1. 偏極 Drell-Yan 実験による 核子構造の多次元的理解に向け て 「核子構造研究の新展開 2011 」 @KEK 2011 年 1 月 8 日 ( 土 ) 後藤雄二（理研）

2. January 8, 20112 Outline of this talk Introduction – Transverse structure of the proton – Drell-Yan measurement Polarized Drell-Yan experiments – COMPASS – GSI – Fermilab – RHIC – J-PARC Summary 2

3. January 8, 20113 Introduction Transverse-spin asymmetry measurement – Theoretical development to understand the transverse structure of the nucleon Sivers effect, Collins effect, higher-twist effect, … Relation to orbital angular momentum inside the nucleon FNAL-E704  s = 20 GeVRHIC-STAR  s = 200 GeV 3

4. January 8, 20114 Introduction Transverse-spin asymmetry – Sivers effect (Sivers function) Transverse-momentum dependent (TMD) distribution function – Collins effect (transversity & Collins fragmentation function) – higher-twist effect – … Drell-Yan process – to distinguish Sivers effect – to separate initial-state and final-state interaction with remnant partons Comparison with semi-inclusive DIS results

5. January 8, 20115 Introduction Transverse structure of the proton – Transversity distribution function – Correlation between nucleon transverse spin and parton transverse spin – TMD distribution functions Sivers function – Correlation between nucleon transverse spin and parton transverse momentum (k T ) Boer-Mulders function – Correlation between parton transverse spin and parton transverse momentum (k T ) Leading-twist transverse momentum dependent (TMD) distribution functions 5

6. January 8, 20116 Sivers function Single-spin asymmetry (SSA) measurement – < 1% level multi-points measurements have been done for SSA of DIS process Valence quark region: x = 0.005 – 0.3 (more sensitive in lower-x region) M. Anselmino, et al. EPJA 39, 89 (2009) Sivers function u-quark d-quark 6

7. January 8, 20117 Polarized Drell-Yan Many new inputs for remaining proton-spin puzzle – flavor asymmetry of the sea-quark polarization – transversity distribution – transverse-momentum dependent (TMD) distributions Sivers function, Boer-Mulders function, etc. “Non-universality” of Sivers function – Sign of Sivers function determined by SSA measurement of DIS and Drell-Yan processes should be opposite each other final-state interaction with remnant partons in DIS process Initial-state interaction with remnant partons in Drell-Yan process – Fundamental QCD prediction – One of the next milestones for the field of hadron physics

8. January 8, 20118 Goal of the experiment Comparison with DIS data – DIS data < 1% level multi-points measurements have already been done for SSA of DIS process 0.005 < x < 0.3 – Comparable level measurement needs to be done for SSA of Drell-Yan process for comparison Measure not only the sign of the Sivers function but also the shape of the function x region – Valence quark region: x ~ 0.2 Expect to show the largest asymmetry – … and explore larger x region M. Anselmino, et al. EPJA 39, 89 (2009) Sivers function u-quark d-quark 8

9. January 8, 20119 Boer-Mulders function Single transverse-spin asymmetry – Transversity  Boer-Mulders function measurement – Distinguished from Sibers function measurement by different angular distribution Unpolarized measurement – Angular distribution – Violation of the Lam-Tung relation L.Y. Zhu,J.C. Peng, P. Reimer et al. hep-ex/0609005 With Boer-Mulders function h 1 ┴ : ν(π - W  µ + µ - X)~valence h 1 ┴ (π)*valence h 1 ┴ (p) ν(pd  µ+µ-X)~valence h 1 ┴ (p)*sea h 1 ┴ (p) 9

10. January 8, 201110 Double-spin asymmetries Double transverse-spin asymmetry – transversity – quark  antiquark for p+p collisions Double helicity asymmetry – flavor asymmetry of sea- quark polarization SIDIS data from HERMES and COMPASS preliminary data available W data from RHIC will be available in the near future Polarized Drell-Yan data will be able to cover higher-x region 10

