1 K* Photoproduction off the proton at CLAS via Ishaq Hleiqawi OHIO UNIVERSITY NSTAR2005 Oct. 12, 2005

2 Experiment and Physics Motivation Background and Analysis Cuts Results: –Cross sections –Systematic Uncertainties Conclusion OUTLINE

3 Experiment and Motivation “g1c” data set Motivation : - K* production mechanism - Looking for N* resonances Goal: Measuring Cross Sections - dσ/dcosθ vs. E - dσ/dcosθ vs. cosθ N* E= GeV Target: LH2 (L=17.85 cm)

4 Background ( signal) ( b.g.) N*

5 Analysis Cuts Particle identification - 2 detected particles : & - 3 timing cuts : Δβ, (TOF-ST), and (TOF/T tag ) Δβ = - < 0.1 ; = TOF-ST = |TOF - (Start Counter) vtime | < 1.0 ns TOF/Ttag = |TOF – (T tag +zvertex/c) | < 1.0 ns Kinematic cuts –Kinematic coverage (cos vs. ) –zvertex & R at vertex cuts –Fiducial cuts Mass cuts – missing mass – K* invariant mass E ToF-T tag (K) zvertex (K)

6 PID Timing cuts (kaons) K β P P (before cuts) P (after cuts) M (before cuts) M (after cuts) K

7 MM(K+) IM(K*) vs. MM(K+) K* and Σ+ Peaks K* from IM( ) from MM( ) for a cut on K* peak from MM( ) for a cut on K* SBs peak From MM ( )

8 IM(K*) vs. MM(K*)

9 Kinematic Coverage K* Cut Y* Cut cos(θ) E

10 Dalitz Plots IM( ) IM( Σ ) E= GeV E=2.00 GeV E= GeV E=2.300 GeV E=2.600 GeV E=2.475 GeV E= GeV E= GeVE= GeV

11 Normalized cross section Extracting Cross Sections M H = number of grams/mole of target ρ and L = detector’s density and length N a = Avogadro’s number A = detector’s acceptance = photon flux

12 Angular distribution of the diff. x-sec. (E=3.115 GeV) dσ/dcosθ (nb) cosθ

13 dσ/d(cosθ) for K* photoproduction (E=3.115GeV) E (nb) dσ/dcos θ

14 dσ/d(cosθ) for K* photoproduction (E=3.115GeV) E (nb) dσ/dcos θ

15 Systematic Uncertainties 6.65% CutsUncertainty 3.11% 2.51% 2.17% 3.0% 2.0%

16 Conclusion We have measured the differential cross sections for the K* Photoproduction. Our results agree with theory at the "middle to backward" angles but disagree at forward angles. - Small angles: forward-peaking strongly correlated to the t-channel kaon exchange - Large angle: backward cross sections have less interferences from the t-channel meson exchange Our data are expected to play a role in constraining the quark-vector-meson couplings and in improving the model Q. Zhao, J. Al-Khalili, And C. Bennhold, Phys. Rev. C64(2001) † †

17 Appendix Y* background

18 Y* b.g. contributions

19 Contribution from Λ(1520) From Λ(1520) peak From Λ(1520) SBs

20 (nb) dσ/d MM (K+)

21 dσ/d(cosθ) for K* photoproduction (E=3.115GeV) E (nb) dσ/dcos θ

22 dσ/d(cosθ) for K* photoproduction (E=3.115GeV) E (nb) dσ/dcos θ