Displaying publications 1 - 20 of 209 in total

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  1. Ibrahim Z, Amin MF, Yahya A, Aris A, Umor NA, Muda K, et al.
    Water Sci Technol, 2009;60(3):683-8.
    PMID: 19657163 DOI: 10.2166/wst.2009.440
    Microbial flocs formed from raw textile wastewater in a prototype Aerobic Biofilm Reactor (ABR) system were characterised and studied for their potential use in the treatment of textile wastewater. After 90-100 days of operation, microbial flocs of loose irregular structures were obtained from the reactor with good settling velocity of 33 m/h and sludge volume index (SVI) of 48.2 mL/g. Molecular analysis of the flocs using PCR-amplified 16S rDNA sequence showed 98% homology to those of Bacillus sp, Paenibacillus sp and Acromobacter sp. Detection of Ca(2+)(131 mg/g) and Fe(2+)(131 mg/g) using atomic absorption spectrometer might be implicated with the flocs formation. In addition, presence of Co(2+) and Ni(2+) were indicative of the flocs ability to accumulate at least a fraction of the metals' present in the wastewater. When the flocs were used for the treatment of raw textile wastewater, they showed good removal of COD and colour about 55% and 70% respectively, indicating their potential application.
  2. Ibrahim Z, Amin MF, Yahya A, Aris A, Muda K
    Water Sci Technol, 2010;61(5):1279-88.
    PMID: 20220250 DOI: 10.2166/wst.2010.021
    Textile wastewater, one of the most polluted industrial effluents, generally contains substantial amount of dyes and chemicals that will cause increase in the COD, colour and toxicity of receiving water bodies if not properly treated. Current treatment methods include chemical and biological processes; the efficiency of the biological treatment method however, remains uncertain since the discharged effluent is still highly coloured. In this study, granules consisting mixed culture of decolourising bacteria were developed and the physical and morphological characteristics were determined. After the sixth week of development, the granules were 3-10 mm in diameter, having good settling property with settling velocity of 70 m/h, sludge volume index (SVI) of 90 to 130 mL/g, integrity coefficient of 3.7, and density of 66 g/l. Their abilities to treat sterilised raw textile wastewater were evaluated based on the removal efficiencies of COD (initial ranging from 200 to 3,000 mg/L), colour (initial ranging from 450 to 2000 ADMI) of sterilised raw textile wastewater with pH from 6.8 to 9.4. Using a sequential anaerobic-aerobic treatment cycle with hydraulic retention time (HRT) of 24 h, maximum removal of colour and COD achieved was 90% and 80%, respectively.
  3. Muda K, Aris A, Salim MR, Ibrahim Z, van Loosdrecht MC, Ahmad A, et al.
    Water Res, 2011 Oct 15;45(16):4711-21.
    PMID: 21714982 DOI: 10.1016/j.watres.2011.05.012
    The physical characteristics, microbial activities and kinetic properties of the granular sludge biomass were investigated under the influence of different hydraulic retention times (HRT) along with the performance of the system in removal of color and COD of synthetic textile wastewater. The study was conducted in a column reactor operated according to a sequential batch reactor with a sequence of anaerobic and aerobic reaction phases. Six stages of different HRTs and different anaerobic and aerobic reaction time were evaluated. It was observed that the increase in HRT resulted in the reduction of organic loading rate (OLR). This