PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos...
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Transcript of PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos...
![Page 1: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/1.jpg)
PANIC05 M. Liu 1
Probing the Gluon Polarization with ALL of J/ at RHIC
Ming X. Liu
Los Alamos National Lab
(PHENIX Collaboration)
![Page 2: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/2.jpg)
PANIC05 M. Liu 2
Spin Crisis and Gluon Polarization• Proton Spin Puzzle:
• Asymptotic limit
Gq
qG
JJ
LG
+=
Δ+Δ+ΔΣ= +21
21
∞→2Q
fGG
f
fqq
nLGQJ
n
nLQJ
316
16
2
1)(
316
3
2
1
2
1)(
2
2
+→Δ+Δ=
+→Δ+ΔΣ=
Gluons may play a significant role !€
Δ˜ Σ exp = ΔΣ − N f
α s
2πΔg
ΔΣ = 0.6 → Δg ~ 3
• PCAC
€
ΔΣ ≈0.3 vs ΔΣQCD ≈ 0.6
![Page 3: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/3.jpg)
PANIC05 M. Liu 3
Gluon Polarization Measurements: (SI)DIS • Semi-inclusive DIS
– HERMES @ DESY• high-pT hadron pairs
– SMC @ CERN• high-pT hadron pairs
– COMPASS @ CERN• high-pT hadron pairs• open charm
lepton beam
or
or nucleon target
*
gluon
heavy flavor
![Page 4: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/4.jpg)
PANIC05 M. Liu 4
@RHIC-SPIN• Polarized hadron collisions
– double longitudinal spin asymmetry
– leading-order gluon interactions• direct-photon production• heavy-flavor production
proton beam
proton beam
or
or
gluon
photon
proton beam
proton beam
or
or gluongluon
heavy flavor
€
ALL =σ ++ −σ +−
σ ++ + σ +−
![Page 5: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/5.jpg)
PANIC05 M. Liu 5
The PHENIX Detectors
• Central Arms– || < 0.35, Δ ~ – , , e, +-, ... –
Identified– Momentum, Energy
• Muon Arms– 1.2 < || < 2.4– Momentum (MuTr)– Open charm, J/ etc
![Page 6: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/6.jpg)
PANIC05 M. Liu 6
A New Probe: Heavy Quarks Sensitive to gluon polarization: Δg(x)
Gluon-gluon interaction dominates at LO
PHYTHA estimate:GeV Charm Beauty200 95:5 85:15500 97:3 92:8
Double spin asymmetry:
€
ALL ≈Δg(x1)
g(x1)
Δg(x2)
g(x2)aLL
gg →J / Ψ +X
Decay modes:
e+e-, +-, e, eX, X1.5
2
5
aLL
Karliner & Robinett,
Phys.Lett.B324 (1994)
J/bbeX
cceX
x
![Page 7: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/7.jpg)
PANIC05 M. Liu 7
J/ production mechanism
• LO NRQCD:
]})()()2
11(
9[)2,
4()2,(
32
15
)()1()2,4
()2,(
{27
01)(/
803)(/
8021
2
1
13)(/
801
2
1
1
1
12
23
))(/(24
><−><−×⋅
Δ⋅Δ+
><−×⋅
Δ⋅Δ
⋅⋅≈Δ
→ ∫
SOPOm
msx
mfmxf
SOmsx
mfmxf
xdx
ms
JJgg
Jqq
sJpp
sm
λλλ
λλ
λ
δ
δ
ασ
mix of various processes
2~ sα
hep-ph/0509335 G. Nayak et al.
![Page 8: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/8.jpg)
PANIC05 M. Liu 8
J/ production mechanism (cont.)
• NLO RNQCD:
gccgg
gccqq
qccqg
+→++→++→+
},{},{},{
“final state” mixture ratios: fixed from other data
)/,/4( max22/ ppxsma TTc
XJggLL ==→
Partonic asymmetry for ggJ/ X3~ sαTeryaev and Tkabladze PRD56(97)7331
![Page 9: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/9.jpg)
PANIC05 M. Liu 9
NLO NRQCD and PHENIX data
Theoretical predictions of J/Ψ production at RHIC are in good agreement with the PHENIX data: COM process dominant
– PRD 68 (2003) 034003 G. Nayak, M. Liu, F. Cooper– PRL 93 (2004) 171801 F. Cooper, M. Liu, G. Nayak
PHENIX, PRL 92, 051802 (2004)
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PANIC05 M. Liu 10
ALL Measurement with J/+-
• Experimental approach– Polarization=47% (average)– R is from Beam-Beam-Counter scalers– N_Jpsi Yield
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PANIC05 M. Liu 11
J/ Yield Measurements • Fill by fill: (N+- - N++,--)
– Detector efficiency variation canceled out
– Have Open charm, DY and other background (<10%)
• Gaussian+Exponential background
– Used to estimate the background under J/Psi peak
2
2'
2
2?
