Polarized Drell-Yan Experiment at J-PARC
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Polarized Drell-Yan Experimentat J-PARC
J-PARC Meeting for Spin and Hadron Physics
Nishina Hall at RIKEN
April 7th, 2008
Yuji Goto (RIKEN/RBRC)
April 7, 2008 2
J-PARC proposals• P04: measurement of high-mass dimuon production at the 50
-GeV proton synchrotron– spokespersons: Jen-Chieh Peng (UIUC) and Shinya Sawadas (KEK)– collaboration: Abilene Christian Univ., ANL, Duke Univ., KEK, UIUC, L
ANL, Pusan National Univ., RIKEN, Seoul National Univ., TokyoTech, Tokyo Univ. of Science, Yamagata Univ.
– including polarized physics program, but not discussed– “deferred”
• P24: polarized proton acceleration at J-PARC– contact persons: Yuji Goto (RIKEN) and Hikaru Sato (KEK)– collaboration: ANL, BNL, UIUC, KEK, Kyoto Univ., LANL, RCNP, RIK
EN, RBRC, Rikkyo Univ., TokyoTech, Tokyo Univ. of Science, Yamagata Univ.
– polarized Drell-Yan included as a physics case– “no decision”
• Next proposal for the polarized physics program– to be submitted
April 7, 2008 3
Origin of the nucleon spin 1/2 ?
• EMC experiment at CERN– total quark spin constitutes a small fraction of the nucleon
spin• integration in x = 0 ~ 1 makes uncertainty• more data to cover wider x region with more precise data necessa
ry
– SLAC/CERN/DESY/JLAB experiments
• Gluon spin contribution ?– scaling violation in polarized DIS
• success of the evolution equation of the perturbative QCD • limited sensitivity due to a limited range of Q2
– semi-inclusive polarized DIS– polarized hadron collision
• Orbital angular momentum ?
Lg 2
1
2
1
)%syst(14)stat(912
J. Ashman et al., NPB 328, 1 (1989).
“proton spin crisis”
%20~
longitudinally polarized measurements
transversely polarized measurements
dd
ddALL
April 7, 2008 4
Gluon spin contribution• ALL in neutral pion production
– mid-rapidity at RHIC, s = 200 GeV][][][ qqgqggA qqgqggLL
gg + qg dominantsensitive to the gluon reaction
G = 0.4at Q2=1(GeV/c)2
G = 0.1at Q2=1(GeV/c)2
GRSV-std scenario, G = 0.4 at Q2 = 1(GeV/c)2,excluded by data on more than 3-sigma level
April 7, 2008 5
Flavor-sorted quark polarization
• Weak boson production– RHIC spin
s = 500 GeV• 2009 –
– parity-violating asymmetry AL
– reduction of uncertainties to determine the quak spin contribution and gluon spin contribution G to the proton spin
)()()()(
)()()()(
baba
babaWL xuxdxdxu
xuxdxdxuA
April 7, 2008 6
Transverse single-spin asymmetry (SSA)
+
K
p
p
• Link to orbital angular momentum in the nucleon– forward rapidity
• Fermilab E704, s = 20 GeV• RHIC, s = 200 GeV
explained by many undetermineddistribution and fragmentationfunctions: transversity, Sivers function,Collins function
April 7, 2008 7
Drell-Yan experiment• The simplest process in hadron-hadron reactions
– no QCD final-state effect– no polarized Drell-Yan experiment done yet– flavor asymmetry of the sea-quark distributions
• unpolarized and longitudinally-polarized measurements
– orbital angular momentum in the nucleon• Sivers effect (no Collins effect)
– transversity distribution function, etc.
• Why at J-PARC ?– polarized beam feasible in discussions with J-PARC and B
NL accelerator physicists– high intensity/luminosity for small Drell-Yan cross section
DIS Drell-Yan
April 7, 2008 8
Flavor asymmetry of sea-quark distribution
• Fermilab E866
• Possible origins– meson-cloud model
• virtual meson-baryon state
– chiral quark model
– instanton model– chiral quark soliton model
)(
)(1
2
1~
2 2
2
xu
xdpp
pd
012.0118.0)]()([
011.00803.0)]()([
CTEQ5Mwith
1
0
35.0
015.0
xuxddx
xuxddx
, , npp
April 7, 2008 9
Flavor asymmetry of sea-quark distribution + is the origin of -quark
excess in the proton?d
April 7, 2008 10
Dimuon experiment at J-PARC (P04)– based on the Fermilab spectrometer for 800 GeV– length to be reduced but the aperture to be increased– two vertically bending magnets with pT kick of 2.5 GeV/c a
nd 0.5 GeV/c– tracking by three stations of MWPC and drift chambers– muon id and tracking
tapered copper beam dump and Cu/C absorbers placed within the first magnet
April 7, 2008 11
Polarized Drell-Yan experiment at J-PARC
• Longitudinally-polarized measurement– ALL measurement
– flavor asymmetry of sea-quark polarization
chiral quark solitonmodel prediction
120-day run75% polarization for a 51011 protons/spillpolarized solid NH3 target, 75% hydrogen polarization and 0.15 dilution factor
GS-CGS-AGRSV
April 7, 2008 12
Flavor asymmetry of sea-quark polarization• Polarized Drell-Yan experiment at J-PARC
– x = 0.25 – 0.5
• W production at RHIC– x = 0.05 – 0.1
GS-CGS-AGRSV
reduction of uncertainties to determine the quak spin contribution and gluon spin contribution G to the proton spin
April 7, 2008 13