11. January 8, 201111 Future polarized Drell-Yan experiments experimentparticlesenergyx1 or x2luminosity COMPASS   + p  160 GeV  s = 17.4 GeV x2 = 0.2 – 0.32 × 10 33 cm -2 s -1 COMPASS (low mass)   + p  160 GeV  s = 17.4 GeV x2 ~ 0.052 × 10 33 cm -2 s -1 PAX p  + pbar collider  s = 14 GeV x1 = 0.1 – 0.92 × 10 30 cm -2 s -1 PANDA (low mass) pbar + p  15 GeV  s = 5.5 GeV x2 = 0.2 – 0.42 × 10 32 cm -2 s -1 J-PARC p  + p 50 GeV  s = 10 GeV x1 = 0.5 – 0.910 35 cm -2 s -1 NICA p  + p collider  s = 20 GeV x1 = 0.1 – 0.810 30 cm -2 s -1 RHIC PHENIX Muon p  + p collider  s = 500 GeV x1 = 0.05 – 0.12 × 10 32 cm -2 s -1 RHIC Internal Target phase-1 p  + p 250 GeV  s = 22 GeV x1 = 0.2 – 0.52 × 10 33 cm -2 s -1 RHIC Internal Target phase-2 p  + p 250 GeV  s = 22 GeV x1 = 0.2 – 0.53 × 10 34 cm -2 s -1 11

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23. January 8, 201123 Drell-Yan experiment Fermilab E966/SeaQuest – Dimuon spectrometer – Main injector beam E beam = 120 GeV – Higher-x region: x = 0.1 – 0.45 – Beam time: 2010 – 2013 Focusing magnet Hadron absorber Beam dump Momentum analysis 23

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30. January 8, 201130 Polarized Drell-Yan experiments at RHIC “Transverse-Spin Drell-Yan Physics at RHIC” – http://spin.riken.bnl.gov/rsc/write-up/dy_final.pdf – Les Bland, et al., May 1, 2007 –  s = 200 GeV – PHENIX muon arm – STAR FMS (Forward Muon Spectrometer) Discussions at PHENIX and STAR underway in their decadal plan discussion with their upgrade plan Two new Letter-of-Intent submitted to BNL PAC – Collider experiment dedicated to the polarized Drell-Yan experiment “Feasibility Test of Large Rapidity Drell-Yan Production at RHIC” – Fixed-target experiment “Measurement of Dimuons from Drell-Yan Process with Polarized Proton Beams and an Internal Target at RHIC” 30

31. January 8, 201131 Collider experiment LoI http://www.bnl.gov/npp/docs/pac0610/Crawford_LoI.100524.v1.pdf 31

32. January 8, 201132 Collider experiment LoI 32

33. January 8, 201133 Fixed-target experiment LoI Measurement of Dimuons from Drell-Yan Process with Polarized Proton Beams and an Internal Target at RHIC – http://www.bnl.gov/npp/docs/pac0610/Goto_rhic-drell-yan.pdf – Academia Sinica (Taiwan): W.C. Chang – ANL (USA): D.F. Geesaman, P.E. Reimer, J. Rubin – UC Riverside (USA): K.N. Barish – UIUC (USA): M. Groose Perdekamp, J.-C. Peng – KEK (Japan): N. Saito, S. Sawada – LANL (USA): M.L. Brooks, X. Jiang, G.L. Kunde, M.J. Leitch, M.X. Liu, P.L. McGaughey – RIKEN/RBRC (Japan/USA): Y. Fukao, Y. Goto, I. Nakagawa, K. Okada, R. Seidl, A. Taketani – Seoul National Univ. (Korea): K. Tanida – Stony Brook Univ. (USA): A. Deshpande – Tokyo Tech. (Japan): K. Nakano, T.-A. Shibata – Yamagata Univ. (Japan): N. Doshita, T. Iwata, K. Kondo, Y. Miyachi 33

