study of proton helicity structure in polarized p+p collisions at phenix
DESCRIPTION
Study of Proton Helicity Structure in Polarized p+p Collisions at PHENIX. Kensuke Okada (RBRC) for the PHENIX collaboration DIS2007 Munich. RHIC PHENIX. proton beam. or . △q. L. gluon. photon. △g. or . proton beam. The first polarized proton collider (up to s= 500GeV). - PowerPoint PPT PresentationTRANSCRIPT
April 17, 2007 K.Okada 1
Study of Proton Helicity Structure in Polarized p+p Collisions at PHENIX
Kensuke Okada (RBRC)for the PHENIX collaboration
DIS2007 Munich
April 17, 2007 K.Okada 2
RHIC PHENIXThe first polarized proton collider (up to s=500GeV).Gluon in proton interacts in leading order process.
The missing proton spin component (g) can be probed by the production asymmetries.
proton beam
proton beam
or
or
gluonphoton △q
△g
L
Proton spin component
Example: direct photon production
2
1P
ALL
April 17, 2007 K.Okada 3
PHENIX detectorCentral arm (||<0.35, 2*0.5)Muon arm (1.2< || < 2.4, 2)
April 17, 2007 K.Okada 4
PHENIX detectorCentral arm (||<0.35, 2*0.5)Muon arm (1.2< || < 2.4, 2)
Trigger EMCal and/or RICH MPC (forward EMCal) Muon (E>~2GeV)
MPC(EMCal)
Collision counter BBC,ZDC
BBC
Longitudinal spin collision(s=200GeV)
L(/pb) 0.35 (2003:Run3) 0.12 (2004:Run4) 3.4 (2005:Run5) 7.5 (2006:Run6) pol~60%!! 70 (2008:Run8) (plan)
April 17, 2007 K.Okada 5
Cross section measurementBefore going to asymmetry measurements, we need to confirm the applicability of factorized pQCD.
— Luminosity measurement by our beam-beam counter (BBC)
L = #BBC / BBC
BBC is determined by the transverse beam size measurement#BBC rate = BBC L (beam current)2 / (beam size)2
Un-pol
pQCD calculation is used to extract g (for example sensitive x region) Is the PDF measured by DIS experiments valid for p+p collisions?
Cross section measurements
April 17, 2007 K.Okada 6
(Run2: PRL 91 241803)
g2 gq q2
2P 2 2x P
1P1 1x P
0
Un-pol
pQCD calculation works well.
Cross section measurements
April 17, 2007 K.Okada 7
Un-pol
Direct
2P 2 2x P
1P1 1x P
qqgq
pQCD calculation works well.
Run 5
(Run3: PRL 98 012002)
Cross section measurements
April 17, 2007 K.Okada 8
(charm) PRL97 252002: Run5
Un-pol
Electron (from Charm, Beauty)
gg QQ
gg
FONLL upper limit
pQCD calculation works well.
April 17, 2007 K.Okada 9
Asymmetry measurementRHIC
Yellow + - + - + - ………Blue + + - - + + 120 bunches (revolution time = 1.2 [s])
yellowblue
Check bunch related systematic uncertainty
Enough statistics in a bunch check rate per bunchIf it’s not enough assign random spin pattern confirm null asymmetry
RNNRNN
PALL 2
1
LLR Relative luminosity
determined by BBC,ZDC counts
Check relative luminosity measurementUsing the same hard scattering as the luminosity measurement Need to check if there is no ALL in BBC Comparison between BBC and ZDC
April 17, 2007 K.Okada 10
Mid rapidity 0 asymmetry
g2 gq q2
2P 2 2x P
1P1 1x P
(1.8/pb)(“7.5/pb” fast track)
s=200GeV 0
April 17, 2007 K.Okada 11
0 asymmetry with theory calculations
g = 0.42at Q2=1(GeV/c)2
best fit to DIS data available in 2001
s=200GeV
It is consistent to g=0 and even negative g.
0
2 analysis
April 17, 2007 K.Okada 12
A way to access higher xgluonLower collision energy ( s=62GeV)
Run6 62.4GeV ~0.06 pb-1
Run5 200GeV 1.8 pb-1
x 0.1 instantaneous luminosity,x100 production for the same xT
pT[GeV/c](@s=200GeV)(@s=62GeV)
51.6
82.5
0
Theory applicability at 62 GeV not yet verified by cross section
!!
