Transcript Slide 1

RHIC Spin Experiments
• Long-term goals
• Polarized protons in RHIC
• STAR and PHENIX
• Results from first polarized proton collisions
• Plans for the future
• Summary
L.C. Bland, for the RHIC spin collaboration
Brookhaven National Laboratory
Workshop on Hadron Structure and Spectroscopy
Paris, March 1-3, 2004
RHIC Spin Collaboration Organization
• RHIC Spin Collaboration (Spokesman: G. Bunce)
Develops overall spin plan; forum to coordinate spin issues for RHIC accelerator and experiments.
Spin physics is an integral part of the goals of the STAR, PHENIX and pp2pp experiments.
• RHIC Accelerator Spin Group (Spokesman: T. Roser, Project Manager: W. Mackay)
Accelerator physics for spin (Siberian Snakes, Spin Rotators,`Spin Flipper’); polarized ion source; polarimeters.
• RIKEN and RIKEN/BNL Research Center (Group Leaders: H. En’yo, G. Bunce)
Funds spin physics equipment; develops polarimetry; organizes spin workshops; supports young physicists.
• STAR Spin Physics Working Group (Conveners: L. Bland, H. Spinka)
• PHENIX Spin Physics Working Group (Conveners: Y. Goto, K. Barish)
• pp2pp Experiment (Spokesman: W. Guryn)
• BNL Groups: RHIC Spin Group (Group Leader: G. Bunce); RBRC/Nuclear Theory
Develop / exploit spin capability of RHIC; coordinates accelerator / experiment activities; complete
measurements; members in STAR, PHENIX and pp2pp experiments.
• Laboratory / University participation
BRAHMS collaboration, PHENIX collaboration, pp2pp collaboration, STAR collaboration
New groups: Cal Tech, Colorado, Illinois, MIT
The Relativistic Heavy Ion Collider
at Brookhaven National Laboratory
R-HI
Brhams
pp2pp
PHENIX
STAR
New state of matter
QGP
De-confinement
…
polarized proton
Nucleon Spin Structure
Spin Fragmentation
pQCD
…
RHIC is a QCD lab
Polarized Proton Operation at RHIC
Equipment
to be
installed
after FY03
Equipment/developments for runs 2 (1/02) and 3 (3/03  5/03)…
• Helical dipole snake magnets
• CNI polarimeters in RHIC,AGS
 fast feedback
• b*=1m operataion
• spin rotators  longitudinal polarization
qg Compton scattering with polarized protons
provides a direct measure of gluon polarization.
Gluon Contribution
to the proton’s spin
Coincident detection of g and away-side jet  event determination of initial-state partonic kinematics.
Flavor Decomposition
of the proton’s spin
 W ± production probes flavor structure analogous to
n deep inelastic scattering.
 Polarized proton beams allows the measurement of
(the expected large) parity violation in W ± production.
 Forward m,e detection (dominated by production of
W ’s with large longitudinal momentum) gives direct
probe of quark (antiquark) polarization:
projections
STAR
STAR Au+Au, s NN = 200 GeV
STAR
EMC (Half)
Barrel
BBC
West
EndCap
EMC (1/3)
BBC
East
• STAR features large
acceptance
• Run 2003 configuration
Forward
Pion
Detectors
(E & W)
• Complete endcap EMC
towers in place for run 2004
• Complete barrel EMC
towers in place for run 2005
STAR
STAR Electromagnetic Calorimeters
Barrel EMC: 2400/4800 towers installed for 2003, with SMD but not yet preshower readout
0 (pT > 3 GeV/c) Reconstruction with Barrel EMC
Invariant Mass (GeV/c 2)
Endcap EMC: 240/720 towers installed; no SMD, preshower or postshower readout yet
PHENIX Detector
Philosophy:
 High rate capability & granularity
 Good mass resolution and particle ID
 Sacrifice acceptance
0 reconstruction and
high pT photon trigger:
EMCal: ||<0.38, =
Granularity  = 0.010.01
Minimum Bias trigger and
Relative Luminosity:
Beam-Beam Counter (BBC):
3.0<||<3.9, =2
What is required for a spin experiment at RHIC?
