The STAR iTPC Upgrade Daniel Cebra University of California Davis - PowerPoint PPT Presentation

The STAR iTPC Upgrade Daniel Cebra University of California – Davis For the STAR Collaboration Daniel Cebra RHIC Program Advisory Meeting Slide 1 of 40 Daniel Cebra RHIC Program Advisory Meeting Slide 1 of 40 18-Jun-2015 Brookhaven National Laboratory 18-Jun-2015 Brookhaven National Laboratory

BES Phase II – Physics Cases for iTPC Beam Energy Scan – Phase I Results: • Seen the turn-off of QGP signatures. • Seen suggestions of the first order phase transition. • Not seen conclusive evidence of a critical point. The most promising region for refining the search is in the lower energies  19.6, 15, 11.5, 7.7, and lower. The iTPC Upgrades strengthen the BES II physics program, and enables new key measurements: • Rapidity dependence of proton kurtosis • Dilepton program (sys. errors and intermediate mass region) • Enables the internal fixed target program to cover 7.7 to 3.0 GeV Daniel Cebra RHIC Program Advisory Meeting Slide 2 of 40 18-Jun-2015 Brookhaven National Laboratory

The STAR Upgrades and BES Phase II Major improvements Endcap TOF for BES-II EPD Upgrade: • Improves trigger • Reduces background • Allows a better and independent reaction plane measurement iTPC Upgrade: critical to BES physics • Rebuilds the inner sectors of the TPC • Continuous Coverage EndCap TOF Upgrade: • Improves dE/dx • Rapidity coverage is critical • Extends coverage • PID at = 0.9 to 1.5 from 1.0 to 1.5 • Improves the fixed target • Lowers p T cut-in from program 125 MeV/c to 60 MeV/c • Provided by CBM-FAIR Daniel Cebra RHIC Program Advisory Meeting Slide 3 of 40 18-Jun-2015 Brookhaven National Laboratory

What is the Current TPC? • 24 sectors • 12 on each side • Large pads for good Inner sector 1/12 dE/dx resolution in the Outer sector • Small pads for good two track resolution in the inner sector Outer Inner 32 Rows 13 Rows 6.2 X 19.5 mm 2.85 X 11.5 mm 3940 pads 1750 pads Daniel Cebra RHIC Program Advisory Meeting Slide 4 of 40 18-Jun-2015 Brookhaven National Laboratory

Current Inner Sector Limitations • Staggered readout – Only 13 maximum possible points • Issues in Tracking: recognition and resolution – Only reads ~20% of possible gas path length • Inner sectors essentially not used in dE/dx • Essentially limits TPC effective acceptance • to | η |<1 • • • Daniel Cebra RHIC Program Advisory Meeting Slide 5 of 40 18-Jun-2015 Brookhaven National Laboratory

What is the iTPC Upgrade? 32 Rows 6.2 X 19.5 mm 3940 Pads 190 cm Rebuild the readout regions 40 Rows for the inner 4.5 X 15.5 mm sectors: 3370 Pads • Pad Planes 13 Rows 2.85 X 11.5 mm • Wire Planes • Electronics 1750 Pads 60 cm Daniel Cebra RHIC Program Advisory Meeting Slide 6 of 40 18-Jun-2015 Brookhaven National Laboratory

Pad plane • Increase coverage. Higher density FEE • Prototype has been produced and tested Daniel Cebra RHIC Program Advisory Meeting Slide 7 of 40 18-Jun-2015 Brookhaven National Laboratory

BES Phase II – Relationship to TPC Upgrade Basic performance improvements The TPC inner sector upgrade is important for three reasons: 1) It extends the accessible rapidity range 2) It reduces the low p t cut-in threshold 3) Improves dE/dx resolution 4) Also Improves the momentum resolution Daniel Cebra RHIC Program Advisory Meeting Slide 8 of 40 18-Jun-2015 Brookhaven National Laboratory

Simple Geometry  acceptance What determines if a track is accepted? 20 hits… fraction of possible > 50%... Enough dE/dx hits L T η=0 cm η=0.9 200 η= 1.0  Current TPC “limit” Outer Sectors η =1.2 32 pad rows η =1.3 130 η= 1.5  iTPC “limit” 120 Inner Sectors η =1.9 13 or 40 pads rows 60 40 15 200 Daniel Cebra RHIC Program Advisory Meeting Slide 9 of 40 18-Jun-2015 Brookhaven National Laboratory

Simple Geometry  p T acceptance 40 MeV/c STAR Low p T acceptance is dependent on the track quality cuts. 60 MeV/c 120 MeV/c Quality tracks require at least 20 160 MeV/c hits. Current TPC low p T limit is 125 MeV/c iTPC low p T limit is 60 MeV/c Daniel Cebra RHIC Program Advisory Meeting Slide 10 of 40 18-Jun-2015 Brookhaven National Laboratory

Do we have any such low p T tracks? 60 MeV/c tracks Not found 60 MeV/c This is an actual event 120 MeV/c 125 MeV/c track 160 MeV/c 160 MeV/c tracks Daniel Cebra RHIC Program Advisory Meeting Slide 11 of 40 18-Jun-2015 Brookhaven National Laboratory

