PHENIX local polarimeter @ RUN9

2009/03/30 @ RHIC meeting

Manabu Togawa for the PHENIX

1

Leading neutron asymmetry from polarized pp collision

• Discovered at ZDC kinematics, ±2.8 mrad, in RHIC RUN2. – -10% level in forward kinematics

– Consistent with zero in backward

2

RL

RLN

dd

ddA

Interaction

LR definition

RUN 2

Asymmetry for neutron ID sample

Phys. Lett. B650 : 325-330 (2007)

150

unit:mm

100

Hadronshower

5

PHENIX Setup

3

ZDC(Zero Degree Calorimeter)

10*10cm ±2.8 mrad

3 modules150X0 5.1λI

SMD

1 ZDC

SMD(Shower Max Detector)

Neutron position can be decided by centroid method.

Dx magnet

Slat :7 for x-position8 for y-position

Data set for PHENIX local pol.• DAQ mode (offline)

Good neutron ID (taking with BBC trigger)

Can see phi-dependent

trigger is DAQ band limit (8-10 kHz as maximum)

need time to analysis

• Scaler mode

Many statistics without DAQ band width

Get result rapidly

can be high BG

need to start PHENIX DAQ so far (for clock sync.)

4

Detector(ZDC,SMD)

FEM DAQ

LL1 scaler(FPGA)

Start (clock sync.)

ADC, TDCCharge

SMD : hit map according to TDC hit

Until RUN8, we have done LP with DAQ mode.From RUN9, scaler mode is implimented.

Accumulating data in each 5 mins. (to DB)

* SMD is standby mode except for collision due to the high BG before collimation

DAQ modePhi-dependent asymmetry @ RUN9

5

From first transverse collision at PHENIX, Fill#10228 (2/25)

BBCLL1&(ZDCN|S) ~20 M evtsBy square root formula

Blue forward

Blue backward

Yellow forward

Yellow backward

Local pol. scaler

• Threshold for making pattern– 20 MIP equivalent

– High threshold is expected to select neutron

New!

SMD scintillators for x (7 scnti.)

LEFT RIGHT

Bottom

TOP

SMD scintillators for y (8 scinti.)

Hit patterns are sent by fibers

Make hit pattern by TDC in FEM(with high threshold) ZDC

LL1

Make scaler in ZDC LL1 board4 patterns ×2 (N or S) ×120 channels , 20 bits in each!

Local pol. scaler is developing by : Cheng-Yi Chi, Ed Desmond, Yuji Goto, John Haggerty, John Lajoie and Manabu Togawa

6

Scaler counts(Fill#10454)

- 5 mins data (2009/03/29 15:50-55)- Small BG can be confirmed by unfilled bunch

7

Blue : unfilled + yellow : filled

Blue : filled + yellow : unfilled

Background not related to collision is very low, 10-3 level for beam gas.

Fill#10371 (transverse pol.)

5 mins data

RED : yell pol. ↑ BLUE : yell pol. ↓ RED : blue pol. ↑ BLUE : blue pol. ↓)()(

)()(

TRBL

TRBL

NN

NNA

Systematic study by unpol. beam

• Unpolarized beam was delivered as Fill#10372– Cross check for all polarimeters.

– Asymmetries in DAQ mode (phi-dependent asymmetry) and scaler mode were consistent with zero.

9

DAQ mode : Fill#10372 (unpol.)

10

Blue forward

Blue backward

Yellow forward

Yellow backward

Scaler mode : Fill#10372 (unpol.)RED : yell pol. ↑ BLUE : yell pol. ↓ RED : blue pol. ↑ BLUE : blue pol. ↓

Time dependent @ transverse data• From data, polarization is same

bunch-by-bunch

• Fit by following parameters with spin pattern– Blue asymmetry

– Yellow asymmetry

– Detector asymmetry

• In this case,– Blue backward asymmetry

– Yellow forward asymmetry

– Detector asym. in SOUTH ZDC12

Cross#

Measured @ SOUTH

RED : yell pol. ↑ BLUE : yell pol. ↓

Fill#10288

• Extract from SOUTH measurement– Yellow forward asym.