has caused a decrease in biomass concentration (MLSS), reduction in mean size of the granules, lowered the settling ability of the granules and reduction of oxygen uptake rate (OUR), overall specific biomass growth rate (ìoverall), endogeneous decay rate (kd) and biomass yield (Yobs, Y). When the OLR was increased by adding carbon sources (glucose, sodium acetate and ethanol), there was a slight increase in the MLSS, the granules mean size, ìoverall, and biomass yield. Under high HRT, increasing the anaerobic to aerobic reaction time ratio caused an increase in the concentration of MLSS, mean size of granules and lowered the SVI value and biomass yield. The ìoverall and biomass yield increased with the reduction in anaerobic/aerobic time ratio. The HRT of 24 h with anaerobic and aerobic reaction time of 17.8 and 5.8 h respectively appear to be the best cycle operation of SBR. Under these conditions, not only the physical properties of the biogranules have improved, the highest removal of color (i.e. 94.1±0.6%) and organics (i.e. 86.5±0.5%) of the synthetic textile dyeing wastewater have been achieved.
  4. Muda K, Aris A, Salim MR, Ibrahim Z, Yahya A, van Loosdrecht MC, et al.
    Water Res, 2010 Aug;44(15):4341-50.
    PMID: 20580402 DOI: 10.1016/j.watres.2010.05.023
    Microbial granular sludge that is capable to treat textile wastewater in a single reactor under intermittent anaerobic and aerobic conditions was developed in this study. The granules were cultivated using mixed sewage and textile mill sludge in combination with anaerobic granules collected from an anaerobic sludge blanket reactor as seed. The granules were developed in a single sequential batch reactor (SBR) system under alternating anaerobic and aerobic condition fed with synthetic textile wastewater. The characteristics of the microbial granular sludge were monitored throughout the study period. During this period, the average size of the granules increased from 0.02 +/- 0.01 mm to 2.3 +/- 1.0 mm and the average settling velocity increased from 9.9 +/- 0.7 m h(-1) to 80 +/- 8 m h(-1). This resulted in an increased biomass concentration (from 2.9 +/- 0.8 g L(-1) to 7.3 +/- 0.9 g L(-1)) and mean cell residence time (from 1.4 days to 8.3 days). The strength of the granules, expressed as the integrity coefficient also improved. The sequential batch reactor system demonstrated good removal of COD and ammonia of 94% and 95%, respectively, at the end of the study. However, only 62% of color removal was observed. The findings of this study show that granular sludge could be developed in a single reactor with an intermittent anaerobic-aerobic reaction phase and is capable in treating the textile wastewater.
  5. Basari N, Mustafa NS, Yusrihan NEN, Yean CW, Ibrahim Z
    Trop Life Sci Res, 2019 Jan;30(1):23-31.
    PMID: 30847031 MyJurnal DOI: 10.21315/tlsr2019.30.1.2
    Ficus plants are commonly planted as ornamentals along roadsides in Malaysia. In 2010, Ficus plants in Kuala Terengganu were found to be attacked by a moth, identified as Trilocha varians. The larvae of this moth fed on Ficus leaves causing up to 100% defoliation. This study was conducted to determine the life cycle of T. varians under two different environmental temperatures and to control this pest using two different insecticides. Our findings showed that there were significant differences in the time taken for eggs to hatch and larval and pupation period between low and high environmental temperatures. Results also showed that fipronil had lower LT50 and LT95 than malathion. This study provides new information on the life history of T. varians under two different conditions and the efficiency in controlling T. varians larvae using insecticides. The results of this study are important for future management in controlling T. varians population especially in Kuala Terengganu, Malaysia.
