scattering at CERN Horst Fischer Universität Freiburg Boer-Mulders, Sivers & Transversity from Drell Yan on behalf of the COMPASS Collaboration

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1 GPDs Boer-Mulders, Sivers & Transversity from Drell Yan Future Muon- & Pion-Nucleon scattering at CERN Horst Fischer Universität Freiburg on behalf of the COMPASS Collaboration

2 Physics Goals of COMPASS Contribute to the understanding of the non-erturbative hysics of the nucleon nucleon sin structure Gluon Polarization ΔG/G Transverse sin structure functions on and d-target Sivers on and d-target Inclusive Asymmetries (low x) Flavor deendent olarized quark helicity densities Δq(x) sin deendent fragmentation functions ΔD Λ q Diffractive VM-Production nucleon sectroscoy Primakoff-Reactions - olarizability of π and K glueballs and hybrids charmed mesons and baryons - semi-letonic decays - double-charmed baryons

3 Physics Goals of COMPASS Contribute to the understanding of the non-erturbative hysics of the nucleon nucleon sin structure Gluon Polarization ΔG/G Transverse sin structure functions on and d-target Sivers on and d-target near future: flavor decomosition! Inclusive Asymmetries (low x) Flavor deendent olarized quark helicity densities Δq(x) sin deendent fragmentation functions ΔD Λ q Diffractive VM-Production nucleon sectroscoy Primakoff-Reactions - olarizability of π and K glueballs and hybrids charmed mesons and baryons - semi-letonic decays - double-charmed baryons

4 Beam: COMPASS - Fixed Target Exeriment at CERN Muons Hadrons (, π /K) Intensity: µ + /sill (4.8s/16.2s) µ + /sill momentum: 160 GeV/c GeV/c olarization: -80% COMPASS SPS LHC

5 The COMPASS CERN μ Filter ECal & HCal ECal & HCal RICH SM1 SM2 μ Filter 50 m 6 LiD Target 160 GeV/c μ + TWO STAGE SPECTROMETER: Polarized μ beam Unolarized, π /K beam Polarized target Particle identification

6 Many new technologies for tracking and PID Trigger-System MicroMegas GEM Straws Readout electronics RICH readout Scintillating fiber trackers

7 COMPASS ugrades for 2006 New solenoid magnet: accetance 70 mrad 180 mrad RICH ugrade Central region: MAPMT system More hotons Imroved S/N Outer region: samling ADC Imroved S/N Other imortant ugrades: Large Drift Chamber RICHWall Full ECAL coverage trigger

8 Exected statistics from 2006 run Collins and Sivers Asymmetries

9 Collins/Sivers: Transverse running with NH3 in 2006 Collins Sivers COMPASS roj. HERMES Prel. results

10 Measurement of GPDs at COMPASS

11 GPD 3-D icture of the artonic nucleon structure Dee Inelastic Scattering e ex γ* Q²x Bj x z x P x boost y x 1 Parton Density q ( x ) P x 0

12 GPD 3-D icture of the artonic nucleon structure Dee Inelastic Scattering e ex γ* Q²x Bj x Hard Exclusive Scattering Deely Virtual Comton Scattering e eγ γ* Q² γ z x+ξ GPDs t x-ξ z x P x P r x boost y x boost y x 1 Parton Density q ( x ) P x 0 Generalized Parton Distribution H( x,ξ,t ) ( P x, r y,z ) Burkardt,Belitsky,Müller,Ralston,Pire

13 Generalized Parton Distributions µ µγ (µρ ) γ* Q² γ,ρ x+ξ x-ξ GPDs t z GPDs deend on 3 variables: x: longitudinal quark momentum fraction x Bj 2ξ: longitudinal momentum transfer: ξ=x Bj /(2-x Bj ) t: momentum transfer squared to the target nucleon (fourier conjugate to the transverse imact arameter r) Dee Virtual Comton Scattering x P x boost r y GPD: H, H, E, E Hard Exclusive Meson Production Vektormeson: E, H Pseudoscalar: E, H

