pac34, jlab, january 27 1 harut avakian (jlab) pac34 jlab, january 27, 2009 proposal pr12-09-09:...
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PAC34, JLab, January 271
Harut Avakian (JLab)Harut Avakian (JLab)
PAC34 JLab, January 27, 2009
Proposal PR12-09-09:
Measure helicity distributions and the Collins fragmentation of kaons in SIDIS
Studies of spin-orbit correlations in kaon electroproduction in DIS with longitudinally polarized hydrogen and deuterium targets
Spokespersons: H. Avakian, E. Cisbani, K. Griffioen, K. Hafidi, P. Rossi
PAC34, JLab, January 272
The CLAS Collaboration
PAC34, JLab, January 273
Outline
IntroductionkT-effects with longitudinally polarized target
Double spin asymmetries and kT-widthsSingle Spin Asymmetries and the Collins effect
Projections for 12 GeVSummary
Transverse structure of the nucleon and correlations between longitudinal and transverse degrees of freedom.
PAC34, JLab, January 274
z
sin2moment of the cross section for unpolarized beam and longitudinal target
U unpolarizedL long.polarizedT trans.polarized
SIDIS kinematical plane and observables
Transverse spin effects are observable as correlations of transverse spin and transverse momentum of quarks.
PAC34, JLab, January 275
Single hadron production in hard scattering
h
Target fragmentation Current fragmentation
Fracture Functions
xF
M
0-1 1
h
h
PDF GPD
kT-dependent PDFs Generalized PDFs
Wide kinematic coverage of large acceptance detectors allows studies of hadronization both in the target and current fragmentation regions
xF - momentum
in the CM frame
xF>0 (current fragmentation)
xF<0 (target fragmentation)
h
PAC34, JLab, January 276
Transverse Momentum Dependent (TMD) Distributions
Quark polarization
Nucleon polarization
Real and imaginary parts of the L≠0 interference contributions
•kT – leads to 3D description with 8PDFs
Factorization of kT-dependent PDFs proven at low PT of hadrons (Ji et al)
Twist-3
PAC34, JLab, January 277
A1 PT-dependence in SIDIS
M.Anselmino et al hep-ph/0608048
+ ALL can be explained in terms of broader kT distributions for f1 compared to g1
02=0.25GeV2
D2=0.2GeV2
In perturbative limit predicted to be constant
Como-2005
constituent quark model (Pasquini et al).
PAC34, JLab, January 278
u/u
(dipole formfactor), J.Ellis, D-S.Hwang, A.Kotzinian
Helicity distributions: Diquark model
Difference in q+=f1+g1 (quark aligned with proton spin) and q-=f1-g1 - (anti-aligned) kT-dependences may lead to observable effects
JMR model
Jakob, Mulders, Rodrigues, Nucl. Phys. A 1997
q
DqMR , R=s,a
For given x the sign of the polarization is changing at large kT
PAC34, JLab, January 279
A1 PT-dependence in SIDIS
M.Anselmino et al hep-ph/0608048
+ A1 suggests broader kT distributions for f1 compared to g1
- A1 may require non-Gaussian kT-dependence for different helicities and/or flavors
02=0.25GeV2
D2=0.2GeV2
0.4<z<0.7
PAC34, JLab, January 2710
Collins asymmetry with longitudinally pol. proton
Collins effect measurement with longitudinally pol. target provide access to the chiral-odd Ralston-Soper-Mulders-Tangerman (RSMT)
distribution functions and probes the polarized fragmentation function
Correlation between the transverse momentum and transverse spin of quarks in longitudinally polarized proton
First discussed by Kotzinian & Mulders (1996)
-
Clean observable: no Sivers type contributions, no twist-3 contributions
PAC34, JLab, January 2711
Transversely polarized quarks in the long. polarized nucleon
Light cone constituent quark model Pasquini,Cazzaniga & Boffi, Phys.Rev.D78:034025,2008
Brodsky & Yuan (2006)
PAC34, JLab, January 2712
Collins SSA measurements
+(u,d) K+ (u,s)
• K+ and + asymmetries consistent within error bars •K- and - asymmetries may have opposite sign
e+e-→hhX
Observed SSA show strong dependence on the final state hadron
BRAHMS
p↑p→hX
PAC34, JLab, January 2713
Collins effect
Simple string fragmentation (Artru model)
Sub-leading pion opposite to leading
(into page)
L=1
production may produce an opposite sign AUT
Leading opposite to leading (into page)
hep-ph/9606390 Fraction of in eX
% left from eX asm
20%
40%
~75%
~50%Fraction of direct kaons may be significantly higher than the fraction of direct pions. LUND-MC
PAC34, JLab, January 2714
The Collins function
First calculation of the Collins functionBacchetta et al, Phys.Lett.B659:234-243,2008
The Kaon Collins effect may be significant!