  6. Sinniah B, Hassan A KR, Sabaridah I, Soe MM, Ibrahim Z, Ali O
    Trop Biomed, 2014 Jun;31(2):190-206.
    PMID: 25134888 MyJurnal
    Intestinal parasitic infections are among the most common diseases affecting mankind causing major public health problems to billions of people living in developing countries. The aim of this study is to determine the prevalence of intestinal parasites in various communities residing in different habitats in Malaysia and compare the findings with 101 studies conducted over the past 42 years (1970-2013). A cross-sectional study design was conducted with the aid of a questionnaire to collect relevant information about the study population. Faecal samples were examined using the direct smear and formal ether sedimentation techniques. A total of 342 children were examined amongst whom 24.6% were positive for intestinal parasitic infections. Results showed that 32.3% of rural children, 20.6% of urban squatters and 5.4% of children from flats were positive for one or more parasites. The most common parasite encountered was Trichuris trichiura (20.2%) followed by Ascaris lumbricoides (10.5%) and hookworm (6.7%). No case of hookworm was reported in urban children whereas 12.2% of rural children were positive. The most common protozoan parasite detected was Entamoeba coli (3.2%) followed by Giardia intestinalis (1.8%), Entamoeba histolytica (1.8%) and Blastocystis hominis (1.2%). Nearly one-fifth (18.4%) of the children had single infection followed by double (12.0%) and triple infections (1.2%). Orang Asli (indigenous) children (44.3%) had the highest infection rate followed by Indians (20.2%), Malays (14.0%) and Chinese (11.9%). Twenty-eight studies carried out on plantation communities with regards to intestinal parasitic infections in Malaysia from 1970 to 2013 showed a steady decline in the prevalence rate ranging from 95.0% in the seventies to 37.0 % in 2012. Intestinal parasitic infections were more common in Orang Asli communities with prevalence ranging from over 90% in the seventies and fluctuating below 70% in most studies between 2000 to 2013 except for two studies that showed a prevalence of 98.2% and 100%. The prevalence rate among urban squatters, urban residents and those living in flats showed dramatic decrease in prevalence rate.
  7. Ho CY, Ibrahim Z, Abu Zaid Z, Mat Daud Z', Md Yusop NB
    Trials, 2020 Jun 16;21(1):533.
    PMID: 32546217 DOI: 10.1186/s13063-020-04462-4
    INTRODUCTION: There has been growing evidence on the favourable outcomes of fast-track-recovery (FTR) surgery; to expedite recovery, minimise complications, and reduce the length of hospital stay for surgical patients. However, there is lack of evidence on the effectiveness of FTR in surgical gynaecological cancer (GC) patients. Most of the previous studies did not focus on feeding composition in the FTR surgery protocol. This study aims to determine the effectiveness of FTR feeding with a whey-protein-infused carbohydrate-loading drink pre-operatively and early oral feeding post-operatively on post-operative outcomes among surgical GC patients.

