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Rejeb Sfar, H.

Publications and source records attributed to Rejeb Sfar, H..

At least 37 records · Page 2
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DOE OSTI2023

Search for a vector-like quark T' → tH via the diphoton decay mode of the Higgs boson in proton-proton collisions at $ \sqrt{s}$ = 13 TeV

A search for the electroweak production of a vector-like quark T', decaying to a top quark and a Higgs boson is presented. The search is based on a sample of proton-proton collision events recorded at the LHC at $ \sqrt{s} $ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{–1}$. This is the first T' search that exploits the Higgs boson decay to a pair of photons. For narrow isospin singlet T' states with masses up to 1.1 TeV, the excellent diphoton invariant mass resolution of 1–2% results in an increased sensitivity compared to previous searches based on the same production mechanism. The electroweak production of a T' quark with mass up to 960 GeV is excluded at 95% confidence level, assuming a coupling strength κ$_{T}$ = 0.25 and a relative decay width Γ/M$_{T'}$< 5%.

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DOE OSTI2023

Search for new physics in the τ lepton plus missing transverse momentum final state in proton-proton collisions at $ \sqrt{s}$ = 13 TeV

A search for physics beyond the standard model (SM) in the final state with a hadronically decaying tau lepton and a neutrino is presented. This analysis is based on data recorded by the CMS experiment from proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, corresponding to a total integrated luminosity of 138 fb$^{–1}$. The transverse mass spectrum is analyzed for the presence of new physics. No significant deviation from the SM prediction is observed. Limits are set on the production cross section of a W' boson decaying into a tau lepton and a neutrino. Lower limits are set on the mass of the sequential SM-like heavy charged vector boson and the mass of a quantum black hole. Upper limits are placed on the couplings of a new boson to the SM fermions. Constraints are put on a nonuniversal gauge interaction model and an effective field theory model. For the first time, upper limits on the cross section of t-channel leptoquark (LQ) exchange are presented. These limits are translated into exclusion limits on the LQ mass and on its coupling in the t-channel. The sensitivity of this analysis extends into the parameter space of LQ models that attempt to explain the anomalies observed in B meson decays. The limits presented for the various interpretations are the most stringent to date. Additionally, a model-independent limit is provided.

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DOE OSTI2023

Search for a charged Higgs boson decaying into a heavy neutral Higgs boson and a W boson in proton-proton collisions at $ \sqrt{s}$ = 13 TeV

A search for a charged Higgs boson H ± decaying into a heavy neutral Higgs boson H and a W boson is presented. The analysis targets the H decay into a pair of tau leptons with at least one of them decaying hadronically and with an additional electron or muon present in the event. The search is based on proton-proton collision data recorded by the CMS experiment during 2016–2018 at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb –1 . The data are consistent with standard model background expectations. Upper limits at 95% confidence level are set on the product of the cross section and branching fraction for an H ± in the mass range of 300–700 GeV, assuming an H with a mass of 200 GeV. The observed limits range from 0.085 pb for an H ± mass of 300 Ge V to 0.019 pb for a mass of 700 GeV. These are the first limits on H ± production in the H ± → HW ± decay channel at the LHC.

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DOE OSTI2023

Measurement of differential cross sections for the production of a Z boson in association with jets in proton-proton collisions at s = 13 TeV

A measurement is presented of the production of Z bosons that decay into two electrons or muons in association with jets, in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data were recorded by the CMS Collaboration at the LHC with an integrated luminosity of 35.9 fb$^{-1}$. The differential cross sections are measured as a function of the transverse momentum ($p_\mathrm{T}$) of the Z boson and the transverse momentum and rapidities of the five jets with largest $p_\mathrm{T}$. The jet multiplicity distribution is measured for up to eight jets. The hadronic activity in the events is estimated using the scalar sum of the $p_\mathrm{T}$ of all the jets. All measurements are unfolded to the stable particle-level and compared with predictions from various Monte Carlo event generators, as well as with expectations at leading and next-to-leading orders in perturbative quantum chromodynamics.

