Displaying publications 1 - 20 of 97 in total

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  1. Chowdhury SR, binti Ismail A, Chee SC, bin Laupa MS, binti Jaffri F, Saberi SE, et al.
    Tissue Eng Part C Methods, 2015 Nov;21(11):1135-42.
    PMID: 26061720 DOI: 10.1089/ten.TEC.2015.0015
    Skeletal myoblasts have been extensively used to study muscle growth and differentiation, and were recently tested for their application as cell therapy and as a gene delivery system to treat muscle and nonmuscle diseases. However, contamination of fibroblasts in isolated cells from skeletal muscle is one of the long-standing problems for routine expansion. This study aimed to establish a simple one-step process to purify myoblasts and maintain their purity during expansion. Mixed cells were preplated serially on laminin- and collagen type I-coated surfaces in a different array for 5, 10, and 15 min. Immunocytochemical staining with antibodies specific to myoblasts was performed to evaluate myoblast attachment efficiency, purity, and yield. It was found that laminin-coated surface favors the attachment of myoblasts. Highest myoblast purity of 78.9% ± 6.8% was achieved by 5 min of preplating only on the laminin-coated surface with a yield of 56.9% ± 3.3%. Primary cells, isolated from skeletal muscle (n = 4), confirm the enhancement of purity through preplating on laminin-coated surface for 5 min. Subsequent expansion after preplating enhanced myoblast purity due to an increase in myoblast growth than fibroblasts. Myoblast purity of ∼ 98% was achieved when another preplating was performed during passaging. In conclusion, myoblasts can be purified and efficiently expanded in one step by preplating on laminin-coated surface, which is a simple and robust technique.
  2. Hasmad H, Yusof MR, Mohd Razi ZR, Hj Idrus RB, Chowdhury SR
    Tissue Eng Part C Methods, 2018 06;24(6):368-378.
    PMID: 29690856 DOI: 10.1089/ten.TEC.2017.0447
    Fabrication of composite scaffolds is one of the strategies proposed to enhance the functionality of tissue-engineered scaffolds for improved tissue regeneration. By combining multiple elements together, unique biomimetic scaffolds with desirable physical and mechanical properties can be tailored for tissue-specific applications. Despite having a highly porous structure, the utility of electrospun fibers (EF) as scaffold is usually hampered by their insufficient mechanical strength. In this study, we attempted to produce a mechanically competent scaffold with cell-guiding ability by fabricating aligned poly lactic-co-glycolic acid (PLGA) fibers on decellularized human amniotic membrane (HAM), known to possess favorable tensile and wound healing properties. Decellularization of HAM in 18.75 μg/mL of thermolysin followed by a brief treatment in 0.25 M sodium hydroxide efficiently removed the amniotic epithelium and preserved the ultrastructure of the underlying extracellular matrix. The electrospinning of 20% (w/v) PLGA 50:50 polymer on HAM yielded beadless fibers with straight morphology. Subsequent physical characterization revealed that EF-HAM scaffold with a 3-min fabrication had the most aligned fibers with the lowest fiber diameter in comparison with EF-HAM 5- and 7-min scaffolds. Hydrated EF-HAM scaffolds with 3-min deposition had a greater tensile strength than the other scaffolds despite having thinner fibers. Nevertheless, wet HAM and EF-HAMs regardless of the fiber thicknesses had a significantly lower Young's modulus, and hence, a higher elasticity compared with dry HAM and EF-HAMs. Biocompatibility analysis showed that the viability and migration rate of skeletal muscle cells on EF-HAMs were similar to control and HAM alone. Skeletal muscle cells seeded on HAM were shown to display random orientation, whereas cells on EF-HAM scaffolds were oriented along the alignment of the electrospun PLGA fibers. In summary, besides having good mechanical strength and elasticity, EF-HAM scaffold design decorated with aligned fiber topography holds a promising potential for use in the development of aligned tissue constructs.
  3. Mat Afandi MA, Maarof M, Chowdhury SR, Bt Hj Idrus R
    Tissue Eng Regen Med, 2020 12;17(6):835-845.
    PMID: 32767029 DOI: 10.1007/s13770-020-00283-3
    BACKGROUND: One of the long-standing problems of myoblasts in vitro expansion is slow cell migration and this causes fibroblast population to exceed myoblasts. In this study, we investigated the synergistic effect of laminin and epidermal growth factor (EGF) on co-cultured myoblasts and fibroblasts for cell attachment, proliferation and migration.

    METHODS: Skeletal human muscle cells were cultured in four different conditions; control, EGF, laminin (Lam) and laminin EGF (Lam + EGF). Using live imaging system, their cellular properties; attachment, migration and growth were exposed to Rho kinase inhibitor, Y-27632, and EGF-receptor (EGF-R) inhibitor, gefitinib were measured.

