K* photoproduction from g11

K. Hicks

Ohio University

HSG meeting, 12 June 2009

OUTLINE

• Review of K* photoproduction data

• Theoretical interest

• Presentations of preliminary analysis (Ohio students).

CLAS data (2007)I. Hleiqawi et al., Phys. Rev. C 76 (2007) 039905E.

New Data

Comparison

Red (open) = CLAS, Black (solid) = TAPS

Note the strong forward-peaking of TAPS data at higher photon energies.

K*+ (CLAS preliminary)L. Guo and D. Weygand, N* 2005 Conf., hep-ex/060101.

K*+ shown by the RED points, quoted with 20% uncertainty.

Theory calculations: K*0+

Y. Oh and H. Kim, hep-ph/0605105.

Model I (blue): no kappa form factor; Model II (red): with kappa form factor.

Theory comparison: K*+Y. Oh and H. Kim, PRC 73:065202 (2006).

Full calculation (solid line)K+ t-channel only (dashed)

Regge model (kaon trajectory)

Theory: a) K*+ , b) K*0+

SOLID BLUE: no kappa form factor; DASHED RED: with kappa form factor

Y. Oh and H. Kim, hep-ph/0605105.

New: K*+ Photoproduction

• Analysis by Wei Tang (Ohio grad student)

• Using g11 data set

• Detecting: pair plus another .

• Missing mass of Lambda and Sigma

• Acceptance using fsgen + GSIM

• Absolute normalization (new)– Checked using K+ photoproduction.

Details on data and cuts

• Runs 43526 – 44107 used (E=4.02 GeV).

• Bad paddles were removed.

• Photon identified using 1.0 ns time cuts.

• Particle ID from SC and tagger time cuts.

• Standard fiducial and vertex cuts applied.

• Sideband subtraction to isolate K0 events.

• K*+ mass cut from 0.80-0.98 GeV.

Details on Normalization

• Used gflux method to get photons.

• Applied “trigger efficiency” map.– Mike Williams supplied this method.

• Applied “dead time” correction.– INFN’s “current dependent correction” (18%)

• No additional correction for start counter.– Lambda decay products not needed to fire the

trigger (a la Mike McCracken).

K0 mass peak

K*+ Mass

Left s.b.

Right s.b.

K0 peak

K0 peak minus sidebands

K*+ Missing Mass

K*+ peak minusSidebands.

MM: one kinematic binE=1.6-1.7 GeV and -1 < cos < -.078

MM: higher-E binE = 2.3-2.4 GeV and -0.11 < cos < 0.11

Sample fit using gaussians

p K*+ Cross Sections

E (GeV)

W (GeV)

Units: b

Check: K0+ cross sections

Previous K0+ dataE = 1.65 GeV

B. Carnahan, PhD, Catholic U. (pub. in Sarantsev et al., Eur. Phys. J. A25, 411 (2005).

SAPHIR data(not shown) also published.

Status of K*+ analysis

• Preliminary differential cross sections OK.

• Next step: systematic studies.

• Just started: Lambda decay asymmetry– Statistics reduced by about ¼.

• Plan:– Finish cross sections (1 month)– Preliminary Lambda asymmetries (1 month)– Write analysis note by end of summer.

Status of K*0+ analysis

• This analysis is at a similar stage.– Normalization check requires more work

• This is a “redo” of the published data.– I. Hleiqawi et al. (CLAS publication).

• Overlap with nucleon resonances– Final state requires a PWA-like analysis.– This procedure was done for Hleiqawi data,

but now we have good statistics!

Summary

• K*0 and K*+ final states are nearly final. – Normalization issues took a lot of time.– Good agreement with previous data, but much

higher precision.– For K*+, can also do asymmetry.

• Plan to have analysis note by the end of the summer.– This will be part of the PhD thesis of W. Tang.