Contalbrigo Marco INFN Ferrara Workshop on Partonic Transverse
Momentum in Hadrons: Quark Spin-Orbit Correlations and Quark-Gluon
Interactions March 12-13, 2010 Duke University
Slide 2
PDFs f p u (x), Form Factors F 1p u (t),F 2p u (t ).. TMD PDFs:
f p u (x,k T ), d2kTd2kT =0,t=0 dx W p u (x,k T,r) Mother Wigner
distributions d3rd3r d2kTd2kT Quantum Phase-Space Distributions of
Quarks Measure momentum transfer to target Direct info about
spatial distributions Measure momentum transfer to quark Direct
info about momentum distributions GPD Probability to find a quark u
in a nucleon P with a certain polarization in a position r and
momentum k (FT) GPDs: H p u (x, ,t), 2 Duke Workshop 2010 M.
Contalbrigo
Slide 3
3 Duke Workshop 2010 g 1L h1h1 Fragmentation Functions (FF)
Distribution Functions (DF) M. Contalbrigo Interference between
wave functions with different angular momenta: contains infos about
parton orbital angular momenta Testing QCD at the amplitude level
i.e. Sivers: spin-orbit correlations with same matrix element of
anomaluos magnetic moment, and GPD E Off-diagonal elements are
important objects: 3D description in momentum space PRD 78 (2008)
074010
Slide 4
Distribution Functions (DF) anti-green remnant green quark GPD
EGPD E T SIVERS Quark orbital angular momentum BOER-MULDERS Spin
orbit effect M. Contalbrigo4 Duke Workshop 2010 Off-diagonal
elements: interference of wave- function components with different
orbital momenta
Slide 5
e+e- annihilation: FFs Not zero Collins & IFF Drell-Yan:
PDFs Not zero Boer-Mulders SIDIS: PDFs x FFs Not zero Sivers Not
zero h 1, Collins & IFF Non zero Boer-Mulders . pp reactions:
PDFs (x FFs) Strong SSA at large x F ISI FSI ISI x FSI FSI RICH
CLEAN Hadron probe Lepton probe M. Contalbrigo5 Duke Workshop
2010
Slide 6
Distribution Functions (DF) Correlation Functions and SIDIS
N/qULT U Fragmentation Functions (FF) D q h (z) q(x) Rich
phenomenology but rather involved observables Target type and
hadron ID provide flavor tagging !! constrain valence and sea
disentangle distribution and fragmentation functions
Muldidimensional analysis resolves kinematic correlations !! M.
Contalbrigo6 Duke Workshop 2010
Slide 7
CollinsSivers Boer- Mulders M. Contalbrigo7 Several observables
already measured with matches and mismatches Duke Workshop
2010
Slide 8
8 Executive summary Crucial: completeness flavor tagging and
five-fold differential extraction in all variables (x,z,Q 2,P T )
to have all dependencies resolved TMDs are a new class of phenomena
providing novel insights into the rich nuclear structure Limited
knowledge on transverse momentum dependences Flavor decomposition
often missing Evolution properties to be defined Role of the higher
twist to be quantified Universality Fundamental test of QCD Still
incomplete phenomenology is asking for new inputs Non-zero results
from DIS experiments provide promises but also open questions
Contalbrigo Marco CLAS12 European Workshop 26 February 2009 M.
Contalbrigo8 Duke Workshop 2010
Slide 9
M. Contalbrigo9 Duke Workshop 2010 Reccomendation 1 We
recommend the completion of the 12 GeV Upgrade at Jefferson Lab. It
will enable three-dimensional imaging of the nucleon, revealing
hidden aspects of its internal dynamics. It will complete our
understanding of the transition between the hadronic and the
quark/gluon descriptions of nuclei.
