COMPASS における高横方向運動量ハドロンを
用いたグルーオン偏極度解析
岩田高広，石元茂1 ，近藤薫，鈴木肇2 ，堂下典弘，糠塚元気，橋本亮，
堀川直顕2 ，松田達郎3 ，@松田洋樹，宮地義之,
他 COMPASS Collaboration
山形大理 1 KEK 2中部大工 3宮崎大工
28.Mar.2014
28.Mar.2014
日本物理学会 28aSD-9
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.
Outline
Introduction
COMPASS
Recent published results @ COMPASS
Data taking @ COMPASS
Theory
Theoretical estimations
Results
Asymmetry calculation
Kinematic distributions
Deuteron
Proton
Summary
28.Mar.2014
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2 / 15
.
Outline
Introduction
COMPASS
Recent published results @ COMPASS
Data taking @ COMPASS
Theory
Theoretical estimations
Results
Asymmetry calculation
Kinematic distributions
Deuteron
Proton
Summary
28.Mar.2014
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COMPASS @ CERN
.
Setup
▶
▶
Polarised µ+ beam with 160/200 GeV energy
1 × 108 muons per spill
▶
▶
▶
▶
.
▶
µ filter
spill: ∼ 10 sec.
cycle time: ∼ 50 sec.
Beam polarisation: ∼ 80 %
acceptance: ∼ ±180 mrad
two stages: ∼ 60 m
Magnet
Magnet
RICH
µ+
Polarised target
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Kinematic acceptance
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∆g/g results @ COMPASS
.
Recent published results
LO @ high-pT hadron pair
NLO @ open charm
COMPASS, high p , Q2>1 (GeV/c) 2, prel., 02-06
T
COMPASS, high p , Q2<1 (GeV/c) 2, prel., 02-04
0.8
Q2 = 13 (GeV/c)2
T
HERMES, high p , all Q2
∆g/g
∆g/g
T
COMPASS, open charm, prel., 02-07
SMC, high p , Q2>1 (GeV/c)2
0.6
T
COMPASS Global fit with ∆ G>0, µ2=3(GeV/c)2
0.4
COMPASS Global fit with ∆ G<0, µ =3(GeV/c)
2
2
COMPASS open charm
0.6
COMPASS (∆g>0)
COMPASS (∆g<0)
DSSV
0.4
LSS (∆g>0)
0.2
LSS (∆g sign changing)
0.2
0
0
-0.2
−0.2
−0.4
-0.4
10−2
-0.6
-2
10
-1
10
10−1
x
xg
PRD 87 (2013) 052018
PLB 718 (2013) 922
∆g/g @ COMPASS
▶
+0.02 ± 0.09 ± 0.06 @ xg = ⟨0.01⟩ LO, high-pT pair, Q2 < 1, PLB 633 (2006) 25
▶
+0.13 ± 0.06 ± 0.06 @ xg = ⟨0.09⟩ LO, high-pT pair, Q2 > 1, PLB 718 (2013) 922
▶
−0.47 ± 0.44 ± 0.15 @ xg = ⟨0.11⟩ LO, open charm, arXiv:0802.3023
▶
−0.49 ± 0.27 ± 0.11 @ xg = ⟨0.11⟩ LO, open charm, PLB 676 (2009) 31
▶
−0.06 ± 0.21 ± 0.08 @ xg = ⟨0.20⟩ LO, open charm, PRD 87 (2013) 052018
▶
−0.13 ± 0.15 ± 0.15 @ xg = ⟨0.11⟩ NLO, open charm, PRD 87 (2013) 052018
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.
Data taking
2002-2011 muon program
Year
2002
2003
2004
2006
2007
2011
Target
Beam Energy(GeV/c)
Acceptance(mrad)
75
LiD
160
180
NH3
200
.
high-pT Hadron yield in this analysis (cut: pT > 1, Q2 < 1)
Year
Hadron yield(×106 )
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2002
16.3
2003
30.9
2004
53.3
日本物理学会 28aSD-9
2006
34.2
2007
65.7
2011
39.8
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Theory
.
Purpose
▶
∆g/g evaluation from double longitudinal spin asymmetry ALL (pT )
▶
▶
High-pT (> 1.0 GeV/c) and low-Q2 (< 1 (GeV/c)2 )
All COMPASS data(2002 - 2011)
Theoretical framework
▶
▶
photoproduction of single inclusive hadrons: l + N → l′ + H + X
based on JSV framework (Eur.Phys.J. C44, 533 (2005), hep-ph/0505157)
Direct γ-contribution
Resolved γ-contribution
l
l
H
Dc
γ
H
b
Δ fp
(a)
28.Mar.2014
H
Dc
X
∆ fγ : Photon’s parton density
∆ f p : Nucleon p’s parton density
∆σ:
ˆ spin-dependent partonic
hard scattering cross section
a, b, c = q, q,
¯ g
H
Dc : fragmentation function
日本物理学会 28aSD-9
H
c
a
´`
Δσ
p
γ
Δ fγ
c
´`
Δσ
X
b
p
Δ fp
(b)
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Theoretical estimations of ALL
.
