Physics investigations with CBM – and the importance of tracking – Claudia Höhne, Universität Gießen

Claudia Höhne Tracking Workshop – GSI June Physics case of CBM Compressed Baryonic 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)

Claudia Höhne Tracking Workshop – GSI June 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

Claudia Höhne Tracking Workshop – GSI June 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', D 0, 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 Book – in print soon –

Claudia Höhne Tracking Workshop – GSI June 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+/+ K-/-K-/- /-/- /-/- /-/-

Claudia Höhne Tracking Workshop – GSI June Exploring nuclear matter with penetrating probes p n  ++  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 T c and at high  B connection to chiral symmetry restoration? "SPS" "FAIR" [R. Rapp, priv. com. (CBM physics book)]

Claudia Höhne Tracking Workshop – GSI June Exploring nuclear matter with penetrating probes NA60: Phys.Rev.Lett. 96 (2006) 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

Claudia Höhne Tracking Workshop – GSI June Charmonium suppression charm newly produced: m c ~ 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

Claudia Höhne Tracking Workshop – GSI June 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!

Claudia Höhne Tracking Workshop – GSI June 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  10 4 PSD for event characterization high speed DAQ and trigger → rare probes! muon ID: absorber + detector layer sandwich  move out absorbers for hadron runs RICH TRD TOF ECAL magnet absorber + detectors STS + MVD

Claudia Höhne Tracking Workshop – GSI June CBM: interaction and data storage rates FAIR will provide high intensity beams up to 10 9 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  = efficiency T = trigger?Y/10w = yield in 10 weeks fast and efficient tracking for all particles fast and efficient trigger algorithms

Claudia Höhne Tracking Workshop – GSI June CBM feasibility studies feasibility studies performed for all major channels including event reconstruction and semirealistic detector setup J/   di-electronsdi-muons '' '' cc events D0D0

Claudia Höhne Tracking Workshop – GSI June Parallelization in CBM Reconstruction ! Vector SIMDMultiThreadingNVIDIA CUDAOpenCL STS++++ MuCh++ RICH++ TRD++ Vertexing+ Open Charm Analysis+ + March October 2009 DELL Server with: Core i7/Nehalem24 Core i7/Nehalem 2x(Xeon X5550 4x2.66 GHz, 8 MB L3 cache) 36 GB DDR GB main memory NVIDIA 2x240 FPUs NVIDIA GTX 295 2x240 FPUs, 1792 MB LRB optional LRB fast event reconstruction is a must for CBM!

Claudia Höhne Tracking Workshop – GSI June 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

Claudia Höhne Tracking Workshop – GSI June STS tracking – heart of CBM Challenge: high track density:  600 charged particles in  25 10MHz Task track reconstruction: 0.1 GeV/c < p  GeV/c  p/p ~ 1% (p=1 GeV/c) primary and secondary vertex reconstruction (resolution  50  m) V 0 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!

Claudia Höhne Tracking Workshop – GSI June Monolithic Acitive Pixel Sensors in commercial CMOS process CBM: 5 µm single point resolution Micro Vertex Detecor (MVD) Development first station 5cm downstream of target high position resolution! first demonstrator tested in beam!

Claudia Höhne Tracking Workshop – GSI June D-meson reconstruction sts K-K- ++ MVD ++ MAPS D+D+ high resolution pixel detector with little multiple scattering (low material budget) essential!

Claudia Höhne Tracking Workshop – GSI June 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

Claudia Höhne Tracking Workshop – GSI June °15°30° 45°60° 80°

Claudia Höhne Tracking Workshop – GSI June Pixel multiplicity in cluster

Claudia Höhne Tracking Workshop – GSI June D0K-+D0K-+ v 21 v 22 v 11 5 cm 10 cm target M.Ryzhinsky Christina Dritsa 5cm Open charm z-vertex reconstruction

Claudia Höhne Tracking Workshop – GSI June D 0 → π + + K - S/B=2.5 Eff=0,9% Signif=21 no event pile up realistic MVD description including clusters, delta-electrons event pile up of 5 S/B=0.6 Sign=26 Eff=0.55%

