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PHENIX Local Polarimeter

PHENIX Local Polarimeter. Manabu Togawa (RBRC) for the PHENIX LP team 2009/07/31 Polarimeter workshop. Local polarimeter. Measurement of spin direction of proton beams at collision point - as function of spin rotator operation. Transverse RUN setting. Longitudinal RUN setting.

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PHENIX Local Polarimeter

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  1. PHENIX Local Polarimeter Manabu Togawa (RBRC) for the PHENIX LP team 2009/07/31 Polarimeter workshop

  2. Local polarimeter Measurement of spin direction of proton beams at collision point - as function of spin rotator operation • Transverse RUN setting • Longitudinal RUN setting pp, pC pol. : finite eN Spin rotator ON pp, pC pol. : finite eN Spin rotator OFF PHENIX local pol. : finite eN PHENIX local pol. : eN ~ 0 Spin direction in transverse plain can be measured by phi-dependent eN Residual transverse components can be estimated by residual eN

  3. RUN 2 Leading neutron asymmetry from polarized pp collision • PHENIX LP has been operated by measuring leading neutron AN. • Discovered at ZDC kinematics, ±2.8 mrad, at RHIC RUN2.  -10% in forward kinematics  Consistent with zero in backward Interaction LR definition Asymmetry for neutron ID sample Phys. Lett. B650 : 325-330 (2007)

  4. ZDC (Zero Degree Calorimeter) 10*10cm  ±2.8 mrad 3 modules 150X0 5.1λI SMD (Shower Max Detector) Dx magnet Charge veto counter SMD Neutron position can be decided by centroid method. veto Proton shower event (In case of proton mom. = 50GeV/c) 1 ZDC PHENIX LP Setup Beam Beam Counter (BBC) Beam Beam Counter (BBC) Schematic view from simulation. - GEANT3 (Geisha) - From the pythia simulation, Main backgrounds are gand proton. • 2 identical parts • BBC-north and -south • Quartz Cherenkov counter • Count charged particles. • 64 segments each. • 3.0 < |h| < 3.9 Collision point 1800 cm BBC

  5. Asymmetries at PHENIX ZDC Red : Transverse run (Fill#10340) Blue : Longitudinal run (Fill#10382) √ s = 500 GeV data @ RUN9 • First measurement at √ s = 500 GeV • Large asymmetry is seen in such higher energy  Local polarimeter can be done by neutron asymmetry too. BLUE beam YELLOW beam

  6. PHENIX LP until RUN8 • Calculate longitudinal component via vertical component • Beam direction is extracted through the run. • Data rate is 100-200 Hz during physics run in PHENIX DAQ • Offline analysis Local results are shown for longitudinal runs. RUN8 : transverse run only. RUN9 : under investigation

  7. Local polarimeter scaler @ RUN9 • Scaler mode improves, •  Human resource.(during commissioning time, waiting for beam at CH) • Also offline analysis is slow operation •  Occupation of PHENIX DAQ band • During physics data taking, it is only 100-200 kHz Charge ADC, TDC Detector (ZDC,SMD) FEM DAQ Scaler data has been recorded in DB in each 5 mins. Trigger SMD: Make hit map according to the energy deposit above 20 MIP ZDCinfo. LL1 FPGA By fiber Analyzed by PHENIX online monitor, and result has also been sent in CDEV. SMDinfo. TOP Make scaler in LL1 board 4 * 2 (N or S) * 120 (bunch) 20 bits in each scaler RHICExparimentPhenix by LogView BOTTOM LEFT RIGHT

  8. - 5 mins data (2009/03/29 15:50-55) - Small BG can be confirmed by unfilled bunch Scaler counts(Fill#10454) Blue : unfilled +Yellow : filled Blue : filled +Yellow : unfilled Background not related to collision is very low, 10-3 level for beam gas.

