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Drell-Yan scattering and the structure of hadrons, long term program

This long-term program focuses on the Drell-Yan scattering process to study the 3D structure of hadrons. The program covers the status of theory and experiments, as well as the potential of Drell-Yan physics as a probe for accessing the 3D structure of nucleons.

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Drell-Yan scattering and the structure of hadrons, long term program

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  1. Drell-Yan scattering and the structure of hadrons, long term program Oleg Denisov, INFN section of Turin Oleg Denisov

  2. Outline • Introduction (to the Spin crisis?) • 3D structure of hadrons • Drell-Yan scattering: • Status of the theory • Status of the experiment • Physics with DY process as a probe  access to the 3D stucture • Present and future DY experiments: • E906 (SeaQuest) • COMPASS-II (unpolarised DY physics – attached letter) • NICA • Some conclusions Oleg Denisov

  3. Introduction to the nucleon Spin Almost all visible matter of the universe we are able to observe using conventional methods consists of nucleons. Better we understand what this object is constructed from and its “properties”. SPIN is a fundamental quantum number (Pauli principle), to some extent define a rules on how the atomic/nuclear matter is constructed. So it is extremely important to know where does it (Nucleon Spin) come from Oleg Denisov

  4. Introduction to the Spin Nucleon spin ½ = ½ ΔΣ + ΔG + L quark gluonorbital mom. First two component were extensively studied in the SIDIS experiments with the longitudinally polarised target (collinear case approach): spin fraction carried by quarks and gluons is not sufficient to describe ½ nucleon spin (Spin Crisis, continued): • Quark spin contribution ΔΣ=0.24 (Q2=10 (GeV/c)2 DSSV arXiv:0804.0422) • COMPASS Open charm measurement and other direct measurements  ΔG/G is small In order to create Angular Momentum of partons spin-orbit correlation has to be taken into account  transverse momentum of the quark kT appears  3D structure of the Nucleon has to be studied Oleg Denisov

  5. 3D structure of nucleon Oleg Denisov

  6. 3D structure of nucleon (un)Polarised Drell-Yan Oleg Denisov

  7. Drell-Yan process Oleg Denisov

  8. Status of the theory: Pion-induced DY, DY Cross section calculations theoretical calculations Very big progress recently achieved: NLL threshold re-summation mechanism with non-perturbative term - good experimental data description – K-factors issue is not there anymore (M. Aicher, A. Sch¨afer and W. Vogelsang, Phys.Rev.Lett. 105 (2010) 252003) The case of COMPASS (M. Aicher, A. Sch¨afer and . Vogelsang Phys.Rev. D83 (2011) 114023) Oleg Denisov

  9. Status of the theory: Drell-Yan cross-section – general (full) angular distribution Phys. Rev. D72 (2005) 054027 2008: S. Arnold, (Ruhr U., Bochum) , A. Metz, (Temple U.) , M. Schlegel, (Jefferson Lab) Phys.Rev.D79:034005,2009, e-Print: arXiv:0809.2262 Oleg Denisov

  10. Drell-Yan studies, status of the experiment In the past (70’-80’) a series of the DY experiments has been carried out in SLAC, CERN and Fermilab (E615, NA3, NA10, NA50 etc.) Excellent results has been obtained on various unpolarised PDFs, pion structure etc. The only running unpolarised DY: E906 (SeaQuest) NO Polarised DY experiment has been done so far. Oleg Denisov

  11. Leading order (TMD) PDFs At leading order, three PDFs are needed to describe the nucleon in the collinear case. If one admit a non-zero transverse quark momentum kTin the nucleon five more PDFs (TMD PDFs) are needed. Access to angular momentum Oleg Denisov

  12. (un)Polarised Drell-Yan – access to the 3-D structure of the hadron via Azimuthal Asymmetries Oleg Denisov

  13. 3D hadron structure: Leading Order PDFs It is extremely important to access the same physics quantities via different probes (SIDIS and DY), only in case if TMDs manifest themselves similarly we can claim that we are studying hadron structure Oleg Denisov

  14. TMDs restricted universality SIDISDY Universality test includes not only the sing-reversal character of the TMDs but also the comparison of the amplitude as well as the shape of the corresponding TMDs Oleg Denisov

