1 Yamagata University Past and Future of the COMPASS Polarized Target Norihiro DOSHITA SPIN-Praha-2008 Prague, July 20 - July 26, 2008

2 COMPASS Polarized Target Group Bielefeld, Gernany –G. Baum Bochum, Germany –Ch. Hess, F. Gautheron, J. Heckmann, Y. Kisselev, J. Koivuniemi, –W. Meyer, E. Radtke, G. Reicherz Bonn, Germany –St. Goertz CEA Saclay, France –J. Ball, A. Magnon, C. Marchand Chubu, Japan –N. Horikawa KEK, Japan –S. Ishimoto Miyazaki, Japan –T. Hasegawa, T. Matsuda Prague, Czech Republic –M. Finger Yamagata, Japan –N. Doshita, T. Iwata, K. Kondo, T. Michigami, H. Yoshida

3 Outline 2007 run –Muon program –Polarized target system –NH 3 target material –Polarization and relaxation time Drell-Yan program –Introduction –Influence of heat input from the pion beam to the polarized target –New target material ( 7 LIH)

4 CERN and COMPASS

5 The COMPASS experiment Muon beam - Secondary beam - 2 x 10 8 /spill (1spill 16.8sec, 5sec bunch) GeV/c - ~80% polarization Double spin asymmetry of muon beam and nuclear solid target Study of the nucleon spin structure Polarized target LiD NH 3 - Muon program

6 COMPASS polarized solid target system (upgraded in 2006) 50mK 350mW cooling power at 300mK Dilution refrigerator 180mrad Magnet Homogenized 2.5T solenoid (60ppm) 0.6T dipole (field rotation, trans. pol.) 180mrad acceptance Target cell 3 cells (30, 60, 30cm long)  3cm in 2006, 4cm in microwave systems (for 2.5 T) New large acceptance cavity Microwave for DNP beam NMR for determination of polarization 10 channels (3, 4, 3)

7 Polarized target in photo Beam Dilution refrigerator 3 He Pumping line Magnet

8 Acceptance gains in 2006 Larger magnet acceptance mrad acceptance

9 Target material in 2007 NH 3 as proton target Used in the SMC experiment (1996) Paramagnetic centers were produced by electron beam in the liquid argon. Critical temperature of 117K (W. Meyer, 1984 Bonn) Stored for more than 10 years in liquid nitrogen Material property changed color : violet pale paramagnetic centers density : 6 x x /cm 3

10 Dynamic Nuclear Polarization Electron fast relaxation Dipolar-dipolar interaction and 0.2K Electron: 99.9% Proton: 1.3% Transfer the high electron polarization to proton polarization Paramagnetic centers (Free electrons) are needed Free

11 Dynamic Nuclear Polarization Dipolar-dipolar interaction and 0.3K Electron: 99.9% Proton: 1.3% Transfer the high electron polarization to proton polarization Electron fast relaxation Free Paramagnetic centers (Free electrons) are needed

12 NMR system material 6 LiD or NH3 NMR coil Liverpool Q-meter UT-85 Cable Cu jacket semi-rigid Splitter frequency control PTS 250 Microwave generator Yale card scope 10 ch ADC 12 bit 16 ch ADC 16 bit 96 ch digital I/O bus extender VME-MXI VME-bus NI MXI-2 cable PC in the control room Windows 2000 data acquisition program (LabVIEW) data storage gain selection signal DC offset subtraction ADC/DAC 12 bit trigger signal 10 coils can be operated at the same time. to determine polarization

13 - Target cell material: Polyamide Calibration of proton polarization for NH 3 - Thermal equilibrium NMR signal S 0 : target material + background - BG measurement is needed: with empty target P= S P0P0 S0S0 calibration coefficient high proton contamination P 0 is determined by temperature. - Polarization (P) is proportional to area of NMR signal (S).

