m. brooks, 17-jul-03 phenix review july 17, 2003 p-p physics from muon arm—j/ melynda brooks rhic...

M. Brooks, 17-Jul-03PHENIX Review

PHENIX ReviewJuly 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


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 GeVRun 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


QGP-Physics Goals of Muon Subsystem

Contribute to systematic study of expected QGPsignatures:

•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…


Spin-Physics Goals of Muon Subsystem

Spin Physics•anti-quark polarizations

•W± (high-pT single muons) •Drell-Yan (high-mass dimuons)

•gluon polarization •J/ (dimuons) •heavy-flavor (high-pT single muons)

Require relatively high luminosity and good polarization


The Experiment

MVD - multiplicity and vertexBeam-Beam - trigger, timeCentral Arms:

•|y| < .35 (±20o), = 180o

•excellent p resolution•PID covering wide p range and particle types•Detect e, , , K

Muon Arms:•1.2 < |y| < 2.4, = 360o

•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


The Reality

• Run-1: CDR Rates:– Au-Au at 130 GeV 104 higher AuAu

• Expectation: 20 b-1

• Reality : ~ 1 b-1

• Output: 11 publications (to date; 1 pending) Spin Proposal:• Run-2: 103 higher p-p

– Au-Au at 200 GeV• Expectation: 300 b-1 600k 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 Installedacceptance 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


What Can you do with 65 J/ Events?

•Calibrate your detector(!)•Some actual physics

•Cross section measurement•Differential cross section vs. pT, 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 fusiongluon distribution functions need to be understood)•Hadronization of the pair into a charmonium (non-perturbative QCD phenomenon) not clearly understood yetTotal cross section correct?

•Color-evaporation model (CEM)•Color-singlet model (CSM)•Color-octet model (COM)


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/


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


How to Extract J/ Cross Section

• NJ/: number of J/ measured within rapidity, pT bin• Arec 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, pT 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)

• Lint: 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)

yLA

N

dy

dJB

JBBCdeeprec

JJr

int/

//)/(


Reconstructing Pairs to Extract NJ/

•Good J/ yield requires: high efficiency for finding tracks, properly collecting all the hits, reconstructing track accurately•Much work done, primarily by LANL folksto improve reconstruction efficiency andaccuracy:

36 J/s 65Mass 400 MeV 150 MeV

2/15/2002

△M~400MeV

△M~250MeV △M~150MeV

Final production

Preliminary,Proposed: Final


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


Muon Tracker Detector in Monte Carlo

Track reconstruction well represented by Monte Carlo also

Monte CarloReal Data


Central Arm also measured J/Ye+e-

Central and forward rapidity measurements can be combined to get total cross section


p-p J/psi Measurement

Pythia rapidity shape used to extract total cross section:

= 3.99 +/- 0.61(stat) +/- 0.58(sys) +/- 0.40(abs) b

Shape variations due primarily to various PDFs. All consistent within error bars.


p-p J/psi Measurement—pT Distributions

•pT 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 pT J/ Production in pp Collisions at √s = 500 and 200 GeV at RHIC”, Gouranga C. Nayak, Ming X. Liu, Fred Cooper (LANL)

*


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


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 pT

•Would want to measure polarization vs. pT

•J/ contaminated by feed-down but still should retain measurable polarization’ would be cleaner measurement

= 11.3 – 11.9(I1/I2) + 2.81(I1/I2)2

= 0.15 ± 1.8(stat)I1

I2


Future Outlook

•Polarization measurement should further constrain models (requires more luminosity)

•More luminosity could extend pT 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.


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 pT, 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:

m. brooks, 17-jul-03 phenix review july 17, 2003 p-p physics from muon arm—j/ melynda brooks rhic...

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