Future Drell-Yan program of the COMPASS cllaboration Norihiro DOSHITA (Yamagata University) On behalf of the COMPASS collaboration 2016/7/31N. Doshita KEK theory center workshop on High-energy hadron physics with hadron beams January 6 - 8, 2010Seminar Hall, Building No.3, KEK, Tsukuba, Japan

Outline Access TMDs from (polarized) Drell-Yan process Experimental setup - Spectrometer - Polarized target - Statistics estimations Beam test in 2007 – 2009 Summary 2016/7/32N. Doshita

3 In the COMPASS experiment Longitudinal polarized target - gluon spin distribution:  G - quark helicity distribution :  q(x) Transversal polarized target - quark transversity distribution :  T q(x) - Sivers function : f 1T muon program (2002 ~ 2007)  Quark orbital angular momentum Since SMC experiment Polarized Drell-Yan program (2012 ~ ) with pion beam and transversally polarized target Drell-Yan process ** l+l+ l-l- -- p nucleonquarkDeeply Inelastic Scattering with polarized muon and polarized nucleon target 2016/7/3N. Doshita

4 - Boer-Mulders function Unpolarized Drell-Yan Motivation The cos2  angular dependent weighted cross section of (    p) at valence region ( x  > 0.1) : Boer-Mulders functions of the valence and sea quarks inside the pion respectively : Boer-Mulders functions of the quark flavor inside the proton The ratio of the weighted cross sections of (    p) and (    p) Phys.Lett. B639 (2006) /7/3N. Doshita Flavor separation: (    p) and (    D)

5 - Transversity and Sivers function SIDIS Polarized Drell-Yan Uncertainty of Fragmentation Function (single spin DY asymmetries) many components of transverse target spin dependent azimuthal modulations Motivation prediction Unpol. PDF FF free (polarized beam with transversal polarized target) 2016/7/3N. Doshita

2016/7/3N. Doshita6 Double polarized Drell-Yan: direct access to Transversity M.Nekipelov -> PAX Feasibility study is underway, polarized antiprotons(>20%) - not a trivial issue With polarized antiproton beam and polarized proton target

2016/7/3N. Doshita7 J/  – Drell-Yan duality J/  – DY duality  close analogy between Drell-Yan and J/  production mechanism: –Occurs when the gluon-gluon fusion mechanism of the J/  production is dominated by the quark-quark fusion mechanism –We can expect that the duality is valid in the COMPASS kinematic range Key issue for the applicability of the J/  signal for the study of hadron spin structure J/  production mechanism by itself is an important issue   J/  substitution

The COMPASS spectrometer Polarized target and hadron absorber 1. Large angular acceptance spectrometer 2. Various secondary beams with the intensity up to 6x10 7 particles/s 3. A detection system designed to stand relatively high particle fluxes 4. The dedicated muon trigger system 5. Hadron absorber is needed     2016/7/38N. Doshita

9 COMPASS polarized solid target system 180mrad Many secondly particels – nuclear interaction 2 mW heat input expected with 6 x 10 7 pions/s 5 mW cooling power at 70mK Transverse polarization Target area: 130 cm long with < ±30 ppm 10 cm gap 3 cells (27.5, 55, 27.5cm long) 20 cm gap 2 cells (50, 50 cm long) beam Cooling power Frozen spin target at 0.6 T dipole magnet (after polarizing at 2.5 T solenoid) Target cell mmol/sec mK Cooling power Large acceptance COMPASS Magnet 2016/7/3N. Doshita

Proton target materials f : dilution factor  : density F f : packing factor H-butanolNH 3 7 LiH PTPT (H) * 0.38 ( 7 Li)  f (H) ( 7 Li) FfFf PT FoM Figure of Merit -Normalized by H-butanol -Magnetic field 2.5T - Relaxation time NH3 4000h at 60 mK and 0.6T - If 7 LiH reach 90%, PT FoM is 2.1. * J. Ball, NIM. A 526 (2004) /7/310N. Doshita

