Displaying publications 81 - 100 of 365 in total

Abstract:
Sort:
  1. Aerobic oxidation of 5-hydroxymethylfurfural into 2,5-diformylfuran using manganese dioxide with different crystal structures: A comparative study
    Lin KA, Oh WD, Zheng MW, Kwon E, Lee J, Lin JY, et al.
    J Colloid Interface Sci, 2021 Jun 15;592:416-429.
    PMID: 33691223 DOI: 10.1016/j.jcis.2021.02.030
    Aerobic oxidation of 5-Hydroxymethylfurfural (HMF) to 2,5-Diformylfuran (DFF) using O2 gas represents a sustainable approach for valorization of lignocellulosic compounds. As manganese dioxide (MnO2) is validated as a useful oxidation catalyst and many crystalline forms of MnO2 exist, it is critical to explore how the crystalline structures of MnO2 influence their physical/chemical properties, which, in turn, determine catalytic activities of MnO2 crystals for HMF oxidation to DFF. In particular, six MnO2 crystals, α-MnO2, β-MnO2, γ-MnO2, δ-MnO2, ε-MnO2, and λ-MnO2 are prepared and investigated for their catalytic activities for HMF oxidation to DFF. With different morphologies and crystalline structures, these MnO2 crystals possess very distinct surficial chemistry, redox capabilities, and textural properties, making these MnO2 exhibit different catalytic activities towards HMF conversion. Especially, β-MnO2 can produce much higher DFF per surface area than other MnO2 crystals. β-MnO2 could achieve the highest CHMF = 99% and YDFF = 97%, which are much higher than the reported values in literature, possibly because the surficial reactivity of β-MnO2 appears to be highest in comparison to other MnO2 crystals. Especially, β-MnO2 could exhibit YDFF > 90% over 5 cycles of reusability test, and maintain its crystalline structure, revealing its advantageous feature for aerobic oxidation of HMF to DFF. Through this study, the relationship between morphology, surface chemistry, and catalytic activity of MnO2 with different crystal forms is elucidated for providing scientific insights into design, application and development of MnO2-based materials for aerobic oxidation of bio-derived molecules to value-added products.
  2. Metal-complexed covalent organic frameworks derived N-doped carbon nanobubble-embedded cobalt nanoparticle as a magnetic and efficient catalyst for oxone activation
    Nguyen HT, Lee J, Kwon E, Lisak G, Thanh BX, Oh WD, et al.
    J Colloid Interface Sci, 2021 Jun;591:161-172.
    PMID: 33601102 DOI: 10.1016/j.jcis.2021.01.108
    While Cobalt nanoparticles (Co NPs) are useful for catalytic Oxone activation, it is more advantageous to embed/immobilize Co NPs on nitrogen-doped carbon substrates to provide synergy for enhancing catalytic performance. Herein, this study proposes to fabricate such a composite by utilizing covalent organic frameworks (COF) as a precursor. Through complexation of COF with Co, a stable product of Co-complexed COF (Co-COF) can be synthesized. This Co-COF is further converted through pyrolysis to N-doped carbon in which cobaltic NPs are embedded. Owing to its well-defined structures of Co-COF, the pyrolysis process transforms COF into N-doped carbon with a bubble-like morphology. Such Co NP-embedded N-doped carbon nanobubbles (CoCNB) with pores, magnetism and Co, shall be a promising catalyst. Thus, CoCNB shows a much stronger catalytic activity than commercial Co3O4 NPs to activate Oxone to degrade toxic Amaranth dye (AMD). CoCNB-activated Oxone also achieves a significantly lower Ea value of AMD degradation (i.e., 27.9 kJ/mol) than reported Ea values in previous literatures. Besides, CoCNB is still effective for complete elimination of AMD in the presence of high-concentration NaCl and surfactants, and CoCNB is also reusable over five consecutive cycles.
  3. Heterojunction photocatalysts for artificial nitrogen fixation: fundamentals, latest advances and future perspectives
    Lee J, Tan LL, Chai SP
    Nanoscale, 2021 Apr 21;13(15):7011-7033.
