Elsayed Salama

Elsayed Salama

Academy of Scientific Research and Technology
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Elsayed Salama has a total of 1000 co-authors. Here are the top co-authors by number of shared publications:

Latest Publications

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    Measurement of Z γ production in proton-proton collisions at s = 13.6     TeV and constraints on neutral triple gauge couplings

    by A. Hayrapetyan, V. Makarenko, A. Tumasyan, W. Adam, J. W. Andrejkovic, L. Benato, T. Bergauer, M. Dragicevic, C. Giordano, P. S. Hussain, et al.

    A measurement of the Z γ production cross section in proton-proton collisions at a center-of-mass energy of 13.6 TeV is presented. Data corresponding to an integrated luminosity of 34.8 fb − 1 , collected by the CMS experiment at the LHC in 2022 are used. Events with an oppositely charged pair of muons or electrons, with an invariant mass corresponding to a Z boson, together with an isolated photon are selected. The measured fiducial cross section for the combined electron and muon channels is 1.896 ± 0.033 ( stat ) ± 0.054 ( syst ) ± 0.006 ( theo ) pb , in agreement with the standard model prediction of 1.922 ± 0.094 pb . Constraints on neutral triple gauge couplings generated by dimension-8 operators in a recently proposed effective field theory framework are determined for the first time.

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    Search for long-lived particles decaying into muons in proton-proton collisions at $ \sqrt{s}=13.6 $ TeV using data scouting

    by A. Gevorgyan, A. Hayrapetyan, V. Makarenko, A. Tumasyan, W. Adam, L. Benato, T. Bergauer, M. Dragicevic, S. Gundacker, A. K. Guven, et al.

    A bstract: A search for long-lived particles decaying into muons is performed using proton-proton collisions at $$ \sqrt{s}=13.6 $$ s = 13.6 TeV, collected by the CMS experiment at the LHC in 2022 and 2023, corresponding to an integrated luminosity of 62.4 fb − 1 . The data were collected using dedicated dimuon triggers with low transverse momentum thresholds, recorded with a high-rate data scouting trigger stream. This data stream retains a reduced amount of information at the high-level trigger, to explore otherwise inaccessible phase space at low multimuon invariant mass and nonzero displacement from the primary interaction vertex. No significant excess of events above the standard model prediction is found. Upper limits on branching fractions at 95% confidence level are set for a wide range of mass and lifetime hypotheses in several beyond the standard model frameworks, where the Higgs boson decays into long-lived dark photons or into dark partons that produce showers containing long-lived particles, or where a long-lived scalar resonance is produced from the decay of a b hadron. The resulting constraints improve and extend existing ones in large regions of the parameter space.

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    First measurements of vector boson scattering in W±W± and WZ production in all-leptonic final states at $ \sqrt{s}=13.6 $ TeV

    by A. Gevorgyan, A. Hayrapetyan, V. Makarenko, A. Tumasyan, W. Adam, L. Benato, T. Bergauer, M. Dragicevic, S. Gundacker, A. K. Guven, et al.

    A bstract: The production cross sections of W ± W ± and WZ boson pairs in association with two jets in proton-proton collisions are measured at $$ \sqrt{s}=13.6 $$ s = 13.6 TeV. The data sample corresponds to an integrated luminosity of 171 fb − 1 , collected with the CMS detector during 2022–2024. The measurements are performed in the leptonic decay modes: W ± Z → ℓ ± νℓ′ ± ℓ′ ∓ and W ± W ± → ℓ ± νℓ′ ± ν , where ℓ , ℓ′ = e or μ . The electroweak productions of W ± W ± and WZ bosons are each observed with a significance greater than five standard deviations from the background-only hypothesis. Differential fiducial cross sections as functions of several observables are also measured.

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    Influence of strangeness on the anisotropic flow of prompt Ds± mesons in PbPb collisions at [b]sNN=5.02TeV

    by A. Belyaev, A. Hayrapetyan, A. Tumasyan, W. Adam, J.W. Andrejkovic, L. Benato, T. Bergauer, M. Dragicevic, C. Giordano, P.S. Hussain, et al.

