Brian Raue
(Florida International University)
9/12/17, 8:40 AM
Since the discovery of the discrepancy between Rosenbluth and polarization-transfer measurements of the proton form-factor ratio $G_E/G_M$ there has been a renewed interest in measuring contributions to the elastic cross section from two-photon exchange (TPE). Three recent experiments conducted at CLAS, VEPP-3, and OLYMPUS directly determined the real part of the TPE amplitude by measuring the...
Peter Blunden
(University of Manitoba)
9/12/17, 9:50 AM
In this talk I will give an overview of recent progress in theoretical calculations of two-photon exchange (TPE) effects in elastic electron-proton scattering. This will include a survey of existing models and theoretical frameworks. TPE effects are relevant for extractions of proton form factors at high $Q^2$, and of the proton radius at low $Q^2$. Recent experiments to directly measure hard...
Volker Burkert
(Jefferson Lab)
9/12/17, 10:35 AM
Larry cardman
(Jefferson Lab)
9/12/17, 11:20 AM
Oral Contribution
The Polarized Electrons for Polarized Positrons (PEPPo) experiment at the injector of the Continuous Electron Beam Accelerator Facility demonstrated for the first time the efficient transfer of polarization from electrons to positrons via a two-step process: polarized bremsstrahlung radiation is induced by a polarized electron beam in a high-Z target; and then the polarized bremsstrahlung...
Francois-Xavier Girod
(JLab)
9/12/17, 1:50 PM
The exclusive electroproduction of a hard photon off a nucleon $eN\rightarrow eN\gamma$
provides three-dimensional information on the nucleon structure.
This reaction proceeds via the Bethe-Heitler (BH) process (with the photon emitted by the electron),
and the Deeply Virtual Compton Scattering (DVCS) process (with the photon emitted by the proton).
BH and DVCS are indistinguishable, and...
Ferdinand Willeke
(Brookhaven National Lab)
9/12/17, 3:00 PM
Yves Roblin
(Jefferson Lab)
9/12/17, 3:30 PM
We will discuss the possibility of using CEBAF as a positron machine. After a review of the current machine capabilities, we will examine one particular scenario for generating, accelerating and transporting positrons in CEBAF. Modifications to the existing CEBAF machine will be discussed as well as expected performance and impact on the regular program.
Michael Tiefenback
(Jefferson Lab)
9/12/17, 4:00 PM
Operation of CEBAF with positrons using the standard electron beam direction (clockwise as viewed from above) requires inverting the polarity of the recirculation arc and Spreader/Recombiner dipoles. Retaining the focusing optics used for electrons requires inverting the quadrupole gradients. The hardware readily supports reversed polarity, and no observations are known to suggest any change...
David Gaskell
(Jefferson Lab)
9/12/17, 5:00 PM
Jeff Owens
(Florida State University)
9/13/17, 9:10 AM
In order to better understand the behavior of parton distribution functions in x and Q, it is necessary to be able to separate the contributions from various flavors. Such flavor differentiation can be greatly assisted by charged current deep inelastic scattering. The status of flavor differentiation will be discussed and some useful examples utilizing charged current interactions will be given.
Charlotte Van Hulse
(University of the Basque Country UPV/EHU)
9/13/17, 9:40 AM
The study of the nucleon spin structure has been approached from two complementary perspectives. From the one hand, generalized parton distributions (GPDs) give information about the distribution of quarks and gluons inside the nucleon as a function of the fraction of their longitudinal momentum with respect to the longitudinal nucleon momentum and as a function of their transverse...
Tanja Horn
(Catholic University of America)
9/13/17, 10:40 AM
Michael Murray
(University of Kansas)
9/13/17, 11:40 AM
Oral Contribution
The unprecedented energies, luminosities and experimental capabilities of the LHC have given physicists opportunities to search for new physics over a very wide mass range using photon induced reactions. This talk will summarize recent LHC results on photon-photon, photon proton and photon-proton reactions at both the electroweak and QCD scales. These results will be placed in the context of...
