1,739 research outputs found

    Heavy resonances (W', Z', jets) in ATLAS and CMS in Run 2

    Full text link
    An overview of the searches for heavy resonances that decay to leptons or quarks is presented. The results are based on the data collected by the ATLAS and CMS experiments in proton-proton collisions at s=13 TeV\sqrt{s} = 13~\textrm{TeV}, and include for the first time the entire LHC Run 2 data set.Comment: Proceedings of the 54th Rencontres de Moriond on Electroweak Interactions and Unified Theories (Moriond EW 2019

    Searches for signatures of an extended Higgs sector in final states with leptons and Higgs to bb decays at CMS

    Get PDF
    The Standard Model (SM) of elementary particles, a model experimentally verified to an un-precedented level of accuracy, foresees the existence a scalar particle, the so-called Higgs boson, that breaks the electroweak symmetry and explains the non-null value of fermion masses. The pursue of the Higgs boson has been carried out by several experiments at the LEP II and Tevatron colliders in the past, but unsuccessfully. However, during the year 2011, the ATLAS and CMS experiments at LHC began to observe some evidence of the elusive particle, finally confirming the discovering in 2012. Even if the Higgs boson and its observed properties represent a triumph for the Standard Model, there are many unresolved phenomena that the SM cannot explain. Several extensions have been proposed; some of the most relevant foresee several Higgs bosons instead of only one. After the commissioning of the LHC collider in 2011 and the first evidences of a light scalar boson, one of the fundamental questions to be answered was whether the new particle was the SM Higgs boson, or the lightest among the bosons foreseen by the theories extending the SM. The confirmation could come from the measurements of the Higgs couplings to the SM particles, or alternatively from the observation of new production processes and decays not predicted by the SM, or measured at a different rate. The associated production with b quarks of a Higgs boson, and its decay into pairs of b quarks, is a process with a small predicted cross section in the SM, and its observation would imply the presence of new physics. Previous searches at the Tevatron collider reported a slight excess in this channel. Afterwards the discovery of the Higgs boson in July 2012 by the CMS and ATLAS experiments, the knowledge of the properties of the Higgs boson and its mass become a valuable handle to increase the sensitivity of new physics searches. One of the most beneficial channels is the search of a heavy pseudoscalar A, and its decay into a Z boson and a light Higgs boson h, the latter assumed to be the recently-discovered 125 GeV boson. The Z boson is sought in its decay into a pair of electrons or muons, and the Higgs into a pair of b quarks. This channel, not predicted by the SM, probes a region in the parameter phase-space of beyond the SM theories which is, to some extent, complementary to the one of the multi-b search

    Recreational fishing on the West coast of the Northern Adriatic Sea (Western Mediterranean) and its possible ecological implications

    Get PDF
    The marine recreational fishing (MRF) represents one of the most popular activities along the coasts of numerous countries around the world, in particular in the Mediterranean Sea. Despite the evidences of potential effects on the marine biodiversity and commercially exploited stocks, a sound information base and adequate management plans are still lacking, both at the national and basin level. An analysis of the MRF on the West coasts of the Adriatic Sea was carried out, in 2014, by using a standardized questionnaires approach, aiming to describe the state of the art and to preliminarily assess catches, in comparison with the commercial ones, at the regional scale. Gilt-headed seabream, European seabass, cuttlefish, squid and Atlantic bluefin tuna resulted the anglers' preferred species, even if the top five in term of caught biomass were bluefin tuna, seabream, cuttlefish, common dolphinfish and little tunny, in the order (accounting up to 60% of total catches). The exploitation level resulted to be significant, as confirmed by the comparison with commercial fisheries, being the MRF captures 30% or 45% of the artisanal fishery in the same area, with some species, such as bluefish, bonito, pandora and picarel, showing larger values. The preliminary assessment of ecological effects, highlighted that the exploitation use about 10%-16% of energy fixed by the primary production (Primary Production Required to sustain fishery), but the ecosystem effects are still sustainable (Lindex and probability to be sustainable fished). However, combining catches by MRF with those by small scale fishery completely changes the situation, showing an unsustainable condition, suggesting the need for taking into the account also MRF in the future management planning for the Adriatic coastal area. (C) 2015 Elsevier B.V. All rights reserved

    The Role of Positron Emission Tomography in Clinical Management of Intraductal Papillary Mucinous Neoplasms of the Pancreas