Slide 10
M. Contalbrigo10 Duke Workshop 2010
Slide 11
Limit defined by luminosity 10 32 10 31 10 35 Different Q2 for
same x range EIC 10 34 Resonance region M. Contalbrigo11
Complementary experiments Duke Workshop 2010
Slide 12
6 GeV CEBAF CHL-2 Upgrade magnets and power supplies 12 GeV
CEBAF Enhance equipment in existing halls add Hall D (and beam
line) 2008-2014: Construction (funded at 99%) May 2012 6 GeV
Accelerator Shutdown starts May 2013 Accelerator Commissioning
starts October 2013 Hall Commissioning starts 2013-2015 Pre-Ops
(beam commissioning) M. Contalbrigo12 Duke Workshop 2010
Slide 13
13 CLAS12: experimental set-up Polarized beam multi-purpose
detector for fixed target electron scattering experiments Pion and
kaon, . SSA broad kinematical range large luminosity H and D
targets Contalbrigo Marco CLAS12 European Workshop 26 February 2009
Q 2 >1GeV 2 W 2 >4 GeV 2 y2GeV Large kinematic ranges
accessible with CLAS12 are important for separation of Valence
region Higher Twist contributions (Q 2 ) Perturbative regime (P T
1)
Slide 14
LTCC FTOF PCAL EC HTCC Lumi = 10 35 cm -2 s -1 High beam
polarization 80% High target polarization 85% NH 3 (30 days) ND 3
(50 days) HD-ice target !!! Replace 2 sectors of LTCC with a
proximity RICH detector to identify Kaons approved by JLab PAC34
charged particle radiator drift electrode Proximity gap CLAS12 Wide
detector acceptance allows current & target fragmentation
measur. Photocathode M. Contalbrigo14 Duke Workshop 2010
Slide 15
Pros 1.Small field (Bdl~0.005-0.05Tm) 2.Small dilution
(fraction of events from polarized material) 3.Less radiation
length 4.Less nuclear background (no nuclear attenuation) 5.Wider
acceptance much better FOM, especially for deuteron Cons 1.HD
target is highly complex and there is a need for redundancy due to
the very long polarizing times (months). 2.Need to demonstrate that
the target can remain polarized for long periods with an electron
beam with currents of order of 1-2 nA 3.Additional shielding of
Moller electrons necessary (use minitorus) Heat extraction is
accomplished with thin aluminum wires running through the target
(can operate at T~500- 750mK) HD-Ice target at ~2nA NH3 at ~5 nA
HD-Ice target vs std nuclear targets CLAS transversely polarized
HD-Ice target M. Contalbrigo15 Duke Workshop 2010 P= 95 % H, 70 % D
???
Slide 16
16 Duke Workshop 2010 M. Contalbrigo g 1L h1h1 Distribution
Functions (DF)
Slide 17
Boer-Mulders asymmetry @ CLAS12 Band: Phys Rev D78 034035
Boer-Mulders from DY data Collins from chiral limit Line: Phys Rev
D78 045022 Boer-Mulders from Sivers Collins from e+e- data 56 days
at L=1x10 35 cm -2 s -1 kaon Boer-Mulders: excellent precision vs
model uncertainties M. Contalbrigo17 Duke Workshop 2010
Slide 18
High statistics investigation @ CLAS12 M. Contalbrigo18
PT-dependence of azimuthal moments allows studies of transition
from non-perturbative to perturbative description (Unified theory
by Ji et al, P T matches and mismatches by Bacchetta et al). In the
perturbative limit 1/P T 2 behavior expected Perturbative region
Non-perturbative TMD Duke Workshop 2010
Slide 19
Beam polarization @ CLAS12 M. Contalbrigo19 In the perturbative
limit 1/P T behavior expected A LU ~ 1/Q (Twist-3) Measurements of
kinematic (x,Q 2,z,P T ) will probe HT distribution functions Duke
Workshop 2010
Slide 20
20 Duke Workshop 2010 M. Contalbrigo g 1L h1h1 Distribution
Functions (DF)
