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Measurement of heavy flavour production in p-p and d-Au collisions at

RHIC by the detection of the inclusive

muonsJu Hwan Kang(Yonsei Univ.)

for the PHENIX collaboration

Lake Louise Winter Institute 2004Lake Louise, Alberta, Canada

15-21, February, 2004

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Motivation

Heavy flavour production in pp collisions at s1/2 = 200 GeV/cDifferential production cross section: How good is the description

by pQCD-driven parton model at this energy?Charge asymmetry (non-perturbative effect): How big is the

effect of higher twist (recombination)?

Heavy Flavor production in dAu and AuAu collisionsNuclear modification factor (Rcp): Does "binary scaling (by

number of nucleon-nucleon binary collisions)" work for these systems?

Evolution of charge asymmetry: How does the non-perturbative dynamics evolve from p+p to these systems?

Study of the forward/backward hadron production in dAu Probe different “x” ranges: (anti)shadowing/saturation(CGC).

periphcoll

periph

centcoll

cent

Tcp NN

NNyPR

/

/),(

central

peripheral

d2 Au197

3

d[A+BX] = ij f

i/Af

j/B d [ijcc+X] D

cH

+ ...

J.C.Collins,D.E.Soper and G.Sterman, Nucl. Phys. B263, 37(1986)

Factorization theorem for charmed hadron production

fi/A,fj/B

: distribution fuction for parton i,j

DcH

: fragmentation function for c

d [ijcc+X] : parton cross section

+ ... : higher twist (power suppressed by

QCD/m

c, or

QCD/p

t if p

t ≫m

c ) :

e.g. "recombination" PRL, 89 122002 (2002)

fi/Au

79 fi/p

+ 118 fi/n

197 fi/N

fi/d

fi/p

+ fi/n

2 fi/N

Application to nuclei:

An example: Does "binary scaling" work?

d+Au

Au+Au

Binary scaling not working for high pt particles in central AuAu collisions!PHENIX: PRL, 91, 072303 (2003)

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Muon Production

Origins of muonsPYTHIA p+p @

√s=200GeVlow PT:

light hadron decayshigh PT:

Heavy quark decays

Muon PT distribution

%63)(

%99.99)(

%10)(

%10)(

vKBR

vBR

XbBR

XcBR

Direct reconstruction of open charm is ideal, but difficult. Open Direct reconstruction of open charm is ideal, but difficult. Open charm and bottom can be measured via single muons.charm and bottom can be measured via single muons.

By removing muons from /K decays, heavy quark production can be measured.

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RHIC at Brookhaven National Laboratory

Dedicated (relativistic) heavy ion collider: P+P (can be polarized) at s = 200 GeV or s = 500 GeV A+A (d+Au, Au+Au, …) at s = 200 GeV

4 Exp's:PHENIX STAR

PHOBOS BRAHMS

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The PHENIX Experiment(12 Countries; 58 Institutions; 480 Participants as of January 2004)

Two central arms for measuring hadrons, photons and electrons

Two forward arms for measuring muons

Event characterization detectors in middle

The data for this talk is from the muon arms

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The PHENIX Muon Arms

Detect muons with ptot > 2 GeV/c -1.2 > > -2.2 (South Arm) or

1.2 < < 2.4 (North Arm)

Muon Tracker (MuTr)Measure momentum of muons

with cathode-readout strip chambers at 3 stations inside Muon Magnet

Muon Identifier (MuID)/µ separation with 5-layer

sandwich of chambers (Iarocci tubes) and steel

Trigger muons

MuID

MuTr Muon Magnet

Beam Pipe

IP

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1 : Hadrons, interacting and absorbed (4λ or 98%)2 : Charged/K's, "decaying" before absorber (≤1%)3 : Hadrons, penetrating and interacting ("stopped")4 : Hadrons, "punch-through"5 : Prompt muons, desired signal

TrackerIdentifier Absorber

Collision range

Collision1

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4

5

Muon HadronAbsorberSymbols

Detector

Major Sources of Inclusive Tracks

Items 2 and 4 are small fraction of the original hadrons, but are more than prompt muon signal 5.

