RECENT RESULTS AND FUTURE PLANS OF COMPASS

Transcription

1 RECENT RESULTS AND FUTURE PLANS OF COMPASS Andrea Bressan University of Trieste and INFN XCIX CONGRESSO NAZIONALE SIF, TRIESTE 3-7 SETTEMBRE 013

2 Trieste 3-7/013 XCIX Congresso SIF COmmon Muon and Proton Apparatus for Structure and Spectroscopy Collaboration ~ 50 physicists from 4 Institutions of 13 Countries fixed target experiment at the CERN SPS data taking: since 00

3 Trieste 3-7/013 XCIX Congresso SIF 3 COMPASS-II Collaboration Дубна (LPP and LNP), Москва (INR, LPI, State University),. Протвино CERN Bochum, Bonn (ISKP & PI), Erlangen, Freiburg, Mainz, München TU Warsawa (NCBJ), Warsawa (TU) Warsawa (U) Praha (CU/CTU) Liberec (TU) Brno (ISI-ASCR) Calcutta (Matrivian) Yamagata Lisboa/Aveiro Tel Aviv USA (UIUC) Saclay Torino (University,INFN), Trieste (University,INFN) Taipei (AS)

4 Trieste 3-7/013 XCIX Congresso SIF 4 COMPASS high energy beam large angular acceptance broad kinematical range two stages spectrometer radiator C 4 F 10 Large Angle threshold: Spectrometer p ~ (SM1) GeV/c Small Angle Spectrometer K ~ 10 (SM) GeV/c SM1 RICH SM MuonWall E/HCAL Target E/HCAL MuonWall variety of tracking detectors to cope with different particle flux from θ = 0 to θ 00 mrad

5 Trieste 3-7/013 XCIX Congresso SIF 5 COMPASS some facts Located at CERN North Area beam line Possible beams: µ +, µ -, p +, p -, K Several physics programs Experiments with muon beam Experiments with hadron beams COMPASS - I (00 011) Spin structure, Gluon polarization Flavor decomposition Transversity Transverse Momentumdependent PDF Pion polarizability Diffractive and Central production Light meson spectroscopy Baryon spectroscopy COMPASS - II (01 017) DVCS and HEMP Unpolarized SIDIS and TMDs Pion and Kaon polarizabilities Drell-Yan studies

6 Trieste 3-7/013 XCIX Congresso SIF 6 COMPASS some facts Located at CERN North Area beam line Possible beams: µ +, µ -, p +, p -, K Several physics programs Experiments with muon beam Experiments with hadron beams COMPASS - I (00 011) Spin structure Hadron spectroscopy p, d polarized target (L & T) Small LH or nuclear targets COMPASS - II (01 017) DVCS/Unpol SIDIS Drell-Yan studies Long LH target Polarized target (T) Reconfigurable target region - versatile experimental setup!

7 Trieste 3-7/013 XCIX Congresso SIF 7 The spin of the nucleon Three twist- quark DF s in collinear approximation ( dk ) F Tw- Coll (x) = 1 { q(x)+ S Lg 5 Dq(x)+ S T g 5 g 1 D T q(x) }n + helicity transversity S z N = 1 = 1 DS+ DG+ L q g z + L z J q 30% : Spin puzzle NR limit [boost, rotat.]=0 D T q(x,q ) = Dq(x,Q) J g

8 Trieste 3-7/013 XCIX Congresso SIF 8 TMD Distribution Functions

9 Trieste 3-7/013 XCIX Congresso SIF 9 SIDIS x-section w, h S F w, h S U L, T A U L, T F F UU, T UU, L 1 1 y y 4 xm d y, F F UU T UU L 1 y y y Q,, 4 dxdydzdp d d xyq 1 x h h ( ) cos cos( ) sin h h h 1 cos ( 1 ) A cos( ) A sin ( 1 ) A h UU h UU h LU h h S sin sin( ) 1 A A L sin ( ) sin( ) h UL h UL h S cos 1 A cos ( 1 ) A + L LL h LL sin S 1 A sin ( ) S UT h S sin( ) sin( ) h S A UT h S S sin( ) sin( ) T h S AUT ' sin( ) h S sin( ) ( 1 ) A h S UT sin( 3 ) h S sin( 3 ) h S A UT coss 1 A cos ( ) S LT h S cos( ) 1 T h S A S cos( ) UT cos( ) h S cos( ) ( 1 ) A h S UT