    METHODS/DESIGN: This open-labelled, randomised controlled trial (RCT) will randomly allocate patients into intervention and control groups. Ambulated Malaysian aged over 18 years and scheduled for elective surgery for (suspected) GC, will be included in this study. The intervention group will be given whey-protein-infused carbohydrate-loading drinks on the evening before their operation and 3 h before their operation as well as started on early oral feeding 4 h post-operatively. The control group will be fasted overnight pre-operation and only allowed plain water, and return to a normal diet is allowed when bowel sounds return post-operatively. The primary outcomes of study are length of post-operative hospital stay, length of clear-fluid tolerance, solid-food tolerance and bowel function. Additional outcome measures are changes in nutritional status, biochemical profile and functional status. Data will be analysed on an intention-to-treat basis.

    TRIAL REGISTRATION: ClinicalTrials.gov, ID: NCT03667755. Retrospectively registered on 12 September 2018; Protocol version: version 3 dated 27 September 2017.

  8. Murugesu S, Khatib A, Ahmed QU, Ibrahim Z, Uzir BF, Benchoula K, et al.
    Toxicol Rep, 2019;6:1148-1154.
    PMID: 31993329 DOI: 10.1016/j.toxrep.2019.10.020
    Clinacanthus nutans, an herbal shrub belonging to the Acanthaceae family, is traditionally used as a functional food to treat various ailments in Malaysia and Indonesia. Although the polar fraction of this plant shows non-toxic effect, the toxicity of the non-polar extract is not reported so far. The present study aimed to assess the toxic effect and determine the lethal concentration of this non-polar fraction using zebrafish embryos. The n-hexane fraction was partitioned from the crude extract of C. nutans obtained using 80% methanolic solution. After spawning of the adult male and female zebrafish, the eggs were collected, transferred into a 96-well plate and incubated with the n-hexane fraction at concentrations of 15.63 μg/ml, 31.25 μg/ml, 62.5 μg/ml, 125 μg/ml, 250 μg/ml and 500 μg/ml in 2% DMSO. The survival and sublethal endpoint were assessed, the mortality and hatchability rates were calculated based on microscopic observation, while the heartbeat rate was measured using DanioScope software. The median lethal concentration (LC50) of the C. nutans n-hexane fraction, which was determined using probit analysis, was calculated to be 75.49 μg/mL, which is harmful. Moreover, gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of palmitic acid, phytol, hexadecanoic acid, 1-monopalmitin, stigmast-5-ene, pentadecanoic acid, heptadecanoic acid, 1-linolenoylglycerol and stigmasterol in the n-hexane fraction.
  9. Lim KS, Ibrahim Z, Buyamin S, Ahmad A, Naim F, Ghazali KH, et al.
    ScientificWorldJournal, 2013;2013:510763.
    PMID: 23737718 DOI: 10.1155/2013/510763
    The Vector Evaluated Particle Swarm Optimisation algorithm is widely used to solve multiobjective optimisation problems. This algorithm optimises one objective using a swarm of particles where their movements are guided by the best solution found by another swarm. However, the best solution of a swarm is only updated when a newly generated solution has better fitness than the best solution at the objective function optimised by that swarm, yielding poor solutions for the multiobjective optimisation problems. Thus, an improved Vector Evaluated Particle Swarm Optimisation algorithm is introduced by incorporating the nondominated solutions as the guidance for a swarm rather than using the best solution from another swarm. In this paper, the performance of improved Vector Evaluated Particle Swarm Optimisation algorithm is investigated using performance measures such as the number of nondominated solutions found, the generational distance, the spread, and the hypervolume. The results suggest that the improved Vector Evaluated Particle Swarm Optimisation algorithm has impressive performance compared with the conventional Vector Evaluated Particle Swarm Optimisation algorithm.
  10. Razak AA, Abu-Hassan MI, Al-Makramani BM, Al-Sanabani FA, Al-Shami IZ, Almansour HM
    J Contemp Dent Pract, 2016 Nov 01;17(11):920-925.
    PMID: 27965501
    AIM: The aim of this study was to evaluate the effect of surface treatments on shear bond strength (SBS) of Turkom-Cera (Turkom-Ceramic (M) Sdn. Bhd., Puchong, Malaysia) all-ceramic material cemented with resin cement Panavia-F (Kuraray Medical Inc., Okayama, Japan).

    MATERIALS AND METHODS: Forty Turkom-Cera ceramic disks (10 mm × 3 mm) were prepared and randomly divided into four groups. The disks were wet ground to 1000-grit and subjected to four surface treatments: (1) No treatment (Control), (2) sandblasting, (3) silane application, and (4) sandblasting + silane. The four groups of 10 specimens each were bonded with Panavia-F resin cement according to manufacturer's recommendations. The SBS was determined using the universal testing machine (Instron) at 0.5 mm/min crosshead speed. Failure modes were recorded and a qualitative micromorphologic examination of different surface treatments was performed. The data were analyzed using the one-way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests.

    RESULTS: The SBS of the control, sandblasting, silane, and sandblasting + silane groups were: 10.8 ± 1.5, 16.4 ± 3.4, 16.2 ± 2.5, and 19.1 ± 2.4 MPa respectively. According to the Tukey HSD test, only the mean SBS of the control group was significantly different from the other three groups. There was no significant difference between sandblasting, silane, and sandblasting + silane groups.

    CONCLUSION: In this study, the three surface treatments used improved the bond strength of resin cement to Turkom-Cera disks.

    CLINICAL SIGNIFICANCE: The surface treatments used in this study appeared to be suitable methods for the cementation of glass infiltrated all-ceramic restorations.