(a summary of the multiple concurrent experiments)
• Production of high-energy/intensity/polarization proton bunches that collide
 A successful accelerator physics experiment employing ‘snakes’,rotators,etc.
Rarest probes require Pbeam=70% and L dt = 320(800) pb-1 at s = 200(500) GeV
• Large experimental facilities capable of detecting hadrons/jets, g, e,m …
 Experimental sophistication comparable to other colliders (Tevatron, HERA,…)
• Polarimeters to monitor polarization and establish its absolute magnitude
 Coulomb-nuclear interference / polarized gas jet target / local polarimeters
Require Pbeam / Pbeam ~ 5%
• Interaction-region monitors of spin-dependent relative luminosity
 Precision experiments to minimize systematic errors in final answer
Ultra-thin Carbon
target 5 mg/cm2
600 mm width
CNI Polarimeters
RHIC
AGS
(new for run 3)
6
beam
direction
50cm
1
5
2
3
4
Si strip detectors
(Time, Energy)
 2 rings
30cm
Polarimetry Procedure
• Measure recoil carbons from
pC  pC elastic scattering
• Exploit analyzing power, AN  0.01, originating from anomalous magnetic moment
of proton. Calibration of AN required.
• Measure left/right (more generally, azimuthal variation) spin-dependent asymmetry
 LR 
N L N R  N L N R
N L N R  N L N R
, Pbeam 
 LR
AN
AN (%)
AN: pC  pC at RHIC energy (100 GeV)
for normalization assume
AN (24.3 GeV) = AN (100 GeV)
i.e. no energy dependence
[0.009 < |t| < 0.022 (GeV/c)2 ]
“ CNI ”
very similar shape of the t dependence
at 24 and 100 GeV
 suggestive of very small
energy dependence for AN between
24 and 100 GeV
blue beam
yellow beam
AGS
systematic error for RHIC data < 30 %
recoil Carbon energy (keV)
Spin-03
Alessandro Bravar
Luminosity
BBC E•W counts
Luminosity Monitoring and
Relative Luminosity Measurement
Abort gaps
-To determine the relative luminosity of
bunch crossings with different polarization
directions
- abort gaps  beam-gas background
Bunch Crossing
Polarization pattern at STAR:
Spin Up
Spin Down
Unpolarized
J. Kiryluk (UCLA)
SPIN 2002
Relative Luminosity Measurement
- Beam-Beam Counters – high rates
- BBC scaler information available for each STAR run; typical STAR run duration
from a few minutes to several hours )
- total number of counts from the BBC scaler and used in the analysis: N=8 x 109
- statistical accuracy of relative luminosity d Rstat~ 10-4 – 10-3
Example of R
R
L
1

L
01/11/02
J. Kiryluk (UCLA)
SPIN 2002
01/23/02
Machine Progress Toward RHIC Spin
 RHIC is first polarized collider: an enormous technical achievement!

 Significant technical challenges remain to reach pp design goals.
 To reach design goals on which spin program was based –
Pbeam=0.70, L = 6  1031 at s = 200 GeV  factor of ~1000 improvement
¯
in P4L – requires additional equipment and beam development time!
A typical store at RHIC, 5/15/03
STAR BBC MinBias
Background Blue beam
Background Yellow beam
Rate (kHz)
300
Polarization (Pbeam)
200
(Pbeam)
0.5
0.4
0.3
100
L = 2 x 1030 cm-2 s-1
0.2
0.1
0
06:00
0.0
08:00
10:00
12:00
Time of Day
Run 2 Progress / Results
Siberian Snakes
work to preserve
polarization through
acceleration and
store.
• L dt ~350 nb-1 and <Pbeam> ~ 18% (Yellow) / 15% (Blue) delivered to experiments.
Polarization limited by performance of AGS.
• STAR / PHENIX / pp2pp experiments commissioned for pp collisions at s = 200 GeV.
• Critical pp reference measurements for heavy-ion program completed providing
important physics results.
