Download or read book A Measurement of the Parity Violating Asymmetry in Aluminum and Its Contribution to a Measurement of the Proton s Weak Charge written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Q_weak experiment, which ran at the Thomas Jefferson National Accelerator Facility, made a precision measurement of the proton's weak charge, Q^p_W. The weak charge is extracted via a measurement of the parity-violating asymmetry in elastic electron-proton scattering from hydrogen at low momentum transfer (Q^2=0.025 GeV^2). This result is directly related to the electroweak mixing angle, sin^2(Theta_W), a fundamental parameter in the Standard Model of particle physics. This provides a precision test sensitive to new, as yet unknown, fundamental physics. This dissertation focuses on two central corrections to the Q_weak measurement: the target window contribution and sub-percent determination of the electron beam polarization. The aluminum target windows contribute approximately 30% of the measured asymmetry. Removal of this background requires precise measurements of both the elastic electron-aluminum scattering rate and its parity-violating asymmetry. The results reported here are the most precise measurement of the Q_weak target dilution and asymmetry to date. The parity-violating asymmetry for the aluminum alloy was found to be 1.6174 +/- 0.0704 (stat.) +/- 0.0113 (sys.) parts-per-million. The first sub-percent precision polarization measurements made from the Hall C Moller polarimeter are also reported, with systematic uncertainties of 0.84%.
Download or read book A Measurement of the Parity violating Asymmetry in Aluminum and Its Contribution to a Measurement of the Proton s Weak Charge written by Joshua Allen Magee (Ph.D.) and published by . This book was released on 2016 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment, which ran at the Thomas Jefferson National Accelerator Facility, made a precision measurement of the protons weak charge, Q_p^W . The weak charge is extracted via a measurement of the parity-violating asymmetry in elastic electron-proton scattering from hydrogen at low momentum transfer (Q^2=0.025 GeV^2). This result is directly related to the electroweak mixing angle, sin2 (theta_W), a fundamental parameter in the Standard Model of particle physics. This provides a precision test sensitive to new, as yet unknown, fundamental physics. This dissertation focuses on two central corrections to the Qweak measurement: the target window contribution and sub-percent determination of the electron beam polarization. The aluminum target windows contribute approximately 30% of the measured asymmetry. Removal of this background requires precise measurements of both the elastic electron-aluminum scattering rate and its parity-violating asymmetry. The results reported here are the most precise measurement of the Qweak target dilution and asymmetry to date. The parity-violating asymmetry for the aluminum alloy was found to be 1.6174 0.0704 (stat.) 0.0113 (sys.) parts-per-million. The first sub-percent precision polarization measurements made from the Hall C Mller polarimeter are also reported, with systematic uncertainties of 0.84%.
Download or read book First Measurements of the Parity violating and Beam normal Single spin Asymmetries in Elastic Electron aluminum Scattering written by Kurtis David Bartlett and published by . This book was released on 2018 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak collaboration has made the first measurements of the elastic parity-violating and beam-normal single-spin asymmetries from the $^{27}$Al nucleus. Both are the result of ancillary measurements conducted during the Qweak experiment at Jefferson Lab. The goal of the experimental was to determine the proton's weak charge, $Q_{W}^{p}$, via a measurement of the elastic parity-violating electron-proton scattering asymmetry. During the experiment, ancillary measurements were made with different beam configurations on a separate aluminum alloy target, in an effort to directly measure the aluminum background coming from the experiment's liquid hydrogen target cell. This dissertation discusses three primary results: the parity-violating $^{27}$Al asymmetry analysis used to correct for the aluminum target background in the final Qweak analysis, its extended analysis leading to the extraction of the pure elastic parity-violating {\aluminum} asymmetry, and the determination of the elastic beam-normal single-spin $^{27}$Al asymmetry. The parity-violating result was also used to make a semi model-independent determination of $^{27}$Al neutron distribution radius, an important test for models used to describe neutron-rich matter. The beam-normal single-spin asymmetry stands to possibly shed light on an observed disagreement between theory and a previous measurement performed on $^{208}$Pb, as $^{27}$Al is the next highest atomic mass nucleus to have this observable measured. The elastic parity-violating $^{27}$Al asymmetry was found to be $1.927 \pm 0.173$ ppm at $\langle Q^{2} \rangle = 0.0236 \pm 0.0001$ GeV$^{2}$. This measured parity-violating asymmetry implies a $^{27}$Al neutron distribution radius of $3.024 \pm 0.104$ fm. Calculating the difference between this radius and the $^{27}$Al proton distribution radius yields the neutron skin, which was found to be $0.092 \pm 0.104$ fm. This skin value is consistent with zero, within its uncertainty, and it confirms the naive expectation for a light nucleus like $^{27}$Al. The beam-normal single-spin $^{27}$Al asymmetry was found to be $-16.322 \pm 2.679$ ppm at $\langle Q \rangle = 0.154$ GeV. This value agrees with the previous observed trend of beam-normal single-spin asymmetries measured from light nuclei, which motivates the need for future measurements of higher atomic mass nuclei.
