Werner Vogelsang

3/27/12, 9:00 AM

Spin physics

We give an overview of the recent developments
on longitudinal spin physics and the nucleon's
helicity structure. We highlight the status of
theoretical calculations and the impact of recent
data.

Mr
Scott Wolin
(University of Illinois at Urbana-Champaign)

3/27/12, 9:35 AM

Spin physics

The determination of the gluon polarization within the proton, $\Delta G$, is one of the critical pieces to understanding the proton spin puzzle. Using collisions of polarized protons with $\sqrt{s}=200 \:GeV$ and $\sqrt{s}=500 \:GeV$ at the Relativistic Heavy Ion Collider (RHIC), PHENIX can access gluons and $\Delta G$ at leading order. Constraints on $\Delta G$ come from measurements of...

Marcin Stolarski
(LIP Laboratorio de Instrumentacao e Fisica Experimental de Part)

3/27/12, 10:00 AM

Spin physics

A short review of the COMPASS results concerning gluon polarization
inside the nucleon, DG/G, is given including two new measurements:
Firstly, a DG/G determination in leading order and in three bin of
the gluon momentum fraction x_g from asymmetries in high-p$_T$
hadron pair production for Q$^2>$1 (GeV/c)$^2$;
secondly, a preliminary next-to-leading order analysis
based on open charm...

Piet J Mulders
(VU University)

3/27/12, 11:00 AM

Spin physics

Transverse momentum dependent (TMD) distribution and fragmentation functions are described as Fourier transforms of matrix elements containing non-local combinations of quark and gluon fields. While the collinear functions are light-cone correlators in which the non-locality is restricted along the light-cone, the transverse momentum dependent functions are light-front correlators including a...

Christoph Adolph
(Friedrich-Alexander-Univ. Erlangen (DE))

3/27/12, 11:35 AM

Spin physics

The quark content of the nucleon at twist-two level in the collinear case can be fully characterized by three independent distribution functions for each quark flavour: the unpolarized distribution function f1(x), the helicity distribution function g1(x) and the transverse spin distribution function h1(x), also called transversity.
The measurements of single spin asymmetries in semi-inclusive...

Francesca Giordano
(U)

3/27/12, 12:00 PM

Spin physics

The azimuthal $\cos\phi$ and $\cos2\phi$ modulations of the distribution of hadrons produced in unpolarized semi-inclusive deep-inelastic scattering of electrons and positrons off hydrogen and deuterium targets have been measuread at the HERMES experiment.
For the first time these modulations were determined in a four-dimensional kinematic space for positively and negatively charged pions and...

Prof.
Bernd Surrow
(MIT)

3/27/12, 4:30 PM

Spin physics

The STAR experiment at the Relativistic Heavy-Ion Collider at Brookhaven National
Laboratory is carrying out a spin physics program in high-energy polarized proton collisions at $\sqrt{s}=200\,$GeV and $\sqrt{s}=500\,$GeV
to gain a deeper insight into the spin structure and
dynamics of the proton.
The completion of the first $\sqrt{s}=500\,$GeV polarized proton run in 2009 opened a new...

Emanuele Roberto Nocera
(Universita degli Studi di Milano and INFN, Milano)

3/27/12, 5:00 PM

Spin physics

We present a preliminary determination of a set of polarized parton
distributions of the nucleon, at next-to-leading order, from a global set of
deep-inelastic scattering data. The determination is based on the NNPDF
methodology: a Monte Carlo sampling with neural networks used as unbiased
interpolants. This method, which has already been applied to a...

Dr
Polina Kravchenko
(DESY)

3/27/12, 5:20 PM

Spin physics

Final measurements are reported on the double-spin asymmetries for a longitudinally polarized hydrogen and deuterium targets at HERMES using the27.6 GeV HERA lepton beam. The kinematic dependences of the longitudinal semi-inclusive asymmetry simultaneously on Bjorken-x and hadron transverse momentum p_h, and Bjorken-x and the hadron energy fraction z are explored. Additionally, the hadron...

