<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi All,<br><br>We published an even higher-statistics paper on "p pi0 eta" at ELSA last year (2014): <br><span class="Apple-tab-span" style="white-space:pre"> </span><a href="http://dx.doi.org/10.1140/epja/i2014-14074-1">http://dx.doi.org/10.1140/epja/i2014-14074-1</a><br><br>The a0(980) is a dominant isobar and actually nicely observed (even visible in the "pi0 eta" mass distributions); but surprisingly, it is not produced dominantly in the forward direction as expected from t-channel exchange. A significant fraction is produced in the decay of high-mass N* / Delta resonances.<br><br>An ELSA paper on "p pi0 pi0" including polarization observables (linear beam; unpolarized target) was published this summer:<br><span class="Apple-tab-span" style="white-space:pre"> </span>http://dx.doi.org/10.1140/epja/i2015-15095-x<br><br>The f0(980) contributes to "pi0 pi0" but not as strong as the a0(980) to "pi0 eta" if I recall correctly. The energy for the ELSA measurements was less than 2.5 GeV.<br><br>CLAS has a few data on "p pi0 eta" but with low statistics and poor angular coverage.<br><br>- Volker<br><br><br>On Sep 1, 2015, at 11:06 PM, Justin Stevens <jrsteven@jlab.org> wrote:<br><br><blockquote type="cite">Hi All,<br><br>On Aug 31, 2015, at 8:18 AM, Elton Smith wrote:<br><br><blockquote type="cite">1) Are there examples of C=+ neutral states produced in photoproduction (i.e. is there evidence for rho-exchange)<br></blockquote><br>Following up on this, here are a few examples if people are interested:<br><br>1) f0(980) -> pi+ pi- (CLAS): http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.102.102001<br><span class="Apple-tab-span" style="white-space:pre"> </span>-Observed in a moment analysis of the unpolarized pi+ pi- angular distributions<br><span class="Apple-tab-span" style="white-space:pre"> </span>-There is also a signal for f2(1270) (JPC=2++) in the same analysis <br><br>2) a0(980) -> pi0 eta (CB-ELSA): http://link.springer.com/article/10.1140%2Fepja%2Fi2008-10657-7<br><span class="Apple-tab-span" style="white-space:pre"> </span>-This is lower energy so not ideal for meson spectroscopy, but they did see the a0(980) in the PWA<br><br>3) pi0 photoproduction (SLAC): http://journals.aps.org/prd/abstract/10.1103/PhysRevD.4.1937<br><span class="Apple-tab-span" style="white-space:pre"> </span>-Similar beam energy to GlueX, measured dsigma/dt and Sigma beam asymmetry<br><br>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.<br><br>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.<br><br>-Justin <br>_______________________________________________<br>Halld-physics mailing list<br>Halld-physics@jlab.org<br>https://mailman.jlab.org/mailman/listinfo/halld-physics<br></blockquote><div apple-content-edited="true"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><br></div></div></span></div></span><br class="Apple-interchange-newline"></span><br class="Apple-interchange-newline">
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