The HERMES Experiment

10.1142/11692 ◽  
2020 ◽  
Author(s):  
Richard Milner ◽  
Erhard Steffens
Keyword(s):  
Hermes Experiment

MEASUREMENT OF POLARIZED QUARK DISTRIBUTIONS AT HERMES

2003 ◽  
Vol 18 (08) ◽  
pp. 1185-1192
Author(s):  
◽  
STEFAN BERNREUTHER
Keyword(s):  
Cross Section ◽  
Kinematic Range ◽  
Spin Asymmetries ◽  
Double Spin ◽  
Hermes Experiment ◽  
Down Quark ◽  
Up Quark ◽  
Rich Detector ◽  
The Individual ◽  
Quark Flavors

The HERMES experiment has measured double spin asymmetries in the cross section for deep–inelastic scattering of longitudinally polarized positrons on longitudinally polarized 3 He (1995), 1 H (1996/97), and 2 D (1998) targets. A kinematic range of 0.023 < x < 0.6, and 1 GeV 2 < Q2 < 15 GeV 2 has been covered. From these asymmetries, based on inclusive and semi–inclusive measurements, polarized quark distributions are extracted as a function of x for up [Formula: see text] and down [Formula: see text] flavors as well as for valence and sea quarks. In the measured range, the up quark polarization is positive while the down quark polarization is negative. The sea quark polarization is compatible with zero. In this analysis all sea quark polarizations have been assumed to be flavor symmetric. Presently HERMES is analyzing a high statistics 2 D data sample taken in 1999-2000. For these data it is possible to identify pions and kaons with a RICH detector which was installed in 1998. This will enable an extraction of the individual sea quark flavors [Formula: see text], [Formula: see text], and [Formula: see text] without any symmetry assumptions.

The luminosity monitor of the HERMES experiment at DESY

2001 ◽  
Vol 471 (3) ◽  
pp. 314-324 ◽  
Author(s):  
Th. Benisch ◽  
S. Bernreuther ◽  
E. Devitsin ◽  
V. Kozlov ◽  
S. Potashov ◽  
...  
Keyword(s):  
Hermes Experiment ◽  
Luminosity Monitor

scholarly journals Recent results from the HERMES experiment

2010 ◽  
Vol 34 (9) ◽  
pp. 1247-1253
Author(s):  
Keyword(s):  
Hermes Experiment

The HERMES experiment

1997 ◽  
Vol 622 (1-2) ◽  
pp. c16-c30
Author(s):  
R.G. Milner
Keyword(s):  
Hermes Experiment

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.

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