[Halld-physics] Friday Journal Club

[Justin Stevens]

Hi All,

On Aug 31, 2015, at 8:18 AM, Elton Smith wrote:

> 1) Are there examples of C=+ neutral states produced in photoproduction (i.e. is there evidence for rho-exchange)

Following up on this, here are a few examples if people are interested:

1) f0(980) -> pi+ pi- (CLAS):  http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.102.102001
	-Observed in a moment analysis of the unpolarized pi+ pi- angular distributions
	-There is also a signal for f2(1270) (JPC=2++) in the same analysis 

2) a0(980) -> pi0 eta (CB-ELSA): http://link.springer.com/article/10.1140%2Fepja%2Fi2008-10657-7
	-This is lower energy so not ideal for meson spectroscopy, but they did see the a0(980) in the PWA

3) pi0 photoproduction (SLAC): http://journals.aps.org/prd/abstract/10.1103/PhysRevD.4.1937
	-Similar beam energy to GlueX, measured dsigma/dt and Sigma beam asymmetry

The a0 and f0 papers are referenced in a recent theory paper by Donnachie and Kalashnikova (http://arxiv.org/abs/1507.07408) which has a Regge model for the vector and axial-vector (ie. rho/omega and b1/h1) exchanges that could produce such states in photoproduction and compares their model to the results from CLAS and CB-ELSA.  The pi0 channel is used to develop the model for f0/a0 production in the paper by Donnachie.  The pi0 channel was also looked at recently by our JPAC colleagues (Mathieu et. al. http://arxiv.org/abs/1505.02321) and they provided code for amplitudes that are incorporated in one of our event generators.

I think there may also be some analyses of CLAS data in the "pi0 eta p" and "Ks Ks p" final states which are neutral and have C=+.  I've seen these in some talks, but I haven't seen any papers to reference.

-Justin