    RESULTS: Myoblast migration and proliferation was enhanced significantly by synergistic stimulation of laminin and EGF (0.61 ± 0.14 µm/min, 0.008 ± 0.001 h-1) compare to that by EGF alone (0.26 ± 0.13 µm/min, 0.004 ± 0.0009 h-1). However, no changes in proliferation and migration were observed for fibroblasts among the culture conditions. Inhibition of Rho kinase resulted in the increase of the myoblast migration on the laminin-coated surface with EGF condition (0.64 ± 0.18 µm/min). Compared to the untreated conditions, myoblasts cultured on the laminin-coated surface and EGF demonstrated elongated morphology, and average cell length increase significantly. In contrast, inhibition of EGF-R resulted in the decrease of myoblast migration on the laminin coated surface with EGF supplemented condition (0.43 ± 0.05 µm/min) in comparison to the untreated control (0.53 ± 0.05 µm/min).

    CONCLUSION: Laminin and EGF preferentially enhance the proliferation and migration of myoblasts, and Rho kinase and EGF-R play a role in this synergistic effect. These results will be beneficial for the propagation of skeletal muscle cells for clinical applications.

  4. Lim WL, Liau LL, Ng MH, Chowdhury SR, Law JX
    Tissue Eng Regen Med, 2019 Dec;16(6):549-571.
    PMID: 31824819 DOI: 10.1007/s13770-019-00196-w
    BACKGROUND: Tendon and ligament injuries accounted for 30% of all musculoskeletal consultations with 4 million new incidences worldwide each year and thus imposed a significant burden to the society and the economy. Damaged tendon and ligament can severely affect the normal body movement and might lead to many complications if not treated promptly and adequately. Current conventional treatment through surgical repair and tissue graft are ineffective with a high rate of recurrence.

    METHODS: In this review, we first discussed the anatomy, physiology and pathophysiology of tendon and ligament injuries and its current treatment. Secondly, we explored the current role of tendon and ligament tissue engineering, describing its recent advances. After that, we also described stem cell and cell secreted product approaches in tendon and ligament injuries. Lastly, we examined the role of the bioreactor and mechanical loading in in vitro maturation of engineered tendon and ligament.

    RESULTS: Tissue engineering offers various alternative ways of treatment from biological tissue constructs to stem cell therapy and cell secreted products. Bioreactor with mechanical stimulation is instrumental in preparing mature engineered tendon and ligament substitutes in vitro.

    CONCLUSIONS: Tissue engineering showed great promise in replacing the damaged tendon and ligament. However, more study is needed to develop ideal engineered tendon and ligament.

  5. Yunus MH, Siang KC, Hashim NI, Zhi NP, Zamani NF, Sabri PP, et al.
    Tissue Cell, 2014 Aug;46(4):233-40.
    PMID: 24973262 DOI: 10.1016/j.tice.2014.05.003
    The culture of human airway epithelial cells has played an important role in advancing our understanding of the metabolic and molecular mechanisms underlying normal function and disease pathology of airway epithelial cells. The present study focused on investigating the effects of human serum (HS) on the qualitative and quantitative properties of the human respiratory epithelium compared to the fetal bovine serum (FBS), as a supplement in culture. Respiratory epithelial (RE) cells derived from human nasal turbinate were co-cultured with fibroblasts, subsequently separated at 80-90% confluency by differential trypsinization. RE cells were then sub-cultured into 2 different plates containing 5% allogenic HS and FBS supplemented media respectively up to passage 1 (P1). Cell morphology, growth rate, cell viability and population doubling time were assessed under light microscope, and levels of gene expression were measured via real time reverse transcriptase-polymerase chain reaction (qRT-PCR). RE cells appeared as polygonal shape and expanded when cultured in HS whereas RE cells in FBS were observed to be easily matured thus limit the RE cells expansion. Proliferation rate of RE cells in HS supplemented media (7673.18 ± 1207.15) was 3 times higher compared to RE in FBS supplemented media (2357.68 ± 186.85). Furthermore, RE cells cultured in HS-supplemented media required fewer days (9.15 ± 1.10) to double in numbers compared to cells cultured in FBS-supplemented media (13.66 ± 0.81). Both the differences were significant (p<0.05). However, there were no significant differences in the viability of RE cells in both groups (p=0.105). qRT-PCR showed comparable expressions of gene Cytokeratin-14 (CK-14), Cytokeratin-18 (CK-18) and Mucin-5 subtype B (MUC5B) in RE cells cultured in both groups (p>0.05). In conclusion, HS is a comparatively better choice of media supplement in accelerating growth kinetics of RE cells in vitro thus producing a better quality of respiratory epithelium for future tracheal reconstruction.
  6. Maarof M, Lokanathan Y, Ruszymah HI, Saim A, Chowdhury SR
    Protein J, 2018 12;37(6):589-607.
    PMID: 30343346 DOI: 10.1007/s10930-018-9800-z
    Growth factors and extracellular matrix (ECM) proteins are involved in wound healing. Human dermal fibroblasts secrete wound-healing mediators in culture medium known as dermal fibroblast conditioned medium (DFCM). However, the composition and concentration of the secreted proteins differ with culture conditions and environmental factors. We cultured human skin fibroblasts in vitro using serum-free keratinocyte-specific media (EpiLife™ Medium [KM1] and defined keratinocyte serum-free medium [KM2]) and serum-free fibroblast-specific medium (FM) to obtain DFCM-KM1, DFCM-KM2 and DFCM-FM, respectively. We identified and compared their proteomic profiles using bicinchoninic acid assay (BCA), 1-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (1D SDS-PAGE), enzyme-linked immunosorbent assay (ELISA), matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry (MALDI-TOF/TOF MS/MS) and liquid chromatography MS (LC-MS/MS). DFCM-KM1 and DFCM-KM2 had higher protein concentrations than DFCM-FM but not statistically significant. MALDI-TOF/TOF MS identified the presence of fibronectin, serotransferrin, serpin and serum albumin. LC-MS/MS and bioinformatics analysis identified 59, 46 and 58 secreted proteins in DFCM-KM1, DFCM-KM2 and DFCM-FM, respectively. The most significant biological processes identified in gene ontology were cellular process, metabolic process, growth and biological regulation. STRING® analysis showed that most secretory proteins in the DFCMs were associated with biological processes (e.g. wound healing and ECM organisation), molecular function (e.g. ECM binding) and cellular component (e.g. extracellular space). ELISA confirmed the presence of fibronectin and collagen in the DFCMs. In conclusion, DFCM secretory proteins are involved in cell adhesion, attachment, proliferation and migration, which were demonstrated to have potential wound-healing effects by in vitro and in vivo studies.
  7. Busra FM, Lokanathan Y, Nadzir MM, Saim A, Idrus RBH, Chowdhury SR
    Malays J Med Sci, 2017 Mar;24(2):33-43.
    PMID: 28894402 DOI: 10.21315/mjms2017.24.2.5
    INTRODUCTION: Collagen type I is widely used as a biomaterial for tissue-engineered substitutes. This study aimed to fabricate different three-dimensional (3D) scaffolds using ovine tendon collagen type I (OTC-I), and compare the attachment, proliferation and morphological features of human dermal fibroblasts (HDF) on the scaffolds.

