The G^0 experiment(JLab experiment E00-006, D.H. Beck, spokesperson.) will measure the parity-vio... more The G^0 experiment(JLab experiment E00-006, D.H. Beck, spokesperson.) will measure the parity-violating asymmetries in elastic electron-nucleon scattering. The experiment will be performed in Hall C at Jefferson Lab using a dedicated apparatus. In order to achieve the required statistical accuracy of the measurements, a super-conducting toroidal spectrometer, with azimuthally symmetric angular acceptance, and an associated cryogenic target have been constructed. The Focal Plane Detectors are arranged in 8 arrays of 16 arc-shaped scintillator pairs providing a fast signal compatible with the high rates of this counting experiment. For the forward angle measurement, custom built electronics will provide a time-of-flight measurement discriminating elastic recoil protons from pions and inelastic protons. For the backward angle measurements, additional scintillators and Cerenkov counters will provide separation of the elastic electrons from inelastic electrons and pions. An overview of the experimental apparatus and method for the G^0 measurement will be presented.
The complete world set of parity-violating electron scattering data up to Q2 approximately 0.3 Ge... more The complete world set of parity-violating electron scattering data up to Q2 approximately 0.3 GeV2 is analyzed. We extract the current experimental determination of the strange electric and magnetic form factors of the proton, as well as the weak axial form factors of the proton and neutron, at Q2=0.1 GeV2. Within experimental uncertainties, we find that the strange form factors are consistent with zero, as are the anapole contributions to the axial form factors. Nevertheless, the correlation between the strange and anapole contributions suggest that there is only a small probability that these form factors all vanish simultaneously.
In a global analysis of the latest parity-violating electron scattering measurements on nuclear t... more In a global analysis of the latest parity-violating electron scattering measurements on nuclear targets, we demonstrate a significant improvement in the experimental knowledge of the weak neutral-current lepton-quark interactions at low energy. The precision of this new result, combined with earlier atomic parity-violation measurements, places tight constraints on the size of possible contributions from physics beyond the standard model. Consequently, this result improves the lower-bound on the scale of relevant new physics to ˜1TeV.
In the G^0 experiment(JLab experiment E00-006, D.H. Beck, spokesperson.) parity-violating asymmet... more In the G^0 experiment(JLab experiment E00-006, D.H. Beck, spokesperson.) parity-violating asymmetries in elastic electron scattering from the nucleon will be measured at both forward and backward angles, off both LH2 and LD2 targets and over a range of momentum transfers (Q^2) ranging from about 0.1 to 0.8 GeV^2/c^2. The primary purpose of the experiment is to separate the s quark contributions G_E^s (Q^2) and G_M^s (Q^2) to the overall charge and magnetization densities of the nucleon using these measurements. A special purpose, super-conducting toroidal spectrometer, a cryogenic target, arrays of scintillators and fast dedicated electronics have been constructed for these measurements. Also a special CEBAF beam structure (31 MHz) has been developed to allow recoil particle identification via time of flight measurement. The installation in Hall C / JLab of the apparatus (in the forward mode) took place late 2002 and was followed by three months of initial commissioning in late 2002...
In a global analysis of the latest parity-violating electron scattering measurements on nuclear t... more In a global analysis of the latest parity-violating electron scattering measurements on nuclear targets, we demonstrate a significant improvement in the experimental knowledge of the weak neutral-current lepton-quark interactions at low energy. The precision of this new result, combined with earlier atomic parity-violation measurements, places tight constraints on the size of possible contributions from physics beyond the Standard Model. Consequently, this result improves the lower-bound on the scale of relevant new physics to ∼ 1 TeV. PACS numbers: 13.60.-r 12.15.-y 12.15.Mm 24.80.+y
We propose precision measurements of the helicity-dependent and helicity independent cross sectio... more We propose precision measurements of the helicity-dependent and helicity independent cross sections for the ep â epγ reaction in Deeply Virtual Compton Scattering (DVCS) kinematics. DVCS scaling is obtained in the limits Q² >> Î{sub QCD}², x{sub Bj} fixed, and -β = -(q-qâ²)² << Q². We consider the specific kinematic range Q² > 2 GeV², W > 2 GeV, and -β ⤠1 GeV². We will use our successful technique from the 5.75 GeV Hall A DVCS experiment (E00-110). With polarized 6.6, 8.8, and 11 GeV beams incident on the liquid hydrogen target, we will detect the scattered electron in the Hall A HRS-L spectrometer (maximum central momentum 4.3 GeV/c) and the emitted photon in a slightly expanded PbFâ calorimeter. In general, we will not detect the recoil proton. The H(e,eâ²Î³)X missing mass resolution is sufficient to isolate the exclusive channel with 3% systematic precision.