Atsuo Kawasuso
(QST)
9/13/17, 1:30 PM
Oral Contribution
Positrons emitted from radioisotopes are longitudinally spin-polarized due to parity non-conservation in the weak interaction. In 1960's, the angular correlation of annihilation radiation measurement with spin-polarized positrons was demonstrated to be useful in studying the ferromagnetic band structures. In 1982, the first experiment on surface ferromagnetism with spin-polarized positron beam...
Allen Mills, Jr.
(University of California Riverside)
9/13/17, 2:05 PM
One goal of the JPos-17 International Workshop on Physics with Positrons is to ascertain whether it would be a good idea to expand the mission of the Thomas Jefferson National Accelerator Facility to include science with low energy (i.e. “slow”) spin polarized positrons. It is probably true that experimentation with slow positrons would potentially have wide-ranging benefits comparable to...
Stephen Benson
(Jefferson Lab)
9/13/17, 3:05 PM
Though there are many applications of low energy positrons, many experiments are source limited. Using the LERF accelerator at the Thomas Jefferson National Accelerator Facility, it is possible to produce a high brightness source of very low-energy positrons. The accelerator requirements are well within the capabilities of the installed hardware. The accelerator can easily produce 50 kW of...
Andreas Wagner
(Helmholtz-Zentrum Dresden-Rossendorf)
9/13/17, 3:40 PM
The Helmholtz-Center at Dresden-Rossendorf operates several user beamlines for materials research using positron annihilation energy and lifetime spectroscopy. Two beamlines are being operated at a superconducting electron linear accelerator [1] producing hard X-rays from electron-bremsstrahlung and in turn generating positrons from pair production. Both installations employ bunched...
Toshio HYODO
(Slow positron applications at Slow Positron Facility of Institute of Materials Structure Science, KEK)
9/13/17, 4:15 PM
Positron Applications
Slow Positron Facility at KEK (High Energy Accelerator Research Organization) is a user dedicated facility with an energy-tunable (0.1 - 35 keV) slow positron beam created by a dedicated 50MeV linac [1]. It operates in a short pulse (width 1-12 ns, variable, \5\times 10 ^6\ e\^+\/s) and a long pulse (width 1.2 \mu s, \5\times 10 ^7\ e\^+\/s) modes of 50 Hz.
High energy positrons from pair...
Nagendra Nath MONDAL
(Techno India Batanagar (Techno India Group))
9/13/17, 4:50 PM
Rolland Johnson
(Muons, Inc.)
9/13/17, 5:20 PM
Bogdan Wojtsekhowski
(Jefferson Lab)
9/14/17, 8:30 AM
Seamus Riordan
(Stony Brook University)
9/14/17, 9:25 AM
Test of the Standard Model
Weak neutral current interactions with charged leptons have offered unique
opportunities to study novel aspects of hadronic structure and search for
physics beyond the standard model. These studies in the medium energy
community have been primarily through parity-violating processes with electron
beams, but with the possibility of polarized positron beams, new and
complementary...
Paolo Valente
(INFN Rome)
9/14/17, 10:10 AM
Dark Matter elusiveness could be explained by speculating that it lives in a separate sector with respect to the Standard Model (SM) and that interacts with it only by means of messengers. The simplest model foresees just one messenger: a possibly massive vector boson given by a new U(1) symmetry. This mediator can faintly mix with the photon and, hence, interact with SM charged particles,...
Luca Marsicano
(INFN Genova)
9/14/17, 10:45 AM
The interest in the Dark Photon (A' or U) has recently grown, since it could act as a light mediator to a new sector of Dark Matter particles. In this paradigm, the electron-positron annihilation can rarely produce a $\gamma $ U couple. Various experiments (e.g. PADME@LNF, Adv. High Energy Phys. 2014:959802; VEPP-3, arXiv:1207.5089[hep-ex]) have been proposed to detect this process using ...