34. January 8, 201134 Internal target position IP2 (overplotted on BRAHMS) F MAG3.9 m Mom.kick 2.1 GeV/c KMAG 2.4 m Mom.kick 0.55 GeV/c St.4 MuID 14 m 18 m St.1 St.2St.3 34

35. January 8, 201135 Experimental sensitivities PYTHIA simulation –  s = 22 GeV (E lab = 250 GeV) – luminosity assumption 10,000 pb -1 Phase-1 (parasitic operation) 10,000 pb -1 Phase-2 (dedicated operation) 30,000 pb -1 – 4.5 GeV < M  < 8 GeV – acceptance for Drell-Yan dimuon signal is studied all generated dumuon from Drell-Yan accepted by all detectors 35

36. January 8, 201136 Experimental sensitivities About 50K events for 10,000pb -1 luminosity x-coverage: 0.2 < x < 0.5 Mass (GeV/c 2 )Total Rapidity45 – 5050 – 6060 – 8045 – 80 -0.4 – 03.1 K 1.4 K7.6 K 0 – 0.46.2 K6.1 K3.0 K15.3 K 0.4 – 0.87.6 K6.4 K2.3 K16.3 K 0.8 – 1.24.4 K2.5 K0.4 K7.3 K x 1 : x of beam proton (polarized) x 2 : x of target proton 36

37. January 8, 201137 Experimental sensitivities Phase-1 (parasitic operation) – L = 2×10 33 cm -2 s -1 – 10,000 pb -1 with 5×10 6 s ~ 8 weeks, or 3 years (10 weeks×3) of beam time by considering efficiency and live time Phase-2 (dedicated operation) – L = 3×10 34 cm -2 s -1 – 30,000 pb -1 with 10 6 s ~ 2 weeks, or 8 weeks of beam time by considering efficiency and live time 10,000 pb -1 (phase-1) 40,000 pb -1 (phase-1 + phase-2) Theory calculation: U. D’Alesio and S. Melis, private communication; M. Anselmino, et al., Phys. Rev. D79, 054010 (2009) Measure not only the sign of the Sivers function but also the shape of the funcion 37

38. January 8, 201138 J-PARC Drell-Yan proposals P04: measurement of high-mass dimuon production at the 50-GeV proton synchrotron – spokespersons: Jen-Chieh Peng (UIUC) and Shinya Sawadas (KEK) – collaboration: Abilene Christian Univ., ANL, Duke Univ., KEK, UIUC, LANL, Pusan National Univ., RIKEN, Seoul National Univ., TokyoTech, Tokyo Univ. of Science, Yamagata Univ. – including polarized physics program, but not discussed – “deferred” P24: polarized proton acceleration at J-PARC – contact persons: Yuji Goto (RIKEN) and Hikaru Sato (KEK) – collaboration: ANL, BNL, UIUC, KEK, Kyoto Univ., LANL, RCNP, RIKEN, RBRC, Rikkyo Univ., TokyoTech, Tokyo Univ. of Science, Yamagata Univ. – polarized Drell-Yan included as a physics case – “no decision” Next proposal for the polarized physics program – not yet submitted

39. January 8, 201139 Dimuon experiment at J-PARC (P04) – based on the Fermilab spectrometer for 800 GeV – length to be reduced but the aperture to be increased – two bending magnets with p T kick of 2.5 GeV/c and 0.5 GeV/c – tracking by three stations of MWPC and drift chambers – muon id and tracking tapered copper beam dump and Cu/C absorbers placed within the first magnet

40. January 8, 201140 Polarized Drell-Yan experiment at J-PARC Single transverse-spin asymmetry – Sivers effect measurement Experimental condition – higher beam intensity is possible for unpolarized liquid H 2 target, or nuclear target 5  10 12 ppp = 2.5  10 12  2sec in 1pulse (5sec) possible? – PYTHIA simulation 75% polarization beam 120 days, beam on target 5  10 17 (with 50% duty factor) ~5% liquid H 2 target – 10000 fb -1 luminosity ~20% nuclear target – 40000 fb -1 luminosity mass 4 – 5 GeV/c 2 40 red liquid H2 target blue nuclear target analyzing magnet 127cm51cm polarized beam 4 < M  +  - < 5 GeV integrated over q T

41. January 8, 201141 pQCD studies of Drell-Yan cross section pQCD correction can be controlled at J-PARC energy NNLO calculation Hamberg, van Neerven, Matsuura, Harlander, Kilgore NLL, NNLL calculation Yokoya, et al...

