Measurement of 0 + / Photoproduction off the Deuteron and - - PowerPoint PPT Presentation

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Measurement of 0 + / Photoproduction off the Deuteron and - - PowerPoint PPT Presentation

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Measurement of 0 + / 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

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Measurement of π0π+/− Photoproduction off the Deuteron and D-butanol targets

Meson Conference ’18, Krakow Debdeep Ghosal

  • n 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

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Overview

Introduction and Motivation for Photoproduction Motivation for Photoproduction with π0π+/− 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

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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

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Motivation for Photoproduction with π0π+/−

For nucleon resonances the effective degrees of freedom are not well understood and many more states have been predicted than

  • bserved.[larger mass region of the spectrum]

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 4 / 29

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Motivation for Photoproduction with π0π+/−

  • 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

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Experimental Setup of A2 Mainz

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 6 / 29

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Experimental Setup of A2 Mainz

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 6 / 29

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SLIDE 8

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

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Parameters for Data taking with Unpolarized and Polarized targets

Parameters Unpolarized target Polarized target Target type Liq Deuterium[LD2] 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

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About the Interested Channels

Investigated reactions of baryon spectrum: NN, πN and γN(limited extent) Interested Amplitudes:

Phase space Phase space

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 8 / 29

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Analysis

Background Rejection

Various Cuts for event selection: charged particle identification via energy left in PID versus energy in CB (”dE-E cut”)

π

π

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 9 / 29

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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 π0 reconstructed from γγ in case of three neutral particles, get neutron candidate via χ2 test

π

π

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 9 / 29

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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 π0 reconstructed from γγ in case of three neutral particles, get neutron candidate via χ2 test missing mass of either a charged π+/− or the proton

π

π

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 9 / 29

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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 π0 reconstructed from γγ in case of three neutral particles, get neutron candidate via χ2 test missing mass of either a charged π+/− or the proton coplanarity of the final state (φ-angle between the π+/−π0 system and the participant nucleon)

π

π

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 9 / 29

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SLIDE 15

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 π0 reconstructed from γγ in case of three neutral particles, get neutron candidate via χ2 test missing mass of either a charged π+/− or the proton coplanarity of the final state (φ-angle between the π+/−π0 system and the participant nucleon)

π

π

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 9 / 29

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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

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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

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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

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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

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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

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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

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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

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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

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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

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Preliminary Results

Total Cross section comparison for LD2 target [May 2009 beamtime]

[MeV]

γ

E 400 600 800 1000 1200 1400 b] µ [ σ 10 20 30 40 50 60 Phase space by Sebi Phase space by Debdeep: same CB Esum, no gap correction Phase space by Debdeep: different CB Esum, gap correction

cshist

By S. Lutterer without gap correction Analysis I [ with same CB Esum, without gap correction] Analysis II [ with different CB Esum, with gap correction]

(a) For reaction with final state π0π+

[MeV]

γ

E 600 800 1000 1200 1400 b] µ [ σ 10 20 30 40 50 60

  • f May_09_Debdeep

σ

  • f May_09_Sebastian without CB corr.

σ

Total integral (summation over CT Bin 0 to 5)

  • S. Lutterer without CB Esum correction

CS for Phase space with CB Esum correction

(b) Influence of the CB energy sum correction on total Cross section for π0π−p final state

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 13 / 29

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Preliminary Results

Comparison plot of total cross sections in terms of Eγ with LD2 and d-Butanol targets

[MeV]

γ

E 600 800 1000 1200 1400 b] µ [ σ 10 20 30 40 50 60

p π p-> γ

  • f Debdeep_May_09 beamtime

σ

  • f Sebastian_May_09 beamtime

σ _1/2 of Dec_15 beamtime σ

Total integral (summation over CT Bin 0 to 19)

  • Unpol. CS with Liq Deuterium
  • Unpol. CS by S. Lutterer with Liq Deuterium

Pol CS [σ1/2] with d-Butanol

(a) Comparison for reaction with final state π0π+

[MeV]

γ

E 600 800 1000 1200 1400 b] µ [ σ 10 20 30 40 50 60

p π p-> γ

  • f Debdeep_May_09 beamtime

σ

  • f Sebastian_May_09 beamtime

σ _3/2 of Dec_15 beamtime σ

Total integral (summation over CT Bin 0 to 19)

  • Unpol. CS with Liq Deuterium
  • Unpol. CS by S. Lutterer with Liq Deuterium

Pol CS [σ3/2] with d-Butanol

(b) Comparison for reaction with final state π0π+

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 14 / 29

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Preliminary Results

Comparison plot of total cross sections in terms of W(COM energy) with LD2 and d-Butanol targets

[MeV] γ W 1300 1400 1500 1600 1700 1800 1900 b] µ [ σ 10 20 30 40 50 60 p π p-> γ
  • f May_09 beamtime
σ _1/2 of Dec_15 beamtime σ

Total integral (summation over CT Bin 0 to 5)

CS with Liq. Deuterium CS [σ1/2] with d-Butanol [MeV] γ W 1300 1400 1500 1600 1700 1800 1900 b] µ [ σ 10 20 30 40 50 60 p π p-> γ
  • f May_09 beamtime
σ _3/2 of Dec_15 beamtime σ

Total integral (summation over CT Bin 0 to 5)

CS with Liq. Deuterium CS [σ3/2] with d-Butanol

Figure: For γp → π0π+n channel

[MeV] γ W 1300 1400 1500 1600 1700 1800 1900 b] µ [ σ 10 20 30 40 50 60 (n) π n-> γ
  • f May_09 beamtime
σ _1/2 of Dec_15 beamtime σ

