John Collins
(Penn State University)
28/04/2015, 09:00
WG6 Spin Physics
In using transverse-momentum-dependent (TMD) parton densities and
fragmentation functions, important non-perturbative information is at
large transverse position $b_T$. This concerns both the TMD functions
and their evolution. Fits to high energy data tend to predict too
rapid evolution when extrapolated to low energies where larger values
of $b_T$ dominate. I summarize a new analysis...
Prof.
Yuji Koike
(Niigata University)
28/04/2015, 09:25
WG6 Spin Physics
In this talk, I will present an overview on the current status of the analyses of the
spin asymmetries, in particular, single spin asymmetries, using the framework of
the collinear twist-3 (CT3) factorization.
In this framework, twist-3 quark-gluon or three-gluon correlation functions
in the initial nucleon and the twist-3 fragmentation function for the final hadron
play a critical...
Daniel Pitonyak
(Brookhaven National Lab)
28/04/2015, 09:50
WG6 Spin Physics
Transverse single-spin asymmetries (TSSAs), denoted A_N, in single-inclusive hard scattering processes are fundamental observables to test perturbative QCD that have been around for almost 40 years. However, many open issues remain as to the origin of TSSAs. Currently two theoretical formalisms are widely used: collinear twist-3 (CT3) factorization and the Generalized Parton Model (GPM). We...
Anselm Vossen
(Indiana University)
28/04/2015, 10:45
WG6 Spin Physics
Fragmentation functions are fundamental objects that describe the process by which partons hadronize to colorless hadrons.
Precision measurements of fragmentation functions are necessary for the extraction of most aspects of the nucleon structure from semi-inclusive deep inelastic scattering and p+p collision data.
Examples are transverse polarization dependent fragmentation functions that...
Isabella Garzia
(INFN)
28/04/2015, 11:10
WG6 Spin Physics
Inclusive hadron production cross sections and angular distributions in
e+e- collisions shed light on fundamental questions of hadronization and
fragmentation processes. We present measurements of the so-called Collins azimuthal asymmetries in inclusive production of hadron pairs, in the e+e- -> h1 h2 X annihilation process, where the two hadrons (either kaon or pions) are produced in...
Isabella Garzia
(INFN)
28/04/2015, 11:35
WG6 Spin Physics
There has been increasing interest in understanding the spin phenomena in the nucleon, such as the transverse spin structure (the so-called transversity). The semi-inclusive observables in SIDIS experiments are only connected to the product of quark transversity distribution and the Collins fragmentation function (FF). An independent measurement of the Collins FFs in e+e- annihilation makes...
Dr
Erin SEDER
(CEA Saclay, DSM/IRFU/SPhN)
28/04/2015, 12:00
WG6 Spin Physics
The latest measurements of $K^{\pm}$ multiplicities in semi-inclusive deep-inelastic scattering from the COMPASS experiment at CERN are presented. The data were collected using a $160$ $GeV$ muon beam incident on an isoscalar $^{6}LiD$ target. The large statistics collected cover a wide kinematic range and the results are presented in 3-dimensional bins of $x_{Bjorken}$, $y$, and $z$. These...
Wenjuan Mao
(Southeast University)
28/04/2015, 14:00
WG6 Spin Physics
We study the single-spin asymmetries with the $\sin\phi_S$
and $\sin(2\phi_h -\phi_S)$ angular dependencies of pion production in semi-inclusive deep inelastic scattering off a transversely polarized proton target. We investigate the role of the distributions $f_T$, $h_T$ and $h_T^\perp$ in the $\sin\phi_S$ asymmetry, as well as the role of the distributions $f_T^\perp$, $h_T$ and $h_T^\perp$...
Mr
Peter Lowdon
(University of Zurich)
28/04/2015, 14:25
WG6 Spin Physics
The decomposition of nucleon spin into spin and orbital angular momentum contributions from partons is revisited in the context of quantum field theory. It is shown that commonly used decompositions rely on classical-type arguments for their justification, and that these arguments may no longer hold in the full quantum theory, in particular with respect to the treatment of boundary terms. The...
