Displaying publications 1 - 20 of 28 in total

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  1. Khachatryan V, Sirunyan AM, Tumasyan A, Adam W, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2017;77(2):92.
    PMID: 28331430 DOI: 10.1140/epjc/s10052-016-4573-z
    The production cross section of a W boson in association with two b jets is measured using a sample of proton-proton collisions at [Formula: see text] collected by the CMS experiment at the CERN LHC. The data sample corresponds to an integrated luminosity of 19.8[Formula: see text]. The W bosons are reconstructed via their leptonic decays, [Formula: see text], where [Formula: see text] or [Formula: see text]. The fiducial region studied contains exactly one lepton with transverse momentum [Formula: see text] and pseudorapidity [Formula: see text], with exactly two b jets with [Formula: see text] and [Formula: see text] and no other jets with [Formula: see text] and [Formula: see text]. The cross section is measured to be [Formula: see text]+[Formula: see text], in agreement with standard model predictions.
  2. Khachatryan V, Sirunyan AM, Tumasyan A, Adam W, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2017;77(3):172.
    PMID: 28408859 DOI: 10.1140/epjc/s10052-017-4718-8
    The cross section of top quark-antiquark pair production in proton-proton collisions at [Formula: see text] is measured by the CMS experiment at the LHC, using data corresponding to an integrated luminosity of 2.2[Formula: see text]. The measurement is performed by analyzing events in which the final state includes one electron, one muon, and two or more jets, at least one of which is identified as originating from hadronization of a b quark. The measured cross section is [Formula: see text], in agreement with the expectation from the standard model.
  3. Khachatryan V, Sirunyan AM, Tumasyan A, Adam W, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2017;77(4):236.
    PMID: 28515665 DOI: 10.1140/epjc/s10052-017-4730-z
    The WZ production cross section is measured by the CMS experiment at the CERN LHC in proton-proton collision data samples corresponding to integrated luminosities of 4.9[Formula: see text] collected at [Formula: see text], and 19.6[Formula: see text] at [Formula: see text]. The measurements are performed using the fully-leptonic WZ decay modes with electrons and muons in the final state. The measured cross sections for [Formula: see text] are [Formula: see text] [Formula: see text] and [Formula: see text] [Formula: see text]. Differential cross sections with respect to the [Formula: see text] boson [Formula: see text], the leading jet [Formula: see text], and the number of jets are obtained using the [Formula: see text] data. The results are consistent with standard model predictions and constraints on anomalous triple gauge couplings are obtained.
  4. 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.
  5. 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.
  6. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(5):421.
    PMID: 31178657 DOI: 10.1140/epjc/s10052-019-6909-y
    Combined measurements of the production and decay rates of the Higgs boson, as well as its couplings to vector bosons and fermions, are presented. The analysis uses the LHC proton-proton collision data set recorded with the CMS detector in 2016 at


    s

    =
    13


    Te



    , corresponding to an integrated luminosity of 35.9



    fb

    -
    1



    . The combination is based on analyses targeting the five main Higgs boson production mechanisms (gluon fusion, vector boson fusion, and associated production with a
    W
    or
    Z
    boson, or a top quark-antiquark pair) and the following decay modes:

    H

    γ
    γ

    ,

    Z
    Z

    ,

    W
    W

    ,

    τ
    τ

    ,

    b
    b

    , and

    μ
    μ

    . Searches for invisible Higgs boson decays are also considered. The best-fit ratio of the signal yield to the standard model expectation is measured to be

    μ
    =
    1.17
    ±
    0.10

    , assuming a Higgs boson mass of

    125.09


    Ge



    . Additional results are given for various assumptions on the scaling behavior of the production and decay modes, including generic parametrizations based on ratios of cross sections and branching fractions or couplings. The results are compatible with the standard model predictions in all parametrizations considered. In addition, constraints are placed on various two Higgs doublet models.
  7. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2018;78(9):707.
    PMID: 30839784 DOI: 10.1140/epjc/s10052-018-6143-z
    A search for pair production of heavy scalar leptoquarks (LQs), each decaying into a top quark and a
    τ
    lepton, is presented. The search considers final states with an electron or a muon, one or two
    τ
    leptons that decayed to hadrons, and additional jets. The data were collected in 2016 in proton-proton collisions at


    s

    =
    13


    Te



    with the CMS detector at the LHC, and correspond to an integrated luminosity of 35.9



    fb

    -
    1



    . No evidence for pair production of LQs is found. Assuming a branching fraction of unity for the decay

