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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 307 records · Page 17
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DOE OSTI2016

Search for the suppressed decays B + → K + K + π – and B + → π + π + K –

A search is made for the highly-suppressed B meson decays B + → K + K + π – and B + → π + π + K – using a data sample corresponding to an integrated luminosity of 3.0 fb–1collected by the LHCb experiment in proton–proton collisions at centre-of-mass energies of 7 and 8 TeV. No evidence is found for the decays, and upper limits at 90% confidence level are determined to be $\mathscr{B}$(B + →K + K + π – ) < 1.1 × 10 –8 and $\mathscr{B}$(B + →π + π + K – ) < 4.6 × 10 –8 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of forward t t - , W + b b ¯ and W + c c ¯ production in pp collisions at s = 8 TeV

The production of $t\bar{t}$, W + $b\bar{b}$ and W + $c\bar{c}$ is studied in the forward region of proton–proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98±0.02 fb -1 . The W bosons are reconstructed in the decays W→ℓν, where ℓ denotes muon or electron, while the b and c quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of η c ( 2 S ) → p p ¯ and search for X ( 3872 ) → p p ¯ decays

The first observation of the decay η c ( 2 S ) → p p ¯ is reported using proton–proton collision data corre-sponding to an integrated luminosity of 3.0fb –1 recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The η c (2S) resonance is produced in the decay B + →[$c\bar{c}$]K + . The product of branching fractions normalised to that for the J/ψ intermediate state, $\mathscr{R}_{η_{c}(2S)}$, is measured to be $\mathscr{R}_{η_{c}(2S)}$ ≡ $\frac{\mathscr{B}(B^{+}→η_{c}(2S)K^{+})×\mathscr{B}(η_{c}(2S)→ p\overline{p})}{\mathscr{B}(B^{+}→ J/ψ K^{+})×\mathscr{B}(J/ψ →p\overline{p})}$ = (1.58±0.33±0.09)×10 –2 , where the first uncertainty is statistical and the second systematic. No signals for the decays B + → X(3872)(→$p\overline{p}$)K + and B + →ψ(3770)(→$p\overline{p}$)K + are seen, and the 95% confidence level upper limits on their relative branching ratios are found to be $\mathscr{R}_{X(3872)}$ < 0.25 ×10 –2 and $\mathscr{R}_{ψ(3770)}$ < 0.10. In addition, the mass differences between the η c (1S)and the J/ψ states, between the η c (2S)and the ψ(2S)states, and the natural width of the η c (1S)are measured as M J/ψ – M ηc(1S) = 110.2±0.5 ±0.9 MeV, M ψ(2S) – M ηc(2S) = 52.5±1.7±0.6 MeV, Γ ηc(1S) = 34.0±1.9±1.3MeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for CP violation in the phase space of D 0 → π + π – π + π – decays

A search for time-integrated CP violation in the Cabibbo-suppressed decay D 0 → π + π – π + π – is performed using an unbinned, model-independent technique known as the energy test. This is the first application of the energy test in four-body decays. The search is performed for P-even CP asymmetries and, for the first time, is extended to probe the P-odd case. Using proton–proton collision data corresponding to an integrated luminosity of 3.0 fb –1 collected by the LHCb detector at centre-of-mass energies of $\sqrt{s}$ = 7 TeV and 8 TeV, the world's best sensitivity to CP violation in this decay is obtained. The data are found to be consistent with the hypothesis of CP symmetry with a p-value of (4.6±0.5)% in the P-even case, and marginally consistent with a p-value of (0.6±0.2)% in the P-odd case, corresponding to a significance for CP non-conservation of 2.7 standard deviations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Prompt and nonprompt J / ψ production and nuclear modification in p Pb collisions at s N N = 8.16 TeV

The production of J/ψ mesons is studied in proton-lead collisions at the centre-of-mass energy per nucleon pair s N N = 8.16 TeV with the LHCb detector at the LHC. The double differential cross-sections of prompt and nonprompt J/ψ production are measured as a function of the J/ψ transverse momentum and rapidity in the nucleon–nucleon centre-of-mass frame. Forward-to-backward ratios and nuclear modification factors are determined. The results are compared with theoretical calculations based on collinear factorisation using nuclear parton distribution functions, on the colour glass condensate or on coherent energy loss models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

