Measurement of π 0 π + / − Photoproduction off the Deuteron and D-butanol targets Meson Conference ’18, Krakow Debdeep Ghosal on behalf of A2-collaboration University of Basel– Krusche Group debdeep.ghosal@unibas.ch June 11, 2018 Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 1 / 29
Overview Introduction and Motivation for Photoproduction Motivation for Photoproduction with π 0 π + / − Experimental Setup Analysis Preliminary Results Summary and Outlook References Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 2 / 29
Introduction and Motivation for Photoproduction � An efficient tool for the study of decays of nucleon resonances � Excitation spectrum of hadrons → the underlying symmetries and the internal degrees of freedom Photoproduction of pion pairs off nuclei insight into low energy QCD (large α ) in medium resonances of nucleons Baryons could have less internal degrees of freedom than predicted in quark models possibilities of more complex baryonic structures(e.g pentaquarks etc.) Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 3 / 29
Motivation for Photoproduction with π 0 π + / − For nucleon resonances the effective degrees of freedom are not well understood and many more states have been predicted than observed.[ larger mass region of the spectrum ] Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 4 / 29
Motivation for Photoproduction with π 0 π + / − • Higher lying resonances have tendency of cascade-like decays with an intermediate state → double pion production interesting. Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 5 / 29
Experimental Setup of A2 Mainz Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 6 / 29
Experimental Setup of A2 Mainz Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 6 / 29
Experimental Setup of A2 Mainz Figure: Schematic overview of the Exp. Setup Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 6 / 29
Parameters for Data taking with Unpolarized and Polarized targets Parameters Unpolarized target Polarized target Target type Liq Deuterium[ LD 2 ] dButanol Target length[cm] 3.02 1.88 Multiplicity trigger M2+ M2+ Photon tagger range[MeV] 400 to 1400 400 to 1400 Radiator Moeller Moeller e − beam energy[MeV] 1575.5 MeV 1557 MeV Table: Parameters for deuterium(May 2009) and dButanol(Dec 2015) beamtimes Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 7 / 29
About the Interested Channels Investigated reactions of baryon spectrum: NN, π N and γ N(limited extent) Interested Amplitudes: Phase Phase space space Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 8 / 29
π π Analysis Background Rejection Various Cuts for event selection: charged particle identification via energy left in PID versus energy in CB (”dE-E cut”) Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 9 / 29
π π Analysis Background Rejection Various Cuts for event selection: charged particle identification via energy left in PID versus energy in CB (”dE-E cut”) invariant mass of the π 0 reconstructed from γγ in case of three neutral particles, get neutron candidate via χ 2 test Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 9 / 29
π π Analysis Background Rejection Various Cuts for event selection: charged particle identification via energy left in PID versus energy in CB (”dE-E cut”) invariant mass of the π 0 reconstructed from γγ in case of three neutral particles, get neutron candidate via χ 2 test missing mass of either a charged π + / − or the proton Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 9 / 29
π π Analysis Background Rejection Various Cuts for event selection: charged particle identification via energy left in PID versus energy in CB (”dE-E cut”) invariant mass of the π 0 reconstructed from γγ in case of three neutral particles, get neutron candidate via χ 2 test missing mass of either a charged π + / − or the proton coplanarity of the final state ( φ -angle between the π + / − π 0 system and the participant nucleon) Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 9 / 29
Analysis Background Rejection Various Cuts for event selection: charged particle identification via energy left in PID versus energy in CB (”dE-E cut”) invariant mass of the π 0 reconstructed from γγ in case of three neutral particles, get neutron candidate via χ 2 test missing mass of either a charged π + / − or the proton coplanarity of the final state ( φ -angle between the π + / − π 0 system and the participant nucleon) π π Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 9 / 29
Special Corrections on MC data Nucleon Detection Efficiency [to compensate for imperfections in the implementation of the experimental setup in GEANT and inefficiencies in the PID and the TAPS vetoes] Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 10 / 29
Special Corrections on MC data Nucleon Detection Efficiency [to compensate for imperfections in the implementation of the experimental setup in GEANT and inefficiencies in the PID and the TAPS vetoes] CB Energy sum correction/CDF [The energy-sum trigger checks the sum of the deposited energies of the particles in CB against a threshold value] Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 10 / 29
Special Corrections on MC data Nucleon Detection Efficiency [to compensate for imperfections in the implementation of the experimental setup in GEANT and inefficiencies in the PID and the TAPS vetoes] CB Energy sum correction/CDF [The energy-sum trigger checks the sum of the deposited energies of the particles in CB against a threshold value] Gap correction [acceptance hole between the CB and TAPS, where no particles are detected] Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 10 / 29
Analysis Calculating Cross sections apply all cuts and corrections to data Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 11 / 29
Analysis Calculating Cross sections apply all cuts and corrections to data retrieve photon flux from tagger channels Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 11 / 29
Analysis Calculating Cross sections apply all cuts and corrections to data retrieve photon flux from tagger channels generate MC data for channels with Geant4 simulation Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 11 / 29
Analysis Calculating Cross sections apply all cuts and corrections to data retrieve photon flux from tagger channels generate MC data for channels with Geant4 simulation apply all the cuts and corrections to MC data Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 11 / 29
Analysis Calculating Cross sections apply all cuts and corrections to data retrieve photon flux from tagger channels generate MC data for channels with Geant4 simulation apply all the cuts and corrections to MC data divide data yield by the efficiency Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 11 / 29
Analysis-Result dE-E Proton exclusion and selection cut Proton and Charged Pion identification with PID and CB (a) For π + channel : pion (b) For π − channel : pion and proton Figure: Identification of charged particle Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 12 / 29
Preliminary Results Total Cross section comparison for LD 2 target [May 2009 beamtime] Total integral (summation over CT Bin 0 to 5) b] cshist µ [ σ σ 60 CS for Phase space with CB Esum correction of May_09_Debdeep 60 Phase space by Sebi By S. Lutterer without gap correction σ of May_09_Sebastian without CB corr. S. Lutterer without CB Esum correction Analysis I [ with same CB Esum, without gap correction] Phase space by Debdeep: same CB Esum, no gap correction 50 50 Analysis II [ with different CB Esum, with gap correction] Phase space by Debdeep: different CB Esum, gap correction 40 40 b] 30 µ 30 [ σ 20 20 10 10 600 800 1000 1200 1400 E [MeV] γ 0 (b) Influence of the CB energy sum 400 600 800 1000 1200 1400 E [MeV] γ correction on total Cross section for (a) For reaction with final state π 0 π + π 0 π − p final state Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 13 / 29
Recommend
More recommend