  15. Sivers, Boer-Mulders functions SIDIS  DY QCD QCD factorization, valid for hard processes only (Q, qT are large) σ h≅ σ p × PDF Cross-sections are gauge-invariant objects, to provide the gauge invariance of the PDFs the gauge-link was introduced (intrinsic feature of PDF). The presence of gauge-link provides the possibility of existence of non-zero T-odd TMD PDFs Direction of the gauge-link of the kT dependent PDF is process-dependent (gauge-link is resummation of all collinear soft gluons) and it changes to the opposite in SIDIS wrt DY Sivers and Boer-Mulders functions are T-odd, and to provide the time-invariance they change the sign in SIDIS wrt DY due to the opposite direction of the gauge-link J.C. Collins, Phys. Lett. B536 (2002) 43 J. Collins, talk at LIGHT CONE 2008

  16. SIDISDY – QCD test Andreas Metz (Trento-TMD’2010): Oleg Denisov

  17. E906 Drell-Yan experiment at Fermilab Oleg Denisov

  18. E906 Drell-Yan experiment at Fermilab Oleg Denisov

  19. E906 Drell-Yan experiment at Fermilab Oleg Denisov

  20. E906 Drell-Yan experiment at Fermilab Oleg Denisov

  21. E906 Drell-Yan experiment at Fermilab Oleg Denisov

  22. 3D structure on nucleon I Main goal of the COMPASS-II is a study of 3D hadron structure, FIRST EVER POLARISED DY experiment  access via DVCS  Access to TMDs Oleg Denisov

  23. COMPASS facility at CERN (SPS) Oleg Denisov

  24. COMPASS facility at CERN • Most important features: • Muon, electron or hadron secondary beams • Solid state polarised targets (NH3 or 6LiD) as well as liquid hydrogen target and nuclear targets • Powerful tracking system – 350 planes • PiD – Muon Walls, Calorimeters, RICH Oleg Denisov

  25. COMPASS-II (New Physics) a piece of history • COMPASS is very sophisticated, universal and flexible facility  Physics beyong SIDIS and hadron spectroscopy is possible: • Unique COMPASS Polarised Target and a possibility to substitute it with the long (2,5 meters) liquid hydrogen target • Both hadron and lepton beams • Flexible spectrometer structure  easy-accessible spectrometer components • All together that has generated new physics proposals with COMPASS – DVCS(GPDs) and polarised DY (TMDs) • For the first time the idea of the polarised DY experiment was reported in Sep. 2004 at CERN SPSC meeting in Villars • First version of the Letter of Intent on the polarised DY program was written in the beginning 2005 (Dubna-Torino coll., Teryaev, Denisov) • The COMPASS-II proposal was submitted to the CERN SPSC on May 17th 2010 • Approved by the CERN research board on December 1st 2010. Oleg Denisov

  26. Single-polarised π-p DY cross-section: Leading order QCD parton model At LO the general expression of the DY cross-section simplifies to: Thus the measurement of 4 asymmetries (modulations in the DY cross-section): Oleg Denisov

  27. TMDs restricted universality SIDISDY Universality test includes not only the sing-reversal character of the TMDs but also the comparison of the amplitude as well as the shape of the corresponding TMDs Oleg Denisov

  28. Where to measure: indications forthe future Drell-Yan experiments 1. TMD PDFs – ALL are sizable in the valence quark region Sivers effect in Drell-Yan processes.
M. Anselmino, M. Boglione U. D'Alesio, S. Melis, F. Murgia, A. Prokudin 
Published in Phys.Rev.D79:054010, 2009 2. – - PT should be small (~ 1 GeV), can be generated by intrinsic motion of quarks and/or by soft gluon emission. This is the region where TMD formalism applies. Oleg Denisov

  29. DY@COMPASS - set-upπ- p  μ- μ X π- Key elements: • COMPASS PT • Tracking system (both LAS abs SAS) and beam telescope in front of PT • Muon trigger (in LAS is of particular importance - 60% of the DY acceptance) • HCal1 based trigger (veto) in LAS (to reduce DY di-muon trigger rate if needed) • RICH1, Calorimetry – also important to reduce the background (the hadron flux downstream of the hadron absorber ~ 10 higher then muon flux) 190 GeV Oleg Denisov

