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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

First measurement of the cross section for top quark pair production with additional charm jets using dileptonic final states in pp collisions at $\sqrt{s}$= 13 TeV

The first measurement of the inclusive cross section for top quark pairs ($t\bar{t}$) produced in association with two additional charm jets is presented. The analysis uses the dileptonic final states of $t\bar{t}$ events produced in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 41.5 fb -1 recorded by the CMS experiment at the LHC. A new charm jet identification algorithm provides input to a neural network that is trained to distinguish among $t\bar{t}$ events with two additional charm ($t\bar{t}c\bar{c}$), bottom ($t\bar{t}b\bar{b}$), and light-flavour or gluon ($t\bar{t}LL$) jets. By means of a template fitting procedure, the inclusive $t\bar{t}c\bar{c}$, $t\bar{t}b\bar{b}$, and $t\bar{t}LL$ cross sections are simultaneously measured, together with their ratios to the inclusive $t\bar{t}$ + two jets cross section. This provides measurements of the $t\bar{t}c\bar{c}$ and $t\bar{t}b\bar{b}$ cross sections of 10.1 ± 1.2 (stat) ± 1.4 (syst) pb and 4.54 ± 0.35 (stat) ± 0.56 (syst) pb, respectively, in the full phase space. The results are compared and found to be consistent with predictions from two different matrix element generators with next-to-leading order accuracy in quantum chromodynamics, interfaced with a parton shower simulation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Measurement of prompt ${\mathrm{D^0}}$ and ${\mathrm{\overline{D}}{}^0}$ meson azimuthal anisotropy and search for strong electric fields in PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV

The strong Coulomb field created in ultrarelativistic heavy ion collisions is expected to produce a rapidity-dependent difference ( Δv 2 ) in the second Fourier coefficient of the azimuthal distribution (elliptic flow, v 2 ) between D 0 ( $\bar{u}c$ ) and ${\mathrm{\overline{D}}{}^0}$ ( $u\bar{c}$ ) mesons. Motivated by the search for evidence of this field, the CMS detector at the LHC is used to perform the first measurement of Δv 2 . The rapidity-averaged value is found to be ⟨Δv2⟩=0.001±0.001(stat)±0.003(syst) in PbPb collisions at $\sqrt{s_{NN}}$=5.02 TeV . In addition, the influence of the collision geometry is explored by measuring the D 0 and ${\mathrm{\overline{D}}{}^0}$ mesons v 2 and triangular flow coefficient ( v 3 ) as functions of rapidity, transverse momentum ( p T ), and event centrality (a measure of the overlap of the two Pb nuclei). A clear centrality dependence of prompt D 0 meson v 2 values is observed, while the v 3 is largely independent of centrality. These trends are consistent with expectations of flow driven by the initial-state geometry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

In memoriam: Sheldon Leslie Stone

Sheldon Stone (Feb. 14, 1946 – Oct. 6, 2021), distinguished professor of physics at Syracuse University, passed away in early October at the age of 75. He graduated from Brooklyn College in 1967 and earned his doctorate at the University of Rochester in 1972 under the guidance of Thomas Ferbel. He devoted most of his career to the study of particles containing charm and bottom quarks.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Measurement of the associated production of a $Z$ boson with charm or bottom quark jets in proton-proton collisions at $\sqrt {s}$=13 TeV

Ratios of cross sections, σ(Z+c jets)/σ(Z+jets), σ(Z+b jets)/σ(Z+jets), and σ(Z+c jets)/σ(Z+b jets) in the associated production of a Z boson with at least one charm or bottom quark jet are measured in proton-proton collisions at s=13 TeV. The data sample, collected by the CMS experiment at the CERN LHC, corresponds to an integrated luminosity of 35.9 fb-1, with a fiducial volume of pT>30 GeV and |η|<2.4 for the jets, where pT and η represent transverse momentum and pseudorapidity, respectively. The Z boson candidates come from leptonic decays into electrons or muons with pT>25 GeV and |η|<2.4, and the dilepton mass satisfies 71

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

On the physics potential to study the gluon content of proton and deuteron at NICA SPD

The Spin Physics Detector (SPD) is a future multipurpose experiment foreseen to run at the NICA collider, which is currently under construction at the Joint Institute for Nuclear Research (JINR, Dubna, Russia). The physics program of the experiment is based on collisions of longitudinally and transversely polarized protons and deuterons at √s up to 27 GeV and luminosity up to 10 32 cm –2 s –1 . SPD will operate as a universal facility for the comprehensive study of the unpolarized and polarized gluon content of the nucleon, using complementary probes such as: charmonia, open-charm, and prompt-photon production processes. Furthermore, the aim of this work is to provide a thorough review of the physics objectives that can potentially be addressed at SPD, underlining related theoretical aspects and discussing relevant experimental results when available. Among different pertinent phenomena particular attention is drawn to the study of the gluon helicity, gluon Sivers and Boer-Mulders functions in the nucleon, as well as the gluon transversity distribution in the deuteron, via the measurement of single and double spin asymmetries.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Test of lepton flavor universality with measurements of 𝑅⁡(𝐷 + ) and 𝑅⁡(𝐷* + ) using semileptonic 𝐵 tagging at the Belle II experiment

