# Presentation: 664576

## 0 ALL results from pp Run3: 

- A.Bazilevsky
- For PHENIX Collaboration
- September 11, 2003

## Nothing but Data

## Data set

- Data collected with high pT photon trigger
- Based on EMCal; Threshold ~1.4 GeV/c
- Rejection factor ~110
- Analyzed data sample: 	**42.7M events (~0.215 pb****-1****)**
**	****	****	****	****sqrt(<P****b****P****y****>)~26%**
- Minimum Bias data
- To obtain “unbiased” 0 cross section at low pT
- For high pT photon trigger efficiency study

## 0: Pi0 reconstruction

## Photon trigger efficiency for 0

- Data
- MC

- Pi0 efficiency plateaus for pT>4 GeV/c
- Limitted efficiency at      pT<4 GeV/c:
- 	1-2 GeV/c: 6%
- 	2-3 GeV/c: 60%
- 	3-4 GeV/c: 90%
- 	4-5 GeV/c: 95%
- Monte Carlo reproduces Data well

- 0 pT (GeV/c)

## 0 Cross section

- Results consistent with pQCD calculation
- Favours a larger gluon-to-pion FF (KKP)
- Run3 results reproduces Run2 results
- Confirms the Run-3 data reliability and consistency
- Run3 data reaches even higher pTs; results will be finalized soon

- Run-2 results

- 9.6% normalization error not shown

## ALL

- (L) Relative Luminosity
- (P) Polarization
- (N) Number of pi0s

- ++ same helicity
- + opposite helicity

## Relative Luminosity

- Special GL1P scalers used
- Counts live trigger _in each bunch crossing_
- 4 inputs (detectors) – for syst. error study
- Systematic error study through comparison of counts from different detectors
-  look at ratio of 2 detector scalers crossing-by-crossing:
- a(i) = NA(i)/NB(i)
- Ratio should be the same for all crossings (constant) if:
- NA(i) = L  * εA  and   NB(i) = L  * εB
- B is always the counts from the beam-beam counter (BBCLL1), A is one of the other scalers.
- Fit this by the expected pattern:
- a(i) = C[1+ALLP1(i)P2(i)]
- C, ALL are the fitting parameters.
-  2 is a very important check of systematic errors

- ALL vs fill

- 2/NDF  vs (ALL)

- 20

- 30

- 10

- Not so good ... so far, but ...

## Relative Luminosity

- ZDC/BBC vs z-vertex width

- ALL vs fill

- 2/NDF  vs (ALL)

- After vertex correction

- 2

- 3

- 1

- 

- Now 2/NDF1

- Vertex width affects    Rel. Lum. measurements

## Relative Luminosity: Results

- Achieved relative luminosity precision R=2.510-4
- Pessimistic estimation limited by ZDC statistics (30 times less than BBC statistics used in Rel. Lum. measurements)
- Rel. Lum. contribution for pi0 ALL less than 0.2%
- For average beam polarizations of 26%
- ALL of BBC relative to ZDC consistent with 0
- Strong indication that both ALLs are zero (very different kinematical regions)

## Beam Polarization

- Spin direction confirmation
- With Spin Rotators and PHENIX Local Polarimeter
- Confirmed
- Long. component of the spin direction
- PHENIX Local Polarimeter
- Absolute polarization scale
- With RHIC CNI polarimeter
- Estimated to be  ~30%
- This error does not change the significance of non-zero ALL, because it scales both value and error in the same way (but it does change the comparison to theory)

## Spin Long. Component

*S**T* is measured with PHENIX Local Polarimeter

- Up-Down asymmetry

- Left-Right asymmetry

## ALL: Pi0 reconstruction

- 2-3 GeV/c
- Bckgr=17%

- 3-4 GeV/c
- Bckgr=7%

- 4-5 GeV/c
- Bckgr=5%

- 1-2 GeV/c
- Bckgr=45%

- Results obtained for four pt bins from 1 to 5 GeV/c
- Pi0 peak width varies from 12 to 9.5 MeV/c2 from lowest to highest pt bins
- Background contribution under pi0 peak for 25 MeV/c2 mass cut varies from 45% to 5% from lowest to highest pt bins

## Pi0 counting for ALL

**N********0****: **
- 25 MeV/c2 around ***0* peak (and also 15 and 35 MeV/c2 for cross checks)
**N****bck1****: **
- Two 50 MeV/c2 wide areas adjacent to ***0* peak
**N****bck2****: **
- 250 MeV/c2 wide area between  ***0* and ** peaks

| pt
GeV/c | N0
15 MeV/c2 | N0
25 MeV/c2 | N0
35 MeV/c2 | Nbck1 | Nbck2
 |
| --- | --- | --- | --- | --- | --- |
| 1-2 | 1278k | 1777k | 2129k | 1470k | 3478k |
| 2-3 | 874k | 1059k | 1146k | 335k | 989k |
| 3-4 | 176k | 201k | 208k | 27k | 83k |
| 4-5 | 34k | 38k | 39k | 3.9k | 12k |

