W-D. Nowak - INFN
W-D. Nowak - INFN
W-D. Nowak - INFN
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Wolf-Dieter <strong>Nowak</strong>, Perspectives in Hadronic Physics, May 15, 2008 – p. 5<br />
DIS: Kinematics, Cross Sections, Asymmetry<br />
e<br />
N<br />
(E, p)<br />
γ *<br />
(E,<br />
’<br />
p ’)<br />
u<br />
q<br />
u<br />
d<br />
h<br />
h<br />
π<br />
Virtual-photon kinematics:<br />
Q 2 = −q 2 ν = E − E ′<br />
Fraction of nucleon momentum<br />
carried by struck quark: x = Q2<br />
2Mν<br />
fraction of virtual-photon energy<br />
carried by produced hadron h: z = E h<br />
ν<br />
π +<br />
Hadron transverse momentum: P h⊥<br />
Unpolarized cross section: σ UU ≡ 1 2 (σ →⇐ + σ →⇒ )<br />
Cross section (helicity) difference: σ LL ≡ 1 2 (σ →⇐ − σ →⇒ )<br />
Double-spin asymmetry: A || ≡ σ LL<br />
σ UU<br />
≃ g 1<br />
F 1<br />
(neglecting small g 2 contribution)<br />
Measured asymmetry: A || =<br />
1<br />
〈P B 〉〈P T 〉<br />
( N L ) → ⇐−( N<br />
L ) → ⇒<br />
( N L ) → ⇐+( N<br />
L ) → ⇒<br />
with P B (P T ) : longitudinal beam (target) polarization
Change language