Straw tube detector performance for the PANDA and COSY-TOF - PowerPoint PPT Presentation

I NTERNATI ONAL PHD PROJECTS I N APPLI ED NUCLEAR PHYSI CS AND I NNOVATI VE TECHNOLOGI ES This project is supported by the Foundation for Polish Science – M PD program, co-financed by the European Union within the European Regional Development Fund Straw tube detector performance for the PANDA and COSY-TOF experiments Sedigheh Jowzaee November 25, 2014 Jagiellonian University, Krakow, Poland

Outline • PANDA experiment • Straw tube tracker • Simulation of straw tube performance • PID with straw tube • COSY-TOF experiment • Analysis of p p→pK + Λ reaction with STT data • Summary November 25, 2014 Sedigheh Jowzaee 2

1. PANDA Experiment PANDA (antiProton Annihilation at Darmstdat) Program • PANDA is an experiment in the FAIR facility at Darmstadt ,Germany • Interaction of antiproton with momentum range (1.5-15 GeV/c) • Hydrogen Target ( Charmonium spectroscopy, Exotic hadrons , …) • Nuclear Target ( Hadron properties in the nuclear medium, spectroscopy of hypernuclei) November 25, 2014 Sedigheh Jowzaee 3

1. PANDA Experiment PANDA Detector • Full angular acceptance Particle identification (p, π , K, e, µ) in the range up to ~ 8 GeV/c • Target spectrometer Forward spectrometer November 25, 2014 Sedigheh Jowzaee 4

2. Straw Tube Tracker • The straw tube is a proportional counter, gas-filled cylindrical tube as a cathode and a thin wire stretched along the tube axis as an anode reconstruction of particle trajectory measure: t Drift  x November 25, 2014 Sedigheh Jowzaee 5

2. Straw Tube Tracker • Straw tube structure • Al-mylar tube, Ø=10 mm • Gold-plated anode, Ø=20 µm • End plug, crimp pin and spring • Gas pipe (PVC med) • 2.5 g weight per tube • Advantages of straws • Modules (easy to exchange, high flexibility) • Low mass (self supporting by gas overpressure ) • High rates (1 MHz/wire) • Low aging • Fast readout (pulse shaping and digitization) November 25, 2014 Sedigheh Jowzaee 6

3. Simulation of Straw Tube Performance • Garfield 7.40: program for the detailed simulation of gas detectors • Simulation of transport properties of electrons and ions with Magboltz 7, 8.9.5 • Gas mixture 90% Ar, 10% CO 2 • Excellent for high-rate experiments (low aging) • Temperature 300 K, absolute pressure 2 atm Drift velocity Townsend Pure Ar 10% Argon+ 30% CO 2 20% 20% 10% 50% 2% 1% Ar+75% CO 2 Pure Argon November 25, 2014 Sedigheh Jowzaee 7

3. Simulation of Straw Tube Performance Gas Gain Simulation Full Penning transfer Agreement with 34% Penning transfer rate No Penning transfer The gain curve with 0%, 20%, 34%, Comparison the measured gain with 40%, 60% and 100% Penning rate Diethorn’s formula November 25, 2014 Sedigheh Jowzaee 8

3. Simulation of Straw Tube Performance Front-end Electronics of Straw • The first prototype new front-end chip • Preamplifier with variable gain CR-RC 2 with variable T peak • • Tail-cancelation with 2 variable time constants • Baseline stabilizer • Leading edge discriminator for timing • Buffered analog output November 25, 2014 Sedigheh Jowzaee 9

3. Simulation of Straw Tube Performance TOT spectra measured with 55 Fe source show good agreement with simulation for HV 1750 V and threshold based on 10% primary ionization November 25, 2014 Sedigheh Jowzaee 10

4. PID with Straw Tubes PID based on dE/dx: TOT ? Q • • Response of 24 single straws to 400 tracks • Set the low threshold for high position resolution • Correction to distance dependence • Truncated average for 24 straw layers Straw Tracks November 25, 2014 Sedigheh Jowzaee 11

4. PID with Straw Tubes Single straws response for 0.7 GeV/c particles before distance correction After distance correction After truncated average by removing 30% of the highest numbers Reasonable for PID November 25, 2014 Sedigheh Jowzaee 12

4. PID with Straw Tubes Separation power for p- π , p-K and π -K pairs based on TOT ( ■ ) and charge ( ▲ ) measurement. The threshold level was set based on 10% primary ionization  ( ) ( ) Mean A Mean B  ( , ) Separation A B    ( ) / 2 A B November 25, 2014 Sedigheh Jowzaee 13

