K +  photoproduction with the Crystal Ball at MAMI T.C. Jude The University of Edinburgh New method of K + detection with the Crystal Ball Extraction of  (p,K + )  cross sections from threshold to 1.4 GeV photon beam T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

 (p,K + )  Cross Section Measurements Predicted nucleon resonances which have not been observed experimentally may couple to strange decay channels 1 A crucial test of QCD based chiral effective field theories in the strange quark sector 2 E  [GeV] [1] S Capstick and W Roberts, Phys. Rev. D58, (1998) [2] B Borasoy et al. Eur. Phys. J. A 34, (2007) [3] R. Bradford et al., Phys Rev. C 73, (2006) [4] K.H. Glander et al., Eur Phys. J. A 19, 251 (2004) [5] T. Mart arXiv: v1 [nucl-th] (2008) [6] T. Nelson and T. Mart. Mod. Phys. Lett. A, 24, 964 (2007) [7] T.S.H Lee et al. Phys. Rev. C. 73, (2006) [8] T. Van Cauteren et al. Phys. Rev. C 73, (2006) T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010 Significant discrepancies exist between cross-sections measurements 3,4 Fits to these data sets reveal differences in nucleon resonances when describing the photoproduction process 5,6 Theoretical models (Coupled channel analysis 7, Regge models 8 ) cannot at present discern between data sets. No detailed measurements close to threshold energies.  p  K + +  p +  - (~ 64%) n +  0 (~ 36%)   p  K + +   

K + meson detection in segmented calorimeters K +     ( ~ 63%) Mean lifetime of K + ~ 12 ns     (~ 21%) Incident sub-cluster from K + ~ 3ns Decay sub-cluster from K +      decay ~ 20ns Identify the K + decay within the crystals of the Crystal Ball and TAPS Eliminates the need of expensive magnetic spectrometers T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

Number of crystals in decay sub-cluster Furthest crystal in decay sub-cluster Crystal Ball – PID  E-E cut (Blue line) T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

Decay sub-cluster energy Incident and decay sub- cluster time difference K + missing mass T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

K + energy loss correction GEANT4 simulation of K + phase space distribution in the Crystal Ball. The decay of the K + “switched off” Measure K + energy difference on a NaI crystal by crystal basis T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

K + Remnant energy correction Correction for energy of the K + decay left in the K + cluster Identify the type of K + decay (muonic or pionic) from parameters of the decay cluster Experimental data. 2D cuts to select muonic and pionic events. Simulated data. K + weak decay muonic / pionic T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

K + Remnant energy correction T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

GEANT4 simulation Effect of the ADC integration time interval on the K + decay cluster energy spectrum. Use the Crystal Ball timing of the real data to set the simulated cut off as 600 ns. Simulated timing resolution set by measuring time differences of crystals in the same cluster for photon detection. Energy resolution set by width of proton mass peak from  0 missing mass spectrum T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

GEANT4 simulation Simulation of the Crystal Ball energy sum Select  (p,K + )  events in real and simulated data M2 trigger simulated (20 MeV threshold for each trigger section) Use cumulative distribution fit to give probability of accepting simulated events T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

Decay sub-cluster energy. Measured K + energy < 250 MeV Decay sub-cluster energy. Measured K + energy < 100 MeV 90 <  cm < < E  <1.2 GeV Experimental data (red), simulated data (blue ) Reconstructed to measured K + energy difference K + missing mass T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

(simulation) Detection of  0 decay Distinguish between  (p, K + )  and  (p, K + )  0 by the identifying the photon from  0 decay T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

Identification of the photon from  0 decay Use TOF techniques to discriminate between neutrons and photons in TAPS From the K + events identified (in simulation): ~ 55% of K +  0 events correctly identified by detection of the decay photon ~ 5% of K +  events misidentified Detection of  0 decay T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

Simulated data Experimental data Train fits to K + missing mass spectra with simulated data T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

Fit independent method of yield extraction 2 missing mass histograms per energy and polar angle range: Positive and negative identification of  0 decay photon. Subtract scaled histogram of decay  ID to leave only K +  contribution

~ 12%. SAID distribution of 30 million K +  events July 2007: 9.62 x 10 4 K + events April 2009: 2.82 x 10 5 K + events  (p,K + )  Cross Section Measurements July 2007 data set July 2007: x protons /m 2 April 2009: x protons /m 2 July 2007 and April 2009 data sets Empty target subtracted, M1 tagger hits included (approximately 4%) July 2007: MeV April 2009: MeV T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

