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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
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Recent results from low-x and forward physics at HERA

The production of forward jets in inclusive as well as diffractive deep inelastic scattering at HERA is studied with the H1 detector. For inclusive DIS events at low Q{sup 2} with a forward jet, produced close to the proton remnant, differential cross sections and normalised distributions are measured as a function of the azimuthal angle difference between the forward jet and the scattered positron. Results on dijet production cross sections are also presented for diffractive DIS events in which the final state proton is tagged in the H1 Forward Proton Spectrometer. Two topologies are investigated by either requiring the two jets being produced centrally or by requiring that one of the jets is going in the forward direction. The data are compared with NLO QCD predictions as well as leading order Monte Carlo models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Physics updates from HERMES

The HERMES collaboration presents two sets of recent results: the first related to an extraction of the g{sub 2} nucleon structure function determined for DIS on a polarised target and the second related to the measurement of asymmetries related to the deeply virtual Compton scattering process that can be used to discover information on generalised parton distributions and hence nucleon structure.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

GPD physics with polarized muon beams at COMPASS-II

A major part of the future COMPASS program is dedicated to the investigation of the nucleon structure through Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP). COMPASS will measure DVCS and DVMP reactions with a high intensity muon beam of 160 GeV and a 2.5 m-long liquid hydrogen target surrounded by a new TOF system. The availability of muon beams with high energy and opposite charge and polarization will allow to access the Compton form factor related to the dominant GPD H and to study the x{sub B}-dependence of the t-slope of the pure DVCS cross section and to study nucleon tomography. Projections on the achievable accuracies and preliminary results of pilot measurements will be presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

GPDs at an electron ion collider

The feasibility for a precise determination of Generalized Parton Distribution (GPDs) functions at an Electron Ion Collider (EIC) has been explored. The high luminosity of the machine, together with the large resolution and rapidity acceptance of the new dedicated detector, will open opportunity for high precision measurements of GPDs. We report on the study of GPDs from deeply virtual Compton scattering (DVCS). We also point out that such measurements at a proposed EIC provide insight to both, the transverse distribution of sea quarks and gluons as well as the proton spin decomposition.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Deeply virtual Compton scattering from gauge/gravity duality

We use gauge/gravity duality to study deeply virtual Compton scattering (DVCS) in the limit of high center of mass energy at fixed momentum transfer, corresponding to the limit of low Bjorken x, where the process is dominated by the exchange of the pomeron. At strong coupling, the pomeron is described as the graviton Regge trajectory in AdS space, with a hard wall to mimic confinement effects. This model agrees with HERA data in a large kinematical range. The behavior of the DVCS cross section for very high energies, inside saturation, can be explained by a simple AdS black disk model. In a restricted kinematical window, this model agrees with HERA data as well.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Diffractive production of charm quark/antiquark pairs at RHIC and LHC

We have discussed single and central diffractive production of c(bar sign)c pairs in the Ingelman-Schlein model. In these calculations we have included diffractive parton distributions obtained by the H1 collaboration at HERA and absorption effects neglected in some early calculations in the literature. The absorption effects which are responsible for the naive Regge factorization breaking cause that the cross section for diffractive processes is much smaller than that for the fully inclusive case, but could be measured at RHIC and LHC by imposing special condition on rapidity gaps. We discuss also different approaches to diffractive production of heavy quark/antiquark [1, 2, 3]. The particular mechanism is similar to the diffractive dissociation of virtual photons into quarks, which drives diffractive deep inelastic production of charm in the low-mass diffraction, or large {beta}-region.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Dark matter at colliders

We show that colliders can impose strong constraints on dark matter. We take an effective field theory approach where dark matter couples to quarks and gluons through high dimensional operators. We discuss limits on interactions of dark matter and hadronic matter from the ATLAS experiment at the Large Hadron Collider (LHC). For spin-independent scattering, the LHC limits are stronger than those from direct detection experiments for light WIMPs. For spin-dependent scattering, the LHC sets better limits over much of parameter space.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Direct observation of time reversal violation

A direct evidence for Time Reversal Violation (TRV) means an experiment that, considered by itself, clearly shows TRV independent of, and unconnected to, the results for CP Violation. No existing result before the recent BABAR experiment with entangled neutral B mesons had demonstrated TRV in this sense. There is a unique opportunity for a search of TRV with unstable particles thanks to the Einstein-Podolsky-Rosen (EPR) Entanglement between the two neutral mesons in B, and PHI, Factories. The two quantum effects of the first decay as a filtering measurement and the transfer of information to the still living partner allow performing a genuine TRV asymmetry with the exchange of 'in' and 'out' states. With four independent TRV asymmetries, BABAR observes a large deviation of T-invariance with a statistical significance of 14 standard deviations, far more than needed to declare the result as a discovery. This is the first direct observation of TRV in the time evolution of any system.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Low-background tracker development for SuperNEMO

The SuperNEMO experiment will search for neutrinoless double beta decay (0νββ) with a target sensitivity of T{sub 1/2}(0ν) > 10{sup 26} years, corresponding to an effective neutrino mass of 50-100 meV. At its heart there is a low-background gaseous tracking detector which allows for extremely efficient background rejection and, if 0νββ is observed, may provide important insights into the mechanism via which it may be mediated. Radon inside the tracker, which can mimic rare ββ events, is one of the most dangerous backgrounds for SuperNEMO. To reach the target sensitivity the radon concentration inside the tracking volume must be < 0.15 mBq/m{sup 3}. To reach this challengingly-low level of radon, a considerable program of R and D has been undertaken. This includes automation of the tracker-wiring process, development of a dedicated setup to measure radon diffusion and a 'radon concentration line' which will be able to measure levels of radon in the μBq/m{sup 3} range.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Background considerations for SuperCDMS

