X. DongSept. 3rd, 2013 USTC, Hefei, China 1 The Heavy Flavor Tracker for STAR Xin Dong Lawrence Berkeley National Laboratory SSD IST PXL HFT

X. DongSept. 3rd, 2013 USTC, Hefei, China Phase Transition in Quantum ChromoDynamics 2 Quark-hadron t = sec T = 1 GeV t = 5  sec T=1 MeV The Planck epoch Today Universe evolution H Higgs boson QCD Phase Diagram Quark Gluon Plasma Temperature Baryon Density Hadrons NucleiNeutron Star

X. DongSept. 3rd, 2013 USTC, Hefei, China 3 Water phase diagram (QED)Quarks/gluons phase diagram (QCD) arXiv: wikipedia

X. DongSept. 3rd, 2013 USTC, Hefei, China High Energy Nucleus-Nucleus Collisions 4 Time Initial hard scatterings Partonic stage Hadronic stage Freeze-out Nuclear modification factor (R AA ) Characterize the medium effect Elliptic flow (v 2 ) = 2 nd Fourier coefficient Sensitive to the early stage properties Observables

X. DongSept. 3rd, 2013 USTC, Hefei, China Heavy Ion Experiments 5 Currently under operation: PHENIX, RHIC (BNL) ALICE, ATLAS, LHC (CERN) RHIC since 2000 LHC since 2010 ALICEATLASCMS

X. DongSept. 3rd, 2013 USTC, Hefei, China Evidences of the Formation of sQGP 6 PRL 99 (2007) v2v2 PRL 91 (2003) “Jet Quenching” - Significant suppression in particle yield at high p T 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, China 7 Heavy Ion Frontiers

X. DongSept. 3rd, 2013 USTC, Hefei, China Heavy Quarks – Ideal Probes to Study QCD 8 MeV m u, m d  QCD T QGP mcmc mbmb m c,b >>  QCD amenable to perturbative QCD m c,b >> T QGP predominately created from initial hard scatterings B. Mueller, nucl-th/ Heavy quark masses not easily modified in QCD medium TcTc msms

X. DongSept. 3rd, 2013 USTC, Hefei, China Heavy Quarks to Probe Medium Thermalization 9  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) HQ propagation in QCD medium – Brownian Motion, described by Langevin Equation  D /  drag/diffusion coefficients related to the medium transport properties

X. DongSept. 3rd, 2013 USTC, Hefei, China 10 Lee, et. al, PRL 100 (2008) 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 v2v2

X. DongSept. 3rd, 2013 USTC, Hefei, China 11 Charm Cross Section STAR, PRL 94 (2005) , PHENIX, PRL 96 (2006) Yifei 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, China 12 STAR PRL 98 (2007) , Yifei Zhang QM11 Heavy Quark Energy Loss in Hot QCD Medium  Heavy quark decay electrons - mixture of charm and bottom decays  R AA (e) ~ R AA (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, China 13 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, China 14 Requirements to Micro-Vertex Detector for STAR Ultimate position resolution and solid mechanical support Thin detector material to allow precision measurement at low p T 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) D0D D+D Ds+Ds c+c B0B B+B

X. DongSept. 3rd, 2013 USTC, Hefei, China 15 Solenoidal Tracker At RHIC (STAR)

X. DongSept. 3rd, 2013 USTC, Hefei, China 16 TPC Volume Outer Field Cage Inner Field Cage SSD IST PXL FGT HFT Heavy Flavor Tracker

X. DongSept. 3rd, 2013 USTC, Hefei, China 17  HFT consists of 3 sub-detector systems inside the STAR Inner Field Cage Heavy Flavor Tracker Detector Radius (cm) Hit Resolution R/  - Z (  m -  m) Radiation length SSD2230 / 8601% X 0 IST14170 / %X 0 PIXEL 812 / 12~0.37 %X / 12~0.37% X 0  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 TPCSSDISTPXL ~1mm~300µm~250µm vertex < 30µm

X. DongSept. 3rd, 2013 USTC, Hefei, China cm radius 8 cm radius Inner layer Outer layer End view 20 cm  coverage +-1 total 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 competitionMAPS Hybrid Pixel Sensors CCD Granularity+-+ Small material budget+-+ Readout speed+++- Radiation tolerance

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 20

X. DongSept. 3rd, 2013 USTC, Hefei, China 21 Pointing resolution(12  19GeV/p  c)  m LayersLayer 1 at 2.6* cm radius Layer 2 at 8 cm radius Pixel size20.7  m X 20.7  m Hit resolution8  m rms Position stability8  m (30  m envelope) Radiation thickness per layer X/X 0 = 0.37% Number of pixels360 M Integration time (affects pileup) 0.2 ms Radiation requirement20-90 kRad (*) Rapid detector replacement < 8 Hours critical and difficult 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, China 22 Pointing Resolution Performance 22 GEANT: Realistic detector geometry + Standard STAR tracking including the pixel pileup hits at RHIC-II luminosity Hand Calculation: Multiple Coulomb Scattering + Detector hit resolution PXL telescope limit: Two PIXEL layers only, hit resolution only Mean p T 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) 23

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 24

X. DongSept. 3rd, 2013 USTC, Hefei, China 25 Reconstruction of Displaced Vertices D 0 decays particle c  (  m) Mass (GeV) D0D D+D Ds+Ds c+c B0B B+B Direct topological reconstruction of charm and bottom decays

X. DongSept. 3rd, 2013 USTC, Hefei, China 26 Golden Physics Outcome Assuming D 0 v 2 distribution from quark coalescence. 1 billion Au+Au m.b. events at 200 GeV. - Charm v 2 Thermalization of light-quarks! Drag/diffusion coefficients! Assuming D 0 R AA as charged hadron 1 billion Au+Au m.b. events at 200 GeV + 8pb -1 sampled L in p+p 200 GeV - Charm R AA  Energy loss mechanism! Interaction with QCD matter!

X. DongSept. 3rd, 2013 USTC, Hefei, China Uniqueness 27 Uniqueness of HFT: Fine pixel granularity provides ultimate hit resolution Thin detector design allows precision measurements down to low p T 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 29 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 30 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 31 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 beforeAfter

X. DongSept. 3rd, 2013 USTC, Hefei, China Detector single hit resolution 32 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 33

X. DongSept. 3rd, 2013 USTC, Hefei, China 34 Physics Run Plan 1) First run with HFT: Au+Au 200 GeV a)v 2 and R cp of D-mesons with 1B minimum bias collisions b)v 2 and R cp of charm/bottom decay (separated) electrons/muons 2) Second run with HFT: p+p 200 GeV a)R AA of D-mesons/electrons/muons 3) Third run with HFT: Au+Au 200 GeV high statistics a)Systematic studies of v 2 and R AA b)  c baryon with sufficient statistics c)Charm correlation / Electron pair 4) p+p / p+Au 200 GeV …

X. DongSept. 3rd, 2013 USTC, Hefei, China Muon Telescope Detector for STAR 35 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 % coverage % coverage % 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 36 Precision measurements on HF and dileptons: Quantify the sQGP properties (hot QCD) Precision measurements on focused energies Map out the QCD phase structure Precision measurements on pA and eA Study QCD in cold matter HF/Dilepton with HFT/MTD BES-II (√s NN <=20 GeV) pA/eA physics (HFT’)

X. DongSept. 3rd, 2013 USTC, Hefei, China Summary 37 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, China 38 HFT/MTD Workshop at USTC September 9-11, 2013, USTC Chair of local organizer: Prof. Ming Shao