first result from the pp2pp experiment włodek guryn for pp2pp collaboration brookhaven national...
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First Result from the pp2pp Experiment Włodek Guryn
for pp2pp collaboration Brookhaven National Laboratory, Upton, NY, USA
•Introduction – pp2pp physics program;
•Description of the experiment;
•Engineering run in 2002;
•Data analysis and results;
•Summary and outlook.
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Total and Differential Cross Sections, and Polarization Effects in pp Elastic Scattering at RHIC
S. Bueltmann, B. Chrien, A. Drees, R. Gill, W. Guryn*, I. H. Chiang, D. Lynn, C. Pearson, P. Pile, A. Rusek, M. Sakitt, S. Tepikian
Brookhaven National Laboratory, USA
J. Chwastowski, B. PawlikInstitute of Nuclear Physics, Cracow, Poland
M. HaguenauerEcole Polytechnique/IN2P3-CNRS, Palaiseau, France
A. A. Bogdanov, S.B. Nurushev, M.F Runtzo, M. N. StrikhanovMoscow Engineering Physics Institute (MEPHI), Moscow, Russia
I. G. Alekseev, V. P. Kanavets, L. I. Koroleva, B. V. Morozov, D. N. SviridaITEP, Moscow, Russia
M. Rijssenbeek, C. Tang, S. YeungSUNY Stony Brook, USA
K. De, N. Guler, J. Li, N. OzturkUniversity of Texas at Arlington, USA
A. SandaczInstitute for Nuclear Studies, Warsaw, Poland
* spokesman
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Polarized Proton Collisions in RHIC
~12 10-6m after scraping
BRAHMS & PP2PP (p)
STAR (p)
PHENIX (p)
AGS
LINACBOOSTER
Pol. Proton Source500 A, 300 s
GeVs
cmsL
50050
onPolarizati%70
102 2132max
Spin Rotators
Partial Siberian Snake
Siberian Snakes
200 MeV Polarimeter AGS Internal Polarimeter
Rf Dipoles
RHIC pC PolarimetersAbsolute Polarimeter (H jet)
2 1011 Pol. Protons / Bunch = 20 mm mrad
AGS pC Polarimeters
Strong AGS Snake
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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RHIC has the UNIQUE capability for colliding POLARIZED proton beams, further elucidating the exchange dynamics:
– Beam energy between 25 and 250 GeV;– Transverse polarization up to 70%;– Polarization can be chosen on a bunch-by-bunch basis (good for eliminating detection systematics!);
Allows to measure spin dependence of proton-proton elastic scattering
CNI region:
0.0004 < -t < 0.02 (GeV/c)2 √s = 200 GeV
0.0004 < -t < 0.13 (GeV/c)2 √s = 500 GeV
tot, , B, d/dt, AN(t), ANN(t)
ot = 600 barn (~1%), = 0.005 (4%), AN(t), ANN(t) = 0.001
Medium |t| region:
0.02 < -t < 1.3 (GeV/c)2 √s = 500 GeV
diffractive minimum (peaks and bumps) and their spin dependence
PP2PP Physics program
Design parameters
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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pp2pp experiment studies the dynamics and spin dependence of hadronic interaction through proton-proton elastic scattering
P, O -1Cor 1 C
Vacuum QM exchanged
p
pp
pp
pp
p
Pomeron(C=+1)
Odderon(C=1)+
Perturbative QCD Picture
OP
OP
AAppppA
AAppppA
)(
)(
s = (p1 + p2 )2 = (C.M energy)2 t = (p1 – p3 )2 = - (four momentum transfer)2
s t 1 (GeV/c)2 – Non-perturbative regimeElastic scattering d/dt + optical theorem total cross section tot
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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M
50 500
PP2PPHighest energy so far:
pp: 63 GeV (ISR)
pp: 1.8 TeV (Tevatron)
pp2pp energy range:
50 GeV s 500 GeV
pp2pp t-range:
(at s = 500 GeV)
4•10–4 GeV2 |t | 1.3 GeV2
Summary of Existing Data
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Principle of Measurement
Elastically scattered protons have very small scattering angle θ, hence beam transport magnets determine trajectory scattered protons
The optimal position for the detectors is where scattered protons are well separated from beam protons
Need Roman Pot to measure scattered protons close to beam without breaking accelerator vacuum
Beam transport equations relate measured position at detector to scattering angle x = a11 x0 + Leff θx Optimize so that a11 small and Leff large
θx = a12 x0 + a22 θx x0 can be eliminated by measuring θx
*
x : Position at Detector
θx : Angle at Detector
x0 : Position at Interaction Point
θx : Scattering Angle at IP*
Similar equations for y-coordinate
We found that because of the roll, misalignment, of the quadrupoles there is a mixing between x and y.