Increased rapidity coverage Increased efficiency for | <1 mostly due to lower p T cut-in values Increased efficiency for |η| < 1.5 mostly due to tracks exiting the end cap Daniel Cebra RHIC Program Advisory Meeting Slide 12 of 40 18-Jun-2015 Brookhaven National Laboratory

Additional Tracks Available for Physics 11.5 GeV Total Standard Inner p T < 60 TPC Upgrade MeV/c Pions 234 152 +17% 18% | |<0.5 Kaons 25.3 12.4 +30% 4% Protons 34 26 +10% 6% Pions 435 283 +21% | |<1.0 Kaons 47 22.9 +35% Protons 66 50 +13% Pions <20% 90% 1.0<| |<1.5 Kaons <20% 80% Protons <20% 90% Daniel Cebra RHIC Program Advisory Meeting Slide 13 of 40 18-Jun-2015 Brookhaven National Laboratory

Improvements to dE/dx Daniel Cebra RHIC Program Advisory Meeting Slide 14 of 40 18-Jun-2015 Brookhaven National Laboratory

iTPC Physics Daniel Cebra RHIC Program Advisory Meeting Slide 15 of 40 18-Jun-2015 Brookhaven National Laboratory

BES Phase II Energy B (MeV) Events (M) 200 GeV Quark-Gluon Plasma 62.4 GeV 19.6 205 150 300 39 GeV 15.0 255 150 27 GeV 11.5 315 50 Temperature (MeV) 19.6 GeV 7.7 420 70 14.5 GeV 11.5 GeV 5.0 550 TBD 200 9.1 GeV 7.7 GeV 6.2 GeV 5.2 GeV Goals of BES I: 4.5 GeV 1) Turn – off of QGP 3.9 GeV 2) Onset of 100 3.5 GeV Color Deconfinement 3.2 GeV Super 3) Critical Point conductor 3.0 GeV Hadronic Gas Goals of BES II: 1) Onset of 0 Deconfinement 2) Critical Point 0 250 500 750 1000 Baryon Chemical Potential B (MeV) Daniel Cebra RHIC Program Advisory Meeting Slide 16 of 40 18-Jun-2015 Brookhaven National Laboratory

Statistics Needed in BES phase II Collision Energies (GeV): 7.7 11.5 14.5 19.6 9.1 Chemical Potential (MeV): 420 370 315 260 205 Observables Millions of Events Needed R CP up to p T 4.5 GeV NA NA 160 92 22 QGP Elliptic Flow of meson ( v 2 ) 100 150 200 300 400 Local Parity Violation (CME) 50 50 50 50 50 1 st P.T. Directed Flow studies (v 1 ) 50 75 100 100 200 asHBT (proton-proton) 35 40 50 65 80 C.P. net-proton kurtosis ( 2 ) 80 100 120 200 400 EM Probes Dileptons 100 160 230 300 400 Proposed Number of Events: 100 160 230 300 400 Daniel Cebra RHIC Program Advisory Meeting Slide 17 of 40 18-Jun-2015 Brookhaven National Laboratory

Elliptic Flow Elliptic flow results are improved Daniel Cebra RHIC Program Advisory Meeting Slide 18 of 40 18-Jun-2015 Brookhaven National Laboratory

Directed Flow Directed flow of net protons is one of the key BES-I results Daniel Cebra RHIC Program Advisory Meeting Slide 19 of 40 18-Jun-2015 Brookhaven National Laboratory

Directed Flow Open questions remain about the iTPC dramatically improves rapidity dependence of the the results above y = 1.0 directed flow Daniel Cebra RHIC Program Advisory Meeting Slide 20 of 40 18-Jun-2015 Brookhaven National Laboratory

Directed Flow The added reach of the iTPC allows a significant measurement of v1 for most centralities Daniel Cebra RHIC Program Advisory Meeting Slide 21 of 40 18-Jun-2015 Brookhaven National Laboratory

Rapidity Density Widths The Width of the pion rapidity distribution have been suggested to be sensitive to the speed of sound Current TPC cannot make this measurement Added acceptance of the iTPC allows a measurement of the rapidity widths E895 Daniel Cebra RHIC Program Advisory Meeting Slide 22 of 40 18-Jun-2015 Brookhaven National Laboratory

Fluctuation Analysis Published STAR results for beam energy dependence of 2 (top panels) and S /Skellam (lower panels for net protons in Au+Au collisions. The left panel illustrate the effect of p T selections while the right panels indicate the effects of rapidity selections Daniel Cebra RHIC Program Advisory Meeting Slide 23 of 40 18-Jun-2015 Brookhaven National Laboratory

Fluctuation Analysis The iTPC brings significant new physics with the rapidity dependence of the net-proton kurtosis BES II Proposal This panel shows the effects of rapidity selections on the ks 2 signal and the projected errors for BESII With iTPC Daniel Cebra RHIC Program Advisory Meeting Slide 24 of 40 18-Jun-2015 Brookhaven National Laboratory

Di-lepton program • The dominate systematic error on the Di-electron program in the di-electon experiment is the purity of Intermediate mass region is now electrons. The added pad-rows will possible with the iTPC improve dE/dx The expected purity for electrons as a function of transverse momentum. The expected systematic uncertainty of dielectron excess mass spectrum with the iTPC upgrade compared to the current TPC case Daniel Cebra RHIC Program Advisory Meeting Slide 25 of 40 18-Jun-2015 Brookhaven National Laboratory