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Results for “Hadronic physics”
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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Study of the process e + e − → π + π − η using initial state radiation
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Cross section and longitudinal single-spin asymmetry A L for forward W ± → μ ± ν production in polarized p + p collisions at s = 510 GeV
We have measured the cross section and single-spin asymmetries from forward W ± → μ ± ν production in longitudinally polarized $p+p$ collisions at $\sqrt{s}=510\text{ }\text{ }\mathrm{GeV}$ using the PHENIX detector at the Relativistic Heavy Ion Collider. The cross sections are consistent with previous measurements at this collision energy, while the most forward and backward longitudinal single spin asymmetries provide new insights into the sea quark helicities in the proton. The charge of the $W$ bosons provides a natural flavor separation of the participating partons.
Search for chargino-neutralino production using recursive jigsaw reconstruction in final states with two or three charged leptons in proton-proton collisions at s = 13 TeV with the ATLAS detector
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Percolation Transition in Yang-Mills Matter at a Finite Number of Colors
We examine baryonic matter at a quark chemical potential of the order of the confinement scale {mu}{sub q{approx}{Lambda}QCD}. In this regime, quarks are supposed to be confined but baryons are close to the 'tightly packed limit' where they nearly overlap in configuration space. We show that this system will exhibit a percolation phase transition when varied in the number of colors N{sub c}: at high N{sub c}, large distance correlations at the quark level are possible even if the quarks are essentially confined. At low N{sub c}, this does not happen. We discuss the relevance of this for dense nuclear matter, and argue that our results suggest a new 'phase transition', varying N{sub c} at constant {mu}{sub q}.
Observation of D 0 meson nuclear modifications in Au + Au collisions at s NN = 200 GeV
We report the first measurement of charmed-hadron (D 0 ) production via the hadronic decay channel (D 0 → K - + π + ) in Au + Au collisions at √ s NN = 200 GeV with the STAR experiment. The charm production cross section per nucleon-nucleon collision at midrapidity scales with the number of binary collisions, N bin , from p + p to central Au + Au collisions. The D 0 meson yields in central Au + Au collisions are strongly suppressed compared to those in p + p scaled by N bin , for transverse momenta p T > 3 GeV/c, demonstrating significant energy loss of charm quarks in the hot and dense medium. Here, an enhancement at intermediate p T is also observed. Model calculations including strong charm-medium interactions and coalescence hadronization describe our measurements.
Heavy-Quark Symmetry Implies Stable Heavy Tetraquark Mesons Q i Q j q ¯ k q ¯ l
For very heavy quarks Q, relations derived from heavy-quark symmetry predict the existence of novel narrow doubly heavy tetraquark states of the form Q i Q j ¯q k ¯q l (subscripts label flavors), where q designates a light quark. By evaluating finite-mass corrections, we predict that double-beauty states composed of bb¯u¯d, bb¯u¯s, and bb¯d¯s will be stable against strong decays, whereas the double-charm states cc¯q k ¯q l , mixed beauty+charm states bc¯q k ¯q l , and heavier bb¯qk¯ql states will dissociate into pairs of heavy-light mesons. Furthermore, observation of a new double-beauty state through its weak decays would establish the existence of tetraquarks and illuminate the role of heavy color-antitriplet diquarks as hadron constituents.
Observation of Higgs Boson Decay to Bottom Quarks
Here, the observation of the standard model (SM) Higgs boson decay to a pair of bottom quarks is presented. The main contribution to this result is from processes in which Higgs bosons are produced in association with a W or Z boson (VH), and are searched for in final states including 0, 1, or 2 charged leptons and two identified bottom quark jets. The results from the measurement of these processes in a data sample recorded by the CMS experiment in 2017, comprising 41.3 fb -1 of proton-proton collisions at $\sqrt{s}$ = 13 TeV, are described. When combined with previous VH measurements using data collected at $\sqrt{s}$ = 7, 8, and 13 TeV, an excess of events is observed at m H =125 GeV with a significance of 4.8 standard deviations, where the expectation for the SM Higgs boson is 4.9. The corresponding measured signal strength is 1.01 ± 0.22. The combination of this result with searches by the CMS experiment for H→$b\bar{b}$ in other production processes yields an observed (expected) significance of 5.6 (5.5) standard deviations and a signal strength of 1.04±0.20.