Kaon Pion
HERMES/COMPASS/Belle
spectator model
PAC34, JLab, January 2715
CLAS12LTCC
FTOF
PCAL
ECHTCC
Lumi = 1035cm-2s-1
High beam polarization 80%High target polarization 85%NH3 (30 days) ND3 (50 days)
Wide detector and physics acceptance (current/target fragmentation)
Replace 2 sectors of LTCC with a proximity RICH detector
2/3 cm
60/80 cm
pad cathode coated with CsI film
Proximity Gap
~4 K- separation at ~5 GeV/c
PAC34, JLab, January 2716
Q2>1GeV2
W2>4 GeV2(10)y<0.85MX>2GeV
SIDIS kinematics
Kaon distributions in ep e’KX
High energy kaons are at small angles (<30o)
LUND-MC
More kaons at small x
forward
PAC34, JLab, January 2717
ALL PT-dependence
•Azimuthal asymmetry sensitive to the difference of widths in PDFs•Proton and deutron data provide a complete set required for the flavor decomposition
Anselmino et al, Phys.Rev.D74:074015,2006.
proton deuteron
GRSV-2000+Kretzer
PAC34, JLab, January 2718
Collins fragmentation: Longitudinally polarized target
•Study the Collins function of kaons•Provides independent information on the RSMT TMD
Kotzinian-Mulders Asymmetry
proton deuteron
Pasquini et al.
PAC34, JLab, January 2719
Collins Effect: from asymmetries to distributions
Combined analysis of Collins fragmentation asymmetries from proton and deuteron may provide independent to e+e- (BELLE)Information on the underlying Collins function.
need
PAC34, JLab, January 2720
Summary
Probe the Collins polarized fragmentation function of kaons
Provide complementary to pions info on the flavor and helicity dependence of quark transverse momentum distributions
Study the transverse polarization of quarks in the longitudinally polarized nucleon through measurements of the leading twist chiral-odd Ralston-Soper-Mulders-Tangerman distribution function.
Study higher twist effects and probe T-odd distributions in a wide range of Q2
Beam request: 80 days of CLAS12@ 11 GeV with L=1035cm-2sec-1 (shared with E12-07-107) with longitudinally polarized NH3(30days) and ND3(50 days) with RICH upgrade
Latest experimental data indicate that spin-orbit correlations may be significant, leading to hadron flavor dependent
observable spin and azimuthal asymmetries
Precision measurement of spin and azimuthal asymmetries (sin2, cos and sin in kaon production in DIS will allow us to:
PAC34, JLab, January 2721
Support slides….
PAC34, JLab, January 2722
A Rich detector for CLAS12
A Rich detector would strongly enhance the CLAS12
capabilities in particle identification and would open
possibilities for new physics
Contalbrigo Marco PAC34 27 January 2009
2/3 cm
60/80 cm
pad cathode coated with CsI film
Proximity Gap
Replacement of LTCC with proximity focusing CsI Rich detector
good separation of /K/p in the 2-5 GeV/c momentum range
no impact on the baseline design of CLAS 12 minimum impact on spectrometer performaces
RICH
PAC34, JLab, January 2723
Low energy electromagnetic processes, especially Møller scattering of beam electrons off atomic electrons are the main contributor to the background load in an open large acceptance spectrometer such as CLAS12.
The full event and background load has been measured with CLAS, e.g. for DVCS process at 5.7 GeV. The GEANT simulation reproduces hit occupancy on tracking chambers.
We used the calibrated simulation code to extrapolate to 11 GeV and simulate the same process at higher luminosity for CLAS12 situation.
This background was also studied in a full Geant4 simulation.
CLAS12 - Electromagnetic Background
PAC34, JLab, January 2724
5 T Magnetic Field and Shielding
Photons
One Event
Electrons
Photons
One Event
Shielding
Background at L=1035cm-2s-1, T = 150ns
CLAS12
PAC34, JLab, January 2725
CLAS12 – Electromagnetic & Hadronic Rates
Deposited Energy detector > 20 KeV
32.3 0.85
RICH (5o-30o) (in 2 sectors)
Photons Hadrons
(in MHz)
L1 31.3 2.5 L2 31.1 2.2 L3 24.6 2.2
SVT (5o-35o)
Photons Hadrons
DC1 (5o-35o)
1.7 3.1
Photons Hadrons
Comment: For deposited energy of 20 KeV RICH would see about 35 hits in 1μsec window, randomly distributed over ~20 m2 and uncorrelated with track in DC. This is a very conservative estimate as for electrons to be knocked out from the RICH radiator > 500 KeV energy deposition is needed.
