The first measurements of $x_F$-dependent single spin asymmetries of identified charged hadrons, $π^{\pm}$, $K^{\pm}$, and protons, from transversely polarized proton-proton collisions at 62.4 GeV at RHIC are presented. The measurements extend to high-$x_F$ ($|x_F|\sim 0.6$) in both the forward and backward directions.Large asymmetries are seen in the pion and kaon channels. The asymmetries in inclusive $π^{+}$ production, $A_N(π^+)$, increase with $x_F$ from 0 to $\sim$0.25 %at $x_F = 0.6$ and $A_N(π^{-})$ decrease from 0 to $\sim$$-$0.4. Even though $K^-$ contains no valence quarks, observed asymmetries for $K^-$ unexpectedly show positive values similar to those for $K^+$, increasing with $x_F$, whereas proton asymmetries are consistent with zero over the measured kinematic range. Comparisons of the data with predictions of QCD-based models are presented. The flavor dependent single spin asymmetry measurements of identified hadrons allow for stringent tests of theoretical models of partonic dynamics in the RHIC energy regime.
The only comparative study of the inclusive pion single-spin asymmetries produced in the interactions of the polarized protons and antiprotons in collisions with unpolarized proton was carried out at E-704 experiment. Significant asymmetries were found at large $x_{F}$ and middle $p_{T}$, $π^{+}$ and $π^{0}$ asymmetries have positive signs while $π^{-}$ has negative one in the $p^{\uparrow}+p$ collisions, while in the $\bar{p}^{\uparrow}+p$ interactions the $π^{-}$ and $π^{0}$ asymmetries have positive signs while $π^{+}$ has negative sign. Similar experimental study can be done in the SPASCHA…
Single-beam, single-target, and double-spin asymmetries for hard exclusive photon production on the proton $\vec{e}\vec{p} \to e' p'γ$ are presented. The data were taken at Jefferson Lab using the CLAS detector and a longitudinally polarized ${}^{14}$NH$_3$ target. The three asymmetries were measured in 165 4-dimensional kinematic bins, covering the widest kinematic range ever explored simultaneously for beam and target-polarization observables in the valence quark region. The kinematic dependences of the obtained asymmetries are discussed and compared to the predictions of models of Generaliz…
Measurements of cross-sections and transverse single spin asymmetries of identified charged hadrons at forward rapidities from transversely polarized proton collisions at $\sqrt{s}$ = 200 GeV are presented. The results are discussed in the context of interplay between perturbative and non-perturbative QCD effects.
Measurements of the angular distributions of target and double spin asymmetries for the Delta(1232) in the exclusive channel (polarized-p polarized-e,e-prime p)pi0 obtained at Jefferson Lab in the Q2 range from 0.5 to 1.5 gev2 are presented. Results of the asymmetries are compared with the unitary isobar model, dynamical models, and the effective Lagrangian theory. Sensitivity to the different models was observed, particularly in relation to the description of background terms on which the target asymmetry depends significantly.
We study the azimuthal asymmetries in proton-proton Drell-Yan processes with one incident proton being transversely or longitudinally polarized. We consider particularly the asymmetries contributed by the leading-twist chiral-odd quark distributions. We analyze the asymmetries with $\sin(2ϕ+ϕ_S)$ and $\sin(2ϕ-ϕ_S)$ modulations in transverse single polarized $p^\uparrow p$ Drell-Yan and $\sin2ϕ$ asymmetries in longitudinal single polarized $p^\rightarrow p$ Drell-Yan at RHIC, J-PARC, E906 (Fermi Lab) and NICA (JINR). We show that the measurements of the asymmetries in those facilities can provi…
This paper focuses on a measurement of deeply virtual Compton scattering (DVCS) performed at Jefferson Lab using a nearly-6-GeV polarized electron beam, two longitudinally polarized (via DNP) solid targets of protons (NH3) and deuterons (ND3) and the CEBAF Large Acceptance Spectrometer. Here, preliminary results for target-spin asymmetries and double (beam-target) asymmetries for proton DVCS, as well as a very preliminary extraction of beam-spin asymmetry for neutron DVCS, are presented and linked to Generalized Parton Distributions.