Unified Description of Polarized and Unpolarized Quark Distributions in the Proton
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Cornering Higgsinos Using Soft Displaced Tracks
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Search for a Narrow Resonance Lighter than 200 GeV Decaying to a Pair of Muons in Proton-Proton Collisions at $\sqrt{s} =$ TeV
A search is presented for a narrow resonance decaying to a pair of oppositely charged muons using s=13 TeV proton-proton collision data recorded at the LHC. In the 45–75 and 110–200 GeV resonance mass ranges, the search is based on conventional triggering and event reconstruction techniques. In the 11.5–45 GeV mass range, the search uses data collected with dimuon triggers with low transverse momentum thresholds, recorded at high rate by storing a reduced amount of trigger-level information. The data correspond to integrated luminosities of 137 and 96.6 fb-1 for conventional and high-rate triggering, respectively. No significant resonant peaks are observed in the probed mass ranges. The search sets the most stringent constraints to date on a dark photon in the ∼30–75 and 110–200 GeV mass ranges.
Probing Gluon Spin-Momentum Correlations in Transversely Polarized Protons through Midrapidity Isolated Direct Photons in p ↑ + p Collisions at s = 200 GeV
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Search for Long-Lived Particles Decaying in the CMS End Cap Muon Detectors in Proton-Proton Collisions at s = 13 TeV
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Measurement of the Inclusive and Differential Higgs Boson Production Cross Sections in the Decay Mode to a Pair of τ Leptons in p p Collisions at s = 13 TeV
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First Search for Exclusive Diphoton Production at High Mass with Tagged Protons in Proton-Proton Collisions at $\sqrt{s} = 13$
A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp $\to$ p$\gamma\gamma$p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons matches the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% CL are $\lvert\zeta_1\rvert$ $\lt$ 2.9 $\times$ 10$^{-13}$ GeV$^{-4}$ and $\lvert\zeta_2\rvert$ $\lt$ 6.0 $\times$ 10$^{-13}$ GeV$^{-4}$.
Measurement of Direct-Photon Cross Section and Double-Helicity Asymmetry at s = 510 GeV in p → + p → Collisions
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Enhanced Deuteron Coalescence Probability in Jets
The transverse-momentum ($p_T$) spectra and coalescence parameters $B_2$ of (anti)deuterons are measured in p-p collisions at $\sqrt{s}=13$ $\text{TeV}$ for the first time in and out of jets. In this measurement, the direction of the leading particle with the highest $p_T$ in the event ($p^{lead}_T > 5 GeV/c$) is used as an approximation for the jet axis. The event is consequently divided into three azimuthal regions, and the jet signal is obtained as the difference between the toward region, that contains jet fragmentation products in addition to the underlying event (UE), and the transverse region, which is dominated by the UE. The coalescence parameter in the jet is found to be approximately a factor of 10 larger than that in the underlying event. This experimental observation is consistent with the coalescence picture and can be attributed to the smaller average phase-space distance between nucleons in the jet cone as compared with the underlying event. The results presented in this Letter are compared to predictions from a simple nucleon coalescence model, where the phase-space distributions of nucleons are generated using pythia8 with the Monash 2013 tuning, and to predictions from a deuteron production model based on ordinary nuclear reactions with parametrized energy-dependent cross sections tuned on data. The latter model is implemented in pythia8.3. Both models reproduce the observed large difference between in-jet and out-of-jet coalescence parameters, although the almost flat trend of the $B^{Jet}_2$ is not reproduced by the models, which instead give a decreasing trend.