scholarly journals Spin asymmetries in electron-jet production at the future electron ion collider

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Zhong-Bo Kang ◽  
Kyle Lee ◽  
Ding Yu Shao ◽  
Fanyi Zhao
Keyword(s):  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Proton Collisions ◽  
Jet Production ◽  
The Future ◽  
Jet Fragmentation ◽  
Unpolarized Electron ◽  
Azimuthal Asymmetries

Abstract We study all the possible spin asymmetries that can arise in back-to-back electron-jet production, ep → e + jet + X, as well as the associated jet fragmentation process, ep → e+jet(h)+X, in electron-proton collisions. We derive the factorization formalism for these spin asymmetries and perform the corresponding phenomenology for the kinematics relevant to the future electron ion collider. In the case of unpolarized electron-proton scattering, we also give predictions for azimuthal asymmetries for the HERA experiment. This demonstrates that electron-jet production is an outstanding process for probing unpolarized and polarized transverse momentum dependent parton distribution functions and fragmentation functions.

scholarly journals GENERALIZED UNIVERSALITY FOR TMD DISTRIBUTION FUNCTIONS

2012 ◽  
Vol 20 ◽  
pp. 66-74 ◽  
Author(s):  
M. G. A. BUFFING ◽  
P. J. MULDERS
Keyword(s):  
Transverse Momentum ◽  
Parton Distribution ◽  
Azimuthal Angle ◽  
High Energy ◽  
Distribution Functions ◽  
Transverse Spin ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Azimuthal Asymmetries

Azimuthal asymmetries in high-energy processes, most pronounced showing up in combination with single or double (transverse) spin asymmetries, can be understood with the help of transverse momentum dependent (TMD) parton distribution and fragmentation functions. These appear in correlators containing expectation values of quark and gluon operators. TMDs allow access to new operators as compared to collinear (transverse momentum integrated) correlators. These operators include nontrivial process dependent Wilson lines breaking universality for TMDs. Making an angular decomposition in the azimuthal angle, we define a set of universal TMDs of definite rank, which appear with process dependent gluonic pole factors in a way similar to the sign of T-odd parton distribution functions in deep inelastic scattering or the Drell-Yan process. In particular, we show that for a spin 1/2 quark target there are three pretzelocity functions.

Color Entanglement in Hadronic Processes for Transverse Momentum Dependent Parton Distribution Functions

2015 ◽  
Vol 37 ◽  
pp. 1560022
Author(s):  
M. G. A. Buffing ◽  
P. J. Mulders
Keyword(s):  
Transverse Momentum ◽  
Parton Distribution ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Initial State ◽  
Color Flow ◽  
Transverse Momentum Dependent ◽  
Gauge Link ◽  
Azimuthal Asymmetries ◽  
Different Parts

In the description of protons, we go beyond the ordinary collinear parton distribution functions (PDFs), by including transverse momentum dependent PDFs (TMDs). As such, we become sensitive to polarization modes of the partons and protons that one cannot probe without accounting for transverse momenta of partons, in particular when looking at azimuthal asymmetries. Hadronic processes require the inclusion of gluon contributions forming the gauge links, which are path-ordered exponentials tracing the color flow. In processes with two hadrons in the initial state, such as Drell-Yan (DY), the gauge links from different parts of the process get entangled. We show that in color disentangling this gauge link structure, one becomes sensitive to this color flow. After disentanglement, particular combinations of TMDs will require a different numerical color factor than one naively might have expected. Such color factors will even play a role for azimuthal asymmetries in the simplest hadronic processes such as DY.

HADRON STRUCTURE STUDY IN FORTHCOMING DRELL–YAN EXPERIMENTS: COMPASS PROJECT AT CERN

2009 ◽  
Vol 24 (35n37) ◽  
pp. 3033-3044 ◽  
Author(s):  
◽  
OLEG DENISOV
Keyword(s):  
Transverse Momentum ◽  
Structure Study ◽  
Distribution Functions ◽  
Proton Target ◽  
Production Mechanism ◽  
Hadron Structure ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Hadron Beam

The study of Drell–Yan (DY) processes involving the collision of an (un)polarised hadron beam on an (un)polarised proton target can result in a fundamental improvement of our knowledge on the transverse momentum dependent (TMDs) parton distribution functions (PDFs) of hadrons. The production mechanism of J/ψ and J/ψ - DY duality can also be addressed. One of the forthcoming polarised DY experiments (COMPASS (SPS, CERN)) is discussed in this context. The most important features of this project are briefly reviewed, as well as its sensitivity to the various transverse momentum dependent spin asymmetries.

OVERVIEW OF EXPERIMENTAL RESULTS FROM HERMES

2012 ◽  
Vol 20 ◽  
pp. 19-28
Author(s):  
MARCO CONTALBRIGO
Keyword(s):  
Degrees Of Freedom ◽  
Distribution Functions ◽  
Real Photon ◽  
Final States ◽  
Spin Orbit ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Hermes Experiment ◽  
Electrons And Positrons ◽  
Azimuthal Asymmetries

The investigation of the partonic degrees of freedom beyond collinear approximation (3D description) has been gained increasing interest in the last decade. At the HERMES experiment, azimuthal asymmetries in hard exclusive reactions and in semi-inclusive deep-inelastic scattering of electrons and positrons off a (polarized) hydrogen and deuterium target have been measured. Such asymmetries provide new insights on crucial aspects of the parton dynamics. By measuring various hadron types in the initial and final states, flavor sensitivity is achieved. Non zero signals are reported for azimuthal asymmetries with respect the transverse target polarization in real-photon exclusive-electroproduction, which are related (still in a model dependent way) to the elusive quark orbital motion. Evidence is reported of the poorly known transversity function and of naive-T-odd transverse-momentum-dependent parton distribution functions related to spin-orbit effects. Evidence of spin-orbit effects in quark fragmentation is also observed, which are opposite in sign for favored and disfavored processes.

scholarly journals Longitudinal Double Spin Asymmetries of π0 - Jet Correlations in Polarized Proton Collisions at s = 510 GeV at STAR

2018 ◽  
Vol 46 ◽  
pp. 1860011
Author(s):  
Yaping Wang
Keyword(s):  
Spin Asymmetry ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Final State ◽  
Model Calculations ◽  
Spin Asymmetries ◽  
Proton Collisions ◽  
Rapidity Region ◽  
Double Spin ◽  
Polarized Proton

One of the primary goals of the spin physics program at STAR is to constrain the polarized gluon distribution function, [Formula: see text], by measuring the longitudinal double-spin asymmetry ([Formula: see text]) of various final-state channels. Using a jet in the mid-rapidity region [Formula: see text] correlated with an azimuthally back-to-back [Formula: see text] in the forward rapidity region [Formula: see text] provides a new possibility to access the [Formula: see text] distribution at Bjorken-[Formula: see text] down to 0.01. Compared to inclusive jet or inclusive [Formula: see text] measurements, this channel also allows to constrain the initial parton kinematics. In these proceedings, we will present the status of the analysis of the [Formula: see text]-jet [Formula: see text] in longitudinally polarized proton+proton collisions at [Formula: see text] =510 GeV with 80 pb[Formula: see text] of data taken during the 2012 RHIC run. We also compare the projected [Formula: see text] uncertainties to theoretical predictions of the [Formula: see text] by next-to-leading order (NLO) model calculations with different polarized parton distribution functions.

scholarly journals Polarized Drell-Yan at COMPASS-II: Transverse Spin Physics Program

2016 ◽  
Vol 40 ◽  
pp. 1660109
Author(s):  
Bakur Parsamyan
Keyword(s):  
High Energy ◽  
Muon Beam ◽  
Distribution Functions ◽  
Transverse Spin ◽  
Spin Physics ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Compass Experiment ◽  
Physics Program ◽  
Azimuthal Asymmetries

Successful realization of polarized Drell-Yan physics program is one of the main goals of the second stage of the COMPASS experiment. Drell-Yan measurements with high energy (190 GeV/c) pion beam and transversely polarized NH3 target have been initiated by a pilot-run in the October 2014 and will be followed by 140 days of data taking in 2015. In the past twelve years COMPASS experiment performed series of SIDIS measurements with high energy muon beam and transversely polarized deuteron and proton targets. Results obtained for Sivers effect and other target transverse spin dependent and unpolarized azimuthal asymmetries in SIDIS serve as an important input for general understanding of spin-structure of the nucleon and are being used in numerous theoretical and phenomenological studies being carried out in the field of transvers-spin physics. Measurement of the Sivers and all other azimuthal effects in polarized Drell-Yan at COMPASS will reveal another side of the spin-puzzle providing a link between SIDIS and Drell-Yan branches. This will be a unique possibility to test universality and key-features of transverse momentum dependent distribution functions (TMD PDFs) using essentially same experimental setup and exploring same kinematic domain. In this review main physics aspects of future COMPASS polarized Drell-Yan measurement of azimuthal transverse spin asymmetries will be presented, giving a particular emphasis on the link with very recent COMPASS results obtained for SIDIS transverse spin asymmetries from four ”Drell-Yan” [Formula: see text]-ranges.

