International Workshop on Transverse Polarisation Phenomena in Hard Processes Como, September 7- 10, 2005 SINGLE AND DOUBLE SPIN INTERACTIONSAT GSI Marco Maggiora Dipartimento di Fisica ``A. Avogadro'' and INFN - Torino, Italy
Introduction • SIS300 @ GSI: • HESR as (asym) collider: • A complete description of nucleonic structure requires: • @ leading twist and @ NLO ( kT dependence) • Physics objectives: • quark and gluon distribution functions • quark fragmentation functions • Drell-Yan di-lepton production • spin observables in hadron production • electromagnetic form factors
κT-dependent Parton Distributions Twist-2 PDFs f1, g1 studied for decades: h1 essentially unknown
Drell-Yan Di-Lepton Production — 3 planes: plane to polarisation vectors plane plane plenty of (single) spin effects Why Drell Yan? Asymmetries depend on PD only (SIDIS→convolution with QFF) Why ? Each valence quark can contribuite to the diagram Kinematics
Drell-Yan Di-Lepton Production Scaling: Full x1,x2 range . needed  Anassontzis et al., Phys. Rev. D38 (1988) 1377
Phase space for Drell-Yan processes A. Bianconi and M. Radici, Phys. Rev. D71 (2005) 074014 = const: hyperbolae xF = const: diagonal 15 GeV/c PANDA ASSIA/PAX (SIS300 or HESR) 40÷100 GeV/c
Drell-Yan Asymmetries — Uncorrelated quark helicities access chirally-odd functions TRANSVERSITY • Ideal because: • h1 not to be unfolded with fragmentation functions • chirally odd functions • not suppressed (like in DIS)
Drell-Yan Asymmetries — To be corrected for: Collins-Soper frame: Phys. Rev. D16(1977) 2219.
Drell-Yan Asymmetries — RICH energies: small x1 and/or x2 evolution much slower than Δq(x,Q2) and q(x,Q2) at small x ATT @ RICH very small, smaller would help Barone, Colarco and Drago, Phys.Rev. D56 (1997) 527.
Drell-Yan Asymmetries — ATT still small @ large and M2 due to slow evolution of Large ATT expected for and M2 not too large and τ not too small HESR: ATT direct access to valence quark h1 M. Anselmino et al., Phys. Lett. B594 (2004) 97.
Drell-Yan Asymmetries — Di-Lepton Rest Frame NLO pQCD: λ 1, 0, υ 0 Experimental data : υ 30 % J.S.Conway et al., Phys. Rev. D39 (1989) 92. υinvolves transverse spin effects at leading twist : cos2φ contribution to angular distribution provide: D. Boer et al., Phys. Rev. D60 (1999) 014012.
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 - Conway et al, Phys. Rev. D39 (1989) 92
Angular distributions for and -—-N, N @ 125 GeV/c vs vs E537 @ Fermilab Anassontzis et al., Phys. Rev. D38 (1988) 1377
Drell-Yan Asymmetries — 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.
Drell-Yan Asymmetries — s ~ 80 GeV2 small asymmetries different dependencies cannot be resolved s ~ 200 GeV2 bigger asymmetries different dependencies can be partially resolved A. Bianconi and M. Radici, Phys. Rev. D71 (2005) 074014
Drell-Yan Asymmetries — s ~ 200 GeV2 different dependencies can be partially resolved A. Bianconi and M. Radici, hep-ph/0504261 Phys. Rev. D in press.
Drell-Yan Asymmetries — At higher energy ( s ~ 200 GeV2) perturbative corrections are sensibly smaller in the safe region H. Shimizu et al., Phys. Rev. D71 (2005) 114007
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  •  T.A.DeGrand et al.,Phys. Rev. D23 (1981) 1227. •  B. Andersoon et al., Phys. Lett. B85 (1979) 417. •  W.G.D.Dharmaratna, Phys. Rev. D41 (1990) 1731. •  M. Anselmino et al.,Phys. Rev. D63 (2001) 054029. Analysing power 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 Depolarisation Key to distinguish between these models
Hyperon production Spin Asymmetries Polarised target: . Transverse target polarisation Existing data: PS185 (LEAR)   K.D. Paschke et al., Phys. Lett. B495 (2000) 49.  PS185 Collaboration, K.D: Paschke et al., Nucl. Phys. A692 (2001) 55.  complete determination of the spin structure of reaction Models account correctly for cross sections. Models do not account for or . NEW DATA NEEDED
E704 Tevatron FNAL 200GeV/c Transverse Single Spin Asymmetries • Production @ large xF originate from valence quark: +: AN > 0 ; -: AN < 0Correlated 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
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 • analysing power alternative way to FF angular distribution separation of electric and magnetic FF analysing power transverse polarisation of p↑ leads to non zero analysing power Different prediction for models well reproducing SL data
Beam and Target SIS 100 Tm SIS 300 Tm U: 35 AGeV p: 90 GeV SIS UNILAC FRS ESR HESR Super FRS CR NESR FLAIR RESR Key features: Generation of intense, high-quality secondary beams of rare isotopes and antiprotons. Two rings: simultaneous beams.
Summary Slow extraction from SIS300 polarised target, both PL and PT minimal PANDA interactions HESR (collider) no diluition factor 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 ) • MORE WORK, SIMULATIONS NEEDED • DISCUSSION WITH GSI MANAGEMENT: • what is feasable ▪ physics iussues • KEY POINT: how much and how long can we polarise ?
Drell-Yan Di-Lepton Production vector couplings same spinor structure Measure ATT in J/Ψ resonance region in reactions Cross section large enough in this region ~ 160 ev/day , <x>≈0.4
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
Alternative GSI solution HESR collider polarised p and beams • 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