Simulation and data analysis with the BGO-OD experiment

Transcription

1 Simulation and data analysis with the BGO-OD experiment Tom Jude Physikalisches Institut, Universität Bonn On behalf of the BGO-OD collaboration Supported by the DFG 1/15

2 BGO-OD experiment Commissioning phase of the BGO - Open Dipole experiment for photonuclear physics at the ELSA electron accelerator facility Nearly 4π acceptance, excellent charged and neutral particle ID BGO ball: a highly segmented calorimeter, ideal for neutral meson reconstruction Forward spectrometer: tracking detectors, dipole magnet, drift chambers and TOF walls Charged particle ID and momentum reconstruction 2/14

3 BGO-OD experiment SciFi Photon Tagger 128 channels 8-83% of e- energy spectrum Goal of linear and circ. pol 2 layers of 288 (x) and 352 (y) fibres, 3mm diameter, 90 deg rotation 66 x 51 cm, t ~ 2ns BGO Ball Cu/crystal radiator e- TOF walls 480 Bi4Ge3O16 crystals degrees Internal plastic scintillator & MWPC for particle tracking Drift Chambers MOMO 3 layers of 244 fibres, 60 deg rotation. Spatial resolution ~ 1.5mm 8 chambers, 2 layers each x, y, u (+9deg), v(-9deg) 8.5 mm drift cell radius ELSA e- beam < 3.5 GeV Each wall 14 bars, 20cm wide, 3m long Time resolution < 1ns Dipole magnet lh2 target 0.5 T max field Centre of BGO Ball Forward spectrometer +/- 8 deg (vertical), +/- 10 deg (horizontal) acceptance, see Hannappel, HK 27.5, Wed 15:15 3/14

4 BGO-OD simulation Simulation and data analysis based on Explora[1]: an xml interface to C++ and root libraries Event generator: kinematics follow cross sections and bremsstrahlung beam distributions Simulation geometry complete z Measured magnetic field map (thanks to the GSI magnet group) Extra shielding around detectors may change fringe field (~1 %). Needs to be checked y x y x [1] J. Hartmann, D Piontek, C Schmidt, R Schmitz, A Suele and U Thoma. Version 1.3 (Crystal Barrel collaboration) (2011) z 4/14

5 Clustering in the BGO (simulated data) 0 invariant mass reconstruction, kinetic energy MeV 2 cluster invariant mass [MeV] Resolution ~5% in polar angle: 5/14

6 Charged particle ID with the BGO (simulated data) Energy deposited in inner, plastic scintillator barrel versus energy in BGO Select time and phi coincidences (~10 deg and ~ 10 ns) 6/14

7 K+ Identification with the BGO (simulated data) Time delayed, K+ weak decay within the BGO crystals, for example: lifetime ~12ns, 2 prominent decay modes: < 150 MeV Decay cluster from K+ decay < 350 MeV Incident cluster from Stopping the K+ 7/14

8 Particle tracking with forward detectors (simulated data) Reconstruct 1-D clusters in each layer of MOMO and SciFi Combine clusters from different layers to identify particle hit position MOMO ~ 80 % efficient, SciFi ~ 100% efficient MOMO hits SciFi hits Tracking behind the magnet: Track reconstruction with drift chambers & time of flight walls 8/14

9 Momentum reconstruction with the forward spectrometer (simulated data) Analysis assumes a uniform field, 0.4T with definite bounding edges. Small correction as a function of x and y positions accounts for field non-uniformity & fringe field Momentum = 0.3 x magnetic field strength x radius of curvature Time of track normalised against distance (includes arc of curvature) Particle charge determined by change in x-component of direction 9/14

10 Momentum reconstruction with the forward spectrometer (simulated data) Compare measured particle momentum to the actual, generated momentum Momentum resolution for protons and pions ~2% 10/14

11 Reconstruction of and masses (real data) 0 Commissioning beam time March 2012 Each cluster contains at least 3 crystals (reject protons no charged particle ID) Summed energy of clusters > 400 MeV Approximately 2 hours of data: 11/14

12 Identification of the proton in the BGO (real data) Identify 3 clusters in the BGO 2 clusters with at least 3 crystals ( 0 decay photons) 1 cluster with less than 3 crystals (proton) Select events where reconstructed proton and 0 are back to back in azimuthal angle Require 0 cluster energy > 400 MeV 12/14

