# Presentation: 547529

##            STAR Spin Analysis Update

-                  Stephen Trentalange

## Beam-Beam Counters 

**            ********BBC********~ 50% of ********tot ****(pp) = 26 mb  Large!**
**- **Van der Meer scans at RHIC ( Run2 and Run3 data)
-   are consistent with Geant simulations for STAR**   **

**~2m**

**~0.5m**

-    18 pixels (16 PMT)  covering **3.3<|********|< 5.0 and  0<******** <2******
-    - **azimuthal segmentation !**

_**Small hexagonal annulus**__**:**_

**ADC (PMT Sum) **

**Data**
**MC**

**Data and MC agree**

**A coincidence condition between BBC East and West -**
**suppresses beam-gas background and used for:**
**       ****-  triggering in pp (minimum bias, jet triggers), **
**       ****-  (relative) luminosity measurements **
**       ****-  local polarimetery**

- Beam-Beam Counters

**- scintillator annulus** installed around the beam pipe,  on the east and  west poletips of STAR magnet at ±3.74m  from IR for _detection of charged particles in forward region_ 2 < || < 5

## Transverse Single Spin Asymmetries

**                                                                                                                     **
- Number of counts from the BBC (L,R,T,B) sorted by beam polarization states
- _Example_:**  ****Polarized Yellow beam**   (sum over  Blue beam polarization states)
-      heads towards **BBC East**

**BBC West**

**BBC East**

**Left**

**Right**

**Top**

**Bottom**

- X

**Interaction Vertex**

- +

**RHIC CNI polarimeter**

- +

- N L(R,T,B)  -nr of counts from BBC East or West in Left, Right, Top, Bottom part counted every bunch crossing by scaler system ]

**Zero at RHIC**
**(Vertical pol)**

## Local Polarimetry 

**  **Spin rotators worked as designed and stable,
-   BBC worked very well as a local polarimeter
-                         - vertical and radial polarization components  smaller than 3%
**   ****Longitudinal polarization for the first time!**

**       ****Blue beam,  BBC West**** **

**Run#**

**Run#**

- Local Polarimetry

**Rotators ON**

**OFF**

**   ****Rotators                                         OFF                   ON**
**   ****CNI polarimeter                            non-zero           non-zero**
**   ****BBC Left-Right     ( vertical )       NON_ZERO       ZERO****    **
**   ****BBC Top-Bottom  ( radial    )       zero                   zero****         **

**    ********    ****CNI (ON-LINE)**
**    ********LR**** BBC  =   0.13(2)**
**    ********TB**** BBC  = -0.24(2)**

**      ****Measured asymmetry**

**      ****Yellow beam,  BBC East**

**    ********    ****CNI (ON-LINE)**
**    ********LR**** BBC**** ****= - 0.07(2)**
**    ********TB**** BBC = - 0.04(2)**

**drop**

**drop**

**CNI**

**CNI**

**BBC**

**BBC**

**Rotators ON**

**OFF**

- Joanna Kiryluk

##      Transverse Single Spin Asymmetries – Preliminary Results

**     **Transverse Single Spin Asymmetries – Preliminary Results

**Left-Right**** ****BBC asymmetry **
** ****( ****Vertical**** P****beam**** component )   **

**Top-Bottom**** ****BBC asymmetry **
** ****( ****Radial**** P****beam**** component )   **

** ****Blue Beam**

** ****Yellow Beam**

** ****Blue Beam**

******(CNI)**

******(CNI)**

******(CNI)**

******(CNI)**

**Ratio:**** ********(BBC East)/******** (CNI) **
**consistent with **
** ********(BBC West)/******** (CNI)**
**We get:**
**A****N****(BBC)=0.0066(8)**
**Stat. error only!**
** ****using: A****N****(CNI) = 0.0118 (10)**
**from CNI online analysis**

**    ****Yellow Beam**

**    ****BBC East**

**    ****BBC East**

**    ****BBC West**

**    ****BBC West**

- 5 effect
-  may be a result of a broken snake?

