TMD flavor decomposition at CLAS12 Patrizia Rossi - Laboratori Nazionali di Frascati, INFN  Introduction  Spin-orbit correlations in kaon production  Kaon identification with CLAS12  Kaon TMDs with CLAS12  Conclusion International conference on the structure of baryons - BARYONS’10 Dec. 7-11, 2010, Osaka - Japan

The internal structure of the nucleon  Spin origin  Flavor content  3-dim space & momentum distribution of quarks Goal is to study the complex structure of the nucleon  +L q + J g  SIDIS DIS PDF (E’,p’) (E,p) e e’ pX more complex PDF  TMDs (E’,p’) (E,p) e e’ p h h 1 (x)

Hadronic P T distribution - data HERMES preliminary (hep-ex v1) Differences in between h +, h − and K s 0 can be explained by the flavor dependence of the intrinsic transverse momentum distributions of quarks in the initial nucleon COMPASS 2004 LiD (part) Preliminary h+h-h+h- NJL-Jet model predicts that kaons produced from the light quarks have larger average transverse momentum than the pions NJL model H. Matevosyan et al. arXiv: [hep-ph] GeV

Helicity distribution  s puzzle  u  d  s (  q = q f + - q f - ) More SIDIS kaon data needed to resolve that puzzle From DIS From SIDIS DIS vs SIDIS → additional hadron detection HERMES  s  s  / (stat) +/-0.027(syst) (for 0.02<x<0.6) - COMPASS  s +  s = / (stat) +/ (evol) COMPASS data only - COMPASS  s +  s = / / (for 0.003<x<0.3) - HERMES  s  s  / (th) +/ (exp) +/ (evol) -

Collins and Sivers Kaon PLB 693 (2010) 11PRL 103 (2009)  K + ampl. >  + ampl. Unespected from u-quark dominance  role of s quarks?

TMDs 12 GeV in Hall B E : E : Pion SIDIS E : E : Kaon SIDIS E : E : Pion SIDIS E : E : Kaon SIDIS LOI : LOI : Pion SIDIS LOI : LOI : Kaon SIDIS PAC approved experiments N q U L T Complete program of TMDs studies for pions and kaons Kaon measurements crucial for a better understanding of the TMDs “kaon puzzle” Kaon SIDIS program requires an upgrade of the CLAS12 detector PID  RICH detector to replace LTCC

CLAS12 Forward Detector 2m 7 Central Detector Cebaf Large Angle Spectrometer broad kinematical range high luminosity H, D and nuclear targets 5°< θ< 140° L =10 35 Polarized beam for fixed target electron scattering experiments

RICH full pion / kaon / proton separation over whole accessible momentum range of 2 – 8 GeV for SIDIS exp.  /K separation of GeV/c for a rejection factor 1:1000 Ratio K/  ~ for SIDIS experiments GeV/c  /K  /p K/p TOF LTCC HTCC LTCC TOF LTCC RICH  ratio K/  ~

RICH RIC  Large Detector area (several m 2 )  Operation with high intensity e - beam, presence of magnetic fields Innovative new technologies for radiator material and photo-detection Challenging project PHOTO-DETECTOR Collection of the visible Cherenkov light mandatory small pad size (~0.5 cm) for 4   /K at 8 GeV/c RADIATOR Aerogel mandatory to separate hadrons in the range 2-8 GeV/c Charged particle Proximity gap RADIATOR

CLAS12: Kaon distributions in ep  e’KX Q 2 >1GeV 2 W 2 >4 GeV 2 (10) y<0.85 M X >2GeV SIDIS kinematics: High energy kaons are at small angles (  <30 o ) Q2Q2

Collins fragmentation: Longitudinally polarized target Kotzinian-Mulders Asymmetry protondeuteron

Collins effect: from asymmetries to distributions Combined analysis of Collins fragmentation asymmetries from proton and deuteron may provide independent to e + e - (BELLE/BABAR) information on the underlying Collins function. need

A LL P T -dependence  Azimuthal asymmetry sensitive to the difference of widths in PDFs  Proton and deuteron data provide a complete set required for the flavor decomposition proton deuteron Curves are calculated using different k T widths for helicity distributions (Anselmino et al, Phys.Rev.D74:074015, 2006)

Boer-Mulders kaon asymmetry 14 Excellent precision vs model uncertainties Band: Phys Rev D Boer-Mulders from DY data Collins from chiral limit Line: Phys Rev D Boer-Mulders from Sivers Collins from e+e- data 56 days at L=1x10 35 cm -2 s -1

Sivers kaon asymmetry  /K CLAS12 will provide a more detailed knowledge of Sivers effect ep  e’K + X S.Arnold et al M. Anselmino et al  HD-Ice target Pros Small field (∫Bdl~ Tm) Small dilution (fraction of events from polarized material) Less nuclear background Cons Need to demonstrate that the target can remain polarized for long periods with an electron beam with currents of order of 1-2 nA

Conclusions  Correlation of spin and transverse momentum of partons is crucial in understanding of the nucleon structure in terms of quark and gluon degrees of freedom of QCD  Studies of the spin-structure of the nucleon is one of the main driving forces behind the upgrade of Jefferson Lab  “Strange” observables open up new avenues in studies of the 3D structure of the nucleon and in its quark flavor content  identification of Kaons is crucial for these studies  The CLAS12 experiments with polarized/unpolarized NH3 and ND3 targets provides superior sample of events allowing multidimensional binning to study SSAs for  and K in SIDIS