  11. Cheong I, Lim A, Lee C, Ibrahim Z, Sarvanathan K
    Med J Malaysia, 1997 Dec;52(4):313-7.
    PMID: 10968106
    Between 1987 to 1995, a total of 334 patients infected with HIV were treated at the Hospital Kuala Lumpur. There were 159 Malays, 108 Chinese, 64 Indians, and 3 from other ethnic groups. Three hundred and twenty-one (96.1%) of these individuals were males and 262 (65.9%) were between the ages of 26-45 years. Intravenous drug users made up 77% (256) of the attributable risk behaviour from the group although many of them also had added risk behaviours like heterosexual activity with multiple partners (50 patients), tattoos (7 patients), homosexual practice (4 patients) and previous transfusions (3 patients). The others acquired their infection through heterosexual promiscuity (59 patients), homo/bisexual activity (7 patients), previous transfusion (5 patients) and tattoos (1 patient). Sixty-six patients (all males) had since progressed to full blown AIDS and 10 have died. The two commonest AIDS-defining events were tuberculosis infection and Pneumocystic carinii pneumonia occurring in 37 (56%) and 15 (22.7%) of patients respectively. Forty-one patients with AIDS presented for the first time with their AIDS-defining infections. The mean CD4 count of the patients when they progressed to AIDS was 130/mm3. The mean time for progression from "known" seropositivity to AIDS was 2.42 years. These results suggest that Malaysians infected with HIV are not coming forward for treatment until they are in the advanced stage of the disease.
  12. Ibrahim ZH, Al-Diwan JK
    Med J Malaysia, 2023 Nov;78(6):717-720.
    PMID: 38031212
    INTRODUCTION: Coronavirus disease 2019 (COVID-19) has high morbidity and mortality especially in preexisting risk groups. In atopic diseases the IgE and eosinophils are commonly elevated. This study aims to determine the potential association between COVID-19 and atopic diseases in Iraqi patients.

    MATERIALS AND METHODS: A cross-sectional study done in Baghdad on 112 patients who attended Al-Zahraa Allergic Center. Their demographic characteristics, total IgE, eosinophil counts and PCR result for COVID-19 were determined.

    RESULTS: The means for IgE and eosinophils were 245.7±260.1IU/ml and 444.5±117.1cells/microliter sequentially. Around 32.1% had high IgE level (i.e., atopic) and 11.6% had COVID-19. Among the atopic patients, 33.3%, 30.5% and 36.2% had atopic dermatitis, allergic rhinitis and asthma respectively. More than half (58.3%) of them were male, 55.5% aged <45 years, 36.2% were retired or had no job, 69.5% were graduated from secondary school or more and 88.8% lived in urban areas. There is no significant association in IgE level between those with and without COVID-19, which means that exposure to SARS Cov2 virus could not be a trigger or exacerbation for atopic diseases. Also, there was no association between atopic patients with COVID-19 and those without it regarding type of atopy, age, sex, occupation, education, type of living area.

    CONCLUSIONS: Atopy is not a risk factor for COVID-19.

  13. Nassir KF, Ali BM, Ibrahim ZH, Qasim ZJ, Mahdi SG, Mustafa NM, et al.
    Med J Malaysia, 2024 Jan;79(1):74-79.
    PMID: 38287761
    INTRODUCTION: Salmonella typhi could infect the intestinal tract and the bloodstream or invade body organs and secrete endotoxins. It is endemic in developing countries. It is increasingly evolving antimicrobial resistance to several commonly used antimicrobial agents.

    MATERIALS AND METHODS: A cross-sectional study was done at Iraqi Communicable Disease Control Center, where all confirmed cases of Salmonella typhi are reported, for a period 2019-2021. All demographic, epidemiological and clinical characteristics of patients, comorbidities, type of samples, distribution of S. typhi by age and gender, time distribution in each year and profile of bacterial resistance and sensitivity to antibiotics were gathered and analysed.