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    Search for a new heavy scalar resonance decaying to a pair of Z bosons in the four-lepton final state in proton-proton collisions at $ \sqrt{s}=13 $ TeV

    by A. Hayrapetyan, V. Makarenko, A. Tumasyan, W. Adam, L. Benato, T. Bergauer, M. Dragicevic, C. Giordano, P. S. Hussain, M. Jeitler, et al.

    A bstract: A search for a new heavy scalar resonance decaying to two Z bosons, each subsequently decaying to a pair of electrons or muons, is presented. The results are based on a proton-proton collision data set collected by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb − 1 . The search is performed over a wide range of resonance masses from 130 GeV to 3 TeV, considering both narrow- and broad-width scenarios, and considering the gluon fusion and vector boson fusion production processes. For the broad-width scenario, the interference between the new resonance, the 125 GeV Higgs boson production, and the continuum background is taken into account. No significant excess with respect to the standard model background expectation is observed in the examined phase space. Upper limits at the 95% confidence level are set on the product of the heavy scalar resonance production cross section and the branching fraction for its decay into two Z bosons. The exclusion limits range from 0.05–0.1 pb in the low-mass region to 0.005 pb in the high-mass region.

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    Observation of ϒ ( 1 S ) + Z Associated Production and Measurement of the Effective Double-Parton Scattering Cross Section in Proton-Proton Collisions at s = 13     TeV

    by A. Hayrapetyan, V. Makarenko, A. Tumasyan, W. Adam, J. W. Andrejkovic, L. Benato, T. Bergauer, M. Dragicevic, C. Giordano, P. S. Hussain, et al.

    The observation of the associated production of an ϒ ( 1 S ) meson with a Z boson and a measurement of the ratio of its fiducial cross section to the fiducial cross section of the Z boson are presented. Both the ϒ ( 1 S ) meson and the Z boson are identified via decays into a pair of opposite-sign muons. The analysis is based on proton-proton ( p p ) collision data at s = 13 TeV collected with the CMS detector in 2016–2018 and corresponding to an integrated luminosity of 138 fb − 1 . Using the production of the Z boson decaying into four muons as a normalization channel, the ratio of the fiducial cross sections σ [ p p → Z + ϒ ( 1 S ) ] B ( Z → μ + μ − ) B [ ϒ ( 1 S ) → μ + μ − ] to σ ( p p → Z ) B ( Z → 4 μ ) is measured to be R Z + ϒ ( 1 S ) = [ 21.1 ± 5.5 ( stat ) ± 0.6 ( syst ) ] × 10 − 3 , where stat and syst denote the statistical and systematic uncertainties, respectively. The result is used to extract the effective double-parton scattering cross section σ eff = 13.0 − 3.4 + 7.7 mb . In addition, for the first time, σ eff is measured in bins of the transverse momentum of the ϒ ( 1 S ) meson or of the Z boson.

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    Simultaneous measurements of N-subjettiness observables in jets from gluons and light-flavour quarks, and in decays of boosted W bosons and top quarks

    by A. Hayrapetyan, V. Makarenko, A. Tumasyan, W. Adam, L. Benato, T. Bergauer, M. Dragicevic, C. Giordano, P. S. Hussain, M. Jeitler, et al.

    A bstract: A simultaneous measurement of 25 substructure observables is presented using large-radius jets with high transverse momentum from proton-proton collisions at $$ \sqrt{s}=13 $$ s = 13 TeV. The measurement is carried out on dijet events and $$ t\overline{t} $$ t t ¯ events enriched in Lorentz-boosted W bosons and top quarks decaying hadronically. The three data samples consist of jets with one, two, or three prongs from the showering and hadronization of a gluon or light-flavour quark, two quarks, or three quarks, respectively. The data correspond to an integrated luminosity of 138 fb − 1 , recorded by the CMS experiment in 2016–2018. A detailed characterization of the jet substructure is provided using a 6-body basis of N -subjettiness observables that overconstrains the phase space of the resolved emissions in the jet. The measurements are unfolded to the level of stable particles, and an estimate of the particle-level correlations between observables is provided, ensuring that the results can be used to systematically assess and refine the modelling of radiation in jets.

