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Status and plans of the COMPASS experiment

Status and plans of the COMPASS experiment. Fabienne KUNNE CEA /IRFU Saclay, France On behalf of the COMPASS Collaboration. Outline. New results from muon beam data Longitudinal Spin: quark and gluon helicities Unpolarized data : h cross-sections & p, K multiplicities

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Status and plans of the COMPASS experiment

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  1. Status and plans of the COMPASS experiment Fabienne KUNNE CEA /IRFU Saclay, France On behalf of the COMPASS Collaboration

  2. Outline • New resultsfrom muon beam data • Longitudinal Spin: quark and gluon helicities • Unpolarized data : h cross-sections & p, K multiplicities • Transverse Spin: status of analysis - 2010 data • New resultsfrom hadron beam data • pdiffractive dissociation, low t - Ch PT • Search for exotics : PWA for 3p final states, 2008-2009 • PWA for Kpp • Data taking • Overview of 2010 run & status of 2011 run • Future plans • 2012 beamrequest • Plans for COMPASS-II

  3. The COMPASS experiment • Two stage spectrometer • Large angular acceptance, • Broad kinematical range • ~250000 channels • ~ 1TB/year Hadron spectroscopy & Primakoff Nucleon spin structure • 2002-2004:160 GeV m on 6LiD L,T • 2006 :160 GeV m on 6LiD L • 2007 :160 GeV m on 6LiD T • 2010 :160 GeV m on NH3 T • 2011 :200 GeV m on NH3 L • 190 GeV p-, m onPb(2 weeks) • 2008 190 GeV p-onLH2 • 2009 190 GeV p,p+on LH2, Pb, Ni, W

  4. ΔG/G from m N scattering Photon Gluon Fusion (PGF) process Spin asymmetry of cross sections for longitudinal polarizations of beam and target, parallel and antiparallel q q ALL = RPGF<aLL> <DG/G> + Abackground Fraction of process • Analyzingpower • Calculable (LO, NLO?) Two signatures for PGF: Final result at LO (5 channels &5 years) First extraction at NLO ALL(pT) • 1/ q=c open charm cgD0g K p • Clean signature of PGF • Combinatorial background & limited statistics → Difficult experiment • 2/ q= u,d,shigh pThadron pairq qg h h • High statistics • Physical background Final result at LO : 3 x bins Bothpapers in preparation

  5. G/G at LO High pT hadrons: Q2~ 3 with model for physical background Open charm: Q2= 13 LSS10 Q2=3 DSSV at Q2= 4 preliminary LSS10, LO, DG~ + 0.32 LSS10, LO, DG~ - 0.33 (node) at Q2=3 DSSV, LO, DG= 0.02 • 5 points from COMPASS • All measurements compatible with 0 • Constraint on <DG> for 0.05 < x < 0.3 • Results disfavour value of the integral larger than… ~ ± 0.3, i.e. ± 60% of the ½ nucleon spin

  6. G/G from charm: from LO to NLO aLL xG Analysing power aLLcalculatedat NLO NLO LO  distribution isshifted. Induces a change in <D G>, but also in the relative weight of events, hence a change in <x> • +1 -1 • 0 aLLfor one channel Theoreticaluncertaintyunderstudy • DG_NLO= -0.20 ± 0.21± 0.08(syst) at <x>=0.28 Value still compatible with zero, <x> range higher

  7. G/G from charm: from LO to NLO NLO Charmat NLO,all other points at LO • First extraction of DG at NLO • ConstrainsDG atlarger x • Charmresultcanbeincluded in global NLO fits: • Model independentasymmetries ALL(pT, ED) available

  8. Quark helicities from Semi-Inclusive DIS Extraction at LO • COMPASS final result • PLB693(2010)227, using DSS FF o HERMES __ DSSV Q2=3 (GeV/c)2 COMPASS PLB 693(2010)227 COMPASSDs =-0.01 ± 0.01 (stat) ± 0.01 (syst), 0.003<x<0.3 Ds – Ds compatible with 0 • Full flavour separation  x~0.004 • Sea quark distributions ~ zero • Good agreement with global fits

