13th International Conference on Elastic & Diffractive Scattering
The First Measurement of the Elastic pp-scattering Spin Parameters at s =200 GeV
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Transcript of The First Measurement of the Elastic pp-scattering Spin Parameters at s =200 GeV
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
SPIN 2006, Kyoto, October 2 - 7, 2006
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