PAC34, JLab, January 2726
Rpd-
Both ratios agree with PDF models for z<0.7 (Mx>1.4 GeV)
PAC34, JLab, January 2727
Unfavored to favored ratio consistent with HERMES and EMC for z=0.55
D-/D+ from Deuteron + to - ratio
PAC34, JLab, January 2728
multiplicities in SIDIS ep→e’X
+/- multiplicities at large z diverge from SIDIS predictions0 multiplicities less affected by higher twists0.4<z<0.7 kinematical range, where higher twists are expected to be small
DSS (Q2=2.5GeV2)
DSS (Q2=25GeV2)
M.AghasyanHall-C
PAC34, JLab, January 2729
Uncertainties
PAC34, JLab, January 2730
Collins Effect: from asymmetries to distributions
Combined analysis of Collins fragmentation asymmetries from proton and deuteron may provide independent to e+e- (BELLE)Information on the underlying Collins function.
need
PAC34, JLab, January 2731
Higher Twist SSAs and Quark-Gluon Correlations
Target sin SSA (Bacchetta et al. 0405154)
Discussed as main sources of SSA due to the Collins fragmentation
In jet SIDIS only contributions ~ D1 (Sivers type)
With H1┴ (0)≈0 (or measured) Target and Beam SSA can be a valuable source of info on HT T-odd distribution functions
Transversely polarized quarks
PAC34, JLab, January 2732
SSA with unpolarized target
quark polarization
PAC34, JLab, January 2733
SSA with unpolarized target
quark polarization
PAC34, JLab, January 2734
SSA with long. polarized target
quark polarization
PAC34, JLab, January 2735
SSA with long. polarized target
quark polarization
PAC34, JLab, January 2736
CLAS: Fraction from baryonic decays in SIDIS
Significant fraction from target fragmentation at pion momenta below 2 GeV
PAC34, JLab, January 2737
Dilution factor in SIDIS
Multiple scattering and attenuation in nuclear environment introduces
additional PT-dependence for hadrons
Fraction of events from polarized hydrogen in NH3
Nu,Np -total counts from NH3 and carbon normalized by lumi
u, p -total areal thickness of hydrogen (in NH3), and carbon target
Cn=Nitr/Carbon ratio (~0.98)Diff. symbols for diff x-bins
-
PAC34, JLab, January 2738
CLAS12: Acceptance deformation due to incomplete azimuthal coverage
No significant effect seen from limited coverage by RICH
Lab
PAC34, JLab, January 2739
Inbendin/outbending configurations
Different polarities increase the acceptance of positive and negative hadrons.
PAC34, JLab, January 2740
Critical for separation moment range 2<PK<5 and <25 degree
Kinematic dependence of K/ ratios
PAC34, JLab, January 2741
Q2>1GeV2
W2>4 GeV2(10)y<0.85MX>2GeV
SIDIS kinematics
Kaon distributions in ep e’KX
High energy kaons are at small angles
PAC34, JLab, January 2742
A Rich detector for CLAS12MC simulation: 3 cm thick C5F12 radiator 80 cm CH4 proximity gap 1 cm pixel pad size 5 o-30 o radiator polar angle
4 K- separation at 5 GeV/c 80 % kaon eff. with 1:1000 rejection 95 % kaon eff. with 1:100 rejection
Contalbrigo Marco PAC34 27 January 2009
Already with 2 sectors gain of factor~3 in the relevant z region of interest
PAC34, JLab, January 2743
Transverse Momentum Dependent (TMD) Distributions
Quark polarization
Nucleon polarization
Real and imaginary parts of the L=0 and L=1 interference contribution
Related to transversity by Lorentz Invariant relations.
In constituent quark model (Pasquini et al).
•kT – leads to 3D description with 8PDFs
PAC34, JLab, January 2744
Compare SIDIS experiments
COMPASS/HERMES/CLAS
cover different Q2 for the
same x-range
x=0.3 → Q2=~2 GeV2 (CLAS),
~7 GeV2 (HERMES)
~30 GeV2 (COMPASS)
PAC34, JLab, January 2745
HERMES: Diffractive corrections to DIS
PAC34, JLab, January 2746
Collins Effect: from asymmetries to distributions
Combined analysis of Collins fragmentation asymmetries from SIDIS and e+e- (BELLE) would allow separation of transverse spin distributions (Anselmino et al., arXiv:0707.1197 )
need
Brodsky & Yuan (2006)
CLAS12
PAC34, JLab, January 2747
JLab@12GeV: Inclusive DIS
BBS/LSS no OAM
PDF measurements at large x provide additional information on OAM
BBS/LSS with OAM
PAC34, JLab, January 2748
The Large-Nc Behavior of the PDFs
Use the large Nc limit of QCD to study TMD PDFs
qg interaction constant
In color singlet Feynman diagrams every vertex
loop
Introduced by ‘t Hooft in1974
isospin
Nc-
power
P.Pobylitsa hep-ph/0301236
PAC34, JLab, January 2749
The Large-Nc limit of QCD to study TMD PDFs
3 – isospin Pauli matrice
t1,t2 – isospin projection of
quark fields
(3)uu =1, (3)dd=-1
Change sign from + (SIDIS) to – (DY)
Nucleon mass M=O(Nc)
Large-Nc approach predicts signs and relative Nc power of TMDs, used in phenomenology.