    RESULTS: Most samples were taken from blood. The mean age of cases during 2019, 2020 and 2021 was 18.7 ± 6.5, 17.7 ± 14.1 and 17.3 ± 12.8. Males constituted 56.7%, 58.5% and 39.8%, respectively. Some cases had comorbidities. Most cases had headache and fever. Some of them had nausea, diarrhoea, vomiting and epigastric pain. The age and sex were significantly associated with years of reporting. The most months of case reporting were June-July (2019 and 2021), Jan. -Feb. (2020). There was an obvious increase in S. typhi resistance to ceftriaxone (92.2%, 86.1%, 88.8%) and ampicillin (77.1%, 76.9%, 81.27%). There was a gradual increase in sensitivity to tetracycline (83.1%, 88.1%, 94%), cotrimoxazole (86.7%, 86.1%, 92.2%), ciprofloxacin (78.3%, 90.1%, 87.8%) and cefixime (77.7%, 72.3%, 72.7%).

    CONCLUSIONS: There was a sharp rise in resistance rates of the S. typhi in Iraq (during 2019-2021) to ceftriaxone and ampicillin, while there were highest sensitivity rates to imipenem, aztreonam and chloramphenicol. The following recommendations were made: (1) Improvement of general hygiene and food safety measures. (2) Emphasis on vaccination and surveillance of Salmonella infection. (3) Rational use of appropriate antibiotics through implementation of treatment guidelines. (5) Educate communities and travelers about the risks of S. typhi and its preventive measures.

  14. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(5):444.
    PMID: 31265003 DOI: 10.1140/epjc/s10052-019-6926-x
    A search for supersymmetry is presented based on events with at least one photon, jets, and large missing transverse momentum produced in proton-proton collisions at a center-of-mass energy of 13



    Te



    . The data correspond to an integrated luminosity of 35.9



    fb

    -
    1



    and were recorded at the LHC with the CMS detector in 2016. The analysis characterizes signal-like events by categorizing the data into various signal regions based on the number of jets, the number of
    b
    -tagged jets, and the missing transverse momentum. No significant excess of events is observed with respect to the expectations from standard model processes. Limits are placed on the gluino and top squark pair production cross sections using several simplified models of supersymmetric particle production with gauge-mediated supersymmetry breaking. Depending on the model and the mass of the next-to-lightest supersymmetric particle, the production of gluinos with masses as large as 2120



    Ge



    and the production of top squarks with masses as large as 1230



    Ge



    are excluded at 95% confidence level.
  15. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(2):90.
    PMID: 30814908 DOI: 10.1140/epjc/s10052-019-6556-3
    A search is presented for the single production of vector-like quarks in proton-proton collisions at


    s

    =
    13

    TeV

    . The data, corresponding to an integrated luminosity of 35.9



    fb

    -
    1



    , were recorded with the CMS experiment at the LHC. The analysis focuses on the vector-like quark decay into a top quark and a
    W
    boson, with one muon or electron in the final state. The mass of the vector-like quark candidate is reconstructed from hadronic jets, the lepton, and the missing transverse momentum. Methods for the identification of
    b
    quarks and of highly Lorentz boosted hadronically decaying top quarks and
    W
    bosons are exploited in this search. No significant deviation from the standard model background expectation is observed. Exclusion limits at 95% confidence level are set on the product of the production cross section and branching fraction as a function of the vector-like quark mass, which range from 0.3 to 0.03


    pb

    for vector-like quark masses of 700 to 2000


    GeV

    . Mass exclusion limits up to 1660


    GeV

    are obtained, depending on the vector-like quark type, coupling, and decay width. These represent the most stringent exclusion limits for the single production of vector-like quarks in this channel.
  16. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(11):969.
    PMID: 31886778 DOI: 10.1140/epjc/s10052-019-7451-7
    Measurements are presented of the triple-differential cross section for inclusive isolated-photon+jet events in

