Installed and commissioned during run 4 To be commissioned Installed/commissioned in run /10/2005 Raimondo Bertini

Transcription

1 Installed and commissioned during run 4 To be commissioned Installed/commissioned in run /10/005 Raimondo Bertini

2 Transverse Structure Functions Twist- PDFs f 1 g 1L g 1T h 1T Distribution functions Chirality even odd f 1T h 1 Twist- U L T f 1 g 1 h 1L, h 1, f 1T g 1T h 1 h 1T P S k p x P+ k quark p f1(x) d k T T f 1 (x,k T ) T h 1L h 1T 9-15/10/005 Raimondo Bertini

3 Transversity and Λ Polarisation 9-15/10/005 Raimondo Bertini

4 Semi-inclusive deep inelastic scattering 9-15/10/005 Raimondo Bertini

5 9-15/10/005 Raimondo Bertini Kinematics of Λ production ( ) ( ) E P k P q y EE m m k k E E q Q M Q x E E M P q l l ν ϑ ν ν r r r r r r r r sin 4 ;

6 Definition of Λ polarisation axis 9-15/10/005 Raimondo Bertini

7 The COMPASS setup μω SDC SciFi Target Rich1 ECal1 HCal1 μwall1 First Spectrometer: LAS Geometrical Acceptance: θ>30 mrad Gap: 17 9 cm Integral field: 1 Tm Analyzed momentum: p<60 GeV/c SDC GEM Straw SM1 SciFi GEM MWPC SM Second Spectrometer: SAS Geometrical Acceptance: θ<30 mrad Gap: cm Integral field: 4.4 Tm Analyzed momentum: p>10 GeV/c 50 m ECal HCal MWPC μwall 9-15/10/005 Raimondo Bertini

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9 Selection of Λ events 9-15/10/005 Raimondo Bertini

10 Data Analysis /10/005 Raimondo Bertini

11 Data Analysis 9-15/10/005 Raimondo Bertini

12 Available statistics 9-15/10/005 Raimondo Bertini

13 COMPASS Trigger 9-15/10/005 Raimondo Bertini

14 Λ Polarisation, Q² > /10/005 Raimondo Bertini

15 Λ Polarisation all Q² 9-15/10/005 Raimondo Bertini

16 Study of systematic effects 9-15/10/005 Raimondo Bertini

17 Transverse Structure Functions For q non collinear with hadron ( k xp+ k ) f 1 (x,k ) g 1 (x,k ) h 1 (x,k ) f(x) f(x,k ) integrating on k f(x), Δf(x), Δ T f(x) g 1T (x,k ) h 1L (x,k ) h 1T (x,k ) integrating on k 0 relaxing time reversal invariance f 1T (x,k ) for unpolarized quark in transversally polarized hadron (Sivers function) h 1 (x,k ) for transversally polarized quark in unpolarized hadron 9-15/10/005 Raimondo Bertini

18 9-15/10/005 Raimondo Bertini Transverse Structure Functions (Drell-Yan) X μ μ p) pp( + π Kinematics q P M x 1 1 x x x 1 F q P M x s M x x τ 1

19 Drell-Yan Asymmetries Polarised beam and target 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) 9-15/10/005 Raimondo Bertini

20 Transverse Structure Functions (Drell-Yan) 1 σ dσ dω Di-Lepton Rest Frame 3 1 ν 1+ λcos θ + μsin θcosφ + sin 4π λ + 3 θcosφ Fermilab π-n 5 GeV/c -0.6 < cosϑ < < M < 8.5 GeV/c 9-15/10/005 Raimondo Bertini

21 Transverse Structure Functions (Drell-Yan) Initial state interactions non zero σ dσ dω h (x κ 1, 3 1 ν 1+ λcos θ + μsin θcosφ + sin 4π λ + 3 θcosφ 1 NLO pqcd: λ 1, μ 0, υ 0 Experimental data [1] : υ 30 % ) [1] J.S.Conway et al., Phys. Rev. D39(1989)9. υ involves transverse spin effects at leading twist [] : cosφ contribution to angular distribution provide: h 1 (x, κ ) h1 (x1, κ ) [] D. Boer et al., Phys. Rev. D60(1999)01401, D.Boer, S.Brodsky and D.S.Hwang 9-15/10/005 Phys.Rev.D67(003) Raimondo Bertini

22 Transverse Structure Functions (Drell-Yan) Drell-Yan asymmetries - Polarized target, Unpolarized beam 1 σ dσ dω 1+ cos 9-15/10/005 Raimondo Bertini θ + ν sin sin θsin(φ φ S ) 1 A T S1T 1+ cos θ θcosφ + ρs λ 1, μ 0 M Q e 1T sin θsin(φ φ S 1 ) + L [ ] a a a a x f (x )f (x ) + x h (x )h (x ) a a a a e a af1 (x 1)f1 (x ) Unpolarised beam and polirized target is a powerful tool to investigate к T dependence of QDF D. Boer et al., Phys. Rev. D60(1999)01401, D. Boer et al Phys.Rev.D67,054003,003

23 Transverse Structure Functions (Drell-Yan) Phase space τ const: hyperbolae x F const: diagonal 15 GeV/c 30 GeV/c PANDA (GSI) 40 GeV/c ASSIA (GSI) COMPASS (CERN) 9-15/10/005 Raimondo Bertini

24 Transverse Structure Functions (Drell-Yan) Upgraded COMPASS spectrometer New polirazed target (wide acceptance) GEM, MICROMEGA detetors σ 70 μmsmall angle MWPC, STRAW detectors vertex resolution σ mm LARGE AREA HODOSCOPEs Trigger mmlarge angle Iarocci like tubes or large area drift chambers μid New Powerful E-calorimery σ cm 9-15/10/005 Raimondo Bertini

25 Transverse Structure Functions (Drell-Yan) Drell-Yan Counting rate: Realistic approach, the intensity of the beam 10 8 π s 1 Target: 15 g/cm Luminosity: L NH cm s 17 (4GeV M 9GeV ) μ + μ Cross section value A nb/nucl Acceptance A 0.5 Expected rate: R 9-15/10/005 Raimondo Bertini events/s

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27 Drell-Yan Di-Lepton Production pp μ + μ X d σ dm dx F 4α π 9M s x x [ ] a a a a f (x )f (x ) f (x1)f (x ) ea 1 + a Scaling: d d σ τdx F 1 s Full x 1,x range τ 0,1. r p BEAM 40 Gev/c needed [ ] σ pp μ + μ X 0.3 nb [ 1] [1] Anassontzis et al., Phys. Rew. D38 (1988) /10/005 Raimondo Bertini

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31 Open Charm ΔG Open charm from Λ + c X production and subsequent + Λ π + weak decay Λ c low branching ratio: B.R. 0.9% huge self-analysing asymmetry: α 0.98 σ pp 40 c [1] Assume GeV? 1 μb r p r, Λ longitudinally polarised 9-15/10/005 c c Raimondo Bertini -3 # ev /s ev/100 days [1] Smith Vogt Z. Phys. C75 (1997)71

32 Strong Spin Flip Interaction 9-15/10/005 Raimondo Bertini