Download or read book The First Direct Measurement of the Weak Charge of the Proton written by John Poague Leckey and published by . This book was released on 2012 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Q Weak written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment, which took data at Jefferson Lab in the period 2010 - 2012, will precisely determine the weak charge of the proton by measuring the parity-violating asymmetry in elastic e-p scattering at 1.1 GeV using a longitudinally polarized electron beam and a liquid hydrogen target at a low momentum transfer of Q2 = 0.025 (GeV/c)2. The weak charge of the proton is predicted by the Standard Model and any significant deviation would indicate physics beyond the Standard Model. The technical challenges and experimental apparatus for measuring the weak charge of the proton will be discussed, as well as the method of extracting the weak charge of the proton. Finally, the results from a small subset of the data, that has been published, will also be presented. Furthermore an update will be given of the current status of the data analysis.
Download or read book Qweak written by and published by . This book was released on 2014 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Qweak experiment at Hall C of Thomas Jefferson National Accelerator Facility has made the first direct measurement of the weak charge of the proton, QWp, through a precision measurement of the parity-violating asymmetry in elastic e-p scattering at low momentum transfer Q2= 0.025 (GeV/c)2 with incident electron beam energy of 1.155 GeV. The Qweak experiment, along with earlier results of parity violating elastic scattering experiments, is expected to determine the most precise value of QWp which is suppressed in the Standard Model. If this result is further combined with the 133Cs atomic parity violation (APV) measurement, significant constraints on the weak charge of the up quark, down quark, and neutron can be extracted. This data will also be used to determine the weak-mixing angle, sin2?W, with a relative uncertainty of
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 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 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 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 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 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 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 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 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 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 Nuclear Physics written by National Research Council and published by National Academies Press. This book was released on 1999-03-31 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dramatic progress has been made in all branches of physics since the National Research Council's 1986 decadal survey of the field. The Physics in a New Era series explores these advances and looks ahead to future goals. The series includes assessments of the major subfields and reports on several smaller subfields, and preparation has begun on an overview volume on the unity of physics, its relationships to other fields, and its contributions to national needs. Nuclear Physics is the latest volume of the series. The book describes current activity in understanding nuclear structure and symmetries, the behavior of matter at extreme densities, the role of nuclear physics in astrophysics and cosmology, and the instrumentation and facilities used by the field. It makes recommendations on the resources needed for experimental and theoretical advances in the coming decade.
Download or read book The Proceedings of the International Symposium on Nuclear Electro Weak Spectroscopy for Symmetries in Electro Weak Nuclear Processes written by H. Toki and published by World Scientific. This book was released on 2002 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: The NEWS99 international symposium discusses symmetries in electroweak processes in nuclei. Many phenomena in nuclear and particle physics are related to symmetry. It is known that we are living in a left-handed world as far as the Weak interaction is concerned, but neutrino physics suggests that a right-handed world may also be relevant. Chiral symmetry and its breaking plays an essential role in generating hadron masses. Symmetries related to flavor in the strong interaction like isospin, SU(3) and so on are known to be violated although they play a crucial role for the understanding of phenomena in nuclear and particle physics. The treatment of tiny breaking is of particular importance. Weak and electromagnetic interactions are well established at the fundamental level and can be used to probe the structure of nuclei and hadrons. A wide variety of phenomena in nuclear and particle physics were discussed in NEWS99 with an emphasis on symmetry. Topics ranged from nuclear structure to neutrino properties,,covering highly phenomenological to fundamental fields.
Download or read book Measuring the Weak Charge of the Proton at Jefferson Lab written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The JLab Q weak Collaboration is designing and constructing an experiment to measure the protonâ s weak charge, Q W p, by measuring the parity violating asymmetry in elastic electron-proton scattering at very low momentum transfer. The standard model predicts Q W p = 1 - 4 sin2 theta w from the running of the weak mixing angle sin2 theta w, corresponding to a 10sigma effect in the experiment. The experiment will determine Q W p with 4% combined statistical and systematic uncertainties, which leads to 0.3% uncertainty in sin2 theta w . Installation of the experiment will begin in September 2009.
Download or read book The Proton written by Fred Bortz and published by The Rosen Publishing Group, Inc. This book was released on 2003-12-15 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt: A look into the discovery of the most fundamental subatomic particle in nature, the proton, which determines why elements have different physical and chemical properties.
