x. dongsept. 3rd, 2013 ustc, hefei, china 1 the heavy flavor tracker for star xin dong lawrence...
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X. DongSept. 3rd, 2013 USTC, Hefei, China 1
The Heavy Flavor Tracker for STAR
Xin Dong Lawrence Berkeley National Laboratory
SSDISTPXL
HFT
X. DongSept. 3rd, 2013 USTC, Hefei, China
Phase Transition in Quantum ChromoDynamics
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Quark-hadron
t = 10-6 secT = 1 GeV
t = 51017 secT=1 MeV
The Planck epoch
Today
Uni
vers
e ev
olut
ion
HHiggs boson
QCD Phase Diagram
Quark Gluon Plasma
Tem
pera
ture
Baryon Density
Hadrons
Nuclei Neutron Star
X. DongSept. 3rd, 2013 USTC, Hefei, China3
Water phase diagram (QED) Quarks/gluons phase diagram (QCD)
arXiv:1111.5475wikipedia
X. DongSept. 3rd, 2013 USTC, Hefei, China
High Energy Nucleus-Nucleus Collisions
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Time
Initial hardscatterings
Partonic stage
Hadronicstage
Freeze-out
Nuclear modification factor (RAA)
€
RAA =d2N AA /dpTdy
Nbind2N pp /dpTdy
Characterize the medium effect
Elliptic flow (v2) = 2nd Fourier coefficient
Sensitive to the early stage properties
Observables
X. DongSept. 3rd, 2013 USTC, Hefei, China
Heavy Ion Experiments
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Currently under operation:
PHENIX, STAR @ RHIC (BNL)ALICE, ATLAS, CMS @ LHC (CERN)
RHIC since 2000LHC since 2010
ALICE ATLAS CMS
X. DongSept. 3rd, 2013 USTC, Hefei, China
Evidences of the Formation of sQGP
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PRL 99 (2007) 112301
v2
PRL 91 (2003) 072304
“Jet Quenching”
- Significant suppression in particle yield at high pT in central heavy ion collisions
“Partonic Collectivity”
- Strong collective flow, even for multi-strange hadrons (, )- Flow driven by Number-of-Constituent-Quark (NCQ) in hadrons
Strongly-coupled Quark-Gluon Plasma (sQGP)
RHIC discoveries reaffirmed by LHC experiments
X. DongSept. 3rd, 2013 USTC, Hefei, China7
Heavy Ion Frontiers
X. DongSept. 3rd, 2013 USTC, Hefei, China
Heavy Quarks – Ideal Probes to Study QCD
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MeV
1 10 102 103 104
mu, md QCD
TQGP
mc mb
mc,b >> QCD amenable to perturbative QCDmc,b >> TQGP predominately created from initial hard scatterings
B. Mueller, nucl-th/0404015
Heavy quark masses not easily modified in QCD medium
Tc
ms
X. DongSept. 3rd, 2013 USTC, Hefei, China
Heavy Quarks to Probe Medium Thermalization
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Heavy quarks created at early stage of HIC, and sensitive to the partonic re-scatterings. Heavy quark collectivity/flow to experimentally quantify medium thermalization.