Dr
LINGYUN DAI
(Indiana University)
28/04/2015, 14:50
WG6 Spin Physics
We study the Sivers asymmetry in semi-inclusive hadron production in deep inelastic scattering. In particular, we concentrate on the contribution from the photon-gluon fusion channel, where the three-gluon correlation functions play the major role within a twist-3 collinear factorization formalism. We establish the matching between such a formalism and the usual transverse momentum dependent...
Harleen Dahiya
(Dr. B.R. Ambedkar National Institute of Technology)
28/04/2015, 15:15
WG6 Spin Physics
The axial-vector form factors of the low lying octet baryons ($N$, $\Sigma$, $\Xi$ and $\Lambda$) have been studied for the implications of chiral symmetry breaking and SU(3) symmetry breaking for the singlet ($g^0_{A}$) and non-singlet ($g^3_{A}$ and $g^8_{A}$) axial-vector coupling constants. In addition to studying the total strange singlet and non-singlet contents ($G_s^0(Q^2)$,...
Mr
giulio sbrizzai
(Trieste University and INFN)
28/04/2015, 16:15
WG6 Spin Physics
Recent results on the transverse spin azimuthal asymmetries in
semi-inclusive DIS reactions extracted by the COMPASS Collaboration
from the data collected with a transversely polarised proton target
are presented.
In particular, the interesting kinematical dependencies shown by the Collins
and Sivers asymmetries have been further investigated in a multi-dimensional analysis in x, Q^2, z...
Dr
Salvatore Fazio
(Brookhaven National Laboratory)
28/04/2015, 16:40
WG1 Structure Functions and Parton Densities
We present the status and preliminary results on the analysis of kinematically fully reconstructed weak bosons at the STAR experiment.
The transverse single spin asymmetry ($A_{N}$) has been measured in transversely
polarized proton-proton collisions at $\sqrt{s} = 500$~GeV, with a recorded integrated luminosity of $25~\text{pb}^{-1}$.
The measured observable is sensitive to the...
J. Osvaldo Gonzalez H.
(University of Turin)
28/04/2015, 17:05
WG6 Spin Physics
In order to describe SIDIS over a wide region of transverse momentum qT , one must confront both the perturbative and non-perturbative regimes. In this sense, when extracting the non-perturbative TMDs from experimental data, one should ensure that there exists a smooth transition between the soft gluon resummation regime and the pQCD predictions, at large qT. We present recent results on the...
Aurore Courtoy
(IFPA)
28/04/2015, 17:30
WG6 Spin Physics
We present an updated extraction of the valence transversity PDF using the most recent COMPASS data with identified pion pairs. The new analysis was carried out using the replica method for both the chiral-odd DiFF and the transversity PDF. This picture represents the current most realistic estimate of the uncertainties on our knowledge of the valence components of the transversity function...
Prof.
simonetta liuti
(university of virginia)
29/04/2015, 08:30
WG6 Spin Physics
We discuss the canonical (Ji) and kinetic/mechanical (Jaffe and Manohar)
definitions of partonic orbital angular momentum (OAM). It was recently
shown by Hatta and Burkardt that the two definitions correspond to the
second moment in intrinsic k_T of the same generalized transverse momentum
distribution (GTMD), while they differ in their gauge link structure. At
the same time, as...
Philipp Karl Jorg
(Albert-Ludwigs-Universitaet Freiburg (DE))
29/04/2015, 08:55
WG6 Spin Physics
A major part of the COMPASS-II program will be dedicated to the investigation of generalized parton distributions (GPDs)
and transverse momentum dependent parton distributions (TMDs), which aim for the most complete
description of the partonic structure of the nucleon.
GPDs are experimentally accessible via lepton-induced exclusive reactions, in particular
the Deeply Virtual Compton...
