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Dean C Hines - One of the best experts on this subject based on the ideXlab platform.
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hubble space telescope pre perihelion acs wfc imaging polarimetry of comet ison c 2012 s1 at 3 81 au
The Astrophysical Journal, 2013Co-Authors: Dean C Hines, Gorden Videen, Evgenij Zubko, Karri Muinonen, Yuriy Shkuratov, V G Kaydash, Matthew M KnightAbstract:We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (r h = 3.81 AU, Δ = 4.34 AU), when the phase angle was α ≈ 1216. This phase angle is approximately centered in the negative polarization branch for cometary dust. The region beyond 1000 km (~0.32 arcsec ≈ 6 pixels) from the nucleus shows a negative polarization amplitude of p% ~ –1.6%. Within 1000 km of the nucleus, the polarization position angle rotates to be approximately perpendicular to the Scattering Plane, with an amplitude p% ~ +2.5%. Such positive polarization has been observed previously as a characteristic feature of cometary jets, and we show that Comet ISON does indeed harbor a jet-like feature. These HST observations of Comet ISON represent the first visible light, imaging polarimetry with subarcsecond spatial resolution of a Nearly Isotropic Comet beyond 3.8 AU from the Sun at a small phase angle. The observations provide an early glimpse of the properties of the cometary dust preserved in this Oort-Cloud comet.
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hubble space telescope pre perihelion acs wfc imaging polarimetry of comet ison c 2012 s1 at 3 81 au
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: Dean C Hines, Gorden Videen, Evgenij Zubko, Karri Muinonen, Yuriy Shkuratov, V G Kaydash, Matthew M KnightAbstract:We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (rh = 3.81 AU, Delta = 4.34 AU), when the phase angle was alpha = 12.16 degrees. This phase angle is approximately centered in the negative polarization branch for cometary dust. The region beyond 1000 km from the nucleus shows a negative polarization amplitude of p% -1.6%. Within 1000 km of the nucleus, the polarization position angle rotates to be approximately perpendicular to the Scattering Plane, with an amplitude p% +2.5%. Such positive polarization has been observed previously as a characteristic feature of cometary jets, and we show that Comet ISON does indeed harbor a jet-like feature. These HST observations of Comet ISON represent the first visible light, imaging polarimetry with sub-arcsecond spatial resolution of a Nearly Isotropic Comet (NIC) beyond 3.8 AU from the Sun at a small phase angle. The observations provide an early glimpse of the properties of the cometary dust preserved in this Oort-cloud comet.
A Airapetian - One of the best experts on this subject based on the ideXlab platform.
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measurement of azimuthal asymmetries associated with deeply virtual compton Scattering on a longitudinally polarized deuterium target
Nuclear Physics, 2010Co-Authors: A Airapetian, N Akopov, Z Akopov, M Amarian, E C Aschenauer, W Augustyniak, R Avakian, A Avetissian, E AvetisyanAbstract:Azimuthal asymmetries in exclusive electroproduction of a real photon from a longitudinally polarized deuterium target are measured with respect to target polarization alone and with respect to target polarization combined with beam helicity and/or beam charge. The asymmetries appear in the distribution of the real photons in the azimuthal angle ϕ around the virtual photon direction, relative to the lepton Scattering Plane. The asymmetries arise from the deeply virtual Compton Scattering process and its interference with the Bethe–Heitler process. The results for the beam-charge and beam-helicity asymmetries from a tensor polarized deuterium target with vanishing vector polarization are shown to be compatible with those from an unpolarized deuterium target, which is expected for incoherent Scattering dominant at larger momentum transfer. Furthermore, the results for the single target-spin asymmetry and for the double-spin asymmetry are found to be compatible with the corresponding asymmetries previously measured on a hydrogen target. For coherent Scattering on the deuteron at small momentum transfer to the target, these findings imply that the tensor contribution to the cross section is small. Furthermore, the tensor asymmetry is found to be compatible with zero.
