HLAB meeting paper 2011/1/18 T.Gogami CLAS ( CEBAF Large Acceptance Spectrometer ) Clam shell is...

Click here to load reader

download HLAB meeting paper 2011/1/18 T.Gogami CLAS ( CEBAF Large Acceptance Spectrometer ) Clam shell is open.

of 38

description

Abstract

Transcript of HLAB meeting paper 2011/1/18 T.Gogami CLAS ( CEBAF Large Acceptance Spectrometer ) Clam shell is...

HLAB meeting paper 2011/1/18 T.Gogami CLAS ( CEBAF Large Acceptance Spectrometer ) Clam shell is open Paper Abstract Introduction In this article CLAS g11a data set (5/7/2004 7/29/2004) p K + differential cross section recoil polarization (P ) Experimental setup Tagger E/E MAGNET photon electron [GeV] gravity 6.06 [m] E-plane (384) T-plane (61) 4mm thickness 20mm thickness time 110 [ps] ( intrinsic resolution 210 -4 ) Radiator Gold foil (10 -4 rad. length ) The bremsstrahlung tagged photon beam in Hall B at JLab, D.I. Sober, Nuclear Instruments and Methods in Physics Research A 440 (2000) 263}284 CLAS CLAS ( CEBAF Large Acceptance Spectrometer ) Toroidal Magnet Superconducting toroidal magnet Temperature : 4.4 [K] (Liquid He) 1920 [A], 1.8 [T] ( Max : 3861[A], 3.5 [T] ) B B People Toroidal Magnet Superconducting toroidal magnet Temperature : 4.4 [K] (Liquid He) 1920 [A], 1.8 [T] ( Max : 3861[A], 3.5 [T] ) B B Magnetic field in midplane between two coils CLAS (CEBAF Large Acceptance Spectrometer) Target : Liquid H 2 (cylindrical Kapton chamber 40cm L 4cm D ) Momentum resolution ~ 510 -3 Trigger tagger 2/6 ( Start TOF ) DAQ rate ~ 5 [kHz] Tracking ~300 [m] Timing (~80 160 [ps]) p K + Spec The CEBAF large acceptance spectrometer (CLAS), B.A. Mecking, Nuclear Instruments and Methods in Physics Research A 503 (2003) 513553 DATA and EVENT selection Want to see p K + p K + p - Tree track analysis p K + p( - ) Two track analysis +28% of full set 1.Momentum, Energy correction 2.Loose cut Missing mass, Invariant mass 3.Kinematic fit confidence level cut Confidence level cut ~ 8 [MeV/c 2 ] Confidence level The effect of the confidence level cut is dramatic ! Missing mass Background reduction Cut misidentified particles Background reduction (2) 1.Given event i neighbors 3.Missing mass 4.Maximum likelihood fit Gaussian signal (s) linear background (b) 5.Quality factor weighted by (1-Q) All events Missing Mass s = GeV bin Other consideration Detector acceptance Extracting P Normalization Systematic Uncertainties Result Mandelstam variables proton photon Kaon Lambda Cross section Count Corrected Number of photons Target Binning width Acceptance Cross section( ) Red : two track analysis Blue : three track analysis Error Statistic Acceptance Cross section( ) Red : two track analysis Blue : three track analysis Error Statistic Acceptance Cross section( ) Red : two track analysis Blue : three track analysis Error Statistic Acceptance Agreement between the two analysis Agreement between the two analysis, Very little systematic offset Consistent within statistical and acceptance uncertainties Weighted mean differential cross sections Weighted mean differential cross sections : i = 2,3 j = 2,3 = 0.28 For kinematic points where only a two-track measurement exists, Cross section : its value Uncertainty : scaling by 1 + || = 1.136 Cross section p K + Red : CLAS Blue : previous CLAS Green : SAPHIR Measurement of p->K+ and p->K+ 0 at photon energies up to 2.6 GeV, K.H. Glander, arXiv:nucl-ex/ v1 26 Aug 2003 The p K+ and p K+0 reactions at forward angles with photon energies from 1.5 to 2.4 GeV, M. Sumihama, PHYSICAL REVIEW C 73, (2006) Measurement of the p K+ reaction at backward angles, K. Hicks, PHYSICAL REVIEW C 76, (R) (2007) LEPS SAPHIR Model comparison ( ) K-MAID (fit with SAPHIR) K+,K*(892),K 1 (1270) RPR (fit with p CLAS) K+ Regge trajectory, K* Regge trajectory N(1650)S 11,N(1710)P 11, N(1720)P 13,N(1900)P 13, missing D 13 Forward angle Bonn-Gatchina (fit with p CLAS) Partial wave analysis Model comparison ( ) K-MAID (fit with SAPHIR) K+,K*(892),K 1 (1270) RPR (fit with p CLAS) K+ Regge trajectory, K* Regge trajectory N(1650)S 11,N(1710)P 11, N(1720)P 13,N(1900)P 13, missing D 13 Forward angle Bonn-Gatchina (fit with p CLAS) Partial wave analysis Model comparison ( ) K-MAID (fit with SAPHIR) K+,K*(892),K 1 (1270) RPR (fit with p CLAS) K+ Regge trajectory, K* Regge trajectory N(1650)S 11,N(1710)P 11, N(1720)P 13,N(1900)P 13, missing D 13 Forward angle Bonn-Gatchina (fit with p CLAS) Partial wave analysis Conclusion END Start counters Introduction (p K + ) p K + Polarization Pseudoscalar nature of the K+ Self-analyzing decay of the Isospin structure of the final state Allows coupling only to I=1/2 N* (not the I=3/2 *) PP CLAS : Blue SAPHIR2004 : Green GRALL2007 : Black Tagger