Transverse spin effects in SIDIS at 11 Ge

Transverse spin effects in SIDIS at 11 Ge. V with transversely polarized target using the CLAS 12 detector (A CLAS 12 experiment proposal for PAC 39) Contalbrigo Marco INFN Ferrara JLab PAC 39 – Open session June 18, 2012 Newport News

A CLAS 12 Proposal For PAC 38 A CLAS 12 proposal for PAC 38

Quantum phase-space distributions of quarks Wpq(x, k. T, r) “Mother” Wigner distributions 2 d d 3 r Probability to find a quark q in a nucleon P with a certain polarization in a position r & momentum k k. T T) (F TMD PDFs: fpu(x, k. T), … Semi-inclusive measurements Momentum transfer to quark Direct info about momentum distribution d 2 k T May explain SSA AN GPDs: Hpu(x, x, t), … √s = 20 Ge. V p. T< 2 Ge. V/c PDFs fp 0 t, = 0 x= u(x), … PR 12 -105 Exclusive Measurements Momentum transfer to target Direct info about spatial distribution PR 12 -105 Exclusive Physics: DVCS with Transverse Target May solve proton spin puzzle SIDIS Physics: di-hadron with Transverse Target x. F Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 4

Leading Twist TMDs Quark polarisation Nucleon polarisation U U L Number Density L E 12 -09 -007 Quark number and helicities T Boer Mulders Helicity E 12 -06 -112 E 12 -09 -008 Boer-Mulders for pions and kaons E 12 -07 -107 E 12 -09 -009 Spin-effects for pions and kaons Worm-gear C 12 -11 -111 This proposal Transversity T Sivers Worm-gear Pretzelosity CLAS 12 has access to all of them through specific azimuthal modulations (f, f. S) of the cross-section thanks to the polarized beam and target Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 5

Leading Twist TMDs quark polarisation nucleon polarisation N/q U U L Number Density L T Boer-Mulders Worm-gear Transversity Sivers DF Contalbrigo M. Survives transverse momentum integration (missing leading-twist collinear piece) Differs from helicity due to relativistic effects and no mix with gluons in the spin-1/2 nucleon Wants multidimensional approach to investigate factorization and transverse momentum dependence Helicity T Transversity: Worm-gear Other elements: Interference between wave functions with different angular momenta: contains information about parton orbital angular motion and spin-orbit effects FF JLab PAC 39, 18 th June 2012, Newport News 6

The Collins amplitude HERMES Access to transversity and Collins functions Consistent non-zero signals for pions Opposite sign for pions reveal Collins features Puzzle in (low-statistics) kaon signals: K+ amplitudes larger then p+ K- amplitudes are not in agreement COMPASS Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 7

Transversity Signals First extractions ? NO DATA 1 st collinear extraction ! xhu 1(x, k ) xhd 1(x, k ) Soffer bound T xhd 1(x) High-x and tensor charge T xhu 1(x) 1 st extraction of Transversity! Role of Q 2 evolution Gauss Ansatz Anselmino et al. Phys. Rev. D 75 (2007) Contalbrigo M. Bacchetta et al. , PRL 107 (2011) JLab PAC 39, 18 th June 2012, Newport News 8

The Sivers effect HERMES ar. Xiv: 1112. 4423 Related to quark orbital angular momentum Non zero signals for p+ and K+ Significant Q 2 evolution ? K+ signals larger than p+ ? ar. Xiv: 1107. 4446 Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 9

The Sivers effect from SIDIS to Drell-Yan ar. Xiv: 0901. 3078 Coverage at large x and relation with Drell-Yan Sign change is a crucial test of TMDs factorization ? ar. Xiv: 1103. 1591 Coverage at large p. T and relation with twist-3 collinear approach Sign mismatch between SIDIS and pp SSA ? T 3 correlator from pp Contalbrigo M. ? Sivers moment from SIDIS JLab PAC 39, 18 th June 2012, Newport News 10

The Pretzelosity HERMES p COMPASS p Sensitive to the D-wave component and the non spherical shape of the nucleon Statistical power of existing data is not enough to observe significant signals “pretzelosity” still basically unknown! p+ proton 0. 5<p. T<0. 6 Ge. V/c Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News ? ar. Xiv: 0812. 3246 Few % signal expected at Jlab from relativistic covariant model 11

