M. Brooks, 17-Jul-03 PHENIX Review July 17, 2003 p-p Physics from Muon Arm—J/  Melynda Brooks RHIC and the PHENIX Detector Physics Goals of the PHENIX Muon System, “the plan” Physics Goals, “the reality” J/  measurements from p-p data set Future expectations Summary

M. Brooks, 17-Jul-03 PHENIX Review The Collider Heavy-Ion collisions to search for the Quark-Gluon Plasma. Polarized p-p collisions to study the spin-structure of the nucleon and give baseline p-p measurements for heavy-ion analyses p-Nucleus to study nuclear interactions Variable energy of beams and various nuclei Run I, 2001 Au-Au beams at  s=130 GeV Run II, 2002 Au-Au beams and p-p (200 GeV) Run III, 2003 d-Au, p-p at  s=200 GeV Run IV, 2004 Au-Au, 200 GeV

M. Brooks, 17-Jul-03 PHENIX Review QGP-Physics Goals of Muon Subsystem Contribute to systematic study of expected QGP signatures: Debye screening --> varying suppression of vector mesons (J/ ,  ’,  ) Strangeness production --> enhancement of  other? Charm production -->cross section measurement, understanding required for background subtraction (from single  s or e-  coincidence) p-Nucleus experiments: study of nuclear effects (shadowing, energy loss, etc.) p-p: Also needed for full understanding of production rates, nuclear effects Physics program expectation: ~600K J/  s per year…

M. Brooks, 17-Jul-03 PHENIX Review Spin-Physics Goals of Muon Subsystem Spin Physics anti-quark polarizations W ± (high-p T single muons) Drell-Yan (high-mass dimuons) gluon polarization J/  (dimuons) heavy-flavor (high-p T single muons) Require relatively high luminosity and good polarization

M. Brooks, 17-Jul-03 PHENIX Review The Experiment MVD - multiplicity and vertex Beam-Beam - trigger, time Central Arms: |y| <.35 (±20 o ),  = 180 o excellent p resolution PID covering wide p range and particle types Detect e, , , K Muon Arms: 1.2 < |y| < 2.4,  = 360 o higher geom. acceptance Detect single and di- muons complementary to Central arm measurements J/  analysis used: Beam-Beam counter: trigger and vertex position Muon Tracker: track finding and momentum reconstruction Muon Identifier: trigger and track finding Run I Run II Run III

M. Brooks, 17-Jul-03 PHENIX Review The Reality Run-1:CDR Rates: –Au-Au at 130 GeV 10 4 higher AuAu Expectation: 20  b -1 Reality : ~ 1  b -1 Output: 11 publications (to date; 1 pending) Spin Proposal: Run-2: 10 3 higher p-p – Au-Au at 200 GeV Expectation: 300  b k J/   60 J/  Reality : ~ 24  b -1 Output: 4 submissions (to date; 8 others pending) –p-p at 200 GeV Expectations: 3 pb -1 Reality : 0.15 pb -1 Output: 1 submission (to date; 1 other pending) –Newly Installed  acceptance loss Run-3: –d-Au at 200 GeV Expectation: 10 nb -1 Reality: : 2.7 nb -1 Output: 0 submissions (to date; 1 pending) –p-p at 200 GeV Expectation: 3 pb -1 Reality : 0.35 pb -1 Output: TBD

M. Brooks, 17-Jul-03 PHENIX Review What Can you do with 65 J/  Events? Calibrate your detector(!) Some actual physics Cross section measurement Differential cross section vs. p T, rapidity Add data point to cross section vs  s Compare model predictions to real data to see if production appears to be well understood or not J/  production involves: Production of a cc pair (dominated by gluon-gluon fusion  gluon distribution functions need to be understood) Hadronization of the pair into a charmonium (non-perturbative QCD phenomenon)  not clearly understood yet  Total cross section correct? Color-evaporation model (CEM) Color-singlet model (CSM) Color-octet model (COM)

M. Brooks, 17-Jul-03 PHENIX Review J/  Production Color-evaporation model (CEM) Assumes a certain fraction of cc (determined from experimental data) form J/  by emission of several soft gluons Predicts 0 polarization Color-singlet model (CSM) cc pair in color-singlet state, with same quantum numbers as J/  forms into J/  Color-octet model (COM) J/  formed from cc color-octet state with one or more soft gluons emitted Total cross section much more consistent with Tevatron data Predicts polarization of J/ 