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    Full event interpretation with machine-learning-based particle-flow reconstruction in the CMS detector

    by A. Hayrapetyan, V. Makarenko, A. Tumasyan, W. Adam, L. Benato, T. Bergauer, M. Dragicevic, P. S. Hussain, M. Jeitler, N. Krammer, et al.

    The particle-flow (PF) algorithm constructs a global description of each particle collision by producing a comprehensive list of final-state particles, and is central to event reconstruction in the CMS experiment at the CERN LHC. The existing PF implementation relies on physics-motivated heuristics and assumptions that can be replaced by machine-learning (ML) models trained directly on simulated data and naturally suited to modern graphics processing units (GPUs). A state-of-the-art ML-based PF (MLPF) reconstruction algorithm, implemented within the CMS software framework, is presented. The MLPF algorithm performs a learnable full-event reconstruction on GPUs, generalizes across detector conditions and collision energies, and replaces multiple modular reconstruction steps with a single unified model. Physics performance comparable to standard PF reconstruction is achieved in both simulation and data, with improved jet energy resolution and inference time. In simulated top quark-antiquark events under LHC Run-3 (2023–2024) conditions, the jet energy resolution improves by 10–20% for jets with transverse momentum between 30–100 GeV. Inference time is evaluated using simulated multijet events, with a median of $$20\,\hbox {ms}$$ 20 ms per event on an Nvidia L4 GPU, compared to approximately $$110\,\hbox {ms}$$ 110 ms for the standard CMS PF reconstruction.

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    Search for heavy scalar resonances decaying to Lorentz-boosted Higgs and Higgs-like bosons in the $ \mathrm{b}\overline{\mathrm{b}}4\mathrm{q} $ final state at $ \sqrt{s}=13 $ TeV

    by A. Hayrapetyan, V. Makarenko, A. Tumasyan, W. Adam, J. W. Andrejkovic, L. Benato, T. Bergauer, M. Dragicevic, C. Giordano, P. S. Hussain, et al.

    A bstract: A search is performed for a heavy scalar resonance X decaying to a Higgs boson (H) and a Higgs-like scalar boson (Y) in the two bottom quark ( $$ \mathrm{H}\to \mathrm{b}\overline{\mathrm{b}} $$ H → b b ¯ ) and four quark (Y → VV → 4q) final state, where V denotes a W or Z boson. Masses of the X between 900 and 4000 GeV and the Y between 60 and 2800 GeV are considered. The search is performed in data collected by the CMS experiment at the CERN LHC from proton-proton collisions at 13 TeV center-of-mass energy, with a data set corresponding to a total integrated luminosity of 138 fb − 1 . It targets the Lorentz-boosted regime, in which the products of the $$ \mathrm{H}\to \mathrm{b}\overline{\mathrm{b}} $$ H → b b ¯ decay can be reconstructed as a single large-area jet, and those from the Y → VV → 4q decay as either one Y → 4q or two $$ \mathrm{V}\to \mathrm{q}\overline{\mathrm{q}} $$ V → q q ¯ jets. Jet identification and mass reconstruction exploit machine-learning tools, including a novel attention-based “particle transformer” for Y → 4q identification. No significant excess is observed in the data above the standard model background expectation. Upper limits on the product of production cross section and branching fraction as low as 0.2 fb are derived at 95% confidence level for various mass hypotheses. This is the first search at the LHC for scalar resonances in the all-hadronic $$ \mathrm{b}\overline{\mathrm{b}}\mathrm{VV} $$ b b ¯ VV decay channel.

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    Search for a new heavy resonance decaying to a top quark and a neutral scalar boson in proton-proton collisions at s=13TeV

    by A. Hayrapetyan, V. Makarenko, A. Tumasyan, W. Adam, L. Benato, T. Bergauer, M. Dragicevic, P.S. Hussain, M. Jeitler, N. Krammer, et al.

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