14 TE signal from background K Background proton signal Target proton signal NMR frequency [mV]

15 NMR proton enhanced signal Asymmetry signal: line shape polarization positive polarization negative polarization This will be presented by Y. Kisselev

16 Proton polarization build up (at 2.5T) upstream central downstream

17 Polarization in full period in 2007 upstream central downstream % during data taking

18 Spin frozen target (for data taking) muon beam target Longitudinal polarization Solenoid 1.0T Transversal polarization Dipole 0.6T The fringe field of solenoid is strong. - Polarization decreases with a relaxation time. - The target has to be re-polarized at somewhere.

19 Proton spin relaxation at 0.6T

20 Relaxation time Temperature ~60mK MaterialMagnetic field Relaxation time COMPASS 6 LiD2.5 T>15000 h COMPASS 6 LiD1.0 T~ h COMPASS NH T~ 9000 h COMPASS NH T~ 4000 h SMC NH T500 h COMPASS 6 LiD0.0 T2.5 min. for positive COMPASS NH T~ 70 min. for positive ~ 10 min. for negative

21 NH 3 materialSMCCOMPASS colorvioletpale spin density [/cm 3 ] 6 x x relaxation time (60mK) 500h at 0.5T4000h at 0.6T Polarization [%]~ 90 Summary for the 2007 run The 2007 run successfully finished. (new magnet, 3 target cells, large microwave cavity ) NH 3 is used in the 2007 run. Y. Kisselev will show detail proton polarization analysis.

22 Outline 2007 run –Muon program –Polarized target system –NH 3 target material –Polarization and relaxation time Drell-Yan program –Introduction –Influence of heat input from the pion beam to the polarized target –New target material ( 7 LIH)

23 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) with polarized muon beam  Quark orbital angular momentum Since SMC experiment Drell-Yan program (2011? ~ ) with pion beam and transversally polarized target Drell-Yan process ** l+l+ l-l- -- p nucleonquark

24  k - Transversity and Sivers function SIDIS Drell-Yan   Uncertainty of Fragmentation Function unpol. DY 1st moment of Boer-Mulders function single spin DY asymmetries many components of transverse target spin dependent azimuthal modulations   Coefficient at cos2  dependent part of the properly integrated over q T ratio of the cross-section FF free Motivation prediction Unpol. PDF

25 Experimental condition in terms of DY target - Frozen spin mode with 0.62 T for transverse polarization - Proton target - High intensity hadron beam (~2 x 10 7 hadrons/s) - Smaller beam focus size High polarization, high dilution factor and long relaxation time Nuclear interaction produces secondly hadrons heat input Cannot be polarized (only at 2.5T can be) Smaller diameter target is preferred Transverse mode with hadron beam - The present system can be used Total probability factor of secondly particle productions multiplicity = Material temp. warms up Fast spin relaxation time - Target length of cm x 2 cells The beam intensity gets higher on a material bead NH3

26 Energy deposition in 30-30cm target Gaussian beam  x =  y = 0.5 cm z(cm) GeV/cm 3 per primary Targets done by H. Vincke and E. Feldbaumer  3cm beam spot beam Cell 1Cell 2Cell 3 Liquid He

27 cell 1cell 2cell x (2.8) 9.04 x (3.5) x (2.3) 4.89 x (2.9) x (2.3) 1.97 x (3.9) 1.20 x (4.7) Average multiplicity per a incoming hadron Energy deposition[GeV] (Multiplicity) 2 [MeV/g/cm2] x 0.85 [g/cm3] x L [cm]x 0.5 Energy deposition [GeV] Multiplicity = Heinz and Eduard’s result packing factor

28 DY beam test, November 2007 Feasibility study of the Drell-Yan program with COMPASS spectrometer -160 GeV negative pion beam -COMPASS PT performance during the operation with the high intensity hadron beam -Radiation conditions in the experimental hall with COMPASS PT (full length ~ 100% int.leng.); operation with high intensity hadron beam: 2×10 7 hadrons/spill L ~10 31 cm -2 s -1 ( ~ equivalent to 10 8 hadrons/spill on 25% int.leng. PT) - J/  event rates (good normalization for DY and background) -COMPASS spectrometer performance during the operation with high intensity hadron beam -Background/Signal level and trigger rates