• Transverse single-spin measurements completed providing physics results + local
polarimeters for spin-rotator tuning in Run 3.
0 Cross Section
•The data covers over 8 orders
of magnitude
–by combining minimum bias
trigger and EMCal trigger data
•NLO pQCD calculation is
consistent with data
–CTEQ5M PDF + KKP FF
S.S. Adler et al. (PHENIX), PRL 91,
241803 (2003).
Di-jet Reference for Heavy-Ion Physics
(jet physics is central to spin program)
STAR p+p, s = 200 GeV
Hadronic high-pT azimuthal correlations in pp collisions
Phys. Rev. Lett. 90 (2003) 082302
• di-jet events clearly observed in pp collisions
at s = 200 GeV.
• di-hadrons serve as di-jet surrogates for
heavy-ion collisions.
STAR
• clear near-side and away-side di-hadron
correlations in pp collisions serve as contrast for
central AuAu collisions where away-side
correlations are strongly suppressed.
pp2pp
Run-2 Results
Measurement of small-angle pp
elastic scattering at
50  s  500 GeV;
4 x 10-4  t  1.3 (GeV/c)2
using Si strip detectors in Roman
Pots above and below the beam.
Slope
parameter
(b)
acceptance
S. Bueltmann, et al.
Phys. Lett. B579
(2004) 245.
Forward Cross Sections vs. NLO pQCD
• Results for forward 0 production
cross sections measured at STAR
(details, and final results, follow) are
in fair agreement with NLO pQCD
calculations that use factorization and
renormalization scales equal to pT of
the 0.
• Data compares much more favorably
to NLO pQCD for forward 0
production at RHIC than for fixed
target (s ~ 20 GeV) or ISR energies
(s ~ 60 GeV).
Final results for =3.8 were submitted to PRL and are
available at hep-ex/0310058
STAR-Spin Results from Run 2
STAR collaboration
Submitted to PRL for publication
hep-ex/0310058
The analyzing power result for forward 0 production is proportional to the (presently unmeasured)
analyzing power of the CNI polarimeter. A hydrogen gas jet target is ready for installation in RHIC run 4
for calibration of the CNI polarimeter effective analyzing power via pp elastic scattering.
• Measured cross sections consistent with pQCD calculations
• Large transverse single-spin effects observed for s = 200 GeV pp collisions
Analyzing Power
for Forward
Neutron Production
at s = 200 GeV
(Run 2 Result)
Neutron Veto
EM Cal Base
PbWO4
Charge Veto
Hadron Cal Base
Post-shower
W+Fiber Cal
Scintillator
Results from run 2
are basis for PHENIX
local polarimeter
used in run 3
Pb
Y. Fukao (Kyoto)
SPIN 2002
RHIC performance at FY03 run
70
Blue Ring
Yellow Ring Max at injection ~50%,
Polarization at Store
60
Max at 100GeV P~40%
50
40
Average Pbeam ~25%
30
Improved by factor of ~2
20
over FY02
10
Yellow ring affected by
0
Integrated Luminosity
0
10
20 30
Transverse
0.5/pb
40
50
0
10 20 30 40 50
Time in days (1=04/01/03)
problem with snake magnet
Longitudinal
0.4/pb
New problem
‘beam-beam tune shifts’
surfaced, limiting luminosity
Adequate to accomplish
physics goals from Run 3.
Spin Rotators and Local Polarimetry
Calculations establish
a working point and
the dependence of
transverse polarization
components on spin
rotator currents.
Local polarimeters are
needed to measure
vertical,radial
polarization components
at interaction region.
PHENIX Local Polarimeter
 Forward neutron transverse asymmetry (AN) measurements
 SMD (position) + ZDC (energy)
f distribution
SMD
Vertical  f ~ ±/2
Radial  f ~ 0
Longitudinal  no asymmetry
ZDC
PHENIX Local Polarimeter:
Spin direction confirmation
Spin Rotators OFF
Vertical polarization
Spin Rotators ON
Current Reversed
Radial polarization
Spin Rotators ON
Correct Current !
Longitudinal polarization!
