Download or read book Determination of the Proton s Weak Charge Via Parity Violating E p Scattering written by Joshua Russell Hoskins (Ph. D.) and published by . This book was released on 2015 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Determination of the Proton s Weak Charge Via Parity Violating Electron Scattering written by and published by . This book was released on 2015 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment, which completed running in May of 2012 at Jefferson Laboratory, has measured the parity-violating asymmetry in elastic electron-proton scattering at four-momentum transfer Q2=0.025 (GeV/c)2 in order to provide the first direct measurement of the proton's weak charge, Qpw. The Standard Model makes firm predictions for the weak charge; deviations from the predicted value would provide strong evidence of new physics beyond the Standard Model. Using an 89% polarized electron beam at 145 microA scattering from a 34.4 cm long liquid hydrogen target, scattered electrons were detected using an array of eight fused-silica detectors placed symmetric about the beam axis. The parity-violating asymmetry was then measured by reversing the helicity of the incoming electrons and measuring the normalized difference in rate seen in the detectors. The low Q2 enables a theoretically clean measurement; the higher order hadronic corrections are constrained using previous parity-violating electron scattering world data. The experimental method will be discussed, with recent results constituting 4% of our total data and projections of our proposed uncertainties on the full data set.

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 Via Elastic Electron Proton Scattering written by and published by . This book was released on 2015 with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment which ran in Hall C at Jefferson Lab in Newport News, VA, and completed data taking in May 2012, measured the weak charge of the proton QpW via elastic electron-proton scattering. Longitudinally polarized electrons were scattered from an unpolarized liquid hydrogen target. The helicity of the electron beam was flipped at approximately 1 kHz between left and right spin states. The Standard Model predicts a small parity-violating asymmetry of scattering rates between right and left helicity states due to the weak interaction. An initial result using 4% of the data was published in October 2013 [1] with a measured parity-violating asymmetry of -279 ± 35(stat) ± 31 (syst) ppb. This asymmetry, along with other data from parity-violating electron scattering experiments, provided the world's first determination of the weak charge of the proton. The weak charge of the proton was found to be pW = 0.064 ± 0.012, in good agreement with the Standard Model prediction of pW(SM) = 0.0708 ± 0.0003[2].

Download or read book A Measurement of the Weak Charge of the Proton Through Parity Violating Electron Scattering Using the Qweak Apparatus written by and published by . This book was released on 2013 with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt: After a decade of preparations, the Qweak experiment at Jefferson Lab is making the first direct measurement of the weak charge of the proton, Qp̂_W. This quantity is suppressed in the Standard Model making a good candidate for search for new physics beyond the SM at the TeV scale. Operationally, we measure a small (about -0.200 ppm) parity-violating asymmetry in elastic electron-proton scattering in integrating mode while flipping the helicity of the electrons 1000 times per second. Commissioning took place Fall 2010, and we finished taking data in early summer 2012. This dissertation is based on the data taken on an initial two weeks period (Wien0). It will provide an overview of the Qweak apparatus, description of the data acquisition and analysis software systems, and final analysis and results from the Wien0 data set. The result is a 16% measurement of the parity violating electron-proton scattering asymmetry, A = -0.2788 +/- 0.0348 (stat.) +/- 0.0290 (syst.) ppm at Q2̂ = 0.0250 +/- 0.0006 (GeV)2̂. From this a 21% measurement of the weak charge of the proton, Q_wp̂(msr)= +0.0952 +/- 0.0155 (stat.) +/- 0.0131 (syst.) +/- 0.0015 (theory) is extracted. From this a 2% measurement of the weak mixing angle, sin2̂theta_W(msr)= +0.2328 +/- 0.0039 (stat.) +/- 0.0033 (syst.) +/- 0.0004 (theory) and improved constraints on isoscalar/isovector effective coupling constants of the weak neutral hadronic currents are extracted. These results deviate from the Standard Model by one standard deviation. The Wien0 results are a proof of principle of the Qweak data analysis and a highlight of the road ahead for obtaining full results.