– Blue backward asym.

– Detector asymmetry in SOUTH

• 2/25 3:00-7:00

13

Fill#10325• Extract from SOUTH

measurement– Yellow forward asym.

– Blue backward asym.

– Detector asymmetry in SOUTH

• 3/10 0:00-11:00

• We have small asymmetry in first 3-4 hours.– High BG from collision related?

– Collision angle has been changing?

– Situation was changed fill by fill.

– For asymmetry value, we took flat region. 14

pC vs PHENIX Loc. Pol.Polarization (%), not normalized (!) vs fill

Raw asymmetry (%)

Online Polarization (%), not normalized (!) vs fill

Ratio

2/NDF=21/102/NDF=14/9

Fill-by-fill systematics

From Sasha’s slide

To longitudinal run

• First beam with rotator on was delivered as fill#10382.

16

phi asymmetry (Fill#10382)

Value@transversefor BLUE: 0.072±0.004

BLUE forward

BLUE backward

Yellow forward

Yellow backward

Value@transversefor YELLOW : 0.079±0.005

17

Scaler (Fill#10382)

18

RED : yell pol. ↑ BLUE : yell pol. ↓ RED : blue pol. ↑ BLUE : blue pol. ↓

First rotator ON : Fill#10382

Raw asym./CNI pol. BLUE YELLOW

@ Transverse 0.072±0.004 0.079±0.005

@ Rotator ON 0.011±0.002 0.005±0.002

Transverse component 15±3 % 6±3 %

From phi fit (only amplitude)

From the scaler

Raw asym./CNI pol. BLUE YELLOW

@ Transverse 0.0338 0.0379

@ Rotator ON : LR 0.0015 0.0004

@ Rotator ON : UD 0.0039 (11.5%) -0.0020

Transverse component 12.4 % 5.4 %

19

Offline and scaler asymmetries are consistent Switch to physics data taking at PHENIX

Rotator tune at Fill#10399

• Rotator feed back during fill : Successfully

20

Rotator current was changed

Summary• PHENIX LP work is successful.

– Scaler mode works well, consistent with offline analysis.

• Asymmetry is not correct, typically smaller, in the begging of fill due to

– High backgroud collision related?

– Beam orbit or collision angles are changed? (also appears in detector asymmetry)

– First longitudinal data looks transverse component is remained at BLUE beam (radial direction)

• Feed back is successful during fill.

• Now it is back to original one due to blue pol. life time.

21

Decrease during blue pol.?Fill#10439

22Increase BG after CNI measurement

Detector asymmetryhas been changed during fill

23Increase BG after CNI measurement

backup

24

Event structure study using pythia input.@ 200 GeV

pid pid

1 Gamma 10 K0 long

2 Positron 11 K+

3 Electron 12 K-

5 Mu+ 13 Neutron

6 Mu- 14 Proton

8 Pi+ 15 Antiproton

9 Pi- 25 Antineutron

Black : sumGreen : gammaBlue : neutronRed : proton

n

p

ZDC threshold is ~5GeV

25

Detector asymmetry

26

Raw

asy

mm

etry Blue forward

Blue backward

Yellow forward

Yellow backward

Luminosity asymmetry~ 0.5-1.5%

Detector asymmetries are up to 50%, but it is cancelled according to backward asymmetry.

ZDC energy distribution with high threshold cut for SMD (in ZDCN|S sample @ RUN5 data)

• SMD threshold corresponds to 20 MIP– With high SMD cut can be help to select neutron sample.

• BG1 : photon will stop at 1st module; not hit SMD.• BG2 : proton event is only distributed low energy region. 27

NORTHSOUTH

Bottom cut Top cut

Left cut Right cut

Bottom cut Top cut

Left cut Right cut

Measured energy in ZDC (GeV)

70 GeV

Raw asymmetry for Fill#10228

28Crossing#

(NL-N

R)/

(NL+

NR)

(NB-N

T)/

(NB+

NT)

Measured @ SOUTH LR Measured @ NORTH LR

Measured @ SOUTH TB Measured @ NORTH TB