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Carvalho, W.

Publications and source records attributed to Carvalho, W..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Searches for additional Higgs bosons and for vector leptoquarks in $ττ$ final states in proton-proton collisions at $\sqrt{s}$ = 13 TeV

Three searches are presented for signatures of physics beyond the standard model (SM) in $ττ$ final states in proton-proton collisions at the LHC, using a data sample collected with the CMS detector at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb -1 . Upper limits at 95% confidence level (CL) are set on the products of the branching fraction for the decay into $τ$ leptons and the cross sections for the production of a new boson $\phi$, in addition to the H(125) boson, via gluon fusion (gg$\phi$) or in association with b quarks, ranging from $\mathcal{O}$(10 pb) for a mass of 60 GeV to 0.3 fb for a mass of 3.5 TeV each. The data reveal two excesses for gg$\phi$ production with local $p$-values equivalent to about three standard deviations at m $\phi$ = 0.1 and 1.2 TeV. In a search for $t$-channel exchange of a vector leptoquark U 1 , 95% CL upper limits are set on the dimensionless U 1 leptoquark coupling to quarks and $τ$ leptons ranging from 1 for a mass of 1 TeV to 6 for a mass of 5 TeV, depending on the scenario. In the interpretations of the $M^{125}_{h}$ and $M^{125}_{h,EFT}$ minimal supersymmetric SM benchmark scenarios, additional Higgs bosons with masses below 350 GeV are excluded at 95% CL.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of the top quark pole mass using $ \textrm{t}\overline{\textrm{t}} $+jet events in the dilepton final state in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

A measurement of the top quark pole mass $\mathcal{m}^\text{pole}_\text{t}$ in events where a top quark-antiquark pair ($\text{t}\bar{\text{t}}$) is produced in association with at least one additional jet ($\text{t}\bar{\text{t}}$ +jet) is presented. This analysis is performed using proton-proton collision data at $\sqrt{s}$ = 13 TeV collected by the CMS experiment at the CERN LHC, corresponding to a total integrated luminosity of 36.3 fb -1 . Events with two opposite-sign leptons in the final state (e + e – , μ + μ – , e ± μ ∓ ) are analyzed. The reconstruction of the main observable and the event classification are optimized using multivariate analysis techniques based on machine learning. The production cross section is measured as a function of the inverse of the invariant mass of the $\text{t}\bar{\text{t}}$ +jet system at the parton level using a maximum likelihood unfolding. Given a reference parton distribution function (PDF), the top quark pole mass is extracted using the theoretical predictions at next-to-leading order. For the ABMP16NLO PDF, this results in $\mathcal{m}^\text{pole}_\text{t}$ = 172.93 ± 1.36 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Measurement of inclusive and differential cross sections for single top quark production in association with a W boson in proton-proton collisions at $\sqrt{s}$ = 13 TeV

Measurements of the inclusive and normalised differential cross sections are presented for the production of single top quarks in association with a W boson in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data used were recorded with the CMS detector at the LHC during 2016–2018, and correspond to an integrated luminosity of 138 fb -1 . Events containing one electron and one muon in the final state are analysed. For the inclusive measurement, a multivariate discriminant, exploiting the kinematic properties of the events is used to separate the signal from the dominant t$\overline{t}$ background. A cross section of 79.2 ± 0.9(stat)$^{+7.7}_{-8.0}$ (syst) ± 1.2 (lumi) pb is obtained, consistent with the predictions of the standard model. For the differential measurements, a fiducial region is defined according to the detector acceptance, and the requirement of exactly one jet coming from the fragmentation of a bottom quark. The resulting distributions are unfolded to particle level and agree with the predictions at next-to-leading order in perturbative quantum chromodynamics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Search for nonresonant Higgs boson pair production in the four leptons plus twob jets final state in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The first search for nonresonant production of Higgs boson pairs (HH) with one H decaying into four leptons and the other into a pair of b quarks is presented, using proton-proton collisions recorded at a center-of-mass energy of √s = 13 TeV by the CMS experiment. The analyzed data correspond to an integrated luminosity of 138 fb–1. A 95% confidence level upper limit of 32.4 is set on the signal strength modifier μ, defined as the ratio of the observed HH production rate in the HH → ZZ*b$\overline{b}$ → 4lb$\overline{b}$ decay channel to the standard model (SM) expectation. Possible modifications of the H trilinear coupling λHHH with respect to the SM value are investigated. The coupling modifier κ λ , defined as λHHH divided by its SM prediction, is constrained to be within the observed (expected) range –8.8 (–9.8) < κ λ < 13.4 (15.0) at 95% confidence level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Analysis of a tau neutrino origin for the near-horizon air shower events observed by the fourth flight of the Antarctic Impulsive Transient Antenna