13 Conclusions The BGO-OD experiment: excellent particle identification and momentum reconstruction (ideal for many particle final states of mixed charge, for example K+ (1405) Setup complete, commissioning ongoing A promising first analysis of experimental data Simulation and first analysis code is complete Production beam time coming soon 13/14

14 BGO-OD presentations Mon 17:00 room P3: HK 12.2 Datenerfassung für das BGO-OD Experiment an ELSA, Daniel Hammann Wed 15:15 room P3: HK 27.5 Tracking detectors of the BGO-OD experiment, Jürgen Hannappel Wed 15:30 room P3: HK 27.6 Photonen Flussmonitor für das BGO-OD Experiment, Thomas Zimmermann Thurs 18:30 room P2: HK 41.7 Rückstoß-Protonen-Polarisationsmessung am BGO-OD-Experiment mit Silizium-Streifen-Sensoren, Max Becker, Karsten Koop and Gordon Diefenthal Thurs 14:00 P Foyer: HK 53.9 Tagger electronics for the BGO-OD experiment, Francesco Messi (poster) Collaborating institutions Physikalisches Institut, Bonn, Germany Helmholtz-Institur für Strahlen und Kernphysik, Bonn, Germany INFN sezione di Pavia, Pavia, Italy National Science Center Kharkov Institute of Physics and Technology, Kharkov, Ukraine Universita degli Studi di Messina,Messina, Italy INFN sezione di Catania, Catania, Italy INFN Roma Tor Vergata, Rome, Italy University of Rome ``Tor Vergata'', Rome, Italy INFN sezione di Torino, Torino, Italy INFN sezione di Roma, Rome, Italy INFN - ISS, Rome, Italy INFN - LNF, Frascati (Rome), Italy The University of Edinburgh, Edinburgh, UK Petersburg Nuclear Physics Institute, Gatchina, Russia Russian Academy of Sciences Institute for Nuclear Research, Moscow, Russia Institut für Physik, Basel, Switzerland Supported by the DFG 14/14

15 Simulation and data analysis with the BGO-OD experiment Tom Jude Physikalisches Institut, Universität Bonn On behalf of the BGO-OD collaboration Supported by the DFG 1/15

16 BGO-OD experiment Commissioning phase of the BGO - Open Dipole experiment for photonuclear physics at the ELSA electron accelerator facility Nearly 4π acceptance, excellent charged and neutral particle ID BGO ball: a highly segmented calorimeter, ideal for neutral meson reconstruction Forward spectrometer: tracking detectors, dipole magnet, drift chambers and TOF walls Charged particle ID and momentum reconstruction 2/14

17 BGO-OD experiment 128 channels 8-83% of e- energy spectrum Goal of linear and circ. pol 2 layers of 288 (x) and 352 (y) fibres, 3mm diameter, 90 deg rotation 66 x 51 cm, t ~ 2ns BGO Ball Cu/crystal radiator e- TOF walls SciFi Photon Tagger 480 Bi4Ge3O16 crystals degrees Internal plastic scintillator & MWPC for particle tracking MOMO Drift Chambers 3 layers of 244 fibres, 60 deg rotation. Spatial resolution ~ 1.5mm 8 chambers, 2 layers each x, y, u (+9deg), v(-9deg) 8.5 mm drift cell radius ELSA e- beam < 3.5 GeV Each wall 14 bars, 20cm wide, 3m long Time resolution < 1ns Dipole magnet lh2 target 0.5 T max field Centre of BGO Ball Forward spectrometer +/- 8 deg (vertical), +/- 10 deg (horizontal) acceptance, see Hannappel, HK 27.5, Wed 15:15 3/14

18 BGO-OD simulation Simulation and data analysis based on Explora[1]: an xml interface to C++ and root libraries Event generator: kinematics follow cross sections and bremsstrahlung beam distributions Simulation geometry complete z Measured magnetic field map (thanks to the GSI magnet group) Extra shielding around detectors may change fringe field (~1 %). Needs to be checked y x y x [1] J. Hartmann, D Piontek, C Schmidt, R Schmitz, A Suele and U Thoma. Version 1.3 (Crystal Barrel collaboration) (2011) z 4/14