M. Brooks, 17-Jul-03 PHENIX Review How To Collect and Extract J/  Events? Trigger: BBC fired, |z|<38 cm, two “deep roads” found (these events filtered) Find tracks in muon tracker which match up with roads in muon identifier Rejection of “ghost” tracks Fit track using vertex, muon tracker and identifier points Combine all like-sign and unlike-sign pairs of tracks in event, calculate mass Subtract like-sign pairs from unlike sign pairs to extract signal Select pairs which fall within a mass cut and kinematic bin of interest * * * * * * * B-field

M. Brooks, 17-Jul-03 PHENIX Review How to Extract J/  Cross Section N J/  : number of J /  measured within rapidity, p T bin A  rec  deep : J/  in acceptance, reconstructed and passed simulated trigger. Requires: –Accurate representation of detector –Detector efficiencies understood –Run-to-run variations understood –Using accurate vertex distributions, p T and y distributions so they don’t introduce significant systematic error  BBC J/  : BBC trigger efficiency for p+p  J /  X events (calculated and measured = 0.74) L int : Integrated luminosity with a good vertex cut (|z-vertex|<38cm) – (number of MB events)/(MB trigger cross section). Cross section seen by BBC measured and calculated (~0.52*total cross section)

M. Brooks, 17-Jul-03 PHENIX Review Reconstructing Pairs to Extract N J/  Good J/  yield requires: high efficiency for finding tracks, properly collecting all the hits, reconstructing track accurately Much work done, primarily by LANL folks to improve reconstruction efficiency and accuracy: 36 J/  s  65 Mass 400 MeV  150 MeV 2/15/2002 △ M~ 400MeV △ M~ 250MeV △ M~ 150MeV Final production Preliminary, Proposed: Final

M. Brooks, 17-Jul-03 PHENIX Review Muon Tracker Detector in Monte Carlo Accurate representation of detector required to keep systematic error on efficiency minimal First year of operating detector, performance was not optimal and needed to be understood Detector well understood and efficiency about as high as could be achieved Systematic error from MC representation small

M. Brooks, 17-Jul-03 PHENIX Review Muon Tracker Detector in Monte Carlo Track reconstruction well represented by Monte Carlo also Monte Carlo Real Data

M. Brooks, 17-Jul-03 PHENIX Review Central Arm also measured J/Y  e+e- Central and forward rapidity measurements can be combined to get total cross section

M. Brooks, 17-Jul-03 PHENIX Review p-p J/psi Measurement Pythia rapidity shape used to extract total cross section:  = /- 0.61(stat) +/- 0.58(sys) +/- 0.40(abs)  b Shape variations due primarily to various PDFs. All consistent within error bars.

M. Brooks, 17-Jul-03 PHENIX Review p-p J/psi Measurement—p T Distributions p T distributions relatively consistent with COM predictions CSM vastly underpredicts cross sections, as had been found for CDF results *Calculations from “Color Octet Contribution to High p T J/  Production in pp Collisions at √s = 500 and 200 GeV at RHIC”, Gouranga C. Nayak, Ming X. Liu, Fred Cooper (LANL) *

M. Brooks, 17-Jul-03 PHENIX Review p-p J/  Measurement—√s Dependence Total cross section consistent with various models if PDF and other input parameters tuned. Too many variables to be able to make concrete conclusion about models(?). (CEM also consistent with our data) Highest √s measurement to date

M. Brooks, 17-Jul-03 PHENIX Review p-p J/  Measurement—Polarization done by A. Hoover No Polarization Longitudinal Polarization Transverse Polarization Angular distribution of  + from J/  Color Octet Model predicts transverse polarization at high p T Would want to measure polarization vs. p T J/  contaminated by feed-down but still should retain measurable polarization  ’ would be cleaner measurement  = 11.3 – 11.9(I 1 /I 2 ) (I 1 /I 2 ) 2  = 0.15 ± 1.8(stat) I1I1 I2I2

M. Brooks, 17-Jul-03 PHENIX Review Future Outlook Polarization measurement should further constrain models (requires more luminosity) More luminosity could extend p T measurement and enter regime where gluon fragmentation dominates—further constraining models Tagging J/  production from , B decays rounds out picture of J/  production (more luminosity and/or detector upgrade) as will measurement of  ’ Run 2003 data set should provide ~10 times statistics. Other runs possible in 2+ years.

M. Brooks, 17-Jul-03 PHENIX Review Summary You can do physics with only 65 events (!) Most modern model predictions are reasonably consistent with our measurements. Production reasonably well understood(?), though further tests (polarization, higher p T, etc.) will make more stringent tests of these models Detector well understood and performing very close to design specifications Allowed quick turn-around of dAu data set, poised to work on further tuning for Au-Au data analyses Publication submitted to Physical Review Letters: