Browsing by Author "Luo W."

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    Erratum: Polarization transfer observables in elastic electron-proton scattering at Q2=2.5, 5.2, 6.8, and 8.5 GeV2 (Physical Review C (2017) 96 (055203) DOI: 10.1103/PhysRevC.96.055203)
    (2018-07-25) Puckett A.J.R.; Brash E.J.; Jones M.K.; Luo W.; Meziane M.; Pentchev L.; Perdrisat C.F.; Punjabi V.; Wesselmann F.R.; Afanasev A.; Ahmidouch A.; Albayrak I.; Aniol K.A.; Arrington J.; Asaturyan A.; Baghdasaryan H.; Benmokhtar F.; Bertozzi W.; Bimbot L.; Bosted P.; Boeglin W.; Butuceanu C.; Carter P.; Chernenko S.; Christy M.E.; Commisso M.; Cornejo J.C.; Covrig S.; Danagoulian S.; Daniel A.; Davidenko A.; Day D.; Dhamija S.; Dutta D.; Ent R.; Frullani S.; Fenker H.; Frlez E.; Garibaldi F.; Gaskell D.; Gilad S.; Gilman R.; Goncharenko Y.; Hafidi K.; Hamilton D.; Higinbotham D.W.; Hinton W.; Horn T.; Hu B.; Huang J.; Huber G.M.; Jensen E.; Keppel C.; Khandaker M.; King P.; Kirillov D.; Kohl M.; Kravtsov V.; Kumbartzki G.; Li Y.; Mamyan V.; Margaziotis D.J.; Marsh A.; Matulenko Y.; Maxwell J.; Mbianda G.; Meekins D.; Melnik Y.; Miller J.; Mkrtchyan A.; Mkrtchyan H.; Moffit B.; Moreno O.; Mulholland J.; Narayan A.; Nedev S.; Nuruzzaman; Piasetzky E.; Pierce W.; Piskunov N.M.; Prok Y.; Ransome R.D.; Razin D.S.; Reimer P.; Reinhold J.; Rondon O.; Shabestari M.; Shahinyan A.; Shestermanov K.; Širca S.; Sitnik I.; Smykov L.; Smith G.; Solovyev L.; Solvignon P.; Subedi R.; Tomasi-Gustafsson E.; Vasiliev A.; Veilleux M.; Wojtsekhowski B.B.; Wood S.; Ye Z.; Zanevsky Y.; Zhang X.; Zhang Y.; Zheng X.; Zhu L.
    Subsequent to the release of our original paper, we discovered in the context of preparing our technical supplement [1] for journal publication that a typographical error had existed in the text file that the analysis program used to construct the beam polarization ``database`` for both the original analysis, published in Ref. [2], and our final analysis. The electron-beam polarization P e and the analyzing power A y cancel exactly in the ratio R , which is proportional to the ratio P t / P l of the transferred polarization components. On the other hand, the extraction of the relative e dependence of P l / P Born l relies on knowledge of the beam polarization. As such, data taking was interrupted roughly every two days during the GEp - 2 ? experiment to perform invasive measurements of the beam polarization using the Hall C Moller polarimeter [3]. The run range affected by the typographical error was entirely contained within the data collected at Q 2 = 2.5 GeV 2 with a beam energy of E e = 3.680 GeV during January 2008. The data from this configuration were combined with the data collected at E e = 3.548 GeV due to the nearly complete overlap of these two settings in terms of Q 2 and e acceptance. It is worth remarking that this typographical error went unnoticed for so long because it only affected a small fraction of the data (less than half of the combined data for ? e ? = 0.790 ) and the difference between the actually assigned beam polarization and the polarization that should have been assigned was comparable in magnitude to the point-to-point systematic uncertainty of the measurement itself. As such, its effect did not show up in various diagnostic plots and statistical tests, such as the time stability of the extracted P l / P Born l ratio. The data for both E e = 3.548 and E e = 3.680 GeV were reprocessed using the corrected beam polarizations to determine the effect of the typographical error on the combined physics results at ? e ? = 0.790 . Because the value of P e cancels in the ratio R , changes in the assumed beam polarization can only affect the results for R via statistical fluctuations due to changes in the relative weighting of different run ranges in the unbinned maximum-likelihood estimators for R . These effects are negligible on the scale of both the statistical and the systematic uncertainties of the data. More noticeable changes are expected in the ratio P l / P Born l since the extracted value of P l is inversely proportional to the assumed value of P e . Table I shows the effect of the corrected beam polarization database on the polarization transfer observables for the combined data for the ? e ? = 0.790 setting, the only measurement affected by the typographical error. The analyzing power did not need to be recalibrated since it was determined using the ? e ? = 0.153 data, which were not affected by the typographical error. As expected, the change in the ratio R is negligible. The value of P Born l , which is computed event by event from the global fit described in the Appendix of the original paper and does not depend on P e , is also unchanged. The magnitudes of P t , P l , and P l / P Born l are reduced by a common multiplicative factor, reflecting the fact that the beam polarization had been underestimated for the run range affected by the typographical error. The most important result of the corrected analysis is that the ratio P l / P Born l has decreased by 0.0024 from 1.0167 to 1.0143, a change comparable in magnitude to the statistical uncertainty but small compared to the total and point-to-point systematic uncertainties. The P l / P Born l result for the original publication [2] would be reduced by the same multiplicative factor as the final result. The physics conclusions of both publications are not materially changed by this correction. (Table Presented). (Figure Presented).