19 Clustering in the BGO (simulated data) 0 invariant mass reconstruction, kinetic energy MeV 2 cluster invariant mass [MeV] Resolution ~5% in polar angle: 5/14

20 Charged particle ID with the BGO (simulated data) Energy deposited in inner, plastic scintillator barrel versus energy in BGO Select time and phi coincidences (~10 deg and ~ 10 ns) 6/14

21 K+ Identification with the BGO (simulated data) Time delayed, K+ weak decay within the BGO crystals, for example: lifetime ~12ns, 2 prominent decay modes: < 150 MeV Decay cluster from K+ decay < 350 MeV Incident cluster from Stopping the K+ 7/14

22 Particle tracking with forward detectors (simulated data) Reconstruct 1-D clusters in each layer of MOMO and SciFi Combine clusters from different layers to identify particle hit position MOMO ~ 80 % efficient, SciFi ~ 100% efficient MOMO hits SciFi hits Tracking behind the magnet: Track reconstruction with drift chambers & time of flight walls 8/14

23 Momentum reconstruction with the forward spectrometer (simulated data) Analysis assumes a uniform field, 0.4T with definite bounding edges. Small correction as a function of x and y positions accounts for field non-uniformity & fringe field Momentum = 0.3 x magnetic field strength x radius of curvature Time of track normalised against distance (includes arc of curvature) Particle charge determined by change in x-component of direction 9/14

24 Momentum reconstruction with the forward spectrometer (simulated data) Compare measured particle momentum to the actual, generated momentum Momentum resolution for protons and pions ~2% 10/14

25 Reconstruction of 0 and masses (real data) Commissioning beam time March 2012 Each cluster contains at least 3 crystals (reject protons no charged particle ID) Summed energy of clusters > 400 MeV Approximately 2 hours of data: 11/14

26 Identification of the proton in the BGO (real data) Identify 3 clusters in the BGO 2 clusters with at least 3 crystals ( 0 decay photons) 1 cluster with less than 3 crystals (proton) Select events where reconstructed proton and 0 are back to back in azimuthal angle Require 0 cluster energy > 400 MeV 12/14

27 Conclusions The BGO-OD experiment: excellent particle identification and momentum reconstruction (ideal for many particle final states of mixed charge, for example K+ (1405) Setup complete, commissioning ongoing A promising first analysis of experimental data Simulation and first analysis code is complete Production beam time coming soon 13/14

28 BGO-OD presentations Mon 17:00 room P3: HK 12.2 Datenerfassung für das BGO-OD Experiment an ELSA, Daniel Hammann Wed 15:15 room P3: HK 27.5 Tracking detectors of the BGO-OD experiment, Jürgen Hannappel Wed 15:30 room P3: HK 27.6 Photonen Flussmonitor für das BGO-OD Experiment, Thomas Zimmermann Thurs 18:30 room P2: HK 41.7 Rückstoß-Protonen-Polarisationsmessung am BGO-OD-Experiment mit Silizium-Streifen-Sensoren, Max Becker, Karsten Koop and Gordon Diefenthal Thurs 14:00 P Foyer: HK 53.9 Tagger electronics for the BGO-OD experiment, Francesco Messi (poster) Collaborating institutions Physikalisches Institut, Bonn, Germany Helmholtz-Institur für Strahlen und Kernphysik, Bonn, Germany INFN sezione di Pavia, Pavia, Italy National Science Center Kharkov Institute of Physics and Technology, Kharkov, Ukraine Universita degli Studi di Messina,Messina, Italy INFN sezione di Catania, Catania, Italy INFN Roma Tor Vergata, Rome, Italy University of Rome ``Tor Vergata'', Rome, Italy INFN sezione di Torino, Torino, Italy INFN sezione di Roma, Rome, Italy INFN - ISS, Rome, Italy INFN - LNF, Frascati (Rome), Italy The University of Edinburgh, Edinburgh, UK Petersburg Nuclear Physics Institute, Gatchina, Russia Russian Academy of Sciences Institute for Nuclear Research, Moscow, Russia Institut für Physik, Basel, Switzerland Supp Supported by the DFG 14/14