    LQ

    t
    τ

    , upper limits on the production cross section are set as a function of LQ mass, excluding masses below 900



    Ge



    at 95% confidence level. These results provide the most stringent limits to date on the production of scalar LQs that decay to a top quark and a
    τ
    lepton.
  8. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2018;78(9):697.
    PMID: 30839770 DOI: 10.1140/epjc/s10052-018-6144-y
    Pseudorapidity, transverse momentum, and multiplicity distributions are measured in the pseudorapidity range

    |
    η
    |
    <
    2.4

    for charged particles with transverse momenta satisfying


    p
    T

    >
    0.5

    GeV

    in proton-proton collisions at a center-of-mass energy of


    s

    =
    13

    TeV

    . Measurements are presented in three different event categories. The most inclusive of the categories corresponds to an inelastic
    p

    p
    data set, while the other two categories are exclusive subsets of the inelastic sample that are either enhanced or depleted in single diffractive dissociation events. The measurements are compared to predictions from Monte Carlo event generators used to describe high-energy hadronic interactions in collider and cosmic-ray physics.
  9. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(2):94.
    PMID: 30872972 DOI: 10.1140/epjc/s10052-019-6562-5
    A search is presented for decays of
    Z
    and Higgs bosons to a

    J
    /
    ψ

    meson and a photon, with the subsequent decay of the

    J
    /
    ψ

    to


    μ
    +


    μ
    -


    . The analysis uses data from proton-proton collisions with an integrated luminosity of 35.9



    fb

    -
    1



    at


    s

    =
    13

    TeV

    collected with the CMS detector at the LHC. The observed limit on the

    Z


    J
    /
    ψ

    γ

    decay branching fraction, assuming that the

    J
    /
    ψ

    meson is produced unpolarized, is

    1.4
    ×

    10

    -
    6



    at 95% confidence level, which corresponds to a rate higher than expected in the standard model by a factor of 15. For extreme-polarization scenarios, the observed limit changes from

    -
    13.6

    to

    +
    8.6
    %

    with respect to the unpolarized scenario. The observed upper limit on the branching fraction for

    H


    J
    /
    ψ

    γ

    where the

    J
    /
    ψ

    meson is assumed to be transversely polarized is

    7.6
    ×

    10

    -
    4



    , a factor of 260 larger than the standard model prediction. The results for the Higgs boson are combined with previous data from proton-proton collisions at


    s

    =
    8

    TeV

    to produce an observed upper limit on the branching fraction for

    H


    J
    /
    ψ

    γ

    that is a factor of 220 larger than the standard model value.
  10. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(1):20.
    PMID: 30872964 DOI: 10.1140/epjc/s10052-018-6482-9
    Measurements of inclusive isolated-photon and photon+jet production in proton-proton collisions at


    s

    =
    13

    TeV

    are presented. The analysis uses data collected by the CMS experiment in 2015, corresponding to an integrated luminosity of 2.26



    fb

    -
    1



    . The cross section for inclusive isolated photon production is measured as a function of the photon transverse energy in a fiducial region. The cross section for photon+jet production is measured as a function of the photon transverse energy in the same fiducial region with identical photon requirements and with the highest transverse momentum jet. All measurements are in agreement with predictions from next-to-leading-order perturbative QCD.
  11. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(3):280.
    PMID: 31007587 DOI: 10.1140/epjc/s10052-019-6730-7
    A search for dark matter produced in association with a Higgs boson decaying to a pair of bottom quarks is performed in proton-proton collisions at a center-of-mass energy of 13



