130 research outputs found
On the beam spin asymmetries of electroproduction of charged hadrons off the nucleon targets
We study the beam single-spin asymmetries for charged
hadrons produced in semi-inclusive deep inelastic scattering process, by
considering the term and the term simultaneously.
Besides the asymmetries for charged pions, for the first time we present the
analysis on the asymmetries in the production of charged kaons, protons and
antiprotons by longitudinally polarized leptons scattered off unpolarized
proton and deuteron targets. In our calculation we use two sets of transverse
momentum dependent distributions and
calculated from two different spectator models, and compare the numerical
results with the preliminary data recently obtained by the HERMES
Collaboration. We also predict the beam spin asymmetries for ,
, electroproduction in semi-inclusive deep-inelastic
scattering of 12 GeV polarized electrons from unpolarized proton and deuteron
targets.Comment: 9 pages, 6 figures, version accepted by EPJ
Beam Spin Asymmetries of Charged and Neutral Pion Productions in Semi-inclusive DIS
We present a study on the beam single spin asymmetries
of , and production in semi-inclusive deep inelastic
scattering process, by considering Collins effect and the term
simultaneously. We calculate the twist-3 distributions and
for the valence quarks inside the proton in a spectator
model. We consider two different options for the form of diquark propagator, as
well as two different choices for the model parameters in the calculation.
Using the model results, we estimate the beam spin asymmetries
for the charged and neutral pions and compare the results
with the measurement from the HERMES Collaboration. We also make predictions on
the asymmetries at CLAS with a beam using the same model
results. It is found that different choices for the diquark propagator will not
only lead to different expressions for the distribution functions, but also
result in different sizes of the asymmetries. Our study also shows that,
although the spectator model calculation can describe the asymmetries for
certain pion production in some kinematic regions, it seems difficult to
explain the asymmetries of pion production for all three pions in a consistent
way from the current versions.Comment: 9 pages, 8 figure
Transverse single-spin asymmetries of pion production in semi-inclusive DIS at subleading twist
We study the single-spin asymmetries with the and angular dependences for charged and neutral pions produced in
semi-inclusive deep inelastic scattering on the transversely polarized proton
target. The theoretical interpretations of the two asymmetries are presented in
terms of the convolution of the twist-3 quark transverse momentum dependent
distributions and twist-2 fragmentation functions. Specifically, we investigate
the role of the distributions , and in the
asymmetry, as well as the role of the distributions , and
in the asymmetry. We calculate these
distributions in a spectator-diquark model and predict the corresponding
asymmetries for the first time, considering the kinematics at HERMES, JLab and
COMPASS. The numerical estimates show that the asymmetries are sizable, and the
dominant contribution to the asymmetry comes from the T-odd
distribution , while gives the main contribution to the
asymmetry. The future measurements on these asymmetries
can shed light on the information of twist-3 transverse momentum dependent
distributions.Comment: 11 pages, 12 figures, version published in PR
Boer-Mulders effect in the unpolarized pion induced Drell-Yan process at COMPASS within TMD factorization
We investigate the theoretical framework of the azimuthal
asymmetry contributed by the coupling of two Boer-Mulders functions in the
dilepton production unpolarized Drell-Yan process by applying the
transverse momentum dependent factorization at leading order. We adopt the
model calculation results of the unpolarized distribution function and
Boer-Mulders function of pion meson from the light-cone wave
functions. We take into account the transverse momentum evolution effects for
both the distribution functions of pion and proton by adopting the existed
extraction of the nonperturbative Sudakov form factor for the pion and proton
distribution functions. An approximate kernel is included to deal with the
energy dependence of the Boer-Mulders function related twist-3 correlation
function needed in the calculation. We numerically
estimate the Boer-Mulders asymmetry as the functions of ,
, and considering the kinematics at COMPASS Collaboration.Comment: 11 pages, 2 figures, typos correcte
Double Spin Asymmetries and in semi-inclusive DIS
We investigate the double spin asymmetries of pion production in
semi-inclusive deep inelastic scattering with a longitudinal polarized beam off
a transversely polarized proton target. Particularly, we consider the
and modulations, which can be interpreted
by the convolution of the twist-3 transverse momentum dependent distributions
and twist-2 fragmentation functions. Three different origins are taken into
account simultaneously for each asymmetry: the term, the term, and the term in the
asymmetry; and the term, the term, and the
term in the asymmetry. We
calculate the four twist-3 distributions ,
, , and
in a spectator-diquark model including vector
diquarks. Then we predict the two corresponding asymmetries for charged and
neutral pions at the kinematics of HERMES, JLab, and COMPASS for the first
time. The numerical estimates indicate that the two different
angular-dependence asymmetries are sizable by several percent at HERMES and
JLab, and the asymmetry has a strong dependence on the Bjorken
. Our predictions also show that the dominant contribution to the
asymmetry comes from the term, while the
term gives the main contribution to the asymmetry; the
other two -odd terms almost give negligible contributions. In particular,
the asymmetry provides a unique opportunity to probe
the distribution .Comment: minor revision, match the published version in PRD. arXiv admin note:
text overlap with arXiv:1405.387
Last-Layer Fairness Fine-tuning is Simple and Effective for Neural Networks
As machine learning has been deployed ubiquitously across applications in
modern data science, algorithmic fairness has become a great concern and
varieties of fairness criteria have been proposed. Among them, imposing
fairness constraints during learning, i.e. in-processing fair training, has
been a popular type of training method because they don't require accessing
sensitive attributes during test time in contrast to post-processing methods.
Although imposing fairness constraints have been studied extensively for
classical machine learning models, the effect these techniques have on deep
neural networks is still unclear. Recent research has shown that adding
fairness constraints to the objective function leads to severe over-fitting to
fairness criteria in large models, and how to solve this challenge is an
important open question. To address this challenge, we leverage the wisdom and
power of pre-training and fine-tuning and develop a simple but novel framework
to train fair neural networks in an efficient and inexpensive way. We conduct
comprehensive experiments on two popular image datasets with state-of-art
architectures under different fairness notions to show that last-layer
fine-tuning is sufficient for promoting fairness of the deep neural network.
Our framework brings new insights into representation learning in training fair
neural networks
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