scholarly journals Measurement of azimuthal asymmetries of the unpolarized cross section at HERMES

2009 ◽  
Author(s):  
Francesca Giordano ◽  
Rebecca Lamb ◽  
Donald G. Crabb ◽  
Yelena Prok ◽  
Matt Poelker ◽  
...  
Keyword(s):  
Cross Section ◽  
Unpolarized Cross Section ◽  
Azimuthal Asymmetries

scholarly journals π-N Drell-Yan Process in TMD Factorization

2019 ◽  
Vol 2019 ◽  
pp. 1-20
Author(s):  
Xiaoyu Wang ◽  
Zhun Lu
Keyword(s):  
Cross Section ◽  
Point Of View ◽  
Current Understanding ◽  
Theoretical Expression ◽  
Unpolarized Cross Section ◽  
Pion Nucleon ◽  
Kinematical Configuration

This article presents the review of the current understanding on the pion-nucleon Drell-Yan process from the point of view of the TMD factorization. Using the evolution formalism for the unpolarized and polarized TMD distributions developed recently, we provide the theoretical expression of the relevant physical observables, namely, the unpolarized cross section, the Sivers asymmetry, and the cos⁡2ϕ asymmetry contributed by the double Boer-Mulders effects. The corresponding phenomenology, particularly at the kinematical configuration of the COMPASS πN Drell-Yan facility, is displayed numerically.

STUDY OF THE η MESON PRODUCTION IN THE $\vec{d}+d\to{}^4He+\eta$ REACTION USING THE POLARIZED BEAM

2007 ◽  
Vol 22 (02n03) ◽  
pp. 523-527
Author(s):  
◽  
M. Lesiak ◽  
M. Abdel-Bary ◽  
A. Budzanowski ◽  
A. Chatterjee ◽  
...  
Keyword(s):  
Cross Section ◽  
Meson Production ◽  
Excess Energy ◽  
Unpolarized Cross Section ◽  
Preliminary Results ◽  
Polarized Beam

The measurement of the η meson production in [Formula: see text] reaction has been performed at the Big Karl magnetic spectograph at COSY synchrotron in Jülich. The vector and tensor polarized deuetron beam at the excess energy of Q=16 MeV was used. The preliminary results for the unpolarized cross section are presented here.

scholarly journals Colour unwound - disentangling colours for azimuthal asymmetries in Drell-Yan scattering

2017 ◽  
Vol 3 (6) ◽  
Author(s):  
Daniël Boer ◽  
Tom van Daal ◽  
Jonathan Gaunt ◽  
Tomas Kasemets ◽  
Piet Mulders
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Gluon Vertex ◽  
Gluon Exchange ◽  
Azimuthal Asymmetries ◽  
The Given ◽  
Spectator Model

It has been suggested that a colour-entanglement effect exists in the Drell-Yan cross section for the ‘double T-odd’ contributions at low transverse momentum \bm{Q_\st}, rendering the colour structure different from that predicted by the usual factorisation formula . These T-odd contributions can come from the Boer-Mulders or Sivers transverse momentum dependent distribution functions. The different colour structure should be visible already at the lowest possible order that gives a contribution to the double Boer-Mulders (dBM) or double Sivers (dS) effect, that is at the level of two gluon exchanges. To discriminate between the different predictions, we compute the leading-power contribution to the low-\bm{Q_\st} dBM cross section at the two-gluon exchange order in the context of a spectator model. The computation is performed using a method of regions analysis with Collins subtraction terms implemented. The results conform with the predictions of the factorisation formula. In the cancellation of the colour entanglement, diagrams containing the three-gluon vertex are essential. Furthermore, the Glauber region turns out to play an important role – in fact, it is possible to assign the full contribution to the dBM cross section at the given order to the region in which the two gluons have Glauber scaling. A similar disentanglement of colour is found for the dS effect.

scholarly journals Measurement of the proton scalar polarizabilities at MAMI

2019 ◽  
Vol 199 ◽  
pp. 05020 ◽  
Author(s):  
Edoardo Mornacchi
Keyword(s):  
Cross Section ◽  
High Precision Measurement ◽  
Unpolarized Cross Section ◽  
Beam Asymmetry ◽  
Fundamental Properties ◽  
Structure And Dynamics ◽  
Alternative Approach ◽  
Using Data ◽  
First Time ◽  
Data Group

The electric (αE1) and magnetic (βM1) scalar polarizabilities describe the response of the nucleon to an applied electric or magnetic field. They are not only fundamental properties related to the internal structure and dynamics of the nucleon, but they are important also in other areas of physics, such as atomic structure. The values of αE1 and βM1 quoted by the Particle Data Group were determined using data on the unpolarized differential cross-section of the Compton scattering $\gamma p \to \gamma p$. The measurement of the beam asymmetry Σ3, provides an alternative approach to the extraction of the scalar polarizabilities, with different sensitivity and systematics compared to the unpolarized crosssection. This asymmetry was measured recently for the first time below the pion photoproduction threshold by the A2 Collaboration with the Crystal Ball/TAPS experiment at MAMI (Mainz, Germany). A new high precision measurement of both a unpolarized cross-section and beam asymmetry Σ3a is ongoing at MAMI and the polarizabilities αE1 and βM1 will be extracted with unprecedented precision.

scholarly journals Azimuthal Asymmetries for eA/eN Semi-Inclusive DIS and Its Nuclear Dependence

2016 ◽  
Vol 40 ◽  
pp. 1660036
Author(s):  
Yu-Kun Song
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Correlation Functions ◽  
Scattering Process ◽  
Gauge Invariant ◽  
Polarized Target ◽  
Nuclear Dependence ◽  
Polarized Beam ◽  
Nucleus Scattering ◽  
Azimuthal Asymmetries

We applied collinear expansion to the semi-inclusive deeply inelastic lepton-nucleon (nucleus) scattering process [Formula: see text] with both polarized beam and polarized target up to twist-3, and unpolarized process up to twist-4. The differential cross section and azimuthal asymmetries are expressed in terms of gauge invariant twist-3 and twist-4 TMD parton distribution/correlation functions. Measurements of such azimuthal asymmetries provide methods to study different spin and transverse momentum aspects of the partonic structure of nucleon. We further study the nuclear dependence of azimuthal asymmetries and adopt Gaussian ansatz for TMD distribution/correlation functions to estimat the semi-quantitive behaviour of the nuclear dependence. We predict the A-dependence of azimuthal asymmetries which can be tested in the planned EIC’s.

scholarly journals TWO-PHOTON ANNIHILATION INTO PROTON-ANTIPROTON IN A QUARK-DIQUARK SCHEME

1989 ◽  
Vol 04 (19) ◽  
pp. 5213-5234 ◽  
Author(s):  
M. ANSELMINO ◽  
F. CARUSO ◽  
P. KROLL ◽  
W. SCHWEIGER
Keyword(s):  
Experimental Data ◽  
Form Factor ◽  
Cross Section ◽  
Electromagnetic Form Factor ◽  
Wave Functions ◽  
Proton Antiproton ◽  
Unpolarized Cross Section ◽  
Two Photon ◽  
Photon Annihilation ◽  
Good Agreement

We consider [Formula: see text] in the framework of the Brodsky-Farrar-Lepage scheme allowing for (scalar) diquarks as quasi-elementary constituents. We compute the unpolarized cross section using different proton wave functions. Their normalization is fixed by computing the electromagnetic form factor of the proton in the same framework. Good agreement with the experimental data can be obtained. Two-photon annihilation into other baryons is also discussed.

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