- N0 and Nbck accumulated statistics

## ALL measurements

- Luminosity approach
- Collect *N* and *L *for ++ and + configurations (sum over all crossings) and calculate ALL for each fill
- Average ALL over fills; use 2/NDF to control fit quality; use “bunch shuffling” to check syst. errors
- Bunch fitting approach (just for consistency check)
- Collect *N* and *L *for each crossing *i* and fit *A**LL* from *N(i)/L(i)=C*{*1+A**LL**P**B**(i)P**Y**(i)*} for each fill; use 2/NDF to control fit quality
- Average ALL over fills ; use 2/NDF to control fit quality; use “bunch shuffling” to use bunch shuffling to check syst. errors

- ++ same helicity
- + opposite helicity

## Luminosity approach

- ALL averaged over fills

- 3-4 GeV/c

- 1-2 GeV/c

- 4-5 GeV/c

- 2-3 GeV/c

- 1-2 GeV/c
- ALL= -2.8%±1.2%
- 2/ndf = 64/48
- 2-3 GeV/c
- ALL= -2.2%±1.5%
- 2/ndf = 34/48
- 3-4 GeV/c
- ALL= -0.2%±3.3%
- 2/ndf = 49/48
- 4-5 GeV/c
- ALL= -2.3%±7.4%
- 2/ndf = 39/48

## Bunch shufflingto check for syst. errors

**Bunch shuffling**to check for syst. errors

- ALL

- 2-3 GeV/c

- All <2/NDF> are ~1

- Bunch shuffling = Randomly assigns helicity for each crossing

- 2/NDF

- 3-4 GeV/c

- 4-5 GeV/c

- 1-2 GeV/c

- Widths are consistent with obtained errors (ALL)

## Luminosity approach: background

- ALL averaged over fills

- 1-2 GeV/c
- ALL= 0.4%±1.0%
- 2/ndf = 47/48
- <2/ndf> = 48/48
- 2-3 GeV/c
- ALL= -2.2%±1.7%
- 2/ndf = 35/48
- <2/ndf> = 50/48
- 3-4 GeV/c
- ALL= 1.9%±5.5%
- 2/ndf = 33/47
- <2/ndf> = 45/47
- 4-5 GeV/c
- ALL= 10%±14%
- 2/ndf = 47/44
- <2/ndf> = 41/44

- 2-3 GeV/c

- 3-4 GeV/c

- 4-5 GeV/c

- 1-2 GeV/c

## ALL results

| pt
GeV/c | N0
15 MeV/c2 | N0
25 MeV/c2 | N0
35 MeV/c2 | Nbck1 | Nbck2
 |
| --- | --- | --- | --- | --- | --- |
| 1-2 | -2.31.4
1.02 | -2.81.2
1.04 | -2.41.1
1.03 | -0.61.4
0.99 | 0.41.0
0.99 |
| 2-3 | -2.71.6
0.99 | -2.21.5
1.01 | -2.21.4
1.03 | -3.52.7
1.01 | -2.21.7
1.05 |
| 3-4 | -1.73.5
1.08 | -0.23.3
1.07 | -0.13.2
1.06 | 9.49.2
0.96 | 1.95.5
0.95 |
| 4-5 | -1.47.9
0.99 | -2.37.4
0.90 | -1.37.3
0.93 | 3824
0.94 | 1014
0.94 |

- ALL (%) and <2/NDF>

## ALL results: plots

- N0
- 35 MeV/c2

- N0
- 15 MeV/c2

- Bck2

- N0
- 25 MeV/c2

- Bck1

## Bunch fitting approach

- 2-3 GeV/c

- 3-4 GeV/c

- 4-5 GeV/c

- 1-2 GeV/c

- 2/NDF from bunch fitting for each fill
- All 2/NDF ~ 1 => no problem seen within fills