Nathan Sherrill
(Indiana University Bloomington)
9/14/17, 11:10 AM
Proposed theories beyond the Standard Model (SM) can support the breaking of Lorentz and CPT symmetry. Searches for violations of these symmetries are often performed within the framework of the Standard Model Extension (SME), the most general effective field theory parametrizing CPT and Lorentz violation. The breaking of CPT and Lorentz symmetries in the SME is characterized by coefficients...
Varghese Anto Chirayath
(Department of Physics, University of Texas at Arlington, 76019)
9/14/17, 1:00 PM
We discuss our recent report on the direct observation of a low-energy Auger electron emission process initiated by the creation of a deep valence hole in single layer graphene through positron annihilation. Here, an electron from a higher energy level in the valence band fills the valence hole created by positron-electron annihilation. The energy released because of this relaxation is...
Jan Kuriplach
(Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic)
9/14/17, 1:25 PM
Positronium can be very helpful when studying the electronic structure of materials. Indeed, the recent experiment [1], where the Ps emission from a copper (110) surface was examined, allowed for the precise determination of the electron chemical potential of copper by means of measuring the Ps affinity. This affinity ($A_{Ps}$) [1] is defined formally via the electron ($\Phi_-$) and positron...
J. David Van Horn
(University of Missouri-Kansas City)
9/14/17, 1:50 PM
Asymmetry is a basic property found at multiple scales in the universe [1]. Asymmetric molecular interactions are fundamental to the operation of biological systems in both signaling and structural roles. Other aspects asymmetry are observed and useful in many areas of science and engineering and have been studied since the discovery of chirality in tartrate salts [2]. The observation of...
Ali R. Koymen
(University of Texas at Arlington)
9/14/17, 2:15 PM
The ability of positrons to create polarized core holes stems from the fact that the annihilation rate for spin singlet collisions is 1115 times faster than for spin triplet collisions and thus ~558 times faster with an electron of opposite spin. It is therefore possible to use the inherent polarization of positron beams to create polarized core holes with a net polarization approximately...
Fanglei Lin
(Jefferson Lab)
9/15/17, 8:30 AM
Both polarized and unpolarized positron beams with an energy range from a few eV to hundreds of GeV have diverse applications in medicine, material science and nuclear physics. In many cases, they are the unique tools for the study of the physical world. However, the creation of polarized positrons with sufficient intensity is particularly challenging. We propose a dedicated scheme to generate...
David Gaskell
(Jefferson Lab)
9/15/17, 9:45 AM
Measurements of Deep Inelastic Scattering (DIS) from nuclei, aimed at
understanding the nuclear dependence of inelastic structure functions (the
EMC effect), are typically performed at high energies, hence effects due to
the acceleration of electrons in the Coulomb field of a large $Z$ nucleus are
usually ignored. However, there are certain kinematics, in particular at
large...
Michael Paolone
(Temple University)
9/15/17, 10:40 AM
In order to determine the Coulomb sum in nuclei, a precision measurement of inclusive electron scattering cross sections in the quasi-elastic region was performed at Jefferson Lab. Incident electrons with energies ranging from 0.4 GeV to 4 GeV scattered from $^{4}He$,$^{12}C$,$^{56}Fe$ and $^{208}Pb$ nuclei at four scattering angles ($15^{\circ},60^{\circ},90^{\circ},120^{\circ}$) and...
Oleksandr Koshchii
(George Washington University)
9/15/17, 11:15 AM
Elastic electron/positron scattering off a nucleus has proved to be an efficient tool to study the
structure of nucleons. Modern cross section and asymmetry measurements at Jlab require radiative corrections to be taken into account. In particular, two-photon exchange (TPE) effects beyond the standard model-independent contributions have to be considered at the current level of precision....
Riad Suleiman
(Jefferson Lab)
9/15/17, 1:30 PM
Highlights of R&D to improve the performance of polarized electron sources and prolong the lifetime of GaAs Superlattice will be presented.
