International Workshop on Transverse Polarisation Phenomena in Hard Processes Como, September 7- 10, 2005 Marco Maggiora Dipartimento di Fisica ``A. Avogadro'' and INFN - Torino, Italy SINGLE AND DOUBLE SPIN INTERACTIONS AT GSI

Introduction GSI: HESR as (asym) collider: A complete description of nucleonic structure leading twist NLO ( k T dependence) Physics objectives:  Drell-Yan di-lepton production  spin observables in hadron production  electromagnetic form factors  quark and gluon distribution functions  quark fragmentation functions

f 1, g 1 studied for decades: h 1 essentially unknown Twist-2 PDFs κ T -dependent Parton Distributions Distribution functions Chirality even odd Twist-2 ULTULT f 1 g 1,h1,h1,

Why Drell Yan? Asymmetries depend on PD only (SIDIS→convolution with QFF) Why ? Each valence quark can contribuite to the diagram Kinematics plenty of (single) spin effects 3 planes: plane to polarisation vectors plane Drell-Yan Di-Lepton Production —

Scaling: Full x 1,x 2 range. needed [1] Anassontzis et al., Phys. Rev. D38 (1988) 1377 Drell-Yan Di-Lepton Production

Phase space for Drell-Yan processes 15 GeV/c 40÷100 GeV/c  = const: hyperbolae x F = const: diagonal PANDA ASSIA/PAX (SIS300 or HESR) [1]A. Bianconi and M. Radici, Phys. Rev. D71 (2005)

Uncorrelated quark helicities access chirally-odd functions TRANSVERSITY Ideal because: h 1 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: [1] Phys. Rev. D16 (1977) Drell-Yan Asymmetries —

RICH energies: small x 1 and/or x 2 evolution much slower [1] than Δq(x,Q 2 ) and q(x,Q 2 ) at small x A RICH very small, smaller would help [1] [1] Barone, Colarco and Drago, Phys.Rev. D56 (1997) 527. Drell-Yan Asymmetries —

A TT still large and M 2 due to slow evolution of Large A TT expected [1] for and M 2 not too large and τ not too small [1] M. Anselmino et al., Phys. Lett. B594 (2004) 97. HESR: A TT direct access to valence quark h 1 Drell-Yan Asymmetries —

NLO pQCD: λ  1,   0, υ  0 Experimental data [1] : υ  30 % [1] J.S.Conway et al., Phys. Rev. D39 (1989) 92. υ involves transverse spin effects at leading twist [2] : cos2φ contribution to angular distribution provide: [2] D. Boer et al., Phys. Rev. D60 (1999) Di-Lepton Rest Frame Drell-Yan Asymmetries —

Conway et al, Phys. Rev. D39 (1989) 92 Angular distribution in CS frame Fermilab  -N   +  252 GeV/c -0.6 < cos < < M < 8.5 GeV/c 2 cut on P T selects asymmetry 30% asymmetry observed for  -

Angular distributions for and  - — Angular distributions for and  - —  -N, 125 GeV/c Fermilab Anassontzis et al., Phys. Rev. D38 (1988) 1377 vs vs

λ  1,   0 Even unpolarised beam on polarised p, or polarised on unpolarised p are powerful tools to investigate к T dependence of QDF D. Boer et al., Phys. Rev. D60 (1999) Drell-Yan Asymmetries —

[1] A. Bianconi and M. Radici, Phys. Rev. D71 (2005) s ~ 80 GeV 2 small asymmetries different dependencies cannot be resolved s ~ 200 GeV 2 bigger asymmetries different dependencies can be partially resolved Drell-Yan Asymmetries —

[1] A. Bianconi and M. Radici, hep-ph/ Phys. Rev. D in press. s ~ 200 GeV 2 different dependencies can be partially resolved Drell-Yan Asymmetries —

[1] H. Shimizu et al., Phys. Rev. D71 (2005) At higher energy ( s ~ 200 GeV 2 ) perturbative corrections [1] are sensibly smaller in the safe region Drell-Yan Asymmetries —

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 [4] [1] T.A.DeGrand et al.,Phys. Rev. D23 (1981) [2] B. Andersoon et al., Phys. Lett. B85 (1979) 417. [3] W.G.D.Dharmaratna, Phys. Rev. D41 (1990) [4] M. Anselmino et al.,Phys. Rev. D63 (2001) Analysing power Depolarisation Key to distinguish between these models Data available for D NN : 3.67 GeV/c D NN < GeV/c D NN ~ GeV/c D NN > 0 D 100 GeV/c MISSING

Hyperon production Spin Asymmetries Polarised target:. Transverse target polarisation Existing data: PS185 (LEAR) [2] [1] K.D. Paschke et al., Phys. Lett. B495 (2000) 49. [2] PS185 Collaboration, K.D: Paschke et al., Nucl. Phys. A692 (2001) 55. [1] complete determination of the spin structure of reaction Models account correctly for cross sections. Models do not account for or. NEW DATA NEEDED

Transverse Single Spin Asymmetries  large x F originate from valence quark:  + : A N > 0 ;  - : A N < 0 Correlated with expected u and d-quark polarisation A N similar for ranging from 6.6 up to 200 GeV A N 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 (A T ) possible RICH, p ↑ smaller s large s E704 Tevatron FNAL 200GeV/c

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

Open charm from production and subsequent weak decay low branching ratio: B.R. = 0.9% huge self-analysing asymmetry: [1] Smith Vogt Z. Phys. C75 (1997) 271 Open Charm ΔG longitudinally polarised

Beam and Target UNILAC SIS FRS ESR HESR Super FRS NESR CR RESR FLAIR SIS 100 Tm SIS 300 Tm U: 35 AGeV p: 90 GeV Key features: Generation of intense, high-quality secondary beams of rare isotopes and antiprotons. Two rings: simultaneous beams.

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 Gev 2, PAC: 200 GeV 2 ), luminosity ( > ) Summary Slow extraction from SIS300 polarised target, both P L and P T minimal PANDA interactions HESR (collider) no diluition factor MORE WORK, SIMULATIONS NEEDED DISCUSSION WITH GSI MANAGEMENT: what is feasable ▪ physics iussues KEY POINT: how much and how long can we polarise ?

Question time

vector couplings same spinor structure Drell-Yan Di-Lepton Production Measure A TT in J/Ψ resonance region in reactions Cross section large enough in this region ~ 160 ev/day, ≈0.4

vector couplings same spinor structure Drell-Yan Di-Lepton Production Measure A TT in J/Ψ resonance region in reactions Cross section large enough in this region ~ 160 ev/day, ≈0.4

Beam and Target NH 3 10g/cm 3 : 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 Luminosity comparable to external target → KEY IUSSUE dilution factor f~1 difficult to achieve polarisation P p ~ 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 PANDA AS WELL HESR collider polarised p and beams