10 Trieste 3-7/013 XCIX Congresso SIF 10 New A 1 p & g 1 p from GeV data Phys. Lett. B 690 (010) 466 Phys. Lett. B 647 (007) 8 COMPASS new 011 proton data: 00 GeV muon beam lower x, higher Q, improve statistics on proton, Bjorken sum rule

11 New world data on g 1 p,d (x,q ) Trieste 3-7/013 XCIX Congresso SIF 11

12 Polarized PDF from SIDIS Trieste 3-7/013 XCIX Congresso SIF 1 PRL 101 (008) 07001; PR D80 (009) Soon: new 011 data (Δs+Δs) = -0.0 ± 0.0 ± 0.0 Good agreement between COMPASS data and DSSV parametrization, but

13 Strange sea polarization Trieste 3-7/013 XCIX Congresso SIF 13 PLB 693(010)7 (Compass) LSS: ArXiv: Large sensitivity of Δs to «strange to favoured» FF ratio try to extract R SF from Kaon multiplicities

14 Hadron multiplicities Trieste 3-7/013 XCIX Congresso SIF 14 h=π,k (identified by Ring Imaging Cerenkov) M h depend on unpolarized PDF s: u(x),d(x) unpolarized PDF well known strange PDF s(x) less well known

15 Gluon polarization via PGF: open charm Trieste 3-7/013 XCIX Congresso SIF 15 Photon-Gluon fusion A mn(lo) LL = R PGF PGF Dg a LL g (x) NLO PRD 87 (013) ΔG/G(x=0.) = ± 0.15 ± 0.15 DSSV: D. de Florian et al., Phys. Rev. D80(009) LSS: E. Leader, A.V. Sidorov, D.B. Stamenov, arxiv (010)

16 Trieste 3-7/013 XCIX Congresso SIF 16 Gluon polarization via PGF: high p T Photon-Gluon fusion at LO A mn(lo) LL = R PGF PGF Dg a LL g (x)+... Caveat: LO extractions of ΔG/G(x) Can not directly be compared to NLO fits Need for reliable NLO for high p T in COMPASS c.m. energy range A LL h /D(x,p T ) available for Q >1 data Phys. Lett. B 718 (013) 9

17 A LL 1h (p T ):polarized hadron γ-production Trieste 3-7/013 XCIX Congresso SIF 17 Projections by Jäger et al. for COMPASS with 1 fb -1 (=1/4 COMPASS stat.) But L = 4 / fb for all COMPASS data Jäger, Stratmann & Vogelsang: EPJ C44 (005) 533 So far, only NLO pqcd for polarized case (no resum.) In perspective: constraining ΔG by A LL 1h (p T ) (working on)

18 Trieste 3-7/013 XCIX Congresso SIF 18 Collins and Sivers asym. T polarized target, SIDIS: Measure azimuthal asymmetries: m p m p h +/- Collins: Outgoing hadron direction & quark transverse spin Sivers: Nucleon spin & quark transverse momentum k T at LO: Collins T q transverse spin distr. q q e Δ T q Δ D A Coll e q D q q T h q h q Collins fragmentation function, depends on spin note: T q also measured using Two hadron fragmentation function Sivers TMD h q eqf 1Tq Dq h q q q A Siv e q D Quark fragmentation function

19 Collins Asymmetry on p - p, K id. Trieste 3-7/013 XCIX Congresso SIF 19 Correlation between outgoing hadron & quark transverse spin T u & T d π- combined results ~ h + / h - π+ preliminary compatible with π + / π - K - K + preliminary Agreement HERMES/COMPASS (not shown) no Q dependence seen (factor of ~3 inq ) Now also produced in bins of z and y

20 Trieste 3-7/013 XCIX Congresso SIF 0 Transversity from Collins Combined analyses of HERMES, COMPASS and BELLE fragm.fct. data Anselmino et al. arxiv:

21 Sivers Asymmetry on p - p, K id. Correlation between nucleon spin & quark transverse momentum k T π+ combined results ~ h + / h - π- preliminary larger than for π + K + K - preliminary In region of overlap, agreement with HERMES, but smaller strength Now also produced in separate bins of z and y. Trieste 3-7/013 XCIX Congresso SIF 1

22 Trieste 3-7/013 XCIX Congresso SIF Sivers asymmetry on p, x > 0.03 charged pions (and kaons), 010 data comparison with HERMES results as for h+, smaller values measured by COMPASS; same indication for K+