29 Temperature sensors behavior during the beam test magnet 2 x 10 7  1 x 10 7 /spill 1 spill = ~ 5 sec

cell 1cell 2cell x (2.8) 9.04 x (3.5) x (2.3) 4.89 x (2.9) x (2.3) 1.97 x (3.9) 1.20 x (4.7) Average multiplicity per a incoming hadron Energy deposition[GeV] (Multiplicity) 2.9 x 2  10 7 [/s] = 5.8 x 10 7 [/s] ~ muon intensity for muon program 4.7 x 1  10 7 [/s] = 4.7 x 10 7 [/s] Beam test Physics run 5 x 10 7 muons/spill1 x 10 7 pions/spill Multiplicity ~ 5 with cm long Comparing with data with muon beam,

31 Limitation of target cell size heat input by high intensity of hadron beam - Diameter  beam intensity  Temperature in terms of a bead of material bead - Length  total heat  Temperature input into cells of Mixing chamber with -NH 3 Investigate the possibility of -smaller beam focus size and target cell -higher beam intensity via -temperature variation of the material -total heat input into Mixing chamber Cooling power of DR (20 cm x 2)

32 Heat flow diagram MIP heat flow = constant T 2 MeV · cm 2 /g Temperature of target material Temperature of Mixing chamber

33 Specific Heat C phonon (T) =  4 N A k B ( ) DD T  D : Debye temperature 7 LiD ~1030K 14 NH 3 ~235K C cryocrystal (T) = ?? For NH 3,ND 3 C non-crystal (T) = ?? For butanol?, CH 2, CD 2 C L = C phonon + C cryocrystal + C non-crystal

34 multiplicity Model for calculation of temp. variation D mm d mm - Target material : spherical shape, LiD: d=4 mm, NH 3 : d=3 mm - Beam focus = target size: circular cross section (D=30mm for muon program)  beam s -1 - Beam intensity :  bead in terms of one bead ·  beam · N m D2D2 d2d2 =

35 Algorithm for the calculation  0 Q dt =  0 (T(t i-1 ) 4 - T 0 4 ) dt RKRK A n C L (T(t i-1 )) E deposit - Q + T(t i-1 )T'(t i ) = E deposit = n C L (T(t i-1 )) (T(t i ) - T'(t i-1 )) T(t i ) Beam interval: t i - t i-1 = sec = 1/  bead T 0 = 65 mK R K = 50 cm 2 K 4 /W (CrK crystal - 4 He)

36 NH 3 material temperature It should be kept below 100 mK. 2 x 10 7 /s.

37 Total heat input in the target cells mmol/sec mK Cooling power of refrigerator Q total = Nm · (  m ·  +  He · (1 -  )) · 2L · E MIP ·  beam This heat should be removed by Dilution refrigerator NmNm   L E MIP  beam : Multiplicity : Material or helium density : Packing factor : Target cell length =20cm : 2 MeV · cm 2 /g : Beam intensity 1 mW at 60mK Q total = 0.6 mW

38 New target cells idea 15 – 30 cm Liq. He 50cm = 10% int. length NH3 target cell 20cm x 2 = 30% int. length - The cells will be put in the downstream to get higher acceptance. - The present microwave cavity can be used.

LiH 1960s : Abragam used 6 LiF to check experimentally DNP. 1980s : Saclay group investigated 7 LiH and 6 LiD. (J. Ball, NIM A 526 (2004) 7-11) High dilution factor 7 Li can be recognized as  + 2n + p. (J. Phys. G: Nucl. Part. Phys. 30 (2004) ) Dilution factor : 2/8 spin 3/2 How can be extracted proton polarization in 7 Li ? New target material It doesn’t have exact same proton polarization with spin 1/2.

