Constraining D g with p 0 ALL: Experimental issues. Kieran Boyle Stony Brook University December 4, 2006. Tell them what you will tell them. Outline. The Concept p + p p 0 + X The Equation A LL The Measurement Luminosity How do you define a collision Relative Luminosity
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Outline
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with DS ~25%, Dg not well constrained, DL ?
l, k’
(SI)DIS:
Clean but mostly colorblind
l, k
h
Dq
Dg
Hard Scattering Process
p0
P+P:
Dirty but colorful
Dg2
DgDq
Dq2
3

Ds =
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p+p Dg ?bias Trigger bias
From experimental data
geom Geometrical acceptance
From MC
reco Reconstruction efficiency (cut efficiencies)
From MC or/and experimental data
smear Smearing effect (due to finite resolutions):
From MC
Each efficiency has a systematic uncertainty (~110%), which makes measuring a (small) difference difficult
where
5
From ep (&pp)
(HERA mostly)
From e+e
pQCD NLO
+ =
+
=
++
+
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and that e can give large systematics
ALL =
Assume f++ = f+
i.e. helicity independent
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PHENIX (p)
STAR (p)
Does f++ = f+ ?RHIC CNI (pC) Polarimeters
Absolute Polarimeter
(H jet)
RHIC allows a great reduction in systematics
Spin Rotators
Siberian Snakes
Partial Siberian Snake
LINAC
BOOSTER
Pol. Proton Source
AGS
AGS Internal Polarimeter
200 MeV Polarimeter
Rf Dipoles
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Relative Luminosity (R)
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LUMINOSITY
Luminosity is the number of particles per unit area per unit time times the
Opacity of the target, usually expressed in either the cgs units cm2 s1 or b1 s1.
The integrated luminosity is the integral of the luminosity with respect to time.
The luminosity is an important value to characterize the performance of an accelerator.
Where
}
n, A, N1, N2 all have uncertainty:
stat. and systematic
What are you saying?!?
Assume s++ = s+ for ppX
i.e. helicity independent
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Calculate
c*(T1T2)/2
c=spd of light
We call this Minimum Bias (minbias) trigger
2.887m
0.6m
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a) High Luminosity “Bunch”
a) Low Luminosity “Bunch”
b) Low Luminosity Bunch
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A fill is defined as from beam injection to beam dump, ~78 hours long.
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where ALL is the asymmetry in the ratio.
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(I am not an expert on this)
slow, low statistics but absolute
Quick, high statistics, relative
proton target
BRAHMS & PP2PP (p)
RHIC proton beam
recoil proton measure!
Carbon target
PHENIX (p)
90º in Lab frame
STAR (p)
Recoil carbon
Polarized proton
Polarimetry at RHICRHIC CNI (pC) Polarimeters
Absolute Polarimeter
(H jet)
Spin Rotators
Siberian Snakes
Partial Siberian Snake
LINAC
BOOSTER
Pol. Proton Source
AGS
AGS Internal Polarimeter
200 MeV Polarimeter
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Rf Dipoles
Hiromi Okada, Spin2006
Single spin asymmetry
Double spin asymmetry
Physics topics of pp elastic scattering in the CNI regionspin non–flip
double spin flip
spin non–flip
double spin flip
single spin flip
Well known
Unpolarized pp elastic scattering experiment
Very small
No one photon exchange contribution to ANN. Sensitive to 5had and 2had !
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Ultra thin Carbon ribbon Target
(3.5mg/cm2)
6
1
3s Mass cut
15cm
carbon
2
5
nonrelativistic kinematics
Time of Flight (ns)
MC ~ 11.17 GeV
sM ~ 1.5 GeV
Si strip detectors
(TOF, EC)
3
4
prompts
alpha
Thin dead layer for low energy
carbon spectroscopy
Invariant Mass
2mm pitch 12 strips
Energy (keV)
10mm
p+ implants
~150 nm depth
With alternating spin pattern (+,,+,)
squareroot formula
72 strips in total
CNI Detector setupSo we know Pbeam if we know AN
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JET target
FWHM ~6.5mm
RHIC 24, 100GeV/c proton beam ~1mm
Recoil particle
JET
80cm
left
Si detectors
Measuring AN: Two in Oneproton beam
proton target
Recoil proton
goal
scaling uncertainty
right
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PHENIX (p)
STAR (p)
Transverse
Longitudinal
Radial
(Transverse)
Use Spin RotatorsSpin rotators are partial siberian snakes, and can rotate the polarization direction to many different orientations.
RHIC CNI (pC) Polarimeters
Absolute Polarimeter
(H jet)
Spin Rotators
Siberian Snakes
Partial Siberian Snake
LINAC
BOOSTER
Pol. Proton Source
AGS
AGS Internal Polarimeter
200 MeV Polarimeter
Rf Dipoles
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Run 5
charged
particles
neutron
But How Longitudinal is Longitudinal?forward pions (before
J. Koster et al. built MPC)
(hepex/0610030) found a
very forward neutron
asymmetry at RHIC.
longitudinal,
asymmetry0
by parity
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p
Charged
particles
Neutral
particles
Neutral
particles
How do you measure forward neutrons?Yellow
Blue
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SMD
Raw asymmetry
YELLOW
BLUE
f
f
Raw asymmetry
Raw asymmetry
YELLOW
BLUE
f
f
X
Y
How do you measure AN for neutrons?X
Y
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c2/NDF = 82.5/97
p0 = 0.00423±0.00057
c2/NDF = 88.1/97
p0 = 0.00323±0.00059
UD
XF>0
XF>0
UD
c2/NDF = 119.3/97
p0 = 0.00056±0.00063
c2/NDF = 81.7/97
p0 = 0.00026±0.00056
LR
XF<0
XF<0
Measured Asymmetry During Longitudinal Running<PT/P>=
10.25±2.05(%)
<PL/P> =
99.48±0.12±0.02(%)
<PT/P>=
14.47±2.20(%)
<PL/P> =
98.94±0.21±0.04(%)
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Fill Number
Fill Number
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#
Combinatorial background
Mgg
p0
h
gg Invariant Mass Spectrum32
g
Apply Some Cuts to the Data33
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ALL(p0+BG) = wp0· ALL(p0) + wBG · ALL(BG)
p0+BG region :
±25 MeV around
p0peak
BG region :
two 50 MeV regions
around peak
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GRSV: M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 63 (2001) 094005.
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Range is from varying ALL by polarization scale uncertainty
* At input scale: Q2 = .4 GeV2
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