physics investigations with cbm – and the importance of tracking – claudia höhne, universität...
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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)
3 Claudia Höhne Tracking Workshop – GSI June 2010
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
4 Claudia Höhne Tracking Workshop – GSI June 2010
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 –
5 Claudia Höhne Tracking Workshop – GSI June 2010
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-/-
/-
/-
/-
6 Claudia Höhne Tracking Workshop – GSI June 2010
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)]
7 Claudia Höhne Tracking Workshop – GSI June 2010
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
8 Claudia Höhne Tracking Workshop – GSI June 2010
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
9 Claudia Höhne Tracking Workshop – GSI June 2010
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!
10 Claudia Höhne Tracking Workshop – GSI June 2010
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
11 Claudia Höhne Tracking Workshop – GSI June 2010
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
12 Claudia Höhne Tracking Workshop – GSI June 2010
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
13 Claudia Höhne Tracking Workshop – GSI June 2010
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!
14 Claudia Höhne Tracking Workshop – GSI June 2010
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
15 Claudia Höhne Tracking Workshop – GSI June 2010
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!
16 Claudia Höhne Tracking Workshop – GSI June 2010
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!
17 Claudia Höhne Tracking Workshop – GSI June 2010
D-meson reconstruction
stsK-
+
MVD +
MAPS
D+
• high resolution pixel detector with little multiple scattering (low material budget) essential!
18 Claudia Höhne Tracking Workshop – GSI June 2010
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
19 Claudia Höhne Tracking Workshop – GSI June 2010
0° 15° 30°
45° 60° 80°
20 Claudia Höhne Tracking Workshop – GSI June 2010
Pixel multiplicity in cluster
21 Claudia Höhne Tracking Workshop – GSI June 2010
D0K-+
v21
v22 v115 cm 10 cm
target
M.Ryzhinsky
Christina Dritsa
MAPS @ 5cm
Open charm z-vertex reconstruction
22 Claudia Höhne Tracking Workshop – GSI June 2010
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%
23 Claudia Höhne Tracking Workshop – GSI June 2010
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)
24 Claudia Höhne Tracking Workshop – GSI June 2010
Incident angle in STS
Station Station 11
Station Station 55
• large incident angles in outer parts
• distribution of charge on many strips
• hit losses?!
25 Claudia Höhne Tracking Workshop – GSI June 2010
Hit finding efficiency
26 Claudia Höhne Tracking Workshop – GSI June 2010
Hit finding efficiency
27 Claudia Höhne Tracking Workshop – GSI June 2010
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
28 Claudia Höhne Tracking Workshop – GSI June 2010
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!
29 Claudia Höhne Tracking Workshop – GSI June 2010
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
30 Claudia Höhne Tracking Workshop – GSI June 2010
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
31 Claudia Höhne Tracking Workshop – GSI June 2010
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-
32 Claudia Höhne Tracking Workshop – GSI June 2010
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
33 Claudia Höhne Tracking Workshop – GSI June 2010
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!
34 Claudia Höhne Tracking Workshop – GSI June 2010
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