charm quarks
G. Moore & D. Teaney, PRC 71 (2005) 064904
HQ propagation in QCD medium – Brownian Motion, described by Langevin Equation
D / drag/diffusion coefficientsrelated to the medium transport properties
X. DongSept. 3rd, 2013 USTC, Hefei, China10
Lee, et. al, PRL 100 (2008) 222301
Direct (hard) fragmentation in elementary collisions. However, in heavy ion collisions …
Charm Quark Hadronization
V. Greco et al., PLB 595(2004)202
Hadronization through coalescence
Charm baryon enhancement ? - coalescence of c and di-quark
v2
X. DongSept. 3rd, 2013 USTC, Hefei, China11
Charm Cross Section
STAR, PRL 94 (2005) 062301,PHENIX, PRL 96 (2006) 032001Yifei Zhang, QM11
• Sizable experimental (statistical & systematical) uncertainties• Crucial to interpret both open charm and charmonia data in heavy ion collisions• Need precision measurements on various charm hadrons via displaced vertices
X. DongSept. 3rd, 2013 USTC, Hefei, China12
STAR PRL 98 (2007) 192301, Yifei Zhang QM11
Heavy Quark Energy Loss in Hot QCD Medium
Heavy quark decay electrons - mixture of charm and bottom decays
RAA(e) ~ RAA(h)
Contradict to the naïve radiative energy loss mechanism
Re-visit the energy loss mechanisms Require precision measurements of direct topological reconstruction of charm or bottom hadrons for clear understanding
X. DongSept. 3rd, 2013 USTC, Hefei, China13
Electrons - Incomplete Kinematics
New micro-vertex detector is needed for precision measurements on charmed hadrons production in heavy ion collisions
X. DongSept. 3rd, 2013 USTC, Hefei, China14
Requirements to Micro-Vertex Detector for STAR
• Ultimate position resolution and solid mechanical support
• Thin detector material to allow precision measurement at low pT
• Full azimuthal angle coverage at mid-rapidity
• Fast DAQ readout to be able to handle RHIC-II luminosity
• Sufficient radiation tolerance to be operated in RHIC collider environment
particle c (m) Mass (GeV)
D0 123 1.865
D+ 312 1.869
Ds+ 150 1.968
c+ 60 2.286
B0 459 5.279
B+ 491 5.279
X. DongSept. 3rd, 2013 USTC, Hefei, China15
Solenoidal Tracker At RHIC (STAR)
X. DongSept. 3rd, 2013 USTC, Hefei, China16
TPC Volume
Outer Field Cage
Inner Field CageSSDISTPXL
FGT
HFT
Heavy Flavor Tracker
X. DongSept. 3rd, 2013 USTC, Hefei, China17
HFT consists of 3 sub-detector systems inside the STAR Inner Field Cage
Heavy Flavor Tracker
DetectorRadius
(cm)Hit Resolution
R/ - Z (m - m)Radiation
length
SSD 22 30 / 860 1% X0
IST 14 170 / 1800 1.32 %X0
PIXEL8 12 / 12 ~0.37 %X0
2.6 12 / 12 ~0.37% X0
SSD existing single layer detector, double side strips (electronic upgrade)
IST one layer of silicon strips along beam direction, guiding tracks from the SSD through PIXEL detector - proven strip technology
PIXEL double layers, 20.7x20.7 mm pixel pitch, 2 cm x 20 cm each ladder, 10 ladders, delivering ultimate pointing resolution. - new active pixel technology
TPC SSD IST PXL~1mm ~300µm ~250µm
vertex< 30µm
X. DongSept. 3rd, 2013 USTC, Hefei, China18
2.6 cm radius
8 cm radius
Inner layer
Outer layer
End view
20 cm
coverage +-1total 40 ladders
Pixel Geometry
One of two half cylinders
X. DongSept. 3rd, 2013 USTC, Hefei, China
Monolithic Active Pixel Sensors (MAPS)
Properties:
Standard commercial CMOS technology
Sensor and signal processing are integrated in the same silicon wafer
Signal is created in the low-doped epitaxial layer (typically ~10-15 μm) → MIP signal is limited to <1000 electrons
Charge collection is mainly through thermal diffusion (~100 ns), reflective boundaries at p-well and substrate
MAPS pixel cross-section (not to scale)
MAPS and competition MAPS
Hybrid Pixel
SensorsCCD
Granularity + - +
Small material budget + - +
Readout speed + ++ -
