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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Lepton-pair production at hadron colliders at N 3 LO in QCD

We compute for the first time the complete corrections at N 3 LO in the strong coupling constant to the inclusive neutral-current Drell-Yan process including contributions from both photon and Z-boson exchange. Our main result is the computation of the QCD corrections to the inclusive production cross section of an axial-vector boson to third order in the strong coupling in a variant of QCD with five massless quark flavours. Since the axial anomaly does not cancel for an odd number of flavours, we also consistently include non-decoupling effects in the top-quark mass through three loops. We perform a phenomenological study of our results, and we present for the first time predictions for the inclusive Drell-Yan process at the LHC at this order in QCD perturbation theory.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Asymmetries in electron-induced breakup of polarized {sup 3}He

The Jefferson Lab Experiment E05-102 'Measurement of A{sub x}{sup '} and A{sub z}{sup '} asymmetries in the quasi-elastic {sup 3}He(e,e'd) reaction' was performed in Hall A in 2009. The main physics motivation of the experiment was to investigate the effects of small components of the {sup 3}He ground-state wave-function by a simultaneous measurement of double-polarization asymmetries in quasi-elastic kinematics for three exclusive channels, (e,e'd), (e,e'p), and (e,e'n), at almost identical momentum transfers, as well as for (e,e'). This experiment will help map the spin structure of the {sup 3}He nucleus onto the picture of the ''free'' polarized neutron. As such, it is of great relevance to the polarized-neutron programs at Jefferson Lab and beyond.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Neutrino neutral-current elastic scattering on {sup 12}C

The neutral-current elastic scattering of neutrinos on carbon and CH{sub 2} targets is computed using the relativistic distorted-wave impulse approximation with a relativistic optical potential. Results for exclusive and inclusive neutrino reactions on a {sup 12}C target are presented. We show that the nuclear effects on the shape of the four-momentum transferred squared distribution d{sigma}/dQ{sub QE}{sup 2} in neutrino neutral-current and charged-current quasielastic scattering are similar. We also calculate the flux-averaged neutral-current elastic differential cross section d{sigma}/dQ{sub QE}{sup 2} for neutrino scattering from CH{sub 2}, as well as the neutral-current to charged-current cross section ratio as functions of Q{sub QE}{sup 2}. The axial mass M{sub A} is extracted from a fit of the d{sigma}/dQ{sub QE}{sup 2} cross section measured in the MiniBooNE experiment. The extracted value of M{sub A}=1.28{+-}0.05 GeV is consistent within errors with the MiniBooNE result. Additionally, for proton kinetic energies above the Cherenkov threshold, the strange-quark contribution to the neutral-current axial vector form factor at Q{sub QE}{sup 2}=0, {Delta}s, was extracted from a fit to MiniBooNE data for the {nu}p{yields}{nu}p to {nu}N{yields}{nu}N cross section ratio. This value is found to be {Delta}s=-0.11{+-}0.36

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Optical Spectroscopic Diagnostics Of Dusty Plasma In RF Discharge

The parameters of the buffer plasma containing dust particles were measured by means of spectroscopic methods. The change in the emission spectrum of the buffer plasma with addition of dust was observed. It seems to relate to changing in temperature and number density of electrons due to the influence of dusts.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Design, construction and commissioning of the Digital Hadron Calorimeter—DHCAL

A novel hadron calorimeter is being developed for future lepton colliding beam detectors. The calorimeter is optimized for the application of Particle Flow Algorithms (PFAs) to the measurement of hadronic jets and features a very finely segmented readout with 1 × 1 cm(2) cells. The active media of the calorimeter are Resistive Plate Chambers (RPCs) with a digital, i.e. one-bit, readout. To first order the energy of incident particles in this calorimeter is reconstructed as being proportional to the number of pads with a signal over a given threshold. A large-scale prototype calorimeter with approximately 500,000 readout channels has been built and underwent extensive testing in the Fermilab and CERN test beams. This paper reports on the design, construction, and commissioning of this prototype calorimeter.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Neutrino Flavor Model Building and the Origins of Flavor and CP Violation