Deuteron target materials f : dilution factor  : density F f : packing factor ND 3 D- butanol 6 LiD PTPT 0.30 – **0.55 (H) 0.54 ( 6 Li)  f (H) ( 7 Li) FfFf PT FoM 1 – Figure of Merit -Normalized by ND 3. -Magnetic field 2.5T - Relaxation time 6 LiD 2000h at 0.42T and 60 mK. ** S.T. Goertz et al, NIM. A 526 (2004) /7/311N. Doshita

2 backgrounds sources Physics background D, D and J/  decays to  +  - X Combinatorial background  and K decaying to  Better region to study Drell- Yan is 4 < M GeV/c 2. Dimuon mass spectrum (NA50) Signal and background Drell-Yan J/  ’ Open charm Empty target Comb. bkg 2016/7/312N. Doshita

Some indications for statistics –High luminosity (DY Cross Section is a fractions of nanobarns) and large angular acceptance, better pion or antiproton beams (valence anti-quark) –Sufficiently high energy to access ‘safe’ of background free M ll range ( 4 GeV/c < M ll < 9 GeV/c) –Good acceptance in the valence quark range x B > 0.1 and kinematic range: τ = x A x B = M 2 /s > 0.1 –Good figure of merit (PT FoM ), which can be represented as a product of the luminosity and beam (target) polarization (dilution factor) (PT FoM ~ L × P beam (f)) /7/3N. Doshita

COMPASS acceptance is in the valence quarks regions (x > 0.1). This is also the best region to measure the spin asymmeties, as expected from theory predictions. Cross section and acceptance 2016/7/314N. Doshita

Expected statistical error for Sivers asymmetry With a beam intensity of 6 x 10 7 particles/s, a luminosity of 1.7 x /cm 2 s can be obtained. Assuming 2 years of data-taking, more than 200k DY events in the region 4 < M < 9 GeV/c 2. Predictions of Sivers asymmetry in the COMPASS phase space. Solid and dashed: Etremov et. Al, PLB612(2005)233. Dot-dashed; Collins et al, PRD73(2006) Solid, dot-dased; Ansemino et al, PRD79(2009) Bixes; Blanconi et al, PRD73(2006) Short-dashed; Bacchetta et al; PRD78(2008) X F 2016/7/315N. Doshita

Beam test in /7/3N. Doshita Feasibility test at COMPASS

2016/7/3N. Doshita17 Drell – Yan Beam test 2009 Data taking: Nov Beam : 190 GeV negative pion Target : 40+40cm CH2 target with 5cm diameter (100% interaction length) Nominal intensity: 7-9 x 10^7 / spill Total data : 4800 good spills High intensity beam test was also done. (1.5 x 10^8 / spill) Radiation level : low ( < 0.5 uSv/h )

DY Beam Test 2009 (with hadron absorber I) 03/07/ target

2016/7/3N. Doshita19 DY Beam Test 2009 (with hadron absorber III) target Top view

2016/7/3N. Doshita20 Some results of 2009 DY beam test I: radio-protection issues and tracking detectors occupancies RP - the detected radiation level is factor 6 lower than allowed one (3 uSv), in a good agreement with simulations done by COMPASS and CERN RP (pion beam intensity ~8x10^7 pions per spill (10 seconds)) The tracking detectors occupancy downstream of hadron absorber is factor 10 lower compare to the normal muon running conditions 20

2016/7/3N. Doshita21 Some results of 2009 DY beam test II: J/Psi – monitoring signal for DY Very clean J/Psi signal observed Combinatorial background for such a beam intensity seem absent in high dimuon mass range The J/Psi production/registration/reconstruction rate is high even with not optimised hadron absorber (number of radiation/interaction length ratio) and very raw reconstruction procedure (no hadron absorber in the standard COMPASS reconstruction program). VERY PRELIMINARY

summary COMPASS will be able to perform several combinations of beams (  -,  +, p(?)) and targets (p, D ) for Drell-Yan measurement. We will perform the first measurement with  - beam and transversal polarized p target. The expected accuracy after 2 years data taking is enough to provide unique information of hadron structure and of transverse momentum PDFs. 2016/7/322N. Doshita