Rejection and protection from background is a key issue for the next generation SuperCDMS SNOLAB experiment that will have a cross-section sensitivity of better than 8 × 10{sup −46} cm{sup 2} for spin-independent WIMP-nucleon interactions. This paper presents the details of the methods used to reject electromagnetic backgrounds using the new iZIP detectors that are currently operated in the Soudan Underground Laboratory, MN and the methods the collaboration is investigating to protect against neutron background in the next generation SuperCDMS experiment.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

The frontier of high energy physics and the large hadron collider

High Energy Physics explores the most fundamental questions about the nature of the universe, e.g., basic building blocks of matter and energy, existence of the smallest sub-atomic particles, dark matter, dark energy etc. The Large Hadron Collider (LHC) is the most powerful accelerator on earth located near Geneva, Switzerland. It recreates the conditions just after the Big Bang by colliding two proton beams head-on at very high energy every 25-50 nanosecond. With the recent discovery of Higgs boson, the LHC is firmly marching on to explore the TeV energy scale.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Measurements of W/Z production with the ATLAS detector

W and Z boson production have been measured in the electron, muon and tau decay channels at the LHC with the ATLAS detector. Total and differential cross sections, defined in terms of the decay lepton kinematics, have been measured as a function of rapidity and transverse momentum. Ratios of the cross sections demonstrate sensitivity to lepton universality. The kinematic distributions constrain parton densities and QCD calculations, including resummations of soft gluon radiation and the matching of NLO matrix elements (or high multiplicity tree-level matrix elements) to parton shower approximations. The polarization of W bosons is also measured, as, for the first time, is the polarization of the tau lepton in W → τν decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Result and perspectives on meson spectroscopy with KLOE and KLOE-2

From 2000 to 2006 KLOE has collected 2.5 fb{sup −1} of e{sup +}e{sup −} collisions at the peak of the φ(1020) and 250 pb{sup −1} off-peak. In this paper the most recent results on meson spectroscopy are presented, with emphasis on rare eta meson decays, the search for the U boson, and γγ collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Searches for dark photons at e{sup +}e{sup −} colliders

Searches for new, light, neutral vector particles are being pursued by several different experiments in the world, using e{sup +}e{sup −} collsion data at center-of-mass energies ranging between ∼1 and ∼10 GeV. In this paper I will review the most recent results from KLOE, BESIII, BaBar and Belle and briefly discuss open issues and future perspectives in the field.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Experimental concept and design of DarkLight, a search for a heavy photon

This talk gives an overview of the DarkLight experimental concept: a search for a heavy photon A′ in the 10-90 MeV/c{sup 2} mass range. After briefly describing the theoretical motivation, the talk focuses on the experimental concept and design. Topics include operation using a half-megawatt, 100 MeV electron beam at the Jefferson Lab FEL, detector design and performance, and expected backgrounds estimated from beam tests and Monte Carlo simulations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Searches for dark photons at the Mainz Microtron

The A1 Collaboration at the Mainz Microtron (MAMI) operates high resolution spectrometers at very high luminosities for fixed target electron scattering experiments. The setup is well suited for the search for dark photons in the mass range between 50 MeV and 300 MeV. In these experiments, a possible dark photon would appear as a sharp peak in the mass spectrum of di-lepton electro-production. In this presentation the potential of the setup is presented and the possibilities for future experiments for dark photon searches at MAMI are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

APEX: An electron fixed-target experiment to search for a new vector boson A′ Decaying to e{sup +}e{sup −}

The A' EXperiment (APEX) is designed to search for new vector bosons that have small couplings to charged particles. Such vectors can arise naturally from a small kinetic mixing of a new 'dark photon' (A') with the photon - one of the very few ways in which new forces can couple to the Standard Model - and have received considerable attention as an explanation of various dark matter related anomalies. A' bosons are produced by radiation off an electron beam, and could appear as narrow resonances with small production cross-section in the QED e{sup +}e{sup −} spectrum. We plan to search for an A' using the CEBAF electron beam at energies of 1-4 GeV incident on 0.5-10% radiation length multi-foil tungsten targets, and measure the resulting e{sup +}e{sup −} pairs using the High Resolution Spectrometers and a septum magnet in Hall A at Jefferson Lab. With a 33-day run, APEX will explore the region 50 MeV < m{sub A′} < 550 MeV with couplings alpha'/alpha down to 10{sup −7}. This proceeding summarizes the experiment, test run results, and comments on future plans.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Heavy photon search experiment at JLAB

The Heavy Photon Search (HPS) experiment in Hall-B at Jefferson Lab will search for new heavy vector boson(s), aka 'heavy photons', in the mass range of 20 MeV/c{sup 2} to 1000 MeV/c{sup 2} using the scattering of high energy, high intensity electron beams off a high Z target. The proposed measurements will cover the region of parameter space favored by the muon g-2 anomaly, and will explore a significant region of parameter space, not only at large couplings (α′/α > 10{sup −7}), but also in the regions of small couplings, down to α′/α∼10{sup −10}. The excellent vertexing capability of the Si-tracker uniquely enables HPS to cover the small coupling region. Also, HPS will search for heavy photons in an alternative to the e{sup +}e{sup −} decay mode, in the heavy photon's decay to μ{sup +}μ−.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