physics investigations with cbm – and the importance of tracking – claudia höhne, universität...

Physics investigations with CBM– and the importance of tracking –

Claudia Höhne, Universität Gießen

2 Claudia Höhne Tracking Workshop – GSI June 2010

Physics case of CBMCompressed Baryonic Matter @ FAIR – high B, moderate T:

searching for the landmarks of the QCD phase diagram• first order deconfinement phase transition • chiral phase transition (high baryon densities!)• QCD critical endpoint

in A+A collisions from 2-45 AGeV starting in 2018 (CBM + HADES)

• physics program complementary to RHIC, LHC

• rare probes being sensitive to the created matter! (charm, dileptons)


Particle multiplicity ∙ branching ratio for min. bias Au+Au collisions at 25 GeV (from HSD and thermal model)

SPS Pb+Pb 30 A GeV

Particle multiplicities


CBM: Physics topics and Observables

Onset of chiral symmetry restoration at high B

• in-medium modifications of hadrons (,, e+e-(μ+μ-), D)

Deconfinement phase transition at high B • excitation function and flow of strangeness (K, , , , )• excitation function and flow of charm (J/ψ, ψ', D0, D, c)• charmonium suppression, sequential for J/ψ and ψ' ?

The equation-of-state at high B

• collective flow of hadrons• particle production at threshold energies (open charm)

QCD critical endpoint• excitation function of event-by-event fluctuations (K/π,...)

Systematics & precision!!

→ characterization of the created medium!

CBM Physics B

ook

– in p

rint s

oon –


Excitation function of produced hadrons

• measure all produced hadrons in particular multistrange hyperons!

• test: strangeness equilibration in statistical hadron gas model: equilibrated hadron gas?

[A. Andronic et al., Phys. Lett. B 673 (2009) 142]

SIS

100

SIS

300

p/+

K+/+

K-/-

/-

/-

/-


Exploring nuclear matter with penetrating probes

pn

++

p

e+, μ+

e-, μ-

• dileptons are penetrating probes – direct radiation from the created hot and dense matter

- meson

• vacuum lifetime 0 = 1.3 fm/c

• couples to the medium → change of hadronic properties: "melts" close to Tc and at high B

• connection to chiral symmetry restoration?

"SPS""FAIR"

[R. Rapp, priv. com. (CBM physics book)]


Exploring nuclear matter with penetrating probes

%2MM

NA60: Phys.Rev.Lett. 96 (2006) 162302

• SPS: dilepton spectra measured by NA60 (µ+µ-) and CERES (e+e-)

• excess spectrum shows strong modification of -meson in medium

calculations: H. v. Hees, R. Rapp, Nucl.Phys.A806:339,2008

“excess spectrum”: di-lepton radiation from the high-density phase


Charmonium suppression

• charm newly produced: mc ~ 1.3 GeV ! → new scale, production in initial hard scattering

• distribution among charmed hadrons depending on medium

• appealing early idea: charmonia will be dissolved in QGP

→ suppressed yield compared to hadron gas

[R. Arnaldi, NA60, QM09]

NA60, preliminary, 158 AGeV

• J/ suppression measured

• difficult corrections, many open questions

• no good open-charm (D-meson) measurement

• no data at lower energies

Pb+Pb

In+In


Charm propagation

[HSD: O. Linnyk et al., Int.J.Mod.Phys.E17, 1367 (2008)] [SHM: A. Andronic et al., Phys. Lett. B 659 (2008) 149]

Propagation of produced charm quarks in the dense phase –quark like or (pre-)hadron like?

• charmonium to open charm ratio as indicator – measure both!• indications of collectivity?

• first charm measurements in A+A below 158 AGeV!

• aim at detailed information including phase space distributions, flow!


The CBM experiment• tracking, momentum determination, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field

• hadron ID: TOF (& RICH)• photons, 0, : ECAL

• electron ID: RICH & TRD suppression 104

• PSD for event characterization• high speed DAQ and trigger → rare probes!

