SemiInclusive Present DIS in COMPASS and Future Massimo

Semi-Inclusive Present DIS in COMPASS and Future Massimo Lamanna CERN and INFN Trieste 9/17/2020 Massimo Lamanna CERN-INFN Trieste 1

Plan of the talk • Physics motivations • Detector performances in 2001 – Highlights (not all detectors!) • Conclusions and outlook 9/17/2020 Massimo Lamanna CERN-INFN Trieste 2

COMPASS programme Nucleon structure • Gluon polarisation G(x) • Flavour-dependent helicity functions q(x) • Transverse-spin distribution functions Tq(x) • Spin-dependent fragmentation ( D q) 9/17/2020 Spectroscopy • Primakov reactions • Polarizability of and K • Glueballs and hybrids • Charmed mesons and baryons • Semileptonic decays • HQET • Observe double-charmed baryons Massimo Lamanna CERN-INFN Trieste 3

Semi Inclusive Deep-Inelastic Scattering 9/17/2020 Massimo Lamanna CERN-INFN Trieste 4

G measurements • Single out gg fusion graphs – Heavy quark lines (cc) – High transverse momentum • Experimentally: – DIS + D 0 (e. g. via ++K-) – DIS + D+* ( ++D 0) – DIS with high Pt hadrons 9/17/2020 Massimo Lamanna CERN-INFN Trieste 5

G measurements 9/17/2020 Massimo Lamanna CERN-INFN Trieste 6

D 0 reconstructed via Kp decay • Signal over background ~1/30 ( M 20 Me. V/c 2) • Signal over background 1/3 -1/4 (|cosq*|<0. 5 and z>0. 25 (z=ED 0/n)) 9/17/2020 Massimo Lamanna CERN-INFN Trieste 7

Other methods to assess G • More abundant channels – Hadron pairs (with opposite charge) – High Pt (Pt 1 Ge. V) – K+K- pairs • More difficult interpretation – Systematic effects (concurrent microscopic mechanisms with the same final channel) – Theoretical interpretation • Originally proposed by A. Bravar, D. von Harrach and A. Kotziniam 9/17/2020 Massimo Lamanna CERN-INFN Trieste 8

Flavour-dependent helicity functions q(x) • Flavour decomposition of quark contribution to nucleon spin S = uv + dv + 6 q • Pioneered in SMC using Ag. N h X • Particle identification: Ag. N X and Ag. N K X • Unique in COMPASS: low x (x~0. 003 at E=190 Ge. V) 9/17/2020 Massimo Lamanna CERN-INFN Trieste 9

2001 Apparatus Muon Wall Muon trigger Spectrometer Magnet 1 Calorimetry Spectrometer Magnet 2 Muon Wall Calorimetry RICH Polarised Target SPS 160 Ge. V m beam 9/17/2020 Massimo Lamanna CERN-INFN Trieste 10

COMPASS 2001 • All types of detectors on the floor • Many systems fully commissioned • Many novel detectors operated in nominal conditions (2 108 m/s) • Tracking: half of the channels • RICH fully equipped • The target is hosted in the SMC magnet 9/17/2020 Massimo Lamanna CERN-INFN Trieste 11

Target system Two-cell target solid target (2 X 60 cm) with opposite polarisation 2. 5 T solenoid field 3 He-4 He dilution refrigerator (T~50 m. K) Dynamic Nuclear Polarization 6 Li. D Dilution factor ~50% Preliminary P values P- = -43% (max – 48%) P+ =+ 48 % (max 55%) 9/17/2020 Massimo Lamanna CERN-INFN Trieste 12

Micro. Megas 40 cm • Novel tracking detector – High rate gaseous detector – High precision ( 70 mm) – High fluxes (before first dipole) – Very good efficiency Spatial resolution Efficiency 9/17/2020 Massimo Lamanna CERN-INFN Trieste 13

GEMs – High rate gaseous detector – High precision ( 70 um) – Small area tracking in SM 1 and SM 2 Efficiency Spatial resolution 9/17/2020 Massimo Lamanna CERN-INFN Trieste 14

STRAWs • Drift tubes (STRAW tubes) arranged in “double layers” to provide high resolution (150 -200 mm) after SM 1 Installation of a double layer • Very large area (~8 m 2) • Low material budget • First modules could be installed and operated (4 “double layers”). Basic principle demonstrated: 10 double layers are expected in 2002 9/17/2020 Massimo Lamanna CERN-INFN Trieste 15

RICH Ring Imaging Cherenkov • • • 90 m 3 (3 m C 4 F 10) 120 mirrors (3. 3 m focal length) Over 20 m 2 UV detectors – MWPC Cs. I photon-sensitive cathods – 8 x 8 mm 2 pads 83 k channels p/K/ separation up to 60 Ge. V Photon detector (Up) Beam halo Photon detector (Down) 9/17/2020 Massimo Lamanna CERN-INFN Trieste 16

RICH “Ring event” The cross indicates the track “image ” The blue dots are the pads The black dots are the selected cluster 9/17/2020 Massimo Lamanna CERN-INFN Trieste 17

2001 data taking Beg. Jul Beg. Oct 15 TB of data • Setting up period – New detectors put in place and commissioned – On-line system fully commissioned – First look to the data • Two week “smooth data taking” Smooth data taking (2 weeks) – Event size close to 15 TB of data nominal (30 k. B) – Event rate close to nominal (35 MB/s) 9/17/2020 Massimo Lamanna CERN-INFN Trieste 18

2001 events 9/17/2020 Massimo Lamanna CERN-INFN Trieste 19

9/17/2020 preliminary Muon vertex (primary vertex) IT, LT, MT: different trigger combinations (different angles/Q 2) Massimo Lamanna CERN-INFN Trieste 20

preliminary Vertex invariant mass 9/17/2020 Massimo Lamanna CERN-INFN Trieste 21

Conclusions and outlook • Successful 2001 pilot run – All detectors tested in realistic environment • Excellent perspectives for 2002 – This is our “initial setup” • Complete the first phase of the tracking • Measure G!!! – Room for upgrades and further evolution 9/17/2020 Massimo Lamanna CERN-INFN Trieste 22