    PMID: 33889914 DOI: 10.1039/d1nr00783a
    As an indispensable energy source, ammonia plays an essential role in agriculture and various industries. Given that the current ammonia production is still dominated by the energy-intensive and high carbon footprint Haber-Bosch process, photocatalytic nitrogen fixation represents a low-energy consuming and sustainable approach to generate ammonia. Heterostructured photocatalysts are hybrid materials composed of semiconductor materials containing interfaces that make full use of the unique superiorities of the constituents and synergistic effects between them. These promising photocatalysts have superior performances and substantial potential in photocatalytic reduction of nitrogen. In this review, a wide spectrum of recently developed heterostructured photocatalysts for nitrogen fixation to ammonia are evaluated. The fundamentals of solar-to-ammonia conversion, basic principles of various heterojunction photocatalysts and modification strategies are systematically reviewed. Finally, a brief summary and perspectives on the ongoing challenges and directions for future development of nitrogen photofixation catalysts are also provided.
  4. Fulltext Towards complete and error-free genome assemblies of all vertebrate species
    Rhie A, McCarthy SA, Fedrigo O, Damas J, Formenti G, Koren S, et al.
    Nature, 2021 Apr;592(7856):737-746.
    PMID: 33911273 DOI: 10.1038/s41586-021-03451-0
    High-quality and complete reference genome assemblies are fundamental for the application of genomics to biology, disease, and biodiversity conservation. However, such assemblies are available for only a few non-microbial species1-4. To address this issue, the international Genome 10K (G10K) consortium5,6 has worked over a five-year period to evaluate and develop cost-effective methods for assembling highly accurate and nearly complete reference genomes. Here we present lessons learned from generating assemblies for 16 species that represent six major vertebrate lineages. We confirm that long-read sequencing technologies are essential for maximizing genome quality, and that unresolved complex repeats and haplotype heterozygosity are major sources of assembly error when not handled correctly. Our assemblies correct substantial errors, add missing sequence in some of the best historical reference genomes, and reveal biological discoveries. These include the identification of many false gene duplications, increases in gene sizes, chromosome rearrangements that are specific to lineages, a repeated independent chromosome breakpoint in bat genomes, and a canonical GC-rich pattern in protein-coding genes and their regulatory regions. Adopting these lessons, we have embarked on the Vertebrate Genomes Project (VGP), an international effort to generate high-quality, complete reference genomes for all of the roughly 70,000 extant vertebrate species and to help to enable a new era of discovery across the life sciences.
  5. Effects of drying methods on oxidative stability of roselle seed oil (Hibiscus Sabdariffa): an optimization approach
    Jahurul MHA, Shian OK, Sharifudin MS, Hasmadi M, Lee JS, Mansoor AH, et al.
    J Food Sci Technol, 2021 Mar;58(3):902-910.
    PMID: 33678873 DOI: 10.1007/s13197-020-04604-1
    The objective of this study was to optimize the extraction of oil from pre-dried roselle seeds using response surface methodology (RSM). We also determined the oxidative stability of oil extracted from oven and freeze-dried roselle seed in terms of iodine value (IV), free fatty acid (FFA) value, peroxide value (PV), P-anisidine and total oxidation values (TOTOX value). The RSM was designated based on the central composite design with the usage of three optimum parameters ranged from 8 to 16 g of sample weight, 250-350 mL of solvent volume, and 6-8 h of extraction time. The highest oil yielded from roselle seed using the optimization process was 22.11% with the parameters at sample weight of 14.4 g, solvent volume of 329.70 mL, and extraction time of 7.6 h. Besides, the oil extracted from the oven dried roselle seed had the values of 89.04, 2.11, 4.13, 3.76 and 12.03 for IV, FFA, PV, P-anisidine, and TOTOX values, respectively. While for the oil extracted from freeze-dried roselle seed showed IV of 90.31, FFA of 1.64, PV of 2.47, P-anisidine value of 3.48, and TOTOX value of 8.42. PV and TOTOX values showed significant differences whereas; IV, FFA, and P-anisidine values showed no significant differences between the oven and freeze-dried roselle seed oils.
  6. Evaluation of potential feedstock for biogas production via anaerobic digestion in Malaysia: kinetic studies and economics analysis
    Lim YF, Chan YJ, Abakr YA, Sethu V, Selvarajoo A, Singh A, et al.