The Worm-gear function COMPASS p HERMES p Worm-gear function: longitudinally polarized quarks in a transversely polarized nucleon Related to quark orbital motion Statistics not enough to investigate relations supported by many theoretical models: ? (supported by Lattice QCD and first data) (Wandura-Wilczek type approximation) Jlab Hall-A 3 He Contalbrigo M. From constituent quark model: JLab PAC 39, 18 th June 2012, Newport News ? ar. Xiv: 0903. 1271 12

Honour and Duty TMDs are a new class of phenomena providing novel insights into the rich nuclear structure DIS experiments get access to all PDFs and FFs, but in a convoluted way, first generation non-zero results provide promises but also open questions Full coverage of valence region not achieved 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 Crucial: completeness flavor tagging and four-fold differential extraction in all variables (x, z, Q 2, PT) to have all dependencies resolved Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 13

The CLAS 12 Spectrometer FTOF Luminosity up to 1035 cm-2 s-1 H and D polarized targets EC Broad kinematic range coverage (current to target fragmentation) DC R 3 R 2 R 1 RICH HTCC HD-Ice: Transverse Target new concept HD-Ice (common to LOI 11 -105) RICH: Hadron ID for flavor separation (common to SIDIS approved exp. ) Contalbrigo M. PCAL Solenoid Torus JLab PAC 39, 18 th June 2012, Newport News 15

Transversely Polarized HD-Ice Target HD-ice ran from Nov/11 to May/12 at Jlab with 15 mm Ø × 50 mm long HD cells HD-Ice target vs standard nuclear targets Advantages: Ø Minimize nuclear background small dilution, no attenuation at large p. T Ø Weak holding field (Bd. L ~ 0. 1 Tm) wide acceptance, negligible beam deflection Disadvantages: Ø Very long polarizing times (months) Ø Sensitivity to local heating by charged beams Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 16

Question 1: HD-Ice vs Electron Beam • HD targets used for e. HD tests in Feb/12 and Mar/12 H polarization does not appear to suffer radiation damage with 1 n. A; D does heat removal needs improvement – faster raster, larger diameter cell, additional cooling wires, … PLOT ? ? ? Target wider but not-longer than the existing one (5 cm) Ø Luminosity 5 1033 cm 2 s-1 (minor impact on projections) Ø Magnet configuration simplifies (smaller zero-field volume) Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 17

Question 2: Magnet Configuration Main Solenoid Ø 2 T compensating, 0. 5 T transverse field Ø Enhanced version of the existing NMR magnet system inside HD-ice cryostat Solenoid compensation Transverse saddle coil Ø Free forward acceptance (up to 35°) Ø Recoiling proton detection (>0. 4 Ge. V/c) Ø No impact on CLAS 12 central detector 70 o 60 o 50 o 35 o 5 o Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 18

Question 2: Magnet Configuration 2 T longitudinal field for Møller containment Drift chamber occupancy Bz Ø Good homogeneity (< 5 m. T long. field) Ø Moeller background under control Ø Working point below critical current of existing SC wires Ø Dimensioned for standard quench protection Ø Static forces one order of magnitude smaller than G 10 epoxy tensile strength Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 19

Question 3: Tracking Resolutions fulfill TDR general specifications Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 20

The RICH Detector DC R 3 Mirrors MA-PMTs Simulation of n=1. 05 aerogel + H 8500: ≥ 10 p. e. for direct rings (confirmed by preliminary test-beam results) Aerogel ≥ 5 p. e. for reflected rings ≥ 500 pion rejection factor @ 99% kaon eff. RICH goal: p/K/p separation of 4 -5 s @ 8 Ge. V/c for a pion rejection factor 1: 1000 Contalbrigo M. Pion Contamination JLab PAC 39, 18 th June 2012, Newport News 21

The RICH Detector About 30 H 8500 & 10 R 8900 under test Aerogel characterization: - dispersion law - transmittance fiber head + collimator + filters Ongoing R&D with Budker Institute to improve transmittance Contalbrigo M. MAPMT – H 8500 C Realistic prototype under construction for beam test in July 2012 JLab PAC 39, 18 th June 2012, Newport News 22

CLAS 12 Kinematic Coverage 0. 05 < x < 0. 6 0. 3 < z < 0. 7 for Q 2>1 Ge. V 2 and W 2 > 4 Ge. V 2 Cover valence region at several Ge. V Q 2 Constrain sub-leading twist terms Contalbrigo M. Current fragmentation No exclusivity corner JLab PAC 39, 18 th June 2012, Newport News PT > 1 Ge. V/c Limit given by cross-section 23