scholarly journals The Sivers asymmetry in hadronic dijet production

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Zhong-Bo Kang ◽  
Kyle Lee ◽  
Ding Yu Shao ◽  
John Terry
Keyword(s):  
Spin Asymmetry ◽  
Star Collaboration ◽  
Heavy Ion ◽  
Distribution Functions ◽  
Relativistic Heavy Ion Collider ◽  
Parton Distribution Functions ◽  
Dijet Production ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Polarized Proton

Abstract We study the single spin asymmetry in the back-to-back dijet production in transversely polarized proton-proton collisions. Such an asymmetry is generated by the Sivers functions in the incoming polarized proton. We propose a QCD formalism in terms of the transverse momentum dependent parton distribution functions, which allow us to resum the large logarithms that arise in the perturbative calculations. We make predictions for the Sivers asymmetry of hadronic dijet production at the kinematic region that is relevant to the experiment at the Relativistic Heavy Ion Collider (RHIC). We further compute the spin asymmetries in the selected positive and negative jet charge bins, to separate the contributions from u- and d-quark Sivers functions. We find that both the sign and size of our numerical results are roughly consistent with the preliminary results from the STAR collaboration at the RHIC.

scholarly journals ANALYTIC PROPERTIES OF MULTI-PARTON POLE MATRIX ELEMENTS AND UNIVERSALITY OF FRAGMENTATION FUNCTIONS

2011 ◽  
Vol 04 ◽  
pp. 115-125
Author(s):  
LEONARD GAMBERG ◽  
ASMITA MUKHERJEE ◽  
P. J. MULDERS
Keyword(s):  
High Energy ◽  
Distribution Functions ◽  
Analytic Structure ◽  
Matrix Elements ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Fragmentation Functions ◽  
High Energy Scattering

Gluonic pole matrix elements explain the appearance of single spin asymmetries (SSA) in high-energy scattering processes. They involve a combination of operators which are odd under time reversal (T-odd). Such matrix elements appear in principle both for parton distribution functions and parton fragmentation functions. We show that for parton fragmentation functions these gluonic pole matrix elements vanish as a consequence of the analytic structure of scattering amplitudes in Quantum Chromodynamics. We extend this analysis to the case of multi-partonic pole matrix elements. This result is important in the study of the universality of transverse momentum dependent (TMD) fragmentation functions.

scholarly journals INSIGHTS ON NON-PERTURBATIVE ASPECTS OF TMDs FROM MODELS

2009 ◽  
Vol 24 (35n37) ◽  
pp. 2995-3004 ◽  
Author(s):  
H. AVAKIAN ◽  
A. V. EFREMOV ◽  
P. SCHWEITZER ◽  
O. V. TERYAEV ◽  
F. YUAN ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Inelastic Scattering ◽  
Deep Inelastic Scattering ◽  
Parton Distribution ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Perturbative Calculations ◽  
Transverse Momentum Dependent ◽  
Azimuthal Asymmetries

Transverse momentum dependent parton distribution functions are a key ingredient in the description of spin and azimuthal asymmetries in deep-inelastic scattering processes. Recent results from non-perturbative calculations in effective approaches are reviewed, with focus on relations among different parton distribution functions in QCD and models.

Recent Key Measurements for Accessing the Transverse Spin and Momentum Structure of the Nucleon

2016 ◽  
Vol 40 ◽  
pp. 1660028 ◽  
Author(s):  
Anna Martin
Keyword(s):  
Transverse Momentum ◽  
Parton Distribution ◽  
Distribution Functions ◽  
Transverse Spin ◽  
Nucleon Structure ◽  
Nucleon Spin ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Azimuthal Asymmetries ◽  
Selection Of

A selection of recent key results obtained in semi-inclusive deeply inelastic scattering (SIDIS) experiments is presented. The observations strongly support the description of the nucleon structure in terms of transverse momentum dependent parton distribution functions, which represent the various correlations between the quarks spins, the quarks transverse momenta and the nucleon spin which give rise to specific spin-dependent azimuthal asymmetries.

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