23 Trieste 3-7/013 XCIX Congresso SIF 3 -hadron asymmetries Another access to transversity h 1 A RS 1 A f P D T q qx Hq z,mh h D z,m q x h 1 u & h 1 d extraction Also measured for the first time for K + K -, p + K - and K + p - pairs e q q e Δ q T q h

24 Trieste 3-7/013 XCIX Congresso SIF 4 -h multiplicities First time measured in lp Needed for pol. PDF extraction; will complete e+ e- data

25 Trieste 3-7/013 XCIX Congresso SIF 5 Other Transverse Target spin asymmetries k T effects modulations in SIDIS cross-section Major progress in TMD measurement Powerful tool to understand correlations m p m p h +/- shown as example In agreement with HERMES prelim., and with theoretical predictions

26 Trieste 3-7/013 XCIX Congresso SIF 6 Physics from hadron beam Rich program on hadron spectroscopy at COMPASS, search for exotic mesons - Diffractive resonance production - Central production p, K, p beams GeV : large energy transfer spectrum t Spectrometer : flat acceptance, ECALs/ HCALs, RICH id. charged & neutral channels Huge statistics Major progress on analysis Potential for discovery of small intensity new states Selected results Diffractive processes p p p p p p recoil Pion polarisability p Ni p Ni - (009 Primakoff )

27 Trieste 3-7/013 XCIX Congresso SIF 7 s Diffractive resonance production in p p p p p p recoil t Isobar model Partial waves : J PC M [isobar] L J PC -exotic mesons Study 008 data, large statistics Partial Wave Analysis (PWA): Step 1: In (M 3p, t ) bins, 88 PW, (7 with thresholds) Impose isobar description Step : M 3p dependent fits on selected waves, combined fit of t bins (same mass, width; different background and couplings) Extract resonance parameters

28 Trieste 3-7/013 XCIX Congresso SIF 8 Shape of mass in t bins t ~ 0.1 GeV /c t ~ t M 3p M 3p M 3p t dependence for M 3p bins M 3p ~ 0.8 GeV/c M 3p ~ x 100 (t,m 3p ) bins t t

29 Step 1: PWA in (M, t ) bins Intensities for 3 major waves vs M 3p [rp]S ++ 1+[rp]D -+ 0+[f170p]S t ~0.1 (GeV /c ) 100 M 3p bins % a1(160) a(130) p(1670) Peak position M 3p strength strength t ~ % M 3p a1 as benchmark Possibility of separation of resonant and non resonant content high statistics & fine binning Trieste 3-7/013 XCIX Congresso SIF 9

30 Trieste 3-7/013 XCIX Congresso SIF 30 Step : PWA M 3p dependent fit, ex: [rp]D Mass dependent fits for 5 selected waves, using a model for 3p resonance + bkgd. 11 t bins log scale, data model : BW-a (130) + BW-a (1950) + Bkgd 10 4 sum of 11 bins a(130) a(1950) sum of 11 bins

31 Trieste 3-7/013 XCIX Congresso SIF 31 PWA M 3p dependent fit, ex: [rp]S data --- model : BW-a1 (160) + BW-a1 (1930) + Bckgd sum of 11 bins (log scale) 10 6 a1(160) Sum of 11 bins (linear scale) 10 4 a1(1930)

32 Trieste 3-7/013 XCIX Congresso SIF 3 PWA M 3p dependent fit, ex: small wave [rp]G <1% of total intensity, a4(040) well established data --- model : BW-a4 (040) + Bckgd sum of 11 bins

33 Trieste 3-7/013 XCIX Congresso SIF 33 Pion polarisabilities - Primakoff 009 data Polarisabilities: deviation from pointlike particle electric () and magnetic (b) Predictions from Ch PT: Experiments inconclusive: p b p = assuming ( p b p =0) At LO, Compton cross section is proportional to p b p p p measured via p Z p Z

34 Trieste 3-7/013 XCIX Congresso SIF 34 Pion polarisability - result 009 data p Ni p Ni exclusive reaction high resolution vertexing, precise calorimetry, calibrations, alignment precise MC description of spectrometer performance, p b p extracted from comparison of data to MC(pointlike) Ratio: data/mc (pointlike) p b p = (3.7 ± 1.4) x 10-4 fm 3 p = (1.9 ± 0.7)x 10-4 fm 3 (assuming p b p =0)

35 Trieste 3-7/013 XCIX Congresso SIF 35 Pion polarisability result vs world data COMPASS result : in agreement with ChPT expectation, does not confirm other dedicated measurements COMPASS Ch. PT World average 01 data: 5-6 times more statistics & extended kin range