Blue: Yield extraction from fitting to K + missing mass spectra Red: Yield extraction from identifying  0 decay photon

T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010  (p, K + )  cross sections with different data sets and methods of yield extraction July ’07, Fit to missing mass spectra (red) July ’07, ID  0 decay  (blue) April ’09, Fit missing mass spectra (Green) April ’09, ID  0 decay  (black)

T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010 Cross sections on the next two slides: Data points (black), weighted sum of both data sets. Select K +  using decay photon ID. Selecting K +  by fitting to missing mass spectra (green) Previous SAPHIR 1 data points (red). Each angular bin backwards by cos  = Previous CLAS 2 data points (blue). Kaon-MAID prediction (Magenta). Includes S 11 (1650), P 11 (1710), P 13 (1720) and D 13 (1900) Regge-Plus-Resonance (RPR) model 3,4 (light blue). Constrain fits from forward angle cross section data. [1] K.H. Glander et al., Eur Phys. J. A 19, 251 (2004) [2] R. Bradford et al., Phys Rev. C 73, (2006) [3] T. Van Cauteren et al. Phys. Rev. C 73, (2006), [4] Pieter Vancraeyveld, The University of Ghent. Private communication (2010) JLab notation adopted: Do not integrate out azimuthal angle from differential cross sections (multiply by 2  )

T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

Cross section measurements as a function of centre of mass polar angle. Important constraints on chiral effective field theories near threshold. Blue line: Cross section extraction from a chiral effective Lagrangian 1  2 fits performed to available photoproduction data [1] B Borasoy et al. Eur. Phys. J. A 34, (2007) [2] K.H. Glander et al., Eur Phys. J. A 19, 251 (2004) Black points: This data Red points: SAPHIR data 2 T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

Systematic uncertainties PID detection efficiency: reconstruction of proton from  (p,p)  0. (Pauline’s talk.) K +  yield extraction: Comparison between methods of yield extraction. Detection efficiency and modelling energy sum. Compare SAID and uniform distributions. Extract cross sections with each K + decay mode. K + hadronic interactions in the NaI crystals 1. T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010 Simulated with K + hadronic interactions Simulated with no K + hadronic interactions Experimental data. 1 D.H. Wright and A. Heikkinen. Adding Kaons to the Bertini cascade model. Proceedings of CHEP04 (2004)

K +  photoproduction with the Crystal Ball at MAMI T.C. Jude The University of Edinburgh

T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010 Extra slides....

GEANT4 simulation Separate energy scale for the K + decay cluster Compare peak position from K + muonic decay for real and simulated data Energy scale varies with K + energy due to NaI crystal dimensions and light attenuation. T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

New opportunities with K + detection in the Crystal Ball Asymmetry of  decay distribution with circular polarised beam 1.0 – 1.2 GeV  [deg]cos(  ) 1.0 – 1.2 GeV Extraction of the polarisation observables C X and C Z via the distribution of the  weak decay products. T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

100 MeV energy sum in the CB 330 MeV energy sum in the CB K + detection in TAPS (simulation) Energy [MeV] Energy of decay sub-cluster Time difference of incident and decay sub-cluster Time [ns] Lab polar angle of K + detection  [deg]

T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010

Isobar models: describe hadronic interactions from a series of Feynman contributions of resonant and non-resonant meson exchange. Coupled channel analysis 1. Include multistep processes (  N   N  KY). Regge trajectories: constrain the background terms and interpolate into the resonance region superimposing resonance structure (Regge-Plus-Resonance model 2 ). Multipole analysis 3. Background described by born terms and t-channel (vector meson) exchange. Include “PDG five star” resonances and constrain from experimental data. Conclusion: K +  resonant structure is poorly understood with the available data to constrain theoretical models. Theoretical approaches to K +  photoproduction [1] T.S.H Lee et al. Phys. Rev. C. 73, (2006) [2] T. Van Cauteren et al. Phys. Rev. C 73, (2006) [3] T. Nelson and T. Mart. Mod. Phys. Lett. A, 24, 964 (2007) T.C. Jude, K + photoproduction off the proton. A2 collaboration meeting, 10 th March 2010