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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Search for the rare decay $K^+\to\mu^+\nu\bar\nu\nu$

Evidence of the $K^+\to\mu^+\nu\bar\nu\nu$ decay was searched for using E949 experimental data with an exposure of $1.70\times 10^{12}$ stopped kaons. The data sample is dominated by the backgrond process $K^+\to\mu^+\nu_\mu\gamma$. An upper limit on the decay rate $\Gamma(K^+\to\mu^+\nu\bar\nu\nu)< 2.4\times 10^{-6}\Gamma(K^+\to all)$ at 90% confidence level was set assuming the Standard Model muon spectrum. The data are presented in such a way as to allow calculation of rates for any assumed $\mu^+$ spectrum.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Chiral matrix model of the semi-QGP in QCD

Previously, a matrix model of the region near the transition temperature, in the “semi”quark gluon plasma, was developed for the theory of SU(3) gluons without quarks. In this paper we develop a chiral matrix model applicable to QCD by including dynamical quarks with 2+1 flavors. This requires adding a nonet of scalar fields, with both parities, and coupling these to quarks through a Yukawa coupling, y. Treating the scalar fields in mean field approximation, the effective Lagrangian is computed by integrating out quarks to one loop order. As is standard, the potential for the scalar fields is chosen to be symmetric under the flavor symmetry of SU (3) L × SU(3) R × Z (3) A , except for a term linear in the current quark mass, m qk . In addition, at a nonzero temperature T it is necessary to add a new term, ~ m qk T 2 . The parameters of the gluon part of the matrix model are identical to those for the pure glue theory without quarks. The parameters in the chiral matrix model are fixed by the values, at zero temperature, of the pion decay constant and the masses of the pions, kaons, η , and η' . The temperature for the chiral crossover at T$χ$ = 155 MeV is determined by adjusting the Yukawa coupling y . We find reasonable agreement with the results of numerical simulations on the lattice for the pressure and related quantities. In the chiral limit, besides the divergence in the chiral susceptibility there is also a milder divergence in the susceptibility between the Polyakov loop and the chiral order parameter, with critical exponent β $-$ 1 . We compute derivatives with respect to a quark chemical potential to determine the susceptibilities for baryon number, the $χ$ 2n . Especially sensitive tests are provided by $χ$ 4 $-$ $χ$ 2 and by $χ$ 6 , which changes in sign about T$χ$ . In conclusion, the behavior of the susceptibilities in the chiral matrix model strongly suggests that as the temperature increases from T$χ$ , that the transition to deconfinement is significantly quicker than indicated by the measurements of the (renormalized) Polyakov loop on the lattice.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Observation of charmless baryonic decays B ( s ) 0 → p p ¯ h + h ' –

Decays of B 0 and B 0 s mesons to the charmless baryonic final states p¯ph + h' – , where h and h' each denote a kaon or a pion, are searched for using the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb –1 . Four-body charmless baryonic B 0 s decays are observed for the first time. The decays B 0 s →p¯pK + K – , B 0 s →p¯pK ± π ∓ , B 0 →p¯pK ± π ∓ and B 0 →p¯pπ + π – are observed with a significance greater than 5 standard deviations; evidence at 4.1 standard deviations is found for the B 0 →p¯pK + K – decay and an upper limit is set on the branching fraction for B 0 s →p¯pπ + π – . Branching fractions in the kinematic region m(p¯p) < 2850 MeV/c 2 are measured relative to the B 0 →J/ψ(→p¯p)K*(892) 0 channel.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Möbius domain-wall fermions on gradient-flowed dynamical HISQ ensembles