    Environ Technol, 2021 Feb 18.
    PMID: 33502966 DOI: 10.1080/09593330.2021.1882587
    As the population increases, energy demands continue to rise rapidly. In order to satisfy this increasing energy demand, biogas offers a potential alternative. Biogas is economically viable to be produced through anaerobic digestion (AD) from various biomass feedstocks that are readily available in Malaysia, such as food waste (FW), palm oil mill effluent (POME), garden waste (GW), landfill, sewage sludge (SS) and animal manure. This paper aims to determine the potential feedstocks for biogas production via AD based on their characteristics, methane yield, kinetic studies and economic analysis. POME and FW show the highest methane yield with biogas yields up to 0.50 L/g VS while the lowest is 0.12 L/g VS by landfill leachate. Kinetic study shows that modified Gompertz model fits most of the feedstock with R 2 up to 1 indicating that this model can be used for estimating treatment efficiencies of full-scale reactors and performing scale-up analysis. The economic analysis shows that POME has the shortest payback period (PBP), highest internal rate of return (IRR) and net present value (NPV). However, it has already been well explored, with 93% of biogas plants in Malaysia using POME as feedstock. The FW generation rate in Malaysia is approximately 15,000 tonnes per day, at the same time FW as the second place shows potential to have a PBP of 5.4 years and 13.3% IRR, which is close to the results achieved with POME. This makes FW suitable to be used as the feedstock for biogas production.
  7. Fulltext Nocardia kroppenstedtii: a rare pathogen isolated from the spinal vertebral abscess of a patient on long-term immunosuppressive therapy
    Tay ST, Wong PL, Chiu CK, Tang SN, Lee JL, Hamdan NW, et al.
    Eur Rev Med Pharmacol Sci, 2021 01;25(2):605-608.
    PMID: 33577013 DOI: 10.26355/eurrev_202101_24618
    OBJECTIVE: Nocardia kroppenstedtii was isolated from the spinal vertebral abscess of a 78-year-old patient presenting with mid-thoracic pain and bilateral lower limb weakness and numbness. The patient was on long-term immunosuppressive therapy with steroids for underlying autoimmune hemolytic anemia. Investigations showed a T5 pathological fracture and vertebra plana with the erosion of the superior and inferior endplates. There was evidence of paraspinal collection from the T4-T6 vertebrae with an extension into the spinal canal. Analysis of Nocardia 16S rRNA (99.9%, 1395/1396 nt) and secA1 gene (99.5%, 429/431 nt) fragments showed the highest sequence similarity with Nocardia kroppenstedtii type strain (DQ157924), and next with Nocardia farcinica (Z36936). The patient was treated with intravenous carbapenem and oral trimethoprim-sulfamethoxazole for four weeks, followed by another six months of oral trimethoprim-sulfamethoxazole. Despite the improvement of neurological deficits, the patient required assistive devices to ambulate at discharge. This study reports the first isolation of N. kroppenstedtii from the spinal vertebral abscess of a patient from Asia. Infections caused by N. kroppenstedtii may be underdiagnosed as the bacterium can be misidentified as N. farcinica in the absence of molecular tests in the clinical laboratory.
  8. Fulltext Development and validation of HERWIG 7 tunes from CMS underlying-event measurements
    Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Bergauer T, Dragicevic M, et al.
    Eur Phys J C Part Fields, 2021;81(4):312.
    PMID: 34727148 DOI: 10.1140/epjc/s10052-021-08949-5
    This paper presents new sets of parameters ("tunes") for the underlying-event model of the H E R W I G 7 event generator. These parameters control the description of multiple-parton interactions (MPI) and colour reconnection in H E R W I G 7 , and are obtained from a fit to minimum-bias data collected by the CMS experiment at s = 0.9 , 7, and 13 Te . The tunes are based on the NNPDF 3.1 next-to-next-to-leading-order parton distribution function (PDF) set for the parton shower, and either a leading-order or next-to-next-to-leading-order PDF set for the simulation of MPI and the beam remnants. Predictions utilizing the tunes are produced for event shape observables in electron-positron collisions, and for minimum-bias, inclusive jet, top quark pair, and Z and W boson events in proton-proton collisions, and are compared with data. Each of the new tunes describes the data at a reasonable level, and the tunes using a leading-order PDF for the simulation of MPI provide the best description of the data.