We report measurements of the ratios of branching fractions ℛ⁡(𝐷 (*)+ ) = ℬ⁡($\bar{𝐵}$ 0 → 𝐷 (*)+ ⁢𝜏 −⁢ $\bar{𝜈}$ 𝜏 )/ℬ⁡($\bar{𝐵}$ 0 → 𝐷 (*)+ ⁢ℓ − $\bar{𝜈}$ ℓ ), where ℓ denotes either an electron or a muon. These ratios test the universality of the charged-current weak interaction. The results are based on a 365 fb −1 data sample collected with the Belle II detector at the SuperKEKB 𝑒 + ⁢𝑒 − collider, which operates at a center-of-mass energy corresponding to the ϒ⁡(4⁢𝑆) resonance, just above the threshold for $𝐵\bar{𝐵}$ production. Signal candidates are reconstructed by selecting events in which the companion 𝐵 meson from the ϒ⁡(4⁢𝑆) → $𝐵\bar{𝐵}$ decay is identified in semileptonic modes. The 𝜏 lepton is reconstructed via its leptonic decays. We obtain ℛ⁡(𝐷 + ) = 0.418$^{+0.075}_{−0.073}$⁢(stat)$^{+0.049}_{−0.056}$⁢(syst) and ℛ⁡(𝐷 *+ ) = 0.306$^{+0.035}_{−0.033}$⁢(stat)$^{+0.016}_{−0.018⁢}$(syst), which are consistent with world average values. Accounting for the correlation between them, these values differ from the Standard Model expectation by a collective significance of 1.7 standard deviations.

bottom quark↗
DOE OSTI2020

Dalitz analysis of $D^0 → K^–π^+η$ decays at Belle

We present the results of the first Dalitz plot analysis of the decay D 0 → K – π + η . The analysis is performed on a data set corresponding to an integrated luminosity of 953 fb – 1 collected by the Belle detector at the asymmetric-energy e + e – KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels K ¯ * ( 892 ) 0 η , K – a 0 ( 980 ) + , K – a 2 ( 1320 ) + , K ¯ * ( 1410 ) 0 η , K * ( 1680 ) – π + and K 2 * ( 1980 ) – π + , together with K π and K η S-wave components. The decays K * ( 1680 ) – → K – η and K 2 * ( 1980 ) – → K – η are observed for the first time. We measure ratio of the branching fractions, B ( D 0 → K – π + η ) B ( D 0 → K – π + ) = 0.500 ± 0.002 ( stat ) ± 0.020 ( syst ) ± 0.003 ( B PDG ) . Using the Dalitz fit result, the ratio B ( K * ( 1680 ) → K η ) B ( K * ( 1680 ) → K π ) is measured to be 0.11 ± 0.02 ( stat ) – 0.04 + 0.06 ( syst ) ± 0.04 ( B PDG ) ; this is much lower than the theoretical expectations ( ≈ 1 ) made under the assumption that K * ( 1680 ) is a pure 1 3 D 1 state. The product branching fraction B ( D 0 → [ K 2 * ( 1980 ) – → K – η ] π + ) = ( 2. 2 – 1.9 + 1.7 ) × 10 – 4 is determined. In addition, the π η ' contribution to the a 0 ( 980 ) ± resonance shape is confirmed with 10.1 σ statistical significance using the three-channel Flatté model. We also measure B ( D 0 → K ¯ * ( 892 ) 0 η ) = ( 1.4 1 – 0.12 + 0.13 ) % . This is consistent with, and more precise than, the current world average ( 1.02 ± 0.30 ) % , deviates with a significance of more than 3 σ from the theoretical predictions of (0.51–0.92)%.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

CP violation searches and distributed computing development with the Belle II Experiment at the University of Mississippi and Brookhaven National Laboratory (Final Report)

This report reflects the work performed at the University of Mississippi under the support of DOE EPSCoR grant DE‐SC0021274 during the period of September 2020 through August 2024, including a one-year, no-cost extension. A summary of the research outcomes is given, with reference to the project goals as stated in the proposal. This successful project supported the mission of the DOE High Energy Physics program by leveraging the complimentary expertise of researchers at the University of Mississippi and Brookhaven National Lab to search for CP violation in charmed baryon decays using data from the Belle II experiment and to provide vital support for Belle II distributed computing.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Study of Heavy Flavor Mesons and Flavor-Tagged Jets with the CMS Detector

The goal of this research program is to implement heavy flavor meson triggers in heavy-ion collisions for the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) at CERN, including algorithm design, timing studies, offline validation, and online performance monitoring. The physics analyses which can be achieved by data from these new triggers is to address one of the most important questions in the field: parton flavor dependence of jet-quenching for the understanding of the transport properties of the Quark-Gluon Plasma. This program will allow CMS to collect the highest statistics heavy flavor meson and jet data ever recorded in heavy-ion colliders. The program includes two objectives: (1) Build and maintain the heavy flavor meson and jet triggers for heavy-ion collisions and deploy the trigger algorithms for 2015-2018 PbPb and pPb run at the LHC; (2) Perform heavy flavor meson and jet physics analyses, which can be used to study the parton flavor dependence of jet quenching, to extract the elastic energy loss coefficient of the QGP, and to test whether massive quarks also participate in collective expansion dynamics in heavy-ion collisions. With the heavy flavor physics trigger developed in this project, a competitive heavy flavor physics program in heavy-ion collisions has been established in CMS. This program allows studies of the fully reconstructed and flavor identified charm, beauty, and exotic hadrons that cover the widest transverse momentum range. The novel measurements supported by the award provide new constraints on the size of the flavor dependence of parton energy loss, the value of the in-medium charm quark diffusion coefficient, the mechanism of charm and beauty quark hadronization, and provide new insights to the nature of the X(3872) hadron.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