42. January 8, 201142 Polarized proton acceleration (P24) Polarized beam feasible in discussions with J-PARC and BNL accelerator physicists How to keep the polarization given by the polarized proton source – depolarizing resonance imperfection resonance – magnet errors and misalignments intrinsic resonance – vertical focusing field – weaken the resonance fast tune jump harmonic orbit correction – intensify the resonance and flip the spin rf dipole snake magnet How to monitor the polarization – polarimeters

43. January 8, 201143 Polarized proton acceleration at AGS/RHIC Proposed scheme for the polarized proton acceleration at J- PARC is based on the successful experience of accelerating polarized protons to 25 GeV at BNL AGS BRAHMS & PP2PP STAR PHENIX AGS LINAC BOOSTER Pol. H - Source Spin Rotators 200 MeV Polarimeter AGS Internal Polarimeter rf Dipole RHIC pC Polarimeters Absolute Polarimeter (H  jet) AGS pC Polarimeters Cold Partial Helical Siberian Snake Warm Partial Helical Siberian Snake PHOBOS Spin Rotators Full Helical Siberian Snakes Partial Solenoidal Snake

44. January 8, 201144 Polarized proton acceleration at J-PARC BRAHMS & PP2PP STAR PHENIX AGS LINAC BOOSTER Pol. H - Source 200 MeV Polarimeter AGS Internal Polarimeter rf Dipole RHIC pC Polarimeters Absolute Polarimeter (H  jet) AGS pC Polarimeters Cold Partial Helical Siberian Snake Warm Partial Helical Siberian Snake PHOBOS Pol. H - Source 180/400 MeV Polarimeter rf Dipole 30% Partial Helical Siberian Snakes pC CNI Polarimeter Extracted Beam Polarimeter

45. January 8, 201145 Accelerating polarized protons in the MR AGS 25% superconducting helical snake helical dipole coil correction solenoid and dipoles measured twist angle 2 deg/cm in the middle ~4 deg/cm at ends

46. January 8, 201146 Accelerating polarized protons in the MR Possible location of partial helical snake magnets in the MR First 30% snakeSecond 30% snake

47. January 8, 201147 Summary Polarized Drell-Yan measurement – The simplest process in hadron-hadron reaction – But, not yet done because of technical difficulties so far Sivers function measurement in the valence-quark region from the SSA of Drell-Yan process – Test of the QCD prediction “Sivers function in the Drell-Yan process has an opposite sign to that in the DIS process” – Milestone for the field of hadron physics Several proposed (some approved and not-yet-proposed) experiments – COMPASS/GSI/Fermilab/RHIC/J-PARC/… – In this decade Measurement not only the sign of the Sivers function, but also the shape of the function feasible 47

48. Backup slides

49. January 8, 201149 RHIC/PHENIX in the future PHENIX upgrades – Muon trigger – Silicon VTX – More upgrades discussed in the decadal plan RHIC upgrades – Electron lens & 56 MHz storage RF EIC (Electron Ion Collider) – 2020 ? Spin physics – 2009-2014(?) W measurement – Helicity structure of the proton Quark-spin contribution Gluon-spin contribution – Transverse structure of the proton Orbital angular momentum – Drell-Yan measurement 49 from PHENIX decadal plan