  9. Fulltext MUSiC: a model-unspecific search for new physics in proton-proton collisions at s = 13 TeV
    CMS Collaboration, Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Bergauer T, et al.
    Eur Phys J C Part Fields, 2021;81(7):629.
    PMID: 34727144 DOI: 10.1140/epjc/s10052-021-09236-z
    Results of the Model Unspecific Search in CMS (MUSiC), using proton-proton collision data recorded at the LHC at a centre-of-mass energy of 13 TeV , corresponding to an integrated luminosity of 35.9 fb - 1 , are presented. The MUSiC analysis searches for anomalies that could be signatures of physics beyond the standard model. The analysis is based on the comparison of observed data with the standard model prediction, as determined from simulation, in several hundred final states and multiple kinematic distributions. Events containing at least one electron or muon are classified based on their final state topology, and an automated search algorithm surveys the observed data for deviations from the prediction. The sensitivity of the search is validated using multiple methods. No significant deviations from the predictions have been observed. For a wide range of final state topologies, agreement is found between the data and the standard model simulation. This analysis complements dedicated search analyses by significantly expanding the range of final states covered using a model independent approach with the largest data set to date to probe phase space regions beyond the reach of previous general searches.
  10. Fulltext Combined searches for the production of supersymmetric top quark partners in proton-proton collisions at s = 13 Te
    Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, Dragicevic M, et al.
    Eur Phys J C Part Fields, 2021;81(11):970.
    PMID: 34793584 DOI: 10.1140/epjc/s10052-021-09721-5
    A combination of searches for top squark pair production using proton-proton collision data at a center-of-mass energy of 13 Te at the CERN LHC, corresponding to an integrated luminosity of 137 fb - 1 collected by the CMS experiment, is presented. Signatures with at least 2 jets and large missing transverse momentum are categorized into events with 0, 1, or 2 leptons. New results for regions of parameter space where the kinematical properties of top squark pair production and top quark pair production are very similar are presented. Depending on the model, the combined result excludes a top squark mass up to 1325 Ge for a massless neutralino, and a neutralino mass up to 700 Ge for a top squark mass of 1150 Ge . Top squarks with masses from 145 to 295 Ge , for neutralino masses from 0 to 100 Ge , with a mass difference between the top squark and the neutralino in a window of 30 Ge around the mass of the top quark, are excluded for the first time with CMS data. The results of theses searches are also interpreted in an alternative signal model of dark matter production via a spin-0 mediator in association with a top quark pair. Upper limits are set on the cross section for mediator particle masses of up to 420 Ge .
  11. Fulltext Precision luminosity measurement in proton-proton collisions at s = 13 TeV in 2015 and 2016 at CMS
    Sirunyan AM, Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, et al.
    Eur Phys J C Part Fields, 2021;81(9):800.
    PMID: 34781320 DOI: 10.1140/epjc/s10052-021-09538-2
    The measurement of the luminosity recorded by the CMS detector installed at LHC interaction point 5, using proton-proton collisions at s = 13 TeV in 2015 and 2016, is reported. The absolute luminosity scale is measured for individual bunch crossings using beam-separation scans (the van der Meer method), with a relative precision of 1.3 and 1.0% in 2015 and 2016, respectively. The dominant sources of uncertainty are related to residual differences between the measured beam positions and the ones provided by the operational settings of the LHC magnets, the factorizability of the proton bunch spatial density functions in the coordinates transverse to the beam direction, and the modeling of the effect of electromagnetic interactions among protons in the colliding bunches. When applying the van der Meer calibration to the entire run periods, the integrated luminosities when CMS was fully operational are 2.27 and 36.3 fb - 1 in 2015 and 2016, with a relative precision of 1.6 and 1.2%, respectively. These are among the most precise luminosity measurements at bunched-beam hadron colliders.
  12. Fulltext Measurements of angular distance and momentum ratio distributions in three-jet and Z + two-jet final states in pp collisions
    Sirunyan AM, Tumasyan A, Adam W, Bergauer T, Dragicevic M, Erö J, et al.