3 – nucleon isospin
P.Pobylitsa hep-ph/0301236
Do not change sign (isoscalar)
All others change sign u→d (isovector)
Introduced by ‘t Hooft in1974
qg interaction constantIn color singlet Feynman diagrams every vertex
loop
PAC34, JLab, January 2750
GSIM12
Events for exclusive + production on proton (ep→e’+n)
Typical event
PAC34, JLab, January 2751
SIDIS (*p→X) cross section at leading twist (Ji et al.)
structure functions = pdf × fragm × hard × soft (all universal)
eUnpolarized target
Longitudinally pol. target
Transversely pol. target e
e
p
pBoer-Mulders
1998
Kotzinian-Mulders1996
Collins-1993
To observe the transverse polarization of quarks in SIDIS spin dependent fragmentation is required!
Do we understand well the helicity distributions?
PAC34, JLab, January 2752
Azimuthal Asymmetries in SIDIS
Due to color coherence the configuration with gluon inside the quark cone is more probable
Why <cos> < 0 ? Chay,Ellis,Stirling-1991
x
=180
=0
PAC34, JLab, January 2753
HT and Semi-Exclusive Pion Production E. Berger, S. Brodsky 1979 (DY), E.Berger 1980,A.Brandenburg, V. Khoze, D. Muller 1995
A.Afanasev, C.Carlson, C. Wahlquist Phys.Lett.B398:393-399,1997
+
Fragmentation +
0
• Azimuthal asymmetries with opposite sign from HT effects
• Effect may be suppressed for semi-exclusive 0 compared to +/-
PAC34, JLab, January 2754
Flavor Decomposition
Use double spin asymmetries for different targets and final state particles to extract the helicity distributions for different flavors
Sum over quark flavors
Extraction of kT-dependent distributions q+ (f1+g1) and q- (f1-g1) will require
unfolding of spin independent and spin dependent contributions
BBS/LSS no OAM
BBS/LSS with OAM
H.A.,S.Brodsky,A.Deur,F.Yuan (2007)
PAC34, JLab, January 2755
HT and Semi-Exclusive Pion Production E. Berger, S. Brodsky 1979 (DY), E.Berger 1980,A.Brandenburg, V. Khoze, D. Muller 1995
A.Afanasev, C.Carlson, C. Wahlquist Phys.Lett.B398:393-399,1997
+
Fragmentation +
0
• Azimuthal asymmetries with opposite sign from HT effects
• Effect may be suppressed for semi-exclusive 0 compared to +/-
PAC34, JLab, January 2756
3D structure of the nucleon
Wide kinematic coverage of large acceptance detectors allows studies of exclusive (GPDs) and semi-inclusive (TMDs) processes providing complementary information on transverse structure of nucleon
h
TMDs
Semi-Inclusive processes and transverse momentum distributions
,h
Hard exclusive processes and spatial distributions of partons
GPDs
PAC34, JLab, January 2757
Flavor DecompositionSum over quark flavors
Extraction of kT-dependent distributions q+ (f1+g1) and q- (f1-g1) will require
unfolding of spin independent and spin dependent contributions
BBS/LSS
BBS/LSS +OAM H.A.,S.Brodsky,A.Deur,F.Yuan (2007)
Large contribution from orbital motion
PAC34, JLab, January 2758
Non-perturbative TMD Perturbative region
Boer-Mulders Asymmetry: PT-dependence
In the perturbative limit 1/PT
2 behavior
expected (F.Yuan)
Missing: predictions for K-, dedicated predictions for K+
CLAS12
2<Q2<5 (2000h @ 11 GeV with 1035sec-1cm-2)
PAC34, JLab, January 2759
SSA in ep→e’X
contribution to SSA (~20%) may be responsible for the difference in andbeam SSA at large z
Larger fraction of from at low x and large z
PYTHIA at 5.7 GeV
PAC34, JLab, January 2760
Target SSA in exclusive production
Large positive 0 target SSA in the exclusive limit confirmed by CLAS at 5.7 GeV
HERMES 27.5 GeV
CLAS @5.7GeV
ep->e’p
PAC34, JLab, January 2761
Space and size of RICH sector (LTCC option)