Conveners
Nucleon Helicity Structure: Chair: Jinlong Zhang
- Itaru Nakagawa (RIKEN)
- Maria Zurek (Argonne National Laboratory)
Nucleon Helicity Structure: Chair: Jinlong Zhang
- Maria Zurek (Argonne National Laboratory)
- Itaru Nakagawa (RIKEN)
Nucleon Helicity Structure: Chair: Maria Żurek (ANL)
- There are no conveners in this block
Nucleon Helicity Structure: Chair: Maria Żurek (ANL)
- There are no conveners in this block
Sum rules for structure functions and their twist-2 relations have important roles in constraining their magnitudes and $x$ dependencies and in studying higher-twist effects. The Wandzura-Wilczek (WW) relation and the Burkhardt-Cottingham (BC) sum rule are such examples for the polarized structure functions $g_1$ and $g_2$. Recently, new twist-3 and twist-4 parton distribution functions were...
We discuss the properties of the helicity quark quasi-distributions in the large Nc limit. Within the framework of the chiral quark-soliton model, we review the properties of the quasi-PDFs such as the sum rules and the positivity. Numerical results for quark and antiquark isovector helicity distributions are presented. Significant antiquark flavor asymmetry is observed in a wide range of...
The flavor asymmetry of the unpolarized distributions of light anti-quarks (i.e. $\bar{u}(x)$ and $\bar{d}(x)$) in the proton was observed by several deep-inelastic muon scattering experiments. The ratio $\bar{d}(x)/\bar{u}(x)$ was measured by Drell-Yan experiments NA51 at CERN and E866 at Fermilab and a large asymmetry was reported.
The mechanism of this asymmetry has been studied via...
Since the first surprising results on the spin structure of the proton by the EMC experiment in the late 1980s, much progress has been made in understanding the origin of the proton spin. However, the sea quark contribution to the proton spin, for example, the helicity distributions of the strange quark (anti-quark), $s(\bar{s})$, is still not well constrained by experimental data. Since the...
The MicroBooNE experiment is an 85 ton active volume liquid-argon time projection chamber (LArTPC) located in the Booster Neutrino Beamline at Fermilab. The excellent calorimetric and spatial resolution of the LArTPC allows us to identify isolated proton tracks with lengths as short as 2 cm, which is equivalent to proton kinetic energy T = 50 MeV. We report the progress towards the first...
We discuss the production of transversely polarized hyperons in semi-inclusive deep inelastic scattering in the framework of the collinear twist-3 factorization. In this framework, the twist-3 cross section consists of three contributions depending on the origins for the polarizations: (i) Twist-3 distribution in the initial proton combined with the twist-2 transversity fragmentation function...
We report on the first phenomenological analysis of the world polarized deep-inelastic scattering (DIS) data incorporating small-x helicity (Kovchegov-Pitonyak-Sievert) evolution. This framework allows for one to predict the behavior of helicity parton distribution functions (PDFs) down to very low x. Consequently, one can control the uncertainties in these functions beyond the measured...
We present the first global QCD analysis of helicity parton distribution functions (PDFs) to include the latest polarized $W$-lepton production data from the STAR collaboration at the Relativistic Heavy-Ion Collider. This data allows the first extraction of a nonzero helicity light quark sea asymmetry within a global QCD analysis. By performing a simultaneous extraction of the unpolarized...
Studies of heavy quark bound states, like J/psi meson, provide a useful tool to investigate QCD properties. Many general features of J/psi production, such as cross-sections and transverse momentum distributions are well described by many existing models. In order to differentiate between various theoretical models one has to study J/psi production in more details. One of the observables which...
I’ll discuss the role of the chiral anomaly in deep inelastic scattering (DIS) of electrons off polarized protons employing a worldline formalism, which is a powerful framework for the computation of perturbative multi-leg Feynman amplitudes. I’ll demonstrate how the triangle anomaly appears at high energies in the DIS box diagram for the polarized structure function $g_1(x_B,Q^2)$ in both the...
The proton spin decomposition provides key information about the structure of the nucleons. Since late 1980s, experiments showed that the quark spin contributes only $\sim$30\% to the proton spin, with remaining part coming from gluon spin as well as quark and gluon orbital angular momentum. While the quark spin contribution was better constrained by polarized deep inelastic scattering (DIS),...
Operated at the Relativistic Heavy Ion Collider at Brookhaven until beginning its recent upgrade into sPHENIX, the PHENIX experiment has collected a wealth of data from polarized proton collisions. Analysis of these data sets continues to offer insight into the spin structure of the proton. In particular, RHIC's polarized proton-proton data help constrain polarized PDFs in the proton, and...
The contribution of the gluon spin to the spin of the proton is being studied through the use of the unique capability of the Relativistic Heavy Ion Collider (RHIC) to collide longitudinally polarized protons at $\sqrt{s}=200\,$GeV and $\sqrt{s}=510\,$GeV. The kinematic coverage of the Solenoidal Tracker At RHIC (STAR) allows access to gluons through quark-gluon and gluon-gluon scattering...
I will discuss the extension of the nucleon spin sum rule to QCDxQED. I will present the QED corrections to the evolution of the quark and gluon helicity and orbital-angular-momentum (OAM) distributions, which are calculated for the first time, and the necessary inclusion of photon and lepton helicity and OAM distributions.
