experiment NA 58 The COMPASS experiment at CERN
- Slides: 55
experiment NA 58 The COMPASS experiment at CERN Oleg Kouznetsov JINR, Dubna On behalf of the COMPASS Collaboration 27/09/2013 TRENDS, Alushta 23 -29 September
LHC COMPASS Lake LEMAN CN G Gr an S S 732 asso km CERN (France) N SPS 27/09/2013 CERN (Suisse) TRENDS, Alushta 23 -29 September
~210 physicists COmmon Muon and Proton Apparatus 11 counties 29 Institutes for Structure and Spectroscopy Hadron beam 27/09/2013 COMPASS I 2002 -2011 TRENDS, Alushta 23 -29 September Muon beam
~210 physicists COmmon Muon and Proton Apparatus 11 counties 29 Institutes for Structure and Spectroscopy Hadron beam COMPASS I 2002 -2011 Muon beam Unpolarised physics 27/09/2013 TRENDS, Alushta 23 -29 September Polarised physics
~210 physicists COmmon Muon and Proton Apparatus 11 counties 29 Institutes for Structure and Spectroscopy Hadron beam COMPASS I 2002 -2011 Muon beam Polarised physics Unpolarised physics Exc. V meson production hyperon polarization Heavy hyperons 27/09/2013 Quark densities Tq TRENDS, Alushta 23 -29 September Trans polar. . Long. polar. Quark densities q Gluon densities g
~210 physicists COmmon Muon and Proton Apparatus 11 counties 29 Institutes for Structure and Spectroscopy Hadron beam Coulomb production Diffractive scattering COMPASS I 2002 -2011 Muon beam Central production Exc. V meson production hyperon polarization Heavy hyperons 27/09/2013 Polarised physics Unpolarised physics Quark densities Tq TRENDS, Alushta 23 -29 September Trans polar. . Long. polar. Quark densities q Gluon densities g
~210 physicists COmmon Muon and Proton Apparatus 11 counties 29 Institutes for Structure and Spectroscopy COMPASS I 2002 -2011 Hadron beam Coulomb production Diffractive scattering Glueballs Hybrids Multiquarks 27/09/2013 Polarised physics Unpolarised physics Central production Polarizabilities Muon beam Exc. V meson production Trans polar. . Long. polar. Spectroscopy hyperon polarization Heavy hyperons Quark densities Tq TRENDS, Alushta 23 -29 September Quark densities q Gluon densities g
COMPASS in run NIM A 577(2007) 455 Trigger Hodoscopes ECALs & HCALs MWPCs m 0 5 SM 2 RICH Drift Chambers Filters/Walls SM 1 Straws 16 e 0 G V e. V G 0 veto 1927/09/2013 Si Sci. Fi GEMs Micromegas TRENDS, Alushta 23 -29 September
COMPASS in run NIM A 577(2007) 455 6 Li. D target run Trigger Hodoscopes ECALs & HCALs MWPCs m 0 5 SM 2 RICH Drift Chambers Filters/Walls SM 1 Straws 16 e 0 G V e. V G 0 veto 1927/09/2013 Si Sci. Fi GEMs Micromegas TRENDS, Alushta 23 -29 September
COMPASS in run NIM A 577(2007) 455 6 Li. D target run Trigger Hodoscopes ECALs & HCALs MWPCs m 0 5 SM 2 RICH Drift Chambers Filters/Walls SM 1 LH 2 target run Straws 16 e 0 G V e. V G 0 veto 1927/09/2013 Si Sci. Fi GEMs Micromegas TRENDS, Alushta 23 -29 September
Outline Part I: nucleon spin structure 27/09/2013 TRENDS, Alushta 23 -29 September
Outline Asymmetry measurement 27/09/2013 Part I: nucleon spin structure TRENDS, Alushta 23 -29 September
Outline Data taken 2002 -2004: 160 Ge. V on 6 Li. D L, T 2006 : 160 Ge. V on 6 Li. D L 2007 : 160 Ge. V on NH 3 T 2010 2011 27/09/2013 Part I: nucleon spin structure : 160 Ge. V on NH 3 T : 200 Ge. V on NH 3 L TRENDS, Alushta 23 -29 September