Young Jin Kim
(University of Illinois at Urbana-Champaign)

3/27/12, 5:40 PM

Spin physics

A major direction of the physics program at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) is to explore the origin of proton spin structure. Parity violating single spin asymmetries, $A_L$, for $W$-bosons in longitudinally polarized $p + p$ collisions at a center of mass energy of $\sqrt{s}$ = 500 GeV will give access to the flavor separated quark and...

Sara Collins
(University of Regensburg)

3/28/12, 8:30 AM

Spin physics

Flavour singlet contributions to the nucleon spin are elusive due to
the fact that they cannot be determined directly in experiment but
require extrapolations to the small x region. Direct calculations of
these contributions are possible using Lattice QCD, however, they pose
a significant computational challenge due to the presence of
disconnected quark line diagrams. I report on...

Mayya Golembiovskaya
(DESY)

3/28/12, 9:05 AM

Spin physics

The HERMES experiment at DESY, Hamburg collected a set of data on hard exclusive vector meson (rho,phi,omega) leptoproduction using the 27.6 GeV self-polarized lepton beam of HERA accelerator and longitudinally or transversely polarized or unpolarized gas target. The latest results on spin density matrix elements of exclusive phi meson production using the full statistics collected at HERMES,...

Mr
Martin Leitgab
(University of Illinois at Urbana-Champaign)

3/28/12, 9:30 AM

Spin physics

Fragmentation functions (FFs) describe the formation of final state particles from a partonic initial state. Precise knowledge of these functions is a key ingredient in accessing quantities such as the nucleon spin structure in semi-inclusive deep inelastic scattering and proton proton collisions. However, fragmentation functions can currently not be determined from first principles Quantum...

Dr
Jian-Wei Qiu
(Brookhaven National Lab)

3/28/12, 10:30 AM

Spin physics

Large transverse single spin asymmetries (SSAs) of cross sections with a large momentum transfer in high energy collisions were once thought impossible in QCD. With over 30 years of experimental as well as theoretical efforts, large SSAs are not only possible in QCD, but also carry extremely valuable information on the motion and structure of quarks and gluons inside a polarized hadron. In...

Dr
Yousef Makdisi
(Brookhaven National Laboratory)

3/28/12, 11:05 AM

Spin physics

Utilizing the RHIC polarized proton collider with transverse spin the PHENIX detector carried out cross section and asymmetry measurements in inclusive pizero and eta production at mid rapidity |n| < 0.35 using the central EM calorimeters where vanishing asymmetries were found. However, significant pizero and eta asymmetries were measured in the forward rapidity 3.1 < n < 3.9 using the MPC...

Vincent Sulkosky
(MIT)

3/28/12, 11:30 AM

Spin physics

Jefferson Lab experiment E06-010 measured the target-single spin (SSA)
and double spin asymmetries (DSA) in semi-inclusive deep inelastic pion electroproduction on a transversely polarized He-3 target. The
measured asymmetry (A_UT) is sensitive to the nucleon transversity and
Sivers distribution functions, whereas the measured A_LT asymmetry is
related to the transverse momentum...

Dr
Feng Yuan
(Lawrence Berkeley National Laboratory)

3/28/12, 4:00 PM

Spin physics

In this talk, we will summarize recent developments on the orbital angular momentum of partons in nucleon, from various observables in high energy processes, including generalized parton distributions, transverse momentum dependent parton distributions, etc.

Alessandro Bacchetta
(University of Pavia)

3/28/12, 4:30 PM

Spin physics

The determination of quark angular momentum requires the knowledge of the generalized parton distribution E in the forward limit. We assume a connection between this function and the Sivers transverse-momentum distribution, based on model calculations and theoretical considerations. Using this assumption, we show that it is possible to fit at the same time nucleon magnetic moments and...

Mariaelena Boglione
(University of Turin)

3/28/12, 4:50 PM

Spin physics

Following the TMD evolution scheme recently proposed for the Sivers distribution function, we propose a simple strategy to take into account this TMD Q^2 dependence in our phenomenological extraction of the Sivers function from SIDIS data. New results are presented and possible future applications are discussed.

