new open charm results at star via hadronic decay channels
DESCRIPTION
New Open Charm Results at STAR via Hadronic Decay Channels. Stephen Baumgart Yale University For the STAR Collaboration. Outline. D 0 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 - PowerPoint PPT PresentationTRANSCRIPT
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