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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
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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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the $B_s^0$ → μ + μ - decay properties and search for the B 0 → μ + μ - decay in proton-proton collisions at $\sqrt{s}$ = 13 TeV

Measurements are presented of the $B_s^0$ → μ + μ - branching fraction and effective lifetime, as well as results of a search for the B 0 → μ + μ - decay in proton-proton collisions at at the LHC. The analysis is based on data collected with the CMS detector in 2016–2018 corresponding to an integrated luminosity of 140 fb -1 . The branching fraction of the $B_s^0$ → μ + μ - decay and the effective $B_s^0$ meson lifetime are the most precise single measurements to date. No evidence for the B 0 → μ + μ - decay has been found. All results are found to be consistent with the standard model predictions and previous measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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

Observation of four top quark production in proton-proton collisions at s = 13 TeV

The observation of the production of four top quarks in proton-proton collisions is reported, based on a data sample collected by the CMS experiment at a center-of-mass energy of 13 TeV in 2016–2018 at the CERN LHC and corresponding to an integrated luminosity of 138 fb − 1 . Events with two same-sign, three, or four charged leptons (electrons and muons) and additional jets are analyzed. Compared to previous results in these channels, updated identification techniques for charged leptons and jets originating from the hadronization of b quarks, as well as a revised multivariate analysis strategy to distinguish the signal process from the main backgrounds, lead to an improved expected signal significance of 4.9 standard deviations above the background-only hypothesis. Four top quark production is observed with a significance of 5.6 standard deviations, and its cross section is measured to be 17.7 − 3.5 + 3.7 (stat) − 1.9 + 2.3 (syst) fb , in agreement with the available standard model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measurements of azimuthal anisotropy of nonprompt D 0 mesons in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

Measurements of the elliptic ($v$ 2 ) and triangular ($v$ 3 ) azimuthal anisotropy coefficients are presented for D 0 mesons produced in b hadron decays (nonprompt D 0 mesons) in lead-lead collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. The results are compared with previously published charm meson anisotropies measured using prompt D 0 mesons. The data were collected with the CMS detector in 2018 with an integrated luminosity of 0.58 nb –1 . Azimuthal anisotropy is sensitive to the interactions of quarks with the hot and dense medium created in heavy ion collisions. Comparing results for prompt and nonprompt D 0 mesons can assist in understanding the mass dependence of these interactions. The nonprompt results show lower magnitudes of $v$ 2 and $v$ 3 and weaker dependences on the meson transverse momentum and collision centrality than those found for prompt D 0 mesons. The results are in agreement with theoretical predictions that include a mass dependence in the interactions of quarks with the medium

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Search for new Higgs bosons via same-sign top quark pair production in association with a jet in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search is presented for new Higgs bosons in proton-proton (pp) collision events in which a same-sign top quark pair is produced in association with a jet, via the pp $\to$ tH/A $\to$ t$\mathrm{\bar{t}}$c and pp $\to$ tH/A $\to$ t$\mathrm{\bar{t}}$u processes. Here, H and A represent the extra scalar and pseudoscalar boson, respectively, of the second Higgs doublet in the generalized two-Higgs-doublet model (g2HDM). The search is based on pp collision data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb$^{-1}$. Final states with a same-sign lepton pair in association with jets and missing transverse momentum are considered. New Higgs bosons in the 200-1000 GeV mass range and new Yukawa couplings between 0.1 and 1.0 are targeted in the search, for scenarios in which either H or A appear alone, or in which they coexist and interfere. No significant excess above the standard model prediction is observed. Exclusion limits are derived in the context of the g2HDM.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Study of azimuthal anisotropy of $\Upsilon$ (1S) mesons in pPb collisions at $\sqrt{S_{NN}}$ = 8.16 TeV

The azimuthal anisotropy of Image 1 mesons in high-multiplicity proton-lead collisions is studied using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 8.16 TeV. The Image 1 mesons are reconstructed using their dimuon decay channel. The anisotropy is characterized by the second Fourier harmonic coefficients, found using a two-particle correlation technique, in which the Image 1 mesons are correlated with charged hadrons. A large pseudorapidity gap is used to suppress short-range correlations. Nonflow contamination from the dijet background is removed using a low-multiplicity subtraction method, and the results are presented as a function of Image 1 transverse momentum. The azimuthal anisotropies are smaller than those found for charmonia in proton-lead collisions at the same collision energy, but are consistent with values found for Image 1 mesons in lead-lead interactions at a nucleon-nucleon center-of-mass energy of 5.02 TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Search for an exotic decay of the Higgs boson into a Z boson and a pseudoscalar particle in proton-proton collisions at s = 13 TeV

