Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Measurement of the Charge-averaged Elastic Lepton-proton Scattering Cross Section by the OLYMPUS Experiment
A Precision Measurement of the E+p/e−p Elastic Scattering Cross Section Ratio at the OLYMPUS Experiment
Author: Brian Scott Henderson
Publisher:
ISBN:
Category :
Languages : en
Pages : 288
Book Description
Measurements of the ratio of the proton elastic form factors ([mu]pGe/Gm) using Rosenbluth separation and those using polarization-based techniques show a strong discrepancy, which has persisted both in modern experimental results and in re-analyses of previous data. The most widely accepted hypothesis to explain this discrepancy is the treatment of the contributions from hard two-photon exchange (TPE) to elastic electron-proton scattering in the radiative corrections applied to the Rosenbluth separation measurements. Calculations of the hard TPE contribution are highly model dependent, but the effect may be measured experimentally with a precise determination of the ratio of the positron-proton and electron-proton elastic scattering cross sections. The OLYMPUS experiment collected approximately 4 fb-1 of e+p and e-p scattering data at the DORIS storage ring at DESY in 2012, with the goal of measuring the elastic [sigma]e+p/[sigma]e-p ratio over the kinematic range (0.4
Publisher:
ISBN:
Category :
Languages : en
Pages : 288
Book Description
Measurements of the ratio of the proton elastic form factors ([mu]pGe/Gm) using Rosenbluth separation and those using polarization-based techniques show a strong discrepancy, which has persisted both in modern experimental results and in re-analyses of previous data. The most widely accepted hypothesis to explain this discrepancy is the treatment of the contributions from hard two-photon exchange (TPE) to elastic electron-proton scattering in the radiative corrections applied to the Rosenbluth separation measurements. Calculations of the hard TPE contribution are highly model dependent, but the effect may be measured experimentally with a precise determination of the ratio of the positron-proton and electron-proton elastic scattering cross sections. The OLYMPUS experiment collected approximately 4 fb-1 of e+p and e-p scattering data at the DORIS storage ring at DESY in 2012, with the goal of measuring the elastic [sigma]e+p/[sigma]e-p ratio over the kinematic range (0.4
Measuring the Lepton Sign Asymmetry in Elastic Electron-proton Scattering with OLYMPUS
Author: Axel William Schmidt
Publisher:
ISBN:
Category :
Languages : en
Pages : 273
Book Description
OLYMPUS is a particle physics experiment that collected data in 2012 at DESY, in Hamburg, Germany, on the asymmetry between positron-proton and electron-proton elastic scattering cross sections. A non-zero asymmetry is evidence of hard two-photon exchange, which has been hypothesized to cause the discrepancy in measurements of the proton's electromagnetic form factors. Alternating electron and positron beams, accelerated to 2 GeV, were directed through a windowless, gaseous, hydrogen target, and the scattered lepton and recoiling proton were detected in coincidence using a large acceptance magnetic spectrometer. Determining the relative integrated luminosity between the electron and positron data sets was critical, and a new technique, involving multi-interaction events, was developed to achieve the desired sub-percent accuracy. A detailed Monte Carlo simulation was built in order to reproduce the convolution of systematic effects at every stage of the experiment. The first stage in the simulation was new radiative event generator, which permitted the full simulation of the non-trivial radiative corrections to the measurement. The analysis of the data and simulation showed that the lepton sign asymmetry rises by several percent between a momentum transfer of 0.5 GeV2 /c2 and 2.25 GeV2 /c2 . This rise as a function of increasing momentum transfer confirms that two photon exchange at least partially contributes to the proton form factor discrepancy.
Publisher:
ISBN:
Category :
Languages : en
Pages : 273
Book Description
OLYMPUS is a particle physics experiment that collected data in 2012 at DESY, in Hamburg, Germany, on the asymmetry between positron-proton and electron-proton elastic scattering cross sections. A non-zero asymmetry is evidence of hard two-photon exchange, which has been hypothesized to cause the discrepancy in measurements of the proton's electromagnetic form factors. Alternating electron and positron beams, accelerated to 2 GeV, were directed through a windowless, gaseous, hydrogen target, and the scattered lepton and recoiling proton were detected in coincidence using a large acceptance magnetic spectrometer. Determining the relative integrated luminosity between the electron and positron data sets was critical, and a new technique, involving multi-interaction events, was developed to achieve the desired sub-percent accuracy. A detailed Monte Carlo simulation was built in order to reproduce the convolution of systematic effects at every stage of the experiment. The first stage in the simulation was new radiative event generator, which permitted the full simulation of the non-trivial radiative corrections to the measurement. The analysis of the data and simulation showed that the lepton sign asymmetry rises by several percent between a momentum transfer of 0.5 GeV2 /c2 and 2.25 GeV2 /c2 . This rise as a function of increasing momentum transfer confirms that two photon exchange at least partially contributes to the proton form factor discrepancy.