• muon ID: absorber + detector layer sandwich move out absorbers for hadron runs

RICHTRD

TOF ECAL

magnet

absorber +

detectorsSTS + MVD


CBM: interaction and data storage rates

• FAIR will provide high intensity beams up to 109 ions/s• 1% interaction target → 10 MHz interaction rate→ rare probes! → trigger in particular for D, J/ • data storage rate 25 kHz: fast offline event reconstruction!

BR = branching ratio = efficiencyT = trigger? Y/10w = yield in 10 weeks

fast and efficient tracking for all particles

fast and efficient trigger algorithms


CBM feasibility studies

• feasibility studies performed for all major channels including event reconstruction and semirealistic detector setup

J/ J/

di-electrons di-muons

' '

c

1010 events

D0


Parallelization in CBM Reconstruction !

Vector SIMD

MultiThreading

NVIDIA CUDA

OpenCL

STS + + + +

MuCh + +

RICH + +

TRD + +

Vertexing +

Open Charm Analysis

+

+ March 2009+ October 2009

DELL Server with: DELL Server with: • Core i7/NehalemCore i7/Nehalem 22x(Xeon X5550 44x2.66 GHz, 8 MB L3 cache)• DDR3-1333 36 GB36 GB main memory• NVIDIA NVIDIA GTX 295 2x240 FPUs2x240 FPUs, 1792 MB• optional LRBLRB

• fast event reconstruction is a must for CBM!


CBM tracking challenges

• fast tracking routines

• trigger algorothms

• fast offline event reconstruction of large data volumes

→ many discussions at this workshop

• highly efficient tracking routines

• detector inefficiencies, frames

• large hit densities (granularity?)

→ adopt tracking to more realistic detector descriptions

→ close cooperation with hardware developers, evaluation of new, more realistic detector layouts!

→ show examples: D-mesons, low-mass vector mesons


STS tracking – heart of CBM

Challenge: high track density: 600 charged particles in 25o @ 10MHz

Task

• track reconstruction: 0.1 GeV/c < p 10-12 GeV/c p/p ~ 1% (p=1 GeV/c)

• primary and secondary vertex reconstruction (resolution 50 m)

• V0 track pattern recognition

c = 312 m

radiation hard and fast silicon pixel and strip detectors

self triggered FEE

high speed DAQ and trigger

online track reconstruction!

fast & rad. hard detectors!


Monolithic Acitive Pixel Sensors in commercial CMOS processCBM: 5 µm single point resolution

Micro Vertex Detecor (MVD) Development

• first station 5cm downstream of target

• high position resolution!

first demonstrator tested in beam!


D-meson reconstruction

stsK-

+

MVD +

MAPS

D+

• high resolution pixel detector with little multiple scattering (low material budget) essential!


Simulated incident angle

~100% of particles from primary collision are within -30°<θ<30°

100 Au Ions, 25 AGeV

Incident angle (°)

>10% of delta electrons are outside -30°<θ<30°

challenges in MVD:

delta electrons, large cluster sizes for large incident angles


0° 15° 30°

45° 60° 80°


Pixel multiplicity in cluster


D0K-+

v21

v22 v115 cm 10 cm

target

M.Ryzhinsky

Christina Dritsa

MAPS @ 5cm

Open charm z-vertex reconstruction


D0 → π+ + K-

S/B=2.5Eff=0,9%Signif=21

no event pile up

• realistic MVD description including clusters, delta-electrons

event pile up of 5

S/B=0.6Sign=26Eff=0.55%


Sensor development:double-sided micro-strips, stereo angle 15o, pitch 60 μm300 μm thick, bonded toultra-thin micro-cables,radiation hardness

STS in thermalenclosure

Detector planes: ultra-light weight ladder structure

Prototypes: full CBM sensor, ultrathin cables

Development of the Silicon Tracking System (STS)


Incident angle in STS

Station Station 11

Station Station 55

• large incident angles in outer parts

• distribution of charge on many strips

• hit losses?!