The neutrino sector offers one of the most sensitive probes of new physics beyond the Standard Model of Particle Physics (SM). The mechanism of neutrino mass generation is still unknown. The observed suppression of neutrino masses hints at a large scale, conceivably of the order of the scale of a rand unified theory (GUT), which is a unique feature of neutrinos that is not shared by the charged fermions. The origin of neutrino masses and mixing is part of the outstanding puzzle of fermion masses and mixings, which is not explained ab initio in the SM. Flavor model building for both quark and lepton sectors is important in order to gain a better understanding of the origin of the structure of mass hierarchy and flavor mixing, which constitute the dominant fraction of the SM parameters. Recent activities in neutrino flavor model building based on non-Abelian discrete flavor symmetries and modular flavor symmetries have been shown to be a promising direction to explore. The emerging models provide a framework that has a significantly reduced number of undetermined parameters in the flavor sector. In addition, such a framework affords a novel origin of CP violation from group theory due to the intimate connection between physical CP transformation and group theoretical properties of non-Abelian discrete groups. Model building based on non-Abelian discrete flavor symmetries and their modular variants enables the particle physics community to interpret the current and anticipated upcoming data from neutrino experiments. Non-Abelian discrete flavor symmetries and their modular variants can result from compactification of a higher-dimensional theory. Pursuit of flavor model building based on such frameworks thus also provides the connection to possible UV completions: in particular, to string theory. We emphasize the importance of constructing models in which the uncertainties of theoretical predictions are smaller than, or at most compatible with, the error bars of measurements in neutrino experiments. While there exist proof-of-principle versions of bottom-up models in which the theoretical uncertainties are under control, it is remarkable that the key ingredients of such constructions were discovered first in top-down model building. We outline how a successful unification of bottom-up and top-down ideas and techniques may guide us towards a new era of precision flavor model building in which future experimental results can give us crucial insights into the UV completion of the SM.

Almumin, Yahya (ORCID:0000000196396772)↗
DOE OSTI2023

Studying the hadron structure with PANDA and CLAS using machine learning techniques

The hadron spectroscopy and structure are currently very active fields of research to study the non-perturbative regime of quantum chronodynamics. The first one studies the complex structure of excited hadrons by looking at their decay products, while the latter uses lepton scattering on nucleons. Both methods require reconstruction algorithms with great efficiency and good particle identification and background rejection rates. This work aims to provide these by either improving the existing methods or developing new ones. The first part of this document presents a feasibility study of a predicted hybrid charmonium state for the PANDA experiment. Lattice QCD calculations predict the ground state hybrid charmonium to be a spin exotic with quantum numbers of JP C = 1?+ at a mass of around 4.3 GeV with a width to be around 20 MeV. A machine learning based data analysis scheme is proposed to further improve the signal efficiency and the background reduction, alongside with improvements of the analysis software (PandaRoot), that are vital for this study. These improvements include a reworked clustering algorithm for the electromagnetic calorimeter (EMC) and an optimized monte carlo matching for neutral particles. The second part of this document is about studying the proton structure. A multidimensional study of the structure function ratio Fsin(?)LU /FUU has been performed for K±, based on the measurement of beam-spin asymmetries. It uses the high statistics data recorded with the CLAS12 spectrometer at Jefferson Laboratory. Fsin(?)LU is a twist-3 quantity that provides information about the quark gluon correlations in the proton. This document will present for the first time a simultaneous analysis of two kaon channels over a large kinematic range of z, xB , PT and Q2 with virtualities Q2 ranging from 1 GeV2 up to 8 GeV2 using machine learning techniques for improved particle identification.

Kripko, Aron↗
DOE OSTI2024

Radiative Majorana neutrino masses in a parity solution to the strong CP problem

The strong CP problem is solved in Parity symmetric theories, with the electroweak gauge group containing SU(2) L × SU(2) R broken by the minimal set of Higgs fields. Neutrino masses may be explained by adding the same number of gauge singlet fermions as the number of generations. The neutrino masses vanish at tree-level and are only radiatively generated, leading to larger couplings of right-handed neutrinos to Standard Model particles than with the tree-level seesaw mechanism. We compute these radiative corrections and the mixing angles between left- and right-handed neutrinos. We discuss sensitivities to these right-handed neutrinos from a variety of future experiments that search for heavy neutral leptons with masses from tens of MeV to the multi-TeV scale.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Prominent Higher-Order Contributions to Electronic Recombination

Intershell higher-order (HO) electronic recombination is reported for highly charged Ar, Fe, and Kr ions, where simultaneous excitation of one K-shell electron and one or two additional L-shell electrons occurs upon resonant capture of a free electron. For the mid-Z region, HO resonance strengths grow unexpectedly strong with decreasing atomic number Z ({proportional_to}Z{sup -4}), such that, for Ar ions the 2nd-order overwhelms the 1st-order resonant recombination considerably. The experimental findings are confirmed by multiconfiguration Dirac-Fock calculations including hitherto neglected excitation pathways.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Full event particle-level unfolding with variable-length latent variational diffusion

