62 research outputs found
Transverse single-spin asymmetries in proton-proton collisions at the AFTER@LHC experiment
We present results for transverse single-spin asymmetries in proton-proton
collisions at kinematics relevant for AFTER, a proposed fixed-target experiment
at the Large Hadron Collider. These include predictions for pion, jet, and
direct photon production from analytical formulas already available in the
literature. We also discuss specific measurements that will benefit from the
higher luminosity of AFTER, which could help resolve an almost 40-year puzzle
of what causes transverse single-spin asymmetries in proton-proton collisions.Comment: 10 pages, 4 figures; more details/discussion added to the text,
references added/updated, version to appear in Advances in High Energy
Physics for the Special Issue "Physics at a Fixed-Target Experiment Using the
LHC Beams
Small- Asymptotics of the Quark Helicity Distribution: Analytic Results
In this Letter, we analytically solve the evolution equations for the
small- asymptotic behavior of the (flavor singlet) quark helicity
distribution in the large- limit. These evolution equations form a set of
coupled integro-differential equations, which previously could only be solved
numerically. This approximate numerical solution, however, revealed simplifying
properties of the small- asymptotics, which we exploit here to obtain an
analytic solution. We find that the small- power-law tail of the quark
helicity distribution scales as with , in excellent agreement with the numerical estimate obtained previously. We then
verify this solution by cross-checking the predicted scaling behavior of the
auxiliary "neighbor dipole amplitude" against the numerics, again finding
excellent agreement.Comment: 5 pages, 2 figure
Single-spin asymmetries in the leptoproduction of transversely polarized hyperons
We analyze single-spin asymmetries (SSAs) in the leptoproduction of
transversely polarized hyperons within the collinear twist-3
formalism. We calculate both the distribution and fragmentation terms in two
different gauges (lightcone and Feynman) and show that the results are
identical. This is the first time that the fragmentation piece has been
analyzed for transversely polarized hadron production within the collinear
twist-3 framework. In lightcone gauge we use the same techniques that were
employed in computing the analogous piece in , which
has become an important part to that reaction. With this in mind, we also
verify the gauge invariance of the formulas for the transverse SSA in the
leptoproduction of pions.Comment: 12 pages, 1 figure, reference added, version to appear in Phys. Lett.
Longitudinal-transverse double-spin asymmetries in single-inclusive leptoproduction of hadrons
We analyze the longitudinal-transverse double-spin asymmetry in
lepton-nucleon collisions where a single hadron is detected in the final state,
i.e., . This is a subleading-twist
observable in collinear factorization, and we look at twist-3 effects in both
the transversely polarized nucleon and the unpolarized outgoing hadron. Results
are anticipated for this asymmetry from both HERMES and Jefferson Lab Hall A,
and it could be measured as well at COMPASS and a future Electron-Ion Collider.
We also perform a numerical study of the distribution term, which, when
compared to upcoming experimental results, could allow one to learn about the
"worm-gear"-type function as well as assess the role of
quark-gluon-quark correlations in the initial-state nucleon and twist-3 effects
in the fragmenting unpolarized hadron.Comment: 14 pages, 7 figures, minor changes to the text, version to appear in
Phys. Lett.
Transversity distributions and tensor charges of the nucleon: extraction from dihadron production and their universal nature
We perform the first global quantum chromodynamics (QCD) analysis of dihadron
production for a comprehensive set of data in electron-positron annihilation,
semi-inclusive deep-inelastic scattering, and proton-proton collisions, from
which we extract simultaneously the transversity distributions of the nucleon
and dihadron fragmentation functions. We incorporate in our fits
known theoretical constraints on transversity, namely, its small- asymptotic
behavior and the Soffer bound. We furthermore show that lattice-QCD results for
the tensor charges can be successfully included in the analysis. This resolves
the previously reported incompatibility between the tensor charges extracted
from dihadron production data and lattice QCD. We also find agreement with
results for the transversity and tensor charges obtained from measurements on
single-hadron production. Overall, our work demonstrates for the first time the
universal nature of all available information for the transversity
distributions and the tensor charges of the nucleon
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