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    Polarization components in π0 photoproduction at photon energies up to 5.6 GeV
    (2012-05-31) Luo W.; Brash E.J.; Gilman R.; Jones M.K.; Meziane M.; Pentchev L.; Perdrisat C.F.; Puckett A.J.R.; Punjabi V.; Wesselmann F.R.; Ahmidouch A.; Albayrak I.; Aniol K.A.; Arrington J.; Asaturyan A.; Ates O.; Baghdasaryan H.; Benmokhtar F.; Bertozzi W.; Bimbot L.; Bosted P.; Boeglin W.; Butuceanu C.; Carter P.; Chernenko S.; Christy M.E.; Commisso M.; Cornejo J.C.; Covrig S.; Danagoulian S.; Daniel A.; Davidenko A.; Day D.; Dhamija S.; Dutta D.; Ent R.; Frullani S.; Fenker H.; Frlez E.; Garibaldi F.; Gaskell D.; Gilad S.; Goncharenko Y.; Hafidi K.; Hamilton D.; Higinbotham D.W.; Hinton W.; Horn T.; Hu B.; Huang J.; Huber G.M.; Jensen E.; Kang H.; Keppel C.; Khandaker M.; King P.; Kirillov D.; Kohl M.; Kravtsov V.; Kumbartzki G.; Li Y.; Mamyan V.; Margaziotis D.J.; Markowitz P.; Marsh A.; Matulenko Y.; Maxwell J.; Mbianda G.; Meekins D.; Melnik Y.; Miller J.; Mkrtchyan A.; Mkrtchyan H.; Moffit B.; Moreno O.; Mulholland J.; Narayan A.; Nuruzzaman; Nedev S.; Piasetzky E.; Pierce W.; Piskunov N.M.; Prok Y.; Ransome R.D.; Razin D.S.; Reimer P.E.; Reinhold J.; Rondon O.; Shabestari M.; Shahinyan A.; Shestermanov K.; Airca S.; Sitnik I.; Smykov L.; Smith G.; Solovyev L.; Solvignon P.; Strakovsky I.I.; Subedi R.; Suleiman R.; Tomasi-Gustafsson E.; Vasiliev A.; Veilleux M.; Wood S.; Ye Z.; Zanevsky Y.; Zhang X.; Zhang Y.; Zheng X.; Zhu L.
    We present new data for the polarization observables of the final state proton in the H1(γ→,p→)π0 reaction. These data can be used to test predictions based on hadron helicity conservation and perturbative QCD. These data have both small statistical and systematic uncertainties and were obtained with beam energies between 1.8 and 5.6GeV and for π0 scattering angles larger than 75° in the center-of-mass frame. The data extend the polarization measurements database for neutral pion photoproduction up to E γ=5.6GeV. The results show a nonzero induced polarization above the resonance region. The polarization transfer components vary rapidly with the photon energy and π0 scattering angle in the center-of-mass frame. This indicates that hadron helicity conservation does not hold and that the perturbative QCD limit is still not reached in the energy regime of this experiment. © 2012 American Physical Society.
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    Polarization transfer observables in elastic electron-proton scattering at Q2=2.5, 5.2, 6.8, and 8.5 GeV2 POLARIZATION TRANSFER OBSERVABLES in ELASTIC ... A. J. R. PUCKETT et al.