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DOE OSTI2023

Observation of Same-Sign W W Production from Double Parton Scattering in Proton-Proton Collisions at s = 13 TeV

The first observation of the production of W$^\pm$W$^\pm$ bosons from double parton scattering processes using same-sign electron-muon and dimuon events in proton-proton collisions is reported. The data sample corresponds to an integrated luminosity of 138 fb$^{-1}$ recorded at a center-of-mass energy of 13 TeV using the CMS detector at the CERN LHC. Multivariate discriminants are used to distinguish the signal process from the main backgrounds. A binned maximum likelihood fit is performed to extract the signal cross section. The measured cross section for production of same-sign W bosons decaying leptonically is 80.7 $\pm$ 11.2 (stat) $^{+9.5}_{-8.6}$ (syst) $\pm$ 12.1 (model) fb, whereas the measured fiducial cross section is 6.28 $\pm$ 0.81 (stat) $\pm$ 0.69 (syst) $\pm$ 0.37 (model) fb. The observed significance of the signal is 6.2 standard deviations above the background-only hypothesis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the electroweak production of W$\gamma$ in association with two jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A measurement is presented for the electroweak production of a W boson, a photon ($\gamma$), and two jets (j) in proton-proton collisions. The leptonic decay of the W boson is selected by requiring one identified electron or muon and large missing transverse momentum. The two jets are required to have large invariant dijet mass and large separation in pseudorapidity. The measurement is performed with the data collected by the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb –1 . The cross section for the electroweak W$\gamma$jj production is 23.5$^{+4.9}_{–4.7}$ fb , whereas the total cross section for W$\gamma$jj production is 113 ± 13 fb . Differential cross sections are also measured with the distributions unfolded to the particle level. All results are in agreement with the standard model expectations. Constraints are placed on anomalous quartic gauge couplings (aQGCs) in terms of dimension-8 effective field theory operators. These are the most stringent limits to date on the aQGCs parameters $f$ M,2–5 /Λ 4 and $f$ T,6–7 /Λ 4 .

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DOE OSTI2023

Constraints on anomalous Higgs boson couplings to vector bosons and fermions from the production of Higgs bosons using the 𝜏⁢𝜏 final state

A study of anomalous couplings of the Higgs boson to vector bosons and fermions is presented. The data were recorded by the CMS experiment at a center-of-mass energy of pp collisions at the LHC of 13 TeV and correspond to an integrated luminosity of 138 fb −1 . The study uses Higgs boson candidates produced mainly in gluon fusion or electroweak vector boson fusion at the LHC that subsequently decay to a pair of 𝜏 leptons. Matrix-element and machine-learning techniques were employed in a search for anomalous interactions. The results are combined with those from the four-lepton and two-photon decay channels to yield the most stringent constraints on anomalous Higgs boson couplings to date. The pure 𝐶⁢𝑃-odd scenario of the Higgs boson coupling to gluons is excluded at 2.4 standard deviations. The results are consistent with the standard model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Search for Higgs Boson Decay to a Charm Quark-Antiquark Pair in Proton-Proton Collisions at s = 13 TeV

A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, $H → c\bar{c}$, produced in association with a leptonically decaying $V (W \text{or} Z)$ boson is presented. The search is performed with proton-proton collisions at $\sqrt{s}=13\,\text {TeV}$ collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb -1 . Novel charm jet identification and analysis methods using machine learning techniques are employed. The analysis is validated by searching for $Z → c\bar{c}$ in $VZ$ events, leading to its first observation at a hadron collider with a significance of 5.7 standard deviations. The observed (expected) upper limit on $σ(VH)\mathscr{B}(H → c\bar{c}$) is 0.94 (0.50$^{+0.22}_{– 0.15}$)pb at 95% confidence level (C.L.), corresponding to 14 (7.6$^{+3.4}_{–2.3}$) times the standard model prediction. For the Higgs-charm Yukawa coupling modifier, $κ_c$, the observed (expected) 95% C.L. interval is 1.1 < |$κ_c$| < 5.5 (|$κ_c$| < 3.4), the most stringent constraint to date.

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DOE OSTI2023

Search for high-mass exclusive γγ → WW and γγ → ZZ production in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search is performed for exclusive high-mass γγ → WW and γγ → ZZ production in proton-proton collisions using intact forward protons reconstructed in near-beam detectors, with both weak bosons decaying into boosted and merged jets. The analysis is based on a sample of proton-proton collisions collected by the CMS and TOTEM experiments at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 100 fb -1 . No excess above the standard model background prediction is observed, and upper limits are set on the pp → pWWp and pp → pZZp cross sections in a fiducial region defined by the diboson invariant mass m(VV) > 1 TeV (with V = W, Z) and proton fractional momentum loss 0.04 < ξ < 0.20. The results are interpreted as new limits on dimension-6 and dimension-8 anomalous quartic gauge couplings.