Blue
Yellow
Blue
Yellow
Blue
Yellow
STAR Spin Rotator Magnet Tuning
(Run 3 Result) • RHIC polarimeter (CNI) establishes
Interaction
Vertex
*
polarization magnitude.
T
L
• Local polarimeter (BBC) establishes
polarization direction at STAR.
R
B
STAR spin OFF
rotator:
 Pvert
( 103)
3.3<||< 5.0 BBC East
ON
 Plong
BBC West
 Longitudinal Polarization at STAR
Mistuned rotators
• use segmentation of inner tiles of BBC as a
Local Polarimeter monitoring pp collisions.
• Rotators OFF  BBC L/R spin asymmetries
comparable to RHIC polarimeter (CNI).
• Rotators ON  adjust rotator currents to
minimize BBC L/R and T/B spin asymmetries.
( Radial Pbeam component )
( Vertical Pbeam component )
Top-Bottom BBC asymmetry Left-Right BBC asymmetry
Transverse Single Spin Asymmetries – Preliminary Results
Yellow Beam
 103
Blue Beam
 103
BBC East
BBC West
Ratio:  (BBC East)/ (CNI)
consistent with
 (BBC West)/ (CNI)
We get:
AN(BBC)=0.0066(8)
Stat. error only!
using: AN(CNI) = 0.0118 (10)
from CNI online analysis
 103
 103
 (CNI)
Yellow Beam

33
10
10
BBC East
 (CNI)
Blue Beam
5 s effect
- may be a result of
a broken snake?
 103
BBC West
Consistent with zero
- as expected for
vertical polarization
 103
 103
 (CNI)
 (CNI)
PHENIX and STAR
Jet/Hadron ALL Measurements in 2003
PHENIX
Preliminary
STAR projected 2003
statistical uncert. from
ongoing jet analysis
Both collaborations are ready to make high-impact ALL measurements
as soon as machine performance and available beam time permit!
Back-to-Back Correlations
p + p  0 + h± + X, s = 200 GeV
• E > 25 GeV
0
p
p
•   3.8
  1
  1
h±
p
Midrapidity h tracks…
Vector sum of all tracks with:
• -1 <  < +1
• pT > 200 MeV/c
• Require |p|T> 1 GeV/c
Define:
df  f  fp
PYTHIA expectations for back-to-back correlations:
p + p  0 + charged hadrons + X (s = 200 GeV, no detector effects)
E (GeV)
Forward 0 : =3.8…
20-30
Midrapidity h …
Vector sum of all h momenta with:
• -1 <  < +1
• pT > 200 MeV/c
30-40
Require |p|T> 1 GeV/c
Represent d distribution with
40-50
Gaussian (s) + constant (b)
hadrons
• d
 - p -  |p|T (GeV/c)
s:b increases with increasing xF
• d width decreases with increasing xF
p + p  0 + h± + X (=3.8)
STAR
E (GeV)
25-35
Forward 0 : =3.8…
Midrapidity tracks…
Vector sum of all tracks
with:
• -1 <  < +1
35-45
• pT > 200 MeV/c
•Require |p|T> 1 GeV/c
45-55
Statistical
uncertainties
only…
Significant back-to-back correlations for all xF , in
agreement with PYTHIA
Quantitative comparison to models  determinations of kT and jT smearing in p + p…
STAR
Conclusions
Forward 0 from p + p collisions
•NLO pQCD (and PYTHIA  LO + parton showers) agrees
with inclusive cross section measurement, unlike lower s data
•PYTHIA says large-xF, large- 0 come from 2  2 and 2  3
parton scattering with small contributions from soft processes
• Back-to-back particle correlations with midrapidity charged
particles qualitatively agree with PYTHIA
 Forward 0 meson production at
RHIC energies comes from hard
partonic scattering
Important result for:

• Spin effects
• Comparison with d + Au
• Flavor tagging
PP FY04 Run Goal
•
55 bunches with 1x1011 per bunch,
emittance: 15  mm-mrad
•
Achieved in PP FY03
55 bunches w. 0.7x1011 per bunch,
emittnace: 15  mm-mrad
•