40 expectation Definition of vector polarization Proton polarization B=2.5T at COMPASS Ts: Spin temperature k B : Boltzmann constant  : Magnetic moment

41 7 Li polarization 7Li and H have same spin temperature. 7 LiH Proton polarization vs 7Li polarization

42 Proton polarization in 7 Li 7 Li : 1p state in energy level proton : J = 3/2 Clebsch-Gordan coefficients of 1 x 1/2 system J = S + L S : spin L : orbital angular momentum Jz = +3/2 : Jz = +1/2 : Jz = -1/2 : Jz = -3/2 : Sz = +1/2, Lz=+1:: 1/1 Sz = +1/2, Lz= 0:: 2/3 Sz = -1/2, Lz=+1:: 1/3 Sz = -1/2, Lz= 0:: 2/3 Sz = +1/2, Lz=-1:: 1/3 Sz = -1/2, Lz=-1:: 1/1 same as 7Li by chance!  + 2n + p

43 Polarization of proton in 7 Li vs proton polarization Proton polarization in 7 Li

44 NH 3 7 LiH polarization0.90 at 2.5T 0.56 at 2.5T density [kg/m3] :  dilution factor : f for proton for proton in 7Li packing factor :  0.55 FoM FoM II FoM =  f 2 P 2 Liq He as non-polarized material is included in FoM II. Figure of Merit for the target materials in 1988 at Saclay

45 Figure of Merit for NH 3 and 7 LiH 7LiH NH3

46 1K, 2.5T200mK, 2.5T 60mK, 2.5T (COMPASS) 6 LiD deuteron 12.5 %> 30%55% 7 LiH proton 14.5 %?? Temperature and dose of irradiation have to be optimized. Bochum group’s results in 1995 Irradiation : temperature 180K and 1 x e-/cm 2. (additional irradiation of e-/cm 2 at 1K) Investigations in 1990s

47 Summary of the DY program Compass plans for the Drell-Yan program. Multiplicity of 3 in the 20-20cm long target is estimated. Any problems of the material temperature cannot be expected at the beam spot size more than 10 mm diameter. The modification of the target place is needed. 7 LiH has a higher dilution factor. Investigation of 7 LiH is needed. Another future program (GPD) A 2.5m long liquid hydrogen target for GPD program A long transverse PT surrounded by recoil detector Discussion has already started.

48 Back up

49 Very first J/  signal Just a fraction of statistics (~1/3) No cut tuning No Coral and option files modification – just everything standard J/  yield close to expected

50  +  - Invariant mass 450 GeV

51 Very preliminary DY event rates estimate - Target: NH3 and L NH3 =15 cm x 2, (  NH3 : 0.85 g/cm 3 ) - PT material filling factor F f = Number of nucleon in NH 3 molecule: A NH3 =17 -  - beam intensity: I beam = 2  10 7 p/s - N A = 6.0 ×10 23 mol -1 Luminosity: L = L NH3 × N cell ×  NH3 × F f × N A × 1/A NH3 × I beam ≈ 1.1×10 31 cm -2 s -1 - Compass DY pairs reconstruction efficiency (acceptance included) : A ≈ DY cross section on NH 3 :  NH3 = N nucl ×   p, where N nucl =17 -D spill = 5 s (duration of spill), N spill =4000 (number of spills per day), E sps = 80% (efficiency of the machine) - Duration of the Run 150 days: D RUN =150 R = L × N nucl ×   p × A × D spill × N spill × E SPS × D RUN

52 DY cross sections and statistics estimate (150 days of running) Cross section values were taken from AB_5 A.Bianconi generator cross- checked with PYTHIA data (A.Nagaytsev, Dubna), without J/  contribution Statistical error ~ 4% for 2 years M (  +  - ), GeV S, GeV M (  +  - ), GeV S, GeV nb 0.03 nb nb 0.10 nb nb 0.15 nb

53 Figure of Merit II for NH 3 and 7 LiH 7LiH NH3

54 130cm Dipole magnetic field

55 Proton spin relaxation at 1.0T

56 Total heat input in the cells 2 x 10 7 /s.