Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 1

New Open Charm Results at STAR via Hadronic Decay Channels

Stephen BaumgartYale University

For the STAR Collaboration

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 2

Outline

A) D0 in 200 GeV Cu+Cu Collisions– 1) Motivation

– 2) Previous Open Charm Results in STAR

– 3) Analysis Method

– 4) Charm Cross Section in Cu+Cu Collisions

B) Ds in 200 GeV d+Au Collisions– 1) Motivation

– 2) Results

C) Conclusions

D) Outlook

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 3

Why Study Charm Production?

• Prediction of Charm Cross Section in p+p from QCD (FONLL)

– Deviations from prediction in Cu+Cu, Au+Au will show medium effects.

Ref: M. Cacciari, P. Nason, R. Vogt, Phys. Rev. Lett. 95, 122001 (2005)

• Charm production is a good probe of early state of medium

– Charm produced during initial gluon fusion

– Charm produced before thermalization. Ref: Kuznetsova, J. Rafelski Eur. Phys. J. C 51, 113-133 (2007)

Basic Gluon Fusion Diagram

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 4

Previous D0 Results

D0 measured via K channel in Au+Au, d+Au.

pt spectra obtained, cross sections measured.

D0 Peak Reconstructed from Kin d+AuSTAR Collaboration, J. Adams et al., Phys. Rev. Lett. 94, 062301 (2005).

D0 Peak Reconstructed from K in Au+Au,STAR Preliminary

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 5

STAR Detector at RHIC

The Relativistic Heavy Ion Collider

The STAR Detector

The Relativistic Heavy Ion Collider (RHIC) is located at Brookhaven.

The Solenoidal Tracker at RHIC (STAR) is one of four detectors.

Data from the Time Projection Chamber (TPC) was used for this analysis.

RHIC uses p+p, d+A, and A+A beams.

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 6

Analysis Method

Combinatorial Technique

Rotational Background Subtraction

Kaon TracksPion TracksUnused Tracks

Momentum and dE/dx cuts used

py

px

5 degree rotations

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 7

D0 + D0 in Cu+Cu

STAR Preliminary

Significance of peak = 4.7 %07.080.3..

,, 00

RB

KDKD

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 8

(stat.) 0.025 -/ 0.132/

)(22

1

0

0

00

/)(2

dydN

TmT

e

dy

dN

dydpp

Nd

N

D

D

Tmm

D

ttevts

Dt

( D0 + D0)/2 Spectra in Cu+Cu

STAR Preliminary

Fitting Function:

*Systematic error evaluation for dN/dy in progress.

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 9

Conversion from dN/dy to Cross-Section

mbstat

NNR

f

mb

N

dydN

NNcc

ccD

ppinel

CuCubinary

D

.)( 18.094.0

05.054.0/

7.07.4

42

2.9-1.051.5

(stat.) 0.025 -/ 0.132/

0

0

RfNdydN CuCubin

ppinel

CuCu

D

NNcc ///0

p+p inelastic cross section

conversion to full rapidity

ratio from e+e- collider data

number of binary collisions

mb 18.017.0 conversion dy todN fromerror sys. *Systematic error evaluation for dN/dy in progress.

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 10

Charm Cross-Section Comparison at 200 GeV

FONLL upper limit

FONLL lower limit

FONLL prediction

STAR d+Au (MinBias)

STAR Cu+Cu (MinBias)STAR Preliminary

STAR Au+Au (MinBias)

PHENIX Au+Au (MinBias)PHENIX p+p (MinBias + trigger)

*Systematic error evaluation for STAR Cu+Cu in progress.

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 11

Studying the Ds Meson in RHI Collisions

• Ds yields enhanced by deconfinement.• Ds production uses charm that might otherwise go into J/production

or other charmed mesons.• The strangeness/entropy ratio can be used to predict the D/Ds ratio .

Ref: I. Kuznetsova, J. Rafelski “Charm and bottom flavored hadrons production from strangeness rich quark gluon plasma hadronization”. APS 2007 April Meeting

Ref: I. Kuznetsova, J. Rafelski Eur. Phys. J. C 51, 113-133 (2007)

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 12

D/Ds Peak in d+Au

STAR Preliminary

D+ Ds+

Ds+ Significance = 3.4

D+ Significance = 2.4

X Efficiency Corrections not done yetX Low statistics for D, not resilient to large changes in cutsX No negatively charged D or Ds found yet %04.032.0..

%28.016.2..

RBKKD

RBKKDs

*Mass differencefixed

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 13

Conclusions

• 4.7 D0 peak found in Cu+Cu Collisions– First D0 measurement in Cu+Cu at RHIC

• Charm cross section in Cu+Cu measured to be 0.94 +/- 0.18 (stat.) mb

– Consistent with Binary Scaling

• 3.4Ds+ peak found in d+Au Collisions

– First Ds measurement in a heavy ion experiment

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 14

Outlook

• Need accounting of systematic errors for D0 in Cu+Cu

• More Au+Au statistics will improve open charm measurements

• Ds search in Au+Au planned

• TOF & HFT upgrades to STAR will improve charm measurements

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 15

References (Backup)

[1] M. Cacciari, P. Nason, R. Vogt, Phys. Rev. Lett. 95, 122001 (2005)

[2] I. Kuznetsova, J. Rafelski Eur. Phys. J. C 51, 113-133 (2007)

[3] I. Kuznetsova, J. Rafelski “Charm and bottom flavored hadrons production from strangeness rich quark gluon plasma hadronization”. APS 2007 April Meeting

Stephen Baumgart (Yale)

INPC 2007 – Tokyo, June 4, 2007Slide 16

Pt Bins (Backup)

STAR PreliminarySTAR Preliminary

STAR Preliminary

1.3 < pt < 2.3 GeV/c0.3 < pt < 1.3 GeV/c

2.3 < pt < 3.3 GeV/c