    Te



    collected with the CMS detector at the LHC. The analyzed data sample corresponds to an integrated luminosity of 35.9



    fb

    -
    1



    . The signal is characterized by a large missing transverse momentum recoiling against a bottom quark-antiquark system that has a large Lorentz boost. The number of events observed in the data is consistent with the standard model background prediction. Results are interpreted in terms of limits both on parameters of the type-2 two-Higgs doublet model extended by an additional light pseudoscalar boson
    a
    (2HDM+
    a
    ) and on parameters of a baryonic


    Z

    '

    simplified model. The 2HDM+
    a
    model is tested experimentally for the first time. For the baryonic


    Z

    '

    model, the presented results constitute the most stringent constraints to date.
  12. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2018;78(4):291.
    PMID: 31007582 DOI: 10.1140/epjc/s10052-018-5740-1
    A search for new physics in events with a Z boson produced in association with large missing transverse momentum at the LHC is presented. The search is based on the 2016 data sample of proton-proton collisions recorded with the CMS experiment at


    s

    =
    13

    TeV

    , corresponding to an integrated luminosity of 35.9



    fb

    -
    1



    . The results of this search are interpreted in terms of a simplified model of dark matter production via spin-0 or spin-1 mediators, a scenario with a standard-model-like Higgs boson produced in association with the Z boson and decaying invisibly, a model of unparticle production, and a model with large extra spatial dimensions. No significant deviations from the background expectations are found, and limits are set on relevant model parameters, significantly extending the results previously achieved in this channel.
  13. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2018;78(4):287.
    PMID: 31007580 DOI: 10.1140/epjc/s10052-018-5752-x
    A study of the associated production of a
    Z
    boson and a charm quark jet (

    Z
    +
    c

    ), and a comparison to production with a
    b
    quark jet (

    Z
    +
    b

    ), in

    p
    p

    collisions at a centre-of-mass energy of 8


    TeV

    are presented. The analysis uses a data sample corresponding to an integrated luminosity of 19.7



    fb

    -
    1



    , collected with the CMS detector at the CERN LHC. The
    Z
    boson candidates are identified through their decays into pairs of electrons or muons. Jets originating from heavy flavour quarks are identified using semileptonic decays of
    c
    or
    b
    flavoured hadrons and hadronic decays of charm hadrons. The measurements are performed in the kinematic region with two leptons with


    p

    T



    >
    20

    GeV

    ,



    |


    η



    |


    <
    2.1

    ,

    71
    <

    m





    <
    111

    GeV

    , and heavy flavour jets with


    p

    T

    jet

    >
    25

    GeV

    and



    |


    η
    jet


    |


    <
    2.5

    . The

    Z
    +
    c

    production cross section is measured to be

    σ

    (
    p
    p

    Z
    +
    c
    +
    X
    )

    B

    (
    Z



    +



    -

    )

    =
    8.8
    ±
    0.5

    (stat)
    ±
    0.6

    (syst)

    pb

    . The ratio of the

    Z
    +
    c

    and

    Z
    +
    b

    production cross sections is measured to be

    σ
    (
    p
    p

    Z
    +
    c
    +
    X
    )
    /
    σ
    (
    p
    p

    Z
    +
    b
    +
    X
    )
    =
    2.0
    ±
    0.2

    (stat)
    ±
    0.2

    (syst)

    . The

    Z
    +
    c

    production cross section and the cross section ratio are also measured as a function of the transverse momentum of the
    Z
    boson and of the heavy flavour jet. The measurements are compared with theoretical predictions.
  14. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(4):313.
    PMID: 31031568 DOI: 10.1140/epjc/s10052-019-6788-2
    A top quark mass measurement is performed using

    35.9



    fb

    -
    1




    of LHC proton-proton collision data collected with the CMS detector at


    s

    =
    13

    TeV

    . The measurement uses the

    t

    t
    ¯


    all-jets final state. A kinematic fit is performed to reconstruct the decay of the

    t

    t
    ¯


     system and suppress the multijet background. Using the ideogram method, the top quark mass (

    m
    t

    ) is determined, simultaneously constraining an additional jet energy scale factor (
    JSF
    ). The resulting value of


    m
    t

    =
    172.34
    ±
    0.20

    (stat+JSF)
    ±
    0.70

    (syst)

