Study of two pion channel from photoproduction on the deuteron Lewis Graham Proposal Phys 745 Class May 6, 2009

Overview Physics Motivation EG3 Data Set Analysis Outlook

This CLAS Analysis… will use eg3 data set will study 2π decays measuring the cross section for γd → Δ ++( pπ + )π - and the angular dependent cross sections detecting all final state particles will study final-state interactions with the “spectator” neutron

a first measurement of the Δ ++ π - channel covering the energies and kinematics required to investigate higher lying resonances. a first look at cross sections for kinematic and systematic effects. a better understanding of the eg3 systematics. The proposal is based on results from this analysis! The main motivations are to provide…

N* photoproduction experiments at JLab on the proton g1: circular beam polarization g8b: linear beam polarization FROST: polarized beam and target Analysis of current photoproduction data on the proton finds all PDG 2*, 3*, and 4* resonances below 2.1 GeV no 1* resonances (P 31 (1750), S 11 (2090), P 11 (2100), …) no ‘missing’ N* resonances

High lying (W >1.7 GeV) nucleon resonances study. Current study of high lying (W >1.6 GeV) nucleon resonances (can compare). Extraction of known resonances with data extending to high energy range ( ~ 5.5 GeV). Existing data is only up to 5.1 GeV. Search for possible signals from missing baryon states. Physics Goals

From S. Capstick and W. Roberts, Phys. Rev. D49, (1994) 4570 (Relativized 3 P 0 model) Predicted but not observed in the experiment states are expected to decouple from  N channel but couple to the ,  N,  N channels. Most of the Nucleon Spectroscopy information was obtained from  N   N(X) reactions Res.  (  ) (MeV)  (  ) (MeV)  (  ) (MeV)  (  ) (MeV) N 1 (1880) N 3 (1910) N 3 (1950) N 1 (1975) N 5 (1980) Therefore, missing states may be observed in the channels of multihadron production by photons for instance in two pion channel. Missing States

Jefferson Lab Hall B

C EBAF L arge A cceptance S pectrometer Drift chambers argon/CO 2 gas, 35,000 cells Electromagnetic calorimeters Lead/scintillator, 1296 PMTs Torus magnet 6 superconducting coils Gas Cherenkov counters e/  separation, 216 PMTs Time-of-flight counters plastic scintillators, 684 PMTs Large angle calorimeters Lead/scintillator, 512 PMTs Liquid D 2 (H 2 )target, NH3, ND3  start counter; e minitorus

CLAS 4  detector  torodail magnetic field  3 drift chamber regions  time of flight  electromagnetic calorimeter  Cerenkov Counter  Electron Beam Energy 5.7 GeV  Luminosity cm -2 s -1  Momentum Resolution < 1%  Capability of detecting multiparticle final states Particle production in CLAS

CLAS Detection Allows simultaneous detection of multiple particles in the final state.

EG3 Run Conditions

Analysis of γd →∆ ++ (pπ + )π - Particle Identification Cuts Timing Extracting Yield Fitting Procedure Detector Simulation GSIM Parameters (MC Events) Normalization GFlux Method Systematic Errors d  ∆ ++ p π+π+  (n) on a deuteron target

Particle Identification

∆ ++ Identification ∆ ++ = 1232 MeV p + π+

Cuts PID: 3-track Requirement Missing Mass 2 Cut (.8 GeV2< MM2 <.97 GeV2 ) Skim Cut (0.7 GeV < M < 1.2 GeV) Proton Momentum – 450 MeV Timing: Max. Vertex time of protons and pions - 2ns TOF difference of photon and avg. particle – 2ns.

Simulation Generated 10M Events. Events Generated with same parameters as Data. Binned in 44 Energy bins and fit with breit-wigner. Yield Extracted for each fit energy bin.

Acceptance Calculation Acceptance = Reconstructed / Generated Events Reconstructed Generated Events Acceptance

Normalization Data was normalized by the photon flux Each event in the data sample is corrected by a corresponding number of photons in the flux spectrum

Corrections Acceptance (simulation) Timing cuts Eloss Correction Proton Momentum Cut GFlux Correction Prescale Luminosity Fiducial Cuts Energy Bin Correction

Data Fits with Corrections

Cross Section Extraction After Luminosity After Acceptance Luminosity = target density * target length * Avogadro’s Number /Mole mass

Comparison of Preliminary Results

Next Steps in Analysis!

Fit of  +  -p single differential cross-sections and the contributions from particular mechanisms with the JLAB-MSU (JM) model. Full calculations  p  -  ++ p+0p+0 pppp  p  - P (1600)  p  + F 0 15 (1685) direct 2  production  p  + D 13 (1520) Combined fit of various 1-diff. cross-sections allowed to establish all significant mechanisms.

Complete set of unpolarized 1-differential cross-sections in  r,v →  -  + p reactions. For unpolarized beam/target, the final state,  r,v →  -  + p reaction offers 9 independent single-differential cross- sections in each (W&Q 2 ) bin. All these cross-sections are available from CLAS for the first time.

fit within the framework of JM06 model resonant part non-resonant part differences in the shapes of resonant/non-resonant cross- sections make possible to isolate N* contribution. Resonant and non-resonant contributions fit within the framework of JM model

What’s to Come Angular Dependence Cross Sections Theoretical Model Incorporation and Interpretations to Data Comparisons to Published Data Contribution to World Data Possible Missing Resonances found