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single spin asymmetries in semi inclusive deep inelastic Scattering on a transversely polarized hydrogen target
Physical Review Letters, 2005Co-Authors: A Airapetian, N Akopov, Z Akopov, M Amarian, A Andrus, E C Aschenauer, W Augustyniak, R Avakian, A Avetissian, E AvetissianAbstract:Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic Scattering of positrons are measured for the first time with transverse target polarization. The asymmetry depends on the azimuthal angles of both the pion ($\ensuremath{\phi}$) and the target spin axis (${\ensuremath{\phi}}_{S}$) about the virtual-photon direction and relative to the lepton Scattering Plane. The extracted Fourier component $\mathbf{⟨}\mathrm{sin}(\ensuremath{\phi}+{\ensuremath{\phi}}_{S}){\mathbf{⟩}}_{UT}^{\ensuremath{\pi}}$ is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component $\mathbf{⟨}\mathrm{sin}(\ensuremath{\phi}\ensuremath{-}{\ensuremath{\phi}}_{S}{\mathbf{⟩}}_{UT}^{\ensuremath{\pi}}$ arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production.
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measurement of single spin azimuthal asymmetries in semi inclusive electroproduction of pions and kaons on a longitudinally polarised deuterium target
Physics Letters B, 2003Co-Authors: A Airapetian, N Akopov, Z Akopov, M Amarian, V V Ammosov, A Andrus, E C Aschenauer, W Augustyniak, H Avakian, R AvakianAbstract:Abstract Single-spin asymmetries have been measured for semi-inclusive electroproduction of π + , π − , π 0 and K + mesons in deep-inelastic Scattering off a longitudinally polarised deuterium target. The asymmetries appear in the distribution of the hadrons in the azimuthal angle φ around the virtual photon direction, relative to the lepton Scattering Plane. The corresponding analysing powers in the sin φ moment of the cross section are 0.012±0.002(stat.)±0.002(syst.) for π + , 0.006±0.003(stat.)±0.002(syst.) for π − , 0.021±0.005(stat.)±0.003(syst.) for π 0 and 0.013±0.006(stat.)±0.003(syst.) for K + . The sin2 φ moments are compatible with zero for all particles.
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measurement of the beam spin azimuthal asymmetry associated with deeply virtual compton Scattering
Physical Review Letters, 2001Co-Authors: A Airapetian, N Akopov, Z Akopov, M Amarian, E C Aschenauer, H Avakian, R Avakian, A Avetissian, E Avetissian, P BaileyAbstract:The beam-spin asymmetry in hard electroproduction of photons has been measured. The data have been accumulated by the HERMES experiment at DESY using the HERA 27.6 GeV longitudinally polarized positron beam and an unpolarized hydrogen-gas target. The asymmetry in the azimuthal distribution of the produced photons in the angle φ relative to the lepton Scattering Plane was determined with respect to the helicity state of the incoming positron beam. The beam-spin analyzing power in the sinφ moment was measured to be -0.23±0.04(stat)±0.03(syst) in the missing-mass range below 1.7 GeV. The observed asymmetry is attributed to the interference of the Bethe-Heitler and deeply virtual Compton Scattering processes.
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evidence for a single spin azimuthal asymmetry in semi inclusive pion electroproduction
Physical Review Letters, 2000Co-Authors: A Airapetian, M Amarian, E C Aschenauer, J Blouw, H J Bulten, De Witt P K A Huberts, M Guidal, Th Henkes, H Ihssen, M KolsteinAbstract:Single-spin asymmetries for semi-inclusive pion production in deep-inelastic Scattering have been measured for the first time. A significant target-spin asymmetry of the distribution in the azimuthal angle φ of the pion relative to the lepton Scattering Plane was formed for π^+ electroproduction on a longitudinally polarized hydrogen target. The corresponding analyzing power in the sinφ moment of the cross section is 0.022±0.005±0.003. This result can be interpreted as the effect of terms in the cross section involving chiral-odd spin distribution functions in combination with a chiral-odd fragmentation function that is sensitive to the transverse polarization of the fragmenting quark.