  9. High pT hadron cross sections Absolute cross-section measurement quasi real photo production of hadron μ+d → μ+h±X • 2004 data, 4 weeks • Huge statistics: rapidity bins COMPASS Q2<0.1 √s =17GeV In agreement with NLO pQCD, within theory’s uncertainty over 6 orders of magnitude  Settles the theory framework for ΔG high pT Nextstep: produce spin asymmetriesALL(pT) for sameevents

  10. Pion and kaon multiplicities μ+d → μ+h±X Q2>0.1 at LO Hadron production in semi-inclusive deep inelastic scattering PDFsFFs • 2004 data, 4 weeks • Finer binning in z, Q2 possible p- p+ at LO K- K+ x x Input to global QCD analyses to extract quark fragmentionfunctions

  11. Collins and Siversasymmetries in SIDIS m pmp h+/- • Transversely polarized target • Measure simultaneously several azimuthalasymmetries, out of which : Collins: Outgoing hadron direction & quark transverse spin Sivers: Nucleon spin & quark transverse momentum kT Collins Sivers at LO: Usual quark fragmentation function q transverse spin distr. Collins fragmentation function, depends on spin note: DTqalsomeasuredusing • ‘’Two hadron’’ fragmentation function • lambda Transverse. Polarization

  12. Transversity : Collins Asymmetry m pmp h+/- Correlation between outgoing hadron & quark transverse spin  DTu & DTd New results for identifiedparticles: p & K from 2007 NH3 data p+- K+- • Large signals in valence region for p+- & K+-both DTu & DTd and Collins FF sizable • Opposite for + and – hadrons:opposite u and d CollinsFF • larger for K+ than for p+ role of sea quarks • Excellent agreement between HERMES p and COMPASS p data (not shown here)

  13. Transversity : SiversAsymmetry m pmp h+/- Correlation between nucleon spin & quark transverse momentum kT New results for identifiedparticles: p & K from 2007 NH3 data p+- K+- Comparison to HERMES • COMPASS • ° HERMES p+ K+ • Clear signal in HERMES p+ and K+ • Smaller signal in COMPASS, howeverenhancedatlower W • Additional data will come from COMPASS 2010 run

  14. Other Transverse MomentumDependentDFs kTeffects modulations in (unpolarized) SIDIS cross-section. Ex., spin orbiteffectBoer-Mulders DF , Cahneffect… correlation between quark transverse motion and transverse spin • cosf Boer-Mulders DF + Cahneffect… • cos 2f • Major progress in TMD measurement: all 6 asymmetries released • Powerful tool to understand correlations • also since Lattice calculations indicate strong correlations between spin, position and momentum V.Barone,A.Prokudin, B.Q.Ma, arXiv:0804.3024

  15. Hadron reactions - 2008 and 2009 data • 190 GeV p-, m onPb(2 weeks) • 2008 190 GeV p-onLH2 • 2009 190 GeV p,p+,p-on LH2, Pb, Ni, W •  StudyJPC-exoticmesons(lowt’) • photoprod/diffraction/ChPT(verylowt’ <0.001) • Enormousprogress in data analysis • Many new resultsshownat HADRON-2011 • - Diffractive dissociation into 3p • - Comparison of charged /neutralchannels in 3 psystems • - Diffractive dissociation of K-p-p+ • Exotic’ pwave in pion diff. scattering • Update on 3patlow t compared to ChPT

  16. Pion diffractive dissociation atlow t’ • 2004 lead data • PWA analysis • Absolute cross-section induced by photon exchange cross section in this range First measurement of Result in agreement with LO Ch.PT calculation More data avalable from 2009 running on lead

