The First Measurement of the Elastic pp-scattering Spin Parameters at s=200 GeV

I.G. Alekseev for pp2pp Collaboration

S. Bűeltmann, I. H. Chiang, B. Chrien, A. Drees, R. Gill, W. Guryn*, D. Lynn, J. Landgraf, T.A. Ljubičič, C. Pearson, P. Pile, A. Rusek, M. Sakitt, S. Tepikian, K. Yip:

Brookhaven National Laboratory, USA

J. Chwastowski, B. Pawlik: Institute of Nuclear Physics, Cracow, Poland

M. Haguenauer: Ecole Polytechnique/IN2P3-CNRS, Palaiseau, France

A. A. Bogdanov, S.B. Nurushev, M.F Runtzo, M.N.Strikhanov: Moscow Engineering Physics Institute (MEPHI), Moscow, Russia

I. G. Alekseev, V. P. Kanavets, L.I. Koroleva, B. V. Morozov, D. N. Svirida: ITEP, Moscow, Russia

A.Khodinov, M. Rijssenbeek, L. Whithead, S. Yeung: SUNY Stony Brook, USA

K. De, N. Guler, J. Li, N. Őztűrk: University of Texas at Arlington, USA

A. Sandacz: Institute for Nuclear Studies, Warsaw, Poland

*spokesperson

RSC 2006, RIKEN, September 29-30, 2006

Results of 2003 run – 10 hours of data taking

*=10m

Igor Alekseev (ITEP) for pp2pp 2

Helicity amplitudes for spin ½ ½ → ½ ½Helicity amplitudes for spin ½ ½ → ½ ½

Matrix elements:

Useful notations:

Formalism is well developed,

however not much data ! At high energy only AN measured to some extent.

Matrix elements:

Useful notations:

Formalism is well developed,

however not much data ! At high energy only AN measured to some extent.

||,

||,

||,

||,

||,

5

4

3

2

1

Mts

Mts

Mts

Mts

Mts

spin non–flip

double spin flip

spin non–flip

double spin flip

single spin flip

031Im4

ttot s

02Im8

tT s

031Imπ8

σσσΔ

tL s

Observables: cross sections and spin asymmetries

25

24

23

22

212

||4||||||||2

sdt

d

4321*52 Im

4),(

sdtd

tsAN

NA

.

31

31

)(21

)(21

),(),(),(

Asympti

Ri

hadi

hadi

emii tststs

4*32

*1

2

52Re2

4),(

sdt

dtsANN

NNA also ASS, ASL, ALL

Igor Alekseev (ITEP) for pp2pp 3

AN & Coulomb nuclear interferenceAN & Coulomb nuclear interference

The left – right scattering asymmetry AN arises from the interference ofthe spin non-flip amplitude with the spin flip amplitude (Schwinger)

In absence of hadronic spin – flip Contributions AN is exactly calculable (Kopeliovich & Lapidus)

Hadronic spin- flip modifies the QED ‘predictions’. Hadronic spin-flip isusually parametrized as:

The left – right scattering asymmetry AN arises from the interference ofthe spin non-flip amplitude with the spin flip amplitude (Schwinger)

In absence of hadronic spin – flip Contributions AN is exactly calculable (Kopeliovich & Lapidus)

Hadronic spin- flip modifies the QED ‘predictions’. Hadronic spin-flip isusually parametrized as:

emflipnon

hadflip

hadflipnon

emflipN CCA **

21

1)p pp

tot

needed phenomenological input: σtot, ρ, δ (diff. of Coulomb-hadronic phases), also for nuclear targets em. and had. formfactors

hadhad

p

had

m

tr 3155 2

1

Im

Igor Alekseev (ITEP) for pp2pp 4

Polarized cross-sections and spin parametersPolarized cross-sections and spin parameters

- single spin asymmetry. - cross-section for one beam fully

polarized along normal to the scattering plane.

- double spin asymmetry. + - cross-section for both

beams fully polarized along the unit vector normal to the scattering plane.ASS has the same definition as ANN, but + is a cross-section for both beams fully polarized along the unit vector in the scattering plane along axis :

, where - beam momentum.

Cross-section azimutual angular dependence for transversely polarized beams:

- blue beam polarization vector - yellow beam polarization vector

- single spin asymmetry. - cross-section for one beam fully

polarized along normal to the scattering plane.

- double spin asymmetry. + - cross-section for both

beams fully polarized along the unit vector normal to the scattering plane.ASS has the same definition as ANN, but + is a cross-section for both beams fully polarized along the unit vector in the scattering plane along axis :

, where - beam momentum.