We report on salient features of a mixed lattice QCD action using valence Möbius domain-wall fermions solved on the dynamical 𝑁 𝑓 = 2 + 1 + 1 highly improved staggered quark sea-quark ensembles generated by the MILC Collaboration. The approximate chiral symmetry properties of the valence fermions are shown to be significantly improved by utilizing the gradient-flow scheme to first smear the highly improved staggered quark configurations. The greater numerical cost of the Möbius domain-wall inversions is mitigated by the highly efficient QUDA library optimized for NVIDIA GPU accelerated compute nodes. We have created an interface to this optimized QUDA solver in Chroma. We provide tuned parameters of the action and performance of QUDA using ensembles with the lattice spacings 𝑎 ≃ {0.15,0.12,0.09} fm and pion masses 𝑚 𝜋 ≃ {310,220,130} MeV. We have additionally generated two new ensembles with 𝑎 ∼ 0.12 fm and 𝑚 𝜋 ∼ {400,350} MeV. Furthermore, with a fixed flow time of 𝑡 𝑔⁡𝑓 =1 in lattice units, the residual chiral symmetry breaking of the valence fermions is kept below 10% of the light quark mass on all ensembles, 𝑚 res ≲ 0.1 × 𝑚 𝑙 , with moderate values of the fifth dimension 𝐿 5 and a domain-wall height 𝑀 5 ≤ 1.3. As a benchmark calculation, we perform a continuum, infinite volume, physical pion and kaon mass extrapolation of 𝐹 𝐾 ±⁡ /𝐹 𝜋 ± and demonstrate our results are independent of flow time and consistent with the FLAG determination of this quantity at the level of less than one standard deviation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Unified scenario for composite right-handed neutrinos and dark matter

In this study, we entertain the possibility that neutrino masses and dark matter (DM) originate from a common composite dark sector. A minimal effective theory can be constructed based on a dark SU(3) D interaction with three flavors of massless dark quarks; electroweak symmetry breaking gives masses to the dark quarks. By assigning a Z 2 charge to one flavor, a stable “dark kaon” can provide a good thermal relic DM candidate. We find that “dark neutrons” may be identified as right handed Dirac neutrinos. Some level of “neutron-anti-neutron” oscillation in the dark sector can then result in non-zero Majorana masses for light standard model neutrinos. A simple ultraviolet completion is presented, involving additional heavy SU(3) D -charged particles with electroweak and lepton Yukawa couplings. At our benchmark point, there are “dark pions” that are much lighter than the Higgs and we expect spectacular collider signals arising from the UV framework. This includes the decay of the Higgs boson to ττℓℓ', where ℓ(ℓ ') can be any lepton, with displaced vertices. Finally, we discuss the observational signatures of this UV framework in dark matter searches and primordial gravitational wave experiments; the latter signature is potentially correlated with the H → ττℓℓ' decay.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

| V u s | from K ℓ 3 decay and four-flavor lattice QCD

Using highly improved staggered quark (HISQ) N$_f$=2+1+1 MILC ensembles with five different values of the lattice spacing, including four ensembles with physical quark masses, we perform the most precise computation to date of the K→πℓν vector form factor at zero momentum transfer, $f_+^{K^0π^-}$(0)=0.9696(15) stat (12) syst . This is the first calculation that includes the dominant finite-volume effects, as calculated in chiral perturbation theory at next-to-leading order. Our result for the form factor provides a direct determination of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |$V_{us}$|=0.22333(44) $_{f_+}$ (0) (42) exp , with a theory error that is, for the first time, at the same level as the experimental error. The uncertainty of the semileptonic determination is now similar to that from leptonic decays and the ratio $f_{K+}$/f π +, which uses |$V_{ud}$| as input. Our value of |$V_{us}$| is in tension at the 2–2.6σ level both with the determinations from leptonic decays and with the unitarity of the CKM matrix. In the test of CKM unitarity in the first row, the current limiting factor is the error in |$V_{ud}$|, although a recent determination of the nucleus-independent radiative corrections to superallowed nuclear β decays could reduce the |$V_{ud}$| 2 uncertainty nearly to that of |$V_{us}$| 2 . Alternative unitarity tests using only kaon decays, for which improvements in the theory and experimental inputs are likely in the next few years, reveal similar tensions and could be further improved by taking correlations between the theory inputs. As part of our analysis, we calculated the correction to $f_+^{Kπ}$0) due to nonequilibrated topological charge at leading order in chiral perturbation theory, for both the full-QCD and the partially quenched cases. We also obtain the combination of low-energy constants in the chiral effective Lagrangian [C$^{12}_r$+C$^{34}_r$-(L$_5^r$)2](M ρ )=(2.92±0.31)×10 -6 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Evidence for C P Violation in the Decay D + → K S 0 π +

Here we observe evidence for CP violation in the decay D + →K$0\atop{S}$π + using a data sample with an integrated luminosity of 977 fb -1 collected by the Belle detector at the KEKB e + e - asymmetric-energy collider. The CP asymmetry in the decay is measured to be (-0.363±0.094±0.067)%, which is 3.2 standard deviations away from zero, and is consistent with the expected CP violation due to the neutral kaon in the final state.