    METHODS: This study was conducted between the years 2014 to 2016 at the Tissue Engineering Centre, UKM Medical Centre. OTC-I was extracted from ovine tendon, and fabricated into 3D scaffolds in the form of sponge, hydrogel and film. A polystyrene surface coated with OTC-I was used as the 2D culture condition. Genipin was used to crosslink the OTC-I. A non-coated polystyrene surface was used as a control. The mechanical strength of OTC-I scaffolds was evaluated. Attachment, proliferation and morphological features of HDF were assessed and compared between conditions.

    RESULTS: The mechanical strength of OTC-I sponge was significantly higher than that of the other scaffolds. OTC-I scaffolds and the coated surface significantly enhanced HDF attachment and proliferation compared to the control, but no differences were observed between the scaffolds and coated surface. In contrast, the morphological features of HDF including spreading, filopodia, lamellipodia and actin cytoskeletal formation differed between conditions.

    CONCLUSION: OTC-I can be moulded into various scaffolds that are biocompatible and thus could be suitable as scaffolds for developing tissue substitutes for clinical applications and in vitro tissue models. However, further study is required to determine the effect of morphological properties on the functional and molecular properties of HDF.

  8. Shamsul BS, Chowdhury SR, Hamdan MY, Ruszymah BHI
    Indian J Med Res, 2019 05;149(5):641-649.
    PMID: 31417032 DOI: 10.4103/ijmr.IJMR_45_17
    Background & objectives: Seeding density is one of the major parameters affecting the quality of tissue-engineered cartilage. The objective of this study was to evaluate different seeding densities of osteoarthritis chondrocytes (OACs) to obtain the highest quality cartilage.

    Methods: The OACs were expanded from passage 0 (P0) to P3, and cells in each passage were analyzed for gross morphology, growth rate, RNA expression and immunochemistry (IHC). The harvested OACs were assigned into two groups: low (1×10[7] cells/ml) and high (3×10[7] cells/ml) cell density. Three-dimensional (3D) constructs for each group were created using polymerised fibrin and cultured for 7, 14 and 21 days in vitro using chondrocyte growth medium. OAC constructs were analyzed with gross assessments and microscopic evaluation using standard histology, IHC and immunofluorescence staining, in addition to gene expression and biochemical analyses to evaluate tissue development.

    Results: Constructs with a high seeding density of 3×10[7] cells/ml were associated with better quality cartilage-like tissue than those seeded with 1×10[7] cells/ml based on overall tissue formation, cell association and extracellular matrix distribution. The chondrogenic properties of the constructs were further confirmed by the expression of genes encoding aggrecan core protein and collagen type II.

    Interpretation & conclusions: Our results confirmed that cell density was a significant factor affecting cell behaviour and aggregate production, and this was important for establishing good quality cartilage.

  9. 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.
  10. 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.
  11. 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.
  12. 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.
  13. 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 .
  14. 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.
  15. 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.
  16. 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.
  17. 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.
  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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