Radiation tolerance + ++ -
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X. DongSept. 3rd, 2013 USTC, Hefei, China
Prototype Detector Performance
Meets PIXEL requirements
Test beam results for Mimosa 16 prototype - sensor– Integration time of 640 µs– Continuous binary readout of all pixels
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X. DongSept. 3rd, 2013 USTC, Hefei, China21
Pointing resolution (12 19GeV/pc) m
Layers Layer 1 at 2.6* cm radiusLayer 2 at 8 cm radius
Pixel size 20.7 m X 20.7 m
Hit resolution 8 m rms
Position stability 8 m (30 m envelope)
Radiation thickness per layer
X/X0 = 0.37%
Number of pixels 360 M
Integration time (affects pileup) 0.2 ms
Radiation requirement
20-90 kRad (*)
Rapid detector replacement
< 8 Hours
criticalanddifficult
more than a factor of 3 better than other vertex detectors (ATLAS, ALICE and PHENIX)
Some pixel features and specifications
0.52% Cu-cable
X. DongSept. 3rd, 2013 USTC, Hefei, China22
Pointing Resolution Performance
2 2
GEANT: Realistic detector geometry + Standard STAR trackingincluding the pixel pileup hits at RHIC-II luminosity
Hand Calculation: Multiple Coulomb Scattering + Detector hit resolutionPXL telescope limit: Two PIXEL layers only, hit resolution only
Mean pT
30 m
X. DongSept. 3rd, 2013 USTC, Hefei, China
24 ladders, liquid cooling.
S:N > 20:1, >99.9% live and functioning channels
Intermediate Silicon Tracker (IST)
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X. DongSept. 3rd, 2013 USTC, Hefei, China
Silicon Strip Detector (SSD)
~ 1 Meter
44
cm
20 Ladders
Ladder Cards
“Old” SSD
New/Faster Readout“Old” Ladders, refurbished New, direct mounting on support
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X. DongSept. 3rd, 2013 USTC, Hefei, China25
Reconstruction of Displaced Vertices
D0 decays
particle c (m) Mass (GeV)
D0 123 1.865
D+ 312 1.869
Ds+ 150 1.968
c+ 60 2.286
B0 459 5.279
B+ 491 5.279
Direct topological reconstruction of charm and bottom decays
X. DongSept. 3rd, 2013 USTC, Hefei, China26
Golden Physics Outcome
Assuming D0 v2 distribution from quark coalescence.
1 billion Au+Au m.b. events at 200 GeV.
- Charm v2 Thermalization of light-quarks!Drag/diffusion coefficients!
Assuming D0 RAA as charged hadron
1 billion Au+Au m.b. events at 200 GeV + 8pb-1 sampled L in p+p 200 GeV
- Charm RAA Energy loss mechanism!Interaction with QCD matter!
X. DongSept. 3rd, 2013 USTC, Hefei, China
Uniqueness
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Uniqueness of HFT:
Fine pixel granularity provides ultimate hit resolution
Thin detector design allows precision measurements down to low pT
State-of-art mechanical design retains detector stability
Full azimuthal acceptance allows high statistics correlation measurements
HF measurements at RHIC – not just complementary to those at LHC
Uniqueness of HF measurements at RHIC
Heavy quarks are calibrated probes at RHIC - predominately created via initial gluon-gluon hard scatterings.
Heavy quarks are mostly created through the leading order 2->2 process at RHIC – clean physics interpretation of results, particularly correlation measurements.
X. DongSept. 3rd, 2013 USTC, Hefei, China
Specific Engineering Goals for 2013 Run
Test PXL system (3/10 sectors) in beam conditions before deployment of full system
Integrate it with the STAR DAQ and Trigger system. Explore many configurations/settings to optimize response and identify
problems Environment not optimal (p-p 500 GeV collisions at high luminosity) but
still good for: Offline/reconstruction chain development/testing Calibration/Alignment code/procedures development/testing Estimates of efficiency, pointing resolutions limited physics results expected from this sample ?
