1. Update on the CNI polarimeter results for Run02 1.Bunch-by-bunch polarization study 2.Profiles of 0-pol bunches Osamu Jinnouchi

2. 5/22/2002RHIC Spin Collaboration Meeting2 1. Bunch by bunch polarization study  Interests for spin physics analysis  Luminosity weighted polarization info (bunch per bunch polarization) is needed  Each detector sees different bunch combinations (clockwise,anti-clockwise) STAR (i,i+20) 6 o ’ clock PHENIX,pp2pp,BRAHMS (i,i+40) 2 or 8 o ’ clock PHOBOS (i,i) 10 o ’ clock for machine physicists  Bunch profile Is there any weird bunches? Polarization profile within 55-bunches

3. 5/22/2002RHIC Spin Collaboration Meeting3 Polarimeter dedicated run  10 successive measurements at the end of store for both rings (fill ID :2301 Jan. 23th, 02)  The data can be summed up to gain statistics  0-pol bunches are available (3-bunches 1 st,21 st,41 st ) 2min x 10 = 20min measurement

4. 5/22/2002RHIC Spin Collaboration Meeting4 Bunch by bunch asymmetry  Good statistics  Used square-root formula  The values are averages of X90 and X45 1.Origin of gaps 2.Separation of Plus spin and Minus spin  can we trust 0-pol bunches ? Naive calculation shows terrible distributions BLUE YELLOW BUNCH ID Asymmetry x Spin pattern(+1,-1,0) gap separation Up-spin Dn-spin 0-pol

5. 5/22/2002RHIC Spin Collaboration Meeting5 Origin of gaps  Location of the gaps are corresponding to small population bunches  There are hits on the empty bunches (56-60th)  Found out that several strips are noisy 1.Noisy strips can be excluded from calculation 2.How about other normal fills? BLUE BUNCH ID Asymmetry x Spin pattern(+1,-1,0) gap Dedicated run (fill:2301) BUNCH ID Bunch luminosity at RHIC polarimeter Up-spin Dn-spin

6. 5/22/2002RHIC Spin Collaboration Meeting6 Consistency between 0-pol bunches  Triplets turned out to be identical twins (2 nd – 3 rd pair)  Y components are rather large (vertical target)  Generating false asymmetries of comparable size 1.How about other fills? BLUEYELLOW 0.01 -0.01 0.01 -0.01 1 st -2 nd 2 nd -3 rd 3 rd -1 st 1 st -2 nd 2 nd -3 rd 3 rd -1 st X90 X45 Y45 Square-root asymmetries Dedicated run (fill:2301)

7. 5/22/2002RHIC Spin Collaboration Meeting7 Luminosity ratio  Typical run (fill ID:2277)  Supposed to be flat if two bunches are identical  Fit with horizontal line and yield reduced chi-square Si-1 Si-2 Si-3 Si-4 Si-5 Si-6 #1 #2 #3 #4 #5 #6 1 st /2 nd 2 nd /3 rd 3 rd /1 st Count ratio for each detector

8. 5/22/2002RHIC Spin Collaboration Meeting8 Luminosity ratio (cont ’ d)  Reduced Chi-square dists. for all the fills including 0-pol bunches (fill id: 2277~ last)  Generally 1 st 0-pol bunch is strange 1 st /2 nd 2 nd /3 rd 3 rd /1 st

9. 5/22/2002RHIC Spin Collaboration Meeting9 Bunch profile (fill id:2277 last measurement at 100GeV)  Similar analysis applied for polarized bunches  Fitting with Sin function instead of flat constant 1.Luminosity ratio is getting worse at low populated bunches, which would result in false asymmetry 2.Adjacent bunches are also affected 3.Need a criteria to throw away those weird bunches Luminosity of RHIC polarimeter Wall Current Monitor Typical Run

10. 5/22/2002RHIC Spin Collaboration Meeting10 Improved bunch by bunch asymmetry  Exclude noisy strips Gaps disappeared  Use combined 0-pol (2 nd and 3 rd ) Separation disappeared 1.Still some bunches behave strange low populated bunches introduce false asymmetries 2.Tendency up drops and down grows in yellow Need further study Up-spin Dn-spin BLUE YELLOW BUNCH ID Asymmetry x Spin pattern(+1,-1,0) 0-pol Dedicated run (fill:2301)

11. 5/22/2002RHIC Spin Collaboration Meeting11 Summary  1 st 0-pol bunch is strange Tail effect of the kicker field?  Low populated bunches will create false asymmetries Need certain criteria to throw them away (fitting   is a good candidate)