Cross-section azimutual angular dependence for transversely polarized beams:

- blue beam polarization vector - yellow beam polarization vector

NA

n

NNA

n

|| pn

pns

s

p

))(())(()(10 sPsPAnPnPAnPPA YBSSYBNNYBN

BP

YP

Igor Alekseev (ITEP) for pp2pp 5

AN measurements in the CNI regionAN measurements in the CNI region

pp Analyzing Power

no hadronicspin-flip

E704@FNALp = 200 GeV/cPRD48(93)3026

pC Analyzing Power

with hadonicspin-flip

no hadronicspin-flip

Re r5 = 0.088 0.058

Im r5 = 0.161 0.226

highly anti-correlated

E950@BNLp = 21.7 GeV/cPRL89(02)052302

Igor Alekseev (ITEP) for pp2pp 6

AN @ 100 GeV from RHIC HJetAN @ 100 GeV from RHIC HJet

Re r5 = 0.0008 0.0091

Im r5 = 0.015 0.029

highly anti-correlated

p = 100 GeV/cPLB638(06)450

Igor Alekseev (ITEP) for pp2pp 7

The setup of PP2PPThe setup of PP2PP

221121 yxyxpp

,,

Igor Alekseev (ITEP) for pp2pp 8

Si detector packageSi detector package

• 4 planes of 400 µm Silicon microstrip detectors: 4.5 x 7.5 cm2 sensitive area; 8 mm trigger scintillator with two PMT readout behind

Silicon planes.• Run 2003: new Silicon manufactured by Hamamatsu

Photonics. • Only 6 dead strips per 14112 active strips.

• 4 planes of 400 µm Silicon microstrip detectors: 4.5 x 7.5 cm2 sensitive area; 8 mm trigger scintillator with two PMT readout behind

Silicon planes.• Run 2003: new Silicon manufactured by Hamamatsu

Photonics. • Only 6 dead strips per 14112 active strips.

Trigger Scintillator

Al strips:512 (Y), 768 (X),

50µm wide100 µm pitch

implanted resistors

bias ring guard ring

1st stripedge: 490 µm

SiSi Detector boardDetector board

LV regulationLV regulation

Michael Rijssenbeek

SVX chipsSVX chips

Igor Alekseev (ITEP) for pp2pp 9

Elastic events selectionElastic events selection

Hit correlations before the cuts

Note: the background appears enhanced because of the “saturation” of the main band

• Only inner roman pots were used.• “OR” of X and Y silicon pairs in each roman pot was used.

• A match of hit coordinates (x,y) from detectors on the opposite sides of the IP was used to select elastic events.

•Elastic events loss due to selection criteria < 3.5%

•Total number of elastic events selected 2.3·106

t-range

Igor Alekseev (ITEP) for pp2pp 10

Calculation of asymmetry ANCalculation of asymmetry AN

)()()()(

)()()()(

)(1

cos)()(

NNNN

NNNNAPP NYBN

)sincos(cos)(12 222

SSNNYBNYB AAPPAPP

dt

d

dtd

d

)()()()(

)()()()(

)(1

cos)()(

NNNN

NNNNAPP NYBN

103.0)sincos()( 22 NNSSYB AAPP

Polarized crossection:

Square root formula:

where

Beam polarization: (PB+PY)++/-- = 0.88±0.12, (PB - PY)+-/-+ = -0.05±0.05

Crosscheck:

`N (predicted) (PB - PY)+-/-+AN -0.0011 `N (measured)=-0.0016±0.0023

Igor Alekseev (ITEP) for pp2pp 11

Single spin asymmetry ANSingle spin asymmetry AN

|t|-range, (GeV/c)2

<|t|>, (GeV/c)2

AN stat

0.010-0.015 0.0127 0.0277 0.0061

0.015-0.020 0.0175 0.0250 0.0043

0.020-0.030 0.0236 0.0178 0.0030

0.010-0.030 0.0185 0.0212 0.0023

Arm A Arm B

Statistical errors only

Raw asymmetry N for 0.01<|t|<0.03 (GeV/c)2

Sources of systematic errors

background 4.5%

beam positions at the detectors

1.8%

corrections to the standard transport matrices

1.4%

uncertainties on Lxeff and Ly

eff 6.4%

neglected term with double-spin asymmetries

2.8%

All above 8.4%

Beam polarization error 17.0%S. Bűeltmann et al.