- Consistent with zero
- - as expected for vertical polarization

**P~24%**

**P~24%**

******(BBC)**

******(BBC)**

******(BBC)**

******(BBC)**

- Joanna Kiryluk

## Relative Luminosity - Motivation

- N i   where  i=++, +-    are spin dependent yields
-                -   relative luminosity of bunch crossings with
-                        different spin directions

- Requirements for a  luminosity process/detector:
-   -  high rates
-   -  small background
-   -  no  (or small)  spin dependence

- Assumption:   ALL = 0.01

**R=0.7**

**R=1.3**

-   Double spin longitudinal asymmetry (e.g.  p+p -> jet + X )  is defined as:

- ALL / ALL

- 0.07

- 0.01

- 10-4

- 10-3

- Relative luminosity  -  one of the dominant systematic errors in ALL measurement  It  must be known at (least) 10-3  level

## Relative Luminosity - Measurement

- BBC E.W coincidence counts

- bunch crossing#

- abort gaps (beam-gas background)

-    - RHIC filled with 55 - transversly polarized -  proton bunches,
-    - spin orientation related to the bunch crossing number 1-120,  **polarization  pattern at STAR**:

- Spin Up        Spin Down      Unpolarized

**Blue ****      ****                              ****Yellow**

- Time [Run Number]

-     Relative Luminosity

- Run 4150010

- and time dependent!

** **integrated luminosity (number of BBC E.W counts ) recorded every 5 minutes  - scaler board system
-  relative luminosities calculated for each STAR run, which typically lasts from a few minutes to ~ hour
-  statistical   uncertainty  Rstat~ 10-4 – 10-3

** **05/16/03                                                05/30/03

**1.0**

- Joanna Kiryluk

## Relative Luminosity – Systematics

- Run#

- Contribution to systematic uncertainty on R   R(sys) ~ 0.004 x 0.2 ~ 8 x 10-4
- - **must correct for background**

- Yellow beam-gas bg
- Blue beam-gas bg

**Bg/2 [%]**

- Beam-Gas Background Contribution

**0.2**

- Joanna Kiryluk

## Summary

**Single transverse spin asymmetry measured with the Beam Beam Counters**  in 2003  were found to be** A****N****(BBC)=0.0066(8)**  using AN(CNI)=0.0118(10) from CNI online analysis.  Systematic studies in progress.
- The BBC was used to tune  spin rotators needed to get longitudinally  polarized beams at STAR IP and to monitor on-line transverse and radial beam polarization components. They are found to be small:  Prad(vert) < 3%.
- 3.    The BBC in STAR is a good luminosity monitoring detector. **The relative luminosity  is known at the level of ~ 3 x10****-3**
-       -   statistical uncertainty: 10-4 –10 -3
-       -  (conservative) systematic uncertainty (BBC and ZDC comparison) ~ 3 x 10-3
-               This needs further studies (background contribution)

- Joanna Kiryluk

## 2003 Detector Configuration

**STAR**

**EndCap**
**EMC (1/3)**

**BBC**
**West**

**EMC **
**(Half) **
**Barrel**

**BBC **
**East**

**TPC**

**EMC **
**Full **
**Barrel**
**2005**

**   ****Full**
**EndCap**
**  ****2004**

## Leading Jet Asymmetries are Sensitive to Gluon

- Best Fit to DIS Data

-     Max Allowed Gluon Polarization

- Simulations by  Les Bland

- Simulation based on Pythia
- Use Fast TPC and EMC Simulators
- EMC+TPC Jets Reconstructed using Cone Algorithm
- Includes Jet-Patch Trigger ( ET > 5)  covering the Full Half Barrel Calorimeter
- ALL includes all jet processes (not a direct measure of delta G)

**Notes:**
Gluck-Reya-Stratmann-Vogelsang 
GRSV-std- Best fit to previously measured polarized and unpolarized quark structure functions

## pp Longitudinal Data Set

## Jet Finder (Mike Miller/Thomas Henry)

- Using an Iterative, Midpoint, Cone Algorithm
- Cone Angle = 0.7 in eta-phi
- Seed Energy = 0.5 GeV
- pT Track > 0.1 GeV
- Track Range = +/- 1.6
- pT Jet > 5 GeV
- Z = +/- 75 cm

- For this Analysis, Jets are defined as a grouping of one
- or more (charged) Tracks measured in the TPC and satisfying
- the  following requirements...

## TPC Jet Characteristics – EMC Trigger

- Select 0.2 < eta < 0.8 for Analysis

- EMC points

- Strong Trigger Bias at low ET

- TPC Tracks

- Total

- Ratio of EMC to Charged Et

## Longitudinal Spin Asymmetries

*REQUIRES* luminosity ratios to be measured much more accurately than desired asymmetry

- Violates Parity

- Does Not Violate Parity

- momentum

- spin

**Notes:**
Physics asymmetries cannot be measured to a
higher accuracy than the measurements of relative
luminosity

## TPC-Jet, Single-Spin Asymmetries

- Parity-Violating Asymmetries are Consistent with Zero

- Blue Beam

- Yellow Beam

- Run (time)

- Dylan Thein

## 2003 Outlook

| Data | Statistical Precision on LL |
| --- | --- |
| TPC Jets | +/- 0.057 |
| EMC+TPC Jets | +/- 0.030 |