    Eur Phys J C Part Fields, 2021;81(9):852.
    PMID: 34727147 DOI: 10.1140/epjc/s10052-021-09570-2
    Collinear (small-angle) and large-angle, as well as soft and hard radiations are investigated in three-jet and Z  + two-jet events collected in proton-proton collisions at the LHC. The normalized production cross sections are measured as a function of the ratio of transverse momenta of two jets and their angular separation. The measurements in the three-jet and Z  + two-jet events are based on data collected at a center-of-mass energy of 8 TeV , corresponding to an integrated luminosity of 19.8 fb - 1 . The Z  + two-jet events are reconstructed in the dimuon decay channel of the Z  boson. The three-jet measurement is extended to include s = 13 TeV data corresponding to an integrated luminosity of 2.3 fb - 1 . The results are compared to predictions from event generators that include parton showers, multiple parton interactions, and hadronization. The collinear and soft regions are in general well described by parton showers, whereas the regions of large angular separation are often best described by calculations using higher-order matrix elements.
  13. Fulltext Search for top squark pair production using dilepton final states in pp collision data collected at s = 13 TeV
    Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Bergauer T, Dragicevic M, et al.
    Eur Phys J C Part Fields, 2021;81(1):3.
    PMID: 33465186 DOI: 10.1140/epjc/s10052-020-08701-5
    A search is presented for supersymmetric partners of the top quark (top squarks) in final states with two oppositely charged leptons (electrons or muons), jets identified as originating from b quarks, and missing transverse momentum. The search uses data from proton-proton collisions at s = 13 TeV collected with the CMS detector, corresponding to an integrated luminosity of 137 fb - 1 . Hypothetical signal events are efficiently separated from the dominant top quark pair production background with requirements on the significance of the missing transverse momentum and on transverse mass variables. No significant deviation is observed from the expected background. Exclusion limits are set in the context of simplified supersymmetric models with pair-produced lightest top squarks. For top squarks decaying exclusively to a top quark and a lightest neutralino, lower limits are placed at 95 % confidence level on the masses of the top squark and the neutralino up to 925 and 450 GeV , respectively. If the decay proceeds via an intermediate chargino, the corresponding lower limits on the mass of the lightest top squark are set up to 850 GeV for neutralino masses below 420 GeV . For top squarks undergoing a cascade decay through charginos and sleptons, the mass limits reach up to 1.4 TeV and 900 GeV respectively for the top squark and the lightest neutralino.
  14. Fulltext Search for dark matter produced in association with a leptonically decaying Z boson in proton-proton collisions at s = 13 Te
    Sirunyan AM, CMS Collaboration, Tumasyan A, Adam W, Bergauer T, Dragicevic M, et al.
    Eur Phys J C Part Fields, 2021;81(1):13.
    PMID: 33493254 DOI: 10.1140/epjc/s10052-020-08739-5
    A search for dark matter particles is performed using events with a Z boson candidate and large missing transverse momentum. The analysis is based on proton-proton collision data at a center-of-mass energy of 13 Te , collected by the CMS experiment at the LHC in 2016-2018, corresponding to an integrated luminosity of 137 fb - 1 . The search uses the decay channels Z → e e and Z → μ μ . No significant excess of events is observed over the background expected from the standard model. Limits are set on dark matter particle production in the context of simplified models with vector, axial-vector, scalar, and pseudoscalar mediators, as well as on a two-Higgs-doublet model with an additional pseudoscalar mediator. In addition, limits are provided for spin-dependent and spin-independent scattering cross sections and are compared to those from direct-detection experiments. The results are also interpreted in the context of models of invisible Higgs boson decays, unparticles, and large extra dimensions.
  15. Fulltext Measurements of production cross sections of the Higgs boson in the four-lepton final state in proton-proton collisions at s = 13 TeV
    CMS Collaboration, Sirunyan AM, Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, et al.
    Eur Phys J C Part Fields, 2021;81(6):488.
