Table Of ContentBNL-52635
Formal Report
Proceedings of RIKEN BNL Research Center Workshop Volume 33
SPIN PHYSICS AT RHIC IN
YEAR-1 AND BEYOND
May 14-18,2001
Organizing Committee:
Leslie.Bland, Daniel Boer, Naohito Saito, Werner Vogelsang
RIKEN BNL Research Center
Building 510A, Brookhaven National Laboratory, Upton, NY 11973-5000, USA
OtherRIKENBNLResearchCenterProceedingsVolumes:
Vchrne 33– SpinPhysicsatRHIC inYear-1 andBeyond – BNL
Vchrne 32– RHIC SpinPhysicsV – BNL -52628
Vchune31 – RHIC SpinPhysicsIII&IV PolarizedPartonsatHigh QA2Region - BNL-5261 7
Vcdume30- RBRC Scientific Review CommitteeMeeting– BNL-52603
Vcdume29- FutureTransversityMeasurements- BNL-52612
Vcdume28- Equilibrium& Non-Equilibrium Aspects of Hot, DenseQCD – BNL-526 13
Vchrne 27 – PredictionsandUncertaintiesfor RHIC SpinPhysics& EventGeneratorfor RHIC SpinPhysics
III– TowardsPrecisionSpinPhysicsatRHIC – BNL-52596
VcJume26- Circum-Pan-Pacific RIKEN Symposium onHighEnergy SpinPhysics- BNL-52588
Vchxne 25- RHIC Spin- BNL-52581
Vc,lme 24- physics Society of JapanBiannualMeeting Symposium on QCD Physics atRIKEN BNL
ResearchCenter- BNL-52578
Vchme 23- Coulomb andPion-Asymmetry PolarimetryandHadronic SpinDependence atRHIC Energies–
BNL-52589
VcJ~e 22- OSCAR II: predictions for ~IC - BNL-52591
Volume 21- RBRC Scientific Review CommitteeMeeting - BNL-52568
Volume 20- Gauge-InvariantVariablesinGaugeTheories– BNL-52590
Volume 19- NumericalAlgorithms atNon-Zero ChemicalPotential-BNL-52573
Vahme 18- EventGeneratorfor RHIC SpinPhysics -BNL-52571
Volume 17- HardPartonPhysicsinHigh-Energy NuclearCollisions - BNL-52574
Volume 16- RIKEN WinterSchool - Structureof Hadrons- Introductionto QCD HardProcesses–
BNL-52569
Volume 15- QCD PhaseTransitions-BNL-52561
Volume 14- QuantumFieldsInandOutof Equilibrium- BNL-52560
Volume 13- Physicsof the 1Teraflop RIKEN-BNL-Columbia QCD ProjectFirstAnniversaryCelebration–
BNL-66299
Volume 12- QuarkoniumProductioninRelativisticNuclearCollisions – BNL-52559
Volume 11- EventGeneratorfor RHIC SpinPhysics -BNL-66116
Volume 10- Physicsof PolarimetryatRHIC - BNL-65926
Volume 9- HighDensityMatterinAGS, SPSandRHIC Collisions - BNL-65762
Volume 8- FermionFrontiersinVector LatticeGauge Theories- BNL-65634
Volume 7- RHIC SpinPhysics -BNL-65615
Volume 6- QuarksandGluons intheNucleon - BNL-65234
Volume 5- Color Superconductivity,InstantonsandParity(Non?)-Conservation atHighBaryonDensity–
BNL-65105
Volume 4- InaugurationCeremony, September22 andNon -EquilibriumMany Body Dynamics –
BNL- 64912
Volume 3- HadronSpin-FlipatRHIC Energies- BNL-64724
Volume 2- PerturbativeQCD asaProbe of HadronStructure-BNL-64723
Volume 1- Open Standardsfor CascadeModels for RHIC - BNL-64722
Preface to the Series
The RIKEN BNL Research Center(RJ3RC)was establishedin April 1997 at
Broolihaven National Laboratory. It is tided by the “Rikagaku Kenkysho”
(RIKEN, The Instituteof Physical and Chemical Research) of Japan. The Center
is dedicatedto the studyof stronginteractions,includingspinphysics, latticeQCD
andRI-HCphysics throughthenurturingof anew generationof young physicists.
During the fist year, the Centerhad only a Theory Group. In the second
year:,anExperimentalGroup was also establishedattheCenter. At present,there
are seven Fellows andnine post dots in thesetwo groups. During the thirdyear,
we starteda new Tenure Track Strong InteractionTheory RHIC Physics Fellow
Program, with six positions in the academic year 1999-2000; this program will
increase to include eleven theorists in the next academic year, and, in the year
after, also be extended to experimental physics. In addition, the Center has an
active workshop program on strong interactionphysics, about ten workshops a
year, with each workshop focused on a specific physics problem. Each workshop
spea:keris encouraged to select few of themost importanttransparenciesfrom his
or her presentation, accompanied by a page of explanation. This material is
collected atthe end of the workshop by the organizerto form proceedings, which
can thereforebe availablewithin ashorttime.
