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DOE OSTI2011

Compton scattering from positronium and validity of the impulse approximation

The cross sections for Compton scattering from positronium are calculated in the range from 1 to 100 keV incident photon energy. The calculations are based on the A{sup 2} term of the photon-electron or photon-positron interaction. Unlike in hydrogen, the scattering occurs from two centers and the interference effect plays an important role for energies below 8 keV. Because of the interference, the criterion for validity of the impulse approximation for positronium is more restrictive compared to that for hydrogen.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2010

Measurement of the absolute branching fractions for D{sub s}{sup -}{yields}l{sup -}{nu}{sub l} and extraction of the decay constant f{sub D{sub s}}

The absolute branching fractions for the decays D{sub s}{sup -}{yields}l{sup -}{nu}{sub l} (l=e, {mu}, or {tau}) are measured using a data sample corresponding to an integrated luminosity of 521 fb{sup -1} collected at center-of-mass energies near 10.58 GeV with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at SLAC. The number of D{sub s}{sup -} mesons is determined by reconstructing the recoiling system DKX{gamma} in events of the type e{sup +}e{sup -}{yields}DKXD{sub s}{sup *-}, where D{sub s}{sup *-}{yields}D{sub s}{sup -}{gamma} and X represents additional pions from fragmentation. The D{sub s}{sup -}{yields}l{sup -}{nu}{sub l} events are detected by full or partial reconstruction of the recoiling system DKX{gamma}l. The branching fraction measurements are combined to determine the D{sub s}{sup -} decay constant f{sub D{sub s}}=(258.6{+-}6.4{+-}7.5) MeV, where the first uncertainty is statistical and the second is systematic.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Hydrogen Bonding Inside Anionic Polymeric Brush Layer: Machine Learning-Driven Exploration of the Relative Roles of the Polymer Steric Effect, Charging, and Type of Screening Counterions

This paper employs a combination of all-atom molecular dynamics (MD) simulations and unsupervised machine learning (ML) for studying the water-water hydrogen bonds (HBs) inside the anionic poly-acrylic acid (PAA) brushes modeled using all-atom MD simulations. PAA brush layer with different charge fraction (f), namely f=0, f=0.25, and f=1, is considered. Water-water interactions, both inside and outside the brush layer, are represented through distinct clusters of tupules of variables representing distances associated with the interacting water molecules. While clusters representing the HBs are present for water inside and outside the brushes, several clusters representing the long-range water-water interactions are missing for the water molecules inside the highly charged (f=1) PAA brushes. More importantly, inside highly charged brushes, the edge of the clusters representing the water-water HBs is progressively shortened, as compared to that in the bulk. Both these results stem from the presence of the PAA brushes imparting the steric effect and the charge effect, or the effect associated with enhanced interactions of water molecules with PE charges and counterions, thereby disrupting the water connectivity. This water-charged-species interaction also increases the water-water HB angle, i.e., makes the water-water HBs less stable inside the highly charged PAA brush layer. The narrowing of the clusters representing the HBs and the alteration of the angle characterizing the HBs confirm that the conditions defining the water-water HBs change inside the PAA brush layer as a function of the charges on the PAA brush layer. Furthermore, we show that the use of the generic definition of HBs, as compared to using our simulation-motivated modified definition of water-water HBs, overpredict the number of water-water HBs inside the PAA brush layer. Finally, we employ this all-atom-MD-ML framework to quantify the effect of other types of screening counterions (Li + , Ca 2+ , and Y 3+ ions) in determining the water-water interactions and water-water HB properties inside the PAA brush layer. Furthermore, the findings of the present study, confirming the weakening of water-water HBs inside the PAA brush layer, points to the possibility that the water molecules will be more available for hydrating the brush layer and counterions, thereby leading to a more pronounced wetting of the PAA brush layer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

Towards a numu CC exclusive cross section measurement with one proton and one muon in the final state at the NOvA near detector

NOvA is a long-baseline neutrino experiment at Fermilab that studies neutrino oscillations via electron neutrino appearance and muon neutrino disappearance. The NOvA Near Detector, located 1 km from the NuMI target, records a high rate of neutrino interactions in the energy range of 1-5 GeV. One of the limitations in precise extraction of oscillations is the large systematic uncertainty on neutrino-nucleus interactions. The high rate of neutrino interactions in the NOvA Near Detector provides the opportunity to probe various neutrino interaction processes and nuclear models, via the extraction of cross sections of particular final states. Nuclear models can be improved by measuring neutrino-nucleus cross sections with respect to kinematic variables which are known to be more sensitive to nuclear effects, such as transverse kinematic imbalance (TKI) variables. Usage of TKI variables allows for more direct constraints on models of neutrino scattering, as these variables can more directly investigate, for instance, effects of Fermi motion and final state interactions. In this work, we describe progress towards a method of identifying and reconstructing protons in the NOvA near detector to enable the cross section measurement of charged current neutrino interactions with a visible muon and a proton in the final state, reported in TKI variables.