A Measurement of the Two-photon Exchange Effect in Elastic Electron-proton Scattering with OLYMPUS
Author: Rebecca Lynn Russell
Publisher:
ISBN:
Category :
Languages : en
Pages : 190
Book Description
Elastic electron-proton scattering has long been the tool of choice for the study of the proton form factors, GE(Q 2 ) and GM(Q2 ), which describe the electric and magnetic distributions of the proton as a function of momentum transfer. Recent experiments, measuring the form factors from polarization observables in polarized elastic electron-proton scattering, have found values of the ratio GE(Q2 )/GM(Q2) at high Q2 that contradict the results from unpolarized measurements. A proposed explanation for this discrepancy is the unaccounted two-photon exchange radiative correction, which could affect the unpolarized measurements. As this effect is currently not possible to calculate in a model-independent way, the OLYMPUS experiment was designed to make a direct measurement of it by measuring the elastic positron-proton to electron-proton scattering cross section ratio. The experiment was run in 2012 at DESY using the BLAST spectrometer and the DORIS positron and electron beams at 2 GeV incident on a gaseous hydrogen target. To analyze the data, a careful reconstruction of the scattering events, detailed simulation of the experimental setup, and full radiative corrections to the measured cross sections were performed. Preliminary results for the experiment show a statistically significant two-photon exchange effect, increasing over the measurement range of 0.6 GeV2
Publisher:
ISBN:
Category :
Languages : en
Pages : 190
Book Description
Elastic electron-proton scattering has long been the tool of choice for the study of the proton form factors, GE(Q 2 ) and GM(Q2 ), which describe the electric and magnetic distributions of the proton as a function of momentum transfer. Recent experiments, measuring the form factors from polarization observables in polarized elastic electron-proton scattering, have found values of the ratio GE(Q2 )/GM(Q2) at high Q2 that contradict the results from unpolarized measurements. A proposed explanation for this discrepancy is the unaccounted two-photon exchange radiative correction, which could affect the unpolarized measurements. As this effect is currently not possible to calculate in a model-independent way, the OLYMPUS experiment was designed to make a direct measurement of it by measuring the elastic positron-proton to electron-proton scattering cross section ratio. The experiment was run in 2012 at DESY using the BLAST spectrometer and the DORIS positron and electron beams at 2 GeV incident on a gaseous hydrogen target. To analyze the data, a careful reconstruction of the scattering events, detailed simulation of the experimental setup, and full radiative corrections to the measured cross sections were performed. Preliminary results for the experiment show a statistically significant two-photon exchange effect, increasing over the measurement range of 0.6 GeV2
Measurement of the Two-photon Exchange Contribution to Lepton-proton Scattering with OLYMPUS
Author: Lauren Ice
Publisher:
ISBN:
Category : Elastic scattering
Languages : en
Pages : 147
Book Description
The OLYMPUS experiment measured the two-photon exchange contribution to elastic electron-proton scattering, over a range of four-momentum transfer from \(0.6
Publisher:
ISBN:
Category : Elastic scattering
Languages : en
Pages : 147
Book Description
The OLYMPUS experiment measured the two-photon exchange contribution to elastic electron-proton scattering, over a range of four-momentum transfer from \(0.6
The Contribution of Two-photon Exchange in Elastic Lepton-proton Scattering
Author: Colton David Graham O'Connor
Publisher:
ISBN:
Category :
Languages : en
Pages : 307
Book Description
Measurements of the electric-to-magnetic ratio of the proton's elastic form factors, GE/GM, have recently been shown to diverge at high momentum transfer, Q2, based on which of two experimental methods is employed. Reanalysis of all results might be able to bring them into agreement if some previously neglected correction were introduced whose magnitude increases with Q2. In the high-energy community, two-photon exchange has become the favored candidate for such a correction. But theoretical models disagree on the size and form of a two-photon exchange correction term entering into elastic lepton-proton scattering and existent empirical data is not sufficiently precise to settle the matter. OLYMPUS is one of several new experiments designed to evaluate R2[gamma], the ratio of the elastic cross sections for positron-proton and electron-proton scattering, whose difference from unity provides a direct measure of the amplitude of the two-photon exchange matrix elements. In this dissertation, OLYMPUS is considered from its motivation, construction, and operation to its analysis, along with the associated Monte Carlo simulation. Special attention is given to the symmetric Møller/Bhabha detector system, which is not described in full elsewhere. The results achieved by the OLYMPUS collaboration, reported herein, achieve unprecedented precision over a wide kinematic range and make a significant contribution to the understanding of two-photon exchange.