    Get PDF
    Intraductal papillary mucinous neoplasms (IPMNs) of the pancreas represent a heterogeneous group of tumors, increasingly diagnosed in clinical practice. An early differential diagnosis between malignant and benign lesions is crucial to patient management and the choice of surgery or observation. The therapeutic approach is currently based on a patient's clinical, biochemical, and morphological characteristics. The latest published International Consensus Guidelines (ICG) make no mention of the role of metabolic assessments of IPMNs. The aim of this study was to review the current literature, examining the role of 18-fluorodeoxyglucose (FDG) positron emission tomography (PET) in IPMN management. An extensive literature review was conducted according to the 2009 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and 10 articles were analyzed in detail, focusing on the value of PET as opposed to other standard imaging criteria. Data were retrieved on 419 patients. The 18-FDG-PET proved more sensitive, specific, and accurate than the ICG criteria in detecting malignant IPMNs (reaching 80%, 95%, and 87% vs. 67%, 58%, and 63%, respectively). Metabolic assessments may be used as an additional tool for the appropriate management of patients with doubtful imaging findings

    Permanent trawl fishery closures in the Mediterranean Sea: An effective management strategy?

    Get PDF
    Since June 2010 the Italian government prohibited the trawling activity within three nautical miles from the coast or within the 50 m isobath. This decision was expected to have a great impact on trawl fishing activities, but at the moment no real assessment of the effects on catches and possible ecological implications has been undertaken. In order to fill this gap, an assessment on the North Western Adriatic Sea coast has been performed. Landings per Unit of Effort (kilograms per boat per day) for each trawling fleet segment have been analysed, by comparing on a monthly basis the before (2007-2009) and after ban (2011-2013) period. The comparison was carried out considering total landings and the six main species targeted inside the three miles area (sand smelt, cuttlefish, red mullet, sole, turbot, and mantis shrimp). Within a general reduction of total landings, a differential effect based on the analysed metiers was detected, with small trawlers being more negatively affected than the large and rapido ones, which showed, for some species, positive impacts. From an ecological point of view, though, no positive overall effects were detected, probably due to the fact that the adopted measure is not sufficient to reduce the overexploitation. In any case, all this is affecting the structure of the small-scale fishery in the area, since small trawlers are changing métier, moving towards the artisanal fishery, with deep impacts on the very coastal area that the trawling ban was designated to protect, compromising all possible benefitsSince June 2010 the Italian government prohibited the trawling activity within three nautical miles from the coast or within the 50 m isobath. This decision was expected to have a great impact on trawl fishing activities, but at the moment no real assessment of the effects on catches and possible ecological implications has been undertaken. In order to fill this gap, an assessment on the North Western Adriatic Sea coast has been performed. Landings per Unit of Effort (kilograms per boat per day) for each trawling fleet segment have been analysed, by comparing on a monthly basis the before (2007-2009) and after ban (2011-2013) period. The comparison was carried out considering total landings and the six main species targeted inside the three miles area (sand smelt, cuttlefish, red mullet, sole, turbot, and mantis shrimp). Within a general reduction of total landings, a differential effect based on the analysed m tiers was detected, with small trawlers being more negatively affected than the large and rapido ones, which showed, for some species, positive impacts. From an ecological point of view, though, no positive overall effects were detected, probably due to the fact that the adopted measure is not sufficient to reduce the overexploitation. In any case, all this is affecting the structure of the small-scale fishery in the area, since small trawlers are changing m tier, moving towards the artisanal fishery, with deep impacts on the very coastal area that the trawling ban was designated to protect, compromising all possible benefits. (C) 2015 Elsevier Ltd. All rights reserved

    Whole-body low-dose CT recognizes two distinct patterns of lytic lesions in multiple myeloma patients with different disease metabolism at PET/MRI

    Get PDF
    We evaluated differences in density and 18F-FDG PET/MRI features of lytic bone lesions (LBLs) identified by whole-body low-dose CT (WB-LDCT) in patients affected by newly diagnosed multiple myeloma (MM). In 18 MM patients, 135 unequivocal LBLs identified by WB-LDCT were characterized for inner density (negative or positive Hounsfield unit (HU)), where negative density (HU\u2009<\u20090) characterizes normal yellow marrow whereas positive HU correlates with tissue-like infiltrative pattern. The same LBLs were analyzed by 18F-FDG PET/DWI-MRI, registering DWI signal with ADC and SUV max values. According to HU, 35 lesions had a negative density (-\u200956.94\u2009\ub1\u200931.87 HU) while 100 lesions presented positive density (44.87\u2009\ub1\u200923.89 HU). In seven patients, only positive HU LBLs were demonstrated whereas in eight patients, both positive and negative HU LBLs were detected. Intriguingly, in three patients (16%), only negative HU LBLs were shown. At 18F-FDG PET/DWI-MRI analysis, negative HU LBLs presented low ADC values (360.69\u2009\ub1\u2009154.38\u2009 7\u200910-6 mm2/s) and low SUV max values (1.69\u2009\ub1\u20090.56), consistent with fatty marrow, whereas positive HU LBLs showed an infiltrative pattern, characterized by higher ADC (mean 868.46\u2009\ub1\u2009207.67\u2009 7\u200910-6 mm2/s) and SUV max (mean 5.04\u2009\ub1\u20091.94) values. Surprisingly, histology of negative HU LBLs documented infiltration by neoplastic plasma cells scattered among adipocytes. In conclusion, two different patterns of LBLs were detected by WB-LDCT in MM patients. Both types of lesions were indicative for active disease, although only positive HU LBL were captured by 18F-FDG PET/DWI-MRI imaging, indicating that WB-LDCT adds specific information

