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.)