First observation of forward Z → b b ¯ production in pp collisions at s = 8 TeV

The decay Z → b b ¯ is reconstructed in pp collision data, corresponding to 2 fb -1 of integrated luminosity, collected by the LHCb experiment at a centre-of-mass energy of s = 8 TeV. The product of the Z production cross-section and the Z → b b ¯ branching fraction is measured for candidates in the fiducial region defined by two particle-level b -quark jets with pseudorapidities in the range 2.2 < η < 4.2 , with transverse momenta p T > 20 GeV and dijet invariant mass in the range 45 < m j j < 165 GeV. From a signal yield of 5462 ± 763 Z → b b ¯ events, where the uncertainty is statistical, a production cross-section times branching fraction of 332 ± 46 ± 59 pb is obtained, where the first uncertainty is statistical and the second systematic. The measured significance of the signal yield is 6.0 standard deviations. This measurement represents the first observation of the Z → b b ¯ production in the forward region of pp collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

First measurement of quarkonium polarization in nuclear collisions at the LHC

The polarization of inclusive J/ψ and Υ(1S) produced in Pb–Pb collisions at √ s NN = 5.02 TeV at the LHC is measured with the ALICE detector. The study is carried out by reconstructing the quarkonium through its decay to muon pairs in the rapidity region 2.5 < y < 4 and measuring the polar and azimuthal angular distributions of the muons. The polarization parameters λ θ , λ φ and λ θφ are measured in the helicity and Collins-Soper reference frames, in the transverse momentum interval 2 < p T < 10 GeV/c and p T < 15 GeV/c for the J/ψ and Υ(1S), respectively. The polarization parameters for the J/ψ are found to be compatible with zero, within a maximum of about two standard deviations at low p T , for both reference frames and over the whole p T range. The values are compared with the corresponding results obtained for pp collisions at √s = 7 and 8 TeV in a similar kinematic region by the ALICE and LHCb experiments. Although with much larger uncertainties, the polarization parameters for Υ(1S) production in Pb–Pb collisions are also consistent with zero

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Measurement of the polarizations of prompt and non-prompt J/ψ and ψ ( 2S ) mesons produced in pp collisions at s = 13 TeV

The polarizations of prompt and non-prompt Image 2 and ψ ( 2S ) mesons are measured in proton-proton collisions at s = 13 TeV, using data samples collected by the CMS experiment in 2017 and 2018, corresponding to a total integrated luminosity of 103.3 fb − 1 . Based on the analysis of the dimuon decay angular distributions in the helicity frame, the polar anisotropy, λ ϑ , is measured as a function of the transverse momentum, p T , of the charmonium states, in the 25–120 and 20–100 GeV ranges for the Image 2 and ψ ( 2S ) , respectively. The non-prompt polarizations agree with predictions based on the hypothesis that, for p T ≳ 25 GeV , the non-prompt Image 2 and ψ ( 2S ) are predominantly produced in two-body B meson decays. The prompt results clearly exclude strong transverse polarizations, even for p T exceeding 30 times the Image 2 mass, where λ ϑ tends to an asymptotic value around 0.3. Taken together with previous measurements, by CMS and LHCb at s = 7 TeV, the prompt polarizations show a significant variation with p T , at low p T .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

A fixed-target programme at the LHC: Physics case and projected performances for heavy-ion, hadron, spin and astroparticle studies

Here we review the context, the motivations and the expected performances of a comprehensive and ambitious fixed-target programme using the multi-TeV proton and ion LHC beams. We also provide a detailed account of the different possible technical implementations ranging from an internal wire target to a full dedicated beam line extracted with a bent crystal. The possibilities offered by the use of the ALICE and LHCb detectors in the fixed-target mode are also reviewed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Observation of structure in the J/ψ-pair mass spectrum

Using proton-proton collision data at centre-of-mass energies of $\sqrt{s}$ = 7, 8 and 13 TeV recorded by the LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 9 fb -1 , the invariant mass spectrum of J/ψ pairs is studied. A narrow structure around 6.9 GeV/c 2 matching the lineshape of a resonance and a broad structure just above twice the J/ψ mass are observed. The deviation of the data from nonresonant J/ψ-pair production is above five standard deviations in the mass region between 6.2 and 7.4 GeV/c 2 , covering predicted masses of states composed of four charm quarks. The mass and natural width of the narrow X(6900) structure are measured assuming a Breit-Wigner lineshape.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Evidence of a $J/ψΛ$ structure and observaton of excited $Ξ_{b}^{-}$ → $J/ψΛΚ^{-}$ decay

