Andrew Glenn(University of Tennessee)

For the PHENIX CollaborationFall DNP Meeting Tucson, AZ

October 31, 2003

Single Muon Production in . = 200 GeV Au+Au

Collisions at thePHENIX Experiment

NNs

2

Andrew Glenn, University of Tennessee, 2003

The ApparatusDetector (Iarocci Tubes)

Steel Absorber

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Andrew Glenn, University of Tennessee, 2003

Sources of Muon CandidatesD (B) meson semi-leptonic decays(D K …) Prompt Signal

Decay muons from hadron decays (±± , K±± )

‘Hadron’ Punch Through(±, K±, p)

Decays from J/, , Drell-Yan…(Small Contribution)

PH

MuID

Bac

kgro

un

d

Gap 0 1 2 3 4

Steel absorber

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Andrew Glenn, University of Tennessee, 2003

Data SampleRHIC Run II Au+Au (The first muon capable run)Start With 7.7M Minimum-Bias Events(Cleanest section of running period)

Cuts on:Vertex (-20 to 38cm)

Track Quality (2/DOF < 7, NTrHits >=12)

(-1.51 to -1.79 or = 155 -161o) Uniform acceptance in event vertex.

Azimuthal Cut

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Andrew Glenn, University of Tennessee, 2003

Muon Identification

Sharp Muon Peak

Long tail from interacting hadrons(more evidence to come)

Main muon identification is from momentum/depth matchingPH

3 GeV

1 GeV

3 GeV

MuID

Gap (Plain) 0 1 2 3 4

ste

el

Last Gap = 2

Centrality > 20%

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Andrew Glenn, University of Tennessee, 2003

Peripheral Data Vs Simulation

Simulation: Muons From Central Hijing Data: Centrality > 60 (For cleaner events)

Falsely extended tracksLast Gap = 2

Last Gap = 3

Last Gap = 4

No clear peak or tailsince last gap.

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Andrew Glenn, University of Tennessee, 2003

We want to separate the contribution from prompt muon production and /K decays

Collision Point

nosecone

magnet

Muon trackerMuon ID

40 cm

• D c = 0.03 cm Decays before absorber• c = 780 cm Most are absorbed, but some decay first • K c = 371 cm Most are absorbed, but some decay firstγcτ >> 80cm → Decay Probability nearly constant between nosecones

Collisions occurring closer to the absorber will have fewer decay contributions. Should see a linear increase in decay background with increasing vertex.

Decay Contribution

X

Z

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Andrew Glenn, University of Tennessee, 2003

Vertex Dependence

=Centrality > 20%

Very Linear Shape Due to Decays

Not due to vertex detector resolution Centrality > 20%

Centrality > 20%

1 < pT > 3 GeV/c

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Andrew Glenn, University of Tennessee, 2003

Interacting Hadron Vertex

Interacting Hadrons: Last Gaps 2 and 3, Pz St3 tail. Flat shape indicates little to no decay (hence muon) component

Last Gap = 2

Centrality > 20%

Centrality > 20%

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Andrew Glenn, University of Tennessee, 2003

From simple (event vertex corrected) subtraction of near muons from far muons

(Hence NOT NORMALIZED, also NOT ACCEPTANCE/EFFICIENCY CORRECTED)

Decay pT Distribution

Centrality > 20%

Region II – Region I

Z vertex

Muon Vertex

Region I Region II

Decays

prompt decay + punchthrough??

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Andrew Glenn, University of Tennessee, 2003

SimulationsA first approach to estimate the fraction of decay contribution used HIJING+GEANT Au+Au simulations.

Large statistical error and large error due to lack of HIJING tuning (K/ Ratios, pT distribtions etc.)

With the recent availability of BRAHMS and K data at Muon Arm rapidities, we can examine a data driven simulation approach.

An accurate modeling of K and (and p) production for simulation input is needed for punchthrough estimations.

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Andrew Glenn, University of Tennessee, 2003

Data Driven Particle Generator

Use scaled PHENIX central arm data to for basis of event generator. BRAHMS preliminary data helps with scaling and justification ( P(y,pT) ≈ P(y)P(pT) ). Only measurements for 5% most central events are available from BRAHMS.

5% Most Central Events

BRAHMS data extractedfrom Djamel Ouerdane’s thesis

BRAHMS5% most central

Provides scaling

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Andrew Glenn, University of Tennessee, 2003

Generator First LookSingle K’s and ’s thrown with BRAHMS (preliminary, 5% most central) pT and dN/dy shapes. pT > 1 GeV required. Passed through full simulation/reconstruction.

Decays: 900K Single Hadrons Gives:

Punchthrough: 800K Single Hadrons Gives:

Last Gap Reached Reconstructed Decay Muons

2 161

3 297

4 712

Last Gap Reached Reconstructed Punch Through

2 222

3 150

4 66

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Andrew Glenn, University of Tennessee, 2003

Summary

A significant number of muons were measured in Run II Au+Au.

A fraction of interacing hadrons can be clearly identified. (Helps understand punchthrough)

Muon candidate vertex dependence provides important information about decay contribution.

A simulation procedure is being developed which should allow good estimation of decay and punchthrough contributions.

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Andrew Glenn, University of Tennessee, 2003

Backup Slide

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Andrew Glenn, University of Tennessee, 2003

Simulated Decay MuonsCentral HIJING events ran through GEANT simulation.Closest cuts possible to match data (without full reconstruction).17100 total events distributed over Z=±10, ±20, ±38

Projected contribution of decay muons ends at ~75 cm

Not in fit, Geometric effect also seen in data

Large statistical errorand large error due to lack of HIJING tuning(K/ Ratios etc.)

A better method is needed for both decay and punchthrough estimation.