A search for an exotic decay of the Higgs boson to a Z boson and a light pseudoscalar particle (a), decaying to a pair of leptons and a pair of photons, respectively, is presented. The search is based on proton-proton collision data at a center-of-mass energy of s = 13 TeV , collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 138 fb − 1 . The analysis probes pseudoscalar masses m a between 1 and 30 GeV, leading to two pairs of well-isolated leptons and photons. Upper limits at 95% confidence level are set on the Higgs boson production cross section times its branching fraction to two leptons and two photons. The observed (expected) limits are in the range of 1.1–17.8 (1.7–17.9)fb within the probed m a interval. An excess of data above the expected standard model background with a local (global) significance of 2.6 (1.3) standard deviations is observed for a mass hypothesis of m a = 3 GeV . Limits on models involving axion-like particles, formulated as an effective field theory, are also reported.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Search for the lepton flavor violating τ → 3μ decay in proton-proton collisions at s = 13 TeV

A search for the lepton flavor violating τ → 3 μ decay is performed using proton-proton collision events at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC in 2017–2018, corresponding to an integrated luminosity of 97.7 fb − 1 . Tau leptons produced in both heavy-flavor hadron and W boson decays are exploited in the analysis. No evidence for the decay is observed. The results of this search are combined with an earlier null result based on data collected in 2016 to obtain a total integrated luminosity of 131 fb − 1 . The observed (expected) upper limits on the branching fraction B ( τ → 3 μ ) at confidence levels of 90 and 95% are 2.9 × 10 − 8 ( 2.4 × 10 − 8 ) and 3.6 × 10 − 8 ( 3.0 × 10 − 8 ), respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Evidence for tWZ production in proton-proton collisions at s = 13 TeV in multilepton final states

The first evidence for the standard model production of a top quark in association with a W boson and a Z boson is reported. The measurement is performed in multilepton final states, where the Z boson is reconstructed via its decays to electron or muon pairs. At least one W boson, associated or from top quark decay, decays leptonically, too. The analysed data were recorded by the CMS experiment at the CERN LHC in 2016–2018 in proton-proton collisions at s = 13 TeV, and correspond to an integrated luminosity of 138 fb −1 . The measured cross section is 354 ± 54 ( stat ) ± 95 ( syst ) fb, and corresponds to a statistical significance of 3.4 standard deviations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

$K^0_S$ and $Λ(\overline{Λ})$ two-particle femtoscopic correlations in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02TeV

Two-particle correlations are presented for $K^0_S$, $Λ$, and $\overline{Λ}$ strange hadrons as a function of relative momentum in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The dataset corresponds to an integrated luminosity of 0.607 nb -1 and was collected using the CMS detector at the CERN LHC. These correlations are sensitive to quantum statistics and to final-state interactions between the particles. The source size extracted from the $K^0_S$$K^0_S$ correlations is found to decrease from 4.6 to 1.6 fm in going from central to peripheral collisions. Strong interaction scattering parameters (i.e., scattering length and effective range) are determined from the $ΛK^0_S$ and $ΛΛ$ (including their charge conjugates) correlations using the Lednický–Lyuboshitz model and are compared to theoretical and other experimental results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measurement of the production cross section of a Higgs boson with large transverse momentum in its decays to a pair of τ leptons in proton-proton collisions at s = 13 TeV

A measurement of the production cross section of a Higgs boson with transverse momentum greater than 250GeV is presented where the Higgs boson decays to a pair of τ leptons. It is based on proton-proton collision data collected by the CMS experiment at the CERN LHC at a center-of-mass energy of 13TeV. The data sample corresponds to an integrated luminosity of 138 fb − 1 . Because of the large transverse momentum of the Higgs boson the τ leptons from its decays are boosted and produced spatially close, with their decay products overlapping. Therefore, a dedicated algorithm was developed to reconstruct and identify them. The observed (expected) significance of the measured signal with respect to the standard model background-only hypothesis is 3.5 (2.2) standard deviations. The product of the production cross section and branching fraction is measured to be 1.64 − 0.54 + 0.68 times the standard model expectation. The fiducial differential production cross section is also measured as functions of the Higgs boson and leading jet transverse momenta. This measurement extends the probed large-transverse-momentum region in the ττ final state beyond 600GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Searches for violation of Lorentz invariance in top quark pair production using dilepton events in 13 TeV proton-proton collisions

A search for violation of Lorentz invariance in the production of top quark pairs ($t\bar{t}$) is presented. The measured normalized differential $t\bar{t}$production cross section, as a function of the sidereal time, is examined for potential modulations induced by Lorentz-invariance breaking operators in an effective field theory extension of the standard model (SM). The cross section is measured from collision events collected by the CMS detector at a center-of-mass-energy of 13 TeV, corresponding to an integrated luminosity of 77.8 fb −1 , and containing one electron and one muon. The results are found to be compatible with zero, in agreement with the SM, and are used to place upper limits at 68% confidence level on the magnitude of the Lorentz-violating couplings ranging from 1–8 × 10 −3 . This is the first precision test of the isotropy in special relativity with top quarks at the LHC, restricting further the bounds on such couplings by up to two orders of magnitude with respect to previous searches conducted at the Tevatron.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Search for a standard model-like Higgs boson in the mass range between 70 and 110 GeV in the diphoton final state in proton-proton collisions at $\sqrt{s} = 13$ TeV