50. January 8, 201150 Introduction Origin of the proton spin 1/2 - “proton-spin puzzle” – Polarized DIS experiments – Polarized hadron collision experiments Longitudinal-spin asymmetry measurement – Helicity structure of the proton Quark-spin contribution Gluon-spin contribution – Large restriction for the gluon-spin contribution or gluon helicity distribution Midrapidity  0 at PHENIX Midrapidity jet at STAR 50

51. January 8, 201151 RHIC 51

52. January 8, 201152 Polarized proton acceleration at AGS/RHIC Successfully operational as a polarized proton collider BRAHMS & PP2PP STAR PHENIX AGS LINAC BOOSTER Pol. H - Source Spin Rotators 200 MeV Polarimeter AGS Internal Polarimeter rf Dipole RHIC pC Polarimeters Absolute Polarimeter (H  jet) AGS pC Polarimeters Cold Partial Helical Siberian Snake Warm Partial Helical Siberian Snake PHOBOS Spin Rotators Full Helical Siberian Snakes Partial Solenoidal Snake 52

53. January 8, 201153 Polarized Drell-Yan experiment Single transverse-spin asymmetry – Sivers function measurement – Transversity  Boer-Mulders function Double transverse-spin asymmetry – Transversity (quark  antiquark for p+p collisions) Double helicity asymmtry – Flavor asymmetry of quark polarization Other physics – Parity violation asymmetry? 53

54. January 8, 201154 Single transverse-spin asymmetry Sivers effect – Correlation between nucleon transverse spin and parton transverse momentum (Sivers distribution function) – Related to the orbital angular momentum in the proton (and the shape of the proton) Multi-dimensional structure of the proton – Initial-state or final-state interaction with remnant partons Anselmino, et al., PRD79, 054010 (2009) J-PARC 50-GeV polarized beam  s ~ 10 GeV RHIC collider  s = 200 GeV 54

55. January 8, 201155 DISDrell-Yan “toy” QED QCD attractiverepulsive Sivers function measurement Sign of Sivers function determined by single transverse-spin (SSA) measurement of DIS and Drell-Yan processes – Should be opposite each other Initial-state interaction or final-state interaction with remnant partons – Test of TMD factorization – Explanation by Vogelsang and Yuan… From “Transverse-Spin Drell-Yan Physics at RHIC,” Les Bland, et al., May 1, 2007 55

56. January 8, 201156 Sivers function measurement < 1% level multi-points measurements have already been done for SSA of DIS process – x = 0.005 – 0.3 (more sensitive in lower-x region) comparable level measurement needs to be done for SSA of Drell-Yan process for comparison 56

57. January 8, 201157 Drell-Yan experiment The simplest process in hadron- hadron reactions – No QCD final state effect Fermilab E866/NuSea – Unpolarized Drell-Yan experiment with E beam = 800 GeV – Flavor asymmetry of sea-quark distribution x = 0.02 – 0.35 (valence region) Fermilab E906/SeaQuest – Similar experiment with main-injector beam E beam = 120 GeV x = 0.1 – 0.45 DISDrell-Yan 57

58. January 8, 201158 Drell-Yan experiment Fermilab E906/SeaQuest – Dimuon spectrometer – Main injector beam E beam = 120 GeV – Higher-x region: x = 0.1 – 0.45 – Beam time: 2010 – 2013 Focusing magnet Hadron absorber Beam dump Momentum analysis 58

59. January 8, 201159 Drell-Yan experiment Flavor asymmetry of sea-quark distribution – Possible origins meson-cloud model – virtual meson-baryon state chiral quark model instanton model chiral quark soliton model –  + in the proton as an origin of anti-d quark excess pseudo-scaler meson should have orbital angular momentum in the proton… Polarized Drell-Yan experiment – Not yet done! – Many new inputs for remaining proton-spin puzzle flavor asymmetry of the sea-quark polarization transversity distribution transverse-momentum dependent (TMD) distributions – Sivers function, Boer-Mulders function, etc. 59

