Open Heavy Flavor Measurements at RHIC with STAR Santa Fe Jets and Heavy Flavor Workshop, January 11-13, 2016 Zhenyu Ye 1,2 (for the STAR collaboration) 1. University of Illinois at Chicago 2. Central China Normal University
Heavy Flavor Quarks Heavy quark tomography • produced mostly from initial hard parton scatterings at RHIC energies; exposed to the whole evolution of the QGP • total yield or mass not (significantly) altered within the QGP Sensitive to parton-medium interactions and medium properties • Comparing light, charm and bottom to disentangle radiative vs collisional energy losses • Extraction of temperature-dependent JET Coll. 2014 parton transport properties needs precise experimental data on heavy flavor production from RHIC Zhenyu Ye 2
Open Charm Production at RHIC Heavy flavor quarks can serve as calibrated probes for the QGP at RHIC: • production in p+p collisions are described by pQCD calculations • produced mostly in the initial hard scatterings at RHIC energies 400 d+Au S = 200 GeV NN 0 (D +e) 350 Sys. error 300 NLO err. p+p b) 250 0 µ 0 (D +D*) Au+Au (D ) ( y=0 /dy| 200 NN c c σ run12 d 150 100 run9 FONLL in p+p STAR Preliminary 50 STAR Preliminary FONLL err. 0 2 3 10 10 1 10 number of binary collisions N bin Theory: M. Cacciari et al., PRL 95 (2005) 122001, R. Vogt, EPJ ST 155 (2008) 213 Talk on Bottom production by Zach Miller tomorrow Zhenyu Ye 3
Open Charm Production at RHIC Heavy flavor quarks can serve as calibrated probes for the QGP at RHIC: • production in p+p collisions are described by pQCD calculations • produced mostly in the initial hard scatterings at RHIC energies • has only a small contribution from gluon splitting STAR Preliminary NLO charn: M. Cacciari et al, PRL 95 (2005) 122001 gluon splitting charm: STAR Jet*pQCD R(g->ccbar) STAR R(g->ccbar): PRD79 (2009) 112006 pQCD R(g->ccbar): Mueller & Nason PLB 157 (1985) 226; Mangano & Nason PLB 285 (1992) 160 Zhenyu Ye 4
STAR Experiment at RHIC EEMC Magnet MTD BEMC TPC TOF VPD BBC HFT/TPC/TOF: -1< η <1 BEMC: -1< η <1 EEMC: 1< η <2 MTD: | η |<0.5 HFT Zhenyu Ye 5
STAR Heavy Flavor Tracker PiXeL detector (PXL) • two layers of thin Monolithic Active Pixel Sensors with 356M 20.7x20.7 µ m pixels • excellent DCA resolution for HF studies Intermediate Silicon Tracker (IST) • one layer of fast readout single-sided double-metal silicon strip detector Silicon Strip Detector (SSD) • existing one layer of double-sided silicon strip detector with electronic upgrade Radius Hit Resolution Radiation Detector (cm) R/ ϕ - Z ( µ m) length SSD 22 20 / 740 1% X 0 IST 14 170 / 1800 <1.5 %X 0 PXL 2.8/8 6 / 6 ~0.4 %X 0 PXL IST SSD Zhenyu Ye 6
STAR Heavy Flavor Tracker Au+Au 200 GeV 30 µm A factor of ~4 improvement in D 0 significance by the HFT. First results on D ± and D s . D 0 D ± D s STAR Preliminary Zhenyu Ye 7
New Results from the HFT – D 0 R AA • R AA (D)>1 for p T ~1.5 GeV/c 0 2 Au+Au D @ 200 GeV 0-10% → Charm coalescence with a radially 0 D 2014 flowing bulk medium 1.5 0 D 2010/11 • High p T : significant suppression in AA central Au+Au collisions. R 1 p+p uncert. Strong charm-medium interaction 0.5 • Improved Au+Au precision at high p T thanks to the HFT. R AA at low p T with Run14 Au+Au and Run15 p+p STAR Preliminary 0 HFT data are underway. 0 2 4 6 8 p (GeV/c) T dN AA dy R AA = STAR D 0 2010/11: PRL 113 (2014) 142301 N binary ⋅ dN pp dy Zhenyu Ye 8
New Results from the HFT – D 0 R AA • R AA (D)>1 for p T ~1.5 GeV/c 0 2 Au+Au D @ 200 GeV 0-10% → Charm coalescence with a radially 0 D 2014 flowing bulk medium 0 D 2010/11 1.5 0-12% STAR π • High p T : significant suppression in AA central Au+Au collisions. R 1 p+p uncert. Strong charm-medium interaction 0.5 • R AA (D) ~ R AA ( π ) at p T >4 GeV/c Similar suppression for light partons STAR Preliminary 0 and charm quarks at high p T 0 2 4 6 8 p (GeV/c) T dN AA dy R AA = STAR D 0 2010/11: PRL 113 (2014) 142301 N binary ⋅ dN pp dy STAR π 0-12%: PLB 655 (2007) 104 Zhenyu Ye 9
New Results from the HFT – D 0 v 2 0.3 • Finite D 0 v 2 for p T >1 GeV/c Au+Au 200GeV, 0-80% Non-flow est. 0 0.25 D EP 0 D v {2} 2 0.2 0.15 2 v 0.1 0.05 0 STAR Preliminary 0.05 � 0 1 2 3 4 5 6 7 Transverse Momentum p (GeV/c) T " % dN ∑ d φ = N 0 1 + 2 v n cos n φ $ ' # & n Zhenyu Ye 10
New Results from the HFT – D 0 v 2 0.3 • Finite D 0 v 2 for p T >1 GeV/c Au+Au 200GeV, 0-80% Non-flow est. 0 0.25 D Favors charm quark diffusion TAMU w c diff. TAMU w/o c diff. 0.2 0.15 2 v 0.1 0.05 0 STAR Preliminary 0.05 � 0 1 2 3 4 5 6 7 Transverse Momentum p (GeV/c) Theory curves: latest calculations from T private communications " % dN TAMU: PRC 86 (2012) 014903, PRL ∑ d φ = N 0 1 + 2 v n cos n φ 110 (2013) 112301 $ ' # & n Zhenyu Ye 11