Outline Data taken 2002 -2004: 160 Ge. V on 6 Li. D L, T 2006 : 160 Ge. V on 6 Li. D L 2007 : 160 Ge. V on NH 3 T 2010 2011 Part I: nucleon spin structure : 160 Ge. V on NH 3 T : 200 Ge. V on NH 3 L Part II: hadron reactions 27/09/2013 TRENDS, Alushta 23 -29 September
Outline Data taken 2002 -2004: 160 Ge. V on 6 Li. D L, T 2006 : 160 Ge. V on 6 Li. D L 2007 : 160 Ge. V on NH 3 T 2010 2011 Part I: nucleon spin structure : 160 Ge. V on NH 3 T : 200 Ge. V on NH 3 L Before and After PWA Part II: hadron reactions This picture was taken from the talk of S. Paul who has been inspired by M. Pennington 27/09/2013 TRENDS, Alushta 23 -29 September
Outline Data taken 2002 -2004: 160 Ge. V on 6 Li. D L, T 2006 : 160 Ge. V on 6 Li. D L 2007 : 160 Ge. V on NH 3 T 2010 2011 Part I: nucleon spin structure : 160 Ge. V on NH 3 T : 200 Ge. V on NH 3 L 2004 190 Ge. V -, on Pb (2 weeks ) Part II: hadron reactions 2008 190 Ge. V - on LH 2 2009 190 Ge. V p, on LH 2, Pb, Ni, W 27/09/2013 TRENDS, Alushta 23 -29 September
Outline Data taken 2002 -2004: 160 Ge. V on 6 Li. D L, T 2006 : 160 Ge. V on 6 Li. D L 2007 : 160 Ge. V on NH 3 T 2010 2011 Part I: nucleon spin structure : 160 Ge. V on NH 3 T : 200 Ge. V on NH 3 L 2004 190 Ge. V -, on Pb (2 weeks ) Part II: hadron reactions 2008 190 Ge. V - on LH 2 2009 190 Ge. V p, on LH 2, Pb, Ni, W 2112, SPS/LHC shutdown, 2015, 2016, 2017 27/09/2013 Part III: COMPASS-II or our future TRENDS, Alushta 23 -29 September
Part I: nucleon spin structure 1970 1980 1990 2000 E 130 E 142/3 E 154/5 SLAC E 80 CERN EMC SMC COMPASS I DESY HERMES JLab CLAS/HALL-A RHIC Phenix/Star u A worldwide effort since decades 27/09/2013 TRENDS, Alushta 23 -29 September
Nucleon spin puzzle since 1988 ½= ½ΔΣ + ΔG + <Lz> quarks gluons orb. mom. “past” “present” Measurement of ΔG is important for two reasons: - as an element of nucleon spin puzzle possible role of axial anomaly in the a 0 interpretation (a 0 ≠ ΔΣ) a 0 (= ΔΣ) is measured to be ~0. 30 -0. 35 instead of expected 0. 6 27/09/2013 TRENDS, Alushta 23 -29 September a 0 = “future” experiments
Gluon polarisation Δg/g from m N scattering Photon Gluon Fusion (PGF) Open Charm → clean channel → but experimentally difficult ≈ 100 nb… limited statistics High-p. T Hadron Pairs N A|| = RPGF <a. LL> < g/g> + Abkg Spin asymmetry of cross sections for longitudinal polarizations of beam and target, parallel and antiparallel 27/09/2013 → easy to get a statistics → but physical background 2 cases Q 2 <1 Ge. V 2 (90% stat) & Q 2 > 1 Ge. V 2 (10% stat) TRENDS, Alushta 23 -29 September
Open charm (example) D* tag D 0 → K π ND=8650 on ly D 0→ K π π 0 no D* tag D 0 → K π ND=37750 Also were used: D 0 K 0 (no 0 rec) D 0 Ksub (no K ID) Total number: 86250 D 0 mesons 27/09/2013 TRENDS, Alushta 23 -29 September
high p. T hadron pairs 10% of statistics QCDCompton gq 27/09/2013 - considerably higher statistics … but physical background, resolved photons processes (last 4) are important only for low Q 2 LO DIS qq gg TRENDS, Alushta 23 -29 September qg
5 points from COMPASS World direct measurements on g/g in LO Phys. Lett. B 718 (2013) 922 Δg/g(x=0. 09) = 0. 125 ± 0. 06 ± 0. 63 All measurements compatible with 0 Open charm NLO (first time) PRD 87 (2013) 052018 Δg/g(x=0. 2) = -0. 13 ± 0. 15 27/09/2013 TRENDS, Alushta 23 -29 September