60. January 8, 201160 Single transverse-spin asymmetry Sivers function – Correlation between nucleon transverse spin and parton transverse momentum (Sivers distribution function) – Related to the orbital angular momentum in the proton (and the shape of the proton) “Non-universality” of Sivers function – Sign of Sivers function determined by SSA measurement of DIS and Drell-Yan processes should be opposite each other final-state interaction with remnant partons in DIS process Initial-state interaction with remnant partons in Drell-Yan process – Fundamental QCD prediction – One of the next milestones for the field of hadron physics 60

61. January 8, 201161 Polarized and unpolarized Drell-Yan experiment A TT measurement – h 1 (x): transversity quark  antiquark in p+p collisions Unpolarized measurement – angular distribution of unpolarized Drell-Yan – Boer-Mulders function violation of the Lam-Tung relation L.Y. Zhu,J.C. Peng, P. Reimer et al. hep-ex/0609005 With Boer-Mulders function h 1 ┴ : ν(π - W  µ + µ - X)~valence h 1 ┴ (π)*valence h 1 ┴ (p) ν(pd  µ+µ-X)~valence h 1 ┴ (p)*sea h 1 ┴ (p) 61

62. January 8, 201162 Collider experiment “Transverse-Spin Drell-Yan Physics at RHIC” – Les Bland, et al., May 1, 2007 –  s = 200 GeV – PHENIX muon arm – STAR FMS (Forward Muon Spectrometer) – Large background from b- quark –  s = 500 GeV may be better… Higher luminosity and larger cross section 62

63. January 8, 201163 Beam time request Phase-1: parasitic beam time – Option-1 – Beam intensity 2×10 11 ×10MHz = 2×10 18 /s – Cluster-jet or pellet target 10 15 atoms/cm 2 50 times thinner than RHIC CNI carbon target – Luminosity 2×10 33 /cm 2 /s – 10,000pb -1 with 5×10 6 s 8 weeks, or 3 years (10 weeks×3) with efficiency and live time – Hadronic reaction rate 2×10 33 ×50mb = 10 8 /sec = 100MHz 10% beams are used by hadronic reactions in ~6 hours – Beam lifetime 2×10 11 ×100bunch / 10 8 = 2×10 5 s from hadronic reactions 5×10 4 s = ~15 hours from small-angle scatterings (by D. Trbojevic) from energy loss? ~6 hours 10% beam used for reaction collider & internal-target parasitic run 63

64. January 8, 201164 Beam time request Phase-1: parasitic beam time – Option-2 (beam dump mode) – Beam time at the end of every fill after stopping collider experiments and dumping one beam – Beam intensity assuming 10 11 ×10MHz = 10 18 /s – Target with ~10 17 atoms/cm 2 thickness (if available) Comparable thickness with RHIC CNI carbon target – Luminosity 10 35 /cm 2 /s – Hadronic reaction rate 10 35 ×50mb = 5×10 9 /s = 5GHz 20% beams are assumed to be used = 40 pb -1 In ~ 1,000s depending on how fast the beam dumps? – We request 250 fills to accumulate 10,000 pb -1 8 weeks, or 3 years (10 weeks×3) with efficiency and live time? 20% beam used for reaction collider run internal- target run 64

65. January 8, 201165 Beam time request Phase-2: dedicated beam time – Beam intensity 2×10 11 ×15MHz = 3×10 18 /s, 1.5 times more number of bunches as assumed at eRHIC – Pellet or solid target 10 16 /cm 2 5 times thinner than RHIC CNI carbon target – Luminosity 3×10 34 /cm 2 /s – 30,000pb -1 with 10 6 s 2 weeks, or 8 weeks with efficiency and live time – Hadronic reaction rate 3×10 34 ×50mb = 1.5×10 9 /s = 1.5GHz 10% beams are used by hadronic reactions in ~30 minutes – Beam lifetime 2×10 11 ×150bunch / 1.5×10 9 = 2×10 4 s from hadronic reactions 5×10 3 s = ~1.5 hours from small-angle scatterings (by D. Trbojevic) from energy loss ? – Even higher luminosity possible, if target with ~10 17 atoms/cm 2 thickness available (beam dump mode) e.g. 20% beams are used in a shorter period internal- target run 10% beam used for reaction ~30 mins 65