36 FUTURE Trieste 3-7/013 XCIX Congresso SIF 36

37 d d p cm d d p cm pt ( s m ) C. p ( (1 cosθ ) s 3 ( s m p ) 1 cosθ ) ( b ) ) ) ( ) (1 cosθ ( ) cm p bp cm p bp ( cm Polarisability effect with increasing s at backward or forward angle 4s s m 4 p 009 data p - b p (in 10-4 fm 3 )= stat 1.6 syst AgreeMt with ChPT still preliminary 01 data, 3 components ( p - b p ) ( p + b p ) ( - b ) can be measured with an accuracy of 10% point-like case for ChPT prediction and kaon polarizabilities Trieste 3-7/013 XCIX Congresso SIF 37

38 Trieste 3-7/013 XCIX Congresso SIF 38 Semi-Inclusive Deep Inelastic Scattering Semi-Inclusive DIS measurements with polarized targets (00-011) with a pure proton target (with GPD program Use of RICH detector and Calorimeters Charge separation and identification K +, K -, K 0, p +, p -, p 0, Major progress as compared to previous experiments to strange PDFs: s(x) and s(x) Hadron multiplicities at LO PDF depend on x quark Fragmentation Function depend on z (fraction of energy of the outgoing hadron) Final goal: extensive measurements (x, z, Q, p Th ) to provide inputs to NLO global analysis for both PDF and FF

39 TMDs Asymmetries in the azimuthal angle h of the outgoing hadron around the virtual photon can reveal quark transverse spin and quark transverse momentum (k T ) effects beyond the collinear approximation ' At leading twist, not only f 1 (x, k T ), g 1L (x, k T ), h 1 (x, k T ) but also 5 othertransverse Momentum Dependent PDF (TMD (x, k T )) which do not survive after integration on k T The Boer-Mulders function examples of TMDs The Sivers function correlates the quark k T and the quark transverse spin (unpol N) Chiral-odd and T-odd correlates the quark k T and the nucleon spin (transv. Pol. N) Chiral-even and T-odd Trieste 3-7/013 XCIX Congresso SIF 39

40 Boer-Mulders and Cahn effects many data collected and still to be collected in SIDIS with GPD program Trieste 3-7/013 XCIX Congresso SIF 40

41 Trieste 3-7/013 XCIX Congresso SIF 41 After SIDIS, polarized Drell-Yan to study TMDs Drell Yan π - p m + m - X - Cross sections: In SIDIS: convolution of a TMD with a fragmentation function In DY: convolution of TMDs complementary information and universality test

42 The polarized Drell-Yan process in π - p d F F 1 A cos UU UU UU d qd Fq cos( ) cos h 1 cos D A cos( ) D A UU sin UU sin S A A L sin sin( ) UL UL sin sin S S sin D A D A S 1 UT cos UT sin( ) S sin( ) S D A UT sin sin( ) S S sin( ) T S D A UT sin sin( ) S sin( ) D A S UT sin sin( ) h S sin( ) D A S UU sin sin sin( ) D D sin sin Collins-Soper frame (of virtual photon), lepton plane wrt hadron plane target rest frame S target transverse spin vector /virtual photon Access to TMDs for incoming pion target nucleon TMD as Transversity, Sivers, Boer- Mulders, pretzelosity Hadron plane Trieste 3-7/013 XCIX Congresso SIF Lepton plane 4

43 Trieste 3-7/013 XCIX Congresso SIF 43 Experimental check of the change of sign of TMDs confronting Drell-Yan and SIDIS results T-odd character of the Boer-Mulders and Sivers functions In order not to be forced to vanish by time-reversal invariance the SSA requires an interaction phase generated by a rescattering of the struck parton in the field of the hadron remnant Time reversal SIDIS these functions are process dependent, they change sign to provide the gauge invariance Boer-Mulders Sivers h 1 ( SIDIS ) h1 ( DY) f1t ( SIDIS ) f1t ( DY)

44 Trieste 3-7/013 XCIX Congresso SIF 44 Why DY pp is very favourable at COMPASS? DY dominated by the annihilation of a valence anti-quark from the pion and a valence quark from the polarised proton 18 Competitive experiments at RHIC (STAR, PHENIX) collider Fermilab fixed target J-PARC fixed target FAIR (PAX) collider NICA collider large acceptance of COMPASS in the valence quark region for p and π where SSA are expected to be larger COMPASS has the chance to be the first experiment to collect single polarized DY