    p
    p

    collisions at


    s

    =
    8

    TeV as a function of photon transverse momentum (

    p

    T


    γ




    ), photon pseudorapidity (

    η

    γ




    ), and jet pseudorapidity (

    η
    jet

    ). The data correspond to an integrated luminosity of

    19.7



    fb

    -
    1




    that probe a broad range of the available phase space, for


    |


    η

    γ





    |
    <
    1.44


    and


    1.57
    <
    |


    η

    γ





    |
    <
    2.50


    ,


    |


    η
    jet


    |
    <
    2.5


    ,

    40
    <

    p

    T


    γ




    <
    1000




    GeV

    , and jet transverse momentum,

    p

    T

    jet

    , > 25


    GeV

    . The measurements are compared to next-to-leading order perturbative quantum chromodynamics calculations, which reproduce the data within uncertainties.
  17. Sirunyan AM, Tumasyan A, Adam W, Asilar E, Bergauer T, Brandstetter J, et al.
    Eur Phys J C Part Fields, 2017;77(12):845.
    PMID: 31985736 DOI: 10.1140/epjc/s10052-017-5317-4
    A search is presented for an excess of events with heavy-flavor quark pairs (

    t

    t
    ¯


    and

    b

    b
    ¯


    ) and a large imbalance in transverse momentum in data from proton-proton collisions at a center-of-mass energy of 13


    TeV

    . The data correspond to an integrated luminosity of 2.2



    fb

    -
    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

    t

    t
    ¯


    and

    b

    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.
  18. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(9):773.
    PMID: 31713548 DOI: 10.1140/epjc/s10052-019-7276-4
    A measurement for inclusive 2- and 3-jet events of the azimuthal correlation between the two jets with the largest transverse momenta, Δ ϕ 12 , is presented. The measurement considers events where the two leading jets are nearly collinear ("back-to-back") in the transverse plane and is performed for several ranges of the leading jet transverse momentum. Proton-proton collision data collected with the CMS experiment at a center-of-mass energy of 13 Te and corresponding to an integrated luminosity of 35.9 fb - 1 are used. Predictions based on calculations using matrix elements at leading-order and next-to-leading-order accuracy in perturbative quantum chromodynamics supplemented with leading-log parton showers and hadronization are generally in agreement with the measurements. Discrepancies between the measurement and theoretical predictions are as large as 15%, mainly in the region 177 ∘ < Δ ϕ 12 < 180 ∘ . The 2- and 3-jet measurements are not simultaneously described by any of models.
  19. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(7):564.
    PMID: 31397444 DOI: 10.1140/epjc/s10052-019-7058-z
    A search is presented for a heavy pseudoscalar boson A decaying to a Z  boson and a Higgs boson with mass of 125 GeV . In the final state considered, the Higgs boson decays to a bottom quark and antiquark, and the Z  boson decays either into a pair of electrons, muons, or neutrinos. The analysis is performed using a data sample corresponding to an integrated luminosity of 35.9 fb - 1 collected in 2016 by the CMS experiment at the LHC from proton-proton collisions at a center-of-mass energy of 13 Te . The data are found to be consistent with the background expectations. Exclusion limits are set in the context of two-Higgs-doublet models in the A boson mass range between 225 and 1000 GeV .
  20. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(4):364.
    PMID: 31180390 DOI: 10.1140/epjc/s10052-019-6855-8
    A search for the pair production of heavy vector-like partners T and B of the top and bottom quarks has been performed by the CMS experiment at the CERN LHC using proton-proton collisions at s = 13 Te . The data sample was collected in 2016 and corresponds to an integrated luminosity of 35.9 fb - 1 . Final states studied for T T ¯ production include those where one of the T quarks decays via T → t Z and the other via T → b W , t Z , or t H , where H is a Higgs boson. For the B B ¯ case, final states include those where one of the B quarks decays via B → b Z and the other B → t W , b Z , or b H . Events with two oppositely charged electrons or muons, consistent with coming from the decay of a Z boson, and jets are investigated. The number of observed events is consistent with standard model background estimations. Lower limits at 95% confidence level are placed on the masses of the T and B quarks for a range of branching fractions. Assuming 100% branching fractions for T → t Z , and B → b Z , T and B quark mass values below 1280 and 1130 Ge , respectively, are excluded.
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