    PMID: 34727143 DOI: 10.1140/epjc/s10052-021-09200-x
    Production cross sections of the Higgs boson are measured in the H → Z Z → 4 ℓ ( ℓ = e , μ ) decay channel. A data sample of proton-proton collisions at a center-of-mass energy of 13 TeV , collected by the CMS detector at the LHC and corresponding to an integrated luminosity of 137 fb - 1 is used. The signal strength modifier μ , defined as the ratio of the Higgs boson production rate in the 4 ℓ channel to the standard model (SM) expectation, is measured to be μ = 0.94 ± 0.07 (stat) - 0.08 + 0.09 (syst) at a fixed value of m H = 125.38 GeV . The signal strength modifiers for the individual Higgs boson production modes are also reported. The inclusive fiducial cross section for the H → 4 ℓ process is measured to be 2 . 84 - 0.22 + 0.23 (stat) - 0.21 + 0.26 (syst) fb , which is compatible with the SM prediction of 2.84 ± 0.15 fb for the same fiducial region. Differential cross sections as a function of the transverse momentum and rapidity of the Higgs boson, the number of associated jets, and the transverse momentum of the leading associated jet are measured. A new set of cross section measurements in mutually exclusive categories targeted to identify production mechanisms and kinematical features of the events is presented. The results are in agreement with the SM predictions.
  16. Fulltext Carica papaya L. Leaf: A Systematic Scoping Review on Biological Safety and Herb-Drug Interactions
    Lim XY, Chan JSW, Japri N, Lee JC, Tan TYC
    Evid Based Complement Alternat Med, 2021;2021:5511221.
    PMID: 34040647 DOI: 10.1155/2021/5511221
    INTRODUCTION: The Carica papaya L. leaf is gaining interest as a potential therapeutic agent for alleviating dengue- and non-dengue-associated thrombocytopaenia. In that regard, safety considerations are as important as efficacy potential. The safety evaluation of botanical products for human use is complicated by variable formulations, complex phytochemical composition, and extrinsic toxicants. This review aimed to systematically collate related safety clinical and preclinical data, as well as reports on herb-drug interactions of C. papaya leaf consumption.

    METHODS: A systematic search using predetermined keywords on electronic databases (MEDLINE, Cochrane Library Central, LILACS, and Web of Science) and grey literature was conducted. Relevant clinical and preclinical studies were identified, screened, and analysed to present an overall safety profile of C. papaya leaf consumption.

    RESULTS: A total of 41 articles were included (23 clinical, 5 ongoing trials, and 13 preclinical) for descriptive analysis on study characteristics, adverse reactions, toxicity findings, and herb-drug interactions, from which 13 randomised controlled and quasiexperimental trials were further assessed for risk of bias and reporting quality. Overall, C. papaya leaf consumption (in the form of juice and standardised aqueous extract) was well tolerated by adult humans for short durations (

  17. Fulltext Measurements of p p → Z Z production cross sections and constraints on anomalous triple gauge couplings at s = 13 TeV
    Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Bergauer T, Dragicevic M, et al.
    Eur Phys J C Part Fields, 2021;81(3):200.
    PMID: 33750993 DOI: 10.1140/epjc/s10052-020-08817-8
    The production of Z boson pairs in proton-proton ( p p ) collisions, p p → ( Z / γ ∗ ) ( Z / γ ∗ ) → 2 ℓ 2 ℓ ' , where ℓ , ℓ ' = e or μ , is studied at a center-of-mass energy of 13 TeV with the CMS detector at the CERN LHC. The data sample corresponds to an integrated luminosity of 137 fb - 1 , collected during 2016-2018. The Z Z production cross section, σ tot ( p p → Z Z ) = 17.4 ± 0.3 (stat) ± 0.5 (syst) ± 0.4 (theo) ± 0.3 (lumi) pb , measured for events with two pairs of opposite-sign, same-flavor leptons produced in the mass region 60 < m ℓ + ℓ - < 120 GeV is consistent with standard model predictions. Differential cross sections are also measured and agree with theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous Z Z Z and Z Z γ couplings.
  18. Fulltext Measurement of the Higgs boson production rate in association with top quarks in final states with electrons, muons, and hadronically decaying tau leptons at s = 13 TeV
    Sirunyan AM, Tumasyan A, Adam W, Bergauer T, Dragicevic M, Erö J, et al.