∑
▶
ALL
∆σ
≡
=
σ
∆ fal ⊗∆ fbN ⊗∆σ
ˆ ab→cX ⊗Dhc
∑
a, b, c
fal ⊗ fbN ⊗σ
ˆ ab→cX ⊗Dhc
a, b, c
▶
ALL @ COMPASS Kinematic range
h, d
ALL
0.3
0.2
h, p
ALL
0.3
'Δg = -g'
'Δg = -g'
0.2
'max. γ '
'min. γ '
'Δg = 0'
0.1
'Δg = 0'
'std. Δg'
0.1
'Δg = g'
input
'std. Δg'
0
'Δg = g'
input
L = 1 / fb
-0.1
1
2
3
pT [GeV]
4
0
-0.1
L = 1 / fb ⇒ 4 /fb for all COMPASS data
1
2
3
pT [GeV]
4
Proton
Deuteron
ref: Eur.Phys.J. C44, 533 (2005), hep-ph/0505157
▶
Different curves with different ∆g scenarios
.
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.
Outline
Introduction
COMPASS
Recent published results @ COMPASS
Data taking @ COMPASS
Theory
Theoretical estimations
Results
Asymmetry calculation
Kinematic distributions
Deuteron
Proton
Summary
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Asymmetry calculation
.
Double longitudinal asymmetry
( ⇄
)
( ⇄
)
∆σ
1
σ − σ⇔
1
N − N⇔
ALL ≡
≈
=
σ
f Pb Pt σ⇄ + σ⇔
f P b Pt N ⇄ + N ⇔
▶
f : Dilution factor: 0.4(6 LiD), 0.16(NH3 )
▶
Pb : Beam polarisation: ∼ 80 %
Pt : Target polarisation: ∼ 50 %(6 LiD), ∼ 85 %(NH3 )
N: Hadron yield
▶
▶
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Kinematic distributions
.
pT , Q2 in 2004 and 2007
105
hadrons
hadrons
pT
105
2004 (1 week)
deuteron
2007 (1 week)
proton
104
102
el
im
10
103
1
0
1
Pr
10
Pr
10
ry
ry
in
a
2
in
a
Before cut
After cut
103
el
im
104
2
3
4
1
0
5
pT (GeV/c)
1
2
3
events
2004 (1 week)
deuteron
2
5
pT (GeV/c)
Proton
×103
events
Deuteron
Q2
4
×103
2007 (1 week)
proton
1.5
1.5
ar
y
im
in
im
in
ar
y
1
1
0
10-4
10-3
10-2
el
Pr
el
0.5
Pr
0.5
10-1
Q2
1 (GeV2/c 2) 10
0
10-4
Deuteron
28.Mar.2014
10-3
10-2
10-1
Q2
1 (GeV2/c 2) 10
Proton
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Asymmetry: deuteron
.
2002-2006
COMPASS
Deuteron
y
r
ina
0
-0.02 0.6
0.8
1
0.2
m
i
l
re
1.2
1.4
pT (GeV/c)
1.6
1.8
2
0.3
0.1
ALL
ALL
0.02
P
0
-0.1
1
2
3
4
p (GeV/c)
T
.
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Asymmetry: deuteron
.
2002-2006
0
h, d
ALL
0.3
0.2
-0.02 0.6
0.3
COMPASS
Deuteron
'Δg = -g'
y
r
ina
'max. γ '
'min. γ '
0.8
1
0.1
m
i
l
re
1.2
1.4
pT (GeV/c)
1.6
1.8
2
P
0
'Δg = 0'
0.1
'std. Δg'
0
'Δg = g'
input
L = 1 / fb
-0.1
0.2
ALL
ALL
0.02
-0.1
1
2
3
1
2
3
pT [GeV]
4
4
p (GeV/c)
T
.
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Asymmetry: proton
.
2007-2011
COMPASS
Proton
y
r
ina
0
-0.02 0.6
0.8
1
0.2
m
i
l
re
1.2
1.4
pT (GeV/c)
1.6
1.8
2
0.3
0.1
ALL
ALL
0.02
P
0
-0.1
1
2
3
4
p (GeV/c)
T
.
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Asymmetry: proton
.
2007-2011
0
h, p
ALL
0.3
0.3
'Δg = -g'
COMPASS
Proton
y
r
ina
0.2
-0.02 0.6
0.8
1
0.1
m
i
l
re
1.2
1.4
pT (GeV/c)
1.6
1.8
2
P
0
0.2
'Δg = 0'
'std. Δg'
0.1
'Δg = g'
input
ALL
ALL
0.02
0
L = 1 / fb
-0.1
-0.1
1
2
3
1
2
3
pT [GeV]
4
4
p (GeV/c)
T
.
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.
Outline
Introduction
COMPASS
Recent published results @ COMPASS
Data taking @ COMPASS
Theory
Theoretical estimations
Results
Asymmetry calculation
Kinematic distributions
Deuteron
Proton
Summary
28.Mar.2014
日本物理学会 28aSD-9
14 / 15
Summary & Outlook
.