Ko, B. R.↗
DOE OSTI2013

Search for Bottomonium States in Exclusive Radiative Υ ( 2 S ) Decays

We search for bottomonium states in $\Upsilon(2S)$ → ($\bar{bb}$) gamma decays with an integrated luminosity of 24.7fb -1 recorded at the $\Upsilon(2S)$ resonance with the Belle detector at KEK, containing (157.8 ± 3.6) X 10 6 $\Upsilon(2S)$ events. The ($\bar{bb}$) system is reconstructed in 26 exclusive hadronic final states composed of charged pions, kaons, protons, and $K^0_S$ mesons. We find no evidence for the state recently observed around 9975 MeV ($X_{\bar{bb}}$) in an analysis based on a data sample of 9.3 X 10 6 $\Upsilon(2S)$ events collected with the CLEO III detector. We set a 90 % confidence-level upper limit on the branching fraction $Β$[$\Upsilon(2S)$ → $X_{\bar{bb}\gamma}$] X $\sum_i$ $B$[$X_{\bar{bb}}$ → $h_i$] $<$ 4.9 X 10 -6 , summed over the exclusive hadronic final states employed in our analysis. This result is an order of magnitude smaller than the measurement reported with CLEO data. We also set an upper limit for the $\eta_b(1S)$ state of $B$[$\Upsilon(2S)$ → $\eta_b(1S)\gamma$] X $\sum_i$B[$\eta_b(1S)$ → $h_i$] $<$ 3.7 X 10 -6 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Massive photons: An infrared regularization scheme for lattice QCD + QED

The commonly adopted approach for including electromagnetic interactions in lattice QCD simulations relies on using finite volume as the infrared regularization for QED. The long-range nature of the electromagnetic interaction, however, implies that physical quantities are susceptible to power-law finite volume corrections, which must be removed by performing costly simulations at multiple lattice volumes, followed by an extrapolation to the infinite volume limit. In this work, we introduce a photon mass as an alternative means for gaining control over infrared effects associated with electromagnetic interactions. We present findings for hadron mass shifts due to electromagnetic interactions (i.e., for the proton, neutron, charged and neutral kaon) and corresponding mass splittings, and compare the results with those obtained from conventional QCD+QED calculations. Results are reported for numerical studies of three flavor electroquenched QCD using ensembles corresponding to 800 MeV pions, ensuring that the only appreciable volume corrections arise from QED effects. The calculations are performed with three lattice volumes with spatial extents ranging from 3.4 - 6.7 fm. As a result, we find that for equal computing time (not including the generation of the lattice configurations), the electromagnetic mass shifts can be extracted from computations on a single (our smallest) lattice volume with comparable or better precision than the conventional approach.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of J / ψ &straightphi; Structures Consistent with Exotic States from Amplitude Analysis of B + → J / ψ &straightphi; K + Decays

The first full amplitude analysis of B + → J/ψ&straightphi;K + with J/ψ → μ + μ - , &straightphi; → K + K - decays is performed with a data sample of 3 fb -1 of pp collision data collected at $\sqrt{s}$ =7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into &straightphi;K + , and four J/ψ&straightphi; structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Beam Energy Dependence of Jet-Quenching Effects in Au+Au Collisions at √ s NN = 7.7, 11.5, 14.5, 19.6, 27, 39, and 62.4GeV

Here, we report measurements of the nuclear modification factor, RCP, for charged hadrons as well as identified π +(–) , K +(–) , and p(p¯) for Au+Au collision energies of √ s NN = 7.7, 11.5, 14.5, 19.6, 27, 39, and 62.4 GeV. We observe a clear high-p T net suppression in central collisions at 62.4 GeV for charged hadrons which evolves smoothly to a large net enhancement at lower energies. This trend is driven by the evolution of the pion spectra, but is also very similar for the kaon spectra. While the magnitude of the proton RCP at high p T does depend on collision energy, neither the proton nor the anti-proton RCP at high p T exhibit net suppression at any energy. As a result, a study of how the binary collision scaled high-p T yield evolves with centrality reveals a non-monotonic shape that is consistent with the idea that jet-quenching is increasing faster than the combined phenomena that lead to enhancement.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Quark-Mass Dependence of Elastic $πK$ Scattering from QCD

