# Presentation: 502985

## CNI polarimetry status

- Osamu Jinnouchi (RIKEN BNL Research Center)
- / Sandro Bravar (BNL)
***RHIC-Spin-Collaboration Meeting ***
***November 18, 2003***

## Update of RHIC polarization status

- During the run, polarization from the scaler numbers was distributed to the experiments. The number depends on,
- T1/4,  ADCmax  determined by WFD algorithm
- WFD look-up-table banana cut
- This online results were defined as tentative “official polarization” for run-03
- The calibration and correction were done at some level at the online stage, and the recoil Carbon energy is one of the most important value which determine the AN
- Energy calibration (Correction)
- Scale – 241 Am source
- Stable within a few % throughout the run (c.f. 20% in RUN-02)
- Scale and shift –Energy loss in SSD dead layer
- Estimated by kinetic fit to E-T banana curve
- Would generate 50-80keV shift in detection energy

- O.Jinnouchi @ RHIC-Spin-J

- Nov. 14, 2003

## Comparison WFD algorithm vs. Waveform

-  ( A, T ) values from the WFD FPGA algorithm were compared with the result from waveform data samples
- Clear correspondence in each event
- The Event mode data and scaler mode data were confirmed to be correct for the first time
- Storing the timing info at the maximum pulse height will be also useful

- Tdc_WFD

- 1bin~2.5ns

- ADC_calc

- TDC_calc

- RHIC** CNI Waveform**

- A quarter of max pulse height

- ADC

- TDC

- WFD

- Waveform

- WFD

- Waveform

- O.Jinnouchi @ RHIC-Spin-J

- Nov. 14, 2003

## SSD dead layer estimation

- Ambiguity about dead layer width is one of the systematic error source in AN  polarization error
- The width could be different in each Si detector, and each strip
- It can be roughly (and indirectly) estimated by kinetic fit for banana distribution
- Direct measurement using the test beam was done during the last three weeks at Tandem in Kyoto (Basic data sets were collected for 3 SSDs) The run was very successful !!
- It is desirable to perform this test for all the detectors, each year – Since this is time consuming, we need to develop test bench system in Lab space

- Kinetic Energy =
- Deposit on dead layer + deposit on Si

- recoil carbon

- Dead layer thickness

**p****+**

**n**

**n****+**

- O.Jinnouchi @ RHIC-Spin-J

- Nov. 14, 2003

## The radial component (at BLUE Flattop)

- False asymmetry (radial component) had been seen throughout the Run-03
- The effect was significant and there are many possible candidates for the source

- Radial asymmetry
- (from 45 degree Si’s)

- Physics asymmetry

- APRIL

- MAY

- O.Jinnouchi @ RHIC-Spin-J

- Nov. 14, 2003

## Limitation of the square root formula

- Square root formula (actually any other formula) can generate false asymmetry with 45 degree SSDs,  when AN of each detector is different
- Also it is possible to generate false asymmetry by just eliminating the suspicious Si strip channels
- AN for each strip would be the useful parameter to look at so that we can visually understand the anomalous behavior of asymmetries

- The Ratio(i) = (Ui-RDi)/(Ui+RDi)
-             Ui : Spin Up counts for i-th strip
- 	   Di : Spin Down counts for i-th strip
- 	   R : luminosity ratio Lu/Ld
- represents AN for each strip

- O.Jinnouchi @ RHIC-Spin-J

- Nov. 14, 2003

## AN for each strip (in YELLOW)

- Both energies in yellow can indicate the tilted spin from vertical
-  Opposite direction btw injection and flattop
- Other things look to be normal

- YELLOW FLATTOP

- YELLOW INJECTION

**strip #**

**strip #**

**RATIO**

**RATIO**

- 1

- 2

- 3

- 4

- 5

- 6

- 1

- 2

- 3

- 4

- 5

- 6

- average of 5/1-5/10

- average of 5/1-5/10

- Ratio (AN) is corrected with the sign (1-3 for
- plus and 4-6 for minus) and factor 2 for 45
- degree SSDs

- Si-1

- Si-3

- Si-4

- Si-5

- Si-6

- Si-2

- O.Jinnouchi @ RHIC-Spin-J

- Nov. 14, 2003

## AN for each strip (in BLUE)

*A**N** **for each strip (in BLUE)*

- AN for BLUE Si-3 is extremely small and this has created the large asymmetry in radial direction
- The reduction cannot be explained by,
- Wrong dead layer estimation
- Wrong energy scale
- Banana cut is not right
-       because the size is too significant

- BLUE FLATTOP

- BLUE INJECTION

**strip #**

**strip #**

**RATIO**

**RATIO**

- 1

- 2

- 3

- 4

- 5

- 6

- 2

- 3

- 4

- 5

- 6

- 1

- O.Jinnouchi @ RHIC-Spin-J

- Nov. 14, 2003

## Mass distribution 

- One way to check the consistency in kinematics is to see the mass distribution
- The width has similar behavior, but centroid has different slope only in Si-3

- Mass distribution for
- Every strips in Si-3

- Si-1

- Si-3

- Si-4

- Si-6

- C Energy

- C Energy

- C Energy

- C Energy

- Mass vs. C Energy

***Sigmas***

***Centroids***

- O.Jinnouchi @ RHIC-Spin-J

- Nov. 14, 2003

## Beam position was off-centered

- The data from BPM and survey group indicates the target (and beam) was not centered w.r.t. polarimeter chamber
- The effective angle for each 45 degree detector (= effective AN) was changed (cos45 = 1./2 ??)
- The size of this effect can even become ±10% according to the geometrical displacement
- Only Si-3 could be largely affected while the others get small effects

- O.Jinnouchi @ RHIC-Spin-J

- Nov. 14, 2003

## Summary

- Algorithm of WFD has been studies with  waveform analysis
- SSD dead layer measurement in Kyoto successfully finished
- To understand the anomaly in Blue flattop is the top priority
- The mechanism has been understood, then we need to find out the source and how to avoid it  in the run-04

- O.Jinnouchi @ RHIC-Spin-J

- Nov. 14, 2003