International Workshop on Transverse Polarisation Phenomena in Hard Processes
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Transcript of International Workshop on Transverse Polarisation Phenomena in Hard Processes
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International Workshop on Transverse Polarisation Phenomena in Hard Processes
Como, September 7- 10, 2005
Marco MaggioraDipartimento di Fisica ``A. Avogadro'' and INFN - Torino, Italy
SINGLE AND DOUBLE SPIN INTERACTIONS AT GSIN - N
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Introduction
• SIS300 @ GSI: HESR as (asym) collider:
• A complete description of nucleonic structure requires:
@ leading twist and @ NLO ( kT dependence)
• Physics objectives: Drell-Yan di-lepton production
spin observables in hadron production
electromagnetic form factors
quark and gluon distribution functions
quark fragmentation functions
p) GeV 200 :PAC ( GeV80 22s
3110 L
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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
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Why Drell Yan?Asymmetries depend on PD only (SIDIS→convolution with QFF)
Why ?Each valence quark can contribuite to the diagram
Kinematics
p
q2P
Mx
1
2
1
xxx 21F
q2P
Mx
2
2
2
s
Mxxτ
2
21
0QM 22
plenty of (single) spin effects3 planes: plane to polarisation vectors
plane plane
*γp
*γ
Drell-Yan Di-Lepton Production — Xμμpp
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Scaling:
Full x1,x2 range .
needed
[1] Anassontzis et al., Phys. Rev. D38 (1988) 1377
Drell-Yan Di-Lepton Production Xμμpp
a 2
a1
a2
a1
a2a
212
2
F2
2
)(x)f(xf)(x)f(xfexx
1
s9M
π4α
dxdM
σd
0,1τ
s
1
dxτd
σd
F
2
2Gev 20080s 1
Xμμppnb 0.123.0σ
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Phase space for Drell-Yan processes
15 GeV/c
40÷100 GeV/c
= const: hyperbolaexF = const: diagonal
PANDA
ASSIA/PAX(SIS300 or HESR)
[1]A. Bianconi and M. Radici, Phys. Rev. D71 (2005) 074014
2p
[1] GeV/c 9M4 target,p fixed aon GeV 40E with ev K04
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Uncorrelated quark helicities access chirally-odd functions
TRANSVERSITY
Ideal because:
• h1 not to be unfolded with fragmentation functions
• chirally odd functionsnot suppressed (like in DIS)
Drell-Yan Asymmetries — Xμμpp
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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
To be corrected for:
pp PfP
1
Collins-Soper frame: [1]Phys. Rev. D16 (1977) 2219.
Drell-Yan Asymmetries — Xμμpp
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RICH energies: small x1 and/or x2
evolution much slower[1] than Δq(x,Q2) and q(x,Q2) at small x
ATT @ RICH very small, smaller would help[1]
GeV 100s 100M2 -210τ
)Q(x,h 2a1
s
[1]Barone, Colarco and Drago, Phys.Rev. D56 (1997) 527.
220 GeV 0.23Q
22 GeV 25Q
Drell-Yan Asymmetries — Xμμpp
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ATT still small @ large and M2 due to slow evolution of
Large ATT expected[1] for and M2 not too large and τ not too small
)Q(x,h 2a1s
[1]M. Anselmino et al., Phys. Lett. B594 (2004) 97.
2GeV 30s
2GeV 45s
q2
p1
p2q
q2
p1q1
p1q
2q
TT x large
q2
p1
p2
p1
p2q
q2
p1q1
pq12
pq11
p1q
2q
TTTT )x(q)x(qe
)x(h)x(he
a
)x(q)x(q)x(q)x(qe
)x(h)x(h)x(h)x(he
aA
220
20
201q
[1] GeV/c 23.0Q @ )Qx,(q)Qx,(h Assuming
s
HESR:
ATT direct accessto valence quark h1
)x(h )x(h 21q11q VV
0.3 M M
GeV 4530s 2J
2
2max
Drell-Yan Asymmetries — Xμμpp
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θcos2φsin
2
νθcosφμsinθλcos1
3λ
1
4π
3
dΩ
dσ
σ
1 222
NLO pQCD: λ 1, 0, υ 0Experimental data [1]: υ 30 %
[1] J.S.Conway et al., Phys. Rev. D39 (1989) 92.
υ involves transverse spin effects at leading twist [2]:
cos2φ contribution to angular distribution provide:
[2] D. Boer et al., Phys. Rev. D60 (1999) 014012.
)κ,(xh )κ(xh 211
22,1
Di-Lepton Rest Frame
Drell-Yan Asymmetries — Xμμpp
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Conway et al, Phys. Rev. D39 (1989) 92
Angular distribution in CS frame
E615 @ Fermilab
-N +-X @ 252 GeV/c
-0.6 < cos < 0.6
4 < M < 8.5 GeV/c2
• cut on PT selects asymmetry• 30% asymmetry observed for -
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Angular distributions for and Angular distributions for and -- —— -N, N @ 125 GeV/cp p
E537 @ FermilabAnassontzis et al., Phys. Rev. D38 (1988) 1377
•
cosd
dvs cos
• d
dvs
p
pπ
π
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)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 on polarised p, or polarised on unpolarised p
