# Presentation: 342210

##  Double Longitudinal Spin Asymmetry in Polarized pp Collisions at  ..   = 200 GeV

- Kieran Boyle (Stony Brook U.)
- for
- the PHENIX Collaboration

## Motivation

- Hard Scattering Process

- with    ~20%, g, L unknown

- How to measure g:

- 0

- ~ agg * g2 + bgq * g + cqq

## ALL Requirements

- PHENIX
- 0 Cross section
- Relative Luminosity (R=L++/L+-)
-  R=1.0e-4
- (Local) Polarimetry
- ALL
- Method
- Result

- ++ same helicity
- + opposite helicity

## PHENIX Detector

- detection
- Electromagnetic Calorimeter:
- High pT photon trigger to collect 0's
- Acceptance: x 
- High granularity (~10*10mrad2)
- Relative Luminosity
- Beam Beam Counter (BBC)
- Acceptance: 3.0< 3.9
- Zero Degree Calorimeter (ZDC)
- Acceptance: ±2 mrad
- Local Polarimetry
- ZDC

- PbSc

- PbGl

##  Mass Spectrum

## Run5 0 Cross Section

- Consistent with previous results.
- Extends previous results to pT of 20 GeV/c.
- Theory is consistent with data over nine orders of magnitude.

## Relative Luminosity

- Number of BBC triggered events used to calculate Relative Luminosity.
- For estimate of Uncertainty, fit
- 	where

-  R=1.0e-4
-  ALL=2.3e-4
-  ALL of BBC to ZDC consistent with zero

## Local Polarimetry at PHENIX

- Use ZDC to measure a L-R and U-D asymmetry in forward neutrons.
- When transversely polarized, we see clear asymmetry.
- When longitudinally polarized, there should be no asymmetry.

**BLUE**

**YELLOW**

**Raw asymmetry**

**Raw asymmetry**

****

****

- Idea:  Use neutron asymmetry to study transversely polarized component.

## Measured Asymmetry                                     During Longitudinal Running

- <PT/P>=
- 10.25±2.05(%)
- <PL/P> =
- 99.48±0.12±0.02(%)
- <PT/P>=
- 14.47±2.20(%)
- <PL/P> =
- 98.94±0.21±0.04(%)

- Fill Number

- Fill Number

## Calculating ALL

- Calculate ALL(+BG) and ALL(BG) separately.
- Get background ratio (wBG) from fit of all data.
- Subtract ALL(BG) from ALL(+BG):
- 	ALL(+BG) = w· ALL() + wBG · ALL(BG)

- +BG region :
- 	±25 MeV around
- peak
- BG region :
- 	two 50 MeV regions
-  	around peak

## Fill by Fill ALL

## Bunch shuffle

- Randomly reassign helicity for each fill and recalculate asymmetry.
- Do 1000 times and look at distribution.
- Agree with expected distribution
- Bunch to bunch systematics smaller than current statistics.

- 5<pT<6 GeV/c   6<pT<7 GeV/c    7<pT<8 GeV/c     8<pT<9 GeV/c

- 1<pT<2 GeV/c   2<pT<3 GeV/c    3<pT<4 GeV/c     4<pT<5 GeV/c

## AL consistent with zero

## 0 ALL

- Comparison with previous Runs
- Confidence levels:
- Run3 : 17.6 %
- Run4 : 18.7 %
- They are consistent.  (Scale error is not considered.)

| Run | Int.Lum. | Pol. | Figure of Merit (P4L) |
| --- | --- | --- | --- |
| Run 3 (2003) | 220nb-1 | 27% | 1.17nb-1 |
| Run 4 (2004) | 75nb-1 | 40% | 1.92nb-1 |
| Run 5 (2005) | 1.8 pb-1 | 47% | 87.8nb-1 |

## Comparison with theory

- GRSV:  M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775.