The measurements performed by particle physics experiments must account for the imperfect response of the detectors used to observe the interactions. One approach, unfolding, statistically adjusts the experimental data for detector effects. Recently, generative machine learning models have shown promise for performing unbinned unfolding in a high number of dimensions. However, all current generative approaches are limited to unfolding a fixed set of observables, making them unable to perform full-event unfolding in the variable dimensional environment of collider data. A novel modification to the variational latent diffusion model (VLD) approach to generative unfolding is presented, which allows for unfolding of high- and variable-dimensional feature spaces. The performance of this method is evaluated in the context of semi-leptonic t\bar{t} t t ‾ production at the Large Hadron Collider.

Shmakov, Alexander↗
DOE OSTI2020

A supersymmetric theory of baryogenesis and sterile sneutrino dark matter from B mesons

Low-scale baryogenesis and dark matter generation can occur via the production of neutral B mesons at MeV temperatures in the early Universe, which undergo CP-violating oscillations and subsequently decay into a dark sector. In this work, we discuss the consequences of realizing this mechanism in a supersymmetric model with an unbroken U(1) R symmetry which is identified with baryon number. B mesons decay into a dark sector through a baryon number conserving operator mediated by TeV scale squarks and a GeV scale Dirac bino. The dark sector particles can be identified with sterile neutrinos and their superpartners in a type-I seesaw framework for neutrino masses. The sterile sneutrinos are sufficiently long lived and constitute the dark matter. The produced matter-antimatter asymmetry is directly related to observables measurable at B factories and hadron colliders, the most relevant of which are the semileptonic-leptonic asymmetries in neutral B meson systems and the inclusive branching fraction of B mesons into hadrons and missing energy. We discuss model independent constraints on these experimental observables before quoting predictions made in the supersymmetric context. Constraints from astrophysics, neutrino physics and flavor observables are studied, as are potential LHC signals with a focus on novel long lived particle searches which are directly linked to properties of the dark sector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for new physics in B{yields}D*{tau}nu-bar {sub {tau}} decay

B physics offers important tests of the Standard Model at low energies. Recently, BaBar observed significant deviations from the Standard Model expectations in the semileptonic B{yields}D{sup (*)}{tau}{nu}{sub {tau}} decays. Interestingly, the measured leptonic B{yields}{tau}{nu} branching fraction also deviates from CKM unitarity predictions. Motivated by these results we investigate the most general set of lowest dimensional effective operators leading to modifications of b{yields}c(u) (semi)tauonic transitions. Allowing for general flavor violation, we find that among possible operator structures, new contributions from right-right vector and right-left scalar quark currents provide viable explanations of the anomalies. In addition, we identify a number of B{yields}D*{tau}{nu}{sub {tau}} transition observables with the power to discriminate among the various effective operators' contributions. They are the differential decay rate, longitudinal D* polarization fraction, D*-{tau} opening angle asymmetry and the {tau} helicity asymmetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Measurements of the inclusive and differential production cross sections of a top-quark–antiquark pair in association with a Z boson at $\sqrt{s}$ = 13 TeV with the ATLAS detector

Measurements of both the inclusive and differential production cross sections of a top-quark–antiquark pair in association with a Z boson ($t\bar{t}Z$) are presented. The measurements are performed by targeting final states with three or four isolated leptons (electrons or muons) and are based on $\sqrt{s}$=13 TeV proton–proton collision data with an integrated luminosity of 139 fb -1 , recorded from 2015 to 2018 with the ATLAS detector at the CERN Large Hadron Collider. The inclusive cross section is measured to be σ $t\bar{t}Z$ =0.99 ± 0.05 (stat.) ± 0.08 (syst.) pb, in agreement with the most precise theoretical predictions. The differential measurements are presented as a function of a number of kinematic variables which probe the kinematics of the $t\bar{t}Z$ system. Both absolute and normalised differential cross-section measurements are performed at particle and parton levels for specific fiducial volumes and are compared with theoretical predictions at different levels of precision, based on a χ 2 /ndf and p value computation. Overall, good agreement is observed between the unfolded data and the predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