Weber, Colin [Minnesota U.] (ORCID:000000031117067↗

DOE OSTI2010

Long-Range Beam-Beam Compensation in RHIC

In order to avoid the effects of long-range beam-beam interactions which produce beam blow-up and deteriorate beam life time, a compensation scheme with current carrying wires has been proposed. Two long-range beam-beam compensators were installed in RHIC rings in 2006. The effects of the compensators have been experimentally investigated. An indication was observed that the compensators are beneficial to beam life time in measurements performed in RHIC during 2009. In this paper, we report the effects of wire compensator on beam loss and emittance for proton-proton beams at collision energy.

43 PARTICLE ACCELERATORS↗

DOE OSTI2017

Limits to the Optical Response of Graphene and Two-Dimensional Materials

Two-dimensional (2D) materials provide a platform for strong light–matter interactions, creating wide-ranging design opportunities via new-material discoveries and new methods for geometrical structuring. Here we derive general upper bounds to the strength of such light–matter interactions, given only the optical conductivity of the material, including spatial nonlocality, and otherwise independent of shape and configuration. Our material figure-of-merit shows that highly doped graphene is an optimal material at infrared frequencies, whereas single-atomic-layer silver is optimal in the visible. For quantities ranging from absorption and scattering to near-field spontaneous-emission enhancements and radiative heat transfer, we consider canonical geometrical structures and show that in certain cases the bounds can be approached, while in others there may be significant opportunity for design improvement. The bounds can encourage systematic improvements in the design of ultrathin broadband absorbers, 2D antennas, and near-field energy harvesters.

2D materials↗

DOE OSTI2025

Mechanical sensors for ultraheavy dark matter searches via long-range forces

Dark matter candidates with masses around the Planck scale are theoretically well-motivated, and it has been suggested that it might be possible to search for dark matter solely via gravitational interactions in this mass range. In this work, we explore the pathway towards searching for dark matter candidates with masses around the Planck scale using mechanical sensors while considering realistic experimental constraints, and develop analysis techniques needed to conduct such searches. These dark matter particles are expected to leave tracks as their signature in mechanical sensor arrays, and we show that we can effectively search for such tracks using statistical approaches to track-finding. We analyze a range of possible experimental setups and compute sensitivity projections for searches for ultraheavy dark matter coupling to the Standard Model via long-range forces. We find that while a search for Planck-scale dark matter purely via gravitational couplings would be exceedingly difficult, requiring ∼80 dB of quantum noise reduction with a 100 3 array of devices, there is a wide range of currently unexplored dark matter candidates which can be searched for with already existing or near-term experimental platforms.

Qin, Juehang [Rice Univ., Houston, TX (United Stat↗

DOE OSTI2014

Dynamics of gas phase Ne{sup } + NH{sub 3} and Ne{sup } + ND{sub 3} Penning ionisation at low temperatures

Two isotopic chemical reactions, Ne{sup *} + NH{sub 3}, and Ne{sup *} + ND{sub 3}, have been studied at low collision energies by means of a merged beams technique. Partial cross sections have been recorded for the two reactive channels, namely, Ne{sup *} + NH{sub 3} → Ne + NH{sub 3}{sup +} + e{sup −}, and Ne{sup *} + NH{sub 3} → Ne + NH{sub 2}{sup +}+ H + e{sup −}, by detecting the NH{sub 3}{sup +} and NH{sub 2}{sup +} product ions, respectively. The cross sections for both reactions were found to increase with decreasing collision energy, E{sub coll}, in the range 8 μeV < E{sub coll} < 20 meV. The measured rate constant exhibits a curvature in a log(k)-log(E{sub coll}) plot from which it is concluded that the Langevin capture model does not properly describe the Ne{sup *} + NH{sub 3} reaction in the entire range of collision energies covered here. Calculations based on multichannel quantum defect theory were performed to reproduce and interpret the experimental results. Good agreement was obtained by including long range van der Waals interactions combined with a 6-12 Lennard-Jones potential. The branching ratio between the two reactive channels, Γ=([NH{sub 2}{sup +}])/([NH{sub 2}{sup +}]+[NH{sub 3}{sup +}]) , is relatively constant, Γ ≈ 0.3, in the entire collision energy range studied here. Possible reasons for this observation are discussed and rationalized in terms of relative time scales of the reactant approach and the molecular rotation. Isotopic differences between the Ne{sup *} + NH{sub 3} and Ne{sup *} + ND{sub 3} reactions are small, as suggested by nearly equal branching ratios and cross sections for the two reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2010