The construction of a 0.6 teraflop parallelprocessor, which was begun atthe
Centeron February19, 1998, was completed on August28, 1998.
T. D. Lee
September29,2000
*Work performed undertheauspicesof U.S.D.O.E. ContractNo. DE-AC02-98CH1 0886.
CONTENTS
Prefa.ce tothe Sefies ......................................................................... i
Spin Physics at RHIC in Year-1 and Beyond – Introduction and Overview –
Organizers: L. Bland.D. Boer, N. Saito, and W. Vogelsang .................. 1
ST&? Spin Plans in Year-1
G. Rakness............................................................................. 3
PHENIX Spin Plans in Year-1
Y.Goto................................................................................... 9
Introduction to A_LL (pi)
W. Vogelsmg .......................................................................... 15
Fragmentation Functions for Light Hadrons
S.Kretzer..............................................................................- 21
Studies of Quark Fragmentation at HERMES
M. Vetterli............................................................................... 27
Vector Boson Production with Longitudinally Polarized Beams: Lepton-Level
Results
P. Nadols~ ............................................................................ 33
Vectc)r Boson Production at Small Transverse Momentum
A..Kulesza.............................................................................. 39
Determining Delta g: Polarized Hadro- and Photoproduction of Heavy Quarks in
NLO QCD
I. Bojak................................................................................. 45
Physics Beyond the Standard Model at RHIC
J–M. Virey............................................................................ 51
Gluon Contributions to Parity-Violating Asymmetries in Polarized Proton-Proton
Scattering
S.Moretti.............................................................................. 57
Highw-Order QCD Corrections to the Parity-Violating Jet Asymmetry
W. Vogelsang......................................................................... 63
Parity Violation in bb-bar Production by Polarized Protons
D. Amood .............................................................................. 69
Photon- and Gluon-Fusion as a Probe of Higgs-Sector CP Violation
B. Grzadkowski........................................................................ 75
Parity Violation and New Physics at RHIC in Year-01 and Beyond
JMurata .............................................................................. 83
RHIC-Spin and Lorentz Structure of Electroweak Current
ZRybv ................................................................................ 89
Introduction Talk on Single-Spin Asymmetries AN,Theory and Experiment
M.Anselmino.......................................................................... 95
ANfor Pion Production
G. Stennan............................................................................. 105
Polarized Proton Nucleus Scattering
L. Trueman............................................................................ 111
RHIC pC CNI Polarimeter Status
LAletiew ............................................................................. 119
pp2pp in Year-1 at RHIC
S.Bueltmann........................................................................... 125
Introduction to Experimental Issues at RHIC
L. Bland................................................................................ 131
Discussion of Experimental Issues in Year-1
G.Bunce............................................................................... 137
Comments on Polarimetry at High Energy Accelerators
H. Spinh .............................................................................. 141
Expectations for RHIC ~
G.Bunce................................................................................ 147
Towards a Global QCD Analysis of Polarized PDF’s
ill Stratmann......................................................................... 155
Statistical Approach to Polarized Parton Distributions
JSoffer ................................................................................ 163
Uncertainties in Polarised Parton Fits
S. Gupta............................................................................... 171
Error Analysis of PDF’s
H. Kob~ashi ......................................................................... 177
Towards A Global Analysis of Polarized Scattering Data for Determination of
Polarized Gluon Distribution
A. Deshpande .......................................................................... 183
Lambda Polarization in Semi-Inclusive DIS
MAnselmino .........................................................................- 189
Strangeness in Neutrino DIS
S.Kretzer.............................................................................. 199
Flavor Dependent PDFs
M.Liu....................................`.............................................. 205
Transversity Single-Spin Asymmetries
D. Boer................................................................................. 213
Measuring Transversity at RHIC
ill Grosse Perdehmp ............................................................... 219
Azimuthal QCD Asymmetries in e+e- Collisions & Chiral Odd Fragmentation
Functions
A. Ogwa .............................................................................. 225
List(~fRegistered Ptiicipmk ............................................................. 231
Agenda .......................................................................................... 236
Workshop Photos
Spin Physics at RHIC in Year-1 and Beyond
– Introduction and Overview –
The much anticipated RHIC spin physics program will commence this fall when the first
physics run with colliding beams of polarized protons is expected. More specifically, the
pla,nned year-1 RHIC-Spin measurements are 1) the double-spin asymmetry A~~ in pro-
duction of pions by collisions of longitudinally polarized protons (in order to obtain first
information on the proton’s spin-dependent gluon density, Ag); 2) the transverse single-spin
asymmetry A% for pion production.
