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 年 1 月 8 日 ( 土 ) 後藤雄二（理研）

January 8, 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

January 8, 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

January 8, 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

January 8, 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

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

January 8, 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

January 8, Goal of the experiment Comparison with DIS data – DIS data < 1% level multi-points measurements have already been done for SSA of DIS process < 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

January 8, 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/ 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

January 8, 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

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

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January 8, 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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January 8, Polarized Drell-Yan experiments at RHIC “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) 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

January 8, Collider experiment LoI 31

January 8, Collider experiment LoI 32

January 8, Fixed-target experiment LoI Measurement of Dimuons from Drell-Yan Process with Polarized Proton Beams and an Internal Target at RHIC – – 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

January 8, 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

January 8, 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

January 8, 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 – – 03.1 K 1.4 K7.6 K 0 – K6.1 K3.0 K15.3 K 0.4 – K6.4 K2.3 K16.3 K 0.8 – K2.5 K0.4 K7.3 K x 1 : x of beam proton (polarized) x 2 : x of target proton 36

January 8, 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, (2009) Measure not only the sign of the Sivers function but also the shape of the funcion 37

January 8, 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

January 8, 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

January 8, 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  ppp = 2.5   2sec in 1pulse (5sec) possible? – PYTHIA simulation 75% polarization beam 120 days, beam on target 5  (with 50% duty factor) ~5% liquid H 2 target – fb -1 luminosity ~20% nuclear target – 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

January 8, 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...

January 8, 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

January 8, 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

January 8, 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

January 8, 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

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

January 8, 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

Backup slides

January 8, 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 – (?) 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

January 8, 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

January 8, RHIC 51

January 8, 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

January 8, 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

January 8, 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, (2009) J-PARC 50-GeV polarized beam  s ~ 10 GeV RHIC collider  s = 200 GeV 54

January 8, 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,

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

January 8, 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

January 8, 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

January 8, 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

January 8, 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

January 8, 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/ 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

January 8, 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

January 8, 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 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

January 8, 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 ×10MHz = /s – Target with ~10 17 atoms/cm 2 thickness (if available) Comparable thickness with RHIC CNI carbon target – Luminosity /cm 2 /s – Hadronic reaction rate ×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

January 8, 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 /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

January 8, 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

January 8, 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

January 8, 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

January 8, 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

January 8, 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

January 8, 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

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

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

January 8, Comparison x 1 & x 2 coverage – PHENIX muon arm Single arm: x 1 = 0.05 – 0.1 (x 2 = – 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

January 8, Issues for the fixed-target experiment Requirement for target thickness – In phase-1 (parasitic operation), /cm 2 thickness is necessary to achieve L = 2  cm -2 s -1 Pellet target (~10 15 /cm 2 ) or cluster-jet target (up to 8  /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)  is expected and cross section (  acceptance) is >10 times larger – In phase-2 (dedicated operation), 10-times larger thickness, /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

January 8, 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

January 8, Internal target Cluster-jet target – H 2, D 2, N 2, CH 4, Ne, Ar, Kr, Xe, … – – 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, … – – atoms/cm 2 – First-generation target was developed in Uppsala and is in use with the experiment – Prototype of the PANDA target is available at Juelich which has been developed in collaboration with Moscow groups (ITEP and MPEI) 77

January 8, Experimental sensitivities accepted GeV/c GeV/c GeV/c 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

January 8, 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 = – 0.002) – 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

January 8, 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

January 8, 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 GeV mass region At 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