Post on 07-Jan-2016
description
MENU2004, Bejing, August 29- September 5, 2004
Raimondo BertiniDipartimento di Fisica ``A. Avogadro'' and INFN - Torino, Italy
Λ POLARISATION TO PROBE N STRUCTURE
polarisation in inclusive hadron production
• strong pT dependence:
increase with pT up to
~1GeV/c, then constant
ΛTP
• strong xF dependence:
near with xFlinear increase of
ΛTP
Transverse polarisation , normal to the production plane [1]ΛTP
[1]L. G. Pondrom, Phys. Rep. 122(1985)57
• polarisation magnitude indipendent of beam energy
polarisation in inclusive hadron production
Transverse polarisation , normal to the production plane [1]ΛTP
[1]L. G. Pondrom, Phys. Rep. 122(1985)57
• polarisation transfer:
00xD Fyy TFR CFR
Hyperon production Spin Asymmetries
production in unpolarised pp-collision:
Several theoretical models:• Static SU(6) + spin dependence in parton fragmentation/recombination [1-3]
• pQCD spin and transverse momentum of hadrons in fragmentation [4]
[1] T.A.DeGrand et al.,Phys. Rev D23 (1981) 1227.[2] B. Andersoon et al., Phys. Lett. B85 (1979) 417. [3] W.G.D.Dharmaratna, Phys. Rev. D41 (1990) 1731.[4] M. Anselmino et al.,Phys. Rev. D63 (2001) 054029.
φ)(Nφ)(N
φ)(N-φ)(N
θcosP
1A
BN
φcosAP1PφcosAP1Pφcos2P
1D NBNB
BNN
Analysing power
Depolarisation
Key to distinguish between these models
Data available for DNN:
3.67 GeV/c DNN < 0
13.3 -18.5 GeV/c DNN ~ 0
200 GeV/c DNN > 0
DNN @ 40 GeV/c MISSING
f1, g1 studied for decades: h1 essentially unknown
)kx,(fkd)x(f T1T2
1
Twist-2 PDFs
κT-dependent Parton Distributions
Distribution functions
Chirality
even odd
Twist-2
U
L
T
f1
g1
, h1,
h1
h1L
h1T
f 1T
g1T
Λ polarisation with longitudinally polarised lepton beam along ê³
Unpolarised beam and longitudinally pol. target
Transverselly polarised target
Assuming u-quark dominance
R. L. Jaffe Phys. Rev. D54 (1996) R6581
Semi-inclusive deep inelastic scattering
Hyperon production Spin Asymmetries
Polarised target: .
Transverse target polarisation
Existing data: PS185 (LEAR) [2]
[1] K.D. Paschke et al., Phys. Lett. B495 (2000) 49.
[2] PS185 Collaboration, K.D: Paschke et al., Nucl. Phys. A692 (2001) 55.
ΛΛpp
[1] complete determination of the spin structure of reaction
Models account correctly for cross sections.
Models do not account for or .
NEW DATA NEEDED
ΛNND Λ
NNK
Open charm from production and subsequent weak decay
• low branching ratio: B.R. = 0.9%
• huge self-analysing asymmetry:
πΛΛc
[1] Smith Vogt Z. Phys. C75 (1997)271
Open Charm ΔG
XΛc
Λ , p cc
longitudinally polarised
0.98 α ? GeV 40 @
cpp
days ev/100 36000
/s10 5 ev. #
μb 1 Assume
3-
[1]
Beam and Target
SIS 100 Tm
SIS 300 Tm
U: 35 AGeV
p: 90 GeV
Key features:Generation of intense, high-quality secondary beams of rare isotopes and antiprotons.Two rings: simultaneous beams.
Scaling:
Full x1,x2 range .
needed
[1] Anassontzis et al., Phys. Rew. D38 (1988) 1377
Drell-Yan Di-Lepton Production Xμμpp
a 2
aa2
a1
a2a
212
2
F2
2
)(x(x1)ff)(x)f(xfexx
1
s9M
π4α
dxdM
σd
0,1τ
s
1
dxτd
σd
F
2
Gev/c 40pBEAM
1Xμμpp
nb 0.3σ
Kinematics
Why Drell-Yan?
Asymmetries depend on PD only (SIDIS→convolution with QFF)
Why ?
Each valence quark can contribuite to the diagram
Drell-Yan Di-Lepton Production Xμμpp
p
q2P
Mx
1
2
1
xxx 21F
q2P
Mx
2
2
2
s
Mτ
2
21xx
0QM 22μμ
Uncorrelated quark helicities access chirally-odd functions
TRANSVERSITY
Drell-Yan Asymmetries — Polarised beam and target
Ideal because:
• h1 not to be unfolded with fragmentation functions
• chirally odd functionsnot suppressed (like in DIS)
Drell-Yan Asymmetries — Polarised beam and target
a 2
a
11
a
1
2
a
a 2
a
11
a
1
2
a
LL)()(
)()(
xfxfexgxge
A
a 2
a
11
a
1
2
a
a 2
a
11
a
1
2
a2
2
TT )()(
)()(
θcos1
θcos2φsin
xfxfexhxheA
a 2
a
11
a
1
2
a
a 2
a
11
a
L2
a
T21
a
1
2
a
22LT )()(
)()(1-)()(
Q
M
θcos1
cosφ 2sin2θ
xfxfexhxhxxgxxge
A
Drell-Yan Asymmetries — Unpolarised beam, polarised target
)φθsin(φsinSρθcos2φsin
2
νθcos1
dΩ
dσ
σ
11S
21T
22
a 2a
11a
12a
a 2a11
a122
a11
a11
2a
22
S1TT )(x)f(xfe
)(x)h(xhx)(x)f(xfxe
Q
M
θcos1
)φθsin(φ2sin2SA 1
λ 1, 0
Even unpolarised beam isa powerful tool to investigate
кT dependence of QDF
D. Boer et al., Phys. Rev. D60(1999)014012.
Phase space for Drell-Yan processes
30 GeV/c
15 GeV/c
40 GeV/c
= const: hyperbolaexF = const: diagonal
PANDA
ASSIA
Drell-Yan Asymmetries — Unpolarised beam, polarised target
)φθsin(φsinSρθcos2φsin
2
νθcos1
dΩ
dσ
σ
11S
21T
22
a 2a
11a
12a
a 2a11
a122
a11
a11
2a
22
S1TT )(x)f(xfe
)(x)h(xhx)(x)f(xfxe
Q
M
θcos1
)φθsin(φ2sin2SA 1
λ 1, 0
Even unpolarised beam isa powerful tool to investigate
кT dependence of QDF
D. Boer et al., Phys. Rev. D60(1999)014012.
A. Bianconi (ASSIA col.)