CLAS 12 Kinematic Coverage Electron Large electron scattering angles (> 20 o) mandatory to reach high Q 2 values acceptance p+ Intermediate anguar range (15 -25 o) mandatory to reach high PT values Electron The CLAS 12 forward detector is perfectly suitable for high-Q 2 and high-p. T measurements since designed to cover up to 40 degrees angles Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 24

Systematic uncertainty 1÷ 4 4 1÷ 3 3÷ 6 1÷ 3 2 ~ 5÷ 8 Estimates based on: - Current knowledge on HD-Ice target Dominated by uncertainties in transfer losses between cryostats Optimization after tests in fall - Experience from CLAS/HERMES measurements Reduces with statistics and bin number Benefits from the large acceptance Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 26

Single- and Double-Spin asymmetries Ø Experiment: CLAS 12 with HD-Ice transversely polarized target 75 % polarization and 1/3 dilution for Hydrogen @ 10 34 cm-2 s-1 RICH detector flavor tagging pions, kaons and protons ID in the 3 -8 Ge. V/c momentum range equivalent to the crosssection asymmetry for opposite spin states Ø Analysis: the relevant Fourier amplitudes (Collins, Sivers, etc) are extracted simultaneously, thanks to their specific azimuthal dependence, by fitting (ML unbinned in f, f. S) the yield (cross-section) asymmetries for opposite spin states Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 27

CLAS 12 Projections Large p. T important to test perturbative to non-perturb. transient and for Bessel function analysis Large x important to constrain the tensor charge Collins asymmetry Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News Sivers asymmetry 28

Statistical precision Stat. error for a 4 D analysis of the p+ Sivers asymmetry on proton (x 1. 5 on D) target 4 D analysis is possible The wanted high-Q 2 high-p. T defines the beam-time request 2 D projection (x-p. T) of the p+ Sivers asymmetry Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 29

The main goals Transverse spin effects in SIDIS at 11 Ge. V with transversely polarized target using the CLAS 12 detector Ø Main interest on transverse-target single and double spin asymmetries; Ø Access to leading-twist poorly known or unmeasured TMD PDFs which provide 3 -dimensional picture of the nucleon in momentum space (nucleon tomography); * SSA Transversity, Sivers, Pretzelosity functions; * DSA Worm-gear function; Ø Multi dimensional analysis in x, Q 2, z, p. T thanks to large-acceptance and high-luminosity; Ø * disentangle parton distribution from fragmentation functions (x vs z); * isolate sub-leading-twist effects from 1/Q dependence; * investigate transverse degrees of freedom and perturbative to non-perturbative QCD transient from p. T dependence; Together with already approved experiments with unpolarized and longitudinally polarized targets, complete the mapping of the TMD table at CLAS 12. Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 30

Beam time request FTOF The proposed experiment requires: Ø 11 Ge. V (highly polarized) electron beam EC RICH Ø CLAS 12 detector equipped with: HTCC - HD-Ice transversely polarized target - Suitable magnetic system (compensation + saddle coil) - RICH (pion/kaon separation within 3 -8 Ge. V/c) DC R 3 R 2 R 1 HD-Ice PCAL Torus Solenoid In order to reach the desired statistical precision at high-x (valence region) and high p. T for both pion and kaons, and to allow a fully differentyal analysis in x, Q 2, z, p. T we ask the PAC to award 110 days of beam time (including 10 days for calibrations, empty target runs, supportive tests, etc. ) Contalbrigo M. JLab PAC 39, 18 th June 2012, Newport News 31

HDice operations during g 14 / E 06 -101 • HD targets condensed, polarized and aged to the Frozen-Spin state in HDice Lab (Test. Lab annex) • transferred as solid, polarized HD between cryostats; moved to Hall B • In-Beam Cryostat (IBC) operates in Hall at 50 m. K, 0. 9 tesla • g 14 ran from Nov/11 to May/12 with 15 mm Ø × 50 mm long HD cells • γ-beam lifetimes ~ years with 108 γ/s • HD targets used for e. HD tests in Feb/12 and Mar/12 H polarization does not appear to suffer radiation damage with 1 n. A; D does heat removal needs improvement – faster raster, larger diameter cell, additional cooling wires, …

HD polarization during g 14/E 06 -101