Download or read book The First Determination of the Proton s Weak Charge Through Parity Violating Asymmetry Measurements in Elastic e p and e Al Scattering written by Katherine E. Myers and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Determination of the Weak Charge of the Proton Through Parity Violating Asymmetry Measurements in the Elastic E p Scattering written by Adesh Subedi and published by . This book was released on 2014 with total page 269 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment has taken data to make a 2.5 percent measurement of parity violating elastic e + p asymmetry in the four momentum transfer region of 0.0250 (GeV/c)2. This asymmetry is proportional to the weak charge of the proton, which is related to the weak mixing angle, sin2 (thetaW). The final Qweak measurement will provide the most precise measurement of the weak mixing angle below the Z _ pole to test the Standard Model prediction. A description of the experimental apparatus is provided in this dissertation.The experiment was carried out using a longitudinally polarized electron beam of up to 180 microampere on a 34.5 cm long unpolarized liquid hydrogen target. The Qweak target is not only the world's highest cryogenic target ever built for a parity experiment but also is the least noisy target. This dissertation provides a detailed description of this target and presents a thorough analysis of the target performance. Statistical analysis of Run 1 data, collected between Feb - May 2011, is done to extract a blinded parity violating\ asymmetry of size 299.7 +/- 13.4 (stat.) +/- 17.2 (syst.) +/- 68 (blinding) parts-per-billion. This resulted in a preliminary proton's weak charge of value 0.0865 +/- 0.0085, a 9% measurement. Based on this blinded asymmetry, the weak mixing angle was determined to be sin2 (thetaW) = 0.23429 +/- 0.00211.
Download or read book Determination of the Weak Charge of the Proton Through Parity Violating Asymmetry Measurements in the Elastic E p Scattering written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment has taken data to make a 2.5% measurement of parity violating elastic e+p asymmetry in the four momentum transfer region of 0.0250 (GeV/c)^2. This asymmetry is proportional to the weak charge of the proton, which is related to the weak mixing angle, sin^2(theta_W). The final Qweak measurement will provide the most precise measurement of the weak mixing angle below the Z^0 pole to test the Standard Model prediction. A description of the experimental apparatus is provided in this dissertation. The experiment was carried out using a longitudinally polarized electron beam of up to 180 microampere on a 34.5 cm long unpolarized liquid hydrogen target. The Qweak target is not only the world's highest cryogenic target ever built for a parity experiment but also is the least noisy target. This dissertation provides a detailed description of this target and presents a thorough analysis of the target performance. Statistical analysis of Run 1 data, collected between Feb - May 2011, is done to extract a blinded parity violating asymmetry of size -299.7 " 13.4 (stat.) " 17.2 (syst.) " 68 (blinding) parts-per-billion. This resulted in a preliminary proton's weak charge of value 0.0865 " 0.0085, a 9% measurement. Based on this blinded asymmetry, the weak mixing angle was determined to be sin^2(theta_W) = 0.23429 " 0.00211.