Abstract We have measured parity violating asymmetries in elastic electron-proton and quasi-elast... more Abstract We have measured parity violating asymmetries in elastic electron-proton and quasi-elastic electrondeuteron scattering at backward electron angle. These measurements have been done at two momentum transfers: Q 2= 0.22 and 0.63 (GeV/c) 2. Together with ...
BARYONS 2002 - Proceedings of the 9th International Conference on the Structure of Baryons, 2003
The ratio of the electric to the magnetic form factor of the neutron, GEn/GMn, was measured via r... more The ratio of the electric to the magnetic form factor of the neutron, GEn/GMn, was measured via recoil polarimetry from the quasielastic d (vec e,e&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;vec n)p reaction at three values of Q2 [ viz., 0.45, 1.15, and 1.47 (GeV/c)2] in Hall C of the Thomas Jefferson National Accelerator Facility. Preliminary data indicate that GEn follows the Galster parameterization up to
ABSTRACT A subset of results from the recently completed Jefferson Lab Qweak experiment are repor... more ABSTRACT A subset of results from the recently completed Jefferson Lab Qweak experiment are reported. This experiment, sensitive to physics beyond the Standard Model, exploits the small parity-violating asymmetry in elastic ep scattering to provide the first determination of the protons weak charge Qweak(p). The experiment employed a 180 uA longitudinally polarized 1.16 GeV electron beam on a 35 cm long liquid hydrogen target. Scattered electrons corresponding to Q2 of 0.025 GeV2 were detected in eight Cerenkov detectors arrayed symmetrically around the beam axis. The goals of the experiment were to provide a measure of Qweak(p) to 4.2 percent (combined statistical and systematic error), which implies a measure of sin2(thetaw) at the level of 0.3 percent, and to help constrain the vector weak quark charges C1u and C1d. The experimental method is described, with particular focus on the challenges associated with the worlds highest power LH2 target. The new constraints on C1u and C1d provided by the subset of the experiments data analyzed to date will also be shown, together with the extracted weak charge of the neutron.
K. GARROWb, DF GEESAMANc, P. GUEYEf, K. GUSTAFSSONk, K. HAFIDIc, JO HANSENc, W. HINTONf, HE JACKS... more K. GARROWb, DF GEESAMANc, P. GUEYEf, K. GUSTAFSSONk, K. HAFIDIc, JO HANSENc, W. HINTONf, HE JACKSONc, H. JUENGSTs, C. KEPPELf , A. KLEINt, D. KOLTENUKq, Y. LIANGu, JH LIUs, A. LUNGb, D. MACKb, R. MADEYfe, P. MARKOWITZab, CJ ...
We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely po... more We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasi-elastic scattering on the deuteron, at backward angles (lab scattering angle of 108 • ) for Q 2 = 0.22 GeV 2 /c 2 and 0.63 GeV 2 /c 2 at beam energies of 362 MeV and 687 MeV, respectively. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic (πN) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasi-static deuterium approximation, and is also in agreement with theory.