These two reactions provided part of the motivation for our workshop. On the first day there
were informative talks on the specific plans of STAR (by Rakness) and PHENIX (by Goto)
for the polarized run of Year-1. Some of the theoretical questions related to the double-spin
asymmetry A~~ were discussed on the first day by Vogelsang and Kretzer, which centered
mostly around the questions of how well the unpolarized fragmentation functions are known,
the need for next-to-leading order calculations, and on how sensitive the asymmetry is to
the possible Ag dktributions. Vetterli presented HERMES measurements of fragmentation
functions, which overlap in Q2 with the future lower-p~ measurements at RHIC.
The single-spin asymmetry Afi was a main topic of the third day. Anselmino and Ster-.
man showed theoretical predictions for RHIC based on different methods, but nonetheless
resulting in very similar expectations. A related observable, also interesting for Year-1, is
a certain single-spin asymmetry Afi+”-, where the pion system is in the p – o interference
region. On the last day, Boer, Grosse-Perdekamp and Ogawa discussed how Afi+”- could.
be used for an extraction of the transversity densities. This topic had been the focus of an
earlier RBRC workshop (Future Transversity Measurements, September 2000), but much
prclgress has been made since then, because of the new insight that some required input can
possibly be obtained from off-resonance data of B-factories.
It was a further major motivation of the workshop to address the experimental issues con-
cerning the first RHIC spin physics run. On the third day, Bland, Spinka and Bunce reviewed
the key issues; their presentations were followed by a long and lively discussion session. Po-
larimetry was one important topic here, as discussed by Alekseev.
The other RHIC experiment that will be exploiting the polarization of the protons is the
PP2PP experiment. It was discussed, also on the third day, by Bueltmann. An interesting
theoretical talk in this context was given by Trueman.
Apart from the talks and discussions on’~he main Year-1 observable, the workshop also had
a broader goal, namely the discussion of the status, progress and open problems of three
more topics very relevant to RHIC-Spin: 1) “global analyses” of the available and future
data in terms of spin-dependent parton densities ; 2) measurement of the polarized strange
qua,rk density, As; 3) sensitivity to physics beyond the Standard Model. Again we managed
1
to have many experts on these topics amongst the participants, and a lot of original work
was”discussed. Stratmann critically discussed the first topic and presented a new practical
method for incorporating higher-order calculations into global analyses. He also pointed out
that serious studies of the uncertainties in the extractions of polarized parton densities are
only just starting – no clear-cut, generally accepted way exists yet. Talks along similar lines
were given by Gupta, Kobayashi and Deshpande. Soffer presented new work on a statistical
approach to polarized parton distributions, with which he could fit a remarkable wealth of
data with fewer parameters than other descriptions of the data. Related issues of higher
order corrections and resummation calculations, which are at the very basis of a successful
theoretical framework for precise predictions for RHIC, were discussed in a separate session
on the first day by Nadolsky, Kulesza and Bojak.
The measurement of As was topic of the discussion on the fourth day. Talks by Anselmino,
Kretzer and Liu explored the possibilities for RHIC, also comparing to the potential of deep
inelastic scattering for giving information on As. The feasibility study by Liu using PYTHIA
was based on a spectator-like picture that might provide information on a polarized s-quark
fracture function, rather than on As, which is a new idea and interesting in itself.
The second day was reserved for talks on the sensitivity to physics beyond the Standard
Model at RHIC. Many interesting ideas were put forward (by Virey, Atwood, Grzadkowski
and Rykov), relating to signatures of contact interactions, parity violation in b~production,
and CP violation in the Higss sector. For some specific observable more detailed studies,
also of Standard Model backgrounds, were presented (by Moretti, Vogelsang and Murata).
The main conclusion was that for design energy and luminosity the sensitivity will most
likely not be sufficient, but that a conceivable future upgrade to @ = 650 GeV and an
improvement in luminosity of a factor 25 would enhance the possibilities considerably.
In summary, all topics were discussed in detail, most of the time by more than one expert
speaker, and in the interesting talks and lively discussions many new ideas were proposed.
The large number of 51 registered participants, with 36 scheduled talks, demonstrates the
large interest in the RHIC spin physics program and the excitement created by the start of
the program only a few months from now. We would like to end with the general conclusion
that Year-1 of the polarized running will undoubtedly produce interesting results. It will
already broaden our understanding of the nucleon spin and will also lead to the test of some
theoretical models. The prospects for spin physics at RHIC after Year-1 are even more
exciting.