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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pp2pp Experimental Setup in Engineering run 2002Elastic and Inelastic Detectors
2×4 Scintillation Counter planes, 2.5|| 5.5
0. 100. m -100. m
D0
RP Stations
IR DX D0
RP Stations
-50. m 50. m
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Running Conditions in 2002Running conditions during a pp2pp, 14 hour dedicated run:
Beam momentum p = 100 GeV/c
Number of bunches per beam NB = 55 used 35 bunches
Beam scraped to emittance ε 12 π •10-6 m
and intensity I 5•1011 protons in each beam
Beam optics used β* = 10 m
Beam polarization (working #) Pb = 0.24 0.02
Closest approach of first detector strip to beam about
15 mm 15 beam tmin = -4•10-3 GeV2
Collected ~1 million triggers of which >30 % are elastic events
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Data Analysis: ColinearityCorrelation plots of x- and y-coordinates using elastic triggers with reconstructed tracks of scattered protons
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Beam Angular Divergence
Good agreement between width of θx and θy distributions for measured and simulated events with emittance of:
ε = 12 π •10-6 m
And vertex size:
z = 70 cm
Δθx 150 μrad
Δθy 70 μrad
N. Öztürk
ΔθyΔθx
N. Öztürk
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Event Reconstruction
Elastic event: good track in two “opposite” set of detectors
• SSD coordinate was calculated using energy weighted average of the position of the strips belonging to the isolated cluster of no more than three hits;
• Correlation between tracks in two Roman Pots:
require that (x2 + y2) be within “radius” : (x2 + y2) < 16 (x2 + y
2 );
• At least six out of eight hits belong to the track;
• No more than two planes with hits in “non” elastic arm;
• Select events within uniform t-acceptance tcut
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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|t |--AcceptanceFind region in |t |- and -space with full acceptance coverage and high statistics
t = - ( pbeam •θ ) 2
= azimuthal angle
Event Sample 196,000 events:
159,250 events ( 0 < < 180º )
122,437 events ( 45º < < 135º )
58,511 events ( 45º < < 135º )
& 0.010 GeV2 |t | 0.019 GeV2 )
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Extracting B from dN/dt-Distribution
ddt
= GE
t2
tot2
e+Bt
GE tot
e+½Bt t
+
+
[
]
C
Fit |t |-distribution with
fixing tot51.6 mb and 0.13 and keeping B as a free parameter in range 0.010 GeV2 |t | 0.019 GeV2results in
B = ( 16.3 1.6 ) GeV-2
Depends on detector position
Depends on beam transport element positions
B = ( 16.3 1.6 ) GeV-2
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Systematic and Correlation Errors
Systematic Errors were evaluated using Monte Carlo simulations:
1. Beam emmitence;
2. Vertex position spread in x, y, z;
3. Incoming beam angels – major source;
4. Beam transport uncertainty;
Total Systematic Error 0.9 (GeV/c)-2
Correlation between fitted parameter B and values of and :
±4 mb => –/+ 0.07 (GeV/c)-2
±0.02 => ±0.32 (GeV/c)-2
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RESULTb = 16.3 ± 1.6 (stat.) ± 0.9 (syst.) (GeV/c)-2
Analysis done by two independent groups is in agreement.
