STAR Heavy Flavor and Spin Program --Lessons learned and other opportunities Huan Zhong Huang (黄焕中) Department of Physics and Astronomy University of California Los Angeles Workshop on Heavy Flavor Production in High Energy Nuclear Collisions June 17-18, 2012 @UIC Priscilla Kurnadi, Ph.D. 2010

Outline Spin and Heavy Flavor Probes Gluon Spin Results – Reality and Limitations Transverse Spin Opportunities Outlook 11/23/2018

Proton Structure Proton spin Naïve picture: from valence quarks, e.g u(+)u(+)d(-) = p(+) In reality, not so simple: Parton contribution to proton spin: Quark, gluon distribution inside proton given by probability density function as a function of momentum fraction x Parton distribution functions from Deep Inelastic Scattering (DIS) experiments Polarized parton distribution functions (PDFs): 11/23/2018

Double spin asymmetry LO pQCD Model-dependent ALL predictions rely on experimental data (PDF, FF) and pQCD calculations (partonic , aLL) 11/23/2018

Ignorance is a blessing Pre-RHIC Spin data Period Integrated (down to pTmin) charm ALL 11/23/2018

pQCD for HQ production at RHIC Inclusive NPE from HQ semi-leptonic decays Run05, 08 Phys. Rev. D 83 (2011) 052006 2 4 6 8 10 pT (GeV/c) pQCD Works for Heavy Quark Production at RHIC ! 11/23/2018

Works for Charm and Bottom Separately too ! STAR used NPE-hadron correlations to statistically separate Charm and Bottom decay electrons. pQCD describes experimental data well ! 11/23/2018

Longitudinal Double Spin Asymmetry Spin-dependent cross sections Relative luminosity btw bunch crossings w/ different spin configs Average polarization over entire dataset Spin-dependent non-photonic electron yield 11/23/2018

ALL NPE ALLMeasurement Statistically limited Systematics: polarization STAR Preliminary Statistically limited Systematics: polarization STAR Preliminary STAR Data: Prior 2008 -- major photonic electron background -- limited data sample size 11/23/2018

Major Improvement in STAR Electron Data Quality since 2008 NPE/PE Run 2005 . Gamma conversion only happens in material 0.5 STAR inner trackers were removed in Run 2008~2011, much less material budget photonic electron yield is significantly lower than previous runs. Best shot for non-photonic electrons: Much higher signal to background ratio + Less sensitive to the accuracy of background removal efficiency in simulation Run 2010 0.5 11/23/2018

STAR Data Quality and Quantity A factor of Ten increase in STAR data sample Improved beam polarization ! See http://www.phy.bnl.gov/cnipol/fills/ 11/23/2018

Nature is also less kind on DG Inclusive Jet STAR de Florian et al., PRL 101, 072001 (2008) 11/23/2018

2009 Inclusive Jet ALL 2009 results are a factor of 3 or greater more precise than 2006 Data falls between predictions from DSSV and GRSV-STD 11/23/2018

Even Less Kind to NPE Probes STAR Jet ALL Favors between DSSV and GRSV(std) Riedl, Schafer and Stratmann PRD 80, 114020 (2009) 11/23/2018

A Clever Observable Helps May not enough Need calculations for STAR acceptance 11/23/2018

Try New Direction – Transverse Spin arXiv:1205.6826v1 TSSA – Transverse Single-Spin Asymmetry (AN) E704 1991-1992 Right Left A long standing physics issue: -- quark transversity -- Sivers effect and/or Collins fragmentation -- Higher twist calculations 11/23/2018

Particle Formation Dynamics 0 cross section in good agreement with PQCD calculation. / 0 cross section ratio similar to that observed where jet fragmentation is dominant. AN () > AN(0 ) for XF > 0.55 What is the physics origin for the possible dependence p0h? Extend to Vector Mesons – r/w and J/y Extend to heavy quark mesons – NPE from heavy quark semi-leptonic decays Extend to direct photons/jets AN from polarized p+A collisions to probe CGC state in A -- Kovchegov and Sievert hep-ph/1201.5890 11/23/2018

STAR HFT Upgrade HFT SSD IST Inner Field Cage PXL PIXEL Magnet Detector Radius (cm) Hit Resolution R/ - Z (m - m) Radiation length SSD 22 20 / 740 1% X0 IST 14 170 / 1800 <1.5 %X0 PIXEL 8 12/ 12 ~0.4 %X0 2.5 12 / 12 ~0.4% X0 TPC Volume Magnet Return Iron Solenoid Outer Field Cage Inner Field Cage EAST WEST FGT PIXEL two layers 18.4x18.4 m pixel pitch 10 sector, delivering ultimate pointing resolution that allows for direct topological identification of charm. new monolithic active pixel sensors (MAPS) technology 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 11/23/2018

STAR MTD Upgrade MRPC based Detector Modules Schedule: Run 12 – 10%; Run 13 – 43%; Run 14 – 80% Completion – Mar 2014. 11/23/2018

STAR forward instrumentation upgrade proton nucleus ~ 2016 FMS FHC ~ 6 GEM disks Tracking: 2.5 < η < 4 W powder HCal Preshower 1/2” Pb radiator Shower “max” RICH Baryon/meson separation Forward instrumentation optimized for p+A and transverse spin physics Charged-particle tracking e/h and γ/π0 discrimination Baryon/meson separation 11/23/2018 20 11/23/2018

Outlook The likely small DG makes it difficult to make precision ALL for heavy quarks from gluon fusion channel ! It may be worthwhile to measure ALL for high pT electrons and e-m pairs to confirm small DG. Probing transverse spin dynamics with heavy quarks – unexplored territory ! STAR HFT/MTD upgrades and future Forward Instrumentation upgrades will greatly enhance STAR capability of HQ measurements for both heavy ion and polarized p+p and p+A collisions. 11/23/2018