We present a determination of the isospin-½ elastic $πK$ scattering amplitudes in $S$ and $P$ partial waves using lattice quantum chromodynamics. The amplitudes, constrained for a large number of real-valued energy points, are obtained as a function of light-quark mass, corresponding to four pion masses between 200 and 400 MeV, at a single lattice spacing. Below the first inelastic threshold, the $P$-wave scattering amplitude is dominated by a single pole singularity that evolves from being a stable bound state at the highest quark mass into a narrow resonance that broadens as the pion and kaon masses are reduced. As in experiment, the $S$-wave amplitude does not exhibit an obviously resonant behavior, but instead shows a slow rise from threshold, which is not inconsistent with the presence of a $κ/K_{0}^{*}$(700)-like resonance at the considered quark masses. As has been found in analyses of experimental scattering data, simple analytic continuations into the complex energy plane of precisely determined lattice QCD amplitudes on the real energy axis are not sufficient to model-independently determine the existence and properties of this state. The spectra and amplitudes we present will serve as an input for increasingly elaborate amplitude analysis techniques that implement more of the analytic structure expected at complex energies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

First Observation of the Directed Flow of D 0 and D 0 ¯ in Au + Au Collisions at s N N = 200 GeV

We report the first measurement of rapidity-odd directed flow ($v_{1}$) for $D^{0}$ and $\overline{D^{0}}$ mesons at midrapidity (|y|<0.8) in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV using the STAR detector at the Relativistic Heavy Ion Collider. In 10-80% Au+Au collisions, the slope of the $v_{1}$ rapidity dependence ($dv_{1}/dy$), averaged over $D^{0}$ and $\overline{D^{0}}$ mesons, is -0.080 ± 0.017(stat) ± 0.016(syst) for transverse momentum $p_{T}$ above 1.5 GeV/c. The absolute value of $D^{0}$ meson $dv_{1}/dy$ is about 25 times larger than that for charged kaons, with 3.4σ significance. These data give a unique insight into the initial tilt of the produced matter, and offer constraints on the geometric and transport parameters of the hot QCD medium created in relativistic heavy-ion collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Probing the Partonic Degrees of Freedom in High-Multiplicity p–Pb collisions at √ s NN = 5.02 TeV

We investigate the role of partonic degrees of freedom in high-multiplicity p–Pb collisions at √ s NN = 5.02 TeV carried out at the Large Hadron Collider (LHC) by studying the production and collective flow of identified hadrons at intermediate p T via the coalescence of soft partons from the viscous hydrodynamics (VISH 2 + 1) and hard partons from the energy loss model, linear Boltzmann transport (LBT). We find that combining these intermediate p T hadrons with the low p T hadrons from the hydrodynamically expanding fluid and high p T hadrons from the fragmentation of quenched jets, the resulting hydro-dynamics-coalescence-fragmentation model provides a nice description of measured p T spectra and differential elliptic flow v 2 (p T ) of pions, kaons, and protons over the p T range from 0 to 6 GeV. We further demonstrate the necessity of including the quark coalescence contribution to reproduce the experimentally observed approximate number of constituent quark scaling of hadron v 2 at intermediate p T . Furthermore, our results thus indicate the importance of partonic degrees of freedom and also hint at the possible formation of quark-gluon plasma in high-multiplicity p–Pb collisions at the LHC.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

From Hydrodynamics to Jet Quenching, Coalescence, and Hadron Cascade: A Coupled Approach to Solving the $R_{AA}Ⓧv_{2}$ Puzzle

