1,171 research outputs found
Unveiling the Proton Spin Decomposition at a Future Electron-Ion Collider
We present a detailed assessment of how well a future Electron-Ion Collider
could constrain helicity parton distributions in the nucleon and, therefore,
unveil the role of the intrinsic spin of quarks and gluons in the proton's spin
budget. Any remaining deficit in this decomposition will provide the best
indirect constraint on the contribution due to the total orbital angular
momenta of quarks and gluons. Specifically, all our studies are performed in
the context of global QCD analyses based on realistic pseudo-data and in the
light of the most recent data obtained from polarized proton-proton collisions
at BNL-RHIC that have provided evidence for a significant gluon polarization in
the accessible, albeit limited range of momentum fractions. We also present
projections on what can be achieved on the gluon's helicity distribution by the
end of BNL-RHIC operations. All estimates of current and projected
uncertainties are performed with the robust Lagrange multiplier technique.Comment: 12 pages, 8 eps figure
A Fiber Detector Radiation Hardness Test
An intense 146 MeV/c pion beam was stopped inside a scintillating fiber
detector made out of 12 planes with 16 pixels each, where every pixel consists
out of 8 times 8 scintillating fibers of 500 mkm diameter dense packed. The
detector was irradiated for 52 hours to more than 1 Mrad at its center. Before
and directly after the irradiation the detector has been exposed to a particle
beam to compare the corresponding light output. This study was continued during
the following three months using cosmic rays. No damage was found taking into
account the measurement errors of 5-10 %. In contrast a 9 cm deep lucite
degrader became irreversibly non-transparent in the irradiation region.Comment: 16 pages, 11 figure
Determination of electron-nucleus collision geometry with forward neutrons
There are a large number of physics programs one can explore in
electron-nucleus collisions at a future electron-ion collider. Collision
geometry is very important in these studies, while the measurement for an
event-by-event geometric control is rarely discussed in the prior deep
inelastic scattering experiments off a nucleus. This paper seeks to provide
some detailed studies on the potential of tagging collision geometries through
forward neutron multiplicity measurements with a zero degree calorimeter. This
type of geometry handle, if achieved, can be extremely beneficial in
constraining nuclear effects for the electron-nucleus program at an
electron-ion collider
Probing Gluon Saturation through Dihadron Correlations at an Electron-Ion Collider
Two-particle azimuthal angle correlations have been proposed to be one of the
most direct and sensitive probes to access the underlying gluon dynamics
involved in hard scatterings. In anticipation of an Electron-Ion Collider
(EIC), detailed studies of dihadron correlation measurements in electron-proton
and electron-ion collisions at an EIC have been performed. The impact of such
measurements on the understanding of the different gluon distribution
functions, as a clean signature for gluon saturation and to constrain
saturation models further, has been explored. It is shown that dihadron
correlation measurements will be one of the key methods to probe gluon
saturation phenomena at a future EIC.Comment: 13 pages, 13 eps figure
Helicity Parton Distributions at a Future Electron-Ion Collider: A Quantitative Appraisal
We present a quantitative assessment of the impact a future electron-ion
collider will have on determinations of helicity quark and gluon densities and
their contributions to the proton spin. Our results are obtained by performing
a series of global QCD analyses at next-to-leading order accuracy based on
realistic sets of pseudo-data for the inclusive and semi-inclusive
deep-inelastic scattering of longitudinally polarized electrons and protons at
different, conceivable center-of-mass system energies.Comment: 11 pages, 8 figure
Predictions for Sivers single spin asymmetries in one- and two-hadron electroproduction at CLAS12 and EIC
The study of the Sivers effect, describing correlations between the
transverse polarization of the nucleon and its constituent (unpolarized)
parton's transverse momentum, has been the topic of a great deal of
experimental, phenomenological and theoretical effort in recent years.
Semi-inclusive deep inelastic scattering measurements of the corresponding
single spin asymmetries (SSA) at the upcoming CLAS12 experiment at JLab and the
proposed Electron-Ion Collider will help to pinpoint the flavor structure and
the momentum dependence of the Sivers parton distribution function describing
this effect. Here we describe a modified version of the Monte
Carlo event generator that includes the Sivers effect. Then we use it to
estimate the size of these SSAs, in the kinematics of these experiments, for
both one and two hadron final states of pions and kaons. For this purpose we
utilize the existing Sivers parton distribution function (PDF) parametrization
extracted from HERMES and COMPASS experiments. Using this modified version of
, we also show that the the leading order approximation commonly
used in such extractions may provide significantly underestimated values of
Sivers PDFs, as in our Monte Carlo simulations the omitted parton showers and
non-DIS processes play an important role in these SSAs, for example in the
COMPASS kinematics.Comment: 18 pages, 27 figures. V2: updated to version published in PRD, two
references have been added and some minor changes done to the tex
Reply to Comment on "Reevaluation of the parton distribution of strange quarks in the nucleon"
A Comment on the recently published reevaluation of the polarization-averaged
parton distribution of strange quarks in the nucleon using final data on the
multiplicities of charged kaons in semi-inclusive deep-inelastic scattering is
reviewed. Important features of the comparison of one-dimensional projections
of the multidimensional HERMES data are pointed out. A test of the
leading-order extraction of xS(x) using the difference between charged-kaon
multiplicities is repeated. The results are consistent with leading-order
predictions within the uncertainties in the input data, and do not invalidate
the earlier extraction of xS(x).Comment: Reply Comment to arXiv:1407.372
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