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| Author | : W. VOGELSANG |
| Publisher | : |
| Total Pages | : 6 |
| Release | : 2006 |
| Genre | : |
| ISBN | : |
We give a brief overview of some of the recent results on single-transverse spin asymmetries, highlighting in particular progress in theoretical understanding.
| Author | : F. YUAN |
| Publisher | : |
| Total Pages | : 4 |
| Release | : 2006 |
| Genre | : |
| ISBN | : |
We derive a unique formula for the single-transverse-spin asymmetry in semi-inclusive hadron production in deep inelastic scattering, valid for all transverse momentum region. Based on this, we further study the integrated asymmetry weighted with transverse-momentum. They can be evaluated in terms of the twist-three quark-gluon correlation functions, which are responsible for the single spin asymmetry in single inclusive hadron production in hadronic collisions. By using the fitted twist-three functions from the hadronic collision data, we find a consistent description for SSAs in deep inelastic scattering. This demonstrates that we have a unique picture for SSAs in these two processes, and shall provide important guidelines for future studies.
| Author | : Dr. Vincenzo Barone |
| Publisher | : World Scientific |
| Total Pages | : 308 |
| Release | : 2003 |
| Genre | : Science |
| ISBN | : 9812795510 |
This study deals with the theory and phenomenology of transverse spin effects in high-energy hadronic physics. Contrary to common past belief, it is now rather clear that these effects are far from irrelevant. A decade or so of intense theoretical work has shed much light on the subject and brought to the surface an entire class of new phenomena, which now await thorough experimental investigation. Over the next few years a number of experiments worldwide (at DESY, CERN and Brookhaven) will run with transversely polarised particles, providing data that will enrich our knowledge of the transverse spin structure of hadrons. The principle aim of this work is to assess the state of the art as it stands in 2002. After a few introductory remarks (Chapter 1), in the first part (Chapters 2-4) attention is directed to polarised deep inelastic scattering (DIS), particularly DIS on transversely polarised targets, which probes the transverse spin structure function g2. This structure function is examined within the framework of the quark-parton model and its improvement via perturbative QCD. The existing data are reviewed and commented on (for completeness and comparison, a brief presentation of longitudinally polarised DIS and of the helicity structure of the proton is provided). The second part of the book (Chapters 5-8) focuses on the transverse polarisation of quarks, the so-called "transversity". The partonic content and the QCD evolution of the transversity distributions are presented in detail. The phenomenology of transversity is then studied in the context of Drell-Yan processes and of semi-inclusive lepto- and hadroproduction. The interpretation of data on single-spin asymmetries is discussed and, finally, the prospects for future measurements are reviewed.
| Author | : Yuxi Pan |
| Publisher | : |
| Total Pages | : 129 |
| Release | : 2015 |
| Genre | : |
| ISBN | : |
Asymmetries in the production of final state particles from collider or fixed-target experiments with polarized beams or target could provide valuable information on the spin structure of the nucleon. Transverse and longitudinal spin asymmetry measurements are complementary approaches for probing the nucleon spin structure functions and understanding the QCD dynamics for such phenomena, due to the non-commutative nature of boosts and rotations in relativistic regime. The research presented in this thesis focuses on characterizing the Transverse Single Spin Asymmetries (TSSA) of inclusive pi0 and jet productions in polarized proton collisions at large Feynman (xF) region. Theoretically these observables are explained by means of collinear twist-3 multi-parton correlations. In this picture the asymmetries originate from initial-state twist-3 parton distributions in the polarized proton and/or through the coupling between proton's initial-state transversity distribution and the final-state twist-3 fragmentation functions. The measurement of SSA for forward inclusive pi0 produced in pp collisions up to high transverse momentum helps examine the validity and interplay of these initial- and final-state models. These models can be further explored by investigating the dependence of the TSSA on event topologies. This thesis presents the STAR measurement of TSSA for forward inclusive pi0 at $2.8
| Author | : |
| Publisher | : |
| Total Pages | : 16 |
| Release | : 2011 |
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Jefferson Lab (JLab) 12 GeV energy upgrade provides a golden opportunity to perform precision studies of the transverse spin and transverse-momentum-dependent structure in the valence quark region for both the proton and the neutron. In this paper, we focus our discussion on a recently approved experiment on the neutron as an example of the precision studies planned at JLab. The new experiment will perform precision measurements of target Single Spin Asymmetries (SSA) from semi-inclusive electro-production of charged pions from a 40-cm long transversely polarized $^3$He target in Deep-Inelastic-Scattering kinematics using 11 and 8.8 GeV electron beams. This new coincidence experiment in Hall A will employ a newly proposed solenoid spectrometer (SoLID). The large acceptance spectrometer and the high polarized luminosity will provide precise 4-D ($x$, $z$, $P_T$ and $Q^2$) data on the Collins, Sivers, and pretzelocity asymmetries for the neutron through the azimuthal angular dependence. The full 2$\pi$ azimuthal angular coverage in the lab is essential in controlling the systematic uncertainties. The results from this experiment, when combined with the proton Collins asymmetry measurement and the Collins fragmentation function determined from the e$^+$e$^-$ collision data, will allow for a quark flavor separation in order to achieve a determination of the tensor charge of the d quark to a 10% accuracy. The extracted Sivers and pretzelocity asymmetries will provide important information to understand the correlations between the quark orbital angular momentum and the nucleon spin and between the quark spin and nucleon spin.
