Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Hard Two-photon Contributions to Elastic Lepton-proton Scattering Determined by the OLYMPUS Experiment
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.
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
Particle Physics At The Silver Jubilee Of Lomonosov Conferences - Proceedings Of The Eighteenth Lomonosov Conference On Elementary Particle Physics
Author: Studenikin Alexander I
Publisher: World Scientific
ISBN: 9811202346
Category : Science
Languages : en
Pages : 612
Book Description
The volume of these proceedings is devoted to a wide variety of items, both in theory and experiment, of particle physics such as neutrino and astroparticle physics, tests of standard model and beyond, hadron physics, gravitation and cosmology, physics at the present and future accelerators.
Publisher: World Scientific
ISBN: 9811202346
Category : Science
Languages : en
Pages : 612
Book Description
The volume of these proceedings is devoted to a wide variety of items, both in theory and experiment, of particle physics such as neutrino and astroparticle physics, tests of standard model and beyond, hadron physics, gravitation and cosmology, physics at the present and future accelerators.
Two-photon Exchange Contribution to Elastic Electron–proton Scattering: Measurements at the VEPP-3 Storage Ring
Two-photon Exchange and Elastic Electron-proton Scattering
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Two-photon exchange contributions to elastic electron-proton scattering cross sections are evaluated in a simple hadronic model including the finite size of the proton. The corrections are found to be small, but with a strong angular dependence at fixed Q2. This is significant for the Rosenbluth technique for determining the ratio of electric and magnetic form factors of the proton, and partly reconciles the apparent discrepancy with the results of the polarization transfer technique.
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Two-photon exchange contributions to elastic electron-proton scattering cross sections are evaluated in a simple hadronic model including the finite size of the proton. The corrections are found to be small, but with a strong angular dependence at fixed Q2. This is significant for the Rosenbluth technique for determining the ratio of electric and magnetic form factors of the proton, and partly reconciles the apparent discrepancy with the results of the polarization transfer technique.
Particle Physics At The Year Of Centenary Of Bruno Pontecorvo - Proceedings Of The Sixteenth Lomonosov Conference On Elementary Particle Physics
Author: Alexander I Studenikin
Publisher: World Scientific
ISBN: 981466362X
Category : Science
Languages : en
Pages : 450
Book Description
These proceedings are devoted to a wide variety of items, both in theory and experiment, of particle physics such as neutrino and astroparticle physics, tests of the standard model and beyond, and hadron physics. Also covered are gravitation and cosmology, and physics from present and future accelerators.
Publisher: World Scientific
ISBN: 981466362X
Category : Science
Languages : en
Pages : 450
Book Description
These proceedings are devoted to a wide variety of items, both in theory and experiment, of particle physics such as neutrino and astroparticle physics, tests of the standard model and beyond, and hadron physics. Also covered are gravitation and cosmology, and physics from present and future accelerators.