... 6. TA Armstrong, JP Bocquet, G. Ericsson, et al., Phys. Rev. C 47, 1957 (1993). 7. W. Cassing... more ... 6. TA Armstrong, JP Bocquet, G. Ericsson, et al., Phys. Rev. C 47, 1957 (1993). 7. W. Cassing, L. Jarczyk, B. Kamys, et al., Eur. Phys. J. A 16, 549 (2003). 8. V. Metag, E. Liukkonen, G. Sletten, et al., Nucl. Instrum. Methods Phys. Res. 114, 445 (1974). 9. DH Davis, Nucl. Phys. ...
We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson La... more We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson Lab. For heavy nuclei, we observe a rapid falloff in the cross section for x > 1, which is sensitive to short range contributions to the nuclear wave-function, and in deep inelastic scattering corresponds to probing extremely high momentum quarks. This result agrees with higher energy muon scattering measurements, but is in sharp contrast to neutrino scattering measurements which suggested a dramatic enhancement in the distribution of the 'super-fast' quarks probed at x > 1. The falloff at x > 1 is noticeably stronger in 2 H and 3 He, but nearly identical for all heavier nuclei.
We have extracted QCD matrix elements from our data on doubly polarized inelastic scattering of e... more We have extracted QCD matrix elements from our data on doubly polarized inelastic scattering of electrons on nuclei. We find the higher twist matrix elementd2, which arises strictly from quarkgluon interactions, to be unambiguously non zero. The data also reveal an isospin dependence of higher twist effects if we assume that the Burkhardt-Cottingham Sum rule is valid. The fundamental Bjorken sum rule obtained from the a0 matrix element is satisfied at our low momentum transfer.
We have examined the spin structure of the proton in the region of the nucleon resonances (1.085 ... more We have examined the spin structure of the proton in the region of the nucleon resonances (1.085 GeV < W < 1.910 GeV) at an average four momentum transfer of Q 2 = 1.3 GeV 2 . Using the Jefferson Lab polarized electron beam, a spectrometer, and a polarized solid target, we measured the asymmetries A and A ⊥ to high precision, and extracted the asymmetries A1 and A2, and the spin structure functions g1 and g2. We found a notably non-zero A ⊥ , significant contributions from higher-twist effects, and only weak support for polarized quark-hadron duality.
The G^0 experiment(JLab experiment E00-006, D.H. Beck, spokesperson.) will measure the parity-vio... more The G^0 experiment(JLab experiment E00-006, D.H. Beck, spokesperson.) will measure the parity-violating asymmetries in elastic electron-nucleon scattering. The experiment will be performed in Hall C at Jefferson Lab using a dedicated apparatus. In order to achieve the required statistical accuracy of the measurements, a super-conducting toroidal spectrometer, with azimuthally symmetric angular acceptance, and an associated cryogenic target have been constructed. The Focal Plane Detectors are arranged in 8 arrays of 16 arc-shaped scintillator pairs providing a fast signal compatible with the high rates of this counting experiment. For the forward angle measurement, custom built electronics will provide a time-of-flight measurement discriminating elastic recoil protons from pions and inelastic protons. For the backward angle measurements, additional scintillators and Cerenkov counters will provide separation of the elastic electrons from inelastic electrons and pions. An overview of the experimental apparatus and method for the G^0 measurement will be presented.
The complete world set of parity-violating electron scattering data up to Q2 approximately 0.3 Ge... more The complete world set of parity-violating electron scattering data up to Q2 approximately 0.3 GeV2 is analyzed. We extract the current experimental determination of the strange electric and magnetic form factors of the proton, as well as the weak axial form factors of the proton and neutron, at Q2=0.1 GeV2. Within experimental uncertainties, we find that the strange form factors are consistent with zero, as are the anapole contributions to the axial form factors. Nevertheless, the correlation between the strange and anapole contributions suggest that there is only a small probability that these form factors all vanish simultaneously.
In a global analysis of the latest parity-violating electron scattering measurements on nuclear t... more In a global analysis of the latest parity-violating electron scattering measurements on nuclear targets, we demonstrate a significant improvement in the experimental knowledge of the weak neutral-current lepton-quark interactions at low energy. The precision of this new result, combined with earlier atomic parity-violation measurements, places tight constraints on the size of possible contributions from physics beyond the standard model. Consequently, this result improves the lower-bound on the scale of relevant new physics to ˜1TeV.
