international workshop on transverse polarisation phenomena in hard processes como, september 7- 10,...
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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
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
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
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
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
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
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
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
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
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
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
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 -
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
)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
[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
[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
[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
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
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
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
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
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.
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
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
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
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
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