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 The Weak Charge of the Proton written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment, which completed running in May of 2012 at Jefferson Laboratory, has measured the parity-violating asymmetry in elastic electron-proton scattering at four-momentum transfer Q^2=0.025 (GeV/c)^2 in order to provide the first direct measurement of the proton?s weak charge, Qpw. The Standard Model makes firm predictions for the weak charge; deviations from the predicted value would provide strong evidence of new physics beyond the Standard Model. Using an 89% polarized electron beam at 145 microA scattering from a 34.4 cm long liquid hydrogen target, scattered electrons were detected using an array of eight fused-silica detectors placed symmetric about the beam axis. The parity-violating asymmetry was then measured by reversing the helicity of the incoming electrons and measuring the normalized difference in rate seen in the detectors. The low Q^2 enables a theoretically clean measurement; the higher order hadronic corrections are constrained using previous parity-violating electron scattering world data. The experimental method will be discussed, with recent results constituting 4% of our total data and projections of our proposed uncertainties on the full data set.

Download or read book First Determination of the Weak Charge of the Proton written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment has measured the parity-violating asymmetry in polarized e-p elastic scattering at Q2 = 0.025(GeV/c)2, employing 145 microamps of 89% longitudinally polarized electrons on a 34.4cm long liquid hydrogen target at Jefferson Lab. The results of the experiment's commissioning run are reported here, constituting approximately 4% of the data collected in the experiment. From these initial results the measured asymmetry is Aep = -279 +- 35 (statistics) +- 31 (systematics) ppb, which is the smallest and most precise asymmetry ever measured in polarized e-p scattering. The small Q2 of this experiment has made possible the first determination of the weak charge of the proton, QpW, by incorporating earlier parity-violating electron scattering (PVES) data at higher Q2 to constrain hadronic corrections. The value of QpW obtained in this way is QnW(PVES) = 0.064 +- 0.012, in good agreement with the Standard Model prediction of QpW(SM) = 0.0710 +- 0.0007. When this result is further combined with the Cs atomic parity violation (APV) measurement, significant constraints on the weak charges of the up and down quarks can also be extracted. That PVES+APV analysis reveals the neutron's weak charge to be QnW(PVES+APV) = -0.975 +- 0.010.

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 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 289 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, sin2(theta_W). The final Qweak measurement will provide the most precise measurement of the weak mixing angle below the Z0 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(theta_W) = 0.23429 ± 0.00211.

Download or read book The Weak Charge of the Proton written by Scott James MacEwan and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment will provide the most precise determination of the proton's weak charge Q^p_W by measuring the parity-violating asymmetry in elastic electron-proton scattering at low momentum transfer Q^2 = 0.0250 (GeV/c)^2. Qpw is related to the weak mixing angle sin^2\theta_W, a fundamental parameter of the standard model. A final measurement of the weak charge at the proposed 4% relative uncertainty is sensitive to certain types of new parity-violating physics beyond the standard model at the TeV mass-scale. Data were taken over a two year period beginning in 2010, using a custom apparatus installed in Hall-C at the Thomas Jefferson National Accelerator Facility in Newport News, Virginia. A 180 microamp beam of longitudinally polarized electrons was accelerated to 1.165 GeV and then scattered from unpolarized protons in a liquid hydrogen target. The scattered electrons were then collimated and steered using a magnetic spectrometer onto a set of azimuthally symmetric quartz bar Cherenkov detectors. The performance of this main detector subsystem will be described in detail in this dissertation. A blinded analysis of Run-II, roughly 2/3 of the entire Qweak data set, resulted in an elastic ep asymmetry of -235.6 +/- 8.7 (Stat) +/- 9.3 (Syst.) +/- 39.3 (Blind) ppb. Using this value, the proton's weak charge was calculated to be QpW = 0.0714 +/- 0.0093. This constitutes a 17% relative measurement, that will reduce to