5. COSY-TOF Experiment COSY-TOF Program • Strangeness physics study Λ -hyperon study in p p→ pK + Λ reaction • • Strange quark does not exist in nucleon as a constituent • How they create and how they interact • Theoretical description of the reaction by strange and non strange meson exchange Λ N N N π K Λ N N N N* K K • Analysis different physical effects involved to the reaction • N*-resonances • YN interaction N Σ cusp effect (N Σ –p Λ couple channel effect) • November 25, 2014 Sedigheh Jowzaee 14

5. COSY-TOF Experiment COSY-TOF Detector • COSY-TOF detector is Excellent for strangeness study • Upgraded with STT for tracking • Large acceptance p p • High statistics measurement Λ • Beam momentum= 2.95 GeV/c • Polarization (87.5 ± 2.0)% π - • Reconstruction of events with STT K + • 140 µm spatial resolution • 130000 reconstructed events November 25, 2014 Sedigheh Jowzaee 15

5. COSY-TOF Experiment STT Calibration • Reconstruction of pK + Λ events with STT→ precise calibration • Calibration steps • TDC correction • Multiple hits removal , Signal width cut, Electronics offset correction • Estimation of correlation between drift time and radius • Straw double layers geometrical position correction • Spatial resolution determination November 25, 2014 Sedigheh Jowzaee 16

6. Data analysis of pp→pK + Λ reaction pK + Λ event selection criteria • • 20 % reconstruction efficiency with Χ 2 /ndf of kinematic fit < 5 MC simulation • z- component of Ʌ decay vertex > 3 cm • Invariant mass resolution 1 MeV/c 2 • angle between Ʌ and its decay proton with STT → 3 times better than the old • > 2° setup without STT E miss =E init -(E p +E K +E Λ ) November 25, 2014 Sedigheh Jowzaee 17

6. Data analysis of pp→pK + Λ reaction Dalitz Plot Analysis • The experiment covers kinematically complete phase space • Strong deviations from homogenous distribution over phase space • Strong enhancements seen on the left and center MC Exp November 25, 2014 Sedigheh Jowzaee 18

6. Data analysis of pp→pK + Λ reaction Dalitz Plot Analysis • Interference between physical effects in K Λ and p Λ subsystems • Nucleon excited states (N*-resonances) • N Λ interaction (p Λ -FSI ) • N Σ -p Λ coupled channel effect (N Σ cusp) November 25, 2014 Sedigheh Jowzaee 19

6. Data analysis of pp→pK + Λ reaction • Dividing the Dalitz plot into three equal phase space volume regions in p Λ channel with Helicity angle cos θ pK in p Λ rest frame • m 2 p Λ distribution at upper region of Dalitz plot is significantly less than other regions - Interference with other physical effects including N* resonances November 25, 2014 Sedigheh Jowzaee 20

6. Data analysis of pp→pK + Λ reaction p Λ Invariant Mass Analysis • Cusp effect is stronger at lower parts of the Dalitz plot • p Λ -FSI effect seems to be same in three parts in the low enough range of the m p Λ • Cusp effect fitted with two Breit-Wigner functions • Shape of the cusp is different in three sections • No theoretical description of cusp in p Λ channel November 25, 2014 Sedigheh Jowzaee 21

6. Data analysis of pp→pK + Λ reaction Cusp Effect Angular Distribution • The cusp angular distribution is obtained by subtraction the background from the cusp effect • The cusp effect study is limited to the range of 2.11 to 2.18 MeV/c 2 in pΛ subsystem • The distributions are fitted with Legendre polynomial functions NΣ cusp angular distribution is • symmetric and has a dominant S-  d 2 wave contribution      cusp 2 5 a P (cos ) a P (cos )  0 0 2 2 cms d cos K      2 4 cos cos p p p 0 1 2 November 25, 2014 Sedigheh Jowzaee 22

6. Data analysis of pp→pK + Λ reaction Particles Angular Distribution in Helicity Frame In 1 + 2 → a + b + c reaction the Helicity • angle is the angle between particle (a) and b or c in the {bc} rest frame • Physical effects in the Dalitz plot can be seen in Helicity angle distributions • The N * (1650) and N * (1720) resonances introduces an asymmetry with enhancement at cos θ Rp Λ Kp = -1 The p Λ -FSI enhances the distributions • towards cos θ RK Λ pK = -1 and cos θ RpK Λ p = 1 • No structure for cusp due to its dominant S-wave contribution November 25, 2014 Sedigheh Jowzaee 23

6. Data analysis of pp→pK + Λ reaction Particles Angular Distribution in CMS • The angular distributions in the CMS are symmetric due to the identical particles in the entrance channel • Some asymmetries are seen in the forward and backward regions • Incomplete MC description of the detector at small angles • Angular distributions described by Legendre polynomials 2  d      2 1 ( l ) a P (cos )  l l d  0 l       2 4 cos cos ... C C C 0 1 2 November 25, 2014 Sedigheh Jowzaee 24