    GeV

    is in good agreement with previous measurements. In addition, a combined measurement that uses the

    t

    t
    ¯


    lepton+jets and all-jets final states is presented, using the same mass extraction method, and provides an

    m
    t

    measurement of

    172.26
    ±
    0.07

    (stat+JSF)
    ±
    0.61

    (syst)

    GeV

    . This is the first combined

    m
    t

    extraction from the lepton+jets and all-jets channels through a single likelihood function.
  15. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(2):123.
    PMID: 30863200 DOI: 10.1140/epjc/s10052-019-6620-z
    Measurements of normalized differential cross sections as functions of the multiplicity and kinematic variables of charged-particle tracks from the underlying event in top quark and antiquark pair production are presented. The measurements are performed in proton-proton collisions at a center-of-mass energy of 13



    Te



    , and are based on data collected by the CMS experiment at the LHC in 2016 corresponding to an integrated luminosity of 35.9



    fb

    -
    1



    . Events containing one electron, one muon, and two jets from the hadronization and fragmentation of
    b
    quarks are used. These measurements characterize, for the first time, properties of the underlying event in top quark pair production and show no deviation from the universality hypothesis at energy scales typically above twice the top quark mass.
  16. 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

    .
  17. 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.
  18. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2018;78(9):789.
    PMID: 30956565 DOI: 10.1140/epjc/s10052-018-6242-x
    A search is presented for physics beyond the standard model, based on measurements of dijet angular distributions in proton-proton collisions at


    s

    =
    13
    TeV

    . The data collected with the CMS detector at the LHC correspond to an integrated luminosity of 35.9



    fb

    -
    1



    . The observed distributions, corrected to particle level, are found to be in agreement with predictions from perturbative quantum chromodynamics that include electroweak corrections. Constraints are placed on models containing quark contact interactions, extra spatial dimensions, quantum black holes, or dark matter, using the detector-level distributions. In a benchmark model where only left-handed quarks participate, contact interactions are excluded at the 95% confidence level up to a scale of 12.8 or 17.5TeV, for destructive or constructive interference, respectively. The most stringent lower limits to date are set on the ultraviolet cutoff in the Arkani-Hamed-Dimopoulos-Dvali model of extra dimensions. In the Giudice-Rattazzi-Wells convention, the cutoff scale is excluded up to 10.1TeV. The production of quantum black holes is excluded for masses below 5.9 and 8.2TeV, depending on the model. For the first time, lower limits between 2.0 and 4.6TeVare set on the mass of a dark matter mediator for (axial-)vector mediators, for the universal quark coupling


    g
    q

    =
    1.0

    .
  19. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2019;79(4):305.
    PMID: 31007588 DOI: 10.1140/epjc/s10052-019-6800-x
    A search is presented for resonant production of second-generation sleptons (


    μ
    ~

    L

    ,


    ν
    ~

    μ

    ) via the R-parity-violating coupling

    λ
    211
    '

    to quarks, in events with two same-sign muons and at least two jets in the final state. The smuon (muon sneutrino) is expected to decay into a muon and a neutralino (chargino), which will then decay into a second muon and at least two jets. The analysis is based on the 2016 data set of proton-proton collisions at


    s

    =
    13

    TeV

    recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9



    fb

    -
    1



    . No significant deviation is observed with respect to standard model expectations. Upper limits on cross sections, ranging from 0.24 to 730


    fb

    , are derived in the context of two simplified models representing the dominant signal contributions leading to a same-sign muon pair. The cross section limits are translated into coupling limits for a modified constrained minimal supersymmetric model with

    λ
    211
    '

    as the only nonzero R-parity violating coupling. The results significantly extend restrictions of the parameter space compared with previous searches for similar models.
  20. 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.
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