Slide 21
Longitudinal Target Spin @ CLAS12 proton 2000h @ 11 GeV with 10
35 sec -1 cm -2 ) M. Contalbrigo21 Helicity dependence of k T -
distribution of quarks Duke Workshop 2010 M.Anselmino et al
hep-ph/0608048 Phys.Rev.D74:074015,2006 0 2 =0.25GeV 2 D 2 =0.2GeV
2 Constituent quark model (Pasquini et al).
Slide 22
Longitudinal Target Spin @ CLAS12 2000h @ 11 GeV NH 3 and ND 3
target with 10 35 sec -1 cm -2 M. Contalbrigo22 Flavor sensitivity
thanks to deuteron/proton target pion/kaon detection Duke Workshop
2010 proton 2000h @ 11 GeV HD-ice target proton
Slide 23
deuteron Longitudinal Target Spin @ CLAS12 M. Contalbrigo23
Curves, QSM, Efremov et al, Czech J Phys 55 (2005) A189
Transversely polarized quarks in long polarized nucleon Leading
twist, sensitive to spin-orbit correlations Duke Workshop 2010
Curves colored: CQM, Pasquini et al, PRD78 (2008) 034025 black:
Avakian et al, PRD77 (2008) 014012 2000h @ 11 GeV NH 3 and ND 3
target with 10 35 sec -1 cm -2
Slide 24
Simple string fragmentation (Artru model) Sub-leading pion
opposite to leading (into page) L=1 production may produce an
opposite sign A UT Leading opposite to leading (into page)
hep-ph/9606390 Fraction of in e X% left from e X asm 20% 40% ~75%
~50% Fraction of direct kaons may be significantly higher than the
fraction of direct pions. LUND-MC M. Contalbrigo24 Duke Workshop
2010
Slide 25
25 Duke Workshop 2010 M. Contalbrigo g 1L h1h1 Distribution
Functions (DF)
Slide 26
UT ~ Collins Study A UT at large x (valence) where models are
mostly unconstrined Collins asymmetry @ CLAS12 26 Duke Workshop
2010 M. Contalbrigo 2000h @ 11 GeV NH 3 target (P=85%, f=0.14) L=
10 35 sec -1 cm -2 Curves fom A.V. Efremov et al PRD76:094025,2006
Tensor charge
Slide 27
unpolarized beam, transv. target Exciting relation: (in bag
& spectator model) Avakian et al., PRD78,114024 non spherical
shape of the nucleon u quark k =0 k =2.0 GeV SS B. Pasquini et al.
arXiv:0806.2298 kk Pretzelosity @ CLAS12 27 Duke Workshop 2010 M.
Contalbrigo 2000h @ 11 GeV NH 3 target (P=85%, f=0.14) L= 10 35 sec
-1 cm -2
Slide 28
unpolarized beam, transverse target S. ArnoldS. Arnold et al
arXiv:0805.2137 M. AnselminoM. Anselmino et al arXiv:0805.2677
Eur.Phys.J.A39:89-100,2009 Sivers effect @ CLAS12 28 Duke Workshop
2010 M. Contalbrigo 2000h @ 11 GeV NH 3 target (P=85%, f=0.14) L=
10 35 sec -1 cm -2
Slide 29
Proton form factors, transverse charge & current densities
D. Mueller, X. Ji, A. Radyushkin, A. Belitsky, M. Burkardt,
Interpretation in impact parameter space Structure functions, quark
longitudinal momentum & helicity distributions How is the
proton charge density related to its quark momentum distribution? ?
Correlated quark momentum and helicity distributions in transverse
space - GPDs 29 Duke Workshop 2010 M. Contalbrigo
Slide 30
CLAS12 - DVCS/BH Target Asymmetry Asymmetries highly sensitive
to the u-quark contributions to the proton spin. Transverse
polarized target e p ep ~ sin Im{k 1 (F 2 H F 1 E ) +}d Q 2 =2.2
GeV 2, x B = 0.25, -t = 0.5GeV 2 E = 11 GeV Sample kinematics A UTx
Target polarization in the scattering plane A UTy Target
polarization perpendicular to the scattering plane 30 Duke Workshop
2010 M. Contalbrigo 2000h @ 11 GeV NH 3 target (P=85%, f=0.14) L=
10 35 sec -1 cm -2
Slide 31
Exclusive production on transverse target 2 (Im(AB*)) T UT A ~
2H u + H d B ~ 2E u + E d 00 K. Goeke, M.V. Polyakov, M.
Vanderhaeghen, 2001 Q 2 =5 GeV 2 E u, E d allow to map the orbital
motion of quarks. 00 B A ~ H u - H d B ~ E u - E d ++ 31 Duke
Workshop 2010 M. Contalbrigo 2000h @ 11 GeV NH 3 target (P=85%,
f=0.14) L= 10 35 sec -1 cm -2