14 GPDs and Relations to Physical Observables x+ξ x-ξ factorization t The observables are some integrals of GPDs integrated over x Dynamics of artons in the Nucleon Models: Parametrization H, H, E, E (x,ξ,t) Fit of Parameters to the data Elastic Form Factors Ji s sum rule 2J q = x(h q +E q )(x,ξ,0)dx ordinary arton density x 1/2 = 1/2 Σ + Lq + G + Lg x H(x,ξ,t)dx = F(t) H(x,0,0) = q(x) H (x,0,0) = q(x)

15 DVCS and Bethe Heitler Advantage of flexibility in selection of muon beam energy at COMPASS: μ μ BH calculable Higher energy: DVCS >> BH DVCS Cross section Smaller energy: DVCS BH Interference term will rovide the DVCS amlitude μ μ γ* γ θ φ

16 Advantage of µ + and µ - for DVCS (+BH) A DVCS + 1 H(x, ξ, t) + 1 H(x, ξ, t) dx = = P ( μ μγ ) dx - i π H(x = 1 x ξ + iε 1 x ξ t, ξ~x Bj /2 fixed ξ, ξ, t) dσ (μ μγ) = dσ BH + dσ DVCS unol + P μ dσ DVCS ol + e μ a BH Re A DVCS + e μ P μ a BH Im A DVCS cos nφ sin nφ μ γ* γ μ φ P μ+ =-0.8 P μ- =+0.8 θ

17 Advantage of µ + and µ - for DVCS (+BH) A DVCS + 1 H(x, ξ, t) + 1 H(x, ξ, t) dx = = P ( μ μγ ) dx - i π H(x = 1 x ξ + iε 1 x ξ t, ξ~x Bj /2 fixed ξ, ξ, t) dσ (μ μγ) = dσ BH + dσ DVCS unol + P μ dσ DVCS ol + e μ a BH Re A DVCS + e μ P μ a BH Im A DVCS cos nφ sin nφ μ γ* γ μ φ P μ+ =-0.8 P μ- =+0.8 θ μ + μ + σ σ ~ H (x = ξ,ξ, t)

18 Advantage of µ + and µ - for DVCS (+BH) A DVCS + 1 H(x, ξ, t) + 1 H(x, ξ, t) dx = = P ( μ μγ ) dx - i π H(x = 1 x ξ + iε 1 x ξ t, ξ~x Bj /2 fixed ξ, ξ, t) dσ (μ μγ) = dσ BH + dσ DVCS unol + P μ dσ DVCS ol + e μ a BH Re A DVCS + e μ P μ a BH Im A DVCS cos nφ sin nφ μ γ* γ μ φ P μ+ =-0.8 P μ- =+0.8 θ σ μ + σ μ ~ P dx H(x, ξ, t) x ξ

19 Exerimental Setu: Target & Detektor 2.5 m Liquid H 2 target ( L = cm -2 s -1 ) -to be designed and built μ all COMPASS trackers: SciFi, Si, MM, GEM, DC, Straw, MWPC γ resently ECAL1/2: θ γ 12 μ Beam: Energy: 100 GeV Intensity: 2*10 8 /sill Polarization: P(µ -) = +0.8 P(µ +) = -0.8 additional calorimetry at large angle (π 0 bkg) Recoil detector to insure exclusivity -to be designed and built

20 Recoil Detector Design ECAL Beam 4m Detect rotons of MeV/c ToF with 200 s resolution required 2 concentric barrels of 24 scintillators read out at both sides, fast multi-hit ADC / wave form digitizer

21 Recoil Detector Prototye 4m 30 sector design Test at COMPASS beam this year Funded by EU FP6 (Bonn, Mainz, Saclay, Warsaw)