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 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 First Determination of the Weak Charge of the Proton written by Fang Guo (Ph. D.) and published by . This book was released on 2016 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment measures the parity violating asymmetry in elastic e[upper script right arrow]p scattering at Q2 = 0.02455 (GeV/c)2 with a 180 [mu]A and 88.7% longitudinally polarized electron beam of 1.165 GeV and a 34.4 cm liquid hydrogen target in experimental Hall C at Jefferson Lab. As the Q2 at the Qweak experiment is much lower than all previous experiments, the Qweak measurement can be considered as the first direct determination of the weak charge of the proton, Qp/w, which is related to the weak mixing angle, sin2 [theta]w, an important Standard Model parameter. The preliminary and blinded asymmetry of the Run 2 data set, which constitutes approximately 60% of all the data collected in the experiment, is Aep/PV = -232.7 +/- 8.7 (stat) +/- 6.4 (syst) ppb. The value of Qp/w obtained by fitting this blinded asymmetry and earlier parity violating electron scattering (PVES) data at higher Q2 is Qp/w (PVES) = 0.0705 +/- 0.0051. When combining this result with the 133Cs atomic parity violation (APV) measurement, further constraints can be placed on the neutral weak quark coupling constants C1u and C1d. The combined PVES and APV analysis yields the blinded neutron's weak charge to be Qn/w (PVES+APV) = -0.9798 +/- 0.0065. The Qweak experiment also measures the parity violating asymmetry in nonresonance inelastic e[upper script right arrow]p scattering at Q2 ~/= 0.09 (GeV/c)2 with 3.35 GeV electron beams to provide inputs for the [gamma]Z box calculation. The preliminary measured inelastic asymmetry is Aep/inelastic-PV = 2.91 +/- 0.35 ppm.

Download or read book Towards a Precision Measurement of Parity Violating E p Elastic Scattering at Low Momentum Transfer written by and published by . This book was released on 2012 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of the Q-weak experiment is to make a measurement of the proton's weak charge QWp = 1 - 4 sin2([theta]W

Download or read book Parity Violation In Electron Scattering Proceedings Of The Workshop written by E J Beise and published by World Scientific. This book was released on 1990-08-23 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings cover the recent progress and future directions of parity violation in electron scattering. Both experimental and theoretical issues are discussed, such as those of hadronic structure, radiative corrections, and tests of the standard model. There are three sessions, the first of which serves as a general overview of theory and experiment. The second session deals with the technical aspects of making a measurement of the parity violating asymmetry in electron scattering, including not only detector design but polarized electron beams and beam polarimeters.. The remaining session covers the corrections to lowest order parity violating cross sections.

Download or read book The Qweak Experiment written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The $Q_{weak}$ Collaboration has completed a challenging measurement of the parity-violating asymmetry in elastic electron-proton ($\vec{e}$p) scattering at the Thomas Jefferson National Accelerator Facility (Jefferson Lab). The initial result reported here is extracted from the commissioning part of the experiment, constituting about 4% of the full data set. The parity-violating asymmetry at a low momentum transfer $Q^2$=0.025 GeV$^2$ is $A_{ep}$ = -279 $\pm$ 35 (stat) $\pm$ 31 (syst) ppb, which is the smallest and most precise asymmetry ever measured in $\vec{e}$p scattering. This result allowed the first determination of the weak charge of the proton $Q_W^p$ from a global fit of parity-violating elastic scattering (PVES) results from nuclear targets, where earlier data at higher $Q^2$ constrain uncertainties of hadronic structure. The value extracted from the global fit is $Q_W^p$ (PVES) = 0.064 $\pm$ 0.012, in agreement with the standard model prediction $Q_W^p$ (SM) = 0.0710 $\pm$ 0.0007. The neutral weak charges of up and down quarks are extracted from a combined fit of the PVES results with a previous atomic parity violation (APV) measurement on $^$Cs. The analysis of the full $Q_{weak}$ data is ongoing and expected to yield a value for the asymmetry within 10 ppb of precision. Because of the suppression of $Q_W^p$, such a high precision measurement will place significant constraints to models of physics beyond the standard model.