Most commissioning data are taken with the low-luminosity at STAR. De-steer beam to ~1-2% of full luminosity to reduce pile-up in TPC and PXL
Run finished early June
X. DongSept. 3rd, 2013 USTC, Hefei, China
Engineering Run: Installation
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May 8, 2013 – PXL detector installed within 12 hours - 3 (out of 10) sectors in the prototype - Data seen from DAQ on the next day
• Integration with the STAR TRG/DAQ system• Sensor threshold scan to optimize the performance• Test robustness of electronics/firmware - a few issues and solutions identified• Detector performance in collider environment• Online/offline software for the PXL• Offline alignment calibration
Successful commissioning run for the PXL!
X. DongSept. 3rd, 2013 USTC, Hefei, China
Detector Performance
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Dedicated low luminosity runs taken for tracking / alignment calibration
TPC-PXL association!One snap-shot of sensor status
X. DongSept. 3rd, 2013 USTC, Hefei, China
Survey / Alignment Calibration
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Pixel positions within the (half-)PXL detector - Survey via high precision CMM machine - similar survey measurements for IST/SSD
Global position w.r.t. the TPC CS – use tracks (cosmic/beam collisions) seen in the TPC
before After
X. DongSept. 3rd, 2013 USTC, Hefei, China
Detector single hit resolution
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Single hit resolution < 20/2 ~ 14 m – close to the designed goal – 12 m- slight offset likely due to residual misalignment
X. DongSept. 3rd, 2013 USTC, Hefei, China
Pointing resolution
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X. DongSept. 3rd, 2013 USTC, Hefei, China34
Physics Run Plan
1) 2014 - First run with HFT: Au+Au 200 GeV
a) v2 and Rcp of D-mesons with 1B minimum bias collisions
b) v2 and Rcp of charm/bottom decay (separated) electrons/muons
2) 2015 - Second run with HFT: p+p 200 GeV
a) RAA of D-mesons/electrons/muons
a) 2016 - Third run with HFT: Au+Au 200 GeV high statistics
1) Systematic studies of v2 and RAA
2) c baryon with sufficient statistics
3) Charm correlation / Electron pair
1) 2017+ - p+p / p+Au 200 GeV …
X. DongSept. 3rd, 2013 USTC, Hefei, China
Muon Telescope Detector for STAR
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Characteristics
• Long MRPC gas detector
• Magnet iron yoke as the absorber
• Acceptance: 45% in azimuth, ||<0.5
Physics goals
• Mid-rapidity quarkonia production
• Separated Upsilon states
• e- correlation – heavy flavor correlation
Schedule
•2012 10% coverage
•2013 63% coverage
•2014 100% coverage
HFT+TPC+TOF+EMC+MTD
Precision measurements of open heavy flavor and quakonia production and correlations at RHIC
X. DongSept. 3rd, 2013 USTC, Hefei, China
STAR Physics Focus in Future
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Precision measurements on HF and dileptons:Quantify the sQGP properties (hot QCD)
Precision measurements on focused energiesMap out the QCD phase structure
Precision measurements on pA and eAStudy QCD in cold matter
2014 2015 2016 2017 2018 2019 2020 2021 2022
HF/Dilepton with HFT/MTD
BES-II (√sNN<=20 GeV)
pA/eA physics (HFT’)
X. DongSept. 3rd, 2013 USTC, Hefei, China
Summary
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Quantifying the QGP medium properties is one of the main goals of the heavy ion program in the next decade.
STAR HFT – a state-of-art silicon pixel detector will enable precision measurements of heavy quark production at RHIC.
HFT project has been processing very well. HFT is now under installation, and will become operational next year.
Go Heavy or Go Home !
X. DongSept. 3rd, 2013 USTC, Hefei, China38
http://hepg-work.ustc.edu.cn/star2013/
HFT/MTD Workshop at USTC
September 9-11, 2013, USTC
Chair of local organizer: Prof. Ming Shao