The results of a search for a standard model-like Higgs boson decaying into two photons in the mass range between 70 and 110 GeV are presented. The analysis uses the data set collected by the CMS experiment in proton-proton collisions at $\sqrt{s} = 13$ TeV corresponding to integrated luminosities of 36.3 fb -1 , 41.5 fb -1 and 54.4 fb -1 during the 2016, 2017, and 2018 LHC running periods, respectively. No significant excess over the background expectation is observed and 95% confidence level upper limits are set on the product of the cross section and branching fraction for decays of an additional Higgs boson into two photons. The maximum deviation with respect to the background is seen for a mass hypothesis of 95.4 GeV with a local (global) significance of 2.9 (1.3) standard deviations. The observed upper limit ranges from 15 to 73 fb.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Girth and groomed radius of jets recoiling against isolated photons in lead-lead and proton-proton collisions at $\sqrt{s_{NN}} = 5.02$ TeV

This Letter presents the first measurements of the groomed jet radius R g and the jet girth g in events with an isolated photon recoiling against a jet in lead-lead (PbPb) and proton-proton (pp) collisions at the LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The observables R g and g provide a quantitative measure of how narrow or broad a jet is. The analysis uses PbPb and pp data samples with integrated luminosities of 1.7 nb -1 and 301 pb -1 , respectively, collected with the CMS experiment in 2018 and 2017. Events are required to have a photon with transverse momentum $p^{γ}_{T} > 100$ GeV and at least one jet back-to-back in azimuth with respect to the photon and with transverse momentum $p^{jet}_{T}$ such that $p^{jet}_{T}/p^{γ}_{T} > 0.4$ . The measured R g and g distributions are unfolded to the particle level, which facilitates the comparison between the PbPb and pp results and with theoretical predictions. It is found that jets with $p^{jet}_{T}/p^{γ}_{T} > 0.8$ , i.e., those that closely balance the photon $p^{γ}_{T}$ , are narrower in PbPb than in pp collisions. Relaxing the selection to include jets with $p^{jet}_{T}/p^{γ}_{T} > 0.4$ reduces the narrowing of the angular structure of jets in PbPb relative to the pp reference. This shows that selection bias effects associated with jet energy loss play an important role in the interpretation of jet substructure measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Search for bottom quark associated production of the standard model Higgs boson in final states with leptons in proton-proton collisions at $\sqrt{s}$ =13 TeV

This Letter presents the first search for bottom quark associated production of the standard model Higgs boson, in final states with leptons. Higgs boson decays to pairs of tau leptons and pairs of leptonically decaying W bosons are considered. The search is performed using data collected from 2016 to 2018 by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb -1 . Upper limits at the 95% confidence level are placed on the signal strength for Higgs boson production in association with bottom quarks; the observed (expected) upper limit is 3.7 (6.1) times the standard model prediction

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Search for the Higgs boson decays to a ρ 0 , ϕ, or K ⁎0 meson and a photon in proton-proton collisions at $\sqrt{s} = 13$ TeV

Three rare decay processes of the Higgs boson to a ρ(770) 0 , Φ(1020), or K ⁎ (892) 0 meson and a photon are searched for using $\sqrt{s} = 13$ TeV proton-proton collision data collected by the CMS experiment at the LHC. Events are selected assuming the mesons decay into a pair of charged pions, a pair of charged kaons, or a charged kaon and pion, respectively. Depending on the Higgs boson production mode, different triggering and reconstruction techniques are adopted. The analyzed data sets correspond to integrated luminosities up to 138 fb -1 , depending on the reconstructed final state. After combining various data sets and categories, no significant excess above the background expectations is observed. Upper limits at 95% confidence level on the Higgs boson branching fractions into ρ(770) 0 $γ$, Φ(1020)$γ$, and K ⁎ (892) 0 are determined to be 3.7 x 10 -4 , 3.0 x 10 -4 , and 3.0 x 10 -4 , respectively. In case of the ρ(770) 0 $γ$ and Φ(1020)$γ$ channels, these are the most stringent experimental limits to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Angular analysis of the B 0 → K ⁎ (892) 0 μ + μ − decay in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A full set of optimized observables is measured in an angular analysis of the decay B 0 → K* (892) 0 μ + μ – using a sample of proton-proton collisions at $\sqrt{s}$ = 13 TeV, collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 140fb –1 . The analysis is performed in six bins of the squared invariant mass of the dimuon system, q 2 , over the range 1.1 < q 2 < 16 GeV 2 . The results are among the most precise experimental measurements of the angular observables for this decay and are compared to a variety of predictions based on the standard model. Some of these predictions exhibit tension with the measurements.

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