are powerful tools to investigate кT dependence of QDF
D. Boer et al., Phys. Rev. D60 (1999) 014012.
pp
Drell-Yan Asymmetries — Xμμpp
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[1]A. Bianconi and M. Radici, Phys. Rev. D71 (2005) 074014
GeV/c 1q ,GeV/c 9M4 target,fixed aon GeV 40E with ev K04 T2
p[1]
GeV/c 1q ,GeV/c 9M4 GeV, 3.3Eon GeV 15E with ev K8 T2
pp[1]
s ~ 80 GeV2
small asymmetries different dependencies
cannot be resolved
s ~ 200 GeV2
bigger asymmetries different dependencies
can be partially resolved
2
21
21 2xxf
xh
2
21
21 12 xxf
xh
Drell-Yan Asymmetries — Xμμpp
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[1]A. Bianconi and M. Radici, hep-ph/0504261 Phys. Rev. D in press.
GeV/c 1q ,GeV/c 9M4 GeV, 3.3Eon GeV 15E with ev K8 T2
pp[1]
s ~ 200 GeV2
different dependencies can be partially resolved
1
21
21 xf
xh
0
21
21 xf
xh
Drell-Yan Asymmetries — Xμμpp
pxxf
xh
21
21
pxxf
xh 1
21
21
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[1]H. Shimizu et al., Phys. Rev. D71 (2005) 114007
2GeV 30s GeV 5.14s
At higher energy ( s ~ 200 GeV2) perturbative corrections[1] are sensibly smaller
in the safe region
Drell-Yan Asymmetries — Xμμpp
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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 @ 100 GeV/c MISSING
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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
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Transverse Single Spin Asymmetries
dσdσ
dσdσAN πXpp πXpp
• Production @ large xF originate from valence quark: +: AN > 0 ; -: AN < 0 Correlated with expected u and d-quark polarisation
• AN similar for ranging from 6.6 up to 200 GeV
AN related to fundamental properties of quark distribution/fragmentation
New experiment with polarised nucleon target, and in a new kinematical region:
• new data available
• vs
• DY-SSA (AT) possible only @ RICH, p↑p-scattering:
@ smaller s >> @ large s
p
πXpp N,A
DYppσ DY
ppσ
s
πXpp N,A
E704 Tevatron FNAL 200GeV/c
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Electromagnetic form-factors
FF in TL region ( ) related to nucleon structure
New information with respect to SL FF (eN-scattering)
TL - FF:
:
• low statistic• no polarisation phenomena
μμpp •
• analysing power
dΩ
dσalternative way to FF
eepp
angular distribution separation of electric and magnetic FFanalysing power transverse polarisation of p↑ leads
to non zero analysing power
Different prediction for models well reproducing SL data
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Beam and Target
UNILACSIS
FRS
ESR
HESRSuperFRS
NESR
CR
RESR FLAIR
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.
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Main goal: spin physics nucleon structure DY di-lepton production distribution functions Spin observables in hadron production fragmentation Electromagnetic form factors
Ideal tools: polarised , polarised p
Key issue: s (> 80 Gev2, PAC: 200 GeV2), luminosity ( > 1031 )
Summary
Slow extraction from SIS300
polarised target, both PL and PT
minimal PANDA interactions
HESR (collider)
no diluition factor
pp
MORE WORK, SIMULATIONS NEEDEDDISCUSSION WITH GSI MANAGEMENT:
• what is feasable ▪ physics iussues
KEY POINT: how much and how long can we polarise ?
p
p
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Question time
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vector couplings
same spinor structure
Drell-Yan Di-Lepton Production XμμΨJpp
vγuM
1uγv μ
2μvγug
MMM
1uγvg μV
lJ
2J
2μV
q
i
aa*γ
TT
J
TT
)x(u)x(u
)x(h)x(ha
)x(q)x(qg
)x(h)x(hg
21
21u11u
x, xlarge TT
q 21Vq
q 21q11qVqJ
TT21
A
Measure ATT in J/Ψ resonance
region in reactions
Cross section large enough in this region
~ 160 ev/day , <x>≈0.4
2
1u
TT
TT
2J
F u(x)
)x(h
a
A
s
M x, 0x
pp
contrib.) (cont. GeV 10 6.9dMdM
d
scm 10 1.5 GeV 45s 16
6
2-7-22
-1 -2312
L
days 240 %90P %5P
NPP
1δ 11%δ
pp
ppATT
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Beam and Target
NH3 10g/cm3 : 2 x 10cm cells with opposite polarisation
GSI modifications:• extraction SIS100 → SIS300 or injection CR → SIS300 • slow extraction SIS300 → beamline adapted to • experimental area adapted to handle expected radiation from
GeV40Ep
17
3f 85.0PT
1231723 sm105.1105.11061017
3L
sp102 7
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Alternative GSI solution
• Luminosity comparable to external target → KEY IUSSUE • dilution factor f~1• difficult to achieve polarisation Pp ~ 0.85• required achievable with present HESR performances (15 GeV/c)• only transverse asymmetries can be measured• p↑-beam required polarisation proton source and acceleration scheme preserving polarisation• no additional beam extraction lines needed• PHYSICS PARTIALLY FEASIBLE @ PANDA AS WELL
HESR collider polarised p and beams p
s
GeV/c15 Pp