  17. Spin ExoticSearch • Hybrid candidates (1.3 - 2.2 GeV/c²): • lightest hybrid predicted: exotic JPC =1-+ • p1(1400):VES, E852, Crystal Barrel ->hp • p1(1600):E852, VES->rp, h‘p, f1p, b1p • p1(2000): E852-> f1(1285)p, b1(1235)p • …. still controversal  COMPASS • Diffractivescattering • studyofJPC exoticmesons • t-channelReggeonexchange • forwardkinematics, targetstaysintact Charged/neutral p • Diffractive pion dissociation • incomingp-excitedtoresonanceX- • X-decaysinto final state, e.g. (3p)-: • p-p -->p-p+p-p (chargedmode) • smallmomentumtransfer

  18. Diffractivedissociationinto 3p final states 2008 data, p target Massofoutgoing 3psystem chargedmode: p-p -->p-p+p-p neutral mode:p-p -->p-p0p0p PWA: ~ 24M events(acceptancecorr.) PWA: ~ 1M events

  19. PWA using isobar model • X-decay described using isobar model: • Intermediate di-pion resonance (isobar) • Spin S and rel. orbital angular • momentum L w.r.t bachelor p- • L+S couple to J • Partial waves (reflectivity basis): JPC Me [isobar] L • Partial waveanalysis: • program: Illinois/Protvino/Munich(D.Ryabchikov)software(IHEP/VES, TUM/COMPASS) • 5 Isobars:(pp)S [broad f0(600)+f0(1370)], f0(980), r(770), f2(1270), r3(1690) • Acceptance: corrections(2004: ~60%, rather flat, 2008: similarforcharged, neutral not yetincluded) • Massindependent PWA:(40MeV/c² bins, 52+1 partial waves)

  20. Diffractivedissociation3pcharged searchforp1(1600) 2008 p p1(1600) ? • a1(1260) • Intensity: • signalat ~1.6GeV, • leakagefrom a1 • Phase: • clean phasemotion

  21. Diffractivedissociation3pcharged 1++total M dependenceandtargetmass JPCMe M=0, Pb M=0, p M=1, p M=1, Pb • Observed M-dependence: • productionstrengthfor M=1 vs. M=0 statesdepend on target material • seen in 2004, confirmed on 2009 data Total p Total Pb

  22. Diffractivedissociation3pchargedvsneutral searchforp1(1600) isospinsymmetry in spintotals: rp f2p • Data follows rp / f2p symmetry: • throughout full wave-set • main and small waves, next slides

  23. Diffractivedissociation3pchargedvsneutral isospinsymmetry in selected (small) partial waves a4(2040) -> rp a4(2040) -> f2 p Small intensity (few %)

  24. Diffractivedissociation3pchargedvsneutral Selected partial wavesandphases Reference • Evensmallerintensity • & separated in mass Rathersmallintensity vs ref a4(2040) -> rp a1(1260) -> rp p2(1670) -> f2 p • Relative phases • partial wavesshowphasemotions • w.r.t. to well-knownresonances • rather robust w.r.t. to absolute • intensities • veryconsistentpicture Resonance w tail of a1 Resonanceagainst a1

  25. Diffractivedissociation3pchargedvsneutral Selected partial wavesandphases 1-+ p1(1600) ? -> rp a1(1260) -> rp Not released yet • Relative phases • partial wavesshowphasemotions • w.r.t. to well-knownresonances • rather robust w.r.t. absolute intensities • veryconsistentpicture Resonanceagainst a1

  26. Study interferencesof Coulomb and strong diffr. productionofcharged 3p final states (Pbtarget) 2004 data, low t Same final state & similaranalysis but differentreaction Not maingoal, but also: searchforp1(1600) Preliminary confirmation of CLAS experiment: no spin-exotic 1 -+ signal in photoproduction (structures at 1.1 GeV: non-resonating contribution (ChPT), at 1.9 GeV: some leakage)