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DOE OSTI2023

Search for long-lived particles using out-of-time trackless jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search for long-lived particles decaying in the outer regions of the CMS silicon tracker or in the calorimeters is presented. The search is based on a data sample of proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded with the CMS detector at the LHC in 2016–2018, corresponding to an integrated luminosity of 138 fb −1 . A novel technique, using nearly trackless and out-of-time jet information combined in a deep neural network discriminator, is employed to identify decays of long-lived particles. The results are interpreted in a simplified model of chargino-neutralino production, where the neutralino is the next-to-lightest supersymmetric particle, is long-lived, and decays to a gravitino and either a Higgs or Z boson. This search is most sensitive to neutralino proper decay lengths of approximately 0.5 m, for which masses up to 1.18 TeV are excluded at 95% confidence level. The current search is the best result to date in the mass range from the kinematic limit imposed by the Higgs boson mass up to 1.8 TeV.

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DOE OSTI2023

Search for direct pair production of supersymmetric partners of τ leptons in the final state with two hadronically decaying τ leptons and missing transverse momentum in proton-proton collisions at s = 13 TeV

A search for the direct production of a pair of $τ$ sleptons, the supersymmetric partners of $τ$ leptons, is presented. Each $τ$ slepton is assumed to decay to a $τ$ lepton and the lightest supersymmetric particle (LSP), which is assumed to be stable and to not interact in the detector, leading to an imbalance in the total reconstructed transverse momentum. The search is carried out in events identified as containing two $τ$ leptons, each decaying to one or more hadrons and a neutrino, and significant transverse momentum imbalance. In addition to scenarios in which the $τ$ sleptons decay promptly, the search also addresses scenarios in which the $τ$ sleptons have sufficiently long lifetimes to give rise to nonprompt $τ$ leptons. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV at the CERN LHC with the CMS detector in 2016–2018, and correspond to an integrated luminosity of 138 fb -1 . No significant excess is seen with respect to standard model expectations. Upper limits on cross sections for the pair production of $τ$ sleptons are obtained in the framework of simplified models. In a scenario in which the $τ$ sleptons are superpartners of left-handed $τ$ leptons, and each undergoes a prompt decay to a $τ$ lepton and a nearly massless LSP, $τ$ slepton masses between 115 and 340 GeV are excluded. In a scenario in which the lifetime of the $τ$ sleptons corresponds to c$τ$ 0 = 0.1 mm, where $τ_{0}$ represents the mean proper lifetime of the $τ$ slepton, masses between 150 and 220 GeV are excluded.

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DOE OSTI2023

Azimuthal anisotropy of dijet events in PbPb collisions at $$ \sqrt{s_{\textrm{NN}}} $$ = 5.02 TeV

A bstract The path-length dependent parton energy loss within the dense partonic medium created in lead-lead collisions at a nucleon-nucleon center-of-mass energy of $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5 . 02 TeV is studied by determining the azimuthal anisotropies for dijets with high transverse momentum. The data were collected by the CMS experiment in 2018 and correspond to an integrated luminosity of 1.69 nb − 1 . For events containing back-to-back jets, correlations in relative azimuthal angle and pseudorapidity ( η ) between jets and hadrons, and between two hadrons, are constructed. The anisotropies are expressed as the Fourier expansion coefficients v n , n = 2–4 of these azimuthal distributions. The dijet v n values are extracted from long-range (1 . 5 < |∆ η | < 2 . 5) components of these correlations, which suppresses the background contributions from jet fragmentation processes. Positive dijet v 2 values are observed which increase from central to more peripheral events, while the v 3 and v 4 values are consistent with zero within experimental uncertainties.

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DOE OSTI2023

Evidence for four-top quark production in proton-proton collisions at s = 13 TeV

The production of four top quarks ($\mathrm{t\bar{t}t\bar{t}}$) is studied with LHC proton-proton collision data samples collected by the CMS experiment at a center-of-mass energy of 13 TeV, and corresponding to integrated luminosities of up to 138 fb$^{-1}$. Events that have no leptons (all-hadronic), one lepton, or two opposite-sign leptons (where lepton refers only to prompt electrons or prompt muons) are considered. This is the first $\mathrm{t\bar{t}t\bar{t}}$ measurement that includes the all-hadronic final state. The observed significance of the $\mathrm{t\bar{t}t\bar{t}}$ signal in these final states of 3.9 standard deviations (1.5 expected) provides evidence for $\mathrm{t\bar{t}t\bar{t}}$ production, with a measured cross section of 36 $^{+12}_{-11}$ fb. Combined with earlier CMS results in other final states, the signal significance is 4.0 standard deviations (3.2 expected). The combination returns an observed cross section of 17 $\pm$ 4 (stat) $\pm$ 3 (syst) fb, which is consistent with the standard model prediction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Search for medium effects using jets from bottom quarks in PbPb collisions at $\sqrt{^SNN}$ = 5.02 TeV

The first study of the shapes of jets arising from bottom (b) quarks in heavy ion collisions is presented. Jet shapes are studied using charged hadron constituents as a function of their radial distance from the jet axis. Lead-lead (PbPb) collision data at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{NN}}$ = 5.02 TeV were recorded by the CMS detector at the LHC, with an integrated luminosity of 1.69 nb-1. Compared to proton-proton collisions, a redistribution of the energy in b jets to larger distances from the jet axis is observed in PbPb collisions. This medium-induced redistribution is found to be substantially larger for b jets than for inclusive jets.