    Combination of searches for heavy resonances decaying to WW, WZ, ZZ, WH, and ZH boson pairs in proton–proton collisions at s\sqrt{s} = 8 and 13 TeV

    Full text link
    A statistical combination of searches is presented for massive resonances decaying to WW, WZ, ZZ, WH, and ZH boson pairs in proton–proton collision data collected by the CMS experiment at the LHC. The data were taken at centre-of-mass energies of 8 and 13 TeV, corresponding to respective integrated luminosities of 19.7 and up to 2.7 fb−1fb^{−1}. The results are interpreted in the context of heavy vector triplet and singlet models that mimic properties of composite-Higgs models predicting W′ and Z′ bosons decaying to WZ, WW, WH, and ZH bosons. A model with a bulk graviton that decays into WW and ZZ is also considered. This is the first combined search for WW, WZ, WH, and ZH resonances and yields lower limits on masses at 95% confidence level for W′ and Z′ singlets at 2.3 TeV, and for a triplet at 2.4 TeV. The limits on the production cross section of a narrow bulk graviton resonance with the curvature scale of the warped extra dimension k~=0.5\tilde{k}=0.5, in the mass range of 0.6 to 4.0 TeV, are the most stringent published to date

    Search for supersymmetry in pp collisions at s\sqrt{s} = 13 tev in the single-lepton final state using the sum of masses of large-radius jets

    Full text link
    Results are reported from a search for supersymmetric particles in proton-proton collisions in the final state with a single lepton, multiple jets, including at least one b-tagged jet, and large missing transverse momentum. The search uses a sample of proton-proton collision data at s\sqrt{s} = 13 TeV recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9  fb−1fb^{−1}. The observed event yields in the signal regions are consistent with those expected from standard model backgrounds. The results are interpreted in the context of simplified models of supersymmetry involving gluino pair production, with gluino decay into either on- or off-mass-shell top squarks. Assuming that the top squarks decay into a top quark plus a stable, weakly interacting neutralino, scenarios with gluino masses up to about 1.9 TeV are excluded at 95% confidence level for neutralino masses up to about 1 TeV

    Search for dark matter produced in association with heavy-flavor quark pairs in proton-proton collisions at s\sqrt{s} = 13 TeV

    Full text link
    A search is presented for an excess of events with heavy-flavor quark pairs (tt‾t\overline{t} and bb‾b\overline{b}) and a large imbalance in transverse momentum in data from proton–proton collisions at a center-of-mass energy of 13TeV. The data correspond to an integrated luminosity of 2.2 fb−1fb^{−1} collected with the CMS detector at the CERN LHC. No deviations are observed with respect to standard model predictions. The results are used in the first interpretation of dark matter production in tt‾t\overline{t} and bb‾b\overline{b} final states in a simplified model. This analysis is also the first to perform a statistical combination of searches for dark matter produced with different heavy-flavor final states. The combination provides exclusions that are stronger than those achieved with individual heavy-flavor final states

    The CMS trigger system

    Full text link
    This paper describes the CMS trigger system and its performance during Run 1 of the LHC. The trigger system consists of two levels designed to select events of potential physics interest from a GHz (MHz) interaction rate of proton-proton (heavy ion) collisions. The first level of the trigger is implemented in hardware, and selects events containing detector signals consistent with an electron, photon, muon, Ï„ lepton, jet, or missing transverse energy. A programmable menu of up to 128 object-based algorithms is used to select events for subsequent processing. The trigger thresholds are adjusted to the LHC instantaneous luminosity during data taking in order to restrict the output rate to 100 kHz, the upper limit imposed by the CMS readout electronics. The second level, implemented in software, further refines the purity of the output stream, selecting an average rate of 400 Hz for offline event storage. The objectives, strategy and performance of the trigger system during the LHC Run 1 are described
    • …
    corecore