In this work, we study in detail the sensitivity of the Antarctic Impulsive Transient Antenna (ANITA) to possible ν τ point source fluxes detected via τ-lepton-induced air showers. This investigation is framed around the observation of four upward-going extensive air shower events very close to the horizon seen in ANITA-IV. We find that these four upgoing events are not observationally inconsistent with τ-induced EASs from Earth-skimming ν τ both in their spectral properties as well as in their observed locations on the sky. These four events as well as the overall diffuse and point source exposure to Earth-skimming ν τ are also compared against published ultrahigh-energy neutrino limits from the Pierre Auger Observatory. While none of these four events occurred at sky locations simultaneously visible by Auger, the implied fluence necessary for ANITA to observe these events is in strong tension with limits set by Auger across a wide range of energies and is additionally in tension with ANITA’s Askaryan in-ice neutrino channel above 10 19 eV. We conclude by discussing some of the technical challenges with simulating and analyzing these near horizon events and the potential for future observatories to observe similar events.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Search for a heavy resonance decaying to a top quark and a W boson at $\sqrt{s}$ = 13 TeV in the fully hadronic final state

A search for a heavy resonance decaying to a top quark and a W boson in the fully hadronic final state is presented. The analysis is performed using data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb -1 recorded by the CMS experiment at the LHC. The search is focused on heavy resonances, where the decay products of each top quark or W boson are expected to be reconstructed as a single, large-radius jet with a distinct substructure. The production of an excited bottom quark, b*, is used as a benchmark when setting limits on the cross section for a heavy resonance decaying to a top quark and a W boson. The hypotheses of b* quarks with left-handed, right-handed, and vector-like chiralities are excluded at 95% confidence level for masses below 2.6, 2.8, and 3.1 TeV, respectively. These are the most stringent limits on the b* quark mass to date, extending the previous best limits by almost a factor of two.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Search for long-lived particles decaying to jets with displaced vertices in proton-proton collisions at √ s = 13 TeV

A search is presented for long-lived particles produced in pairs in proton-proton collisions at the LHC operating at a center-of-mass energy of 13 TeV . The data were collected with the CMS detector during the period from 2015 through 2018, and correspond to a total integrated luminosity of 140 fb –1 . This search targets pairs of long-lived particles with mean proper decay lengths between 0.1 and 100 mm , each of which decays into at least two quarks that hadronize to jets, resulting in a final state with two displaced vertices. No significant excess of events with two displaced vertices is observed. In the context of R-parity violating supersymmetry models, the pair production of long-lived neutralinos, gluinos, and top squarks is excluded at 95% confidence level for cross sections larger than 0.08 fb, masses between 800 and 3000 GeV, and mean proper decay lengths between 1 and 25 mm.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Measurements of $t\overline tH$ Production and the CP Structure of the Yukawa Interaction between the Higgs Boson and Top Quark in the Diphoton Decay Channel

The first observation of the t t ¯ H process in a single Higgs boson decay channel with the full reconstruction of the final state ( H → γ γ ) is presented, with a significance of 6.6 standard deviations ( σ ). The C P structure of Higgs boson couplings to fermions is measured, resulting in an exclusion of the pure C P -odd structure of the top Yukawa coupling at 3.2 σ . The measurements are based on a sample of proton-proton collisions at a center-of-mass energy s = 13 TeV collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb – 1 . The cross section times branching fraction of the t t ¯ H process is measured to be σ t t ¯ H B γ γ = 1.56 – 0.32 + 0.34 fb , which is compatible with the standard model prediction of 1.13 – 0.11 + 0.08 fb . The fractional contribution of the C P -odd component is measured to be f C P H t t = 0.00 ± 0.33 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