  27. Physicswith kaon beam: Kaon diffraction 2% K- Oneexemplary partial wave, mas-independent fit: • Statistics ~5 x WA03 • Severalstatesneedconfirmation, •  e.g. the K(1460) • Kaon beam potential

  28. p TAX 1 failing Q1 -Q6 TAX 2 o.k. !! SPS T6 TAX 1 TAX 2 target Absorber Absorber Absorber Absorber beam p Absorber Absorber 2011 run failed Started with1 monthdelay, due to failure of TAX1 in beam line ok ~ 10 mSv / h • Found solution in agreement with ALARA committee • TAX1 crankinto right position • Use only TAX2

  29. 2011 run • Otherproblems: • New beamaccess system : • somepbsat startup (3 days), however new system more reliable • COMPASS Polarized target: • - 3He Heat Exchangers: major leaks; complex repair • - Magnet Power Supply • - some reduction in He Supply • GEM readout upgrade • During May: Fixed most of the problems and commissioned as far as • possible detectors without beam • From June 9 on: Normal start-up, commissioning & • Perform specific DVCS tests • June 23 Start data taking

  30. 2012 Beamrequest: • Primakoff: p,Kpolarisabilities • DVCS test run

  31. Pion polarizabilitiesfromPrimakoff Deviationfrompointlikeparticle: electric (a) and magnetic (b) polarisabilities Leadingorder (non point like)

  32. Primakoffat COMPASS • High energyidentifiedp/K beams • High precisiontracking and calorimetry • Muon beam for control measurement • New kinematical range for COMPASS: • verylow angles < few mrad • Difficulttracking • more difficultthanwhat has been done for otherchannels

  33. Status of 2009 Primakoffanalysis pions Ep+ Eg-Ebeam(GeV) • ECAL2 new calibration and clusteringalgorithm • Run by runalignment • High resolution in energy (exclusivity) • and momentumtransfer (quasi real photon signature) • New tracking and bridgingalgorithms (betterprimary vertex resolution)

  34. Primakoffanalysis– muon control run OngoingMonte-Carlo investigation to look for possible systematics RD/MC description of m Ni m Ni g not fullyunderstoodyet Investigating in detail: Tracking:requirespreciseefficiency close to dead zones of detectors RICH beam pipe: screenslowmomentamuons Samerestricted to lowmomenta muons, 20<pm<30 GeV/c (relevant region) Muon tracksextrapolated to RICH position z=770 cm • Need to buildand install new RICH beam pipe • withlightermaterial, for 2012 running

  35. Status of 2009 Primakoffanalysis p RD/(MC pointlike) First look atavailablestatistics However, improvements not includedyet  Polarisabilitiesnot extracted w=Eg/Ebeam • Nextsteps for the analysis • Improvedescription in MC • Bettertrackingatsmall angle (increasetolerance for angularstraggling) • Restrict phase space to similar range for p and m

  36. Proposal for 2012 Primakoff running • COMPASS isconvinced to achieve the requiredtrackingperformance, i.e. understanding the trackingefficienciesat the 1-2 % level • Assumingthis, estimateduncertaintiesremain as in proposal: • From the same data set, itwillbe possible to extract kaon polarisability (5s effectassumingChPTprediction) •  world first measurement

  37. Conclusions for 2012 Primakoff running • Plans to improve • Addredundancy to trackingatverysmall angle – couldbeSciFis as in 2004 • Exchange RICH beampipe • Improvementof digital trigger (test in 2011) • Withproposed running time: • 500k evts for pion, Primakoff Compton (25k evts in 2009) • 3k evts for kaon

  38. 2012 DVCS test run

  39. 2012 DVCS test run μ p  μ’ p    μ  μ μ’ * θ μ p p p  BH calculable DVCS • Goal: • evaluate contributions of BH,”pure” DVCS and 0 as a function of xB (DVCS and 0 still unknown in COMPASS kinematics) • investigation of `Beam Charge & Spin’ Sum and Difference • first measurement of the t-slope of the DVCS cross section

