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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Constraining Dg with p0 ALL:Experimental issues
Kieran Boyle
Stony Brook University
December 4, 2006
Outline
2
withDS ~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 =
4
where , is rapidity
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
+ =
+
=
++
+
6
and that e can give large systematics
ALL =
Assume f++ = f+
i.e. helicity independent
7
BRAHMS & PP2PP (p)
PHENIX (p)
STAR (p)
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
8
Relative Luminosity (R)
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Luminosity
From Astrid Morreale
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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Relative Luminosity
BBC
Calculate
c*(T1T2)/2
c=spd of light
We call this Minimum Bias (minbias) trigger
2.887m
0.6m
14
8
a) High Luminosity “Bunch”
a) Low Luminosity “Bunch”
b) Low Luminosity Bunch
15
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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Polarization—Magnitude
(I am not an expert on this)
Forward scattered proton
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
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
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Rf Dipoles
and Carbon proton
Hiromi Okada, Spin2006
Single spin asymmetry
Double spin asymmetry
spin 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
So we know Pbeam if we know AN
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Forward scattered proton
JET target
FWHM ~6.5mm
RHIC 24, 100GeV/c proton beam ~1mm
Recoil particle
JET
80cm
left
Si detectors
proton beam
proton target
Recoil proton
goal
scaling uncertainty
right
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Polarization—Direction
BRAHMS & PP2PP (p)
PHENIX (p)
STAR (p)
Transverse
Longitudinal
Radial
(Transverse)
Spin 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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ZDC
Run 5
charged
particles
neutron
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
p
Charged
particles
Neutral
particles
Neutral
particles
Yellow
Blue
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Raw asymmetry
SMD
Raw asymmetry
YELLOW
BLUE
f
f
Raw asymmetry
Raw asymmetry
YELLOW
BLUE
f
f
X
Y
X
Y
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LR
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
<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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p0 Yield
g
g
p0
p
p
X
31
CARTOON
#
Combinatorial background
Mgg
p0
h
32
h
g
33
34
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The Asymmetry
ALL(p0+BG) = wp0· ALL(p0) + wBG · ALL(BG)
p0+BG region :
±25 MeV around
p0peak
BG region :
two 50 MeV regions
around peak
37
The Result and (Possible) Interpretation
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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x
So if Dg>0, p0 provides a
powerful constraint of Dg.
AAC
Or Not?
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