In the G^0 experiment(JLab experiment E00-006, D.H. Beck, spokesperson.) parity-violating asymmet... more In the G^0 experiment(JLab experiment E00-006, D.H. Beck, spokesperson.) parity-violating asymmetries in elastic electron scattering from the nucleon will be measured at both forward and backward angles, off both LH2 and LD2 targets and over a range of momentum transfers (Q^2) ranging from about 0.1 to 0.8 GeV^2/c^2. The primary purpose of the experiment is to separate the s quark contributions G_E^s (Q^2) and G_M^s (Q^2) to the overall charge and magnetization densities of the nucleon using these measurements. A special purpose, super-conducting toroidal spectrometer, a cryogenic target, arrays of scintillators and fast dedicated electronics have been constructed for these measurements. Also a special CEBAF beam structure (31 MHz) has been developed to allow recoil particle identification via time of flight measurement. The installation in Hall C / JLab of the apparatus (in the forward mode) took place late 2002 and was followed by three months of initial commissioning in late 2002...
In a global analysis of the latest parity-violating electron scattering measurements on nuclear t... more In a global analysis of the latest parity-violating electron scattering measurements on nuclear targets, we demonstrate a significant improvement in the experimental knowledge of the weak neutral-current lepton-quark interactions at low energy. The precision of this new result, combined with earlier atomic parity-violation measurements, places tight constraints on the size of possible contributions from physics beyond the Standard Model. Consequently, this result improves the lower-bound on the scale of relevant new physics to ∼ 1 TeV. PACS numbers: 13.60.-r 12.15.-y 12.15.Mm 24.80.+y
We propose precision measurements of the helicity-dependent and helicity independent cross sectio... more We propose precision measurements of the helicity-dependent and helicity independent cross sections for the ep â epγ reaction in Deeply Virtual Compton Scattering (DVCS) kinematics. DVCS scaling is obtained in the limits Q² >> Î{sub QCD}², x{sub Bj} fixed, and -β = -(q-qâ²)² << Q². We consider the specific kinematic range Q² > 2 GeV², W > 2 GeV, and -β ⤠1 GeV². We will use our successful technique from the 5.75 GeV Hall A DVCS experiment (E00-110). With polarized 6.6, 8.8, and 11 GeV beams incident on the liquid hydrogen target, we will detect the scattered electron in the Hall A HRS-L spectrometer (maximum central momentum 4.3 GeV/c) and the emitted photon in a slightly expanded PbFâ calorimeter. In general, we will not detect the recoil proton. The H(e,eâ²Î³)X missing mass resolution is sufficient to isolate the exclusive channel with 3% systematic precision.
Abstract We have measured parity violating asymmetries in elastic electron-proton and quasi-elast... more Abstract We have measured parity violating asymmetries in elastic electron-proton and quasi-elastic electrondeuteron scattering at backward electron angle. These measurements have been done at two momentum transfers: Q 2= 0.22 and 0.63 (GeV/c) 2. Together with ...
BARYONS 2002 - Proceedings of the 9th International Conference on the Structure of Baryons, 2003
The ratio of the electric to the magnetic form factor of the neutron, GEn/GMn, was measured via r... more The ratio of the electric to the magnetic form factor of the neutron, GEn/GMn, was measured via recoil polarimetry from the quasielastic d (vec e,e&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;vec n)p reaction at three values of Q2 [ viz., 0.45, 1.15, and 1.47 (GeV/c)2] in Hall C of the Thomas Jefferson National Accelerator Facility. Preliminary data indicate that GEn follows the Galster parameterization up to
ABSTRACT A subset of results from the recently completed Jefferson Lab Qweak experiment are repor... more ABSTRACT A subset of results from the recently completed Jefferson Lab Qweak experiment are reported. This experiment, sensitive to physics beyond the Standard Model, exploits the small parity-violating asymmetry in elastic ep scattering to provide the first determination of the protons weak charge Qweak(p). The experiment employed a 180 uA longitudinally polarized 1.16 GeV electron beam on a 35 cm long liquid hydrogen target. Scattered electrons corresponding to Q2 of 0.025 GeV2 were detected in eight Cerenkov detectors arrayed symmetrically around the beam axis. The goals of the experiment were to provide a measure of Qweak(p) to 4.2 percent (combined statistical and systematic error), which implies a measure of sin2(thetaw) at the level of 0.3 percent, and to help constrain the vector weak quark charges C1u and C1d. The experimental method is described, with particular focus on the challenges associated with the worlds highest power LH2 target. The new constraints on C1u and C1d provided by the subset of the experiments data analyzed to date will also be shown, together with the extracted weak charge of the neutron.