  9. Scaler mode : Fill#10371 (transverse pol.) RED : yell pol. ↑ BLUE : yell pol. ↓ RED : blue pol. ↑ BLUE : blue pol. ↓ Significant asymmetry bunch-by-bunch ! 5 mins data

  10. Scaler mode : Fill#10372 (unpol.) RED : yell pol. ↑ BLUE : yell pol. ↓ RED : blue pol. ↑ BLUE : blue pol. ↓ Consistent with unpol. 5 mins data

  11. Time dependenceFill#10288 (2/25 3:00-7:00)

  12. Rotator tune at Fill#10399 • Result of scaler mode is consistent with offline mode. • Rotator feed back during fill  Success ! Rotator current was changed

  13. Unknown behaviors • Spin direction of blue beam is tilted at PHENIX collision point (transverse run) • Observed at RUN8 and 9. • PHEINX collision point only ? • Small asymmetries are observed in scaler mode at the beginning of fill. • Only seen at 500 GeV. • Beam is shifted to ZDC center (x-y plane) • Measured by 500 GeV data.

  14. Blue spin at trans. run was measured as tilted RUN8 (offline analysis) RUN9 (scaler data, Fill#11020) LR asymmetry 0.0154 ± 0.0001 UD asymmetry 0.0038 ± 0.0001 Phase tan-1(0.0038/0.0154) ~ 14o  c.f. yellow~ 3o PHENIX IP only ?

  15. LP scaler : unstable behavior at 500 GeVFill#10325 • We have small asymmetry in first 3-4 hours. • High BG from collision related? (e.g. proton event) • Collision angle has been changing? • Situation was changed fill by fill. • c.f. It is more stable at 200 GeV upgrade

  16. Beam position in x-y plane at ZDC • To investigate beam position, calculate f-dependent AN by luminosity formula. • R is relative luminosity (by BBC count) f =±p f = 0 Raw asymmetry Asymmetry shape should be symmetric around f = 0. -p < f < p

  17. Phi-dep. asymmetry scan for y-position by simulation • Beam center : y=0 at ZDC for the simulation input. •  Asymmetry shape be far from sine modulation if beam center is wrong. • We can extract beam position at ZDC by scan center position of phi-dep. calculation -p < f < p

  18. Center : y = -1.5 cm Center : y = -1.0 cm Center : y = -0.5 cm 500 GeV data (Fill#10340+ 10368+10373) Center : y = 0 cm Center : y = +0.5 cm Center : y = +1.0 cm SOUTH side Scan is just in y-direction. c2/NDF vs. y-center Amplitude vs. y-center Center : y = +1.5 cm Looks shifted in y : -1.0 - -1.5 cm

  19. Compare to other data • 200 GeV pp • It tends to be shifted, but statistically not so significant. • 200 GeV CuCu • In this case, 100 GeV neutrons are on beam axis, they only spread by fermi momentum in x-y plane. • ±2 cm at ZDC region edge effect is not so significant. • Beam center is consistent with ZDC center Select ZDC energy above 300 GeV for reliable measurement. (RUN5 data) Different beam orbit in x-y plane btw pp and heavy ion collision?

  20. Summary • PHENIX LP work is successful at RUN9 too, • First measurement of significant neutron AN at √ s = 500 GeV. • Scaler mode works well, consistent with offline analysis. • Spin rotator feedback during fill was succeeded. • PHENIX LP observed following behaviors, • Spin direction of blue beam at transverse mode is tilted at PHENIX collision point. (~14o) • Asymmetries in scaler mode at 500 GeV are sometimes smaller at the beginning of fill. • Beam position in x-y plane is shifted to ZDC center. (y offset : ~ -1.0 cm)

  21. Future plan for PHENIX LP • Upgrade to select pure neutron sample for LP scaler . • Add charge veto information. • Coincidence with BBC hits • Make LP scaler by BBC for 62 GeV run • Proton BG is significantly high for neutron • Charge veto counter is critical. • ZDC rate significantly down to BBC rate • Use BBC asymmetry like STAR LP. Will be next run

  22. backup

  23. Event structure study using pythia input.@ 200 GeV ZDC threshold is ~5GeV n g p Black : sum Green : gamma Blue : neutron Red : proton

  24. Detector asymmetry Blue forward Yellow forward Raw asymmetry Luminosity asymmetry ~ 0.5-1.5% f Blue backward Yellow backward Detector asymmetries are up to 50%, but it is cancelled according to backward asymmetry.