Summary
▶
∆g/g evaluation from double longitudinal asymmetry ALL
from high-pT hadrons with low-Q2
▶
▶
All COMPASS data with longitudinal beam/target used
Asymmetries: compatible with zero except high-pT bin
▶
Systematic error: of the order of statistical error
Outlook
▶
▶
▶
further quantification of systematic errors
comparisons between data and theoretical calculation
evaluation of ∆g/g
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Backup
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Comparison unpolarised cross section
.
COMPASS data v.s. theoretical calculation
COMPASS data in 2004
▶
▶
C. Adolph, et. al., PRD 88 (2013) 091101
µ + d → µ′ + h± + X cross section at Q2 < 0.1 (GeV/c)2
µ+ + d → µ+ + h± + X
103
102
Theoretical calculations
▶
D. Florian, et. al., arXiv:1305.6468
Higher-order QCD corrections
to the cross section
Large logarithmic “threshold”
corrections
→ improved the agreement
between data and theory
pb c2
G eV 2
▶
1
dσ
2π pT dpT
▶
10
1
10− 1
10− 2
η ∈ [−0.10 : 2.38]
10− 3
⇒ Valid within theoretical uncertainty
28.Mar.2014
L O µ = pT / 2, 2pT
NL O µ = pT / 2, 2pT
resum µ = pT / 2, 2pT
LO
NL O
resum
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2.5
pT (GeV / c)
3
3.5
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Contributions to total cross section
.
From each process
1.5
dΔσres / dΔσ
1
0.5
0
dΔσdir / dΔσ
(a)
-0.5
dΔσab / dΔσ
2
0
-2
qg
gq
qq
gg
(b)
1
2
▶
Resolved photon contribution
dominates over the direct
contribution
▶
Large cancellation between γg and γq
→ Numerically smaler resolved
subprocesses become important
γg
γq
3
pT [GeV]
4
F ig. 5. (a) Direct and resolved NLO(MS) contributions and
(b) NLO(MS) contributions of different partonic channels a+
b → c + X to the full NLO polarized photoproduction cross
section shown in Fig. 2.
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Difference between previous analyses
.
Fit method(This analysis)
▶
▶
pQCD collinear NLO
All hadrons with high-pT
Compare data with theoretical curve
▶
quark distributions: from global fit
▶
Direct methods(COMPASS’s main stream method)
high-pT hadron pair
▶
open charm
LO
2 hadrons pair with high-pT
▶
▶
▶
(Neural Network tuned)
Mote Carlo simulation
High statistics
▶
(Neural Network tuned)
Mote Carlo simulation
Low statistics
▶
Large background
▶
Small background
▶
▶
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▶
LO or NLO
D meson from PGF
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.
PGF contribution
PYTHIA simulation
Contributions from each process @ Q2 < 1
PGF
R
0.3
0.2
0.1
0
*
QCDC
γ g→qq
*
γ q→qg
*
γ q→q
qq’→qq’
qg→qg
gg→gg
low pT
Leading
Ref: PLB 633 (2006) 25–32
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COMPASS data taking
.
Year
Target
Ebeam
Detail
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
Deuteron
Deuteron
Deuteron
160
160
160
Deuteron
Proton
160
160
Proton
Proton
Hydrogen
160
200
Longitudinal mode(∼20 % transverse mode)
Longitudinal mode(∼20 % transverse mode)
Longitudinal mode(∼20 % transverse mode)
Shutdown & upgrade
New setup, longitudinal mode
1/2 longitudinal, 1/2 transverse
Phase-I
Hadron physiscs
Hadron physiscs
Transverse
Longitudinal
Hadron physics(Primakoff) + DVCS test run and SIDIS
Shutdown & upgrade
2014
2015
2016
2017
Proton
Proton
Hydrogen
Hydrogen
Drell-Yan
Drell-Yan
DVCS
DVCS
Phase-II
.
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Asymmetry: year by year
.
2002-2011
COMPASS
2003(Deuteron)
1
y
nar
i
m
i
p (GeV/c)
T
1
1
COMPASS
2006(Deuteron)
0
lim
Pre
COMPASS
2007(Proton)
0
-0.02
-0.02
1
y
nar
i
m
i
2
3
28.Mar.2014
T
2
mi
li
Pre
4
p (GeV/c)
-0.2
0.02
COMPASS
2011(Proton)
0.4
0.2
-0.02
2
l
Pre
1
0
0
-0.02
1
2
T
0.02
T
A LL (p )
T
A LL (p )
Pre
0.2
ry
ina
-0.02
2
li
l
Pre
0.02
ary
min
-0.02
2
0.02
0.4
0
A LL
0
-0.02
A LL
COMPASS
2004(Deuteron)
1
1
y
nar
2
3
T
y
nar
i
lim
Pre
4
p (GeV/c)
日本物理学会 28aSD-9
2
A LL
0
-0.02
0
0.02
T
A LL (p )
COMPASS
2002(Deuteron)
A LL (p )
A LL
0
0.02
T
A LL (p )
0.02
T
A LL (p )
0.02
1
0
2
3
4
-0.2
p (GeV/c)
T
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