x. dongsept. 3rd, 2013 ustc, hefei, china 1 the heavy flavor tracker for star xin dong lawrence...

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

2

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


High Energy Nucleus-Nucleus Collisions

4

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


Heavy Ion Experiments

5

Currently under operation:

PHENIX, STAR @ RHIC (BNL)ALICE, ATLAS, CMS @ LHC (CERN)

RHIC since 2000LHC since 2010

ALICE ATLAS CMS


Evidences of the Formation of sQGP

6

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


Heavy Ion Frontiers


Heavy Quarks – Ideal Probes to Study QCD

8

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


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) 064904

HQ propagation in QCD medium – Brownian Motion, described by Langevin Equation

D / drag/diffusion coefficientsrelated to the medium transport properties


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


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


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


Electrons - Incomplete Kinematics

New micro-vertex detector is needed for precision measurements on charmed hadrons production in heavy ion collisions


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


Solenoidal Tracker At RHIC (STAR)


TPC Volume

Outer Field Cage

Inner Field CageSSDISTPXL

FGT

HFT

Heavy Flavor Tracker


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


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


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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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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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


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


24 ladders, liquid cooling.

S:N > 20:1, >99.9% live and functioning channels

Intermediate Silicon Tracker (IST)

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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


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


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!


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.


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


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!


Detector Performance

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Dedicated low luminosity runs taken for tracking / alignment calibration

TPC-PXL association!One snap-shot of sensor status


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


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


Pointing resolution

33


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 …


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



HFT+TPC+TOF+EMC+MTD

Precision measurements of open heavy flavor and quakonia production and correlations at RHIC


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’)


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 !


http://hepg-work.ustc.edu.cn/star2013/

HFT/MTD Workshop at USTC

September 9-11, 2013, USTC

Chair of local organizer: Prof. Ming Shao

x. dongsept. 3rd, 2013 ustc, hefei, china 1 the heavy flavor tracker for star xin dong lawrence...

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