Another results from muon beam data Taken from the “COMPASS status report to SPSC” June 25 • g 1 p spin structure function 200 Ge. V (2011) • /K multiplicities for quark FF • Collins/ Sivers asymmetries for / K • 2 -h asym. ( / K) + 2 -h multiplicities • Six TT-spin asymmetries (TMDs) • Cross section: high p. T hadron g-prod. • (1385) and (1321) production in DIS 27/09/2013 TRENDS, Alushta 23 -29 September L T T T
g 1 p spin structure function 2011 data - First polarised DIS data at 200 Ge. V
g 1 p world data • COMPASS 200 Ge. V • COMPASS 160 Ge. V --- LSS QCD fit • Large set of data, extending to lower x and higher Q 2 region • Will be included in QCD global analyses
High p. T hadron photo production cross-section Absolute cross-section measurement m d m’ h+/- X 2004 data, 4 weeks p. QCD calculation with resummation ‘all orders’ (soft gluons, leading logs) --- Resummation --- NLO --- LO Bands= scale uncertainty De Florian, Pfeuffer; Schaeffer, Vogelsang, APS/123 -QED Data /Theory in agreement over 4 orders of magnitude
(1385) and (1321) hyperon and antihyperon production in DIS (1) Decay channel (1385), (1321) hep-ex/1304. 0952 accepted by EPJC for publication Best hyperon statistics Example (1321) signal 2320 ± 68 27/09/2013 TRENDS, Alushta 23 -29 September 1147 ± 49.
(1385) and (1321) hyperon and antihyperon production in DIS (2) First time the yields of antihyperons were measured in DIS Measured ratios Tuning of LEPTO/JETSET parameters related to the strange baryon productions was done fraction of indirectly produced (anti- ) was found to be 37(32)% 27/09/2013 TRENDS, Alushta 23 -29 September
Part II: Hadron reactions Gluon-rich environment Rapidity gap 2009 run 27/09/2013 Spin-exotic mesons Forward kinematics 2008 run TRENDS, Alushta 23 -29 September Test of Ch. PT Radiative widths 2012 run
Mesons in the Constituent Quark Model Spin-parity rules for bound system Quark spins couple to total intrinsic spin S = 0 (singlet) or 1 (triplet) Relative orbital angular Momentum and total spin couple to meson spin Parity P = (_1)L+1 Charge conjugation C = (_1)L+S Forbidden JPC = 0 -- , 0+-, 1 -+, 2+- , 3 -+ , . . . QCD allows for states beyond the CQM Hybrids , glueballs , multi-quark states “Exotic” mesons have quantum numbers forbidden for Particularly interesting: JPC-exotic states 27/09/2013 TRENDS, Alushta 23 -29 September
From old experiments: hybrids with JPC = 1−+ Light meson sector exotics JPC=1 -+: • 1(1400) • • 1(1600) • • • 1(2000) • (E 852, VES) (Crystal Barrel) The identification of exotics demands complete information on all neighbouring states and thus requires in particular: • Reconstruction of final states containing both neutral and charged particles • Observation of the same meson resonance in several different channels • Production of resonances in different reactions resonant nature controversial. . . 27/09/2013 TRENDS, Alushta 23 -29 September
Hadron reactions: processes & beam & statistics - p + - - and 0 0 - (2008/2009 data) - p 5 -final state at low four-momentum transfer (2004 data) - p and ’ (2008/2009 data) + - in central production pp pfast + −pslow (2009 data) Spectroscopy using initial/final states with strangeness Beam intensity: 5· 106 had/s Negative: 96% , 3. 5% K Positive: 75% p, 25% A large amount of data were collected with hadron beam in 2008/2009 (10 – 100 times world statistics). The hybrids, glueballs , multi-quark states are still “terra incognita” 27/09/2013 TRENDS, Alushta 23 -29 September