Average current/ring: 70mA
•
Average current/ring: 48mA
•
Peak luminosity:
11x1030 cm-2s-1
•
Peak luminosity:
Average luminosity:
6.0x1030 cm-2s-1
•
•
6.0x1030 cm-2s-1
Average luminosity:
3.0x1030 cm-2s-1
•
b* = 1m at STAR and PHENIX
•
b* = 1m at STAR and PHENIX
•
Polarization at store >=0.40
•
Polarization at store: 0.30
•
Ultimate goal for PP FY2004:
–
–
01/22/04
55 bunches w. 2x1011 per bunch
112 bunches w. 1x1011 per bunch
1
RHIC Run-4
Delivered 762 (mb)-1 to Phenix
128 (mb)-1 last week [best week:
Au+Au Luminosity evolution
153]
As of 02/22/04 22:00
Star
0.9
Phobos 0.3
Brahms 0.4
maximum
projection
physics
target
minimum
projection
[projection and target for
14 weeks of physics run]
Wolfram Fischer
Atomic Hydrogen
Beam Source
H2 dissociator
separation
magnets
(sextupoles)
RF transitions
focusing
magnets
(sextupoles)
recoil detectors
holding field magnet
RHIC beam
Breit-Rabi
polarimeter
p recoil arms
Recoil spectrometer
2004 RUN
WILL INSTALL
6 DETECTORS
ON BLUE BEAM
ONLY
B
will have “design”
azimuthal coverage
one Si layer only
 smaller energy range
 reduced bkg rejection
power
January 21, 2004
Alessandro Bravar
The road to Pbeam
Requires several independent measurements
0 target polarization Ptarget (Breit-Rabi polarimeter)
1 AN for elastic pp in CNI region: AN = 1 / Ptarget N’
2 Pbeam = 1 / AN N”
1 & 2 can be combined in a single measurement: Pbeam / Ptarget = - N’ / N”
3 CALIBRATION: ANpC for pC CNI polarimeter in detector kinematical range:
ANpC = 1 / Pbeam N”’
(1 +) 2 + 3 measured almost simultaneously alternating p and C CNI polarimeters
4 BEAM POLARIZATION: Pbeam = 1 / ANpC N”” to experiments
at each step pick-up some measurement errors:
Pbeam
Pbeam
 Pt arg et 
 AN 
 AN 



     10%

  




   pC
 AN  pp
 AN  pC
 Pt arg et 
transfer calibration measurement
January 21, 2004
Alessandro Bravar
requires
< 107 pp
CNI events
Where we are in the program…
•
Siberian Snakes – demonstrated to work
• Pbeam at RHIC injection energy – now 0.4 / goal is 0.7
• Fast polarimeters in AGS and RHIC – demonstrated to work
• Pbeam transfer AGSRHIC – demonstrated to work
• Pbeam preserved in RHIC ramp to 100 GeV– demonstrated to work
• Pbeam preserved in RHIC ramp to 250 GeV – to do
• Pbeam maintained during RHIC store – 14 hours observed
• longitudal Pbeam at PHENIX,STAR / local polarimetry – demonstrated to work
• Pbeam / Pbeam to 5% – commission gas jet in 2004; 10% in 2004; 5% in 2005
• Lavg week to 20(50) pb-1 at s=200(500) GeV – now ~0.3 pb-1 at s=200 GeV
• Polarization reversal of stored beam – to do
Summary of RHIC Spin Program
as of 3/04
• Measured cross sections and particle correlations from p + p collisions
at s = 200 GeV are consistent with expectations of pQCD.
• Analyzing powers observed for mulitple processes from p + p collisions
at s = 200 GeV.
• Spin rotator magnets were successfully tuned to produce longitudinal
polarization at PHENIX and STAR interaction regions.
• First measurements of ALL for midrapidity 0 and jet production are
underway and will continue for RHIC runs 4,5  sensitivity to gluon
polarization.
• Polarized gas jet target is ready for commissioning and is planned for
the calibration of the RHIC beam polarization via pp elastic scattering.