Hit finding efficiency


Pluto simulation10k

ρ0 → e+e-

-5%

Hit Finding Efficiency in STS

77% of electrons from ρ0 have incident angle in STS<20◦

Implications for -mesons


Correlation of the number of STS traversedby e+e- pairs from conversion and π0-Dalitz

Combinatorial background (CB) topology

Track Fragment - x, y position; no charge informationTrack Segment - reconstructed trackGlobal Track - identified in RICH

ee0

ee 0

Track Segment

Global Track

eemedium

Track Fragment

signal

fake

pair

Small (moderate) opening angle and/or Small (moderate) opening angle and/or asymmetric laboratory momenta.asymmetric laboratory momenta.

tracking of low momentum tracks even more important for background suppression!


CB suppression II: hit topology

Global Track

Track Fragment

dsts vs. plab of the edsts vs. plab of the e

Develo

pm

ent

of

story

Develo

pm

ent

of

story

Mai

nly

conv

ersi

onMVD

STS

signal

background


CB suppression III: track topology

e + closest track

Track Segment

Global Track

Mai

nly

Dal

itz

Develo

pm

ent

of

story

Develo

pm

ent

of

story

eπ0 + closest track

signal

background


Global tracking in CBM

electron setup with RICH and TRD

• tracking through the whole CBM detector setup including TRD, TOF, ECAL

• RICH ring recognition

needs:

• high efficiency

• fast tracking routines at high particle/ hit densities

• robust, fast ring finding

• tolerance with respect to detector inefficiencies, frames

• trigger for J/ → e+e-


Challenges of the di-muon measurement• major background from ,K decays into , punch through of hadrons and track mismatches

→ use TOF information to reject punch through K,p → compact layout to minimize K, decays → use excellent tracking to reject ,K decays in the STS by kink detection → absorber-detector sandwich for continous tracking

• low momentum !

125 cm Fe ≡ 7.5 I → p > 1.5 GeV/c225 cm Fe ≡ 13.5 I → p > 2.8 GeV/c


Summary

• CBM will explore the intermediate range of the QCD phase diagram including rare probes being particularly sensitive to the created medium

• highly efficient and fast tracking is essential!


CBM collaboration

Russia:IHEP ProtvinoINR TroitzkITEP MoscowKRI, St. Petersburg

China:Tsinghua Univ., BeijingCCNU WuhanUSTC Hefei

Croatia:

University of SplitRBI, Zagreb

Romania: NIPNE BucharestBucharest University

Poland:Krakow Univ.Warsaw Univ.Silesia Univ. KatowiceNucl. Phys. Inst. Krakow

Ukraine: INR, KievShevchenko Univ. , Kiev

Univ. MannheimUniv. MünsterFZ RossendorfGSI DarmstadtUniv. WuppertalCzech Republic:

CAS, RezTechn. Univ. Prague

Germany: Univ. Heidelberg, Phys. Inst.Univ. HD, Kirchhoff Inst. Univ. Frankfurt

Hungaria:KFKI BudapestEötvös Univ. Budapest

India:Aligarh Muslim Univ., AligarhIOP BhubaneswarPanjab Univ., ChandigarhGauhati Univ., Guwahati Univ. Rajasthan, JaipurUniv. Jammu, JammuIIT KharagpurSAHA KolkataUniv Calcutta, KolkataVECC KolkataUniv. Kashmir, SrinagarBanaras Hindu Univ., Varanasi

Norway:Univ. Bergen

Kurchatov Inst. MoscowLHE, JINR DubnaLPP, JINR Dubna

Cyprus: Nikosia Univ.

55 institutions, > 400 members Split, Oct 2009

LIT, JINR DubnaMEPHI MoscowObninsk State Univ.PNPI GatchinaSINP, Moscow State Univ. St. Petersburg Polytec. U.

Korea:Korea Univ. SeoulPusan National Univ.

France: IPHC Strasbourg

physics investigations with cbm – and the importance of tracking – claudia höhne, universität...

Documents

high b excitation function

created matter

flow of charm j

high mbconnection

charm propagationhsd

physics topics

nuclear matter

physics investigations