1(1600) 27/09/2013 TRENDS, Alushta 23 -29 September
1(1600) 27/09/2013 TRENDS, Alushta 23 -29 September
1(1600) 27/09/2013 TRENDS, Alushta 23 -29 September
Diffractive pion dissociation exotic 1(1600) state COMPASS, Phys. Rev. Lett. 104 (2010) 241803 PWA analysis of 420000 events mom transfer 0. 1 < t’< 1 (Ge. V/c)2 quasi-free nucleons in Pb a 1(1260), a 2(1320) and 2(1670) are clearly visible 27/09/2013 TRENDS, Alushta 23 -29 September
Diffractive dissociation: 3 final states 420 k events • Target: 3 mm Pb • Trigger: Multiplicity • No RPD 96 M events • Target: 40 cm LH 2 • Trigger: Recoil proton • RPD > 2. 4 M events • Cross-check: • tracking vs • ECAL Search for exotic JPC=1−+ in all 3 samples 27/09/2013 TRENDS, Alushta 23 -29 September
Difractive dissociation: - p - - + p 96 M exclusive events (2008) 27/09/2013 TRENDS, Alushta 23 -29 September
Difractive dissociation: - p - - + p Left: Dalitz plot for a 2(1320), events selected by ± 0 around a 2 mass. Right: Dalitz plot for 2(1670) with ± 0. 5 0 27/09/2013 TRENDS, Alushta 23 -29 September
2004 data Pb target vs 2008 proton target 27/09/2013 TRENDS, Alushta 23 -29 September
2008 proton target: + - vs 0 0 Peak at 1. 67 Ge. V/c 2 Phase motion indicates resonant behavior Structure at 1. 2 Ge. V/c 2 unstable w. r. t. fit model 27/09/2013 TRENDS, Alushta 23 -29 September
2008 proton target: + - vs 0 0 Peak at 1. 67 Ge. V/c 2 Phase motion indicates resonant behavior Structure at 1. 2 Ge. V/c 2 unstable w. r. t. fit model Non-resonant background to be understood (Deck effect) 27/09/2013 TRENDS, Alushta 23 -29 September
Final states with strangeness: & K beams Glueball candidates decaying into KK f 0(1380), f 0(1500): qq mixing with gg ? Hybrid candidates decaying into KK (1800): usual 31 S 0 or Hybrid? K from beam identified by CEDAR + - K K identified by RICH: 10 Ge. V/c< PK < 30 Ge. V/c – p p K K p – p, p – p Ks 0 p – p, 0 0 – – p p Ks KL p p, – – – + K p p p, – + …. 27/09/2013 TRENDS, Alushta 23 -29 September
First Measurement of Chiral Dynamics in PRL 108, 192001 (2012) 27/09/2013 TRENDS, Alushta 23 -29 September
Part III: COMPASS II phase COMPASS-II was approved by the CERN Research Board: Dec. 1, 2010. COMPASS II 2012, SPS/LHC shutdown, 2015, 2016, 2017 Polarizabilities DVSC & DVMP Study Generalised Parton distributions 27/09/2013 Primakoff Unpolarized SIDIS Fragmentation Functions, s. PDFs, TMDs TRENDS, Alushta 23 -29 September of and K Drell-Yan Universality of TMDs
Polarized Drell-Yan measurements pion valence anti-u annihilates with proton u access to 4 azimuthal modulations: Boer-Mulders, Sivers, pretzelosity and transversity PDFs gauge link changes sign for T-odd TMD’, restricted universality of T-odd TMDs J. C. Collins, PLB 536 (2002) 43 27/09/2013 TRENDS, Alushta 23 -29 September
Feasibility of the measurement (DY test 2009) di-muon mass Expected Found J/ψ 3600± 600 3170± 70 DY M>4 Ge. V 110± 22 84± 10 J/ψ region Promising results of the test 4 < M + - < 9 Ge. V For future : intensity up to 109 /spill new full size Absorber new tracking planes after the target Safe region Possible region Z vertex position Absorber 27/09/2013 TRENDS, Alushta 23 -29 September