  25. ZDC energy distribution with high threshold cut for SMD (in ZDCN|S sample @ RUN5 data) NORTH SOUTH • SMD threshold corresponds to 20 MIP • With high SMD cut can be help to select neutron sample. • BG1 : photon will stop at 1st module; not hit SMD. • BG2 : proton event is only distributed low energy region. Bottom cut Top cut Bottom cut Top cut Left cut Right cut Left cut Right cut 70 GeV Measured energy in ZDC (GeV)

  26. Raw asymmetry for Fill#10228 Measured @ SOUTH LR Measured @ NORTH LR (NL-NR)/(NL+NR) Measured @ SOUTH TB Measured @ NORTH TB (NB-NT)/(NB+NT) Crossing#

  27. DAQ mode : Fill#10372 (unpol.) Blue forward Yellow forward Yellow backward Blue backward

  28. Scaler mode : Fill#10372 (unpol.) RED : yell pol. ↑ BLUE : yell pol. ↓ RED : blue pol. ↑ BLUE : blue pol. ↓

  29. Event structure in ZDC for pp collision

  30. DAQ modePhi-dependent asymmetry @ RUN9 Blue forward Yellow forward From first transverse collision at PHENIX, Fill#10228 (2/25) BBCLL1&(ZDCN|S) ~20 M evts By square root formula Blue backward Yellow backward

  31. pCvs PHENIX Loc. Pol. From Sasha’s slide Polarization (%), not normalized (!) vs fill Online Polarization (%), not normalized (!) vs fill Raw asymmetry (%) 2/NDF=14/9 2/NDF=21/10 Ratio Fill-by-fill systematics

  32. Systematic study by unpol. beam • Unpolarized beam was delivered as Fill#10372 • Cross check for all polarimeters. • Asymmetries in DAQ mode (phi-dependent asymmetry) and scaler mode were consistent with zero.

  33. DAQ mode : Fill#10372 (unpol.) Blue forward Yellow forward Yellow backward Blue backward

  34. Time dependent @ transverse data • From data, polarization is same bunch-by-bunch • Fit by following parameters with spin pattern • Blue asymmetry • Yellow asymmetry • Detector asymmetry • In this case, • Blue backward asymmetry • Yellow forward asymmetry • Detector asym. in SOUTH ZDC Measured @ SOUTH Cross# RED : yell pol. ↑ BLUE : yell pol. ↓

  35. Fill#10288 • Extract from SOUTH measurement • Yellow forward asym. • Blue backward asym. • Detector asymmetry in SOUTH • 2/25 3:00-7:00

  36. Fill#10325 • Extract from SOUTH measurement • Yellow forward asym. • Blue backward asym. • Detector asymmetry in SOUTH • 3/10 0:00-11:00 • We have small asymmetry in first 3-4 hours. • High BG from collision related? • Collision angle has been changing? • Situation was changed fill by fill. • For asymmetry value, we took flat region.

  37. To longitudinal run • First beam with rotator on was delivered as fill#10382.

  38. phi asymmetry (Fill#10382) Value@transverse for YELLOW : 0.079±0.005 Value@transverse for BLUE : 0.072±0.004 BLUE forward Yellow forward BLUE backward Yellow backward

  39. Scaler (Fill#10382) RED : yell pol. ↑ BLUE : yell pol. ↓ RED : blue pol. ↑ BLUE : blue pol. ↓

  40. First rotator ON : Fill#10382 From phi fit (only amplitude) From the scaler Offline and scaler asymmetries are consistent  Switch to physics data taking at PHENIX

  41. Yellow angle for remaining transverse component INSIDE NORTH INSIDE : Pol. Direction for residual transverse component at CDEV=“+” q Yellow Beam OUTSIDE OUTSIDE SOUTH

  42. Yellow angle for remaining transverse component INSIDE NORTH INSIDE : Pol. Direction for residual transverse component at CDEV=“+” q Yellow Beam OUTSIDE OUTSIDE SOUTH

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