)1'(2
0
40
)(/
)/ln()(
t
dtd
s
stFdtd
where
dtdtb
E710: 0.02<-t<0.08
CDF: 0.025 <-t < 0.08
UA4: 0.0008<-t < 0.12
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Donnachie&Landshoff
OPE ModelBourrely, Soffer, Wu
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Single spin asymmetry AN arises in CNI region mainly from interference of hadronic non-flip amplitude with electromagnetic spin-flip amplitude
AN(t ) =N (t) + N(t) - N (t) - N(t) 1
Pbeam• cos N (t) + N(t) + N (t) + N(t) Im [ Φ5
* Φ+ ]
dσ / dtfor small t
Preliminary
Fit N / cos = 0.016 ± 0.007
Preliminary
AN = 0.033 ± 0.018
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Running Conditions 2002-03 2002 2003 Beam momentum 100 GeV Number of bunches 55 * 10m |t|-range 0.01-0.02 (GeV/c)2 Proton intensity 51011 191011 Proton polarization 0.24 0.37 Number of Roman Pot stations 2 4 Number of Silicon planes 16 32 Number of elastic events 3105 3106
Expected statistical errors Difraction cone slope: b 1.6 0.35 Raw asymmetry:
N 0.007 0.001 Total crossection:
tot - 5-10%
Systematic error improvement in 2003 due to: Excellent silicon detector efficiency; Measurement of local angles with new Roman Pot stations; Improved beam optics measurement; Van der Meer beam scans for luminosity measurement.
Systematic error improvement in 2003 due to: Excellent silicon detector efficiency; Measurement of local angles with new Roman Pot stations; Improved beam optics measurement; Van der Meer beam scans for luminosity measurement.
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Conclusions and Plans
•ConclusionsA promising physics result for b and AN from engineering run 2002
Excellent silicon detector performance in physics run 2003
Good statistics obtained - waiting for physics results.
•New proposal for 2004 and beyond (to be considered by PAC Sept 29, 2003)Run with current setup (tot, d/dt, b, , AN, ANN)
*=20 m, pbeam=100 GeV/c 0.003<|t|<0.02(GeV/c)2;
*=10 m, pbeam=250 GeV/c 0.025<|t|<0.12(GeV/c)2.
Put Roman Pots between DX and D0 magnets (d/dt, b, AN, ANN)
*=3m, pbeam= 250 [100] GeV/c 0.2<|t|<1.3(GeV/c)2 [0.02<|t|<0.12(GeV/c)2 .]
Upgrade RHIC quadrupoles power supply at our IP to run with *=100m and move Roman Pots to 70m position (tot, d/dt, b, , AN, ANN)
*=100m, pbeam=100 and 250 GeV/c |t| CNI region
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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Spin Physics with pp2ppFive helicity amplitudes describe proton-proton elastic scattering
Φ1(s,t ) <++|M|++>
Φ2(s,t ) <++|M|-->
Φ3(s,t ) <+-|M|+->
Φ4(s,t ) <+-|M|-+>
Φ5(s,t ) <++|M|+->
σtot = Im [ Φ+(s,t ) ]t=0
8 π
sMeasure:
Φn(s,t ) <h3 h4 |M|h1 h2>
with hx = s-channel helicity
p1 = -p2 incoming protons
p3 = -p4 scattered protons
Φ+(s,t ) = ½ ( Φ1(s,t ) + Φ3(s,t ) )
dσdt = ( |Φ1|2 + |Φ2|2 + |Φ3|2 + |Φ4|2 | + 4|Φ5|2 )
2 πs 2
ΔσT = - Im [ Φ2(s,t ) ]t=0 = σ
- σ
8 π
s
ΔσL = Im [ Φ1(s,t ) - Φ3(s,t ) ]t=0 = σ
- σ
8 π
s
Small x and Diffraction Sept. 17-20, 2003 FNAL Włodek Guryn
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