    (2017-11-06) Puckett A.J.R.; Brash E.J.; Jones M.K.; Luo W.; Meziane M.; Pentchev L.; Perdrisat C.F.; Punjabi V.; Wesselmann F.R.; Afanasev A.; Ahmidouch A.; Albayrak I.; Aniol K.A.; Arrington J.; Asaturyan A.; Baghdasaryan H.; Benmokhtar F.; Bertozzi W.; Bimbot L.; Bosted P.; Boeglin W.; Butuceanu C.; Carter P.; Chernenko S.; Christy M.E.; Commisso M.; Cornejo J.C.; Covrig S.; Danagoulian S.; Daniel A.; Davidenko A.; Day D.; Dhamija S.; Dutta D.; Ent R.; Frullani S.; Fenker H.; Frlez E.; Garibaldi F.; Gaskell D.; Gilad S.; Gilman R.; Goncharenko Y.; Hafidi K.; Hamilton D.; Higinbotham D.W.; Hinton W.; Horn T.; Hu B.; Huang J.; Huber G.M.; Jensen E.; Keppel C.; Khandaker M.; King P.; Kirillov D.; Kohl M.; Kravtsov V.; Kumbartzki G.; Li Y.; Mamyan V.; Margaziotis D.J.; Marsh A.; Matulenko Y.; Maxwell J.; Mbianda G.; Meekins D.; Melnik Y.; Miller J.; Mkrtchyan A.; Mkrtchyan H.; Moffit B.; Moreno O.; Mulholland J.; Narayan A.; Nedev S.; Nuruzzaman; Piasetzky E.; Pierce W.; Piskunov N.M.; Prok Y.; Ransome R.D.; Razin D.S.; Reimer P.; Reinhold J.; Rondon O.; Shabestari M.; Shahinyan A.; Shestermanov K.; Širca S.; Sitnik I.; Smykov L.; Smith G.; Solovyev L.; Solvignon P.; Subedi R.; Tomasi-Gustafsson E.; Vasiliev A.; Veilleux M.; Wojtsekhowski B.B.; Wood S.; Ye Z.; Zanevsky Y.; Zhang X.; Zhang Y.; Zheng X.; Zhu L.
    Background: Interest in the behavior of nucleon electromagnetic form factors at large momentum transfers has steadily increased since the discovery, using polarization observables, of the rapid decrease of the ratio GEp/GMp of the proton's electric and magnetic form factors for momentum transfers Q21 GeV2, in strong disagreement with previous extractions of this ratio using the traditional Rosenbluth separation technique. Purpose: The GEp-III and GEp-2γ experiments were carried out in Jefferson Laboratory's (JLab's) Hall C from 2007 to 2008, to extend the knowledge of GEp/GMp to the highest practically achievable Q2 given the maximum beam energy of 6 GeV and to search for effects beyond the Born approximation in polarization transfer observables of elastic ∫ - p scattering. This article provides an expanded description of the common experimental apparatus and data analysis procedures, and reports the results of a final reanalysis of the data from both experiments, including the previously unpublished results of the full-acceptance dataset of the GEp-2γ experiment. Methods: Polarization transfer observables in elastic ∫ - p→∫ - scattering were measured at central Q2 values of 2.5, 5.2, 6.8, and 8.54 GeV2. At Q2=2.5GeV2, data were obtained for central values of the virtual photon polarization parameter ϵ of 0.149, 0.632, and 0.783. The Hall C High Momentum Spectrometer detected and measured the polarization of protons recoiling elastically from collisions of JLab's polarized electron beam with a liquid hydrogen target. A large-acceptance electromagnetic calorimeter detected the elastically scattered electrons in coincidence to suppress inelastic backgrounds. Results: The final GEp-III data are largely unchanged relative to the originally published results. The statistical uncertainties of the final GEp-2γ data are significantly reduced at ϵ=0.632 and 0.783 relative to the original publication. Conclusions: The final GEp-III results show that the decrease with Q2 of GEp/GMp continues to Q2=8.5GeV2, but at a slowing rate relative to the approximately linear decrease observed in earlier Hall A measurements. At Q2=8.5GeV2, GEp/GMp remains positive but is consistent with zero. At Q2=2.5GeV2, GEp/GMp derived from the polarization component ratio R-Pt/P shows no statistically significant ϵ dependence, as expected in the Born approximation. On the other hand, the ratio P````/P````Born of the longitudinal polarization transfer component to its Born value shows an enhancement of roughly 1.7% at ϵ=0.783 relative to ϵ=0.149, with ≈2.2σ significance based on the total uncertainty, implying a similar effect in the transverse component Pt that cancels in the ratio R.
