scholarly journals HADRON SPIN DYNAMICS

2003 ◽  
Vol 18 (08) ◽  
pp. 1531-1550 ◽  
Author(s):  
STANLEY J. BRODSKY
Keyword(s):  
Spin Asymmetry ◽  
Spin Dynamics ◽  
Probability Distributions ◽  
Magnetic Moments ◽  
Hadron Structure ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Spin Effects ◽  
Single Spin Asymmetries ◽  
Fock State

Spin effects in exclusive and inclusive reactions provide an essential new dimension for testing QCD and unraveling hadron structure. Remarkable new experiments from SLAC, HERMES (DESY), and Jefferson Lab present many challenges to theory, including measurements at HERMES and SMC of the single spin asymmetries in ep → e′ π X where the proton is polarized normal to the scattering plane. This type of single spin asymmetry may be due to the effects of rescattering of the outgoing quark on the spectators of the target proton, an effect usually neglected in conventional QCD analyses. Many aspects of spin, such as single-spin asymmetries and baryon magnetic moments are sensitive to the dynamics of hadrons at the amplitude level, rather than probability distributions. I will illustrate the novel features of spin dynamics for relativistic systems by examining the explicit form of the light-front wavefunctions for the two-particle Fock state of the electron in QED, thus connecting the Schwinger anomalous magnetic moment to the spin and orbital momentum carried by its Fock state constituents and providing a transparent basis for understanding the structure of relativistic composite systems and their matrix elements in hadronic physics. I also present a survey of outstanding spin puzzles in QCD, particularly ANN in elastic pp scattering, the J/ψ → ρπ puzzle, and J/ψ polarization at the Tevatron.

SINGLE SPIN ASYMMETRIES IN INCLUSIVE DIS AND MULTI-PARTON CORRELATIONS IN THE NUCLEON

2012 ◽  
Vol 20 ◽  
pp. 137-144
Author(s):  
ANDREAS METZ ◽  
DANIEL PITONYAK ◽  
ANDREAS SCHÄFER ◽  
MARC SCHLEGEL ◽  
WERNER VOGELSANG ◽  
...  
Keyword(s):  
Experimental Data ◽  
Spin Asymmetry ◽  
Recent Experimental Data ◽  
Hard Scattering ◽  
Photon Exchange ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Two Photon ◽  
Single Spin Asymmetries ◽  
Dependent Relation

Transverse single spin asymmetries in inclusive deep-inelastic lepton-nucleon scattering can be generated through multi-photon exchange between the leptonic and the hadronic part of the process. Here we consider two-photon exchange, and mainly focus on the transverse target spin asymmetry. In particular, we investigate the case where two photons couple to different quarks. Such a contribution involves a quark-photon-quark correlator in the nucleon, which has a (model-dependent) relation to the Efremov-Teryaev-Qiu-Sterman quark-gluon-quark correlator TF. Using different parameterizations for TF we compute the transverse target spin asymmetry for both a proton and a neutron target, and compare the results to recent experimental data. Potential implications on our general understanding of single spin asymmetries in hard scattering processes are discussed as well.

scholarly journals Single-Spin Asymmetries AULsinϕh in Semi-Inclusive Pions Production

2016 ◽  
Vol 40 ◽  
pp. 1660045 ◽  
Author(s):  
Zhun Lu ◽  
Wenjuan Mao
Keyword(s):  
Pion Production ◽  
Neutral Pion ◽  
Spin Asymmetry ◽  
Distribution Functions ◽  
Proton Target ◽  
Deuteron Target ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Single Spin Asymmetries

The single-spin asymmetry [Formula: see text] of charged and neutral pion production in semi-inclusive deep-inelastic scattering on longitudinally polarized nucleon targets is studied. We particularly consider the effects of the twist-3 transverse-momentum dependent distribution functions [Formula: see text] and [Formula: see text], which are calculated in two different spectator-diquark models. We estimate the asymmetry for [Formula: see text], [Formula: see text] and [Formula: see text] produced off the proton target at HERMES and compare the results with the HERMES measurements. We also predict the same asymmetric moment for different pions at the kinematics of CLAS 5.5 GeV on a proton target, as well as at COMPASS on a deuteron target for comparison.

scholarly journals AN of Single Heavy Flavor Decay Muon in the PHENIX Experiment at RHIC

2016 ◽  
Vol 40 ◽  
pp. 1660043 ◽  
Author(s):  
Xiaorong Wang ◽  
Feng Wei
Keyword(s):  
Transverse Momentum ◽  
Spin Asymmetry ◽  
Single Spin Asymmetry ◽  
Transverse Spin ◽  
Heavy Flavor ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Phenix Experiment ◽  
Single Spin Asymmetries ◽  
Heavy Flavor Production