66. January 8, 201166 PYTHIA simulation with IP2 configuration IP2 configuration shown in the next slide – detector components from FNAL-E906 apparatus E906: total z-length ~25 m IP2: available z-lengh ~14 m – z-length of FMAG (1 st magnet) is shortened because of limited z-length at IP2 PYTHIA simulation – just acceptance for Drell-Yan dimuon signal is studied – momentum resolution needs to be studied – background rate needs to be studied Beam needs to be restored on axis – after passing through two bending magnets – both beams needs to be restored in parasitic operation 66

67. January 8, 201167 Collider experiment Very simple PYTHIA simulation for PHENIX muon arm –  s = 500 GeV – Angle & E  cut only 1.2 < |  | < 2.2 (0.22 < |  | < 0.59) E  > 2, 5, 10 GeV (no magnetic field, no detector acceptance) – RHIC-II luminosity assumption 1,000 pb -1 – M  = 4.5  8 GeV 110K events total with 2-GeV cut Red: E  > 2 GeV cut Green: E  > 5 GeV cut Blue: E  > 10 GeV cut 67

68. January 8, 201168 Collider experiment Very simple PYTHIA simulation for a dedicated collider experiment –  s = 500 GeV – Angle & E  cut only |  | < 2.2 E  > 2, 5, 10 GeV (no magnetic field, no detector acceptance) – RHIC-II luminosity assumption 1,000 pb -1 – M  = 4.5  8 GeV 550K events total with 2-GeV cut 68

69. January 8, 201169 Experimental sensitivities PYTHIA simulation –  s = 22 GeV (E lab = 250 GeV) – luminosity assumption 10,000 pb -1  10 times larger luminosity necessary than that of the collider experiments because of ~10 times smaller cross section  acceptance (in the same mass region) – 4.5 GeV < M  < 8 GeV – acceptance for Drell-Yan dimuon signal is studied all generated dumuon from Drell-Yan accepted by all detectors 69

70. January 8, 201170 Fixed-target experiment PYTHIA simulation with FNAL-E906 geometry –  s = 22 GeV (E lab = 250 GeV) – luminosity assumption 10,000 pb -1 – M  = 4.5  8 GeV – Magnetic field and detector location should be tuned to optimize the acceptance, and fit to available experimental hall 16K events total 70

71. January 8, 201171 all generated dumuon from Drell-Yan accepted by St. 1 passed through St. 1 passed through St. 2 passed through St. 3 accepted by all detectors Drell-Yan dimuon rapidity 71

72. January 8, 201172 Drell-Yan x 1 vs x 2 (accepted events) x 1 : x of beam proton (polarized) x 2 : x of target proton 72

73. January 8, 201173 Drell-Yan E 1 vs E 2 (accepted events) E 1, E 2 : energy of dimuons – energy cut shown at 5 – 10 GeV 73

74. January 8, 201174 Comparison x 1 & x 2 coverage – PHENIX muon arm Single arm: x 1 = 0.05 – 0.1 (x 2 = 0.001 – 0.002) – Very sensitive x-region of SIDIS data Back-to-back: small x 1 & x 2 – Fixed-target experiment x 1 = 0.25 – 0.4 (x 2 = 0.1 – 0.2) – Can explore higher-x region with better sensitivity PHENIX muon armFixed-target experiment x1x1 x2x2 x1x1 x2x2 rapidity 74

