoted to a singlet superfield, whose all self-couplings are absent from the renormalizable superpotential. Such a particularly simple form of the renormalizable superpotential may be enforced by discrete RR-symmetries which are extended to the gravity-induced non-renormalizable operators as well. We show explicitly that within the supergravity-mediated supersymmetry-breaking scenario, the potentially dangerous divergent tadpoles associated with the presence of the gauge singlet first appear at loop levels higher than 5 and therefore do not destabilize the gauge hierarchy. The model provides a natural explanation for the origin of the Îź\mu-term, without suffering from the visible axion or the cosmological domain-wall problem. Focusing on the Higgs sector of this minimal non-minimal supersymmetric standard model, we calculate its effective Higgs potential by integrating out the dominant quantum effects due to stop squarks. We then discuss the phenomenological implications of the Higgs scalars predicted by the theory for the present and future high-energy colliders. In particular, we find that our new minimal non-minimal supersymmetric model can naturally accommodate a relatively light charged Higgs boson, with a mass close to the present experimental lower bound.Comment: 63 pages (12 figures), extended versio

    Colorectal cancer screening among Hispanics/Latinos in the HCHS/SOL sociocultural ancillary study

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    Latino adults are more likely to be diagnosed with colorectal cancer (CRC) at later stages compared to white adults which may be explained by disparities in screening rates. The aim of this study was to examine factors associated with three CRC screening indicators [i.e., 1) any CRC screening ever (via, fecal occult blood test (FOBT), sigmoidoscopy, or colonoscopy); 2) FOBT in last year, 3) sigmoidoscopy/colonoscopy in last 10 years) among US Hispanics/Latinos. We analyzed population-based data collected in 2008–2011 from 2265 adults aged 50–75 from San Diego, Bronx, Miami and Chicago from the Hispanic Community Health Study/Study of Latinos Sociocultural Ancillary Study. Based on the Behavioral Model of Health Services Use, the following correlates of CRC screening were examined: predisposing (i.e., age, education, income, acculturation), enabling (i.e., recent physician visit, insurance, recent mammogram), and need (i.e., health-related quality of life and family/personal history of cancer) factors. Separate logistic regression models were analyzed for the three CRC screening indicators. Enabling factors associated with all CRC screening indicators included: health insurance, a recent physician visit, and a mammogram in the last year (women only). For women, being older, more acculturated (i.e., English language or foreign-born but in the US for 10 or more years), and having a personal history of cancer was associated with at least one CRC screening. Findings suggest that improving access and utilization of care among Hispanics/Latinos may be critical for earlier CRC diagnosis and survival

    Extra-familial social factors and obesity in the Hispanic Community Children’s Health Study/Study of Latino Youth

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    Hispanic/Latino youth are disproportionately affected by obesity. However, how social factors outside of the family relate to Hispanic/Latino youth obesity is not well understood. We examined associations of extra-familial social factors with overweight/obesity prevalence, and their variation by sex and age, in 1444 Study of Latino Youth participants [48.6% female; 43.4% children (8–11 years); 56.6% adolescents (12–16 years)], who were offspring of the Hispanic Community Health Study/Study of Latinos participants. Youth self-reported general social support from friends, dietary-, and physical activity (PA)-specific support from peers, and awareness/internalization of thinness ideals. Overweight/obesity was defined as body mass index ≥ 85th percentile. Logistic regression models assessed effects of social factors and their interactions with age-group and sex, adjusting for potential confounders. Social support from friends interacted with both age and sex in relation to overweight/obesity. Female children who reported lesser (OR 0.60; 95% CI [0.39, 0.91]) and female adolescents who reported greater (OR 1.35; 95% CI [1.06, 1.74]) social support from friends had higher odds of overweight/obesity. Among males, greater awareness/internalization of thinness ideals related to higher odds of overweight/obesity (OR 2.30; 95% CI [1.59, 3.31]). Awareness/internalization of thinness ideals was not associated with overweight/obesity among females. Dietary and PA-specific peer support did not relate to overweight/obesity. Social support from friends and awareness/internalization of thinness ideals were significantly related to odds of overweight/obesity in Hispanic/Latino youth; associations varied by age and sex, and persisted after control for intra-familial factors (overall family support/function; diet and activity specific support)

    Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

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    Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
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