Transverse single-spin asymmetries provide valuable information about the spin structure of the nucleon. At RHIC energies, heavy-flavor production is dominated by gluon-gluon fusion, and the subsequent decay into high [Formula: see text] electrons or muons can be observed statistically in a collider detector like PHENIX. The transverse single-spin asymmetry in heavy-flavor production originates from the initial state correlation between the internal transverse momentum of the parton and the transverse spin of the nucleon (similar with the known Sivers effect). The measurement of transverse single-spin asymmetry of single muons from heavy flavor decay at RHIC serves as a clean probe and would provide important information on the gluon Sivers function. In 2012, the PHENIX experiment collected 9.2 [Formula: see text] integrated luminosity in transversely polarized [Formula: see text] collisions at [Formula: see text] = 200 GeV with a polarization of [Formula: see text]. The signal-to-background ratio was improved by a factor of two compared to the previous RHIC 2006 and 2008 results in high transverse momentum region ([Formula: see text]GeV). The recent PHENIX preliminary results of transverse single-spin asymmetries of single heavy flavor decay muon at forward-rapidity will be shown and the possible improvement on this measurement in 2015 with the help of the FVTX detector will be discussed.

scholarly journals Azimuthal Single-Spin Asymmetries of Charged Pions in Jets in s = 200 GeV p↑p Collisions at STAR

2016 ◽  
Vol 40 ◽  
pp. 1660040 ◽  
Author(s):  
J. Kevin Adkins ◽  
James L. Drachenberg
Keyword(s):  
Spin Asymmetry ◽  
Heavy Ion ◽  
Relativistic Heavy Ion Collider ◽  
Spin Asymmetries ◽  
Proton Collisions ◽  
Single Spin ◽  
Single Spin Asymmetries ◽  
Polarized Proton ◽  
Charged Pions ◽  
200 Gev

Single spin asymmetry measurements ([Formula: see text]) of the azimuthal distribution of charged pions inside jets produced in transversely polarized proton collisions are sensitive to the transversity distribution and the Collins fragmentation function. The STAR Detector at the Relativistic Heavy Ion Collider is well suited for these types of measurements as it is capable of full jet reconstruction and charged pion identification in the mid-rapidity region ([Formula: see text][Formula: see text][Formula: see text][Formula: see text]). We report here the first observation of Collins [Formula: see text] asymmetries in [Formula: see text] GeV [Formula: see text] collisions.

scholarly journals Transverse Single-Spin Asymmetries in Proton-Proton Collisions at the AFTER@LHC Experiment in a TMD Factorisation Scheme

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
M. Anselmino ◽  
U. D’Alesio ◽  
S. Melis
Keyword(s):  
Spin Asymmetry ◽  
Parton Model ◽  
Fixed Target ◽  
Proton Proton ◽  
Spin Asymmetries ◽  
Proton Collisions ◽  
Single Spin ◽  
Single Spin Asymmetries ◽  
Target Experiment ◽  
Proton Proton Collisions

The inclusive large-pTproduction of a single pion, jet or direct photon, and Drell-Yan processes, are considered for proton-proton collisions in the kinematical range expected for the fixed-target experiment AFTER, proposed at LHC. For all these processes, predictions are given for the transverse single-spin asymmetry,AN, computed according to a Generalised Parton Model previously discussed in the literature and based on TMD factorisation. Comparisons with the results of a collinear twist-3 approach, recently presented, are made and discussed.

DOUBLE SPIN ASYMMETRY ALT IN THE PRODUCTION OF PHOTONS, HADRONS, AND JETS

2012 ◽  
Vol 20 ◽  
pp. 29-36
Author(s):  
DANIEL PITONYAK
Keyword(s):  
Spin Asymmetry ◽  
Pp Collisions ◽  
Proton Proton ◽  
Spin Asymmetries ◽  
Double Spin Asymmetry ◽  
Single Spin ◽  
Double Spin ◽  
Single Spin Asymmetries ◽  
Complete Set ◽  
First Time

We calculate the double spin asymmetry (DSA) ALT in proton-proton (pp) collisions for the production of photons, hadrons, and jets in the collinear twist-3 framework. These processes allows us for the first time to access a complete set of collinear twist-3 functions. We also give numerical estimates for the asymmetries of which photon production shows the most promise of a measurable effect. Furthermore, we comment on how these asymmetries would allow us to probe the gluon helicity down to as of yet unexplored x values, remark on the importance of these effects in determining the evolution of the Efremov-Teryaev-Qiu-Sterman (ETQS) function TF(x, x), and discuss their usefulness in resolving the true mechanism behind the large transverse single spin asymmetries (SSAs) measured in pp collisions.

scholarly journals Target Single-Spin Asymmetry in Inclusive Hadron Production

2015 ◽  
Vol 37 ◽  
pp. 1560067
Author(s):  
Xiaodong Jiang
Keyword(s):  
Spin Asymmetry ◽  
Center Of Mass ◽  
Hadron Production ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Center Of Mass Energy ◽  
Average Momentum ◽  
Single Spin Asymmetries ◽  
Energy Formula ◽  
Effective Neutron