45 Q vs x phase space at COMPASS The phase spaces of the two processes overlap at COMPASS Consistent extraction of TMD DPFs in the same region Trieste 3-7/013 XCIX Congresso SIF 45

46 Predictions for Drell-Yan at COMPASS Sivers asymmetry in the safe dimuon mass region 4 < M m+m- < 9 GeV years of data 190 GeV pion beam π - /spill (of 9.6s) 1.1 m transv. pol. NH 3 target Lumi= cm - s -1 Red solid and dod-dashed line Anselmino et al., PRD79 (009) Black solid and dashed: Efremov et al., PLB61 (005) Black dot-dashed: Collins et al., PRD73 (006) Squares: Bianconi et al., PRD73 (006) Green short-dashed: Bacchetta et al., PRD78 (008) Trieste 3-7/013 XCIX Congresso SIF 46

47 m p From inclusive to exclusive reactions (3D tomography) Deep Inelastic Scattering m Q²x B γ* x mp m X z Deeply Virtual Compton Scattering p * Q² x+ GPDs t mp m p x- P z x P x P b x boost y x boost y Distrib. de Partons q ( x ) P x Generalized Partons Distrib. H( x,,t ) ( P x, b ) Beyond collinear approximation -> Trans. Position (b ) Dependent GPD in Excl. React. -> as Trans. Momentum (k ) Dep. PDF or TMD in SIDIS & DY Trieste 3-7/013 XCIX Congresso SIF 47

48 Trieste 3-7/013 XCIX Congresso SIF 48 Kinematic domain (Q, x B ) for GPDs collider fixed target COMPASS unique for GPDs CERN High energy muon beam GeV μ + and μ - available 80% Polarisation with opposite polarization m + Lumi= 10 3 cm - s -1 with.5m LH target Explore the intermediate x Bj region Uncovered region between ZEUS+H1 & HERMES + Jlab before new colliders may be available It s time to show the impact of COMPASS => goal of the 01 DVCS pilot run

49 Trieste 3-7/013 XCIX Congresso SIF 49 Upgrades of the COMPASS spectrometer DVCS : μ p μ p μ p New equipements:.5m LH target 4m ToF Barrel CAMERA ECAL0 μ CAMERA

50 Trieste 3-7/013 XCIX Congresso SIF 50 ECAL1 ECAL ECAL0 CAMERA recoil proton detector surrounding the.5m long LH target m

51 Trieste 3-7/013 XCIX Congresso SIF 51 Deeply Virtual Compton Scattering dσ (μpμp) = dσ BH + dσ DVCS unpol + P μ dσ DVCS pol Phase 1: the transverse imaging with m +, m - beam + unpolarized.5m long LH (proton) target S CS,U + e μ a BH Re A DVCS + e μ P μ a BH Im A DVCS BH DVCS Int CS,U d(m + ) + d(m - ) d dunpol K s1 sin Using S CS,U and BH subtraction and integration over d DVCS /dt ~ exp(-b t ) μ μ * p θ

52 Trieste 3-7/013 XCIX Congresso SIF 5 Transverse imaging DVCS /dt ~ exp(-b t ) d DVCS as soft Pomeron years of data 160 GeV muon beam.5m LH target global = 10% with 40 weeks in rst bar= stat. error; nd = stat + syst. errors ansatz at small x B inspired by Regge Phenomenology: B(x B ) = b 0 + α ln(x 0 /x B ) α slope of Regge traject

53 Deeply Virtual Compton Scattering dσ (μpμp) = dσ BH + dσ DVCS unpol + P μ dσ DVCS pol + e μ a BH Re A DVCS + e μ P μ a BH Im Phase 1: DVCS experiment to constrain GPD H with m +, m - beam + unpolarized.5m long LH (proton) target D CS,U d(m + ) - d(m - ) S CS,U d(m + ) + d(m - ) x B / (-x B ) c c Int 0 cos and c Int 0, Re(F 1 H) 1 Int and Im(F 1 H) Trieste 3-7/013 XCIX Congresso SIF 53 Int 1 BH DVCS Int d c0 K s1 sin Note: dominance of H at COMPASS kinematics Im H (,t)= H(x=,,t) Re H (,t)= P dx H(x,,t) = P dx H(x,x,t) + D(t) Re part of the x- the Compton Form Factors linked to the D term s 1 x-