75. January 8, 201175 Issues for the fixed-target experiment Requirement for target thickness – In phase-1 (parasitic operation), 10 15 /cm 2 thickness is necessary to achieve L = 2  10 33 cm -2 s -1 Pellet target (~10 15 /cm 2 ) or cluster-jet target (up to 8  10 14 /cm 2 ?) is necessary If it is not achieved, the internal-target experiment would not be competitive against collider experiments In collider experiments, L = 2(or 3)  10 32 is expected and cross section (  acceptance) is >10 times larger – In phase-2 (dedicated operation), 10-times larger thickness, 10 16 /cm 2 is expected Requirement for accelerator – Compensation of dipole magnets in the experimental apparatus (in two colliding-beam operation) – Size of the experimental site and possible target-position (with proper beam operation) – Reaction rate (peak rate) and beam lifetime – Radiation issues Beam loss/dump requirement 75

76. January 8, 201176 To-do list Low-mass region study – 2 – 2.5 GeV – Larger yield – covering lower x region 0.1 < x < 0.45 – With lower magnetic field? – Charm background < 20% (PYTHIA) Geometry optimization – Opposite polarity of two magnets May be better for restoring beams on axis – Aperture study of the magnets For inventory check of BNL magnets GEANT simulation – Background rate study From the beam pipe? Effect for the DX magnet? Peak rate? Internal target study 2<M  <2.5 GeV (1,000 pb-1) 4.5<M  <8 GeV (10,000 pb-1) 2<M  <2.5 GeV Drell-Yan Charm 76

77. January 8, 201177 Internal target Cluster-jet target – H 2, D 2, N 2, CH 4, Ne, Ar, Kr, Xe, … – 10 14 – 10 15 atoms/cm 2 – Prototype of the PANDA target is operational at the Univ. of Muenster with a thickness of 8×10 14 atoms/cm 2 Pellet target – H 2, D 2, N 2, Ne, Ar, Kr, Xe, … – 10 15 – 10 16 atoms/cm 2 – First-generation target was developed in Uppsala and is in use with the WASA@COSY experiment – Prototype of the PANDA target is available at Juelich which has been developed in collaboration with Moscow groups (ITEP and MPEI) 77

78. January 8, 201178 Experimental sensitivities accepted 4.5 - 8 GeV/c 2 4.5 - 5 GeV/c 2 5 - 6 GeV/c 2 6 - 8 GeV/c 2 rapidity x1x1 xFxF pTpT all generated dumuon from Drell-Yan passed through FMAG passed through St. 1 passed through St. 2 passed through St. 3 accepted by all detectors 78

79. January 8, 201179 Collider vs fixed-target x 1 & x 2 coverage – Collider experiment with PHENIX muon arm (simple PYTHIA simulation)  s = 500 GeV Angle & E  cut only – 1.2 2, 5, 10 GeV – (no magnetic field, no detector acceptance) luminosity assumption 1,000 pb -1 M  = 4.5  8 GeV Single arm: x 1 = 0.05 – 0.1 (x 2 = 0.001 – 0.002) – Very sensitive x-region of SIDIS data – Fixed-target experiment x 1 = 0.2 – 0.5 (x 2 = 0.1 – 0.2) – Can explore higher-x region with better sensitivity PHENIX muon arm (angle & E  cut only) x1x1 x2x2 x2x2 x1x1 Fixed-target experiment 79

80. January 8, 201180 Charm/bottom background In collider energies, there is non-negligible background from open beauty production In fixed-target energies, background from charm & bottom production is negligible charm bottom Drell-Yan PHENIX muon arm  s = 200 GeV FNAL-E866 E lab = 800 GeV 80

81. January 8, 201181 Charm/bottom background In collider energies, there is non-negligible background from open beauty production In fixed-target energies, background from charm & bottom production is negligible at 4.5 - 8 GeV mass region At 2 - 2.5 GeV low-mass region – Larger yield – covering lower x region 0.1 < x < 0.45 – Charm background < 20% (PYTHIA) charm bottom Drell-Yan PHENIX muon arm  s = 200 GeV 2<M  <2.5 GeV (1,000 pb-1) 4.5<M  <8 GeV (10,000 pb-1) 2<M  <2.5 GeV Drell-Yan Charm 81