First evidence of a structure in the $J/ψΛ$ invariant mass distribution is obtained from an amplitude analysis of $Ξ_{b}^{-}$ → $J/ψΛΚ^{-}$ decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of 3.1σ including systematic uncertainties and look elsewhere effect. Its mass and width are determined to be 4458.8 ± $2.9_{-1.1}^{+4.7}$ MeV and 17.3 ± $6.5_{-5.7}^{+8.0}$ MeV respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited $Ξ^{-}$ states, $Ξ(1690)^{-}$ and $Ξ(1820)^{-}$, are seen for the first time in a $Ξ_{b}^{-}$ decay, and their masses and widths are measured with improved precision. The analysis is performed using $pp$ collision data corresponding to a total integrated luminosity of 9 fb -1 , collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Measurement of matter–antimatter differences in beauty baryon decays

Differences in the behaviour of matter and antimatter have been observed in K and B meson decays, but not yet in any baryon decay. Such differences are associated with the non-invariance of fundamental interactions under the combined charge-conjugation and parity transformations, known as CP violation. Here, using data from the LHCb experiment at the Large Hadron Collider, we search for CP-violating asymmetries in the decay angle distributions of Λ$^0_b$ baryons decaying to pπ - π + π - and pπ - K + K - final states. These four-body hadronic decays are a promising place to search for sources of CP violation both within and beyond the standard model of particle physics. We find evidence for CP violation in Λ$^0_b$ to pπ - π + π - decays with a statistical significance corresponding to 3.3 standard deviations including systematic uncertainties. This represents the first evidence for CP violation in the baryon sector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Study of the doubly charmed tetraquark $\mathrm{T}$ $^+_{cc}$

Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D 0 D 0 π + mass spectrum just below the D *+ D 0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar T$^{+}_{cc}$ tetraquark with a quark content of cc$\bar{u}\bar{d}$ and spin-parity quantum numbers J P = 1 + . Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D *+ mesons is consistent with the observed D 0 π+ mass distribution. To analyse the mass of the resonance and its coupling to the D*D system, a dedicated model is developed under the assumption of an isoscalar axial-vector T$^{+}_{cc}$ state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the T$^{+}_{cc}$ state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Test of lepton universality in beauty-quark decays

The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton–proton collision data collected with the LHCb detector at CERN’s Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

RDataFrame: Easy Parallel ROOT Analysis at 100 Threads

The Physics programmes of LHC Run III and HL-LHC challenge the HEP community. The volume of data to be handled is unprecedented at every step of the data processing chain: analysis is no exception. Physicists must be provided with first-class analysis tools which are easy to use, exploit bleeding edge hardware technologies and allow to seamlessly express parallelism. This document discusses the declarative analysis engine of ROOT, RDataFrame, and gives details about how it allows to profitably exploit commodity hardware as well as high-end servers and manycore accelerators thanks to the synergy with the existing parallelised ROOT components. Real-life analyses of LHC experiments’ data expressed in terms of RDataFrame are presented, highlighting the programming model provided to express them in a concise and powerful way. The recent developments which make RDataFrame a lightweight data processing framework are described, such as callbacks and I/O capabilities. Finally, the flexibility of RDataFrame and its ability to read data formats other than ROOT’s are characterised, as an example it is discussed how RDataFrame can directly read and analyse LHCb’s raw data format MDF.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Software Citation in HEP: Current State and Recommendations for the Future

In November 2022, the HEP Software Foundation and the Institute for Research and Innovation for Software in High-Energy Physics organized a workshop on the topic of Software Citation and Recognition in HEP. The goal of the workshop was to bring together different types of stakeholders whose roles relate to software citation, and the associated credit it provides, in order to engage the community in a discussion on: the ways HEP experiments handle citation of software, recognition for software efforts that enable physics results disseminated to the public, and how the scholarly publishing ecosystem supports these activities. Reports were given from the publication board leadership of the ATLAS, CMS, and LHCb experiments and HEP open source software community organizations (ROOT, Scikit-HEP, MCnet), and perspectives were given from publishers (Elsevier, JOSS) and related tool providers (INSPIRE, Zenodo). This paper summarizes key findings and recommendations from the workshop as presented at the 26th International Conference on Computing in High Energy and Nuclear Physics (CHEP 2023).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