Hydrodynamics and jet quenching are responsible for the elliptic flow $v_{2}$ and suppression of large transverse momentum ($p_{T}$) hadrons, respectively, two of the most important phenomena leading to the discovery of a strongly coupled quark-gluon plasma in high-energy heavy-ion collisions. A consistent description of the hadron suppression factor $R_{AA}$ and $v_{2}$, especially at intermediate $p_{T}$, however, remains a challenge. We solve this long-standing $R_{AA}Ⓧv_{2}$ puzzle by including quark coalescence for hadronization and final state hadron cascade in the coupled linear Boltzmann transport-hydro model that combines concurrent jet transport and hydrodynamic evolution of the bulk medium. We illustrate that quark coalescence and hadron cascade, two keys to solving the puzzle, also lead to a splitting of $v_{2}$ for pions, kaons, and protons in the intermediate $p_{T}$ region. We demonstrate for the first time that experimental data on $R_{AA}, v_{2}$, and their hadron flavor dependence from low to intermediate and high $p_{T}$ in high-energy heavy-ion collisions can be understood within this coupled framework.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Search for Rare Decays of D s + to Final States π + e + e − , ρ + e + e − , π + π 0 e + e − , K + π 0 e + e − , and K S 0 π + e + e −

Using 7.33 fb − 1 of e + e − collision data collected by the BESIII detector at center-of-mass energies in the range of s = 4.128 – 4.226 GeV , we search for the rare decays D s + → h + ( h 0 ) e + e − , where h represents a kaon or pion. By requiring the e + e − invariant mass to be consistent with a ϕ ( 1020 ) , 0.98 < M ( e + e − ) < 1.04 GeV / c 2 , the decay D s + → π + ϕ , ϕ → e + e − is observed with a statistical significance of 7.8 σ , and evidence for the decay D s + → ρ + ϕ , ϕ → e + e − is found for the first time with a statistical significance of 4.4 σ . The decay branching fractions are measured to be B ( D s + → π + ϕ , ϕ → e + e − ) = ( 1.1 7 − 0.21 + 0.23 ± 0.03 ) × 10 − 5 , and B ( D s + → ρ + ϕ , ϕ → e + e − ) = ( 2.4 4 − 0.62 + 0.67 ± 0.16 ) × 10 − 5 , where the first uncertainties are statistical and the second systematic. No significant signals for the three four-body decays of D s + → π + π 0 e + e − , D s + → K + π 0 e + e − , and D s + → K S 0 π + e + e − are observed. For D s + → π + π 0 e + e − , the ϕ mass region is vetoed to minimize the long-distance effects. The 90% confidence level upper limits set on the branching fractions of these decays are in the range of ( 7.0 – 8.1 ) × 10 − 5 . Published by the American Physical Society 2024

Physics↗
DOE OSTI2024

QCD Predictions for Meson Electromagnetic Form Factors at High Momenta: Testing Factorization in Exclusive Processes

We report the first lattice QCD computation of pion and kaon electromagnetic form factors, 𝐹 𝑀⁡ (𝑄 2 ), at large momentum transfer up to 10 and 28 GeV 2 , respectively. Utilizing physical masses and two fine lattices, we achieve good agreement with JLab experimental results at 𝑄 2 ≲ 4 GeV 2 . For 𝑄 2 ≳ 4 GeV 2 , our results provide ab initio QCD benchmarks for the forthcoming experiments at JLab 12 GeV and future electron-ion colliders. We also test the QCD collinear factorization framework utilizing our high-𝑄 2 form factors at next-to-next-to-leading order in perturbation theory, which relates the form factors to the leading Fock-state meson distribution amplitudes. Comparisons with independent lattice QCD calculations using the same framework demonstrate, within estimated uncertainties, the universality of these nonperturbative quantities.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Probing Strangeness Hadronization with Event-by-Event Production of Multistrange Hadrons

This Letter presents the first measurement of event-by-event fluctuations of the net number (difference between the particle and antiparticle multiplicities) of multistrange hadrons Ξ − and $\overline{Ξ}$ + and its correlation with the net-kaon number using the data collected by the ALICE Collaboration in pp, p-Pb, and Pb-Pb collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{NN}}$ = 5.02 TeV. The statistical hadronization model with a correlation over three units of rapidity between hadrons having the same and opposite strangeness content successfully describes the results. On the other hand, string-fragmentation models that mainly correlate strange hadrons with opposite strange quark content over a small rapidity range fail to describe the data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