spT2
April 17, 2007 K.Okada 13
Various channels other than 0
Jet componentsg+gg+qq+q
Direct photong+q
Heavy particleg+g
0
±
h±
“jet”
open charm to e to
J/ to e+e to +
Yield & purity
photonCentral armMPC (forward EMCal)Muon arm (but not only for muon)
PHENIX
For the high precision,
Complementary measurements
open beauty
April 17, 2007 K.Okada 14
Yield comparison
0: preferred by EMCal trigger small BG at high pT
7.5/pb 60%
65/pb 70%
Lpol
ALL[%] for 1GeV bin
0.2 0.05
2 0.5
20 5
Yiel
d (a
rbitr
arily
) (PHENIX Central Arm)
pT[GeV/c]
April 17, 2007 K.Okada 15
Yield comparison
0
±: quark flavor dependence Cherenkov turn-on Background rejection
(PHENIX Central Arm)
0.2 0.05
2 0.5
20 5
Yiel
d (a
rbitr
arily
)
pT[GeV/c]
7.5/pb 60%
65/pb 70%
Lpol
ALL[%] for 1GeV bin
April 17, 2007 K.Okada 16
Yield comparison
0
±
Direct : gluon Compton BG from hadron decay
0.2 0.05
2 0.5
20 5
Yiel
d (a
rbitr
arily
) (PHENIX Central Arm)
Effective yield
pT[GeV/c]
7.5/pb 60%
65/pb 70%
Lpol
ALL[%] for 1GeV bin
April 17, 2007 K.Okada 17
Yield comparison (PHENIX Central Arm)
0
±
Electron (charm) : g+g, hard scattering EMCal trigger threshold BG from conversion
Yiel
d (a
rbitr
arily
)
0.2 0.05
2 0.5
20 5
Waiting for high statistics.pT[GeV/c]
7.5/pb 60%
65/pb 70%
Lpol
ALL[%] for 1GeV bin
ALL : various channels
April 17, 2007 K.Okada 18
J/ ±
, preliminary result from Run5,and others are under way. “jet”
Complementary measurements to high statistics 0 measurement
Run 5
April 17, 2007 K.Okada 19
Di-Hadron Azimuthal Correlations
Possible helicitydependence
Spin-correlated transverse momentum (orbital angular momentum) may contribute to jet kT.
kT asymmetry (out of ~3GeV)
Errors are correlated,1/P2 (~4) is multiplied
With 0 - h± correlation
April 17, 2007 K.Okada 20
Summary With RHIC PHENIX, we measured production cross sections of variousparticles in p+p collisions at s=200GeV. The results confirm our theoretical understanding of hard scattering, which is important for the next step (= measurement of proton spin structure)
Double helicity asymmetry measurement of 0 excludes a large △g scenario. From other channels, complementary results will be obtained.
The longitudinal polarization program at s=200GeV will be accomplishedwith about 70pb-1, 70% polarization in 2008.
Does the angular momentum play a big role? Jet kT asymmetry may berelated.
PHENIX detector upgrade project talk by J. Lajoie session 9 (Apr.19th)
April 17, 2007 K.Okada 21
backups
C. Aidala, COMPASS Workshop, March 19, 2007
22
)()2/(
0
0
HERMES
(hadron pairs)
COMPASS(hadron pairs)
RHIC(direct photon)
CDF(direct photon) CDFdirect photon
PHENIX (direct photon)
pQCD Scale Dependence at RHIC
Statistical errors only
Theoretical uncertainty of pQCD calculations in channels relevant for gluon polarization measurements:
0 data vs pQCD with different factorization scales:
PHENIX (inclusive hadrons)
μ/2 (factorization scale)
μ
2μ
April 17, 2007 K.Okada 23
0 Run2
April 17, 2007 K.Okada 24
PRL 91 241803 (2003)
h± Run2
April 17, 2007 K.Okada 25
PRL 95, 202001 (2005)
Direct Run3
April 17, 2007 K.Okada 26
PRL 98, 012002 (2007)
Electron Run5
April 17, 2007 K.Okada 27
PRL 97, 252002 (2006)
April 17, 2007 K.Okada 28
Yield comparisons
=200
GeV
Yie
ld (a
rbitr
ary)
ALL of at s=200GeV
Run 5
Tp ~ 5GeV
+ 0 -
+ 0 -u u u
LL LL LL
qg starts to dominate for and D D >DExpect sensitivity to sign of G, e.g., positive A A A
K. Barish
C. Aidala, UMass Amherst, Plenary session 9/26/06
30
Plots for preliminary (1)
C. Aidala, UMass Amherst, Plenary session 9/26/06
31
Plots for preliminary (2)
C. Aidala, UMass Amherst, Plenary session 9/26/06
32
Plots for preliminary (3)
April 17, 2007 K.Okada 33
April 17, 2007 K.Okada 34
April 17, 2007 K.Okada 35
Run 5
ALL of jet-like cluster at s=200GeV
2P 2 2x P
1P1 1x P
– “Jet” detection: tag one high energy photon and sum energy of nearby photons and charged particles
– Definition of pT cone: sum of pT measured by EMCal and tracker with R = (||2+||2)
– Real pT of jet is evaluated by tuned PYTHIA
g