-  ̈

| Theory model | C.L. (%) |
| --- | --- |
| GRSV-std | 17.1-21.7 |
| *GRSV-max
(g=g) | 0.0-0.0 |
| *GRSV g=0 | 16.7-18.4 |
| *GRSV g=−g | 0.0-0.7 |

- * At input scale:       Q2 = .4 GeV

## Values for ALL and AL

| pT (GeV/c) | pT mean (GeV/c) | ALL (%) | AL (%) | ALL (Run-3) | ALL (Run-4) |
| --- | --- | --- | --- | --- | --- |
| 1-2 | 1.56 | 0.08±0.15 | -0.06±0.05 | -2.7±1.3 | 0.0±0.9 |
| 2-3 | 2.38 | -0.17±0.16 | -0.09±0.06 | -1.3±1.3 | 0.7±1.0 |
| 3-4 | 3.36 | 1.05±0.34 | 0.05±0.12 | -1.7±2.8 | -1.8±2.2 |
| 4-5 | 4.38 | -0.05±0.77 | 0.13±0.27 | 0.7±6.2 | 9.7±4.9 |
| 5-6 | 5.40 | -0.41±1.55 | -0.45±0.55 | -- | -- |
| 6-7 | 6.41 | 2.03±2.80 | 0.52±1.00 | -- | -- |
| 7-8 | 7.42 | -2.92±4.58 | -0.12±1.62 | -- | -- |
| 8-9 | 8.44 | -0.43±7.17 | 0.25±2.53 | -- | -- |

|  | 2 | NDF | C.L. (%) |
| --- | --- | --- | --- |
| Run-3 (pT<5GeV/c) | 6.33 | 4 | 17.6 |
| Run-4 (pT<5GeV/c) | 6.16 | 4 | 18.7 |
| GRSV standard | 10.8 | 8 | 17.1-21.7 |
| *GRSV maximum (G = G) | 156.37 | 8 | 0.0-0.0 |
| *GRSV G=0 | 11.49 | 8 | 16.7-18.4 |
| *GRSV G=-G | 40.86 | 8 | 0.7-0.0 |
| ALL=0 | 11.94 | 8 | 15.4 |

- * At input scale:       Q2 = .4 GeV

## Conclusions

- We measured cross section and double helicity asymmetry ALL in 0 production from Run5 pp collision.
- The results of ALL are consistent with Run3/4.
- The data are compared with theoretical models.
- Run5 conclusively excludes GRSV maximal scenarios.
- Data consistent with GRSV standard and   GRSV G = 0.

## Backups

## Photon Trigger Efficiency

| Detector  | 1<pT<2 GeV/c | 2<pT<3 GeV/c | 3<pT<4 GeV/c | pT> 4GeV |
| --- | --- | --- | --- | --- |
| PbSc | 6% | 50% | 81% | 88% |
| PbGl | 21% | 72% | 87% | 90% |

## Distinct and Merged Photons

## Minimum Bias (BBC |z|<30)
Minimum Bias in coincidence with High Energy Photon trigger (Cluster Energy>1.4GeV)

- Minimum Bias in coincidence with High Energy Photon trigger (Cluster Energy>1.4GeV)

- Cross Section consistant with Run3 result.

## Yellow Beam

- LR

- LR

- UD

- UD

- XF>0

- XF>0

- XF<0

- XF<0

- 2/NDF = 68.1/97
- p0 = -0.00226±0.00069

- 2/NDF = 119.3/97
- p0 = 0.00727±0.00060

- <PT/P>=
- 14.47±2.20(%)
- <PL/P> =
- 98.94±0.21±0.04(%)

- 2/NDF = 82.3/97
- p0 = -0.00067±0.00064

- 2/NDF = 83.0/97
- p0 = -0.00089±0.00061

## RHIC

**AGS**

**LINAC**

**BOOSTER**

- Pol. Proton Source
- 500 A, 300 s

**Spin Rotators**

- Partial Siberian Snake

- Siberian Snakes

- 200 MeV Polarimeter

- AGS Internal Polarimeter

- Rf Dipoles

- RHIC CNI (pC) Polarimeters

- Absolute Polarimeter
-              (H jet)

- 2  1011 Pol. Protons / Bunch
-  = 20  mm mrad

- RHIC accelerates polarized protons to (presently) 100 GeV

## 0 Production