Carlos Munoz Camacho
29/04/2015, 09:20
WG6 Spin Physics
Deeply Virtual Compton Scattering (DVCS) is the easiest reaction that probes the Generalized Parton Distributions (GPDs) of the nucleon. GPDs offer the exciting possibility of mapping the 3-D internal structure of protons and neutrons by providing a transverse image of the constituents as a function of their longitudinal momentum.
An extensive experimental program is currently pursued at...
Mr
Maxime DEFURNE
(CEA)
29/04/2015, 09:45
WG6 Spin Physics
The deeply virtual $\pi^0$ production cross section can be decomposed according to the polarization of the virtual photon.
\begin{equation}
\frac{d\sigma}{dt}=\frac{d\sigma_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)
\end{equation}
where $\epsilon$ represents the degree of polarization of...
Kazuhiro Tanaka
29/04/2015, 10:45
WG6 Spin Physics
The measurement of exclusive mesoproduction of lepton pair, $\pi^- p \to \ell^+ \ell^- n$, may be performed using the high-intensity pion beams at J-PARC in the near future. The leading hard exclusive amplitude for this process was obtained by E.R. Berger, M. Diehl, and B. Pire [Phys. Lett. B 523 (2001) 265] in terms of the partonic subprocess convoluted with the relevant nonperturbative...
Pawel Sznajder
(National Centre for Nuclear Research (PL))
29/04/2015, 11:10
WG6 Spin Physics
Hard exclusive leptoproduction of mesons on nucleons has played an important role in studies of the hadron structure and recently gained a renewed interest as it allows an access to generalised parton distributions (GPDs). The GPDs provide a novel and comprehensive description of the nucleon partonic structure and contain a wealth of new information. In particular, the GPDs give a description...
Andreas Metz
(Temple University, Philadelphia)
29/04/2015, 11:35
WG6 Spin Physics
In this talk we will address new theoretical work on twist-3 spin asymmetries for the process l + N -> h + X, for which recent data have been obtained. Specifically, we will address the longitudinal-transverse double-spin asymmetry A_LT, and the transverse single-spin asymmetry A_N for a polarized final state hyperon. Open questions and future prospects will be mentioned as well.
Carlos Granados
(Uppsala University)
29/04/2015, 12:00
WG6 Spin Physics
The nucleon's peripheral transverse charge and magnetization densities are computed in chiral effective field theory in the light--front formulation. The densities are represented in first--quantized form, as overlap integrals of chiral light--front wave functions describing
the transition of the nucleon to soft pion--nucleon intermediate states. The new representation leads to a simple...
Hari Guragain
(PHENIX Collaboration)
29/04/2015, 14:00
WG6 Spin Physics
One of the major objectives of the RHIC spin program at BNL is the
measurement of the gluon helicity contribution, $\Delta G$, to the proton spin via
measuring the double longitudinal spin asymmetry ($A_{LL}$) in various
channels. In PHENIX (Pioneering High Energy Nuclear Interaction
eXperiment) the $A_{LL}$ in $\pi^{0}$, $\eta$, $J/\psi$ etc. are measured in wide...
Dr
Xuan Li
(Temple University)
29/04/2015, 14:25
WG6 Spin Physics
Inclusive jet- and di-jet productions in polarized p+p collisions at $\sqrt{s} = 200$ GeV and $\sqrt{s} = 500$ GeV provide powerful probes to study gluons inside the proton. Inclusive jet production is sensitive to the integral of the gluon distribution over a broad range of $x$. Di-jet production provides better sensitivity to $x$ dependence of gluons. The Solenoidal Tracker at RHIC (STAR)...
DEVIKA S GUNARATHNE
(urn:Google)
29/04/2015, 14:50
WG6 Spin Physics
Devika Gunarathne for the STAR Collaboration
Temple University, Philadelphia, PA, USA
Email: devika.gunarathne@temple.edu
$W^\pm$ boson production in longitudinally polarized $p+p$ collisions provides unique and clean access to the individual helicity polarizations of $u$ / $d$ quarks and anti-quarks. Due to maximal violation of parity, $W$ bosons couple to left-handed quarks and...