Expected event rates & projections With a beam intensity Ibeam=6 x 107 particles/second, a luminosity of L=1. 2 x 1032 cm-2 s-1 can be obtained: → expect 800/day DY events with Assuming 2 years of data-taking (140 days/year), one can collect: ≈230000 events Expected statistical error of the Sivers asymmetry for a measurement in three (left) and five (right) bins in x. F. The smaller error bar is the statistical only, while the larger one corresponds to the quadratic sum of statistical and systematic errors. The theoretical prediction of the asymmetry from Anselmino et al. is also shown. 27/09/2013 TRENDS, Alushta 23 -29 September
Exclusive single-photon production COMPASS experiment has excellent opportunity for studying Generalized Parton Distributions (GPDs), through Deeply Virtual Compton Scattering (DVCS) using highly-polarized beam line of the CERN SPS. DVCS is considered to be theoretically cleanest of the experimentaly accessible processes to measure GPDs. The physical background - Bethe-Heitler (BH) process - is well studied. 27/09/2013 TRENDS, Alushta 23 -29 September
Kinematic domain accessible at COMPASS CERN High energy muon beam 100 - 190 Ge. V μ+ and μ- available 80% Polarisation with opposite polarization Luminosity limit with a 2. 5 m long LH 2 target L = 1032 cm-2 s-1 Q 2 → 8 Ge. V 2 → 16 Ge. V 2 if luminosity increased by factor 4 ~10 -2 < x < ~10 -1 x → 0. 20 with extension of present calorimetry 27/09/2013 TRENDS, Alushta 23 -29 September
DVCS data taking from 1 -11 to 2 -12 -2012 ECAL 1 ECAL 0 CAMERA recoil proton detector surrounding the 2. 5 m long LH 2 target � 27/09/2013 TRENDS, Alushta 23 -29 September
DVCS 2012 pilot run - projection for t-slope DVCS/dt ~ exp-B|t| B(x. B) = ½ < r 2 (x. B) > transverse size of the nucleon • 2 weeks in 2012 • 40 weeks > 2015 Projection for ~ 2 weeks : B 5 0. 7 ~ 80 DVCS events. Full experiment : 40 weeks B 5 0. 15
Conclusion COMPASS is one of major players in nucleon spin studies and in particular in the direct measurements of the gluon polarisation g/g … but the "spin crisis” is unsolved yet COMPASS has excellent potential to contribute for hybrids, glueballs , multi-quark states searches in diffractive dissociation & central production � Evidence for these QCD allowed states still not beyond doubt Future The feasibility of the Drell-Yan measurements was confirmed by the 4 beam tests performed in 2007 -2012. The feasibility of the DVCS measurements was confirmed by the 3 beam tests performed in 2008 -2012. 27/09/2013 TRENDS, Alushta 23 -29 September
ECAL 1&2 New large-angle electromagnetic calorimeter ECAL 0 (Dubna) Requirements - Photon energy range 0. 2 - 30 Ge. V - Size: 360 cm x 360 cm ; - Granularity 4 x 4 – 6 x 6 cm 2 - Energy resolution < 10. 0%/√E (Ge. V) - Thickness < 50 cm, - Insensitive to the magnetic field. DVCS+BH Prototype under studies Shaschlyk module with AMPD readout new shashlyk modules for tests in 2011 109 plates made of Sc 0. 8 mm /Pb 1. 5 mm 251 mm or 15 radiation length Avalanche Micropixel Photo Diodes 3 x 3 mm 2, density of pixels 40 000/mm 2 Total length 470 mm with electronics 27/09/2013 342 mm TRENDS, Alushta 23 -29 September
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