Total integral (summation over CT Bin 0 to 5)

CS with Liq. Deuterium CS [σ1/2] with d-Butanol [MeV] γ W 1300 1400 1500 1600 1700 1800 1900 b] µ [ σ 10 20 30 40 50 60 (n) π n-> γ
  • f May_09 beamtime
σ _3/2 of Dec_15 beamtime σ

Total integral (summation over CT Bin 0 to 5)

CS with Liq. Deuterium CS [σ3/2] with d-Butanol

Figure: For γn → π0π−p channel

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 15 / 29

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Preliminary Results

Cross section Comparison with LD2 and d-Butanol targets

W[MeV] 1300 1400 1500 1600 1700 1800 1900 b] µ [ σ 10 20 30 40 50 60

n

+

pi π p-> γ beamtime)

2

(LD σ

  • Unpol. CS

]/2 (d-Butanol beamtime)

3/2

σ +

1/2

σ [

Total integral (summation over CT Bin 0 to 19)

Figure: Comparison for reaction with final state π0π+

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 16 / 29

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Preliminary Results: E-observable extraction

Asymmetry between the two helicity states

E-observable determines the conribution from σ1/2 and σ3/2 components Eversion1 =

σ1/2−σ3/2 σ1/2+σ3/2 = σdiff σsum or, Eversion2 = σdiff 2σunpol.

where, σ1/2 : photon − spin ∦ target − spin and σ3/2 : photon − spin target − spin

  • V1(Carbon subtraction method): to determine the carbon and oxygen

contributions to the dButanol

  • V2(Direct method): extract tot. CS from dButanol beamtime → to be

normalized using 2×unpolarized CS. Circularly polarized photon beam impinging on a longitudinally polarized nucleon target

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 17 / 29

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Preliminary Results: E-observable extraction

Figure: Preliminary E-observable for reaction with final state π0π+

Preliminary result indicates no significant asymmetry!

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 18 / 29

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Summary and Outlook

Summary : Preliminary cross sections for both mixed charge double pion production channels extracted Compare results from final analysis with previous data Extraction of E-observable with hydrogen normalization and carbon subtraction metods d-Butanol measurements are still in early stage of analysis

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 19 / 29

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Summary and Outlook

Summary : Preliminary cross sections for both mixed charge double pion production channels extracted Compare results from final analysis with previous data Extraction of E-observable with hydrogen normalization and carbon subtraction metods d-Butanol measurements are still in early stage of analysis Outlook : Need further investigation on detection efficiency and bkg. subtraction Data from further beamtimes to be analyzed

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 19 / 29

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References

https: //jazz.physik.unibas.ch/site/talks/krusche_dnp08.pdf

  • F. Zehr and B. et al. Krusche. Photoproduction of π0π− and π0π+
  • pairs off the proton from threshold to the second resonance region.

The European Physical Journal A, 48(7):98, 2012. ISSN 1434-6001. doi: 10.1140/epja/i2012-12098-1. https://jazz.physik.unibas.ch/site/talks/Abt_DPG_17_03_ talk.pdf https://jazz.physik.unibas.ch/site/talks/lutterer_dpg_ talk_pion_photoproduction_30032017.pdf. https://edoc.unibas.ch/39089/1/Lilian_Witthauer.pdf https://edoc.unibas.ch/55107/1/thesis_kaeser_2017.pdf

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THANK YOU

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 21 / 29

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backup

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 22 / 29

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Presort

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E-observable calculation

double polarization observable E, which allows to split the results for total cross sections and angular distributions into their helicity 1/2 and helicity 3/2 parts. ’normalization factors’ consisting of the detection efficiency ǫ, target density ρ and the branching ratio Γi/Γ

Figure: Example of a standard E-obs plot

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Analysis

mn[part.] =

  • (p4

beam + p4 target − p4 π+ − p4 π0)2

where, p4

beam = (0,0,Eγ, Eγ) incoming tagged photon

p4

target = (0,0,0,mp[part.]) participant proton initially assumed at rest

(fermi momentum smearing increases inaccuracy of this assumption) p4

π+ and p4 π0 measured final state pions

(accurate for p4

π0 and with slight correction factor for low energy p4 π+)

mn[part.] = mass of the final state participant neutron spectator omitted from this calculation (assumed p4

n[spec.](initial) = p4 n[spec.](final))

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Background Rejection

Coplanarity cut− meson candiate(red) and recoil nucleon(blue) lie in the reaction plane, separated by azi. δφ = 180o Missing mass cut− mass M of the nucleon can be calculated from the initial state and the detected final state particles, assuming that the nucleon in the initial state is at rest:

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Corrections

software trigger [cdf/CB energy sum]: The CB energy sum trigger is checking the total sum of the analog signals of all NaI(Tl) crystals against a threshold, which corresponds to a certain energy. photon energy sum depends on the energy and angular distribution of the -meson and thus a certain model dependence is introduced

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Corrections

nucleon detection efficiency correction: The PID detector was shifted upstream during the December 2007 beamtime and to ensure a clean discrimination of protons and neutrons, a strict cut on the nucleon polar angle was applied in the data analysis. The corrections described here were determined for deuterium beamtime by setting the same detector thresholds in the hydrogen analysis and the corresponding deuterium

  • analysis. This is most crucial for the PID and Veto thresholds that have a

strong influence on the proton detection efficiency, and the TAPS CFD thresholds, which are important for the detection of neutrons.

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SLIDE 42

Example of mm-fit for C-subtraction method

Debdeep Ghosalon behalf of A2-collaboration (University of Basel) Talk @Krakow June 11, 2018 29 / 29