Phys. Lett. B632(2006)167

Igor Alekseev (ITEP) for pp2pp 12

Fit r5Fit r5

22

5555

12

ImRe2]ImRe21[

tt

tt

rrtt

rr

m

ttA

cc

c

N

where tc = -8πα / σtot

κ is anomalous magnetic moment of the proton

N. H. Buttimore et. al. Phys. Rev. D59, 114010 (1999)

Only statistical errors shown

Re r5 = -0.033 ± 0.035 Im r5 = -0.43 ± 0.56

no hadronic spin flip

our fit

hadhad

p

had

m

tr 3155 2

1

Im

Igor Alekseev (ITEP) for pp2pp 13

Calculation of double spin asymmetriesCalculation of double spin asymmetries

))(sin)(cos(

/)(/)(/)(/)(

/)(/)(/)(/)()(

22

NNSSYB AAPP

LNLNLNLN

LNLNLNLN

External normalization using the machine bunch intensities:

Lij~I

i

B·Ij

Y

on bunches with given i,j combination

Raw asymmetry:

E.Leader, T.L.Trueman“The Odderon and spin

dependence of high-energy proton-proton

scattering”, PR D61, 077504 (2000)

2/+=0.05(1+i)

i

Igor Alekseev (ITEP) for pp2pp 14

Statistical errors only

PRELIMINARY

PB·PY=0.198 ± 0.064 Asym|scale=32%

Distributions () were fitted with

(P1·sin2+ P2·cos2):

P1=PB·PY·ASS, P2=PB·PY·ANN

and

((P3–P4)·sin2+(P3+P4)·cos2):

P3=PB·PY·(ANN+ASS), P4=PB·PY·(ANN–ASS)

and

(P5+C·t·cos2):

P5=PB·PY·ASS, C·t=PB·PY·(ANN–ASS)

Raw double spin asymmetriesRaw double spin asymmetries

Igor Alekseev (ITEP) for pp2pp 15

r2 and r4r2 and r4

At collider energies:

Igor Alekseev (ITEP) for pp2pp 16

r2 and Tr2 and T

Im r2 = 0.0019±0.0052Im r2 = 0.0019±0.0052

At t0=–0.01 (GeV/c)2: (–t0/tc)=0 and ASS=0.0037±0.0104

Im r2 = 0.0019±0.0052 and T = –0.19±0.53 mb

If we assume that only Regge cuts contribute to 2 and 4 then phase of 2 is 90o shifted to the phase of + (Pomeron-Odderon cut exchange).

Re r2 = –0.025±0.065

Our results support predictions of none or weak spin coupling of the Odderon

T.L. Trueman hep-ph/0604153

N.H. Buttimore et el.

Phys. Rev. D59(1999)

114010

Igor Alekseev (ITEP) for pp2pp 17

Conclusions and plansConclusions and plans

• Conclusions The first measurement of AN, ANN and ASS at collider energy:

√s=200 GeV, small t AN is more than 4 different from 0 AN systematically ≈ 1σ above CNI curve with no hadronic spin-flip Double spin asymmetries are consistent with zero, though small

contribution of the Odderon is not excluded

• What is next ? Rotate RP1,3 (full acceptance over !) and move to the STAR IP (spin

rotators !!) (tot, d/dt, b, , AN , ANN , ASS , ALL , ALS):*=20m, pbeam=100 GeV/c 0.003<|t|<0.02(GeV/c)2;*=10m, pbeam=250 GeV/c 0.025<|t|<0.12(GeV/c)2.

• Conclusions The first measurement of AN, ANN and ASS at collider energy:

√s=200 GeV, small t AN is more than 4 different from 0 AN systematically ≈ 1σ above CNI curve with no hadronic spin-flip Double spin asymmetries are consistent with zero, though small

contribution of the Odderon is not excluded

• What is next ? Rotate RP1,3 (full acceptance over !) and move to the STAR IP (spin

rotators !!) (tot, d/dt, b, , AN , ANN , ASS , ALL , ALS):*=20m, pbeam=100 GeV/c 0.003<|t|<0.02(GeV/c)2;*=10m, pbeam=250 GeV/c 0.025<|t|<0.12(GeV/c)2.

Igor Alekseev (ITEP) for pp2pp 18

Rotating RP1 and RP3Rotating RP1 and RP3

dN/dt, 20 meter*, Kicker & IPM IN,15 mm pot position (V&H)

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

0.000 0.010 0.020 0.030 0.040

-t (GeV/c)2

dN

/dt

With IPM and kicker

Full acceptance at s 200 GeV

Without IPM and kicker

The STAR 3 Year Beam Use Request:2008