Matthew M Knight - One of the best experts on this subject based on the ideXlab platform.
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hubble space telescope pre perihelion acs wfc imaging polarimetry of comet ison c 2012 s1 at 3 81 au
The Astrophysical Journal, 2013Co-Authors: Dean C Hines, Gorden Videen, Evgenij Zubko, Karri Muinonen, Yuriy Shkuratov, V G Kaydash, Matthew M KnightAbstract:We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (r h = 3.81 AU, Δ = 4.34 AU), when the phase angle was α ≈ 1216. This phase angle is approximately centered in the negative polarization branch for cometary dust. The region beyond 1000 km (~0.32 arcsec ≈ 6 pixels) from the nucleus shows a negative polarization amplitude of p% ~ –1.6%. Within 1000 km of the nucleus, the polarization position angle rotates to be approximately perpendicular to the Scattering Plane, with an amplitude p% ~ +2.5%. Such positive polarization has been observed previously as a characteristic feature of cometary jets, and we show that Comet ISON does indeed harbor a jet-like feature. These HST observations of Comet ISON represent the first visible light, imaging polarimetry with subarcsecond spatial resolution of a Nearly Isotropic Comet beyond 3.8 AU from the Sun at a small phase angle. The observations provide an early glimpse of the properties of the cometary dust preserved in this Oort-Cloud comet.
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hubble space telescope pre perihelion acs wfc imaging polarimetry of comet ison c 2012 s1 at 3 81 au
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: Dean C Hines, Gorden Videen, Evgenij Zubko, Karri Muinonen, Yuriy Shkuratov, V G Kaydash, Matthew M KnightAbstract:We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (rh = 3.81 AU, Delta = 4.34 AU), when the phase angle was alpha = 12.16 degrees. This phase angle is approximately centered in the negative polarization branch for cometary dust. The region beyond 1000 km from the nucleus shows a negative polarization amplitude of p% -1.6%. Within 1000 km of the nucleus, the polarization position angle rotates to be approximately perpendicular to the Scattering Plane, with an amplitude p% +2.5%. Such positive polarization has been observed previously as a characteristic feature of cometary jets, and we show that Comet ISON does indeed harbor a jet-like feature. These HST observations of Comet ISON represent the first visible light, imaging polarimetry with sub-arcsecond spatial resolution of a Nearly Isotropic Comet (NIC) beyond 3.8 AU from the Sun at a small phase angle. The observations provide an early glimpse of the properties of the cometary dust preserved in this Oort-cloud comet.
Gorden Videen - One of the best experts on this subject based on the ideXlab platform.
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hubble space telescope pre perihelion acs wfc imaging polarimetry of comet ison c 2012 s1 at 3 81 au
The Astrophysical Journal, 2013Co-Authors: Dean C Hines, Gorden Videen, Evgenij Zubko, Karri Muinonen, Yuriy Shkuratov, V G Kaydash, Matthew M KnightAbstract:We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (r h = 3.81 AU, Δ = 4.34 AU), when the phase angle was α ≈ 1216. This phase angle is approximately centered in the negative polarization branch for cometary dust. The region beyond 1000 km (~0.32 arcsec ≈ 6 pixels) from the nucleus shows a negative polarization amplitude of p% ~ –1.6%. Within 1000 km of the nucleus, the polarization position angle rotates to be approximately perpendicular to the Scattering Plane, with an amplitude p% ~ +2.5%. Such positive polarization has been observed previously as a characteristic feature of cometary jets, and we show that Comet ISON does indeed harbor a jet-like feature. These HST observations of Comet ISON represent the first visible light, imaging polarimetry with subarcsecond spatial resolution of a Nearly Isotropic Comet beyond 3.8 AU from the Sun at a small phase angle. The observations provide an early glimpse of the properties of the cometary dust preserved in this Oort-Cloud comet.