We present the first measurement of target single-spin asymmetries (AN) in the inclusive hadron production reaction, e+3 He ↑ →h+X, using a transversely polarized 3 He target at an electron-nucleon center-of-mass energy [Formula: see text] GeV. The experiment was conducted at Jefferson Lab in Hall A using a 5.9-GeV electron beam. Several types of hadrons (π±, K± and proton) were detected with an average momentum 〈Ph〉 = 2.35 GeV/c, and an average transverse momentum 〈pT〉 = 0.64 GeV/c. The observed asymmetry strongly depends on the type of hadron. A positive asymmetry is observed for π+ and K+. A negative asymmetry is observed for π-. The π+ and π- asymmetries measured for the 3 He target and extracted the "effective- neutron" SSA. Amazingly, we found that the ratio of our observed SSA between π+ and π- productions closely resemble the ratio of up- to down-quark's contributions to neutron's anomalous magnetic moment.

scholarly journals ESTIMATING THE SIGN AND SIZE OF THE TRANSVERSE SINGLE TARGET-SPIN ASYMMETRY IN INCLUSIVE DIS

2014 ◽  
Vol 25 ◽  
pp. 1460012 ◽  
Author(s):  
MARC SCHLEGEL
Keyword(s):  
Correlation Functions ◽  
Spin Asymmetry ◽  
Photon Correlation ◽  
Photon Exchange ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Two Photon ◽  
Single Spin Asymmetries ◽  
Single Target ◽  
Perturbative Part

The single-spin asymmetry of unpolarized leptons scattering deep-inelastically off transversely polarized nucleons is discussed. This observable is generated by a two-photon exchange between lepton and nucleon. In a partonic description of the asymmetry the non-perturbative part is given in terms of multiparton correlations: quark-gluon correlation functions and quark-photon correlation functions. Using input from models and data fits for these twist-3 correlation functions, estimates for the single-spin asymmetries for a proton and a neutron are presented.

scholarly journals FINAL-STATE INTERACTIONS AND SINGLE-SPIN ASYMMETRIES IN SEMI-INCLUSIVE DEEP INELASTIC SCATTERING

2003 ◽  
Vol 18 (08) ◽  
pp. 1327-1334 ◽  
Author(s):  
STANLEY J. BRODSKY ◽  
DAE SUNG HWANG ◽  
IVAN SCHMIDT
Keyword(s):  
Spin Asymmetry ◽  
Proton Spin ◽  
Final State ◽  
Complex Phase ◽  
Target Nucleon ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Polarized Target ◽  
Single Spin Asymmetries ◽  
Final State Interactions

Recent measurements from the HERMES and SMC collaborations show a remarkably large azimuthal single-spin asymmetries AUL and AUT of the proton in semi-inclusive pion leptoproduction γ*(q) p → π X. We show that final-state interactions from gluon exchange between the outgoing quark and the target spectator system leads to single-spin asymmetries in deep inelastic lepton-proton scattering at leading twist in perturbative QCD; i.e., the rescattering corrections are not power-law suppressed at large photon virtuality q2 at fixed xbj. The existence of such single-spin asymmetries requires a phase difference between two amplitudes coupling the proton target with [Formula: see text] to the same final-state, the same amplitudes which are necessary to produce a nonzero proton anomalous magnetic moment. We show that the exchange of gauge particles between the outgoing quark and the proton spectators produces a Coulomb-like complex phase which depends on the angular momentum Lz of the proton's constituents and thus is distinct for different proton spin amplitudes. The single-spin asymmetry which arises from such final-state interactions does not factorize into a product of structure function and fragmentation function, and it is not related to the transversity distribution δq(x,Q) which correlates transversely polarized quarks with the spin of the transversely polarized target nucleon.

scholarly journals Transverse Single Spin Asymmetry of π0 and η Mesons at RHIC/PHENIX

2016 ◽  
Vol 40 ◽  
pp. 1660044
Author(s):  
Xiaorong Wang
Keyword(s):  
Spin Asymmetry ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Photon Decay ◽  
Pqcd Calculation ◽  
Single Spin Asymmetries ◽  
Central Rapidity ◽  
200 Gev ◽  
Sivers Function ◽  
Energy Formula

We presented measurements of the transverse single spin asymmetries ([Formula: see text]) for neutral [Formula: see text] and [Formula: see text] meson at forward rapidities and central rapidity with the PHENIX detector at RHIC at 62.4 GeV and 200 GeV. At mid-rapidity, [Formula: see text] and [Formula: see text] are reconstructed from di-photon decay. At forward rapidities, [Formula: see text] and [Formula: see text] meson are measured using di-photons decays and electromagnetic clusters due to the photon merging effects are significant for energy [Formula: see text]. The neutral-pion measurement of [Formula: see text] at mid-rapidity is consistent with zero with uncertainties a factor of 20 smaller than previous publications, which will lead to improved constraints on the gluon Sivers function. At higher rapidities, both neutral [Formula: see text] and [Formula: see text] [Formula: see text] exhibit sizable asymmetries. The origin of the forward [Formula: see text] is presently not understood quantitatively. We also measured [Formula: see text] meson cross section for [Formula: see text] GeV/c and [Formula: see text]. It is well described by a NLO pQCD calculation.

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