  40. Resultfrom 2009 DVCS test run (10 days, short RPD+target μ p  μ’ p  251 evts 135 evts 54 evts Single photon events: first hint for DVCS + 0 contribution |BH|2 |BH|2 |BH|2 PRELIMINARY PRELIMINARY PRELIMINARY BH 0.005 < xB < 0.01 0.01 < xB < 0.03 0.03 < xB • εp ’ p = 0.35 • Global efficiency ε= 0.10 confirmed • (value used in proposal) 54 evts = 20 BH expected  22 DVCS  12 evts from 0 ?

  41. 2012 DVCS TEST RUN • new LH2 target, 2.5m long • new Recoil Proton Detector, 2 rings, 4m long • part (1/5) of new ECAL0 large angle calorimeter ECAL0248 modules (12  12 cm2) of 9 cellsread by 9 MAPDs • LH2 target • Developed and built by CERN/ TE/ CRG group 2.20m

  42. 4m long Recoil Proton Detector ToFbetween 2 rings of scintillators(ToF) < 300ps light guide downstreamside • Final installation should be • ready by September 2012 3.90m

  43. DVCS: Transverse imaging dDVCS/dt ~ exp(-B|t|) 14 Tomographic parton images of the nucleon Model independent extraction of B(xB) B(xB) = ½ < r2 (xB) > r : transverse size of the nucleon

  44. DVCS: Transverse imaging dDVCS/dt ~ exp(-B|t|) 14 Transverse size of the nucleon 1. 0.5 0.65 0.02 fm H1 PLB659(2008) ? COMPASS xB Model independent extraction of B(xB) B(xB) = ½ < r2 (xB) > r : transverse size of the nucleon

  45. DVCS: Transverse imaging dDVCS/dt ~ exp(-B|t|) DVCS test in 2012 1week (1/40 of total stat.)  2012: first determination of <B> for 0.01<x<0.1

  46. 2012 Beamrequest - summary • Primakoff : 18 weeks • 90 days 190 GeV p- (59 x 1011p- on target) • 30 days 190 GeV m- (12 x 1011m- on target) • Change over: 3 weeks • removal of Primakoff setup • Installation of 2.5m long LH2 target, long RPD & part ECAL0 • DVCS : 3 weeks • 160 GeV m, commissioning + data taking

  47. COMPASS-II tentative schedule Tentative schedule agreed upon by COMPASS (GLB April,7 2011), after announcement that LHC would run in 2012 - 2012: Primakoff run, and GPD commissioning - 2013 :Use long shut down to install polarized target plus absorber for Drell-Yan program - 2014 : Polarized Drell-Yan - 2015 & 2016 : GPD

  48. Main requirements for Drell-Yan setup Absorber2 m long tungsten beam plug, alumina absorber and stainless steel shielding sandwiches Polarized target movement by 2m upstream New scheme for the He, exhaust and quench lines. Vacuum system? Transfer Lines. New scheme for microwave guides (New target cell geometry and cavity). Control System: New positions for control and power supply racks? New cabling scheme. Target filling platform. Layout and Procedure. Layout details of the absorber Assembly and Installation scheme for compatibility with target maintenance Radiation shield of the experimental zone. Passages andother safety issues. New entrance door to 888? Linear movement of the target platform. Alignment of the system.

  49. Quench and Exhaust Lines Cable trays Transfer Line Control Racks Absorber He-pipes Micro Wave guides

  50. Publications / Conferences in 2010 • Presentationsatconferences : 86 • Publications • JPC = 1–+ exotic resonance PRL 104 (2010) 241803 • g1p and a Test of the Bjorken Sum Rule PLB 690 (2010) 466–472 Collins and Sivers asymmetries-proton PLB 692 (2010) 240–246Azimuthal asymmetries, L deuterons EPJC 70 (2010) 39–49 Quark HelicitiesPLB 693 (2010) 227–235

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