- 2/NDF

## ALL from bunch fitting

- ALL averaged over fills

- 2-3 GeV/c

- 3-4 GeV/c

- 4-5 GeV/c

- 1-2 GeV/c

- 1-2 GeV/c
- ALL= -2.8%±1.2%
- 2/ndf = 62/48
- <2/ndf> = 51/48
- 2-3 GeV/c
- ALL= -2.2%±1.5%
- 2/ndf = 35/48
- <2/ndf> = 48/48
- 3-4 GeV/c
- ALL= -0.7%±3.3%
- 2/ndf = 56/48
- <2/ndf> = 56/48
- 4-5 GeV/c
- ALL= -7.2%±7.6%
- 2/ndf = 46/48
- <2/ndf> = 56/48

## Luminosity vs bunch fitting

| pt
GeV/c | N0
Bunch fit | N0
Luminosity |
| --- | --- | --- |
| 1-2 | -2.81.2
1.06 | -2.81.2
1.04 |
| 2-3 | -2.21.5
0.99 | -2.21.5
1.01 |
| 3-4 | -0.73.3
1.17 | -0.23.3
1.07 |
| 4-5 | -7.27.6
1.17 | -2.37.4
0.90 |

- Results are identical at lower pt bins
- Results start deviate at higher pt bins
- Pure statistical effect: too low statistics in each crossings to be used in bunch fitting
- Confirmed from simple MC: deviations may be comparable to stat. error

- We use luminosity approach for final ALL for all pt bins

## Checks

| pt
GeV/c | ++ vs   | +  vs  + |
| --- | --- | --- |
| 1-2 | 0.71.7 | -1.31.7 |
| 2-3 | 0.22.1 | 0.52.1 |
| 3-4 | 6.14.6 | -2.74.6 |
| 4-5 | -8.610.5 | -6.710.4 |

- PID = Shower profile cut

- Consistent with 0 within 1.5

- PID check

| pt
GeV/c | N0
noPID | N0
PID |
| --- | --- | --- |
| 1-2 | -3.11.0 | -2.81.2 |
| 2-3 | -1.91.4 | -2.21.5 |
| 3-4 | -0.43.2 | -0.23.3 |
| 4-5 | -3.97.3 | -2.37.4 |

- ++ vs  and + vs +

- The same results

## AL check for yellow beam

| pt
GeV/c | N0
15 MeV/c2 | N0
25 MeV/c2 | N0
35 MeV/c2 | Nbck1 | Nbck2
 |
| --- | --- | --- | --- | --- | --- |
| 1-2 | 0.10.4 | -0.020.3 | -0.040.3 | 0.20.4 | 0.000.3 |
| 2-3 | 0.10.4 | -0.030.4 | -0.010.4 | 0.20.7 | 0.20.5 |
| 3-4 | 0.70.9 | 1.10.9 | 0.80.9 | -3.32.5 | -1.01.5 |
| 4-5 | -0.12.1 | 0.42.0 | 0.82.0 | 2.06.4 | 5.03.9 |

- AL (%)

- All are zeros within 1.5 except

## AL check for blue beam

| pt
GeV/c | N0
15 MeV/c2 | N0
25 MeV/c2 | N0
35 MeV/c2 | Nbck1 | Nbck2
 |
| --- | --- | --- | --- | --- | --- |
| 1-2 | -0.060.4 | 0.060.3 | 0.000.3 | -0.20.4 | -0.020.3 |
| 2-3 | 0.10.4 | 0.000.4 | 0.20.4 | 0.90.7 | 0.010.5 |
| 3-4 | 0.40.9 | 0.60.9 | 0.60.8 | -0.42.4 | -3.61.5 |
| 4-5 | -2.42.1 | -1.62.0 | -1.61.9 | -1.16.2 | 1.33.8 |

- AL (%)

- All are zeros within 1.5, except

## 0 ALL from pp at 200 GeV

| pT
GeV/c | 
(rbck) |  | 
(Background subtracted) |
| --- | --- | --- | --- |
| 1-2 | -0.0280.012 (45%) | -0.0060.014 | -0.0460.025 |
| 2-3 | -0.0220.015 (17%) | -0.0350.027 | -0.0190.019 |
| 3-4 | -0.0020.033 (7%) | 0.0940.092 | -0.0090.036 |
| 4-5 | -0.0230.074 (5%) | 0.380.24 | -0.0450.079 |

- Polarization scaling error ***P/P *~30%: is not included
- Analyzing power AN(100 GeV) = AN(22GeV) is assumed
***P/P*~30%: combined stat. and syst. error for AN(22GeV) (AGS E950)

## Summary

- First Pi0 ALL results from long. polarized pp collisions with average beam polarizations of 26% presented
- Results presented in four pT bins in the range 1-5 GeV/c
- ALL sensitivity in the lowest pT bin (1-2 GeV/c) is 1.2%
- 2.5 (1.5 ) effect seen at 1-2 GeV/c (2-3 GeV/c) bin