GlueX a new facility to search for gluonic degrees of freedom in mesons

The GlueX detector facility in Hall-D at Jefferson lab in Newport News is part of the 12 GeV upgrade and dedicated to the search for gluonic degrees of freedom in mesons by scattering high energy linearly polarized real photons of up to 9 GeV from nucleon targets. Civil construction of the Hall-D complex has started as well as the construction of the various detector components. The current status of the project is outlined here.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2011

Photoproduction of K{Sigma}(1385) from the nucleon

The reactions of K{Sigma}(1385) photoproduction, i.e., {gamma}p {yields} K{sup +}{Sigma}{sup 0}(1385) and {gamma} {yields} K{sup +}{Sigma}{sup -}(1385), are investigated in the resonance energy region for studying the role of the nucleon and {Delta} resonances of masses around 2 GeV. The Lagrangians for describing the decays of these resonances into the K{Sigma}(1385) channel are constructed and the decay amplitudes are obtained, which allows us to determine the coupling constants using the predictions of quark models or the data listed by the Particle Data Group. The resulting cross sections are compared to the data from the Thomas Jefferson National Accelerator Facility and the SPring-8, which indicates nontrivial contributions from the two-star-rated resonances in the Particle Data Group as well as from some missing resonances predicted by a quark model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2011

Timelike Compton Scattering

Generalized Parton Distributions (GPDs) have become a key concept in our studies of hadron structure in QCD. The measurement of suitable experimental observables and the extraction of GPDs from these data is one of the high priority 12 GeV programs at Jefferson Lab. Deeply Virtual Compton Scattering (DVCS) is generally thought of as the most promising channel for probing GPDs in the valence quark region. However, the inverse process, Timelike Compton Scattering (TCS) can provide an important complementary measurement, in particular of the real part of the Compton amplitude and power corrections at intermediate values of Q{sup 2}. The first studies of TCS using real tagged and quasi-real untagged photons were performed in Hall B at Jefferson Lab.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2011

A resonance interpretation for the nonmonotonic behavior of the {phi} photoproduction cross section near threshold

We study whether the nonmonotonic behavior found in the differential cross section of the {phi}-meson photoproduction near threshold can be described by a resonance. The resonant contribution is evaluated by using an effective Lagrangian approach. We find that, with the assumption of a J{sup P} 3/2{sup -} resonance with mass of 2.10{+-}0.03 GeV and width of 0.465{+-}0.141 GeV, LEPS data can indeed be well described. The ratio of the helicity amplitudes A{sub 1/2}/A{sub 3/2} calculated from the resulting coupling constants differs in sign from that of the known D{sub 13}(2080). We further find that the addition of this postulated resonance can substantially improve the agreement between the existing theoretical predictions and the recent {omega} photoproduction data if a large value of the OZI evading parameter xOZI = 12 is assumed for the resonance.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2015

Deep and shallow inelastic scattering

In this session we focused on the higher energy deep and shallow inelastic particle interactions, DIS and SIS. DIS interactions occur when the energy of the incident particle beam is so large that the beam is able to penetrate the nucleons inside of the target nuclei. These interactions occur at the smallest level possible, that of the quark-gluon, or parton, level. SIS interactions occur in an intermediate energy range, just below the energy required for DIS interactions. The DIS cross section formula contains structure functions that describe our understanding of the underlying parton structure of nature. The full description of DIS interactions requires three structure functions: two may be measured in charged lepton or neutrino scattering, but one can only be extracted from neutrino DIS data. There are reasons to expect that the impact of nuclear effects could be different for neutrinos engaging in the DIS interaction, vs those felt by leptons. In fact, fits by the nCTEQ collaboration have found that the neutrino-Fe structure functions appear to differ from those extracted from lepton scattering data [1]. To better understand the global picture of DIS and SIS, we chose a three-pronged attack that examined recent experimental results, data fits, and latest theory predictions. Experimental results from neutrino and lepton scattering, as well as collider experiments, were presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Toward precision Fermi-liquid theory in two dimensions