| Author | : F. YUAN |
| Publisher | : |
| Total Pages | : 5 |
| Release | : 2005 |
| Genre | : |
| ISBN | : |
In this talk, we will discuss the single transverse spin asymmetries and their relations to the quark-orbital-angular-momentum of the nucleon.
| Author | : |
| Publisher | : |
| Total Pages | : 6 |
| Release | : 2014 |
| Genre | : |
| ISBN | : |
In this study, transverse single-spin asymmetries are among the most intriguing observables in hadronic physics. Though such asymmetries were already measured for the first time about four decades ago, their origin is still under debate. Here we consider transverse single-spin asymmetries in semi-inclusive lepton-nucleon scattering, in nucleon-nucleon scattering, and in inclusive lepton-nucleon scattering. It is argued that, according to recent work, the single-spin asymmetries for those three processes may be simultaneously described in perturbative QCD, where the re-scattering of the active partons plays a crucial role. A comparison of single-spin asymmetries in different reactions can also shed light on the universality of transverse momentum dependent parton correlation functions. In particular, we discuss what existing data may tell us about the predicted process dependence of the Sivers function.
| Author | : |
| Publisher | : |
| Total Pages | : |
| Release | : 2014 |
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Some estimates for the transverse Single Spin Asymmetry, A_N, in the inclusive processes l p(transv. Pol.) --> h X, given in a previous paper, are expanded and compared with new experimental data. The predictions are based on the Sivers distributions and the Collins fragmentation functions which fit the azimuthal asymmetries measured in Semi-Inclusive Deep Inelastic Scattering (SIDIS) processes (l p(transv. Pol.) --> l' h X). The factorisation in terms of Transverse Momentum Dependent distribution and fragmentation functions (TMD factorisation) -- i.e., the theoretical framework in which SIDIS azimuthal asymmetries are analysed -- is assumed to hold also for the inclusive process l p --> h X at large P_T. The values of A_N thus obtained agree in sign and shape with the data. Some predictions are given for future experiments.
| Author | : |
| Publisher | : |
| Total Pages | : 190 |
| Release | : 2015 |
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| ISBN | : |
Spin-dependent observables are a powerful tool to probe the internal structure of the nucleon and to study the dynamics of the strong interaction. Experimental study of the nucleon spin structure has provided us with many exciting and often surprising results. The so-called "spin crisis" in the 1980s revealed the limitation of naive quark-parton models and led to a worldwide effort to study the nucleon spin structure. However, this effort has been focused mainly on the nucleon's longitudinal spin structure. Recently, when the pioneer work revealed the significant role that transverse spin plays in understanding the full structure of the nucleon and in understanding the dynamics of the strong interaction, the study of the transverse spin structure became the new focus of the worldwide effort. Jefferson Lab (JLab) is located at Newport News, VA, US. It is equipped with the continuous electron beam accelerator facility (CEBAF) and four experimental halls: A, B, C and D. The accelerator can provide a continuous electron beam (2 ns beam bunch) with high polarization (up to ~ 90%) and high current (up to ~ 200[mu]A) for fixed target experiments in all experimental halls. Hall A consists of two standard high-resolution spectrometers (HRS): left HRS (LHRS) and right HRS (RHRS). Another spectrometer, the BigBite spectrometer, can be installed on request by certain experiments. The experiment E06-010 ("Transversity Experiment") at JLab Hall A is the first measurement of the transverse spin structure of the neutron using a transversely polarized 3He target and a 5.89 GeV incident electron beam. The experiment measured target single spin asymmetries (SSA) and beam-target double-pin asymmetries (DSA) in semi-inclusive deep-inelastic scattering (SIDIS) and in deep-inelastic scattering (DIS) processes. It also collected inclusive hadron (pion, kaon and proton) production data parasitically. The scattered electrons were detected in the BigBite spectrometer with associated detectors while the hadrons were detected with the LHRS which had excellent particle identification capabilities. In this dissertation, the first measurement of target single spin asymmetries of charged kaons produced in semi-inclusive deep inelastic scattering of electrons off a transversely polarized 3He target will be discussed. Both the Collins and Sivers moments, which are related to the nucleon transversity and Sivers distributions, respectively, are extracted over the kinematical range of 0.1xbj
| Author | : |
| Publisher | : |
| Total Pages | : 20 |
| Release | : 2006 |
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| ISBN | : |
The large-x behavior of the transverse-momentum dependent quark distributions is analyzed in the factorization-inspired perturbative QCD framework, particularly for the naive time-reversal-odd quark Sivers function which is responsible for the single transverse-spin asymmetries in various semi-inclusive hard processes. By examining the dominant hard gluon exchange Feynman diagrams, and using the resulting power counting rule, we find that the Sivers function has power behavior (1-x)4 at x --> 1, which is one power of (1-x) suppressed relative to the unpolarized quark distribution. These power-counting results provide important guidelines for the parameterization of quark distributions and quark-gluon correlations.
