Transversity and inclusive 2p production

1
Transversity and inclusive 2p production
M. Radici - Pavia
chiral-odd partner
2h asymmetry R Ph ST
Collins effect k Ph ST
Dihadron Fragmentation Functions (DiFF)
1992-1996
1998
2000-2002
2003-2004
2005-
(LM) analysis Bacchetta Radici (03) twist 3
DiFF Bacchetta Radici (04) ee- pp Boer,
Jakob, Radici (03) Bacchetta Radici (04)
new data SIDIS ee- (Belle)
quark spin analyzer jet handedness
Jaffe asymmetry in 2p SIDIS s-p
interference predicted sign change _at_ m? Jaffe
et al. (98)
Pavia twist 2 DiFF analysis 1st model
calculation predicted no sign change
Efremov et al. (92) Collins et al. (94) Collins
Ladinsky (94) Artru Collins (96)
A-A Majumder et al. (05)
Bianconi et al. (00) Radici et al. (02)
2
Kinematics of e p" ! e (h1h2) X
scattering plane
RT
LM
partial wave (LM)
1
2
3
leading-twist cross section
(LM)
(LM)
ee- ( Boer, Jakob, Radici P.R. D67 (03) 094003
- Belle ) pp collisions ( Bacchetta Radici
P.R. D90 (04) 094032 - RHIC2 )
from
4
color-gauge invariance and universality
inserting all unsuppressed A- gluons makes the
nonlocal q-q correlator color-gauge invariant
leading-twist projections are semipositive
definite in Dirac space ! probabilistic
interpretation
5
ee-
Boer, Jakob, Radici P.R. D67 (03) 094003 - Belle
same in SIDIS as in ee- at twist 2 ? 1st check
of universality
p-p collision
Bacchetta Radici P.R. D90 (04) 094032
p p" ! (??) X
p p ! (??)C (??)D X
6
single spin asymmetry
(following Trento conventions!)
(here)
(previous work)
( Hermes analysis? )
7
published models
ep" ! e (??-) X
(Jaffe, Jin, Tang, P.R.L. 80 (98) 1166)

• no calculation of ?qI (z) ? figure of merit
• s-p interference from ?-? elastic scattering
• phase shifts only sign change from Re?

(Radici, Jakob, Bianconi, P.R. D65 (02) 074031 )
spectator model interference (s) Im?

• uncertainty band from
• different fp / fs strength
• ratio
• PDF input

P. van der Nat DIS2005
Trento conventions ! ? ( 8/? - 2.55)
8
improved model
( Bacchetta Radici, in preparation )
ep" ! e (??-) X PYTHIA output on
HERMES kinematics 0.1ltylt0.85 Q2 gt 1
GeV2 0.023ltxlt0.4 W2gt4 GeV2 excludes elastic
and single/double diffractive events ?
semi-inclusive
Mh
2. q ? ? X2 ? ??- X2 (14.81)
395 114 events
3. q ? ? X3 ? ??- X3 (0.31)
239 043 events
4. q ? ? X4 ? ??- (?0 X4) (8.65)
5. q ? ? X5 ? ??- (X X5) (2.05)
Total 2 667 889 (??-) pairs
6. q ? K0 X6 ? ??- X6 (3.41)
1. All (2..6) background (70.77)
1 888 065 events
9
spectator model approximation
2. q ? ? X2 ? ??- X2
X2 X3 X4 X p-wave channel coherent sum
2.3.4.
3. q ? ? X3 ? ??- X3
4. q ? ? X4 ? ??- (?0 X4)
Warning ? ? (? ?)L1 ?J1
X4
1. background ? q ? ??- X no resonance ?
real s-wave channel
max number of (??-) pairs in s-p interference
Im p-wave channel
parameters
s-wave
p-wave
10
fit of PYTHIA distributions in invariant mass and
z
2.3.4. p-wave 1. background
s-wave Total Total 5.6.
Mh
z
11
models for transversity
Strat Soffer, Stratmann, Vogelsang P.R. D65
[phone] Kor Korotkov, Nowak, Oganessian
E.P.J. C18 (01) 639 Sch Schweitzer et al. P.R.
D64 (01) 034013 Wak Wakamatsu P.L. B509 (01) 59
u
d
x
from GRV98-LO _at_ Q2 2.5 GeV2
12
prediction of max spin asymmetry
Mh
z
13
fit of spin asymmetry
HERMES PRELIMINARY 6.6 scale uncertainty
? ? ??-
z
? ? (??-) ?0
Mh
bins 0.15 0.15 0.22 1.23
14
deuteron
0.004ltxlt0.4 0.1ltylt0.9 Q2gt1 GeV2
spin asymmetry _at_ COMPASS
Mh
z
Joosten DIS2005
15
proton
0.004ltxlt0.4 0.1ltylt0.9 Q2gt1 GeV2
spin asymmetry _at_ COMPASS
..
Mh
z