We study the cross section for vector boson ($W^{\pm}/Z^0/γ^*$) production in polarized nucleon-nucleon collisions for low transverse momentum of the observed vector boson. For the case where one measures the transverse momentum and azimuthal angle of the vector bosons, we present the cross sections and the associated spin asymmetries in terms of transverse momentum dependent parton distribution functions (TMDs) at tree level within the TMD factorization formalism. To assess the feasibility of experimental measurements, we estimate the spin asymmetries for $W^{\pm}/Z^0$ boson production in pol…
The exclusive channel polarized proton(polarized e,e prime p)pi0 was studied in the first and second nucleon resonance regions in the Q2 range from 0.187 to 0.770 GeV2 at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). Longitudinal target and beam-target asymmetries were extracted over a large range of center-of-mass angles of the pi0 and compared to the unitary isobar model MAID, the dynamic model by Sato and Lee, and the dynamic model DMT. A strong sensitivity to individual models was observed, in particular for the target asymmetry and in the higher invariant mass region…
An apparatus for measuring parity-violating asymmetries in gamma-ray emission following polarized cold neutron capture was constructed as a 1/10th scale test of the design for the forthcoming n+p->d+gamma experiment at LANSCE. The elements of the polarized neutron beam, including a polarized 3He neutron spin filter and a radio frequency neutron spin rotator, are described. Using CsI(Tl) detectors and photodiode current mode readout, measurements were made of asymmetries in gamma-ray emission following neutron capture on 35Cl, 113Cd, and 139La targets. Upper limits on the parity-allowed asymmet…
We demonstrate that partonic correlations that would traditionally be identified as subleading on the basis of a generalized TMD-factorization conjecture can become leading-power because of TMD-factorization breaking that arises in hadron-hadron collisions with large transverse momentum back-to-back hadrons produced in the final state. General forms of TMD-factorization fail for such processes because of a previously noted incompatibility between the requirements for TMD-factorization and the Ward identities of non-Abelian gauge theories. We first review the basic steps for factorizing the glu…
Global analysis has been performed within the next-to-leading order in Quantum Chromodynamics (QCD) to determine polarized parton distributions with new experimental data in spin asymmetries. The new data set includes JLab, HERMES, and COMPASS measurements on spin asymmetry A_1 for the neutron and deuteron in lepton scattering. Our new analysis also utilizes the double-spin asymmetry for pi^0 production in polarized pp collisions, A_{LL}^{pi^0}, measured by the PHENIX collaboration. Because of these new data, uncertainties of the polarized PDFs are reduced. In particular, the JLab, HERMES, and…
Asymmetry measurements were conducted in Jefferson Lab's experimental Hall A through electron scattering from a polarized $^3$He target in the quasi-elastic $^3\mathrm{He}(e,e'n)$ reaction. Measurements were made with the target polarized in the longitudinal direction with respect to the incoming electrons ($A_L$), in a transverse direction that was orthogonal to the beam-line and parallel to the q-vector ($A_T$), and in a vertical direction that was orthogonal to both the beam-line and the q-vector ($A_y^0$). The experiment measured $A_y^0$ at four-momentum transfer squared (Q$^2$) of 0.127 (…
In the RHIC run of 2006, PHENIX recorded data from about 20/nb of transversely polarized p+p collisions at sqrt(s) = 62.4 GeV and polarization of about 50%. Also in this last run PHENIX successfully commissioned a new lead-tungstate based electromagnetic calorimeter, the Muon Piston Calorimeter (MPC), covering 2 pi in azimuth and 3.1<eta<3.7. The forward coverage allows PHENIX to measure high x_F pi^0 production. We present the current status of the analysis for the single inclusive pi^0 transverse asymmetry A_N at forward rapidities in PHENIX.