    Eur Phys J C Part Fields, 2021;81(4):378.
    PMID: 34727142 DOI: 10.1140/epjc/s10052-021-09014-x
    The rate for Higgs ( H ) bosons production in association with either one ( t H ) or two ( t t ¯ H ) top quarks is measured in final states containing multiple electrons, muons, or tau leptons decaying to hadrons and a neutrino, using proton-proton collisions recorded at a center-of-mass energy of 13 TeV by the CMS experiment. The analyzed data correspond to an integrated luminosity of 137 fb - 1 . The analysis is aimed at events that contain H → W W , H → τ τ , or H → Z Z decays and each of the top quark(s) decays either to lepton+jets or all-jet channels. Sensitivity to signal is maximized by including ten signatures in the analysis, depending on the lepton multiplicity. The separation among t H , t t ¯ H , and the backgrounds is enhanced through machine-learning techniques and matrix-element methods. The measured production rates for the t t ¯ H and t H signals correspond to 0.92 ± 0.19 (stat) - 0.13 + 0.17 (syst) and 5.7 ± 2.7 (stat) ± 3.0 (syst) of their respective standard model (SM) expectations. The corresponding observed (expected) significance amounts to 4.7 (5.2) standard deviations for t t ¯ H , and to 1.4 (0.3) for t H production. Assuming that the Higgs boson coupling to the tau lepton is equal in strength to its expectation in the SM, the coupling y t of the Higgs boson to the top quark divided by its SM expectation, κ t = y t / y t SM , is constrained to be within - 0.9 < κ t < - 0.7 or 0.7 < κ t < 1.1 , at 95% confidence level. This result is the most sensitive measurement of the t t ¯ H production rate to date.
  19. Fulltext Search for a heavy vector resonance decaying to a Z  boson and a Higgs boson in proton-proton collisions at s = 13 Te
    Sirunyan AM, Tumasyan A, Adam W, Bergauer T, Dragicevic M, Erö J, et al.
    Eur Phys J C Part Fields, 2021;81(8):688.
    PMID: 34780582 DOI: 10.1140/epjc/s10052-021-09348-6
    A search is presented for a heavy vector resonance decaying into a Z boson and the standard model Higgs boson, where the Z boson is identified through its leptonic decays to electrons, muons, or neutrinos, and the Higgs boson is identified through its hadronic decays. The search is performed in a Lorentz-boosted regime and is based on data collected from 2016 to 2018 at the CERN LHC, corresponding to an integrated luminosity of 137 fb - 1 . Upper limits are derived on the production of a narrow heavy resonance Z ' , and a mass below 3.5 and 3.7 Te is excluded at 95% confidence level in models where the heavy vector boson couples predominantly to fermions and to bosons, respectively. These are the most stringent limits placed on the Heavy Vector Triplet Z ' model to date. If the heavy vector boson couples exclusively to standard model bosons, upper limits on the product of the cross section and branching fraction are set between 23 and 0.3 fb for a Z ' mass between 0.8 and 4.6 Te , respectively. This is the first limit set on a heavy vector boson coupling exclusively to standard model bosons in its production and decay.
  20. Fulltext Search for charged Higgs bosons produced in vector boson fusion processes and decaying into vector boson pairs in proton-proton collisions at s = 13 TeV
    Sirunyan AM, Tumasyan A, Adam W, Andrejkovic JW, Bergauer T, Chatterjee S, et al.
    Eur Phys J C Part Fields, 2021;81(8):723.
    PMID: 34780581 DOI: 10.1140/epjc/s10052-021-09472-3
    A search for charged Higgs bosons produced in vector boson fusion processes and decaying into vector bosons, using proton-proton collisions at s = 13 TeV at the LHC, is reported. The data sample corresponds to an integrated luminosity of 137 fb - 1 collected with the CMS detector. Events are selected by requiring two or three electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass. No excess of events with respect to the standard model background predictions is observed. Model independent upper limits at 95% confidence level are reported on the product of the cross section and branching fraction for vector boson fusion production of charged Higgs bosons as a function of mass, from 200 to 3000 GeV . The results are interpreted in the context of the Georgi-Machacek model.
Related Terms
Filters
Contact Us

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links