We thank T.D. Lee and his RIKEN-BNL Research Center for the generous funding of
the workshop and for continuous support. Special thanks go to Tammy Heinz and Pamela
Esposito for their invaluable work – it would certainly have been impossible to run a workshop
like this without them. We also thank all participants for their visit to the Center and for
having made this workshop a great success.
I Leslie Bland Daniel Boer Naohito Saito Werner Vogelsang
2
STAR Spin Plans in Year-1
G. Rakness
Indiana University Cyclotron Facility
Representing the STAR Spin Collaboration
A plan ispresented outlining the goals which the STAR Spin group believes cm be achieved
during the first ~ – ~ physics run at RHIC, scheduled for Fall, 2001. The goals are aimed at
making interesting physics measurements as well as taking important steps towards the long-
term success of the overall spin program at RHIC. Ultimately, the RHIC spin program will
provicle several new insights about the structure of the proton, including the fraction of the
proton’s spin carried by gluons. The collider environment differs from that of fixed target
experiments. As such, this first ~ – ~ run will provide important lessons about how to make
spin asymmetry measurements at RHIC.
Following the commissioning of RHIC and STAR, the central focus of the STAR Spin
group for this run is to measure a beam spin asymmetry for the first time in a ~– ~ collider.
According to model calculations, the transverse single-spin asymmetry for the production of
leading To mesons at large-z~ and moderate-p~ is expected to be significantly different from
zero at RHIC collider energies. During this year’s data collection period, the background, the
rates, and the value of the inclusive To asymmetry will be studied in detail. If the conditions
are appropriate, the plan is to identify detectors suitable for an in situ beam polarimeter at
the STAR interaction region to use in subsequent years’ running. An important issue which
will be addressed during this measurement is the determination of the relative luminosity
between bunch crossings which have polarization directions pointed in the same and in opposite
direct ions. Concurrent with this measurement, STAR will measure single-spin asymmetries
for the production of high-p~ leading charged hadrons at mid-rapidity. These asymmetries
are expected to vanish according to leading-twist perturbative QCD predictions.
The majority of the beam time in Year-1 will be spent with longitudinally polarized proton
beams. The STAR Spin group will spend this time studying the production of leading charged
particles and neutral pi-mesons at mid-rapidity, with the aim understanding the systematic
uncertainties that could limit an eventual measurement of the double-spin asymmetry, ALL.
Ccmcurrent with the preceding measurements, the ~– ~ beam collisions this year will also
be used to accumulate an unpolarized reference data set to aid the heavy ion program in the
interpret ation of the Au – Au data which are being collected with STAR.
Spin Run at RHIC i
I STllR Spin Plans in Year-1
I
l Begincommissioningof15– Z7collisionsOctober 2001
G. Ralmess
IndiamaUniversity Cyclotron Facility . Spin run mid-Ott. – end ofNov.
Representingthe ST.ARSpin Collaboration
+ Have5week to collectdata fromZ3—F collisions....
Spin Physicsat RHIC in Year-1and Beyond
RIKEN-BNL Workshop
Expectations:
14May2001
. .C= 5 x 1030cm–2s–l
l P&~~ = 0.5
l Colliderexpectations
l Polarization direction:
l STAR goals —vertical: N 1.5pb–l
- radial fewdays
l SingI&spinasymmetries - longitudinal: -5 pb–l
c Luminosity measurements
l Doublespin considerations
l Other plans
I
Asymmetry Measurements I Goals for Year-1 Spin I
singl~spin (n = 1) and doublespin (n = 2) ssymmetry
. Commissionaccelerator and detectors foroperation during
measurements havethe form
l?– $ running
.
~_ lN+– RN.
P N+ + RN_ l Measure asymmetries forthe firsttime in aZ5– ~ collider
whichrequiresthree measurements o Determine limitingsystematicuncertainties formeasurements
ofALL
l N+(_) =Yield of particles born bunch crmsings with one
polarization vectorpointiig in the +(–) direction
QAccumulate reference p —p data sample for heavy ion
program
l R=relative luminosity ofbeun crossingsfor bunches with
poltition pointing in the + and – dkctions (PndA w
6R/(1+ R)2) + Measurements aimed at maldng interesting physim
messurementx, AND makingsteps towards the successofthe
longerterm spin program....
l P = l?bl(~ P~2)=beam polarization(s)
+ Focuson singkspin asymmetries....
+ RHIC will provide the first measurements of beam spin
asymmetries in afl– 15collider....
.AN=smsJl pT-t-p+ h*+ Xatlql<l.2
SpeciaJdifficultiesina collide~
l Depolarization resonances .AN#O:pT+p+?TO+X at 0.2<xF<0.6 and
l<~<4GeV
l Luminosityfluctuations (correlated with Pb)
l Backgrounds 4