Erdong Wang
(bnl)
9/15/17, 2:00 PM
Jiquan Guo
(Jefferson Lab)
9/15/17, 2:50 PM
JLEIC polarized positron program calls for a luminosity no more than one order of magnitude lower than the electron program. In this talk, a PEPPo based positron beam formation scheme will be presented. The combination of PEPPo’s low positron yield, the low duty factor injection bunch train required by JLEIC e-/e+ ring, as well as the mismatch of the JLEIC and CEBAF RF frequency, pose major...
Chase Boulware
(Niowave, Inc.)
9/15/17, 3:20 PM
High power electron beams from superconducting radio-frequency (SRF) linacs have numerous commercial applications including x-ray sterilization, active interrogation and radiography, industrial and medical isotope production, and free electron lasers. Many of these applications use an x-ray beam generated when the electrons strike a high-Z target. Such a target can be optimized for production...
Andrei Afanasev
(GWU)
Interference Physics
Oral Contribution
I will present an overview of the higher-order QED effects in lepton scattering on nucleons and nuclei. Availability of the positron beams provides a unique opportunity for direct measurements of C-odd asymmetries, when compared to their counterparts in electron scattering.
The studies of TMD’s in semi-inclusive lepton scattering show that T-odd spin asymmetries are typically a few per...
Petr Stepanov
(1Center for Photochemical Sciences, Bowling Green State University, OH, USA)
Poster
Coincidence Doppler broadening (CDB) spectroscopy is a powerful technique to characterize defects and study electron-positron states in a wide range of materials.
A new method for processing a two-dimensional Doppler spectrum into a single-dimensional one was developed. The new routine performs two-dimensional background fitting of the CDB spectra and its subtraction from raw experimental...
Alessandro Pilloni
(Jefferson Lab)
We discuss the activities of the Joint Physics Analysis Center in the field of hadron spectroscopy, in particular about the identification of the exotic XYZ states
Erdong Wang
(bnl)
Positron Source and Beam Physics
Oral Contribution
In order to construct a future electron-ion collider with high luminosity, a high average current, and high bunch charge, a polarized electron source is under R&D at Brookhaven National Laboratory. We present the R&D plan for achieving the required charge and current in the polarized eRHIC gun. The background is the low-risk Linac-Ring eRHIC plan of using a number of individual guns with RF...
Volodymyr Myronenko
(Deutsches-Elektronen Synchrotron)
Test of the Standard Model
Oral Contribution
The electron-proton collide HERA (Hamburg, Germany) has proven to be a valuable facility for studying proton structure, hard QCD processes, EW phenomena and searches for new physics. For the run period from 2000 till 2007 the HERA collider was upgraded with spin rotators in order to study various physical phenomena using precisely known longitudinal polarisation of the lepton beam. We give an...
J. David Van Horn
(University of Missouri-Kansas City)
Poster
The interactions of energy and particles in asymmetric substances has been of fundamental research interest since the discovery of chirality [1]. A well-studied asymmetric crystalline material is α-quartz [2], which has a helical structure associated with its crystallographic z-axis. Previously, we reported a large difference in ‘free positron’ annihilation lifetime and intensity between...
Ms
Pooneh Saadatkia
(Bowling Green State University)
Poster
Complex oxides with the ABO3 perovskite crystal structure reveal a range of spectacular phenomena such as superconductivity, ferroelectricity, and metal-insulator transitions. SrTiO3, has been the focus of intense research in the world of oxide materials due to its functional, dielectric and ferroelectric properties. Vacancies are usually suggested to be the dominant point defects in...
Rolland Johnson
(Muons, Inc.)
Positron Source and Beam Physics
Oral Contribution
Novel electron gun features are required to enhance the peak and/or average beam brightness by reducing the emittances of electron bunches while allowing the guns to operate at a high repetition rate using laser excitation of the photocathode. The generation of surface acoustical waves (SAW) on piezoelectric substrates is known to produce strong piezoelectric fields that propagate on the...