  30. DY@COMPASS – kinematics - valence quark rangeπ- p  μ- μ X (190 GeV pion beam) Sivers effect in Drell-Yan processes.
M. Anselmino, M. Boglione U. D'Alesio, S. Melis, F. Murgia, A. Prokudin 
Published in Phys.Rev.D79:054010, 2009 • In our case (π- p  μ- μ X) contribution from valence quarks is dominant • In COMPASS kinematics u-ubar dominance • <PT> ~ 1GeV – TMDs induced effects expected to be dominant with respect to the higher QCD corrections COMPASS acceptance Typical acceptance of the DY experiments performed so far was 4-6% (NA10, NA50, E615) Oleg Denisov

  31. DY@COMPASS - feasibility - Signal Oleg Denisov

  32. DY@COMPASS projections II (NH3)140 days of running with 108 pions per second In the first two years we plan to collect ~500.000 DY events what would be factor of ~10 larger statistics compare to any other DY experiment performed so far Oleg Denisov

  33. DY@COMPASS projections II (6LiD, LH)140 days of running with 108 pions per second In order to achieve complete flavour separation and to further reduce the influence of nuclear effects 6LiD and liquid H2 targets has to be used LH2 6LiD Oleg Denisov

  34. SIDISDY – QCD test VERY IMPORTANT – Kinematics compatibility SIDIS DY Oleg Denisov

  35. Final data analysis SSA extraction in DY kinematic range Oleg Denisov

  36. COMPASS Running until LS2 (2019) and beyond (2020 ) • Currently the strategy (proposal by the COMPASS management) look like follows: • End of 2012 – mid of 2014 => preparation of the Drell-Yan set-up, PT movement in the DY position, Hadron Absorber installation and PT test with the refurbished Solenoid in plane with new DY infrastructure, new MSS and MCS • Mid October – beginning of December 2014 => Pilot polarised Drell-Yan experiment • In 2015 full year for DY data taking (NH3) • 2016-2017 – DVCS • 2018 – Drell-Yan •  2020 polarised Drell-Yan with 6LiD target and unpolarised DY on LH2 and other nuclear targets Oleg Denisov

  37. NICA collider at JINR (Dubna) Oleg Denisov

  38. NICA collider at JINR (Dubna) Oleg Denisov

  39. SPD at NICA collider (JINR, Dubna) Oleg Denisov

  40. SPD at NICA collider (JINR, Dubna)projections Oleg Denisov

  41. Other Collider experiments • L ≈ 1031 cm-2s-1 (polarized pp) • s = 200 GeV • pp collision • x1x2 = 4×10-4 ÷ 1×10-2 • >2016 • L = 1031 cm-2 s-1 • S = 30 GeV2 • ppbar collisions, e+e- final state • x1x2 = 0.2 ÷ 0.4 • YEAR 202?

  42. Drell-Yan Experiments 10 years Running plan • Fermilab E-906: data taking will resume in September 2013 and will last for at least 1 year (experiment is approved for 2 years running period) • Polarised DY at Fermilab – hopefully in a few years from now • COMPASS polarized Drell-Yan measurement will be started in the mid of October 2014, with a Pilot Run. Physics data taking will take place over the whole 2015. Second DY run most probable in 2018. • COMPASS 6LiD and LH2 DY data-taking is planned in the period 2020-2025. • RHIC > 2016 • SPD at NICA > 2020 Oleg Denisov

  43. Summary • Main goal is to study 3D nucleon spin structure, in particular hunting for the missing part of the proton spin • Tooling: polarised Drell-Yan processes • Polarised Drell-Yan experiment at COMPASS – first ever polarised DY. It starts a series of polarised DY measurements over the whole world • Fermilab, CERN, RHIC and NICA Drell-Yan experiments are rather collaborators then competitors, almost 100% complementary to each other • A lots of new and highly awaited data just behind the corner, scientific primacy belong to COMPASS  there are all reasons to extend the DY program beyond the already approved proposal Oleg Denisov

  44. Spares

  45. TMDs at Drell-Yan: road map • 2010 – COMPASS polarised SIDIS data (Sivers, transversity via global data fit) • 2010 – 2013? E906 (SeaQuest) – pp Drell-Yan – Boer-Mulders of the proton • 2013 - 2016 COMPASS polarised Drell-Yan pi-p data – TMDs universality and T-odd TMDs sign change SIDISDY (for Boer-Mulders funtion study the input from E906 as well as new transversity fit from the global data analysis is very welcome) • 2015  …… RHIC, NICA pp (un)polarised DY data – very welcome – complimentary to COMPASS • 2017  more COMPASS data, antiprotons?..... • MANY NEW data - just behind the corner Oleg Denisov

  46. Coordinate systems TF Collins-Soper

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