Polarized Drell-Yan experiment at J-PARC• Orbital angular momentum
– in hadron-hadron reaction, no direct link between measurement and theory (yet)
– but, any partonic transverse motion and correlation should be related
• Sivers effect / higher-twist effect
• SSA (AN) measurement– Sivers effect and higher-twist effe
ct provide the same description of SSA on Drell-Yan and semi-inclusive DIS at moderate qT: QCD << qT
<< Q– Sivers function in Drell-Yan shoul
d have a sign opposite to that in DIS
• sensitive QCD test between e+p data and p+p data
4 < M+- < 5 GeVintegrated over qT
1000 fb-1 (120-day run), 75% polarization, no dilution factorTheory calculation by Ji, Qiu, Vogelsang and Yuan based on Sivers function fit of HERMES data
April 7, 2008 14
Polarized Drell-Yan experiment at J-PARC
• ATT measurement
– h1(x): transversity• remaining leading-order
distribution function of the nucleon
• SSA measurement, sin(+S) term
– h1(x): transversity
– h1(1)(x): Boer-Mulders f
unction (1st moment of)
2
2
21112
21112
cos1
)2cos(sinˆ
))21()()((
))21()()((
ˆ
21
SSTT
qqqq
qqqq
TTTT
a
xfxfe
xhxhe
aA
qqqq
qqqq
xfxfe
xhxhe
A))21()()((
))21()()((
2
1ˆ2111
2
211)1(
12
April 7, 2008 15
Unpolarized Drell-Yan experiment at J-PARC• Boer-Mulders function h1
(x, kT2)
– angular distribution of unpolarized Drell-Yan
– Lam-Tung relation reflect the spin-1/2 nature of quarks– violation of the Lam-Tung relation suggests non-perturbati
ve origin– correlation between transverse quark spin and quark tran
sverse momentum
2 21 31 cos sin 2 cos sin cos 2
4 2
d
d
21 ,
L.Y. Zhu,J.C. Peng, P. Reimer et al.hep-ex/0609005
With Boer-Mulders function h1┴:
ν(π-Wµ+µ-X)~valence h1┴(π)*valence h1
┴(p)
ν(pdµ+µ-X)~valence h1┴(p)*sea h1
┴(p)
April 7, 2008 16
Experimental condition study• Previous simulation study which made the figure below w
as wrong– target position was fixed at z = 0 (at the edge of the first magnet)– correctly, this should be z = -1800 cm ~ -1300 cm (50 cm target)– yield should be ~5 times smaller
– but, higher beam intensity is possible for unpolarized liq.H2 target– 10 times higher possible? 51012 ppp = 11012 /sec ?
1000 fb-1 (120-day run),75% polarization, no dilution factorTheory calculation by Ji, Qiu, Vogelsang and Yuan based on Sivers function fit of HERMES data
PYTHIA simulation: mass = 4 – 5 GeV/c2
beam intensity: 51011 ppp = 11011 /sec120 day = 107 secbeam on target: 51017 (with 50% duty factor)number density of liq.H2 target: 0.429x1023 /cm3
luminosity = botnumber densitytarget length= 1000 fb-1
April 7, 2008 17
Experimental condition study• J-PARC experiment should be optimized for 4 GeV/c2 virt
ual photon– PYTHIA simulation: mass = 4 – 4.1 GeV/c2, xF = 0.2 – 0.4– each of magnet/detector geometry same as E906, but total appa
ratus length 60% shorter
April 7, 2008 18
Experimental condition study
• E906 optimized for 7 GeV/c2 virtual photon– PYTHIA simulation
mass = 7 – 7.1 GeV/c2, xF = 0.2 – 0.4 mass = 4 – 4.1 GeV/c2, xF = 0.2 – 0.4
April 7, 2008 19
Experimental condition study
• Smaller boost– wider aperture of the first magnet necessary
• Sivers effect measurement– single beam-spin asymmetry– maybe easier to use nuclear targets
• More studies– absorber & beam target thickness, etc.– trigger rate and resolution
April 7, 2008 20
pQCD studies by Yokoya-san, et al.
• NLO/NNLO
April 7, 2008 21
pQCD studies by Yokoya-san, et al.
• Scheme dependence
April 7, 2008 22
pQCD studies by Yokoya-san, et al.
April 7, 2008 23
pQCD studies by Yokoya-san, et al.
April 7, 2008 24
pQCD studies by Yokoya-san, et al.
April 7, 2008 25
pQCD studies by Yokoya-san, et al.
April 7, 2008 26
pQCD studies by Yokoya-san, et al.
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pQCD studies by Yokoya-san, et al.
April 7, 2008 28
pQCD studies by Yokoya-san, et al. s = 62 GeV
April 7, 2008 29
pQCD studies by Yokoya-san, et al. s = 10 GeV
April 7, 2008 30
pQCD studies by Yokoya-san, et al.
April 7, 2008 31
pQCD studies by Kawamura-san, et al.
April 7, 2008 32
pQCD studies by Kawamura-san, et al.
April 7, 2008 33
Summary• Polarized Drell-Yan experiment with dimuon measurment
using polarized proton beam at J-PARC has a rich physics programs– flavor asymmetry of sea-quark polarization higher precision fo
r and G– SSA measurements for Sivers and higher-twist effects and trans
versity link to orbital-angular momentum
• We propose to make the J-PARC facility allow acceleration of polarized proton beams to 30-50 GeV– feasible in discussion with J-PARC and BNL accelerator physicis
ts– technically, there is no showstopper
• Theoretical studies at J-PARC energy has progressed– showing convergence to compare with experimental data
• More studies for experimental condition to be done– for the next proposal