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Case 2, Decaying hadrons

* We need to understand “Decaying hadrons” to determine background to “Prompt Muons”

* Daughter muons from the hadrons can be measured separately from other sources using the dependence of yields on the location of collision points.

The longer the distance from the collision point to the front absorber, the more daughter muons from hadrons.

Almost linear dependence:Flight distance is much smaller compared to the mean decay length.e-L/λ ~ (1-L/λ)=(1+Zcoll/λ)

Arb

itra

ry u

nit

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Measured decay muons with the

expectation

Green band represents systematic uncertainty.

Red and blue dotted linescorrespond to expectation.

Red and blue lines showstatistical uncertainty.μ -

μ +

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Tracks reaching the second last (4th) MuId layer exclusively are made up of stopping tracks & interacting hadrons.

Stoppingtracks

Interacting hadrons

Stopping (range-out) tracks: Lose all of its energy by ionization and stop before reaching the last MuId layer.

Interacting hadrons: Even when hadrons have large momenta to reach the last MuId layer, they can undergo hadron interaction in the last absorber layer to stop before reaching the last MuId layer.

Momentum distribution of the tracks with DEPTH 4

Use of interacting hadrons for data driven punch-through estimation?

Case 4, Punch-through hadrons

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Extraction of Interaction Length

There is relation between hadon flux at collision point (I0) and hadron flux at depth 4 (I4) obtained in the previous page. In simplified picture, assume hadrons experience damping by an exponential absorption, exp(-L as they propagate

through the absorber material.

Then, simplified picture works to the 1st order: some differences exist due to the details of hardon propagation (decay, shower, uncertainty on hadron interaction)

I0 : Flux at collision

I3 : Flux at 3rd ID layer

I4 : Flux at 4th ID layer

I5 : punch-through's

I0

I4

I5

I3

Estimate punch-through by extrapolating to depth 5

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d Au

Phenix Preliminary

Central

Depletion on the d-going side ( low x partons in Au) : Shadowing/suppression region (depletion of low x in Au compared to nucleon)

As a by-product, measured backgrounds (abundant hadrons, especially stopped hadrons in MuId) also lead to an interesting physics (study of shadowing/saturation).

Backgrounds is also Signals !

Rcp: nuclear modification factor

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Prompt muon production: In Progress

Remaining to the measurement of the prompt yields,N

inclusive – N

decay – N

punch through = N

prompt + N

background

In Control In Evaluation (about 10-20%)

Expected plot

No absolute value yet; final efforts in progress

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Summary

Systematic study of heavy flavor production at RHIC can be possible by measuring single muons resulting from semi-leptonic decays of heavy flavour.

From this study, perturbative and non-perturbative aspects of collisions (p+p, d+Au, Au+Au) can be explored.

As major sources of backgrounds, decays and punch-through's of the abundant hadrons were identified.

As a by-product, measured backgrounds (abundant hadrons; mostly )also lead to an interesting physics (study of shadowing/saturation by measuring Rcp in different x).

Final efforts to estimate non-trivial sources of backgrounds (10 ~ 20%) and determine prompt muon production is in progress.

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Backup Slides

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X pmean

Dominance of multiple scattering suggests

is distributed as

where is 0.13 (GeV/c).

DATA

How do we quantify purity of the selected tracks?We utilize multiple scattering!

)2

exp()(2

2

0 X

XCXf

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Observation of interests :1. Large charge asymmetry in interacting hadrons is seen in data and

simulation. This is mostly due to penetrating power of the K+ particlesaccording to the GEANT.

2. While data and simulations with different interaction models showqualitative agreement, quantitative description shows substancial difference.

Comparison with Models

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Probed “x” region of Au

Saturation?

shadowing

enhancement

EMC effect

Fermi Effect

Blue band: d directionShadowing/suppression regime

Yellow band: Au directionAnti-shadowing/Cronin regime

yes

Mx