Polarized electron-deuteron DIS with spectator proton tagging offers a way of measuring the neutron spin structure functions with maximal theoretical control of nuclear effects. We calculate the nuclear structure factors in the longitudinal double-spin asymmetries using methods of light-front nuclear structure. A unique feature of the spin-1 system is that spin asymmetries can be formed either relative to the cross section in all three spin states ($λ_d = \pm 1, 0$) or in the two maximum-spin states only ($\pm 1$, involving tensor polarization). We find that the two-state deuteron spin asymmet…
Parity-odd asymmetries in the electromagnetic decays of compound nuclei can sometimes be amplified above values expected from simple dimensional estimates by the complexity of compound nuclear states. In this work we use a statistical approach to estimate the root mean square (RMS) of the distribution of expected parity-odd correlations $\vec{s_{n}} \cdot \vec{k_γ}$, where $\vec {s_{n}}$ is the neutron spin and $\vec{k_γ}$ is the momentum of the gamma, in the integrated gamma spectrum from the capture of cold polarized neutrons on Al, Cu, and In and we present measurements of the asymmetries i…
We present the first measurements of the double spin asymmetries A_NN and A_SS at sqrt{s}=200 GeV, obtained by the pp2pp experiment using polarized proton beams at the Relativistic Heavy Ion Collider (RHIC). The data were collected in the four momentum transfer t range 0.01<|t|<0.03 (GeV/c)^2. The measured asymmetries, which are consistent with zero, allow us to estimate upper limits on the double helicity-flip amplitudes phi_2 and phi_4 at small t as well as on the difference Delta(sigma_T) between the total cross sections for transversely polarized protons with antiparallel or parallel spin …
The particle-antiparticle asymmetries of $Λ$ production in 250 GeV/c $π^{\pm}$, $K^{\pm}$, and $p$ --nucleon collisions are studied with two model parametrizations of quark to $Λ$ fragmentation functions. It is shown that the available data can be qualitatively explained by the calculated results in both the quark-diquark model and a pQCD based analysis of fragmentation functions. The differences in the two model predictions are significant for $K^{\pm}$ beams, and high precision measurements of the asymmetries with detailed $x_F$ and $P_T$ information can discriminate between different predic…
Large transverse single-spin asymmetries (TSSA) in hadron production at forward rapidity have been observed in polarized $p$+$p$ interactions for many decades, over a large range of center-of-mass energies, and have led to the investigation of spin-momentum correlations such as the Sivers and Collins effects. In the last few years, it has been discovered at RHIC that these single-spin asymmetries may be enhanced or suppressed in $p$+$A$ collisions, and the nuclear-size and centrality dependence have been studied. A variety of phenomena have been observed and likely they do not have all a singl…
This thesis is dedicated to a study of a spin-isospin structure of the polarized ${}^3\mathrm{He}$. First, an introduction to the spin structure of ${}^3\mathrm{He}$ is given, followed by a brief overview of past experiments. The main focus of the thesis is the E05-102 experiment at Jefferson Lab, in which the reactions ${}^3\vec{\mathrm{He}}(\vec{\mathrm{e}},\mathrm{e'} \mathrm{d})$ and ${}^3\vec{\mathrm{He}}(\vec{\mathrm{e}},\mathrm{e'} \mathrm{p})$ in the quasi-elastic region were studied. The purpose of this experiment was to better understand the effects of the S'- and D-state contributio…
The non-mesonic weak decay of polarized Lambda-hypernuclei is studied for the first time by taking into account, with a Monte Carlo intranuclear cascade code, the nucleon final state interactions. A one-meson-exchange model is employed to describe the Lambda N-> n N processes in a finite nucleus framework. The relationship between the intrinsic Lambda asymmetry parameter a_Λand the asymmetry a^M_Λaccessible in experiments is discussed. A strong dependence of a^M_Λon nucleon final state interactions and detection threshold is obtained. Our results for a^M_Λare consistent with ^{11}_ΛB and ^{12}…
We study the single spin asymmetries for the $D$-meson production, Drell-Yan lepton-pair production and the direct-photon production in the $pp$ collision induced by the twist-3 three-gluon correlation functions in the transversely polarized nucleon. We present a corresponding polarized cross section formula in the leading-order with respect to the QCD coupling and a model calculation for the asymmetries, illustrating the sensitivity to the form of the correlation functions.
We report on two pion-photoproduction measurements in the threshold region conducted in the A2 collaboration at MAMI with the almost 4π Crystal Ball detector. The first was with a linearly polarized photon beam and unpolarized liquid-hydrogen target. The data analysis is now complete and the linearly polarized beam asymmetry along with differential cross sections provide the most stringent test to date of the predictions of Chiral Perturbation Theory and its energy region of convergence. More recently, a measurement was performed using both circularly polarized photons and a transversely polar…
