A complete, fundamental understanding of the proton must include knowledge of the underlying spin structure. The transversity distribution, h1(x), which describes the transverse spin structure of quarks inside of a transversely polarized proton, is only accessible through channels that couple h1(x) to another chiral odd distribution, such as the Collins fragmentation function (ΔN Dπ/q↑(z,jT)). Significant Collins asymmetries of charged pions have been observed in semi-inclusive deep inelastic scattering (SIDIS) data. These SIDIS asymmetries combined with e+e- process asymmetries have allowed for the extraction of h1(x) and ΔN Dπ/q↑(z,jT). However, the current uncertainties on h1(x) are large compared to the corresponding quark momentum and helicity distributions and reflect the limited statistics and kinematic reach of the available data. In transversely polarized hadronic collisions, Collins asymmetries may be isolated and extracted by measuring the spin dependent azimuthal distributions of charged pions in jets. This thesis will report on the first statistically significant Collins asymmetries extracted from √ s = 200 GeV hadronic collisions using 14 pb-1 of transversely polarized proton collisions at 57% average polarization.

The transversity distribution function, $h_1^{q}(x)$, where $x$ is the longitudinal momentum fraction of the proton carried by quark $q$, encodes the proton's transverse spin structure at leading twist. Difficulties arise when extracting $h_1^q(x)$ due to its chiral-odd nature. However, it can be coupled with a spin-dependent interference fragmentation function (FF), $H_1^{\sphericalangle, h_1h_2}$, in a dihadron ($h_1h_2$) production channel in polarized proton-proton ($p^\uparrow p$) collisions. The coupling of $h_1^{q}(x)$ and $H_1^{\sphericalangle, h_1h_2}$ produces an experimentally measurable azimuthal correlation asymmetry, $A_{UT}$, between the spin of the fragmenting quark and the final state dihadron. A model-independent extraction of transversity from these measurements relies on the knowledge of dihadron FFs, namely the unpolarized dihadron FFs, $D_1^{h_1h_2/q(g)}$ for quarks, \emph{q} (gluons, \emph{g}). Extraction of these FFs requires measurements of the unpolarized dihadron cross-section in $pp$ collisions, which are urgently needed. In $pp$ collisions, the unpolarized cross-section measurement provides access to the $D_1^{h_1h_2}$ for both quarks and gluons. This thesis outlines the measurements of the \dipion azimuthal correlation asymmetry in the forward ($\eta > 0$) and backward ($\eta < 0$) pseudorapidity regions with respect to the polarized beam using the RHIC Run 2015 polarized $pp$ data and the measurement of the unpolarized \dipion cross-section in the invariant mass bins in the mid-pseudorapidity ($|\eta|<1$) region using the RHIC Run 2012 $pp$ data at $\sqrt{s}=200$ GeV. These data sets were collected at the STAR experiment. The STAR Time Projection Chamber (TPC), Barrel Electromagnetic Calorimeter (BEMC), and Time-of-Flight Detector (TOF) were used in conjunction to measure outgoing particle energy, tracking, and identification. / Physics

The experiment E06010 measured the target single spin asymmetry (SSA) in the semiinclusive deep inelastic (SIDIS) n↑(e,éπ¯)X reaction with a transversely polarized 3He target as an effective neutron target. This is the very first independent measurement of the neutron SSA, following the measurements at HERMES and COMPASS on the proton and the deuteron. The experiment acquired data in Hall A at Jefferson Laboratory with a continuous electron beam of energy 5.9 GeV, probing the valence quark region, with x = 0.13→0.41, at Q2 = 1.31→3.1 GeV2. The two contributing mechanisms to the measured asymmetry, viz, the Collins effect and the Sivers effect can be realized through the variation of the asymmetry as a function of the Collins and Sivers angles. The neutron Collins and Sivers moments, associated with the azimuthal angular modulations, are extracted from the measured asymmetry for the very first time and are presented in this thesis. The kinematics of this experiment is comparable to the HERMES proton measurement. However, the COMPASS measurements on deuteron and proton are in the low-x region. The results of this experiment are crucial as the first step toward the extraction of quark transversity and Sivers distribution functions in SIDIS. With the existing results on proton and deuteron, these new results on neutron will provide powerful constraints on the transversity and Sivers distributions of both the u and d-quarks in the valence region.

What constitutes the spin of the nucleon? The answer to this question is still not completely understood. Although we know the longitudinal quark spin content very well, the data on the transverse quark spin content of the nucleon is still very sparse. Semi-inclusive Deep Inelastic Scattering (SIDIS) using transversely polarized targets provide crucial information on this aspect. The data that is currently available was taken with proton and deuteron targets. The E06-010 experiment was performed at Jefferson Lab in Hall-A to measure the single spin asymmetries in the SIDIS reaction n↑(e,éπ±/K±)X using transversely polarized 3He target. The experiment used the continuous electron beam provided by the CEBAF accelerator with a beam energy of 5.9 GeV. Hadrons were detected in a high-resolution spectrometer in coincidence with the scattered electrons detected by the BigBite spectrometer. The kinematic coverage focuses on the valence quark region, x = 0.19 to 0.34, at Q2 = 1.77 to 2.73 (GeV/c)2. This is the first measurement on a neutron target. The data from this experiment, when combined with the world data on the proton and the deuteron, will provide constraints on the transversity and Sivers distribution functions on both the u and d-quarks in the valence region. In this work we report on the single spin asymmetries in the SIDIS n↑(e,éπ+)X reaction.

At leading twist, the spin structure of the nucleon is described by three fundamental parton distribution functions (PDFs): unpolarized PDFs (f_1 (x)), helicity PDFs (g_1 (x)), and transversity PDFs (h_1^q (x)). Unlike f_1 (x) and g_1 (x), h_1^q (x) is a chiral-odd function that must couple with another chiral-odd function to manifest in experimentally observable chiral-even physical quantities such as cross-sections or asymmetries. Due to its chiral-odd nature, h_1^q (x) remains inaccessible in inclusive deep inelastic scattering (DIS) experiments, where f_1 (x) and g_1 (x) garner a larger amount of experimental data to constrain them, hence making h_1^q (x) one of the least constrained fundamental PDFs. In the Standard Model, only a few channels exist where h_1^q (x) couples with another chiral-odd function. The production of di-hadron in the final state from transversely polarized pp collisions represents one of the theoretically cleanest channels, where h_1^q (x) couples with another chiral-odd distribution function known as the interference fragmentation function (IFF, H_1^∢ (z,M_h^2)) and gives experimentally observable di-hadron azimuthal correlation asymmetry (A_UT^sin⁡(φ_RS ) ). This thesis work presents the most precise measurement, to date, of the di-pion A_UT^sin⁡(φ_RS ) in the mid-pseudorapidity region (-1 <η<1) using STAR 2017 transversely polarized pp data at a center-of-mass energy (√s) of 500 GeV. In 2017, STAR collected a dataset of 350 pb^(-1), approximately 15 times larger than the previous STAR 2011 dataset. Consequently, this new dataset improves the statistical precision of A_UT^sin⁡(φ_RS ) by a factor of 4, which will contribute significantly to constraining the h_1^q (x) in the global analyses.¬ / Physics