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hubble space telescope pre perihelion acs wfc imaging polarimetry of comet ison c 2012 s1 at 3 81 au
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: Dean C Hines, Gorden Videen, Evgenij Zubko, Karri Muinonen, Yuriy Shkuratov, V G Kaydash, Matthew M KnightAbstract:We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (rh = 3.81 AU, Delta = 4.34 AU), when the phase angle was alpha = 12.16 degrees. This phase angle is approximately centered in the negative polarization branch for cometary dust. The region beyond 1000 km from the nucleus shows a negative polarization amplitude of p% -1.6%. Within 1000 km of the nucleus, the polarization position angle rotates to be approximately perpendicular to the Scattering Plane, with an amplitude p% +2.5%. Such positive polarization has been observed previously as a characteristic feature of cometary jets, and we show that Comet ISON does indeed harbor a jet-like feature. These HST observations of Comet ISON represent the first visible light, imaging polarimetry with sub-arcsecond spatial resolution of a Nearly Isotropic Comet (NIC) beyond 3.8 AU from the Sun at a small phase angle. The observations provide an early glimpse of the properties of the cometary dust preserved in this Oort-cloud comet.
Karri Muinonen - One of the best experts on this subject based on the ideXlab platform.
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hubble space telescope pre perihelion acs wfc imaging polarimetry of comet ison c 2012 s1 at 3 81 au
The Astrophysical Journal, 2013Co-Authors: Dean C Hines, Gorden Videen, Evgenij Zubko, Karri Muinonen, Yuriy Shkuratov, V G Kaydash, Matthew M KnightAbstract:We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (r h = 3.81 AU, Δ = 4.34 AU), when the phase angle was α ≈ 1216. This phase angle is approximately centered in the negative polarization branch for cometary dust. The region beyond 1000 km (~0.32 arcsec ≈ 6 pixels) from the nucleus shows a negative polarization amplitude of p% ~ –1.6%. Within 1000 km of the nucleus, the polarization position angle rotates to be approximately perpendicular to the Scattering Plane, with an amplitude p% ~ +2.5%. Such positive polarization has been observed previously as a characteristic feature of cometary jets, and we show that Comet ISON does indeed harbor a jet-like feature. These HST observations of Comet ISON represent the first visible light, imaging polarimetry with subarcsecond spatial resolution of a Nearly Isotropic Comet beyond 3.8 AU from the Sun at a small phase angle. The observations provide an early glimpse of the properties of the cometary dust preserved in this Oort-Cloud comet.
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hubble space telescope pre perihelion acs wfc imaging polarimetry of comet ison c 2012 s1 at 3 81 au
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: Dean C Hines, Gorden Videen, Evgenij Zubko, Karri Muinonen, Yuriy Shkuratov, V G Kaydash, Matthew M KnightAbstract:We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (rh = 3.81 AU, Delta = 4.34 AU), when the phase angle was alpha = 12.16 degrees. This phase angle is approximately centered in the negative polarization branch for cometary dust. The region beyond 1000 km from the nucleus shows a negative polarization amplitude of p% -1.6%. Within 1000 km of the nucleus, the polarization position angle rotates to be approximately perpendicular to the Scattering Plane, with an amplitude p% +2.5%. Such positive polarization has been observed previously as a characteristic feature of cometary jets, and we show that Comet ISON does indeed harbor a jet-like feature. These HST observations of Comet ISON represent the first visible light, imaging polarimetry with sub-arcsecond spatial resolution of a Nearly Isotropic Comet (NIC) beyond 3.8 AU from the Sun at a small phase angle. The observations provide an early glimpse of the properties of the cometary dust preserved in this Oort-cloud comet.