22 Prosects: Kinematical Range Limit for ρ (DVMP) 2 times higher Q² E=190, 100GeV Limitation by luminosity Today: N μ = μ er SPS sill for DVCS Q 2 < 7.5 GeV 2 At fixed x Bj, study in Q 2

23 μ flux at COMPASS in > Sharing roton beam with CNGS - New LINAC4 u to 10 times more rotons + imrovements on μ beam line necessary

24 Prosects: Kinematical Range if N μ 5 Q 2 < 17 GeV 2 for DVCS if N μ 2 Q 2 < 11 GeV 2 for DVCS E=190, 100GeV Limit for ρ (DVMP) 2 times higher Q² Limitation by luminosity Today: N μ = μ er SPS sill for DVCS Q 2 < 7.5 GeV 2 At fixed x Bj, study in Q 2

25 Simulations with two Models for GPDs Use different arametrisations of GPDs Model 1: H(x,ξ,t) ~ q(x) F(t) Vanderhaeghen et al., PRD60 (1999) Model 2: Chiral quark-soliton model: Goeke et al., NP47 (2001) 401 H(x,0,t) = q(x) e t <b 2 > = q(x) / x α t (α : sloe of Regge trajectory) <b 2 > = α ln 1/x transverse extension of artons in hadronic collisions considers fast artons in the small valence core and slow artons at larger distance (wider meson cloud) includes correlation between x and t

26 DVCS Simulations for COMPASS at 100 GeV σ μ + σ μ ~ P H(x,ξ, t) dx x ξ Model 1: H(x,ξ,t) ~ q(x) F(t) BCA Q 2 =4±0.5 GeV 2 x = 0.05 ± 0.02 Model 2: H(x,0,t) = q(x) e t <b 2 > = q(x) / x α t BCA φ 6 bins in Q 2 from 1.5 to 7.5 GeV 2 (1 shown) 3 bins in x Bj =0.05,0.1,0.2 (2 shown) x = 0.10 ± 0.03 Assumtions L= cm -2 s days efficiency=25% φ

27 Advantage of COMPASS kinematics σ μ + σ μ ~ P dx H(x,ξ, t) x ξ Model 1: H(x,ξ,t) ~ q(x) F(t) model 1 model 2 Model 2: H(x,0,t) = q(x) e t <b 2 > = q(x) / x α t COMPASS sensitive to different satial distributions at different x

28 Hard Exclusive Meson Production (ρ,ω,φ,π,η ) hard soft γ* L x + ξ GPDs t =Δ 2 meson x - ξ Scaling redictions: 1/Q 6 Collins et al. ( PRD ): 1/Q 4 1. factorization alies only for γ* 2. σ T << σ L L vector mesons seudo-scalar mesons ρ 0 largest roduction resent study ρ 0 π + π - with COMPASS

29 Roadma for GPDs at COMPASS 2005: Exression of interest SPSC-EOI : Test of recoil detector rototye Proosal : construction of recoil detector LH 2 target ECAL0 2010: Study of GPDs at COMPASS In arallel COMPASS analysis of existing data: Comlete analysis of ρ, φ, 2π roduction GPD E/H investigations with the trans. olarized target

30 Boer-Mulders Mulders, Transversity and Sivers Functions from Drell Yan reliminary studies!

31 Transversity LO: 3 distribution functions necessary to describe fully the sin structure of the nucleon Inclusive DIS l + l - X l l hx imossible direct measurement ΣΔ T q(x) Δ T q(x) convolution with sin deendent fragment. func. Δ T q (x) FF

32 Transversity from Drell-Yan alternative way to access transversity no need of any fragmention functions double olarized Drell-Yan allows direct extraction of transverstiy A TT ( ) ( ) 2 q 1 q 1 1q 2 eh x h x e f x f x 2 q 1q ( ) ( ) 1 1q 2 + l l X Could become ossible at GSI - exerimentally challenging!

