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SUMMARY:First L/T separation of $\\pi^0$ electroproduction from Jefferson
Laboratory Hall A
DTSTART;VALUE=DATE-TIME:20150429T144500Z
DTEND;VALUE=DATE-TIME:20150429T151000Z
DTSTAMP;VALUE=DATE-TIME:20191118T090922Z
UID:indico-contribution-1739335@indico.cern.ch
DESCRIPTION:Speakers: Maxime DEFURNE (CEA)\nThe deeply virtual $\\pi^0$ pr
oduction cross section can be decomposed according to the polarization of
the virtual photon.\n\\begin{equation}\n\\frac{d\\sigma}{dt}=\\frac{d\\sig
ma_T}{dt}+\\epsilon \\frac{d\\sigma_L}{dt}+\\sqrt{2\\epsilon (\\epsilon+1)
}\\frac{d\\sigma_{TL}}{dt} \\cos(\\phi)+\\epsilon \\frac{d\\sigma_{TT}}{dt
} \\cos(2\\phi)\n\\end{equation}\nwhere $\\epsilon$ represents the degree
of polarization of the virtual photon and $\\phi$ the angle between the le
ptonic and the hadronic plane. \n\nThe unseparated $\\pi^0$ electroproduct
ion cross sections have been extracted in the Halls A and B of Jefferson L
aboratory. Using the $\\phi$-dependence\, both experiments measured a larg
e $\\sigma=\\sigma_T+\\epsilon \\sigma_L$. However generalized parton dist
ributions-based models predict a small contribution $\\sigma_L$ in a theor
etical framework where factorization has only been proven for longitudinal
polarized photons.\n\nAssuming the validity of factorization for transver
se photons\, Kroll and Goloskokov developed a model where the transversity
GPDs would couple to the twist-3 distribution amplitudes of the pion\, am
plifying the $\\sigma_T$ signal. In order to verify this prediction\, the
E07-007 experiment measured the $\\pi^0$ electroproduction cross section o
n proton in the Hall A of Jefferson Laboratory. Using two beam energies to
measure the cross section at same $Q^2$ and $x_B$\, we change the $\\epsi
lon$ value and are able to separate the transverse from the longitudinal c
ontribution. For the first time\, I will present the fully separated $\\pi
^0$ electroproduction cross section and compare it to the existing models.
\n\nhttps://indico.cern.ch/event/341292/contributions/1739335/
LOCATION: BALLROOM EAST
URL:https://indico.cern.ch/event/341292/contributions/1739335/
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