2
)(
2
)(
2
1'
2
1 σσ
σσ
PsipsiJ MMMMMK eNeNeA
dMdN −
−−
−⋅− ⋅+⋅+⋅=
Dimuon mass distributions
+ - +(-) +(-)
![Page 12: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/12.jpg)
PANIC05 M. Liu 12
NJ/ > 10 per fill
2 sigma cut:
2.78 < Mass < 3.42
<RL> = 1.0089(3)
€
ALL (raw) =NJ / Psi
++ − R ⋅NJ / Psi+−
NJ / Psi++ + R ⋅NJ / Psi
+−= −0.007 ± 0.013
Raw Asymmetries Fill by Fill:
![Page 13: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/13.jpg)
PANIC05 M. Liu 13
Statistical Test• Beam polarization shuffling
– random beam polarization values – repeat 10,000 times
LLALL
LL
A
A
δ
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PANIC05 M. Liu 14
Background Raw Asymmetry:
Left of the peak: 2.0 < Mass < 2.5
ALL(raw)= 0.0107 0.0220
Under the peak:
ALL(raw) = -0.0351 0.0318
N = 988 31
Background Estimation
018.00041.0)( ±−=RAWABGLL
Dimuon mass distributionsr
ArAA
r
ArAA
BGLL
inclLLPsiJ
LL
BGLL
inclLLPsiJ
LL
−⋅+
=
−⋅−
=
1)()(
1222
/
/
δδδ
+-
++, --
![Page 15: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/15.jpg)
PANIC05 M. Liu 15
ALL vs pT
Log(x)
XJggLLLL a
xg
xg
xg
xgA +→ΔΔ
≈ /
2
2
1
1
)()(
)()(
First spin physics result from J/ - J/: produced via almost pure gluon fusion - sensitive to gluon polarization
![Page 16: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/16.jpg)
PANIC05 M. Liu 16
Summary and Outlook• First measurement of double spin asymmetry with J/Psi from
longitudinally polarized p-p collisions– Almost pure gluon fusion– 10k J/psi, statistically limited– Expect x100 more statistics in the future
• Work in progress– J/Psi polarization measurement– Open charm - much larger statistics from run5 and will tell us more
about gluon polarization• Need more theoretical work
– J/ production mechanism– Polarized gluon PDFs – Excellent QCD test ground with polarization
• Where does the nucleon get its spin?– Still don’t know … but RHIC-SPIN will help us to find the answer– and we will learn a lot more about the nature of strong interactions
![Page 17: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/17.jpg)
PANIC05 M. Liu 17
More on J/ Production Mechanism
- J/Psi polarization - a key probe?- Spin dynamics in pQCD
*cos1*cos
2θαθ
σ+∝
dd
α= +1: transversely polarizedα= -1: longitudinally polarizedα= 0: no polarization
+J/
θ*-
hep-ph/0106120 M. Kramer
![Page 18: PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/ at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)](https://reader034.fdocuments.us/reader034/viewer/2022051418/56649f165503460f94c2bf56/html5/thumbnails/18.jpg)
PANIC05 M. Liu 18
NRQCD Calculations of ALL
• NRQCD LO Helicity dependent double-spin
asymmetry
]})()()2
11(
9[)2,
4()2,(
32
15
)()1()2,4
()2,(
{27
01)(/
803)(/
8021
2
1
13)(/
801
2
1
1
1
12
23
))(/(24
><−><−×⋅
Δ⋅Δ+
><−×⋅
Δ⋅Δ
⋅⋅≈Δ
→ ∫
SOPOm
msx
mfmxf
SOmsx
mfmxf
xdx
ms
JJgg
Jqq
sJpp
sm
λλλ
λλ
λ
δ
δ
ασ
λ=1
λ=0
GRSV+
J/
θ*-
hep-ph/0509335 G. Nayak et al.