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DOE OSTI2023

Search for new heavy resonances decaying to WW, WZ, ZZ, WH, or ZH boson pairs in the all-jets final state in proton-proton collisions at √s = 13 TeV

A search for new heavy resonances decaying to WW, WZ, ZZ, WH, or ZH boson pairs in the all-jets final state is presented. The analysis is based on proton-proton collision data recorded by the CMS detector in 2016–2018 at a centre-of-mass energy of 13 TeV at the CERN LHC, corresponding to an integrated luminosity of 138 fb –1 . The search is sensitive to resonances with masses between 1.3 and 6 TeV, decaying to bosons that are highly Lorentz-boosted such that each of the bosons forms a single large-radius jet. Machine learning techniques are employed to identify such jets. No significant excess over the estimated standard model background is observed. A maximum local significance of 3.6 standard deviations, corresponding to a global significance of 2.3 standard deviations, is observed at masses of 2.1 and 2.9 TeV. In a heavy vector triplet model, spin-1 Z' and W' resonances with masses below 4.8 TeV are excluded at the 95% confidence level (CL). These limits are the most stringent to date. In a bulk graviton model, spin-2 gravitons and spin-0 radions with masses below 1.4 and 2.7 TeV, respectively, are excluded at 95% CL. Production of heavy resonances through vector boson fusion is constrained with upper cross section limits at 95% CL as low as 0.1 fb.

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DOE OSTI2023

Measurement of the Higgs boson inclusive and differential fiducial production cross sections in the diphoton decay channel with pp collisions at $\sqrt{s}$ = 13 TeV

The measurements of the inclusive and differential fiducial cross sections of the Higgs boson decaying to a pair of photons are presented. The analysis is performed using proton-proton collisions data recorded with the CMS detector at the LHC at a centre-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 137 fb -1 . The inclusive fiducial cross section is measured to be σ fid = 73.4$^{+5.4}_{-5.3}$ (stat)$a^{+2.4}_{-2.2 }$(syst) fb, in agreement with the standard model expectation of 75.4 ± 4.1 fb. The measurements are also performed in fiducial regions targeting different production modes and as function of several observables describing the diphoton system, the number of additional jets present in the event, and other kinematic observables. Two double differential measurements are performed. No significant deviations from the standard model expectations are observed.

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DOE OSTI2023

Search for CP violation in t$\overline{\textrm{t}}$H and tH production in multilepton channels in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The charge-parity (CP) structure of the Yukawa interaction between the Higgs (H) boson and the top quark is measured in a data sample enriched in the t$\overline{t}$H and tH associated production, using 138 fb -1 of data collected in proton-proton collisions at $\sqrt{s}$ = 13 TeV by the CMS experiment at the CERN LHC. The study targets events where the H boson decays via H → WW or H → ττ and the top quarks decay via t → Wb: the W bosons decay either leptonically or hadronically, and final states characterized by the presence of at least two leptons are studied. Machine learning techniques are applied to these final states to enhance the separation of CP -even from CP -odd scenarios. Two-dimensional confidence regions are set on $κ$ t and $\widetilde{k}$t, which are respectively defined as the CP -even and CP -odd top-Higgs Yukawa coupling modifiers. No significant fractional CP -odd contributions, parameterized by the quantity |$f^{Htt}_{CP}$| are observed; the parameter is determined to be |$f^{Htt}_{CP}$| = 0.59 with an interval of (0.24, 0.81) at 68% confidence level. The results are combined with previous results covering the H → ZZ and H → γγ decay modes, yielding two- and one-dimensional confidence regions on $κ$ t and $\widetilde{k}$t, while |$f^{Htt}_{CP}$| is determined to be |$f^{Htt}_{CP}$| = 0.28 with an interval of |$f^{Htt}_{CP}$| < 0.55 at 68% confidence level, in agreement with the standard model CP -even prediction of |$f^{Htt}_{CP}$| = 0.

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