Claudia Höhne Tracking Workshop – GSI June Sensor development: double-sided micro-strips, stereo angle 15 o, pitch 60 μm 300 μm thick, bonded to ultra-thin micro-cables, radiation hardness STS in thermal enclosure Detector planes: ultra-light weight ladder structure Prototypes: full CBM sensor, ultrathin cables Development of the Silicon Tracking System (STS)

Claudia Höhne Tracking Workshop – GSI June Incident angle in STS Station 1 Station 5 large incident angles in outer parts distribution of charge on many strips hit losses?!

Claudia Höhne Tracking Workshop – GSI June Hit finding efficiency

Claudia Höhne Tracking Workshop – GSI June Hit finding efficiency

Claudia Höhne Tracking Workshop – GSI June Pluto simulation10k ρ 0 → e + e - -5% Hit Finding Efficiency in STS 77% of electrons from ρ 0 have incident angle in STS<20◦ Implications for  -mesons

Claudia Höhne Tracking Workshop – GSI June Correlation of the number of STS traversed by e + e - pairs from  conversion and π 0 -Dalitz Combinatorial background (CB) topology Track Fragment- x, y position; no charge information Track Segment- reconstructed track Global Track- identified in RICH Track Segment Global Track Track Fragment signalsignal fakepairfakepair Small (moderate) opening angle and/or asymmetric laboratory momenta. tracking of low momentum tracks even more important for background suppression!

Claudia Höhne Tracking Workshop – GSI June CB suppression II: hit topology Global Track Track Fragment d sts vs. p lab of the e  d sts vs. p lab of the e  Development of story Mainly  conversion MVD STS signal background

Claudia Höhne Tracking Workshop – GSI June CB suppression III: track topology e  + closest track Track Segment Global Track Mainly   Dalitz Development of story e π0 + closest track signal background

Claudia Höhne Tracking Workshop – GSI June 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-

Claudia Höhne Tracking Workshop – GSI June 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/c 225 cm Fe ≡ 13.5 I → p > 2.8 GeV/c

Claudia Höhne Tracking Workshop – GSI June 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!

Claudia Höhne Tracking Workshop – GSI June CBM collaboration Russia: IHEP Protvino INR Troitzk ITEP Moscow KRI, St. Petersburg China: Tsinghua Univ., Beijing CCNU Wuhan USTC Hefei Croatia: University of Split RBI, Zagreb Romania: NIPNE Bucharest Bucharest University Poland: Krakow Univ. Warsaw Univ. Silesia Univ. Katowice Nucl. Phys. Inst. Krakow Ukraine: INR, Kiev Shevchenko Univ., Kiev Univ. Mannheim Univ. Münster FZ Rossendorf GSI Darmstadt Univ. Wuppertal Czech Republic: CAS, Rez Techn. Univ. Prague Germany: Univ. Heidelberg, Phys. Inst. Univ. HD, Kirchhoff Inst. Univ. Frankfurt Hungaria: KFKI Budapest Eötvös Univ. Budapest India: Aligarh Muslim Univ., Aligarh IOP Bhubaneswar Panjab Univ., Chandigarh Gauhati Univ., Guwahati Univ. Rajasthan, Jaipur Univ. Jammu, Jammu IIT Kharagpur SAHA Kolkata Univ Calcutta, Kolkata VECC Kolkata Univ. Kashmir, Srinagar Banaras Hindu Univ., Varanasi Norway: Univ. Bergen Kurchatov Inst. Moscow LHE, JINR Dubna LPP, JINR Dubna Cyprus: Nikosia Univ. 55 institutions, > 400 membersSplit, Oct 2009 LIT, JINR Dubna MEPHI Moscow Obninsk State Univ. PNPI Gatchina SINP, Moscow State Univ. St. Petersburg Polytec. U. Korea: Korea Univ. Seoul Pusan National Univ. France: IPHC Strasbourg