Mike Beaumier
(urn:Google)
29/04/2015, 15:15
WG6 Spin Physics
Over the past ten years, the RHIC spin program has deepened our knowledge of proton spin structure as part of a worldwide effort to solve the proton spin puzzle. While we now precisely understand the contribution of valence quarks to the total proton spin, large uncertainties still dominate the predictions describing the contributions of the sea of anti-up and anti-down quarks. In 2013, PHENIX...
Dr
Nobuo Sato
(Jefferson Lab)
29/04/2015, 16:15
WG6 Spin Physics
A new global QCD analysis of spin-dependent PDFs has been performed
by the JAM (Jefferson Lab Angular Momentum) Collaboration, including
all available data on inclusive spin structure functions from CERN,
SLAC, DESY and JLab. In particular, we explore the impact of recent
high-precision JLab data at high x and low *Q*^2 on the determination
of large-*x* PDFs and the extraction of higher...
Nilanga Liyanage
(University of Virginia (US))
29/04/2015, 16:40
WG6 Spin Physics
Jefferson lab is well known for its high quality, high polarization electron beam. Jefferson lab
polarized beam, combined with the range of polarized proton, deuteron and 3He targets in
experimental halls A, B and C, allows for high precision exploration of spin structures of both
proton and neutron in the low to intermediate Q2 region. The impact of Jefferson lab precision spin
data is...
Tomas Kasemets
(DESY)
29/04/2015, 17:05
WG6 Spin Physics
We discuss the impact of double parton scattering at the LHC. In particular we focus on the impact of polarization, arising from the spin correlations between two partons inside an unpolarized proton. We demonstrate that the effects can be large in certain kinematic regions and processes and compare our results to data. We further discuss angular asymmetries and similarities as well as...
Cristian Pisano
(Vrije Universiteit Amsterdam)
29/04/2015, 17:30
WG6 Spin Physics
We consider Higgs plus jet production as a process that is sensitive to the linear polarization of gluons inside the unpolarized protons of the LHC. The leading order expressions for the transverse momentum distribution of the Higgs plus jet pair are calculated in terms of transverse momentum dependent quark and gluon distributions. Both angular independent and azimuthal angular dependent...
Matthias Burkardt
(NMSU)
30/04/2015, 10:45
WG6 Spin Physics
Transverse single-spin asymmetries are not the only observable where the transverce force on quarks in DIS plays a role. For example, higher-twist effects in polarized inclusive DIS can be related to that force. Furthermore the torque due to that force is relevant when comparing the Jaffe-Manohar with the Ji definition for quark orbital angular momentum. I explain the origin of that force in...
Dr
Kalyan Allada
(Massachusetts Institute of Technology)
30/04/2015, 11:10
WG6 Spin Physics
Semi-inclusive deep inelastic scattering (SIDIS) is a powerful tool to explore the 3-d structure of nucleon in momentum space. Through a combination of polarized/unpolarized lepton beam and nucleon target one can study various transverse-momentum dependent parton distribution functions (TMDs) that appear in the SIDIS cross-section. TMDs provide a description of nucleon structure in terms of...
Kenneth Barish
(UC Riverside)
30/04/2015, 11:35
WG6 Spin Physics
(for the PHENIX Collaboration)
Transverse single-spin asymmetries (TSSA) provide valuable information about
the spin structure of the nucleon. Here, we report results of TSSA in $\eta$ and single-muon production channels in p+p collision. Non-vanishing TSSA in eta meson production channel has been reported for Run-2008 data (Phys. Rev. D 90, 072008), in the forward rapidity region, which...
Dr
James L. Drachenberg
(Valparaiso University)
30/04/2015, 12:00
WG6 Spin Physics
Current knowledge of nucleon transverse-polarization structure comes from measurements of transverse single-spin asymmetries (SSAs) from semi-inclusive deep inelastic scattering (SIDIS). These measurements, combined with those of $e^{+}e^{-}$ collisions, have allowed the first extraction of transversity with limited constraints at higher values of Bjorken-$x$. One avenue to enrich...