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    Recoil polarization measurements of the proton electromagnetic form factor ratio to Q2=8.5GeV2
    (2010-06-18) Puckett A.J.R.; Brash E.J.; Jones M.K.; Luo W.; Meziane M.; Pentchev L.; Perdrisat C.F.; Punjabi V.; Wesselmann F.R.; Ahmidouch A.; Albayrak I.; Aniol K.A.; Arrington J.; Asaturyan A.; Baghdasaryan H.; Benmokhtar F.; Bertozzi W.; Bimbot L.; Bosted P.; Boeglin W.; Butuceanu C.; Carter P.; Chernenko S.; Christy E.; Commisso M.; Cornejo J.C.; Covrig S.; Danagoulian S.; Daniel A.; Davidenko A.; Day D.; Dhamija S.; Dutta D.; Ent R.; Frullani S.; Fenker H.; Frlez E.; Garibaldi F.; Gaskell D.; Gilad S.; Gilman R.; Goncharenko Y.; Hafidi K.; Hamilton D.; Higinbotham D.W.; Hinton W.; Horn T.; Hu B.; Huang J.; Huber G.M.; Jensen E.; Keppel C.; Khandaker M.; King P.; Kirillov D.; Kohl M.; Kravtsov V.; Kumbartzki G.; Li Y.; Mamyan V.; Margaziotis D.J.; Marsh A.; Matulenko Y.; Maxwell J.; Mbianda G.; Meekins D.; Melnik Y.; Miller J.; Mkrtchyan A.; Mkrtchyan H.; Moffit B.; Moreno O.; Mulholland J.; Narayan A.; Nedev S.; Nuruzzaman; Piasetzky E.; Pierce W.; Piskunov N.M.; Prok Y.; Ransome R.D.; Razin D.S.; Reimer P.; Reinhold J.; Rondon O.; Shabestari M.; Shahinyan A.; Shestermanov K.; Širca S.; Sitnik I.; Smykov L.; Smith G.; Solovyev L.; Solvignon P.; Subedi R.; Tomasi-Gustafsson E.; Vasiliev A.; Veilleux M.; Wojtsekhowski B.B.; Wood S.; Ye Z.; Zanevsky Y.; Zhang X.; Zhang Y.; Zheng X.; Zhu L.
    Among the most fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon's quark constituents; indeed, recent proton data have attracted intense theoretical interest. In this Letter, we report new measurements of the proton electromagnetic form factor ratio using the recoil polarization method, at momentum transfers Q2=5.2, 6.7, and 8.5GeV2. By extending the range of Q2 for which GEp is accurately determined by more than 50%, these measurements will provide significant constraints on models of nucleon structure in the nonperturbative regime. © 2010 The American Physical Society.
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    Search for effects beyond the born approximation in polarization transfer observables in e→p elastic scattering
    (2011-03-29) Meziane M.; Brash E.J.; Gilman R.; Jones M.K.; Luo W.; Pentchev L.; Perdrisat C.F.; Puckett A.J.R.; Punjabi V.; Wesselmann F.R.; Ahmidouch A.; Albayrak I.; Aniol K.A.; Arrington J.; Asaturyan A.; Ates O.; Baghdasaryan H.; Benmokhtar F.; Bertozzi W.; Bimbot L.; Bosted P.; Boeglin W.; Butuceanu C.; Carter P.; Chernenko S.; Christy E.; Commisso M.; Cornejo J.C.; Covrig S.; Danagoulian S.; Daniel A.; Davidenko A.; Day D.; Dhamija S.; Dutta D.; Ent R.; Frullani S.; Fenker H.; Frlez E.; Garibaldi F.; Gaskell D.; Gilad S.; Goncharenko Y.; Hafidi K.; Hamilton D.; Higinbotham D.W.; Hinton W.; Horn T.; Hu B.; Huang J.; Huber G.M.; Jensen E.; Kang H.; Keppel C.; Khandaker M.; King P.; Kirillov D.; Kohl M.; Kravtsov V.; Kumbartzki G.; Li Y.; Mamyan V.; Margaziotis D.J.; Markowitz P.; Marsh A.; Matulenko Y.; Maxwell J.; Mbianda G.; Meekins D.; Melnik Y.; Miller J.; Mkrtchyan A.; Mkrtchyan H.; Moffit B.; Moreno O.; Mulholland J.; Narayan A.; Nuruzzaman; Nedev S.; Piasetzky E.; Pierce W.; Piskunov N.M.; Prok Y.; Ransome R.D.; Razin D.S.; Reimer P.E.; Reinhold J.; Rondon O.; Shabestari M.; Shahinyan A.; Shestermanov K.; Åirca S.; Sitnik I.; Smykov L.; Smith G.; Solovyev L.; Solvignon P.; Subedi R.; Suleiman R.; Tomasi-Gustafsson E.; Vasiliev A.; Vanderhaeghen M.; Veilleux M.; Wojtsekhowski B.B.; Wood S.; Ye Z.; Zanevsky Y.; Zhang X.; Zhang Y.; Zheng X.; Zhu L.
    Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, GE/GM, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic H(e→,e′p→) reaction for three different beam energies at a Q2=2.5GeV2, spanning a wide range of the kinematic parameter μ. The ratio R, which equals μpGE/GM in the Born approximation, is found to be independent of μ at the 1.5% level. The μ dependence of the longitudinal polarization transfer component P ℓ shows an enhancement of (2.3±0.6)% relative to the Born approximation at large μ. © 2011 American Physical Society.
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    Technical supplement to “Polarization transfer observables in elastic electron-proton scattering at Q2=2.5,5.2,6.8 and 8.5GeV2”
    (2018-12-01) Puckett A.J.R.; Brash E.J.; Jones M.K.; Luo W.; Meziane M.; Pentchev L.; Perdrisat C.F.; Punjabi V.; Wesselmann F.R.; Afanasev A.; Ahmidouch A.; Albayrak I.; Aniol K.A.; Arrington J.; Asaturyan A.; Baghdasaryan H.; Benmokhtar F.; Bertozzi W.; Bimbot L.; Bosted P.; Boeglin W.; Butuceanu C.; Carter P.; Chernenko S.; Christy M.E.; Cornejo J.C.; Covrig S.; Danagoulian S.; Daniel A.; Davidenko A.; Day D.; Dhamija S.; Dutta D.; Ent R.; Frullani S.; Fenker H.; Frlez E.; Garibaldi F.; Gaskell D.; Gilad S.; Gilman R.; Goncharenko Y.; Hafidi K.; Hamilton D.; Higinbotham D.W.; Hinton W.; Horn T.; Hu B.; Huang J.; Huber G.M.; Jensen E.; Keppel C.; Khandaker M.; King P.; Kirillov D.; Kohl M.; Kravtsov V.; Kumbartzki G.; Li Y.; Mamyan V.; Margaziotis D.J.; Marsh A.; Matulenko Y.; Maxwell J.; Mbianda G.; Meekins D.; Melnik Y.; Miller J.; Mkrtchyan A.; Mkrtchyan H.; Moffit B.; Moreno O.; Mulholland J.; Narayan A.; Nedev S.; Nuruzzaman; Piasetzky E.; Pierce W.; Piskunov N.M.; Prok Y.; Ransome R.D.; Razin D.S.; Reimer P.; Reinhold J.; Rondon O.; Shabestari M.; Shahinyan A.; Shestermanov K.; Širca S.; Sitnik I.; Smykov L.; Smith G.; Solovyev L.; Solvignon P.; Subedi R.; Tomasi-Gustafsson E.; Vasiliev A.; Veilleux M.; Wojtsekhowski B.B.; Wood S.; Ye Z.; Zanevsky Y.; Zhang X.; Zhang Y.; Zheng X.; Zhu L.
    The GEp-III and GEp-2γ experiments, carried out in Jefferson Lab's Hall C from 2007–2008, consisted of measurements of polarization transfer in elastic electron–proton scattering at momentum transfers of Q2=2.5,5.2,6.8, and 8.54 GeV 2. These measurements were carried out to improve knowledge of the proton electromagnetic form factor ratio R=μpGE p∕GM p at large values of Q2 and to search for effects beyond the Born approximation in polarization transfer observables at Q2=2.5GeV2. The final results of both experiments were reported in a recent archival publication. A full reanalysis of the data from both experiments was carried out in order to reduce the systematic and, for the GEp-2γ experiment, statistical uncertainties. This technical note provides additional details of the final analysis omitted from the main publication, including the final evaluation of the systematic uncertainties.