Dr
Asmita Mukherjee
(IIT Bombay)

3/28/12, 5:10 PM

Spin physics

We discuss the possibility of using electroproduction of $J/\psi $ as a probe of gluon Sivers function
by measuring single spin asymmetry in experiments with transversely polarized protons and electron beams.
We estimate SSA for JLab, HERMES, COMPASS and eRHIC energies using color evaporation
model of charmonium production and find asymmetry up to 25 $\%$ for certain
choices of model...

Jakub Wagner
(National Center for Nuclear Research)

3/29/12, 9:20 AM

Spin physics

Generalized Parton Distributions (GPDs) offer a new way to access the quark and gluon nucleon structure. We advocate the need to supplement the experimental study of deeply virtual Compton scattering by its crossed version, timelike Compton scattering (TCS) i.e. the exclusive photoproduction of a lepton pairs with large invariant mass. We review recent progress in this domain, in particular...

A. L. Kataev
(Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia)

3/29/12, 9:50 AM

Spin physics

Using operator-product expansion approach for the triangle
diagram of Axial-Vector-Vector currents symmetry I derive the singlet variant of the
Crewther
relation, which is valid in the conformal -invariant limit
of perturbative approach. I demonstrate that in the conformal-invariant
limit of U(1)-model the non-singlet coefficient function of Bjorken and Ellis-Jaffe sum
rule identically...

Dr
jian zhou
(Regensburg University)

3/29/12, 10:10 AM

Spin physics

I will discuss the color glass condensate (CGC) based calculation of two gluon TMDs inside a large nucleus at small x. The main focus is on the linearly polarized gluon TMD which is often referred to as the gluon Boer-Mulders function. With the derived gluon TMDs at small x, it is shown that an effective TMD factorization can be established at small x in a certain kinematical region. As a...

Mr
Wilco den Dunnen
(VU University Amsterdam)

3/29/12, 11:00 AM

Spin physics

We investigate the possible role of linearly polarized gluons in Higgs production from unpolarized pp collisions. The angular independent transverse momentum distribution of the produced Higgs boson is found to exhibit a modulation (max 30%) with respect to the naive, unpolarized expectation, with the sign depending on the CP nature of the Higgs boson. The transverse momentum distribution of a...

Christopher Braun
(Friedrich-Alexander-Univ. Erlangen (DE))

3/29/12, 11:20 AM

Spin physics

For each quark flavour three independent parton distribution functions (PDF) are necessary to describe the nucleon at twist-two level, the quark distribution f1(x), the helicity distribution g1(x) and the transversity distribution h1(x). The transversity distribution function is chiral-odd and therefore is not accessible in deep inelastic scattering (DIS). However, h1(x) can be observed in...

Aurore Courtoy
(IFPA, AGO Dpt., Universite de Liege)

3/29/12, 11:40 AM

Spin physics

We report on the first extraction of interference fragmentation functions from the semi-inclusive production of two hadron pairs in back-to-back jets in $e^+e^-$ annihilation. A nonzero asymmetry in the correlation of azimuthal orientations of opposite $\pi^+\pi^-$ pairs is related to the transverse polarization of fragmenting quarks through a significant polarized dihadron fragmentation...

Christian Hoeppner
(Technische Universitaet Muenchen (DE))

3/29/12, 12:00 PM

Spin physics

Lepton-nucleon scattering experiments are performed to investigate the (spin-)structure of nucleons. The theoretical framework for the interpretation of such measurements is perturbative QCD (pQCD). In this contribution we present the measurement of the cross section for the quasi-real photoproduction of charged hadrons with high transverse momenta in muon-deuteron scattering at COMPASS...

Mrs
Melanie Pfeuffer
(University of Regensburg)

3/29/12, 12:20 PM

Spin physics

We consider the cross section for the photoproduction reaction
gamma + p -> h+ X in fixed-target scattering at COMPASS, where the hadron is produced at large transverse momentum. We investigate the role played by higher-order corrections to the cross section. In particular we adress large logarithmic ``threshold'' corrections to the partonic cross sections, which we resum to all orders.