Publisher:
ISBN:
Category :
Languages : en
Pages : 307
Book Description
Measurements of the electric-to-magnetic ratio of the proton's elastic form factors, GE/GM, have recently been shown to diverge at high momentum transfer, Q2, based on which of two experimental methods is employed. Reanalysis of all results might be able to bring them into agreement if some previously neglected correction were introduced whose magnitude increases with Q2. In the high-energy community, two-photon exchange has become the favored candidate for such a correction. But theoretical models disagree on the size and form of a two-photon exchange correction term entering into elastic lepton-proton scattering and existent empirical data is not sufficiently precise to settle the matter. OLYMPUS is one of several new experiments designed to evaluate R2[gamma], the ratio of the elastic cross sections for positron-proton and electron-proton scattering, whose difference from unity provides a direct measure of the amplitude of the two-photon exchange matrix elements. In this dissertation, OLYMPUS is considered from its motivation, construction, and operation to its analysis, along with the associated Monte Carlo simulation. Special attention is given to the symmetric Møller/Bhabha detector system, which is not described in full elsewhere. The results achieved by the OLYMPUS collaboration, reported herein, achieve unprecedented precision over a wide kinematic range and make a significant contribution to the understanding of two-photon exchange.
Hard Two-photon Contributions to Elastic Lepton-proton Scattering Determined by the OLYMPUS Experiment
Precision Measurements of Electron-proton Elastic Scattering Cross Sections at Large Q2
Author: Longwu Ou
Publisher:
ISBN:
Category :
Languages : en
Pages : 192
Book Description
The electromagnetic form factors are fundamental quantities characterizing the internal structure of the nucleon. Their measurements have provided significant insight into the spatial distribution and interaction of quarks inside the proton. The knowledge of high Q2 form factors proves essential in understanding the properties of quantum chromodynamics in the transition region from non-perturbative to perturbative behavior. It also provides important links to generalized parton distributions, which describe the three-dimensional structure of hadrons at the parton level. In view of the significant theoretical research activities in this field, high quality experimental data are crucial for providing stringent tests and benchmarks to guide and test different models. The form factors can be accessed in experiments by measuring elastic scattering of electrons off a hydrogen target. Experiment E12-07-108, which took place at the Thomas Jefferson National Accelerator Facility, conducted precise measurements of the unpolarized e-p elastic scattering cross section over a Q2 range of 0.6-16.5 GeV2 . This thesis presents the results for 7 kinematic settings with total uncertainties that are 1.5 times smaller than those of the existing data at large Q2 . The proton magnetic form factors were extracted using a parameterization of the form factor ratio obtained from recent polarized e-p scattering experiments. Comparisons to existing global and phenomenological fits are presented.
Publisher:
ISBN:
Category :
Languages : en
Pages : 192
Book Description
The electromagnetic form factors are fundamental quantities characterizing the internal structure of the nucleon. Their measurements have provided significant insight into the spatial distribution and interaction of quarks inside the proton. The knowledge of high Q2 form factors proves essential in understanding the properties of quantum chromodynamics in the transition region from non-perturbative to perturbative behavior. It also provides important links to generalized parton distributions, which describe the three-dimensional structure of hadrons at the parton level. In view of the significant theoretical research activities in this field, high quality experimental data are crucial for providing stringent tests and benchmarks to guide and test different models. The form factors can be accessed in experiments by measuring elastic scattering of electrons off a hydrogen target. Experiment E12-07-108, which took place at the Thomas Jefferson National Accelerator Facility, conducted precise measurements of the unpolarized e-p elastic scattering cross section over a Q2 range of 0.6-16.5 GeV2 . This thesis presents the results for 7 kinematic settings with total uncertainties that are 1.5 times smaller than those of the existing data at large Q2 . The proton magnetic form factors were extracted using a parameterization of the form factor ratio obtained from recent polarized e-p scattering experiments. Comparisons to existing global and phenomenological fits are presented.
Description of a Counter Experiment to Measure the Elastic Proton-proton Scattering Cross Section at Bevatron Energies
Author: Charles Wesley Causey
Publisher:
ISBN:
Category : Nuclear physics
Languages : en
Pages : 0
Book Description
Publisher:
ISBN:
Category : Nuclear physics
Languages : en
Pages : 0
Book Description
Measurement of Pion Proton Deep Elastic Scattering at 13.7 and 19.4 Gev Center of Mass Energies
Author: Paul Edmond Karchin
Publisher:
ISBN:
Category : Pions
Languages : en
Pages : 284
Book Description
Publisher:
ISBN:
Category : Pions
Languages : en
Pages : 284
Book Description