The ultracold and weakly coupled Fermi gas in two spatial dimensions is studied in an effective field theory framework. It has long been observed that universal corrections to the energy density to two orders in the interaction strength do not agree with Monte Carlo simulations in the weak-coupling regime. Here, universal corrections to three orders in the interaction strength are obtained, and are shown to provide agreement between theory and simulation. Special consideration is given to the scale ambiguity associated with the nontrivial renormalization of the singular contact interactions. Further, the isotropic superfluid gap is obtained to next-to-leading order, and nonuniversal contributions to the energy density due to effective range effects, p -wave interactions, and three-body forces are computed. Results are compared with precise Monte Carlo simulations of the energy density and the contact in the weakly coupled attractive and repulsive Fermi-liquid regimes. In addition, the known all-orders sum of ladder and ring diagrams is compared with Monte Carlo simulations at weak coupling and beyond.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2010

10 GeV dark matter candidates and cosmic-ray antiprotons

Recent measurements performed with some direct dark matter detection experiments, e.g. CDMS-II and CoGENT (after DAMA/LIBRA), have unveiled a few events compatible with weakly interacting massive particles. The preferred mass range is around 10 GeV, with a quite large spin-independent cross section of 10{sup -43}-10{sup -41} cm{sup 2}. In this paper, we recall that a light dark matter particle with dominant couplings to quarks should also generate cosmic-ray antiprotons. Taking advantage of recent works constraining the Galactic dark matter mass profile on the one hand and on cosmic-ray propagation on the other hand, we point out that considering a thermal annihilation cross section for such low mass candidates very likely results in an antiproton flux in tension with the current data, which should be taken into account in subsequent studies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2010

Near-Threshold {Lambda}(1520) Production by the {gamma}-vectorp{yields}K{sup +{Lambda}}(1520) Reaction at Forward K{sup +} Angles

Differential cross sections and photon-beam asymmetries for the {gamma}-vectorp{yields}K{sup +{Lambda}}(1520) reaction have been measured with linearly polarized photon beams at energies from the threshold to 2.4 GeV at 0.6<cos{theta}{sub c.m.}{sup K}<1. A new bump structure was found at W{approx_equal}2.11 GeV in the cross sections. The bump is not well reproduced by theoretical calculations introducing a nucleon resonance with J{<=}(3/2). This result suggests that the bump might be produced by a nucleon resonance possibly with J{>=}(5/2) or by a new reaction process, for example, an interference effect with the {phi} photoproduction having a similar bump structure in the cross sections.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2013

Potential of the neutron lloyd's mirror interferometer for the search for new interactions

We discuss the potential of the neutron Lloyd's mirror interferometer in a search for new interactions at small scales. We consider three hypothetical interactions that may be tested using the interferometer. The chameleon scalar field proposed to solve the enigma of accelerating expansion of the Universe produces interaction between particles and matter. The axion-like spin-dependent coupling between a neutron and nuclei or/and electrons may result in a P- and T-noninvariant interaction with matter. Hypothetical non-Newtonian gravitational interactions mediates an additional short-range potential between neutrons and bulk matter. These interactions between the neutron and the mirror of a Lloyd-type neutron interferometer cause a phase shift of neutron waves. We estimate the sensitivity and systematic effects of possible experiments.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

NASA NTRS1973

Methods for structural design at elevated temperatures

A procedure which can be used to design elevated temperature structures is discussed. The desired goal is to have the same confidence in the structural integrity at elevated temperature as the factor of safety gives on mechanical loads at room temperature. Methods of design and analysis for creep, creep rupture, and creep buckling are presented. Example problems are included to illustrate the analytical methods. Creep data for some common structural materials are presented. Appendix B is description, user's manual, and listing for the creep analysis program. The program predicts time to a given creep or to creep rupture for a material subjected to a specified stress-temperature-time spectrum. Fatigue at elevated temperature is discussed. Methods of analysis for high stress-low cycle fatigue, fatigue below the creep range, and fatigue in the creep range are included. The interaction of thermal fatigue and mechanical loads is considered, and a detailed approach to fatigue analysis is given for structures operating below the creep range.

Ellison, A. M.↗