Download or read book A Measurement of the Weak Charge of the Proton Through Parity Violating Electron Scattering Using the Qweak Apparatus written by Rakitha S. Beminiwattha and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measuring the Weak Charge of the Proton and the Hadronic Parity Violation of the N 2 Delta Transition written by and published by . This book was released on 2012 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: Qweak will determine the weak charge of the proton, Qp{sub W}, via an asymmetry measurement of parity-violating elastic electron-proton scattering at low four momentum transfer to a precision of 4%. QpW has a firm Standard Model prediction and is related to the weak mixing angle, sin2 [Phi]W, a well-defined Standard Model parameter. Qweak will probe a subset of new physics to the TeV mass scale and test the Standard Model. The details of how this measurement was performed and the analysis of the 25% elastic dataset will be presented in this thesis. Also, an analysis of an auxiliary measurement of the parity-violating asymmetry in the N → [Delta] transition is presented. It is used as a systematic inelastic background correction in the elastic analysis and to extract information about the hadronic parity violation through the low energy constant, d[Delta]. The elastic asymmetry at Q2 = 0.0252 ± 0.0007 GeV2 was measured to be Aep = -265 ± 40 ± 22 ± 68 ppb (stat., sys., and blinding). Extrapolated to Q2 = 0, the value of the proton's weak charge was measured to be QpW = 0.077 ± 0.019 (stat. and sys.) ± 0.026 (blinding). This is within 1 [sigma] of the Standard Model prediction of QpW = 0.0705 ± 0.0008. The N → [Delta] inelastic asymmetry at Q2 = 0.02078 ± 0.0005 GeV2 and W = 1205 MeV was measured to be Ainel = -3.03 ± 0.65 ± 0.73 ± 0.07 ppm (stat., sys., and blinding). This result constrains the low energy constant to be d[Delta] = 5.8 ± 22g[pi], and, if the result of the G0 experiment is included, d[Delta] = 5.8 ± 17g[pi]. This result rules out suggested large values of d[Delta] motivated by radiative hyperon decays. The elastic measurement is the first direct measurement of the weak charge of the proton while the inelastic measurement is only the second measurement of the neutral current excitation of the [Delta]resonance. It is currently the best constraint for the low energy constant, d[Delta].
Download or read book Testing the Standard Model written by Christophe Match and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamental interactions between electrons and protons, coupling between photons and Z bosons, and the underlying substructure of the proton, can all be probed through scattering experiments designed to measure the parity-violating asymmetry due to a mixing of electromagnetic and weak forces. Our research involves testing the limits of the standard model in search of new physics, by comparing high precision theoretical predictions of this asymmetry, along with the proton's weak charge and the weak mixing angle, to recent experimental measurements. We were ultimately able to achieve results consistent with experimental observations, by accounting for radiative corrections beyond single boson exchange. Our calculations include up to first-order Feynman diagrams containing 1 loop integrals, soft-photon bremsstrahlung, and we account for additional box diagram corrections. We also consider the addition of a new weakly-interacting dark Z boson (Z') to the Standard Model, and investigate how it affects the calculated asymmetry.
Download or read book Measurement of the Proton s Weak Charge at the Qweak Experiment written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment at Jefferson Laboratory measures the parity violating asymmetry of polarized electrons scattering from a proton target at very low momentum transfer. In the Standard Model, this asymmetry reveals the proton's coupling to the neutral vector current, the weak charge. This value, measured directly for the first time, will provide a precision test of the Standard Model and will constrain the possibility of relevant physics beyond the Standard Model. The planned precision will probe certain classes of new physics at the 2̃ TeV scale. In order to challenge the precise predictions, the asymmetry will be measured with a 2.5 percent accuracy. To achieve such a precision, great care has to be taken on many aspects of the experiment. The very low momentum transfer reduces the hadronic effects to the asymmetry and must be determined to half of a percent accuracy. Beam stability is controlled and monitored constantly and background events are carefully studied.
Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2352 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Parity Violation in Elastic Electron Scattering written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of Experiment E04-115 (the G0 backward angle measurement) at Jefferson Lab is to investigate the contributions of strange quarks to the fundamental properties of the nucleon. The experiment measures parity-violating asymmetries in elastic electron scattering off hydrogen and quasielastic electron scattering off deuterium at backward angles at Q2 = 0.631 (GeV/c)2 and Q2 = 0.232 (GeV/c)2. The backward angle measurement represents the second phase of the G0 experiment. The first phase, Experiment E00-006 (the G0 forward angle experiment), measured parity-violating asymmetries in elastic electron scattering off hydrogen at forward angles over a Q2 range of 0.1-1.0 (GeV/c)2. The experiments used a polarized electron beam and unpolarized hydrogen and deuterium liquid targets. From these measurements, along with the electromagnetic form factors, one can extract the contribution of the strange quark to the proton's charge and magnetization distributions. This thesis represents a fi.
Download or read book Parity violating Electroweak Asymmetry in rvec E P Scattering written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from protons. Significant contributions to this asymmetry could arise from the contributions of strange form factors in the nucleon. The measured asymmetry is A = -15.05 ± 0.98(stat) ± 0.56(syst) ppm at the kinematic point [theta]{sub lab} = 12.3{sup o} and Q2 = 0.477 (GeV/c)2. Based on these data as well as data on electromagnetic form factors, we extract the linear combination of strange form factors G{sub E}{sup s} + 0.392G{sub M}{sup s} = 0.014 ± 0.020 ± 0.010 where the first error arises from this experiment and the second arises from the electromagnetic form factor data. This paper provides a full description of the special experimental techniques employed for precisely measuring the small asymmetry, including the first use of a strained GaAs crystal and a laser-Compton polarimeter in a fixed target parity-violation experiment.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1981 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Parity Violation In Atoms And In Polarized Electron Scattering written by Marie-anne Bouchiat and published by World Scientific. This book was released on 1999-07-13 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last few years there has been considerable progress in improving the accuracy of parity violation experiments in electron scattering at high energy and in atomic physics. Recent results are a challenge to the standard electroweak theory and our understanding of hadron structure. This book is an extensive review of the advances in this field. The theoretical framework is presented at a pedagogical level, experiments and future projects are reviewed, and the results and their interpretation are discussed in depth.
Download or read book New Measurement of Parity Violation in Elastic Electron Proton Scattering and Implications for Strange Form Factors written by and published by . This book was released on 2001 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The result is A = -15.05 +- 0.98(stat) ± 0.56(syst) ppm at the kinematic point theta{sub lab} = 12.3 degrees and Q2 = 0.477 (GeV/c)2. The measurement implies that the value for the strange form factor (G{sub E}{sup s} + 0.392 G{sub M}{sup s})/(G{sub M}{sup p} [mu]{sub p}) = 0.069 +- 0.056 +- 0.039, where the first error is experimental and the second arises from the uncertainties in electromagnetic form factors. This measurement is the first fixed-target parity violation experiment that used either a ''strained'' GaAs photocathode to produce highly polarized electrons or a Compton polarimeter to continuously monitor the electron beam polarization.
Download or read book Measurement of the Parity violating Asymmetry in Inclusive Electroproduction of pi Near the Delta0 Resonance written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The parity-violating (PV) asymmetry of inclusive [pi]- production in electron scattering from a liquid deuterium target was measured at backward angles. The measurement was conducted as a part of the G0 experiment, at a beam energy of 360 MeV. The physics process dominating pion production for these kinematics is quasi-free photoproduction off the neutron via the [Delta]0 resonance. In the context of heavy-baryon chiral perturbation theory (HB[chi]PT), this asymmetry is related to a low energy constant d[Delta]- that characterizes the parity-violating [gamma]N[Delta] coupling. Zhu et al. calculated d[Delta]- in a model benchmarked by the large asymmetries seen in hyperon weak radiative decays, and predicted potentially large asymmetries for this process, ranging from A[gamma]- = -5.2 to +5.2 ppm. The measurement performed in this work leads to A[gamma]- = -0.36 " 1.06 " 0.37 " 0.03 ppm (where sources of statistical, systematic and theoretical uncertainties are included), which would disfavor enchancements considered by Zhu et al. proportional to Vud/Vus. The measurement is part of a program of inelastic scattering measurements that were conducted by the G0 experiment, seeking to determine the N-[Delta] axial transition form-factors using PV electron scattering.