New Results from the HFT – D 0 v 2 • Finite D 0 v 2 for p T >1 GeV/c Favors charm quark diffusion • Lower than light hadron v 2 Indicates that charm quarks are not fully thermalized with the medium STAR Preliminary 2 + m 0 2 m T = p T Zhenyu Ye 12
New Results from the HFT - D s M. He et al ., PRL 110, 112301 (2013) • Strangeness enhancement in heavy-ion • Elliptic flow of D S < D 0 is expected collisions is expected to affect the yield of due to earlier freeze out of D S . D S: relative increase of D S yield than D 0 predicted. Zhenyu Ye 13
New Results from the HFT - D s STAR Preliminary STAR Preliminary • Strangeness enhancement in heavy-ion • Elliptic flow of D S < D 0 is expected collisions is expected to affect the yield of due to earlier freeze out of D S : D S: relative increase of D S yield than D 0 predicted: The ratio of D S /D 0 yield measured in Au+Au First measurement of D S v 2 in collisions is found to be higher than that in heavy-ion experiment. More data p+p collisions from PYTHIA are needed to draw conclusion. Zhenyu Ye 14
Comparison with LHC Results • D meson R AA @ RHIC ~ R AA @LHC 0 2 Au+Au D @ 200 GeV 0-10% → at p T >4 GeV/c 0 D 2014 Strong charm-medium interaction at 0 D 2010/11 1.5 RHIC and LHC D 0-10% ALICE AA R 1 p+p uncert. 0.5 STAR Preliminary 0 0 2 4 6 8 p (GeV/c) T Zhenyu Ye 15
Comparison with LHC Results • D meson R AA @ RHIC ~ R AA @LHC at p T >4 GeV/c Strong charm-medium interaction at RHIC and LHC • D 0 v 2 LHC results are compatible with light flavor v 2 0.3 • D 0 v 2 STAR results are lower than Au+Au 200GeV, 0-80% Non-flow est. 0 0.25 D EP light flavor v 2 K s 0.2 Charm thermalized at LHC energy but 0.15 not fully thermalized at RHIC? 2 v 0.1 0.05 • More precise data and systematic theoretical studies of heavy flavor 0 STAR Preliminary production at RHIC and LHC will be 0.05 � very helpful. 0 1 2 3 4 5 6 7 Transverse Momentum p (GeV/c) Zhenyu Ye 16 T
Comparison with Theory TAMU: non-perturb. T-matrix (2 π T)D = 2-11 SUBATECH: perturb.+resummation (2 π T)D = 2-4 STAR Preliminary DUKE: Langevin simulation with input parameter tuned to the LHC data （ 2 π T ） D = 7 STAR D 0 2010/11: PRL 113 (2014) 142301 Theory curves: latest calculations from private communications STAR Preliminary DUKE: PRC 92 (2015) 024907 A.Andronic arXiv:1506.03981(2015) Zhenyu Ye 17
Comparison with Theory STAR Preliminary Models with charm diffusion coefficient of 2- ~10 describe STAR D 0 R AA and v 2 results. Lattice calculations are consistent with values inferred from data. STAR D 0 2010/11: PRL 113 (2014) 142301 Theory curves: latest calculations from private communications STAR Preliminary DUKE: PRC 92 (2015) 024907 A.Andronic arXiv:1506.03981(2015) Zhenyu Ye 18
Comparison with Theory STAR Preliminary Models with charm diffusion coefficient of 2- ~10 describe STAR D 0 R AA and v 2 results. Lattice calculations are consistent with values inferred from data. More precise results expected from STAR Run15 (pp, pAu) and Run16 (AuAu) data: improved p+p baseline, CNM, a factor of ~3 STAR Preliminary increase in Au+Au data size, improved DCA resolution at low p T with Al cables for PXL Zhenyu Ye 19
STAR Heavy Flavor II (2021-2022) W. Horowitz and M. Gyulassy, arXiv:0710.0703 Without Bottom from RHIC, can we claim that we fully understand the energy loss mechanisms, or mass- and temperature-dependent parton transport coefficients of the QGP? Does b quark diffuse in the QGP at RHIC energies and if so how much? 20
STAR Heavy Flavor II (2021-2022) HFT+ with Faster MAPS sensors • integration time from ~185 µs to below 40 µs – less pile-up hits and thus better tracking efficiency • use chips developed for ALICE ITS upgrade and existing HFT Projected R AA (0-10%) stat. uncertainty infrastructure – cost effective for RHIC pp and AuAu running in 2021-22 • experienced team worked on HFT Precise bottom measurements with the HFT+ to complete the heavy flavor physics at RHIC. Complementary to ALICE HF and sPHENIX Jet and Upsilon programs. 21
Summary and Outlook STAR HFT in Run14-16 Run14: Au+Au, results based on ~70% stat. 70% of Run14 data Run15: p+p baseline, p+Au for CNM effects Run16(+14): x4 Au+Au data size than QM15, inner PXL 0.5->0.4%X 0 with Al cables • Precise charm results • First bottom results STAR Preliminary Zhenyu Ye 22
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