54 Trieste 3-7/013 XCIX Congresso SIF 54 Summary for COMPASS GPDs investigated with Hard Exclusive Photon and Meson Production COMPASS-II : 17: with LH target + RPD (phase 1) m +, m GeV the t-slope of the DVCS and HEMP cross section transverse distribution of partons the Beam Charge and Spin Sum and Difference Re T DVCS and Im T DVCS for the GPD H determination Vector Meson r 0,r +,, Φ Pseudo-saclarsaclar p 0 Using the data: transv. polarized NH 3 target without RPD In a future addendum > 017: transv. polarised NH 3 target with RPD (phase ) the Transverse Target Spin Asymm GPD E and chiral-odd (transverse) GPDs

55 Trieste 3-7/013 XCIX Congresso SIF 55 For the next 10 years, before any collider is available, and complementary to Jlab 1 GeV, COMPASS@CERN can be a major player in QCD physics using its unique high energy (00 GeV) hadron and polarised positive and negative muon beams

56 Thank You Trieste 3-7/013 XCIX Congresso SIF 56

57 Trieste 3-7/013 XCIX Congresso SIF 57 Sensitivity of M K to strange FF D s K S(x)<<5Q(x) Directly related to strange PDF and FF of strange quark into K Small x dependence small D sk (z),r SF or S(x) solves tension for Δs between DIS & SIDIS? Arxiv New tension with HERMES? more work needed (higher twist )

58 With transv. polarized target Constraints on other GP Trieste 3-7/013 XCIX Congresso SIF 58 Chiral-even GPDs H q A sin( - S ) UT E f 1T Chiral-odd GPDs Sivers correlates quark k T and nucleon spin (transv. pol. N) A sin( S ) H T h 1 UT Transversity correlates quark spin and nucleon spin (transv. pol. N) ~ E T = H T +E T h 1 Boer-Mulders correlates quark k T and quark transverse spin (unpol N)

59 Trieste 3-7/013 XCIX Congresso SIF 59 SIDIS x-section h h h UU T UU L h h S UU UU LU UT T h h S S h S d y F F x dxdydzdp d d xyq A A A A P,, cos cos( ) sin sin ( ) sin si co cos cos( ) s ( ) ( ) ( n cos sin sin ) si s in n S h h h h S h S h S UL U h S UT L h S UT U h S h T U S L A A A A A A sin( ) sin sin sin ( ) s ( in in s ) sin( ) sin( ) s sin ( ) si co in( ) si n ( n( s ( ) ) s cos n cos i h h S S h S h UT T LT h S LL S U S L S T UL L h A A A A A A P sin cos sin( ) cos cos( ) sin si sin sin ( ) s n ) sin( ) cos c in ( ) cos cos os( ) o ( cs ) h S h UT h L S h S L A A cos( ) cos cos( ) cos( ) s cos ( ) in ( )

60 Trieste 3-7/013 XCIX Congresso SIF 60 the polarized target system (>005) 3 He 4 He dilution refrigerator (T~50mK) solenoid.5t dipole magnet 0.6T acceptance > ± 180 mrad μ 3 target cells 30, 60, and 30 cm long opposite polarisation d ( 6 LiD) p (NH 3 ) polarization 50% 90% dilution factor 40% 16% no evidence for relevant nuclear effects (160 GeV)

61 DY and COMPASS set-up two 55cm long cells separated by 0cm p GeV Key elements for a small cross section investigation at high luminosity 1. high intensity pion beam 10 8 p - per second on a thick target (~1 interaction length). a hadron absorber to stop secondary particles and a beam plug to stop the non-interacting beam 3. rearrangement of the target area to place the absorber - a new muon trigger in the first stage spectrometer (60% of the DY acceptance) - a vertex detector (SciFi) to improve the cell separation 4. RICH1, Calorimetry also important to reduce the background Trieste 3-7/013 XCIX Congresso SIF 61

62 Trieste 3-7/013 XCIX Congresso SIF 6 Predictions for Drell-Yan at COMPASS -0. < x F < 0.85 x F =x p -x p x F =x p -x p he first ever polarised Drell-Yan experiment sensitive to TMDs

63 Trieste 3-7/013 XCIX Congresso SIF 63 Deep Inelastic Scattering Inclusive DIS Semi Inclusive DIS

64 Contributions of DVCS and BH at E m =160 GeV Deep VCS Bethe-Heitler d T DVCS + T BH + Interference Term μ μ * p θ Monte-Carlo Simulation for COMPASS set-up with only ECAL1+ Missing DVCS acceptance without ECAL0 BH dominates excellent study of Interference DVCS dominates Re T DVCS study of d DVCS /dt reference yield or Im T DVCS Transverse Imaging Trieste 3-7/013 XCIX Congresso SIF 64