K. GARROWb, DF GEESAMANc, P. GUEYEf, K. GUSTAFSSONk, K. HAFIDIc, JO HANSENc, W. HINTONf, HE JACKS... more K. GARROWb, DF GEESAMANc, P. GUEYEf, K. GUSTAFSSONk, K. HAFIDIc, JO HANSENc, W. HINTONf, HE JACKSONc, H. JUENGSTs, C. KEPPELf , A. KLEINt, D. KOLTENUKq, Y. LIANGu, JH LIUs, A. LUNGb, D. MACKb, R. MADEYfe, P. MARKOWITZab, CJ ...
We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely po... more We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasi-elastic scattering on the deuteron, at backward angles (lab scattering angle of 108 • ) for Q 2 = 0.22 GeV 2 /c 2 and 0.63 GeV 2 /c 2 at beam energies of 362 MeV and 687 MeV, respectively. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic (πN) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasi-static deuterium approximation, and is also in agreement with theory.
... 6. TA Armstrong, JP Bocquet, G. Ericsson, et al., Phys. Rev. C 47, 1957 (1993). 7. W. Cassing... more ... 6. TA Armstrong, JP Bocquet, G. Ericsson, et al., Phys. Rev. C 47, 1957 (1993). 7. W. Cassing, L. Jarczyk, B. Kamys, et al., Eur. Phys. J. A 16, 549 (2003). 8. V. Metag, E. Liukkonen, G. Sletten, et al., Nucl. Instrum. Methods Phys. Res. 114, 445 (1974). 9. DH Davis, Nucl. Phys. ...
We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson La... more We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson Lab. For heavy nuclei, we observe a rapid falloff in the cross section for x > 1, which is sensitive to short range contributions to the nuclear wave-function, and in deep inelastic scattering corresponds to probing extremely high momentum quarks. This result agrees with higher energy muon scattering measurements, but is in sharp contrast to neutrino scattering measurements which suggested a dramatic enhancement in the distribution of the 'super-fast' quarks probed at x > 1. The falloff at x > 1 is noticeably stronger in 2 H and 3 He, but nearly identical for all heavier nuclei.
We have extracted QCD matrix elements from our data on doubly polarized inelastic scattering of e... more We have extracted QCD matrix elements from our data on doubly polarized inelastic scattering of electrons on nuclei. We find the higher twist matrix elementd2, which arises strictly from quarkgluon interactions, to be unambiguously non zero. The data also reveal an isospin dependence of higher twist effects if we assume that the Burkhardt-Cottingham Sum rule is valid. The fundamental Bjorken sum rule obtained from the a0 matrix element is satisfied at our low momentum transfer.
We have examined the spin structure of the proton in the region of the nucleon resonances (1.085 ... more We have examined the spin structure of the proton in the region of the nucleon resonances (1.085 GeV < W < 1.910 GeV) at an average four momentum transfer of Q 2 = 1.3 GeV 2 . Using the Jefferson Lab polarized electron beam, a spectrometer, and a polarized solid target, we measured the asymmetries A and A ⊥ to high precision, and extracted the asymmetries A1 and A2, and the spin structure functions g1 and g2. We found a notably non-zero A ⊥ , significant contributions from higher-twist effects, and only weak support for polarized quark-hadron duality.
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Papers by Julie Roche