On the origin of X-ray spectra in luminous blazars

Gamma-ray luminosities of some quasar-associated blazars imply jet powers reaching values comparable to the accretion power even if assuming very strong Doppler boosting and very high efficiency of gamma-ray production. With much lower radiative efficiencies of protons than of electrons, and the recent reports of very strong coupling of electrons with shock-heated protons indicated by particle-in-cell simulations, the leptonic models seem to be strongly favored over the hadronic ones. However, the electron-proton coupling combined with the external-radiation-Compton (ERC) models of gamma-ray production in leptonic models predict extremely hard X-ray spectra, with energy indices α {sub x} ∼ 0. This is inconsistent with the observed 2-10 keV slopes of blazars, which cluster around α {sub x} ∼ 0.6. This problem can be resolved by assuming that electrons can be efficiently cooled down radiatively to non-relativistic energies, or that blazar spectra are entirely dominated by the synchrotron self-Compton (SSC) component up to at least 10 keV. Here, we show that the required cooling can be sufficiently efficient only at distances r < 0.03 pc. SSC spectra, on the other hand, can be produced roughly co-spatially with the observed synchrotron and ERC components, which are most likely located roughly at a parsec scale. We show that the dominant SSC component can also be produced much further than the dominant synchrotron and ERC components, at distances of ≳ 10 pc. Hence, depending on the spatial distribution of the energy dissipation along the jet, one may expect to see γ-ray/optical events with either correlated or uncorrelated X-rays. In all cases the number of e{sup +}e{sup –} pairs per proton is predicted to be very low. The direct verification of the proposed SSC scenario, and particularly the question of the co-spatiality of the SSC component with other spectral components, requires sensitive observations in the hard X-ray band. This is now possible with the deployment of the NuSTAR satellite, providing the required sensitivity to monitor the details of the hard X-ray spectra of blazars in the range where the ERC component is predicted to start dominating over the SSC component.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Commissioning of the Mu2e Data AcQuisition System and the Vertical Slice Test of the Straw Tracker

The report discusses the commissioning of the DAQ system of the Mu2e experiment. We studied how the tracker works and especially the tracker readout. We used a generator to send pulses and we tried to understand the output and non-output of the DTC, in order to validate the event and run format and all the failure modes. In section one, we describe Charged Lepton Flavour Violation, the main purpose of Mu2e, in section two we describe Mu2e experiment. Section three presents the tracker description and readout, meanwhile section four the DAQ system and event building. In section five, we start explaining the analysis we have done on events and all the failure modes we discovered. In section six, we have done an analysis of the logger and boardreader rate, we validated the generator frequency in section seven and studied the number of hits in function of the channel number in section eight. To conclude we investigated the channel to channel time differences in section nine and in section ten we explain our Monte Carlo simulation, reproducing ROCs readout.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Neutrino-Nucleus Coherent NC({pi}{sup 0}) Scattering in the MINOS Near Detector

Neutrino reactions recorded by the MINOS Near Detector in exposures totalling 2.8x10{sup 20} protons-on-target were searched for single, highly-forward {pi}{sup 0} mesons produced by coherent neutral current interactions {nu}{sub {mu}}+A{yields}{nu}{sub {mu}}+A+{pi}{sup 0}. Events having topologies consistent with single electromagnetic showers were isolated. Contributions from neutrino-induced backgrounds are determined using a data-driven fit of Monte Carlo distributions over sideband regions. The fit is used to project the background levels into signal regions. An excess of events above the best-fit background is observed for shower topologies of few GeV energies and at very forward angles. The partial cross section for NC({pi}{sup 0}) coherent scattering yielding E{sub vis}({pi}{sup 0})>1.0 GeV averaged over incident neutrino energies 2.4{<=}E{sub {nu}{<=}9}.0 GeV is (31.6{+-}10.5)x10{sup -40} cm{sup 2}/nucleus. Total cross sections for coherent scattering from nuclei of average nucleon number A{sub eff} = 48 and for iron (A = 56) nuclei are estimated for <E{sub {nu}>} = 4.9 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Crystal Ball: On the Future High Energy Colliders

High energy particle colliders have been in the forefront of particle physics for more than three decades. At present the near term US, European and international strategies of the particle physics community are centered on full exploitation of the physics potential of the Large Hadron Collider (LHC) through its high-luminosity upgrade (HL-LHC). A number of next generation collider facilities have been proposed and are currently under consideration for the medium- and far-future of the accelerator-based high energy physics. In this paper we offer a uniform approach to evaluation of various accelerators based on the feasibility of their energy reach, performance reach and cost range. We briefly review such post-LHC options as linear e+e- colliders in Japan (ILC) or at CERN (CLIC), muon collider, and circular lepton or hadron colliders in China (CepC/SppC) and Europe (FCC). We conclude with a look into ultimate energy reach accelerators based on plasmas and crystals, and some perspectives for the far future of accelerator-based particle physics.

43 PARTICLE ACCELERATORS↗