33 COMPASS: transversity from Bianconi, Radici he-h/ , he-h/ A.Sissakian et al., Phys. Rev. D72, (2005), he-h/ π μ μ X + Use unolarized Drell-Yan R π μ μ X (0) dq T qt MM π dσ dω dqσ 2 (0) T q T weighted angular distribution of transvese momentum of virtual hoton l k 1 q T beam( π) φ k 2 l k 1 k 2 q= k1+ k2 h q 3 R = π ( γ 1 cos 2 θ k cos2φsin 2 θ) ( ) k ( x x ) π, = 8 q e h x h x x x 2 e q q f 1q xπ f1 q x xπ x π ( ) ( ) + ( ) 2 (1) (1) q 1q π 1q π π ( ) ( ) + ( ) leton air CM frame z k k 1 2

34 How to extract transversity? + + use single olarized Drell-Yan π μ μ X 2 dω dφ S2 d qt ( qt Mπ ) sin ( φ+ φs2) dσ ( S2T) dσ ( S2T) A 2 dω dφ S 2 d qt d σ ( S2T ) + dσ ( S2T ) A( xπ, x ) φs 2 1 = 2 : azimuthal angle of the target sin vector : target sin vector q 2 (1) e q h1q x h q 1q x π e f x f x x x ( π ) ( ) S 2T ( π ) 1 ( ) + ( π ) 2 q 1q π q neglect s-quark, sea quark in roton, and d-quark contributions (d-quark suressed by ¼ due to its charge) Boer-Mulders ( ) = ( ) h x f x (1) 1u 1u k ( x, x) 8C u π Transversity ( ) Ah ( x, x) ( ) π h1u x = 4 2 f1 u x C k ( x, x) u π Sivers sin(φ φ s )

35 π μ + μ X Single-olarized Drell-Yan exerimentally less difficult unique environment of COMPASS: hadron beam olarized target high rate trackers muon identification

36 Count rate estimates Beam: 10 8 π /s, 100 GeV/c Target: 60 g/cm 2 NH 3 Luminosity: Cross section value: Accetance : 3 L = cm s A GeV M GeV μμ 23 8 σ = 0.1nb/nucl ( E. Anassontzis et al. Phys. Rev. D38 (1988) 1377 ) Very reliminary! E.A. Hawker et al. Phys. Rev. Lett. 80 (1998) 3715 Exected rate for DY: R = events/s A 0.08 events/sill (4000 sills/day) 320 events/day Total statistics: (SPS eff=80%) 120 days 30k/year

37 Comarison to resent running conditions resently Drell-Yan beam ol. μ GeV/c unol. π GeV/c intensity 2x10 8 μ + /sill (4.8/16.2s) 4.8x10 8 π - /sill (4.8/16.2s) ol. target 6 LiD 60 g/cm 2 (NH 3 60 g/cm 2 art of 2006 ) NH 3 60 g/cm 2 olarization mode longitudinal & transverse transverse total event rate ~10 5 /s ~10 8 /s charged articles/event ~ 4 ~ 6

38 Comarison to resent running conditions resently Drell-Yan beam ol. μ GeV/c unol. π GeV/c intensity 2x10 8 μ + /sill (4.8/16.2s) 4.8x10 8 π - /sill (4.8/16.2s) ol. target 6 LiD 60 g/cm 2 (NH 3 60 g/cm 2 art of 2006 ) NH 3 60 g/cm 2 olarization mode longitudinal & transverse transverse total event rate ~10 5 /s ~10 8 /s charged articles/event ~ 4 ~ 6 Sectrometer: high rate caability required ( for trackers near the target) ugrading SciFi, GEM, MicroMegas no need of comlete article ID (only muon ID with muon filters) Polarized target: heat load increase by x ~ 10 (0.5mW, ~ 2mW/sill) running in frozen sin mode ( for transverse olarization ) de-focused beam or better cooling efficiency to maintain olarization

39 Summary and Outlook Let s s start start the the next next generation generation of of exeriments exeriments towards towards the the full full understanding understanding of of structure structure of of the the nucleon nucleon Let